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Sample records for order wavefront sensor

  1. The AOLI Non-Linear Curvature Wavefront Sensor: High sensitivity reconstruction for low-order AO

    Science.gov (United States)

    Crass, Jonathan; King, David; Mackay, Craig

    2013-12-01

    Many adaptive optics (AO) systems in use today require bright reference objects to determine the effects of atmospheric distortions on incoming wavefronts. This requirement is because Shack Hartmann wavefront sensors (SHWFS) distribute incoming light from reference objects into a large number of sub-apertures. Bright natural reference objects occur infrequently across the sky leading to the use of laser guide stars which add complexity to wavefront measurement systems. The non-linear curvature wavefront sensor as described by Guyon et al. has been shown to offer a significant increase in sensitivity when compared to a SHWFS. This facilitates much greater sky coverage using natural guide stars alone. This paper describes the current status of the non-linear curvature wavefront sensor being developed as part of an adaptive optics system for the Adaptive Optics Lucky Imager (AOLI) project. The sensor comprises two photon-counting EMCCD detectors from E2V Technologies, recording intensity at four near-pupil planes. These images are used with a reconstruction algorithm to determine the phase correction to be applied by an ALPAO 241-element deformable mirror. The overall system is intended to provide low-order correction for a Lucky Imaging based multi CCD imaging camera. We present the current optical design of the instrument including methods to minimise inherent optical effects, principally chromaticity. Wavefront reconstruction methods are discussed and strategies for their optimisation to run at the required real-time speeds are introduced. Finally, we discuss laboratory work with a demonstrator setup of the system.

  2. The AOLI low-order non-linear curvature wavefront sensor: laboratory and on-sky results

    Science.gov (United States)

    Crass, Jonathan; King, David; MacKay, Craig

    2014-08-01

    Many adaptive optics (AO) systems in use today require the use of bright reference objects to determine the effects of atmospheric distortions. Typically these systems use Shack-Hartmann Wavefront sensors (SHWFS) to distribute incoming light from a reference object between a large number of sub-apertures. Guyon et al. evaluated the sensitivity of several different wavefront sensing techniques and proposed the non-linear Curvature Wavefront Sensor (nlCWFS) offering improved sensitivity across a range of orders of distortion. On large ground-based telescopes this can provide nearly 100% sky coverage using natural guide stars. We present work being undertaken on the nlCWFS development for the Adaptive Optics Lucky Imager (AOLI) project. The wavefront sensor is being developed as part of a low-order adaptive optics system for use in a dedicated instrument providing an AO corrected beam to a Lucky Imaging based science detector. The nlCWFS provides a total of four reference images on two photon-counting EMCCDs for use in the wavefront reconstruction process. We present results from both laboratory work using a calibration system and the first on-sky data obtained with the nlCWFS at the 4.2 metre William Herschel Telescope, La Palma. In addition, we describe the updated optical design of the wavefront sensor, strategies for minimising intrinsic effects and methods to maximise sensitivity using photon-counting detectors. We discuss on-going work to develop the high speed reconstruction algorithm required for the nlCWFS technique. This includes strategies to implement the technique on graphics processing units (GPUs) and to minimise computing overheads to obtain a prior for a rapid convergence of the wavefront reconstruction. Finally we evaluate the sensitivity of the wavefront sensor based upon both data and low-photon count strategies.

  3. High order dark wavefront sensing simulations

    Science.gov (United States)

    Ragazzoni, Roberto; Arcidiacono, Carmelo; Farinato, Jacopo; Viotto, Valentina; Bergomi, Maria; Dima, Marco; Magrin, Demetrio; Marafatto, Luca; Greggio, Davide; Carolo, Elena; Vassallo, Daniele

    2016-07-01

    Dark wavefront sensing takes shape following quantum mechanics concepts in which one is able to "see" an object in one path of a two-arm interferometer using an as low as desired amount of light actually "hitting" the occulting object. A theoretical way to achieve such a goal, but in the realm of wavefront sensing, is represented by a combination of two unequal beams interferometer sharing the same incoming light, and whose difference in path length is continuously adjusted in order to show different signals for different signs of the incoming perturbation. Furthermore, in order to obtain this in white light, the path difference should be properly adjusted vs the wavelength used. While we incidentally describe how this could be achieved in a true optomechanical setup, we focus our attention to the simulation of a hypothetical "perfect" dark wavefront sensor of this kind in which white light compensation is accomplished in a perfect manner and the gain is selectable in a numerical fashion. Although this would represent a sort of idealized dark wavefront sensor that would probably be hard to match in the real glass and metal, it would also give a firm indication of the maximum achievable gain or, in other words, of the prize for achieving such device. Details of how the simulation code works and first numerical results are outlined along with the perspective for an in-depth analysis of the performances and its extension to more realistic situations, including various sources of additional noise.

  4. Combined shearing interferometer and hartmann wavefront sensor

    International Nuclear Information System (INIS)

    Hutchin, R. A.

    1985-01-01

    A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point. A quadrant detector is provided for each subaperture to detect the position of the focal point therein, which provides a first indication, in the manner of a Hartmann wavefront sensor, of the local wavefront slope in each subaperture. The total radiation in each subaperture, as modulated by the diffraction grating, is also detected by the quadrant detector which produces a modulated output signal representative thereof, the phase of which relative to modulation by the diffraction grating provides a second indication of the local wavefront slope in each subaperture, in the manner of an AC shearing interferometer wavefront sensor. The data from both types of sensors is then combined by long term averaging thereof to provide an extremely sensitive wavefront sensor

  5. Correlator optical wavefront sensor COWS

    Science.gov (United States)

    1991-02-01

    This report documents the significant upgrades and improvements made to the correlator optical wavefront sensor (COWS) optical bench during this phase of the program. Software for the experiment was reviewed and documented. Flowcharts showing the program flow are included as well as documentation for programs which were written to calculate and display Zernike polynomials. The system was calibrated and aligned and a series of experiments to determine the optimum settings for the input and output MOSLM polarizers were conducted. In addition, design of a simple aberration generation is included.

  6. Ultra-high resolution coded wavefront sensor

    KAUST Repository

    Wang, Congli; Dun, Xiong; Fu, Qiang; Heidrich, Wolfgang

    2017-01-01

    Wavefront sensors and more general phase retrieval methods have recently attracted a lot of attention in a host of application domains, ranging from astronomy to scientific imaging and microscopy. In this paper, we introduce a new class of sensor

  7. A zonal wavefront sensor with multiple detector planes

    Science.gov (United States)

    Pathak, Biswajit; Boruah, Bosanta R.

    2018-03-01

    A conventional zonal wavefront sensor estimates the wavefront from the data captured in a single detector plane using a single camera. In this paper, we introduce a zonal wavefront sensor which comprises multiple detector planes instead of a single detector plane. The proposed sensor is based on an array of custom designed plane diffraction gratings followed by a single focusing lens. The laser beam whose wavefront is to be estimated is incident on the grating array and one of the diffracted orders from each grating is focused on the detector plane. The setup, by employing a beam splitter arrangement, facilitates focusing of the diffracted beams on multiple detector planes where multiple cameras can be placed. The use of multiple cameras in the sensor can offer several advantages in the wavefront estimation. For instance, the proposed sensor can provide superior inherent centroid detection accuracy that can not be achieved by the conventional system. It can also provide enhanced dynamic range and reduced crosstalk performance. We present here the results from a proof of principle experimental arrangement that demonstrate the advantages of the proposed wavefront sensing scheme.

  8. Ultra-high resolution coded wavefront sensor

    KAUST Repository

    Wang, Congli

    2017-06-08

    Wavefront sensors and more general phase retrieval methods have recently attracted a lot of attention in a host of application domains, ranging from astronomy to scientific imaging and microscopy. In this paper, we introduce a new class of sensor, the Coded Wavefront Sensor, which provides high spatio-temporal resolution using a simple masked sensor under white light illumination. Specifically, we demonstrate megapixel spatial resolution and phase accuracy better than 0.1 wavelengths at reconstruction rates of 50 Hz or more, thus opening up many new applications from high-resolution adaptive optics to real-time phase retrieval in microscopy.

  9. Coded Shack-Hartmann Wavefront Sensor

    KAUST Repository

    Wang, Congli

    2016-12-01

    Wavefront sensing is an old yet fundamental problem in adaptive optics. Traditional wavefront sensors are limited to time-consuming measurements, complicated and expensive setup, or low theoretically achievable resolution. In this thesis, we introduce an optically encoded and computationally decodable novel approach to the wavefront sensing problem: the Coded Shack-Hartmann. Our proposed Coded Shack-Hartmann wavefront sensor is inexpensive, easy to fabricate and calibrate, highly sensitive, accurate, and with high resolution. Most importantly, using simple optical flow tracking combined with phase smoothness prior, with the help of modern optimization technique, the computational part is split, efficient, and parallelized, hence real time performance has been achieved on Graphics Processing Unit (GPU), with high accuracy as well. This is validated by experimental results. We also show how optical flow intensity consistency term can be derived, using rigor scalar diffraction theory with proper approximation. This is the true physical law behind our model. Based on this insight, Coded Shack-Hartmann can be interpreted as an illumination post-modulated wavefront sensor. This offers a new theoretical approach for wavefront sensor design.

  10. Model wavefront sensor for adaptive confocal microscopy

    Science.gov (United States)

    Booth, Martin J.; Neil, Mark A. A.; Wilson, Tony

    2000-05-01

    A confocal microscope permits 3D imaging of volume objects by the inclusion of a pinhole in the detector path which eliminates out of focus light. This configuration is however very sensitive to aberrations induced by the specimen or the optical system and would therefore benefit from an adaptive optics approach. We present a wavefront sensor capable of measuring directly the Zernike components of an aberrated wavefront and show that it is particularly applicable to the confocal microscope since only those wavefronts originating in the focal region contribute to the measured aberration.

  11. X-ray digital wavefront sensor development

    International Nuclear Information System (INIS)

    Idir, Mourad; Fricker, Sebastien; Modi, Mohammed H.; Potier, Jonathan

    2010-01-01

    Phase contrast imaging (PCI) is a wavefront sensing method that uses a series of intensity images to reconstruct the wavefront. The lateral resolution of PCI is limited mainly by the resolution of the intensity images. PCI provides a simple and efficient technique for characterizing X-ray mirrors. A simulation experiment was conducted to demonstrate the performances of PCI. The results of these experiments have shown the feasibility and potential performances of this method. The use of phase retrieval presents opportunities for greatly simplifying the techniques and apparatus used for characterizing optical surfaces and systems, particularly aspherical surfaces. This paper addresses the design, implementation and performances of an integrated at wavelength digital wavefront sensor.

  12. A modified phase diversity wavefront sensor with a diffraction grating

    International Nuclear Information System (INIS)

    Luo Qun; Huang Lin-Hai; Gu Nai-Ting; Rao Chang-Hui

    2012-01-01

    The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency

  13. Photon counting arrays for AO wavefront sensors

    CERN Document Server

    Vallerga, J; McPhate, J; Mikulec, Bettina; Clark, Allan G; Siegmund, O; CERN. Geneva

    2005-01-01

    Future wavefront sensors for AO on large telescopes will require a large number of pixels and must operate at high frame rates. Unfortunately for CCDs, there is a readout noise penalty for operating faster, and this noise can add up rather quickly when considering the number of pixels required for the extended shape of a sodium laser guide star observed with a large telescope. Imaging photon counting detectors have zero readout noise and many pixels, but have suffered in the past with low QE at the longer wavelengths (>500 nm). Recent developments in GaAs photocathode technology, CMOS ASIC readouts and FPGA processing electronics have resulted in noiseless WFS detector designs that are competitive with silicon array detectors, though at ~40% the QE of CCDs. We review noiseless array detectors and compare their centroiding performance with CCDs using the best available characteristics of each. We show that for sub-aperture binning of 6x6 and greater that noiseless detectors have a smaller centroid error at flu...

  14. CMOS optical centroid processor for an integrated Shack-Hartmann wavefront sensor

    OpenAIRE

    Pui, Boon Hean

    2004-01-01

    A Shack Hartmann wavefront sensor is used to detect the distortion of light in an optical wavefront. It does this by sampling the wavefront with an array of lenslets and measuring the displacement of focused spots from reference positions. These displacements are linearly related to the local wavefront tilts from which the entire wavefront can be reconstructed. In most Shack Hartmann wavefront sensors, a CCD is used to sample the entire wavefront, typically at a rate of 25 to 60 Hz, and a who...

  15. An Optical Wavefront Sensor Based on a Double Layer Microlens Array

    Directory of Open Access Journals (Sweden)

    Hsiang-Chun Wei

    2011-10-01

    Full Text Available In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin, the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution.

  16. Wavefront-sensor-induced beam size error: physical mechanism, sensitivity-analysis and correction method

    NARCIS (Netherlands)

    Koek, W.D.; Zwet, E.J. van

    2015-01-01

    When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders

  17. X-ray active mirror coupled with a Hartmann wavefront sensor

    International Nuclear Information System (INIS)

    Idir, Mourad; Mercere, Pascal; Modi, Mohammed H.; Dovillaire, Guillaume; Levecq, Xavier; Bucourt, Samuel; Escolano, Lionel; Sauvageot, Paul

    2010-01-01

    This paper reports on the design and performances of a test prototype active X-ray mirror (AXM) which has been designed and manufactured in collaboration with the French Small and Medium Enterprise mechanical company ISP System for the national French storage ring SOLEIL. Coupled with this active X-ray mirror and also in collaboration with another French Small and Medium Enterprise (Imagine Optic) a lot of efforts have been done in order to design and fabricate a wavefront X-ray analyzer based on the Hartmann principle (Hartman wavefront sensor, HWS).

  18. Hough transform used on the spot-centroiding algorithm for the Shack-Hartmann wavefront sensor

    Science.gov (United States)

    Chia, Chou-Min; Huang, Kuang-Yuh; Chang, Elmer

    2016-01-01

    An approach to the spot-centroiding algorithm for the Shack-Hartmann wavefront sensor (SHWS) is presented. The SHWS has a common problem, in that while measuring high-order wavefront distortion, the spots may exceed each of the subapertures, which are used to restrict the displacement of spots. This artificial restriction may limit the dynamic range of the SHWS. When using the SHWS to measure adaptive optics or aspheric lenses, the accuracy of the traditional spot-centroiding algorithm may be uncertain because the spots leave or cross the confined area of the subapertures. The proposed algorithm combines the Hough transform with an artificial neural network, which requires no confined subapertures, to increase the dynamic range of the SHWS. This algorithm is then explored in comprehensive simulations and the results are compared with those of the existing algorithm.

  19. Precise starshade stationkeeping and pointing with a Zernike wavefront sensor

    Science.gov (United States)

    Bottom, Michael; Martin, Stefan; Seubert, Carl; Cady, Eric; Zareh, Shannon Kian; Shaklan, Stuart

    2017-09-01

    Starshades, large occulters positioned tens of thousands of kilometers in front of space telescopes, offer one of the few paths to imaging and characterizing Earth-like extrasolar planets. However, for a starshade to generate a sufficiently dark shadow on the telescope, the two must be coaligned to just 1 meter laterally, even at these large separations. The principal challenge to achieving this level of control is in determining the position of the starshade with respect to the space telescope. In this paper, we present numerical simulations and laboratory results demonstrating that a Zernike wavefront sensor coupled to a WFIRST-type telescope is able to deliver the stationkeeping precision required, by measuring light outside of the science wavelengths. The sensor can determine the starshade lateral position to centimeter level in seconds of open shutter time for stars brighter than eighth magnitude, with a capture range of 10 meters. We discuss the potential for fast (ms) tip/tilt pointing control at the milli-arcsecond level by illuminating the sensor with a laser mounted on the starshade. Finally, we present early laboratory results.

  20. Real-time wavefront correction system using a zonal deformable mirror and a Hartmann sensor

    International Nuclear Information System (INIS)

    Salmon, J.T.; Bliss, E.S.; Long, T.W.; Orham, E.L.; Presta, R.W.; Swift, C.D.; Ward, R.S.

    1991-07-01

    We have developed an adaptive optics system that corrects up to five waves of 2nd-order and 3rd-order aberrations in a high-power laser beam to less than 1/10th wave RMS. The wavefront sensor is a Hartmann sensor with discrete lenses and position-sensitive photodiodes; the deformable mirror uses piezoelectric actuators with feedback from strain gauges bonded to the stacks. The controller hardware uses a VME bus. The system removes thermally induced aberrations generated in the master-oscillator-power-amplifier chains of a dye laser, as well as aberrations generated in beam combiners and vacuum isolation windows for average output powers exceeding 1 kW. The system bandwidth is 1 Hz, but higher bandwidths are easily attainable

  1. Performance analysis of coherent free space optical communications with sequential pyramid wavefront sensor

    Science.gov (United States)

    Liu, Wei; Yao, Kainan; Chen, Lu; Huang, Danian; Cao, Jingtai; Gu, Haijun

    2018-03-01

    Based-on the previous study on the theory of the sequential pyramid wavefront sensor (SPWFS), in this paper, the SPWFS is first applied to the coherent free space optical communications (FSOC) with more flexible spatial resolution and higher sensitivity than the Shack-Hartmann wavefront sensor, and with higher uniformity of intensity distribution and much simpler than the pyramid wavefront sensor. Then, the mixing efficiency (ME) and the bit error rate (BER) of the coherent FSOC are analyzed during the aberrations correction through numerical simulation with binary phase shift keying (BPSK) modulation. Finally, an experimental AO system based-on SPWFS is setup, and the experimental data is used to analyze the ME and BER of homodyne detection with BPSK modulation. The results show that the AO system based-on SPWFS can increase ME and decrease BER effectively. The conclusions of this paper provide a new method of wavefront sensing for designing the AO system for a coherent FSOC system.

  2. Higher-Order Wavefront Aberrations for Populations of Young Emmetropes and Myopes

    Directory of Open Access Journals (Sweden)

    Jinhua Bao

    2009-01-01

    Conclusions: Human eyes have systematical higher order aberrations in population, and factors that cause bilateral symmetry of wavefront aberrations between the right and left eyes made important contribution to the systematical aberrations.

  3. Accuracy of Shack-Hartmann wavefront sensor using a coherent wound fibre image bundle

    Science.gov (United States)

    Zheng, Jessica R.; Goodwin, Michael; Lawrence, Jon

    2018-03-01

    Shack-Hartmannwavefront sensors using wound fibre image bundles are desired for multi-object adaptive optical systems to provide large multiplex positioned by Starbugs. The use of a large-sized wound fibre image bundle provides the flexibility to use more sub-apertures wavefront sensor for ELTs. These compact wavefront sensors take advantage of large focal surfaces such as the Giant Magellan Telescope. The focus of this paper is to study the wound fibre image bundle structure defects effect on the centroid measurement accuracy of a Shack-Hartmann wavefront sensor. We use the first moment centroid method to estimate the centroid of a focused Gaussian beam sampled by a simulated bundle. Spot estimation accuracy with wound fibre image bundle and its structure impact on wavefront measurement accuracy statistics are addressed. Our results show that when the measurement signal-to-noise ratio is high, the centroid measurement accuracy is dominated by the wound fibre image bundle structure, e.g. tile angle and gap spacing. For the measurement with low signal-to-noise ratio, its accuracy is influenced by the read noise of the detector instead of the wound fibre image bundle structure defects. We demonstrate this both with simulation and experimentally. We provide a statistical model of the centroid and wavefront error of a wound fibre image bundle found through experiment.

  4. BER Analysis of Coherent Free-Space Optical Communication Systems with a Focal-Plane-Based Wavefront Sensor

    Science.gov (United States)

    Cao, Jingtai; Zhao, Xiaohui; Liu, Wei; Gu, Haijun

    2018-03-01

    A wavefront sensor is one of most important units for an adaptive optics system. Based on our previous works, in this paper, we discuss the bit-error-rate (BER) performance of coherent free space optical communication systems with a focal-plane-based wavefront sensor. Firstly, the theory of a focal-plane-based wavefront sensor is given. Then the relationship between the BER and the mixing efficiency with a homodyne receiver is discussed on the basis of binary-phase-shift-keying (BPSK) modulation. Finally, the numerical simulation results are shown that the BER will be decreased obviously after aberrations correction with the focal-plane-based wavefront sensor. In addition, the BER will decrease along with increasing number of photons received within a single bit. These analysis results will provide a reference for the design of the coherent Free space optical communication (FSOC) system.

  5. Semiconductor sensor for optically measuring polarization rotation of optical wavefronts using rare earth iron garnets

    Science.gov (United States)

    Duncan, Paul G.

    2002-01-01

    Described are the design of a rare earth iron garnet sensor element, optical methods of interrogating the sensor element, methods of coupling the optical sensor element to a waveguide, and an optical and electrical processing system for monitoring the polarization rotation of a linearly polarized wavefront undergoing external modulation due to magnetic field or electrical current fluctuation. The sensor element uses the Faraday effect, an intrinsic property of certain rare-earth iron garnet materials, to rotate the polarization state of light in the presence of a magnetic field. The sensor element may be coated with a thin-film mirror to effectively double the optical path length, providing twice the sensitivity for a given field strength or temperature change. A semiconductor sensor system using a rare earth iron garnet sensor element is described.

  6. Sorting method to extend the dynamic range of the Shack-Hartmann wave-front sensor

    International Nuclear Information System (INIS)

    Lee, Junwon; Shack, Roland V.; Descour, Michael R.

    2005-01-01

    We propose a simple and powerful algorithm to extend the dynamic range of a Shack-Hartmann wave-front sensor. In a conventional Shack-Hartmann wave-front sensor the dynamic range is limited by the f-number of a lenslet, because the focal spot is required to remain in the area confined by the single lenslet. The sorting method proposed here eliminates such a limitation and extends the dynamic range by tagging each spot in a special sequence. Since the sorting method is a simple algorithm that does not change the measurement configuration, there is no requirement for extra hardware, multiple measurements, or complicated algorithms. We not only present the theory and a calculation example of the sorting method but also actually implement measurement of a highly aberrated wave front from nonrotational symmetric optics

  7. The low-order wavefront control system for the PICTURE-C mission: high-speed image acquisition and processing

    Science.gov (United States)

    Hewawasam, Kuravi; Mendillo, Christopher B.; Howe, Glenn A.; Martel, Jason; Finn, Susanna C.; Cook, Timothy A.; Chakrabarti, Supriya

    2017-09-01

    The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) mission will directly image debris disks and exozodiacal dust around nearby stars from a high-altitude balloon using a vector vortex coronagraph. The PICTURE-C low-order wavefront control (LOWC) system will be used to correct time-varying low-order aberrations due to pointing jitter, gravity sag, thermal deformation, and the gondola pendulum motion. We present the hardware and software implementation of the low-order ShackHartmann and reflective Lyot stop sensors. Development of the high-speed image acquisition and processing system is discussed with the emphasis on the reduction of hardware and computational latencies through the use of a real-time operating system and optimized data handling. By characterizing all of the LOWC latencies, we describe techniques to achieve a framerate of 200 Hz with a mean latency of ˜378 μs

  8. Automatic centroid detection and surface measurement with a digital Shack–Hartmann wavefront sensor

    International Nuclear Information System (INIS)

    Yin, Xiaoming; Zhao, Liping; Li, Xiang; Fang, Zhongping

    2010-01-01

    With the breakthrough of manufacturing technologies, the measurement of surface profiles is becoming a big issue. A Shack–Hartmann wavefront sensor (SHWS) provides a promising technology for non-contact surface measurement with a number of advantages over interferometry. The SHWS splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. So the accuracy of the centroid measurement determines the accuracy of the SHWS. In this paper, we have presented a new centroid measurement algorithm based on an adaptive thresholding and dynamic windowing method by utilizing image-processing techniques. Based on this centroid detection method, we have developed a digital SHWS system which can automatically detect centroids of focal spots, reconstruct the wavefront and measure the 3D profile of the surface. The system has been tested with various simulated and real surfaces such as flat surfaces, spherical and aspherical surfaces as well as deformable surfaces. The experimental results demonstrate that the system has good accuracy, repeatability and immunity to optical misalignment. The system is also suitable for on-line applications of surface measurement

  9. Rapid and highly integrated FPGA-based Shack-Hartmann wavefront sensor for adaptive optics system

    Science.gov (United States)

    Chen, Yi-Pin; Chang, Chia-Yuan; Chen, Shean-Jen

    2018-02-01

    In this study, a field programmable gate array (FPGA)-based Shack-Hartmann wavefront sensor (SHWS) programmed on LabVIEW can be highly integrated into customized applications such as adaptive optics system (AOS) for performing real-time wavefront measurement. Further, a Camera Link frame grabber embedded with FPGA is adopted to enhance the sensor speed reacting to variation considering its advantage of the highest data transmission bandwidth. Instead of waiting for a frame image to be captured by the FPGA, the Shack-Hartmann algorithm are implemented in parallel processing blocks design and let the image data transmission synchronize with the wavefront reconstruction. On the other hand, we design a mechanism to control the deformable mirror in the same FPGA and verify the Shack-Hartmann sensor speed by controlling the frequency of the deformable mirror dynamic surface deformation. Currently, this FPGAbead SHWS design can achieve a 266 Hz cyclic speed limited by the camera frame rate as well as leaves 40% logic slices for additionally flexible design.

  10. Development of a hard x-ray wavefront sensor for the EuXFEL

    Science.gov (United States)

    Berujon, Sebastien; Ziegler, Eric; Cojocaru, Ruxandra; Martin, Thierry

    2017-05-01

    We present developments on a hard X-ray wavefront sensing instrument for characterizing and monitoring the beam of the European X-ray Free Electron Lasers (EuXFEL). The pulsed nature of the intense X-ray beam delivered by this new class of facility gives rise to strong challenges for the optics and their diagnostic. In the frame of the EUCALL project Work Package 7, we are developing a sensor able to observe the beam in the X-ray energy range [8-40] keV without altering it. The sensor is based on the speckle tracking principle and employs two semi-transparent optics optimized such that their X-ray absorption is reduced. Furthermore, this instrument requires a scattering object with small random features placed in the beam and two cameras to record images of the beam at two different propagation distances. The analysis of the speckle pattern and its distortion from one image to the other allows absolute or differential wavefront recovery from pulse to pulse. Herein, we introduce the stakes and challenges of wavefront sensing at an XFEL source and explain the strategies adopted to fulfil the high requirements set by such a source.

  11. Sparse aperture differential piston measurements using the pyramid wave-front sensor

    Science.gov (United States)

    Arcidiacono, Carmelo; Chen, Xinyang; Yan, Zhaojun; Zheng, Lixin; Agapito, Guido; Wang, Chaoyan; Zhu, Nenghong; Zhu, Liyun; Cai, Jianqing; Tang, Zhenghong

    2016-07-01

    In this paper we report on the laboratory experiment we settled in the Shanghai Astronomical Observatory (SHAO) to investigate the pyramid wave-front sensor (WFS) ability to measure the differential piston on a sparse aperture. The ultimate goal is to verify the ability of the pyramid WFS work in close loop to perform the phasing of the primary mirrors of a sparse Fizeau imaging telescope. In the experiment we installed on the optical bench we performed various test checking the ability to flat the wave-front using a deformable mirror and to measure the signal of the differential piston on a two pupils setup. These steps represent the background from which we start to perform full close loop operation on multiple apertures. These steps were also useful to characterize the achromatic double pyramids (double prisms) manufactured in the SHAO optical workshop.

  12. High-QE fast-readout wavefront sensor with analog phase reconstruction

    Science.gov (United States)

    Baker, Jeffrey T.; Loos, Gary C.; Restaino, Sergio R.; Percheron, Isabelle; Finkner, Lyle G.

    1998-09-01

    The contradiction inherent in high temporal bandwidth adaptive optics wavefront sensing at low-light-levels (LLL) has driven many researchers to consider the use of high bandwidth high quantum efficiency (QE) CCD cameras with the lowest possible readout noise levels. Unfortunately, the performance of these relatively expensive and low production volume devices in the photon counting regime is inevitably limited by readout noise, no matter how arbitrarily close to zero that specification may be reduced. Our alternative approach is to optically couple a new and relatively inexpensive Ultra Blue Gen III image intensifier to an also relatively inexpensive high bandwidth CCD camera with only moderate QE and high rad noise. The result is a high bandwidth broad spectral response image intensifier with a gain of 55,000 at 560 nm. Use of an appropriately selected lenslet array together with coupling optics generates 16 X 16 Shack-Hartmann type subapertures on the image intensifier photocathode, which is imaged onto the fast CCD camera. An integral A/D converter in the camera sends the image data pixel by pixel to a computer data acquisition system for analysis, storage and display. Timing signals are used to decode which pixel is being rad out and the wavefront is calculated in an analog fashion using a least square fit to both x and y tilt data for all wavefront sensor subapertures. Finally, we present system level performance comparisons of these new concept wavefront sensors versus the more standard low noise CCD camera based designs in the low-light-level limit.

  13. Prototype of a laser guide star wavefront sensor for the Extremely Large Telescope

    Science.gov (United States)

    Patti, M.; Lombini, M.; Schreiber, L.; Bregoli, G.; Arcidiacono, C.; Cosentino, G.; Diolaiti, E.; Foppiani, I.

    2018-06-01

    The new class of large telescopes, like the future Extremely Large Telescope (ELT), are designed to work with a laser guide star (LGS) tuned to a resonance of atmospheric sodium atoms. This wavefront sensing technique presents complex issues when applied to big telescopes for many reasons, mainly linked to the finite distance of the LGS, the launching angle, tip-tilt indetermination and focus anisoplanatism. The implementation of a laboratory prototype for the LGS wavefront sensor (WFS) at the beginning of the phase study of MAORY (Multi-conjugate Adaptive Optics Relay) for ELT first light has been indispensable in investigating specific mitigation strategies for the LGS WFS issues. This paper presents the test results of the LGS WFS prototype under different working conditions. The accuracy within which the LGS images are generated on the Shack-Hartmann WFS has been cross-checked with the MAORY simulation code. The experiments show the effect of noise on centroiding precision, the impact of LGS image truncation on wavefront sensing accuracy as well as the temporal evolution of the sodium density profile and LGS image under-sampling.

  14. Design of pre-optics for laser guide star wavefront sensor for the ELT

    Science.gov (United States)

    Muslimov, Eduard; Dohlen, Kjetil; Neichel, Benoit; Hugot, Emmanuel

    2017-12-01

    In the present paper, we consider the optical design of a zoom system for the active refocusing in laser guide star wavefront sensors. The system is designed according to the specifications coming from the Extremely Large Telescope (ELT)-HARMONI instrument, the first-light, integral field spectrograph for the European (E)-ELT. The system must provide a refocusing of the laser guide as a function of telescope pointing and large decentring of the incoming beam. The system considers four moving lens groups, each of them being a doublet with one aspherical surface. The advantages and shortcomings of such a solution in terms of the component displacements and complexity of the surfaces are described in detail. It is shown that the system can provide the median value of the residual wavefront error of 13.8-94.3 nm and the maximum value <206 nm, while the exit pupil distortion is 0.26-0.36% for each of the telescope pointing directions.

  15. Least-squares wave-front reconstruction of Shack-Hartmann sensors and shearing interferometers using multigrid techniques

    International Nuclear Information System (INIS)

    Baker, K.L.

    2005-01-01

    This article details a multigrid algorithm that is suitable for least-squares wave-front reconstruction of Shack-Hartmann and shearing interferometer wave-front sensors. The algorithm detailed in this article is shown to scale with the number of subapertures in the same fashion as fast Fourier transform techniques, making it suitable for use in applications requiring a large number of subapertures and high Strehl ratio systems such as for high spatial frequency characterization of high-density plasmas, optics metrology, and multiconjugate and extreme adaptive optics systems

  16. Improvement of correlation-based centroiding methods for point source Shack-Hartmann wavefront sensor

    Science.gov (United States)

    Li, Xuxu; Li, Xinyang; wang, Caixia

    2018-03-01

    This paper proposes an efficient approach to decrease the computational costs of correlation-based centroiding methods used for point source Shack-Hartmann wavefront sensors. Four typical similarity functions have been compared, i.e. the absolute difference function (ADF), ADF square (ADF2), square difference function (SDF), and cross-correlation function (CCF) using the Gaussian spot model. By combining them with fast search algorithms, such as three-step search (TSS), two-dimensional logarithmic search (TDL), cross search (CS), and orthogonal search (OS), computational costs can be reduced drastically without affecting the accuracy of centroid detection. Specifically, OS reduces calculation consumption by 90%. A comprehensive simulation indicates that CCF exhibits a better performance than other functions under various light-level conditions. Besides, the effectiveness of fast search algorithms has been verified.

  17. Measurement of nonlinear refractive index and ionization rates in air using a wavefront sensor.

    Science.gov (United States)

    Schwarz, Jens; Rambo, Patrick; Kimmel, Mark; Atherton, Briggs

    2012-04-09

    A wavefront sensor has been used to measure the Kerr nonlinear focal shift of a high intensity ultrashort pulse beam in a focusing beam geometry while accounting for the effects of plasma-defocusing. It is shown that plasma-defocusing plays a major role in the nonlinear focusing dynamics and that measurements of Kerr nonlinearity and ionization are coupled. Furthermore, this coupled effect leads to a novel way that measures the laser ionization rates in air under atmospheric conditions as well as Kerr nonlinearity. The measured nonlinear index n₂ compares well with values found in the literature and the measured ionization rates could be successfully benchmarked to the model developed by Perelomov, Popov, and Terentev (PPT model) [Sov. Phys. JETP 50, 1393 (1966)].

  18. Adaptive thresholding and dynamic windowing method for automatic centroid detection of digital Shack-Hartmann wavefront sensor

    International Nuclear Information System (INIS)

    Yin Xiaoming; Li Xiang; Zhao Liping; Fang Zhongping

    2009-01-01

    A Shack-Hartmann wavefront sensor (SWHS) splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. The accuracy of the centroid measurement determines the accuracy of the SWHS. Many methods have been presented to improve the accuracy of the wavefront centroid measurement. However, most of these methods are discussed from the point of view of optics, based on the assumption that the spot intensity of the SHWS has a Gaussian distribution, which is not applicable to the digital SHWS. In this paper, we present a centroid measurement algorithm based on the adaptive thresholding and dynamic windowing method by utilizing image processing techniques for practical application of the digital SHWS in surface profile measurement. The method can detect the centroid of each focal spot precisely and robustly by eliminating the influence of various noises, such as diffraction of the digital SHWS, unevenness and instability of the light source, as well as deviation between the centroid of the focal spot and the center of the detection area. The experimental results demonstrate that the algorithm has better precision, repeatability, and stability compared with other commonly used centroid methods, such as the statistical averaging, thresholding, and windowing algorithms.

  19. Measurement of M2-Curve for Asymmetric Beams by Self-Referencing Interferometer Wavefront Sensor

    Directory of Open Access Journals (Sweden)

    Yongzhao Du

    2016-11-01

    Full Text Available For asymmetric laser beams, the values of beam quality factor M x 2 and M y 2 are inconsistent if one selects a different coordinate system or measures beam quality with different experimental conditionals, even when analyzing the same beam. To overcome this non-uniqueness, a new beam quality characterization method named as M2-curve is developed. The M2-curve not only contains the beam quality factor M x 2 and M y 2 in the x-direction and y-direction, respectively; but also introduces a curve of M x α 2 versus rotation angle α of coordinate axis. Moreover, we also present a real-time measurement method to demonstrate beam propagation factor M2-curve with a modified self-referencing Mach-Zehnder interferometer based-wavefront sensor (henceforth SRI-WFS. The feasibility of the proposed method is demonstrated with the theoretical analysis and experiment in multimode beams. The experimental results showed that the proposed measurement method is simple, fast, and a single-shot measurement procedure without movable parts.

  20. Novel Detecting Methods of Shack-Hartmann Wavefront Sensor at Low Light Levels

    International Nuclear Information System (INIS)

    Zhang, A; Rao, C H; Zhang, Y D; Jiang, W H

    2006-01-01

    A study of novel detecting methods of Shack-Hartmann wavefront sensor at low light levels has been made. Three methods of images processing before slope estimating are presented: Linear Enhancing (LE), Exponential Enhancing (EE) and Fourier Spectrum Filtering (FSF). The idea of LE method is to time the image intensity with a special coefficient before slope estimation. The image points are powered by a selected exponent in EE method. The FSF method is based on the spectrum difference between signal and noise. Most of noise spectrum is filtered and the noise is restrained. The simulated and experimental results show that the LE method does not work effectively, and the other two methods can improve the slope estimation when the Signal-to-noise ratio is higher than 3.0. When the Signal-to-noise ratio is less than 3.0, especially when it is less than 1.0, the FSF is the only method that can overcome the readout noise of the CCD detector

  1. Changes in higher order aberrations after wavefront guided FS-LASIK for myopia combined with moderate to high astigmatism

    Directory of Open Access Journals (Sweden)

    Cang-Yu Guan

    2018-02-01

    Full Text Available AIM: To assess the changes in higher order aberrations after wavefront guided femtosecond laser assisted laser in situ keratomileusis(FS-LASIKfor moderate to high astigmatism. METHODS: Eighty-eight eyes of 50 myopia patients with moderate to high astigmatism were included in this prospective study. There were 51 eyes with moderate astigmatism(≥-1.50D and RESULTS: At the 3mo after operation, the mean UDVA of all eyes was above 20/20, better than before operation(PP=0.36and no eyes lost ≥2 lines of CDVA. Mean astigmstism of 85 eyes(97%was reduced below -1.00D, mean astigmatism of 70 eyes(80%was reduced below -0.50D(PPP=0.078, 0.065. The spherical aberration, secondary astigmatism and the HOA root mean square(RMSincreased from 0.19±0.06, 0.05±0.02 and 0.42±0.12, preoperatively to 0.32±0.17, 0.26±0.08 and 0.78±0.28(PCONCLUSION: Wavefront-guided FS-LASIK is a safe and effective option for the patients with moderate to high astigmstism although parts of HOAs increased.

  2. Spherical aberration and other higher-order aberrations in the human eye : from summary wave-front analysis data to optical variables relevant to visual perception

    NARCIS (Netherlands)

    Jansonius, Nomdo M.

    Wave-front analysis data from the human eye are commonly presented using the aberration coefficient c(4)(0) (primary spherical aberration) together with an overall measure of all higher-order aberrations. If groups of subjects are compared, however, the relevance of an observed difference cannot

  3. Correction of the wavefront using the irradiance transport equation

    Science.gov (United States)

    García, M.; Granados, F.; Cornejo, A.

    2008-07-01

    The correction of the wavefront in optical systems implies the use of wavefront sensors, software, and auxiliary optical systems. We propose evaluated the wavefront using the fact that the wavefront and its intensity are related in the mathematical expression the irradiance transport equation (ITE)

  4. Multi-optical-axis measurement of freeform progressive addition lenses using a Hartmann-Shack wavefront sensor

    Science.gov (United States)

    Xiang, Huazhong; Guo, Hang; Fu, Dongxiang; Zheng, Gang; Zhuang, Songlin; Chen, JiaBi; Wang, Cheng; Wu, Jie

    2018-05-01

    To precisely measure the whole-surface characterization of freeform progressive addition lenses (PALs), considering the multi-optical-axis conditions is becoming particularly important. Spherical power and astigmatism (cylinder) measurements for freeform PALs, using a Hartmann-Shack wavefront sensor (HSWFS) are proposed herein. Conversion formulas for the optical performance results were provided as HSWFS Zernike polynomial expansions. For each selected zone, the studied PALs were placed and tilted to simulate the multi-optical-axis conditions. The results of two tested PALs were analyzed using MATLAB programs and represented as contour plots of the spherical equivalent and cylinder of the whole-surface. The proposed experimental setup can provide a high accuracy as well as a possibility of choosing 12 lines and positions of 193 measurement zones on the entire surface. This approach to PAL analysis is potentially an efficient and useful method to objectively evaluate the optical performances, in which the full lens surface is defined and expressed as the contour plots of power in different regions (i.e., the distance region, progressive region, and near region) of the lens for regions of interest.

  5. Correcting the wavefront aberration of membrane mirror based on liquid crystal spatial light modulator

    Science.gov (United States)

    Yang, Bin; Wei, Yin; Chen, Xinhua; Tang, Minxue

    2014-11-01

    Membrane mirror with flexible polymer film substrate is a new-concept ultra lightweight mirror for space applications. Compared with traditional mirrors, membrane mirror has the advantages of lightweight, folding and deployable, low cost and etc. Due to the surface shape of flexible membrane mirror is easy to deviate from the design surface shape, it will bring wavefront aberration to the optical system. In order to solve this problem, a method of membrane mirror wavefront aberration correction based on the liquid crystal spatial light modulator (LCSLM) will be studied in this paper. The wavefront aberration correction principle of LCSLM is described and the phase modulation property of a LCSLM is measured and analyzed firstly. Then the membrane mirror wavefront aberration correction system is designed and established according to the optical properties of a membrane mirror. The LCSLM and a Hartmann-Shack sensor are used as a wavefront corrector and a wavefront detector, respectively. The detected wavefront aberration is calculated and converted into voltage value on LCSLM for the mirror wavefront aberration correction by programming in Matlab. When in experiment, the wavefront aberration of a glass plane mirror with a diameter of 70 mm is measured and corrected for verifying the feasibility of the experiment system and the correctness of the program. The PV value and RMS value of distorted wavefront are reduced and near diffraction limited optical performance is achieved. On this basis, the wavefront aberration of the aperture center Φ25 mm in a membrane mirror with a diameter of 200 mm is corrected and the errors are analyzed. It provides a means of correcting the wavefront aberration of membrane mirror.

  6. Comparison of Higher Order Aberrations after Wavefront-guided LASIK and PRK: One Year Follow-Up Results.

    Science.gov (United States)

    Jahadi Hosseini, Seyed Hamid Reza; Abtahi, Seyed Mohammad Bagher; Khalili, Mohammad Reza

    2016-01-01

    To evaluate the changes and predictability of higher order aberrations (HOAs) after personalized laser in situ keratomileusis (LASIK) and personalized photorefractive keratectomy (PRK) for simple myopia and compound myopic astigmatism. In this prospective cross-sectional study, 100 eyes were included. A total of 50 eyes underwent personalized LASIK and 50 eyes underwent personalized PRK. Preoperative and postoperative wavefront data were compared between the two groups. The influential factors and predictability of HOAs were also assessed. Total HOA increased in the amount of 0.01 ± 0.14 μm for the 5 mm pupil ( P = 0.55) and 0.08 ± 0.22 μm for the 6 mm pupil ( P = 0.02) after PRK; however after LASIK the corresponding values for the 5 and 6 mm pupil sizes were 0.05 ± 0.12 and 0.15 ± 0.18 μm, respectively ( P PRK and LASIK groups for both 5 and 6 mm pupil sizes ( P = 0.21 and P = 0.13, respectively). Spherical aberration increased following LASIK more than following PRK ( P PRK and LASIK with no significant difference between the two groups. Change of the total HOA RMS was influenced by the preoperative values. The known influencing factors could predict nearly 50% of the changes in total HOA.

  7. WAVEFRONT TESTER: Un nuevo laboratorio virtual para el estudio de los sensores frente de onda.

    Directory of Open Access Journals (Sweden)

    Vicente Ferrando Martín

    2016-01-01

    Full Text Available Se presenta un laboratorio virtual desarrollado en MATLAB GUI (Graphical User Interface para ser utilizado en la asignatura de "Tecnología de Sensores Optoelectrónicos" que se imparte en  "Escuela Técnica Superior de Ingeniería del Diseño" de la Universitat Politècnica de València. El objetivo de este laboratorio es servir de herramienta informática para el estudio de un sensor Shack Hartman y los parámetros que determinan el rango dinámico del mismo en la medida de las aberraciones. Se presentan distintos ejemplos realizados con diferentes aberraciones (desenfoque, astigmatismo, coma y para diferentes configuraciones del sensor.

  8. SMILE and Wavefront-Guided LASIK Out-Compete Other Refractive Surgeries in Ameliorating the Induction of High-Order Aberrations in Anterior Corneal Surface

    OpenAIRE

    Ye, Min-jie; Liu, Cai-yuan; Liao, Rong-feng; Gu, Zheng-yu; Zhao, Bing-ying; Liao, Yi

    2016-01-01

    Purpose. To compare the change of anterior corneal higher-order aberrations (HOAs) after laser in situ keratomileusis (LASIK), wavefront-guided LASIK with iris registration (WF-LASIK), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). Methods. In a prospective study, 82 eyes underwent LASIK, 119 eyes underwent WF-LASIK, 88 eyes underwent FS-LASIK, and 170 eyes underwent SMILE surgery. HOAs were measured with Pentacam device pr...

  9. Closed-loop focal plane wavefront control with the SCExAO instrument

    Science.gov (United States)

    Martinache, Frantz; Jovanovic, Nemanja; Guyon, Olivier

    2016-09-01

    Aims: This article describes the implementation of a focal plane based wavefront control loop on the high-contrast imaging instrument SCExAO (Subaru Coronagraphic Extreme Adaptive Optics). The sensor relies on the Fourier analysis of conventional focal-plane images acquired after an asymmetric mask is introduced in the pupil of the instrument. Methods: This absolute sensor is used here in a closed-loop to compensate for the non-common path errors that normally affects any imaging system relying on an upstream adaptive optics system.This specific implementation was used to control low-order modes corresponding to eight zernike modes (from focus to spherical). Results: This loop was successfully run on-sky at the Subaru Telescope and is used to offset the SCExAO deformable mirror shape used as a zero-point by the high-order wavefront sensor. The paper details the range of errors this wavefront-sensing approach can operate within and explores the impact of saturation of the data and how it can be bypassed, at a cost in performance. Conclusions: Beyond this application, because of its low hardware impact, the asymmetric pupil Fourier wavefront sensor (APF-WFS) can easily be ported in a wide variety of wavefront sensing contexts, for ground- as well space-borne telescopes, and for telescope pupils that can be continuous, segmented or even sparse. The technique is powerful because it measures the wavefront where it really matters, at the level of the science detector.

  10. Wavefront error sensing for LDR

    Science.gov (United States)

    Tubbs, Eldred F.; Glavich, T. A.

    1988-01-01

    Wavefront sensing is a significant aspect of the LDR control problem and requires attention at an early stage of the control system definition and design. A combination of a Hartmann test for wavefront slope measurement and an interference test for piston errors of the segments was examined and is presented as a point of departure for further discussion. The assumption is made that the wavefront sensor will be used for initial alignment and periodic alignment checks but that it will not be used during scientific observations. The Hartmann test and the interferometric test are briefly examined.

  11. Ocular aberrations with ray tracing and Shack-Hartmann wave-front sensors: Does polarization play a role?

    Science.gov (United States)

    Marcos, Susana; Diaz-Santana, Luis; Llorente, Lourdes; Dainty, Chris

    2002-06-01

    Ocular aberrations were measured in 71 eyes by using two reflectometric aberrometers, employing laser ray tracing (LRT) (60 eyes) and a Shack-Hartmann wave-front sensor (S-H) (11 eyes). In both techniques a point source is imaged on the retina (through different pupil positions in the LRT or a single position in the S-H). The aberrations are estimated by measuring the deviations of the retinal spot from the reference as the pupil is sampled (in LRT) or the deviations of a wave front as it emerges from the eye by means of a lenslet array (in the S-H). In this paper we studied the effect of different polarization configurations in the aberration measurements, including linearly polarized light and circularly polarized light in the illuminating channel and sampling light in the crossed or parallel orientations. In addition, completely depolarized light in the imaging channel was obtained from retinal lipofuscin autofluorescence. The intensity distribution of the retinal spots as a function of entry (for LRT) or exit pupil (for S-H) depends on the polarization configuration. These intensity patterns show bright corners and a dark area at the pupil center for crossed polarization, an approximately Gaussian distribution for parallel polarization and a homogeneous distribution for the autofluorescence case. However, the measured aberrations are independent of the polarization states. These results indicate that the differences in retardation across the pupil imposed by corneal birefringence do not produce significant phase delays compared with those produced by aberrations, at least within the accuracy of these techniques. In addition, differences in the recorded aerial images due to changes in polarization do not affect the aberration measurements in these reflectometric aberrometers.

  12. Changes in higher order aberrations after wavefront-guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow-up.

    Science.gov (United States)

    Wigledowska-Promienska, D; Zawojska, I

    2007-01-01

    To assess efficacy, safety, and changes in higher order aberrations after wavefront-guided photorefractive keratectomy (PRK) in comparison with conventional PRK for low to moderate myopia with myopic astigmatism using a WASCA Workstation with the MEL 70 G-Scan excimer laser. A total of 126 myopic or myopic-astigmatic eyes of 112 patients were included in this retrospective study. Patients were divided into two groups: Group 1, the study group; and Group 2, the control group. Group 1 consisted of 78 eyes treated with wavefront-guided PRK. Group 2 consisted of 48 eyes treated with spherocylindrical conventional PRK. Two years postoperatively, in Group 1, 5% of eyes achieved an uncorrected visual acuity (UCVA) of 0.05; 69% achieved a UCVA of 0.00; 18% of eyes experienced enhanced visual acuity of -0.18 and 8% of -0.30. In Group 2, 8% of eyes achieved a UCVA of 0.1; 25% achieved a UCVA of 0.05; and 67% achieved a UCVA of 0.00 according to logMAR calculation method. Total higher-order root-mean square increased by a factor 1.18 for Group 1 and 1.6 for Group 2. There was a significant increase of coma by a factor 1.74 in Group 2 and spherical aberration by a factor 2.09 in Group 1 and 3.56 in Group 2. The data support the safety and effectiveness of the wavefront-guided PRK using a WASCA Workstation for correction of low to moderate refractive errors. This method reduced the number of higher order aberrations induced by excimer laser surgery and improved uncorrected and spectacle-corrected visual acuity when compared to conventional PRK.

  13. Wavefront sensorless adaptive optics ophthalmoscopy in the human eye

    Science.gov (United States)

    Hofer, Heidi; Sredar, Nripun; Queener, Hope; Li, Chaohong; Porter, Jason

    2011-01-01

    Wavefront sensor noise and fidelity place a fundamental limit on achievable image quality in current adaptive optics ophthalmoscopes. Additionally, the wavefront sensor ‘beacon’ can interfere with visual experiments. We demonstrate real-time (25 Hz), wavefront sensorless adaptive optics imaging in the living human eye with image quality rivaling that of wavefront sensor based control in the same system. A stochastic parallel gradient descent algorithm directly optimized the mean intensity in retinal image frames acquired with a confocal adaptive optics scanning laser ophthalmoscope (AOSLO). When imaging through natural, undilated pupils, both control methods resulted in comparable mean image intensities. However, when imaging through dilated pupils, image intensity was generally higher following wavefront sensor-based control. Despite the typically reduced intensity, image contrast was higher, on average, with sensorless control. Wavefront sensorless control is a viable option for imaging the living human eye and future refinements of this technique may result in even greater optical gains. PMID:21934779

  14. Comparison between iterative wavefront control algorithm and direct gradient wavefront control algorithm for adaptive optics system

    International Nuclear Information System (INIS)

    Cheng Sheng-Yi; Liu Wen-Jin; Chen Shan-Qiu; Dong Li-Zhi; Yang Ping; Xu Bing

    2015-01-01

    Among all kinds of wavefront control algorithms in adaptive optics systems, the direct gradient wavefront control algorithm is the most widespread and common method. This control algorithm obtains the actuator voltages directly from wavefront slopes through pre-measuring the relational matrix between deformable mirror actuators and Hartmann wavefront sensor with perfect real-time characteristic and stability. However, with increasing the number of sub-apertures in wavefront sensor and deformable mirror actuators of adaptive optics systems, the matrix operation in direct gradient algorithm takes too much time, which becomes a major factor influencing control effect of adaptive optics systems. In this paper we apply an iterative wavefront control algorithm to high-resolution adaptive optics systems, in which the voltages of each actuator are obtained through iteration arithmetic, which gains great advantage in calculation and storage. For AO system with thousands of actuators, the computational complexity estimate is about O(n 2 ) ∼ O(n 3 ) in direct gradient wavefront control algorithm, while the computational complexity estimate in iterative wavefront control algorithm is about O(n) ∼ (O(n) 3/2 ), in which n is the number of actuators of AO system. And the more the numbers of sub-apertures and deformable mirror actuators, the more significant advantage the iterative wavefront control algorithm exhibits. (paper)

  15. Induced Higher-order aberrations after Laser In Situ Keratomileusis (LASIK) Performed with Wavefront-Guided IntraLase Femtosecond Laser in moderate to high Astigmatism.

    Science.gov (United States)

    Al-Zeraid, Ferial M; Osuagwu, Uchechukwu L

    2016-03-22

    Wavefront-guided Laser-assisted in situ keratomileusis (LASIK) is a widespread and effective surgical treatment for myopia and astigmatic correction but whether it induces higher-order aberrations remains controversial. The study was designed to evaluate the changes in higher-order aberrations after wavefront-guided ablation with IntraLase femtosecond laser in moderate to high astigmatism. Twenty-three eyes of 15 patients with moderate to high astigmatism (mean cylinder, -3.22 ± 0.59 dioptres) aged between 19 and 35 years (mean age, 25.6 ± 4.9 years) were included in this prospective study. Subjects with cylinder ≥ 1.5 and ≤2.75 D were classified as moderate astigmatism while high astigmatism was ≥3.00 D. All patients underwent a femtosecond laser-enabled (150-kHz IntraLase iFS; Abbott Medical Optics Inc) wavefront-guided ablation. Uncorrected (UDVA), corrected (CDVA) distance visual acuity in logMAR, keratometry, central corneal thickness (CCT) and higher-order aberrations (HOAs) over a 6 mm pupil, were assessed before and 6 months, postoperatively. The relationship between postoperative change in HOA and preoperative mean spherical equivalent refraction, mean astigmatism, and postoperative CCT were tested. At the last follow-up, the mean UDVA was increased (P < 0.0001) but CDVA remained unchanged (P = 0.48) and no eyes lost ≥2 lines of CDVA. Mean spherical equivalent refraction was reduced (P < 0.0001) and was within ±0.50 D range in 61% of eyes. The average corneal curvature was flatter by 4 D and CCT was reduced by 83 μm (P < 0.0001, for all), postoperatively. Coma aberrations remained unchanged (P = 0.07) while the change in trefoil (P = 0.047) postoperatively, was not clinically significant. The 4th order HOAs (spherical aberration and secondary astigmatism) and the HOA root mean square (RMS) increased from -0.18 ± 0.07 μm, 0.04 ± 0.03 μm and 0.47 ± 0.11 μm, preoperatively, to 0.33 ± 0

  16. Wavefront Measurement for Laser-Guiding Diagnostic

    International Nuclear Information System (INIS)

    Shiraishi, S.; Gonsalves, A.J.; Lin, C.; Nakamura, K.; Osterhoff, J.; Sokollik, T.; van Tilborg, J.; Geddes, C.G.R.; Schroeder, C.B.; Toth, Cs.; Esarey, E.; Leemans, W.P.

    2010-01-01

    The wavefront of a short laser pulse after interaction in a laser-plasma accelerator (LPA) was measured to diagnose laser-guiding quality. Experiments were performed on a 100 TW class laser at the LOASIS facility of LBNL using a hydrogenfilled capillary discharge waveguide. Laser-guiding with a pre-formed plasma channel allows the laser pulse to propagate over many Rayleigh lengths at high intensity and is crucial to accelerate electrons to the highest possible energy. Efficient coupling of laser energy into the plasma is realized when the laser and the channel satisfy a matched guiding condition, in which the wavefront remains flat within the channel. Using a wavefront sensor, the laser-guiding quality was diagnosed based on the wavefront of the laser pulse exiting the plasma channel. This wavefront diagnostic will contribute to achieving controlled, matched guiding in future experiments.

  17. Wavefront-guided versus wavefront-optimized laser in situ keratomileusis: contralateral comparative study.

    Science.gov (United States)

    Padmanabhan, Prema; Mrochen, Michael; Basuthkar, Subam; Viswanathan, Deepa; Joseph, Roy

    2008-03-01

    To compare the outcomes of wavefront-guided and wavefront-optimized treatment in fellow eyes of patients having laser in situ keratomileusis (LASIK) for myopia. Medical and Vision Research Foundation, Tamil Nadu, India. This prospective comparative study comprised 27 patients who had wavefront-guided LASIK in 1 eye and wavefront-optimized LASIK in the fellow eye. The Hansatome (Bausch & Lomb) was used to create a superior-hinged flap and the Allegretto laser (WaveLight Laser Technologie AG), for photoablation. The Allegretto wave analyzer was used to measure ocular wavefront aberrations and the Functional Acuity Contrast Test chart, to measure contrast sensitivity before and 1 month after LASIK. The refractive and visual outcomes and the changes in aberrations and contrast sensitivity were compared between the 2 treatment modalities. One month postoperatively, 92% of eyes in the wavefront-guided group and 85% in the wavefront-optimized group had uncorrected visual acuity of 20/20 or better; 93% and 89%, respectively, had a postoperative spherical equivalent refraction of +/-0.50 diopter. The differences between groups were not statistically significant. Wavefront-guided LASIK induced less change in 18 of 22 higher-order Zernike terms than wavefront-optimized LASIK, with the change in positive spherical aberration the only statistically significant one (P= .01). Contrast sensitivity improved at the low and middle spatial frequencies (not statistically significant) and worsened significantly at high spatial frequencies after wavefront-guided LASIK; there was a statistically significant worsening at all spatial frequencies after wavefront-optimized LASIK. Although both wavefront-guided and wavefront-optimized LASIK gave excellent refractive correction results, the former induced less higher-order aberrations and was associated with better contrast sensitivity.

  18. Wavefront Measurement in Ophthalmology

    Science.gov (United States)

    Molebny, Vasyl

    Wavefront sensing or aberration measurement in the eye is a key problem in refractive surgery and vision correction with laser. The accuracy of these measurements is critical for the outcome of the surgery. Practically all clinical methods use laser as a source of light. To better understand the background, we analyze the pre-laser techniques developed over centuries. They allowed new discoveries of the nature of the optical system of the eye, and many served as prototypes for laser-based wavefront sensing technologies. Hartmann's test was strengthened by Platt's lenslet matrix and the CCD two-dimensional photodetector acquired a new life as a Hartmann-Shack sensor in Heidelberg. Tscherning's aberroscope, invented in France, was transformed into a laser device known as a Dresden aberrometer, having seen its reincarnation in Germany with Seiler's help. The clinical ray tracing technique was brought to life by Molebny in Ukraine, and skiascopy was created by Fujieda in Japan. With the maturation of these technologies, new demands now arise for their wider implementation in optometry and vision correction with customized contact and intraocular lenses.

  19. Quantitative comparison of different-shaped wavefront sensors and preliminary results for defocus aberrations on a mechanical eye Comparações quantitativas entre o sensor Hartmann-Shack e o sensor de Castro e resultados preliminares para um olho mecânico

    Directory of Open Access Journals (Sweden)

    Luis Alberto Carvalho

    2006-04-01

    Full Text Available PURPOSE: There is a general acceptance among the scientific community of Cartesian symmetry wavefront sensors (such as the Hartmann-Shack (HS sensor as a standard in the field of optics and vision science. In this study it is shown that sensors of different symmetries and/or configurations should also be tested and analyzed in order to quantify and compare their effectiveness when applied to visual optics. Three types of wave-aberration sensors were developed and tested here. Each sensor has a very different configuration and/or symmetry (dodecagonal (DOD, cylindrical (CYL and conventional Hartmann-Shack (HS. METHODS: All sensors were designed and developed in the Physics Department of the Universidade de São Paulo - São Carlos. Each sensor was mounted on a laboratory optical bench used in a previous study. A commercial mechanical eye was used as control. This mechanical eye has a rotating mechanism that allows the retinal plane to be positioned at different axial distances. Ten different defocus aberrations were generated: 5 cases of myopia from -1D to -5D and 5 cases of hyperopia, from +1D to +5D, in steps of 1D following the scale printed on the mechanical eye. For each wavefront sensor a specific image-processing and fitting algorithm was implemented. For all three cases, the wavefront information was fit using the first 36 VSIA standard Zernike polynomials. Results for the mechanical eye were also compared to the absolute Zernike surface generated from coefficients associated with the theoretical sphere-cylinder aberration value. RESULTS: Precision was analyzed using two different methods: first, a theoretical approach was used by generating synthetic Zernike coefficients from the known sphere-cylinder aberrations, simply by applying sphere-cylinder equations in the backward direction. Then comparisons were made of these coefficients with the ones obtained in practice. Results for DOD, HS and CYL sensors were, respectively, as follows

  20. Multigrid preconditioned conjugate-gradient method for large-scale wave-front reconstruction.

    Science.gov (United States)

    Gilles, Luc; Vogel, Curtis R; Ellerbroek, Brent L

    2002-09-01

    We introduce a multigrid preconditioned conjugate-gradient (MGCG) iterative scheme for computing open-loop wave-front reconstructors for extreme adaptive optics systems. We present numerical simulations for a 17-m class telescope with n = 48756 sensor measurement grid points within the aperture, which indicate that our MGCG method has a rapid convergence rate for a wide range of subaperture average slope measurement signal-to-noise ratios. The total computational cost is of order n log n. Hence our scheme provides for fast wave-front simulation and control in large-scale adaptive optics systems.

  1. High signal-to-noise ratio sensing with Shack–Hartmann wavefront sensor based on auto gain control of electron multiplying CCD

    International Nuclear Information System (INIS)

    Zhu Zhao-Yi; Li Da-Yu; Hu Li-Fa; Mu Quan-Quan; Yang Cheng-Liang; Cao Zhao-Liang; Xuan Li

    2016-01-01

    High signal-to-noise ratio can be achieved with the electron multiplying charge-coupled-device (EMCCD) applied in the Shack–Hartmann wavefront sensor (S–H WFS) in adaptive optics (AO). However, when the brightness of the target changes in a large scale, the fixed electron multiplying (EM) gain will not be suited to the sensing limitation. Therefore an auto-gain-control method based on the brightness of light-spots array in S–H WFS is proposed in this paper. The control value is the average of the maximum signals of every light spot in an array, which has been demonstrated to be kept stable even under the influence of some noise and turbulence, and sensitive enough to the change of target brightness. A goal value is needed in the control process and it is predetermined based on the characters of EMCCD. Simulations and experiments have demonstrated that this auto-gain-control method is valid and robust, the sensing SNR reaches the maximum for the corresponding signal level, and especially is greatly improved for those dim targets from 6 to 4 magnitude in the visual band. (special topic)

  2. Simulation of eye-tracker latency, spot size, and ablation pulse depth on the correction of higher order wavefront aberrations with scanning spot laser systems.

    Science.gov (United States)

    Bueeler, Michael; Mrochen, Michael

    2005-01-01

    The aim of this theoretical work was to investigate the robustness of scanning spot laser treatments with different laser spot diameters and peak ablation depths in case of incomplete compensation of eye movements due to eye-tracker latency. Scanning spot corrections of 3rd to 5th Zernike order wavefront errors were numerically simulated. Measured eye-movement data were used to calculate the positioning error of each laser shot assuming eye-tracker latencies of 0, 5, 30, and 100 ms, and for the case of no eye tracking. The single spot ablation depth ranged from 0.25 to 1.0 microm and the spot diameter from 250 to 1000 microm. The quality of the ablation was rated by the postoperative surface variance and the Strehl intensity ratio, which was calculated after a low-pass filter was applied to simulate epithelial surface smoothing. Treatments performed with nearly ideal eye tracking (latency approximately 0) provide the best results with a small laser spot (0.25 mm) and a small ablation depth (250 microm). However, combinations of a large spot diameter (1000 microm) and a small ablation depth per pulse (0.25 microm) yield the better results for latencies above a certain threshold to be determined specifically. Treatments performed with tracker latencies in the order of 100 ms yield similar results as treatments done completely without eye-movement compensation. CONCWSIONS: Reduction of spot diameter was shown to make the correction more susceptible to eye movement induced error. A smaller spot size is only beneficial when eye movement is neutralized with a tracking system with a latency <5 ms.

  3. Comparison between iterative wavefront control algorithm and direct gradient wavefront control algorithm for adaptive optics system

    Science.gov (United States)

    Cheng, Sheng-Yi; Liu, Wen-Jin; Chen, Shan-Qiu; Dong, Li-Zhi; Yang, Ping; Xu, Bing

    2015-08-01

    Among all kinds of wavefront control algorithms in adaptive optics systems, the direct gradient wavefront control algorithm is the most widespread and common method. This control algorithm obtains the actuator voltages directly from wavefront slopes through pre-measuring the relational matrix between deformable mirror actuators and Hartmann wavefront sensor with perfect real-time characteristic and stability. However, with increasing the number of sub-apertures in wavefront sensor and deformable mirror actuators of adaptive optics systems, the matrix operation in direct gradient algorithm takes too much time, which becomes a major factor influencing control effect of adaptive optics systems. In this paper we apply an iterative wavefront control algorithm to high-resolution adaptive optics systems, in which the voltages of each actuator are obtained through iteration arithmetic, which gains great advantage in calculation and storage. For AO system with thousands of actuators, the computational complexity estimate is about O(n2) ˜ O(n3) in direct gradient wavefront control algorithm, while the computational complexity estimate in iterative wavefront control algorithm is about O(n) ˜ (O(n)3/2), in which n is the number of actuators of AO system. And the more the numbers of sub-apertures and deformable mirror actuators, the more significant advantage the iterative wavefront control algorithm exhibits. Project supported by the National Key Scientific and Research Equipment Development Project of China (Grant No. ZDYZ2013-2), the National Natural Science Foundation of China (Grant No. 11173008), and the Sichuan Provincial Outstanding Youth Academic Technology Leaders Program, China (Grant No. 2012JQ0012).

  4. SMILE and Wavefront-Guided LASIK Out-Compete Other Refractive Surgeries in Ameliorating the Induction of High-Order Aberrations in Anterior Corneal Surface

    Science.gov (United States)

    2016-01-01

    Purpose. To compare the change of anterior corneal higher-order aberrations (HOAs) after laser in situ keratomileusis (LASIK), wavefront-guided LASIK with iris registration (WF-LASIK), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). Methods. In a prospective study, 82 eyes underwent LASIK, 119 eyes underwent WF-LASIK, 88 eyes underwent FS-LASIK, and 170 eyes underwent SMILE surgery. HOAs were measured with Pentacam device preoperatively and 6 months after surgery. The aberrations were described as Zernike polynomials, and analysis focused on total HOAs, spherical aberration (SA), horizontal coma, and vertical coma over 6 mm diameter central corneal zone. Results. Six months postoperatively, all procedures result in increase of anterior corneal total HOAs and SA. There were no significant differences in the induced HOAs between LASIK and FS-LASIK, while SMILE induced fewer total HOAs and SA compared with LASIK and FS-LASIK. Similarly, WF-LASIK also induced less total HOAs than LASIK and FS-LASIK, but only fewer SA than FS-LASIK (P LASIK, whereas SMILE induced more horizontal coma and vertical coma compared with WF-LASIK (P LASIK and LASIK induced comparable anterior corneal HOAs. Compared to LASIK and FS-LASIK, both SMILE and WF-LASIK showed advantages in inducing less total HOAs. In addition, SMILE also possesses better ability to reduce the induction of SA in comparison with LASIK and FS-LASIK. However, SMILE induced more horizontal coma and vertical coma compared with WF-LASIK, indicating that the centration of SMILE procedure is probably less precise than WF-LASIK. PMID:27818792

  5. Wavefront-ray grid FDTD algorithm

    OpenAIRE

    ÇİYDEM, MEHMET

    2016-01-01

    A finite difference time domain algorithm on a wavefront-ray grid (WRG-FDTD) is proposed in this study to reduce numerical dispersion of conventional FDTD methods. A FDTD algorithm conforming to a wavefront-ray grid can be useful to take into account anisotropy effects of numerical grids since it features directional energy flow along the rays. An explicit and second-order accurate WRG-FDTD algorithm is provided in generalized curvilinear coordinates for an inhomogeneous isotropic medium. Num...

  6. Laboratory and On-sky Validation of the Shaped Pupil Coronagraph’s Sensitivity to Low-order Aberrations With Active Wavefront Control

    Science.gov (United States)

    Currie, Thayne; Kasdin, N. Jeremy; Groff, Tyler D.; Lozi, Julien; Jovanovic, Nemanja; Guyon, Olivier; Brandt, Timothy; Martinache, Frantz; Chilcote, Jeffrey; Skaf, Nour; Kuhn, Jonas; Pathak, Prashant; Kudo, Tomoyuki

    2018-04-01

    We present early laboratory simulations and extensive on-sky tests validating of the performance of a shaped pupil coronagraph (SPC) behind an extreme-AO corrected beam of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system. In tests with the SCExAO internal source/wavefront error simulator, the normalized intensity profile for the SPC degrades more slowly than for the Lyot coronagraph as low-order aberrations reduce the Strehl ratio from extremely high values (S.R. ∼ 0.93–0.99) to those characteristic of current ground-based extreme AO systems (S.R. ∼ 0.74–0.93) and then slightly lower values down to S.R. ∼ 0.57. On-sky SCExAO data taken with the SPC and other coronagraphs for brown dwarf/planet-hosting stars HD 1160 and HR 8799 provide further evidence for the SPC’s robustness to low-order aberrations. From H-band Strehl ratios of 80% to 70%, the Lyot coronagraph’s performance versus that of the SPC may degrade even faster on sky than is seen in our internal source simulations. The 5-σ contrast also degrades faster (by a factor of two) for the Lyot than the SPC. The SPC we use was designed as a technology demonstrator only, with a contrast floor, throughput, and outer working angle poorly matched for SCExAO’s current AO performance and poorly tuned for imaging the HR 8799 planets. Nevertheless, we detect HR 8799 cde with SCExAO/CHARIS using the SPC in broadband mode, where the S/N for planet e is within 30% of that obtained using the vortex coronagraph. The shaped-pupil coronagraph is a promising design demonstrated to be robust in the presence of low-order aberrations and may be well-suited for future ground and space-based direct imaging observations, especially those focused on follow-up exoplanet characterization and technology demonstration of deep contrast within well-defined regions of the image plane.

  7. Structure and Sensor Properties of Thin Ordered Solid Films

    Directory of Open Access Journals (Sweden)

    Jadwiga Sołoducho

    2009-09-01

    Full Text Available Miniaturized gas sensors and biosensors based on nanostructured sensing elements have attracted considerable interest because these nanostructured materials can be used to significantly improve sensor sensitivity and the response time. We report here on a generic, reversible sensing platform based on hybrid nanofilms. Thin ordered Langmuir-Blodgett (LB films built of fluorene derivatives were used as effective gas sensors for both oxidative and reductive analytes. A novel immobilization method based on thin LB films as a matrix has been developed for construction of sensing protein layers. Biomolecules can often be incorporated into and immobilized on Langmuir-Blodgett films using adsorption methods or by covalent immobilization of proteins. The sensor sensitisation was achieved by an amphiphilic N-alkyl-bis(thiophenearylenes admixed into the film. The interlaced derivative was expected to facilitate the electron transfer, thereby enhancing the sensor sensitivity. The results suggest that this may be very promising approach for exploring the interactions between proteins and high throughput detection of phenol derivatives in wastewater.

  8. Measurement and statistical analysis of the wavefront distortions induced by atmospheric turbulence using two-channel moiré deflectometry

    International Nuclear Information System (INIS)

    Dashti, Mohsen; Rasouli, Saifollah

    2012-01-01

    Recently, an adjustable, high-sensitivity, wide dynamic range, two-channel wavefront sensor based on moiré deflectometry was proposed by Rasouli et al (2010 Opt. Express 18 23906). In this work we have used this sensor on a telescope for measuring turbulence-induced wavefront distortions. A slightly divergent laser beam passes through turbulent ground level atmosphere and enters the telescope’s aperture. The laser beam is collimated behind the telescope’s focal point by means of a collimator and the beam enters the wavefront sensor. First, from deviations in the moiré fringes we calculate the two orthogonal components of the angle of arrival at each location across the wavefront. The deviations have been deduced in successive frames which allows evolution of the wavefront shape and Fried’s seeing parameter r 0 to be determined. Mainly, statistical analysis of the reconstructed wavefront distortions are presented. The achieved accuracy in the measurements and comparison between the measurements and the theoretical models are presented. Owing to the use of the sensor on a telescope, and using sub-pixel accuracy for the measurement of the moiré fringe displacements, the sensitivity of the measurements is improved by more than one order of magnitude. In this work we have achieved a minimum measurable angle of arrival fluctuations equal to 3.7 × 10 −7 rad or 0.07 arc s. Besides, because of the large area of the telescope’s aperture, a high spatial resolution is achieved in detecting the spatial perturbations of the atmospheric turbulence. (paper)

  9. Comparison of wavefront aberrations under cycloplegic, scotopic and photopic conditions using WaveScan

    Directory of Open Access Journals (Sweden)

    Rong Fan

    2012-04-01

    Full Text Available PURPOSE: To evaluate the differences of wavefront aberrations under cycloplegic, scotopic and photopic conditions. METHODS: A total of 174 eyes of 105 patients were measured using the wavefront sensor (WaveScan® 3.62 under different pupil conditions: cycloplegic 8.58 ± 0.54 mm (6.4 mm - 9.5 mm, scotopic 7.53 ± 0.69 mm (5.7 mm - 9.1 mm and photopic 6.08 ± 1.14 mm (4.1 mm - 8.8 mm. The pupil diameter, standard Zernike coefficients, root mean square of higher-order aberrations and dominant aberrations were compared between cycloplegic and scotopic conditions, and between scotopic and photopic conditions. RESULTS: The pupil diameter was 7.53 ± 0.69 mm under the scotopic condition, which reached the requirement of about 6.5 mm optical zone design in the wavefront-guided surgery and prevented measurement error due to the pupil centroid shift caused by mydriatics. Pharmacological pupil dilation induced increase of standard Zernike coefficients Z3-3, Z4(0 and Z5-5. The higher-order aberrations, third-order aberration, fourth-order aberration, fifth-order aberration, sixth-order aberration, and spherical aberration increased statistically significantly, compared to the scotopic condition (P<0.010. When the scotopic condition shifted to the photopic condition, the standard Zernike coefficients Z4(0, Z4², Z6-4, Z6-2, Z6² decreased and all the higher-order aberrations decreased statistically significantly (P<0.010, demonstrating that accommodative miosis can significantly improve vision under the photopic condition. Under the three conditions, the vertical coma aberration appears the most frequently within the dominant aberrations without significant effect by pupil size variance, and the proportion of spherical aberrations decreased with the decrease of the pupil size. CONCLUSIONS: The wavefront aberrations are significantly different under cycloplegic, scotopic and photopic conditions. Using the wavefront sensor (VISX WaveScan to measure scotopic

  10. Wavefront error budget development for the Thirty Meter Telescope laser guide star adaptive optics system

    Science.gov (United States)

    Gilles, Luc; Wang, Lianqi; Ellerbroek, Brent

    2008-07-01

    This paper describes the modeling effort undertaken to derive the wavefront error (WFE) budget for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility, laser guide star (LGS), dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The budget describes the expected performance of NFIRAOS at zenith, and has been decomposed into (i) first-order turbulence compensation terms (120 nm on-axis), (ii) opto-mechanical implementation errors (84 nm), (iii) AO component errors and higher-order effects (74 nm) and (iv) tip/tilt (TT) wavefront errors at 50% sky coverage at the galactic pole (61 nm) with natural guide star (NGS) tip/tilt/focus/astigmatism (TTFA) sensing in J band. A contingency of about 66 nm now exists to meet the observatory requirement document (ORD) total on-axis wavefront error of 187 nm, mainly on account of reduced TT errors due to updated windshake modeling and a low read-noise NGS wavefront sensor (WFS) detector. A detailed breakdown of each of these top-level terms is presented, together with a discussion on its evaluation using a mix of high-order zonal and low-order modal Monte Carlo simulations.

  11. Advanced Imaging Optics Utilizing Wavefront Coding.

    Energy Technology Data Exchange (ETDEWEB)

    Scrymgeour, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boye, Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Adelsberger, Kathleen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-06-01

    Image processing offers a potential to simplify an optical system by shifting some of the imaging burden from lenses to the more cost effective electronics. Wavefront coding using a cubic phase plate combined with image processing can extend the system's depth of focus, reducing many of the focus-related aberrations as well as material related chromatic aberrations. However, the optimal design process and physical limitations of wavefront coding systems with respect to first-order optical parameters and noise are not well documented. We examined image quality of simulated and experimental wavefront coded images before and after reconstruction in the presence of noise. Challenges in the implementation of cubic phase in an optical system are discussed. In particular, we found that limitations must be placed on system noise, aperture, field of view and bandwidth to develop a robust wavefront coded system.

  12. Correlations between corneal and total wavefront aberrations

    Science.gov (United States)

    Mrochen, Michael; Jankov, Mirko; Bueeler, Michael; Seiler, Theo

    2002-06-01

    Purpose: Corneal topography data expressed as corneal aberrations are frequently used to report corneal laser surgery results. However, the optical image quality at the retina depends on all optical elements of the eye such as the human lens. Thus, the aim of this study was to investigate the correlations between the corneal and total wavefront aberrations and to discuss the importance of corneal aberrations for representing corneal laser surgery results. Methods: Thirty three eyes of 22 myopic subjects were measured with a corneal topography system and a Tschernig-type wavefront analyzer after the pupils were dilated to at least 6 mm in diameter. All measurements were centered with respect to the line of sight. Corneal and total wavefront aberrations were calculated up to the 6th Zernike order in the same reference plane. Results: Statistically significant correlations (p the corneal and total wavefront aberrations were found for the astigmatism (C3,C5) and all 3rd Zernike order coefficients such as coma (C7,C8). No statistically significant correlations were found for all 4th to 6th order Zernike coefficients except for the 5th order horizontal coma C18 (p equals 0.003). On average, all Zernike coefficients for the corneal aberrations were found to be larger compared to Zernike coefficients for the total wavefront aberrations. Conclusions: Corneal aberrations are only of limited use for representing the optical quality of the human eye after corneal laser surgery. This is due to the lack of correlation between corneal and total wavefront aberrations in most of the higher order aberrations. Besides this, the data present in this study yield towards an aberration balancing between corneal aberrations and the optical elements within the eye that reduces the aberration from the cornea by a certain degree. Consequently, ideal customized ablations have to take both, corneal and total wavefront aberrations, into consideration.

  13. A video Hartmann wavefront diagnostic that incorporates a monolithic microlens array

    International Nuclear Information System (INIS)

    Toeppen, J.S.; Bliss, E.S.; Long, T.W.; Salmon, J.T.

    1991-07-01

    we have developed a video Hartmann wavefront sensor that incorporates a monolithic array of microlenses as the focusing elements. The sensor uses a monolithic array of photofabricated lenslets. Combined with a video processor, this system reveals local gradients of the wavefront at a video frame rate of 30 Hz. Higher bandwidth is easily attainable with a camera and video processor that have faster frame rates. When used with a temporal filter, the reconstructed wavefront error is less than 1/10th wave

  14. Wavefront correction and high-resolution in vivo OCT imaging with an objective integrated multi-actuator adaptive lens.

    Science.gov (United States)

    Bonora, Stefano; Jian, Yifan; Zhang, Pengfei; Zam, Azhar; Pugh, Edward N; Zawadzki, Robert J; Sarunic, Marinko V

    2015-08-24

    Adaptive optics is rapidly transforming microscopy and high-resolution ophthalmic imaging. The adaptive elements commonly used to control optical wavefronts are liquid crystal spatial light modulators and deformable mirrors. We introduce a novel Multi-actuator Adaptive Lens that can correct aberrations to high order, and which has the potential to increase the spread of adaptive optics to many new applications by simplifying its integration with existing systems. Our method combines an adaptive lens with an imaged-based optimization control that allows the correction of images to the diffraction limit, and provides a reduction of hardware complexity with respect to existing state-of-the-art adaptive optics systems. The Multi-actuator Adaptive Lens design that we present can correct wavefront aberrations up to the 4th order of the Zernike polynomial characterization. The performance of the Multi-actuator Adaptive Lens is demonstrated in a wide field microscope, using a Shack-Hartmann wavefront sensor for closed loop control. The Multi-actuator Adaptive Lens and image-based wavefront-sensorless control were also integrated into the objective of a Fourier Domain Optical Coherence Tomography system for in vivo imaging of mouse retinal structures. The experimental results demonstrate that the insertion of the Multi-actuator Objective Lens can generate arbitrary wavefronts to correct aberrations down to the diffraction limit, and can be easily integrated into optical systems to improve the quality of aberrated images.

  15. The size effect of searching window for measuring wavefront of laser beam

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Baik, Sung Hoon; Lim, Chang Hwan; Kim, Jung Cheol; Yi, Seung Jun; Ra, Sung Woong

    2003-01-01

    We investigated the size effect of the searching window for measuring of a laser beam using a Shack-Hartmann sensor. The shapes of spot images on an acquired wavefront image by using a Shack-Hartmann sensor are usually imbalanced. Also, the distributed intensity pattern of each spot image is varied according to successively acquired wavefront image. We studied on the optimized size of searching window to get wavefront with high measurement resolution. We experimented on the various size effect of searching window on an acquired wavefront image to get fine wavefront information using a Shack-Hartmann sensor. As the experimental results, we proposed the optimum size of searching window to measure improved wavefront.

  16. Wavefront-Guided and Wavefront-Optimised Laser Treatments

    Directory of Open Access Journals (Sweden)

    Canan Aslı Utine

    2012-12-01

    Full Text Available Optical aberrations of the eye are the errors of the optical system that limit the resolution, contrast and amount of detail in the image formed on the retina. Wavefront technology allows us to measure these optical aberrations, calculate mathematically, and transfer this information into excimer laser system to perform customized treatment on the cornea. Two treatment algorithms developed to create low aberration-corneal profile are wavefront-optimised (WF-O and wavefront-guided (WF-G treatments. WF-O treatment, aims not to increase the existing spherical aberration while treatment is based on manifest refractive error as in conventional laser treatments. By increasing the number of laser spots applied peripherally in order to optimize the corneal asphericity, the preoperative central:peripheral keratometry ratio is preserved and optic zone shrinkage is prevented. On the other hand, WF-G treatment is based on aberrometry measurements and aims to correct the existing high-order aberrations in the eye. Thus, retinal image with high spatial details can be achieved. However, presence of postoperative defocus can abolish the successful results obtained with WF-G treatment. Clinical randomized controlled trials showed that in patients with preoperative RMS value of <0.3 μm, higher order aberration outcomes are similar after WF-G and WF-O treatments, but WF-G treatment yields better results when it is ≥0.4 μm. In normal eyes, very limited visual advantage can be achieved with WF-G treatment and preservation of asphericity value with WF-O treatment carries greater importance. On the other hand, in case of high astigmatism or higher order aberrations other than spherical aberration, decreasing aberrations with WF-G treatment becomes more important. In this study, we aimed to make a comparative analysis of characteristics and outcomes of the two treatment algorithms. (Turk J Ophthalmol 2012; 42: 474-8

  17. A wavefront analyzer for terahertz time-domain spectrometers

    DEFF Research Database (Denmark)

    Abraham, E.; Brossard, M.; Fauche, P.

    2017-01-01

    the terahertz wavefront and calculate its Zernike coefficients. In particular, we especially show that the focus spot of the spectrometer suffers from optical aberrations such as remaining defocus, first and second order astigmatisms, as well as spherical aberration. This opens a route to wavefront correction...

  18. Advances in detector technologies for visible and infrared wavefront sensing

    Science.gov (United States)

    Feautrier, Philippe; Gach, Jean-Luc; Downing, Mark; Jorden, Paul; Kolb, Johann; Rothman, Johan; Fusco, Thierry; Balard, Philippe; Stadler, Eric; Guillaume, Christian; Boutolleau, David; Destefanis, Gérard; Lhermet, Nicolas; Pacaud, Olivier; Vuillermet, Michel; Kerlain, Alexandre; Hubin, Norbert; Reyes, Javier; Kasper, Markus; Ivert, Olaf; Suske, Wolfgang; Walker, Andrew; Skegg, Michael; Derelle, Sophie; Deschamps, Joel; Robert, Clélia; Vedrenne, Nicolas; Chazalet, Frédéric; Tanchon, Julien; Trollier, Thierry; Ravex, Alain; Zins, Gérard; Kern, Pierre; Moulin, Thibaut; Preis, Olivier

    2012-07-01

    The purpose of this paper is to give an overview of the state of the art wavefront sensor detectors developments held in Europe for the last decade. The success of the next generation of instruments for 8 to 40-m class telescopes will depend on the ability of Adaptive Optics (AO) systems to provide excellent image quality and stability. This will be achieved by increasing the sampling, wavelength range and correction quality of the wave front error in both spatial and time domains. The modern generation of AO wavefront sensor detectors development started in the late nineties with the CCD50 detector fabricated by e2v technologies under ESO contract for the ESO NACO AO system. With a 128x128 pixels format, this 8 outputs CCD offered a 500 Hz frame rate with a readout noise of 7e-. A major breakthrough has been achieved with the recent development by e2v technologies of the CCD220. This 240x240 pixels 8 outputs EMCCD (CCD with internal multiplication) has been jointly funded by ESO and Europe under the FP6 programme. The CCD220 and the OCAM2 camera that operates the detector are now the most sensitive system in the world for advanced adaptive optics systems, offering less than 0.2 e readout noise at a frame rate of 1500 Hz with negligible dark current. Extremely easy to operate, OCAM2 only needs a 24 V power supply and a modest water cooling circuit. This system, commercialized by First Light Imaging, is extensively described in this paper. An upgrade of OCAM2 is foreseen to boost its frame rate to 2 kHz, opening the window of XAO wavefront sensing for the ELT using 4 synchronized cameras and pyramid wavefront sensing. Since this major success, new developments started in Europe. One is fully dedicated to Natural and Laser Guide Star AO for the E-ELT with ESO involvement. The spot elongation from a LGS Shack Hartman wavefront sensor necessitates an increase of the pixel format. Two detectors are currently developed by e2v. The NGSD will be a 880x840 pixels CMOS

  19. Wavefront division digital holography

    Science.gov (United States)

    Zhang, Wenhui; Cao, Liangcai; Li, Rujia; Zhang, Hua; Zhang, Hao; Jiang, Qiang; Jin, Guofan

    2018-05-01

    Digital holography (DH), mostly Mach-Zehnder configuration based, belongs to non-common path amplitude splitting interference imaging whose stability and fringe contrast are environmental sensitive. This paper presents a wavefront division DH configuration with both high stability and high-contrast fringes benefitting from quasi common path wavefront-splitting interference. In our proposal, two spherical waves with similar curvature coming from the same wavefront are used, which makes full use of the physical sampling capacity of the detectors. The interference fringe spacing can be adjusted flexibly for both in-line and off-axis mode due to the independent modulation to these two waves. Only a few optical elements, including the mirror-beam splitter interference component, are used without strict alignments, which makes it robust and easy-to-implement. The proposed wavefront division DH promotes interference imaging physics into the practical and miniaturized a step forward. The feasibility of this method is proved by the imaging of a resolution target and a water flea.

  20. Plasmonic devices and sensors built from ordered nanoporous materials.

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, Benjamin W.; Kobayashi, Yoji (University of California, Berkeley); Houk, Ronald J. T.; Allendorf, Mark D.; Long, Jeffrey R. (University of California, Berkeley); Robertson, Ian M. (University of Illinois Urbana-Champaign, Urbana, IL); House, Stephen D. (University of Illinois Urbana-Champaign, Urbana, IL); Graham, Dennis D. (University of Illinois Urbana-Champaign, Urbana, IL); Talin, Albert Alec (National Institute of Standards & Technology, Gaithersburg, MD); Chang, Noel N. (University of Illinois Urbana-Champaign, Urbana, IL); El Gabaly Marquez, Farid

    2009-09-01

    The objective of this project is to lay the foundation for using ordered nanoporous materials known as metal-organic frameworks (MOFs) to create devices and sensors whose properties are determined by the dimensions of the MOF lattice. Our hypothesis is that because of the very short (tens of angstroms) distances between pores within the unit cell of these materials, enhanced electro-optical properties will be obtained when the nanopores are infiltrated to create nanoclusters of metals and other materials. Synthetic methods used to produce metal nanoparticles in disordered templates or in solution typically lead to a distribution of particle sizes. In addition, creation of the smallest clusters, with sizes of a few to tens of atoms, remains very challenging. Nanoporous metal-organic frameworks (MOFs) are a promising solution to these problems, since their long-range crystalline order creates completely uniform pore sizes with potential for both steric and chemical stabilization. We report results of synthetic efforts. First, we describe a systematic investigation of silver nanocluster formation within MOFs using three representative MOF templates. The as-synthesized clusters are spectroscopically consistent with dimensions {le} 1 nm, with a significant fraction existing as Ag{sub 3} clusters, as shown by electron paramagnetic resonance. Importantly, we show conclusively that very rapid TEM-induced MOF degradation leads to agglomeration and stable, easily imaged particles, explaining prior reports of particles larger than MOF pores. These results solve an important riddle concerning MOF-based templates and suggest that heterostructures composed of highly uniform arrays of nanoparticles within MOFs are feasible. Second, a preliminary study of methods to incorporate fulleride (K{sub 3}C{sub 60}) guest molecules within MOF pores that will impart electrical conductivity is described.

  1. Deep Tissue Wavefront Estimation for Sensorless Aberration Correction

    Directory of Open Access Journals (Sweden)

    Ibrahimovic Emina

    2015-01-01

    Full Text Available The multiple light scattering in biological tissues limits the measurement depth for traditional wavefront sensor. The attenuated ballistic light and the background noise caused by the diffuse light give low signal to noise ratio for wavefront measurement. To overcome this issue, we introduced a wavefront estimation method based on a ray tracing algorithm to overcome this issue. With the knowledge of the refractive index of the medium, the wavefront is estimated by calculating optical path length of rays from the target inside of the samples. This method can provide not only the information of spherical aberration from the refractive-index mismatch between the medium and biological sample but also other aberrations caused by the irregular interface between them. Simulations based on different configurations are demonstrated in this paper.

  2. Preliminary results of a high-resolution refractometer using the Hartmann-Shack wave-front sensor: part I Resultados preliminares com refratrômetro de alta resolução, usando sensor de frente de onda de Hartmann-Shack: parte I

    Directory of Open Access Journals (Sweden)

    Luis Alberto Carvalho

    2003-06-01

    Full Text Available In this project we are developing an instrument for measuring the wave-front aberrations of the human eye using the Hartmann-Shack sensor. A laser source is directed towards the eye and its diffuse reflection at the retina generates an approximately spherical wave-front inside the eye. This wave-front travels through the different components of the eye (vitreous humor, lens, aqueous humor, and cornea and then leaves the eye carrying information about the aberrations caused by these components. Outside the eye there is an optical system composed of an array of microlenses and a CCD camera. The wave-front hits the microlens array and forms a pattern of spots at the CCD plane. Image processing algorithms detect the center of mass of each spot and this information is used to calculate the exact wave-front surface using least squares approximation by Zernike polynomials. We describe here the details of the first phase of this project, i. e., the construction of the first generation of prototype instruments and preliminary results for an artificial eye calibrated with different ametropias, i. e., myopia, hyperopia and astigmatism.Neste projeto estamos desenvolvendo instrumento para medidas das aberrações de frente de onda do olho humano usando um sensor Hartmann-Shack. Uma fonte de luz laser é direcionada ao olho e sua reflexão difusa na retina gera frente de onda aproximadamente esférica dentro do olho. Esta frente de onda atravessa os diferentes componentes do olho (humor vítreo, lente, humor aquoso e córnea trazendo informações sobre as aberrações ópticas causadas por estes componentes. No meio externo ao olho existe sistema óptico formado por uma matriz de microlentes e uma câmera CCD. A frente de onda incide nesta matriz e forma um padrão aproximadamente matricial de "spots" no plano do CCD. Algoritmos de processamento de imagens são utilizados para detectar os centróides de cada "spot" e esta informação é utilizada para

  3. Whole eye wavefront aberrations in Mexican male subjects.

    Science.gov (United States)

    Cantú, Roberto; Rosales, Marco A; Tepichín, Eduardo; Curioca, Andrée; Montes, Victor; Bonilla, Julio

    2004-01-01

    To analyze the characteristics, incidence, and appearance of wavefront aberrations in undilated, normal, unoperated eyes. Eighty-eight eyes of 44 healthy male Mexican subjects (mean age 25.32 years, range 18 to 36 yr) were divided into three groups based on uncorrected visual acuity of greater than or equal to 20/20, 20/30, or 20/40. UCVA measurements were obtained using an Acuity Max computer screen chart. Wavefront aberrations were measured with the Nidek OPD-Scan ARK 10000, Ver. 1.11b. All measurements were carried out at the same center by the same technician during a single session, following manufacturer instructions. Background illumination was 3 Lux. Wavefront aberration measurements for each group were statistically analyzed using StatView; an average eye was characterized and the resulting aberrations were simulated using MATLAB. We obtained wavefront aberration maps for the 20/20 undilated normal unoperated eyes for total, low, and high order aberration coefficients. Wavefront maps for right eyes were practically the same as those for left eyes. Higher aberrations did not contribute substantially to total wavefront analysis. Average aberrations of this "normal eye" will be used as criteria to decide the necessity of wavefront-guided ablation in our facilities. We will focus on the nearly zero average of high order aberrations in this normal whole eye as a reference to be matched.

  4. Optimal Shack-Hartmann Wavefront Sensing For Low-Light-Levels

    National Research Council Canada - National Science Library

    Solomon, Christopher

    1997-01-01

    .... He will analyze the sensitivity gains achievable in shack-hartmann wavefront sensors using bayesian estimators and compare the results with those achieved using a standard least squares approach...

  5. WFIRST: Managing Telescope Wavefront Stability to Meet Coronagraph Performance

    Science.gov (United States)

    Noecker, Martin; Poberezhskiy, Ilya; Kern, Brian; Krist, John; WFIRST System Engineering Team

    2018-01-01

    The WFIRST coronagraph instrument (CGI) needs a stable telescope and active wavefront control to perform coronagraph science with an expected sensitivity of 8x10-9 in the exoplanet-star flux ratio (SNR=10) at 200 milliarcseconds angular separation. With its subnanometer requirements on the stability of its input wavefront error (WFE), the CGI employs a combination of pointing and wavefront control loops and thermo-mechanical stability to meet budget allocations for beam-walk and low-order WFE, which enable stable starlight speckles on the science detector that can be removed by image subtraction. We describe the control strategy and the budget framework for estimating and budgeting the elements of wavefront stability, and the modeling strategy to evaluate it.

  6. Manipulating Acoustic Wavefront by Inhomogeneous Impedance and Steerable Extraordinary Reflection

    Science.gov (United States)

    Zhao, Jiajun; Li, Baowen; Chen, Zhining; Qiu, Cheng-Wei

    2013-08-01

    We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

  7. Wavefront correction system based on an equilateral triangular arrangement of actuators

    International Nuclear Information System (INIS)

    Salmon, J.T.; Bergum, J.W.; Kartz, M.W.; Presta, R.W.; Swift, C.D.

    1993-02-01

    Atomic Vapor Laser Isotope Separation (AVLIS) requires the copropagation of multiple beams at different wavelengths and at average powers exceeding 1 kW. Although mirror coatings are used that absorb less than one part in 10 5 , the beams still suffer from thermally induced phase distortions, both in the dye amplifiers and in transmissive optics, such as beam combiners and vacuum windows. These aberrations are 2nd-order and 3rd-order and can reach 5 waves peak-to-valley (p-v), which causes the beam to distort and break up when propagated over large distances. The magnitude of the aberrations scales with power, with time constants on the order of 30 seconds. Previous adaptive systems that have been developed corrected these thermally induced phase distortions of both 2nd-order and 3rd-order; however, these systems had limited spatial resolution and in some cases marginal stability. The authors have developed a new adaptive optics system where both the actuators of the deformable mirror and the lenslets of the Hartmann sensor are arranged with centers at the vertices of equilateral triangles. The wavefront sensor is a video Hartmann sensor that also uses an equilateral array of lenslets. The controller hardware uses a VME bus. The design minimizes the generation of reflected wavefronts higher than first order across each lenslet for large excursions of actuators from positions where the mirror is flat and, thus maximizes the precision of the slopes measured by the Hartmann sensor. The design is also immune to the waffle mode that is present in the reconstructors of adaptive optics systems where actuators are arranged in a square array

  8. The Infrared Imaging Spectrograph (IRIS) for TMT: multi-tiered wavefront measurements and novel mechanical design

    Science.gov (United States)

    Dunn, Jennifer; Andersen, David; Chapin, Edward; Reshetov, Vlad; Wierzbicki, Ramunas; Herriot, Glen; Chalmer, Dean; Isbrucker, Victor; Larkin, James E.; Moore, Anna M.; Suzuki, Ryuji

    2016-08-01

    The InfraRed Imaging Spectrograph (IRIS) will be the first light adaptive optics instrument on the Thirty Meter Telescope (TMT). IRIS is being built by a collaboration between Caltech, the University of California, NAOJ and NRC Herzberg. In this paper we present novel aspects of the Support Structure, Rotator and On-Instrument Wavefront Sensor systems being developed at NRC Herzberg. IRIS is suspended from the bottom port of the Narrow Field Infrared Adaptive Optics System (NFIRAOS), and provides its own image de-rotation to compensate for sidereal rotation of the focal plane. This arrangement is a challenge because NFIRAOS is designed to host two other science instruments, which imposes strict mass requirements on IRIS. As the mechanical design of all elements has progressed, we have been tasked with keeping the instrument mass under seven tonnes. This requirement has resulted in a mass reduction of 30 percent for the support structure and rotator compared to the most recent IRIS designs. To accomplish this goal, while still being able to withstand earthquakes, we developed a new design with composite materials. As IRIS is a client instrument of NFIRAOS, it benefits from NFIRAOS's superior AO correction. IRIS plays an important role in providing this correction by sensing low-order aberrations with three On-Instrument Wavefront Sensors (OIWFS). The OIWFS consists of three independently positioned natural guide star wavefront sensor probe arms that patrol a 2-arcminute field of view. We expect tip-tilt measurements from faint stars within the IRIS imager focal plane will further stabilize the delivered image quality. We describe how the use of On-Detector Guide Windows (ODGWs) in the IRIS imaging detector can be incorporated into the AO correction. In this paper, we present our strategies for acquiring and tracking sources with this complex AO system, and for mitigating and measuring the various potential sources of image blur and misalignment due to properties of

  9. Wavefront optimized nonlinear microscopy of ex vivo human retinas

    Science.gov (United States)

    Gualda, Emilio J.; Bueno, Juan M.; Artal, Pablo

    2010-03-01

    A multiphoton microscope incorporating a Hartmann-Shack (HS) wavefront sensor to control the ultrafast laser beam's wavefront aberrations has been developed. This instrument allowed us to investigate the impact of the laser beam aberrations on two-photon autofluorescence imaging of human retinal tissues. We demonstrated that nonlinear microscopy images are improved when laser beam aberrations are minimized by realigning the laser system cavity while wavefront controlling. Nonlinear signals from several human retinal anatomical features have been detected for the first time, without the need of fixation or staining procedures. Beyond the improved image quality, this approach reduces the required excitation power levels, minimizing the side effects of phototoxicity within the imaged sample. In particular, this may be important to study the physiology and function of the healthy and diseased retina.

  10. [Monochromatic aberration in accommodation. Dynamic wavefront analysis].

    Science.gov (United States)

    Fritzsch, M; Dawczynski, J; Jurkutat, S; Vollandt, R; Strobel, J

    2011-06-01

    Monochromatic aberrations may influence the visual acuity of the eye. They are not stable and can be affected by different factors. The subject of the following paper is the dynamic investigation of the changes in wavefront aberration with accommodation. Dynamic measurement of higher and lower order aberrations was performed with a WASCA Wavefront Analyzer (Carl-Zeiss-Meditec) and a specially constructed target device for aligning objects in far and near distances on 25 subjects aged from 15 to 27 years old. Wavefront aberrations showed some significant changes in accommodation. In addition to the characteristic sphere reaction accompanying miosis and changes in horizontal prism (Z(1) (1)) in the sense of a convergence movement of the eyeball also occurred. Furthermore defocus rose (Z(2) (0)) and astigmatism (Z(2) (-2)) changed. In higher-order aberrations a decrease in coma-like Zernike polynomials (Z(3) (-1), Z(3) (1)) was found. The most obvious change appeared in spherical aberration (Z(4) (0)) which increased and changed from positive to negative. In addition the secondary astigmatism (Z(4) (-2)) and quadrafoil (Z(4) (4)) rise also increased. The total root mean square (RMS), as well as the higher-order aberrations (RMS-HO) significantly increased in accommodation which is associated with a theoretical reduction of visual acuity. An analysis of the influence of pupil size on aberrations showed significant increases in defocus, spherical aberration, quadrafoil, RMS and RMS HO by increasing pupil diameter. By accommodation-associated miosis, the growing aberrations are partially compensated by focusing on near objects. Temporal analysis of the accommodation process with dynamic wavefront analysis revealed significant delays in pupil response and changing of prism in relation to the sphere reaction. In accommodation to near objects a discrete time ahead of third order aberrations in relation to the sphere response was found. Using dynamic wavefront measurement

  11. Advanced wavefront measurement and analysis of laser system modeling

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, C.R.; Auerback, J.M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    High spatial resolution measurements of the reflected or transmitted wavefronts of large aperture optical components used in high peak power laser systems is now possible. These measurements are produced by phase shifting interferometry. The wavefront data is in the form of 3-D phase maps that reconstruct the wavefront shape. The emphasis of this work is on the characterization of wavefront features in the mid-spatial wavelength range (from 0.1 to 10.0 mm) and has been accomplished for the first time. Wavefront structure from optical components with spatial wavelengths in this range are of concern because their effects in high peak power laser systems. At high peak power, this phase modulation can convert to large magnitude intensity modulation by non-linear processes. This can lead to optical damage. We have developed software to input the measured phase map data into beam propagation codes in order to model this conversion process. We are analyzing this data to: (1) Characterize the wavefront structure produced by current optical components, (2) Refine our understanding of laser system performance, (3) Develop a database from which future optical component specifications can be derived.

  12. Wavefront measurement of plastic lenses for mobile-phone applications

    Science.gov (United States)

    Huang, Li-Ting; Cheng, Yuan-Chieh; Wang, Chung-Yen; Wang, Pei-Jen

    2016-08-01

    In camera lenses for mobile-phone applications, all lens elements have been designed with aspheric surfaces because of the requirements in minimal total track length of the lenses. Due to the diffraction-limited optics design with precision assembly procedures, element inspection and lens performance measurement have become cumbersome in the production of mobile-phone cameras. Recently, wavefront measurements based on Shack-Hartmann sensors have been successfully implemented on injection-molded plastic lens with aspheric surfaces. However, the applications of wavefront measurement on small-sized plastic lenses have yet to be studied both theoretically and experimentally. In this paper, both an in-house-built and a commercial wavefront measurement system configured on two optics structures have been investigated with measurement of wavefront aberrations on two lens elements from a mobile-phone camera. First, the wet-cell method has been employed for verifications of aberrations due to residual birefringence in an injection-molded lens. Then, two lens elements of a mobile-phone camera with large positive and negative power have been measured with aberrations expressed in Zernike polynomial to illustrate the effectiveness in wavefront measurement for troubleshooting defects in optical performance.

  13. The PALM-3000 high-order adaptive optics system for Palomar Observatory

    Science.gov (United States)

    Bouchez, Antonin H.; Dekany, Richard G.; Angione, John R.; Baranec, Christoph; Britton, Matthew C.; Bui, Khanh; Burruss, Rick S.; Cromer, John L.; Guiwits, Stephen R.; Henning, John R.; Hickey, Jeff; McKenna, Daniel L.; Moore, Anna M.; Roberts, Jennifer E.; Trinh, Thang Q.; Troy, Mitchell; Truong, Tuan N.; Velur, Viswa

    2008-07-01

    Deployed as a multi-user shared facility on the 5.1 meter Hale Telescope at Palomar Observatory, the PALM-3000 highorder upgrade to the successful Palomar Adaptive Optics System will deliver extreme AO correction in the near-infrared, and diffraction-limited images down to visible wavelengths, using both natural and sodium laser guide stars. Wavefront control will be provided by two deformable mirrors, a 3368 active actuator woofer and 349 active actuator tweeter, controlled at up to 3 kHz using an innovative wavefront processor based on a cluster of 17 graphics processing units. A Shack-Hartmann wavefront sensor with selectable pupil sampling will provide high-order wavefront sensing, while an infrared tip/tilt sensor and visible truth wavefront sensor will provide low-order LGS control. Four back-end instruments are planned at first light: the PHARO near-infrared camera/spectrograph, the SWIFT visible light integral field spectrograph, Project 1640, a near-infrared coronagraphic integral field spectrograph, and 888Cam, a high-resolution visible light imager.

  14. Integrated Wavefront Corrector, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — One of the critical issues for NASA missions requiring high contrast astrophysical imaging such as Terrestrial Planet Finder (TPF) is wavefront control. Without use...

  15. Wavefront reconstruction using computer-generated holograms

    Science.gov (United States)

    Schulze, Christian; Flamm, Daniel; Schmidt, Oliver A.; Duparré, Michael

    2012-02-01

    We propose a new method to determine the wavefront of a laser beam, based on modal decomposition using computer-generated holograms (CGHs). Thereby the beam under test illuminates the CGH with a specific, inscribed transmission function that enables the measurement of modal amplitudes and phases by evaluating the first diffraction order of the hologram. Since we use an angular multiplexing technique, our method is innately capable of real-time measurements of amplitude and phase, yielding the complete information about the optical field. A measurement of the Stokes parameters, respectively of the polarization state, provides the possibility to calculate the Poynting vector. Two wavefront reconstruction possibilities are outlined: reconstruction from the phase for scalar beams and reconstruction from the Poynting vector for inhomogeneously polarized beams. To quantify single aberrations, the reconstructed wavefront is decomposed into Zernike polynomials. Our technique is applied to beams emerging from different kinds of multimode optical fibers, such as step-index, photonic crystal and multicore fibers, whereas in this work results are exemplarily shown for a step-index fiber and compared to a Shack-Hartmann measurement that serves as a reference.

  16. Iterative wave-front reconstruction in the Fourier domain.

    Science.gov (United States)

    Bond, Charlotte Z; Correia, Carlos M; Sauvage, Jean-François; Neichel, Benoit; Fusco, Thierry

    2017-05-15

    The use of Fourier methods in wave-front reconstruction can significantly reduce the computation time for large telescopes with a high number of degrees of freedom. However, Fourier algorithms for discrete data require a rectangular data set which conform to specific boundary requirements, whereas wave-front sensor data is typically defined over a circular domain (the telescope pupil). Here we present an iterative Gerchberg routine modified for the purposes of discrete wave-front reconstruction which adapts the measurement data (wave-front sensor slopes) for Fourier analysis, fulfilling the requirements of the fast Fourier transform (FFT) and providing accurate reconstruction. The routine is used in the adaptation step only and can be coupled to any other Wiener-like or least-squares method. We compare simulations using this method with previous Fourier methods and show an increase in performance in terms of Strehl ratio and a reduction in noise propagation for a 40×40 SPHERE-like adaptive optics system. For closed loop operation with minimal iterations the Gerchberg method provides an improvement in Strehl, from 95.4% to 96.9% in K-band. This corresponds to ~ 40 nm improvement in rms, and avoids the high spatial frequency errors present in other methods, providing an increase in contrast towards the edge of the correctable band.

  17. Wavefront Derived Refraction and Full Eye Biometry in Pseudophakic Eyes.

    Directory of Open Access Journals (Sweden)

    Xinjie Mao

    Full Text Available To assess wavefront derived refraction and full eye biometry including ciliary muscle dimension and full eye axial geometry in pseudophakic eyes using spectral domain OCT equipped with a Shack-Hartmann wavefront sensor.Twenty-eight adult subjects (32 pseudophakic eyes having recently undergone cataract surgery were enrolled in this study. A custom system combining two optical coherence tomography systems with a Shack-Hartmann wavefront sensor was constructed to image and monitor changes in whole eye biometry, the ciliary muscle and ocular aberration in the pseudophakic eye. A Badal optical channel and a visual target aligning with the wavefront sensor were incorporated into the system for measuring the wavefront-derived refraction. The imaging acquisition was performed twice. The coefficients of repeatability (CoR and intraclass correlation coefficient (ICC were calculated.Images were acquired and processed successfully in all patients. No significant difference was detected between repeated measurements of ciliary muscle dimension, full-eye biometry or defocus aberration. The CoR of full-eye biometry ranged from 0.36% to 3.04% and the ICC ranged from 0.981 to 0.999. The CoR for ciliary muscle dimensions ranged from 12.2% to 41.6% and the ICC ranged from 0.767 to 0.919. The defocus aberrations of the two measurements were 0.443 ± 0.534 D and 0.447 ± 0.586 D and the ICC was 0.951.The combined system is capable of measuring full eye biometry and refraction with good repeatability. The system is suitable for future investigation of pseudoaccommodation in the pseudophakic eye.

  18. Wavefront propagation from one plane to another with the use of Zernike polynomials and Taylor monomials.

    Science.gov (United States)

    Dai, Guang-ming; Campbell, Charles E; Chen, Li; Zhao, Huawei; Chernyak, Dimitri

    2009-01-20

    In wavefront-driven vision correction, ocular aberrations are often measured on the pupil plane and the correction is applied on a different plane. The problem with this practice is that any changes undergone by the wavefront as it propagates between planes are not currently included in devising customized vision correction. With some valid approximations, we have developed an analytical foundation based on geometric optics in which Zernike polynomials are used to characterize the propagation of the wavefront from one plane to another. Both the boundary and the magnitude of the wavefront change after the propagation. Taylor monomials were used to realize the propagation because of their simple form for this purpose. The method we developed to identify changes in low-order aberrations was verified with the classical vertex correction formula. The method we developed to identify changes in high-order aberrations was verified with ZEMAX ray-tracing software. Although the method may not be valid for highly irregular wavefronts and it was only proven for wavefronts with low-order or high-order aberrations, our analysis showed that changes in the propagating wavefront are significant and should, therefore, be included in calculating vision correction. This new approach could be of major significance in calculating wavefront-driven vision correction whether by refractive surgery, contact lenses, intraocular lenses, or spectacles.

  19. Wavefront cellular learning automata.

    Science.gov (United States)

    Moradabadi, Behnaz; Meybodi, Mohammad Reza

    2018-02-01

    This paper proposes a new cellular learning automaton, called a wavefront cellular learning automaton (WCLA). The proposed WCLA has a set of learning automata mapped to a connected structure and uses this structure to propagate the state changes of the learning automata over the structure using waves. In the WCLA, after one learning automaton chooses its action, if this chosen action is different from the previous action, it can send a wave to its neighbors and activate them. Each neighbor receiving the wave is activated and must choose a new action. This structure for the WCLA is necessary in many dynamic areas such as social networks, computer networks, grid computing, and web mining. In this paper, we introduce the WCLA framework as an optimization tool with diffusion capability, study its behavior over time using ordinary differential equation solutions, and present its accuracy using expediency analysis. To show the superiority of the proposed WCLA, we compare the proposed method with some other types of cellular learning automata using two benchmark problems.

  20. Wavefront cellular learning automata

    Science.gov (United States)

    Moradabadi, Behnaz; Meybodi, Mohammad Reza

    2018-02-01

    This paper proposes a new cellular learning automaton, called a wavefront cellular learning automaton (WCLA). The proposed WCLA has a set of learning automata mapped to a connected structure and uses this structure to propagate the state changes of the learning automata over the structure using waves. In the WCLA, after one learning automaton chooses its action, if this chosen action is different from the previous action, it can send a wave to its neighbors and activate them. Each neighbor receiving the wave is activated and must choose a new action. This structure for the WCLA is necessary in many dynamic areas such as social networks, computer networks, grid computing, and web mining. In this paper, we introduce the WCLA framework as an optimization tool with diffusion capability, study its behavior over time using ordinary differential equation solutions, and present its accuracy using expediency analysis. To show the superiority of the proposed WCLA, we compare the proposed method with some other types of cellular learning automata using two benchmark problems.

  1. Zonal wavefront sensing using a grating array printed on a polyester film

    Science.gov (United States)

    Pathak, Biswajit; Kumar, Suraj; Boruah, Bosanta R.

    2015-12-01

    In this paper, we describe the development of a zonal wavefront sensor that comprises an array of binary diffraction gratings realized on a transparent sheet (i.e., polyester film) followed by a focusing lens and a camera. The sensor works in a manner similar to that of a Shack-Hartmann wavefront sensor. The fabrication of the array of gratings is immune to certain issues associated with the fabrication of the lenslet array which is commonly used in zonal wavefront sensing. Besides the sensing method offers several important advantages such as flexible dynamic range, easy configurability, and option to enhance the sensing frame rate. Here, we have demonstrated the working of the proposed sensor using a proof-of-principle experimental arrangement.

  2. Zonal wavefront sensing using a grating array printed on a polyester film

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Biswajit; Boruah, Bosanta R., E-mail: brboruah@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati, Assam 781039 (India); Kumar, Suraj [Department of Applied Sciences, Gauhati University, Guwahati, Assam 781014 (India)

    2015-12-15

    In this paper, we describe the development of a zonal wavefront sensor that comprises an array of binary diffraction gratings realized on a transparent sheet (i.e., polyester film) followed by a focusing lens and a camera. The sensor works in a manner similar to that of a Shack-Hartmann wavefront sensor. The fabrication of the array of gratings is immune to certain issues associated with the fabrication of the lenslet array which is commonly used in zonal wavefront sensing. Besides the sensing method offers several important advantages such as flexible dynamic range, easy configurability, and option to enhance the sensing frame rate. Here, we have demonstrated the working of the proposed sensor using a proof-of-principle experimental arrangement.

  3. Wavefront control performance modeling with WFIRST shaped pupil coronagraph testbed

    Science.gov (United States)

    Zhou, Hanying; Nemati, Bijian; Krist, John; Cady, Eric; Kern, Brian; Poberezhskiy, Ilya

    2017-09-01

    NASA's WFIRST mission includes a coronagraph instrument (CGI) for direct imaging of exoplanets. Significant improvement in CGI model fidelity has been made recently, alongside a testbed high contrast demonstration in a simulated dynamic environment at JPL. We present our modeling method and results of comparisons to testbed's high order wavefront correction performance for the shaped pupil coronagraph. Agreement between model prediction and testbed result at better than a factor of 2 has been consistently achieved in raw contrast (contrast floor, chromaticity, and convergence), and with that comes good agreement in contrast sensitivity to wavefront perturbations and mask lateral shear.

  4. Wavefront Propagation and Fuzzy Based Autonomous Navigation

    Directory of Open Access Journals (Sweden)

    Adel Al-Jumaily

    2005-06-01

    Full Text Available Path planning and obstacle avoidance are the two major issues in any navigation system. Wavefront propagation algorithm, as a good path planner, can be used to determine an optimal path. Obstacle avoidance can be achieved using possibility theory. Combining these two functions enable a robot to autonomously navigate to its destination. This paper presents the approach and results in implementing an autonomous navigation system for an indoor mobile robot. The system developed is based on a laser sensor used to retrieve data to update a two dimensional world model of therobot environment. Waypoints in the path are incorporated into the obstacle avoidance. Features such as ageing of objects and smooth motion planning are implemented to enhance efficiency and also to cater for dynamic environments.

  5. Extended use of two crossed Babinet compensators for wavefront sensing in adaptive optics

    Science.gov (United States)

    Paul, Lancelot; Kumar Saxena, Ajay

    2010-12-01

    An extended use of two crossed Babinet compensators as a wavefront sensor for adaptive optics applications is proposed. This method is based on the lateral shearing interferometry technique in two directions. A single record of the fringes in a pupil plane provides the information about the wavefront. The theoretical simulations based on this approach for various atmospheric conditions and other errors of optical surfaces are provided for better understanding of this method. Derivation of the results from a laboratory experiment using simulated atmospheric conditions demonstrates the steps involved in data analysis and wavefront evaluation. It is shown that this method has a higher degree of freedom in terms of subapertures and on the choice of detectors, and can be suitably adopted for real-time wavefront sensing for adaptive optics.

  6. A novel electrochemical sensor based on zirconia/ordered macroporous polyaniline for ultrasensitive detection of pesticides.

    Science.gov (United States)

    Wang, Yonglan; Jin, Jun; Yuan, Caixia; Zhang, Fan; Ma, Linlin; Qin, Dongdong; Shan, Duoliang; Lu, Xiaoquan

    2015-01-21

    A simple and mild strategy was proposed to develop a novel electrochemical sensor based on zirconia/ordered macroporous polyaniline (ZrO2/OMP) and further used for the detection of methyl parathion (MP), one of the organophosphate pesticides (OPPs). Due to the strong affinity of phosphate groups with ZrO2 and the advantages of OMP such as high catalytic activity and good conductivity, the developed sensor showed a limit of detection as low as 2.28 × 10(-10) mol L(-1) (S/N = 3) by square-wave voltammograms, and good selectivity, acceptable reproducibility and stability. Most importantly, this novel sensor was successfully applied to detect MP in real samples of apple and cabbage. It is expected that this method has potential applications in electrochemical sensing platforms with simple, sensitive, selective and fast analysis.

  7. Wavefront Sensing for WFIRST with a Linear Optical Model

    Science.gov (United States)

    Jurling, Alden S.; Content, David A.

    2012-01-01

    In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.

  8. Atmospheric turbulence temperature on the laser wavefront properties

    Science.gov (United States)

    Contreras López, J. C.; Ballesteros Díaz, A.; Tíjaro Rojas, O. J.; Torres Moreno, Y.

    2017-06-01

    Temperature is a physical magnitude that if is higher, the refractive index presents more important random fluctuations, which produce a greater distortion in the wavefront and thus a displacement in its centroid. To observe the effect produced by the turbulent medium strongly influenced by temperature on propagation laser beam, we experimented with two variable and controllable temperature systems designed as optical turbulence generators (OTG): a Turbulator and a Parallelepiped glass container. The experimental setup use three CMOS cameras and four temperature sensors spatially distributed to acquire synchronously information of the laser beam wavefront and turbulence temperature, respectively. The acquired information was analyzed with MATLAB® software tool, that it allows to compute the position, in terms of the evolution time, of the laser beam center of mass and their deviations produced by different turbulent conditions generated inside the two manufactured systems. The results were reflected in the statistical analysis of the centroid shifting.

  9. Atmospheric turbulence temperature on the laser wavefront properties

    International Nuclear Information System (INIS)

    López, J C Contreras; Rojas, O J Tíjaro; Díaz, A Ballesteros; Moreno, Y Torres

    2017-01-01

    Temperature is a physical magnitude that if is higher, the refractive index presents more important random fluctuations, which produce a greater distortion in the wavefront and thus a displacement in its centroid. To observe the effect produced by the turbulent medium strongly influenced by temperature on propagation laser beam, we experimented with two variable and controllable temperature systems designed as optical turbulence generators (OTG): a Turbulator and a Parallelepiped glass container. The experimental setup use three CMOS cameras and four temperature sensors spatially distributed to acquire synchronously information of the laser beam wavefront and turbulence temperature, respectively. The acquired information was analyzed with MATLAB® software tool, that it allows to compute the position, in terms of the evolution time, of the laser beam center of mass and their deviations produced by different turbulent conditions generated inside the two manufactured systems. The results were reflected in the statistical analysis of the centroid shifting. (paper)

  10. Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors.

    Science.gov (United States)

    McAlpine, Michael C; Ahmad, Habib; Wang, Dunwei; Heath, James R

    2007-05-01

    The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a 'nano-electronic nose' library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors.

  11. Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

    Science.gov (United States)

    McAlpine, Michael C.; Ahmad, Habib; Wang, Dunwei; Heath, James R.

    2007-05-01

    The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a `nano-electronic nose' library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors.

  12. Optical Aberrations and Wavefront

    Directory of Open Access Journals (Sweden)

    Nihat Polat

    2014-08-01

    Full Text Available The deviation of light to create normal retinal image in the optical system is called aberration. Aberrations are divided two subgroup: low-order aberrations (defocus: spherical and cylindrical refractive errors and high-order aberrations (coma, spherical, trefoil, tetrafoil, quadrifoil, pentafoil, secondary astigmatism. Aberrations increase with aging. Spherical aberrations are compensated by positive corneal and negative lenticular spherical aberrations in youth. Total aberrations are elevated by positive corneal and positive lenticular spherical aberrations in elderly. In this study, we aimed to analyze the basic terms regarding optic aberrations which have gained significance recently. (Turk J Ophthalmol 2014; 44: 306-11

  13. Automatic low-order aberration correction based on geometrical optics for slab lasers.

    Science.gov (United States)

    Yu, Xin; Dong, Lizhi; Lai, Boheng; Yang, Ping; Liu, Yong; Kong, Qingfeng; Yang, Kangjian; Tang, Guomao; Xu, Bing

    2017-02-20

    In this paper, we present a method based on geometry optics to simultaneously correct low-order aberrations and reshape the beams of slab lasers. A coaxial optical system with three lenses is adapted. The positions of the three lenses are directly calculated based on the beam parameters detected by wavefront sensors. The initial sizes of the input beams are 1.8  mm×11  mm, and peak-to-valley (PV) values of the wavefront range up to several tens of microns. After automatic correction, the dimensions may reach nearly 22  mm×22  mm as expected, and PV values of the wavefront are less than 2 μm. The effectiveness and precision of this method are verified with experiments.

  14. Differences between wavefront and subjective refraction for infrared light.

    Science.gov (United States)

    Teel, Danielle F W; Jacobs, Robert J; Copland, James; Neal, Daniel R; Thibos, Larry N

    2014-10-01

    To determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light. Objective refractions were obtained with a commercial wavefront aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 30 subjects with a speckle optometer validated against objective Zernike wavefront refractions on a physical model eye (Teel et al., Design and validation of an infrared Badal optometer for laser speckle, Optom Vis Sci 2008;85:834-42). Both instruments used near-infrared (NIR) radiation (835 nm for COAS, 820 nm for the speckle optometer) to avoid correction for ocular chromatic aberration. A 3-mm artificial pupil was used to reduce complications attributed to higher-order ocular aberrations. For comparison with paraxial (Seidel) and minimum root-mean-square (Zernike) wavefront refractions, objective refractions were also determined for a battery of 29 image quality metrics by computing the correcting lens that optimizes retinal image quality. Objective Zernike refractions were more myopic than subjective refractions for 29 of 30 subjects. The population mean discrepancy was -0.26 diopters (D) (SEM = 0.03 D). Paraxial (Seidel) objective refractions tended to be hyperopically biased (mean discrepancy = +0.20 D, SEM = 0.06 D). Refractions based on retinal image quality were myopically biased for 28 of 29 metrics. The mean bias across all 31 measures was -0.24 D (SEM = 0.03). Myopic bias of objective refractions was greater for eyes with brown irises compared with eyes with blue irises. Our experimental results are consistent with the hypothesis that reflected NIR light captured by the aberrometer originates from scattering sources located posterior to the entrance apertures of cone photoreceptors, near the retinal pigment epithelium. The larger myopic bias for brown eyes suggests that a greater fraction of NIR light is reflected from choroidal melanin in brown eyes compared with blue eyes.

  15. A hybrid system for beam steering and wavefront control

    Science.gov (United States)

    Nikulin, Vladimir V.

    2004-06-01

    Performance of long-range mobile laser systems operating within Earth's atmosphere is generally limited by several factors. Movement of the communicating platforms, such as aircraft, terrain vehicles, etc., complemented by mechanical vibrations, is the main cause of pointing errors. In addition, atmospheric turbulence causes changes of the refractive index along the propagation path that lead to phase distortions (aberrations), thus creating random redistribution of optical energy in the spatial domain. The combined effect of these factors leads to an increased bit-error probability under adverse operation conditions. While traditional approaches provide separate treatment of these problems, suggesting the development of high-bandwidth beam steering systems to perform tracking and jitter rejection, and wavefront control for the mitigation of atmospheric effects, the two tasks could be integrated. In this paper we present a hybrid laser beam steering/wavefront control system comprising an electrically addressed spatial light modulator (SLM) installed on the Omni-Wrist sensor mount platform. The function of the Omni-Wrist is to provide coarse steering over a wide range of pointing angles, while the purpose of the SLM is twofold: it performs wavefront correction and fine steering. The control law for the Omni-Wrist is synthesized using the decentralized approach that provides independent access to the azimuth and declination channels, while the algorithm for calculating the required phase profile for the SLM is optimization-based. This paper presents the control algorithms, the approach to coordinating the operation of the both systems and the simulation results.

  16. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Measurement of wavefront distortions by the method of aperture sounding with spatially separated channels

    Science.gov (United States)

    Prilepskiy, Boris V.; Alikhanov, Alexey N.; Berchenko, Evgeniy A.; Kiselev, Vladimir Yu; Narusbek, Ernest A.; Filatov, Aleksander S.

    2005-08-01

    Features of the formation of signals in wavefront sensors with the single-frequency light wave phase modulation and spatial separation of control channels are considered. Analysis is performed for sensors in which phase modulation is governed by a controlled element located in the pupil of the optical system of a sensor or in the focal plane of the objective of this system. Peculiarities of the signal formation for a tilted wavefront are considered separately for internal points of the exit pupil in the case of light wave phase modulation in the pupil. It is shown that a signal at the modulation frequency in these wavefront sensors for points located far from the pupil boundaries is determined by the wavefront curvature.

  17. Wavefront compensation applied to AVLIS laser systems

    International Nuclear Information System (INIS)

    Gonsiorowski, T.; Wirth, A.

    1995-01-01

    The efficiency of an AVLIS system depends upon the power density and uniformity of the laser system. Because of wavefront aberrations the realized beam quality is not ideal. Wavefront compensation provides a means to improve beam quality and system efficiency. (author)

  18. Optimizing a Water Simulation based on Wavefront Parameter Optimization

    OpenAIRE

    Lundgren, Martin

    2017-01-01

    DICE, a Swedish game company, wanted a more realistic water simulation. Currently, most large scale water simulations used in games are based upon ocean simulation technology. These techniques falter when used in other scenarios, such as coastlines. In order to produce a more realistic simulation, a new one was created based upon the water simulation technique "Wavefront Parameter Interpolation". This technique involves a rather extensive preprocess that enables ocean simulations to have inte...

  19. Wavefront sensing and adaptive control in phased array of fiber collimators

    Science.gov (United States)

    Lachinova, Svetlana L.; Vorontsov, Mikhail A.

    2011-03-01

    A new wavefront control approach for mitigation of atmospheric turbulence-induced wavefront phase aberrations in coherent fiber-array-based laser beam projection systems is introduced and analyzed. This approach is based on integration of wavefront sensing capabilities directly into the fiber-array transmitter aperture. In the coherent fiber array considered, we assume that each fiber collimator (subaperture) of the array is capable of precompensation of local (onsubaperture) wavefront phase tip and tilt aberrations using controllable rapid displacement of the tip of the delivery fiber at the collimating lens focal plane. In the technique proposed, this tip and tilt phase aberration control is based on maximization of the optical power received through the same fiber collimator using the stochastic parallel gradient descent (SPGD) technique. The coordinates of the fiber tip after the local tip and tilt aberrations are mitigated correspond to the coordinates of the focal-spot centroid of the optical wave backscattered off the target. Similar to a conventional Shack-Hartmann wavefront sensor, phase function over the entire fiber-array aperture can then be retrieved using the coordinates obtained. The piston phases that are required for coherent combining (phase locking) of the outgoing beams at the target plane can be further calculated from the reconstructed wavefront phase. Results of analysis and numerical simulations are presented. Performance of adaptive precompensation of phase aberrations in this laser beam projection system type is compared for various system configurations characterized by the number of fiber collimators and atmospheric turbulence conditions. The wavefront control concept presented can be effectively applied for long-range laser beam projection scenarios for which the time delay related with the double-pass laser beam propagation to the target and back is compared or even exceeds the characteristic time of the atmospheric turbulence change

  20. Stability of therapeutic retreatment of corneal wavefront customized ablation with the SCHWIND CAM: 4-year data.

    Science.gov (United States)

    Aslanides, Ioannis M; Kolli, Sai; Padroni, Sara; Padron, Sara; Arba Mosquera, Samuel

    2012-05-01

    To evaluate the long-term outcomes of aspheric corneal wavefront ablation profiles for excimer laser retreatment. Eighteen eyes that had previously undergone LASIK or photorefractive keratectomy (PRK) were retreated with LASIK using the corneal wavefront ablation profile. Custom Ablation Manager (SCHWIND eye-tech-solutions, Kleinostheim, Germany) software and the ESIRIS flying spot excimer laser system (SCHWIND) were used to perform the ablations. Refractive outcomes and wavefront data are reported up to 4 years after retreatment. Pre- and postoperative data were compared with Student t tests and (multivariate) correlation tests. P<.05 was considered statistically significant. A bilinear correlation of various postoperative wavefront aberrations versus planned correction and preoperative aberration was performed. Mean manifest refraction spherical equivalent (MRSE) before retreatment was -0.38±1.85 diopters (D) and -0.09±0.22 D at 6 months and -0.10±0.38 D at 4 years postoperatively. The reduction in MRSE was statistically significant at both postoperative time points (P<.005). Postoperative aberrations were statistically lower (spherical aberration P<.05; coma P<.005; root-mean-square higher order aberration P<.0001) at 4 years postoperatively. Distribution of the postoperative uncorrected distance visual acuity (P<.0001) and corrected distance visual acuity (P<.01) were statistically better than preoperative values. Aspheric corneal wavefront customization with the ESIRIS yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for the correction of myopia and myopic astigmatism. The corneal wavefront customized approach shows its strength in cases where abnormal optical systems are expected. Systematic wavefront customized corneal ablation appears safe and efficacious for retreatment cases. Copyright 2012, SLACK Incorporated.

  1. On distributed wavefront reconstruction for large-scale adaptive optics systems.

    Science.gov (United States)

    de Visser, Cornelis C; Brunner, Elisabeth; Verhaegen, Michel

    2016-05-01

    The distributed-spline-based aberration reconstruction (D-SABRE) method is proposed for distributed wavefront reconstruction with applications to large-scale adaptive optics systems. D-SABRE decomposes the wavefront sensor domain into any number of partitions and solves a local wavefront reconstruction problem on each partition using multivariate splines. D-SABRE accuracy is within 1% of a global approach with a speedup that scales quadratically with the number of partitions. The D-SABRE is compared to the distributed cumulative reconstruction (CuRe-D) method in open-loop and closed-loop simulations using the YAO adaptive optics simulation tool. D-SABRE accuracy exceeds CuRe-D for low levels of decomposition, and D-SABRE proved to be more robust to variations in the loop gain.

  2. Image system analysis of human eye wave-front aberration on the basis of HSS

    Science.gov (United States)

    Xu, Ancheng

    2017-07-01

    Hartmann-Shack sensor (HSS) has been used in objective measurement of human eye wave-front aberration, but the research on the effects of sampling point size on the accuracy of the result has not been reported. In this paper, point spread function (PSF) of the whole system mathematical model was obtained via measuring the optical imaging system structure of human eye wave-front aberration measurement. The impact of Airy spot size on the accuracy of system was analyzed. Statistics study show that the geometry of Airy spot size of the ideal light source sent from eye retina formed on the surface of HSS is far smaller than the size of the HSS sample point image used in the experiment. Therefore, the effect of Airy spot on the precision of the system can be ignored. This study theoretically and experimentally justifies the reliability and accuracy of human eye wave-front aberration measurement based on HSS.

  3. Optically sensitive Medipix2 detector for adaptive optics wavefront sensing

    CERN Document Server

    Vallerga, John; Tremsina, Anton; Siegmund, Oswald; Mikulec, Bettina; Clark, Allan G; CERN. Geneva

    2005-01-01

    A new hybrid optical detector is described that has many of the attributes desired for the next generation adaptive optics (AO) wavefront sensors. The detector consists of a proximity focused microchannel plate (MCP) read out by multi-pixel application specific integrated circuit (ASIC) chips developed at CERN ("Medipix2") with individual pixels that amplify, discriminate and count input events. The detector has 256 x 256 pixels, zero readout noise (photon counting), can be read out at 1 kHz frame rates and is abutable on 3 sides. The Medipix2 readout chips can be electronically shuttered down to a temporal window of a few microseconds with an accuracy of 10 ns. When used in a Shack-Hartmann style wavefront sensor, a detector with 4 Medipix chips should be able to centroid approximately 5000 spots using 7 x 7 pixel sub-apertures resulting in very linear, off-null error correction terms. The quantum efficiency depends on the optical photocathode chosen for the bandpass of interest.

  4. Optically sensitive Medipix2 detector for adaptive optics wavefront sensing

    International Nuclear Information System (INIS)

    Vallerga, John; McPhate, Jason; Tremsin, Anton; Siegmund, Oswald; Mikulec, Bettina; Clark, Allan

    2005-01-01

    A new hybrid optical detector is described that has many of the attributes desired for the next generation adaptive optics (AO) wavefront sensors. The detector consists of a proximity focused microchannel plate (MCP) read out by multi-pixel application specific integrated circuit (ASIC) chips developed at CERN ('Medipix2') with individual pixels that amplify, discriminate and count input events. The detector has 256x256 pixels, zero readout noise (photon counting), can be read out at 1 kHz frame rates and is abutable on 3 sides. The Medipix2 readout chips can be electronically shuttered down to a temporal window of a few microseconds with an accuracy of 10 ns. When used in a Shack-Hartmann style wavefront sensor, a detector with 4 Medipix chips should be able to centroid approximately 5000 spots using 7x7 pixel sub-apertures resulting in very linear, off-null error correction terms. The quantum efficiency depends on the optical photocathode chosen for the bandpass of interest

  5. Evaluating noise performance of the IUCAA sidecar drive electronics controller (ISDEC) based system for TMT on-instrument wavefront sensing (OIWFS) application

    Science.gov (United States)

    Burse, Mahesh; Chattopadhyay, Sabyasachi; Ramaprakash, A. N.; Sinha, Sakya; Prabhudesai, Swapnil; Punnadi, Sujit; Chordia, Pravin; Kohok, Abhay

    2016-07-01

    As a part of a design study for the On-Instrument Low Order Wave-front Sensor (OIWFS) for the TMT Infra-Red Imaging Spectrograph (IRIS), we recently evaluated the noise performance of a detector control system consisting of IUCAA SIDECAR DRIVE ELECRONICS CONTROLLER (ISDEC), SIDECAR ASIC and HAWAII-2RG (H2RG) MUX. To understand and improve the performance of this system to serve as a near infrared wavefront sensor, we implemented new read out modes like multiple regions of interest with differential multi-accumulate readout schemes for the HAWAII-2RG (H2RG) detector. In this system, the firmware running in SIDECAR ASIC programs the detector for ROI readout, reads the detector, processes the detector output and writes the digitized data into its internal memory. ISDEC reads the digitized data from ASIC, performs the differential multi-accumulate operations and then sends the processed data to a PC over a USB interface. A special loopback board was designed and used to measure and reduce the noise from SIDECAR ASIC DC biases2. We were able to reduce the mean r.m.s read noise of this system down to 1-2 e. for any arbitrary window frame of 4x4 size at frame rates below about 200 Hz.

  6. GTSO: Global Trace Synchronization and Ordering Mechanism for Wireless Sensor Network Monitoring Platforms

    Science.gov (United States)

    Bonastre, Alberto; Ors, Rafael

    2017-01-01

    Monitoring is one of the best ways to evaluate the behavior of computer systems. When the monitored system is a distributed system—such as a wireless sensor network (WSN)—the monitoring operation must also be distributed, providing a distributed trace for further analysis. The temporal sequence of occurrence of the events registered by the distributed monitoring platform (DMP) must be correctly established to provide cause-effect relationships between them, so the logs obtained in different monitor nodes must be synchronized. Many of synchronization mechanisms applied to DMPs consist in adjusting the internal clocks of the nodes to the same value as a reference time. However, these mechanisms can create an incoherent event sequence. This article presents a new method to achieve global synchronization of the traces obtained in a DMP. It is based on periodic synchronization signals that are received by the monitor nodes and logged along with the recorded events. This mechanism processes all traces and generates a global post-synchronized trace by scaling all times registered proportionally according with the synchronization signals. It is intended to be a simple but efficient offline mechanism. Its application in a WSN-DMP demonstrates that it guarantees a correct ordering of the events, avoiding the aforementioned issues. PMID:29295494

  7. GTSO: Global Trace Synchronization and Ordering Mechanism for Wireless Sensor Network Monitoring Platforms.

    Science.gov (United States)

    Navia, Marlon; Campelo, José Carlos; Bonastre, Alberto; Ors, Rafael

    2017-12-23

    Monitoring is one of the best ways to evaluate the behavior of computer systems. When the monitored system is a distributed system-such as a wireless sensor network (WSN)-the monitoring operation must also be distributed, providing a distributed trace for further analysis. The temporal sequence of occurrence of the events registered by the distributed monitoring platform (DMP) must be correctly established to provide cause-effect relationships between them, so the logs obtained in different monitor nodes must be synchronized. Many of synchronization mechanisms applied to DMPs consist in adjusting the internal clocks of the nodes to the same value as a reference time. However, these mechanisms can create an incoherent event sequence. This article presents a new method to achieve global synchronization of the traces obtained in a DMP. It is based on periodic synchronization signals that are received by the monitor nodes and logged along with the recorded events. This mechanism processes all traces and generates a global post-synchronized trace by scaling all times registered proportionally according with the synchronization signals. It is intended to be a simple but efficient offline mechanism. Its application in a WSN-DMP demonstrates that it guarantees a correct ordering of the events, avoiding the aforementioned issues.

  8. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  9. Visual optics under the wavefront perspective

    Directory of Open Access Journals (Sweden)

    Sidney Júlio Faria-E-Sousa

    2014-08-01

    Full Text Available Some intriguing concepts of visual optics cannot be explained by ray tracing. However, they can be clarified using wavefront formalism. Its main advantage is in the use of the concept of vergence, which is very helpful in interpreting the optical phenomena involved in the neutralization of the ametropias. In this line of thinking, the major role of a lens is in the creation of a new light source (the image point that orientates the refracted waves. Once the nature and position of this source is known, one can easily predict the behavior of the wavefronts. The formalism also allows for an easier understanding on how wavefronts relate to light rays and on how algebraic signs are assigned to optical distances.

  10. Biometric iris image acquisition system with wavefront coding technology

    Science.gov (United States)

    Hsieh, Sheng-Hsun; Yang, Hsi-Wen; Huang, Shao-Hung; Li, Yung-Hui; Tien, Chung-Hao

    2013-09-01

    Biometric signatures for identity recognition have been practiced for centuries. Basically, the personal attributes used for a biometric identification system can be classified into two areas: one is based on physiological attributes, such as DNA, facial features, retinal vasculature, fingerprint, hand geometry, iris texture and so on; the other scenario is dependent on the individual behavioral attributes, such as signature, keystroke, voice and gait style. Among these features, iris recognition is one of the most attractive approaches due to its nature of randomness, texture stability over a life time, high entropy density and non-invasive acquisition. While the performance of iris recognition on high quality image is well investigated, not too many studies addressed that how iris recognition performs subject to non-ideal image data, especially when the data is acquired in challenging conditions, such as long working distance, dynamical movement of subjects, uncontrolled illumination conditions and so on. There are three main contributions in this paper. Firstly, the optical system parameters, such as magnification and field of view, was optimally designed through the first-order optics. Secondly, the irradiance constraints was derived by optical conservation theorem. Through the relationship between the subject and the detector, we could estimate the limitation of working distance when the camera lens and CCD sensor were known. The working distance is set to 3m in our system with pupil diameter 86mm and CCD irradiance 0.3mW/cm2. Finally, We employed a hybrid scheme combining eye tracking with pan and tilt system, wavefront coding technology, filter optimization and post signal recognition to implement a robust iris recognition system in dynamic operation. The blurred image was restored to ensure recognition accuracy over 3m working distance with 400mm focal length and aperture F/6.3 optics. The simulation result as well as experiment validates the proposed code

  11. Manipulations of Wavefront Propagation: Useful Methods and Applications for Interferometric Measurements and Scanning

    Directory of Open Access Journals (Sweden)

    Avi Karsenty

    2017-01-01

    Full Text Available Phase measurements obtained by high-coherence interferometry are restricted by the 2π ambiguity, to height differences smaller than λ/2. A further restriction in most interferometric systems is for focusing the system on the measured object. We present two methods that overcome these restrictions. In the first method, different segments of a measured wavefront are digitally propagated and focused locally after measurement. The divergent distances, by which the diverse segments of the wavefront are propagated in order to achieve a focused image, provide enough information so as to resolve the 2π ambiguity. The second method employs an interferogram obtained by a spectrum constituting a small number of wavelengths. The magnitude of the interferogram’s modulations is utilized to resolve the 2π ambiguity. Such methods of wavefront propagation enable several applications such as focusing and resolving the 2π ambiguity, as described in the article.

  12. Wavefront sensing in space: flight demonstration II of the PICTURE sounding rocket payload

    Science.gov (United States)

    Douglas, Ewan S.; Mendillo, Christopher B.; Cook, Timothy A.; Cahoy, Kerri L.; Chakrabarti, Supriya

    2018-01-01

    A NASA sounding rocket for high-contrast imaging with a visible nulling coronagraph, the Planet Imaging Concept Testbed Using a Rocket Experiment (PICTURE) payload, has made two suborbital attempts to observe the warm dust disk inferred around Epsilon Eridani. The first flight in 2011 demonstrated a 5 mas fine pointing system in space. The reduced flight data from the second launch, on November 25, 2015, presented herein, demonstrate active sensing of wavefront phase in space. Despite several anomalies in flight, postfacto reduction phase stepping interferometer data provide insight into the wavefront sensing precision and the system stability for a portion of the pupil. These measurements show the actuation of a 32 × 32-actuator microelectromechanical system deformable mirror. The wavefront sensor reached a median precision of 1.4 nm per pixel, with 95% of samples between 0.8 and 12.0 nm per pixel. The median system stability, including telescope and coronagraph wavefront errors other than tip, tilt, and piston, was 3.6 nm per pixel, with 95% of samples between 1.2 and 23.7 nm per pixel.

  13. Sensors

    CERN Document Server

    Pigorsch, Enrico

    1997-01-01

    This is the 5th edition of the Metra Martech Directory "EUROPEAN CENTRES OF EXPERTISE - SENSORS." The entries represent a survey of European sensors development. The new edition contains 425 detailed profiles of companies and research institutions in 22 countries. This is reflected in the diversity of sensors development programmes described, from sensors for physical parameters to biosensors and intelligent sensor systems. We do not claim that all European organisations developing sensors are included, but this is a good cross section from an invited list of participants. If you see gaps or omissions, or would like your organisation to be included, please send details. The data base invites the formation of effective joint ventures by identifying and providing access to specific areas in which organisations offer collaboration. This issue is recognised to be of great importance and most entrants include details of collaboration offered and sought. We hope the directory on Sensors will help you to find the ri...

  14. Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, H. [PBI-Dansensor A/S (Denmark); Toft Soerensen, O. [Risoe National Lab., Materials Research Dept. (Denmark)

    1999-10-01

    A new type of ceramic oxygen sensors based on semiconducting oxides was developed in this project. The advantage of these sensors compared to standard ZrO{sub 2} sensors is that they do not require a reference gas and that they can be produced in small sizes. The sensor design and the techniques developed for production of these sensors are judged suitable by the participating industry for a niche production of a new generation of oxygen sensors. Materials research on new oxygen ion conducting conductors both for applications in oxygen sensors and in fuel was also performed in this project and finally a new process was developed for fabrication of ceramic tubes by dip-coating. (EHS)

  15. Implementation of a Wavefront-Sensing Algorithm

    Science.gov (United States)

    Smith, Jeffrey S.; Dean, Bruce; Aronstein, David

    2013-01-01

    A computer program has been written as a unique implementation of an image-based wavefront-sensing algorithm reported in "Iterative-Transform Phase Retrieval Using Adaptive Diversity" (GSC-14879-1), NASA Tech Briefs, Vol. 31, No. 4 (April 2007), page 32. This software was originally intended for application to the James Webb Space Telescope, but is also applicable to other segmented-mirror telescopes. The software is capable of determining optical-wavefront information using, as input, a variable number of irradiance measurements collected in defocus planes about the best focal position. The software also uses input of the geometrical definition of the telescope exit pupil (otherwise denoted the pupil mask) to identify the locations of the segments of the primary telescope mirror. From the irradiance data and mask information, the software calculates an estimate of the optical wavefront (a measure of performance) of the telescope generally and across each primary mirror segment specifically. The software is capable of generating irradiance data, wavefront estimates, and basis functions for the full telescope and for each primary-mirror segment. Optionally, each of these pieces of information can be measured or computed outside of the software and incorporated during execution of the software.

  16. MORPHOLOGICAL DESCRIPTIONS USING THREE-DIMENSIONAL WAVEFRONTS

    Directory of Open Access Journals (Sweden)

    Jean Serra

    2011-05-01

    Full Text Available The present study deals with the analysis of three-dimensional binary objects whose structure is not obvious nor generally clearly visible. Our approach is illustrated through three examples taken from biological microscopy. In one of our examples, we need to extract the osteocytes contained in sixty confocal sections. The cells are not numerous, but are characterized by long branches, hence they will be separated using a directional wavefront The two other objects are more complex and will be analysed by means of a spherical wavefront In the first case, a kidney of a rat embryo, the tissue grows like a tree, where we want to detect the branches, their extremities,and their spatial arrangement. The wavefront method enables us to define precisely branches and extremities, and gives flexible algorithms. The last example deals with the embryonic growth of the chicken shinbone. The central part of the bone (or shaft is structured as a series of nested cylinders following the same axis, and connected by more or less long bridges. Using wavefronts, we show that it is possible to separate the cylinders,and to extract and count the bridges that connect them.

  17. Measurement of wavefront aberrations in cortex and peripheral nerve using a two-photon excitation guidestar

    Science.gov (United States)

    Futia, Gregory L.; Fontaine, Arjun; McCullough, Connor; Ozbay, Baris N.; George, Nickolas M.; Caldwell, John; Restrepo, Diego; Weir, Richard; Gibson, Emily A.

    2018-02-01

    Neural-machine interfaces using optogenetics are of interest due to their minimal invasiveness and potential for parallel read in and read out of activity. One possible biological target for such an interface is the peripheral nerve, where axonlevel imaging or stimulation could greatly improve interfacing with artificial limbs or enable neuron/fascicle level neuromodulation in the vagus nerve. Two-photon imaging has been successful in imaging brain activity using genetically encoded calcium or voltage indicators, but in the peripheral nerve, this is severely limited by scattering and aberrations from myelin. We employ a Shack-Hartman wavefront sensor and two-photon excitation guidestar to quantify optical scattering and aberrations in peripheral nerves and cortex. The sciatic and vagus nerves, and cortex from a ChAT-Cre ChR-eYFP transgenic mouse were excised and imaged directly. In peripheral nerves, defocus was the strongest aberration followed by astigmatism and coma. Peripheral nerve had orders of magnitude higher aberration compared with cortex. These results point to the potential of adaptive optics for increasing the depth of two-photon access into peripheral nerves.

  18. Intraocular straylight and contrast sensitivity after contralateral wavefront-guided LASIK and wavefront-guided PRK for myopia.

    Science.gov (United States)

    Barreto, Jackson; Barboni, Mirella T S; Feitosa-Santana, Claudia; Sato, João R; Bechara, Samir J; Ventura, Dora F; Alves, Milton Ruiz

    2010-08-01

    To compare intraocular straylight measurements and contrast sensitivity after wavefront-guided LASIK (WFG LASIK) in one eye and wavefront-guided photorefractive keratectomy (WFG PRK) in the fellow eye for myopia and myopic astigmatism correction. A prospective, randomized study of 22 eyes of 11 patients who underwent simultaneous WFG LASIK and WFG PRK (contralateral eye). Both groups were treated with the NIDEK Advanced Vision Excimer Laser System, and a microkeratome was used for flap creation in the WFG LASIK group. High and low contrast visual acuity, wavefront analysis, contrast sensitivity, and retinal straylight measurements were performed preoperatively and at 3, 6, and 12 months postoperatively. A third-generation straylight meter, C-Quant (Oculus Optikgeräte GmbH), was used for measuring intraocular straylight. Twelve months postoperatively, mean uncorrected distance visual acuity was -0.06 +/- 0.07 logMAR in the WFG LASIK group and -0.10 +/- 0.10 logMAR in the WFG PRK group. Mean preoperative intraocular straylight was 0.94 +/- 0.12 logs for the WFG LASIK group and 0.96 +/- 0.11 logs for the WFG PRK group. After 12 months, the mean straylight value was 1.01 +/- 0.1 log s for the WFG LASIK group and 0.97 +/- 0.12 log s for the WFG PRK group. No difference was found between techniques after 12 months (P = .306). No significant difference in photopic and mesopic contrast sensitivity between groups was noted. Intraocular straylight showed no statistically significant increase 1 year after WFG LASIK and WFG PRK. Higher order aberrations increased significantly after surgery for both groups. Nevertheless, WFG LASIK and WFG PRK yielded excellent visual acuity and contrast sensitivity performance without significant differences between techniques.

  19. An Efficient Pipeline Wavefront Phase Recovery for the CAFADIS Camera for Extremely Large Telescopes

    Directory of Open Access Journals (Sweden)

    Eduardo Magdaleno

    2009-12-01

    Full Text Available In this paper we show a fast, specialized hardware implementation of the wavefront phase recovery algorithm using the CAFADIS camera. The CAFADIS camera is a new plenoptic sensor patented by the Universidad de La Laguna (Canary Islands, Spain: international patent PCT/ES2007/000046 (WIPO publication number WO/2007/082975. It can simultaneously measure the wavefront phase and the distance to the light source in a real-time process. The pipeline algorithm is implemented using Field Programmable Gate Arrays (FPGA. These devices present architecture capable of handling the sensor output stream using a massively parallel approach and they are efficient enough to resolve several Adaptive Optics (AO problems in Extremely Large Telescopes (ELTs in terms of processing time requirements. The FPGA implementation of the wavefront phase recovery algorithm using the CAFADIS camera is based on the very fast computation of two dimensional fast Fourier Transforms (FFTs. Thus we have carried out a comparison between our very novel FPGA 2D-FFTa and other implementations.

  20. Hybrid wavefront sensing and image correction algorithm for imaging through turbulent media

    Science.gov (United States)

    Wu, Chensheng; Robertson Rzasa, John; Ko, Jonathan; Davis, Christopher C.

    2017-09-01

    It is well known that passive image correction of turbulence distortions often involves using geometry-dependent deconvolution algorithms. On the other hand, active imaging techniques using adaptive optic correction should use the distorted wavefront information for guidance. Our work shows that a hybrid hardware-software approach is possible to obtain accurate and highly detailed images through turbulent media. The processing algorithm also takes much fewer iteration steps in comparison with conventional image processing algorithms. In our proposed approach, a plenoptic sensor is used as a wavefront sensor to guide post-stage image correction on a high-definition zoomable camera. Conversely, we show that given the ground truth of the highly detailed image and the plenoptic imaging result, we can generate an accurate prediction of the blurred image on a traditional zoomable camera. Similarly, the ground truth combined with the blurred image from the zoomable camera would provide the wavefront conditions. In application, our hybrid approach can be used as an effective way to conduct object recognition in a turbulent environment where the target has been significantly distorted or is even unrecognizable.

  1. In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography.

    Science.gov (United States)

    Wong, Kevin S K; Jian, Yifan; Cua, Michelle; Bonora, Stefano; Zawadzki, Robert J; Sarunic, Marinko V

    2015-02-01

    Wavefront sensorless adaptive optics optical coherence tomography (WSAO-OCT) is a novel imaging technique for in vivo high-resolution depth-resolved imaging that mitigates some of the challenges encountered with the use of sensor-based adaptive optics designs. This technique replaces the Hartmann Shack wavefront sensor used to measure aberrations with a depth-resolved image-driven optimization algorithm, with the metric based on the OCT volumes acquired in real-time. The custom-built ultrahigh-speed GPU processing platform and fast modal optimization algorithm presented in this paper was essential in enabling real-time, in vivo imaging of human retinas with wavefront sensorless AO correction. WSAO-OCT is especially advantageous for developing a clinical high-resolution retinal imaging system as it enables the use of a compact, low-cost and robust lens-based adaptive optics design. In this report, we describe our WSAO-OCT system for imaging the human photoreceptor mosaic in vivo. We validated our system performance by imaging the retina at several eccentricities, and demonstrated the improvement in photoreceptor visibility with WSAO compensation.

  2. Clinical outcomes of wavefront-guided laser in situ keratomileusis: 6-month follow-up.

    Science.gov (United States)

    Aizawa, Daisuke; Shimizu, Kimiya; Komatsu, Mari; Ito, Misae; Suzuki, Masanobu; Ohno, Koji; Uozato, Hiroshi

    2003-08-01

    To evaluate the clinical outcomes 6 months after wavefront-guided laser in situ keratomileusis (LASIK) for myopia in Japan. Department of Ophthalmology, Sanno Hospital, Tokyo, Japan. This prospective study comprised 22 eyes of 12 patients treated with wavefront-guided LASIK who were available for evaluation at 6 months. The mean patient age was 31.2 years +/- 8.4 (SD) (range 23 to 50 years), and the mean preoperative spherical equivalent refraction was -7.30 +/- 2.72 diopters (D) (range -2.75 to -11.88 D). In all cases, preoperative wavefront analysis was performed with a Hartmann-Shack aberrometer and the Technolas 217z flying-spot excimer laser system (Bausch & Lomb) was used with 1.0 mm and 2.0 mm spot sizes and an active eye tracker with a 120 Hz tracking rate. The clinical outcomes of wavefront-guided LASIK were evaluated in terms of safety, efficacy, predictability, stability, complications, and preoperative and postoperative aberrations. At 6 months, 10 eyes had no change in best spectacle-correct visual acuity and 10 gained 1 or more lines. The safety index was 1.11 and the efficacy index, 0.82. Slight undercorrections were observed in highly myopic eyes. In all eyes, the postoperative refraction tended slightly toward myopia for 3 months and stabilized after that. No complication such as epithelial ingrowth, diffuse lamellar keratitis, or infection was observed. Comparison of the preoperative and postoperative aberrations showed that 2nd-order aberrations decreased and higher-order aberrations increased. In the 3rd order, aberrations increased in the high-myopia group (-6.0 D or worse) and decreased in the low to moderate-myopia group (better than -6.0 D). Wavefront-guided LASIK was a good option for refractive surgery, although a longer follow-up in a larger study is required.

  3. Wavefront analysis for plenoptic camera imaging

    International Nuclear Information System (INIS)

    Luan Yin-Sen; Xu Bing; Yang Ping; Tang Guo-Mao

    2017-01-01

    The plenoptic camera is a single lens stereo camera which can retrieve the direction of light rays while detecting their intensity distribution. In this paper, to reveal more truths of plenoptic camera imaging, we present the wavefront analysis for the plenoptic camera imaging from the angle of physical optics but not from the ray tracing model of geometric optics. Specifically, the wavefront imaging model of a plenoptic camera is analyzed and simulated by scalar diffraction theory and the depth estimation is redescribed based on physical optics. We simulate a set of raw plenoptic images of an object scene, thereby validating the analysis and derivations and the difference between the imaging analysis methods based on geometric optics and physical optics are also shown in simulations. (paper)

  4. Adaptable Diffraction Gratings With Wavefront Transformation

    Science.gov (United States)

    Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christoph M.

    2010-01-01

    Diffraction gratings are optical components with regular patterns of grooves, which angularly disperse incoming light by wavelength. Traditional diffraction gratings have static planar, concave, or convex surfaces. However, if they could be made so that they can change the surface curvature at will, then they would be able to focus on particular segments, self-calibrate, or perform fine adjustments. This innovation creates a diffraction grating on a deformable surface. This surface could be bent at will, resulting in a dynamic wavefront transformation. This allows for self-calibration, compensation for aberrations, enhancing image resolution in a particular area, or performing multiple scans using different wavelengths. A dynamic grating gives scientists a new ability to explore wavefronts from a variety of viewpoints.

  5. Dynamic wavefront creation for processing units using a hybrid compactor

    Energy Technology Data Exchange (ETDEWEB)

    Puthoor, Sooraj; Beckmann, Bradford M.; Yudanov, Dmitri

    2018-02-20

    A method, a non-transitory computer readable medium, and a processor for repacking dynamic wavefronts during program code execution on a processing unit, each dynamic wavefront including multiple threads are presented. If a branch instruction is detected, a determination is made whether all wavefronts following a same control path in the program code have reached a compaction point, which is the branch instruction. If no branch instruction is detected in executing the program code, a determination is made whether all wavefronts following the same control path have reached a reconvergence point, which is a beginning of a program code segment to be executed by both a taken branch and a not taken branch from a previous branch instruction. The dynamic wavefronts are repacked with all threads that follow the same control path, if all wavefronts following the same control path have reached the branch instruction or the reconvergence point.

  6. Imprint-coating synthesis of selective functionalized ordered mesoporous sorbents for separation and sensors

    Science.gov (United States)

    Dai, Sheng; Burleigh, Mark C.; Shin, Yongsoon

    2001-01-01

    The present invention relates generally to mesoporous sorbent materials having high capacity, high selectivity, fast kinetics, and molecular recognition capability. The invention also relates to a process for preparing these mesoporous substrates through molecular imprinting techniques which differ from convention techniques in that a template molecule is bound to one end of bifunctional ligands to form a complex prior to binding of the bifunctional ligands to the substrate. The present invention also relates to methods of using the mesoporous sorbent materials, for example, in the separation of toxic metals from process effluents, paints, and other samples; detection of target molecules, such as amino acids, drugs, herbicides, fertilizers, and TNT, in samples; separation and/or detection of substances using chromatography; imaging agents; sensors; coatings; and composites.

  7. JWFront: Wavefronts and Light Cones for Kerr Spacetimes

    Science.gov (United States)

    Frutos Alfaro, Francisco; Grave, Frank; Müller, Thomas; Adis, Daria

    2015-04-01

    JWFront visualizes wavefronts and light cones in general relativity. The interactive front-end allows users to enter the initial position values and choose the values for mass and angular momentum per unit mass. The wavefront animations are available in 2D and 3D; the light cones are visualized using the coordinate systems (t, x, y) or (t, z, x). JWFront can be easily modified to simulate wavefronts and light cones for other spacetime by providing the Christoffel symbols in the program.

  8. Study of wavefront aberration in DR patients with different degree of dry eye

    Directory of Open Access Journals (Sweden)

    Jin-Ran Fang

    2018-05-01

    Full Text Available AIM: To compare the changes of wavefront aberrations in patients with diabetic retinopathy(DRand with different degrees of dry eye and to explore the reasons of visual quality decline in them. METHODS: We randomly selected 40 eyes in our hospital for treatment with DR and varying degrees of dry eye, and 40 eyes of normal control group. Topcon KR-1W visual quality analyzer was used to record the mean square the total high order corneal aberration, spherical aberration, comatic aberration and trefoil aberration of cornea with pupil diameters of 4mm and 6mm. Analysis of variance were used to compare the wavefront aberrations and the aberration values in the control group and in patients with diabetic retinopathy and with different degrees of dry eye. RESULTS: For 4mm and 6mm pupil diameters, nondiabetic retinopathy(NDRwith dry eye group, the nonproliferative diabetic retinopathy(NPDRwith dry eye group and proliferative diabetic retinopathy(PDRdry eye group had significantly increased tHOA, coma and trefoil compared with the contrast group(PPCONCLUSION: Dry eye of diabetic retinopathy with different degrees is closely related to the increase of wavefront aberration. Increased wavefront aberration may be one of the reasons to reduced visual quality in patients with diabetic retinopathy and with dry eye, and provide the basis for the decline of visual function of diabetic patients with dry eye.

  9. Towards Sensor-Actuator Coupling in an Automated Order Picking System by Detecting Sealed Seams on Pouch Packed Goods

    Directory of Open Access Journals (Sweden)

    Frank Weichert

    2014-10-01

    Full Text Available In this paper, a novel concept of coupling the actuators of an automated order picking system for pouch packed goods with an embedded CCD camera sensor by means of image processing and machine learning is presented. The picking system mechanically combines the conveyance and singularization of a still-connected chain of pouch packed goods in a single machinery. The proposed algorithms perform a per-frame processing of the captured images in real-time to detect the sealed seams of the ongoing pouches. The detections are used to deduce cutting decisions in order to control the system’s actuators, namely the drive pulley for conveyance and the cutting device for the separation. Within this context, two controlling strategies are presented as well which specify the interaction of the sensor and the actuators. The detection is carried out by two different marker detection strategies: enhanced Template Matching as a heuristic and Support Vector Machines as a supervised classification based concept. Depending on the employed marker, detection rates of almost 100% with a calculation time of less than 40 ms are possible. From a logistic point of view, sealed seam widths of 20 mm prove feasible.

  10. Ultrahigh-sensitive multimode interference-based fiber optic liquid-level sensor realized using illuminating zero-order Bessel-Gauss beam

    Science.gov (United States)

    Saha, Ardhendu; Datta, Arijit; Kaman, Surjit

    2018-03-01

    A proposal toward the enhancement in the sensitivity of a multimode interference-based fiber optic liquid-level sensor is explored analytically using a zero-order Bessel-Gauss (BG) beam as the input source. The sensor head consists of a suitable length of no-core fiber (NCF) sandwiched between two specialty high-order mode fibers. The coupling efficiency of various order modes inside the sensor structure is assessed using guided-mode propagation analysis and the performance of the proposed sensor has been benchmarked against the conventional sensor using a Gaussian beam. Furthermore, the study has been corroborated using a finite-difference beam propagation method in Lumerical's Mode Solutions software to investigate the propagation of the zero-order BG beam inside the sensor structure. Based on the simulation outcomes, the proposed scheme yields a maximum absolute sensitivity of up to 3.551 dB / mm and a sensing resolution of 2.816 × 10 - 3 mm through the choice of an appropriate length of NCF at an operating wavelength of 1.55 μm. Owing to this superior sensing performance, the reported sensing technology expedites an avenue to devise a high-performance fiber optic-level sensor that finds profound implication in different physical, biological, and chemical sensing purposes.

  11. Fusion of adaptive beam steering and optimization-based wavefront control for laser communications in atmosphere

    Science.gov (United States)

    Nikulin, Vladimir V.

    2005-10-01

    The performance of mobile laser communication systems operating within Earth's atmosphere is generally limited by the pointing errors due to movement of the platforms and mechanical vibrations. In addition, atmospheric turbulence causes changes of the refractive index along the propagation path, creating random redistribution of the optical energy in the spatial domain. Under adverse conditions these effects lead to increased bit error rate. While traditional approaches provide separate treatment of these problems, suggesting high-bandwidth beam steering systems for tracking and wavefront control for the mitigation of atmospheric effects, the two tasks can be integrated. This paper presents a hybrid laser beam-steering-wavefront-control system comprising an electrically addressed spatial light modulator (SLM) installed on the Omni-Wrist sensor mount. The function of the Omni-Wrist is to provide coarse steering over a wide range of pointing angles, while that of the SLM is twofold: wavefront correction and fine steering. The control law for the Omni-Wrist is synthesized using a decentralized approach that provides independent access to the azimuth and declination channels; calculation of the required phase profile for the SLM is optimization-based. This paper presents the control algorithms, the approach to coordinating the operation of the two systems, and the results.

  12. High-resolution wavefront control of high-power laser systems

    International Nuclear Information System (INIS)

    Brase, J.; Brown, C.; Carrano, C.; Kartz, M.; Olivier, S.; Pennington, D.; Silva, D.

    1999-01-01

    Nearly every new large-scale laser system application at LLNL has requirements for beam control which exceed the current level of available technology. For applications such as inertial confinement fusion, laser isotope separation, laser machining, and laser the ability to transport significant power to a target while maintaining good beam quality is critical. There are many ways that laser wavefront quality can be degraded. Thermal effects due to the interaction of high-power laser or pump light with the internal optical components or with the ambient gas are common causes of wavefront degradation. For many years, adaptive optics based on thing deformable glass mirrors with piezoelectric or electrostrictive actuators have be used to remove the low-order wavefront errors from high-power laser systems. These adaptive optics systems have successfully improved laser beam quality, but have also generally revealed additional high-spatial-frequency errors, both because the low-order errors have been reduced and because deformable mirrors have often introduced some high-spatial-frequency components due to manufacturing errors. Many current and emerging laser applications fall into the high-resolution category where there is an increased need for the correction of high spatial frequency aberrations which requires correctors with thousands of degrees of freedom. The largest Deformable Mirrors currently available have less than one thousand degrees of freedom at a cost of approximately $1M. A deformable mirror capable of meeting these high spatial resolution requirements would be cost prohibitive. Therefore a new approach using a different wavefront control technology is needed. One new wavefront control approach is the use of liquid-crystal (LC) spatial light modulator (SLM) technology for the controlling the phase of linearly polarized light. Current LC SLM technology provides high-spatial-resolution wavefront control, with hundreds of thousands of degrees of freedom, more

  13. Conical wavefronts in optics and tomography

    International Nuclear Information System (INIS)

    Soroko, L.M.

    1990-01-01

    A wide range of techniques in which the information is transferred by conical (nonspherical and nonplanar) wave fronts is considered. This is the first summary of papers published in the field of mesooptics and optical tomography. After the introduction into the new branch of modern optics - mesooptics -the properties of conical wavefronts are treated in detail. Some possible applications of mesooptics in science and technology are considered. The long history of mesooptics treated in the last chapter of this review lecture goes from the early stage of our Universe, gravitational lens, first publications in the last century and up-to-date innovations in optics, mesooptics and optical tomography. 3 refs

  14. Sensor

    OpenAIRE

    Gleeson, Helen; Dierking, Ingo; Grieve, Bruce; Woodyatt, Christopher; Brimicombe, Paul

    2015-01-01

    An electrical temperature sensor (10) comprises a liquid crystalline material (12). First and second electrically conductive contacts (14), (16), having a spaced relationship there between, contact the liquid crystalline material (12). An electric property measuring device is electrically connected to the first and second contacts (14), (16) and is arranged to measure an electric property of the liquid crystalline material (12). The liquid crystalline material (12) has a transition temperatur...

  15. Wavefront correction performed by a deformable mirror of arbitrary actuator pattern within a multireflection waveguide.

    Science.gov (United States)

    Ma, Xingkun; Huang, Lei; Bian, Qi; Gong, Mali

    2014-09-10

    The wavefront correction ability of a deformable mirror with a multireflection waveguide was investigated and compared via simulations. By dividing a conventional actuator array into a multireflection waveguide that consisted of single-actuator units, an arbitrary actuator pattern could be achieved. A stochastic parallel perturbation algorithm was proposed to find the optimal actuator pattern for a particular aberration. Compared with conventional an actuator array, the multireflection waveguide showed significant advantages in correction of higher order aberrations.

  16. Numerical evaluation of the intensity transport equation for well-known wavefronts and intensity distributions

    Science.gov (United States)

    Campos-García, Manuel; Granados-Agustín, Fermín.; Cornejo-Rodríguez, Alejandro; Estrada-Molina, Amilcar; Avendaño-Alejo, Maximino; Moreno-Oliva, Víctor Iván.

    2013-11-01

    In order to obtain a clearer interpretation of the Intensity Transport Equation (ITE), in this work, we propose an algorithm to solve it for some particular wavefronts and its corresponding intensity distributions. By simulating intensity distributions in some planes, the ITE is turns into a Poisson equation with Neumann boundary conditions. The Poisson equation is solved by means of the iterative algorithm SOR (Simultaneous Over-Relaxation).

  17. Propagation and wavefront ambiguity of linear nondiffracting beams

    Science.gov (United States)

    Grunwald, R.; Bock, M.

    2014-02-01

    Ultrashort-pulsed Bessel and Airy beams in free space are often interpreted as "linear light bullets". Usually, interconnected intensity profiles are considered a "propagation" along arbitrary pathways which can even follow curved trajectories. A more detailed analysis, however, shows that this picture gives an adequate description only in situations which do not require to consider the transport of optical signals or causality. To also cover these special cases, a generalization of the terms "beam" and "propagation" is necessary. The problem becomes clearer by representing the angular spectra of the propagating wave fields by rays or Poynting vectors. It is known that quasi-nondiffracting beams can be described as caustics of ray bundles. Their decomposition into Poynting vectors by Shack-Hartmann sensors indicates that, in the frame of their classical definition, the corresponding local wavefronts are ambiguous and concepts based on energy density are not appropriate to describe the propagation completely. For this reason, quantitative parameters like the beam propagation factor have to be treated with caution as well. For applications like communication or optical computing, alternative descriptions are required. A heuristic approach based on vector field based information transport and Fourier analysis is proposed here. Continuity and discontinuity of far field distributions in space and time are discussed. Quantum aspects of propagation are briefly addressed.

  18. Geometry of fast magnetosonic rays, wavefronts and shock waves

    Energy Technology Data Exchange (ETDEWEB)

    Núñez, Manuel, E-mail: mnjmhd@am.uva.es

    2016-11-25

    Fast magnetosonic waves in a two-dimensional plasma are studied in the geometrical optics approximation. The geometry of rays and wavefronts influences decisively the formation and ulterior evolution of shock waves. It is shown that the curvature of the curve where rays start and the angle between rays and wavefronts are the main parameters governing a wide variety of possible outcomes. - Highlights: • Magnetosonic waves are studied in a genuinely multidimensional setting. • Curvature and the angle between rays and wavefronts are the main parameters. • Shock waves may exist or not, depending on initial conditions. • Both velocity and shape of those waves present a large variety of possible outcomes.

  19. Manipulation of wavefront using helical metamaterials.

    Science.gov (United States)

    Yang, Zhenyu; Wang, Zhaokun; Tao, Huan; Zhao, Ming

    2016-08-08

    Helical metamaterials, a kind of 3-dimensional structure, has relatively strong coupling effect among the helical nano-wires. Therefore, it is expected to be a good candidate for generating phase shift and controlling wavefront with high efficiency. In this paper, using the finite-difference time-domain (FDTD) method, we studied the phase shift properties in the helical metamaterials. It is found that the phase shift occurs for both transmitted and reflected light waves. And the maximum of reflection coefficients can reach over 60%. In addition, the phase shift (φ) is dispersionless in the range of 600 nm to 860 nm, that is, it is only dominated by the initial angle (θ) of the helix. The relationship between them is φ = ± 2θ. Using Jones calculus we give a further explanation for these properties. Finally, by arranging the helixes in an array with a constant phase gradient, the phenomenon of anomalous refraction was also observed in a broad wavelength range.

  20. Wavefront measurement using computational adaptive optics.

    Science.gov (United States)

    South, Fredrick A; Liu, Yuan-Zhi; Bower, Andrew J; Xu, Yang; Carney, P Scott; Boppart, Stephen A

    2018-03-01

    In many optical imaging applications, it is necessary to correct for aberrations to obtain high quality images. Optical coherence tomography (OCT) provides access to the amplitude and phase of the backscattered optical field for three-dimensional (3D) imaging samples. Computational adaptive optics (CAO) modifies the phase of the OCT data in the spatial frequency domain to correct optical aberrations without using a deformable mirror, as is commonly done in hardware-based adaptive optics (AO). This provides improvement of image quality throughout the 3D volume, enabling imaging across greater depth ranges and in highly aberrated samples. However, the CAO aberration correction has a complicated relation to the imaging pupil and is not a direct measurement of the pupil aberrations. Here we present new methods for recovering the wavefront aberrations directly from the OCT data without the use of hardware adaptive optics. This enables both computational measurement and correction of optical aberrations.

  1. Method and apparatus for wavefront sensing

    Science.gov (United States)

    Bahk, Seung-Whan

    2018-03-20

    A method for performing optical wavefront sensing includes providing an amplitude transmission mask having a light input side, a light output side, and an optical transmission axis passing from the light input side to the light output side. The amplitude transmission mask is characterized by a checkerboard pattern having a square unit cell of size .LAMBDA.. The method also includes directing an incident light field having a wavelength $ \\lamda $ to be incident on the light input side and propagating the incident light field through the amplitude transmission mask. The method further includes producing a plurality of diffracted light fields on the light output side and detecting, at a detector disposed a distance L from the amplitude transmission mask, an interferogram associated with the plurality of diffracted light fields.

  2. Authentication via wavefront-shaped optical responses

    Science.gov (United States)

    Eilers, Hergen; Anderson, Benjamin R.; Gunawidjaja, Ray

    2018-02-01

    Authentication/tamper-indication is required in a wide range of applications, including nuclear materials management and product counterfeit detection. State-of-the-art techniques include reflective particle tags, laser speckle authentication, and birefringent seals. Each of these passive techniques has its own advantages and disadvantages, including the need for complex image comparisons, limited flexibility, sensitivity to environmental conditions, limited functionality, etc. We have developed a new active approach to address some of these short-comings. The use of an active characterization technique adds more flexibility and additional layers of security over current techniques. Our approach uses randomly-distributed nanoparticles embedded in a polymer matrix (tag/seal) which is attached to the item to be secured. A spatial light modulator is used to adjust the wavefront of a laser which interacts with the tag/seal, and a detector is used to monitor this interaction. The interaction can occur in various ways, including transmittance, reflectance, fluorescence, random lasing, etc. For example, at the time of origination, the wavefront-shaped reflectance from a tag/seal can be adjusted to result in a specific pattern (symbol, words, etc.) Any tampering with the tag/seal would results in a disturbance of the random orientation of the nanoparticles and thus distort the reflectance pattern. A holographic waveplate could be inserted into the laser beam for verification. The absence/distortion of the original pattern would then indicate that tampering has occurred. We have tested the tag/seal's and authentication method's tamper-indicating ability using various attack methods, including mechanical, thermal, and chemical attacks, and have verified our material/method's robust tamper-indicating ability.

  3. Space-Variant Post-Filtering for Wavefront Curvature Correction in Polar-Formatted Spotlight-Mode SAR Imagery

    Energy Technology Data Exchange (ETDEWEB)

    DOREN,NEALL E.

    1999-10-01

    Wavefront curvature defocus effects occur in spotlight-mode SAR imagery when reconstructed via the well-known polar-formatting algorithm (PFA) under certain imaging scenarios. These include imaging at close range, using a very low radar center frequency, utilizing high resolution, and/or imaging very large scenes. Wavefront curvature effects arise from the unrealistic assumption of strictly planar wavefronts illuminating the imaged scene. This dissertation presents a method for the correction of wavefront curvature defocus effects under these scenarios, concentrating on the generalized: squint-mode imaging scenario and its computational aspects. This correction is accomplished through an efficient one-dimensional, image domain filter applied as a post-processing step to PF.4. This post-filter, referred to as SVPF, is precalculated from a theoretical derivation of the wavefront curvature effect and varies as a function of scene location. Prior to SVPF, severe restrictions were placed on the imaged scene size in order to avoid defocus effects under these scenarios when using PFA. The SVPF algorithm eliminates the need for scene size restrictions when wavefront curvature effects are present, correcting for wavefront curvature in broadside as well as squinted collection modes while imposing little additional computational penalty for squinted images. This dissertation covers the theoretical development, implementation and analysis of the generalized, squint-mode SVPF algorithm (of which broadside-mode is a special case) and provides examples of its capabilities and limitations as well as offering guidelines for maximizing its computational efficiency. Tradeoffs between the PFA/SVPF combination and other spotlight-mode SAR image formation techniques are discussed with regard to computational burden, image quality, and imaging geometry constraints. It is demonstrated that other methods fail to exhibit a clear computational advantage over polar-formatting in conjunction

  4. High precision wavefront control in point spread function engineering for single emitter localization

    Science.gov (United States)

    Siemons, M.; Hulleman, C. N.; Thorsen, R. Ø.; Smith, C. S.; Stallinga, S.

    2018-04-01

    Point Spread Function (PSF) engineering is used in single emitter localization to measure the emitter position in 3D and possibly other parameters such as the emission color or dipole orientation as well. Advanced PSF models such as spline fits to experimental PSFs or the vectorial PSF model can be used in the corresponding localization algorithms in order to model the intricate spot shape and deformations correctly. The complexity of the optical architecture and fit model makes PSF engineering approaches particularly sensitive to optical aberrations. Here, we present a calibration and alignment protocol for fluorescence microscopes equipped with a spatial light modulator (SLM) with the goal of establishing a wavefront error well below the diffraction limit for optimum application of complex engineered PSFs. We achieve high-precision wavefront control, to a level below 20 m$\\lambda$ wavefront aberration over a 30 minute time window after the calibration procedure, using a separate light path for calibrating the pixel-to-pixel variations of the SLM, and alignment of the SLM with respect to the optical axis and Fourier plane within 3 $\\mu$m ($x/y$) and 100 $\\mu$m ($z$) error. Aberrations are retrieved from a fit of the vectorial PSF model to a bead $z$-stack and compensated with a residual wavefront error comparable to the error of the SLM calibration step. This well-calibrated and corrected setup makes it possible to create complex `3D+$\\lambda$' PSFs that fit very well to the vectorial PSF model. Proof-of-principle bead experiments show precisions below 10~nm in $x$, $y$, and $\\lambda$, and below 20~nm in $z$ over an axial range of 1 $\\mu$m with 2000 signal photons and 12 background photons.

  5. Parallel-Computing Architecture for JWST Wavefront-Sensing Algorithms

    Science.gov (United States)

    2011-09-01

    results due to the increasing cost and complexity of each test. 2. ALGORITHM OVERVIEW Phase retrieval is an image-based wavefront-sensing...broadband illumination problems we have found that hand-tuning the right matrix sizes can account for a speedup of 86x faster. This comes from hand-picking...Wavefront Sensing and Control”. Proceedings of SPIE (2007) vol. 6687 (08). [5] Greenhouse, M. A., Drury , M. P., Dunn, J. L., Glazer, S. D., Greville, E

  6. Design and realization of adaptive optical principle system without wavefront sensing

    Science.gov (United States)

    Wang, Xiaobin; Niu, Chaojun; Guo, Yaxing; Han, Xiang'e.

    2018-02-01

    In this paper, we focus on the performance improvement of the free space optical communication system and carry out the research on wavefront-sensorless adaptive optics. We use a phase only liquid crystal spatial light modulator (SLM) as the wavefront corrector. The optical intensity distribution of the distorted wavefront is detected by a CCD. We develop a wavefront controller based on ARM and a software based on the Linux operating system. The wavefront controller can control the CCD camera and the wavefront corrector. There being two SLMs in the experimental system, one simulates atmospheric turbulence and the other is used to compensate the wavefront distortion. The experimental results show that the performance quality metric (the total gray value of 25 pixels) increases from 3037 to 4863 after 200 iterations. Besides, it is demonstrated that our wavefront-sensorless adaptive optics system based on SPGD algorithm has a good performance in compensating wavefront distortion.

  7. Asymmetric wavefront aberrations and pupillary shapes induced by electrical stimulation of ciliary nerve in cats measured with compact wavefront aberrometer.

    Directory of Open Access Journals (Sweden)

    Suguru Miyagawa

    Full Text Available To investigate the changes in the wavefront aberrations and pupillary shape in response to electrical stimulation of the branches of the ciliary nerves in cats. Seven eyes of seven cats were studied under general anesthesia. Trains of monophasic pulses (current, 0.1 to 1.0 mA; duration, 0.5 ms/phase; frequency, 5 to 40 Hz were applied to the lateral or medial branch of the short ciliary nerve near the posterior pole of the eye. A pair of electrodes was hooked onto one or both branch of the short ciliary nerve. The electrodes were placed about 5 mm from the scleral surface. The wavefront aberrations were recorded continuously for 2 seconds before, 8 seconds during, and for 20 seconds after the electrical stimulation. The pupillary images were simultaneously recorded during the stimulation period. Both the wavefront aberrations and the pupillary images were obtained 10 times/sec with a custom-built wavefront aberrometer. The maximum accommodative amplitude was 1.19 diopters (D produced by electrical stimulation of the short ciliary nerves. The latency of the accommodative changes was very short, and the accommodative level gradually increased up to 4 seconds and reached a plateau. When only one branch of the ciliary nerve was stimulated, the pupil dilated asymmetrically, and the oblique astigmatism and one of the asymmetrical wavefront terms was also altered. Our results showed that the wavefront aberrations and pupillary dilations can be measured simultaneously and serially with a compact wavefront aberrometer. The asymmetric pupil dilation and asymmetric changes of the wavefront aberrations suggest that each branch of the ciliary nerve innervates specific segments of the ciliary muscle and dilator muscle of the pupil.

  8. Illumination of the Spatial Order of Intracellular pH by Genetically Encoded pH-Sensitive Sensors

    Directory of Open Access Journals (Sweden)

    Mojca Benčina

    2013-12-01

    Full Text Available Fluorescent proteins have been extensively used for engineering genetically encoded sensors that can monitor levels of ions, enzyme activities, redox potential, and metabolites. Certain fluorescent proteins possess specific pH-dependent spectroscopic features, and thus can be used as indicators of intracellular pH. Moreover, concatenated pH-sensitive proteins with target proteins pin the pH sensors to a definite location within the cell, compartment, or tissue. This study provides an overview of the continually expanding family of pH-sensitive fluorescent proteins that have become essential tools for studies of pH homeostasis and cell physiology. We describe and discuss the design of intensity-based and ratiometric pH sensors, their spectral properties and pH-dependency, as well as their performance. Finally, we illustrate some examples of the applications of pH sensors targeted at different subcellular compartments.

  9. Fabrication of Well-Ordered Three-Phase Boundary with Nanostructure Pore Array for Mixed Potential-Type Zirconia-Based NO2 Sensor.

    Science.gov (United States)

    Wang, Bin; Liu, Fangmeng; Yang, Xue; Guan, Yehui; Ma, Ce; Hao, Xidong; Liang, Xishuang; Liu, Fengmin; Sun, Peng; Zhang, Tong; Lu, Geyu

    2016-07-06

    A well-ordered porous three-phase boundary (TPB) was prepared with a polystyrene sphere as template and examined to improve the sensitivity of yttria-stabilized zirconia (YSZ)-based mixed-potential-type NO2 sensor due to the increase of the electrochemical reaction active sites. The shape of pore array on the YSZ substrate surface can be controlled through changing the concentration of the precursor solution (Zr(4+)/Y(3+) = 23 mol/L/4 mol/L) and treatment conditions. An ordered hemispherical array was obtained when CZr(4+) = 0.2 mol/L. The processed YSZ substrates were used to fabricate the sensors, and different sensitivities caused by different morphologies were tested. The sensor with well-ordered porous TPB exhibited the highest sensitivity to NO2 with a response value of 105 mV to 100 ppm of NO2, which is approximately twice as much as the smooth one. In addition, the sensor also showed good stability and speedy response kinetics. All these enhanced sensing properties might be due to the structure and morphology of the enlarged TPB.

  10. Design and implementation of a scene-dependent dynamically selfadaptable wavefront coding imaging system

    Science.gov (United States)

    Carles, Guillem; Ferran, Carme; Carnicer, Artur; Bosch, Salvador

    2012-01-01

    A computational imaging system based on wavefront coding is presented. Wavefront coding provides an extension of the depth-of-field at the expense of a slight reduction of image quality. This trade-off results from the amount of coding used. By using spatial light modulators, a flexible coding is achieved which permits it to be increased or decreased as needed. In this paper a computational method is proposed for evaluating the output of a wavefront coding imaging system equipped with a spatial light modulator, with the aim of thus making it possible to implement the most suitable coding strength for a given scene. This is achieved in an unsupervised manner, thus the whole system acts as a dynamically selfadaptable imaging system. The program presented here controls the spatial light modulator and the camera, and also processes the images in a synchronised way in order to implement the dynamic system in real time. A prototype of the system was implemented in the laboratory and illustrative examples of the performance are reported in this paper. Program summaryProgram title: DynWFC (Dynamic WaveFront Coding) Catalogue identifier: AEKC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 10 483 No. of bytes in distributed program, including test data, etc.: 2 437 713 Distribution format: tar.gz Programming language: Labview 8.5 and NI Vision and MinGW C Compiler Computer: Tested on PC Intel ® Pentium ® Operating system: Tested on Windows XP Classification: 18 Nature of problem: The program implements an enhanced wavefront coding imaging system able to adapt the degree of coding to the requirements of a specific scene. The program controls the acquisition by a camera, the display of a spatial light modulator

  11. Beam geometry, alignment, and wavefront aberration effects on interferometric differential wavefront sensing

    International Nuclear Information System (INIS)

    Yu, Xiangzhi; Gillmer, S R; Ellis, J D

    2015-01-01

    Heterodyne interferometry is a widely accepted methodology with high resolution in many metrology applications. As a functionality enhancement, differential wavefront sensing (DWS) enables simultaneous measurement of displacement, pitch, and yaw using a displacement interferometry system and a single beam incident on a plane mirror target. The angular change is measured using a weighted phase average between symmetrically adjacent quadrant photodiode pairs. In this paper, we present an analytical model to predict the scaling of differential phase signals based on fundamental Gaussian beams. Several numerical models are presented to discuss the effects of physical beam parameters, detector size, system alignment errors, and beam wavefront aberrations on the DWS technique. The results of our modeling predict rotational scaling factors and a usable linear range. Furthermore, experimental results show the analytically predicted scaling factor is in good agreement with empirical calibration. Our three degree-of-freedom interferometer can achieve a resolution of 0.4 nm in displacement and 0.2 μrad in pitch and yaw simultaneously. (paper)

  12. Spatial-temporal-covariance-based modeling, analysis, and simulation of aero-optics wavefront aberrations.

    Science.gov (United States)

    Vogel, Curtis R; Tyler, Glenn A; Wittich, Donald J

    2014-07-01

    We introduce a framework for modeling, analysis, and simulation of aero-optics wavefront aberrations that is based on spatial-temporal covariance matrices extracted from wavefront sensor measurements. Within this framework, we present a quasi-homogeneous structure function to analyze nonhomogeneous, mildly anisotropic spatial random processes, and we use this structure function to show that phase aberrations arising in aero-optics are, for an important range of operating parameters, locally Kolmogorov. This strongly suggests that the d5/3 power law for adaptive optics (AO) deformable mirror fitting error, where d denotes actuator separation, holds for certain important aero-optics scenarios. This framework also allows us to compute bounds on AO servo lag error and predictive control error. In addition, it provides us with the means to accurately simulate AO systems for the mitigation of aero-effects, and it may provide insight into underlying physical processes associated with turbulent flow. The techniques introduced here are demonstrated using data obtained from the Airborne Aero-Optics Laboratory.

  13. Phase Diversity Wavefront Sensing for Control of Space Based Adaptive Optics Systems

    National Research Council Canada - National Science Library

    Schgallis, Richard J

    2007-01-01

    Phase Diversity Wavefront Sensing (PD WFS) is a wavefront reconstruction technique used in adaptive optics, which takes advantage of the curvature conjugating analog physical properties of a deformable mirror (MMDM or Bi-morph...

  14. Iterative-Transform Phase Diversity: An Object and Wavefront Recovery Algorithm

    Science.gov (United States)

    Smith, J. Scott

    2011-01-01

    Presented is a solution for recovering the wavefront and an extended object. It builds upon the VSM architecture and deconvolution algorithms. Simulations are shown for recovering the wavefront and extended object from noisy data.

  15. Wavefront Tilt And Beam Walk Correction For A Pulsed Laser System

    Science.gov (United States)

    Bartosewcz, Mike; Tyburski, Joe

    1986-05-01

    The Lockheed Beam Alignment Assembly (BAA) is designed to be a space qualifiable, long life, low bandwidth beam stabilization system. The BAA will stabilize a wandering pulsed laser beam with an input beam tilt of ±750 microradians and translation of ±2.5 mm by two orders of magnitude at the bandwidth of interest. A bandwidth of three hertz was selected to remove laser and optical train thermal drifts and launch induced strain effects. The lambda over twenty RMS wavefront will be maintained in the optics at full power under vacuum test, to demonstrate space qualifiability and optical performance.

  16. Traveling wavefront solutions to nonlinear reaction-diffusion-convection equations

    International Nuclear Information System (INIS)

    Indekeu, Joseph O; Smets, Ruben

    2017-01-01

    Physically motivated modified Fisher equations are studied in which nonlinear convection and nonlinear diffusion is allowed for besides the usual growth and spread of a population. It is pointed out that in a large variety of cases separable functions in the form of exponentially decaying sharp wavefronts solve the differential equation exactly provided a co-moving point source or sink is active at the wavefront. The velocity dispersion and front steepness may differ from those of some previously studied exact smooth traveling wave solutions. For an extension of the reaction-diffusion-convection equation, featuring a memory effect in the form of a maturity delay for growth and spread, also smooth exact wavefront solutions are obtained. The stability of the solutions is verified analytically and numerically. (paper)

  17. Traveling wavefront solutions to nonlinear reaction-diffusion-convection equations

    Science.gov (United States)

    Indekeu, Joseph O.; Smets, Ruben

    2017-08-01

    Physically motivated modified Fisher equations are studied in which nonlinear convection and nonlinear diffusion is allowed for besides the usual growth and spread of a population. It is pointed out that in a large variety of cases separable functions in the form of exponentially decaying sharp wavefronts solve the differential equation exactly provided a co-moving point source or sink is active at the wavefront. The velocity dispersion and front steepness may differ from those of some previously studied exact smooth traveling wave solutions. For an extension of the reaction-diffusion-convection equation, featuring a memory effect in the form of a maturity delay for growth and spread, also smooth exact wavefront solutions are obtained. The stability of the solutions is verified analytically and numerically.

  18. Statistical learning methods for aero-optic wavefront prediction and adaptive-optic latency compensation

    Science.gov (United States)

    Burns, W. Robert

    Since the early 1970's research in airborne laser systems has been the subject of continued interest. Airborne laser applications depend on being able to propagate a near diffraction-limited laser beam from an airborne platform. Turbulent air flowing over the aircraft produces density fluctuations through which the beam must propagate. Because the index of refraction of the air is directly related to the density, the turbulent flow imposes aberrations on the beam passing through it. This problem is referred to as Aero-Optics. Aero-Optics is recognized as a major technical issue that needs to be solved before airborne optical systems can become routinely fielded. This dissertation research specifically addresses an approach to mitigating the deleterious effects imposed on an airborne optical system by aero-optics. A promising technology is adaptive optics: a feedback control method that measures optical aberrations and imprints the conjugate aberrations onto an outgoing beam. The challenge is that it is a computationally-difficult problem, since aero-optic disturbances are on the order of kilohertz for practical applications. High control loop frequencies and high disturbance frequencies mean that adaptive-optic systems are sensitive to latency in sensors, mirrors, amplifiers, and computation. These latencies build up to result in a dramatic reduction in the system's effective bandwidth. This work presents two variations of an algorithm that uses model reduction and data-driven predictors to estimate the evolution of measured wavefronts over a short temporal horizon and thus compensate for feedback latency. The efficacy of the two methods are compared in this research, and evaluated against similar algorithms that have been previously developed. The best version achieved over 75% disturbance rejection in simulation in the most optically active flow region in the wake of a turret, considerably outperforming conventional approaches. The algorithm is shown to be

  19. Broadband manipulation of acoustic wavefronts by pentamode metasurface

    International Nuclear Information System (INIS)

    Tian, Ye; Wei, Qi; Cheng, Ying; Xu, Zheng; Liu, Xiaojun

    2015-01-01

    An acoustic metasurface with a sub-wavelength thickness can manipulate acoustic wavefronts freely by the introduction of abrupt phase variation. However, the existence of a narrow bandwidth and a low transmittance limits further applications. Here, we present a broadband and highly transparent acoustic metasurface based on a frequency-independent generalized acoustic Snell's law and pentamode metamaterials. The proposal employs a gradient velocity to redirect refracted waves and pentamode metamaterials to improve impedance matching between the metasurface and the background medium. Excellent wavefront manipulation based on the metasurface is further demonstrated by anomalous refraction, generation of non-diffracting Bessel beam, and sub-wavelength flat focusing

  20. Focusing light through dynamical samples using fast continuous wavefront optimization.

    Science.gov (United States)

    Blochet, B; Bourdieu, L; Gigan, S

    2017-12-01

    We describe a fast continuous optimization wavefront shaping system able to focus light through dynamic scattering media. A micro-electro-mechanical system-based spatial light modulator, a fast photodetector, and field programmable gate array electronics are combined to implement a continuous optimization of a wavefront with a single-mode optimization rate of 4.1 kHz. The system performances are demonstrated by focusing light through colloidal solutions of TiO 2 particles in glycerol with tunable temporal stability.

  1. Evaluation of the True Wavefront Aberrations in Eyes Implanted With a Rotationally Asymmetric Multifocal Intraocular Lens.

    Science.gov (United States)

    Akondi, Vyas; Pérez-Merino, Pablo; Martinez-Enriquez, Eduardo; Dorronsoro, Carlos; Alejandre, Nicolás; Jiménez-Alfaro, Ignacio; Marcos, Susana

    2017-04-01

    Standard evaluation of aberrations from wavefront slope measurements in patients implanted with a rotationally asymmetric multifocal intraocular lens (IOL), the Lentis Mplus (Oculentis GmbH, Berlin, Germany), results in large magnitude primary vertical coma, which is attributed to the intrinsic IOL design. The new proposed method analyzes aberrometry data, allowing disentangling the IOL power pupillary distribution from the true higher order aberrations of the eye. The new method of wavefront reconstruction uses retinal spots obtained at both the near and far foci. The method was tested using ray tracing optical simulations in a computer eye model virtually implanted with the Lentis Mplus IOL, with a generic cornea or with anterior segment geometry obtained from custom quantitative spectral-domain optical coherence tomography in a real patient. The method was applied to laser ray tracing aberrometry data at near and far fixation obtained in a patient implanted with the Lentis Mplus IOL. Higher order aberrations evaluated from simulated and real retinal spot diagrams following the new reconstruction approach matched the nominal aberrations (approximately 98%). Previously reported primary vertical coma in patients implanted with this IOL lost significance with the application of the proposed reconstruction. Custom analysis of ray tracing-based retinal spot diagrams allowed decoupling of the true higher order aberrations of the patient's eye from the power pupillary distribution of a rotationally asymmetric multifocal IOL, therefore providing the appropriate phase map to accurately evaluate through-focus optical quality. [J Refract Surg. 2017;33(4):257-265.]. Copyright 2017, SLACK Incorporated.

  2. Enabling Super-Nyquist Wavefront Control on WFIRST

    Science.gov (United States)

    Bendek, Eduardo; Belikov, Ruslan; Sirbu, Dan; Shaklan, Stuart B.; Eldorado Riggs, A. J.

    2018-01-01

    A large fraction of sun-like stars is contained in Binary systems. Within 10pc there are 70 FGK stars from which, 43 belong to a multi-star system, and 28 of them have companion leak that is greater than 1e-9 contrast assuming typical Hubble-quality space optics. Currently, those binary stars are not included in the WFIRST-CGI target list, but they could be observed if high-contrast imaging around binary star systems using WFIRST is possible, increasing by 70% the number of possible FGK targets for the mission. The Multi-Star Wavefront Control (MSWC) algorithm can be used to suppress the companion star leakage. If the targets have angular separations larger than the Nyquist controllable region of the Deformable Mirror the MSWC must operate in its Super-Nyquist (SN) mode. This mode requires a target star replica within the SN region in order to provide the energy, and coherent light necessary to null speckles at SN angular separations. For the case of WFIRST, about half of the targets that can be observed using MSWC have angular separations larger than the Nyquist controllable region of the 48x48 actuator Deformable Mirror (DM) to be used. Here, we discuss multiple alternatives to generate those PSF replicas with minimal or no impact to the WFIRST Coronagraph instrument such as 1) the addition of a movable diffractive pupil mounted of the Shape Pupil wheel. 2) Design of a modified Shape Pupil design able to create a dark zone and at the same time diffract a small fraction of the starlight on the SN region. 3) Predict the minimum residual quilting on Xinetics DM that would allow observing a given target.

  3. Optical design of a novel instrument that uses the Hartmann-Shack sensor and Zernike polynomials to measure and simulate customized refraction correction surgery outcomes and patient satisfaction

    Science.gov (United States)

    Yasuoka, Fatima M. M.; Matos, Luciana; Cremasco, Antonio; Numajiri, Mirian; Marcato, Rafael; Oliveira, Otavio G.; Sabino, Luis G.; Castro N., Jarbas C.; Bagnato, Vanderlei S.; Carvalho, Luis A. V.

    2016-03-01

    An optical system that conjugates the patient's pupil to the plane of a Hartmann-Shack (HS) wavefront sensor has been simulated using optical design software. And an optical bench prototype is mounted using mechanical eye device, beam splitter, illumination system, lenses, mirrors, mirrored prism, movable mirror, wavefront sensor and camera CCD. The mechanical eye device is used to simulate aberrations of the eye. From this device the rays are emitted and travelled by the beam splitter to the optical system. Some rays fall on the camera CCD and others pass in the optical system and finally reach the sensor. The eye models based on typical in vivo eye aberrations is constructed using the optical design software Zemax. The computer-aided outcomes of each HS images for each case are acquired, and these images are processed using customized techniques. The simulated and real images for low order aberrations are compared using centroid coordinates to assure that the optical system is constructed precisely in order to match the simulated system. Afterwards a simulated version of retinal images is constructed to show how these typical eyes would perceive an optotype positioned 20 ft away. Certain personalized corrections are allowed by eye doctors based on different Zernike polynomial values and the optical images are rendered to the new parameters. Optical images of how that eye would see with or without corrections of certain aberrations are generated in order to allow which aberrations can be corrected and in which degree. The patient can then "personalize" the correction to their own satisfaction. This new approach to wavefront sensing is a promising change in paradigm towards the betterment of the patient-physician relationship.

  4. Design and Parametric Study of the Magnetic Sensor for Position Detection in Linear Motor Based on Nonlinear Parametric model order reduction.

    Science.gov (United States)

    Paul, Sarbajit; Chang, Junghwan

    2017-07-01

    This paper presents a design approach for a magnetic sensor module to detect mover position using the proper orthogonal decomposition-dynamic mode decomposition (POD-DMD)-based nonlinear parametric model order reduction (PMOR). The parameterization of the sensor module is achieved by using the multipolar moment matching method. Several geometric variables of the sensor module are considered while developing the parametric study. The operation of the sensor module is based on the principle of the airgap flux density distribution detection by the Hall Effect IC. Therefore, the design objective is to achieve a peak flux density (PFD) greater than 0.1 T and total harmonic distortion (THD) less than 3%. To fulfill the constraint conditions, the specifications for the sensor module is achieved by using POD-DMD based reduced model. The POD-DMD based reduced model provides a platform to analyze the high number of design models very fast, with less computational burden. Finally, with the final specifications, the experimental prototype is designed and tested. Two different modes, 90° and 120° modes respectively are used to obtain the position information of the linear motor mover. The position information thus obtained are compared with that of the linear scale data, used as a reference signal. The position information obtained using the 120° mode has a standard deviation of 0.10 mm from the reference linear scale signal, whereas the 90° mode position signal shows a deviation of 0.23 mm from the reference. The deviation in the output arises due to the mechanical tolerances introduced into the specification during the manufacturing process. This provides a scope for coupling the reliability based design optimization in the design process as a future extension.

  5. Predicting crystalline lens fall caused by accommodation from changes in wavefront error

    Science.gov (United States)

    He, Lin; Applegate, Raymond A.

    2011-01-01

    PURPOSE To illustrate and develop a method for estimating crystalline lens decentration as a function of accommodative response using changes in wavefront error and show the method and limitations using previously published data (2004) from 2 iridectomized monkey eyes so that clinicians understand how spherical aberration can induce coma, in particular in intraocular lens surgery. SETTINGS College of Optometry, University of Houston, Houston, USA. DESIGN Evaluation of diagnostic test or technology. METHODS Lens decentration was estimated by displacing downward the wavefront error of the lens with respect to the limiting aperture (7.0 mm) and ocular first surface wavefront error for each accommodative response (0.00 to 11.00 diopters) until measured values of vertical coma matched previously published experimental data (2007). Lens decentration was also calculated using an approximation formula that only included spherical aberration and vertical coma. RESULTS The change in calculated vertical coma was consistent with downward lens decentration. Calculated downward lens decentration peaked at approximately 0.48 mm of vertical decentration in the right eye and approximately 0.31 mm of decentration in the left eye using all Zernike modes through the 7th radial order. Calculated lens decentration using only coma and spherical aberration formulas was peaked at approximately 0.45 mm in the right eye and approximately 0.23 mm in the left eye. CONCLUSIONS Lens fall as a function of accommodation was quantified noninvasively using changes in vertical coma driven principally by the accommodation-induced changes in spherical aberration. The newly developed method was valid for a large pupil only. PMID:21700108

  6. Low-cost fabrication of highly sensitive room temperature hydrogen sensor based on ordered mesoporous Co-doped TiO2 structure

    Science.gov (United States)

    Li, Zhong; Haidry, Azhar Ali; Wang, Tao; Yao, Zheng Jun

    2017-07-01

    The development of cost-effective gas sensors with improved sensing properties and minimum power consumption for room temperature hydrogen leakage monitoring is in increasing demand. In this context, this report focus on the facile fabrication of ordered mesoporous TiO2 via evaporation-induced self-assembly route. With the controlled doping threshold (3%Co-TiO2), the output resistance change to 1000 ppm H2 is ˜4.1 × 103 with the response time of 66 s. The sensor response exhibits power law dependence with an increase in the hydrogen concentration, where the power law coefficient was found not only specific to the kind of target gas but also related to temperature. Further, the effect of structure integrity with doping level and humidity on sensing characteristics is interpreted in terms of variation in surface potential eVS and depletion region w caused by the adsorption of molecular oxygen O2-.

  7. Linear-constraint wavefront control for exoplanet coronagraphic imaging systems

    Science.gov (United States)

    Sun, He; Eldorado Riggs, A. J.; Kasdin, N. Jeremy; Vanderbei, Robert J.; Groff, Tyler Dean

    2017-01-01

    A coronagraph is a leading technology for achieving high-contrast imaging of exoplanets in a space telescope. It uses a system of several masks to modify the diffraction and achieve extremely high contrast in the image plane around target stars. However, coronagraphic imaging systems are very sensitive to optical aberrations, so wavefront correction using deformable mirrors (DMs) is necessary to avoid contrast degradation in the image plane. Electric field conjugation (EFC) and Stroke minimization (SM) are two primary high-contrast wavefront controllers explored in the past decade. EFC minimizes the average contrast in the search areas while regularizing the strength of the control inputs. Stroke minimization calculates the minimum DM commands under the constraint that a target average contrast is achieved. Recently in the High Contrast Imaging Lab at Princeton University (HCIL), a new linear-constraint wavefront controller based on stroke minimization was developed and demonstrated using numerical simulation. Instead of only constraining the average contrast over the entire search area, the new controller constrains the electric field of each single pixel using linear programming, which could led to significant increases in speed of the wavefront correction and also create more uniform dark holes. As a follow-up of this work, another linear-constraint controller modified from EFC is demonstrated theoretically and numerically and the lab verification of the linear-constraint controllers is reported. Based on the simulation and lab results, the pros and cons of linear-constraint controllers are carefully compared with EFC and stroke minimization.

  8. Describing the Corneal Shape after Wavefront-Optimized Photorefractive Keratectomy

    NARCIS (Netherlands)

    de Jong, Tim; Wijdh, Robert H. J.; Koopmans, Steven A.; Jansonius, Nomdo M.

    2014-01-01

    PURPOSE: To develop a procedure for describing wavefront-optimized photorefractive keratectomy (PRK) corneas and to characterize PRK-induced changes in shape. METHODS: We analyzed preoperative and postoperative corneal elevation data of 41 eyes of 41 patients (mean [±SD] age, 38 [±11] years) who

  9. Wavefront reversal in a copper vapor active medium

    Energy Technology Data Exchange (ETDEWEB)

    Bunkin, F.V.; Savranskii, V.V.; Shafeev, G.A.

    1981-09-01

    Wavefront reversal in the resonator of a copper vapor laser was observed. The frequencies of the signal and reversed waves were the same. The dependence of the reversed signal power on the input signal power had a threshold. Photographs were obtained of the reconstructed image of an object when a distorting phase plate was inserted in the resonator.

  10. Receding-horizon adaptive contyrol of aero-optical wavefronts

    NARCIS (Netherlands)

    Tesch, J.; Gibson, S.; Verhaegen, M.

    2013-01-01

    A new method for adaptive prediction and correction of wavefront errors in adaptive optics (AO) is introduced. The new method is based on receding-horizon control design and an adaptive lattice filter. Experimental results presented illustrate the capability of the new adaptive controller to predict

  11. Grazing Incidence Wavefront Sensing and Verification of X-Ray Optics Performance

    Science.gov (United States)

    Saha, Timo T.; Rohrbach, Scott; Zhang, William W.

    2011-01-01

    Evaluation of interferometrically measured mirror metrology data and characterization of a telescope wavefront can be powerful tools in understanding of image characteristics of an x-ray optical system. In the development of soft x-ray telescope for the International X-Ray Observatory (IXO), we have developed new approaches to support the telescope development process. Interferometrically measuring the optical components over all relevant spatial frequencies can be used to evaluate and predict the performance of an x-ray telescope. Typically, the mirrors are measured using a mount that minimizes the mount and gravity induced errors. In the assembly and mounting process the shape of the mirror segments can dramatically change. We have developed wavefront sensing techniques suitable for the x-ray optical components to aid us in the characterization and evaluation of these changes. Hartmann sensing of a telescope and its components is a simple method that can be used to evaluate low order mirror surface errors and alignment errors. Phase retrieval techniques can also be used to assess and estimate the low order axial errors of the primary and secondary mirror segments. In this paper we describe the mathematical foundation of our Hartmann and phase retrieval sensing techniques. We show how these techniques can be used in the evaluation and performance prediction process of x-ray telescopes.

  12. Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation

    Science.gov (United States)

    Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

    2015-01-01

    A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

  13. Effect of ordered mesoporous carbon contact layer on the sensing performance of sputtered RuO2 thin film pH sensor.

    Science.gov (United States)

    Lonsdale, W; Maurya, D K; Wajrak, M; Alameh, K

    2017-03-01

    The effect of contact layer on the pH sensing performance of a sputtered RuO 2 thin film pH sensor is investigated. The response of pH sensors employing RuO 2 thin film electrodes on screen-printed Pt, carbon and ordered mesoporous carbon (OMC) contact layers are measured over a pH range from 4 to 10. Working electrodes with OMC contact layer are found to have Nernstian pH sensitivity (-58.4mV/pH), low short-term drift rate (5.0mV/h), low hysteresis values (1.13mV) and fast reaction times (30s), after only 1h of conditioning. A pH sensor constructed with OMC carbon contact layer displays improved sensing performance compared to Pt and carbon-based counterparts, making this electrode more attractive for applications requiring highly-accurate pH sensing with reduced conditioning time. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Wavefront-guided laser in situ keratomileusis (Lasik) versus wavefront-guided photorefractive keratectomy (Prk): a prospective randomized eye-to-eye comparison (an American Ophthalmological Society thesis).

    Science.gov (United States)

    Manche, Edward E; Haw, Weldon W

    2011-12-01

    To compare the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) vs photorefractive keratectomy (PRK) in a prospective randomized clinical trial. A cohort of 68 eyes of 34 patients with -0.75 to -8.13 diopters (D) of myopia (spherical equivalent) were randomized to receive either wavefront-guided PRK or LASIK in the fellow eye using the VISX CustomVue laser. Patients were evaluated at 1 day, 1 week, and months 1, 3, 6, and 12. At 1 month, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), 5% and 25% contrast sensitivity, induction of higher-order aberrations (HOAs), and subjective symptoms of vision clarity, vision fluctuation, ghosting, and overall self-assessment of vision were worse (PPRK group. By 3 months, these differences had resolved (P>0.05). At 1 year, mean spherical equivalent was reduced 94% to -0.27 ± 0.31 D in the LASIK group and reduced 96% to -0.17 ± 0.41 D in the PRK group. At 1 year, 91% of eyes were within ±0.50 D and 97 % were within ±1.0 D in the PRK group. At 1 year, 88% of eyes were within ±0.50 D and 97% were within ±1.0 D in the LASIK group. At 1 year, 97% of eyes in the PRK group and 94% of eyes in the LASIK group achieved an UCVA of 20/20 or better (P=0.72). Refractive stability was achieved in both PRK and LASIK groups after 1 month. There were no intraoperative or postoperative flap complications in the LASIK group. There were no instances of corneal haze in the PRK group. Wavefront-guided LASIK and PRK are safe and effective at reducing myopia. At 1 month postoperatively, LASIK demonstrates an advantage over PRK in UCVA, BSCVA, low-contrast acuity, induction of total HOAs, and several subjective symptoms. At postoperative month 3, these differences between PRK and LASIK results had resolved.

  15. Optimization of Broadband Wavefront Correction at the Princeton High Contrast Imaging Laboratory

    Science.gov (United States)

    Groff, Tyler Dean; Kasdin, N.; Carlotti, A.

    2011-01-01

    Wavefront control for imaging of terrestrial planets using coronagraphic techniques requires improving the performance of the wavefront control techniques to expand the correction bandwidth and the size of the dark hole over which it is effective. At the Princeton High Contrast Imaging Laboratory we have focused on increasing the search area using two deformable mirrors (DMs) in series to achieve symmetric correction by correcting both amplitude and phase aberrations. Here we are concerned with increasing the bandwidth of light over which this correction is effective so we include a finite bandwidth into the optimization problem to generate a new stroke minimization algorithm. This allows us to minimize the actuator stroke on the DMs given contrast constraints at multiple wavelengths which define a window over which the dark hole will persist. This windowed stroke minimization algorithm is written in such a way that a weight may be applied to dictate the relative importance of the outer wavelengths to the central wavelength. In order to supply the estimates at multiple wavelengths a functional relationship to a central estimation wavelength is formed. Computational overhead and new experimental results of this windowed stroke minimization algorithm are discussed. The tradeoff between symmetric correction and achievable bandwidth is compared to the observed contrast degradation with wavelength in the experimental results. This work is supported by NASA APRA Grant #NNX09AB96G. The author is also supported under an NESSF Fellowship.

  16. [Cyclorotation of the eye in wavefront-guided LASIK using a static eyetracker with iris recognition].

    Science.gov (United States)

    Kohnen, T; Kühne, C; Cichocki, M; Strenger, A

    2007-01-01

    Centration of the ablation zone decisively influences the result of wavefront-guided LASIK. Cyclorotation of the eye occurs as the patient changes from the sitting position during aberrometry to the supine position during laser surgery and may lead to induction of lower and higher order aberrations. Twenty patients (40 eyes) underwent wavefront-guided LASIK (B&L 217z 100 excimer laser) with a static eyetracker driven by iris recognition (mean preoperative SE: -4.72+/-1.45 D; range: -1.63 to -7.00 D). The iris patterns of the patients' eyes were memorized during aberrometry and after flap creation. The mean absolute value of the measured cyclorotation was -1.5+/-4.2 degrees (range: -11.0 to 6.9 degrees ). The mean cyclorotation was 3.5+/-2.7 masculine (range: 0.1 to 11.0 degrees ). In 65% of all eyes cyclorotation was >2 masculine. A static eyetracker driven by iris recognition demonstrated that cyclorotation of up to 11 degrees may occur in myopic and myopic astigmatic eyes when changing from a sitting to a supine position. Use of static eyetrackers with iris recognition may provide a more precise positioning of the ablation profile as they detect and compensate cyclorotation.

  17. Dynamic wavefront sensing and correction with low-cost twisted nematic spatial light modulators

    International Nuclear Information System (INIS)

    Duran, Vicente; Climent, Vicent; Lancis, Jesus; Tajahuerce, Enrique; Bara, Salvador; Arines, Justo; Ares, Jorge; Andres, Pedro; Jaroszewicz, Zbigniew

    2010-01-01

    Off-the-shelf twisted nematic liquid crystal displays (TNLCDs) show some interesting features such as high spatial resolution, easy handling, wide availability, and low cost. We describe a compact adaptive optical system using just one TNLCD to measure and compensate optical aberrations. The current system operates at a frame rate of the order of 10 Hz with a four level codification scheme. Wavefront estimation is performed through conventional Hartmann-Shack sensing architecture. The system has proved to work properly with a maximum rms aberration of 0.76 microns and wavefront gradient of 50 rad/mm at a wavelength of 514 nm. These values correspond to typical aberrations found in human eyes. The key of our approach is careful characterization and optimization of the TNLCD for phase-only modulation. For this purpose, we exploit the so-called retarder-rotator approach for twisted nematic liquid crystal cells. The optimization process has been successfully applied to SLMs working either in transmissive or in reflective mode, even when light depolarization effects are observed.

  18. Derivation of preliminary specifications for transmitted wavefront and surface roughness for large optics used in inertial confinement fusion

    International Nuclear Information System (INIS)

    Aikens, D.; Roussel, A.; Bray, M.

    1995-01-01

    In preparation for beginning the design of the Nation Ignition Facility (NIF) in the United States and the Laser Mega-Joule (LMJ) in France, the authors are in the process of deriving new specifications for the large optics required for these facilities. Traditionally, specifications for transmitted wavefront and surface roughness of large ICF optics have been based on parameters which were easily measured during the early 1980's, such as peak-to-valley wavefront error (PV) and root-mean-square (RMS) surface roughness, as well as wavefront gradients in terms of waves per cm. While this was convenient from a fabrication perspective, since the specifications could be easily interpreted by fabricators in terms which were understood and conventionally measurable, it did not accurately reflect the requirements of the laser system. For the NIF and LMJ laser systems, the authors use advances in metrology and interferometry and an enhanced understanding of laser system performance to derive specifications which are based on power spectral densities (PSD's.) Such requirements can more accurately reflect the requirements of the laser system for minimizing the amplitude of mid- and high-spatial frequency surface and transmitted wavefront errors, while not over constraining the fabrication in terms of low spatial frequencies, such as residual coma or astigmatism, which are typically of a very large amplitude compared to periodic errors. In order to study the effect of changes in individual component tolerances, it is most useful to have a model capable of simulating real behavior. The basis of this model is discussed in this paper, outlining the general approach to the open-quotes theoreticalclose quotes study of ICF optics specifications, and an indication of the type of specification to be expected will be shown, based upon existing ICF laser optics

  19. Computational wavelength resolution for in-line lensless holography: phase-coded diffraction patterns and wavefront group-sparsity

    Science.gov (United States)

    Katkovnik, Vladimir; Shevkunov, Igor; Petrov, Nikolay V.; Egiazarian, Karen

    2017-06-01

    In-line lensless holography is considered with a random phase modulation at the object plane. The forward wavefront propagation is modelled using the Fourier transform with the angular spectrum transfer function. The multiple intensities (holograms) recorded by the sensor are random due to the random phase modulation and noisy with Poissonian noise distribution. It is shown by computational experiments that high-accuracy reconstructions can be achieved with resolution going up to the two thirds of the wavelength. With respect to the sensor pixel size it is a super-resolution with a factor of 32. The algorithm designed for optimal superresolution phase/amplitude reconstruction from Poissonian data is based on the general methodology developed for phase retrieval with a pixel-wise resolution in V. Katkovnik, "Phase retrieval from noisy data based on sparse approximation of object phase and amplitude", http://www.cs.tut.fi/ lasip/DDT/index3.html.

  20. Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations

    Science.gov (United States)

    Liu, Yong-Ji; Mu, Guo-Guang; Wang, Zhao-Qi; Wang-Yan

    2006-06-01

    Monochromatic aberrations in post laser in-situ keratomileusis (LASIK) eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function (MTF) of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations.

  1. Computer-generated holograms by multiple wavefront recording plane method with occlusion culling.

    Science.gov (United States)

    Symeonidou, Athanasia; Blinder, David; Munteanu, Adrian; Schelkens, Peter

    2015-08-24

    We propose a novel fast method for full parallax computer-generated holograms with occlusion processing, suitable for volumetric data such as point clouds. A novel light wave propagation strategy relying on the sequential use of the wavefront recording plane method is proposed, which employs look-up tables in order to reduce the computational complexity in the calculation of the fields. Also, a novel technique for occlusion culling with little additional computation cost is introduced. Additionally, the method adheres a Gaussian distribution to the individual points in order to improve visual quality. Performance tests show that for a full-parallax high-definition CGH a speedup factor of more than 2,500 compared to the ray-tracing method can be achieved without hardware acceleration.

  2. Wavefront modulation of water surface wave by a metasurface

    International Nuclear Information System (INIS)

    Sun Hai-Tao; Cheng Ying; Liu Xiao-Jun; Wang Jing-Shi

    2015-01-01

    We design a planar metasurface to modulate the wavefront of a water surface wave (WSW) on a deep sub-wavelength scale. The metasurface is composed of an array of coiling-up-space units with specially designed parameters, and can take on the work of steering the wavefront when it is pierced into water. Like their acoustic counterparts, the modulation of WSW is ascribed to the gradient phase shift of the coiling-up-space units, which can be perfectly tuned by changing the coiling plate length and channel number inside the units. According to the generalized Snell’s law, negative refraction and ‘driven’ surface mode of WSW are also demonstrated at certain incidences. Specially, the transmitted WSW could be efficiently guided out by linking a symmetrically-corrugated channel in ‘driven’ surface mode. This work may have potential applications in water wave energy extraction and coastal protection. (paper)

  3. Wavefront sensing with all-digital Stokes measurements

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2014-09-25

    Full Text Available to wavefront sensing [8] based on Stokes polarimetry which makes use of the amplitude and phase relationship between orthogonal states of polarization. With our approach a field of interest is generated by encoding an appropriate hologram on a spatial light... modulator (SLM). Since SLMs are diffraction-inefficient, we can exploit the amplitude relationship between the orthogonal polarization states allowing the execution of Stokes polarimetry of the co-linear superposition of the reference beam and the beam...

  4. X-ray pulse wavefront metrology using speckle tracking

    International Nuclear Information System (INIS)

    Berujon, Sebastien; Ziegler, Eric; Cloetens, Peter

    2015-01-01

    The theoretical description and experimental implementation of a speckle-tracking-based instrument which permits the characterisation of X-ray pulse wavefronts. An instrument allowing the quantitative analysis of X-ray pulsed wavefronts is presented and its processing method explained. The system relies on the X-ray speckle tracking principle to accurately measure the phase gradient of the X-ray beam from which beam optical aberrations can be deduced. The key component of this instrument, a semi-transparent scintillator emitting visible light while transmitting X-rays, allows simultaneous recording of two speckle images at two different propagation distances from the X-ray source. The speckle tracking procedure for a reference-less metrology mode is described with a detailed account on the advanced processing schemes used. A method to characterize and compensate for the imaging detector distortion, whose principle is also based on speckle, is included. The presented instrument is expected to find interest at synchrotrons and at the new X-ray free-electron laser sources under development worldwide where successful exploitation of beams relies on the availability of an accurate wavefront metrology

  5. Control algorithms and applications of the wavefront sensorless adaptive optics

    Science.gov (United States)

    Ma, Liang; Wang, Bin; Zhou, Yuanshen; Yang, Huizhen

    2017-10-01

    Compared with the conventional adaptive optics (AO) system, the wavefront sensorless (WFSless) AO system need not to measure the wavefront and reconstruct it. It is simpler than the conventional AO in system architecture and can be applied to the complex conditions. Based on the analysis of principle and system model of the WFSless AO system, wavefront correction methods of the WFSless AO system were divided into two categories: model-free-based and model-based control algorithms. The WFSless AO system based on model-free-based control algorithms commonly considers the performance metric as a function of the control parameters and then uses certain control algorithm to improve the performance metric. The model-based control algorithms include modal control algorithms, nonlinear control algorithms and control algorithms based on geometrical optics. Based on the brief description of above typical control algorithms, hybrid methods combining the model-free-based control algorithm with the model-based control algorithm were generalized. Additionally, characteristics of various control algorithms were compared and analyzed. We also discussed the extensive applications of WFSless AO system in free space optical communication (FSO), retinal imaging in the human eye, confocal microscope, coherent beam combination (CBC) techniques and extended objects.

  6. Focal plane based wavefront sensing with random DM probes

    Science.gov (United States)

    Pluzhnik, Eugene; Sirbu, Dan; Belikov, Ruslan; Bendek, Eduardo; Dudinov, Vladimir N.

    2017-09-01

    An internal coronagraph with an adaptive optical system for wavefront control is being considered for direct imaging of exoplanets with upcoming space missions and concepts, including WFIRST, HabEx, LUVOIR, EXCEDE and ACESat. The main technical challenge associated with direct imaging of exoplanets is to control of both diffracted and scattered light from the star so that even a dim planetary companion can be imaged. For a deformable mirror (DM) to create a dark hole with 10-10 contrast in the image plane, wavefront errors must be accurately measured on the science focal plane detector to ensure a common optical path. We present here a method that uses a set of random phase probes applied to the DM to obtain a high accuracy wavefront estimate even for a dynamically changing optical system. The presented numerical simulations and experimental results show low noise sensitivity, high reliability, and robustness of the proposed approach. The method does not use any additional optics or complex calibration procedures and can be used during the calibration stage of any direct imaging mission. It can also be used in any optical experiment that uses a DM as an active optical element in the layout.

  7. Partial coherence and imperfect optics at a synchrotron radiation source modeled by wavefront propagation

    Science.gov (United States)

    Laundy, David; Alcock, Simon G.; Alianelli, Lucia; Sutter, John P.; Sawhney, Kawal J. S.; Chubar, Oleg

    2014-09-01

    A full wave propagation of X-rays from source to sample at a storage ring beamline requires simulation of the electron beam source and optical elements in the beamline. The finite emittance source causes the appearance of partial coherence in the wave field. Consequently, the wavefront cannot be treated exactly with fully coherent wave propagation or fully incoherent ray tracing. We have used the wavefront code Synchrotron Radiation Workshop (SRW) to perform partially coherent wavefront propagation using a parallel computing cluster at the Diamond Light Source. Measured mirror profiles have been used to correct the wavefront for surface errors.

  8. A study on high speed wavefront control algorithm for an adaptive optics system

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Baik, Sung Hoon; Kim, Cheol Jung; Seo, Young Seok

    2000-01-01

    We developed a high speed control algorithm and system for measuring and correcting the wavefront distortions based on Windows operating system. To get quickly the information of wavefront distortion from the Hartman spot image, we preprocessed the image to remove background noises and extracted the centroid position by finding the center of weights. We moved finely the centroid position with sub-pixel resolution repeatedly to get the wavefront information with more enhanced resolution. We designed a differential data communication driver and an isolated analog driver to have robust system control. As the experimental results, the measurement resolution of the wavefront was 0.05 pixels and correction speed was 5Hz

  9. 5-D interpolation with wave-front attributes

    Science.gov (United States)

    Xie, Yujiang; Gajewski, Dirk

    2017-11-01

    Most 5-D interpolation and regularization techniques reconstruct the missing data in the frequency domain by using mathematical transforms. An alternative type of interpolation methods uses wave-front attributes, that is, quantities with a specific physical meaning like the angle of emergence and wave-front curvatures. In these attributes structural information of subsurface features like dip and strike of a reflector are included. These wave-front attributes work on 5-D data space (e.g. common-midpoint coordinates in x and y, offset, azimuth and time), leading to a 5-D interpolation technique. Since the process is based on stacking next to the interpolation a pre-stack data enhancement is achieved, improving the signal-to-noise ratio (S/N) of interpolated and recorded traces. The wave-front attributes are determined in a data-driven fashion, for example, with the Common Reflection Surface (CRS method). As one of the wave-front-attribute-based interpolation techniques, the 3-D partial CRS method was proposed to enhance the quality of 3-D pre-stack data with low S/N. In the past work on 3-D partial stacks, two potential problems were still unsolved. For high-quality wave-front attributes, we suggest a global optimization strategy instead of the so far used pragmatic search approach. In previous works, the interpolation of 3-D data was performed along a specific azimuth which is acceptable for narrow azimuth acquisition but does not exploit the potential of wide-, rich- or full-azimuth acquisitions. The conventional 3-D partial CRS method is improved in this work and we call it as a wave-front-attribute-based 5-D interpolation (5-D WABI) as the two problems mentioned above are addressed. Data examples demonstrate the improved performance by the 5-D WABI method when compared with the conventional 3-D partial CRS approach. A comparison of the rank-reduction-based 5-D seismic interpolation technique with the proposed 5-D WABI method is given. The comparison reveals that

  10. Wavefront Control and Image Restoration with Less Computing

    Science.gov (United States)

    Lyon, Richard G.

    2010-01-01

    PseudoDiversity is a method of recovering the wavefront in a sparse- or segmented- aperture optical system typified by an interferometer or a telescope equipped with an adaptive primary mirror consisting of controllably slightly moveable segments. (PseudoDiversity should not be confused with a radio-antenna-arraying method called pseudodiversity.) As in the cases of other wavefront- recovery methods, the streams of wavefront data generated by means of PseudoDiversity are used as feedback signals for controlling electromechanical actuators of the various segments so as to correct wavefront errors and thereby, for example, obtain a clearer, steadier image of a distant object in the presence of atmospheric turbulence. There are numerous potential applications in astronomy, remote sensing from aircraft and spacecraft, targeting missiles, sighting military targets, and medical imaging (including microscopy) through such intervening media as cells or water. In comparison with prior wavefront-recovery methods used in adaptive optics, PseudoDiversity involves considerably simpler equipment and procedures and less computation. For PseudoDiversity, there is no need to install separate metrological equipment or to use any optomechanical components beyond those that are already parts of the optical system to which the method is applied. In Pseudo- Diversity, the actuators of a subset of the segments or subapertures are driven to make the segments dither in the piston, tilt, and tip degrees of freedom. Each aperture is dithered at a unique frequency at an amplitude of a half wavelength of light. During the dithering, images on the focal plane are detected and digitized at a rate of at least four samples per dither period. In the processing of the image samples, the use of different dither frequencies makes it possible to determine the separate effects of the various dithered segments or apertures. The digitized image-detector outputs are processed in the spatial

  11. Numerical tilting compensation in microscopy based on wavefront sensing using transport of intensity equation method

    Science.gov (United States)

    Hu, Junbao; Meng, Xin; Wei, Qi; Kong, Yan; Jiang, Zhilong; Xue, Liang; Liu, Fei; Liu, Cheng; Wang, Shouyu

    2018-03-01

    Wide-field microscopy is commonly used for sample observations in biological research and medical diagnosis. However, the tilting error induced by the oblique location of the image recorder or the sample, as well as the inclination of the optical path often deteriorates the imaging quality. In order to eliminate the tilting in microscopy, a numerical tilting compensation technique based on wavefront sensing using transport of intensity equation method is proposed in this paper. Both the provided numerical simulations and practical experiments prove that the proposed technique not only accurately determines the tilting angle with simple setup and procedures, but also compensates the tilting error for imaging quality improvement even in the large tilting cases. Considering its simple systems and operations, as well as image quality improvement capability, it is believed the proposed method can be applied for tilting compensation in the optical microscopy.

  12. Preconditioned conjugate gradient wave-front reconstructors for multiconjugate adaptive optics

    Science.gov (United States)

    Gilles, Luc; Ellerbroek, Brent L.; Vogel, Curtis R.

    2003-09-01

    Multiconjugate adaptive optics (MCAO) systems with 104-105 degrees of freedom have been proposed for future giant telescopes. Using standard matrix methods to compute, optimize, and implement wave-front control algorithms for these systems is impractical, since the number of calculations required to compute and apply the reconstruction matrix scales respectively with the cube and the square of the number of adaptive optics degrees of freedom. We develop scalable open-loop iterative sparse matrix implementations of minimum variance wave-front reconstruction for telescope diameters up to 32 m with more than 104 actuators. The basic approach is the preconditioned conjugate gradient method with an efficient preconditioner, whose block structure is defined by the atmospheric turbulent layers very much like the layer-oriented MCAO algorithms of current interest. Two cost-effective preconditioners are investigated: a multigrid solver and a simpler block symmetric Gauss-Seidel (BSGS) sweep. Both options require off-line sparse Cholesky factorizations of the diagonal blocks of the matrix system. The cost to precompute these factors scales approximately as the three-halves power of the number of estimated phase grid points per atmospheric layer, and their average update rate is typically of the order of 10-2 Hz, i.e., 4-5 orders of magnitude lower than the typical 103 Hz temporal sampling rate. All other computations scale almost linearly with the total number of estimated phase grid points. We present numerical simulation results to illustrate algorithm convergence. Convergence rates of both preconditioners are similar, regardless of measurement noise level, indicating that the layer-oriented BSGS sweep is as effective as the more elaborated multiresolution preconditioner.

  13. Preconditioned conjugate gradient wave-front reconstructors for multiconjugate adaptive optics.

    Science.gov (United States)

    Gilles, Luc; Ellerbroek, Brent L; Vogel, Curtis R

    2003-09-10

    Multiconjugate adaptive optics (MCAO) systems with 10(4)-10(5) degrees of freedom have been proposed for future giant telescopes. Using standard matrix methods to compute, optimize, and implement wavefront control algorithms for these systems is impractical, since the number of calculations required to compute and apply the reconstruction matrix scales respectively with the cube and the square of the number of adaptive optics degrees of freedom. We develop scalable open-loop iterative sparse matrix implementations of minimum variance wave-front reconstruction for telescope diameters up to 32 m with more than 10(4) actuators. The basic approach is the preconditioned conjugate gradient method with an efficient preconditioner, whose block structure is defined by the atmospheric turbulent layers very much like the layer-oriented MCAO algorithms of current interest. Two cost-effective preconditioners are investigated: a multigrid solver and a simpler block symmetric Gauss-Seidel (BSGS) sweep. Both options require off-line sparse Cholesky factorizations of the diagonal blocks of the matrix system. The cost to precompute these factors scales approximately as the three-halves power of the number of estimated phase grid points per atmospheric layer, and their average update rate is typically of the order of 10(-2) Hz, i.e., 4-5 orders of magnitude lower than the typical 10(3) Hz temporal sampling rate. All other computations scale almost linearly with the total number of estimated phase grid points. We present numerical simulation results to illustrate algorithm convergence. Convergence rates of both preconditioners are similar, regardless of measurement noise level, indicating that the layer-oriented BSGS sweep is as effective as the more elaborated multiresolution preconditioner.

  14. Ultrafast Fabry-Perot fiber-optic pressure sensors for multimedia blast event measurements.

    Science.gov (United States)

    Zou, Xiaotian; Wu, Nan; Tian, Ye; Zhang, Yang; Fitek, John; Maffeo, Michael; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

    2013-02-20

    A shock wave (SW) is characterized as a large pressure fluctuation that typically lasts only a few milliseconds. On the battlefield, SWs pose a serious threat to soldiers who are exposed to explosions, which may lead to blast-induced traumatic brain injuries. SWs can also be used beneficially and have been applied to a variety of medical treatments due to their unique interaction with tissues and cells. Consequently, it is important to have sensors that can quantify SW dynamics in order to better understand the physical interaction between body tissue and the incident acoustic wave. In this paper, the ultrafast fiber-optic sensor based on the Fabry-Perot interferometric principle was designed and four such sensors were fabricated to quantify a blast event within different media, simultaneously. The compact design of the fiber-optic sensor allows for a high degree of spatial resolution when capturing the wavefront of the traveling SW. Several blast event experiments were conducted within different media (e.g., air, rubber membrane, and water) to evaluate the sensor's performance. This research revealed valuable knowledge for further study of SW behavior and SW-related applications.

  15. Tomographic flow cytometry assisted by intelligent wavefronts analysis

    Science.gov (United States)

    Merola, F.; Memmolo, P.; Miccio, L.; Mugnano, M.; Ferraro, P.

    2017-06-01

    High-throughput single-cell analysis is a challenging target for implementing advanced biomedical applications. An excellent candidate for this aim is label-free tomographic phase microscopy. However, in-line tomography is very difficult to be implemented in practice, as it requires complex setup for rotating the sample and/or illuminate the cell along numerous directions [1]. We exploit random rolling of cells while they are flowing along a microfluidic channel demonstrating that it is possible to obtain in-line phase-contrast tomography by adopting strategies for intelligent wavefronts analysis thus obtaining complete retrieval of both 3D-position and orientation of rotating cells [2]. Thus, by numerical wavefront analysis a-priori knowledge of such information is no longer needed. This approach makes continuos-flow cyto-tomography suitable for practical operation in real-world, single-cell analysis and with substantial simplification of the optical system avoiding any mechanical/optical scanning of light source. Demonstration is given for different classes of biosamples, red-blood-cells (RBCs), diatom algae and fibroblast cells [3]. Accurate characterization of each type of cells is reported despite their very different nature and materials content, thus showing the proposed method can be extended, by adopting two alternate strategies of wavefront-analysis, to many classes of cells. In particular, for RBCs we furnish important parameters as 3D morphology, Corpuscular Hemoglobin (CH), Volume (V), and refractive index (RI) for each single cell in the total population [3]. This could open a new route in blood disease diagnosis, for example for the isolation and characterization of "foreign" cells in the blood stream, the so called Circulating Tumor Cells (CTC), early manifestation of metastasis.

  16. Measuring higher order optical aberrations of the human eye: techniques and applications

    Directory of Open Access Journals (Sweden)

    L. Alberto V. Carvalho

    2002-11-01

    Full Text Available In the present paper we discuss the development of "wave-front", an instrument for determining the lower and higher optical aberrations of the human eye. We also discuss the advantages that such instrumentation and techniques might bring to the ophthalmology professional of the 21st century. By shining a small light spot on the retina of subjects and observing the light that is reflected back from within the eye, we are able to quantitatively determine the amount of lower order aberrations (astigmatism, myopia, hyperopia and higher order aberrations (coma, spherical aberration, etc.. We have measured artificial eyes with calibrated ametropia ranging from +5 to -5 D, with and without 2 D astigmatism with axis at 45º and 90º. We used a device known as the Hartmann-Shack (HS sensor, originally developed for measuring the optical aberrations of optical instruments and general refracting surfaces in astronomical telescopes. The HS sensor sends information to a computer software for decomposition of wave-front aberrations into a set of Zernike polynomials. These polynomials have special mathematical properties and are more suitable in this case than the traditional Seidel polynomials. We have demonstrated that this technique is more precise than conventional autorefraction, with a root mean square error (RMSE of less than 0.1 µm for a 4-mm diameter pupil. In terms of dioptric power this represents an RMSE error of less than 0.04 D and 5º for the axis. This precision is sufficient for customized corneal ablations, among other applications.

  17. Twisted speckle entities inside wave-front reversal mirrors

    International Nuclear Information System (INIS)

    Okulov, A. Yu

    2009-01-01

    The previously unknown property of the optical speckle pattern reported. The interference of a speckle with the counterpropagating phase-conjugated (PC) speckle wave produces a randomly distributed ensemble of a twisted entities (ropes) surrounding optical vortex lines. These entities appear in a wide range of a randomly chosen speckle parameters inside the phase-conjugating mirrors regardless to an internal physical mechanism of the wave-front reversal. These numerically generated interference patterns are relevant to the Brillouin PC mirrors and to a four-wave mixing PC mirrors based upon laser trapped ultracold atomic cloud.

  18. Wavefront-error evaluation by mathematical analysis of experimental Foucault-test data

    Science.gov (United States)

    Wilson, R. G.

    1975-01-01

    The diffraction theory of the Foucault test provides an integral formula expressing the complex amplitude and irradiance distribution in the Foucault pattern of a test mirror (lens) as a function of wavefront error. Recent literature presents methods of inverting this formula to express wavefront error in terms of irradiance in the Foucault pattern. The present paper describes a study in which the inversion formulation was applied to photometric Foucault-test measurements on a nearly diffraction-limited mirror to determine wavefront errors for direct comparison with ones determined from scatter-plate interferometer measurements. The results affirm the practicability of the Foucault test for quantitative wavefront analysis of very small errors, and they reveal the fallacy of the prevalent belief that the test is limited to qualitative use only. Implications of the results with regard to optical testing and the potential use of the Foucault test for wavefront analysis in orbital space telescopes are discussed.

  19. High-speed single-shot optical focusing through dynamic scattering media with full-phase wavefront shaping

    Science.gov (United States)

    Hemphill, Ashton S.; Shen, Yuecheng; Liu, Yan; Wang, Lihong V.

    2017-11-01

    In biological applications, optical focusing is limited by the diffusion of light, which prevents focusing at depths greater than ˜1 mm in soft tissue. Wavefront shaping extends the depth by compensating for phase distortions induced by scattering and thus allows for focusing light through biological tissue beyond the optical diffusion limit by using constructive interference. However, due to physiological motion, light scattering in tissue is deterministic only within a brief speckle correlation time. In in vivo tissue, this speckle correlation time is on the order of milliseconds, and so the wavefront must be optimized within this brief period. The speed of digital wavefront shaping has typically been limited by the relatively long time required to measure and display the optimal phase pattern. This limitation stems from the low speeds of cameras, data transfer and processing, and spatial light modulators. While binary-phase modulation requiring only two images for the phase measurement has recently been reported, most techniques require at least three frames for the full-phase measurement. Here, we present a full-phase digital optical phase conjugation method based on off-axis holography for single-shot optical focusing through scattering media. By using off-axis holography in conjunction with graphics processing unit based processing, we take advantage of the single-shot full-phase measurement while using parallel computation to quickly reconstruct the phase map. With this system, we can focus light through scattering media with a system latency of approximately 9 ms, on the order of the in vivo speckle correlation time.

  20. Military target task performance after wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK)

    Science.gov (United States)

    Maurer, Tana; Deaver, Dawne; Howell, Christopher; Moyer, Steve; Nguyen, Oanh; Mueller, Greg; Ryan, Denise; Sia, Rose K.; Stutzman, Richard; Pasternak, Joseph; Bower, Kraig

    2014-06-01

    Major decisions regarding life and death are routinely made on the modern battlefield, where visual function of the individual soldier can be of critical importance in the decision-making process. Glasses in the combat environment have considerable disadvantages: degradation of short term visual performance can occur as dust and sweat accumulate on lenses during a mission or patrol; long term visual performance can diminish as lenses become increasingly scratched and pitted; during periods of intense physical trauma, glasses can be knocked off the soldier's face and lost or broken. Although refractive surgery offers certain benefits on the battlefield when compared to wearing glasses, it is not without potential disadvantages. As a byproduct of refractive surgery, elevated optical aberrations can be induced, causing decreases in contrast sensitivity and increases in the symptoms of glare, halos, and starbursts. Typically, these symptoms occur under low light level conditions, the same conditions under which most military operations are initiated. With the advent of wavefront aberrometry, we are now seeing correction not only of myopia and astigmatism but of other, smaller optical aberrations that can cause the above symptoms. In collaboration with the Warfighter Refractive Eye Surgery Program and Research Center (WRESP-RC) at Fort Belvoir and Walter Reed National Military Medical Center (WRNMMC), the overall objective of this study is to determine the impact of wavefront guided (WFG) versus wavefront-optimized (WFO) photorefractive keratectomy (PRK) on military task visual performance. Psychophysical perception testing was conducted before and after surgery to measure each participant's performance regarding target detection and identification using thermal imagery. The results are presented here.

  1. Amplification and Attenuation across USArray using Ambient Noise Wavefront Tracking

    KAUST Repository

    Bowden, Daniel C.

    2017-11-15

    As seismic travel-time tomography continues to be refined using data from the vast USArray dataset, it is advantageous to also exploit the amplitude information carried by seismic waves. We use ambient noise cross correlation to make observations of surface-wave amplification and attenuation at shorter periods (8 – 32 seconds) than can be observed with only traditional teleseismic earthquake sources. We show that the wavefront tracking approach of [Lin et al., 2012a] can be successfully applied to ambient noise correlations, yielding results quite similar to those from earthquake observations at periods of overlap. This consistency indicates that the wavefront tracking approach is viable for use with ambient noise correlations, despite concerns of the inhomogeneous and unknown distribution of noise sources. The resulting amplification and attenuation maps correlate well with known tectonic and crustal structure; at the shortest periods, our amplification and attenuation maps correlate well with surface geology and known sedimentary basins, while our longest period amplitudes are controlled by crustal thickness and begin to probe upper mantle materials. These amplification and attenuation observations are sensitive to crustal materials in different ways than travel-time observations and may be used to better constrain temperature or density variations. We also value them as an independent means of describing the lateral variability of observed Rayleigh-wave amplitudes without the need for 3D tomographic inversions.

  2. Manufacturing and testing of wavefront filters for DARWIN

    Science.gov (United States)

    Flatscher, R.; Artjushenko, V.; Sakharova, T.; Pereira do Carmo, Joao

    2017-11-01

    Wavefront filtering is mandatory in the realisation of nulling interferometers with high star light suppression capability required to detect extrasolar planets, such as the one foreseen for the ESA Darwin mission. This paper presents the design, manufacturing, and test results of single mode fibres to be used as wavefront filters in mid-infrared range. Fibres made from chalcogenide glass and silver halide crystals were produced. The first class can serve as wavefront filters up to a wavelength of 11 microns, while silver halide fibres can be used over the full Darwin wavelength range from 6.5 to 18 micron. The chalcogenide glass fibres were drawn by double crucible method whereas polycrystalline fibres from silver halides were fabricated by multiple extrusion from a crystalline preform. Multi-layer AR-coatings for fibre ends were developed and environmentally tested for both types of fibres. Special fibre facet polishing procedures were established, in particular for the soft silver halide fibre ends. Cable design and assembly process were also developed, including termination by SMA-connectors with ceramic ferrules and fibre protection by loose PEEK-tubings to prevent excessive bending and chemical attacks for fibres. The wavefront filtering capability of the fibres was demonstrated on a high quality Mach-Zehnder interferometer. Two different groups of laser sources were used to measure the wavefront filtering of the fibres by using a CO-laser for testing in the lower sub-band and a CO2-laser to check the upper sub-band. Measurements of the fibres far field intensity distribution and transmission were performed for numerous cable samples. Single mode behaviour was observed in more than 25 silver halide fibre cables before AR-coating of their ends, while after that 17 cables were compliant with all technical requirements. Residual cladding modes existing in short single mode fibres were effectively removed by applying of a proper absorbing jacket to the fibre

  3. Refractive Outcomes, Contrast Sensitivity, HOAs, and Patient Satisfaction in Moderate Myopia: Wavefront-Optimized Versus Tissue-Saving PRK.

    Science.gov (United States)

    Nassiri, Nader; Sheibani, Kourosh; Azimi, Abbas; Khosravi, Farinaz Mahmoodi; Heravian, Javad; Yekta, Abasali; Moghaddam, Hadi Ostadi; Nassiri, Saman; Yasseri, Mehdi; Nassiri, Nariman

    2015-10-01

    To compare refractive outcomes, contrast sensitivity, higher-order aberrations (HOAs), and patient satisfaction after photorefractive keratectomy for correction of moderate myopia with two methods: tissue saving versus wavefront optimized. In this prospective, comparative study, 152 eyes (80 patients) with moderate myopia with and without astigmatism were randomly divided into two groups: the tissue-saving group (Technolas 217z Zyoptix laser; Bausch & Lomb, Rochester, NY) (76 eyes of 39 patients) or the wavefront-optimized group (WaveLight Allegretto Wave Eye-Q laser; Alcon Laboratories, Inc., Fort Worth, TX) (76 eyes of 41 patients). Preoperative and 3-month postoperative refractive outcomes, contrast sensitivity, HOAs, and patient satisfaction were compared between the two groups. The mean spherical equivalent was -4.50 ± 1.02 diopters. No statistically significant differences were detected between the groups in terms of uncorrected and corrected distance visual acuity and spherical equivalent preoperatively and 3 months postoperatively. No statistically significant differences were seen in the amount of preoperative to postoperative contrast sensitivity changes between the two groups in photopic and mesopic conditions. HOAs and Q factor increased in both groups postoperatively (P = .001), with the tissue-saving method causing more increases in HOAs (P = .007) and Q factor (P = .039). Patient satisfaction was comparable between both groups. Both platforms were effective in correcting moderate myopia with or without astigmatism. No difference in refractive outcome, contrast sensitivity changes, and patient satisfaction between the groups was observed. Postoperatively, the tissue-saving method caused a higher increase in HOAs and Q factor compared to the wavefront-optimized method, which could be due to larger optical zone sizes in the tissue-saving group. Copyright 2015, SLACK Incorporated.

  4. Prussian blue mediated amplification combined with signal enhancement of ordered mesoporous carbon for ultrasensitive and specific quantification of metolcarb by a three-dimensional molecularly imprinted electrochemical sensor.

    Science.gov (United States)

    Yang, Yukun; Cao, Yaoyu; Wang, Xiaomin; Fang, Guozhen; Wang, Shuo

    2015-02-15

    In this work, we presented a three-dimensional (3D) molecularly imprinted electrochemical sensor (MIECS) with novel strategy for ultrasensitive and specific quantification of metolcarb based on prussian blue (PB) mediated amplification combined with signal enhancement of ordered mesoporous carbon. The molecularly imprinted polymers were synthesized by electrochemically induced redox polymerization of para aminobenzoic acid (p-ABA) in the presence of template metolcarb. Ordered mesoporous carbon material (CMK-3) was introduced to enhance the electrochemical response by improving the structure of the modified electrodes and facilitating charge transfer processes of PB which was used as an inherent electrochemical active probe. The modification process for the working electrodes of the MIECS was characterized by scanning electron microscope (SEM) and cyclic voltammetry (CV), and several important parameters controlling the performance of the MIECS were investigated and optimized in detail. The MIECS with 3D structure had the advantages of ease of preparation, high porous surface structure, speedy response, ultrasensitivity, selectivity, reliable stability, good reproducibility and repeatability. Under the optimal conditions, the MIECS offered an excellent current response for metolcarb in the linear response range of 5.0 × 10(-10)-1.0 × 10(-4) mol L(-1) and the limit of detection (LOD) was calculated to be 9.3 × 10 (-11)mol L(-1) (S/N = 3). The proposed MIECS has been successfully applied for the determination of metolcarb in real samples with satisfactory recoveries. Furthermore, the construction route of this ultrasensitive 3D MIECS may provide a guideline for the determination of non-electroactive analytes in environmental control and food safety. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Identified state-space prediction model for aero-optical wavefronts

    Science.gov (United States)

    Faghihi, Azin; Tesch, Jonathan; Gibson, Steve

    2013-07-01

    A state-space disturbance model and associated prediction filter for aero-optical wavefronts are described. The model is computed by system identification from a sequence of wavefronts measured in an airborne laboratory. Estimates of the statistics and flow velocity of the wavefront data are shown and can be computed from the matrices in the state-space model without returning to the original data. Numerical results compare velocity values and power spectra computed from the identified state-space model with those computed from the aero-optical data.

  6. Phase-preserving wavefront amplification at 590 nm by stimulated Raman scattering

    Science.gov (United States)

    Wick, D. V.; Gruneisen, M. T.; Peterson, P. R.

    1998-03-01

    This paper presents an experimental demonstration of high-gain optical-wavefront amplification by stimulated Raman scattering near the D 1 resonance in atomic sodium vapor. Single-pass weak-field gain of nearly 400 is achieved with only 800 mW of pump power. Through judicious focusing, the weak wavefront is confined to the central region of the focused pump wave where saturation of the dispersion profile minimizes phase distortions due to self-focusing effects. Phase-preserving amplification is demonstrated by interferometric measurements of an amplified TEM 00 wavefront.

  7. Multicore-Optimized Wavefront Diamond Blocking for Optimizing Stencil Updates

    KAUST Repository

    Malas, T.

    2015-07-02

    The importance of stencil-based algorithms in computational science has focused attention on optimized parallel implementations for multilevel cache-based processors. Temporal blocking schemes leverage the large bandwidth and low latency of caches to accelerate stencil updates and approach theoretical peak performance. A key ingredient is the reduction of data traffic across slow data paths, especially the main memory interface. In this work we combine the ideas of multicore wavefront temporal blocking and diamond tiling to arrive at stencil update schemes that show large reductions in memory pressure compared to existing approaches. The resulting schemes show performance advantages in bandwidth-starved situations, which are exacerbated by the high bytes per lattice update case of variable coefficients. Our thread groups concept provides a controllable trade-off between concurrency and memory usage, shifting the pressure between the memory interface and the CPU. We present performance results on a contemporary Intel processor.

  8. Broadband reflected wavefronts manipulation using structured phase gradient metasurfaces

    Directory of Open Access Journals (Sweden)

    Xiao-Peng Wang

    2016-06-01

    Full Text Available Acoustic metasurface (AMS is a good candidate to manipulate acoustic waves due to special acoustic performs that cannot be realized by traditional materials. In this paper, we design the AMS by using circular-holed cubic arrays. The advantages of our AMS are easy assemble, subwavelength thickness, and low energy loss for manipulating acoustic waves. According to the generalized Snell’s law, acoustic waves can be manipulated arbitrarily by using AMS with different phase gradients. By selecting suitable hole diameter of circular-holed cube (CHC, some interesting phenomena are demonstrated by our simulations based on finite element method, such as the conversion of incoming waves into surface waves, anomalous reflections (including negative reflection, acoustic focusing lens, and acoustic carpet cloak. Our results can provide a simple approach to design AMSes and use them in wavefront manipulation and manufacturing of acoustic devices.

  9. TRL-6 for JWST Wavefront Sensing and Control

    Science.gov (United States)

    Feinberg, Lee; Dean, Bruce; Smith, Scott; Aronstein, David; Shiri, Ron; Lyon, Rick; Hayden, Bill; Bowers, Chuck; Acton, D. Scott; Shields, Duncan; hide

    2007-01-01

    NASA's Technology Readiness Level (TRL)-6 is documented for the James Webb Space Telescope (JWST) Wavefront Sensing and Control (WFSC) subsystem. The WFSC subsystem is needed to align the Optical Telescope Element (OTE) after all deployments have occurred, and achieves that requirement through a robust commissioning sequence consisting of unique commissioning algorithms, all of which are part of the WFSC algorithm suite. This paper identifies the technology need, algorithm heritage, describes the finished TRL-6 design platform, and summarizes the TRL-6 test results and compliance. Additionally, the performance requirements needed to satisfy JWST science goals as well as the criterion that relate to the TRL-6 Testbed Telescope (TBT) performance requirements are discussed

  10. Laboratory simulation of atmospheric turbulence induced optical wavefront distortion

    Science.gov (United States)

    Taylor, Travis Shane

    1999-11-01

    Many creative approaches have been taken in the past for simulating the effect that atmospheric turbulence has on optical beams. Most of the experimental architectures have been complicated and consisted of many optical elements as well as moving components. These techniques have shown a modicum of success; however, they are not completely controllable or predictable. A benchtop technique for experimentally producing one important effect that atmospheric turbulence has on optical beams (phase distortion) is presented here. The system is completely controllable and predictable while accurately representing the statistical nature of the problem. Previous experimentation in optical processing through turbulent media has demonstrated that optical wavefront distortions can be produced via spatial light modulating (SLM) devices, and most turbulence models and experimental results indicate that turbulence can be represented as a phase fluctuation. The amplitude distributions in the resulting far field are primarily due to propagation of the phase. Operating a liquid crystal television (LCTV) in the ``phase- mostly'' mode, a phase fluctuation type model for turbulence is utilized in the present investigation, and a real-time experiment for demonstrating the effects was constructed. For an optical system to simulate optical wavefront distortions due to atmospheric turbulence, the following are required: (1)An optical element that modulates the phasefront of an optical beam (2)A model and a technique for generating spatially correlated turbulence simulating distributions (3)Hardware and software for displaying and manipulating the information addressing the optical phase modulation device The LCTV is ideal for this application. When operated in the ``phase-mostly'' mode some LCTVs can modulate the phasefront of an optical beam by as much as 2π and an algorithm for generating spatially correlated phase screens can be constructed via mathematical modeling software such as

  11. Multicore-Optimized Wavefront Diamond Blocking for Optimizing Stencil Updates

    KAUST Repository

    Malas, T.; Hager, G.; Ltaief, Hatem; Stengel, H.; Wellein, G.; Keyes, David E.

    2015-01-01

    The importance of stencil-based algorithms in computational science has focused attention on optimized parallel implementations for multilevel cache-based processors. Temporal blocking schemes leverage the large bandwidth and low latency of caches to accelerate stencil updates and approach theoretical peak performance. A key ingredient is the reduction of data traffic across slow data paths, especially the main memory interface. In this work we combine the ideas of multicore wavefront temporal blocking and diamond tiling to arrive at stencil update schemes that show large reductions in memory pressure compared to existing approaches. The resulting schemes show performance advantages in bandwidth-starved situations, which are exacerbated by the high bytes per lattice update case of variable coefficients. Our thread groups concept provides a controllable trade-off between concurrency and memory usage, shifting the pressure between the memory interface and the CPU. We present performance results on a contemporary Intel processor.

  12. Zyoptix wavefront-guided versus standard photorefractive keratectomy (PRK) in low and moderate myopia: randomized controlled 6-month study.

    Science.gov (United States)

    Mastropasqua, L; Toto, L; Zuppardi, E; Nubile, M; Carpineto, P; Di Nicola, M; Ballone, E

    2006-01-01

    To evaluate the refractive and aberrometric outcome of wavefront-guided photorefractive keratectomy (PRK) compared to standard PRK in myopic patients. Fifty-six eyes of 56 patients were included in the study and were randomly divided into two groups. The study group consisted of 28 eyes with a mean spherical equivalent (SE) of -2.25+/-0.76 diopters (D) (range: -1.5 to -3.5 D) treated with wavefront-guided PRK using the Zywave ablation profile and the Bausch & Lomb Technolas 217z excimer laser (Zyoptix system) and the control group included 28 eyes with a SE of -2.35+/-1.01 D (range: -1.5 to -3.5 D) treated with standard PRK (PlanoScan ablation) using the same laser. A Zywave aberrometer was used to analyze and calculate the root-mean-square (RMS) of total high order aberrations (HOA) and Zernike coefficients of third and fourth order before and after (over a 6-month follow-up period) surgery in both groups. Preoperative and postoperative SE, un-corrected visual acuity (UCVA), and best-corrected visual acuity (BCVA) were evaluated in all cases. There was a high correlation between achieved and intended correction. The differences between the two treatment groups were not statistically significant for UCVA, BCVA, or SE cycloplegic refraction . Postoperatively the RMS value of high order aberrations was raised in both groups. At 6-month control, on average it increased by a factor of 1.17 in the Zyoptix PRK group and 1.54 in the PlanoScan PRK group (p=0.22). In the Zyoptix group there was a decrease of coma aberration, while in the PlanoScan group this third order aberration increased. The difference between postoperative and preoperative values between the two groups was statistically significant for coma aberration (p=0.013). No statistically significant difference was observed for spherical-like aberration between the two groups. In the study group eyes with a low amount of preoperative aberrations (HOA RMS lower than the median value; PRK is as safe and

  13. Alignment error of mirror modules of advanced telescope for high-energy astrophysics due to wavefront aberrations

    Science.gov (United States)

    Zocchi, Fabio E.

    2017-10-01

    One of the approaches that is being tested for the integration of the mirror modules of the advanced telescope for high-energy astrophysics x-ray mission of the European Space Agency consists in aligning each module on an optical bench operated at an ultraviolet wavelength. The mirror module is illuminated by a plane wave and, in order to overcome diffraction effects, the centroid of the image produced by the module is used as a reference to assess the accuracy of the optical alignment of the mirror module itself. Among other sources of uncertainty, the wave-front error of the plane wave also introduces an error in the position of the centroid, thus affecting the quality of the mirror module alignment. The power spectral density of the position of the point spread function centroid is here derived from the power spectral density of the wave-front error of the plane wave in the framework of the scalar theory of Fourier diffraction. This allows the defining of a specification on the collimator quality used for generating the plane wave starting from the contribution to the error budget allocated for the uncertainty of the centroid position. The theory generally applies whenever Fourier diffraction is a valid approximation, in which case the obtained result is identical to that derived by geometrical optics considerations.

  14. Performance and scalability analysis of teraflop-scale parallel architectures using multidimensional wavefront applications

    International Nuclear Information System (INIS)

    Hoisie, A.; Lubeck, O.; Wasserman, H.

    1998-01-01

    The authors develop a model for the parallel performance of algorithms that consist of concurrent, two-dimensional wavefronts implemented in a message passing environment. The model, based on a LogGP machine parameterization, combines the separate contributions of computation and communication wavefronts. They validate the model on three important supercomputer systems, on up to 500 processors. They use data from a deterministic particle transport application taken from the ASCI workload, although the model is general to any wavefront algorithm implemented on a 2-D processor domain. They also use the validated model to make estimates of performance and scalability of wavefront algorithms on 100-TFLOPS computer systems expected to be in existence within the next decade as part of the ASCI program and elsewhere. In this context, they analyze two problem sizes. The model shows that on the largest such problem (1 billion cells), inter-processor communication performance is not the bottleneck. Single-node efficiency is the dominant factor

  15. Corneal-Wavefront guided transepithelial photorefractive keratectomy after corneal collagen cross linking in keratoconus

    Directory of Open Access Journals (Sweden)

    Massimo Camellin

    2017-01-01

    Conclusions: Corneal-Wavefront guided transepithelial PRK ablation profiles after conventional CXL yields to good visual, optical, and refractive results. These treatments are safe and efficacious for the correction of refracto-therapeutic problems in keratoconic patients.

  16. Travelling wavefronts of a generalized Fisher equation with spatio-temporal delay

    International Nuclear Information System (INIS)

    Jin Chunhua; Yin Jingxue; Wang Yifu

    2009-01-01

    We discuss a generalized Fisher equation with a convolution term which introduces a time-delay in the nonlinearity. Special attention is paid to the existence and the asymptotic behavior of travelling wavefronts connecting two uniform steady states.

  17. Wave optics modeling of real-time holographic wavefront compensation systems using OSSim

    Science.gov (United States)

    Carbon, Margarita A.; Guthals, Dennis M.; Logan, Jerry D.

    2005-08-01

    OSSim (Optical System Simulation) is a wave-optics, time-domain simulation toolbox with both optical and data processing components developed for adaptive optics (AO) systems. Diffractive wavefront control elements have recently been added that accurately model optically and electrically addressed spatial light modulators as real time holographic (RTH) devices in diffractive wavefront control systems. The developed RTH toolbox has found multiple applications for a variety of Boeing programs in solving problems of AO system analysis and design. Several complex diffractive wavefront control systems have been modeled for compensation of static and dynamic aberrations such as imperfect segmented primary mirrors and atmospheric and boundary layer turbulence. The results of OSSim simulations of RTH wavefront compensation show very good agreement with available experimental data.

  18. Wavefront picking for 3D tomography and full-waveform inversion

    KAUST Repository

    AlTheyab, Abdullah; Schuster, Gerard T.

    2016-01-01

    We have developed an efficient approach for picking firstbreak wavefronts on coarsely sampled time slices of 3D shot gathers. Our objective was to compute a smooth initial velocity model for multiscale full-waveform inversion (FWI). Using

  19. Transformation of a Plane Wavefront in Hemispherical Lenses Made of Leuco-Sapphire

    Science.gov (United States)

    Vetrov, V. N.; Ignatenkov, B. A.; Yakobson, V. E.

    2018-01-01

    An algorithm for wavefront calculation of ordinary and extraordinary waves after propagation through hemispherical components made of a uniaxial crystal is developed. The influence of frequency dispersion of n o and n e , as well as change in the direction of the optic axis of the crystal, on extraordinary wavefront in hemispheres made of from leuco-sapphire and a plastically deformed analog thereof is determined.

  20. Multiplexed Simultaneous High Sensitivity Sensors with High-Order Mode Based on the Integration of Photonic Crystal 1 × 3 Beam Splitter and Three Different Single-Slot PCNCs.

    Science.gov (United States)

    Zhou, Jian; Huang, Lijun; Fu, Zhongyuan; Sun, Fujun; Tian, Huiping

    2016-07-07

    We simulated an efficient method for the sensor array of high-sensitivity single-slot photonic crystal nanobeam cavities (PCNCs) on a silicon platform. With the combination of a well-designed photonic crystal waveguide (PhCW) filter and an elaborate single-slot PCNC, a specific high-order resonant mode was filtered for sensing. A 1 × 3 beam splitter carefully established was implemented to split channels and integrate three sensors to realize microarrays. By applying the three-dimensional finite-difference-time-domain (3D-FDTD) method, the sensitivities calculated were S₁ = 492 nm/RIU, S₂ = 244 nm/RIU, and S₃ = 552 nm/RIU, respectively. To the best of our knowledge, this is the first multiplexing design in which each sensor cite features such a high sensitivity simultaneously.

  1. Multiplexed Simultaneous High Sensitivity Sensors with High-Order Mode Based on the Integration of Photonic Crystal 1 × 3 Beam Splitter and Three Different Single-Slot PCNCs

    Directory of Open Access Journals (Sweden)

    Jian Zhou

    2016-07-01

    Full Text Available We simulated an efficient method for the sensor array of high-sensitivity single-slot photonic crystal nanobeam cavities (PCNCs on a silicon platform. With the combination of a well-designed photonic crystal waveguide (PhCW filter and an elaborate single-slot PCNC, a specific high-order resonant mode was filtered for sensing. A 1 × 3 beam splitter carefully established was implemented to split channels and integrate three sensors to realize microarrays. By applying the three-dimensional finite-difference-time-domain (3D-FDTD method, the sensitivities calculated were S1 = 492 nm/RIU, S2 = 244 nm/RIU, and S3 = 552 nm/RIU, respectively. To the best of our knowledge, this is the first multiplexing design in which each sensor cite features such a high sensitivity simultaneously.

  2. Avaliação de desempenho e consumo energético para configurações de Wavefront pools de uma GPU AMD

    Directory of Open Access Journals (Sweden)

    Ariel Gustavo Zuquello

    2016-07-01

    Full Text Available O uso de sistemas heterogêneos CPU-GPU para atender à crescente demanda por aplicações com grande paralelismo de dados resulta na necessidade de estudar e avaliar tais arquiteturas para melhorá-las continuamente. Neste artigo foram feitas simulações da execução de uma suíte de benchmark em uma GPU AMD ATI RadeonTM HD 7970, de modo a avaliar o impacto sobre o desempenho e o consumo energético quando alterado o número de Wavefront Pools presentes em cada compute unit da GPU, que é 4 por padrão. O resultado mais significante evidencia um aumento de velocidade de cerca de 5,7% para a configuração com duas Wavefront Pools em conjunto com um aumento no consumo de energia de cerca de 5,1%. Todavia, as outras configurações avaliadas também representam opções para diferentes tipos de necessidades, conforme a categoria de demanda computacional.Palavras-chave: Sistemas heterogêneos. Simulações. Desempenho.Performance evaluation and energy consumption for settings of Wavefront pools of a GPU AMDAbstractThe use of CPU-GPU heterogeneous systems to meet the growing demand for applications with large data parallelism results in the need to study and evaluate these architectures in order to improve them continuously. In this paper we made simulations of running a benchmark suite on an AMD GPU ATI RadeonTM HD 7970 in order to assess the impact on performance and power consumption when tuning the number of Wavefront Pools present in each GPU compute unit, which is 4 by default. The most significant result shows a speedup of about 5.7% for configuration with two Wavefront Pools in conjunction with an increase of about 5.1% in the energy consumption. However, the other evaluated configuration also represent options for different kinds of needs, according to   the  computational demand.Keyworks: Heterogeneous systems. Simulation. Performance.

  3. Alignment and qualification of the Gaia telescope using a Shack-Hartmann sensor

    Science.gov (United States)

    Dovillaire, G.; Pierot, D.

    2017-09-01

    Since almost 20 years, Imagine Optic develops, manufactures and offers to its worldwide customers reliable and accurate wavefront sensors and adaptive optics solutions. Long term collaboration between Imagine Optic and Airbus Defence and Space has been initiated on the Herschel program. More recently, a similar technology has been used to align and qualify the GAIA telescope.

  4. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Kalate Bojdi, Majid [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Behbahani, Mohammad [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Mashhadizadeh, Mohammad Hosein [Faculty of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of); Bagheri, Akbar [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Hosseiny Davarani, Saied Saeed, E-mail: ss-hosseiny@sbu.ac.ir [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of); Farahani, Ali [Department of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of)

    2015-03-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N{sub 2} adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples.

  5. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples

    International Nuclear Information System (INIS)

    Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

    2015-01-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N 2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25 nM to 25 μM with a detection limit of 0.04 nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. - Highlights: • A modified nanoporous carbon as a novel sensor • High stability and good repeatability and reproducibility by the prepared sensor • Trace determination of omeprazole • Biological and pharmaceutical samples

  6. JWST Wavefront Sensing and Control: Operations Plans, Demonstrations, and Status

    Science.gov (United States)

    Perrin, Marshall; Acton, D. Scott; Lajoie, Charles-Philippe; Knight, J. Scott; Myers, Carey; Stark, Chris; JWST Wavefront Sensing & Control Team

    2018-01-01

    After JWST launches and unfolds in space, its telescope optics will be aligned through a complex series of wavefront sensing and control (WFSC) steps to achieve diffraction-limited performance. This iterative process will comprise about half of the observatory commissioning time (~ 3 out of 6 months). We summarize the JWST WFSC process, schedule, and expectations for achieved performance, and discuss our team’s activities to prepare for an effective & efficient telescope commissioning. During the recently-completed OTIS cryo test at NASA JSC, WFSC demonstrations showed the flight-like operation of the entire JWST active optics and WFSC system from end to end, including all hardware and software components. In parallel, the same test data were processed through the JWST Mission Operations Center at STScI to demonstrate the readiness of ground system components there (such as the flight operations system, data pipelines, archives, etc). Moreover, using the Astronomer’s Proposal Tool (APT), the entire telescope commissioning program has been implemented, reviewed, and is ready for execution. Between now and launch our teams will continue preparations for JWST commissioning, including further rehearsals and testing, to ensure a successful alignment of JWST’s telescope optics.

  7. Continuous shearlet frames and resolution of the wavefront set

    KAUST Repository

    Grohs, Philipp

    2010-12-04

    In recent years directional multiscale transformations like the curvelet- or shearlet transformation have gained considerable attention. The reason for this is that these transforms are-unlike more traditional transforms like wavelets-able to efficiently handle data with features along edges. The main result in Kutyniok and Labate (Trans. Am. Math. Soc. 361:2719-2754, 2009) confirming this property for shearlets is due to Kutyniok and Labate where it is shown that for very special functions ψ with frequency support in a compact conical wegde the decay rate of the shearlet coefficients of a tempered distribution f with respect to the shearlet ψ can resolve the wavefront set of f. We demonstrate that the same result can be verified under much weaker assumptions on ψ, namely to possess sufficiently many anisotropic vanishing moments. We also show how to build frames for L2(ℝ2)from any such function. To prove our statements we develop a new approach based on an adaption of the Radon transform to the shearlet structure. © 2010 Springer-Verlag.

  8. The wavefront of the radio signal emitted by cosmic ray air showers

    Energy Technology Data Exchange (ETDEWEB)

    Apel, W.D.; Bekk, K.; Blümer, J.; Bozdog, H.; Daumiller, K.; Doll, P.; Engel, R. [Institut für Kernphysik, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Arteaga-Velázquez, J.C. [Instituto de Física y Matemáticas, Universidad Michoacana, Edificio C-3, Cd. Universitaria, C.P. 58040 Morelia, Michoacán (Mexico); Bähren, L.; Falcke, H. [ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo (Netherlands); Bertaina, M.; Cantoni, E.; Chiavassa, A.; Pierro, F. Di [Dipartimento di Fisica, Università degli Studi di Torino, Via Giuria 1, 10125 Torino (Italy); Biermann, P.L. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn (Germany); Brancus, I.M. [National Institute of Physics and Nuclear Engineering, Str. Reactorului no. 30, P.O. Box MG-6, Bucharest-Magurele (Romania); De Souza, V. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense 400, Pq. Arnold Schmidt, São Carlos (Brazil); Fuchs, B. [Institut für Experimentelle Kernphysik, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Gemmeke, H. [Institut für Prozessdatenverarbeitung und Elektronik, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Grupen, C., E-mail: frank.schroeder@kit.edu [Faculty of Natural Sciences and Engineering, Universität Siegen, Walter-Flex-Straße 3, 57072 Siegen (Germany); and others

    2014-09-01

    Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above 10{sup 17} eV and zenith angles smaller than 45{sup o}, we find that the radio wavefront of cosmic-ray air showers is of approximately hyperbolic shape. The simulations predict a slightly steeper wavefront towards East than towards West, but this asymmetry is negligible against the measurement uncertainties of LOPES. At axis distances ∼> 50 m, the wavefront can be approximated by a simple cone. According to the simulations, the cone angle is clearly correlated with the shower maximum. Thus, we confirm earlier predictions that arrival time measurements can be used to study the longitudinal shower development, but now using a realistic wavefront. Moreover, we show that the hyperbolic wavefront is compatible with our measurement, and we present several experimental indications that the cone angle is indeed sensitive to the shower development. Consequently, the wavefront can be used to statistically study the primary composition of ultra-high energy cosmic rays. At LOPES, the experimentally achieved precision for the shower maximum is limited by measurement uncertainties to approximately 140 g/c {sup 2}. But the simulations indicate that under better conditions this method might yield an accuracy for the atmospheric depth of the shower maximum, X{sub max}, better than 30 g/c {sup 2}. This would be competitive with the established air-fluorescence and air-Cherenkov techniques, where the radio technique offers the advantage of a significantly higher duty-cycle. Finally, the hyperbolic wavefront can be used to reconstruct the shower geometry more accurately, which potentially allows a better reconstruction of all other shower parameters, too.

  9. Open Standards for Sensor Information Processing

    Energy Technology Data Exchange (ETDEWEB)

    Pouchard, Line Catherine [ORNL; Poole, Stephen W [ORNL; Lothian, Josh [ORNL

    2009-07-01

    This document explores sensor standards, sensor data models, and computer sensor software in order to determine the specifications and data representation best suited for analyzing and monitoring computer system health using embedded sensor data. We review IEEE 1451, OGC Sensor Model Language and Transducer Model Language (TML), lm-sensors and Intelligent Platform Management Inititative (IPMI).

  10. Sensors an introductory course

    CERN Document Server

    Kalantar-zadeh, Kourosh

    2013-01-01

    Sensors: An Introductory Course provides an essential reference on the fundamentals of sensors. The book is designed to help readers in developing skills and the understanding required in order to implement a wide range of sensors that are commonly used in our daily lives. This book covers the basic concepts in the sensors field, including definitions and terminologies. The physical sensing effects are described, and devices which utilize these effects are presented. The most frequently used organic and inorganic sensors are introduced and the techniques for implementing them are discussed. This book: Provides a comprehensive representation of the most common sensors and can be used as a reference in relevant fields Presents learning materials in a concise and easy to understand manner Includes examples of how sensors are incorporated in real life measurements Contains detailed figures and schematics to assist in understanding the sensor performance Sensors: An Introductory Course is ideal for university stu...

  11. The measurement and analysis of wavefront structure from large aperture ICF optics

    International Nuclear Information System (INIS)

    Wolfe, C.R.; Lawson, J.K.

    1995-01-01

    This paper discusses the techniques, developed over the past year, for high spatial resolution measurement and analysis of the transmitted and/or reflected wavefront of large aperture ICF optical components. Parts up to 400 mm x 750 mm have been measured and include: laser slabs, windows, KDP crystals and lenses. The measurements were performed using state-of-the-art commercial phase shifting interferometers at a wavelength of 633 μm. Both 1 and 2-D Fourier analysis have been used to characterize the wavefront; specifically the Power Spectral Density, (PSD), function was calculated. The PSDs of several precision optical components will be shown. The PSD(V) is proportional to the (amplitude) 2 of components of the Fourier frequency spectrum. The PSD describes the scattered intensity and direction as a function of scattering angle in the wavefront. The capability of commercial software is limited to 1-D Fourier analysis only. We are developing our own 2-D analysis capability in support of work to revise specifications for NIF optics. 2-D analysis uses the entire wavefront phase map to construct 2D PSD functions. We have been able to increase the signal-to-noise relative to 1-D and can observe very subtle wavefront structure

  12. X-ray wavefront characterization using a rotating shearing interferometer technique.

    Science.gov (United States)

    Wang, Hongchang; Sawhney, Kawal; Berujon, Sébastien; Ziegler, Eric; Rutishauser, Simon; David, Christian

    2011-08-15

    A fast and accurate method to characterize the X-ray wavefront by rotating one of the two gratings of an X-ray shearing interferometer is described and investigated step by step. Such a shearing interferometer consists of a phase grating mounted on a rotation stage, and an absorption grating used as a transmission mask. The mathematical relations for X-ray Moiré fringe analysis when using this device are derived and discussed in the context of the previous literature assumptions. X-ray beam wavefronts without and after X-ray reflective optical elements have been characterized at beamline B16 at Diamond Light Source (DLS) using the presented X-ray rotating shearing interferometer (RSI) technique. It has been demonstrated that this improved method allows accurate calculation of the wavefront radius of curvature and the wavefront distortion, even when one has no previous information on the grating projection pattern period, magnification ratio and the initial grating orientation. As the RSI technique does not require any a priori knowledge of the beam features, it is suitable for routine characterization of wavefronts of a wide range of radii of curvature. © 2011 Optical Society of America

  13. Transmitted wavefront testing with large dynamic range based on computer-aided deflectometry

    Science.gov (United States)

    Wang, Daodang; Xu, Ping; Gong, Zhidong; Xie, Zhongmin; Liang, Rongguang; Xu, Xinke; Kong, Ming; Zhao, Jun

    2018-06-01

    The transmitted wavefront testing technique is demanded for the performance evaluation of transmission optics and transparent glass, in which the achievable dynamic range is a key issue. A computer-aided deflectometric testing method with fringe projection is proposed for the accurate testing of transmitted wavefronts with a large dynamic range. Ray tracing of the modeled testing system is carried out to achieve the virtual ‘null’ testing of transmitted wavefront aberrations. The ray aberration is obtained from the ray tracing result and measured slope, with which the test wavefront aberration can be reconstructed. To eliminate testing system modeling errors, a system geometry calibration based on computer-aided reverse optimization is applied to realize accurate testing. Both numerical simulation and experiments have been carried out to demonstrate the feasibility and high accuracy of the proposed testing method. The proposed testing method can achieve a large dynamic range compared with the interferometric method, providing a simple, low-cost and accurate way for the testing of transmitted wavefronts from various kinds of optics and a large amount of industrial transmission elements.

  14. Probe beam deflection technique as acoustic emission directionality sensor with photoacoustic emission source.

    Science.gov (United States)

    Barnes, Ronald A; Maswadi, Saher; Glickman, Randolph; Shadaram, Mehdi

    2014-01-20

    The goal of this paper is to demonstrate the unique capability of measuring the vector or angular information of propagating acoustic waves using an optical sensor. Acoustic waves were generated using photoacoustic interaction and detected by the probe beam deflection technique. Experiments and simulations were performed to study the interaction of acoustic emissions with an optical sensor in a coupling medium. The simulated results predict the probe beam and wavefront interaction and produced simulated signals that are verified by experiment.

  15. Characterisation of a spinning pipe gas lens using a Shack–Hartmann wavefront sensor

    CSIR Research Space (South Africa)

    Mafusire, C

    2007-01-01

    Full Text Available A heated horizontal spinning pipe causes gases inside it to assume dynamics resulting in a graded index lens – a spinning pipe gas lens (SPGL). A CFD model is presented which shows that gas exchanges of the SPGL with the surroundings resulting in a...

  16. H2-optimal control of an adaptive optics system : Part I, data-driven modeling of the wavefront disturbance

    NARCIS (Netherlands)

    Hinnen, K.; Verhaegen, M.; Doelman, N.

    2005-01-01

    Even though the wavefront distortion introduced by atmospheric turbulence is a dynamic process, its temporal evolution is usually neglected in the adaptive optics (AO) control design. Most AO control systems consider only the spatial correlation in a separate wavefront reconstruction step. By

  17. Measurement of wavefront structure from large aperture optical components by phase shifting interferometry

    International Nuclear Information System (INIS)

    Wolfe, C.R.; Lawson, J.K.; Kellam, M.; Maney, R.T.; Demiris, A.

    1995-01-01

    This paper discusses the results of high spatial resolution measurement of the transmitted or reflected wavefront of optical components using phase shifting interferometry with a wavelength of 6328 angstrom. The optical components studied range in size from approximately 50 mm x 100 mm to 400 mm x 750 mm. Wavefront data, in the form of 3-D phase maps, have been obtained for three regimes of scale length: ''micro roughness'', ''mid-spatial scale'', and ''optical figure/curvature.'' Repetitive wavefront structure has been observed with scale lengths from 10 mm to 100 mm. The amplitude of this structure is typically λ/100 to λ/20. Previously unobserved structure has been detected in optical materials and on the surfaces of components. We are using this data to assist in optimizing laser system design, to qualify optical components and fabrication processes under study in our component development program

  18. Generation of Optical Vortex Arrays Using Single-Element Reversed-Wavefront Folding Interferometer

    Directory of Open Access Journals (Sweden)

    Brijesh Kumar Singh

    2012-01-01

    Full Text Available Optical vortex arrays have been generated using simple, novel, and stable reversed-wavefront folding interferometer. Two new interferometric configurations were used for generating a variety of optical vortex lattices. In the first interferometric configuration one cube beam splitter (CBS was used in one arm of Mach-Zehnder interferometer for splitting and combining the collimated beam, and one mirror of another arm is replaced by second CBS. At the output of interferometer, three-beam interference gives rise to optical vortex arrays. In second interferometric configuration, a divergent wavefront was made incident on a single CBS which splits and combines wavefronts leading to the generation of vortex arrays due to four-beam interference. It was found that the orientation and structure of the optical vortices can be stably controlled by means of changing the rotation angle of CBS.

  19. Optimization of scanning strategy of digital Shack-Hartmann wavefront sensing.

    Science.gov (United States)

    Guo, Wenjiang; Zhao, Liping; Li, Xiang; Chen, I-Ming

    2012-01-01

    In the traditional Shack-Hartmann wavefront sensing (SHWS) system, a lenslet array with a bigger configuration is desired to achieve a higher lateral resolution. However, practical implementation limits the configuration and this parameter is contradicted with the measurement range. We have proposed a digital scanning technique by making use of the high flexibility of a spatial light modulator to sample the reflected wavefront [X. Li, L. P. Zhao, Z. P. Fang, and C. S. Tan, "Improve lateral resolution in wavefront sensing with digital scanning technique," in Asia-Pacific Conference of Transducers and Micro-Nano Technology (2006)]. The lenslet array pattern is programmed to laterally scan the whole aperture. In this paper, the methodology to optimize the scanning step for the purpose of form measurement is proposed. The correctness and effectiveness are demonstrated in numerical simulation and experimental investigation. © 2012 Optical Society of America

  20. Study on the properties of infrared wavefront coding athermal system under several typical temperature gradient distributions

    Science.gov (United States)

    Cai, Huai-yu; Dong, Xiao-tong; Zhu, Meng; Huang, Zhan-hua

    2018-01-01

    Wavefront coding for athermal technique can effectively ensure the stability of the optical system imaging in large temperature range, as well as the advantages of compact structure and low cost. Using simulation method to analyze the properties such as PSF and MTF of wavefront coding athermal system under several typical temperature gradient distributions has directive function to characterize the working state of non-ideal temperature environment, and can effectively realize the system design indicators as well. In this paper, we utilize the interoperability of data between Solidworks and ZEMAX to simplify the traditional process of structure/thermal/optical integrated analysis. Besides, we design and build the optical model and corresponding mechanical model of the infrared imaging wavefront coding athermal system. The axial and radial temperature gradients of different degrees are applied to the whole system by using SolidWorks software, thus the changes of curvature, refractive index and the distance between the lenses are obtained. Then, we import the deformation model to ZEMAX for ray tracing, and obtain the changes of PSF and MTF in optical system. Finally, we discuss and evaluate the consistency of the PSF (MTF) of the wavefront coding athermal system and the image restorability, which provides the basis and reference for the optimal design of the wavefront coding athermal system. The results show that the adaptability of single material infrared wavefront coding athermal system to axial temperature gradient can reach the upper limit of temperature fluctuation of 60°C, which is much higher than that of radial temperature gradient.

  1. Mercapto-ordered carbohydrate-derived porous carbon electrode as a novel electrochemical sensor for simple and sensitive ultra-trace detection of omeprazole in biological samples.

    Science.gov (United States)

    Kalate Bojdi, Majid; Behbahani, Mohammad; Mashhadizadeh, Mohammad Hosein; Bagheri, Akbar; Hosseiny Davarani, Saied Saeed; Farahani, Ali

    2015-03-01

    We are introducing mercapto-mesoporous carbon modified carbon paste electrode (mercapto-MP-C-CPE) as a new sensor for trace determination of omeprazole (OM) in biological samples. The synthesized modifier was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN) and N2 adsorption surface area measurement (BET). The electrochemical response characteristic of the modified-CPE toward OM was investigated by cyclic and differential pulse voltammetry (CV and DPV). The proposed sensor displayed a good electrooxidation response to the OM, its linear range is 0.25nM to 25μM with a detection limit of 0.04nM under the optimized conditions. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Synergistic effects from graphene and carbon nanotubes endow ordered hierarchical structure foams with a combination of compressibility, super-elasticity and stability and potential application as pressure sensors.

    Science.gov (United States)

    Kuang, Jun; Dai, Zhaohe; Liu, Luqi; Yang, Zhou; Jin, Ming; Zhang, Zhong

    2015-01-01

    Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin.

  3. 110 °C range athermalization of wavefront coding infrared imaging systems

    Science.gov (United States)

    Feng, Bin; Shi, Zelin; Chang, Zheng; Liu, Haizheng; Zhao, Yaohong

    2017-09-01

    110 °C range athermalization is significant but difficult for designing infrared imaging systems. Our wavefront coding athermalized infrared imaging system adopts an optical phase mask with less manufacturing errors and a decoding method based on shrinkage function. The qualitative experiments prove that our wavefront coding athermalized infrared imaging system has three prominent merits: (1) working well over a temperature range of 110 °C; (2) extending the focal depth up to 15.2 times; (3) achieving a decoded image being approximate to its corresponding in-focus infrared image, with a mean structural similarity index (MSSIM) value greater than 0.85.

  4. Transmitted wavefront error of a volume phase holographic grating at cryogenic temperature.

    Science.gov (United States)

    Lee, David; Taylor, Gordon D; Baillie, Thomas E C; Montgomery, David

    2012-06-01

    This paper describes the results of transmitted wavefront error (WFE) measurements on a volume phase holographic (VPH) grating operating at a temperature of 120 K. The VPH grating was mounted in a cryogenically compatible optical mount and tested in situ in a cryostat. The nominal root mean square (RMS) wavefront error at room temperature was 19 nm measured over a 50 mm diameter test aperture. The WFE remained at 18 nm RMS when the grating was cooled. This important result demonstrates that excellent WFE performance can be obtained with cooled VPH gratings, as required for use in future cryogenic infrared astronomical spectrometers planned for the European Extremely Large Telescope.

  5. Chirped pulse digital holography for measuring the sequence of ultrafast optical wavefronts

    Science.gov (United States)

    Karasawa, Naoki

    2018-04-01

    Optical setups for measuring the sequence of ultrafast optical wavefronts using a chirped pulse as a reference wave in digital holography are proposed and analyzed. In this method, multiple ultrafast object pulses are used to probe the temporal evolution of ultrafast phenomena and they are interfered with a chirped reference wave to record a digital hologram. Wavefronts at different times can be reconstructed separately from the recorded hologram when the reference pulse can be treated as a quasi-monochromatic wave during the pulse width of each object pulse. The feasibility of this method is demonstrated by numerical simulation.

  6. Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis.

    Science.gov (United States)

    Liu, Hong-Ting; Zhou, Zhou; Luo, Wu-Qiang; He, Wen-Jing; Agbedia, Owhofasa; Wang, Jiang-Xia; Huang, Jian-Zhong; Gao, Xin; Kong, Min; Li, Min; Li, Li

    2018-01-01

    To compare the optical quality after implantation of implantable collamer lens (ICL) and wavefront-guided laser in situ keratomileusis (WG-LASIK). The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index (OSI), the values of modulation transfer function (MTF) cutoff frequency, Strehl ratio, and the Optical Quality Analysis System (OQAS) values (OVs) were accessed. The higher order aberrations (HOAs) data including coma, trefoil, spherical, 2 nd astigmatism and tetrafoil were also obtained. For patients with pupil size LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent ( P LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively (Wilcoxon signed ranks test, P =0.000). None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mm-pupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2 nd astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05, -0.04±0.04, 0.03±0.01 respectively (Wilcoxon signed ranks test, all P LASIK group. ICL implantation has a less disturbance to optical quality than WG-LASIK. The OQAS is a valuable complementary measurement to the wavefront aberrometers in evaluating the optical quality.

  7. Wavefront-Error Performance Characterization for the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) Science Instruments

    Science.gov (United States)

    Aronstein, David L.; Smith, J. Scott; Zielinski, Thomas P.; Telfer, Randal; Tournois, Severine C.; Moore, Dustin B.; Fienup, James R.

    2016-01-01

    The science instruments (SIs) comprising the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) were tested in three cryogenic-vacuum test campaigns in the NASA Goddard Space Flight Center (GSFC)'s Space Environment Simulator (SES). In this paper, we describe the results of optical wavefront-error performance characterization of the SIs. The wavefront error is determined using image-based wavefront sensing (also known as phase retrieval), and the primary data used by this process are focus sweeps, a series of images recorded by the instrument under test in its as-used configuration, in which the focal plane is systematically changed from one image to the next. High-precision determination of the wavefront error also requires several sources of secondary data, including 1) spectrum, apodization, and wavefront-error characterization of the optical ground-support equipment (OGSE) illumination module, called the OTE Simulator (OSIM), 2) plate scale measurements made using a Pseudo-Nonredundant Mask (PNRM), and 3) pupil geometry predictions as a function of SI and field point, which are complicated because of a tricontagon-shaped outer perimeter and small holes that appear in the exit pupil due to the way that different light sources are injected into the optical path by the OGSE. One set of wavefront-error tests, for the coronagraphic channel of the Near-Infrared Camera (NIRCam) Longwave instruments, was performed using data from transverse translation diversity sweeps instead of focus sweeps, in which a sub-aperture is translated andor rotated across the exit pupil of the system.Several optical-performance requirements that were verified during this ISIM-level testing are levied on the uncertainties of various wavefront-error-related quantities rather than on the wavefront errors themselves. This paper also describes the methodology, based on Monte Carlo simulations of the wavefront-sensing analysis of focus-sweep data, used to establish the

  8. Higher order aberrations of the eye: Part one

    Directory of Open Access Journals (Sweden)

    Marsha Oberholzer

    2016-06-01

    Full Text Available This article is the first in a series of two articles that provide a comprehensive literature review of higher order aberrations (HOAs of the eye. The present article mainly explains the general principles of such HOAs as well as HOAs of importance, and the measuring apparatus used to measure HOAs of the eye. The second article in the series discusses factors contributing to variable results in measurements of HOAs of the eye. Keywords: Higher order aberrations; wavefront aberrations; aberrometer

  9. Hartmann wavefront sensing of the corrective optics for the Hubble Space Telescope

    Science.gov (United States)

    Davila, Pam S.; Eichhorn, William L.; Wilson, Mark E.

    1994-06-01

    aberration content of the corrected images. Also, from only this test it was difficult to measure important pupil parameters, such as pupil intensity profiles and pupil sizes and location. To measure the COSTAR wavefront accurately and to determine pupil parameters, another very important test was performed on the COSTAR optics. A Hartmann test of the optical system consisting of the RAS and COSTAR was conducted by the Goddard Independent Verification Team (IVT). In this paper, we first describe the unique Hartmann sensor that was developed by the IVT. Then we briefly describe the RAS and COSTAR optical systems and the test setup. Finally, we present the results of the test and compare our results with results obtained from optical analysis and from image tests with the BIA.

  10. Planoconcave optical microresonator sensors for photoacoustic imaging: pushing the limits of sensitivity (Conference Presentation)

    Science.gov (United States)

    Guggenheim, James A.; Zhang, Edward Z.; Beard, Paul C.

    2016-03-01

    Most photoacoustic scanners use piezoelectric detectors but these have two key limitations. Firstly, they are optically opaque, inhibiting backward mode operation. Secondly, it is difficult to achieve adequate detection sensitivity with the small element sizes needed to provide near-omnidirectional response as required for tomographic imaging. Planar Fabry-Perot (FP) ultrasound sensing etalons can overcome both of these limitations and have proved extremely effective for superficial (beam. However, this has the disadvantage that beam walk-off due to the divergence of the beam fundamentally limits the etalon finesse and thus sensitivity - in essence, the problem is one of insufficient optical confinement. To overcome this, novel planoconcave micro-resonator sensors have been fabricated using precision ink-jet printed polymer domes with curvatures matching that of the laser wavefront. By providing near-perfect beam confinement, we show that it is possible to approach the maximum theoretical limit for finesse (f) imposed by the etalon mirror reflectivities (e.g. f=400 for R=99.2% in contrast to a typical planar sensor value of fbeam walk-off, viable sensors can be made with significantly greater thickness than planar FP sensors. This provides an additional sensitivity gain for deep tissue imaging applications such as breast imaging where detection bandwidths in the low MHz can be tolerated. For example, for a 250 μm thick planoconcave sensor with a -3dB bandwidth of 5MHz, the measured NEP was 4 Pa. This NEP is comparable to that provided by mm scale piezoelectric detectors used for breast imaging applications but with more uniform frequency response characteristics and an order-of-magnitude smaller element size. Following previous proof-of-concept work, several important advances towards practical application have been made. A family of sensors with bandwidths ranging from 3MHz to 20MHz have been fabricated and characterised. A novel interrogation scheme based on

  11. Wavefront improvement in an end-pumped high-power Nd:YAG zigzag slab laser.

    Science.gov (United States)

    Shin, Jae Sung; Cha, Yong-Ho; Lim, Gwon; Kim, Yonghee; Kwon, Seong-Ouk; Cha, Byung Heon; Lee, Hyeon Cheor; Kim, Sangin; Koh, Kwang Uoong; Kim, Hyun Tae

    2017-08-07

    Techniques for wavefront improvement in an end-pumped Nd:YAG zigzag slab laser amplifier were proposed and demonstrated experimentally. First, a study on the contact materials was conducted to improve the heat transfer between the slab and cooling blocks and to increase the cooling uniformity. Among many attempts, only the use of silicon oil showed an improvement in the wavefront. Thus, the appropriate silicone oil was applied to the amplifier as a contact material. In addition, the wavefront compensation method using a glass rod array was also applied to the amplifier. A very low wavefront distortion was obtained through the use of a silicone-oil contact and glass rod array. The variance of the optical path difference for the entire beam height was 3.87 μm at a pump power of 10.6 kW, and that for the 80% section was 1.69 μm. The output power from the oscillator was 3.88 kW, which means the maximum output extracted from the amplifier at a pump power of 10.6 kW.

  12. High speed real-time wavefront processing system for a solid-state laser system

    Science.gov (United States)

    Liu, Yuan; Yang, Ping; Chen, Shanqiu; Ma, Lifang; Xu, Bing

    2008-03-01

    A high speed real-time wavefront processing system for a solid-state laser beam cleanup system has been built. This system consists of a core2 Industrial PC (IPC) using Linux and real-time Linux (RT-Linux) operation system (OS), a PCI image grabber, a D/A card. More often than not, the phase aberrations of the output beam from solid-state lasers vary fast with intracavity thermal effects and environmental influence. To compensate the phase aberrations of solid-state lasers successfully, a high speed real-time wavefront processing system is presented. Compared to former systems, this system can improve the speed efficiently. In the new system, the acquisition of image data, the output of control voltage data and the implementation of reconstructor control algorithm are treated as real-time tasks in kernel-space, the display of wavefront information and man-machine conversation are treated as non real-time tasks in user-space. The parallel processing of real-time tasks in Symmetric Multi Processors (SMP) mode is the main strategy of improving the speed. In this paper, the performance and efficiency of this wavefront processing system are analyzed. The opened-loop experimental results show that the sampling frequency of this system is up to 3300Hz, and this system can well deal with phase aberrations from solid-state lasers.

  13. Athermalization of infrared dual field optical system based on wavefront coding

    Science.gov (United States)

    Jiang, Kai; Jiang, Bo; Liu, Kai; Yan, Peipei; Duan, Jing; Shan, Qiu-sha

    2017-02-01

    Wavefront coding is a technology which combination of the optical design and digital image processing. By inserting a phase mask closed to the pupil plane of the optical system the wavefront of the system is re-modulated. And the depth of focus is extended consequently. In reality the idea is same as the athermalization theory of infrared optical system. In this paper, an uncooled infrared dual field optical system with effective focal as 38mm/19mm, F number as 1.2 of both focal length, operating wavelength varying from 8μm to 12μm was designed. A cubic phase mask was used at the pupil plane to re-modulate the wavefront. Then the performance of the infrared system was simulated with CODEV as the environment temperature varying from -40° to 60°. MTF curve of the optical system with phase mask are compared with the outcome before using phase mask. The result show that wavefront coding technology can make the system not sensitive to thermal defocus, and then realize the athermal design of the infrared optical system.

  14. Performance analysis of multidimensional wavefront algorithms with application to deterministic particle transport

    International Nuclear Information System (INIS)

    Hoisie, A.; Lubeck, O.; Wasserman, H.

    1998-01-01

    The authors develop a model for the parallel performance of algorithms that consist of concurrent, two-dimensional wavefronts implemented in a message passing environment. The model, based on a LogGP machine parameterization, combines the separate contributions of computation and communication wavefronts. They validate the model on three important supercomputer systems, on up to 500 processors. They use data from a deterministic particle transport application taken from the ASCI workload, although the model is general to any wavefront algorithm implemented on a 2-D processor domain. They also use the validated model to make estimates of performance and scalability of wavefront algorithms on 100-TFLOPS computer systems expected to be in existence within the next decade as part of the ASCI program and elsewhere. In this context, the authors analyze two problem sizes. Their model shows that on the largest such problem (1 billion cells), inter-processor communication performance is not the bottleneck. Single-node efficiency is the dominant factor

  15. High-resolution wavefront shaping with a photonic crystal fiber for multimode fiber imaging

    NARCIS (Netherlands)

    Amitonova, L. V.; Descloux, A.; Petschulat, J.; Frosz, M. H.; Ahmed, G.; Babic, F.; Jiang, X.; Mosk, A. P.; Russell, P. S. J.; Pinkse, P.W.H.

    2016-01-01

    We demonstrate that a high-numerical-aperture photonic crystal fiber allows lensless focusing at an unparalleled res- olution by complex wavefront shaping. This paves the way toward high-resolution imaging exceeding the capabilities of imaging with multi-core single-mode optical fibers. We analyze

  16. Wavefront-guided versus standard laser in situ keratomileusis to correct low to moderate myopia.

    NARCIS (Netherlands)

    Nuijts, R.M.; Nabar, V.A.; Hament, W.J.; Eggink, F.A.G.J.

    2002-01-01

    To evaluate the 6-month refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) (Zyoptix, Bausch & Lomb) versus standard LASIK (PlanoScan, Bausch & Lomb).Department of Ophthalmology, University Hospital Maastricht, Maastricht, The Netherlands.In a prospective randomized study,

  17. Wave-front reversal in a copper-vapor active medium

    Energy Technology Data Exchange (ETDEWEB)

    Bunkin, F.V.; Savranskii, V.V.; Shafeev, G.A.

    1981-09-01

    The implementation of wave-front reversal in a copper-vapor laser resonator is reported. The frequencies of the signal wave and the reversed wave are the same, and the dependence of reversed-signal power on input-signal power has a threshold character. Photographs of the reconstructed object image upon insertion of a distorting phase plate into the resonator are presented.

  18. Tool to estimate optical metrics from summary wave-front analysis data in the human eye

    NARCIS (Netherlands)

    Jansonius, Nomdo M.

    Purpose Studies in the field of cataract and refractive surgery often report only summary wave-front analysis data data that are too condensed to allow for a retrospective calculation of metrics relevant to visual perception. The aim of this study was to develop a tool that can be used to estimate

  19. Optimal control strategy to reduce the temporal wavefront error in AO systems

    NARCIS (Netherlands)

    Doelman, N.J.; Hinnen, K.J.G.; Stoffelen, F.J.G.; Verhaegen, M.H.

    2004-01-01

    An Adaptive Optics (AO) system for astronomy is analysed from a control point of view. The focus is put on the temporal error. The AO controller is identified as a feedback regulator system, operating in closed-loop with the aim of rejecting wavefront disturbances. Limitations on the performance of

  20. Characteristic evaluation of acoustic emission sensors

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hyun Kyu; Joo, Y. S.; Lee, N. H

    2000-12-01

    This report introduces the various kinds of Acoustic Emission(AE) sensors as well as the basic principle of AE sensors in order to select AE sensor suitably. The described sensors include : high sensitivity sensor, broadband sensor, underwater sensor, miniature sensor, directional sensor, integral pre-amplifier sensor. Sensor has two critical aspects of reliability and repeatability. For the high reliability, sensor has to be calibrated in accordance with ASTM standard E 1106 which explains to measure the characteristics of AE sensor accurately. For investigating the degradation of AE sensor under the severe environment for example the high radiation condition, It is important to perform the repeatability test which is described in detail in according to the ASTM standard E 976. Two kinds of AE sensor applications are also summarized.

  1. Non-uniform dispersion of the source-sink relationship alters wavefront curvature.

    Directory of Open Access Journals (Sweden)

    Lucia Romero

    Full Text Available The distribution of cellular source-sink relationships plays an important role in cardiac propagation. It can lead to conduction slowing and block as well as wave fractionation. It is of great interest to unravel the mechanisms underlying evolution in wavefront geometry. Our goal is to investigate the role of the source-sink relationship on wavefront geometry using computer simulations. We analyzed the role of variability in the microscopic source-sink relationship in driving changes in wavefront geometry. The electrophysiological activity of a homogeneous isotropic tissue was simulated using the ten Tusscher and Panfilov 2006 action potential model and the source-sink relationship was characterized using an improved version of the Romero et al. safety factor formulation (SFm2. Our simulations reveal that non-uniform dispersion of the cellular source-sink relationship (dispersion along the wavefront leads to alterations in curvature. To better understand the role of the source-sink relationship in the process of wave formation, the electrophysiological activity at the initiation of excitation waves in a 1D strand was examined and the source-sink relationship was characterized using the two recently updated safety factor formulations: the SFm2 and the Boyle-Vigmond (SFVB definitions. The electrophysiological activity at the initiation of excitation waves was intimately related to the SFm2 profiles, while the SFVB led to several counterintuitive observations. Importantly, with the SFm2 characterization, a critical source-sink relationship for initiation of excitation waves was identified, which was independent of the size of the electrode of excitation, membrane excitability, or tissue conductivity. In conclusion, our work suggests that non-uniform dispersion of the source-sink relationship alters wavefront curvature and a critical source-sink relationship profile separates wave expansion from collapse. Our study reinforces the idea that the

  2. Improved Visualization of Gastrointestinal Slow Wave Propagation Using a Novel Wavefront-Orientation Interpolation Technique.

    Science.gov (United States)

    Mayne, Terence P; Paskaranandavadivel, Niranchan; Erickson, Jonathan C; OGrady, Gregory; Cheng, Leo K; Angeli, Timothy R

    2018-02-01

    High-resolution mapping of gastrointestinal (GI) slow waves is a valuable technique for research and clinical applications. Interpretation of high-resolution GI mapping data relies on animations of slow wave propagation, but current methods remain as rudimentary, pixelated electrode activation animations. This study aimed to develop improved methods of visualizing high-resolution slow wave recordings that increases ease of interpretation. The novel method of "wavefront-orientation" interpolation was created to account for the planar movement of the slow wave wavefront, negate any need for distance calculations, remain robust in atypical wavefronts (i.e., dysrhythmias), and produce an appropriate interpolation boundary. The wavefront-orientation method determines the orthogonal wavefront direction and calculates interpolated values as the mean slow wave activation-time (AT) of the pair of linearly adjacent electrodes along that direction. Stairstep upsampling increased smoothness and clarity. Animation accuracy of 17 human high-resolution slow wave recordings (64-256 electrodes) was verified by visual comparison to the prior method showing a clear improvement in wave smoothness that enabled more accurate interpretation of propagation, as confirmed by an assessment of clinical applicability performed by eight GI clinicians. Quantitatively, the new method produced accurate interpolation values compared to experimental data (mean difference 0.02 ± 0.05 s) and was accurate when applied solely to dysrhythmic data (0.02 ± 0.06 s), both within the error in manual AT marking (mean 0.2 s). Mean interpolation processing time was 6.0 s per wave. These novel methods provide a validated visualization platform that will improve analysis of high-resolution GI mapping in research and clinical translation.

  3. Using a CBL Unit, a Temperature Sensor, and a Graphing Calculator to Model the Kinetics of Consecutive First-Order Reactions as Safe In-Class Demonstrations

    Science.gov (United States)

    Moore-Russo, Deborah A.; Cortes-Figueroa, Jose E.; Schuman, Michael J.

    2006-01-01

    The use of Calculator-Based Laboratory (CBL) technology, the graphing calculator, and the cooling and heating of water to model the behavior of consecutive first-order reactions is presented, where B is the reactant, I is the intermediate, and P is the product for an in-class demonstration. The activity demonstrates the spontaneous and consecutive…

  4. MEMS optical sensor

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention relates to an all-optical sensor utilizing effective index modulation of a waveguide and detection of a wavelength shift of reflected light and a force sensing system accommodating said optical sensor. One embodiment of the invention relates to a sensor system comprising...... at least one multimode light source, one or more optical sensors comprising a multimode sensor optical waveguide accommodating a distributed Bragg reflector, at least one transmitting optical waveguide for guiding light from said at least one light source to said one or more multimode sensor optical...... waveguides, a detector for measuring light reflected from said Bragg reflector in said one or more multimode sensor optical waveguides, and a data processor adapted for analyzing variations in the Bragg wavelength of at least one higher order mode of the reflected light....

  5. Taste sensor; Mikaku sensor

    Energy Technology Data Exchange (ETDEWEB)

    Toko, K. [Kyushu University, Fukuoka (Japan)

    1998-03-05

    This paper introduces a taste sensor having a lipid/polymer membrane to work as a receptor of taste substances. The paper describes the following matters: this sensor uses a hollow polyvinyl chloride rod filled with KCl aqueous solution, and placed with silver and silver chloride wires, whose cross section is affixed with a lipid/polymer membrane as a lipid membrane electrode to identify taste from seven or eight kinds of response patterns of electric potential output from the lipid/polymer membrane; measurements of different substances presenting acidic taste, salty taste, bitter taste, sweet taste and flavor by using this sensor identified clearly each taste (similar response is shown to a similar taste even if the substances are different); different responses are indicated on different brands of beers; from the result of measuring a great variety of mineral waters, a possibility was suggested that this taste sensor could be used for water quality monitoring sensors; and application of this taste sensor may be expected as a maturation control sensor for Japanese sake (wine) and miso (bean paste) manufacturing. 2 figs., 1 tab.

  6. Virtual Sensor Test Instrumentation

    Science.gov (United States)

    Wang, Roy

    2011-01-01

    Virtual Sensor Test Instrumentation is based on the concept of smart sensor technology for testing with intelligence needed to perform sell-diagnosis of health, and to participate in a hierarchy of health determination at sensor, process, and system levels. A virtual sensor test instrumentation consists of five elements: (1) a common sensor interface, (2) microprocessor, (3) wireless interface, (4) signal conditioning and ADC/DAC (analog-to-digital conversion/ digital-to-analog conversion), and (5) onboard EEPROM (electrically erasable programmable read-only memory) for metadata storage and executable software to create powerful, scalable, reconfigurable, and reliable embedded and distributed test instruments. In order to maximize the efficient data conversion through the smart sensor node, plug-and-play functionality is required to interface with traditional sensors to enhance their identity and capabilities for data processing and communications. Virtual sensor test instrumentation can be accessible wirelessly via a Network Capable Application Processor (NCAP) or a Smart Transducer Interlace Module (STIM) that may be managed under real-time rule engines for mission-critical applications. The transducer senses the physical quantity being measured and converts it into an electrical signal. The signal is fed to an A/D converter, and is ready for use by the processor to execute functional transformation based on the sensor characteristics stored in a Transducer Electronic Data Sheet (TEDS). Virtual sensor test instrumentation is built upon an open-system architecture with standardized protocol modules/stacks to interface with industry standards and commonly used software. One major benefit for deploying the virtual sensor test instrumentation is the ability, through a plug-and-play common interface, to convert raw sensor data in either analog or digital form, to an IEEE 1451 standard-based smart sensor, which has instructions to program sensors for a wide variety of

  7. A High-Resolution Demodulation Algorithm for FBG-FP Static-Strain Sensors Based on the Hilbert Transform and Cross Third-Order Cumulant

    Directory of Open Access Journals (Sweden)

    Wenzhu Huang

    2015-04-01

    Full Text Available Static strain can be detected by measuring a cross-correlation of reflection spectra from two fiber Bragg gratings (FBGs. However, the static-strain measurement resolution is limited by the dominant Gaussian noise source when using this traditional method. This paper presents a novel static-strain demodulation algorithm for FBG-based Fabry-Perot interferometers (FBG-FPs. The Hilbert transform is proposed for changing the Gaussian distribution of the two FBG-FPs’ reflection spectra, and a cross third-order cumulant is used to use the results of the Hilbert transform and get a group of noise-vanished signals which can be used to accurately calculate the wavelength difference of the two FBG-FPs. The benefit by these processes is that Gaussian noise in the spectra can be suppressed completely in theory and a higher resolution can be reached. In order to verify the precision and flexibility of this algorithm, a detailed theory model and a simulation analysis are given, and an experiment is implemented. As a result, a static-strain resolution of 0.9 nε under laboratory environment condition is achieved, showing a higher resolution than the traditional cross-correlation method.

  8. Multifunctional optical sensor

    NARCIS (Netherlands)

    2010-01-01

    The invention relates to a multifunctional optical sensor, having at least 2 areas which independently react to different input parameters, the sensor comprising a substrate and a polymeric layer comprising polymerized liquid crystal monomers having an ordered morphology, wherein the color, the

  9. Beam quality management by periodic reproduction of wavefront aberrations in end-pumped Nd:YVO4 laser amplifiers.

    Science.gov (United States)

    Liu, Bin; Liu, Chong; Shen, Lifeng; Wang, Chunhua; Ye, Zhibin; Liu, Dong; Xiang, Zhen

    2016-04-18

    A method for beam quality management is presented in a master oscillator power amplifier (MOPA) using Nd:YVO4 as the gain medium by extra-cavity periodic reproduction of wavefront aberrations. The wavefront aberration evolution of the intra-cavity beams is investigated for both symmetrical and asymmetrical resonators. The wavefront aberration reproduction process is successfully realized outside the cavity in four-stage amplifiers. In the MOPA with a symmetrical oscillator, the laser power increases linearly and the beam quality hardly changes. In the MOPA with an asymmetrical oscillator, the beam quality is deteriorated after the odd-stage amplifier and is improved after the even-stage amplifier. The wavefront aberration reproduction during the extra-cavity beam propagation in the amplifiers is equivalent to that during the intra-cavity propagation. This solution helps to achieve the effective beam quality management in laser amplifier chains.

  10. Enhanced Sensitivity to Detection Nanomolar Level of Cu2 + Compared to Spectrophotometry Method by Functionalized Gold Nanoparticles: Design of Sensor Assisted by Exploiting First-order Data with Chemometrics

    Science.gov (United States)

    Rasouli, Zolaikha; Ghavami, Raouf

    2018-02-01

    A simple, sensitive and efficient colorimetric assay platform for the determination of Cu2 + was proposed with the aim of developing sensitive detection based on the aggregation of AuNPs in presence of a histamine H2-receptor antagonist (famotidine, FAM) as recognition site. This study is the first to demonstrate that the molar extinction coefficients of the complexes formed by FAM and Cu2 + are very low (by analyzing the chemometrics methods on the first order data arising from different metal to ligand ratio method), leading to the undesirable sensitivity of FAM-based assays. To resolve the problem of low sensitivity, the colorimetry method based on the Cu2 +-induced aggregation of AuNPs functionalized with FAM was introduced. This procedure is accompanied by a color change from bright red to blue which can be observed with the naked eyes. Detection sensitivity obtained by the developed method increased about 100 fold compared with the spectrophotometry method. This sensor exhibited a good linear relation between the absorbance ratios at 670 to 520 nm (A670/520) and the concentration in the range 2-110 nM with LOD = 0.76 nM. The satisfactory analytical performance of the proposed sensor facilitates the development of simple and affordable UV-Vis chemosensors for environmental applications.

  11. Measuring and modeling intraocular light scatter with Shack-Hartmann wavefront sensing and the effects of nuclear cataract on the measurement of wavefront error

    Science.gov (United States)

    Donnelly, William J., III

    Purpose. The purpose of this research is to determine if Shack/Hartmann (S/H) wavefront sensing (SHWS) can be used to objectively quantify ocular forward scatter. Methods. Patient S/H images from an study of nuclear cataract were analyzed to extract scattering data by examining characteristics of the lenslet point spread functions. Physical and computer eye models with simulated cataract were developed to control variables and to test the underlying assumptions for using SHWS to measure aberrations and light scatter from nuclear cataract. Results. (1) For patients with nuclear opalescence (NO) >=2.5, forward scatter metrics in a multiple regression analysis account for 33% of variance in Mesopic Low Contrast acuity. Prediction of visual acuity was improved by employing a multiple regression analysis that included both backscatter and forward scatter metrics (R2 = 51%) for Mesopic High Contrast acuity. (2) The physical and computer models identified areas of instrument noise (e.g., stray light and unwanted reflections) improving the design of a second generation SHWS for measuring both wavefront error and scatter. (3) Exposure time had the most influence on, and pupil size had negligible influence on forward scatter metrics. Scatter metric MAX_SD predicted changes in simulated cataract up to R2 = 92%. There were small but significant differences (alpha = 0.05) between 1.5-pass and 1-pass wavefront measurements inclusive of variable simulated nuclear cataract and exposure; however, these differences were not visually significant. Improvements to the SHWS imaging hardware, software, and test protocol were implemented in a second generation SHWS to be used in a longitudinal cataract study. Conclusions. Forward light scatter in real eyes can be quantified using a SHWS. In the presence of clinically significant nuclear opalescence, forward scatter metrics predicted acuity better than the LOCS III NO backscatter metric. The superiority of forward scatter metrics over back

  12. A reduced-order adaptive neuro-fuzzy inference system model as a software sensor for rapid estimation of five-day biochemical oxygen demand

    Science.gov (United States)

    Noori, Roohollah; Safavi, Salman; Nateghi Shahrokni, Seyyed Afshin

    2013-07-01

    The five-day biochemical oxygen demand (BOD5) is one of the key parameters in water quality management. In this study, a novel approach, i.e., reduced-order adaptive neuro-fuzzy inference system (ROANFIS) model was developed for rapid estimation of BOD5. In addition, an uncertainty analysis of adaptive neuro-fuzzy inference system (ANFIS) and ROANFIS models was carried out based on Monte-Carlo simulation. Accuracy analysis of ANFIS and ROANFIS models based on both developed discrepancy ratio and threshold statistics revealed that the selected ROANFIS model was superior. Pearson correlation coefficient (R) and root mean square error for the best fitted ROANFIS model were 0.96 and 7.12, respectively. Furthermore, uncertainty analysis of the developed models indicated that the selected ROANFIS had less uncertainty than the ANFIS model and accurately forecasted BOD5 in the Sefidrood River Basin. Besides, the uncertainty analysis also showed that bracketed predictions by 95% confidence bound and d-factor in the testing steps for the selected ROANFIS model were 94% and 0.83, respectively.

  13. Phase shift extraction and wavefront retrieval from interferograms with background and contrast fluctuations

    International Nuclear Information System (INIS)

    Liu, Qian; Wang, Yang; He, Jianguo; Ji, Fang

    2015-01-01

    The fluctuations of background and contrast cause measurement errors in the phase-shifting technique. To extract the phase shifts from interferograms with background and contrast fluctuations, an iterative algorithm is represented. The phase shifts and wavefront phase are calculated in two individual steps with the least-squares method. The fluctuation factors are determined when the phase shifts are calculated, and the fluctuations are compensated when the wavefront phase is calculated. The advantage of the algorithm lies in its ability to extract phase shifts from interferograms with background and contrast fluctuations converging stably and rapidly. Simulations and experiments verify the effectiveness and reliability of the proposed algorithm. The convergence accuracy and speed are demonstrated by the simulation results. The experiment results show its ability for suppressing phase retrieval errors. (paper)

  14. Electro-optic spatial decoding on the spherical-wavefront Coulomb fields of plasma electron sources.

    Science.gov (United States)

    Huang, K; Esirkepov, T; Koga, J K; Kotaki, H; Mori, M; Hayashi, Y; Nakanii, N; Bulanov, S V; Kando, M

    2018-02-13

    Detections of the pulse durations and arrival timings of relativistic electron beams are important issues in accelerator physics. Electro-optic diagnostics on the Coulomb fields of electron beams have the advantages of single shot and non-destructive characteristics. We present a study of introducing the electro-optic spatial decoding technique to laser wakefield acceleration. By placing an electro-optic crystal very close to a gas target, we discovered that the Coulomb field of the electron beam possessed a spherical wavefront and was inconsistent with the previously widely used model. The field structure was demonstrated by experimental measurement, analytic calculations and simulations. A temporal mapping relationship with generality was derived in a geometry where the signals had spherical wavefronts. This study could be helpful for the applications of electro-optic diagnostics in laser plasma acceleration experiments.

  15. Effective wavefront aberration measurement of spectacle lenses in as-worn status

    Science.gov (United States)

    Jia, Zhigang; Xu, Kai; Fang, Fengzhou

    2018-04-01

    An effective wavefront aberration analysis method for measuring spectacle lenses in as-worn status was proposed and verified using an experimental apparatus based on an eye rotation model. Two strategies were employed to improve the accuracy of measurement of the effective wavefront aberrations on the corneal sphere. The influences of three as-worn parameters, the vertex distance, pantoscopic angle, and face form angle, together with the eye rotation and corresponding incident beams, were objectively and quantitatively obtained. The experimental measurements of spherical single vision and freeform progressive addition lenses demonstrate the accuracy and validity of the proposed method and experimental apparatus, which provide a potential means of achieving supernormal vision correction with customization and personalization in optimizing the as-worn status-based design of spectacle lenses and evaluating their manufacturing and imaging qualities.

  16. Study of wavefront error and polarization of a side mounted infrared window

    Science.gov (United States)

    Liu, Jiaguo; Li, Lin; Hu, Xinqi; Yu, Xin

    2008-03-01

    The wavefront error and polarization of a side mounted infrared window made of ZnS are studied. The Infrared windows suffer from temperature gradient and stress during their launch process. Generally, the gradient in temperature changes the refractive index of the material whereas stress produces deformation and birefringence. In this paper, a thermal finite element analysis (FEA) of an IR window is presented. For this purpose, we employed an FEA program Ansys to obtain the time-varying temperature field. The deformation and stress of the window are derived from a structural FEA with the aerodynamic force and the temperature field previously obtained as being the loads. The deformation, temperature field, stress field, ray tracing and Jones Calculus are used to calculate the wavefront error and the change of polarization state.

  17. Tunable wavefront coded imaging system based on detachable phase mask: Mathematical analysis, optimization and underlying applications

    Science.gov (United States)

    Zhao, Hui; Wei, Jingxuan

    2014-09-01

    The key to the concept of tunable wavefront coding lies in detachable phase masks. Ojeda-Castaneda et al. (Progress in Electronics Research Symposium Proceedings, Cambridge, USA, July 5-8, 2010) described a typical design in which two components with cosinusoidal phase variation operate together to make defocus sensitivity tunable. The present study proposes an improved design and makes three contributions: (1) A mathematical derivation based on the stationary phase method explains why the detachable phase mask of Ojeda-Castaneda et al. tunes the defocus sensitivity. (2) The mathematical derivations show that the effective bandwidth wavefront coded imaging system is also tunable by making each component of the detachable phase mask move asymmetrically. An improved Fisher information-based optimization procedure was also designed to ascertain the optimal mask parameters corresponding to specific bandwidth. (3) Possible applications of the tunable bandwidth are demonstrated by simulated imaging.

  18. Layer-oriented multigrid wavefront reconstruction algorithms for multi-conjugate adaptive optics

    Science.gov (United States)

    Gilles, Luc; Ellerbroek, Brent L.; Vogel, Curtis R.

    2003-02-01

    Multi-conjugate adaptive optics (MCAO) systems with 104-105 degrees of freedom have been proposed for future giant telescopes. Using standard matrix methods to compute, optimize, and implement wavefront control algorithms for these systems is impractical, since the number of calculations required to compute and apply the reconstruction matrix scales respectively with the cube and the square of the number of AO degrees of freedom. In this paper, we develop an iterative sparse matrix implementation of minimum variance wavefront reconstruction for telescope diameters up to 32m with more than 104 actuators. The basic approach is the preconditioned conjugate gradient method, using a multigrid preconditioner incorporating a layer-oriented (block) symmetric Gauss-Seidel iterative smoothing operator. We present open-loop numerical simulation results to illustrate algorithm convergence.

  19. Efficient Terahertz Wide-Angle NUFFT-Based Inverse Synthetic Aperture Imaging Considering Spherical Wavefront

    Directory of Open Access Journals (Sweden)

    Jingkun Gao

    2016-12-01

    Full Text Available An efficient wide-angle inverse synthetic aperture imaging method considering the spherical wavefront effects and suitable for the terahertz band is presented. Firstly, the echo signal model under spherical wave assumption is established, and the detailed wavefront curvature compensation method accelerated by 1D fast Fourier transform (FFT is discussed. Then, to speed up the reconstruction procedure, the fast Gaussian gridding (FGG-based nonuniform FFT (NUFFT is employed to focus the image. Finally, proof-of-principle experiments are carried out and the results are compared with the ones obtained by the convolution back-projection (CBP algorithm. The results demonstrate the effectiveness and the efficiency of the presented method. This imaging method can be directly used in the field of nondestructive detection and can also be used to provide a solution for the calculation of the far-field RCSs (Radar Cross Section of targets in the terahertz regime.

  20. Simulation of a plane wavefront propagating in cardiac tissue using a cellular automata model

    International Nuclear Information System (INIS)

    Barbosa, Carlos R Hall

    2003-01-01

    We present a detailed description of a cellular automata model for the propagation of action potential in a planar cardiac tissue, which is very fast and easy to use. The model incorporates anisotropy in the electrical conductivity and a spatial variation of the refractory time. The transmembrane potential distribution is directly derived from the cell states, and the intracellular and extracellular potential distributions are calculated for the particular case of a plane wavefront. Once the potential distributions are known, the associated current densities are calculated by Ohm's law, and the magnetic field is determined at a plane parallel to the cardiac tissue by applying the law of Biot and Savart. The results obtained for propagation speed and for magnetic field amplitude with the cellular automata model are compared with values predicted by the bidomain formulation, for various angles between wavefront propagation and fibre direction, characterizing excellent agreement between the models

  1. Research on a wavefront aberration calculation method for a laser energy gradient attenuator

    International Nuclear Information System (INIS)

    Dong, Tingting; Han, Xu; Chen, Chi; Fu, Yuegang; Li, Ming

    2013-01-01

    When a laser energy gradient attenuator is working, there is an inhomogeneous temperature distribution in the whole of the glass because of the non-uniform light energy absorption. This will lead to optical performance reduction. An integrated opto-thermal–mechanical method is proposed to calculate the wavefront aberration for analysis of the thermal effect of the system. Non-sequential optical analysis is used for computing the absorbed energy distribution. The finite element analysis program solves the temperature distribution and the deformations of nodes on the surfaces. An interface routine is created to fit the surface shape and the index field, and extended Zernike polynomials are introduced to get a higher fitting precision. Finally, the parameters are imported to the CodeV optical design program automatically, and the user defined gradient index material is ray traced to obtain the wavefront aberration. The method can also be used in other optical systems for thermal effect analysis. (letter)

  2. Wavefront control of the Large Optics Test and Integration Site (LOTIS) 6.5m Collimator

    Energy Technology Data Exchange (ETDEWEB)

    West, Steven C.; Bailey, Samuel H.; Burge, James H.; Cuerden, Brian; Hagen, Jeff; Martin, Hubert M.; Tuell, Michael T.

    2010-06-20

    The LOTIS Collimator provides scene projection within a 6.5m diameter collimated beam used for optical testing research in air and vacuum. Diffraction-limited performance (0.4 to 5{mu}m wavelength) requires active wavefront control of the alignment and primary mirror shape. A hexapod corrects secondary mirror alignment using measurements from collimated sources directed into the system with nine scanning pentaprisms. The primary mirror shape is controlled with 104 adjustable force actuators based on figure measurements from a center-of-curvature test. A variation of the Hartmann test measures slopes by monitoring the reflections from 36 small mirrors bonded to the optical surface of the primary mirror. The Hartmann source and detector are located at the f/15 Cassegrain focus. Initial operation has demonstrated a closed-loop 110nmrms wavefront error in ambient air over the 6.5mcollimated beam.

  3. Efficient irregular wavefront propagation algorithms on Intel® Xeon Phi™

    OpenAIRE

    Gomes, Jeremias M.; Teodoro, George; de Melo, Alba; Kong, Jun; Kurc, Tahsin; Saltz, Joel H.

    2015-01-01

    We investigate the execution of the Irregular Wavefront Propagation Pattern (IWPP), a fundamental computing structure used in several image analysis operations, on the Intel® Xeon Phi™ co-processor. An efficient implementation of IWPP on the Xeon Phi is a challenging problem because of IWPP’s irregularity and the use of atomic instructions in the original IWPP algorithm to resolve race conditions. On the Xeon Phi, the use of SIMD and vectorization instructions is critical to attain high perfo...

  4. Performance analysis of large-scale applications based on wavefront algorithms

    International Nuclear Information System (INIS)

    Hoisie, A.; Lubeck, O.; Wasserman, H.

    1998-01-01

    The authors introduced a performance model for parallel, multidimensional, wavefront calculations with machine performance characterized using the LogGP framework. The model accounts for overlap in the communication and computation components. The agreement with experimental data is very good under a variety of model sizes, data partitioning, blocking strategies, and on three different parallel architectures. Using the model, the authors analyzed performance of a deterministic transport code on a hypothetical 100 Tflops future parallel system of interest to ASCI

  5. Photoinjector beam quality improvement by shaping the wavefront of a drive laser with oblique incidence

    International Nuclear Information System (INIS)

    He Zhigang; Wang Xiaohui; Jia Qika

    2012-01-01

    To increase the quantum efficiency (QE) of a copper photocathode and reduce the thermal emittance of an electron beam, a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun. The disadvantageous effects on the beam quality caused by oblique incidence were analyzed qualitatively. A simple way to solve the problems through wavefront shaping was introduced and the beam quality was improved. (authors)

  6. Objective lens simultaneously optimized for pupil ghosting, wavefront delivery and pupil imaging

    Science.gov (United States)

    Olczak, Eugene G (Inventor)

    2011-01-01

    An objective lens includes multiple optical elements disposed between a first end and a second end, each optical element oriented along an optical axis. Each optical surface of the multiple optical elements provides an angle of incidence to a marginal ray that is above a minimum threshold angle. This threshold angle minimizes pupil ghosts that may enter an interferometer. The objective lens also optimizes wavefront delivery and pupil imaging onto an optical surface under test.

  7. Plasma channels during filamentation of a femtosecond laser pulse with wavefront astigmatism in air

    Energy Technology Data Exchange (ETDEWEB)

    Dergachev, A A; Kandidov, V P; Shlenov, S A [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Ionin, A A; Mokrousova, D V; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shustikova, A P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2014-12-31

    We have demonstrated experimentally and numerically the possibility of controlling parameters of plasma channels formed during filamentation of a femtosecond laser pulse by introducing astigmatism in the laser beam wavefront. It is found that weak astigmatism increases the length of the plasma channel in comparison with the case of aberration-free focusing and that strong astigmatism can cause splitting of the plasma channel into two channels located one after another on the filament axis. (interaction of laser radiation with matter. laser plasma)

  8. A database of wavefront measurements for laser system modeling, optical component development and fabrication process qualification

    International Nuclear Information System (INIS)

    Wolfe, C.R.; Lawson, J.K.; Aikens, D.M.; English, R.E.

    1995-01-01

    In the second half of the 1990's, LLNL and others anticipate designing and beginning construction of the National Ignition Facility (NIF). The NIF will be capable of producing the worlds first laboratory scale fusion ignition and bum reaction by imploding a small target. The NIF will utilize approximately 192 simultaneous laser beams for this purpose. The laser will be capable of producing a shaped energy pulse of at least 1.8 million joules (MJ) with peak power of at least 500 trillion watts (TV). In total, the facility will require more than 7,000 large optical components. The performance of a high power laser of this kind can be seriously degraded by the presence of low amplitude, periodic modulations in the surface and transmitted wavefronts of the optics used. At high peak power, these phase modulations can convert into large intensity modulations by non-linear optical processes. This in turn can lead to loss in energy on target via many well known mechanisms. In some cases laser damage to the optics downstream of the source of the phase modulation can occur. The database described here contains wavefront phase maps of early prototype optical components for the NIF. It has only recently become possible to map the wavefront of these large aperture components with high spatial resolution. Modem large aperture static fringe and phase shifting interferometers equipped with large area solid state detectors have made this possible. In a series of measurements with these instruments, wide spatial bandwidth can be detected in the wavefront

  9. Manipulation of plasmonic wavefront and light–matter interaction in metallic nanostructures: A brief review

    International Nuclear Information System (INIS)

    Li Jia-Fang; Li Zhi-Yuan

    2014-01-01

    The control and application of surface plasmons (SPs), is introduced with particular emphasis on the manipulation of the plasmonic wavefront and light–matter interaction in metallic nanostructures. We introduce a direct design methodology called the surface wave holography method and show that it can be readily employed for wave-front shaping of near-infrared light through a subwavelength hole, it can also be used for designing holographic plasmonic lenses for SPs with complex wavefronts in the visible band. We also discuss several issues of light–matter interaction in plasmonic nanostructures. We show theoretically that amplification of SPs can be achieved in metal nanoparticles incorporated with gain media, leading to a giant reduction of surface plasmon resonance linewidth and enhancement of local electric field intensity. We present an all-analytical semiclassical theory to evaluate spaser performance in a plasmonic nanocavity incorporated with gain media described by the four-level atomic model. We experimentally demonstrate amplified spontaneous emission of SP polaritons and their amplification at the interface between a silver film and a polymer film doped with dye molecules. We discuss various aspects of microscopic and macroscopic manipulation of fluorescent radiation from gold nanorod hybrid structures in a system of either a single nanoparticle or an aligned group of nanoparticles. The findings reported and reviewed here could help others explore various approaches and schemes to manipulate plasmonic wavefront and light–matter interaction in metallic nanostructures for potential applications, such as optical displays, information integration, and energy harvesting technologies. (topical review - plasmonics and metamaterials)

  10. Wavefront picking for 3D tomography and full-waveform inversion

    KAUST Repository

    AlTheyab, Abdullah

    2016-09-08

    We have developed an efficient approach for picking firstbreak wavefronts on coarsely sampled time slices of 3D shot gathers. Our objective was to compute a smooth initial velocity model for multiscale full-waveform inversion (FWI). Using interactive software, first-break wavefronts were geometrically modeled on time slices with a minimal number of picks. We picked sparse time slices, performed traveltime tomography, and then compared the predicted traveltimes with the data in-between the picked slices. The picking interval was refined with iterations until the errors in traveltime predictions fell within the limits necessary to avoid cycle skipping in early arrivals FWI. This approach was applied to a 3D ocean-bottom-station data set. Our results indicate that wavefront picking has 28% fewer data slices to pick compared with picking traveltimes in shot gathers. In addition, by using sparse time samples for picking, data storage is reduced by 88%, and therefore allows for a faster visualization and quality control of the picks. Our final traveltime tomogram is sufficient as a starting model for early arrival FWI. © 2016 Society of Exploration Geophysicists.

  11. Coronagraphic Wavefront Control for the ATLAST-9.2m Telescope

    Science.gov (United States)

    Lyon, RIchard G.; Oegerle, William R.; Feinberg, Lee D.; Bolcar, Matthew R.; Dean, Bruce H.; Mosier, Gary E.; Postman, Marc

    2010-01-01

    The Advanced Technology for Large Aperture Space Telescope (ATLAST) concept was assessed as one of the NASA Astrophysics Strategic Mission Concepts (ASMC) studies. Herein we discuss the 9.2-meter diameter segmented aperture version and its wavefront sensing and control (WFSC) with regards to coronagraphic detection and spectroscopic characterization of exoplanets. The WFSC would consist of at least two levels of sensing and control: (i) an outer coarser level of sensing and control to phase and control the segments and secondary mirror in a manner similar to the James Webb Space Telescope but operating at higher temporal bandwidth, and (ii) an inner, coronagraphic instrument based, fine level of sensing and control for both amplitude and wavefront errors operating at higher temporal bandwidths. The outer loop would control rigid-body actuators on the primary and secondary mirrors while the inner loop would control one or more segmented deformable mirror to suppress the starlight within the coronagraphic field-of view. Herein we discuss the visible nulling coronagraph (VNC) and the requirements it levies on wavefront sensing and control and show the results of closed-loop simulations to assess performance and evaluate the trade space of system level stability versus control bandwidth.

  12. Coronagraphic wavefront control for the ATLAST 9.2m telescope

    Science.gov (United States)

    Lyon, Richard G.; Oegerle, William R.; Feinberg, Lee D.; Bolcar, Matthew R.; Dean, Bruce H.; Mosier, Gary E.; Postman, Marc

    2010-07-01

    The Advanced Technology for Large Aperture Space Telescope (ATLAST) concept was assessed as one of the NASA Astrophysics Strategic Mission Concepts (ASMC) studies. Herein we discuss the 9.2-meter diameter segmented aperture version and its wavefront sensing and control (WFSC) with regards to coronagraphic detection and spectroscopic characterization of exoplanets. The WFSC would consist of at least two levels of sensing and control: (i) an outer coarser level of sensing and control to phase and control the segments and secondary mirror in a manner similar to the James Webb Space Telescope but operating at higher temporal bandwidth, and (ii) an inner, coronagraphic instrument based, fine level of sensing and control for both amplitude and wavefront errors operating at higher temporal bandwidths. The outer loop would control rigid-body actuators on the primary and secondary mirrors while the inner loop would control one or more segmented deformable mirror to suppress the starlight within the coronagraphic field-of-view. Herein we discuss the visible nulling coronagraph (VNC) and the requirements it levies on wavefront sensing and control and show the results of closed-loop simulations to assess performance and evaluate the trade space of system level stability versus control bandwidth.

  13. Object-oriented wavefront correction in an asymmetric amplifying high-power laser system

    Science.gov (United States)

    Yang, Ying; Yuan, Qiang; Wang, Deen; Zhang, Xin; Dai, Wanjun; Hu, Dongxia; Xue, Qiao; Zhang, Xiaolu; Zhao, Junpu; Zeng, Fa; Wang, Shenzhen; Zhou, Wei; Zhu, Qihua; Zheng, Wanguo

    2018-05-01

    An object-oriented wavefront control method is proposed aiming for excellent near-field homogenization and far-field distribution in an asymmetric amplifying high-power laser system. By averaging the residual errors of the propagating beam, smaller pinholes could be employed on the spatial filters to improve the beam quality. With this wavefront correction system, the laser performance of the main amplifier system in the Shen Guang-III laser facility has been improved. The residual wavefront aberration at the position of each pinhole is below 2 µm (peak-to-valley). For each pinhole, 95% of the total laser energy is enclosed within a circle whose diameter is no more than six times the diffraction limit. At the output of the main laser system, the near-field modulation and contrast are 1.29% and 7.5%, respectively, and 95% of the 1ω (1053 nm) beam energy is contained within a 39.8 µrad circle (6.81 times the diffraction limit) under a laser fluence of 5.8 J cm-2. The measured 1ω focal spot size and near-field contrast are better than the design values of the Shen Guang-III laser facility.

  14. [Comparison of ocular modulation transfer function measurements by ray tracing wavefront technology and double-pass system].

    Science.gov (United States)

    Qiao, Liya; Cai, Xiaogu; Wan, Xiuhua; Guan, Zheng; Xiong, Ying; Lin, Zhong; Zhang, Ye; Tan, Jiaxuan; Wang, Ningli

    2015-01-01

    To compare the agreement of the ocular modulation transfer function (MTF) measured by double-pass system and ray tracing wavefront aberrometry, and to analyze the correlations of two MTFs with the visual acuity and contrast sensitivity function results. Comparative study. Subjects with no ocular diseases were consecutively enrolled in an epidemic study field located at the Dongyangzhuang Health Center, Yongnian County, Handan City, Hebei Province, China. After comprehensive ophthalmic examinations, the mean values of subtracted lower order aberration MTF at 5, 10, 15, 20, 25, and 30 cycle/degree(c/d) spatial frequencies were obtained with a double-pass system (optical quality analysis system II, OQAS II system) and a ray tracing wavefront aberrometer (iTrace visual function analyzer, iTrace system) in the 4.0 mm and 6.0 mm pupil after dilation, respectively. Paired-sample t test and Bland-Altman analysis were used to compare the difference and agreement of MTFs obtained with two instruments. Correlation analysis was preformed between two MTF measurement results and subjective visual quality including visual acuity and contrast sensitivity function. Two hundred and fifty-one healthy eyes of 163 subjects were enrolled, aged 30 to 60, mean (44.1 ± 9.7) years, including 139 eyes of 81 males and 112 eyes of 82 females. The mean value of MTF at 5, 10, 15, 20.25, 30 c/d obtained by iTrace in 4.0 mm pupil were 0.730 ± 0.138, 0.431 ± 0.159, 0.262 ± 0.120, 0.169 ± 0.078, 0.118 ± 0.053, 0.094 ± 0.043. The value obtained by OQASII were 0.347 ± 0.123, 0.162 ± 0.086, 0.072 ± 0.049, 0.042 ± 0.033, 0.026 ± 0.022, 0.017 ± 0.022, The result of iTrace were all significant higher than OQAS in both 4mm(t = 38.72, 28.03, 27.32, 27.59, 29.23, 28.96, P < 0.01) and 6.0 mm(t = 4.60, 3.19, 9.34, 13.41, 16.96, 20.24, P < 0.01)pupil diameter. The iTrace-OQAS II MTF difference was smaller in the 6.0 mm pupil. Bland-Altman analysis indicated that the agreement of two instruments was

  15. A contralateral eye study comparing apodized diffrative and full diffrative lenses: wavefront analysis and distance and near uncorrected visual acuity

    Directory of Open Access Journals (Sweden)

    Marcony Rodrigues de Santhiago

    2009-01-01

    Full Text Available PURPOSE: To evaluate intraindividual visual acuity, wavefront errors and modulation transfer functions in patients implanted with two diffractive multifocal intraocular lenses. METHODS: This prospective study examined 40 eyes of 20 cataract patients who underwent phacoemulsification and implantation of a spherical multifocal ReSTOR intraocular lens in one eye and an aspheric Tecnis ZM900 multifocal intraocular lens in the other eye. The main outcome measures, over a 3-month follow-up period, were the uncorrected photopic distance and near visual acuity and the defocus curve. The visual acuity was converted to logMAR for statistical analysis and is presented in decimal scale. The wavefront error and modulation transfer function were also evaluated in both groups. RESULTS: At the 3-month postoperative visit, the mean photopic distance uncorrected visual acuity (UCVA was 0.74 ± 0.20 in the ReSTOR group and 0.76 ± 0.22 in the Tecnis group (p=0.286. The mean near UCVA was 0.96 ± 0.10 in the ReSTOR group and 0.93 ± 0.14 in the Tecnis group (p=0.963. The binocular defocus curve showed measurements between the peaks better than 0.2 logMAR. The total aberration, higher-order aberration and coma aberration were not significantly different between the groups. The spherical aberration was significantly lower in the Tecnis group than in the ReSTOR group. (p=0.004. Both groups performed similarly for the modulation transfer function. CONCLUSION: The ReSTOR SN60D3 and Tecnis ZM 900 intraocular lenses provided similar photopic visual acuity at distance and near. The diffractive intraocular lenses studied provided a low value of coma and spherical aberrations, with the Tecnis intraocular lens having a statistically lower spherical aberration compared to the ReSTOR intraocular lens. In the 5 mm pupil diameter analyses, both intraocular lens groups showed similar modulation transfer functions.

  16. Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Hong-Ting Liu

    2018-04-01

    Full Text Available AIM: To compare the optical quality after implantation of implantable collamer lens (ICL and wavefront-guided laser in situ keratomileusis (WG-LASIK. METHODS: The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index (OSI, the values of modulation transfer function (MTF cutoff frequency, Strehl ratio, and the Optical Quality Analysis System (OQAS values (OVs were accessed. The higher order aberrations (HOAs data including coma, trefoil, spherical, 2nd astigmatism and tetrafoil were also obtained. For patients with pupil size <6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded. RESULTS: In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent (P< 0.001. After the ICL implantation, the OSI decreased slightly from 2.34±1.92 to 2.24±1.18 with no statistical significance (P=0.62. While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively (Wilcoxon signed ranks test, P=0.000. None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mm-pupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2nd astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05, -0.04±0.04, 0.03±0.01 respectively (Wilcoxon signed ranks test

  17. Compliant Tactile Sensors

    Science.gov (United States)

    Torres-Jara, Eduardo R.

    2011-01-01

    Tactile sensors are currently being designed to sense interactions with human hands or pen-like interfaces. They are generally embedded in screens, keyboards, mousepads, and pushbuttons. However, they are not well fitted to sense interactions with all kinds of objects. A novel sensor was originally designed to investigate robotics manipulation where not only the contact with an object needs to be detected, but also where the object needs to be held and manipulated. This tactile sensor has been designed with features that allow it to sense a large variety of objects in human environments. The sensor is capable of detecting forces coming from any direction. As a result, this sensor delivers a force vector with three components. In contrast to most of the tactile sensors that are flat, this one sticks out from the surface so that it is likely to come in contact with objects. The sensor conforms to the object with which it interacts. This augments the contact's surface, consequently reducing the stress applied to the object. This feature makes the sensor ideal for grabbing objects and other applications that require compliance with objects. The operational range of the sensor allows it to operate well with objects found in peoples' daily life. The fabrication of this sensor is simple and inexpensive because of its compact mechanical configuration and reduced electronics. These features are convenient for mass production of individual sensors as well as dense arrays. The biologically inspired tactile sensor is sensitive to both normal and lateral forces, providing better feedback to the host robot about the object to be grabbed. It has a high sensitivity, enabling its use in manipulation fingers, which typically have low mechanical impedance in order to be very compliant. The construction of the sensor is simple, using inexpensive technologies like silicon rubber molding and standard stock electronics.

  18. Wavefront holoscopy: application of digital in-line holography for the inspection of engraved marks in progressive addition lenses.

    Science.gov (United States)

    Perucho, Beatriz; Micó, Vicente

    2014-01-01

    Progressive addition lenses (PALs) are engraved with permanent marks at standardized locations in order to guarantee correct centering and alignment throughout the manufacturing and mounting processes. Out of the production line, engraved marks provide useful information about the PAL as well as act as locator marks to re-ink again the removable marks. Even though those marks should be visible by simple visual inspection with the naked eye, engraving marks are often faint and weak, obscured by scratches, and partially occluded and difficult to recognize on tinted or antireflection-coated lenses. Here, we present an extremely simple optical device (named as wavefront holoscope) for visualization and characterization of permanent marks in PAL based on digital in-line holography. Essentially, a point source of coherent light illuminates the engraved mark placed just before a CCD camera that records a classical Gabor in-line hologram. The recorded hologram is then digitally processed to provide a set of high-contrast images of the engraved marks. Experimental results are presented showing the applicability of the proposed method as a new ophthalmic instrument for visualization and characterization of engraved marks in PALs.

  19. Ambient Sensors

    NARCIS (Netherlands)

    Börner, Dirk; Specht, Marcus

    2014-01-01

    This software sketches comprise two custom-built ambient sensors, i.e. a noise and a movement sensor. Both sensors measure an ambient value and process the values to a color gradient (green > yellow > red). The sensors were built using the Processing 1.5.1 development environment. Available under

  20. MITRE sensor layer prototype

    Science.gov (United States)

    Duff, Francis; McGarry, Donald; Zasada, David; Foote, Scott

    2009-05-01

    The MITRE Sensor Layer Prototype is an initial design effort to enable every sensor to help create new capabilities through collaborative data sharing. By making both upstream (raw) and downstream (processed) sensor data visible, users can access the specific level, type, and quantities of data needed to create new data products that were never anticipated by the original designers of the individual sensors. The major characteristic that sets sensor data services apart from typical enterprise services is the volume (on the order of multiple terabytes) of raw data that can be generated by most sensors. Traditional tightly coupled processing approaches extract pre-determined information from the incoming raw sensor data, format it, and send it to predetermined users. The community is rapidly reaching the conclusion that tightly coupled sensor processing loses too much potentially critical information.1 Hence upstream (raw and partially processed) data must be extracted, rapidly archived, and advertised to the enterprise for unanticipated uses. The authors believe layered sensing net-centric integration can be achieved through a standardize-encapsulate-syndicateaggregate- manipulate-process paradigm. The Sensor Layer Prototype's technical approach focuses on implementing this proof of concept framework to make sensor data visible, accessible and useful to the enterprise. To achieve this, a "raw" data tap between physical transducers associated with sensor arrays and the embedded sensor signal processing hardware and software has been exploited. Second, we encapsulate and expose both raw and partially processed data to the enterprise within the context of a service-oriented architecture. Third, we advertise the presence of multiple types, and multiple layers of data through geographic-enabled Really Simple Syndication (GeoRSS) services. These GeoRSS feeds are aggregated, manipulated, and filtered by a feed aggregator. After filtering these feeds to bring just the type

  1. Longitudinal measurements of luminance and chromatic contrast sensitivity: comparison between wavefront-guided LASIK and contralateral PRK for myopia.

    Science.gov (United States)

    Barboni, Mirella Telles Salgueiro; Feitosa-Santana, Claudia; Barreto Junior, Jackson; Lago, Marcos; Bechara, Samir Jacob; Alves, Milton Ruiz; Ventura, Dora Fix

    2013-10-01

    The present study aimed to compare the postoperative contrast sensitivity functions between wavefront-guided LASIK eyes and their contralateral wavefront-guided PRK eyes. The participants were 11 healthy subjects (mean age=32.4 ± 6.2 years) who had myopic astigmatism. The spatial contrast sensitivity functions were measured before and three times after the surgery. Psycho and a Cambridge graphic board (VSG 2/4) were used to measure luminance, red-green, and blue-yellow spatial contrast sensitivity functions (from 0.85 to 13.1 cycles/degree). Longitudinal analysis and comparison between surgeries were performed. There was no significant contrast sensitivity change during the one-year follow-up measurements neither for LASIK nor for PRK eyes. The comparison between procedures showed no differences at 12 months postoperative. The present data showed similar contrast sensitivities during one-year follow-up of wave-front guided refractive surgeries. Moreover, one year postoperative data showed no differences in the effects of either wavefront-guided LASIK or wavefront-guided PRK on the luminance and chromatic spatial contrast sensitivity functions.

  2. An electrokinetic pressure sensor

    International Nuclear Information System (INIS)

    Kim, Dong-Kwon; Kim, Sung Jin; Kim, Duckjong

    2008-01-01

    A new concept for a micro pressure sensor is demonstrated. The pressure difference between the inlet and the outlet of glass nanochannels is obtained by measuring the electrokinetically generated electric potential. To demonstrate the proposed concept, experimental investigations are performed for 100 nm wide nanochannels with sodium chloride solutions having various concentrations. The proposed pressure sensor is able to measure the pressure difference within a 10% deviation from linearity. The sensitivity of the electrokinetic pressure sensor with 10 −5 M sodium chloride solution is 18.5 µV Pa −1 , which is one order of magnitude higher than that of typical diaphragm-based pressure sensors. A numerical model is presented for investigating the effects of the concentration and the channel width on the sensitivity of the electrokinetic pressure sensor. Numerical results show that the sensitivity increases as the concentration decreases and the channel width increases

  3. Tradeoff between insensitivity to depth-induced spherical aberration and resolution of 3D fluorescence imaging due to the use of wavefront encoding with a radially symmetric phase mask

    Science.gov (United States)

    Doblas, Ana; Dutta, Ananya; Saavedra, Genaro; Preza, Chrysanthe

    2018-02-01

    Previously, a wavefront encoded (WFE) imaging system implemented using a squared cubic (SQUBIC) phase mask has been verified to reduce the sensitivity of the imaging system to spherical aberration (SA). The strength of the SQUBIC phase mask and, as consequence, the performance of the WFE system are controlled by a design parameter, A. Although the higher the A-value, the more tolerant the WFE system is to SA, this is accomplished at the expense of the effective imaging resolution. In this contribution, we investigate this tradeoff in order to find an optimal A-value to balance the effect of SA and loss of resolution.

  4. Evaluation of iris recognition system for wavefront-guided laser in situ keratomileusis for myopic astigmatism.

    Science.gov (United States)

    Ghosh, Sudipta; Couper, Terry A; Lamoureux, Ecosse; Jhanji, Vishal; Taylor, Hugh R; Vajpayee, Rasik B

    2008-02-01

    To evaluate the visual and refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) using an iris recognition system for the correction of myopic astigmatism. Centre for Eye Research Australia, Melbourne Excimer Laser Research Group, and Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia. A comparative analysis of wavefront-guided LASIK was performed with an iris recognition system (iris recognition group) and without iris recognition (control group). The main parameters were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, amount of residual cylinder, manifest spherical equivalent (SE), and the index of success using the Alpins method of astigmatism analysis 1 and 3 months postoperatively. A P value less than 0.05 was considered statistically significant. Preoperatively, the mean SE was -4.32 diopters (D) +/- 1.59 (SD) in the iris recognition group (100 eyes) and -4.55 +/- 1.87 D in the control group (98 eyes) (P = .84). At 3 months, the mean SE was -0.05 +/- 0.21 D and -0.20 +/- 0.40 D, respectively (P = .001), and an SE within +/-0.50 D of emmetropia was achieved in 92.0% and 85.7% of eyes, respectively (P = .07). At 3 months, the UCVA was 20/20 or better in 90.0% and 76.5% of eyes, respectively. A statistically significant difference in the amount of astigmatic correction was seen between the 2 groups (P = .00 and P = .01 at 1 and 3 months, respectively). The index of success was 98.0% in the iris recognition group and 81.6% in the control group (P = .03). Iris recognition software may achieve better visual and refractive outcomes in wavefront-guided LASIK for myopic astigmatism.

  5. Professional Android Sensor Programming

    CERN Document Server

    Milette, Greg

    2012-01-01

    Learn to build human-interactive Android apps, starting with device sensors This book shows Android developers how to exploit the rich set of device sensors—locational, physical (temperature, pressure, light, acceleration, etc.), cameras, microphones, and speech recognition—in order to build fully human-interactive Android applications. Whether providing hands-free directions or checking your blood pressure, Professional Android Sensor Programming shows how to turn possibility into reality. The authors provide techniques that bridge the gap between accessing sensors and putting the

  6. Implementation and on-sky results of an optimal wavefront controller for the MMT NGS adaptive optics system

    Science.gov (United States)

    Powell, Keith B.; Vaitheeswaran, Vidhya

    2010-07-01

    The MMT observatory has recently implemented and tested an optimal wavefront controller for the NGS adaptive optics system. Open loop atmospheric data collected at the telescope is used as the input to a MATLAB based analytical model. The model uses nonlinear constrained minimization to determine controller gains and optimize the system performance. The real-time controller performing the adaptive optics close loop operation is implemented on a dedicated high performance PC based quad core server. The controller algorithm is written in C and uses the GNU scientific library for linear algebra. Tests at the MMT confirmed the optimal controller significantly reduced the residual RMS wavefront compared with the previous controller. Significant reductions in image FWHM and increased peak intensities were obtained in J, H and K-bands. The optimal PID controller is now operating as the baseline wavefront controller for the MMT NGS-AO system.

  7. Analysis technique for controlling system wavefront error with active/adaptive optics

    Science.gov (United States)

    Genberg, Victor L.; Michels, Gregory J.

    2017-08-01

    The ultimate goal of an active mirror system is to control system level wavefront error (WFE). In the past, the use of this technique was limited by the difficulty of obtaining a linear optics model. In this paper, an automated method for controlling system level WFE using a linear optics model is presented. An error estimate is included in the analysis output for both surface error disturbance fitting and actuator influence function fitting. To control adaptive optics, the technique has been extended to write system WFE in state space matrix form. The technique is demonstrated by example with SigFit, a commercially available tool integrating mechanical analysis with optical analysis.

  8. Measurement range of phase retrieval in optical surface and wavefront metrology

    International Nuclear Information System (INIS)

    Brady, Gregory R.; Fienup, James R.

    2009-01-01

    Phase retrieval employs very simple data collection hardware and iterative algorithms to determine the phase of an optical field. We have derived limitations on phase retrieval, as applied to optical surface and wavefront metrology, in terms of the speed of beam (i.e., f-number or numerical aperture) and amount of aberration using arguments based on sampling theory and geometrical optics. These limitations suggest methodologies for expanding these ranges by increasing the complexity of the measurement arrangement, the phase-retrieval algorithm, or both. We have simulated one of these methods where a surface is measured at unusual conjugates

  9. Impacto da análise do 'wavefront' na refratometria de pacientes com ceratocone

    OpenAIRE

    Ambrósio Junior,Renato; Caldas,Diogo Leitão; Silva,Renata Siqueira da; Pimentel,Leonardo Nogueira; Valbon,Bruno de Freitas

    2011-01-01

    OBJETIVO: Verificar se a aberrometria ocular total (análise da frente de onda ou 'wavefront') possibilita melhora na acuidade visual corrigida (AVc) com lentes esfero-cilíndricas, obtida com a refratometria manifesta em casos de ceratocone com algum grau de intolerância ao uso de lentes de contato. MÉTODOS: Os prontuários de 46 pacientes (89 olhos), referidos com diagnóstico de ceratocone e intolerantes ao uso de lentes de contato, submetidos ao exame de aberrometria ocular total seguido de r...

  10. Enhanced wavefront reconstruction by random phase modulation with a phase diffuser

    DEFF Research Database (Denmark)

    Almoro, Percival F; Pedrini, Giancarlo; Gundu, Phanindra Narayan

    2011-01-01

    propagation in free space. The presentation of this technique is carried out using two setups. In the first setup, a diffuser plate is placed at the image plane of a metallic test object. The benefit of randomizing the phase of the object wave is the enhanced intensity recording due to high dynamic range...... of the diffusely scattered beam. The use of demagnification optics will also allow the investigations of relatively large objects. In the second setup, a transparent object is illuminated using a wavefront with random phase and constant amplitude by positioning the phase diffuser close to the object. The benefit...

  11. Study and development of a soft X-ray laser seeded by high-order harmonic

    International Nuclear Information System (INIS)

    Goddet, J.Ph.

    2009-05-01

    The work in this thesis aimed to study a geometry of X-UV lasers inspired by high power laser. This architecture, consisting of an injector (a source of high-order harmonics) coupled to an amplifier (plasma created by laser), corresponds to that of a laser chain in the spectral range of the X-UV. The laser at 32.8 nm studied here, is produced by the injection of high-order harmonic in a krypton plasma created by Optical Field Ionization (OFI). This scheme, initially tested by T. Ditmire in 1995, was validated in 2003 with a plasma amplifier created by the interaction of intense laser and a gaseous medium. This thesis is a continuation of that work in trying to address different aspects, not only a better understanding of the physical processes involved, but also of the spatio-temporal characterization of this type of source. We have demonstrated experimentally for the first time a source in the X-UV, which can be highly compact, energetic (1 μJ per pulse), close to the diffraction limit and Fourier transform limited. Indeed, through the spatial filtering of harmonics by the amplifying medium, the injected X-UV laser at 32.8 nm shows a Gaussian spatial profile with a divergence of 0.7 mrad (at 1/e 2 ). The wavefront was measured with a Hartmann sensor and presents a value of λ/17 in standard deviation, demonstrating that the X-UV source is diffraction limited. The temporal characterization of laser shows that the coherence time is of the order of the duration of spontaneous emission of the amplifier. The temporal coherence presents a Gaussian profile with a relative spectral width Δλ/λ equal to 10 -5 (FWHM) corresponding to a pulse duration of about 5 ps. (author)

  12. Attention Sensor

    NARCIS (Netherlands)

    Börner, Dirk; Kalz, Marco; Specht, Marcus

    2014-01-01

    This software sketch was used in the context of an experiment for the PhD project “Ambient Learning Displays”. The sketch comprises a custom-built attention sensor. The sensor measured (during the experiment) whether a participant looked at and thus attended a public display. The sensor was built

  13. Comparison of higher order aberrations after wavefront-guided LASIK and PRK: One year follow-up results

    Directory of Open Access Journals (Sweden)

    Seyed Hamid Reza Jahadi Hosseini

    2016-01-01

    Conclusion: For the 6mm pupil size, the total HOA increased following both personalized PRK and LASIK with no significant difference between the two groups. Change of the total HOA RMS was influenced by the preoperative values. The known influencing factors could predict nearly 50% of the changes in total HOA.

  14. A high sensitivity heterodyne interferometer as a possible optical readout for the LISA gravitational reference sensor and its application to technology verification

    Energy Technology Data Exchange (ETDEWEB)

    Gohlke, Martin; Weise, Dennis; Johann, Ulrich; Braxmaier, Claus [EADS Astrium, Claude-Dornier-Strasse, 88039 Friedrichshafen (Germany); Schuldt, Thilo; Peters, Achim, E-mail: martin.gohlke@astrium.eads.ne [Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2009-03-01

    The space-based gravitational wave detector LISA (Laser Interferometer Space Antenna) utilizes a high performance position sensor in order to measure the translation and tilt of the free flying proof mass with respect to the optical bench. Depending on the LISA optical bench design, this position sensor must have up to pm/sq rootHz sensitivity for the translation measurement and up to nrad/sq rootHz sensitivity for the tilt measurement. We developed a heterodyne interferometer, combined with differential wavefront sensing, for the tilt measurement. The interferometer design exhibits maximum symmetry where measurement and reference arm have the same frequency and polarization and the same optical path-lengths. The interferometer can be set up free of polarizing optical components preventing possible problems with thermal dependencies not suitable for the space environment. We developed a mechanically highly stable and compact setup which is located in a vacuum chamber. We measured initial noise levels below 10 pm/sq rootHz (longitudinal measurement) for frequencies above 10 mHz and below 20 nrad/sq rootHz (tilt measurement) for frequencies above 1 mHz. This setup can also be used for other applications, for example the measurement of the coefficient of thermal expansion (CTE) of structural materials, such as carbon fiber reinforced plastic (CFRP).

  15. Efficient irregular wavefront propagation algorithms on Intel® Xeon Phi™.

    Science.gov (United States)

    Gomes, Jeremias M; Teodoro, George; de Melo, Alba; Kong, Jun; Kurc, Tahsin; Saltz, Joel H

    2015-10-01

    We investigate the execution of the Irregular Wavefront Propagation Pattern (IWPP), a fundamental computing structure used in several image analysis operations, on the Intel ® Xeon Phi ™ co-processor. An efficient implementation of IWPP on the Xeon Phi is a challenging problem because of IWPP's irregularity and the use of atomic instructions in the original IWPP algorithm to resolve race conditions. On the Xeon Phi, the use of SIMD and vectorization instructions is critical to attain high performance. However, SIMD atomic instructions are not supported. Therefore, we propose a new IWPP algorithm that can take advantage of the supported SIMD instruction set. We also evaluate an alternate storage container (priority queue) to track active elements in the wavefront in an effort to improve the parallel algorithm efficiency. The new IWPP algorithm is evaluated with Morphological Reconstruction and Imfill operations as use cases. Our results show performance improvements of up to 5.63 × on top of the original IWPP due to vectorization. Moreover, the new IWPP achieves speedups of 45.7 × and 1.62 × , respectively, as compared to efficient CPU and GPU implementations.

  16. Wavefronts, light rays and caustic of a circular wave reflected by an arbitrary smooth curve

    International Nuclear Information System (INIS)

    Marciano-Melchor, Magdalena; Silva-Ortigoza, Ramón; Montiel-Piña, Enrique; Román-Hernández, Edwin; Santiago-Santiago, José Guadalupe; Silva-Ortigoza, Gilberto; Rosado, Alfonso; Suárez-Xique, Román

    2011-01-01

    The aim of the present work is to obtain expressions for both the wavefront train and the caustic associated with the light rays reflected by an arbitrary smooth curve after being emitted by a point light source located at an arbitrary position in the two-dimensional free space. To this end, we obtain an expression for the k-function associated with the general integral of Stavroudis to the eikonal equation that describes the evolution of the reflected light rays. The caustic is computed by using the definitions of the critical and caustic sets of the two-dimensional map that describes the evolution of an arbitrary wavefront associated with the general integral. The general results are applied to circular and parabolic mirrors. The main motivation to carry out this research is to establish, in future work, the caustic touching theorem in a two-dimensional optical medium and to study the diffraction problem by using the k-function concept. Both problems are important in the computation of the image of an arbitrary object under reflection and refraction

  17. Towards Fast Reverse Time Migration Kernels using Multi-threaded Wavefront Diamond Tiling

    KAUST Repository

    Malas, T.

    2015-09-13

    Today’s high-end multicore systems are characterized by a deep memory hierarchy, i.e., several levels of local and shared caches, with limited size and bandwidth per core. The ever-increasing gap between the processor and memory speed will further exacerbate the problem and has lead the scientific community to revisit numerical software implementations to better suit the underlying memory subsystem for performance (data reuse) as well as energy efficiency (data locality). The authors propose a novel multi-threaded wavefront diamond blocking (MWD) implementation in the context of stencil computations, which represents the core operation for seismic imaging in oil industry. The stencil diamond formulation introduces temporal blocking for high data reuse in the upper cache levels. The wavefront optimization technique ensures data locality by allowing multiple threads to share common adjacent point stencil. Therefore, MWD is able to take up the aforementioned challenges by alleviating the cache size limitation and releasing pressure from the memory bandwidth. Performance comparisons are shown against the optimized 25-point stencil standard seismic imaging scheme using spatial and temporal blocking and demonstrate the effectiveness of MWD.

  18. Using wavefront coding technique as an optical encryption system: reliability analysis and vulnerabilities assessment

    Science.gov (United States)

    Konnik, Mikhail V.

    2012-04-01

    Wavefront coding paradigm can be used not only for compensation of aberrations and depth-of-field improvement but also for an optical encryption. An optical convolution of the image with the PSF occurs when a diffractive optical element (DOE) with a known point spread function (PSF) is placed in the optical path. In this case, an optically encoded image is registered instead of the true image. Decoding of the registered image can be performed using standard digital deconvolution methods. In such class of optical-digital systems, the PSF of the DOE is used as an encryption key. Therefore, a reliability and cryptographic resistance of such an encryption method depends on the size and complexity of the PSF used for optical encoding. This paper gives a preliminary analysis on reliability and possible vulnerabilities of such an encryption method. Experimental results on brute-force attack on the optically encrypted images are presented. Reliability estimation of optical coding based on wavefront coding paradigm is evaluated. An analysis of possible vulnerabilities is provided.

  19. Adapting Wave-front Algorithms to Efficiently Utilize Systems with Deep Communication Hierarchies

    International Nuclear Information System (INIS)

    Kerbyson, Darren J.; Lang, Michael; Pakin, Scott

    2011-01-01

    Large-scale systems increasingly exhibit a differential between intra-chip and inter-chip communication performance especially in hybrid systems using accelerators. Processor cores on the same socket are able to communicate at lower latencies, and with higher bandwidths, than cores on different sockets either within the same node or between nodes. A key challenge is to efficiently use this communication hierarchy and hence optimize performance. We consider here the class of applications that contains wavefront processing. In these applications data can only be processed after their upstream neighbors have been processed. Similar dependencies result between processors in which communication is required to pass boundary data downstream and whose cost is typically impacted by the slowest communication channel in use. In this work we develop a novel hierarchical wave-front approach that reduces the use of slower communications in the hierarchy but at the cost of additional steps in the parallel computation and higher use of on-chip communications. This tradeoff is explored using a performance model. An implementation using the Reverse-acceleration programming model on the petascale Roadrunner system demonstrates a 27% performance improvement at full system-scale on a kernel application. The approach is generally applicable to large-scale multi-core and accelerated systems where a differential in system communication performance exists.

  20. Efficient irregular wavefront propagation algorithms on Intel® Xeon Phi™

    Science.gov (United States)

    Gomes, Jeremias M.; Teodoro, George; de Melo, Alba; Kong, Jun; Kurc, Tahsin; Saltz, Joel H.

    2016-01-01

    We investigate the execution of the Irregular Wavefront Propagation Pattern (IWPP), a fundamental computing structure used in several image analysis operations, on the Intel® Xeon Phi™ co-processor. An efficient implementation of IWPP on the Xeon Phi is a challenging problem because of IWPP’s irregularity and the use of atomic instructions in the original IWPP algorithm to resolve race conditions. On the Xeon Phi, the use of SIMD and vectorization instructions is critical to attain high performance. However, SIMD atomic instructions are not supported. Therefore, we propose a new IWPP algorithm that can take advantage of the supported SIMD instruction set. We also evaluate an alternate storage container (priority queue) to track active elements in the wavefront in an effort to improve the parallel algorithm efficiency. The new IWPP algorithm is evaluated with Morphological Reconstruction and Imfill operations as use cases. Our results show performance improvements of up to 5.63× on top of the original IWPP due to vectorization. Moreover, the new IWPP achieves speedups of 45.7× and 1.62×, respectively, as compared to efficient CPU and GPU implementations. PMID:27298591

  1. Enhancing the performance of the light field microscope using wavefront coding.

    Science.gov (United States)

    Cohen, Noy; Yang, Samuel; Andalman, Aaron; Broxton, Michael; Grosenick, Logan; Deisseroth, Karl; Horowitz, Mark; Levoy, Marc

    2014-10-06

    Light field microscopy has been proposed as a new high-speed volumetric computational imaging method that enables reconstruction of 3-D volumes from captured projections of the 4-D light field. Recently, a detailed physical optics model of the light field microscope has been derived, which led to the development of a deconvolution algorithm that reconstructs 3-D volumes with high spatial resolution. However, the spatial resolution of the reconstructions has been shown to be non-uniform across depth, with some z planes showing high resolution and others, particularly at the center of the imaged volume, showing very low resolution. In this paper, we enhance the performance of the light field microscope using wavefront coding techniques. By including phase masks in the optical path of the microscope we are able to address this non-uniform resolution limitation. We have also found that superior control over the performance of the light field microscope can be achieved by using two phase masks rather than one, placed at the objective's back focal plane and at the microscope's native image plane. We present an extended optical model for our wavefront coded light field microscope and develop a performance metric based on Fisher information, which we use to choose adequate phase masks parameters. We validate our approach using both simulated data and experimental resolution measurements of a USAF 1951 resolution target; and demonstrate the utility for biological applications with in vivo volumetric calcium imaging of larval zebrafish brain.

  2. Measurement of the wave-front aberration of the eye by a fast psychophysical procedure

    International Nuclear Information System (INIS)

    He, J.C.; Marcos, S.; Webb, R.H.; Burns, S.A.

    1998-01-01

    We used a fast psychophysical procedure to determine the wave-front aberrations of the human eye in vivo. We measured the angular deviation of light rays entering the eye at different pupillary locations by aligning an image of a point source entering the pupil at different locations to the image of a fixation cross entering the pupil at a fixed location. We fitted the data to a Zernike series to reconstruct the wave-front aberrations of the pupil. With this technique the repeatability of the measurement of the individual coefficients was 0.019 μm. The standard deviation of the overall wave-height estimation across the pupil is less than 0.3 μm. Since this technique does not require the administration of pharmacological agents to dilate the pupil, we were able to measure the changes in the aberrations of the eye during accommodation. We found that administration of even a mild dilating agent causes a change in the aberration structure of the eye. copyright 1998 Optical Society of America

  3. Extending the Capture Volume of an Iris Recognition System Using Wavefront Coding and Super-Resolution.

    Science.gov (United States)

    Hsieh, Sheng-Hsun; Li, Yung-Hui; Tien, Chung-Hao; Chang, Chin-Chen

    2016-12-01

    Iris recognition has gained increasing popularity over the last few decades; however, the stand-off distance in a conventional iris recognition system is too short, which limits its application. In this paper, we propose a novel hardware-software hybrid method to increase the stand-off distance in an iris recognition system. When designing the system hardware, we use an optimized wavefront coding technique to extend the depth of field. To compensate for the blurring of the image caused by wavefront coding, on the software side, the proposed system uses a local patch-based super-resolution method to restore the blurred image to its clear version. The collaborative effect of the new hardware design and software post-processing showed great potential in our experiment. The experimental results showed that such improvement cannot be achieved by using a hardware-or software-only design. The proposed system can increase the capture volume of a conventional iris recognition system by three times and maintain the system's high recognition rate.

  4. Impacto da análise do "wavefront" na refratometria de pacientes com ceratocone Impact of the wavefront analysis in refraction of keratoconus patients

    Directory of Open Access Journals (Sweden)

    Renato Ambrósio Junior

    2010-10-01

    Full Text Available OBJETIVO: Verificar se a aberrometria ocular total (análise da frente de onda ou wavefront possibilita a melhora na acuidade visual corrigida (AVc com lentes esfero-cilíndricas, obtida com a refratometria manifesta em casos de ceratocone com algum grau de intolerância ao uso de lentes de contato. MÉTODOS: Os prontuários de 46 pacientes (89 olhos referidos com diagnóstico de ceratocone e intolerantes ao uso de lentes de contato, submetidos ao exame de aberrometria ocular total seguido de refração manifesta, foram estudados de forma retrospectiva. A AVc (logMAR com a correção existente antes do exame foi comparada com a obtida com a nova refração manifesta, realizada, considerando-se os dados objetivos da aberrometria. O teste não-paramétrico de Wilcoxon para amostras pareadas foi utilizado para verificação de diferenças estatisticamente significantes na AVc. RESULTADOS: Houve uma melhora estatisticamente significante na AVc com a nova refração manifesta (pOBJECTIVE: To verify if the total ocular aberrometry (wavefront analysis facilitates manifest refraction and improvement in best spectacle distance corrected visual acuity (BSCDVA with sphero-cylindrical lenses, in keratoconus cases with some degree of contact lenses intolerance. METHODS: Retrospective chart review of 46 patients (89 eyes referred with keratoconus and contact lenses intolerance was performed. Ocular aberrometry with ray tracing was followed by manifest refraction. BSCDVA (logMAR with the previous correction was compared with the one obtained based on the wavefront auto-refraction. The nonparametric test of Wilcoxon for paired samples was used to test statistically significant differences in BSCDVA. RESULTS: There was a statistically significant improvement in BSCDVA with the new manifest refraction (p <0,0001. The average BSCDVA changed from 0,37 or 20/47 (varying between 1,3 and 0; standard deviation [SD] = 0,25 with previous refraction to 0,23 or 20

  5. Acoustic/seismic signal propagation and sensor performance modeling

    Science.gov (United States)

    Wilson, D. Keith; Marlin, David H.; Mackay, Sean

    2007-04-01

    Performance, optimal employment, and interpretation of data from acoustic and seismic sensors depend strongly and in complex ways on the environment in which they operate. Software tools for guiding non-expert users of acoustic and seismic sensors are therefore much needed. However, such tools require that many individual components be constructed and correctly connected together. These components include the source signature and directionality, representation of the atmospheric and terrain environment, calculation of the signal propagation, characterization of the sensor response, and mimicking of the data processing at the sensor. Selection of an appropriate signal propagation model is particularly important, as there are significant trade-offs between output fidelity and computation speed. Attenuation of signal energy, random fading, and (for array systems) variations in wavefront angle-of-arrival should all be considered. Characterization of the complex operational environment is often the weak link in sensor modeling: important issues for acoustic and seismic modeling activities include the temporal/spatial resolution of the atmospheric data, knowledge of the surface and subsurface terrain properties, and representation of ambient background noise and vibrations. Design of software tools that address these challenges is illustrated with two examples: a detailed target-to-sensor calculation application called the Sensor Performance Evaluator for Battlefield Environments (SPEBE) and a GIS-embedded approach called Battlefield Terrain Reasoning and Awareness (BTRA).

  6. [Comparative clinical study of wavefront-guided laser in situ keratomileusis with versus without iris recognition for myopia or myopic astigmatism].

    Science.gov (United States)

    Wang, Wei-qun; Zhang, Jin-song; Zhao, Xiao-jin

    2011-10-01

    To explore the postoperative visual acuity results of wavefront-guided LASIK with iris recognition for myopia or myopic astigmatism and the changes of higher-order aberrations and contrast sensitivity function (CSF). Series of prospective case studies, 158 eyes (85 cases) of myopia or myopic astigmatism were divided into two groups: one group underwent wavefront-guided LASIK with iris recognition (iris recognition group); another group underwent wavefront-guided LASIK treatment without iris recognition through the limbus maring point (non-iris recognition group). To comparative analyze the postoperative visual acuity, residual refraction, the RMS of higher-order aberrations and CSF of two groups. There was no statistical significance difference between two groups of the average uncorrected visual acuity (t = 0.039, 0.058, 0.898; P = 0.844, 0.810, 0.343), best corrected visual acuity (t = 0.320, 0.440, 1.515; P = 0.572, 0.507, 0.218), and residual refraction [spherical equivalent (t = 0.027, 0.215, 0.238; P = 0.869, 0.643, 0.626), spherical (t = 0.145, 0.117, 0.038; P = 0.704, 0.732, 0.845) and cylinder (t = 1.676, 1.936, 0.334; P = 0.195, 0.164, 0.563)] at postoperative 10 days, 1 month and 3 month. The security index of iris recognition group at postoperative 3 month was 1.06 and non-iris recognition group was 1.03; the efficacy index of iris recognition group is 1.01 and non-iris recognition group was 1.00. Postoperative 3 month iris recognition group 93.83% eyes and non-iris recognition group of 90.91% eyes spherical equivalent within ± 0.50 D (χ(2) = 0.479, P = 0.489), iris recognition group of 98.77% eyes and non-iris recognition group of 97.40% eyes spherical equivalent within ± 1.00 D (Fisher test, P = 0.613). There was no significance difference between the two groups of security, efficacy and predictability. Non-iris recognition group postoperative 1 month and postoperative 3 months 3-order order aberrations root mean square value (RMS) higher than the

  7. Sensors, Volume 4, Thermal Sensors

    Science.gov (United States)

    Scholz, Jorg; Ricolfi, Teresio

    1996-12-01

    'Sensors' is the first self-contained series to deal with the whole area of sensors. It describes general aspects, technical and physical fundamentals, construction, function, applications and developments of the various types of sensors. This volume describes the construction and applicational aspects of thermal sensors while presenting a rigorous treatment of the underlying physical principles. It provides a unique overview of the various categories of sensors as well as of specific groups, e.g. temperature sensors (resistance thermometers, thermocouples, and radiation thermometers), noise and acoustic thermometers, heat-flow and mass-flow sensors. Specific facettes of applications are presented by specialists from different fields including process control, automotive technology and cryogenics. This volume is an indispensable reference work and text book for both specialists and newcomers, researchers and developers.

  8. Wavefront Aesthetics

    DEFF Research Database (Denmark)

    Højlund, Marie; Riis, Morten S.

    2015-01-01

    . Subscribing to this view also confronts music and sound art as consistent autonomous categories and focuses on how the pieces attune to the environment, emphasising meetings, transformations and translations through and with other objects. These meetings generate an ecological awareness of causal aesthetics...

  9. Wavefront-guided laser-assisted subepithelial keratectomy in low myopia, myopic astigmatism and high myopia

    Directory of Open Access Journals (Sweden)

    Seyed Javad Hashemian

    2015-02-01

    Full Text Available AIM: To compare the safety, efficacy, predictability, stability and complications of wavefront-guided laser-assisted subepithelial keratectomy(LASEKin low myopia, myopic astigmatism and high myopia correction.METHODS: A retrospective analysis of 416 eyes were assigned to 3 groups: 159 eyes with low myopia(LMand mean refractive spherical equivalent(MRSEof -3.68±1.33 dioptre(D; 161 eyes with myopic astigmatism(MAand MRSE of -5.99±2.24D and mean cylinder of 2.41±1.07D; and 96 eyes with high myopia(HMand MRSE of -7.41±0.80D. After an epithelial flap creation, a wavefront-based excimer laser ablation was performed. Safety, efficacy, predictability and stability were evaluated at day 10, 2, 6 and 12mo postoperatively.RESULTS:At 12mo, the MRSE was -0.36±0.31D in LM group, 0.15±0.41D in MA group and 0.58±0.68D in HM group. The uncorrected visual acuity(UCVAwas 20/20 in 90.60% of patients in LM group, 78.90% in MA group and 67% in HM group. Efficacy indices were 0.98, 1.04 and 0.92 in LM, MA and HM groups, respectively. Safety indices were 1.00, 1.07 and 1.05 in LM, MA and HM respectively. Five eyes(3.1%in the LM group gained 1 line. Forty-four eyes(27.3%in MA gained 1-3 lines and eighteen eyes(19.2%of HM group gained 1-2 lines of BSCVA. Only 2 eyes in LM group developed corneal haze. There were not statistically significant differences in efficacy and safety indices amongst three groups. CONCLUSION: Wavefront-guided LASEK is an effective and safe procedure for the treatment of LM, MA, and HM.although in myopic astigmatism the predictability, efficacy and safety indices had been better.

  10. Gas Sensor

    KAUST Repository

    Luebke, Ryan

    2015-01-22

    A gas sensor using a metal organic framework material can be fully integrated with related circuitry on a single substrate. In an on-chip application, the gas sensor can result in an area-efficient fully integrated gas sensor solution. In one aspect, a gas sensor can include a first gas sensing region including a first pair of electrodes, and a first gas sensitive material proximate to the first pair of electrodes, wherein the first gas sensitive material includes a first metal organic framework material.

  11. Gas Sensor

    KAUST Repository

    Luebke, Ryan; Eddaoudi, Mohamed; Omran, Hesham; Belmabkhout, Youssef; Shekhah, Osama; Salama, Khaled N.

    2015-01-01

    A gas sensor using a metal organic framework material can be fully integrated with related circuitry on a single substrate. In an on-chip application, the gas sensor can result in an area-efficient fully integrated gas sensor solution. In one aspect, a gas sensor can include a first gas sensing region including a first pair of electrodes, and a first gas sensitive material proximate to the first pair of electrodes, wherein the first gas sensitive material includes a first metal organic framework material.

  12. Sensor web

    Science.gov (United States)

    Delin, Kevin A. (Inventor); Jackson, Shannon P. (Inventor)

    2011-01-01

    A Sensor Web formed of a number of different sensor pods. Each of the sensor pods include a clock which is synchronized with a master clock so that all of the sensor pods in the Web have a synchronized clock. The synchronization is carried out by first using a coarse synchronization which takes less power, and subsequently carrying out a fine synchronization to make a fine sync of all the pods on the Web. After the synchronization, the pods ping their neighbors to determine which pods are listening and responded, and then only listen during time slots corresponding to those pods which respond.

  13. Time-resolved measurement of thermally induced aberrations in a cryogenically cooled Yb:YAG slab with a wavefront sensor

    Czech Academy of Sciences Publication Activity Database

    Sikocinski, Pawel; Novák, Ondřej; Smrž, Martin; Pilař, Jan; Jambunathan, Venkatesan; Jelínková, H.; Endo, Akira; Lucianetti, Antonio; Mocek, Tomáš

    2016-01-01

    Roč. 122, č. 4 (2016), 1-10, č. článku 73. ISSN 0946-2171 R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143; GA MŠk LO1602; GA ČR GA14-01660S Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : solid-state laser * Yb-Yag Subject RIV: BH - Optics , Masers, Lasers Impact factor: 1.696, year: 2016

  14. Broadband manipulation of refracted wavefronts by gradient acoustic metasurface with V-shape structure

    Science.gov (United States)

    Lan, Jun; Li, Yifeng; Liu, Xiaozhou

    2017-12-01

    We present a space folding acoustic metasurface with a V-shaped structure, which exhibits ultra-broadband and high efficiency transmission compared to previously investigated space folding metasurfaces. The proposal employs a gradient refractive index profile to redirect the refracted wave arbitrarily and an existence of air channels with direct sound propagation to improve impedance matching between the metasurface and the background medium. As expected from frequency-independent generalized Snell's law, the demonstrated acoustic metasurface can steer refracted wavefronts at will, including anomalous refraction, non-diffracting Bessel beam, sub-wavelength flat lens, and conversion of the propagating wave into the surface wave. The designed V-shape metasurface overcomes the limitation of narrowband, which may offer potential applications in medical ultrasound imaging and broadband acoustical devices.

  15. Nonlinear differential equations for the wavefront surface at arbitrary Hartmann-plane distances.

    Science.gov (United States)

    Téllez-Quiñones, Alejandro; Malacara-Doblado, Daniel; Flores-Hernández, Ricardo; Gutiérrez-Hernández, David A; León-Rodríguez, Miguel

    2016-03-20

    In the Hartmann test, a wave aberration function W is estimated from the information of the spot diagram drawn in an observation plane. The distance from a reference plane to the observation plane, the Hartmann-plane distance, is typically chosen as z=f, where f is the radius of a reference sphere. The function W and the transversal aberrations {X,Y} calculated at the plane z=f are related by two well-known linear differential equations. Here, we propose two nonlinear differential equations to denote a more general relation between W and the transversal aberrations {U,V} calculated at any arbitrary Hartmann-plane distance z=r. We also show how to directly estimate the wavefront surface w from the information of {U,V}. The use of arbitrary r values could improve the reliability of the measurements of W, or w, when finding difficulties in adequate ray identification at z=f.

  16. Active wavefront control challenges of the NASA Large Deployable Reflector (LDR)

    Science.gov (United States)

    Meinel, Aden B.; Meinel, Marjorie P.; Manhart, Paul K.; Hochberg, Eric B.

    1989-01-01

    The 20-m Large Deployable Reflector will have a segmented primary mirror. Achieving diffraction-limited performance at 50 microns requires correction for the errors of tilt and piston of the primary mirror. This correction can be obtained in two ways, the use of an active primary or a correction at a demagnified pupil of the primary. A critical requirement is the means for measurement of the wavefront error and maintaining phasing during the observation of objects that may be too faint for determining the error. Absolute phasing can only be determined using a cooperative source. Maintenance of phasing can be done with an on-board source. A number of options are being explored as discussed below. The many issues concerning the assessment and control of an active segmented mirror will be addressed with an early construction of the Precision Segmented Reflector testbed.

  17. Active wavefront control challenges of the NASA Large Deployable Reflector (LDR)

    Science.gov (United States)

    Meinel, Aden B.; Meinel, Marjorie P.; Manhart, Paul K.; Hochberg, Eric B.

    1989-09-01

    The 20-m Large Deployable Reflector will have a segmented primary mirror. Achieving diffraction-limited performance at 50 microns requires correction for the errors of tilt and piston of the primary mirror. This correction can be obtained in two ways, the use of an active primary or a correction at a demagnified pupil of the primary. A critical requirement is the means for measurement of the wavefront error and maintaining phasing during the observation of objects that may be too faint for determining the error. Absolute phasing can only be determined using a cooperative source. Maintenance of phasing can be done with an on-board source. A number of options are being explored as discussed below. The many issues concerning the assessment and control of an active segmented mirror will be addressed with an early construction of the Precision Segmented Reflector testbed.

  18. Diamond x-ray optics: Transparent, resilient, high-resolution, and wavefront preserving

    International Nuclear Information System (INIS)

    Shvyd’ko, Yuri; Blank, Vladimir; Terentyev, Sergey

    2017-01-01

    Diamond features a unique combination of outstanding physical properties perfect for numerous x-ray optics applications, where traditional materials such as silicon fail to perform. In the last two decades, impressive progress has been achieved in synthesizing diamond with high crystalline perfection, in manufacturing efficient, resilient, high-resolution, wavefront-preserving diamond optical components, and in implementing them in cutting-edge x-ray instruments. Diamond optics are essential for tailoring x-rays to the most challenging needs of x-ray research. Furthermore, they are becoming vital for the generation of fully coherent hard x-rays by seeded x-ray free-electron lasers. In this article, we review progress in manufacturing flawless diamond crystal components and their applications in diverse x-ray optical devices, such as x-ray monochromators, beam splitters, high-reflectance backscattering mirrors, lenses, phase plates, diffraction gratings, bent-crystal spectrographs, and windows.

  19. Measuring aberrations in the rat brain by coherence-gated wavefront sensing using a Linnik interferometer.

    Science.gov (United States)

    Wang, Jinyu; Léger, Jean-François; Binding, Jonas; Boccara, A Claude; Gigan, Sylvain; Bourdieu, Laurent

    2012-10-01

    Aberrations limit the resolution, signal intensity and achievable imaging depth in microscopy. Coherence-gated wavefront sensing (CGWS) allows the fast measurement of aberrations in scattering samples and therefore the implementation of adaptive corrections. However, CGWS has been demonstrated so far only in weakly scattering samples. We designed a new CGWS scheme based on a Linnik interferometer and a SLED light source, which is able to compensate dispersion automatically and can be implemented on any microscope. In the highly scattering rat brain tissue, where multiply scattered photons falling within the temporal gate of the CGWS can no longer be neglected, we have measured known defocus and spherical aberrations up to a depth of 400 µm.

  20. An accurate optical design method for synchrotron radiation beamlines with wave-front aberration theory

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Xiaojiang, E-mail: slsyxj@nus.edu.sg; Diao, Caozheng; Breese, Mark B. H. [Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603 (Singapore)

    2016-07-27

    An aberration calculation method which was developed by Lu [1] can treat individual aberration term precisely. Spectral aberration is the linear sum of these aberration terms, and the aberrations of multi-element systems also can be calculated correctly when the stretching ratio, defined herein, is unity. Evaluation of focusing mirror-grating systems which are optimized according to Lu’s method, along with the Light Path Function (LPF) and the Spot Diagram method (SD) are discussed to confirm the advantage of Lu’s methodology. Lu’s aberration terms are derived from a precise wave-front treatment, whereas the terms of the power series expansion of the light path function do not yield an accurate sum of the aberrations. Moreover, Lu’s aberration terms can be individually optimized. This is not possible with the analytical spot diagram formulae.

  1. Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

    Science.gov (United States)

    Yang, Hui; Deng, Yan

    2017-12-01

    All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

  2. Wavefront reconstruction in digital off-axis holography via sparse coding of amplitude and absolute phase.

    Science.gov (United States)

    Katkovnik, V; Shevkunov, I A; Petrov, N V; Egiazarian, K

    2015-05-15

    This work presents the new method for wavefront reconstruction from a digital hologram recorded in off-axis configuration. The main feature of the proposed algorithm is a good ability for noise filtration due to the original formulation of the problem taking into account the presence of noise in the recorded intensity distribution and the sparse phase and amplitude reconstruction approach with the data-adaptive block-matching 3D technique. Basically, the sparsity assumes that low dimensional models can be used for phase and amplitude approximations. This low dimensionality enables strong suppression of noisy components and accurate revealing of the main features of the signals of interest. The principal point is that dictionaries of these sparse models are not known in advance and reconstructed from given noisy observations in a multiobjective optimization procedure. We show experimental results demonstrating the effectiveness of our approach.

  3. Mining robotics sensors

    CSIR Research Space (South Africa)

    Green, JJ

    2012-04-01

    Full Text Available of threedimensional cameras (SR 4000 and XBOX Kinect) and a thermal imaging sensor (FLIR A300) in order to create 3d thermal models of narrow mining stopes. This information can be used in determining the risk of rockfall in an underground mine, which is a major...

  4. Spectral and Wavefront Error Performance of WFIRST/AFTA Prototype Filters

    Science.gov (United States)

    Quijada, Manuel; Seide, Laurie; Marx, Cathy; Pasquale, Bert; McMann, Joseph; Hagopian, John; Dominguez, Margaret; Gong, Qian; Morey, Peter

    2016-01-01

    The Cycle 5 design baseline for the Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Assets (WFIRSTAFTA) instrument includes a single wide-field channel (WFC) instrument for both imaging and slit-less spectroscopy. The only routinely moving part during scientific observations for this wide-field channel is the element wheel (EW) assembly. This filter-wheel assembly will have 8 positions that will be populated with 6 bandpass filters, a blank position, and a Grism that will consist of a three-element assembly to disperse the full field with an undeviated central wavelength for galaxy redshift surveys. All filter elements in the EW assembly will be made out of fused silica substrates (110 mm diameter) that will have the appropriate bandpass coatings according to the filter designations (Z087, Y106, J129, H158, F184, W149 and Grism). This paper presents and discusses the performance (including spectral transmission and reflectedtransmitted wavefront error measurements) of a subset of bandpass filter coating prototypes that are based on the WFC instrument filter compliment. The bandpass coating prototypes that are tested in this effort correspond to the Z087, W149, and Grism filter elements. These filter coatings have been procured from three different vendors to assess the most challenging aspects in terms of the in-band throughput, out of band rejection (including the cut-on and cutoff slopes), and the impact the wavefront error distortions of these filter coatings will have on the imaging performance of the de-field channel in the WFIRSTAFTA observatory.

  5. Spectral and Wavefront Error Performance of WFIRST-AFTA Bandpass Filter Coating Prototypes

    Science.gov (United States)

    Quijada, Manuel A.; Seide, Laurie; Pasquale, Bert A.; McMann, Joseph C.; Hagopian, John G.; Dominguez, Margaret Z.; Gong, Quian; Marx, Catherine T.

    2016-01-01

    The Cycle 5 design baseline for the Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Assets (WFIRST/AFTA) instrument includes a single wide-field channel (WFC) instrument for both imaging and slit-less spectroscopy. The only routinely moving part during scientific observations for this wide-field channel is the element wheel (EW) assembly. This filter-wheel assembly will have 8 positions that will be populated with 6 bandpass filters, a blank position, and a Grism that will consist of a three-element assembly to disperse the full field with an undeviated central wavelength for galaxy redshift surveys. All filter elements in the EW assembly will be made out of fused silica substrates (110 mm diameter) that will have the appropriate bandpass coatings according to the filter designations (Z087, Y106, J129, H158, F184, W149 and Grism). This paper presents and discusses the performance (including spectral transmission and reflected/transmitted wavefront error measurements) of a subset of bandpass filter coating prototypes that are based on the WFC instrument filter compliment. The bandpass coating prototypes that are tested in this effort correspond to the Z087, W149, and Grism filter elements. These filter coatings have been procured from three different vendors to assess the most challenging aspects in terms of the in-band throughput, out of band rejection (including the cut-on and cutoff slopes), and the impact the wavefront error distortions of these filter coatings will have on the imaging performance of the wide-field channel in the WFIRST/AFTA observatory.

  6. An imaging method of wavefront coding system based on phase plate rotation

    Science.gov (United States)

    Yi, Rigui; Chen, Xi; Dong, Liquan; Liu, Ming; Zhao, Yuejin; Liu, Xiaohua

    2018-01-01

    Wave-front coding has a great prospect in extending the depth of the optical imaging system and reducing optical aberrations, but the image quality and noise performance are inevitably reduced. According to the theoretical analysis of the wave-front coding system and the phase function expression of the cubic phase plate, this paper analyzed and utilized the feature that the phase function expression would be invariant in the new coordinate system when the phase plate rotates at different angles around the z-axis, and we proposed a method based on the rotation of the phase plate and image fusion. First, let the phase plate rotated at a certain angle around the z-axis, the shape and distribution of the PSF obtained on the image surface remain unchanged, the rotation angle and direction are consistent with the rotation angle of the phase plate. Then, the middle blurred image is filtered by the point spread function of the rotation adjustment. Finally, the reconstruction images were fused by the method of the Laplacian pyramid image fusion and the Fourier transform spectrum fusion method, and the results were evaluated subjectively and objectively. In this paper, we used Matlab to simulate the images. By using the Laplacian pyramid image fusion method, the signal-to-noise ratio of the image is increased by 19% 27%, the clarity is increased by 11% 15% , and the average gradient is increased by 4% 9% . By using the Fourier transform spectrum fusion method, the signal-to-noise ratio of the image is increased by 14% 23%, the clarity is increased by 6% 11% , and the average gradient is improved by 2% 6%. The experimental results show that the image processing by the above method can improve the quality of the restored image, improving the image clarity, and can effectively preserve the image information.

  7. Refractive outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens power calculation

    Directory of Open Access Journals (Sweden)

    Zina Zhang

    2017-01-01

    Full Text Available Purpose: To compare the outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens (IOL power calculation in eyes undergoing cataract surgery with monofocal IOL implantation. Methods: Preoperative data were obtained with the IOLMaster. Intraoperative aphakic measurements and IOL power calculations were obtained in some patients with the optiwave refractive analysis (ORA system. Analysis was performed to determine the accuracy of monofocal IOL power prediction and postoperative manifest refraction at 1 month of the ORA versus IOLMaster. Results: Two hundred and ninety-five eyes reviewed, 61 had only preoperative IOLMaster measurements and 234 had both IOLMaster and ORA measurements. Of these 234 eyes, 6 were excluded, 107 had the same recommended IOL power by ORA and IOLMaster. Sixty-four percent of these eyes were within ±0.5D. 95 eyes had IOL power implantation based on ORA instead of IOLMaster. Seventy percent of these eyes were within ±0.5D of target refraction. 26 eyes had IOL power chosen based on IOLMaster predictions instead of ORA. Sixty-five percent were within ±0.5D. In the group with IOLMaster without ORA measurements, 80% of eyes were within ±0.5D of target refraction. The absolute error was statistically smaller in those eyes where the ORA and IOLMaster recommended the same IOL power based on preoperative target refraction compared to instances in which IOL selection was based on ORA or IOLMaster alone. Neither prediction errors were statistically different between the ORA and IOLMaster alone. Conclusion: Intraoperative wavefront aberrometry with the ORA system provides postoperative refractive results comparable to conventional biometry with the IOLMaster for monofocal IOL selection.

  8. Incidence, outcomes, and risk factors for retreatment after wavefront-optimized ablations with PRK and LASIK.

    Science.gov (United States)

    Randleman, J Bradley; White, Alfred J; Lynn, Michael J; Hu, Michelle H; Stulting, R Doyle

    2009-03-01

    To analyze and compare retreatment rates after wavefront-optimized photorefractive keratectomy (PRK) and LASIK and determine risk factors for retreatment. A retrospective chart review was performed to identify patients undergoing PRK or LASIK with the wavefront-optimized WaveLight platform from January 2005 through December 2006 targeted for a piano outcome and to determine the rate and risk factors for retreatment surgery in this population. Eight hundred fifty-five eyes were analyzed, including 70 (8.2%) eyes with hyperopic refractions and 785 (91.8%) eyes with myopic refractions. After initial treatment, 72% of eyes were 20/20 or better and 99.5% were 20/40 or better. To improve uncorrected visual acuity, 54 (6.3%) eyes had retreatments performed. No significant differences in retreatment rates were noted based on age (P = .15), sex (P = .8), eye (P = .3), PRK versus LASIK (P = 1.0), room temperature (P = .1) or humidity (P = .9), and no correlation between retreatment rate and month or season of primary surgery (P = .4). There was no correlation between degree of myopia and retreatment rate. Eyes were significantly more likely to undergo retreatment if they were hyperopic (12.8% vs 6.0%, P = .006) or had astigmatism > or = 1.00 diopter (D) (9.1% vs 5.3%, P = .04). Retreatment rate was 6.3% with the WaveLight ALLEGRETTO WAVE excimer laser. This rate was not influenced by age, sex, corneal characteristics, or environmental factors. Eyes with hyperopic refractions or astigmatism > or = 1.00 D were more likely to undergo retreatment.

  9. Chemical sensors

    International Nuclear Information System (INIS)

    Hubbard, C.W.; Gordon, R.L.

    1987-05-01

    The revolution in analytical chemistry promised by recent developments in the field of chemical sensors has potential for significant positive impact on both research and production activities conducted by and for the Department of Energy. Analyses which were, in the past, performed only with a roomful of expensive equipment can now be performed with miniature solid-state electronic devices or small optical probes. Progress in the development of chemical sensors has been rapid, and the field is currently growing at a great rate. In accordance, Pacific Northwest Laboratory initiated a survey of recent literature so that contributors to active programs in research on analytical methods could be made aware of principles and applications of this new technology. This report presents the results of that survey. The sensors discussed here are divided into three types: micro solid-state devices, optical sensors, and piezoelectric crystal devices. The report is divided into three corresponding sections. The first section, ''Micro Solid-State Devices,'' discusses the design, operation, and application of electronic sensors that are produced in much the same way as standard solid-state electronic devices. The second section, ''Optrodes,'' covers the design and operation of chemical sensors that use fiber optics to detect chemically induced changes in optical properties. The final section, ''Piezoelectric Crystal Detectors,'' discusses two types of chemical sensors that depend on the changes in the properties of an oscillating piezoelectric crystal to detect the presence of certain materials. Advantages and disadvantages of each type of sensor are summarized in each section

  10. -Net Approach to Sensor -Coverage

    Directory of Open Access Journals (Sweden)

    Fusco Giordano

    2010-01-01

    Full Text Available Wireless sensors rely on battery power, and in many applications it is difficult or prohibitive to replace them. Hence, in order to prolongate the system's lifetime, some sensors can be kept inactive while others perform all the tasks. In this paper, we study the -coverage problem of activating the minimum number of sensors to ensure that every point in the area is covered by at least sensors. This ensures higher fault tolerance, robustness, and improves many operations, among which position detection and intrusion detection. The -coverage problem is trivially NP-complete, and hence we can only provide approximation algorithms. In this paper, we present an algorithm based on an extension of the classical -net technique. This method gives an -approximation, where is the number of sensors in an optimal solution. We do not make any particular assumption on the shape of the areas covered by each sensor, besides that they must be closed, connected, and without holes.

  11. Surface Embedded Metal Oxide Sensors (SEMOS)

    DEFF Research Database (Denmark)

    Jespersen, Jesper Lebæk; Talat Ali, Syed; Pleth Nielsen, Lars

    SEMOS is a joint project between Aalborg University, Danish Technological Institute and Danish Technical University in which micro temperature sensors and metal oxide-based gas sensors are developed and tested in a simulated fuel cell environment as well as in actual working fuel cells. Initially......, sensors for measuring the temperatures in an operating HT-PEM (High Temperature-Proton Exchange Membrane) fuel cell are developed for detecting in-plane temperature variations. 5 different tracks for embedded thermal sensors are investigated. The fuel cell MEA (Membrane Electrode Assembly) is quite...... complex and sensors are not easily implemented in the construction. Hence sensor interface and sensor position must therefore be chosen carefully in order to make the sensors as non-intrusive as possible. Metal Oxide Sensors (MOX) for measuring H2, O2 and CO concentration in a fuel cell environment...

  12. Automotive sensors

    Science.gov (United States)

    Marek, Jiri; Illing, Matthias

    2003-01-01

    Sensors are an essential component of most electronic systems in the car. They deliver input parameters for comfort features, engine and emission control as well as for the active and passive safety systems. New technologies such as silicon micromachining play an important role for the introduction of these sensors in all vehicle classes. The importance and use of these sensor technologies in today"s automotive applications will be shown in this article. Finally an outlook on important current developments and new functions in the car will be given.

  13. Piezoceramic Sensors

    CERN Document Server

    Sharapov, Valeriy

    2011-01-01

    This book presents the latest and complete information about various types of piezosensors. A sensor is a converter of the measured physical size to an electric signal. Piezoelectric transducers and sensors are based on piezoelectric effects. They have proven to be versatile tools for the measurement of various processes. They are used for quality assurance, process control and for research and development in many different industries. In each area of application specific requirements to the parameters of transducers and sensors are developed. This book presents the fundamentals, technical des

  14. Wavefront correction for static and dynamic aberrations to within 1 second of the system shot in the NIF Beamlet demonstration facility

    International Nuclear Information System (INIS)

    Hartley, R.; Kartz, M.; Behrendt, W.

    1996-10-01

    The laser wavefront of the NIF Beamlet demonstration system is corrected for static aberrations with a wavefront control system. The system operates closed loop with a probe beam prior to a shot and has a loop bandwidth of about 3 Hz. However, until recently the wavefront control system was disabled several minutes prior to the shot to allow time to manually reconfigure its attenuators and probe beam insertion mechanism to shot mode. Thermally-induced dynamic variations in gas density in the Beamlet main beam line produce significant wavefront error. After about 5-8 seconds, the wavefront error has increased to a new, higher level due to turbulence- induced aberrations no longer being corrected- This implies that there is a turbulence-induced aberration noise bandwidth of less than one Hertz, and that the wavefront controller could correct for the majority of turbulence-induced aberration (about one- third wave) by automating its reconfiguration to occur within one second of the shot, This modification was recently implemented on Beamlet; we call this modification the t 0 -1 system

  15. Correlation Wave-Front Sensing Algorithms for Shack-Hartmann-Based Adaptive Optics using a Point Source

    International Nuclear Information System (INIS)

    Poynee, L A

    2003-01-01

    Shack-Hartmann based Adaptive Optics system with a point-source reference normally use a wave-front sensing algorithm that estimates the centroid (center of mass) of the point-source image 'spot' to determine the wave-front slope. The centroiding algorithm suffers for several weaknesses. For a small number of pixels, the algorithm gain is dependent on spot size. The use of many pixels on the detector leads to significant propagation of read noise. Finally, background light or spot halo aberrations can skew results. In this paper an alternative algorithm that suffers from none of these problems is proposed: correlation of the spot with a ideal reference spot. The correlation method is derived and a theoretical analysis evaluates its performance in comparison with centroiding. Both simulation and data from real AO systems are used to illustrate the results. The correlation algorithm is more robust than centroiding, but requires more computation

  16. Optischer Sensor

    OpenAIRE

    Brandenburg, A.; Hutter, F.; Edelhaeuser, R.

    1992-01-01

    WO 2010040565 A1 UPAB: 20100506 NOVELTY - The integrated optical sensor comprises a first waveguide (4), a second waveguide (5) optically coupled to the first waveguide via a directional coupler, a substrate, which carries the first and the second waveguides, a single waveguide coupled with a light source, and an output waveguide coupled with a light-sensitive element. The sensor has a functional surface in the region of the directional coupler for depositing or deposition of the substance to...

  17. Wireless sensor

    Science.gov (United States)

    Lamberti, Vincent E.; Howell, JR, Layton N.; Mee, David K.; Sepaniak, Michael J.

    2016-02-09

    Disclosed is a sensor for detecting a target material. The sensor includes a ferromagnetic metal and a molecular recognition reagent coupled to the ferromagnetic metal. The molecular recognition reagent is operable to expand upon exposure to vapor or liquid from the target material such that the molecular recognition reagent changes a tensile stress upon the ferromagnetic metal. The target material is detected based on changes in the magnetic switching characteristics of the ferromagnetic metal caused by the changes in the tensile stress.

  18. Clinical Outcomes of SMILE With a Triple Centration Technique and Corneal Wavefront-Guided Transepithelial PRK in High Astigmatism.

    Science.gov (United States)

    Jun, Ikhyun; Kang, David Sung Yong; Reinstein, Dan Z; Arba-Mosquera, Samuel; Archer, Timothy J; Seo, Kyoung Yul; Kim, Tae-Im

    2018-03-01

    To comparatively investigate the clinical outcomes, vector parameters, and corneal aberrations of small incision lenticule extraction (SMILE) with a triple centration technique and corneal wavefront-guided transepithelial photorefractive keratectomy (PRK) for the correction of high astigmatism. This retrospective, comparative case series study included 89 eyes (89 patients) that received treatment for myopia with high astigmatism (≥ 2.50 diopters) using SMILE with a triple centration technique (SMILE group; 45 eyes) and corneal wavefront-guided transepithelial PRK (transepithelial PRK group; 44 eyes). Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1, 3, and 6 months after surgery. The safety, efficacy, vector parameters, and corneal aberrations at 6 months after surgery were compared between the two groups. At 6 months after surgery, the transepithelial PRK and SMILE groups exhibited comparable mean uncorrected distance visual acuities (-0.06 ± 0.07 and -0.05 ± 0.07 logMAR, respectively), safety, efficacy, and predictability of refractive and visual outcomes. There was a slight but statistically significant difference in the correction index between the transepithelial PRK and SMILE groups (0.96 ± 0.11 and 0.91 ± 0.10, respectively). Whereas the transepithelial PRK group exhibited increased corneal spherical aberration and significantly reduced corneal coma and trefoil, no changes in aberrometric values were noted in the SMILE group. Both SMILE with a triple centration technique and corneal wavefront-guided transepithelial PRK are effective and provide predictable outcomes for the correction of high myopic astigmatism, although slight undercorrection was observed in the SMILE group. The triple centration technique was helpful in astigmatism correction by SMILE. [J Refract Surg. 2018;34(3):156-163.]. Copyright 2018

  19. Interferometric interrogation concepts for integrated electro-optical sensor systems

    NARCIS (Netherlands)

    Ikkink, T.J.; Ikkink, Teunis Jan

    1998-01-01

    Integrated optical sensors have a high potential in the measurement of a large variety of measurands. Research on integrated optical sensors enjoys increasing interest. In order to reach accurate performance and to facilitate the use of integrated optical sensors, electronic functions for sensor

  20. Wavefront-guided refractive surgery results of training-surgeons Resultados das cirurgias refrativas guiadas por frentes de ondas de cirurgiões em treinamento

    Directory of Open Access Journals (Sweden)

    Iane Stillitano

    2010-08-01

    Full Text Available PURPOSE: To assess clinical outcomes and changes on higher-order aberrations (HOA after wavefront-guided laser in situ keratomileusis (LASIK and photorefractive keratectomy (PRK for correction of myopia and myopic astigmatism performed by training-surgeons. METHODS: One hundred and seventy patients had customized LASIK (207 eyes and PRK (103 eyes performed by surgeons in-training using the LADARVision 4000 (Alcon, Fort Worth, TX. Preoperative and 1, 3, 6 and 12 months postoperative data of spherical equivalent (SE, best spectacle-corrected visual acuity (BSCVA and uncorrected visual acuity (UCVA were analysed. Wavefront changes were determined using the LADARWave Hartmann-Shack wavefront aberrometer and the pupil size was scaled for 6.5 mm. RESULTS: The mean SE in the LASIK group was -3.04 ±1.07 D and in the PRK group was -1.60 ± 0.59 D. At 1-year follow-up, (80.6% (LASIK and (66.7% (PRK were within ± 0.50 D of the intended refraction. The UCVA was 20/20 or better in (58.1% (LASIK and (66.7% (PRK of the operated eyes. A statistically significant positive correlation was found between achieved versus attempted refractive correction in both groups: LASIK (r=0.975, POBJETIVO: Avaliar os resultados clínicos e mudanças nas aberrações de alta-ordem (HOA, após ceratomileuse assistida por excimer laser in situ (LASIK e ceratectomia fotorrefrativa (PRK guiados por frentes de onda para correção da miopia e astigmatismo miópico realizada por cirurgiões em treinamento. MÉTODOS: Estudo prospectivo de 170 pacientes submetidos a LASIK personalizado (207 olhos e PRK (103 olhos realizados por cirurgiões em treinamento utilizando o LADARVision 4000 (Alcon, Fort Worth, TX. Dados do equivalente esférico (SE, melhor acuidade visual corrigida (BSCVA e acuidade visual não corrigida (UCVA foram analisados no pré-operatório e com 1, 3, 6 e 12 meses de pós-operatório. As alterações de frentes de onda foram determinadas usando o aberrômetro Hartmann

  1. Miniaturized thermal flow sensor with planar-integrated sensor structures on semicircular surface channels

    NARCIS (Netherlands)

    Dijkstra, Marcel; de Boer, Meint J.; Berenschot, Johan W.; Lammerink, Theodorus S.J.; Wiegerink, Remco J.; Elwenspoek, Michael Curt

    2008-01-01

    A calorimetric miniaturized flow sensor was realized with a linear sensor response measured for water flow up to flow rates in the order of 300 nl min-1. A versatile technological concept is used to realize a sensor with a thermally isolated freely suspended silicon-rich silicon-nitride microchannel

  2. Aperiodic order

    CERN Document Server

    Grimm, Uwe

    2017-01-01

    Quasicrystals are non-periodic solids that were discovered in 1982 by Dan Shechtman, Nobel Prize Laureate in Chemistry 2011. The mathematics that underlies this discovery or that proceeded from it, known as the theory of Aperiodic Order, is the subject of this comprehensive multi-volume series. This second volume begins to develop the theory in more depth. A collection of leading experts, among them Robert V. Moody, cover various aspects of crystallography, generalising appropriately from the classical case to the setting of aperiodically ordered structures. A strong focus is placed upon almost periodicity, a central concept of crystallography that captures the coherent repetition of local motifs or patterns, and its close links to Fourier analysis. The book opens with a foreword by Jeffrey C. Lagarias on the wider mathematical perspective and closes with an epilogue on the emergence of quasicrystals, written by Peter Kramer, one of the founders of the field.

  3. Peak-locking centroid bias in Shack-Hartmann wavefront sensing

    Science.gov (United States)

    Anugu, Narsireddy; Garcia, Paulo J. V.; Correia, Carlos M.

    2018-05-01

    Shack-Hartmann wavefront sensing relies on accurate spot centre measurement. Several algorithms were developed with this aim, mostly focused on precision, i.e. minimizing random errors. In the solar and extended scene community, the importance of the accuracy (bias error due to peak-locking, quantization, or sampling) of the centroid determination was identified and solutions proposed. But these solutions only allow partial bias corrections. To date, no systematic study of the bias error was conducted. This article bridges the gap by quantifying the bias error for different correlation peak-finding algorithms and types of sub-aperture images and by proposing a practical solution to minimize its effects. Four classes of sub-aperture images (point source, elongated laser guide star, crowded field, and solar extended scene) together with five types of peak-finding algorithms (1D parabola, the centre of gravity, Gaussian, 2D quadratic polynomial, and pyramid) are considered, in a variety of signal-to-noise conditions. The best performing peak-finding algorithm depends on the sub-aperture image type, but none is satisfactory to both bias and random errors. A practical solution is proposed that relies on the antisymmetric response of the bias to the sub-pixel position of the true centre. The solution decreases the bias by a factor of ˜7 to values of ≲ 0.02 pix. The computational cost is typically twice of current cross-correlation algorithms.

  4. An accelerated hologram calculation using the wavefront recording plane method and wavelet transform

    Science.gov (United States)

    Arai, Daisuke; Shimobaba, Tomoyoshi; Nishitsuji, Takashi; Kakue, Takashi; Masuda, Nobuyuki; Ito, Tomoyoshi

    2017-06-01

    Fast hologram calculation methods are critical in real-time holography applications such as three-dimensional (3D) displays. We recently proposed a wavelet transform-based hologram calculation called WASABI. Even though WASABI can decrease the calculation time of a hologram from a point cloud, it increases the calculation time with increasing propagation distance. We also proposed a wavefront recoding plane (WRP) method. This is a two-step fast hologram calculation in which the first step calculates the superposition of light waves emitted from a point cloud in a virtual plane, and the second step performs a diffraction calculation from the virtual plane to the hologram plane. A drawback of the WRP method is in the first step when the point cloud has a large number of object points and/or a long distribution in the depth direction. In this paper, we propose a method combining WASABI and the WRP method in which the drawbacks of each can be complementarily solved. Using a consumer CPU, the proposed method succeeded in performing a hologram calculation with 2048 × 2048 pixels from a 3D object with one million points in approximately 0.4 s.

  5. Modeling of light-emitting diode wavefronts for the optimization of transmission holograms.

    Science.gov (United States)

    Karthaus, Daniela; Giehl, Markus; Sandfuchs, Oliver; Sinzinger, Stefan

    2017-06-20

    The objective of applying transmission holograms in automotive headlamp systems requires the adaptation of holograms to divergent and polychromatic light sources like light-emitting diodes (LEDs). In this paper, four different options to describe the scalar light waves emitted by a typical automotive LED are regarded. This includes a new approach to determine the LED's wavefront from interferometric measurements. Computer-generated holograms are designed considering the different LED approximations and recorded into a photopolymer. The holograms are reconstructed with the LED and the resulting images are analyzed to evaluate the quality of the wave descriptions. In this paper, we show that our presented new approach leads to better results in comparison to other wave descriptions. The enhancement is evaluated by the correlation between reconstructed and ideal images. In contrast to the next best approximation, a spherical wave, the correlation coefficient increased by 0.18% at 532 nm, 1.69% at 590 nm, and 0.75% at 620 nm.

  6. Holographic wavefront characterization of a frequency-tripled high-peak-power neodymium:glass laser

    International Nuclear Information System (INIS)

    Kessler, T.J.

    1984-01-01

    Near-field amplitude and phase distributions from a high-peak-power, frequency converted Nd:glass laser (lambda = 351 nm) have been holographically recorded on silver-halide emulsions. Conventionally, the absence of a suitable reference beam forces one to use some type of shearing interferometry to obtain phasefront information, while the near-field and far-field distributions are recorded as intensity profiles. In this study, a spatially filtered, locally generated reference beam was created to holographically store the complex amplitude distribution of the pulsed laser beam, while reconstruction of the original wavefront was achieved with a continuous-wave laser. Reconstructed near-field and quasi-far-field intensity distributions closely resembled those obtained from conventional techniques, and accurate phasefront reconstruction was achieved. Furthermore, several two-beam interferometric techniques, not practicable with a high-peak-power laser, have been successfully implemented on a continuous-wave reconstruction of the pulsed laser beam. 46 refs., 40 figs., 1 tab

  7. On radiation emission from a microbunched beam with wavefront tilt and its experimental observation

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2017-06-15

    In this paper we compare experimental observations and theory of radiation emission from a microbunched beam with microbunching wavefront tilt with respect to the direction of motion. The theory refers to the work of T. Tanaka, H. Kitamura, and T. Shintake (2004), which predicts, in this case, exponential suppression of coherent radiation along the kicked direction. The observations refer to a recent experiment performed at the LCLS, where a microbunched beam was kicked by a bend and sent to a radiator undulator. The experiment resulted in the emission of strong coherent radiation that had its maximum along the kicked direction of motion, when the undulator parameter was detuned to a value larger than the nominal one. We first analyze the theory in detail, and we confirm the correctness of its derivation according to the conventional theory of radiation emission from charged particles. Subsequently, we look for possible peculiarities in the experiment, which may not be modeled by the theory. We show that only spurious effects are not accounted for. We conclude that the experiment defies explanation in terms of the conventional theory of radiation emission.

  8. On radiation emission from a microbunched beam with wavefront tilt and its experimental observation

    Science.gov (United States)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2018-03-01

    In this paper we compare experimental observations and theory of radiation emission from a microbunched beam with microbunching wavefront tilt with respect to the direction of motion. The theory refers to the work Tanaka et al. (2004) , which predicts, in this case, exponential suppression of coherent radiation along the kicked direction. The observations refer to a recent experiment performed at the LCLS (Nuhn et al., 2015; Lutman etal., 2016), where a microbunched beam was kicked by a bend and sent to a radiator undulator. The experiment resulted in the emission of strong coherent radiation that had its maximum along the kicked direction of motion, when the undulator parameter was detuned to a value larger than the nominal one. We first analyze the theory in detail, and we confirm the correctness of its derivation according to the conventional theory of radiation emission from charged particles. Subsequently, we look for possible peculiarities in the experiment, which may not be modeled by the theory. We show that only spurious effects are not accounted for. We conclude that the experiment defies explanation in terms of the conventional theory of radiation emission.

  9. HIGH-SPEED IMAGING AND WAVEFRONT SENSING WITH AN INFRARED AVALANCHE PHOTODIODE ARRAY

    Energy Technology Data Exchange (ETDEWEB)

    Baranec, Christoph; Atkinson, Dani; Hall, Donald; Jacobson, Shane; Chun, Mark [Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700 (United States); Riddle, Reed [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Law, Nicholas M., E-mail: baranec@hawaii.edu [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States)

    2015-08-10

    Infrared avalanche photodiode (APD) arrays represent a panacea for many branches of astronomy by enabling extremely low-noise, high-speed, and even photon-counting measurements at near-infrared wavelengths. We recently demonstrated the use of an early engineering-grade infrared APD array that achieves a correlated double sampling read noise of 0.73 e{sup −} in the lab, and a total noise of 2.52 e{sup −} on sky, and supports simultaneous high-speed imaging and tip-tilt wavefront sensing with the Robo-AO visible-light laser adaptive optics (AO) system at the Palomar Observatory 1.5 m telescope. Here we report on the improved image quality simultaneously achieved at visible and infrared wavelengths by using the array as part of an image stabilization control loop with AO-sharpened guide stars. We also discuss a newly enabled survey of nearby late M-dwarf multiplicity, as well as future uses of this technology in other AO and high-contrast imaging applications.

  10. Radiation sensor

    International Nuclear Information System (INIS)

    Brown, W.L.; Geronime, R.L.

    1977-01-01

    Radiation sensor and thermocouple, respectively, which can be used for reactor in-core instrumentation. The radiation sensor consists of an inconel conductor wire and rhodium emitter wire, the thermocouple of two intertwined alumel or chromel wires. Both are arranged in the center of a metal tube relative to which they are separated by an insulator made of SiO 2 fibers. This insulator is first introduced as a loose fabric between the radiation sensor and the thermocouple, respectively, and the metal tube and then compacted to a density of 35-73% of pure SiO 2 by drawing the tube. There is no need for soldering or welding. The insulation resistivity at room temperature ist between 10 14 and 10 15 ohms. (ORU) [de

  11. Water Sensors

    Science.gov (United States)

    1992-01-01

    Mike Morris, former Associate Director of STAC, formed pHish Doctor, Inc. to develop and sell a pH monitor for home aquariums. The monitor, or pHish Doctor, consists of a sensor strip and color chart that continually measures pH levels in an aquarium. This is important because when the level gets too high, ammonia excreted by fish is highly toxic; at low pH, bacteria that normally break down waste products stop functioning. Sales have run into the tens of thousands of dollars. A NASA Tech Brief Technical Support Package later led to a salt water version of the system and a DoE Small Business Innovation Research (SBIR) grant for development of a sensor for sea buoys. The company, now known as Ocean Optics, Inc., is currently studying the effects of carbon dioxide buildup as well as exploring other commercial applications for the fiber optic sensor.

  12. New sensors and processing chain

    CERN Document Server

    Yaakoubi, Nourdin

    2014-01-01

    A vital tool for researchers, engineers, and students, New Sensors and Processing Chain focuses on the processing chain to set up in order to extract relevant information on various systems. Highlighting the design of new microsensors and various applications, the authors present recent progress in instrumentation and microsystem design, providing insight to the modification of the sensor itself as well as its environment. Various applications illustrate the presentations, which show how a processing chain is organized from the data acquired by a specific sensor.

  13. Practical Use Technique of Sensor

    International Nuclear Information System (INIS)

    Hwang, Gyu Seop

    1985-11-01

    This book tells of practical use technology of sensor, introducing the recent trend of sensor for electronic industry, IC temperature sensor, radiation temperature sensor of surface acoustic wave, optical fiber temperature sensor, a polyelectrolyte film humidity sensor, semiconductor pressure sensor for industrial instrumentation, silicon integration pressure sensor, thick film humidity sensor and its application, photo sensor reflection type, and color sensor. It also deals with sensor for FA, sensor for a robot and sensor for the chemical industry.

  14. Practical Use Technique of Sensor

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Gyu Seop

    1985-11-15

    This book tells of practical use technology of sensor, introducing the recent trend of sensor for electronic industry, IC temperature sensor, radiation temperature sensor of surface acoustic wave, optical fiber temperature sensor, a polyelectrolyte film humidity sensor, semiconductor pressure sensor for industrial instrumentation, silicon integration pressure sensor, thick film humidity sensor and its application, photo sensor reflection type, and color sensor. It also deals with sensor for FA, sensor for a robot and sensor for the chemical industry.

  15. Open architecture of smart sensor suites

    Science.gov (United States)

    Müller, Wilmuth; Kuwertz, Achim; Grönwall, Christina; Petersson, Henrik; Dekker, Rob; Reinert, Frank; Ditzel, Maarten

    2017-10-01

    Experiences from recent conflicts show the strong need for smart sensor suites comprising different multi-spectral imaging sensors as core elements as well as additional non-imaging sensors. Smart sensor suites should be part of a smart sensor network - a network of sensors, databases, evaluation stations and user terminals. Its goal is to optimize the use of various information sources for military operations such as situation assessment, intelligence, surveillance, reconnaissance, target recognition and tracking. Such a smart sensor network will enable commanders to achieve higher levels of situational awareness. Within the study at hand, an open system architecture was developed in order to increase the efficiency of sensor suites. The open system architecture for smart sensor suites, based on a system-of-systems approach, enables combining different sensors in multiple physical configurations, such as distributed sensors, co-located sensors combined in a single package, tower-mounted sensors, sensors integrated in a mobile platform, and trigger sensors. The architecture was derived from a set of system requirements and relevant scenarios. Its mode of operation is adaptable to a series of scenarios with respect to relevant objects of interest, activities to be observed, available transmission bandwidth, etc. The presented open architecture is designed in accordance with the NATO Architecture Framework (NAF). The architecture allows smart sensor suites to be part of a surveillance network, linked e.g. to a sensor planning system and a C4ISR center, and to be used in combination with future RPAS (Remotely Piloted Aircraft Systems) for supporting a more flexible dynamic configuration of RPAS payloads.

  16. Chemical sensor

    Science.gov (United States)

    Rauh, R. David (Inventor)

    1990-01-01

    A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

  17. Load sensor

    NARCIS (Netherlands)

    Van den Ende, D.; Almeida, P.M.R.; Dingemans, T.J.; Van der Zwaag, S.

    2007-01-01

    The invention relates to a load sensor comprising a polymer matrix and a piezo-ceramic material such as PZT, em not bedded in the polymer matrix, which together form a compos not ite, wherein the polymer matrix is a liquid crystalline resin, and wherein the piezo-ceramic material is a PZT powder

  18. Gas sensor

    Science.gov (United States)

    Schmid, Andreas K.; Mascaraque, Arantzazu; Santos, Benito; de la Figuera, Juan

    2014-09-09

    A gas sensor is described which incorporates a sensor stack comprising a first film layer of a ferromagnetic material, a spacer layer, and a second film layer of the ferromagnetic material. The first film layer is fabricated so that it exhibits a dependence of its magnetic anisotropy direction on the presence of a gas, That is, the orientation of the easy axis of magnetization will flip from out-of-plane to in-plane when the gas to be detected is present in sufficient concentration. By monitoring the change in resistance of the sensor stack when the orientation of the first layer's magnetization changes, and correlating that change with temperature one can determine both the identity and relative concentration of the detected gas. In one embodiment the stack sensor comprises a top ferromagnetic layer two mono layers thick of cobalt deposited upon a spacer layer of ruthenium, which in turn has a second layer of cobalt disposed on its other side, this second cobalt layer in contact with a programmable heater chip.

  19. Optimizing Electrodynamics Sensor Properties for High-AO Fluence Environment

    Data.gov (United States)

    National Aeronautics and Space Administration — To investigate the oxidation of sensor coatings in order to develop more robust sensors that can be used not only for Atmosphere-Space Transition Region Explorer...

  20. Jupiter energetic particle experiment ESAD proton sensor design

    International Nuclear Information System (INIS)

    Gruhn, C.R.; Higbie, P.R.

    1977-12-01

    A proton sensor design for the Jupiter Energetic Particle Experiment is described. The sensor design uses avalanche multiplication in order to lower the effective energy threshold. A complete signal-to-noise analysis is given for this design

  1. Improving slowness estimate stability and visualization using limited sensor pair correlation on seismic arrays

    Science.gov (United States)

    Gibbons, Steven J.; Näsholm, S. P.; Ruigrok, E.; Kværna, T.

    2018-04-01

    Seismic arrays enhance signal detection and parameter estimation by exploiting the time-delays between arriving signals on sensors at nearby locations. Parameter estimates can suffer due to both signal incoherence, with diminished waveform similarity between sensors, and aberration, with time-delays between coherent waveforms poorly represented by the wave-front model. Sensor-to-sensor correlation approaches to parameter estimation have an advantage over direct beamforming approaches in that individual sensor-pairs can be omitted without necessarily omitting entirely the data from each of the sensors involved. Specifically, we can omit correlations between sensors for which signal coherence in an optimal frequency band is anticipated to be poor or for which anomalous time-delays are anticipated. In practice, this usually means omitting correlations between more distant sensors. We present examples from International Monitoring System seismic arrays with poor parameter estimates resulting when classical f-k analysis is performed over the full array aperture. We demonstrate improved estimates and slowness grid displays using correlation beamforming restricted to correlations between sufficiently closely spaced sensors. This limited sensor-pair correlation (LSPC) approach has lower slowness resolution than would ideally be obtained by considering all sensor-pairs. However, this ideal estimate may be unattainable due to incoherence and/or aberration and the LSPC estimate can often exploit all channels, with the associated noise-suppression, while mitigating the complications arising from correlations between very distant sensors. The greatest need for the method is for short-period signals on large aperture arrays although we also demonstrate significant improvement for secondary regional phases on a small aperture array. LSPC can also provide a robust and flexible approach to parameter estimation on three-component seismic arrays.

  2. Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism

    Directory of Open Access Journals (Sweden)

    Li-Kun Xia

    2018-03-01

    Full Text Available AIM: To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs, contrast sensitivity (CS and dry eye parameters after small incision lenticule extraction (SMILE and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK for correction of high myopia and myopic astigmatism. METHODS: In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE of -8.11±1.09 diopters (D received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI and tear break-up time (TBUT were evaluated during a 3-year follow-up. RESULTS: The difference of uncorrected distance visual acuity (UDVA postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant (t=-1.59, P=0.13. The postoperative change of SE was 0.89 D in the FS-LASIK group (t=5.76, P=0.00, and 0.14 D in the SMILE group (t=0.54, P=0.59 from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group (P=0.00, but the coma root mean square (RMS was higher in the SMILE group (0.59±0.26 than in the FS-LASIK group (0.29±0.14, P=0.00. The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. CONCLUSION: Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long

  3. Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism.

    Science.gov (United States)

    Xia, Li-Kun; Ma, Jing; Liu, He-Nan; Shi, Ce; Huang, Qing

    2018-01-01

    To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs), contrast sensitivity (CS) and dry eye parameters after small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for correction of high myopia and myopic astigmatism. In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE) of -8.11±1.09 diopters (D) received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI) and tear break-up time (TBUT) were evaluated during a 3-year follow-up. The difference of uncorrected distance visual acuity (UDVA) postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant ( t =-1.59, P =0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group ( t =5.76, P =0.00), and 0.14 D in the SMILE group ( t =0.54, P =0.59) from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group ( P =0.00), but the coma root mean square (RMS) was higher in the SMILE group (0.59±0.26) than in the FS-LASIK group (0.29±0.14, P =0.00). The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better

  4. Partially coherent X-ray wavefront propagation simulations including grazing-incidence focusing optics.

    Science.gov (United States)

    Canestrari, Niccolo; Chubar, Oleg; Reininger, Ruben

    2014-09-01

    X-ray beamlines in modern synchrotron radiation sources make extensive use of grazing-incidence reflective optics, in particular Kirkpatrick-Baez elliptical mirror systems. These systems can focus the incoming X-rays down to nanometer-scale spot sizes while maintaining relatively large acceptance apertures and high flux in the focused radiation spots. In low-emittance storage rings and in free-electron lasers such systems are used with partially or even nearly fully coherent X-ray beams and often target diffraction-limited resolution. Therefore, their accurate simulation and modeling has to be performed within the framework of wave optics. Here the implementation and benchmarking of a wave-optics method for the simulation of grazing-incidence mirrors based on the local stationary-phase approximation or, in other words, the local propagation of the radiation electric field along geometrical rays, is described. The proposed method is CPU-efficient and fully compatible with the numerical methods of Fourier optics. It has been implemented in the Synchrotron Radiation Workshop (SRW) computer code and extensively tested against the geometrical ray-tracing code SHADOW. The test simulations have been performed for cases without and with diffraction at mirror apertures, including cases where the grazing-incidence mirrors can be hardly approximated by ideal lenses. Good agreement between the SRW and SHADOW simulation results is observed in the cases without diffraction. The differences between the simulation results obtained by the two codes in diffraction-dominated cases for illumination with fully or partially coherent radiation are analyzed and interpreted. The application of the new method for the simulation of wavefront propagation through a high-resolution X-ray microspectroscopy beamline at the National Synchrotron Light Source II (Brookhaven National Laboratory, USA) is demonstrated.

  5. Higher-order aberrations and best-corrected visual acuity in Native American children with a high prevalence of astigmatism.

    Science.gov (United States)

    Miller, Joseph M; Harvey, Erin M; Schwiegerling, Jim

    2015-08-01

    To determine whether higher-order aberrations (HOAs) in children from a highly astigmatic population differ from population norms and whether HOAs are associated with astigmatism and reduced best-corrected visual acuity. Subjects were 218 Tohono O'odham Native American children 5-9 years of age. Noncycloplegic HOA measurements were obtained with a handheld Shack-Hartmann sensor (SHS). Signed (z06s to z14s) and unsigned (z06u to z14u) wavefront aberration Zernike coefficients Z(3,-3) to Z(4,4) were rescaled for a 4 mm diameter pupil and compared to adult population norms. Cycloplegic refraction and best-corrected logMAR letter visual acuity (BCVA) were also measured. Regression analyses assessed the contribution of astigmatism (J0) and HOAs to BCVA. The mean root-mean-square (RMS) HOA of 0.191 ± 0.072 μm was significantly greater than population norms (0.100 ± 0.044 μm). All unsigned HOA coefficients (z06u to z14u) and all signed coefficients except z09s, z10s, and z11s were significantly larger than population norms. Decreased BCVA was associated with astigmatism (J0) and spherical aberration (z12u) but not RMS coma, with the effect of J0 about 4 times as great as z12u. Tohono O'odham children show elevated HOAs compared to population norms. Astigmatism and unsigned spherical aberration are associated with decreased acuity, but the effects of spherical aberration are minimal and not clinically significant. Copyright © 2015 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

  6. Reducing depth induced spherical aberration in 3D widefield fluorescence microscopy by wavefront coding using the SQUBIC phase mask

    Science.gov (United States)

    Patwary, Nurmohammed; Doblas, Ana; King, Sharon V.; Preza, Chrysanthe

    2014-03-01

    Imaging thick biological samples introduces spherical aberration (SA) due to refractive index (RI) mismatch between specimen and imaging lens immersion medium. SA increases with the increase of either depth or RI mismatch. Therefore, it is difficult to find a static compensator for SA1. Different wavefront coding methods2,3 have been studied to find an optimal way of static wavefront correction to reduce depth-induced SA. Inspired by a recent design of a radially symmetric squared cubic (SQUBIC) phase mask that was tested for scanning confocal microscopy1 we have modified the pupil using the SQUBIC mask to engineer the point spread function (PSF) of a wide field fluorescence microscope. In this study, simulated images of a thick test object were generated using a wavefront encoded engineered PSF (WFEPSF) and were restored using space-invariant (SI) and depth-variant (DV) expectation maximization (EM) algorithms implemented in the COSMOS software4. Quantitative comparisons between restorations obtained with both the conventional and WFE PSFs are presented. Simulations show that, in the presence of SA, the use of the SIEM algorithm and a single SQUBIC encoded WFE-PSF can yield adequate image restoration. In addition, in the presence of a large amount of SA, it is possible to get adequate results using the DVEM with fewer DV-PSFs than would typically be required for processing images acquired with a clear circular aperture (CCA) PSF. This result implies that modification of a widefield system with the SQUBIC mask renders the system less sensitive to depth-induced SA and suitable for imaging samples at larger optical depths.

  7. Semiconductor sensors

    International Nuclear Information System (INIS)

    Hartmann, Frank

    2011-01-01

    Semiconductor sensors have been around since the 1950s and today, every high energy physics experiment has one in its repertoire. In Lepton as well as Hadron colliders, silicon vertex and tracking detectors led to the most amazing physics and will continue doing so in the future. This contribution tries to depict the history of these devices exemplarily without being able to honor all important developments and installations. The current understanding of radiation damage mechanisms and recent R and D topics demonstrating the future challenges and possible technical solutions for the SLHC detectors are presented. Consequently semiconductor sensor candidates for an LHC upgrade and a future linear collider are also briefly introduced. The work presented here is a collage of the work of many individual silicon experts spread over several collaborations across the world.

  8. Load sensor

    OpenAIRE

    Van den Ende, D.; Almeida, P.M.R.; Dingemans, T.J.; Van der Zwaag, S.

    2007-01-01

    The invention relates to a load sensor comprising a polymer matrix and a piezo-ceramic material such as PZT, em not bedded in the polymer matrix, which together form a compos not ite, wherein the polymer matrix is a liquid crystalline resin, and wherein the piezo-ceramic material is a PZT powder forming 30-60% by volume of the composite, and wherein the PZT powder forms 40-50% by volume of the composite.

  9. Image Sensor

    OpenAIRE

    Jerram, Paul; Stefanov, Konstantin

    2017-01-01

    An image sensor of the type for providing charge multiplication by impact ionisation has plurality of multiplication elements. Each element is arranged to receive charge from photosensitive elements of an image area and each element comprises a sequence of electrodes to move charge along a transport path. Each of the electrodes has an edge defining a boundary with a first electrode, a maximum width across the charge transport path and a leading edge that defines a boundary with a second elect...

  10. Optischer Sensor

    OpenAIRE

    Brandenburg, A.; Fischer, A.

    1995-01-01

    An optical sensor (1) comprising an integrated optical arrangement has a waveguide (4) and at least one defraction grating (5) arranged in this waveguide. Light can launched into the waveguide via the defraction grating. In the reflection area of defraction grating, part of the light is dispersed through the waveguide at the beam angle for which the launch conditions and thus the defraction in the waveguide are fulfilled, so that, at this angle, a dark line (14) occurs whose position is evalu...

  11. Gas sensor

    International Nuclear Information System (INIS)

    Dorogan, V.; Korotchenkov, Gh.; Vieru, T.; Prodan, I.

    2003-01-01

    The invention relates to the gas sensors on base of metal-oxide films (SnO, InO), which may be used for enviromental control, in the fireextinguishing systema etc. The gas includes an insulating substrate, an active layer, a resistive layer with ohmic contacts. The resistive layer has two or more regions with dofferent resistances , and on the active layer are two or more pairs of ohmic contacts

  12. Wireless sensor network

    Science.gov (United States)

    Perotti, Jose M.; Lucena, Angel R.; Mullenix, Pamela A.; Mata, Carlos T.

    2006-05-01

    Current and future requirements of aerospace sensors and transducers demand the design and development of a new family of sensing devices, with emphasis on reduced weight, power consumption, and physical size. This new generation of sensors and transducers will possess a certain degree of intelligence in order to provide the end user with critical data in a more efficient manner. Communication between networks of traditional or next-generation sensors can be accomplished by a Wireless Sensor Network (WSN) developed by NASA's Instrumentation Branch and ASRC Aerospace Corporation at Kennedy Space Center (KSC), consisting of at least one central station and several remote stations and their associated software. The central station is application-dependent and can be implemented on different computer hardware, including industrial, handheld, or PC-104 single-board computers, on a variety of operating systems: embedded Windows, Linux, VxWorks, etc. The central stations and remote stations share a similar radio frequency (RF) core module hardware that is modular in design. The main components of the remote stations are an RF core module, a sensor interface module, batteries, and a power management module. These modules are stackable, and a common bus provides the flexibility to stack other modules for additional memory, increased processing, etc. WSN can automatically reconfigure to an alternate frequency if interference is encountered during operation. In addition, the base station will autonomously search for a remote station that was perceived to be lost, using relay stations and alternate frequencies. Several wireless remote-station types were developed and tested in the laboratory to support different sensing technologies, such as resistive temperature devices, silicon diodes, strain gauges, pressure transducers, and hydrogen leak detectors.

  13. Vehicle Fault Diagnose Based on Smart Sensor

    Science.gov (United States)

    Zhining, Li; Peng, Wang; Jianmin, Mei; Jianwei, Li; Fei, Teng

    In the vehicle's traditional fault diagnose system, we usually use a computer system with a A/D card and with many sensors connected to it. The disadvantage of this system is that these sensor can hardly be shared with control system and other systems, there are too many connect lines and the electro magnetic compatibility(EMC) will be affected. In this paper, smart speed sensor, smart acoustic press sensor, smart oil press sensor, smart acceleration sensor and smart order tracking sensor were designed to solve this problem. With the CAN BUS these smart sensors, fault diagnose computer and other computer could be connected together to establish a network system which can monitor and control the vehicle's diesel and other system without any duplicate sensor. The hard and soft ware of the smart sensor system was introduced, the oil press, vibration and acoustic signal are resampled by constant angle increment to eliminate the influence of the rotate speed. After the resample, the signal in every working cycle could be averaged in angle domain and do other analysis like order spectrum.

  14. Development of magnetic jxB sensor

    International Nuclear Information System (INIS)

    Kasai, Satoshi; Ishitsuka, Etsuo

    2001-12-01

    The improved mechanical sensor, i.e. magnetic jxB sensor (a mechanical sensor and a part of the steady state hybrid-type magnetic sensor) has been designed. The basic structure of the sensor is similar to the previously developed sensor (old sensor) in EDA phase. In this design, the neutron resistant materials are selected for the load cell (strain gauge and sensor beam) and sensing coil/frame. In order to reduce temperature drift of the sensor signal, four strain gauges with the same electrical property and geometrical size are bonded on the sensor beam by using Al 2 O 3 plasma spraying process, i.e., a couple of strain gauges is bonded on one side of the beam and another couple of gauges is bonded on the other side. These four strain gauges form an electrical bridge circuit. The zero-level drift of the output of the load cell used in the magnetic jxB sensor was reduced to about 1/20 compared with the old sensor. The temperature dependence of the output of the load cell is small. The linearity of the output of the load cell against weight was obtained. A non-linearity was observed in the sensitivity of the magnetic jxB sensor. The deviation of sensitivity from the fitting line was less than 7% in the high magnetic field region. The neutron irradiation effect on sensitivity of the sensor was investigated. The sensitivity of the sensor was gradually decreased by ∼30% at neutron fluence of (1.8-2.8)x10 23 n/m 2 in the high magnetic field. During irradiation, the non-linearity was observed in the sensitivity. (author)

  15. Exploiting the speckle-correlation scattering matrix for a compact reference-free holographic image sensor.

    Science.gov (United States)

    Lee, KyeoReh; Park, YongKeun

    2016-10-31

    The word 'holography' means a drawing that contains all of the information for light-both amplitude and wavefront. However, because of the insufficient bandwidth of current electronics, the direct measurement of the wavefront of light has not yet been achieved. Though reference-field-assisted interferometric methods have been utilized in numerous applications, introducing a reference field raises several fundamental and practical issues. Here we demonstrate a reference-free holographic image sensor. To achieve this, we propose a speckle-correlation scattering matrix approach; light-field information passing through a thin disordered layer is recorded and retrieved from a single-shot recording of speckle intensity patterns. Self-interference via diffusive scattering enables access to impinging light-field information, when light transport in the diffusive layer is precisely calibrated. As a proof-of-concept, we demonstrate direct holographic measurements of three-dimensional optical fields using a compact device consisting of a regular image sensor and a diffusor.

  16. Smart paint sensor for monitoring structural vibrations

    International Nuclear Information System (INIS)

    Al-Saffar, Y; Baz, A; Aldraihem, O

    2012-01-01

    A class of smart paint sensors is proposed for monitoring the structural vibration of beams. The sensor is manufactured from an epoxy resin which is mixed with carbon black nano-particles to make it electrically conducting and sensitive to mechanical vibrations. A comprehensive theoretical and experimental investigation is presented to understand the underlying phenomena governing the operation of this class of paint sensors and evaluate its performance characteristics. A theoretical model is presented to model the electromechanical behavior of the sensor system using molecular theory. The model is integrated with an amplifier circuit in order to predict the current and voltage developed by the paint sensor when subjected to loading. Furthermore, the sensor/amplifier circuit models are coupled with a finite element model of a base beam to which the sensor is bonded. The resulting multi-field model is utilized to predict the behavior of both the sensor and the beam when subjected to a wide variety of vibration excitations. The predictions of the multi-field finite element model are validated experimentally and the behavior of the sensor is evaluated both in the time and the frequency domains. The performance of the sensor is compared with the performance of conventional strain gages to emphasize its potential and merits. The presented techniques are currently being extended to sensors that can monitor the vibration and structural power flow of two-dimensional structures. (paper)

  17. Measuring heart rate with optical sensor

    NARCIS (Netherlands)

    Barachi, M. (Mitra)

    2014-01-01

    The problem addressed in this report is to verify the possibility of using an optical sensor in the SaxShirt in order to extract the heart rate. There are specifically three questions that we try to address. 1) How is it possible to extract heart rate (BPM) from the optical sensor? 2) Is it

  18. Thresholded Range Aggregation in Sensor Networks

    DEFF Research Database (Denmark)

    Yiu, Man Lung; Lin, Zhifeng; Mamoulis, Nikos

    2010-01-01

    ' status in each local region. In order to process the (snapshot) TRA query, we develop energy-efficient protocols based on appropriate operators and filters in sensor nodes. The design of these operators and filters is non-trivial, due to the fact that each sensor measurement influences the actual results...

  19. Impacto da análise do 'wavefront' na refratometria de pacientes com ceratocone

    Directory of Open Access Journals (Sweden)

    Renato Ambrósio Junior

    2011-02-01

    Full Text Available OBJETIVO: Verificar se a aberrometria ocular total (análise da frente de onda ou 'wavefront' possibilita melhora na acuidade visual corrigida (AVc com lentes esfero-cilíndricas, obtida com a refratometria manifesta em casos de ceratocone com algum grau de intolerância ao uso de lentes de contato. MÉTODOS: Os prontuários de 46 pacientes (89 olhos, referidos com diagnóstico de ceratocone e intolerantes ao uso de lentes de contato, submetidos ao exame de aberrometria ocular total seguido de refração manifesta, foram estudados de forma retrospectiva. A AVc (logMAR com a correção existente antes do exame foi comparada com a obtida com a nova refração manifesta, realizada considerando-se os dados objetivos da aberrometria. O teste não-paramétrico de Wilcoxon para amostras pareadas foi utilizado para verificação de diferenças estatisticamente significantes na AVc. RESULTADOS: Houve uma melhora estatisticamente significante na AVc com a nova refração manifesta (p<0,0001. A AVc média passou de 0,37 ou 20/47 (variando entre 1,3 e 0; desvio padrão[DP]=0,25 com a refração prévia para 0,23 ou 20/34 (variando entre 1 e 0,1; DP=0,21. Cinquenta e dois olhos (58,4% de 28 pacientes apresentaram melhora na AVc com a nova refração. A melhora média foi de 0,13 logMAR (1,3 linhas na tabela de Snellen, variando entre nula e 0,6 (6 linhas, com desvio padrão de 0,16. Oito pacientes apresentaram anisometropia significativa que limitou a prescrição de óculos em um dos olhos. CONCLUSÃO: A aberrometria facilitou a refratometria, determinando melhora significativa na acuidade visual corrigida com as lentes esfero-cilíndricas de pacientes com ceratocone intolerantes ao uso de lentes de contato. A anisometropia foi um fator limitante na prescrição de óculos.

  20. Intrusion detection sensors

    International Nuclear Information System (INIS)

    Williams, J.D.

    1978-07-01

    Intrusion detection sensors are an integral part of most physical security systems. Under the sponsorship of the U.S. Department of Energy, Office of Safeguards and Security, Sandia Laboratories has conducted a survey of available intrusion detection sensors and has tested a number of different sensors. An overview of these sensors is provided. This overview includes (1) the operating principles of each type of sensor, (2) unique sensor characteristics, (3) desired sensor improvements which must be considered in planning an intrusion detection system, and (4) the site characteristics which affect the performance of both exterior and interior sensors. Techniques which have been developed to evaluate various intrusion detection sensors are also discussed

  1. Hydrogen sensor

    Science.gov (United States)

    Duan, Yixiang; Jia, Quanxi; Cao, Wenqing

    2010-11-23

    A hydrogen sensor for detecting/quantitating hydrogen and hydrogen isotopes includes a sampling line and a microplasma generator that excites hydrogen from a gas sample and produces light emission from excited hydrogen. A power supply provides power to the microplasma generator, and a spectrometer generates an emission spectrum from the light emission. A programmable computer is adapted for determining whether or not the gas sample includes hydrogen, and for quantitating the amount of hydrogen and/or hydrogen isotopes are present in the gas sample.

  2. Contralateral comparison of wavefront-guided LASIK surgery with iris recognition versus without iris recognition using the MEL80 Excimer laser system.

    Science.gov (United States)

    Wu, Fang; Yang, Yabo; Dougherty, Paul J

    2009-05-01

    To compare outcomes in wavefront-guided LASIK performed with iris recognition software versus without iris recognition software in different eyes of the same patient. A randomised, prospective study of 104 myopic eyes of 52 patients undergoing LASIK surgery with the MEL80 excimer laser system was performed. Iris recognition software was used in one eye of each patient (study group) and not used in the other eye (control group). Higher order aberrations (HOAs), contrast sensitivity, uncorrected vision (UCV), visual acuity (VA) and corneal topography were measured and recorded pre-operatively and at one month and three months post-operatively for each eye. The mean post-operative sphere and cylinder between groups was similar, however the post-operative angles of error (AE) by refraction were significantly smaller in the study group compared to the control group both in arithmetic and absolute means (p = 0.03, p = 0.01). The mean logMAR UCV was significantly better in the study group than in the control group at one month (p = 0.01). The mean logMAR VA was significantly better in the study group than in control group at both one and three months (p = 0.01, p = 0.03). In addition, mean trefoil, total third-order aberration, total fourth-order aberration and the total scotopic root-mean-square (RMS) HOAs were significantly less in the study group than those in the control group at the third (p = 0.01, p = 0.05, p = 0.04, p = 0.02). By three months, the contrast sensitivity had recovered in both groups but the study group performed better at 2.6, 4.2 and 6.6 cpd (cycles per degree) than the control group (p = 0.01, p iris recognition results in better VA, lower mean higher-order aberrations, lower refractive post-operative angles of error and better contrast sensitivity at three months post-operatively than LASIK performed without iris recognition.

  3. Downhole Applications of Magnetic Sensors.

    Science.gov (United States)

    Gooneratne, Chinthaka P; Li, Bodong; Moellendick, Timothy E

    2017-10-19

    In this paper we present a review of the application of two types of magnetic sensors-fluxgate magnetometers and nuclear magnetic resonance (NMR) sensors-in the oil/gas industry. These magnetic sensors play a critical role in drilling wells safely, accurately and efficiently into a target reservoir zone by providing directional data of the well and acquiring information about the surrounding geological formations. Research into magnetic sensors for oil/gas drilling has not been explored by researchers to the same extent as other applications, such as biomedical, magnetic storage and automotive/aerospace applications. Therefore, this paper aims to serve as an opportunity for researchers to truly understand how magnetic sensors can be used in a downhole environment and to provide fertile ground for research and development in this area. A look ahead, discussing other magnetic sensor technologies that can potentially be used in the oil/gas industry is presented, and what is still needed in order deploy them in the field is also addressed.

  4. Review on water quality sensors

    Science.gov (United States)

    Kruse, Peter

    2018-05-01

    Terrestrial life may be carbon-based, but most of its mass is made up of water. Access to clean water is essential to all aspects of maintaining life. Mainly due to human activity, the strain on the water resources of our planet has increased substantially, requiring action in water management and purification. Water quality sensors are needed in order to quantify the problem and verify the success of remedial actions. This review summarizes the most common chemical water quality parameters, and current developments in sensor technology available to monitor them. Particular emphasis is on technologies that lend themselves to reagent-free, low-maintenance, autonomous and continuous monitoring. Chemiresistors and other electrical sensors are discussed in particular detail, while mechanical, optical and electrochemical sensors also find mentioning. The focus here is on the physics of chemical signal transduction in sensor elements that are in direct contact with the analyte. All other sensing methods, and all other elements of sampling, sample pre-treatment as well as the collection, transmission and analysis of the data are not discussed here. Instead, the goal is to highlight the progress and remaining challenges in the development of sensor materials and designs for an audience of physicists and materials scientists.

  5. Sensors for Entertainment.

    Science.gov (United States)

    Lamberti, Fabrizio; Sanna, Andrea; Rokne, Jon

    2016-07-15

    Sensors are becoming ubiquitous in all areas of science, technology, and society. In this Special Issue on "Sensors for Entertainment", developments in progress and the current state of application scenarios for sensors in the field of entertainment is explored.

  6. Sensors for Entertainment

    OpenAIRE

    Fabrizio Lamberti; Andrea Sanna; Jon Rokne

    2016-01-01

    Sensors are becoming ubiquitous in all areas of science, technology, and society. In this Special Issue on ?Sensors for Entertainment?, developments in progress and the current state of application scenarios for sensors in the field of entertainment is explored.

  7. Development of smart active layer sensor

    International Nuclear Information System (INIS)

    Lee, Young Sup; Lee, Sang Il; Yoon, Dong Jin; Kwon, Jae Hwa

    2004-01-01

    Structural health monitoring (SHM) is a new technology that will be increasingly applied at the industrial field as a potential approach to improve cost and convenience of structural inspection. Recently, the development of smart sensor is very active for real application. This study has focused on preparation and application study of SAL sensor. In order to detect elastic wave, smart piezoelectric sensor, SAL, is fabricated by using a piezoelectric element, shielding layer and protection layer. This protection layer plays an important role in a patched network of distributed piezoelectric sensor and shielding treatment. Four types of SAL sensor are designed/prepared/tested, and these details will be discussed in the paper. In this study, SAL sensor can be feasibly applied to perform structural health monitoring and to detect damage sources which result in elastic waves.

  8. Order Aggressiveness and Order Book Dynamics

    OpenAIRE

    Anthony D. Hall; Nikolaus Hautsch

    2004-01-01

    In this paper, we study the determinants of order aggressiveness and traders' order submission strategy in an open limit order book market. Using order book data from the Australian Stock Exchange, we model traders' aggressiveness in market trading, limit order trading as well as in order cancellations on both sides of the market using a six-dimensional autoregressive intensity model. The information revealed by the open order book plays an important role in explaining the degree of order agg...

  9. A Sentinel Sensor Network for Hydrogen Sensing

    Directory of Open Access Journals (Sweden)

    Andrew J. Mason

    2003-02-01

    Full Text Available A wireless sensor network is presented for in-situ monitoring of atmospheric hydrogen concentration. The hydrogen sensor network consists of multiple sensor nodes, equipped with titania nanotube hydrogen sensors, distributed throughout the area of interest; each node is both sensor, and data-relay station that enables extended wide area monitoring without a consequent increase of node power and thus node size. The hydrogen sensor is fabricated from a sheet of highly ordered titania nanotubes, made by anodization of a titanium thick film, to which platinum electrodes are connected. The electrical resistance of the hydrogen sensor varies from 245 Ω at 500 ppm hydrogen, to 10.23 kΩ at 0 ppm hydrogen (pure nitrogen environment. The measured resistance is converted to voltage, 0.049 V at 500 ppm to 2.046 V at 0 ppm, by interface circuitry. The microcontroller of the sensor node digitizes the voltage and transmits the digital information, using intermediate nodes as relays, to a host node that downloads measurement data to a computer for display. This paper describes the design and operation of the sensor network, the titania nanotube hydrogen sensors with an apparent low level resolution of approximately 0.05 ppm, and their integration in one widely useful device.

  10. Wireless sensor platform

    Science.gov (United States)

    Joshi, Pooran C.; Killough, Stephen M.; Kuruganti, Phani Teja

    2017-08-08

    A wireless sensor platform and methods of manufacture are provided. The platform involves providing a plurality of wireless sensors, where each of the sensors is fabricated on flexible substrates using printing techniques and low temperature curing. Each of the sensors can include planar sensor elements and planar antennas defined using the printing and curing. Further, each of the sensors can include a communications system configured to encode the data from the sensors into a spread spectrum code sequence that is transmitted to a central computer(s) for use in monitoring an area associated with the sensors.

  11. Sensor Interaction as a Source of the Electromagnetic Field Measurement Error

    Directory of Open Access Journals (Sweden)

    Hartansky R.

    2014-12-01

    Full Text Available The article deals with analytical calculation and numerical simulation of interactive influence of electromagnetic sensors. Sensors are components of field probe, whereby their interactive influence causes the measuring error. Electromagnetic field probe contains three mutually perpendicular spaced sensors in order to measure the vector of electrical field. Error of sensors is enumerated with dependence on interactive position of sensors. Based on that, proposed were recommendations for electromagnetic field probe construction to minimize the sensor interaction and measuring error.

  12. NAOMI: a low-order adaptive optics system for the VLT interferometer

    Science.gov (United States)

    Gonté, Frédéric Yves J.; Alonso, Jaime; Aller-Carpentier, Emmanuel; Andolfato, Luigi; Berger, Jean-Philippe; Cortes, Angela; Delplancke-Strobele, Françoise; Donaldson, Rob; Dorn, Reinhold J.; Dupuy, Christophe; Egner, Sebastian E.; Huber, Stefan; Hubin, Norbert; Kirchbauer, Jean-Paul; Le Louarn, Miska; Lilley, Paul; Jolley, Paul; Martis, Alessandro; Paufique, Jérôme; Pasquini, Luca; Quentin, Jutta; Ridings, Robert; Reyes, Javier; Shchkaturov, Pavel; Suarez, Marcos; Phan Duc, Thanh; Valdes, Guillermo; Woillez, Julien; Le Bouquin, Jean-Baptiste; Beuzit, Jean-Luc; Rochat, Sylvain; Vérinaud, Christophe; Moulin, Thibaut; Delboulbé, Alain; Michaud, Laurence; Correia, Jean-Jacques; Roux, Alain; Maurel, Didier; Stadler, Eric; Magnard, Yves

    2016-08-01

    The New Adaptive Optics Module for Interferometry (NAOMI) will be developed for and installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. The goal of the project is to equip all four ATs with a low-order Shack- Hartmann adaptive optics system operating in the visible. By improving the wavefront quality delivered by the ATs for guide stars brighter than R = 13 mag, NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker(s) will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE.

  13. Optical beam deflection sensor: design and experiments.

    Science.gov (United States)

    Sakamoto, João M S; Marques, Renan B; Kitano, Cláudio; Rodrigues, Nicolau A S; Riva, Rudimar

    2017-10-01

    In this work, we present a double-pass optical beam deflection sensor and its optical design method. To accomplish that, a mathematical model was proposed and computational simulations were performed, in order to obtain the sensor's characteristic curves and to analyze its behavior as function of design parameters. The mathematical model was validated by comparison with the characteristic curves acquired experimentally. The sensor was employed to detect acoustic pulses generated by a pulsed laser in a sample surface, in order to show its potential for monitoring applications handling high energy input as laser welding or laser ablation.

  14. Sensor Network Disposition Facing the Task of Multisensor Cross Cueing

    Directory of Open Access Journals (Sweden)

    Ce Pang

    2017-01-01

    Full Text Available In order to build the sensor network facing the task of multisensor crossing cueing, the requirements of initiating cueing and being cued are analyzed. Probability theory is used when building models, then probability of sensor cueing in the case of target moving is given, and, after that, the best distance between two sensors is calculated. The operational environment is described by normal distribution function. In the process of distributing sensor network, their elements, operational environment demand of cueing, and the probability of sensor network coverage are considered; then the optimization algorithm of sensor network based on hypothesis testing theory is made. The simulation result indicates that the algorithm can make sensor network which is required. On the basis of that, the two cases, including targets that make linear motion and orbit motion, are used to test the performance of the sensor network, which show that the sensor network can make uninterrupted detection on targets through multisensor cross cuing.

  15. Laboratory course on silicon sensors

    CERN Document Server

    Crescio, E; Roe, S; Rudge, A

    2003-01-01

    The laboratory course consisted of four different mini sessions, in order to give the student some hands-on experience on various aspects of silicon sensors and related integrated electronics. The four experiments were. 1. Characterisation of silicon diodes for particle detection 2. Study of noise performance of the Viking readout circuit 3. Study of the position resolution of a silicon microstrip sensor 4. Study of charge transport in silicon with a fast amplifier The data in the following were obtained during the ICFA school by the students.

  16. A modular optical sensor

    Science.gov (United States)

    Conklin, John Albert

    This dissertation presents the design of a modular, fiber-optic sensor and the results obtained from testing the modular sensor. The modular fiber-optic sensor is constructed in such manner that the sensor diaphragm can be replaced with different configurations to detect numerous physical phenomena. Additionally, different fiber-optic detection systems can be attached to the sensor. Initially, the modular sensor was developed to be used by university of students to investigate realistic optical sensors and detection systems to prepare for advance studies of micro-optical mechanical systems (MOMS). The design accomplishes this by doing two things. First, the design significantly lowers the costs associated with studying optical sensors by modularizing the sensor design. Second, the sensor broadens the number of physical phenomena that students can apply optical sensing techniques to in a fiber optics sensor course. The dissertation is divided into seven chapters covering the historical development of fiber-optic sensors, a theoretical overview of fiber-optic sensors, the design, fabrication, and the testing of the modular sensor developed in the course of this work. Chapter 1 discusses, in detail, how this dissertation is organized and states the purpose of the dissertation. Chapter 2 presents an historical overview of the development of optical fibers, optical pressure sensors, and fibers, optical pressure sensors, and optical microphones. Chapter 3 reviews the theory of multi-fiber optic detection systems, optical microphones, and pressure sensors. Chapter 4 presents the design details of the modular, optical sensor. Chapter 5 delves into how the modular sensor is fabricated and how the detection systems are constructed. Chapter 6 presents the data collected from the microphone and pressure sensor configurations of the modular sensor. Finally, Chapter 7 discusses the data collected and draws conclusions about the design based on the data collected. Chapter 7 also

  17. Wavefront coherence area for predicting visual acuity of post-PRK and post-PARK refractive surgery patients

    Science.gov (United States)

    Garcia, Daniel D.; van de Pol, Corina; Barsky, Brian A.; Klein, Stanley A.

    1999-06-01

    Many current corneal topography instruments (called videokeratographs) provide an `acuity index' based on corneal smoothness to analyze expected visual acuity. However, post-refractive surgery patients often exhibit better acuity than is predicted by such indices. One reason for this is that visual acuity may not necessarily be determined by overall corneal smoothness but rather by having some part of the cornea able to focus light coherently onto the fovea. We present a new method of representing visual acuity by measuring the wavefront aberration, using principles from both ray and wave optics. For each point P on the cornea, we measure the size of the associated coherence area whose optical path length (OPL), from a reference plane to P's focus, is within a certain tolerance of the OPL for P. We measured the topographies and vision of 62 eyes of patients who had undergone the corneal refractive surgery procedures of photorefractive keratectomy (PRK) and photorefractive astigmatic keratectomy (PARK). In addition to high contrast visual acuity, our vision tests included low contrast and low luminance to test the contribution of the PRK transition zone. We found our metric for visual acuity to be better than all other metrics at predicting the acuity of low contrast and low luminance. However, high contrast visual acuity was poorly predicted by all of the indices we studied, including our own. The indices provided by current videokeratographs sometimes fail for corneas whose shape differs from simple ellipsoidal models. This is the case with post-PRK and post-PARK refractive surgery patients. Our alternative representation that displays the coherence area of the wavefront has considerable advantages, and promises to be a better predictor of low contrast and low luminance visual acuity than current shape measures.

  18. Sensor Data Security Level Estimation Scheme for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Alex Ramos

    2015-01-01

    Full Text Available Due to their increasing dissemination, wireless sensor networks (WSNs have become the target of more and more sophisticated attacks, even capable of circumventing both attack detection and prevention mechanisms. This may cause WSN users, who totally trust these security mechanisms, to think that a sensor reading is secure, even when an adversary has corrupted it. For that reason, a scheme capable of estimating the security level (SL that these mechanisms provide to sensor data is needed, so that users can be aware of the actual security state of this data and can make better decisions on its use. However, existing security estimation schemes proposed for WSNs fully ignore detection mechanisms and analyze solely the security provided by prevention mechanisms. In this context, this work presents the sensor data security estimator (SDSE, a new comprehensive security estimation scheme for WSNs. SDSE is designed for estimating the sensor data security level based on security metrics that analyze both attack prevention and detection mechanisms. In order to validate our proposed scheme, we have carried out extensive simulations that show the high accuracy of SDSE estimates.

  19. Sensor Data Security Level Estimation Scheme for Wireless Sensor Networks

    Science.gov (United States)

    Ramos, Alex; Filho, Raimir Holanda

    2015-01-01

    Due to their increasing dissemination, wireless sensor networks (WSNs) have become the target of more and more sophisticated attacks, even capable of circumventing both attack detection and prevention mechanisms. This may cause WSN users, who totally trust these security mechanisms, to think that a sensor reading is secure, even when an adversary has corrupted it. For that reason, a scheme capable of estimating the security level (SL) that these mechanisms provide to sensor data is needed, so that users can be aware of the actual security state of this data and can make better decisions on its use. However, existing security estimation schemes proposed for WSNs fully ignore detection mechanisms and analyze solely the security provided by prevention mechanisms. In this context, this work presents the sensor data security estimator (SDSE), a new comprehensive security estimation scheme for WSNs. SDSE is designed for estimating the sensor data security level based on security metrics that analyze both attack prevention and detection mechanisms. In order to validate our proposed scheme, we have carried out extensive simulations that show the high accuracy of SDSE estimates. PMID:25608215

  20. Sensor data security level estimation scheme for wireless sensor networks.

    Science.gov (United States)

    Ramos, Alex; Filho, Raimir Holanda

    2015-01-19

    Due to their increasing dissemination, wireless sensor networks (WSNs) have become the target of more and more sophisticated attacks, even capable of circumventing both attack detection and prevention mechanisms. This may cause WSN users, who totally trust these security mechanisms, to think that a sensor reading is secure, even when an adversary has corrupted it. For that reason, a scheme capable of estimating the security level (SL) that these mechanisms provide to sensor data is needed, so that users can be aware of the actual security state of this data and can make better decisions on its use. However, existing security estimation schemes proposed for WSNs fully ignore detection mechanisms and analyze solely the security provided by prevention mechanisms. In this context, this work presents the sensor data security estimator (SDSE), a new comprehensive security estimation scheme for WSNs. SDSE is designed for estimating the sensor data security level based on security metrics that analyze both attack prevention and detection mechanisms. In order to validate our proposed scheme, we have carried out extensive simulations that show the high accuracy of SDSE estimates.

  1. Integrated cryogenic sensors

    International Nuclear Information System (INIS)

    Juanarena, D.B.; Rao, M.G.

    1991-01-01

    Integrated cryogenic pressure-temperature, level-temperature, and flow-temperature sensors have several advantages over the conventional single parameter sensors. Such integrated sensors were not available until recently. Pressure Systems, Inc. (PSI) of Hampton, Virginia, has introduced precalibrated precision cryogenic pressure sensors at the Los Angeles Cryogenic Engineering Conference in 1989. Recently, PSI has successfully completed the development of integrated pressure-temperature and level-temperature sensors for use in the temperature range 1.5-375K. In this paper, performance characteristics of these integrated sensors are presented. Further, the effects of irradiation and magnetic fields on these integrated sensors are also reviewed

  2. EDITORIAL: Humidity sensors Humidity sensors

    Science.gov (United States)

    Regtien, Paul P. L.

    2012-01-01

    produced at relatively low cost. Therefore, they find wide use in lots of applications. However, the method requires a material that possesses some conflicting properties: stable and reproducible relations between air humidity, moisture uptake and a specific property (for instance the length of a hair, the electrical impedance of the material), fast absorption and desorption of the water vapour (to obtain a short response time), small hysteresis, wide range of relative humidity (RH) and temperature-independent output (only responsive to RH). For these reasons, much research is done and is still going on to find suitable materials that combine high performance and low price. In this special feature, three of the four papers report on absorption sensors, all with different focus. Aziz et al describe experiments with newly developed materials. The surface structure is extensively studied, in view of its ability to rapidly absorb water vapour and exhibit a reproducible change in the resistance and capacitance of the device. Sanchez et al employ optical fibres coated with a thin moisture-absorbing layer as a sensitive humidity sensor. They have studied various coating materials and investigated the possibility of using changes in optical properties of the fibre (here the lossy mode resonance) due to a change in humidity of the surrounding air. The third paper, by Weremczuk et al, focuses on a cheap fabrication method for absorption-based humidity sensors. The inkjet technology appears to be suitable for mass fabrication of such sensors, which is demonstrated by extensive measurements of the electrical properties (resistance and capacitance) of the absorbing layers. Moreover, they have developed a model that describes the relation between humidity and the electrical parameters of the moisture-sensitive layer. Despite intensive research, absorption sensors still do not meet the requirements for high accuracy applications. The dew-point temperature method is more appropriate

  3. Fabrication of taste sensor for education

    Science.gov (United States)

    Wu, Xiao; Tahara, Yusuke; Toko, Kiyoshi; Kuriyaki, Hisao

    2017-03-01

    In order to solve the unconcern to usefulness of learning science among high school students in Japan, we developed a simple fabricated taste sensor with sensitivity and selectivity to each taste quality, which can be applied in science class. A commercialized Teflon membrane was used as the polymer membrane holding lipids. In addition, a non-adhesive method is considered to combine the membrane and the sensor electrode using a plastic cap which is easily accessible. The taste sensor for education fabricated in this way showed a good selectivity and sensitivity. By adjusting the composition of trioctylmethylammonium chloride (TOMA) and phosphoric acid di(2-ethylhexyl) ester (PAEE) included in lipid solution, we improved the selectivity of this simple taste sensor to saltiness and sourness. To verify this taste sensor as a useful science teaching material for science class, we applied this taste sensor into a science class for university students. By comparing the results between the sensory test and the sensor response, humans taste showed the same tendency just as the sensor response, which proved the sensor as a useful teaching material for science class.

  4. Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia.

    Science.gov (United States)

    Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Takahashi, Masahide; Shimizu, Kimiya

    2018-03-01

    To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism. Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes. Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90). Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  5. Distributed sensor coordination for advanced energy systems

    Energy Technology Data Exchange (ETDEWEB)

    Tumer, Kagan [Oregon State Univ., Corvallis, OR (United States). School of Mechanical, Industrial and Manufacturing Engineering

    2015-03-12

    coordination, and sensor network control in advanced power systems. Each application has specific needs, but they all share the one crucial underlying problem: how to ensure that the interactions of a large number of heterogenous agents lead to coordinated system behavior. This proposal describes a new paradigm that addresses that very issue in a systematic way. Key Results and Findings: All milestones have been completed. Our results demonstrate that by properly shaping agent objective functions, we can develop large (up to 10,000 devices) heterogeneous sensor networks with key desirable properties. The first milestone shows that properly choosing agent-specific objective functions increases system performance by up to 99.9% compared to global evaluations. The second milestone shows evolutionary algorithms learn excellent sensor network coordination policies prior to network deployment, and these policies can be refined online once the network is deployed. The third milestone shows the resulting sensor networks networks are extremely robust to sensor noise, where networks with up to 25% sensor noise are capable of providing measurements with errors on the order of 10⁻³. The fourth milestone shows the resulting sensor networks are extremely robust to sensor failure, with 25% of the sensors in the system failing resulting in no significant performance losses after system reconfiguration.

  6. A Shack-Hartmann Sensor for Single-Shot Multi-Contrast Imaging with Hard X-rays

    Directory of Open Access Journals (Sweden)

    Tomy dos Santos Rolo

    2018-05-01

    Full Text Available An array of compound refractive X-ray lenses (CRL with 20 × 20 lenslets, a focal distance of 20cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX for wavefront sensing and permits for true single-shot multi-contrast imaging the dynamics of materials with a spatial resolution in the micrometer range, sensitivity on nanosized structures and temporal resolution on the microsecond scale. The object’s absorption and its induced wavefront shift can be assessed simultaneously together with information from diffraction channels. In contrast to the established Hartmann sensors the SHARX has an increased flux efficiency through focusing of the beam rather than blocking parts of it. We investigated the spatiotemporal behavior of a cavitation bubble induced by laser pulses. Furthermore, we validated the SHARX by measuring refraction angles of a single diamond CRL, where we obtained an angular resolution better than 4 μ rad.

  7. Development of all solid-state, high average power ultra-short pulse laser for X-ray generation. High average power CPA system and wavefront control of ultra short laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Harayama, Sayaka; Akaoka, Katsuaki; Tei, Kazuyoku; Kato, Masaaki; Niwa, Yoshito; Maruyama, Yoichiro; Matoba, Toru; Arisawa, Takashi; Takuma, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    We developed a prototype CPA laser system which is pumped by a all solid-state Nd:YAG laser. In a preliminary experiment, the output energy of 52mJ before compression was obtained when the pumping energy was 250mJ. To compensate the wavefront distortion, an adaptive optics has been developed. By using this wavefront control system, the laser beam with the distortion of 0.15{lambda} was obtained. (author)

  8. Order aggressiveness and order book dynamics

    DEFF Research Database (Denmark)

    Hall, Anthony D.; Hautsch, Nikolaus

    2006-01-01

    In this paper, we study the determinants of order aggressiveness and traders’ order submission strategy in an open limit order book market. Applying an order classification scheme, we model the most aggressive market orders, limit orders as well as cancellations on both sides of the market...... employing a six-dimensional autoregressive conditional intensity model. Using order book data from the Australian Stock Exchange, we find that market depth, the queued volume, the bid-ask spread, recent volatility, as well as recent changes in both the order flow and the price play an important role...... in explaining the determinants of order aggressiveness. Overall, our empirical results broadly confirm theoretical predictions on limit order book trading. However, we also find evidence for behavior that can be attributed to particular liquidity and volatility effects...

  9. Compact high order schemes with gradient-direction derivatives for absorbing boundary conditions

    Science.gov (United States)

    Gordon, Dan; Gordon, Rachel; Turkel, Eli

    2015-09-01

    We consider several compact high order absorbing boundary conditions (ABCs) for the Helmholtz equation in three dimensions. A technique called "the gradient method" (GM) for ABCs is also introduced and combined with the high order ABCs. GM is based on the principle of using directional derivatives in the direction of the wavefront propagation. The new ABCs are used together with the recently introduced compact sixth order finite difference scheme for variable wave numbers. Experiments on problems with known analytic solutions produced very accurate results, demonstrating the efficacy of the high order schemes, particularly when combined with GM. The new ABCs are then applied to the SEG/EAGE Salt model, showing the advantages of the new schemes.

  10. Application Of FA Sensor 2

    International Nuclear Information System (INIS)

    Park, Seon Ho

    1993-03-01

    This book introduces FA sensor from basic to making system, which includes light sensor like photo diode and photo transistor, photo electricity sensor, CCD type image sensor, MOS type image sensor, color sensor, cds cell, and optical fiber scope. It also deals with direct election position sensor such as proximity switch, differential motion, linear scale of photo electricity type, and magnet scale, rotary sensor with summary of rotary encoder, rotary encoder types and applications, flow sensor, and sensing technology.

  11. Coupled wave sensor technology

    International Nuclear Information System (INIS)

    Maki, M.C.

    1988-01-01

    Buried line guided radar sensors have been used successfully for a number of years to provide perimeter security for high value resources. This paper introduces a new complementary sensor advancement at Computing Devices termed 'coupled wave device technology' (CWD). It provides many of the inherent advantages of leakey cable sensors, such as terrain-following and the ability to discriminate between humans and small animals. It also is able to provide a high or wide detection zone, and allows the sensor to be mounted aerially and adjacent to a wall or fence. Several alternative sensors have been developed which include a single-line sensor, a dual-line hybrid sensor that combines the elements of ported coax and CWD technology, and a rapid-deployment portable sensor for temporary or mobile applications. A description of the technology, the sensors, and their characteristics is provided

  12. System-level Modeling of Wireless Integrated Sensor Networks

    DEFF Research Database (Denmark)

    Virk, Kashif M.; Hansen, Knud; Madsen, Jan

    2005-01-01

    Wireless integrated sensor networks have emerged as a promising infrastructure for a new generation of monitoring and tracking applications. In order to efficiently utilize the extremely limited resources of wireless sensor nodes, accurate modeling of the key aspects of wireless sensor networks...... is necessary so that system-level design decisions can be made about the hardware and the software (applications and real-time operating system) architecture of sensor nodes. In this paper, we present a SystemC-based abstract modeling framework that enables system-level modeling of sensor network behavior...... by modeling the applications, real-time operating system, sensors, processor, and radio transceiver at the sensor node level and environmental phenomena, including radio signal propagation, at the sensor network level. We demonstrate the potential of our modeling framework by simulating and analyzing a small...

  13. Smart Optoelectronic Sensors and Intelligent Sensor Systems

    Directory of Open Access Journals (Sweden)

    Sergey Y. YURISH

    2012-03-01

    Full Text Available Light-to-frequency converters are widely used in various optoelectronic sensor systems. However, a further frequency-to-digital conversion is a bottleneck in such systems due to a broad frequency range of light-to-frequency converters’ outputs. This paper describes an effective OEM design approach, which can be used for smart and intelligent sensor systems design. The design is based on novel, multifunctional integrated circuit of Universal Sensors & Transducers Interface especially designed for such sensor applications. Experimental results have confirmed an efficiency of this approach and high metrological performances.

  14. Ordered photonic microstructures

    Science.gov (United States)

    Chen, Kevin Ming

    2001-09-01

    polystyrene latex colloidal particles into 2D crystals is presented. The colloidal assemblies offer a relatively easy processing route for fabrication of photonic bandgap structures. Large (>1 mm diameter) single crystal grains of colloids were formed using controlled evaporation and fluid flow techniques. A novel solution enabling post-processing of the fragile ordered assemblies is presented in which polyelectrolyte multilayers serve as adsorption platforms that anchor the colloidal assemblies. Tailorability of the polyelectrolyte surface properties (charge density, morphology) enables tuning of the colloid adsorption behavior. The polyelectrolyte surface affects colloid adsorption by influencing its surface diffusion. Observations of colloid surface diffusion were made using optical microscopy. Use of polyelectrolytes patterned via microcontact printing enables fabrication of colloid assemblies containing predesigned point and line defects. The patterned polyelectrolyte adsorption template allows placement of colloids in specific geometric arrangement, making possible the realization of sensors or functional photonic bandgap devices such as waveguides or photon traps. Three mechanisms were used to control adsorption: (1)pH of the colloid suspension, which determines the ionization of the uppermost surface of the polyelectrolyte multilayer; (2)ionic strength of the suspension, which determines the extent of charge screening about the colloid and polyelectrolyte; and (3)concentration of added surfactant, which causes charge screening and introduces hydrophobic interactions between the surfactant and polyelectrolyte. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

  15. Wave-optical evaluation of interference fringes and wavefront phase in a hard-x-ray beam totally reflected by mirror optics.

    Science.gov (United States)

    Yamauchi, Kazuto; Yamamura, Kazuya; Mimura, Hidekazu; Sano, Yasuhisa; Saito, Akira; Endo, Katsuyoshi; Souvorov, Alexei; Yabashi, Makina; Tamasaku, Kenji; Ishikawa, Tetsuya; Mori, Yuzo

    2005-11-10

    The intensity flatness and wavefront shape in a coherent hard-x-ray beam totally reflected by flat mirrors that have surface bumps modeled by Gaussian functions were investigated by use of a wave-optical simulation code. Simulated results revealed the necessity for peak-to-valley height accuracy of better than 1 nm at a lateral resolution near 0.1 mm to remove high-contrast interference fringes and appreciable wavefront phase errors. Three mirrors that had different surface qualities were tested at the 1 km-long beam line at the SPring-8/Japan Synchrotron Radiation Research Institute. Interference fringes faded when the surface figure was corrected below the subnanometer level to a spatial resolution close to 0.1 mm, as indicated by the simulated results.

  16. Towards Sensor Database Systems

    DEFF Research Database (Denmark)

    Bonnet, Philippe; Gehrke, Johannes; Seshadri, Praveen

    2001-01-01

    . These systems lack flexibility because data is extracted in a predefined way; also, they do not scale to a large number of devices because large volumes of raw data are transferred regardless of the queries that are submitted. In our new concept of sensor database system, queries dictate which data is extracted...... from the sensors. In this paper, we define the concept of sensor databases mixing stored data represented as relations and sensor data represented as time series. Each long-running query formulated over a sensor database defines a persistent view, which is maintained during a given time interval. We...... also describe the design and implementation of the COUGAR sensor database system....

  17. Fiber optical sensor system for shape and haptics for flexible instruments in minimally invasive surgery: overview and status quo

    Science.gov (United States)

    Ledermann, Christoph; Pauer, Hendrikje; Woern, Heinz

    2014-05-01

    In minimally invasive surgery, exible mechatronic instruments promise to improve the overall performance of surgical interventions. However, those instruments require highly developed sensors in order to provide haptic feedback to the surgeon or to enable (semi-)autonomous tasks. Precisely, haptic sensors and a shape sensor are required. In this paper, we present our ber optical sensor system of Fiber Bragg Gratings, which consists of a shape sensor, a kinesthetic sensor and a tactile sensor. The status quo of each of the three sensors is described, as well as the concept to integrate them into one ber optical sensor system.

  18. Simple chloride sensors for continuous groundwater monitoring

    DEFF Research Database (Denmark)

    Thorn, Paul; Mortensen, John

    2012-01-01

    The development of chloride sensors which can be used for continuous, on-line monitoring of groundwater could be very valuable in the management of our coastal water resources. However, sensor stability, drift, and durability all need to be addressed in order for the sensors to be used in continu......The development of chloride sensors which can be used for continuous, on-line monitoring of groundwater could be very valuable in the management of our coastal water resources. However, sensor stability, drift, and durability all need to be addressed in order for the sensors to be used...... in continuous application. This study looks at the development of a simple, inexpensive chloride electrode, and evaluates its performance under continuous use, both in the laboratory and in a field test in a monitoring well. The results from the study showed a consistent response to changing chloride...... concentrations over longer periods. The signal was seen to be stable, with regular drift in both laboratory and field test. In the field application, the sensor signal was corrected for drift, and errors were observed to be under 7% of that of conductivity measurements. The study also found that the chloride...

  19. All-plastic fiber-based pressure sensor

    DEFF Research Database (Denmark)

    Bundalo, Ivan-Lazar; Lwin, Richard; Leon-Saval, Sergio

    2016-01-01

    We present a feasibility study and a prototype of an all-plastic fiber-based pressure sensor. The sensor is based on long period gratings inscribed for the first time to the best of our knowledge by a CO2 laser in polymethyl methacrylate (PMMA) microstructured fibers and coupled to a pod......-like transducer that converts pressure to strain. The sensor prototype was characterized for pressures up to 150 mbars, and various parameters related to its construction were also characterized in order to enhance sensitivity. We consider this sensor in the context of future applications in endoscopic pressure...... sensors....

  20. Advanced Communication for Wireless Sensor Networks

    Science.gov (United States)

    2016-08-22

    strategies that could be used to increase the single-hop transmission range of a wireless sensor network, increase energy efficiency (improve battery...substance placed within the reach of the network. Sensor measurements were quantized to save energy and bandwidth during transmission of the...the problem of assigning transmission powers to every node in order to maintain connectivity while minimizing the energy consumption of the whole

  1. Applications of pressure-sensitive dielectric elastomer sensors

    Science.gov (United States)

    Böse, Holger; Ocak, Deniz; Ehrlich, Johannes

    2016-04-01

    Dielectric elastomer sensors for the measurement of compression loads with high sensitivity are described. The basic design of the sensors exhibits two profiled surfaces between which an elastomer film is confined. All components of the sensor were prepared with silicone whose stiffness can be varied in a wide range. Depending on details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression and electrode layers on the elastomer profiles and in the elastomer film approach each other. Different designs of the pressure sensor give rise to very different sensor characteristics in terms of the dependence of electric capacitance on compression force. Due to their inherent flexibility, the pressure sensors can be used on compliant substrates such as seats or beds or on the human body. This gives rise to numerous possible applications. The contribution describes also some examples of possible sensor applications. A glove was equipped with various sensors positioned at the finger tips. When grabbing an object with the glove, the sensors can detect the gripping forces of the individual fingers with high sensitivity. In a demonstrator of the glove equipped with seven sensors, the capacitances representing the gripping forces are recorded on a display. In another application example, a lower limb prosthesis was equipped with a pressure sensor to detect the load on the remaining part of the leg and the load is displayed in terms of the measured capacitance. The benefit of such sensors is to detect an eventual overload in order to prevent possible pressure sores. A third example introduces a seat load sensor system based on four extended pressure sensor mats. The sensor system detects the load distribution of a person on the seat. The examples emphasize the high performance of the new pressure sensor technology.

  2. Flexible magnetoimpedance sensor

    KAUST Repository

    Li, Bodong; Kavaldzhiev, Mincho; Kosel, Jü rgen

    2015-01-01

    Flexible magnetoimpedance (MI) sensors fabricated using a NiFe/Cu/NiFe tri-layer on Kapton substrate have been studied. A customized flexible microstrip transmission line was employed to investigate the MI sensors's magnetic field and frequency

  3. Air Sensor Toolbox

    Science.gov (United States)

    Air Sensor Toolbox provides information to citizen scientists, researchers and developers interested in learning more about new lower-cost compact air sensor technologies and tools for measuring air quality.

  4. Invisible magnetic sensors

    Science.gov (United States)

    Mach-Batlle, Rosa; Navau, Carles; Sanchez, Alvaro

    2018-04-01

    Sensing magnetic fields is essential in many applications in biomedicine, transportation, or smart cities. The distortion magnetic sensors create in response to the field they are detecting may hinder their use, for example, in applications requiring dense packaging of sensors or accurately shaped field distributions. For sensing electromagnetic waves, cloaking shells that reduce the scattering of sensors have been introduced. However, the problem of making a magnetic sensor undetectable remains unsolved. Here, we present a general strategy on how to make a sensor magnetically invisible while keeping its ability to sense. The sensor is rendered undetectable by surrounding it with a spherical shell having a tailored magnetic permeability. Our method can be applied to arbitrary shaped magnetic sensors in arbitrary magnetic fields. The invisibility can be made exact when the sensor is spherical and the probed field is uniform. A metasurface composed of superconducting pieces is presented as a practical realization of the ideal invisibility shell.

  5. Embedded sensor systems

    CERN Document Server

    Agrawal, Dharma Prakash

    2017-01-01

    This inspiring textbook provides an introduction to wireless technologies for sensors, explores potential use of sensors for numerous applications, and utilizes probability theory and mathematical methods as a means of embedding sensors in system design. It discusses the need for synchronization and underlying limitations, inter-relation between given coverage and connectivity to number of sensors needed, and the use of geometrical distance to determine location of the base station for data collection and explore use of anchor nodes for relative position determination of sensors. The book explores energy conservation, communication using TCP, the need for clustering and data aggregation, and residual energy determination and energy harvesting. It covers key topics of sensor communication like mobile base stations and relay nodes, delay-tolerant sensor networks, and remote sensing and possible applications. The book defines routing methods and do performance evaluation for random and regular sensor topology an...

  6. Sensor Substrate Development

    Data.gov (United States)

    National Aeronautics and Space Administration — Novel substrates, such as aerogels and porous, low density ceramics may increase the sensitivities of chemical reaction-based sensors for toxic vapors. These sensors...

  7. Ocular wavefront aberration and refractive error in pre-school children

    Science.gov (United States)

    Thapa, Damber; Fleck, Andre; Lakshminarayanan, Vasudevan; Bobier, William R.

    2011-11-01

    Hartmann-Shack images taken from an archived collection of SureSight refractive measurements of pre-school children in Oxford County, Ontario, Canada were retrieved and re-analyzed. Higher-order aberrations were calculated over the age range of 3 to 6 years. These higher-order aberrations were compared with respect to magnitudes of ametropia. Subjects were classified as emmetropic (range -0.5 to + 0.5D), low hyperopic (+ 0.5 to +2D) and high hyperopic (+2D or more) based upon the resulting spherical equivalent. Higher-order aberrations were found to increase with higher levels of hyperopia (p < 0.01). The strongest effect was for children showing more than +2.00D of hyperopia. The correlation coefficients were small in all of the higher-order aberrations; however, they were significant (p < 0.01). These analyses indicate a weak association between refractive error and higher-order aberrations in pre-school children.

  8. Simultaneous correction of large low-order and high-order aberrations with a new deformable mirror technology

    Science.gov (United States)

    Rooms, F.; Camet, S.; Curis, J. F.

    2010-02-01

    A new technology of deformable mirror will be presented. Based on magnetic actuators, these deformable mirrors feature record strokes (more than +/- 45μm of astigmatism and focus correction) with an optimized temporal behavior. Furthermore, the development has been made in order to have a large density of actuators within a small clear aperture (typically 52 actuators within a diameter of 9.0mm). We will present the key benefits of this technology for vision science: simultaneous correction of low and high order aberrations, AO-SLO image without artifacts due to the membrane vibration, optimized control, etc. Using recent papers published by Doble, Thibos and Miller, we show the performances that can be achieved by various configurations using statistical approach. The typical distribution of wavefront aberrations (both the low order aberration (LOA) and high order aberration (HOA)) have been computed and the correction applied by the mirror. We compare two configurations of deformable mirrors (52 and 97 actuators) and highlight the influence of the number of actuators on the fitting error, the photon noise error and the effective bandwidth of correction.

  9. Digital Sensor Technology

    Energy Technology Data Exchange (ETDEWEB)

    Ted Quinn; Jerry Mauck; Richard Bockhorst; Ken Thomas

    2013-07-01

    The nuclear industry has been slow to incorporate digital sensor technology into nuclear plant designs due to concerns with digital qualification issues. However, the benefits of digital sensor technology for nuclear plant instrumentation are substantial in terms of accuracy, reliability, availability, and maintainability. This report demonstrates these benefits in direct comparisons of digital and analog sensor applications. It also addresses the qualification issues that must be addressed in the application of digital sensor technology.

  10. Sensor equipment for quantification of spatial heterogeneity in large bioreactor

    DEFF Research Database (Denmark)

    Nørregaard, Anders; Formenti, Luca Riccardo; Stocks, Stuart M.

    of sensors and in order to apply more sensor equipment the bioreactor has to be modified which is both costly and results in production downtime. The presence of three phases (gas, liquid, and solid), and the opaque nature of the fermentation broth together with the necessity of heat sterilization further...... increases the requirements to the sensor equipment. In order to address these issues this study aims to make an investigation into freely floating, battery driven sensor particles that can follow the liquid movement in the reactor and make measurements while being distributed in the whole volume...

  11. Focus on image sensors

    NARCIS (Netherlands)

    Jos Gunsing; Daniël Telgen; Johan van Althuis; Jaap van de Loosdrecht; Mark Stappers; Peter Klijn

    2013-01-01

    Robots need sensors to operate properly. Using a single image sensor, various aspects of a robot operating in its environment can be measured or monitored. Over the past few years, image sensors have improved a lot: frame rate and resolution have increased, while prices have fallen. As a result,

  12. Multi-Sensor Architectures

    DEFF Research Database (Denmark)

    Hussain, Dil Muhammad Akbar; Ahmed, Zaki; Khan, M. Z.

    2012-01-01

    The use of multiple sensors typically requires the fusion of data from different type of sensors. The combined use of such a data has the potential to give an efficient, high quality and reliable estimation. Input data from different sensors allows the introduction of target attributes (target ty...

  13. Thermal flow micro sensors

    NARCIS (Netherlands)

    Elwenspoek, Michael Curt

    1999-01-01

    A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow

  14. Sensors for Entertainment

    Directory of Open Access Journals (Sweden)

    Fabrizio Lamberti

    2016-07-01

    Full Text Available Sensors are becoming ubiquitous in all areas of science, technology, and society. In this Special Issue on “Sensors for Entertainment”, developments in progress and the current state of application scenarios for sensors in the field of entertainment is explored.

  15. Electric field sensor studies

    International Nuclear Information System (INIS)

    Griffith, R.D.; Parks, S.

    1977-01-01

    Above-ground intrusion sensors are reviewed briefly. Buried wire sensors are next considered; feasibility studies were conducted. A triangular system of an overhead transmitter wire exciting two buried sensor wires was developed and tested. It failed sometimes to detect a man making a broad jump. A differential receiver was developed to solve this problem

  16. Ultrahigh Temperature Capacitive Pressure Sensor

    Science.gov (United States)

    Harsh, Kevin

    2014-01-01

    Robust, miniaturized sensing systems are needed to improve performance, increase efficiency, and track system health status and failure modes of advanced propulsion systems. Because microsensors must operate in extremely harsh environments, there are many technical challenges involved in developing reliable systems. In addition to high temperatures and pressures, sensing systems are exposed to oxidation, corrosion, thermal shock, fatigue, fouling, and abrasive wear. In these harsh conditions, sensors must be able to withstand high flow rates, vibration, jet fuel, and exhaust. In order for existing and future aeropropulsion turbine engines to improve safety and reduce cost and emissions while controlling engine instabilities, more accurate and complete sensor information is necessary. High-temperature (300 to 1,350 C) capacitive pressure sensors are of particular interest due to their high measurement bandwidth and inherent suitability for wireless readout schemes. The objective of this project is to develop a capacitive pressure sensor based on silicon carbon nitride (SiCN), a new class of high-temperature ceramic materials, which possesses excellent mechanical and electric properties at temperatures up to 1,600 C.

  17. Downhole Applications of Magnetic Sensors

    Directory of Open Access Journals (Sweden)

    Chinthaka P. Gooneratne

    2017-10-01

    Full Text Available In this paper we present a review of the application of two types of magnetic sensors—fluxgate magnetometers and nuclear magnetic resonance (NMR sensors—in the oil/gas industry. These magnetic sensors play a critical role in drilling wells safely, accurately and efficiently into a target reservoir zone by providing directional data of the well and acquiring information about the surrounding geological formations. Research into magnetic sensors for oil/gas drilling has not been explored by researchers to the same extent as other applications, such as biomedical, magnetic storage and automotive/aerospace applications. Therefore, this paper aims to serve as an opportunity for researchers to truly understand how magnetic sensors can be used in a downhole environment and to provide fertile ground for research and development in this area. A look ahead, discussing other magnetic sensor technologies that can potentially be used in the oil/gas industry is presented, and what is still needed in order deploy them in the field is also addressed.

  18. Model-based sensor diagnosis

    International Nuclear Information System (INIS)

    Milgram, J.; Dormoy, J.L.

    1994-09-01

    Running a nuclear power plant involves monitoring data provided by the installation's sensors. Operators and computerized systems then use these data to establish a diagnostic of the plant. However, the instrumentation system is complex, and is not immune to faults and failures. This paper presents a system for detecting sensor failures using a topological description of the installation and a set of component models. This model of the plant implicitly contains relations between sensor data. These relations must always be checked if all the components are functioning correctly. The failure detection task thus consists of checking these constraints. The constraints are extracted in two stages. Firstly, a qualitative model of their existence is built using structural analysis. Secondly, the models are formally handled according to the results of the structural analysis, in order to establish the constraints on the sensor data. This work constitutes an initial step in extending model-based diagnosis, as the information on which it is based is suspect. This work will be followed by surveillance of the detection system. When the instrumentation is assumed to be sound, the unverified constraints indicate errors on the plant model. (authors). 8 refs., 4 figs

  19. Pump depletion limited evolution of the relativistic plasma wave-front in a forced laser-wakefield accelerator

    International Nuclear Information System (INIS)

    Fang, F; Clayton, C E; Marsh, K A; Pak, A E; Ralph, J E; Joshi, C; Lopes, N C

    2009-01-01

    In a forced laser-wakefield accelerator experiment (Malka et al 2002 Science 298 1596) where the length of the pump laser pulse is a few plasma periods long, the leading edge of the laser pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake. Therefore, after some propagation distance, the group velocity of the leading edge of the pump pulse-and thus of the driven electron plasma wave-will slow down. This can have implications for the dephasing length of the accelerated electrons and therefore needs to be understood experimentally. We have carried out an experimental investigation where we have measured the velocity v f of the 'wave-front' of the plasma wave driven by a nominally 50 fs (full width half maximum), intense (a 0 ≅ 1), 0.815 μm laser pulse. To determine the speed of the wave front, time- and space-resolved refractometry, interferometry and Thomson scattering were used. Although a laser pulse propagating through a relatively low-density plasma (n e = 1.3 x 10 19 cm -3 ) showed no measurable changes in v f over 1.3 mm (and no accelerated electrons), a high-density plasma (n e = 5 x 10 19 cm -3 ) generated accelerated electrons and showed a continuous change in v f as the laser pulse propagated through the plasma. Possible causes and consequences of the observed v f evolution are discussed.

  20. Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosonde observations

    Science.gov (United States)

    Helmboldt, J. F.

    2012-07-01

    The results of contemporaneous summer nighttime observations of midlatitude medium scale traveling ionospheric disturbances (MSTIDs) with the Very Large Array (VLA) in New Mexico and nearby ionosondes in Texas and Colorado are presented. Using 132, 20-minute observations, several instances of MSTIDs were detected, all having wavefronts aligned northwest to southeast and mostly propagating toward the southwest, consistent with previous studies of MSTIDs. However, some were also found to move toward the northeast. It was found that both classes of MSTIDs were only found when sporadic-E (Es) layers of moderate peak density (1.5​ foEs​ foEs > ​3 MHz that was not present when 1.5​ foEs < ​3 MHz. No MSTIDs were observed either before midnight or when the F-region height was increasing at a relatively high rate, even when these Es layers were observed. Combining this result with AE indices which were relatively high at the time (an average of about 300 nT and maximum of nearly 700 nT), it is inferred that both the lack of MSTIDs and the increase in F-region height are due to substorm-induced electric fields. The northeastward-directed MSTIDs were strongest post-midnight during times when the F-region was observed to be collapsing relatively quickly. This implies that these two occurrences are related and likely both caused by rare shifts in F-region neutral wind direction from southwest to northwest.

  1. Imaging and image restoration of an on-axis three-mirror Cassegrain system with wavefront coding technology.

    Science.gov (United States)

    Guo, Xiaohu; Dong, Liquan; Zhao, Yuejin; Jia, Wei; Kong, Lingqin; Wu, Yijian; Li, Bing

    2015-04-01

    Wavefront coding (WFC) technology is adopted in the space optical system to resolve the problem of defocus caused by temperature difference or vibration of satellite motion. According to the theory of WFC, we calculate and optimize the phase mask parameter of the cubic phase mask plate, which is used in an on-axis three-mirror Cassegrain (TMC) telescope system. The simulation analysis and the experimental results indicate that the defocused modulation transfer function curves and the corresponding blurred images have a perfect consistency in the range of 10 times the depth of focus (DOF) of the original TMC system. After digital image processing by a Wiener filter, the spatial resolution of the restored images is up to 57.14 line pairs/mm. The results demonstrate that the WFC technology in the TMC system has superior performance in extending the DOF and less sensitivity to defocus, which has great value in resolving the problem of defocus in the space optical system.

  2. Experimental Validation of Advanced Dispersed Fringe Sensing (ADFS) Algorithm Using Advanced Wavefront Sensing and Correction Testbed (AWCT)

    Science.gov (United States)

    Wang, Xu; Shi, Fang; Sigrist, Norbert; Seo, Byoung-Joon; Tang, Hong; Bikkannavar, Siddarayappa; Basinger, Scott; Lay, Oliver

    2012-01-01

    Large aperture telescope commonly features segment mirrors and a coarse phasing step is needed to bring these individual segments into the fine phasing capture range. Dispersed Fringe Sensing (DFS) is a powerful coarse phasing technique and its alteration is currently being used for JWST.An Advanced Dispersed Fringe Sensing (ADFS) algorithm is recently developed to improve the performance and robustness of previous DFS algorithms with better accuracy and unique solution. The first part of the paper introduces the basic ideas and the essential features of the ADFS algorithm and presents the some algorithm sensitivity study results. The second part of the paper describes the full details of algorithm validation process through the advanced wavefront sensing and correction testbed (AWCT): first, the optimization of the DFS hardware of AWCT to ensure the data accuracy and reliability is illustrated. Then, a few carefully designed algorithm validation experiments are implemented, and the corresponding data analysis results are shown. Finally the fiducial calibration using Range-Gate-Metrology technique is carried out and a <10nm or <1% algorithm accuracy is demonstrated.

  3. Optimization of an Electromagnetics Code with Multicore Wavefront Diamond Blocking and Multi-dimensional Intra-Tile Parallelization

    KAUST Repository

    Malas, Tareq M.

    2016-07-21

    Understanding and optimizing the properties of solar cells is becoming a key issue in the search for alternatives to nuclear and fossil energy sources. A theoretical analysis via numerical simulations involves solving Maxwell\\'s Equations in discretized form and typically requires substantial computing effort. We start from a hybrid-parallel (MPI+OpenMP) production code that implements the Time Harmonic Inverse Iteration Method (THIIM) with Finite-Difference Frequency Domain (FDFD) discretization. Although this algorithm has the characteristics of a strongly bandwidth-bound stencil update scheme, it is significantly different from the popular stencil types that have been exhaustively studied in the high performance computing literature to date. We apply a recently developed stencil optimization technique, multicore wavefront diamond tiling with multi-dimensional cache block sharing, and describe in detail the peculiarities that need to be considered due to the special stencil structure. Concurrency in updating the components of the electric and magnetic fields provides an additional level of parallelism. The dependence of the cache size requirement of the optimized code on the blocking parameters is modeled accurately, and an auto-tuner searches for optimal configurations in the remaining parameter space. We were able to completely decouple the execution from the memory bandwidth bottleneck, accelerating the implementation by a factor of three to four compared to an optimal implementation with pure spatial blocking on an 18-core Intel Haswell CPU.

  4. Wavefront error measurement of the concave ellipsoidal mirrors of the METIS coronagraph on ESA Solar Orbiter mission

    Science.gov (United States)

    Sandri, P.

    2017-12-01

    The paper describes the alignment technique developed for the wavefront error measurement of ellipsoidal mirrors presenting a central hole. The achievement of a good alignment with a classic setup at the finite conjugates when mirrors are uncoated cannot be based on the identification and materialization at naked eye of the retro-reflected spot by the mirror under test as the intensity of the retro-reflected spot results to be ≈1E-3 of the intensity of the injected laser beam of the interferometer. We present the technique developed for the achievement of an accurate alignment in the setup at the finite conjugate even in condition of low intensity based on the use of an autocollimator adjustable in focus position and a small polished flat surface on the rear side of the mirror. The technique for the alignment has successfully been used for the optical test of the concave ellipsoidal mirrors of the METIS coronagraph of the ESA Solar Orbiter mission. The presented method results to be advantageous in terms of precision and of time saving also when the mirrors are reflective coated and integrated into their mechanical hardware.

  5. SCExAO: First Results and On-Sky Performance

    Science.gov (United States)

    Currie, Thayne; Guyon, Olivier; Martinache, Frantz; Clergeon, Christophe; McElwain, Michael; Thalmann, Christian; Jovanovic, Nemanja; Singh, Garima; Kudo, Tomoyuki

    2013-01-01

    We present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control ("speckle nulling"). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield greater than 90% Strehl ratio and enable 10(exp 6) -10(exp 7) contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

  6. Hydrostatic force sensor

    International Nuclear Information System (INIS)

    Evans, M.S.; Stoughton, R.S.; Kazerooni, H.

    1994-08-01

    This paper presents a theoretical and experimental investigation of a new kind of force sensor which detects forces by measuring an induced pressure change in a material of large Poisson's ratio. In this investigation we develop mathematical expressions for the sensor's sensitivity and bandwidth, and show that its sensitivity can be much larger and its bandwidth is usually smaller than those of existing strain-gage-type sensors. This force sensor is well-suited for measuring large but slowly varying forces. It can be installed in a space smaller than that required by existing sensors

  7. Multifuctional integrated sensors (MFISES).

    Energy Technology Data Exchange (ETDEWEB)

    Homeijer, Brian D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Roozeboom, Clifton [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-10-01

    Many emerging IoT applications require sensing of multiple physical and environmental parameters for: completeness of information, measurement validation, unexpected demands, improved performance. For example, a typical outdoor weather station measures temperature, humidity, barometric pressure, light intensity, rainfall, wind speed and direction. Existing sensor technologies do not directly address the demand for cost, size, and power reduction in multi-paramater sensing applications. Industry sensor manufacturers have developed integrated sensor systems for inertial measurements that combine accelerometers, gyroscopes, and magnetometers, but do not address environmental sensing functionality. In existing research literature, a technology gap exists between the functionality of MEMS sensors and the real world applications of the sensors systems.

  8. A Nodes Deployment Algorithm in Wireless Sensor Network Based on Distribution

    Directory of Open Access Journals (Sweden)

    Song Yuli

    2014-07-01

    Full Text Available Wireless sensor network coverage is a basic problem of wireless sensor network. In this paper, we propose a wireless sensor network node deployment algorithm base on distribution in order to form an efficient wireless sensor network. The iteratively greedy algorithm is used in this paper to choose priority nodes into active until the entire network is covered by wireless sensor nodes, the whole network to multiply connected. The simulation results show that the distributed wireless sensor network node deployment algorithm can form a multiply connected wireless sensor network.

  9. Sensor mount assemblies and sensor assemblies

    Science.gov (United States)

    Miller, David H [Redondo Beach, CA

    2012-04-10

    Sensor mount assemblies and sensor assemblies are provided. In an embodiment, by way of example only, a sensor mount assembly includes a busbar, a main body, a backing surface, and a first finger. The busbar has a first end and a second end. The main body is overmolded onto the busbar. The backing surface extends radially outwardly relative to the main body. The first finger extends axially from the backing surface, and the first finger has a first end, a second end, and a tooth. The first end of the first finger is disposed on the backing surface, and the tooth is formed on the second end of the first finger.

  10. Planning and Scheduling for Environmental Sensor Networks

    Science.gov (United States)

    Frank, J. D.

    2005-12-01

    Environmental Sensor Networks are a new way of monitoring the environment. They comprise autonomous sensor nodes in the environment that record real-time data, which is retrieved, analyzed, integrated with other data sets (e.g. satellite images, GIS, process models) and ultimately lead to scientific discoveries. Sensor networks must operate within time and resource constraints. Sensors have limited onboard memory, energy, computational power, communications windows and communications bandwidth. The value of data will depend on when, where and how it was collected, how detailed the data is, how long it takes to integrate the data, and how important the data was to the original scientific question. Planning and scheduling of sensor networks is necessary for effective, safe operations in the face of these constraints. For example, power bus limitations may preclude sensors from simultaneously collecting data and communicating without damaging the sensor; planners and schedulers can ensure these operations are ordered so that they do not happen simultaneously. Planning and scheduling can also ensure best use of the sensor network to maximize the value of collected science data. For example, if data is best recorded using a particular camera angle but it is costly in time and energy to achieve this, planners and schedulers can search for times when time and energy are available to achieve the optimal camera angle. Planning and scheduling can handle uncertainty in the problem specification; planners can be re-run when new information is made available, or can generate plans that include contingencies. For example, if bad weather may prevent the collection of data, a contingent plan can check lighting conditions and turn off data collection to save resources if lighting is not ideal. Both mobile and immobile sensors can benefit from planning and scheduling. For example, data collection on otherwise passive sensors can be halted to preserve limited power and memory

  11. Wireless Biological Electronic Sensors.

    Science.gov (United States)

    Cui, Yue

    2017-10-09

    The development of wireless biological electronic sensors could open up significant advances for both fundamental studies and practical applications in a variety of areas, including medical diagnosis, environmental monitoring, and defense applications. One of the major challenges in the development of wireless bioelectronic sensors is the successful integration of biosensing units and wireless signal transducers. In recent years, there are a few types of wireless communication systems that have been integrated with biosensing systems to construct wireless bioelectronic sensors. To successfully construct wireless biological electronic sensors, there are several interesting questions: What types of biosensing transducers can be used in wireless bioelectronic sensors? What types of wireless systems can be integrated with biosensing transducers to construct wireless bioelectronic sensors? How are the electrical sensing signals generated and transmitted? This review will highlight the early attempts to address these questions in the development of wireless biological electronic sensors.

  12. Acoustic Sensor Design for Dark Matter Bubble Chamber Detectors.

    Science.gov (United States)

    Felis, Ivan; Martínez-Mora, Juan Antonio; Ardid, Miguel

    2016-06-10

    Dark matter bubble chamber detectors use piezoelectric sensors in order to detect and discriminate the acoustic signals emitted by the bubbles grown within the superheated fluid from a nuclear recoil produced by a particle interaction. These sensors are attached to the outside walls of the vessel containing the fluid. The acoustic discrimination depends strongly on the properties of the sensor attached to the outer wall of the vessel that has to meet the requirements of radiopurity and size. With the aim of optimizing the sensor system, a test bench for the characterization of the sensors has been developed. The sensor response for different piezoelectric materials, geometries, matching layers, and backing layers have been measured and contrasted with FEM simulations and analytical models. The results of these studies lead us to have a design criterion for the construction of specific sensors for the next generation of dark matter bubble chamber detectors (250 L).

  13. Acoustic Sensor Design for Dark Matter Bubble Chamber Detectors

    Directory of Open Access Journals (Sweden)

    Ivan Felis

    2016-06-01

    Full Text Available Dark matter bubble chamber detectors use piezoelectric sensors in order to detect and discriminate the acoustic signals emitted by the bubbles grown within the superheated fluid from a nuclear recoil produced by a particle interaction. These sensors are attached to the outside walls of the vessel containing the fluid. The acoustic discrimination depends strongly on the properties of the sensor attached to the outer wall of the vessel that has to meet the requirements of radiopurity and size. With the aim of optimizing the sensor system, a test bench for the characterization of the sensors has been developed. The sensor response for different piezoelectric materials, geometries, matching layers, and backing layers have been measured and contrasted with FEM simulations and analytical models. The results of these studies lead us to have a design criterion for the construction of specific sensors for the next generation of dark matter bubble chamber detectors (250 L.

  14. Certified higher-order recursive path ordering

    NARCIS (Netherlands)

    Koprowski, A.; Pfenning, F.

    2006-01-01

    The paper reports on a formalization of a proof of wellfoundedness of the higher-order recursive path ordering (HORPO) in the proof checker Coq. The development is axiom-free and fully constructive. Three substantive parts that could be used also in other developments are the formalizations of the

  15. Out-of-time-ordered correlators in a quantum Ising chain

    Science.gov (United States)

    Lin, Cheng-Ju; Motrunich, Olexei I.

    2018-04-01

    Out-of-time-ordered correlators (OTOC) have been proposed to characterize quantum chaos in generic systems. However, they can also show interesting behavior in integrable models, resembling the OTOC in chaotic systems in some aspects. Here we study the OTOC for different operators in the exactly-solvable one-dimensional quantum Ising spin chain. The OTOC for spin operators that are local in terms of the Jordan-Wigner fermions has a "shell-like" structure: After the wavefront passes, the OTOC approaches its original value in the long-time limit, showing no signature of scrambling; the approach is described by a t-1 power law at long time t . On the other hand, the OTOC for spin operators that are nonlocal in the Jordan-Wigner fermions has a "ball-like" structure, with its value reaching zero in the long-time limit, looking like a signature of scrambling; the approach to zero, however, is described by a slow power law t-1 /4 for the Ising model at the critical coupling. These long-time power-law behaviors in the lattice model are not captured by conformal field theory calculations. The mixed OTOC with both local and nonlocal operators in the Jordan-Wigner fermions also has a "ball-like" structure, but the limiting values and the decay behavior appear to be nonuniversal. In all cases, we are not able to define a parametrically large window around the wavefront to extract the Lyapunov exponent.

  16. Digital Sensor Technology

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Ken D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Quinn, Edward L. [Technology Resources, Dana Point, CA (United States); Mauck, Jerry L. [Technology Resources, Dana Point, CA (United States); Bockhorst, Richard M. [Technology Resources, Dana Point, CA (United States)

    2015-02-01

    The nuclear industry has been slow to incorporate digital sensor technology into nuclear plant designs due to concerns with digital qualification issues. However, the benefits of digital sensor technology for nuclear plant instrumentation are substantial in terms of accuracy and reliability. This paper, which refers to a final report issued in 2013, demonstrates these benefits in direct comparisons of digital and analog sensor applications. Improved accuracy results from the superior operating characteristics of digital sensors. These include improvements in sensor accuracy and drift and other related parameters which reduce total loop uncertainty and thereby increase safety and operating margins. An example instrument loop uncertainty calculation for a pressure sensor application is presented to illustrate these improvements. This is a side-by-side comparison of the instrument loop uncertainty for both an analog and a digital sensor in the same pressure measurement application. Similarly, improved sensor reliability is illustrated with a sample calculation for determining the probability of failure on demand, an industry standard reliability measure. This looks at equivalent analog and digital temperature sensors to draw the comparison. The results confirm substantial reliability improvement with the digital sensor, due in large part to ability to continuously monitor the health of a digital sensor such that problems can be immediately identified and corrected. This greatly reduces the likelihood of a latent failure condition of the sensor at the time of a design basis event. Notwithstanding the benefits of digital sensors, there are certain qualification issues that are inherent with digital technology and these are described in the report. One major qualification impediment for digital sensor implementation is software common cause failure (SCCF).

  17. Construction of a Piezoresistive Neural Sensor Array

    Science.gov (United States)

    Carlson, W. B.; Schulze, W. A.; Pilgrim, P. M.

    1996-01-01

    The construction of a piezoresistive - piezoelectric sensor (or actuator) array is proposed using 'neural' connectivity for signal recognition and possible actuation functions. A closer integration of the sensor and decision functions is necessary in order to achieve intrinsic identification within the sensor. A neural sensor is the next logical step in development of truly 'intelligent' arrays. This proposal will integrate 1-3 polymer piezoresistors and MLC electroceramic devices for applications involving acoustic identification. The 'intelligent' piezoresistor -piezoelectric system incorporates printed resistors, composite resistors, and a feedback for the resetting of resistances. A model of a design is proposed in order to simulate electromechanical resistor interactions. The goal of optimizing a sensor geometry for improving device reliability, training, & signal identification capabilities is the goal of this work. At present, studies predict performance of a 'smart' device with a significant control of 'effective' compliance over a narrow pressure range due to a piezoresistor percolation threshold. An interesting possibility may be to use an array of control elements to shift the threshold function in order to change the level of resistance in a neural sensor array for identification, or, actuation applications. The proposed design employs elements of: (1) conductor loaded polymers for a 'fast' RC time constant response; and (2) multilayer ceramics for actuation or sensing and shifting of resistance in the polymer. Other material possibilities also exist using magnetoresistive layered systems for shifting the resistance. It is proposed to use a neural net configuration to test and to help study the possible changes required in the materials design of these devices. Numerical design models utilize electromechanical elements, in conjunction with structural elements in order to simulate piezoresistively controlled actuators and changes in resistance of sensors

  18. Transmission Power Control for Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Kuo-Hsien Hsia

    2017-02-01

    Full Text Available Wireless sensor networks can be widely applied for a security system or a smart home system. Since some of the wireless remote sensor nodes may be powered by energy storage devices such as batteries, it is a very important issue to transmit signals at lower power with the consideration of the communication effectiveness. In this paper, we will provide a fuzzy controller with two inputs and one output for received signal strength indicator (RSSI and link quality indicator (LQI to adjust transmission power suitably in order to maintaining a certain communication level with a reduced energy consumption. And we will divide the sampling period of a sensor node into four intervals so that the sensor node radio device does not in receiving or transmission status all the time. Hence the sensor node can adjust transmission power automatically and reduce sensor node power consumption. Experimental results show that the battery life can be extended to about 10 times for the designed sensor node comparing to a normal node.

  19. Characterization of Polymeric Chemiresistors for Gas Sensor

    Directory of Open Access Journals (Sweden)

    Hendro Juwono

    2012-06-01

    Full Text Available Composite polymer-carbon has resistance change if come into contact with gas. Composite polymer-carbon can be used as a gas sensor. This research will be characterized the sensor composite polymer-carbon that has been made from 6 types of polymer, which are; PEG6000, PEG20M, PEG200, PEG1540, Silicon and Squelene. The 6 sensors will be tested by 9 types of gas, which are; Aceton, Aceton Nitril, Benzene, Etanol, Methanol, Ethyl Aceton, Chloroform, n-Hexan and Toluene. This characterization will be grouped into 4 claster of characteristics, which are; the selectivity (influence type of gas, the sensitivity (influence volume of gas, the influence of temperature and the influence of humidity. Test using method testing sensors that paleced in an isolated chamber which is connected with data acquisition. variations of temperature, humidity, type and volume of gas will be condition in the chamber. Correspondence analysis and regression will be used to process the data. Test results found that each sensor of type of polymers have different sensitivity and selectivity towards a particular type of gas. Resistance sensors increases with rising temperature and humidity environment with a polynomial equation of order-2 and order-3

  20. Advanced Sensor Arrays and Packaging

    Energy Technology Data Exchange (ETDEWEB)

    Ryter, John Wesley [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Romero, Christopher J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramaiyan, Kannan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brosha, Eric L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-11

    Novel sensor packaging elements were designed, fabricated, and tested in order to facilitate the transition of electrochemical mixed-potential sensors toward commercialization. Of the two designs completed, the first is currently undergoing field trials, taking direct measurements within vehicle exhaust streams, while the second is undergoing preliminary laboratory testing. The sensors’ optimal operating conditions, sensitivity to hydrogen, and long-­term baseline stability were also investigated. The sensing capabilities of lanthanum chromite (La0.8Sr0.2CrO3) and indium-­doped tin oxide (ITO) working electrodes were compared, and the ITO devices were selected for pre-­commercial field trials testing at a hydrogen fuel cell vehicle fueling station in California. Previous data from that fueling station were also analyzed, and the causes of anomalous baseline drift were identified.