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Sample records for video hartmann wavefront

  1. 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.

  2. Shack-Hartmann wavefront sensor using a Raspberry Pi embedded system

    Science.gov (United States)

    Contreras-Martinez, Ramiro; Garduño-Mejía, Jesús; Rosete-Aguilar, Martha; Román-Moreno, Carlos J.

    2017-05-01

    In this work we present the design and manufacture of a compact Shack-Hartmann wavefront sensor using a Raspberry Pi and a microlens array. The main goal of this sensor is to recover the wavefront of a laser beam and to characterize its spatial phase using a simple and compact Raspberry Pi and the Raspberry Pi embedded camera. The recovery algorithm is based on a modified version of the Southwell method and was written in Python as well as its user interface. Experimental results and reconstructed wavefronts are presented.

  3. 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

  4. Experimental detection of optical vortices with a Shack-Hartmann wavefront sensor.

    Science.gov (United States)

    Murphy, Kevin; Burke, Daniel; Devaney, Nicholas; Dainty, Chris

    2010-07-19

    Laboratory experiments are carried out to detect optical vortices in conditions typical of those experienced when a laser beam is propagated through the atmosphere. A Spatial Light Modulator (SLM) is used to mimic atmospheric turbulence and a Shack-Hartmann wavefront sensor is utilised to measure the slopes of the wavefront surface. A matched filter algorithm determines the positions of the Shack-Hartmann spot centroids more robustly than a centroiding algorithm. The slope discrepancy is then obtained by taking the slopes measured by the wavefront sensor away from the slopes calculated from a least squares reconstruction of the phase. The slope discrepancy field is used as an input to the branch point potential method to find if a vortex is present, and if so to give its position and sign. The use of the slope discrepancy technique greatly improves the detection rate of the branch point potential method. This work shows the first time the branch point potential method has been used to detect optical vortices in an experimental setup.

  5. Tear film break-up time evaluated by real-time Hartmann-Shack wavefront sensing.

    Science.gov (United States)

    Mihashi, Toshifumi; Hirohara, Yoko; Koh, Shizuka; Ninomiya, Sayuri; Maeda, Naoyuki; Fujikado, Takashi

    2006-01-01

    To develop a novel method for measuring tear break-up time (BUT) by continuously measuring higher order wavefront aberrations using a Hartmann-Shack (H-S) aberrometer. Wavefront aberrations up to the sixth order for a 4-mm pupil were measured in six eyes of six normal subjects using an H-S aberrometer. The aberrometry was performed once every second for up to 50 s under topical anesthesia. The sequence of the points was divided into two stages, and the BUT was defined as the wavefront border of the stages (WFBUT). The WFBUT was compared with the BUT by the conventional fluorescein method (FLBUT) or by the disruption of placid-ring images (PLBUT). In three eyes, the WFBUT (average, 10.9 +/- 1.1 s) was shorter than the PLBUT (average, 17.5 +/- 2.5 s), while in the other three eyes the WFBUT (average, 21.5 +/- 2.2 s) was longer than PLBUT (average, 8.1 +/- 2.2 s). The FLBUT was shorter than WFBUT or PLBUT in most cases. The tear break-up time measured by H-S aberrometer may be used as a practical measure of tear break-up.

  6. Using Shack-Hartmann wavefront sensors and Zernike coefficients for beam characterisation: numerical procedures

    Science.gov (United States)

    Bosch, Salvador; Vallmitjana, Santiago; Marzoa, Antonio; Arines, Justo; Acosta, Eva

    2017-06-01

    When using Shack-Hartmann wavefront sensors (SH) and Zernike coefficients (Zs) in applications where the position of the measurement and the point of interest are far apart, as it is common practice in ophthalmic optics, problems in the interpretation of the values of the Zs arise, related to how the shape of the wavefront propagates along the beam. One typical example is pupil conjugation where an auxiliary lens is added to match the size of the area of the interest of the beam with the size of the entrance pupil of the SH used for measurements. In the present work, we address this problem in the framework of a numerical scheme for modeling the beam propagation. We calculate the wavefronts with exact ray tracing plus the fitting of the impacts so as to match a rectangular grid. This procedure allows the subsequent calculation of the Zs or, similarly, the pupil function at an arbitrary plane perpendicular to the optical axis. All the numerical methods and procedures have been implemented in MATLAB code and can be illustrated by running the MATLAB script for the setup configuration that is being considered. Several examples are presented to illustrate the previous ideas and to show the real capabilities of our procedures. They will help to clarify the issues actually found in practical setups for beam manipulation, often encountered in ophthalmic optics.

  7. Shack-Hartmann wavefront sensor with large dynamic range by adaptive spot search method.

    Science.gov (United States)

    Shinto, Hironobu; Saita, Yusuke; Nomura, Takanori

    2016-07-10

    A Shack-Hartmann wavefront sensor (SHWFS) that consists of a microlens array and an image sensor has been used to measure the wavefront aberrations of human eyes. However, a conventional SHWFS has finite dynamic range depending on the diameter of the each microlens. The dynamic range cannot be easily expanded without a decrease of the spatial resolution. In this study, an adaptive spot search method to expand the dynamic range of an SHWFS is proposed. In the proposed method, spots are searched with the help of their approximate displacements measured with low spatial resolution and large dynamic range. By the proposed method, a wavefront can be correctly measured even if the spot is beyond the detection area. The adaptive spot search method is realized by using the special microlens array that generates both spots and discriminable patterns. The proposed method enables expanding the dynamic range of an SHWFS with a single shot and short processing time. The performance of the proposed method is compared with that of a conventional SHWFS by optical experiments. Furthermore, the dynamic range of the proposed method is quantitatively evaluated by numerical simulations.

  8. Experimental investigations on characterization of freeform wavefront using Shack-Hartmann sensor

    Science.gov (United States)

    Burada, Dali Ramu; Pant, Kamal K.; Bichra, Mohamed; Khan, Gufran Sayeed; Sinzinger, Stefan; Shakher, Chandra

    2017-08-01

    The metrology of freeform wavefront can be performed by the use of a noninterferometric method, such as a Shack-Hartmann sensor (SHS). Detailed experimental investigations employing an SHS as metrology head are presented. The scheme is of nonnull nature where small subapertures are measured using an SHS and stitched to give the full wavefront. For the assessment of complex misalignment errors during the spiral scanning, a library of residual slope errors has been created, which makes the alignment process fast converging for minimizing the scanning errors. A detailed analysis of the effects of slope and positioning error on reproducibility is presented. It is validated by null test where a null diffractive optical element has been used in a Mach-Zehnder configuration for compensating the freeform shape. A freeform optics is measured by both measurement schemes, and the results are in good agreement. Further, the nonnull-based scanning subaperture stitching scheme is also validated by performing measurements on an aspheric surface and compared with the measurements from the interferometric method (Zygo Verifire).

  9. Optical alignment procedure utilizing neural networks combined with Shack-Hartmann wavefront sensor

    Science.gov (United States)

    Adil, Fatime Zehra; Konukseven, Erhan İlhan; Balkan, Tuna; Adil, Ömer Faruk

    2017-05-01

    In the design of pilot helmets with night vision capability, to not limit or block the sight of the pilot, a transparent visor is used. The reflected image from the coated part of the visor must coincide with the physical human sight image seen through the nonreflecting regions of the visor. This makes the alignment of the visor halves critical. In essence, this is an alignment problem of two optical parts that are assembled together during the manufacturing process. Shack-Hartmann wavefront sensor is commonly used for the determination of the misalignments through wavefront measurements, which are quantified in terms of the Zernike polynomials. Although the Zernike polynomials provide very useful feedback about the misalignments, the corrective actions are basically ad hoc. This stems from the fact that there exists no easy inverse relation between the misalignment measurements and the physical causes of the misalignments. This study aims to construct this inverse relation by making use of the expressive power of the neural networks in such complex relations. For this purpose, a neural network is designed and trained in MATLAB® regarding which types of misalignments result in which wavefront measurements, quantitatively given by Zernike polynomials. This way, manual and iterative alignment processes relying on trial and error will be replaced by the trained guesses of a neural network, so the alignment process is reduced to applying the counter actions based on the misalignment causes. Such a training requires data containing misalignment and measurement sets in fine detail, which is hard to obtain manually on a physical setup. For that reason, the optical setup is completely modeled in Zemax® software, and Zernike polynomials are generated for misalignments applied in small steps. The performance of the neural network is experimented and found promising in the actual physical setup.

  10. Non-contact XUV metrology of Ru/B4C multilayer optics by means of Hartmann wavefront analysis.

    Science.gov (United States)

    Ruiz-Lopez, Mabel; Dacasa, Hugo; Mahieu, Benoit; Lozano, Magali; Li, Lu; Zeitoun, Philippe; Bleiner, Davide

    2018-02-20

    Short-wavelength imaging, spectroscopy, and lithography scale down the characteristic length-scale to nanometers. This poses tight constraints on the optics finishing tolerances, which is often difficult to characterize. Indeed, even a tiny surface defect degrades the reflectivity and spatial projection of such optics. In this study, we demonstrate experimentally that a Hartmann wavefront sensor for extreme ultraviolet (XUV) wavelengths is an effective non-contact analytical method for inspecting the surface of multilayer optics. The experiment was carried out in a tabletop laboratory using a high-order harmonic generation as an XUV source. The wavefront sensor was used to measure the wavefront errors after the reflection of the XUV beam on a spherical Ru/B 4 C multilayer mirror, scanning a large surface of approximately 40 mm in diameter. The results showed that the technique detects the aberrations in the nanometer range.

  11. Nonlinear spline wavefront reconstruction through moment-based Shack-Hartmann sensor measurements.

    Science.gov (United States)

    Viegers, M; Brunner, E; Soloviev, O; de Visser, C C; Verhaegen, M

    2017-05-15

    We propose a spline-based aberration reconstruction method through moment measurements (SABRE-M). The method uses first and second moment information from the focal spots of the SH sensor to reconstruct the wavefront with bivariate simplex B-spline basis functions. The proposed method, since it provides higher order local wavefront estimates with quadratic and cubic basis functions can provide the same accuracy for SH arrays with a reduced number of subapertures and, correspondingly, larger lenses which can be beneficial for application in low light conditions. In numerical experiments the performance of SABRE-M is compared to that of the first moment method SABRE for aberrations of different spatial orders and for different sizes of the SH array. The results show that SABRE-M is superior to SABRE, in particular for the higher order aberrations and that SABRE-M can give equal performance as SABRE on a SH grid of halved sampling.

  12. Nonlinear spline wavefront reconstruction from Shack-Hartmann intensity measurements through small aberration approximations.

    Science.gov (United States)

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

    2017-09-01

    We propose an extension of the Spline based ABerration Reconstruction (SABRE) method to Shack-Hartmann (SH) intensity measurements, through small aberration approximations of the focal spot models. The original SABRE for SH slope measurements is restricted to the use of linear spline polynomials, due to the limited amount of data, and the resolution of its reconstruction is determined by the number of lenslets. In this work, a fast algorithm is presented that directly processes the pixel information of the focal spots, allowing the employment of nonlinear polynomials for high accuracy reconstruction. In order to guarantee the validity of the small aberration approximations, the method is applied in two correction steps, with a first compensation of large, low-order aberrations through the gradient-based linear SABRE followed by compensation of the remaining high-order aberrations with the intensity-based nonlinear SABRE.

  13. 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

  14. Curvature sensing with a Shack-Hartmann sensor

    NARCIS (Netherlands)

    Soloviev, O.A.; Verhaegen, M.H.G.; Vdovine, G.V.; Bonora, S

    2015-01-01

    Shack-Hartmann (SH) sensor, based on sampling of wavefront tilts in subapertures, is a simple, reliable, and widely used in adaptive optics wavefront sensor. A wavefront curvature sensor has the advantage of providing the results suitable for direct control of membrane and bimorph deformable mirrors

  15. Modal processing of Hartmann and Shack-Hartmann patterns by means of a least squares fitting of the transverse aberrations.

    Science.gov (United States)

    Hernández-Gómez, Geovanni; Malacara-Doblado, Daniel; Malacara-Hernández, Zacarías; Malacara-Hernández, Daniel

    2014-11-01

    Instead of measuring the wavefront deformations, Hartmann and Shack-Hartmann tests measure wavefront slopes, which are equivalent to ray transverse aberrations. Numerous integration methods have been described in the literature to obtain the wavefront deformations from these measurements. Basically, they can be classified in two different categories, i.e., modal and zonal. Frequently, a least squares fit of the transverse aberrations in the x direction and a least squares fit of the transverse aberrations in the y direction is performed to obtain the wavefront. In this work, we briefly describe a modal method to integrate Hartmann and Shack-Hartmann patterns by means of a single least squares fit of the transverse aberrations simultaneously instead of the traditional x-y separate method. The proposed method uses monomial calculation instead of using Zernike polynomials, to simplify numerical calculations. Later, a method is proposed to convert from monomials to Zernike polynomials. An important obtained result is that if polar coordinates are used, angular transverse aberrations are not actually needed to obtain all wavefront coefficients.

  16. Shack-Hartmann reflective micro profilometer

    Science.gov (United States)

    Gong, Hai; Soloviev, Oleg; Verhaegen, Michel; Vdovin, Gleb

    2018-01-01

    We present a quantitative phase imaging microscope based on a Shack-Hartmann sensor, that directly reconstructs the optical path difference (OPD) in reflective mode. Comparing with the holographic or interferometric methods, the SH technique needs no reference beam in the setup, which simplifies the system. With a preregistered reference, the OPD image can be reconstructed from a single shot. Also, the method has a rather relaxed requirement on the illumination coherence, thus a cheap light source such as a LED is feasible in the setup. In our previous research, we have successfully verified that a conventional transmissive microscope can be transformed into an optical path difference microscope by using a Shack-Hartmann wavefront sensor under incoherent illumination. The key condition is that the numerical aperture of illumination should be smaller than the numerical aperture of imaging lens. This approach is also applicable to characterization of reflective and slightly scattering surfaces.

  17. Towards Reconfigurable Wavefront Sensing Using a Spatial Light Modulator

    OpenAIRE

    Hieronymus, Jan; Augustin, Sven; Hübers, Heinz-Wilhelm

    2016-01-01

    Measuring the wavefront gives valuable insights into the characteristics of optical instruments. For example, imperfect wavefronts in astronomical instruments, resulting in image degradation, due to misalignment, component tolerances and so forth can be measured. A common device for wavefront sensing is the Hartmann sensor. It consists of a mask made from a regular grid of holes in an opaque substrate and an imaging sensor, onto which the diffraction patterns of the holes ar...

  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. Is Hartmann's the solution?

    National Research Council Canada - National Science Library

    White S.A; Goldhill D.R

    1997-01-01

    As Hartmann's solution is commonly used by anaesthetists, we surveyed a group of Part III FRCA candidates to establish their knowledge of its constituents and the purpose and metabolism of the lactate in solution...

  20. Is Hartmann's the solution?

    Science.gov (United States)

    White, S A; Goldhill, D R

    1997-05-01

    As Hartmann's solution is commonly used by anaesthetists, we surveyed a group of Part III FRCA candidates to establish their knowledge of its constituents and the purpose and metabolism of the lactate in solution. Of the 82 candidates surveyed only three (4%) accurately recorded the electrolytes and their concentrations in Hartmann's solution. Lactate was stated to be a source of bicarbonate by 52 (63%) and a source of glucose by 17 (21%). The descriptions of lactate metabolism were largely imprecise, none was complete and 24 (29%) of candidates offered no explanation. The constituents of Hartmann's solution and their concentrations are designed to match those of plasma, reducing ion and fluid shifts postinfusion. The lactate in Hartmann's solution is metabolised by both oxidation and gluconeogenesis, predominantly in the liver, and bicarbonate is generated by both processes over 1-2 h.

  1. Ultrashort-pulse wave-front autocorrelation.

    Science.gov (United States)

    Grunwald, R; Neumann, U; Griebner, U; Reimann, K; Steinmeyer, G; Kebbel, V

    2003-12-01

    Combined spatially resolved collinear autocorrelation and Shack-Hartmann wave-front sensing of femtosecond laser pulses is demonstrated for the first time to our knowledge. The beam is divided into multiple nondiffracting subbeams by thin-film micro-optical arrays. With hybrid refractive-reflective silica/silver microaxicons, wave-front autocorrelation is performed in oblique-angle reflection. Simultaneous two-dimensional detection of local temporal structure and wave-front tilt of propagating few-cycle wave packets is demonstrated.

  2. 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

  3. Curvature sensor for ocular wavefront measurement.

    Science.gov (United States)

    Díaz-Doutón, Fernando; Pujol, Jaume; Arjona, Montserrat; Luque, Sergio O

    2006-08-01

    We describe a new wavefront sensor for ocular aberration determination, based on the curvature sensing principle, which adapts the classical system used in astronomy for the living eye's measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann-Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.

  4. Extension of the modal wave-front reconstruction algorithm to non-uniform illumination.

    Science.gov (United States)

    Ma, Xiaoyu; Mu, Jie; Rao, ChangHui; Yang, Jinsheng; Rao, XueJun; Tian, Yu

    2014-06-30

    Attempts are made to eliminate the effects of non-uniform illumination on the precision of wave-front measurement. To achieve this, the relationship between the wave-front slope at a single sub-aperture and the distributions of the phase and light intensity of the wave-front were first analyzed to obtain the relevant theoretical formulae. Then, based on the principle of modal wave-front reconstruction, the influence of the light intensity distribution on the wave-front slope is introduced into the calculation of the reconstruction matrix. Experiments were conducted to prove that the corrected modal wave-front reconstruction algorithm improved the accuracy of wave-front reconstruction. Moreover, the correction is conducive to high-precision wave-front measurement using a Hartmann wave-front sensor in the presence of non-uniform illumination.

  5. Specialized wavefront sensors for adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Neal, D.R.; Mansell, J.D.; Gruetzner, J.K. [and others

    1995-08-01

    The performance of an adaptive optical system is strongly dependent upon correctly measuring the wavefront of the arriving light. The most common wavefront measurement techniques used to date are the shearing interferometer and the Shack-Hartmann sensor. Shack-Hartmann sensors rely on the use of lenslet arrays to sample the aperture appropriately. These have traditionally been constructed using ULM or step and repeat technology, and more recently with binary optics technology. Diffractive optics fabrication methodology can be used to remove some of the limitations of the previous technologies and can allow for low-cost production of sophisticated elements. We have investigated several different specialized wavefront sensor configurations using both Shack-Hartmann and shearing interferometer principles. We have taken advantage of the arbitrary nature of these elements to match pupil shapes of detector and telescope aperture and to introduce magnification between the lenslet array and the detector. We have fabricated elements that facilitate matching the sampling to the current atmospheric conditions. The sensors were designed using a far-field diffraction model and a photolithography layout program. They were fabricated using photolithography and RIE etching. Several different designs will be presented with some experimental results from a small-scale adaptive optics brass-board.

  6. Wavefront reconstruction in adaptive optics systems using nonlinear multivariate splines.

    Science.gov (United States)

    de Visser, Cornelis C; Verhaegen, Michel

    2013-01-01

    This paper presents a new method for zonal wavefront reconstruction (WFR) with application to adaptive optics systems. This new method, indicated as Spline based ABerration REconstruction (SABRE), uses bivariate simplex B-spline basis functions to reconstruct the wavefront using local wavefront slope measurements. The SABRE enables WFR on nonrectangular and partly obscured sensor grids and is not subject to the waffle mode. The performance of SABRE is compared to that of the finite difference (FD) method in numerical experiments using data from a simulated Shack-Hartmann lenslet array. The results show that SABRE offers superior reconstruction accuracy and noise rejection capabilities compared to the FD method.

  7. Shack-Hartmann and Interferometric Hybrid Wavefront Sensor

    Science.gov (United States)

    2011-03-24

    detector area Ad (or, equivalently, the intensity integrated over the detector solid angle) and integration time Td of the detector, and σ 2 W is the...Reprinted photographically in 1937, 1946 by Lowe & Brydone, Printers, LTD., London from sheets of the third edi - tion. 49. Noll, R.J. “Zernike polynomials and

  8. Laparoscopic reversal of Hartmann's procedure

    DEFF Research Database (Denmark)

    Svenningsen, Peter Olsen; Bulut, Orhan; Jess, Per

    2010-01-01

    A change in procedure from open to laparoscopic reversal of Hartmann's colostomy was implemented at our department between May 2005 and December 2008. The aim of the study was to investigate if this change was beneficial for the patients.......A change in procedure from open to laparoscopic reversal of Hartmann's colostomy was implemented at our department between May 2005 and December 2008. The aim of the study was to investigate if this change was beneficial for the patients....

  9. Design and performances of the Shack-Hartmann sensor within the Active Phasing Experiment

    Science.gov (United States)

    Mazzoleni, R.; Gonté, F.; Surdej, I.; Araujo, C.; Brast, R.; Derie, F.; Duhoux, P.; Dupuy, C.; Frank, C.; Karban, R.; Noethe, L.; Yaitskova, N.

    2008-07-01

    The Shack-Hartmann Phasing Sensor (SHAPS) has been integrated in the Active Phasing Experiment (APE) at ESO. It is currently under test in the laboratory. The tests on sky are foreseen for the end of 2008, when APE will be mounted at the Nasmyth focus of one of the VLT unit telescopes. SHAPS is based on the Shack-Hartmann principle: the lenslet array is located in a plane which is optically conjugated to the Active Segmented Mirror (ASM) of APE and is composed of two types of microlenses, circular and cylindrical, which give information about the wavefront slope and the piston steps, respectively. This proceeding contains a description of SHAPS and of the algorithms implemented for the wavefront reconstruction and for the phasing. The preliminary results obtained during the laboratory tests are discussed and compared with the theoretical predictions. The performances of SHAPS at the VLT and at the European Extremely Large Telescope (E-ELT) are estimated.

  10. Laparoscopic reversal of Hartmann's procedure

    DEFF Research Database (Denmark)

    Svenningsen, Peter Olsen; Bulut, Orhan; Jess, Per

    2010-01-01

    INTRODUCTION: A change in procedure from open to laparoscopic reversal of Hartmann's colostomy was implemented at our department between May 2005 and December 2008. The aim of the study was to investigate if this change was beneficial for the patients. MATERIAL AND METHODS: The medical records...... of all patients who underwent reversal of a colostomy after a primary Hartmann's procedure during the period May 2005 to December 2008 were reviewed retrospectively in a case-control study. RESULTS: A total of 43 patients were included. Twenty-one had a laparoscopic and 22 an open procedure. The two...... groups matched with regard to age, sex, American Society of Anestheologists (ASA) score, body mass index and indication for Hartmann's operation. A significantly longer operation time was found for laparoscopic than for open surgery (median 285 versus 158 minutes, p

  11. Optimization of zonal wavefront estimation and curvature measurements

    Science.gov (United States)

    Zou, Weiyao

    -number grid sizes for all geometries. The Fried geometry either allows sub-sized wavefront estimations within the testing domain or yields a two-rank deficient estimation matrix over the full aperture; but the latter usually suffers from high error propagation and the waffle mode problem. Hudgin geometry offers an error propagator between those of the Southwell and the Fried geometries. For both wavefront gradient-based and wavefront difference-based estimations, the Southwell geometry is shown to offer the lowest error propagation with the minimum-norm least-squares solution. Noll's theoretical result, which was extensively used as a reference in the previous literature for error propagation estimate, corresponds to the Southwell geometry with an odd-number grid size. For curvature-based wavefront sensing, a concept for a differential Shack-Hartmann (DSH) curvature sensor is proposed. This curvature sensor is derived from the basic Shack-Hartmann sensor with the collimated beam split into three output channels, along each of which a lenslet array is located. Three Hartmann grid arrays are generated by three lenslet arrays. Two of the lenslets shear in two perpendicular directions relative to the third one. By quantitatively comparing the Shack-Hartmann grid coordinates of the three channels, the differentials of the wavefront slope at each Shack-Hartmann grid point can be obtained, so the Laplacian curvatures and twist terms will be available. The acquisition of the twist terms using a Hartmann-based sensor allows us to uniquely determine the principal curvatures and directions more accurately than prior methods. Measurement of local curvatures as opposed to slopes is unique because curvature is intrinsic to the wavefront under test, and it is an absolute as opposed to a relative measurement. A zonal least-squares-based wavefront estimation algorithm was developed to estimate the wavefront shape from the Laplacian curvature data, and validated. An implementation of the DSH

  12. Transmitted wavefront testing of complex optics

    Science.gov (United States)

    Williby, Gregory Allen

    The advancement of optical systems arises from furthering at least one of the three fields of optical development: design, fabrication, and testing. One example of such advancement is the growth in customization of contact lenses, which is occurring in part due to advances in testing. Due to the diverse quantities that can be derived from it, the transmitted wavefront is the tested parameter. There are a number of tests that can evaluate a transmitted wavefront, including moire deflectometry, Shack-Hartmann wavefront sensing, and interferometry. Interferometry is preferred for its sensitivity and spatial resolution. The dynamic range issue is mitigated by the required immersion of the contact lenses in saline due to the complex nature of the lens material. The partial index-match between the lens and surrounding saline reduces the measured power of the lens and enables testing in an absolute, or non-null, configuration. Absolute testing allows for the generation of ophthalmic prescriptions and power maps from the transmitted wavefront. Designing a non-null interferometer is based on three principles. The transmitted light must be collected, the resulting interference must be resolved, and the imaged wavefront must be calibrated. The first two principles are fulfilled by proper choices for the imaging lens and detector. Calibration comes from removing the wavefront-dependent induced aberrations via reverse raytracing. Reverse raytracing demands an accurate model of the interferometer. With such a model, theoretical wavefronts can be produced and compared to measured wavefronts. The difference between measured and modeled wavefronts quantifies the answer to the fundamental question in transmitted wavefront testing: does the optic perform as desired? Immersion in index-matching fluid provides an adjustable increase in the dynamic range of the interferometer. The increase comes at the expense of sensitivity. The tradeoff between dynamic range and sensitivity can be

  13. Comparative study of infrared wavefront sensing solutions for adaptive optics

    Science.gov (United States)

    Plantet, C.; Fusco, T.; Guerineau, N.; Derelle, S.; Robert, C.

    2016-07-01

    The development of new low-noise infrared detectors, such as RAPID (CEA LETI/Sofradir) or SAPHIRA (Selex), has given the possibility to consider infrared wavefront sensing at low ux. We propose here a comparative study of near infrared (J and H bands) wavefront sensing concepts for mid and high orders estimation on a 8m- class telescope, relying on three existing wavefront sensors: the Shack-Hartmann sensor, the pyramid sensor and the quadri-wave lateral shearing interferometer. We consider several conceptual designs using the RAPID camera, making a trade-off between background flux, optical thickness and compatibility with a compact cryostat integration. We then study their sensitivity to noise in order to compare them in different practical scenarios. The pyramid provides the best performance, with a gain up to 0.5 magnitude, and has an advantageous setup.

  14. Modeling of high-precision wavefront sensing with new generation of CMT avalanche photodiode infrared detectors.

    Science.gov (United States)

    Gousset, Silvère; Petit, Cyril; Michau, Vincent; Fusco, Thierry; Robert, Clelia

    2015-12-01

    Near-infrared wavefront sensing allows for the enhancement of sky coverage with adaptive optics. The recently developed HgCdTe avalanche photodiode arrays are promising due to their very low detector noise, but still present an imperfect cosmetic that may directly impact real-time wavefront measurements for adaptive optics and thus degrade performance in astronomical applications. We propose here a model of a Shack-Hartmann wavefront measurement in the presence of residual fixed pattern noise and defective pixels. To adjust our models, a fine characterization of such an HgCdTe array, the RAPID sensor, is proposed. The impact of the cosmetic defects on the Shack-Hartmann measurement is assessed through numerical simulations. This study provides both a new insight on the applicability of cadmium mercury telluride (CMT) avalanche photodiodes detectors for astronomical applications and criteria to specify the cosmetic qualities of future arrays.

  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. Fiber coupler end face wavefront surface metrology

    Science.gov (United States)

    Compertore, David C.; Ignatovich, Filipp V.; Marcus, Michael A.

    2015-09-01

    Despite significant technological advances in the field of fiber optic communications, one area remains surprisingly `low-tech': fiber termination. In many instances it involves manual labor and subjective visual inspection. At the same time, high quality fiber connections are one of the most critical parameters in constructing an efficient communication link. The shape and finish of the fiber end faces determines the efficiency of a connection comprised of coupled fiber end faces. The importance of fiber end face quality becomes even more critical for fiber connection arrays and for in the field applications. In this article we propose and demonstrate a quantitative inspection method for the fiber connectors using reflected wavefront technology. The manufactured and polished fiber tip is illuminated by a collimated light from a microscope objective. The reflected light is collected by the objective and is directed to a Shack-Hartmann wavefront sensor. A set of lenses is used to create the image of the fiber tip on the surface of the sensor. The wavefront is analyzed by the sensor, and the measured parameters are used to obtain surface properties of the fiber tip, and estimate connection loss. For example, defocus components in the reflected light indicate the presence of bow in the fiber end face. This inspection method provides a contact-free approach for quantitative inspection of fiber end faces and for estimating the connection loss, and can potentially be integrated into a feedback system for automated inspection and polishing of fiber tips and fiber tip arrays.

  17. 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.

  18. Integrated Wavefront Corrector Project

    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...

  19. Wavefront reconstruction method based on wavelet fractal interpolation for coherent free space optical communication

    Science.gov (United States)

    Zhang, Dai; Hao, Shiqi; Zhao, Qingsong; Zhao, Qi; Wang, Lei; Wan, Xiongfeng

    2018-03-01

    Existing wavefront reconstruction methods are usually low in resolution, restricted by structure characteristics of the Shack Hartmann wavefront sensor (SH WFS) and the deformable mirror (DM) in the adaptive optics (AO) system, thus, resulting in weak homodyne detection efficiency for free space optical (FSO) communication. In order to solve this problem, we firstly validate the feasibility of liquid crystal spatial light modulator (LC SLM) using in an AO system. Then, wavefront reconstruction method based on wavelet fractal interpolation is proposed after self-similarity analysis of wavefront distortion caused by atmospheric turbulence. Fast wavelet decomposition is operated to multiresolution analyze the wavefront phase spectrum, during which soft threshold denoising is carried out. The resolution of estimated wavefront phase is then improved by fractal interpolation. Finally, fast wavelet reconstruction is taken to recover wavefront phase. Simulation results reflect the superiority of our method in homodyne detection. Compared with minimum variance estimation (MVE) method based on interpolation techniques, the proposed method could obtain superior homodyne detection efficiency with lower operation complexity. Our research findings have theoretical significance in the design of coherent FSO communication system.

  20. Bilinear wavefront transformation.

    Science.gov (United States)

    Dillon, Keith

    2009-08-01

    Truncated expansions such as Zernike polynomials provide a powerful approach for describing wavefront data. However, many simple calculations with data in this form can require significant computational effort. Important examples include recentering, renormalizing, and translating the wavefront data. This paper describes a technique whereby these operations and many others can be performed with a simple matrix approach using monomials. The technique may be applied to other expansions by reordering the data and applying transformations. The key is the use of the vectorization operator to convert data between vector and matrix descriptions. With this conversion, one-dimensional polynomial techniques may be employed to perform separable operations. Examples are also given for differentiation and integration of wavefronts.

  1. Advanced Wavefront Control Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, S S; Brase, J M; Avicola, K; Thompson, C A; Kartz, M W; Winters, S; Hartley, R; Wihelmsen, J; Dowla, F V; Carrano, C J; Bauman, B J; Pennington, D M; Lande, D; Sawvel, R M; Silva, D A; Cooke, J B; Brown, C G

    2001-02-21

    Programs at LLNL that involve large laser systems--ranging from the National Ignition Facility to new tactical laser weapons--depend on the maintenance of laser beam quality through precise control of the optical wavefront. This can be accomplished using adaptive optics, which compensate for time-varying aberrations that are often caused by heating in a high-power laser system. Over the past two decades, LLNL has developed a broad capability in adaptive optics technology for both laser beam control and high-resolution imaging. This adaptive optics capability has been based on thin deformable glass mirrors with individual ceramic actuators bonded to the back. In the case of high-power lasers, these adaptive optics systems have successfully improved beam quality. However, as we continue to extend our applications requirements, the existing technology base for wavefront control cannot satisfy them. To address this issue, this project studied improved modeling tools to increase our detailed understanding of the performance of these systems, and evaluated novel approaches to low-order wavefront control that offer the possibility of reduced cost and complexity. We also investigated improved beam control technology for high-resolution wavefront control. Many high-power laser systems suffer from high-spatial-frequency aberrations that require control of hundreds or thousands of phase points to provide adequate correction. However, the cost and size of current deformable mirrors can become prohibitive for applications requiring more than a few tens of phase control points. New phase control technologies are becoming available which offer control of many phase points with small low-cost devices. The goal of this project was to expand our wavefront control capabilities with improved modeling tools, new devices that reduce system cost and complexity, and extensions to high spatial and temporal frequencies using new adaptive optics technologies. In FY 99, the second year of

  2. Reversal of Hartmann's procedure following acute diverticulitis: is timing everything?

    LENUS (Irish Health Repository)

    Fleming, Fergal J

    2012-02-01

    BACKGROUND: Patients who undergo a Hartmann\\'s procedure may not be offered a reversal due to concerns over the morbidity of the second procedure. The aims of this study were to examine the morbidity post reversal of Hartmann\\'s procedure. METHODS: Patients who underwent a Hartmann\\'s procedure for acute diverticulitis (Hinchey 3 or 4) between 1995 and 2006 were studied. Clinical factors including patient comorbidities were analysed to elucidate what preoperative factors were associated with complications following reversal of Hartmann\\'s procedure. RESULTS: One hundred and ten patients were included. Median age was 70 years and 56% of the cohort were male (n = 61). The mortality and morbidity rate for the acute presentation was 7.3% (n = 8) and 34% (n = 37) respectively. Seventy six patients (69%) underwent a reversal at a median of 7 months (range 3-22 months) post-Hartmann\\'s procedure. The complication rate in the reversal group was 25% (n = 18). A history of current smoking (p = 0.004), increasing time to reversal (p = 0.04) and low preoperative albumin (p = 0.003) were all associated with complications following reversal. CONCLUSIONS: Reversal of Hartmann\\'s procedure can be offered to appropriately selected patients though with a significant (25%) morbidity rate. The identification of potential modifiable factors such as current smoking, prolonged time to reversal and low preoperative albumin may allow optimisation of such patients preoperatively.

  3. 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.

  4. Design, validation and application of an ocular Shack-Hartmann aberrometer

    Science.gov (United States)

    Straub, Jochen

    The design and testing of an ocular Shack-Hartmann aberrometer is presented. The aberrometer objectively measures optical aberrations in the human eye in vivo. The sensor was successfully tested for measurements of refractive error (sphere and cylinder) and spherical aberration. Vignetting limits the measurement range of the wavefront to a range of -10 D to +15 D. Large refractive errors and decentration of the measurement induce aberrations in the test wavefront. Analytical tools to correct for these systematic errors were developed. A clinical study was conducted assessing visual performance in 158 eyes of 89 subjects before and after LARK refractive surgery. The main results of the study were that refractive surgery corrects refractive errors very accurately. A slight regression in refraction during the 12 months after surgery was noted. Measurements of ocular aberrations using the Shack-Hartmann aberrometer revealed that refractive surgery introduced large amounts of higher order aberrations, mainly spherical aberration and coma. The amount of aberrations changed significantly during the 12 months wound healing period. The dark adapted pupil diameter of the eye increased significantly during the first 6 months after surgery. The changes in ocular aberrations and pupil diameter were correlated to changes in contrast sensitivity in the human eye. The analysis of corneal topography showed that while the anterior corneal curvature changed due to surgery, we also saw a change in the posterior corneal curvature as a biomechanical response to surgery. A Customized Eye Model was designed and tested based on the clinical measurements. The model used conic surfaces and modeled defocus and spherical aberration. This computer eye model was then used in optical lens design software to calculate an optimal Customized Ablation Pattern for individual eyes.

  5. The simulation of turbulence effect based on the technology of optical wavefront control

    Science.gov (United States)

    Zhao, Hongming; Fei, Jindong; Du, Huijie; Yu, Hong; Du, Jian; Hu, Xinqi; Dong, Bing

    2013-09-01

    In the process of high-resolution astronomical observation and space optical mapping, the wavefront aberrations caused by atmosphere turbulence effect lead to reduced resolution of optical imaging sensor. Firstly, on the base of influence of atmosphere turbulence effect for the optical observation system, this paper investigates and analyses the development and technical characteristics of deformable mirror, which is the key device of optical wavefront control technology. In this part, the paper describes the basic principles of wavefront control and measurement using the current production line of deformable mirror, including micro-electromechanical systems (MEMS) deformable mirror which is one of the most promising technology for wavefront modulation and Shack-Hartmann wavefront sensors. Secondly, a new method based on the technology of optical wavefront control and the data of optical path difference (OPD) for simulating the effect of optical transmission induced by turbulence is presented in this paper. The modeling and characteristics of atmosphere turbulence effect applied for optical imagery detector of astronomical observation and space optical mapping has been obtained. Finally, based on the theory model of atmosphere turbulence effects and digital simulation results, a preliminary experiment was done and the results verify the feasibility of the new method. The OPD data corresponding to optical propagation effect through turbulent atmosphere can be achieved by the calculation based on the method of ray-tracing and principle of physical optics. It is a common practice to decompose aberrated wavefronts in series over the Zernike polynomials. These data will be applied to the drive and control of the deformable mirror. This kind of simulation method can be applied to simulate the optical distortions effect, such as the dithering and excursion of light spot, in the space based earth observation with the influence of turbulent atmosphere. With the help of the

  6. Simulating the Effects of an Extended Source on the Shack-Hartmann Wavefront Sensor Through Turbulence

    Science.gov (United States)

    2011-03-01

    with extended sources. iv AFIT/GE/ENG/11-08 I dedicate this work to my father, whose successful battle with cancer this year inspired my to see this...gr id 9 [ Th2 r2 ] = ca r t 2po l ( x2 , y2 ) ; % convert to po la r coords 10 11 E gaus = emf i e ld ( U gaus s , wvl , N*∆1 ) ; % Make f i e l d...n ) ; % gr id 13 [ Th2 r2 ] = ca r t2po l ( x2 , y2 ) ; 14 15 E gaus = emf i e ld ( U gaus s , wvl , N*∆1 ) ; % Make f i e l d f o r WaveProp 16

  7. 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...

  8. 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.

  9. Compound sodium lactate (Hartmann's) solution. Caution: risk of clotting.

    Science.gov (United States)

    Edwards, M P; Clark, D J; Mark, J S; Wyld, P J

    1986-10-01

    We have observed blood clotting in blood administration sets where Hartmann's solution (Travenol) has preceded blood transfusion. This is due to calcium ions (Ca++) contained in the Hartmann's solution and is more likely to occur at 37 degrees C. We suggest that this potential hazard be more widely realised and that the practice cease.

  10. Morbidity and Mortality of Hartmann's Procedure for Sigmoid ...

    African Journals Online (AJOL)

    Background: The restoration of intestinal continuity following Hartmann's procedure is associated with high morbidity and mortality rates and low restoration rate. Objective: To determine the causes of complications and deaths associated with Hartmann's procedure and the secondary restoration of digestive continuity for ...

  11. 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.

  12. In-vivo digital wavefront sensing using swept source OCT.

    Science.gov (United States)

    Kumar, Abhishek; Wurster, Lara M; Salas, Matthias; Ginner, Laurin; Drexler, Wolfgang; Leitgeb, Rainer A

    2017-07-01

    Sub-aperture based digital adaptive optics is demonstrated in a fiber based point scanning optical coherence tomography system using a 1060 nm swept source laser. To detect optical aberrations in-vivo, a small lateral field of view of ~[Formula: see text] is scanned on the sample at a high volume rate of 17 Hz (~1.3 kHz B-scan rate) to avoid any significant lateral and axial motion of the sample, and is used as a "guide star" for the sub-aperture based DAO. The proof of principle is demonstrated using a micro-beads phantom sample, wherein a significant root mean square wavefront error (RMS WFE) of 1.48 waves (> 1[Formula: see text]) is detected. In-vivo aberration measurement with a RMS WFE of 0.33 waves, which is ~5 times higher than the Marechal's criterion of [Formula: see text] waves for the diffraction limited performance, is shown for a human retinal OCT. Attempt has been made to validate the experimental results with the conventional Shack-Hartmann wavefront sensor within reasonable limitations.

  13. Enhancing wavefront estimation accuracy by using higher-order iterative compensations in the Southwell configuration.

    Science.gov (United States)

    Guang, Hui; Wang, Yajun; Zhang, Lianxin; Li, Lulu; Li, Ming; Ji, Linhong

    2017-03-10

    Accurate wavefront integration based on gradient fields is crucial for various indirect measurement techniques, such as Shack-Hartmann sensing, shearography, and the fringe reflection technique. In this paper, a higher-order iterative compensation algorithm is proposed to enhance the reconstruction accuracy for the finite-difference-based least-squares integration (FLI) method. In this method, higher-order gradient fields are reconstructed and the calculated residual gradient fields compensate the truncation error with the traditional FLI by iterations. A comparison of different FLI methods, including traditional FLI, iterative FLI, higher-order FLI, and the proposed FLI method, is conducted. The result shows that the reconstructed wavefront with the proposed method is more accurate than those with other FLI methods. In addition, the impact of the gradient measurement noise is also discussed.

  14. Large-optics shearing interferometer for the wavefront sensing of widely tunable laser

    Science.gov (United States)

    Luan, Zhu; Wang, Lijuan; Zhou, Yu; Dai, Enwen; Sun, Jianfeng; Liu, Liren

    2010-08-01

    There is large aperture and diffraction-limited laser beam in the space laser applications such as laser communication. Laser wavefront can be measured by shearing interferometer or Shark-Hartmann sensor etc. Large-Optics shearing interferometer based on Mach-Zehnder plate structure has been manufactured to differentially analyze the laser wavefront from two parts of aperture-divided fringes. One of six optical plates of the interferometer is divided to the up part and the down. The precision of measurement is higher than the full aperture design. It is suitable for the diameter below 290mm with the changeable shear amount from 1mm to 150mm. There are two sets of collimators used for the parallel of the plates. Another single-mode 635nm laser collimator which is measured through double-shearing plate before is serving as a standard wavefront of 150mm diameter. One path of the interference is changed with precise adjustment unit in several microns that the interference may be happened between equal optical path reflection and the other. It can be used for widely tunable laser and other laser system which has short coherent length. The apparatus and the experiments are explained in detail in this paper. Many systems of different quality and diameter and coherent length are measured by the large-optics shearing interferometer. The experimental wavefront results are fitted to Zernike polynomial and the Zernike coefficients are derived.

  15. Lavastaja, kes ei vasta ootustele : Sebastian Hartmann Saksamaalt / Eero Epner

    Index Scriptorium Estoniae

    Epner, Eero, 1978-

    2006-01-01

    6. apr. NO99 teatris esietendunud NO92 Andrei Tarkovski ja vendade Strugatskite stsenaariumi järgi loodud filmil põhinevast lavastusest "Stalker", lavastaja Sebastian Hartmann ja kunstnik Peter Schubert (mõlemad Saksamaalt)

  16. 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.

  17. Wavefront reconstruction by modal decomposition

    CSIR Research Space (South Africa)

    Schulze, C

    2012-08-01

    Full Text Available We propose a new method to determine the wavefront of a laser beam based on modal decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes...

  18. Hartmann's "Ego Psychology and the Problem of Adaptation".

    Science.gov (United States)

    Friedman, L

    1989-10-01

    Hartmann's monograph is an argument for the problem-solving value of all aspects of the mind and for the subordination of intelligence to the organism's larger, primarily social purposes. Hartmann proposed that, in psychoanalytic treatment, intelligent reflection serves one's largest purposes by taking respectful account of non-rational but adaptive ways of appraising reality, with a view toward making the best use of non-rational as well as rational propensities. He regarded it as the kind of thinking that the sociologist, Karl Mannheim, had recommended to government planners faced with immensely complicated, incompletely masterable forces. Hartmann's view of the role of the intellect in analytic treatment suggests that therapists should maintain both their demand for intelligent reflection and their hopefulness about other kinds of work that may be going on sub rosa.

  19. 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.

  20. Data-based online nonlinear extremum-seeker for wavefront sensorless adaptive optics OCT (Conference Presentation)

    Science.gov (United States)

    Jian, Yifan; Verstraete, Hans R. G. W.; Heisler, Morgan; Ju, Myeong Jin; Wahl, Daniel J.; Bliek, Laurens; Kalkman, Jeroen; Bonora, Stefano; Verhaegen, Michel; Sarunic, Marinko V.

    2017-02-01

    Adaptive optics has been successfully applied to cellular resolution imaging of the retina, enabling visualization of the characteristic mosaic patterns of the outer retina. Wavefront sensorless adaptive optics (WSAO) is a novel technique that facilitates high resolution ophthalmic imaging; it replaces the Hartmann-Shack Wavefront Sensor with an image-driven optimization algorithm and mitigates some the challenges encountered with sensor-based designs. However, WSAO generally requires longer time to perform aberrations correction than the conventional closed-loop adaptive optics. When used for in vivo retinal imaging applications, motion artifacts during the WSAO optimization process will affect the quality of the aberration correction. A faster converging optimization scheme needs to be developed to account for rapid temporal variation of the wavefront and continuously apply corrections. In this project, we investigate the Databased Online Nonlinear Extremum-seeker (DONE), a novel non-linear multivariate optimization algorithm in combination with in vivo human WSAO OCT imaging. We also report both hardware and software updates of our compact lens based WSAO 1060nm swept source OCT human retinal imaging system, including real time retinal layer segmentation and tracking (ILM and RPE), hysteresis correction for the multi-actuator adaptive lens, precise synchronization control for the 200kHz laser source, and a zoom lens unit for rapid switching of the field of view. Cross sectional images of the retinal layers and en face images of the cone photoreceptor mosaic acquired in vivo from research volunteers before and after WSAO optimization are presented.

  1. Effect of Hartmann layer resolution for MHD flow in a straight ...

    Indian Academy of Sciences (India)

    Home; Journals; Sadhana; Volume 40; Issue 3. Effect of Hartmann layer resolution for ... For high Hartmann number flows through electrically conducting channels, majority of the current loops close through the walls and the Hartmann layer contributes only a small fraction of the global current path. Hence, the effect on flow ...

  2. Describing ocular aberrations with wavefront vergence maps.

    Science.gov (United States)

    Nam, Jayoung; Thibos, Larry N; Iskander, D Robert

    2009-05-01

    A common optometric problem is to specify the eye's ocular aberrations in terms of Zernike coefficients and to reduce that specification to a prescription for the optimum sphero-cylindrical correcting lens. The typical approach is first to reconstruct wavefront phase errors from measurements of wavefront slopes obtained by a wavefront aberrometer. This paper applies a new method to this clinical problem that does not require wavefront reconstruction. Instead, we base our analysis of axial wavefront vergence as inferred directly from wavefront slopes. The result is a wavefront vergence map that is similar to the axial power maps in corneal topography and hence has a potential to be favoured by clinicians. We use our new set of orthogonal Zernike slope polynomials to systematically analyse details of the vergence map analogous to Zernike analysis of wavefront maps. The result is a vector of slope coefficients that describe fundamental aberration components. Three different methods for reducing slope coefficients to a spherocylindrical prescription in power vector forms are compared and contrasted. When the original wavefront contains only second order aberrations, the vergence map is a function of meridian only and the power vectors from all three methods are identical. The differences in the methods begin to appear as we include higher order aberrations, in which case the wavefront vergence map is more complicated. Finally, we discuss the advantages and limitations of vergence map representation of ocular aberrations.

  3. 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

  4. Measurement and compensation of laser-induced wavefront deformations and focal shifts in near IR optics.

    Science.gov (United States)

    Stubenvoll, Martin; Schäfer, Bernd; Mann, Klaus

    2014-10-20

    We demonstrate the feasibility of passive compensation of the thermal lens effect in fused silica optics, placing suitable optical materials with negative dn/dT in the beam path of a high power near IR fiber laser. Following a brief overview of the involved mechanisms, photo-thermal absorption measurements with a Hartmann-Shack sensor are described, from which coefficients for surface/coating and bulk absorption in various materials are determined. Based on comprehensive knowledge of the 2D wavefront deformations resulting from absorption, passive compensation of thermally induced aberrations in complex optical systems is possible, as illustrated for an F-Theta objective. By means of caustic measurements during high-power operation we are able to demonstrate a 60% reduction of the focal shift in F-Theta lenses through passive compensation.

  5. Wavefront coding for visual optics

    Science.gov (United States)

    Acosta, E.; Arines, J.; Almaguer, C.

    2017-08-01

    Wavefront coding (WFC) enables the depth of field of incoherent optical systems to be extended. This method involves a cubic-phase plate in the system yielding a blurred image nearly invariant to defocus. In visual optics there is a big interest in improving solutions for two different problems: Presbyopia correction and high resolution retinal images with low cost devices. In this work we will show how the use of cubic phases in contact lenses can be an alternative to multifocal lenses and how WFC technique can be applied to record high resolution retinal images reducing the complexity of the actual systems

  6. Atomization in the Acoustic Field of a Hartmann Whistle

    Directory of Open Access Journals (Sweden)

    S. Narayanan

    2013-03-01

    Full Text Available The current work experimentally investigates the effect of Hartmann cavity acoustics on the atomization of droplet sprays. Initially, the experiments are conducted on a single droplet to understand its behavior in the sound field of a Hartmann whistle. The atomization studies on single droplet reveal that the existence of sound field causes the droplet to undergo large deformation and become irregular in shape. The degree of droplet deformation is quantified based on smaller circularity and larger Feret's diameter. The increase in cone angle of spray to a higher value in the presence of acoustics in comparison to its absence shows that the acoustics enhances the atomization. The stroboscopic visualization of sprays in the presence of acoustics further reveals the breakup of ligaments, large scatter as well as the formation of more number of droplets, indicating atomization enhancement.

  7. Hyperglycaemic effects of Hartmann's solution during surgery in patients with maturity onset diabetes.

    Science.gov (United States)

    Thomas, D J; Alberti, K G

    1978-02-01

    The metabolic effect of infusing 1.0-1.5 litre of Hartmann's solution to normal subjects and those with maturity onset diabetes has been studied during surgery. It was found that the use of Hartmann's solution after operation was associated with a 7.5 mmol litre-u increase in plasm glucose concentration compared with an increase of 2.1 mmol litre-1 in diabetic patients who received no i.v. fluids. In non-diabetic subjects who received Hartmann's solution the increase was 2.5 mmol litre-1. It is suggested that Hartmann's solution may be metabolically disadvantageous in diabetic patients.

  8. 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.

  9. Hartmann test of the COMPASS RICH-1 optical telescopes

    CERN Document Server

    Polak, J; Alekseev, M; Angerer, H; Apollonio, M; Birsa, R; Bordalo, P; Bradamante, F; Bressan, A; Busso, L; Chiosso, V M; Ciliberti, P; Colantoni, M L; Costa, S; Dibiase, N; Dafni, T; Dalla Torre, S; Diaz, V; Duic, V; Delagnes, E; Deschamps, H; Eyrich, W; Faso, D; Ferrero, A; Finger, M; Finger, M Jr; Fischer, H; Gerassimov, S; Giorgi, M; Gobbo, B; Hagemann, R; von Harrach, D; Heinsius, F H; Joosten, R; Ketzer, B; Königsmann, K; Kolosov, V N; Konorov, I; Kramer, D; Kunne, F; Levorato, S; Maggiora, A; Magnon, A; Mann, A; Martin, A; Rebourgeard, P; Mutter, A; Nähle, O; Neyret, D; Nerling, F; Pagano, P; Paul, S; Panebianco, S; Panzieri, D; Pesaro, G; Pizzolotto, C; Menon, G; Rocco, E; Robinet, F; Schiavon, P; Schill, C; Schoenmeier, P; Silva, L; Slunecka, M; Steiger, L; Sozzi, F; Sulc, M; Svec, M; Tessarotto, F; Teufel, A; Wollny, H

    2008-01-01

    The central region of COMPASS RICH-1 has been equipped with a new photon detection system based on MultiAnode PhotoMultiplier Tubes (MAPMT). The Cherenkov photons are focused by an array of 576 fused silica telescopes onto 576 MAPMTs. The quality and positioning of all optical components have been tested by Hartmann method. The validation procedures are described. The quality of the optical concentrators was checked and alignment corrections were made. The upgraded detector showed excellent performances during 2006 data taking.

  10. 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.

  11. Life Cycle Management at Brødrene Hartmann A/S - strategy,- organisation and implementation

    DEFF Research Database (Denmark)

    Pedersen, Claus Stig; Alting, Leo; Mortensen, Anna Lise

    1997-01-01

    decisionmaking is under development.The implementation of life cycle management in Hartmann is organised with respect to the divisional areas: strategic management, product development, purchase, production, sale and distribution. The implementation of life cycle managment is assisted by tools to support......Brdr. Hartmann A/S is an international company with subsidiaries and licensed factories worldwide. Hartmann specializes in packaging made of recycled paper. For several years Hartmann has practised life cycle management in order to improve the environmental profile of the products by minimizing...... the total environmental impacts and resource consumptions throughout the full life cycle of the products, with respect to economy and quality.The concept of life cycle management is implemented in Hartmanns environmental strategy and an organisation to take care of the implementation in the every day...

  12. For an aesthetics of communication: Interview with Frank Hartmann Por uma estética da comunicação: entrevista com Frank Hartmann

    Directory of Open Access Journals (Sweden)

    Lucia Leao

    2011-07-01

    Full Text Available In August 18, 2010, Frank Hartmann was present at the Post Graduate Program in Communication and Semiotics of PUC-SP, where he lectured on the following theme: “Towards an aesthetics of communication”. Frank Hartmann is full professor at the Bauhaus University, Weimar in Germany and external faculty member at the Dept. of Communication, University of Vienna, Austria. He is the author, among others, of: Medien und Kommunikation (2008; Mediologie - Ansatz einer der Medientheorie Kulturwissenschaften (2003, and Medienphilosophie (2000. More information on his website: http://www.medienphilosophie.net/f_hartmann.htmlFrank Hartmann esteve no dia 18 de agosto de 2010 no Programa de Pós-Graduação em Comunicação e Semiótica da PUC-SP, onde proferiu a palestra “Towards an aesthetics of communication”. Hartmann é professor titular da Universidade Bauhaus, em Weimar, na Alemanha e professor convidado do Departamento de Comunicação da Universidade de Viena, na Áustria. É autor, entre outros, de: Medien und Kommunikation (2008; Mediologie – Ansätze einer Medientheorie der Kulturwissenschaften (2003; e Medienphilosophie (2000. Mais informações em seu site: http://www.medienphilosophie.net/f_hartmann.html

  13. Sonographically guided hydrostatic reduction of childhood intussusception using Hartmann's solution.

    Science.gov (United States)

    Peh, W C; Khong, P L; Chan, K L; Lam, C; Cheng, W; Lam, W W; Mya, G H; Saing, H; Leong, L L; Low, L C

    1996-11-01

    Currently, the standard methods for therapeutic reduction of intussusception in children involve considerable ionizing radiation. This study tested the effectiveness of sonographically guided hydrostatic reduction of intussusception using Hartmann's solution, a fluid with near-physiologic composition. Between March 1, 1994, and January 31, 1996, all children clinically suspected of having intussusception were evaluated by sonography. Those with positive findings on sonography were entered into the study and underwent confirmatory sonographically guided meglumine diatrizoate enema. During continuous sonographic monitoring, we used Hartmann's solution for attempted reduction of intussusception. Criteria for successful reduction were disappearance of the intussusceptum and passage of fluid through the ileocecal valve. Another sonographically guided meglumine diatrizoate enema was used to confirm successful reduction. We detected 25 consecutive intussusceptions in 22 patients. The patients were 12 girls and 10 boys, with a mean age of 14 months (range, 1-72 months). Sonograms revealed in all patients doughnut or pseudokidney signs or both. The sites of intussusception were the transverse colon (17 of 25), hepatic flexure (4 of 25), ascending colon (2 of 25), splenic flexure (1 of 25), and descending colon (1 of 25). Other findings were dilated fluid-filled small bowel (11 of 25) and free intraperitoneal fluid (9 of 25). The success rate of our sonographically guided attempts at hydrostatic reduction was 76% (19 of 25). Success was proven by meglumine diatrizoate enema in all 19 patients. The mean time of the reduction procedure was 18 min (range, 2-45 min). No complications occurred. All six patients in whom hydrostatic reduction was unsuccessful underwent surgery. Five of these patients had ileoileocolic intussusceptions. On sonography, when surrounded by fluid, ileoileocolic intussusceptions had a typically complex, fronded appearance. The remaining patient in whom

  14. Hyper Suprime-Cam: autoguider and Shack-Hartmann systems

    Science.gov (United States)

    Morokuma, Tomoki; Komiyama, Yutaka; Miyazaki, Satoshi; Nakaya, Hidehiko; Furusawa, Hisanori; Tomono, Daigo; Kawanomoto, Satoshi; Tanaka, Yoko

    2008-07-01

    We present methodology of the autoguider (AG) and Shack-Hartmann (SH) sensing systems which will be used for a wide-field camera, Hyper Suprime-Cam (HSC), on the prime focus of the Subaru 8.2-m telescope. For both systems, stellar images are formed on the HSC science CCDs. Although light from AG stars must pass through bandpass filters, we can obtain enough photons for AG stars brighter than mAB autoguiding. Spatial number density of such bright stars from the SDSS database requires an area of about two 2k×4k CCDs for AG stars. The optics of SH system except for the imaging CCDs is located within the HSC filter unit.

  15. 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.

  16. 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.

  17. (Ab)normal saline and physiological Hartmann's solution: a randomized double-blind crossover study.

    Science.gov (United States)

    Reid, Fiona; Lobo, Dileep N; Williams, Robert N; Rowlands, Brian J; Allison, Simon P

    2003-01-01

    In this double-blind crossover study, the effects of bolus infusions of 0.9% saline (NaCl) and Hartmann's solution on serum albumin, haematocrit and serum and urinary biochemistry were compared in healthy subjects. Nine young adult male volunteers received 2-litre intravenous infusions of 0.9% saline and Hartmann's solution on separate occasions, in random order, each over 1 h. Body weight, haematocrit and serum biochemistry were measured pre-infusion and at 1 h intervals for 6 h. Biochemical analysis was performed on pooled post-infusion urine. Blood and plasma volume expansion, estimated by dilutional effects on haematocrit and serum albumin, were greater and more sustained after saline than after Hartmann's solution (P Hartmann's solution. Subjects voided more urine (median: 1,000 compared with 450 ml) of higher sodium content (median: 122 compared with 73 mmol) after Hartmann's than after saline (both P =0.049), despite the greater sodium content of the latter. The time to first micturition was less after Hartmann's than after saline (median: 70 compared with 185 min; P =0.008). There were no significant differences between the effects of the two solutions on serum sodium, potassium, urea or osmolality. After saline, all subjects developed hyperchloraemia (>105 mmol/l), which was sustained for >6 h, while serum chloride concentrations remained normal after Hartmann's (P Hartmann's solution, due possibly to the more physiological [Na(+)]/[Cl(-)] ratio in Hartmann's solution (1.18:1) than in saline (1:1) and to the hyperchloraemia caused by saline.

  18. 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.

  19. Phase error correction in wavefront curvature sensing via phase retrieval

    DEFF Research Database (Denmark)

    Almoro, Percival; Hanson, Steen Grüner

    2008-01-01

    Wavefront curvature sensing with phase error correction system is carried out using phase retrieval based on a partially-developed volume speckle field. Various wavefronts are reconstructed: planar, spherical, cylindrical, and a wavefront passing through the side of a bare optical fiber. Spurious...

  20. Asymptotic estimates of viscoelastic Green's functions near the wavefront

    OpenAIRE

    Hanyga, Andrzej

    2014-01-01

    Asymptotic behavior of viscoelastic Green's functions near the wavefront is expressed in terms of a causal function $g(t)$ defined in \\cite{SerHanJMP} in connection with the Kramers-Kronig dispersion relations. Viscoelastic Green's functions exhibit a discontinuity at the wavefront if $g(0) < \\infty$. Estimates of continuous and discontinuous viscoelastic Green's functions near the wavefront are obtained.

  1. Ocular aberrations and wavefront aberrometry: A review

    Directory of Open Access Journals (Sweden)

    Holly A. Unterhorst

    2015-03-01

    Full Text Available Wavefront aberrations can be described as deviations of the wavefront exiting the eye froma reference wavefront that is aberration free and diffraction limited. Ocular aberrations canbe sub-categorised as lower and higher order aberrations. Ocular aberrations have promptedinterest amongst the ocular healthcare community owing to their influences on the visualfunctioning of patients as well as differences observed in ocular aberrations through the useof refractive surgery both pre- and post-operatively. Uncompensated refractive error remainsone of the most common reasons for which patients consult optometrists. Compensationof refractive error, or lower order aberrations, has become a routine procedure during anoptometric examination. However, there are some patients who experience visual symptomseven after their refractive errors have been compensated via spectacles or contact lenses.Higher-order aberrations may be the source of these visual disturbances. Refractive surgeryhas been found to influence and even induce various changes in higher-order aberrationspost-operatively, which in turn has led to increased interest in wavefront aberrations and howthe measurement of these aberrations can improve diagnosis and treatment within optometryand ophthalmology.

  2. 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.

  3. Inverse pupil wavefront optimization for immersion lithography.

    Science.gov (United States)

    Han, Chunying; Li, Yanqiu; Dong, Lisong; Ma, Xu; Guo, Xuejia

    2014-10-10

    As the critical dimension of integrated circuits is continuously shrunk, thick mask induced aberration (TMIA) cannot be ignored in the lithography image process. Recently, a set of pupil wavefront optimization (PWO) approaches has been proposed to compensate for TMIA, based on a wavefront manipulator in modern scanners. However, these prior PWO methods have two intrinsic drawbacks. First, the traditional methods fell short in building up the analytical relationship between the pupil wavefront and the cost function, and used time-consuming algorithms to solve for the PWO problem. Second, in traditional methods, only the spherical aberrations were optimized to compensate for the focus exposure matrix tilt and best focus shift induced by TMIA. Thus, the degrees of freedom were limited during the optimization procedure. To overcome these restrictions, we build the analytical relationship between the pupil wavefront and the cost function based on Abbe vector imaging theory. With this analytical model and the Fletcher-Reeves conjugate-gradient algorithm, an inverse PWO method is innovated to balance the TMIA including 37 Zernike terms. Simulation results illustrate that our approach significantly improves image fidelity within a larger process window. This demonstrates that TMIA is effectively compensated by our inverse PWO approach.

  4. [Stefan Hartmann. Revaler Handwerker im Spiegel fer Ratsprotokolle von 1722 bis 1755] / Paul Kaegbein

    Index Scriptorium Estoniae

    Kaegbein, Paul

    2007-01-01

    Arvustus: Stefan Hartmann. Revaler Handwerker im Spiegel fer Ratsprotokolle von 1722 bis 1755. In : Ostseeprovinzen, baltische Staaten und das Nationale. Münster : LIT, 2005. lk. 89-112. Kanuti gildi koondunud ametite organisatsioonist ja struktuurist

  5. More about tunnelling times and superluminal tunnelling (Hartmann effect)

    Energy Technology Data Exchange (ETDEWEB)

    Olkhovsky, V.S. [Ukrainian Akademy of Sciences, Kiev (Ukraine). Inst. for Nuclear Research]|[INFN-Sezione di Catania (Italy); Recami, E. [Bergamo Univ. (Italy). Facolta` di Ingegneria]|[State Univ. at Campinas, Campinas (Brazil); Raciti, F. [Catania Univ. (Italy); Zaichenko, A. [Ukrainian Akademy of Sciences, Kiev (Ukraine). Inst. for Nuclear Reserch

    1995-05-01

    Aims of the present paper are: (i) presenting and analysing the results of various numerical calculations on the penetration and return times <{tau}{sub Pen}>, <{tau}{sub Ret}>, during tunnelling inside a rectangular potential barrier, for various penetration depths x{sub f}; (ii) putting forth and discussing suitable definitions, besides of the mean values, also of the variances (or dispersions) D{sub {tau}T} and D{sub {tau}R} for the time durations of transmission and reflection processes; (iii) mentioning, moreover, that our definition <{tau}{sub T}> for the average transmission time results to constitute an improvement of the ordinary dwell- time formula; (iv) commenting, at last, on the basis of the new numerical results, upon some recent criticism by C.R. Leavens. The paper stresses that numerical evaluations confirm that the approach implied, and implies, the existence of the Hartmann effect: an effect that in these days (due to the theoretical connections between tunnelling and evanescent-wave propagation) is receiving - at Cologne, Berkeley, Florence and Vienna - indirect, but quite interesting, experimental verification.

  6. Wavefronts and caustics associated with Mathieu beams.

    Science.gov (United States)

    Julián-Macías, Israel; Rickenstorff-Parrao, Carolina; Cabrera-Rosas, Omar de Jesús; Espíndola-Ramos, Ernesto; Juárez-Reyes, Salvador Alejandro; Ortega-Vidals, Paula; Silva-Ortigoza, Gilberto; Sosa-Sánchez, Citlalli Teresa

    2018-02-01

    In this work we compute the wavefronts and the caustics associated with the solutions to the scalar wave equation introduced by Durnin in elliptical cylindrical coordinates generated by the function A(ϕ)=ce ν (ϕ,q)+ise ν (ϕ,q), with ν being an integral or nonintegral number. We show that the wavefronts and the caustic are invariant under translations along the direction of evolution of the beam. We remark that the wavefronts of the separable Mathieu beams generated by A(ϕ)=ce ν (ϕ,q) and A(ϕ)=se ν (ϕ,q) are cones and their caustic is the z axis; thus, they are not structurally stable. However, in general, the Mathieu beam generated by A(ϕ)=ce ν (ϕ,q)+ise ν (ϕ,q) is stable because locally its caustic has singularities of the fold and cusp types. To show this property, we present the wavefronts and the caustics for the Mathieu beams with characteristic value a ν =0 and q=0,0.2,0.3,0.5. For q=0, we obtain the Bessel beam of order zero; in this case, the wavefronts are cones and the caustic coincides with the z axis. For q≠0, the wavefronts are deformations of conical ones, and the caustic surface, for some values of q, has singularities of the cusp ridge type. Furthermore, we remark that the set of Mathieu beams with characteristic value a ν =0 and 0≤qbeam is more stable than plane waves, Bessel beams, parabolic beams, and those generated by A(ϕ)=ce ν (ϕ,q) and A(ϕ)=se ν (ϕ,q). To support this conclusion, we present experimental results showing the pattern obtained after obstructing a plane wave, the Bessel beam of order m=5, and the Mathieu beam of order m=5 and q=50 with complex transversal amplitude given by Ce 5 (ξ,50)ce 5 (η,50)+iSe 5 (ξ,50)se 5 (η,50), where (ξ, η) are the elliptical coordinates on the plane.

  7. Frentes de ondas (wavefronts e limites da visão humana Parte 1: fundamentos Wavefronts and the limits of human vision Part 1: fundamentals

    Directory of Open Access Journals (Sweden)

    Mirko Jankov

    2002-12-01

    same speed in all directions. Its position at any given moment is a sphere that connects all the corresponding phase points, having the source at its center. Such imaginary spherical surfaces are called light fronts or wavefronts. There are three principal factors that limit the finest details an eye can see: optical (due to scattering, diffraction, chromatic and monochromatic aberration, retinal and neural factors (limiting visual acuity to an approximate maximum of 20/10 or 2.0. A mathematical system, the Zernike polynomials, can define geometrical surfaces in order to describe the monochromatic aberrations, both for the lower order aberrations ('prism', 'sphere' and 'astigmatism' and the higher order ones ('coma', 'spherical aberration' and others. The wavefront measures the performance of the whole optical system of the eye. Both systems described herein, the aberrometer based on the Tscherning principle and the one originated from the Hartmann-Shack sensor, start from the same logic: to compare the actual position of the wavefronts with the ideal one, calculate mathematically the geometrical surface that describes that discrepancy and represent it in the terms of the Zernike polynomials. Corneal topography measurement, with adequate software, can also express the wavefront, caused by the corneal irregularities, with the Zernike polynomials, but it still represents the anterior corneal surface only. Wavefront technology offers a new way to quantify and classify optical imaging errors of the human eye. The next article will deal with the peculiarities of the wavefront analysis, as well as with some of the clinical and surgical applications to the day-to-day ophthalmic practice.

  8. Wavefront sensorless adaptive optics versus sensor-based adaptive optics for in vivo fluorescence retinal imaging (Conference Presentation)

    Science.gov (United States)

    Wahl, Daniel J.; Zhang, Pengfei; Jian, Yifan; Bonora, Stefano; Sarunic, Marinko V.; Zawadzki, Robert J.

    2017-02-01

    Adaptive optics (AO) is essential for achieving diffraction limited resolution in large numerical aperture (NA) in-vivo retinal imaging in small animals. Cellular-resolution in-vivo imaging of fluorescently labeled cells is highly desirable for studying pathophysiology in animal models of retina diseases in pre-clinical vision research. Currently, wavefront sensor-based (WFS-based) AO is widely used for retinal imaging and has demonstrated great success. However, the performance can be limited by several factors including common path errors, wavefront reconstruction errors and an ill-defined reference plane on the retina. Wavefront sensorless (WFS-less) AO has the advantage of avoiding these issues at the cost of algorithmic execution time. We have investigated WFS-less AO on a fluorescence scanning laser ophthalmoscopy (fSLO) system that was originally designed for WFS-based AO. The WFS-based AO uses a Shack-Hartmann WFS and a continuous surface deformable mirror in a closed-loop control system to measure and correct for aberrations induced by the mouse eye. The WFS-less AO performs an open-loop modal optimization with an image quality metric. After WFS-less AO aberration correction, the WFS was used as a control of the closed-loop WFS-less AO operation. We can easily switch between WFS-based and WFS-less control of the deformable mirror multiple times within an imaging session for the same mouse. This allows for a direct comparison between these two types of AO correction for fSLO. Our results demonstrate volumetric AO-fSLO imaging of mouse retinal cells labeled with GFP. Most significantly, we have analyzed and compared the aberration correction results for WFS-based and WFS-less AO imaging.

  9. Effects of intrapartum intravenous infusion of 5% dextrose or Hartmann's solution on maternal and cord blood glucose.

    Science.gov (United States)

    Loong, E P; Lao, T T; Chin, R K

    1987-01-01

    The effects of intrapartum infusion of dextrose or Hartmann's solution on maternal and cord blood glucose were studied. Patients with and without infusion of intravenous fluids during labor were randomly selected and allocated to one of three groups. Group I received 5% dextrose solution as a vehicle for oxytocin (dextrose group), group II received Hartmann's solution (Hartmann group) and group III did not receive any intravenous infusion (control group). Each group consisted of 16 patients. Routine labor ward procedures were followed. Maternal and cord blood samples were taken at delivery. Maternal blood glucose concentrations were significantly lower in the Hartmann group than in the dextrose and control groups, showing a dilution effect of Hartmann's solution. Cord blood glucose concentrations did not differ significantly between the three groups, indicating that maternal infusion of dextrose or Hartmann's solution in routine intrapartum management would have no adverse effects on fetal blood glucose.

  10. Design considerations for a novel phase-contrast adaptive-optic wavefront sensor

    Science.gov (United States)

    Bloemhof, Eric E.; Westphal, James A.

    2002-02-01

    The wavefront sensor (WFS) is perhaps the most critical adaptive-optic subsystem, particularly for astronomical applications with natural guide stars, where current WFS sensitivity limitations seriously restrict sky coverage. In this paper, we discuss the possibility of a WFS based on a phase-contrast principle of the sort employed by Zernike for microscopy. Such a WFS would be implemented by inserting a focal-plane filter with a (pi) /2 phase-shifting central spot having a transverse size of the order of the diffraction limit. The result would be an image of the pupil in which intensity is directly proportional to the seeing- and aberration-induced phase variations over the pupil. In comparison, the signals produced by the two most common current WFS schemes, Shack-Hartmann and curvature sensing, are proportional to the phase slope and to the second derivative, respectively. The phase-contrast approach might derive some advantages stemming from its more natural match to the control eigenvectors of the electrostrictive deformable mirrors that are expected to predominate in high-order adaptive optics systems, in the same way that curvature sensors are currently well matched to bimorph mirrors. It may thus yield substantial performance improvements with simpler hardware and lighter computational loads. We examine this and other possible advantages of the phase-contrast WFS, and investigate some of the practical design issues involved in its implementation.

  11. Laboratory simulation of atmospheric turbulence induced optical wavefront distortion

    Science.gov (United States)

    Taylor, Travis Shane

    1999-11-01

    Mathcad[2]. The phase screens can then be manipulated and displayed on the LCTV using a computer with an appropriate framegrabber and software. The present system consists of an Epson liquid crystal television (which was optimized to modulate up to 2π of phase), a Macintosh IIci with a framegrabber card, a QuickTime movie consisting of multiple video frames of two dimensional arrays of spatially correlated grayscale images, and two polarizers. The movie is displayed on the television via the framegrabber, and the polarizers are used to operate the television in a mode that mostly modulates the spatial phase distribution of the optical wavefront. The frames of the movie are created using an accepted turbulence model for spatially correlated variations in index of refraction, and each subsequent frame of the movie is calculated following an accepted model for temporally varying turbulence. The model used for generating spatial functions or ``phase screens'' which simulate turbulence is the well known Kolmogorov model. These ``phase screens'' are then used, employing a Taylor's frozen flow model, to simulate temporally varying turbulence. A single ``phase screen'' is given a random velocity vector between 0 and.55 meters per second to simulate temporally varying turbulence. The system is used to distort optical beams as if the beams had propagated through a long pathlength of wavefront distorting medium, such as the atmosphere.

  12. 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

  13. 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.

  14. Sub-pixel spatial resolution wavefront phase imaging

    Science.gov (United States)

    Stahl, H. Philip (Inventor); Mooney, James T. (Inventor)

    2012-01-01

    A phase imaging method for an optical wavefront acquires a plurality of phase images of the optical wavefront using a phase imager. Each phase image is unique and is shifted with respect to another of the phase images by a known/controlled amount that is less than the size of the phase imager's pixels. The phase images are then combined to generate a single high-spatial resolution phase image of the optical wavefront.

  15. [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

  16. Health economic analysis of laparoscopic lavage versus Hartmann's procedure for diverticulitis in the randomized DILALA trial

    DEFF Research Database (Denmark)

    Gehrman, J.; Angenete, E; Björholt, I.

    2016-01-01

    Background: Open surgery with resection and colostomy (Hartmann's procedure) has been the standard treatment for perforated diverticulitis with purulent peritonitis. In recent years laparoscopic lavage has emerged as an alternative, with potential benefits for patients with purulent peritonitis......, Hinchey grade III. The aim of this study was to compare laparoscopic lavage and Hartmann's procedure with health economic evaluation within the framework of the DILALA (DIverticulitis – LAparoscopic LAvage versus resection (Hartmann's procedure) for acute diverticulitis with peritonitis) trial. Methods...... were robust as demonstrated in sensitivity analyses. Conclusion: The significant cost reduction in this study, together with results of safety and efficacy from RCTs, support the routine use of laparoscopic lavage as treatment for complicated diverticulitis with purulent peritonitis....

  17. Wavefront-guided refractive surgery after multifocal lens implantation.

    Science.gov (United States)

    Kuo, Irene C; Reviglio, Victor E

    2009-07-01

    To examine whether wavefront-guided refractive surgery has a role in correcting ametropia after implantation of multifocal intraocular lenses (IOLs). This review begins with an oversight of various multifocal IOLs to help understand how a wavefront might return from the IOL and be captured by an aberrometer. The accuracy of the wavefront may be compromised in eyes with multifocal IOLs by the fact that such lenses provide simultaneous vision--that is, a simultaneous projection of in-focus and out-of-focus images of an object on the retina--and hence returning wavefronts theoretically could be captured in a similar manner by an aberrometer. However, in isolated small series, reproducible wavefront refractions--in which the manifest refraction closely approximates the wavefront refraction and good results after refractive surgery--are attained in eyes with diffractive multifocal IOLs. Small studies suggest that it is possible to perform wavefront-guided excimer light amplification by stimulated emission of radiation (LASER) to correct ametropia following multifocal lens implantation. Larger studies with longer follow-up are needed to determine whether eyes with multifocal lenses derive an added benefit from wavefront-guided refractive surgery over conventional surgery. These studies may help determine whether some IOLs are better suited for subsequent refractive surgery. The age of the patient may affect the outcome of refractive surgery after multifocal IOL implantation.

  18. Wavefront sensing with all-digital Stokes measurements

    CSIR Research Space (South Africa)

    Dudley, Angela L

    2014-09-25

    Full Text Available A long-standing question in optics has been to efficiently measure the phase (or wavefront) of an optical field. This has led to numerous publications and commercial devices such as phase shift interferometry, wavefront reconstruction via modal...

  19. Mitotic wavefronts mediated by mechanical signaling in early Drosophila embryos

    Science.gov (United States)

    Kang, Louis; Idema, Timon; Liu, Andrea; Lubensky, Tom

    2013-03-01

    Mitosis in the early Drosophila embryo demonstrates spatial and temporal correlations in the form of wavefronts that travel across the embryo in each cell cycle. This coordinated phenomenon requires a signaling mechanism, which we suggest is mechanical in origin. We have constructed a theoretical model that supports nonlinear wavefront propagation in a mechanically-excitable medium. Previously, we have shown that this model captures quantitatively the wavefront speed as it varies with cell cycle number, for reasonable values of the elastic moduli and damping coefficient of the medium. Now we show that our model also captures the displacements of cell nuclei in the embryo in response to the traveling wavefront. This new result further supports that mechanical signaling may play an important role in mediating mitotic wavefronts.

  20. Grinding it out: wavefront spectacle lens in clinical practice.

    Science.gov (United States)

    Hagan, John C; Cable, Melissa M; Doane, John F

    2011-01-01

    This is the first literature report of a series of Zeiss iScription process wave guided spectacles (glasses) compared with conventional non-wave guided glasses. We designed a prospective pilot study of our initial clinical experience. Fifty patients with wavefront and fifty non-wavefront glasses were compared for lens changes made for comfort or visual clarity after initial manufacture and fitting. Minimum follow up was 90 days. Forty-six (92%) of the wavefront glasses required no modifications after initial delivery compared to 42 (86%) of non-wavefront glasses. There was a trend for conventional glasses to be returned more often than wavefront glasses but the difference was not statistically significant.

  1. Effect of Hartmann layer resolution for MHD flow in a straight ...

    Indian Academy of Sciences (India)

    for complex geometry MHD simulation. Keywords. Magnetohydrodynamics; Hartmann number; test blanket module. 1. Introduction. Magnetohydrodynamics studies the flow of electrically conducting, non-magnetic fluids sub- jected to an external magnetic field (Muller & Buhler 2001). The relative motion of such a fluid.

  2. A novel wavefront reconstruction algorithm based on interpolation coefficient matrix for radial shearing interferometry

    Science.gov (United States)

    Zhang, Chen; Li, Dahai; Li, Mengyang; E, Kewei

    2017-10-01

    A novel wavefront reconstruction algorithm for radial shearing interferometer (RSI) is proposed in this paper. Based on the shearing relationship of RSI, an interpolation coefficient matrix is established by the radial shearing ratio and the number of discrete points of test wavefront. Accordingly, the expanded wavefront is characterized by the interpolation coefficient matrix and the test wavefront. Consequently the test wavefront can be calculated from the phase difference wavefront. The numerical simulation is conducted to confirm the correctness of the proposed algorithm. Compared with the previous wavefront reconstruction methods, the proposed algorithm is more accurate and stable.

  3. 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.

  4. A wavefront analyzer for terahertz time-domain spectrometers

    DEFF Research Database (Denmark)

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

    2017-01-01

    We report on the development of a terahertz wavefront sensor able to determine the optical aberrations of a terahertz time-domain spectrometer. The system measures point-by-point the amplitude and phase of the terahertz electric field in a given plane. From this measurement, we reconstruct...... 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...... for improved terahertz imaging and spectroscopy....

  5. 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.

  6. Wavefront Propagation and Fuzzy Based Autonomous Navigation

    Directory of Open Access Journals (Sweden)

    Cindy Leung

    2008-11-01

    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.

  7. Extended range interferometry based on wavefront shaping

    Science.gov (United States)

    Szczupak, M. L.; Salbut, L.

    2007-09-01

    There are many cases when absolute measurements of objects with large height differences or height discontinuity is needed. These measurements can not be covered by classical interferometry since the range of non-ambiguity is limited to half the optical wavelength. Several techniques have been already developed for extending of non-ambiguity range. However most of them is based on multi-wavelength methods which demands expensive light sources and special environment conditions. In this work the new interferometric technique for absolute measurements of large steps discontinuities is proposed. Variable wavefront of the illuminating beam and special procedure for calibration of the measurement volume are used for extending of the measurement range without using multispectral sources. Additionally, calibration of the measurement area simplifies fringe processing and quicken measures. Theoretical analysis of this technique, its numerical simulations and experimental verification are presented and discussed.

  8. Hybrid Architecture Active Wavefront Sensing and Control

    Science.gov (United States)

    Feinberg, Lee; Dean, Bruce; Hyde, Tupper

    2010-01-01

    A method was developed for performing relatively high-speed wavefront sensing and control to overcome thermal instabilities in a segmented primary mirror telescope [e.g., James Webb Space Telescope (JWST) at L2], by using the onboard fine guidance sensor (FGS) to minimize expense and complexity. This FGS performs centroiding on a bright star to feed the information to the pointing and control system. The proposed concept is to beam split the image of the guide star (or use a single defocused guide star image) to perform wavefront sensing using phase retrieval techniques. Using the fine guidance sensor star image for guiding and fine phasing eliminates the need for other, more complex ways of achieving very accurate sensing and control that is needed for UV-optical applications. The phase retrieval occurs nearly constantly, so passive thermal stability over fourteen days is not required. Using the FGS as the sensor, one can feed segment update information to actuators on the primary mirror that can update the primary mirror segment fine phasing with this frequency. Because the thermal time constants of the primary mirror are very slow compared to this duration, the mirror will appear extremely stable during observations (to the level of accuracy of the sensing and control). The sensing can use the same phase retrieval techniques as the JWST by employing an additional beam splitter, and having each channel go through a weak lens (one positive and one negative). The channels can use common or separate detectors. Phase retrieval can be performed onboard. The actuation scheme would include a coarse stage able to achieve initial alignment of several millimeters of range (similar to JWST and can use a JWST heritage sensing approach in the science camera) and a fine stage capable of continual updates.

  9. Thin Film Optical Metrology Using Principles of Wavefront Sensing and Interference - Poster Paper

    Science.gov (United States)

    Faichnie, David M.; Greenaway, Alan H.; Bain, Ian

    2008-01-01

    Thin film metrology is an important quality control mechanism used in many industrial processes. Conventional techniques of Ellipsometry and Spectral Reflectance are limited in applicability to in situ measurements during film manufacture. This paper considers the measurement of wavefront shape reflected from interfaces within a laminate for determination of layer thickness and profile. For thick layers a wavefront sensor can provide the requisite wavefront shape data, for thin layers the interference between reflected wavefronts is used to retrieve wavefront shape.

  10. 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.

  11. PIGS - A New Wavefront Sensor Concept for ELTs

    Science.gov (United States)

    Kellner, S.; Ragazzoni, R.; Gässler, W.; Diolaiti, E.; Farinato, J.; Adriciaco, C.; Meyers, R.; Morris, T.; Ghedina, A.

    Adaptive Optics Systems for Extremely Large Telescopes (ELT) will need new wavefront sensing concepts to deploy their full capabilities. In this paper we exemplify the necessity of new wavefront sensing ideas by discussing briefly some major problems and present as a possible solution the pseudo infinite guide star sensor (PIGS). A prototype of a PIGS sensor was already built in the laboratory, which could demonstrate its feasibility.

  12. 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.

  13. On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

    Science.gov (United States)

    Basden, A. G.; Bardou, L.; Bonaccini Calia, D.; Buey, T.; Centrone, M.; Chemla, F.; Gach, J. L.; Gendron, E.; Gratadour, D.; Guidolin, I.; Jenkins, D. R.; Marchetti, E.; Morris, T. J.; Myers, R. M.; Osborn, J.; Reeves, A. P.; Reyes, M.; Rousset, G.; Lombardi, G.; Townson, M. J.; Vidal, F.

    2017-04-01

    The performance of adaptive optics systems is partially dependent on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack-Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40 m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on-sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on-sky H-band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on-sky demonstration.

  14. Amnioinfusion with Hartmann's solution: a safe distention medium for endoscopic fetal surgery in the ovine model.

    Science.gov (United States)

    Evrard, V A; Verbeke, K; Peers, K H; Luks, F I; Lerut, A E; Vandenberghe, K; Deprest, J A

    1997-01-01

    In this study, we have investigated the maternal effects of distending the uterine cavity with Hartmann's solution in 2nd trimester equivalent pregnant sheep. In 7 pregnant ewes, double endoscopic cannulation of the amniotic cavity was performed under general anesthesia, and 1 liter of Hartmann's solution at 38 degrees C, radiolabeled with 99mTc-red blood cells, was infused. Maternal central venous pressure, hematocrit, serum and amniotic fluid osmolarity, and amniotic fluid volume were measured at nine time points within a 2-hour period. Over this time interval, no significant fluid shift to the maternal compartment was observed. We detected no adsorption of radioactivity to the fetus or membranes, and no diffusion of radioactivity to maternal or fetal tissues was noticed. We conclude from these experiments that following double cannulation and intra-amniotic infusion of Hartmann's solution into the 2nd-trimester pregnant ovine uterus, no significant shift of fluid to the maternal compartment was observed over a 2-hour time period.

  15. 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...

  16. An analysis of printing conditions for wavefront overlapping printing

    Science.gov (United States)

    Ichihashi, Y.; Yamamoto, K.; Wakunami, K.; Oi, R.; Okui, M.; Senoh, T.

    2017-03-01

    Wavefront printing for a digitally-designed hologram has got attentions recently. In this printing, a spatial light modulator (SLM) is used for displaying a hologram data and the wavefront is reproduced by irradiating the hologram with a reference light the same way as electronic holography. However, a pixel count of current SLM devices is not enough to display an entire hologram data. To generate a practical digitally-designed hologram, the entire hologram data is divided into a set of sub-hologram data and wavefront reproduced by each sub-hologram is sequentially recorded in tiling manner by using X-Y motorized stage. Due to a lack of positioning an accuracy of X-Y motorized stage and the temporal incoherent recording, phase continuity of recorded/reproduced wavefront is lost between neighboring subholograms. In this paper, we generate the holograms that have different size of sub-holograms with an overlap or nonoverlap, and verify the size of sub-holograms effect on the reconstructed images. In the result, the reconstructed images degrade with decreasing the size of sub-holograms and there is little or no degradation of quality by the wavefront printing with the overlap.

  17. Polarization-resolved microscopy through scattering media via wavefront shaping

    CERN Document Server

    de Aguiar, Hilton B; Brasselet, Sophie

    2015-01-01

    Wavefront shaping has revolutionized imaging deep in scattering media, being able to spatially and temporally refocus light through or inside the medium. However, wavefront shaping is not compatible yet with polarization-resolved microscopy given the need of polarizing optics to refocus light with a controlled polarization state. Here, we show that wavefront shaping is not only able to restore a focus, but it can also recover the injected polarization state without using any polarizing optics at the detection. This counter-intuitive effect occurs up to several transport mean free path thick samples, which exhibit a speckle with a completely scrambled state. Remarkably, an arbitrary rotation of the input polarization does not degrade the quality of the focus. This unsupervised re-polarization - out of the originally scrambled polarization state - paves the way for polarization-resolved structural microscopy at unprecedented depths. We exploit this phenomenon and demonstrate second harmonic generation (SHG) str...

  18. Video microblogging

    DEFF Research Database (Denmark)

    Bornoe, Nis; Barkhuus, Louise

    2010-01-01

    Microblogging is a recently popular phenomenon and with the increasing trend for video cameras to be built into mobile phones, a new type of microblogging has entered the arena of electronic communication: video microblogging. In this study we examine video microblogging, which is the broadcasting...... of short videos. A series of semi-structured interviews offers an understanding of why and how video microblogging is used and what the users post and broadcast....

  19. Changing the priming solution from Ringer's to Hartmann's solution is associated with less metabolic acidosis during cardiopulmonary bypass.

    Science.gov (United States)

    Alston, R P; Theodosiou, C; Sanger, K

    2007-11-01

    Previously, it was noted that changing the solutions used for priming and intravascular volume replacement from Hartmann's to Ringer's resulted in a more profound metabolic acidosis developing during cardiopulmonary bypass (CPB). The aim of this study was to examine the effects of changing the solutions back to Hartmann's on metabolic acidosis that develops during CPB in patients undergoing heart surgery. Two groups of patients were studied sequentially: the first received Ringer's (n = 63) and the second Hartmann's solution (n = 66). Arterial blood samples were taken before induction of anaesthesia and towards the end of CPB. Samples were analysed in a blood gas analyser. Hydrogen ion concentration increased from 38 (4) to 41 (7)mmol/L in the Ringer's group, but decreased from 38 (5) to 36 (6) mmol L(-1) in the Hartmann's group. Changes in PaCO2 (0.77, p 0.10). Changing the solutions used for priming and intravascular volume replacement from Ringer's to Hartmann's was associated with a reduction in metabolic acidosis that developed during CPB.

  20. Broadband manipulation of acoustic wavefronts by pentamode metasurface

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Ye; Wei, Qi, E-mail: weiqi@nju.edu.cn; Cheng, Ying [Key Laboratory of Modern Acoustics, Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Xu, Zheng [School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Liu, Xiaojun, E-mail: liuxiaojun@nju.edu.cn [Key Laboratory of Modern Acoustics, Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-11-30

    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.

  1. Instabilities in free-surface Hartmann flow at low magnetic Prandtl numbers

    Science.gov (United States)

    Giannakis, D.; Rosner, R.; Fischer, P. F.

    2009-10-01

    We study the linear stability of the flow of a viscous electrically conducting capillary fluid on a planar fixed plate in the presence of gravity and a uniform magnetic field. We first confirm that the Squire transformation for MHD is compatible with the stress and insulating boundary conditions at the free surface, but argue that unless the flow is driven at fixed Galilei and capillary numbers, the critical mode is not necessarily two-dimensional. We then investigate numerically how a flow-normal magnetic field, and the associated Hartmann steady state, affect the soft and hard instability modes of free surface flow, working in the low magnetic Prandtl number regime of laboratory fluids. Because it is a critical layer instability, the hard mode is found to exhibit similar behaviour to the even unstable mode in channel Hartmann flow, in terms of both the weak influence of Pm on its neutral stability curve, and the dependence of its critical Reynolds number Re_c on the Hartmann number Ha. In contrast, the structure of the soft mode's growth rate contours in the (Re, alpha) plane, where alpha is the wavenumber, differs markedly between problems with small, but nonzero, Pm, and their counterparts in the inductionless limit. As derived from large wavelength approximations, and confirmed numerically, the soft mode's critical Reynolds number grows exponentially with Ha in inductionless problems. However, when Pm is nonzero the Lorentz force originating from the steady state current leads to a modification of Re_c(Ha) to either a sublinearly increasing, or decreasing function of Ha, respectively for problems with insulating and conducting walls. In the former, we also observe pairs of Alfven waves, the upstream propagating wave undergoing an instability at large Alfven numbers.

  2. Numerical Evaluation of Parameter Correlation in the Hartmann-Tran Line Profile

    Science.gov (United States)

    Adkins, Erin M.; Reed, Zachary; Hodges, Joseph T.

    2017-06-01

    The partially correlated quadratic, speed-dependent hard-collision profile (pCqSDHCP), for simplicity referred to as the Hartmann-Tran profile (HTP), has been recommended as a generalized lineshape for high resolution spectroscopy. The HTP parameterizes complex collisional effects such as Dicke narrowing, speed dependent narrowing, and correlations between velocity-changing and dephasing collisions, while also simplifying to simpler profiles that are widely used, such as the Voigt profile. As advanced lineshape profiles are adopted by more researchers, it is important to understand the limitations that data quality has on the ability to retrieve physically meaningful parameters using sophisticated lineshapes that are fit to spectra of finite signal-to-noise ratio. In this work, spectra were simulated using the HITRAN Application Programming Interface (HAPI) across a full range of line parameters. Simulated spectra were evaluated to quantify the precision with which fitted lineshape parameters can be determined at a given signal-to-noise ratio, focusing on the numerical correlation between the retrieved Dicke narrowing frequency and the velocity-changing and dephasing collisions correlation parameter. Tran, H., N. Ngo, and J.-M. Hartmann, Journal of Quantitative Spectroscopy and Radiative Transfer 2013. 129: p. 89-100. Tennyson, et al., Pure Appl. Chem. 2014, 86: p. 1931-1943. Kochanov, R.V., et al., Journal of Quantitative Spectroscopy and Radiative Transfer 2016. 177: p. 15-30. Tran, H., N. Ngo, and J.-M. Hartmann, Journal of Quantitative Spectroscopy and Radiative Transfer 2013. 129: p. 199-203.

  3. Childhood intussusception: ultrasound-guided Hartmann's solution hydrostatic reduction or barium enema reduction?

    Science.gov (United States)

    Chan, K L; Saing, H; Peh, W C; Mya, G H; Cheng, W; Khong, P L; Lam, C; Lam, W W; Leong, L L; Low, L C

    1997-01-01

    A comparison was made of the efficacy of ultrasound guided Hartmann's solution hydrostatic reduction on 23 patients (US group) with the same number of consecutive patients in whom hydrostatic reduction was done by barium enema (BE group) under fluoroscopy for childhood intussusception. The US group was diagnosed by ultrasound scan and reduction was attempted under the guidance of ultrasonography with Hartmann's solution at 100 mm Hg pressure. Excluded were patients older than 12 years, patients in shock, patients with peritonitis, bowel perforation, and gross abdominal distension as well as recurrent intussusception of more than three episodes. There were three patients excluded in this group. The diagnosis of intussusception and complete reduction were confirmed by gastrografin enema. This US group had three recurrences (3 of 26, 11.5%), one lead point (1 of 23, 4.4%), and 19 successful reductions (19 of 26, 73%). Incidentally, there were also three patients excluded in this period of barium enema reduction. There was only one recurrence (1 of 24, 4.2%), one leadpoint (1 of 23, 4.4%), and 12 successful reductions (12 of 24, 50%) in these 23 BE patients. The success rates for the ileo-colic intussusceptions with Hartmann's solution reduction and barium enema reduction were 91% (19 of 21) and 55% (12 of 22), respectively (P = .00865). There was no complication in either group, and the accuracy of diagnosing a complete reduction was 100% in both forms of reduction. Hence, ultrasound-guided hydrostatic reduction for childhood ileocolic intussusception is preferred because it is safe, accurate, has a higher success rate, and can avoid radiation exposure risk.

  4. The impact of surgeon volume on colostomy reversal outcomes after Hartmann's procedure for diverticulitis.

    Science.gov (United States)

    Aquina, Christopher T; Probst, Christian P; Becerra, Adan Z; Hensley, Bradley J; Iannuzzi, James C; Noyes, Katia; Monson, John R T; Fleming, Fergal J

    2016-11-01

    Colostomy reversal after Hartmann's procedure for diverticulitis is a morbid procedure, and studies investigating factors associated with outcomes are lacking. This study identifies patient, surgeon, and hospital-level factors associated with perioperative outcomes after stoma reversal. The Statewide Planning and Research Cooperative System was queried for urgent/emergency Hartmann's procedures for diverticulitis between 2000-2012 in New York State and subsequent colostomy reversal within 1 year of the procedure. Surgeon and hospital volume were categorized into tertiles based on the annual number of colorectal resections performed each year. Bivariate and mixed-effects analyses were used to assess the association between patient, surgeon, and hospital-level factors and perioperative outcomes after colostomy reversal, including a laparoscopic approach; duration of stay; intensive care unit admission; complications; mortality; and 30-day, unscheduled readmission. Among 10,487 patients who underwent Hartmann's procedure and survived to discharge, 63% had the colostomy reversed within 1 year. After controlling for patient, surgeon, and hospital-level factors, high-volume surgeons (≥40 colorectal resections/yr) were independently associated with higher odds of a laparoscopic approach (unadjusted rates: 14% vs 7.6%; adjusted odds ratio = 1.84, 95% confidence interval = 1.12, 3.00), shorter duration of stay (median: 6 versus 7 days; adjusted incidence rate ratio = 0.87, 95% confidence interval = 0.81, 0.95), and lower odds of 90-day mortality (unadjusted rates: 0.4% vs 1.0%; adjusted odds ratio = 0.30, 95% confidence interval = 0.10, 0.88) compared with low-volume surgeons (1-15 colorectal resections/yr). High-volume surgeons are associated with better perioperative outcomes and lower health care utilization after Hartmann's reversal for diverticulitis. These findings support referral to high-volume surgeons for colostomy reversal. Copyright © 2016

  5. Ion slip effect on unsteady Hartmann flow with heat transfer under exponential decaying pressure gradient

    Directory of Open Access Journals (Sweden)

    Hazem A. Attia

    2006-01-01

    Full Text Available The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel nonconducting porous plates is studied with heat transfer taking the ion slip into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates, while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

  6. Video demystified

    CERN Document Server

    Jack, Keith

    2004-01-01

    This international bestseller and essential reference is the "bible" for digital video engineers and programmers worldwide. This is by far the most informative analog and digital video reference available, includes the hottest new trends and cutting-edge developments in the field. Video Demystified, Fourth Edition is a "one stop" reference guide for the various digital video technologies. The fourth edition is completely updated with all new chapters on MPEG-4, H.264, SDTV/HDTV, ATSC/DVB, and Streaming Video (Video over DSL, Ethernet, etc.), as well as discussions of the latest standards throughout. The accompanying CD-ROM is updated to include a unique set of video test files in the newest formats. *This essential reference is the "bible" for digital video engineers and programmers worldwide *Contains all new chapters on MPEG-4, H.264, SDTV/HDTV, ATSC/DVB, and Streaming Video *Completely revised with all the latest and most up-to-date industry standards.

  7. A randomised controlled trial of Hartmann's solution versus half normal saline in postoperative paediatric spinal instrumentation and craniotomy patients.

    Science.gov (United States)

    Coulthard, Mark G; Long, Debbie A; Ullman, Amanda J; Ware, Robert S

    2012-06-01

    To compare the difference in plasma sodium at 16-18 h following major surgery in children who were prescribed either Hartmann's and 5% dextrose or 0.45% saline and 5% dextrose. A prospective, randomised, open label study. The paediatric intensive care unit (650 admissions per annum) in a tertiary children's hospital in Brisbane, Australia. The study group comprised 82 children undergoing spinal instrumentation, craniotomy for brain tumour resection, or cranial vault remodelling. Patients received either Hartmann's and 5% dextrose at full maintenance rate or 0.45% saline and 5% dextrose at two-thirds maintenance rate. plasma sodium at 16-18 h postoperatively; secondary outcome measure: number of fluid boluses administered. Mean postoperative plasma sodium levels of children receiving 0.45% saline and 5% dextrose were 1.4 mmol/l (95% CI 0.4 to 2.5) lower than those receiving Hartmann's and 5% dextrose (p=0.008). In the 0.45% saline group, seven patients (18%) became hyponatraemic (Na <135 mmol/l) at 16-18 h postoperatively; in the Hartmann's group no patient became hyponatraemic (p=0.01). No child in either fluid group became hypernatraemic. The postoperative fall in plasma sodium was smaller in children who received Hartmann's and 5% dextrose compared to those who received 0.45% saline and 5% dextrose. It is suggested that Hartmann's and 5% dextrose should be administered at full maintenance rate postoperatively to children who have undergone major surgery in preference to hypotonic fluids.

  8. Complex wavefront modulation and holographic display using single spatial light modulator

    Science.gov (United States)

    Kong, Dezhao; Cao, Liangcai; Shen, Xueju; Zhang, Hao; Zong, Song; Jin, Guofan

    2017-08-01

    A holographic display method based on complex wavefront modulation using single spatial light modulator is proposed. The holographic display is achieved from complex wavefront encoded by double phase hologram. The modulated beam by single phase-only spatial light modulator passes through a 4f optical system to synthesize the expected complex modulated wavefront on the output plane, with a low-pass filter in the Fourier plane. The performance of holographic display is also improved by complex wavefront modulation, compared with the holographic display based on phase-only wavefront modulation. The proposed encoding and display technique is theoretically demonstrated, as well as validated in numerical simulations.

  9. 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

  10. Joint fractional Fourier analysis of wavefront-coding systems.

    Science.gov (United States)

    Barwick, Shane; Finnigan, Jerome S

    2009-01-15

    The analysis of wavefront-coding systems is explored via the joint fractional Fourier signal representation (JFF) of the pupil function. The properties of the JFF of the pupil function are presented and are shown to be revealing with regard to the system response to defocus. Numerical examples that illustrate the properties are given.

  11. 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.

  12. 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

  13. Device for wavefront correction in an ultra high power laser

    Science.gov (United States)

    Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.

    2002-01-01

    A system for wavefront correction in an ultra high power laser. As the laser medium flows past the optical excitation source and the fluid warms its index of refraction changes creating an optical wedge. A system is provided for correcting the thermally induced optical phase errors.

  14. Modeling and prediction of turbulence-induced wavefront distortions

    NARCIS (Netherlands)

    Fraanje, P.R.; Doelman, N.J.

    2010-01-01

    In recent years various researchers have proposed an optimal control approach for the rejection of turbulence-induced wavefront distortions in an AO system. The essential element in the design of an optimal controller is the choice for the turbulence model, which predicts the turbulence to

  15. Parallel Implementation of a Frozen Flow Based Wavefront Reconstructor

    Science.gov (United States)

    Nagy, J.; Kelly, K.

    2013-09-01

    Obtaining high resolution images of space objects from ground based telescopes is challenging, often requiring the use of a multi-frame blind deconvolution (MFBD) algorithm to remove blur caused by atmospheric turbulence. In order for an MFBD algorithm to be effective, it is necessary to obtain a good initial estimate of the wavefront phase. Although wavefront sensors work well in low turbulence situations, they are less effective in high turbulence, such as when imaging in daylight, or when imaging objects that are close to the Earth's horizon. One promising approach, which has been shown to work very well in high turbulence settings, uses a frozen flow assumption on the atmosphere to capture the inherent temporal correlations present in consecutive frames of wavefront data. Exploiting these correlations can lead to more accurate estimation of the wavefront phase, and the associated PSF, which leads to more effective MFBD algorithms. However, with the current serial implementation, the approach can be prohibitively expensive in situations when it is necessary to use a large number of frames. In this poster we describe a parallel implementation that overcomes this constraint. The parallel implementation exploits sparse matrix computations, and uses the Trilinos package developed at Sandia National Laboratories. Trilinos provides a variety of core mathematical software for parallel architectures that have been designed using high quality software engineering practices, The package is open source, and portable to a variety of high-performance computing architectures.

  16. Comparison of pentastarch and Hartmann's solution for volume preloading in spinal anaesthesia for elective caesarean section.

    Science.gov (United States)

    French, G W; White, J B; Howell, S J; Popat, M

    1999-09-01

    We studied 160 patients undergoing elective Caesarean section under spinal anaesthesia who received a preloading volume of 15 ml kg-1 of 10% pentastarch in 0.9% saline, or Hartmann's solution, in a prospective, randomized, double-blind study. We compared the incidence of spinal-induced hypotension in each group. Hypotension was defined as a decrease in systolic arterial pressure to less than 70% of baseline values or < or = 90 mm Hg, whichever was the greater. The groups were comparable in physical characteristics and there was no serious morbidity. Fetal outcome was similar in both groups. Significantly more patients in the Hartmann's group (n = 38, 47.5%) developed hypotension than in the pentastarch group (n = 10, 12.5%) (P < 0.0001). Linear regression analysis showed that the only significant variable was type of fluid used. Blood glucose concentrations were not related to the presence of hypotension. We conclude that starches may be suitable for preloading in Caesarean section under spinal anaesthesia and provide an alternative to the aggressive use of vasoconstrictors.

  17. Single-port laparoscopic reversal of Hartmann's procedure via the colostomy site.

    Science.gov (United States)

    Choi, Byung Jo; Jeong, Won Jun; Kim, Young Kyun; Kim, Say-June; Lee, Sang Chul

    2015-02-01

    The aim of this study was to report our initial experience with single-port laparoscopic reversal of Hartmann's procedure (SP-LHR). Between December 2009 and March 2014, 23 patients underwent single-port laparoscopic reversal of Hartmann's procedure. Single-port laparoscopic surgeries (SPLS) were performed through the preexisting stoma site. A commercially available single port with one 5 mm and two 12 mm trocars was used with conventional straight and rigid laparoscopic instruments. Patient demographics and operative and postoperative outcomes were analyzed. SP-LHR was successful in 22 patients. No additional incisions for trocars or conversions to open surgery were necessary. In 1 patient, the procedure was aborted. The median operative time and postoperative length of stay were 165 min (range, 100-340 min) and 8 days (range, 4-31 days), respectively. The median time to the resumption of oral intake was 3 days (range, 1-16 days). No intraoperative complications were noted; there were four postoperative complications including one anastomotic leak. In our experience, SP-LHR via the colostomy site was safe and feasible, and may be considered an additional surgical option for experienced SPLS surgeons in selected patients. Copyright © 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.

  18. Analysis on the misalignment errors between Hartmann-Shack sensor and 45-element deformable mirror

    Science.gov (United States)

    Liu, Lihui; Zhang, Yi; Tao, Jianjun; Cao, Fen; Long, Yin; Tian, Pingchuan; Chen, Shangwu

    2017-02-01

    Aiming at 45-element adaptive optics system, the model of 45-element deformable mirror is truly built by COMSOL Multiphysics, and every actuator's influence function is acquired by finite element method. The process of this system correcting optical aberration is simulated by making use of procedure, and aiming for Strehl ratio of corrected diffraction facula, in the condition of existing different translation and rotation error between Hartmann-Shack sensor and deformable mirror, the system's correction ability for 3-20 Zernike polynomial wave aberration is analyzed. The computed result shows: the system's correction ability for 3-9 Zernike polynomial wave aberration is higher than that of 10-20 Zernike polynomial wave aberration. The correction ability for 3-20 Zernike polynomial wave aberration does not change with misalignment error changing. With rotation error between Hartmann-Shack sensor and deformable mirror increasing, the correction ability for 3-20 Zernike polynomial wave aberration gradually goes down, and with translation error increasing, the correction ability for 3-9 Zernike polynomial wave aberration gradually goes down, but the correction ability for 10-20 Zernike polynomial wave aberration behave up-and-down depression.

  19. Digital video.

    Science.gov (United States)

    Johnson, Don; Johnson, Mike

    2004-04-01

    The process of digital capture, editing, and archiving video has become an important aspect of documenting arthroscopic surgery. Recording the arthroscopic findings before and after surgery is an essential part of the patient's medical record. The hardware and software has become more reasonable to purchase, but the learning curve to master the software is steep. Digital video is captured at the time of arthroscopy to a hard disk, and written to a CD at the end of the operative procedure. The process of obtaining video of open procedures is more complex. Outside video of the procedure is recorded on digital tape with a digital video camera. The camera must be plugged into a computer to capture the video on the hard disk. Adobe Premiere software is used to edit the video and render the finished video to the hard drive. This finished video is burned onto a CD. We outline the choice of computer hardware and software for the manipulation of digital video. The techniques of backup and archiving the completed projects and files also are outlined. The uses of digital video for education and the formats that can be used in PowerPoint presentations are discussed.

  20. Immersive video

    Science.gov (United States)

    Moezzi, Saied; Katkere, Arun L.; Jain, Ramesh C.

    1996-03-01

    Interactive video and television viewers should have the power to control their viewing position. To make this a reality, we introduce the concept of Immersive Video, which employs computer vision and computer graphics technologies to provide remote users a sense of complete immersion when viewing an event. Immersive Video uses multiple videos of an event, captured from different perspectives, to generate a full 3D digital video of that event. That is accomplished by assimilating important information from each video stream into a comprehensive, dynamic, 3D model of the environment. Using this 3D digital video, interactive viewers can then move around the remote environment and observe the events taking place from any desired perspective. Our Immersive Video System currently provides interactive viewing and `walkthrus' of staged karate demonstrations, basketball games, dance performances, and typical campus scenes. In its full realization, Immersive Video will be a paradigm shift in visual communication which will revolutionize television and video media, and become an integral part of future telepresence and virtual reality systems.

  1. Colovaginal anastomosis: an unusual complication of stapler use in restorative procedure after Hartmann operation

    Directory of Open Access Journals (Sweden)

    Liao Guoqing

    2005-11-01

    Full Text Available Abstract Background Rectovaginal fistula is uncommon after lower anterior resection for rectal cancer. The most leading cause of this complication is involvement of the posterior wall of the vagina into the staple line when firing the circular stapler. Case presentation A 50-year-old women underwent resection for obstructed carcinoma of the sigmoid colon with Hartmann procedure. Four months later she underwent restorative surgery with circular stapler. Following which she developed rectovaginal fistula. A transvaginal repair was performed but stool passing from vagina not per rectum. Laporotomy revealed colovaginal anastomosis, which was corrected accordingly. Patient had an uneventful recovery. Conclusion Inadvertent formation of colovaginal anastomosis associated with a rectovaginal fistula is a rare complication caused by the operator's error. The present case again highlights the importance of ensuring that the posterior wall of vagina is away from the staple line.

  2. Wavefront sensing for anisotropic turbulence using digital holography

    Science.gov (United States)

    Thurman, Samuel T.; Gatt, Philip; Alley, Thomas

    2016-09-01

    We report on digital holographic imaging through atmospheric turbulence. Data recorded with aberrations is corrected during post processing using an iterative sharpness-metric maximization algorithm. Assuming the correction cancels the actual wavefront error, this process is equivalent to wavefront sensing. Much of our past work focused on imaging through isotropic turbulence with phase corrections using a Zernike-polynomial expansion. Here, we describe algorithm modifications for imaging through anisotropic turbulence, similar to what is seen when looking through the aero-optic boundary layer surrounding a moving aircraft. Specifically, we explore tradeoffs associated with switching from a Zernike representation to Karhunen-Loève basis functions. In some cases, the dimensionality of the phase correction estimation algorithm can be reduced significantly by this change. This reduces the computational burden

  3. Adaptive wavefront control with asynchronous stochastic parallel gradient descent clusters.

    Science.gov (United States)

    Vorontsov, Mikhail A; Carhart, Gary W

    2006-10-01

    A scalable adaptive optics (AO) control system architecture composed of asynchronous control clusters based on the stochastic parallel gradient descent (SPGD) optimization technique is discussed. It is shown that subdivision of the control channels into asynchronous SPGD clusters improves the AO system performance by better utilizing individual and/or group characteristics of adaptive system components. Results of numerical simulations are presented for two different adaptive receiver systems based on asynchronous SPGD clusters-one with a single deformable mirror with Zernike response functions and a second with tip-tilt and segmented wavefront correctors. We also discuss adaptive wavefront control based on asynchronous parallel optimization of several local performance metrics-a control architecture referred to as distributed adaptive optics (DAO). Analysis of the DAO system architecture demonstrated the potential for significant increase of the adaptation process convergence rate that occurs due to partial decoupling of the system control clusters optimizing individual performance metrics.

  4. Optical design of infrared pyramid wavefront sensor for the MMT

    Science.gov (United States)

    Chen, Shaojie; Sivanandam, Suresh; Liu, Siqi; Veran, Jean-Pierre; Hinz, Phil; Mieda, Etsuko; Hardy, Tim; Lardiere, Olivier

    2017-09-01

    We report the optical design of an infrared (0.85-1.8 μm) pyramid wavefront sensor (IRPWFS) that is designed for the 6.5m MMT on telescope adaptive optics system using the latest developments in low-noise infrared avalanche photodiode arrays. The comparison between the pyramid and the double-roof prism based wavefront sensors and the evaluation of their micro pupils' quality are presented. According to our analysis, the use of two double-roof prisms with achromatic materials produces the competitive performance when compared to the traditional pyramid prism, which is difficult to manufacture. The final micro pupils on the image plane have the residual errors of pupil position, chromatism, and distortion within 1/10 pixel over the 2×2 arcsecond field of view, which meet the original design goals.

  5. 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.

  6. Oral histories in meteoritics and planetary science—XXIV: William K. Hartmann

    Science.gov (United States)

    Sears, Derek W. G.

    2014-06-01

    In this interview, William Hartmann (Bill, Fig. 1) describes how he was inspired as a teenager by a map of the Moon in an encyclopedia and by the paintings by Chesley Bonestell. Through the amateur journal "Strolling Astronomer," he shared his interests with other teenagers who became lifelong colleagues. At college, he participated in Project Moonwatch, observing early artificial satellites. In graduate school, under Gerard Kuiper, Bill discovered Mare Orientale and other large concentric lunar basin structures. In the 1960s and 1970s, he used crater densities to study surface ages and erosive/depositional effects, predicted the approximately 3.6 Gyr ages of the lunar maria before the Apollo samples, discovered the intense pre-mare lunar bombardment, deduced the youthful Martian volcanism as part of the Mariner 9 team, and proposed (with Don Davis) the giant impact model for lunar origin. In 1972, he helped found (what is now) the Planetary Science Institute. From the late 1970s to early 1990s, Bill worked mostly with Dale Cruikshank and Dave Tholen at Mauna Kea Observatory, helping to break down the Victorian paradigm that separated comets and asteroids, and determining the approximately 4% albedo of comet nuclei. Most recently, Bill has worked with the imaging teams for several additional Mars missions. He has written three college textbooks and, since the 1970s, after painting illustrations for his textbooks, has devoted part of his time to painting, having had several exhibitions. He has also published two novels. Bill Hartmann won the 2010 Barringer Award for impact studies and the first Carl Sagan Award for outreach in 1997.

  7. Results of a statewide survey of surgeons' care practices for emergency Hartmann's procedure.

    Science.gov (United States)

    Sheetz, Kyle; Hemmila, Mark R; Duby, Ashley; Krapohl, Greta; Morris, Arden; Campbell, Darrell A; Hendren, Samantha

    2016-09-01

    Emergency general surgery is associated with high morbidity and mortality but has seldom been targeted for practice improvement. The goal of this study was to determine whether perioperative practices vary among surgeons for emergency Hartmann's procedures and whether perioperative care practices are associated with hospitals' complication rates. We conducted a survey of surgeons at 27 Michigan hospitals. Questionnaires focused on preoperative, intraoperative, and postoperative care practices. Hospitals were divided into quartiles of risk-adjusted complication rates. Responses of surgeons at hospitals with the lowest complication rates were compared to those with the highest, to determine whether there were systematic differences. Qualitative content analysis was performed for open-ended questions. A total of 106 surgeons returned questionnaires (response rate 49%). We identified variation in use of bowel preparation, ostomy site marking, rectal stump management, ostomy protrusion, skin closure method, antibiotics duration, and ambulation/physical therapy practices. Surgeons from hospitals with low complication rates were more likely to use a clean instrument tray during wound closure (61% versus 11%, P = 0.001) and reported greater use of laparoscopic lavage without resection for emergency diverticulitis cases (31% versus 6%, P = 0.05). Surgeons in the lower complication rate hospitals listed more modifiable care factors in their open-ended responses to questions about reasons for complications. Surgeons' practices vary for emergency Hartmann's procedure. This study serves as a proof of concept that studying surgeons' practices is feasible within a quality collaborative setting. Such data can be used to generate testable hypotheses for performance improvement aimed in high-risk, emergency surgery. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. The radiation-wavefront instability in pulsed CO2 amplifiers

    Science.gov (United States)

    Fedorov, S. V.; Iur'ev, M. S.

    1987-07-01

    The space-time evolution of a small-scale perturbation against a background of a smooth input beam which is incident on a pulsed CO2 amplifier is studied theoretically. Ranges of transverse frequency, longitudinal coordinate, and time values are found in which the perturbation growth is exponential in nature. It is shown that the wavefront instability is stabilized by the amplification of the main beam and sound damping.

  9. The speed of reaction-diffusion wavefronts in nonsteady media

    Energy Technology Data Exchange (ETDEWEB)

    Mendez, Vicenc [Departament de Medicina, Facultat de Ciencies de la Salut, Universitat Internacional de Catalunya. c/Gomera s/n, 08190-Sant Cugat del Valles (Barcelona) (Spain); Fort, Joaquim [Departament de Fisica, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia (Spain); Pujol, Toni [Departament de Fisica, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia (Spain)

    2003-04-11

    The evolution of the speed of wavefronts for reaction-diffusion equations with time-varying parameters is analysed. We make use of singular perturbative analysis to study the temporal evolution of the speed for pushed fronts. The analogy with Hamilton-Jacobi dynamics allows us to consider the problem for pulled fronts, which is described by Kolmogorov-Petrovskii-Piskunov (KPP) reaction kinetics. Both analytical studies are in good agreement with the results of numerical solutions.

  10. Hybrid architecture active wavefront sensing and control system, and method

    Science.gov (United States)

    Feinberg, Lee D. (Inventor); Dean, Bruce H. (Inventor); Hyde, Tristram T. (Inventor)

    2011-01-01

    According to various embodiments, provided herein is an optical system and method that can be configured to perform image analysis. The optical system can comprise a telescope assembly and one or more hybrid instruments. The one or more hybrid instruments can be configured to receive image data from the telescope assembly and perform a fine guidance operation and a wavefront sensing operation, simultaneously, on the image data received from the telescope assembly.

  11. 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...

  12. 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.

  13. Fresnel wavefront propagation model for shearography shape measurement

    Science.gov (United States)

    Anand, Arun; Groves, Roger M.; Schwab, Xavier; Pedrini, Giancarlo; Osten, Wolfgang

    2007-06-01

    This paper describes a new technique for modelling slope fringes in shearography using Fresnel wavefront propagation. Shearography is a full-field speckle interferometry technique usually used for displacement gradient and for shape measurement. One feature of shearography is that it uses a close to common path interferometer. This has the advantage of reducing sensitivity to environmental disturbances, but the disadvantage of a non-linear response. Previously one of the authors has used a ray tracing model of the fringe formation to improve the shape and slope measurement capabilities of shearography. The calculation involved was relatively time consuming as it required the calculation of the phase for each camera pixel individually. In this new Fresnel wavefront propagation model the approach is different. The system is modelled by propagation of the entire wavefront. This includes propagating the light through optical elements, such as a lens. This initial study has been for the formation of slope fringes in shearography using the source displacement technique. The advantages of this new technique are that it is easier to introduce optical elements and the effects of speckle noise into the simulation.

  14. Wavefront control of main-amplifier system in the SG-Ⅲ laser facility

    Science.gov (United States)

    De'en, Wang; Dongxia, Hu; Qiang, Yuan; Qiao, Xue; Wei, Zhou; Ying, Yang; Xin, Zhang; Xuewei, Deng; Yuancheng, Wang; Junpu, Zhao; Wu, Deng; Xiaofeng, Wei; Wanjun, Dai; Feng, Jing; Qihua, Zhu; Wanguo, Zheng

    2017-07-01

    SG-Ⅲ is a large, 48-beam, high power laser facility mainly for inertial confinement fusion physics experiments. Wavefront distortion is a primary factor decreasing focusability quality of laser beam and impacting secure performance of laser device, and main-amplifier system is one major source of aberrations. Based on the specific configuration of the SG-Ⅲ main amplifier, two wavefront control approaches are studied, termed as traditional four-pass wavefront correction and novel double-pass wavefront correction. Comparison results show that, both of them are feasible for the wavefront compensation, but double-pass mode is more suitable for our system, mainly because it can make the wavefront distributing more evenly in the different spatial filter pinholes, the high power laser passing through the pinholes more secure and the output beam quality meeting the required performance.

  15. Probability of the residual wavefront variance of an adaptive optics system and its application.

    Science.gov (United States)

    Huang, Jian; Liu, Chao; Deng, Ke; Yao, Zhousi; Xian, Hao; Li, Xinyang

    2016-02-08

    For performance evaluation of an adaptive optics (AO) system, the probability of the system residual wavefront variance can provide more information than the wavefront variance average. By studying the Zernike coefficients of an AO system residual wavefront, we derived the exact expressions for the probability density functions of the wavefront variance and the Strehl ratio, for instantaneous and long-term exposures owing to the insufficient control loop bandwidth of the AO system. Our calculations agree with the residual wavefront data of a closed loop AO system. Using these functions, we investigated the relationship between the AO system bandwidth and the distribution of the residual wavefront variance. Additionally, we analyzed the availability of an AO system for evaluating the AO performance. These results will assist in designing and probabilistic analysis of AO systems.

  16. Video games

    OpenAIRE

    Kolář, Vojtěch

    2012-01-01

    This thesis is based on a detailed analysis of various topics related to the question of whether video games can be art. In the first place it analyzes the current academic discussion on this subject and confronts different opinions of both supporters and objectors of the idea, that video games can be a full-fledged art form. The second point of this paper is to analyze the properties, that are inherent to video games, in order to find the reason, why cultural elite considers video games as i...

  17. 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

  18. 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.

  19. Nicolai Hartmann: Una apostilla bibliográfica a propósito de la traducción de su Ética

    OpenAIRE

    Vélez León, Paulo

    2012-01-01

    International audience; In this work (1) it is specified the central aspects of the structure and content of Nicolai Hartmann´s monumental oeuvre, recently translated into Spanish, Ethics, and (2) in correspondence with the above, it is summarily indicated the purpose of his ethical approach.; En este trabajo [1] se especifican los aspectos centrales de la estructura y contenido de la monumental obra de Nicolai Hartmann, recientemente traducida al castellano, Ética, y [2] en correspondencia c...

  20. Ontologie della resistenza: note sul concetto di materia in N. Hartmann e G. Lukács

    Directory of Open Access Journals (Sweden)

    D’Anna, Giuseppe

    2010-01-01

    Full Text Available The essay discusses the topic of matter in N. Hartmann and G. Lukács. It shows how both of them use their own concepts of matter in order to counter correlativistic philosophies – such as Phenomenology, Neo-Kantianism, Existentialism, Pragmatism, Positivism, Empirio-Criticism or Conventionalism – which reduce the real world to the laws of thought, to those of the absolute consciousness or to scientific laws, therefore eliminating the resistance of the reality and the meaning of praxis and dialectic in front of the givenness of the world. While Hartmann uses the concept of matter in order to revive the idea of a reality going beyond the laws of thought, Lukács uses Hartmann’s ontology in order to counter the philosophies that, by excluding the exceedance of reality and matter, provide theories which appear to him functional to the capitalist society.

  1. 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

  2. AM06-14-015 Numerical analyses of MHD convection with use of the Hartmann layer modeling

    OpenAIRE

    田川, 俊夫; Toshio, Tagawa; 首都大; Dept. of Aerospace Engineering, TMU

    2006-01-01

    In the presence of a uniform magnetic field, some characteristics of the convective flows in enclosures are presented numerically. The direction of the uniform magnetic field is parallel to the main circulation of convection flow. The well known analytical solution in the Hartmann layers allows taking directly their influence via new boundary conditions for the core flow. This modeling of the new boundary conditions saves important memory and CPU resources, and its solution is much closer to ...

  3. Susceptibilities for the Müller-Hartmann-Zitartz countable infinity of phase transitions on a Cayley tree.

    Science.gov (United States)

    Sharma, Auditya

    2015-07-01

    We obtain explicit susceptibilities for the countable infinity of phase transition temperatures of Müller-Hartmann-Zitartz on a Cayley tree. The susceptibilities are a product of the zeroth spin with the sum of an appropriate set of averages of spins on the outermost layer of the tree. A clear physical understanding for these strange phase transitions emerges naturally. In the thermodynamic limit, the susceptibilities tend to zero above the transition and to infinity below it.

  4. Video Podcasts

    DEFF Research Database (Denmark)

    Nortvig, Anne Mette; Sørensen, Birgitte Holm

    2016-01-01

    This project’s aim was to support and facilitate master’s students’ preparation and collaboration by making video podcasts of short lectures available on YouTube prior to students’ first face-to-face seminar. The empirical material stems from group interviews, from statistical data created through...... YouTube analytics and from surveys answered by students after the seminar. The project sought to explore how video podcasts support learning and reflection online and how students use and reflect on the integration of online activities in the videos. Findings showed that students engaged actively...

  5. 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.

  6. Wavefront-division lateral shearing autocorrelator for ultrafast laser microscopy.

    Science.gov (United States)

    Quercioli, Franco; Tiribilli, Bruno; Vassalli, Massimo

    2004-09-06

    Nonlinear optical microscopy is a new and rapidly growing technique within which ultrafast laser technology finds a wide range of applications. Pulse widening, due to the microscope optics, is an issue of major concern for nonlinear excitation efficiency. We herewith describe a novel, simple and inexpensive autocorrelation technique to characterize the laser temporal behavior at the microscope focal plane. The method is based on a wavefront-division lateral shearing interferometer which is inserted into the microscope optical path like an ordinary filter, while a spatially uniform fluorescent specimen is observed. The two-photon excited fluorescent image provides the second-order autocorrelation curve.

  7. Towards feasible and effective predictive wavefront control for adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L A; Veran, J

    2008-06-04

    We have recently proposed Predictive Fourier Control, a computationally efficient and adaptive algorithm for predictive wavefront control that assumes frozen flow turbulence. We summarize refinements to the state-space model that allow operation with arbitrary computational delays and reduce the computational cost of solving for new control. We present initial atmospheric characterization using observations with Gemini North's Altair AO system. These observations, taken over 1 year, indicate that frozen flow is exists, contains substantial power, and is strongly detected 94% of the time.

  8. Angular displacement and deformation analyses using speckle-based wavefront sensor

    DEFF Research Database (Denmark)

    Almoro, Percival; Giancarlo, Pedrini; Arun, Anand

    2009-01-01

    undergoing a small rotation or deformation without sign ambiguity. Angular displacement (Delta theta) between incident planar wavefronts is determined from the light source vacuum wavelength (lambda) divided by the fringe spacing (Lambda). Fourier analysis of the wavefront phase difference yields a peak...

  9. Reconstruction of two interfering wavefronts using Zernike polynomials and stochastic parallel gradient descent algorithm.

    Science.gov (United States)

    Yazdani, Roghayeh; Fallah, Hamid R; Hajimahmoodzadeh, Morteza

    2014-03-15

    We numerically and experimentally demonstrate an iterative method to simultaneously reconstruct two unknown interfering wavefronts. A three-dimensional interference pattern is analyzed and then Zernike polynomials and the stochastic parallel gradient descent algorithm are used to expand and calculate wavefronts.

  10. Mechanical signaling via nonlinear wavefront propagation in a mechanically excitable medium

    NARCIS (Netherlands)

    Idema, T.; Liu, A.J.

    2014-01-01

    Models that invoke nonlinear wavefront propagation in a chemically excitable medium are rife in the biological literature. Indeed, the idea that wavefront propagation can serve as a signaling mechanism has often been invoked to explain synchronization of developmental processes. In this paper we

  11. Angles-centroids fitting calibration and the centroid algorithm applied to reverse Hartmann test

    Science.gov (United States)

    Zhao, Zhu; Hui, Mei; Xia, Zhengzheng; Dong, Liquan; Liu, Ming; Liu, Xiaohua; Kong, Lingqin; Zhao, Yuejin

    2017-02-01

    In this paper, we develop an angles-centroids fitting (ACF) system and the centroid algorithm to calibrate the reverse Hartmann test (RHT) with sufficient precision. The essence of ACF calibration is to establish the relationship between ray angles and detector coordinates. Centroids computation is used to find correspondences between the rays of datum marks and detector pixels. Here, the point spread function of RHT is classified as circle of confusion (CoC), and the fitting of a CoC spot with 2D Gaussian profile to identify the centroid forms the basis of the centroid algorithm. Theoretical and experimental results of centroids computation demonstrate that the Gaussian fitting method has a less centroid shift or the shift grows at a slower pace when the quality of the image is reduced. In ACF tests, the optical instrumental alignments reach an overall accuracy of 0.1 pixel with the application of laser spot centroids tracking program. Locating the crystal at different positions, the feasibility and accuracy of ACF calibration are further validated to 10-6-10-4 rad root-mean-square error of the calibrations differences.

  12. A Clinical Study to Validate the Pupil Rescaling Technique by using COAS Shack Hartmann Aberrometer.

    Science.gov (United States)

    Kalikivayi, V; Kannan, K; Ganesan, A R

    2015-01-01

    In any optical system, optical aberrations of the imaging system affect the image quality. The human eye is also like an optical system which has optical aberrations influencing the quality of the retinal image. When pupil size exceeds 3 mm, ocular aberrations increase and play a major role on retinal image degradation. Pupil diameter is made constant in commercially available aberrometers by mathematically rescaling it. The aim of this study is to validate the pupil rescaling technique by using COAS (Complete Ophthalmic Analysis System)Shack Hartmann Aberrometer. Five subjects were recruited for this study. The measurements were taken over a moderately large pupil of 5mm in normal room illumination to allow for natural pupil dilation. The analyses diameter is fixed at 5 mm in COAS which means it rescales the aberration data to 5 mm if the pupil diameter recorded was more than 5 mm at the time of measurement. Ocular aberrations for natural and rescaled pupil sizes were analyzed. Estimation of ocular aberrations showed there was no statistical significance between natural pupil and rescaled pupil diameter.

  13. Ultrasound-guided Hartmann's solution enema: first-choice procedure for reducing idiopathic intussusception.

    Science.gov (United States)

    Di Renzo, D; Colangelo, M; Lauriti, G; De Girolamo, F; Persico, A; Lelli Chiesa, P

    2012-06-01

    This study was undertaken to compare the effectiveness of ultrasound-guided Hartmann's solution enema (US-E) and radiological liquid enema (RX-E) in reducing idiopathic ileocecocolic intussusceptions in relation to patient age and symptom duration. The study group consisted of 42 patients with idiopathic ileocecocolic intussusception treated with US-E (20 patients) or RX-E (23 patients), with one patient undergoing both procedures owing to recurrence. Patients were divided into subgroups according to age (12 months) and symptom duration (24 h). Complete reduction was achieved in 15/20 patients treated with US-E (75%) and in 10/23 treated with RX-E (43.5%) (p=ns). Recurrence was observed in 1/20 US-E and 0/23 RX-E (p=ns) patients. No complications were encountered. US-E had a significantly higher success rate than RX-E in patients >12 months (p=0.0063) and with symptom duration >24 h (p=0.0361). No differences were found in the other subgroups (p=ns). US-E and RX-E are procedures of comparable value and safety in reducing idiopathic intussusception. US-E seems to be more effective in patients >12 months or with symptom duration >24 h. As US-E avoids radiation exposure, it should be considered the first-choice procedure for reducing idiopathic ileocecocolic intussusception, particularly in these two subgroups of patients.

  14. A new species of Cavernocypris Hartmann, 1964 (Crustacea: Ostracoda) from caves in South Korea.

    Science.gov (United States)

    Smith, Robin James; Kamiya, Takahiro; Choi, Yong-Gun; Lee, Jimin; Chang, Cheon Young

    2017-05-17

    Surveys of caves in South Korea yielded a new species of the ostracod genus Cavernocypris Hartmann, 1964, herein described as Cavernocypris danielopoli Smith & Kamiya n. sp. This is the fifth described species in this widely distributed genus, and can be discriminated from its congeners by the highly triangular shape of the carapace in lateral view, caused by a large dorsal protrusion on the left valve. A second triangular-shaped morphotype was also collected, differing from the first by a lower carapace and less pronounced dorsal protrusion. As it is not clear at present if this represents a separate species or intraspecific variation, it is left in open nomenclature. The lack of a pigmented eye, a highly triangular carapace and no carapace pigmentation suggests that Cavernocypris danielopoli Smith & Kamiya n. sp. is the most adapted species in the genus to a stygobiotic lifestyle. Another Korean species, Cavernocypris coreana (McKenzie, 1972), found in caves and spring discharges, has a reduced number of antennule segments, common for stygobiotic species, but this feature is lacking in the new species. This suggests that within the genus, species have followed different evolutionary pathways to adapt to the subterranean realm.

  15. Modeling and characterization of wavefront morphologies of laser induced damages on dielectric coating

    Science.gov (United States)

    Zheng, Yi; Liu, Zhichao; Luo, Jin; Pan, Feng; Wang, Jian; Xu, Qiao

    2017-11-01

    The specific morphologies of laser induced damages on dielectric coating can cause wavefront modulations and influence the downstream propagation properties of transmitted beam, which is so called wavefront morphologies. In this paper, the modeling and characterization of these wavefront morphologies are carried out. In theory, the modulation effects of different morphologies are discussed and their influence on downstream beam propagation properties are simulated based on diffraction integral. In experiment, a pump-and-probe system is developed to characterize different wavefront morphologies, and in correspondence, their geometric morphologies are characterized by microscopic instruments. The simulation and experiment match well with each other, and the geometric characterization explains the origins of wavefront properties of different morphologies.

  16. 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.

  17. Problems with wavefront aberrations applied to refractive surgery: developing standards

    Science.gov (United States)

    Klein, Stanley A.

    2001-06-01

    Refractive surgery is evolving rapidly. A recent development uses wavefront aberration information to improve the surgical outcome. Before the wavefront information can be used effectively a number of problems must first be resolved. One of the main concerns is the presence of halos during night driving conditions. It seems clear that this problem occurs when the pupil is large enough to overlap the ablation transition zone. Several questions associated with the transition zone are examined. Shape descriptors to characterize the transition zone are discussed. Better ways of quantitatively characterizing the transition zone and predicting its properties are needed to help specify the ablation. Many of the issues associated with improving refractive surgery can be addressed by establishing a standards committee that includes basic researchers and clinicians. This committee can become a forum for developing techniques to assess visual outcomes, it can make recommendations for developing a database that would allow researchers to compare the intended outcome of ablation with the actual outcome. In order for this enterprise to be successful increased openness about surgery parameters and surgery outcome would be helpful.

  18. Tunable manipulation of terahertz wavefront based on graphene metasurfaces

    Science.gov (United States)

    Luo, Linbao; Wang, Kuiyuan; Guo, Kai; Shen, Fei; Zhang, Xudong; Yin, Zhiping; Guo, Zhongyi

    2017-11-01

    We have systematically investigated the performances of a tunable graphene metasurface that can dynamically manipulate the terahertz wavefronts. The metasurface consists of a silver substrate, SiO2 interlayer and the top graphene ribbons that can exhibit plasmon resonances to realize a phase shift by changing the Fermi levels of graphene ribbons. The plasmon resonances in graphene ribbons and Fabry–Perot resonances in the SiO2 interlayer work together for making the designed metasurface cover 2π phase range nearly. In the simulations, we can realize anomalous reflection at any angle by using the continuous phase modulation. On this basis, a reflective focusing lens based on the graphene metasurface has also been designed, which is designed in the frequency of 5.0 THz with a reasonable operation bandwidth from 4.5 THz to 6.5 THz. The corresponding focal lengths are designed as 300 μm and 100 μm, and the depths of focus (full width at half maximum along the Z direction) are 114 μm and 104 μm, respectively. Especially, the diameters of focal points (full width at half maximum along the X direction) are 29.5 μm and 24.1 μm, which are smaller than a half-wavelength (30 μm) in the focusing plane. It indicates that our designed focusing lenses have superior performance and can provide an opportunity to develop a tunable wavefront-controlling device.

  19. X-ray wavefront modeling of Bragg diffraction from crystals

    Science.gov (United States)

    Sutter, John P.

    2011-09-01

    The diffraction of an X-ray wavefront from a slightly distorted crystal can be modeled by the Takagi-Taupin theory, an extension of the well-known dynamical diffraction theory for perfect crystals. Maxwell's equations applied to a perturbed periodic medium yield two coupled differential equations in the incident and diffracted amplitude. These equations are discretized for numerical calculation into the determination of the two amplitudes on the points of an integration mesh, beginning with the incident amplitudes at the crystal's top surface. The result is a set of diffracted amplitudes on the top surface (in the Bragg geometry) or the bottom surface (in the Laue geometry), forming a wavefront that in turn can be propagated through free space using the Fresnel- Huygens equations. The performance of the Diamond Light Source I20 dispersive spectrometer has here been simulated using this method. Methods are shown for transforming displacements calculated by finite element analysis into local lattice distortions, and for efficiently performing 3-D linear interpolations from these onto the Takagi-Taupin integration mesh, allowing this method to be extended to crystals under thermal load or novel mechanical bender designs.

  20. Huygens-Fresnel wavefront tracing in non-uniform media

    CERN Document Server

    Volpe, F A; Zhao, A

    2015-01-01

    We present preliminary results on a novel numerical method describing wave propagation in non-uniform media. Following Huygens-Fresnel' principle, we model the wavefront as an array of point sources that emit wavelets, which interfere. We then identify a set of new points where the electric field has equal phase. In fact, without losing generality, we find zeros of the electric field, by means of the bisection method. This obviously corresponds to a specific phase-advance, but is easily generalized, e.g. by phase-shifting all sources. The points found form the new wavefront. One of the advantages of the method is that it includes diffraction. Two examples provided are diffraction around an obstacle and the finite waist of a focused Gaussian beam. Refraction is also successfully modeled, both in slowly-varying media as well as in the presence of discontinuities. The calculations were performed in two dimensions, but can be easily extended to three dimensions. We also discuss the extension to anisotropic, biref...

  1. X-ray pulse wavefront metrology using speckle tracking.

    Science.gov (United States)

    Berujon, Sebastien; Ziegler, Eric; Cloetens, Peter

    2015-07-01

    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.

  2. 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.

  3. Coronagraph-integrated wavefront sensing with a sparse aperture mask

    Science.gov (United States)

    Subedi, Hari; Zimmerman, Neil T.; Kasdin, N. Jeremy; Cavanagh, Kathleen; Riggs, A. J. Eldorado

    2015-07-01

    Stellar coronagraph performance is highly sensitive to optical aberrations. In order to effectively suppress starlight for exoplanet imaging applications, low-order wavefront aberrations entering a coronagraph, such as tip-tilt, defocus, and coma, must be determined and compensated. Previous authors have established the utility of pupil-plane masks (both nonredundant/sparse-aperture and generally asymmetric aperture masks) for wavefront sensing (WFS). Here, we show how a sparse aperture mask (SAM) can be integrated with a coronagraph to measure low-order differential phase aberrations. Starlight rejected by the coronagraph's focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a subsequent detector. Our numerical Fourier propagation models show that the information encoded in the fringe intensity distortions is sufficient to accurately discriminate and estimate Zernike phase modes extending from tip-tilt up to radial degree n=5, with amplitude up to λ/20 RMS. The SAM sensor can be integrated with both Lyot and shaped pupil coronagraphs at no detriment to the science beam quality. We characterize the reconstruction accuracy and the performance under low flux/short exposure time conditions, and place it in context of other coronagraph WFS schemes.

  4. 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

  5. Measuring the wavefront distortion of a phased-array laser radar by using a real-time optoelectronic measurement system

    Science.gov (United States)

    Zheng, Chunyan; Wu, Jian

    2009-11-01

    A real-time optoelectronic measurement system is proposed to measure the wavefront distortions of scanning beams of a phased-array laser radar. This measurement system includes electric control rotating and translating platforms and a cyclic radial shearing interferometer(CRSI). CRSI is an effective interferometry to mesure the laser wavefront. A inversion algorithm is used to precisely reconstruct wavefront phase distribution from interferograms generated by the CRSI. An actual experiment of laser wavefront distortion measurement is implemented successfully. The experimental results show that this optoelectromic measurement system can measure laser wavefront distortion of a phased-array laser radar in accuracy and in real time.

  6. Akademisk video

    DEFF Research Database (Denmark)

    Frølunde, Lisbeth

    2017-01-01

    Dette kapitel har fokus på metodiske problemstillinger, der opstår i forhold til at bruge (digital) video i forbindelse med forskningskommunikation, ikke mindst online. Video har længe været benyttet i forskningen til dataindsamling og forskningskommunikation. Med digitaliseringen og internettet er...... der dog opstået nye muligheder og udfordringer i forhold til at formidle og distribuere forskningsresultater til forskellige målgrupper via video. Samtidig er klassiske metodologiske problematikker som forskerens positionering i forhold til det undersøgte stadig aktuelle. Både klassiske og nye...... problemstillinger diskuteres i kapitlet, som rammesætter diskussionen ud fra forskellige positioneringsmuligheder: formidler, historiefortæller, eller dialogist. Disse positioner relaterer sig til genrer inden for ’akademisk video’. Afslutningsvis præsenteres en metodisk værktøjskasse med redskaber til planlægning...

  7. MHD flows in partially decoupled parallel U-bends at high Hartmann numbers

    Energy Technology Data Exchange (ETDEWEB)

    Stieglitz, R. [Association KfK-EURATOM, Kernforschungszentrum Karlsruhe GmbH, Inst. for Applied Thermo- und Fluiddynamics (IATF) (Germany); Barleon, L. [Association KfK-EURATOM, Kernforschungszentrum Karlsruhe GmbH, Inst. for Applied Thermo- und Fluiddynamics (IATF) (Germany); Reimann, J. [Association KfK-EURATOM, Kernforschungszentrum Karlsruhe GmbH, Inst. for Applied Thermo-und Fluiddynamics (IATF) (Germany); Mack, K.J. [Association KfK-EURATOM, Kernforschungszentrum Karlsruhe GmbH, Inst. for Applied Thermo- und Fluiddynamics (IATF) (Germany)

    1995-12-31

    In self-cooled liquid-metal fusion blanket concepts the radial-toroidal-radial U-bend flow represents an important design issue especially with regard to pressure loss and velocity distribution. If these U-bends are arranged in parallel and are electrically coupled via a common conducting wall large leakage currents can cause unequal pressure drops or flow rates in the individual channels. This effect of flow interaction, called multi-channel effect (MCE), affects the whole flow system and can produce prohibitive pressure losses. In liquid-metal blanket concepts an electrical separation of the bends by means of flow channel inserts is foreseen; however, the minimum requirements for the electrical separation are not investigated up to now. In the experiments presented in this paper, a U-geometry has been investigated where all walls in the radial and toroidal ducts are electrically conducting except for the dividing walls of the radial ducts, which are separated via an insulating foil. The pressure measurements exhibit that MCEs are still present, because electrical currents can short-circuit through the common Hartmann walls of the radial ducts. In the range of blanket relevant conditions a strong dependence of the pressure loss on inertial effects has been measured and the inertial part of the pressure drop was found to scale with N{sup -1/3}. A linear increase of the pressure loss with the number of channels has been found like for the same geometry, where all walls are conducting. Compared to the latter case the separation of the dividing walls leads to a decrease of the pressure drop of about 30%. (orig.).

  8. Video Analytics

    DEFF Research Database (Denmark)

    This book collects the papers presented at two workshops during the 23rd International Conference on Pattern Recognition (ICPR): the Third Workshop on Video Analytics for Audience Measurement (VAAM) and the Second International Workshop on Face and Facial Expression Recognition (FFER) from Real...... World Videos. The workshops were run on December 4, 2016, in Cancun in Mexico. The two workshops together received 13 papers. Each paper was then reviewed by at least two expert reviewers in the field. In all, 11 papers were accepted to be presented at the workshops. The topics covered in the papers...

  9. Clinical outcomes of corneal wavefront customized ablation strategies with SCHWIND CAM in LASIK treatments.

    Science.gov (United States)

    Arbelaez, Maria Clara; Vidal, Camila; Arba-Mosquera, Samuel

    2009-09-01

    To evaluate the clinical outcomes of aspheric corneal wavefront (CW) ablation profiles in LASIK treatments. Thirty eyes treated with CW ablation profiles were included after a follow-up of 6 months. In all cases, standard examinations including preoperative and postoperative wavefront analysis with a CW topographer (Optikon Keratron Scout) were performed. Custom Ablation Manager (CAM) software was used to plan corneal wavefront customized aspheric treatments, and the ESIRIS flying spot excimer laser system was used to perform the ablations (both SCHWIND eye-tech-solutions, Kleinhostheim, Germany). Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. In general, the postoperative uncorrected visual acuity and the best corrected visual acuity improved (p < 0.001). In particular, the trefoil, coma, and spherical aberrations, as well as the total root-mean-square values of higher order aberrations, were significantly reduced (p < 0.05) when the pre-existing aberrations were greater than the repeatability and the biological noise. The study results indicate that the aspheric corneal wavefront customized CAM approach for planning ablation volumes yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for correction of myopia and myopic astigmatism. The CW customized approach shows its strength in cases where abnormal optical systems are expected. Apart from the risk of additional ablation of corneal tissue, systematic wavefront-customized corneal ablation can be considered as a safe and beneficial method.

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

    Science.gov (United States)

    Amitonova, Lyubov V; Descloux, Adrien; Petschulat, Joerg; Frosz, Michael H; Ahmed, Goran; Babic, Fehim; Jiang, Xin; Mosk, Allard P; Russell, Philip St J; Pinkse, Pepijn W H

    2016-02-01

    We demonstrate that a high-numerical-aperture photonic crystal fiber allows lensless focusing at an unparalleled resolution 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 the beam waist and power in the focal spot on the fiber output using different types of fibers and different wavefront shaping approaches. We show that the complex wavefront shaping technique, together with a properly designed multimode photonic crystal fiber, enables us to create a tightly focused spot on the desired position on the fiber output facet with a subwavelength beam waist.

  11. Mechanical signaling via nonlinear wavefront propagation in a mechanically excitable medium

    Science.gov (United States)

    Idema, Timon; Liu, Andrea J.

    2014-06-01

    Models that invoke nonlinear wavefront propagation in a chemically excitable medium are rife in the biological literature. Indeed, the idea that wavefront propagation can serve as a signaling mechanism has often been invoked to explain synchronization of developmental processes. In this paper we suggest a kind of signaling based not on diffusion of a chemical species but on the propagation of mechanical stress. We construct a theoretical approach to describe mechanical signaling as a nonlinear wavefront propagation problem and study its dependence on key variables such as the effective elasticity and damping of the medium.

  12. Wavefront sensorless adaptive optics temporal focusing-based multiphoton microscopy

    Science.gov (United States)

    Chang, Chia-Yuan; Cheng, Li-Chung; Su, Hung-Wei; Hu, Yvonne Yuling; Cho, Keng-Chi; Yen, Wei-Chung; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen

    2014-01-01

    Temporal profile distortions reduce excitation efficiency and image quality in temporal focusing-based multiphoton microscopy. In order to compensate the distortions, a wavefront sensorless adaptive optics system (AOS) was integrated into the microscope. The feedback control signal of the AOS was acquired from local image intensity maximization via a hill-climbing algorithm. The control signal was then utilized to drive a deformable mirror in such a way as to eliminate the distortions. With the AOS correction, not only is the axial excitation symmetrically refocused, but the axial resolution with full two-photon excited fluorescence (TPEF) intensity is also maintained. Hence, the contrast of the TPEF image of a R6G-doped PMMA thin film is enhanced along with a 3.7-fold increase in intensity. Furthermore, the TPEF image quality of 1μm fluorescent beads sealed in agarose gel at different depths is improved. PMID:24940539

  13. 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.

  14. Video Analytics

    DEFF Research Database (Denmark)

    This book collects the papers presented at two workshops during the 23rd International Conference on Pattern Recognition (ICPR): the Third Workshop on Video Analytics for Audience Measurement (VAAM) and the Second International Workshop on Face and Facial Expression Recognition (FFER) from Real W...

  15. Fourier optics for wavefront engineering and wavelength control of lasers

    Science.gov (United States)

    Blanchard, Romain

    Since their initial demonstration in 1994, quantum cascade lasers (QCLs) have become prominent sources of mid-infrared radiation. Over the years, a large scientific and engineering effort has led to a dramatic improvement in their efficiency and power output, with continuous wave operation at room temperature and Watt-level output power now standard. However, beyond this progress, new functionalities and capabilities need to be added to this compact source to enable its integration into consumer-ready systems. Two main areas of development are particularly relevant from an application standpoint and were pursued during the course of this thesis: wavelength control and wavefront engineering of QCLs. The first research direction, wavelength control, is mainly driven by spectroscopic applications of QCLs, such as trace gas sensing, process monitoring or explosive detection. We demonstrated three different capabilities, corresponding to different potential spectroscopic measurement techniques: widely tunable single longitudinal mode lasing, simultaneous lasing on multiple well-defined longitudinal modes, and simultaneous lasing over a broad and continuous range of the spectrum. The second research direction, wavefront engineering of QCLs, i.e. the improvement of their beam quality, is relevant for applications necessitating transmission of the QCL output over a large distance, for example for remote sensing or military countermeasures. To address this issue, we developed plasmonic lenses directly integrated on the facets of QCLs. The plasmonic structures designed are analogous to antenna arrays imparting directionality to the QCLs, as well as providing means for polarization control. Finally, a research interest in plasmonics led us to design passive flat optical elements using plasmonic antennas. All these projects are tied together by the involvement of Fourier analysis as an essential design tool to predict the interaction of light with various gratings and periodic

  16. Fast wavefront optimization for focusing through biological tissue (Conference Presentation)

    Science.gov (United States)

    Blochet, Baptiste; Bourdieu, Laurent; Gigan, Sylvain

    2017-02-01

    The propagation of light in biological tissues is rapidly dominated by multiple scattering: ballistic light is exponentially attenuated, which limits the penetration depth of conventional microscopy techniques. For coherent light, the recombination of the different scattered paths creates a complex interference: speckle. Recently, different wavefront shaping techniques have been developed to coherently manipulate the speckle. It opens the possibility to focus light through complex media and ultimately to image in them, provided however that the medium can be considered as stationary. We have studied the possibility to focus in and through time-varying biological tissues. Their intrinsic temporal dynamics creates a fast decorrelation of the speckle pattern. Therefore, focusing through biological tissues requires fast wavefront shaping devices, sensors and algorithms. We have investigated the use of a MEMS-based spatial light modulator (SLM) and a fast photodetector, combined with FPGA electronics to implement a closed-loop optimization. Our optimization process is just limited by the temporal dynamics of the SLM (200µs) and the computation time (45µs), thus corresponding to a rate of 4 kHz. To our knowledge, it's the fastest closed loop optimization using phase modulators. We have studied the focusing through colloidal solutions of TiO2 particles in glycerol, allowing tunable temporal stability, and scattering properties similar to biological tissues. We have shown that our set-up fulfills the required characteristics (speed, enhancement) to focus through biological tissues. We are currently investigating the focusing through acute rat brain slices and the memory effect in dynamic scattering media.

  17. Colostomia tipo hartmann em ratos: alterações morfológicas e dosagem de hidroxiprolina

    Directory of Open Access Journals (Sweden)

    João Carlos Simões

    Full Text Available A colostomia tem sido um procedimento cirúrgico freqüentemente empregado nas doenças colônicas, lesões traumáticas e neoplásicas. Este trabalho experimental, em ratos, visou estudar as progressivas mudanças morfológicas no cólon proximal e distal , após uma laparotomia e colostomia terminal, tipo Hartmann, que foram estudadas histologicamente e através da dosagem tecidual de hidroxiprolina. Utilizaram-se 40 ratos, machos, raça Wistar, com peso médio de 200 gramas, alocados em dois grupos (grupo I ou experimento e grupo II ou controle, subdivididos em quatro subgrupos: A,B,C e D com 10 animais em cada subgrupo. Os animais do grupo I (subgrupos A e B foram submetidos à colostomia tipo Hartmann, no cólon distal, a 7,5cm do canal anal. Nos ratos do grupo II foi praticada apenas uma laparotomia mediana. Os animais dos subgrupo A e C foram sacrificados no 30º dia de P.O., enquanto que os animais dos subgrupos B e D o sacrifício foi no 60º dia de P.O. A análise histológica dos segmentos colônicos permitiu observar infiltrado inflamatório agudo e crônico na lâmina própria, achatamento pronunciado das criptas, diminuição do número de criptas e da celularidade epitelial, redução das células caliciformes e da mucossecreção, adelgaçamento da muscular da mucosa, mais intensos no coto colônico distal dos animais submetidos à colostomia terminal tipo Hartmann (subgrupos A e B. Os segmentos proximais apresentavam estas alterações, porém mais discretas. A dosagem de hidroxiprolina nos tecidos colônicos não revelou alterações estatisticamente significativas quanto ao conteúdo de colágeno ou do peso desidratado. Estes achados permitem demonstrar alterações morfológicas inflamatórias e hipotróficas mais pronunciadas no cólon distal de ratos submetidos à colostomia tipo Hartmann.

  18. Controlled trial of Hartmann's solution versus 0.9% saline for diabetic ketoacidosis.

    Science.gov (United States)

    Yung, Michael; Letton, Georgia; Keeley, Steve

    2017-01-01

    We aimed to determine whether using a balanced salt solution, Hartmann's solution (HS), in diabetic ketoacidosis (DKA) shortens the time to normalise acid-base status through the avoidance of hyperchloremic metabolic acidosis compared with 0.9% normal saline (NS). We conducted a double-blind, randomised controlled trial comparing HS to NS as the initial intravenous fluid in children with DKA. Patients were stratified by severity (pH < 7.1) and known or new diabetes. Electrolytes, venous blood gases and glucose were measured every 2 h until intravenous fluids were ceased. The primary outcome was the time for the plasma bicarbonate to reach 15 mmol/L. Secondary outcomes included time to normalise pH (7.3), time to receive subcutaneous (SC) insulin, change in sodium and insulin requirement. A total of 77 children were enrolled. The groups were similar at baseline. There was no difference in the time to reach a bicarbonate of 15 mmol/L: geometric mean (SD) 8.6 (2.3) h for NS versus 6.2 (4.7) h for HS, ratio 1.4 (95% confidence interval 0.8-2.5), and no difference in time to normalise pH: NS 8.5 (2.3) h versus HS group 7.5 (1.8) h, ratio 1.1 (0.8-1.6). Kaplan-Meier survival estimates showed shorter times for these end-points in the severe subgroup: log-rank test P = 0.0277 and 0.0024, respectively. There was no difference in time to SC insulin, NS: 15.2 (2.4) h versus HS 14.3 (1.6) h, ratio 1.1 (0.8-1.5). Patients treated with HS received significantly less total fluids/kg. HS is an acceptable alternative to NS in DKA and may benefit those with severe DKA. © 2017 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).

  19. Wavefront aberration changes caused by a gradient of increasing accommodation stimuli

    National Research Council Canada - National Science Library

    Zhou, X-Y; Wang, L; Zhou, X-T; Yu, Z-Q

    2015-01-01

    ...), were included in this study. After dilating the right pupil with 0.5% phenylephrine drops, the wavefront aberration of the right eye was measured continuously either without or with 1, 2, 3, 4, 5, or 6D accommodation stimuli...

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

    Energy Technology Data Exchange (ETDEWEB)

    Jin Chunhua [Department of Mathematics, and Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012 (China)], E-mail: jinchhua@126.com; Yin Jingxue [Department of Mathematics, and Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, Jilin University, Changchun 130012 (China); Wang Yifu [Department of Mathematics, Beijing Institute of Technology, Beijing 100081 (China)

    2009-01-30

    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.

  1. Wavefront Correction of Ionospherically Propagated HF Radio Waves Using Covariance Matching Techniques

    Directory of Open Access Journals (Sweden)

    Y. Zhu

    2017-04-01

    Full Text Available High Frequency (HF radio waves propagating in the ionospheric random inhomogeneous media exhibit a spatial nonlinearity wavefront which may limit the performance of conventional high-resolution methods for HF sky wave radar systems. In this paper, the spatial correlation function of wavefront is theoretically derived on condition that the radio waves propagate through the ionospheric structure containing irregularities. With this function, the influence of wavefront distortions on the array covariance matrix can be quantitatively described with the spatial coherence matrix, which is characterized with the coherence loss parameter. Therefore, the problem of wavefront correction is recast as the determination of coherence loss parameter and this is solved by the covariance matching (CM technique. The effectiveness of the proposed method is evaluated both by the simulated and real radar data. It is shown numerically that an improved direction of arrival (DOA estimation performance can be achieved with the corrected array covariance matrix.

  2. Efficient polarization insensitive complex wavefront control using Huygens' metasurfaces based on dielectric resonant meta-atoms

    CERN Document Server

    Chong, Katie E; Staude, Isabelle; James, Anthony; Dominguez, Jason; Liu, Sheng; Subramania, Ganapathi S; Decker, Manuel; Neshev, Dragomir N; Brener, Igal; Kivshar, Yuri S

    2016-01-01

    Subwavelength-thin metasurfaces have shown great promises for the control of optical wavefronts, thus opening new pathways for the development of efficient flat optics. In particular, Huygens' metasurfaces based on all-dielectric resonant meta-atoms have already shown a huge potential for practical applications with their polarization insensitivity and high transmittance efficiency. Here, we experimentally demonstrate a polarization insensitive holographic Huygens' metasurface based on dielectric resonant meta-atoms capable of complex wavefront control at telecom wavelengths. Our metasurface produces a hologram image in the far-field with 82% transmittance efficiency and 40% imaging efficiency. Such efficient complex wavefront control shows that Huygens' metasurfaces based on resonant dielectric meta-atoms are a big step towards practical applications of metasurfaces in wavefront design related technologies, including computer-generated holograms, ultra-thin optics, security and data storage devices.

  3. 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.

  4. Video Analytics

    DEFF Research Database (Denmark)

    This book collects the papers presented at two workshops during the 23rd International Conference on Pattern Recognition (ICPR): the Third Workshop on Video Analytics for Audience Measurement (VAAM) and the Second International Workshop on Face and Facial Expression Recognition (FFER) from Real...... include: re-identification, consumer behavior analysis, utilizing pupillary response for task difficulty measurement, logo detection, saliency prediction, classification of facial expressions, face recognition, face verification, age estimation, super-resolution, pose estimation, and pain recognition...

  5. Video Analytics

    DEFF Research Database (Denmark)

    include: re-identification, consumer behavior analysis, utilizing pupillary response for task difficulty measurement, logo detection, saliency prediction, classification of facial expressions, face recognition, face verification, age estimation, super-resolution, pose estimation, and pain recognition......This book collects the papers presented at two workshops during the 23rd International Conference on Pattern Recognition (ICPR): the Third Workshop on Video Analytics for Audience Measurement (VAAM) and the Second International Workshop on Face and Facial Expression Recognition (FFER) from Real...

  6. Phase-shift interference-based wavefront characterization for orbital angular momentum modes.

    Science.gov (United States)

    Huang, Hao; Ren, Yongxiong; Yan, Yan; Ahmed, Nisar; Yue, Yang; Bozovich, Amanda; Erkmen, Baris I; Birnbaum, Kevin; Dolinar, Sam; Tur, Moshe; Willner, Alan E

    2013-07-01

    Wavefront characterization for orbital angular momentum (OAM) modes is demonstrated using quadrature phase-shift interference. The phase fronts and intensity profiles of OAM(-2), OAM(-4), OAM(-6), and OAM(-8) are measured. Wavefront correlations between the experimental results and the pure Laguerre-Gaussian modes are calculated to evaluate the measurement. The measured results are in reasonable agreement with the anticipated results based on simulations.

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

    OpenAIRE

    Camellin, Massimo; Guidotti, Jacopo Maria; Arba Mosquera, Samuel

    2016-01-01

    Purpose To evaluate the efficacy and safety of Corneal-Wavefront guided transepithelial photorefractive keratectomy (TransPRK) after corneal collagen cross linking (CXL) in keratoconic patients. Methods In this retrospective, non-comparative, consecutive case series, 39 keratoconic eyes underwent Corneal-Wavefront guided TransPRK for the correction of aberrations at least 4 months after conventional CXL at SEKAL Rovigo Microsurgery Centre, Rovigo, Italy. Two eyes (5%) underwent a secondary la...

  8. Nicolai Hartmann: Una apostilla bio-bibliográfica a propósito de la traducción de su Ética

    Directory of Open Access Journals (Sweden)

    Paulo Vélez León

    2012-06-01

    Full Text Available [ES] En este trabajo [1] se especifican los aspectos centrales de la estructura y contenido de la monumental obra de Nicolai Hartmann, recientemente traducida al castellano, Ética, y [2] en correspondencia con lo anterior, se indica sumariamente el propósito de su planteamiento ético. [EN] In this work (1 it is specified the central aspects of the structure and content of Nicolai Hartmann´s monumental oeuvre, recently translated into Spanish, Ethics, and (2 in correspondence with the above, it is summarily indicated the purpose of his ethical approach.

  9. Hartmann-Hahn 2D-map to optimize the RAMP-CPMAS NMR experiment for pharmaceutical materials.

    Science.gov (United States)

    Suzuki, Kazuko; Martineau, Charlotte; Fink, Gerhard; Steuernagel, Stefan; Taulelle, Francis

    2012-02-01

    Cross polarization-magic angle spinning (CPMAS) is the most used experiment for solid-state NMR measurements in the pharmaceutical industry, with the well-known variant RAMP-CPMAS its dominant implementation. The experimental work presented in this contribution focuses on the entangled effects of the main parameters of such an experiment. The shape of the RAMP-CP pulse has been considered as well as the contact time duration, and a particular attention also has been devoted to the radio-frequency (RF) field inhomogeneity. (13)C CPMAS NMR spectra have been recorded with a systematic variation of (13)C and (1)H constant radiofrequency field pair values and represented as a Hartmann-Hahn matching two-dimensional map. Such a map yields a rational overview of the intricate optimal conditions necessary to achieve an efficient CP magnetization transfer. The map also highlights the effects of sweeping the RF by the RAMP-CP pulse on the number of Hartmann-Hahn matches crossed and how RF field inhomogeneity helps in increasing the CP efficiency by using a larger fraction of the sample. In the light of the results, strategies for optimal RAMP-CPMAS measurements are suggested, which lead to a much higher efficiency than constant amplitude CP experiment. Copyright © 2012 John Wiley & Sons, Ltd.

  10. VizieR Online Data Catalog: Atlas of Galactic Neutral Hydrogen (Hartmann+, 1997)

    Science.gov (United States)

    Hartmann, D.; Burton, W. B.

    1999-04-01

    The Leiden/Dwingeloo HI survey mapped the 21-cm spectral line emission over the entire sky above declinations of -30 degrees using a grid spacing of ~ 0.5 degree and a velocity sampling of ~ 1.03 km/s. The useful velocity (V_lsr) range is from -450 to +400 km/s. The Atlas presents calibrated spectra in units of brightness temperature. Using interpolation and averaging, the authors have placed their data on an evenly-spaced grid in Galactic coordinates (l,b). A detailed discussion of the instrument and calibration procedures is provided in the published Atlas. The average sensitivity level of the survey is 0.07 K (1-sigma, rms). This sensitivity level depends critically on the success of the stray-radiation correction as discussed in Hartmann et al. (1996A&AS..119..115H). In that discussion, several caveats are offered regarding the removal of stray radiation, in particular that component which might be due to reflection from the ground. Some instances have been found where there are residuals which are clearly larger than the mean accuracy quoted as representative of the Leiden/Dwingeloo survey. Users of the data are reminded that the stray-radiation correction was applied conservatively, ensuring that no overestimate was calculated and removed, thereby yielding spurious negative intensities. A specific example of remaining spurious emission is evident towards the North Galactic Pole, a direction notoriously difficult to observe. All spectra taken towards b=+90 degrees should, of course, be identical, no matter the longitude or the orientation of the telescope with respect to the ground or to the meridian. Because the sky was sampled in 5x5 degree boxes, a spectrum was recorded at b=+90 degrees for every Nx5 degrees (N=0..72) in longitude. The spectra in the final dataset were interpolated between these measured spectra to yield a 0.5x0.5 degree grid. So, only every 10th spectrum at this extreme latitude corresponds to an observed spectrum. Comparing all spectra at

  11. The CAFADIS camera: a new tomographic wavefront sensor for Adaptive Optics

    Science.gov (United States)

    Rodríguez, J. M.; Femenía, B.; Montilla, I.; Rodríguez-Ramos, L. F.; Marichal-Hernández, J. G.; Lüke, J. P.; López, R.; Díaz, J. J.; Martín, Y.

    The CAFADIS camera is a new wavefront sensor (WFS) patented by the Universidad de La Laguna. CAFADIS is a system based on the concept of plenoptic camera originally proposed by Adelson and Wang [Single lens stereo with a plenoptic camera, IEEE Transactions on Pattern Analysis and Machine Intelligence 14 (1992)] and its most salient feature is its ability to simultaneously measuring wavefront maps and distances to objects [Wavefront and distance measurements using the CAFADIS camera, in Astronomical telescopes, Marseille (2008)]. This makes of CAFADIS an interesting alternative for LGS-based AO systems as it is capable of measuring from an LGS-beacon the atmospheric turbulence wavefront and simultaneously the distance to the LGS beacon thus removing the need of a NGS defocus sensor to probe changes in distance to the LGS beacon due to drifts of the mesospheric Na layer. In principle, the concept can also be employed to recover 3D profiles of the Na Layer allowing for optimizations of the measurement of the distance to the LGS-beacon. Currently we are investigating the possibility of extending the plenoptic WFS into a tomographic wavefront sensor. Simulations will be shown of a plenoptic WFS when operated within an LGS-based AO system for the recovery of wavefront maps at different heights. The preliminary results presented here show the tomographic ability of CAFADIS.

  12. X-ray grating interferometer for in situ and at-wavelength wavefront metrology.

    Science.gov (United States)

    Kayser, Yves; David, Christian; Flechsig, Uwe; Krempasky, Juraj; Schlott, Volker; Abela, Rafael

    2017-01-01

    A wavefront metrology setup based on the X-ray grating interferometry technique for spatially resolved, quantitative, in situ and at-wavelength measurements of the wavefront at synchrotron radiation and hard X-ray free-electron laser beamlines is reported. Indeed, the ever-increasing demands on the optical components to preserve the wavefront shape and the coherence of the delivered X-ray beam call for more and more sensitive diagnostic instruments. Thanks to its angular sensitivity, X-ray grating interferometry has been established in recent years as an adequate wavefront-sensing technique for quantitatively assessing the quality of the X-ray wavefront under working conditions and hence for the in situ investigation of X-ray optical elements. In order to characterize the optical elements at any given beamline by measuring the aberrations introduced in the wavefront, a transportable X-ray grating interferometry setup was realised at the Swiss Light Source (SLS). The instrument, which is expected to be a valuable tool for investigating the quality of the X-ray beam delivered at an endstation, will be described hereafter in terms of the hardware setup and the related data analysis procedure. Several exemplary experiments performed at the X05DA Optics beamline of the SLS will be presented.

  13. 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.

  14. Gaussian Process Kalman Filter for Focal Plane Wavefront Correction and Exoplanet Signal Extraction

    Science.gov (United States)

    Sun, He; Kasdin, N. Jeremy

    2018-01-01

    Currently, the ultimate limitation of space-based coronagraphy is the ability to subtract the residual PSF after wavefront correction to reveal the planet. Called reference difference imaging (RDI), the technique consists of conducting wavefront control to collect the reference point spread function (PSF) by observing a bright star, and then extracting target planet signals by subtracting a weighted sum of reference PSFs. Unfortunately, this technique is inherently inefficient because it spends a significant fraction of the observing time on the reference star rather than the target star with the planet. Recent progress in model based wavefront estimation suggests an alternative approach. A Kalman filter can be used to estimate the stellar PSF for correction by the wavefront control system while simultaneously estimating the planet signal. Without observing the reference star, the (extended) Kalman filter directly utilizes the wavefront correction data and combines the time series observations and model predictions to estimate the stellar PSF and planet signals. Because wavefront correction is used during the entire observation with no slewing, the system has inherently better stability. In this poster we show our results aimed at further improving our Kalman filter estimation accuracy by including not only temporal correlations but also spatial correlations among neighboring pixels in the images. This technique is known as a Gaussian process Kalman filter (GPKF). We also demonstrate the advantages of using a Kalman filter rather than RDI by simulating a real space exoplanet detection mission.

  15. Advances in Focal Plane Wavefront Estimation for Directly Imaging Exoplanets

    Science.gov (United States)

    Eldorado Riggs, A. J.; Kasdin, N. Jeremy; Groff, Tyler Dean

    2015-01-01

    To image cold exoplanets directly in visible light, an instrument on a telescope needs to suppress starlight by about 9 orders of magnitude at small separations from the star. A coronagraph changes the point spread function to create regions of high contrast where exoplanets or disks can be seen. Aberrations on the optics degrade the contrast by several orders of magnitude, so all high-contrast imaging systems incorporate one or more deformable mirrors (DMs) to recover regions of high contrast. With a coronagraphic instrument planned for the WFIRST-AFTA space telescope, there is a pressing need for faster, more robust estimation and control schemes for the DMs. Non-common path aberrations limit conventional phase conjugation schemes to medium star-to-planet contrast ratios of about 1e-6. High-contrast imaging requires estimation and control of both phase and amplitude in the same beam path as the science camera. Field estimation is a challenge since only intensity is measured; the most common approach, including that planned for WFIRST-AFTA, is to use DMs to create diversity, via pairs of small probe shapes, thereby allowing disambiguation of the electric field. Most implementations of DM Diversity require at least five images per electric field estimate and require narrowband measurements. This paper describes our new estimation algorithms that improve the speed (by using fewer images) and bandwidth of focal plane wavefront estimation. For narrowband estimation, we are testing nonlinear, recursive algorithms such as an iterative extended Kalman filter (IEKF) to use three images each iteration and build better, more robust estimates. We are also exploring the use of broadband estimation without the need for narrowband sub-filters and measurements. Here we present simulations of these algorithms with realistic noise and small signals to show how they might perform for WFIRST-AFTA. Once validated in simulations, we will test these algorithms experimentally in

  16. Beamlet pulse-generation and wavefront-control system

    Energy Technology Data Exchange (ETDEWEB)

    Van Wonterghem, B.M.; Salmon, J.T.; Wilcox, R.W.

    1996-06-01

    The Beamlet pulse-generation system (or {open_quotes}front end{close_quotes}) refers to the laser hardware that generates the spatially and temporally shaped pulse that is injected into the main laser cavity. All large ICF lasers have pulse-generation systems that typically consist of a narrow-band oscillator, elector-optic modulators for temporal and bandwidth shaping, and one or more preamplifiers. Temporal shaping is used to provide the desired laser output pulse shape and also to compensate for gain saturation effects in the large-aperture amplifiers. Bandwidth is applied to fulfill specific target irradiation requirements and to avoid stimulated Brillouin scattering (SBS) in large-aperture laser components. Usually the sharp edge of the beam`s spatial intensity profile is apodized before injection in the main amplifier beam line. This prevents large-amplitude ripples on the intensity profile. Here the authors briefly review the front-end design and discuss improvements to the oscillator and modulator systems. Their main focus, however, is to describe Beamlet`s novel beam-shaping and wavefront-control systems that have recently been fully activated and tested.

  17. 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.

  18. Wavefront aberrations of x-ray dynamical diffraction beams.

    Science.gov (United States)

    Liao, Keliang; Hong, Youli; Sheng, Weifan

    2014-10-01

    The effects of dynamical diffraction in x-ray diffractive optics with large numerical aperture render the wavefront aberrations difficult to describe using the aberration polynomials, yet knowledge of them plays an important role in a vast variety of scientific problems ranging from optical testing to adaptive optics. Although the diffraction theory of optical aberrations was established decades ago, its application in the area of x-ray dynamical diffraction theory (DDT) is still lacking. Here, we conduct a theoretical study on the aberration properties of x-ray dynamical diffraction beams. By treating the modulus of the complex envelope as the amplitude weight function in the orthogonalization procedure, we generalize the nonrecursive matrix method for the determination of orthonormal aberration polynomials, wherein Zernike DDT and Legendre DDT polynomials are proposed. As an example, we investigate the aberration evolution inside a tilted multilayer Laue lens. The corresponding Legendre DDT polynomials are obtained numerically, which represent balanced aberrations yielding minimum variance of the classical aberrations of an anamorphic optical system. The balancing of classical aberrations and their standard deviations are discussed. We also present the Strehl ratio of the primary and secondary balanced aberrations.

  19. Harmonic source wavefront aberration correction for ultrasound imaging

    Science.gov (United States)

    Dianis, Scott W.; von Ramm, Olaf T.

    2011-01-01

    A method is proposed which uses a lower-frequency transmit to create a known harmonic acoustical source in tissue suitable for wavefront correction without a priori assumptions of the target or requiring a transponder. The measurement and imaging steps of this method were implemented on the Duke phased array system with a two-dimensional (2-D) array. The method was tested with multiple electronic aberrators [0.39π to 1.16π radians root-mean-square (rms) at 4.17 MHz] and with a physical aberrator 0.17π radians rms at 4.17 MHz) in a variety of imaging situations. Corrections were quantified in terms of peak beam amplitude compared to the unaberrated case, with restoration between 0.6 and 36.6 dB of peak amplitude with a single correction. Standard phantom images before and after correction were obtained and showed both visible improvement and 14 dB contrast improvement after correction. This method, when combined with previous phase correction methods, may be an important step that leads to improved clinical images. PMID:21303031

  20. 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.

  1. Terahertz wavefront manipulating by double-layer graphene ribbons metasurface

    Science.gov (United States)

    Zhao, Hongliang; Chen, Zhihong; Su, Fei; Ren, Guangjun; Liu, Fei; Yao, Jianquan

    2017-11-01

    It was recently presented that the phase gradient metasurface can focus the reflection in terahertz range. However, narrow bandwidth and complex tuning method are still challenges. For instance, the size is difficult to be changed once the device is built. We propose a tunable double-layer graphene ribbons array (DLGRA) metasurface which has great potentials for applications in terahertz wavefront control. By changing the Fermi level of each graphene ribbon independently, the DLGRA separated by a bonding agent and a thin dielectric spacer can achieve nearly 2 π phase shift with high reflection efficiency. A reflector which can focus terahertz waves over a broad frequency range is demonstrated numerically by the DLGRA. Intriguingly, through a lateral shift between the nearby graphene ribbons, the variation of coupling induces a shift of focusing frequency. Hence, this approach increases the frequency range to a higher degree than the fixed state. The proposed metasurface provides an effective way for manipulating terahertz waves in a broad frequency range.

  2. 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.

  3. Recursive Focal Plane Wavefront and Bias Estimation for the Direct Imaging of Exoplanets

    Science.gov (United States)

    Eldorado Riggs, A. J.; Kasdin, N. Jeremy; Groff, Tyler Dean

    2016-01-01

    To image the reflected light from exoplanets and disks, an instrument must suppress diffracted starlight by about nine orders of magnitude. A coronagraph alters the stellar PSF to create regions of high contrast, but it is extremely sensitive to wavefront aberrations. Deformable mirrors (DMs) are necessary to mitigate these quasi-static aberrations and recover high-contrast. To avoid non-common path aberrations, the science camera must be used as the primary wavefront sensor. Focal plane wavefront correction is an iterative process, and obtaining sufficient signal in the dark holes requires long exposure times. The fastest coronagraphic wavefront correction techniques require estimates of the stellar electric field. The main challenge of coronagraphy is thus to perform complex wavefront estimation quickly and efficiently using intensity images from the camera. The most widely applicable and tested technique is DM Diversity, in which a DM modulates the focal plane intensity and several images are used to reconstruct the stellar electric field in a batch process. At the High Contrast Imaging Lab (HCIL) at Princeton, we have developed an iterative extended Kalman filter (IEKF) to improve upon this technique. The IEKF enables recursive starlight estimation and can utilize fewer images per iteration, thereby speeding up wavefront correction. This IEKF formulation also estimates the bias in the images recursively. Since exoplanets and disks are embedded in the incoherent bias signal, the IEKF enables detection of science targets during wavefront correction. Here we present simulated and experimental results from Princeton's HCIL demonstrating the effectiveness of the IEKF for recursive electric field estimation and exoplanet detection.

  4. Hypotension during epidural analgesia for Caesarean section. Arterial and central venous pressure changes after acute intravenous loading with two litres of Hartmann's solution.

    Science.gov (United States)

    Lewis, M; Thomas, P; Wilkes, R G

    1983-03-01

    The incidence of hypotension occurring in women undergoing Caesarean section with epidural analgesia was investigated in 60 patients receiving an intravenous preload of two litres Hartmann's solution. Hypotension occurred in only 6.7% of patients. Central venous pressure measurements in 20 patients confirmed the safety of the technique. A comparison is made with other preloading techniques.

  5. Management of chronic subdural haematoma: burr hole drainage, replacement with Hartmann's solution, and closed-system drainage.

    Science.gov (United States)

    Aung; Wong; Mo; Tsang

    1999-12-01

    Although the treatment of chronic subdural haematoma by burr hole drainage has been performed in the past with or without using a closed drainage system, the problem of intracranial air entrapment still persists and can cause a deterioration in the level of consciousness or seizures in the postoperative period. Cerebral infarction may also develop a few days after surgery because of the intracranial hypotension that occurs during the drainage procedure. In an attempt to minimise these complications and to prevent cerebral infarction and its attendant morbidity, we have developed a technique of treating chronic subdural haematoma-namely, performing burr hole drainage, irrigation and replacement of the haematoma with Hartmann's solution, and closed-system drainage of the subdural space with a silicone catheter. The blood pressure is closely monitored and maintained by the infusion of fluids throughout the procedure. An illustrative case using this technique is presented in this paper.

  6. Arthropod parasites of springbok, gemsbok, kudus, giraffes and Burchell's and Hartmann's zebras in the Etosha and Hardap Nature Reserves, Namibia.

    Science.gov (United States)

    Horak, I G; Anthonissen, M; Krecek, R C; Boomker, J

    1992-12-01

    A total of 48 springbok, 48 gemsbok, 23 kudus and 6 giraffes were examined for ticks and lice, while 9 Burchell's zebras and 6 Hartmann's mountain zebras were examined only for ticks. Springbok and gemsbok were shot in both the Etosha National Park in the north and the Hardap Nature Reserve in the south of Namibia. All the other animals were shot in the Etosha National Park. A total of 7 ixodid tick species and 8 lice species were recovered. The springbok carried few ticks. The adults of a Rhipicephalus sp. (near R. oculatus) were most numerous on the gemsbok, especially during November. The kudus were the only animals harbouring Rhipicephalus zambeziensis. Adult Hyalomma truncatum, followed by adult Hyalomma marginatum rufipes, were most abundant on the giraffes and adult Rhipicephalus evertsi mimeticus were commonest on the zebras.

  7. Primary anastomosis with a defunctioning stoma versus Hartmann's procedure for perforated diverticulitis--a comparison of stoma reversal rates.

    Science.gov (United States)

    Alizai, P H; Schulze-Hagen, M; Klink, C D; Ulmer, F; Roeth, A A; Neumann, U P; Jansen, M; Rosch, R

    2013-12-01

    The ideal treatment of patients with perforated diverticulitis is still controversial. Hartmann's procedure has been the treatment of choice for decades, but primary anastomosis with a defunctioning stoma has become an accepted alternative. The aim of this study was to evaluate the stoma reversal rates after these two surgical strategies. A retrospective review of the data from patients with perforated sigmoid diverticulitis between 2002 and 2011 undergoing a Hartmann's procedure (HP) versus a primary anastomosis with a defunctioning stoma (PA) was performed. Additionally, patients were contacted by mail or telephone in March 2012 using a standardized questionnaire. A total of 98 patients were identified: 72 undergoing HP and 26 patients receiving PA. The median follow-up time was 63 months (range 4-118). Whilst 85 % of patients with PA have had their stoma reversed, only 58 % of patients with an HP had a stoma reversal (p = 0.046). The median period until stoma reversal was significantly longer for HP (19 weeks) than for PA (12 weeks; p = 0.03). The 30-day mortality for PA was 12 % as opposed to 25 % for HP (p = 0.167). According to the Clavien-Dindo classification, surgical complications occurred significantly less frequently in patients with PA (p = 0.014). The stoma reversal rates for PA are significantly higher than for HP. Thus, depending on the overall clinical situation, primary resection and anastomosis with a proximal defunctioning stoma might be the optimal procedure for selected patients with perforated diverticular disease.

  8. Hartmann's Procedure or Primary Anastomosis for Generalized Peritonitis due to Perforated Diverticulitis: A Prospective Multicenter Randomized Trial (DIVERTI).

    Science.gov (United States)

    Bridoux, Valerie; Regimbeau, Jean Marc; Ouaissi, Mehdi; Mathonnet, Muriel; Mauvais, Francois; Houivet, Estelle; Schwarz, Lilian; Mege, Diane; Sielezneff, Igor; Sabbagh, Charles; Tuech, Jean-Jacques

    2017-12-01

    About 25% of patients with acute diverticulitis require emergency intervention. Currently, most patients with diverticular peritonitis undergo a Hartmann's procedure. Our objective was to assess whether primary anastomosis (PA) with a diverting stoma results in lower mortality rates than Hartmann's procedure (HP) in patients with diverticular peritonitis. We conducted a multicenter randomized controlled trial conducted between June 2008 and May 2012: the DIVERTI (Primary vs Secondary Anastomosis for Hinchey Stage III-IV Diverticulitis) trial. Follow-up duration was up to 18 months. A random sample of 102 eligible participants with purulent or fecal diverticular peritonitis from tertiary care referral centers and associated centers in France were equally randomized to either a PA arm or to an HP arm. Data were analyzed on an intention-to-treat basis. The primary end point was mortality rate at 18 months. Secondary outcomes were postoperative complications, operative time, length of hospital stay, rate of definitive stoma, and morbidity. All 102 patients enrolled were comparable for age (p = 0.4453), sex (p = 0.2347), Hinchey stage III vs IV (p = 0.2347), and Mannheim Peritonitis Index (p = 0.0606). Overall mortality did not differ significantly between HP (7.7%) and PA (4%) (p = 0.4233). Morbidity for both resection and stoma reversal operations were comparable (39% in the HP arm vs 44% in the PA arm; p = 0.4233). At 18 months, 96% of PA patients and 65% of HP patients had a stoma reversal (p = 0.0001). Although mortality was similar in both arms, the rate of stoma reversal was significantly higher in the PA arm. This trial provides additional evidence in favor of PA with diverting ileostomy over HP in patients with diverticular peritonitis. ClinicalTrials.gov Identifier: NCT 00692393. Copyright © 2017. Published by Elsevier Inc.

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

    CERN Document Server

    Apel, W D; Bähren, L; Bekk, K; Bertaina, M; Biermann, P L; Blümer, J; Bozdog, H; Brancus, I M; Cantoni, E; Chiavassa, A; Daumiller, K; de Souza, V; Di Pierro, F; Doll, P; Engel, R; Falcke, H; Fuchs, B; Gemmeke, H; Grupen, C; Haungs, A; Heck, D; Hörandel, J R; Horneffer, A; Huber, D; Huege, T; Isar, P G; Kampert, K -H; Kang, D; Krömer, O; Kuijpers, J; Link, K; Luczak, P; Ludwig, M; Mathes, H J; Melissas, M; Morello, C; Oehlschläger, J; Palmieri, N; Pierog, T; Rautenberg, J; Rebel, H; Roth, M; Rühle, C; Saftoiu, A; Schieler, H; Schmidt, A; Schröder, F G; Sima, O; Toma, G; Trinchero, G C; Weindl, A; Wochele, J; Zabierowski, J; Zensus, J A

    2014-01-01

    Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above $10^{17}$eV and zenith angles smaller than $45^\\circ$, we find that the radio wavefront of cosmic-ray air showers is of hyperbolic shape. At axis distances $\\gtrsim 50$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 lim...

  10. Performance Comparison of Wavefront-Sensorless Adaptive Optics Systems by Using of the Focal Plane

    Directory of Open Access Journals (Sweden)

    Huizhen Yang

    2015-01-01

    Full Text Available The correction capability and the convergence speed of the wavefront-sensorless adaptive optics (AO system are compared based on two different system control algorithms, which both use the information of focal plane. The first algorithm is designed through the linear relationship between the second moment of the aberration gradients and the masked far-field intensity distribution and the second is stochastic parallel gradient descent (SPGD, which is the most commonly used algorithm in wavefront-sensorless AO systems. A wavefront-sensorless AO model is established with a 61-element deformable mirror (DM and a CCD. Performance of the two control algorithms is investigated and compared through correcting different wavefront aberrations. Results show that the correction ability of AO system based on the proposed control algorithm is obviously better than that of AO system based on SPGD algorithm when the wavefront aberrations increase. The time needed by the proposed control algorithm is much less than that of SPGD when the AO system achieves similar correction results. Additionally, the convergence speed of the proposed control algorithm is independent of the turbulence strength while the number of intensity measurements needed by SPGD increases as the turbulence strength magnifies.

  11. Field diversity phase retrieval method for wavefront sensing in monolithic mirror space telescopes.

    Science.gov (United States)

    Ju, Guohao; Yan, Changxiang; Yue, Dan; Gu, Zhiyuan

    2017-05-20

    To guarantee the uniqueness of the solution for the wavefront phase, a series of intensity images with known phase diversities is usually needed in the current phase retrieval wavefront sensing methods. However, to obtain these intensity images with deliberately added diversity phases, some additional instruments (e.g., beam splitters) or operations (e.g., adjustment of the focus) are usually needed, which can pose a challenge for wavefront sensing in space telescopes. This paper proposes a new concept for retrieving the wavefront phase of monolithic mirror space telescopes with perturbations, where the intensity measurements with phase diversities are directly obtained from different field positions of one image, without the need for any additional instruments or operations. To realize this new concept, we present a modified phase diversity method to account for the unknown phase diversities between these intensity measurements based on an in-depth understanding of the net aberration fields induced by misalignments and figure errors. Relevant simulations for different cases are performed to demonstrate the feasibility and accuracy of the proposed method. Since in this method the phase diversities between different intensity measurements are mainly induced by the diversities in the field position, we call it the field diversity phase retrieval method. This work can present great facility for wavefront sensing in monolithic mirror space telescopes.

  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. Effect of wavefront divergence in the quantitative measurement analysis of electronic speckle pattern shearing interferometry (ESPSI)

    Science.gov (United States)

    Wan Abdullah, W. S.; Petzing, Jon N.; Tyrer, John R.

    2005-04-01

    ESPSI or shearography has been successfully used in non-destructive testing (NDT) for measuring the derivative out-of-plane displacement, w/x and/or w/y, and recently a few investigations of derivative in-plain displacement, u/x, v/y, u/y and v/x have been reported. The demand of quantitative measurement has encouraged manufacturers to produce a quantitative shearography system. However, errors arising from numerous sources, including wavefront divergence and object geometry are not taken into account when calculating the interferometer fringe function and quantifying the data. In this paper the novel approach in quantified error that propagates from the divergence illumination wavefront is presented. The theoretical error is formulated by means of mathematical approach that comprises of three dependent variables, the inspected object distance, the object size (field area covered by the CCD camera) and the illumination angle. The error defined by the difference of phase data using divergence illumination object wavefront compared to phase data that is measured by using collimated illumination wavefront. Theoretical analysis and experimental validation indicates that the magnitude of the maximum phase change difference due to the divergence of illumination wavefront to exceed 10% for out-of-plane and 40% for in-plane analysis.

  14. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... NEI YouTube Videos > NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration ... Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: ...

  15. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... YouTube Videos > NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia ... of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: Amblyopia ...

  16. NEI You Tube Videos: Amblyopia

    Science.gov (United States)

    ... YouTube Videos > NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia ... of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: Amblyopia ...

  17. Wavefront reconstruction for lateral shearing interferometry based on difference polynomial fitting

    Science.gov (United States)

    Li, Jie; Tang, Feng; Wang, Xiangzhao; Dai, Fengzhao; Feng, Peng; Li, Sikun

    2015-06-01

    The wavefront reconstruction method for shearing interferometry using difference Zernike polynomial fitting has been the easiest algorithm to implement up to now. The method is extended to using general basis functions in this paper. Simulations and experiments verify that highly accurate reconstructions can be achieved based on difference polynomial fitting regardless, of the pupil shape and the orthogonality of the basis functions. The reconstruction accuracy mainly depends on whether the used terms of the polynomials are enough to represent the wavefront. When the used terms cannot perfectly represent the wavefront, the reconstruction accuracy of Taylor monomials is a little higher than that of Zernike polynomials. It is also presented and proved that the reconstruction accuracy can be estimated using the deviation between the reconstructed difference fronts and the measured difference fronts.

  18. Wavefront aberration function in terms of R. V. Shack's vector product and Zernike polynomial vectors.

    Science.gov (United States)

    Gray, Robert W; Rolland, Jannick P

    2015-10-01

    Previous papers have shown how, for rotationally symmetric optical imaging systems, nodes in the field dependence of the wavefront aberration function develop when a rotationally symmetric optical surface within an imaging optical system is decentered and/or tilted. In this paper, we show how Shack's vector product (SVP) can be used to express the wavefront aberration function and to define vectors in terms of the Zernike polynomials. The wavefront aberration function is then expressed in terms of the Zernike vectors. It is further shown that SVP fits within the framework of two-dimensional geometric algebra (GA). Within the GA framework, an equation for the third-order node locations for the binodal astigmatism term that emerge in the presence of tilts and decenters is then demonstrated. A computer model of a three-mirror telescope system is used to demonstrate the validity of the mathematical development.

  19. 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.

  20. Transient establishment of the wavefronts for negative, zero, and positive refraction.

    Science.gov (United States)

    Zhao, Wenjuan; Wu, Qiang; Wang, Ride; Gao, Jianshun; Lu, Yao; Zhang, Qi; Qi, Jiwei; Zhang, Chunling; Pan, Chongpei; Rupp, Romano; Xu, Jingjun

    2018-01-22

    We quantitatively demonstrate transient establishment of wavefronts for negative, zero, and positive refraction through a wedge-shaped metamaterial consisting of periodically arranged split-ring resonators and metallic wires. The wavefronts for the three types of refractions propagate through the second interface of the wedge along positive refraction angles at first, then reorganize, and finally propagate along the effective refraction angles after a period of establishment time respectively. The establishment time of the wavefronts prevents violating causality or superluminal propagation for negative and zero refraction. The establishment time for negative or zero refraction is longer than that for positive refraction. For all three refraction processes, transient establishment processes precede the establishment of steady propagation. Moreover, some detailed characters are proven in our research, including infinite wavelength, uniform phase inside the zero-index material, and the phase velocity being antiparallel to the group velocity in the negative-index material.

  1. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five videos was designed ... Activity Role of Body Weight in Osteoarthritis Educational Videos for Patients Rheumatoid Arthritis Educational Video Series Psoriatic ...

  2. Hybrid iterative wavefront shaping for high-speed focusing through scattering media

    Science.gov (United States)

    Hemphill, Ashton S.; Wang, Lihong V.

    2016-03-01

    A major limiting factor of optical imaging in biological applications is the diffusion of light by tissue, preventing focusing at depths greater than ~1 mm in the body. To overcome this issue, phase-based wavefront shaping alters the phase of sections of the incident wavefront to counteract aberrations in phase caused by scattering. This enables focusing through scattering media beyond the optical diffusion limit and increases signal compared to amplitude-based compensation. However, in previous studies, speed of optimization has typically been limited by the use of a liquid crystal spatial light modulator (SLM) for measurement and display. SLMs usually have refresh rates of less than 100 Hz and require much longer than the speckle correlation time of tissue in vivo, usually on the order of milliseconds, to determine the optimal wavefront. Here, we present a phase-based iterative wavefront shaping method based on an onaxis digital micromirror device (DMD) in conjunction with an electro-optic modulator (EOM) for measurement and a fast SLM for display. By combining phase modulation from an EOM with the modal selection of the DMD, we take advantage of DMDs higher refresh rate, approximately 23 kHz, for iterative phase measurement. The slower SLM requires one update for display following the rapid determination of the optimal wavefront via the DMD, allowing for high-speed wavefront shaping. Using this system, we are able to focus through scattering media using 64 modes in under 8 milliseconds, on the order of the speckle correlation time for tissue in vivo.

  3. 61214++++','DOAJ-ART-EN'); return false;" href="+++++https://jual.nipissingu.ca/wp-content/uploads/sites/25/2014/06/v61214.m4v">61214++++">Jailed - Video

    Directory of Open Access Journals (Sweden)

    Cameron CULBERT

    2012-07-01

    Full Text Available As the public education system in Northern Ontario continues to take a downward spiral, a plethora of secondary school students are being placed in an alternative educational environment. Juxtaposing the two educational settings reveals very similar methods and characteristics of educating our youth as opposed to using a truly alternative approach to education. This video reviews the relationship between public education and alternative education in a remote Northern Ontario setting. It is my belief that the traditional methods of teaching are not appropriate in educating at risk students in alternative schools. Paper and pencil worksheets do not motivate these students to learn and succeed. Alternative education should emphasize experiential learning, a just in time curriculum based on every unique individual and the students true passion for everyday life. Cameron Culbert was born on February 3rd, 1977 in North Bay, Ontario. His teenage years were split between attending public school and his willed curriculum on the ski hill. Culbert spent 10 years (1996-2002 & 2006-2010 competing for Canada as an alpine ski racer. His passion for teaching and coaching began as an athlete and has now transferred into the classroom and the community. As a graduate of Nipissing University (BA, BEd, MEd. Camerons research interests are alternative education, physical education and technology in the classroom. Currently Cameron is an active educator and coach in Northern Ontario.

  4. Calibration of wavefront distortion in light modulator setup by Fourier analysis of multi-beam interference

    CERN Document Server

    Leszczyński, Adam

    2015-01-01

    We present a method to calibrate wavefront distortion of the spatial light modulator setup by registering far field images of several gaussian beams diffracted off the modulator. The Fourier transform of resulting interference images reveals phase differences between typically 5 movable points on the modulator. Repeating this measurement yields wavefront surface. Next, the amplitude efficiency is calibrated be registering near field image. As a verification we produced a superposition of 7th and 8th Bessel beams with different phase velocities and observed their interference.

  5. 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.

  6. Conformal optical elements for correcting wavefront distortions in YAG : Nd{sup 3+} active elements

    Energy Technology Data Exchange (ETDEWEB)

    Korolkov, V P; Nasyrov, R K; Poleshchuk, A G; Arapov, Yu D; Ivanov, A F

    2013-02-28

    Correction of the wavefront is studied for the light beam passing wide-aperture YAG : Nd3+ single-crystal rods, which are used as active elements in high-power solid-state lasers. A nonideal character of the crystal structure is responsible for the deformation of the wavefront of passing radiation. By using the halftone technology we have developed conformal aberration correctors capable of compensating rod nonuniformities and reducing the laser radiation divergence by an order of magnitude. The results obtained make it possible to employ optically nonuniform active elements in laser constructions. (laser optics 2012)

  7. 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.

  8. Video Design Games

    DEFF Research Database (Denmark)

    Smith, Rachel Charlotte; Christensen, Kasper Skov; Iversen, Ole Sejer

    We introduce Video Design Games to train educators in teaching design. The Video Design Game is a workshop format consisting of three rounds in which participants observe, reflect and generalize based on video snippets from their own practice. The paper reports on a Video Design Game workshop...

  9. Characterization of social video

    Science.gov (United States)

    Ostrowski, Jeffrey R.; Sarhan, Nabil J.

    2009-01-01

    The popularity of social media has grown dramatically over the World Wide Web. In this paper, we analyze the video popularity distribution of well-known social video websites (YouTube, Google Video, and the AOL Truveo Video Search engine) and characterize their workload. We identify trends in the categories, lengths, and formats of those videos, as well as characterize the evolution of those videos over time. We further provide an extensive analysis and comparison of video content amongst the main regions of the world.

  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. Video visual analytics

    OpenAIRE

    Höferlin, Markus Johannes

    2013-01-01

    The amount of video data recorded world-wide is tremendously growing and has already reached hardly manageable dimensions. It originates from a wide range of application areas, such as surveillance, sports analysis, scientific video analysis, surgery documentation, and entertainment, and its analysis represents one of the challenges in computer science. The vast amount of video data renders manual analysis by watching the video data impractical. However, automatic evaluation of video material...

  12. The shape of the radio wavefront of extensive air showers as measured with LOFAR

    NARCIS (Netherlands)

    Corstanje, A.; et al., [Unknown; Swinbank, J.

    2015-01-01

    Extensive air showers, induced by high energy cosmic rays impinging on the Earth’s atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or

  13. Wavefront shaping with an electrowetting liquid lens using surface harmonics (Conference Presentation)

    Science.gov (United States)

    Strauch, Matthias; Konijnenberg, Sander; Shao, Yifeng; Urbach, H. Paul

    2017-02-01

    Liquid lenses are used to correct for low order wavefront aberrations. Electrowetting liquid lenses can nowadays control defocus and astigmatism effectively, so they start being used for ophthalmology applications. To increase the performance and applicability, we introduce a new driving mechanism to create, detect and correct higher order aberrations using standing waves on the liquid interface. The speed of a liquid lens is in general limited, because the liquid surface cannot follow fast voltage changes, while providing a spherical surface. Surface waves are created instead and with them undesired aberrations. We try to control those surface waves to turn them into an effective wavefront shaping tool. We introduce a model, which treats the liquid lens as a circular vibrating membrane with adjusted boundary conditions. Similar to tunable acoustic gradient (TAG) lenses, the nature of the surface modes are predicted to be Bessel functions. Since Bessel functions are a full set of orthogonal basis functions any surface can be created as a linear combination of different Bessel functions. The model was investigated experimentally in two setups. First the point spread functions were studied and compared to a simulation of the intensity distribution created by Fresnel propagated Bessel surfaces. Second the wavefronts were measured directly using a spatial light modulator. The surface resonance frequencies confirm the predictions made by the model as well as the wavefront measurements. By superposition of known surface modes, it is possible to create new surface shapes, which can be used to simulate and measure the human eye.

  14. Existence and uniqueness of travelling wavefronts for a bio-reactor equations with distributed delays

    Directory of Open Access Journals (Sweden)

    Zhihong Zhao

    2007-01-01

    Full Text Available We consider the diffusive single species growth in a plug flow reactor model with distributed delay. For small delay, existence and uniqueness of such wavefronts are proved when the convolution kernel assumes the strong generic delay kernel. The approaches used in this paper are geometric singular perturbation theory and the center manifold theorem.

  15. Precision interferometry for measuring wavefronts of multi-wavelength optical pickups.

    Science.gov (United States)

    Ge, Zongtao; Saito, Takayuki; Kurose, Minoru; Kanda, Hideo; Arakawa, Kazuhisa; Takeda, Mitsuo

    2008-01-07

    A novel wavefront measurement interferometer is developed that enables the user to evaluate the wavefronts of multi-wavelength optical pickups. In this interferometer, instead of transparent pinholes used in Mach-Zehnder interferometers, reflection dot pinhole mirrors are used to generate reference wavefronts for different wavelengths which make the optical system very flexible and simple compared with those using transparent pinholes. The interferometer is designed to operate at wavelengths of 405 nm, 650 nm and 780 nm over an NA range of up to 0.95, which is very difficult to realize when transparent pinholes are used for generating reference wavefronts. The three-beam problem is solved and the optics of the interferometer is simplified by employing a software filter instead of using spatial filters in the optics of the interferometer. The instrument has an equal optical path length that enables the user to measure pickups with a very short coherence length. A new method by which asymmetric aberration components, such as astigmatic and coma aberrations, can be calibrated by rotating the measured lens with 90 and 180 degrees is proposed and the calibration results are verified by using a high precision reference point source. System accuracy is also evaluated by comparing with the measurement results obtained by commercial Fizeau type interferometer and a good agreement is achieved.

  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. Focal-plane wavefront sensing with high-order adaptive optics systems

    NARCIS (Netherlands)

    Korkiakoski, V.; Keller, C.U.; Doelman, N.J.; Kenworthy, M.; Otten, G.; Verhaegen, M.

    2014-01-01

    We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working with an extremely high resolution (larger than 150x150 correcting elements). We use focal-plane images collected successively, the corresponding

  18. Wavefront correction in the extreme ultraviolet wavelength range using piezoelectric thin films

    NARCIS (Netherlands)

    Bayraktar, Muharrem; Chopra, A.; Rijnders, Augustinus J.H.M.; Boller, Klaus J.; Bijkerk, Frederik

    2014-01-01

    A new scheme for wavefront correction in the extreme ultraviolet wavelength range is presented. The central feature of the scheme is the successful growth of crystalline piezoelectric thin films with the desired orientation on an amorphous glass substrate. The piezoelectric films show a high

  19. Efficient Irregular Wavefront Propagation Algorithms on Hybrid CPU-GPU Machines.

    Science.gov (United States)

    Teodoro, George; Pan, Tony; Kurc, Tahsin; Kong, Jun; Cooper, Lee; Saltz, Joel

    2013-04-01

    We address the problem of efficient execution of a computation pattern, referred to here as the irregular wavefront propagation pattern (IWPP), on hybrid systems with multiple CPUs and GPUs. The IWPP is common in several image processing operations. In the IWPP, data elements in the wavefront propagate waves to their neighboring elements on a grid if a propagation condition is satisfied. Elements receiving the propagated waves become part of the wavefront. This pattern results in irregular data accesses and computations. We develop and evaluate strategies for efficient computation and propagation of wavefronts using a multi-level queue structure. This queue structure improves the utilization of fast memories in a GPU and reduces synchronization overheads. We also develop a tile-based parallelization strategy to support execution on multiple CPUs and GPUs. We evaluate our approaches on a state-of-the-art GPU accelerated machine (equipped with 3 GPUs and 2 multicore CPUs) using the IWPP implementations of two widely used image processing operations: morphological reconstruction and euclidean distance transform. Our results show significant performance improvements on GPUs. The use of multiple CPUs and GPUs cooperatively attains speedups of 50× and 85× with respect to single core CPU executions for morphological reconstruction and euclidean distance transform, respectively.

  20. 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.

  1. Zernike Wavefront Sensor Modeling Development for LOWFS on WFIRST-AFTA

    Science.gov (United States)

    Wang, Xu; Wallace, J. Kent; Shi, Fang

    2015-01-01

    WFIRST-AFTA design makes use of an existing 2.4m telescope for direct imaging of exoplanets. To maintain the high contrast needed for the coronagraph, wavefront error (WFE) of the optical system needs to be continuously sensed and controlled. Low Order Wavefront Sensing (LOWFS) uses the rejected starlight from an immediate focal plane to sense wavefront changes (mostly thermally induced low order WFE) by combining the LOWFS mask (a phase plate located at the small center region with reflective layer) with the starlight rejection masks, i.e. Hybrid Lyot Coronagraph (HLC)'s occulter or Shaped Pupil Coronagraph (SPC)'s field stop. Zernike wavefront sensor (ZWFS) measures phase via the phase-contrast method and is known to be photon noise optimal for measuring low order aberrations. Recently, ZWFS was selected as the baseline LOWFS technology on WFIST/AFTA for its good sensitivity, accuracy, and its easy integration with the starlight rejection mask. In this paper, we review the theory of ZWFS operation, describe the ZWFS algorithm development, and summarize various numerical sensitivity studies on the sensor performance. In the end, the predicted sensor performance on SPC and HLC configurations are presented.

  2. Flight path-driven mitigation of wavefront curvature effects in SAR images

    Science.gov (United States)

    Doerry, Armin W [Albuquerque, NM

    2009-06-23

    A wavefront curvature effect associated with a complex image produced by a synthetic aperture radar (SAR) can be mitigated based on which of a plurality of possible flight paths is taken by the SAR when capturing the image. The mitigation can be performed differently for different ones of the flight paths.

  3. Characterization of wavefront errors in mouse cranial bone using second-harmonic generation

    Science.gov (United States)

    Tehrani, Kayvan Forouhesh; Kner, Peter; Mortensen, Luke J.

    2017-03-01

    Optical aberrations significantly affect the resolution and signal-to-noise ratio of deep tissue microscopy. As multiphoton microscopy is applied deeper into tissue, the loss of resolution and signal due to propagation of light in a medium with heterogeneous refractive index becomes more serious. Efforts in imaging through the intact skull of mice cannot typically reach past the bone marrow (˜150 μm of depth) and have limited resolution and penetration depth. Mechanical bone thinning or optical ablation of bone enables deeper imaging, but these methods are highly invasive and may impact tissue biology. Adaptive optics is a promising noninvasive alternative for restoring optical resolution. We characterize the aberrations present in bone using second-harmonic generation imaging of collagen. We simulate light propagation through highly scattering bone and evaluate the effect of aberrations on the point spread function. We then calculate the wavefront and expand it in Zernike orthogonal polynomials to determine the strength of different optical aberrations. We further compare the corrected wavefront and the residual wavefront error, and suggest a correction element with high number of elements or multiconjugate wavefront correction for this highly scattering environment.

  4. 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

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

    NARCIS (Netherlands)

    Amitonova, Lyubov; Descloux, Adrien; Petschulat, Joerg; Frosz, Michael H.; Ahmed, Goran; Babic, Fehim; Mosk, Allard; Russell, Philip St.J.; Pinkse, Pepijn Willemszoon Harry

    2016-01-01

    We demonstrate that a high-numerical-aperture photonic crystal fiber allows lensless focusing at an unparalleled resolution 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 the

  6. New Objective Refraction Metric Based on Sphere Fitting to the Wavefront.

    Science.gov (United States)

    Jaskulski, Mateusz; Martínez-Finkelshtein, Andreí; López-Gil, Norberto

    2017-01-01

    To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes. A sphere is fitted to the ocular wavefront at the center and at a variable distance, t . The optimal fitting distance, t opt , is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius, r 0 , and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes. For pupil radii r 0 ≤ 2 mm, the new metric predicts the equivalent sphere with similar accuracy ( 2 mm, the mean error of traditional metrics can increase beyond 0.25D, and the MTR remains accurate. The proposed metric allows clinicians to obtain an accurate clinical spherical equivalent value without rescaling/refitting of the wavefront coefficients. It has the potential to be developed into a metric which will be able to predict full spherocylindrical refraction for the desired illumination conditions and corresponding pupil size.

  7. Efficient Irregular Wavefront Propagation Algorithms on Hybrid CPU-GPU Machines

    Science.gov (United States)

    Teodoro, George; Pan, Tony; Kurc, Tahsin; Kong, Jun; Cooper, Lee; Saltz, Joel

    2013-01-01

    We address the problem of efficient execution of a computation pattern, referred to here as the irregular wavefront propagation pattern (IWPP), on hybrid systems with multiple CPUs and GPUs. The IWPP is common in several image processing operations. In the IWPP, data elements in the wavefront propagate waves to their neighboring elements on a grid if a propagation condition is satisfied. Elements receiving the propagated waves become part of the wavefront. This pattern results in irregular data accesses and computations. We develop and evaluate strategies for efficient computation and propagation of wavefronts using a multi-level queue structure. This queue structure improves the utilization of fast memories in a GPU and reduces synchronization overheads. We also develop a tile-based parallelization strategy to support execution on multiple CPUs and GPUs. We evaluate our approaches on a state-of-the-art GPU accelerated machine (equipped with 3 GPUs and 2 multicore CPUs) using the IWPP implementations of two widely used image processing operations: morphological reconstruction and euclidean distance transform. Our results show significant performance improvements on GPUs. The use of multiple CPUs and GPUs cooperatively attains speedups of 50× and 85× with respect to single core CPU executions for morphological reconstruction and euclidean distance transform, respectively. PMID:23908562

  8. 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

  9. Autonomia apesar da dependência: a construção de uma Antropologia Dimensional no diálogo entre Frankl e Hartmann

    Directory of Open Access Journals (Sweden)

    Daniel Rubens Santiago da Silva

    2016-12-01

    Full Text Available O artigo se trata de um estudo teórico onde são apresentados alguns pontos da Ontologia Dimensional de Nicolai Hartmann e a relação destes com a Antropologia Ontológico-Dimensional de Viktor Frankl. Além dos pontos em que se percebe uma clara influência de Hartmann no pensamento frankliano, procurou-se chegar a elementos do pensamento do primeiro para além daquilo que serve de fundamento à Logoterapia. Quanto à influência de Hartmann, concluiu-se pela centralidade de sua Ontologia Dimensional no esquema frankliano, atestada pelas concessões ao condicionamento “psicofísico” e pela crítica ao pandeterminismo e ao reducionismo. O resultado é a fórmula: “autonomia apesar da dependência”. Quanto aos elementos que estão para além daquilo que serve de fundamento à Logoterapia, perceberam-se possibilidades fecundas de diálogo, como por ocasião da discussão em torno da vida espiritual “a-temporal” e do “espírito objetivo”.

  10. Response for light scattered in the ocular fundus from double-pass and Hartmann-Shack estimations.

    Science.gov (United States)

    García-Guerra, Carlos E; Aldaba, Mikel; Arjona, Montserrat; Díaz-Doutón, Fernando; Martínez-Roda, Joan A; Pujol, Jaume

    2016-11-01

    Double-pass (DP) and Hartmann-Shack (HS) are complementary techniques based on reflections of light in the ocular fundus that may be used to estimate the optical properties of the human eye. Under conventional data processing, both of these assessment modes provide information on aberrations. In addition, DP data contain the effects of scattering. In the ocular fundus, this phenomenon may arise from the interaction of light with not only the retina, but also deeper layers up to which certain wavelengths may penetrate. In this work, we estimate the response of the ocular fundus to incident light by fitting the deviations between DP and HS estimations using an exponential model. In measurements with negligible intraocular scattering, such differences may be related to the lateral spreading of light that occurs in the ocular fundus due to the diffusive properties of the media at the working wavelength. The proposed model was applied in young healthy eyes to evaluate the performance of scattering in such a population. Besides giving a parameter with information on the ocular fundus, the model contributes to the understanding of the differences between DP and HS estimations.

  11. Validation of a method for measuring the retinal thickness with Shack-Hartmann aberrometry in an artificial eye

    Science.gov (United States)

    Karitans, Varis; Jansone, Liene; Ozolins, Maris; Krumina, Gunta

    2015-05-01

    In Shack-Hartmann aberrometry, it is assumed that a wave front emerges from a single point focused on a retina. However, the retina is a multi-layered structure and reflections may occur from several layers. This may result in several overlapping spot patterns on the CCD due to different vergences of the outgoing wave fronts. The amount by which these spot patterns are displaced may contain information about the retinal thickness. In this study, we perform simulations of formation of double spots in a living eye and also apply this method to measure the thickness of an artificial retina with a simple structure. We also compare the results obtained with artificial eye and compare them to the simulated data. We evaluate the recommended range of the lenslet parameters for analyzing the retinal thickness. We conclude that this method could be used in a living eye for estimating the total retinal thickness and to confirm retinal pathologies associated with significant increase in the retinal thickness like glaucoma, macular edema, etc.

  12. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... support group for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ... group for me? Find a group Back Upcoming events Video Library Photo Gallery One-on-One Support ...

  13. Video Games and Citizenship

    National Research Council Canada - National Science Library

    Bourgonjon, Jeroen; Soetaert, Ronald

    2013-01-01

    ... by exploring a particular aspect of digitization that affects young people, namely video games. They explore the new social spaces which emerge in video game culture and how these spaces relate to community building and citizenship...

  14. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... Doctor Find a Provider Meet the Team Blog Articles News Resources Links Videos Podcasts Webinars For the ... Doctor Find a Provider Meet the Team Blog Articles News Provider Directory Donate Resources Links Videos Podcasts ...

  15. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... Doctor Find a Provider Meet the Team Blog Articles & Stories News Resources Links Videos Podcasts Webinars For ... Doctor Find a Provider Meet the Team Blog Articles & Stories News Provider Directory Donate Resources Links Videos ...

  16. Digital Video in Research

    DEFF Research Database (Denmark)

    Frølunde, Lisbeth

    2012-01-01

    questions of our media literacy pertaining to authoring multimodal texts (visual, verbal, audial, etc.) in research practice and the status of multimodal texts in academia. The implications of academic video extend to wider issues of how researchers harness opportunities to author different types of texts......Is video becoming “the new black” in academia, if so, what are the challenges? The integration of video in research methodology (for collection, analysis) is well-known, but the use of “academic video” for dissemination is relatively new (Eriksson and Sørensen). The focus of this paper is academic...... video, or short video essays produced for the explicit purpose of communicating research processes, topics, and research-based knowledge (see the journal of academic videos: www.audiovisualthinking.org). Video is increasingly used in popular showcases for video online, such as YouTube and Vimeo, as well...

  17. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... Back Support Groups Is a support group for me? Find a Group Upcoming Events Video Library Photo ... Support Groups Back Is a support group for me? Find a group Back Upcoming events Video Library ...

  18. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... group for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork ... for me? Find a group Back Upcoming events Video Library Photo Gallery One-on-One Support Back ...

  19. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... the Team Blog Articles & Stories News Resources Links Videos Podcasts Webinars For the Media For Clinicians For ... Family Caregivers Glossary Menu In this section Links Videos Podcasts Webinars For the Media For Clinicians For ...

  20. Videos, Podcasts and Livechats

    Science.gov (United States)

    ... the Team Blog Articles & Stories News Resources Links Videos Podcasts Webinars For the Media For Clinicians For ... Family Caregivers Glossary Menu In this section Links Videos Podcasts Webinars For the Media For Clinicians For ...

  1. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... a Provider Meet the Team Blog Articles & Stories News Resources Links Videos Podcasts Webinars For the Media ... a Provider Meet the Team Blog Articles & Stories News Provider Directory Donate Resources Links Videos Podcasts Webinars ...

  2. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork Peer ... me? Find a group Back Upcoming events Video Library Photo Gallery One-on-One Support Back ANetwork ...

  3. Video Screen Capture Basics

    Science.gov (United States)

    Dunbar, Laura

    2014-01-01

    This article is an introduction to video screen capture. Basic information of two software programs, QuickTime for Mac and BlueBerry Flashback Express for PC, are also discussed. Practical applications for video screen capture are given.

  4. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... News Resources Links Videos Podcasts Webinars For the Media For Clinicians For Policymakers For Family Caregivers Glossary ... this section Links Videos Podcasts Webinars For the Media For Clinicians For Policymakers For Family Caregivers Glossary ...

  5. Transmission of compressed video

    Science.gov (United States)

    Pasch, H. L.

    1990-09-01

    An overview of video coding is presented. The aim is not to give a technical summary of possible coding techniques, but to address subjects related to video compression in general and to the transmission of compressed video in more detail. Bit rate reduction is in general possible by removing redundant information; removing information the eye does not use anyway; and reducing the quality of the video. The codecs which are used for reducing the bit rate, can be divided into two groups: Constant Bit rate Codecs (CBC's), which keep the bit rate constant, but vary the video quality; and Variable Bit rate Codecs (VBC's), which keep the video quality constant by varying the bit rate. VBC's can be in general reach a higher video quality than CBC's using less bandwidth, but need a transmission system that allows the bandwidth of a connection to fluctuate in time. The current and the next generation of the PSTN does not allow this; ATM might. There are several factors which influence the quality of video: the bit error rate of the transmission channel, slip rate, packet loss rate/packet insertion rate, end-to-end delay, phase shift between voice and video, and bit rate. Based on the bit rate of the coded video, the following classification of coded video can be made: High Definition Television (HDTV); Broadcast Quality Television (BQTV); video conferencing; and video telephony. The properties of these classes are given. The video conferencing and video telephony equipment available now and in the next few years can be divided into three categories: conforming to 1984 CCITT standard for video conferencing; conforming to 1988 CCITT standard; and conforming to no standard.

  6. Making good physics videos

    Science.gov (United States)

    Lincoln, James

    2017-05-01

    Online videos are an increasingly important way technology is contributing to the improvement of physics teaching. Students and teachers have begun to rely on online videos to provide them with content knowledge and instructional strategies. Online audiences are expecting greater production value, and departments are sometimes requesting educators to post video pre-labs or to flip our classrooms. In this article, I share my advice on creating engaging physics videos.

  7. Desktop video conferencing

    OpenAIRE

    Potter, Ray; Roberts, Deborah

    2007-01-01

    This guide aims to provide an introduction to Desktop Video Conferencing. You may be familiar with video conferencing, where participants typically book a designated conference room and communicate with another group in a similar room on another site via a large screen display. Desktop video conferencing (DVC), as the name suggests, allows users to video conference from the comfort of their own office, workplace or home via a desktop/laptop Personal Computer. DVC provides live audio and visua...

  8. 47 CFR 79.3 - Video description of video programming.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Video description of video programming. 79.3... CLOSED CAPTIONING AND VIDEO DESCRIPTION OF VIDEO PROGRAMMING § 79.3 Video description of video programming. (a) Definitions. For purposes of this section the following definitions shall apply: (1...

  9. Video Self-Modeling

    Science.gov (United States)

    Buggey, Tom; Ogle, Lindsey

    2012-01-01

    Video self-modeling (VSM) first appeared on the psychology and education stage in the early 1970s. The practical applications of VSM were limited by lack of access to tools for editing video, which is necessary for almost all self-modeling videos. Thus, VSM remained in the research domain until the advent of camcorders and VCR/DVD players and,…

  10. Tracing Sequential Video Production

    DEFF Research Database (Denmark)

    Otrel-Cass, Kathrin; Khalid, Md. Saifuddin

    2015-01-01

    With an interest in learning that is set in collaborative situations, the data session presents excerpts from video data produced by two of fifteen students from a class of 5th semester techno-anthropology course. Students used video cameras to capture the time they spent working with a scientist...... video, nature of the interactional space, and material and spatial semiotics....

  11. Developing a Promotional Video

    Science.gov (United States)

    Epley, Hannah K.

    2014-01-01

    There is a need for Extension professionals to show clientele the benefits of their program. This article shares how promotional videos are one way of reaching audiences online. An example is given on how a promotional video has been used and developed using iMovie software. Tips are offered for how professionals can create a promotional video and…

  12. Impacto da análise do "wavefront" na refratometria de pacientes com ceratocone Impact of the wavefront analysis in refraction of keratoconus patients

    OpenAIRE

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

    2010-01-01

    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 re...

  13. Advanced video coding systems

    CERN Document Server

    Gao, Wen

    2015-01-01

    This comprehensive and accessible text/reference presents an overview of the state of the art in video coding technology. Specifically, the book introduces the tools of the AVS2 standard, describing how AVS2 can help to achieve a significant improvement in coding efficiency for future video networks and applications by incorporating smarter coding tools such as scene video coding. Topics and features: introduces the basic concepts in video coding, and presents a short history of video coding technology and standards; reviews the coding framework, main coding tools, and syntax structure of AV

  14. Intelligent video surveillance systems

    CERN Document Server

    Dufour, Jean-Yves

    2012-01-01

    Belonging to the wider academic field of computer vision, video analytics has aroused a phenomenal surge of interest since the current millennium. Video analytics is intended to solve the problem of the incapability of exploiting video streams in real time for the purpose of detection or anticipation. It involves analyzing the videos using algorithms that detect and track objects of interest over time and that indicate the presence of events or suspect behavior involving these objects.The aims of this book are to highlight the operational attempts of video analytics, to identify possi

  15. VBR video traffic models

    CERN Document Server

    Tanwir, Savera

    2014-01-01

    There has been a phenomenal growth in video applications over the past few years. An accurate traffic model of Variable Bit Rate (VBR) video is necessary for performance evaluation of a network design and for generating synthetic traffic that can be used for benchmarking a network. A large number of models for VBR video traffic have been proposed in the literature for different types of video in the past 20 years. Here, the authors have classified and surveyed these models and have also evaluated the models for H.264 AVC and MVC encoded video and discussed their findings.

  16. Wave-front sensing by use of a Green's function solution to the intensity transport equation: comment.

    Science.gov (United States)

    Campbell, Charles

    2007-08-01

    In 2003 Woods and Greenaway [J. Opt. Soc. Am. A20, 508 (2003)] published the mathematical details of their method for wavefront sensing by use of a Green's function solution to the intensity transport equation. Upon reviewing this work I have found that there does not seem to be sufficient information in the data they collect to fully characterize all types of aberrations expected in a wavefront. This I will demonstrate.

  17. Plasma-Lyte 148 vs. Hartmann's solution for cardiopulmonary bypass pump prime: a prospective double-blind randomized trial.

    Science.gov (United States)

    Weinberg, Laurence; Chiam, Elizabeth; Hooper, James; Liskaser, Frank; Hawkins, Angela Kim; Massie, Denise; Ellis, Andrew; Tan, Chong O; Story, David; Bellomo, Rinaldo

    2017-11-01

    The mechanisms of acid-base changes during cardiopulmonary bypass (CPB) remain unclear. We tested the hypothesis that, when used as CPB pump prime solutions, Plasma-Lyte 148 (PL) and Hartmann's solution (HS) have differential mechanisms of action in their contribution to acid-base changes. We performed a prospective, double-blind, randomized trial in adult patients undergoing elective cardiac surgery with CPB. Participants received a CPB prime solution of 2000 mL, with either PL or HS. The primary endpoint was the standard base excess (SBE) value measured at 60 minutes after full CPB flows (SBE60min). Secondary outcomes included changes in SBE, pH, chloride, sodium, lactate, gluconate, acetate, strong ion difference and strong ion gap at two (T2min), five (T5min), ten (T10min), thirty (T30min) and sixty (T60min) minutes on CPB. The primary outcome was measured using a two-tailed Welch's t-test. Repeated measures ANOVA was used to test for differences between time points. Twenty-five participants were randomized to PL and 25 to HS. Baseline characteristics, EURO and APACHE scores, biochemistry, hematology and volumes of cardioplegia were similar. Mean (SD) SBE at T60min was -1.3 (1.4) in the PL group and -0.1 (2.7) in the HS group; p=0.55. No significant differences in SBE between the groups was observed during the first 60 minutes (p=0.48). During CPB, there was hyperacetatemia and hypergluconatemia in the PL group and hyperlactatemia and hyperchloremia in the HS group. No significant difference between the groups in plasma bicarbonate levels and total weak acid levels were found. Complications and intensive care unit and hospital length of stays were similar. During CPB, PL and HS did not cause a significant metabolic acidosis. There was hyperacetatemia and hypergluconatemia with PL and hyperchloremia and hyperlactatemia with HS. These physiochemical effects appear clinically innocuous.

  18. The effects of plasmalyte-148 vs. Hartmann's solution during major liver resection: a multicentre, double-blind, randomized controlled trial.

    Science.gov (United States)

    Weinberg, L; Pearce, B; Sullivan, R; Siu, L; Scurrah, N; Tan, C; Backstrom, M; Nikfarjam, M; McNicol, L; Story, D; Christophi, C; Bellomo, R

    2015-12-01

    The acid-base, biochemical and hematological effects of crystalloid solutions have not been comprehensively evaluated in patients with liver resection. multicenter, prospective, double-blind randomized controlled trial investigating the biochemical effects of Hartmann's solution (HS) or Plasmalyte-148 (PL) in 60 patients undergoing major liver resection. base excess immediately after surgery. changes in blood biochemistry and hematology. At completion of surgery, patients receiving HS had equivalent mean standard base excess (-1.7±2.2 vs. -0.9±2.3 meq/L; P=0.17) to those treated with PL. However, patients treated with HS were more hyperchloremic (difference 1.7 mmol/L, 95% CI: 0.2 to 3.2, P=0.03) and hyperlactatemic (difference 0.8 mmol/L, 95% CI: 0.2 to 1.3; P=0.01). In contrast, patients receiving PL had higher mean plasma magnesium levels and lower ionized calcium levels. There were no significant differences in pH, bicarbonate, albumin and phosphate levels. Immediately after surgery, mean PT and aPTT were significantly lower in the PL group. Intraoperatively, the median (IQR) blood loss in the PL group was 300 mL (200:413) vs. 500 mL (300:638) in the HS group (P=0.03). Correspondingly, the postoperative hemoglobin was higher in the PL group. Total complications were more frequent in the HS Group (56% vs. 20%, relative risk 2.8; 95% CI: 1.3 to 6.1; P=0.007). In liver resection patients, HS and PL led to similar base excess values but different post operative plasma biochemistry and hematology values. Understanding of these effects may help clinicians individualize fluid therapy in these patients.

  19. Flip Video for Dummies

    CERN Document Server

    Hutsko, Joe

    2010-01-01

    The full-color guide to shooting great video with the Flip Video camera. The inexpensive Flip Video camera is currently one of the hottest must-have gadgets. It's portable and connects easily to any computer to transfer video you shoot onto your PC or Mac. Although the Flip Video camera comes with a quick-start guide, it lacks a how-to manual, and this full-color book fills that void! Packed with full-color screen shots throughout, Flip Video For Dummies shows you how to shoot the best possible footage in a variety of situations. You'll learn how to transfer video to your computer and then edi

  20. Holographic Video Disc And Laser Scanning Optics.

    Science.gov (United States)

    Weingartner, I.; Rosenbruch, K. J.

    1983-10-01

    Holographic optical elements or systems of holographic elements may replace glass optical imaging systems or may be used for the correction of glass optics. The main advantages of such systems are their low weight, small and compact construction, and their simple and inexpensive manufacture. The disadvantages to be overcome are mainly the low light through-put and chromatic aberrations. In the special case of optics for video discs we present an optical imaging system which is capable of giving the required high resolution for illumination with polychromatic radiation of limited bandwidth in the case of semiconductor laser diodes. Optimization programs based on ray tracing yield highly corrected imaging systems by comparably simple holographic means. The use of only two surfaces gives very compact and lightweight systems, the image quality of which is described for monochromatic and polychro-matic irradiance by means of optical transfer functions. The holograms are recorded on photo-resist material with short wavelength laser radiation. Such holograms have almost no scatter light and do not alter their properties with time or under radiation. These holograms generate wavefronts for the correction of aberrations which, in the case of glass optics, could only be achieved by aspherical surfaces.

  1. Generation and propagation of a sine-azimuthal wavefront modulated Gaussian beam.

    Science.gov (United States)

    Lao, Guanming; Zhang, Zhaohui; Luo, Meilan; Zhao, Daomu

    2016-07-21

    We introduce a method for modulating the Gaussian beam by means of sine-azimuthal wavefront and carry out the experimental generation. The analytical propagation formula of such a beam passing through a paraxial ABCD optical system is derived, by which the intensity properties of the sine-azimuthal wavefront modulated Gaussian (SWMG) beam are examined both theoretically and experimentally. Both of the experimental and theoretical results show that the SWMG beam goes through the process from beam splitting to a Gaussian-like profile, which is closely determined by the phase factor and the propagation distance. Appropriate phase factor and short distance are helpful for the splitting of beam. However, in the cases of large phase factor and focal plane, the intensity distributions tend to take a Gaussian form. Such unique features may be of importance in particle trapping and medical applications.

  2. In vivo deep tissue imaging using wavefront shaping optical coherence tomography

    CERN Document Server

    Yu, Hyeonseung; Lee, KyeoReh; Jang, Jaeduck; Lim, Jaeguyn; Jang, Wooyoung; Jeong, Yong; Park, YongKeun

    2015-01-01

    Multiple light scattering in tissue limits the penetration of optical coherence tomography (OCT) imaging. Here, we present in-vivo OCT imaging of a live mouse using wavefront shaping to enhance the penetration depth. A digital micro-mirror device (DMD) was used in a spectral-domain OCT system for complex wavefront shaping of an incident beam which resulted in the optimal delivery of light energy into deep tissue. Ex-vivo imaging of chicken breasts and mouse ear tissues showed enhancements in the strength of the image signals and the penetration depth, and in-vivo imaging of the tail of a live mouse provided a multilayered structure inside the tissue, otherwise invisible in conventional OCT imaging. Signal enhancements by a factor of 3-7 were acquired for various experimental conditions and samples.

  3. Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue

    Science.gov (United States)

    Horstmeyer, Roarke; Ruan, Haowen; Yang, Changhuei

    2015-09-01

    In the field of biomedical optics, optical scattering has traditionally limited the range of imaging within tissue to a depth of one millimetre. A recently developed class of wavefront-shaping techniques now aims to overcome this limit and achieve diffraction-limited control of light beyond one centimetre. By manipulating the spatial profile of an optical field before it enters a scattering medium, it is possible to create a micrometre-scale focal spot deep within tissue. To successfully operate in vivo, these wavefront-shaping techniques typically require feedback from within the biological sample. This Review summarizes recently developed 'guidestar' mechanisms that provide feedback for intra-tissue focusing. Potential applications of guidestar-assisted focusing include optogenetic control over neurons, targeted photodynamic therapy and deep tissue imaging.

  4. Multi-perturbation stochastic parallel gradient descent method for wavefront correction.

    Science.gov (United States)

    Wu, Kenan; Sun, Yang; Huai, Ying; Jia, Shuqin; Chen, Xi; Jin, Yuqi

    2015-02-09

    The multi-perturbation stochastic parallel gradient descent (SPGD) method for adaptive optics is presented in this work. The method is based on a new architecture. The incoming beam with distorted wavefront is split into N sub-beams. Each sub-beam is modulated by a wavefront corrector and its performance metric is measured subsequently. Adaptive system based on the multi-perturbation SPGD can operate in two modes - the fast descent mode and the modal basis updating mode. Control methods of the two operation modes are given. Experiments were carried out to prove the effectiveness of the proposed method. Analysis as well as experimental results showed that the two operation modes of the multi-perturbation SPGD enhance the conventional SPGD in different ways. The fast descent mode provides faster convergence than the conventional SPGD. The modal basis updating mode can optimize the modal basis set for SPGD with global coupling.

  5. Low-signal, coronagraphic wavefront estimation with Kalman filtering in the high contrast imaging testbed

    Science.gov (United States)

    Riggs, A. J. Eldorado; Cady, Eric J.; Prada, Camilo M.; Kern, Brian D.; Zhou, Hanying; Kasdin, N. Jeremy; Groff, Tyler D.

    2016-07-01

    For direct imaging and spectral characterization of cold exoplanets in reflected light, the proposed Wide-Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) will carry two types of coronagraphs. The High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory has been testing both coronagraph types and demonstrated their abilities to achieve high contrast. Focal plane wavefront correction is used to estimate and mitigate aberrations. As the most time-consuming part of correction during a space mission, the acquisition of probed images for electric field estimation needs to be as short as possible. We present results from the HCIT of narrowband, low-signal wavefront estimation tests using a shaped pupil Lyot coronagraph (SPLC) designed for the WFIRST CGI. In the low-flux regime, the Kalman filter and iterated extended Kalman filter provide faster correction, better achievable contrast, and more accurate estimates than batch process estimation.

  6. Dynamic aberration correction for conformal optics using model-based wavefront sensorless adaptive optics

    Science.gov (United States)

    Han, Xinli; Dong, Bing; Li, Yan; Wang, Rui; Hu, Bin

    2016-10-01

    For missiles and airplanes with high Mach number, traditional spherical or flat window can cause a lot of air drag. Conformal window that follow the general contour of surrounding surface can substantially decrease air drag and extend operational range. However, the local shape of conformal window changes across the Field Of Regard (FOR), leading to time-varying FOR-dependent wavefront aberration and degraded image. So the correction of dynamic aberration is necessary. In this paper, model-based Wavefront Sensorless Adaptive Optics (WSAO) algorithm is investigated both by simulation and experiment for central-obscured pupil. The algorithm is proved to be effective and the correction accuracy of using DM modes is higher than Lukosz modes. For dynamic aberration in our system, the SR can be better than 0.8 when the change of looking angle is less than 2° after t seconds which is the time delay of the control system.

  7. 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.

  8. Wave-front evaluation of the Ni-like Ag laser

    Energy Technology Data Exchange (ETDEWEB)

    Murai, K. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); Sebban, S.; Yoshizumi, Y. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); Osaka Univ., Suita (Japan). Inst. of Laser Engineering; Tang, H.J.; Daido, H. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); Osaka Univ., Suita (Japan). Inst. of Laser Engineering; Kansai Research Establishment, Japan Atomic Energy Research Inst., Kyoto (Japan); Kato, Y.; Klisnick, A. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); Zeitoun, Ph. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); Lab. de Spectroscopie Atomique et Ionique, Univ. Paris-Sud, Orsay (France); Wang, S.; Gu, Y.; Huang, G.; Lin, Z. [Osaka National Research Inst., AIST, Ikeda, Osaka (Japan); National Lab. for High Power Lasers and Physics, Shanghai, SH (China)

    2001-07-01

    Coherent X-ray lasers are desired for various applications such as holography of biological samples and diagnostics of laser-produced plasmas. However, the shape of the X-ray laser had not been examined. Information about its wave-front shape is also important for future application of X-ray lasers in research and industry. In this paper, we report the evaluation of the shape of the wave-front of the X-ray laser. Ni-like Ag lasers at 13.9 nm were examined in IV-01-GXII experiment at GEKKO XII glass laser facility at ILE, Osaka Univ. The fringe patterns generated using crossed wires located in the beam were recorded on the X-ray CCD. Our experimental results indicate that X-ray laser emitted from an end of a plasma column has a property of a point light source. (orig.)

  9. Distortion-free 3D imaging using wavefront shaping

    Science.gov (United States)

    Teich, M.; Sturm, J.; Büttner, L.; Czarske, J.

    2017-06-01

    3-dimensional imaging often requires substantial effort since information along the optical axis is not straight forward gatherable. In many applications it is aimed for depth information along the direction of view. For example fluidic mixing processes and the environmental interaction on a microscopic scale are of particular importance for e.g. pharmaceutical applications and often demand for 3D information. This problem is often solved by stereoscopic approaches, where two cameras are used in order to gather depth information by triangulation technique. Another approach is to scan the object through the focal plane in order to get sharp images of each layer. Since the before mentioned approaches require a lot of video data to be evaluated it would be more convenient to get depth mapping within a single camera recording and without scanning. Here we present a tunable 3D depth-mapping camera technique in combination with dynamic aberration control. By using an incoherent light source, only one camera and a spatial light modulator (LCoS-SLM), it is a simply applicable and highly scalable technique. A double-helix point spread function (DH-PSF) is generated for light emerging from the observed focal plane. Each object appears as a double-image on the camera. Within the orientation of the double-image, depth information along the optical axis is encoded. By using an additional adaptive element (deformable mirror) the technique is combined with wide-field aberration correction. Here we combine a tunable 3D depth camera with dynamic aberration control in one imaging system.

  10. 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)

  11. Biomechanics of the cornea and wavefront-guided laser refractive surgery.

    Science.gov (United States)

    Roberts, Cynthia

    2002-01-01

    Wavefront-guided laser refractive surgery induces postoperative optical aberrations that are not explained by the ablation profile. A conceptual model is presented for a potential mechanism of surgically-induced corneal shape change that is dependent on structural modification, rather than ablation profile. Examples are provided from clinical and basic studies that are consistent with the proposed model. Corneal biomechanical response to ablative surgery may significantly affect outcomes, and should be taken into account when planning customized procedures.

  12. Field tests of elongated Na LGS wavefront sensing for the E-ELT

    Science.gov (United States)

    Rousset, Gérard; Gratadour, Damien; Morris, Tim; Myers, Richard; Bonaccini Calia, Domenico; Gendron, Eric; Pfrommer, Thomas; Talbot, Gordon

    2013-12-01

    Wavefront sensing using extremely elongated Sodium Laser Guide Stars (LGS) is a key concern for the design of a number of first generation ELT AO modules. One of the main challenges is the mitigation of the effects induced by extreme elongation on the wavefront measurements. Before the final design studies of the E-ELT instruments, a Na LGS wavefront (WF) sensing on-sky field experiment at this scale is strategic and mandatory to provide spatial and temporal wavefront measurements on a true LGS, subject to the atmospheric and mesospheric variability. The fine comparative analysis of such data with synchronously acquired WF measurements on a NGS will be unique to test a number of algorithms, configurations for spot sampling and truncation and WF reconstruction schemes including multi-LGS configurations. We propose to use CANARY, the Multi-Object AO demonstrator installed at the WHT (4.2m) . CANARY is now equipped with a Rayleigh LGS and also provides several natural guide star WFS. It shall be adapted to the Na LGS to provide the same pupil sampling than the NGS WFS for direct comparison. A compact, transportable laser system, such as the WLGSU developed at ESO, positioned at a varying distance from the WHT will be used to provide off-axis launching (up to 40m), simulating the whole range of LGS spot elongations obtained on the E-ELT. In addition, this experiment will include varying rate Sodium profiling and open and close-loop operations including offloads from profiling. In this paper, we present the objectives and the design of the proposed experiment and detail our strategy in terms of experimental setup and data reduction. A global error budget for the whole experiment is derived and spin-offs for the adequate dimensioning of E-ELT LGS-AO modules WFS are demonstrated.

  13. LASER PHYSICS: Instability of the radiation wavefront in pulsed CO2 amplifiers

    Science.gov (United States)

    Fedorov, S. V.; Yur'ev, M. S.

    1987-07-01

    A theoretical investigation is reported of the evolution in space and time of a small-scale perturbation against the background of a smooth beam entering a pulsed CO2 amplifier. The ranges of the transverse frequency, longitudinal coordinate, and time in which the perturbation growth is exponential are determined. It is shown that the wavefront instability can be suppressed by amplification of the main beam and by the attenuation of sound.

  14. Underwater Acoustic Wavefront Visualization by Scanning Laser Doppler Vibrometer for the Characterization of Focused Ultrasonic Transducers

    OpenAIRE

    Roberto Longo; Steve Vanlanduit; Galid Arroud; Patrick Guillaume

    2015-01-01

    The analysis of acoustic wave fields is important for a large number of engineering designs, communication and health-related reasons. The visualization of wavefronts gives valuable information about the type of transducers and excitation signals more suitable for the test itself. This article is dedicated to the development of a fast procedure for acoustic fields visualization in underwater conditions, by means of laser Doppler vibrometer measurements. The ultrasonic probe is a focused trans...

  15. Systematic comparison of the use of annular and Zernike circle polynomials for annular wavefronts.

    Science.gov (United States)

    Mahajan, Virendra N; Aftab, Maham

    2010-11-20

    The theory of wavefront analysis of a noncircular wavefront is given and applied for a systematic comparison of the use of annular and Zernike circle polynomials for the analysis of an annular wavefront. It is shown that, unlike the annular coefficients, the circle coefficients generally change as the number of polynomials used in the expansion changes. Although the wavefront fit with a certain number of circle polynomials is identically the same as that with the corresponding annular polynomials, the piston circle coefficient does not represent the mean value of the aberration function, and the sum of the squares of the other coefficients does not yield its variance. The interferometer setting errors of tip, tilt, and defocus from a four-circle-polynomial expansion are the same as those from the annular-polynomial expansion. However, if these errors are obtained from, say, an 11-circle-polynomial expansion, and are removed from the aberration function, wrong polishing will result by zeroing out the residual aberration function. If the common practice of defining the center of an interferogram and drawing a circle around it is followed, then the circle coefficients of a noncircular interferogram do not yield a correct representation of the aberration function. Moreover, in this case, some of the higher-order coefficients of aberrations that are nonexistent in the aberration function are also nonzero. Finally, the circle coefficients, however obtained, do not represent coefficients of the balanced aberrations for an annular pupil. The various results are illustrated analytically and numerically by considering an annular Seidel aberration function.

  16. Real time optimization algorithm for wavefront sensorless adaptive optics OCT (Conference Presentation)

    Science.gov (United States)

    Verstraete, Hans R. G. W.; Heisler, Morgan; Ju, Myeong Jin; Wahl, Daniel J.; Bliek, Laurens; Kalkman, Jeroen; Bonora, Stefano; Sarunic, Marinko V.; Verhaegen, Michel; Jian, Yifan

    2017-02-01

    Optical Coherence Tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. A limitation of the performance and utilization of the OCT systems has been the lateral resolution. Through the combination of wavefront sensorless adaptive optics with dual variable optical elements, we present a compact lens based OCT system that is capable of imaging the photoreceptor mosaic. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient eyes, and a multi-actuator adaptive lens after linearization of the hysteresis in the piezoelectric actuators for aberration correction to obtain near diffraction limited imaging at the retina. A parallel processing computational platform permitted real-time image acquisition and display. The Data-based Online Nonlinear Extremum seeker (DONE) algorithm was used for real time optimization of the wavefront sensorless adaptive optics OCT, and the performance was compared with a coordinate search algorithm. Cross sectional images of the retinal layers and en face images of the cone photoreceptor mosaic acquired in vivo from research volunteers before and after WSAO optimization are presented. Applying the DONE algorithm in vivo for wavefront sensorless AO-OCT demonstrates that the DONE algorithm succeeds in drastically improving the signal while achieving a computational time of 1 ms per iteration, making it applicable for high speed real time applications.

  17. Polarization multiplexed all-dielectric metasurfaces for wavefront manipulation in a transmission mode

    Science.gov (United States)

    Tao, Ze; Chen, Xiuguo; Jiang, Hao; Zhang, Chuanwei; Liu, Shiyuan

    2017-10-01

    All-dielectric metasurfaces are planar structures completely consisting of dielectric materials, which enable the control of phase, amplitude and polarization of light. Due to the good process compatibility and high transmittivity, they have drawn considerable attention in diverse applications for polarization conversion and wavefront manipulation in a transmission mode. Although several kinds of all-dielectric metasurfaces have been reported in literature to achieve wavefront manipulation, they either have only one fixed wavefront output or have susceptible efficiency to the side-wall-angle (SWA) error, which is extremely difficult to be minimized with current top-down fabrication processes. In this work, we propose an elliptical silicon nanopillar array, which possesses a polarization multiplexed response and high transmittivity, and more importantly, it is less sensitive to the SWA error. Two metasurfaces, namely a beam deflector and a vortex convertor, are exemplified to examine the performance of the proposed elliptical nanopillar array at a visible wavelength of 600 nm. We achieve high transmittivity of 76.7% and 81.4% for the beam deflector and the vortex convertor, respectively. Moreover, both the deflecting direction of the beam deflector and the chirality of the generated beam from the vortex convertor can be controlled by the incident polarization. The proposed all-dielectric metasurfaces demonstrate great potential for practical and polarization multiplexed optical elements.

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

    Science.gov (United States)

    Doelman, Niek J.; Hinnen, Karel J. G.; Stoffelen, Freek J. G.; Verhaegen, Michel H.

    2004-10-01

    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 feedback regulator systems are discussed. The concept of optimal control is proposed to minimise the temporal error. The issue of closed-loop feedback controller design is made transparent by using the principle of Internal Model Control. The central issue in reducing the temporal wavefront is the design of a feedforward prediction filter. In three separate tests - a numerical simulation example, measured data from an AO test bench and open-loop telescope data - the advantage of optimal control over the common approach of integral control is demonstrated. Optimal control of the temporal error yields a smaller temporal error, enables a longer integration time in the wavefront sensor, or the use of fainter natural guide stars.

  19. Combining Placido and Corneal Wavefront Data for the Detection of Forme Fruste Keratoconus.

    Science.gov (United States)

    Saad, Alain; Gatinel, Damien

    2016-08-01

    To evaluate the accuracy of a new objective method based on Placido disk-derived data for the detection of eyes at risk of ectasia. One hundred nineteen eyes of 176 patients were included and separated into two groups, normal and forme fruste keratoconus (FFKC), using automated corneal classification software. Normal eyes (n = 114) were classified as negative for keratoconus and keratoconus suspect and had undergone LASIK with unremarkable follow-up for 4 years. The FFKC group was composed of 62 topographically normal eyes of patients with keratoconus in the fellow eye. Anterior topographic parameters, obtained from specular topography using Placido-based indices and corneal wavefront Zernike coefficients, were compared between groups. Receiver operating characteristic (ROC) curves were used to identify cut-off points in discriminating between keratoconic and normal eyes. Validation was performed on an external group of eyes. A discriminant function was built combining four corneal wavefront variables and four Placido variables. The area under the receiver operating characteristic was 0.970 with this eight-variable model. The validation of this function had 63% sensitivity for detecting FFKC and 100% sensitivity for detecting keratoconus, with a specificity of 82%. Indices generated from corneal wavefront and Placido measurements can assist in identifying early or mild forms of keratoconus undetected by a Placido-based neural network program. [J Refract Surg. 2016;32(8):510-516.]. Copyright 2016, SLACK Incorporated.

  20. Laboratory demonstration of a cryogenic deformable mirror for wavefront correction of space-borne infrared telescopes.

    Science.gov (United States)

    Takahashi, Aoi; Enya, Keigo; Haze, Kanae; Kataza, Hirokazu; Kotani, Takayuki; Matsuhara, Hideo; Kamiya, Tomohiro; Yamamuro, Tomoyasu; Bierden, Paul; Cornelissen, Steven; Lam, Charlie; Feinberg, Michael

    2017-08-10

    This paper demonstrates a cryogenic deformable mirror (DM) with 1020 actuators based on micro-electrical mechanical systems (MEMS) technology. Cryogenic space-borne infrared telescopes can experience a wavefront error due to a figure error of their mirror surface, which makes the imaging performance worse. For on-orbit wavefront correction as one solution, we developed a MEMS-processed electro-static DM with a special surrounding structure for use under the cryogenic temperature. We conducted a laboratory demonstration of its operation in three cooling cycles between 5 K and 295 K. Using a laser interferometer, we detected the deformation corresponding to the applied voltages under the cryogenic temperature for the first time. The relationship between voltages and displacements was qualitatively expressed by the quadratic function, which is assumed based on the principle of electro-static DMs. We also found that it had a high operating repeatability of a few nm root-mean-square and no significant hysteresis. Using the measured values of repeatability, we simulated the improvement of the point spread function (PSF) by wavefront correction with our DM. These results show that our developed DM is effective in improving imaging performance and PSF contrast of space-borne infrared telescopes.

  1. 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.

  2. Wavefront correction with Kalman filtering for the WFIRST-AFTA coronagraph instrument

    Science.gov (United States)

    Riggs, A. J. Eldorado; Kasdin, N. Jeremy; Groff, Tyler D.

    2015-09-01

    The only way to characterize most exoplanets spectrally is via direct imaging. For example, the Coronagraph Instrument (CGI) on the proposed Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA) mission plans to image and characterize several cool gas giants around nearby stars. The integration time on these faint exoplanets will be many hours to days. A crucial assumption for mission planning is that the time required to dig a dark hole (a region of high star-to-planet contrast) with deformable mirrors is small compared to science integration time. The science camera must be used as the wavefront sensor to avoid non-common path aberrations, but this approach can be quite time intensive. Several estimation images are required to build an estimate of the starlight electric field before it can be partially corrected, and this process is repeated iteratively until high contrast is reached. Here we present simulated results of batch process and recursive wavefront estimation schemes. In particular, we test a Kalman filter and an iterative extended Kalman filter (IEKF) to reduce the total exposure time and improve the robustness of wavefront correction for the WFIRST-AFTA CGI. An IEKF or other nonlinear filter also allows recursive, real-time estimation of sources incoherent with the star, such as exoplanets and disks, and may therefore reduce detection uncertainty.

  3. Interferometric adaptive optics for high power laser pointing, wave-front control and phasing

    Energy Technology Data Exchange (ETDEWEB)

    Baker, K L; Stappaerts, E A; Homoelle, D C; Henesian, M A; Bliss, E S; Siders, C W; Barty, C J

    2009-01-21

    Implementing the capability to perform fast ignition experiments, as well as, radiography experiments on the National Ignition Facility (NIF) places stringent requirements on the control of each of the beam's pointing and overall wavefront quality. One quad of the NIF beams, 4 beam pairs, will be utilized for these experiments and hydrodynamic and particle-in-cell simulations indicate that for the fast ignition experiments, these beams will be required to deliver 50% (4.0 kJ) of their total energy (7.96 kJ) within a 40 {micro}m diameter spot at the end of a fast ignition cone target. This requirement implies a stringent pointing and overall phase conjugation error budget on the adaptive optics system used to correct these beam lines. The overall encircled energy requirement is more readily met by phasing of the beams in pairs but still requires high Strehl ratios, Sr, and rms tip/tilt errors of approximately one {micro}rad. To accomplish this task we have designed an interferometric adaptive optics system capable of beam pointing, high Strehl ratio and beam phasing with a single pixilated MEMS deformable mirror and interferometric wave-front sensor. We present the design of a testbed used to evaluate the performance of this wave-front sensor below along with simulations of its expected performance level.

  4. Techniques for High Contrast Imaging in Multi-Star Systems II: Multi-Star Wavefront Control

    Science.gov (United States)

    Sirbu, D.; Thomas, S.; Belikov, R.

    2017-01-01

    Direct imaging of exoplanets represents a challenge for astronomical instrumentation due to the high-contrast ratio and small angular separation between the host star and the faint planet. Multi-star systems pose additional challenges for coronagraphic instruments because of the diffraction and aberration leakage introduced by the additional stars, and as a result are not planned to be on direct imaging target lists. Multi-star wavefront control (MSWC) is a technique that uses a coronagraphic instrument's deformable mirror (DM) to create high-contrast regions in the focal plane in the presence of multiple stars. Our previous paper introduced the Super-Nyquist Wavefront Control (SNWC) technique that uses a diffraction grating to enable the DM to generate high-contrast regions beyond the nominal controllable region. These two techniques can be combined to generate high-contrast regions for multi-star systems at any angular separations. As a case study, a high-contrast wavefront control (WC) simulation that applies these techniques shows that the habitable region of the Alpha Centauri system can be imaged reaching 8 times 10(exp -9) mean contrast in 10 percent broadband light in one-sided dark holes from 1.6-5.5 lambda (wavelength) divided by D (distance).

  5. Improved artificial bee colony algorithm for wavefront sensor-less system in free space optical communication

    Science.gov (United States)

    Niu, Chaojun; Han, Xiang'e.

    2015-10-01

    Adaptive optics (AO) technology is an effective way to alleviate the effect of turbulence on free space optical communication (FSO). A new adaptive compensation method can be used without a wave-front sensor. Artificial bee colony algorithm (ABC) is a population-based heuristic evolutionary algorithm inspired by the intelligent foraging behaviour of the honeybee swarm with the advantage of simple, good convergence rate, robust and less parameter setting. In this paper, we simulate the application of the improved ABC to correct the distorted wavefront and proved its effectiveness. Then we simulate the application of ABC algorithm, differential evolution (DE) algorithm and stochastic parallel gradient descent (SPGD) algorithm to the FSO system and analyze the wavefront correction capabilities by comparison of the coupling efficiency, the error rate and the intensity fluctuation in different turbulence before and after the correction. The results show that the ABC algorithm has much faster correction speed than DE algorithm and better correct ability for strong turbulence than SPGD algorithm. Intensity fluctuation can be effectively reduced in strong turbulence, but not so effective in week turbulence.

  6. 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.

  7. 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.

  8. Determination of first-order derivative matrix of wavefront aberration with respect to system variables.

    Science.gov (United States)

    Lin, Psang Dain

    2012-02-01

    The first-order derivative matrix of a function with respect to a variable vector is referred to as the Jacobian matrix in mathematics. Current commercial software packages for the analysis and design of optical systems use a finite difference (FD) approximation methodology to estimate the Jacobian matrix of the wavefront aberration with respect to all of the independent system variables in a single raytracing pass such that the change of the wavefront aberration can be determined simply by computing the product of the developed Jacobian matrix and the corresponding changes in the system variables. The proposed method provides an ideal basis for automatic optical system design applications in which the merit function is defined in terms of wavefront aberration. The validity of the proposed approach is demonstrated by means of two illustrative examples. It is shown that the proposed method requires fewer iterations than the traditional FD approach and yields a more reliable and precise optimization performance. However, the proposed method incurs an additional CPU overhead in computing the Jacobian matrix of the merit function. As a result, the CPU time required to complete the optimization process is longer than that required by the FD method.

  9. Morbimortalidad asociada al cierre de colostomía Hartmann y colostomia en asa en pacientes del Hospital Nacional Arzobispo Loayza, Lima 2010-2014

    OpenAIRE

    Llontop Ramos, Eddar Walter

    2015-01-01

    El presente trabajo de investigación tuvo como objetivo principal determinar la relación entre la morbimortalidad de las técnicas quirúrgicas: colostomía Hartmann frente a colostomía en Asa, en pacientes post-operados de restitución del tránsito intestinal período 2010-2014. La investigación fue de tipo cohorte retrospectivo y de estadística descriptiva. La muestra incluyó a 135 pacientes. Las principales conclusiones fueron que la morbilidad relacionada a la técnica quirúrgica tipo Hartma...

  10. Visible and Infrared Wavefront Sensing detectors review in Europe - part I

    Science.gov (United States)

    Feautrier, Philippe; Gach, Jean-luc

    2013-12-01

    The purpose of this review is to give an overview of the state of the art wavefront sensor detectors developments held in Europe for the last decade. A major breakthrough has been achieved with the development by e2v technologies of the CCD220 between 2004 and 2012. Another major breakthrough is currently achieved with the very successful development of fast low noise infrared arrays called RAPID. The astonishing results of this device will be showed for the first time in an international conference at AO4ELT3.The CCD220, a 240x240 pixels 8 outputs EMCCD (CCD with internal multiplication), offers less than 0.2 e readout noise at a frame rate of 1500 Hz with negligible dark current. The OCAM2 camera is the commercial product that drives this advanced device. This system, commercialized by First Light Imaging, is quickly described in this paper. An upgrade of OCAM2 is currently developed 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. This upgrade and the results obtained are described extensively elsewhere in this conference (Gach et al).Since this major success, new detector developments started in Europe. The NGSD CMOS device 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. The NGSD will be a 880x840 pixels CMOS detector with a readout noise of 3 e (goal 1e) at 700 Hz frame rate. New technologies will be developed for that purpose: advanced CMOS pixel architecture, CMOS back thinned and back illuminated device for very high QE, full digital outputs with signal digital conversion on chip. This innovative device will be used on the European ELT but also interests potentially all giant telescopes.Additional developments also started in 2009 for wavefront sensing in the infrared based on a new technological breakthrough

  11. Understanding Video Games

    DEFF Research Database (Denmark)

    Heide Smith, Jonas; Tosca, Susana Pajares; Egenfeldt-Nielsen, Simon

    From Pong to PlayStation 3 and beyond, Understanding Video Games is the first general introduction to the exciting new field of video game studies. This textbook traces the history of video games, introduces the major theories used to analyze games such as ludology and narratology, reviews...... the economics of the game industry, examines the aesthetics of game design, surveys the broad range of game genres, explores player culture, and addresses the major debates surrounding the medium, from educational benefits to the effects of violence. Throughout the book, the authors ask readers to consider...... larger questions about the medium: * What defines a video game? * Who plays games? * Why do we play games? * How do games affect the player? Extensively illustrated, Understanding Video Games is an indispensable and comprehensive resource for those interested in the ways video games are reshaping...

  12. Collaborative Video Sketching

    DEFF Research Database (Denmark)

    Henningsen, Birgitte; Gundersen, Peter Bukovica; Hautopp, Heidi

    2017-01-01

    This paper introduces to what we define as a collaborative video sketching process. This process links various sketching techniques with digital storytelling approaches and creative reflection processes in video productions. Traditionally, sketching has been used by designers across various...... forms and through empirical examples, we present and discuss the video recording of sketching sessions, as well as development of video sketches by rethinking, redoing and editing the recorded sessions. The empirical data is based on workshop sessions with researchers and students from universities...... and university colleges and primary and secondary school teachers. As researchers, we have had different roles in these action research case studies where various video sketching techniques were applied.The analysis illustrates that video sketching can take many forms, and two common features are important...

  13. Reflections on academic video

    Directory of Open Access Journals (Sweden)

    Thommy Eriksson

    2012-11-01

    Full Text Available As academics we study, research and teach audiovisual media, yet rarely disseminate and mediate through it. Today, developments in production technologies have enabled academic researchers to create videos and mediate audiovisually. In academia it is taken for granted that everyone can write a text. Is it now time to assume that everyone can make a video essay? Using the online journal of academic videos Audiovisual Thinking and the videos published in it as a case study, this article seeks to reflect on the emergence and legacy of academic audiovisual dissemination. Anchoring academic video and audiovisual dissemination of knowledge in two critical traditions, documentary theory and semiotics, we will argue that academic video is in fact already present in a variety of academic disciplines, and that academic audiovisual essays are bringing trends and developments that have long been part of academic discourse to their logical conclusion.

  14. Sound for digital video

    CERN Document Server

    Holman, Tomlinson

    2013-01-01

    Achieve professional quality sound on a limited budget! Harness all new, Hollywood style audio techniques to bring your independent film and video productions to the next level.In Sound for Digital Video, Second Edition industry experts Tomlinson Holman and Arthur Baum give you the tools and knowledge to apply recent advances in audio capture, video recording, editing workflow, and mixing to your own film or video with stunning results. This fresh edition is chockfull of techniques, tricks, and workflow secrets that you can apply to your own projects from preproduction

  15. Green Power Partnership Videos

    Science.gov (United States)

    The Green Power Partnership develops videos on a regular basis that explore a variety of topics including, Green Power partnership, green power purchasing, Renewable energy certificates, among others.

  16. Lexical Culture | Hartmann | Lexikos

    African Journals Online (AJOL)

    Issues of intra lingual variety and interlingual diversity can now also be addressed Within the theoretical framework of contrastive textology, supported by computer-aided parallel text corpus analysis. However, lexicography is not entirely dependent on the results of linguistic research; it needs to move on and develop its ...

  17. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork Peer Support Program Community Connections Overview ... group Back Upcoming events Video Library Photo Gallery One-on-One Support Back ANetwork Peer Support Program ...

  18. Reviews in instructional video

    NARCIS (Netherlands)

    van der Meij, Hans

    2017-01-01

    This study investigates the effectiveness of a video tutorial for software training whose construction was based on a combination of insights from multimedia learning and Demonstration-Based Training. In the videos, a model of task performance was enhanced with instructional features that were

  19. Digital Video Editing

    Science.gov (United States)

    McConnell, Terry

    2004-01-01

    Monica Adams, head librarian at Robinson Secondary in Fairfax country, Virginia, states that librarians should have the technical knowledge to support projects related to digital video editing. The process of digital video editing and the cables, storage issues and the computer system with software is described.

  20. AudioMove Video

    DEFF Research Database (Denmark)

    2012-01-01

    Live drawing video experimenting with low tech techniques in the field of sketching and visual sense making. In collaboration with Rune Wehner and Teater Katapult.......Live drawing video experimenting with low tech techniques in the field of sketching and visual sense making. In collaboration with Rune Wehner and Teater Katapult....

  1. Making Good Physics Videos

    Science.gov (United States)

    Lincoln, James

    2017-01-01

    Online videos are an increasingly important way technology is contributing to the improvement of physics teaching. Students and teachers have begun to rely on online videos to provide them with content knowledge and instructional strategies. Online audiences are expecting greater production value, and departments are sometimes requesting educators…

  2. SECRETS OF SONG VIDEO

    Directory of Open Access Journals (Sweden)

    Chernyshov Alexander V.

    2014-04-01

    Full Text Available The article focuses on the origins of the song videos as TV and Internet-genre. In addition, it considers problems of screen images creation depending on the musical form and the text of a songs in connection with relevant principles of accent and phraseological video editing and filming techniques as well as with additional frames and sound elements.

  3. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... support group for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork Peer ... group for me? Find a group Back Upcoming events Video Library Photo Gallery One-on-One Support Back ANetwork ...

  4. Personal Digital Video Stories

    DEFF Research Database (Denmark)

    Ørngreen, Rikke; Henningsen, Birgitte Sølbeck; Louw, Arnt Vestergaard

    2016-01-01

    agenda focusing on video productions in combination with digital storytelling, followed by a presentation of the digital storytelling features. The paper concludes with a suggestion to initiate research in what is identified as Personal Digital Video (PDV) Stories within longitudinal settings, while...

  5. The Video Generation.

    Science.gov (United States)

    Provenzo, Eugene F., Jr.

    1992-01-01

    Video games are neither neutral nor harmless but represent very specific social and symbolic constructs. Research on the social content of today's video games reveals that sex bias and gender stereotyping are widely evident throughout the Nintendo games. Violence and aggression also pervade the great majority of the games. (MLF)

  6. Decoupled stochastic parallel gradient descent optimization for adaptive optics: integrated approach for wave-front sensor information fusion.

    Science.gov (United States)

    Vorontsov, Mikhail A

    2002-02-01

    A new adaptive wave-front control technique and system architectures that offer fast adaptation convergence even for high-resolution adaptive optics is described. This technique is referred to as decoupled stochastic parallel gradient descent (D-SPGD). D-SPGD is based on stochastic parallel gradient descent optimization of performance metrics that depend on wave-front sensor data. The fast convergence rate is achieved through partial decoupling of the adaptive system's control channels by incorporating spatially distributed information from a wave-front sensor into the model-free optimization technique. D-SPGD wave-front phase control can be applied to a general class of adaptive optical systems. The efficiency of this approach is analyzed numerically by considering compensation of atmospheric-turbulence-induced phase distortions with use of both low-resolution (127 control channels) and high-resolution (256 x 256 control channels) adaptive systems. Results demonstrate that phase distortion compensation can be achieved during only 10-20 iterations. The efficiency of adaptive wave-front correction with D-SPGD is practically independent of system resolution.

  7. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Patient Webcasts / Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five videos ... member of our patient care team. Managing Your Arthritis Managing Your Arthritis Managing Chronic Pain and Depression ...

  8. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Corner / Patient Webcasts / Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five videos was designed to help you learn more about Rheumatoid Arthritis (RA). You will learn how the diagnosis of ...

  9. Rheumatoid Arthritis Educational Video Series

    Science.gov (United States)

    ... Corner / Patient Webcasts / Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five videos was designed to help you learn more about Rheumatoid Arthritis (RA). You will learn how the diagnosis of ...

  10. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... questions Clinical Studies Publications Catalog Photos and Images Spanish Language Information Grants and Funding Extramural Research Division ... Low Vision Refractive Errors Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video ...

  11. Social video content delivery

    CERN Document Server

    Wang, Zhi; Zhu, Wenwu

    2016-01-01

    This brief presents new architecture and strategies for distribution of social video content. A primary framework for socially-aware video delivery and a thorough overview of the possible approaches is provided. The book identifies the unique characteristics of socially-aware video access and social content propagation, revealing the design and integration of individual modules that are aimed at enhancing user experience in the social network context. The change in video content generation, propagation, and consumption for online social networks, has significantly challenged the traditional video delivery paradigm. Given the massive amount of user-generated content shared in online social networks, users are now engaged as active participants in the social ecosystem rather than as passive receivers of media content. This revolution is being driven further by the deep penetration of 3G/4G wireless networks and smart mobile devices that are seamlessly integrated with online social networking and media-sharing s...

  12. A Demonstration of a Versatile Low-order Wavefront Sensor Tested on Multiple Coronographs

    Science.gov (United States)

    Singh, Garima; Lozi, Julien; Jovanovic, Nemanja; Guyon, Olivier; Baudoz, Pierre; Martinache, Frantz; Kudo, Tomoyuki

    2017-09-01

    Detecting faint companions in close proximity to stars is one of the major goals of current/planned ground- and space-based high-contrast imaging instruments. High-performance coronagraphs can suppress the diffraction features and gain access to companions at small angular separation. However, the uncontrolled pointing errors degrade the coronagraphic performance by leaking starlight around the coronagraphic focal-plane mask, preventing the detection of companions at small separations. A Lyot-stop low-order wavefront sensor (LLOWFS) was therefore introduced to calibrate and measure these aberrations for focal-plane phase mask coronagraphs. This sensor quantifies the variations in wavefront error decomposed into a few Zernike modes by reimaging the diffracted starlight rejected by a reflective Lyot stop. The technique was tested with several coronagraphs on the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system at the Subaru Telescope. The wavefront was decomposed into 15 and 35 Zernike modes with an occulting and focal-plane phase mask coronagraph, respectively, which were used to drive a closed-loop correction in the laboratory. Using a 2000-actuator deformable mirror, a closed-loop pointing stability between 10-3-10-4 λ/D was achieved in the laboratory in H-band, with sub nanometer residuals for the other Zernike modes (Noll index > 4). On-sky, the low-order control of 10+ Zernike modes for the phase-induced amplitude apodization and the vector vortex coronagraphs was demonstrated, with a closed-loop pointing stability of {10}-4λ /D under good seeing and {10}-3λ /D under moderate seeing conditions readily achievable.

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

    Science.gov (United States)

    Camellin, Massimo; Guidotti, Jacopo Maria; Arba Mosquera, Samuel

    To evaluate the efficacy and safety of Corneal-Wavefront guided transepithelial photorefractive keratectomy (TransPRK) after corneal collagen cross linking (CXL) in keratoconic patients. In this retrospective, non-comparative, consecutive case series, 39 keratoconic eyes underwent Corneal-Wavefront guided TransPRK for the correction of aberrations at least 4 months after conventional CXL at SEKAL Rovigo Microsurgery Centre, Rovigo, Italy. Two eyes (5%) underwent a secondary laser retreatment for the improvement of post-operative visual acuity and were not included in this retrospective analysis. The mean age of the patients was 35±12 years (19-64 years) at the time of the surgery. Keratron-Scout (Optikon) topographer was used for diagnostic tests and a flying-spot laser (AMARIS; SCHWIND eye-tech-solutions) was used for the refractive surgery. Complete ophthalmic examinations were performed before and after the surgery (4-36 months postoperatively with a mean follow up time of 10±8 months). Preoperatively, eyes showed irregular astigmatism up to 8D. At last postoperative follow-up, 21 eyes (57%) had UDVA better than 20/40, and six eyes (16%) had UDVA of 20/20. Twenty-three eyes (62%) were within 1.50D of attempted correction in spherical equivalent (mean deviation from target was +1.09±2.36D, range -2.50 to +7.38D). No eye lost 2 Snellen lines of CDVA, and 15 eyes (41%) had an increase of more than 2 lines. 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. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

  14. Broadband Interferometer for Measuring Transmitted Wavefronts of Optical Bandpass Filters for HST (ACS)

    Science.gov (United States)

    Boucarut, R. A.; Leviton, D. B.

    1998-01-01

    The transmitted wavefronts of optical filters for the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) are characterized using the Wildly and Openly Modified Broadband Achromatic Twyman Green (WOMBAT) Interferometer developed in the NASA/GSFC Optics Branch's Diffraction Grating Evaluation Facility (DGEF). Because only four of thirty-three of ACS's optical bandpass filters transmit the 633 nm light of most commercial interferometers, a broadband interferometer is required to verify specified transmitted wavefront of ACS filters. WOMBAT's design is a hybrid of the BAT interferometer developed by JPL used for HST Wide Field and Planetary Camera 2 (WFPC-2) filters and a WYKO 400 phase shifting interferometer. It includes a broadband light source, monochromator, off-axis, parabolic collimating and camera mirrors, an aluminum-coated fused silica beam splitter, flat retroreflecting mirrors for the test and reference arms, and a LTV-sensitive CCD camera. An outboarded, piezo-electric phase shifter holds the flat mirror in the interferometer's reference arm. The interferometer is calibrated through interaction between the WYKO system's software and WONMAT hardware for the test wavelength of light entering the beam splitter. Phase-shifted interferograms of the filter mounted in the test arm are analyzed using WYKO's Vision' software. Filters as large as 90 mm in diameter have been measured over a wavelength range from 200 to 1100 nm with a sensitivity of lambda/200 rms at lambda = 633 nm. Results of transmitted wavefront measurements are shown for ACS fixed band pass and spatially-variable bandpass filters for a variety of wavelengths.

  15. Compensation of Hologram Distortion by Controlling Defocus Component in Reference Beam Wavefront for Angle Multiplexed Holograms

    Science.gov (United States)

    Muroi, T.; Kinoshita, N.; Ishii, N.; Kamijo, K.; Kawata, Y.; Kikuchi, H.

    2013-12-01

    Holographic memory has the potential to function as a recording system with a large capacity and high data-transfer-rate. Photopolymer materials are typically used as a write-once recording medium. When holograms are recorded on this medium, they can distort due to shrinkage or expansion of the materials, which degrades the reconstructed image and causes a higher bit error rate (bER) of the reproduced data. We propose optically compensating for hologram distortion by controlling aberration components in the reference beam wavefront while reproducing data, thereby improving the reproduced data quality. First, we investigated the relation between each aberration component of the reference beam and the signal to noise ratio (SNR) of the reproduced data using numerical simulation and found that horizontal tilt and the defocus component affect the SNR. Next, we experimentally evaluated the reproduced data by controlling the defocus component in the reference beam and found that the bER of the reproduced data could be decreased by controlling the defocus center with respect to the hologram position and phase modulation depth of the defocus component. Then, we investigated a practical control method of the defocus component using an evaluation value similar to the definition of the SNR for actual data reproduction from holograms. Using a defocus controlled wavefront enabled us to decrease the bER from 3.54 x 10^-3 with a plane wave to 3.14 x 10^-4. We also investigated how to reduce the bERs of reproduced data in angle multiplexed holograms. By using a defocus controlled wavefront to compensate for hologram distortion on the 40th data page in 80-page angle multiplexed holograms, the bERs of all pages could be decreased to less than 1x10^-3. We showed that controlling the defocus component is an effective way to compensate for hologram distortion and to decrease the bER of reproduced data in holographic memory.

  16. Synchronous model-based approach for wavefront sensorless adaptive optics system.

    Science.gov (United States)

    Lianghua, Wen; Yang, Ping; Kangjian, Yang; Shanqiu, Chen; Shuai, Wang; Wenjing, Liu; Xu, Bing

    2017-08-21

    In this paper, an aberration correction algorithm for wavefront sensorless adaptive optics system is presented, which is based on the approximately linear relation between the mean square of the aberration gradients and the second moment of far-field intensity distribution. To demonstrate algorithm's performance, an experiment system of aberration corrections for Fresnel zone plates imaging is set up. The correction results show the excellent performance of this method in correction speed, and correction capability. Comparing with conventional stochastic parallel gradient descent (SPGD) algorithm, the correction speed with this method is improved about four times for the similar correction effect.

  17. Extended depth of field in an intrinsically wavefront-encoded biometric iris camera

    Science.gov (United States)

    Bergkoetter, Matthew D.; Bentley, Julie L.

    2014-12-01

    This work describes a design process which greatly increases the depth of field of a simple three-element lens system intended for biometric iris recognition. The system is optimized to produce a point spread function which is insensitive to defocus, so that recorded images may be deconvolved without knowledge of the exact object distance. This is essentially a variation on the technique of wavefront encoding, however the desired encoding effect is achieved by aberrations intrinsic to the lens system itself, without the need for a pupil phase mask.

  18. 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...

  19. 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

    2010-01-01

    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 re...

  20. 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...

  1. Adaptive illumination based on direct wavefront sensing in a light-sheet fluorescence microscope.

    Science.gov (United States)

    Wilding, Dean; Pozzi, Paolo; Soloviev, Oleg; Vdovin, Gleb; Verhaegen, Michel

    2016-10-31

    A methodology for the adaptive control and correction of phase aberrations in the illumination arm of a light-sheet fluorescence microscope has been developed. The method uses direct wavefront sensing on epi-fluorescent light to detect the aberration present in the sample. Using this signal, the aberrations in the illumination arm are subsequently corrected with a spatial light modulator in a feedforward mode. Adaptive correction, resulting in significant improvement in the axial resolution, has been demonstrated by imaging Tg(fli:GFP) zebrafish embryos.

  2. Wavefront Sensing and Control Technology for Submillimeter and Far-Infrared Space Telescopes

    Science.gov (United States)

    Redding, Dave

    2004-01-01

    The NGST wavefront sensing and control system will be developed to TRL6 over the next few years, including testing in a cryogenic vacuum environment with traceable hardware. Doing this in the far-infrared and submillimeter is probably easier, as some aspects of the problem scale with wavelength, and the telescope is likely to have a more stable environment; however, detectors may present small complications. Since this is a new system approach, it warrants a new look. For instance, a large space telescope based on the DART membrane mirror design requires a new actuation approach. Other mirror and actuation technologies may prove useful as well.

  3. Acceleration of computer-generated holograms using tilted wavefront recording plane method.

    Science.gov (United States)

    Arai, Daisuke; Shimobaba, Tomoyoshi; Murano, Koki; Endo, Yutaka; Hirayama, Ryuji; Hiyama, Daisuke; Kakue, Takashi; Ito, Tomoyoshi

    2015-01-26

    Computer Generated Holograms (CGH) are generated on computers; however, a great deal of computational power is required because the quality of the image is proportional to the number of point light sources of a 3D object. The Wavefront Recording Plane (WRP) method is an algorithm that enables reduction of the amount of calculations required. However, the WRP method also has a defect; it is not effective in the case of a 3D object with a deep structure. In this study, we propose two improved WRP methods: "Least Square Tilted WRP method" and "RANSAC Multi-Tilted WRP method."

  4. Parity decomposition theory of full wavefront aberration measurement using the intensity differences of aerial images in microlithography.

    Science.gov (United States)

    Yashiki, Satoshi

    2015-06-10

    The theory of full wavefront aberration measurements is developed using the intensity differences of aerial images, which are the projected images of one-dimensional measurement patterns consisting of single- or multibars. The key concept is the parity decomposition about the optical axis for two optical components: illumination pupil and wavefront aberration. An additional mathematical treatment, which is a perturbative approach with regard to aberration, is applied to the partially coherent imaging formula. The intensity difference of the two peaks has terms that are linear to the odd and even aberration with rigorously canceled squared aberration terms. The full wavefront aberration measurement is realized from simultaneous linear equations about the intensity difference. The validity of this approach is numerically confirmed under practical lithography conditions.

  5. Jacobian and Hessian matrices of optical path length for computing the wavefront shape, irradiance, and caustics in optical systems.

    Science.gov (United States)

    Lin, Psang Dain; Liu, Chien-Sheng

    2012-11-01

    The first- and second-order derivative matrices of the ray (i.e., ∂R¯(i)/∂X¯(0) and ∂(2)R¯(i)/∂X¯02) and optical path length (i.e., ∂OPL(i)/∂X¯(0) and (2)OPL(i)/∂X¯02) were derived with respect to the variable vector X¯(0) of the source ray in an optical system by our previous papers. Using the first and second fundamental forms of the wavefront, these four matrices are used to investigate the local principal curvatures of the wavefront at each boundary surface encountered by a ray traveling through the optical system. The proposed method not only yields the data needed to compute the irradiance of the wavefront but also provides the information required to determine the caustics. Importantly, the proposed methodology is applicable to both axisymmetric and nonaxisymmetric optical systems.

  6. Deep-turbulence wavefront sensing using digital holography in the on-axis phase shifting recording geometry

    Science.gov (United States)

    Thornton, Douglas E.; Spencer, Mark F.; Perram, Glen P.

    2017-09-01

    The effects of deep turbulence in long-range imaging applications presents unique challenges to properly measure and correct for aberrations incurred along the atmospheric path. In practice, digital holography can detect the path-integrated wavefront distortions caused by deep turbulence, and di erent recording geometries offer different benefits depending on the application of interest. Previous studies have evaluated the performance of the off-axis image and pupil plane recording geometries for deep-turbulence sensing. This study models digital holography in the on-axis phase shifting recording geometry using wave optics simulations. In particular, the analysis models spherical-wave propagation through varying deep-turbulence conditions to estimate the complex optical field, and performance is evaluated by calculating the field-estimated Strehl ratio and RMS wavefront error. Altogether, the results show that digital holography in the on-axis phase shifting recording geometry is an effective wavefront-sensing method in the presence of deep turbulence.

  7. A new video programme

    CERN Multimedia

    CERN video productions

    2011-01-01

    "What's new @ CERN?", a new monthly video programme, will be broadcast on the Monday of every month on webcast.cern.ch. Aimed at the general public, the programme will cover the latest CERN news, with guests and explanatory features. Tune in on Monday 3 October at 4 pm (CET) to see the programme in English, and then at 4:20 pm (CET) for the French version.   var flash_video_player=get_video_player_path(); insert_player_for_external('Video/Public/Movies/2011/CERN-MOVIE-2011-129/CERN-MOVIE-2011-129-0753-kbps-640x360-25-fps-audio-64-kbps-44-kHz-stereo', 'mms://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2011/CERN-MOVIE-2011-129/CERN-MOVIE-2011-129-Multirate-200-to-753-kbps-640x360-25-fps.wmv', 'false', 480, 360, 'https://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2011/CERN-MOVIE-2011-129/CERN-MOVIE-2011-129-posterframe-640x360-at-10-percent.jpg', '1383406', true, 'Video/Public/Movies/2011/CERN-MOVIE-2011-129/CERN-MOVIE-2011-129-0600-kbps-maxH-360-25-fps-...

  8. Gamifying Video Object Segmentation.

    Science.gov (United States)

    Spampinato, Concetto; Palazzo, Simone; Giordano, Daniela

    2017-10-01

    Video object segmentation can be considered as one of the most challenging computer vision problems. Indeed, so far, no existing solution is able to effectively deal with the peculiarities of real-world videos, especially in cases of articulated motion and object occlusions; limitations that appear more evident when we compare the performance of automated methods with the human one. However, manually segmenting objects in videos is largely impractical as it requires a lot of time and concentration. To address this problem, in this paper we propose an interactive video object segmentation method, which exploits, on one hand, the capability of humans to identify correctly objects in visual scenes, and on the other hand, the collective human brainpower to solve challenging and large-scale tasks. In particular, our method relies on a game with a purpose to collect human inputs on object locations, followed by an accurate segmentation phase achieved by optimizing an energy function encoding spatial and temporal constraints between object regions as well as human-provided location priors. Performance analysis carried out on complex video benchmarks, and exploiting data provided by over 60 users, demonstrated that our method shows a better trade-off between annotation times and segmentation accuracy than interactive video annotation and automated video object segmentation approaches.

  9. Interactive video algorithms and technologies

    CERN Document Server

    Hammoud, Riad

    2006-01-01

    This book covers both algorithms and technologies of interactive videos, so that businesses in IT and data managements, scientists and software engineers in video processing and computer vision, coaches and instructors that use video technology in teaching, and finally end-users will greatly benefit from it. This book contains excellent scientific contributions made by a number of pioneering scientists and experts from around the globe. It consists of five parts. The first part introduces the reader to interactive video and video summarization and presents effective methodologies for automatic abstraction of a single video sequence, a set of video sequences, and a combined audio-video sequence. In the second part, a list of advanced algorithms and methodologies for automatic and semi-automatic analysis and editing of audio-video documents are presented. The third part tackles a more challenging level of automatic video re-structuring, filtering of video stream by extracting of highlights, events, and meaningf...

  10. Categorizing Video Game Audio

    DEFF Research Database (Denmark)

    Westerberg, Andreas Rytter; Schoenau-Fog, Henrik

    2015-01-01

    This paper dives into the subject of video game audio and how it can be categorized in order to deliver a message to a player in the most precise way. A new categorization, with a new take on the diegetic spaces, can be used a tool of inspiration for sound- and game-designers to rethink how...... they can use audio in video games. The conclusion of this study is that the current models' view of the diegetic spaces, used to categorize video game audio, is not t to categorize all sounds. This can however possibly be changed though a rethinking of how the player interprets audio....

  11. Brains on video games

    OpenAIRE

    Bavelier, Daphne; Green, C. Shawn; Han, Doug Hyun; Renshaw, Perry F.; Merzenich, Michael M.; Gentile, Douglas A.

    2011-01-01

    The popular press is replete with stories about the effects of video and computer games on the brain. Sensationalist headlines claiming that video games ‘damage the brain’ or ‘boost brain power’ do not do justice to the complexities and limitations of the studies involved, and create a confusing overall picture about the effects of gaming on the brain. Here, six experts in the field shed light on our current understanding of the positive and negative ways in which playing video games can affe...

  12. High Dynamic Range Video

    CERN Document Server

    Myszkowski, Karol

    2008-01-01

    This book presents a complete pipeline forHDR image and video processing fromacquisition, through compression and quality evaluation, to display. At the HDR image and video acquisition stage specialized HDR sensors or multi-exposure techniques suitable for traditional cameras are discussed. Then, we present a practical solution for pixel values calibration in terms of photometric or radiometric quantities, which are required in some technically oriented applications. Also, we cover the problem of efficient image and video compression and encoding either for storage or transmission purposes, in

  13. 3D video

    CERN Document Server

    Lucas, Laurent; Loscos, Céline

    2013-01-01

    While 3D vision has existed for many years, the use of 3D cameras and video-based modeling by the film industry has induced an explosion of interest for 3D acquisition technology, 3D content and 3D displays. As such, 3D video has become one of the new technology trends of this century.The chapters in this book cover a large spectrum of areas connected to 3D video, which are presented both theoretically and technologically, while taking into account both physiological and perceptual aspects. Stepping away from traditional 3D vision, the authors, all currently involved in these areas, provide th

  14. OCAM2S: an integral shutter ultrafast and low noise wavefront sensor camera for laser guide stars adaptive optics systems

    OpenAIRE

    Gach, Jean-Luc; Feautrier, Philippe; Buey, Tristan; Rousset, Gerard; Gendron, Eric; Morris, Tim(School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ, U.K.); Basden, Alastair; Myers, Richard; Vidal, Fabrice; Chemla, Fanny

    2015-01-01

      To date, the OCAM2 system has demonstrated to be the fastest and lowest noise production ready wavefront sensor, achieving 2067 full frames per second with subelectron readout noise. This makes OCAM2 the ideal system for natural as well as continuous wave laser guide star wavefront sensing. In this paper we present the new gated version of OCAM2 named OCAM2-S, using E2V’s CCD219 sensor with integral shutter. This new camera offers the same superb characteristics than OCAM2 both i...

  15. 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

  16. Videos, Podcasts and Livechats

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    Full Text Available ... Care Disease Types FAQ Handout for Patients and Families Is It Right for You How to Get ... For the Media For Clinicians For Policymakers For Family Caregivers Glossary Menu In this section Links Videos ...

  17. Videos, Podcasts and Livechats

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    Full Text Available ... Donate Search Search What Is It Definition Pediatric Palliative Care Disease Types FAQ Handout for Patients and Families ... Policymakers For Family Caregivers Glossary Resources Browse our palliative care resources below: Links Videos Podcasts Webinars For the ...

  18. Acoustic Neuroma Educational Video

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    Full Text Available ... Click to learn more... LOGIN CALENDAR DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts ... Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video Ronson and Kerri Albany Support ...

  19. Videos, Podcasts and Livechats

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  1. Acoustic Neuroma Educational Video

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    Full Text Available ... Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma Association 600 Peachtree Parkway Suite 108 ... About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video English English ...

  2. Videos, Podcasts and Livechats

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    Full Text Available ... Disease Types Stories FAQ Handout for Patients and Families Is It Right for You How to Get ... For the Media For Clinicians For Policymakers For Family Caregivers Glossary Menu In this section Links Videos ...

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    Full Text Available ... Search Search What Is It Definition Pediatric Palliative Care Disease Types FAQ Handout for Patients and Families ... For Family Caregivers Glossary Resources Browse our palliative care resources below: Links Videos Podcasts Webinars For the ...

  4. Acoustic Neuroma Educational Video

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    Full Text Available ... Educational Video Scott at the Grand Canyon Proton Center load more hold SHIFT key to load all load all Stay Connected with ANA Newly Diagnosed Living with AN Healthcare Providers Acoustic Neuroma Association Donate Now Newly Diagnosed ...

  5. The video violence debate.

    Science.gov (United States)

    Lande, R G

    1993-04-01

    Some researchers and theorists are convinced that graphic scenes of violence on television and in movies are inextricably linked to human aggression. Others insist that a link has not been conclusively established. This paper summarizes scientific studies that have informed these two perspectives. Although many instances of children and adults imitating video violence have been documented, no court has imposed liability for harm allegedly resulting from a video program, an indication that considerable doubt still exists about the role of video violence in stimulating human aggression. The author suggests that a small group of vulnerable viewers are probably more impressionable and therefore more likely to suffer deleterious effects from violent programming. He proposes that research on video violence be narrowed to identifying and describing the vulnerable viewer.

  6. Acoustic Neuroma Educational Video

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    Full Text Available ... a patient kit Keywords Join/Renew Programs Back Support Groups Is a support group for me? Find ... Events Video Library Photo Gallery One-on-One Support ANetwork Peer Support Program Community Connections Overview Find ...

  7. Acoustic Neuroma Educational Video

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    Full Text Available ... Click to learn more... LOGIN CALENDAR DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts ... Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video English English Arabic Catalan Chinese ( ...

  8. Video i VIA

    DEFF Research Database (Denmark)

    2012-01-01

    Artiklen beskriver et udviklingsprojekt, hvor 13 grupper af lærere på tværs af fag og uddannelser producerede video til undervsioningsbrug. Der beskrives forskellige tilgange og anvendelser samt læringen i projektet...

  9. Videos, Podcasts and Livechats

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    Full Text Available ... to your Doctor Find a Provider Meet the Team Blog Articles & Stories News Resources Links Videos Podcasts ... to your Doctor Find a Provider Meet the Team Blog Articles & Stories News Provider Directory Donate Resources ...

  10. Acoustic Neuroma Educational Video

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    Full Text Available ... illness: Toby’s palliative care story Access the Provider Directory Handout for Patients and Families Is it Right ... Provider Meet the Team Blog Articles News Provider Directory Donate Resources Links Videos Podcasts Webinars For the ...

  12. Acoustic Neuroma Educational Video

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    Full Text Available ... Click to learn more... LOGIN EVENTS DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts ... Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video Scott at the Grand Canyon ...

  13. Acoustic Neuroma Educational Video

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    Full Text Available ... Is a support group for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork Peer Support Program Community Connections Overview Find a Meeting ...

  14. Photos and Videos

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Observers are required to take photos and/or videos of all incidentally caught sea turtles, marine mammals, seabirds and unusual or rare fish. On the first 3...

  15. Videos, Podcasts and Livechats

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    Full Text Available ... All rights reserved. GetPalliativeCare.org does not provide medical advice, diagnosis or treatment. ... the Team Blog Articles & Stories News Provider Directory Donate Resources Links Videos ...

  16. SEFIS Video Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a fishery-independent survey that collects data on reef fish in southeast US waters using multiple gears, including chevron traps, video cameras, ROVs,...

  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. Approximation of normalized point source sensitivity using power spectral density and slopes of wavefront aberration.

    Science.gov (United States)

    Seo, Byoung-Joon; Nissly, Carl; Troy, Mitchell; Angeli, George; Ford, Virginia; Stepp, Larry; Williams, Eric

    2013-06-10

    We have investigated two approximation methods for estimating the normalized point source sensitivity (PSSN), which is a recently developed optical performance metric for telescopes. One is an approximation based on the power spectral density (PSD) of the wavefront error. The other is the root-square-sum of the wavefront slope. We call these approximations β approximation and SlopeRMS approximation, respectively. Our analysis shows that for the Thirty Meter Telescope (TMT), the uncertainty of the β approximation is less than 1×10(-3) if the PSSN is better than 0.95, assuming the input PSD estimation is accurate. In addition, we find that the SlopeRMS approximation is a simple method for estimating the worst-case PSSN value in the specific situation when the PSSN is dominated by low-frequency aberrations. Therefore, the SlopeRMS approximation is expected to be useful for specifying a mirror surface for mirror vendors. Accordingly, TMT has a plan to adopt the SlopeRMS approximation for its M2 and M3 polishing specification.

  19. Correction of quasi-static wavefront errors for ELT with two sequential DMs

    Science.gov (United States)

    Pueyo, Laurent; Shaklan, Stuart B.; Give'On, Amir; Troy, Mitchell; Kasdin, N. Jeremy; Kay, Jason; Groff, Tyler; McElwain, Michael; Soummer, Remi

    Detection and spectral characterization of extrasolar planets with Extremely Large Telescopes (ELT) will require the ability to image very faint objects with a wide spectral bandwidth. Such a goal implies the development of new exquisite wavefront control techniques in order to calibrate and correct both the amplitude and phase components of the residual quasi-static halo that remains after the AO loop. Here we focus on the correction stage at time scales orders of magnitude slower than the AO refresh rate. We report laboratory results that exhibit four important features of instrument responses necessary for exo-planet characterization: post coronagraphic, high contrast, broadband, symmetric Point Spread Functions. This experiment was conducted in the Princeton University High Contrast Imaging Laboratory, equipped with a shaped pupil coronagraph and two sequential Boston Micromachines Kilo-DMs. In this paper we first review the theory and algorithms underlying one and two DM wavefront controllers and show why a second DM ultimately leads to improved broadband performances. We then present an experimental validation of such a two DM amplitude and phase controller.

  20. 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.

  1. 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.

  2. 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.

  3. Adapting wave-front algorithms to efficiently utilize systems with deep communication hierarchies

    Energy Technology Data Exchange (ETDEWEB)

    Kerbyson, Darren J [Los Alamos National Laboratory; Lang, Michael [Los Alamos National Laboratory; Pakin, Scott [Los Alamos National Laboratory

    2009-01-01

    Large-scale systems increasingly exhibit a differential between intra-chip and inter-chip communication performance. 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 contain wave-front 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 computation and higher use of on-chip communications. This tradeoff is explored using a performance model and an implementation 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.

  4. 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.

  5. Soft matter interfaces beamline at NSLS-II: geometrical ray-tracing vs. wavefront propagation simulations

    Science.gov (United States)

    Zhernenkov, Mikhail; Canestrari, Niccolo; Chubar, Oleg; DiMasi, Elaine

    2014-09-01

    We report on the implications of the design of a Soft Matter Interfaces beamline, a long energy range canted in-vacuum undulator (IVU) beamline at National Synchrotron Light Source II, based on comparison of geometrical ray-tracing and partially coherent x-ray wavefront propagation simulation software packages, namely, SHADOW and Synchrotron Radiation Workshop (SRW). For SHADOW, we employed an SRW-generated source file which simulated spectralangular distribution and apparent source characteristics of radiation produced by a 2.8 m long IVU with a 23 mm period and allowed us to realistically estimate the beam intensity at the sample positions. We highlight the necessity to use realistic mirror surface profiles with expected slope errors as opposed to "standard" built-in SHADOW surface error options. The beamline performances at three different x-ray photon energies: 20358 eV, 10778 eV, and 2101 eV, under different focusing conditions, have been studied. We compare beamline simulations performed with both software packages. In particular, we stress that the neglect of wavefront diffraction effects in geometrical ray-tracing approach results in significant discrepancies in beam spot size and beam shape, the correct assessments of which are crucial in determining the future performance of an instrument.

  6. Wavefronts matching: a novel paradigm for three-dimensional holographic particle tracking

    Science.gov (United States)

    Memmolo, Pasquale; Miccio, Lisa; Merola, Francesco; Netti, Paolo A.; Ferraro, Pietro

    2015-05-01

    Digital Holography (DH) in microscopy allows to retrieve in an accurate way the spatial coordinates of multiple moving particles, performing 3D tracking of the sample in the entire field of view. In particular, a posteriori quantitative multifocus phase-contrast imaging, suitable for 3D tracking of micro-objects, is one of the main features of the holographic approach. However, classical methods need to decouple amplitude and phase contributions of the reconstructed complex wavefronts to calculate target positions in 3D, due to the fact that the lateral displacements can be calculated only after refocusing step. In order to overcome this limitation, recently, a novel method of the simultaneous calculation of both axial and lateral coordinates of moving particles has been proposed. This is based on the novel concept of wavefronts matching, i.e. the 3D positions of micro-object, moving in 3D volume, are obtained by aligning wo subsequent holographic complex reconstructions, calculated at the same distance. We test this approach in different experimental conditions in order to highlight its effectiveness in bio-microfluidic applications.

  7. Optimization of wavefront-coded infinity-corrected microscope systems with extended depth of field.

    Science.gov (United States)

    Zhao, Tingyu; Mauger, Thomas; Li, Guoqiang

    2013-01-01

    The depth of field of an infinity-corrected microscope system is greatly extended by simply applying a specially designed phase mask between the objective and the tube lens. In comparison with the method of modifying the structure of objective, it is more cost effective and provides improved flexibility for assembling the system. Instead of using an ideal optical system for simulation which was the focus of the previous research, a practical wavefront-coded infinity-corrected microscope system is designed in this paper by considering the various aberrations. Two new optimization methods, based on the commercial optical design software, are proposed to design a wavefront-coded microscope using a non-symmetric phase mask and a symmetric phase mask, respectively. We use polynomial phase mask and rational phase mask as examples of the non-symmetric and symmetric phase masks respectively. Simulation results show that both optimization methods work well for a 32 × infinity-corrected microscope system with 0.6 numerical aperture. The depth of field is extended to about 13 times of the traditional one.

  8. 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

  9. NEI You Tube Videos: Amblyopia

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  10. NEI You Tube Videos: Amblyopia

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    Full Text Available ... Amaurosis Low Vision Refractive Errors Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: Amblyopia NEI Home Contact Us A-Z Site Map NEI on Social Media Information in Spanish (Información en español) Website, ...

  11. Studenterproduceret video til eksamen

    DEFF Research Database (Denmark)

    Jensen, Kristian Nøhr; Hansen, Kenneth

    2016-01-01

    Formålet med denne artikel er at vise, hvordan læringsdesign og stilladsering kan anvendes til at skabe en ramme for studenterproduceret video til eksamen på videregående uddannelser. Artiklen tager udgangspunkt i en problemstilling, hvor uddannelsesinstitutionerne skal håndtere og koordinere...... de fagfaglige og mediefaglige undervisere et redskab til at fokusere og koordinere indsatsen frem mod målet med, at de studerende producerer og anvender video til eksamen....

  12. Video Editing System

    Science.gov (United States)

    Schlecht, Leslie E.; Kutler, Paul (Technical Monitor)

    1998-01-01

    This is a proposal for a general use system based, on the SGI IRIS workstation platform, for recording computer animation to videotape. In addition, this system would provide features for simple editing and enhancement. Described here are a list of requirements for the system, and a proposed configuration including the SGI VideoLab Integrator, VideoMedia VLAN animation controller and the Pioneer rewritable laserdisc recorder.

  13. Video Games and Citizenship

    OpenAIRE

    Bourgonjon, Jeroen; Soetaert, Ronald

    2013-01-01

    In their article "Video Games and Citizenship" Jeroen Bourgonjon and Ronald Soetaert argue that digitization problematizes and broadens our perspective on culture and popular media, and that this has important ramifications for our understanding of citizenship. Bourgonjon and Soetaert respond to the call of Gert Biesta for the contextualized study of young people's practices by exploring a particular aspect of digitization that affects young people, namely video games. They explore the new so...

  14. Android Video Streaming

    Science.gov (United States)

    2014-05-01

    be processed by a nearby high -performance computing asset and returned to a squad of Soldiers with annotations indicating the location of friendly and...is to change the resolution, bitrate, and/or framerate of the video being transmitted to the client, reducing the bandwidth requirements of the...video. This solution is typically not viable because a progressive download is required to have a constant resolution, bitrate, and framerate because

  15. Robust Adaptable Video Copy Detection

    DEFF Research Database (Denmark)

    Assent, Ira; Kremer, Hardy

    2009-01-01

    Video copy detection should be capable of identifying video copies subject to alterations e.g. in video contrast or frame rates. We propose a video copy detection scheme that allows for adaptable detection of videos that are altered temporally (e.g. frame rate change) and/or visually (e.g. change...... in contrast). Our query processing combines filtering and indexing structures for efficient multistep computation of video copies under this model. We show that our model successfully identifies altered video copies and does so more reliably than existing models....

  16. Robust video object cosegmentation.

    Science.gov (United States)

    Wang, Wenguan; Shen, Jianbing; Li, Xuelong; Porikli, Fatih

    2015-10-01

    With ever-increasing volumes of video data, automatic extraction of salient object regions became even more significant for visual analytic solutions. This surge has also opened up opportunities for taking advantage of collective cues encapsulated in multiple videos in a cooperative manner. However, it also brings up major challenges, such as handling of drastic appearance, motion pattern, and pose variations, of foreground objects as well as indiscriminate backgrounds. Here, we present a cosegmentation framework to discover and segment out common object regions across multiple frames and multiple videos in a joint fashion. We incorporate three types of cues, i.e., intraframe saliency, interframe consistency, and across-video similarity into an energy optimization framework that does not make restrictive assumptions on foreground appearance and motion model, and does not require objects to be visible in all frames. We also introduce a spatio-temporal scale-invariant feature transform (SIFT) flow descriptor to integrate across-video correspondence from the conventional SIFT-flow into interframe motion flow from optical flow. This novel spatio-temporal SIFT flow generates reliable estimations of common foregrounds over the entire video data set. Experimental results show that our method outperforms the state-of-the-art on a new extensive data set (ViCoSeg).

  17. 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...

  18. The coronagraphic Modal Wavefront Sensor: a hybrid focal-plane sensor for the high-contrast imaging of circumstellar environments

    Science.gov (United States)

    Wilby, M. J.; Keller, C. U.; Snik, F.; Korkiakoski, V.; Pietrow, A. G. M.

    2017-01-01

    The raw coronagraphic performance of current high-contrast imaging instruments is limited by the presence of a quasi-static speckle (QSS) background, resulting from instrumental Non-Common Path Errors (NCPEs). Rapid development of efficient speckle subtraction techniques in data reduction has enabled final contrasts of up to 10-6 to be obtained, however it remains preferable to eliminate the underlying NCPEs at the source. In this work we introduce the coronagraphic Modal Wavefront Sensor (cMWS), a new wavefront sensor suitable for real-time NCPE correction. This combines the Apodizing Phase Plate (APP) coronagraph with a holographic modal wavefront sensor to provide simultaneous coronagraphic imaging and focal-plane wavefront sensing with the science point-spread function. We first characterise the baseline performance of the cMWS via idealised closed-loop simulations, showing that the sensor is able to successfully recover diffraction-limited coronagraph performance over an effective dynamic range of ±2.5 radians root-mean-square (rms) wavefront error within 2-10 iterations, with performance independent of the specific choice of mode basis. We then present the results of initial on-sky testing at the William Herschel Telescope, which demonstrate that the sensor is capable of NCPE sensing under realistic seeing conditions via the recovery of known static aberrations to an accuracy of 10 nm (0.1 radians) rms error in the presence of a dominant atmospheric speckle foreground. We also find that the sensor is capable of real-time measurement of broadband atmospheric wavefront variance (50% bandwidth, 158 nm rms wavefront error) at a cadence of 50 Hz over an uncorrected telescope sub-aperture. When combined with a suitable closed-loop adaptive optics system, the cMWS holds the potential to deliver an improvement of up to two orders of magnitude over the uncorrected QSS floor. Such a sensor would be eminently suitable for the direct imaging and spectroscopy of

  19. Integrated Wavefront Correction and Bias Estimation for the High-Contrast Imaging of Exoplanets

    Science.gov (United States)

    Riggs, A. J. Eldorado

    Just over two decades ago the first planet outside our solar system was found, and thousands more have been discovered since. Nearly all these exoplanets were indirectly detected by sensing changes in their host stars' light. However, exoplanets must be directly imaged to determine their atmospheric compositions and the orbital parameters unavailable from only indirect detections. The main challenge of direct imaging is to observe stellar companions much fainter than the star and at small angular separations. Coronagraphy is one method of suppressing stellar diffraction to provide high star-to-planet contrast, but coronagraphs are extremely sensitive to quasi-static aberrations in the optical system. Active correction of the stellar wavefront is performed with deformable mirrors to recover high-contrast regions in the image. Estimation and control of the stellar electric field is performed iteratively in the camera's focal plane to avoid non-common path aberrations arising from a separate pupil sensor. Estimation can thus be quite time consuming because it requires several high-contrast intensity images per correction iteration. This thesis focuses on efficient focal plane wavefront correction (FPWC) for coronagraphy. Time is a precious commodity for a space telescope, so there is a strong incentive to reduce the total exposure time required for focal plane wavefront estimation. Much of our work emphasizes faster, more robust estimation via Kalman filtering, which optimally combines prior data with new measurements. The other main contribution of this thesis is a paradigm shift in the use of estimation images. Time for FPWC has generally been considered to be lost overhead, but we demonstrate that estimation images can be used for the detection and characterization of exoplanets and disks. These science targets are incoherent with their host stars, so we developed and implemented an iterated extended Kalman filter (IEKF) for simultaneous estimation of the stellar

  20. Deep video deblurring

    KAUST Repository

    Su, Shuochen

    2016-11-25

    Motion blur from camera shake is a major problem in videos captured by hand-held devices. Unlike single-image deblurring, video-based approaches can take advantage of the abundant information that exists across neighboring frames. As a result the best performing methods rely on aligning nearby frames. However, aligning images is a computationally expensive and fragile procedure, and methods that aggregate information must therefore be able to identify which regions have been accurately aligned and which have not, a task which requires high level scene understanding. In this work, we introduce a deep learning solution to video deblurring, where a CNN is trained end-to-end to learn how to accumulate information across frames. To train this network, we collected a dataset of real videos recorded with a high framerate camera, which we use to generate synthetic motion blur for supervision. We show that the features learned from this dataset extend to deblurring motion blur that arises due to camera shake in a wide range of videos, and compare the quality of results to a number of other baselines.

  1. Talking Video in 'Everyday Life'

    DEFF Research Database (Denmark)

    McIlvenny, Paul

    For better or worse, video technologies have made their way into many domains of social life, for example in the domain of therapeutics. Techniques such as Marte Meo, Video Interaction Guidance (ViG), Video-Enhanced Reflection on Communication, Video Home Training and Video intervention....../prevention (VIP) all promote the use of video as a therapeutic tool. This paper focuses on media therapeutics and the various in situ uses of video technologies in the mass media for therapeutic purposes. Reality TV parenting programmes such as Supernanny, Little Angels, The House of Tiny Tearaways, Honey, We......’re Killing the Kids, and Driving Mum and Dad Mad all use video as a prominent element of not only the audiovisual spectacle of reality television but also the interactional therapy, counselling, coaching and/or instruction intrinsic to these programmes. Thus, talk-on-video is used to intervene...

  2. Video y desarrollo rural

    Directory of Open Access Journals (Sweden)

    Fraser Colin

    2015-01-01

    Full Text Available Las primeras experiencias de video rural fueron realizadas en Perú y México. El proyecto peruano es conocido como CESPAC (Centro de Servicios de Pedagogía Audiovisual para la Capacitación. Con financiamiento externo de la FAO fue iniciado en la década del 70. El proyecto mexicano fue bautizado con el nombre de PRODERITH (Programa de Desarrollo Rural Integrado del Trópico Húmedo. Su componente de video rural tuvo un éxito muy particular a nivel de base.La evaluación concluyó en que el video rural como sistema de comunicación social para el desarrollo es excelente y de bajo costo

  3. A Big Video Manifesto

    DEFF Research Database (Denmark)

    Mcilvenny, Paul Bruce; Davidsen, Jacob

    2017-01-01

    For the last few years, we have witnessed a hype about the potential results and insights that quantitative big data can bring to the social sciences. The wonder of big data has moved into education, traffic planning, and disease control with a promise of making things better with big numbers...... and beautiful visualisations. However, we also need to ask what the tools of big data can do both for the Humanities and for more interpretative approaches and methods. Thus, we prefer to explore how the power of computation, new sensor technologies and massive storage can also help with video-based qualitative...... inquiry, such as video ethnography, ethnovideo, performance documentation, anthropology and multimodal interaction analysis. That is why we put forward, half-jokingly at first, a Big Video manifesto to spur innovation in the Digital Humanities....

  4. Online video examination

    DEFF Research Database (Denmark)

    Qvist, Palle

    courses are accredited to the master programme. The programme is online, worldwide and on demand. It recruits students from all over the world. The programme is organized exemplary in accordance the principles in the problem-based and project-based learning method used at Aalborg University where students......The Master programme in Problem-Based Learning in Engineering and Science, MPBL (www.mpbl.aau.dk), at Aalborg University, is an international programme offering formalized staff development. The programme is also offered in smaller parts as single subject courses (SSC). Passed single subject...... have large influence on their own teaching, learning and curriculum. The programme offers streamed videos in combination with other learning resources. It is a concept which offers video as pure presentation - video lectures - but also as an instructional tool which gives the students the possibility...

  5. Brains on video games.

    Science.gov (United States)

    Bavelier, Daphne; Green, C Shawn; Han, Doug Hyun; Renshaw, Perry F; Merzenich, Michael M; Gentile, Douglas A

    2011-11-18

    The popular press is replete with stories about the effects of video and computer games on the brain. Sensationalist headlines claiming that video games 'damage the brain' or 'boost brain power' do not do justice to the complexities and limitations of the studies involved, and create a confusing overall picture about the effects of gaming on the brain. Here, six experts in the field shed light on our current understanding of the positive and negative ways in which playing video games can affect cognition and behaviour, and explain how this knowledge can be harnessed for educational and rehabilitation purposes. As research in this area is still in its early days, the contributors of this Viewpoint also discuss several issues and challenges that should be addressed to move the field forward.

  6. A decadal survey of AO wavefront sensing detector developments in Europe

    Science.gov (United States)

    Feautrier, Philippe

    2011-09-01

    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 started in the late nineties with the development of the CCD50 detector by e2v under ESO contract for the ESO NAOS AO system. With a 128x128 pixels format, this 8 outputs CCD runs at a 500 Hz frame rate with a readout noise of 7e-. A major breakthrough has been achieved with the recent development of the CCD220, also by e2v technologies. This 240x240 pixels 8 outputs EMCCD (CCD with internal multiplication), also developed by e2v, has been jointly funded by ESO and Europe under the FP6 programme. The CCD220 detector and the OCAM2 camera are now the most sensitive system in the world for advanced adaptive optics systems, offering an astonishing 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 is extensively described elsewhere in this conference (see Gach J-L. et al). An upgrade of OCAM2 is foreseen to boost its frame rate to 2500 Hz, opening the window of XAO wavefront sensing for the ELT. Since this major success, new developments started in Europe. One is fully dedicated to Laser Guide Star AO for the ELT. The spot elongation from a LGS SH wavefront sensor induces an increase of the pixel format. Two detectors are currently developed by e2v. The NGSD will be a 672x672 pixels CMOS detector with a readout noise of 4e (goal 1e) at 700 Hz frame rate. The LGSD is a scaling of the NGSD with 1680x1680 pixels and 3 e readout noise (goal 1e) at 700 Hz frame rate. New technologies will be developed for that purpose: new CMOS pixel architecture, CMOS back thinned and back

  7. Linear prediction of atmospheric wave-fronts for tomographic adaptive optics systems: modelling and robustness assessment.

    Science.gov (United States)

    Jackson, Kate; Correia, Carlos; Lardière, Olivier; Andersen, Dave; Bradley, Colin

    2015-01-15

    We use a theoretical framework to analytically assess temporal prediction error functions on von-Kármán turbulence when a zonal representation of wavefronts is assumed. The linear prediction models analyzed include auto-regressive of an order up to three, bilinear interpolation functions, and a minimum mean square error predictor. This is an extension of the authors' previously published work Correia et al. [J. Opt. Soc. Am. A31, 101 (2014)JOAOD61084-752910.1364/JOSAA.31.000101], in which the efficacy of various temporal prediction models was established. Here we examine the tolerance of these algorithms to specific forms of model errors, thus defining the expected change in behavior of the previous results under less ideal conditions. Results show that ±100% wind speed error and ±50  deg are tolerable before the best linear predictor delivers poorer performance than the no-prediction case.

  8. Wavefront sensorless adaptive optics OCT with the DONE algorithm forin vivohuman retinal imaging [Invited].

    Science.gov (United States)

    Verstraete, Hans R G W; Heisler, Morgan; Ju, Myeong Jin; Wahl, Daniel; Bliek, Laurens; Kalkman, Jeroen; Bonora, Stefano; Jian, Yifan; Verhaegen, Michel; Sarunic, Marinko V

    2017-04-01

    In this report, which is an international collaboration of OCT, adaptive optics, and control research, we demonstrate the Data-based Online Nonlinear Extremum-seeker (DONE) algorithm to guide the image based optimization for wavefront sensorless adaptive optics (WFSL-AO) OCT for in vivo human retinal imaging. The ocular aberrations were corrected using a multi-actuator adaptive lens after linearization of the hysteresis in the piezoelectric actuators. The DONE algorithm succeeded in drastically improving image quality and the OCT signal intensity, up to a factor seven, while achieving a computational time of 1 ms per iteration, making it applicable for many high speed applications. We demonstrate the correction of five aberrations using 70 iterations of the DONE algorithm performed over 2.8 s of continuous volumetric OCT acquisition. Data acquired from an imaging phantom and in vivo from human research volunteers are presented.

  9. 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.

  10. Laser induced wavefront distortion in thick-disk material: An analytical description

    Science.gov (United States)

    Isidro-Ojeda, Michel A.; Alvarado-Gil, Juan J.; Zanuto, Vitor S.; Baesso, Mauro L.; Astrath, Nelson G. C.; Malacarne, Luis C.

    2018-01-01

    Laser induced wavefront distortion is critical for designing and evaluation of optical components for high-power laser and can affect performance and stability of optical systems. The analysis of this effect involves a complex thermoelastic problem only solved in simplified conditions such as the plane-stress or plane-strain configurations. For more realistic descriptions, numerical solutions are required, although recent advances allowed for a unified model to describe the optical path change, regardless of the sample thickness, assuming a sample of infinite radius. In this work, we extend this result for the case of a thick-disk sample by solving the set of differential equations governing the thermoelastic response for the finite radius configuration. These results could represent a significant contribution for designing and characterization of laser systems with potential application in many photothermal methods for material characterization.

  11. Wavefronts in time-delayed reaction-diffusion systems. Theory and comparison to experiment

    Energy Technology Data Exchange (ETDEWEB)

    Fort, Joaquim [Departament de Fisica, Universitat de Girona, Girona (Spain)]. E-mail: joaquim.fort@udg.es; Mendez, Vicenc [Facultat de Ciencies de la Salut, Universitat Internacional de Catalunya, Ssant Cugat del Valles (Spain)]. E-mail: vmendez@csc.unica.edu

    2002-06-01

    We review the recent theoretical progress in the formulation and solution of the front speed problem for time-delayed reaction-diffusion systems. Most of the review is focused on hyperbolic equations. They have been widely used in recent years, because they allow for analytical solutions and yield a realistic description of some relevant phenomena. The theoretical methods are applied to a range of applications, including population dynamics, forest fire models, bistable systems and combustion wavefronts. We also present a detailed account of successful predictions of the models, as assessed by comparison to experimental data for some biophysical systems, without making use of any free parameters. Areas where the work reviewed may contribute to future progress are discussed. (author)

  12. Underwater Acoustic Wavefront Visualization by Scanning Laser Doppler Vibrometer for the Characterization of Focused Ultrasonic Transducers.

    Science.gov (United States)

    Longo, Roberto; Vanlanduit, Steve; Arroud, Galid; Guillaume, Patrick

    2015-08-13

    The analysis of acoustic wave fields is important for a large number of engineering designs, communication and health-related reasons. The visualization of wavefronts gives valuable information about the type of transducers and excitation signals more suitable for the test itself. This article is dedicated to the development of a fast procedure for acoustic fields visualization in underwater conditions, by means of laser Doppler vibrometer measurements. The ultrasonic probe is a focused transducer excited by a chirp signal. The scope of this work is to evaluate experimentally the properties of the sound beam in order to get reliable information about the transducer itself to be used in many kinds of engineering tests and transducer design.

  13. Underwater Acoustic Wavefront Visualization by Scanning Laser Doppler Vibrometer for the Characterization of Focused Ultrasonic Transducers

    Directory of Open Access Journals (Sweden)

    Roberto Longo

    2015-08-01

    Full Text Available The analysis of acoustic wave fields is important for a large number of engineering designs, communication and health-related reasons. The visualization of wavefronts gives valuable information about the type of transducers and excitation signals more suitable for the test itself. This article is dedicated to the development of a fast procedure for acoustic fields visualization in underwater conditions, by means of laser Doppler vibrometer measurements. The ultrasonic probe is a focused transducer excited by a chirp signal. The scope of this work is to evaluate experimentally the properties of the sound beam in order to get reliable information about the transducer itself to be used in many kinds of engineering tests and transducer design.

  14. Optimizing stochastic gradient descent algorithms for serially addressed adaptive-optics wavefront modulators.

    Science.gov (United States)

    Simpkins, Travis; Hui, Jeremy; Warde, Cardinal

    2007-10-20

    High-resolution adaptive-optical systems with thousands to millions of pixels will most likely have to employ serial- or matrix-addressed spatial light modulators (e.g., microelectromechanical-system-on-VLSI spatial light modulators). We compare parallel gradient descent adaptive-optics algorithms with serial gradient descent algorithms running on serially addressed modulators. While serial algorithms have previously been shown to require more iterations than parallel algorithms, we show that, because of the limitations of the databus, each serial iteration of the algorithm on a serial modulator requires significantly less time to complete than a parallel iteration, thereby favoring the serial algorithm when time to convergence is used as the performance metric. Thus, such high-resolution serially addressed devices are generally better matched to the serial-update wavefront correction algorithm owing to the data load penalty imposed by the bandwidth-limited databus of these modulators.

  15. 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.

  16. A high speed model-based approach for wavefront sensorless adaptive optics systems

    Science.gov (United States)

    Lianghua, Wen; Yang, Ping; Shuai, Wang; Wenjing, Liu; Shanqiu, Chen; Xu, Bing

    2018-02-01

    To improve temporal-frequency property of wavefront sensorless adaptive optics (AO) systems, a fast general model-based aberration correction algorithm is presented. The fast general model-based approach is based on the approximately linear relation between the mean square of the aberration gradients and the second moment of far-field intensity distribution. The presented model-based method is capable of completing a mode aberration effective correction just applying one disturbing onto the deformable mirror(one correction by one disturbing), which is reconstructed by the singular value decomposing the correlation matrix of the Zernike functions' gradients. Numerical simulations of AO corrections under the various random and dynamic aberrations are implemented. The simulation results indicate that the equivalent control bandwidth is 2-3 times than that of the previous method with one aberration correction after applying N times disturbing onto the deformable mirror (one correction by N disturbing).

  17. 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.

  18. A practical way to resolve ambiguities in wavefront reconstructions by the transport of intensity equation.

    Science.gov (United States)

    Parvizi, A; Müller, J; Funken, S A; Koch, C T

    2015-07-01

    The transport of intensity equation (TIE) provides a very straight forward way to computationally reconstruct wavefronts from measurements of the intensity and the derivative of this intensity along the optical axis of the system. However, solving the TIE requires knowledge of boundary conditions which cannot easily be obtained experimentally. The solution one obtains is therefore not guaranteed to be accurate. In addition, noise and systematic measurement errors can very easily lead to low-frequency artefacts. In this paper we solve the TIE by the finite element method (FEM). The flexibility of this approach allows us to define additional boundary conditions (e.g. a flat phase in areas where there is no object) that lead to a correct solution of the TIE, even in the presence of noise. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Video library for video imaging detection at intersection stop lines.

    Science.gov (United States)

    2010-04-01

    The objective of this activity was to record video that could be used for controlled : evaluation of video image vehicle detection system (VIVDS) products and software upgrades to : existing products based on a list of conditions that might be diffic...

  20. User aware video streaming

    Science.gov (United States)

    Kerofsky, Louis; Jagannath, Abhijith; Reznik, Yuriy

    2015-03-01

    We describe the design of a video streaming system using adaptation to viewing conditions to reduce the bitrate needed for delivery of video content. A visual model is used to determine sufficient resolution needed under various viewing conditions. Sensors on a mobile device estimate properties of the viewing conditions, particularly the distance to the viewer. We leverage the framework of existing adaptive bitrate streaming systems such as HLS, Smooth Streaming or MPEG-DASH. The client rate selection logic is modified to include a sufficient resolution computed using the visual model and the estimated viewing conditions. Our experiments demonstrate significant bitrate savings compare to conventional streaming methods which do not exploit viewing conditions.

  1. Contextual analysis of videos

    CERN Document Server

    Thida, Myo; Monekosso, Dorothy

    2013-01-01

    Video context analysis is an active and vibrant research area, which provides means for extracting, analyzing and understanding behavior of a single target and multiple targets. Over the last few decades, computer vision researchers have been working to improve the accuracy and robustness of algorithms to analyse the context of a video automatically. In general, the research work in this area can be categorized into three major topics: 1) counting number of people in the scene 2) tracking individuals in a crowd and 3) understanding behavior of a single target or multiple targets in the scene.

  2. Video-based rendering

    CERN Document Server

    Magnor, Marcus A

    2005-01-01

    Driven by consumer-market applications that enjoy steadily increasing economic importance, graphics hardware and rendering algorithms are a central focus of computer graphics research. Video-based rendering is an approach that aims to overcome the current bottleneck in the time-consuming modeling process and has applications in areas such as computer games, special effects, and interactive TV. This book offers an in-depth introduction to video-based rendering, a rapidly developing new interdisciplinary topic employing techniques from computer graphics, computer vision, and telecommunication en

  3. CERN Video News

    CERN Multimedia

    2003-01-01

    From Monday you can see on the web the new edition of CERN's Video News. Thanks to a collaboration between the audiovisual teams at CERN and Fermilab, you can see a report made by the American laboratory. The clip concerns the LHC magnets that are being constructed at Fermilab. Also in the programme: the spectacular rotation of one of the ATLAS coils, the arrival at CERN of the first American magnet made at Brookhaven, the story of the discovery 20 years ago of the W and Z bosons at CERN. http://www.cern.ch/video or Bulletin web page.

  4. Error analysis of compensation cutting technique for wavefront error of KH2PO4 crystal.

    Science.gov (United States)

    Tie, Guipeng; Dai, Yifan; Guan, Chaoliang; Zhu, Dengchao; Song, Bing

    2013-09-20

    Considering the wavefront error of KH(2)PO(4) (KDP) crystal is difficult to control through face fly cutting process because of surface shape deformation during vacuum suction, an error compensation technique based on a spiral turning method is put forward. An in situ measurement device is applied to measure the deformed surface shape after vacuum suction, and the initial surface figure error, which is obtained off-line, is added to the in situ surface shape to obtain the final surface figure to be compensated. Then a three-axis servo technique is utilized to cut the final surface shape. In traditional cutting processes, in addition to common error sources such as the error in the straightness of guide ways, spindle rotation error, and error caused by ambient environment variance, three other errors, the in situ measurement error, position deviation error, and servo-following error, are the main sources affecting compensation accuracy. This paper discusses the effect of these three errors on compensation accuracy and provides strategies to improve the final surface quality. Experimental verification was carried out on one piece of KDP crystal with the size of Φ270 mm×11 mm. After one compensation process, the peak-to-valley value of the transmitted wavefront error dropped from 1.9λ (λ=632.8 nm) to approximately 1/3λ, and the mid-spatial-frequency error does not become worse when the frequency of the cutting tool trajectory is controlled by use of a low-pass filter.

  5. 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.

  6. Single freeform surface design for prescribed input wavefront and target irradiance.

    Science.gov (United States)

    Bösel, Christoph; Gross, Herbert

    2017-09-01

    In beam shaping applications, the minimization of the number of necessary optical elements for the beam shaping process can benefit the compactness of the optical system and reduce its cost. The single freeform surface design for input wavefronts, which are neither planar nor spherical, is therefore of interest. In this work, the design of single freeform surfaces for a given zero-étendue source and complex target irradiances is investigated. Hence, not only collimated input beams or point sources are assumed. Instead, a predefined input ray direction vector field and irradiance distribution on a source plane, which has to be redistributed by a single freeform surface to give the predefined target irradiance, is considered. To solve this design problem, a partial differential equation (PDE) or PDE system, respectively, for the unknown surface and its corresponding ray mapping is derived from energy conservation and the ray-tracing equations. In contrast to former PDE formulations of the single freeform design problem, the derived PDE of Monge-Ampère type is formulated for general zero-étendue sources in Cartesian coordinates. The PDE system is discretized with finite differences, and the resulting nonlinear equation system is solved by a root-finding algorithm. The basis of the efficient solution of the PDE system builds the introduction of an initial iterate construction approach for a given input direction vector field, which uses optimal mass transport with a quadratic cost function. After a detailed description of the numerical algorithm, the efficiency of the design method is demonstrated by applying it to several design examples. This includes the redistribution of a collimated input beam beyond the paraxial approximation, the shaping of point source radiation, and the shaping of an astigmatic input wavefront into a complex target irradiance distribution.

  7. 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.

  8. Analysis of Rayleigh waves with circular wavefront: a maximum likelihood approach

    Science.gov (United States)

    Maranò, Stefano; Hobiger, Manuel; Bergamo, Paolo; Fäh, Donat

    2017-09-01

    Analysis of Rayleigh waves is an important task in seismology and geotechnical investigations. In fact, properties of Rayleigh waves such as velocity and polarization are important observables that carry information about the structure of the subsoil. Applications analysing Rayleigh waves include active and passive seismic surveys. In active surveys, there is a controlled source of seismic energy and the sensors are typically placed near the source. In passive surveys, there is not a controlled source, rather, seismic waves from ambient vibrations are analysed and the sources are assumed to be far outside the array, simplifying the analysis by the assumption of plane waves. Whenever the source is in the proximity of the array of sensors or even within the array it is necessary to model the wave propagation accounting for the circular wavefront. In addition, it is also necessary to model the amplitude decay due to geometrical spreading. This is the case of active seismic surveys in which sensors are located near the seismic source. In this work, we propose a maximum likelihood (ML) approach for the analysis of Rayleigh waves generated at a near source. Our statistical model accounts for the curvature of the wavefront and amplitude decay due to geometrical spreading. Using our method, we show applications on real data of the retrieval of Rayleigh wave dispersion and ellipticity. We employ arrays with arbitrary geometry. Furthermore, we show how it is possible to combine active and passive surveys. This enables us to enlarge the analysable frequency range and therefore the depths investigated. We retrieve properties of Rayleigh waves from both active and passive surveys and show the excellent agreement of the results from the two surveys. In our approach we use the same array of sensors for both the passive and the active survey. This greatly simplifies the logistics necessary to perform a survey.

  9. 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.

  10. Influence of mydriatic eye drops on wavefront sensing with the Zywave aberrometer.

    Science.gov (United States)

    Taneri, Suphi; Oehler, Saskia; Azar, Dimitri T

    2011-09-01

    To investigate a potential influence of mydriatic eye drops on wavefront sensing with the Zywave aberrometer (Technolas Perfect Vision) in terms of predicted phoropter refraction (PPR) and higher order aberrations (HOA). In this prospective study, 200 myopic eyes were measured in miosis and pharmacologically induced mydriasis with an aberrometer and automated refraction. One hundred eyes were dilated with tropicamide 0.5%+phenylephrine 2.5% eye drops (tropicamide/phenylephrine group), and the remaining 100 eyes with tropicamide 0.5% (tropicamide only group). The PPR values for a pupil diameter of 3.5 mm in miosis and mydriasis, respectively, were compared and correlated to the corresponding values of automated refraction. Changes in HOAs up to the 4th order were recorded. Predicted phoropter refraction values obtained in mydriasis were less myopic than in miosis. The spherical equivalent refraction of PPR differed by an average of 0.36 ± 0.36 diopters (D) in the tropicamide/phenylephrine group. In the tropicamide only group, the difference was 0.24 ± 0.43 D. Sphere of PPR differed by an average of 0.33 ± 0.36 D in the tropicamide/phenylephrine group and by an average of 0.24 ± 0.35 D in the tropicamide only group. Patient age had no major influence on the level of difference. Automated refraction yielded a smaller difference in spherical equivalent refraction. Changes in HOA root-mean-square were statistically significant. The cycloplegic effect of mydriatic eye drops should be taken into account when interpreting aberration measurements and planning a wavefront-guided ablation. Ideally, the use of mydriatic eye drops should be avoided to minimize refractive surprises. Copyright 2011, SLACK Incorporated.

  11. Video special effects editing in MPEG-2 compressed video

    OpenAIRE

    Fernando, WAC; Canagarajah, CN; Bull, David

    2000-01-01

    With the increase of digital technology in video production, several types of complex video special effects editing have begun to appear in video clips. In this paper we consider fade-out and fade-in special effects editing in MPEG-2 compressed video without full frame decompression and motion estimation. We estimated the DCT coefficients and use these coefficients together with the existing motion vectors to produce these special effects editing in compressed domain. Results show that both o...

  12. Innovative Solution to Video Enhancement

    Science.gov (United States)

    2001-01-01

    Through a licensing agreement, Intergraph Government Solutions adapted a technology originally developed at NASA's Marshall Space Flight Center for enhanced video imaging by developing its Video Analyst(TM) System. Marshall's scientists developed the Video Image Stabilization and Registration (VISAR) technology to help FBI agents analyze video footage of the deadly 1996 Olympic Summer Games bombing in Atlanta, Georgia. VISAR technology enhanced nighttime videotapes made with hand-held camcorders, revealing important details about the explosion. Intergraph's Video Analyst System is a simple, effective, and affordable tool for video enhancement and analysis. The benefits associated with the Video Analyst System include support of full-resolution digital video, frame-by-frame analysis, and the ability to store analog video in digital format. Up to 12 hours of digital video can be stored and maintained for reliable footage analysis. The system also includes state-of-the-art features such as stabilization, image enhancement, and convolution to help improve the visibility of subjects in the video without altering underlying footage. Adaptable to many uses, Intergraph#s Video Analyst System meets the stringent demands of the law enforcement industry in the areas of surveillance, crime scene footage, sting operations, and dash-mounted video cameras.

  13. A video annotation methodology for interactive video sequence generation

    NARCIS (Netherlands)

    C.A. Lindley; R.A. Earnshaw; J.A. Vince

    2001-01-01

    textabstractThe FRAMES project within the RDN CRC (Cooperative Research Centre for Research Data Networks) has developed an experimental environment for dynamic virtual video sequence synthesis from databases of video data. A major issue for the development of dynamic interactive video applications

  14. Streaming Video--The Wave of the Video Future!

    Science.gov (United States)

    Brown, Laura

    2004-01-01

    Videos and DVDs give the teachers more flexibility than slide projectors, filmstrips, and 16mm films but teachers and students are excited about a new technology called streaming. Streaming allows the educators to view videos on demand via the Internet, which works through the transfer of digital media like video, and voice data that is received…

  15. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... Grants and Funding Extramural Research Division of Extramural Science Programs Division of Extramural Activities Extramural Contacts NEI ... Amaurosis Low Vision Refractive Errors Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded ...

  16. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Corner / Patient Webcasts / Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five ... was designed to help you learn more about Rheumatoid Arthritis (RA). You will learn how the diagnosis ...

  17. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Our Staff Rheumatology Specialty Centers You are here: Home / Patient Corner / Patient Webcasts / Rheumatoid Arthritis Educational Video ... to take a more active role in your care. The information in these videos should not take ...

  18. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... will allow you to take a more active role in your care. The information in these videos ... Stategies to Increase your Level of Physical Activity Role of Body Weight in Osteoarthritis Educational Videos for ...

  19. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... here. Will You Support the Education of Arthritis Patients? Each year, over 1 million people visit this ... of Body Weight in Osteoarthritis Educational Videos for Patients Rheumatoid Arthritis Educational Video Series Psoriatic Arthritis 101 ...

  20. Videos & Tools: MedlinePlus

    Science.gov (United States)

    ... of this page: https://medlineplus.gov/videosandcooltools.html Videos & Tools To use the sharing features on this page, please enable JavaScript. Watch health videos on topics such as anatomy, body systems, and ...

  1. Health Videos: MedlinePlus

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/anatomyvideos.html.htm Health Videos To use the sharing features on this page, please enable JavaScript. These animated videos show the anatomy of body parts and organ ...

  2. Scanning laser video camera/ microscope

    Science.gov (United States)

    Wang, C. P.; Bow, R. T.

    1984-10-01

    A laser scanning system capable of scanning at standard video rate has been developed. The scanning mirrors, circuit design and system performance, as well as its applications to video cameras and ultra-violet microscopes, are discussed.

  3. Astronomy Video Contest

    Science.gov (United States)

    McFarland, John

    2008-05-01

    During Galileo's lifetime his staunchest supporter was Johannes Kepler, Imperial Mathematician to the Holy Roman Emperor. Johannes Kepler will be in St. Louis to personally offer a tribute to Galileo. Set Galileo's astronomy discoveries to music and you get the newest song by the well known acappella group, THE CHROMATICS. The song, entitled "Shoulders of Giants” was written specifically for IYA-2009 and will be debuted at this conference. The song will also be used as a base to create a music video by synchronizing a person's own images to the song's lyrics and tempo. Thousands of people already do this for fun and post their videos on YOU TUBE and other sites. The ASTRONOMY VIDEO CONTEST will be launched as a vehicle to excite, enthuse and educate people about astronomy and science. It will be an annual event administered by the Johannes Kepler Project and will continue to foster the goals of IYA-2009 for years to come. During this presentation the basic categories, rules, and prizes for the Astronomy Video Contest will be covered and finally the new song "Shoulders of Giants” by THE CHROMATICS will be unveiled

  4. Provocative Video Scenarios

    DEFF Research Database (Denmark)

    Caglio, Agnese

    This paper presents the use of ”provocative videos”, as a tool to support and deepen findings from ethnographic investigation on the theme of remote videocommunication. The videos acted as a resource to also investigate potential for novel technologies supporting continuous connection between...

  5. Fast Aerial Video Stitching

    Directory of Open Access Journals (Sweden)

    Jing Li

    2014-10-01

    Full Text Available The highly efficient and robust stitching of aerial video captured by unmanned aerial vehicles (UAVs is a challenging problem in the field of robot vision. Existing commercial image stitching systems have seen success with offline stitching tasks, but they cannot guarantee high-speed performance when dealing with online aerial video sequences. In this paper, we present a novel system which has an unique ability to stitch high-frame rate aerial video at a speed of 150 frames per second (FPS. In addition, rather than using a high-speed vision platform such as FPGA or CUDA, our system is running on a normal personal computer. To achieve this, after the careful comparison of the existing invariant features, we choose the FAST corner and binary descriptor for efficient feature extraction and representation, and present a spatial and temporal coherent filter to fuse the UAV motion information into the feature matching. The proposed filter can remove the majority of feature correspondence outliers and significantly increase the speed of robust feature matching by up to 20 times. To achieve a balance between robustness and efficiency, a dynamic key frame-based stitching framework is used to reduce the accumulation errors. Extensive experiments on challenging UAV datasets demonstrate that our approach can break through the speed limitation and generate an accurate stitching image for aerial video stitching tasks.

  6. Video Content Foraging

    NARCIS (Netherlands)

    van Houten, Ynze; Schuurman, Jan Gerrit; Verhagen, Pleunes Willem; Enser, Peter; Kompatsiaris, Yiannis; O’Connor, Noel E.; Smeaton, Alan F.; Smeulders, Arnold W.M.

    2004-01-01

    With information systems, the real design problem is not increased access to information, but greater efficiency in finding useful information. In our approach to video content browsing, we try to match the browsing environment with human information processing structures by applying ideas from

  7. Internet video search

    NARCIS (Netherlands)

    Snoek, C.G.M.; Smeulders, A.W.M.

    2011-01-01

    In this tutorial, we focus on the challenges in internet video search, present methods how to achieve state-of-the-art performance while maintaining efficient execution, and indicate how to obtain improvements in the near future. Moreover, we give an overview of the latest developments and future

  8. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available ... Donate Resources Links Videos Podcasts Webinars For the Media For Clinicians For Policymakers For Family Caregivers Glossary Sign Up for Our Blog Subscribe to Blog Enter your email address to subscribe to this blog and receive notifications of new posts by email. Email Address CLOSE Home About ...

  9. Scalable Video Coding

    NARCIS (Netherlands)

    Choupani, R.

    2017-01-01

    With the rapid improvements in digital communication technologies, distributing high-definition visual information has become more widespread. However, the available technologies were not sufficient to support the rising demand for high-definition video. This situation is further complicated when

  10. Video processing project

    CSIR Research Space (South Africa)

    Globisch, R

    2009-03-01

    Full Text Available Video processing source code for algorithms and tools used in software media pipelines (e.g. image scalers, colour converters, etc.) The currently available source code is written in C++ with their associated libraries and DirectShow- Filters....

  11. Video narrativer i sygeplejerskeuddannelsen

    DEFF Research Database (Denmark)

    Jensen, Inger

    2009-01-01

    I artiklen gives nogle bud på hvordan video narrativer kan bruges i sygeplejerskeuddannelsen som triggers, der åbner for diskussioner og udvikling af meningsfulde holdninger til medmennesker. Det belyses også hvordan undervisere i deres didaktiske overvejelser kan inddrage elementer fra teori om...

  12. Streaming-video produktion

    DEFF Research Database (Denmark)

    Grønkjær, Poul

    2004-01-01

     E-learning Lab på Aalborg Universitet har i forbindelse med forskningsprojektet Virtuelle Læringsformer og Læringsmiljøer foretaget en række praktiske eksperimenter med streaming-video produktioner. Hensigten med denne artikel er at formidle disse erfaringer. Artiklen beskriver hele produktionsf...... E-learning Lab på Aalborg Universitet har i forbindelse med forskningsprojektet Virtuelle Læringsformer og Læringsmiljøer foretaget en række praktiske eksperimenter med streaming-video produktioner. Hensigten med denne artikel er at formidle disse erfaringer. Artiklen beskriver hele...... produktionsforløbet: fra ide til færdigt produkt, forskellige typer af præsentationer, dramaturgiske overvejelser samt en konceptskitse. Streaming-video teknologien er nu så udviklet med et så tilfredsstillende audiovisuelt udtryk at vi kan begynde at fokusere på, hvilket indhold der er velegnet til at blive gjort...... tilgængeligt uafhængigt af tid og sted. Afslutningsvis er der en række kildehenvisninger, blandt andet en oversigt over de streaming-video produktioner, som denne artikel bygger på....

  13. Characteristics of Instructional Videos

    Science.gov (United States)

    Beheshti, Mobina; Taspolat, Ata; Kaya, Omer Sami; Sapanca, Hamza Fatih

    2018-01-01

    Nowadays, video plays a significant role in education in terms of its integration into traditional classes, the principal delivery system of information in classes particularly in online courses as well as serving as a foundation of many blended classes. Hence, education is adopting a modern approach of instruction with the target of moving away…

  14. Videos, Podcasts and Livechats

    Medline Plus

    Full Text Available Home About Donate Search Search What Is It Definition Pediatric Palliative Care Disease Types FAQ Handout for Patients and Families Is It Right for You How to Get It Talk to your Doctor Find a Provider Meet the Team Blog Articles & Stories News Resources Links Videos Podcasts ...

  15. Mobiele video voor bedrijfscommunicatie

    NARCIS (Netherlands)

    Niamut, O.A.; Weerdt, C.A. van der; Havekes, A.

    2009-01-01

    Het project Penta Mobilé liep van juni tot november 2009 en had als doel de mogelijkheden van mobiele video voor bedrijfscommunicatie toepassingen in kaart te brengen. Dit onderzoek werd uitgevoerd samen met vijf (‘Penta’) partijen: Business Tales, Condor Digital, European Communication Projects

  16. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... Surgery What is acoustic neuroma Diagnosing Symptoms Side effects ... Groups Is a support group for me? Find a Group Upcoming Events Video Library Photo Gallery One-on-One Support ANetwork Peer Support Program Community Connections Overview Find a Meeting ...

  17. Developing a Video Steganography Toolkit

    OpenAIRE

    Ridgway, James; Stannett, Mike

    2014-01-01

    Although techniques for separate image and audio steganography are widely known, relatively little has been described concerning the hiding of information within video streams ("video steganography"). In this paper we review the current state of the art in this field, and describe the key issues we have encountered in developing a practical video steganography system. A supporting video is also available online at http://www.youtube.com/watch?v=YhnlHmZolRM

  18. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... NEI YouTube Videos: Amblyopia NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia Animations Blindness Cataract Convergence Insufficiency Diabetic Eye Disease Dilated Eye Exam Dry Eye For Kids Glaucoma ...

  19. SPECIAL REPORT: Creating Conference Video

    Directory of Open Access Journals (Sweden)

    Noel F. Peden

    2008-12-01

    Full Text Available Capturing video at a conference is easy. Doing it so the product is useful is another matter. Many subtle problems come into play so that video and audio obtained can be used to create a final product. This article discusses what the author learned in the two years of shooting and editing video for Code4Lib conference.

  20. CERN Video News on line

    CERN Multimedia

    2003-01-01

    The latest CERN video news is on line. In this issue : an interview with the Director General and reports on the new home for the DELPHI barrel and the CERN firemen's spectacular training programme. There's also a vintage video news clip from 1954. See: www.cern.ch/video or Bulletin web page

  1. We All Stream for Video

    Science.gov (United States)

    Technology & Learning, 2008

    2008-01-01

    More than ever, teachers are using digital video to enhance their lessons. In fact, the number of schools using video streaming increased from 30 percent to 45 percent between 2004 and 2006, according to Market Data Retrieval. Why the popularity? For starters, video-streaming products are easy to use. They allow teachers to punctuate lessons with…

  2. Social Properties of Mobile Video

    Science.gov (United States)

    Mitchell, April Slayden; O'Hara, Kenton; Vorbau, Alex

    Mobile video is now an everyday possibility with a wide array of commercially available devices, services, and content. These new technologies have created dramatic shifts in the way video-based media can be produced, consumed, and delivered by people beyond the familiar behaviors associated with fixed TV and video technologies. Such technology revolutions change the way users behave and change their expectations in regards to their mobile video experiences. Building upon earlier studies of mobile video, this paper reports on a study using diary techniques and ethnographic interviews to better understand how people are using commercially available mobile video technologies in their everyday lives. Drawing on reported episodes of mobile video behavior, the study identifies the social motivations and values underpinning these behaviors that help characterize mobile video consumption beyond the simplistic notion of viewing video only to kill time. This paper also discusses the significance of user-generated content and the usage of video in social communities through the description of two mobile video technology services that allow users to create and share content. Implications for adoption and design of mobile video technologies and services are discussed as well.

  3. Video Analysis of Rolling Cylinders

    Science.gov (United States)

    Phommarach, S.; Wattanakasiwich, P.; Johnston, I.

    2012-01-01

    In this work, we studied the rolling motion of solid and hollow cylinders down an inclined plane at different angles. The motions were captured on video at 300 frames s[superscript -1], and the videos were analyzed frame by frame using video analysis software. Data from the real motion were compared with the theory of rolling down an inclined…

  4. Video Games and Digital Literacies

    Science.gov (United States)

    Steinkuehler, Constance

    2010-01-01

    Today's youth are situated in a complex information ecology that includes video games and print texts. At the basic level, video game play itself is a form of digital literacy practice. If we widen our focus from the "individual player + technology" to the online communities that play them, we find that video games also lie at the nexus of a…

  5. Rheumatoid Arthritis Educational Video Series

    Medline Plus

    Full Text Available ... Corner / Patient Webcasts / Rheumatoid Arthritis Educational Video Series Rheumatoid Arthritis Educational Video Series This series of five videos ... Your Arthritis Managing Chronic Pain and Depression in Arthritis Nutrition & Rheumatoid Arthritis Arthritis and Health-related Quality of Life ...

  6. Gradient descent algorithm applied to wavefront retrieval from through-focus images by an extreme ultraviolet microscope with partially coherent source.

    Science.gov (United States)

    Yamazoe, Kenji; Mochi, Iacopo; Goldberg, Kenneth A

    2014-12-01

    The wavefront retrieval by gradient descent algorithm that is typically applied to coherent or incoherent imaging is extended to retrieve a wavefront from a series of through-focus images by partially coherent illumination. For accurate retrieval, we modeled partial coherence as well as object transmittance into the gradient descent algorithm. However, this modeling increases the computation time due to the complexity of partially coherent imaging simulation that is repeatedly used in the optimization loop. To accelerate the computation, we incorporate not only the Fourier transform but also an eigenfunction decomposition of the image. As a demonstration, the extended algorithm is applied to retrieve a field-dependent wavefront of a microscope operated at extreme ultraviolet wavelength (13.4 nm). The retrieved wavefront qualitatively matches the expected characteristics of the lens design.

  7. Complicated diverticular disease: Position statement on outpatient management, Hartmann's procedure, laparoscopic peritoneal lavage and laparoscopic approach. Consensus document of the Spanish Association of Coloproctology and the Coloproctology Section of the Spanish Association of Surgeons.

    Science.gov (United States)

    Rosado-Cobián, Rafael; Blasco-Segura, Teresa; Ferrer-Márquez, Manuel; Marín-Ortega, Héctor; Pérez-Domínguez, Lucinda; Biondo, Sebastiano; Roig-Vila, José Vicente

    The Spanish Association of Coloproctology (AECP) and the Coloproctology Section of the Spanish Association of Surgeons (AEC), propose this consensus document about complicated diverticular disease that could be used for decision-making. Outpatient management, Hartmann's procedure, laparoscopic peritoneal lavage, and the role of a laparoscopic approach in colonic resection are exposed. Copyright © 2017 AEC. Publicado por Elsevier España, S.L.U. All rights reserved.

  8. Enhanced video display and navigation for networked streaming video and networked video playlists

    Science.gov (United States)

    Deshpande, Sachin

    2006-01-01

    In this paper we present an automatic enhanced video display and navigation capability for networked streaming video and networked video playlists. Our proposed method uses Synchronized Multimedia Integration Language (SMIL) as presentation language and Real Time Streaming Protocol (RTSP) as network remote control protocol to automatically generate a "enhanced video strip" display for easy navigation. We propose and describe two approaches - a smart client approach and a smart server approach. We also describe a prototype system implementation of our proposed approach.

  9. Digital Video Teach Yourself VISUALLY

    CERN Document Server

    Watson, Lonzell

    2010-01-01

    Tips and techniques for shooting and sharing superb digital videos. Never before has video been more popular-or more accessible to the home photographer. Now you can create YouTube-worthy, professional-looking video, with the help of this richly illustrated guide. In a straightforward, simple, highly visual format, Teach Yourself VISUALLY Digital Video demystifies the secrets of great video. With colorful screenshots and illustrations plus step-by-step instructions, the book explains the features of your camera and their capabilities, and shows you how to go beyond "auto" to manually

  10. Effects of Curved Wavefronts on Conductor-Backed Reflection-Only Free-Space Material Characterization Techniques.

    Science.gov (United States)

    Fenner, Raenita A; Rothwell, Edward J

    2015-01-01

    A true plane wave is often not physically realizable in a laboratory environment. Therefore, wavefront curvature introduces a form of systematic error into Free-space material characterization methods. Free-space material characterization is important to the determination of the electric permittivity and magnetic permeability of conductor-backed and in situ materials. This paper performs an error analysis of the impact on wavefront curvature on a Free-space method called the two-thickness method. This paper compares the extracted electric and magnetic permeability computed with a plane wave versus a line source for a low-loss dielectric and magnetic radar absorbing material. These steps are conducted for TE and TM plane waves and electric and magnetic line sources.

  11. Compact see-through 3D head-mounted display based on wavefront modulation with holographic grating filter.

    Science.gov (United States)

    Gao, Qiankun; Liu, Juan; Duan, Xinhui; Zhao, Tao; Li, Xin; Liu, Peilin

    2017-04-03

    A compact see-through three-dimensional head-mounted display (3D-HMD) is proposed and investigated in this paper. Two phase holograms are analytically extracted from the object wavefront and uploaded on different zones of the spatial light modulator (SLM). A holographic grating is further used as the frequency filter to couple the separated holograms together for wavefront modulation. The developed preliminary prototype has a simple optical facility and a compact structure (133.8mm × 40.4mm × 35.4mm with a 47.7mm length viewing accessory). Optical experiments demonstrated that the proposed system can present 3D images to the human eye with full depth cues. Therefore, it is free of the accommodation-vergence conflict and visual fatigue problem. The dynamic display ability is also tested in the experiments, which provides a promising potential for the true 3D interactive display.

  12. Representing videos in tangible products

    Science.gov (United States)

    Fageth, Reiner; Weiting, Ralf

    2014-03-01

    Videos can be taken with nearly every camera, digital point and shoot cameras, DSLRs as well as smartphones and more and more with so-called action cameras mounted on sports devices. The implementation of videos while generating QR codes and relevant pictures out of the video stream via a software implementation was contents in last years' paper. This year we present first data about what contents is displayed and how the users represent their videos in printed products, e.g. CEWE PHOTOBOOKS and greeting cards. We report the share of the different video formats used, the number of images extracted out of the video in order to represent the video, the positions in the book and different design strategies compared to regular books.

  13. Characterization of optical turbulence in a jet engine exhaust with Shack-Hartmenn wavefront sensor

    Science.gov (United States)

    Deron, R.; Mendez, F.

    2008-10-01

    Airborne laser countermeasure applications (DIRCM) are hampered by the turbulence of jet engine exhaust. The effects of this source of perturbation on optical propagation have still to be documented and analyzed in order to get a better insight into the different mechanisms of the plume perturbations and also to validate CFD/LES codes. For that purpose, wave front sensing has been used as a non-intrusive optical technique to provide unsteady and turbulent optical measurements through a plume of a jet engine installed at a fixed point on the ground. The experiment has been implemented in October 2007 along with other optical measuring techniques at Volvo Aero Corporation (Trollhättan, Sweden). This study is part of a European research programme dealing with DIRCM issues. The Shack- Hartmann (SH) wave front sensing technique was employed. It consisted of 64 x 64 lenslets coupled to a 1024x1024 pixel Dalsa CCD sensor working at a sampling rate of 40 Hz. A 15 ns pulsed laser synchronized with the SH sensor enabled "freezing" turbulence in each SH image. The ability of the technique to substract a reference permitted a simple calibration procedure to ensure accurate and reliable measurements despite vibration environment. Instantaneous phases are reconstructed using Fourier techniques so as to obtain a better spatial resolution against turbulent effects. Under any given plume condition, overall tilt aberration prevails. Phase power spectra derived from phase statistics are drawn according to the plume main axis and to normal axis. They compare favorably well to the decaying Kolmogorov power law on a useful high spatial frequency range. Averaged phases are also decomposed into Zernike polynomials to analyze optical mode behavior according to engine status and to plume abscissa. With overall tilt removed, turbulent DSP's amplitude drops by a factor of 30 to 40 and mean aberrations by a factor of 10 from an abscissa 1 meter to another 3.5 meters away from the engine

  14. Numerical study of the wavefront distortion in an aerodynamical flow field

    Science.gov (United States)

    Sorrente, B.; d'Espiney, P.; Deron, R.

    2008-10-01

    Optical aberrations induced by turbulent flows are critical issues for the performance of an airborne optical system. In that context experiments were performed on a test-body at Mach 3.7 with several high Reynolds number in the S3MA wind tunnel of ONERA. A Shack-Hartman wave front sensing was performed (see companion paper of R. Deron). The objective of this work was to develop a computational algorithm to model the wave front distortions in temporal averaged field. First the aerodynamical flow field is obtained by RANS computation around the test body and mass-density is interpolated in an optical grid. Then wave front has been calculated using ray tracing from eikonal equations. For this validation two Reynolds numbers were retained and the boundary layer is turbulent on downstream window. A planar optical beam is emitted from the window and passes through the inhomogeneous media from the boundary layer to the shock wave. Various pupil, angle positions and lines of sight are considered. Zernike decomposition and MTF computation allow modal analysis in the near field condition and evaluation of the image quality respectively. Tilt effects appear to be the dominant aberration while higher orders have a limited impact on the image quality, except for large departures from the normal of the window. Discrepancies observed according to the line of sight variation are analysed. Finally simulations results compare favorably with the measurements made with the Shack-Hartmann wave front sensing. So this computational study is conforted and allows to complete the experiment.

  15. Computational performance comparison of wavefront reconstruction algorithms for the European Extremely Large Telescope on multi-CPU architecture.

    Science.gov (United States)

    Feng, Lu; Fedrigo, Enrico; Béchet, Clémentine; Brunner, Elisabeth; Pirani, Werther

    2012-06-01

    The European Southern Observatory (ESO) is studying the next generation giant telescope, called the European Extremely Large Telescope (E-ELT). With a 42 m diameter primary mirror, it is a significant step from currently existing telescopes. Therefore, the E-ELT with its instruments poses new challenges in terms of cost and computational complexity for the control system, including its adaptive optics (AO). Since the conventional matrix-vector multiplication (MVM) method successfully used so far for AO wavefront reconstruction cannot be efficiently scaled to the size of the AO systems on the E-ELT, faster algorithms are needed. Among those recently developed wavefront reconstruction algorithms, three are studied in this paper from the point of view of design, implementation, and absolute speed on three multicore multi-CPU platforms. We focus on a single-conjugate AO system for the E-ELT. The algorithms are the MVM, the Fourier transform reconstructor (FTR), and the fractal iterative method (FRiM). This study enhances the scaling of these algorithms with an increasing number of CPUs involved in the computation. We discuss implementation strategies, depending on various CPU architecture constraints, and we present the first quantitative execution times so far at the E-ELT scale. MVM suffers from a large computational burden, making the current computing platform undersized to reach timings short enough for AO wavefront reconstruction. In our study, the FTR provides currently the fastest reconstruction. FRiM is a recently developed algorithm, and several strategies are investigated and presented here in order to implement it for real-time AO wavefront reconstruction, and to optimize its execution time. The difficulty to parallelize the algorithm in such architecture is enhanced. We also show that FRiM can provide interesting scalability using a sparse matrix approach.

  16. Chromatic and Wavefront Aberrations: L-, M- and S-cone Stimulation with Typical and Extreme Retinal Image Quality

    OpenAIRE

    Autrusseau, Florent; Thibos, Larry; Shevell, Steven K.

    2011-01-01

    International audience; The first physiological process influencing visual perception is the optics of the eye. The retinal image is affected by diffraction at the pupil and several kinds of optical imperfections. A model of the eye (Thibos & Bradley, 1999), which takes account of pupil aperture, chromatic aberration and wavefront aberrations, was used to determine wavelength-dependent point-spread functions, which can be convolved with any stimulus specified by its spectral distribution of l...

  17. Far-field beam shaping through static wavefront correction in the near field on the HELEN laser

    Science.gov (United States)

    Bett, Thomas H.; Hopps, N. W.; Nolan, J. R.

    2002-10-01

    This report discusses the design and installation of a phase optic inserted in the near field of the HELEN high power glass laser. The element is designed to shape the intensity distribution at the focal spot of the laser to produce an increase in the peak intensity through correction of static and thermally induced wavefront errors on the beam. A phase element has been fabricated commercially using a magneto-rheological finishing tool. Test data is presented.

  18. Geotail Video News Release

    Science.gov (United States)

    1992-01-01

    The Geotail mission, part of the International Solar Terrestrial Physics (ISTP) program, measures global energy flow and transformation in the magnetotail to increase understanding of fundamental magnetospheric processes. The satellite was launched on July 24, 1992 onboard a Delta II rocket. This video shows with animation the solar wind, and its effect on the Earth. The narrator explains that the Geotail spacecraft was designed and built by the Institute of Space and Astronautical Science (ISAS), the Japanese Space Agency. The mission objectives are reviewed by one of the scientist in a live view. The video also shows an animation of the orbit, while the narrator explains the orbit and the reason for the small launch window.

  19. CARACTERIZACION VOZ Y VIDEO

    Directory of Open Access Journals (Sweden)

    Octavio José Salcedo Parra

    2011-11-01

    Full Text Available La motivación para caracterizar el tráfico de voz y video está en la necesidad de las empresas proveedoras de servicio en mantener redes de transporte de información con capacidades acordes a los requerimientos de los usuarios.  Poder determinar en forma oportuna como los elementos técnicos que hacen parte de las redes afectan su desempeño, teniendo en cuenta que cada tipo de servicio es afectado en mayor o menor medida por dichos elementos dentro de los que tenemos el jitter, las demoras y las pérdidas de paquetes entre otros. El presente trabajo muestra varios casos de caracterización de tráfico tanto de voz como de video en las que se utilizan una diversidad de técnicas para diferentes tipos de servicio.

  20. Video Pulses: User-Based Modeling of Interesting Video Segments

    Directory of Open Access Journals (Sweden)

    Markos Avlonitis

    2014-01-01

    Full Text Available We present a user-based method that detects regions of interest within a video in order to provide video skims and video summaries. Previous research in video retrieval has focused on content-based techniques, such as pattern recognition algorithms that attempt to understand the low-level features of a video. We are proposing a pulse modeling method, which makes sense of a web video by analyzing users' Replay interactions with the video player. In particular, we have modeled the user information seeking behavior as a time series and the semantic regions as a discrete pulse of fixed width. Then, we have calculated the correlation coefficient between the dynamically detected pulses at the local maximums of the user activity signal and the pulse of reference. We have found that users' Replay activity significantly matches the important segments in information-rich and visually complex videos, such as lecture, how-to, and documentary. The proposed signal processing of user activity is complementary to previous work in content-based video retrieval and provides an additional user-based dimension for modeling the semantics of a social video on the web.