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Sample records for adaptive optics demonstrator

  1. New Adaptive Optics Technique Demonstrated

    2007-03-01

    First ever Multi-Conjugate Adaptive Optics at the VLT Achieves First Light On the evening of 25 March 2007, the Multi-Conjugate Adaptive Optics Demonstrator (MAD) achieved First Light at the Visitor Focus of Melipal, the third Unit Telescope of the Very Large Telescope (VLT). MAD allowed the scientists to obtain images corrected for the blurring effect of atmospheric turbulence over the full 2x2 arcminute field of view. This world premiere shows the promises of a crucial technology for Extremely Large Telescopes. ESO PR Photo 19a/07 ESO PR Photo 19a/07 The MCAO Demonstrator Telescopes on the ground suffer from the blurring effect induced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way which delights the poets but frustrates the astronomers, since it blurs the fine details of the images. However, with Adaptive Optics (AO) techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e., approaching space conditions. Adaptive Optics systems work by means of a computer-controlled deformable mirror (DM) that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a 'wavefront sensor' (a special camera) at very high speed, many hundreds of times each second. The concept is not new. Already in 1989, the first Adaptive Optics system ever built for Astronomy (aptly named "COME-ON") was installed on the 3.6-m telescope at the ESO La Silla Observatory, as the early fruit of a highly successful continuing collaboration between ESO and French research institutes (ONERA and Observatoire de Paris). Ten years ago, ESO initiated an Adaptive Optics program to serve the needs for its frontline VLT project. Today, the Paranal Observatory is without any doubt one of the most advanced of its kind with respect to AO with no less than 7 systems currently installed (NACO, SINFONI, CRIRES and

  2. Laboratory Testing the Layer Oriented Wavefront Sensor for the Multiconjugate Adaptive optics Demonstrator

    Arcidiacono, Carmelo; Lombini, Matteo; Diolaiti, Emiliano; Farinato, Jacopo; Ragazzoni, Roberto

    2009-01-01

    The Multiconjugate Adaptive optics Demonstrator (MAD) for ESO-Very Large Telescopes (VLT) will demonstrate on sky the MultiConjugate Adaptive Optics (MCAO) technique. In this paper the laboratory tests relative to the first preliminary acceptance in Europe of the Layer Oriented (LO) Wavefront Sensor (WFS) for MAD will be described: the capabilities of the LO approach have been checked and the ability of the WFS to measure phase screens positioned at different altitudes has been experimented. ...

  3. Laboratory testing the layer oriented wavefront sensor for the multiconjugate adaptive optics demonstrator

    Arcidiacono, Carmelo; Lombini, Matteo; Diolaiti, Emiliano; Farinato, Jacopo; Ragazzoni, Roberto

    2006-06-01

    The Multiconjugate Adaptive optics Demonstrator (MAD) for ESO-Very Large Telescopes (VLT) will demonstrate on sky the MultiConjugate Adaptive Optics (MCAO) technique. In this paper the laboratory tests relative to the first preliminary acceptance in Europe of the Layer Oriented (LO) Wavefront Sensor (WFS) for MAD will be described: the capabilities of the LO approach have been checked and the ability of the WFS to measure phase screens positioned at different altitudes has been experimented. The LO WFS was opto-mechanically integrated and aligned in INAF - Astrophysical Observatory of Arcetri before the delivering to ESO (Garching) to be installed on the final optical bench. The LO WFS looks for up to 8 reference stars on a 2arcmin Field of View and up to 8 pyramids can be positioned where the focal spot images of the reference stars form, splitting the light in four beams. Then two objectives conjugated at different altitudes simultaneously produce a quadruple pupil image of each reference star. An optical bench setup and transparent plastic screens have been used to simulate telescope and static atmospheric layers at different altitudes and a set of optical fibers as (white) light source. The plastic screens set has been characterized using an inteferometer and the wave-front measurements compared to the LO WFS ones have shown correlation up to ~95%.

  4. Science with ESO's Multi-conjugate Adaptive-optics Demonstrator - MAD

    Melnick, Jorge; Marchetti, Enrico; Amico, Paola

    2012-07-01

    ESO's Multi-conjugate Adaptive-optics Demonstrator (MAD) was a prototype designed and built to demonstrate wide-field adaptive optics science on large telescopes. The outstanding results obtained during commissioning and guaranteed time observations (GTO) prompted ESO to issue and open call to the community for 23 science demonstration (SD) observing nights distributed in three runs (in order to provide access to the summer an winter skies). Thus, in total MAD was used for science for 33 nights including the 10 nights of GTO time. date, 19 articles in refereed journals (including one in Nature) have been published based fully or partially o MAD data. To the best of our knowledge, these are not only the first, but also the only scientific publication from MCAO instruments world-wide to date (at least in Astronomy). The scientific impact of these publication, as measured by the h-index, is comparable to that of other AO instruments on the VLT, although over the years these instruments have been allocated many more nights than MAD. In this contribution we present an overview of the scientific results from MAD and a more detailed discussion of the most cited papers.

  5. Demonstration of adaptive optics for mitigating laser propagation through a random air-water interface

    Land, Phillip; Majumdar, Arun K.

    2016-05-01

    This paper describes a new concept of mitigating signal distortions caused by random air-water interface using an adaptive optics (AO) system. This is the first time the concept of using an AO for mitigating the effects of distortions caused mainly by a random air-water interface is presented. We have demonstrated the feasibility of correcting the distortions using AO in a laboratory water tank for investigating the propagation effects of a laser beam through an airwater interface. The AO system consisting of a fast steering mirror, deformable mirror, and a Shack-Hartmann Wavefront Sensor for mitigating surface water distortions has a unique way of stabilizing and aiming a laser onto an object underneath the water. Essentially the AO system mathematically takes the complex conjugate of the random phase caused by air-water interface allowing the laser beam to penetrate through the water by cancelling with the complex conjugates. The results show the improvement of a number of metrics including Strehl ratio, a measure of the quality of optical image formation for diffraction limited optical system. These are the first results demonstrating the feasibility of developing a new sensor system such as Laser Doppler Vibrometer (LDV) utilizing AO for mitigating surface water distortions.

  6. Experimental demonstration of laser tomographic adaptive optics on a 30-meter telescope at 800 nm

    Ammons, S., Mark; Johnson, Luke; Kupke, Renate; Gavel, Donald T.; Max, Claire E.

    2010-07-01

    A critical goal in the next decade is to develop techniques that will extend Adaptive Optics correction to visible wavelengths on Extremely Large Telescopes (ELTs). We demonstrate in the laboratory the highly accurate atmospheric tomography necessary to defeat the cone effect on ELTs, an essential milestone on the path to this capability. We simulate a high-order Laser Tomographic AO System for a 30-meter telescope with the LTAO/MOAO testbed at UCSC. Eight Sodium Laser Guide Stars (LGSs) are sensed by 99x99 Shack-Hartmann wavefront sensors over 75". The AO system is diffraction-limited at a science wavelength of 800 nm (S ~ 6-9%) over a field of regard of 20" diameter. Openloop WFS systematic error is observed to be proportional to the total input atmospheric disturbance and is nearly the dominant error budget term (81 nm RMS), exceeded only by tomographic wavefront estimation error (92 nm RMS). The total residual wavefront error for this experiment is comparable to that expected for wide-field tomographic adaptive optics systems of similar wavefront sensor order and LGS constellation geometry planned for Extremely Large Telescopes.

  7. Integrated Laboratory Demonstrations of Multi-Object Adaptive Optics on a Simulated 10-Meter Telescope at Visible Wavelengths

    Ammons, S Mark; Laag, Edward A; Kupke, Renate; Gavel, Donald T; Bauman, Brian J; Max, Claire E

    2009-01-01

    One important frontier for astronomical adaptive optics (AO) involves methods such as Multi-Object AO and Multi-Conjugate AO that have the potential to give a significantly larger field of view than conventional AO techniques. A second key emphasis over the next decade will be to push astronomical AO to visible wavelengths. We have conducted the first laboratory simulations of wide-field, laser guide star adaptive optics at visible wavelengths on a 10-meter-class telescope. These experiments, utilizing the UCO/Lick Observatory's Multi-Object / Laser Tomography Adaptive Optics (MOAO/LTAO) testbed, demonstrate new techniques in wavefront sensing and control that are crucial to future on-sky MOAO systems. We (1) test and confirm the feasibility of highly accurate atmospheric tomography with laser guide stars, (2) demonstrate key innovations allowing open-loop operation of Shack-Hartmann wavefront sensors (with errors of ~30 nm) as will be needed for MOAO, and (3) build a complete error budget model describing sy...

  8. Demonstration of a 17 cm robust carbon fiber deformable mirror for adaptive optics

    Ammons, S M; Hart, M; Coughenour, B; Romeo, R; Martin, R; Rademacher, M

    2011-09-12

    Carbon-fiber reinforced polymer (CFRP) composite is an attractive material for fabrication of optics due to its high stiffness-to-weight ratio, robustness, zero coefficient of thermal expansion (CTE), and the ability to replicate multiple optics from the same mandrel. We use 8 and 17 cm prototype CFRP thin-shell deformable mirrors to show that residual CTE variation may be addressed with mounted actuators for a variety of mirror sizes. We present measurements of surface quality at a range of temperatures characteristic of mountaintop observatories. For the 8 cm piece, the figure error of the Al-coated reflective surface under best actuator correction is {approx}43 nm RMS. The 8 cm mirror has a low surface error internal to the outer ring of actuators (17 nm RMS at 20 C and 33 nm RMS at -5 C). Surface roughness is low (< 3 nm P-V) at a variety of temperatures. We present new figure quality measurements of the larger 17 cm mirror, showing that the intra-actuator figure error internal to the outer ring of actuators (38 nm RMS surface with one-third the actuator density of the 8 cm mirror) does not scale sharply with mirror diameter.

  9. Conceptual Design of the Adaptive Optics System for the Laser Communication Relay Demonstration Ground Station at Table Mountain

    Roberts, Lewis C., Jr.; Page, Norman A.; Burruss, Rick S.; Truong, Tuan N.; Dew, Sharon; Troy, Mitchell

    2013-01-01

    The Laser Communication Relay Demonstration will feature a geostationary satellite communicating via optical links to multiple ground stations. The first ground station (GS-1) is the 1m OCTL telescope at Table Mountain in California. The optical link will utilize pulse position modulation (PPM) and differential phase shift keying (DPSK) protocols. The DPSK link necessitates that adaptive optics (AO) be used to relay the incoming beam into the single mode fiber that is the input of the modem. The GS-1 AO system will have two MEMS Deformable mirrors to achieve the needed actuator density and stroke limit. The AO system will sense the aberrations with a Shack-Hartmann wavefront sensor using the light from the communication link's 1.55 microns laser to close the loop. The system will operate day and night. The system's software will be based on heritage software from the Palm 3000 AO system, reducing risk and cost. The AO system is being designed to work at r(sub 0) greater than 3.3 cm (measured at 500 nm and zenith) and at elevations greater than 20deg above the horizon. In our worst case operating conditions we expect to achieve Strehl ratios of over 70% (at 1.55 microns), which should couple 57% of the light into the single mode DPSK fiber. This paper describes the conceptual design of the AO system, predicted performance and discusses some of the trades that were conducted during the design process.

  10. Gigashot Optical Laser Demonstrator

    Deri, R. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-13

    The Gigashot Optical Laser Demonstrator (GOLD) project has demonstrated a novel optical amplifier for high energy pulsed lasers operating at high repetition rates. The amplifier stores enough pump energy to support >10 J of laser output, and employs conduction cooling for thermal management to avoid the need for expensive and bulky high-pressure helium subsystems. A prototype amplifier was fabricated, pumped with diode light at 885 nm, and characterized. Experimental results show that the amplifier provides sufficient small-signal gain and sufficiently low wavefront and birefringence impairments to prove useful in laser systems, at repetition rates up to 60 Hz.

  11. [Adaptive optics for ophthalmology].

    Saleh, M

    2016-04-01

    Adaptive optics is a technology enhancing the visual performance of an optical system by correcting its optical aberrations. Adaptive optics have already enabled several breakthroughs in the field of visual sciences, such as improvement of visual acuity in normal and diseased eyes beyond physiologic limits, and the correction of presbyopia. Adaptive optics technology also provides high-resolution, in vivo imaging of the retina that may eventually help to detect the onset of retinal conditions at an early stage and provide better assessment of treatment efficacy. PMID:27019970

  12. Solar Adaptive Optics

    Thomas R. Rimmele

    2011-06-01

    Full Text Available Adaptive optics (AO has become an indispensable tool at ground-based solar telescopes. AO enables the ground-based observer to overcome the adverse effects of atmospheric seeing and obtain diffraction limited observations. Over the last decade adaptive optics systems have been deployed at major ground-based solar telescopes and revitalized ground-based solar astronomy. The relatively small aperture of solar telescopes and the bright source make solar AO possible for visible wavelengths where the majority of solar observations are still performed. Solar AO systems enable diffraction limited observations of the Sun for a significant fraction of the available observing time at ground-based solar telescopes, which often have a larger aperture than equivalent space based observatories, such as HINODE. New ground breaking scientific results have been achieved with solar adaptive optics and this trend continues. New large aperture telescopes are currently being deployed or are under construction. With the aid of solar AO these telescopes will obtain observations of the highly structured and dynamic solar atmosphere with unprecedented resolution. This paper reviews solar adaptive optics techniques and summarizes the recent progress in the field of solar adaptive optics. An outlook to future solar AO developments, including a discussion of Multi-Conjugate AO (MCAO and Ground-Layer AO (GLAO will be given.

  13. Adaptive optical processors.

    Ghosh, A

    1989-06-15

    There are two different approaches for improving the accuracy of analog optical associative processors: postprocessing with a bimodal system and preprocessing with a preconditioner. These two approaches can be combined to develop an adaptive optical multiprocessor that can adjust the computational steps depending on the data and produce solutions of linear algebra problems with a specified accuracy in a given amount of time. PMID:19752909

  14. Optics Demonstrations Using Cylindrical Lenses

    Ivanov, Dragia; Nikolov, Stefan

    2015-01-01

    In this paper we consider the main properties of cylindrical lenses and propose several demonstrational experiments that can be performed with them. Specifically we use simple glasses full of water to demonstrate some basic geometrical optics principles and phenomena. We also present some less standard experiments that can be performed with such…

  15. Adaptive optics projects at ESO

    Hubin, Norbert N.; Arsenault, Robin; Bonnet, Henri; Conan, Rodolphe; Delabre, Bernard; Donaldson, Robert; Dupuy, Christophe; Fedrigo, Enrico; Ivanescu, L.; Kasper, Markus E.; Kissler-Patig, Markus; Lizon, Jean-Luis; Le Louarn, Miska; Marchetti, Enrico; Paufique, J.; Stroebele, Stefan; Tordo, Sebastien

    2003-02-01

    Over the past two years ESO has reinforced its efforts in the field of Adaptive Optics. The AO team has currently the challenging objectives to provide 8 Adaptive Optics systems for the VLT in the coming years and has now a world-leading role in that field. This paper will review all AO projects and plans. We will present an overview of the Nasmyth Adaptive Optics System (NAOS) with its infrared imager CONICA installed successfully at the VLT last year. Sodium Laser Guide Star plans will be introduced. The status of the 4 curvature AO systems (MACAO) developed for the VLT interferometer will be discussed. The status of the SINFONI AO module developed to feed the infrared integral field spectrograph (SPIFFI) will be presented. A short description of the Multi-conjugate Adaptive optics Demonstrator MAD and its instrumentation will be introduced. Finally, we will present the plans for the VLT second-generation AO systems and the researches performed in the frame of OWL.

  16. Demonstrating Fermat's Principle in Optics

    Paleiov, Orr; Pupko, Ofir; Lipson, S. G.

    2011-01-01

    We demonstrate Fermat's principle in optics by a simple experiment using reflection from an arbitrarily shaped one-dimensional reflector. We investigated a range of possible light paths from a lamp to a fixed slit by reflection in a curved reflector and showed by direct measurement that the paths along which light is concentrated have either…

  17. FDM adaptive optics technology development

    Thibault, Simon; Doucet, Michel; Rioux, Myriam

    2004-10-01

    INO supports research on Ferrofluidic Deformable Mirror (FDM) adaptive optics technologies and, as such, its research activities include the development and characterization of FDM and high resolution (ExAO) adaptive optics systems using such FDMs. Liquid mirrors have long been recognized as a potential low-cost alternative to conventional solid mirrors. Since the trend is towards advanced adaptive optics systems, a need for deformable mirrors with a large number of low-cost actuators exists. This paper presents updated experimental results using a new INO FDM prototype (271 actuators, 50 µm stroke) as well as a theoretical model of surface behaviors.

  18. Pulse front adaptive optics in multiphoton microscopy

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The accurate focusing of ultrashort laser pulses is extremely important in multiphoton microscopy. Using adaptive optics to manipulate the incident ultrafast beam in either the spectral or spatial domain can introduce significant benefits when imaging. Here we introduce pulse front adaptive optics: manipulating an ultrashort pulse in both the spatial and temporal domains. A deformable mirror and a spatial light modulator are operated in concert to modify contours of constant intensity in space and time within an ultrashort pulse. Through adaptive control of the pulse front, we demonstrate an enhancement in the measured fluorescence from a two photon microscope.

  19. Maritime adaptive optics beam control

    Corley, Melissa S.

    2010-01-01

    The Navy is interested in developing systems for horizontal, near ocean surface, high-energy laser propagation through the atmosphere. Laser propagation in the maritime environment requires adaptive optics control of aberrations caused by atmospheric distortion. In this research, a multichannel transverse adaptive filter is formulated in Matlab's Simulink environment and compared to a complex lattice filter that has previously been implemented in large system simulations. The adaptive fil...

  20. Adaptive Optics for Large Telescopes

    The use of adaptive optics was originally conceived by astronomers seeking to correct the blurring of images made with large telescopes due to the effects of atmospheric turbulence. The basic idea is to use a device, a wave front corrector, to adjust the phase of light passing through an optical system, based on some measurement of the spatial variation of the phase transverse to the light propagation direction, using a wave front sensor. Although the original concept was intended for application to astronomical imaging, the technique can be more generally applied. For instance, adaptive optics systems have been used for several decades to correct for aberrations in high-power laser systems. At Lawrence Livermore National Laboratory (LLNL), the world's largest laser system, the National Ignition Facility, uses adaptive optics to correct for aberrations in each of the 192 beams, all of which must be precisely focused on a millimeter scale target in order to perform nuclear physics experiments

  1. Adaptive Optics for Large Telescopes

    Olivier, S

    2008-06-27

    The use of adaptive optics was originally conceived by astronomers seeking to correct the blurring of images made with large telescopes due to the effects of atmospheric turbulence. The basic idea is to use a device, a wave front corrector, to adjust the phase of light passing through an optical system, based on some measurement of the spatial variation of the phase transverse to the light propagation direction, using a wave front sensor. Although the original concept was intended for application to astronomical imaging, the technique can be more generally applied. For instance, adaptive optics systems have been used for several decades to correct for aberrations in high-power laser systems. At Lawrence Livermore National Laboratory (LLNL), the world's largest laser system, the National Ignition Facility, uses adaptive optics to correct for aberrations in each of the 192 beams, all of which must be precisely focused on a millimeter scale target in order to perform nuclear physics experiments.

  2. A Demonstration of Automatically Switched Optical Network

    2003-01-01

    We build an automatically switched optical network (ASON) testbed with four optical cross-connect nodes. Many fundamental ASON features are demonstrated, which is implemented by control protocols based on generalized multi-protocol label switching (GMPLS) framework.

  3. Pulse front control with adaptive optics

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The focusing of ultrashort laser pulses is extremely important for processes including microscopy, laser fabrication and fundamental science. Adaptive optic elements, such as liquid crystal spatial light modulators or membrane deformable mirrors, are routinely used for the correction of aberrations in these systems, leading to improved resolution and efficiency. Here, we demonstrate that adaptive elements used with ultrashort pulses should not be considered simply in terms of wavefront modification, but that changes to the incident pulse front can also occur. We experimentally show how adaptive elements may be used to engineer pulse fronts with spatial resolution.

  4. Intelligent Optical Systems Using Adaptive Optics

    Clark, Natalie

    2012-01-01

    Until recently, the phrase adaptive optics generally conjured images of large deformable mirrors being integrated into telescopes to compensate for atmospheric turbulence. However, the development of smaller, cheaper devices has sparked interest for other aerospace and commercial applications. Variable focal length lenses, liquid crystal spatial light modulators, tunable filters, phase compensators, polarization compensation, and deformable mirrors are becoming increasingly useful for other imaging applications including guidance navigation and control (GNC), coronagraphs, foveated imaging, situational awareness, autonomous rendezvous and docking, non-mechanical zoom, phase diversity, and enhanced multi-spectral imaging. The active components presented here allow flexibility in the optical design, increasing performance. In addition, the intelligent optical systems presented offer advantages in size and weight and radiation tolerance.

  5. Adaptive Optics for Industry and Medicine

    Dainty, Christopher

    2008-01-01

    pt. 1. Wavefront correctors and control. Liquid crystal lenses for correction of presbyopia (Invited Paper) / Guoqiang Li and Nasser Peyghambarian. Converging and diverging liquid crystal lenses (oral paper) / Andrew X. Kirby, Philip J. W. Hands, and Gordon D. Love. Liquid lens technology for miniature imaging systems: status of the technology, performance of existing products and future trends (invited paper) / Bruno Berge. Carbon fiber reinforced polymer deformable mirrors for high energy laser applications (oral paper) / S. R. Restaino ... [et al.]. Tiny multilayer deformable mirrors (oral paper) / Tatiana Cherezova ... [et al.]. Performance analysis of piezoelectric deformable mirrors (oral paper) / Oleg Soloviev, Mikhail Loktev and Gleb Vdovin. Deformable membrane mirror with high actuator density and distributed control (oral paper) / Roger Hamelinck ... [et al.]. Characterization and closed-loop demonstration of a novel electrostatic membrane mirror using COTS membranes (oral paper) / David Dayton ... [et al.]. Electrostatic micro-deformable mirror based on polymer materials (oral paper) / Frederic Zamkotsian ... [et al.]. Recent progress in CMOS integrated MEMS A0 mirror development (oral paper) / A. Gehner ... [et al.]. Compact large-stroke piston-tip-tilt actuator and mirror (oral paper) / W. Noell ... [et al.]. MEMS deformable mirrors for high performance AO applications (oral paper) / Paul Bierden, Thomas Bifano and Steven Cornelissen. A versatile interferometric test-rig for the investigation and evaluation of ophthalmic AO systems (poster paper) / Steve Gruppetta, Jiang Jian Zhong and Luis Diaz-Santana. Woofer-tweeter adaptive optics (poster paper) / Thomas Farrell and Chris Dainty. Deformable mirrors based on transversal piezoeffect (poster paper) / Gleb Vdovin, Mikhail Loktev and Oleg Soloviev. Low-cost spatial light modulators for ophthalmic applications (poster paper) / Vincente Durán ... [et al.]. Latest MEMS DM developments and the path ahead

  6. A simplified adaptive optics system

    Ivanescu, Liviu; Racine, René; Nadeau, Daniel

    2003-02-01

    Affordable adaptive optics on small telescopes allow to introduce the technology to a large community and provide opportunities to train new specialists in the field. We have developed a low order, low cost adaptive optics system for the 1.6m telescope of the Mont Megantic Observatory. The system corrects tip-tilt, focus, astigmatisms and one trefoil term. It explores a number of new approaches. The sensor receives a single out-of-focus image of the reference star. The central obstruction of the telescope can free the focus detection from the effect of seeing and allows a very small defocus. The deformable mirror is profiled so as to preserve a parabolic shape under pressure from actuators located at its edge. A separate piezoelectric platform drives the tilt mirror.

  7. Proposed Multiconjugate Adaptive Optics Experiment at Lick Observatory

    Bauman, B J; Gavel, D T; Flath, L M; Hurd, R L; Max, C E; Olivier, S S

    2001-08-15

    While the theory behind design of multiconjugate adaptive optics (MCAO) systems is growing, there is still a paucity of experience building and testing such instruments. We propose using the Lick adaptive optics (AO) system as a basis for demonstrating the feasibility/workability of MCAO systems, testing underlying assumptions, and experimenting with different approaches to solving MCAO system issues.

  8. Demonstrational Optics Part 2: Coherent and Statistical Optics

    Marchenko, Oleg; Windholz, Laurentius

    2007-01-01

    Demonstrational Optics presents a new didactical approach to the study of optics. Emphasizing the importance of elaborate new experimental demonstrations, pictorial illustrations, computer simulations and models of optical phenomena in order to ensure a deeper understanding of wave and geometric optics. It includes problems focused on the pragmatic needs of students, secondary school teachers, university professors and optical engineers. Part 2, Coherent and Statistical Optics, contains chapters on interference, diffraction, Fourier optics, light quanta, thermal radiation (Shot noise and Gaussian light), Correlation of light fields and Correlation of light intensities. A substantial part of this volume is devoted to thermal radiation and its properties, especially with partial coherence. A detailed treatment of the photo-effect with respect to statistical properties leads to the basics of statistical optics. To illustrate the phenomena covered by this volume, a large number of demonstration experiments are de...

  9. Adaptive optics assisted reconfigurable liquid-driven optical switch

    Fuh, Yiin-Kuen; Huang, Wei-Chi

    2013-07-01

    This study demonstrates a mechanical-based, liquid-driven optical switch integrated with adaptive optics and a reconfigurable black liquid (dye-doped liquid). The device aperture can be continuously tuned between 0.6 and 6.9 mm, precisely achieved by a syringe pump for volume control. Adaptive optics (AO) capability and possible enhancement of the lost power intensity of the ink-polluted glass plate have also been experimentally investigated. While measuring power intensity with/without AO indicates only a marginal difference of ˜1%, a significant difference of 3 s in the response characteristic of "switching on" time can be observed. An extremely high contrast ratio of ˜105 for a red-colored light is achieved.

  10. Electron density measurements for plasma adaptive optics

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  11. Innovated set for demonstrative experiments from optics

    VOCHOZKA, Vladimír

    2011-01-01

    This diploma work deals the possibilities of use of demonstration set in teaching of optics in the physics. It is focused on general use of technical didactical means in teaching and various approachs to experiments in the school physics. Comparison of actually available sets for demonstration experiments is incorporated in this work. It contains also set of selected experiments and worksheets which were used for verification of tasks. Results of the worksheets are analysed and form the part ...

  12. Wavefront sensorless adaptive optics ophthalmoscopy in the human eye

    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 ...

  13. Electron density measurements for plasma adaptive optics

    Neiswander, Brian; Matlis, Eric; Corke, Thomas

    2014-01-01

    This study investigates the feasibility of using plasma as an adaptive optical medium for applications such as beam steering, wavefront control, and adaptive filtering. The optical path length of light propagating through plasma depends on the plasma electron density, which may be controlled via the prescribed voltage, frequency, pressure, gas, and electrode geometry. Accurate control of the optical path length requires characterization of the electron density over all operating conditions. E...

  14. Adaptive optical interconnects: the ADDAPT project

    Henker, Ronny; Pliva, Jan; Khafaji, Mahdi; Ellinger, Frank; Toifl, Thomas; Offrein, Bert; Cevrero, Alessandro; Oezkaya, Ilter; Seifried, Marc; Ledentsov, Nikolay; Kropp, Joerg-R.; Shchukin, Vitaly; Zoldak, Martin; Halmo, Leos; Turkiewicz, Jaroslaw; Meredith, Wyn; Eddie, Iain; Georgiades, Michael; Charalambides, Savvas; Duis, Jeroen; van Leeuwen, Pieter

    2015-09-01

    Existing optical networks are driven by dynamic user and application demands but operate statically at their maximum performance. Thus, optical links do not offer much adaptability and are not very energy-efficient. In this paper a novel approach of implementing performance and power adaptivity from system down to optical device, electrical circuit and transistor level is proposed. Depending on the actual data load, the number of activated link paths and individual device parameters like bandwidth, clock rate, modulation format and gain are adapted to enable lowering the components supply power. This enables flexible energy-efficient optical transmission links which pave the way for massive reductions of CO2 emission and operating costs in data center and high performance computing applications. Within the FP7 research project Adaptive Data and Power Aware Transceivers for Optical Communications (ADDAPT) dynamic high-speed energy-efficient transceiver subsystems are developed for short-range optical interconnects taking up new adaptive technologies and methods. The research of eight partners from industry, research and education spanning seven European countries includes the investigation of several adaptive control types and algorithms, the development of a full transceiver system, the design and fabrication of optical components and integrated circuits as well as the development of high-speed, low loss packaging solutions. This paper describes and discusses the idea of ADDAPT and provides an overview about the latest research results in this field.

  15. Demonstration of a Fiber Optic Regression Probe

    Korman, Valentin; Polzin, Kurt A.

    2010-01-01

    The capability to provide localized, real-time monitoring of material regression rates in various applications has the potential to provide a new stream of data for development testing of various components and systems, as well as serving as a monitoring tool in flight applications. These applications include, but are not limited to, the regression of a combusting solid fuel surface, the ablation of the throat in a chemical rocket or the heat shield of an aeroshell, and the monitoring of erosion in long-life plasma thrusters. The rate of regression in the first application is very fast, while the second and third are increasingly slower. A recent fundamental sensor development effort has led to a novel regression, erosion, and ablation sensor technology (REAST). The REAST sensor allows for measurement of real-time surface erosion rates at a discrete surface location. The sensor is optical, using two different, co-located fiber-optics to perform the regression measurement. The disparate optical transmission properties of the two fiber-optics makes it possible to measure the regression rate by monitoring the relative light attenuation through the fibers. As the fibers regress along with the parent material in which they are embedded, the relative light intensities through the two fibers changes, providing a measure of the regression rate. The optical nature of the system makes it relatively easy to use in a variety of harsh, high temperature environments, and it is also unaffected by the presence of electric and magnetic fields. In addition, the sensor could be used to perform optical spectroscopy on the light emitted by a process and collected by fibers, giving localized measurements of various properties. The capability to perform an in-situ measurement of material regression rates is useful in addressing a variety of physical issues in various applications. An in-situ measurement allows for real-time data regarding the erosion rates, providing a quick method for

  16. Optical Design for Extremely Large Telescope Adaptive Optics Systems

    Bauman, B J

    2003-11-26

    Designing an adaptive optics (AO) system for extremely large telescopes (ELT's) will present new optical engineering challenges. Several of these challenges are addressed in this work, including first-order design of multi-conjugate adaptive optics (MCAO) systems, pyramid wavefront sensors (PWFS's), and laser guide star (LGS) spot elongation. MCAO systems need to be designed in consideration of various constraints, including deformable mirror size and correction height. The y,{bar y} method of first-order optical design is a graphical technique that uses a plot with marginal and chief ray heights as coordinates; the optical system is represented as a segmented line. This method is shown to be a powerful tool in designing MCAO systems. From these analyses, important conclusions about configurations are derived. PWFS's, which offer an alternative to Shack-Hartmann (SH) wavefront sensors (WFS's), are envisioned as the workhorse of layer-oriented adaptive optics. Current approaches use a 4-faceted glass pyramid to create a WFS analogous to a quad-cell SH WFS. PWFS's and SH WFS's are compared and some newly-considered similarities and PWFS advantages are presented. Techniques to extend PWFS's are offered: First, PWFS's can be extended to more pixels in the image by tiling pyramids contiguously. Second, pyramids, which are difficult to manufacture, can be replaced by less expensive lenslet arrays. An approach is outlined to convert existing SH WFS's to PWFS's for easy evaluation of PWFS's. Also, a demonstration of PWFS's in sensing varying amounts of an aberration is presented. For ELT's, the finite altitude and finite thickness of LGS's means that the LGS will appear elongated from the viewpoint of subapertures not directly under the telescope. Two techniques for dealing with LGS spot elongation in SH WFS's are presented. One method assumes that the laser will be pulsed and uses a segmented micro

  17. Computational adaptive optics of the human retina

    South, Fredrick A.; Liu, Yuan-Zhi; Carney, P. Scott; Boppart, Stephen A.

    2016-03-01

    It is well known that patient-specific ocular aberrations limit imaging resolution in the human retina. Previously, hardware adaptive optics (HAO) has been employed to measure and correct these aberrations to acquire high-resolution images of various retinal structures. While the resulting aberration-corrected images are of great clinical importance, clinical use of HAO has not been widespread due to the cost and complexity of these systems. We present a technique termed computational adaptive optics (CAO) for aberration correction in the living human retina without the use of hardware adaptive optics components. In CAO, complex interferometric data acquired using optical coherence tomography (OCT) is manipulated in post-processing to adjust the phase of the optical wavefront. In this way, the aberrated wavefront can be corrected. We summarize recent results in this technology for retinal imaging, including aberration-corrected imaging in multiple retinal layers and practical considerations such as phase stability and image optimization.

  18. Teaching Optics and Systems Engineering With Adaptive Optics Workbenches

    Harrington, David; Hunter, Lisa; Max, Claire; Hoffmann, Mark; Pitts, Mark; Armstrong, J D

    2010-01-01

    Adaptive optics workbenches are fully functional optical systems that can be used to illustrate and teach a variety of concepts and cognitive processes. Four systems have been funded, designed and constructed by various institutions and people as part of education programs associated with the Center for Adaptive Optics, the Professional Development Program and the Institute for Science and Engineer Educators. Activities can range from first-year undergraduate explorations to professional level training. These workbenches have been used in many venues including the Center for Adaptive Optics AO Summer School, the Maui Community College hosted Akamai Maui Short Course, classrooms, training of new staff in laboratories and other venues. The activity content has focused on various elements of systems thinking, characterization, feedback and system control, basic optics and optical alignment as well as advanced topics such as phase conjugation, wave-front sensing and correction concepts and system design. The work...

  19. Optical Profilometers Using Adaptive Signal Processing

    Hall, Gregory A.; Youngquist, Robert; Mikhael, Wasfy

    2006-01-01

    A method of adaptive signal processing has been proposed as the basis of a new generation of interferometric optical profilometers for measuring surfaces. The proposed profilometers would be portable, hand-held units. Sizes could be thus reduced because the adaptive-signal-processing method would make it possible to substitute lower-power coherent light sources (e.g., laser diodes) for white light sources and would eliminate the need for most of the optical components of current white-light profilometers. The adaptive-signal-processing method would make it possible to attain scanning ranges of the order of decimeters in the proposed profilometers.

  20. Development of large aperture composite adaptive optics

    Kmetík, Viliam; Vítovec, Bohumil; Jiran, L.; Němcová, Š.; Zicha, J.; Inneman, A.; Mikuličková, L.; Pavlica, R.

    Vol. 9442. Bellingham: SPIE-INT SOC OPTICAL ENGINEERING, 2015 - (Kovačičinová, J.; Vít, T.), 94420L-94420L. (SPIE). ISBN 978-1-62841-557-5. ISSN 0277-786X. [Optics and Measurement Conference 2014 (OaM 2014). Liberec (CZ), 07.10.2014-10.10.2014] R&D Projects: GA TA ČR TA01010878 Institutional support: RVO:61389021 Keywords : Large aperture * adaptive optics * deformable mirror * bimorph deformable mirror * composite optics Subject RIV: BH - Optics, Masers, Lasers http://dx.doi.org/10.1117/12.2175713 .

  1. A Miniaturized Adaptive Optic Device for Optical Telecommunications Project

    National Aeronautics and Space Administration — To advance the state-of-the-art uplink laser communication technology, new adaptive optic beam compensation techniques are needed for removing various time-varying...

  2. Optical ballast and adaptive dynamic stable resonator

    Zhang Guang-Yin; Jiao Zhi-Yong; Guo Shu-Guang; Zhang Xiao-Hua; Gu Xue-Wen; Yan Cai-Fan; Wu Ding-Er; Song Feng

    2004-01-01

    In this paper a new concept of ‘optical ballast' is put forward. Optical ballast is a kind of device that can be used to decrease the variation and fluctuation of the propagation characteristics of light beams caused by the disturbance of refractive index of the medium. To illustrate the idea clearly and concretely, a fully adaptive dynamic stable solid-state laser resonator is presented as application example of optical ballast.

  3. Overview of Advanced LIGO Adaptive Optics

    Brooks, Aidan F.; Abbott, Benjamin; Arain, Muzammil A.; Ciani, Giacomo; Cole, Ayodele; Grabeel, Greg; Gustafson, Eric; Guido, Chris; Heintze, Matthew; Heptonstall, Alastair; Jacobson, Mindy; KIM, WON; King, Eleanor; Lynch, Alexander; O'Connor, Stephen

    2016-01-01

    This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements...

  4. Optical Design and Optimization of Translational Reflective Adaptive Optics Ophthalmoscopes

    Sulai, Yusufu N. B.

    The retina serves as the primary detector for the biological camera that is the eye. It is composed of numerous classes of neurons and support cells that work together to capture and process an image formed by the eye's optics, which is then transmitted to the brain. Loss of sight due to retinal or neuro-ophthalmic disease can prove devastating to one's quality of life, and the ability to examine the retina in vivo is invaluable in the early detection and monitoring of such diseases. Adaptive optics (AO) ophthalmoscopy is a promising diagnostic tool in early stages of development, still facing significant challenges before it can become a clinical tool. The work in this thesis is a collection of projects with the overarching goal of broadening the scope and applicability of this technology. We begin by providing an optical design approach for AO ophthalmoscopes that reduces the aberrations that degrade the performance of the AO correction. Next, we demonstrate how to further improve image resolution through the use of amplitude pupil apodization and non-common path aberration correction. This is followed by the development of a viewfinder which provides a larger field of view for retinal navigation. Finally, we conclude with the development of an innovative non-confocal light detection scheme which improves the non-invasive visualization of retinal vasculature and reveals the cone photoreceptor inner segments in healthy and diseased eyes.

  5. Amplitude variations on the Extreme Adaptive Optics testbed

    Evans, J; Thomas, S; Dillon, D; Gavel, D; Phillion, D; Macintosh, B

    2007-08-14

    High-contrast adaptive optics systems, such as those needed to image extrasolar planets, are known to require excellent wavefront control and diffraction suppression. At the Laboratory for Adaptive Optics on the Extreme Adaptive Optics testbed, we have already demonstrated wavefront control of better than 1 nm rms within controllable spatial frequencies. Corresponding contrast measurements, however, are limited by amplitude variations, including those introduced by the micro-electrical-mechanical-systems (MEMS) deformable mirror. Results from experimental measurements and wave optic simulations of amplitude variations on the ExAO testbed are presented. We find systematic intensity variations of about 2% rms, and intensity variations with the MEMS to be 6%. Some errors are introduced by phase and amplitude mixing because the MEMS is not conjugate to the pupil, but independent measurements of MEMS reflectivity suggest that some error is introduced by small non-uniformities in the reflectivity.

  6. Wavefront sensorless adaptive optics ophthalmoscopy in the human eye

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

    2011-07-01

    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.

  7. Wavelet methods in multi-conjugate adaptive optics

    The next generation ground-based telescopes rely heavily on adaptive optics for overcoming the limitation of atmospheric turbulence. In the future adaptive optics modalities, like multi-conjugate adaptive optics (MCAO), atmospheric tomography is the major mathematical and computational challenge. In this severely ill-posed problem, a fast and stable reconstruction algorithm is needed that can take into account many real-life phenomena of telescope imaging. We introduce a novel reconstruction method for the atmospheric tomography problem and demonstrate its performance and flexibility in the context of MCAO. Our method is based on using locality properties of compactly supported wavelets, both in the spatial and frequency domains. The reconstruction in the atmospheric tomography problem is obtained by solving the Bayesian MAP estimator with a conjugate-gradient-based algorithm. An accelerated algorithm with preconditioning is also introduced. Numerical performance is demonstrated on the official end-to-end simulation tool OCTOPUS of European Southern Observatory. (paper)

  8. Solar Ground-Layer Adaptive Optics

    Ren, Deqing; Jolissaint, Laurent; Zhang, Xi; Dou, Jianpei; Chen, Rui; Zhao, Gang; Zhu, Yongtian

    2015-05-01

    Solar conventional adaptive optics (CAO) with one deformable-mirror uses a small field-of-view (FOV) for wave-front sensing, which yields a small corrected FOV for high-resolution imaging. Solar activities occur in a two-dimensional extended FOV and studies of solar magnetic fields need high-resolution imaging over a FOV at least 60''. Recently, solar Tomography Adaptive Optics (TAO) and Multi-Conjugate Adaptive Optics (MCAO) were being developed to overcome this problem of small AO corrected FOV. However, for both TAO and MCAO, wavefront distortions need to be tomographically reconstructed from measurements on multiple guide stars, which is a complicated and time-consuming process. Solar Ground-Layer Adaptive Optics (S-GLAO) uses one or several guide stars, and does not rely on a tomographic reconstruction of the atmospheric turbulence. In this publication, we present two unique wavefront sensing approaches for the S-GLAO. We show that our S-GLAO can deliver good to excellent performance at variable seeing conditions in the Near Infrared (NIR) J and H bands, and is much simpler to implement. We discuss details of our S-GLAO associated wavefront approaches, which make our S-GLAO a unique solution for sunspot high-resolution imaging that other current adaptive optics systems, including the solar MCAO, cannot offer.

  9. Possibilities of joint application of adaptive optics technique and nonlinear optical phase conjugation to compensate for turbulent distortions

    Lukin, V. P.; Kanev, F. Yu; Kulagin, O. V.

    2016-05-01

    The efficiency of integrating the nonlinear optical technique based on forming a reverse wavefront and the conventional adaptive optics into a unified complex (for example, for adaptive focusing of quasi-cw laser radiation) is demonstrated. Nonlinear optical phase conjugation may provide more exact information about the phase fluctuations in the corrected wavefront in comparison with the adaptive optics methods. At the same time, the conventional methods of adaptive optics provide an efficient control of a laser beam projected onto a target for a rather long time.

  10. The Adaptive Optics Summer School Laboratory Activities

    Ammons, S Mark; Armstrong, J D; Crossfield, Ian; Do, Tuan; Fitzgerald, Mike; Harrington, David; Hickenbotham, Adam; Hunter, Jennifer; Johnson, Jess; Johnson, Luke; Li, Kaccie; Lu, Jessica; Maness, Holly; Morzinski, Katie; Norton, Andrew; Putnam, Nicole; Roorda, Austin; Rossi, Ethan; Yelda, Sylvana

    2011-01-01

    Adaptive Optics (AO) is a new and rapidly expanding field of instrumentation, yet astronomers, vision scientists, and general AO practitioners are largely unfamiliar with the root technologies crucial to AO systems. The AO Summer School (AOSS), sponsored by the Center for Adaptive Optics, is a week-long course for training graduate students and postdoctoral researchers in the underlying theory, design, and use of AO systems. AOSS participants include astronomers who expect to utilize AO data, vision scientists who will use AO instruments to conduct research, opticians and engineers who design AO systems, and users of high-bandwidth laser communication systems. In this article we describe new AOSS laboratory sessions implemented in 2006-2009 for nearly 250 students. The activity goals include boosting familiarity with AO technologies, reinforcing knowledge of optical alignment techniques and the design of optical systems, and encouraging inquiry into critical scientific questions in vision science using AO sys...

  11. Adaptive Optics Simulations for Siding Spring

    Goodwin, Michael; Lambert, Andrew

    2012-01-01

    Using an observational derived model optical turbulence profile (model-OTP) we have investigated the performance of Adaptive Optics (AO) at Siding Spring Observatory (SSO), Australia. The simulations cover the performance for AO techniques of single conjugate adaptive optics (SCAO), multi-conjugate adaptive optics (MCAO) and ground-layer adaptive optics (GLAO). The simulation results presented in this paper predict the performance of these AO techniques as applied to the Australian National University (ANU) 2.3 m and Anglo-Australian Telescope (AAT) 3.9 m telescopes for astronomical wavelength bands J, H and K. The results indicate that AO performance is best for the longer wavelengths (K-band) and in the best seeing conditions (sub 1-arcsecond). The most promising results are found for GLAO simulations (field of view of 180 arcsecs), with the field RMS for encircled energy 50% diameter (EE50d) being uniform and minimally affected by the free-atmosphere turbulence. The GLAO performance is reasonably good over...

  12. A real-time simulation facility for astronomical adaptive optics

    Basden, Alastair

    2014-01-01

    In this paper we introduce the concept of real-time hardware-in-the-loop simulation for astronomical adaptive optics, and present the case for the requirement for such a facility. This real-time simulation, when linked with an adaptive optics real-time control system, provides an essential tool for the validation, verification and integration of the Extremely Large Telescope real-time control systems prior to commissioning at the telescope. We demonstrate that such a facility is crucial for the success of the future extremely large telescopes.

  13. Digital adaptive optics line-scanning confocal imaging system

    Liu, Changgeng; Kim, Myung K.

    2015-11-01

    A digital adaptive optics line-scanning confocal imaging (DAOLCI) system is proposed by applying digital holographic adaptive optics to a digital form of line-scanning confocal imaging system. In DAOLCI, each line scan is recorded by a digital hologram, which allows access to the complex optical field from one slice of the sample through digital holography. This complex optical field contains both the information of one slice of the sample and the optical aberration of the system, thus allowing us to compensate for the effect of the optical aberration, which can be sensed by a complex guide star hologram. After numerical aberration compensation, the corrected optical fields of a sequence of line scans are stitched into the final corrected confocal image. In DAOLCI, a numerical slit is applied to realize the confocality at the sensor end. The width of this slit can be adjusted to control the image contrast and speckle noise for scattering samples. DAOLCI dispenses with the hardware pieces, such as Shack-Hartmann wavefront sensor and deformable mirror, and the closed-loop feedbacks adopted in the conventional adaptive optics confocal imaging system, thus reducing the optomechanical complexity and cost. Numerical simulations and proof-of-principle experiments are presented that demonstrate the feasibility of this idea.

  14. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics

    Jang, Changwon; Kim, Jonghyun; Clark, David C.; Lee, Seungjae; Lee, Byoungho; Kim, Myung K.

    2015-11-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: self­interference incoherent digital holography (SIDH). The SIDH generates a complex-i.e., amplitude plus phase-hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  15. Generating a Style-adaptive Trajectory from Multiple Demonstrations

    Yue Zhao

    2014-07-01

    Full Text Available Trajectory learning and generation from demonstration have been widely discussed in recent years, with promising progress made. Existing approaches, including the Gaussian Mixture Model (GMM, affine functions and Dynamic Movement Primitives (DMPs have proven their applicability to learning the features and styles of existing trajectories and generating similar trajectories that can adapt to different dynamic situations. However, in many applications, such as grasping an object, shooting a ball, etc., different goals require trajectories of different styles. An issue that must be resolved is how to reproduce a trajectory with a suitable style. In this paper, we propose a style-adaptive trajectory generation approach based on DMPs, by which the style of the reproduced trajectories can change smoothly as the new goal changes. The proposed approach first adopts a Point Distribution Model (PDM to get the principal trajectories for different styles, then learns the model of each principal trajectory independently using DMPs, and finally adapts the parameters of the trajectory model smoothly according to the new goal using an adaptive goal-to-style mechanism. This paper further discusses the application of the approach on small-sized robots for an adaptive shooting task and on a humanoid robot arm to generate motions for table tennis-playing with different styles.

  16. Optimized micromirror arrays for adaptive optics

    Michalicek, M. Adrian; Comtois, John H.; Hetherington, Dale L.

    1999-01-01

    This paper describes the design, layout, fabrication, and surface characterization of highly optimized surface micromachined micromirror devices. Design considerations and fabrication capabilities are presented. These devices are fabricated in the state-of-the-art, four-level, planarized, ultra-low-stress polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT). This enabling process permits the development of micromirror devices with near-ideal characteristics that have previously been unrealizable in standard three-layer polysilicon processes. The reduced 1 μm minimum feature sizes and 0.1 μm mask resolution make it possible to produce dense wiring patterns and irregularly shaped flexures. Likewise, mirror surfaces can be uniquely distributed and segmented in advanced patterns and often irregular shapes in order to minimize wavefront error across the pupil. The ultra-low-stress polysilicon and planarized upper layer allow designers to make larger and more complex micromirrors of varying shape and surface area within an array while maintaining uniform performance of optical surfaces. Powerful layout functions of the AutoCAD editor simplify the design of advanced micromirror arrays and make it possible to optimize devices according to the capabilities of the fabrication process. Micromirrors fabricated in this process have demonstrated a surface variance across the array from only 2-3 nm to a worst case of roughly 25 nm while boasting active surface areas of 98% or better. Combining the process planarization with a ``planarized-by-design'' approach will produce micromirror array surfaces that are limited in flatness only by the surface deposition roughness of the structural material. Ultimately, the combination of advanced process and layout capabilities have permitted the fabrication of highly optimized micromirror arrays for adaptive optics.

  17. Optical axis jitter rejection for double overlapped adaptive optics systems

    Luo, Qi; Luo, Xi; Li, Xinyang

    2016-04-01

    Optical axis jitters, or vibrations, which arise from wind shaking and structural oscillations of optical platforms, etc., cause a deleterious impact on the performance of adaptive optics systems. When conventional integrators are utilized to reject such high frequency and narrow-band disturbance, the benefits are quite small despite their acceptable capabilities to reject atmospheric turbulence. In our case, two suits of complete adaptive optics systems called double overlapped adaptive optics systems (DOAOS) are used to counteract both optical jitters and atmospheric turbulence. A novel algorithm aiming to remove vibrations is proposed by resorting to combine the Smith predictor and notch filer. With the help of loop shaping method, the algorithm will lead to an effective and stable controller, which makes the characteristics of error transfer function close to notch filters. On the basis of the spectral analysis of observed data, the peak frequency and bandwidth of vibrations can be identified in advance. Afterwards, the number of notch filters and their parameters will be determined using coordination descending method. The relationship between controller parameters and filtering features is discussed, and the robustness of the controller against varying parameters of the control object is investigated. Preliminary experiments are carried out to validate the proposed algorithms. The overall control performance of DOAOS is simulated. Results show that time delays are a limit of the performance, but the algorithm can be successfully implemented on our systems, which indicate that it has a great potential to reject jitters.

  18. Teaching Optics and Systems Engineering With Adaptive Optics Workbenches

    Harrington, D. M.; Ammons, M.; Hunter, L.; Max, C.; Hoffmann, M.; Pitts, M.; Armstrong, J. D.

    2010-12-01

    Adaptive optics workbenches are fully functional optical systems that can be used to illustrate and teach a variety of concepts and cognitive processes. Four systems have been funded, designed and constructed by various institutions and people as part of education programs associated with the Center for Adaptive Optics, the Professional Development Program and the Institute for Scientist & Engineer Educators. Activities can range from first-year undergraduate explorations to professional level training. These workbenches have been used in many venues including the Center for Adaptive Optics AO Summer School, the Maui Community College-hosted Akamai Maui Short Course, classrooms, training of new staff in laboratories and other venues. The activity content has focused on various elements of systems thinking, characterization, feedback and system control, basic optics and optical alignment as well as advanced topics such as phase conjugation, wave-front sensing and correction concepts, and system design. The workbenches have slightly different designs and performance capabilities. We describe here outlines for several activities utilizing these different designs and some examples of common student learner outcomes and experiences.

  19. Easily Constructed Mini-Sextant Demonstrates Optical Principles.

    Nenninger, Garet G.

    2000-01-01

    Examines the design and construction of a mini-sextant and its use in demonstrating Fresnel reflection, geometric optics, and several common optical techniques. A sidebar explains the basic use of the mini-sextant as a navigational tool. (WRM)

  20. HIGH-EFFICIENCY AUTONOMOUS LASER ADAPTIVE OPTICS

    As new large-scale astronomical surveys greatly increase the number of objects targeted and discoveries made, the requirement for efficient follow-up observations is crucial. Adaptive optics imaging, which compensates for the image-blurring effects of Earth's turbulent atmosphere, is essential for these surveys, but the scarcity, complexity and high demand of current systems limit their availability for following up large numbers of targets. To address this need, we have engineered and implemented Robo-AO, a fully autonomous laser adaptive optics and imaging system that routinely images over 200 objects per night with an acuity 10 times sharper at visible wavelengths than typically possible from the ground. By greatly improving the angular resolution, sensitivity, and efficiency of 1-3 m class telescopes, we have eliminated a major obstacle in the follow-up of the discoveries from current and future large astronomical surveys

  1. High-efficiency Autonomous Laser Adaptive Optics

    Baranec, Christoph; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh; Hogstrom, Kristina; Bui, Khanh; Burse, Mahesh; Chordia, Pravin; Das, Hillol; Dekany, Richard; Kulkarni, Shrinivas; Punnadi, Sujit

    2014-01-01

    As new large-scale astronomical surveys greatly increase the number of objects targeted and discoveries made, the requirement for efficient follow-up observations is crucial. Adaptive optics imaging, which compensates for the image-blurring effects of Earth's turbulent atmosphere, is essential for these surveys, but the scarcity, complexity and high demand of current systems limits their availability for following up large numbers of targets. To address this need, we have engineered and implemented Robo-AO, a fully autonomous laser adaptive optics and imaging system that routinely images over 200 objects per night with an acuity 10 times sharper at visible wavelengths than typically possible from the ground. By greatly improving the angular resolution, sensitivity, and efficiency of 1-3 m class telescopes, we have eliminated a major obstacle in the follow-up of the discoveries from current and future large astronomical surveys.

  2. Adaptive optics without altering visual perception

    Koenig,, I.; NW, Hart; HJ, Hofer

    2014-01-01

    Adaptive optics combined with visual psychophysics creates the potential to study the relationship between visual function and the retina at the cellular scale. This potential is hampered, however, by visual interference from the wavefront-sensing beacon used during correction. For example, we have previously shown that even a dim, visible beacon can alter stimulus perception (Hofer, H. J., Blaschke, J., Patolia, J., & Koenig, D. E. (2012). Fixation light hue bias revisited: Implications for ...

  3. Adaptive optics assisted Fourier domain OCT with balanced detection

    Meadway, A.; Bradu, A.; Hathaway, M.; Van der Jeught, S.; Rosen, R. B.; Podoleanu, A. Gh.

    2011-03-01

    Two factors are of importance to optical coherence tomography (OCT), resolution and sensitivity. Adaptive optics improves the resolution of a system by correcting for aberrations causing distortions in the wave-front. Balanced detection has been used in time domain OCT systems by removing excess photon noise, however it has not been used in Fourier domain systems, as the cameras used in the spectrometers saturated before excess photon noise becomes a problem. Advances in camera technology mean that this is no longer the case and balanced detection can now be used to improve the signal to noise ratio in a Fourier domain (FD) OCT system. An FD-OCT system, enhanced with adaptive optics, is presented and is used to show the improvement that balanced detection can provide. The signal to noise ratios of single camera detection and balanced detection are assessed and in-vivo retinal images are acquired to demonstrate better image quality when using balance detection.

  4. Overview of Advanced LIGO Adaptive Optics

    Brooks, Aidan F; Arain, Muzammil A; Ciani, Giacomo; Cole, Ayodele; Grabeel, Greg; Gustafson, Eric; Guido, Chris; Heintze, Matthew; Heptonstall, Alastair; Jacobson, Mindy; Kim, Won; King, Eleanor; Lynch, Alexander; O'Connor, Stephen; Ottaway, David; Mailand, Ken; Mueller, Guido; Munch, Jesper; Sannibale, Virginio; Shao, Zhenhua; Smith, Michael; Veitch, Peter; Vo, Thomas; Vorvick, Cheryl; Willems, Phil

    2016-01-01

    This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The thermal compensation system was designed to minimize thermally-induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO$_{2}$ laser projectors and Hartmann wavefront sensors. The system meets the requirements of correcting for nominal distortion in Advanced LIGO to a maximum residual error of 5.4nm, weighted across the laser beam, for up to 125W of laser input power into the interferometer.

  5. Experimental demonstration of quantum leader election in linear optics

    Okubo, Yuta; Wang, Xiang-Bin; Jiang, Yun-Kun; Tani, Seiichiro; Tomita, Akihisa

    2007-01-01

    Linear optics is a promising candidate to enable the construction of quantum computers. A number of quantum protocols gates based on linear optics have been demonstrated. However, it is well-known that these gates are non-deterministic and that higher order nonlinearity is necessary for deterministic operations. We found the quantum leader election protocol (QLE) can be operated deterministically only with linear optics, and we have demonstrated the nearly deterministic operation which overco...

  6. Adaption of optical Fresnel transform to optical Wigner transform

    Enlightened by the algorithmic isomorphism between the rotation of the Wigner distribution function (WDF) and the αth fractional Fourier transform, we show that the optical Fresnel transform performed on the input through an ABCD system makes the output naturally adapting to the associated Wigner transform, i.e. there exists algorithmic isomorphism between ABCD transformation of the WDF and the optical Fresnel transform. We prove this adaption in the context of operator language. Both the single-mode and the two-mode Fresnel operators as the image of classical Fresnel transform are introduced in our discussions, while the two-mode Wigner operator in the entangled state representation is introduced for fitting the two-mode Fresnel operator.

  7. Adaptive Data Rates for Flexible Transceivers in Optical Networks

    Brian Thomas Teipen

    2012-05-01

    Full Text Available Efforts towards commercializing higher-speed optical transmission have demonstrated the need for advanced modulation formats, several of which require similar transceiver hardware architecture. Adaptive transceivers can be built to have a number of possible operational configurations selected by software. Such software-defined transceiver configurations can create specific modulation formats to support sets of data rates, corresponding tolerances to system impairments, and sets of electronic digital signal processing schemes chosen to best function in a given network environment. In this paper, we discuss possibilities and advantages of reconfigurable, bit-rate flexible transceivers, and their potential applications in future optical networks.

  8. Performance of a MEMS-base Adaptive Optics Optical Coherency Tomography System

    Evans, J; Zadwadzki, R J; Jones, S; Olivier, S; Opkpodu, S; Werner, J S

    2008-01-16

    We have demonstrated that a microelectrical mechanical systems (MEMS) deformable mirror can be flattened to < 1 nm RMS within controllable spatial frequencies over a 9.2-mm aperture making it a viable option for high-contrast adaptive optics systems (also known as Extreme Adaptive Optics). The Extreme Adaptive Optics Testbed at UC Santa Cruz is being used to investigate and develop technologies for high-contrast imaging, especially wavefront control. A phase shifting diffraction interferometer (PSDI) measures wavefront errors with sub-nm precision and accuracy for metrology and wavefront control. Consistent flattening, required testing and characterization of the individual actuator response, including the effects of dead and low-response actuators. Stability and repeatability of the MEMS devices was also tested. An error budget for MEMS closed loop performance will summarize MEMS characterization.

  9. Experimental demonstration of EON node supporting reconfigurable optical superchannel multicasting.

    Zhu, Paikun; Li, Juhao; Chen, Yuanxiang; Chen, Xin; Wu, Zhongying; Ge, Dawei; Chen, Zhangyuan; He, Yongqi

    2015-08-10

    Elastic optical networks (EON) based on optical superchannel enables higher spectral flexibility, in which the network nodes should provide multiple all-optical functionalities to manipulate bandwidth-variable data traffic. In this paper, we propose and demonstrate an EON node structure supporting reconfigurable optical superchannel multicasting. The node structure incorporates a shared multicasting module, which performs reconfigurable selection of target incoming/outgoing superchannels/replicas and leverages a group of nonlinear devices to satisfy multiple multicast requests. Moreover, an optical comb is utilized to efficiently provide and manage all pump resources for multicasting with potential cost reduction and phase noise inhibition. Based on the node structure, we experimentally demonstrate polarization division multiplexing (PDM) superchannel multicasting scenarios with different replica amount, input/output locations, and modulation formats. Less than 0.7 dB optical signal-to-noise ratio (OSNR) penalties are demonstrated in multiple multicasting scenarios. PMID:26367902

  10. High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography

    Olivier, Scot S.; Werner, John S.; Zawadzki, Robert J.; Laut, Sophie P.; Jones, Steven M.

    2010-09-07

    This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.

  11. Laser Tomography Adaptive Optics (LTAO): A performance study

    Tatulli, E

    2013-01-01

    We present an analytical derivation of the on-axis performance of Adaptive Optics systems using a given number of guide stars of arbitrary altitude, distributed at arbitrary angular positions in the sky. The expressions of the residual error are given for cases of both continuous and discrete turbulent atmospheric profiles. Assuming Shack-Hartmann wavefront sensing with circular apertures, we demonstrate that the error is formally described by integrals of products of three Bessel functions. We compare the performance of Adaptive Optics correction when using natural, Sodium or Rayleigh laser guide stars. For small diameter class telescopes (~5m), we show that a few number of Rayleigh beacons can provide similar performance to that of a single Sodium laser, for a lower overall cost of the instrument. For bigger apertures, using Rayleigh stars may not be such a suitable alternative because of the too severe cone effect that drastically degrades the quality of the correction.

  12. Adaptive optics and laser guide stars at Lick observatory

    Brase, J.M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    For the past several years LLNL has been developing adaptive optics systems for correction of both atmospheric turbulence effects and thermal distortions in optics for high-power lasers. Our early work focused on adaptive optics for beam control in laser isotope separation and ground-based free electron lasers. We are currently developing innovative adaptive optics and laser systems for sodium laser guide star applications at the University of California`s Lick and Keck Observeratories. This talk will describe our adaptive optics technology and some of its applications in high-resolution imaging and beam control.

  13. In vivo cellular visualization of the human retina using optical coherence tomography and adaptive optics

    Olivier, S S; Jones, S M; Chen, D C; Zawadzki, R J; Choi, S S; Laut, S P; Werner, J S

    2006-01-05

    Optical coherence tomography (OCT) sees the human retina sharply with adaptive optics. In vivo cellular visualization of the human retina at micrometer-scale resolution is possible by enhancing Fourier-domain optical-coherence tomography with adaptive optics, which compensate for the eye's optical aberrations.

  14. Extreme Adaptive Optics Planet Imager: XAOPI

    Macintosh, B A; Graham, J; Poyneer, L; Sommargren, G; Wilhelmsen, J; Gavel, D; Jones, S; Kalas, P; Lloyd, J; Makidon, R; Olivier, S; Palmer, D; Patience, J; Perrin, M; Severson, S; Sheinis, A; Sivaramakrishnan, A; Troy, M; Wallace, K

    2003-09-17

    Ground based adaptive optics is a potentially powerful technique for direct imaging detection of extrasolar planets. Turbulence in the Earth's atmosphere imposes some fundamental limits, but the large size of ground-based telescopes compared to spacecraft can work to mitigate this. We are carrying out a design study for a dedicated ultra-high-contrast system, the eXtreme Adaptive Optics Planet Imager (XAOPI), which could be deployed on an 8-10m telescope in 2007. With a 4096-actuator MEMS deformable mirror it should achieve Strehl >0.9 in the near-IR. Using an innovative spatially filtered wavefront sensor, the system will be optimized to control scattered light over a large radius and suppress artifacts caused by static errors. We predict that it will achieve contrast levels of 10{sup 7}-10{sup 8} at angular separations of 0.2-0.8 inches around a large sample of stars (R<7-10), sufficient to detect Jupiter-like planets through their near-IR emission over a wide range of ages and masses. We are constructing a high-contrast AO testbed to verify key concepts of our system, and present preliminary results here, showing an RMS wavefront error of <1.3 nm with a flat mirror.

  15. Thirty meter telescope adaptive optics computing challenges

    The Thirty Meter Telescope (TMT) will be used with Adaptive Optics (AO) systems to allow near diffraction-limited performance in the near-infrared and achieve the main TMT science goals. Adaptive optics systems reduce the effect of the atmospheric distortions by dynamically measuring the distortions with wavefront sensors, performing wavefront reconstruction with a real time controller (RTC), and then compensating for the distortions with deformable mirrors. The requirements for the RTC subsystem of the TMT first light AO system will represent a significant advance over the current generation of astronomical AO control systems. Memory and processing requirements would be at least 2 orders of magnitude greater than the currently most powerful AO systems using conventional approaches, so that innovative wavefront reconstruction algorithms and new hardware approaches will be required. In this paper, we will first present the requirements and challenges for the RTC of the first light AO system, together with the algorithms that have been developed to reduce the memory and processing requirements, and then two possible hardware architectures based on Field Programmable Gate Array (FPGA). (authors)

  16. Lessons Learnt from the Optical Communications Demonstrator (OCD)

    Jeganathan, M.; Portillo, A.; Racho, C.; Lee, S.; Erickson, D.; DePew, J.; Monacos, S.; Biswas, A.

    1999-01-01

    The Optical Communications Demonstrator (OCD) is a laboratory based lasercom terminal that was developed to validate several key technologies such as precision beam pointing, high bandwidth beacon tracking and beacon acquisition.

  17. Performance Analysis and Electronics Packaging of the Optical Communications Demonstrator

    Jeganathan, M.; Monacos, S.

    1998-01-01

    The Optical Communications Demonstrator (OCD), under development at the Jet Propulsion Laboratory (JPL), is a laboratory-based lasercomm terminal designed to validate several key technologies, primarily precision beam pointing, high bandwidth tracking, and beacon acquisition.

  18. Experimental Adaptive Digital Performance Monitoring for Optical DP-QPSK Coherent Receiver

    Borkowski, Robert; Zhang, Xu; Zibar, Darko;

    2011-01-01

    We report on a successful experimental demonstration of a digital optical performance monitoring (OPM) yielding satisfactory estimation accuracy along with adaptive impairment equalization. No observable penalty is measured when equalizer is driven by monitoring module....

  19. Optical design of the adaptive optics laser guide star system

    Bissinger, H. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The design of an adaptive optics package for the 3 meter Lick telescope is presented. This instrument package includes a 69 actuator deformable mirror and a Hartmann type wavefront sensor operating in the visible wavelength; a quadrant detector for the tip-tile sensor and a tip-tilt mirror to stabilize atmospheric first order tip-tile errors. A high speed computer drives the deformable mirror to achieve near diffraction limited imagery. The different optical components and their individual design constraints are described. motorized stages and diagnostics tools are used to operate and maintain alignment throughout observation time from a remote control room. The expected performance are summarized and actual results of astronomical sources are presented.

  20. Dual-thread parallel control strategy for ophthalmic adaptive optics

    Yu, Yongxin; Zhang, Yuhua

    2014-01-01

    To improve ophthalmic adaptive optics speed and compensate for ocular wavefront aberration of high temporal frequency, the adaptive optics wavefront correction has been implemented with a control scheme including 2 parallel threads; one is dedicated to wavefront detection and the other conducts wavefront reconstruction and compensation. With a custom Shack-Hartmann wavefront sensor that measures the ocular wave aberration with 193 subapertures across the pupil, adaptive optics has achieved a ...

  1. DKIST Adaptive Optics System: Simulation Results

    Marino, Jose; Schmidt, Dirk

    2016-05-01

    The 4 m class Daniel K. Inouye Solar Telescope (DKIST), currently under construction, will be equipped with an ultra high order solar adaptive optics (AO) system. The requirements and capabilities of such a solar AO system are beyond those of any other solar AO system currently in operation. We must rely on solar AO simulations to estimate and quantify its performance.We present performance estimation results of the DKIST AO system obtained with a new solar AO simulation tool. This simulation tool is a flexible and fast end-to-end solar AO simulator which produces accurate solar AO simulations while taking advantage of current multi-core computer technology. It relies on full imaging simulations of the extended field Shack-Hartmann wavefront sensor (WFS), which directly includes important secondary effects such as field dependent distortions and varying contrast of the WFS sub-aperture images.

  2. Lens-based wavefront sensorless adaptive optics swept source OCT.

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J; Bonora, Stefano; Sarunic, Marinko V

    2016-01-01

    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. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient's eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects. PMID:27278853

  3. Lens-based wavefront sensorless adaptive optics swept source OCT

    Jian, Yifan; Lee, Sujin; Ju, Myeong Jin; Heisler, Morgan; Ding, Weiguang; Zawadzki, Robert J.; Bonora, Stefano; Sarunic, Marinko V.

    2016-06-01

    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. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high resolution retinal imaging. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient’s eyes, and a novel multi-actuator adaptive lens for aberration correction to achieve near diffraction limited imaging performance at the retina. With a parallel processing computational platform, high resolution cross-sectional and en face retinal image acquisition and display was performed in real time. In order to demonstrate the system functionality and clinical utility, we present images of the photoreceptor cone mosaic and other retinal layers acquired in vivo from research subjects.

  4. Optically sensitive Medipix2 detector for adaptive optics wavefront sensing

    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.

  5. Chemical detection demonstrated using an evanescent wave graphene optical sensor

    Maliakal, Ashok; Reith, Leslie; Cabot, Steve

    2016-04-01

    Graphene devices have been constructed on silicon mirrors, and the graphene is optically probed through an evanescent wave interaction in an attenuated total reflectance configuration using an infrared spectrometer. The graphene is electrically biased in order to tune its optical properties. Exposure of the device to the chemicals iodine and ammonia causes observable and reversible changes to graphene's optical absorption spectra in the mid to near infrared range which can be utilized for the purpose of sensing. Electrical current measurements through the graphene are made simultaneously with optical measurements allowing for simultaneous sensing using two separate detection modalities. Our current results reveal sub-ppm detection limits for iodine and approximately 100 ppm detection limits for ammonia. We have also demonstrated that this approach will work at 1.55 μm, which opens up the possibility for graphene optical sensors that leverage commercial telecom light sources.

  6. Using Site Testing Data for Adaptive Optics Simulations

    Herriot, Glen; Andersen, David; Conan, Rod; Ellerbroek, Brent; Gilles, Luc; Hickson, Paul; Jackson, Kate; Lardière, Olivier; Pfrommer, Thomas; Véran, Jean-Pierre; Wang, Lianqi

    2011-01-01

    Astronomical Site testing data plays a vital role in the simulation, design, evaluation and operation of adaptive optics systems for large telescope. We present the example of TMT and its first light facilitiy adaptive optics system NFIRAOS, and illustrate the many simulations done based on site testing data.

  7. Optical implementation for adaptive beamforming of array antenna

    Liu, Ming; Shi, Xiang quan

    2010-11-01

    It is difficult for the traditional phased array radar to process large array-element and high time-bandwidth-product signal in real time. An optical architecture of implement true time delay adaptive beamforming based on Stimulate Photon Echoes(SPE) is introduced. The principle of how to implement a true time delay based on SPE phenomenon with its theory models is established. the method of how to implement variable time delays using laser beams modulated by linear frequency chirped pulses is discussed, the relationship between chirp bandwidth and delay step is demonstrated by simulation results. As a result, it allows to filter thousands of simultaneous AOAs with 30 GHz dynamically in both spatial and spectral domains, which can be used to adaptively steer a large RF phased array antenna toward the direction of interest while minimizing the effects of unwanted interference signals.

  8. Beam shaping for laser-based adaptive optics in astronomy

    Béchet, Clémentine; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

    2014-01-01

    The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics system (GeMS). A beam shaping concept with two deformable mirrors is investigated in order to provide automated optimization of the laser quality for astronomical AO. This study aims at demonstrating the correction of quasi-static aberrations of the laser, in both amplitude and phase, testing a prototype of this two-deformable mirror concept on GeMS. The paper presents the results of the preparatory study before the experimental phase. An algorithm to control amplitude and phase correction, based on phase retrieval techniques...

  9. Extreme Adaptive Optics Testbed: Results and Future Work

    Evans, J W; Sommargren, G; Poyneer, L; Macintosh, B; Severson, S; Dillon, D; Sheinis, A; Palmer, D; Kasdin, J; Olivier, S

    2004-07-15

    'Extreme' adaptive optics systems are optimized for ultra-high-contrast applications, such as ground-based extrasolar planet detection. The Extreme Adaptive Optics Testbed at UC Santa Cruz is being used to investigate and develop technologies for high-contrast imaging, especially wavefront control. A simple optical design allows us to minimize wavefront error and maximize the experimentally achievable contrast before progressing to a more complex set-up. A phase shifting diffraction interferometer is used to measure wavefront errors with sub-nm precision and accuracy. We have demonstrated RMS wavefront errors of <1.3 nm and a contrast of >10{sup -7} over a substantial region using a shaped pupil. Current work includes the installation and characterization of a 1024-actuator Micro-Electro-Mechanical- Systems (MEMS) deformable mirror, manufactured by Boston Micro-Machines, which will be used for wavefront control. In our initial experiments we can flatten the deformable mirror to 1.8-nm RMS wavefront error within a control radius of 5-13 cycles per aperture. Ultimately this testbed will be used to test all aspects of the system architecture for an extrasolar planet-finding AO system.

  10. Low-cost home experiments and demonstrations in optics

    Mejías, P. M.; Martínez-Herrero, R.; Serna, J.; Piquero, G.

    2005-10-01

    More than 60 demonstrations and basic experiments in Optics have been compiled. They can be carried out by secondary and university students in the classroom or at home, and have been conceived considering low cost and easy-to-get materials. The goal is to offer didactic resources, showing that Optics can be taught in an attractive and amusing way. The experiments try to stimulate scientific curiosity, and generate interest in the observation of our physical world. The work could be collected as a book, where each demonstration would be contained in one or two pages, including a title, a list of the required materials and a concise explanation about what to do and observe. Associated with the experimental content, we propose a web page, namely, http://www.ucm.es/info/expoptic, that accepts experiments sent by anyone interested in Optics, which can be used as a forum to interchange information on this educational topic.

  11. Demonstrations of Optical Spectra with a Video Camera

    Kraftmakher, Yaakov

    2012-01-01

    The use of a video camera may markedly improve demonstrations of optical spectra. First, the output electrical signal from the camera, which provides full information about a picture to be transmitted, can be used for observing the radiant power spectrum on the screen of a common oscilloscope. Second, increasing the magnification by the camera…

  12. Optics Demonstration with Student Eyeglasses Using the Inquiry Method

    James, Mark C.

    2011-01-01

    A favorite qualitative optics demonstration I perform in introductory physics classes makes use of students' eyeglasses to introduce converging and diverging lenses. Taking on the persona of a magician, I walk to the back of the classroom and approach a student wearing glasses. The top part of Fig. 1 shows a glasses-wearing student who is…

  13. The research and development of the adaptive optics in ophthalmology

    Wu, Chuhan; Zhang, Xiaofang; Chen, Weilin

    2015-08-01

    Recently the combination of adaptive optics and ophthalmology has made great progress and become highly effective. The retina disease is diagnosed by retina imaging technique based on scanning optical system, so the scanning of eye requires optical system characterized by great ability of anti-moving and optical aberration correction. The adaptive optics possesses high level of adaptability and is available for real time imaging, which meets the requirement of medical retina detection with accurate images. Now the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are widely used, which are the core techniques in the area of medical retina detection. Based on the above techniques, in China, a few adaptive optics systems used for eye medical scanning have been designed by some researchers from The Institute of Optics And Electronics of CAS(The Chinese Academy of Sciences); some foreign research institutions have adopted other methods to eliminate the interference of eye moving and optical aberration; there are many relevant patents at home and abroad. In this paper, the principles and relevant technique details of the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are described. And the recent development and progress of adaptive optics in the field of eye retina imaging are analyzed and summarized.

  14. Beam shaping for laser-based adaptive optics in astronomy

    Béchet, Clémentine; Guesalaga, Andrés; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

    2014-01-01

    The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics syst...

  15. VASAO: visible all sky adaptive optics

    Veillet, Christian; Lai, Olivier; Salmon, Derrick; Pique, Jean-Paul

    2006-06-01

    Building on an extensive and successful experience in Adaptive Optics (AO) and on recent developments made in its funding nations, the Canada-France-Hawaii-Telescope Corporation (CFHT) is studying the VASAO concept: an integrated AO system that would allow diffraction limited imaging of the whole sky in the visible as well as in the infrared. At the core of VASAO, Pueo-Hou (the new Pueo) is built on Pueo, the current CFHT AO bonnette. Pueo will be refurbished and improved to be able to image the isoplanetic field at 700 nm with Strehl ratios of 30% or better, making possible imaging with a resolution of 50 milliarcseconds between 500 and 700nm, and at the telescope limit of diffraction above. The polychromatic tip-tilt laser guide star currently envisioned will be generated by a single 330nm mode-less laser, and the relative position of the 330nm and 589nm artificial stars created on the mesosphere by the 330nm excitation of the sodium layer will be monitored to provide the atmospheric tip-tilt along the line of sight, following the philosophy developed for the ELP-OA project. The feasibility study of VASAO will take most of 2006 in parallel with the development of a science case making the best possible use of the unique capabilities of the system, If the feasibility study is encouraging, VASAO development could start in 2007 for a full deployment on the sky by 2011-2012.

  16. Stellar photometry with Multi Conjugate Adaptive Optics

    Fiorentino, Giuliana; McConnachie, Alan; Stetson, Peter B; Bono, Giuseppe; Turri, Paolo; Andersen, David; Veran, Jean-Pierre; Diolaiti, Emiliano; Schreiber, Laura; Ciliegi, Paolo; Bellazzini, Michele; Tolstoy, Eline; Monelli, Matteo; Iannicola, Giacinto; Ferraro, Ivan; Testa, Vincenzo

    2016-01-01

    We overview the current status of photometric analyses of images collected with Multi Conjugate Adaptive Optics (MCAO) at 8-10m class telescopes that operated, or are operating, on sky. Particular attention will be payed to resolved stellar population studies. Stars in crowded stellar systems, such as globular clusters or in nearby galaxies, are ideal test particles to test AO performance. We will focus the discussion on photometric precision and accuracy reached nowadays. We briefly describe our project on stellar photometry and astrometry of Galactic globular clusters using images taken with GeMS at the Gemini South telescope. We also present the photometry performed with DAOPHOT suite of programs into the crowded regions of these globulars reaching very faint limiting magnitudes Ks ~21.5 mag on moderately large fields of view (~1.5 arcmin squared). We highlight the need for new algorithms to improve the modeling of the complex variation of the Point Spread Function across the ?eld of view. Finally, we outl...

  17. Adaptive optics at the PHELIX laser

    Heuck, Hans-Martin; Wittrock, Ulrich; Fils, Jérôme; Borneis, Stefan; Witte, Klaus; Eisenbart, Udo; Javorkova, Dasa; Bagnoud, Vincent; Götte, Stefan; Tauschwitz, Andreas; Onkels, Eckehard

    2007-05-01

    GSI Darmstadt currently builds a high-energy petawatt Nd:glass laser system, called PHELIX (Petawatt High-Energy Laser for Heavy-Ion Experiments). PHELIX will offer the world-wide unique combination of a high current, high-energy heavy-ion beam with an intense laser beam. Aberrations due to the beam transport and due to the amplification process limit the focusability and the intensity at the target. We have investigated the aberrations of the different amplification stages. The pre-amplifier stage consists of three rod-amplifiers which cause mainly defocus, but also a small part of coma and astigmatism. The main amplifier consists of five disk amplifiers with a clear aperture of 315 mm. These large disk-amplifiers cause pump-shot aberrations which occur instantly. After a shot, the disk amplifiers need a cooling time of several hours to relax to their initial state. This limits the repetition rate and causes long-term aberrations. We will present first measurements of the pump-shot and long-term aberrations caused by the pre- and the main amplifier in a single-pass configuration. In this context, we will present the adaptive optics system which is implemented in the PHELIX beam line and discuss its capability to compensate for the pump-shot and long-term aberrations.

  18. Competencies Demonstrated by Municipal Employees during Adaptation to Climate Change: A Pilot Study

    Pruneau, Diane; Kerry, Jackie; Blain, Sylvie; Evichnevetski, Evgueni; Deguire, Paul; Barbier, Pierre-Yves; Freiman, Viktor; Therrien, Jimmy; Langis, Joanne; Lang, Mathieu

    2013-01-01

    Since coastal communities are already subjected to the impacts of climate change, adaptation has become a necessity. This article presents competencies demonstrated by Canadian municipal employees during an adaptation process to sea level rise. To adapt, the participants demonstrated the following competencies: problem solving (highlighting…

  19. Functional demonstration of adaptive immunity in zebrafish using DNA vaccination

    Lorenzen, Niels; Lorenzen, Ellen; Einer-Jensen, Katja; Rasmussen, Jesper Skou; Kjær, Torben Egil; Vesely, Thomas

    Due to the well characterized genome, overall highly synteny with the human genome and its suitability for functional genomics studies, the zebrafish is considered to be an ideal animal model for basic studies of mechanisms of diseases and immunity in vertebrates including humans. While several...... studies have documented existence of a classical innate immune response, there is mainly indirect evidence of functional adaptive immunity. To address this aspect, groups of zebrafish were vaccinated with DNA-vaccines against the rhabdoviruses VHSV, IHNV and SVCV. Seven weeks later, the fish were...... challenged with SVCV by immersion. Despite some variability between replicate aquaria, there was a protective effect of the homologous vaccine and no effect of the heterologous vaccines. The results therefore confirm the existence of not only a well developed but also a fully functional adaptive immune...

  20. Large Binocular Telescope Adaptive Optics System: New achievements and perspectives in adaptive optics

    Esposito, Simone; Pinna, Enrico; Puglisi, Alfio; Quirós-Pacheco, Fernando; Arcidiacono, Carmelo; Xompero, Marco; Briguglio, Runa; Agapito, Guido; Busoni, Lorenzo; Fini, Luca; Argomedo, Javier; Gherardi, Alessandro; Brusa, Guido; Miller, Douglas; Guerra, Juan Carlos; Stefanini, Paolo; Salinari, Piero; 10.1117/12.898641

    2012-01-01

    The Large Binocular Telescope (LBT) is a unique telescope featuring two co-mounted optical trains with 8.4m primary mirrors. The telescope Adaptive Optics (AO) system uses two innovative key components, namely an adaptive secondary mirror with 672 actuators and a high-order pyramid wave-front sensor. During the on-sky commissioning such a system reached performances never achieved before on large ground-based optical telescopes. Images with 40mas resolution and Strehl Ratios higher than 80% have been acquired in H band (1.6 micron). Such images showed a contrast as high as 10e-4. Based on these results, we compare the performances offered by a Natural Guide Star (NGS) system upgraded with the state-of-the-art technology and those delivered by existing Laser Guide Star (LGS) systems. The comparison, in terms of sky coverage and performances, suggests rethinking the current role ascribed to NGS and LGS in the next generation of AO systems for the 8-10 meter class telescopes and Extremely Large Telescopes (ELTs)...

  1. Adaptive optics for daytime deep space laser communications to Mars

    Wilson, Keith E.; Wright, Malcolm; Lee, Shinkhak; Troy, Mitchell

    2005-01-01

    This paper describes JPL research in adaptive optics (AO) to reduce the daytime background noise on a Mars-to-Earth optical communications link. AO can reduce atmosphere-induced wavefront aberrations, and enable single mode receiver operation thereby buying back margin in the deep space optical communications link.

  2. FAST-Net optical interconnection prototype demonstration program

    Haney, Michael W.; Christensen, Marc P.; Milojkovik, P.; Ekman, Jeremy T.; Chandramani, Premanand; Rozier, Richard G.; Kiamilev, Fouad E.; Liu, Yue; Hibbs-Brenner, Mary K.; Nohava, Jim; Kalweit, Edith; Bounnak, Sommy; Marta, Terry; Walterson, B.

    1998-05-01

    This paper reports progress toward the experimental demonstration of a smart pixel based optical interconnection prototype currently being developed under the Free-space Accelerator for Switching Terabit Networks (FAST-Net) project. The prototype system incorporates 2D arrays of monolithically integrated high- bandwidth vertical cavity surface emitting lasers (VCSELs) and photodetectors (PDs). A key aspect of the FAST-Net concept is that all smart pixels are distributed across a single multi-chip plane. This plane is connected to itself via an optical system that consists of an array of matched lenses (one for each smart pixel chip position) and a mirror. The optical interconnect system implements a global point-to-point shuffle pattern. The interleaved 2D arrays of VCSELs and PDs in the prototype are arranged on a clustered self-similar grid pattern with a closest element pitch of 100 micrometers . The circular VCSEL elements have a diameter of 10 micrometers and the square PDs have an active region that is 50 micrometers wide. These arrays are packaged and mounted on circuit boards along with the CMOS driver, receiver, and FPGA controller chips. Micro-positioning mounts are used to effect alignment that is consistent with current MCM chip placement accuracy. Shuffled optical data links between the multiple ICs have been demonstrated in preliminary evaluation of this system. These results suggest that a multi-Terabit optically interconnected MCM module is feasible.

  3. Multiple Object Adaptive Optics: Mixed NGS/LGS tomography

    Morris, Tim; Gendron, Eric; Basden, Alastair; Martin, Olivier; Osborn, James; Henry, David; Hubert, Zoltan; Sivo, Gaetano; Gratadour, Damien; Chemla, Fanny; Sevin, Arnaud; Cohen, Matthieu; Younger, Eddy; Vidal, Fabrice; Wilson, Richard; Batterley, Tim; Bitenc, Urban; Reeves, Andrew; Bharmal, Nazim; Raynaud, Henri-François; Kulcsar, Caroline; Conan, Jean-Marc; Guzman, Dani; De Cos Juez, Javier; Huet, Jean-Michel; Perret, Denis; Dickson, Colin; Atkinson, David; Baillie, Tom; Longmore, Andy; Todd, Stephen; Talbot, Gordon; Morris, Simon; Myers, Richard; Rousset, Gérard

    2013-12-01

    Open-loop adaptive optics has been successfully demonstrated on-sky by several groups, including the fully tomographic MOAO demonstration made using CANARY. MOAO instrumentation such as RAVEN will deliver the first astronomical science and other planned instruments aim to extend both open-loop AO performance and the number of corrected fields. Many of these planned systems rely on the use of tomographic open-loop LGS wavefront sensing. Here we present results from the combined NGS/LGS tomographic CANARY system and then compare the NGS- and LGS-based tomographic system performance. We identify the major system performance drivers, and highlight some potential routes for further exploitation of open-loop tomographic AO.

  4. A low-cost compact metric adaptive optics system

    Mansell, Justin D.; Henderson, Brian; Wiesner, Brennen; Praus, Robert; Coy, Steve

    2007-09-01

    The application of adaptive optics has been hindered by the cost, size, and complexity of the systems. We describe here progress we have made toward creating low-cost compact turn-key adaptive optics systems. We describe our new low-cost deformable mirror technology developed using polymer membranes, the associated USB interface drive electronics, and different ways that this technology can be configured into a low-cost compact adaptive optics system. We also present results of a parametric study of the stochastic parallel gradient descent (SPGD) control algorithm.

  5. Simulating Astronomical Adaptive Optics Systems Using Yao

    Rigaut, François; Van Dam, Marcos

    2013-12-01

    Adaptive Optics systems are at the heart of the coming Extremely Large Telescopes generation. Given the importance, complexity and required advances of these systems, being able to simulate them faithfully is key to their success, and thus to the success of the ELTs. The type of systems envisioned to be built for the ELTs cover most of the AO breeds, from NGS AO to multiple guide star Ground Layer, Laser Tomography and Multi-Conjugate AO systems, with typically a few thousand actuators. This represents a large step up from the current generation of AO systems, and accordingly a challenge for existing AO simulation packages. This is especially true as, in the past years, computer power has not been following Moore's law in its most common understanding; CPU clocks are hovering at about 3GHz. Although the use of super computers is a possible solution to run these simulations, being able to use smaller machines has obvious advantages: cost, access, environmental issues. By using optimised code in an already proven AO simulation platform, we were able to run complex ELT AO simulations on very modest machines, including laptops. The platform is YAO. In this paper, we describe YAO, its architecture, its capabilities, the ELT-specific challenges and optimisations, and finally its performance. As an example, execution speed ranges from 5 iterations per second for a 6 LGS 60x60 subapertures Shack-Hartmann Wavefront sensor Laser Tomography AO system (including full physical image formation and detector characteristics) up to over 30 iterations/s for a single NGS AO system.

  6. Adaptive wide-field optical tomography

    Venugopal, Vivek; Intes, Xavier

    2013-03-01

    We describe a wide-field optical tomography technique, which allows the measurement-guided optimization of illumination patterns for enhanced reconstruction performances. The iterative optimization of the excitation pattern aims at reducing the dynamic range in photons transmitted through biological tissue. It increases the number of measurements collected with high photon counts resulting in a dataset with improved tomographic information. Herein, this imaging technique is applied to time-resolved fluorescence molecular tomography for preclinical studies. First, the merit of this approach is tested by in silico studies in a synthetic small animal model for typical illumination patterns. Second, the applicability of this approach in tomographic imaging is validated in vitro using a small animal phantom with two fluorescent capillaries occluded by a highly absorbing inclusion. The simulation study demonstrates an improvement of signal transmitted (˜2 orders of magnitude) through the central portion of the small animal model for all patterns considered. A corresponding improvement in the signal at the emission wavelength by 1.6 orders of magnitude demonstrates the applicability of this technique for fluorescence molecular tomography. The successful discrimination and localization (˜1 mm error) of the two objects with higher resolution using the optimized patterns compared with nonoptimized illumination establishes the improvement in reconstruction performance when using this technique.

  7. Free-space wavelength-multiplexed optical scanner demonstration.

    Yaqoob, Zahid; Riza, Nabeel A

    2002-09-10

    Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of the scanner response, leading to any desired scanned laser beam power shaping. The experimental setup uses a tunable laser centered at 1560 nm and a 600-grooves/mm blazed reflection grating to accomplish an angular scan of 12.92 degrees as the source is tuned over an 80-nm bandwidth. The values for calculated maximum optical beam divergance, required wavelength resolution, beam-pointing accuracy, and measured scanner insertion loss are 1.076 mrad, 0.172 nm, 0.06 mrad, and 4.88 dB, respectively. PMID:12224780

  8. Optics Demonstration with Student Eyeglasses Using the Inquiry Method

    James, Mark C.

    2011-09-01

    A favorite qualitative optics demonstration I perform in introductory physics classes makes use of students' eyeglasses to introduce converging and diverging lenses. Taking on the persona of a magician, I walk to the back of the classroom and approach a student wearing glasses. The top part of Fig. 1 shows a glasses-wearing student who is farsighted in her left eye and has a slight astigmatism in her right eye.

  9. Architecture and performance of astronomical adaptive optics systems

    Bloemhof, E.

    2002-01-01

    In recent years the technological advances of adaptive optics have enabled a great deal of innovative science. In this lecture I review the system-level design of modern astronomical AO instruments, and discuss their current capabilities.

  10. Solar adaptive optics at the Observatorio del Teide, Tenerife

    Soltau, Dirk; Berkefeld, Thomas; Schmidt, Dirk; von der Lühe, Oskar

    2013-10-01

    Observing the Sun with high angular resolution is difficult because the turbulence in the atmosphere is strongest during day time. In this paper we describe the principles of solar adaptive optics exemplified by the two German solar telescopes VTT and GREGOR at the Observatorio del Teide. With theses systems we obtain near diffraction limited images of the Sun. Ways to overcome the limits of conventional AO by applying multiconjugate adaptive optics (MCAO) are shown.

  11. Contrast-based sensorless adaptive optics for retinal imaging

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T. O.; He, Zheng; Metha, Andrew

    2015-01-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In thi...

  12. Demonstration of a Chip-based Nonlinear Optical Isolator

    Hua, Shiyue; Jiang, Xiaoshun; Hua, Qian; Jiang, Liang; Xiao, Min

    2016-01-01

    Despite fundamentally challenging in integrated (nano)photonics, achieving chip-based light nonreciprocity becomes increasingly urgent in signal processing and optical communications. Because of material incompatibilities in conventional approaches based on Faraday effects, alternative solutions have resorted to nonlinear processes to obtain one-way transmission. However, revealed dynamic reciprocity in a recent theoretical analysis has pinned down the functionalities of these nonlinear isolators. To overcome this dynamic reciprocity, we here report the first demonstration of a nonlinear optical isolator on a silicon chip enforced by phase-matched parametric amplification. Using a high-Q microtoroid resonator, we realize highly nonreciprocal transport at the 1,550 nm wavelength when waves are simultaneously launched in both forward and backward directions. Our design, compatible with current CMOS technique, yields convincing isolation performance with sufficiently low insertion loss for a wide range of input ...

  13. `imaka - a ground-layer adaptive optics system on Maunakea

    Chun, Mark; Toomey, Douglas; Lu, Jessica; Service, Max; Baranec, Christoph; Thibault, Simon; Brousseau, Denis; Hayano, Yutaka; Oya, Shin; Santi, Shane; Kingery, Christopher; Loss, Keith; Gardiner, John; Steele, Brad

    2016-01-01

    We present the integration status for `imaka, the ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. This wide-field GLAO pathfinder system exploits Maunakea's highly confined ground layer and weak free-atmosphere to push the corrected field of view to ~1/3 of a degree, an areal field approaching an order of magnitude larger than any existing or planned GLAO system, with a FWHM ~ 0.33 arcseconds in the visible and near infrared. We discuss the unique design aspects of the instrument, the driving science cases and how they impact the system, and how we will demonstrate these cases on the sky.

  14. Kalman filtering to suppress spurious signals in Adaptive Optics control

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  15. Optical Verification Laboratory Demonstration System for High Security Identification Cards

    Javidi, Bahram

    1997-01-01

    Document fraud including unauthorized duplication of identification cards and credit cards is a serious problem facing the government, banks, businesses, and consumers. In addition, counterfeit products such as computer chips, and compact discs, are arriving on our shores in great numbers. With the rapid advances in computers, CCD technology, image processing hardware and software, printers, scanners, and copiers, it is becoming increasingly easy to reproduce pictures, logos, symbols, paper currency, or patterns. These problems have stimulated an interest in research, development and publications in security technology. Some ID cards, credit cards and passports currently use holograms as a security measure to thwart copying. The holograms are inspected by the human eye. In theory, the hologram cannot be reproduced by an unauthorized person using commercially-available optical components; in practice, however, technology has advanced to the point where the holographic image can be acquired from a credit card-photographed or captured with by a CCD camera-and a new hologram synthesized using commercially-available optical components or hologram-producing equipment. Therefore, a pattern that can be read by a conventional light source and a CCD camera can be reproduced. An optical security and anti-copying device that provides significant security improvements over existing security technology was demonstrated. The system can be applied for security verification of credit cards, passports, and other IDs so that they cannot easily be reproduced. We have used a new scheme of complex phase/amplitude patterns that cannot be seen and cannot be copied by an intensity-sensitive detector such as a CCD camera. A random phase mask is bonded to a primary identification pattern which could also be phase encoded. The pattern could be a fingerprint, a picture of a face, or a signature. The proposed optical processing device is designed to identify both the random phase mask and the

  16. Preliminary field demonstration of a fiber-optic TCE sensor

    We have developed a differential-absorption fiber-optic sensor for use in groundwater and vadose zone monitoring of certain volatile organochlorines. The principle of detection is a quantitative, irreversible chemical reaction that forms visible light-absorbing products. The sensor has been evaluated against gas chromatographic (GC) standard measurements and has demonstrated accuracy and sensitivity sufficient for the environmental monitoring of trace levels of trichloroethylene (TCE) and chloroform. This sensor is currently under evaluation in monitoring well and vadose zone applications. In this paper, we describe the principles of the existing single measurement sensor technology and show preliminary field-test results. 3 refs., 8 figs

  17. Demonstration of optical steganography transmission using temporal phase coded optical signals with spectral notch filtering.

    Hong, Xuezhi; Wang, Dawei; Xu, Lei; He, Sailing

    2010-06-01

    A novel approach is proposed and experimentally demonstrated for optical steganography transmission in WDM networks using temporal phase coded optical signals with spectral notch filtering. A temporal phase coded stealth channel is temporally and spectrally overlaid onto a public WDM channel. Direct detection of the public channel is achieved in the presence of the stealth channel. The interference from the public channel is suppressed by spectral notching before the detection of the optical stealth signal. The approach is shown to have good compatibility and robustness to the existing WDM network for optical steganography transmission. PMID:20588368

  18. In vivo high-resolution retinal imaging using adaptive optics.

    Seyedahmadi, Babak Jian; Vavvas, Demetrios

    2010-01-01

    Retinal imaging with conventional methods is only able to overcome the lowest order of aberration, defocus and astigmatism. The human eye is fraught with higher order of aberrations. Since we are forced to use the human optical system in retinal imaging, the images are degraded. In addition, all of these distortions are constantly changing due to head/eye movement and change in accommodation. Adaptive optics is a promising technology introduced in the field of ophthalmology to measure and compensate for these aberrations. High-resolution obtained by adaptive optics enables us to view and image the retinal photoreceptors, retina pigment epithelium, and identification of cone subclasses in vivo. In this review we will be discussing the basic technology of adaptive optics and hardware requirement in addition to clinical applications of such technology. PMID:21090998

  19. Sensorless adaptive optics and the effect of field of view in biological second harmonic generation microscopy

    Vandendriessche, Stefaan; Vanbel, Maarten K.; Verbiest, Thierry

    2014-05-01

    In light of the population aging in many developed countries, there is a great economical interest in improving the speed and cost-efficiency of healthcare. Clinical diagnosis tools are key to these improvements, with biophotonics providing a means to achieve them. Standard optical microscopy of in vitro biological samples has been an important diagnosis tool since the invention of the microscope, with well known resolution limits. Nonlinear optical imaging improves on the resolution limits of linear microscopy, while providing higher contrast images and a greater penetration depth due to the red-shifted incident light compared to standard optical microscopy. It also provides information on molecular orientation and chirality. Adaptive optics can improve the quality of nonlinear optical images. We analyzed the effect of sensorless adaptive optics on the quality of the nonlinear optical images of biological samples. We demonstrate that care needs to be taken when using a large field of view. Our findings provide information on how to improve the quality of nonlinear optical imaging, and can be generalized to other in vitro biological samples. The image quality improvements achieved by adaptive optics should help speed up clinical diagnostics in vitro, while increasing their accuracy and helping decrease detection limits. The same principles apply to in vivo biological samples, and in the future it may be possible to extend these findings to other nonlinear optical effects used in biological imaging.

  20. Cockpit to helmet optical wireless link: prototype hardware demonstration

    Watson, M. A.; White, H. J.; Aldridge, N. B.; Lam, J.; Atkinson, R.

    2009-09-01

    This paper describes recent progress in developing a wireless optical link between the fuselage of a cockpit and an aviation helmet. Such a link is desired to replace the physical umbilical cable existing in current cockpit systems, for reasons of potential bandwidth, immunity to EM interference, and freedom from physical constraints within the cockpit. The link concept consists of multiple transmitters embedded in the cockpit fuselage, each sending video (or symbology) data out in a cone of light over free space, which is detected by an array of receivers positioned on the helmet - the data is then sent to the eyepieces or visor of the pilot (after any intermediate processing). The design is such that one of these links is always maintained throughout possible movement of the head. In a recent proof-of-principle demonstration we showed uncompressed, 100 Mbps video data streamed live from the fuselage of a cockpit simulator to an angled cluster of silicon-based receivers mounted on the helmet, via a pair of ~1 Watt free-space lasers operating at 810 nm. Fast Ethernet media converters were used here for convenience and cost. The bespoke optical and electrical link components were developed in close collaboration with suppliers. The system performance arises from: the high dynamic range of the receivers (up to 25 dB), which are equipped with optical antennae to magnify the optical gain; the high power of the lasers; and the switching electronics used to control the signal path on the helmet. Future potential improvements to the technology are discussed, with an indication of wireless link requirements for relevant BAE Systems applications.

  1. Horizontal Path Laser Communications Employing MEMS Adaptive Optics Correction

    Thompson, C A; Wilks, S C; Brase, J M; Young, R A; Johnson, G W; Ruggiero, A J

    2001-09-05

    Horizontal path laser communications are beginning to provide attractive alternatives for high-speed optical communications, In particular, companies are beginning to sell fiberless alternatives for intranet and sporting event video. These applications are primarily aimed at short distance applications (on the order of 1 km pathlength). There exists a potential need to extend this pathlength to distances much greater than a 1km. For cases of long distance optical propagation, atmospheric turbulence will ultimately limit the maximum achievable data rate. In this paper, we propose a method of improved signal quality through the use of adaptive optics. In particular, we show work in progress toward a high-speed, small footprint Adaptive Optics system for horizontal path laser communications. Such a system relies heavily on recent progress in Micro-Electro-Mechanical Systems (MEMS) deformable mirrors as well as improved communication and computational components. In this paper we detail two Adaptive Optics approaches for improved through-put, the first is the compensated receiver (the traditional Adaptive Optics approach), the second is the compensated transmitter/receiver. The second approach allows for correction of the optical wavefront before transmission from the transmitter and prior to detection at the receiver.

  2. PASSATA - Object oriented numerical simulation software for adaptive optics

    Agapito, G; Esposito, S

    2016-01-01

    We present the last version of the PyrAmid Simulator Software for Adaptive opTics Arcetri (PASSATA), an IDL and CUDA based object oriented software developed in the Adaptive Optics group of the Arcetri observatory for Monte-Carlo end-to-end adaptive optics simulations. The original aim of this software was to evaluate the performance of a single conjugate adaptive optics system for ground based telescope with a pyramid wavefront sensor. After some years of development, the current version of PASSATA is able to simulate several adaptive optics systems: single conjugate, multi conjugate and ground layer, with Shack Hartmann and Pyramid wavefront sensors. It can simulate from 8m to 40m class telescopes, with diffraction limited and resolved sources at finite or infinite distance from the pupil. The main advantages of this software are the versatility given by the object oriented approach and the speed given by the CUDA implementation of the most computational demanding routines. We describe the software with its...

  3. Photonic crystal-adaptive optical devices

    Buss, Thomas

    This Ph.D. thesis presents methods for enhancing the optical functionality of transparent glass panes by introduction of invisible nanoscale surface structures, such as gratings and planar photonic cyrstals. In this way the primary functionality of the glass - transparancy - may be enhanced with...... new properties, turning window glasses or glass surfaces of hand-held electronics into multifunctional devices. Common to all examples discussed, gratings and photonic crystals are used to engineer the optical dispersion and selectively modify the direction of guided light and transfer free...... minimized, thus allowing a homogeneous, glare-free, white-light daylighting into the room. Even more functionality can be achieved when the optical effects are tunable or reconfigurable. This is investigated with photonic crystal dye lasers. These lasers combine a photonic crystal resonator with a dye...

  4. Adaptive optics ophthalmologic systems using dual deformable mirrors

    Jones, S; Olivier, S; Chen, D; Sadda, S; Joeres, S; Zawadzki, R; Werner, J S; Miller, D

    2007-02-01

    Adaptive Optics (AO) have been increasingly combined with a variety of ophthalmic instruments over the last decade to provide cellular-level, in-vivo images of the eye. The use of MEMS deformable mirrors in these instruments has recently been demonstrated to reduce system size and cost while improving performance. However, currently available MEMS mirrors lack the required range of motion for correcting large ocular aberrations, such as defocus and astigmatism. In order to address this problem, we have developed an AO system architecture that uses two deformable mirrors, in a woofer/tweeter arrangement, with a bimorph mirror as the woofer and a MEMS mirror as the tweeter. This setup provides several advantages, including extended aberration correction range, due to the large stroke of the bimorph mirror, high order aberration correction using the MEMS mirror, and additionally, the ability to ''focus'' through the retina. This AO system architecture is currently being used in four instruments, including an Optical Coherence Tomography (OCT) system and a retinal flood-illuminated imaging system at the UC Davis Medical Center, a Scanning Laser Ophthalmoscope (SLO) at the Doheny Eye Institute, and an OCT system at Indiana University. The design, operation and evaluation of this type of AO system architecture will be presented.

  5. Polymer-based micro deformable mirror for adaptive optics applications

    Zamkotsian, Frederic; Conedera, Veronique; Liotard, Arnaud; Schroeder, Andreas; Fabre, Norbert; Camon, Henri; Lanzoni, Patrick

    2005-01-01

    Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems, for studying new fields like circumstellar disks and extrasolar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. However, only limited strokes for large driving voltages have been demonstrated. In order to overcome these limitations, we are currently developing a micro-deformable mirror based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials, using low-temperature process. This process allows the realization of high optical quality mirrors on top of an actuator array made with various techniques. We have developed the first polymer piston-motion actuator in order to reach high strokes for low driving voltages: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V. Preliminary comparison with FEM models show very good agreement and design of a complete polymer-based MDM looks possible.

  6. Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen

    Ali Hassan; Pieter Gouws

    2014-01-01

    Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was su...

  7. An adaptive coded aperture imager: building, testing and trialing a super-resolving terrestrial demonstrator

    Slinger, Christopher W.; Bennett, Charlotte R.; Dyer, Gavin; Gilholm, Kevin; Gordon, Neil; Huckridge, David; McNie, Mark; Penney, Richard W.; Proudler, Ian K.; Rice, Kevin; Ridley, Kevin D.; Russell, Lee; de Villiers, Geoffrey D.; Watson, Philip J.

    2011-09-01

    There is an increasingly important requirement for day and night, wide field of view imaging and tracking for both imaging and sensing applications. Applications include military, security and remote sensing. We describe the development of a proof of concept demonstrator of an adaptive coded-aperture imager operating in the mid-wave infrared to address these requirements. This consists of a coded-aperture mask, a set of optics and a 4k x 4k focal plane array (FPA). This system can produce images with a resolution better than that achieved by the detector pixel itself (i.e. superresolution) by combining multiple frames of data recorded with different coded-aperture mask patterns. This superresolution capability has been demonstrated both in the laboratory and in imaging of real-world scenes, the highest resolution achieved being ½ the FPA pixel pitch. The resolution for this configuration is currently limited by vibration and theoretically ¼ pixel pitch should be possible. Comparisons have been made between conventional and ACAI solutions to these requirements and show significant advantages in size, weight and cost for the ACAI approach.

  8. Beaconless adaptive-optics technique for HEL beam control

    Khizhnyak, Anatoliy; Markov, Vladimir

    2016-05-01

    Effective performance of forthcoming laser systems capable of power delivery on a distant target requires an adaptive optics system to correct atmospheric perturbations on the laser beam. The turbulence-induced effects are responsible for beam wobbling, wandering, and intensity scintillation, resulting in degradation of the beam quality and power density on the target. Adaptive optics methods are used to compensate for these negative effects. In its turn, operation of the AOS system requires a reference wave that can be generated by the beacon on the target. This report discusses a beaconless approach for wavefront correction with its performance based on the detection of the target-scattered light. Postprocessing of the beacon-generated light field enables retrieval and detailed characterization of the turbulence-perturbed wavefront -data that is essential to control the adaptive optics module of a high-power laser system.

  9. Hybrid Deconvolution of Adaptive Optics Retinal Images from Wavefront Sensing

    Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time. However the correction is partial due to the limitation of hardware. We propose a kind of hybrid image post-processing method, which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image. This method is applied in the image restoration of the vivid human retinal images. The results show that it is effective to improve the retinal image quality

  10. Hybrid Deconvolution of Adaptive Optics Retinal Images from Wavefront Sensing

    TIAN Yu; RAO Chang-Hui; RAO Xue-Jun; WANG Cheng; YU Xiang; LIU Qian; XUE Li-Xia; LING Ning; JIANG Wen-Han

    2008-01-01

    Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time.However the correction is partial due to the limitation of hardware.We propose a kind of hybrid image post-processing method.which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image.This method is applied in the image restoration of the vivid human retinal images.The results show that it is effective to improve the retinal image quality.

  11. Characterization and Operation of Liquid Crystal Adaptive Optics Phoropter

    Awwal, A; Bauman, B; Gavel, D; Olivier, S; Jones, S; Hardy, J L; Barnes, T; Werner, J S

    2003-02-05

    Adaptive optics (AO), a mature technology developed for astronomy to compensate for the effects of atmospheric turbulence, can also be used to correct the aberrations of the eye. The classic phoropter is used by ophthalmologists and optometrists to estimate and correct the lower-order aberrations of the eye, defocus and astigmatism, in order to derive a vision correction prescription for their patients. An adaptive optics phoropter measures and corrects the aberrations in the human eye using adaptive optics techniques, which are capable of dealing with both the standard low-order aberrations and higher-order aberrations, including coma and spherical aberration. High-order aberrations have been shown to degrade visual performance for clinical subjects in initial investigations. An adaptive optics phoropter has been designed and constructed based on a Shack-Hartmann sensor to measure the aberrations of the eye, and a liquid crystal spatial light modulator to compensate for them. This system should produce near diffraction-limited optical image quality at the retina, which will enable investigation of the psychophysical limits of human vision. This paper describes the characterization and operation of the AO phoropter with results from human subject testing.

  12. Axial range of conjugate adaptive optics in two-photon microscopy

    Paudel, Hari P; Mertz, Jerome; Bifano, Thomas

    2015-01-01

    We describe an adaptive optics technique for two-photon microscopy in which the deformable mirror used for aberration compensation is positioned in a plane conjugate to the plane of the aberration. We demonstrate in a proof-of-principle experiment that this technique yields a large field of view advantage in comparison to standard pupil-conjugate adaptive optics. Further, we show that the extended field of view in conjugate AO is maintained over a relatively large axial translation of the deformable mirror with respect to the conjugate plane. We conclude with a discussion of limitations and prospects for the conjugate AO technique in two-photon biological microscopy.

  13. Limitations to adaptive optics image quality in rodent eyes

    Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

    2012-01-01

    Adaptive optics (AO) retinal image quality of rodent eyes is inferior to that of human eyes, despite the promise of greater numerical aperture. This paradox challenges several assumptions commonly made in AO imaging, assumptions which may be invalidated by the very high power and dioptric thickness of the rodent retina. We used optical modeling to compare the performance of rat and human eyes under conditions that tested the validity of these assumptions. Results showed that AO image quality ...

  14. Optical Time-Frequency Packing: Principles, Design, Implementation, and Experimental Demonstration

    Secondini, Marco; Fresi, Francesco; Meloni, Gianluca; Cavaliere, Fabio; Colavolpe, Giulio; Forestieri, Enrico; Potì, Luca; Sabella, Roberto; Prati, Giancarlo

    2014-01-01

    Time-frequency packing (TFP) transmission provides the highest achievable spectral efficiency with a constrained modulation format and detector complexity. In this work, the application of the TFP technique to fiber-optic systems is investigated and experimentally demonstrated. The main theoretical aspects, design guidelines, and implementation issues are discussed, focusing on those aspects which are peculiar to TFP systems. In particular, adaptive compensation of propagation impairments, matched filtering, and maximum a posteriori probability detection are obtained by a combination of a butterfly equalizer and four low-complexity parallel Bahl-Cocke-Jelinek-Raviv (BCJR) detectors. A novel algorithm that ensures adaptive equalization, channel estimation, and a proper distribution of tasks between the equalizer and BCJR detectors is proposed. A set of irregular low-density parity-check codes with different rates is designed to operate at low error rates and approach the spectral efficiency limit achievable by...

  15. Adaptative Multigrid and Variable Parameterization for Optical-flow Estimation

    Memin, Etienne; Pérez, Patrick

    1997-01-01

    We investigate the use of adaptative multigrid minimization algorithms for the estimation of the apparent motion field. The proposed approach provides a coherent and efficient framework for estimating piecewise smooth flow fields for different parameterizations relative to adaptative partitions of the image. The performances of the resulting algorithms are demonstrated in the difficult context of a non convex global energy formulation.

  16. Extreme Adaptive Optics Testbed: Performance and Characterization of a 1024 Deformable Mirror

    Evans, J W; Morzinski, K; Severson, S; Poyneer, L; Macintosh, B; Dillon, D; REza, L; Gavel, D; Palmer, D

    2005-10-30

    We have demonstrated that a microelectrical mechanical systems (MEMS) deformable mirror can be flattened to < 1 nm RMS within controllable spatial frequencies over a 9.2-mm aperture making it a viable option for high-contrast adaptive optics systems (also known as Extreme Adaptive Optics). The Extreme Adaptive Optics Testbed at UC Santa Cruz is being used to investigate and develop technologies for high-contrast imaging, especially wavefront control. A phase shifting diffraction interferometer (PSDI) measures wavefront errors with sub-nm precision and accuracy for metrology and wavefront control. Consistent flattening, required testing and characterization of the individual actuator response, including the effects of dead and low-response actuators. Stability and repeatability of the MEMS devices was also tested. An error budget for MEMS closed loop performance will summarize MEMS characterization.

  17. An adaptive optics system for solid-state laser systems used in inertial confinement fusion

    Using adaptive optics the authors have obtained nearly diffraction-limited 5 kJ, 3 nsec output pulses at 1.053 microm from the Beamlet demonstration system for the National Ignition Facility (NIF). The peak Strehl ratio was improved from 0.009 to 0.50, as estimated from measured wavefront errors. They have also measured the relaxation of the thermally induced aberrations in the main beam line over a period of 4.5 hours. Peak-to-valley aberrations range from 6.8 waves at 1.053 microm within 30 minutes after a full system shot to 3.9 waves after 4.5 hours. The adaptive optics system must have enough range to correct accumulated thermal aberrations from several shots in addition to the immediate shot-induced error. Accumulated wavefront errors in the beam line will affect both the design of the adaptive optics system for NIF and the performance of that system

  18. Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen

    Ali Hassan

    2014-01-01

    Full Text Available Optic disc drusen (ODD are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye.

  19. Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen.

    Hassan, Ali; Gouws, Pieter

    2014-05-01

    Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT) of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye. PMID:25136235

  20. Adaptive optics for control of the laser welding process

    Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

    Praha: Institute of Plasma Physics, 2012 - (Vít, T.; Kovačičinová, J.; Lédl, V.), s. 93-98 ISBN 978-80-87026-02-1. [Optics and Measurement 2012. Liberec (CZ), 16.10.2012-18.10.2012] R&D Projects: GA MPO 2A-3TP1/113; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : laser welding beam shaping * adaptive optics, * power optics * beam shaping Subject RIV: JB - Sensors, Measurment, Regulation

  1. Adaptive optical system for astronomical applications

    Merkle, F.; Bille, J.; Freischlad, K.; Frieben, M.; Jahn, G.; Reischmann, H.-L.

    The active optical system being developed for use with the 0.75-m RC telescope at the Landessternwarte in Heidelberg, FRG, is discussed. A 5-cm electrostatically deformable aluminum-coated polymer mirror (sensitivity 0.05 microns/V, maximum local tilt 3 microns/5 mm) is mounted in a gimbal with piezoelectric-actuator tilt control. The mirror control systems being tested are a modified shearing interferometer with crosstalk-compensated feedback and Fourier-modulus wavefront computation, both using a 32 x 32 diode array as detector. Modal phase compensation is achieved using Zernike polynomials and Karhunen-Loeve functions; the correction for the tilt terms of the series expansion is left to the overall-tilt compensation unit, for which preliminary test results are shown.

  2. Diffractive optical interconnected multichip module: Demonstration and design

    Morris, James Edward, Jr.

    2000-07-01

    Growth in the optical telecom and datacom industries is requiting new methods of manufacture in order to increase quantities by an order of magnitude while decreasing cost. An optical manufacturing approach utilizing wafer scale optics and integration of wafer scale electronics has potential of solving some of these manufacturing issues. An optical interconnected multichip module (OIMCM) is designed and manufactured to prove the technology. This OIMCM consists of integrated CMOS photodetectors, flip-chip compatible laser array chips, high efficiency diffractive optics, and flip-chip self- alignment for precision alignment of 1-2μm. A method to design a single diffractive surface to operate over a 25nm range in wavelength, typical of the variation in a laser diode, is presented. Also of importance is operation of optical systems over a temperature range. A novel method to athermalize an optical system with a laser diode is presented which utilizes a refractive surface and diffractive surface.

  3. Optic flow improves adaptability of spatiotemporal characteristics during split-belt locomotor adaptation with tactile stimulation.

    Eikema, Diderik Jan A; Chien, Jung Hung; Stergiou, Nicholas; Myers, Sara A; Scott-Pandorf, Melissa M; Bloomberg, Jacob J; Mukherjee, Mukul

    2016-02-01

    Human locomotor adaptation requires feedback and feed-forward control processes to maintain an appropriate walking pattern. Adaptation may require the use of visual and proprioceptive input to decode altered movement dynamics and generate an appropriate response. After a person transfers from an extreme sensory environment and back, as astronauts do when they return from spaceflight, the prolonged period required for re-adaptation can pose a significant burden. In our previous paper, we showed that plantar tactile vibration during a split-belt adaptation task did not interfere with the treadmill adaptation however, larger overground transfer effects with a slower decay resulted. Such effects, in the absence of visual feedback (of motion) and perturbation of tactile feedback, are believed to be due to a higher proprioceptive gain because, in the absence of relevant external dynamic cues such as optic flow, reliance on body-based cues is enhanced during gait tasks through multisensory integration. In this study, we therefore investigated the effect of optic flow on tactile-stimulated split-belt adaptation as a paradigm to facilitate the sensorimotor adaptation process. Twenty healthy young adults, separated into two matched groups, participated in the study. All participants performed an overground walking trial followed by a split-belt treadmill adaptation protocol. The tactile group (TC) received vibratory plantar tactile stimulation only, whereas the virtual reality and tactile group (VRT) received an additional concurrent visual stimulation: a moving virtual corridor, inducing perceived self-motion. A post-treadmill overground trial was performed to determine adaptation transfer. Interlimb coordination of spatiotemporal and kinetic variables was quantified using symmetry indices and analyzed using repeated-measures ANOVA. Marked changes of step length characteristics were observed in both groups during split-belt adaptation. Stance and swing time symmetries were

  4. Laser guide stars and adaptive optics for astronomy

    Max, C.E. [ed.

    1992-07-15

    Five papers are included: feasibility experiment for sodium-alyer laser guide stars at LLNL; system design for a high power sodium beacon laser; sodium guide star adaptive optics system for astronomical imaging in the visible and near-infrared; high frame-rate, large field wavefront sensor; and resolution limits for ground-based astronomical imaging. Figs, tabs, refs.

  5. Data-Driven Optimal Control for Adaptive Optics

    Hinnen, K.J.G.

    2007-01-01

    Adaptive optics (AO) is a technique to actively correct the wavefront distortions introduced in a light beam as it propagates through a turbulent medium. Nowadays, it is commonly applied in ground-based telescopes to counteract the devastating effect of atmospheric turbulence. This thesis focuses on

  6. New algorithms for adaptive optics point-spread function reconstruction

    Gendron, E; Fusco, T; Rousset, G; Gendron, Eric; Cl\\'{e}net, Yann; Fusco, Thierry

    2006-01-01

    Context. The knowledge of the point-spread function compensated by adaptive optics is of prime importance in several image restoration techniques such as deconvolution and astrometric/photometric algorithms. Wavefront-related data from the adaptive optics real-time computer can be used to accurately estimate the point-spread function in adaptive optics observations. The only point-spread function reconstruction algorithm implemented on astronomical adaptive optics system makes use of particular functions, named $U\\_{ij}$. These $U\\_{ij}$ functions are derived from the mirror modes, and their number is proportional to the square number of these mirror modes. Aims. We present here two new algorithms for point-spread function reconstruction that aim at suppressing the use of these $U\\_{ij}$ functions to avoid the storage of a large amount of data and to shorten the computation time of this PSF reconstruction. Methods. Both algorithms take advantage of the eigen decomposition of the residual parallel phase covari...

  7. On the influence of the Illuminati in astronomical adaptive optics

    Morzinski, Katie M.; Males, Jared R.

    2012-01-01

    Astronomical adaptive optics (AO) has come into its own. Major O/IR telescopes are achieving diffraction-limited imaging; major facilities are being built with AO as an integral part. To the layperson, it may seem that AO has developed along a serpentine path. However, with a little illumination, the mark of Galileo's heirs becomes apparent in explaining the success of AO.

  8. The AVES adaptive optics spectrograph for the VLT: status report

    Pallavicini, Roberto; Delabre, Bernard; Pasquini, Luca; Zerbi, Filippo M.; Bonanno, Giovanni; Comari, Maurizio; Conconi, Paolo; Mazzoleni, Ruben; Santin, Paolo; Damiani, Francesco; Di Marcantonio, Paolo; Franchini, Mariagrazia; Spano, Paolo; Bonifacio, P.; Catalano, Santo; Molaro, Paolo P.; Randich, S.; Rodono, Marcello

    2003-03-01

    We report on the status of AVES, the Adaptive-optics Visual Echelle Spectrograph proposed for the secondary port of the Nasmyth Adaptive Optics System (NAOS) recently installed at the VLT. AVES is an intermediate resolution (R ≍ 16,000) high-efficiency fixed- format echelle spectrograph which operates in the spectral band 500 - 1,000 nm. In addition to a high intrinsic efficiency, comparable to that of ESI at Keck II, it takes advantage of the adaptive optics correction provided by NAOS to reduce the sky and detector contribution in background-limited observations of weak sources, thus allowing a further magnitude gain with respect to comparable non-adaptive optics spectrographs. Simulations show that the instrument will be capable of reaching a magnitude V = 22.5 at S/N > 10 in two hours, two magnitudes weaker than GIRAFFE at the same resolution and 3 magnitudes weaker than the higher resolution UVES spectrograph. Imaging and coronographic functions have also been implemented in the design. We present the results of the final design study and we dicuss the technical and operational issues related to its implementation at the VLT as a visitor instrument. We also discuss the possibility of using a scaled-up non-adaptive optics version of the same design as an element of a double- or triple-arm intermediate-resolution spectrograph for the VLT. Such an option looks attractive in the context of a high-efficiency large-bandwidth (320 - 1,500 nm) spectrograph ("fast-shooter") being considered by ESO as a 2nd-generation VLT instrument.

  9. Modeling for deformable mirrors and the adaptive optics optimization program

    We discuss aspects of adaptive optics optimization for large fusion laser systems such as the 192-arm National Ignition Facility (NIF) at LLNL. By way of example, we considered the discrete actuator deformable mirror and Hartmann sensor system used on the Beamlet laser. Beamlet is a single-aperture prototype of the 11-0-5 slab amplifier design for NIF, and so we expect similar optical distortion levels and deformable mirror correction requirements. We are now in the process of developing a numerically efficient object oriented C++ language implementation of our adaptive optics and wavefront sensor code, but this code is not yet operational. Results are based instead on the prototype algorithms, coded-up in an interpreted array processing computer language

  10. Computational adaptive optics for broadband interferometric tomography of tissues and cells

    Adie, Steven G.; Mulligan, Jeffrey A.

    2016-03-01

    Adaptive optics (AO) can shape aberrated optical wavefronts to physically restore the constructive interference needed for high-resolution imaging. With access to the complex optical field, however, many functions of optical hardware can be achieved computationally, including focusing and the compensation of optical aberrations to restore the constructive interference required for diffraction-limited imaging performance. Holography, which employs interferometric detection of the complex optical field, was developed based on this connection between hardware and computational image formation, although this link has only recently been exploited for 3D tomographic imaging in scattering biological tissues. This talk will present the underlying imaging science behind computational image formation with optical coherence tomography (OCT) -- a beam-scanned version of broadband digital holography. Analogous to hardware AO (HAO), we demonstrate computational adaptive optics (CAO) and optimization of the computed pupil correction in 'sensorless mode' (Zernike polynomial corrections with feedback from image metrics) or with the use of 'guide-stars' in the sample. We discuss the concept of an 'isotomic volume' as the volumetric extension of the 'isoplanatic patch' introduced in astronomical AO. Recent CAO results and ongoing work is highlighted to point to the potential biomedical impact of computed broadband interferometric tomography. We also discuss the advantages and disadvantages of HAO vs. CAO for the effective shaping of optical wavefronts, and highlight opportunities for hybrid approaches that synergistically combine the unique advantages of hardware and computational methods for rapid volumetric tomography with cellular resolution.

  11. Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

    Jian, Yifan; Xu, Jing; Gradowski, Martin A.; Bonora, Stefano; Zawadzki, Robert J.; Sarunic, Marinko V.

    2014-01-01

    We present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimi...

  12. Contrast enhancement in microscopy of human thyroid tumors by means of acousto-optic adaptive spatial filtering

    Yushkov, Konstantin B.; Molchanov, Vladimir Y.; Belousov, Pavel V.; Abrosimov, Aleksander Y.

    2016-01-01

    We report a method for edge enhancement in the images of transparent samples using analog image processing in coherent light. The experimental technique is based on adaptive spatial filtering with an acousto-optic tunable filter in a telecentric optical system. We demonstrate processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  13. Proton irradiation of liquid crystal based adaptive optical devices

    To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence (1010p/cm2). The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

  14. Characterization of a tunable astigmatic fluidic lens with adaptive optics correction for compact phoropter application

    Fuh, Yiin-Kuen; Huang, Chieh-Tse

    2014-07-01

    Fluidically controlled lenses which adaptively correct prescribed refractive error without mechanically moving parts are extensively applied in the ophthalmic applications. Capable of variable-focusing properties, however, the associated aberrations due to curvature change and refractive index mismatch can inherently degrade image quality severely. Here we present the experimental study of the aberrations in tunable astigmatic lens and use of adaptive optics to compensate for the wavefront errors. Characterization of the optical properties of the individual lenses is carried out by Shack-Hartmann measurements. An adaptive optics (AO) based scheme is demonstrated for three injected fluidic volumes, resulting in a substantial reduction of the wavefront errors from -0.12, -0.25, -0.32 to 0.01, -0.01, -0.20 μm, respectively, corresponding to the optical power tenability of 0.83 to 1.84 D. Furthermore, an integrated optical phoroptor consisting of adjustable astigmatic lenses and AO correction is demonstrated such that an induced refraction error of -1 D cylinder at 180° of a model eye vision is experimentally corrected.

  15. Infinite impulse response modal filtering in visible adaptive optics

    Agapito, G; Quirós-Pacheco, F; Puglisi, A; Esposito, S

    2012-01-01

    Diffraction limited resolution adaptive optics (AO) correction in visible wavelengths requires a high performance control. In this paper we investigate infinite impulse response filters that optimize the wavefront correction: we tested these algorithms through full numerical simulations of a single-conjugate AO system comprising an adaptive secondary mirror with 1127 actuators and a pyramid wavefront sensor (WFS). The actual practicability of the algorithms depends on both robustness and knowledge of the real system: errors in the system model may even worsen the performance. In particular we checked the robustness of the algorithms in different conditions, proving that the proposed method can reject both disturbance and calibration errors.

  16. Infinite impulse response modal filtering in visible adaptive optics

    Agapito, G.; Arcidiacono, C.; Quirós-Pacheco, F.; Puglisi, A.; Esposito, S.

    2012-07-01

    Diffraction limited resolution adaptive optics (AO) correction in visible wavelengths requires a high performance control. In this paper we investigate infinite impulse response filters that optimize the wavefront correction: we tested these algorithms through full numerical simulations of a single-conjugate AO system comprising an adaptive secondary mirror with 1127 actuators and a pyramid wavefront sensor (WFS). The actual practicability of the algorithms depends on both robustness and knowledge of the real system: errors in the system model may even worsen the performance. In particular we checked the robustness of the algorithms in different conditions, proving that the proposed method can reject both disturbance and calibration errors.

  17. Fast calibration of high-order adaptive optics systems

    Kasper, Markus; Fedrigo, Enrico; Looze, Douglas P.; Bonnet, Henri; Ivanescu, Liviu; Oberti, Sylvain

    2004-06-01

    We present a new method of calibrating adaptive optics systems that greatly reduces the required calibration time or, equivalently, improves the signal-to-noise ratio. The method uses an optimized actuation scheme with Hadamard patterns and does not scale with the number of actuators for a given noise level in the wave-front sensor channels. It is therefore highly desirable for high-order systems and/or adaptive secondary systems on a telescope without a Gregorian focal plane. In the latter case, the measurement noise is increased by the effects of the turbulent atmosphere when one is calibrating on a natural guide star.

  18. Precision spectral manipulation: A demonstration using a coherent optical memory

    Sparkes, B. M.; Cairns, C.; Hosseini, M.; Higginbottom, D.; Campbell, G. T.; Lam, P. K.; Buchler, B. C. [Centre for Quantum Computation and Communication Technology, The Australian National University, Canberra (Australia)

    2014-12-04

    The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. Here we present experiments that use a multi-element solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

  19. Adaptive optics for control of the laser welding process

    Jedlička Petr; Řeřucha Šimon; Šarbort Martin; Mrňa Libor

    2013-01-01

    The laser head with fixed focus optics is commonly used for the deep penetration laser welding. In such case the geometry and position of the beam waist are defined by the focusing lens. If the laser beam incident on the focusing lens is not well collimated but divergent and its divergence can be varied by proper adaptive optical elements, then also the geometry and position of the focus will be changeable. In this way it is possible to affect the energy coupling from the laser beam to t...

  20. Adaptive optics for improved retinal surgery and diagnostics

    Humayun, M S; Sadda, S R; Thompson, C A; Olivier, S S; Kartz, M W

    2000-08-21

    It is now possible to field a compact adaptive optics (AO) system on a surgical microscope for use in retinal diagnostics and surgery. Recent developments in integrated circuit technology and optical photonics have led to the capability of building an AO system that is compact and significantly less expensive than traditional AO systems. It is foreseen that such an AO system can be integrated into a surgical microscope while maintaining a package size of a lunchbox. A prototype device can be developed in a manner that lends itself well to large-scale manufacturing.

  1. Neptune and Titan Observed with Keck Telescope Adaptive Optics

    Max, C.E.; Macintosh, B.A.; Gibbard, S.; Gavel, D.T.; Roe, H.; De Pater, I.; Ghez, A.M.; Acton, S.; Wizinowich, P.L.; Lai, O.

    2000-05-05

    The authors report on observations taken during engineering science validation time using the new adaptive optics system at the 10-m Keck II Telescope. They observe Neptune and Titan at near-infrared wavelengths. These objects are ideal for adaptive optics imaging because they are bright and small, yet have many diffraction-limited resolution elements across their disks. In addition Neptune and Titan have prominent physical features, some of which change markedly with time. They have observed infrared-bright storms on Neptune, and very low-albedo surface regions on Titan, Saturn's largest moon, Spatial resolution on Neptune and Titan was 0.05-0.06 and 0.04-0.05 arc sec, respectively.

  2. Contrast-based sensorless adaptive optics for retinal imaging.

    Zhou, Xiaolin; Bedggood, Phillip; Bui, Bang; Nguyen, Christine T O; He, Zheng; Metha, Andrew

    2015-09-01

    Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes. PMID:26417525

  3. Laser Guide Star Adaptive Optics without Tip-tilt

    Davies, R; Lidman, C; Louarn, M Le; Kasper, M; Förster-Schreiber, N M; Roccatagliata, V; Ageorges, N; Amico, P; Dumas, C; Mannucci, F

    2008-01-01

    Adaptive optics (AO) systems allow a telescope to reach its diffraction limit at near infrared wavelengths. But to achieve this, a bright natural guide star (NGS) is needed for the wavefront sensing, severely limiting the fraction of the sky over which AO can be used. To some extent this can be overcome with a laser guide star (LGS). While the laser can be pointed anywhere in the sky, one still needs to have a natural star, albeit fainter, reasonably close to correct the image motion (tip-tilt) to which laser guide stars are insensitive. There are in fact many astronomical targets without suitable tip-tilt stars, but for which the enhanced resolution obtained with the Laser Guide Star Facility (LGSF) would still be very beneficial. This article explores what adaptive optics performance one might expect if one dispenses with the tip-tilt star, and in what situations this mode of observing might be needed.

  4. Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

    Zawadzki, RJ; Jones, SM; Pilli, S; Balderas-Mata, S; Kim, DY; Olivier, SS; Werner, JS

    2011-01-01

    We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was integrated into the previously described AO-UHR OCT instrument with minimal changes to the latter. This was done in order to ensure optimal performance and image quality of the AO- UHR OCT. In this d...

  5. Adaptive optics-assisted optical coherence tomography for imaging of patients with age related macular degeneration

    Sudo, Kenta; Cense, Barry

    2013-03-01

    We developed an optical coherence tomography (OCT) prototype with a sample arm that uses a 3.4 mm beam, which is considerably larger than the 1.2 to 1.5 mm beam that is used in commercialized OCT systems. The system is equipped with adaptive optics (AO), and to distinguish it from traditional AO-OCT systems with a larger 6 mm beam we have coined this concept AO-assisted OCT. Compared to commercialized OCT systems, the 3.4 mm aperture combined with AO improves light collection efficiency and imaging lateral resolution. In this paper, the performance of the AOa-OCT system was compared to a standard OCT system and demonstrated for imaging of age-related macular degeneration (AMD). Measurements were performed on the retinas of three human volunteers with healthy eyes and on one eye of a patient diagnosed with AMD. The AO-assisted OCT system imaged retinal structures of healthy human eyes and a patient eye affected by AMD with higher lateral resolution and a 9° by 9° field of view. This combination of a large isoplanatic patch and high lateral resolution can be expected to fill a gap between standard OCT with a 1.2 mm beam and conventional AO-OCT with a 6 mm beam and a 1.5° by 1.5° isoplanatic patch.

  6. Adaptation technology between IP layer and optical layer in optical Internet

    Ji, Yuefeng; Li, Hua; Sun, Yongmei

    2001-10-01

    Wavelength division multiplexing (WDM) optical network provides a platform with high bandwidth capacity and is supposed to be the backbone infrastructure supporting the next-generation high-speed multi-service networks (ATM, IP, etc.). In the foreseeable future, IP will be the predominant data traffic, to make fully use of the bandwidth of the WDM optical network, many attentions have been focused on IP over WDM, which has been proposed as the most promising technology for new kind of network, so-called Optical Internet. According to OSI model, IP is in the 3rd layer (network layer) and optical network is in the 1st layer (physical layer), so the key issue is what adaptation technology should be used in the 2nd layer (data link layer). In this paper, firstly, we analyze and compare the current adaptation technologies used in backbone network nowadays. Secondly, aiming at the drawbacks of above technologies, we present a novel adaptation protocol (DONA) between IP layer and optical layer in Optical Internet and describe it in details. Thirdly, the gigabit transmission adapter (GTA) we accomplished based on the novel protocol is described. Finally, we set up an experiment platform to apply and verify the DONA and GTA, the results and conclusions of the experiment are given.

  7. Adaptive coded spreading OFDM signal for dynamic-λ optical access network

    Liu, Bo; Zhang, Lijia; Xin, Xiangjun

    2015-12-01

    This paper proposes and experimentally demonstrates a novel adaptive coded spreading (ACS) orthogonal frequency division multiplexing (OFDM) signal for dynamic distributed optical ring-based access network. The wavelength can be assigned to different remote nodes (RNs) according to the traffic demand of optical network unit (ONU). The ACS can provide dynamic spreading gain to different signals according to the split ratio or transmission length, which offers flexible power budget for the network. A 10×13.12 Gb/s OFDM access with ACS is successfully demonstrated over two RNs and 120 km transmission in the experiment. The demonstrated method may be viewed as one promising for future optical metro access network.

  8. The Information Adaptive System - A demonstration of real-time onboard image processing

    Thomas, G. L.; Carney, P. C.; Meredith, B. D.

    1983-01-01

    The Information Adaptive System (IAS) program has the objective to develop and demonstrate, at the brassboard level, an architecture which can be used to perform advanced signal procesing functions on board the spacecraft. Particular attention is given to the processing of high-speed multispectral imaging data in real-time, and the development of advanced technology which could be employed for future space applications. An IAS functional description is provided, and questions of radiometric correction are examined. Problems of data packetization are considered along with data selection, a distortion coefficient processor, an adaptive system controller, an image processing demonstration system, a sensor simulator and output data buffer, a test support and demonstration controller, and IAS demonstration operating modes.

  9. Holographic Adaptive Laser Optics System (HALOS): Fast, Autonomous Aberration Correction

    Andersen, G.; MacDonald, K.; Gelsinger-Austin, P.

    2013-09-01

    We present an adaptive optics system which uses a multiplexed hologram to deconvolve the phase aberrations in an input beam. This wavefront characterization is extremely fast as it is based on simple measurements of the intensity of focal spots and does not require any computations. Furthermore, the system does not require a computer in the loop and is thus much cheaper, less complex and more robust as well. A fully functional, closed-loop prototype incorporating a 32-element MEMS mirror has been constructed. The unit has a footprint no larger than a laptop but runs at a bandwidth of 100kHz over an order of magnitude faster than comparable, conventional systems occupying a significantly larger volume. Additionally, since the sensing is based on parallel, all-optical processing, the speed is independent of actuator number running at the same bandwidth for one actuator as for a million. We are developing the HALOS technology with a view towards next-generation surveillance systems for extreme adaptive optics applications. These include imaging, lidar and free-space optical communications for unmanned aerial vehicles and SSA. The small volume is ideal for UAVs, while the high speed and high resolution will be of great benefit to the ground-based observation of space-based objects.

  10. Adaptive Optical Phase Estimation Using Time-Symmetric Quantum Smoothing

    Wheatley, T A; Yonezawa, H; Nakane, D; Arao, H; Pope, D T; Ralph, T C; Wiseman, H M; Furusawa, A; Huntington, E H

    2009-01-01

    Quantum parameter estimation has many applications, from gravitational wave detection to quantum key distribution. We present the first experimental demonstration of the time-symmetric technique of quantum smoothing. We consider both adaptive and non-adaptive quantum smoothing, and show that both are better than their well-known time-asymmetric counterparts (quantum filtering). For the problem of estimating a stochastically varying phase shift on a coherent beam, our theory predicts that adaptive quantum smoothing (the best scheme) gives an estimate with a mean-square error up to $2\\sqrt{2}$ times smaller than that from non-adaptive quantum filtering (the standard quantum limit). The experimentally measured improvement is $2.24 \\pm 0.14$.

  11. Thermally tuneable optical modulator adapted for differential signaling

    Zortman, William A.

    2016-01-12

    An apparatus for optical modulation is provided. The apparatus includes a modulator structure and a heater structure. The modulator structure comprises a ring or disk optical resonator having a closed curvilinear periphery and a pair of oppositely doped semiconductor regions within and/or adjacent to the optical resonator and conformed to modify the optical length of the optical resonator upon application of a bias voltage. The heater structure comprises a relatively resistive annulus of semiconductor material enclosed between an inner disk and an outer annulus of relatively conductive semiconductor material. The inner disk and the outer annulus are adapted as contact regions for a heater activation current. The heater structure is situated within the periphery of the optical resonator such that in operation, at least a portion of the resonator is heated by radial conductive heat flow from the heater structure. The apparatus further includes a substantially annular isolation region of dielectric or relatively resistive semiconductor material interposed between the heater structure and the modulator structure. The isolation region is effective to electrically isolate the bias voltage from the heater activation current.

  12. Manufacturing of glassy thin shell for adaptive optics: results achieved

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  13. Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

    Keller, Brenton; Cunefare, David; Grewal, Dilraj S.; Mahmoud, Tamer H.; Izatt, Joseph A.; Farsiu, Sina

    2016-07-01

    We introduce a metric in graph search and demonstrate its application for segmenting retinal optical coherence tomography (OCT) images of macular pathology. Our proposed "adjusted mean arc length" (AMAL) metric is an adaptation of the lowest mean arc length search technique for automated OCT segmentation. We compare this method to Dijkstra's shortest path algorithm, which we utilized previously in our popular graph theory and dynamic programming segmentation technique. As an illustrative example, we show that AMAL-based length-adaptive segmentation outperforms the shortest path in delineating the retina/vitreous boundary of patients with full-thickness macular holes when compared with expert manual grading.

  14. Adaptive synchronization in chaotic laser diodes subject to optical feedback(s)

    In this paper a proposal is made of an adaptive coupling function for achieving synchronization between two lasers subject to optical feedback. Such a control scheme requires knowledge of the systems' parameters. For the first time we demonstrate that when these parameters are not available on-line parameter estimation can be applied. Generalization of the approach to the multi-feedback systems is also presented. (author)

  15. Experimental demonstration of remote, passive acousto-optic sensing.

    Antonelli, Lynn; Blackmon, Fletcher

    2004-12-01

    Passively detecting underwater sound from the air can allow aircraft and surface vessels to monitor the underwater acoustic environment. Experimental research into an optical hydrophone is being conducted for remote, aerial detection of underwater sound. A laser beam is directed onto the water surface to measure the velocity of the vibrations occurring as the underwater acoustic signal reaches the water surface. The acoustically generated surface vibrations modulate the phase of the laser beam. Sound detection occurs when the laser is reflected back towards the sensor. Therefore, laser alignment on the specularly reflecting water surface is critical. As the water surface moves, the laser beam is reflected away from the photodetector and no signal is obtained. One option to mitigate this problem is to continually steer the laser onto a spot on the water surface that provides a direct back-reflection. Results are presented from a laboratory test that investigates the feasibility of the acousto-optic sensor detection on hydrostatic and hydrodynamic surfaces using a laser Doppler vibrometer in combination with a laser-based, surface normal glint tracker for remotely detecting underwater sound. This paper outlines the acousto-optic sensor and tracker concepts and presents experimental results comparing sensor operation under various sea surface conditions. PMID:15658691

  16. Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

    Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

    2015-12-28

    An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network. PMID:26832033

  17. Computational adaptive optics for broadband optical interferometric tomography of biological tissue

    Boppart, Stephen A.

    2015-03-01

    High-resolution real-time tomography of biological tissues is important for many areas of biological investigations and medical applications. Cellular level optical tomography, however, has been challenging because of the compromise between transverse imaging resolution and depth-of-field, the system and sample aberrations that may be present, and the low imaging sensitivity deep in scattering tissues. The use of computed optical imaging techniques has the potential to address several of these long-standing limitations and challenges. Two related techniques are interferometric synthetic aperture microscopy (ISAM) and computational adaptive optics (CAO). Through three-dimensional Fourierdomain resampling, in combination with high-speed OCT, ISAM can be used to achieve high-resolution in vivo tomography with enhanced depth sensitivity over a depth-of-field extended by more than an order-of-magnitude, in realtime. Subsequently, aberration correction with CAO can be performed in a tomogram, rather than to the optical beam of a broadband optical interferometry system. Based on principles of Fourier optics, aberration correction with CAO is performed on a virtual pupil using Zernike polynomials, offering the potential to augment or even replace the more complicated and expensive adaptive optics hardware with algorithms implemented on a standard desktop computer. Interferometric tomographic reconstructions are characterized with tissue phantoms containing sub-resolution scattering particles, and in both ex vivo and in vivo biological tissue. This review will collectively establish the foundation for high-speed volumetric cellular-level optical interferometric tomography in living tissues.

  18. Demonstration of Optically Controlled re-Routing in a Photonic Crystal Three-Port Switch

    Combrié, S.; Heuck, Mikkel; Xavier, S.;

    2012-01-01

    We present an experimental demonstration of optically controlled re-routing of a signal in a photonic crystal cavity-waveguide structure with 3 ports. This represents a key functionality of integrated all-optical signal processing circuits.......We present an experimental demonstration of optically controlled re-routing of a signal in a photonic crystal cavity-waveguide structure with 3 ports. This represents a key functionality of integrated all-optical signal processing circuits....

  19. Experimental demonstration of a scalable sliceable transceiver for optical access networks

    Spolitis, Sandis; Wagner, Christoph; Vegas Olmos, Juan José; Bobrovs, V.; Ivanovs, G.; Tafur Monroy, Idelfonso

    2014-01-01

    We experimentally demonstrate signal spectrum slicing technique, which is a promising solution to increase the data transmission bitrate in cost sensitive optical access networks without upgrading any existing electrical or optical components.......We experimentally demonstrate signal spectrum slicing technique, which is a promising solution to increase the data transmission bitrate in cost sensitive optical access networks without upgrading any existing electrical or optical components....

  20. Adapting smartphones for low-cost optical medical imaging

    Pratavieira, Sebastião.; Vollet-Filho, José D.; Carbinatto, Fernanda M.; Blanco, Kate; Inada, Natalia M.; Bagnato, Vanderlei S.; Kurachi, Cristina

    2015-06-01

    Optical images have been used in several medical situations to improve diagnosis of lesions or to monitor treatments. However, most systems employ expensive scientific (CCD or CMOS) cameras and need computers to display and save the images, usually resulting in a high final cost for the system. Additionally, this sort of apparatus operation usually becomes more complex, requiring more and more specialized technical knowledge from the operator. Currently, the number of people using smartphone-like devices with built-in high quality cameras is increasing, which might allow using such devices as an efficient, lower cost, portable imaging system for medical applications. Thus, we aim to develop methods of adaptation of those devices to optical medical imaging techniques, such as fluorescence. Particularly, smartphones covers were adapted to connect a smartphone-like device to widefield fluorescence imaging systems. These systems were used to detect lesions in different tissues, such as cervix and mouth/throat mucosa, and to monitor ALA-induced protoporphyrin-IX formation for photodynamic treatment of Cervical Intraepithelial Neoplasia. This approach may contribute significantly to low-cost, portable and simple clinical optical imaging collection.

  1. Adaptive noise reduction for fiber optic gyroscopes in borehole applications

    Yan, Tingyang; Zhang, Chunxi; Gao, Shuang; Ma, Zongfeng

    2006-11-01

    Fiber Optic Gyroscopes (FOGs) have been investigated and proposed as alternative sensors to magnetometers in borehole surveying applications due to their compactness, ruggedness, low cost and high environmental insensitivity. However, FOGs are subject to high measurement noise from various sources, which deteriorates the performance and quality of FOGs, thus the overall system accuracy is limited. To improve the accuracy of the surveying system, adaptive filtering techniques are utilized to reduce the noise level at the output of the FOG. A Forward Linear Prediction (FLP) filter based on Normalized Least-Mean-Square (NLMS) adaptive algorithm was designed and evaluated using kinematic data. Results show that the FLP filter can suppress the FOG noise to a certain degree and a satisfactory signal-to-noise ratio improvement can be achieved using this method.

  2. Night myopia studied with an adaptive optics visual analyzer.

    Pablo Artal

    Full Text Available PURPOSE: Eyes with distant objects in focus in daylight are thought to become myopic in dim light. This phenomenon, often called "night myopia" has been studied extensively for several decades. However, despite its general acceptance, its magnitude and causes are still controversial. A series of experiments were performed to understand night myopia in greater detail. METHODS: We used an adaptive optics instrument operating in invisible infrared light to elucidate the actual magnitude of night myopia and its main causes. The experimental setup allowed the manipulation of the eye's aberrations (and particularly spherical aberration as well as the use of monochromatic and polychromatic stimuli. Eight subjects with normal vision monocularly determined their best focus position subjectively for a Maltese cross stimulus at different levels of luminance, from the baseline condition of 20 cd/m(2 to the lowest luminance of 22 × 10(-6 cd/m(2. While subjects performed the focusing tasks, their eye's defocus and aberrations were continuously measured with the 1050-nm Hartmann-Shack sensor incorporated in the adaptive optics instrument. The experiment was repeated for a variety of controlled conditions incorporating specific aberrations of the eye and chromatic content of the stimuli. RESULTS: We found large inter-subject variability and an average of -0.8 D myopic shift for low light conditions. The main cause responsible for night myopia was the accommodation shift occurring at low light levels. Other factors, traditionally suggested to explain night myopia, such as chromatic and spherical aberrations, have a much smaller effect in this mechanism. CONCLUSIONS: An adaptive optics visual analyzer was applied to study the phenomenon of night myopia. We found that the defocus shift occurring in dim light is mainly due to accommodation errors.

  3. Demonstration of optically controlled data routing with the use of multiple-quantum-well bistable and electro-optical devices

    Koppa, Pàl; Chavel, Pierre; Oudar, Jean-Louis; Kuszelewicz, Robert; Schnell, Jean-Philippe; Pocholle, Jean-Paul

    1997-01-01

    We present experimental results on a 1-to-64-channel free-space photonic switching demonstration system based on GaAs/GaAlAs multiple-quantum-well active device arrays. Two control schemes are demonstrated: data transparent optical self-routing usable in a packet-switching environment and direct optical control with potential signal amplification for circuit switching. The self-routing operation relies on the optical recognition of the binary destination address coded in each packet header. A...

  4. High Resolution Observations using Adaptive Optics: Achievements and Future Needs

    K. Sankarasubramanian; T. Rimmele

    2008-03-01

    Over the last few years, several interesting observations were obtained with the help of solar Adaptive Optics (AO). In this paper, few observations made using the solarAOare enlightened and briefly discussed. A list of disadvantages with the current AO system are presented. With telescopes larger than 1.5 m expected during the next decade, there is a need to develop the existing AO technologies for large aperture telescopes. Some aspects of this development are highlighted. Finally, the recent AO developments in India are also presented.

  5. Self-characterization of linear and nonlinear adaptive optics systems.

    Hampton, Peter J; Conan, Rodolphe; Keskin, Onur; Bradley, Colin; Agathoklis, Pan

    2008-01-10

    We present methods used to determine the linear or nonlinear static response and the linear dynamic response of an adaptive optics (AO) system. This AO system consists of a nonlinear microelectromechanical systems deformable mirror (DM), a linear tip-tilt mirror (TTM), a control computer, and a Shack-Hartmann wavefront sensor. The system is modeled using a single-input-single-output structure to determine the one-dimensional transfer function of the dynamic response of the chain of system hardware. An AO system has been shown to be able to characterize its own response without additional instrumentation. Experimentally determined models are given for a TTM and a DM. PMID:18188192

  6. Third MACAO-VLTI Curvature Adaptive Optics System now installed

    Arsenault, R.; Donaldson, R.; Dupuy, C.; Fedrigo, E.; Hubin, N.; Ivanescu, L.; Kasper, M.; Oberti, S.; Paufique, J.; Rossi, S.; Silber, A.; Delabre, B.; Lizon, J.-L.; Gigan, P.

    2004-09-01

    IN JULY of this year the MACAO team returned to Paranal for the third time to install another MACAOVLTI system. These are 4 identical 60 element curvature adaptive optics systems, located in the Coudé room of each UT whose aim is to feed a turbulence corrected wavefront to the VLTI Recombination Laboratory. This time the activities took place on Yepun (UT4). The naming convention has been to associate the MACAO-VLTI number to the UT number where it is installed. Therefore, although we speak here of MACAO#4, it is the third system installed in Paranal.

  7. Performance of the Gemini Planet Imager's adaptive optics system.

    Poyneer, Lisa A; Palmer, David W; Macintosh, Bruce; Savransky, Dmitry; Sadakuni, Naru; Thomas, Sandrine; Véran, Jean-Pierre; Follette, Katherine B; Greenbaum, Alexandra Z; Ammons, S Mark; Bailey, Vanessa P; Bauman, Brian; Cardwell, Andrew; Dillon, Daren; Gavel, Donald; Hartung, Markus; Hibon, Pascale; Perrin, Marshall D; Rantakyrö, Fredrik T; Sivaramakrishnan, Anand; Wang, Jason J

    2016-01-10

    The Gemini Planet Imager's adaptive optics (AO) subsystem was designed specifically to facilitate high-contrast imaging. A definitive description of the system's algorithms and technologies as built is given. 564 AO telemetry measurements from the Gemini Planet Imager Exoplanet Survey campaign are analyzed. The modal gain optimizer tracks changes in atmospheric conditions. Science observations show that image quality can be improved with the use of both the spatially filtered wavefront sensor and linear-quadratic-Gaussian control of vibration. The error budget indicates that for all targets and atmospheric conditions AO bandwidth error is the largest term. PMID:26835769

  8. Adaptive optics optical coherence tomography for in vivo mouse retinal imaging

    Jian, Yifan; Zawadzki, Robert J.; Sarunic, Marinko V.

    2013-05-01

    Small animal models of retinal diseases are important to vision research, and noninvasive high resolution in vivo rodent retinal imaging is becoming an increasingly important tool used in this field. We present a custom Fourier domain optical coherence tomography (FD-OCT) instrument for high resolution imaging of mouse retina. In order to overcome aberrations in the mouse eye, we incorporated a commercial adaptive optics system into the sample arm of the refractive FD-OCT system. Additionally, a commercially available refraction canceling lens was used to reduce lower order aberrations and specular back-reflection from the cornea. Performance of the adaptive optics (AO) system for correcting residual wavefront aberration in the mice eyes is presented. Results of AO FD-OCT images of mouse retina acquired in vivo with and without AO correction are shown as well.

  9. Six-channel adaptive fibre-optic interferometer

    Romashko, R V; Bezruk, M N; Kamshilin, A A; Kulchin, Yurii N

    2012-06-30

    We have proposed and analysed a scheme for the multiplexing of orthogonal dynamic holograms in photorefractive crystals which ensures almost zero cross talk between the holographic channels upon phase demodulation. A six-channel adaptive fibre-optic interferometer was built, and the detection limit for small phase fluctuations in the channels of the interferometer was determined to be 2.1 Multiplication-Sign 10{sup -8} rad W{sup 1/2} Hz{sup -1/2}. The channel multiplexing capacity of the interferometer was estimated. The formation of 70 channels such that their optical fields completely overlap in the crystal reduces the relative detection limit in the working channel by just 10 %. We found conditions under which the maximum cross talk between the channels was within the intrinsic noise level in the channels (-47 dB).

  10. Experience with wavefront sensor and deformable mirror interfaces for wide-field adaptive optics systems

    Basden, A G; Bharmal, N A; Bitenc, U; Brangier, M; Buey, T; Butterley, T; Cano, D; Chemla, F; Clark, P; Cohen, M; Conan, J -M; de Cos, F J; Dickson, C; Dipper, N A; Dunlop, C N; Feautrier, P; Fusco, T; Gach, J L; Gendron, E; Geng, D; Goodsell, S J; Gratadour, D; Greenaway, A H; Guesalaga, A; Guzman, C D; Henry, D; Holck, D; Hubert, Z; Huet, J M; Kellerer, A; Kulcsar, C; Laporte, P; Roux, B Le; Looker, N; Longmore, A J; Marteaud, M; Martin, O; Meimon, S; Morel, C; Morris, T J; Myers, R M; Osborn, J; Perret, D; Petit, C; Raynaud, H; Reeves, A P; Rousset, G; Lasheras, F Sanchez; Rodriguez, M Sanchez; Santos, J D; Sevin, A; Sivo, G; Stadler, E; Stobie, B; Talbot, G; Todd, S; Vidal, F; Younger, E J

    2016-01-01

    Recent advances in adaptive optics (AO) have led to the implementation of wide field-of-view AO systems. A number of wide-field AO systems are also planned for the forthcoming Extremely Large Telescopes. Such systems have multiple wavefront sensors of different types, and usually multiple deformable mirrors (DMs). Here, we report on our experience integrating cameras and DMs with the real-time control systems of two wide-field AO systems. These are CANARY, which has been operating on-sky since 2010, and DRAGON, which is a laboratory adaptive optics real-time demonstrator instrument. We detail the issues and difficulties that arose, along with the solutions we developed. We also provide recommendations for consideration when developing future wide-field AO systems.

  11. Recent Results and Perspectives for Precision Astrometry and Photometry with Adaptive Optics

    Lu, Jessica R; Yelda, Sylvana; Do, Tuan; Clarkson, Will; McCrady, Nate; Morris, Mark R

    2010-01-01

    Large ground-based telescopes equipped with adaptive optics (AO) systems have ushered in a new era of high-resolution infrared photometry and astrometry. Relative astrometric accuracies of <0.2 mas have already been demonstrated from infrared images with spatial resolutions of 55-95 mas resolution over 10-20'' fields of view. Relative photometric accuracies of 3% and absolute photometric accuracies of 5%-20% are also possible. I will review improvements and current limitations in astrometry and photometry with adaptive optics of crowded stellar fields. These capabilities enable experiments such as measuring orbits for brown dwarfs and exoplanets, studying our Galaxy's supermassive black hole and its environment, and identifying individual stars in young star clusters, which can be used test the universality of the initial mass function.

  12. Image restoration of the open-loop adaptive optics retinal imaging system based on optical transfer function analysis

    Yu, Lei; Qi, Yue; Li, Dayu; Xia, Mingliang; Xuan, Li

    2013-07-01

    The residual aberrations of the adaptive optics retinal imaging system will decrease the quality of the retinal images. To overcome this obstacle, we found that the optical transfer function (OTF) of the adaptive optics retinal imaging system can be described as the Levy stable distribution. Then a new method is introduced to estimate the OTF of the open-loop adaptive optics system, based on analyzing the residual aberrations of the open-loop adaptive optics system in the residual aberrations measuring mode. At last, the estimated OTF is applied to restore the retinal images of the open-loop adaptive optics retinal imaging system. The contrast and resolution of the restored image is significantly improved with the Laplacian sum (LS) from 0.0785 to 0.1480 and gray mean grads (GMG) from 0.0165 to 0.0306.

  13. Ergodic capacity comparison of optical wireless communications using adaptive transmissions.

    Hassan, Md Zoheb; Hossain, Md Jahangir; Cheng, Julian

    2013-08-26

    Ergodic capacity is investigated for the optical wireless communications employing subcarrier intensity modulation with direct detection, and coherent systems with and without polarization multiplexing over the Gamma-Gamma turbulence channels. We consider three different adaptive transmission schemes: (i) variable-power, variable-rate adaptive transmission, (ii) complete channel inversion with fixed rate, and (iii) truncated channel inversion with fixed rate. For the considered systems, highly accurate series expressions for ergodic capacity are derived using a series expansion of the modified Bessel function and the Mellin transformation of the Gamma-Gamma random variable. Our asymptotic analysis reveals that the high SNR ergodic capacities of coherent, subcarrier intensity modulated, and polarization multiplexing systems gain 0.33 bits/s/Hz, 0.66 bits/s/Hz, and 0.66 bits/s/Hz respectively with 1 dB increase of average transmitted optical power. Numerical results indicate that a polarization control error less than 10° has little influence on the capacity performance of polarization multiplexing systems. PMID:24105580

  14. Adaptive Optics Imaging Survey of Luminous Infrared Galaxies

    Laag, E A; Canalizo, G; van Breugel, W; Gates, E L; de Vries, W; Stanford, S A

    2006-03-13

    We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L{sub FIR} {ge} 10{sup 12} L{sub {circle_dot}}) and 19 new LIGs (with L{sub FIR} {ge} 10{sup 11} L{sub {circle_dot}}). Twenty of the galaxies in the sample were imaged with either the Lick or Keck adaptive optics systems in H or K{prime}. Galaxy morphologies were determined using the two dimensional fitting program GALFIT and the residuals examined to look for interesting structure. The morphologies reveal that at least 30% are involved in tidal interactions, with 20% being clear mergers. An additional 50% show signs of possible interaction. Line ratios were used to determine powering mechanism; of the 17 objects in the sample showing clear emission lines--four are active galactic nuclei and seven are starburst galaxies. The rest exhibit a combination of both phenomena.

  15. Multi-Conjugate Adaptive Optics images of the Trapezium Cluster

    Bouy, H; Marchetti, E; Martín, E L; Huélamo, N; Navascues, D Barrado y

    2007-01-01

    Multi-Conjugate Adaptive Optics (MCAO) combines the advantages of standard adaptive optics, which provides high contrast and high spatial resolution, and of wide field ~1' imaging. Up to recently, MCAO for astronomy was limited to laboratory experiments. In this paper, we present the first scientific results obtained with the first MCAO instrument put on the sky. We present a new study of the Trapezium cluster using deep MCAO images with a field of view of 1'x1' obtained at the VLT. We have used deep J, H and Ks images recently obtained with the prototype MCAO facility MAD at the VLT in order to search for new members and new multiple systems in the Trapezium cluster. On bright targets (Ks~9mag), these images allow us to reach DeltaKs~6mag as close as 0.4" We report the detection of 128 sources, including 10 new faint objects in the magnitude range between 16.1

  16. Non-iterative adaptive optical microscopy using wavefront sensing

    Tao, X.; Azucena, O.; Kubby, J.

    2016-03-01

    This paper will review the development of wide-field and confocal microscopes with wavefront sensing and adaptive optics for correcting refractive aberrations and compensating scattering when imaging through thick tissues (Drosophila embryos and mouse brain tissue). To make wavefront measurements in biological specimens we have modified the laser guide-star techniques used in astronomy for measuring wavefront aberrations that occur as star light passes through Earth's turbulent atmosphere. Here sodium atoms in Earth's mesosphere, at an altitude of 95 km, are excited to fluoresce at resonance by a high-power sodium laser. The fluorescent light creates a guide-star reference beacon at the top of the atmosphere that can be used for measuring wavefront aberrations that occur as the light passes through the atmosphere. We have developed a related approach for making wavefront measurements in biological specimens using cellular structures labeled with fluorescent proteins as laser guide-stars. An example is a fluorescently labeled centrosome in a fruit fly embryo or neurons and dendrites in mouse brains. Using adaptive optical microscopy we show that the Strehl ratio, the ratio of the peak intensity of an aberrated point source relative to the diffraction limited image, can be improved by an order of magnitude when imaging deeply into live dynamic specimens, enabling near diffraction limited deep tissue imaging.

  17. AVES: an adaptive optics visual echelle spectrograph for the VLT

    Pasquini, Luca; Delabre, Bernard; Avila, Gerardo; Bonaccini, Domenico

    1998-07-01

    We present the preliminary study of a low cost, high performance spectrograph for the VLT, for observations in the V, R and I bands. This spectrograph is meant for intermediate (R equals 16,000) resolution spectroscopy of faint (sky and/or detector limited) sources, with particular emphasis on the study of solar-type (F-G) stars belonging to the nearest galaxies and to distant (or highly reddened) galactic clusters. The spectrograph is designed to use the adaptive optics (AO) systems at the VLT Telescope. Even if these AO systems will not provide diffraction limited images in the V, R and I bands, the photon concentration will still be above approximately 60% of the flux in an 0.3 arcsecond aperture for typical Paranal conditions. This makes the construction of a compact, cheap and efficient echelle spectrograph possible. AVES will outperform comparable non adaptive optic instruments by more than one magnitude for sky- and/or detector-limited observations, and it will be very suitable for observations in crowded fields.

  18. Adaptive distributed Kalman filtering with wind estimation for astronomical adaptive optics.

    Massioni, Paolo; Gilles, Luc; Ellerbroek, Brent

    2015-12-01

    In the framework of adaptive optics (AO) for astronomy, it is a common assumption to consider the atmospheric turbulent layers as "frozen flows" sliding according to the wind velocity profile. For this reason, having knowledge of such a velocity profile is beneficial in terms of AO control system performance. In this paper we show that it is possible to exploit the phase estimate from a Kalman filter running on an AO system in order to estimate wind velocity. This allows the update of the Kalman filter itself with such knowledge, making it adaptive. We have implemented such an adaptive controller based on the distributed version of the Kalman filter, for a realistic simulation of a multi-conjugate AO system with laser guide stars on a 30 m telescope. Simulation results show that this approach is effective and promising and the additional computational cost with respect to the distributed filter is negligible. Comparisons with a previously published slope detection and ranging wind profiler are made and the impact of turbulence profile quantization is assessed. One of the main findings of the paper is that all flavors of the adaptive distributed Kalman filter are impacted more significantly by turbulence profile quantization than the static minimum mean square estimator which does not incorporate wind profile information. PMID:26831389

  19. Experimental demonstration of an adaptive architecture for direct spectral imaging classification.

    Dunlop-Gray, Matthew; Poon, Phillip K; Golish, Dathon; Vera, Esteban; Gehm, Michael E

    2016-08-01

    Spectral imaging is a powerful tool for providing in situ material classification across a spatial scene. Typically, spectral imaging analyses are interested in classification, though often the classification is performed only after reconstruction of the spectral datacube. We present a computational spectral imaging system, the Adaptive Feature-Specific Spectral Imaging Classifier (AFSSI-C), which yields direct classification across the spatial scene without reconstruction of the source datacube. With a dual disperser architecture and a programmable spatial light modulator, the AFSSI-C measures specific projections of the spectral datacube which are generated by an adaptive Bayesian classification and feature design framework. We experimentally demonstrate multiple order-of-magnitude improvement of classification accuracy in low signal-to-noise (SNR) environments when compared to legacy spectral imaging systems. PMID:27505794

  20. Adaptive optics microscopy enhances image quality in deep layers of CLARITY processed brains of YFP-H mice

    Reinig, Marc R.; Novack, Samuel W.; Tao, Xiaodong; Ermini, Florian; Bentolila, Laurent A.; Roberts, Dustin G.; MacKenzie-Graham, Allan; Godshalk, S. E.; Raven, M. A.; Kubby, Joel

    2016-03-01

    Optical sectioning of biological tissues has become the method of choice for three-dimensional histological analyses. This is particularly important in the brain were neurons can extend processes over large distances and often whole brain tracing of neuronal processes is desirable. To allow deeper optical penetration, which in fixed tissue is limited by scattering and refractive index mismatching, tissue-clearing procedures such as CLARITY have been developed. CLARITY processed brains have a nearly uniform refractive index and three-dimensional reconstructions at cellular resolution have been published. However, when imaging in deep layers at submicron resolution some limitations caused by residual refractive index mismatching become apparent, as the resulting wavefront aberrations distort the microscopic image. The wavefront can be corrected with adaptive optics. Here, we investigate the wavefront aberrations at different depths in CLARITY processed mouse brains and demonstrate the potential of adaptive optics to enable higher resolution and a better signal-to-noise ratio. Our adaptive optics system achieves high-speed measurement and correction of the wavefront with an open-loop control using a wave front sensor and a deformable mirror. Using adaptive optics enhanced microscopy, we demonstrate improved image quality wavefront, point spread function, and signal to noise in the cortex of YFP-H mice.

  1. Fast binarized time-reversed adapted-perturbation (b-TRAP) optical focusing inside scattering media

    Ma, Cheng; Liu, Yan; Wang, Lihong V

    2015-01-01

    Light scattering inhibits high-resolution optical imaging, manipulation and therapy deep inside biological tissue by preventing focusing. To form deep foci, wavefront-shaping and time-reversal techniques that break the optical diffusion limit have been developed. For in vivo applications, such focusing must provide high gain, high speed, and a large number of spatial modes. However, none of the previous techniques meet these requirements simultaneously. Here, we overcome this challenge by rapidly measuring the perturbed optical field within a single camera exposure followed by adaptively time-reversing the phase-binarized perturbation. Consequently, a phase-conjugated wavefront is synthesized within a millisecond, two orders of magnitude shorter than the digitally achieved record. We demonstrated real-time focusing in dynamic scattering media, and extended laser speckle contrast imaging to new depths. The unprecedented combination of fast response, high gain, and large mode count makes this work a major strid...

  2. High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

    Evans, J W

    2006-08-18

    Direct imaging of extrasolar planets is an important, but challenging, next step in planetary science. Most planets identified to date have been detected indirectly--not by emitted or reflected light but through the effect of the planet on the parent star. For example, radial velocity techniques measure the doppler shift in the spectrum of the star produced by the presence of a planet. Indirect techniques only probe about 15% of the orbital parameter space of our solar system. Direct methods would probe new parameter space, and the detected light can be analyzed spectroscopically, providing new information about detected planets. High contrast adaptive optics systems, also known as Extreme Adaptive Optics (ExAO), will require contrasts of between 10{sup -6} and 10{sup -7} at angles of 4-24 {lambda}/D on an 8-m class telescope to image young Jupiter-like planets still warm with the heat of formation. Contrast is defined as the intensity ratio of the dark wings of the image, where a planet might be, to the bright core of the star. Such instruments will be technically challenging, requiring high order adaptive optics with > 2000 actuators and improved diffraction suppression. Contrast is ultimately limited by residual static wavefront errors, so an extrasolar planet imager will require wavefront control with an accuracy of better than 1 nm rms within the low- to mid-spatial frequency range. Laboratory demonstrations are critical to instrument development. The ExAO testbed at the Laboratory for Adaptive Optics was designed with low wavefront error and precision optical metrology, which is used to explore contrast limits and develop the technology needed for an extrasolar planet imager. A state-of-the-art, 1024-actuator micro-electrical-mechanical-systems (MEMS) deformable mirror was installed and characterized to provide active wavefront control and test this novel technology. I present 6.5 x 10{sup -8} contrast measurements with a prolate shaped pupil and flat mirror

  3. MAD Adaptive Optics Imaging of High Luminosity Quasars: A Pilot Project

    Liuzzo, E; Paiano, S; Treves, A; Uslenghi, M; Arcidiacono, C; Baruffolo, A; Diolaiti, E; Farinato, J; Lombini, M; Moretti, A; Ragazzoni, R; Brast, R; Donaldson, R; Kolb, J; Marchetti, E; Tordo, S

    2016-01-01

    We present near-IR images of five luminous quasars at z~2 and one at z~4 obtained with an experimental adaptive optics instrument at the ESO Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these non optimal conditions, the resulting images of point sources have cores of FWHM ~0.2 arcsec. We are able to characterize the host galaxy properties for 2 sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with adaptive optics systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2-3 kpc) quasar host galaxies for QSOs at z = ...

  4. The adaptation of methods in multilayer optics for the calculation of specular neutron reflection

    The adaptation of standard methods in multilayer optics to the calculation of specular neutron reflection is described. Their application is illustrated with examples which include a glass optical flat and a deuterated Langmuir-Blodgett film. (author)

  5. Adaptive Optics Observations of Exoplanets, Brown Dwarfs, & Binary Stars

    Hinkley, Sasha

    2011-01-01

    The current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Fu...

  6. Proposed adaptive optics system for Vainu Bappu Telescope

    Saxena, A. K.; Chinnappan, V.; Lancelot, J. P.

    It is known that the atmospheric turbulence spreads the star image as produced by the medium and large size optical telescopes by many orders resulting in reduction in the resolution of these telescopes. Adaptive optics system can partially or substantially sharpen the image thus improving the resolution and throughput of these telescopes. The atmospheric degradation can be effectively represented by Fried's parameter. We have measured Fried's parameter at very short intervals using speckle interferometer at VBT. Based on this input, an on-line wavefront error measurement and correction system was developed and tested in the laboratory. Low cost, high speed wavefront sensor using CMOS imager and Shack-Hartman lenslet array was developed and tested in the laboratory which could be used for on-line correction experiments. The wavefront errors are computed in terms of Zernike coefficients. MEMS based adaptive mirror with 37 actuators was used for the correction of higher order aberrations. Finite element analysis was carried out to know the mechanical properties and the influence function of the mirror. In-house developed Long Trace Profilometer was used to measure the surface produced by the mirror for various combination of actuator voltages and gave good insight about the behaviour of the mirror. An aberrated wavefront was captured by the wave-front sensor and the computed Zernike polynomials were used for correction of the wavefront. It is found that the peak intensity has increased about 3.8 times with reduction in size of the image. Now, the plan is to make a version that can be mounted at the cassegrain focus of the telescope. Here we deal with the low cost approach used in design; new algorithms developed for wavefront error computation from noisy data, speed optimization and related issues and the interface problems for using the system in the telescope.

  7. Demonstration of optical header recognition for BPSK data using novel design of logic gates

    Kakarla, Ravikiran; Venkitesh, Deepa

    2016-03-01

    We demonstrate the experimental implementation of an all-optical header recognition system for phase modulated data using logic gates, realized with the least number of active elements compared to conventional demonstrations. We experimentally implement the individual optical AND, XNOR/XOR logic gates and optimize their performances. We integrate these logic gates to build an all-optical header recognition system. We verify the working of the header recognition system for different combinations of header and local address bits. We also discuss the implementation challenges of the demonstrated system.

  8. Signal to noise ratio of free space homodyne coherent optical communication after adaptive optics compensation

    Huang, Jian; Mei, Haiping; Deng, Ke; Kang, Li; Zhu, Wenyue; Yao, Zhoushi

    2015-12-01

    Designing and evaluating the adaptive optics system for coherent optical communication link through atmosphere requires to distinguish the effects of the residual wavefront and disturbed amplitude to the signal to noise ratio. Based on the new definition of coherent efficiency, a formula of signal to noise ratio for describing the performance of coherent optical communication link after wavefront compensation is derived in the form of amplitude non-uniformity and wavefront error separated. A beam quality metric is deduced mathematically to evaluate the effect of disturbed amplitude to the signal to noise ratio. Experimental results show that the amplitude fluctuation on the receiver aperture may reduce the signal to noise ratio about 24% on average when Fried coherent length r0=16 cm.

  9. Compact MEMS-based Adaptive Optics Optical Coherence Tomography for Clinical Use

    Chen, D; Olivier, S; Jones, S; Zawadzki, R; Evans, J; Choi, S; Werner, J

    2008-02-04

    We describe a compact MEMS-based adaptive optics (AO) optical coherence tomography system with improved AO performance and ease of clinical use. A typical AO system consists of a Shack-Hartmann wavefront sensor and a deformable mirror that measures and corrects the ocular and system aberrations. Because of the limitation on the current deformable mirror technologies, the amount of real-time ocular-aberration compensation is restricted and small in the previous AO-OCT instruments. In this instrument, we proposed to add an optical apparatus to correct the spectacle aberrations of the patients such as myopia, hyperopia and astigmatism. This eliminated the tedious process of the trial lenses in clinical imaging. Different amount of spectacle aberration compensation was achieved by motorized stages and automated with the AO computer for ease of clinical use. In addition, the compact AO-OCT was optimized to have minimum system aberrations to reduce AO registration errors and improve AO performance.

  10. 4th International Workshop on Adaptive Optics for Industry and Medicine

    Wittrock, Ulrich

    2005-01-01

    This book treats the development and application of adaptive optics for industry and medicine. The contributions describe recently developed components for adaptive-optics systems such as deformable mirrors, wavefront sensors, and mirror drivers as well as complete adaptive optical systems and their applications in industry and medicine. Applications range from laser-beam forming and adaptive aberration correction for high-power lasers to retinal imaging in ophthalmology. The contributions are based on presentations made at the 4th International Workshop on Adaptive Optics in Industry and Medicine which took place in Münster, Germany, in October 2003. This highly successful series of workshops on adaptive optics started in 1997 and continues with the 5th workshop in Beijing in 2005.

  11. Adaptive optics scanning laser ophthalmoscope imaging: technology update

    Merino D

    2016-04-01

    Full Text Available David Merino, Pablo Loza-Alvarez The Institute of Photonic Sciences (ICFO, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain Abstract: Adaptive optics (AO retinal imaging has become very popular in the past few years, especially within the ophthalmic research community. Several different retinal techniques, such as fundus imaging cameras or optical coherence tomography systems, have been coupled with AO in order to produce impressive images showing individual cell mosaics over different layers of the in vivo human retina. The combination of AO with scanning laser ophthalmoscopy has been extensively used to generate impressive images of the human retina with unprecedented resolution, showing individual photoreceptor cells, retinal pigment epithelium cells, as well as microscopic capillary vessels, or the nerve fiber layer. Over the past few years, the technique has evolved to develop several different applications not only in the clinic but also in different animal models, thanks to technological developments in the field. These developments have specific applications to different fields of investigation, which are not limited to the study of retinal diseases but also to the understanding of the retinal function and vision science. This review is an attempt to summarize these developments in an understandable and brief manner in order to guide the reader into the possibilities that AO scanning laser ophthalmoscopy offers, as well as its limitations, which should be taken into account when planning on using it. Keywords: high-resolution, in vivo retinal imaging, AOSLO

  12. Adaptive optics scanning laser ophthalmoscope imaging: technology update

    Merino, David; Loza-Alvarez, Pablo

    2016-01-01

    Adaptive optics (AO) retinal imaging has become very popular in the past few years, especially within the ophthalmic research community. Several different retinal techniques, such as fundus imaging cameras or optical coherence tomography systems, have been coupled with AO in order to produce impressive images showing individual cell mosaics over different layers of the in vivo human retina. The combination of AO with scanning laser ophthalmoscopy has been extensively used to generate impressive images of the human retina with unprecedented resolution, showing individual photoreceptor cells, retinal pigment epithelium cells, as well as microscopic capillary vessels, or the nerve fiber layer. Over the past few years, the technique has evolved to develop several different applications not only in the clinic but also in different animal models, thanks to technological developments in the field. These developments have specific applications to different fields of investigation, which are not limited to the study of retinal diseases but also to the understanding of the retinal function and vision science. This review is an attempt to summarize these developments in an understandable and brief manner in order to guide the reader into the possibilities that AO scanning laser ophthalmoscopy offers, as well as its limitations, which should be taken into account when planning on using it. PMID:27175057

  13. The Inner Kiloparsec of Mrk 273 with Keck Adaptive Optics

    Vivian, U; Sanders, David; Max, Claire; Armus, Lee; Iwasawa, Kazushi; Evans, Aaron; Kewley, Lisa; Fazio, Giovanni

    2013-01-01

    There is X-ray, optical, and mid-infrared imaging and spectroscopic evidence that the late-stage ultraluminous infrared galaxy merger Mrk 273 hosts a powerful active galactic nucleus (AGN). However, the exact location of the AGN and the nature of the nuclei have been difficult to determine due to dust obscuration and the limited wavelength coverage of available high-resolution data. Here we present near-infrared integral-field spectra and images of the nuclear region of Mrk 273 taken with OSIRIS and NIRC2 on the Keck II Telescope with laser guide star adaptive optics. We observe three spatially resolved components, and analyze the local molecular and ionized gas emission lines and their kinematics. We confirm the presence of the hard X-ray AGN in the southwest nucleus. In the north nucleus, we find a strongly rotating gas disk whose kinematics indicate a central black hole of mass 1.04 +/- 0.1 x 10^9 Msun. The H2 emission line shows an increase in velocity dispersion along the minor axis in both directions, a...

  14. Bi-photon propagation control with optimized wavefront by means of Adaptive Optics

    Minozzi, M; Sergienko, A V; Vallone, G; Villoresi, P

    2012-01-01

    We present an efficient method to control the spatial modes of entangled photons produced through SPDC process. Bi-photon beam propagation is controlled by a deformable mirror, that shapes a 404nm CW diode laser pump interacting with a nonlinear BBO type-I crystal. Thanks to adaptive optical system, the propagation of 808nm SPDC light produced is optimized over a distance of 2m. The whole system optimization is carried out by a feedback between deformable mirror action and entangled photon coincidence counts. We also demonstrated the improvement of the two-photon coupling into single mode fibers.

  15. Demonstration of all-optical beam steering in modulated photonic lattices

    Rosberg, Christian R.; Garanovich, Ivan L.; Sukhorukov, Andrey A.; Neshev, Dragomir N.; Krolikowski, Wieslaw; Kivshar, Yuri S.

    2005-01-01

    We demonstrate experimentally all-optical beam steering in modulated photonic lattices induced optically by three beam interference in a biased photorefractive crystal. We identify and characterize the key physical parameters governing the beam steering, and show that the spatial resolution can be enhanced by the additional effect of nonlinear beam self-localization.

  16. Demonstration of whispering-gallery-mode resonant enhancement of optical forces

    Li, Yangcheng; Limberopoulos, Nicholaos I; Astratov, Vasily N

    2015-01-01

    We experimentally studied whispering-gallery modes(WGMs) and demonstrated resonance enhancement of optical forces evanescently exerted on dielectric microspheres. We showed that the resonant light pressure can be used for optical sorting of microparticles with extraordinary uniform resonant properties that is unachievable by conventional sorting techniques.

  17. Experimental demonstration of an analytic method for image reconstruction in optical tomography with large data sets

    Wang, Zheng-Min; Panasyuk, George Y.; Markel, Vadim A.; Schotland, John C.

    2005-01-01

    We report the first experimental test of an analytic image reconstruction algorithm for optical tomography with large data sets. Using a continuous-wave optical tomography system with 10^8 source-detector pairs, we demonstrate the reconstruction of an absorption image of a phantom consisting of a highly-scattering medium with absorbing inhomogeneities.

  18. Demonstration of the spatial separation of the entangled quantum sidebands of an optical field

    Quantum optics experiments on 'bright' beams are based on the spectral analysis of field fluctuations and typically probe correlations between radio-frequency sideband modes. However, the extra degree of freedom represented by this dual-mode picture is generally ignored. We demonstrate the experimental operation of a device which can be used to separate the quantum sidebands of an optical field. We use this device to explicitly demonstrate the quantum entanglement between the sidebands of a squeezed beam

  19. Demonstration of the spatial separation of the entangled quantum side-bands of an optical field

    Huntington, E H; Robilliard, C; Ralph, T C; Glöckl, O; Andersen, U L; Lorenz, S; Leuchs, G

    2005-01-01

    Quantum optics experiments on "bright" beams typically probe correlations between side-band modes. However the extra degree of freedom represented by this dual mode picture is generally ignored. We demonstrate the experimental operation of a device which can be used to separate the quantum side-bands of an optical field. We use this device to explicitly demonstrate the quantum entanglement between the side-bands of a squeezed beam.

  20. Transfer of adapted water supply technologies through a demonstration and teaching facility

    Nestmann, F.; Oberle, P.; Ikhwan, M.; Stoffel, D.; Blaß, H. J.; Töws, D.; Schmidt, S.

    2016-05-01

    Water scarcity can be defined as a lack of sufficient water resources or as the limited or even missing access to a safe water supply. Latter can be classified as `economic water scarcity' which among others can commonly be met in tropical and subtropical karst regions of emerging and developing countries. Karst aquifers, mostly consisting of limestone and carbonate rock, show high infiltration rates which leads to a lack of above ground storage possibilities. Thus, the water will drain rapidly into the underground and evolve vast river networks. Considering the lack of appropriate infrastructure and limited human capacities in the affected areas, these underground water resources cannot be exploited adequately. Against this, background innovative and adapted technologies are required to utilize hard-to-access water resources in a sustainable way. In this context, the German-Indonesian joint R&D project "Integrated Water Resources Management (IWRM) Indonesia" dealt with the development of highly adaptable water technologies and management strategies. Under the aegis of the Karlsruhe Institute of Technology (KIT) and funded by the German Ministry of Education and Research (BMBF), these innovative technical concepts were exemplarily implemented to remedy this deficiency in the model region Gunung Sewu, a karst area situated on the southern coast of Java Island, Indonesia. The experiences gained through the interdisciplinary joint R&D activities clearly showed that even in the case of availability of appropriate technologies, a comprising transfer of knowhow and the buildup of capabilities (Capacity Development) is inevitable to sustainably implement and disseminate new methods. In this context, an adapted water supply facility was developed by KIT which hereafter shall serve for demonstration, teaching, and research purposes. The plant's functionality, its teaching and research concept, as well as the design process, which was accomplished in collaboration with the

  1. Application of a photorefractive bismuth titanate crystal for the construction of adaptive fiber optic seismic receivers

    The possibility of using a photorefractive Bi12TiO20 crystal to create an adaptive fiber optic geophone has been studied. It is shown that this crystal provides efficient phase demodulation in and adaptive interferometer scheme at low optical powers

  2. Efficient wave function simulations in nonlinear quantum optics using an adaptive coherent state basis

    Full text: We show that a suitable set of coherent basis states placed on a discrete hexagonal grid can be used to numerically very accurately represent general quantum states in a memory efficient way. Adding an algorithm for dynamic basis adaptation allows highly accurate Quantum Monte Carlo wave function simulations with small basis sets. At the example of the intricate nonlinear dynamics of an optical parametric oscillator around threshold, we demonstrate that this approach yields accurate time dependent solutions with a substantially smaller basis sets than required for a photon number basis. Above threshold the adaptive basis splits into localized subsets allowing efficient representation of bimodal or even more complex phase space distributions and directly yields an intuitive physical picture of the ongoing dynamics. (author)

  3. Wavefront sensorless adaptive optics fluorescence biomicroscope for in vivo retinal imaging in mice.

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

    2016-01-01

    Cellular-resolution in vivo fluorescence imaging is a valuable tool for longitudinal studies of retinal function in vision research. Wavefront sensorless adaptive optics (WSAO) is a developing technology that enables high-resolution imaging of the mouse retina. In place of the conventional method of using a Shack-Hartmann wavefront sensor to measure the aberrations directly, WSAO uses an image quality metric and a search algorithm to drive the shape of the adaptive element (i.e. deformable mirror). WSAO is a robust approach to AO and it is compatible with a compact, low-cost lens-based system. In this report, we demonstrated a hill-climbing algorithm for WSAO with a variable focus lens and deformable mirror for non-invasive in vivo imaging of EGFP (enhanced green fluorescent protein) labelled ganglion cells and microglia cells in the mouse retina. PMID:26819812

  4. Modern optical signal processing experiments demonstrating intensity and pulse-width modulation using an acousto-optic modulator

    Poon, Ting-Chung; McNeill, Mark D.; Moore, Daniel J.

    1997-09-01

    Two experiments are presented to introduce undergraduate students in electrical engineering or physics to modern optical signal processing. Both experiments use an acousto-optic (AO) Bragg cell together with additional electronics to modify the intensity of a laser beam. Specifically, we show how an AO feedback system operating in the Bragg regime can be configured to produce amplitude modulated (AM) and pulse-width modulated optical signals. The basic components of the AO feedback system include a laser, an AO Bragg cell, an electronic AM modulator, a photodetector, an amplifier, and an electronic adder. Except for the laser, the AM modulator, and the Bragg cell, each of these components can be constructed with low cost electronics. A tutorial outlining the principles of acousto-optics is included to provide sufficient understanding of the Bragg cell. The project described in the paper has been used as a demonstration for junior- and senior-level undergraduate students in electrical engineering communications and optics classes.

  5. Stochastic parallel gradient descent based adaptive optics used for high contrast imaging coronagraph

    Dong, Bing; Zhang, Xi

    2011-01-01

    An adaptive optics (AO) system based on stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of stellar coronagraph in order to further improve the contrast. The principle of SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of SPGD algorithm is demonstrated by experimental system featured with a 140-actuators deformable mirror (DM) and a Hartmann- Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array (LCA) based coronagraph. The LCA can modulate the incoming light to generate a pupil apodization mask in any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10^-3 to 10^-4.5 at angular distance of 2{\\lambda}/D after corrected by SPGD based AO.

  6. Status Update and Closed-Loop Performance of the Magellan Adaptive Optics VisAO Camera

    Kopon, Derek; Close, Laird M.; Males, Jared; Gasho, Victor; Morzinski, Katie; Follette, Katherine

    2014-01-01

    We present laboratory results of the closed-loop performance of the Magellan Adaptive Optics (AO) Adaptive Secondary Mirror (ASM), pyramid wavefront sensor (PWFS), and VisAO visible adaptive optics camera. The Magellan AO system is a 585-actuator low-emissivity high-throughput system scheduled for first light on the 6.5 meter Magellan Clay telescope in November 2012. Using a dichroic beamsplitter near the telescope focal plane, the AO system will be able to simultaneously perform visible (500...

  7. Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems

    Wu, Zhizheng; Ben Amara, Foued

    2013-01-01

    Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems presents a novel design of wavefront correctors based on magnetic fluid deformable mirrors (MFDM) as well as corresponding control algorithms. The presented wavefront correctors are characterized by their linear, dynamic response. Various mirror surface shape control algorithms are presented along with experimental evaluations of the performance of the resulting adaptive optics systems. Adaptive optics (AO) systems are used in various fields of application to enhance the performance of optical systems, such as imaging, laser, free space optical communication systems, etc. This book is intended for undergraduate and graduate students, professors, engineers, scientists and researchers working on the design of adaptive optics systems and their various emerging fields of application. Zhizheng Wu is an associate professor at Shanghai University, China. Azhar Iqbal is a research associate at the University of Toronto, Canada. Foue...

  8. Automated interferometric synthetic aperture microscopy and computational adaptive optics for improved optical coherence tomography.

    Xu, Yang; Liu, Yuan-Zhi; Boppart, Stephen A; Carney, P Scott

    2016-03-10

    In this paper, we introduce an algorithm framework for the automation of interferometric synthetic aperture microscopy (ISAM). Under this framework, common processing steps such as dispersion correction, Fourier domain resampling, and computational adaptive optics aberration correction are carried out as metrics-assisted parameter search problems. We further present the results of this algorithm applied to phantom and biological tissue samples and compare with manually adjusted results. With the automated algorithm, near-optimal ISAM reconstruction can be achieved without manual adjustment. At the same time, the technical barrier for the nonexpert using ISAM imaging is also significantly lowered. PMID:26974799

  9. Development of active/adaptive lightweight optics for the next generation of telescopes

    Ghigo, M.; Basso, S.; Citterio, O.; Mazzoleni, F.; Vernani, D.

    2006-02-01

    The future large optical telescopes will have such large dimensions to require innovative technical solutions either in the engineering and optical fields. Their optics will have dimensions ranging from 30 to 100 m. and will be segmented. It is necessary to develop a cost effective industrial process, fast and efficient, to create the thousands of segments neeededs to assemble the mirrors of these instruments. INAF-OAB (Astronomical Observatory of Brera) is developing with INAF-Arcetri (Florence Astronomical Observatory) a method of production of lightweight glass optics that is suitable for the manufacturing of these segments. These optics will be also probably active and therefore the segments have to be thin, light and relatively flexible. The same requirements are valid also for the secondary adaptive mirrors foreseen for these telescopes and that therefore will benefit from the same technology. The technique under investigation foresees the thermal slumping of thin glass segments using a high quality ceramic mold (master). The sheet of glass is placed onto the mold and then, by means of a suitable thermal cycle, the glass is softened and its shape is changed copying the master shape. At the end of the slumping the correction of the remaining errors will be performed using the Ion Beam Figuring technique, a non-contact deterministic technique. To reduce the time spent for the correction it will be necessary to have shape errors on the segments as small as possible. A very preliminary series of experiments already performed on reduced size segments have shown that it is possible to copy a master shape with high accuracy (few microns PV) and it is very likely that copy accuracies of 1 micron or less are possible. The paper presents in detail the concepts of the proposed process and describes our current efforts that are aimed at the production of a scaled demonstrative adaptive segment of 50 cm of diameter.

  10. A visual classroom demonstration of frustrated total internal reflection as an analogue to optical tunnelling

    Salman, Rabiya; Rashid, Shama; Sabieh Anwar, Muhammad

    2013-11-01

    Frustrated total internal reflection is presented as a visually attractive and convenient classroom demonstration. Optical evanescent waves penetrating through a dielectric barrier is a classical analogue to quantum mechanical tunnelling. We use the traditional double prism arrangement to demonstrate the pickup and relaunching of the evanescent wave. Total internal reflection could be completely frustrated by the insertion of an index matching fluid.

  11. A Reflective Gaussian Coronagraph for Extreme Adaptive Optics: Laboratory Performance

    Park, Ryeojin; Close, Laird M.; Siegler, Nick; Nielsen, Eric L.; Stalcup, Thomas

    2006-11-01

    We report laboratory results of a coronagraphic test bench to assess the intensity reduction differences between a ``Gaussian'' tapered focal plane coronagraphic mask and a classical hard-edged ``top hat'' function mask at extreme adaptive optics (ExAO) Strehl ratios of ~94%. However, unlike a traditional coronagraph design, we insert a reflective focal plane mask at 45° to the optical axis. We also use an intermediate secondary mask (mask 2) before a final image in order to block additional mask-edge-diffracted light. The test bench simulates the optical train of ground-based telescopes (in particular, the 8.1 m Gemini North Telescope). It includes one spider vane, different mask radii (r = 1.9λ/D, 3.7λ/D, and 7.4λ/D), and two types of reflective focal plane masks (hard-edged top-hat and Gaussian tapered profiles). In order to investigate the relative performance of these competing coronagraphic designs with regard to extrasolar planet detection sensitivity, we utilize the simulation of realistic extrasolar planet populations (Nielsen et al.). With an appropriate translation of our laboratory results to expected telescope performance, a Gaussian tapered mask radius of 3.7λ/D with an additional mask (mask 2) performs best (highest planet detection sensitivity). For a full survey with this optimal design, the simulation predicts that ~30% more planets would be detected than with a top-hat function mask of similar size with mask 2. Using the best design, the point contrast ratio between the stellar point-spread function (PSF) peak and the coronagraphic PSF at 10λ/D (0.4" in the H band if D = 8.1 m) is ~10 times higher than a classical Lyot top-hat coronagraph. Hence, we find that a Gaussian apodized mask with an additional blocking mask is superior (~10 times higher contrast) to the use of a classical Lyot coronagraph for ExAO-like Strehl ratios.

  12. Wavefront sensorless approaches to adaptive optics for in vivo fluorescence imaging of mouse retina

    Wahl, Daniel J.; Bonora, Stefano; Mata, Oscar S.; Haunerland, Bengt K.; Zawadzki, Robert J.; Sarunic, Marinko V.; Jian, Yifan

    2016-03-01

    Adaptive optics (AO) is necessary to correct aberrations when imaging the mouse eye with high numerical aperture. In order to obtain cellular resolution, we have implemented wavefront sensorless adaptive optics for in vivo fluorescence imaging of mouse retina. Our approach includes a lens-based system and MEMS deformable mirror for aberration correction. The AO system was constructed with a reflectance channel for structural images and fluorescence channel for functional images. The structural imaging was used in real-time for navigation on the retina using landmarks such as blood vessels. We have also implemented a tunable liquid lens to select the retinal layer of interest at which to perform the optimization. At the desired location on the mouse retina, the optimization algorithm used the fluorescence image data to drive a modal hill-climbing algorithm using an intensity or sharpness image quality metric. The optimization requires ~30 seconds to complete a search up to the 20th Zernike mode. In this report, we have demonstrated the AO performance for high-resolution images of the capillaries in a fluorescence angiography. We have also made progress on an approach to AO with pupil segmentation as a possible sensorless technique suitable for small animal retinal imaging. Pupil segmentation AO was implemented on the same ophthalmic system and imaging performance was demonstrated on fluorescent beads with induced aberrations.

  13. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Simeoni, G. G.; Valicu, R. G.; Borchert, G.; Böni, P.; Rasmussen, N. G.; Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A.

    2015-12-01

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4-10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  14. Adaptive optics images. III. 87 Kepler objects of interest

    Dressing, Courtney D.; Dupree, Andrea K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Adams, Elisabeth R. [Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719 (United States); Kulesa, Craig; McCarthy, Don, E-mail: cdressing@cfa.harvard.edu [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-11-01

    The Kepler mission has revolutionized our understanding of exoplanets, but some of the planet candidates identified by Kepler may actually be astrophysical false positives or planets whose transit depths are diluted by the presence of another star. Adaptive optics images made with ARIES at the MMT of 87 Kepler Objects of Interest place limits on the presence of fainter stars in or near the Kepler aperture. We detected visual companions within 1'' for 5 stars, between 1'' and 2'' for 7 stars, and between 2'' and 4'' for 15 stars. For those systems, we estimate the brightness of companion stars in the Kepler bandpass and provide approximate corrections to the radii of associated planet candidates due to the extra light in the aperture. For all stars observed, we report detection limits on the presence of nearby stars. ARIES is typically sensitive to stars approximately 5.3 Ks magnitudes fainter than the target star within 1'' and approximately 5.7 Ks magnitudes fainter within 2'', but can detect stars as faint as ΔKs = 7.5 under ideal conditions.

  15. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers

  16. Micron narrowband adaptive optics imaging in the arches cluster

    Blum, R D; Pasquali, A; Heydari-Malayeri, M; Conti, P S; Schmutz, W

    2001-01-01

    Canada-France-Hawaii-Telescope adaptive optics bonnette images through narrow-band filters in the $K-$band are presented for the Arches cluster. Continuum fluxes, line fluxes, and equivalent widths are derived from high angular resolution images, some near diffraction limited, for the well known massive stars in the Arches cluster. Images were obtained in the lines of \\ion{He}{1} 2.06 \\mic, \\ion{H}{1} Br$\\gamma$ (2.17 \\mic), and \\ion{He}{2} 2.19 \\mic as well as continuum positions at 2.03 \\mic, 2.14 \\mic, and 2.26 \\mic. In addition, fluxes are presented for \\ion{H}{1} P$\\alpha$ (1.87 \\mic) and a nearby continuum position (1.90 \\mic) from Hubble Space Telescope archival data. The 2 \\mic and P$\\alpha$ data reveal two new emission-line stars and three fainter candidate emission-line objects. Indications for a spectral change of one object between earlier observations in 1992/1993 and our data from 1999 are found. The ratio of \\ion{He}{2} 2.19 \\mic to Br$\\gamma$ emission exhibits a narrow distribution among the s...

  17. Adaptive optics for ultra short pulsed lasers in UHV environment

    Deneuville, Francois; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-02-01

    ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.

  18. Improvement in the performance of solar adaptive optics

    Adaptive optics (AO), which provides diffraction limited imaging over a field-of-view (FOV), is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor (WFS) is looking at a single reference that acts as a guide star. This allows a 3D reconstruction of the distorted wavefront to be made. The correction is applied by one or more deformable mirrors (DMs). This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. With the assistance of the MAOS software package, we consider the tomography errors and WFS aliasing errors, and focus on how the performance of a solar telescope (pointing toward zenith) is related to atmospheric anisoplanatism. We theoretically quantify the performance of the tomographic solar AO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope in a 10″ – 80″ diameter FOV by only employing one DM conjugated to the telescope pupil. Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the AO system by selecting two atmospheric models that differ mainly in terms of atmospheric properties at ground level, and present the optimum DM conjugate altitudes for different observation sites

  19. Adaptive Optics Images of Kepler Objects of Interest

    Adams, Elisabeth R; Dupree, Andrea K; Gautier, T Nick; Kulesa, Craig; McCarthy, Don

    2012-01-01

    All transiting planets are at risk of contamination by blends with nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or produce a false positive detection when the target star is blended with eclipsing binary stars. This paper reports on high spatial-resolution adaptive optics images of 90 Kepler planetary candidates. Companion stars are detected as close as 0.1 arcsec from the target star. Images were taken in the near-infrared (J and Ks bands) with ARIES on the MMT and PHARO on the Palomar Hale 200-inch. Most objects (60%) have at least one star within 6 arcsec separation and a magnitude difference of 9. Eighteen objects (20%) have at least one companion within 2 arcsec of the target star; 6 companions (7%) are closer than 0.5 arcsec. Most of these companions were previously unknown, and the associated planetary candidates should receive additional scrutiny. Limits are placed on the presence of additional companions for every system observed,...

  20. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Simeoni, G. G., E-mail: ggsimeoni@outlook.com [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Valicu, R. G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Borchert, G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Böni, P. [Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Rasmussen, N. G. [Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A. [Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln (Germany)

    2015-12-14

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  1. New challenges for Adaptive Optics Extremely Large Telescopes

    Le Louarn, M; Sarazin, M; Tokovinin, A

    2000-01-01

    The performance of an adaptive optics (AO) system on a 100m diameter ground based telescope working in the visible range of the spectrum is computed using an analytical approach. The target Strehl ratio of 60% is achieved at 0.5um with a limiting magnitude of the AO guide source near R~10, at the cost of an extremely low sky coverage. To alleviate this problem, the concept of tomographic wavefront sensing in a wider field of view using either natural guide stars (NGS) or laser guide stars (LGS) is investigated. These methods use 3 or 4 reference sources and up to 3 deformable mirrors, which increase up to 8-fold the corrected field size (up to 60\\arcsec at 0.5 um). Operation with multiple NGS is limited to the infrared (in the J band this approach yields a sky coverage of 50% with a Strehl ratio of 0.2). The option of open-loop wavefront correction in the visible using several bright NGS is discussed. The LGS approach involves the use of a faint (R ~22) NGS for low-order correction, which results in a sky cov...

  2. 3.2Gbps multi-channel optical backplane bus demonstrator using photopolymer volume gratings

    Bi, Hai; Choi, Jinho; Jiang, Wei; Han, Xuliang; Ellis, Jonathan; Chen, Ray T.

    2007-02-01

    A 3-slot optical backplane bus demonstrator based on glass substrate with photopolymer volume gratings array (PVGA) on top surface is built to allow 16 channels of data to be broadcast from central slot to two daughter slots or uploaded from any daughter slot to central slot. VCSELs and photodetectors packaged in the form of TO-46 can are assembled on top of each PVG and interleaved to reduce the crosstalk to below noise level. By carefully aligning the fabrication system, the incident angle deviation from Bragg condition is reduced to below 0.1° to maximize optical power delivery. The orientation and period of hologram fringes are uniform in the active area by collimating recording beams. Above 4.8Gbps aggregated data transmission is successfully demonstrated using the multi-channel system. Three computer mother boards using FPGA are made to verify the data transmission among the slots. Interface boards between the FPGA boards and optical transceivers are designed and fabricated to separate the implementation of digital layer and optical layer. Single channel transmissions with 3.2Gbps and even 10Gbps data rate are also tested with above 100uW input power, showing the potential to improve the total two-way bandwidth to above 102.4Gbps. Alignment tolerance of the optical interconnect system is investigated theoretically and experimentally. By analyzing the diffractive characteristics, the bandwidth limit of the optical layer is determined to be in the order of Terahertz. Design and fabrication issues are discussed for future optical backplane bus to make terahertz bandwidth into reality. Based on the experiments for Bit-interleaved Optical Backplane bus and Multi-channel optical backplane bus demonstrators, theoretical analysis of the bandwidth limit of the optical backplane bus using photopolymer volume gratings has been carried out.

  3. Experimental demonstration of a cognitive quality of transmission estimator for optical communication systems

    Caballero Jambrina, Antonio; Aguado, Juan Carlos; Borkowski, Robert;

    2012-01-01

    The impact of physical layer impairments in optical network design and operation has received significant attention in the last years, thereby requiring estimation techniques to predict the quality of transmission (QoT) of optical connections before being established. In this paper, we report on...... the experimental demonstration of a case-based reasoning (CBR) technique to predict whether optical channels fulfill QoT requirements, thus supporting impairment-aware networking. The validation of the cognitive QoT estimator is performed in a WDM 80 Gb/s PDM-QPSK testbed, and we demonstrate that even...... with a very small and not optimized underlying knowledge base, it achieves between 79% and 98.7% successful classifications based on the error vector magnitude (EVM) parameter, and approximately 100% when the classification is based on the optical signal to noise ratio (OSNR)....

  4. Are integral controllers adapted to the new era of ELT adaptive optics?

    Conan, J.-M.; Raynaud, H.-F.; Kulcsár, C.; Meimon, S.

    2011-09-01

    With ELTs we are now entering a new era in adaptive optics developments. Meeting unprecedented level of performance with incredibly complex systems implies reconsidering AO concepts at all levels, including controller design. Concentrating mainly on temporal aspects, one may wonder if integral controllers remain an adequate solution. This question is all the more important that, with ever larger degrees of freedom, one may be tempted to discard more sophisticated approaches because they are deemed too complex to implement. The respective performance of integrator versus LQG control should therefore be carefully evaluated in the ELT context. We recall for instance the impressive correction improvement brought by such controllers for the rejection of windshake and vibration components. LQG controller significantly outperforms the integrator because its disturbance rejection transfer function closely matches the energy concentration, respectively at low temporal frequencies for windshake, and around localized resonant peaks for vibrations. The application to turbulent modes should also be investigated, especially for very low spatial frequencies now explored on the huge ELT pupil. The questions addressed here are: 1/ How do integral and LQG controllers compare in terms of performance for a given sampling frequency and noise level?; 2/ Could we relax sampling frequency with LQG control?; 3/ Does a mode to mode adaptation of temporal rejection bring significant performance improvement?; 4/ Which modes particularly benefit from this fine tuning of the rejection transfer function? Based on a simplified ELT AO configuration, and through a simple analytical formulation, performance is evaluated for several control approaches. Various assumptions concerning the perturbation parameters (seeing and outer-scale value, windshake amplitude) are considered. Bode's integral theorem allows intuitive understanding of the results. Practical implementation and computation complexity

  5. Coherence gated wavefront sensorless adaptive optics for two photon excited fluorescence retinal imaging (Conference Presentation)

    Jian, Yifan; Cua, Michelle; Bonora, Stefano; Pugh, Edward N.; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    We present a novel system for adaptive optics two photon imaging. We utilize the bandwidth of the femtosecond excitation beam to perform coherence gated imaging (OCT) of the sample. The location of the focus is directly observable in the cross sectional OCT images, and adjusted to the desired depth plane. Next, using real time volumetric OCT, we perform Wavefront Sensorless Adaptive Optics (WSAO) aberration correction using a multi-element adaptive lens capable of correcting up to 4th order Zernike polynomials. The aberration correction is performed based on an image quality metric, for example intensity. The optimization time is limited only by the OCT acquisition rate, and takes ~30s. Following aberration correction, two photon fluorescence images are acquired, and compared to results without adaptive optics correction. This technique is promising for multiphoton imaging in multi-layered, scattering samples such as eye and brain, in which traditional wavefront sensing and guide-star sensorless adaptive optics approaches may not be suitable.

  6. On application of constrained receding horizon control in astronomical adaptive optics

    Konnik, Mikhail V.; De Doná, José; Welsh, James Stuart

    2012-07-01

    Control system design for adaptive optics is becoming more complex and sophisticated with increasing demands on the compensation of atmospheric turbulence. Contemporary controllers used in adaptive optics systems are optimised in the sense of a cost function (linear quadratic regulators) or to a worst case scenario (robust H∞ controllers). Prediction, to some extent, can be incorporated into the controllers using the Kalman filter and a model of the atmospheric turbulence. Despite the growing number of publications on adaptive optics control systems, only the unconstrained case is usually considered. Accounting for the physical constraints of the adaptive optics system components, such as limited actuator stroke, still represents a problem. As a possible solution, one can consider constrained receding horizon control (RHC), also known as Model Predictive Control (MPC). The ability of RHC to handle constraints and make predictions of the future control signals makes it attractive for application in astronomical adaptive optics. The main potential difficulty with the application of RHC is its heavy computational load. This paper presents preliminary results on numerical simulations of an adaptive optics system controlled by constrained RHC. In particular, the case of output disturbance rejection is considered. The results of numerical simulations are provided. Finally, methods for improving the computational performance of constrained receding horizon controllers in adaptive optics are also discussed.

  7. Local Ensemble Transform Kalman Filter: a non-stationary control law for complex adaptive optics systems on ELTs

    Gray, Morgan; Rodionov, Sergey; Bertino, Laurent; Bocquet, Marc; Fusco, Thierry

    2013-01-01

    We propose a new algorithm for an adaptive optics system control law which allows to reduce the computational burden in the case of an Extremely Large Telescope (ELT) and to deal with non-stationary behaviors of the turbulence. This approach, using Ensemble Transform Kalman Filter and localizations by domain decomposition is called the local ETKF: the pupil of the telescope is split up into various local domains and calculations for the update estimate of the turbulent phase on each domain are performed independently. This data assimilation scheme enables parallel computation of markedly less data during this update step. This adapts the Kalman Filter to large scale systems with a non-stationary turbulence model when the explicit storage and manipulation of extremely large covariance matrices are impossible. First simulation results are given in order to assess the theoretical analysis and to demonstrate the potentiality of this new control law for complex adaptive optics systems on ELTs.

  8. The optical design of a visible adaptive optics system for the Magellan Telescope

    Kopon, Derek

    The Magellan Adaptive Optics system will achieve first light in November of 2012. This AO system contains several subsystems including the 585-actuator concave adaptive secondary mirror, the Calibration Return Optic (CRO) alignment and calibration system, the CLIO 1-5 microm IR science camera, the movable guider camera and active optics assembly, and the W-Unit, which contains both the Pyramid Wavefront Sensor (PWFS) and the VisAO visible science camera. In this dissertation, we present details of the design, fabrication, assembly, alignment, and laboratory performance of the VisAO camera and its optical components. Many of these components required a custom design, such as the Spectral Differential Imaging Wollaston prisms and filters and the coronagraphic spots. One component, the Atmospheric Dispersion Corrector (ADC), required a unique triplet design that had until now never been fabricated and tested on sky. We present the design, laboratory, and on-sky results for our triplet ADC. We also present details of the CRO test setup and alignment. Because Magellan is a Gregorian telescope, the ASM is a concave ellipsoidal mirror. By simulating a star with a white light point source at the far conjugate, we can create a double-pass test of the whole system without the need for a real on-sky star. This allows us to test the AO system closed loop in the Arcetri test tower at its nominal design focal length and optical conjugates. The CRO test will also allow us to calibrate and verify the system off-sky at the Magellan telescope during commissioning and periodically thereafter. We present a design for a possible future upgrade path for a new visible Integral Field Spectrograph. By integrating a fiber array bundle at the VisAO focal plane, we can send light to a pre-existing facility spectrograph, such as LDSS3, which will allow 20 mas spatial sampling and R˜1,800 spectra over the band 0.6-1.05 microm. This would be the highest spatial resolution IFU to date, either

  9. Polymer-based micro-deformable mirror for adaptive optics

    Liotard, Arnaud; Zamkotsian, Frederic; Conedera, Veronique; Fabre, Norbert; Lanzoni, Patrick; Camon, Henri; Chazallet, Frederic

    2006-01-01

    Highly performing adaptive optical (AO) systems are mandatory for next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes, for studying new fields like circumstellar disks and extra-solar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. We are currently developing a micro-deformable mirror (MDM) based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. In order to reach large stroke for low driving voltage, the originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials. We have developed the first polymer piston-motion actuator: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V, and measured resonance frequency of 6.5kHz is well suited for AO systems. The electrostatic force provides a non-linear actuation, while AO systems are based on linear matrices operations. We have successfully developed a dedicated 14-bit electronics in order to "linearize" the actuation. Actual location of the actuator versus expected location of the actuator is obtained with a standard deviation of 21 nm. Comparison with FEM models shows very good agreement, and design of a complete polymer-based MDM has been done.

  10. Ultrahigh-speed ultrahigh-resolution adaptive optics: optical coherence tomography system for in-vivo small animal retinal imaging

    Jian, Yifan; Xu, Jing; Zawadzki, Robert J.; Sarunic, Marinko V.

    2013-03-01

    Small animal models of human retinal diseases are a critical component of vision research. In this report, we present an ultrahigh-resolution ultrahigh-speed adaptive optics optical coherence tomography (AO-OCT) system for small animal retinal imaging (mouse, fish, etc.). We adapted our imaging system to different types of small animals in accordance with the optical properties of their eyes. Results of AO-OCT images of small animal retinas acquired with AO correction are presented. Cellular structures including nerve fiber bundles, capillary networks and detailed double-cone photoreceptors are visualized.

  11. Demonstration of 720×720 optical fast circuit switch for intra-datacenter networks

    Ueda, Koh; Mori, Yojiro; Hasegawa, Hiroshi; Matsuura, Hiroyuki; Ishii, Kiyo; Kuwatsuka, Haruhiko; Namiki, Shu; Sato, Ken-ichi

    2016-03-01

    Intra-datacenter traffic is growing more than 20% a year. In typical datacenters, many racks/pods including servers are interconnected via multi-tier electrical switches. The electrical switches necessitate power-consuming optical-to- electrical (OE) and electrical-to-optical (EO) conversion, the power consumption of which increases with traffic. To overcome this problem, optical switches that eliminate costly OE and EO conversion and enable low power consumption switching are being investigated. There are two major requirements for the optical switch. First, it must have a high port count to construct reduced tier intra-datacenter networks. Second, switching speed must be short enough that most of the traffic load can be offloaded from electrical switches. Among various optical switches, we focus on those based on arrayed-waveguide gratings (AWGs), since the AWG is a passive device with minimal power consumption. We previously proposed a high-port-count optical switch architecture that utilizes tunable lasers, route-and-combine switches, and wavelength-routing switches comprised of couplers, erbium-doped fiber amplifiers (EDFAs), and AWGs. We employed conventional external cavity lasers whose wavelength-tuning speed was slower than 100 ms. In this paper, we demonstrate a large-scale optical switch that offers fast wavelength routing. We construct a 720×720 optical switch using recently developed lasers whose wavelength-tuning period is below 460 μs. We evaluate the switching time via bit-error-ratio measurements and achieve 470-μs switching time (includes 10-μs guard time to handle EDFA surge). To best of our knowledge, this is the first demonstration of such a large-scale optical switch with practical switching time.

  12. Creating a Forest-Wide Context for Adaptive Management at Jackson Demonstration State Forest

    Liquori, M.; Helms, J.; Porter, D.

    2010-12-01

    At nearly 50,000 acres, Jackson Demonstration State Forest (JDSF) is the largest State-owned forest in California. In 2008, the CALFIRE Director appointed a 13-member Jackson Advisory Group to provide recommendations to the California State Board of Forestry for how to transition JDSF into a “world-class research forest”. After nearly 3 years of deliberations, we have developed a draft Research-Oriented Management Framework (ROMF) that, if adopted, will introduce a new model for adaptive management within the forestry sector. Our approach integrates several core elements. Scientific “Centers of Excellence” (including one focused on Coho recovery and/or watershed processes) would be developed around a Research-Oriented Landscape Allocation, that considers the existing distribution of forest attributes both within JDSF as well as within the broader coastal Redwood Region. The ROMF would establish an Experimental Basis for Management that seeks to leverage harvest activities with explicit experimental designs and monitoring objectives. Like many of the forests that comprise its customer-base, JDSF has a mandate to produce timber revenues. We view this as an opportunity to mimic the management constraint imposed on most private and conservation trust landowners to routinely harvest timber to support operational and capital costs. Timber revenues on JDSF would be used (in part) to support the research and monitoring program. Such a system would support both passive and active modes of forest manipulation and research, and would make JDSF research activities more relevant to stakeholders, potentially increasing opportunities for collaborative, landscape-scale studies that seek to resolve outstanding management issues and uncertainties. The ROMF also would seek to develop and improve practices related to sustainable forestry. Both Late-Seral Development Areas and Old-Forest Structure Zones would be established that will utilize uneven-aged management treatments to

  13. MAD Adaptive Optics Imaging of High-luminosity Quasars: A Pilot Project

    Liuzzo, E.; Falomo, R.; Paiano, S.; Treves, A.; Uslenghi, M.; Arcidiacono, C.; Baruffolo, A.; Diolaiti, E.; Farinato, J.; Lombini, M.; Moretti, A.; Ragazzoni, R.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

    2016-08-01

    We present near-IR images of five luminous quasars at z ∼ 2 and one at z ∼ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ∼ 0.2 arcsec. We are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2–3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K-magnitude spanning from 15 to 20 (corresponding to absolute magnitude ‑31 to ‑26) and host galaxies that are 4 mag fainter than their nuclei.

  14. Efficient reconstruction method for ground layer adaptive optics with mixed natural and laser guide stars.

    Wagner, Roland; Helin, Tapio; Obereder, Andreas; Ramlau, Ronny

    2016-02-20

    The imaging quality of modern ground-based telescopes such as the planned European Extremely Large Telescope is affected by atmospheric turbulence. In consequence, they heavily depend on stable and high-performance adaptive optics (AO) systems. Using measurements of incoming light from guide stars, an AO system compensates for the effects of turbulence by adjusting so-called deformable mirror(s) (DMs) in real time. In this paper, we introduce a novel reconstruction method for ground layer adaptive optics. In the literature, a common approach to this problem is to use Bayesian inference in order to model the specific noise structure appearing due to spot elongation. This approach leads to large coupled systems with high computational effort. Recently, fast solvers of linear order, i.e., with computational complexity O(n), where n is the number of DM actuators, have emerged. However, the quality of such methods typically degrades in low flux conditions. Our key contribution is to achieve the high quality of the standard Bayesian approach while at the same time maintaining the linear order speed of the recent solvers. Our method is based on performing a separate preprocessing step before applying the cumulative reconstructor (CuReD). The efficiency and performance of the new reconstructor are demonstrated using the OCTOPUS, the official end-to-end simulation environment of the ESO for extremely large telescopes. For more specific simulations we also use the MOST toolbox. PMID:26906596

  15. Multi-conjugate adaptive optics observations of the Orion Trapezium Cluster

    We obtained very deep and high spatial resolution near-infrared images of the Orion Trapezium Cluster using the Multi-Conjugate Adaptive Optics Demonstrator (MAD) instrument at the VLT. The goal of these observations has been to search for objects at the very low-mass end of the IMF down to the planetary-mass regime. Three fields in the innermost dense part of the Trapezium Cluster, with a total area of 3.5 sq.arcmin have been surveyed at 1.65μm and 2.2μm. Several new candidate planetary mass objects with potential masses Jup have been detected based on their photometry and on their location in the colour-magnitude diagram. The performance of the multi-conjugate adaptive optics correction is excellent over a large field-of-view of ∼ 1'. The final data has a spatial resolution of Jup), however, must await future confirmation by spectroscopic and/or photometric observations.

  16. Top-Down Visual Saliency Detection in Optical Satellite Images Based on Local Adaptive Regression Kernel

    Xiaoguang Cui

    2014-01-01

    Full Text Available This paper proposes a novel top-down visual saliency detection method for optical satellite images using local adaptive regression kernels. This method provides a saliency map by measuring the likeness of image patches to a given single template image. The local adaptive regression kernel (LARK is used as a descriptor to extract feature and compare against analogous feature from the target image. A multi-scale pyramid of the target image is constructed to cope with large-scale variations. In addition, accounting for rotation variations, the histogram of kernel orientation is employed to estimate the rotation angle of image patch, and then comparison is performed after rotating the patch by the estimated angle. Moreover, we use the bounded partial correlation (BPC to compare features between image patches and the template so as to rapidly generate the saliency map. Experiments were performed in optical satellite images to find airplanes, and experimental results demonstrate that the proposed method is effective and robust in complex scenes.

  17. An adaptable dual species effusive source and Zeeman slower design demonstrated with Rb and Li

    Bowden, William; Gunton, Will; Semczuk, Mariusz; Dare, Kahan; Madison, Kirk W.

    2016-04-01

    We present a dual-species effusive source and Zeeman slower designed to produce slow atomic beams of two elements with a large mass difference and with very different oven temperature requirements. We demonstrate this design for the case of 6Li and 85Rb and achieve magneto-optical trap (MOT) loading rates equivalent to that reported in prior work on dual species (Rb+Li) Zeeman slowers operating at the same oven temperatures. Key design choices, including thermally separating the effusive sources and using a segmented coil design to enable computer control of the magnetic field profile, ensure that the apparatus can be easily modified to slow other atomic species. By performing the final slowing using the quadrupole magnetic field of the MOT, we are able to shorten our Zeeman slower length making for a more compact system without compromising performance. We outline the construction and analyze the emission properties of our effusive sources. We also verify the performance of the source and slower, and we observe sequential loading rates of 12 × 108 atoms/s for a Rb oven temperature of 140 °C and 1.1 × 108 atoms/s for a Li reservoir at 460 °C, corresponding to reservoir lifetimes for continuous operation of 10 and 4 years, respectively.

  18. Anisotropic optical flow algorithm based on self-adaptive cellular neural network

    Zhang, Congxuan; Chen, Zhen; Li, Ming; Sun, Kaiqiong

    2013-01-01

    An anisotropic optical flow estimation method based on self-adaptive cellular neural networks (CNN) is proposed. First, a novel optical flow energy function which contains a robust data term and an anisotropic smoothing term is projected. Next, the CNN model which has the self-adaptive feedback operator and threshold is presented according to the Euler-Lagrange partial differential equations of the proposed optical flow energy function. Finally, the elaborate evaluation experiments indicate the significant effects of the various proposed strategies for optical flow estimation, and the comparison results with the other methods show that the proposed algorithm has better performance in computing accuracy and efficiency.

  19. Parallel processing demonstrator with plug-on-top free-space interconnect optics

    Berger, Christoph; Wang, Xiaoqing; Ekman, Jeremy T.; Marchand, Philippe J.; Spaanenburg, Henk; Wang, Mark M.; Kiamilev, Fouad E.; Esener, Sadik C.

    2001-05-01

    We demonstrate a setup with 10 optically interconnected chips,k which can perform a distributed radix-2-butterfly calculation for fast Fourier transformation. The setup consists of a motherboard, five multi-chip-modules (MCMs, with processor/transceiver chips and laser/detector chips), four plug-on-top optics modules that provide the bi- directional optical links between the MCMs, and external control electronics. The design of the optics and optomechanics satisfies numerous real-world constraints, such as compact size (< 1 inch thick), suitability for mass-production, suitability for large arrays (up to 103 parallel channels), compatibility with standard electronics fabrication and packaging technology, and potential for active misalignment compensation by integrating MEMS technology.

  20. Experimental demonstration of software defined data center optical networks with Tbps end-to-end tunability

    Zhao, Yongli; Zhang, Jie; Ji, Yuefeng; Li, Hui; Wang, Huitao; Ge, Chao

    2015-10-01

    The end-to-end tunability is important to provision elastic channel for the burst traffic of data center optical networks. Then, how to complete the end-to-end tunability based on elastic optical networks? Software defined networking (SDN) based end-to-end tunability solution is proposed for software defined data center optical networks, and the protocol extension and implementation procedure are designed accordingly. For the first time, the flexible grid all optical networks with Tbps end-to-end tunable transport and switch system have been online demonstrated for data center interconnection, which are controlled by OpenDayLight (ODL) based controller. The performance of the end-to-end tunable transport and switch system has been evaluated with wavelength number tuning, bit rate tuning, and transmit power tuning procedure.

  1. The numerical simulation tool for the MAORY multiconjugate adaptive optics system

    Arcidiacono, Carmelo; Bregoli, Giovanni; Diolaiti, Emiliano; Foppiani, Italo; Agapito, Guido; Puglisi, Alfio; Xompero, Marco; Oberti, Sylvain; Cosentino, Giuseppe; Lombini, Matteo; Butler, Chris R; Ciliegi, Paolo; Cortecchia, Fausto; Patti, Mauro; Esposito, Simone; Feautrier, Philippe

    2016-01-01

    The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is a hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implements the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and uses libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

  2. A plan for the development and demonstration of optical communications for deep space

    Lesh, James R.; Deutsch, Leslie J.; Weber, William J.

    1991-01-01

    A development history, current status, and prospective development account are given for deep-space optical communications, giving attention to overall systems-related activities and to the generic technology developments required for their implementation. An account is given of the progression envisioned from laboratory subsystems demonstrations to the full-scale flight experiment for the Mars Communications Relay Orbiter missions.

  3. Adaptive Integrated Optical Bragg Grating in Semiconductor Waveguide Suitable for Optical Signal Processing

    Moniem, T. A.

    2016-05-01

    This article presents a methodology for an integrated Bragg grating using an alloy of GaAs, AlGaAs, and InGaAs with a controllable refractive index to obtain an adaptive Bragg grating suitable for many applications on optical processing and adaptive control systems, such as limitation and filtering. The refractive index of a Bragg grating is controlled by using an external electric field for controlling periodic modulation of the refractive index of the active waveguide region. The designed Bragg grating has refractive indices programmed by using that external electric field. This article presents two approaches for designing the controllable refractive indices active region of a Bragg grating. The first approach is based on the modification of a planar micro-strip structure of the iGaAs traveling wave as the active region, and the second is based on the modification of self-assembled InAs/GaAs quantum dots of an alloy from GaAs and InGaAs with a GaP traveling wave. The overall design and results are discussed through numerical simulation by using the finite-difference time-domain, plane wave expansion, and opto-wave simulation methods to confirm its operation and feasibility.

  4. Fixation light hue bias revisited: implications for using adaptive optics to study color vision

    Hofer, H. J.; Blaschke, J.; Patolia, J.; Koenig, D. E.

    2012-01-01

    Current vision science adaptive optics systems use near infrared wavefront sensor ‘beacons’ that appear as red spots in the visual field. Colored fixation targets are known to influence the perceived color of macroscopic visual stimuli(Jameson, D. and Hurvich, L. M., 1967. Fixation-light bias: an unwanted by-product of fixation control. Vis. Res. 7, 805 – 809.), suggesting that the wavefront sensor beacon may also influence perceived color for stimuli displayed with adaptive optics. Despite i...

  5. Experimental demonstration of large capacity WSDM optical access network with multicore fibers and advanced modulation formats.

    Li, Borui; Feng, Zhenhua; Tang, Ming; Xu, Zhilin; Fu, Songnian; Wu, Qiong; Deng, Lei; Tong, Weijun; Liu, Shuang; Shum, Perry Ping

    2015-05-01

    Towards the next generation optical access network supporting large capacity data transmission to enormous number of users covering a wider area, we proposed a hybrid wavelength-space division multiplexing (WSDM) optical access network architecture utilizing multicore fibers with advanced modulation formats. As a proof of concept, we experimentally demonstrated a WSDM optical access network with duplex transmission using our developed and fabricated multicore (7-core) fibers with 58.7km distance. As a cost-effective modulation scheme for access network, the optical OFDM-QPSK signal has been intensity modulated on the downstream transmission in the optical line terminal (OLT) and it was directly detected in the optical network unit (ONU) after MCF transmission. 10 wavelengths with 25GHz channel spacing from an optical comb generator are employed and each wavelength is loaded with 5Gb/s OFDM-QPSK signal. After amplification, power splitting, and fan-in multiplexer, 10-wavelength downstream signal was injected into six outer layer cores simultaneously and the aggregation downstream capacity reaches 300 Gb/s. -16 dBm sensitivity has been achieved for 3.8 × 10-3 bit error ratio (BER) with 7% Forward Error Correction (FEC) limit for all wavelengths in every core. Upstream signal from ONU side has also been generated and the bidirectional transmission in the same core causes negligible performance degradation to the downstream signal. As a universal platform for wired/wireless data access, our proposed architecture provides additional dimension for high speed mobile signal transmission and we hence demonstrated an upstream delivery of 20Gb/s per wavelength with QPSK modulation formats using the inner core of MCF emulating a mobile backhaul service. The IQ modulated data was coherently detected in the OLT side. -19 dBm sensitivity has been achieved under the FEC limit and more than 18 dB power budget is guaranteed. PMID:25969194

  6. Demonstrated survivability of a high temperature optical fiber cable on a 1500 pound thrust rocket chamber

    Sovie, Amy L.

    1992-01-01

    A demonstration of the ability of an existing optical fiber cable to survive the harsh environment of a rocket engine was performed at the NASA Lewis Research Center. The intent of this demonstration was to prove the feasibility of applying fiber optic technology to rocket engine instrumentation systems. Extreme thermal transient tests were achieved by wrapping a high temperature optical fiber, which was cablized for mechanical robustness, around the combustion chamber outside wall of a 1500 lb Hydrogen-Oxygen rocket engine. Additionally, the fiber was wrapped around coolant inlet pipes which were subject to near liquid hydrogen temperatures. Light from an LED was sent through the multimode fiber, and output power was monitored as a function of time while the engine was fired. The fiber showed no mechanical damage after 419 firings during which it was subject to transients from 30 K to 350 K, and total exposure time to near liquid hydrogen temperatures in excess of 990 seconds. These extreme temperatures did cause attenuation greater than 3 dB, but the signal was fully recovered at room temperature. This experiment demonstrates that commercially available optical fiber cables can survive the environment seen by a typical rocket engine instrumentation system, and disclose a temperature-dependent attenuation observed during exposure to near liquid hydrogen temperatures.

  7. Demonstration of multilayer reflective optics at photon energies above 0.6 MeV

    Brejnholt, Nicolai F.; Soufli, Regina; Descalle, Marie-Anne;

    2014-01-01

    Focusing optics operating in the soft gamma-ray photon energy range can advance a range of scientific and technological applications that benefit from the large improvements in sensitivity and resolution that true imaging provides. An enabling technology to this end is multilayer coatings. We show...... that very short period multilayer coatings deposited on super-polished substrates operate efficiently above 0.6 MeV. These experiments demonstrate that Bragg scattering theory established for multilayer applications as low as 1 eV continues to work well into the gamma-ray band. (C) 2014 Optical Society...

  8. Demonstration Of A Continuously Guided Atomic Interferometer Using A Single-Zone Optical Excitation

    Shahriar, M S; Jheeta, M; Morzinksi, J; Hemmer, P R; Pradhan, P

    2003-01-01

    We demonstrate an atomic interferometer in which the atom passes through a single-zone optical beam, consisting of a pair of bichromatic counter-propagating fields. During the passage, the atomic wave packets in two distinct internal states trace out split trajectories, guided by the optical beams, with the amplitude and spread of each wave-packet varying continuously, producing fringes that can reach a visibility close to unity. We show that the rotation sensitivity of this continuous interferometer (CI) can be comparable to that of the Borde-Chu Interferometer (BCI). The relative simplicity of the CI makes it a potentially better candidate for practical applications.

  9. Demonstration of a High-Efficiency Free-Space Optical Communications Link

    Birnbaum, Kevin; Farr, William; Gin, Jonathan; Moision, Bruce; Quirk, Kevin; Wright, Malcolm

    2009-01-01

    In this paper we discuss recent progress on the implementation of a hardware free-space optical communications test-bed. The test-bed implements an end-to-end communications system comprising a data encoder, modulator, laser-transmitter, telescope, detector, receiver and error-correction-code decoder. Implementation of each of the component systems is discussed, with an emphasis on 'real-world' system performance degradation and limitations. We have demonstrated real-time data rates of 44 Mbps and photon efficiencies of approximately 1.8 bits/photon over a 100m free-space optical link.

  10. Experience with wavefront sensor and deformable mirror interfaces for wide-field adaptive optics systems

    Basden, A. G.; Atkinson, D.; Bharmal, N. A.; Bitenc, U.; Brangier, M.; Buey, T.; Butterley, T.; Cano, D.; Chemla, F.; Clark, P.; Cohen, M.; Conan, J.-M.; de Cos, F. J.; Dickson, C.; Dipper, N. A.; Dunlop, C. N.; Feautrier, P.; Fusco, T.; Gach, J. L.; Gendron, E.; Geng, D.; Goodsell, S. J.; Gratadour, D.; Greenaway, A. H.; Guesalaga, A.; Guzman, C. D.; Henry, D.; Holck, D.; Hubert, Z.; Huet, J. M.; Kellerer, A.; Kulcsar, C.; Laporte, P.; Le Roux, B.; Looker, N.; Longmore, A. J.; Marteaud, M.; Martin, O.; Meimon, S.; Morel, C.; Morris, T. J.; Myers, R. M.; Osborn, J.; Perret, D.; Petit, C.; Raynaud, H.; Reeves, A. P.; Rousset, G.; Sanchez Lasheras, F.; Sanchez Rodriguez, M.; Santos, J. D.; Sevin, A.; Sivo, G.; Stadler, E.; Stobie, B.; Talbot, G.; Todd, S.; Vidal, F.; Younger, E. J.

    2016-06-01

    Recent advances in adaptive optics (AO) have led to the implementation of wide field-of-view AO systems. A number of wide-field AO systems are also planned for the forthcoming Extremely Large Telescopes. Such systems have multiple wavefront sensors of different types, and usually multiple deformable mirrors (DMs). Here, we report on our experience integrating cameras and DMs with the real-time control systems of two wide-field AO systems. These are CANARY, which has been operating on-sky since 2010, and DRAGON, which is a laboratory AO real-time demonstrator instrument. We detail the issues and difficulties that arose, along with the solutions we developed. We also provide recommendations for consideration when developing future wide-field AO systems.

  11. A Fossil Bulge Globular Cluster revealed by VLT Multi-Conjugate Adaptive Optics

    Ortolani, Sergio; Momany, Yazan; Saviane, Ivo; Bica, Eduardo; Jilkova, Lucie; Salerno, Gustavo Malta; Jungwiert, Bruno

    2011-01-01

    The globular cluster HP1 is projected on the bulge, very close to the Galactic center. The Multi-Conjugate Adaptive Optics (MCAO) Demonstrator (MAD) at the Very Large Telescope (VLT) allowed to acquire high resolution deep images that, combined with first epoch New Technology Telescope (NTT) data, enabled to derive accurate proper motions. The cluster and bulge field stellar contents were disentangled by means of this process, and produced unprecedented definition in the color-magnitude diagrams for this cluster. The metallicity of [Fe/H] ~ -1.0 from previous spectroscopic analysis is confirmed, which together with an extended blue horizontal branch, imply an age older than the halo average. Orbit reconstruction results suggest that HP1 is spatially confined within the bulge.

  12. Large-Stroke Self-Aligned Vertical Comb Drive Actuators for Adaptive Optics Applications

    Carr, E J; Olivier, S S; Solgaard, O

    2005-10-27

    A high-stroke micro-actuator array was designed, modeled, fabricated and tested. Each pixel in the 4x4 array consists of a self-aligned vertical comb drive actuator. This micro-actuator array was designed to become the foundation of a micro-mirror array that will be used as a deformable mirror for adaptive optics applications. Analytical models combined with CoventorWare{reg_sign} simulations were used to design actuators that would move up to 10{micro}m in piston motion with 100V applied. Devices were fabricated according to this design and testing of these devices demonstrated an actuator displacement of 1.4{micro}m with 200V applied. Further investigation revealed that fabrication process inaccuracy led to significantly stiffer mechanical springs in the fabricated devices. The increased stiffness of the springs was shown to account for the reduced displacement of the actuators relative to the design.

  13. Photoreceptor counting and montaging of en-face retinal images from an adaptive optics fundus camera

    Xue, Bai; Choi, Stacey S.; Doble, Nathan; Werner, John S.

    2007-05-01

    A fast and efficient method for quantifying photoreceptor density in images obtained with an en-face flood-illuminated adaptive optics (AO) imaging system is described. To improve accuracy of cone counting, en-face images are analyzed over extended areas. This is achieved with two separate semiautomated algorithms: (1) a montaging algorithm that joins retinal images with overlapping common features without edge effects and (2) a cone density measurement algorithm that counts the individual cones in the montaged image. The accuracy of the cone density measurement algorithm is high, with >97% agreement for a simulated retinal image (of known density, with low contrast) and for AO images from normal eyes when compared with previously reported histological data. Our algorithms do not require spatial regularity in cone packing and are, therefore, useful for counting cones in diseased retinas, as demonstrated for eyes with Stargardt's macular dystrophy and retinitis pigmentosa.

  14. Enhancement and bias removal of optical coherence tomography images: An iterative approach with adaptive bilateral filtering.

    Sudeep, P V; Issac Niwas, S; Palanisamy, P; Rajan, Jeny; Xiaojun, Yu; Wang, Xianghong; Luo, Yuemei; Liu, Linbo

    2016-04-01

    Optical coherence tomography (OCT) has continually evolved and expanded as one of the most valuable routine tests in ophthalmology. However, noise (speckle) in the acquired images causes quality degradation of OCT images and makes it difficult to analyze the acquired images. In this paper, an iterative approach based on bilateral filtering is proposed for speckle reduction in multiframe OCT data. Gamma noise model is assumed for the observed OCT image. First, the adaptive version of the conventional bilateral filter is applied to enhance the multiframe OCT data and then the bias due to noise is reduced from each of the filtered frames. These unbiased filtered frames are then refined using an iterative approach. Finally, these refined frames are averaged to produce the denoised OCT image. Experimental results on phantom images and real OCT retinal images demonstrate the effectiveness of the proposed filter. PMID:26907572

  15. 3-D Adaptive Sparsity Based Image Compression With Applications to Optical Coherence Tomography.

    Fang, Leyuan; Li, Shutao; Kang, Xudong; Izatt, Joseph A; Farsiu, Sina

    2015-06-01

    We present a novel general-purpose compression method for tomographic images, termed 3D adaptive sparse representation based compression (3D-ASRC). In this paper, we focus on applications of 3D-ASRC for the compression of ophthalmic 3D optical coherence tomography (OCT) images. The 3D-ASRC algorithm exploits correlations among adjacent OCT images to improve compression performance, yet is sensitive to preserving their differences. Due to the inherent denoising mechanism of the sparsity based 3D-ASRC, the quality of the compressed images are often better than the raw images they are based on. Experiments on clinical-grade retinal OCT images demonstrate the superiority of the proposed 3D-ASRC over other well-known compression methods. PMID:25561591

  16. Adaptive Optics: Arroyo Simulation Tool and Deformable Mirror Actuation Using Golay Cells

    Lint, Adam S.

    2005-01-01

    The Arroyo C++ libraries, written by Caltech post-doc student Matthew Britton, have the ability to simulate optical systems and atmospheric signal interference. This program was chosen for use in an end-to-end simulation model of a laser communication system because it is freely distributed and has the ability to be controlled by a remote system or "smart agent." Proposed operation of this program by a smart agent has been demonstrated, and the results show it to be a suitable simulation tool. Deformable mirrors, as a part of modern adaptive optics systems, may contain thousands of tiny, independently controlled actuators used to modify the shape of the mirror. Each actuator is connected to two wires, creating a cumbersome and expensive device. Recently, an alternative actuation method that uses gas-filled tubes known as Golay cells has been explored. Golay cells, operated by infrared lasers instead of electricity, would replace the actuator system thereby creating a more compact deformable mirror. The operation of Golay cells and their ability to move a deformable mirror in excess of the required 20 microns has been demonstrated. Experimentation has shown them to be extremely sensitive to pressure and temperature, making them ideal for use in a controlled environment.

  17. High-Resolution Adaptive Optics Scanning Laser Ophthalmoscope with Dual Deformable Mirrors

    Chen, D C; Jones, S M; Silva, D A; Olivier, S S

    2006-08-11

    Adaptive optics scanning laser ophthalmoscope (AO SLO) has demonstrated superior optical quality of non-invasive view of the living retina, but with limited capability of aberration compensation. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina. We used a bimorph mirror to correct large-stroke, low-order aberrations and a MEMS mirror to correct low-stroke, high-order aberration. The measured ocular RMS wavefront error of a test subject was 240 nm without AO compensation. We were able to reduce the RMS wavefront error to 90 nm in clinical settings using one deformable mirror for the phase compensation and further reduced the wavefront error to 48 nm using two deformable mirrors. Compared with that of a single-deformable-mirror SLO system, dual AO SLO offers much improved dynamic range and better correction of the wavefront aberrations. The use of large-stroke deformable mirrors provided the system with the capability of axial sectioning different layers of the retina. We have achieved diffraction-limited in-vivo retinal images of targeted retinal layers such as photoreceptor layer, blood vessel layer and nerve fiber layers with the combined phase compensation of the two deformable mirrors in the AO SLO.

  18. Adaptive optics scanning laser ophthalmoscope with integrated wide-field retinal imaging and tracking

    Ferguson, R. Daniel; Zhong, Zhangyi; Hammer, Daniel X.; Mujat, Mircea; Patel, Ankit H.; Deng, Cong; Zou, Weiyao; Burns, Stephen A.

    2010-01-01

    We have developed a new, unified implementation of the adaptive optics scanning laser ophthalmoscope (AOSLO) incorporating a wide-field line-scanning ophthalmoscope (LSO) and a closed-loop optical retinal tracker. AOSLO raster scans are deflected by the integrated tracking mirrors so that direct AOSLO stabilization is automatic during tracking. The wide-field imager and large-spherical-mirror optical interface design, as well as a large-stroke deformable mirror (DM), enable the AOSLO image fi...

  19. Principle of adaptive optical current transducer on independent variables and its test

    LU Zhong-feng; GUO Zhi-zhong

    2008-01-01

    In order to improve the measurement precision of the optical current transducer (OCT), the adaptive optical transducing principle on independent variables is presented in this paper. And one of the adaptive opti-cal current transducer(AOCT) on the independent variables of the output of the electricmegnet current trans-ducer is introduced. According to IEC660044-8, the performance of AOCT was examined roundly applying the standard testing system authenticated by the state authority. The results indicate that the measurement precision of the AOCT has already reached 0.2 class under the temperature from -40℃ to 60℃,which proves the feasi-bility of the method.

  20. High-Resolution Adaptive Optics Test-Bed for Vision Science

    Wilks, S C; Thomspon, C A; Olivier, S S; Bauman, B J; Barnes, T; Werner, J S

    2001-09-27

    We discuss the design and implementation of a low-cost, high-resolution adaptive optics test-bed for vision research. It is well known that high-order aberrations in the human eye reduce optical resolution and limit visual acuity. However, the effects of aberration-free eyesight on vision are only now beginning to be studied using adaptive optics to sense and correct the aberrations in the eye. We are developing a high-resolution adaptive optics system for this purpose using a Hamamatsu Parallel Aligned Nematic Liquid Crystal Spatial Light Modulator. Phase-wrapping is used to extend the effective stroke of the device, and the wavefront sensing and wavefront correction are done at different wavelengths. Issues associated with these techniques will be discussed.

  1. Demonstration of hybrid orbital angular momentum multiplexing and time-division multiplexing passive optical network.

    Wang, Andong; Zhu, Long; Liu, Jun; Du, Cheng; Mo, Qi; Wang, Jian

    2015-11-16

    Mode-division multiplexing passive optical network (MDM-PON) is a promising scheme for next-generation access networks to further increase fiber transmission capacity. In this paper, we demonstrate the proof-of-concept experiment of hybrid mode-division multiplexing (MDM) and time-division multiplexing (TDM) PON architecture by exploiting orbital angular momentum (OAM) modes. Bidirectional transmissions with 2.5-Gbaud 4-level pulse amplitude modulation (PAM-4) downstream and 2-Gbaud on-off keying (OOK) upstream are demonstrated in the experiment. The observed optical signal-to-noise ratio (OSNR) penalties for downstream and upstream transmissions at a bit-error rate (BER) of 2 × 10(-3) are less than 2.0 dB and 3.0 dB, respectively. PMID:26698429

  2. Adaptive optics for deeper imaging of biological samples.

    Girkin, John M; Poland, Simon; Wright, Amanda J

    2009-02-01

    Optical microscopy has been a cornerstone of life science investigations since its first practical application around 400 years ago with the goal being subcellular resolution, three-dimensional images, at depth, in living samples. Nonlinear microscopy brought this dream a step closer, but as one images more deeply the material through which you image can greatly distort the view. By using optical devices, originally developed for astronomy, whose optical properties can be changed in real time, active compensation for sample-induced aberrations is possible. Submicron resolution images are now routinely recorded from depths over 1mm into tissue. Such active optical elements can also be used to keep conventional microscopes, both confocal and widefield, in optimal alignment. PMID:19272766

  3. Demonstration of multilayer reflective optics at photon energies above 0.6 MeV

    Brejnholt, Nicolai F.; Soufli, Regina; Descalle, Marie-Anne; Fernandez-Perea, Monica; Christensen, Finn Erland; Jakobsen, Anders Clemen; Honkimaeki, Veijo; Pivovaroff, Michael J.

    2014-01-01

    Focusing optics operating in the soft gamma-ray photon energy range can advance a range of scientific and technological applications that benefit from the large improvements in sensitivity and resolution that true imaging provides. An enabling technology to this end is multilayer coatings. We show that very short period multilayer coatings deposited on super-polished substrates operate efficiently above 0.6 MeV. These experiments demonstrate that Bragg scattering theory established for multil...

  4. Imaging human retinal pigment epithelium cells using adaptive optics optical coherence tomography

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2016-03-01

    Retinal pigment epithelium (RPE) cells are vital to health of the outer retina, but are often compromised in ageing and major ocular diseases that lead to blindness. Early manifestation of RPE disruption occurs at the cellular level, and while biomarkers at this scale hold considerable promise, RPE cells have proven extremely challenging to image in the living human eye. We present a novel method based on optical coherence tomography (OCT) equipped with adaptive optics (AO) that overcomes the associated technical obstacles. The method takes advantage of the 3D resolution of AO-OCT, but more critically sub-cellular segmentation and registration that permit organelle motility to be used as a novel contrast mechanism. With this method, we successfully visualized RPE cells and characterized their 3D reflectance profile in every subject and retinal location (3° and 7° temporal to the fovea) imaged to date. We have quantified RPE packing geometry in terms of cell density, cone-to-RPE ratio, and number of nearest neighbors using Voronoi and power spectra analyses. RPE cell density (cells/mm2) showed no significant difference between 3° (4,892+/-691) and 7° (4,780+/-354). In contrast, cone-to- RPE ratio was significantly higher at 3° (3.88+/-0.52:1) than 7° (2.31+/- 0.23:1). Voronoi analysis also showed most RPE cells have six nearest neighbors, which was significantly larger than the next two most prevalent associations: five and seven. Averaged across the five subjects, prevalence of cells with six neighbors was 51.4+/-3.58% at 3°, and 54.58+/-3.01% at 7°. These results are consistent with histology and in vivo studies using other imaging modalities.

  5. A simplified free-space adaptive optics system against atmospheric turbulence

    Sharma, Sanjay

    2012-03-01

    Optical free-space communications have the distinct advantages over conventional radio frequency and microwave systems in terms of information capacity and increased security. However, optical carrier frequencies drastically suffer due to atmospheric turbulence. This effect is a random process and time-varying process; therefore, it is very difficult to overcome the effect. Adaptive optics is the technology used to mitigate chaotic optical wave-front distortions in real time by measuring the wave-front distortion with the help of a sensor and then adapting the wave-front corrector to lessen the phase distortions and ultimately to recover a closely approximated signal to its original counterpart. But these systems are too expensive and large. This study employs the various aspects of Adaptive Optics system, such as wave-front corrector, wave-front sensors and analytical analysis of open and closed-loop systems using loop equations, in order to make free-space optics communication links more vulnerable against atmospheric turbulence and wave-front phase distributions. The purpose of this study is to investigate a wave-front sensorless adaptive optics system, which would provide reduced complexity, size and cost.

  6. Adaptive optics OCT using 1060nm swept source and dual deformable lenses for human retinal imaging

    Jian, Yifan; Lee, Sujin; Cua, Michelle; Miao, Dongkai; Bonora, Stefano; Zawadzki, Robert J.; Sarunic, Marinko V.

    2016-03-01

    Adaptive optics concepts have been applied to the advancement of biological imaging and microscopy. In particular, AO has also been very successfully applied to cellular resolution imaging of the retina, enabling visualization of the characteristic mosaic patterns of the outer retinal layers using flood illumination fundus photography, Scanning Laser Ophthalmoscopy (SLO), and Optical Coherence Tomography (OCT). Despite the high quality of the in vivo images, there has been a limited uptake of AO imaging into the clinical environment. The high resolution afforded by AO comes at the price of limited field of view and specialized equipment. The implementation of a typical adaptive optics imaging system results in a relatively large and complex optical setup. The wavefront measurement is commonly performed using a Hartmann-Shack Wavefront Sensor (HS-WFS) placed at an image plane that is optically conjugated to the eye's pupil. The deformable mirror is also placed at a conjugate plane, relaying the wavefront corrections to the pupil. Due to the sensitivity of the HS-WFS to back-reflections, the imaging system is commonly constructed from spherical mirrors. In this project, we present a novel adaptive optics OCT retinal imaging system with significant potential to overcome many of the barriers to integration with a clinical environment. We describe in detail the implementation of a compact lens based wavefront sensorless adaptive optics (WSAO) 1060nm swept source OCT human retinal imaging system with dual deformable lenses, and present retinal images acquired in vivo from research volunteers.

  7. Optical design and laser ablation of surface textures: demonstrating total internal reflection

    Gommans, Hans; Booij, Silvia; Pijlman, Fetze; Krijn, Marcel; de Zwart, Siebe; Sepkhanov, Ruslan; Beaumont, Dave; van der Schaft, Hans; Sanders, Rene

    2015-09-01

    In lighting applications key drivers for optical design of surface textures are integration of optical elements, the disentanglement of optical functionality and appearance and late stage configuration. We investigated excimer laser ablation as a mastering technology for micro textured surfaces, where we targeted an increase in correspondence between surface design and ablated surface for high aspect ratio structures. To achieve this we have improved the photo mask design using a heuristic algorithm that corrects for the angular dependence of the ablation process and the loss of image resolution at ablation depths that exceed the depth of field. Using this approach we have been able to demonstrate close correspondence between designed and ablated facet structures up to 75° inclination at 75 μm depth. These facet design parameters allow for total internal reflection (TIR) as a means of beam deflection which is demonstrated in a range of mono shaped cone arrays in hexagonal tessellation. BSDF analysis was used to characterize the narrow TIR deflection beams that matched the peak positions of the design down to 28° apex. In addition, a single surface TIR-Fresnel lens design with focal distance 5 mm has been manufactured using this photo mask design algorithm and beam collimation up to 12° beam angle and 32° field angle is shown. These outcomes demonstrate that the laser ablation process intrinsically yields sufficient small dispersion in structure and fillet radii for lighting applications.

  8. Compensation of modal dispersion in multimode fiber systems using adaptive optics via convex optimization

    Panicker, Rahul Alex

    show that CPSCA is able to compensate for modal dispersion over up to 2.2 km, even in the presence of mid-span connector offsets up to 4 mum (simulated in experiment by offset splices). A known non-adaptive launching technique using a fusion-spliced single-mode-to-multimode patchcord is shown to fail under these conditions. Finally, we demonstrate 10 x 10 Gb/s dense WDM transmission over 2.2 km of 50-mum GRIN MMF. We combine transmitter-based adaptive optics and receiver-based single-mode filtering, and control the launched field pattern for ten 10-Gb/s non-return-to-zero channels, wavelength-division multiplexed on a 200-GHz grid in the C band. We achieve error-free transmission through 2.2 km of 50-mum GRIN MMF for launch offsets up to 10 mum and for worst-case launched polarization. We employ a ten-channel transceiver based on parallel integration of electronics and photonics.

  9. Quality evaluation of adaptive optical image based on DCT and Rényi entropy

    Xu, Yuannan; Li, Junwei; Wang, Jing; Deng, Rong; Dong, Yanbing

    2015-04-01

    The adaptive optical telescopes play a more and more important role in the detection system on the ground, and the adaptive optical images are so many that we need find a suitable method of quality evaluation to choose good quality images automatically in order to save human power. It is well known that the adaptive optical images are no-reference images. In this paper, a new logarithmic evaluation method based on the use of the discrete cosine transform(DCT) and Rényi entropy for the adaptive optical images is proposed. Through the DCT using one or two dimension window, the statistical property of Rényi entropy for images is studied. The different directional Rényi entropy maps of an input image containing different information content are obtained. The mean values of different directional Rényi entropy maps are calculated. For image quality evaluation, the different directional Rényi entropy and its standard deviation corresponding to region of interest is selected as an indicator for the anisotropy of the images. The standard deviation of different directional Rényi entropy is obtained as the quality evaluation value for adaptive optical image. Experimental results show the proposed method that the sorting quality matches well with the visual inspection.

  10. Magnetic smart material application to adaptive x-ray optics

    Ulmer, M. P.; Graham, Michael E.; Vaynman, Semyon; Cao, J.; Takacs, Peter Z.

    2010-09-01

    We discuss a technique of shape modification that can be applied to thin walled ({100-400 micron thickness) electroformed replicated optics or slumped glass optics to improve the near net shape of the mirror as well as the midfrequency ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a permanently magnetic material. The MSM material exhibits strains about 400 times stronger than ordinary ferromagnetic materials. The deformation process involves a magnetic write head which traverses the surface, and under the guidance of active metrology feedback, locally magnetizes the surface to impart strain where needed. Designs and basic concepts as applied to space borne X-ray optics will be described.

  11. Packetisation in Optical Packet Switch Fabrics using adaptive timeout values

    Mortensen, Brian Bach

    2006-01-01

    either because the timer reaches a specific timeout value, or because the optical packet is completely filled with segments. Only two distinct values of the timeout value are used. Which of the two timeout values to use, is selected by 3 different control thresholds. The first threshold level applies to...... the inter arrival rate at the individual VOQs. The remaining thresholds applies to the optical slot level inter arrival rate at the input and output line cards. If any measurements are beyond a given threshold, the higher timeout value is used. The proposed method can be used to make a trade...

  12. Experimental demonstration of adaptive digital monitoring and compensation of chromatic dispersion for coherent DP-QPSK receiver

    Borkowski, Robert; Zhang, Xu; Zibar, Darko;

    2011-01-01

    We experimentally demonstrate a digital signal processing (DSP)-based optical performance monitoring (OPM) algorithm for inservice monitoring of chromatic dispersion (CD) in coherent transport networks. Dispersion accumulated in 40 Gbit/s QPSK signal after 80 km of fiber transmission is successfu...

  13. Demonstration of the stabilization technique for nonplanar optical resonant cavities utilizing polarization

    Akagi, T.; Araki, S.; Funahashi, Y.; Honda, Y.; Okugi, T.; Omori, T.; Shimizu, H.; Terunuma, N.; Urakawa, J. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Miyoshi, S.; Takahashi, T., E-mail: tohru-takahashi@hiroshima-u.ac.jp; Tanaka, R.; Uesugi, Y.; Yoshitama, H. [AdSM Hiroshima University, 1-3-1 Kagamiyama, Higashi, Hiroshima 739-8530 (Japan); Sakaue, K.; Washio, M. [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku 169-8555 (Japan)

    2015-04-15

    Based on our previously developed scheme to stabilize nonplanar optical resonant cavities utilizing polarization caused by a geometric phase in electromagnetic waves traveling along a twisted path, we report an application of the technique for a cavity installed in the Accelerator Test Facility, a 1.3-GeV electron beam accelerator at KEK, in which photons are generated by laser-Compton scattering. We successfully achieved a power enhancement of 1200 with 1.4% fluctuation, which means that the optical path length of the cavity has been controlled with a precision of 14 pm under an accelerator environment. In addition, polarization switching utilizing a geometric phase of the nonplanar cavity was demonstrated.

  14. Demonstration of a novel dispersive spectral splitting optical element for cost- effective photovoltaic conversion

    Maragliano, Carlo; Bronzoni, Matteo; Rampino, Stefano; Fitzgerald, Eugene A; Chiesa, Matteo; Stefancich, Marco

    2015-01-01

    In this letter we report the preliminary validation of a low-cost paradigm for photovoltaic power generation that utilizes a prismatic Fresnel-like lens to simultaneously concentrate and separate sunlight into continuous laterally spaced spectral bands, which are then fed into spectrally matched single-junction photovoltaic cells. A prismatic lens was designed using geometric optics and the dispersive properties of the employed material, and its performance was simulated with a ray- tracing software. After device optimization, it was fabricated by injection molding, suitable for large-scale mass production. We report an average optical transmittance of ~ 90% over the VNIR range with spectral separation in excellent agreement with our simulations. Finally, two prototype systems were tested: one with GaAsP and c-Si photovoltaic devices and one with a pair of copper indium gallium selenide based solar cells. The systems demonstrated an increase in peak electrical power output of 51% and 64% respectively under wh...

  15. Ground Demonstration of Planetary Gas Lidar Based on Optical Parametric Amplifier

    Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephen R.; Krainak, Michael; Abshire, James

    2012-01-01

    We report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OPA output has high spectral purity and is widely tunable both at near-infrared and mid-infrared wavelengths, with an optical-optica1 conversion efficiency of up to approx 39 %. Using this laser source, we demonstrated open-path measurements of CH4 (3291 nm and 1651 nm), CO2 (1573 nm), H2O (1652 nm), and CO (4764 nm) on the ground. The simplicity, tunability. and power scalability of the OPA make it a strong candidate for general planetary lidar instruments, which will offer important information on the origins of the planet's geology, atmosphere, and potential for biology,

  16. Development of a scalable generic platform for adaptive optics real time control

    Surendran, Avinash; Ramaprakash, A N; Parihar, Padmakar

    2015-01-01

    The main objective of the present project is to explore the viability of an adaptive optics control system based exclusively on Field Programmable Gate Arrays (FPGAs), making strong use of their parallel processing capability. In an Adaptive Optics (AO) system, the generation of the Deformable Mirror (DM) control voltages from the Wavefront Sensor (WFS) measurements is usually through the multiplication of the wavefront slopes with a predetermined reconstructor matrix. The ability to access several hundred hard multipliers and memories concurrently in an FPGA allows performance far beyond that of a modern CPU or GPU for tasks with a well defined structure such as Adaptive Optics control. The target of the current project is to generate a signal for a real time wavefront correction, from the signals coming from a Wavefront Sensor, wherein the system would be flexible to accommodate all the current Wavefront Sensing techniques and also the different methods which are used for wavefront compensation. The system ...

  17. Monte Carlo simulation of ELT-scale multi-object adaptive optics deformable mirror requirements and tolerances

    Basden, A. G.; Bharmal, N. A.; Myers, R. M.; Morris, S. L.; Morris, T. J.

    2013-10-01

    Multi-object adaptive optics (MOAO) has been demonstrated by the CANARY instrument on the William Herschel Telescope. However, for proposed MOAO systems on the next-generation extremely large telescopes (ELTs), such as ELT Adaptive optics for GaLaxy Evolution (EAGLE), many challenges remain. Here we investigate requirements that MOAO operation places on deformable mirrors (DMs) using a full end-to-end Monte Carlo adaptive optics (AO) simulation code. By taking into consideration a prior global ground-layer (GL) correction, we show that actuator density for the MOAO DMs can be reduced with little performance loss. We note that this reduction is only possible with the addition of a GL DM, whose order is greater than or equal to that of the original MOAO mirrors. The addition of a GL DM of lesser order does not affect system performance (if tip/tilt star sharpening is ignored). We also quantify the maximum mechanical DM stroke requirements (3.5 μm desired) and provide tolerances for the DM alignment accuracy, both lateral (to within an eighth of a sub-aperture) and rotational (to within 0.2°). By presenting results over a range of laser guide star asterism diameters, we ensure that these results are equally applicable for laser tomographic AO systems. We provide the opportunity for significant cost savings to be made in the implementation of MOAO systems, resulting from the lower requirement for DM actuator density.

  18. Experimental demonstration of 2.5 Gbit/S incoherent two-dimensional optical code division multiple access system

    We demonstrated error-free operation of 4 simultaneous users in a fast frequency-hopping time-spreading optical code division multiple access system operating at 2.5 Gbit/s a Star architecture. Effective power penalty was ≤0.5dB. Novel optical code division multiple access receiver based on Terahertz Optical Asymmetric Demultiplexer was demonstrated to eliminate multiple access interference (Authors)

  19. Adaptive optics for control of the laser welding process

    Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

    Vol. 48. Liberec : EDP Sciences, 2013, 00017:1-6. ISBN 9781632661944. [OaM 2012 International Conference on Optics and Measurement. Liberec (CZ), 16.10.2012-18.10.2012] R&D Projects: GA MPO 2A-3TP1/113; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : Fresnel absorption * multiple reflections * keyhole * evolution Subject RIV: JB - Sensors, Measurment, Regulation

  20. Silicon carbide deformable mirror with 37 actuators for adaptive optics

    Ahn, Kyohoon; Rhee, Hyug-Gyo; Yang, Ho-Soon; Kihm, Hagyong

    2015-11-01

    We present a prototype of a silicon carbide (SiC) deformable mirror (DM) for high power laser applications. The DM has a continuous SiC faceplate, the diameter and the thickness of which are 100 mm and 2 mm, respectively, and 37 stack-type piezoelectric actuators arranged in a rectangular grid. Compared with the glass faceplates used for conventional DMs, SiC has a high thermal diffusivity that effectively minimizes mirror distortions due to thermal gradients. The faceplate is thick enough for possible integration with monolithic cooling channels inside the faceplate. The faceplate without cooling channels presented in this paper has a high bending stiffness compared with glass DMs, but the proposed actuator configuration has flexure supports to reduce the shear stress at the adhesive while preserving optical performances. To examine the characteristics of the SiC DM, we simulated influence functions (IFs) by using a finite element analysis and then compared these results with the IF measured by using an optical interferometer. The optical performance of the DM was verified by generating Zernike polynomial modes based on the measured IF.

  1. Real-Time Adaptive Management of Soil Salinity Using a Receding Horizon Control Algorithm: A Pilot-Scale Demonstration

    Park, Yeonjeong; Thomas C. Harmon

    2009-01-01

    This work demonstrates the application of real-time adaptive management principles to the problem of controlling the salinity levels in, and/or protecting groundwater quality beneath, soils undergoing irrigation with relatively saline water (e.g., reclaimed wastewater) under arid/semi- arid conditions. Here, optimal feedback-control scheme known as Receding Horizon Control (RHC) previously applied offline to control soil moisture levels during irrigation (Park et al., 2009) is applied inline ...

  2. A Phase-Shifting Zernike Wavefront Sensor for the Palomar P3K Adaptive Optics System

    Wallace, J. Kent; Crawford, Sam; Loya, Frank; Moore, James

    2012-01-01

    A phase-shifting Zernike wavefront sensor has distinct advantages over other types of wavefront sensors. Chief among them are: 1) improved sensitivity to low-order aberrations and 2) efficient use of photons (hence reduced sensitivity to photon noise). We are in the process of deploying a phase-shifting Zernike wavefront sensor to be used with the realtime adaptive optics system for Palomar. Here we present the current state of the Zernike wavefront sensor to be integrated into the high-order adaptive optics system at Mount Palomar's Hale Telescope.

  3. Investigation of Power8 processors for astronomical adaptive optics real-time control

    Basden, Alastair

    2015-01-01

    The forthcoming Extremely Large Telescopes all require adaptive optics systems for their successful operation. The real-time control for these systems becomes computationally challenging, in part limited by the memory bandwidths required for wavefront reconstruction. We investigate new POWER8 processor technologies applied to the problem of real-time control for adaptive optics. These processors have a large memory bandwidth, and we show that they are suitable for operation of first-light ELT instrumentation, and propose some potential real-time control system designs. A CPU-based real-time control system significantly reduces complexity, improves maintainability, and leads to increased longevity for the real-time control system.

  4. An adaptive optics approach to the reduction of misalignments and beam jitters in gravitational wave interferometers

    We describe a study and the preliminary experimental results on the possibility of using adaptive optics systems for the reduction of geometrical fluctuations of input laser beams in long baseline interferometric detectors of gravitational waves. The experimental tests aimed to test the efficiency of Hermite-Gauss versus Shack-Hartmann wavefront reconstruction and feedback diagonalization. These preliminary results seem to indicate that the adaptive optics systems may be integrated in the near future as stabilization stages before a passive mode cleaner cavity, provided that the operational band of the mirror is increased together with the efficiency of the control system

  5. Modelling of multi-conjugate adaptive optics for spatially variant aberrations in microscopy

    Adaptive optics has been implemented in a range of high-resolution microscopes in order to overcome the problems of specimen-induced aberrations. Most implementations have used a single aberration correction across the imaged field. It is known, however, that aberrations often vary across the field of view, so a single correction setting cannot compensate all aberrations. Multi-conjugate adaptive optics (MCAO) has been suggested as a possible method for correction of these spatially variant aberrations. MCAO is modelled to simulate the correction of aberrations, both for simple model specimens and using real aberration data from a biological specimen. (special issue article)

  6. AVES-IMCO: an adaptive optics visible spectrograph and imager/coronograph for NAOS

    Beuzit, Jean-Luc; Lagrange, A.-M.; Mouillet, D.; Chauvin, G.; Stadler, E.; Charton, J.; Lacombe, F.; AVES-IMCO Team

    2001-05-01

    The NAOS adaptive optics system will very soon provide diffraction-limited images on the VLT, down to the visible wavelengths (0.020 arcseconds at 0.83 micron for instance). At the moment, the only instrument dedicated to NAOS is the CONICA spectro-imager, operating in the near-infrared from 1 to 5 microns. We are now proposing to ESO, in collaboration with an Italian group, the development of a visible spectrograph/imager/coronograph, AVES-IMCO (Adaptive Optics Visual Echelle Spectrograph and IMager/COronograph). We present here the general concept of the new instrument as well as its expected performances in the different modes.

  7. Software defined networking (SDN) over space division multiplexing (SDM) optical networks: features, benefits and experimental demonstration.

    Amaya, N; Yan, S; Channegowda, M; Rofoee, B R; Shu, Y; Rashidi, M; Ou, Y; Hugues-Salas, E; Zervas, G; Nejabati, R; Simeonidou, D; Puttnam, B J; Klaus, W; Sakaguchi, J; Miyazawa, T; Awaji, Y; Harai, H; Wada, N

    2014-02-10

    We present results from the first demonstration of a fully integrated SDN-controlled bandwidth-flexible and programmable SDM optical network utilizing sliceable self-homodyne spatial superchannels to support dynamic bandwidth and QoT provisioning, infrastructure slicing and isolation. Results show that SDN is a suitable control plane solution for the high-capacity flexible SDM network. It is able to provision end-to-end bandwidth and QoT requests according to user requirements, considering the unique characteristics of the underlying SDM infrastructure. PMID:24663655

  8. An adaptive optics approach for laser beam correction in turbulence utilizing a modified plenoptic camera

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2015-09-01

    Adaptive optics has been widely used in the field of astronomy to correct for atmospheric turbulence while viewing images of celestial bodies. The slightly distorted incoming wavefronts are typically sensed with a Shack-Hartmann sensor and then corrected with a deformable mirror. Although this approach has proven to be effective for astronomical purposes, a new approach must be developed when correcting for the deep turbulence experienced in ground to ground based optical systems. We propose the use of a modified plenoptic camera as a wavefront sensor capable of accurately representing an incoming wavefront that has been significantly distorted by strong turbulence conditions (C2n distortions. After the large distortions have been corrected, a secondary mode utilizing more traditional adaptive optics algorithms can take over to fine tune the wavefront correction. This two-stage algorithm can find use in free space optical communication systems, in directed energy applications, as well as for image correction purposes.

  9. Analysis of adaptive laser scanning optical system with focus-tunable components

    Pokorný, P.; Mikš, A.; Novák, J.; Novák, P.

    2015-05-01

    This work presents a primary analysis of an adaptive laser scanner based on two-mirror beam-steering device and focustunable components (lenses with tunable focal length). It is proposed an optical scheme of an adaptive laser scanner, which can focus the laser beam in a continuous way to a required spatial position using the lens with tunable focal length. This work focuses on a detailed analysis of the active optical or opto-mechanical components (e.g. focus-tunable lenses) mounted in the optical systems of laser scanners. The algebraic formulas are derived for ray tracing through different configurations of the scanning optical system and one can calculate angles of scanner mirrors and required focal length of the tunable-focus component provided that the position of the focused beam in 3D space is given with a required tolerance. Computer simulations of the proposed system are performed using MATLAB.

  10. The jet of the BL Lac object PKS 0521 -365 in the near-IR : MAD adaptive optics observations

    Falomo, R; Treves, A; Giovannini, G; Venturi, T; Moretti, A; Arcidiacono, C; Farinato, J; Ragazzoni, R; Diolaiti, E; Lombini, M; Tavecchio, F; Brast, R; Marchetti, E; Tordo, S

    2009-01-01

    BL Lac objects are low--power active nuclei exhibiting a variety of peculiar properties that are caused by the presence of a relativistic jet and orientation effects. We present here adaptive optics near-IR images at high spatial resolution of the nearby BL Lac object PKS 0521-365, which is known to display a prominent jet both at radio and optical frequencies. The observations were obtained in Ks--band using the ESO multi-conjugated adaptive optics demonstrator at the Very Large Telescope. This allowed us to obtain images with 0.1 arcsec effective resolution. We performed a detailed analysis of the jet and its related features from the near-IR images, and combined them with images previously obtained with HST in the R band and by a re-analysis of VLA radio maps. We find a remarkable similarity in the structure of the jet at radio, near-IR, and optical wavelengths. The broad--band emission of the jet knots is dominated by synchrotron radiation, while the nucleus also exhibits a significant inverse Compton com...

  11. Images of photoreceptors in living primate eyes using adaptive optics two-photon ophthalmoscopy

    Hunter, Jennifer J.; Masella, Benjamin; Dubra, Alfredo; Sharma, Robin; Yin, Lu; Merigan, William H.; Palczewska, Grazyna; Palczewski, Krzysztof; Williams, David R.

    2010-01-01

    In vivo two-photon imaging through the pupil of the primate eye has the potential to become a useful tool for functional imaging of the retina. Two-photon excited fluorescence images of the macaque cone mosaic were obtained using a fluorescence adaptive optics scanning laser ophthalmoscope, overcoming the challenges of a low numerical aperture, imperfect optics of the eye, high required light levels, and eye motion. Although the specific fluorophores are as yet unknown, strong in vivo intrins...

  12. Fuzzy-Based Adaptive Hybrid Burst Assembly Technique for Optical Burst Switched Networks

    Abubakar Muhammad Umaru; Muhammad Shafie Abd Latiff; Yahaya Coulibaly

    2014-01-01

    The optical burst switching (OBS) paradigm is perceived as an intermediate switching technology for future all-optical networks. Burst assembly that is the first process in OBS is the focus of this paper. In this paper, an intelligent hybrid burst assembly algorithm that is based on fuzzy logic is proposed. The new algorithm is evaluated against the traditional hybrid burst assembly algorithm and the fuzzy adaptive threshold (FAT) burst assembly algorithm via simulation. Simulation results sh...

  13. Implantable collamer lens and femtosecond laser for myopia: comparison using an adaptive optics visual simulator

    Cari Pérez-Vives; César Albarrán-Diego; Santiago García-Lázaro; Teresa Ferrer-Blasco; Robert Montés-Micó

    2014-01-01

    Purpose: To compare optical and visual quality of implantable collamer lens (ICL) implantation and femtosecond laser in situ keratomileusis (F-LASIK) for myopia. Methods: The CRX1 adaptive optics visual simulator (Imagine Eyes, Orsay, France) was used to simulate the wavefront aberration pattern after the two surgical procedures for -3-diopter (D) and -6-D myopia. Visual acuity at different contrasts and contrast sensitivities at 10, 20, and 25 cycles/degree (cpd) were measured for 3-mm an...

  14. Adaptive micro-optical phase modulators based on liquid crystal technology

    Algorri Genaro, José Francisco

    2015-01-01

    This thesis began with the project “Advanced Devices of Liquid Crystal and Electroluminescent Organic Diodes. Hybrid Applications for 3D Vision” funded by the Spanish government. The goal of this project was the development of optical devices to achieve 3D vision in portable devices without glasses or external elements. In order to achieve the goals of this project, solutions based on liquid crystal are considered. Specifically, adaptive micro-optical phase modulators based on liquid crystal ...

  15. Optical Multi-Gas Monitor Technology Demonstration on the International Space Station

    Pilgrim, Jeffrey S.; Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Johnson, Michael D.; Mudgett, Paul D.

    2014-01-01

    The International Space Station (ISS) employs a suite of portable and permanently located gas monitors to insure crew health and safety. These sensors are tasked with functions ranging from fixed mass spectrometer based major constituents analysis to portable electrochemical sensor based combustion product monitoring. An all optical multigas sensor is being developed that can provide the specificity of a mass spectrometer with the portability of an electrochemical cell. The technology, developed under the Small Business Innovation Research program, allows for an architecture that is rugged, compact and low power. A four gas version called the Multi-Gas Monitor was launched to ISS in November 2013 aboard Soyuz and activated in February 2014. The portable instrument is comprised of a major constituents analyzer (water vapor, carbon dioxide, oxygen) and high dynamic range real-time ammonia sensor. All species are sensed inside the same enhanced path length optical cell with a separate vertical cavity surface emitting laser (VCSEL) targeted at each species. The prototype is controlled digitally with a field-programmable gate array/microcontroller architecture. The optical and electronic approaches are designed for scalability and future versions could add three important acid gases and carbon monoxide combustion product gases to the four species already sensed. Results obtained to date from the technology demonstration on ISS are presented and discussed.

  16. Demonstration of Non-Deterministic Quantum Logic Operations using Linear Optical Elements

    Pittman, T B; Franson, J D

    2002-01-01

    In an earlier Article[1], Knill, Laflamme, and Milburn showed that non-deterministic quantum logic operations could be performed using linear optical elements, additional photons (ancilla), and post-selection based on the output of single-photon detectors. These devices succeed in producing the desired logical output with a probability that can approach unity and they may form the basis for a scalable approach to quantum computing. Here we report the experimental demonstration of two logic devices of this kind, a quantum parity check and a destructive controlled-NOT (CNOT) gate[2]. These devices have a very simple structure and they are relatively insensitive to errors due to phase drifts. The quantum parity check and destructive CNOT gates demonstrated here could be combined with a pair of entangled photons to implement a conventional (non-destructive) CNOT gate, the basic building-block for a quantum computer, that succeeds with a probability of 1/4.

  17. Binary Optical True-Time Delay Based on the White Cell: Design and Demonstration

    Anderson, Betty Lise; Rabb, David J.; Warnky, Carolyn M.; Abou-Galala, Feras

    2006-04-01

    An optical true-time delay device that uses a binary counting system in a modified White cell is demonstrated. The switching engine uses four spherical mirrors and a three-state digital micromirror array. The delay part, as designed, provides 6 bits of delay ranging from 78 ps to 5 ns, using a combination of dielectric blocks for short delays and lens trains for longer ones. Long lens trains are folded for compactness. The authors describe the design and demonstrate two of the 6 bits of delays experimentally. Delays were accurate to within the measurement resolution of 1.25 ps. The insertion loss varied from 3.1-5.2 dB, depending on delay. It was found that the micromirrors do not contribute significantly to the loss.

  18. Experimental demonstration of optical phase conjugation using counter-propagating dual pumped four-wave mixing in semiconductor optical amplifier

    Anchal, Abhishek; Pradeep Kumar, K.; O'Duill, Sean; Anandarajah, Prince M.; Landais, Pascal

    2016-06-01

    We report optical phase conjugation in C-band by counter-propagating dual pumped non-degenerate four-wave mixing in a semiconductor optical amplifier (SOA). The co-propagating signal and pump waves create a grating inside SOA which diffracts counter-propagating pump and generates the conjugate wave. Since the signal and conjugate waves appear at opposite ends, the conjugate is easily filtered out from the rest of spectrum with minimal spectral shift of the conjugate with respect to the incoming signal. With pump powers of -3.2 dBm each and signal input power of -7 dBm, conjugate power was of -27.2 dBm, giving a conversion efficiency of 1% at 18 GHz pump-signal detuning. By modulating the signal by a periodic pattern '1000' at 10 Gbps using a non-zero chirp intensity modulator and resolving the temporal profile of the electric field envelope of the conjugate wave, we demonstrate spectral inversion.

  19. Optical Demonstration of THz, Dual-Polarization Sensitive Microwave Kinetic Inductance Detectors

    Dober, B.; Austermann, J. A.; Beall, J. A.; Becker, D.; Che, G.; Cho, H. M.; Devlin, M.; Duff, S. M.; Galitzki, N.; Gao, J.; Groppi, C.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; McKenney, C. M.; Li, D.; Lourie, N.; Mauskopf, P.; Vissers, M. R.; Wang, Y.

    2016-07-01

    Polarization sensitive, microwave kinetic inductance detectors (MKIDs) are under development for the next generation BLAST instrument (BLAST-TNG). BLAST-TNG is a balloon-borne submillimeter polarimeter designed to study magnetic fields in diffuse dust regions and molecular clouds. We present the design and performance of feedhorn-coupled, dual-polarization sensitive MKIDs fabricated from TiN/Ti multilayer films, which have been optimized for the 250 \\upmu m band. Measurements show effective selection of linear polarization and good electrical isolation between the orthogonally crossed X and Y detectors within a single spatial pixel. The detector cross-polar coupling is <3 %. Passband measurements are presented, which demonstrate that the desired band-edges (1.0-1.4 THz) have been achieved. We find a near linear response to the optical load from a blackbody source, which has been observed in previous devices fabricated from TiN. Blackbody-coupled noise measurements demonstrate that the sensitivity of the detectors is limited by photon noise when the optical load is greater than 1 pW.

  20. In-hardware demonstration of model-independent adaptive tuning of noisy systems with arbitrary phase drift

    Scheinker, Alexander, E-mail: alexscheinker@gmail.com; Baily, Scott; Young, Daniel; Kolski, Jeffrey S.; Prokop, Mark

    2014-08-21

    In this work, an implementation of a recently developed model-independent adaptive control scheme, for tuning uncertain and time varying systems, is demonstrated on the Los Alamos linear particle accelerator. The main benefits of the algorithm are its simplicity, ability to handle an arbitrary number of components without increased complexity, and the approach is extremely robust to measurement noise, a property which is both analytically proven and demonstrated in the experiments performed. We report on the application of this algorithm for simultaneous tuning of two buncher radio frequency (RF) cavities, in order to maximize beam acceptance into the accelerating electromagnetic field cavities of the machine, with the tuning based only on a noisy measurement of the surviving beam current downstream from the two bunching cavities. The algorithm automatically responds to arbitrary phase shift of the cavity phases, automatically re-tuning the cavity settings and maximizing beam acceptance. Because it is model independent it can be utilized for continuous adaptation to time-variation of a large system, such as due to thermal drift, or damage to components, in which the remaining, functional components would be automatically re-tuned to compensate for the failing ones. We start by discussing the general model-independent adaptive scheme and how it may be digitally applied to a large class of multi-parameter uncertain systems, and then present our experimental results.

  1. In-hardware demonstration of model-independent adaptive tuning of noisy systems with arbitrary phase drift

    In this work, an implementation of a recently developed model-independent adaptive control scheme, for tuning uncertain and time varying systems, is demonstrated on the Los Alamos linear particle accelerator. The main benefits of the algorithm are its simplicity, ability to handle an arbitrary number of components without increased complexity, and the approach is extremely robust to measurement noise, a property which is both analytically proven and demonstrated in the experiments performed. We report on the application of this algorithm for simultaneous tuning of two buncher radio frequency (RF) cavities, in order to maximize beam acceptance into the accelerating electromagnetic field cavities of the machine, with the tuning based only on a noisy measurement of the surviving beam current downstream from the two bunching cavities. The algorithm automatically responds to arbitrary phase shift of the cavity phases, automatically re-tuning the cavity settings and maximizing beam acceptance. Because it is model independent it can be utilized for continuous adaptation to time-variation of a large system, such as due to thermal drift, or damage to components, in which the remaining, functional components would be automatically re-tuned to compensate for the failing ones. We start by discussing the general model-independent adaptive scheme and how it may be digitally applied to a large class of multi-parameter uncertain systems, and then present our experimental results

  2. Experimental Demonstration of Optical Switching of Tbit/s Data Packets for High Capacity Short-Range Networks

    Medhin, Ashenafi Kiros; Kamchevska, Valerija; Hu, Hao; Galili, Michael; Oxenløwe, Leif Katsuo

    2015-01-01

    Record-high 1.28-Tbit/s optical data packets are experimentally switched in the optical domain using a LiNbO3 switch. An in-band notch-filter labeling scheme scalable to 65,536 labels is employed and a 3-km transmission distance is demonstrated.......Record-high 1.28-Tbit/s optical data packets are experimentally switched in the optical domain using a LiNbO3 switch. An in-band notch-filter labeling scheme scalable to 65,536 labels is employed and a 3-km transmission distance is demonstrated....

  3. Adaptive PMD Compensation in 10 Gbit/s RZ Optical Communication System

    Yu; Li; Zhang; Xiaoguang; Zhou; Guangtao; Shen; Yu; Zheng; Yuan; Li; Chaoyang; Liu; Yumin; Chen; Lin; Yang; Bojun

    2003-01-01

    We report an experiment of adaptive compensation for polarization mode dispersion (PMD) in 10Gbit/s return zero (RZ) optical communication system. The quasi-real-time PMD compensation is realized. The algorithm so-called particle swarm optimization (PSO) is used to control feedback compensation system.

  4. Placing Limits on Extragalactic Substructure with Gravitational Lenses and Adaptive Optics

    Lagattuta, David J.; Vegetti, S.; Auger, M. W.; Fassnacht, C. D.; Koopmans, L. V. E.; McKean, J. P.

    2011-01-01

    We present the first results from a systematic search for extragalactic substructure, using high resolution Adaptive Optics (AO) images of known strong gravitational lenses. In particular we focus on two lens systems, B0128+437 and B1939+666, placing limits on both luminous and dark matter substruct

  5. Using 50-mm electrostatic membrane deformable mirror in astronomical adaptive optics

    Tokovinin, A.; Thomas, S.; Vdovin, G.

    2004-01-01

    Membrane micro-machined deformable mirrors (MMDM) feature low cost, low power consumption, small size and absence of hysteresis. Interested in using such a device for the adaptive optics system at the SOAR 4.1-m telescope, we evaluated the performance of a 79-channel 50-mm (pupil size 35mm) MMDM fro

  6. Operation of the adaptive optics system at the Large Binocular Telescope Observatory

    Miller, Douglas L.; Guerra, Juan Carlos; Boutsia, Konstantina; Fini, Luca; Argomedo, Javier; Biddick, Chris; Agapito, Guido; Arcidiacono, Carmelo; Briguglio, Runa; Brusa, Guido; Busoni, Lorenzo; Esposito, Simone; Hill, John; Kulesa, Craig; McCarthy, Don; Pinna, Enrico; Puglisi, Alfio T.; Quiros-Pacheco, Fernando; Riccardi, Armando; Xompero, Marco

    2012-07-01

    The Adaptive Optics System at the Large Binocular Telescope Observatory consists of two Adaptive Secondary (ASM) mirrors and two Pyramid Wavefront sensors. The first ASM/Pyramid pair has been commissioned and is being used for science operation using the NIR camera PISCES on the right side of the binocular telescope. The left side ASM/Pyramid system is currently being commissioned, with completion scheduled for the Fall of 2012. We will discuss the operation of the first Adaptive Optics System at the LBT Observatory including interactions of the AO system with the telescope and its TCS, observational modes, user interfaces, observational scripting language, time requirement for closed loop and offsets and observing efficiency.

  7. Adaptive optics imaging of the outer retinal tubules in Bietti's crystalline dystrophy.

    Battu, R; Akkali, M C; Bhanushali, D; Srinivasan, P; Shetty, R; Berendschot, T T J M; Schouten, J S A G; Webers, C A

    2016-05-01

    PurposeTo study the outer retinal tubules using spectral domain optical coherence tomography and adaptive optics and in patients with Bietti's crystalline dystrophy.MethodsTen eyes of five subjects from five independent families with Bietti's crystalline Dystrophy (BCD) were characterized with best-corrected visual acuity (BCVA), full-field electroretinography, and fundus autofluorescence (FAF). High-resolution images were obtained with the spectral domain optical coherence tomography (SD-OCT) and adaptive optics (AO).ResultsSD-OCT showed prominent outer retinal layer loss and outer retinal tubulations at the margin of outer retinal loss. AO images displayed prominent macrotubules and microtubules with characteristic features in eight out of the 10 eyes. Crystals were present in all ten eyes. There was a reduction in the cone count in all eyes in the area outside the outer retinal tubules (ORT).ConclusionsThis study describes the morphology of the outer retinal tubules when imaged enface on the adaptive optics in patients with BCD. These findings provide insight into the macular structure of these patients. This may have prognostic implications and refine the study on the pathogenesis of BCD. PMID:26915747

  8. Demonstration of a Fiber Optic Regression Probe in a High-Temperature Flow

    Korman, Valentin; Polzin, Kurt

    2011-01-01

    The capability to provide localized, real-time monitoring of material regression rates in various applications has the potential to provide a new stream of data for development testing of various components and systems, as well as serving as a monitoring tool in flight applications. These applications include, but are not limited to, the regression of a combusting solid fuel surface, the ablation of the throat in a chemical rocket or the heat shield of an aeroshell, and the monitoring of erosion in long-life plasma thrusters. The rate of regression in the first application is very fast, while the second and third are increasingly slower. A recent fundamental sensor development effort has led to a novel regression, erosion, and ablation sensor technology (REAST). The REAST sensor allows for measurement of real-time surface erosion rates at a discrete surface location. The sensor is optical, using two different, co-located fiber-optics to perform the regression measurement. The disparate optical transmission properties of the two fiber-optics makes it possible to measure the regression rate by monitoring the relative light attenuation through the fibers. As the fibers regress along with the parent material in which they are embedded, the relative light intensities through the two fibers changes, providing a measure of the regression rate. The optical nature of the system makes it relatively easy to use in a variety of harsh, high temperature environments, and it is also unaffected by the presence of electric and magnetic fields. In addition, the sensor could be used to perform optical spectroscopy on the light emitted by a process and collected by fibers, giving localized measurements of various properties. The capability to perform an in-situ measurement of material regression rates is useful in addressing a variety of physical issues in various applications. An in-situ measurement allows for real-time data regarding the erosion rates, providing a quick method for

  9. KNOW THE STAR, KNOW THE PLANET. I. ADAPTIVE OPTICS OF EXOPLANET HOST STARS

    The results of an adaptive optics survey of exoplanet host stars for stellar companions are presented. We used the Advanced Electro-Optical System telescope and its adaptive optics system to collect deep images of the stars in the I band. Sixty-two exoplanet host stars were observed and fifteen multiple star systems were resolved. Of these eight are known multiples, while seven are new candidate binaries. For all binaries, we measured the relative astrometry of the pair and the differential magnitude in the I band. We improved the orbits of HD 19994 and τ Boo. These observations will provide improved statistics on the duplicity of exoplanet host stars and provide an increased understanding of the dynamics of known binary star exoplanet hosts.

  10. 15 Gbit/s indoor optical wireless systems employing fast adaptation and imaging reception in a realistic environment

    Alsaadi, Fuad E.

    2016-03-01

    Optical wireless systems are promising candidates for next-generation indoor communication networks. Optical wireless technology offers freedom from spectrum regulations and, compared to current radio-frequency networks, higher data rates and increased security. This paper presents a fast adaptation method for multibeam angle and delay adaptation systems and a new spot-diffusing geometry, and also considers restrictions needed for complying with eye safety regulations. The fast adaptation algorithm reduces the computational load required to reconfigure the transmitter in the case of transmitter and/or receiver mobility. The beam clustering approach enables the transmitter to assign power to spots within the pixel's field of view (FOV) and increases the number of such spots. Thus, if the power per spot is restricted to comply with eye safety standards, the new approach, in which more spots are visible within the FOV of the pixel, leads to enhanced signal-to-noise ratio (SNR). Simulation results demonstrate that the techniques proposed in this paper lead to SNR improvements that enable reliable operation at data rates as high as 15 Gbit/s. These results are based on simulation and not on actual measurements or experiments.

  11. Optical Vectorial Vortex Coronagraphs using Liquid Crystal Polymers: theory, manufacturing and laboratory demonstration

    Mawet, D; Liewer, K; Hanot, Ch; McEldowney, S; Shemo, D; O'Brien, N

    2009-01-01

    In this paper, after briefly reviewing the theory of vectorial vortices, we describe our technological approach to generating the necessary phase helix, and report results obtained with the first optical vectorial vortex coronagraph (OVVC) in the laboratory. To implement the geometrical phase ramp, we make use of Liquid Crystal Polymers (LCP), which we believe to be the most efficient technological path to quickly synthesize optical vectorial vortices of virtually any topological charge. With the first prototype device of topological charge 2, a maximum peak-to-peak attenuation of 1.4e-2 and a residual light level of 3e-5 at an angular separation of 3.5 l/d (at which point our current noise floor is reached) have been obtained at a wavelength of 1.55 microns. These results demonstrate the validity of using space-variant birefringence distributions to generate a new family of coronagraphs usable in natural unpolarized light, opening a path to high performance coronagraphs that are achromatic and have low-sensi...

  12. An investigation of the influence of reconceptualization of demonstrative experimental activities of optics in high school

    Jair Lúcio Prados Ribeiro

    2013-08-01

    Full Text Available In this work, we analyze the influence that the use of demonstrative experiments can bring to the learning of optics. It is assumed that the development of experimental activities, when reconceptualized according to Hodson proposal, tends to contribute to the generation of cognitive conflicts when compared to traditional didactic experience. Justifications are given for an analysis of changes under a Piagetian bias, reconciled with Hodson proposal. The methodology used to structure the topics presentations was quasi-experimental, contrasting an experimental group with a control group. The measuring of the effectiveness of the suggested working method was made from a quantitative analysis, which identified some of the topics discussed had better results in learning, being more tied to the experiments carried out.

  13. PALM-3000: EXOPLANET ADAPTIVE OPTICS FOR THE 5 m HALE TELESCOPE

    We describe and report first results from PALM-3000, the second-generation astronomical adaptive optics (AO) facility for the 5.1 m Hale telescope at Palomar Observatory. PALM-3000 has been engineered for high-contrast imaging and emission spectroscopy of brown dwarfs and large planetary mass bodies at near-infrared wavelengths around bright stars, but also supports general natural guide star use to V ≈ 17. Using its unique 66 × 66 actuator deformable mirror, PALM-3000 has thus far demonstrated residual wavefront errors of 141 nm rms under ∼1'' seeing conditions. PALM-3000 can provide phase conjugation correction over a 6.''4 × 6.''4 working region at λ = 2.2 μm, or full electric field (amplitude and phase) correction over approximately one-half of this field. With optimized back-end instrumentation, PALM-3000 is designed to enable 10–7 contrast at 1'' angular separation, including post-observation speckle suppression processing. While continued optimization of the AO system is ongoing, we have already successfully commissioned five back-end instruments and begun a major exoplanet characterization survey, Project 1640

  14. PALM-3000: Exoplanet Adaptive Optics for the 5-meter Hale Telescope

    Dekany, R; Burruss, R; Bouchez, A; Truong, T; Baranec, C; Guiwits, S; Hale, D; Angione, J; Trinh, T; Zolkower, J; Shelton, J C; Palmer, D; Henning, J; Croner, E; Troy, M; McKenna, D; Tesch, J; Hildebrandt, S; Milburn, J

    2013-01-01

    We describe and report first results from PALM-3000, the second-generation astronomical adaptive optics facility for the 5.1-m Hale telescope at Palomar Observatory. PALM-3000 has been engineered for high-contrast imaging and emission spectroscopy of brown dwarfs and large planetary mass bodies at near-infrared wavelengths around bright stars, but also supports general natural guide star use to V ~ 17. Using its unique 66 x 66 actuator deformable mirror, PALM-3000 has thus far demonstrated residual wavefront errors of 141 nm RMS under 1 arcsecond seeing conditions. PALM-3000 can provide phase conjugation correction over a 6.4 x 6.4 arcsecond working region at an observing wavelength of 2.2 microns, or full electric field (amplitude and phase) correction over approximately one half of this field. With optimized back-end instrumentation, PALM-3000 is designed to enable as high as 10e-7 contrast at ~1 arc second angular separation, after including post-observation speckle suppression processing. While optimizati...

  15. High-resolution adaptive optics scanning laser ophthalmoscope with dual deformable mirrors for large aberration correction

    Chen, D; Jones, S M; Silva, D A; Olivier, S S

    2007-01-25

    Scanning laser ophthalmoscopes with adaptive optics (AOSLO) have been shown previously to provide a noninvasive, cellular-scale view of the living human retina. However, the clinical utility of these systems has been limited by the available deformable mirror technology. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina, making the AOSLO system a viable, non-invasive, high-resolution imaging tool for clinical diagnostics. We used a bimorph deformable mirror to correct low-order aberrations with relatively large amplitudes. The bimorph mirror is manufactured by Aoptix, Inc. with 37 elements and 18 {micro}m stroke in a 10 mm aperture. We used a MEMS deformable mirror to correct high-order aberrations with lower amplitudes. The MEMS mirror is manufactured by Boston Micromachine, Inc with 144 elements and 1.5 {micro}m stroke in a 3 mm aperture. We have achieved near diffraction-limited retina images using the dual deformable mirrors to correct large aberrations up to {+-} 3D of defocus and {+-} 3D of cylindrical aberrations with test subjects. This increases the range of spectacle corrections by the AO systems by a factor of 10, which is crucial for use in the clinical environment. This ability for large phase compensation can eliminate accurate refractive error fitting for the patients, which greatly improves the system ease of use and efficiency in the clinical environment.

  16. Adaptive optics self-calibration using differential OTF (dOTF)

    Rodack, Alexander T.; Knight, Justin M.; Codona, Johanan L.; Miller, Kelsey L.; Guyon, Olivier

    2015-09-01

    We demonstrate self-calibration of an adaptive optical system using differential OTF [Codona, JL; Opt. Eng. 0001; 52(9):097105-097105. doi:10.1117/1.OE.52.9.097105]. We use a deformable mirror (DM) along with science camera focal plane images to implement a closed-loop servo that both flattens the DM and corrects for non-common-path aberrations within the telescope. The pupil field modification required for dOTF measurement is introduced by displacing actuators near the edge of the illuminated pupil. Simulations were used to develop methods to retrieve the phase from the complex amplitude dOTF measurements for both segmented and continuous sheet MEMS DMs and tests were performed using a Boston Micromachines continuous sheet DM for verification. We compute the actuator correction updates directly from the phase of the dOTF measurements, reading out displacements and/or slopes at segment and actuator positions. Through simulation, we also explore the effectiveness of these techniques for a variety of photons collected in each dOTF exposure pair.

  17. Tracking and imaging of dynamic objects in scattering media by time-reversed adapted-perturbation (TRAP) optical focusing

    Ma, Cheng; Liu, Yan; Wang, Lihong V

    2014-01-01

    The ability to steer light propagation inside scattering media has long been sought-after due to its potential widespread applications. To form optical foci inside scattering media, the only feasible strategy is to guide photons by using either implanted or virtual guide stars. However, all of these guide stars must be introduced extrinsically, either invasively or by physical contact, limiting the scope of their application. Here, we focus light inside scattering media by employing intrinsic dynamics as guide stars. By time-reversing the perturbed component of the scattered light adaptively, we concentrate light to the origin of the perturbation, where the permittivity varied spontaneously. We demonstrate dynamic light focusing onto moving targets and imaging of a time-variant object obscured by highly scattering media, without invasiveness and physical contact. Anticipated applications include all-weather optical communication with airplanes or satellites, tracking vehicles in thick fogs, and imaging and ph...

  18. A new network architecture for future optical networks : coarse optical circuit switching by default, rerouting over circuits for adaptation

    Chou, Jerry

    2009-01-01

    As Internet traffic continues to grow unabated at an exponential rate, it is unclear whether or not the existing packet routing network architecture based on electronic routers will continue to scale at the necessary pace. On the other hand, optical fiber and switching elements have demonstrated an abundance of capacity that appears to be unmatched by electronic routers. In particular, the simplicity of circuit switching makes it well-suited for optical implementations. Therefore, given the r...

  19. Comparison of Adaptive Optics and Phase-Conjugate Mirrors for Correction of Aberrations in Double-Pass Amplifiers

    Jackel, Steven; Moshe, Inon; Lavi, Raphy

    2003-02-01

    Correction of birefringence-induced effects (depolarization and bipolar focusing) were achieved in double-pass amplifiers by use of a Faraday rotator between the laser rod and the retroreflecting optic. A necessary condition was ray retrace. Retrace was limited by imperfect conjugate-beam fidelity and by nonreciprocal refractive indices. We compared various retroreflectors: stimulated-Brillouin-scatter phase-conjugate mirrors (PCMs), PCMs with rod-to-PCM relay imaging (IPCM), IPCMs with astigmatism-correcting adaptive optics, and all-adaptive-optics imaging variable-radius mirrors. Results with flash-lamp-pumped, Nd:Cr:GSGG double-pass amplifiers showed the superiority of adaptive optics over nonlinear optics retroreflectors in terms of maximum average power, improved beam quality, and broader oscillator pulse duration /bandwidth operating range. Hybrid PCM-adaptive optics retroreflectors yielded intermediate power /beam-quality results.

  20. A laboratory demonstration of an LQG technique for correcting frozen flow turbulence in adaptive optics systems

    Rudy, Alexander; Srinath, Srikar; Ammons, S Mark; Gavel, Donald

    2015-01-01

    We present the laboratory verification of a method for re- moving the effects of frozen-flow atmospheric turbulence using a Linear Quadratic Gaussian (LQG) controller, also known as a Kalman Filter. This method, which we term "Predictive Fourier Control," can identify correlated atmospheric motions due to layers of frozen flow turbulence, and can predictively remove the effects of these correlated motions in real-time. Our laboratory verification suggests a factor of 3 improvement in the RMS residual wavefront error and a 10% improvement in measured Strehl of the system. We found that the RMS residual wavefront error was suppressed from 35.0 nm to 11.2 nm due to the use of Predictive Fourier Control, and that the far field Strehl improved from 0.479 to 0.520.

  1. Fiber Optic Adaptive Probe as a Cuvette Substitution for UV-Vis Spectrophotometer (Genesis 10S

    Fredy Kurniawan

    2014-04-01

    Full Text Available Fiber optic adaptive probe UV-Vis for Genesis 10S has been fabricated to substitute cuvette for real time analysis. Most of standard spectrophotometers UV-Vis (the common type use cuvette to place sample which is being analyzed. The light pass through the sample in the cuvette to detector then the intensity of the absorption of the solution is measured. Most of the cuvette system requires to transferring sample solution to cuvette from its original vessel, so the real time analysis cannot be conducted. The probe with special design using fiber optic cable FT-Au tonics 420-10 has been made to substitute the cuvette system. The light from the source moved inside fiber optic cable, which has been cut in the middle of the cable (the sample can passes through at this gap, to the detector. The end (entrance and exit of the fiber optic was designed so that it fit to the compartment of the Genesis 10S spectrophotometer without any modification from the standard instrument condition. The spectrum results from the probe in varies gap, in the range 0.2 – 1 cm, was observed. The gap in the middle of the fiber optic was equal to the length of the pathway in the cuvette system. Rhoda mine B was used as the sample with variation concentration 4.175 × 10-5 M, 3.34 × 10-5 M, 2.5 × 10-5 M, and 1.67 × 10-5 M. The spectrum result of adaptive fiber optic probe was compared to the spectrum of standard cuvette system. The optimum result was provided using 0.2 cm gap. The maximum wavelength absorbance of adaptive fiber optic probe was at 533 nm which similar to the cuvette system.

  2. Fiber-wireless integrated mobile backhaul network based on a hybrid millimeter-wave and free-space-optics architecture with an adaptive diversity combining technique.

    Zhang, Junwen; Wang, Jing; Xu, Yuming; Xu, Mu; Lu, Feng; Cheng, Lin; Yu, Jianjun; Chang, Gee-Kung

    2016-05-01

    We propose and experimentally demonstrate a novel fiber-wireless integrated mobile backhaul network based on a hybrid millimeter-wave (MMW) and free-space-optics (FSO) architecture using an adaptive combining technique. Both 60 GHz MMW and FSO links are demonstrated and fully integrated with optical fibers in a scalable and cost-effective backhaul system setup. Joint signal processing with an adaptive diversity combining technique (ADCT) is utilized at the receiver side based on a maximum ratio combining algorithm. Mobile backhaul transportation of 4-Gb/s 16 quadrature amplitude modulation frequency-division multiplexing (QAM-OFDM) data is experimentally demonstrated and tested under various weather conditions synthesized in the lab. Performance improvement in terms of reduced error vector magnitude (EVM) and enhanced link reliability are validated under fog, rain, and turbulence conditions. PMID:27128036

  3. Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

    Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

    2016-05-01

    A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

  4. Optimal control techniques for the adaptive optics system of the LBT

    Agapito, G.; Quiros-Pacheco, F.; Tesi, P.; Esposito, S.; Xompero, M.

    2008-07-01

    In this paper we will discuss the application of different optimal control techniques for the adaptive optics system of the LBT telescope which comprises a pyramid wavefront sensor and an adaptive secondary mirror. We have studied the application of both the Kalman and the H∞ filter to estimate the temporal evolution of the phase perturbations due to the atmospheric turbulence and the telescope vibrations. We have evaluated the performance of these control techniques with numerical simulations in preparation of the laboratory tests that will be carried out in the Arcetri laboratories.

  5. Adaptive Bit Rate Video Streaming Through an RF/Free Space Optical Laser Link

    A. Akbulut

    2010-06-01

    Full Text Available This paper presents a channel-adaptive video streaming scheme which adjusts video bit rate according to channel conditions and transmits video through a hybrid RF/free space optical (FSO laser communication system. The design criteria of the FSO link for video transmission to 2.9 km distance have been given and adaptive bit rate video streaming according to the varying channel state over this link has been studied. It has been shown that the proposed structure is suitable for uninterrupted transmission of videos over the hybrid wireless network with reduced packet delays and losses even when the received power is decreased due to weather conditions.

  6. Architecture Design and Experimental Platform Demonstration of Optical Network based on OpenFlow Protocol

    Xing, Fangyuan; Wang, Honghuan; Yin, Hongxi; Li, Ming; Luo, Shenzi; Wu, Chenguang

    2016-02-01

    With the extensive application of cloud computing and data centres, as well as the constantly emerging services, the big data with the burst characteristic has brought huge challenges to optical networks. Consequently, the software defined optical network (SDON) that combines optical networks with software defined network (SDN), has attracted much attention. In this paper, an OpenFlow-enabled optical node employed in optical cross-connect (OXC) and reconfigurable optical add/drop multiplexer (ROADM), is proposed. An open source OpenFlow controller is extended on routing strategies. In addition, the experiment platform based on OpenFlow protocol for software defined optical network, is designed. The feasibility and availability of the OpenFlow-enabled optical nodes and the extended OpenFlow controller are validated by the connectivity test, protection switching and load balancing experiments in this test platform.

  7. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation. (paper)

  8. Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography

    Naser, Mohamed A.; Patterson, Michael S.; Wong, John W.

    2014-04-01

    A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation.

  9. A benchmark for multiconjugated adaptive optics: VLT-MAD observations of the young massive cluster Trumpler 14

    Rochau, B.; Brandner, W.; Stolte, A.; Henning, T.; Da Rio, N.; Gennaro, M.; Hormuth, F.; Marchetti, E.; Amico, P.

    2011-12-01

    The Multi-conjugate Adaptive optics Demonstrator (MAD) is the first multiconjugated adaptive optics system at the Very Large Telescope (VLT). We present H and KS observations of the young massive cluster Trumpler 14 revealing the power of MCAO systems by providing a homogeneous Strehl ratio over a large field of view. Mean Strehl ratios of 6.0 and 5.9 per cent with maximum Strehl ratios of 9.8 and 12.6 per cent in H and KS, respectively, show significant improvement of the spatial point spread function (PSF) stability compared to single-conjugated adaptive optics systems. Photometry of our observations cover a dynamic range of ˜10 mag including 2-3 times greater number of sources than comparable seeing-limited observations. The colour-magnitude diagram reveals that the massive cluster originated in a recent starburst-like event 1 ± 0.5 Myr ago. We tentatively detect hints for an older population of 3 Myr suggesting that low intensity star formation might have been going on in the HII region for a few Myr. We derive the luminosity function and mass function between 0.1 and 3.2 M⊙ and identify a change in the power-law slope of the mass function at mc˜ 0.53+0.12- 0.10 M⊙. The MF appears shallow with power-law slopes of Γ1=-0.50 ± 0.11 above mc and Γ2= 0.63 ± 0.32 below mc. Based on Observations with VLT-MAD collected during the Science Verification campaign at the European Southern Observatory, Paranal, Chile.

  10. Time domain zero-padding based adaptive-PAM signal transmission with high spectral efficiency in IMDD optical communication system

    Zhang, Fangliu; He, Jing; Deng, Rui; Cheng, Yun; Xiao, Minlei; Chen, Lin

    2016-08-01

    In this paper, an adaptive pulse amplitude modulation (APAM) scheme is proposed and experimentally demonstrated in the intensity-modulation and direct-detection (IMDD) optical communications system. In the proposed scheme, the channel is divided into two sub-channels, and different PAM mapping can be chosen for different sub-channel according to the fading conditions. In addition, the 20-km standard single mode fiber (SSMF) transmission of 24 Gbit/s 16/4-APAM signal with the spectral efficiency (SE) up to 6 bit/s/Hz is experimentally demonstrated. The experiment results show that the bit error rate (BER) of the 16/4-APAM signal can be achieved less than 2.4e-2.

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

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

    2016-05-01

    The distributed-spline-based aberration reconstruction (D-SABRE) method is proposed for distributed wavefront reconstruction with applications to large-scale adaptive optics systems. D-SABRE decomposes the wavefront sensor domain into any number of partitions and solves a local wavefront reconstruction problem on each partition using multivariate splines. D-SABRE accuracy is within 1% of a global approach with a speedup that scales quadratically with the number of partitions. The D-SABRE is compared to the distributed cumulative reconstruction (CuRe-D) method in open-loop and closed-loop simulations using the YAO adaptive optics simulation tool. D-SABRE accuracy exceeds CuRe-D for low levels of decomposition, and D-SABRE proved to be more robust to variations in the loop gain. PMID:27140879

  12. Gemini multi-conjugate adaptive optics system review I: Design, trade-offs and integration

    Rigaut, Francois; Boccas, Maxime; d'Orgeville, Céline; Vidal, Fabrice; van Dam, Marcos A; Arriagada, Gustavo; Fesquet, Vincent; Galvez, Ramon L; Gausachs, Gaston; Cavedoni, Chad; Ebbers, Angelic W; Karewicz, Stan; James, Eric; Lührs, Javier; Montes, Vanessa; Perez, Gabriel; Rambold, William N; Rojas, Roberto; Walker, Shane; Bec, Matthieu; Trancho, Gelys; Sheehan, Michael; Irarrazaval, Benjamin; Boyer, Corinne; Ellerbroek, Brent L; Flicker, Ralf; Gratadour, Damien; Garcia-Rissmann, Aurea; Daruich, Felipe

    2013-01-01

    The Gemini Multi-conjugate adaptive optics System (GeMS) at the Gemini South telescope in Cerro Pach{\\'o}n is the first sodium-based multi-Laser Guide Star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near infrared, with uniform quality over a field of view of two square arcminutes. The present paper (I) is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light.

  13. The Robo-AO KOI Survey: laser adaptive optics imaging of every Kepler exoplanet candidate

    Ziegler, Carl; Baranec, Christoph; Morton, Tim; Riddle, Reed; Atkinson, Dani; Nofi, Larissa

    2016-01-01

    The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star (KOI) with laser adaptive optics imaging to hunt for blended nearby stars which may be physically associated companions. With the unparalleled efficiency provided by the first fully robotic adaptive optics system, we perform the critical search for nearby stars (0.15" to 4.0" separation with contrasts up to 6 magnitudes) that dilute the observed planetary transit signal, contributing to inaccurate planetary characteristics or astrophysical false positives. We present 3313 high resolution observations of Kepler planetary hosts from 2012-2015, discovering 479 nearby stars. We measure an overall nearby star probability rate of 14.5\\pm0.8%. With this large data set, we are uniquely able to explore broad correlations between multiple star systems and the properties of the planets which they host, providing insight into the formation and evolution of planetary systems in our galaxy. Several KOIs of particular interest...

  14. Characterization and Design of Digital Pointing Subsystem for Optical Communication Demonstrator

    Racho, C.; Portillo, A.

    1998-01-01

    The Optical Communications Demonstrator (OCD) is a laboratory-based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision bearn pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field-of-view acquisition and permits effective platform jitter compensation and point-ahead control using only one steering mirror. This paper describes the detailed design and characterization of the digital control loop system which includes the Fast Steering Mirror (FSM), the CCD image tracker, and the associated electronics. The objective is to improve the overall system performance using laboratory measured data. The. design of the digital control loop is based on a linear time invariant open loop model. The closed loop performance is predicted using the theoretical model. With the digital filter programmed into the OCD control software, data is collected to verify the predictions. This paper presents the results of the, system modeling and performance analysis. It has been shown that measurement data closely matches theoretical predictions. An important part of the laser communication experiment is the ability of FSM to track the laser beacon within the. required tolerances. The pointing must be maintained to an accuracy that is much smaller than the transmit signal beamwidth. For an earth orbit distance, the system must be able to track the receiving station to within a few microradians. The failure. to do so will result in a severely degraded system performance.

  15. Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

    Martin, S.C.; De Pater, I.; Marcus, P.

    2011-01-01

    We present H-band (1.4–1.8 μm) images of Neptune with a spatial resolution of ∼0.06″, taken with the W.M. Keck II telescope using the slit-viewing camera (SCAM) of the NIRSPEC instrument backed with Adaptive Optics. Images with 60-second integration times span 4 hours each on UT 20 and 21 August, 20

  16. Optical Digital Imitation Painting Design Based on Self-Adaptive Image Feature

    Zhu Liyan; Qin Jianfei; Qu Liyong; Song Shuwei; Xu Weidong

    2016-01-01

    Based on the study of existing digital imitation camouflage technology, we propose a kind of optical digital imitation camouflage design algorithm which is based on the characteristic of self-adaptive image. Picking main color feature of the background by using K-means clustering algorithm, counting the shape characteristics of each main color spots by separating layers, we generated digital camouflage pattern automatically by segmenting the background region characteristics and fill the back...

  17. Ferrofluid Based Deformable Mirrors - a New Approach to Adaptive Optics Using Liquid Mirrors

    Laird, P.; Bergamasco, R.; Berube, V.; Borra, E. F.; Ritcey, A.; Rioux, M.; Robitaille, N.; Thibault, S.; Silva Jr, L. Vieira da; Yockell-Lelievre, H.

    2002-01-01

    The trend towards ever larger telescopes and more advanced adaptive optics systems is driving the need for deformable mirrors with a large number of low cost actuators. Liquid mirrors have long been recognized a potential low cost alternative to conventional solid mirrors. By using a water or oil based ferrofluid we are able to benefit from a stronger magnetic response than is found in magnetic liquid metal amalgams and avoid the difficulty of passing a uniform current through a liquid. Depos...

  18. Adaptive Optics Parameters connection to wind speed at the Teide Observatory

    Garcia-Lorenzo, B.; Eff-Darwich, A.; J. J. Fuensalida; Castro-Almazan, J.

    2009-01-01

    Current projects for large telescopes demand a proper knowledge of atmospheric turbulence to design efficient adaptive optics systems in order to reach large Strehl ratios. However, the proper characterization of the turbulence above a particular site requires long-term monitoring. Due to the lack of long-term information on turbulence, high-altitude winds (in particular winds at the 200 mbar pressure level) were proposed as a parameter for estimating the total turbulence at a particular site...

  19. “Lucky Averaging”: Quality improvement on Adaptive Optics Scanning Laser Ophthalmoscope Images

    Huang, Gang; Zhong, Zhangyi; Zou, Weiyao; Burns, Stephen A.

    2011-01-01

    Adaptive optics(AO) has greatly improved retinal image resolution. However, even with AO, temporal and spatial variations in image quality still occur due to wavefront fluctuations, intra-frame focus shifts and other factors. As a result, aligning and averaging images can produce a mean image that has lower resolution or contrast than the best images within a sequence. To address this, we propose an image post-processing scheme called “lucky averaging”, analogous to lucky imaging (Fried, 1978...

  20. Registration of adaptive optics corrected retinal nerve fiber layer (RNFL) images

    Ramaswamy, Gomathy; Lombardo, Marco; Devaney, Nicholas

    2014-01-01

    Glaucoma is the leading cause of preventable blindness in the western world. Investigation of high-resolution retinal nerve fiber layer (RNFL) images in patients may lead to new indicators of its onset. Adaptive optics (AO) can provide diffraction-limited images of the retina, providing new opportunities for earlier detection of neuroretinal pathologies. However, precise processing is required to correct for three effects in sequences of AO-assisted, flood-illumination images: uneven illumina...

  1. The Effect of Aberrations and Scatter on Image Resolution Assessed by Adaptive Optics Retinal Section Imaging

    Wanek, Justin; Mori, Marek; Shahidi, Mahnaz

    2007-01-01

    The effect of increased high order wavefront aberrations on image resolution was investigated and the performance of adaptive optics (AO) for correcting wavefront error in the presence of increased light scatter was assessed in a model eye. An AO section imaging system provided an oblique view of a simulated model eye retina and incorporated a wavefront sensor and deformable mirror for measurement and compensation of wavefront aberrations. Image resolution was quantified by the width of a Lor...

  2. Observer-Based Control Techniques for the LBT Adaptive Optics under Telescope Vibrations

    Agapito, Guido; Quirós-Pacheco, Fernando; Tesi, Pietro; Riccardi, Armando; Esposito, Simone

    2011-01-01

    This paper addresses the application of observer-based control techniques for the adaptive optics system of the LBT telescope. In such a context, attention is focused on the use of Kalman and H∞ filters to estimate the temporal evolution of phase perturbations due to the atmospheric turbulence and the telescope vibrations acting on tip/tilt modes. We shall present preliminary laboratory experiments carried out at the Osservatorio Astrofisico di Arcetri using the Kalman filter.

  3. Prediction of wavefronts in adaptive optics to reduce servo lag errors using data mining

    Vyas, Akondi; Roopashree, M. B.; Prasad, B Raghavendra

    2009-01-01

    Servo lag errors in adaptive optics lead to inaccurate compensation of wavefront distortions. An attempt has been made to predict future wavefronts using data mining on wavefronts of the immediate past to reduce these errors. Monte Carlo simulations were performed on experimentally obtained data that closely follows Kolmogorov phase characteristics. An improvement of 6% in wavefront correction is reported after data mining is performed. Data mining is performed in three steps (a) Data cube Se...

  4. Progressive Prediction of Turbulence Using Wave-Front Sensor Data in Adaptive Optics Using Data Mining

    Vyas, Akondi; Roopashree, M. B.; Prasad, B Raghavendra

    2009-01-01

    Nullifying the servo bandwidth errors improves the strehl ratio by a substantial quantity in adaptive optics systems. An effective method for predicting atmospheric turbulence to reduce servo bandwidth errors in real time closed loop correction systems is presented using data mining. Temporally evolving phase screens are simulated using Kolmogorov statistics and used for data analysis. A data cube is formed out of the simulated time series. Partial data is used to predict the subsequent phase...

  5. Demonstrations of Wave Optics (Interference and Diffraction of Light) for Large Audiences Using a Laser and a Multimedia Projector

    Ivanov, Dragia; Nikolov, Stefan

    2011-01-01

    This article presents a new technique for performing most well-known demonstrations of wave optics. Demonstrations which are normally very hard to show to more than a few people can be presented easily to very large audiences with excellent visibility for everyone. The proposed setup is easy to put together and use and can be very useful for…

  6. Development and demonstration of optical polarization controller; Hikari henpa seigyo sochi no kaihatsu to jissho

    Kurono, M. [Central Research Institute of Electric Power Industry, Tokyo (Japan)

    1997-04-01

    If fiber transmission light can be controlled in a stabilized polarization state, realization of coherent optical communication is anticipated. In the case of adopting it to OPGW, however, it is necessary to compensate high speed polarization variation caused by lightning strike. But this was difficult in the conventional method. Accordingly, a high speed polarization control method was proposed which uses an electric effect of lithium niobate (LN) crystals. In the study, a polarization control unit was manufactured based on the method proposed and the performance was demonstrated. As a result of measuring output light with input light changed in every state of polarization, the object horizontal polarization component obtained a stabilized light intensity at {+-}0.1dB, and a light intensity of the component slipped out of the horizontal polarization was suppressed under -20dB. To cope with the polarization variation by lightning strike, it is necessary to make the control delay 10{mu}sec or below, and improvement in processing unit, etc. may make it possible since LN crystals respond below 1{mu}sec. High speed control of the infinitely continuing arbitrary polarization variation became possible. 14 refs., 19 figs.

  7. Validation Through Simulations of a Cn2 Profiler for the ESO/VLT Adaptive Optics Facility

    Garcia-Rissmann, A; Kolb, J; Louarn, M Le; Madec, P -Y; Neichel, B

    2015-01-01

    The Adaptive Optics Facility (AOF) project envisages transforming one of the VLT units into an adaptive telescope and providing its ESO (European Southern Observatory) second generation instruments with turbulence corrected wavefronts. For MUSE and HAWK-I this correction will be achieved through the GALACSI and GRAAL AO modules working in conjunction with a 1170 actuators Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). Multiple wavefront sensors will enable GLAO and LTAO capabilities, whose performance can greatly benefit from a knowledge about the stratification of the turbulence in the atmosphere. This work, totally based on end-to-end simulations, describes the validation tests conducted on a Cn2 profiler adapted for the AOF specifications. Because an absolute profile calibration is strongly dependent on a reliable knowledge of turbulence parameters r0 and L0, the tests presented here refer only to normalized output profiles. Uncertainties in the input parameters inherent t...

  8. Practical High-Order Adaptive Optics Systems For Extrasolar Planet Searches

    Macintosh, B A; Olivier, S; Bauman, B; Brase, J; Carr, E; Carrano, C J; Gavel, D; Max, C E; Patience, J

    2001-08-29

    Direct detection of photons emitted or reflected by an extrasolar planet is an extremely difficult but extremely exciting application of adaptive optics. Typical contrast levels for an extrasolar planet would be 10{sup 9}-Jupiter is a billion times fainter than the sun. Current adaptive optics systems can only achieve contrast levels of 10{sup 6}, but so-called ''extreme'' adaptive optics systems with 10{sup 4}-10{sup 5} degrees of freedom could potentially detect extrasolar planets. We explore the scaling laws defining the performance of these systems, first set out by Angel (1994), and derive a different definition of an optimal system. Our sensitivity predictions are somewhat more pessimistic than the original paper, due largely to slow decorrelation timescales for some noise sources, though choosing to site an ExAO system at a location with exceptional r{sub 0} (e.g. Mauna Kea) can offset this. We also explore the effects of segment aberrations in a Keck-like telescope on ExAO; although the effects are significant, they can be mitigated through Lyot coronagraphy.

  9. High-resolution Imaging of Living Retina through Optic Adaptive Retinal Imaging System

    Chunhui Jiang; Wenji Wang; Ning Ling; Gezhi Xu; Xuejun Rao; Xinyang Li; Yudong Zhang

    2002-01-01

    Purpose: To evaluate the possibility as well as the usage of adaptive optics in high-resolution retinal imaging.Methods:From March to November 2001, the fundus of 25 adults were checked by using Optic Adaptive Retinal Imaging System (OAS). The age of the subjects varied from 18~48 years. All had normal visual acuity from 0.9 to 1.0. No abnormality was found in the ocular examination, and their medical as well as ocular history was unremarkable. Results: High-resolution images of the retinal cells, photoreceptor and bipolar cell, were analysed. In these images, the cells are clearly resolved. The density of the photoreceptor at area 1.5 degree from the foveloa is around 40 000~50 000/mm2. At area 3 degree, it drops to less than 30 000/mm2.Conclusion:Optic Adaptive Retinal Imaging System (AOS) is able to get high-resolution image of retinal cells in living human eyes. It may be widely used in ophthalmology experimentally and clinically.

  10. Real-time blind deconvolution of retinal images in adaptive optics scanning laser ophthalmoscopy

    Li, Hao; Lu, Jing; Shi, Guohua; Zhang, Yudong

    2011-06-01

    With the use of adaptive optics (AO), the ocular aberrations can be compensated to get high-resolution image of living human retina. However, the wavefront correction is not perfect due to the wavefront measure error and hardware restrictions. Thus, it is necessary to use a deconvolution algorithm to recover the retinal images. In this paper, a blind deconvolution technique called Incremental Wiener filter is used to restore the adaptive optics confocal scanning laser ophthalmoscope (AOSLO) images. The point-spread function (PSF) measured by wavefront sensor is only used as an initial value of our algorithm. We also realize the Incremental Wiener filter on graphics processing unit (GPU) in real-time. When the image size is 512 × 480 pixels, six iterations of our algorithm only spend about 10 ms. Retinal blood vessels as well as cells in retinal images are restored by our algorithm, and the PSFs are also revised. Retinal images with and without adaptive optics are both restored. The results show that Incremental Wiener filter reduces the noises and improve the image quality.

  11. Ship detection for high resolution optical imagery with adaptive target filter

    Ju, Hongbin

    2015-10-01

    Ship detection is important due to both its civil and military use. In this paper, we propose a novel ship detection method, Adaptive Target Filter (ATF), for high resolution optical imagery. The proposed framework can be grouped into two stages, where in the first stage, a test image is densely divided into different detection windows and each window is transformed to a feature vector in its feature space. The Histograms of Oriented Gradients (HOG) is accumulated as a basic feature descriptor. In the second stage, the proposed ATF highlights all the ship regions and suppresses the undesired backgrounds adaptively. Each detection window is assigned a score, which represents the degree of the window belonging to a certain ship category. The ATF can be adaptively obtained by the weighted Logistic Regression (WLR) according to the distribution of backgrounds and targets of the input image. The main innovation of our method is that we only need to collect positive training samples to build the filter, while the negative training samples are adaptively generated by the input image. This is different to other classification method such as Support Vector Machine (SVM) and Logistic Regression (LR), which need to collect both positive and negative training samples. The experimental result on 1-m high resolution optical images shows the proposed method achieves a desired ship detection performance with higher quality and robustness than other methods, e.g., SVM and LR.

  12. Status update and closed-loop performance of the Magellan adaptive optics VisAO camera

    Kopon, Derek; Close, Laird M.; Males, Jared; Gasho, Victor; Morzinski, Katie; Follette, Katherine

    2012-07-01

    We present laboratory results of the closed-loop performance of the Magellan Adaptive Optics (AO) Adaptive Secondary Mirror (ASM), pyramid wavefront sensor (PWFS), and VisAO visible adaptive optics camera. The Magellan AO system is a 585-actuator low-emissivity high-throughput system scheduled for first light on the 6.5 meter Magellan Clay telescope in November 2012. Using a dichroic beamsplitter near the telescope focal plane, the AO system will be able to simultaneously perform visible (500-1000 nm) AO science with our VisAO camera and either 10 μm or 3-5 μm science using either the BLINC/MIRAC4 or CLIO cameras, respectively. The ASM, PWS, and VisAO camera have undergone final system tests in the solar test tower at the Arcetri Institute in Florence, Italy, reaching Strehls of 37% in i'-band with 400 modes and simulated turbulence of 14 cm ro at v-band. We present images and test results of the assembled VisAO system, which includes our prototype advanced Atmospheric Dispersion Corrector (ADC), prototype calcite Wollaston prisms for SDI imaging, and a suite of beamsplitters, filters, and other optics. Our advanced ADC performs in the lab as designed and is a 58% improvement over conventional ADC designs. We also present images and results of our unique Calibration Return Optic (CRO) test system and the ASM, which has successfully run in closedloop at 1kHz. The CRO test is a retro reflecting optical test that allows us to test the ASM off-sky in close-loop using an artificial star formed by a fiber source.

  13. Adaptive Optics at Optical Wavelengths: Test Observations of Kyoto 3DII Connected to Subaru Telescope AO188

    Matsubayashi, K.; Sugai, H.; Shimono, A.; Akita, A.; Hattori, T.; Hayano, Y.; Minowa, Y.; Takeyama, N.

    2016-09-01

    Adaptive optics (AO) enables us to observe objects with high spatial resolution, which is important in most astrophysical observations. Most AO systems are operational at near-infrared wavelengths but not in the optical range, because optical observations require a much higher performance to obtain the same Strehl ratio as near-infrared observations. Therefore, to enable AO-assisted observations at optical wavelengths, we connected the Kyoto Tridimensional Spectrograph II (Kyoto 3DII), which can perform integral field spectroscopy, to the second generation AO system of the Subaru Telescope (AO188). We developed a new beam-splitter that reflects light below 594 nm for the wavefront sensors of AO188 and transmits above 644 nm for Kyoto 3DII. We also developed a Kyoto 3DII mount at the Nasmyth focus of the Subaru Telescope. In test observations, the spatial resolution of the combined AO188–Kyoto 3DII was higher than that in natural seeing conditions, even at 6500 Å. The full width at half maximum of an undersampled (1.5 spaxels) bright guide star (7.0 mag in the V-band) was 0.″12.

  14. Real-time experimental demonstrations of software reconfigurable optical OFDM transceivers utilizing DSP-based digital orthogonal filters for SDN PONs.

    Duan, X; Giddings, R P; Bolea, M; Ling, Y; Cao, B; Mansoor, S; Tang, J M

    2014-08-11

    Real-time optical OFDM (OOFDM) transceivers with on-line software-controllable channel reconfigurability and transmission performance adaptability are experimentally demonstrated, for the first time, utilizing Hilbert-pair-based 32-tap digital orthogonal filters implemented in FPGAs. By making use of an 8-bit DAC/ADC operating at 2GS/s, an oversampling factor of 2 and an EML intensity modulator, the demonstrated RF conversion-free transceiver supports end-to-end real-time simultaneous adaptive transmissions, within a 1GHz signal spectrum region, of a 2.03Gb/s in-phase OOFDM channel and a 1.41Gb/s quadrature-phase OOFDM channel over a 25km SSMF IMDD system. In addition, detailed experimental explorations are also undertaken of key physical mechanisms limiting the maximum achievable transmission performance, impacts of transceiver's channel multiplexing/demultiplexing operations on the system BER performance, and the feasibility of utilizing adaptive modulation to combat impairments associated with low-complexity digital filter designs. Furthermore, experimental results indicate that the transceiver incorporating a fixed digital orthogonal filter DSP architecture can be made transparent to various signal modulation formats up to 64-QAM. PMID:25321051

  15. Demonstration of a VOC in-situ fiber optic sensor for use with a penetrometer analysis system

    Hartenstein, S.; Moore, G. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Nelson, B.; Kane, J.; Lowe, M. [GEO-CENTERS, Inc., Newton Center, MA (United States)

    1996-11-01

    Researchers at the Idaho National Engineering Laboratory with their industrial CRADA partner GEOCENTERS demonstrated a fiber optic based VOC sensor at the Army Environmental Center (AEC) technology demonstration at Dover Air Force Base. The sensor used during the demonstration was a single fiber optic cable coupled to an in situ sensor element contained in a cone penetrometer tip. The sensor`s fluorescence response was measured at the surface using an optical breadboard-based instrument. Results from this demonstration showed that the sensor provided semi-quantitative results for total VOCs comparable to the historical values of VOCs. In addition, the demonstration identified several technical challenges for improvement of the sensor. This paper describes the analytical properties of the reversible sensing materials, construction of an improved sensor system, and the planned demonstration of the modified in-situ VOC sensor system. This sensor system is tentatively scheduled for demonstration at the Army Environmental Center`s Aberdeen Proving Ground Test site. Improvements to the VOC sensor system include an optical configuration that will correct for soil matrix interferences and multiple sensing substrates to learn whether VOC selectivity can be achieved.

  16. Demonstration of a VOC in-situ fiber optic sensor for use with a penetrometer analysis system

    Hartenstein, Steven D.; Moore, Glenn A.; Nelson, Bruce N.; Kane, James; Lowe, Mark

    1996-11-01

    Researchers at the Idaho National Engineering Laboratory with their industrial CRADA partner GEO-CENTERS demonstrated a fiber optic based VOC sensor at the Army Environmental Center technology demonstration at Dover Air Force Base. The sensor used during the demonstration was a single fiber optic cable coupled to an in situ sensor element contained in a cone penetrometer tip. The sensor's fluorescence response was measured at the surface using an optical breadboard-based instrument. Results from this demonstration showed that the sensor provided semi-quantitative results for total VOCs comparable to the historical values of VOCs. In addition, the demonstration identified several technical challenges for improvement of the sensor. This paper describes the analytical properties of the reversible sensing materials, construction of an improved sensor system, and the planned demonstration of the modified in- situ VOC sensor system. This sensor system is tentatively scheduled for demonstration at the Army Environmental Center's Aberdeen Proving Ground Test site. Improvements to the VOC sensor system include an optical configuration that will correct for soil matrix interferences and multiple sensing substrates to learn whether VOC selectivity can be achieved.

  17. Retinal axial focusing and multi-layer imaging with a liquid crystal adaptive optics camera

    With the help of adaptive optics (AO) technology, cellular level imaging of living human retina can be achieved. Aiming to reduce distressing feelings and to avoid potential drug induced diseases, we attempted to image retina with dilated pupil and froze accommodation without drugs. An optimized liquid crystal adaptive optics camera was adopted for retinal imaging. A novel eye stared system was used for stimulating accommodation and fixating imaging area. Illumination sources and imaging camera kept linkage for focusing and imaging different layers. Four subjects with diverse degree of myopia were imaged. Based on the optical properties of the human eye, the eye stared system reduced the defocus to less than the typical ocular depth of focus. In this way, the illumination light can be projected on certain retina layer precisely. Since that the defocus had been compensated by the eye stared system, the adopted 512 × 512 liquid crystal spatial light modulator (LC-SLM) corrector provided the crucial spatial fidelity to fully compensate high-order aberrations. The Strehl ratio of a subject with −8 diopter myopia was improved to 0.78, which was nearly close to diffraction-limited imaging. By finely adjusting the axial displacement of illumination sources and imaging camera, cone photoreceptors, blood vessels and nerve fiber layer were clearly imaged successfully. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  18. Adaptive optics full-field OCT: a resolution almost insensitive to aberrations (Conference Presentation)

    Xiao, Peng; Fink, Mathias; Boccara, A. Claude

    2016-03-01

    A Full-Field OCT (FFOCT) setup coupled to a compact transmissive liquid crystal spatial light modulator (LCSLM) is used to induce or correct aberrations and simulate eye examinations. To reduce the system complexity, strict pupil conjugation was abandoned. During our work on quantifying the effect of geometrical aberrations on FFOCT images, we found that the image resolution is almost insensitive to aberrations. Indeed if the object channel PSF is distorted, its interference with the reference channel conserves the main feature of an unperturbed PSF with only a reduction of the signal level. This unique behavior is specific to the use of a spatially incoherent illumination. Based on this, the FFOCT image intensity was used as the metric for our wavefront sensorless correction. Aberration correction was first conducted on an USAF resolution target with the LSCLM as both aberration generator and corrector. A random aberration mask was induced, and the low-order Zernike Modes were corrected sequentially according to the intensity metric function optimization. A Ficus leaf and a fixed mouse brain tissue slice were also imaged to demonstrate the correction of sample self-induced wavefront distortions. After optimization, more structured information appears for the leaf imaging. And the high-signal fiber-like myelin fiber structures were resolved much more clearly after the whole correction process for mouse brain imaging. Our experiment shows the potential of this compact AO-FFOCT system for aberration correction imaging. This preliminary approach that simulates eyes aberrations correction also opens the path to a simple implementation of FFOCT adaptive optics for retinal examinations.

  19. SAXO: the extreme adaptive optics system of SPHERE (I) system overview and global laboratory performance

    Sauvage, Jean-Francois; Fusco, Thierry; Petit, Cyril; Costille, Anne; Mouillet, David; Beuzit, Jean-Luc; Dohlen, Kjetil; Kasper, Markus; Suarez, Marcos; Soenke, Christian; Baruffolo, Andrea; Salasnich, Bernardo; Rochat, Sylvain; Fedrigo, Enrico; Baudoz, Pierre; Hugot, Emmanuel; Sevin, Arnaud; Perret, Denis; Wildi, Francois; Downing, Mark; Feautrier, Philippe; Puget, Pascal; Vigan, Arthur; O'Neal, Jared; Girard, Julien; Mawet, Dimitri; Schmid, Hans Martin; Roelfsema, Ronald

    2016-04-01

    The direct imaging of exoplanet is a leading field of today's astronomy. The photons coming from the planet carry precious information on the chemical composition of its atmosphere. The second-generation instrument, Spectro-Polarimetric High contrast Exoplanet Research (SPHERE), dedicated to detection, photometry and spectral characterization of Jovian-like planets, is now in operation on the European very large telescope. This instrument relies on an extreme adaptive optics (XAO) system to compensate for atmospheric turbulence as well as for internal errors with an unprecedented accuracy. We demonstrate the high level of performance reached by the SPHERE XAO system (SAXO) during the assembly integration and test (AIT) period. In order to fully characterize the instrument quality, two AIT periods have been mandatory. In the first phase at Observatoire de Paris, the performance of SAXO itself was assessed. In the second phase at IPAG Grenoble Observatory, the operation of SAXO in interaction with the overall instrument has been optimized. In addition to the first two phases, a final check has been performed after the reintegration of the instrument at Paranal Observatory, in the New Integration Hall before integration at the telescope focus. The final performance aimed by the SPHERE instrument with the help of SAXO is among the highest Strehl ratio pretended for an operational instrument (90% in H band, 43% in V band in a realistic turbulence r0, and wind speed condition), a limit R magnitude for loop closure at 15, and a robustness to high wind speeds. The full-width at half-maximum reached by the instrument is 40 mas for infrared in H band and unprecedented 18.5 mas in V band.

  20. Mission to Mars: Adaptive Identifier for the Solution of Inverse Optical Metrology Tasks

    Krapivin, Vladimir F.; Varotsos, Costas A.; Christodoulakis, John

    2016-04-01

    A human mission to Mars requires the solution of many problems that mainly linked to the safety of life, the reliable operational control of drinking water as well as health care. The availability of liquid fuels is also an important issue since the existing tools cannot fully provide the required liquid fuels quantities for the mission return journey. This paper presents the development of new methods and technology for reliable, operational, and with high availability chemical analysis of liquid solutions of various types. This technology is based on the employment of optical sensors (such as the multi-channel spectrophotometers or spectroellipsometers and microwave radiometers) and the development of a database of spectral images for typical liquid solutions that could be the objects of life on Mars. This database exploits the adaptive recognition of optical images of liquids using specific algorithms that are based on spectral analysis, cluster analysis and methods for solving the inverse optical metrology tasks.

  1. Demonstration of 100 GHz electrically tunable liquid-crystal Bragg gratings for application in dynamic optical networks

    Adikan, F.R.Mahamd; J.C.Gates; Dyadyusha, A.; Major, H.E.; Gawith, C.B.E.; Sparrow, I.J.G.; Emmerson, G.D.; Kaczmarek, M.; P.G.R.Smith

    2007-01-01

    We demonstrate liquid crystal-based integrated optical devices with >140GHz electrical tuning for potential applications in dynamic optical networks. Bragg wavelength tuning covering five 25GHz WDM channel spacings has been achieved with 170V (peak-to-peak) sinusoidal voltages applied across electro-patterned ITO-covered glass electrodes placed 60?m apart. This tunability range was limited only by the initial grating strength and supply voltage level. We also observed two distinct threshold b...

  2. Low complexity Reed-Solomon-based low-density parity-check design for software defined optical transmission system based on adaptive puncturing decoding algorithm

    Pan, Xiaolong; Liu, Bo; Zheng, Jianglong; Tian, Qinghua

    2016-08-01

    We propose and demonstrate a low complexity Reed-Solomon-based low-density parity-check (RS-LDPC) code with adaptive puncturing decoding algorithm for elastic optical transmission system. Partial received codes and the relevant column in parity-check matrix can be punctured to reduce the calculation complexity by adaptive parity-check matrix during decoding process. The results show that the complexity of the proposed decoding algorithm is reduced by 30% compared with the regular RS-LDPC system. The optimized code rate of the RS-LDPC code can be obtained after five times iteration.

  3. Experimental demonstration of OpenFlow-based control plane for elastic lightpath provisioning in Flexi-Grid optical networks.

    Zhang, Jiawei; Zhang, Jie; Zhao, Yongli; Yang, Hui; Yu, Xiaosong; Wang, Lei; Fu, Xihua

    2013-01-28

    Due to the prominent performance on networking virtualization and programmability, OpenFlow is widely regarded as a promising control plane technology in packet-switched IP networks as well as wavelength-switched optical networks. For the purpose of applying software programmable feature to future optical networks, we propose an OpenFlow-based control plane in Flexi-Grid optical networks. Experimental results demonstrate its feasibility of dynamic lightpath establishment and adjustment via extended OpenFlow protocol. Wireshark captures of the signaling procedure are printed out. Additionally, the overall latency including signaling and hardware for lightpath setup and adjustment is also reported. PMID:23389119

  4. Experimental Demonstration of Mixed Formats and Bit Rates Signal Allocation for Spectrum-flexible Optical Networking

    Borkowski, Robert; Karinou, Fotini; Angelou, Marianna; Arlunno, Valeria; Zibar, Darko; Klonidis, Dimitrios; Guerrero Gonzalez, Neil; Caballero Jambrina, Antonio; Tomkos, Ioannis; Monroy, Idelfonso Tafur

    2012-01-01

    We report on an extensive experimental study for adaptive allocation of 16-QAM and QPSK signals inside spectrum flexible heterogeneous superchannel. Physical-layer performance parameters are extracted for use in resource allocation mechanisms of future flexible networks....

  5. Experimental Demonstration of Mixed Formats and Bit Rates Signal Allocation for Spectrum-flexible Optical Networking

    Borkowski, Robert; Karinou, Fotini; Angelou, Marianna; Arlunno, Valeria; Zibar, Darko; Klonidis, Dimitrios; Guerrero Gonzalez, Neil; Caballero Jambrina, Antonio; Tomkos, Ioannis; Monroy, Idelfonso Tafur

    2012-01-01

    We report on an extensive experimental study for adaptive allocation of 16-QAM and QPSK signals inside spectrum flexible heterogeneous superchannel. Physical-layer performance parameters are extracted for use in resource allocation mechanisms of future flexible networks.

  6. White Light Schlieren Optics Using Bacteriorhodopsin as an Adaptive Image Grid

    Peale, Robert; Ruffin, Boh; Donahue, Jeff; Barrett, Carolyn

    1996-01-01

    A Schlieren apparatus using a bacteriorhodopsin film as an adaptive image grid with white light illumination is demonstrated for the first time. The time dependent spectral properties of the film are characterized. Potential applications include a single-ended Schlieren system for leak detection.

  7. A correction algorithm to simultaneously control dual deformable mirrors in a woofer-tweeter adaptive optics system

    Li, Chaohong; Sredar, Nripun; Ivers, Kevin M.; Queener, Hope; Porter, Jason

    2010-01-01

    We present a direct slope-based correction algorithm to simultaneously control two deformable mirrors (DMs) in a woofer-tweeter adaptive optics system. A global response matrix was derived from the response matrices of each deformable mirror and the voltages for both deformable mirrors were calculated simultaneously. This control algorithm was tested and compared with a 2-step sequential control method in five normal human eyes using an adaptive optics scanning laser ophthalmoscope. The mean ...

  8. Commissioning of the Adaptive Optics System NAOS-CONICA for the VLT : the way to First Light

    Hartung, Markus

    2003-01-01

    In October 2002 NAOS-CONICA, one of the most powerful adaptive optics systems was offered to the astronomical community. The instrument is installed at the Very Large Telescope in Chile and operated by the European Southern Observatory. The adaptive optics system NAOS corrects for atmospheric turbulence and provides the near-infrared multi-mode camera and spectrograph CONICA with diffraction limited images. Development of NAOS was achieved by a French consortium, while CONICA was developed ...

  9. Adaptive management of the Great Barrier Reef: a globally significant demonstration of the benefits of networks of marine reserves.

    McCook, Laurence J; Ayling, Tony; Cappo, Mike; Choat, J Howard; Evans, Richard D; De Freitas, Debora M; Heupel, Michelle; Hughes, Terry P; Jones, Geoffrey P; Mapstone, Bruce; Marsh, Helene; Mills, Morena; Molloy, Fergus J; Pitcher, C Roland; Pressey, Robert L; Russ, Garry R; Sutton, Stephen; Sweatman, Hugh; Tobin, Renae; Wachenfeld, David R; Williamson, David H

    2010-10-26

    The Great Barrier Reef (GBR) provides a globally significant demonstration of the effectiveness of large-scale networks of marine reserves in contributing to integrated, adaptive management. Comprehensive review of available evidence shows major, rapid benefits of no-take areas for targeted fish and sharks, in both reef and nonreef habitats, with potential benefits for fisheries as well as biodiversity conservation. Large, mobile species like sharks benefit less than smaller, site-attached fish. Critically, reserves also appear to benefit overall ecosystem health and resilience: outbreaks of coral-eating, crown-of-thorns starfish appear less frequent on no-take reefs, which consequently have higher abundance of coral, the very foundation of reef ecosystems. Effective marine reserves require regular review of compliance: fish abundances in no-entry zones suggest that even no-take zones may be significantly depleted due to poaching. Spatial analyses comparing zoning with seabed biodiversity or dugong distributions illustrate significant benefits from application of best-practice conservation principles in data-poor situations. Increases in the marine reserve network in 2004 affected fishers, but preliminary economic analysis suggests considerable net benefits, in terms of protecting environmental and tourism values. Relative to the revenue generated by reef tourism, current expenditure on protection is minor. Recent implementation of an Outlook Report provides regular, formal review of environmental condition and management and links to policy responses, key aspects of adaptive management. Given the major threat posed by climate change, the expanded network of marine reserves provides a critical and cost-effective contribution to enhancing the resilience of the Great Barrier Reef. PMID:20176947

  10. Experimental demonstration of optical transport, sorting and selfarrangement using a "tractor beam"

    Brzobohatý, Oto; Karásek, Vítězslav; Šiler, Martin; Chvátal, Lukáš; Čižmár, T.; Zemánek, Pavel

    Bellingham: SPIE, 2013, 881003:1-7. ISSN 0277-786X. [Optical Trapping and Optical Micromanipulation /10./. San Diego (US), 25.08.2013-29.08.2013] R&D Projects: GA TA ČR TE01020233; GA ČR GA202/09/0348; GA ČR GPP205/11/P294; GA MŠk LH12018; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : laser beam propagation * particles * photons * polarization Subject RIV: BH - Optics, Masers, Laser s

  11. Status Update and Closed-Loop Performance of the Magellan Adaptive Optics VisAO Camera

    Kopon, Derek; Males, Jared; Gasho, Victor; Morzinski, Katie; Follette, Katherine

    2014-01-01

    We present laboratory results of the closed-loop performance of the Magellan Adaptive Optics (AO) Adaptive Secondary Mirror (ASM), pyramid wavefront sensor (PWFS), and VisAO visible adaptive optics camera. The Magellan AO system is a 585-actuator low-emissivity high-throughput system scheduled for first light on the 6.5 meter Magellan Clay telescope in November 2012. Using a dichroic beamsplitter near the telescope focal plane, the AO system will be able to simultaneously perform visible (500-1000 nm) AO science with our VisAO camera and either 10 micron or 3-5 micron science using either the BLINC/MIRAC4 or CLIO cameras, respectively. The ASM, PWS, and VisAO camera have undergone final system tests in the solar test tower at the Arcetri Institute in Florence, Italy, reaching Strehls of 37% in i'-band with 400 modes and simulated turbulence of 14 cm ro at v-band. We present images and test results of the assembled VisAO system, which includes our prototype advanced Atmospheric Dispersion Corrector (ADC), prot...

  12. Adaptive cancellation of light relative intensity noise for fiber optic gyroscope

    Zhong xiao Ji

    2013-07-01

    Full Text Available In order to reduce the relative intensity noise (RIN in the interferometric signal of the fiber optic gyroscope (FOG, an adaptive noise subtraction method is presented, which aims to overcome to the drawbacks that the fixed delay time and gain of the digital noise subtraction method. The drawbacks will make the performance of FOG to be degraded greatly in the changing environment. In the paper the adaptive noise subtraction system based on the recursive least squares algorithm (RLS is formed in FPGA, in which the interferometric signal is regarded as the signal source, and RIN in the free end of the optical fiber coupler of FOG is looked as the noise reference signal. The two critical parameters that minimum delay time and its varying range result from measuring the minimum and maximum delay times of the interferometric signal in a certain temperature range. The off-line and on-line temperature experimental results verify the capability of adapting to the environmental temperature.

  13. Adaptive Cancellation of Light Relative Intensity Noise for Fiber Optic Gyroscope

    Zhongxiao Ji

    2013-07-01

    Full Text Available In order to reduce the relative intensity noise (RIN in the interferometric signal of the fiber optic gyroscope (FOG, an adaptive noise subtraction method is presented, which aims to overcome to the drawbacks that the fixed delay time and gain of the digital noise subtraction method. The drawbacks will make the performance of FOG to be degraded greatly in the changing environment. In the paper the adaptive noise subtraction system based on the recursive least squares algorithm (RLS is formed in FPGA, in which the interferometric signal is regarded as the signal source, and RIN in the free end of the optical fiber coupler of FOG is looked as the noise reference signal. The two critical parameters that minimum delay time and its varying range result from measuring the minimum and maximum delay times of the interferometric signal in a certain temperature range. The off-line and on-line temperature experimental results verify the capability of adapting to the environmental temperature.      

  14. Experimental Demonstration of a Cognitive Optical Network for Reduction of Restoration Time

    Kachris, Christoforos; Klonidis, Dimitris; Francescon, Antonio; Siracusa, Domenico; Salvadori, Elio; Barroso, Ramón J. Durán; de Miguel, Ignacio; Borkowski, Robert; Caballero Jambrina, Antonio; Tafur Monroy, Idelfonso; Ye, Yabin; Tymecki, Andrzej; Tomkos, Ioannis

    2014-01-01

    This paper presents the implementation and performance evaluation of a cognitive heterogeneous optical network testbed. The testbed integrates the CMP, the data plane and the cognitive system and reduces by 48% the link restoration time....

  15. Long-baseline optical intensity interferometry: Laboratory demonstration of diffraction-limited imaging

    Dravins, Dainis; Nuñez, Paul D

    2015-01-01

    A long-held vision has been to realize diffraction-limited optical aperture synthesis over kilometer baselines. This will enable imaging of stellar surfaces and their environments, and reveal interacting gas flows in binary systems. An opportunity is now opening up with the large telescope arrays primarily erected for measuring Cherenkov light in air induced by gamma rays. With suitable software, such telescopes could be electronically connected and also used for intensity interferometry. Second-order spatial coherence of light is obtained by cross correlating intensity fluctuations measured in different pairs of telescopes. With no optical links between them, the error budget is set by the electronic time resolution of a few nanoseconds. Corresponding light-travel distances are approximately one meter, making the method practically immune to atmospheric turbulence or optical imperfections, permitting both very long baselines and observing at short optical wavelengths. Previous theoretical modeling has shown ...

  16. Demonstration of a 3-bit optical digital-to-analog converter based on silicon microring resonators.

    Yang, Lin; Ding, Jianfeng; Chen, Qiaoshan; Zhou, Ping; Zhang, Fanfan; Zhang, Lei

    2014-10-01

    We propose an N-bit optical digital-to-analog converter based on silicon microring resonators (MRRs), which can transform an N-bit electrical digital signal to an optical analog signal. A 3-bit optical digital-to-analog convertor is fabricated as proof of concept through a CMOS-compatible process on a silicon-on-insulator platform. The silicon MRRs are modulated through the electric-field-induced carrier injection in forward biased PN junctions embedded in the ring waveguides. The electro-optical 3-dB bandwidths of the silicon MRRs are approximately 800 MHz. The device works well at a speed of 500  MSample/s under driving voltage swings of 0.75 V. PMID:25360972

  17. Adaptive neuro-fuzzy prediction of modulation transfer function of optical lens system

    Petković, Dalibor; Shamshirband, Shahaboddin; Anuar, Nor Badrul; Md Nasir, Mohd Hairul Nizam; Pavlović, Nenad T.; Akib, Shatirah

    2014-07-01

    The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to predict MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using MATLAB/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

  18. Modulation transfer function estimation of optical lens system by adaptive neuro-fuzzy methodology

    Petković, Dalibor; Shamshirband, Shahaboddin; Pavlović, Nenad T.; Anuar, Nor Badrul; Kiah, Miss Laiha Mat

    2014-07-01

    The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to estimate MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

  19. Wavefront detection method of a single-sensor based adaptive optics system.

    Wang, Chongchong; Hu, Lifa; Xu, Huanyu; Wang, Yukun; Li, Dayu; Wang, Shaoxin; Mu, Quanquan; Yang, Chengliang; Cao, Zhaoliang; Lu, Xinghai; Xuan, Li

    2015-08-10

    In adaptive optics system (AOS) for optical telescopes, the reported wavefront sensing strategy consists of two parts: a specific sensor for tip-tilt (TT) detection and another wavefront sensor for other distortions detection. Thus, a part of incident light has to be used for TT detection, which decreases the light energy used by wavefront sensor and eventually reduces the precision of wavefront correction. In this paper, a single Shack-Hartmann wavefront sensor based wavefront measurement method is presented for both large amplitude TT and other distortions' measurement. Experiments were performed for testing the presented wavefront method and validating the wavefront detection and correction ability of the single-sensor based AOS. With adaptive correction, the root-mean-square of residual TT was less than 0.2 λ, and a clear image was obtained in the lab. Equipped on a 1.23-meter optical telescope, the binary stars with angle distance of 0.6″ were clearly resolved using the AOS. This wavefront measurement method removes the separate TT sensor, which not only simplifies the AOS but also saves light energy for subsequent wavefront sensing and imaging, and eventually improves the detection and imaging capability of the AOS. PMID:26367988

  20. Optimized calibration strategy for high order adaptive optics systems in closed-loop: the slope-oriented Hadamard actuation.

    Meimon, Serge; Petit, Cyril; Fusco, Thierry

    2015-10-19

    The accurate calibration of the interaction matrix affects the performance of an adaptive optics system. In the case of high-order systems, when the number of mirror modes is worth a few thousands, the calibration strategy is critical to reach the maximum interaction matrix quality in the minimum time. This is all the more true for the future European Extremely Large Telescope. Here, we propose a novel calibration scheme, the Slope-Oriented Hadamard strategy. We then build a tractable interaction matrix quality criterion, and show that our method tends to optimize it. We demonstrate that for a given level of quality, the calibration time needed using the Slope-Oriented Hadamard method is seven times less than with a classical Hadamard scheme. These analytic and simulation results are confirmed experimentally on the SPHERE XAO system (SAXO). PMID:26480374

  1. Fabrication and demonstration of 1 × 8 silicon–silica multi-chip switch based on optical phased array

    Katayose, Satomi; Hashizume, Yasuaki; Itoh, Mikitaka

    2016-08-01

    We experimentally demonstrated a 1 × 8 silicon–silica hybrid thermo-optic switch based on an optical phased array using a multi-chip integration technique. The switch consists of a silicon chip with optical phase shifters and two silica-based planar lightwave circuit (PLC) chips composed of optical couplers and fiber connections. We adopted a rib waveguide as the silicon waveguide to reduce the coupling loss and increase the alignment tolerance for coupling between silicon and silica waveguides. As a result, we achieved a fast switching response of 81 µs, a high extinction ratio of over 18 dB and a low insertion loss of 4.9–8.1 dB including a silicon–silica coupling loss of 0.5 ± 0.3 dB at a wavelength of 1.55 µm.

  2. woptic: Optical conductivity with Wannier functions and adaptive k-mesh refinement

    Assmann, E.; Wissgott, P.; Kuneš, J.; Toschi, A.; Blaha, P.; Held, K.

    2016-05-01

    We present an algorithm for the adaptive tetrahedral integration over the Brillouin zone of crystalline materials, and apply it to compute the optical conductivity, dc conductivity, and thermopower. For these quantities, whose contributions are often localized in small portions of the Brillouin zone, adaptive integration is especially relevant. Our implementation, the woptic package, is tied into the WIEN2WANNIER framework and allows including a local many-body self energy, e.g. from dynamical mean-field theory (DMFT). Wannier functions and dipole matrix elements are computed with the DFT package WIEN2k and Wannier90. For illustration, we show DFT results for fcc-Al and DMFT results for the correlated metal SrVO3.

  3. woptic: optical conductivity with Wannier functions and adaptive k-mesh refinement

    Assmann, E; Kuneš, J; Toschi, A; Blaha, P; Held, K

    2015-01-01

    We present an algorithm for the adaptive tetrahedral integration over the Brillouin zone of crystalline materials, and apply it to compute the optical conductivity, dc conductivity, and thermopower. For these quantities, whose contributions are often localized in small portions of the Brillouin zone, adaptive integration is especially relevant. Our implementation, the woptic package, is tied into the wien2wannier framework and allows including a many-body self energy, e.g. from dynamical mean-field theory (DMFT). Wannier functions and dipole matrix elements are computed with the DFT package Wien2k and Wannier90. For illustration, we show DFT results for fcc-Al and DMFT results for the correlated metal SrVO$_3$.

  4. Adaptive Sensor Optimization and Cognitive Image Processing Using Autonomous Optical Neuroprocessors; TOPICAL

    Measurement and signal intelligence demands has created new requirements for information management and interoperability as they affect surveillance and situational awareness. Integration of on-board autonomous learning and adaptive control structures within a remote sensing platform architecture would substantially improve the utility of intelligence collection by facilitating real-time optimization of measurement parameters for variable field conditions. A problem faced by conventional digital implementations of intelligent systems is the conflict between a distributed parallel structure on a sequential serial interface functionally degrading bandwidth and response time. In contrast, optically designed networks exhibit the massive parallelism and interconnect density needed to perform complex cognitive functions within a dynamic asynchronous environment. Recently, all-optical self-organizing neural networks exhibiting emergent collective behavior which mimic perception, recognition, association, and contemplative learning have been realized using photorefractive holography in combination with sensory systems for feature maps, threshold decomposition, image enhancement, and nonlinear matched filters. Such hybrid information processors depart from the classical computational paradigm based on analytic rules-based algorithms and instead utilize unsupervised generalization and perceptron-like exploratory or improvisational behaviors to evolve toward optimized solutions. These systems are robust to instrumental systematics or corrupting noise and can enrich knowledge structures by allowing competition between multiple hypotheses. This property enables them to rapidly adapt or self-compensate for dynamic or imprecise conditions which would be unstable using conventional linear control models. By incorporating an intelligent optical neuroprocessor in the back plane of an imaging sensor, a broad class of high-level cognitive image analysis problems including geometric

  5. DESIGN ISSUES FOR BIT RATE-ADAPTIVE 3R O/E/OTRANSPONDER IN INTELLIGENT OPTICAL NETWORKS

    朱栩; 曾庆济; 杨旭东; 刘逢清; 肖石林

    2002-01-01

    This paper reported the design and implementation of a bit rate-adaptive Optical-Electronic-Optical (O/E/O) transponder accomplishing almost full data rate transparency up to 2.5 Gb/s with 3R (Reamplifying, Reshaping and Retiming) processing in electronic domain. Based on the chipsets performing clock recovery in several continuous bit rate ranges, a clock and data regenerating circuit self-adaptive to the bit rate of input signal was developed. Key design issues were presented, laying stress on the functional building blocks and scheme for the bit rate-adaptive retiming circuit. The experimental results show a good scalability performance.

  6. Advancing adaptive optics technology: Laboratory turbulence simulation and optimization of laser guide stars

    Rampy, Rachel A.

    Since Galileo's first telescope some 400 years ago, astronomers have been building ever-larger instruments. Yet only within the last two decades has it become possible to realize the potential angular resolutions of large ground-based telescopes, by using adaptive optics (AO) technology to counter the blurring effects of Earth's atmosphere. And only within the past decade have the development of laser guide stars (LGS) extended AO capabilities to observe science targets nearly anywhere in the sky. Improving turbulence simulation strategies and LGS are the two main topics of my research. In the first part of this thesis, I report on the development of a technique for manufacturing phase plates for simulating atmospheric turbulence in the laboratory. The process involves strategic application of clear acrylic paint onto a transparent substrate. Results of interferometric characterization of the plates are described and compared to Kolmogorov statistics. The range of r0 (Fried's parameter) achieved thus far is 0.2--1.2 mm at 650 nm measurement wavelength, with a Kolmogorov power law. These plates proved valuable at the Laboratory for Adaptive Optics at University of California, Santa Cruz, where they have been used in the Multi-Conjugate Adaptive Optics testbed, during integration and testing of the Gemini Planet Imager, and as part of the calibration system of the on-sky AO testbed named ViLLaGEs (Visible Light Laser Guidestar Experiments). I present a comparison of measurements taken by ViLLaGEs of the power spectrum of a plate and the real sky turbulence. The plate is demonstrated to follow Kolmogorov theory well, while the sky power spectrum does so in a third of the data. This method of fabricating phase plates has been established as an effective and low-cost means of creating simulated turbulence. Due to the demand for such devices, they are now being distributed to other members of the AO community. The second topic of this thesis pertains to understanding and

  7. VLT/NACO infrared adaptive optics images of small scale structures in OMC1

    Lacombe, F; Rouan, D; Clénet, Y; Lemaire, J L; Lagrange, A M; Mouillet, D; Rousset, G; Marlot, C; Feautrier, P; Gustafsson, M; Field, D; Lacombe, Francois; Gendron, Eric; Rouan, Daniel; Clenet, Yann; Lemaire, Jean-Louis; Lagrange, Anne-Marie; Mouillet, David; Rousset, Gerard; Marlot, Claude; Feautrier, Philippe; Field, David; Proxy, Bernard Servan; ccsd-00000915, ccsd

    2003-01-01

    Near-infrared observations of line emission from excited H2 and in the continuum are reported in the direction of the Orion molecular cloud OMC1, using the European Southern Observatory Very Large Telescope UT4, equipped with the NAOS adaptive optics system and the CONICA infrared array camera. Spatial resolution has been achieved at close to the diffraction limit of the telescope (0.08" - 0.12") and images show a wealth of morphological detail. Structure is not fractal but shows two preferred scale sizes of 2.4" (1100 AU) and 1.2" (540 AU), where the larger scale may be associated with star formation.

  8. Fast Fourier and Wavelet Transforms for Wavefront Reconstruction in Adaptive Optics

    Dowla, F U; Brase, J M; Olivier, S S

    2000-07-28

    Wavefront reconstruction techniques using the least-squares estimators are computationally quite expensive. We compare wavelet and Fourier transforms techniques in addressing the computation issues of wavefront reconstruction in adaptive optics. It is shown that because the Fourier approach is not simply a numerical approximation technique unlike the wavelet method, the Fourier approach might have advantages in terms of numerical accuracy. However, strictly from a numerical computations viewpoint, the wavelet approximation method might have advantage in terms of speed. To optimize the wavelet method, a statistical study might be necessary to use the best basis functions or ''approximation tree.''

  9. The Subaru Coronagraphic Extreme Adaptive Optics Imager: First Results and On-Sky Performance

    Currie, Thayne; Martinache, Frantz; Clergeon, Christophe; McElwain, Michael; Thalmann, Christian; Jovanovic, Nemanja; Singh, Garima; Kudo, Tomoyuki

    2013-01-01

    We present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control ("speckle nulling"). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield > 90% Strehl ratio and enable 10^6--10^7 contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

  10. Object-oriented software design for the Mt. Wilson 100-inch Hooker telescope adaptive optics system

    Schneider, Thomas G.

    2000-06-01

    The object oriented software design paradigm has been instrumented in the development of the Adoptics software used in the Hooker telescope's ADOPT adaptive optics system. The software runs on a Pentium-class PC host and eight DSP processors connected to the host's motherboard bus. C++ classes were created to implement most of the host software's functionality, with the object oriented features of inheritance, encapsulation and abstraction being the most useful. Careful class design at the inception of the project allowed for the rapid addition of features without comprising the integrity of the software. Base class implementations include the DSP system, real-time graphical displays and opto-mechanical actuator control.

  11. Clock recovering characteristics of adaptive finite-impulse-response filters in digital coherent optical receivers.

    Kikuchi, Kazuro

    2011-03-14

    We analyze the clock-recovery process based on adaptive finite-impulse-response (FIR) filtering in digital coherent optical receivers. When the clock frequency is synchronized between the transmitter and the receiver, only five taps in half-symbol-spaced FIR filters can adjust the sampling phase of analog-to-digital conversion optimally, enabling bit-error rate performance independent of the initial sampling phase. Even if the clock frequency is not synchronized between them, the clock-frequency misalignment can be adjusted within an appropriate block interval; thus, we can achieve an asynchronous clock mode of operation of digital coherent receivers with block processing of the symbol sequence. PMID:21445201

  12. High-resolution adaptive optics scanning laser ophthalmoscope with multiple deformable mirrors

    Chen, Diana C.; Olivier, Scot S.; Jones; Steven M.

    2010-02-23

    An adaptive optics scanning laser ophthalmoscopes is introduced to produce non-invasive views of the human retina. The use of dual deformable mirrors improved the dynamic range for correction of the wavefront aberrations compared with the use of the MEMS mirror alone, and improved the quality of the wavefront correction compared with the use of the bimorph mirror alone. The large-stroke bimorph deformable mirror improved the capability for axial sectioning with the confocal imaging system by providing an easier way to move the focus axially through different layers of the retina.

  13. Precise Astrometry of Visual Binaries with Adaptive Optics. A Way for Finding Exoplanets?

    Hełminiak, Krzysztof

    2008-01-01

    We present the results of our study of astrometric stability of 200-in Hale (Mt. Palomar) and 10-m Keck II (Mauna Kea) telescopes, both with Adaptive Optics (AO) facilities. A group of nearby visual binaries and multiples was observed in near infrared, relative separations and position angles measured. We have also checked the influence of some systematic effects (e.g. atmospherical refraction, varying plate scale factor) on result and precision of astrometric measurements. We conclude that in visual binaries astrometrical observations it is possible to achieve much better precision than 1 miliarcsecond, which in many cases allows detection of the astrometrical signal produced by planetary-mass object.

  14. Titan imagery with Keck adaptive optics during and after probe entry

    De Pater, Imke; Ádámkovics, Máte; Bouchez, Antonin H.; Brown, Michael E.; Gibbard, Seran G.; Marchis, Franck; Roe, Henry G.; Schaller, Emily L.; Young, Eliot

    2006-01-01

    We present adaptive optics data from the Keck telescope, taken while the Huygens probe descended through Titan's atmosphere and on the days following touchdown. No probe entry signal was detected. Our observations span a solar phase angle range from 0.05° up to 0.8°, with the Sun in the west. Contrary to expectations, the east side of Titan's stratosphere was usually brightest. Compiling images obtained with Keck and Gemini over the past few years reveals that the east-west asymmetry can be e...

  15. Progress with multi-conjugate adaptive optics at the Big Bear Solar Observatory

    Schmidt, Dirk; Gorceix, Nicolas; Marino, Jose; Zhang, Xianyu; Berkefeld, Thomas; Rimmele, Thomas R.; Goode, Philip R.

    2016-05-01

    The MCAO system at BBSO is the pathfinder system for a future system at the 4-meter DKIST. It deploys three DMs, one in the pupil and two in higher altitudes. The design allows to move the latter independently to adapt to the turbulence profile within about 2-9 km.The optical path has been improved in 2015, and has shown satisfying solar images. The MCAO loop was able to improve the wavefront error across the field slightly compared to classical AO.We will report on the latest improvements, on-Sun results and motivate the design of the system.

  16. Bi-photon propagation control with optimized wavefront by means of Adaptive Optics

    Minozzi, M.; Bonora, S.; Sergienko, A. V.; G. Vallone; Villoresi, P.

    2012-01-01

    We present an efficient method to control the spatial modes of entangled photons produced through SPDC process. Bi-photon beam propagation is controlled by a deformable mirror, that shapes a 404nm CW diode laser pump interacting with a nonlinear BBO type-I crystal. Thanks to adaptive optical system, the propagation of 808nm SPDC light produced is optimized over a distance of 2m. The whole system optimization is carried out by a feedback between deformable mirror action and entangled photon co...

  17. LBT adaptive secondary mirrors: chopping procedures and optical calibration on the test bench

    Briguglio, Runa; Xompero, Marco; Riccardi, Armando

    2012-07-01

    In this paper we will describe the chopping capabilities of the Large Binocular Telescope adaptive secondary mirrors. The chopping testing procedure has been implemented at the Arcetri Test Tower in Florence, Italy, together with the optical testing set-up. The deformable mirror static figuring error, after the flattening calibration at both chopping positions (+/- 25 μm tilt with respect to the nominal position), is measured to be compatible to the figuring at the zero tilt position, i.e. 30 nm RMS. The figuring error measured at a +25 μm tilted position, while the mirror was chopping at 10Hz, is within requirements for seeing limited mode observations.

  18. Smart microscope: an adaptive optics learning system for aberration correction in multiphoton confocal microscopy.

    Albert, O; Sherman, L; Mourou, G; Norris, T B; Vdovin, G

    2000-01-01

    Off-axis aberrations in a beam-scanning multiphoton confocal microscope are corrected with a deformable mirror. The optimal mirror shape for each pixel is determined by a genetic learning algorithm, in which the second-harmonic or two-photon fluorescence signal from a reference sample is maximized. The speed of the convergence is improved by use of a Zernike polynomial basis for the deformable mirror shape. This adaptive optical correction scheme is implemented in an all-reflective system by use of extremely short (10-fs) optical pulses, and it is shown that the scanning area of an f:1 off-axis parabola can be increased by nine times with this technique. PMID:18059779

  19. Images of photoreceptors in living primate eyes using adaptive optics two-photon ophthalmoscopy.

    Hunter, Jennifer J; Masella, Benjamin; Dubra, Alfredo; Sharma, Robin; Yin, Lu; Merigan, William H; Palczewska, Grazyna; Palczewski, Krzysztof; Williams, David R

    2010-01-01

    In vivo two-photon imaging through the pupil of the primate eye has the potential to become a useful tool for functional imaging of the retina. Two-photon excited fluorescence images of the macaque cone mosaic were obtained using a fluorescence adaptive optics scanning laser ophthalmoscope, overcoming the challenges of a low numerical aperture, imperfect optics of the eye, high required light levels, and eye motion. Although the specific fluorophores are as yet unknown, strong in vivo intrinsic fluorescence allowed images of the cone mosaic. Imaging intact ex vivo retina revealed that the strongest two-photon excited fluorescence signal comes from the cone inner segments. The fluorescence response increased following light stimulation, which could provide a functional measure of the effects of light on photoreceptors. PMID:21326644

  20. Recovery Management in All Optical Networks Using Biologically-Inspired Complex Adaptive System

    Inadyuti Dutt

    2013-01-01

    Full Text Available All-Optical Networks have the ability to display varied advantages like performance efficiency, throughput etc but their efficiency depends on their survivability as they are attack prone. These attacks can be categorised as active or passive because they try to access information within the network or alter the information in the network. The attack once detected has to be recovered by formulating back-up or alternative paths. The proposed heuristic uses biologically inspired Complex Adaptive System, inspired by Natural Immune System. The study shows that natural immune system exhibit unique behaviour of detecting foreign bodies in our body and removing them on their first occurrences. This phenomenon is being utilised in the proposed heuristic for recovery management in All-optical Network

  1. Adaptive information interchange system of the fiber-optic measuring networks with the computer

    Denisov, Igor V.; Drozdov, Roman S.; Sedov, Victor A.

    2005-06-01

    In the present paper the characteristics and opportunities of application of the system of parallel input-output of information from the fiber-optical measuring network into computer are considered. The system consists of two pars: on manframe and several expansion blocks. The first part is internal, is connected directly in the socket of the motherboard of the personal computer. It is designed for buffering system signals and development of cojmands of controlling by the system for input-output of signals into personal computer and signals generation onto expansion blocks. The second part is external, connects to the mainframe by means of cables. It designed for transformation of information from the fiber-optical measuring network into signalsof rthe mainframe and instrument settings adaptation. The analysis of speed of procesing of analog and digital data by system is presented. The possible schemes of use of the system for processing quasistationary and dynamic fields are considered.

  2. Ferrofluid Based Deformable Mirrors - a New Approach to Adaptive Optics Using Liquid Mirrors

    Laird, P; Berube, V; Borra, E F; Ritcey, A; Rioux, M; Robitaille, N; Thibault, S; Yockell-Lelievre, H

    2002-01-01

    The trend towards ever larger telescopes and more advanced adaptive optics systems is driving the need for deformable mirrors with a large number of low cost actuators. Liquid mirrors have long been recognized a potential low cost alternative to conventional solid mirrors. By using a water or oil based ferrofluid we are able to benefit from a stronger magnetic response than is found in magnetic liquid metal amalgams and avoid the difficulty of passing a uniform current through a liquid. Depositing a thin silver colloid known as a metal liquid-like film (MELLF) on the ferrofluid surface solves the problem of low reflectivity of pure ferrofluids. This combination provides a liquid optical surface that can be precisely shaped in a magnetic field. We present experimental results obtained with a prototype deformable liquid mirror based on this combination.

  3. Ferrofluid based deformable mirrors: a new approach to adaptive optics using liquid mirrors

    Laird, Phil R.; Bergamasco, R.; Bérubé, Vincent; Borra, Ermanno F.; Gingras, Julie; Ritcey, Anna-Marie R.; Rioux, Myriam; Robitaille, Nathalie; Thibault, Simon; Vieira da Silva, L., Jr.; Yockell-Lelièvre, Helene

    2003-02-01

    The trend towards ever larger telescopes and more advanced adaptive optics systems is driving the need for deformable mirrors with a large number of low cost actuators. Liquid mirrors have long been recognized a potential low cost alternative to conventional solid mirrors. By using a water or oil based ferrofluid we are able to benefit from a stronger magnetic response than is found in magnetic liquid metal amalgams and avoid the difficulty of passing a uniform current through a liquid. Depositing a thin silver colloid known as a metal liquid like film (MELLF) on the ferrofluid surface solves the problem of low reflectivity of pure ferrofluids. This combination provides a liquid optical surface that can be precisely shaped in a magnetic field. We present experimental results obtained with a prototype deformable liquid mirror based on this combination.

  4. Combinational-deformable-mirror adaptive optics system for compensation of high-order modes of wavefront

    Huafeng Yang; Guilin Liu; Changhui Rao; Yudong Zhang; Wenhan Jiang

    2007-01-01

    A new kind of adaptive optics (AO) system, in which several low spatial frequency deformable mirrors(DMs) with optical conjugation relationship are combined to correct high-order aberrations, is proposed.The phase compensation principle and the control method of the combinational AO system are introduced.The numerical simulations for the AO system with two 60-element DMs are presented. The results indicate that the combinational DM in the AO system can correct different aberrations effectively as one single DM with more actuators, and there is no change of control method. This technique can be applied to a large telescope AO system to improve the spatial compensation capability for wavefront by using current DM.

  5. Numerical control matrix rotation for the LINC-NIRVANA Multi-Conjugate Adaptive Optics system

    Arcidiacono, Carmelo; Ragazzoni, Roberto; Farinato, Jacopo; Esposito, Simone; Riccardi, Armando; Pinna, Enrico; Puglisi, Alfio; Fini, Luca; Xompero, Marco; Busoni, Lorenzo; Quiros-Pacheco, Fernando; Briguglio, Runa; 10.1117/12.857347

    2010-01-01

    LINC-NIRVANA will realize the interferometric imaging focal station of the Large Binocular Telescope. A double Layer Oriented multi-conjugate adaptive optics system assists the two arms of the interferometer, supplying high order wave-front correction. In order to counterbalance the field rotation, mechanical derotation for the two ground wave-front sensors, and optical derotators for the mid-high layers sensors fix the positions of the focal planes with respect to the pyramids aboard the wave-front sensors. The derotation introduces pupil images rotation on the wavefront sensors: the projection of the deformable mirrors on the sensor consequently change. The proper adjustment of the control matrix will be applied in real-time through numerical computation of the new matrix. In this paper we investigate the temporal and computational aspects related to the pupils rotation, explicitly computing the wave-front errors that may be generated.

  6. Adaptive Optics Imaging of Lyman Break Galaxies as Progenitors of Spheroids in the Local Universe

    Akiyama, M; Kobayashi, N; Ohta, K; Iwata, I

    2007-01-01

    In order to reveal the stellar mass distribution of z~3 galaxies, we are conducting deep imaging observations of U-dropout Lyman Break Galaxies (LBGs) with Adaptive Optics (AO) systems in K-band, which corresponds to rest-frame V-band of z~3 galaxies. The results of the Subaru intensive-program observations with AO36/NGS/IRCS indicate that 1) the K-band peaks of some of the LBGs brighter than K=22.0 mag show significant offset from those in the optical images, 2) the z~3 Mv* LBGs and serendipitously observed Distant Red Galaxies (DRGs) have flat profiles similar to disk galaxies in the local universe (i.e., Sersic with n2 systems among the luminous z~3 LBGs and DRGs, and their strong spatial clustering, we infer that the dense n2 spheroids of nearby galaxies through relaxations due to major merger events.

  7. Noiseless imaging detector for adaptive optics with kHz frame rates

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

    2004-10-01

    A new hybrid optical detector is described that has many of the attributes desired for the next generation AO wavefront sensors. The detector consists of a proximity focused MCP read out by four 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 512 x 512 pixels, zero readout noise (photon counting) and can be read out at 1kHz frame rates. The Medipix2 readout chips can be electronically shuttered down to a temporal window of a few microseconds with an accuracy of 10 nanoseconds. When used in a Shack-Hartman style wavefront sensor, it 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. A three year development effort for this detector technology has just been funded as part of the first Adaptive Optics Development Program managed by the National Optical Astronomy Observatory.

  8. Multi-modal adaptive optics system including fundus photography and optical coherence tomography for the clinical setting.

    Salas, Matthias; Drexler, Wolfgang; Levecq, Xavier; Lamory, Barbara; Ritter, Markus; Prager, Sonja; Hafner, Julia; Schmidt-Erfurth, Ursula; Pircher, Michael

    2016-05-01

    We present a new compact multi-modal imaging prototype that combines an adaptive optics (AO) fundus camera with AO-optical coherence tomography (OCT) in a single instrument. The prototype allows acquiring AO fundus images with a field of view of 4°x4° and with a frame rate of 10fps. The exposure time of a single image is 10 ms. The short exposure time results in nearly motion artifact-free high resolution images of the retina. The AO-OCT mode allows acquiring volumetric data of the retina at 200kHz A-scan rate with a transverse resolution of ~4 µm and an axial resolution of ~5 µm. OCT imaging is acquired within a field of view of 2°x2° located at the central part of the AO fundus image. Recording of OCT volume data takes 0.8 seconds. The performance of the new system is tested in healthy volunteers and patients with retinal diseases. PMID:27231621

  9. Multi-modal adaptive optics system including fundus photography and optical coherence tomography for the clinical setting

    Salas, Matthias; Drexler, Wolfgang; Levecq, Xavier; Lamory, Barbara; Ritter, Markus; Prager, Sonja; Hafner, Julia; Schmidt-Erfurth, Ursula; Pircher, Michael

    2016-01-01

    We present a new compact multi-modal imaging prototype that combines an adaptive optics (AO) fundus camera with AO-optical coherence tomography (OCT) in a single instrument. The prototype allows acquiring AO fundus images with a field of view of 4°x4° and with a frame rate of 10fps. The exposure time of a single image is 10 ms. The short exposure time results in nearly motion artifact-free high resolution images of the retina. The AO-OCT mode allows acquiring volumetric data of the retina at 200kHz A-scan rate with a transverse resolution of ~4 µm and an axial resolution of ~5 µm. OCT imaging is acquired within a field of view of 2°x2° located at the central part of the AO fundus image. Recording of OCT volume data takes 0.8 seconds. The performance of the new system is tested in healthy volunteers and patients with retinal diseases.

  10. In-vivo imaging of inner retinal cellular morphology with adaptive optics - optical coherence tomography: challenges and possible solutions

    Zawadzki, Robert J.; Jones, Steven M.; Kim, Dae Yu; Poyneer, Lisa; Capps, Arlie G.; Hamann, Bernd; Olivier, Scot S.; Werner, John S.

    2012-03-01

    Recent progress in retinal image acquisition techniques, including optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO), combined with improved performance of adaptive optics (AO) instrumentation, has resulted in improvement in the quality of in vivo images of cellular structures in the outer layers of the human retina. Despite the significant progress in imaging cone and rod photoreceptor mosaics, visualization of cellular structures in the inner retina has been achieved only with extrinsic contrast agents that have not been approved for use with humans. In this paper we describe the main limiting factors in visualizing inner retinal cells and the methods we implemented to reduce their effects on images acquired with AO-OCT. These include improving the system point spread function (AO performance), monitoring of motion artifacts (retinal motion tracking), and speckle pattern reduction (temporal and spatial averaging). Results of imaging inner retinal morphology and the improvement offered by the new UC Davis AOOCT system with spatio-temporal image averaging are presented.

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

    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.

  12. Spatio-angular Minimum-variance Tomographic Controller for Multi-Object Adaptive Optics systems

    Correia, Carlos M; Veran, Jean-Pierre; Andersen, David; Lardiere, Olivier; Bradley, Colin

    2015-01-01

    Multi-object astronomical adaptive-optics (MOAO) is now a mature wide-field observation mode to enlarge the adaptive-optics-corrected field in a few specific locations over tens of arc-minutes. The work-scope provided by open-loop tomography and pupil conjugation is amenable to a spatio-angular Linear-Quadratic Gaussian (SA-LQG) formulation aiming to provide enhanced correction across the field with improved performance over static reconstruction methods and less stringent computational complexity scaling laws. Starting from our previous work [1], we use stochastic time-progression models coupled to approximate sparse measurement operators to outline a suitable SA-LQG formulation capable of delivering near optimal correction. Under the spatio-angular framework the wave-fronts are never explicitly estimated in the volume,providing considerable computational savings on 10m-class telescopes and beyond. We find that for Raven, a 10m-class MOAO system with two science channels, the SA-LQG improves the limiting mag...

  13. Robotic Laser-Adaptive-Optics Imaging of 715 Kepler Exoplanet Candidates using Robo-AO

    Law, Nicholas M; Baranec, Christoph; Riddle, Reed; Ravichandran, Ganesh; Ziegler, Carl; Johnson, John Asher; Tendulkar, Shriharsh P; Bui, Khanh; Burse, Mahesh P; Das, H K; Dekany, Richard G; Kulkarni, Shrinivas; Punnadi, Sujit; Ramaprakash, A N

    2013-01-01

    The Robo-AO Kepler Planetary Candidate Survey is designed to observe every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper we present the results from the 2012 observing season, searching for stars close to 715 representative Kepler planet candidate hosts. We find 53 companions, 44 of which are new discoveries. We detail the Robo-AO survey data reduction methods including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for large adaptive optics surveys. Our survey is sensitive to objects from 0.15" to 2.5" separation, with contrast ratios up to delta-m~6. We measure an overall nearby-star-probability for Kepler planet candidates of 7.4% +/- 1.0%, and calculate the effects of each detected nearby star on the Kepler-measured plan...

  14. Adaptive Optics Parameters connection to wind speed at the Teide Observatory

    García-Lorenzo, B; Fuensalida, J J; Castro-Almazan, J

    2009-01-01

    Current projects for large telescopes demand a proper knowledge of atmospheric turbulence to design efficient adaptive optics systems in order to reach large Strehl ratios. However, the proper characterization of the turbulence above a particular site requires long-term monitoring. Due to the lack of long-term information on turbulence, high-altitude winds (in particular winds at the 200 mbar pressure level) were proposed as a parameter for estimating the total turbulence at a particular site, with the advantage of records of winds going back several decades. We present the first complete study of atmospheric adaptive optics parameters above the Teide Observatory (Canary Islands, Spain) in relation to wind speed. On-site measurements of CN2(h) profiles (more than 20200 turbulence profiles) from G-SCIDAR observations and wind vertical profiles from balloons have been used to calculate the seeing, the isoplanatic angle and the coherence time. The connection of these parameters to wind speeds at ground and 200 m...

  15. Gemini multi-conjugate adaptive optics system review II: Commissioning, operation and overall performance

    Neichel, Benoit; Vidal, Fabrice; van Dam, Marcos A; Garrel, Vincent; Carrasco, Eleazar Rodrigo; Pessev, Peter; Winge, Claudia; Boccas, Maxime; d'Orgeville, Céline; Arriagada, Gustavo; Serio, Andrew; Fesquet, Vincent; Rambold, William N; Lührs, Javier; Moreno, Cristian; Gausachs, Gaston; Galvez, Ramon L; Montes, Vanessa; Vucina, Tomislav B; Marin, Eduardo; Urrutia, Cristian; Lopez, Ariel; Diggs, Sarah J; Marchant, Claudio; Ebbers, Angelic W; Trujillo, Chadwick; Bec, Matthieu; Trancho, Gelys; McGregor, Peter; Young, Peter J; Colazo, Felipe; Edwards, Michelle L

    2014-01-01

    The Gemini Multi-conjugate Adaptive Optics System - GeMS, a facility instrument mounted on the Gemini South telescope, delivers a uniform, near diffraction limited images at near infrared wavelengths (0.95 microns- 2.5 microns) over a field of view of 120 arc seconds. GeMS is the first sodium layer based multi laser guide star adaptive optics system used in astronomy. It uses five laser guide stars distributed on a 60 arc seconds square constellation to measure for atmospheric distortions and two deformable mirrors to compensate for it. In this paper, the second devoted to describe the GeMS project, we present the commissioning, overall performance and operational scheme of GeMS. Performance of each sub-system is derived from the commissioning results. The typical image quality, expressed in full with half maximum, Strehl ratios and variations over the field delivered by the system are then described. A discussion of the main contributor to performance limitation is carried-out. Finally, overheads and future ...

  16. Interferometric adaptive optics for high-power laser pointing, wavefront control, and phasing

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

    2009-02-01

    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 μm 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 μrad. 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.

  17. Astrometric performance of the Gemini multi-conjugate adaptive optics system in crowded fields

    Neichel, Benoit; Rigaut, Francois; Ammons, S Mark; Carrasco, Eleazar R; Lassalle, Emmanuel

    2014-01-01

    The Gemini Multi-conjugate adaptive optics System (GeMS) is a facility instrument for the Gemini-South telescope. It delivers uniform, near-diffraction-limited image quality at near-infrared wavelengths over a 2 arcminute field of view. Together with the Gemini South Adaptive Optics Imager (GSAOI), a near-infrared wide field camera, GeMS/GSAOI's combination of high spatial resolution and a large field of view will make it a premier facility for precision astrometry. Potential astrometric science cases cover a broad range of topics including exo-planets, star formation, stellar evolution, star clusters, nearby galaxies, black holes and neutron stars, and the Galactic center. In this paper, we assess the astrometric performance and limitations of GeMS/GSAOI. In particular, we analyze deep, mono-epoch images, multi-epoch data and distortion calibration. We find that for single-epoch, un-dithered data, an astrometric error below 0.2 mas can be achieved for exposure times exceeding one minute, provided enough star...

  18. The Orion Fingers: Near-IR Adaptive Optics Imaging of an Explosive Protostellar Outflow

    Bally, John; Silvia, Devin; Youngblood, Allison

    2015-01-01

    Aims. Adaptive optics images are used to test the hypothesis that the explosive BN/KL outflow from the Orion OMC1 cloud core was powered by the dynamical decay of a non-hierarchical system of massive stars. Methods. Narrow-band H2, [Fe II], and broad-band Ks obtained with the Gemini South multi-conjugate adaptive optics (AO) system GeMS and near-infrared imager GSAOI are presented. The images reach resolutions of 0.08 to 0.10", close to the 0.07" diffraction limit of the 8-meter telescope at 2.12 microns. Comparison with previous AO-assisted observations of sub-fields and other ground-based observations enable measurements of proper motions and the investigation of morphological changes in H2 and [Fe II] features with unprecedented precision. The images are compared with numerical simulations of compact, high-density clumps moving ~1000 times their own diameter through a lower density medium at Mach 1000. Results. Several sub-arcsecond H2 features and many [Fe ii] 'fingertips' on the projected outskirts of th...

  19. Experimental demonstration of optical transport, sorting and self-arrangement using a “tractor beam"

    Brzobohatý, Oto; Karásek, Vítězslav; Šiler, Martin; Chvátal, Lukáš; Čižmár, T.; Zemánek, Pavel

    2013-01-01

    Roč. 7, č. 2 (2013), s. 123-127. ISSN 1749-4885 R&D Projects: GA ČR GA202/09/0348; GA ČR GPP205/11/P294; GA MŠk LH12018; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : theoretical determination * radiation force * tweezers * binding Subject RIV: BH - Optics, Masers, Laser s Impact factor: 29.958, year: 2013

  20. Demonstration of Passive W-Band Millimeter Wave Imaging Using Optical Upconversion Detection Methodology with Applications

    Samluk, Jesse P.; Schuetz, Christopher A.; Dillon, Thomas; Martin, Richard D.; Stein, E. Lee; Mackrides, Daniel G.; Wilson, John; Robbins, Andrew; Shi, Shouyuan; Chen, Caihua; Yao, Peng; Shireen, Rownak; Macario, Julien; Prather, Dennis W.

    2012-11-01

    Millimeter wave (mmW) imaging has enjoyed a measure of success due to the unique properties of imaging in this spectral region, some of which are still being discovered. For example, a key advantage of mmW imaging is the ability to penetrate through various atmospheric obscurants, including fog, dust, sand, and smoke, due to its longer wavelengths as compared to visible or infrared imaging. Various methods of imaging with mmW energy exist, such as direct detection, downconversion, and upconversion, where this manuscript focuses on the latter. Until now, passive imaging using an optical upconversion method was limited to Q-band frequencies due to the lack of commercially available parts, namely a sufficiently high frequency optical modulator. To overcome this limitation, a custom-built modulator using in-house fabrication facilities was realized to allow imaging within the W-band frequency range (75-110 GHz). Therefore, in this manuscript we report new results of passive imaging in the W-band frequency range using a unique optical upconversion technique, where the higher frequency operation allows for greater detail in the imagery thus collected.

  1. Gas concentration measurement by optical similitude absorption spectroscopy: methodology and experimental demonstration.

    Anselmo, Christophe; Welschinger, Jean-Yves; Cariou, Jean-Pierre; Miffre, Alain; Rairoux, Patrick

    2016-06-13

    We propose a new methodology to measure gas concentration by light-absorption spectroscopy when the light source spectrum is larger than the spectral width of one or several molecular gas absorption lines. We named it optical similitude absorption spectroscopy (OSAS), as the gas concentration is derived from a similitude between the light source and the target gas spectra. The main OSAS-novelty lies in the development of a robust inversion methodology, based on the Newton-Raphson algorithm, which allows retrieving the target gas concentration from spectrally-integrated differential light-absorption measurements. As a proof, OSAS is applied in laboratory to the 2ν3 methane absorption band at 1.66 µm with uncertainties revealed by the Allan variance. OSAS has also been applied to non-dispersive infra-red and the optical correlation spectroscopy arrangements. This all-optics gas concentration retrieval does not require the use of a gas calibration cell and opens new tracks to atmospheric gas pollution and greenhouse gases sources monitoring. PMID:27410280

  2. Adapt

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  3. Robo-AO KP: A new era in robotic adaptive optics

    Riddle, Reed L.; Baranec, Christoph; Law, Nicholas M.; Kulkarni, Shrinivas R.; Duev, Dmitry; Ziegler, Carl; Jensen-Clem, Rebecca M.; Atkinson, Dani Eleanor; Tanner, Angelle M.; Zhang, Celia; Ray, Amy

    2016-01-01

    Robo-AO is the first and only fully automated adaptive optics laser guide star AO instrument. It was developed as an instrument for 1-3m robotic telescopes, in order to take advantage of their availability to pursue large survey programs and target of opportunity observations that aren't possible with other AO systems. Robo-AO is currently the most efficient AO system in existence, and it can achieve an observation rate of 20+ science targets per hour. In more than three years of operations at Palomar Observatory, it has been quite successful, producing technology that is being adapted by other AO systems and robotic telescope projects, as well as several high impact scientific publications. Now, Robo-AO has been selected to take over operation of the Kitt Peak National Observatory 2.1m telescope. This will give Robo-AO KP the opportunity to pursue multiple science programs consisting of several thousand targets each during the three years it will be on the telescope. One-sixth of the observing time will be allocated to the US community through the NOAO TAC process. This presentation will discuss the process adapting Robo-AO to the KPNO 2.1m telescope, the plans for integration and initial operations, and the science operations and programs to be pursued.

  4. General demonstration of principal states of polarization and real-time monitoring of polarization mode dispersion in optical fibres

    Dong Hui; Wu Chong-Qing; Fu Song-Nian

    2004-01-01

    We investigated the general properties of polarization effects in optical fibres and demonstrated the existence of socalled principal states of polarization (PSP), which mean the fixed points in mathematics, in different polarization effects,such as birefringence and polarization mode dispersion, by using fixed point theory. Furthermore, a time evolution vector is defined to describe the time evolution of polarization state in optical fibres, which is used to investigate the time evolution of polarization mode dispersion vector (PDV), including differential group delay and PSP. The experimentalresults of real-time monitoring of PDV by using this method are reported. To our knowledge, this is the first report on monitoring PSP evolution in optical fibres.

  5. Demonstration of a novel optical code-division multiple-access system at 800 megachips per second.

    Vethanayagam, N; Macdonald, R I

    1991-07-01

    A novel optical code-division multiple-access system using Alberta codes and complementary correlation is demonstrated at 800 megachips per second. Completely passive optical multiplexing and demultiplexing is performed throughout the process. Complementary correlation permits code orthogonality because bipolar electrical signals are generated from unipolar optical ones. The correlator is implemented optoelectronically with an array of metal-semiconductor-metal photodiodes. We show that the bit-error-rate performance of the system is not degraded by interfering signals and that zero cross talk is nominally achieved. An unusual property of such systems is confirmed: The bit error rate on a channel can be reduced by the presence of an interfering channel if the two transmitters are not chip asynchronous. PMID:19776859

  6. Computational hydrodynamics and optical performance of inductively-coupled plasma adaptive lenses

    Mortazavi, M.; Urzay, J., E-mail: jurzay@stanford.edu; Mani, A. [Center for Turbulence Research, Stanford University, Stanford, California 94305-3024 (United States)

    2015-06-15

    This study addresses the optical performance of a plasma adaptive lens for aero-optical applications by using both axisymmetric and three-dimensional numerical simulations. Plasma adaptive lenses are based on the effects of free electrons on the phase velocity of incident light, which, in theory, can be used as a phase-conjugation mechanism. A closed cylindrical chamber filled with Argon plasma is used as a model lens into which a beam of light is launched. The plasma is sustained by applying a radio-frequency electric current through a coil that envelops the chamber. Four different operating conditions, ranging from low to high powers and induction frequencies, are employed in the simulations. The numerical simulations reveal complex hydrodynamic phenomena related to buoyant and electromagnetic laminar transport, which generate, respectively, large recirculating cells and wall-normal compression stresses in the form of local stagnation-point flows. In the axisymmetric simulations, the plasma motion is coupled with near-wall axial striations in the electron-density field, some of which propagate in the form of low-frequency traveling disturbances adjacent to vortical quadrupoles that are reminiscent of Taylor-Görtler flow structures in centrifugally unstable flows. Although the refractive-index fields obtained from axisymmetric simulations lead to smooth beam wavefronts, they are found to be unstable to azimuthal disturbances in three of the four three-dimensional cases considered. The azimuthal striations are optically detrimental, since they produce high-order angular aberrations that account for most of the beam wavefront error. A fourth case is computed at high input power and high induction frequency, which displays the best optical properties among all the three-dimensional simulations considered. In particular, the increase in induction frequency prevents local thermalization and leads to an axisymmetric distribution of electrons even after introduction of

  7. Computational hydrodynamics and optical performance of inductively-coupled plasma adaptive lenses

    This study addresses the optical performance of a plasma adaptive lens for aero-optical applications by using both axisymmetric and three-dimensional numerical simulations. Plasma adaptive lenses are based on the effects of free electrons on the phase velocity of incident light, which, in theory, can be used as a phase-conjugation mechanism. A closed cylindrical chamber filled with Argon plasma is used as a model lens into which a beam of light is launched. The plasma is sustained by applying a radio-frequency electric current through a coil that envelops the chamber. Four different operating conditions, ranging from low to high powers and induction frequencies, are employed in the simulations. The numerical simulations reveal complex hydrodynamic phenomena related to buoyant and electromagnetic laminar transport, which generate, respectively, large recirculating cells and wall-normal compression stresses in the form of local stagnation-point flows. In the axisymmetric simulations, the plasma motion is coupled with near-wall axial striations in the electron-density field, some of which propagate in the form of low-frequency traveling disturbances adjacent to vortical quadrupoles that are reminiscent of Taylor-Görtler flow structures in centrifugally unstable flows. Although the refractive-index fields obtained from axisymmetric simulations lead to smooth beam wavefronts, they are found to be unstable to azimuthal disturbances in three of the four three-dimensional cases considered. The azimuthal striations are optically detrimental, since they produce high-order angular aberrations that account for most of the beam wavefront error. A fourth case is computed at high input power and high induction frequency, which displays the best optical properties among all the three-dimensional simulations considered. In particular, the increase in induction frequency prevents local thermalization and leads to an axisymmetric distribution of electrons even after introduction of

  8. Computational hydrodynamics and optical performance of inductively-coupled plasma adaptive lenses

    Mortazavi, M.; Urzay, J.; Mani, A.

    2015-06-01

    This study addresses the optical performance of a plasma adaptive lens for aero-optical applications by using both axisymmetric and three-dimensional numerical simulations. Plasma adaptive lenses are based on the effects of free electrons on the phase velocity of incident light, which, in theory, can be used as a phase-conjugation mechanism. A closed cylindrical chamber filled with Argon plasma is used as a model lens into which a beam of light is launched. The plasma is sustained by applying a radio-frequency electric current through a coil that envelops the chamber. Four different operating conditions, ranging from low to high powers and induction frequencies, are employed in the simulations. The numerical simulations reveal complex hydrodynamic phenomena related to buoyant and electromagnetic laminar transport, which generate, respectively, large recirculating cells and wall-normal compression stresses in the form of local stagnation-point flows. In the axisymmetric simulations, the plasma motion is coupled with near-wall axial striations in the electron-density field, some of which propagate in the form of low-frequency traveling disturbances adjacent to vortical quadrupoles that are reminiscent of Taylor-Görtler flow structures in centrifugally unstable flows. Although the refractive-index fields obtained from axisymmetric simulations lead to smooth beam wavefronts, they are found to be unstable to azimuthal disturbances in three of the four three-dimensional cases considered. The azimuthal striations are optically detrimental, since they produce high-order angular aberrations that account for most of the beam wavefront error. A fourth case is computed at high input power and high induction frequency, which displays the best optical properties among all the three-dimensional simulations considered. In particular, the increase in induction frequency prevents local thermalization and leads to an axisymmetric distribution of electrons even after introduction of

  9. Optical solar energy adaptations and radiative temperature control of green leaves and tree barks

    Henrion, Wolfgang; Tributsch, Helmut [Department of Si-Photovoltaik and Solare Energetik, Hahn-Meitner-Institut Berlin, 14109 Berlin (Germany)

    2009-01-15

    Trees have adapted to keep leaves and barks cool in sunshine and can serve as interesting bionic model systems for radiative cooling. Silicon solar cells, on the other hand, loose up to one third of their energy efficiency due to heating in intensive sunshine. It is shown that green leaves minimize absorption of useful radiation and allow efficient infrared thermal emission. Since elevated temperatures are detrimental for tensile water flow in the Xylem tissue below barks, the optical properties of barks should also have evolved so as to avoid excessive heating. This was tested by performing optical studies with tree bark samples from representative trees. It was found that tree barks have optimized their reflection of incoming sunlight between 0.7 and 2 {mu}m. This is approximately the optical window in which solar light is transmitted and reflected by green vegetation. Simultaneously, the tree bark is highly absorbing and thus radiation emitting between 6 and 10 {mu}m. These two properties, mainly provided by tannins, create optimal conditions for radiative temperature control. In addition, tannins seem to have adopted a function as mediators for excitation energy towards photo-antioxidative activity for control of radiation damage. The results obtained are used to discuss challenges for future solar cell optimization. (author)

  10. A formal protocol test procedure for the Survivable Adaptable Fiber Optic Embedded Network (SAFENET)

    High, Wayne

    1993-03-01

    This thesis focuses upon a new method for verifying the correct operation of a complex, high speed fiber optic communication network. These networks are of growing importance to the military because of their increased connectivity, survivability, and reconfigurability. With the introduction and increased dependence on sophisticated software and protocols, it is essential that their operation be correct. Because of the speed and complexity of fiber optic networks being designed today, they are becoming increasingly difficult to test. Previously, testing was accomplished by application of conformance test methods which had little connection with an implementation's specification. The major goal of conformance testing is to ensure that the implementation of a profile is consistent with its specification. Formal specification is needed to ensure that the implementation performs its intended operations while exhibiting desirable behaviors. The new conformance test method presented is based upon the System of Communicating Machine model which uses a formal protocol specification to generate a test sequence. The major contribution of this thesis is the application of the System of Communicating Machine model to formal profile specifications of the Survivable Adaptable Fiber Optic Embedded Network (SAFENET) standard which results in the derivation of test sequences for a SAFENET profile. The results applying this new method to SAFENET's OSI and Lightweight profiles are presented.

  11. Handling complex adaptive optics concepts including the third and fourth dimensions

    Dima, Marco; Viotto, Valentina; Arcidiacono, Carmelo; Bergomi, Maria; Brunelli, Alessandro; Farinato, Jacopo; Gentile, Giorgia; Magrin, Demetrio; Ragazzoni, Roberto; Satta, Antonello

    2010-07-01

    Adaptive Optics (AO) concepts involve sometimes very complex behaviors of rays, waves and optical elements. Just think, to be convinced, the way multiple probes aim to correct for a large field of view Multi Conjugated AO, and to how these deploy onto a dynamic turbulent atmosphere. In order to explain the behavior of novel concepts we developed visualization techniques that involve the display of three dimensional images and the creation of movies to explain how the concept deals with an evolving situation, or, in other words, adding the fourth dimension of time. We produce solid models of the optical concepts we are developing, including the evolving temporal behavior of the turbulence, and these can be manipulated in a virtual manner in order to allow for the production of different means of visualization. These ranges from so called "static movies" where a three dimensional concept is just explored in three dimension by handling it around the observer, to the creation of three dimensional anaglyphs or anaglyphs movies. While the paper is mainly focused onto the ways these techniques are exploited in order to produce satisfactory results, the poster allow the visitor to experience some of these images and movies. The aim of this work is not only of a sort of high level didactical purpose, but we think it would be useful into scientific discussion and during meeting to develop engineering concepts of several AO concepts.

  12. LSPV+7, a branch-point-tolerant reconstructor for strong turbulence adaptive optics.

    Steinbock, Michael J; Hyde, Milo W; Schmidt, Jason D

    2014-06-20

    Optical wave propagation through long paths of extended turbulence presents unique challenges to adaptive optics (AO) systems. As scintillation and branch points develop in the beacon phase, challenges arise in accurately unwrapping the received wavefront and optimizing the reconstructed phase with respect to branch cut placement on a continuous facesheet deformable mirror. Several applications are currently restricted by these capability limits: laser communication, laser weapons, remote sensing, and ground-based astronomy. This paper presents a set of temporally evolving AO simulations comparing traditional least-squares reconstruction techniques to a complex-exponential reconstructor and several other reconstructors derived from the postprocessing congruence operation. The reconstructors' behavior in closed-loop operation is compared and discussed, providing several insights into the fundamental strengths and limitations of each reconstructor type. This research utilizes a self-referencing interferometer (SRI) as the high-order wavefront sensor, driving a traditional linear control law in conjunction with a cooperative point source beacon. The SRI model includes practical optical considerations and frame-by-frame fiber coupling effects to allow for realistic noise modeling. The "LSPV+7" reconstructor is shown to offer the best performance in terms of Strehl ratio and correction stability-outperforming the traditional least-squares reconstructed system by an average of 120% in the studied scenarios. Utilizing a continuous facesheet deformable mirror, these reconstructors offer significant AO performance improvements in strong turbulence applications without the need for segmented deformable mirrors. PMID:24979411

  13. Morphologies of High Redshift, Dust Obscured Galaxies from Keck Laser Guide Star Adaptive Optics

    Melbourne, J; Armus, Lee; Dey, Arjun; Brand, K; Thompson, D; Soifer, B T; Matthews, K; Jannuzi, B T; Houck, J R

    2008-01-01

    Spitzer MIPS images in the Bootes field of the NOAO Deep Wide-Field Survey have revealed a class of extremely dust obscured galaxy (DOG) at z~2. The DOGs are defined by very red optical to mid-IR (observed-frame) colors, R - [24 um] > 14 mag, i.e. f_v (24 um) / f_v (R) > 1000. They are Ultra-Luminous Infrared Galaxies with L_8-1000 um > 10^12 -10^14 L_sun, but typically have very faint optical (rest-frame UV) fluxes. We imaged three DOGs with the Keck Laser Guide Star Adaptive Optics (LGSAO) system, obtaining ~0.06'' resolution in the K'-band. One system was dominated by a point source, while the other two were clearly resolved. Of the resolved sources, one can be modeled as a exponential disk system. The other is consistent with a de Vaucouleurs profile typical of elliptical galaxies. The non-parametric measures of their concentration and asymmetry, show the DOGs to be both compact and smooth. The AO images rule out double nuclei with separations of greater than 0.1'' (< 1 kpc at z=2), making it unlikely ...

  14. High Redshift Dust Obscured Galaxies, A Morphology-SED Connection Revealed by Keck Adaptive Optics

    Melbourne, J; Brand, K; Desai, V; Armus, L; Dey, Arjun; Jannuzi, B T; Houck, J R; Matthews, K; Soifer, B T

    2009-01-01

    A simple optical to mid-IR color selection, R-[24] > 14, i.e. f_nu(24) / f_nu(R) > 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z~2 +/- 0.5. Extreme mid-IR luminosities (L_{IR} > 10^{12-14}) suggest that DOGs are powered by a combination of AGN and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest frame optical morphologies, we obtained high spatial resolution (0.05 -0.1") Keck Adaptive Optics (AO) K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including: small exponential disks (8 of 15), small ellipticals (4 of 15), and unresolved sources (2 of 15). One particularly diffuse source could not be classified because of low signal to noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral ene...

  15. MACAO-VLTI: An Adaptive Optics system for the ESO VLT interferometer

    Arsenault, Robin; Alonso, Jaime; Bonnet, Henri; Brynnel, Joar; Delabre, Bernard; Donaldson, Robert; Dupuy, Christophe; Fedrigo, Enrico; Farinato, Jacopo; Hubin, Norbert N.; Ivanescu, L.; Kasper, Markus E.; Paufique, J.; Rossi, S.; Tordo, Sebastien; Stroebele, Stefan; Lizon, Jean-Luis; Gigan, Pierre; Delplancke, Francoise; Silber, A.; Quattri, Marco; Reiss, Roland

    2003-02-01

    MACAO stands for Multi Application Curvature Adaptive Optics. A similar concept is applied to fulfill the need for wavefront correction for several VLT instruments. MACAO-VLTI is one of these built in 4 copies in order to equip the Coude focii of the ESO VLT's. The optical beams will then be corrected before interferometric recombination in the VLTI (Very Large Telescope Interferometer) laboratory. MACAO-VLTI uses a 60 elements bimorph mirror and curvature wavefront sensor. A custom made board processes the signals provided by the wavefront detectors, 60 Avalanche Photo-diodes, and transfer them to a commercial Power PC CPU board for Real Time Calculation. Mirrors Commands are sent to a High Voltage amplifier unit through an optical fiber link. The tip-tilt correction is done by a dedicated Tip-tilt mount holding the deformable mirror. The whole wavefront is located at the Coude focus. Software is developed in house and is ESO compatible. Expected performance is a Strehl ratio sligthly under 60% at 2.2 micron for bright reference sources (star V<10) and a limiting magnitude of 17.5 (Strehl ~0.1). The four systems will be installed in Paranal successively, the first one being planned for June 2003 and the last one for June 2004.

  16. Ultra-lightweight telescope with MEMS adaptive optic for distortion correction.

    Spahn, Olga Blum; Cowan, William D.; Shaw, Michael J.; Adams, David Price; Sweatt, William C.; Dagel, Daryl James; Grine, Alejandro J.; Mani, Seethambal S.; Resnick, Paul James; Gass, Fawn Renee; Grossetete, Grant David

    2004-12-01

    Recent world events have underscored the need for a satellite based persistent global surveillance capability. To be useful, the satellite must be able to continuously monitor objects the size of a person anywhere on the globe and do so at a low cost. One way to satisfy these requirements involves a constellation of satellites in low earth orbit capable of resolving a spot on the order of 20 cm. To reduce cost of deployment, such a system must be dramatically lighter than a traditional satellite surveillance system with a high spatial resolution. The key to meeting this requirement is a lightweight optics system with a deformable primary and secondary mirrors and an adaptive optic subsystem correction of wavefront distortion. This proposal is concerned with development of MEMS micromirrors for correction of aberrations in the primary mirror and improvement of image quality, thus reducing the optical requirements on the deployable mirrors. To meet this challenge, MEMS micromirrors must meet stringent criteria on their performance in terms of flatness, roughness and resolution of position. Using Sandia's SUMMIT foundry which provides the world's most sophisticated surface MEMS technology as well as novel designs optimized by finite element analysis will meet severe requirements on mirror travel range and accuracy.

  17. Implantable collamer lens and femtosecond laser for myopia: comparison using an adaptive optics visual simulator

    Cari Pérez-Vives

    2014-04-01

    Full Text Available Purpose: To compare optical and visual quality of implantable collamer lens (ICL implantation and femtosecond laser in situ keratomileusis (F-LASIK for myopia. Methods: The CRX1 adaptive optics visual simulator (Imagine Eyes, Orsay, France was used to simulate the wavefront aberration pattern after the two surgical procedures for -3-diopter (D and -6-D myopia. Visual acuity at different contrasts and contrast sensitivities at 10, 20, and 25 cycles/degree (cpd were measured for 3-mm and 5-mm pupils. The modulation transfer function (MTF and point spread function (PSF were calculated for 5-mm pupils. Results: F-LASIK MTF was worse than ICL MTF, which was close to diffraction-limited MTF. ICL cases showed less spread out of PSF than F-LASIK cases. ICL cases showed better visual acuity values than F-LASIK cases for all pupils, contrasts, and myopic treatments (p0.05. For -6-D myopia, however, statistically significant differences in contrast sensitivities were found for both pupils for all evaluated spatial frequencies (p<0.05. Contrast sensitivities were better after ICL implantation than after F-LASIK. Conclusions: ICL implantation and F-LASIK provide good optical and visual quality, although the former provides better outcomes of MTF, PSF, visual acuity, and contrast sensitivity, especially for cases with large refractive errors and pupil sizes. These outcomes are related to the F-LASIK producing larger high-order aberrations.

  18. KAPAO: a MEMS-based natural guide star adaptive optics system

    Severson, Scott A; Contreras, Daniel S; Gilbreth, Blaine N; Littleton, Erik; McGonigle, Lorcan P; Morrison, William A; Rudy, Alex R; Wong, Jonathan R; Xue, Andrew; Spjut, Erik; Baranec, Christoph; Riddle, Reed; 10.1117/12.2005959

    2013-01-01

    We describe KAPAO, our project to develop and deploy a low-cost, remote-access, natural guide star adaptive optics (AO) system for the Pomona College Table Mountain Observatory (TMO) 1-meter telescope. We use a commercially available 140-actuator BMC MEMS deformable mirror and a version of the Robo-AO control software developed by Caltech and IUCAA. We have structured our development around the rapid building and testing of a prototype system, KAPAO-Alpha, while simultaneously designing our more capable final system, KAPAO-Prime. The main differences between these systems are the prototype's reliance on off-the-shelf optics and a single visible-light science camera versus the final design's improved throughput and capabilities due to the use of custom optics and dual-band, visible and near-infrared imaging. In this paper, we present the instrument design and on-sky closed-loop testing of KAPAO-Alpha as well as our plans for KAPAO-Prime. The primarily undergraduate-education nature of our partner institutions,...

  19. Demonstration of Optical Phase-conjugation in Methyl Green Dye-doped Thin Film

    T. Geethakrishnan

    2005-01-01

    Full Text Available Optical Phase-Conjugation (OPC has been observed in Methyl Green (MG dye sensitized gelatin films in Degenerate Four-Wave Mixing (DFWM configuration at 633 nm radiation from a He-Ne laser of total power 35 mW. The mechanism of Phase-Conjugate (PC wave generation associated with this dye-doped system was discussed. The dependence of the PC wave generation on the incident angle between the forward-pump and the probe beams and time of evolution were also studied. A maximum phase-conjugate beam reflectivity of about 0.13% has been observed in this dye-doped gelatin films.

  20. Demonstration of a Rocket-Borne Fiber-Optic Measurement System: The FOVS Experiment of REXUS 15

    Rossner, M. R.; Benes, N.; Grubler, T.; Plamauer, S.; Koch, A. W.

    2015-09-01

    As an in-flight experiment in the REXUS 15 programme, the “Fiber-Optic Vibration Sensing Experiment (FOVS)” aimed at the application of so-called fiber Bragg grating sensors. Fiber Bragg gratings are optical gratings inscribed into the core of an optical fiber. They allow for entirely optical measurements of temperatures, mechanical strain and of deduced quantities, such as vibration. Due to their properties - mechanical robustness, high dynamic range etc. - fiber Bragg gratings are particularly suited for withstanding the harsh environmental conditions in a rocket vehicle (very high and very low temperatures, intense vibrations, presence of flammable propellants, etc.). Measurement systems based on fiber Bragg gratings have the potential to contribute to emerging technologies in the commercial launcher segment. Particularly, large sets of measurement data can be acquired with minor mass contribution. This can be applied to techniques such as structural health monitoring, active vibration damping, and actuator monitoring, enabling lighter structures without compromising on reliability. The FOVS experiment demonstrated a fiber-optic vibration and temperature measurement system in an actual flight, and evaluated its benefits compared to conventional electrical sensing in the challenging launcher environment. As a side product, measurements regarding the environmental conditions on the REXUS platform have been acquired.

  1. Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

    TÜRK, Ayşe Gözde; SABUNCU, Metin; ÜNAL, Sena; ÖNAL, Banu; ULUSOY, Mübin

    2016-01-01

    ABSTRACT Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light beam of OCT (Thorlabs), allowing measurement in 200 µm intervals. Restorations were cemented with a self-adhesive cement resin (SmartCem2, Dentsply), and then marginal adaptations were again measured with OCT. Mean values were statistically compared by using independent-samples t-test and paired samples t-test (pinlays presented statistically smaller marginal discrepancy values than indirect inlays, before (p=0.00001442) and after (p=0.00001466) cementation. Marginal discrepancy values were increased for all restorations after cementation (p=0.00008839, p=0.000000952 for direct and indirect inlays, respectively). The mean marginal discrepancy value of the direct group increased from 56.88±20.04 µm to 91.88±31.7 µm, whereas the indirect group increased from 107.54±35.63 µm to 170.29±54.83 µm. Different techniques are available to detect marginal adaptation of restorations, but the OCT system can give quantitative information about resin cement thickness and its interaction between tooth and restoration in a nondestructive manner. Conclusions Direct inlays presented smaller marginal discrepancy than indirect inlays. The marginal discrepancy values were increased for all restorations that refer to cement thickness after cementation. PMID:27556210

  2. Demonstration of a stand-alone cylindrical fiber coil for optical amplifiers

    Laxton, Steven R.; Bravo, Tyler; Madsen, Christi K.

    2015-08-01

    The design, fabrication and measurement of a cylindrical fiber coil structure is presented that has applications for compact fiber-optic amplifiers. A multimode fiber is used as a surrogate for a dual clad, rare-earth doped fiber for coil fabrication and optical testing. A ray trace algorithm, written in Python, was used to simulate the behavior of light travelling along the waveguide path. An in-house fabrication method was developed using 3D printed parts designed in SolidWorks and assembled with Arduino-controlled stepper motors for coil winding. Ultraviolet-cured epoxy was used to bind the coils into a rigid cylinder. Bend losses are introduced by the coil, and a measurement of the losses for two coil lengths was obtained experimentally. The measurements confirm that bend losses through a multimode fiber, representative of pump light propagating in a dual-clad rare-earth doped fiber, are relatively wavelength independent over a large spectral range and that higher order modes are extinguished quickly while lower order modes transmit through the windings with relatively low loss.

  3. High resolution adaptive optics imaging complements standard spectral domain optical coherent tomography in retinal diseases with micro-structural details: a case series

    Gibran Syed Khurshid; Sasha Strul; Adam Boretsky; Massoud Motamedi; Praveena Gupta

    2016-01-01

    Purpose: To evaluate if high resolution adaptive optics confocal scanning laser ophthalmoscopy (AO-SLO) can be used as an adjunct complementary diagnostic tool to spectral domain optical coherent tomography (SD-OCT) in characterizing three macular diseases: rod-cone dystrophy, acute retinal pigment epitheliitis (Krill’s disease), and occult macular dystrophy. Methods: As part of a complete clinical examination, each patient was subjected to color fundus pictures, multimodal imaging scans with...

  4. Experimental demonstration of broadband femtosecond optical parametric amplification based on YCOB crystal at near critical wavelength degeneracy

    Guo, Xiaoyang; Leng, Yuxin; Li, Yanyan; Li, Wenkai; Lu, Xiaoming; Xu, Yi; Li, Ruxin

    2016-07-01

    Broadband optical parametric amplification (OPA) in the near-infrared region (1.3-1.8 μm) is demonstrated in YCOB crystal pumped by 1 kHz Ti:sapphire based femtosecond laser at near critical wavelength degeneracy phase matching condition at first time. The gain bandwidth is closed to BIBO or BBO crystal OPA gain bandwidth. The energy obtained with 3.5 mm-thick YCOB reached 20 μJ with RMS 1.9%. After second harmonic generation, 17.6 fs pulse is obtained, and the pulse compressibility is demonstrated.

  5. Correction of distortion for optimal image stacking in Wide Field Adaptive Optics: Application to GeMS data

    Bernard, A; Neichel, B; Fusco, T; Bounissou, S; Samal, M; Andersen, M; Zavagno, A; Plana, H

    2016-01-01

    The advent of Wide Field Adaptive Optics (WFAO) systems marks the beginning of a new era in high spatial resolution imaging. The newly commissioned Gemini South Multi-Conjugate Adaptive Optics System (GeMS) combined with the infrared camera Gemini South Adaptive Optics Imager (GSAOI), delivers quasi diffraction-limited images over a field of 2 arc-minutes across. However, despite this excellent performance, some variable residues still limit the quality of the analyses. In particular, distortions severely affect GSAOI and become a critical issue for high-precision astrometry and photometry. In this paper, we investigate an optimal way to correct for the distortion following an inverse problem approach. Formalism as well as applications on GeMS data are presented.

  6. Monte-Carlo modelling of multi-conjugate adaptive optics performance on the European Extremely Large Telescope

    Basden, Alastair

    2015-01-01

    The performance of a wide-field adaptive optics system depends on input design parameters. Here we investigate the performance of a multi-conjugate adaptive optics system design for the European Extremely Large Telescope, using an end-to-end Monte-Carlo adaptive optics simulation tool, DASP. We consider parameters such as the number of laser guide stars, sodium layer depth, wavefront sensor pixel scale, number of deformable mirrors, mirror conjugation and actuator pitch. We provide potential areas where costs savings can be made, and investigate trade-offs between performance and cost. We conclude that a 6 laser guide star system using 3 DMs seems to be a sweet spot for performance and cost compromise.

  7. Demonstration of skull bones mobility using optical methods: practical importance in medicine

    Zakharov, Alexander V.; Okushko, Vladimir R.; Vturin, Sergey A.; Moseychuk, Vladimir V.; Petrov, Aleksey A.; Suetenkov, Dmitry E.

    2014-01-01

    Unprompted skull bones mobility not related to breathing, heart beating and other physiological reactions, using installation of original construction with control of physiological parameters by biofeedback hardware-software complex BOS-lab and BOS-pulse appliance (COMSIB, Novosibirsk, Russia) has been confirmed. Teeth eruption occurs through odontiasis canals, emerging from the funiculus. The main driving force for promoting a tooth into odontiasis canal during eruption is the unprompted skull bones mobility. A simple optical installation was made for the visualization of skull bones mobility during the investigation of the median palatine and incisors sutures. Early detection of failures of unprompted skull bones mobility and its normalization can lead to prevention of impact teeth, malocclusion, extrudocclusion and other anomalies and deformations of teeth, teeth rows, TMJ and skull. The skull bones mobility should be considered during the early preventive treatment and therapy of the consequences of injuries and malfunction of the maxillofacial area.

  8. A mechanical model of stereocilia that demonstrates a shift in the high-sensitivity region due to the interplay of a negative stiffness and an adaptation mechanism

    Stereocilia are the basic sensory units of nature's inertial sensors and are highly sensitive over broad dynamic ranges, which is a major challenge in the design of conventional engineering sensors. The high sensitivity that is maintained by stereocilia was hypothesized to exist due to a combination of adaptation and negative stiffness mechanisms, which shift the region of highest sensitivity toward the active operation range of the stereocilia bundle. To examine the adaptation hypothesis in terms of its potential applicability to future applications regarding the design of inertial sensors, we developed a mechanical mimicry of the interplay between negative stiffness and the adaptation of the stereocilia that produces spontaneous oscillation of the hair bundle. The mechanical model consists of an inverted pendulum and a fixed T-bar that mimic the interaction of two adjacent stereocilia. To focus on the interaction of one gating spring and the corresponding adaptation motor without the effect of coupling from the other gating springs attached to the neighboring stereocilia, we fixed one bar that contains the adaptation motor. To emulate the negative resistance of the tip-link due to the transient stiffness softening by the gating ion channel, a magnet pair was attached to the top of the inverted pendulum and the fixed T-bar. Readjustment of the tip-link tension by the ‘slipping down and climbing up’ motion of the adaptation molecular motors was demonstrated by the side-to-side movement of the magnet by a step motor. The negative stiffness region was observed near the equilibrium position and shifted with the activation of the adaptation motor. The temporal demonstration of the stiffness shift was measured as a spontaneous oscillation. The results showed that the interplay between the negative stiffness and the adaptation mechanism was mechanically produced by the combination of a repulsive force and its continuous readjustment and is better understood through a

  9. Experimental Demonstration of Multidimensional Switching Nodes for All-Optical Data Centre Networks

    Kamchevska, Valerija; Medhin, Ashenafi Kiros; Da Ros, Francesco; Ye, Feihong; Asif, Rameez; Fagertun, Anna Manolova; Ruepp, Sarah Renée; Berger, Michael Stübert; Dittmann, Lars; Morioka, Toshio; Oxenløwe, Leif Katsuo; Galili, Michael

    t We experimentally demonstrate network nodes that enable SDM/WDM/TDM switching. 1 Tbit/s/core error-free performance is achieved for connections with different granularities being switched between three network nodes interconnected with 7-core multicore fibres....

  10. On-sky results of the adaptive optics MACAO for the new IR-spectrograph CRIRES at VLT

    Paufique, J; Delabre, B; Donaldson, R; Esteves, R; Fedrigo, E; Gigan, P; Gojak, D; Hubin, N; Kasper, M; Kaeufl, U; Lizon, J L; Marchetti, E; Oberti, S; Pirard, J F; Pozna, E; Santos, J; Stroebele, S; Tordo, S; Lizon, JL.; Pirard, JF.

    2006-01-01

    The adaptive optics MACAO has been implemented in 6 focii of the VLT observatory, in three different flavors. We present in this paper the results obtained during the commissioning of the last of these units, MACAO-CRIRES. CRIRES is a high-resolution spectrograph, which efficiency will be improved by a factor two at least for point-sources observations with a NGS brighter than R=15. During the commissioning, Strehl exceeding 60% have been observed with fair seeing conditions, and a general description of the performance of this curvature adaptive optics system is done.

  11. WE-G-BRF-01: Adaptation to Intrafraction Tumor Deformation During Intensity-Modulated Radiotherapy: First Proof-Of-Principle Demonstration

    Purpose: Intrafraction tumor deformation limits targeting accuracy in radiotherapy and cannot be adapted to by current motion management techniques. This study simulated intrafractional treatment adaptation to tumor deformations using a dynamic Multi-Leaf Collimator (DMLC) tracking system during Intensity-modulated radiation therapy (IMRT) treatment for the first time. Methods: The DMLC tracking system was developed to adapt to the intrafraction tumor deformation by warping the planned beam aperture guided by the calculated deformation vector field (DVF) obtained from deformable image registration (DIR) at the time of treatment delivery. Seven single phantom deformation images up to 10.4 mm deformation and eight tumor system phantom deformation images up to 21.5 mm deformation were acquired and used in tracking simulation. The intrafraction adaptation was simulated at the DMLC tracking software platform, which was able to communicate with the image registration software, reshape the instantaneous IMRT field aperture and log the delivered MLC fields.The deformation adaptation accuracy was evaluated by a geometric target coverage metric defined as the sum of the area incorrectly outside and inside the reference aperture. The incremental deformations were arbitrarily determined to take place equally over the delivery interval. The geometric target coverage of delivery with deformation adaptation was compared against the delivery without adaptation. Results: Intrafraction deformation adaptation during dynamic IMRT plan delivery was simulated for single and system deformable phantoms. For the two particular delivery situations, over the treatment course, deformation adaptation improved the target coverage by 89% for single target deformation and 79% for tumor system deformation compared with no-tracking delivery. Conclusion: This work demonstrated the principle of real-time tumor deformation tracking using a DMLC. This is the first step towards the development of an

  12. WE-G-BRF-01: Adaptation to Intrafraction Tumor Deformation During Intensity-Modulated Radiotherapy: First Proof-Of-Principle Demonstration

    Ge, Y; OBrien, R; Shieh, C; Booth, J; Keall, P [Radiation Physics Laboratory, University of Sydney (Australia)

    2014-06-15

    Purpose: Intrafraction tumor deformation limits targeting accuracy in radiotherapy and cannot be adapted to by current motion management techniques. This study simulated intrafractional treatment adaptation to tumor deformations using a dynamic Multi-Leaf Collimator (DMLC) tracking system during Intensity-modulated radiation therapy (IMRT) treatment for the first time. Methods: The DMLC tracking system was developed to adapt to the intrafraction tumor deformation by warping the planned beam aperture guided by the calculated deformation vector field (DVF) obtained from deformable image registration (DIR) at the time of treatment delivery. Seven single phantom deformation images up to 10.4 mm deformation and eight tumor system phantom deformation images up to 21.5 mm deformation were acquired and used in tracking simulation. The intrafraction adaptation was simulated at the DMLC tracking software platform, which was able to communicate with the image registration software, reshape the instantaneous IMRT field aperture and log the delivered MLC fields.The deformation adaptation accuracy was evaluated by a geometric target coverage metric defined as the sum of the area incorrectly outside and inside the reference aperture. The incremental deformations were arbitrarily determined to take place equally over the delivery interval. The geometric target coverage of delivery with deformation adaptation was compared against the delivery without adaptation. Results: Intrafraction deformation adaptation during dynamic IMRT plan delivery was simulated for single and system deformable phantoms. For the two particular delivery situations, over the treatment course, deformation adaptation improved the target coverage by 89% for single target deformation and 79% for tumor system deformation compared with no-tracking delivery. Conclusion: This work demonstrated the principle of real-time tumor deformation tracking using a DMLC. This is the first step towards the development of an

  13. ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

    Gavel, Donald; Dillon, Daren; Norton, Andrew; Ratliff, Chris; Cabak, Jerry; Phillips, Andrew; Rockosi, Connie; McGurk, Rosalie; Srinath, Srikar; Peck, Michael; Deich, William; Lanclos, Kyle; Gates, John; Saylor, Michael; Ward, Jim; Pfister, Terry

    2014-01-01

    A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3-meter telescope in California. This system uses a high return efficiency sodium beacon and a combination of low and high-order deformable mirrors to achieve diffraction-limited imaging over a wide spectrum of infrared science wavelengths covering 0.8 to 2.2 microns. We present the design performance goals and the first on-sky test results. We discuss several innovations that make this system a pathfinder for next generation AO systems. These include a unique woofer-tweeter control that provides full dynamic range correction from tip/tilt to 16 cycles, variable pupil sampling wavefront sensor, new enhanced silver coatings developed at UC Observatories that improve science and LGS throughput, and tight mechanical rigidity that enables a multi-hour diffraction- limited exposure in LGS mode for faint object spectroscopy science.

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

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

    2016-02-01

    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. PMID:26906850

  15. A novel high precision adaptive equalizer in digital coherent optical receivers

    Ma, Xiurong; Xu, Yujun; Wang, Xiao; Ding, Zhaocai

    2015-10-01

    A novel high precision adaptive equalization method is introduced and applied to dynamic equalization for quadrature phase shift keying (QPSK) coherent optical communication system in this paper. A frequency-domain constant modulus algorithm (CMA) method is used to equalize the received signal roughly. Then, some non-ideal output signals will be picked out through the error measurement, and they will be equalized accurately further in a fixed time-domain CMA equalizer. This high precision equalization method can decrease the equalization error, then it can reduce the bit error ratio (BER) of coherent communication system. Simulation results show that there is a 6% decrease for computation complexity by proposed scheme when compared with time-domain CMA. Furthermore, compared with time-domain CMA and frequency-domain CMA, about 2 dB and 2.2 dB in OSNR improvement can be obtained by proposed scheme at the BER value of 1e-3, respectively.

  16. A Status Report on the Thirty Meter Telescope Adaptive Optics Program

    B. L. Ellerbroek

    2013-06-01

    We provide an update on the recent development of the adaptive optics (AO) systems for the Thirty Meter Telescope (TMT) since mid-2011. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) architecture will provide uniform, diffraction-limited performance in the J, H and K bands over 17–30 arcsec diameter fields with 50 per cent sky coverage at the galactic pole, as is required to support TMT science cases. The NFIRAOS and LGSF subsystems completed successful preliminary and conceptual design reviews, respectively, in the latter part of 2011. We also report on progress in AO component prototyping, control algorithm development, and system performance analysis, and conclude with an outline of some possible future AO systems for TMT.

  17. Optical Digital Imitation Painting Design Based on Self-Adaptive Image Feature

    Zhu Liyan

    2016-01-01

    Full Text Available Based on the study of existing digital imitation camouflage technology, we propose a kind of optical digital imitation camouflage design algorithm which is based on the characteristic of self-adaptive image. Picking main color feature of the background by using K-means clustering algorithm, counting the shape characteristics of each main color spots by separating layers, we generated digital camouflage pattern automatically by segmenting the background region characteristics and fill the background color image according to the statistics expected value. The simulation results show that, the digital camouflage generated automatically is blend well with the background .It keeps the background color and shape features, so has good camouflage effect. This algorithm can also provide the basic algorithm foundation for digital deformation camouflage.

  18. Real-Time Wavefront Control for the PALM-3000 High Order Adaptive Optics System

    Truong, Tuan N.; Bouchez, Antonin H.; Dekany, Richard G.; Guiwits, Stephen R.; Roberts, Jennifer E.; Troy, Mitchell

    2008-01-01

    We present a cost-effective scalable real-time wavefront control architecture based on off-the-shelf graphics processing units hosted in an ultra-low latency, high-bandwidth interconnect PC cluster environment composed of modules written in the component-oriented language of nesC. The architecture enables full-matrix reconstruction of the wavefront at up to 2 KHz with latency under 250 us for the PALM-3000 adaptive optics systems, a state-of-the-art upgrade on the 5.1 meter Hale Telescope that consists of a 64 x 64 subaperture Shack-Hartmann wavefront sensor and a 3368 active actuator high order deformable mirror in series with a 241 active actuator tweeter DM. The architecture can easily scale up to support much larger AO systems at higher rates and lower latency.

  19. Simulation of a ground-layer adaptive optics system for the Kunlun Dark Universe Survey Telescope

    Peng Jia; Sijiong Zhang

    2013-01-01

    Ground Layer Adaptive Optics (GLAO) is a recently developed technique extensively applied to ground-based telescopes,which mainly compensates for the wavefront errors induced by ground-layer turbulence to get an appropriate point spread function in a wide field of view.The compensation results mainly depend on the turbulence distribution.The atmospheric turbulence at Dome A in the Antarctic is mainly distributed below 15 meters,which is an ideal site for applications of GLAO.The GLAO system has been simulated for the Kunlun Dark Universe Survey Telescope,which will be set up at Dome A,and uses a rotating mirror to generate several laser guide stars and a wavefront sensor with a wide field of view to sequentially measure the wavefronts from different laser guide stars.The system is simulated on a computer and parameters of the system are given,which provide detailed information about the design of a practical GLAO system.

  20. Adaptive optics retinal imaging reveals S-cone dystrophy in tritan color-vision deficiency

    Baraas, Rigmor C.; Carroll, Joseph; Gunther, Karen L.; Chung, Mina; Williams, David R.; Foster, David H.; Neitz, Maureen

    2007-05-01

    Tritan color-vision deficiency is an autosomal dominant disorder associated with mutations in the short-wavelength-sensitive- (S-) cone-pigment gene. An unexplained feature of the disorder is that individuals with the same mutation manifest different degrees of deficiency. To date, it has not been possible to examine whether any loss of S-cone function is accompanied by physical disruption in the cone mosaic. Two related tritan subjects with the same novel mutation in their S-cone-opsin gene, but different degrees of deficiency, were examined. Adaptive optics was used to obtain high-resolution retinal images, which revealed distinctly different S-cone mosaics consistent with their discrepant phenotypes. In addition, a significant disruption in the regularity of the overall cone mosaic was observed in the subject completely lacking S-cone function. These results taken together with other recent findings from molecular genetics indicate that, with rare exceptions, tritan deficiency is progressive in nature.

  1. A Tilt-correction Adaptive Optical System for the Solar Telescope of Nanjing University

    Chang-Hui Rao; Xiu-Fa Gao; Tian Mi; Wen-Han Jiang; Cheng Fang; Ning Ling; Wei-Chao Zhou; Ming-De Ding; Xue-Jun Zhang; Dong-Hong Chen; Mei Li

    2003-01-01

    A tilt-correction adaptive optical system installed on the 430 mm Solar Telescope of Nanjing University has been put in operation. It consists of a tip-tilt mirror, a correlation tracker and an imaging CCD camera. An absolute difference algorithm is used for detecting image motion in the correlation tracker. The sampling frequency of the system is 419 Hz. We give a description of the system's configuration, an analysis of its performance and a report of our observational results. A residual jitter of 0.14 arcsec has been achieved. The error rejection bandwidth of the system can be adjusted in the range 5-28 Hz according to the beacon size and the strength of atmospheric turbulence.

  2. Fast-adaptive fiber-optic sensor for ultra-small vibration and deformation measurement

    Adaptive fiber-optic interferometer measuring system based on a dynamic hologram recorded in photorefractive CdTe crystal without applying an external electric field is developed. Vectorial mixing of two waves with different polarizations in the anisotropic diffraction geometry allows for the realization of linear regime of phase demodulation at the diffusion hologram. High sensitivity of the interferometer is achieved due to recording of the hologram in reflection geometry at high spatial frequencies in a crystal with sufficient concentration of photorefractive centers. The sensitivity obtained makes possible a broadband detection of ultra-small vibrations with amplitude of less then 0.1 nm. High cut-off frequency of the interferometer achieved using low-power light sources due to fast response of CdTe crystal allows one to eliminate temperature fluctuations and other industrial noises

  3. MACAO-VLTI first light: adaptive optics at the service of interferometry

    Arsenault, R.; Alonso, J.; Bonnet, H.; Brynnel, J.; Delabre, B.; Donaldson, R.; Dupuy, C.; Fedrigo, E.; Spyromilio, J.; Erm, T.; Farinato, J.; Hubin, N.; Ivanescu, L.; Kasper, M.; Oberti, S.; Paufique, J.; Rossi, S.; Tordo, S.; Stroebele, S.; Lizon, J.-L.; Gigan, P.; Pouplard, F.; Delplancke, F.; Silber, A.; Quattri, M.; Reiss, R.

    2003-06-01

    The AO department of ESO has completed the design of an adaptive AO system for the VLT Interferometer. Ordering of components, manufacturing and integration took place in 2001 and 2002. The system is built in four copies, one for each VLT. It is installed at the Coudé room and the Coudé train is used as a 'science path'. Only one of the mirrors (M8, pupil conjugated) is replaced by the corrective optics. The 60 elements system should allow a Strehl ratio of ~0.6 on bright sources. Commissioning activities started in April 2003 and the delivery of the 4th system is planned for late 2004. At the time of this writing the first commissioning of the first MACAO has been completed and results are encouraging. The integration and test phase of the 2nd system is in full swing.

  4. Performance Testing of an Off-Limb Solar Adaptive Optics System

    Taylor, G E; Marino, J; Rimmele, T R; McAteer, R T J

    2015-01-01

    Long-exposure spectro-polarimetry in the near-infrared is a preferred method to measure the magnetic field and other physical properties of solar prominences. In the past, it has been very difficult to observe prominences in this way with sufficient spatial resolution to fully understand their dynamical properties. Solar prominences contain highly transient structures, visible only at small spatial scales; hence they must be observed at sub-arcsecond resolution, with a high temporal cadence. An adaptive optics (AO) system capable of directly locking-on to prominence structure away from the solar limb has the potential to allow for diffraction-limited spectro-polarimetry of solar prominences. In this paper, the performance of the off-limb AO system and its expected performance, at the desired science wavelength {\\CaII} 8542A, are shown.

  5. Capacity achieving nonbinary LDPC coded non-uniform shaping modulation for adaptive optical communications.

    Lin, Changyu; Zou, Ding; Liu, Tao; Djordjevic, Ivan B

    2016-08-01

    A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the same SNR values. The matched nonbinary (NB) LDPC code is used for this scheme, which further improves the coding gain and the overall performance. We analyze both coding performance and system SNR performance. We show that the proposed NB LDPC-coded 9-QAM has more than 2dB gain in symbol SNR compared to traditional LDPC-coded star-8-QAM. On the other hand, the proposed NB LDPC-coded 5-QAM and 7-QAM have even better performance than LDPC-coded QPSK. PMID:27505775

  6. On-sky performance during verification and commissioning of the Gemini Planet Imager's adaptive optics system

    Poyneer, Lisa A; Macintosh, Bruce; Palmer, David W; Perrin, Marshall D; Sadakuni, Naru; Savransky, Dmitry; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey K; Dillon, Daren; Gavel, Donald; Goodsell, Stephen J; Hartung, Markus; Hibon, Pascale; Rantakyro, Fredrik T; Thomas, Sandrine; Veran, Jean-Pierre

    2014-01-01

    The Gemini Planet Imager instrument's adaptive optics (AO) subsystem was designed specifically to facilitate high-contrast imaging. It features several new technologies, including computationally efficient wavefront reconstruction with the Fourier transform, modal gain optimization every 8 seconds, and the spatially filtered wavefront sensor. It also uses a Linear-Quadratic-Gaussian (LQG) controller (aka Kalman filter) for both pointing and focus. We present on-sky performance results from verification and commissioning runs from December 2013 through May 2014. The efficient reconstruction and modal gain optimization are working as designed. The LQG controllers effectively notch out vibrations. The spatial filter can remove aliases, but we typically use it oversized by about 60% due to stability problems.

  7. Experimental Demonstration of Frequency Autolocking an Optical Cavity Using a Time-Varying Kalman Filter

    Schütte, Dirk; Hassen, S. Z. Sayed; Karvinen, Kai S.; Boyson, Toby K.; Kallapur, Abhijit G.; Song, Hongbin; Petersen, Ian R.; Huntington, Elanor H.; Heurs, Michèle

    2016-01-01

    We propose and demonstrate a new autolocking scheme using a three-mirror ring cavity consisting of a linear quadratic regulator and a time-varying Kalman filter. Our technique does not require a frequency scan to acquire resonance. We utilize the singular perturbation method to simplify our system dynamics and to permit the application of linear control techniques. The error signal combined with the transmitted power is used to estimate the cavity detuning. This estimate is used by a linear time-varying Kalman filter which enables the implementation of an optimal controller. The experimental results validate the controller design, and we demonstrate improved robustness to disturbances and a faster locking time than a traditional proportional-integral controller. More important, the time-varying Kalman filtering approach automatically reacquires lock for large detunings, where the error signal leaves its linear capture range, a feat which linear time-invariant controllers cannot achieve.

  8. Multi-laser-guided adaptive optics for the Large Binocular Telescope

    Lloyd-Hart, M.; Angel, R.; Green, R.; Stalcup, T.; Milton, N. M.; Powell, K.

    2007-09-01

    We describe the conceptual design of an advanced laser guide star facility (LGSF) for the Large Binocular Telescope (LBT), to be built in collaboration with the LBT's international partners. The highest priority goal for the facility is the correction of ground-layer turbulence, providing partial seeing compensation in the near IR bands over a 4' field. In the H band, GLAO is projected to improve the median seeing from 0.55" to 0.2". The new facility will build on the LBT's natural guide star AO system, integrated into the telescope with correction by adaptive secondary mirrors, and will draw on Arizona's experience in the construction of the first multi-laser adaptive optics (AO) system at the 6.5 m MMT. The LGSF will use four Rayleigh beacons at 532 nm, projected to an altitude of 25 km, on each of the two 8.4 m component telescopes. Initial use of the system for ground layer correction will deliver image quality well matched to the LBT's two LUCIFER near IR instruments. They will be used for direct imaging over a 4'×4' field and will offer a unique capability in high resolution multi-object spectroscopy. The LGSF is designed to include long-term upgrade paths. Coherent imaging at the combined focus of the two apertures will be exploited by the LBT Interferometer in the thermal IR. Using the same launch optics, an axial sodium or Rayleigh beacon can be added to each constellation, for tomographic wavefront reconstruction and diffraction limited imaging over the usual isoplanatic patch. In the longer term, a second DM conjugated to high altitude is foreseen for the LBT's LINC-NIRVANA instrument, which would extend the coherent diffraction-limited field to an arcminute in diameter with multi-conjugate AO.

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

    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. PMID:14503692

  10. Robotic laser adaptive optics imaging of 715 Kepler exoplanet candidates using Robo-AO

    The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper, we present the results from the 2012 observing season, searching for stars close to 715 Kepler planet candidate hosts. We find 53 companions, 43 of which are new discoveries. We detail the Robo-AO survey data reduction methods including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for large adaptive optics surveys. Our survey is sensitive to objects from ≈0.''15 to 2.''5 separation, with magnitude differences up to Δm ≈ 6. We measure an overall nearby-star probability for Kepler planet candidates of 7.4% ± 1.0%, and calculate the effects of each detected nearby star on the Kepler-measured planetary radius. We discuss several Kepler Objects of Interest (KOIs) of particular interest, including KOI-191 and KOI-1151, which are both multi-planet systems with detected stellar companions whose unusual planetary system architecture might be best explained if they are 'coincident multiple' systems, with several transiting planets shared between the two stars. Finally, we find 98% confidence evidence that short-period giant planets are two to three times more likely than longer-period planets to be found in wide stellar binaries.

  11. The optical microscopy with virtual image breaks a record: 50-nm resolution imaging is demonstrated

    Wang, Zengbo; Li, Lin; Liu, Zhu; Luk'yanchuk, Boris; Chen, Zaichun; Hong, Minghui

    2010-01-01

    We demonstrate a new 'microsphere nanoscope' that uses ordinary SiO2 microspheres as superlenses to create a virtual image of the object in near field. The magnified virtual image greatly overcomes the diffraction limit. We are able to resolve clearly 50-nm objects under a standard white light source in both transmission and reflection modes. The resolution achieved for white light opens a new opportunity to image viruses, DNA and molecules in real time.

  12. Experimental demonstration of elastic optical networks based on enhanced software defined networking (eSDN) for data center application.

    Zhang, Jie; Yang, Hui; Zhao, Yongli; Ji, Yuefeng; Li, Hui; Lin, Yi; Li, Gang; Han, Jianrui; Lee, Young; Ma, Teng

    2013-11-01

    Due to the high burstiness and high-bandwidth characteristics of the applications, data center interconnection by elastic optical networks have attracted much attention of network operators and service providers. Many data center applications require lower delay and higher availability with the end-to-end guaranteed quality of service. In this paper, we propose and implement a novel elastic optical network based on enhanced software defined networking (eSDN) architecture for data center application, by introducing a transport-aware cross stratum optimization (TA-CSO) strategy. eSDN can enable cross stratum optimization of application and elastic optical network stratum resources and provide the elastic physical layer parameter adjustment, e.g., modulation format and bandwidth. We have designed and verified experimentally software defined path provisioning on our testbed with four real OpenFlow-enabled elastic optical nodes for data center application. The overall feasibility and efficiency of the proposed architecture is also experimentally demonstrated and compared with individual CSO and physical layer adjustment strategies in terms of path setup/release/adjustment latency, blocking probability and resource occupation rate. PMID:24216922

  13. Large Binocular Telescope Interferometer Adaptive Optics: On-sky performance and lessons learned

    Bailey, Vanessa P; Puglisi, Alfio T; Esposito, Simone; Vaitheeswaran, Vidhya; Skemer, Andrew J; Defrere, Denis; Vaz, Amali; Leisenring, Jarron M

    2014-01-01

    The Large Binocular Telescope Interferometer is a high contrast imager and interferometer that sits at the combined bent Gregorian focus of the LBT's dual 8.4~m apertures. The interferometric science drivers dictate 0.1'' resolution with $10^3-10^4$ contrast at $10~\\mu m$, while the $4~\\mu m$ imaging science drivers require even greater contrasts, but at scales $>$0.2''. In imaging mode, LBTI's Adaptive Optics system is already delivering $4~\\mu m$ contrast of $10^4-10^5$ at $0.3''-0.75''$ in good conditions. Even in poor seeing, it can deliver up to 90\\% Strehl Ratio at this wavelength. However, the performance could be further improved by mitigating Non-Common Path Aberrations. Any NCPA remedy must be feasible using only the current hardware: the science camera, the wavefront sensor, and the adaptive secondary mirror. In preliminary testing, we have implemented an ``eye doctor'' grid search approach for astigmatism and trefoil, achieving 5\\% improvement in Strehl Ratio at $4~\\mu m$, with future plans to tes...

  14. MagAO: Status and on-sky performance of the Magellan adaptive optics system

    Morzinski, Katie M; Males, Jared R; Kopon, Derek; Hinz, Phil M; Esposito, Simone; Riccardi, Armando; Puglisi, Alfio; Pinna, Enrico; Briguglio, Runa; Xompero, Marco; Quirós-Pacheco, Fernando; Bailey, Vanessa; Follette, Katherine B; Rodigas, T J; Wu, Ya-Lin; Arcidiacono, Carmelo; Argomedo, Javier; Busoni, Lorenzo; Hare, Tyson; Uomoto, Alan; Weinberger, Alycia

    2014-01-01

    MagAO is the new adaptive optics system with visible-light and infrared science cameras, located on the 6.5-m Magellan "Clay" telescope at Las Campanas Observatory, Chile. The instrument locks on natural guide stars (NGS) from 0$^\\mathrm{th}$ to 16$^\\mathrm{th}$ $R$-band magnitude, measures turbulence with a modulating pyramid wavefront sensor binnable from 28x28 to 7x7 subapertures, and uses a 585-actuator adaptive secondary mirror (ASM) to provide flat wavefronts to the two science cameras. MagAO is a mutated clone of the similar AO systems at the Large Binocular Telescope (LBT) at Mt. Graham, Arizona. The high-level AO loop controls up to 378 modes and operates at frame rates up to 1000 Hz. The instrument has two science cameras: VisAO operating from 0.5-1 $\\mu$m and Clio2 operating from 1-5 $\\mu$m. MagAO was installed in 2012 and successfully completed two commissioning runs in 2012-2013. In April 2014 we had our first science run that was open to the general Magellan community. Observers from Arizona, Ca...

  15. Optical Communication System for Remote Monitoring and Adaptive Control of Distributed Ground Sensors Exhibiting Collective Intelligence

    Cameron, S.M.; Stantz, K.M.; Trahan, M.W.; Wagner, J.S.

    1998-11-01

    Comprehensive management of the battle-space has created new requirements in information management, communication, and interoperability as they effect surveillance and situational awareness. The objective of this proposal is to expand intelligent controls theory to produce a uniquely powerful implementation of distributed ground-based measurement incorporating both local collective behavior, and interoperative global optimization for sensor fusion and mission oversight. By using a layered hierarchal control architecture to orchestrate adaptive reconfiguration of autonomous robotic agents, we can improve overall robustness and functionality in dynamic tactical environments without information bottlenecks. In this concept, each sensor is equipped with a miniaturized optical reflectance modulator which is interactively monitored as a remote transponder using a covert laser communication protocol from a remote mothership or operative. Robot data-sharing at the ground level can be leveraged with global evaluation criteria, including terrain overlays and remote imaging data. Information sharing and distributed intelli- gence opens up a new class of remote-sensing applications in which small single-function autono- mous observers at the local level can collectively optimize and measure large scale ground-level signals. AS the need for coverage and the number of agents grows to improve spatial resolution, cooperative behavior orchestrated by a global situational awareness umbrella will be an essential ingredient to offset increasing bandwidth requirements within the net. A system of the type described in this proposal will be capable of sensitively detecting, tracking, and mapping spatial distributions of measurement signatures which are non-stationary or obscured by clutter and inter- fering obstacles by virtue of adaptive reconfiguration. This methodology could be used, for example, to field an adaptive ground-penetrating radar for detection of underground structures in

  16. Develop techniques for ion implantation of PLZT [lead-lanthanum-zirconate-titanate] for adaptive optics

    Research was conducted at Pacific Northwest Laboratory to develop high photosensitivity adaptive optical elements utilizing ion implanted lanthanum-doped lead-zirconate-titanate (PLZT). One centimeter square samples were prepared by implanting ferroelectric and anti-ferroelectric PLZT with a variety of species or combinations of species. These included Ne, O, Ni, Ne/Cr, Ne/Al, Ne/Ni, Ne/O, and Ni/O, at a variety of energies and fluences. An indium-tin oxide (ITO) electrode coating was designed to give a balance of high conductivity and optical transmission at near uv to near ir wavelengths. Samples were characterized for photosensitivity; implanted layer thickness, index of refraction, and density; electrode (ITO) conductivity; and in some cases, residual stress curvature. Thin film anti-ferroelectric PLZT was deposited in a preliminary experiment. The structure was amorphous with x-ray diffraction showing the beginnings of a structure at substrate temperatures of approximately 5500C. This report summarizes the research and provides a sampling of the data taken during the report period

  17. Marginal adaptation analysis performed with en face optical coherence tomography in fixed partial dentures

    Sinescu, Cosmin; Negrutiu, Meda Lavinia; Antonie, Sergiu; Dobre, George; Bradu, Adrian; Hughes, Michael; Rominu, Mihai; Podoleanu, Adrian Gh.

    2009-02-01

    Frameworks for fixed partial denture made out of dental alloys thought classic techniques currently involve many errors like marginal and internal gaps. The aim of this study is to present alternative technologies in making frameworks from dental alloys using selective laser sintering/ selective laser melting (SLS/ SLM) and to investigate the marginal adaptation of the fixed dental prostheses using the en face optical coherence tomography. These procedures imply the use of a scanning device PROBIS, SMART OPTICS with the help of 3D Dental Scanner software. For digitizing the 3D model we used the Dental Wings Kunde Software. The files obtained were sent to a SLS/ SLM machine, Hint-Els rapidPro, where the CoCr powder was sintered/melt by selectively consolidating successive layers of powder material on top of each other, using thermal energy supplied by a focused and computer controlled laser beam. Through this technique can be produced up to 80 pieces in only one step. A parallel between the classic casting technique and this new technology reveal the least has several advantages: fast finishing time, excellent marginal and internal fit, biocompatibility and superior chemical properties. SLS/ SLM proved to be a promising technology that may overcome the classic ones, because of the superior marginal fit of the fixed dental prostheses to the teeth.

  18. Intelligent correction of laser beam propagation through turbulent media using adaptive optics

    Ko, Jonathan; Wu, Chensheng; Davis, Christopher C.

    2014-10-01

    Adaptive optics methods have long been used by researchers in the astronomy field to retrieve correct images of celestial bodies. The approach is to use a deformable mirror combined with Shack-Hartmann sensors to correct the slightly distorted image when it propagates through the earth's atmospheric boundary layer, which can be viewed as adding relatively weak distortion in the last stage of propagation. However, the same strategy can't be easily applied to correct images propagating along a horizontal deep turbulence path. In fact, when turbulence levels becomes very strong (Cn 2>10-13 m-2/3), limited improvements have been made in correcting the heavily distorted images. We propose a method that reconstructs the light field that reaches the camera, which then provides information for controlling a deformable mirror. An intelligent algorithm is applied that provides significant improvement in correcting images. In our work, the light field reconstruction has been achieved with a newly designed modified plenoptic camera. As a result, by actively intervening with the coherent illumination beam, or by giving it various specific pre-distortions, a better (less turbulence affected) image can be obtained. This strategy can also be expanded to much more general applications such as correcting laser propagation through random media and can also help to improve designs in free space optical communication systems.

  19. First-order design of off-axis reflective ophthalmic adaptive optics systems using afocal telescopes

    Gómez-Vieyra, Armando; Dubra, Alfredo; Williams, David R.; Malacara-Hernández, Daniel

    2009-09-01

    Scanning laser ophthalmoscopes (SLOs) and optical coherence tomographs are the state-of-the-art retinal imaging instruments, and are essential for early and reliable diagnosis of eye disease. Recently, with the incorporation of adaptive optics (AO), these instruments have started to deliver near diffraction-limited performance in both humans and animal models, enabling the resolution of the retinal ganglion cell bodies, their processes, the cone photoreceptor and the retinal pigment epithelial cells mosaics. Unfortunately, these novel instruments have not delivered consistent performance across human subjects and animal models. One of the limitations of current instruments is the astigmatism in the pupil and imaging planes, which degrades image quality, by preventing the wavefront sensor from measuring aberrations with high spatial content. This astigmatism is introduced by the sequence of off-axis reflective elements, typically spherical mirrors, used for relaying pupil and imaging planes. Expressions for minimal astigmatism on the image and pupil planes in off-axis reflective afocal telescopes formed by pairs of spherical mirrors are presented. The formulas, derived from the marginal ray fans equation, are valid for small angles of incidence (systems. An example related to this last application is discussed.

  20. The Last Gasps of VY Canis Majoris Aperture Synthesis and Adaptive Optics Imagery

    Monnier, J D; López, B; Cruzalebes, P; Danchi, W C; Haniff, C A

    1999-01-01

    We present new observations of the red supergiant VY CMa at 1.25 micron, 1.65 micron, 2.26 micron, 3.08 micron and 4.8 micron. Two complementary observational techniques were utilized: non-redundant aperture masking on the 10-m Keck-I telescope yielding images of the innermost regions at unprecedented resolution, and adaptive optics imaging on the ESO 3.6-m telescope at La Silla attaining extremely high (~10^5) peak-to-noise dynamic range over a wide field. For the first time the inner dust shell has been resolved in the near-infrared to reveal a one-sided extension of circumstellar emission within 0.1" (~15 R_star) of the star. The line-of-sight optical depths of the circumstellar dust shell at 1.65 micron, 2.26 micron, and 3.08 micron have been estimated to be 1.86 +/- 0.42, 0.85 +/- 0.20, and 0.44 +/- 0.11. These new results allow the bolometric luminosity of VY~CMa to be estimated independent of the dust shell geometry, yielding L_star ~ 2x10^5 L_sun. A variety of dust condensations, including a large sca...