Showing papers on "Adaptive optics published in 2009"
TL;DR: Using analysis of the image-formation process, an optimized correction scheme permitting image-quality improvement with minimal additional exposure of the sample is developed and it is shown that this correction process induces little photobleaching and significantly improves the quality of images of biological samples.
Abstract: We demonstrate wavefront sensorless aberration correction in a two-photon excited fluorescence microscope. Using analysis of the image-formation process, we have developed an optimized correction scheme permitting image-quality improvement with minimal additional exposure of the sample. We show that, as a result, our correction process induces little photobleaching and significantly improves the quality of images of biological samples. In particular, increased visibility of small structures is demonstrated. Finally, we illustrate the use of this technique on various fresh and fixed biological tissues.
343 citations
TL;DR: Results obtained with the first optical vectorial vortex coronagraph (OVVC) in the laboratory 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-sensitivity to low-order wavefront aberrations.
Abstract: 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 1.4×10^(-2) and a residual light level of 3×10^(-5) at an angular separation of 3.5 λ/d (at which point our current noise floor is reached) have been obtained at a wavelength of 1.55 μm. 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-sensitivity to low-order wavefront aberrations.
194 citations
TL;DR: Astrophotonics, a field that has already created new photonic capabilities, is now extending its reach down to the Rayleigh scattering limit at ultraviolet wavelengths, and out to mid infrared wavelengths beyond 2500 nm.
Abstract: Astrophotonics lies at the interface of astronomy and photonics. This burgeoning field has emerged over the past decade in response to the increasing demands of astronomical instrumentation. Early successes include: (i) planar waveguides to combine signals from widely spaced telescopes in stellar interferometry; (ii) frequency combs for ultra-high precision spectroscopy to detect planets around nearby stars; (iii) ultra-broadband fibre Bragg gratings to suppress unwanted background; (iv) photonic lanterns that allow single-mode behaviour within a multimode fibre; (v) planar waveguides to miniaturize astronomical spectrographs; (vi) large mode area fibres to generate artificial stars in the upper atmosphere for adaptive optics correction; (vii) liquid crystal polymers in optical vortex coronographs and adaptive optics systems. Astrophotonics, a field that has already created new photonic capabilities, is now extending its reach down to the Rayleigh scattering limit at ultraviolet wavelengths, and out to mid infrared wavelengths beyond 2500nm.
149 citations
TL;DR: In this paper, a coherent fiber array system composed of densely packed fiber collimators with built-in capabilities for adaptive wavefront phase piston and tilt control at each collimator is discussed.
Abstract: We discuss development and integration of a coherent fiber array system composed of densely packed fiber collimators with built-in capabilities for adaptive wavefront phase piston and tilt control at each fiber collimator. In this system, multi-channel fiber-integrated phase shifters are used for phase locking of seven fiber collimators and the precompensation of laboratory-generated turbulence-induced phase aberrations. Controllable x and y displacements of the fiber tips in the fiber collimator array provide additional adaptive compensation of the tip and tilt phase aberration components. An additional control system is utilized for equalization of the intensity of each of the fiber collimator beams. All three control systems are based on the stochastic parallel gradient descent optimization technique. The paper presents the first experimental results of adaptive dynamic phase distortion compensation with an adaptive phase-locked fiber collimator array system.
132 citations
TL;DR: In this paper, the authors used the Keck laser guide star AO system and the OSIRIS integral field unit spectrograph to resolve kinematic and morphological detail in a sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ~100 pc.
Abstract: We present spatially-resolved dynamics for six strongly lensed star-forming galaxies at z=1.7-3.1, each enlarged by a linear magnification factor ~8. Using the Keck laser guide star AO system and the OSIRIS integral field unit spectrograph we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ~100 pc. With one exception our sources have diameters ranging from 1-7 kpc, star formation rates of 2-40 Msun/yr (uncorrected for extinction) and dynamical masses of 10^(9.7-10.3) Msun. With this exquisite resolution we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disk model, which can only be recovered with the considerably improved spatial resolution and sampling from the combination of adaptive optics and strong gravitational lensing. Our model fits imply ratios for the systemic to random motion, V sin(i)/sigma, ranging from 0.5-1.3 and Toomre disk parameters Q<1. The large fraction of well-ordered velocity fields in our sample is consistent with data analyzed for larger, more luminous sources at this redshift. Our high resolution data further reveal that all six galaxies contain multiple giant star-forming HII regions whose resolved diameters are in the range 300 pc - 1.0 kpc, consistent with the Jeans length expected in the case of dispersion support. The density of star formation in these regions is ~100 times higher than observed in local spirals; such high values are only seen in the most luminous local starbursts. The global dynamics and demographics of star formation in these HII regions suggest that vigorous star formation is primarily governed by gravitational instability in primitive rotating disks.
123 citations
TL;DR: The introduction of both positive and negative spherical aberration using adaptive optics technology significantly shifted and expanded the subject's overall depth of focus; simulating coma or trefoil did not produce such effects.
Abstract: Purpose To evaluate the impact of higher-order aberrations on depth of focus using an adaptive optics visual simulator. Setting Refractive Surgery Department, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Methods An adaptive optics simulator was used to optically introduce individual aberrations in eyes of subjects with a 6.0 mm pupil under cycloplegia (coma and trefoil, magnitudes ±0.3 μm; spherical aberration, magnitudes ±0.3, ±0.6, ±0.9 μm). A through-focus response curve was assessed by recording the percentage of Sloan letters at a fixed size identified at various target distances. The subject's ocular depth of focus and center of focus were computed as the half-maximum width and the midpoint of the through-focus response curve. Results The dominant eyes of 10 subjects were evaluated. The simulation of positive or negative spherical aberration had the effect of enhancing depth of focus and resulted in linearly shifting of the center of focus by 2.6 diopters (D)/μm of error. This increase in depth of focus reached a maximum of approximately 2.0 D with 0.6 μm of spherical aberration and became smaller when the aberration was increased to 0.9 μm. Trefoil and coma appeared to neither shift the center of focus nor significantly modify the depth of focus. Conclusion The introduction of both positive and negative spherical aberration using adaptive optics technology significantly shifted and expanded the subject's overall depth of focus; simulating coma or trefoil did not produce such effects.
114 citations
TL;DR: The compact optical design of a high-resolution 3D scanning microscope with adaptive optics capability for refocusing with no moving parts designed for clinical research and can find applications in biomedical imaging, white light interferometry for surface roughness measurements, and other 3D imaging systems.
Abstract: We report on the compact optical design of a high-resolution 3D scanning microscope with adaptive optics capability for refocusing with no moving parts designed for clinical research. The optical aberrations arising from refocusing are compensated for as part of the multiconfiguration optical design process. The lateral scanning is provided by a scanning mirror, and the depth scan is provided by an adaptive liquid lens embedded within the microscope as an integrated component of a custom optical design. The microscope achieves a performance of 250 lp/mm—a tenfold increase in performance over a liquid lens used as a stand-alone optical element. Results show that the optical design provides invariant modular transfer function over a 2 mm×2 mm×2 mm imaging volume, fully compensating (i.e., diffraction limited) for dynamic aberrations contributed by the scanning, the variation in the shape of the liquid lens, and the change in spherical aberration with depth in a slab of average index of refraction of skin. This design can find applications in biomedical imaging, white light interferometry for surface roughness measurements, and other 3D imaging systems.
104 citations
TL;DR: Novel visualization methods that simplify AO-OCT data viewing are presented, and include co-registration of AO+OCT volumes with fundus photography and stitching of multiple AO/OCT sub-volumes to create a large field of view (FOV) high-resolution volume.
Abstract: Ultrahigh-resolution adaptive optics-optical coherence tomography (UHR-AO-OCT) instrumentation allowing monochromatic and chromatic aberration correction was used for volumetric in vivo retinal imaging of various retinal structures including the macula and optic nerve head (ONH). Novel visualization methods that simplify AO-OCT data viewing are presented, and include co-registration of AO-OCT volumes with fundus photography and stitching of multiple AO-OCT sub-volumes to create a large field of view (FOV) high-resolution volume. Additionally, we explored the utility of Interactive Science Publishing by linking all presented AO-OCT datasets with the OSA ISP software.
99 citations
TL;DR: Open-loop deformable mirror telemetry from Altair and Keck adaptive optics is used to determine whether atmospheric turbulence follows the frozen flow hypothesis, indicating that the atmosphere is stable enough for predictive control to measure and adapt to prevailing atmospheric conditions before they change.
Abstract: We use closed-loop deformable mirror telemetry from Altair and Keck adaptive optics (AO) to determine whether atmospheric turbulence follows the frozen flow hypothesis. Using telemetry from AO systems, our algorithms (based on the predictive Fourier control framework) detect frozen flow >94% of the time. Usually one to three layers are detected. Between 20% and 40% of the total controllable phase power is due to frozen flow. Velocity vector RMS variability is less than 0.5 m/s (per axis) on 10-s intervals, indicating that the atmosphere is stable enough for predictive control to measure and adapt to prevailing atmospheric conditions before they change.
99 citations
TL;DR: In this paper, a liquid-liquid interface with a pinned contact line as a variable refractive surface was used to achieve high optical performance, and the measured wavefront error suggests that the method of pinning the contact line to a precise shape is an important factor in achieving higher optical performance.
Abstract: A liquid lens structure with a step response time of 2 ms, a refractive power range of 52 D, and a root-mean-square (rms) wavefront error of 80.3 nm is reported. This lens uses a liquid-liquid interface with a pinned contact line as a variable refractive surface, and its shape is controlled by a piezostack actuator via a built-in hydraulic amplifier. The measured wavefront error suggests that the method of pinning the contact line to a precise shape is an important factor in achieving higher optical performance.
94 citations
TL;DR: The use of wavefront coding for the mitigation of optical aberrations in a thermal imaging system with a simple singlet which enables an approximate halving in length and mass of the optical system compared to an equivalent two-element lens.
Abstract: We describe the use of wavefront coding for the mitigation of optical aberrations in a thermal imaging system. Diffraction-limited imaging is demonstrated with a simple singlet which enables an approximate halving in length and mass of the optical system compared to an equivalent two-element lens.
TL;DR: In this article, the authors describe the results from a new instrument which combines Lucky Imaging and adaptive optics (AO) to give the first routine direct diffraction-limited imaging in the visible on a 5 m telescope.
Abstract: We describe the results from a new instrument which combines Lucky Imaging and adaptive optics (AO) to give the first routine direct diffraction-limited imaging in the visible on a 5 m telescope. With fast image selection and alignment behind the Palomar AO system we obtained Strehl ratios of 5%-20% at 700 nm in a typical range of seeing conditions, with a median Strehl of approximately 12% when 10% of the input frames are selected. At wavelengths around 700 nm the system gave diffraction-limited 35 mas full width at half-maxima (FWHMs). At 950 nm the output Strehl ratio was as high as 36% and at 500 nm the FWHM resolution was as small as 42 mas, with a low Strehl ratio but with resolution improved by a factor of ~20 compared to the prevailing seeing. To obtain wider fields we also used multiple Lucky Imaging guide stars in a configuration similar to a ground layer AO system. With eight guide stars but very undersampled data we obtained 300 mas resolution across a 30" × 30" field of view in the i' band.
TL;DR: In this article, an optical configuration for target-in-the-loop single-mode fiber amplifier coherent combining through turbulence is presented, with a lambda/15 residual phase error, and theoretical analysis demonstrate that detection subsystem aperture reduction is paramount to lower sensitivity to backward turbulence when using a detector in the laser emitter plane.
Abstract: We report experimental results and theoretical analysis of coherent beam combining with active phase control fiber beam shaping. An original optical configuration for target-in-the-loop single-mode fiber amplifier coherent combining through turbulence is presented, with a lambda/15 residual phase error. The experimental results and theoretical analysis demonstrate that detection subsystem aperture reduction is paramount to lower sensitivity to backward turbulence when using a detector in the laser emitter plane. In this configuration, coherent combining is achieved on a remote scattering surface with sole compensation of the onward turbulence. We also present a numerical model capable of assessing the combining efficiency in the case of high-power multimode large-mode-area (LMA) fiber amplifiers. Preliminary theoretical investigations point out that multiple-transverse-mode combining can result in severe wavefront distortion. In the case of multimode LMA fibers, control of the transverse modes phase relationship has to be achieved to preserve combining efficiency.
Book•
28 May 2009
TL;DR: A brief history of optical telescope systems can be found in this article, where the authors present a detailed overview of the fundamental requirements for optical mirror design and support mechanisms for optical mirrors.
Abstract: Table of Contents.- Dedication.- Contributing Authors.- Preface of English edition.- Preface of Chinese edition.- Acknowledgments.- Fundamentals of Optical Telescopes.- A brief history of optical telescopes.- General astronomical requirements.- Angular resolution.- Light collecting power.- Field-of-view and combined efficiency.- Atmospheric windows and site selection.- Fundamentals of astronomical optics.- Optical systems for astronomical telescopes.- Aberrations and their calculations.- Formulas of telescope aberrations.- Field corrector design.- Ray tracing, spot diagram, and merit function.- Modern optical theory.- Optical transfer function.- Wave aberrations and modulation transfer function.- Wavefront error and the Strehl ratio.- Image spatial frequency.- Image property of a segmented mirror system.- References.- Mirror Design of Optical Telescopes.- Specifications for optical mirror design.- Fundamental requirements for optical mirrors.- Mirror surface error and support systems.- Surface error fitting and slope error expression.- Lightweight primary mirror design.- Significance of lightweight mirrors for telescopes.- Thin mirror design.- Honeycomb mirror design.- Multi-mirror telescopes.- Segmented mirror telescopes.- Metal and lightweight mirrors.- Mirror polishing and mirror supporting.- Material properties of optical mirrors.- Optical mirror polishing.- Vacuum coating.- Mirror support mechanisms.- Mirror seeing and stray light control.- Mirror seeing effect.- Stray light control.- References.- Telescope Structures and Control System.- Telescope mounting.- Equatorial mounting.- Altitude-azimuth mounting.- Stewart platform mounting telescope.- Fixed mirror or fixed altitude mountings.- Telescope tube and other structure design.- Specifications for telescope tube design.- Telescope tube design.- Support vane design for secondary mirror.- Telescope bearing design.- Structural static analysis.- Telescope drive and control.- Specifications of telescope drive system.- Trends in drive system design.- Encoder systems for telescopes.- Pointing error corrections.- Servo control and distributed intelligence.- Star guiding.- Structural dynamic analysis.- Wind and earthquake spectrums.- Dynamic simulation of telescope structures.- Combined structural and control simulation.- Structural vibration control.- Telescope foundation design.- References.- Advanced Techniques for Optical Telescopes.- Active and adaptive optics.- Basic principles of active and adaptive optics.- Wavefront sensors.- Actuators, deformable mirrors, phase correctors, and metrology system.- Active optical system and phasing sensors.- Curvature sensors and tip-tilt devices.- Atmosphere disturbance and adaptive optics compensation.- Artificial laser guide star and adaptive optics.- Atmosphere tomography and multi-conjugate adaptive optics.- Adaptive secondary mirror design.- Optical interferometers.- Speckle interferometer technique.- Michelson interferometer.- Fizeau interferometry.- Intensity interferometry.- Amplitude interferometer.- References.- Space Telescopes and Their Development.- Orbit environmental conditions.- Orbit definition.- Orbit thermal conditions.- Other orbit conditions.- Attitude control of space telescopes.- Attitude sensors.- Attitude actuators.- Space telescope projects.- Hubble Space Telescope.- James Webb Space Telescope.- Space Interferometry Mission and other space programs.- References.- Fundamentals of Radio Telescopes.- Brief history of radio telescopes.- Scientific requirements for radio telescopes.- Atmospheric radio windows and site selection.- Parameters of radio antennas.- Radiation pattern.- Antenna gain.- Antenna temperature and noise temperature.- Antenna efficiency.- Polarization properties.- Optical arrangement of radio antennas.- Characteristics of offset antennas.- Radio telescope receivers.- References.- Radio Telescope Design.- Antenna tolerance and homologous design.- Transmission loss of electromagnetic waves.- Ante
TL;DR: Submicron resolution images are now routinely recorded from depths over 1mm into tissue, and active compensation for sample-induced aberrations is possible by using optical devices originally developed for astronomy, whose optical properties can be changed in real time.
TL;DR: This work compares the performance of a Femtolasers Integral Ti:Sapphire laser and a Superlum BroadLighter T840 using the same AO-OCT system and the same subject, and investigates the capability of the instrument equipped with the Integral to capture volume images of the fovea and adjacent regions on a second subject using the AO to control focus in the retina.
Abstract: Ultrabroadband sources, such as multiplexed superluminescent diodes (SLDs) and femtosecond lasers, have been successfully employed in adaptive optics optical coherence tomography (AO-OCT) systems for ultrahigh resolution retinal imaging. The large cost differential of these sources, however, motivates the need for a performance comparison. Here, we compare the performance of a Femtolasers Integral Ti:Sapphire laser and a Superlum BroadLighter T840, using the same AO-OCT system and the same subject. In addition, we investigate the capability of our instrument equipped with the Integral to capture volume images of the fovea and adjacent regions on a second subject using the AO to control focus in the retina and custom and freeware image registration software to reduce eye motion artifacts. Monochromatic ocular aberrations were corrected with a woofer-tweeter AO system. Coherence lengths of the Integral and BroadLighter were measured in vivo at 3.2 μm and 3.3 μm, respectively. The difference in dynamic range was 5 dB, close to the expected variability of the experiment. Individual cone photoreceptors, retinal capillaries and nerve fiber bundles were distinguished in all three dimensions with both sources. The acquired retinal volumes are provided for viewing in OSA ISP, allowing the reader to data mine at the microscope level.
TL;DR: Analysis of the performance of these four imaging modalities applied in normal and pathologic eyes focusing on motion artifact free volumetric retinal imaging and revealing novel, complementary morphological information due to enhanced resolution, speed and penetration is presented.
Abstract: Recent substantial developments in light source and detector technology have initiated a paradigm shift in retinal optical coherence tomography (OCT) performance. Broad bandwidth light sources in the 800 nm and 1060 nm wavelength region enable axial OCT resolutions of 2-3 mum and 5-7 mum, respectively. Novel high speed silicon based CMOS cameras at 800 nm and InGaAs based CCD cameras in combination with frequency domain OCT technology enable data acquisition speeds of up to 47,000 A-scans/s at 1060 nm and up to 312,500 A-scans/s at 800 nm. Combining ultrahigh axial resolution, ultrahigh speed OCT at 800 nm with pancorrected adaptive optics allows volumetric in vivo cellular resolution retinal imaging. Commercially available three-dimensional (3D) retinal OCT at 800 nm (20,000 A-scans/s, 6 mum axial resolution) is compared to ultrahigh speed 3D retinal imaging at 800 nm (160,000 A-scans/s, 2-3 mum axial resolution), high speed 3D choroidal imaging at 1060 nm (47,000 Ascan/ second, 6-7 mum axial resolution) and cellular resolution retinal imaging at 800 nm using adaptive optics OCT at 160,000 A-scans/second with isotropic resolution of ~2 mum. Analysis of the performance of these four imaging modalities applied in normal and pathologic eyes focusing on motion artifact free volumetric retinal imaging and revealing novel, complementary morphological information due to enhanced resolution, speed and penetration is presented.
TL;DR: In this article, the authors proposed a low-order wavefront sensor (CLOWFS) which produces a defocused image of a reflective focal plane ring to measure loworder aberrations.
Abstract: High-contrast coronagraphic imaging of the immediate surrounding of stars requires exquisite control of low-order wave-front aberrations, such as tip-tilt (pointing) and focus. We propose an accurate, efficient, and easy to implement technique to measure such aberrations in coronagraphs which use a focal plane mask to block starlight. The coronagraphic low-order wave-front sensor (CLOWFS) produces a defocused image of a reflective focal plane ring to measure low-order aberrations. Even for small levels of wave-front aberration, the proposed scheme produces large intensity signals which can easily be measured, and therefore does not require highly accurate calibration of either the detector or optical elements. The CLOWFS achieves nearly optimal sensitivity and is immune from noncommon path errors. This technique is especially well suited for high-performance low inner working angle coronagraphs. On phase-induced amplitude apodization (PIAA)-type coronagraphs, it can unambiguously recover aberrations which originate from either side of the beam shaping introduced by the PIAA optics. We show that the proposed CLOWFS can measure sub-milliarcsecond telescope pointing errors several orders of magnitude faster than would be possible in the coronagraphic science focal plane alone, and can also accurately calibrate residual coronagraphic leaks due to residual low-order aberrations. We have demonstrated 10–3λ/D pointing stability in a laboratory demonstration of the CLOWFS on a PIAA-type coronagraph.
TL;DR: In this paper, the authors derived the spectra of the scattered light from the circumstellar disk around HD-142527 and detected an H2O ice absorption feature in the spectrum.
Abstract: Coronagraphic imaging for the Herbig Ae star, HD 142527, was performed using the Coronagraphic Imager with Adaptive Optics (CIAO) on the 8.2 m Subaru Telescope. The images were obtained in the H2O ice filter (λ = 3.08 μm) using adaptive optics (AO), and in the L' band without AO. Combining these data with previous observational results in the H and K bands, we derived the spectra of the scattered light from the circumstellar disk around HD 142527 and detected an H2O ice absorption feature in the spectra. This result can be explained by the presence of silicate and H2O ice grains of ~1 μm in size, according to the prediction model by Inoue et al. This grain size is consistent with previous observational study by Fukagawa et al. and Fujiwara et al. The present result demonstrates that high-resolution imaging of disk-scattered light in the ice band is useful for detecting H2O ice grain distributions in circumstellar disks.
TL;DR: Different reconstruction algorithms and their fundamental limitations are explored, conducting this analysis in the Fourier domain, and some examples of different WFAO systems and their expected performance on a 42 m telescope case are shown.
Abstract: Several wide-field-of-view adaptive optics (WFAO) concepts such as multi-conjugate AO (MCAO), multi-object AO (MOAO), and ground-layer AO (GLAO) are currently being studied for the next generation of Extremely Large Telescopes (ELTs). All these concepts will use atmospheric tomography to reconstruct the turbulent-phase volume. In this paper, we explore different reconstruction algorithms and their fundamental limitations, conducting this analysis in the Fourier domain. This approach allows us to derive simple analytical formulations for the different configurations and brings a comprehensive view of WFAO limitations. We then investigate model and statistical errors and their effect on the phase reconstruction. Finally, we show some examples of different WFAO systems and their expected performance on a 42 m telescope case.
Journal Article•
TL;DR: In this paper, the capability of ultra-high-resolution optical coherence tomography with adaptive optics (UHR-AO-OCT) for imaging the RNFL axonal bundles (RNFBs) with 3×3×3μm(3) resolution in the eye was evaluated.
Abstract: Early detection of axonal tissue loss in retinal nerve fiber layer (RNFL) is critical for effective treatment and management of diseases such as glaucoma. This study aims to evaluate the capability of ultrahigh-resolution optical coherence tomography with adaptive optics (UHR-AO-OCT) for imaging the RNFL axonal bundles (RNFBs) with 3×3×3μm(3) resolution in the eye. We used a research-grade UHR-AO-OCT system to acquire 3°×3° volumes in four normal subjects and one subject with an arcuate retinal nerve fiber layer defect (n=5; 29-62years). Cross section (B-scans) and en face (C-scan) slices extracted from the volumes were used to assess visibility and size distribution of individual RNFBs. In one subject, we reimaged the same RNFBs twice over a 7month interval and compared bundle width and thickness between the two imaging sessions. Lastly we compared images of an arcuate RNFL defect acquired with UHR-AO-OCT and commercial OCT (Heidelberg Spectralis). Individual RNFBs were distinguishable in all subjects at 3° retinal eccentricity in both cross-sectional and en face views (width: 30-50μm, thickness: 10-15μm). At 6° retinal eccentricity, RNFBs were distinguishable in three of the five subjects in both views (width: 30-45μm, thickness: 20-40μm). Width and thickness RNFB measurements taken 7months apart were strongly correlated (p<0.0005). Mean difference and standard deviation of the differences between the two measurement sessions were -0.1±4.0μm (width) and 0.3±1.5μm (thickness). UHR-AO-OCT outperformed commercial OCT in terms of clarity of the microscopic retina. To our knowledge, these are the first measurements of RNFB cross section reported in the living human eye.
TL;DR: Adaptive optics is implemented in a harmonic generation microscope using a wavefront sensorless correction scheme and images of live mouse embryos show an improved signal level and resolution.
Abstract: Adaptive optics is implemented in a harmonic generation microscope using a wavefront sensorless correction scheme. Both the second- and third-harmonic intensity signals are used as the optimization metric. Aberration correction is performed to compensate both system- and specimen-induced aberrations by using an efficient optimization routine based upon Zernike polynomial modes. Images of live mouse embryos show an improved signal level and resolution.
TL;DR: Adaptive optics (AO) is a technology used in ground-based astronomy to correct for the wavefront aberrations and loss of image quality caused by atmospheric turbulence.
Abstract: Adaptive optics (AO) is a technology used in ground-based astronomy to correct for the wavefront aberrations and loss of image quality caused by atmospheric turbulence. Provided some difficult technical problems can be overcome, AO will enable future astronomers to achieve nearly diffraction-limited performance with the extremely large telescopes that are currently under development, thereby greatly improving spatial resolution, spectral resolution and observing efficiency which will be achieved. The goal of this topical review is to present to the inverse problems community a representative sample of these problems. In this review, we first present a tutorial overview of the mathematical models and techniques used in current AO systems. We then examine in detail the following topics: laser guidestar adaptive optics, multi-conjugate and multi-object adaptive optics, high-contrast imaging and deformable mirror modeling and parameter identification.
Journal Article•
TL;DR: SD-OCT and AO detected abnormalities that correlate topographically with visual field loss from hydroxychloroquine toxicity as demonstrated by HVF 10-2 and may be useful in the detection of subclinical abnormalities that precede symptoms or objectiveVisual field loss.
Abstract: Purpose:
To describe spectral-domain optical coherence tomography (SD-OCT) and adaptive optics (AO) imaging in hydroxychloroquine retinal toxicity.
TL;DR: These formulae which are derived from the marginal ray fan equation can be used for designing laser cavities, spectrographs and adaptive optics retinal imaging systems, but are limited by spherical aberration and coma for small and large angles respectively.
Abstract: Expressions for minimal astigmatism in image and pupil planes in off-axis afocal reflective telescopes formed by pairs of spherical mirrors are presented. These formulae which are derived from the marginal ray fan equation can be used for designing laser cavities, spectrographs and adaptive optics retinal imaging systems. The use, range and validity of these formulae are limited by spherical aberration and coma for small and large angles respectively. This is discussed using examples from adaptive optics retinal imaging systems. The performance of the resulting optical designs are evaluated and compared against the configurations with minimal wavefront RMS, using the defocus-corrected wavefront RMS as a metric.
TL;DR: In this article, the authors investigate the limits of ground-based differential astrometry with adaptive optics using the core of the Galactic globular cluster M5 and find that the dominant limitation on astrometric performance is caused by tilt anisoplanatism.
Abstract: We investigate the limits of ground-based astrometry with adaptive optics using the core of the Galactic globular cluster M5. Adaptive optics systems provide near diffraction-limit imaging with the world's largest telescopes. The substantial improvement in both resolution and signal-to-noise ratio enables high-precision astrometry from the ground. We describe the dominant systematic errors that typically limit ground-based differential astrometry, and enumerate observational considerations for mitigating their effects. After implementing these measures, we find that the dominant limitation on astrometric performance in this experiment is caused by tilt anisoplanatism. We then present an optimal estimation technique for measuring the position of one star relative to a grid of reference stars in the face of this correlated random noise source. Our methodology has the advantage of reducing the astrometric errors to and faster than the square root of the number of reference stars, effectively eliminating noise caused by atmospheric tilt to the point that astrometric performance is limited by centering accuracy. Using 50 reference stars, we demonstrate a single-epoch astrometric precision of ≈1 mas in 1 s, decreasing to 100 μas in 2 minutes of integration time at the Hale 200 inch telescope. We also show that our astrometry is accurate to 100 μas for observations separated by 2 months. Finally, we discuss the limits and potential of differential astrometry with current and next-generation large-aperture telescopes. At this level of accuracy, numerous astrometric applications become accessible, including planet detection, astrometric microlensing signatures, and kinematics of distant Galactic stellar populations.
TL;DR: In this paper, a binocular adaptive optics visual simulator is presented, which allows for measuring and manipulating ocular aberrations of the two eyes simultaneously, while the subject performs visual testing under binocular vision.
Abstract: A binocular adaptive optics visual simulator is presented. The instrument allows for measuring and manipulating ocular aberrations of the two eyes simultaneously, while the subject performs visual testing under binocular vision. An important feature of the apparatus consists on the use of a single correcting device and wavefront sensor. Aberrations are controlled by means of a liquid-crystal-on-silicon spatial light modulator, where the two pupils of the subject are projected. Aberrations from the two eyes are measured with a single Hartmann-Shack sensor. As an example of the potential of the apparatus for the study of the impact of the eye's aberrations on binocular vision, results of contrast sensitivity after addition of spherical aberration are presented for one subject. Different binocular combinations of spherical aberration were explored. Results suggest complex binocular interactions in the presence of monochromatic aberrations. The technique and the instrument might contribute to the better understanding of binocular vision and to the search for optimized ophthalmic corrections.
TL;DR: In this article, a self-coherent camera sequentially used as a focal-plane wavefront sensor for active correction and differential imaging is proposed, where stellar speckles are spatially encoded in the science image so that differential aberrations are strongly minimized.
Abstract: Direct detection of exoplanets requires high dynamic range imaging. Coronagraphs could be the solution, but their performance in space is limited by wavefront errors (manufacturing errors on optics, temperature variations, etc.), which create quasi-static stellar speckles in the final image. Several solutions have been suggested for tackling this speckle noise. Differential imaging techniques substract a reference image to the coronagraphic residue in a post-processing imaging. Other techniques attempt to actively correct wavefront errors using a deformable mirror. In that case, wavefront aberrations have to be measured in the science image to extremely high accuracy. We propose the self-coherent camera sequentially used as a focal-plane wavefront sensor for active correction and differential imaging. For both uses, stellar speckles are spatially encoded in the science image so that differential aberrations are strongly minimized. The encoding is based on the principle of light incoherence between the hosting star and its environment. In this paper, we first discuss one intrinsic limitation of deformable mirrors. Then, several parameters of the self-coherent camera are studied in detail. We also propose an easy and robust design to associate the self-coherent camera with a coronagraph that uses a Lyot stop. Finally, we discuss the case of the association with a four-quadrant phase mask and numerically demonstrate that such a device enables the detection of Earth-like planets under realistic conditions. The parametric study of the technique lets us believe it can be implemented quite easily in future instruments dedicated to direct imaging of exoplanets.
TL;DR: A polarization-sensitive optical coherence tomography system that incorporates adaptive optics (AO) in the sample arm and a single line scan camera in the detection arm that demonstrates polarization scrambling in the retinal pigment epithelium at the highest resolution reported to date is demonstrated.
Abstract: Various layers of the retina are well known to alter the polarization state of light. Such changes in polarization may be a sensitive indicator of tissue structure and function, and as such have gained increased clinical attention. Here we demonstrate a polarization-sensitive optical coherence tomography (PS-OCT) system that incorporates adaptive optics (AO) in the sample arm and a single line scan camera in the detection arm. We quantify the benefit of AO for PS-OCT in terms of signal-to-noise, lateral resolution, and speckle size. Double pass phase retardation per unit depth values ranging from 0.25 degrees/microm to 0.65 degrees/microm were found in the birefringent nerve fiber layer at 6 degrees eccentricity, superior to the fovea, with the highest values being noticeably higher than previously reported with PS-OCT around the optic nerve head. Moreover, fast axis orientation and degree of polarization uniformity measurements made with AO-PS-OCT demonstrate polarization scrambling in the retinal pigment epithelium at the highest resolution reported to date.
TL;DR: In this article, the authors systematically investigate the error sources for high-precision astrometry from adaptive optics based near-infrared imaging data and show that at the level of <=100 micro-arcseconds, a number of effects are limiting the accuracy.
Abstract: We systematically investigate the error sources for high-precision astrometry from adaptive optics based near-infrared imaging data. We focus on the application in the crowded stellar field in the Galactic Center. We show that at the level of <=100 micro-arcseconds a number of effects are limiting the accuracy. Most important are the imperfectly subtracted seeing halos of neighboring stars, residual image distortions and unrecognized confusion of the target source with fainter sources in the background. Further contributors to the error budget are the uncertainty in estimating the point spread function, the signal-to-noise ratio induced statistical uncertainty, coordinate transformation errors, the chromaticity of refraction in Earth's atmosphere, the post adaptive optics differential tilt jitter and anisoplanatism. For stars as bright as mK=14, residual image distortions limit the astrometry, for fainter stars the limitation is set by the seeing halos of the surrounding stars. In order to improve the astrometry substantially at the current generation of telescopes, an adaptive optics system with high performance and weak seeing halos over a relatively small field (r<=3") is suited best. Furthermore, techniques to estimate or reconstruct the seeing halo could be promising.