A correction algorithm to simultaneously control dual deformable mirrors in a woofer-tweeter adaptive optics system

Background: Scanning laser ophthalmoscopes with adaptive optics correction of ocular aberrations provide retinal images of unprecedented resolution, allowing for real-time imaging of photoreceptors. Eye movements made by the subject/patient during recording produce distortions that must be corrected before multiple frames can be added together to achieve noise reduction or to build a mosaic image from different retinal areas. These distortions also provide a high spatial and temporal resolution record of the miniature eye movements made during fixation. Here we report simultaneous measurements of fixation eye movements with an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) and a dual-Purkinje image (dPi) eye tracker in order to cross-validate these two methods of recording miniature eye movement. Method: Foveas of three subjects were imaged with a one degree square scan using the Houston AOSLO, at a resolution of 8 pixels per arc minute. A Generation V dPi tracker from SRI was placed in front of the AOSLO, and eye movements were recorded at the same time from the same eye being imaged by the AOSLO. AOSLO movies were analyzed off line to extract retinal image motion. The resulting traces were then overlaid on the dPi recordings for comparison. Results: The two methods produced records that agreed to within about one arc minute, with more significant disagreements occurring after eye blinks. Microsaccades in the dPi record were accompanied by overshoots that have previously been associated with lens wobble. AOSLO traces also showed saccade-related overshoots, but of much smaller amplitude. Conclusions: Eye movement recordings measured with dual Purkinje image trackers predict retinal image motion to a precision of about 1 arc minute, except for 10–20 milliseconds following each saccade and 500 – 1000 milliseconds following each eye blink. Retinal image motion measured directly from AOSLO recordings can be recovered to a precision of just a few arc seconds.

High-Resolution Imaging of Retinal Nerve Fiber Bundles in Glaucoma Using Adaptive Optics Scanning Laser Ophthalmoscopy

Since atmosphere turbulence has an effect on laser propagation, it causes wavefront error usually , changes intensity and coherence of laser, disturbs detection of lidar. The adaptive optical system has broad application in the field of laser transmission because it can adjust characters of optical system ,detect and correct the wavefront error at the same time. Adaptive optics technology uses deformable mirrors to perform dynamic phase modulation and endow optical system the ability to decrease the influence of dynamic wavefront errors. In this paper ,a correction method of the micro-miniature adaptive optical system based on Micro Electromechanical System (MEMS) technology is proposed by analyzing the working theory of the adaptive optical system. An experimental system including deformable mirror based on Micro Electromechanical System (MEMS) technology is designed to correct a factitious wavefront error.The influence function and voltage-deflection curve are researched, and the voltage control matrix is educed. By using the voltage control , the static wavefront aberration is corrected. Several important capabilities of deformable mirrors is tested. With the voltage control matrix, the corrected capability of the adaptive optical system is achieved successfully .The experimental results show that the adaptive optical system can preferably correct the wavefront error, that has small volume and steady capability, and greatly improve the capability of lidar detection.

It is well known that using two or more deformable mirrors (DMs) can improve the compensation ability of an adaptive optics (AO) system. However, to keep the stability of an AO system, the correlation between the multiple DMs must be suppressed during the correction. In this paper, we proposed a slope-based decoupling algorithm to simultaneous control the multiple DMs. In order to examine the validity and practicality of this algorithm, a typical woofer-tweeter (W-T) AO system was set up. For the W-T system, a theory model was simulated and the results indicated in theory that the algorithm we presented can selectively make woofer and tweeter correct different spatial frequency aberration and suppress the cross coupling between the dual DMs. At the same time, the experimental results for the W-T AO system were consistent with the results of the simulation, which demonstrated in practice that this algorithm is practical for the AO system with dual DMs.

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

Dysflective cones: Visual function and cone reflectivity in long-term follow-up of acute bilateral foveolitis

Lifecycles of Individual Subretinal Drusenoid Deposits and Evolution of Outer Retinal Atrophy in Age-Related Macular Degeneration

The purpose of this study was to report a case of acute zonal occult outer retinopathy (AZOOR) with spontaneous remission that was followed up using adaptive optics scanning laser ophthalmoscopy (AO-SLO). The right eye of a 31-year old myopic man diagnosed with AZOOR was followed up. The patient underwent a full ophthalmologic examination, spectral-domain optical coherence tomography (SD-OCT), multifocal electroretinography (mfERG) and imaging with prototype AO-SLO systems (Canon Inc) at the first visit, 1 month after, and 2 months after. Images focused on the photoreceptor layer were recorded in the area, and a montage of AO-SLO images was created. The patient presented with acute onset of a blind spot and photopsia in his right eye. On AO-SLO, focal dark areas could be observed on the right eye but not on the left eye at the first examination (cone density 8,589/mm(2), mosaic regularity of cone photoreceptors 38.5 %, cone spacing 0.567). The dark areas on AO-SLO corresponded to areas of disrupted inner segments and outer segments (IS/OS) line or ellipsoid of the IS and abnormal area in mfERG. After 1 and 2 months, his symptoms tended to disappear gradually without any treatment. IS/OS line and mfERG could be nearly normalized. Furthermore, normal cone mosaic could be observed in areas where some focal dark spots could be observed at the first examination (cone density 10,112/mm(2), mosaic regularity of cone photoreceptors 39.9 %, cone spacing 0.606). AO-SLO is a useful tool of diagnosis and follow-up of AZOOR. This study might suggest reversible cone damage could occur in some cases of AZOOR with spontaneous remission.

In astronomy and microscopy, distortions in the wavefront affect the dynamic range of a high-contrast imaging system. These aberrations are either imposed by a turbulent medium such as the atmosphere, by static or thermal aberrations in the optical path, or by imperfectly phased subapertures in a segmented mirror. Active and adaptive optics (AO), consisting of a wavefront sensor and a deformable mirror, are employed to address this problem. Nevertheless, the non-common-path between the wavefront sensor and the science camera leads to persistent quasi-static speckles that are difficult to calibrate and which impose a floor on the image contrast. In this paper, we present the first experimental demonstration of a novel wavefront sensor requiring only a minor asymmetric obscuration of the pupil, using the science camera itself to detect high-order wavefront errors from the speckle pattern produced. We apply this to correct errors imposed on a deformable microelectromechanical segmented mirror in a closed loop, restoring a high-quality point spread function and residual wavefront errors of the order of ∼10 nm using 1600 nm light, from a starting point of ∼300 nm in piston and ∼0.3 mrad in tip–tilt. We recommend this as a method for measuring the non-common-path error in AO-equipped ground based telescopes, as well as an approach to phasing difficult segmented mirrors such as on the James Webb Space Telescope primary and as a future direction for extreme AO.

Current high-contrast "extreme" adaptive optics (ExAO) systems are partially limited by deformable mirror technology. Mirror requirements specify thousands of actuators, all of which must be functional within the clear aperture, and which give nanometer flatness yet micron stroke when operated in closed loop.¹ Micro-electrical mechanical-systems (MEMS) deformable mirrors have been shown to meet ExAO actuator yield, wavefront error, and cost considerations. This study presents the performance of Boston Micromachines' 1024-actuator continuous-facesheet MEMS deformable mirrors under tests for actuator stability, position repeatability, and practical operating stroke. To explore whether MEMS actuators are susceptible to temporal variation, a series of long-term stability experiments were conducted. Each actuator was held fixed and the motion over 40 minutes was measured. The median displacement of all the actuators tested was 0.08 nm surface, inclusive of system error. MEMS devices are also appealing for adaptive optics architectures based on open-loop correction. In experiments of actuator position repeatability, 100% of the tested actuators returned repeatedly to their starting point with a precision of < 1 nm surface. Finally, MEMS devices were tested for maximum stroke achieved under application of spatially varying one-dimensional sinusoids. Given a specified amplitude in voltage, the measured stroke was 1 &#956;m surface at the low spatial frequencies, decreasing to 0.2 &#956;m surface for the highest spatial frequency. Stroke varied somewhat linearly as inverse spatial frequency, with a flattening in the relation at the high spatial frequency end.

A general approach is presented for evaluating and optimizing the degree of atmospheric turbulence compensation achieved by an adaptive optics system employed as part of a extended field-of-view astronomical telescope. This method applies to an adaptive optics system incorporating either one or multiple natural and/or laser guide stars sensed by wave-front slope sensors, a wave-front reconstruction algorithm equivalent to a matrix multiply, a servo control law to temporally filter the output of the wave-front reconstructor, and one or several deformable mirrors optically conjugate to different ranges along the telescope’s line-of-sight. The degree of atmospheric turbulence compensation achieved by such a configuration is evaluated in terms of the residual mean-square phase distortion and turbulence-induced optical transfer function at each point in the telescope’s field-of-view. This evaluation accounts for the combined, interacting effects of the atmospheric turbulence C n 2 ( h ) profile and wind velocity profile, wave-front sensor and deformable mirror fitting error, wave-front sensor noise, finite control system bandwidth, and the net anisoplanatism associated with a given constellation of natural and/or laser guide stars. Optimal wave-front reconstruction algorithms are derived which minimize the telescope’s field-of-view-averaged residual mean-square phase distortion. These evaluation and optimization results are first-order in the sense that they neglect diffraction effects and assume that all adaptive optics components are strictly linear. Results for the case of a finite servo bandwidth also require the wave-front reconstruction algorithm coefficients to satisfy a set of linear constraints; the reconstructor must precisely predict the deformable mirror actuator command vector in the absense of sensor noise and atmospheric turbulence. Numerical results are presented for a variety of adaptive optics configurations incorporating either a single guide star, multiple guide stars and a single deformable mirror, or multiple guide stars and two deformable mirrors.

High-Resolution Imaging of Resolved Central Serous Chorioretinopathy Using Adaptive Optics Scanning Laser Ophthalmoscopy

ObjectiveDiabetic retinopathy (DR), a major diabetes complication, is the fifth leading cause of global blindness and moderate-to-severe visual impairment. DR is categorized into non-proliferative and proliferative forms, with the latter involving neovascularization. Adaptive optics (AO) imaging provides high-resolution, in vivo visualization of retinal microstructures, offering enhanced insight into disease pathology.MethodsA comprehensive PubMed search was conducted for studies published before August 1, 2025, using the keywords “diabetic retinopathy” and “adaptive optics”. The review focused on studies assessing cone photoreceptors, retinal vasculature, and clinical signs using AO imaging.ResultsForty-two studies were included. Many examined cone photoreceptor integrity across DR stages, with or without diabetic macular edema (DME). AO imaging revealed microstructural changes, enabling the correlation of cone metrics with other imaging modalities, including optical coherence tomography angiography, electroretinography, microperimetry, and color vision tests. Several studies analyzed capillary-level vascular alterations and their association with DR severity and DME. Some works have integrated AO data with blood flow assessments using techniques such as laser speckle flowgraphy and AO scanning laser ophthalmoscopy. Lastly, several studies have identified clinical signs related to DR and described their features on AO imaging.DiscussionAdaptive optics imaging reveals early and progressive alterations in photoreceptors, retinal microvasculature, and clinical signs such as microaneurysms and hard exudates in diabetic retinopathy, supporting its role as a valuable tool for understanding disease mechanisms and guiding early diagnosis and monitoring.ConclusionsAdaptive optics is a valuable imaging tool that improves understanding of retinal microarchitecture in diabetic retinopathy. It aids diagnosis, monitoring, and prognosis by enabling detailed evaluation of cellular and vascular alterations.

PurposeTo investigate distances from retinal capillaries to arterioles or venules noninvasively.MethodsAn adaptive optics scanning laser ophthalmoscope (AOSLO) and optical coherence tomography angiography (OCTA) imager acquired detailed maps of retinal vasculature. Using OCTA, we quantified the distance from the edge of an arteriole or venule to the middle of the nearest capillaries (periarteriole or perivenule capillary-free zones, respectively) within the superficial vascular plexus of 20 young healthy subjects with normal axial lengths. These distances were compared to AOSLO images for three subjects. We tested the relation between the peripheral capillary-free zones and FAZ horizontal, vertical, effective diameters, and asymmetry indices in the deep vascular plexus. We examined enlargement with OCTA of capillary-free zones in a type 2 diabetic patient.ResultsThe periarteriole capillary-free zone (67.2 ± 25.3 μm) was readily visible and larger than the perivenule capillary-free zone (42.7 ± 14.4 μm), F(1, 998) = 771, P < 0.0001. The distance from foveal center (P = 0.003) and diameter (P = 0.048) were predictive of perivenule capillary-free zone values. OCTA and AOSLO corresponded for arterioles. FAZ effective diameter was positively associated with asymmetry indices, r = 0.49, P = 0.028, but not peripheral capillary-free zones, although focal enlargements were found in a diabetic patient.ConclusionsFor normal retinas, periarteriole and perivenule capillary-free zones are readily visible with OCTA and AOSLO. Periarteriole capillary-free zones were larger, consistent with arterioles carrying oxygen rich blood that diffuses to support the retina.

High average power operation of the Mercury Laser induces dynamic aberrations to the laser beam wavefront. Analysis of recent data indicates that up to 4 waves of low order aberration (mainly focus error or power, with spatial resolution < 0.5 cm{sup -1}) could be expected at each pass. Because of the magnitude of the wavefront error, the logical position is to place a deformable mirror (DM) at the M11 position, where the DM will correct the beam between passes 1 & 2 and 3 & 4. Currently, there are only two established commercial vendors offering complete adaptive optic (AO) systems that can accommodate the Mercury beam size (45 x 75 mm) which are compatible with high damage threshold coatings. Xinetics (MA, USA) offers a complete AO system along with a Shack-Hartmann wavefront sensor. The Xinetics DM is based on lead magnesium niobate (PMN) technology. A number of US aerospace firms as well as NIF use Xinetics PMN technology for their DMs. Phasics (Paris, France) offers a complete AO solution with its proprietary SID-4, a four-way shearing interferometric wavefront sensor capable of high resolution (over 100 x 100 sampling points). The Phasics system includes a bimorph deformable mirror from Night-n-Opt (Moscow, Russia) that uses lead zirconate titanate (PZT) technology. Various high power laser laboratories around the world such as LULI (France), HELEN (UK), and GEKKO (Japan) are using the PZT-based bimorph DM in their system. While both DM technologies are equivalent and have been deployed in high-energy laser systems, the PZT based bimorph DM offers two distinct features that makes it more attractive for high average power laser systems. The bimorph DM uses two layers of PZT actuators with the outer layer acting as power correctors, capable of correcting up to 20 waves of power. The Xinetics DM offers a maximum stroke of 4 waves. In addition, Night-N-Opt has also designed a water-cooled DM with a silicon based substrate (as opposed to a glass substrate) specifically for high average power laser systems--an option that is currently not available for PMN based DMs.