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Earth-based gravitational waves interferometric detectors are shot-noise limited in the high-frequency region of their sensitivity band. While enhancing the laser input power is the natural solution to improve on the shot noise limit, higher power also increases the optical aberration budget due to the laser absorption in the highly reflective coatings of mirrors, resulting in a drop of the sensitivity of the detector. Advanced Virgo exploits Hartmann Wavefront Sensors (HWSs) to locally measure the absorption-induced optical aberrations by monitoring the optical path length change in the core optics. Despite the very high sensitivity of Hartmann sensors, temperature fluctuations can cause a spurious curvature term to appear in the reconstructed wavefront due to the thermal expansion of the Hartmann plate, that could affect the accuracy of the aberration monitoring. We present the implementation and validation of a control loop to stabilize the Advanced Virgo HWS temperature at the order of Δ T ⩽ 0.01 K, keeping the spurious curvature within the detector's requirements on wavefront sensing accuracy. [ABSTRACT FROM AUTHOR]

Spherical aberration is an imperfection of the optical system of the human eye. The role of spherical aberration of the human eye in the quality of vision and pseudoaccommodation is reviewed. Spherical aberration is an imperfection of the optical system of the human eye. In most cases, due to well-developed neuroadaptation, it is insignificant for the perception of the image. Nevertheless, its role in modern ophthalmology is far from straightforward. On the one hand, there are clinical scenarios in which an excess of spherical aberration degrades the retinal image and leads to a high dissatisfaction rate among patients.©Recently, there is a growing interest in the modulation of spherical aberration in the clinical setting. Modern intraocular lenses as well as laser refractive procedures are aimed at interfering with spherical aberrations of the optical system in order to increase range of pseudoaccommodation. Here, we review the role of spherical aberration of the human eye in the quality of vision and pseudoaccommodation. [ABSTRACT FROM AUTHOR]

Introduction: This study performs optical aberration assessment in patients using a novel ultra-high-resolution device. The objective of this study is to analyze optical aberrations, especially the very high order wavefront (more than 10th order of Zernike coefficients), and compare between keratoconus and healthy patients. Methods: In this cross-sectional study, we analyzed 43 eyes from 25 healthy patients and 43 eyes from 27 patients with keratoconus using corneal tomography and a very high-resolution (8.55 µm) aberrometer prototype (T-eyede) outfitted with a sensor originally developed for use in the field of astrophysics. Corneal aberration values were assessed using an optical model built with Zemax optical software, while ocular aberrations were assessed using T-eyede. In addition, image-processing analysis was performed of the wavefront phase, creating a high-pass filter map. Results: We found lower values for ocular aberrations than corneal aberrations in both groups (p < 0.001). Specifically, we found a reduction in primary astigmatism (0.145 µm) and primary coma (0.017 µm). Also, the keratoconus group showed significantly higher wavefront aberration values compared with controls (p < 0.001). An analysis of the high-pass filter map revealed 2 contrasting results: one smooth or clear, while the other presented a banding pattern. Almost all in the control group (95%) showed the first pattern, while 77% of the keratoconus group showed a banding pattern on the filtered map (chi-squared test, p < 0.001). Conclusion: This device provides reliable, precise measurements of ocular aberrations that correlate well with corneal aberrations. Furthermore, the extraordinary high-resolution measurements revealed unprecedented micro changes in the wavefront phase of patients with keratoconus that varied with disease stage. These findings could lead to new screening or follow-up methods. [ABSTRACT FROM AUTHOR]

Introduction: This study investigated differences in peripheral image quality with refractive error. Peripheral blur orientation is determined by the interaction of optical aberrations (such as oblique astigmatism) and retinal shape. By providing the eye with an optical signal for determining the sign of defocus, peripheral blur anisotropy may play a role in mechanisms of accommodation, emmetropisation and optical myopia control interventions. This study investigated peripheral through‐focus optical anisotropy and image quality and how it varies with the eye's refractive error. Methods: Previously published Zernike coefficients across retinal eccentricity (0, 10, 20 and 30° horizontal nasal visual field) were used to compute the through‐focus modulation transfer function (MTF) for a 4 mm pupil. Image quality was defined as the volume under the MTF, and blur anisotropy was defined as the ratio of the horizontal to vertical meridians of the MTF (HVRatio). Results: Across the horizontal nasal visual field (at 10, 20 and 30°), the peak image quality for emmetropes was within 0.3 D of the retina, as opposed to myopes whose best focus was behind the retina (−0.1, 0.4 and 1.5 D, respectively), while for hyperopes it lay in front of the retina (−0.5, −0.6 and −0.6 D). At 0.0 D (i.e., on the retina), emmetropes and hyperopes both exhibited horizontally elongated blur, whereas myopes had vertically elongated blur (HVRatio = 0.3, 0.7 and 2.8, respectively, at 30° eccentricity). Conclusions: Blur in the peripheral retina is dominated by the so‐called "odd‐error" blur signals, primarily due to oblique astigmatism. The orientation of peripheral blur (horizontal or vertical) provides the eye with an optical cue for the sign of defocus. All subject groups had anisotropic blur in the nasal visual field; myopes exhibited vertically elongated blur, perpendicular to the blur orientation of emmetropes and hyperopes. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) devices use imaging optics to magnify the microdisplay images for providing an immersive viewing experience. A microdisplay is preferred to have high-resolution density and high dynamic range to meet the demanding requirements of human vision system (HVS), for example, visual acuity >60 pixels per degree and grayscale depth >10 bits. However, increasing resolution density and dynamic range often lead to a reduced optical efficiency and sophisticated fabrication process of the microdisplay panels. In this paper, we systematically analyze the image degradation mechanisms of VR devices caused by both imaging optics and microdisplay and find that the image degradation caused by imaging optics significantly unleash the requirements of microdisplay, such as contrast ratio, number of local dimming zones, and resolution density. For example, aberrations of the imaging optics reduce the resolution density requirement of the microdisplay, and stray light of the imaging optics relieves the contrast ratio requirement of the microdisplay. These results help prevent excessive design of microdisplay, for example, mini-light-emitting diode (LED) backlit liquid-crystal displays (LCDs), organic LEDs, or micro-LEDs, in a pancake lens-based VR headset. [ABSTRACT FROM AUTHOR]

Recent progress in microspherical superlens nanoscopy raises a fundamental question about the transition from super-resolution properties of mesoscale microspheres, which can provide a subwavelength resolution ∼ λ / 7 , to macroscale ball lenses, for which the imaging quality degrades because of aberrations. To address this question, this work develops a theory describing the imaging by contact ball lenses with diameters 30 < D / λ < 4000 covering this transition range and for a broad range of refractive indices 1.3 < n < 2.1 . Starting from geometrical optics we subsequently proceed to an exact numerical solution of the Maxwell equations explaining virtual and real image formation as well as magnification M and resolution near the critical index n ≈ 2 which is of interest for applications demanding the highest M such as cellphone microscopy. The wave effects manifest themselves in a strong dependence of the image plane position and magnification on D / λ , for which a simple analytical formula is derived. It is demonstrated that a subwavelength resolution is achievable at D / λ ≲ 1400 . The theory explains the results of experimental contact-ball imaging. The understanding of the physical mechanisms of image formation revealed in this study creates a basis for developing applications of contact ball lenses in cellphone-based microscopy. [ABSTRACT FROM AUTHOR]

Studying how to use the coupling characteristics of net aberration fields induced by different perturbation parameters to realize the wave aberration compensation correction of perturbed telescopes is of great significance for the development of active optics. Based on nodal aberration theory, this paper studies the wave aberration compensation correction method of an unobscured off-axis three-mirror telescope. Specifically, first of all, it theoretically analyzes the coupling effects and compensation relationships of net aberration fields induced by different perturbation parameters of the telescope. Furthermore, it establishes wave aberration correction models with the secondary mirror as the compensator and the third mirror as the compensator for the telescope, respectively. In the end, it verifies the two compensation correction models by simulations. The results show that the tolerance of the secondary mirror compensation correction mode (SMCM) to the perturbation parameter threshold is significantly better than that of the third mirror compensation correction model (TMCM). When the introduced perturbation parameter threshold is small, the correction accuracy of the two models for the wave aberrations is equivalent, and both reach the order of 10 − 3 λ (RMS, λ = 632.8 nm). When the perturbation parameter threshold is increased, the correction accuracy of SMCM can still be maintained at the order of 10 − 3 λ but the correction accuracy of TMCM would decrease by an order of magnitude. [ABSTRACT FROM AUTHOR]

Stereovision is the ability to perceive fine depth variations from small differences in the two eyes' images. Using adaptive optics, we show that even minute optical aberrations that are not clinically correctable, and go unnoticed in everyday vision, can affect stereo acuity. Hence, the human binocular system is capable of using fine details that are not experienced in everyday vision. Interestingly, stereo acuity varied considerably across individuals even when they were provided identical perfect optics. We also found that individuals' stereo acuity is better when viewing with their habitual optics rather than someone else's (better) optics. Together, these findings suggest that the visual system compensates for habitual optical aberrations through neural adaptation and thereby optimizes stereovision uniquely for each individual. Thus, stereovision is limited by small optical aberrations and by neural adaptation to one's own optics. [ABSTRACT FROM AUTHOR]

The eye's optics are a major determinant of visual perception. Elucidating how long-term exposure to optical defects affects visual processing is key to understanding the capacity for, and limits of, sensory plasticity. Here, we show evidence of functional reallocation of sensory processing resources following long-term exposure to poor optical quality. Using adaptive optics to bypass all optical defects, we assessed visual processing in neurotypically-developed adults with healthy eyes and with keratoconus - a corneal disease causing severe optical aberrations. Under fully-corrected optical conditions, keratoconus patients showed altered contrast sensitivity, with impaired sensitivity for fine spatial details and better-than-typical sensitivity for coarse spatial details. Both gains and losses in sensitivity were more pronounced in patients experiencing poorer optical quality in their daily life and mediated by changes in signal enhancement mechanisms. These findings show that adult neural processing adapts to better match the changes in sensory inputs caused by long-term exposure to altered optics. [ABSTRACT FROM AUTHOR]

The optical axes of electrically tunable liquid crystal (LC) lenses are usually tilted, and the corresponding asymmetric wavefront aberrations hinder the lenses from being diffraction-limited. Looking back at the literature studies since 1979, researchers used different approaches to compensate the tilting of the optical axis for achieving a perfect lens, or they utilized the intrinsically asymmetric wavefront aberration as a physical-planar free-form optics. However, the physics behind axis tilting has not been discussed yet, and the origin of the oblique optical axes of LC lenses in terms of anisotropic properties of molecules requires an investigation. In this paper, we study the origin of the asymmetrical tilting of optical axes of LC lenses. We found that the initial anisotropic molecular tilts (the so-called pretilt angle) result in the dielectric torque difference even under a rotationally symmetric electric field. Moreover, it is discovered that the rotational symmetry of the wavefront can be broken by generating uneven tilt angles of the LC molecules even though the electric potential is rotationally symmetric. Numerical results are presented and discussed to illustrate the mechanism. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to compare the visual outcomes and subjective visual quality between bilateral implantation of an extended depth of focus intraocular lens, J&J Vision Tecnis Symfony® ZXR00 (Group A) and bilateral implantation of a diffractive trifocal intraocular lens, Alcon Acrysof IQ PanOptix® TNFT00 (Group B). Methods: This prospective, nonrandomized, comparative study of consecutive cases assessed 52 eyes of 26 patients operated on by the same surgeon (WTH) and binocularly implanted with multifocal intraocular lenses between May 2016 and July 2018. Binocular visual acuity for far, intermediate and near was tested in all cases. Ophthalmological evaluation included the measurement of binocular uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), uncorrected near visual acuity (UNVA) at 40 cm, uncorrected intermediate visual acuity (UIVA) at 70 cm, monocular visual defocus curve and the quality of life (QoL) questionnaire, National Eye Institute Visual Functioning Questionnaire - 25 (NEI-VFQ 25). Results: Postoperative UDVA was 0.00 and 0.09 logMAR (P<0.001), UIVA was 0.20 and 0.39 logMAR (P<0.001) and UNVA was 0.16 and −0.01 logMAR (P<0.001) in groups A and B, respectively; postoperative CDVA was −0.05 and 0.06 logMAR (P<0.001) in groups A and B, respectively. Conclusion: Both groups reported good subjective quality of vision regarding long, intermediate and short distances. Group A had a better performance for binocular UDVA, UIVA at 70 cm and CDVA, while regarding the monocular defocus curve, Group A outperformed Group B for long distances. Furthermore, Group B surpassed it in the short to very short distances, between the range of ≥2.00 D to 5.00 D of vergence. While Group A had a better performance regarding the vergences between 0.00 and 1.00 D (P<0.05) and at the vergence of +2.50 D (P=0.007). Group B outran Group A for UNVA at 40 cm. [ABSTRACT FROM AUTHOR]

This technique of performing pinhole pupilloplasty helps filter the straylight from the periphery of the cornea in cases with higher-order corneal aberrations. The pinhole effect blocks distorted and unfocused light rays and isolates more focused central and paracentral rays through the central aperture, thereby reducing aberrations of the optical system as a whole and enhancing visual acuity and its image quality. [ABSTRACT FROM AUTHOR]

A computational method is proposed to measure the aberration of a lens using an extended ptychographic iterative engine. By reconstructing the entering wavefront φin and exiting wavefront φex of the lens under detection from two sets of diffraction patterns iteratively, the lens aberration can be easily extracted by subtracting the phase of φin and theoretical lens phase from the phase of φex. Since it needs no extra reference beam and high quality optics, this suggested method has advantages of simplicity in structure, high accuracy, and low requirement on working environment, and it is free of the aberration of other optical elements in the experimental system, indicating it can find lots of applications in lens evaluation. [ABSTRACT FROM AUTHOR]

Freeform surfaces have been introduced in the optical design of a two-mirror Cassegrain telescope for Earth observation purposes. The application requires two field positions at the image plane with minimum aberrations where two micro spectrometers (HAMAMATSU C12880MA) shall be placed. These micro spectrometers are small and compact devices that incorporate the slit, a concave diffractive element and the CMOS sensor in the same component. Although these are very small components their position at the image plane are slightly deviated from the optical axis, where it is well known minimum aberrations occurs for classical optical systems. Freeform surfaces are introduced to correct those aberrations, mainly astigmatism and coma, for the specific fields determined by the positions of the micro spectrometers. Nodal Aberration Theory (NAT) will be used to determine the mirrors surface deformation as a set of ϕ-polynomials calculating, at the same time, the effects of such deformations on the total aberrations. [ABSTRACT FROM AUTHOR]

We describe a method for designing freeform optics based on the aberration theory of freeform surfaces that guides the development of a taxonomy of starting-point geometries with an emphasis on manufacturability. An unconventional approach to the optimization of these starting designs wherein the rotationally invariant 3rd-order aberrations are left uncorrected prior to unobscuring the system is shown to be effective. The optimal startingpoint geometry is created for an F/3, 200mm aperture-class three-mirror imager and is fully optimized using a novel step-by-step method over a 4 × 4 degree field-of-view to exemplify the design method. We then optimize an alternative starting-point geometry that is common in the literature but was quantified here as a sub-optimal candidate for optimization with freeform surfaces. A comparison of the optimized geometries shows the performance of the optimal geometry is at least 16× better, which underscores the importance of the geometry when designing freeform optics. [ABSTRACT FROM AUTHOR]

The article focuses on a study related to metasurface optics for full-color computational imaging. Topics discussed include miniaturize imaging systems by replacing bulky components with flat and compact implementations; build a system with a single metalens of numerical aperture computational imaging and metasurface optics; and reducing aberrations and downsizing imaging systems using simpler optics.

In his Opticks, published in 1704, Newton thought he had demonstrated the impossibility to eliminate chromatic aberration for lens systems. However, in 1748 Euler proposed a theory supposed to eliminate both chromatic and spherical aberrations in telescopes' objectives. A controversy soon ensued between Dollond who built the first achromatic glasses in 1758 and Euler whose theory appeared to be problematical because it was based on a wrong law of light scattering. In the early 1760s Clairaut and D'Alembert developed in competition a theory of optical aberrations that addresses both the chromatic aberration and geometric aberrations, including off‐axis, which appeared in four of the five so‐called Seidel aberrations. However several sociological, technological, and scientific factors precluded its application to the manufacturing of optical instruments. Subsequent scholars thus ignored these contributions until almost a century later. This article examines the work of Clairaut and D'Alembert, which undoubtedly constitutes one of the major progresses in theoretical optics in the age of Enlightenment, and intends to offer a new light on this period, which is often considered as an era of stagnation in optics. [ABSTRACT FROM AUTHOR]

• We describe the role of spherical aberration in interferometric particle imaging. • We propose a wave optics model to predict the interferometric images of rough particles in presence of this aberration. • We propose a method to correct numerically the interferometric images affected by this aberration. Interferometric Particle Imaging (IPI) is a convenient technique to determine the size and the shape of irregular rough particles. But it requires the analysis and the correction of all sources of noise that can modify the interferometric images and thus the reconstruction procedure. This study describes the role of spherical aberration in IPI. It proposes a numerical model to predict IPI images in presence of this aberration and a method to correct his effect. [ABSTRACT FROM AUTHOR]

In ground-based astronomy, aberrations due to structural vibrations, such as piston, limit the achievable resolution and cannot be corrected using adaptive optics (AO) for large telescopes. We present a model-free strategy to estimate and compensate piston aberrations due to the vibrations of optical components using accelerometer disturbance feed forward, eventually allowing the use of fainter guide stars both for the fringe detector and in the AO loop. Because the correction performance is very sensitive to signal delays, we present a strategy to add a delay compensation to the developed disturbance estimator, which can, in principle, be applied to many other applications outside of astronomy that lack observer performance due to a measurement delay or need a prediction to compensate for input delays. The ability to estimate vibration disturbances in the critical frequency range of 8–60 Hz is demonstrated with on sky data from the Large Binocular Telescope (LBT) Interferometer, an interferometer at the LBT. The experimental results are promising, indicating the ability to suppress differential piston induced by telescope vibrations by a factor of about 3 (rms), which is significantly better than any currently commissioned system. [ABSTRACT FROM PUBLISHER]

A stationary phase method and ambiguity function (AF) method were used to conduct an analytical study of a modulation transfer function (MTF). From the perspective of mathematic models, there was a double integral relationship between the MTF and system wave aberrations. Based on the stationary phase and AF methods, the wave aberration term in the MTF expression was analytically discussed to achieve an aberration function derivation and extreme point analysis, thereby obtaining the analytical expressions of an every field-ofview (FOV) MTF and defocusing distance (i.e., the deviation of an MTF optimal imaging plane from an axial imaging plane) in the full FOV of an optical system. From the obtained image quality evaluation function, the defocusing distance and system image quality could be effectively controlled in a full FOV, which was verified using the examples. [ABSTRACT FROM AUTHOR]

Highly aberrated keratoconic (KC) eyes do not elicit the expected visual advantage from customized optical corrections. This is attributed to the neural insensitivity arising from chronic visual experience with poor retinal image quality, dominated by low spatial frequencies. The goal of this study was to investigate if targeted perceptual learning with adaptive optics (AO) can stimulate neural plasticity in these highly aberrated eyes. The worse eye of 2 KC subjects was trained in a contrast threshold test under AO correction. Prior to training, tumbling 'E' visual acuity and contrast sensitivity at 4, 8, 12, 16, 20, 24 and 28 c/deg were measured in both the trained and untrained eyes of each subject with their routine prescription and with AO correction for a 6mm pupil. The high spatial frequency requiring 50% contrast for detection with AO correction was picked as the training frequency. Subjects were required to train on a contrast detection test with AO correction for 1h for 5 consecutive days. During each training session, threshold contrast measurement at the training frequency with AO was conducted. Pre-training measures were repeated after the 5 training sessions in both eyes (i.e., post-training). After training, contrast sensitivity under AO correction improved on average across spatial frequency by a factor of 1.91 (range: 1.77-2.04) and 1.75 (1.22-2.34) for the two subjects. This improvement in contrast sensitivity transferred to visual acuity with the two subjects improving by 1.5 and 1.3 lines respectively with AO following training. One of the two subjects denoted an interocular transfer of training and an improvement in performance with their routine prescription post-training. This training-induced visual benefit demonstrates the potential of AO as a tool for neural rehabilitation in patients with abnormal corneas. Moreover, it reveals a sufficient degree of neural plasticity in normally developed adults who have a long history of abnormal visual experience due to optical imperfections. [ABSTRACT FROM AUTHOR]

Aberration-corrected microscopy in a scanning transmission electron microscope requires the fast and accurate measurement of lens aberrations to align or 'tune' the corrector. Here, we demonstrate a method to measure aberrations based on acquiring a 4D data set on a pixelated detector. Our method is compared to existing procedures and the choice of experimental parameters is examined. The accuracy is similar to existing methods, but in principle this procedure can be performed in a few seconds and extended to arbitrary order. This method allows rapid measurement of aberrations and represents a step towards more automated electron microscopy. [ABSTRACT FROM AUTHOR]

Vision-realistic rendering is the computer generation of synthetic images that incorporate the characteristics of a par- ticular individual's entire optical system. Specifically, we simulate the scanned foveal image from wavefront data of actual human subjects. The concept of a vision correcting display involves digitally modifying the content of a display using measurements of the optical aberrations of the viewer's eye so that the display can be seen in sharp focus by the user without requiring the use of eyeglasses or contact lenses. Given the measurements of the optical aberrations of a user's eye, a vision correcting display will present a transformed image that when viewed by this individual will appear in sharp focus. Vision correction could be provided in some cases where spectacles are ineffective. [ABSTRACT FROM AUTHOR]

The Frequency Selective Surface is the key component in the Quasi-Optic instrument for feeding large reflector antennas, because of that beams from horns in different frequency band can be combined on a sharing feeding aperture. The aberration to the transmitted beam through FSS is an important problem in fabricating a multi-band QO feed, and must be evaluated in the design stage. Recently, an efficient anticipation method was reported, which can be used to predict the tangential beam shift caused by the FSS and one FSS design is considered. In this paper, we will further discuss the longitude transmitted beam shift anticipation, and consider another FSS structure to show that method can be universal to different FSS structural types. [ABSTRACT FROM AUTHOR]

Abstract: In the recent two decades the technique of high-resolution transmission electron microscopy experienced an unprecedented progress through the introduction of hardware aberration correctors and by the improvement of the achievable resolution to the sub-Ångström level. The important aspect that aberration correction at a given resolution requires also a well defined amount of optical stability has received little attention so far. Therefore we investigate the qualification of a variety of high-resolution electron microscopes to maintain an aberration corrected optical state in terms of an optical lifetime. We develop a comprehensive statistical framework for the estimation of the optical lifetime and find remarkably low values between tens of seconds and a couple of minutes. Probability curves are introduced, which inform the operator about the chance to work still in the fully aberration corrected state. [Copyright &y& Elsevier]

Novel spherical aberration (Cs) and chromatic aberration (Cc) correctors, which correct aberrations using a new principle, were developed. The asymmetric Cs correctors were designed for use in the probe- and imageforming systems at 300 kV to diminish undesired parasitic aberrations. The correctors composed of non-equivalent multipoles connecting with a demagnifying transfer doublet in the system. The axial aberrations were corrected well up to the fifth order except 6-fold astigmatism (A6) experimentally. Next, we developed superior Cs correctors for probe- and image-forming systems of low voltage microscope that uses triple dodecapoles to correct 6-fold astigmatism (A6). An important feature of this system is the rotation of the 3-fold astigmatism azimuth at the second dodecapole. The optimum rotation of the three hexapole fields for the compensation of A6 was derived from theoretical calculations. The experimental results confirmed the compensation of A6 and the third-order Cs. Finally, a unique Cc corrector, which utilized the concave lens effect formed by a long quadrupole field, was designed. The performance of the Cc corrector was investigated using a 30-kV transmission electron microscope. The results confirmed that Cc correction was achieved. [ABSTRACT FROM AUTHOR]

Different aberrometry methods exist and the magnitude of measured wavefront aberrations may differ depending on the method used. Even several Shack-Hartmann wavefront sensors may demonstrate clinically significant differences between ocular aberrations measured. In this study, we tested a hypothesis that a possible source of systematic error in Shack-Hartmann aberrometry may be the presence of spherical aberration in the wavefront used for calibrating the Shack-Hartmann wavefront sensor. Six subjects participated in the study. The Shack-Hartmann wavefront sensor was calibrated by using a spherical and an aspheric lens. Statistically significant changes in wavefront aberrations were observed when comparing both references. Clinically significant changes in magnitude of spherical aberration were also observed. We conclude that for precise measurement of aberrations the use of an aspheric lens for wavefront sensor calibration is essential and different sphericity of the wavefront used for calibration purposes may give rise to variability between wavefront data measured by different Shack-Hartmann wavefront sensors. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new method that can extract aberrations using aerial image measurements and present its experimental results on lithographic tools. Based on physical simulation and statistical analysis, a linear regression matrix is obtained establishing a connection between principal component coefficients of specific aerial images and Zernike coefficients. In the application phase, the aberrations of the projection lens are solved via the use of this regression matrix. An engineering model is established based on an extension of theoretical model that incorporates all the significant systematic errors. The performance of the engineering model as applied on a 0.75 NA ArF scanner is reported. In the experiment, measurement marks oriented in orthogonal directions are used and aerial images at 9 field points are measured. To verify the repeatability of this technique, every point is measured 20 times. By inputting the aerial images into the engineering model, Zernike coefficients are solved and the results are analyzed. The wafer exposures were performed to evaluate the results of aberration correction. [ABSTRACT FROM AUTHOR]

Abstract: The first physiological process influencing visual perception is the optics of the eye. The retinal image is affected by diffraction at the pupil and several kinds of optical imperfections. A model of the eye (), which takes account of pupil aperture, chromatic aberration and wavefront aberrations, was used to determine wavelength-dependent point-spread functions, which can be convolved with any stimulus specified by its spectral distribution of light at each point. The resulting retinal spectral distribution of light was used to determine the spatial distribution of stimulation for each cone type (S, M and L). In addition, individual differences in retinal-image quality were assessed using a statistical model () for population values of Zernike coefficients, which characterize imperfections of the eye’s optics. The median and relatively extreme (5th and 95th percentile) modulation transfer functions (MTFs) for the S, M and L cones were determined for equal-energy-spectrum (EES) ‘white’ light. The typical MTF for S cones was more similar to the MTF for L and M cones after taking wavefront aberrations into account but even with aberrations the S-cone MTF typically was below the M- or L-cone MTF by a factor of at least 10 (one log unit). More generally, the model presented here provides a technique for estimating retinal image quality for the S, M and L cones for any stimulus presented to the eye. The model is applied to some informative examples. [Copyright &y& Elsevier]

Abstract: The weakly nonlinear dynamics in repetitive systems like synchrotrons, storage rings, linacs, and many new compact accelerators in the class of FFAGs is determined by criteria different from those in single pass optical systems. In the latter case, a clean description is obtained by the aberrations, i.e. nonlinear terms in the Taylor representation of the transfer map, and possible connections between them because of the symplectic symmetry of Hamiltonian systems or geometric symmetries of the system under consideration. For repetitive systems other criteria are relevant because conventional aberrations can be either enhanced or weakened by the repeated passage through the same system. We begin with methods that provide highly accurate representations of fields, a pre-requisite for a detailed analysis of nonlinear motion, and discuss surface-based methods that assure accurate field representation far from midplane or axis. We then discuss methods to enforce the symplectic symmetry of the motion by minimal deformations in a suitable metric of Hamiltonian spaces, which is important in the attempt of long-term tracking of the dynamics. We then develop an analytical mechanism most closely related to the conventional aberration correction in conventional systems, the method of normal forms. As a result, quantitative measures of those linearities that matter are obtained in the form of resonance strengths and tune shifts. Residual effects can be described quantitatively using normal form defect methods, which allow rigorous predictions of long-term stability. For practical calculations, the above methods can be expressed seamlessly in terms of differential algebraic structures on Taylor representations, either in a truncated representation in the conventional DA framework, or under consideration of remainder error terms in a fully rigorous setting. [Copyright &y& Elsevier]

Abstract: There are many examples where the aberrational approach does not work very well for long periodical CPO systems. This paper considers some typical tasks where the aberrational approach can be used effectively also for periodical systems. [Copyright &y& Elsevier]

Human stereopsis, the perception of depth from differences in the two eyes' images, is very precise: image differences smaller than a single photoreceptor can be converted into a perceived difference in depth. To better understand what determines this precision, we examined how the eyes' optics affects stereo resolution. We did this by comparing performance with normal, well-focused optics and with optics improved by eliminating chromatic aberration and correcting higher-order aberrations. We first measured luminance contrast sensitivity in both eyes and showed that we had indeed improved optical quality significantly. We then measured stereo resolution in two ways: by finding the finest corrugation in depth that one can perceive, and by finding the smallest disparity one can perceive as different from zero. Our optical manipulation had no effect on stereo performance. We checked this by redoing the experiments at low contrast and again found no effect of improving optical quality. Thus, the resolution of human stereopsis is not limited by the optics of the well-focused eye. We discuss the implications of this remarkable finding. [ABSTRACT FROM AUTHOR]

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Abstract: Neural contrast sensitivity functions (NCSFs) of isolated color mechanisms are obtained based on the measurements of wave-front aberrations and isoluminant color contrast sensitivity functions (CSFs). Our study indicates that the mean NCSF and CSF of the red mechanism are higher than those of the green mechanism, respectively, while those of the blue mechanism are the lowest. However, the relative heights of the peak of NCSF and CSF between red and green mechanisms vary in subjects. There are some individuals whose peak values of NCSF and/or CSF of green mechanism are higher than that of the red mechanism. On the other hand, we find that the NCSFs and CSFs of isolated color mechanisms all exhibit the similar characteristics and variation tendency. With the statistical average, the NCSFs of the red, green and blue mechanisms are higher than the corresponding CSFs in the whole spatial frequency. The peaks of the NCSFs of isolated color mechanisms, comparing with the corresponding CSFs curves, shift toward higher spatial frequencies, especially for that of blue mechanism which has a largest shift of 3.9c/deg. [Copyright &y& Elsevier]

We report a topography-wavefront–guided repair procedure in a patient with a decentered optical zone and significant higher-order aberrations (HOAs) following radial keratotomy 14 years previously. The CRS-Master custom ablation software was used to generate a topography-wavefront–guided ablation profile based on Atlas front corneal surface topography data, and the MEL 80 excimer laser was used to treat the patient. Very high-frequency digital ultrasound scanning (Artemis) was performed before and after surgery to measure epithelial and stromal thickness changes to evaluate the anatomical congruity of the planned and achieved irregular ablation. Nine months postoperatively, the optical zone centration was topographically improved and HOAs were significantly lower, with a 90% reduction in spherical aberration. The stromal thickness change map demonstrated that the profile of stromal tissue removed matched the irregular ablation profile. However, the measured stromal thickness change at the maximum point was 33% higher than the predicted ablation depth. The epithelial thickness change measured in this case indicates that topography-guided treatments could be improved by taking epithelial thickness changes into account. Financial Disclosure: T.J. Archer and M. Gobbe have no financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

An alignment method for holographic data storage system (HDSS) is proposed in this paper. Due to several types of noises encountered in the HDSS, the signal-to-noise ratio (SNR) is degraded. Errors can be corrected using a channel code for some sorts of noise, while it may require a high quality optical system to reduce the error probability for the other types of noise. A checkerboard pattern is proposed using intensity weighting to find the fiducial points, which could work in a lower SNR system and thus reduce the error likelihood effectively. Reed-solomon (RS) code and oversampling are both made available in the HDSS. As a consequence, the aberration effects are eliminated using the fiducial points, leading to a low SNR system clear of errors after performing decoding. The lowest SNR system is out of error-free recovery condition, so that all the alignment methods proposed in this paper could not reduce the aberration effects to restore the images into the original data. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of critical dimension uniformity caused by trefoil aberration of lithographic projection optics is a serious problem in the production of dynamic random access memory devices. In the present paper, we propose a novel method for measuring the trefoil aberration of lithographic projection optics. The trefoil aberration can be extracted from the linewidth asymmetry of the aerial image of brick-wall patterns. The present method has an advantage of timesaving. The test mark used in the present method is easy and cheap to fabricate, and the model for aberration extraction is simple. The PROLITH simulation results show that the trefoil aberration can be measured with high accuracy. [Copyright &y& Elsevier]

Abstract: Targeted patch-clamp recordings are a promising technique that can directly address the physiological properties of a specific neuron embedded in a neuronal network. Typically, neurons are visualized through fluorescent dyes or fluorescent proteins with fluorescence microscopy. After switching to transmitted light microscopy, neurons of interest are re-identified and visually approached in situ with patch-clamp pipettes. Here we introduce a simpler method for neuron targeting. With fluorophore-coated pipettes, fluorescently labeled neurons and the pipette tips are simultaneously imaged at the same fluorescence wavelength in the same microscope field, so that the neurons and even their neurites are targeted without suffering from chromatic aberration or mechanical complication in optics. We did not find that the coated fluorophores affected the electric properties of pipettes or neurons. The novel technique will be wildly available for pipette micromanipulation under online visual control. [Copyright &y& Elsevier]

Microlenses have been developed over recent years for a variety of applications including coupling of light from optical fibres and light emitting diodes (LEDs), improving the optical efficiency of charge coupled devices (CCDs) for cameras, liquid crystal display (LCD) panels for projectors and flat panel displays, and the generation of three-dimensional images. Microlenses are loosely defined as lenses with a diameter less than 1 mm and usually have dimensions measured in micrometres. They may be fabricated individually or in regular arrays on a single substrate. Because of the small apertures and the relatively thick substrates involved, it is generally not possible to use traditional definitions and test methods for the parameters involved. This paper describes a brief history of microlenses and reviews the development of the ISO 14880 series of standards, developed to assist manufacturers and users to specify and assess microlenses and microlens arrays. [ABSTRACT FROM AUTHOR]

Tilted illumination exit-wave restoration is compared for two aberration-corrected instruments at different accelerating voltages. The experimental progress of this technique is also reviewed and the significance of off-axial aberrations examined. Finally, the importance of higher order aberration compensation combined with careful correction of the lower order aberrations is highlighted. [ABSTRACT FROM PUBLISHER]