Abstract: PURPOSE: Wavefront analysis has demonstrated that refractive surgery-induced corneal first surface aberrations are large, are dominated by symmetric aberrations (spherical-like aberrations), and are correlated to measures of visual performance. It is not clear whether the correlation between corneal first surface aberrations and visual performance can be generalized to other corneal conditions where large asymmetric aberrations (coma-like aberrations) may dominate the aberration structure. The purpose of the research reported here was to determine the general utility of corneal first surface wavefront analysis in predicting visual performance. METHODS: Patients were 13 normals and 78 patients with a variety of corneal conditions including surgically removed pterygia, penetrating keratoplasty, keratoconus, radial keratotomy, laser in situ keratomileusis, and others. Videokeratographs were taken for all patients and used to calculate corneal first surface wavefront variance for 3 and 7 mm pupils. Similarly, visual performance was quantified by measurements of contrast sensitivity and high and low contrast acuities through both 3 and 7 mm pupils. RESULTS: Statistically significant correlations existed between all three measures of visual performance and the corneal wavefront variance. All relationships were stronger for the 7 mm diameter-pupil condition than the 3 mm pupil. CONCLUSION: Regardless of the cause, corneas with increased wavefront variance showed a quantifiable decrease in visual performance that was pupil size dependent.

Abstract: A Long Time Ago, in a Laboratory Far, Far, Really Far, Far Away Adaptive Optics Systems - Optics is Our Middle Name Speaking the Language - a Few Definitions Atmospheric Turbulence - Bad Air... Bad, Bad Air Laser Guide Stars - a Beacon in the Wilderness Systems -Putting it All Together Wavefront Sensors - the Eyes Deformable Mirrors - the Hands Control Computers and Reconstructors - the Brains.

Abstract: We present a new design of a modal wave-front sensor capable of measuring directly the Zernike components of an aberrated wave front. The sensor shows good linearity for small aberration amplitudes and is particularly suitable for integration in a closed-loop adaptive system. We introduce a sensitivity matrix and show that it is sparse, and we derive conditions specifying which elements are necessarily zero. The sensor may be temporally or spatially multiplexed, the former using a reconfigurable optical element, the latter using a numerically optimized binary optical element. Different optimization schemes are discussed, and their performance is compared.

Abstract: We demonstrate aberration correction in two-photon microscopy. Specimen-induced aberrations were measured with a modal wavefront sensor, implemented using a ferro-electric liquid crystal spatial light modulator (FLCSLM). Wavefront correction was performed using the same FLCSLM. Axial scanned (xz) images of fluorescently labelled polystyrene beads using an oil immersion lens show restored sectioning ability at a depth of 28 mm in an aqueous specimen.

Abstract: The authors develop a model for the parallel performance of algorithms that consist of concurrent, two-dimensional wavefronts implemented in a message-passing environment. The model, based on a LogGP machine parameterization, combines the separate contributions of computation and communication wavefronts. The authors validate the model on three important supercomputer systems, on up to 500 processors. They use data from a deterministic particle transport application taken from the ASCI workload, although the model is general to any wavefront algorithm implemented on a 2-D processor domain. They also use the validated model to make estimates of performance and scalability of wavefront algorithms on 100 TFLOPS computer systems expected to be in existence within the next decade as part of the ASCI program and elsewhere. In this context, the authors analyze two problem sizes. Their model shows that on the largest such problem (1 billion cells), interprocessor communication performance is not the bottleneck. Single-node efficiency is the dominant factor.

Abstract: Adaptive-optics systems can in principle allow a telescope to achieve performance at its theoretical maximum (limited only by diffraction), by correcting in real time for the distortion of starlight by atmospheric turbulence1. For such a system installed on an 8-m-class telescope2,3, the spatial resolution and sensitivity could be up to 100 times better than conventional imaging4,5. Adaptive-optics corrections have hitherto been achieved only for regions of the sky within a few arcseconds of a bright reference source. But it has been proposed theoretically that by using multiple guide stars, the tomography of atmospheric turbulence could be probed and used to extend adaptive-optics corrections to the whole sky6,7. Here we report the experimental verification of such tomographic8 corrections, using three off-axis reference stars ∼15 arcsec from the central star. We used the observations of the off-axis stars to calculate the deformations of the wavefront of the central star, and then compare them with the real measured values. This tomographic approach is found to reduce variations in the wavefront by ∼92%. Our result demonstrates that a serious barrier to achieving diffraction-limited seeing over the whole sky has been removed.

Abstract: A system and method is provided for integrating corneal topographic data and ocular wavefront data with primary ametropia measurements to create a soft contact lens design. Corneal topographic data is used to design a better fitting soft contact lens by achieving a contact lens back surface which is uniquely matched to a particular corneal topography, or which is an averaged shape based on the particular corneal topography. In the case of a uniquely matched contact lens back surface, the unique back surface design also corrects for the primary and higher order optical aberrations of the cornea. Additionally, ocular wavefront analysis is used to determine the total optical aberration present in the eye. The total optical aberration, less any corneal optical aberration corrected utilizing the contact lens back surface, is corrected via the contact lens front surface design. The contact lens front surface is further designed to take into account the conventional refractive prescription elements required for a particular eye. As a result, the lens produced exhibits an improved custom fit, optimal refractive error correction and vision.

Abstract: For giant, 100 m-class, telescopes, a completely new class of problems arises. Trying to solve them adopting the techniques used for the classical 4 ... 10 m-class telescope systems is indeed a reductive approach. Because of the cone effect and of the difficulties in retrieving the tilt due to the use of LGSs, tomography and multiconjugation will play a central role in the development of these systems. We review the tomographic concept and we report about recent experiments to validate the concept using sky observations. The Field of View requirement is another crucial step in the design of the optical system of these telescopes and hence it needs to be attacked in a detailed and as wide as possible approach. The adoption of classical wavefront sensors looking to different stars is here overcome with wavefront sensors directly conjugated to different layers, with big advantages in term of intrinsic complication of the system, both from the optomechanical point of view (less complexity and saving of a huge amount of light) and from the computational point of view. The adoption of these new sensing techniques (that, gaining from the close loop situation, can be efficiently coupled to a number of very faint stars, whose complexity does not scale with the number of references but, rather, to the number of sensed layers) is here reviewed. This concept of multiple object wavefront sensing leads to an example of a system with a minimum number of independent adaptive optics loop, in which each layer represented in a wavefront sensor can be conjugated to a specifically conjugated deformable mirror.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: A method for improving the visual performance of a person involves correcting higher-order monochromatic aberrations in combination with the correction of chromatic aberration. Such correction results in a visual benefit greater than that realized by correcting only the higher-order monochromatic aberrations or the chromatic aberration alone. The higher-order monochromatic aberrations are corrected by introducing appropriate phase profiles to compensate for the wavefront aberrations of the eye. This compensation can be provided by contact lenses, IOLs, inlays and onlays having appropriate surface shapes or by corneal shaping achieved through refractive surgery or other techniques. Chromatic aberration can be corrected by spectral filtering or artificial apodization. An apodization filter is described that provides a non-uniform amplitude transmission across the pupil of the eye. Contact lenses or other ocular devices for correcting higher-order monochromatic aberrations may include an appropriate apodization filter for correcting chromatic aberration, or an external optical device for correcting chromatic aberration may be used in combination with a contact lens, etc. for correcting the higher-order monochromatic aberrations. A device and method for improved retinal imaging is also described.

Abstract: For practical holographic video system, it is important to generated holographic fringe as fast as possible. We have proposed an approximation method that can calculate the Fresnel hologram fast. To compute the hologram, an object is assumed as a collection of self-illuminated points and the fringes from each object point are superposed. To determine the fringe, a distance between object point and sampling point on the hologram is used to obtain phase of the light. Since sampled hologram usually has small pixel intervals, the difference of the distance values between adjacent pixels is also small and its n-th order difference becomes a constant. Therefore, the distance value at certain pixel can be obtained from the neighbor pixel with simple additions. We have investigated approximation errors and computational speed of the method. The numerical results show that the proposed method is quite effective. The distance error can be reduced less that one wavelength with practical parameters and the computational speed becomes 16 times faster than conventional method. With the proposed method, a hologram, which has horizontal parallax only, 1.3 mega- pixels and 1,000 object points, can be calculated less than on second with a personal computer.

Abstract: A method for enhancing vision of an eye includes a laser delivery system having a laser beam for ablating corneal material from the cornea of the eye Measurements are made to determine an optical path difference between a plane wave and a wavefront emanating from the retina of the eye for a location at a surface of the cornea An optical correction is provided to the laser delivery system for the location based on the optical path difference and refractive indices of media through which the wavefront passes The optical correction includes dividing the optical path difference by a difference between an index of refraction of corneal material and an index of refraction of air The laser beam is directed to the location on the surface of the cornea and corneal material ablated at the location in response to the optical correction to cause the wavefront to approximate the shape of the plane wave at that location

Abstract: A speckle reduction system divides pulses of coherent radiation into successions of temporally separated and spatially aberrated pulselets. One or more beamsplitters divide the pulses into the successions of pulselets that are circulated through delay lines. Spatial aberrators located along the delay lines modify wavefront shapes of the pulselets. Together, the temporal separation and spatial aberration of the pulselets produce a succession of different speckle patterns that can be averaged together within the integration interval of a detector to reduce speckle contrast.

Abstract: We describe the practical implementation of a closed-loop adaptive-optics system incorporating a novel modal wave-front sensor. The sensor consists of a static binary-phase computer-generated holographic element, which generates a pattern of spots in a detector plane. Intensity differences between symmetric pairs of these spots give a direct measure of the Zernike mode amplitudes that are present in the input wave front. We use a ferroelectric liquid-crystal spatial light modulator in conjunction with a 4–f system and a spatial filter as a wave-front correction element. We present results showing a rapid increase in Strehl ratio and focal spot quality as the system corrects for deliberately introduced aberrations.

Abstract: We describe a novel wave-front sensor comprising a distorted diffraction grating, simple optics, and a single camera. A noniterative phase-diversity algorithm is used for wave-front reconstruction. The sensor concept and practical implementation are described in detail, and performance is validated against different Zernike modes and a representative atmospheric phase map.

Abstract: The invention features an interferometry system for a measuring a surface profile or thickness of a measurement object In one aspect, the interferometry system includes: a broadband infrared source which during operation generates broadband infrared radiation including central wavelengths greater than about 1 micron; a scanning interferometer which during operation directs a first infrared wavefront along a reference path and a second infrared wavefront along a measurement path contacting the measurement object, and, after the second wavefront contacts the measurement object, combines the wavefronts to produce an optical interference pattern, the first and second infrared wavefronts being derived from the broadband infrared radiation; a detector producing data in response to the optical interference pattern; and a controller which during operation causes the scanning interferometer to vary the optical path difference between the reference and measurement paths over a range larger than the coherence length of the broadband source and analyzes the data as a function of the varying optical path difference to determine the surface profile

Abstract: A customized corneal profile is provided by combining corneal topography data with captured wavefront aberration data to form a course of refractive treatment of the eye. In one embodiment, the captured wavefront data is employed within the area of a pupil, while the corneal topography data is employed in the area outside of the pupil. In other embodiments, the topography data is adjusted based on the wavefront data, a course of refractive treatment is simulated and displayed upon the topography data, and an initial evaluation of the suitability of a patient for treatment is performed based on the topography data.

Abstract: The concept of slope discrepancy developed in the mid-1980’s to assess measurement noise in a wave-front sensor system is shown to have additional contributions that are due to fitting error and branch points. This understanding is facilitated by the development of a new formulation that employs Fourier techniques to decompose the measured gradient field (i.e., wave-front sensor measurements) into two components, one that is expressed as the gradient of a scalar potential and the other that is expressed as the curl of a vector potential. A key feature of the theory presented here is the fact that both components of the phase (one corresponding to each component of the gradient field) are easily reconstructable from the measured gradients. In addition, the scalar and vector potentials are both easily expressible in terms of the measured gradient field. The work concludes with a wave optics simulation example that illustrates the ease with which both components of the phase can be obtained. The results obtained illustrate that branch point effects are not significant until the Rytov number is greater than 0.2. In addition, the branch point contribution to the phase not only is reconstructed from the gradient data but is used to illustrate the significant performance improvement that results when this contribution is included in the correction applied by an adaptive optics system.

Abstract: A diffractive Alvarez lens is demonstrated that consists of two separate phase plates, each having complementary 16-level surface-relief profiles that contain cubic phase delays. Translation of these two components in the plane of the phase plates is shown to produce a variable astigmatic focus. Both spherical and cylindrical phase profiles are demonstrated with good accuracy, and the discrete surface-relief features are shown to cause less than λ/10 wave-front aberration in the transmitted wave front over a 40 mm×80 mm region.

Abstract: Spatial planar projection techniques propagate field measurements from a single plane in front of a transmitter to arbitrary new planes closer to or further away from the source. A linear wave vector frequency-domain projection algorithm is applied to the acoustic fields measured from several focused transducer arrays designed for ultrasound therapy. A polyvinylidene difluoride hydrophone is first scanned in a water tank over a plane using a three-dimensional positioning system to measure the complex pressure field as a function of position. The field is then projected to a series of new planes using the algorithm. Results of the projected fields are compared with direct measurements taken at corresponding distances. Excellent correlation is found between the projected and measured data. The method is shown to be accurate for use with phase-controlled field patterns, providing a rapid and accurate method for obtaining field information over a large spatial volume. This method can significantly simplify the characterization procedure required for phased-array application used for therapy. Most significantly, the wavefront propagated back to a phased array can be used to predict the field produced by different phase and amplitude settings of the array elements. A field back-projected to the source could be used as an improved source function in acoustic modeling.

Abstract: We describe two electro-optical systems for adaptive focusing of linearly polarized light. The aperture size is 5 mm and the focal length can be varied from 1 to 4 m for wavelengths from 0.663 to 0.85 μm. The first is a commercially available system including a PC compatible control unit and software, and an adaptive liquid crystal lens. The other is an experimental system consisting of a self-contained unit with an autonomous power supply and an adaptive lens. The safe operating limit in the visible region is 10 W/cm2 with a transmission of 70% without antireflection coating. The switching speed of focus variation from 2 to 1 m and from 1 to 2 m is 780 and 860 ms, respectively. The operating principles of the spherical adaptive lenses and their control units are described. Phase aberrations of the lenses were measured by a Zygo phase shifting interferometer, and the results are presented.

Abstract: A method is proposed for exact discrete reconstruction of a two-dimensional wave front from four suitably designed lateral shearing experiments. The method reconstructs any wave front at evaluation points of a circular aperture exactly up to an arbitrary constant for noiseless data, and it shows excellent stability properties in the case of noisy data. Application of large shears is allowed, and high resolution of the reconstructed wave front can be achieved. Results of numerical experiments are presented that demonstrate the capability of the method.

Abstract: Linewidth control across an exposure field is becoming increasingly challenging as design rules shrink. Contributions to linewidth variation can arise from the reticle, the exposure tool and the resist process. For the exposure system, errors may originate from the illuminator ste-up, the projection lens aberrations using a new reticle and measurement technique. The technique uses a special reticle, which converts wavefront phase errors to displacements on the wafer. These offsets can be measured using conventional overlay tools with greater speed and accuracy than SEM measurements of small linewidths. Reconstruction of the wavefront using this data provides a more reliable in-situ characterization of aberrations.

Abstract: Many of the limitations of traditional optical-only imaging systems can be eliminated with jointly optimized optical and digital imaging systems. Jointly optimized optical and digital imaging systems exploit the complementary aspects of optics and digital signal processing to form systems with characteristics not possible with traditional optics-only systems. For example, in traditional imaging systems light gathering and large depth of field are competing goals and are inversely related. On the other hand, in optimized optical/digital imaging systems light gathering and large depth of field can be independent parameters. Instead of requiring a small aperture to produce a large depth of field, a large aperture and a large depth of field are both possible and practical. We can jointly optimized optical and digital imaging systems Wavefront Coded imaging systems. Concepts of Wavefront Coding are illustrated below through an athermalized, refractive, silicon/germanium IR imaging system with aluminum optical mounts subject to an ambient temperature range of -20 degree(s)C to +70 degree(s)C.

Abstract: Wavefront aberrations in an eye are detected by illuminating the retina, receiving the light reflected by the retina and using a Hartmann-Shack detector (112) or the like to detect the aberrations The illuminating light (102) is applied to the eye of the optical axis of the eye (A) Light reflected from the cornea and light reflected from the retina travel in different directions The former can be blocked with a stop (108), while the latter is passed to the detector

Abstract: A new interferometry configuration combines the strengths of two existing interferometry methods, improving the quality and extending the dynamic range of both. On the same patterned mask, placed near the image-plane of an optical system under test, patterns for phase-shifting point diffraction interferometry and lateral shearing interferometry coexist. The former giving verifiable high accuracy for the measurement of nearly diffraction-limited optical systems. The latter enabling the measurement of optical systems with more than one wave of aberration in the system wavefront. The interferometry configuration is a hybrid shearing and point diffraction interferometer system for testing an optical element that is positioned along an optical path including: a source of electromagnetic energy in the optical path; a first beam splitter that is secured to a device that includes means for maneuvering the first beam splitter in a first position wherein the first beam splitter is in the optical path dividing light from the source into a reference beam and a test beam and in a second position wherein the first beam splitter is outside the optical path: a hybrid mask which includes a first section that defines a test window and at least one reference pinhole and a second section that defines a second beam splitter wherein the hybrid mask is secured to a device that includes means for maneuvering either the first section or the second section into the optical path positioned in an image plane that is created by the optical element, with the proviso that the first section of the hybrid mask is positioned in the optical path when first beam splitter is positioned in the optical path; and a detector positioned after the hybrid mask along the optical path.

Abstract: The use of a Shack–Hartmann wave-front sensor as a position-sensing device is proposed and demonstrated. The coordinates of a pointlike object are determined from the modal Zernike coefficients of the wave fronts emitted by the object and detected by the sensor. The position of the luminous centroid of a moderately extended incoherent flat object can also be measured with this device. Experimental results with off-the-shelf CCD cameras and conventional relay optics as well as inexpensive diffractive microlens arrays show that axial positioning accuracies of 74 µm rms at 300 mm and angular accuracies of 4.3 µrad rms can easily be achieved.