Showing papers on "Wavefront published in 1993"
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TL;DR: In this article, the authors proposed a wave front synthesis method based on the Kirchhoff-Helmholtz integral (KHE) integral, where the wave fields of the sound sources on stage are measured by directive microphones; next they are extrapolated away from the stage, and finally they are re-emitted in the hall by one or more loudspeaker arrays.
Abstract: The acoustics in auditoria are determined by the properties of both the direct sound and the later arriving reflections. If electroacoustic means are used to repair disturbing deficiencies in the acoustics, one has to cope with unfavorable side effects such as localization problems and artificial impressions of the reverberant field (electronic flavor). To avoid those side effects, the concept of electroacoustic wave front synthesis is introduced. The underlying theory is based on the Kirchhoff–Helmholtz integral. In this new concept the wave fields of the sound sources on stage are measured by directive microphones; next they are electronically extrapolated away from the stage, and finally they are re‐emitted in the hall by one or more loudspeaker arrays. The proposed system aims at emitting wave fronts that are as close as possible to the real wave fields. Theoretically, there need not be any differences between the electronically generated wave fields and the real wave fields. By using the image source concept, reflections can be generated in the same way as direct sound.
865 citations
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TL;DR: In this article, a wavefront (WF) construction approach is proposed to estimate a new WF from the old one by using ray tracing, which is defined as a curve (in 2D) of constant traveltime from the source.
Abstract: We have developed and implemented a new method for estimating traveltimes and amplitudes in a general smooth two‐dimensional (2-D) model. The basic idea of this wavefront (WF) construction approach is to use ray tracing to estimate a new WF from the old one. The WF is defined as a curve (in 2-D) of constant traveltime from the source. The ray direction and amplitude will then be a function of s, the distance along the front. To maintain a sufficiently small sampling distance along the WF, it is scanned at every time step and new rays are interpolated whenever the distance between two rays becomes larger than a predefined limit. As the wavefronts are constructed, the data (i.e. traveltimes, amplitude coefficients, etc.) are transferred to the receivers by interpolation within the ray cells. Advantages of the WF construction method are its flexibility, robustness, and accuracy. First, second, and later arrivals may be found at any point in the model. Any shape of the initial wavefront is possible. The drawb...
301 citations
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TL;DR: Improved algorithms permit a more accurate characterization of complicated optical systems from their point spread functions, independent of the number of coefficients or phase points.
Abstract: Phase-retrieval algorithms have been developed that handle a complicated optical system that requires multiple Fresnellike transforms to propagate from one end of the system to the other including the absorption by apertures in more than one plane and allowance for bad detector pixels. Gradient-search algorithms and generalizations of the iterative-transform phase-retrieval algorithms are derived. Analytic expressions for the gradient of an error metric, with respect to polynomial coefficients and with respect to point-by-point phase descriptions, are given. The entire gradient can be computed with the number of transforms required to propagate a wave front from one end of the optical system to the other and back again, independent of the number of coefficients or phase points. This greatly speeds the computation. The reconstruction of pupil amplitude is also given. A convergence proof of the generalized iterative transform algorithm is given. These improved algorithms permit a more accurate characterization of complicated optical systems from their point spread functions.
280 citations
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TL;DR: The Cramer-Rao lower bounds show that point spread functions taken well out of focus result in smaller errors when aberrations are estimated and that, for those images, photon noise is not a limiting factor.
Abstract: We describe several results characterizing the Hubble Space Telescope from measured point spread functions by using phase-retrieval algorithms. The Cramer-Rao lower bounds show that point spread functions taken well out of focus result in smaller errors when aberrations are estimated and that, for those images, photon noise is not a limiting factor. Reconstruction experiments with both simulated and real data show that the calculation of wave-front propagation by the retrieval algorithms must be performed with a multiple-plane propagation rather than a simple fast Fourier transform to ensure the high accuracy required. Pupil reconstruction was performed and indicates a misalignment of the optical axis of a camera relay telescope relative to the main telescope. After we accounted for measured spherical aberration in the relay telescope, our estimate of the conic constant of the primary mirror of the HST was - 1.0144.
268 citations
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TL;DR: In this article, a new Fabry-Perot-based interferometric gravitational wave detector is proposed, which greatly reduces the amount of power that must be transmitted through optical substrates to obtain a given light power in its arms.
191 citations
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TL;DR: In this article, a new method has been developed for testing the optical quality of ground-based telescopes using wideband long-exposure defocused stellar images recorded with current astronomical CCD cameras using an iterative algorithm that simulates closed-loop wavefront compensation in adaptive optics.
Abstract: A new method has been developed for testing the optical quality of ground-based telescopes Aberrations are estimated from wideband long-exposure defocused stellar images recorded with current astronomical CCD cameras An iterative algorithm is used that simulates closed-loop wave-front compensation in adaptive optics Compared with the conventional Hartmann test, the new method is easier to implement, has similar accuracy, and provides a higher spatial resolution on the reconstructed wave front It has been applied to several astronomical telescopes and has been found to be a powerful diagnostic tool for improving image quality
188 citations
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TL;DR: In this article, it was shown that whenever traveling waves exist, the solutions of the initial value problem with either frontlike or pulselike data propagate with the constant effective speeds of traveling waves in all suitable directions.
Abstract: We review the existence results of traveling wave solutions to the reaction-diffusion equations with periodic diffusion (convection) coefficients and combustion (bistable) nonlinearities. We prove that whenever traveling waves exist, the solutions of the initial value problem with either frontlike or pulselike data propagate with the constant effective speeds of traveling waves in all suitable directions. In the case of bistable nonlinearity and one space dimension, we give an example of nonexistence of traveling waves which causes “quenching” (“localization”) of wavefront propagation. Quenching (localization) only occurs when the variations of the media from their constant mean values are large enough. Our related numerical results also provide evidence for this phenomenon in the parameter regimes not covered by the analytical example. Finally, we comment on the role of the effective wave speeds in determining the effective wavefront equation (Hamilton-Jacobi equation) of the reactiondiffusion equations under the small-diffusion, fast-reaction limit with a formal geometric optics expansion.
125 citations
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TL;DR: A predictive linear quadratic Gaussian (LQG) controller is designed that generates commanded control voltages to the mirror actuators based on a set of time-delayed wave-front slope measurements from a Hartmann-type wave- front sensor.
Abstract: We present a technique for controlling a ground-based deformable mirror adaptive optics telescope to compensate for optical wave-front phase distortion induced by a turbulent atmosphere. Specifically, a predictive linear quadratic Gaussian (LQG) controller is designed that generates commanded control voltages to the mirror actuators based on a set of time-delayed wave-front slope measurements from a Hartmann-type wave-front sensor.
117 citations
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TL;DR: The three-wave lateral shearing interferometer is an interferometers specially designed for optical testing that determines three noncollinear phase gradients from one single-fringe pattern and can be easily adjusted to the analyzed aberrations.
Abstract: The three-wave lateral shearing interferometer is an interferometer specially designed for optical testing. It determines three noncollinear phase gradients from one single-fringe pattern. From these quantities, two orthogonal derivatives and the measurement error are estimated, allowing the reconstruction of the aberrated wave front. This new interferometer has several benefits; among them is that its sensitivity and dynamics can be easily adjusted to the analyzed aberrations.
98 citations
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06 Apr 1993
TL;DR: In this article, the authors proposed a virtual image display optical system, which consists of an image source, a combiner, and a relay group consisting of a catatrioptic relay group and a refractive lens group.
Abstract: A virtual image display optical system. The system includes an image source, a combiner, and a relay group. The relay group is a catatrioptic relay group that includes a reflective optical element, and a refractive lens group that includes at least one doublet and a diffractive lens. For some applications, the catatrioptric relay group may be replaced by a hybrid refractive-diffractive relay group, thus eliminating the reflective element. The diffractive optical element of the hybrid optical element is encoded on one side of a lens. The hybrid optical element forms a refractive/diffractive achromat to provide for primary chromatic aberration correction. The refractive lens group is also an achromat to provide for chromatic aberration correction. Power distribution between the hybrid optical element and the refractive lens group is such that secondary chromatic aberration of the refractive lens group is balanced out by the secondary chromatic aberration of the hybrid optical element. The diffractive optical element is designed using higher order wavefront correction terms encoded on one side to reduce spherochromatism and secondary spherochromatism of the relay group. One lens may have a conic or an aspherical surface to further reduce the spherochromatism and secondary spherochromatism. Asymmetrical aberration and distortion resulting from the combiner are compensated for by the reflective optical element. To minimize the residual aberration of the optical system, the reflective optical element is tilted and/or decentered. The system has a relatively wide spectral bandwidth, has good image quality, has simple optics, is ultracompact, and provides wide field coverage and large field overlaying.
82 citations
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29 Dec 1993TL;DR: In this paper, a beam-shaping element for converting a beam having an elliptical cross-section into a beam with a circular cross-sectional area was proposed. But this element was designed to be close to a diode laser so that the risk of wavefront deviations due to defocusing is reduced.
Abstract: A beam-shaping element for converting a beam having an elliptical cross-section into a beam having a circular cross-section. This element has a cylindrical entrance surface and a toriodal exit surface and can be arranged close to a diode laser so that the risk of wavefront deviations due to defocusing is reduced. The element has a high coupling efficiency.
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TL;DR: In this article, the authors combine near-infrared intensity-modulated illumination with frequency domain detection methods to obtain the first detailed optical images of thick tissues (1-3 cm), which are characterized by millimetre resolution and high contrast.
Abstract: By combining near-infrared intensity-modulated illumination with frequency domain detection methods, we have obtained the first detailed optical images of thick tissues (1–3 cm). The raw data of these images are characterized by millimetre resolution and high contrast. The method employs a pulsed laser coupled to a cross-correlation frequency domain detection scheme. The near-infrared imaging method is non-invasive and inexpensive, uses non-ionizing radiation and is potentially fast enough for real-time imaging in the seconds time range. In the frequency domain, diffusional wave optics provides the framework for a description of the light propagation in tissues. Our approach results in a theoretically and experimentally simple way to exploit the advantages of time resolution in optical imaging of inhomogeneous highly scattering materials. At any given modulation frequency, the light wavefront advances at constant velocity in a spherical wave. Objects with scattering or absorption coefficients that are different from the surrounding medium cause a deformation of the propagating wavefront that can be accurately measured using frequency domain detection methods. The visualization (on a computer screen) of these wavefront deformations provides a projection of the interior's image.
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TL;DR: Stellar images taken by the Hubble Space Telescope at various focus positions have been analyzed to estimate wave-front distortion and it was found that better results were obtained by combining the advantages of various algorithms.
Abstract: Stellar images taken by the HST at various focus positions have been analyzed to estimate wave-front distortion. Rather than using a single algorithm, we found that better results were obtained by combining the advantages of various algorithms. For the planetary camera, the most accurate algorithms consistently gave a spherical aberration of -0.290-micron rms with a maximum deviation of 0.005 micron. Evidence was found that the spherical aberration is essentially produced by the primary mirror. The illumination in the telescope pupil plane was reconstructed and evidence was found for a slight camera misalignment.
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TL;DR: Techniques are described for at-wavelength interferometry of multilayer coated optics designed for use in extreme-ultraviolet lithography and several types of interferometer that might be suitable at these short wavelengths.
Abstract: Techniques are described for at-wavelength interferometry of multilayer coated optics designed for use in extreme-ultraviolet lithography. Broadly tunable undulator radiation, which covers the spectral region from 45 to 400 A, is described. The coherent power available at these wavelengths is described, and several types of interferometer that might be suitable at these short wavelengths are also described.
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TL;DR: In this paper, the authors used the reference-phase technique for body-wave computations for models with real caustics in 2D and for a single-valued wavefront in 3D.
Abstract: SUMMARY
Maslov ray summation is ‘less local’ than ordinary ray theory, because the receiver waveform depends on non-Fermat or neighbouring rays and more information about the wavefront than just local Gaussian curvature. In this way, the Maslov solution is able to remain valid at caustics, where geometrical rays and corresponding stationary points of the Maslov phase coalesce. the wavefront information is expressed via the Legendre transformation, whereby the physical wavefront is represented as the envelope of a family of tangent ‘planes’ (Snell fronts). the actual form of the Snell fronts (true planes, sections of curves or surfaces, etc.) depends on the spatial coordinates used. Given a selection for the Snell fronts and Maslov phase, one can substitute the Maslov integral solution directly into the wave equation and obtain a transport equation for the Maslov amplitude. This direct substitution is analogous to that used in ordinary ray theory and avoids pseudo-differential operators.
Sometimes the relative curvature of the physical wavefront and a tangential Snell front is zero. the envelope-forming process breaks down, because the local correspondence between the physical front and the Snell fronts is not one to one and invertible. This situation corresponds to a so-called ‘pseudo-caustic’ (slowness-domain caustic or telescopic point) in the Maslov solution. Pseudo-caustics are not real. A particular ray from the source may touch a pseudo-caustic at some time in one coordinate system, but in another system this ray will not have a pseudo-caustic (at the same time and place). It is easy to design a change of coordinates (e.g. from cartesian to curvilinear or polar) to deform a single-valued traveltime function appropriately, but a multi-valued or folded wavefront, as at a physical or real caustic, is less simple. Catastrophe theory is concerned with putting multi-valued functions into ‘normal forms’ which do not have psuedo-caustics. the manifold here is ‘Lagrangian’ and V. I. Arnold showed that a special type of deformation or ‘canonical transformation’ must be used. A ‘Lagrangian equivalence’ consists of a deformation of the ‘base’ (x-space) and/or the addition of a function on the base. the latter simply means factoring out an appropriate reference phase before Legendre transformation and we have found that this simple step is often sufficient for removing pseudo-caustics. It requires no new numerical work, only an inspection or understanding of the ray-tracing results at hand.
We present some body-wave computations using the reference-phase technique for models with real caustics in 2-D and for a single-valued wavefront in 3-D. We point out that a Lagrangian equivalence may be used to turn a maximum of the Maslov phase function into a minimum. This has no effect on the frequency-domain solution, but may affect the causality of the computed waveform when the Chapman method is used to obtain the time-domain response. Causality is a property which one may need to impose explicitly. Only the non-delta or one-sided function part of the response (waveform tail) is affected by this consideration.
Although zeroth-order Maslov theory correctly describes the severe waveform is clear from Secdistortion due to wavefront catastrophes, it may not adequately model the more subtle effects of smooth wavefront bending. Zeroth-order Maslov theory contains some but not all of the first-order (ω−1) terms of ordinary asymptotic ray theory. First-order Maslov theory is needed for complete consistency up to ω−1. Experimentation will several different zeroth-order Maslov representations is a simple, rapid way to ascertain the potential importance of thse more subtle waveform effects. If the waveform tails are too strong, the assumption that the Maslov (and ray theory) amplitude function can be expanded in powers of ω− may break down. Numerical integration of a wave equation is then necessary.
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01 Jan 1993TL;DR: In this paper, a direct measurement of the zero crossings of the beat signal between two optical frequencies is performed with radio frequency accuracy that is to better than 1 Hz, that is, the measurement of optical frequencies therefore only is limited by the frequency standard.
Abstract: Due to their high intrinsic stability, solid state lasers can be powerful tools for the precise measurement of optical frequencies The rapid increase in reacent years of the spectral bandwidth covered by semiconductor lasers offers new perspectives foroptical frequency measurements In the visible up to now only an interferometric comparison with the I2 stabilized HeNe laser, a secondary optical frequency standard, has been possible, and the accuracy was limited by the errors introduced by dispersion, wavefront, and calibration problems occurring in an interferometric measurement By contrast, a direct frequency comparison, the counting of the zero crossings of the beat signal between two optical frequencies, can be performed with radio frequency accuracy, that is to better than 1 Hz An absolute measurement of optical frequencies therefore only is limited by the frequency standard
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09 Jun 1993
TL;DR: In this paper, a ray tracing based wavefront (WF) construction method is proposed to find arrivals in general 3D models consisting of blocks with smooth velocity and density variation separated by interfaces where the velocity and densities change discontinuously.
Abstract: We have developed a ray tracing based wavefront (WF) construction method that finds arrivals in general 3D models consisting of blocks with smooth velocity and density variation separated by interfaces where the velocity and density change discontinuously. The method is based on the ideas in Vinje et. al. (1992) and it mimics the true wave propagation in the lense that entire WFs are propagated time step by time step creating a moving surface travelling through the model. The WF may stretch, twist and fold in any way as it moves through the medium and the spatial sampling rate of the WF is kept above a pre-defined limit. The receivers are given value as the WFs pass them, one arrival for each sheet of WF that passes. Multi-arrival travel times, amplitudes, geometric spreading etc. are thus found in an efficient way in all areas of the model that are reachable by conventional rays.
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TL;DR: In this work, the advantages of phase shifting have been applied to a conventional moire interferometer, yielding a system capable of recording phase shifted fringe patterns for both in-plane displacement components.
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25 Feb 1993TL;DR: In this article, an apodizer is used to split a light beam into a plurality of beam components such that each adjacent pair of them have phases differing from each other, and converges in a desired position of an image-forming surface.
Abstract: An apodizer according to the present invention subjects a light beam to wavefront splitting, to thereby split it into a plurality of beam components such that each adjacent pair of them have phases differing from each other. The light beam components through the apodizer have phases inverted to one another, and are converged in a desired position of an image-forming surface. The beam spot of the converged light beam is smaller than a size limited by the refractive index of an objective lens. The intensities of sidelobes occurring around the beam spot are sufficiently reduced. When the apodizer is incorporated in an optical head device, the intensity of the center beam spot of a reflected laser beam is emphasized, which enables data reading from a disk medium of a high recording density.
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02 Dec 1993TL;DR: In this paper, the authors used a variation of a Shack-Hartmann wavefront sensor to make wavefront measurements that have extremely large dynamic range coupled with excellent sensitivity at high temporal and spatial resolution.
Abstract: Optical measurement techniques are extremely useful in fluid mechanics because of their non- invasive nature. However, it is often difficult to separate measurement effects due to pressure, temperature and density in real flows. Using a variation of a Shack-Hartmann wavefront sensor, we have made wavefront measurements that have extremely large dynamic range coupled with excellent sensitivity at high temporal and spatial resolution. These wavefront variations can be directly related to density perturbations in the fluid. We have examined several classes of flow including volumetrically heated gas, grid turbulence and droplet evaporation.
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23 Nov 1993TL;DR: In this article, the authors measured the distribution of wavefront distortions in the optics while changing the positions of a light source and an image point inside an exposure field of the optics being observed.
Abstract: A technique and exposure apparatus measures, with a high degree of accuracy, figure and placement errors of individual optical elements constituting optics embedded inside of an exposure apparatus or the like, with the optics kept in an embedded state as they are. The system measures the distribution of wavefront distortions in the optics while changing the positions of a light source and an image point inside an exposure field of the optics being observed. Optimal displacements of reflective surfaces constituting the optics are then found by calculation based on the measured distribution of wave-front distortions. Finally, the positions of the reflective surfaces are corrected in accordance with the calculated optimal displacements. The positions of the reflective surfaces are corrected by individually controlling displacements output by a plurality of actuators attached to each reflective surface and by mechanically modifying appropriate portions of the reflective surfaces.
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TL;DR: It is estimated that at least a 3-kHz search rate is achievable from a 1000template memory with system components currently available, and shift invariance, one of the major advantages of the correlation technique, is preserved.
Abstract: . A hybrid optical/digital configuration to implement a high- speed correlator is described. The input data is digitally Fourier trans-formed at video rates utilizing specialized digital signal processing chip sets and the computed spectral phase data passed to an electrically addressed phase modulating spatial light modulator (SLM). Successivetemplates, which are stored as angle multiplexed volume holograms ina photorefractive crystal, are reconstructed and optically correlated with the current input scene during an interval in which the SLM display is held stable. In this way, shift invariance, one of the major advantages of the correlation technique, is preserved. Of critical importance to thespeed of operation are the energy losses of the coherent wavefront through the system and the rate at which correlation plane data can beconverted to an electronic signal; both of these issues are consideredto estimate that at least a 3-kHz search rate is achievable from a 1000template memory with system components currently available.
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01 Apr 1993
TL;DR: In this article, the authors give a relation between Euler characteristics of a generic closed Legendrian surface and its wavefront, and show that the relation between the Euler properties of the wavefront and the surface can be used to estimate the wave-front of a closed Legendian surface.
Abstract: We give a relation between Euler characteristics of a generic closed Legendrian surface and its wavefront
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TL;DR: It is shown here that wave-front information in a closed-loop adaptive-optics system, used in a postprocessing scheme, can improve the phase of the compensated optical-transfer function in systems with finite delays between wave- front sensing and phase correction.
Abstract: Theoretical and experimental investigations of the imaging technique referred to as speckle holography have shown that wave-front information can be used in the postprocessing of astronomical data to improve the quality of images. In a closed-loop adaptive-optics system the wave-front sensor is continuously measuring the residual wave-front error. Thus wave-front information is continuously available for use in image reconstruction. We show here that wave-front information in a closed-loop adaptive-optics system, used in a postprocessing scheme, can improve the phase of the compensated optical-transfer function in systems with finite delays between wave-front sensing and phase correction. This technique is closely related to speckle holography and is referred to here as compensated speckle holography. This method requires good spatial sampling of the residual phase error and degrades gracefully as the wave-front sensor signal-to-noise ratio decreases. Also, the technique can be used to reduce the required closed-loop bandwidth of an imaging system, permitting longer integration times in the wave-front sensor, and thus allowing dimmer objects to be imaged without the use of an artificial guide star.
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10 Jun 1993TL;DR: A lamp configuration particularly for infrared radiation provides an internal arrangement and environment adapted to overcome failure modes of prior art broad band infrared sources, and may incorporate optical elements including spectral filters and lenses enabling wavelength selection, beam shaping, external focusing, collimating, and wave front shaping as mentioned in this paper.
Abstract: A lamp configuration particularly for infrared radiation provides an internal arrangement and environment adapted to overcome failure modes of prior art broad band infrared sources, and may incorporate optical elements including spectral filters and lenses enabling wavelength selection, beam shaping, external focusing, collimating, and wave front shaping. It also facilitates optical coupling to external devices including a rotating mirror, shutter and modulator devices.
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TL;DR: A generalized linear-algebra vectornotation model of the interferogram sampling and fitting process is developed that is based on a three-step process of sampling, ordering, and fitting.
Abstract: Interferometry is an optical testing technique that quantifies the optical path difference (OPD) between a reference wave front and a test wave front based on the interference of light Fringes are formed when the OPD is an integral multiple of the illuminating wavelength The resultant two-dimensional pattern is called an interferogram The function of any interferogram analysis program is to extract this OPD and to produce a representation of the test wave front (or surface) This is accomplished through a three-step process of sampling, ordering, and fitting We develop a generalized linear-algebra vector-notation model of the interferogram sampling and fitting process
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TL;DR: In this article, the wavelet propagation is employed to describe the evolution of surface topography during ion bombardment-induced sputtering erosion of solids, and it is demonstrated that Huygen's wavelet or characteristics (ray) tracing methods are equally valid but that the former is preferable when multiple gradient discontinuities can develop on generally rough surfaces and the latter is preferable for more gently contoured surfaces.
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TL;DR: New contactless techniques using laser-generated ultrasound have been applied to the inspection of composite materials and it is shown with this point-source measurement technique that the wavefront arrival times agree with the energy velocities rather than with the phase Velocities.
Abstract: New contactless techniques using laser-generated ultrasound have been applied to the inspection of composite materials. Transient elastic waves were launched thermoelastically in half cylindrical composite samples using a long pulse dye laser or a Q-switched Nd-YAG laser. The waves were detected with piezoelectric transducers or with an optical heterodyne interferometer. The measurements have been carried out on two different lay up design composites: carbon/epoxy: undirectional and cross-ply 0 degrees /45 degrees /90 degrees /-45 degrees . Quasi-longitudinal, quasi-shear, and shear bulk waves and head waves are clearly discerned in the stacking of a large number of waveforms. Velocities of the different types of waves simultaneously generated are compared to the phase and group velocities computed using Christoffel equations and an hexagonal model. It is shown with this point-source measurement technique that the wavefront arrival times agree with the energy velocities rather than with the phase velocities. A pronounced anisotropy is observed in the amplitudes of the wave arrivals. Angular directivity patterns of quasi-longitudinal, quasi-shear, and transverse bulk waves are plotted. >
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25 Aug 1993
TL;DR: The Aberrated Beam Analyzer (ABA) as discussed by the authors is a Hartmann-style wavefront sensor and pupil parameter measurement tool, which is used to measure the wavefront of both aberrated HST simulators and the unaberrated output of the correction optics.
Abstract: As part of the HST repair mission it is necessary to verify the performance of the correction optics before their installation in the telescope. To accomplish this precision testing a Hartmann style wavefront sensor and pupil parameter measurement tool has been designed and built. This instrument, termed the Aberrated Beam Analyzer (ABA), will be used to measure the wavefront of both aberrated HST simulators and the unaberrated output of the correction optics. In addition, the ABA measures the location, size, and obscuration ratio of the exit pupil of the system under test. Parameters such as the chief ray angle, PSF, MTF, encircled energy, and Strehl ratio are calculated from the measured data. Operation of the ABA is fully automated and is controlled via a high level scripting language. All data is permanently archived on optical disks for later analysis. The design and theory of operation of the ABA will be discussed. Particular emphasis will be given to the error budget and the measurement performance of the ABA. Some preliminary data will be presented.