Two-dimensional fringe-pattern analysis.
TL;DR: Two-dimensional sinusoid fitting and Fourier transform methods of analyzing fringes to determine the wave-front topography are described and are accurate.
Abstract: Two-dimensional sinusoid fitting and Fourier transform methods of analyzing fringes to determine the wave-front topography are described. The methods are easy to apply because they do not require finding fringe centers and fringe orders. Also, they are accurate. For an active optics experiment in which we have used these techniques, experimental noise exceeds the error resulting from analysis of noise-free theoretical fringe patterns.
Citations
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Journal Article•
TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
3,742 citations
01 Dec 1988
TL;DR: In this survey, the relative capabilities of different sensors and sensing methods are evaluated using a figure of merit based on range accuracy, depth of field, and image acquisition time.
Abstract: Active, optical range imaging systems collect three-dimensional coordinate data from object surfaces. These systems can be useful in a wide variety of automation applications, including shape acquisition, bin picking, assembly, inspection, gauging, robot navigation, medical diagnosis, cartography, and military tasks. The range-imaging sensors in such systems are unique imaging devices in that the image data points explicitly represent scene surface geometry in a sampled form. At least six different optical principles have been used to actively obtain range images: (1) radar, (2) triangulation, (3) moire, (4) holographic interferometry, (5) lens focusing, and (6) diffraction. The relative capabilities of different sensors and sensing methods are evaluated using a figure of merit based on range accuracy, depth of field, and image acquisition time.
670 citations
TL;DR: In this paper, a method for accurate phase determination in holographic interferometry using a one- or two-dimensional Fourier transform is described, which calculates the interference phase pointwise, even between fringe extrema, and thus has advantages over conventional fringe-finding and tracking methods.
Abstract: A method for accurate phase determination in holographic interferometry using a one- or two-dimensional Fourier transform is described. The method calculates the interference phase pointwise, even between fringe extrema, and thus has advantages over conventional fringe-finding and -tracking methods. Only one interference pattern may be used, although the use of two patterns reconstructed with a mutual phase shift permits an easier phase unwrapping and determination of nonmonotonic fringe-order variations. Additionally, the method offers a means for filtering out disturbances such as speckle noise and background variations.
433 citations
TL;DR: A line-imaging velocity interferometer has been implemented at the OMEGA laser facility of the University of Rochester as mentioned in this paper, which is the primary diagnostic for a variety of experiments involving laser-driven shockwave propagation, including high pressure equation of state experiments, materials characterization experiments, shock characterization for Rayleigh-Taylor experiments, and shock timing experiments for inertial confinement fusion research.
Abstract: A line-imaging velocity interferometer has been implemented at the OMEGA laser facility of the Laboratory for Laser Energetics, University of Rochester. This instrument is the primary diagnostic for a variety of experiments involving laser-driven shock-wave propagation, including high-pressure equation of state experiments, materials characterization experiments, shock characterization for Rayleigh–Taylor experiments, and shock timing experiments for inertial confinement fusion research. Using a laser probe beam to illuminate a target, the instrument measures shock breakout times at temporal resolutions as low as 20 ps, and spatial resolution ∼4 μm. For velocity measurements the detection limit is <0.1 km/s, and velocities of interfaces, free surfaces, and shock fronts traveling through transparent media can be measured with accuracies ∼1% over the range from 4 km/s to greater than 50 km/s. Quantitative measurements of the optical reflectance of ionizing shock fronts can also be obtained simultaneously with the velocity measurements.
371 citations
TL;DR: A refinement of the Fourier transform fringe-pattern analysis technique which uses a 2-D Fouriertransform permits better separation of the desired information components from unwanted components than a 1-D transform.
Abstract: A refinement of the Fourier transform fringe-pattern analysis technique which uses a 2-D Fourier transform is described. The 2-D transform permits better separation of the desired information components from unwanted components than a 1-D transform. The accuracy of the technique when applied to real data recorded by a system with a nonlinear response function is investigated. This leads to simple techniques for optimizing an interferogram for analysis by these Fourier transform methods and to an estimate of the error in the retrieved fringe shifts. This estimate is tested on simulated data and found to be reliable.
363 citations
References
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Journal Article•
TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
3,742 citations
TL;DR: In this paper, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
3,650 citations
TL;DR: A system for extracting the phase components of an optical traveling wave field has been constructed using the Mach-Zehnder interferometer to capture the wave field as the hologram, a photoelectronic scanning system, and an analog computing circuit.
Abstract: A system for extracting the phase components of an optical traveling wave field has been constructed. This system consists of the Mach-Zehnder interferometer to capture the wave field as the hologram, a photoelectronic scanning system, and an analog computing circuit. The detected phase signal is immediately displayed on a cathode ray tube as continuous-tone patterns. The method has been confirmed through the experimental results.
151 citations
TL;DR: The task is to learn the phases of real positive intensity fringes from an optical testing interferometer using a direct analog-to-digital arctangent converter, coupled to a turns counter that automatically registers unwrapped phase.
Abstract: The task is to learn the phases of real positive intensity fringes from an optical testing interferometer The introduction of substantial tilt into the interferometer establishes a field of finely spaced fringes that serve as a spatial heterodyne carrier Sequential pixel values from a TV video signal of the picture are distributed among three separate signal channels, every third pixel going to the same channel The distribution rate is set at ~3 pixels/fringe so that each channel senses one phase of a three-phase stroboscope or moire Complex weighting of the channel signals eliminates the common mode to provide in-phase and quadrature analog fringe signals A direct analog-to-digital arctangent converter, with that analog signal pair as input, provides 4-bit (1/16-cycle resolution) fringe phase at a 5-MHz sampling rate The converter is coupled to a turns counter that automatically registers unwrapped phase The similarity of the signals to ntsc color TV encoding is noted along with certain other applications
129 citations