Author
Noé Alcalá Ochoa
Bio: Noé Alcalá Ochoa is an academic researcher from Centro de Investigaciones en Optica. The author has contributed to research in topics: Interferometry & Electronic speckle pattern interferometry. The author has an hindex of 10, co-authored 41 publications receiving 331 citations.
Papers
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TL;DR: In this article, a method to calibrate a nonlinear phase modulator is proposed based on the minimization of a function obtained from a sequence of interferometric images. But this method is not applicable to smooth wavefront and speckled wavefront interferometry, allowing con- venient in situ calibration for a wide range of inter-ferometer configura- tions.
Abstract: A method to calibrate a nonlinear phase modulator is de- scribed that is based on the minimization of a function obtained from a sequence of interferometric images. The method is equally applicable to smooth wavefront and speckled wavefront interferometry, allowing con- venient in situ calibration for a wide range of interferometer configura- tions. The main advantage over previous calibration methods is that both the linear and quadratic phase variation terms are measured. The per- formance of the proposed method is verified by experiments in which the phase shift is determined independently by a Fourier transform method. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)02709-3) Subject terms: Calibration; piezoelectric translator; phase-shifting interferometry; phase modulator.
51 citations
TL;DR: A fringe pattern normalization and noise-reduction algorithm related to the directional derivatives of the intensity fringes and two-dimensional Fourier series is presented.
37 citations
TL;DR: Based on fringe projection of a single composite fringe pattern containing three different frequencies, the difficulty to discern between surface discontinuities that cause phase shifts greater than 2 π can be solved.
27 citations
TL;DR: To increase this range, to be limited by only the pulse separation, the contrast enhancement of double-pulsed addition-fringe patterns with a spatial filter based on local-standard-deviation measurements is investigated.
Abstract: The electronic speckle pattern interferometer in the double-pulse addition mode can be used to measure physical parameters in unstable environmental conditions. Owing to additive optical noise, however, the fringe patterns obtained have poor contrast. Some methods that use subtraction of addition double-pulsed fringe patterns improve fringe visibility but impose a limitation in measurement time ranges. To increase this range, to be limited by only the pulse separation, the contrast enhancement of double-pulsed addition-fringe patterns with a spatial filter based on local-standard-deviation measurements is investigated. Computer simulations and experimental results are presented.
22 citations
TL;DR: In this paper, a low cost liquid crystal display (LCD) is used to perform the optical test of polished mirrors, based on a typical Ronchi test configuration where the LCD acts like a grating and a phase shifting device.
21 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
Journal Article•
TL;DR: In this article, a self-scanned 1024 element photodiode array and a minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100.
Abstract: A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.
1,300 citations
Journal Article•
TL;DR: In this article, the diffraction tomography theorem is adapted to one-dimensional length measurement and the resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.
Abstract: The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.
1,237 citations
TL;DR: The current state-of-the-art in structured light profilometry systems is described, as well as the main advancements in hardware technology and coding strategy that have led to their successful development.
286 citations
TL;DR: A new approach to reconstructing the object wave front in phase-shifting interferometry with arbitrary unknown phase steps is proposed, capable of retrieving the original object field, including its amplitude and phase distributions simultaneously, with arbitrary and unequal phase steps in a three- or four-frame method.
Abstract: A new approach to reconstructing the object wave front in phase-shifting interferometry with arbitrary unknown phase steps is proposed. With this method the actual phase steps are first determined from measured intensities with an algorithm based on the statistic property of the object phase distribution in the recording plane. Then the original object field is calculated digitally with a derived formula. This method is simple, accurate, and capable of retrieving the original object field, including its amplitude and phase distributions simultaneously, with arbitrary and unequal phase steps in a three- or four-frame method. The effectiveness and correctness of this approach are verified by a series of computer simulations for both smooth and diffusing surfaces.
158 citations