Applications of higher-order phase shifting algorithms for multiple-wavelength metrology
04 Mar 2019-Vol. 10887, pp 182-187
TL;DR: Various phase shifting algorithms, and their tolerance for phase shift error are discussed, and the applications of higher-order phased shifting algorithms will be presented, useful for multiple-wavelength and white light interferometry where more than one wavelength is used for optical phase measurements.
Abstract: Multiple-wavelength interferometric techniques have been successfully used for large step-height and large deformation measurements. Also it could resolve the step height between smooth and rough surfaces which is not possible with single wavelength interferometry. Temporal phase shifting algorithm, which requires a phase shifter such as PZT, has been widely used for accurate phase evolution in interferometry. The phase shifter needs to be calibrated at every wavelength if multiple wavelengths are used for measurement, it is a time consuming process. If phase shifter is not calibrated accurately, it can introduce phase shift errors. In this work, we will discuss various phase shifting algorithms, and their tolerance for phase shift error. And the applications of higher-order phased shifting algorithms will be presented. The study is useful for multiple-wavelength and white light interferometry where more than one wavelength is used for optical phase measurements.
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01 Jan 2016
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184 citations
14 Feb 2020
TL;DR: In this article, a dual-wavelength approach to measure surface profile of both smooth and rough surfaces simultaneously is presented, where the wrapped phases at each wavelength are calculated and subtracted to generate contour phase map.
Abstract: Interferometers are widely used in industry for surface profiling of microsystems. It can be used to inspect both smooth (reflective) and rough (scattering) surfaces in wide range of sizes. If the object surface is smooth, the interference between reference and object beam results in visible fringes. If the object surface is optically rough, the interference between reference and object beam results in speckles. Typical microsystems such as MEMS consist of both smooth and rough surfaces on a single platform. Recovering the surface profile of such samples with single-wavelength is not straight forward. In this paper, we will discuss a dual-wavelength approach to measure surface profile of both smooth and rough surfaces simultaneously. Interference fringe pattern generated on a combined surface is acquired at two different wavelengths. The wrapped phases at each wavelength are calculated and subtracted to generate contour phase map. This subtraction reveals the contour fringes of rough and smooth surfaces simultaneously. The dual-wavelength contour measurement procedure and experimental results will be presented.
1 citations
TL;DR: In this article , a wire-grid polarizer (WGP) is placed on the laser beam illuminating the sample, where the WGP serves the dual purpose of a beam splitter and a polarization separator where the reference and sample beams reflected and transmitted from it respectively are orthogonally polarized.
Abstract: This work describes a full-field and near-common-path in-line laser interferometer and interferometric microscope utilizing a wire-grid polarizer (WGP) placed normally on the laser beam illuminating the sample. The WGP serves the dual purpose of a beam splitter and a polarization separator where the reference and sample beams reflected and transmitted from it respectively are orthogonally polarized so that, unlike other conventional interferometers, polarization phase shifting is inherent in its architecture. This arrangement presents experimental results showing quantitative phase analysis of transparent and reflecting phase samples.
1 citations
References
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TL;DR: In this paper, a completely rewritten chapter was added to cover wavefront fitting and evaluation as well as holographic and Moire methods, and an appendix was added suggesting appropriate tests for typical optical surfaces.
Abstract: Fringe scanning techniques, now renamed heterodyning or phase shift interferometry, are covered in a completely rewritten chapter. New chapters have been added to cover wavefront fitting and evaluation as well as holographic and Moire methods. The chapter on parameter measurements has been completely rewritten and an appendix added suggesting appropriate tests for typical optical surfaces.
2,372 citations
TL;DR: La difference de phase entre les 2 faisceaux interferant varie de maniere connue et on fait des mesures de the distribution d'intensite a travers la pupille correspondant a au moins 3 dephasages differents.
Abstract: La difference de phase entre les 2 faisceaux interferant varie de maniere connue et on fait des mesures de la distribution d'intensite a travers la pupille correspondant a au moins 3 dephasages differents
979 citations
TL;DR: One application of phase-shifting techniques to speckle interferometry is finding the phase of deformations, where up to ten waves of wavefront deformation can easily be measured.
Abstract: Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern; however, the phase of the difference between two correlated speckle patterns can be determined. This is done by applying phase-shifting techniques to speckle interferometry, which will quantitatively determine the phase of double-exposure speckle measurements. The technique uses computer control to take data and calculate phase without an intermediate recording step. The randomness of the speckle causes noisy data points which are removed by data processing routines. One application of this technique is finding the phase of deformations, where up to ten waves of wavefront deformation can easily be measured. Results of deformations caused by tilt of a metal plate and a disbond in a honeycomb structure brazed to an aluminum plate are shown.
740 citations
TL;DR: The new 5-frame algorithm and two new 6-frame algorithms have smaller phase errors caused by phase-shifter miscalibration than any of the common 3-, 4- or 5- frame algorithms.
Abstract: Phase-shifting interferometry suffers from two main sources of error: phase-shift miscalibration and detector nonlinearity. Algorithms that calculate the phase of a measured wave front require a high degree of tolerance for these error sources. An extended method for deriving such error-compensating algorithms patterned on the sequential application of the averaging technique is proposed here. Two classes of algorithms were derived. One class is based on the popular three-frame technique, and the other class is based on the 4-frame technique. The derivation of algorithms in these classes was calculated for algorithms with up to six frames. The new 5-frame algorithm and two new 6-frame algorithms have smaller phase errors caused by phase-shifter miscalibration than any of the common 3-, 4- or 5-frame algorithms. An analysis of the errors resulting from algorithms in both classes is provided by computer simulation and by an investigation of the spectra of sampling functions.
383 citations
TL;DR: An extension of the static technique to real- time dynamic testing is proposed and an operational variable-sensitivity interferometer utilizing the real-time technique is described.
Abstract: Previous methods of two-wavelength variable-sensitivity interferometry are reviewed and a simplified two-wavelength technique for interferometric testing under static conditions is discussed. An extension of the static technique to real-time dynamic testing is proposed and an operational variable-sensitivity interferometer utilizing the real-time technique is described.
240 citations