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Center Wavelength Measurement based on Higher Steps phase-shifting algorithms in White-light Scanning Interferometry

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Procedia Engineering 2014年 79卷 447-455页

作者： Ming-Hsing Shen Chi-Hung Hwang Wei-Chung Wang Department of Power Mechanical Engineering National Tsing Hua University No.101 Sec. 2 Kuang Fu Rd. East Dist. Hsinchu City Taiwan 30013 Republic of China

Traditionally, monochromatic wavelength interferometry is applied to the measurement of smooth surfaces. Owing to the phase ambiguity, the range of depth measurement with a monochromatic light source is limited. To overcome this problem, with the fact that white-light source is continuous in spectrum, the white-light scanning interferometry (WLSI) can be used to measure discontinuous profile. In this paper, envelope function based on local linear conditions was developed and WLSI using higher steps phase-shifting algorithms (PSAs) was proposed. Maximum intensity peak positions at five points were used to calculate the center wavelength of the light source by both phase unwrapping and linear least-squares fitting. Both simulated and experimental results showed that the proposed PSAs have good linearity and robustness to accurately measure center wavelength of the white-light source

关键词： White-light scanning interferometry phase-shifting algorithm Linear least-squares fitting Local linear condition.

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Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

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Chinese Physics B 2014年第4期23卷 324-329页

作者：张万祯陈浙泊夏彬峰林斌曹向群 State Key Laboratory of Modern Optical Instrumentation CNERC for Optical Instruments Zhejiang University Hangzhou Dianzi University

Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.

关键词： structured light profilometry depth measurement phase-shifting algorithm nonlinear effect

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Error compensation of four and five buckets wavefront extraction algorithms in phase-shifting interferometer

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OPTIK 2013年第22期124卷 5624-5627页

作者： Zhu, Mingxin Bai, Fuzhong Gan, Shiming Huang, Kaizheng Huang, Linhai Wang, Jianxin Inner Mongolia Univ Technol Coll Mech Engn Hohhot 010051 Peoples R China Chinese Acad Sci Inst Opt & Elect Lab Adapt Opt Chengdu 610209 Peoples R China Southwest Univ Sci & Technol Coll Sci Mianyang 621010 Peoples R China

The phase-shifting method is all along an important wavefront extraction technique in the interferometer. Moreover, to require almost real-time measurement an algorithm with a small number of grabbed buckets is very helpful to the phase-shifting interferometer. Therefore, those algorithms within five buckets are very practical and are given more attention. In the paper, popular phase shifting algorithms within five buckets are compared and new four and five buckets algorithms are developed to compensate for two dominate error sources which are linear phase shift deviation and detector nonlinearity. Numerical simulations and wavefront extraction experiment verify that the proposed compensation algorithms are insensitive to linear phase shift deviation and detector nonlinearity compared with classical four and five bucket algorithm. (C) 2013 Elsevier GmbH. All rights reserved.

关键词： phase-shifting algorithm phase extraction phase shift deviation Detector nonlinearity

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N-step linear phase-shifting algorithms with optimum signal to noise phase demodulation

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JOURNAL OF MODERN OPTICS 2011年第14期58卷 1278-1284页

作者： Gonzalez, A. Servin, M. Estrada, J. C. Rosu, H. C. Ctr Invest Opt AC Leon 37150 Mexico Inst Potosino Invest Cient & Tecnol IPICYT San Luis Potosi Slp 78216 Mexico

A common way to test an optical wavefront is to use a phase-shifting interferometer along with (for example) a three-step linear phase-shifting algorithm (PSA). The following fundamental question arises: what phase step should be used? Typically, pi/2, 2 pi/3 or pi/3 are used and, in fact, any phase step within the open interval (0, pi) can be employed. In the absence of any measuring noise, all these phase shifts yield the same estimate for the modulating phase. However, which of these phase steps omega(0) is the best to obtain the least noisy phase estimation from a temporal set of three noisy interferograms? Working in frequency space, a general procedure to obtain the optimum phase step omega(0) of a given linear N-step PSA is presented. This general procedure is exemplified for some particular linear PSAs, notably 3-, 5-, 7-, and 27-step PSAs.

关键词： phase-shifting algorithm quadrature filter signal to noise ratio

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Efficient iterative algorithm for phase-shifting interferometry

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OPTICS AND LASERS IN ENGINEERING 2007年第2期45卷 281-292页

作者： Guo, Hongwei Zhao, Zhan Chen, Mingyi Shanghai Univ Lab Appl Opt & Metrol Shanghai 200072 Peoples R China

This paper presents an efficient iterative least-squares algorithm for phase-shifting interferometry. If the phase shifts contain errors, the residuals (i.e. the differences between the recorded intensities and their recalculated values) of least-squares algorithm are dependent on these errors. Based on this fact, an approach that allows estimating the phase shift errors from these residuals is derived. Using the results, the values of phase shifts are corrected. By iterating the two steps: phase evaluation and phase shift correction, the phase distribution can be accurately reconstructed. Its validity and performances have been investigated by both the numerical simulation and experiment results. The convergence condition with this algorithm is also discussed. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： interferometry phase measurement phase-shifting algorithm iterative algorithm

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Nonlinearity correction in digital fringe projection profilometry by using histogram matching technique - art. no. 66162I

Nonlinearity correction in digital fringe projection profilo...

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Conference on Optical Measurement Systems for Industrial Inspection V

作者： Guo, Hongwei Zhao, Zhan Shanghai Univ Dept Precis Mech Engn Lab Appl Opt & Metrol Shanghai 200072 Peoples R China

ISBN: (纸本)9780819467584

Digital fringe projection profilometry employs a digital video projector as a structured light source and thus gains great flexibility. However, the luminance nonlinearity of the video projector may decrease measurement accuracy and resolution. To overcome this problem, we propose a nonlinearity correction technique for digital fringe projection profilometry. This technique allows determining the response curve of a digital video projector by matching the histogram of the fringe images with that of a standard sinusoid signal. By iterating the two steps, histogram matching and phase evaluation, the phase distribution of the fringe pattern is finally solved with higher accuracy. In so doing, neither photometric calibration nor knowledge about the device is required. Both computer simulation and experiment are carried out to demonstrate the validity of this technique.

关键词： fringe projection profilometry phase measurement phase-shifting algorithm nonlinearity correction

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Real-time multi-camera system for measurement of 3D coordinates by pattern projection - art. no. 66160A

Real-time multi-camera system for measurement of 3D coordina...

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Conference on Optical Measurement Systems for Industrial Inspection V

作者： Sainov, Ventseslav Stoykova, Elena Hanizanova, Jana Bulgarian Acad Sci Cent Lab Opt Storage & Proc Informat BU-1113 Sofia Bulgaria

ISBN: (纸本)9780819467584

The report describes a real-time pattern-projection system for measurement of 3D coordinates with simultaneous illumination and recording of four phase-shifted fringe patterns which are projected at four different wavelengths and captured by four synchronized CCD cameras. This technical solution overcomes the main drawback of the temporal phase-shifting profilometry in which the pattern acquisition is made successively in time. The work considers the use of a sinusoidal phase grating as a projection element which is made by analysis of the frequency content of the projected fringes in the Fresnel diffraction zone and by test measurements of relative 3D coordinates that are performed with interferometrically recorded sinusoidal phase gratings on holographic plates. Finally, operation of a four-wavelength profilometric system with four spatially phase-shifted at pi/2 sinusoidal phase gratings illuminated with four diode lasers at wavelengths 790 nm, 810 nm, 850 nm and 910 nm is simulated and the systematical error of the profilometric measurement is evaluated.

关键词： pattern projection profilometry gratings phase-shifting algorithm

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Full-field optical coherence tomography by achromatic phase shifter with a rotating half-wave plate

Full-field optical coherence tomography by achromatic phase ...

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5th International Conference on Photonics and Imaging in Biology and Medicine

作者： Yang, Yaliang Ding, Zhihua Zhejiang Univ State Key Lab Modern Opt Instrumentat Hangzhou 310027 Peoples R China

ISBN: (纸本)9780819466563

In optical coherence tomography (OCT), broad-bandwidth optical sources are required to achieve high axial resolution. Introducing a variable phase shift achromatically between the probe and reference beams is required for phase-shifting algorithms implemented to extract the coherence signal. We propose a full-field OCT using an achromatic phase shifter based on wave plates. The phase shifter that is almost independent of the wavelength over a range of 240 nm, can provide a phase shift of eight times the rotating angle of the half-wave plate. The system is based on a Michelson interferometer, illuminated by a white light source, and has several advantages compared with previous implementation of full-field OCT based an achromatic phase shifter. Numerical simulation on phase shift error and amplitude ratio between orthogonal polarization components at nominal phase shifts required for two typical phase-stepping algorithms is conducted. Approach for extracting OCT signal by the revised Carre algorithm is presented.

关键词： optical coherence tomography (OCT) full-field OCT achromatic phase shifter phase-shifting algorithm

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500-mm-aperture wavelength-tuning phase-shifting interferometer

500-mm-aperture wavelength-tuning phase-shifting interferome...

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2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies

作者： Chai, LQ Xu, Q Deng, Y Cheng, GP Xu, JC Shi, QK Fine Opt Engn Res Ctr Chengdu Peoples R China

ISBN: (纸本)081946189X

phase-shifting interferometer (PSI) can be used to accurately determine the phase differences and the corresponding profile of the measurement surface([1]). Using PZT(piezoelectric transducer) to translate reference plane for the realization of phase shift have been commonly employed in commercial interferometer. However, moving a large TF(transmission reference flat) which weighs dozens of kilogram with PZT actuators smoothly along the optical axis introduces considerable challenges and increases the difficulty of the system design. Wavelength-tuning phase-shifting([2][3]) is a quasi-soft technique and can be realized by changing the laser wavelength. No parts in the interferometer are needed to be moved in the phase-shifting process. All of these contribute the advantages of the technique, such as good applicability in large size interferometer system, fast response, expanded application in the simultaneous measurement of the multiple surface of the transparent plates([4,5]). However, The technique also has its own problems, such as necessary recalibration of the phase shift at every measurement and accuracy and repeatability of system is related to characteristics of tunable laser diode.

关键词： interferometer wavelength-tuning phase-shifting algorithm

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500-mm-aperture wavelength-tuning phase-shifting interferometer

500-mm-aperture wavelength-tuning phase-shifting interferome...

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Conference on Optical Measurement Systems for Industrial Inspection IV

作者： Chai, LQ Xu, Q Yu, YJ Deng, Y Xu, JC Fine Opt Engn Res Ctr Chengdu Peoples R China

ISBN: (纸本)0819458562

A 500-mm-aperture wavelength-tuning phase-shifting interferometer has been developed in FOERC applied to the measurement of large optics. Also it can switches to a smaller 130-mm-aperture. We describes in detail the optical and mechanical design as well as calibration technique of phase shifter and phase-shifting algorithm design. A Zygo 4 inch standard reflective flat is used to evaluate the accuracy and repeatability of our wavelength-tuning phase-shifting system.

关键词： interferometer wavelenth-tuning phase-shifting algorithm

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