carre ' algorithm is a classic phase shifting measurement method due to its advantage in resisting the error caused by inaccurate phase step. The conventional carre ' algorithm only calculates the wrapped phas...
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carre ' algorithm is a classic phase shifting measurement method due to its advantage in resisting the error caused by inaccurate phase step. The conventional carre ' algorithm only calculates the wrapped phase, so multiple frequencies are used to unwrap the phase so as to obtain the absolute phase, which increases the number of patterns and decreases the measuring speed. We propose a high-accuracy and 4-pattern phase retrieval method based on carre ' algorithm. The phase step in carre ' algorithm is encoded as a linear variable. With the linear phase step, we obtain both the wrapped phase and absolute phase simultaneously from only 4 patterns. The proposed method is non-sensitive to the errors in phase step, the same as the conventional carre ' algorithm. In addition, because only 4 patterns are required for obtaining the wrapped phase and absolute phase, the proposed method is practical in high-speed 3D measurement. Experimental results demonstrate its performance in high accuracy (absolute accuracy is higher than 0.02 mm and relative accuracy is higher than 0.03%), efficiency (requires only 4 patterns) and robustness.
This work proposed a temporal phase-shift digital shearography system for simultaneous measurement of first-order displacement derivative in orthogonal shear directions. Dual lasers with wavelengths of 532 and 637 nm,...
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This work proposed a temporal phase-shift digital shearography system for simultaneous measurement of first-order displacement derivative in orthogonal shear directions. Dual lasers with wavelengths of 532 and 637 nm, three splitter prism structure, two dichroic mirrors with different response wavelengths, and the color complementary metal-oxide-semiconductor are used in the system. Two dichroic mirrors can be used as shear mirrors to realize shearing in orthogonal directions at the same time. The system realizes the measurement of the first-order displacement derivative information in the orthogonal direction of the round metal aluminum plate of diameter 250 mm. The experimental results show that the overall displacement integral peak to valley error in the x and y directions is 2.7% to 14.8%, which verified the reliability of the system. (c) 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)
Dynamic deformation measurement with a large in-plane deformation is performed by using virtual speckle patterns. The virtual speckle pattern has been generally produced by using Fourier technology. However, it takes ...
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ISBN:
(纸本)9780819476708
Dynamic deformation measurement with a large in-plane deformation is performed by using virtual speckle patterns. The virtual speckle pattern has been generally produced by using Fourier technology. However, it takes a long calculating time to produce a virtual speckle pattern under Fourier technology, because the method requires Fourier transform operation at each pixel of CCD. In the proposed method, virtual speckle patterns are produced by carre algorithm without any operation by Fourier transform. As the results, it is confirmed that the calculating cost of virtual speckle patterns is improved remarkably, and that the new method also is almost equal to the ordinary methods in measurement accuracy.
A phase-shifting interferometer with a tunable external-cavity laser diode has been constructed for forming three-dimensional (3-D) phase profiles. The interference phase is shifted equally in four steps by varying th...
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A phase-shifting interferometer with a tunable external-cavity laser diode has been constructed for forming three-dimensional (3-D) phase profiles. The interference phase is shifted equally in four steps by varying the source wavelength. Profilometry is achieved by measuring the phase shifts that are extracted by the carre algorithm. The linear regression of the distance measurement from 40 mu m to 13mm has been experimentally demonstrated by phase-shifting interferometry. A laser-diode interferometer has been applied to 3-D profile measurement for a step-mirror object at a deep depth. (C) 2014 The Japan Society of Applied Physics
The present work offers new algorithms for phase evaluation in optics measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. The algo...
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The present work offers new algorithms for phase evaluation in optics measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. The algorithms are derived similarly to the so called carre algorithm. The idea is to develop a generalization of carre that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty due to its effects can be reduced by increasing the number of observations. The advantages of the proposed algorithm are its precision in the measures taken and immunity to noise in images.
Phase retrieval techniques are powerful tools used in interferometry, fringe projection, and other methods of image and signal analysis. The popular linear phase stepping algorithms combine weighted sums of signal val...
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Phase retrieval techniques are powerful tools used in interferometry, fringe projection, and other methods of image and signal analysis. The popular linear phase stepping algorithms combine weighted sums of signal values to obtain sine and cosine parts of the phase of interest. The coefficients and phase step angles are chosen to minimize the measurement uncertainty due to some experimental influence quantities. While a general treatment of measurement uncertainty for linear phase stepping algorithms has been given elsewhere, in this article a treatment of non-linear, carre-type algorithms is given. We show that such algorithms can be viewed as a geometrical mean of linear phase stepping algorithms, and we express the measurement uncertainty in terms of the measurement uncertainty of an equivalent linear phase-stepping algorithm. Using the general expression for the measurement uncertainty, we show explicitly that the influence of a linear phase step miscalibration is suppressed. (C) 2012 Elsevier Ltd. All rights reserved.
The difficulty of implementing the phase shifting method in shadow moire ties in the fact that the phase shift due to the displacement of the light source, the imaging sensor, or the grating is non-uniform across the ...
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ISBN:
(纸本)9780819472861
The difficulty of implementing the phase shifting method in shadow moire ties in the fact that the phase shift due to the displacement of the light source, the imaging sensor, or the grating is non-uniform across the field of view. Typical phase shifting algorithms fail to produce accurate results. In the past few decades, various approximation methods have been developed to overcome this difficulty. In this paper, we describe an elegant solution that provides exact close-form result. In our proposed system, the grating is translated in equal steps to introduce phase shifts. The phase value at each point is determined by the carre algorithm, which only requires uniform phase shifts for each point, instead of in the whole field of view. The 3-D shape of the object is then reconstructed from the phase map retrieved from the carre algorithm. The simulation results demonstrate the effectiveness of the carre algorithm for shadow moire.
Experimental stress analysis can be conveniently investigated by classical shadow Moire technique. Moire is a non-contact and non-destructive technique, with a fast digitisation process. The phenomena of Moire fringes...
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Experimental stress analysis can be conveniently investigated by classical shadow Moire technique. Moire is a non-contact and non-destructive technique, with a fast digitisation process. The phenomena of Moire fringes are the result of the projection of the fringes of a ruling on a certain object. It has measurement accuracy comparable with other systems and also low cost. The present study offers new algorithms for phase evaluation in measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity signs are proposed. The algorithms are similarly derived as the so-called 'carre algorithm'. The idea is to develop a generalisation of carre algorithm that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty caused by their effects can be reduced by increasing the number of observations. An experimental analysis of the mistakes of the technique was made, as well as a detailed analysis of mistakes of the measurement. The advantages of the proposed algorithm are its precision in the measures taken, speed of processing and the immunity to noise in signs and images.
We demonstrate an electro-optic phase modulator based demodulation system for acoustic frequency modulated optical signals. The system is free from polarisation fading and is capable of retrieving high frequency signa...
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ISBN:
(纸本)9780819472045
We demonstrate an electro-optic phase modulator based demodulation system for acoustic frequency modulated optical signals. The system is free from polarisation fading and is capable of retrieving high frequency signals, ultimately limited by the time of flight of the interferometer itself. Digital interrogation method is based on the carre algorithm and does not require fine tuning of the introduced phase and is suitable for simultaneous phase retrieval at multiple wavelengths without the need for correction transfer filters.
The presented work offers new algorithms for phase evaluation in interferometric measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are propose...
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The presented work offers new algorithms for phase evaluation in interferometric measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. These phase calculation algorithms need to measure five frames of the intensity of the interference field. The algorithms are similarly derived as so called carre algorithm. The phase evaluation process then does not depend on the linear phase shift errors. Furthermore, the detailed analysis of the algorithms with respect to most important factors, which affect interferometric measurements, is carried out. It is also studied the dependency of the evaluation algorithms on the phase shift values, and the proposed phase calculation algorithms are compared with respect to the resulting phase errors. The influence of most important factors in the measurement and evaluation process was simulated as systematic and random errors using a proposed mathematical model.
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