The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Anh Kiet Tieu - One of the best experts on this subject based on the ideXlab platform.
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Comprehensive influence of In-Plane Displacement, double-aperture orientation and wedge-shearing direction on slope fringe formation in speckle shearing interferometry
Journal of Modern Optics, 2003Co-Authors: K.f. Wang, Anh Kiet TieuAbstract:The comprehensive influence of the In-Plane Displacement, double-aperture orientation and wedge-shearing direction on the slope fringe formation in speckle shearing interferometry is discussed in this paper. The results show that the two In-Plane Displacement components have an influence on the slope fringe formation and that the double-aperture orientation and wedge-shearing direction also have an important influence on the slope fringe formation. A theoretical analysis and experimental results are given. The experimental results are in good agreement with the theoretical analysis.
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Influence of In-Plane Displacement on slope fringe formation in electronic speckle shearing interferometry
Optics Communications, 2003Co-Authors: K.f. Wang, Anh Kiet TieuAbstract:The influence of In-Plane Displacement on slope fringe formation in electronic speckle shearing interferometry is discussed in this paper. It is shown that the In-Plane Displacement has an influence on slope fringe formation in electronic speckle shearing interferometry and that the influence is increased when the In-Plane Displacement is increased. In addition, it is shown that the object-to-wedge distance also has an important influence on slope fringe formation in existence of an In-Plane Displacement and that the influence is increased when the object-to-wedge distance is decreased. Theoretical contours and experimental fringes are presented. And experimental results are in good agreement with theoretical results.
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Influence of shearing direction on slope fringe distributions in the presence of In-Plane Displacement and strain components in double-aperture speckle shearing interferometry
Optics Communications, 2000Co-Authors: Kangni Wang, Anh Kiet TieuAbstract:The influence of shearing direction on slope (first-order derivative of out-of-plane Displacement component) fringe distributions in the presence of In-Plane Displacement and strain components in double-aperture speckle shearing interferometry is discussed in detail. The research results show: (1) only In-Plane Displacement component parallel to the centre line of double apertures influences slope fringe distributions; (2) In-Plane strain components have no influence on slope fringe distributions if utilising normal illumination and an axisymmetric system; and (3) shearing direction has an important influence on slope fringe distributions in the presence of In-Plane Displacement and strain components. Theoretical analysis and experimental demonstrations are given. The experimental results are in good agreement with the quantitative analysis.
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Influence of In-Plane Displacement and strain components on slope fringe distributions in double-aperture speckle wedge-shearing interferometry
Optics and Laser Technology, 1999Co-Authors: Kaif. U. F. Wang, Anh Kiet Tieu, Enbang LiAbstract:Abstract The influence of In-Plane Displacement and strain components on slope (first-order derivative of out-of-plane Displacement component) fringe distributions in double-aperture speckle wedge-shearing interferometry is discussed in detail. The research results show that only the In-Plane Displacement component parallel to the centre line of double apertures has an influence on the slope fringe distributions. It is also shown that the In-Plane strain components have no influence on the slope fringe distributions when utilising normal illumination and an axisymmetric system. A theoretical analysis and an experimental demonstration are given. The experimental results are in good agreement with the quantitative analysis.
Shunsuke Yokozeki - One of the best experts on this subject based on the ideXlab platform.
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In-Plane Displacement measurement using electronic-speckle-pattern-interferometry-based on spatial fringe analysis method
Optical Engineering, 2004Co-Authors: Yasuhiko Arai, Shunsuke YokozekiAbstract:Speckle interferometry is used to measure the deformation of an object with a rough surface. In particular, the precise measurement can be easily performed with electronic-speckle-pattern interferometry (ESPI) using fringe scanning technology. Then, the measurement accuracy is influenced by the ratio between the speckle size and the pixel size of a CCD. Sometimes, this causes a problem concerning optical dislocations. An In-Plane Displacement is measured by the optical measurement arrangement using the two collimated beams. The measurement is performed by ESPI technology with the spatial fringe analysis method under an optimal measurement condition. Then, the optimum condition is discussed as the measurement parameters concerning the speckle's size and the passband of the bandpass filter. In the experimental measurement of In-Plane Displacement, it is shown that the optimal measurement condition can evade the problem of optical dislocations. At the same time, it is confirmed that a precise measurement can be performed.
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In-Plane Displacement measurement using ESPI based on spatial fringe analysis method
Interferometry XI: Applications, 2002Co-Authors: Yasuhiko Arai, Shunsuke YokozekiAbstract:The speckle interferometry is used to measure the shape of an object with a rough surface. In particular, the precise measurement can be easily performed with ESPI using fringe scanning technology. Then, the measurement accuracy is influenced with the ratio between the speckle size and the pixel size of a CCD. Sometimes, this causes the problem concerning an optical dislocation. In this paper, an In-Plane Displacement is measured by the arrangement using the two collimated beams. The measurement is performed by ESPI technology with the spatial fringe analysis method under the optimal condition. The condition is discussed as the measurement parameters concerning the speckle's size and the passband of band pass filter. In the experiment of the measurement of In-Plane Displacement, the optimal condition can evade the problem of occurrence of optical Displacements. At the same time, the precise measurement can be performed.
Michel Grediac - One of the best experts on this subject based on the ideXlab platform.
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Comparing several spectral methods used to extract Displacement fields from checkerboard images
Optics and Lasers in Engineering, 2020Co-Authors: Michel Grediac, Benoit Blaysat, Frédéric SurAbstract:Checkerboard represents the best pattern for In-Plane Displacement measurement in terms of sensor noise propagation because this pattern maximizes image gradient. It also exhibits other interesting properties in terms of pattern-induced bias for instance. Digital Image Correlation (DIC) is not the best option to extract Displacement fields from such periodic patterns, and spectral methods should be used instead. In this paper, it is shown that three different spectral techniques initially developed for classic bidimensional grids can be adapted to process checkerboard images. These three techniques are the Geometric Phase Analysis (GPA), the windowed version of the Geometric Phase Analysis (WGPA), and the Localized Spectrum Analysis (LSA), which can be regarded as the ultimate version of WGPA. The main features of these three techniques as well as the link between them are given in this paper. Their metrological performance are compared in terms of Displacement resolution, spatial resolution and bias. Synthetic checkerboard images deformed with a suitable reference Displacement field are considered for this purpose. It is shown that GPA is the fastest method. According to the metric used in this paper, the best metrological performance is obtained with WGPA with suitable settings. LSA followed by a deconvolution algorithm is just behind, but the calculation time is approximately 10 times lower than that of WGPA for the examples considered in this paper, which makes it a reasonable choice for the determination of In-Plane Displacement fields from checkerboard images.
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the grid method for in plane Displacement and strain measurement a review and analysis
Strain, 2016Co-Authors: Michel Grediac, Benoit BlaysatAbstract:The grid method is a technique suitable for the measurement of In-Plane Displacement and strain components on specimens undergoing a small deformation. It relies on a regular marking of the surfaces under investigation. Various techniques are proposed in the literature to retrieve these sought quantities from images of regular markings, but recent advances show that techniques developed initially to process fringe patterns lead to the best results. The grid method features a good compromise between measurement resolution and spatial resolution, thus making it an efficient tool to characterise strain gradients. Another advantage of this technique is the ability to establish closed-form expressions between its main metrological characteristics, thus enabling to predict them within certain limits. In this context, the objective of this paper is to give the state of the art in the grid method, the information being currently spread out in the literature. We propose first to recall various techniques that were used in the past to process grid images, to focus progressively on the one that is the most used in recent examples: the windowed Fourier transform. From a practical point of view, surfaces under investigation must be marked with grids, so the techniques available to mark specimens with grids are presented. Then we gather the information available in the recent literature to synthesise the connection between three important characteristics of full-field measurement techniques: the spatial resolution, the measurement resolution and the measurement bias. Some practical information is then offered to help the readers who discover this technique to start using it. In particular, programmes used here to process the grid images are offered to the readers on a dedicated website. We finally present some recent examples available in the literature to highlight the effectiveness of the grid method for In-Plane Displacement and strain measurement in real situations.
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towards deconvolution to enhance the grid method for in plane strain measurement
Inverse Problems and Imaging, 2014Co-Authors: Michel GrediacAbstract:The grid method is one of the techniques available to measure In-Plane Displacement and strain components on a deformed material. A periodic grid is first transferred on the specimen surface, and images of the grid are compared before and after deformation. Windowed Fourier analysis-based techniques permit to estimate the In-Plane Displacement and strain maps. The aim of this article is to give a precise analysis of this estimation process. It is shown that the retrieved Displacement and strain maps are actually a tight approximation of the convolution of the actual Displacements and strains with the analysis window. The effect of digital image noise on the retrieved quantities is also characterized and it is proved that the resulting noise can be approximated by a stationary spatially correlated noise. These results are of utmost importance to enhance the metrological performance of the grid method, as shown in a separate article.
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Towards deconvolution to enhance the grid method for In-Plane strain measurement
2012Co-Authors: Frédéric Sur, Michel GrediacAbstract:The grid method is one of the available techniques to measure In-Plane Displacement and strain components on a deformed material. A periodic grid is first transferred on the specimen surface, and then images of the grid are compared before and after deformation. Windowed Fourier analysis-based techniques then permits to estimate the In-Plane Displacement maps and the strain components. In this report, we give a precise analysis of this estimation process. We show that the retrieved Displacement maps and strain components are actually a tight approximation of the convolution of the actual Displacements and strains with the analysis window. We also characterize the effect of digital image noise on the retrieved quantities and we prove that the resulting noise can be approximated by a stationary spatially correlated noise. These results are of utmost importance to enhance the metrological performance of the grid method, as shown in a separate report.
Frédéric Sur - One of the best experts on this subject based on the ideXlab platform.
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Comparing several spectral methods used to extract Displacement fields from checkerboard images
Optics and Lasers in Engineering, 2020Co-Authors: Michel Grediac, Benoit Blaysat, Frédéric SurAbstract:Checkerboard represents the best pattern for In-Plane Displacement measurement in terms of sensor noise propagation because this pattern maximizes image gradient. It also exhibits other interesting properties in terms of pattern-induced bias for instance. Digital Image Correlation (DIC) is not the best option to extract Displacement fields from such periodic patterns, and spectral methods should be used instead. In this paper, it is shown that three different spectral techniques initially developed for classic bidimensional grids can be adapted to process checkerboard images. These three techniques are the Geometric Phase Analysis (GPA), the windowed version of the Geometric Phase Analysis (WGPA), and the Localized Spectrum Analysis (LSA), which can be regarded as the ultimate version of WGPA. The main features of these three techniques as well as the link between them are given in this paper. Their metrological performance are compared in terms of Displacement resolution, spatial resolution and bias. Synthetic checkerboard images deformed with a suitable reference Displacement field are considered for this purpose. It is shown that GPA is the fastest method. According to the metric used in this paper, the best metrological performance is obtained with WGPA with suitable settings. LSA followed by a deconvolution algorithm is just behind, but the calculation time is approximately 10 times lower than that of WGPA for the examples considered in this paper, which makes it a reasonable choice for the determination of In-Plane Displacement fields from checkerboard images.
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Towards deconvolution to enhance the grid method for In-Plane strain measurement
2012Co-Authors: Frédéric Sur, Michel GrediacAbstract:The grid method is one of the available techniques to measure In-Plane Displacement and strain components on a deformed material. A periodic grid is first transferred on the specimen surface, and then images of the grid are compared before and after deformation. Windowed Fourier analysis-based techniques then permits to estimate the In-Plane Displacement maps and the strain components. In this report, we give a precise analysis of this estimation process. We show that the retrieved Displacement maps and strain components are actually a tight approximation of the convolution of the actual Displacements and strains with the analysis window. We also characterize the effect of digital image noise on the retrieved quantities and we prove that the resulting noise can be approximated by a stationary spatially correlated noise. These results are of utmost importance to enhance the metrological performance of the grid method, as shown in a separate report.
Yushan Tan - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous measurement of whole In-Plane Displacement using phase-shifting ESPI
Optics and Lasers in Engineering, 1997Co-Authors: Hua Fan, Jun Wang, Yushan TanAbstract:Abstract A novel method for simultaneously measuring whole field In-Plane Displacements by using optical fiber phase-shifting electronic speckle pattern interferometry (ESPI) is presented in this paper. A 1 × 4 single mode optical fiber beamsplitter is employed to split the laser beam into four beams of equal intensity. One pair of fibers is utilized to illuminate the diffuse target at equal angles in the horizontal plane so it is sensitive only to horizontal In-Plane Displacement. Another pair of optical fibers is set to be sensitive only to vertical In-Plane Displacement. The polarization directions of light emitted by fibers are the same for each pair, but are at a right angle between pairs. The optical fibers are equal in length for each pair, but are not equal between two pairs. In this case the speckles are interference between each pair of fibers, thus the horizontal and vertical Displacement components can be obtained simultaneously. By means of a fiber phase shift technique we can obtain the quantitative data of whole field Displacements. This method has made it possible to study the In-Plane Displacement of a thin metal plate, and the examples of the results are shown to demonstrate the novel method.
