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Moiré pattern

About: Moiré pattern is a research topic. Over the lifetime, 1917 publications have been published within this topic receiving 27176 citations. The topic is also known as: moiré fringes & moire pattern.


Papers
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Journal ArticleDOI
TL;DR: A Talbot-Lau interferometer using two-dimensional gratings and a conventional x-ray tube has been used to investigate a phase-contrast imaging technique that is sensitive to phase gradients in two orthogonal directions and found that the choice of phase retrieval method made little difference in image blur.
Abstract: A Talbot–Lau interferometer using two-dimensional gratings and a conventional x-ray tube has been used to investigate a phase-contrast imaging technique that is sensitive to phase gradients in two orthogonal directions. Fourier analysis of Moire fringe patterns was introduced to obtain differential phase images and scattering images from a single exposure. Two-dimensional structures of plastic phantoms and characteristic features of soft tissue were clearly obtained at 17.5 keV. The phase-stepping technique was also examined to investigate the spatial resolution of different phase retrieval methods. In the presented setup we found that the choice of phase retrieval method made little difference in image blur, and a large effective source size was found to give a high intensity in the image plane.

71 citations

Journal ArticleDOI
TL;DR: In this paper, the phase distribution of moire fringes can be analyzed from a single grating image by simultaneously performing down-sampling image processing and intensity-interpolation to generate multiple phase-shifted moire fringe images.
Abstract: Measuring accurate displacement distributions for large-scale structures is an important issue and a very challenging task. Recently, a simple and accurate phase measurement technique called sampling moire method [Exp Mech 50–4:501–508, (2010)] has been developed for small-displacement distribution measurements. In this method, the phase distribution of moire fringes can be analyzed from a single grating image by simultaneously performing down-sampling image processing and intensity-interpolation to generate multiple phase-shifted moire fringe images. In addition, the phase of the original grating can also be obtained from the phase of the moire fringe by adding the phase of the sampling grating. In this study, the measurement accuracy of the sampling moire method was analyzed through computer simulations and a displacement measurement experiment. Four factors of the sampling moire method were investigated, including the sampling pitch, the order of the intensity-interpolation, random noise, and the form of grating. The results show that determining the optimal sampling pitch is an important factor for obtaining better results but it is not critical. In addition, a practical application of the sampling moire method is presented that involves a deflection measurement on a 10-meter-long crane. The experimental results demonstrate that submillimeter deflections of the crane can be successfully detected.

69 citations

Proceedings ArticleDOI
01 Mar 1974
Abstract: A camera having a lens with two apertures and equipped with a shearing mechanism is employed to image a specimen which is illuminated by coherent light. With this arrangement, the speckle from one point on the surface is allowed to interfere with the speckle from a neighboring point so that a speckle-grid pattern may be detected in the image plane. By double-exposure or real-time techniques, the speckle-grid pattern corresponding to the deformed state of the specimen is added to the speckle-grid pattern corresponding to the undeformed state of the specimen. The resulting mechanical interference produces a moire-fringe pattern which depicts derivatives of surface-displacements. The camera will be referred to as "Speckle-shearing Interferometric Camera". Three applications of the speckle-shearing interferometric camera are described: (1) mea-surement of slopes of structural deflections, (2) in-plane strain measurement, (3) vibration analy-sis. Experimental demonstrations for each case of the applications are presented. Although the speckle-shearing interferometric camera is based on interferometric principles, it overcomes several of the limitations associated with holographic and speckle interferometries, namely: (1) the setup is simple and does not re-quire laborous alignment of optical components, (2) it does not require stringent mechanical and ambient atmospheric stabilities, (3) coherent requirements of light are greatly relaxed, (4) the sensitivity is greatly reduced, and (5) it does not require differentiation to obtain strains.© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

69 citations

Patent
23 Oct 1989
TL;DR: In this article, a printed image (It4) is produced with halftone images for respective color printers while so-called rosette moire and a color shift from an original image are prevented.
Abstract: OF THE DISCLOSURE A printed image (It4) is produced with halftone images for respective color printers while so-called rosette moire and a color shift from an original image are prevented. Halftone dots (Hm4, Hc4, Hk4) linear shapes extending in respective prescribed directions, thereby forming parallel lines with respective intervals (dm4, dc4, dk4). These extensional directions and intervals of parallel lines are so established that they effectively prevent the rosette moire and the color shift.

68 citations

Journal ArticleDOI
TL;DR: The design and operation of the phase-locked moire contouring system, which permits a more favorable trade-off between accuracy and working depth, are described and the results of measurements made with the instrument are presented.
Abstract: Phase-locked moire systems have the advantage of rapid data acquisition and accuracy of better than one twentieth of the fringe spacing. In conventional moire systems data acquisition is performed by making a photographic plate and taking measurements from the plate either visually or with a microdensitometer. This is slow, and the accuracy is about one-quarter of the fringe spacing. The phase-locked system is more accurate and permits a more favorable trade-off between accuracy and working depth. The equations governing moire contouring are examined, and the theory of phase-locked moire fringe analysis is presented. The design and operation of the phase-locked moire contouring system are described, and the results of measurements made with the instrument are presented.

67 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023181
2022321
202126
202048
201946
201844