Topic
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.
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TL;DR: In this paper, a technique was developed to reproduce a crossed model grating of a density of 500 lines/in. on the surface of the specimens in both principal directions, which yielded the displacement distribution of the specimen with great accuracy.
Abstract: The differential moire method was used for the analysis of strains and stresses in externally loaded bodies at elevated temperatures. A technique was developed to reproduce a crossed grating of a density of 500 lines/in. on the surface of the specimens in both principal directions. This grating resisted temperatures up to the glowing point of the material tested. An arrangement of cameras allowed full-scale copying of the crossed model grating on the ground glass of a camera. Mechanical-interference patterns in both directions were obtained by superimposing various linear reference gratings on the image of the model grating. The moire fringes produced in both principal directions of the specimen with reference gratings of slightly different pitch were photographed by a second camera. These fringes yielded the displacement distribution of the specimen with great accuracy.
30 citations
TL;DR: In this paper, the Moire pattern is interpreted as function of displacements, from which strains in Lagrangian and Eulerian descriptions are determined, and formulas for determining strains in 2D models are given.
Abstract: Application of moire fringes in determination of strains in 2-dimensional models; Moire pattern is interpreted here as function of displacements, from which strains in Lagrangian and Eulerian descriptions are determined; formulas given.
30 citations
TL;DR: In this paper, a theory on the formation of moire patterns by mutually interfering radial gratings is developed, and it is shown that the moire fringes formed inside the circle, which has as diameter the centre-to-centre distance of the gratings, belong to the additive moire type and they represent families of confocal equilateral hyperbolae.
Abstract: A theory on the formation of moire patterns by mutually interfering radial gratings is developed. It is shown that the moire fringes formed inside the circle, which has as diameter the centre-to-centre distance of the gratings, belong to the additive moire type and they represent families of confocal equilateral hyperbolae. Outside this circle the subtractive moire pattern is valid, which consists of circles of different radii whose centres lie on the perpendicular bisector of the centre-to-centre distance. For the radial grating moire gauge the additive moire pattern is of importance since two sectors of radial gratings are used with a large centre-to-centre distance. The radial gauge is convenient for determining the normal components of strains. The advantage of this type of gauge over the line grating gauge is that the radial grating corresponds to an infinite number of line gratings of progressively varying pitch. This allows a correct evaluation of displacement and strain at a suitably selected gauge length.
29 citations
TL;DR: In this article, the effect of diffraction on the transmission pattern of an infinite Ronchi grid and the moire image of two equal Ronchi grids was studied, at a wide range of conditions.
Abstract: The effect of diffraction on the transmission pattern of an infinite Ronchi grid and the moire image of two equal Ronchi grids was studied. Transmission patterns and moire images of two equal Ronchi grids with and without a phase object, at a wide range of conditions, are presented. Diffractional phenomena were found to affect the transmission pattern and the moire image significantly. In order to minimize their effect, the distance between the grids must be exactly one of the Fourier-image planes of the grid. The moire image of a given phase object, even under these conditions, has an inherent error that can be precisely calculated. Deflection mapping and the uncertainty (because of diffraction) of lenses were calculated.
29 citations
TL;DR: This work proposes to resolve the freedom in moire synthesis by choosing the images that optimize the chosen criteria based on the visibility of the moire patterns to the human visual system and on the digitization that takes place when the images are presented on discrete displays.
Abstract: Moire phenomena occur when two or more images are nonlinearly combined to create a new superposition image. Moire patterns are patterns that do not exist in any of the original images but appear in the superposition image, for example as the result of a multiplicative superposition rule. The topic of moire pattern synthesis deals with creating images that when superimposed will reveal certain desired moire patterns. Conditions that ensure that a desired moire pattern will be present in the superposition of two images are known; however, they do not specify these images uniquely. The freedom in choosing the superimposed images can be exploited to produce various degrees of visibility and ensure desired properties. Performance criteria for the images that measure when one superposition is better than another are introduced. These criteria are based on the visibility of the moire patterns to the human visual system and on the digitization that takes place when the images are presented on discrete displays. We propose to resolve the freedom in moire synthesis by choosing the images that optimize the chosen criteria.
29 citations