Showing papers on "Moiré pattern published in 1969"
TL;DR: The appearance of circular Moiré fringes when a random dot pattern is superimposed on itself provides new evidence that the human visual process may include the computation of local autocorrelations by excitation of line detectors.
Abstract: The appearance of circular Moire fringes when a random dot pattern is superimposed on itself provides new evidence that the human visual process may include the computation of local autocorrelations by excitation of line detectors.
482 citations
TL;DR: A moiré technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects, useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.
Abstract: This paper describes a moire technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects. A grid pattern is generated on the object by illuminating it with a laser interference pattern, and a master negative is made by photographing the illuminated object with a view camera. With the negative occupying its original position, the moire pattern corresponding to changes in the object can be observed in real time by viewing the image of the deformed or second object through the negative. The technique is noncontacting and quantitative. It is useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.
105 citations
Patent•
21 Jan 1969
TL;DR: In this article, a technique for observing and measuring the contour of a surface with moire optical interference patterns was proposed, which can be viewed as contour lines appearing on the surface and representing actual regions of equal elevation of the surface contour.
Abstract: A technique for observing and measuring the contour of a surface with moire optical interference patterns. Illumination diverging from a source passes through a periodically repetitive image structure to cast a shadow image of such structure onto a surface being examined. The surface and the shadow image cast thereon are viewed through a periodically repetitive image structure to establish moire interference patterns. These moire interference patterns can be viewed as contour lines appearing on the surface and representing actual regions of equal elevation of the surface contour, and the actual increments of elevation between adjacent moire fringes can be determined.
49 citations
49 citations
TL;DR: Characteristics of the moiré pattern and hence its reconstructed ghost images are so tabulated that visualization is made easier, and theoretical predictions show perfect agreement.
Abstract: The moire pattern resulting from superposition of two zone plates is analyzed in a general manner. Characteristics of the moire pattern and hence its reconstructed ghost images are so tabulated that visualization is made easier. Experiments are performed to substantiate the theoretical predictions, and their results show perfect agreement.
21 citations
TL;DR: In this paper, it was shown that the maximum number of fringes that can be observed for a given model is independent of the gratings utilized and depend only on the geometry of the employed optical system.
Abstract: Two principal problems associated with the practical application of moire fringes are to obtain sufficient sensitivity for measuring small strains and to develop a simple and inexpensive technique for engraving lines on the surface of a model. This paper deals with simple solutions to both problems. It is shown that the maximum number of fringes that can be observed for a given model is independent of the gratings utilized and depend only on the geometry of the employed optical system. Examples of moire patterns corresponding to the equivalent of 6000 lines per inch and patterns of the derivatives of the displacements corresponding to the same number of lines illustrate the paper.
19 citations
09 Dec 1969
TL;DR: The proposed data retrieving and data processing technique increases both the sensitivity and the accuracy of the moire and photoelasticity and extends its applicability to the ranges of interest of practically all engineering materials.
Abstract: It is shown that the light intensity distribution in the image plane of an optical system producing a moire patterns the relevant information is the phase angle. The above described analysis forms the basis of a method for data retrieval. The intensity of light distribution on a pattern is recorded in the form of density changes in a photographic film negative. The changes of density are then retrieved by a light sensor. If one analyzes the density record, one can see that the trace is not only modulated by the relevant quantities but also by various other processes. Furthermore the effect of the nonlinear characteristic curve of the recording film is to generate for each narrow-band componet of the signal, an infinite number of narrow-band high order components of the fundamental argument. To eliminate the effect of unwanted componets, of the fundamental or the effect of unwanted comonents, the digitalized vision of the signal is filtered by numerical narrow-band pass filters in-quadrature. The computer program gives the strains in the case of moire patterns and relative retardations in the case of photoelasticity. The given examples of application show that the proposed data retrieving and data processing technique increases both the sensitivity and the accuracy of the moire and photoelasticity. This result is of great practical value particularly in the moire method since it extends its applicability to the ranges of interest of practically all engineering materials.© (1969) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
16 citations
TL;DR: In this article, the general equations of the moire patterns from a surface of known topography are given in both cases for the first time and confirmed by experiment, from the experimental shape and spacing of the Moire patterns of an unknown surface, the topography of the unknown surface can be deduced.
Abstract: A viewing grid with equally spaced parallel lines (parallel to the y axis) combines with its mirror image or its shadow on the surface to form moire patterns. Under the condition that the x-coordinate distance of the eye is much larger than the width of the viewing grid, the moire patterns approximate to the equal-elevation lines of the surface. The general equations of the moire patterns from a surface of known topography are given in both cases for the first time and are confirmed by experiment. On the other hand, from the experimental shape and spacing of the moire patterns of an unknown surface, the topography of the unknown surface can be deduced.
6 citations
TL;DR: In this paper, a simple method for measurement of wavelength and decay of travelling waves on the surface of transparent liquids is described, where light transmitted through a fixed line grating is deviated by the wave-carrying surface, producing a distorted image of the grating.
4 citations
TL;DR: In this paper, an experiment was carried out on the intensity distributions resulting from the superposition of the images formed in the direction of each resultant order to the diffraction and optical interference pattern of a plane amplitude grating viewing a set of slits lying in a parallel plane.
Abstract: An experiment was carried out on the intensity distributions resulting from the superposition of the images formed in the direction of each resultant order to the diffraction and optical interference pattern of a plane amplitude grating viewing a set of slits lying in a parallel plane. The experiment demonstrated the causes of blurring of the moire fringes formed by two gratings separated by an air gap. From experiments conducted with pairs of identical amplitude gratings the blurring of spatial moire fringes is demonstrated by microdensity tracings. It was found that the optical effects did not affect the interfringe spacing of the fringes.
1 citations