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.

A position sensor based on grating projection with spatial filtering and polarization modulation

Abstract: A position sensor based on grating projection with spatial filtering and polarization modulation is presented A grating is projected onto the object to be measured through a 4f optical system with a spatial filter After reflected by the object, the grating projection is imaged on a detection grating through another 4f optical system to form moire fringes The polarization modulated moire signal is detected to obtain the position information of the object In the position sensor, the moire signal varies sinusoidally with the position of object The measurement is independent of the incident intensity on the projection grating and the reflectivity of the object to be measured In experiments, the effectiveness of the position sensor is proved, and the root mean square (RMS) error at each measurement position is less than 13 nm

In-plane motion measurement by using digital sampling moiré method

Abstract: Digital sampling moire (DSM) method is a newly developed vision-based technique that uses the phase information of moire fringes to measure movement of an object. The moire fringes are generated from a sequence of digital images, containing a cosinusoidal grating pattern attached to the object, through down-sampling and interpolation. As the moire fringes can magnify the pattern’s movement, this technique is expected to provide more accurate displacement measurement than the other vision based approaches. In this study, a method combining DSM with monocular videogrammetric technique is proposed to measure in-plane rotation and translation of structures. In this method, images of a two-dimensional (2D) grating pattern attached to a moving structure are acquired and decomposed into two perpendicular gratings through Fourier transform. The DSM method is used to obtain 2D phase distributions of the gratings which provide an estimation of physical coordinates for those points on the grating pattern. A previously developed monocular videogrammetric technique can then be used to obtain the rotation angle and the translation of the grating pattern. The proposed method is validated using both numerical simulation and laboratory tests.

Holographic moire patterns processed by the Fourier transform method

Abstract: Spatial-carrier fringe pattern analysis is a wide-spread technique and has found a lot of applicationsto optical metrology. Introducing spatial- carrier into a holographic moire pattern is also a well-known technique to obtain observable moire fringes. Preprocessing of the holographic moire pattern in- cludes optical or digital Fourier filtering to remove the carrier. The fringe pattern is then processed byusing time-consuming fringe-counting algorithms. The current work presents a new application of theFourier transform method to automated analysis of holographic moire fringe patterns. The method ownsthe advantage of instantaneous determination of both phase functions in the pattern. Investigations are carried out on the frequency restrictions imposed on the phase functions. The technique is demon- strated on computer generated noisy holographic moire patterns. The technique does not complicate theconventional experimental holographic moire arrangement. 1. INTRODUCTIONPrincipal problem in fringe pattern analysis is how to reveal the phase information from a fringepattern by separating it from the background intensity and local contrast variation. One solution to

Animation et migration : la mémoire autobiographique diasporique dans les documentaires animés

Abstract: Cet article présente le rapport entre animation et migration par le biais d’un corpus sélectionné de documentaires animés autobiographiques francophones réalisés par des sujets diasporiques. L’auteur montre comment l’animation est un langage particulièrement efficace dans la représentation des récits migratoires et de la mémoire autobiographique diasporique, à travers l’identification de certaines fonctions principales, telles que l’hybridation de la forme, l’exaltation de l’imagination subjective, la juxtaposition et la reconstruction de l’absence.

Stereometric Analysis Of The Human Body And Articular Surfaces

Abstract: In this paper we introduce the method of Moir4 contourography to measure human body and animal's articular facies and teeth. The animal facies of articulation is rather compli­ cated. We haven't seen an expression of a complete mathrnatic formula yet. Hence, we adopt Moire contourography to express three dimensions of animal's articular facies.1We show here also the characteristic equation of Moire contourography of irradiation grating, and the relationship of the contour Moire frings and influence coefficients. So it is very useful to measure errors. Then we introduce some of our research on animal's arti­ culation surface and teeth.introductionMoire is an old expression. It means the fabric, especially silk having wavy patterns. It was first used in Europe to describe the fiqure on silk imported from ancient China. But now in technic Moire is generally meant to show the interference fringes which are created by the superposition of two black-white liner gratings. One of these gratings is to^be dis­ torted by an object whose deformation of shape is represented by the resulting Moire fring­ es. Here we shall discuss method whose primary purpos is used to measure the out-of-plane shape of object.We also use two gratings, one as a reference and another for specimen. But specimen grating is not a separate one, rather it is the shadow of the reference grating as cast on the object surface. The specimen grating will be distorted by the out side of plane form of the surface. When they are viewed together with the reference grating by a camera, Moire fringes are created which represent the topology of the surface.^Examine lumbar vertebrae of human bodyMoire contourography is non-contact measurements which can measure three dimensional ob­ jects and rough surfaces. The Moire contourography is not a new measurement method but it was used on human body's examination since 1970 by H. Takasaki.2 Since then many studies have published about application of Moire contourography to examine three dimension of hu­ man body and K. Ashizawa applied it in human trunk and researches on measure errors,3Application of Moire contourography is not only the optical system which can be easily used but it is also the illumination of light which is not harmful to human. It dosn't like x-ray, so it has further development of usage.4 We have shown one of our experiments to examine lumbar vertebrae of human body.sThere are two kinds of grating, one is the grating irradiation type, the other is the grating projection type. The grating irradiation type always measures small objects, the grating projection may be used to measure big objects. But both of the two kinds of grating can examine lumbar vertebrae of human body.Characteristic equation of Moir^ contourography of irradiation gratingFor obtaining the Moire contour lines we always use two kinds of optical systems, one is the parrallel illumination and parrallel receiving. If the object is small enough and the camera is at approximation it can be achieved.The assumption of the camera being at infinity is not a practical one, so it limits the method to small models only. The other system is the point illumination and point receiving.The principle of the grating irradiation type of Moire contourography for point illumunation and point receiving optical system is that both light source and the camera are assumed at a finite distance away from object. Both the light source and the camera lens focal points are located at the same distance away from the grating plane. The re­ ference grating configuation is a transmission section placed immediately before the ob­ ject. The vertical distance from the grating plane to Moire stripe degree of the object is given by