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.

Visual integration of vibrating images in time

Abstract: The ability of the human visual system to integrate a rapidly oscillating image in time is investigated in this paper. A secret image is encoded into a stochastic geometric moire grating. The secret is leaked in the form of a pattern of time-averaged moire fringes when the cover image is oscillated according to a predetermined law of motion. Special encoding algorithms are designed for an effective real-time implementation of the scheme on a digital computer screen. A series of experiments is performed to determine the minimum frequency of oscillations required for the interpretation of the embedded secret image.

Method of measuring physical quantity

Abstract: PURPOSE:To measure physical quantities of an object such as length, angle, distortion, etc. with ease and high accuracy, by confronting one end surfaces of multi-core optical fibers which are spaced a small distance from each other in a movable manner, thereby to observe moire fringes generated at the other end surface of the fiber. CONSTITUTION:In the case where the rotating angles of a flywheel 10 is desired to be measured, an image fiber 2 is fixed to the flywheel 10 while the flywheel 10 is illuminated by a light source 1. Another image fiber 3 is confrontingly provided several mum away from one end surface of the image fiber 2. Many cores are aligned on the end surfaces of the fibers 2 and 3. When the fiber 2 is rotated in parallel to the one end surface of the other fiber 3, moire fringes are formed, which can be observed at the projecting end surface of the fiber 3. Therefore, in the above-described construction, if the flywheel 10 is rotated, the moire fringes at the end surface of the fiber 3 are moved, and accordingly, by measuring the amount of the movement of the moire fringes on a screen of a television monitor 6 or automatically detecting the amount of the movement by an image processor 7, the rotating angles of the flywheel 10 can be measured in a simple arrangement with high accuracy.

Applications of moire techniques in biomedicine (Proceedings Only)

Abstract: An overview of the moire techniques most frequently used for three-dimensional human form measurements is given. The spatial-carrier phase-shifting method for automatic fringe pattern analysis in moire topography is introduced. The multipurpose system for shape determination using both temporal and spatial phase-shifting method is presented.

Design of an optical level using the Talbot effect

Abstract: An optical arrangement for liquid-level measuring is proposed. The method is based on self- imaging or Talbot effect. Knowing the container dimensions of a liquid, it is possible to obtain the volume changes by the liquid variation in the container. The optical arrangement consists in detecting a diffraction field of a Ronchi grating illuminated by a collimated beam. This field is first reflected by the interface liquid-air, afterwards casting on a second Ronchi grating. This superposition produces a Moire pattern when the Talbot plane of the first grating coincides with the second one. If the travelled path of the wavefront is not a Talbot distance, the Moire pattern is lost. In this way, it is necessary to move the second grating up to see the sharper Moire fringes. The grating change gives directly the level change. Description of the experimental setup and results are shown. Strengths and weaknesses of the method are presented. The future lines of work are given in order to have an automatic and compact instrument.

Reconstruction of planar periodic structures based on Fourier analysis of moiré patterns

Abstract: In recent years, inverse moire methods have been developed to reconstruct micro/nano-scale planar periodic structures with a larger field of view than those constructed using conventional methods. In these methods, moire fringes generated by superposition of the periodic structure and a reference grating are analyzed to reconstruct the periodic structure. There are two approaches to inverse moire methods: the fringe-centerlines method and the phase-shifting method. The former has lower accuracy and is difficult to automate, while the latter requires at least three moire images with complicated processing. A reconstruction method for planar periodic structures using Fourier analysis is proposed. This method can be used to characterize the micro/nano periodic structure from a single microscope moire pattern. At the same time, when combined with a linewidth characterization method, the period and linewidth of the microstructure can be obtained simultaneously. As practical examples, the period and linewidth of a scanning electron microscopy raster are calibrated. Then the microstructures of a micro-electroformed grating and a butterfly wing are reconstructed using the calibrated system. The proposed method provides a tool for the characterization of large area micro/nano periodic structures. Further, this is a promising approach to detect defects in periodic structures.