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.

Holographic illumination for comparison in interferometry

Abstract: Conventional holographic interferometric and speckle pattern interferometric techniques are tailored basically to compare the two states of the very same object, which may have optically rough surface or optically distorting transparent walls around. The direct comparison of the behavior of two different--but macroscopically quite similar--objects does not fit naturally in the process. At present, this type of extension can go three different ways. In holographic interferometry, one can mix the interferograms of the two objects at some sublevel of interferogram making and the moire effect of the individual fringe systems can be produced. In speckle pattern interferometry, the reference surface can be replaced by the other object itself and it serves as a live reference: changing according to the test object. Finally, although really first if time of birth is regarded, holographically recorded and reconstructed images of a master object can be used for illumination of test objects--in an otherwise conventional holographic or speckle interferometric arrangement. The present paper deals with this latter technique. Some new developments are reported in difference holographic interferometry and partly as a consequence of this--a really successful realization is introduced in holographically illuminated difference ESPI.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Corneal surface reconstruction by using heterodyne Moiré method

Abstract: In this paper, we propose a simple method for reconstructing the corneal surface profile by using the Talbot effect, projection moire method, and heterodyne interferometry. A linear grating is obliquely illuminated by an expanding collimated light, and a self-image of this grating can be generated and projected on the corneal surface. The deformed grating fringes are imaged on the second grating to form the moire fringes. If the first grating is moved with a constant velocity along the grating plane, a series of sampling points of the sinusoidal wave which behave like the heterodyne interferometric signal can be recorded by a CMOS camera. The phase distribution of the corneal surface then can be obtained with the IEEE 1241 least-square sine fitting algorithm and 2D phase unwrapping. Finally, the corneal surface profile can be reconstructed by substituting the phase distribution into special derived equation. This method provides the advantages of a simple optical setup, ease of operation, high stability, and high resolution.

Multi-color printed matter with latent image and method for revealing latent image

Abstract: PROBLEM TO BE SOLVED: To provide multi-color printed matter with a latent image which is hardly recognizable with the naked eye and difficult to forge/reproduce with another advantage that the latent image is easily revealable as a clear image whose genuineness can be simply determined, in the multi-color offset printed matter with a latent image such as a concealed letter, and a method for revealing the latent image. SOLUTION: This multi-color printed matter 1 has the latent image formed of a latent image part 22 which has the same number of screen lines as a nonlatent image part 24 and comprises halftone dots of different angles of a yellow plate out of four color plates. In the assembly process of the multi-color offset printing, the printer matter 1 is loaded into a scanner in the way that the halftone dots are highlighted, then only the yellow plate constituting the halftone dots is unloaded onto the scanner. In addition, a Moire fringe is generated in the latent image part 22 by synthesizing a flat halftone image with the same screen angle as the latent image part 22. COPYRIGHT: (C)2004,JPO&NCIPI

The Influences Of Several Parameters Of Grating Sensor On The Modulation Depth Of Moire Signal Under Incoherent Illumination

Abstract: In this paper, the theoretical expressions of modulation depth of moire signal under the incoherent illumination are derived. It follows as a concequence that, the modulation depth of moire signal is in relation to the following factors: the geometric share and size of light source, the diffraction effect of grating,which relates to the line numbers of grating, the line and space ratio, the gap of grating pairs, the geometric shape and size of receiving window, etc. In addition, the influences of grating fair on the period and inclination of moire fringes under the noncollimated illumination are discussed, and the comparisons of the changes of modulation depth of moire signals and the noncollimated illumination with that under the collimated illumination are made. Finally, some exoeriment results are given to verify the theoretical expressions. This parer is useful to the actual design of grating sensors.© (1986) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Analysis of measurement principle of moiré interferometer using Fourier method

Abstract: A simple spatial filtering is added in moire deflectometry (MD) which raises the sensitivity, improves the contrast of moire patterns, and makes the viewing plate conjugate to the phase objects under test. This modified system is called moire interferometer (MI). Using the Fourier method, this paper analyzes the measurement principle of MI and obtains a strict relationship between a tested wave function and the shift of moire fringes.