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.

3-D Contouring of Diffuse Objects by Talbot-projected Fringes

Abstract: Talbot fringe projection, a moire technique, is applied to three-dimensional contouring of diffuse targets for absolute shape measurement. The basic system relies on depth coding the test target surface by projecting the Talbot image of a linear grating. A second grating, similar to that used for the Talbot image, is employed to obtain the moire fringes. These fringes represent surface contours of equal depth. Using a phase measurement technique and digital image processing algorithms, the surface shape information is obtained from the contour maps. Experimental results, merits and limitations of the system are discussed.

High precision computer-generated moiré profilometry

Abstract: Recently, a computer-generated moire profilometry was proposed by our research group. It can effectively avoid the influence of the transient caused by moire fringes’ direct acquisition and generally owns a higher accuracy. But when the spatial spectrum of the captured deformed pattern is severely aliased caused by the measured object, the accuracy of this method may be affected to some extent due to the impure background light component extraction. So, a high precision computer-generated moire profilometry based on background light component’s accurate elimination is proposed. By adding an additional special phase-shifting sinusoidal grating to accurately extract valid information in the spatial domain and improve the sinusoidal feature of the pattern, the measurement precision can be improved effectively. Though the single-shot feature is broken, the real-time measuring feature is still maintained successfully. Experimental results show the feasibility and validity of the proposed method.

Method and equipment for mapping radiation deflection

Abstract: Equipment and method for mapping an object using moire deflectometry wherein collimated radiation deflected from the object is used to generate a moire pattern and wherein by measuring linear deflections in the pattern, variations in characteristics of the object is determined.

Geometric parameters of moiré fringes

Abstract: The incoherent illumination moire phenomenon between a periodic and a quasiperiodic structure is examined by the use of the spatial frequency analysis of the resultant transmittance. This approach has an advantage in that it completely explains all the fringe parameters without considering the averaging effect of the detecting system. We obtain the basic equation of the original moire pattern due to the beat phenomenon exclusively, without any external factors like, for example, the influence of the observing system. From the basic equation, we derive the fringe profile equation representing the moire fringe shape and the fringe equation expressing the spacing, the orientation, and the local displacement of the moire fringes. The fringe profile equation is experimentally verified. The sensitivity enhancement by the fringe multiplication method is readily interpreted by the use of the derived fringe equation.

Moiré method and measuring system for measuring the distortion of an optical imaging system

Abstract: In the case of a method and a measuring system for measuring the distortion of an optical imaging system (1) with the aid of moire patterns, an object grating (3) with an object pattern is arranged in the object plane of the imaging system, and an image grating (4) with an image pattern is arranged in the image plane of the imaging system. Both the object pattern and the image pattern in each case have a multiplicity of cells with sub-gratings of different grating properties, it being possible, in particular, for the sub-gratings to have different directions of periodocity and different phase angles. The object pattern and the image pattern are coordinated with one another in such a way that, when the object pattern is projected onto the image pattern with the aid of the imaging system (1), images of the sub-gratings (15, 16) of the object pattern superimpose in each case with assigned sub-gratings of the image pattern, accompanied by the generation of moire sub-patterns, which are likewise present in the form of cells situated next to one another. As a result, it is possible simultaneously to determine distortion components for a plurality of image directions aligned transverse to one another. It is preferred to use phase-shift methods in order to evaluate the moire sub-pattern.