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.

Projection moire interferometer for vibration analysis.

Abstract: A projection moire interferometer is presented which was developed to study rotating vibrating objects such as turbine blade assemblies. Three methods of moire interferometry were used in this study: pulsed; time-average; and real time. Real-time moire interferometry used in conjunction with image derotation and strobe techniques is shown to be a viable method of studying traveling wave modes on a rotating disk.

Deformation measurement during powder compaction by a scanning-moiré method

Abstract: The mechanical behavior of powders during compaction has been studied in previous papers. It has been shown that a moire method may be used to determine the resulting strain distribution. Some difficulties were encountered, however, in the method used. In the present paper, therefore, an image-processing system employing a personal computer to analyze the moire pattern is introduced. Many strain distributions obtained in this way from moire-fringe patterns are presented. Further, using this image-processing system, a scanning-moire technique is developed in which the master grating is replaced by the scanning lines of a television camera. The use of image processing in conjunction with the mismatch technique allows measurement of both small and large strains from one image picture.

Sandwich hologram interferometry. 3:Contouring.

Abstract: This new holographic contouring method produces interference fringes formed by illumination shearing during recording in combination with observation shearing during reconstruction. One holographic plate is exposed after which the point source of light illuminating the object is displaced laterally to produce a shear of the illumination beam. A second exposure is made on another plate, whereupon the two plates are processed and bonded together with their emulsions outward. When this sandwich hologram is reconstructed, contouring fringes are formed that represent the intersection of the object by a set of interference surfaces. A tilt of the sandwich hologram produces a shear of the observation that results in a corresponding rotation of the intersecting surfaces of up to 180° in every direction of the three-dimensional reconstructed object space. Thus, sign, direction, and magnitude of object slant can be evaluated by measuring the analogous sandwich tilt. The possibility of studying cross sections in any random orientation from a single sandwich hologram could be very useful for measuring and demonstration purposes.

Theory of Electron Beam Moiré.

Abstract: When a specimen surface carrying a high-frequency line grating is examined under a scanning electron microscope (SEM), moire fringes are observed at several different magnifications. The fringes are characterized by their spatial frequency, orientation, and contrast. These features of the moire pattern depend on the spatial frequency mismatch between the specimen grating and the raster scan lines, the diameter of the electron beam, and the detailed topography of the lines on the specimen. A mathematical model of e-beam moire is developed that expresses the spatial dependence of the SEM image brightness as a product of the local intensity of the scanning beam and the local scattering function from the specimen grating. Equations are derived that give the spatial frequency of the moire fringes as functions of the microscope settings and the spatial frequency of the specimen grating. The model also describes the contrast of several different types of moire fringes that are observed at different magnifications. We analyze the formation of these different fringe patterns, and divide them into different categories including natural fringes, fringes of multiplication, fringes of division, and fringes of rotation.

Moiré Methods for Engineering and Science — Moiré Interferometry and Shadow Moiré

Abstract: Moire interferometry and shadow moire are extraordinarily versatile and effective methods for determining in-plane and out-of-plane displacement fields, respectively. The basic concepts are reviewed for both methods, topics on practice and analysis are addressed, and numerous examples of important applications are presented.