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.

Vibration error-compensation technique in phase shifting moiré interferometry

Abstract: Undesirable vibrations can greatly degrade the accuracy of phase shifting moire interferometry. Although moire interferometry is always equipped with a somehow elaborate system to dampen or to eliminate vibration, such as granite slab and air table, it is common to see the phase fluctuation of moire diagram attributable to the various vibration during the measurement process. The sensitivity of moire interferometry to vibration is rooted in the fundamental principles of the instrument. Typically, an imaging system collects interference patterns for a sequence of reference phases, and then a computer unwraps the original wave-front phase by analyzing the variations of intensity. Compared with classical interferometry, an experiment by grating rosette moire interferometry with different principle of image formation is carried out and a corresponding efficient phase calculation method is developed to eliminate or compensate the effects of mechanical vibrations. In the decomposition and reconstitution of phase-shifting fringe patterns using discrete Fourier series, the phase-shifting fundamental coefficients (a 0, a 1 and b 1) are extracted from 10 samples in one phase shift cycle, with which three images with 120 degree intervals are obtained. Besides, a mathematical model for the phase error is derived by vibration frequency content or spectrum. Combined with traditional phase shifting algorithm, the proposed data post-processing technique can effectively reduce the phase ripple caused by vibrations. The result is supported by numerical simulations in MATLAB software and experiments with grating rosette moire interferometry.

An equivalent configuration approach for the moiré patterns appearing due to the reflecting surface in display system.

Abstract: A new moire pattern appearing in the off-state of a display system with a reflecting surface under illumination of an external ambient light source was analyzed. The origin of the new moire pattern was attributed to the moire pattern which is formed on the reflecting surface by external light and plays as a new light source with intensity profile. Configuring an optically equivalent system with no reflecting surface layer was proposed in order to overcome the limitation of new simulation program, which was previously proved to be very efficient in computation time but unable to handle a non-sequential system containing a reflecting surface. It was verified that the new simulation algorithm combined with an equivalent configuration could provide an accurate and computation time-efficient analyses even for a system containing non-sequential stacked layer such as a reflecting surface.

Three-dimensional image scanner

Abstract: PROBLEM TO BE SOLVED: To quickly and easily input the three-dimensional shape information of an object ot be measured by the large degree of freedom of measurement by utilizing a grating projection type moire topography for a three-dimentional image scanner and to easily input also the pattern information of the object to be measured by using a prescribed lamp. SOLUTION: Three-dimensional shape information is inputted by using a measuring head 12 having a function of a grating projection type moire device. Consequently a reference grating is not required for a grating irradiation type moire device and limitation to the size and arrangement of an object to be measured can be eased. Pattern information is inputted by using a measuring optical system 28 in the head 12. At the time, a measuring reference grating 46 is retreated to a position deviation from the optical path of the optical system by a grating retreating mechanism 58, an illuminating lamp 64 is turned on interlocking with the retreat to irradiate the object to be measured with light and the two-dimensional image of the object to be measured is photographed, so that the required pattern information can be easily and accurately inputted.

Projection moire interferometer for research in otology

Abstract: A moire interferometer is presented which was specially designed for the study of middle ear mechanics. The apparatus is based on phase shift projection moire interferometry, and allows full field quantitative measurement of the shape and deformation of three-dimensional surfaces. Phase shifting and grating noise removal is obtained by piezo-actuated movements of the gratings in the projection and the viewing optical path, respectively. Object shape is then calculated from the recordings of four phase shift moire topograms. The angle between projection and viewing direction is very small, so that observation of the eardrum is possible with minimal shadow problems caused by the bony structures in the vicinity of the eardrum. Measurements obtained on a calibration object and on in-vitro middle ear preparations are presented.