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.

Application of phase shifting technique for SEM scanning moire method im MEMS

Abstract: A new phase shifting SEM scanning moire method is proposed in this paper. The phase shifting technique is realized in four steps from 0 to 2 π by shifting electron beam in y-axis direction controlled by SEM system. It is successfully applied to measure the virtual strain of a MEMS structure with grating of 5000 lines/mm. The experiments prove the technique can be widely used in meso-deformation measurement, and also show the sensitivity of experiments is highly improved after phase shifting technique. It provides a new way for disposal of fringes patterns in sub-micro moire method.

Optimization of 3-D topography measurement based on Moiré technique

Abstract: To provide a non-contact, simple, high speed and high accuracy measuring technique for industry measurement, the advanced Moire fringe method is developed in this paper. Based on virtual grating, fringe doubling, spatial filtering and phase shifting technique, a three-dimensional topography is measured. The virtual grating, spatial filtering and phase shifting technique are used to eliminate the phase shifting errors. Four step phase shifting virtual gratings, generated by computer, are superposited with testing grating and Moire fringe patterns are formed. Four phase-shifting patterns can be gained by filtering four Moire fringe patterns. An experiment equipment is designed and built. With the fo spatial filtering, phase shifting technique and phase unwrapped of virtual grating, the three-dimensional topography is measured, and the measuring accuracy is also evaluated. The obtained result shows that the improvement of the phase-shifting topography measurement methods is suitable for testing industrial product topography featuring non-contact, simplicity, high speed and high-precision.

Moiré signal distortion caused by phase and amplitude nonuniformities of light beams.

Abstract: The distortion suffered by the amplitude and phase of a moire signal when the illuminating beam is not a coherent and monochromatic plane wave has been measured by using different kinds of illuminating sources and a phase-sensitive intensity subtraction technique. A phenomenological model is proposed that explains these effects in terms of an irregular amplitude distribution and a phase evolution of the moire signal with a grating gap. These effects are of great interest in all the measurement techniques related to the moire effect, especially when compact light sources such as light-emitting diodes and incandescent lamps are used.

Apparatus and method for three dimensional measurement using moire and dynamic stereo vision

Abstract: An apparatus and a method for three dimensional measurement using moire and dynamic stereo vision are provided to improve the reliability by measuring a three-dimensional shape via an integrated phase wherein phase noise is removed. An apparatus for three dimensional measurement using moire and dynamic stereo vision comprises a measuring head(10), a measuring head transfer part(20), a transfer table(30), and a control device(40). The measuring head, comprising a projection part(11) and an image part(12), images a moire pattern reflected after projecting a moire pattern lamp to an object to be measured. The transfer table installed at the lower part of the measuring head moves the object to a first measurement position. The control device measures a three-dimensional shape of the object by receiving first and second phase information, and first and second brightness images acquired by the measuring head.

An automatic angular positioning of mask with wafer using modified moire technique

Abstract: An automatic and accurate technique for angular positioning of mask with respect to wafer is reported.. Alignment marks are in the form of gratings and the moire signal is obtained by the relative displacement between the gratings. The higher slope region of the moire signal is used to obtain higher sensitivity and better position control accuracy. The experiments are performed with 25 micrometer pitch gratings and Piezo- Electric Transducer is used for the angular displacement. The angular -7 accuracy of the order of 2 x 10 radian is reported with a time constant of 0.2 sec. In the recent years, use of moire interference technique for mask to wafer alignment has attracted much attention especially in VLSI fabrication technology where a highly accurate linear and angular positioning is involved. In this technique the alignment marks are in the form of gratings. A laser beam is passed normally through a mask grating and reflected from the wafer grating. Intensity variation in the reflection mode due to relative angular rotation is detected by a photodetector and converted into the electrical signal, known as moire signal.