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.

Moiré profilometry using liquid crystals for projection and demodulation.

Abstract: A projection moire profilometer is presented in which both projection and optical demodulation are realized with liquid crystal light modulators. The computer generated grids, realized on thin film transistor matrices, allow phase-stepping and discrete grid averaging without the need for any mechanically moving component. Spatial line pitch and phase steps can thus be readily adjusted to suit the measurement precision and object geometry. The device is able to perform topographic measurements with a height resolution of 15 microm on every pixel of the recording device.

Sharpening and multiplication of moiré fringes: Moiré patterns of modified intensity distribution are analyzed and demonstrated

Abstract: Moire fringe sharpening is produced when the widths of clear and opaque bands in a pair of super-imposed screens are complementary. Fringe multiplication is produced when the frequency of lines in the reference screen exceeds the frequency in the specimen screen by an integral factor. The number of moire fringes then formed corresponds to the greater frequency.

Video-rate fringe analyzer based on phase-shifting electronic moiré patterns

Abstract: We have developed a fringe analyzer that delivers the phase distribution at a video rate from a fringe pattern containing a spatial carrier. It is based on parallel generations of three phase-shifted moire patterns through electronic multiplication with computer-generated reference gratings and low-pass filtering. The phase distribution is derived by the subsequent parallel processing of these patterns on the basis of a three-step phase-shifting algorithm. By modification of the bias phase distribution of the reference gratings, several functions, such as correction of an initial wave-front error, are realized in real time. The usefulness of this analyzer is demonstrated experimentally for phase measurements by grating-projection surface topography and interferometry.

Focusing Errors in a Collimating Lens or Mirror: Use of a Moiré Technique

Abstract: The Fresnel diffraction pattern of a grating periodically gives an exact reproduction of the grating. By superposing a second grating on such an image, we form a moire pattern that depends upon the degree of parallelism of the incident beam. We present here the possibility of using this technique for studying the focusing errors in a collimating lens or a mirror.

Fourier-based analysis of moiré fringe patterns of superposed gratings in alignment of nanolithography.

Abstract: Considering the necessity of alignment in practical applications of photolithography, distribution of complex amplitude of moire fringe patterns that are produced in superposition of two gratings is analyzed in the viewpoint of Fourier Optics and the relationship between fringes and properties of these two gratings is concluded by means of an analysis model. The rule of one-dimensional gratings (1D-gratings) is extended to other form of the gratings which have quasi-periodic repetitive structures. Especially, moire fringes generated by the two superposed 1D-gratings (used in alignment of lithography) can be expressed by an arithmetical operation of two vectors which include enough information about these 1D-gratings. Numerical analyses regarding the moire model and its application in the alignment process of lithography are carried out. Our computational analyses results show that the moire fringes of the two extended gratings can be refined as a transformed fringe pattern of two standard 1D-gratings. Finally, the results also make it out that the fringes which have magnified periods versus that of two 1D-gratings are highly sensitive to relative shift of two gratings thus might be applicable in alignment of lithography or correlated fields.