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.

Image input apparatus having a spatial filter controller

Abstract: The Invention is an image input apparatus equipped with means of image shifting which is capable of inputting images of different resolutions, and enables the transmission band of the spatial filter to be switched in accordance with resolution in order to prevent moire. When a flat transparent refraction plate 22 is inclined relative to the optical axis 10 by which light from the object is introduced, the position where the image is formed on the imaging surface of the CCD 14 is shifted, thus making image shifting possible. High resolution images are obtained by shifting the image a distance shorter than the distance between the photosensitive parts of the CCD 14, and then combining the images. The transmission band of the spatial filter 12 for preventing moire can be switched by changing the relative angles of the double refraction plates 20, 21. The transmission band of the spatial filter 12 is switched to the high frequency side when inputting high resolution images by means of the image shift mechanism 13, thus obtaining images of good resolution.

STEM moiré analysis for 2D strain measurements.

Abstract: A moire pattern is created in a scanning transmission electron microscope (STEM) when the scan step is close to a crystalline periodicity. Usually, fringes are visible in only one direction, corresponding to a single set of lattice planes, but fringes can be formed in two directions or more. Using an accurate independent calibration, the strains in silicon devices have been determined from the spacing and orientation of one-directional STEM moire fringes. In this report, we first discuss the origin of the STEM moire, and then we show how an accurate calibration of the scan step can be obtained from the STEM moire pattern itself, providing that we know initially only an approximate scan step and the planar spacing. The new calibration scheme also makes the STEM moire experiments easier, since it can be applied for the moire where the scan direction is not precisely aligned with the crystalline lattice. Finally, we show how the two-dimensional strain information will be readily extracted from two one-directional moire patterns using the concept of geometric phase.

Moiré topography, sampling theory, and charged-coupled devices

Abstract: Projection-type moire contouring can be done without a reference grid by undersampling projected cosine fringes with a charged-coupled-device detector array to eliminate entirely the unwanted sum, shadow, and grid terms of classical moire methods as well as the spurious moire fringes that are due to higher harmonics. The technique produces a high-visibility sampled version of the moire difference contour fringes. Higher-order aliasing can provide increased sensitivity when the same detector array is used. The sampling conditions are formulated as a moire extension to the Whittaker–Shannon sampling theorem.

An adjustable, high sensitivity, wide dynamic range two channel wave-front sensor based on moiré deflectometry

Abstract: An adjustable, high sensitivity, wide dynamic range two channel wave-front sensor based on moire deflectometry has been constructed for measuring distortions of light wave-front transmitted through the atmosphere. In this approach, a slightly divergent laser beam is passed through the turbulent ground level atmosphere and then a beam-splitter divides it into two beams. The beams pass through a pair of moire deflectometers which are installed parallel and close together. From deviations in the moire fringes we calculate the two orthogonal components of angle of arrival at each location across the wave-front. The deviations have been deduced in successive frames which allows evolution of the wave-front shape to be determined. The dynamic range and sensitivity of detection are adjustable by merely changing the separation of the gratings and the angle between the rulings of the gratings in both of channels. The spatial resolution of the method is also adjustable by means of bright, dark, and virtual traces for given moire fringes without paying a toll in the measurement precision.

Moiré method and zone plate pattern inaccuracies

Abstract: Moire patterns obtained from superimposed zone plates with common types of pattern inaccuracies are analyzed. Tolerances for the distortions characterized as ellipticity, radial displacement, and nonconcentricity of the zones, are obtained from the corresponding equations for lenses. The formulas for moire fringes resulting from superimposed zone plate patterns having these defects are derived. The feasibility of moire pattern techniques to detect and measure inaccuracies of the zone plate is demonstrated. The sensitivity and the limitations of the method are discussed.