Showing papers on "Moiré pattern published in 2004"

A Study on the Digital Nano-Moire Method and its Phase Shifting Technique

Abstract: A novel digital nano-moire method is proposed to measure the in-plane nanoscopic deformation of an object. In the measurement, the periodic lattice of a single-crystal material acts as a specimen grating while a digital reference grating (DRG) is prepared by computer software. These two gratings overlap to generate a moire fringe pattern. The preparation of the grating, the formation principle of digital nano-moire fringes and its relative phase shifting technique are described in detail. A typical experiment was conducted with a highly oriented pyrolytic graphite (HOPG) sample. The residual deformation of the irradiated HOPG sample was measured using this method. The experiment result verifies the feasibility of this method, and demonstrates the potential for further applications.

Band moiré images

Abstract: We propose a new powerful way of synthesizing moire images that enables the creation of dynamically moving messages incorporating text, symbols, and color elements. Moire images appear when superposing a base layer made of replicated base bands and a revealing layer made of a line grating comprising thin transparent lines. Each replicated base band contains the same image, e.g. text or color motifs. Since the base bands and the revealing line grating have similar periods, the revealed moire image is the image located within each base band, enlarged along one dimension. By considering the formation of the moire image as a line sampling process, we derive the linear transformation between the base layer and the moire image. We obtain the geometric layout of the resulting moire image, i.e. its orientation, size and displacement direction when moving the revealing layer on top of the base layer. Interesting moire images can be synthesized by applying geometric transformations to both the base and the revealing layers. We propose a mathematical model describing the geometric transformation that a moire image undergoes, when its base layer and its revealing layer are subject to different freely chosen non-linear geometric transformations. By knowing in advance the layout of a moire image as a function of the layouts of the base layer and of the revealing layer, we are able to create moire components running up and down at different speeds and orientations upon translation of the revealing layer. We also derive layer transformations which yield periodic moire images despite the fact that both the base and the revealing layers are curved. By offering a new means of artistic expression, band moire images can be used to create new designs and to synthesize visually appealing applications.

Phase shifting SEM moiré method

Abstract: A new phase shifting scanning electron microscope (SEM) moire method is proposed in this paper The phase shifting technique is realized in four steps from 0 to 2π by shifting electron beam in the y-axis direction controlled by the SEM system It is successfully applied to determine the residual strain of a deformed holographic grating with a frequency of 1200 lines / mm in an electronic package As a further application, it is used to measure the virtual strain of a MEMS structure with a 5000-line/mm grating and to determine the phase distribution of a SEM moire formed with a 6000-line/mm grating fabricated by electron beam lithography The experiments show the feasibility of this method It provides a new way for disposal of fringes pattern in sub-micro moire method

Method and system for minimizing the appearance of image distortion in a high speed inkjet paper printing system

Abstract: A method and system for a printing device is disclosed. The method and system comprise printing a test pattern on a print medium and generating a digital image of the printed test pattern by an imaging device. The method and system include analyzing an interference pattern to measure for distortion of the print medium and calibrating the printing device based upon the measured distortion. In a preferred embodiment, the present invention utilizes the reticle patterns, which are printed in the margins of the paper, which are measured real-time during printing. The interference or Moire patterns created by superimposed reticles may be used to measure image distortion, process direction misalignment, and misregistration caused by web distortion. The advantage of this invention is that image distortion compensation, RIP (Raster Image Processor) parameters, timing, or other printer characteristics may be adjusted on-the-fly in a closed feedback system, for high-speed textile or paper color printing, utilizing on-the-fly distortion or stretch measurement for accurate color and/or duplex images registration. In a duplex printer, automatic images alignment front-to-back is obtained by combining optically or logically the two images for the evaluation of interference patterns and amount of distortion in the process and scan direction.

Diffusion plate and surface light source device

Abstract: PROBLEM TO BE SOLVED: To provide a diffusion plate which can suppress moire fringes and color flickering of the screen of a liquid crystal display device, and can reduce the luminance degrade of the screen. SOLUTION: On the surface of a transparent substrate 83, a pattern is formed where almost rectangular shapes are arranged in grid by using a synthetic pattern 86. The synthetic pattern 86 is made by synthesizing a plurality of first uneven patterns 84 having a linear shape long in one direction , and a plurality of second uneven patterns 85 of concave lens shape which are arranged at random. COPYRIGHT: (C)2006,JPO&NCIPI

Moiré interferometry formulas for hard x-ray wavefront sensing

Abstract: We derive mathematical relations for hard X-ray moire wavefront analysis with a grating interferometer. In particular, the first derivative of the wavefront phase profile and the local radius of curvature of the wavefront are related to the position and inclination of the observed moire fringes.

Three-dimensional pattern ornament body

Abstract: PROBLEM TO BE SOLVED: To provide a three-dimensional pattern ornament body capable of three-dimensionally displaying gradation moire patterns (interference stripes) having a fine area and a coarse area. SOLUTION: A pattern 4a colored into a desired color is printed in a pattern Ba on the surface of a transparent or opaque sheet-like ornament body 2 constituting the three-dimensional pattern ornament body 1, a pattern 4b colored different from the pattern 4a is printed in a pattern Bb on the surface of the pattern 4a, and a transparent convex lens 3 having almost a hemispherical shape cross section is printed in a pattern A on the pattern Bb surface of the pattern 4b. The pattern A and the patterns Ba, Bb are displaced or crossed at angles θ1, θ2 where the moire patterns appear, to three-dimensionally display gradation moire patterns wherein the pattern concentration and the color density change between the fine area and coarse area. COPYRIGHT: (C)2005,JPO&NCIPI

The Projected Pattern Correlation Technique for Vibration Measurements

Abstract: The objective of this paper is the description of the Projected Pattern Correlation method for measuring surface velocities and to present results of a feasibility study. Similar to the Moire technique the local surface velocities of a large area are determined simultaneously, which replace a time consuming point wise scanning as it is necessary in e.g. Laser Doppler Vibrometry. Furthermore, the dynamics of non-periodic processes can be resolved temporally and spatially. In difference to the Moire or grid projection techniques the evaluation step is fast (real-time measurements are possible) more robust and provides a high spatial resolution. The measurement precision is assessed using a simple test arrangement. Vibration measurements are performed on a satellite model structure and a honeycomb sandwich plate.

Low-cost optoelectronic system for three-dimensional artwork texture measurement

Abstract: A new optoelectronic system is proposed for three-dimensional (3D) texture measurement. It is based on a projection unit in which light, coming from a laser diode coupled to an optical fiber, impinges on a diffractive optical element (DOE) to produce sinusoidal fringes. If the projected fringe pattern is viewed at an angle different from the projection angle, the fringe profile is phase-modulated by the 3D object shape. The 3D map information is obtained with the aid of a fringe analyzer based on phase-shifting a synthetic moire pattern, fast Fourier transform (FFT), signal demodulation techniques and a robust and fast phase unwrapping performed by specially developed software. The proposed system is based on simple and low cost equipment; furthermore, it is suitable for in situ measurements by nonskilled operators. Some experimental examples illustrate its performance.

Liquid diffusion coefficients by digital moire

Abstract: In studying hydrodynamic instabilities between two miscible fluid mixtures, one often faces the problem of assigning a reliable value to very small diffusion coefficients. It is also difficult that for diffusion between two binary mixtures, such as water and glycerin, water and salt, etc., no complete data are available in the literature. To measure the isothermal diffusivity of liquid binary mixtures, we propose an improved version of digital projection moire. The system uses a simple and flexible fringe generator realized with a diffractive optical element (DOE). The fringe patterns are projected onto the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a charge-coupled device (CCD) camera and stored in a computer at different times. With the aid of fast Fourier transform (FFT) and signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical basis of the technique is presented. We also report experiments conducted for validating the system.

Digital moiré fringe-scanning method for centering a circular fringe image

Abstract: A digital moire fringe-scanning method for centering a circular fringe image is proposed. The image of a nondiffracting beam, whose cross section is a circular fringe, is first downloaded onto a computer. The image is then superposed with a digital circular grating, whose center is close to the center of the image, to generate circular moire fringes. Changing the phase of a digital grating can cause moire fringe scanning. The global center of the image can be calculated by use of sets of the scanned picture. Because all the image data are used for the calculation, the effect of random noise on centering is greatly reduced and the center position resolution can reach the order of a subelement of a CCD. The measurement of spatial straightness is discussed.

A passive sensor for position and attitude estimation using an interferometric target

Abstract: In this paper, we describe a new sensor technology aimed at better identifying the relative motion of two vehicles (eg the motion of a car from another car, or that of a ship from an helicopter etc.) or in general two objects of large or small sizes. The system described in this paper consists of an optical setup aimed at generating interference fringes made visible to one vehicle by the other vehicle (or, in general, to one object by the other object). The setup consists, on the one hand, of a flat target that generates interference fringes by using superimposed gratings; on the other hand, it includes an image acquisition system, such as a digital camera. There is a very widely documented use of gratings and moire effects to obtain relevant information about object shape and position.

Vector representation of binary images containing halftone dots

Abstract: Vector representation of graphics has the advantage that the image can be displayed at any size. When the resolution of a bitmap image is changed, the lack of a line segment arises. In addition, moire occurs when the resolution of an image with halftone dots is changed. We propose a new technique to convert a binary image with halftone dots into its vector representation. Resolution conversion of a binary image can easily be performed without moire by using a continuous tone approximation of the halftone dots. First, we separate the area of halftone dots and line drawings in the image. Next, a continuous tone approximation is applied to the area of halftone dots. Then, conventional vectorization is applied to both continuous tone areas and line drawings. Finally, these components are mixed and reconstructed. Our approach provides an efficient way of displaying cartoon-like images at any size with a limited amount of data.

Nanometre moire fringes in scanning tunnelling microscopy of surface lattices

Abstract: A novel class of moire fringe patterns in scanning tunnelling microscope (STM) imaging is presented and analysed in this paper. The moire fringe is generated from the interference of the atomic lattice of the specimen and STM scanning lines. Both parallel and rotational STM moire fringes of the surface of highly oriented pyrolytic graphite (HOPG) are investigated. The formation principle and experimental techniques of STM moire fringes are discussed. Nanometre scale resolution and sensitivity are found in the moire fringe patterns. They precisely magnify the STM image of lattice irregularities. A potential application—measuring surface deformation and defects in the nanometre range—is proposed.

Simplified Phase Shifting Moiré Interferometer Using a Computer Generated Grid Pattern

Abstract: A simplified phase-shifting moire interferometer for generating moire fringes from projected linear gratings and computer generated grid patterns without using a low-pass filter is presented. In particular, it is demonstrated that moire fringes can be successfully obtained even when there is no clear frequency separation between the moire fringe and the grid pattern. It is also pointed out that our proposed method produces fewer phase jumps than conventional phase-measuring profilometry, enabling us to realize more robust phase unwrapping.

An Optical Interferometry System for Measuring Three-Dimensional Displacements

Abstract: The system is a combination of a Moire interferometer (which measures the displacement in the plane of a sample) and a Twyman–Green interferometer used for measurements in the perpendicular plane. The diffraction grating that is applied to the sampleis also used as a beam splitter. As a result, the system is simple in design and easy to adjust, and its sensitivity is higher than that of a two-grating Moire interferometer by a factor of two. The fringe pattern is distinguished by its high contrast and spatial resolution. The system has been tested in measuring the three-dimensional thermal deformation of microelectronic devices.

Color Moiré interferometry

Abstract: Color-coding is used to simplify the prior art floating-element Moire shear-stress sensor. The use of color-coding allows conversion of the Moire sensor into a 2-D area array sensor, provides a simplified method that saves costs associated with data acquisition and analysis and permits the use of color in the mapping of shear stress distribution.

Out-of-plane displacement measurement by means of endoscopic moiré interferometry

Abstract: An endoscopic moire technique is proposed for measuring out-of-plane displacements in difficult to reach places. The Ronchi grid is projected onto the tilted object with one endoscope with a 0° viewing angle. The object with the projected grid is imaged by a second endoscope with a 30° viewing angle onto a charge-coupled device. The captured images are stored in a PC, and are used to calculate the out-of-plane displacement of the object with a phase stepping technique. A computer generated grating method is used instead of a physical phase-shift device in the optical setup. This allows designing a set of three reference grids with profiles closely similar to the projected grating. The technique is robust against problems associated with the temporal shifting method, such as nonlinear phase shift and noise. To test the feasibility of the technique the measurement of out-of-plane displacements of about 35 μm of a latex membrane under deformation is demonstrated. The advantages and disadvantages are discussed.

Research on digital grating vibration sensor

Abstract: Digital grating sensor of vibration measurement is a pattern of geophone, which picks up seismic signals with grating vibrator. Along with the request of higher precision method to identify more complex geological targets, higher precision and accurate information of oil reservoirs underground must be provided through geophysical technologies for reservoirs prospecting and developing. By digital grating sensor of vibration measurement, mechanical vibrating signal of the seismic wave can be transformed into light modulating signal - moire fringes, and then converts by photoelectric element to digital electrical signal. The sensor samples the signal by counting the numbers of the moire fringes, which may prevent quality of the output data from being influenced by electric circuits, and the packaging technology is also simplified. The working principle, theoretical arithmetic, configuration design, test method and acquired data by digital grating sensor are presented in the paper.

Unevenness inspection method and system of periodical pattern

Abstract: PROBLEM TO BE SOLVED: To accurately inspect periodical patterns without being influenced by moire fringes by inputting the just focused image of an object. SOLUTION: When the object W with narrow patterns repeatedly formed in the widthwise direction is inspected, the pixel line direction of a line sensor camera 12 is squared with the formation direction of the patterns; the proper focus is set; each pattern in an imaging range is set in a visual field of one pixel over the total width; the object image is imaged by setting a scan rate causing an aspect ratio to exceed one in an optical condition where a luminance value in the case that two patterns are partially included in the visual field of one pixel is not equal to that in the case that only one of the patterns is included; a transmittance image is formed by dividing the image by a light source image imaged by excluding the object; a pattern image of a pixel corresponding to the luminance value of the total width of the each pattern is created from the image; and the pattern is inspected based on the image. COPYRIGHT: (C)2004,JPO

Wavemeter Based on Moiré Effect

Abstract: A moire-effect-based procedure used to measure the wavelength of coherent sources is shown. Two plane waves, individually coherent but mutually incoherent and located at the entrance pupil of a Michelson interferometer with slightly tilted mirrors, generate a moire pattern at the output plane. The spatial period of that moire pattern is determined by the spatial frequencies of the interferograms superimposed on intensity. Thus the spatial frequency of such moire patterns allows the establishment of a ratio between the wavelengths of the sources that illuminate the interferometer. This ratio can be applied for the accurate determination of determining an unknown wavelength in terms of a reference wavelength, as we show both theoretically and experimentally.

Shape measuring device using moire optical system and its method

Abstract: PROBLEM TO BE SOLVED: To provide a device for measuring the shape of a moving planar component such as a roller component or a sheet by changing a distance d between a light source and an observation point for shifting the phase of moire fringes by applying a phase shifting method to a moire method. SOLUTION: The shape measuring device uses a solid lattice type moire optical system which consists of the light sources for generating the moire fringes, a patterned lattice, a lens for imaging the moire fringes of the patterned lattice, and a light receiving element. The light receiving element consists of a pixel array with accumulated pixels, and at least three light sources are arranged at positions differently distant from the lens. The pixel array constituting the light receiving element uses the moire optical system, which consists of a means for controlling the light sources to be lit in sequence in synchronization with the scanning cycles of the pixel array, a mechanism for moving a relative position relationship between the moire optical system and a planar inspected surface to the direction perpendicular to the pixel array of the light receiving element, a shape computing means for calculating the shape of the circular or planar inspected surface using the phase shifting method from data for the pixel array, for measuring the shape of a cylindrical or planar inspected object. COPYRIGHT: (C)2004,JPO

Development of a Virtually Calibrated Projection Moire Interferometry Technique Capable of Inaccessible Surface Measurements

Abstract: ABSTRACT DEVELOPMENT OF A VIRTUALLY CALIBRATED PROJECTION MOIRÉ INTERFEROMETRY TECHNIQUE CAPABLE OF INACCESSIBLE SURFACE MEASUREMENTSDEVELOPMENT OF A VIRTUALLY CALIBRATED PROJECTION MOIRÉ INTERFEROMETRY TECHNIQUE CAPABLE OF INACCESSIBLE SURFACE MEASUREMENTS Mark L. Kimber Department of Mechanical Engineering Masters of Science Optical-based techniques have found merit in measuring displacement and strain for decades. These techniques are commonly used in numerous applications ranging from large displacements in wind tunnel experiments to displacement measurements on the submicron scale. Projection Moiré Interferometry (PMI) is an out-of-plane displacement measurement technique, and consists of capturing reference and deformed images of a grid pattern projected on the test object. By differencing the reference and deformed images of the projected grid pattern, a fringe pattern is generated from which the displacement field can be extracted. This computation requires calibration procedures that analyze a number of fringe patterns from known displacements to compute the fringe sensitivity constant (FSC) values. This process can be time consuming and for largescale applications, very costly. In addition, due to the projection-oriented nature of this

A modified moire interferometer for three-dimensional displacement measurement

Abstract: This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system are described. The experimental results of thermal displacement of an electronic device are shown.