Showing papers on "Moiré pattern published in 2009"

Color moiré pattern simulation and analysis in three-dimensional integral imaging for finding the moiré-reduced tilted angle of a lens array

Abstract: We propose a color moire pattern simulation and analysis method in integral imaging for finding the moire-reducing tilted angle of a lens array. According to the tilted angle, the color moire patterns are simulated on the assumption of ray optics. The spatial frequencies of the color moire patterns are numerically analyzed using a spatial Fourier transform for finding the optimal angle where the moire is reduced. With the proposed technique the visualization of the color moire pattern and its analysis are enabled. The moire-reduced three-dimensional images can be displayed. The principle of the proposed method, simulation results, and their analysis are provided. Experimental results verify the validity of the proposed method.

Theoretical analysis for moiré deflectometry from diffraction theory.

Abstract: Theories of moire deflectometry are presented based on scalar diffraction theory. It is shown that the moire effect is not a pure geometric phenomenon but actually the result of multishearing interference. By performing zeroth-order or first-order filtering, the field in the plane of observation is seen to be the result of double- or triple-shearing interference, respectively. With first-order filtering, the intensity distribution is proved to be a strict cosinusoidal intensity distribution, and the diffraction effect, which depends on the distance between two gratings, affects just the phase shift of the moire fringes. Compared with previous research, a more precise relation between the unwrapped phase and the deflection angles is obtained. The results will be very useful for image processing of moire patterns with Fourier transform profilometry and phase-shift methods.

A novel moiré fringe assisted method for nanoprecision alignment in wafer bonding

Abstract: High precision alignment is essential to 3D integrated circuit and other multilayer structure fabrication. A novel centrosymmetric square moire grating is developed for aligning between the top and bottom wafers. The mismatched moire fringes produced by the two superimposed centrosymmetric square gratings are highly sensitive with the misalignments and misaligned directions without requiring any external reference. Using two pairs of these square moire gratings, misalignments of the bonded wafers are determined in X-Y-θ direction simultaneously on wafer scale. In our experiment, the misalignments in the order of ± 0.5 µm in X-Y direction can be easily identified using a simple infrared (IR) microscope. Moreover, the measurement of misalignments using the moire fringe distances does not depend on the gap between the two wafers changing from tens of micrometers to zero during alignment process. Therefore, these moire gratings are suitable for being secondary alignment mark to achieve high-precision alignment as well. A moire fringe assisted alignment method is proposed for realization of alignment accuracy in nanometer-scale.

The structure of moiré grating lines and its influence to time-averaged fringes

Abstract: G eometric moiré 1,2 is a classical in-plane whole-field non-destructive optical experimental technique based on analysis of visual patterns produced by superposition of two regular gratings that geometrically interfere. Examples of gratings are equispaced parallel lines, concentric circles, and arrays of dots. The gratings can be superposed by double-exposure photography, by reflection, by shadowing, or by direct contact. Moiré patterns are used to measure variables such as displacements, rotations, curvature, and strain throughout the viewed area. In-plane moiré is typically conducted with gratings of equispaced, parallel lines.2,4

Method for producing large area holographic grating based on second exposure of reference grating

Abstract: The invention discloses a preparation method of a large area holographic grating based on reference grating double exposure to prepare diffraction grating; the method comprises the following steps: (1) a reference holographic plate is fixed; (2) a main holographic plate is shielded, the holographic grating recording optical field is used for preparing reference grafting; (3) more non-dense Moire fringe is formed by the reference grafting and the recording grafting, the direction of the Moire fringe is vertical to the line direction of the reference grafting, and the Moire fringe information is recorded; (4) the first part of the main holographic plate is exposed and developed; (5) the main holographic plate and the reference holographic plate are moved simultaneously, the relative position of the reference grafting and the recording optical field is adjusted so as to lead the redivious Moire fringe information to be the same as the Moire fringe information in the step (3); and (6) thesecond part of the main holographic plate is exposed and developed, and the production of holographic exposure splicing grating is finished. The preparation method realizes splicing of adjacent sections in the preparation process of diffraction grating guarantees the parallelism precision and the phase relationship and can be used for preparing the large area diffraction grating.

Accurate Displacement Measurement for Landslide Prediction by Sampling Moiré Method

Abstract: Sampling moire method is useful to measure shape, displacement and strain distributions of multi-functional materials and structures. When a specimen grating pattern on an object is recorded by a digital camera, a moire fringe pattern is obtained by sampling the digitized grating image with a constant pixel pitch. The method can analyze phase values from one image of a grating pattern. By using this sampling moire method, the displacement measurement of land is analyzed to develop a landslide prediction system. The theory and the application for measuring the displacement of land are shown in this paper.

Development of dynamic shape and strain measurement system by sampling moiré method

Abstract: Shape measurement and strain distribution measurement are important to analyze the behavior of a moving object. In this paper, a dynamic shape and strain measurement system by the sampling moire method is developed. Recently, phase analysis method using phase-shifting moire patterns generated in a computer from a grating image is proposed. This method is very suitable for dynamic measurement because the phase can be obtained from a one-dimensional or two-dimensional (2-D) grating image with high accuracy. It is possible to analyze strain distribution and shape measurement of a moving object using a grating pattern attached on the specimen surface. A dynamic shape and strain measurement system by the sampling moire method is developed. The principle and experimental results applied to a rotating object are shown.

Fabrication of micromodel grid for various moiré methods by femtosecond laser exposure

Abstract: The femtosecond laser exposure system was used to fabricate model grids for the charge-coupled device (CCD) moire method, scanning laser moire method, and electron moire method for microstrain deformation measurements. The femtosecond laser exposure produces mesoscopic variation patterns on the surface. These variation patterns make the grid in the scanning laser microscope and CCD images darker and make the grid in the scanning electron microscope image brighter. The CCD moire fringe, scanning laser moire fringe, and electron moire fringe consisting of bright and dark lines were generated. As a demonstration, microstrain distribution of the three-point bending tested specimen was measured.

Two-channel wavefront sensor arrangement employing moire deflectometry

Abstract: A wavefront sensor which takes advantage of the moire deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moire deflectometers. Directions of the grating's rulings are parallel in each moire deflectometer but are perpendicular in the two beams. Using a suitable array of lenses and mirrors two sets of moire patterns are projected on a CCD camera. A suitable spatial filter removes the unwanted frequencies. Recording the successive moire patterns by the CCD camera and feeding them to a computer, allow temporal fluctuations of the laser beam wavefront phase to be measured highly accurately. Displacements of the moire fringes in the recorded patterns correspond to the fluctuations of two orthogonal components of the angle of arrival (AA) across the wavefront. The fluctuations have been deduced in successive frames, and then evolution of the wavefront shape is determined. The implementation of the technique is straightforward and it overcomes some of the technical difficulties of the Schlieren and Shack-Hartmann techniques. The sensitivity of detection is adjustable by merely changing the distance between two gratings in both moire deflectometers and relative grating ruling orientation. This overcomes the deficiency of the Shack-Hartman sensors in that these require expensive retrofitting to change sensitivity. Besides, in the moire deflectometry, the measurement is relatively insensitive to the alignment of the beam into the device. Hence this setup has a very good potential for adaptive optics applications in astronomy. Since tilts are measured in the Shack-Hartmann method at discrete locations, it cannot detect discontinuous steps in the wavefront. By this method discontinuous steps in the wavefront are detectable, because AA fluctuations are measured across the wavefront.

MOIRÉ PATTERNS FROM A CCD CAMERA - Are They Annoying Artifacts or Can They be Useful?

Abstract: When repetitive high frequency patterns appear in the view of a charge-coupled device (CCD) camera, annoying low frequency Moire patterns are often observed. This paper demonstrates that such Moire pattern can useful in measuring surface deformation and displacement. What is required, in our case, is that the surface in question is textured with appropriately aligned black and white line gratings and this surface is imaged using a grey scaled CCD camera. The characteristics of the observed Moire patterns are described along with a spatial domain model-fitting algorithm that is able to extract a dense camera-to-surface displacement measures. The experimental results discuss the reconstruction of planar incline and curved surfaces using only a coarse 33 lines per inch line grating patterns printed from a 600 dpi printer.

Vibration measurement by spatiotemporal analysis of shadow moiré fringes

Abstract: A 3D Fourier transform for vibration measurement of an object based on shadow moire technique is presented A sinusoidal grating is placed closed to a vibrating object The moire fringe patterns generated by the interference of grating lines and shadow lines are captured by a high-speed camera The joint spatial and temporal information of the fringe sequence is processed by use of the 3D Fourier transform simultaneously rather than separately, then a 3D space-time phase distribution can be obtained from the filtered spatiotemporal spectra From the phase values, the surface profile, and displacement of the object at different time can be retrieved The experiment for measurement of a vibrating cantilever beam is used to demonstrate the validity of the technique The results show that shadow moire with spatiotemporal analysis can be applied to dynamic measurement

Threshold matrix generation method, halftone image generation method, and halftone image generating apparatus

Abstract: Each of moire elements which are repeat elements of first-order moire appearing by overlaying halftone images of first and second color components is positioned at one of candidate positions arranged at a moire pitch Pm in first and second moire directions orthogonal to each other. In a matrix area of a third color component, dot centers are arranged in a first tilt direction tilted relatively to the first moire direction by an angle of arctan((Pm)/(Pm)) and a second tilt direction orthogonal to the first tilt direction at a pitch of the square root of ((Pm 2 )+(Pm 2 )), and a threshold matrix of the color component is generated so that a halftone dot grows from each dot center in accordance with increase of gray level of the color component of the original image. Thus, it is possible to suppress second-order moire appearing in overlaying halftone images of the first to third color components.

Pattern for strain measurement

Abstract: PROBLEM TO BE SOLVED: To provide a strain measuring means capable of measuring consistently each strain each having a scale level without changing a sample SOLUTION: Following means are used, wherein this pattern for strain measurement is formed on a sample surface for visualizing strain of the sample by a strain-measuring method, and a plurality of patterns fit to each strain having each different scale level are formed in piles, on the same sample surface, and each pattern has each different regularity, shape or size mutually Furthermore, following means are also adopted, wherein, in the pattern for strain measurement, a grid pattern for a moire method and a dot pattern for an image correlation method are piled together, and the pattern is constituted of a milli-scale pattern and a nano-scale pattern COPYRIGHT: (C)2011,JPO&INPIT

Large-area and high-resolution distortion measurement based on Moiré fringe method for hot embossing process.

Abstract: A moire fringe approach is developed to identify simultaneously the global and local distortions in hot-embossed polymeric samples. A square grid pattern with a pitch of 63.5 μm is hot-embossed on the polymer substrate. When a reference grid, a polymeric film with the same pattern, is placed on top of the sample, a moire fringe pattern is observed and recorded by a document scanner. The deviation of the intersections of the fringes from their ideal positions presents the residual distortion in the sample. With different sample-reference rotation angles eight images are acquired for the same sample to achieve the optimal result by a data fitting technique. The validity of this method is proved by the self-consistency of the results from the eight images. To the best of our knowledge, this is the first time distortion quantification has been achieved both in a large area up to that of a scanner and with a high resolution at the level of 1 μm. Furthermore, we do not use any expensive instrument, nor need to measure the sample–reference rotation angle or position the sample precisely, and the process is run automatically by a computer instead of manual operation.

Substrate media distortion analysis

Abstract: Embodiments described herein are directed to detecting and/or measuring distortions of substrate media that can occur during a printing process. The distortion can be detected and/or measured using a composite image generated from a reference image having a first periodic pattern and print image, disposed on a test substrate media, having a second periodic pattern. The first and second periodic patterns are specified so that the composite image includes a moire pattern having moire fringes resulting from interference between the first periodic pattern associated with the reference image and the second periodic pattern associated with the print image. The moire fringes can be used to detect and calculate an amount of distortion of the test substrate media.

Using CCD Moiré Pattern Analysis to Implement Pressure-Sensitive Touch Surfaces

Abstract: The Moire fringe patterns obtained when a CCD camera views a repetitive line grating can be exploited to measure small changes to surface displacements. We describe how curved surfaces with line grating patterns can be reconstructed by analysing the instantaneous frequency of the extracted 1D Moire waveform. Experimental results show that monotonically increasing displacements of a stretched canvas of less than 1mm can be clearly separated, suggesting the possibility of using the proposed Moire-based vision technique to construct accurate pressure-sensitive touch surfaces.

One-shot three-dimensional surface profilometry using dmd-based two-frequency moiré and fourier transform technique

Abstract: This article presents an optical measurement method for acquiring rapidly accurate geometric 3-D surface morphology of objects. To achieve high-speed profilometry and avoid disturbance due to in-field vibration, one-shot Fourier transform profilometry (FTP) using two- wavelength digital moire pattern was developed to detect the morphology of the measured object at a speed of up to 60 frames or more per second. Single-fringe interferogram sufficient for FTP can be rapidly captured within a theoretical CCD acquisition time of down to 1 μs. The interferogram thus captured can be applied for further phase retrieving using the developed frequency transform and band-pass filtering strategies. The band-pass filter is designed to obtain phase information for optimizing the 3-D surface reconstruction with both dimensional and structural measurement accuracy. Furthermore, a standard step-height target was measured to analyze accuracy and repeatability of the developed methodology. Experimental results verified that the measurable step height can be effectively increased using the equivalent wavelength established by analyzing two-frequency moire pattern, thus increasing practical applicability of the developed system while achieving a micro-scale measuring depth resolution. The maximum measured error can be kept within 3.5% of the overall measuring range.

Using the moiré effect to increase the accuracy of diffraction methods for monitoring the geometrical parameters and the spatial position of objects

Abstract: This paper discusses a diffraction method of monitoring that makes it possible to use a measurement signal's phase component that carries data concerning the geometrical shape and spatial position of an object. To increase the measurement accuracy and sensitivity, a data-processing optical system was implemented in which the test object is illuminated by two beams of coherent radiation displaced in space. This made it possible to introduce a phase shift between their frequency spectra while varying the parameters of the object and to obtain moire interference fringes in the recording plane, by analyzing which data can be obtained concerning the test object. An example is given of the use of the method to investigate the shape of the edge profile of an object.

Method of extracting high-resolution digital Moiré fringe in warpage measurement

Abstract: Thermally induced stresses play a very important role in controlling the structural reliability of microchip packages. To address this issue, the shadow moire interferometry is developed, which has been widely used in the field of observation for its real-time and high resolution. But how to extract the moire fringes by using digital image processing method from a original Moire fringe pattern is the key to accurate measurement of the warpage. The paper mainly concentrates on the method of effectively extracting the shadow moire fringes from interference pattern produced by warpage of the PWB board and BGA package. Firstly, the low passing filtering and the dynamic threshold binarization proposed in this paper are applied to preprocess the moire pattern. Then, the medial axis transformation and pruning algorithm applied to extract skeleton of moire fringe have been put forward. Because the forficate fringes and noise fringes are main factors to affect precision of measurement, a effective main fringe extracting algorithm is proposed, which not only identifies and removes the forficate fringes and noise fringes from the main fringes, but also can connect the crack fringes which are hardly avoided after thinning operation. Finally, the information of warpage can be obtained from the location and orientation of moire fringes. The three-dimensional delineation of detected object is resolved according to the moire fringes extracted from shadow moire pattern.

Moire shape measurement apparatus using liquid crystal display panel

Abstract: Disclosed herein is a moire shape measurement apparatus using a Liquid Crystal Display (LCD) panel. The moire shape measurement apparatus includes a light source, a variable grating, a viewing lens, a light receiving unit, a computation unit, and a driving device. The light source emits light. The variable grating passes the emitted light therethrough, and creates a projection grating pattern. The viewing lens focuses a reflected grating pattern that is obtained when the projection grating pattern is reflected from the object. The light receiving unit receives the light of the reflected grating pattern passed through the viewing lens. The computation unit previously stores the viewing grating pattern, forms the moire pattern by overlaying the reflected grating pattern, received from the light receiving unit, on the stored viewing grating pattern, and computes the shape of the object using the moire pattern. The driving device adjusts a direction and a pitch in order to form a grating of the variable grating.

Moire device using digital micromirror device

Abstract: A Moire device using a digital micromirror device is provided to reduce a measuring time by measuring two kinds of lattices with different colors in one frame at the same time using a color camera. An optical source(100) produces the collimated light. Two kinds of filters have different colors and make one frame. A DMD(Digital Micromirror Device)(300) generates a lattice pattern about the filter with different colors. A projection lens(400) projects the lattice pattern to one object. An imaging lens(600) receives respective lattice pattern which is projected to the object and transformed. A camera sensor(700) calculates an initial phase value by the sum of the received lattice pattern.

Extracting projections from laser moire interference spectra

Abstract: Laser Moire Interference spectra of rocket exhausted plumes were analyzed. Projections for reconstruction were figured out, and air density distribution was reconstructed. Moire deflectograms of the plumes were produced and captured with a home-made, wide-range, high-sensitivity Moire deflectometer. Moire interference spectra were processed by phase unwrapping technique with Fourier transform, so the space phase distribution of Moire deflectograms was extracted. The background was worked out based on the margin of the Moire deflectograms, and so was the space phase distribution of the background. The phase shift distribution of distorted Moire interference spectra could easily be obtained by calculating the difference between the two space phase distributions. The relative projections could be extracted from the phase shift distribution. The air density distribution of the plumes was calculated by simple self-correlative algebraic reconstruction technique (SSART) based on deflected angles for projections. Eight projections with equal direction interval of 20 degree were used for reconstructing the air density distribution of a plume section. As a result, with phase unwrapping technique based on Fourier transform, any cross section projection could conveniently be worked out from the Moire deflectogram of rocket exhausted plumes. The air density distribution of the cross section could be reconstructed by SSART. So, SSART with deflected angle for projection is a kind of super nonlinear deflection tomography.

Moire type heat distortion measuring device

Abstract: PROBLEM TO BE SOLVED: To dispense with such a pretreatment as coating of paint and the like for a measurement object with black or mirror surface in a moire type heat distortion measuring device. SOLUTION: Desired temperature change is given to a measurement object 6 in a thermostatic chamber 2 and the heat distortion of the measurement object caused by the temperature change is to be measured by a moire sensor 3 through a transparent plate 12 at a window part 11 of the thermostatic chamber in a moire type heat distortion measuring device 1. The moire sensor comprises: a grid 15 where predetermined grid pattern is formed; an illuminating system 16 causing generation of the distortion grid pattern on the measurement object by irradiating illumination light to the measurement object through the grid; and a photographing system 17 obtaining images containing the moire pattern by photographing the distortion grid pattern in the measurement object through the grid. Parallel light beam is used as illumination light of the illumination system. COPYRIGHT: (C)2009,JPO&INPIT

Method and apparatus for measuring image

Abstract: PROBLEM TO BE SOLVED: To achieve an apparatus for subjectively evaluating moire generated on a flat display panel. SOLUTION: On a screen of the display panel 6, there are formed many display elements. On an image sensor built in a digital camera 1, there are formed many imaging pixels. The imaging pixels of the image sensor are smaller than the display pixels of the display panel 6. A plurality of points of the display pixels of the display panel are imaged by the imaging pixels of the image sensor. With respect to all display pixels of the display panel 6, a brightness evaluation is performed by a personal computer 5 to synthesize moire patterns. Thus, only the moire of the display image can be evaluated without being affected by moire between the display panel and the image sensor. COPYRIGHT: (C)2011,JPO&INPIT

Method for inspecting scanning accuracy of scanning irradiation device

Abstract: PROBLEM TO BE SOLVED: To provide a method for easily inspecting the scanning accuracy of a scanning irradiation device by using a moire method for enlarging a slight difference in interval and showing it, especially an electron beam moire method excellent in measurement in a minute region. SOLUTION: An image is obtained by making a board and a material for grids different in permeability, or reflection characteristics, or electron/ion generating characteristics to a particle beam or an energy beam, and emitting the particle beam or energy beam in parallel or with an acute angle to a reference board as an inspection sample acquired by forming grids on the board, in such a way as to perform scanning. A grid to be a reference is manufactured so as to be proportionate to the capability of a device to calibrate the grid so as to perform inspection of a wide range of magnification, and by using the grid, moire fringes are generated. By the shape of these moire fringes, ununiformity and inaccuracy of a scanning width are inspected and calibrated. COPYRIGHT: (C)2009,JPO&INPIT

Grid projection type moire device and shape measuring method

Abstract: PROBLEM TO BE SOLVED: To provide a grid projection type moire device capable of easily changing the pitches of both grids, removing an unnecessary fringe, and performing irregularity determination of a measurement object with a simple constitution. SOLUTION: A grid projection type moire device for measuring shape of a measurement object comprises: a projection optical system 20 for projecting the shape of a first liquid crystal grid 26 on a measurement object 42; an image-forming optical system 30 for image-forming the deformation grid image formed on the measurement object 42 on a second liquid crystal grid 38; a photographing part 32 for photographing the moire fringe formed by the image-forming to acquire the moire fringe image; and a control part 50 for controlling the grid patterns of the first liquid crystal grid 26 and the second liquid crystal grid 38. COPYRIGHT: (C)2009,JPO&INPIT

Vertical reflective type moire measurement structure for measuring the surface curvature of an object

Abstract: A vertical reflective type moire measurement structure for measuring the surface curvature of an object includes a light source device capable of producing light source and forming a collimation expandable light through a light beam collimator; the collimation expandable light penetrates a first amplitude gratings and reflects the collimation expandable light onto the surface of an object to be tested through a spectrometer; to generate a self- image is; the self- image is reflected again from the surface of the tested object to form an image on the second amplitude gratings to constitute a moire image; a measurement device is employed to detect the moire image and calculate the inclination angle of the moire image so that the surface curvature of the object can be measured.