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Showing papers on "Moiré pattern published in 2006"


Journal ArticleDOI
TL;DR: An accurate pixel-to-pixel correspondence adjustment in the DMD camera by means of the phase-shifting moiré method is proposed, which provided very accurate adjustment whose error was less than 1/25 pixel.
Abstract: A camera based on the digital micromirror device (DMD) technology has been previously developed. In this optical system, the correspondence of each mirror of the DMD to each pixel of the CCD cannot readily be done since the pixel sizes of the DMD and the CCD are very small. An accurate pixel-to-pixel correspondence adjustment in the DMD camera by means of the phase-shifting moire method is proposed. To perform high accurate adjustment of the optical system, the phase distribution of a moire fringe pattern is analyzed when the CCD pixels and the DMD mirrors have a mismatch and/or misalignment with each other. This technique does not need a complicated setting or complex image processing to generate the moire fringe pattern, and it needs only one captured image. In the adjustment experiment, the proposed method provided very accurate adjustment whose error was less than 1/25 pixel. An experiment of phase analysis to demonstrate the usefulness was performed.

52 citations


Journal ArticleDOI
TL;DR: In this paper, a high-precision approach for determining fluctuaions in the angle of arrival was proposed, based on the use of the moire technique, where a low frequency grating (carrier grating) is installed at a suitable distance from a telescope, its image, practically, forms on the focal plane of the telescope objective.
Abstract: There are several methods for measuring ground-level atmospheric turbulence parameters, such as the refractive index profile and its fluctuations, correlations of the fluctuations in space and time, and the atmospheric refractive-index structure constant. These methods are based mainly on the measurement of fluctuations in intensity and location of an image formed by light propagating in the turbulent atmosphere or the fluctuations in impinging points of narrow light beams traversing the ground-level atmosphere. Exploiting the moire technique, we suggest a high-precision approach for determining fluctuaions in the angle of arrival. When a low-frequency grating (carrier grating) is installed at a suitable distance from a telescope, its image, practically, forms on the focal plane of the telescope objective. Superimposing a physical grating (probe grating) of the same pitch as the image grating on the image forms the moire pattern. The atmospheric turbulence distorts the image grating. Processing the fluctuations of successive moire fringes can yield the mentioned parameters across a rather large cross section of the atmosphere with high accuracy, because of the moire technique's magnifying character and access to a large volume of data, and does so in a comparatively simple and reliable manner.

31 citations


Patent
Shen-ge Wang1, Robert P. Loce1
30 Nov 2006
TL;DR: In this paper, a method and apparatus for moire-free color halftone printing with up to four color image separations is presented, which utilizes a plurality of non-orthogonal halFTone screens to produce outputs that are moire free and form uniform periodic rosettes.
Abstract: Disclosed herein is a method and apparatus for moire-free color halftone printing with up to four color image separations. The method and apparatus utilize a plurality of non-orthogonal halftone screens to produce outputs that are moire free and form uniform periodic rosettes. The method and apparatus provide for defining a first and a second color halftone screen fundamental frequency vector for each of three halftone screens such that the halftone screen set output forms uniform hexagonal rosettes; then defining a fourth color halftone screen where a first fundamental vector of the fourth screen shares a fundamental frequency vector with one of said three halftone screens and a second fundamental frequency vector of the fourth screen shares a fundamental frequency vector with a different one of said three color halftone screens.

16 citations


Journal ArticleDOI
TL;DR: In this article, a novel class of moire patterns, i.e., LSCM moire pattern, is presented and investigated by experiment by integrating moire method with laser scanning confocal microscopy (LSCM).
Abstract: By integrating moire method with laser scanning confocal microscopy (LSCM), a novel class of moire patterns, i.e., LSCM moire patterns, is presented and investigated by experiment in this article. The moire patterns are formed by the interference of a 1200line∕mm cross-line holographic grating and the scanning lines of LSCM. The principles and conditions of forming LSCM moire are described in detail. The measured parameters of moire fringes from experimental images agree well with theoretical analysis. The experimental results verify the feasibility and reality of the proposed moire method to be another effective and high accuracy technique for measuring and observing in-plane microdeformation at micrometer scale.

14 citations


Proceedings ArticleDOI
TL;DR: In this article, an advanced NUC procedure is described in which the Moire patterns are successfully subtracted, leading to improved levels of residual non-uniformity, and it is shown that Moire fringes exist at the unit-under-test image plane where they appear in general as sampling noise.
Abstract: Resistor array infrared projector nonuniformity correction (NUC) is currently limited in fidelity. In the flood technique a fundamental limitation has been the inevitable presence of Moire fringes. In this paper, an advanced NUC procedure is described in which the Moire patterns are successfully subtracted, leading to improved levels of residual nonuniformity. It is shown that, irrespective of the projection technology, the Moire fringes exist at the unit-under-test image plane where they appear in general as sampling noise. Their control through choice of mapping ratio is discussed.

14 citations


Patent
Shen-ge Wang1, Robert P. Loce1
30 Nov 2006
TL;DR: In this article, a method and apparatus for moire-free color halftone printing with up to five color image separations is presented, which utilizes a plurality of non-orthogonal halFTone screens to produce outputs that are moire free and form rosettes.
Abstract: Disclosed herein is a method and apparatus for moire-free color halftone printing with up to five color image separations. The method and apparatus utilize a plurality of non-orthogonal halftone screens to produce outputs that are moire free and form rosettes. The method and apparatus provide for defining a first and a second color halftone screen fundamental frequency vector for each of three halftone screens such that the halftone screen set output forms moire-free rosettes; then defining a fourth color halftone screen where a first fundamental vector of the fourth screen shares a fundamental frequency vector with one of said three halftone screens and a second fundamental frequency vector of the fourth screen shares a fundamental frequency vector with a different one of said three color halftone screens; and further defining a fifth color halftone screen where a first fundamental vector of the fifth screen shares a fundamental frequency vector with one of said three halftone screens and a second fundamental frequency vector of the fifth screen shares a fundamental frequency vector with a different one of said three color halftone screens, and the neither of the fundamental frequency vectors of the fifth screen are equal to either of the fundamental frequency vectors of the fourth screen.

12 citations


Proceedings ArticleDOI
28 Jan 2006
TL;DR: In this paper, the refractive index profile of optical fiber preform is measured by a nondestructive technique based on Talbot interferometry, which is done by means of 4-step phase shift technique.
Abstract: The refractive index profile of optical fiber preform is measured by a nondestructive technique based on Talbot interferometry. In this technique the preform is placed between two ronchi ruling gratings of 10 lines/mm and the system is illuminated by an expanded and collimated beam of He-Ne laser. In this arrangement the 2nd grating is positioned in the Talbot image of the 1st grating and the preform axis is parallel to the gratings planes. To eliminate the effect of clad on the light beam deflection during the measurements, the preform is immersed in an index matching liquid. The phase front of the laser light over the 2nd grating can be monitored by analysis of the moire pattern which is formed over there. The analysis is done by means of 4-step phase shift technique. In this technique the second grating is moved in four steps of 1/4 of the grating vector and in each step the intensity profile of the moire pattern is recorded. The phasefront can be specified by using the recorded intensities. The refractive index profile of the preform can be calculated from the changes on phasefront while the preform is placed between the gratings respect to the case when it is absent. The whole procedure is automated and computer controlled by using a CCD camera to record the moire fringes, a stepper motor for linear translation of the 2nd grating and a code in MATLAB to control the system and measurements.

12 citations


Journal ArticleDOI
TL;DR: In this article, a multi-point diffraction strain sensor was developed using a moire interferometer with the added feature of whole-field strain determination, which was implemented by simultaneous tracking of sampled wavefront diffracted from the component under test.
Abstract: A multipoint diffraction strain sensor has been developed using a moire interferometer with the novel added feature of whole-field strain determination. This unique feature has been implemented by simultaneous tracking of sampled wavefront diffracted from the component under test. In this sensor a high-frequency diffraction grating is bonded on the specimen, which is illuminated by two symmetric collimated laser beams, as in a typical moire interferometer. The first orders of diffracted beams impinge on a CCD camera, via a microlens array. The lens array serves a dual purpose—to sample the diffracted wavefront and to focus the wavefront to a number of spots on the CCD. The deviation of the individual spots generated by both the beams is directly proportional to the normal strain and a component of the shear strain. Simultaneous strain measurement at more than a thousand points can be readily obtained and is demonstrated in this paper. This novel technique is expected to be very valuable in numerous industrial metrology applications.

10 citations


Journal ArticleDOI
TL;DR: In this paper, a digital nano-moire method with wavelet transformation is explored to measure nanoscale in-plane displacement fields by applying e-beam lithography, a periodic PMMA nanostructure array is fabricated directly on the specimen and used as the specimen grating.
Abstract: A digital nano-moire method with wavelet transformation is explored to measure nanoscale in-plane displacement fields. By applying e-beam lithography, a periodic PMMA nanostructure array is fabricated directly on the specimen and used as the specimen grating. Moire patterns are generated by overlapping the images of the PMMA specimen grating obtained from AFM scanning and the virtual reference grating produced by a digital image generating process. Then, the overlapped images are filtered by the 2D wavelet transformation (WT) to capture the target moire patterns. Existing methods, by overlapping the monitor-generated scanning lines with the image of the specimen grating, cause a mismatch problem. Previously, the carrier moire method was explored with the aim of curing the mismatch problem. Unfortunately, the carrier moire method, in addition to suffering from increased complexity of mathematical calculations, is incapable of directly obtaining the displacement field. Thus, the mismatch problem will result in inconveniences and restrictions in the practical application. Instead of using monitor-generated scanning lines, the proposed method applies the virtual reference grating, and thus puts the mismatch problem to rest. Nevertheless, the resultant moire image suffers from low contrast which, if left untreated, might distort the measurement result. Therefore, the WT, known for its sharpened abilities of characteristic and edge detection, is used to capture the target moire patterns and improve the measurement accuracy. The proposed method has been carried out in the laboratory. Experimental results have shown that the proposed method is convenient and efficient for nanoscale displacement measurement.

9 citations


Patent
30 Jun 2006
TL;DR: In this article, the authors provide a moire removing method, along with a manufacturing method of a display, to acquire an image of high resolution and reduced moire, where the image where the moire has occurred is converted into the signal of frequency axis (step S1).
Abstract: PROBLEM TO BE SOLVED: To provide a moire removing method, along with a manufacturing method of a display, to acquire an image of high resolution and reduced moire. SOLUTION: The signal of spatial axis representing the image where a moire occurs is converted into the signal of frequency axis (step S1). The signal of frequency axis is subtracted with a frequency component corresponding to the moire (step S2). The signal of frequency axis in which a frequency component corresponding to moire is removed is converted into the signal of spatial axis (step S3). Thus, the moire is removed from the image where the moire has occurred. COPYRIGHT: (C)2008,JPO&INPIT

8 citations


Proceedings ArticleDOI
TL;DR: In this article, the authors introduced a new method for measuring the MTF of the atmosphere in the surface layer, based on moire technique, using a low frequency Ronchi grating installed at a certain distance from a digital camera equipped with a tele lens.
Abstract: The turbulence of the atmosphere puts an upper limit on the quality of the image of a ground object obtained by long-exposure photography from low or high altitudes in the atmosphere or in the space By using good optics and high resolution film or CCD and a stable platform, this limit could be approached but not exceeded A useful quantity for indicating the magnitude of this limit is the integral of the modulation transfer function (MTF) associated with the turbulence In this work, we introduce a new method for measuring the MTF of the atmosphere in the surface layer, based on moire technique In this technique, from a low frequency Ronchi grating, installed at a certain distance from a digital camera equipped with a tele lens, successive images are recorded and then transferred to a PC By rotating each image by θ/2 and -θ/2, say ±3°, and superimposing them, a large number moire patterns are produced The average transmittance function of the superimposed image gratings is measured in a moire fringe interval The latter function is measured by scanning the moire pattern by a slit parallel to moire fringes It is shown theoretically that from the Fourier transform of the latter function the MTF of the atmosphere can be deduced, if the MTFs of the imaging system and the grating are given or their effects are negligible The atmospheric MTFs have been measured at different turbulence conditions Also, we have studied the behavior of the atmospheric MTF respect to exposure time

Journal ArticleDOI
TL;DR: In this article, an improved method for testing the collimation of an incoherent optical beam using Lau interferometry is presented, which consists of a white light source and a set of three identical gratings.
Abstract: An improved method for testing the collimation of an incoherent optical beam using Lau interferometry is presented. The experimental setup consists of a white light source and a set of three identical gratings. A source grating G1 is placed in front of a collimating lens. Beyond the collimating lens gratings G2 and G3 are so aligned that the lines of the gratings make a small but equal and opposite angle with the vertical. The self-image of grating G2 is superimposed on the grating G3, resulting in the generation of moire fringes. Decollimation of the optical beam results in a change in the dimensions of the self-image. This change is detected using the magnification effect of the moire method. The horizontal moire fringes are indicative of collimation of the optical beam. Deviation from the horizontal inclination of the moire fringes indicates setting in of decollimation. Theoretical and experimental investigations to determine the sensitivity achievable in this collimation testing technique are undertaken and results of the investigations are reported. Experimental results are in close agreement with the theoretical predictions.

Proceedings ArticleDOI
10 Feb 2006
TL;DR: In this paper, a structured light projection technique for measuring the relief of objects, or object areas, of micrometric size (approximately 500μm x 500 μm), is described.
Abstract: Implementation of a structured light projection technique for measuring the relief of objects, or object areas, of micrometric size (approximately 500 μm x 500 μm), is described. It is well-known that when a fringe pattern is projected on an object, the fringes are deformed according to the topography of its surface. This deformed fringe pattern is a modulated optical signal that allows us to measure the relief of the object. Through one of the oculars of a stereomicroscope, previously focused on the object under study, the fringe pattern of one the Talbot self-image is projected. The deformed fringe patterns are observed by the other ocular, in which a CCD camera is mounted to digitize them. Digitized fringe patterns are demodulated by means of a second virtual reference grating. As a result, a moire fringe pattern is obtained delivering a wrapped phase map when is digitally processed by means of a phase recover technique. Phase recovery techniques for obtaining the wrapped phase maps are phase-shifting and spatial phase synchronous. Experimental results and the conditions, under which the topography of an object section is determined, are shown. Also, comparisons over quality between the phase recovery techniques are discussed.

Patent
11 Oct 2006
TL;DR: In this article, a Mohr pattern adjust method was used to detect the optical path of plane holographic grating, where spherical convex lens was used as collimator.
Abstract: The invention relates to a Mohr pattern adjust method of preparing optical path of holographic grating. Wherein, it uses spherical convex lens as collimator, uses Mohr pattern adjust method to detect the preparing optical path of plane holographic grating. Therefore, the axial and off-axis adjust errors in traditional optical path adjust method can be effectively eliminated; and the wave aberration of prepared pulse compress grating can be reduced most; and it can be used in other general grating.

Proceedings ArticleDOI
13 Feb 2006
TL;DR: In this paper, a simple and practical method for regulating light path of large size pulse compression grating with big size is introduced, where the real grating and the imaginary one produced by two constructive beams interference overlap to produce the moire fringe pattern.
Abstract: Large size pulse compression grating (PCG) with needs high adjusting precision in the light path of PCG fabrication. Note that the longitudinal error is the most error source of diffraction wavefront aberration of grating. It is difficult from conventional light path regulation to obtain such small longitudinal regulative error. A simple and practical method for regulating light path of PCG with big size is introduced. Rotate the grating fabricated by conventional light path adjustment and place it on the original recorded plane. The real grating and the imaginary one produced by two constructive beams interference overlap to produce the moire fringe pattern. Generally speaking, conventional regulation generates longitudinal error that results in cirques. Regulating the pinhole till Moire fringes become parallel and straight, and then backtrack with half of the regulating quantity, which is called Moire fringe method (MFM). With that, the problem that longitudinal precision of conventional light path adjustment is low is solved. To begin with the imaging formula of holographic lens, the principle of MFM is deduced theoretically. From results generated by ZEMAX software, the diffraction wavefront aberration of grating can be reduced to the least by MFM effectively. Proceeding with the relationship between optical system of holographic grating and the diffraction wavefront aberration of grating, the aberration of moire fringes obtained by analyzing the deviation of the fringes from parallel straight lines is about twice as the diffraction wavefront aberration of grating by reference to primary aberration theory.

Journal ArticleDOI
TL;DR: In this article, a multichannel imaging position-sensitive detector has been developed and characterized, with the novel feature of simultaneous measurement of strain and tilt at a large array of points, using principles of diffraction to directly measure strain at the desired points.
Abstract: A multipoint diffraction strain and tilt sensor using a multichannel imaging position-sensitive detector has been developed and characterized, with the novel feature of simultaneous measurement of strain and tilt at a large array of points. Unlike conventional interferometry based systems, this new whole-field measurement system uses principles of diffraction to directly measure strain at the desired points. The system utilizes a moire interferometer for the generation of two coherent and symmetric beams, which illuminate a high-frequency diffraction grating, bonded on the surface of the sample under test. The core of the system is a charge coupled device camera fitted with an array of microlenses, which samples the diffracted beam into an array of beamlets. The camera with lens array, which is being used as array-type multichannel position-sensitive detectors, senses the shift of the individual microspots. The deviation is then processed and the normal and shear strains are calculated at that spot along ...

Journal ArticleDOI
01 Aug 2006-Strain
TL;DR: In this article, an optical experimental method for analysis of derivatives of dynamic displacements from patterns of time-average moire fringes is proposed for two-dimensional elastic structures performing in-plane vibrations.
Abstract: Optical experimental method for analysis of derivatives of dynamic displacements from patterns of time-average moire fringes is proposed in this paper. Derived analytical relationships for one-dimensional optical model are validated for two-dimensional elastic structures performing in-plane vibrations. The fact that digital image filtering techniques are normally required for the identification of time-averaged super-fringes does not lessen the practical value of the proposed method.

Patent
20 Nov 2006
TL;DR: In this article, the design of periodic screens for halftone patterns is based upon a series of constrained optimization problems, where a pattern is found that minimizes a cost function, which is a spatial-frequency weighted difference between an ideal, continuous-space pattern and a predicted reconstructed pattern.
Abstract: The design of periodic screens for halftone patterns is based upon a series of constrained optimization problems. For each of a number of input levels, a pattern is found that minimizes a cost function. The cost function is a spatial-frequency weighted difference between an ideal, continuous-space pattern and a predicted reconstructed pattern. The frequency weighting is a parameterized trade-off between the preservation of periodic components and the introduction of non-harmonic components.

Journal ArticleDOI
TL;DR: In this article, an electron moire method for a common scanning electron microscope without the beam control device is presented, and a grating based on a multi-scanning concept is fabricated in any observing mode.
Abstract: In the electron moire method, a high-frequency grating is used to measure microscopic deformation, which promises significant potential applications for the method in the microscopic analysis of materials. However, a special beam scanning control device is required to produce a grating and generate a moire fringe pattern for the scanning electron microscope (SEM). Because only a few SEMs used in the material science studies are equipped with this device, the use of the electron moire method is limited. In this study, an electron moire method for a common SEM without the beam control device is presented. A grating based on a multi-scanning concept is fabricated in any observing mode. A real-time moire pattern can also be generated in the SEM or an optical filtering system. Without the beam control device being a prerequisite, the electron moire method can be more widely used. The experimental results from three different types of SEMs show that high quality gratings with uniform lines and less pitch error can be fabricated by this method, and moire patterns can also be correctly generated.

Journal ArticleDOI
Yi Zhao1, Xin Zhang1
TL;DR: In this article, a geometric moire pattern is generated by the inference between the polymer nanostructures and the scanning lines of a CCD video camera, which is observed at different temperatures from 298 to 398 K. The change of the strain/pitch as the temperature varied was calculated from the pure extension and the angular moire fringes.
Abstract: The nanometer-scale in-plane deformation of a PDMS nanostructure array was demonstrated using a geometric moire technique. The polymer nanostructures with cylindrical profile were fabricated by using the combination of e-beam lithography, reactive ion etching, and replica molding. The moire pattern is generated by the inference between the polymer nanostructures and the scanning lines of a CCD video camera. A uniform thermal expansion was induced in the polymer nanostructures. The moire pattern change was observed at different temperatures from 298 to 398 K. The change of the strain/pitch in the nanostructures as the temperature varied was calculated from the pure extension and the angular moire fringes. The results show the feasibility of using such polymer nanostructures as force sensors to measure the mechanical forces on the order of a few nanonewtons or less. This work has a representative application in mechanics study of the biological objects, e.g. living cells and protein, under their environmental conditions.

Journal ArticleDOI
TL;DR: In this article, the sharpening of fringes in time averaged moire patterns is proposed for the analysis of dynamical systems with non-harmonic motion as the produced moire pattern is particularly blurred.
Abstract: Time averaging interferometry is an experimental technique widely applied in different areas of optical engineering. Typical example is an application of time averaging techniques for the analysis of fringes produced by a moire grating formed on the surface of oscillating elastic structure. Unfortunately, time averaged moire produces blurred images. Therefore, special digital image filtering is to be used for highlighting the pattern of time averaged fringes. Such a procedure is essential for the investigation of dynamical systems with non-harmonic motion as the produced moire pattern is particularly blurred. This paper proposes some techniques for the sharpening of fringes in time averaged moire patterns.

Journal ArticleDOI
TL;DR: In this article, it was shown that moire fringes can also arise in the spatial distribution of the coincidence count rate of twin photons from the parametric down-conversion, when spatial structures with different frequencies are placed in the path of each one of the twin beams.
Abstract: Moire patterns are produced when two periodic structures with different spatial frequencies are superposed. The transmission of the resulting structure gives rise to spatial beatings which are called moire fringes. In classical optics, the interest in moire fringes comes from the fact that the spatial beating given by the frequency difference gives information about details (high spatial frequency) of a given spatial structure. We show that moire fringes can also arise in the spatial distribution of the coincidence count rate of twin photons from the parametric down-conversion, when spatial structures with different frequencies are placed in the path of each one of the twin beams. In other words, we demonstrate how moire fringes can arise from quantum images.

Journal Article
TL;DR: In this paper, a rotary moire deflectometer is designed to capture multidirectional optical projections, and the information of fringe pattern is Abstracted by phase unwrapping using Fourier transform.
Abstract: Moire tomography is applied in fully quantitative measurement of temperature distribution.Rotary moire deflectometer is designed to capture multidirectional optical projections,and moire patterns of temperature field can be obtained in 180 degrees.The information of fringe pattern is Abstracted by phase unwrapping using Fourier transform.The temperature distribution of asymmetric flow field is calculated from incomplete projection data by a new iterative reconstruction algorithm,which is derived from basic moire deflection formula and discrete element reconstruction technique.The deflection angle is applied directly in iteration,which is completely different from the previous transform methods and existing series expansion methods.In experiment,the asymmetric temperature distribution was reconstructed by 8 projections with different view angles,and some measurement errors were discussed.The results prove that it is an accurate and practical tomography technique.

Proceedings ArticleDOI
26 Jan 2006
TL;DR: In this paper, a CCD camera is used to image a large-scale low frequency linear periodical pattern painted on a vertical plane on a transmission grating, and a probe grating is shifted in definite steps in its plane in a direction perpendicular to its lines.
Abstract: In glass casting or shaping processes, some times wavy and distortion defects are developed in glass sheets. Specifying the locations of these defects and measuring the deflections they cause are significant parameters in many applications. There are several techniques for observing and measuring these defects, but the technique we introduce in this work is more simple and flexible and can be easy installed in production line for quality controlling purposes. The presented deflectometer functions in the following way. The imaging system of the device forms an image of large-scale low frequency linear periodical pattern painted on a vertical plane on a transmission grating. The distance between the object grating (painted pattern) and the second grating is so that the frequencies of the image grating and the second (probe) grating are practically the same. There is a small angle between the lines of the latter gratings to form moire fringes. A CCD camera transfers the moire fringes to a PC. By applying phase shifting technique, which is realized by shifting the probe grating in definite steps in its plane in a direction perpendicular to its lines, the phase distribution due to imprecations in optical system and gratings, are specified, At this stage the defected sheet glass is installed between the object grating and the imaging system and the distorted moire pattern is processed as described before. The difference between two-phase distributions is the phase distribution caused by the defects in the glass, which can be easily converted into the required ray deflections. All the processes are carried out automatically in a time less than 30 seconds and the accuracy of the measurement is of the order of 20 arc seconds.

Patent
31 Oct 2006
TL;DR: In this article, the authors proposed a method to eliminate potential moire patterns in digitized images by employing a one-dimensional sensor array and a sampling method of the sensor signals which produces a data set of non-uniformly spaced sensor positions.
Abstract: A device and process which eliminates potential moire patterns in digitized images by employing a one-dimensional sensor array and a sampling method of the sensor signals which produces a data set of non-uniformly spaced sensor positions. This allows the spacing of the sensors to avoid having a strong “harmonic” which may interfere with details or harmonics present in the image source, which eliminates the occurrence of moire patterns and the need for application of image processing to remove moire patterns. Sensors are non-uniformly spaced along a first axis according to a predetermined, deterministic and predictable schema or function. Sensors are sampled during scanning according a non-uniform function in order to realize a non-uniform sampling scheme in a second dimension. Linear interpolation is applied to the non-uniformly spaced data set, synthesizing a uniformly-spaced data set for use in common imaging formats and processing.

Proceedings ArticleDOI
12 Oct 2006
TL;DR: In this article, the approach described here takes advantage of moire methods used in connection with the fringe projection method to provide high resolution over key reference areas, while still provided a less precision measurement over a larger region.
Abstract: Projected fringe methods have lead to a wide selection of commercial sensors for 3D measurement applications. The basis of these systems is a projector such as an LCD presentation projector that is used to generate a coarse pattern that is shifted across the part and viewed by a camera. Three or more images with a small pattern shift between each are sufficient to obtain a detailed 3D map using phase shift analysis methods. The limitation of these systems has been that to obtain high resolution the system is limited to viewing only a small field-of-view. Moire methods are a way to leverage this resolution, particularly on flat or only slightly contoured areas. The approach described here takes advantage of moire methods used in connection with the fringe projection method to provide high resolution over key reference areas, while still provided a less precision measurement over a larger region.

Proceedings ArticleDOI
TL;DR: Compared with traditional digital moire methods, this method achieves an absolute measurement of 3D surfaces because the information contained in the pattern is globally structured, and discontinuity measurement can be solved more easily.
Abstract: In this paper, a two-dimensional, binary fringe pattern is designed as structured light for 3D measurement. A feature, i.e., a white cross, is placed in the center of the fringe grating. The cross serves as the axes of a reference frame. White square grids are alternated by black stripes vertically or horizontally elsewhere. The relative position of a given point on the fringe with respect to the center can be identified. When the fringe pattern is projected onto the surface of the object, its image is distorted. Therefore, image processing and pattern recognition algorithms are designed to calculate which row and column the particular point belongs to in the original fringe-frame. The pair of emitting and receiving angles for each point in the fringe and CCD frames, respectively, is acquired. Also the coordinate of each 3D point can be calculated. Compared with traditional digital moire methods, this method achieves an absolute measurement of 3D surfaces because the information contained in the pattern is globally structured. Therefore, discontinuity measurement can be solved more easily. Resolution of the proposed method is higher than that of current methods of coding patterns under the same line width limitation due to the principle of pattern design.

Proceedings ArticleDOI
TL;DR: A non-contact system for obtaining three-dimensional objects topography that combines the fringe projection technique and the Talbot effect which is knowed like Talbot interferometry is presented.
Abstract: We present a non-contact system for obtaining three-dimensional objects topography The described system combines the fringe projection technique and the Talbot effect which is knowed like Talbot interferometry In fringe projection technique, the digitalization is realized when black and white lines are projected over the object and this image is captured by the CCD In Talbot interferometry, the object is collocated on one of the grating auto-image planes The deformed grating image is captured by the CCD and superposed with other reference one that can be physical or computer generated (virtual/synthetic) for obtaining a moire pattern which gives information about the object topography The topography of a coin and phalangeal articulation are obtained by using of this technique The Spatial Synchronous Detection and Fourier Method were incorporate to retrieve the phase

Patent
15 May 2006
TL;DR: In this article, a method of setting frequency rate and angle differences between screens where moire patterns are not generated is provided, where the frequency component (cost) is calculated with respect to the binary image using the calculated average reflectivity.
Abstract: A method of setting frequency rate and angle differences between screens where moire patterns are not generated is provided. The method of setting the frequency rate and angle differences of the screens includes forming a binary image using at least two overlapped screens, and low-pass filtering the binary image to calculate an average reflectivity. A frequency component (cost) is calculated with respect to the binary image using the calculated average reflectivity. It is determined whether a moire pattern with respect to the binary image is generated based on the frequency component. Accordingly, the binary image where the moire pattern is not generated may be formed.

Patent
25 Oct 2006
TL;DR: In this paper, the authors used standard raster specimen, using LSCM scanning moire method to obtain scan moire image, to proceed four steps phase shift processing to originality image though moire phase shift technology to obtain phase map, after unpackaging to obtain originality phase map according to phase and displacement field relation to obtain scanning perturbed field.
Abstract: The present invention adopts standard raster specimen, using LSCM scanning moire method to obtain scanning moire image, to proceed four steps phase shift processing to originality image though moire phase shift technology to obtain phase shift moire image, according to moire phase shift theory to obtain phase map, after unpackaging to obtain originality phase map, according to phase and displacement field relation to obtain scanning perturbed field, thereby reaching correction target. Compared with current method, the present invention can directly measure scan line perturbed field resulted from scanning control unit distortion phenomena through scanning moire and moire phase shift technology , with high precision, simple operation, and real time and all field measurement.