Showing papers on "Moiré pattern published in 1984"

Absolute and comparative measurements of three-dimensional shape by phase measuring moiré topography

Abstract: We describe a phase-measuring version of projection moire topography which allows fully automatic on-line analysis of moire fringe contour patterns. The technique can be used for both absolute and comparative measurements of surface form and an example of each type of measurement is presented.

Measurements of phase objects using the Talbot effect and moire techniques.

Abstract: In this paper, we describe deflection mapping of phase objects using a Talbot interferometer. To examine the deflection of light by the phase objects, the moire fringes are generated by superimposing the Fourier image of the first grating on the second one in the interferometer. The phase object is placed in front of the first grating. The light passing through the objects and impinging on the first grating produces the shifted Fourier image, and the resultant moire fringes give the deflection mapping, which depends on the distribution of the refractive index of the phase object. The experiments show deflection mapping of a piece of plastic plate and a candle flame. This technique is used for measuring the focal length of a lens.

Automatic moire contouring.

Abstract: A method of automatically reconstructing the 3-D surface of an object from a 2-D moire pattern has been extended to interpret ambiguous fringe patterns by displacing the object. Potential applications of the surface reconstruction technique include inspection, cad/cam, microscopy, and robot vision. The digitized binary image was segmented into labeled fringes, the contours were detected, and the surface was reconstructed. A coin was used as an example to illustrate the procedure. The feasibility of using automatic moire contouring to inspect surfaces is discussed.

Deformation measurement during powder compaction by a scanning-moiré method

Abstract: The mechanical behavior of powders during compaction has been studied in previous papers. It has been shown that a moire method may be used to determine the resulting strain distribution. Some difficulties were encountered, however, in the method used. In the present paper, therefore, an image-processing system employing a personal computer to analyze the moire pattern is introduced. Many strain distributions obtained in this way from moire-fringe patterns are presented. Further, using this image-processing system, a scanning-moire technique is developed in which the master grating is replaced by the scanning lines of a television camera. The use of image processing in conjunction with the mismatch technique allows measurement of both small and large strains from one image picture.

Moiré topography, sampling theory, and charged-coupled devices

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

Comparative holographic moire interferometry in real time.

Abstract: A holographic moire technique is developed which allows one to compare the resistance to strength in real time of two nominally identical specimens. The moire interference pattern gives contours of path variations related to the difference in displacements of the two specimens. The method is whole field and noncontacting; it is demonstrated by comparing deflections of two square plates clamped along the edges and subjected to centrally concentrated loads.

Direct determination of modulation transfer function by moire deflectrometry

Abstract: A system and method for determining modulation transfer function (MTF) of an optical element or system employs a moire deflectometer. A selected central portion of monochromatic light is directed to the first grating of the moire deflectometer through or from the optical system, resulting in a moire pattern in which the contrast along an axis incident to the moire fringes is indicative of the MTF of the optical system for a particular spatial frequency, which is dependent on the spacing between the gratings of the moire deflectometer.

Strain Measurement by Scanning-moire Method

Abstract: A master camera. scanning-moire method is a moire method in which the grating is replaced by the scanning lines of a television In the present paper, the principle of moire pattern appearance. the effects of thinning out of scanning lines and the relation between moire fringes and strain are studied by the sampling theorem. If deformed model gratings are sampled by a television camera and they are thinned out properly by using an image processing system, the strain distribution in a wide strain range can be analyzed from one picture.

Method and apparatus for adjusting CRT geometry

Abstract: An improved method and apparatus for rapidly and accurately adjusting CRT image geometry for the purpose of removing defects in an image reproduced by a CRT. The method and apparatus include a conventional pattern generator for producing a grid-like test pattern, in the form of two mutually perpendicular sets of closely spaced parallel lines, on the viewing screen of the CRT whose geometry or image-forming apparatus is to be adjusted. A reference pattern image formed on a transparent base material suitable for viewing by transmitted light and having the same general characteristics as the CRT formed image is supported in superposed relationship with respect to the CRT formed, pattern generator produced test pattern image. Moire pattern bands or fringes indicative of defects in the displayed test pattern and therefore in the CRT geometry viewable by an equipment operator when viewing the displayed test pattern through the transparent reference pattern in such a superposed relationship may be readily removed by adjusting various component parts of the image-forming electron beam deflection system until the moire fringes resulting from image-defect generated misalignment between the CRT formed test pattern image and the transparent material formed reference pattern image are nulled or are no longer visible to an equipment operator.

Phase grating use in moire interferometry.

Abstract: When using coherent light in projected fringe moire interferometry, a phase grating will often produce a higher contrast pattern with greater light efficiency than will an amplitude grating. This paper describes the nature and mechanics of this phenomenon and presents experimental examples using this technique.

A Real-time Holographic Moiré Technique for the Measurement of Slope Change

Abstract: A holographic moire technique is developed which allows one to obtain whole field contour maps of the slope fields (derivatives of the out-of-plane displacements) in real time. A theoretical analysis of the fringe formation is presented and the factors affecting the fringe visibility are briefly discussed. Experimental demonstration of the method is carried out by studying a centrally loaded square plate clamped along its edges.

Fringe sharpening and information coupling in speckle shear interferometry.

Abstract: Fringe sharpening is required to obtain a higher accuracy of measurement. Nonlinear recording and consequently filtering at the higher-order halos for image formation give sharpened fringes in the image. Furthermore, if the apertures during recording are properly arranged, cross-frequency orders appear, which when used for filtering provide moire fringes of higher contrast due to intercoupling.

Low Cost Moire Pattern Sheet For The Analysis Of Image Unstability

Abstract: Chung Shan Institute of Science and TechnologyP.O.Box 1 -2 -6, Lung -tan, Taiwan, Republic of ChinaAbstractImage unstability can be measured by simple, low cost moire pattern sheet. Two types ofmoire are suggested: the linear read out moire and the angular read out moire. A referencesheet with scale is placed on the screen, such that the moire fringes can be produced whenthe reference sheet is overlapping with a grating or a Zone plate pattern which are projectedfrom recorded film. Using this simple technique, the defect of the film flatness can be meas-ured from the slope of the curved moire fringes, and the vibration of the film can be meas-ured by measuring the moire shiftness. An automatic real time test method is also suggestedfor measuring the curved moire fringe and the moire shiftness.IntroductionThe measurement of image unsteadiness has been studied by interferometer, by laser spotand testing ch rtl,2 or by position sensing system3, which are expansive compared to themoire

Moire Technique For Overlay Metrology

Abstract: Overlay performance is usually determined by exposing wafers twice, processing the wafer, and then using vernier or electrical probe techniques to measure the overlay error. In this paper, we describe a very different technique where the overlay error is evaluated in situ on the lithographic exposure tool. The basis of this approach is the examination of moire fringes between the projected image of a grating test mask and a grating test wafer. This is a particularly attractive approach to lithographic metrology because the moire fringes contain information about both resolution and overlay error. A measurement instrument has been constructed which attaches to a MicralignTM projection printer. The fringe intensity is measured by a solid state detector array positioned on an image of the illuminated arc-shaped field. Since the overlay measurement can be done many times per second, we can directly observe vibrations between mask and wafer.

Shape inspecting device

Abstract: PURPOSE:To erase unnecessary fringes other than moire fringes by the oscillation of a reference grating and to improve measurement precision by using a liquid-crystal panel which moves a grating pattern in a stripe shape electrically. CONSTITUTION:This device is provided with a spot light source 1 which irradiates an objective body 2 with light, the liquid-crystal panel 14 which displays selectively >=2 kinds of stripe pattern 13 which have stripes in parallel at different positions during the application of a voltage to an electrode 12, a TV camera 8 which photodetects reflected light from the objective body 2 through the panel 14, a picture processing circuit 11 which analyzes the video signal from the camera 8 and inspects the shape by moire fringes, and a circuit which controls the application state of the voltage to the electrodes 12 so that the electrodes 12 move at right angles to the direction of the fringes synchronously with the frame synchronizing signal of the camera 8. Then, the voltage is applied to each electrode 12 to display shielded beams corresponding to the electrodes on the panel 14.

Test The High Building Vibration And The Deformation During Earthquake by High Speed Camera With Moire Fringe Technique

Abstract: Test the High Building Vibration and the DeformationDuring Earthquake by High Speed Camera withMoire Fringe TechniqueRong -Seng Chang, Chin -Wu LinChung Shan Institute of TechnologyP.O. Box 1 -2 -6, Lung -Tan, Taiwan, Rep. of ChinaAbstractTo measure the building vibration and deformation during earthquake or typhone by highspeed camera or video camera with the telephoto lens is the simple, low cost method, andit can give us the two dimensional information as well. With the grid pattern painted onthe building and pass this image through another grid plate to the camera will generatea moire pattern on the film. The change of the shape of moire pattern will give us thevibration and 3 D deformation information to a very high degree of precision order.

Deflection mapping of flames using the moire effect.

Abstract: A computer simulation was used to perform a sensitivity analysis on the deflection mapping technique based on the moire effect. The refractive index and the temperature of a hot gas mixture were calculated. The accuracy of the method is shown to have strong dependence on the experimental accuracy. The best mode of experimental operation was found to be the construction of the moire image by using a physical grid and a computer simulated grid.

Real Time Measurement Of An Object's Small Displacement By High Speed Video Camera With Moire Pattern

Abstract: The resolution of a high speed video camera is not so high as photographic film, therefore the measurement of a small shift, such as the vibration of object is sometimes impossible. Here we suggest to use a grids cover on the object and pass this image through another transparent grids to the camera. It will generate a moire fringe which produce the equivalent resolution thousand times than before. We also put a corrdina te mask on the screen of the video TV, it is not only let us get a possibility to measure the small displacement of object which we can not see by video camera before, but also gives us a real time 3 Dimensional data. The mask errors generated hr the curved screen are also discussed.

Application of moiré topography to mantle treatment.

Abstract: We believe moire topography is a particularly suitable technique for establishing contours on patients receiving mantle treatment. We derive the fundamental moire equation from a novel, but simple, consideration of moire phenomena. Our apparatus is designed to give a difference in height of approximately 1.0 cm between successive moire fringes. Using an inclined plane test object, an accuracy of better than 3 mm is obtained.

Moiré optical spatial correlator.

Abstract: A new optical method to obtain the spatial-correlation integral of moire maps is described and demonstrated. This method permits the direct and quantitative determination of the optical spatial correlation between two objects. The method can be applied to any optical quantity mapped by any moire technique. Application to optical metrology and pattern recognition is discussed.

Electron beam hologram reproducing device

Abstract: PURPOSE:To erase a basic fringe which becomes noise by moving the interference fringe pattern of a hologram and basic fringe pattern of a hologram which overlaps it synchronously in parallel. CONSTITUTION:A hologram image formed by an electron microscope 9 is recorded by a television camera 14 and processed by a signal multiplier 16 together with the image of a fringe image generator 15 to obtain a moire image. At this time, the signal of a synchronizing signal generator 12 is sent to an electron biprism 10 and a fringe image moving device 13 to move the fringe pattern shot by the television camera 14 in parallel according to the synchronizing signal. Then, the moire image is stored in a signal processor 17 to obtain such a background that the basic linear fringes are uniform. Thus, the basic linear fringe which becomes noise is erased.

Fourier Coded Aperture Imaging In Nuclear Medicine

Abstract: Fourier Aperture (FA) consists of two sinusoidal gratings in contact with each other. One possible mode of operation, both gratings are rotated about the same axis through equal angles in opposite directions. A clear difference moire fringes is shown. The moire frequency depends on the angle between two gratings. This aperture of moire fringes is used as a variable frequency grating. It is able to scan the object spectrum in frequency domain. The summation filtered back projection alqorithm with three different apodizing functions were introduced in the reconstruction. 99mTc gamma ray source and 1" diameter NaI scintillation detector was used in the experiment. The thyroid phantom images show the spatial resolution of FA agree with the theoretical prediction. Three-D images capability is also discussed. The matrix inversion algorithm was used in the computer simulation of 3-D images. The depth resolution of FA is limited by the restricted view angle of the detector. Two plane objects with noise free in different depth were reconstructed.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The interpretation of x-ray interferometer moiré patterns

Abstract: In most experiments the x-ray-interferometer moire bands take the form of curves which complicate the problem of reconstructing the distribution pattern of deformations in single-crystal blocks giving rise to such moires. In the paper we consider the regularities in the variation of the interplane distances and relative rotations of these planes for which moire lines close in form to the experimental ones are obtained.

Moire simulator and method of using same

Abstract: A moire simulator comprises a moire detecting pattern constituted by grating patterns having equal grating constants and equal grating shapes, and an angle scale. The moire detecting pattern and the angle scale are positioned on at least one transparent plate. The moire simulator is superposed on an original and rotated thereon to read a rotation angle with respect to the original, at which the extent of generation of a moire pattern is the lowest, by using the angle scale. A setting angle of a screen during screening at which the extent of generation of a moire pattern is the lowest is then calculated before a screening process is started.