Showing papers on "Moiré pattern published in 1975"
TL;DR: An analytic expression has been developed that can be used for computing the Fourier spectrum of any halftone image as a function of the original continuous-tone image and theHalftone process, and takes into account the nonlinear effects of the threshold step in the halft one process.
Abstract: An analytic expression has been developed that can be used for computing the Fourier spectrum of any halftone image as a function of the original continuous-tone image and the halftone process. This result takes into account the nonlinear effects of the threshold step in the halftone process. Although the result is general and can be applied to any original image, in some cases of periodic images the Fourier components of the halftone image are particularly easy to compute. We show important differences between spectra of halftone images and scanned or sampled images. In halftone images, significant image detail is maintained at spatial frequencies greater than half of the screen frequency and aliasing or moire patterns depend upon object contrast and upon the halftone function differently from similar patterns which occur in scanned or sampled imagery.
80 citations
TL;DR: The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique, and the technique is compared to laser speckle photography.
Abstract: If a camera is to be used for the special purpose of recording periodic grid-like patterns, the range of spatial frequencies which it must handle is limited, and its imaging performance for a given range can be optimized by installing a suitably slotted mask inside the lens aperture. With this modification, a standard 35 mm single lens reflex camera has been found to resolve up to 600 lines/mm in both vertical and horizontal directions across the full format. The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique. Some preliminary results are described, and the technique is compared to laser speckle photography.
67 citations
TL;DR: The conditions for and formation of low-spatial-frequency beat patterns between superposed grid structures are studied in this article, where the application of moire techniques for Fourier analysis of incoherently illuminated distributions is demonstrated.
Abstract: The conditions for and formation of low-spatial-frequency beat patterns between superposed grid structures are studied. The application of moire techniques for Fourier analysis of incoherently illuminated distributions is demonstrated. The different multiples of the fundamental spatial frequency of a grating are used to form distinguishable moire patterns. Two particular applications are treated: increased sensitivity from fringe multiplication in a moire display and examination of the element-profile shape of gratings. Moire procedures with two, and with multiple, gratings are discussed. Indications of moire pattern microstructures and moire fringe profiles are indicated.
47 citations
TL;DR: Moire fringes representing contours of equal distance from a reference plane may be produced when two gratings, one projected onto the surface of the animal and the other an equispaced line grating are superimposed as discussed by the authors.
Abstract: A moire method for recording the surface topography of living animals is presented. Moire fringes representing contours of equal distance from a reference plane may be produced when two gratings, one projected onto the surface of the animal and the other an equispaced line grating are superimposed. The levels at which contours are observed may be adjusted on a single photographic record by lateral movement of the equispaced grating. In this way any point on the surface may be made to coincide with a contour line and its coordinates determined. The technique is suitable for measuring surface gradients and a method of automating the reading of surface coordinates is suggested.
35 citations
TL;DR: The experimental and quantitative study of the measurement of the lateral spherical aberration with the shearing interferometer using Fourier imaging and the moire method is given and the fringe pattern directly illustrating the lateralherical aberration can be obtained by the proposed optical arrangement using the plane reference wavefront.
Abstract: The experimental and quantitative study of the measurement of the lateral spherical aberration with the shearing interferometer using Fourier imaging and the moire method is given. When the aberration of a camera lens with small f/number(1.7) is measured with an optical arrangement employing the spherical wavefront as a reference at the observation plane, the distortion correction of the obtained fringes is necessary. However, the fringe pattern directly illustrating the lateral spherical aberration can be obtained by the proposed optical arrangement using the plane reference wavefront, without correcting the fringe distortion.
26 citations
TL;DR: In this article, a special case of a Denisyuk set-up is used for double-exposure holographic interferometry, namely, with the photographic plate fixed to one point of the object under study and plane illumination through the plate, some interesting advantages can be obtained.
Abstract: When a special case of a Denisyuk set-up [1] is used for double-exposure holographic interferometry, namely, with the photographic plate fixed to one point of the object under study and plane illumination through the plate, some interesting advantages can be obtained. The stability requirements are drastically reduced (a general translation and a rotation around an axis parallel to the illumination direction can be allowed); the optical set-up is very simple; white-light reconstruction can be used. For the determination of in-plane displacement patterns, one can either use fringe-order subtraction between two symmetrical off-axis views (eventually Moire subtraction), or use speckle correlation techniques. The most important advantage is that Cartesian components of displacements can be determined with complete object motion compensation by combining holographic and speckling techniques. Some practical applications of the method and its drawbacks are presented.
26 citations
12 citations
TL;DR: In this article, the applications of the moire phenomenon in scanning electron microscopy are discussed, including adjustment of the spatial period and angle of a scan raster, analysis of distortion in a scan Raster, and registration of the scan field relative to coded patterns on a substrate.
Abstract: When a grating is viewed by scanning electron microscopy, a moire pattern is observed. Applications of the moire phenomenon in scanning‐electron‐beam lithography and microscopy are discussed, including adjustment of the spatial period and angle of a scan raster, analysis of distortion in a scan raster, analysis of stray‐field beam deflection and measurement errors, and registration of a scan field relative to coded patterns on a substrate.
11 citations
TL;DR: In this article, the Fourier series was used to predict the shape and harmonic structure of the moire fringes of two overlapping zone plates, and a generalization of the theory to the case of N overlapping plates was presented.
Abstract: When two or more patterns, each exhibiting some form of periodicity, overlap there usually result distinct moire fringes. If the periodicities in the original patterns are represented by Fourier series, the shape and harmonic structure of the moire fringes can be predicted. Such a theory is developed for two overlapping zone plates and some illustrations are given. Finally the outline of a generalization of the theory to the case of N overlapping plates is presented.
6 citations
TL;DR: In this paper, the self-imaging property of a circular grating is applied to centring error detection and to alignment in space, which is easy and comfortable to make visual observations.
Abstract: Optical alignment operations and Fourier imaging phenomena have the common property that both occur in space along a straight line. The self-imaging property of a circular grating is applied to centring-error detection and to alignment in space. Moire fringes due to the interaction of Fourier (or Fresnel) images with a detecting grating provide an indicator of the alignment state. The merit of this approach is that it is easy and comfortable to make visual observations. Various applications of the method depending on the choice of the reference points used are discussed and some experimental data are presented.
5 citations
TL;DR: In this paper, a detailed analysis is made of the moire pattern formed on superposing a Fresnel zone plate with an equispaced grating or a rectangular grid, and information regarding the focal length, location and phase of the Moire zone plates so produced is extracted.
Abstract: A detailed analysis is made of the moire pattern formed on superposing a Fresnel zone plate with an equispaced grating or a rectangular grid. Information regarding the focal length, location and phase of the moire zone plates so produced is extracted. The relevance of this work to a number of physical situations is discussed.
TL;DR: In this paper, an application of the moire method to the interferometric testing of the plane gratings is presented, which can measure the slowly changing aperiodic spacing error separately from the other errors, that is, the error in the figure of the grating surface and the optical thickness variation.
Abstract: An application of the moire method to the interferometric testing of the plane gratings is presented. By this method, we can measure the slowly changing aperiodic spacing error separately from the other errors, that is, the error in the figure of the grating surface and the optical thickness variation. The principle is presented theoretically and verified experimentally.
TL;DR: A new quantitative measurement of strain distributions is performed by optical spatial filtering in an optical differentiation system, and three strain components can be obtained by a microphotometric method from only a single specimen without time-consuming numerical calculations.
Abstract: A new quantitative measurement of strain distributions is performed by optical spatial filtering in an optical differentiation system. In this method, the strain distribution can be converted to the light intensity distributions in the image plane, and three strain components can be obtained by a microphotometric method from only a single specimen without time-consuming numerical calculations, such as in Moire or photoelastic methods. An experimental example is performed in order to show the practical usefulness of the present method, and some considerations on deterioration in the fidelity of the system performance are also given.
TL;DR: In this paper, a method for measuring the distortion by the use of moire patterns was described, which greatly magnifies any nonlinearities and it is possible to measure distortions as small as 0.1%.
Abstract: SUMMARY
Scanning electron microscope images are subject to an appreciable amount of non-linear distortion which must be allowed for when quantitative analyses are made. A method is described for measuring the distortion by the use of moire patterns. These greatly magnify any non-linearities and it is possible to measure distortions as small as 0ṁ1%. In addition, the use of moire patterns permits a separation of the distortion produced in the cathode-ray display tube from that occurring in the microscope itself.