Showing papers on "Moiré pattern published in 1978"

Extension to three dimensions of a holographic moire technique to separate patterns corresponding to components of displacement

Abstract: The holographic-moire technique to obtain separate patterns for the Cartesian components of the displacement vector is extended to curved surfaces. An initial pattern which is often required for the observation of the displacement fringes is analyzed for this case. Criteria are established for the localization of this initial pattern to follow close to the contour of the object surface. A PVC pipe subjected to torsion demonstrates the proposed technique and, when analytical arguments are checked experimentally, a close correlation is observed.

Moiré fringe profile prediction method and its application to fringe sharpening.

Abstract: The fringe profile of the moire pattern resulting from the interaction between a regular and a distorted binary grating is studied. The moire fringe profile prediction method in a generalized form is deduced and summarized in a table illustrating the relationship between the profile parameters of superposed gratings and those of moire fringes. The method is confirmed by computer simulation and experiment. The conditions for dark and bright fringe sharpening are obtained by using the derived prediction method.

Ceramic decorated glassware

Abstract: Halftone printing of a plurality of different colors is employed to produce a composite graphic display on the surface of the glass. Precise alignment is utilized in order to register the halftone printing screens for each color that is deposited on the glass surface. The opaque enamels employed in the decorative process are carefully balanced with respect to each other to obtain the desired color hues. The deposition angles for the alignment of the halftone dots is controlled to minimize the undesirable moire effect.

High resolution alignment technique and apparatus

Abstract: There is provided a technique and apparatus for aligning a mask to a substrate with high precision using Moire fringe effects produced by superimposing diffraction gratings. The gratings comprise first and second patterns of horizontal and vertical lines and spaces, respectively. The first pattern comprises horizontal and vertical lines and spaces of a first width. The second pattern comprises horizontal and vertical lines of a second width which differs from the lines in the first pattern by a small amount Δ. The patterns are superimposed to provide a Moire fringe effect. When alignment occurs, a symmetrical pattern is provided. If misalignment in the X, Y or θ coordinate occurs, an assymmetrical or skewed pattern of Moire fringe effects is generated.

Differentiation of holographic-moire patterns

Abstract: Partial derivatives of displacement are optically determined by superimposing two shifted holographic reconstructions which correspond to single components of displacement. Two different methods are proposed, one of which involves shifting a holographic-moire pattern on itself. A second method takes advantage of holographic multiplexing techniques to incorporate an initial pattern into the shifting process. The latter facilitates the formation of the moire corresponding to strain information. This paper demonstrates that either method of obtaining derivatives is feasible by documenting an investigation of a disk subjected to diametral compression.

Effect of magnification change in laser speckle photography

Abstract: When double-exposure speckle photography is used for stress analysis of solids, displacement along the line of sight arises naturally as a consequence of specimen deformation such as Poisson’s effect, etc. This displacement causes magnification change of the speckle pattern recorded. In the this paper a model is proposed to analyze this effect. It is shown that, upon Fourier filtering of the double-exposed speckle pattern with small magnification change, contour fringes of equivalent in-plane displacement along the direction of filtering are obtained and that the fringe density is linearly proportional to the magnification change incurred. The phenomenon is quite analogous to the moire fringes created when identical gratings are superimposed with a gap between them.

Optical Differentiation Of Moire-Holographic Fringes By Wavefront Reconstruction With White Light Sources

Abstract: Moire-holograms contain a parallel-line grating recorded during the exposure process of the model grid under three-dimensional deformation. Utilizing the diffraction of a white light beam striking the holoplate, frozen moire patterns can be observed, under proper angles, directly by reflection. With a Fourier transform optical system, the reconstruction is achieved by means of a white source, filtering one among the chromatic wavefronts at the first diffracted order. If the wavefronts of two complementary colors are allowed to pass through the filter, direct derivatives of displacement fringes will appear on the planes where the images are slightly shifted, before or after overlapping. By a grounded glass the image plane is determined where the differentiation fringes exibit the neatest pattern, which may be recorded on a photographic film.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Measuring deformation or variations in position or refractive index - using holographic-interferometric or Moire patterns for rapid evaluation

Abstract: A holographic interferometric, or moire metric method of determining deformations or position variations of objects or refractive index variations in transparent bodies, fluids or gases uses at least two object images contg. frequency patterns for different object conditions sequentially imposed at a scanning plane. The method enables the images to be quickly and practically evaluated and to be made visible. The local intensity modulations of the hologram image or moire pattern of two distinct object conditions are imposed on a radiation sensitive storage screen, pref. a t.v. screen. The patterns are scanned electronically and the corresp. overlayed output signals converted in an evaluation unit using time modulation.

Moire contour line measuring app aratus

Abstract: PURPOSE:To eliminate the need for photographing by uing the horizontal scanning lines of a TV camera as a second optical grating in a system of using first, second optical gratings.

Contouring Method by Parallel Light Moire Holography

Abstract: Moire contouring method by parallel light is realized using holography. In Fourier-transform holography, the object placed at the focus of a collimating lens is equivalent to the one placed at infinity. Regular fringes are projected onto the object by tilting the illuminating parallel light slightly between the exposures of double exposure holography. These fringes are deformed by the relief of the object. Imaginary hyperboloids of interference fringes are formed by fine lateral displacement between the two exposures. As the plate is located at the focus of the lens, it is considered that the hyperboloids can be approximated by a set of parallel planes after passing through the lens. These parallel fringes are observed at infinity as a regular grid. The combination of this regular grid with the deformed fringes produces contouring fringes on the object at infinity.

Electronic Processing Of Moire Fringes. Application To Moire Topography And Elements Of Comparison With Photogrammetry

Abstract: Some elements of comparison are given between the projection-type Moire topography and photogrammetry. The basic mathematics of photogrammetry is applied to reconstruct the 3.D. Shape of the object from the Moire pattern. Some particular aspects of the Moire method are discussed and a general methodology is proposed. In connection with this, an opto-electro nic technique is described, which measures the Moire phase with high resolution and sign determination. The experimental results show that this technique is especially suitable for high accuracy automatic reconstruction of 3.D. Shapes.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multiple Beam Holographic Interferometry

Abstract: An analysis of the formation of Moire fringes by the intensity addition of two high-frequency fringe systems shows that the resulting Moire fringes will retain sinusoidal intensity distribution regardless of whether the contributing fringe systems follow the Airy formula or the cos2 law. This, it is shown, is due to the creation in each diffracted order of a ‘double source juxtaposition’. True Airy-type Moire fringes were realized in holography. The contributing fringe systems were of a multiple-beam Fizeau-Tolansky type. The holographic reconstruction, for each diffracted order of the multiple sources of the interferometer, results in the formation of narrow, sensitive, high-resolution Moire fringes. These may be applied to real time tests of a micro-object's deformation.

Forming method for contour line moire fringes corresponding to plane in each direction of 3d form objects

Abstract: PURPOSE:To form fringes without relatively moving the apparatus and object by controlling the shutter opening time of projecting optical systems on both sides of a camera and photographing the contour line moire interference fringes of the 3 sets of the front, right and left within a short time.

Contour moire fringe measuring method

Abstract: PURPOSE:To make possible easy identification of undulations even with a colored object and simplify the apparatus by making superposed display of plural moire fringes for contour layers varied by changing the relative position of a projection grating and an image grating, through the use of different colors