Showing papers on "Moiré pattern published in 1999"

Overlay measurement technique using moire patterns

Abstract: Misalignment between two masking steps used in the manufacture of semiconductive devices in a wafer is determined by having a special alignment pattern on each of two masks used in the process and forming images of the masks on the semiconductor devices with the images of the alignment patterns being superimposed over one another to form a Moire pattern. The Moire pattern is compared with other Moire patterns known to correspond to particular amounts of misalignment of the masks to see if it corresponds to an acceptable alignment.

Image processing algorithm for characterization of uniformity of printed images

Abstract: This invention specifically covers one of the many image quality (IQ) metrics that can be part of an overall image quality analysis engine. The specific problem with image quality addressed with this metric is that of a region of a printed (or copied) image, which was intended to have a uniform color, but which shows visible color variations. The color variation can have many different forms, both with respect to the type of color difference and with respect to the spatial nature of the non-uniformities. The image quality analysis system readily distinguishes between non-uniformities in the following different categories, including: (a) amplitude modulated cluster dot halftone patterns; (b) frequency modulated halftone patterns (e.g., stochastic screens); (c) irregular two-dimensional variations from noise; (d) isolated (non-periodic) one-dimensional streaks; (e) periodic, one-dimensional bands; and (f) two-dimensional periodic variations (Moire). The results from the image quality analysis can then be used as a basis for diagnosing machine problems.

Reverse engineering : high speed digitization of free-form surfaces by phase-shifting grating projection moiré topography

Abstract: A new digitization method is presented for automatic acquisition of geometric information on free-form surfaces for the sake of reverse engineering. Principles of grating projection moire topography are utilized with emphasis on enhancing the measuring resolution by incorporating phase-shifting fringe analysis. The measuring range and resolution can be readily adjusted to suit the object size to be measured, simply by varying the spatial line pitch of the moire gratings. In addition, no time-consuming beam scanning is required in the measurement, keeping the measuring time relatively low as compared with other existing techniques. Experimental results demonstrate that the three-dimensional coordinate data of 640×480 points can be attained within 5 seconds run on an IBM PC 586, with measuring resolutions of 0.1 mm down to 0.001 mm.

Real-time shape measurement by integrated phase-shifting method

Abstract: Phase distribution analysis of deformed gratings in moire method and grating projection method provides accurate shape of specimen. We previously proposed the phase-shifting method using correlation with a rectangular function. The phase analysis uses many images during phase shifting of the projected grating. In this paper, we propose a new real-time phase analysis method, that is, the integrated phase- shifting method using four images of phase-shifted grating patterns with a rectangular brightness distribution. The theory and some applications to shape measurement are shown.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nano-moire method*

Abstract: Nano-moire method presented in this paper is an experimental technique which allows direct measurement of nanoscopic mechanical parameters, such as displacement, strain and dislocation distribution. The basic idea is the formation of moire fringes when a HREM (high resolution electron microscopy) image of crystal material is superimposed with a unidirectional grating. Fourier filtering technique is used to increase the contrast of fringes and to multiple the fringes. This method has atom-size sensitivity and spatial resolution, and relatively large range. It provides a new experimental technique with very high sensitivity and spatial resolution for nanomechanics.

Effects of unparallel grating planes in Talbot interferometry. II

Abstract: The properties of moire fringes in Talbot interferometry are analyzed when the angle between the two grating planes is small. The results indicate that the tilt angle of the moire fringes, observed just behind the test grating, is sensitive to the small angle. Based on this sensitivity, several features of parallelism of the two grating planes are presented, and the influence of the small angle when checking the beam collimation of a lens is also discussed. The validity of the theoretical analysis is illustrated by experiment.

Moire apparatus having projection optical system and observation optical system which have optical axes parallel to each other

Abstract: In a moire apparatus having a projection grating 40, three-dimensional data of an object to be measured 2 is computed from the moire fringe observed while the projection grating 40 is moved, a distance-measuring reference point P (X, Y, Z) on the object 2 is selected from the three-dimensional data, and the distance L between the distance-measuring reference point P (X, Y, Z) and a taking lens 44 is measured The distance L can automatically be measured by detecting the peak of video output signal of a CCD camera 52 while moving its lens 52L along the optical axis Also, the distance-measuring reference point P (X, Y, Z) may be displayed with a flag on a monitor 18 for observing the moire fringe, and the distance between the object 2 and the taking lens 44 may be measured with reference to the flag-displayed pixel A stationary grating 102 having a pitch identical to that of the projection grating 40 is disposed near the projection grating 40, so as to form a moire fringe From the change in this moire fringe generated when the projection grating 40 is moved, the amount of movement of the projection grating 40 is computed The change in moire fringe is detected when a photocell 104 placed near the stationary grating 102 detects the illuminance of the moire fringe

Dot matrix hologram for hiding a moire pattern

Abstract: A moire pattern technology about a dot matrix hologram for hiding a moire pattern is invented. In the moire pattern hidden region of a dot matrix hologram, the moire pattern foreground area and the moire pattern background area are formed identically by interlacing bright lines and dark lines. While position shifting is formed between the lines of the two areas. This position shifting is several times of the size of the grating dots. Thus, a moire pattern hidden in the moire pattern hidden region without being processed specially has a poor hiding ability. Often the above moire pattern can be identified by eyes directly without using a decoding film. Therefore, such kinds of moire patterns have poor hidden effects. However, the moire pattern of the present invention can prevent the aforesaid phenomenon by a well designed pretended pattern. Moreover, the appearance of such a dot matrix hologram can be beautified by the addition of the pretended patern. Furthermore, in the present invention, a technology of one-dimensional moire patterns is upgraded to a technology of two-dimensional moire patterns.

Intensity-modulated moiré topography.

Abstract: Moire topography has the advantage of requiring only a single image to obtain a three-dimensional measurement, but it cannot discern the fringe order. Because there is an ambiguity problem when calculating the depth range by use of fringe intensity or phase unwrapping, it is impossible to obtain an absolute phase and an absolute depth range. It is therefore difficult to discern the relation between fringes in the cases in which the fringes are discontinuous or the objects are isolated. An intensity-modulated moire topography method is presented. By modulation of the transmission factors of the projection and the observation gratings by exponential functions a new moire pattern whose fringe intensity changes with its order can be produced. The fringe order can be extracted easily from the fringe intensity, and the absolute range of the skeleton line can be obtained solely from its intensity. At the same time, we can segment the moire pattern by its fringe order. For every segment the absolute phase and the absolute depth range of every point of the moire pattern can be obtained solely from its intensity with no need for interaction with the user.

Improvement of measurement accuracy in shadow moiré by considering the influence of harmonics in the moiré profile

Abstract: A method for high-resolution three-dimensional shape measurement for a shadow moire system is proposed. To increase the resolving power of the method, the problem caused by the harmonics of the moire profile needs to be solved. It is well known that moire fringes in a shadow moire system have a nonsinusoidal profile caused by harmonics. The influence of the harmonics in moire profile on the measurement accuracy of the method is discussed. The method is improved to eliminate the error caused by the harmonics in the moire profile. Both simulation and experimental results show that the improved method can effectively reduce the influence of harmonics.

Tone-variation-resistant phase-shiftable halftone screen system and method of using

Abstract: An image generating system that warps both the image data and halftone screens of a halftone screen system to minimize moire patterns. Merely warping image data to minimize moire patterns results in offsets within the image data which should have a corresponding adjustment or warp in halftone screens used in the image generating system to render the color image separation layers. Therefore, the image generating system provides moire pattern minimization by warping screens of the halftone screen system to correspond to the warping of the image data. The image generating system uses line screens for halftoning the chromatic image separation layers of color images and a hexagonal dot screen for halftoning the luminescent image separation layer. The halftone screen system uses the relatively large average screen displacement angles offered by line screening while providing a dynamic tone range performance similar to that of the performance of dot screening.

Three-dimensional image scanner and heat-insulating device for optical apparatus

Abstract: In a three-dimensional image scanner, a grating projection type moire topography is used, so as to capture three-dimensional form information of an object to be measured easily in a short time with a high degree of freedom in measurement. Also, a heat-insulating partition comprising at least two partition walls forming a cooling/heat-insulating path is disposed between a light source and a heat-sensitive section, so as to effectively inhibit the heat generated by the light source from being transmitted to the heat-sensitive section. The three-dimensional form information of the object is captured by a measurement head 12 having a function as a grating projection type moire device. As a consequence, a reference grating such as that in a grating shadow type moire device is unnecessary, and it will be sufficient if a virtual reference grating surface is set at a position conjugate with both of a projection grating 40 and an observation reference grating 46 , whereby the size of the measurable object would not be restricted, and the object can be disposed fore and aft through the virtual reference grating surface. A first partition wall 74 is disposed so as to separate a projection lamp 32 and an illumination lamp 64 from a CCD camera 52 , and a second partition wall 76 is disposed on the side of the lamps 32, 64 , so as to form a cooling passage 102 for guiding the heat generated by both lamps 32, 64 to a cooling fan 70 . As a consequence, heat insulation is attained between the lamps 32, 64 and the CCD camera 52 , and the temperature rise of the partition wall 74 is suppressed. Further, a cooling fan 72 and a third partition wall 78 are disposed on the side of the CCD camera 52 with respect to the first partition wall 74 , so as to form an exhaust heat-insulating path 104 . As a consequence, heat is effectively inhibited from being transmitted to the CCD camera 52 via the first partition wall 74.

Optical inspection of periodic structures using lens arrays and moire magnification

Abstract: This paper describes a technique that uses the phenomenon of moire magnification, developed recently for the measurement and inspection of periodic structures. Moire magnification occurs when an array of lenses is used to view an array of identical objects situated at the focal plane of the lenses. As the lens array is aligned with the object array, a moire pattern is observed in which each moire fringe consists of a magnified image of the repeat element of the object array. As the arrays are rotated with respect to each other, the magnification and orientation of the image changes. The moire magnifier builds up an image from a large number of components of an array and therefore gives a representation of the average unit. It is a very simple and robust device and may well be more convenient to use, for example in an industrial production environment, than a microscope. A large number of components used in electronic imaging systems are periodic in nature and can conveniently be inspected using this technique. Examples are shown.

Method to decrease moire fringe and liquid crystal display device

Abstract: PROBLEM TO BE SOLVED: To reduce moire fringes produced when sheets having regular patterns are overlapped. SOLUTION: Relating to a liquid crystal display device, moire fringes are produced by the interference between the regular pattern of pixel lines formed on a liquid crystal panel and the regular pattern of groove lines formed on the optical sheet such as a light transmission plate to be overlapped on the liquid crystal panel, and the pitch P1 of the pixel lines and the pitch P2 of the groove lines are controlled to reduce the period of the moire fringes to the min.

Systems and methods for moiré-reduced halftoning

Abstract: By using negative feedback, moire patterns can be reduced, or virtually eliminated, from input black-and-white or color original images. In particular, by feeding back an image containing the difference between the original input image and the halftone output with possible moire patterns, and subtracting the low-frequency part of this image from the original input image, a resultant halftone image can be achieved that has reduced moire patterns.

X-ray diffraction moiré topography as a means to reconstruct relative displacement fields in weakly deformed bicrystals.

Abstract: X-ray diffraction topographs of wafers produced by separation by implanted oxygen (SIMOX) show moire fringes in both reflection and transmission geometry. These fringes reveal deformations of the order of 10−6 to 10−8 between the layer and the substrate of the SIMOX material. A new method for a quantitative analysis of moire fringes is developed and allows reconstruction with a high sensitivity of the three components of the relative displacement field between layer and substrate directly from a set of topographs. This method is used for the interpretation of moire topographs of entire 4 in SIMOX wafers and of regions around crystal defects. Finally, the capabilities of an analysis of moire fringes are compared with those of the usual diffraction topo­graphy.

Single-frame evaluation of object-adapted fringes

Abstract: We present two fast methods for the evaluation of object- adapted fringe images. One method, a fast and simple skeleton method, is purely digital. The method is stable against varying object reflectivities and illumination conditions. We also demonstrate the optical evaluation of object-adapted fringe images by means of a moire technique. This second method uses a Ronchi grating for the optical processing of the images in order to detect topographic defects with high speed. Additionally, we present a new method for the generation of object-adapted fringe masks where only a few images have to be recorded in order to obtain the mask.

Removing color moire patterns from digital images having known chromaticities

Abstract: A method for removing color moire pattern noise having known chromaticities from a digital image is disclosed. The chromaticities are used to determine the region of color moire. The chromaticities within the region of color moire are then changed in accordance with the chromaticities of the located pixels in the region of color moire so that the color moire pattern noise is reduced.

Thermal deformation measurement of the solder joints in electronic packages using electron moiré method

Abstract: In this paper, electron moire method is used to measure the thermal deformation of electronic packages. In order to observe the electron moire fringe, a holographic grid was replicated on the cross section of the BGA type package at 150°C. This grid was fabricated on a glass plate using a moving point holographic system, and was replicated to measured area at high temperature. Under SEM, the holographic grid(specimen grid) and a programmed electron beam scan(master grid) interfere and form electron moire patterns. The shear strain measurement technique using electron moire method is described. Using the electron moire method, the shear strains in the different solder joints were measured and analysed. Some useful results were obtained.

Video moire cancellation filter for high-resolution CRTs

Abstract: The appearance of moire limits the performance of high-resolution cathode ray tubes (CRTs). Until now, cancellation circuits have used a small alternating image shift (wobble) to disguise moire, but these circuits introduce other artefacts like flicker. We present a novel solution for suppressing video moire with a specific non-linear filter. Advantages include simple digital video signal processing and negligible degradation of the image quality, even in graphics with very fine detail.

Moire fringe eliminating apparatus and a method for eliminating moire fringes

Abstract: In a moire fringes eliminating apparatus, a moire fringe eliminating unit comprises a halftone dot feature extracting unit, a re-calculation unit, a re-calculation deciding unit, and a halftone dot shape changing unit. The halftone dot feature extracting unit extracts features of the halftone dots. The re-calculation unit obtains a re-calculation deciding value which represents a ratio between a total number of the halftone dots in a neighboring area and the number of the halftone dots having a similarity of feature being smaller than a predetermined threshold value in the neighboring area. The re-calculation deciding unit decides whether the threshold value should be changed in order to decide necessity of change of the number of dots based on the re-calculation deciding value. The halftone dot shape changing unit obtains an amount of change of the number of dots to be increased or decreased for a target halftone dot, based on an amount of feature of the halftone dots which are output when the threshold value is not changed in the neighboring area, an amount of the feature of the target halftone dot, and the number of dots of the target halftone dot.

Stress distribution detection method for semiconductor chip

Abstract: PROBLEM TO BE SOLVED: To obtain a detection method that detects stress distribution in an on-board inspection process for semiconductor chips mounted flip chips on using a relative low cost and an easy inspection method. SOLUTION: Pattern P for detecting Moire interference is formed on the surface of a semiconductor chip 1 to detect deformation of the chip 1 caused from stress occurred by Moire interference method using the pattern. The pattern P for detecting Moire interference formed on the surface of the chip 1 is preferably chosen one from among linear-, fringe-, concentration-, or grid-like shapes. Also, a forming method that forms the pattern P for Moire interference on the chip 1 is chosen either a method that digs a ditch on a wafer by anisotropy etching or a method that adds pattern by printing and imprinting on the surface of the chip 1 already mounted a flip chip on.

High resolution, high sensitivity moire method

Abstract: Based on geometric moire method, moire interferometry and microscopic moire interferometry, a high spatial resolution and high sensitivity geometric microscopic moire method is presented. Geometric micron-moire patterns are produced by the superposition of two high frequency gratings through a microscope system. Compared with other grating-based photo-mechanics methods, microscopic moire method could provide whole-field moire patterns of both high spatial resolution and high sensitivity. The frequency of specimen and reference gratings used in this method can be from 1 line/mm to 10000 lines/mm. Additionally, a 4F optical filter system is used to enhance the contrast of microscopic moire patterns effectively.

Method for detecting misalignment of two masking steps in manufacture of semiconductor device

Abstract: PROBLEM TO BE SOLVED: To detect mask misalignment by comparing a moire pattern which is optically observed with a moire pattern which is relevant to allowable alignment between two masks. SOLUTION: When two patterns are superposed each other, a repetition pattern which generates a moire pattern being a scale of the degree of misalignment between the two patterns is provided in each of two masks used in two masking steps. Each mask is used one by one and is put one upon another on a surface of a treated semiconductor wafer for printing a pattern of a mark of two masks. Then, a moire pattern formed by two pattern of a mark is optically observed. A known moire pattern which defines the range of allowable misalignment between two masks is compared with an observed moire pattern and it is judged whether or not the continuous treatment of the wafer is proper. COPYRIGHT: (C)2000,JPO