Showing papers on "Moiré pattern published in 2005"

Moire fringe reduction by optical filters in integral three-dimensional imaging on a color flat-panel display

Abstract: We propose a method to reduce the color moire fringes that are attributable to the structure of a color flat-panel display in integral three-dimensional imaging. The method uses two types of optical low-pass filter, diffuser and defocus. The effectiveness of the method was confirmed in an experiment. We describe a way to design these filters with moire's residual energy and video signal energy as indices and demonstrate the validity of the model, which combines two filters to reduce moire fringes.

Automated small tilt-angle measurement using Lau interferometry.

Abstract: A technique for a tilt-angle measurement of reflecting objects based on the Lau interferometry coupled with the moire readout has been proposed. A white-light incoherent source illuminates a set of two gratings, resulting in the generation of the Fresnel image due to the Lau effect. The Fresnel image is projected onto a reflecting object. The image reflected from the object is superimposed onto an identical grating, which results in the formation of a moire fringe pattern. The inclination angle of moire fringes is a function of tilt angle of the object. Theory and experimental arrangement of the proposed technique is presented and results of the investigation are reported.

Diffracted moiré fringes as analysis and alignment tools for multilayer fabrication in soft lithography

Abstract: We studied the first-order diffracted moire fringes of transparent multilayered structures comprised of irregularly deformed periodic patterns. By a comparison study of the diffracted moire fringe pattern and detailed microscopy of the structure, we show that the diffracted moire fringe can be used as a nondestructive tool to analyze the alignment of multilayered structures. We demonstrate the alignment method for the case of layer-by-layer microstructures using soft lithography. The alignment method yields high contrast of fringes even when the materials being aligned have very weak contrasts. The imaging method of diffracted moire fringes is a versatile visual tool for the microfabrication of transparent deformable microstructures in layer-by-layer fashion.

Moiré-free color halftone configuration

Abstract: Disclosed herein is a Moire-free color halftone configuration for clustered dots. Unlike conventional methods, the disclosed method produces periodic hexagon rosettes of identical shapes. These exemplary hexagon rosettes have three fundamental spatial frequencies exactly equal to half of the fundamental frequency of the three halftone screens. The resultant halftone outputs are truly Moire free, as all the fundamentals and harmonic frequencies are multiples of and thus higher in frequency than the rosette fundamental frequency. The halftone outputs resulting from the employment of the exemplary rosette design methodology provided herein, are also robust to the typical misregistration among color separations commonly found in color systems.

Profiling of objects with height steps by wavelet analysis of shadow moiré fringes

Abstract: A temporal wavelet analysis algorithm is proposed for shadow-moire-based three-dimensional surface profiling on objects having discontinuous height steps. A grating is positioned close to an object, and its shadow is observed through the grating. The moire fringe patterns vary when the grating is in-plane rotating. A series of fringe patterns are captured by a CCD camera at different rotating angles. Phase values are evaluated point by point with the continuous wavelet transform. From the phase values of each point on the object, the distance between the object and the grating can be retrieved. The surface profile is obtained without temporal or spatial phase unwrapping. This technique is applicable to objects with discontinuous height steps, which are impossible to measure with conventional shadow moire topography. Two specimens are tested to demonstrate the validity of the method: One is an object with a height step of 1.6 mm, and another is a small coin with unevenness of less than 0.2 mm. The experimental results are compared with test results by use of the mechanical stylus method.

Mirror shape detection by reflection grating moire method with optical design validation

Abstract: Shape detection on objects of large and huge dimensions has always represented a challenging task, mostly by the practical point of view due to the size of the related measurement equipment. When the tested object is a mirror the measurements is additionally complicated, since the classical techniques of structured light cannot be directly applied. The method proposed in this paper has been applied to measure the curvature of a deformable mirror of 1-meter diameter for a heliostat plant. The mirror shape is obtained studying the spatial variations of a grating projected on the sample and reflected by it on a screen. The measurement set-up employs a PC projector and a digital camera. The results of this curvature assessment are compared to those derived from a simulation obtained by an optical design programme.

A method of building pixel cells with an arbitrary vertex angle

Abstract: Moire fringes appearing in contact-type three-dimensional imaging systems cause serious image quality deterioration. The fringes are inevitable because the systems require overlapping a viewing-zone-forming optical plate on a display panel. An analysis shows that the visual effects of the fringes can be minimized by finding a proper overlapping angle between the panel and the plate. This angle imposes that pixel cell in full-parallax imaging systems should have the shape of either rhombus or parallelogram with a specific vertex angle. The pixel cell with the shape of the rhombus or parallelogram is implemented by approximating the boundaries of each pixel cell by staircase lines drawn along sides of the pixel. The slopes of the lines are determined by the ratio of the pixel numbers in the vertical and horizontal directions. This method allows creating pixel cells with a desired vertex angle for minimizing the moire fringes, especially in full-parallax imaging systems.

Moiré-based auto-stereoscopic watermarks

Abstract: Provided herein are teachings directed to the creation of moire-based auto-stereoscopic watermarks in rendered images. By choosing different halftone structures, which differ by having different spatial frequencies for each of two delineated partitions in an image, it becomes possible to embed arbitrary binary patterns into printed documents as digital watermarks. The invisible watermarks become moire auto-stereoscopic images when the prints are viewed through an overlaid transparency “decoder” suitably prepared by virtue of being rendered with a uniform halftone structure having the correct special frequency in relationship with the partition frequencies employed in the printed document.

Visualisation of the wave-front deformations caused by a phase object by the method of successive double lateral shear interferometry

Abstract: The method of moire visualisation of the wave-front deformations of a light beam propagated through a phase object is proposed. The method is based on the recording of double shear interferograms and makes it possible to obtain real-time moire pictures of the phase object with doubled sensitivity, in which the behaviour of fringes is similar to that in usual double-beam, reference-wave interferometry. The method was tested by studying the regions of thermal treatment of a polymethyl methacrylate plate.

Digital phase-shifting atomic force microscope Moiré method

Abstract: In this study, the digital atomic force microscope (AFM) Moire method with phase-shifting technology is established to measure the in-plane displacement and strain fields. The Moire pattern is generated by the interference between the specimen grating and the virtual reference grating formed by digital image processes. The overlapped image is filtered by two-dimensional wavelet transformation to obtain the clear interference Moire patterns. The four-step phase-shifting method is realized by translating the phase of the virtual reference grating from 0 to 2π. The principle of the digital AFM Moire method and the phase-shifting technology are described in detail. Experimental results show that this method is convenient to use and efficient in realizing the microscale measurement.

Two-wavelength phase-shifting interferometry with a superimposed grating displayed on an electrically addressed spatial light modulator

Abstract: A two-wavelength moire phase-shifting interferometer that uses a superimposed grating has been developed. The optical phase shifts for the two wavelengths are given by digital phase shifts of a superimposed grating displayed on a liquid-crystal spatial light modulator. A phase shift of the moire fringe is achieved by equal phase shifts with opposite signs in the two gratings. A moire phase-shifting interferometer with no moving parts and no requirement for calibration of the value of the phase shifts was obtained. Our experimental result shows measurements of the profile of a step object with a 2.65-microm synthetic wavelength.

Thermal Properties Measurement of Micro-Electromechanical System Sensors by Digital Moire Method

Abstract: The thermal properties of a micro-electromechanical system sensor were analysed by a novel digital moire method. A double-layer micro-cantilever sensor (60 μm long, 10 μm width and 2 μm thick) was prepared by focused ion beam milling. A grating with frequency of 5000 lines mm−1 was etched on the cantilever. The sensor was placed into a scanning electron microscope system with a high temperature device. The observation and recording of the thermal deformation of the grating were realised in real-time as the temperature rose from room temperature to 300 °C at intervals of 50 °C. Digital moire was generated by interference of the deformed grating and a digital virtual grating. The thermal properties including strain distribution of the sensor and the linear expansion coefficient of polysilicon were accurately measured by the phase-shifted moire patterns.

Optical modal analysis using white-light projected fringes

Abstract: This paper describes a non-contacting optical technique for vibration measurement, which can be used to determine the magnitude and phase of every point of a continuous surface under steady-state conditions. In this method, the vibrating surface to be studied is illuminated by a white-light, sinusoidal grating projected from an oblique angle. A series of precisely timed digital images of the vibrating object is recorded as the grid is moved across the surface. An automated analysis then extracts magnitude and phase data at each pixel in the recorded images. The use of white light makes it possible to study the motion of larger surfaces than might be conveniently possible with more conventional Moire or holographic techniques, and the optical arrangement used seems relatively insensitive to external disturbances. The method seems particularly well suited to the study of structures undergoing relatively low-frequency, large-amplitude vibrations.

Image processing device and method

Abstract: PROBLEM TO BE SOLVED: To efficiently prevent a Moire fringe from occurring by a simple processing without increasing speed and accuracy of the detecting and smoothing processes of a halftone region, in an image processing device for generating recording image data for imaging based on input image data. SOLUTION: In the image processing device, an image processing circuit 50 is designed to restrain a Moire fringe to be generated in an image formed using the recording image data acquired by an error diffusion circuit 60 by detecting the halftone region of an input image using a halftone detection circuit 52 and smoothing image data in the halftone region with the help of a smoothing/highlighting circuit 54. In this circuit 50 and further, the error diffusion circuit 60, a threshold value setting circuit 62 is provided which changes a threshold value to be used for deciding whether a dot with a large diameter (or a dot of a high density ink) of the halftone region, is to be set, among the threshold values to be used for setting the diameter of an ink dot (or the thickness of the ink) to either of "large", "small" or "zero" per pixel, in the error diffusion circuit 60, to a large value than the threshold value to be used in a character region. COPYRIGHT: (C)2005,JPO&NCIPI

Determination of mechanical vibration properties of one-dimensional structures using a fringe projection method

Abstract: This work is concerning with the use of the fringe projection technique to determine amplitude and frequency of a vibrating one-dimensional structure Fringe projection on to a flat fixed end large cantilever, plastic made, excited mechanically by means of a loudspeaker is studied By means of a CCD camera, images of the projected fringes are registered and subtracted to video ratio As a result, a moire pattern is obtained and seen on a monitor screen It is shown that the vibration amplitude is obtained from the period of the moire pattern, and the frequency by means of the synchronization (triggering) of the moire images The future of this investigation is to apply this technique to electricity transmission lines

Removal of AFM moiré measurement errors due to non-linear scan and creep of probe

Abstract: In this paper, we propose a technique to remove the fringe distortion and measurement error of AFM moire due to the non-linear scan and creep of the probe. In this technique, the scanned AFM image of a standard holography grating and a virtual grating were used to generate the AFM moire fringe pattern. Two sets of moire fringe patterns, i.e. the initial fringe pattern prior to loading and the subsequent fringe pattern after uniform 'loading', were achieved in this way. Fringe pattern distortion can be found due to the non-linear scan and creep of the AFM probe. Then, phase shifting is precisely realized to AFM moire fringe patterns with the aid of a virtual grating and a logical moire technique. Wrapped and unwrapped phase maps of the two fringe patterns were calculated respectively. Finally, the unwrapped phase map of the initial fringe pattern was subtracted from that of the fringe pattern after loading and a new fringe pattern free from distortion was reconstructed; this corresponded to the uniform 'loading'. In this way, the fringe distortion and measurement errors due to the non-linear scan and creep of the AFM probe were removed.

Method for detecting deviation, pattern rotation, distortion, and positional deviation by using moire fringe

Abstract: PROBLEM TO BE SOLVED: To easily carry out pixel alignment and positioning at accuracy of pixel order or less by observing moire fringes. SOLUTION: A pattern displaying or adhering a test pattern with a pitch of two pixels is photographed by an imaging element with pixels arranged in two dimensions. Image processing is carried out to calculate a sum of absolute values of differences with four adjacent pixels in four directions with respect to the photographed image. By obtaining a moire pattern provided with a predetermined number of moire fringes, the deviation, pattern rotation, and positional deviation of an optical system is detected. COPYRIGHT: (C)2007,JPO&INPIT

Optical interference dilatometer

Abstract: The shadow moire technique, which is a straightforward method for contactless non-destructive metrological measurements associated with digital image processing, was used to erect a micro-movement measurement system and to design a dilatometer. By adjusting the angle of inclination of the reference grating and the angle of incident light, the sensitivity of the measurement system could be controlled. A piezoelectric material with nanometer precision was used to calibrate the measurement system. The moire interference fringes grabbed by a CCD camera were obtained and then input into the computer, in which the digital image processing technique was employed to improve the resolution of the fringes dramatically. The results revealed that one could measure the micro-movement accurately with a slight error of about 4% using the present set-up. A dilatometer equipped with the above-mentioned measurement system was established. By comparing the thermal expansion of the specimen with the reference material, the thermal expansion coefficient of the specimen can be determined precisely, which agrees well with the literature values.

Moiré-based auto-stereoscopic images by duplex printing on transparencies

Abstract: Method for duplex printing on transparencies to create auto-stereoscopic images. By choosing different halftone structures, differing by having different spatial frequencies for each of the two sides of a transparency, a moire pattern resulting due to halftone overlapping can be observed. On one side of the transparency is provided a uniform halftone with a selected median spatial frequency as printed. On the other side, the printing consists of two partitions: what is to be perceived as the background is printed using a halftone with spatial frequency equal to the median plus some delta x, while a desired image partition is printed using a halftone with a spatial frequency equal to the median minus the same delta x. The spatial frequency difference creates a corresponding shift-magnification factor M with an amplified total depth of the shift-magnification factor M times the thickness of the transparency.

Study of deformation fields as a function of the temperature gradient in the mirror block of an interferometer

Abstract: The formation of moire fringes in an X-ray interferometer is studied. It is shown experimentally that the well-known expression for calculating the period of moire pattern cannot be always used to calculate the period of moire patterns obtained in an X-ray interferometer. The change in the moire period caused by the temperature gradient in the crystal block of an interferometer is calculated.

New three-dimensional displacement measurement system: modified four-beam moire ´ interferometer-Twyman'Green

Abstract: An MMI-T/G system composed of a modified four-beam moire interferometer (MMI) and a Twyman/Green (T/G) interferometer is developed. The MMI-T/G can measure 3-D displacement fringe patterns with a single loading on the specimen. In the MMI-T/G system, one incident laser beam is diffracted into multiple beams by the cross-line grating on the specimen, where the ±1 order diffractive beams are redirected back to the specimen by flat mirrors, then rediffracted by the specimen grating onto the CCD, generating the in-plane displacement fringe pattern; the zero-order diffractive beam interferes with a reference beam of the T/G, generating the out-of-plane displacement fringe pattern. Details of the derivation of the fringe-governing equations are given based on the wavefront interference theory. The fringe-governing equations so obtained are comparable with those derived previously based the Doppler frequency shift theory and conventional moire interferometry. The in-plane displacement sensitivity of the new system can be shown to be twice of that of a normal moire interferometer. The optical setup has the advantages of structure novelty, flexibility, and high fringe contrast. Experiments are carried out to validate the derived governing equations, and clear thermodeformation fringe patterns of an electronic package are shown.

Holographic Fourier synthesis of dynamic Moiré-like patterns in the photorefractive Bi12TiO20 crystal

Abstract: We propose and physically discuss a kind of holographic Fourier synthesis in the profile of dynamic Moire-like patterns. The interference patterns are obtained by progressively controlling the superposition of more than two dynamic sinusoidal phase gratings. It represents a new holographic optical nondestructive testing routine in real time for metrological purposes. The sinusoidal phase gratings with slightly different pitches are dynamically generated by photorefraction in the Bi 12 TiO 20 (BTO) crystal sample. The photorefractive holographic medium is used in anisotropic self-diffraction configuration and in a diffusion-only recording mechanism.

Image forming apparatus and image processor

Abstract: PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image processor that can decide whether document moire due to interference between a document and a screen is generated, warn a user to switch the screen to a halftone screen by giving notice, then switch the screen to an aperiodic halftone screen where electrophotographic characteristics are taken into consideration, and obtain a moire-free output image from any input image. SOLUTION: The image forming apparatus equipped with an image processing means of generating printable image data by processing the input image as specified, is equipped with a moire deciding means of deciding document moire due to interference between the input image and screen before the image data are output and a halftone processing switching means (S307) of switching a halftone processing method according to whether the document moire is generated. COPYRIGHT: (C)2007,JPO&INPIT

Moire stabilized thermal imaging

Abstract: A new method of backside thermal mapping based on the relationship between mechanical strain and local interference pattern shifts will be shown for the first time. Sensitivity will be shown to be far superior to IR camera imaging methods and comparable to fluorescence microthermal imaging (FMI), allowing entire array blocks with low power consumption to be identified. This new method of acquisition controls synchronously the thermal propagation, while building up the thermal signal to enhance the Moire pattern sensitivity.

Model-based processing of a holographic moiré.

Abstract: A state space model for the determination of dual phase distributions in a holographic moire in the presence of nonsinusoidal waveforms, random noise, and miscalibration of the piezoelectric (PZT) devices is proposed. The extraction of these phase terms requires incorporating two PZTs into the moire setup. A Toeplitz approximation method (TAM) is applied for phase determination, and modification to the Toeplitz covariance matrix formed from the phase-shifted moire fringes by application of a denoising step in the state-feedback matrix is proposed. This step ensures that the phase terms can even be estimated at a signal-to-noise ratio much lower than that of the original TAM or by our previously suggested polynomial based method.

Fiber optic moiré interferometric profilometry

Abstract: Based on three-fiber optic Moire interferometric technique, a novel profilometry has been proposed and demonstrated in this paper. The square and hexagon grid interferometric fringe pattern formed by fiber optic interferometric grid generator have been designed and performed. The designing and realizing methods of the fiber optic interferometric grid pattern by using three PM fibers are discussed. Theoretically, the three-fiber coherence optical field intensity distribution has been deduced and the simulation results are also presented. The configuration of the fiber optic Moire three-dimensional shape measuring system is introduced. For example, a small half-sphere has been used to demonstrate how to reconstruct the three-dimensional shape by fiber optic Moire interferometric technique.

Moire-based auto-stereoscopic enhancement of images for duplex rendering on transparencies

Abstract: Method for duplex printing on transparencies to create auto-stereoscopic enhancement to rendered images. On one side of the transparency is provided a uniform halftone with a selected median spatial frequency as printed. On the other side, the image for enhanced rendering consisting of two partitions is printed: that partition which is to be perceived as the background is printed using a halftone with spatial frequency equal to the median plus some delta x, while the other image partition is printed using a halftone with a spatial frequency equal to the median minus the same delta x. The spatial frequency difference creates a corresponding shift-magnification factor M with an amplified total depth of the shift-magnification factor M times the thickness of the transparency.

Method for frequency-modulation screening using error diffusion based on dual-feedback

Abstract: The present invention relates to a method for producing halftone dots in the field of image hard copying, more particularly to a method for frequency-modulation screening using error diffusion based on dual-feedback. In the known frequency-modulation and amplitude-modulation screening technology, it is hard to output a halftone image with high quality using an output equipment with a low resolution (600 dpi) and the satisfactory effect of representing the gradations of the original image in detail and holding the smoothness of the original image can not be achieved. By using the dual-feedback technology based on a basic algorithm of the error distribution, the method in the present invention realizes the organic combination of the conventional frequency-modulation and amplitude-modulation screens and achieves the effect of mixed screening. The method in the present invention can effectively solve the problem of losing gradations of dots in an output equipment with low resolution and can reduce the moire caused by the random distribution characteristic so as to output halftone images with high quality and full gradations.