共查询到20条相似文献,搜索用时 31 毫秒
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Shaked NT Rosen J 《Journal of the Optical Society of America. A, Optics, image science, and vision》2008,25(8):2129-2138
We present a theoretical framework for recording and reconstructing incoherent correlation holograms of real-existing three-dimensional scenes observed from multiple viewpoints. This framework is demonstrated by generating and reconstructing a modified Fresnel hologram as well as a new correlation hologram called a protected correlation hologram. The reconstructed scene obtained from the protected correlation hologram has a significantly improved transverse resolution for the far objects in the scene compared to the modified Fresnel hologram. Additionally, the three-dimensional information encoded into the protected correlation hologram is scrambled by a secretive point spread function and thus the hologram can be used for encrypting the observed scene. The proposed holography methods are demonstrated by both simulations and experiments. 相似文献
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Abstract In this paper, a new artifact reduction algorithm for compressed color images using MMRCVQ is proposed. The algorithm extends and modifies vector quantization (VQ) for discovering the relationships between the uncompressed color images and their deblocked compressed versions by classifying the deblocked compressed blocks into several categories using information from their neighboring blocks. The discovered relationships are stored in two codebooks and are used to recover the missing information of compressed color images. To increase the availability of codewords and reduce the memory needed for storing codewords, mean‐removed vectors are used to generate codebooks. The experimental results show that the proposed approach can remove, effectively, the artifacts caused by high compression and improve perceptual quality significantly. Compared to existing methods, the proposed approach usually uses much less computing time to recover a compressed color image and has much better image quality. 相似文献
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A color transmission approach between a computer display and a color computer-generated holography (CCGH) colorimetric system is proposed based on color matching theory. Firstly, the conversion between color quantities of a computer display and a CCGH colorimetric system is discussed based on color matching theory. Secondly, the isochromatic transfer relationship of color quantity and amplitude of the object light field is proposed. Thirdly, the color object light field was encoded into a hologram, and then the hologram was reconstructed numerically. The simulation results demonstrate that our novel approach is feasible. 相似文献
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Binarization of Fresnel holograms by direct thresholding based on the polarity of the fringe pattern is studied. It is found that if the hologram is binarized (i.e., for black and white hologram pixels) in this manner, only the edges of the object are preserved in the reconstructed image. To alleviate the errors caused by binarization, the use of error diffusion has been routinely employed. However, the reconstructed image using such standard technique is heavily contaminated with random noise. In this paper, we propose a novel noniterative method for generating Fresnel holograms that are suitable for binarization. Our method is capable of preserving good visual quality on the reconstructed images. 相似文献
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Abstract A generalized solution in the scope of the Fresnel approximation for diffractive optical elements producing focal curves is derived in this paper. The method includes planar and non-planar focal lines parametrized by differentiable functions and different types of holograms (Fourier, Fresnel). The integral describing the complex amplitude distribution generated by such a focal curve is evaluated with the help of the stationary phase method and the points in the hologram plane contributing to a particular point of the focal curve are found to be circles or straight lines. As the result equations for stationary points turn out to be solvable analytically only in some specific cases, an approximate approach is proposed additionally. In this way the class of analytic solutions for non-planar curves can be broadened into cases for which there exists a solution related to their projection on to the hologram plane. The paper is completed by presentation of non-paraxial ray tracing diagrams for elements designed with the help of both methods. 相似文献
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Three types of computer-generated hologram synthesized from multiple angular viewpoints of a three-dimensional scene 总被引:1,自引:0,他引:1
We describe various techniques to synthesize three types of computer-generated hologram (CGH): the Fresnel-Fourier CGH, the Fresnel CGH, and the image CGH. These holograms are synthesized by fusing multiple perspective views of a computer-generated scene. An initial hologram is generated in the computer as a Fourier hologram. Then it can be converted to either a Fresnel or an image hologram by computing the desired wave propagation and imitating an interference process of optical holography. By illuminating the CGH, a 3D image of the objects is constructed. Computer simulations and experimental results underline the performance of the suggested techniques. 相似文献
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We propose a novel optical method to display a complex Fresnel hologram using a single spatial light modulator (SLM). The method consists of a standard coherent image processing system with a sinusoidal grating at the Fourier plane. Two or three position-shifted amplitude holograms displayed at the input plane of the processing system can be coupled via the grating and will be precisely overlapped at the system's output plane. As a result, we can synthesize a complex hologram that is free of the twin image and the zero-order light using a single SLM. Because the twin image is not removed via filtering, the full bandwidth of the SLM can be utilized for displaying on-axis holograms. In addition, the degree of freedom of the synthesized complex hologram display can be extended by involving more than three amplitude holograms. 相似文献
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In this paper we propose an alternative technique for producing digital Fresnel holograms. The evaluation of a diffraction pattern in a wide region is implemented in such a way as to avoid redundant calculations and preserve the precision. Because of the symmetry of the kernel, the complex amplitude is calculated at four points in the registration plane simultaneously. This algorithm decreases the required CPU time 4 times with respect to direct calculation. The digital Fresnel hologram is numerically and optically reconstructed, and some qualitative comparisons are made. 相似文献
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An efficient method for obtaining modified Fresnel holograms of real existing three-dimensional (3-D) scenes illuminated by incoherent white light is presented. To calculate the hologram, the method uses multiple-viewpoint projections of the 3-D scene. However, contrary to other similar methods, this one is able to calculate the Fresnel hologram of the 3-D scene directly rather than calculating a Fourier hologram first. This significantly decreases the amount of calculations needed to obtain the hologram and also reduces the reconstruction errors. The proposed method is first mathematically introduced and then demonstrated by both simulations and experiments. 相似文献
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We demonstrate the validity of wavelet-based processing for recognition and classification of three-dimensional phase objects. One Fresnel digital hologram of each of the three-dimensional (3-D) phase objects to be classified is recorded. The electronic holograms are processed digitally to permit 3-D object information to be retrieved as two-dimensional digital complex images. We use a Mexican-hat wavelet- matched filter (WMF) to enhance the correlation peak and discriminate between the objects. The WMF performs a wavelet transform (WT) to enhance the significant features of the images and the correlation of the WT coefficients thus obtained. We compare the feasibility of a WMF-based object classifier with the matched-filter-based classifier to classify our four 3-D phase objects in a 3-D scene into true or false classes with minimal error. 相似文献
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A complete absolute interferometric test of axially symmetric aspheres is presented. The method is based on a specially designed computer-generated hologram (CGH) that reconstructs an aspherical wave as well as a spherical auxiliary wave. Since both phase functions have the same symmetry and their pattern is simultaneously encoded, we call this type of multiplex hologram a Twin-CGH. The spherical wave is used for calibration. The aberrations of the spherical auxiliary wave are measured absolutely with either a spherical mirror or an absolute test for Fresnel zone plates. Thus the two types of aberration inherent in the CGH can be identified and separated from each other. The errors of the spherical wave can be transferred to those of the aspherical wave. Two different methods thatuse Twin-CGHs for absolute testing of aspheric surfaces are described. Test procedures are explained, equations are derived, and experimental results are presented. A mutual comparison of the two results and a comparison with the established N-position rotation test are given. 相似文献
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一种基于 Contourlet 变换的彩色图像全息水印算法 总被引:2,自引:5,他引:2
提出了一种结合了全息水印加密技术和 Contourlet 变换技术的彩色图像水印算法。 算法首先将 RGB 模式的水印载体图像转换至 YCrCb 颜色空间,选取亮度分量作为水印载体通道,对其进行多层 Contourlet 分解,得到细节子带图像;而后对二值水印图像进行傅里叶全息加密,将加密后的图像嵌入至载体图像的 Contourlet变换系数中。 仿真实验结果表明,该水印算法具有良好的不可见性,对于常见的几何变换及多种攻击具有良好的鲁棒性。 相似文献
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We present an optical imaging system and mathematical algorithms for three-dimensional sensing and identification of stem cells. Data acquisition of stem cells is based on holographic microscopy in the Fresnel domain by illuminating the cells with a laser. In this technique, the holograms of stem cells are optically recorded with an image sensor array interfaced with a computer and three-dimensional images of the stem cells are reconstructed from the Gabor-filtered digital holograms. The Gabor wavelet transformation for feature extraction of the digital hologram is performed to improve the process of identification. The inverse Fresnel transformation of the Gabor-filtered digital hologram is performed to reconstruct the multi-scale three-dimensional images of the stem cells at different depths along the longitudinal direction. For recognition and classification of stem cells, a statistical approach using an empirical cumulative density function is introduced. The experiments indicate that the proposed system can be potentially useful for recognizing and classifying stem cells. To the best of our knowledge, this is the first report on using three-dimensional holographic microscopy for automated identification of stem cells. 相似文献
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Three-dimensional Displacement Analysis by Windowed Phase-shifting Digital Holographic Interferometry 总被引:1,自引:0,他引:1
Abstract: Phase-shifting digital holography is a new method for measuring the displacement distribution on the surface of an object. The authors previously proposed a windowed phase-shifting digital holographic interferometry (windowed PSDHI). This method provides accurate displacement distributions by decreasing the effect of speckle patterns. In this study, the method is extended to analyse three-dimensional displacement components in a microscope. Three object laser beams in the optical system are used. Four phase-shifted holograms are recorded for each object laser beam. The complex amplitude of each reconstructed light at the object is calculated by the Fresnel diffraction integral of the complex amplitude of the hologram. The reconstructed distance is obtained at the point with the maximum of the standard deviation of the intensities of the object reconstructed with changing the reconstruction distance. The three phase-difference values between before and after deformation provide the three-dimensional displacement components. Theoretical treatment and experimental results of three-dimensional displacement measurement using this method are shown. 相似文献
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We present multiple-image encryption (MIE) based on compressive holography. In the encryption, a holographic technique is employed to record multiple images simultaneously to form a hologram. The two-dimensional Fourier data of the hologram are then compressed by nonuniform sampling, which gives rise to compressive encryption. Decryption of individual images is cast into a minimization problem. The minimization retains the sparsity of recovered images in the wavelet basis. Meanwhile, total variation regularization is used to preserve edges in the reconstruction. Experiments have been conducted using holograms acquired by optical scanning holography as an example. Computer simulations of multiple images are subsequently demonstrated to illustrate the feasibility of the MIE scheme. 相似文献