共查询到17条相似文献,搜索用时 93 毫秒
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将分数傅里叶变换用于全息图制作,针对各种记录方式,全面研究了分数傅里叶变换全息图无透镜再现像的共轭关系和放大率关系,确切完整地给出了分数傅里叶全息术傍轴几何光学理论的数学表达和物理解释.计算机模拟实验证明了结论的可靠与可行. 相似文献
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一种新的三维计算全息图的计算方法 总被引:1,自引:0,他引:1
介绍了一种制作真实三维物体计算全息图的新方法。用摄像机记录三维物体在非相干光照明条件下两个正交方向上不同视角的一系列投影像,将这些投影像导入计算机,在MATLAB中对其作快速傅里叶变换。对这一系列二维投影像的傅里叶变换图进行抽样,得到三维物体在透镜后焦平面上的光场分布,进而制成一张计算全息图。结果证明该方法可以实现对真实物体三维全息图的合成,并且在算法实现上更加简单,提高了程序的运行速度,有利于改善全息图再现像的质量。为解决真实物体相干全息记录中光源功率和相干长度对全息记录可行性的限制指出了一个新的方向。 相似文献
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分数傅里叶变换光学实现的基本单元 总被引:12,自引:0,他引:12
提出一些实现分数傅里叶变换的新型的基本光学单元。这些基本单元仅使用一个透镜和一个菲涅耳衍射,给光学设计增加一些新的可选基本类型,对于给定焦距的透镜,它能完成的分数傅里叶变换是Lohmann给出的单透镜结构无法实现。 相似文献
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分数傅里叶变换计算全息 总被引:1,自引:0,他引:1
在计算全息和分数傅里叶变换的基础上提出了不对称分数傅里叶变换计算全息和双随机相位不对称分数傅里叶变换计算全息。在这种方法中,首先用一随机相位函数乘以输入图像信息,然后沿x方向实施α级次的一维分数傅里叶变换,再乘以第二个随机相位函数,最后,沿y方向实施β级次的一维分数傅里叶变换。采用迂回位相编码法对变换后的结果编码,绘出计算全息图。为了恢复原始图像,需要知道变换级次和随机相位函数。利用这种方法进行图像加密,使加密图像的密钥由原来两重增加到四重,从而提高了系统的保密性能。 相似文献
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无透镜傅里叶变换全息图数值再现中的图像处理 总被引:6,自引:4,他引:2
针对无透镜傅里叶变换全息图数值再现过程的特点,提出了一套不同于以往的削弱或消除全息图0级衍射和孪生像的数字图像处理算法。该算法分为三步。首先,对所拍摄的数字全息图通过高通滤波实现衬比度增强预处理,以提高全息图的衍射效率并消除再现图像的0级衍射斑;其次,对再现图像进行带通及Ⅴ型滤波,以降低背景噪声并使再现视场均匀;最后,对所得到的再现像进行平滑处理,通过小波滤噪和中值滤波进一步提高再现像的信噪比。实验结果表明,该方法只需记录一幅数字全息图,通过简单的数字图像处理,便可明显改善图像质量,尤其适用于无透镜傅里叶变换全息图的数值再现,并且更加实用化。 相似文献
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1 Introduction FRT(FractionalFourierTransform )wasfirstlyintroducedbyNamiasin 1 980asamathematictoolinquantummechanics[1] .In1 993,MendlovicandOzaktasimplementedtheFRTatopticalfieldwhentheystudiedgradientindex (GRIN )fiber[2 ] andappliedthepuremathematicformulatio… 相似文献
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FRTH(fractional Fourier transform hologram) is a new kind of hologram that differs from common Fresnel holograms and Fourier transform holograms. Due to the flexibility of zone plate. A method that uses the -1 order diffraction wave of zone plate as the object wave and the 0 order diffraction wave as the reference wave to record FRTH is presented. It provides a new simple way to record FRTH. In this paper, the theory of achieving FRT and recording FRTH using holographic zone plate is presented and experimental results are given. 相似文献
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Rahul Bhatt Sanjay K. Mishra D. Mohan A.K. Gupta 《Optics and Lasers in Engineering》2008,46(6):428-439
A fast holographic wavefront sensor is proposed using a computer-generated hologram (CGH). This CGH is a multiplexed hologram of different Zernike mode–amplitude combinations, and is designed in such a manner as to get the corresponding spots on the detector according to the presence and strength of a particular aberration. Interference between the aberrated wavefront (with a single mode–amplitude combination) and the Fourier transform of an image with single bright pixel (defined as dot image) is numerically calculated for one hologram. Different mode–amplitude combination and corresponding different positions of bright pixels (dots) are taken to compute various holograms and then all the holograms are multiplexed to get the final hologram. When the aberrated wavefront with a particular mode–amplitude combination is incident onto the multiplexed hologram, the corresponding dot is generated in the Fourier plane. A lens performs the Fourier transform in optical domain and provides the instant detection of amplitude of the respective Zernike mode. The main advantage of the scheme is to avoid the need of any computations, which makes it really fast. The simulation results are presented with the cross-talk analysis for few Zernike terms. 相似文献
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We generalize the definition of the fractional Fourier transform (FRFT) by extending the new definition proposed by Shih. The generalized FRFT, called the high order generalized permutational fractional Fourier transform (HGPFRFT), is a generalized permutational transform. It is shown to have arbitrary natural number M periodic eigenvalues not only with respect to the order of Hermite-Gaussian functions but also to the order of the transform. This HGPFRFT will be reduced to the original FRFT proposed by Namias and Liu's generalized FRFT and Shih's FRFT at the three limits with M=+∞, M=4k(k is a natural number), and M=4, respectively. Therefore the HGPFRFT introduces a comprehensive approach to Shih's FRFT and the original definition. Some important properties of HGPFRFT are discussed. Lastly the results of computer simulations and symbolic representations of the transform are provided. 相似文献