共查询到17条相似文献,搜索用时 671 毫秒
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提出了一种基于基元全息图频谱分析的计算全息参考光角度选择方法.通过分析基元全息图的空间频谱成分,导出全息图正确再现需要满足的约束条件;求解了基于空间光调制器的计算全息再现系统的参考光角度取值范围;用N-LUT算法计算了成像距离为1 000mm时,一幅22.5mm×26.1mm的二维图像取不同参考光角度时的全息图,并进行了数字再现和光学再现实验.结果表明:参考光角度在0.893 8°到1.398 0°之间选择可以获得质量良好的再现像;参考光角度小于0.893 8°时,再现像与共轭像不能完全分离,参考光角度大于1.398 0°时,全息图频率过高会造成欠采样,导致再现像与下一级共轭像互相交叠.实验现象与理论分析一致,验证了参考光夹角选择方法的正确性. 相似文献
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基于香农采样定理和傅里叶频谱分析,通过模拟数字全息光栅的实验,对非同步采样数字全息图的一些基本问题进行了分析。模拟实验结果表明:全息图透射率函数中的低频调制现象随非同步采样光栅空间频率的增大而变得更明显;全息图再现过程中的频谱泄漏使再现波前发生高频起伏,其影响大小取决于非同步采样的偏离程度,与光栅本身的空间频率无关。另由数值模拟实验表明,频谱泄漏对再现波前的影响可通过数字全息图加窗切趾方法来抑制,以提高再现像质量。 相似文献
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在数字全息成像中, 利用CCD的RGB模式采样全息图时, 全息重构像会出现特定的周期性分布. 本文从理论和实验上详细研究了这种周期像产生的机理、分布特性和应用. 研究结果显示, 由于CCD的光谱滤镜会使全息图的RGB三个单色采样阵列出现部分像素信号的缺失, 因此, 需要通过特定的demosaicing数学算法对缺失的像素信号进行重建以形成完整的单色采样阵列, 这是数字全息再现像周期分布产生的根源. 而基于demosaicing算法的采样阵列重建会在全息图频谱中引入调制函数, 导致物体再现像和零级衍射斑的周期分布差异. 本文揭示了全息图的RGB采样、demosaicing算法与全息重构像周期性之间的内在关联. 最后, 讨论了结合空间移位和图像形态学技术, 利用重构像的周期性抑制零级衍射斑的应用. 所有理论与实验研究结果完全一致.
关键词:
数字全息
图像周期性
零级斑抑制 相似文献
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像面数字全息是数字全息技术中常用的测量和成像方式,它通常采用离散傅里叶变换和频率滤波的方法进行物光波的重建.本文讨论了这些算法对重建相位的影响.首先分析了频谱泄露对于相位误差的影响,结果表明当采样周期为整数时,重建相位误差很小,因此具有极高的相位重建精度;而当不满足整周期采样时,相位重建误差有了明显的增加.为了改善频谱泄露所引起的相位误差,采用Hanning函数对数字全息图进行了预处理,结果表明Hanning窗的加入能够有效地提高重建相位的准确程度. 相似文献
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A new phase plate has been developed for noise-free coherent imaging system. The phase plate consists of a bleached holographic lens whose frequency is modulated in such a way that the information from each point of the object is distributed in a small three dimensional space at the Fourier plane. This introduces redundancy in the hologram and helps in smoothing out the amplitude variations in the Fourier plane. Experimental results are presented which show the capabilities of the phase plate. 相似文献
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A new method to protect the copyright of digital museum based on digital holography is proposed. The Fresnel hologram of watermark image is embedded in the object to be protected through discrete wavelet transform (DWT). After the watermark detection, the copyright information appears in the reconstructed hologram. With the higher redundancy feature in the hologram, the proposed technique can actually survive several kinds of image processing. Experimental results prove that the presented method has good robustness in image protection. 相似文献
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Study on information content of the 3D object's coherent imaging and hologram information redundancy
On the basis of the light field distribution of objects with coherent illumination, and the most basic physical mechanism of binocular stereoscopic vision, we calculate the information content of the light field in ‘the smallest observation window’ produced by a point source and multi-points source respectively, and ‘the smallest observation window’ means that the size of the window just satisfies the demand of binocular stereo vision. As a result, the minimum information content of the light field that the binocular stereo vision needed is acquired. Comparing the information content of hologram with that of the light field in the hologram plane, we make out the redundancy of holographic information content and point out the direction of the holographic compression. 相似文献
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A hologram always contains redundancy. Its huge information content brings difficulties in the storage and transmission. In addition, when a computer-generated hologram (CGH) is reproduced, the zero-order diffraction spot which occupies most of energy reduces the contrast of reproduced image and disturbs the observation and recording. In this paper, discrete cosine transform (DCT) is used to compress the information content of a CGH and to eliminate the zero-order spot. Numerical simulation results showed that, DCT could effectively remove about 64.8% of the redundancy without affecting the quality of reconstruction. It also eliminated the zero-order spot and improved the contrast of reproduced image. Finally, the optical reconstruction results were shown. Numerical and optical experiments both proved that, the reconstructed image after compression almost did not lose any resolution that human eyes could perceive. 相似文献
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通过分析两步法制彩色全息图中全息图空间带宽积与物体大小、全息图记录距离的关系,提出了一种拍摄大尺寸物体彩色全息图的方法。经编码,设置参数,在视窗处平面记录下三分色全息图, 以保证用最小的幅面记录下物体的完整信息,并且H1rgb处于同一平面经原参考光的共轭光再现时,他们的再现像能完全重合;将H1rgb再现,获得大视场的物光波信息,三基色物波信息重合后,用光学方法记录大幅面的彩色全息。该方法能提高全息图再现像的视场和解决大尺寸物体的全息图难拍摄问题。 经实验验证,该方法能将全息图再现像的视场提高6倍左右。 相似文献