共查询到18条相似文献,搜索用时 162 毫秒
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数字全息三维显示关键技术与系统综述 总被引:7,自引:2,他引:5
三维全息显示能够表现出与真实物体一样的深度和视差,是一种理想的三维显示方法.但是,三维物体计算全息图计算复杂且计算量巨大,因此,如何快速生成三维物体计算全息图是数字三维全息动态显示中的关键问题之一.本文首先论述了数字全息三维显示的关键技术,包括物点散射法、体视全息法、层析法等三种三维物体计算全息图实现方法,一种RGB分离的真彩色全息显示实现方法和若干提高全息再现像质的方法;然后对几种最新典型的数字三维全息显示系统进行了技术分析;最后总结了数字全息三维显示领域的发展动态,指出三维全息显示技术会朝着实时、动态、更大尺寸、更高分辨率方向发展. 相似文献
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针对传统全息技术对三维数据源要求高、计算量大以及实现速度慢等问题,提出了一种三维物体全视差全息体视图的快速计算方法。该方法对全息面和再现面分别进行空间分割和频谱采样,通过迭代傅里叶变换算法计算多个基元全息图,叠加构成全息图单元。由摄像机获取三维物体不同角度的二维视差图像,基于人眼双目视差立体视觉原理,构建视差图像与全息图单元的对应关系。最后,利用全视差图像调制全息图单元中对应衍射方向的基元全息图,快速合成三维物体全视差全息体视图。基于液晶空间光调制器构建的光学系统对全息体视图进行了再现实验。结果表明,与传统全息图计算方法相比,本文方法容易获取数据源,计算量较小,能够快速计算全息体视图,实现三维物体不同视角图像的再现。 相似文献
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多重计算全息水印技术 总被引:3,自引:0,他引:3
为了增强水印安全性,用三维物体作为水印信息嵌入载体,提出了一种基于层析法的多重计算全息数字水印技术.该方法用层析技术得到三维物体的菲涅尔(Fresnel)全息图;利用Arnold变换对全息图进行置乱加密,置乱后的图像作为待嵌入水印;选择离散余弦变换(DCT)作为嵌入与提取算法;将Arnold变换次数与三维物体每层的衍射距离作为加密密钥.数字仿真与实验结果显示,当密钥正确时,从水印中提取的全息图的再现结果与直接再现全息图的结果一致,可以再现出三维物体相应层次的信息;密钥错误时,从水印中提取的全息图的再现结果无法识别,水印提取失败.实验结果证明了水印嵌入及提取算法的正确性,表明提出的方法可以实现水印信息的立体化和多重化,具有较高的安全性和易于实现等优点. 相似文献
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计算全息图的基本理论与制作 总被引:1,自引:1,他引:0
与传统光学全息相比,计算全息图因具有极高灵活性,制作简单并且能够记录实际不存在物体的特点而被广泛应用。越来越多的专家和学者致力于研究计算全息图。在介绍计算全息基本理论后,采用四阶迂回相位编码方法,基于MatLab平台分别制作了傅里叶二元计算全息图和菲涅耳二元计算全息图。再现实验中得到的再现像直观明显,对研究和开拓计算全息图更广泛的应用具有参考价值。 相似文献
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为实现基于数字全息的三维轮廓测量,本文探讨了菲涅耳近似算法实现数字全息相位再现的误差及抑制技术。首先理论分析了基于菲涅耳近似算法实现全息相位再现所包含的误差项,然后计算机模拟了数字离轴全息图的记录和相位再现结果,在此基础,模拟分析了离焦误差、数字再现光波误差及样本深度对相位再现的影响。针对记录参考光波和光学器件所引入的相位误差及其不定性,本文提出利用相位相减全息图处理方法加以消除,并给出了实验结果加以验证。模拟分析结果表明,菲涅耳近似算法误差、离焦误差、数字再现光波倾斜误差、解包裹错误对相位再现结果都有不同程度的影响。若获得高精度的再现结果,对记录过程、再现参数选择和处理方法都要进行严格控制或适当的选取。 相似文献
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探讨了菲涅耳近似算法实现数字全息相位再现的误差及抑制技术.理论分析了基于菲涅耳近似算法实现全息相位再现所包含的误差项,计算机模拟了数字离轴全息图的记录和相位再现结果.在此基础上,模拟分析了离焦误差、数字再现光波误差及样本深度对相位再现的影响.针对记录参考光波和光学器件所引入的相位误差及其不定性,提出了利用相位相减全息图处理方法加以消除,并给出了实验结果加以验证.模拟分析结果表明,菲涅耳近似算法误差、离焦误差、数字再现光波倾斜误差、解包裹错误对相位再现结果都有不同程度的影响,相位相减全息图处理方法可以减小再现相位误差至0.4%.对记录过程、再现参数选择和处理方法都进行严格控制或适当选取,可得到高精度的再现结果. 相似文献
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Satoshi Hasegawa 《International Journal of Optomechatronics》2014,8(2):73-88
Parallel femtosecond laser processing using a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM), called holographic femtosecond laser processing, provides the advantages of high throughput and high energy-use efficiency. Use of a light wave with spatially controlled polarization fields, called a vector wave, also offers novel properties in various applications. In this study, we demonstrated holographic femtosecond laser processing with a vector wave by using a pair of SLMs. In particular, we performed three-dimensional reconstruction with multifocal radial beams. We also realized simultaneous reconstruction with two different types of vector beams by using a novel design method of a CGH composed of multiple small CGHs. To our knowledge, this is the first demonstration of its kind. The polarization fields of the multifocal vector beams at the sample plane were analyzed from the orientations of periodic nanostructures fabricated with femtosecond laser light. 相似文献
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Different arrangements for digital double-pulse holographic and speckle interferometry for vibration analysis are described. In the case of digital double-pulse holographic interferometry, two separate holograms of an object under test are recorded within a few microseconds using a CCD camera and stored in a frame grabber. The phases of the two reconstructed wave fields are calculated from the complex amplitudes which are obtained by digital reconstruction of the wavefront produced by the hologram. The deformation is obtained from the phase difference. In the case of ESPI (or image plane hologram) the phase can be calculated by using the sinusoid-fitting method or the Fourier method. Using three directions of illumination and one direction of observation, all the information necessary for the reconstruction of the three-dimensional deformation vector can be recorded at the same time. Applications of the method for measuring rotating objects are discussed, together with the derotator needed. 相似文献
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An accurate surface reconstruction method is important to fluorescence molecular tomography (FMT) for it provides boundary information of the domain occupied by the image object which is essential to modeling light propagation in free space and inside the object. In this paper, a method based on cross-beam edge back projection (CEBP) is proposed to achieve fast and three-dimensional (3D) surface reconstruction for FMT. This method consists of a cost effective and easy-to-implement setup; it back-projects the edge of an image object of all projection angles along the actual light propagation path to perform 3D surface reconstruction. Simulation studies and experiments were performed to compare the reconstruction accuracy and computational cost of the CEBP based method and the conventional radon transform (RT) based method. Results demonstrate that the CEBP based method significantly accelerates surface reconstruction compared with the RT based method while keeping similar accuracy. 相似文献
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LOïC DENIS THIERRY FOURNEL CORINNE FOURNIER & DOMINIQUE JEULIN† 《Journal of microscopy》2007,225(3):283-292
Digital holography makes it possible to acquire quickly the interference patterns of objects spread in a volume. The digital processing of the fringes is still too slow to achieve on line analysis of the holograms. We describe a new approach to obtain information on the direction of illuminated objects. The key idea is to avoid reconstruction of the volume followed by classical three-dimensional image processing. The hologram is processed using a global analysis based on autocorrelation. A fundamental property of diffraction patterns leads to an estimate of the mean geometric covariogram of the objects projections. The rose of directions is connected with the mean geometric covariogram through an inverse problem. In the general case, only the two-dimensional rose of the object projections can be reconstructed. The further assumption of unique-size objects gives access with the knowledge of this size to the three-dimensional direction information. An iterative scheme is suggested to reconstruct the three-dimensional rose in this special case. Results are provided on holograms of paper fibres. 相似文献
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《Ultramicroscopy》2006,106(1):18-27
The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals. 相似文献
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The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals. 相似文献
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Staier F Eipel H Matula P Evsikov AV Kozubek M Cremer C Hausmann M 《The Review of scientific instruments》2011,82(9):093701
With the development of novel fluorescence techniques, high resolution light microscopy has become a challenging technique for investigations of the three-dimensional (3D) micro-cosmos in cells and sub-cellular components. So far, all fluorescence microscopes applied for 3D imaging in biosciences show a spatially anisotropic point spread function resulting in an anisotropic optical resolution or point localization precision. To overcome this shortcoming, micro axial tomography was suggested which allows object tilting on the microscopic stage and leads to an improvement in localization precision and spatial resolution. Here, we present a miniaturized device which can be implemented in a motor driven microscope stage. The footprint of this device corresponds to a standard microscope slide. A special glass fiber can manually be adjusted in the object space of the microscope lens. A stepwise fiber rotation can be controlled by a miniaturized stepping motor incorporated into the device. By means of a special mounting device, test particles were fixed onto glass fibers, optically localized with high precision, and automatically rotated to obtain views from different perspective angles under which distances of corresponding pairs of objects were determined. From these angle dependent distance values, the real 3D distance was calculated with a precision in the ten nanometer range (corresponding here to an optical resolution of 10-30 nm) using standard microscopic equipment. As a proof of concept, the spindle apparatus of a mature mouse oocyte was imaged during metaphase II meiotic arrest under different perspectives. Only very few images registered under different rotation angles are sufficient for full 3D reconstruction. The results indicate the principal advantage of the micro axial tomography approach for many microscopic setups therein and also those of improved resolutions as obtained by high precision localization determination. 相似文献