数字全息光刻技术

文章阐述了实现全息图数字化的重要意义，介绍了数字化全息光刻技术的原理和图像特征；叙述了计算机全息数字打印机的光学的一般结构，简述了国内外现状和应用前景。     

数字全息中的一些基本问题分析

利用全息理论、傅里叶频谱分析和采样定理，在模拟和数字全息光栅实验基础上，分析了数字全息记录和再现中的一些基本问题。结果表明：在物体和CCD尺寸确定的情况下，记录光路结构参量只取决于对图像采样的要求及CCD的像素尺寸，只要物体到CCD的距离满足采样要求，数字全息图再现光场的三个部分就可以分离；用准直平行光作为记录参考光和模拟再现光，可以得到与物体大小和形状完全一致的再现像；采样条件对再现像的影响大于分离条件，减小参物光的夹角记录适当过采样的数字全息图，有利于提高再现像的质量；另外，在获得高质量再现像方面，根据物体的具体特征，尽可能记录高质量的数字全息图，与满足采样条件和分离条件具有同样重要的意义。     

超分辨率数字全息实验研究

为提高全息成像的分辨率,对超分辨率数字全息进行实验研究,介绍了全息和超分辨率的基本理论。试验中以激光二极管尾纤发射端作为点光源,采用非放大的光路系统,拍摄了一组亚像素位移的LR全息图。通过对LR全息图和SR全息图重建的结果对比,结果显示该方法能够实现全息图亚像素位移,经超分辨率重建的图像分辨率明显提升。通过使用更高精度的位移装置和更有针对性的超分辨率算法将会进一步提升效果。     

基于数字闪耀光栅的位相全息图光电再现优化

针对利用液晶空间光调制器（LC-SLM）进行全息图光电再现过程中,再现像面存在多级衍射像造成单一像能量利用率低的问题,提出了一种在位相全息图中加载数字闪耀光栅的方法,以提高全息图光电再现中单一衍射像的衍射效率.分析了闪耀光栅作为衍射光学元件的特性及其对光波进行位相调制的原理,并阐述了在LC-SLM中加载数字闪耀光栅对位相全息图光电再现时像面能量分布的影响.搭建了基于LC-SLM的位相全息图光电再现实验系统.理论分析表明：在其他条件不变的情况下,加载竖直（或水平）槽向周期为2 pixels的数字闪耀光栅可使 关键词： 全息光电再现 位相全息图 数字闪耀光栅 液晶空间光调制器     

原子束计算全息片的设计与制作研究

在分析原子束计算全息片特点的基础上,提出采用罗曼Ⅲ型傅里叶变换计算全息图设计原子束计算全息片,给出设计步骤,然后提出采用电子束光刻编码矩孔图形,ICP各向异性刻蚀SiN薄膜的全息片制作方案,对全息片的制作工艺流程详细予以介绍,最后给出制作完成的SiN薄膜计算全息片.     

一种基于超复数系的数字全息图像生成方法

提出了一种基于超复数系的数字全息图像生成方法，通过定义超复数系，由此构成n维向量空间，然后采用分形迭代方法在n维向量空间中选择不同截面来绘制分形图像，因而能够在高维空间生成分形数字图像序列，并能够制作出具有动态效果和美感的激光全息图。由于分形数字全息图像生成具有较好的参数可控制性和不可逆转性，全盛的防伪标专难以仿制，在激光全息防伪领域有着良好的应用前景。     

数字全息周期像的产生机理及在抑制零级衍射上的应用

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     

数字全息图的非同步采样对再现像的影响

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。     

一种可用于原子全息光刻的二元计算全息新方法

 原子全息光刻即采用二元计算全息片掩模来操纵原子，实现微细结构的制作。传统二元计算全息产生的全息片在重现时会产生不止一个实像，这对于原子全息光刻的操作是不利的。提出了一种非相位编码的方法，该方法利用基元函数叠加方式产生实的编码前全息图，再利用类似罗曼Ⅲ型的编码方式产生二元计算全息图。模拟结果表明，利用该方法产生的掩模板可以产生单一的同原始图案相对应的微细结构。     

Gyrator变换全息图及其在图像加密中的应用

提出了gyrator变换全息图,利用gyrator变换快速算法模拟实现了gyrator变换全息图的产生和再现,并研究了基于相移数字全息的gyrator变换全息图.在此基础上提出了采用正弦相位光栅实现光学图像加密的新方法.该方法利用gyrator变换在相空间的旋转特性,将gyrator变换的角度、光栅的频率及光栅的旋转角度作为加密密钥,并利用两个或两个以上的gyrator变换系统的级联实现图像加密,增加了系统的安全性.依据相移数字全息进行的两个gyrator变换系统级联的仿真实验验证了该方法的可行性、有效性及其良好的安全性能.     

Analysis of Volume Hologram Using Fresnel Coefficient Matrix

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Analysis of Volume Hologram Using Fresnel Coefficient Matrix

The spectral characteristics of volume hologram is analyzed using Fresnel coefficient matrix. The volume hologram is treated as a medium in which the refractive index changes continuously. The analysis is in good consistency with previous experimental results of volume hologram.     

数字无透镜傅里叶变换全息术中非傍轴及离焦像差的校正

对数字无透镜傅里叶变换全息图直接采用逆傅里叶变换进行物场的数值重建时.需要满足两个条件:第一,全息图的记录过程必须满足傍轴近似条件,否则再现过程中会产生非傍轴像差;第二,记录全息图时物平面与参考点光源到全息图记录平面的距离必须相等,否则再现过程中会产生离焦像差.理论分析了非傍轴及离焦记录条件下数字无透镜傅里叶变换全息图的灰度分布特点,并提出了相应的非傍轴及离焦像差的数值校正方法.根据实际的非傍轴或离焦记录情况.分别给所记录的数字全息图灰度分布矩阵乘以适当的非傍轴或离焦校正因子,以消除灰度矩阵中非傍轴或离焦因素的影响.然后再对校正后的伞息图灰度矩阵做逆傅里叶变换处理.即可得到准确的数字再现像.实验结果表明.该数值重建方法能够有效地消除无透镜傅里叶变换全息术中数字再现像的非傍轴像差及离焦像差,提高再现像的质量.     

镀膜激光全息光子晶体梳状滤波特性研究

提出将成熟的光学薄膜技术和激光全息技术结合起来制作一维镀膜激光全息光子晶体,用特征矩阵方法研究了该光子晶体的梳状滤波特性,发现:随着两端薄膜的周期数增大,透射峰的中心波长向中间收拢,透射峰之间的间隔变小;随着激光全息光子晶体的周期数增大,透射峰的个数增加,透射峰之间的间隔变小;随着制作激光全息光子晶体时的激光的强度增大,透射峰的中心波长向长波方向移动,透射峰的宽度变小.     

Running holograms in azopolymer films

We report investigations on running holograms recorded in an azopolymer film made of a poly(methyl methacrylate) matrix doped with Disperse Red 1. Two-wave mixing experiments were carried out in the symmetrical transmission geometry. A stabilization technique was employed for active control of the phase shift between the real-time hologram and the interference pattern. Depending on the imposed phase shift, a running hologram propagates in the material in the form of an isomerization wave created by a continuous erasing–rewriting process. Diffraction efficiencies and the hologram velocities were measured as functions of the holographic phase shift at the wavelengths 515 and 488 nm. The experimental results were compared to theoretical curves obtained from a simplified model of the isomerization kinetics. The selective contributions of the phase and the amplitude gratings to the whole hologram were also determined.     

用一种矩阵计算方法分析体积全息光栅

本文在用于分析体积全息光栅衍射特性的法布里珀罗腔理论模型的基础上,利用矩阵法计算并分析了体积全息光栅的衍射特性.基于该理论模型的数值模拟结果与耦合波理论和以前的实验结果能较好地符合.     

Use of Fresnel synthetic holograms in an optical processor

We describe a synthetic Fresnel hologram matrix inserted in a high energy physics oriented optical processor. The purpose of the device is to detect alignment of points in real time.     

Effect of sensor proximity over the non-conformal hologram plane in the near-field acoustical holography based on the inverse boundary element method

Near-field acoustical holography (NAH) is a useful tool for the identification and visualization of vibro-acoustic sources. In particular, NAH can be applied to many practical sources having irregular shape if the inverse boundary element method (BEM) is employed. Once the relation between the source and the radiated field is defined in the transfer matrix modeled by the BEM, the reconstruction of acoustic parameters on the source surface can be conducted by the multiplication of the inverse transfer matrix and the field data measured over the hologram surface. The usual practical way to measure the field data radiated from an irregular shaped source is to adopt a regular hologram surface, which can be a flat, cylindrical, or spherical shape, for the measurement ease. Then, the hologram surface is not conformal to the source surface and the resulting transfer matrix becomes further ill-posed than the conformal case. To investigate the effect of sensor proximity and distance variability on the reconstruction error, simulation and measurement were conducted for an interior problem comprised of a parallelepiped rigid box with a vibrating end plate. Flat, tilted, and randomized hologram surfaces were adopted in the test. It was shown that the reconstruction error is greatly affected by the conditioning of transfer matrix which is related to the positioning of sensor. To improve the reconstruction accuracy, an investigation was conducted to find proper field points among a large number of overdetermined field points. The number of field data was reduced gradually under various reduction schemes using condition number, effective independence value, and sensor distance. It was demonstrated that the quality of reconstruction result given by the non-conformal measurement can be improved by removing some field points that contribute to the ill-conditioning of the inverse problem. A small improvement of the reconstruction accuracy was observed by reducing the field points in the overdetermined situation. However, further reduction of the field points, becoming an underdetermined situation, yielded a drastic improvement of the reconstruction accuracy.     

Matrix and linear interference patterns in photographic emulsions of transmission holograms recorded at different wavelengths

Matrix and linear interference patterns formed in emulsion layers of transmission holograms are considered. Boundary effects are observed between matrix and linear interference patterns, as well as between a linear interference pattern and the unexposed part of a hologram.     

Photopolymeric Material Based on an Organic-Inorganic Sol-Gel Matrix for Holography

The methods of formation and properties of a holographic photopolymeric material (PPM) of thickness 0.5–1.0 mm in a hybrid organic-inorganic matrix are investigated. The matrix is formed by synthesizing the cofspolymer N-vinylpyrrolidone with triethoxyvinylsilane with subsequent hydrolytic condensation of this copolymer with tetraethoxysilane pre-sol. It is shown that a solid hybrid matrix, stable against cracking, can be formed at a pre-sol-copolymer weight ratio of 1:4. Transmission and reflection holograms in a hybrid PPM of thickness 0.46 mm are recorded, and it is shown that the angular selectivity of the transmission hologram is 0.17° and that the material shrinkage measured from changes in the Bragg angle of the transmission hologram does not exceed 0.7%. The holographic characteristics obtained have been improved by an order of magnitude as against PPM in an organic polymeric matrix. Formation of a photopolymeric material for recording highly selective holograms in a hybrid organic-inorganic matrix is a promising approach in the development of photosensitive media for a three-dimensional holographic memory. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 551–556, July–August, 2005.