双层深度编码探测器的晶体表面优化

设计了双层LSO晶体和位置灵敏型光电倍增管耦合构成的用于小动物PET成像的 深度编码探测器. 众所周知, 晶体的不同的表面处理影响着光输出量, 进而影响着它们构建的PET探测器的性能. 为了优化设计的深度编码探测器的性能, 测试了两种不同表面处理的LSO闪烁晶体阵列探测器的晶体分辨能力及其能量、时间和空间分辨率, 结果表明, 光滑表面LSO晶体构建的深度编码探测器显示出良好的空间、能量及时间分辨特性.     

偏振学编码及解码研究

提出了用LiNbO3晶体制作的光耦合双泡克耳斯楔编码器的设计方法，分析了在远场空间的偏振编码原理，并对其用琼斯矩阵法作了解码分析。     

光折变晶体中高速调制光放大特性的研究

本文对光折变晶体中高速调制光的放大特性进行了理论分析,给出了在Ce:SBN晶体中进行的实验结果,并从物理概念上进行了讨论,指出光折变晶体中的双光束耦合可以用于时域编码通讯。     

集成空变光学逻辑处理器

利用晶体的双折射效应，在自编程双轨编码及空变逻辑控制单元的基础上，研究两种空变光学逻辑处理器，它们具有体积小，结构紧凑，性能稳定及使用灵活方便等优点，同时给出了实验结果。     

光折变晶体中高速调制光简并四波混频特性的研究

本文对光折变晶体中高速调制光简并四波混频过程的特性进行了理论分析、给出了在Ce:SBN晶体中进行的实验结果;并指出,光折变晶体中的简并四波混频可应用于消空间畸变的时域编码通信和双向时域信息的传输、放大。     

PET用新型深度编码探测器设计

平行性问题或作用深度问题影响着正电子放射层析系统(PET)的成象分辨率。本文提出和评价了一种二阶深度编码探测器,这个探测器是由两层LSO晶体和位置灵敏型光电倍增管(PS-PMT)组成,上层的晶体相对于下层的晶体的位置在X和Y方向上都有半个晶体阵列单元的错位,因为每个晶体的输出光的重心位置分布在PS-PMT上不同的位置,所以通过计算其重心位置就可在象平面上区别开每个晶体。根据PET系统的应用要求,我们验证了探测器的性能。伽马射线垂直入射时,上层晶体阵列的固有空间分辨率为1.15mmFWHM,下层晶体列阵为1.34mm FWHM.钠伽马辐射源的511keV能量峰处的平均能量分辨率对于下层晶体为19.7%,上层为23.6%.通过类似的技术亦可实现3阶、4阶深度编码探测器。     

用家电遥控器做演示实验

家电遥控器是由一块编码集成块和一个455kHz的晶体与红外发射二极管构成的红外光遥控发射装置.利用它可做一组简单有趣的物理实验,现介绍如下.     

一种混合负二进制编码的光学矩阵乘法系统

将数学中的编码方法与光学原理相结合,利用光折变晶体的四波混频效应,提出了一种可实现矩阵-矩阵的混合负二进制编码的光学系统.介绍了该系统的工作原理,分析了其工作性能.研究表明,此系统的矩阵面编码信息简单,便于扩展,可实现大规模矩阵乘法运算,对光计算的研究有一定的指导作用.     

LiNbO3:Fe光折变晶体实时光学相关存贮研究

在ＬｉＮｂO₃：Ｆｅ晶体中实现了光折变实时相关存贮。它兼备存贮器与相关器两种器件的优点，又具有光折变器件的实时特点，因而可从数个被存贮的信息中实时、快速地挑选出与输入信息相关的信息。从相关点的强度和位置可立即得到孩信息与输入信息的相关程度和编码序数，其原理基于光折变匹配滤波器的筛远性。因此该器件具有广阔的应用前景。 关键词：     

光折变晶体均匀多重全息图存储研究

本文推导了光折变晶体角度编码多重全息存储中写入均匀光栅时的曝光时间递推公式.分析了散射效应对光栅写入时间常数的影响和写入光耦合对光栅振幅的影响,给出了两种因素影响下曝光时间计算的修正递推公式.数值计算结果表明,按照这种修正公式计算所得多重存储中各幅全息光栅振幅不仅均匀性好,而且振幅相对较大,这种曝光方法有利于提高晶体的存储容量.实验中以递推公式所得时间进行曝光记录,在厚度为0.6mm的Fe:LiNbO₃晶体中采用角度编码很容易存储了30幅全息图.     

基于级联分数傅里叶变换系统的数字水印技术

提出一种基于分数傅里叶变换和随机相位编码的光学加密数字水印技术,可成为一种信息隐藏及保护的有效方案.该数字水印技术对于噪音叠加和常见的图像处理操作具有较强的稳健性.该技术根据光学级联分数傅里叶变换系统,利用两个随机相位分布函数对水印信息编码并经过迭代分数傅里叶变换嵌入到变换域的载体图像中.在水印检测和提取过程中,两个相位分布函数作为密钥.随机相位编码技术的引入,进一步提高了数字水印系统的密钥空间.增强了系统的安全性.该数字水印技术基于光学分数傅里叶变换原理,可以利用光学变换系统方便地实现.     

Free control of far-field scattering angle of transmission terahertz wave using multilayer split-ring resonators’ metasurfaces

To enhance transmission efficiency of Pancharatnam–Berry (PB) phase metasurfaces, multilayer splitring resonators were proposed to develop encoding sequences. As per the generalized Snell’s law, the deflection angle of the PB phase encoding metasurfaces depends on the metasurface period’s size. Therefore, it is impossible to design an infinitesimal metasurface unit; consequently, the continuous transmission scattering angle cannot be obtained. In digital signal processing, this study introduces the Fourier convolution principle on encoding metasurface sequences to freely control the transmitted scattering angles. Both addition and subtraction operations between two different encoding sequences were then performed to achieve the continuous variation of the scattering angle. Furthermore, we established that the Fourier convolution principle can be applied to the checkerboard coded metasurfaces.     

Multiparameter estimation using only a chaotic time series and its applications

An important extension to the techniques of synchronization-based parameter estimation is presented. Based on adaptive chaos synchronization, several methods are proposed to dynamically estimate multiple parameters using only a scalar chaotic time series. In comparison with previous schemes, the presented methods decrease the cost of parameter estimation and are more applicable in practice. Numerical examples are used to demonstrate the effectiveness and robustness of the presented methods. As an example application, an implementation of multichannel digital communication is proposed, where multiparameter modulation is used to simultaneously transmit more than one digital message. From a theoretical perspective, such an encoding increases the difficulty to directly read out the message from the transmitted signal and decreases the implementation cost.     

基于两步正交相移干涉的振幅图像光学加密技术

提出一种基于两步正交相移干涉的光学图像加密技术.这种相移干涉数字全息只要记录两幅干涉图,不需要记录物光波和参考光波的强度信息,就可以再现没有零级像和共轭像的再现像.物光波对应的光路经过两次菲涅尔变换,并结合双随机相位编码.参考光分别引入0和π/2相位,用数字化记录介质记录两幅数字全息图作为加密图像.解密时只要获得正确的密钥,经过简单的计算就可以重建清晰的原始图像.模拟实验验证了它的可行性和有效性,分析了抗裁剪和噪音的鲁棒性.     

Digital audio information hiding based on Arnold transformation and double random-phase encoding technique

In this paper, Arnold transformation and double random-phase encoding technique widely used in digital image information hiding are introduced to digital audio information hiding. The digital audio is transformed into a 2-D image called sound map and then the sound map will be divided into many windows and each window will be encrypted based on the Arnold transformation. Finally sound map will be re-encrypted based on double random-phase encoding technique. This method offers many advantages for digital audio information hiding: improve security and high attack immunity.     

基于数字微镜器件改进的罗曼编码

全息光刻可通过空间光调制器数字微镜器件（DMD）加载计算全息图构建数字掩膜来实现,罗曼编码是常用的编制计算全息图的方法,它采用透明矩形孔的高度和位置分别编码全息图抽样单元的幅值和相位。通常,DMD再现此类二元全息图需合并多个微镜来表示单个矩形孔,这会大大降低其像素利用率和分辨率。针对这个问题,提出一种改进的罗曼编码,该编码充分利用DMD的二进制脉宽调制特性,采用灰度值编码全息图抽样单元的幅值,将全息图的透过率由二元型转换成灰阶型,从而有效减少单个抽样单元所占用的微镜数。采用MATLAB编程对改进的罗曼编码和博奇编码计算全息图进行模拟再现分析,得到改进的罗曼编码衍射效率约是博奇编码的3倍。以DMD为核心搭建了全息再现实验,得到改进的罗曼编码衍射效率约是博奇编码的2倍。可得出采用改进的罗曼编码可以显著提高衍射效率。     

The multiple-parameter discrete fractional Hadamard transform

Discrete fractional Hadamard transform (DFrHaT) is a generalization of the Hadamard transform, which has been widely used in signal processing. In this paper, we present the multiple-parameter discrete fractional Hadamard transform (MPDFrHaT), which has multiple order parameters instead of only one in DFrHaT. The proposed MPDFrHaT is shown to possess all of the desired properties of DFrHaT. In fact, it will reduce to DFrHaT when all of its order parameters are the same. We also propose a novel encryption technique, double random amplitude (DRA) encoding scheme, by cascading twofold random amplitude filtering. As a primary application, we exploit the multiple-parameter feature of MPDFrHaT and double random amplitude encoding scheme for digital image encryption in the MPDFrHaT domain. Results show that this method can enhance data security.     

Photonic analog-to-digital converter based on the robust symmetrical number system

A novel approach to realizing photonic analog-to-digital conversion with Gray-code-like property is proposed and demonstrated. Instead of using Mach-Zehnder modulators (MZMs) with different half-wave voltages, an array of MZMs with identical half-wave voltages are applied to realize quantization and encoding, which greatly simplifies the implementation. Multiple comparators with preset thresholds are applied at the output of each MZM to improve the number of bits. Through properly setting the bias voltages of the MZMs, a photonic analog to digital converter (ADC) based on the robust symmetrical number system (RSNS) coding method is realized. As an example, a 3-channel structure with maximum quantization level of 17 (corresponding to 4.09 bits) is investigated in detail. We show that the differential encoding technique can be applied in the proposed structure, which increases the equivalent number of bits of the ADC system.     

光电跟踪系统轴角编码与数字显示

介绍一种光电跟踪系统所采用的轴角编码与数字显示器。分析跟踪型轴角编码器的基本原理，探讨并提出了提高分辨率的具体方法，保证系统测角精度并可进行数字显示。     

Watermarking of three-dimensional objects by digital holography

We present an optical method for information watermarking of three-dimensional (3D) objects by digital holography. A hidden image is embedded by double phase encoding in a phase-shift digital hologram of the 3D object. We decode the watermarked hologram to reconstruct the hidden image and the 3D object. We use either the entire hologram or a part of it to decode the hidden image. Experiments are presented to illustrate the ability to recover both the 3D object and the decoded hidden image. Digital holograms of the 3D object are obtained by optical experiments. The watermarking process, 3D object reconstruction, and hidden image recovery are performed digitally. To the best of our knowledge, this is the first report of 3D object watermarking by use of a phase encoding technique and digital holography.