基于液晶光阀微分处理的实时联合变换相关器

提出了一种用液晶光阀实现对输入图像的微分预处理和对功率谱微分处理的实时联合变换相关器。两个液晶光阀均处于非线性变换态,分别在输入面和频谱面上实现对输入图像和联合功率谱的微分处理。微分功率谱经傅里叶透镜变换后得到相关输出。实验表明,该相关器采用全光方式不仅保证了实时性,而且锐化了相关峰;经该相关器微分后的图像,其相关性能明显优于常规联合变换相关器输出的结果。     

二元联合变换相关器的实现方法研究

采用中值取阈，局部取阈，参考图像功率谱取阈和联合功率谱（JPS）取阈四种方法对传统联合变换相关器的功率谱二值化，从而将振幅调制的功率谱转化为脉冲调制的功率谱。计算机模拟结果表明二值化可以获得更清晰更尖锐的相关峰，其中联合功率谱取阈法的识别效果最佳。     

用于模式识别的一种新的光学相关器

我们研究了一种新的白光联合变换相关器，即在频谱面上利用液晶光阀对联合傅氏干涉谱进行变换，然后用白光做为液晶光阀的读出光，实现相关变换。利用部份相干光传播模式，导出这种白光联合相关器保留了对复振幅的线性运算能力，结果表明，这种相关器能得到较好的相关结果，并能有效地抑制相干噪声。     

用功率谱复制技术实现高效联合变换相关

提出利用复制技术对高通滤波后的功率谱复制多份以获得高效的联合变换相关。平方律探测器CCD将功率谱输入计算机,经相减运算和Butter-worth高通滤波后,将其复制成N份,戍阵列形式呈现在空间光调制器上,经光学傅里叶变换得到信号相叠加的高效相关输出。计算机模拟和光学实验结果表明,这种高效相关器能够抑制相关面上的中央零级项,增强、锐化一级相关峰,信噪比提高了4倍多,N份功率谱阵列对应的输出峰值强度约是单份功率谱对应强度的N倍。     

基于拉普拉斯滤波的形态相关器

本文提出了一种基于拉普拉斯滤波的形态相关器(LBMC),用来改进传统光学形态相关器的性能.与形态相关器不同,在执行最后的傅里叶变换之前,LBMC还须对传统形态相关器的联合功率谱做拉普拉斯能谱强度滤波处理.计算机模拟测试结果表明,与线性相关和形态相关器相比,LBMC能够产生强而尖锐的相关信号,具有更强的识别能力.当输入图像受椒盐噪声影响时,LBMC保持了高且稳定的自相关-互相关比和峰噪比,从而表现出更强的鲁棒性.尽管当乘法照明因子大于1时,LBMC丧失了传统MC的照明不变识别能力,但其保证相当高的识别度.     

实时联合变换相关器目标探测与识别

光学自动图像识别的基本结构是光学相关器,由于光学相关是所有采样点并行处理,运算速度高于计算机千百倍.本文用电寻址液晶EALCD作为空间光调制器SLM,用计算机控制的EALCD并排显示参考信号和实时扫描的目标信号,并用面阵CCD作为平方律探测器记录其联合变换功率谱,通过光学傅立叶变换,输出相关信号,识别目标并确定目标在空间的方位.其特点是,由于用CCD探测功率谱,可以用各种数字处理技术提高系统的信噪比,并能更精确的探测和识别目标.     

新型联合变换相关器光学系统设计

以往联合变换相关器的光学系统结构是一支光路反馈,实时性差且体积大。针对其缺点,设计了一种具有双光路的联合变换相关器。其中,最主要的特点是傅里叶透镜组与准直扩束系统共用同一片正透镜。改进后的装置可以清晰地探测到相关点,并具有体积小的特点。     

基于声音信号的托辊故障诊断方法

为实现对远程带式输送机托辊故障的检测，研发了基于声音信号的托辊故障诊断方法。结合远程带式输送机托辊轴承的特性，针对性提出了多种分析方法结合的方案。诊断系统中包括时域检测、快速傅里叶变换（FFT）峰值检测、功率谱检测、小波包分解与重构和希尔伯特（Hilbert）包络分析结合、经验模态值分解（EMD）检测方法，实现了采集数据显示、波形分析和故障诊断。其中，时域检测、快速傅里叶变换峰值检测、功率谱检测可初步判断托辊是否发生故障，经验模态值分解可以预估出带式输送机托辊发生故障的区段，小波包分解与重构和希尔伯特包络分析联合法可进一步提取托辊轴承故障频率，确定轴承发生故障的部位。最后，通过实验验证了基于声音信号的托辊故障诊断方法的有效性。     

自适应运动目标跟踪实验

利用以非线性联合变换相关器为核心的自适应运动目标跟踪系统，对运动目标进行了跟踪实验研究，并对实验结果及有关问题进行了分析讨论。     

微波功率对a—C：F薄膜结构和光学性质的影响

用苯（C6H6）和四氟甲烷（CF4）混合气体作源气体,用微波电子回旋共振等离子体化学气相沉积技术制备了含氟非晶碳膜（a-C:F)。着重讨论了输入的微波功率对成膜结构和性质的影响。我们对沉积的膜作了膜厚、扫描电子显微表面形貌（SEM）、紫外－可见光透射谱（UV-VIS)`冷静叶红外变换（FTIR）等的测量。结果表明随着微波功率的增加沉积速率一直在上升;同时膜中缺陷增多;从FTIR的结果我们发现膜中主要以C－F、CF2和F－芳基成键;通过UV－VIS吸收谱的测量的结果我们求出了折射率和光学带隙;并且将光学带隙和膜中的sp^2碳浓度建立关系。     

Multiple-target detection with use of a modified amplitude-modulated joint transform correlator

Multiple-target detection with a modified amplitude-modulated joint transform correlator is proposed. With this technique the joint power spectrum is first modified by the subtraction of the power spectrum of the input scene only and of the reference image from it; the resultant modified joint power spectrum is next multiplied by the amplitude-modulated filter function. The effect of noise in the input scene on the performance of the joint transform correlator is analyzed and quantified. This technique is found to deliver a correlation output and the capacity to accommodate noise in the input scene better than both the fringe-adjusted filter-based joint transform correlator and the modified fringe-adjusted filter-based joint transform correlator.     

Modified fringe-adjusted joint transform correlation to accommodate noise in the input scene

A modified fringe-adjusted joint transform correlator is proposed that is able to accommodate noise in the input scene. The effect of noise in the input scene on the performance of the joint transform correlator is analyzed and quantified. When the target is embeddedin aseverely noise-corrupted input scene, it is shown that the proposed modified fringe-adjusted filter joint transform correlator delivers a better correlation performance and the capacity to accommodate this noise than does the fringe-adjusted filter-based correlator. When the power spectra of the input image and the reference image are subtracted from the power spectrum of the joint-input image, it is found that the noise effect on the output plane is independent of the objects in the input scene and originates from the convolution of the reference image and noise in the input scene.     

Binary joint transform correlator based on differential processing of the joint transform power spectrum

A novel binary joint transform correlator with differential processing in the joint transform power spectrum is proposed. The new model of the binary joint transform correlator can eliminate the dc component and sharpen the correlation intensity peaks, hence increasing its discrimination ability but with a lower complexity of computation. Preliminary results are shown by computer simulations.     

All-optical subtracted joint transform correlator with a holographic interferometer

A new, to our knowledge, subtracted joint transform correlator (SJTC) is proposed that has no digital processing in a computer. All processing for obtaining correlation signals between an object and multiple reference patterns were treated optically by use of a joint transform correlator with a holographic interferometer similar to the Mach-Zehnder one. The joint power spectrum of the reference patterns was subtracted from that of the input image (the object pattern plus the reference patterns), and the spurious correlation signals between the different reference patterns were removed. Because of the optical parallel computations of the Fourier spectra and the subtraction, the real-time SJTC is possible to achieve by use of only an optical system. An experimental arrangement of the system and system performances of the shift-invariant characteristics and discriminability are described. The results show the good performance of this system.     

Nonlinear filtering in object and Fourier space in a joint transform optical correlator: comparison and experimental realization

The use of different kinds of nonlinear filtering in a joint transform correlator are studied and compared. The study is divided into two parts, one corresponding to object space and the second to the Fourier domain of the joint power spectrum. In the first part, phase and inverse filters are computed; their inverse Fourier transforms are also computed, thereby becoming the reference in the object space. In the Fourier space, the binarization of the power spectrum is realized and compared with a new procedure for removing the spatial envelope. All cases are simulated and experimentally implemented by a compact joint transform correlator.     

Modified joint transform correlator binarized by error diffusion. II. Spatially variant range limit

Nonlinear scaling of the joint power spectrum in one approach and noise-subtraction followed by nonlinear scaling in a second approach are analyzed in conjunction with error-diffusion binarization for joint transform correlator configurations in the presence of input-additive white Gaussian noise. Nonlinear scaling is performed with a spatially variant range limit. For the second approach the subtracted noise value is an estimate of the noise power spectral density. Computer simulations and optical experiments demonstrate the advantages of the proposed error-diffusion-based joint transform correlator approaches. In particular the approach based on noise subtraction before nonlinear scaling is advantageous even for very high noise levels.     

Distortion-invariant fringe-adjusted joint transform correlation

A distortion-invariant joint transform correlator based on the concepts of the fringe-adjusted joint transform correlator and the synthetic discriminant function is presented. Computer-simulation results show that the proposed joint transform correlator is distortion-invariant for the target image from the training set and produces sharper correlation peaks and lower sidelobes compared with the classical joint transform correlator.     

Binary nonlinear joint transform correlator performance with different thresholding methods under unknown illumination conditions

The correlation performance of binary joint transform correlators with unknown input-image light illumination is investigated for different thresholding methods used in the Fourier plane. It is shown that a binary joint transform correlator that uses a spatial frequency dependent threshold function for binarization of the joint power spectrum is invariant to uniform input-image illumination. Computer simulations and optical experimental results are provided.