Performances of an all-optical subtracted joint transform correlator that uses a photorefractive crystal

An all-optical subtracted joint transform correlator (JTC) was proposed and it was experimentally shown that the correlator successfully performs the pattern recognition with the number of reference patterns. In the correlator, an optical interferometer was introduced to remove the additional correlation signals between the reference patterns themselves from the output plane and a photorefractive crystal was also introduced to record the joint power spectra as volume holograms. The processing for removing the additional correlation signals was performed by the parallel computations in the interferometer in real time. In this study it has been found that the correlator yields significantly better correlation results than the classical joint transform correlator does and the recording of the volume hologram corresponds to a nonlinear processing of the joint power spectrum in the fringe-adjusted joint transform correlator. However the volume hologram has angular selectivity for matching the Bragg condition. It would restrict the shift-invariant area of the input image plane. This restriction has been investigated experimentally.     

Performance of an image-encrypted joint transform correlator for pattern recognition

An image-encrypted joint transform correlator for pattern recognition is proposed and evaluated. The correlator performs twofold correlation for recognizing the primary image and cipher, and the encrypting cipher acts to enhance or inhibit the correlation peak if the cipher is correctly input. By incorporating the original image with an appropriate cipher, the correlator achieves better pattern discrimination and is robust against distortion. Simulation results show that the pixel number and the cell size of cipher affect the characteristics of the correlator.     

The use of a consumer grade photo camera in optical-digital correlator for pattern recognition and input scene restoration

In this work an optical-digital correlator for pattern recognition and input scene restoration is described. Main features of the described correlator are portability and ability of multi-element input scenes processing. The correlator consists of a consumer grade digital photo camera with a diffractive optical element (DOE) inserted as a correlation filter. Correlation of an input scene with a reference image recorded on the DOE are provided optically and registered by the digital photo camera for further processing. Using obtained correlation signals and DOE’s point spread function (PSF), one can restore the image of the input scene from the image of correlation signals by digital deconvolution algorithms.The construction of the correlator based on the consumer grade digital photo camera is presented. The software procedure that is necessary for images linearization of correlation signals is described. Experimental results on optical correlation are compared with numerical simulation. The results of images restoration from conventionally and specially processed correlation signals are reported. Quantitative estimations of accuracy of correlation signals as well as restored images of the input scene are presented.     

基于液晶光阀非线性变换的实时光学相关识别

提出了一种高鉴别能力的实时光学相关器，它采用液晶光阀作为实时输入器件，并利用其非线性变换特性对图像微分预处理，全息记录材料采用光折变晶体，且使用全取球面波作参考光。所给出的实验结果表明，该光学相关具有鉴别能力高，实时性和灵活性强，以及结构２紧凑的特点。     

基于阴极射线管耦合液晶光阀空间光调制器的联合变换相关器

描述了一种基于电寻址空间调制器的二值化联合变换相关器，该系统主要包括阴极射线管耦合液晶光阀（ＣＲＴ－ＬＣＬＶ）、ＣＣＤ摄象机和ＣＯＭＰＡＱ３８６计算机，文中在理论分析的基础上给出了计算机模拟和初步的实验结果，表明该相关器具有良好的识别性能。     

Synthetic optical processor for generalized logic realization problems

A synthetic joint Fourier transform (SJFT) correlator is proposed for the realization of generalized logic problems. As a case study, a multi-channel SJFT correlator is employed to realize a multi-output logic unit. For a given correlator set-up, this particular scheme ensures the maximal utilization of space bandwidth product. This work establishes a pragmatic approach for implementing real-time programmable content addressable memory for information processing.     

基于KNSBN:Cu晶体的光折变联合变换相关器

给出基于KNSBN:Cu晶体的光折变二波耦合联合变换相关器(TBJTC).以KNSBN:Cu晶体作为平方律转换器,将强度较大且携带参考图象和待识别图象联合频谱的信号光波与一强度较弱的相干平面参考光波同时输入于KNSBN:Cu晶体,通过光折变二波耦合过程的非线性能量转移,实现功率谱转换,进而实现相关识别.理论分析和实验结果表明,除输入输出外,该光学相关器无需CCD、LCLV等器件和相应的数字处理,是一个全光光学相关器.     

Three-dimensional image correlator using fast computational integral imaging reconstruction method based on pixel-to-pixel mapping

In this paper, a three-dimensional (3D) image correlator using a fast computational integral imaging reconstruction (CIIR) method based on a pixel-to-pixel mapping is proposed. In order to implement the fast CIIR method, we replace the magnification process in the conventional CIIR by a pixel-to-pixel mapping. The proposed fast CIIR method reconstructs two sorts of plane images; a plane image whose quality is sufficient, and a dot pattern plane image insufficient to view. This property is very useful to enhance the performance of a CIIR-based image correlator. Thus, we apply the fast CIIR method to a CIIR-based image correlator. To show the feasibility of the proposed method, some preliminary experiments on both pattern correlation and computational cost are carried out, and the results are presented. Our experimental results indicate that the proposed image correlator is superior to the previous method in terms of both correlation performance and complexity.     

An anomalous correlator of resonantly scattered light

The space-time properties of the correlator of the light intensities scattered from resonant atoms are studied. It is shown that in measuring such a correlator by the method of optical shifts, an appreciable contribution appears from the anomalous correlator of the scattered field amplitudes. It is simple to observe this correlator in the field of a standing wave by measuring the correlation of oppositely scattered rays. The spectral and polarization properties of such a correlator are studied. Its investigation is of interest for high-resolution spectroscopy because it allows information to be obtained on the natural width of a line in conditions of strong Doppler broadening. It is important to stress that this is possible in a linear approximation with respect to the strength of the external field in contrast to the methods of laser spectroscopy based on nonlinear effects.     

菲涅尔全息滤波光强相关识别的理论与实验依据

本文对用菲涅尔全息滤波器进行无透镜光强相关识别的问题重新进行了论证,结果再次证明菲涅尔全息滤波器完全可以用作相关识别。     

The time dependent correlation function of an Impenetrable Bose gas as a Fredholm minor.I

We study the two field correlator of an Impenetrable Bose gas. Lenard [1] proved that the equal time correlator can be represented as a Fredholm minor. We generalize this representation to the time dependent correlator.     

Analysis of influence of black matrix effect in spatial light modulator on optical correlation detection

Motion detection with a joint transform optical correlator is based on the maximally correlated bright spots in a correlation image; therefore, the quality of a correlation image greatly influences optical correlation detection. As the core component of a joint transform optical correlator, a spatial light modulator has an opaque part (black matrix structure) that is an important factor that needs to be considered. In this paper, we first analyzed the effect of the fill factor on the light energy distribution in the image plane according to the mechanism of the spatial light modulator using a multiple-subpixel matrix to simulate a single pixel, while zeroing some subpixels to simulate the black matrix part in the single pixel and employing computer software to simulate the joint transform optical correlator to obtain the simulated correlation image result with a black matrix effect. In addition, we built an experimental setup to obtain an actually photographed correlation image, which was well consistent with the simulated result.     

光学相关器的研究进展及军事应用

介绍了范德卢格特型和联合变换型光学相关器的基本原理和结构,给出了目前世界各国光学相关器的最新研究进展情况,最后探讨了其在军事上的应用前景及下一步的重点研究方向。     

Real-time Optical Wavelet-Transform with Positive and Negative Signals

An opto-electronic hybrid system that is based on the joint transform correlator (JTC) is suggested for the implementation of real-time wavelet transform. Holographic encoding of both the object signal and wavelet function enables the JTC-based real-time correlator to execute the optical wavelet transformation involving positive and negative values. We suggest an interferometric method to retain the information about the polarity of the final wavelet transform. The principle of this method is verified by experiments.Presented at 1996 International Topical Meeting on Optical Computing (OC ‘96), April 21-25, Sendai, Japan.     

Spatial Position Detection of Three-Dimensional Objects by Effective Three-Dimensional Correlation Based on Fourier Transform Profilometry

Spatial position detection of a three-dimensional (3D) object by a correlator based on Fourier transform profilometry is discussed. The presence of the 3D object and its precise spatial position can be recognized by the correlator using the position and phase of the correlation peak. The spatial position is obtained by the relative displacement from the position where the reference object is originally placed. The characteristic of the correlator with respect to the moving direction of a 3D object is experimentally verified. Effects of the baseline factor on 3D object recognition are also investigated.     

Effect of dynamic range input image on performance of binary subtracted joint transform correlator

A demand for the dynamic range of input images in the binary subtracted joint transform correlator was studied by computer simulations using input scenes containing multiple halftone images of human faces. To realize good discriminability the correlator requires use of an image-conversion subsystem with a dynamic range larger than 50:1 and 16:1 in amplitude for input scenes having (1) a reference image and many target images and (2) a target image and many reference images, respectively.     

光电混合综合判别相关器

论述了综合判别函数（ＳＤＦ）的基本理论，简明地给出了用综合判别函数实现畸变不变相关的技术途径。在此基础上，构造了一个光电混合综合判别相关器实验系统，并用它实现了三重（位移、旋转、尺度）畸变不变实时相关识别。     

Rotation-invariant pattern recognition using morphological phase-only correlation

We present a rotation-invariant nonlinear correlator based on the circular harmonic filter (CHF) and the previously proposed morphological phase-only correlator (MPC) [Q. Wang, S. Liu, Opt. Commun. 244 (2005) 93]. We refer to this correlator as a rotation-invariant MPC (RIMPC). Through computer simulation, we compare the output results of RIMPC with those of rotation-invariant MC (RIMC) and CHF when input scene is corrupted by salt-and-pepper noise, white additive Gaussian noise and cluttered background. Our results show that RIMPC yields higher discriminability, sharper and higher correlation peaks and displays better stability against the above three kinds of noise than do the RIMC and common CHF.     

利用液晶光阀实现二值化联合变换相关器的研究

二值化联合变换相关器，通过对联合变换的功率谱进行二值化操作可以提高联合变换相关器的图像识别。本文正是基于此观点，首次提出利用液晶光阀本身的饱和区实现反转二值化联合变换功率谱。     

大动态范围高速光子相关器

目前光子相关器在处理速度和动态范围上还不能满足光子相关光谱技术的需求,为解决此问题,对比分析了比例相关器和多采样时间相关器的结构,并结合两者的优点提出利用多采样时间相关结构来设计相关器的高速通道,利用比例相关结构来设计相关器的低速通道,并将高速通道和低速通道相结合,实现大动态范围高速光子相关器的设计。实验结果表明:大动态范围高速光子相关器的采样时间下限可以达到10 ns,动态范围达到1.11012,采用改进归一化方法时,基线误差为0.095 %,相关函数具有足够的精度。