基于光学联合变换相关器的像移探测技术

针对稳像中运动矢量的求取,提出了一种基于光学联合变换相关器的像移探测技术.给出了基于光学联合变换相关器的像移探测原理,并给出了仿真结果.为了验证联合变换相关器的探测准确度,进行了实验验证,验证结果表明探测最大误差为0.8个像素.结果表明,光学联合变换相关器能够很好地探测出运动矢量,进而完成图像稳定工作.相比单纯的软件算法求取运动矢量,基于光学联合变换相关器的像移探测技术能够更快更好地达到目的.     

光学多目标识别的新方案

介绍一种数学形态学的击中与否（Ｈｉｔ－ｏｒ－Ｍｉｓｓ）算法，能快速准确实现光学多目标识别的新方案，避免了普通光学相关目标识别方法中经常出现的错误信号，因此，其目标识别结果更为有效可靠。     

基于光学联合变换相关器的像移探测技术*

针对稳像中运动矢量的求取,提出了一种基于光学联合变换相关器的像移探测技术.给出了基于光学联合变换相关器的像移探测原理,并给出了仿真结果.为了验证联合变换相关器的探测准确度,进行了实验验证,验证结果表明探测最大误差为0.8个像素.结果表明,光学联合变换相关器能够很好地探测出运动矢量,进而完成图像稳定工作.相比单纯的软件算法求取运动矢量,基于光学联合变换相关器的像移探测技术能够更快更好地达到目的.     

Measurement of small phase shifts of radio signals using acoustooptic reduction

Results are presented of model-based experimental investigations of an interference correlator intended for the measurement of small phase shifts of radar signals received from two antennas. The correlator is based on a Mach-Zender interferometer system. Introduction of a radio signal for the data reduction was simulated by phase diffraction gratings placed in the interferometer arms and displaced relative to one another. The operation of the system was investigated in a regime with measurements in the region of the extrema of the correlation function and in a regime with measurements near zeros (extrema of the derivative) of the correlation function. The investigations were carried out for signals formed in first, second, and third order of diffraction. It is shown that the sensitivity of the system for measurements in the region of a correlation-function zero is higher by an order of magnitude than in the extrem~ m region. It is shown that for radio signals in the 100-MHz band, with allowance for the experimental measurement error, the accuracy of determining the time delays reaches 10^–11 sec. The accuracy with which geometric displacements of diffraction gratings are determined reaches 5·10^-5 mm.Lebedev Physics Institute. Severo-Osetinsk State University.     

利用偏振编码实现取零阈值的单通道击中与否运算

基于数学形态学的对偶法则以及数学形态学理论与线性位移不变系统理论间的关系,引入了偏振编码技术,提出使击中与否运算通过单通道取零阈值非相干光学相关器来实现的方案。该方案采用偏振编码,将图像的前景和背景都包含在一个编码图像中,从而使击中与否运算可以用一个腐蚀算子完成(即通过单通道实现),大大简化了实验装置,节约了空间,降低了对光路调节的要求。同时,通过取零阈值,消除了由于入射光强分布不均匀及CCD光电响应的非完全线性所导致的对输出图像取阈值时出现的误差。最后,还对该方案进行了实验验证,结果表明这是一种方便、准确、有效的图像处理方法。     

位相调制的实时联合变换相关器

提出一种位相调制的实时联合变换相关器。它采用液晶显示屏作为输入器件，用液晶光阀记录和显示联合功率谱。利用液晶显示屏上的光栅状结构的衍射级，提高光能的利用率，并充分利用液晶光阀的有效使用面积。采用成像透镜放大各衍射级的联合频谱，适应液晶光阀较低的分辨率要求。在相关器的光路中插入两块倾斜的平行平面玻璃板，以改变各衍射级的参考图像和目标图像之间的位相差。这种方法可产生比传统的实时联合变换相关器更好的输出相关性能。实验结果证实了该系统设计及性能分析的正确性     

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.     

Pure phase correlator with photorefractive filter memory

We report on the investigation of a new compact configuration of an inverted VanderLugt-type correlator system. The phase of the Fourier transform of the image to be recognized is displayed on a phase-modulating electrically addressed spatial light modulator. This phase display is compared with the phase of the Fourier transforms of a reference library recorded in a photorefractive LiNbO(3) crystal. Angular hologram multiplexing permits fast data access, and the use of the conjugated replica of the stored templates leads to an elimination of phase distortions introduced by the optical system. With such a configuration, the correlator is fully shift invariant in spite of the photorefractive crystal thickness and has good discrimination with sharp correlation peaks.     

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。     

利用色散补偿白光相关器及高通滤波技术检测粒子大小

本文提出了一种可用以检测相同形状粒子的大小、具色散补偿作用的白光相关系统,并完成了理论分析及实验验证.通过自动扫描光谱强度(位于固定点的相关峰的)分布,可方便地确定输入物的几何标度.本系统与高通滤波技术相结合,可检测圆环状粒子的大小,其相对误差的精度<2%.     

Correlator-aided alignment of phase key in encrypted holographic storage systems

An encrypted holographic scheme with a compact alignment system for a phase key is proposed. Alignment for a phase key is performed by a holographic correlator. A filter in the correlator system contains the phase information used for encryption. Thus, it can be used to check the authorization of the phase key. Owing to the shift-invariant property of the holographic correlator, the location of the correlation peak is highly related to the alignment of the phase key. Therefore, the phase key can be repositioned on the desired location by searching for the specific position of the correlation peak. With the help of the correlator, alignment of the phase key can be done in 1 min. Experimental results using a correlator system in support of our proposed idea are demonstrated as well.     

Fast Face-Recognition Optical Parallel Correlator Using High Accuracy Correlation Filter

We designed and fabricated a fully automatic fast face recognition optical parallel correlator [E. Watanabe and K. Kodate: Appl. Opt. 44 (2005) 5666] based on the VanderLugt principle. The implementation of an as-yet unattained ultra high-speed system was aided by reconfiguring the system to make it suitable for easier parallel processing, as well as by composing a higher accuracy correlation filter and high-speed ferroelectric liquid crystal-spatial light modulator (FLC-SLM). In running trial experiments using this system (dubbed FARCO), we succeeded in acquiring remarkably low error rates of 1.3% for false match rate (FMR) and 2.6% for false non-match rate (FNMR). Given the results of our experiments, the aim of this paper is to examine methods of designing correlation filters and arranging database image arrays for even faster parallel correlation, underlining the issues of calculation technique, quantization bit rate, pixel size and shift from optical axis. The correlation filter has proved its excellent performance and higher precision than classical correlation and joint transform correlator (JTC). Moreover, arrangement of multi-object reference images leads to 10-channel correlation signals, as sharply marked as those of a single channel. This experiment result demonstrates great potential for achieving the process speed of 10000 face/s.     

Apochromatic optical correlation

Optical correlation, or matched filtering, can now be applied more widely than before, because the light is now allowed to be totally incoherent, spatially and spectrally. Two such correlators were demonstrated recently. Their state of chromatic correction can be called achromatic, since the scaling error has two zero crossings within the visible range of wavelengths. We present a new apochromatic correlator, in which the scaling error has three zero crossings. The maximum error and the rms error are reduced by a factor of 5. Our apochromatic correlator is composed of two highly dispersive heavy flint lenses that are in contact with two diffractive lenses and two chromatic corrected refractive lenses. The uncommon combination of flint dispersion and diffractive dispersion enabled us to achieve apochromatic correction of the scaling factor of the correlator.     

一种用于相似图象识别的光电混合处理系统

针对以传统的光学相关为基础的图像识别难以识别相似图形的缺陷,提出并构建了解决这类问题的一种光电混合系统.该系统不仅结构简单,处理具有准实时的特点,而且实验结果表明这一系统对微小差异图形有很强的识别功能.     

Analysis and design of impulse attack free generalized joint transform correlator optical encryption scheme

We demonstrate in this paper that the generalized joint transform correlator (JTC) optical encryption method shows vulnerability to chosen-plaintext attacks. An unauthorized user, who has access to probe the encryption machine, can obtain the encryption keys with the help of the impulse function as chosen plaintext. The vulnerability of traditional joint transform correlator encryption is also analyzed in this paper. To prevent this attack, an enhanced angular multiplexing double-arm encryption solution is proposed. Cryptanalysis indicates that the improved scheme is robust to the chosen-plaintext attacks. Based on the analysis, a guideline for designing impulse attack free encryption system is discussed. Numerical simulation is also presented to show the validity of the proposed approach.     

基于联合变换相关器的Dempster-Shafer理论计算

提出了用联合变换相关器(JTC)来实现证据理论概率分配函数正交和的光学计算,在理论上对于如何用联合变像相关器实现证据理论分配函数正交和作了详细的讨论,并作了相应的仿真测试,结果显示该方法是可行的。与John Caulfield提出的用声光器件矢量外积实现的正交和计算相比,在该结构中由于采用二进制编码的数值计算,因此其计算精度得到了提高,同时对联合变换相关器输入端二进制编码的数值空间位置的适当调整可以直接得到所需要的证据理论正交和矢量,在处理步骤上得到了简化。     

Multitarget Detection Using a Hybrid Optical Joint Transform Correlator with Power Spectrum Subtraction

Multitarget detection using a hybrid optical joint transform correlator with power spectrum subtraction is proposed. This architecture is a programmable single spatial light modulator joint transform correlator. It consists of a liquid crystal display panel, an imaging lens, and a liquid crystal light valve to enhance resolution and space-bandwidth production. In this technique, it has two joint images in the input plane. In the second joint image, the reference image is contrast-reversal. With this technique, the second joint power spectrum is subtracted from the first joint power spectrum and the subtracted joint power spectrum is then taken the inverse Fourier transform. This technique is found to yield better correlation output performance than that of the classical joint transform correlator. Computer simulation results and the optical experimental results for input scene of the multitarget are given.The results have verified the correctness of the system design and performance analysis.     

新型平面集成光学相关器设计与分析

基于微光学与二元光学技术,设计了一种新型的平面折叠式光学相关器,将相关器中组成4f系统的傅里叶变换透镜、全息匹配滤波器、输入面和输出集成到一个平面器件上,与另一平面偏振反射镜构成一个反射型的平面光学系统.讨论了相关器的系统结构设计、系统参数的设计,给出了具体的设计模型,计算出其体积可减小至约12 cm3.利用菲涅耳衍射数值模拟方法对系统的图像识别过程进行了仿真,得到了良好的相关输出结果,证实平面集成光学相关器具有很好的识别性能.     

Multitarget Detection Using a Hybrid Optical Joint Transform Correlator with Power Spectrum Subtraction

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