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利用液晶光阀实现二值化联合变换相关器的研究 总被引:4,自引:0,他引:4
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。 相似文献
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光电混合实时指纹识别新方法 总被引:6,自引:0,他引:6
在实验上建立了一套基于联合变换相关的1f光电混合实时指纹识别系统,用棱镜和CCD摄像机结合实现指纹的实时采集,提出了用二次微分边缘提取算法对指纹进行预处理,用监视器上亮度和对比度调节来实现联合变换功率谱的视觉二值化。 相似文献
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Leonid I. Muravsky Olexander M. Sakharuk Nazar V. Fityo Pavel V. Yezhov 《Optics and Lasers in Engineering》2007,45(10):993-1000
The optical speckle-displacement correlation (OSDC) technique was developed to increase the reliability of surface displacement field recovery near stress concentrators. The performance of optical speckle correlators based on joint transform correlator (JTC) architecture and a joint power spectrum (JPS) nonlinear filtering (median thresholding, adaptive median thresholding, ring median thresholding) is studied by using computer models of these correlators. The design of hybrid joint transform speckle correlator is detailed. Example results of correlation signal using computer models of digital speckle correlation and OSDC techniques and created hybrid joint transform speckle correlator setup are described. 相似文献
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傅里叶-梅林变换(FMT)在畸变-不变图像识别中的应用 总被引:1,自引:0,他引:1
针对尺度缩放和角度旋转变化目标相关识别率低的问题,在联合相关识别中加入傅里叶-梅林变换方法.采用傅里叶-梅林变换(FMT)中的对数极坐标变换、梅林变换、傅里叶变换具有的旋转、尺度、平移(RST)不变性,可以提高JTC图像识别的性能,实现畸变-不变图像的识别.利用联合变换相关器对角度旋转0°~40°、尺度变化0~20%的目标进行计算机仿真实验.实验结果表明:在JTC中采用FMT可以实现畸变-不变图像的识别. 相似文献
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基于联合子波变换的目标轮廓抽取技术 总被引:1,自引:1,他引:0
子波变换是目标特征抽取的有效方法。本文把联合变换相关技术与子波变换结合起来,建立了一套新的子波变换光学实验系统。推导了联合子波变换的基本理论,并给出了联合子波换相关器在目标特征抽取应用中的实验结果。 相似文献
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Images of a target in a specific spectral band in general show no correlation with images of the same target in a different spectral band. Hence in a joint transform correlator (JTC) architecture, if the reference and input target are the images captured through a visible (e.g., charge-coupled device or CCD camera) and infrared (IR) detector, autocorrelation peaks are not obtained. This drawback has been overcome in this paper by the use of a CCD–IR fused image as the reference image. Daubechies wavelet transform, which produces the least root-mean-square (RMS) error in the fusion process in comparison to other wavelets, has been used for the purpose. A comparative analysis of the proposed idea has been carried out for the classical JTC (CJTC), binary JTC (BJTC) and differential binary JTC (DBJTC) algorithms. Since the DBJTC removes the dc completely and produces sharp correlation peaks compared to the other techniques, computer simulation and experimental results are shown for the proposed idea using DBJTC. The same fused reference image has also been used to identify multiple targets in a scene using DBJTC. Performance measures like correlation peak intensity (CPI), dc/ac and peak correlation energy (PCE) have been calculated as metrics of goodness for the proposed scheme. 相似文献
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Based on the conventional correlation and fractional correlation, the extended fractional correlation (EFC) is presented. And based on the configuration of the nonconventional joint transform correlator, we propose the joint extended fractional Fourier transform correlator (JEFRTC). The properties of the extended fractional cross correlation peak (EFCCP) in theory are analyzed. A sound conclusion is drawn that the width of EFCCP is narrower than that of fractional correlation peak under some conditions. This JEFRTC can permit lower precision of the systemic parameters when implemented with optical configuration. That will improve correlator’s character discriminability. 相似文献
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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. 相似文献
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1IntroductionFormultitargetdetection,thejointtransformcorelator(JTC)isanextremelyusefularchitecture[1].HowevertheclasicalJTCp... 相似文献
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Wavelet-modified fringe-adjusted joint transform correlator 总被引:1,自引:1,他引:0
Alpana Bhagatji Naveen K. Nishchal Arun K. Gupta B.P. Tyagi 《Optics & Laser Technology》2008,40(1):99-112
In this paper, we implement a wavelet-modified fringe-adjusted joint transform correlator (JTC) for real-time target recognition applications. In real-time situation the input scene is captured using a charge-coupled device (CCD) camera. The obtained joint power spectrum is multiplied by a pre-synthesized fringe-adjusted filter and the resultant function is processed with an appropriately scaled wavelet filter. Three performance measure parameters: correlation peak intensity, peak-to-sidelobe ratio, and signal-to-clutter ratio have been calculated for fringe-adjusted joint transform correlator (FJTC) and wavelet-modified fringe-adjusted joint transform correlator (WFJTC). The WFJTC has been found to yield better results in comparison to conventional FJTC. To suppress the undesired strong dc, the resultant function is differentiated. Differential processing wavelet-modified fringe-adjusted joint power spectrum removes the zero-order spectra and hence improves the detection efficiency. To focus the correlation terms in different planes in order to capture one of the desired autocorrelation peaks and discard the strong dc and another autocorrelation peak, chirp-encoding technique has also been applied. Targets with Gaussian and speckle noise have also been used to check the correlation outputs. Computer simulation and experimental results are presented. 相似文献
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联合功率谱的高频成份对相关峰识别具有重要作用,实验中记录的联合功率谱随着频率的增加其强度迅速降低。为增强联合功率谱的高频成分,改善其调制程度,可对功率谱进行对数变换,从而有效保留更多的高频成份,压低零级衍射光斑,提高联合变换相关器的识别能力。 相似文献
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The joint transform correlator (JTC) is one of the two main optical image processing architecture which provides a highly effective way of comparing images in a wide range of applications. Traditionally, an optical correlator is used to compare an unknown input scene with a pre-captured reference image library, to detect if the reference occurs within the input. Strength of the correlation signal decreases rapidly as the input object rotates or varies in scale relative to the reference object. The aim of this paper is to overcome the intolerance of the JTC to rotation and scale changes in the target image. Many JTC systems are constructed with the use of ferroelectric liquid crystal (FLC) spatial light modulators (SLMs) as they provide fast two-dimensional binary modulation of coherent light. Due to the binary nature of the FLC SLMs used in the JTC systems, any image addressed to the device need to have some form of thresholding. Carefully thresholding the grey scale input plane and the joint power spectrum (JPS) has significant effect on the quality of correlation peaks and zero order (DC) noise. A new thresholding technique to binarise the JPS has been developed and implemented optically. This algorithm selectively enhances the desirable fringes in the JPS which provide correlation peaks of higher intensity. Zero order noise is further reduced when compared to existing thresholding techniques.Keeping in mind the architecture of the JTC and limitations of FLC SLMs, a new technique to design rotation and scale invariant binary phase only filters for the JTC architecture is presented. Filers design with this technique have limited dynamic range, higher discriminability among target and non-target objects, and convenience for implementation on FLC SLMs. Simulation and experiments shows excellent results of various rotation and scale invariant filters designed with this technique. A rotation invariant filter is needed for various machine vision applications of the JTC. By fixing the distance between camera and input object, the scale sensitivity of the correlator can be avoided. In contrast to the industrial machine vision applications, scale factor is very important factor for the applications of the JTC systems in defence and security. A security system using a scale invariant JTC will be able to detect a target object well in advance and will provide more time to take a decision. 相似文献
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实时高效联合变换相关器 总被引:13,自引:0,他引:13
提出一种利用光学波分复用器实现实时高效联合变换相关的方案。通过计算机控制把输入面分为多个大小相等的窗口,分别写入参考与目标图像,利用光学波分复用器于相关系统中,使对应不同窗口的读出光学信息在第一个焦面上形成联合功率谱阵列,在输出面上可以实时地获得增强了相关信号。 相似文献