共查询到20条相似文献,搜索用时 31 毫秒
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A conventional joint transform correlator (JTC) often generates large correlation sidelobes as well as a large correlation peak width, strong zero-order peak, and low diffraction efficiency in target detection and recognition, which make the detection ability of JTC lower. To conquer these difficulties, firstly, a joint power spectrum (JPS) subtraction technique was proposed in Fourier plane, where power spectrum of reference image and power spectrum of object image are subtracted from the JPS before inverse Fourier-transform operation, it is evident that the improved JPS removes the zero-order term. Secondly, a fringe-adjusted filter (FAF) was presented to restrain sidelobes and noises. The revised JPS is multiplied by a FAF before the inverse Fourier-transform operation to obtain the cross-correlation peak. Computer simulations showed the improved method can markedly eliminate zero-order diffraction and effectively control the sidelobes and noises compared to traditional JTC, and then enhance the detection ability for JTC. Experimental results presented the sharp correlation peak and also demonstrated this approach effectiveness. 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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In order to utilize the space of an input plane efficiently and make the optical structure more flexible, an image displacement measurement based on phase-encoded reference joint fractional transform correlator (PER-JFrTC) is proposed. We use a random phase mask to encode the reference image and overlay it with the target image forming the input image. Joint power spectrum (JPS) of the input image is obtained by Fourier transform and the resultant is encoded by the same phase mask. Then a fractional Fourier transform with an order p is applied to the phase-encoded JPS (PJPS), resulting in a correlation output with a sharp cross-correlation peak, which includes the displacement information between the reference and the target image. Contrast to displacement measurement based on traditional joint transform correlator (JTC), PER-JFrTC can use the space of the input plane efficiently and reduces the influence of the auto-correlation. Also the position of cross-correlation peak can be fixed arbitrarily according to the fractional order p as well as the optical set-up can be more flexible and easier to implement. Results based on digital computation show that PER-JFrTC could detect the displacement accurately and verify our proposal. A possible optical set-up is suggested. 相似文献
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Leonid I. Muravsky Olexander P. Maksymenko Olexander M. Sakharuk 《Optics Communications》2004,240(4-6):275-291
The optical speckle–displacement correlation technique (OSDCT) is proposed for study of in-plane speckle displacements. The joint transform correlator architecture is used to evaluate the displacements of speckle subimages of strained surfaces. The procedure of the correlation response producing as a result of cross-correlation of strainless and strained surfaces in a conventional joint transform correlator (JTC) is considered. The convenient techniques for a joint power spectrum transformation are selected. The systematic and random errors of a mean speckle pattern displacement of a rigid body motion calculated by using the OSDCT and the digital speckle–displacement measurement technique are compared. The robustness of some JTC versions (a conventional JTC, a JTC with median thresholding, a JTC with subset median thresholding, and a fringe adjusted filter JTC) to input noise of speckle patterns and output noise of a correlation response is studied. 相似文献
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Optical correlators have been widely used for such applications as automatic target identification, invariant pattern recognition and machine vision. In hybrid optical correlators, Spatial light modulators (SLMs) are used to dynamically update the input and the filter. However, implementation is difficult because of the interference of “ghost” images; rigorous requirements for filter registration, accurate and effective filter sizing and complex valued filtering functions. This paper proposes some practical approaches to handle these issues and provides engineering details of how to build a hybrid optical correlator, where a SLM serves as an updateable intensity filter for real-time pattern recognition. 相似文献
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A new method for rotation and brightness invariant pattern recognition was proposed by applying multiple circular harmonic expansions to the joint transform correlator. The amplitudes of the multiple orders of circular harmonic expansions made from a detecting image were synthetically modified to respond to the same auto-correlation peaks. These modified circular harmonic expansions were arranged in the input plane as reference patterns together with an arbitrary target pattern, and the correlation signals between them were calculated in the subtracted joint transform correlator. The fraction of the correlation-peak intensities between the target and the references were extracted as a new discrimination parameter. This new parameter performs pattern recognition under rotation and brightness invariance with good discriminability. Its high discriminability has been proved in computer simulations using the face image patterns of many individuals. 相似文献
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HUANG Xiaojing 《Chinese Journal of Lasers》1999,8(1):49-54
1IntroductionForrotationinvariantpaternrecognition,thespatialmatchedcorelatorisoftenusedbytakingacircularharmoniccomponent(CH... 相似文献
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对联合变换相关器的功率谱进行对数变换可强化其高频分量,锐化相关峰,但同时也会增强其噪声成分,影响抗噪性能。针对这一问题,提出了一种改进的对数联合变换相关器模型。通过改变对数函数形式来提高对数联合变换相关器的抗噪能力。计算机仿真结果表明,在附加高斯白噪声、非重叠低频和高频有色噪声的条件下,改进的对数联合变换相关器的抗噪能力均优于传统的对数联合变换相关器。 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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修正振幅调制的光电混合圆谐联合变换相关器作旋转不变的目标检测 总被引:1,自引:0,他引:1
提出一种修正振幅调制的光电混合圆谐联合变换相关器作旋转不变的目标检测的实验系统。参考图像(即圆谐展开分量的实部和虚部)、圆盘状的局部偏置函数以及目标图像同时显示于输入面。此方法对联合功率谱作了修正,先将联合功率谱减去纯输入景物(含局部偏置函数)的功率谱和参考图像(含局部偏置函数)的功率谱,再加上局部偏置函数的功率谱,然后将所得修正的联合功率谱乘以振幅调制滤波函数。这种方法能产生比普通的圆谐联合变换 相似文献
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为增强联合变换相关器输入面图像去噪和边缘检测的可调节性,改善相关器的识别效果,将形态学算法引入输入面图像去噪和边缘检测,提出利用形态学边缘检测的宽度可调节性来改善联合变换相关器的识别效果。计算机模拟表明,改进后的算法是有效的。 相似文献
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l.IntroductionAVanderLugtcomp1exlnatchingspatialcorreIator[1jandajointtransformcorrela-tor[z~ejaret``omaJorkindsofcorrelators,however,theyaresensitivetoscalingandro-tationvariance.Thisdisadvantageisaseverelimitationforthemtobeusedinpracticalapplications-Invariantprocessingwiththeclassicalopticalcorre1atorwithproPertiesotherthanPOsitiondemandsthatthepropertyisrepresentedasashift.WithaIog-POlarmafrping[="j,thesizeandorientationw'il1beexpressedasshiftparameters,orratherrotationascyc1icshift.… 相似文献
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联合变换相关器形态学处理可调节性研究 总被引:8,自引:7,他引:1
为改善联合变换相关器的实际识别效果,将形态学算法引入输入面图象边缘检测,提出利用形态学边缘检测的宽度可调节性来改善联合变换相关器的实际识别效果,实验表明,改进后的算法使相关器既有足够的光强,又有较高的鉴别率. 相似文献
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We propose a Fourier-plane encryption technique based on a joint transform correlator (JTC). The technique is based on removing
the effect of phase terms in JTC and the auto-correlation terms contribute to reconstructing the original image. Computer
simulations and optical experiments show the proposed method is very useful for JTC architecture. 相似文献
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光学相关识别是图像识别的重要方法,有效识别相关器输出平面的相关峰信号是保证光学相关器图像识别准确性的关键。由于激光器输出功率的波动、光学系统本身的误差以及SLM器件本身带来的噪声,采用一般的阈值方法很难达到理想的效果。该文提出对相关器的输出平面进行预处理,充分考虑相关信号的形状信息,提取感兴趣区域(ROI),采用BP神经网络对输入矢量进行计算,可达到对相关峰信号和噪声的有效分类识别,从而提高了光学相关器识别的可靠性,降低了误判的概率。 相似文献
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A new optical security system is proposed using a shifted phase-encoded joint transform correlation (JTC) architecture. In the proposed technique, at first, the address code is fed into two channels where one channel is shifted by 180°. The output signals from both the channels are phase-masked and then added with the input image to be encrypted. The joint power spectrum (JPS) obtained from one channel is subtracted from the JPS of the other channel, and the modified JPS is inverse Fourier transformed to yield the encrypted image. For decryption, the received signal is Fourier transformed and multiplied by the phase mask and the address code, which is then inverse Fourier transformed to generate the output signal. The proposed technique does not require complex conjugate of the address code otherwise required in the classical double random phase encryption. Also the decryption result is much more enhanced when compared to the output generated by alternate JTC techniques. Computer simulation results verify that the encryption and decryption are very much secure and efficient in both noise-free and noisy conditions. 相似文献