共查询到20条相似文献,搜索用时 187 毫秒
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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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A displacement measurement technology based on joint fractional Fourier transform is firstly proposed. Contrast to conventional displacement measurement based on joint Fourier transform correlator, the position of cross correlation peak in the proposed technology could be fixed arbitrarily according to the order of fractional Fourier transform. The optical setup in the proposed technology is more flexible and easier to implement. Simulation and experiment results are given out to verify the analysis. 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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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. 相似文献
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We propose a novel approach to implement nonlinear morphological correlation. Previous implementation was based on a time sequential approach that consists on displaying different binary image decomposition in a joint transform correlator adding each joint power spectra sequentially. A second Fourier transformation of the sum of joint power spectra gives the correlation output. In this paper, we propose to interlace the different binary images into one single distribution. Then, we introduce the distribution in a conventional joint transform correlator. The correlation output gives the morphological correlation at a specific location. The advantage is important considering that no sequential approach is needed anymore, so the necessary number of correlations is reduced. Optical implementation results are provided. 相似文献
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1IntroductionFormultitargetdetection,thejointtransformcorelator(JTC)isanextremelyusefularchitecture[1].HowevertheclasicalJTCp... 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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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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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. 相似文献
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A new system of multi-channel single-output joint fractional Fourier transform correlator (JFRTC) for color pattern recognition is proposed based on the conventional system of multi-channel single-output joint transform correlator (JTC). The theoretical analysis and optical experiments are performed. With this method, one can obtain three correlation peaks at the output plane which show a pair of desired cross-correlation peaks and one auto-correlation peak. In comparison, the conventional system leads to more correlation peaks playing a noise role in color pattern recognition. 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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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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A conjugate image plane correlator with holographic disk memory is proposed. Optical correlation between conjugate images reconstructed from a holographic disk and an input image on liquid-crystal television is executed with the rotation of the disk. Regardless of Fourier hologram recording with the pseudorandom diffuser, it is found possible to take out the diffuser from the original hologram recording scheme using an image reconstruction process and to get correlation signals between input and reconstructed conjugate images in the output plane of a two-lens imaging system. Generation of conjugate replicas with high contrast causes exact matching with an input image which results in high recognition performance for autocorrelation signals. The transfer function of an optical system can be controlled by adjustment of either hologram size or hologram area illuminated with a laser beam. Hence, the output intensity distribution can be adjusted by selecting a proper pupil function and the size of an output pupil defined by the input pupil size and the optical system magnification factor. The real-time character recognition by optical parallel high-speed processing for two dimensional images with position normalization is demonstrated. 相似文献
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光学相关器在自动目标识别中的应用 总被引:2,自引:2,他引:0
为使光学相关器更好地应用于自动目标识别领域,保证在较高识别速度下,具备良好的识别效果,介绍了应用于自动目标识别领域的联合变换相关器和匹配滤波相关器.针对匹配滤波相关器实现过程中的两项关键技术,在滤波器编码技术上提出了构造等相关峰综合鉴别函数以解决畸变不变识别问题.在相关峰识别技术上,针对阈值法存在的不足,提出利用BP神经网络对相关平面相关峰进行识别,采用划分感兴趣区域的方法减少了输入层神经元数目,简化了神经网络结构.借助搭建的光学相关器系统验证了该方法可对相关信号和噪声进行有效分类,提高了光学相关器的识别效果. 相似文献
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A scaling correlator optical pattern recognition system is described in which a lensless matched spatial filter (with the second Fourier transform lens and the matched spatial filter recorded on the same plate) is used with a first Fourier transform lens that is also an holographic optical element. The matched spatial filter is recorded at one wavelength and correlation is obtained at a second wavelength. Experimental demonstration and output correlation SNR data are reported, together with a comparison of the system's noise level using conventional optics and holographic elements. 相似文献
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A prototype real-time Chinese character recognition processor, which utilizes the Vander Lugt type complex spatial filter is presented. A real-time correlation operation is performed with a photoconductor-liquid crystal device as an incoherent-to-coherent image converter. Bandpass Fourier transform images passing through a bandpass spatial filter are sequentially recorded on a rotating hologram recording plate as stored reference patterns. It makes possible holding the stable discrimination for noisy unknown input patterns and storing a huge number of reference patterns. The typewritten Chinese characters in practice are experimentally discriminated from very similar ones in the real-time optical correlator. This indicates the possibility of more than 2000 printed Chinese character recognition with the optical correlation. 相似文献