灰度人脸识别形态学相关的一般理论研究

提出一般形态学相关概念,并提出一种小型联合变换相关器的硬件设计以实现一般形态学相关.提出两种改进的一般形态学相关算法,灰度图像按某种分解方法分解成一系列二值图像片.在第一种算法中,每片二值联合图像片的边缘被检测,其功率谱求和.在第二种算法中,一种情况是每片的联合变换功率谱被二值化或细化再求和;另一种情况是这些片的联合变换功率谱的总和被二值化或细化.计算机模拟结果表明,改进后的算法能改善高相似度灰度人脸图像识别的鉴别率.     

改进形态学相关算法以识别高相似度灰度图像

从形态学角度定义了灰度联合图像相似度，提出两种基于位表示法形态学相关算法的改进算法，通过提取位表示法的图像片边缘特征或二元化位表示法的图像片功率谱，以提高位表示法形态学相关算法对高相似度灰度图像的识别能力。     

联合变换相关器形态学处理可调节性研究

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.     

Implementation of an algorithm for detecting patterns in defocused scenes using binary joint transform correlation

An original method to detect images in defocused scenes by means of a binary joint transform correlation is presented. Defocused images are described in frequency domain as the product between the Fourier transform of the in-focus scene by the optical transfer function of the imaging lens. This function, which presents positive and negative values, introduces sign errors in the joint power spectrum. The goal of this study is to detect the sign of the optical transfer function starting from the defocused image by means of a digital algorithm. Information provided by the algorithm allows to compensate the sign errors in the binary joint power spectrum and to obtain invariant correlations with respect to defocusing. Theoretical analysis and digital experiments to test the procedure are provided.     

基于双二次微分的联合变换相关识别

提出一种提高联合相关识别的有效方法，该方法通过对识别图像和联合变换功率谱分别进行二次微分，抽取识别图像的特征信息，增强联合变换功率谱中调制条纹的对比度和调制条纹的结构，有效地提高了联合变换相关器的相关输出；在此基础上，构造了基于双二次微分的１ｆ实时光电联合相关识别系统，实验结果表明：该方法较二元联合变换相关，提高了图像相关识别能力     

高通滤波的二元联合变换相关器

提出一种新的采用高通滤波的二元联合变换相关器，这种相关器与一般的二元联合变换相关器的差别在于联合功率谱作二元处理之前先进高通滤波，使用这种技术，可以产生比二元联合变换相关器更好地相关输出性能，给出对含有灰度级场体的输入景物的计算机模拟结果。     

基于灰度空间相关性的双谱微光图像融合方法

图像的灰度空间相关性可以反映图像的清晰度，而图像融合的主要目的之一就是改善图像的清晰度.根据微光全波图像和微光短波图像的光谱特点，在分析微光全波图像和微光短波图像的一维灰度直方图及二维灰度空间相关性图的基础上，提出了一种新型的基于灰度空间相关性的图像融合方法.该融合方法由基于标准偏差的灰度调制和灰度统计平衡两部分实现，同灰度调制融合法及谱域融合法比较，此方法能够有效地改善图像的清晰度，同时便于硬件实现.文中详细阐述了该融合方法的理论公式，并分析了其在不同场景时的实验结果. 关键词： 图像融合 微光全波图像 微光短波图像 灰度空间相关性     

Evaluation of a suitable threshold for binarization of power spectrum in a noise-free joint transform correlator

An analysis by digital simulation of the influence of the threshold level on the binary power spectrum of a joint transform correlator has been carried out. The correlation results are studied where binarized intensity takes the values [0, 1] and [-1, 1]. The influence of threshold level on the efficiency and discrimination are analyzed. The results obtained allow us to propose an appropriate level of binarization for noise-free scenes.     

基于输入面形态学处理的联合变换相关器研究

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。     

多目标识别的联合变换相关器的研究

提出了一种可用于多目标识别的联合变换相关器。为改善相关信号的性能,对功率谱作了优化处理。为消除相关面上的零级项和目标间的相关项,可用联合功率谱减去纯目标输入的功率谱和参考图像的功率谱;为增强和锐化相关峰,将相减的功率谱作指数函数滤波处理。分析了指数滤波参数对相关结果的影响。计算机模拟结果表明,这种相关器所输出的相关信号比经典联合变换相关器和二元联合变换相关器输出的相关信号更好,互相关得到了抑制,自相关得到了增强,具有很好的抗噪能力。     

Interlacing multiplexing techniques for optical morphological correlation

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.     

二值化联合变换相关器的最佳阈值

从实验和计算机模拟两方面讨论二值化联合变换相关器的最佳阈值选取原则.实验研究表明,不同阈值对二值化联合变换相关结果有着较大影响,阈值过高或过低都会使联合变换相关结果变差.也就是说,二值化联合变换相关器存在一个最佳阈值.计算机模拟结果表明,最佳阈值位于联合变换功率谱的平均灰度值附近.在该阈值下,二值化联合变换相关器输出的相关峰值将相对提高,半宽度减小,同时噪音得到抑制.     

使用振幅调制和功率谱相减的联合变换相关器作多目标检测

提出一种使用振幅调制和功率谱相减的联合变换相关器作多目标检测，这一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的功率谱和参考图象的功率谱，再将所得修正的联合功率谱乘以振幅调制滤波函数。分析和量化了输入景物噪声对联合变换相关器性能的影响。这种方法比条纹调节的联合变换相关器和修正的条纹调节的联合变换相关器能产生更好的相关输出和适应输入景物噪声的能力。     

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

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     

Improved approach for target detection and recognition on optoelectronic hybrid joint transform correlator

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.     

Binary phase only filters for rotation and scale invariant pattern recognition with the joint transform correlator

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.     

改进Canny算法的红外人脸图像边缘轮廓提取

红外人脸图像的边缘轮廓特征对于红外人脸检测、识别等相关应用具有重要价值。针对红外人脸图像边缘轮廓提取时存在伪边缘的问题,提出了一种改进Canny算法的红外人脸图像边缘轮廓提取方法。首先通过对引导滤波算法引入“动态阈值约束因子”替换原始算法中的高斯滤波,解决了原始算法滤波处理不均匀和造成红外人脸图像弱边缘特征丢失的弊端;接着对原始算法的非极大值抑制进行了改进,在原始计算梯度方向的基础上又增加了4个梯度方向,使得非极大值抑制的插值较原始算法更加精细;最后改进OTSU(大津)算法,构造灰度-梯度映射函数确定最佳阈值,解决了原始算法人为经验确定阈值的局限性。实验结果表明:提出的改进Canny算法的红外人脸轮廓提取方法滤波后的图像,相较于原始Canny算法滤波处理,信噪比性能提升了34.40%,结构相似度性能提升了21.66%;最终的红外人脸边缘轮廓提取实验的优质系数值高于对比实验的其他方法,证明改进后的算法对于红外人脸图像边缘轮廓提取具有优越性。     

Modified nonlinear morphological correlation using Laplace filtering

A Laplace filtering based morphological correlation (LBMC) is proposed as a modified approach to improve the properties of the classical morphological correlation (MC). For the LBMC, power spectrum of Laplace operator is introduced to filter the joint power spectrum (JPS) of the MC before final inverse Fourier transform. Computer simulation results show that, as compared with the linear correlation (LC) and the conventional MC, LBMC provides better discrimination capability with sharp and unmistakable correlation signal and its performance metrics are more stable when input scene is corrupted by outlier noise (salt-and-pepper noise) and additive white Gaussian noise. Although the LBMC is not illumination invariant when multiplication illumination factor is larger than unity, considerable discrimination capability is still obtained.     

用于指纹识别的基于离散余弦变换的二值化联合变换相关器

提出了一种利用离散斜弦变换对联合功率谱进行处理的二值化联合变换相关算法,利用这种二值联合变换相关器,进行了一个待识别指纹同四个参考指纹的比较,这种相关器同采用局部中值阈值技术的二值化联合变换相关器相比,能提高输出峰边比,提高相关峰的强度。光电混合处理实验的结果表明,这种方法能大大提高多指纹识别系统的识别性能。     

Optical security system employing shifted phase-encoded joint transform correlation

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.