基于功率谱分析的指纹实时识别系统

把实时获取指纹的装置与功率谱分析系统结合起来，实现完整的指纹实时识别系统．从实验上研究了相干光源和非相干光源获取指纹的两种情况．实验表明，用非相干光源获取指纹的情况具有较好识别效果．     

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。     

使用非晶态As_2S_3膜的接合变换实时光学相关器

使用非晶态As_2S_3膜作为接合变换光学处理器的非线性记录材料,实现两个相同透明图片之间的实时互相关.在接合变换处理器中使用氩离子激光器的4880(?)波长的光来记录参考物和检测物的傅里叶变换谱,记录的同时用氦-氖激光器的6328(?)波长的光读数.作者利用这种装置在输出平面上实时地观察到相同的透明指纹照片和相同的字符照片的互相关峰.     

利用联合付里叶变换谱干涉法测量透镜焦距

本文提出了采用联合付里叶变换频谱干涉法测量透镜焦距的方法。输入面上两个分布完全相同的图像经光学付里叶变换在频谱面上得到二者付里叶变换频谱的干涉条纹，通过测量干涉条纹的间距即可得到透镜的焦距。该方法装置简单、操作调整方便；易于采用实时空间光调制器、ＣＣＤ及微机实现快速自动测量，且具有较高的精度。文中进行了原理分析和实验验证。     

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     

基于数字全息技术的实时指纹识别

指纹识别技术是通过计算机来实现身份识别的一种手段,在生物识别技术中占有非常重要的地位。为了提高指纹识别系统的准确度和实时性,搭建了以光学器件傅里叶透镜和空间光调制为主的联合变换相关识别全息光学系统,记录相关图像的频谱,通过比较指纹图像的像素强度,从而实现实时指纹识别的目的。     

基于数字全息技术的实时指纹识别

指纹识别技术是通过计算机来实现身份识别的一种手段,在生物识别技术中占有非常重要的地位。为了提高指纹识别系统的准确度和实时性,搭建了以光学器件傅里叶透镜和空间光调制为主的联合变换相关识别全息光学系统,记录相关图像的频谱,通过比较指纹图像的像素强度,从而实现实时指纹识别的目的。     

实时光电混合联合变换相关器单元的实验研究

本文根据联合变换相关的原理，提出了一种实时光电混合联合变换相关器，它采用一个液晶光阀作为输入器件，用另一个液晶光阀记录和显示联合功率谱，所给出的实验结果证实了该系统设计及性能分析的正确性。     

利用液晶光阀实现二值化联合变换相关器的研究

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。     

旋转不变二值化联合变换相关识别方法

介绍一种基于二值化联合变换相关的综合鉴别函数算法，用等相关峰及Gram-schmidt展开获得的综合鉴别函数对迭代算法进一步优化，获得了适用于二值化联合变换相关的综合鉴别函数。采用这种算法制作的综合鉴别滤波器既有相关峰值高和相关峰尖锐等特点,又能识别旋转图像。计算机模拟结果表明：这种相关器在信噪比、光能效率、相关峰尖锐度和鉴别能力上都有一定程度地提高，实现了较高鉴别率旋转不变光学模式识别。     

Fingerprint identification by an optical joint transform correlation system

An optical correlator has been used in fingerprint identification, and in order to test its properties in a practical application a compact joint transform correlation system was constructed. The system’s identification performance was qualitatively and statistically evaluated, based on fingerprint data gathered from 500 fellow workers. The power of parallelism and fast processing of optical processing enabled the system to verify an individual’s identity in less than 0.1 s on each try. The system performed a verification with a 4.1% false rejection rate and no false acceptance in “three-try.”     

Optical image asymmetric cryptosystem using fingerprint based on iterative fraction Fourier transform

A novel asymmetric cryptosystem for optical image is proposed using fingerprint based on iterative fractional Fourier transform. To enhance the security, a hyperchaotic phase generated by a 4D Lorenz system is considered as the public key in the proposed encryption system, while the private key is emerged by the retrieved phase and fingerprint. In the encryption process, the secret information is hid into the hyperchaotic phase. Subsequently, the private key can be obtained by a reversible operation. To decrypt the original image, the ciphertext and private key are imported into the input plane of fractional Fourier system. This system is also applicable for information authentication because the fingerprint is used both in encryption and decryption approach. Some numerical simulations have been done to test the validity and capability of the encryption system.     

基于光学小波微分预处理的联合变换相关目标识别

提出了一种基于光学小波变换微分预处理的光电混合联合变换相关系统,该系统利用同一光路可实时实现对输入图象的小波变换微分预处理和联合变换相关识别.实验结果表明:该系统能得到很尖锐的互相关峰,可显著提高联合变换相关器的识别能力.     

Optics based biometric encryption using log polar transform

We propose an optics based biometric encryption technique using log polar transform. In this method, the key of the encryption process has been linked to the fingerprint of the enrolled person. The order of fractional Fourier transform and the seed values of the chaotic random phase masks in combination act as the key for the encryption process. In order to link the combined key to the fingerprint, a lookup table has been formed by the key and the log polar transform of the fingerprint. The linking algorithm not only encrypts the image of the enrolled person but also authenticates the input image. The main advantage of this method is its capability to retrieve the same key in the decryption process by using the live fingerprint. The key is not required to be communicated to the receiver side. The retrieval of the image is possible only when the live fingerprint of the enrolled person is presented at the decryption side. The real life fingerprints have been used to demonstrate the proposed technique. Simulations have been performed on the Matlab platform to validate the proposed technique. The signal to noise ratio and mean square error has been calculated in order to support the proposed technique. The effect of the rotation and the scaling of the fingerprints have been studied to check the key retrieval from the live fingerprint of the enrolled person. The study of the different whorl types of fingerprint of different persons has also been done to check the efficacy of the key retrieval from the whorl types of the live fingerprints of different person.     

空变菲涅耳联合变换相关器

提出了菲涅耳联合变换相关器(Fresnel Joint Transform Correlator,FnJTC)结构,给出了数学推导过程,并通过计算机模拟验证了可行性及其与传统相关器所不同的相关特性。在相关过程第一阶段中,菲涅耳联合变换相关器对输入的联合图像作菲涅耳变换,代替了传统联合变换相关器(JTC)的傅里叶变换。与传统相关器相比,菲涅耳联合变换相关器是空变系统,相关峰值依赖于输入参考图像与目标图像的相似性、两图像之间的相对位置及参考图像(或目标图像)的线性相位调制。     

Study on the Performance of the nonlinear Joint Transform Correlator

l.IntroductionJointtransformcorrelation[1]hasbeeninvestigatedwidelyinrecentyears[2~4]be-causeitsreferenceimagesandobjectimagescanbeuPdatedinreal-time[5J.Nonlinearjointtransformcorre1ationtheoretica1ana1ysis[']showsthatcomparedwiththelinearjointtransformcorrelation,non1inearjointtransformcorrelationcanproducemorehighautcacorre1ationPeakintensity,andthelargerPeaktosideloberatiothataregoodforelectronicdevicestodetectandana]yze.Onthebasisofthemodu1ationprincipleana1ysisoftheliq-uidcrysta11ightva…     

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.     

基于Harris角点检测器的指纹细节点提取算法

提出了一种基于Harris角点检测器的指纹细节点提取算法。先将Harris角点检测器应用于增强后的指纹图像,检测出指纹的细节点和曲率变化大的点,随后进行后处理操作。在后处理操作中,根据细节点的空间分布特征,删除虚假点。使用细节点的邻域灰度信息,判定细节点的类型。利用细节点的原始方向以及得到的类型,确定细节点的精确方向。与经典的细节点提取算法相比,不需要对指纹图像进行二值化、细化,直接在灰度指纹图像当中提取细节点,大大减少了计算时间,有效地提高了效率。使用FVC2002指纹数据库测试,结果表明,该算法可靠、快速,适合实际应用。     

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

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