Degradation of linear filter performance due to modeling error

Differential equations for determining the dynamic and steady-state effects of a particular class of disturbances on the error in the estimate of the state vector of a stochastic linear dynamic system are obtained. For the problem of evaluating near optimal filter performance, the technique permits the performance degradation due to the deletion of certain state vector components in the design of a Kalman filter to be obtained.     

虹膜识别综述

回顾了虹膜识别的研究背景及发展,对近年来虹膜识别方法的研究进展进行综述,并对各种方法加以介绍和评价,总结了存在的研究难点并提出了解决方法及今后的发展方向。     

Toward accurate localization and high recognition performance for noisy iris images

Iris recognition plays an important role in biometrics. Until now, many scholars have made different efforts in this field. However, the recognition performances of most proposed methods degrade dramatically when the image contains some noise, which inevitably occurs during image acquisition such as reflection spots, inconsistent illumination, eyelid, eyelash, hair, etc. In this paper, an accurate iris localization and high recognition performance approach for noisy iris images is presented. After filling the reflection spots using the inpainting method which is based on Navier-Stokes (NS) equations, the Probable boundary (Pb) edge detection operator is used to detect pupil edge initially, which can eliminate the interference of inconsistent illumination, eyelid, eyelash and hair. Besides, the accurate circle parameters are obtained in delicately to reduce the input space of Hough transforms. The iris feature code is constructed based on 1D Log-Gabor filter. Our thorough experimental results on the challenging iris image database CASIA-Iris-Thousand achieve an EER of 1.8272 %, which outperforms the state-of-the-art methods.     

Efficient and robust segmentation of noisy iris images for non-cooperative iris recognition

This paper describes the winning algorithm we submitted to the recent NICE.I iris recognition contest. Efficient and robust segmentation of noisy iris images is one of the bottlenecks for non-cooperative iris recognition. To address this problem, a novel iris segmentation algorithm is proposed in this paper. After reflection removal, a clustering based coarse iris localization scheme is first performed to extract a rough position of the iris, as well as to identify non-iris regions such as eyelashes and eyebrows. A novel integrodifferential constellation is then constructed for the localization of pupillary and limbic boundaries, which not only accelerates the traditional integrodifferential operator but also enhances its global convergence. After that, a curvature model and a prediction model are learned to deal with eyelids and eyelashes, respectively. Extensive experiments on the challenging UBIRIS iris image databases demonstrate that encouraging accuracy is achieved by the proposed algorithm which is ranked the best performing algorithm in the recent open contest on iris recognition (the Noisy Iris Challenge Evaluation, NICE.I).     

Selection of parameters in iris recognition system

This paper presents the detailed analysis of implementation issues occurred during preparation of the novel iris recognition system. First, we shortly describe the currently available acquisition systems and databases of iris images, which were used for our tests. Next, we concentrate on the feature extraction and coding with the execution time analysis. Results of the average execution time of loading the image, segmentation, normalization, and feature encoding, are presented. Finally, DET plots illustrate the recognition accuracy for IrisBath database.     

An eye detection method robust to eyeglasses for mobile iris recognition

Finding the accurate position of an eye is crucial for mobile iris recognition system in order to extract the iris region quickly and correctly. Unfortunately, this is very difficult to accomplish when a person is wearing eyeglasses because of the interference from the eyeglasses. This paper proposes an eye detection method that is robust to eyeglass interference in mobile environment. The proposed method comprises two stages: eye candidate generation and eye validation. In the eye candidate generation stage, multi-scale window masks consisting of 2 × 3 subblocks are used to generate all image blocks possibly containing an eye image. In the ensuing eye validation stage, two methods are employed to determine which blocks actually contain true eye images and locate their precise positions as well: the first method searches for the glint of an NIR illuminator on the pupil region. If this first method fails, the next method computes the intensity difference between the assumed pupil and its surrounding region using multi-scale 3 × 3 window masks. Experimental results show that the proposed method detects the eye position more accurately and quickly than competing methods in the presence of interference from eyeglass frames.     

小波包分解在虹膜识别中的应用研究

小波包分解是从小波变换延伸而来的一种更精细的信号分析算法，具有分析高频特征信息的优势。文中结合小波包分解的特点，提出了一种基于小波包分解的虹膜识别算法。该算法首先对虹膜图像实行分窗小波包分解，并对各窗口的子带图像作筛选处理；然后通过奇异值分解对筛选后的各子带图像作进一步的特征提取和压缩，得到虹膜识别特征；最后利用加权欧氏距离分类器进行识别。实验结果表明了该算法的有效性。     

基于PKI机制下的虹膜识别应用

在虹膜识别系统的实际应用中,只靠传统的虹膜识别算法不具有理想中的可靠性,同时基于PKI的安全通信机制,也不能保证密钥保存的安全性。结合虹膜识别与加密算法提出一种可靠的应用方式。基于左、右眼虹膜编码各产生一个1024位素数,进行数字签名、可靠性通信等应用,较好地解决了虹膜识别的可靠性和密钥保存的安全性问题。     

基于非线性降维的虹膜识别方法

在虹膜识别的研究和应用领域,虹膜特征提取是虹膜识别中的核心技术,传统的特征提取算法都为滤波的方法,实现过程计算较为复杂.为了解决虹膜特征提取中计算复杂的问题,应用非线性降维Laplacian Eigenmap算法实现人眼虹膜图像的特征提取,降维问题就是寻找从高维空间到低维空间的映射,从而达到简化计算的目的.统计理论分析识别数据的结果表明,较大地改善常用方法的效能,获得了较好的识别效果.     

面向虹膜识别的Gabor特征筛选研究

针对2D-Gabor虹膜特征并不稳定,影响虹膜识别率的问题,提出了一种从多尺度、多方向2D-Gabor小波提取的虹膜特征中,筛选稳定特征应用于虹膜识别的方法。对虹膜图像采用多通道Gabor小波提取虹膜图像特征,然后通过自定义筛选准则从多维特征中筛选出最优特征参数并编码,用Hamming距进行特征匹配识别。基于CASIA虹膜图像库进行实验,结果表明该方法扩大了类内匹配与类间匹配之间的Hamming距,降低了等错率,同时降低了编码的长度,加快了特征匹配速度。     

The relative distance of key point based iris recognition

Iris recognition has received increasing attention in recent years as a reliable approach to human identification. This paper makes an attempt to analyze the local feature structure of iris texture information based on the relative distance of key points. When preprocessed, the annular iris is normalized into a rectangular block. Multi-channel 2-D Gabor filters are used to capture the iris texture. In every filtered sub-image, we extract the points that can represent the local texture most effectively in each channel. The barycenter of these points in each channel is called the key point and a group of key points are obtained. Then, the distance between the center of key points of each sub-image and every key point is called relative distance, which is regarded as the iris feature vector. Iris feature matching is based on the Euclidean distance. Experimental results on public and private databases show that the performance of the proposed method is encouraging.     

基于Zynq的虹膜识别系统设计与实现

针对虹膜识别系统存在成本高、操作难度大等不足,给出一种基于Zynq的虹膜识别系统设计方法,进一步拓展虹膜识别系统在民用市场中的运用面。具体讲,就是将虹膜图像存储在SD卡内,通过linux的ramfs(am file system)将SD卡中的虹膜图像加载到RAM,使用VDMA将虹膜数据从RAM搬运至虹膜降噪IP核进行算法加速,完成矩阵卷积的硬件加速,加速完成的数据通过VDMA,搬运回至RAM,供虹膜处理的下一个阶段使用。实验结是证明了所提方法的有效性。     

基于Gabor滤波的虹膜识别系统设计

随着科学技术的发展,信息安全在各个领域显得越来越重要,生物识别技术由于其特有的性质,在传统的识别领域中脱颖而出;其中,虹膜识别以高可靠性和差异性,成为目前安全性最高,最理想的生物识别技术;为增强虹膜识别算法的定位效率,提出一种改进定位算法,即二值化分割出瞳孔区域时,修正瞳孔边界,提高虹膜定位精度,有效提高识别速度;虹膜识别算法是整个系统的核心,要使虹膜识别具有良好的效果,需要对虹膜图像进行一系列的处理;为了完整高效地实现虹膜识别系统,对Gabor滤波器的原理及实现方法进行具体分析,研究Daugman虹膜识别算法,设计并完成了虹膜图像预处理,特征提取,二维Gabor滤波器的构建及参数选取等,经仿真实验,能够非常高效地完成虹膜特征提取并识别比对,计算速度和效果均优于传统算法。     

基于双正交多小波的虹膜特征提取与识别

用具有自仿映射特性的区间双正交多小波滤波器提取虹膜的纹理特征,并采用局部和全局特征相结合的方法对虹膜进行识别。虹膜图像经过多小波变换后,对低频部分多小波变换系数进行局部的粗量化二值编码,然后用Hamming距离进行识别。对因为睫毛、眼睑、虹膜变形等影响而不能有效识别的虹膜图像,再对多小波变换系数提取均值和方差作为全局特征,用方差倒数加权欧氏距离进行识别。实验结果证明,这种方法能快速而可靠地对虹膜进行识别。     

Towards enhancing the security and accuracy of iris recognition systems

The intricate structure of the iris constitutes a powerful biometric characteristic utilized by iris recognition algorithms to extract discriminative biometric templates. Iris recognition is field-proven but consequential issues, e.g. privacy protection or recognition in unconstrained environments, still to be solved, raise the need for further investigations. In this paper different improvements focused on template protection and biometric comparators are presented. Experimental evaluations are performed on a public dataset confirming the soundness of proposed enhancements.     

基于ICA-MJE和SVM的虹膜特征提取与识别

提出了一种新的虹膜特征提取与识别方法。对虹膜纹理采用最大判别熵的独立分量分析(ICA-MJE)实现特征提取,通过支持向量机(SVM)完成模式匹配。与Gabor小波的方法比较，在编码长度和编码时间方面有明显地改进。实验结果表明，该算法能更好地提高虹膜的识别率并能够有效地应用于身份识别系统中。     

基于小波过零点检测的虹膜识别方法研究*

在经典过零点算法的基础上,改进特征提取与匹配算法。分析各阶高通小波系数在同一算法下的识别率,以此选择小波系数来综合编码分析。采用不同的小波滤波器进行分析,考察不同的小波滤波器对算法的影响。DB3小波的识别率为99.61%,等错率为0.41%;四次B样条小波识别率为99.75%,等错率为0.25%;Coif3小波识别率为99.72%,等错率为0.29%。第五、六阶小波高通系数涵盖了虹膜纹理的主要信息,可采用第五、六阶小波系数进行编码识别。不同的小波滤波器得到的结果区别不是很大,DB3、四次B样条、Coif3     

基于小波过零点检测的虹膜识别方法研究*

在经典过零点算法的基础上,改进特征提取与匹配算法。分析各阶高通小波系数在同一算法下的识别率,以此选择小波系数来综合编码分析。采用不同的小波滤波器进行分析,考察不同的小波滤波器对算法的影响。DB3小波的识别率为99.61%,等错率为0.41%;四次B样条小波识别率为99.75%,等错率为0.25%;Coif3小波识别率为99.72%,等错率为0.29%。第五、六阶小波高通系数涵盖了虹膜纹理的主要信息,可采用第五、六阶小波系数进行编码识别。不同的小波滤波器得到的结果区别不是很大,DB3、四次B样条、Coif3小波编码识别效果好。DB3小波符合识别速度与效果的综合要求。     

Using semantic analysis to improve speech recognition performance

Although syntactic structure has been used in recent work in language modeling, there has not been much effort in using semantic analysis for language models. In this study, we propose three new language modeling techniques that use semantic analysis for spoken dialog systems. We call these methods concept sequence modeling, two-level semantic-lexical modeling, and joint semantic-lexical modeling. These models combine lexical information with varying amounts of semantic information, using annotation supplied by either a shallow semantic parser or full hierarchical parser. These models also differ in how the lexical and semantic information is combined, ranging from simple interpolation to tight integration using maximum entropy modeling. We obtain improvements in recognition accuracy over word and class N-gram language models in three different task domains. Interpolation of the proposed models with class N-gram language models provides additional improvement in the air travel reservation domain. We show that as we increase the semantic information utilized and as we increase the tightness of integration between lexical and semantic items, we obtain improved performance when interpolating with class language models, indicating that the two types of models become more complementary in nature.