Elsevier

Neurocomputing

Volume 137, 5 August 2014, Pages 198-204
Neurocomputing

Robust iris recognition using sparse error correction model and discriminative dictionary learning

https://doi.org/10.1016/j.neucom.2013.06.051Get rights and content

Abstract

Robust iris recognition is a hot research topic in the biometrics community and the sparse representation-based methods are promising to achieve desirable robustness and accuracy. Motivated by the fact that corruptions and occlusions incurred by eyelash occlusions, eyelid overlapping, specular and cast reflection in iris images are spatially localized but large in magnitude, we present a robust iris recognition method based on a sparse error correction model. In the proposed method, all the training images are concatenated as a dictionary and the iris recognition task is cast to an optimization problem to seek a sparse representation of the test sample in terms of the dictionary. And a sparse error correction term is introduced into the objective function of the optimization problem to deal with gross and spatially localized errors. Furthermore, in order to compact the huge dictionary, we introduce a discriminative dictionary learning framework to reduce computational complexity. Experimental results on CASIA Iris Image Database V3.0 show that the proposed methods achieve competitive performance in both recognition accuracy and efficiency.

Introduction

Iris recognition is one of the most reliable and secure methods for personal identification and authentication [1], which has been attracted an increasing attention in the past two decades. Two most well-known and representative iris recognition frameworks were developed by Daugman [2] and Wildes [3]. Daugman [2] applied a 2-D Gabor filter to extract the features from the scale-normalized iris images and quantized them to 256 bytes iris codes. Then, the normalized Hamming distance between the iris codes was employed as the measure for recognition. In contrast, Wildes [3] used convolution with Laplacian of Gaussian filter at multiple scales to produce a template of the iris texture and then computes the normalized correlation as the similarity metric. Motivated by their pioneer works, a lot of iris recognition algorithms have been presented to pursue more excellent performance. The earlier works were summarized in [1] and some recent efforts were reported in [5], [6], [7], [8], [9], [10]. Existing iris recognition algorithms based on feature extraction and matching have achieved very high recognition accuracy for clean iris images [4].

However, the quality of the acquired iris images is often poor in practical scenarios due to various side effects such as motion blur, defocus blur, eyelid overlapping, specular and cast reflection. This leads to heavy performance degradation for most existing methods so far [1], [5]. Improving the robustness of the iris recognition algorithm is still a challenging issue in the iris biometric community. Si et al. [8] focused on the robustness of iris segmentation and developed an eyelash detection algorithm based on directional filters to enhance the iris segmentation, achieving promising results. Li and Ma [9] presented a robust method based on the Random Sample Consensus (RANSAC) to localize the non-circular iris boundaries and an image registration method based on the optical flow algorithm to account for iris image deformation. Instead of the traditional feature extraction and matching framework, Pillai et al. [10] proposed a novel framework based on random projection and sparse representation-based classification (SRC) [11]. This method achieves desirable robustness to blur, segmentation error and small level occlusions. However, when the level of occlusions is relatively high, the recognition rate of the algorithm decreases remarkably. Moreover, the SRC algorithm requires a sufficiently large number of training images from each class to span subspace of each class and stacks all training images to form a dictionary directly, which leads to a large size of dictionary and intensive computation complexity.

In this paper, we firstly present an improved SRC iris recognition method based on sparse error correction (SEC) mode [11] to improve the robustness of the recognition algorithm to the high level occlusions and corruptions. The extra robustness derived from the SEC mode comes from the presence of a sparse error term which corresponds to the occlusions and corruptions of the iris image. Since the errors incurred by occlusions, secularities and cast shadows are large in magnitude but sparse in space, it is more reasonable that a test sample is better represented by a combination of the training samples with additive sparse and large-magnitude errors than by the standard SRC model used in [10]. Furthermore, a discriminative dictionary learning method for sparse error correction model (SEC-DKSVD) derived from discriminative K-SVD (D-KSVD) [12] is introduced to compact dictionary to improve both the efficiency and accuracy of the iris recognition algorithm. Finally, in order to detect and reject those invalid test images, we propose a validation scheme based on the cumulative sparsity concentration index (CSCI) [10]. Differing from [11], [10] in which SCI of the recovered sparse representation coefficient vector was applied as the confidence of the recognition result, the suggested CSCI-based strategy employs SCI of the label vector obtained by the learned classifier. Besides the ability of detecting and rejecting the invalid samples, this scheme improves the robustness of iris recognition as well.

The rest of the paper is organized as follows. In Section 2, the adaptability of the SR-based method for iris recognition task is discussed, and the proposed sparse error correction model for iris recognition is presented. In Section 3, the improved discriminative dictionary learning method for error correction model is introduced. In Section 4, the validation scheme for recognition results is suggested. Experimental results are reported in Section 5, and we conclude the paper in Section 6.

Section snippets

Sparse error correction model for iris recognition

Recently, Wright et al. [11] reported a powerful tool, the SRC algorithm, for face recognition. SRC depends on low-dimensional linear models for illumination variation in recognition tasks. The SRC algorithm relies on low-dimensional linear models for illumination variation in recognition tasks. More specifically, given n training samples di,1,di,2,,di,nRm of the ith class object, the new test sample yiRm of this object will lie near the linear span of the training samplesyi=di,1xi,1+di,2xi,2

D-KSVD for sparse error correction model

The sparse error correction model-based iris recognition algorithm uses the entire iris images training set as a dictionary to classify a new test sample, which may result in a huge size dictionary as the basic SRC method and expensive computation. Therefore, shrinking the size of the dictionary becomes a practical issue. The K-SVD algorithm proposed in [21] addressed this issue by learning a compact dictionary from the training set with N items (N<n ) for each class by solving the following

Validation scheme based on CSCI

In a practical recognition system, a new test sample could be an iris image of a subject that is not authorized or an image that is not an iris at all. Thus, the ability to detect and reject suspect recognition results and invalid test samples is crucial for an iris recognition system. The validity of the test sample is implicated in the distribution of the coefficient vector and the label vector given by (12). The notion of sparsity concentration index (SCI) was introduced in [11] to validate

Experimental results

In this section, we evaluate the proposed recognition methods on CASIA-IrisV3 [14]. There are three subsets in CASIA-IrisV3, CASIA-Iris-Interval, CASIA-Iris-Lamp and CASIA-Iris-Twins, containing a total of 22,034 iris images from more than 700 subjects and 1500 classes (eyes) acquired by CASIA close-up iris cameras or OKI IRISPASS-h hand-held iris sensors. To evaluate robustness of recognition algorithms to elastic deformation of iris texture, CASIA-Iris-Lamp subset collected under different

Conclusion

In this paper, we introduced a SEC mode-based method and a SEC-DKSVD-based method for the iris recognition. Furthermore, a CSCI-based results validation strategy employing the sparsity of the label vector obtained by the classifier learned by SEC-DKSVD was proposed. Our experiments on CASIA-Iris-Lamp indicate that the proposed methods show competitive performance when a sufficiently large number of training samples are available. On one hand, under the same conditions, the proposed SEC-based

Acknowledgment

This task is supported by the Nation Natural Science Foundation of China (Grant nos. 61001123, 60973113); Hunan Province Science and Technology Planning Project (Nos. 2013FJ4033, 2009FJ3005, 2012FJ4129, 2012GK3056); the Science Research Key Project of the Education Department of Hunan Province (No. 13A107); and Changsha Science and Technology Planning Key Project (Nos. K1104022-11, K1207027-11).

Yun Song received his M.S. in computer application from Changsha University of Science & Technology, China in 2008. He is currently is an associate professor in the School of Computer and Communication Engineering of Changsha University of Science & Technology, China. And he is pursuing his PhD from Hunan University, China. His major research interests include video coding, multimedia communication and security, compressive video sensing, video analysis, and image processing.

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Yun Song received his M.S. in computer application from Changsha University of Science & Technology, China in 2008. He is currently is an associate professor in the School of Computer and Communication Engineering of Changsha University of Science & Technology, China. And he is pursuing his PhD from Hunan University, China. His major research interests include video coding, multimedia communication and security, compressive video sensing, video analysis, and image processing.

Wei Cao received his M.S. in computer application from National University of Defense Technology in 1989, China. He is currently an assistant associate professor in the School of Computer and Communication Engineering of Changsha University of Science & Technology, China. His major research interests include video processing technology, multimedia technology, signal processing, pattern recognition, and image processing.

Zunliang He was born in 1988. He is pursuing his M.S. degree at Computer and Communication Engineering Institute, Changsha University of Science & Technology, Changsha, PR China. His research interests include video analysis and image processing.

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