The massive availability of cameras and personal devices results in a wide variability between imaging conditions, producing large intra-class variations and performance drop if such images are compared for person recognition. However, as biometric solutions are extensively deployed, it will be common to replace acquisition hardware as it is damaged or newer designs appear, or to exchange information between agencies or applications in heterogeneous environments. Furthermore, variations in imaging bands can also occur. For example, faces are typically acquired in the visible (VW) spectrum, while iris images are captured in the near-infrared (NIR) spectrum. However, cross-spectrum comparison may be needed if for example a face from a surveillance camera needs to be compared against a legacy iris database. Here, we propose a multialgorithmic approach to cope with cross-sensor periocular recognition. We integrate different systems using a fusion scheme based on linear logistic regression, in which fused scores tend to be log-likelihood ratios. This allows easy combination by just summing scores of available systems. We evaluate our approach in the context of the 1st Cross-Spectral Iris Periocular Competition, whose aim was to compare person recognition approaches when periocular data from VW and NIR images is matched. The proposed fusion approach achieves reductions in error rates of up to 20-30 in cross-spectral NIR-VW comparison, leading to an EER of 0.22 and a FRR of just 0.62 for FAR=0.01 , representing the best overall approach of the mentioned competition.. Experiments are also reported with a database of VW images from two different smartphones, achieving even higher relative improvements in performance. We also discuss our approach from the point of view of template size and computation times, with the most computationally heavy system playing an important role in the results.
Regarding cross-sensor recognition across different spectra, the work @cite_70 proposes to compare the ocular region cropped from VW face images against NIR iris images, since face images are usually captured in the visible range, while iris images in commercial systems are usually acquired using near-infrared illumination. They employ three different feature descriptors, namely Local Binary Patterns (LBP), Normalized Gradient Correlation (NGC), and Joint Database Sparse Representation (JDSR). Using a self-captured database, they report a cross-spectral performance of EER=23 of the three experts.
@cite_70
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We consider the problem of matching face against iris images using ocular information. In biometrics, face and iris images are typically acquired using sensors operating in visible (VIS) and near-infrared (NIR) spectra, respectively. This presents a challenging problem of matching images corresponding to different biometric modalities, imaging spectra, and spatial resolutions. We propose the usage of ocular traits that are common between face and iris images (viz., iris and ocular region) to perform matching. Iris matching is performed using a commercial software, while ocular regions are matched using three different techniques: Local Binary Patterns (LBP), Normalized Gradient Correlation (NGC), and Joint Dictionary-based Sparse Representation (JDSR). Experimental results on a database containing 1358 images of 704 subjects indicate that ocular region can provide better performance than iris biometric under a challenging cross-modality matching scenario. A new compound operator is proposed for heterogeneous periocular recognition.The new operator outperforms three basic operators and three state-of-the-art compound operators.NIR, SWIR, MWIR and LWIR spectra at different standoff distances are considered.A metric is introduced to measure image quality and explain its impact on performance.The new operator does not require training and can be applied to various datasets. Cross-spectral matching of active and passive infrared (IR) periocular images to a visible light periocular image gallery is a challenging research problem. This scenario is motivated by a number of surveillance applications such as recognition of subjects at night or in harsh environmental conditions. This problem becomes even more challenging with a varying standoff distance. To address this problem a new compound operator named GWLH that fuses three local descriptors - Histogram of Gradients (HOG), Local Binary Patterns (LBP) and Weber Local Descriptors (WLD) - applied to the outputs of Gabor filters is proposed. The local operators encode both magnitude and phase information. When applied to periocular regions, GWLH outperforms other compound operators that recently appeared in the literature. During performance evaluation LBP, Gabor filters, HOG, and a fusion of HOG and LBP establish a baseline for the performance comparison, while other compound operators such as Gabor followed by HOG and LBP as well as Gabor followed by WLD, LBP and GLBP present the state-of-the-art. The active IR band is presented by short-wave infrared (SWIR) and near-infrared (NIR) and passive IR is presented by mid-wave infrared (MWIR) and long-wave infrared (LWIR). In addition to varying spectrum, we also vary the standoff distance of SWIR and NIR probes. In all but one case of the combination of spectrum and range, GWLH outperforms all the other operators. A sharpness metric is introduced to measure the quality of heterogeneous periocular images and to emphasize the need in development of image enhancement approaches for heterogeneous periocular biometrics. Based on the statistics of the sharpness metric, the performance difference between compound and single operators is increasing proportionally with increasing sharpness metric values. Surveillance cameras today often capture NIR (near infrared) images in low-light environments. However, most face datasets accessible for training and verification are only collected in the VIS (visible light) spectrum. It remains a challenging problem to match NIR to VIS face images due to the different light spectrum. Recently, breakthroughs have been made for VIS face recognition by applying deep learning on a huge amount of labeled VIS face samples. The same deep learning approach cannot be simply applied to NIR face recognition for two main reasons: First, much limited NIR face images are available for training compared to the VIS spectrum. Second, face galleries to be matched are mostly available only in the VIS spectrum. In this paper, we propose an approach to extend the deep learning breakthrough for VIS face recognition to the NIR spectrum, without retraining the underlying deep models that see only VIS faces. Our approach consists of two core components, cross-spectral hallucination and low-rank embedding, to optimize respectively input and output of a VIS deep model for cross-spectral face recognition. Cross-spectral hallucination produces VIS faces from NIR images through a deep learning approach. Low-rank embedding restores a low-rank structure for faces deep features across both NIR and VIS spectrum. We observe that it is often equally effective to perform hallucination to input NIR images or low-rank embedding to output deep features for a VIS deep model for cross-spectral recognition. When hallucination and low-rank embedding are deployed together, we observe significant further improvement; we obtain state-of-the-art accuracy on the CASIA NIR-VIS v2.0 benchmark, without the need at all to re-train the recognition system. Face recognition algorithms need to deal with variable lighting conditions. Near infrared (NIR) image based face recognition technology has been proposed to effectively overcome this difficulty. However, it requires that the enrolled face images be captured using NIR images whereas many applications require visual (VIS) images for enrollment templates. To take advantage of NIR face images for illumination-invariant face recognition and allow the use of VIS face images for enrollment, we encounter a new face image pattern recognition problem, that is, heterogeneous face matching between NIR versus VIS faces. In this paper, we present a subspace learning framework named Coupled Spectral Regression (CSR) to solve this challenge problem of coupling the two types of face images and matching between them. CSR first models the properties of different types of data separately and then learns two associated projections to project heterogeneous data (e.g. VIS and NIR) respectively into a discriminative common subspace in which classification is finally performed. Compared to other existing methods, CSR is computational efficient, benefiting from the efficiency of spectral regression and has better generalization performance. Experimental results on VIS-NIR face database show that the proposed CSR method significantly outperforms the existing methods.