Adapting iris feature extraction and matching to the local and global quality of iris image
Sandra Cremer · HAL (Le Centre pour la Communication Scientifique Directe) · 2012
Iris recognition has become one of the most reliable and accurate biometric systems available. However its robustness to degradations of the input images is limited. Generally iris based systems can be cut into four steps : segmentation, normalization, feature extraction and matching. Degradations of the input image quality can have repercussions on all of these steps. For instance, they make the segmentation more difficult which can result in normalized iris images that contain distortion or undetected artefacts. Moreover the amount of information available for matching can be reduced. In this thesis we propose methods to improve the robustness of the feature extraction and matching steps to degraded input images. We work with two algorithms for these two steps. They are both based on convolution with 2D Gabor filters but use different techniques for matching. The first part of our work is aimed at controlling the quality and quantity of information selected in the normalized iris images for matching. To this end we defined local and global quality metrics that measure the amount of occlusion and the richness of texture in iris images. We use these measures to determine the position and the number of regions to exploit for feature extraction and matching. In the second part, we study the link between image quality and the performance of the two recognition algoritms just described. We show that the second one is more robust to degraded images that contain artefacts, distortion or a poor iris texture. Finally, we propose a complete system for iris recognition that combines the use of our local and global quality metrics to optimize recognition performance