Iris-based human recognition is very attractive because of the high accuracy achievable. However, existing encoding methods are unable to handle iris images acquired when the ambient lighting is non-uniform. In this paper we propose a novel encoding technique which can handle images acquired under such conditions. The method is based on 2D median filters, which are commonly used as de-noising tools in image processing domain, and uses their nonlinear characteristics to generate binary codes from gray scale iris images. The application of this method for robust iris recognition is discussed and compared with two more traditional iris encoding techniques: the 2D Gabor filter based method and the 1D log-Gabor method. Our algorithm is usable for the whole range of conditions encountered in the MMU1 iris database, performs well in a synthetic uneven illumination study, and gets comparable results on other tests.
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