A Study on Restoration of Iris Images with Motion-and-Optical Blur on Mobile Iris Recognition Devices

Iris recognition is a form of biometric technology that authenticates individuals by using the unique iris patterns between the pupil and the sclera. To solve security problems in mobile environments, mobile iris recognition devices have been commercialized recently. A motion-and-optical blurred image can be sometimes captured because users capture the iris images of a testee by holding the recognition devices. Motion-and-optical blurred images reduce iris recognition accuracy. Previous researches of restoring iris image only dealt with optical or motion blurred image. To overcome these problems, we propose a new method of restoring motion-and-optical blurred iris images at the same time. This article presents three contributions over previous research. (1) A new focus assessment method is proposed to measure accurate focus scores regardless of motion blurring. (2) Previous research restored coexisting motion-and-optical blurred images in terms of visibility, but in this article, we restored them in terms of recognition. (3) We used a modified CLS (Constrained Least Square) filter to prevent the zero-crossing of the PSF (Point Spread Function) of motion blurring with a uniform shape. So, the iris recognition accuracy was better than when using a conventional CLS filter. Experimental results showed that the EER was 0.796% when using the proposed method and it was 1.431% when not using the proposed method. Consequently, the EER was reduced as much as 0.635% (1.431-0.796%) when using the proposed method. (C) 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 323-331, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ima.20209