一类离焦虹膜图像复原算法的研究

通常,虹膜识别系统中采集设备的景深(Depth of field, DOF)都很小,在采集过程中经常出现离焦现象,理论和实际应用都需 要研究这种离焦图像的复原方法.本文研究了一种点扩散函数 (Point spread function, PSF)为正六边形的示性函数的离焦虹膜图像复原问题. 通过分析PSF频域零点的分布规律,从理论上证明了距频域中心最近的第一圈零点的零点定理, 证明过程中也提供了计算这些零点的方法,在此基础上,给出了这一类离焦图像复原的快速算法. 实验结果验证了算法的有效性与实时性.

A Study on Defocused Iris Image Restoration

Generally, acquisition equipments in iris recognition systems have a shallow depth of field (DOF), which are very sensitive to defocus. Methods to recover defocused images are needed both in theoretical researches and in real-world applications. In this paper, an indicator function of regular hexagon was used as the point spread function (PSF) to solve the recovery problem of defocused iris images. By analyzing the zero distribution of PSF in frequency domain, we theoretically, proved the zero theorem for the round of zero points nearest to the center of frequency domain. We also provided the computational method to find zero points and the fast algorithm to recovery this kind of defocused images. The experimental results showed the efficiency of the algorithm.