在虹膜识别系统中,质量较差的虹膜图像可能被系统拒识,导致身份识别或身份认证的失败。因此有必要在虹膜图像的采集端引入质量评价环节,从虹膜图像采集仪输出的视频序列中挑选出符合识别系统要求的虹膜图像。首先提出了一种快速的基于连通域分析的瞳孔定位方法,然后在此基础上,针对具有散焦模糊和眼皮睫毛遮挡的虹膜图像,提出了一种分步式的虹膜图像质量评价算法。实验结果表明,该算法能够有效地筛选出符合要求的虹膜图像。

The iris image with bad quality will be rejected by the automatic iris recognition system, which will result in the failure of identification or verification. Therefore it is necessary to introduce the quality assessment process of iris images in the phase of image acquisition, which aims to pick out the iris image with high quality from the video sequence captured by the image acquisition device. This paper proposes a fast localization method based on connective region analysis to find out the position of the pupil in an iris image, and then proposes a new iris image quality assessment algorithm which can be divided into two steps. In the first step, the high frequency power of right and left part of the pupil is calculated to find out the undefocused images. And in the second step, the gradient information of the upper region of the pupil is computed to distinguish between the occluded images and unoccluded images. The experimental results indicate that the new algorithm is effective to pick out the iris images with high quality.