虹膜图像采集的自动调焦技术研究

摘要

For the iris image blurring problem existing in iris image acquisition, an iris image acquisition automatic focusing method based on image definition evaluation function is proposed. The method defines image definition by computing the largest gray gradient of the area near iris' inner border, carries out CCD focusing with an improved climbing program, extracts part of feature points during the focusing process to execute curve fitting to find out the best focusing point, and move the camera to its best focusing position to get a clear iris image. Experiment results show thai the method can achieve fast and accurate automatic focusing in iris image acquisition.%针对虹膜图像采集中存在的图像模糊问题,提出一种基于图像清晰度评价函数的虹膜图像采集自动调焦方法.该方法通过计算虹膜内边界附近区域的最大灰度梯度来定义图像清晰度,运用改进的爬坡方案进行CCD对焦,提取对焦过程中的部分特征点进行曲线拟合求出最佳聚焦点,移动相机到最佳成像位置得到清晰的虹膜图像.实验结果表明,该方法能快速准确实现虹膜拍摄中的自动对焦.