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为实现快速、准确的自动聚焦,采用理论分析和实验验证相结合的方法,对显微数字全息自动聚焦所采用的数值重建算法、全息图零级谱滤除和聚焦评价函数等相关问题进行了研究。结果表明:菲涅耳变换重建算法完全可以用于数字全息自动聚焦中;全息图零级谱的滤除使得基于菲涅耳变换算法的自动聚焦过程无法实现;灰度方差函数、傅里叶频谱加权对数函数和标准偏差相关函数可以有效地用于显微数字全息数中的自动聚焦,其中傅里叶频谱对数函数计算时间最短,是首选的聚焦评价函数;利用再现像光场中部分区域作为聚焦判断依据,可以大大缩短自动聚焦时间。
In order to achieve fast and accurate auto-focusing, a combination of theoretical analysis and experimental verification is used to analyze the numerical reconstruction algorithms of holographic digital holographic auto-focusing, the zero-order spectral filtering of hologram and the focusing evaluation function the study. The results show that the Fresnel transform reconstruction algorithm can be used in digital holographic auto-focusing. The zero-order hologram filtering can not realize the auto-focusing process based on Fresnel transform algorithm. The gray variance function, Fourier spectrum The weighted logarithmic function and the standard deviation correlation function can be effectively used for auto-focusing in the micro-holographic digital holography, wherein the calculation time of the logarithm function of the Fourier spectrum is the shortest, which is the preferred focusing evaluation function; Area as a basis for judging the focus, you can greatly reduce the auto focus time.