显微镜自动粗调焦的TennenGrad改进算法

提出了使用Sobel算子或Laplace算子做卷积,对图像像素点进行绝对值相加的TennenGrad改进算法,以及Laplace改进算法,和几种已有评价函数进行分析比较。为了判断粗调评价函数的优劣,对评价函数的判断准则进行了逐一分析,并且将平滑性、高效率、强壮性作为最主要的衡量标准。在搭建的显微镜粗调实验系统中,对较为复杂的MEMS器件-微加速度计进行粗调成像。另外,对显微成像系统的调焦策略进行分析研究,提出并比较分析了3种调焦策略,其中n点灰度比较策略是较优的策略。实验处理结果表明,改进的TennenGrad算法具有最优的粗调特性,调焦范围较大,达到了210 μm;调焦分辨率高,达到7 μm,同时调焦图像显示出曲线变得更加平滑,曲线部极值点由5个减为0个。

Improved TennenGrad function for microscopic coarse autofocuing

An improved TennenGrad criterion function and an improved Laplace criterion function are proposed for microscopic coarse autofocusing, which use Sobel operators and Laplacian operators to convolve and add together the absolute values of matrix pixels for a image. Several different existed criterion functions in microscope autofocusing are compared and analyzed. To judge the efficiencies of criterion functions, function criteria are analysed with smoothness, efficiency and robustness as the main criteria. In the CCD camera microscope experiment system, a micro accelerometer is used as the measured object. Three autofocusing strategies are proposed and compared, and the n-pixel grey level method is preferred for microscopic autofocusing. Coarse autofocusing results show that the improved TennenGrad function has the best performance, autofocusing range is 210 μm, and autofocusing resolution is 7 μm. Image results show that autofocusing curve becomes smoother, and the number of extremums reduce from 5 to 0.