在自动显微测量技术中,为了在保证对焦精度的同时具有较强的噪声抑制能力,在研究显微镜成像和聚焦原理的基础上提出了一种新的用于显微测量的聚焦评价函数。该聚焦评价函数利用改进的SUSAN算法识别待测边缘,当待测边缘点的数目最少时,显微镜聚焦最佳。实验表明,在粗调焦、细调焦、加高斯噪声后调焦和加椒盐噪声后调焦时,对同一位置的物体重复对焦30次,测得对焦位置的标准差分别为0.000,0.0011,0.0126,0.0033。与经典的聚焦评价函数相比,BW聚焦评价函数在精确性、单峰性、灵敏度、抗噪性能方面性能优越,是一种原理简单综合性能优越的聚焦评价函数,特别适用于显微测量。

A new auto-focusing function for microscope measurement is presented after the research of imaging and focusing principles in order to,in automatic microscope measurement techniques,not only enhance the accuracy of the focus value but also suppress noise. At first,the measuring edges are detected by the improved SUSAN algorithm and lens is moved. When the total of edge points detected is least,then the best-focused lens position is found. We tests in the same condition for 30 times,and experimental results indicate that standard deviation of focusing position in coarse focusing and in fine focusing is 0.000 and 0.0011 respectively,focusing in Gauss noise case is 0.0126,and focusing in salt-and-pepper noise case is 0.0033. BW is accurate in focusing degree,unimodal,sensitive to focusing position and insensitive to noise compared with traditional focusing functions. BW is one of the superexcellent focusing evaluation functions with simple principles,which is a computationally efficient alternative for microstructure measurement.