一般扫描电镜和电子探针电子束是采用手动聚焦,即一边调节聚焦电流,一边观察图象对比度的变化,反复寻求最清晰的图象.所以聚焦是一种既重要而又麻烦的操作.自动聚焦能快速选取最佳图象,免除麻烦操作.扫描成象中精细聚焦电子束所激发出的二次电子信号的微分极大值(以下简称为二次电子信号微分值),总比散焦状态下同一位置激 General scanning electron microscopy and electron microprobe electron beam is the use of manual focus, that is, while adjusting the focus current, while observing the changes in image contrast, and repeatedly seek the clearest picture, so focusing is an important and cumbersome operation. Focused to quickly select the best image, eliminating the hassle of operation. Scanning imaging fine focus electron beam excited by the secondary electronic signal differential maximum (hereinafter referred to as the secondary electronic signal differential value), than the defocus The same state excited state