通过扫描头前方聚焦透镜的反射单元，调焦发生了变化。
The focusing is effected after the deflection unit via a focusing lens in front of the scanner head.
以上的图像聚焦判别函数特性分析结果对于图像自动测量所需要的自动调焦控制具有指导意义。
These analysis results of image focusing criterion functions are useful for autofocusing in the automatic image measurement application.
本文分析了自动聚焦的理论依据，提出了实现自动调焦的总体方案和电路设计。
Theoretical basis of automatic focussing are analysed and its system and circuit design are proposed in this paper.
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