楼主的问题把JEOLzxj给惊动了:),迷思难解啊,其实驰奔也想弄明白!jeolzxj是正确的。而且确实,相比较没有该配置的电镜而言,在调节机械对中的时候显得方便,非常直观的方式来迅速调节对中,配合波形观察模式,容易找到最佳饱和点,而且更精确! 以下查了一个资料中描述分享一下:emission pattern can be readily observed in a TEM, and some SEMs are also equipped with scanning coils in the gun which permit a very similar visualization of the emission pattern. We provide this kind of "source imaging" feature on our Personal SEMTM and it is my preferred way to optimize the gun. Calling this kind of optimization "saturation" is a reasonably apt way to describe how the emission pattern seems to collapse into a dense spot. You can also accomplish a rather equivalent kind of optimization on a SEM which does not have this source imaging feature by maximizing the beam current under high magnification conditions (typically done by observing the waveform signal). So ideally when microscopists are talking about saturation, they are visualizing this kind of optimization procedure.