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Sorry for previous post – something went wrong.

Are you asking about electron spin? Scan rotation? Something else?

Hello Lili,

I am not sure that i understood your question, so i'll try to explain it in two ways.

Firstly, unlike optical and transmission electron microscopes, image magnification in the SEM is not a function of the power of the objective lens. SEMs may have condenser and objective lenses, but their function is to focus the beam to a spot, and not to image the specimen. SEM could in principle work entirely without condenser or objective lenses, although it might not be very versatile or achieve very high resolution. 

So, the main purpose of objective lens is focusing the beam on sample surface. And have little distribution on spot size. These two parameters enhence the resolution of image but imaging is all about scan coils for SEM.

And second answer for electron movement, objective lens is electromagnetic coil. So that a coil of wire through which current flows. Because the current flow produces a magnetic field at right angles, the field pushes inwards into the hole in the centre. This acts to shape a beam of electrons travelling in their natural spiral path down the central hole. It is all about magnetic forces on moving electron. You can change its spiral radius due to current of coil or accelerating voltage of electrons. So spot size might have change anyway. If your spot size gets bigger, resolution rises and qualty of image decrease.

I hope you can find the answer in all of this :)

Good Luck!