Practical Electron Microscopy and Database

The electron columns in electron microscopes (EMs) consist of an electron gun and some electromagnetic lenses. Electrons can be focused either by electrostatic or magnetic field. However, all the three components, including illumination system, objective lens/stage, and the imaging system, are normally using electromagnetic lens rather than electrostatic lens. The lenses are the key components in EMs, which allow us to utilize the electron beam in either forming images or focusing the beam in a spot. The function of the lenses is to transform a point in an object to a point in an image and to focus rays to a point in the focal plane of the lens.