Electrostatic lens, electrons collection

Compare a TEM to a tremsmitted light optical microscope being used to take a photomicrograph, and the principles of design are very similar. Illumination of the object is very important, and in both microscopes the resolution and contrast of the image may be degraded if the illumination is not properly adjusted. The source of illumination may be a small, hot tungsten filament in both cases. The electrons or photons emitted from the filament are collected by a condenser lens. To increase efficiency in the TEM, an electrostatic lens electron gun) is used to steer more of the flux into this lens. In the optical microscope, a mirror behind the lamp performs this function. A second condenser lens controls the transfer of this illumination to the specimen plane. In the TEM, these are simply called condenser lens 1 (Ci) and condenser... 

Electrons ejected from the sample are collected by an electrostatic lens (h in Fig. 7), and they are sorted out according to their kinetic energy in an energy analyzer (i in Fig. 7), as schematized in Fig. 2. 

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