This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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Almost all commercial TEM systems (see schematic diagram of TEM systems) have the incident electrons emitted from the top of the systems and the screens and/or detectors at the bottom for observation convenience. But some TEMs with computer-observation only can have the incident electrons emitted from the bottom of the systems and the detectors on the top. The example in Figure 3606 shows this type of TEM systems facilitated with a C₃/C₅ corrector. The QLM is a quadrupole triplet, used for coupling the corrector electron-optically to the OL (objective lens). The QOCM is used for optimized coupling of inelastically scattered electrons into the electron energy loss spectrometer (EELS).

	【*】 Detectors: HAADF, BF, EELS 【*】 QOCM: Quadrupole/octupole module called quadrupole– octupole coupling module 【*】 Four round projector lenses: PL1, PL2, PL3, and PL4. 【*】 OL: Objective lens 【*】 QLM: Quadrupole lens module 【*】 C3/C5 corrector: quadrupole–octupole C3/C5 corrector 【*】 Three round condenser lenses: CL1, CL2, and CL3 【*】 CFEG: Cold field emission gun
Figure 3606. (a) The TEM column and (b) Schematic cross-section of the column. [1]

Because of the limit of depth of focus and because no lens in between the recording media and TEM viewing screen can be used to compensate for the out-of-focus, the recording film or CCD camera is arranged to locate just several centimeters below the screen. However, the specimen image on the recording media is still out of focus if the image has been brought to exact focus on the TEM screen.

[1] Krivanek OL, Corbin GJ, Dellby N, Elston BF, Keyse RJ, Murfitt MF, Own CS, Szilagyi ZS, Woodruff JW. An electron microscope for the aberration-corrected era, Ultramicroscopy, 108 (2008) 179–195.