Application of a Scanning Device to a Transmission Electron Microscope - 1. Fundamentals and Imaging of Amorphous Objects.

The electron optical properties of a scanning device for a conventional transmission electron microscope are discussed. A knowledge of the apertures is necessary for the interpretation of the image contrast and the resolution. A method is described to measure the electron probe and detector apertures by the diffraction diagram in the detector plane. It is shown how the apertures in the scanning mode modify the transmission of amorphous specimens. A method of measuring the edge resolution is used for the determination of the electron probe diameter, the chromatic error in the conventional transmission mode and the beam broadening caused by multiple scattering in the scanning mode. The video signal of transmission can be transformed by a logarithmic amplifier into a signal proportional to the local mass thickness of organic specimens.