Electron Microscope Image Intensification and Specimen Exposure

Abstract

The efficiency of electron microscope image intensification (EMII) systems is often represented in terms of signal-to-noise ratio as a function of current density in the final microscope image plane. Such a characteristic is one way of evaluating the sensitivity of an EMII-system. It determines the intensification necessary to raise the signals of individual electrons well above the equipment noise level of the intensifier/display chain.This approach to the problem of EMU may lead to misinterpretations since it does not consider the spatial resolution in the specimen. Usually, the spatial resolution of the EMII-chain is considerably inferior to the resolution of conventional photographic material. In internal photography one can, therefore, normally work with considerably lower electron optical magnifications than with an image intensifier system to resolve specimen details of the same dimensions.