ELEKTRONMIKROSKOP MED EN RINGFORMIG BLENDARE

摘要

In an electron microscope dark-field illumination is obtained by including an annular diaphragm between the electron source and the second condenser lens and by varying the energisation of the condenser lenses whilst retaining imaging of the electron source on the specimen. The specimen is illuminated by a beam in the form of a hollow cone of varying apical angle. By means of a known objective diaphragm those electrons are selected from the scattered beam for the purpose of image formation which leave the specimen within a narrow cone about the optical axis, irrespective of the angle of incidence.