Optical shadowing in the electron microscope

Abstract

SUMMARY Optical shadowing offers a valuable technique for the study of many transmission electron microscope specimens. Simply blocking half of the illumination with the objective aperture produces an image with a striking shadowed effect which gives a distinctly three‐dimensional appearance to the specimen's surface topography. Theoretical analysis shows that this is due primarily to a discrimination between electrons refracted in opposite directions, and that the characteristic features of the effect are successfully explained by a refraction model. The capability of visualizing surface topography is applicable up to the full resolving power of the instrument and accordingly opens many new avenues of investigation.