The intensity characteristics of electron microscope images are briefly discussed with examples of Fresnel diffraction fringes and edge luminosity to illustrate the intensity contours at sharp edges. The preparation and properties of silica replicas of surfaces are reviewed and some examples of the application to metallography and grinding and polishing are exhibited. The use of stereoscopy in determining elevations is demonstrated and profiles of diffraction gratings are shown as examples.
ROBERT D. HEIDENREICH, "Techniques in Applied Electron Microscopy," J. Opt. Soc. Am. 35, 139-148 (1945)