2 1/2D electron microscopy: Through‐focus dark‐field image shifts

A novel technique for transmission electron microscopy is described and some possible applications illustrated. The technique involves the formation of a stereo‐optic effect using a through‐focus pair of dark‐field images. While such stereo‐optic pairs do not show the spatial relationships between various objects in the specimen microstructure, they do convey information about the crystallographic relationships. It is shown that this technique, called 2 1/2D imaging, is useful in the study of precipitated phases and it facilitates clear distinction between small precipitates and other microstructural features. This is a powerful method of analysis of complex microstructures in crystallographic terms. Intended as the first report of the technique, the paper broadly discusses the possible applications of 2 1/2D imaging, giving as examples some of the elementary uses in studies of precipitation, recrystallization, deformation, and recovery processes in crystalline materials.