Electron diffraction and microscopy in Japan past and present

This article is the text of a general lecture given at the Ninth International Congress of Crystallography, September 1972, at Kyoto, Japan. The lecture begins with the famous experiment of Kikuchi and continues with results of work carried out under the leadership of Miyake and the author. The main topics in the former part are: anomalous enhancement and splitting of Bragg peaks, appearance of non-Bragg maxima, dynamical multiple refraction, etc. Dynamical theories including inelastic scattering are introduced, and the formation mechanism of Kikuchi bands and absorption effects are explained. Electron diffraction and electron microscopy, which were originally developed as different fields, have been unified after 1950. The development of high-voltage electron microscopy is emphasized. The reason for the enhancement of dynamical effects at very high voltages is explained in terms of relativistic diffraction theory. As an example of some most remarkable dynamical effects, the vanishing of the second-order reflexion is described. Finally, the findings and developments in moiré patterns and lattice images are reviewed briefly. The lecture is devoted to diffraction phenomena themselves and applications to structural studies are excluded.