Procedures for focusing, stigmating and alignment in high resolution electron microscopy

Several different approaches to the alignment, stigmating and focusing of a high resolution electron microscope are evaluated theoretically and experimentally. Ambiguities in the interpretation of diffractograms are pointed out which make it necessary to explore a range of incident beam directions before the correct alignment can be established. The variation of image contrast with the imaging conditions is examined in detail, and its global minimization is shown to be a reliable criteria for adjustment of all parameters. Recommendations are made as to the best procedures to adopt in various circumstances, and a computer‐controlled procedure based on the image contrast is described which sets all parameters automatically in less than a minute. 1983 Blackwell Science Ltd