Improved low dose technique for high resolution electron microscopy

Abstract
SUMMARY: The use of low‐dose electron micrography can result in unacceptable focusing errors if the specimen plane between focus and micrography areas is tilted. The corrective method applied here involves the use of two focus areas symmetrically disposed with respect to the area to be recorded. A reasonable estimate of correct focus can be made by interpolation between the two known settings.Annular illumination applied to the specimen immediately prior to recording is recommended to reduce any likelihood of specimen drift caused by changing thermal gradients.The methods involve only minor modifications to existing circuitry, are easy to implement, and have resulted in a dramatically improved percentage of well‐focused micrographs.