Method and apparatus for correcting axial coma in electron microscopy

摘要

Method and apparatus for correcting the axial coma in the image created by an electron microscope without requiring skillfulness or any other peripheral device. The microscope is equipped with a beam wobbler and brings the voltage center or current center into the middle of the final image by controlling the deflection coils. The amount of the deviation of the voltage center or current center from the coma-free axis is previously found and stored in an area of a memory. This beam is tilted by the amount of the deviation read from the memory. For this purpose, a deflecting signal corresponding to the amount of the deviation is produced to the deflection coils. Therefore, once the deviation is found, the axial coma can be corrected simply and routinely by correcting the beam tilt by the amount of deviation after the voltage center or current center is brought into the middle of the final image.