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Accurate stigmating of a high voltage electron microscope
Author(s) -
Krivanek O. L.,
Isoda S.,
Kobayashi K.
Publication year - 1977
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1977.tb00068.x
Subject(s) - astigmatism , optics , microscope , micrograph , electron microscope , resolution (logic) , materials science , lens (geology) , voltage , diffraction , physics , computer science , artificial intelligence , quantum mechanics
SUMMARY To reach the 0·2 nm point‐to‐point resolution possible with some high voltage electron microscopes, the astigmatism of the objective lens must be compensated to within 5 nm. Due to a number of factors the resolution of the image seen on the viewing screen of the high voltage microscope is, however, quite poor and does not permit compensation of such accuracy. We describe a technique for evaluating and correcting the astigmatism that starts from a recorded micrograph of a thin amorphous specimen. The astigmatism is determined from the optical diffraction pattern using a variation of the Thon method. This variation avoids any direct measurement of the radii of the contrast transfer zones, and is extremely rapid and convenient. Adjusting the stigmator coil currents, calibrated in terms of their stigmating power, for zero astigmatism completes the correction in less than 10 min after the recording of the micrograph.