rotation-free image

"Rotation-free image" means an image that does not rotate even when the magnification is changed. To prevent both inconvenience caused by the change of an observation position and disappearance of the orientation relationship between the diffraction pattern (magnification: zero) and the corresponding image, an image rotation created by the first two-parts of the intermediate lens are corrected by the final-part of the intermediate lens, so that the image rotation is eliminated or minimized. When the excitation of the third- (final-) part is changed, the magnification is also changed. Thus, it is necessary to change the excitation of the second part of the lens. Combinations of appropriate excitation of each part in obtaining a rotation-free image are available in tables.

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