無回転像

rotation-free image

[目次：レンズ系]

倍率を変えても像が回転していかない像のこと。像の回転によって、観察したい場所が動き観察に不便なことと回折図形（倍率ゼロ）と像との方位関係がなくなることの両方を防ぐために、像の回転がないようにあるいは最小になるように3段中間レンズ系の最終段のレンズによって、上の2段で作られる像の回転を補正する。3段目の励磁を変えると倍率も変わるので、2段目の励磁も変える必要が生じる。適正な励磁の組み合わせがテーブル化されている。

"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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