| 摘要 |
PROBLEM TO BE SOLVED: To provide a secondary charged particle image projection device having a small distortion aberration in the wide-field observation even when existing an ExB as a beam separator. SOLUTION: In this device, a prestage image projection optical system is constituted making a group of two prestage lenses 3 and 4 as a center and these lenses 3 and 4 constitute a telecentric system on both sides. Thereby, as shown in a solid line, a main light ray becomes parallel to the optical axis in the first prestage lens 3 and does not become divergent, thus incident on a point near the optical axis of a projection lens 7 compared with a conventional technique. Therefore, even when under the wide-field and low magnification, a bobbin-like distortion aberration is suppressed from generating and the light ray to be used is close to the paraxial ray so that other aberrations can be suppressed smaller.
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