| 摘要 |
PURPOSE:To make optical axis alignment between an optical axis and the restriction center of an aperture member ever so easy and accurate, by installing an auxiliary aperture member in space between a charged beam source and the aperture member. CONSTITUTION:Charged beams 2 out of a source 1 is passed through one of restrictions 4a-4c of an aperture member 5 being made shiftable in a horizontal direction, irradiated to a sample 8 by way of a focusing lens 6 and a deflecting system 7, displaying the scanning secondary electron image on a display 11. At this time, an auxiliary aperture member 51 provided with an auxiliary restriction 41 made smaller in diameter than a minimum restriction of the aperture member 5 is set up in space between the source 1 and the aperture member 5. And, this auxiliary aperture 51 is moved to an application position (a) by a driving device 13, and optical axis alignment between an optical axis and a restriction 4 of the aperture 5 is carried out. Therefore, the optical axis alignment is accurately performable at constant accuracy irrespective of an opening diameter of the restriction 4.
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