| 摘要 |
An electron beam emitted from an electron gun (G) forms a reduced image on a sample (S) through a non-dispersion Wien-filter (5-1), an electromagnetic deflector (11-1), a beam separator (12-1), and a tablet lens (17-1) as an objective lens. The beam separator (12-1) is configured such that a distance by which a secondary electron beam passes through the beam separator is approximately three times longer than a distance by which a primary electron beam passes through the beam separator. Therefore, even if a magnetic field in the beam separator is set to deflect the primary electron beam by a small angle equal to or less than approximately 10 degrees, the secondary electron beam can be deflected by approximately 30 degrees, so that the primary and secondary electron beams are sufficiently separated. Also, since the primary electron beam is deflected by a small angle, less aberration occurs in the primary electron beam. Accordingly, since a light path length of a primary electro-optical system, it is possible to reduce the influence of space charge and the occurrence of deflection aberration.
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