| 摘要 |
PURPOSE:To provide possibility of locating a motive surface or an image surface lens outside by designing the optical axis side radius-of-curvature of the low- voltage side electrode of at least either of a decelerative and an accelerative lens with a specific relationship to the interelectrode distance, furnishing a protrusion at the end on the optical axis side, and thereby quickening damping of the electric field inside the electrodes. CONSTITUTION:Electron beam which has penetrated a specimen is cast onto a filter through a decelerative lens, and the emitted electron beam from this filter is sensed by an electron beam device with the aid of an accelerative lens. The optical axis side radius-of-curvature R of the low-voltage side electrode of at least either of these decelerative and accelerative lenses of this electron beam device shall be related to the interelectrode distance as 0.2<=R<=0.7L. Provision of a protrusion 23 at the end on the optical axis side quickens damping of the electric field, to enable location of the motive surface or image surface lens outside, that should facilitate construction of electron beam device.
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