| 摘要 |
PURPOSE:To make an electro-optical body tube smaller in size as well as to facilitate adjustment of an electron beam by forming a reduced image of a beam shaping aperture on a specimen by means of the objective lens as well as by forming an enlarged image of the cross-over produced by the electron gun on the main surface of the objective lens. CONSTITUTION:Electrons emitted from the electron gun which consists of the cathode 1a, Wehnelt cylinder 1b, and anode 1c made of lanthanumhexaboride are converged by a condenser 3 with magnetic poles 3a through alignment coils for condenser 2. The converged beam shoots through a beam shaping aperture 4 to irradiate a specimen 9 for projection by means of the objective lens 8 through blanking deflection plates 5, alignment coils for objective lens 6, and X-axis and Y-axis scanning deflection plates 7a, 7b. In this setup, by means of the condenser 3, a reduced image of the aperture 4 can be formed on the specimen 9 as well as an enlarged image of the cross-over produced by the electron gun 1 can be formed on the aperture surface of the lens 8. |
