| 摘要 |
PURPOSE:To make an electro-optical body tube smaller in size as well as to facilitate adjustment of lenses and beam current by mechanically sliding a beam shaping aperature for electron beam projectors or the like along the direction of electron beam movement in order to vary the distance between the aperture and the cross-over produced by the electron gun for proper control. CONSTITUTION:Electrons emitted from the electron gun 1 which consists of the cathode 1a, Wehnelt cylinder 1b, and anode 1c made of lanthanumhexaboride irradiates a specimen 4 for projection by means of the objective lens 3 through the beam shaping aperture 2 by which an enlarged image of the cross-over produced by the electron gun can be formed on the main surface of the lens 3. Simultaneously, a reduced image of the aperture 2 can be formed on the specimet 4 by the lens 3. In such a setup, current density on the specimen 4 is detected by an electronic detector or the like to send detected information to a control system 5 so that a drive system 6 is operated by commands from the control system to move the aperture 2 up and down. |
