| 摘要 |
PURPOSE:To minimize the number of condenser lenses, hold its magnifying power of a desired value with good accuracy, simplify its construction, facilitate its adjustment, and stabilize a beam by providing at least one of the condenser lenses that magnify electron gun crossover morably in the direction perpendicular to the principal plane of the lens. CONSTITUTION:A deflector 50 performs a deflection for the purpose of varying the dimensions and shape of an electron beam and a deflector 60 restores a deflected beam. Aperture masks 30 and 40 and the deflectors 50 and 60 variably control the dimensions and shape of the electron beam and the variably controlled electron beam is radiated on a sample and then the sample is exposed. Pole pieces 24 and 24b and spacer 25 are energized upward by the pressing of a spring 26 and are moved vertically by the screwing of an adjusting screw 27. As a result, the distance between electron gun crossover P and the principal plane Q of a lens can be varied. |
