| 摘要 |
PURPOSE:To prevent any decrease in the visual field which might be caused by a movable diaphragm and produce high contrast images by enabling an electron ray flux to be focused upon the movable diaphragm even when the excitation of a focusing lens is changed by enabling the excitation of an objective or an intermediate lens to be varied within a given range. CONSTITUTION:When a focusing lens 1 is strongly excited and the cross over point of an electron microscope is adjusted to be point (A) in the figure, an electron ray flux 3 extends over the surface of a sample 5. The electron ray flux 3 is then focused upon a movable diaphragm 6 by a weakly excited objective 4. In contrast, when the focusing lens 1 is more weakly excited than above and the cross over point is adjusted to be point (B), an electron ray flux 5 extends within a smaller area than above on the surface of the sample 5 (the area surrounded by a dotted line). The electron ray flux 7 is then focused upon the movable diaphragm 6 by the objective 4 which is excited in a degree different from above. |
