| 摘要 |
PURPOSE:To make a beam diametral characteristic selectable in a state of being desired as well as to simplify the changeover control of a diaphragm aperture, by securing a large aperture diaphragm upon rigid positional adjustment, while making a small aperture diaphragm free of going in and out at will. CONSTITUTION:Requirements for making an objective diaphragm turn to a small aperture is the case alone that one wants to secure the high resolution image of a sample surface by the secondary electron emitted out of a sample, in general so that positional slippage in the objective diaphragm toward an optical axis is inconsiderable indeed. Therefore, although positional adjustment in case of using the small aperture diaphragm is required, it is enough to merely use a positioning stopper at the most. A large aperture objective diaphragm B is secured upon rigid positional adjustment in time of assembling a beam irradiator for charged particle. A small aperture objective diaphragm B2 is made to be free of going in and out in a direction at a right angle to the optical axis and can be controlled from the outside of a vacuum device's wall and its positioning in time of application takes place in a way of hitting the stopper. For your information, the small aperture diaphragm B2 may be situated at the lower side of the large aperture diaphragm B, if necessary, but the nearer to an objective lens L2 the smaller in the influence of positional errors. |
