| 摘要 |
PROBLEM TO BE SOLVED: To provide an image having excellent S/N ratio by providing a mechanism for adjusting the positional relation of an electron source and throttle so as to obtain the maximum ratio of the mean current capacity in relation to the fluctuation of the passing electron with a diaphragm for passing the only specified angle component of the electron extracted from an electron source. SOLUTION: A diaphragm 5 passes the only specified angle component of the electron beam 6 extracted from an electron source 1 by a extraction electrode 2 through a center hole, and a scanning deflecting unit 8 scans the passed angle component of the electron beam 6 on the basis of the signal from a scanning signal generating unit 13. The electron beam 6 is converged to a sample 10 by an objective lens 7, and the reflected electron is detected by a detecting unit 9 as the electronic signal, and displayed as an image in an image display device 12. An image SN measuring device 11 outputs the fluctuation/mean current of the electric signal, and an axis adjusting mechanism 4 moves position of the electron source 1 for adjustment. With this structure, a component of the emitted electron having a large current density and capable of restricting the fluctuation thereof is aligned at the center of the diaphragm so as to obtain an image of high quality.
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