| 摘要 |
A condenser means for focusing an electron beam onto a specimen and a scanning means for scanning the beam in two dimensions on the specimen placed inside a specimen chamber are disposed inside an electron beam column. The top portion of the specimem chamber is connected with the column by an annular member of a high magnetic permeability which surrounds the column. Magnetic flux passed through the top wall of the chamber is made to penetrate the annular member of a high magnetic permeability. The flux is then caused to enter the portion of the upper wall remote from the column, after which the flux leaks out. Thus, leakage of the magnetic flux into the specimem chamber is prevented.
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