| 摘要 |
PURPOSE:To decrease scars on a sample due to electrons by changing bias voltages, which control the amount of electrons at the time of photographing, so as to interlock with means for a changeover of photographed positions so that the amount of electrons on the sample surface is controlled. CONSTITUTION:When voltages suitable for observation and focusing are supplied from reference voltages to respective systems by means of a changeover switch 13, lenses 4 and 5 and deflecting coils 6 are excited via controlling circuits 11. Brightness is determined by a wehnelt 2 to which a bias voltage is supplied from a bias voltage circuit 14. Photographed positions are changed by the deflecting coils 6. When a changeover operation of the switch 13 is performed at the time of photographing, bias voltages suitable for the photographing are applied to the wehnelt 2 in advance via a controlling circuit 17 and a biasing voltage circuit 14 by the use of a reference voltage circuit 17.
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