| 摘要 |
PURPOSE:To perform a high-SN and efficient measurement with high precision for a long time, by obtaining a position to be measured of a sample on a basis of the difference between a reference voltage and an applied voltage set to an analyzing grid so that the detection signal level of an electron detector coincides with a reference detection signal level. CONSTITUTION:In the reference state where a sample is in a known potential state or a specific phase state, a proper voltage is applied to an analyzing grid 12 from a grid voltage generator 20, and a power source 22 is set the voltage value similarly. In this state, when a reference voltage controller 18 adjusts a reference voltage generator so that the output of an analog comparator 16 is zero. That is, the output of the reference voltage generator 15 coincides with a detected secondary electron signal value amplified by an amplifier 14. A changeover switch 17 is connected to a contact S2; and when the detected secondary electron signal value amplified by an output amplifier 14 of the analog comparator 16 coincides with the output of the reference voltage generator 15, the output of a differentiator 21 indicates the potential difference of the sample 2 from the reference state. |
