摘要 |
PURPOSE:To adjust the position of an objective diaphragm in a short time responding to the secondary electron picture for the edge section of a sample by providing a means that syncyronizes with a line scanning signal and generates a determined minute change of timing. CONSTITUTION:A sample 4 is irradiated with an electron beam whose focal point is matched by an objective lens 3 and is scanned by a deflector 1. In addition, the secondary electron 7 emitted from the sample 4 is detected by a secondary electron detector 8 and the output signal is displayed on a display unit 9. A scanning generator 10 is connected to the deflector 1 and an oscillator 11 which generates an oscillation output signal by being triggered by a line scanning signal generated from the scanning generator is connected to a line scanning signal output. Furthermore, the output signal of the oscillator 11 is added to the objective lens current from a lens current supply source 12 in an adder 13 and is supplied to an objective lens 3. |