| 摘要 |
PROBLEM TO BE SOLVED: To align the position of an objective lens with that of a diaphragm of the objective lens so as to mostly stop an electron beam even when the acceleration of the electron beam is low. SOLUTION: The correction current in X-direction and the correction current in Y-direction in a condition where an electron beam is most stopped are stored in a memory 24 together with a condition of the acceleration voltage of the electronic beam. After the writing of the necessary data in the memory 24 is completed, when the acceleration voltage of an electron gun 11 is changed, the value of the correction current to an alignment coil 21 is set to be zero, the position of an objective lens stop 19 is regulated based on the wobbler action, and the correction current is read from the memory 24 according to the acceleration voltage, based on the signal from an acceleration voltage power supply 12. An image can be observed under the condition where the electron beam is most stopped by supplying the correction current to the alignment coil 21.
|
