ELECTRON MICROSCOPE

PURPOSE:To make it possible to perform automatic control and aberration compensation of an electron lens even if the position of a virtual electron source is changed by performing focussing control of the electron lens and aberration compensation control in response to changes in acceleration voltage V0 of an electron gun and voltage V1 extracting electrons. CONSTITUTION:Relation between the position of an electron source corresponding to any change in voltage V0, V1 and distance S from said position to an anode 3 is calculated by a high voltage control circuit 18, and a signal corresponding to the distance S is sent out from the same circuit. By receiving this signal. a lens 4's focal distance fc and an exciting current Ic are calculated by a control circuit 19, and the lens 4 is controlled by sending a signal of Ic value to a lens power supply 14. And, by getting A0 from Bc value determined by an operator, f0, Io of an objective lens 6 are calculated by using these values, and the lens 6 is controlled by sending the output signal to an objective lens power supply 16. And, by measuring an astigmatism and an aberration compensate current value at each focal distance of each lens and by storing them in compensate power supplies 15, 17, and by calling a memorized compensate current by tc, t0 which are given from the control circuits 18, 19 and an electric current is forced to flow through a compensate coil from the power supplies 15, 17.