PURPOSE: To enable optimum correction of astigmatism to be achieved according to correction values by installing two astigmatism correctors with different directions and controlling one of the correctors while the other one is maintained at a constant value to obtain one of the correction values and then controlling the latter one while the former one is maintained at a constant value to obtain the other correction value.
CONSTITUTION: An astigmatism correcting device consisting of installed correctors 8A and 8B with different directions, is installed in the path of a microprobe 3 for a scanning electron microscope or a similar device. First, while the corrector 8A is maintained at a constant value, the corrector 8B is used to obtain a first correction value with which the probe diameter is minimized and then the first correction value is stored in a memory circuit 18A. Next, while the corrector 8B is maintained at a constant value, the corrector 8A is used to obtain a second correction value with which the probe diameter is minimized and then the second correction value is stored in a memory circuit 18B. After that, the first and the second correction values are combined by a computing circuit 19 before being used to control the correctors 8A and 8B through a controller 17. Therefore, optimum correction of the astigmatism can be achieved in a short time and the correction can be automatically performed.
ICHIHASHI MIKIO
FUKUHARA SATORU
KIYOFUJI SHIGEMITSU
TODOKORO HIDEO
