| 摘要 |
PURPOSE:To eliminate the compasation of the astigmatism or to ease the compensation by feeding a compensation signal to compensate the specific astigmatism where the compensation signal is stored in memory means previously. CONSTITUTION:An electron beam 3 from an electron gun 1 is focused with a condenser lens 4, and projected on a sample 7. The electron beam passes through the sample 7, is focused and enlarged with an object lens 5 and a projecting lens 6, and an image is formed on a fluorescent plate 12. An astigmatism compensation coil 8 provided near the condenser lens 4 and astigmatism compensation coil 10 provided near the object lens 5 are excited with a compensation current fed from the astigmatism compensation power sources 9, 11 which are connected to the coils 8, 10. The compensation current is manually variable through adjusting a vabiable resistance 15 which is connected to the compensation power source 9, and another compensation current is also manufally variable through adjusting a variable resistance 16 which is connected to the compensation power source 11. The compensation current is also set with a value previously stored in a preset circuit 14 which is connected to both power sources 9, 10. |
