| 摘要 |
PURPOSE:To facilitate the limited field diaphragm image without requiring the skill, by providing a deflection system for varying the incident direction periodically under the state where the electron beam is fixed to the limited field diaphragm hole. CONSTITUTION:A limited field diaphragm 13 is arranged between an objective lens 6 and an intermediate lens 7 while two step deflection coils 14, 15 are arranged between a focus lens 4 and a specimen 5, where the sweeping current is supplied from a power source 16 through an exchange switch 17 to the first step deflection coil 14 while the sweep current is supplied from the power source 16 through an exchange switch 18 and a resistor 19 to the deflection coil 15. The exchange switches 17, 18 are interlocked and also interlocked with another switch 11. It is also constructed such that the deflection angle of the deflection coil 15 is larger than that of the deflection coil 14 where the deflecting direction is reversed. Consequently the limited field refraction image corresponding accurately with the field limited by the limited field diaphragm can be obtained. |
