| 摘要 |
PURPOSE:To prevent the change of a visual field scanning direction by a method wherein a main deflecter which operates visual field scanning is positioned closer to the specimen than the magnetic focused flux made by a dynamic focus coil and at the same position as the magnetic focused flux made by an object lens or closer to an electron gun than said focused flux. CONSTITUTION:A crossover made by an electron gun 1 is converged by a condensor lens 2 and an object lens 3 and radiated and focused on a target 4. A dynamic focus coil 5 is provided above the object lens 3 to adjust the focus of the electron beam with a high speed and deflecters 6, 7 are provided inside the object lens 3 to scan the electron beam to x-direction and y-direction on the target 4. The main deflecters 6, 7 which operate visual field scanning are provided to approximately the same position as the magnetic focused flux made by the object lens 3 and closer to the specimen than the magnetic focused flux made by the dynamic focus coil 5. With this constitution, the direction of the deflection given by the deflecters 6, 7 is not changed even if the adjustment of the focus is made by changing the exciting current of the coil 5. |
