| 摘要 |
PURPOSE:To vary the deflection fulcrum position and enable use under the minimum conditions of various types of aberration in a wide focal length range by varying the ratio of the deflection of a two-stage deflection coil depending on the excitation intensity of the final step convergent lens. CONSTITUTION:First and second state deflection coils 1 and 2 are driven by separate deflection amplifiers 3 and 4. Deflection signals are applied to the deflection amplifier 3 through a magnification switching circuit 6 and a variable gain width circuit 5 is inserted between the deflection amplifier 4 and magnification switching circuit 6. A final step convergent lens 10 is excited by a lens power supply 7 and the excitation current value can be varied by a focal point coarse adjustment switch 8 and a focal point fine adjustment potentiometer 9. The gain of the variable gain amplifier 5 is switched by a switch 8' that is switched interlocking with the focal point coarse adjustment switch 8 and the output current ratio I2/I1 of the deflection amplifier is varied interlocking with the exciation current value of the final step convergent lens, that is, the focal point. |
