| 摘要 |
PURPOSE:To correct a display error of an electron beam detector due to the reduction of an irradiation range of an electron beam, by changing the amplification degree of a circuit, that amplifies an output of the electron beam detector, in an interlocking action to the change of the irradiation range of the electron beam on a fluorescent plate. CONSTITUTION:When the magnification for obtaining a smaller area of irradiation of an electron beam is selected by a magnification selector switch 5, a solenoid relay 6a is operated to connect a resistor 10 and apply a resistance Ri2 in parallel to a resistance Ri1. Accordingly an input to an amplifier 3 is increased to increase the display value of a quantity of electron beams. When further changed the magnification, the magnification selector switch 5 is connected to the next terminal to actuate the other solenoid relay 6b, connect a resistor 9 further apply a resistance Ri3 in parallel. In this way, an adequate quantity of electron beams per unit area is displayed on a display panel 4. |
