| 摘要 |
PURPOSE:To raise the SN ratio of picture as well as obtain a long-term stable field radiation current by providing the scale factor-changing means of picture and the current cotrol means of electron rays from electron gun by interlocking it with scale factor. CONSTITUTION:The electron rays 7 radiated from the field-radiation type electron guns 2, 1, 4, and 6 under the control of the high-tension power source 21 is focused at the focusing lens 16 and the object lens 17 and then irradiated as electron ray spot. The electron rays are deflected by the deflecting coils 18a and 18b provided on the way of the lens system, and also the deflecting angle, or scale factor, of the electron rays is controlled by the deflection power source 24. Then, the scale factor condition from the deflection power source 24 and the lens focusing condition from the lens power sources 22 and 25 are introduced into the radiation current control power source 23 by which the high-tension power source 21 is driven to control field radiation current. Thus, the life of the electron gun can be lengthened and optimum SN ratio can be obtained. |
