| 摘要 |
PURPOSE:To improve focussing characteristics by making an opposed electrode which forms the principal focussing lens of a collective three-electron gun consisting of thick and thin porous plate-type members with beam pass holes and the members which support them. CONSTITUTION:The opposed electrode elements of the third and fourth grids 44 and 45 which form the principal focussing lens of a collective three-electron gun 38 consist of the first members 442a and 45a and the second members 442b and 45b. The first members are formed it long cylindrical members consisting of a flange section 55, side wall section 56, and implantation section and a thick porous plate- type member 442b (second member) with beam pass holes 52, 53, and 54 is mounted on its flange section 55 of a thickness of l. This enables punching of the second member and improvement of the roundness of the beam pass holes. As a result, the effective length l of the electron gun lens is increased and its focussing characteristics are improved. |
