| 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, second member 442b and 45b, and third memebers 442c and 45c. The first members are formed in long cylindrical members consisting of a flange section 631, side wall section 632, and implantation section 633. A thin porous plate-type member 442b (second member) with beam pass holes 521, 531, and 541 and a thick porous plate-type member (third member) are mounted on its flange section 631. This enables punching of the third member and improvement of the roundness of the beam pass holes. As a result, the effective length of the electron gun lens is increased and its focussing characteristics are improved. |
