| 摘要 |
PURPOSE:To improve the focusing peformance by comprising an electrode element that forms principal electron len with a plate in which larger diameter beam passing holes are perforated and a cylindrical member that is made to adhere to the plate. CONSTITUTION:The third grid 5 of an electron gun 1 consists of an elemen 51 at a second grid 4 side and an element 52 on a fourth grid 6 side and the element 52 consits of first members 5a and 5b and independent three cylindrical members 5c. The members 5a and 5b allow larger diameter electron beam passing holes 10, 11 and 12 to be perforated in a plate-type metal sheet 9 with a preset thickness l. As a result of this structure, the diameter of a principal electron lens can be increased and the focusing performance can be improved. |
