| 摘要 |
PURPOSE:To reduce spherical aberration further by mechanically integrating the third grid and the fifth grid mutually and supporting the fourth grid through a window section using an insulating support rod in such a condition that the large diameter section of the fourth grid is arranged inside the fifth grid. CONSTITUTION:The fifth grid G5 and the third grid G3 are integrated mechanically and the fifth grid G5 is simultaneously retained by the support of the third grid G3 onto an insulating support rod without being supported by the insulating support rod 4 of the fifth grid 5. Besides, the fourth grid G4 is supported by the linear insulating support rod 4 through the window section 3 of the extended section 2 of the fifth grid together with the third, second, and first grids G3, G2, and G1. For this reason, the distance between the outside surfaces of the both opposed insulating support rods 4 can be made smaller than the diameter D3 of the fifth grid G5. As a result, the diameter D3 of the fifth grid G5 can be increased until the diameter sufficiently approaches the inner diameter D4 of a neck section 6 and the spherical aberration of the main electronic lens can be reduced. |
