| 摘要 |
An electron gun has five grids (G1, G2, G3, G4, G5), and an additional grid (G2s) is disposed between the second grid and the third grid (G3) and is impressed with a potential lower than that of the second grid (G2), and a trimming electrode (G5a) with a trimming aperture 14 is provided in the fifth grid (G5), and by trimming the outer shell part of the electron beam having crossed the electron gun axis twice a very small beam spot is produced. |
