| 摘要 |
PURPOSE:To improve the focus characteristic by providing two facing gaps of magnetic yoke while reversing the directions of the focus field in each gap. CONSTITUTION:Electron guns 1, 2, 3 are arranged in a neck section 4 while magnetic yokes 11, 12, 13 are arranged while facing each other with predetermined interval on the same axis to form two facing gap sections at the back stage. While two pairs of cylindrical permanent magnets 5a, 5b magnetized in axial direction are arranged on the outer-circumferential face of the nack section 4 that circular magnetic members 14a, 14b, 14c will be held between them thus to contact the same poles each other. Consequently the focusing field is produced between the magnetic chips 11 and 12a in reverse direction from the advancing direction of the beam while the focusing field in the advancing direction is produced between the magnetic chips 12b and 13 to form two pairs of magnetic field lenses resulting in the considerable improvement of the focus characteristic. |
