| 摘要 |
PURPOSE:To reduce the distortion of a spot, which is caused by coma, by displacing the axes of the apertures, through which the outer electron beams pass, of electrodes constituting the main lens of an electron gun, from the axes of the initial passage of the outer electron beams toward a central electron beam. CONSTITUTION:An electron gun comprises a cathode 6 and the like for generating a plurality of electron beams, electrodes 9, 10 for directing the beams in parallel with each other, and electrodes 11, 12, 13 constituting a main lens. Each axis 15 of the outer apertures of the electrodes 9, 10, 11 is displaced from that 21 of the outer apertures of the main lens having the electrodes 11, 12 at a distance from each other, opposite the axis of the electrodes 16. The cylindrical tip portions projecting into the inside of each electrode the outer apertures of the electrodes 11, 12 are inclined to the axis 21. The outer electron beams are caused to pass near the centers of the main lenses. As a result, electrostatic convergence operation is facilitated and the distortion of a spot is reduced.
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