| 摘要 |
PURPOSE:To reduce beam spot diameter by providing at least one focusing electrode between the third focusing electrode of a primary lens and its final electrode and applying intermediate and high potential between the potentials of the third focusing electrode and final electrode. CONSTITUTION:An electron gun is comprised with a tetrode section 56 consisting of a cathode 9, a first grid 12, and a second grid 13 and a primary lens section 57 consisting of third to seventh grids 14-18. In addition, relatively low potential is applied to the third grid 14 and high potential is appied to the fourth grid 15. Low potential is applied to the fifth grid 16 and high potential is applied to the seventh grid 18 and the intermediate and high potential between the potentials of the fifth grid 16 and the seventh grid 18 is applied. As a result, the beam spot diameter focused on a screen can be reduced by using a focusing electrode that makes the beam incident on the primary lens section 57 from the tetrode section 56 set in the best quality state. |
