| 摘要 |
PURPOSE:To improve the luminance, the contrast and the resolution of a picture tube by adjusting the shape of an electron beam spot irradiated on the front panel after being discharged from an electron gun to be nearly square. CONSTITUTION:A first grid 16 is installed in front of a cathode 7 apart from it. It is provided with a nearly square electron-beam-passing hole 17 which has nearly arc angles and is almost concentric with the electron-discharging surface of the cathode 7. A second grid 18 is installed in front of the first grid 16 apart from it on the opposite side to the cathode 7. It is provided with an electron- beam-passing hole 19 having almost the same shape as the hole 17 in such a manner that the hole 19 is concentric with the hole 17 and that the sides of the hole 19 are respectively parallel to those of the hole 17. When the electric potential of the first grid 16 is made the same or negative and that of the second grid 18 is made positive to the cathode 7, the electric potential of the second grid 18 can form a positive electric field over the electron-discharging surface of the cathode 7. As a result, an electron beam 20 having a nearly square cross section, becomes incident upon a main lens after forming a single cross-over point. |
