| 摘要 |
PURPOSE: An electron gun for a beam index type cathode ray tube is provided to achieve improved vertical resolution of screen by minimizing changes of diameter of vertical beam with respect to each part of the screen. CONSTITUTION: An electron gun(4) comprises a cathode(K) for emitting thermal electrons; the first grid electrode(G1) and the second grid electrode(G2) for controlling emission of thermal electrons; a plurality of third grid electrodes(G3-1,G3-2,G3-3) constituted by a plurality of electrodes which are electrically separated, wherein at least one of electrodes is provided with a variable focus voltage and focuses the thermal electrons to an electron beam; the fourth grid electrode(G4) provided with an anode voltage, and which focuses the electron beam to a phosphor screen; and a support for aligning the cathode and grids. The cathode and the first and second grids constitute a triode unit, and the electrodes of the triode unit and one of the third grid electrodes opposed to the triode unit are provided with a static voltage, to thereby allow the triode unit to maintain its electric field constant.
|
