| 摘要 |
PURPOSE:To prevent blooming without giving adverse effect on parts other than the high luminance part, by detecting only a signal of the high luminance part having a prescribed level or over among luminance signals and controlling the grid of a cathode ray tube with the detected output signal. CONSTITUTION:In setting a voltage applied to the base of a transistor (TR) 10 with variable resistor 14 so as to bring it to a level a little smaller than the level where the blooming starts, the TR10 is conductive when a luminance signal A is at a high luminance part exceeding this level toward the white level, and a detected output signal is produced in the collector. In taking the detected output signal B as a negative signal and applying it to the 1st grid of a color cathode ray tube 1, the beam current is suppressed when the detected output signal B is produced. When the beam current C is excessive, the blooming takes place, but the level is limited by suppressing the beam current of the high luminance part with the detected output signal B in this way, allowing to display excellent picture without blooming. |
