| 摘要 |
PURPOSE:To prevent generation of blooming by turning on a diode through the detection of the increase in a beam current to actuate a feedback circuit thereby applying gamma correction. CONSTITUTION:The beam current flows from a collector of a PNP transistor (TR)3 to the ground through a series resistors comprising resistors 7, 8, and 5. A voltage across the resistor 5 is led to a controller 6 as a beam current detection output. The controller 6 controls the DC level and the amplification factor of a video amplifier 1. When the beam current is increased, the diode 10 is first turned on because of the voltage drop of the resistors 7, 8 and 5, the resistor 9 increases the emitter voltage of a TR2 and negative feedback is applied thereby preventing blooming. When the beam current increases further, the diode 12 is turned on also and the gamma correcting function is attained to suppress the beam current further. |
