| 摘要 |
PURPOSE:To correct the sag of a video signal by generating a correction signal, which varies in level following up the luminance level of the video signal, synchronously with the scanning of the video signal. CONSTITUTION:A signal with a luminance level from a video device is applied to the inverted input terminal of an amplifier 12 to perform integrating operation with a capacitor 13, and is reset by a switch 14 at a constant period which corresponds to an unblanking pulse. A signal A of an inverted-saw-tooth wave obtained by integrating the luminance-level signal is added by an adding circuit 3 to the output signal B of a saw-tooth wave generating circuit 2 to generate an output signal C, which is supplied to and compared by a trailing comparator 4 with a video signal, thereby generating a PWM signal. This PWM signal turns on an LED5 to form an infrared-ray video screen through a scanning mirror 6. Thus, a sag phenomenon based upon a decrease in gain in the low frequency range of infrared rays is corrected. |
