| 摘要 |
<p>PURPOSE:To prevent picture quality from being deteriorated due to the generation of moire by correcting a change in a duty ratio resultantly generated due to the delay of a signal and adjusting the duty ratio of an undelayed signal. CONSTITUTION:A detecting circuit 33 detects the average duty ratio of a signal outputted from a buffer amplifier 6. A differential amplifier 34 computes a difference between the output of the circuit 33 and a reference level outputted from a reference level generator 35 and outputs the computed result to a comparator 32 to correct a change in the duty ratio of a variable delay circuit 5. Namely, the comparator 32, the variable delay circuit 5, the buffer amplifier 6, the detecting circuit 33, and the difference amplifier 34 constitute a negative feedback servo circuit for holding the duty ratio on a fixed value. If the duty ratio is shifted from 50%, moire is generated and picture quality is deteriorated. However, the fixed duty ratio held by the negative feedback servo circuit makes it possible to prevent the generation of moire.</p> |
