| 摘要 |
PURPOSE:To enable extremely accurate centering by obtaining a relative error signal of a picture center position from the output signal of each image pickup tube and perform positioning on the basis of the signal. CONSTITUTION:For positioning on the basis of green image pickup tube 1, video output G' is passed through delay lines 4 and 11 to obtain main line signal G0 and also supplied to differential amplifier 6 via delay lines 4 and 5 to output edge signal EDG. Either one of video outputs R0 and B0 is supplied to differential amplifier 15 together with signal G0 to obtain position-shift signal REG. This signal EDG and signal REG are supplied to multiplier 9 for multiplication to generate signal ER of a horizontal error from the center position. The mean voltage of signal ER in the gate section of gate circuit 13 by gate signal SG obtained by supplying the edge signal to gate signal generating circuit 10 is held at capacitor C4 to obtain sampleheld signal SH that corresponds to signal ER. The substantially total time of sampling pulses is measured and when it is less than a specified value, a frequency in sampling is considered to be insufficient, thereby stopping operation. |
