| 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 by converting its magnitude into a counter count value. 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 vertical error from the center position. This signal ER is compared by the comparator through control circuit 16 and its output is converted into the count value of the up-down counter to change a deflection bias. Then frequency in inversion (m) of signal ER inverted when passing by the center position is measured and when frequency (m) reaches a prescribed value, the control loop is considered to be concentrated. |
