| 摘要 |
PURPOSE:To stabilize a tracking device in level by sampling an envelope signal produced from a reproduction signal with a sampling pulse produced from a horizontal synchronizing signal and producing an error signal to give tracking to a reproduction head. CONSTITUTION:The detection signal fed from a reproduction head 1 is amplified by a preamplifier 2, and one of both signals is supplied to a BPF3 with the other signal applied to a frequency demodulator 5 respectively. The reproduction output signal fed from the head 1 receives the variance in amplitude level, and the envelope signal fed from an envelope detecting circuit 4 is supplied to a control circuit 8. While the signal of the demodulator 5 is supplied to a horizontal synchronizing signal separating circuit 6. The pulses phi1 and phi2 are obtained by a sampling pulse producing circuit 7 and supplied to the circuit 8. The circuit 8 samples and holds the envelope signals of the positions of horizontal synchronizing signals b1 and b1' synchronously with pulses phi1 and phi2 and compares the amplitude values of these envelope signals. Then a control signal is supplied to a piezoelectric element drive circuit 9 so that the head 1 is moved in the direction where the level of the envelope signal is increased. Thus it is possible to obtain a tracking error signal at a stable level and high S/N. |
