| 摘要 |
PURPOSE:To perform servo controlling of playback heads with high accuracy and high stability by passing the signal showing the envelope of reproduction outputs through a limiter and phase comparing the same with alternating signals and supplying the compared output thereof to an electro-mechanical transducer. CONSTITUTION:The FM signal Sf from a switch circuit 3 is supplied to an envelope detection circuit 24, whereby it is made to the detection signal Sd showing the level of the signal Sf. After the higher harmonic components thereof are removed with a trap circuit 25, the signal is passed through a limiter 26, from where it is applied to a phase comparator 27 and at the same time alternating signals So are applied from an oscillation circuit 21. The compared output thereof is then supplied to an LPF 28, whereby the output signal Eomega is obtained. This signal is applied to a bimorph plate 1 through adder 22 and cmplifier 23. The polarities and bveles of the signal Eomega hange in square waveform in the mean center spacing of the heads 1A, 1B and track 9, in correspondence to which the bimorph plate 11 shifts. Thereby, the plabyack heads may be servo-controlled with high accuracy and high stability. |
