| 摘要 |
PURPOSE:To simplify the constitution of a disk record reproducer and to prevent a malfunction due to a drop-out, etc. by using two level comparators to produce a focus OK signal and a tracking error signal. CONSTITUTION:The frequency signals of terminals 21 and 22 are set lower than the reference voltage VREF due to a drop-out, etc. between time points T3 and T4 as shown by a figure (a) while a focus OK signal is delivered. Then the outputs of level comparators 44 and 45 and the output of an NOT circuit 58 are shown by figures (b) and (c) respectively. As a result, a timing control circuit 58 is going to be reset to H. In this case, however, the output of the circuit 58 is not reset immediately to H but reset after a prescribed period of time. Therefore the output of the circuit 58 is kept at L as long as the drop-out period is short. Then the focus OK signal is kept at L and H as shown in figures (d) and (f), and a servo state is maintained. While a tracking error is produced from a phase comparator circuit 43. In addition, the noises of comparators 44 and 45 are masked even though the drop-out period is long and noises are mixed during the drop-out period. |
