| 摘要 |
<p>PURPOSE:To obtain stable reproducing video signals by adding a reproducing envelope detection circuit to the conventional basic constitution of automatic tracking control and calculating a tracking shift amount corresponding to a detection gain. CONSTITUTION:During a conventional lower edge detection operation, the sampling time of a reproducing envelope level S1k is determined with the input of S1b as a reference in a detection part 111 and sampling is performed at the voltage level of the S1k. An obtained envelope detection level Ev1 is stored. Then, at the point TR1 of the time of detecting lower edge detection conditions, the detection part 111 samples the S1k and stores the envelope detection level Ev2. The detection gain Ga=Ev1-Ev2 of a reproducing envelope detection circuit 109 in use is calculated and converted into a DC voltage signal and the signal S1n is sent to an automatic tracking processing part 107. The tracking shift amount is determined corresponding to the voltage level of the signal S1n, a shift direction is changed, shifting is performed and a final tracking convergence position is defined.</p> |
