| 摘要 |
<p>PURPOSE:To surely obtain the optimum tracking value in a short time and with high accuracy by initializing the start point for the change of a tracking phase and designating an optional output level difference rank to the maximum reproduction output level. CONSTITUTION:The video signal that converges in a short time and with high accuracy to the tracking convergence value and has a high S/N and the high resistance to the disturbance is obtained through the tracking initialization, decision of the change direction and calculation of the optimum value. For instance, the tracking phase value of a servo circuit 9 is initialized at the value tQ with which an optimum image is obtained in an SP state for example. Then the tracking phase value of the circuit 9 changes at every DELTAt toward the smaller tracking phase value by a command of a microcomputer 7 simultaneously with start of the reproduction. Thus the reproduction outputs H0, H1...H8 obtained sequentially are processed by an envelope wave detecting circuit 5 and an A/D converter 6. The front and back levels of the reproduction output are compared with each other within the computer 7. Thus the maximum value H8 is set.</p> |
