| 摘要 |
<p>A device for tracking an optical memory card comprising gradient data sampling means (6) for finding a change within a unit time of a low-frequency component in a tracking error signal, detecting means (8) for producing detection signals during the period in which the tracking deviation exceeds a predetermined reference range, cumulative adder means (5) which cumulates and adds output of the gradient data sampling means for every unit time during the period in which the detection signals are generated for the low-frequency component in the tracking error signal when the detection signal is generated, and switching means (3) which usually produces the tracking error signal and which, during the period in which the detection signal is produced, produces the output of the cumulative adder means as a tracking control signal for the optical system. Therefore, even when a proper tracking error signal is lost or is going to be lost during short periods of time due to direct or scars on the card, the proper tracking condition is maintained without interrupting the writing or reading of the optical memory card. After this period of time has passed, the proper initial condition can be resumed.</p> |
