| 摘要 |
PURPOSE:To prevent sufficiently the resonance of a pickup arm and to obtain high tracking performance even when a record disk is curved by processing the outputs of the 1st and the 2nd optical sensors, and controlling a pickup and the record disk in invariably constant relative position relation according to the outputs of said processing. CONSTITUTION:Light emitted from a light source 9 is reflected by the record disk 4 and enters photodetecting elements 10 and 11 at a detection part 9, but when the optical path is long, namely, when the height H of detection part 3 from the record disk 4 is large (Hl) as shown by a figure (A), the output levels of the photodetecting elements 10 and 11 are generally large. When the optical path is short, namely, when the height H is small (Hs) as shown in a figure (B), the output levels of the photodetecting elements 10 and 11 are large. On the other hand, the 2nd optical sensor 2 provided with a long-sized light shielding plate 13b has the optical path shielded as shown by the figure (B) as the height H decreases and the amount of photodetection by the photodetecting element 11, therefore, decreases. The outputs of the 1st and the 2nd optical sensors 1 and 2 are supplied to an arithmetic processing circuit 14. |
