| 摘要 |
PURPOSE:To apply stably tracking servo at all times by controlling the loop gain of a tracking servo equally when an incident light to a disc traces a pre- coupling section or a user recording enable section. CONSTITUTION:A difference of output signals of photodetectors 11A, 11B of a tracking error detector 11 is calculated by a subtraction circuit 21 and a tracking error signal TE is inputted to a gain control circuit 41. On the other hand, sum signals of the outputs of photodetectors 12A, 12C and 12B, 12D in diagonal direction of a photodetector 12 are calculated by adder circuits 22, 23, the sum signals are added at an adder circuit 25 and which is traced by the optical beam, the pre-coupling (P) section or the user recording enable (U) section is detected from the sum signal RF. The signal RF is compared with a reference voltage V1 at a comparator circuit 31, a signal of a level depending on the intensity is fed to the circuit 41, where the TE signal is controlled so as to be equal for both cases at all times. |
