| 摘要 |
PURPOSE:To stabilize pull-in action of a servo loop and to attain quick pull-in by providing an attitude detection section detecting the attitude of a pickup section and giving a bias voltage in response to the attitude to a sawtooth wave signal from an oscillating section. CONSTITUTION:The bias voltage in response to the attitude is superimposed on the sawtooth wave signal by an adder circuit 34 in a focus search circuit 30 and a focus search signal FSE is outputted. The signal FSE is given to a focus coil 22 via a switch 18, a phase compensation circuit 20 and a drive circuit 21. The focus of an objective lens 14 is adjusted. An electric signal output in response to the polarized light state is obtained by a photodetecting section 16 and inputted to a matrix circuit 17. When an output of the photodetecting section 16 is within a prescribed range, the circuit 17 outputs a switching signal SWS of the switch 18 to form a servo loop. Further, focus control is attained by the servo loop and the distance between the objective lens 14 and the face of the disc 11 is kept constant. |
