| 摘要 |
PURPOSE:To enable tracking control at all times, by eliminating the influence of the DC components in a tracking signal at the pull-in stage of tracking. CONSTITUTION:The quantities of the light detected with a photodetecting surface 11b and a photodetecting surface 11d are summed by an adder 21 and the quantities of the light detected with a photodetecting surface 11a and a photodetecting surface 11c are summed by an adder 22. The difference in the summed quantities of light between both is obtained with a subtractor 28.The differential quantity of light is inputted as a tracking signal through a phase compansating circuit 24 and an amplifier circuit 25 to a driving part 26 for tracking control, by which said signal is used on controlling the driving of a pickup device. A tracking control circuit T is turned on and off with a switch 27. An LPF 28 and a sampling and holding circuit 29 are connected to the connected point of the attenuator 28 of the circuit T and the circuit 24 and the circuit 29 is connected through a compensating resistor 31 to the minus terminal of the adder 22. |
