| 摘要 |
PURPOSE:To obtain a tracking signal and a defocusing signal from outputs of four photodetecting parts, in the optical disc reproducing device. CONSTITUTION:Dividing lines of four-divided photodetectors 11a-11d are placed in parallel with axes 61 and 62. Axis 61 indicates the direction of the track. Signals of 11a and 11e are input to adder 12', and signals of 11b and 11d are input to adder 13', and outputs of adders 12' and 13' are input to differential amplifier 14', and a defocusing signal is obtained as the output of amplifier 14'. Meanwhile, in respect to the tracking signal, signals of 11a and 11b are added by adder 28', and signals of 11d and 11c are added by adder 29', and outputs of them are input to differntial amplifier 18' to obtain their difference, and thus, the tracking signal is obtained. |
