| 摘要 |
PURPOSE:To remove a DC offset component by sampling and holding a tracking error signals outputted from a photodetector separately as the signal of a pit part of an optical disk and the signal of a land part, and supplying those sample holding outputs to an operational amplifier. CONSTITUTION:This system has the photodetecting element 6 on which a spot of reflected light from the optical disk is formed, a subtracting circuit 7 which detects a tracking signal, and an adding circuit 8 which outputs the sum of detection signals of photodetection surfaces A and B. The 1st sample and hold circuit 9 samples a tracking error signal when a pit is irradiated with a light beam and the 2nd sample and hold circuit 10 samples a signal when a gap between pits, i.e. land part is irradiated with the light beam. Signals obtained by the 1st and the 2nd sample and hold circuits 9 and 10 are inputted to the differential amplifier circuit 11 to cancel the DC offset component, and then the differential amplifier circuit 11 outputs only the tracking error signal. |
