| 摘要 |
PURPOSE:To eliminate the variation of sensitivity of a tracking error signal due to the variation of amplitude level of the output signal of a photoelectric transducer, by detecting the position information contained in the output signal of the photoelectric transducer to obtain the tracking error signal. CONSTITUTION:When a light spot is at the right of a track, the output signal of an LPF21 is set at a low level by the voltage obtained when the light spot is on the center of the track. At the same time, the output signal of an LPF22 is set at a high level in the same way. Then a tracking error signal with which the light spot is shifted to the right of the track is obtained through the differential amplification of a differential amplifier 23. While the levels of the output signals of filters 21 and 22 change in the direction opposite to a case where the light spot is shifted to the right of the track. Thus a tracking error signal with which the light spot is shifted to the left of the track is obtained through the output terminal of the amplifier 23. |
