| 摘要 |
An apparatus for recording and/or reproducing information in and/or from an optically inscribable and readable disk-shaped record carrier with a pre-formed tracks with a track modulation constituted by a radial wobble, in order to obtain a tracking signal. A reference signal for deriving the tracking signal by synchronous detection is obtained by rectifying the difference signal which is the difference between the signals supplied by the two photo-detectors disposed on opposite sides of a line which extends in the track direction, by subsequently extracting the component of twice the frequency via a phase-locked loop and by frequency-dividing the signal, so that phase shifts of 180 DEG in the difference signal do not affect the synchronous detection. |
