| 摘要 |
PURPOSE:To prevent a pickup from coming off a track by detecting it when a track error signal of a tracking means reaches an upper limit value or more to feed a slider of the pickup by each prescribed amount. CONSTITUTION:A part of the transmitted light of a polarized beam splitter 8 is received by track error detecting photodetectors 13, 14, the remaining light is received by focus detecting photodetectors 15, 16 to detect a shift to a track 11. An output signal of a differential amplifier 25 changes with a shift between the pickup and the track 11 on an optomagnetic disc 7 and given to an upper/ lower limit comparator 27. The upper/lower limit comparator 27 gives an output signal until a tack error signal reaches the lower voltage when the signal level becomes an upper limit voltage of feed a slider 17 and does not give an output signal until the voltage reaches again the upper limit voltage when the level of the error signal is 0V to stop the slider 17. Thus, the pickup does not come off the track. |
