| 摘要 |
PURPOSE:To detect stably a tracking shift by irradiating the light to a recording medium to which the binary information is recorded through a pit train, giving the photoelectric conversion to the reflected light from the recording medium to produce the 1st and 2nd signals and multiplying the 1st signal after smoothing the 2nd signal. CONSTITUTION:A light spot is irradiated to a discoid recording medium where binary information is recorded by a pit string, and the reflected light is received by a photoelectric conversion means 1 consisting of photodiodes D1-D4. An adder 2 adds the outputs of diodes D1 and D2; while an adder 3 adds the outputs of diodes D3 and D4 respectively. The outputs of adders 2 and 3 are applied to a voltage adder 4 and a differential amplifier 5. The outputs of the adder 4 undergoes waveform shaping and is used as an NRZ signal. The output of the amplifier 5 is applied to a smoothing circuit 11, and the delivered inverse IDL signal is applied to two switch circuits of a control means 12. The NRZ signal is applied to the means 12 from a waveform shaping circuit 6 in the form of a switch control signal. Then the means 12 gives the synchronizing wave detection to the inverse IDL signal and delivers a tracking error signal TE. Thus a tracking shift is detected with high stability. |
