| 摘要 |
PURPOSE:To decrease the variance in loop gain by using a detection level of a tracking error detection signal at track jump to set the gain of a variable gain amplifier circuit amplifying the level. CONSTITUTION:Both detection signals from a 2-split photodetector to which a couple of beams are irradiated are fed to a differential amplifier 2. A tracking error signal obtained from the amplifier 2 is fed to a level detection circuit 3 and a variable gain amplifier circuit 8. A control pulse generating circuit 10 generates a control pulse for track jump. An output of the circuit 8 and the control pulse from the circuit 10 are fed to a tracking coil 13 via a changeover switch 11 and an amplifier circuit 12. The circuit 3 detects the peak level of the tracking error detection signal at track jump, the detection output is held in a hold circuit 7 and a hold output sets the gain of the circuit 8. Thus, the variation in the loop gain is reduced.
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