| 摘要 |
PURPOSE:To attain stable servo control at all times by holding a tracking error signal in the state of level shift when a detection signal is outputted to as to automate the level adjustment of the tracking error signal. CONSTITUTION:The tracking error signal TE outputted from an operation circuit 13 is inputted respectively to a non-inverting input + and an inverting input (-) of comparator circuits 17, 18 respectively. When the tracking error signal TE having an offset to a ground level is outputted from the operation circuit 13, the tracking error signal TE is compared with a common level by the comparator circuits 17, 18 so as to be converted into pulse signals TE1, TE2 in opposite phase to each other. Then the said pulses TE1, TE2 are converted into voltage signals TE1P, TE2P by integration circuits 19, 20 to produce a detection signal TEO corresponding to the offset component of the tracking error signal TE. Thus, no level adjustment is required and always stable servo control is attained.
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