| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily detect a wobble signal from a wobbled track. SOLUTION: The wobble signal detector is provided with a first bandpass filter 33 which extracts and outputs a first sine wave-shaped (or cosine wave- shape) wobble signal 33a corresponding to the wobble of the track in a variable amplitude push-pull signal 31a in which a push-pull signal 16a outputted from a push-pull signal generating circuit 16 is amplified by a variable gain amplifier 31, a second bandpass filter 34 which extracts a signal corresponding to the wobble of the track in the variable amplitude push-pull signal outputted from the variable gain amplifier, shifts a phase by 90 degrees to the first wobble signal and outputs a second cosine wave-shaped (or sine wave-shaped) wobble signal 34a, and arithmetic means 39 and 40 which calculate the amplitude values of both wobble signals from the first and second wobble signals outputted from the first and second bandpass filters, respectively.
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