| 摘要 |
In order that a measurement error of a phase difference based on an eccentricity produced when an optical disc is inserted into a disc spindle and rotated can be eliminated to improve a measurement accuracy, a polarity adding circuit is provided between an exclusive-OR circuit for detecting an absolute value of a phase difference and a low-pass filter to determine the polarity to thereby eliminate a measurement error in the vicinity of a portion where a phase difference is zero.
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