| 摘要 |
PURPOSE:To obtain a skew detecting part which can detect the skew accurately by obtaining a signal which varies in response only to the change due to the skew of the arriving position of a returned optical beam on a photodetecting part. CONSTITUTION:Detection signals Up and Uq which vary in accordance with the arriving position of a returned laser beam on a photodetecting part 10 are formed within a signal processing part 12. These signals Up and Uq correspond to a change of the direction crossing a recording track and a change of the direction along the recording track respectively. While detecting parts 21 and 22 for position shift of incident light beam are provided to detect the shift of the incident laser beam due to the tracking control and the compensation control of time axis. Then a detection signal Ut which varies in response to the change of the direction crossing the recording track is produced together with a detection signal Ub which varies in response to the change of the direction along the recording track. The synthetic detection signals Ux and Uy vary in response only to the change produced by the skew. Thus it is possible to detect accurately both radial and tangential skews.
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