| 摘要 |
An optical head which detects the tracking error by irradiating the light beam onto data medium and detecting the reflected light therefrom, is provided with a light source generating a first light beam for detecting the tracking error signal and a second light beam whose distribution of the amount of the reflected beam from the data medium in its reflecting direction is not effected by the occurrence of the tracking error. The optical head irradiates both the light beams on the data medium, guides the reflected light of each light beam in different directions, detects the tracking error signal temporarily by the first light beam, detects the offset corresponding to the displacement of an objective lens by the second light beam, and cancels an offset being included in the temporarily detected tracking error signal by that detected offset.
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