| 摘要 |
PURPOSE:To eliminate track offset and to facilitate the adjustment of a detector, by setting the width of a photodetecting part in a direction perpendicular to a track almost equal to that of an interaction area on which the diffracted light of a reflected beam of light is superposed in the direction perpendicular to the track. CONSTITUTION:When track deviation detecting beams of light exist on the photodetecting parts 1a and 1b, the displacement of the interaction areas 4a and 4b are generated. Since the photodetecting parts 1a and 1b are arranged in the centers of the areas 4a and 4b in such a way that the width (u) of them are narrowed than the width in which the double of the maximum travel quantity of the displacement is subtracted from the width (x) of the areas 4a and 4b, small amount of unbalance occurs in a photoreceiving quantity due to the inclination of a recording medium or the travel of an objective lens in the direction perpendicular to the track. Therefore, a stable track deviation signal can be obtained. Also, even when deviation in a direction in parallel with the track occurs, since the width (v) on the other sides of the photodetecting parts 1a and 1b are larger the width (y) of the areas 4a and 4b, no unbalancing occurs in the photoreceiving quantity. In such a way, it is possible to obtain a stable deviation signal for the deviation, and to facilitate the adjustment of an optical detector.
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