| 摘要 |
PURPOSE:To accurately detect tracking error signal, by making the size of a photodetector corresponding to the radial direction of a disk smaller than the size of the spot when projecting light is focused in a signal pit. CONSTITUTION:In a photodetector (quartered photodiode) 19 whose size corresponding to the radial direction of a disk 15 is smaller than the spot when projecting light is focused in a signal pit, a light spot is formed through a signal pit and the tracking error signal of an optical pickup is obtained in accordance with the detecting value of the photodetector 19. Therefore, even when the diameter of the spot in the radial direction becomes larger than that of the photodetector and the light spot is moved by tracking servo, variation of the area of the spot 19 on the divided photodetector is reduced. Accordingly, accuracy of the tracking error signal is improved.
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