| 摘要 |
PURPOSE:To prevent noise from entering, which results from that a light spot traverses a track by interposing a light dividing element for dividing a part in which the quantity of light of both edges of a pit is changed from the reflected light into the advancing path of the reflected light and providing a pair of photosensors for tracking only for receiving the light divided by the light dividing element. CONSTITUTION:The part in which the quantity of light is changed by a diffraction produced according to the position of the light spot in the pit 12 of the reflected light from an optical disk 10 is deflected and the light is received only by the photosensors 30a, 30b for tracking. The quantity of light of the reflected light received on the light receiving surfaces of focussing photosensors 28a, 28b, 28c, 28d is not changed according to the position of the light spot in the pit 12. Therefore, even if an optical head 14 is moved diametrically of the optical disk 10 for changing a track and the light spot is traversed on the track, the noise related to the traverse of the track for the light spot does not enter a focussing error signal FE. |
