| 摘要 |
PURPOSE:To improve the linear characteristic of the focusing control by providing a 3-beam generating means, a direct changing means of the detected light, a 1st photometric sensor, and a 2nd photometric sensor. CONSTITUTION:The detected light 9 is divided into the 1st and 2nd detected beams 12 and 13 by a direction changing means 11 having a knife-edge 11a parallel to the displacement direction of a tracking error. At the same time, both beams 12 and 13 undergo the relative changes of their directions and the focusing and tracking errors are detected by the photometric sensors 14 and 15 provided in each optical path. Thus the influence of the crosstalk due to the tracking error can be prevented to the focusing error signal by the knife- edge method together with the stable tracking optical secured as it is. Furthermore the linear characteristic of the focusing control is improved with the mutual compensating combination of both sensors 14 and 15. |
