| 摘要 |
PROBLEM TO BE SOLVED: To prevent an optical characteristic from being deteriorated by an orthogonal movement to an optical axis of an objective lens even when a divergent angle of a bundle of rays from a semiconductor laser is small, by detecting an inclination to the optical axis of the objective lens from an output of each photodetecting part of a light output detector. SOLUTION: An inclination angle θ to an optical axis of an objective lens 5 in a divergent direction of a bundle of rays from an LD 1 is detected from a plurality of outputs of photodetecting parts 7, 8 of a light output detector 6. In other words, when the inclination angle θ is generated, the bundle of rays moves on the photodetecting parts 7, 8 in an arrangement direction of the photodetecting parts 7, 8. Therefore, the inclination angle θcan be detected by obtaining a difference signal of the detection signals of the photodetecting parts 7, 8. A movable range of an objective lens-driving mechanism in a tracking direction of the objective lens 5 is moved in accordance with the inclination angle θ. Even when the inclination angle θ exists, a center of the movable area is agreed with a center of a usable area corresponding to an intensity distribution of the bundle of rays. Accordingly, the objective lens 5 is prevented from being outside the usable range and an optical characteristic is prevented from being deteriorated as a result of the movement of the lens 5 in the tracking direction. |
