| 摘要 |
PROBLEM TO BE SOLVED: To suit it to recording/reproducing of optical disks with different thickness by moving a position of an optical element focusing light outgoing from a semiconductor laser element in the optical axial direction. SOLUTION: When the optical disk D of a DVD is recorded/reproduced, a distance between the semiconductor laser element 1 and a collimate lens 4 is set large, and its outgoing light is made so as to become parallel rays of light. This outgoing light is focused on the recording surface of the optical disk D by an objective lens 5. The reflection light is returned inversely on an optical path to be made incident on a photodetector 7. In the case of a CD, the collimate lens 4 is brought more close to the semiconductor laser element 1 side being a light source by a prescribed distance L1 than the case of the DVD. Thus, the light outgoing from the second surface 4B of the lens 4 is converted into the diffused light. The luminous flux size of the diffused light is set so as to become smaller than the case of the DVD. |
