| 摘要 |
PROBLEM TO BE SOLVED: To always keep the incident quantity of a returning light beam to a photodetector at an optimal level by adjusting the output of a light source with an output adjusting device according to the kind of an optical disk to be reproduced. SOLUTION: In an optical pickup 20, a light beam from a semiconductor laser element 21 is divided into three light beams by a grating 22, then reflected by the reflection surface 23a of a beam splitter 23 and reflected by a rising mirror 24 toward an optical disk 11. Further, the light beams is converted into a parallel light by a collimator lens 25 and an image is formed on the signal recording surface of the optical disk 11 via an objective lens 26a. In this case, a numerical aperture is properly set by the lens 26a corresponding to a high density optical disk and an image is correctly formed on the signal recording surface of the disk 11. A returning light from this disk 11 is transmitted through the splitter 23 again via the lens 26a and the rising mirror 24, an image is formed by a photodetector 27 and based on its detecting signal, a recording signal is reproduced. |
