| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the need to provide a moving mechanism even in the case of performing the recording or reproducing of optical disks having different thicknesses of transparent base plates by providing 1st and 2nd light sources, an objective lens condensing lights from the light sources and an auxiliary lens arranged between the 2nd light source and the objective lens. SOLUTION: The light from the 1st light source 1 is guided and converged on a 1st information recording surface 6b through an optical medium 12 for a 1st photodetector 11, an optical medium 2 and the objective lens 3. The light from the 2nd light source 4 is guided and converged on a 2nd information recording surface 7b through an optical medium 22 for a 2nd photodetector 21, the auxiliary lens 5, the optical medium 2 and the objective lens 3. In such a case, the lens 3 is optimized so that the light from the light source 1 is excellently converged on the recording surface 6b corresponding to the thickness of the 1st transparent base plate 6a. Furthermore, the combination of the lenses 5 and 3 is optimized so that the light from the light source 4 is excellently converged on the recording surface 7b corresponding to the thickness of the 2nd transparent base plate 7a. |
