| 摘要 |
PROBLEM TO BE SOLVED: To reproduce high and standard density disks. SOLUTION: The peripheral section of the reflected light beams from the information recording medium, to which the optical characteristics of an objective lens are not optimally designed, is greatly affected by the spherical aberration effect. A passing light quantity control means, which has a light quantity control member 114 having an aperture window 113, is provided between a detection lens 10 and a light receiving means 20 so that the peripheral section is not received by the means 20 and the quality of the reproduced signals is improved. When reflected light beams from the medium are made incident on the means 20, the position of the member 114 is controlled by a prescribed position 121 of the lens 10 side, the peripheral section, in which the adverse effect caused by the spherical aberration of the reflected light beams is great, is shielded and the beams only pass through a central section. |
