| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens having high light utilization efficiency and a low spherical aberration. SOLUTION: The light beam passing region of a barrel facing an optical disk is divided into a central region A1 corresponding to the near optical axis region of incident light beams, a peripheral region A3 corresponding to the far optical axis region of the incident light beams and an intermediate region A2, corresponding to the region between the near and the far optical axis regions. The region A1 is optimized to be focused on thick as well as thin disks. The region A2 is optimized for the thick disk, and the region A3 has a surface to be optimized for the thin disk. |
