| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens capable of reading information in a wide range by improving the off-axis characteristic of a objective lens to be used in an optical pickup which is to be used in a recording and reproducing device to an optical information recording medium. SOLUTION: When at least one surface of a lens to be a non-rotation symmetrical plane and the radius of paraxial curvature of the meridional plane of the non-rotation symmetrical plane and the radius of paraxial curvature of the sagital plane are respectively defined as Rm, Rs, this plane is constituted to be |Rm|>|Rs|. In an objective lens 1, the lens can be constituted by making the first surface a rotation symmetrical aspherical surface and the second surface a non-rotation symmetrical plane. In the objective lens 1, when the radius of paraxial curvature of the meridional plane of the non-rotation symmetrical plane and the radius of paraxial curvature of the sagital plane are respectively defined as Rm, Rs, this lens is constituted to be 0< |Rn|-|Rs|}<0.01 mm. |
