OBJECTIVE LENS

摘要

PROBLEM TO BE SOLVED: To provide an objective lens capable of forming a proper spot, by suppressing the occurrence of a coma aberrations, even when optical disks having different standards are used, and effectively preventing the problem such as step sagging, caused by a transfer failure during its formation.

SOLUTION: The objective lens has inner and outer side areas different from each other in shape in each surface. In each surface, the outer area reduces coma aberrations during the use of a first optical disk. The inner side area reduces an aberration amount rather than a coma aberration, when a luminous flux is made incident on the outer side area obliquely, with respect to an optical axis at the boundary position of each area during the use of a second optical disk. At a boundary position in a second surface, a distance XAbetween the extended surface of the inner side area and the tangential plane of the second surface in the optical axis and a distance XBbetween the extended surface of the outer side area and the tangential plane satisfy condition (1). In the boundary position of the second surface, surface inclination θ2Aat the inner side area and surface inclination θ2Bat the outer side area satisfy a condition (2). The condition (1): -1.0×10-3B-XA<1.0×10-3, and the condition (2): -2.50<θ2B-θ2A<-0.05, respectively.

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