OBJECTIVE LENS

摘要

PROBLEM TO BE SOLVED: To provide an objective lens which can generate an appropriate spot on a recording surface of a disk by suppressing the occurrence of coma aberration even if any optical disks with different standards are used and which is designed to effectively prevent a failure such as the sagging etc. of a step caused by detective transfer during molding.

SOLUTION: The objective lens has on each surface thereof an inner area and an outer area different from each other in shape. On each surface, the inner area reduces the quantity of the aberration occurring on a border position between the inner area and the outer area rather than the coma aberration occurring when a beam is injected on a skew with respect to an optical axis in the outer area when a second optical disk is used. At the border position between the two areas on the second surface, the distance XAbetween the extended surface of the inner area and a tangent plane at the optical axis of the second surface and the distance XBbetween the extended surface of the outer area and the tangent plane at the second surface satisfy the following conditional expression (1):-1.0×10-3B-XA<1.0×10-3, and a tilt of the surface in the inner area θ2Aand a tilt of the surface in the inner area θ2Bsatisfy a conditional expression (2):-2.50<θ2B-θ2A<-0.05.

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