Patent ID: 8018816
Filing Date: 2011-09-13
Classification: G02B,G11B

Abstract:
1. An objective lens used for an optical information recording/reproducing apparatus for recording information to and/or reproducing information from an optical disc based on a predetermined standard, the objective lens being made of resin and having a numerical aperture larger than or equal to 0.75; the objective lens satisfying a condition: where f denotes a focal length (unit: mm) of the objective lens with respect to a wavelength λ (unit: nm) used for recording information to and/or reproducing information from the optical disc, and |SC| the objective lens being configured such that the offence against the sine condition at a 100% point of the effective beam radius is smaller than the offence against the sine condition at a 90% point of the effective beam radius, at least a light source side surface of the objective lens being formed to be an aspherical surface, wherein: when SAG denotes a sag amount defined as a distance between a point on the aspherical surface at a height of h (unit: mm) from the optical axis and a plane tangential to the aspherical surface at the optical axis, r denotes a curvature radius (unit: mm) of the aspherical surface on the optical axis, κ denotes a conical coefficient, and A where, the objective lens is configured to satisfy a condition: where (SAG1)′