Patent ID: 8004955
Filing Date: 2011-08-23
Classification: G11B

Abstract:
1. A coupling lens used in an optical information recording/reproducing device for recording information to and/or reproducing information from an optical disc, the coupling lens comprising a first surface and a second surface, wherein the coupling lens is configured to have a value Z which satisfies a following condition (1): wherein the value Z in the condition (1) is obtained from a following equation (E1): r1 denotes a curvature radius of the first surface the coupling lens, r2 denotes a curvature radius of the second surface of the coupling lens, n denotes a design refractive index of the coupling lens, L denotes a working distance defined for an object point, L′ denotes an working distance defined for an image point, and t denotes a center thickness of the coupling lens at a central axis of the coupling lens.