Patent ID: 7570547
Filing Date: 2009-08-04
Classification: G11B

Abstract:
1. An objective lens unit, comprising: an objective lens for irradiating and converging laser light on an optical disc as an a light information recording medium; and a lens frame for retaining the objective lens, wherein the lens frame is structured so that at least a portion closer to a rotation center of the optical disc is offset to an inner side of the lens frame with regards to a virtual edge section closer to the rotation center of the optical disc, wherein the virtual edge section is in a nodal line of a virtual plane that includes an end face which is closest to the optical disc in the lens frame and the objective lens, and that is perpendicular to an optical axis and a virtual rotation curved surface that is obtained when a virtual straight line passing a portion which is farthest from the optical axis in the lens frame and the objective lens, in parallel with the optical axis, is rotated around the optical axis as a center axis.