Patent ID: 7453788
Filing Date: 2008-11-18
Classification: G01C,G11B

Abstract:
1. An optical head, comprising: a light source; a beam-shaping lens shaping an elliptical divergent beam that is emitted from the light source into a substantially circular divergent beam; a collimating lens that converts the substantially circular divergent beam into a substantially parallel beam; an objective lens that focuses the substantially parallel beam onto an optical information recording medium; and a detector that detects a beam that is reflected from the optical information recording medium; wherein the beam-shaping lens has a pair of cylindrical surfaces that are curved in the same direction; wherein one of the pair of cylindrical surfaces is an aspherical surface, and the other one of the pair of cylindrical surfaces is a spherical surface; and wherein the cylindrical surface that is closer to the light source is the aspherical surface, and the cylindrical surface that is further away from the light source is the spherical surface.