Patent ID: 7606136
Filing Date: 2009-10-20
Classification: G02B,G11B

Abstract:
1. An objective lens used for an optical pickup device, the optical pickup device comprising: a light source; and a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium, wherein the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system, and wherein the objective lens is a plastic single lens and satisfies following formulas: where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information to the optical information recording medium, f(mm) is a focal length of the objective lens, λ wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.