Patent ID: 6927923
Filing Date: 2005-08-09
Classification: G11B

Abstract:
1. An objective lens for recording and/or reproducing information of an optical information recording medium, comprising: a first lens group having a positive refractive power and a second lens group having a positive refractive power; wherein the first lens group and the second lens group are arranged in this order from a light source side, and wherein the objective lens is a finite conjugate type to converge a divergent light flux having a wavelength of 600 nm or less from a light source onto an information recording plane of the optical information recording medium and satisfies the following formula: wherein NA is an image-side numerical aperture necessary for conducting recording and/or reproducing information of the optical information recording medium, wherein the following formula is satisfied: wherein m is a lateral magnification of the objective lens defined by the formula: NA wherein the following formula is satisfied: where WD is a working distance (mm) of the objective lens, and f is a focal length (mm) of a total system of the objective lens.