Patent ID: 6665130
Filing Date: 2003-12-16
Classification: G11B

Abstract:
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 and second lens groups are arranged in this order from a light source side of the objective lens and are made of a plastic material respectively; and wherein the following formula is satisfied: NA>0.85 where NA is a necessary image side numerical aperture for recording or reproducing information of the optical information recording medium, and wherein the following formula is satisfied: DIN<4.5 mm where DIN is an effective diameter of a light flux incident surface of the first lens group, and wherein the following formula are satisfied: in the case that 0.850.020<WD/DIN<0.150, â€ƒand in the case that NA&gE;0.90, 0.015<WD/DIN<0.120, where WD is a working distance (mm) of the objective lens.