Patent ID: 6927923

Claim:
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: NA≧0.65 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: 0.01 ≦/m/≦ 0.30 wherein m is a lateral magnification of the objective lens defined by the formula: NA OBJ /NA IMG , where NA OBJ is an object-side numerical aperture of the objective lens and NA IMG is an image-side numerical aperture, wherein the following formula is satisfied: 0.10≦ NA·WD/f≦ 0.35 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.