Patent ID: 6922289

Claim:
An objective lens system for optical pickups reading and/or writing information by condensing a luminous flux from a light source onto an optical information recording medium, consisting of: a single lens having, from a light source side, a first surface convex to the light source side and a second surface convex to an image side, a medium of the single lens being a homogeneous medium, at least one of the two surfaces being aspherical, and wherein the following conditions are satisfied: −0.45 <r 1 /r 2<−0.1803 1.05 <d/f <1.4 −40<θ1−θ2<20 where r1 is the radius of curvature of the first surface; r2 is the radius of curvature of the second surface; d is the axial thickness of the single lens; f is the focal length of the single lens, θ1 is the angle (°) which the ray incident on the margin of the effective diameter of the first surface forms with the first surface; and θ2 is the angle (°) which the ray exiting from the margin of the effective diameter of the second surface forms with the second surface.