Patent ID: 7830774

Claim:
An optical pickup lens with a numerical aperture NA of 0.84 or larger for focusing a light beam from a laser light source with a wavelength of 410 nm or shorter on an optical disc, the optical disc including an optical disc substrate and a light transmitting layer in the optical disc, wherein the optical pickup lens is a single lens with a first surface having a continuous shape on which the light beam from the laser light source is incident and a second surface opposite to the first surface, the second surface facing the optical disc, for a parallel light beam from the laser light source, a light is converged at a point having an inter-surface distance of 0.0875 mm from a surface of the light transmitting layer in the optical disc, an effective diameter D is 2.042≦D≦2.45 mm, the second surface of the optical pickup lens has a surface shape with radii h 1 , h 2 and h 3 from an optical axis to a lens periphery, the radii satisfying a first expression h 1 <h 2 <h 3 , wherein sags in the radii h 1 , h 2 , and h 3 are sag 1 , sag 2 , and sag 3 , and differentials in the sags are Δsag 1 , Δsag 2 , and Δsag 3 , respectively, the differentials satisfying second and third expressions 0>Δsag 1 >Δsag 2 and Δsag 2 <Δsag 3 , a refractive index n for a wavelehgth of 405 nm is 1.5895≦n≦1.64, an Abbe number υd is 55.0≦υd≦81, and a curvature radius r 1 of the first surface is 0.8001256≦r 1 ≦1.022536 mm.