Patent ID: 7859978
Filing Date: 2010-12-28
Classification: G02B,G11B

Abstract:
1. An optical pickup lens with a numerical aperture NA of 0.84 or larger for focusing a light beam of a parallel light or a sub-finite light with a coherent wavefront from a laser light source with a wavelength of 410 nm or shorter on an optical information recording medium in such a state that, as off-axis characteristics, an aberration becomes no more than 15 mλrms when an angle of view is 0.3 degrees, wherein the optical pickup lens is a biconvex single lens with a first surface on which the light beam from the laser light source is incident and a second surface opposite to the first surface, the first surface and the second surface having convex shapes, the second surface has a continuous shape, a shape of the second surface of the optical pickup lens having radii h the second surface has a convex-shaped portion in its center part and does not have a concave-shaped portion in a periphery thereof so that a slope (Δsag), from a lens center h a refractive index n for a wavelength of 405 nm is 1.59≦n≦1.62.