Patent ID: 8274876

Claim:
An optical disc apparatus that reads out information from an optical disc by focusing a light beam having a wavelength of 410 nm or shorter from a laser light source onto the optical disc, which includes an optical disc substrate and a light transmitting layer, through a collimator lens and an optical pickup lens, wherein the optical disc apparatus comprises, as the optical pickup lens, a single lens for focusing a light beam from the laser light source onto the optical disc without passing through any diffraction ring zone, in which: a numerical aperture NA is equal to or larger than 0.84; an effective diameter D satisfies 1.8 mm≦D≦2.45 mm; and a refractive index n for 405 nm wavelength light beam is 1.51≦n≦1.5899, the single lens comprising: a first surface on which the light beam from the laser light source is made incident; and a second surface opposed to the optical disc positioned at an opposite side against the first surface, and the second surface has a convex aspherical shape on an optical disc side, having radii h 1 , h 2 , and h 3 from an optical axis to a lens periphery side, where h 1 <h 2 <h 3 , and sags at the radii h 1 , h 2 , and h 3 , wherein the sags at the radii h 1 , h 2 , and h 3 are sag 1 , sag 2 , and sag 3 , respectively, and differentials in the sag 1 , sag 2 , and sag 3 are Δsag 1 , Δsag 2 , and Δsag 3 , respectively, where 0>Δsag 1 >Δsag 2 and Δsag 2 <Δsag 3 .