Lens for an optical recording/reproducing apparatus.

摘要

A lens (9) for an optical recording/reproducing apparatus has a graded refractive index n (r) at a position a distance r from its optical axis along a radial direction which is given by: n<2>(r)=n0<2>1-(g.r)<2>+h4(g.r)<4>+h6(g.r)<6>+h8(g.r)<8>+... and the following conditions are satisfied: R2= chi 3.0>/=R1/(1 +0.75S)>/=0.8 1.40</=n0</=1.87-0.6g.S 0.75>/=g.f>/=0.45 where n0: refractive index on the optical axis g,h4,h6,h8:coefficients R1: radius of curvature of a first surface R2: radius of curvature of a second surface S: working surface f: working distance of an overall optical system at an image side. An optical recording/reproducing apparatus using such a lens as an objective lens can be capable of high-density recording/reproduction, does not require very high precision in assembly, and allows good response characteristics of its optical pickup to focussing and tracking control.