Optics using a gradient index lens

摘要

Objective lens optics that can realize NA higher than 1.623 without suffering from increased aberrations and which can be manufactured in a sufficiently smaller size to be suitable for use in an optical head on optical disk systems. The optics is made up of the combination of a single gradient index lens (1) having a gradient refractive index in a radial direction thereof and a single planoconvex lens (2) having a homogeneous refractive index. The gradient index lens has a planar or convexospherical lens surface. The planoconvex lens is made of a material whose refractive index (n) is greater than 2.2; it has its convex surface opposed to the gradient index lens such that the optical axes of the two lenses are aligned. Typically, the gradient index lens is provided on the object side and the planar surface of the planoconvex lens on the image side to make the optics suitable for use as an objective lens in optical heads.