Abstract

A plano-convex axial gradient index (Z-GI) lens is able to correct both spherical aberration and coma. However, it is difficult to fabricate a Z-GI singlet with a numerical aperture (N.A.) of over 0.3, because a large refractive index change (Δn) and a precise refractive index profile are required. To make the N.A. larger, a homogeneous meniscus lens was added to a Z-GI singlet. Several types of Z-GI doublet with large N.A. (0.53-0.60) were designed and fabricated as the objectives for optical disk systems. The specifications of a Z-GI doublet are given as follows: λ: 780 nm N.A.: 0.55 focal length: 3.07 mm conjugate length: ∞ working distance: 1.10 mm disk thickness: 1.20 mm (n = 1.57).

© 1989 Optical Society of America