SELFOC Micro Lens with Spherical Surface

Abstract

Gradient index rod lenses have been successfully applied to imaging systems and micro-optical circuits in electro-optical systems. When the rod lens is used as a light-focusing micro device such as a pick-up lens in the video disk, a high numerical aperture (NA) is necessary in order to get a small focused spot. NA of the rod lens is determined by the quadratic gradient constant g of the refractive-index profile, the diameter, and the length of the lens. However, NA can be changed by making an end surface spherical even if those parameters are made constant. On the other hand, the spherical surface has the minus spherical aberration, so it becomes possible to compensate the plus aberration of the rod lens by the spherical surface.1)