Realization of a bi-aspherical objective lens for the Philips Video Long Play system

Abstract

An objective lens for focusing monochromatic laser light on an optical video disk has been machined in polymethyl methacrylate on a lathe numerically controlled by a computer. The objective is a single-element lens and has two steeply aspherical surfaces. It has a numerical aperture of 0.43, and its field has a diffraction-limited quality over a radius of 300 μm. Some details of the computer-numerically controlled hydraulic lathe are given.