Study on Precision Machining of Glass Lens Mold with Minute Structures

Abstract

In optical devices, the demand of glass lenses with complicated shapes like Fresnel shape is recently growing up for the purpose of improving its heat resistance and optical performances. The study suggests a new machining process for cemented tungsten carbide mold with Fresnel shape, aiming at high precision machining. In the proposed process, the curved surfaces except for sharp edges are at first machined by the conventional grinding method with a disk type metal bonded diamond wheel. Then, sharp edges are created on curved surfaces by fly cutting method with knife edged single crystal diamond tool. Fly cutting method is expected to reduce tool wear due to the intermittent machining process. From fundamental V-microgrooving experiments of WC by fly cutting and shaping, it is clarified that the damage of cutting tool by fly cutting is reduced, compared to shaping. Therefore, complex machining of Fresnel shape by proposed machining method allows sharp edges to create to WC mold. As a result, it is found that the proposed machining method has the potential of producing a high precision glass lens mold with Fresnel shape effectively.