Re-Ir coating effect of molding core (WC) surface for aspheric glass lens

Abstract

Recently, with increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass lens has increased because plastic and spherical lenses are unable to satisfy the required performance. An aspheric glass lens is fabricated by high temperature and pressure molding using a tungsten carbide molding core, so precision grinding and coating technology for the molding core surface is required. In this paper, the optimal grinding condition of the tungsten carbide molding core was found after applying DOE to the development of the aspheric glass lens for the 3 mega pixel and 2.5 magnifications optical zoom for camera phone module. Also, the ultra precision grinding process was investigated under this condition by experiment. Rhenium-Iridium(Re-Ir) coating was applied on the ground surface of the tungsten carbide molding core. The influence of Re-Ir coating on the form accuracy and surface roughness was compared and evaluated. The form accuracy and surface roughness of the molding core were improved by application of Re-Ir coating on the surface of the tungsten carbide molding core. Aspheric lenses were also molded with the non-coated molding core and the Re-Ir coated molding core. Form accuracy(PV) and surface roughness(Ra) were measured. The form accuracy of the aspheric glass lens improved about 0.01 μm (aspheric surface) and the surface roughness by about 0.5 nm (aspheric surface).