Ultra-precision machining of radial Fresnel lens on roller moulds

In Roll-to-Roll manufacturing of optical films, direct diamond turning of radial Fresnel lens structures on a roller mould was considered infeasible, due to the incapability to cut steep circular grooves on the outer cylindrical surface using conventional approach. This paper presents a novel solution to this problem. A four-axis interactive tool-workpiece motion is designed to precisely fabricate the complex microstructures. The tool path is generated from geometrical calculations considering the lens design, tool geometries and roller parameters. This process is experimentally verified with qualified profile quality and surface finish, thus making direct machining of radial Fresnel lens possible.