Ultra-precision machining of polygonal Fresnel lens on roller mold

Roll-to-roll (R2R) embossing is a low-cost and high-productivity manufacturing process that replicates the microstructures from a cylindrical impression mold onto flexible films with high resolution and accuracy. However, discontinuous non-rotationally symmetric microstructures are very difficult to fabricate on either planar or cylindrical surfaces. In this paper, a novel machining method, diamond micro-scraping (DMS), is developed to provide a possible solution for the fabrication of polygonal Fresnel lens structure on the roller mold. In the proposed DMS machining method, the tool path is generated according to geometrical calculations considering the structural design of the drum roll lathe, the polygonal Fresnel lens structure designed, diamond tool geometries, and parameters of the roller mold. Through a series of processing experiments, the feasibility of DMS machining method is verified, and polygonal Fresnel lens structure is fabricated on the roller mold. The experimental results show that the profile accuracy of the processed polygonal Fresnel lens structure is at the submicron level and the surface roughness is several nanometers. The proposed DMS machining method can meet the requirement of embossing high-precision optical roller mold.