ULTRA-PRECISION MACHINING OF RADIAL FRESNEL LENS ON ROLLER MOLDS USING ROTATING-TOOL DIAMOND TURNING

Abstract

In Roll-to-Roll manufacturing of optical films, direct diamond turning of radial Fresnel lens structures on a roller mould was considered infeasible. This thesis presents a novel solution to this problem. A four-axis interactive tool-workpiece motion is designed to precisely fabricate the complex microstructures. This process is experimentally verified. The evaluation of the machined feature is conducted through off-machine measurement with a novel compensation and comparison model. A set of cutting parameters is recommended through optimization study. By utilizing the RDT, a roller mold with both radial and linear Fresnel lens arrays is machined for a Roll-to-roll UV embossing process. The roller dimensions, lens specifications and the shrinkage phenomenon are considered for the machining process. The machined roller mold thereafter is used as the impression roller. The embossed flat optics undergoes both profile measurement and light concentration testing. The results are satisfactory in terms of both physical profile and optical performance.