Optimizing the Cutting Processes of Mold Dies to Improve Optical Characteristics on Fresnel Screens

Abstract

An experimental study of precision cutting of molding dies using single crystal diamond cutting tools for large Fresnel screens (size: T3×921×714 mm, Fresnel angle: 0.004-55.0), for improving the optical characteristics of the screens is described. The conclusions are as follows: (1) A burr is generated at the shoulder of the grooves during cutting, which causes compressed chip material to accumulate and laterally compress both sidewalls of the grooves; (2) The burr generation is suppressed by increase of the rake angle of the diamond cutters, decrease of the down feed rate, and reduction of stock removal; (3) Generation of a color corn on the Fresnel screen is caused by light escaping through non-lens surfaces; this is avoided by making the non-lens surfaces semi-transparent where the surface roughness is around 1μm R_max Through use of the above-mentioned information to improve the cutting process, desirable optical characteristics were achieved for Fresnel screens used in projection TVs.