Abstract
An experimental study of precision cutting of molding dies using single crystal diamond cutting tools for large Fresnel screens(size : T3×921×714mm3, 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 Rmax. Using the above-mentioned information to improve the cutting process, desirable optical characteristics were achieved for Fresnel screens used in projection TVs.
