These ruled- inserts, made of hardened steel, optimizing the imaging characteristic of the molded optical surface by minimizing color separation thereby improving the vitality of the image displayed. They were produced by diamond turning a pair of inserts, one with concave and the other convex profile (of mirror image) and subsequently matched together by these surfaces and honed with each other by rotating them at differential speed. Such action with appropriate speed and lubricating setting, enable the reduction of the waviness to a minimum on the diamond cut surfaces.
This picture illustrates a couple of spherical (R 70mm) ruled-inserts with radius deviation of 0.015%; surface finish < 5nm. The size of the square insert is 10×10 mm whilst the round ones is 19 mm diameter.