Diamond Milling System for Fabricating Infrared Micro-optics Arrays

A growing variety of sophisticated infrared optic systems need infrared micro-optic arrays (MOAs) with several micro-freeform lenticles. High-form-accurate MOA fabrication has been accomplished using a variety of ultra-precision diamond cutting processes. Because of the poor fracture toughness, the high anisotropy of the infrared materials, and the variable thickness of the chip due to the constant change in the height and gradient of the desired MOAs, the nonhomo-geneous fractured surface of infrared MOAs may be readily caused by the current technologies. In this chapter, a unique self-tuned diamond milling (STDM) approach is presented, which can improve the surface homogeneity and the processing effi-ciency of infrared MOAs and develops a matching tool path programming algorithm. Based on the local surface morphology, a double-axial rapid servo movement plat-form is incorporated into the raster milling system of STDM system, so that the maximum chip thickness of each rotation tool cycle can be matched with the critical cut deepness of infrared material, improving the surface homogeneity of the lens, and do not produce cracks. To prove the feasibility of the proposed cutting method, micro-aspheric MOAs without cracks have been successfully processed on a typical infrared material on single-crystal silicon. The proposed STDM has advantages over standard diamond milling in that it can prevent uneven fractures without decreasing the feed speed, leading to a surface roughness of only 4 nm and approximately double processing efficiency.