Improving the profile integrity of germanium fresnel lenses in micro grooving processes

Ductile mode micro grooving with a sharply-pointed diamond tool under three-axis numerical control can fabricate precise micro Fresnel structures on single crystal germanium. However, in a practical durable machining process, the tool tip will wear gradually and finally produce micro chippings at the edges of the micro prisms. In the present paper, a new tool path is proposed in order to prevent the occurrence of micro chippings. The micro fractures occurred in machining can be completely removed during the following cut, thus leave the micro prisms damage free. Experimental results have demonstrated that the proposed method can significantly improve the profile integrity of a Fresnel lens and enable longer effective tool life.