Design and fabrication of a microlens array by use of a slow tool servo

TLDR

Free‑form optics can now be fabricated using multiaxis ultraprecision machines. The study develops a novel diamond‑tool trajectory enabling a 5×5 microlens array to be machined in one operation. A four‑axis ultraprecision diamond‑turning machine with a novel tool trajectory fabricates the array, which is then characterized by curve conformity and surface roughness measurements. The process yields microlenses with accurate geometry and optical surface finish, and it enables fabrication of arbitrary shapes.

Abstract

In recent years it has become possible to fabricate free-form optics by use of multiaxis ultraprecision machines. Here a 5 x 5 microlens array is fabricated by using an ultraprecision diamond turning machine equipped with four independent axes. Unlike the conventional process where a single diamond tool is used to machine one lens at a time, this research demonstrates the development of an innovative diamond tool trajectory that allows the entire microlens array to be machined in a single operation. The machined microlens array is measured for both curve conformity and surface roughness. Compared to the conventional approach where indexing the workpiece is difficult and unreliable, this process can produce microlenses with accurate geometry and optical surface finish. This unique process is described in detail from optical measurement to machining process design and development to final results. This research also demonstrates the possibility of fabricating any arbitrary shape with the same approach.