Fabrication of infrared hexagonal microlens array by novel diamond turning method and precision glass molding

Single-point diamond turning assisted with slow/fast tool servo is a viable technique for complex microlens arrays manufacturing. However, there are still challenges one must overcome when efficiently fabricating microlens arrays with discontinuous features. In this study, a novel slow-tool-servo diamond turning method, termed toroid-surface-based slow tool servo turning method, was proposed for generation of discontinuously structured microlens arrays. A discussion on the advantages for processing discontinuous features was presented and a hexagonal spherical microlens array over a large area was fabricated using the proposed method. This toolpath generation strategy, combined with a segmented turning approach, was adopted with consideration of both the geometry of the diamond tool and the profile of the microlens array. The surface roughness, form accuracy and geometry periodicity, were investigated. Results indicated that the entire microlens array has high homogeneous quality for optical elements. The fabricated microlens array was further utilized as a mold insert in a precision chalcogenide glass molding process. Compared with conventional fabrication methods, this novel technique method can be successfully implemented to fabricate various discontinuous microlens arrays with high accuracy and great efficiency. (paper)