Fabrication of a microlens array featuring a high aspect ratio with a swinging diamond tool

Abstract

Microlens arrays are gaining wider applications due to their unique optical geometry and excellent optical properties. Ultra-precision diamond turning is preferable for fabricating microlens arrays with high form accuracy. However, the interference between the flank face of the diamond tool and the finished surface restricts its application in machining microlens arrays with a high aspect ratio. In this paper, a novel method based on the slow tool servo turning technique is proposed to fabricate these microlens arrays by introducing a rotational motion (A-axis) to swing the diamond cutting tool and adjust the actual tool clearance angle in real time, which can prevent tool interference effectively. The machining system and method principle are introduced first. Then, the toolpath is generated, and the influence of the tool nose radius is compensated for. Finally, machining experiments of cutting spherical lens arrays with high aspect ratios are conducted on a Nanotech 650UPL ultraprecision lathe, and the machined lenses are inspected with an optical microscope, a stylus profilometer and a white light interferometer. The measurement results of the spherical lens arrays machined by the proposed method and the conventional slow tool servo turning method are compared, which demonstrates the superiority of the proposed method in fabricating high-quality lens arrays featuring a high aspect ratio.