Design and characterization of 3D-printed freeform lenses for random illuminations

A combination of light-emitting diodes (LEDs) with freeform optics has been recently investigated widely for energy efficient illumination due to its high optical performance and compact size. The freeform optics design methods are application specific. The transformation of the light source into the target irradiance distribution using freeform optics usually leads to solving an inverse problem, which can be formulated by using a point light source, geometrical optics, monotonic ray bending and lossless system. Here, a customized algorithm is proposed to design freeform lenses for both LED source based simple uniform rectangular illumination and collimated light source based complex image target irradiance distributions by numerically solving the elliptic Monge-Ampere equation. The optical performance of the lenses is examined theoretically by using commercial ray tracing software. Additive manufacturing (also called as 3D printing), a layer-by-layer printing of patterned material, is considered as novel option for low-cost and rapid manufacturing of optics. Recently, 3D printed ISO-standard ophthalmic lenses have been produced using Printoptical (R) technology (US Patent No. 13/924,974): a modified ink-jet printing technology that deposits micro-droplets Opticlear, which is a PMMA-like UV-curable polymer. In our work, the Printoptical (R) technology is further extended to 3D-print freeform lenses. The metrology of the freeform lenses is studied using white-light interferometry and VR-3000 series 3D surface profile macroscope.