Aspheric surface lens for LED collimating illumination with low Fresnel loss

Abstract

An aspheric surface lens is presented to realize collimating illumination with low Fresnel loss based on Fresnel equations and Snell’s law. The smooth 2D contour of refractive optical surface is constructed from a set of cubic Bezier segments, whose control points are computed by deCasteljau algorithm. Simulation results show that the optical efficiency of 90.82% is achieved under a divergence angle of ±2.87° for an extended light-emitting diode (LED) source with chip size of 1 mm × 1 mm and the Fresnel loss is only 8.76%, whose optical efficiency has improved 14.3% than traditional collimating lens. By employing this proposed surface construction method, the largest divergence angle of collimating lens for point source is only 0.26° with 15 feature points on each refractive surface, while more than 2° for the traditional method. Therefore, the beams are well controlled with fewer feature data points. Tolerance analyses are also conducted in detail.