双自由曲面LED均匀照明准直透镜设计

Abstract

A LED collimator with double freeform surfaces was designed for uniform illumination in both near field and far field. The collimator includes refractive part and reflective part, and each part has double freeform surfaces. Based on Malus Law, the constant optical path length equations that realize the rays collimating were derived. Then associating with tangent-plane iterative method, the date both up freeform surface and down freeform surface simultaneously could be calculated. The simulations show that, 84.55% of the energy is collected in 2 for 1 mm1 mm size white LED after considering the Fresnel loss, reflective surfaces loss and material absorbing. The uniformity in near field is 94.59%, and the uniformity in far field is 89.01%. The uniformity in near field and the optical efficiency in 4 are above 90% and 83.5% respectively, while the LED chip sizes are under 2 mm2 mm. It is illustrated that the LED collimator can realize uniform illumination in both near field and far field with high light efficiency and the tolerance meet the requirements of alignment.