Design of uniformly collimating light-emitting diode lenses of multiple freeform and Fresnel surfaces with different inter-surface mapping orders

In this work, we propose a design method of composite freeform collimating lenses that integrates freeform reflection, refraction, and Fresnel surfaces to realize highly collimated and uniformed light output in a single lens element. The algorithm is designed considering a consistent combination of different surfaces, so the light rays reaching the Fresnel surface through refraction and reflection should generate the same luminous intensity. The Fresnel rings can be designed in two different ways, depending on the sequence of light rays propagating between the reflection and the Fresnel surfaces. The lighting effects of the lenses are analyzed in a 3D simulation, and the light output of both schemes reaches a high level of collimation and uniformity, agreeing well with design expectations. The obtained lenses have the advantages of a compact volume, high light extraction efficiency, and variable geometry by changing the combination form of the freeform surfaces. (C) 2018 Optical Society of America