Design of uniform illumination is one of the most crucial topics for LED to replace the traditional light sources. Based on the theory of Etendue from non-imaging optics and the edge ray principle, in combination with the theory of freeform surfaces, this paper sets up mathematical models of the refractive freeform surface lens and the total internal reflection (TIR) freeform surface lens, which are solved by numerical method to obtain the shape of surfaces, simulates the optical systems by 3D modeling and the ray-tracing software Trace-pro, and analyzes the lighting effects. The results show that both of the lens can generate uniform illumination in the cone of 120° spatial angle. When the diameter of the emitting surface of the LED is less than 2mm, the refractive freeform surface lens can generate uniformity above 0.8 and energy efficiency above 0.83; when the diameter is less than 4mm, the TIR freeform surface lens can generate uniformity above 0.7 and energy efficiency up to 0.86.

Date Published: 15 November 2011
PDF: 9 pages
Proc. SPIE 8321, Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 832110 (15 November 2011);

Published in SPIE Proceedings Vol. 8321:
Seventh International Symposium on Precision Engineering Measurements and Instrumentation
Kuang-Chao Fan; Man Song; Rong-Sheng Lu, Editor(s)