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Proceedings Paper

Design of freeform surface lens for LED of random light distribution in road lighting
Author(s): Si-si Xiong; Jun Zhu; Zhi-cong Bao; Guo-fan Jin
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Paper Abstract

Previous secondary optical designs, however, have approximated the LED light distribution curve as a Lambertian distribution which is unable to suit all custom sources. In this paper, a freeform surface lens is utilized to redistribute the light rays emitted from a LED device with a random light distribution curve in order to effect a prescribed illumination distribution on the target area. A mapping relationship is also established between the spatial light intensity distribution of a light source and the rectangular uniform illumination used for road-going cases. A set of first-order partial differential equations is deduced according to Snell’s Law and the Law of Energy Conservation. A numerical solution is obtained through MATLAB software, and freeform surface data of the secondary optical lens is recorded to aid in modeling the freeform surface lens. Simultaneously, an analysis and comparison of different differential algorithm and mapping methods is carried out in order to solve the differential equations and designate the most superior mapping relationship. With the help of 3D software, a 3D model of the freeform surface lens is established, and Light Tools software is employed to simulate the effects of illumination. In this model, the light distribution curve of the LED source is described as an eighth-order polynomial. According to the simulated results, a 10m height, 40m×40m road uniform illumination is realized by the secondary optical design. The energy efficiency and uniformity of this illumination is 99.7% and 91.52% respectively. This method of secondary optical design is easy to operate and can be applied to any other lighting systems with random LED sources.

Paper Details

Date Published: 20 August 2013
PDF: 8 pages
Proc. SPIE 8913, International Symposium on Photoelectronic Detection and Imaging 2013: Optical Storage and Display Technology, 891315 (20 August 2013); doi: 10.1117/12.2041203
Show Author Affiliations
Si-si Xiong, Tsinghua Univ. (China)
Jun Zhu, Tsinghua Univ. (China)
Zhi-cong Bao, Tsinghua Univ. (China)
Guo-fan Jin, Tsinghua Univ. (China)

Published in SPIE Proceedings Vol. 8913:
International Symposium on Photoelectronic Detection and Imaging 2013: Optical Storage and Display Technology
Changsheng Xie; Yikai Su; Liangcai Cao, Editor(s)

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