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Proceedings Paper

The design of freeform surface lens for LED lighting system
Author(s): Zhi-cong Bao; Jun Zhu; Si-si Xiong; Guo-fan Jin
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Paper Abstract

LED has many advantages, such as high luminous efficiency, small size, low-voltage DC drive, etc. so it has been widely used in many lighting situations. But in certain circumstances, such as uniform illumination requirements in the micro-display projection system, because LED has an analogous Lambertian radiation distribution resulting in its non-uniform light intensity, the secondary optical design should be done to achieve the specific illumination requirements. In this paper, a freeform surface lens is designed to obtain a square area with uniform illumination on the target plane with LED: Firstly, based on the law of conservation of energy, the source-target light energy mapping relationship between the incident plane and the target plane is achieved. Secondly, according to the vector form of Snell’s law, the differential equations of the freeform surface are established. Finally, in order to solve the problem of surface discontinuity during the progress of designing the lens, the process of solving the differential equations is described in detail and the integrability condition is introduced to modify and adjust the points’ position of freeform surface, thus reducing the errors accumulating during the progress of numerical calculation and improving the continuity of the freeform surface. By simulation, the continuity of the freeform surface and the uniform illumination improve a lot, so it is validated that the results meet the requirements and the design method using integrability condition can improve the continuity of the surface and lighting uniformity of the lighting system.

Paper Details

Date Published: 20 August 2013
PDF: 11 pages
Proc. SPIE 8913, International Symposium on Photoelectronic Detection and Imaging 2013: Optical Storage and Display Technology, 89130T (20 August 2013); doi: 10.1117/12.2033282
Show Author Affiliations
Zhi-cong Bao, Tsinghua Univ. (China)
Jun Zhu, Tsinghua Univ. (China)
Si-si Xiong, 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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