高均勻度及高效率LED照明之自由曲面透鏡設計

欲達到高均勻度及高效率的LED照明，二次光學透鏡是必需的。本篇主要根據LED初始光源強度分佈來設計自由曲面透鏡來達到高均勻度及高效率的照明。由於整個光學系統屬於旋轉對稱，所以只需找出二維軌跡並旋轉掃出成三維立體透鏡即可。整個設計流程主要是根據折射定律、邊緣光線定理、及能量映射等理論。設計初步先分析LED光源強度分佈並於經緯度方向作等角度分割，接著計算每個區塊被分配到目標平面上的區域大小，接著利用近似解析方法來建構自由曲面透鏡。完成透鏡建構後，使用光學模擬軟體LightTools®對整個模型作光追跡分析，模擬結果發現確實可達到高均勻度極高效率照明。最後將二次透鏡設計進行修正調制，並使用Cree XR-E光源針對1公尺遠半徑1公尺之圓形照明(半視角45度)可達均勻度94.8%、效率89.1%。

關鍵字

二次光學； LED照明；自由曲面

並列摘要

In this paper, design examples related to LED illumination are presented. We design a freeform lens according to the initial LED light source intensity distribution so that the light rays emitted from a LED through the lens can achieve high uniformity and efficiency on the prescribed target plane. Because the model is of rotational symmetry, we consider just a 2-D lens shape and then sweep to get the 3-D result. Here a procedure based on the Snell’s law and “edge-ray principle” for designing the freeform lens is proposed. First of all, we analyze the LED intensity distribution and subdivide it into parts. Then we calculate the zones on the target plane where the subdivided light rays should be distributed to. Finally we use an analytic approximate method to construct the freeform lens. After constructing the freeform lens, we simulate for the optical model by using the ray-tracing software LightTools®. The simulation results are very close to our expectation, that is, most light rays are distributed to the zones as designed. Finally we modulated the design process and the simulation results show that the Cree XLamp XR-E LED light source through the freeform lens can achieve up to 94.8% uniformity and 89.1% efficiency including Fresnel losses for a 1 m distance away and 1 m radius of circular illumination plane. This method utilizes simple processes and the model can be easily constructed; so they can be very useful for designing LED illumination. As long as variables such as the distance and range of the illumination plane are prescribed, the lens of secondary optics can be designed to achieve high uniformity and efficiency for LED illumination.

並列關鍵字

Secondary optics ； LED illumination ； freeform lens

參考文獻

[21] Warren J. Smith, Modern Optical Engineering, Mc Graw Hill, 2008.

[19] Robert E. Fischer, Biljana Tadic-Galeb, and Paul R. Yoder, Optical System Design, Mc Graw Hill, 2008.

[5] Julio Chaves, Introduction to NONIMAGING OPTICS, CRC Press, 2008.

[6] P. Benítez, J. C. Miñano, J. Blen, J. Chaves, O. Dross, M. Hernández, and W. Falicoff, “Simultaneous multiple surface optical design method in three dimensions,” Opt. Eng. 43(7), 2004, 1489–1502.

[7] K. L. Huang, J. J. Chen, T. Y. Wang, and L. L. Huang, “Free-form lens design for LED indoor illumination,” Proc. SPIE 7852, 2010, 78521D.

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高均勻度及高效率LED照明之自由曲面透鏡設計

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