[1] [1] Liu Zuming, Li Xiaotao. LED lighting design and applications［M］. 2nd ed. Beijing: Publishing House of Electronics Industry, 2014: 1-33.

[2] [2] Chen Yu. LED Manufacturing technology and applications［M］. 3rd ed. Beijing: Publishing House of Electronic Industry, 2013: 2-28.

[3] [3] Guo Jianying. Summary of rainfall sensor products［J］. Auto Electric Parts, 2007(11): 1-3.

[4] [4] Li Lin. Modern optical design method［M］. Beijing: Beijing Institute of Technology Press, 1998: 162-165.

[5] [5] Gu Changxin. Computation physics［M］. Shanghai: Fudan University Press, 2010: 152-158.

[6] [6] Ding Y, Liu X, Zheng Z R, et al. Freeform LED lens for uniform illumination［J］. Optics Express, 2008, 16(17): 12958-12966.

[7] [7] Jing Lei, Liu Hua, Zhao Huifu, et al. Compact collimator design for high-brightness light-emitting diode［J］. Acta Optica Sinica, 2011, 31(12): 1222001.

[8] [8] Luo Xiaoxia, Liu Hua, Lu Zhenwu, et al. Automated optimization of free-form surface lens for LED collimation［J］. Acta Photonica Sinica, 2011, 40(9): 1351-1355.

[9] [9] Oliker V. Geometric and variational methods in optical design of reflecting surfaces with prescribed irradiance properties［C］. SPIE, 2005, 5924: 594207.

[10] [10] Hao Jian, Liu Hua, Sun Qiang, et al. Optimization of freeform surface lens for collimating illumination of LED［J］. Laser & Optoelectronics Progress, 2014, 51(3): 032302.

[11] [11] Wan Yunjie, Lin Haobo, Liu Jie, et al. Design of LED lens with ultra-high light efficiency and small light-gathering angle for realizing uniform light distribution［J］. Laser & Optoelectronics Progress, 2016, 53(12): 122202.

[12] [12] Cheng Zhiming, Zeng Ping, Zhang Zhihai, et al. Reaearch on multi-direction collimation beam on the plane parallel with LED lighting plane［J］. Acta Optica Sinica, 2014, 34(10): 1008001.

[13] [13] Benitez P, Minano J C, Blen J, et al. Simultaneous multiple surface optical design method in three dimensions［J］. Optical Engineering, 2004, 43(7): 1489-1502.

[14] [14] Wang C L, Li X N, He L Q. Constructing user defined surface in ZEMAX［J］. Optical Instruments, 2001, 23(3): 23-26.