[1] [1] Feng Qibin, Li Ya′ni, Li Qigong, et al. Lens array with double freeform surface for LED backlight in LED imaging engine of helmet-mounted display［J］. Acta Optica Sinica, 2015, 35(11): 1123003.

[2] [2] Gui Li, Sun Xiuhui, Yin Shaoyun, et al. Modeling error analysis and compensation design for free-form uniform illumination lens［J］. Acta Optica Sinica, 2015, 35(10): 1022008.

[3] [3] Chen H C, Lin J Y, Chiu H Y. Rectangular illumination using a secondary optics with cylindrical lens for LED street light［J］. Optics Express, 2013, 21(3): 3201-3212.

[4] [4] Pan J W, Su Y C, Chen Y S. Secondary optical element design for intracorporeal LED illumination system［J］. Optics Letters, 2014, 39(2): 224-227.

[5] [5] Chen J J, Lin C T. Freeform surface design for a light-emitting diode-based collimating lens［J］. Optical Engineering, 2010, 49(9): 093001.

[6] [6] Ries H, Muschaweck J A. Tailoring freeform lenses for illumination［C］. SPIE, 2001, 4442: 43-50.

[7] [7] Wang G, Wang L, Li L, et al. Secondary optical lens designed in the method of source-target mapping［J］. Applied Optics, 2011, 50(21): 4031-4036.

[8] [8] Zhao S, Wang K, Chen F, et al. Lens design of LED searchlight of high brightness and distant spot［J］. Journal of the Optical Society of America A, 2011, 28(5): 815-820.

[9] [9] Chen Enguo, Liu Peng, Yu Feihong. Synchronized parameter optimization of the double freeform lenses illumination system used for the CF-LCoS pico-projectors［J］. Optics & Laser Technology, 2012, 44(7): 2080-2087.

[10] [10] Wang Guangzhen, Wang Lili, Li Fuli, et al. Design of optical element combining Fresnel lens with microlens array for uniform light-emitting diode lighting［J］. Journal of the Optical Society of America A, 2012, 29(9): 1877-1884.

[11] [11] Chen J, Wang T, Huang K, et al. Freeform lens design for LED collimating illumination［J］. Optics Express, 2012, 20(10): 10984-10995.

[12] [12] Aslanov E, Doskolovich L L, Moiseev M A. Thin LED collimator with free-form lens array for illumination applications［J］. Applied Optics, 2012, 51(30): 7200-7205.

[13] [13] Chen Chen, Zhang Xiaohui. Design of optical system for collimating the light of an LED uniformly［J］. Journal of the Optical Society of America A, 2014, 31(5): 1118-1125.

[14] [14] Liu Zhengquan, Sun Yaojie, Lin Yandan. Freeform reflector design for rectangular illuminance distribution based on differential geometry［J］. Acta Optica Sinica, 2012, 32(10): 1022006.

[15] [15] Shen Y N, Huang Y F, Han X. Design of collimating system for LED source［C］. SPIE, 2013, 9042: 90420V.