[1] Schruben J S. Analysis of rotationally symmetric reflectors for illuminating systems[J]. Journal of the Optical Society of America, 64, 55-58(1974). http://www.opticsinfobase.org/josa/abstract.cfm?uri=josa-64-1-55

[2] Ding Y, Liu X, Zheng Z R et al. Freeform LED lens for uniform illumination[J]. Optics Express, 16, 12958-12966(2008). http://www.ncbi.nlm.nih.gov/pubmed/18711534

[3] Wu R, Zheng Z, Li H et al. Optimization design of irradiance array for LED uniform rectangular illumination[J]. Applied Optics, 51, 2257-2263(2012). http://www.ncbi.nlm.nih.gov/pubmed/22614399

[4] Liu Z Q, Sun Y J, Lin Y D. Freeform reflector design for rectangular illumination distribution based on differential geometry[J]. Acta Optica Sinica, 32, 1022006(2012).

[5] He Z H, Dong Q M, Wang S L et al. LED freeform lens design for street uniform illumination[J]. China illuminating Engineering Journal, 25, 85-89(2014).

[6] Cvetkovic A, Dross O, Chaves J et al. Etendue-preserving mixing and projection optics for high-luminance LEDs, applied to automotive headlamps[J]. Optics Express, 14, 13014-13020(2006). http://www.opticsinfobase.org/oe/abstract.cfm?id=121420

[7] Xing S S, Wu R M, Li H F et al. Freeform-surface design of off-axis illumination in projection lithography[J]. Acta Optica Sinica, 31, 0322002(2011).

[8] Zeng D, Peng D S, Jiang Y. LED freeform lens design for roundabout crossing illumination[J]. Laser & Optoelectronics Progress, 53, 072202(2016).

[9] Pan H, Chen G Q, Du B J. Design of double freeform surface lens for LED uniform illumination based on cubic splines[J]. Laser & Optoelectronics Progress, 53, 032201(2016).

[10] Chen J J, Wang T Y, Huang K L et al. Freeform lens design for LED collimating illumination[J]. Optics Express, 20, 10984-10995(2012). http://www.ncbi.nlm.nih.gov/pubmed/22565721

[11] Zhao H, Li C G, Chen Z T et al. Design of collimating lens with uniform illumination for LED based on double freeform surface[J]. Acta Optica Sinica, 37, 0422001(2017).

[12] John H, Kurtis D[M]. Numerical methods using Matlab, 376-387(2005).