Freeform lens design for small-angle lighting with uniform distribution of correlated color temperature and illumination

In this paper we propose a method realizes the uniform distribution of both correlated color temperature (CCT) and illumination on the target plane. A lens with a flat bottom surface and a freeform top surface is designed. The simulation run by optical software shows that the lens designed in the new method has a better uniformity of CCT than the lens designed in conventional method, and the uniformity of illumination and the efficiency of energy are also quite good. This lens is much easier and more economical to manufacture comparing the lenses with double freeform surfaces or the systems with several lenses which are also used to improve the uniformity of CCT distribution.