Secondary light distribution design for LED street light

The secondary optics design is a critical issue for the light distribution and output efficiency of the LED street light. Traditional light distribution methods are simple but difficult to get high energy efficiency and illumination uniformity together. In this paper, the adoption of the unsymmetrical freeform surface lens can obtain a rectangular light distribution pattern just cover the road with little waste of light. In this paper, an unsymmetrical freeform optic lens is designed which is combining with theory of non-imaging optics and freeform surface. The result shows that light energy efficiency and illumination uniformity under the freeform surface lens can reach 81% and 77% respectively.