Optimization optical design for tunnel lamps with LED source

Tunnel lighting design should be energy saving as much as possible in precondition of satisfying the visual requirements, which is highly depended on the light distributions of tunnel luminaires. In this paper, an optimization model is built to seek for the most energy-saving light distribution as well as satisfy lighting requirements set by International Commission on Illumination (CIE). A polynomial of cosine function for the illumination distribution on the road is used to make the optimization model solvable. The optimal light distribution is obtained based on a given tunnel. Then, a smooth freeform lens is designed according to the variable separation method. Compared with the LED tunnel luminaire currently used in Chongqing, the luminaire with the optimal light distribution can not only meet the requirements of tunnel lighting specified by CIE quite well, but also save energy about 12%.