Design of LED Street Lighting Adapted for Free-Form Roads

Street lighting, which is one of the main players in energy waste and light pollution at night, still faces the challenge of efficient lighting of roadways with curved and twisted shapes. To meet this challenge, we propose an effective and efficient adaptive light-emitting diode (LED) luminaire. This LED lamp delivers a roadway-shape light pattern, which maximizes illumination performance. The light is efficiently and homogeneously directed only where is needed; which reduces glare, and improves both the eye comfort and the visual discrimination ability of car drivers and pedestrians. The proposed luminaire is very practical in that it only requires to replace the cover plate, which is a special microlens array sheet, to produce different shape light patterns. The adaptive mechanism is simple and effective: LED light is first collimated and then efficiently distributed on a freeform roadway by the special microlens sheet. We present an extensive analysis of the lighting adaptability of the proposed luminaire by Monte Carlo ray tracing. In particular, we studied the effect of the main microlens structural parameters in the shape and size of the delivered illumination distribution on the roadway. We present a design example, a prototype construction, and an experimental confirmation on a scale street lighting system. Simulations and experimental results show the advantages of adaptive luminaires over the traditional nonadaptive approaches.