Freeform surface design for high-efficient LED low-beam headlamp lens

Realizing the high energy efficiency of LED-based low-beam headlamp while maintaining a sharp 15°inclined cut-off line is still an important issue in the automobile industry. In this paper, we introduce a new method to design the high-efficient freeform lens for LED low-beam headlamp. The lens is designed with the integrable ray mapping method, which is aimed to produce a prescribed irradiance distribution conformed to the United Nations Economic Commission for Europe vehicle regulations (ECE) R112. The results of Monte Carlo ray tracing simulation demonstrate that the designed LED low-beam headlamp can fully comply with the ECE R112 regulation without any other baffles or reflectors. The structure of the lens is simple and easy to be fabricated. The energy efficiency of the obtained optical system is more than 83.5% considering the Fresnel loss, which is much higher than the traditional designs. •The smooth freeform lens is designed for LED low-beam headlamp optical system.•The integrable mapping is obtained via symplectic transformation.•The optical performance can fully comply with the ECE R112 regulation when the light source is the actual extended LED.•The energy efficiency of the optical system can reach up to 83.5% considering the Fresnel loss.