Achromatic LED-based Projection Lens Design for Automobile Headlamp

Abstract In this paper, an achromatic LED projection headlamp (ALPH) is proposed for compensating color dispersion on the cut-off line of the light pattern. The ALPH consists of a white light LED, an elliptical reflector, a stop, an achromatic doublet lens (ADL). The ALPH is optimized and designed by computer programs firstly and its prototype is verified in experiments. According to the simulation results, the distance between the cut-off lines of the red light and the blue light is about 5.4 mm at 25 m and much less than that of the conventional LED projection headlamp. The measurements of the spectrometer and the illuminometer show that the ALPH can effectively enhance the consistency of the light pattern of the red and blue light and reduces the color dispersion near the cut-off line simultaneously. Moreover, all test points conform with the ECE R112 regulation except for only one point. By the determination of the integrating sphere, the optical efficiency of the prototype is 59%.