Design of a bike headlamp based on a power whitelightemitting diode.pdf

Design of a bike headlamp based on a power white-light-emitting diode Yi-Chien Lo Cheng-Chien Chen Hung-Yu Chou Kai-Yu Yang Ching-Cherng Sun Downloaded from SPIE Digital Library on 06 Apr 2012 to 2. Terms of Use: /terms OE Letters Design of a bike headlamp based on a power white-light-emitting diode Yi-Chien Lo, Cheng-Chien Chen, Hung-Yu Chou, Kai-Yu Yang, and Ching-Cherng Sun National Central University, Department of Optics and Photonics, Chung-Li 320, Taiwan E-mail: ccsun@.tw Abstract. In this letter, we present a new design for a light- emitting diode- based bike headlamp. The optical design con- tains two horizontal reflectors and a light pipe with two hor- izontal parallel mirrors. The designed illumination pattern in our simulations performs a contrast of 250 in the K-mark regulation, and it was measured to be 21 in the experiment with a not well-finished prototype, which was operated at 1 W. The contrast is higher than 5 as requested in the reg- Fig. 1 The geometry by the K-mark regulation. ulation. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE) . [DOI: 10.1117/1.3615278] In such an application, the volume of the TIR lens will be Subject terms: light-emitting diode; optical design; bike lamp. large and an aspherical surface or microstructure could be Paper 110252LR received Mar. 14, 2011; revised manuscript re- implanted on the exit surface to perform the cut-off line and ceived May 1, 2011; accepted for publication Jul. 5, 2011; published requested pattern. The difficulty in mass production and high online Aug. 22, 2011. cost will make such a design impractical. Another design