適應性LED車頭燈之自由曲面透鏡光學系統設計

Abstract

汽車頭燈的演變從鹵素燈、HID一直到現今，儼然已成為主流的LED頭燈，目的無非是在漆黑的夜裡，點亮一條安全又舒適的道路。光源的更迭也為光學設計帶來嶄新的可能性，近年來，許多廠商投注許多心力，研究對應不同路況的燈具—即所謂的適應性車燈，雖然市面上已有配備此類型的車頭燈，但其價格昂貴，需要數十顆以上的LED，目前只限應用於BMW、Audi或Benz等高階車款。本篇論文提出以自由曲面透鏡設計為光學系統架構，利用折射定律及能量映射，建構出自由曲面，利用透鏡將光源對應到劃分好的數個矩形目標，再以LightTools®軟體模擬找出最佳效率及均勻度之自由曲面座標，最後依據車燈法規的量測標準，在軟體內進行測試分析。整個光學系統以21個LED光源、12個自由曲面透鏡排列於16cm×8cm×4cm的空間中，將符合ECE R123法規中的四種情境模式規範，分別為一般駕駛模式、城鎮模式、高速公路模式和惡劣天氣模式，每種情境之光學效率也都能達到70%左右。

The main idea of the evolution of automotive headlamp developed from halogen lamp, HID to the popular light source LED is just to provide a safety and comfort road illumination in dark night. The development of light source also brings a novel possibility for optical design. Lately, great quantity of manufactures put much effort in adaptive headlamp which designs for various traffic conditions, though they actually only apply on the luxury cars such as BMW, Audi and Benz currently. Moreover, the headlamps need at least 50 LEDs to complete their optical designs. Hence, the thesis proposed an optical design fulfilled by freeform lens, which are based on Snell’s law and source-target intensity mapping. We divided several areas of rectangle on the target plane according to the distribution of test points and test regions, and each rectangle corresponds to a set of freeform lens and LEDs. With simulation in LightTools® software, we could predict the final design of freeform lens with optimal efficiency and uniformity performance on the target. Finally, the optical design will be examined by the adaptive headlamp standard of ECE R123. To sum up, 21 LEDs and 12 freeform lens are composed of the optical design of headlamp, which arranged in a volume of 16 by 8 by 4 cubic centimeters. The module achieves the requests of ECE R123 photometric requirements, including Class V, Class C, Class E as well as Class W. Furthermore, the efficiency of each mode could reach optical efficiency around 70%.