Optical Design of LED Street Lamps

根據實際的道路規格，設計光學元件，讓LED的光經過該光學元件後能夠在道路上形成均勻照明，並且能夠符合道路規範。一般LED的光強分布為Lambertian，由於道路為長方形，若是單純設計對稱型的光學元件只能讓目標面圓形區域內達到均勻照明，將使部分光照在道路外圍造成不必要的浪費，甚至會造成環境光害、眩光產生交通事故等等的問題。所以本文設計非對稱透鏡並配合反射板，使路燈發出的光在平行於行車方向與垂直於行車方向為不同的配光分布，因而達到長方型區域內均勻照明。最後進行實際道路照明的模擬，確認其照明結果能夠符合道路照明規範。Based upon the practical specifications of street illumination, we design the secondary optical elements so that the LED illumination can be transformed into a uniform illumination on the road to meet the street illumination standards. Generally, LED light intensity distribution is Lambertian, however, the geometry of the road area are rectangular. Therefore, traditionally symmetric design of an original LED lens can only produce uniform illumination on a circular area. A major portion of light will fall outside the street and will results in unnecessary power consumption, environmental light pollution, the glare issues, and even traffic accidents, etc. Consequently, the lens design should be asymmetric in order that the emitted light can be distributed uniformly in the directions parallel and perpendicular to the driving direction and thus can achieve uniform illumination within the rectangular area of the road. In this thesis, free-form lens and reflector are developed to create a batwing light intensity distribution in the direction parallel to the driving direction and asymmetrical intensity distribution in perpendicular direction to create a rectangular light pattern and achieve high efficiency of uniform illumination. Finally, our simulations validate their compliance with the street lighting specifications