本論文主要目的在研究LED光源之中場傳遞行為,了解其強度在不同傳輸距離時之變化情形進而定義其準遠場距離,並利用中場擬合法建立出精確LED光學模型,依據此精確光學模型來設計符合歐洲ECE法規的自行車後警示燈,並將自行車後警示燈與反射片做結合,設計出被動與主動安全兼具之車後燈組,以提升自行車在夜晚行進時之安全。The main purpose of this thesis is to study the mid-field behavior of LED. Considering the changes of LED’s intensity distribution in different distances and defining a quasi far-field distance. And use the accurate LED model which is built with “Cross correlation in the mid-field region” principle to design a bicycle tail lamp combined with reflector to conform to ECE regulation. The design is supposed to provide both active and passive safeties.