Light Coupling of LED Plastic Optical Fiber: Design and Application

• Main Authors: Chien-yu Chou, 周建宇
• Other Authors: Shien-kuei Liaw
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/57949026617113675805

碩士 === 國立臺灣科技大學 === 電子工程系 === 98 === The thesis presents the guide-light structure by using fiber to deliver the visible light. We put LEDs where they can be easily replaced, repaired such as locate at neat floor. Then optical components are used to couple visible light and plastic optical fiber (POF) is used as transmission medium. The guide-light structure also composed of LED TIR lens and Fresnel lens to increase the coupling efficiency. The light-coupling research focus on LED TIR lens and Fresnel lens design, respectively. In order to allow more convenient add or drop LED numbers, both TIR lens and Fresnel lens are used. Firstly, the divergent light source can be transferred into a parallel light by using TIR lens, then the parallel light goes through the Fresnel lens and finally arrives the POF with high coupling efficiency. All the processes are designed by FRED. The key point for TIR lens design are on parabolic reflector and the convex surface. According to various parabolic focal lengths, we analyze the effect of the light emitting efficiency and the angular displacement. The LED constitutes ±10 degree angle of the light distribution for a Lambertian distribution LED. The design of Fresnel lens is based on designing approach let the ring to face imaging space. The coupling efficiency is analyzed according to vary the ring numbers and focal length. The parallel light source goes through the Fresnel lens and then transfer into a spotlight before couple into POF, where high coupling efficiency up to 84.4% may be obtained. Based on the same method to integrate TIR lens and Fresnel lens together in simulation, we can calculate the average coupling efficiency per LED lamp no matter how many LEDs are used., The average coupling efficiency are increase from 71.28% for 2 LEDs to 57.79% for 7 LEDs. Total power is 142.60 lm for 2 LEDs and404.53 lm for 7 LEDs with 3 to 6 LED lamps in between. In summary, the visible light can be coupled into POF by appropriately design optical structure so as to reduce the required LED lamps.