Speaker: Hao-Wen Chuang ( 莊浩彣 ) Advisor: Prof. Chung-Hao Tien ( 田仲豪 助理教授 ) Prof. Yi-Pai Huang ( 黃乙白 助理教授 ) Display Institute, National Chiao Tung University, Hsinchu, Taiwan Jul, Design and Applications of Total Internal Reflection Lens

2 Advanced Display Optics Lab Enhancement of Brightness and Uniformity by LED Backlight Using a Total Internal Reflection (TIR) Lens Jang Hwan Hwang, and Dong Myoung Shin Dept. of Information Display, Univ. of HongIk, Seoul , Korea Doo Won Gong, Chang Wook Park, and Won Il Kang Research Center, Namotek Corporation, Ilsan , Korea Ji Hoon Seo and Young Kwan Kim* Dept. of Information Display, Univ. of HongIk, Seoul , Korea Gun Woo Hyung Dept. of Materials Science and Engineering, Univ. of HongIk, Seoul , Korea 2008 SID P-121

3 Advanced Display Optics Lab Outline  Issues of LED edge-type backlight  Design of TIR lens  Experimental results  Summary

4 Advanced Display Optics Lab Issues of LED Edge-type Backlight  inferior in lighting efficiency  A lot of LEDs are required to have high brightness  inappropriate for a wide-area liquid crystal panel  Bright-lines LED Light guide Optical films

5 Advanced Display Optics Lab TIR(Total Internal Reflection) Lens TIR lens: Polycarbonate, n d =1.59 Lightguide: PMMA, n d =1.49 Diffusion sheet: Tsujiden, D120 Prism sheet: 3M, BEF-II White LED: Amosense, 350 mA θ1: angle of primary reflection surface θ2: angle of secondary reflection surface

6 Advanced Display Optics Lab Experimental Results  Screen image using LED backlight with TIR lens Bright-lines can be minimized by TIR lens !!  Brightness:16436 nits, 40% higher than conventional BL Uniformity: 83.3%

7 Advanced Display Optics Lab Experimental Results (conti.)  Comparison of brightness/uniformity between conventional LED BL and LED BL with TIR lens as a function of the applied current

8 Advanced Display Optics Lab Summary  TIR lens can convert LED spot light source into linear light source.  TIR lens internally reflects the light on each TIR surface twice instead of lighting out directly.  The light guide using TIR lens has 40% brightness enhancement and 83% uniformity.  The bright-lines occurred in the conventional backlight can be eliminated by TIR lens.

9 Advanced Display Optics Lab The Optimal Design of TIR Lens for Improving LED Illumination Uniformity and Efficiency Yankun Zhen* a, Zhenan Jia a, Wenzi Zhang b a School of Science, Xian Shiyou University, Xian, China b State Key Laboratory of Modern Optical Instrumentation, Optical Engineering Department, Zhejiang University, Hangzhou, China Proc. of SPIE Vol. 6834, 68342K, (2007)

10 Advanced Display Optics Lab Outline  Design of the LED Illumination System  Design and optimization of TIR lens  Simulation results  Summary

11 Advanced Display Optics Lab Design of the LED Illumination System  Design TIR lens to couple out most of the light from LED and distribute on rectangular target plane uniformly LED: 2.1 mm square light emitting area peak wavelength = 525 nm 13 mm*10 mm 30 mm

12 Advanced Display Optics Lab Efficiency & Uniformity on RTP  Illumination efficiency  Illumination uniformity

13 Advanced Display Optics Lab Design of TIR Lens (1) (2) (3) (6) (5) (4) curveparametersdescription (1)(6)3radius, central position of the circle, length of this curve (2)(5)5Major/minor radius of the ellipse, start and end position of this curve(polar angles),rotated angle (3)1length

14 Advanced Display Optics Lab Optimization of the TIR Lens E: illumination efficiency on RTP U: illumination uniformity on RTP W: weight of terms respectively E 0 : threshold value of illumination efficiency to adjust the optimization emphasis efficiency uniformity

15 Advanced Display Optics Lab Simulation Results LED illumination result on RTP with the original TIR lens with the optimized TIR lens

16 Advanced Display Optics Lab Summary  An optimal design of TIR lens was proposed to control the light distribution on RTP.  The TIR lens has six surfaces controlled by 17 parameters.  The illumination efficiency and uniformity has respectively achieved 61.9%, 78%  The optimized TIR lens can provide greater compactness, simplified assembly for the entire LED projection system design.

17 Advanced Display Optics Lab 17