Abstract

This paper utilizes the Taguchi design method to optimize the design parameters of a light-emitting diode (LED) backlight unit for wide color gamut liquid crystal displays (LCDs). In optimizing the design, the parametric analyses consider two particular regions of the backlight unit, namely, the color-mixing zone and the extractor zone. The Taguchi experiments are configured in ${\rm L} _{9} (3 ^{4} )$ orthogonal arrays and are designed to evaluate the effects of the design parameters on the color-difference, optical efficiency and luminance of the unit. The analysis of variance (ANOVA) results reveal that the optical efficiency and color-difference properties are determined primarily by the reflector design and the length of the color mixing zone, respectively, while the luminance to the LCD panel is affected principally by the taper angle of the optical microstructures in the extractor zone. The optimal design parameters of the color-mixing zone and extractor zone are estimated from the Taguchi ${\rm S}/{\rm N}$ ratio data and the ANOVA results, and are verified via ray-tracing simulations. For an input flux of 1501 lm, the optimal design shows 0.01 of the color differences in CIE 1976 color space, 85% of the optical efficiency, and 10675 nits of luminance. Thus, the optimized backlight unit provides an ideal solution for the illumination of large-scale LCD display devices.

© 2009 IEEE

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  1. T. Murata, I. Fujieda, "Input couplers for thin light-guides and light-emitting diodes," Opt. Eng. 47, 027001 (2008).
  2. C. C. Sun, I. Moreno, S. H. Chung, W. T. Chien, C. T. Hsieh, T. H. Yang, "Direct LED backlight for large area LCD TVs: Brightness analysis," Proc. SPIE (2007) pp. 666909.
  3. K. Kalantar, "Modulation of viewing angle on an LCD surface through backlight optics," SID Int. Symp. Dig. Tech. Papers (2003) pp. 647-652.
  4. Y. Martynov, H. Konijn, N. Pfeffer, S. Kuppens, W. Timmers, "High-efficiency slim LED backlight system with mixing light guide," SID Int. Symp. Dig. Tech. Papers (2003) pp. 1259-1261.
  5. W. P. Tseng, Incident assembly of light guide plate U.S. Patent 20 060 203 511 Filed: Mar. 9, 2005.
  6. M. S. Choi, C. H. Lee, S. H. Lim, S. M. Yamg, Back light unit having light guide buffer plate U.S. Patent 20 080 137 374 Filed: Nov. 29, 2007.
  7. R. S. West, H. Konijn, W. Sillevis-Smitt, S. Kuppens, N. Pfeffer, Y. Martynov, Y. Takaaki, S. Eberle, G. Harbers, T. W. Tan, C. E. Chan, "High brightness direct LED backlight for LCD-TV," SID Int. Symp. Dig. Tech. Papers (2003) pp. 1262-1265.
  8. P. C. P. Chao, L. D. Liao, C. W. Chiu, "Design of a novel LED lens cap and optimization of LED placement in a large area direct backlight for LCD-TVs," Proc. SPIE (2006) pp. 61960N.
  9. D. Feng, G. Jin, Y. Yan, S. Fan, "High quality light guide plates that can control the illumination angle based on microprism structures," Appl. Phys. Lett. 85, 6016-6018 (2004).
  10. J. C. Minano, P. Benitez, J. Chaves, M. Hernandez, O. Dross, A. Santamaria, "High-efficiency LED backlight optics designed with the flow-line method," Proc. SPIE (2005) pp. 594202.
  11. P. Xu, X. Chen, J. Huang, X. Zhang, L. Wan, K. Wang, J. Liu, "A novel highly integrated light guide plate using micro optical technique," Proc. SPIE (2007) pp. 683409.
  12. J. C. William, "Backlight pattern optimization," Proc. SPIE (2007) pp. 683407.
  13. T. L. R. Davenport, W. J. Cassarly, "Optimizing density patterns to achieve desired light extraction for displays," Proc. SPIE (2007) pp. 63420T.
  14. J. G. Chang, Y. B. Fang, "Dot-pattern design of a light guide in an edge-lit backlight using a regional partition approach," Opt. Eng. 46, 043002 (2007).
  15. J. H. Kim, M. Y. Park, J. J. Kim, H. Kim, J. H. Jun, J. H. Park, S. M. Cho, D. W. Lee, S. R. Hwang, H. S. Jeong, "High-efficiency trichromatic LED backlight for mobile LCDs," Proc. SPIE (2006) pp. 613409.
  16. C. M. Chang, Y. C. Fang, C. R. Lee, "A new design with mixing R.G.B. LED (red, green, blue light-emitting diode) for modern LCD (liquid crystal display) backlight system," Proc. SPIE (2006) pp. 63380Q.
  17. A. G. Olabi, "Using Taguchi method to optimize welding pool of dissimilar laser-welded components," Opt. Laser Technol. 40, 379-388 (2008).
  18. F. R. Tony, A. C. David, "Optimized selection of benchmark test parameters for image watermark algorithms based on Taguchi methods and corresponding influence on design decisions for real-world applications," Proc. SPIE (2003) pp. 215-228.
  19. K. S. Kwon, R. M. Lin, "Robust finite element model updating using Taguchi method," J. Sound and Vibration 280, 77-99 (2005).
  20. G. Taguchi, T. Yokoyama, Taguchi Methods: Design of Experiments (ASI Press, 1993).
  21. H. H. Le, Taguchi Methods: Principles and Practices of Quality Design (Gau Lih, 2008).
  22. H. Oktem, T. Erzurumlu, I. Uzman, "Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part," Mater. Des. 28, 1271-1278 (2007).

2008

T. Murata, I. Fujieda, "Input couplers for thin light-guides and light-emitting diodes," Opt. Eng. 47, 027001 (2008).

A. G. Olabi, "Using Taguchi method to optimize welding pool of dissimilar laser-welded components," Opt. Laser Technol. 40, 379-388 (2008).

2007

J. G. Chang, Y. B. Fang, "Dot-pattern design of a light guide in an edge-lit backlight using a regional partition approach," Opt. Eng. 46, 043002 (2007).

H. Oktem, T. Erzurumlu, I. Uzman, "Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part," Mater. Des. 28, 1271-1278 (2007).

2005

K. S. Kwon, R. M. Lin, "Robust finite element model updating using Taguchi method," J. Sound and Vibration 280, 77-99 (2005).

2004

D. Feng, G. Jin, Y. Yan, S. Fan, "High quality light guide plates that can control the illumination angle based on microprism structures," Appl. Phys. Lett. 85, 6016-6018 (2004).

Appl. Phys. Lett.

D. Feng, G. Jin, Y. Yan, S. Fan, "High quality light guide plates that can control the illumination angle based on microprism structures," Appl. Phys. Lett. 85, 6016-6018 (2004).

J. Sound and Vibration

K. S. Kwon, R. M. Lin, "Robust finite element model updating using Taguchi method," J. Sound and Vibration 280, 77-99 (2005).

Mater. Des.

H. Oktem, T. Erzurumlu, I. Uzman, "Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part," Mater. Des. 28, 1271-1278 (2007).

Opt. Eng.

J. G. Chang, Y. B. Fang, "Dot-pattern design of a light guide in an edge-lit backlight using a regional partition approach," Opt. Eng. 46, 043002 (2007).

T. Murata, I. Fujieda, "Input couplers for thin light-guides and light-emitting diodes," Opt. Eng. 47, 027001 (2008).

Opt. Laser Technol.

A. G. Olabi, "Using Taguchi method to optimize welding pool of dissimilar laser-welded components," Opt. Laser Technol. 40, 379-388 (2008).

Other

F. R. Tony, A. C. David, "Optimized selection of benchmark test parameters for image watermark algorithms based on Taguchi methods and corresponding influence on design decisions for real-world applications," Proc. SPIE (2003) pp. 215-228.

J. H. Kim, M. Y. Park, J. J. Kim, H. Kim, J. H. Jun, J. H. Park, S. M. Cho, D. W. Lee, S. R. Hwang, H. S. Jeong, "High-efficiency trichromatic LED backlight for mobile LCDs," Proc. SPIE (2006) pp. 613409.

C. M. Chang, Y. C. Fang, C. R. Lee, "A new design with mixing R.G.B. LED (red, green, blue light-emitting diode) for modern LCD (liquid crystal display) backlight system," Proc. SPIE (2006) pp. 63380Q.

J. C. Minano, P. Benitez, J. Chaves, M. Hernandez, O. Dross, A. Santamaria, "High-efficiency LED backlight optics designed with the flow-line method," Proc. SPIE (2005) pp. 594202.

P. Xu, X. Chen, J. Huang, X. Zhang, L. Wan, K. Wang, J. Liu, "A novel highly integrated light guide plate using micro optical technique," Proc. SPIE (2007) pp. 683409.

J. C. William, "Backlight pattern optimization," Proc. SPIE (2007) pp. 683407.

T. L. R. Davenport, W. J. Cassarly, "Optimizing density patterns to achieve desired light extraction for displays," Proc. SPIE (2007) pp. 63420T.

C. C. Sun, I. Moreno, S. H. Chung, W. T. Chien, C. T. Hsieh, T. H. Yang, "Direct LED backlight for large area LCD TVs: Brightness analysis," Proc. SPIE (2007) pp. 666909.

K. Kalantar, "Modulation of viewing angle on an LCD surface through backlight optics," SID Int. Symp. Dig. Tech. Papers (2003) pp. 647-652.

Y. Martynov, H. Konijn, N. Pfeffer, S. Kuppens, W. Timmers, "High-efficiency slim LED backlight system with mixing light guide," SID Int. Symp. Dig. Tech. Papers (2003) pp. 1259-1261.

W. P. Tseng, Incident assembly of light guide plate U.S. Patent 20 060 203 511 Filed: Mar. 9, 2005.

M. S. Choi, C. H. Lee, S. H. Lim, S. M. Yamg, Back light unit having light guide buffer plate U.S. Patent 20 080 137 374 Filed: Nov. 29, 2007.

R. S. West, H. Konijn, W. Sillevis-Smitt, S. Kuppens, N. Pfeffer, Y. Martynov, Y. Takaaki, S. Eberle, G. Harbers, T. W. Tan, C. E. Chan, "High brightness direct LED backlight for LCD-TV," SID Int. Symp. Dig. Tech. Papers (2003) pp. 1262-1265.

P. C. P. Chao, L. D. Liao, C. W. Chiu, "Design of a novel LED lens cap and optimization of LED placement in a large area direct backlight for LCD-TVs," Proc. SPIE (2006) pp. 61960N.

G. Taguchi, T. Yokoyama, Taguchi Methods: Design of Experiments (ASI Press, 1993).

H. H. Le, Taguchi Methods: Principles and Practices of Quality Design (Gau Lih, 2008).

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