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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 8 — Apr. 12, 2010
  • pp: 8595–8604

Eliminating hotspots in a multi-chip LED array direct backlight system with optimal patterned reflectors for uniform illuminance and minimal system thickness

Byungwook Kim, Joongeok Kim, Won-Suk Ohm, and Shinill Kang  »View Author Affiliations

Optics Express, Vol. 18, Issue 8, pp. 8595-8604 (2010)

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We propose an optical design process that significantly reduces the time and costs in direct backlight unit (BLU) development. In it, the basic system specifications are derived from the optical characteristics of RGB light-emitting diodes (LEDs) comprising the BLU. The driving currents are estimated to determine the theoretical RGB flux ratio for a desired white point. The number of LEDs needed to produce the target luminance is then calculated from the combined optical efficiencies of the components. Last, an appropriate array configuration is sought based on the illuminance distribution function for meeting the target uniformity. To showcase the design process we built two 42-inch triangular cluster arrays of 40 × 16 LED elements. When a flat reflective sheet was used, the minimum thickness required of the system to satisfy the target uniformity was 30 mm. Introducing a patterned reflective sheet removed hotspots that resulted from reducing the system thickness without the aid of additional optical components. Using an optimized patterned reflective sheet, reduction in system thickness as much as 5 mm was possible.

© 2010 OSA

OCIS Codes
(220.2740) Optical design and fabrication : Geometric optical design
(220.4830) Optical design and fabrication : Systems design
(230.3670) Optical devices : Light-emitting diodes
(330.1730) Vision, color, and visual optics : Colorimetry
(220.2945) Optical design and fabrication : Illumination design

ToC Category:
Optical Design and Fabrication

Original Manuscript: March 10, 2010
Revised Manuscript: April 7, 2010
Manuscript Accepted: April 7, 2010
Published: April 8, 2010

Byungwook Kim, Joongeok Kim, Won-Suk Ohm, and Shinill Kang, "Eliminating hotspots in a multi-chip LED array direct backlight system with optimal patterned reflectors for uniform illuminance
and minimal system thickness," Opt. Express 18, 8595-8604 (2010)

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  1. D. M. Brown, R. Dean, and J. D. Brown, “LED backlight: design, fabrication, and testing,” Proc. SPIE 3938, 180–187 (2000). [CrossRef]
  2. E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science 308(5726), 1274–1278 (2005). [CrossRef] [PubMed]
  3. M. Anandan, “Progress of LED backlights for LCDs,” J. Soc. Inf. Disp. 16(2), 287–310 (2008). [CrossRef]
  4. G. Wyszecki and W. S. Stiles, Color Science 2nd Edition (Wiley, New York, 1982).
  5. K. Liang, W. Li, H. R. Ren, X. L. Liu, W. J. Wang, R. Yang, and D. J. Han, “Color measurement for RGB white LEDs in solid-state lighting using a BDJ photodetector,” Displays 30(3), 107–113 (2009). [CrossRef]
  6. S. Muthu and J. Gaines, “Red, green and blue LED-based white light source: Implementation challenges and control design,” in Proc. IEEE IAS Annu. Meeting 1 515–522 (2003).
  7. P. Deurenberg, C. Hoelen, J. van Meurs, and J. Ansems, “Achieving color point stability in RGB multi-chip LED modules using various color control loops,” Proc. SPIE 5941, 59410C (2005). [CrossRef]
  8. Ki-Chan Lee, Seung-Hwan Moon, Brian Berkeley, and Sang-Soo Kim,“Optical feedback system with integrated color sensor on LCD,” Sens, Actuators A 130–131, 214–219 (2006).
  9. W. Robert, Boyd, Radiometry and Dectection of Optical Radiation (Wiley, New York, 1983).
  10. G. Harbers, S. J. Bierhuizen, and M. R. Krames, “Performance of high power light emitting diodes in display illumination applications,” J. Display Technol. 3(2), 98–109 (2007). [CrossRef]
  11. I. Moreno, M. Avendaño-Alejo, and R. I. Tzonchev, “Designing light-emitting diode arrays for uniform near-field irradiance,” Appl. Opt. 45(10), 2265–2272 (2006). [CrossRef] [PubMed]
  12. P. C.-P. Chao, L.-D. Liao, and 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 6196, 61960N (2006). [CrossRef]
  13. Yankun Zhen, Zhenan Jiaa, and Wenzi Zhang, “The Optimization of Directly-Under-Light Type Backlight Module Structure for Brightness Uniformity,” Key Engineering Materials 364 – 366, 166–171 (2008).
  14. B. Kim, M. Choi, H. Kim, J. Lim, and S. Kang, “Elimination of flux loss by optimizing the groove angle in modified Fresnel lens to increase illuminance uniformity, color uniformity and flux efficiency in LED illumination,” Opt. Express 17(20), 17916–17927 (2009). [CrossRef] [PubMed]

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