Abstract

A novel LED backlight unit implementing a light guide plate (LGP) with a two-dimensional array of grating micro-dots is proposed. By optimizing grating-vector orientations of local gratings and applying suitable grating-depth modulation in the array, taking into consideration of the radiation pattern of the LED source, uniform out-coupled light distribution within a narrow luminance angle was achieved without recognizable hot spots. Such a light guide plate was fabricated using a dot-matrix holographic interferometer setup and a UV embossing replication. Fabricated polycarbonate LGP showed ~62% intensity uniformity within ~8° and ~20° luminance angles in two main directions.

© 2007 Optical Society of America

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References

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  1. M. Parikka, T. Kaikuranta, P. Laakkonen, J. Tauyanen, J. Tervo, M. Honkanen, M. Kuittnen, and J. Turunen, "Deterministic diffractive diffusers for displays," Appl. Opt. 40, 2239-2246 (2001).
    [CrossRef]
  2. J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
    [CrossRef]
  3. A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
    [CrossRef]
  4. J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
    [CrossRef]
  5. S. I. Ochiai, "Light guide plate and light guide plate assembly utilizing diffraction grating," US Patent 5703667 (1997).
  6. S. Nam, M. G. Lee, J. H. Kim, J. H. Min, J. S. Choi, S. M. Lee, and H. Y. Choi, "Hologram based light-guide plate for LCD-backlights," IDW 01 (2001).
  7. M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).
  8. C.-K. Lee, J. Wu, S.-L. Yeh, C.-W Tu, Y.-A. Han, E. Liao, L. Chang, I.-E. Tsai, H.-H. Lin, J. Hsieh, and J. Lee, "Optical configuration and color-representation range of a variable-pitch dot matrix holographic printer," Appl. Opt. 39, 40-53 (2000).
    [CrossRef]
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    [CrossRef]
  10. M. G. Moharam and T. K. Gaylord, "Three-dimensional vector coupled-wave analysis of planar grating diffraction," J. Opt. Soc. Am 73, 1105-1112 (1983).
    [CrossRef]
  11. M. Neviere, Electromagnetic theory of gratings R. Petei, Ed., (Springer Verlag, Berlin, 1980).
  12. R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
    [CrossRef]
  13. P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
    [CrossRef]

2002

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

2001

2000

1998

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

1997

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

1996

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
[CrossRef]

1983

M. G. Moharam and T. K. Gaylord, "Three-dimensional vector coupled-wave analysis of planar grating diffraction," J. Opt. Soc. Am 73, 1105-1112 (1983).
[CrossRef]

1982

Baba, M.

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

Chang, L.

Choi, H. Y.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Choi, J. S.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Dandlinger, R.

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
[CrossRef]

Gaylord, T. K.

M. G. Moharam and T. K. Gaylord, "Three-dimensional vector coupled-wave analysis of planar grating diffraction," J. Opt. Soc. Am 73, 1105-1112 (1983).
[CrossRef]

M. G. Moharam and T. K. Gaylord, "Diffractin analysis of dielectric surface-relief gratings," J. Opt. Soc. Am. 72, 1385-1392 (1982).
[CrossRef]

Han, Y.-A.

Herzig, H. P.

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
[CrossRef]

Honkanen, M.

Horibe, A.

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

Hsieh, J.

Husser, A.

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

Kaikuranta, T.

Kim, J. H.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Koike, Y.

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

Kuittnen, M.

Laakkonen, P.

Lee, C.-K.

Lee, J.

Lee, M. G.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Lee, S. M.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Liao, E.

Lin, H.-H.

Liu, Z. S.

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

Magnusson, R.

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

Min, J. H.

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

Moharam, M. G.

M. G. Moharam and T. K. Gaylord, "Three-dimensional vector coupled-wave analysis of planar grating diffraction," J. Opt. Soc. Am 73, 1105-1112 (1983).
[CrossRef]

M. G. Moharam and T. K. Gaylord, "Diffractin analysis of dielectric surface-relief gratings," J. Opt. Soc. Am. 72, 1385-1392 (1982).
[CrossRef]

Nihei, E.

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

Nussbaum, P.

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

Parikka, M.

Philipoussis, I.

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

Shin, D.

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

Tauyanen, J.

Teijido, J. M.

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
[CrossRef]

Tervo, J.

Tsai, I.-E.

Tu, C.-W

Turunen, J.

Wawro, D.

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

Wu, J.

Yeh, S.-L.

Young, P. P.

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

Appl. Opt.

Eurodisplay

M. G. Lee, H. Y. Choi, J. H. Min, J. S. Choi, J. H. Kim, and S. M. Lee, "Optical characteristics of holographic light-guide plate for LCD," Eurodisplay 2002, 343-346 (2002).

J. Opt. Soc. Am

M. G. Moharam and T. K. Gaylord, "Three-dimensional vector coupled-wave analysis of planar grating diffraction," J. Opt. Soc. Am 73, 1105-1112 (1983).
[CrossRef]

J. Opt. Soc. Am.

Opt. Eng.

P. Nussbaum, I. Philipoussis, A. Husser, and H. P. Herzig, "Simple technique for replication of micro-optical elements," Opt. Eng. 371804-8 (1998).
[CrossRef]

Proc. SPIE

R. Magnusson, Z. S. Liu, D. Wawro, P. P. Young, and D. Shin, "Waveguide-grating coupler for illumination of photonic antennas," Proc. SPIE 3075, 101-108 (1997).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Diffraction properties of volume holographic diffusers," Proc. SPIE 2774,747-756 (1996).
[CrossRef]

J. M. Teijido, H. P. Herzig, and R. Dandlinger, "Design of a non-conventional illumination system using a scattering light pipe," Proc. SPIE 2951,146-155 (1996).
[CrossRef]

SID

A. Horibe, M. Baba, E. Nihei, and Y. Koike, "High Efficiency and High Visual Quality LCD Backlighting System," SID 29, 153-156 (1998).
[CrossRef]

Other

S. I. Ochiai, "Light guide plate and light guide plate assembly utilizing diffraction grating," US Patent 5703667 (1997).

S. Nam, M. G. Lee, J. H. Kim, J. H. Min, J. S. Choi, S. M. Lee, and H. Y. Choi, "Hologram based light-guide plate for LCD-backlights," IDW 01 (2001).

M. Neviere, Electromagnetic theory of gratings R. Petei, Ed., (Springer Verlag, Berlin, 1980).

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Figures (12)

Fig. 1.
Fig. 1.

(a) A schematic diagram of a grating micro-dot patterned LGP under study. (b) Portion of the non-overlapped propagating beam, covering the LGP, which mainly contributes the out-coupling. The P1 and P2 are virtual LED sources responsible for two covered regions. Two important directions D1 and D2 are illustrated.

Fig. 2.
Fig. 2.

Schematic diagrams of (a) conical grating diffraction and (b) classical in-plane grating diffraction.

Fig. 3.
Fig. 3.

(a) Calculated forward -1stdiffraction order as functions of the grating period and the inclination incident angle. (b) Diffraction efficiency weighted by the intensity pattern of the LED.

Fig. 4.
Fig. 4.

A grating period that maximize the diffraction efficiency of the forward -1st order, which is coupled-out in the vertical direction.

Fig. 5.
Fig. 5.

(a) Optimized grating-depth distribution and (b) corresponding normalized out-coupling intensity distribution from the LGP.

Fig. 6.
Fig. 6.

Luminance angular distributions when each local grating-vector orientation is (a) aligned with respect to LED’s azimuth beam profile and (b) fixed to D2 directions.

Fig. 7.
Fig. 7.

The schematic diagram of a dot-matrix holographic interferometer setup used in the fabrication of a grating micro-dot pattern.

Fig. 8.
Fig. 8.

(a) An optical microscope image of the micro-grating dots recorded in photoresist. (b) An SEM picture of the grating inside a micro-grating dot.

Fig. 9.
Fig. 9.

SEM pictures of the fabricated gratings with varying laser exposure times.

Fig. 10.
Fig. 10.

(a) A schematic of the diffraction efficiency measurement. (b) Comparison of efficiencies of -1st order backward diffracted order as a function of the grating depth obtained by theoretical calculation and experimental measurements.

Fig. 11.
Fig. 11.

(a) A camera image of the fabricated LGP and (b) corresponding intensity distributions.

Fig. 12.
Fig. 12.

Measured luminance angular distributions in the direction of (a) D1, (b) D2. (c) Simulated luminance angular distribution using a white LED and (d) cross-sectional view of those in the direction of D1 and D2.

Equations (1)

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Δ d = { I I avg I max I avg ( d d min ) , I < I avg I avg I I avg I min ( d max d ) , I > I avg }

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