Abstract

For the first time to our knowledge, a hybrid normal-reverse prism coupler was formed on the bottom surface of a light guide in a LED backlight system to achieve a thin, lightweight, LED backlight system. The hybrid prism coupler (HPC) simultaneously exhibits two functions: extraction of guided light from the light guide and focusing the radiated light from the light guide, corresponding to the optical functions of the prism and diffusive sheets used in conventional LED backlight systems. Therefore, using a HPC eliminates the prism and diffusive sheets that have been indispensable optical elements in conventional LED backlight systems, which consequently reduces the thickness of the LED backlight system by 40% compared with conventional systems.

© 2006 Optical Society of America

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References

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    [CrossRef]
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2004 (3)

2001 (2)

1994 (1)

S. Aoyama and T. Yamashita, "Superimposed grating for use with magneto-optical disk heads," Opt. Eng. 33, 3589-3595 (1994).
[CrossRef]

Aoyama, S.

S. Aoyama and T. Yamashita, "Superimposed grating for use with magneto-optical disk heads," Opt. Eng. 33, 3589-3595 (1994).
[CrossRef]

Cai, J.

Chien, K.-W.

Cornelissen, H.

Flores, A.

Honkanen, M.

Jiang, J.

Kaikuranta, T.

Kim, S.

Koïke, Y.

Kuittinen, M.

Laakkonen, P.

Lautanen, J.

Nagai, M.

Nordin, G. P.

Oba, M.

M. Shinohara, J. Takagi, M. Oba, and M. Takeuchi, "Curved prism array for controlling directivity of LED backlight," in Proceedings of the Tenth International Display Workshops (Society of Information Display, 2003), pp. 665-668.

Parikka, M.

Shieh, H.-P. D.

Shinohara, M.

M. Shinohara, J. Takagi, M. Oba, and M. Takeuchi, "Curved prism array for controlling directivity of LED backlight," in Proceedings of the Tenth International Display Workshops (Society of Information Display, 2003), pp. 665-668.

Tagaya, A.

Takagi, J.

M. Shinohara, J. Takagi, M. Oba, and M. Takeuchi, "Curved prism array for controlling directivity of LED backlight," in Proceedings of the Tenth International Display Workshops (Society of Information Display, 2003), pp. 665-668.

Takeuchi, M.

M. Shinohara, J. Takagi, M. Oba, and M. Takeuchi, "Curved prism array for controlling directivity of LED backlight," in Proceedings of the Tenth International Display Workshops (Society of Information Display, 2003), pp. 665-668.

Tervo, J.

Turunen, J.

Wang, M. R.

Yamashita, T.

S. Aoyama and T. Yamashita, "Superimposed grating for use with magneto-optical disk heads," Opt. Eng. 33, 3589-3595 (1994).
[CrossRef]

Yang, J. J.

Yokoyama, K.

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Figures (10)

Fig. 1
Fig. 1

Illustration of a hybrid normal-reverse prism coupler for a LED backlight system.

Fig. 2
Fig. 2

Cross-sectional illustration of (a) a conventional prism coupler and (b) a HPC.

Fig. 3
Fig. 3

Calculated results for the peak intensity of radiated light from a light guide versus the base angle of a normal prism.

Fig. 4
Fig. 4

Calculated results for dependence of the FWHM of radiated light intensity from the light guide on the ratio of the base length between normal and reverse prisms.

Fig. 5
Fig. 5

Derivation of light coupling efficiency. Light with power P 0 strikes in region r δ r δ θ from the light source. L denotes the distance from the light source to the point at which the guided light power becomes zero. Radiated light intensity in the r δ r δ θ region at distance r from the light source is q, which is assumed to be constant in the r δ r δ θ region.

Fig. 6
Fig. 6

Numerical results for the relation between the transverse length of the HPC and the coupling efficiency.

Fig. 7
Fig. 7

Process flow diagram for the HPC.

Fig. 8
Fig. 8

SEM photographs showing the top view arrangement of a replicated HPC: (a) 23 mm and (b) 30 mm from the LED light source.

Fig. 9
Fig. 9

SEM photographs of a replicated HPC: (a) cross-sectional view and (b) top view.

Fig. 10
Fig. 10

Experimental results for the light intensity profile of a LED backlight system using (a) a HPC and (b) a conventional prism coupler.

Equations (7)

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P 0 = 0 L q r d r .
q = ( 2 P 0 / L 2 ) .
Q ( r ) = ( 2 P 0 / L 2 ) r d r .
S ( r ) = P 0 0 r q r d r ,
S ( r ) = P 0 ( 1 r 2 L 2 ) .
α ( r ) = [ Q ( r ) / S ( r ) ] ,
α ( r ) = [ 2 r / ( L 2 r 2 ) ] d r .

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