Abstract

Microlens array (MLA) diffusers for light-emitting diode (LED) backlight systems have been developed. A high fill-factor photoresist mold for the MLA was fabricated using three-dimensional diffuser lithography, and the patterns were transferred to a nickel master mold for UV-curable polymer replication. The fabricated microlens had various paraboloidal profiles, and its aspect ratio was controlled from 1.0 to 2.1. The MLA diffuser showed a batwing radiation pattern with a radiation angle of 150°. The fabricated MLA diffuser may greatly enhance the color-mixing characteristics of LED backlight systems and help reduce the number of LEDs required.

© 2006 Optical Society of America

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References

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2005 (1)

2004 (3)

S.-I. Chang and J.-B. Yoon, Opt. Express 12, 6366 (2004).
[CrossRef] [PubMed]

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

2002 (1)

S.-D. Moon, S. Kang, and J.-U. Bu, Opt. Eng. 41, 2267 (2002).
[CrossRef]

1999 (1)

1997 (1)

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

1994 (1)

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

1988 (1)

Baker, K. M.

Bu, J.-U.

S.-D. Moon, S. Kang, and J.-U. Bu, Opt. Eng. 41, 2267 (2002).
[CrossRef]

Chakmakjian, S.

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Chang, S.-I.

Chao, C.-K.

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

Chen, T.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Cox, W. R.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Eisner, M.

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

Haselbeck, S.

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

Hayes, D. J.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Herzig, H. P.

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

Kang, S.

S.-D. Moon, S. Kang, and J.-U. Bu, Opt. Eng. 41, 2267 (2002).
[CrossRef]

Lin, C.-P.

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

MacFarlane, D. L.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Moon, S.-D.

S.-D. Moon, S. Kang, and J.-U. Bu, Opt. Eng. 41, 2267 (2002).
[CrossRef]

Morris, G. M.

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Narayan, V.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Neville Connel, G. A.

Nussbaum, Ph.

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

Popovic, Z. D.

Powell, K. D.

Sales, M.

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Schertler, D. J.

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Sprague, R. A.

Tasso, R.

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Tatum, J. A.

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

Urey, H.

Völkel, R.

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

Wei, M.-K.

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

Yang, H.

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

Yoon, J.-B.

Appl. Opt. (3)

IEEE Photon. Technol. Lett. (1)

D. L. MacFarlane, V. Narayan, J. A. Tatum, W. R. Cox, T. Chen, and D. J. Hayes, IEEE Photon. Technol. Lett. 6, 1112 (1994).
[CrossRef]

J. Micromech. Microeng. (1)

H. Yang, C.-K. Chao, M.-K. Wei, and C.-P. Lin, J. Micromech. Microeng. 14, 1197 (2004).
[CrossRef]

Opt. Eng. (1)

S.-D. Moon, S. Kang, and J.-U. Bu, Opt. Eng. 41, 2267 (2002).
[CrossRef]

Opt. Express (1)

Proc. SPIE (1)

R. Tasso, M. Sales, S. Chakmakjian, D. J. Schertler, and G. M. Morris, in Proc. SPIE 5530, 133 (2004).
[CrossRef]

Pure Appl. Opt. (1)

Ph. Nussbaum, R. Völkel, H. P. Herzig, M. Eisner, and S. Haselbeck, Pure Appl. Opt. 6, 617 (1997).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

Fabrication process of a MLA diffuser: (a) UV exposure on the photoresist through a diffuser and photomask, (b) UV flood exposure, (c) fabricated photoresist mold after development, (d) fabrication of a copper intermediate mold, (e) nickel master mold made by electroplating, (f) plastic replication from the nickel master mold.

Fig. 2
Fig. 2

Scanning electron microscopy photographs of the fabricated plastic MLAs with a pitch of 10 μ m and heights of (a) 10 μ m , (b) 12 μ m , (c) 17 μ m , and (d) 21 μ m .

Fig. 3
Fig. 3

Actual profile of the fabricated microlens (dotted curves) and the ideal parabolic profiles (solid curves) with aspect ratios of (a) 1.0, (b) 1.2, (c) 1.7, and (d) 2.1.

Fig. 4
Fig. 4

(a) Schematic view of the measurement setup for the radiation patterns of the MLA diffusers. The radiation pattern of the MLA diffuser with an aspect ratio of 1.0 is shown in (b) polar and (c) Cartesian coordinates. The radiation pattern of the red LED without the MLA diffuser is also shown in (b) and (c) by dashed–dotted curves. (d) Semi-Lambertian radiation pattern of the MLA diffuser with an aspect ratio of 1.2.

Equations (2)

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h ( r ) = 1 R r 2 1 + [ 1 ( K + 1 ) r 2 R 2 ] ,
h ( x ) = 1 2 R x 2 + h m ,

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