Abstract

A polarized backlight for LCD illumination is designed and fabricated in which s-polarized light is extracted owing to selective total internal reflection at microstructures in the anisotropic layer. From the measurement, the contrast ratio in normal viewing direction can be as high as 64. Luminous uniformity of higher than 80% is achieved for polarized backlights. Furthermore, 1.6 gain in efficiency is obtained aiming for high-efficiency LCD illumination.

© 2004 Optical Society of America

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References

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  1. M. F. Weber, “Retroreflecting sheet polarizer,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1992), pp. 427–429.
  2. Z. Pang, L. Li, “Novel high efficiency polarizing backlighting system with a polarizing beam splitter,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1999), pp. 916–919.
    [CrossRef]
  3. H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
    [CrossRef]
  4. E. Hecht, Optics, 2nd ed. (Addison-Wesley, Reading, Mass., 1987), p. 84.
  5. F. J. Pedrotti, L. S. Pedrotti, Introduction to Optics, 2nd ed. (Prentice Hall, London, 1993), p. 38.
  6. H. Jagt, Polymeric Polarisation Optics for Energy Efficient Liquid Crystal Display Illumination (University Press Facilities, Eindhoven, The Netherlands, 2001), p. 114.
  7. G. R. Fowles, Introduction to Modern Optics, 2nd ed. (Holt, Rineheart Winston, New York, 1975), p. 168.

Bastiaansen, C.

H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
[CrossRef]

Broer, D.

H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
[CrossRef]

Cornelissen, H.

H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
[CrossRef]

Fowles, G. R.

G. R. Fowles, Introduction to Modern Optics, 2nd ed. (Holt, Rineheart Winston, New York, 1975), p. 168.

Hecht, E.

E. Hecht, Optics, 2nd ed. (Addison-Wesley, Reading, Mass., 1987), p. 84.

Jagt, H.

H. Jagt, Polymeric Polarisation Optics for Energy Efficient Liquid Crystal Display Illumination (University Press Facilities, Eindhoven, The Netherlands, 2001), p. 114.

H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
[CrossRef]

Li, L.

Z. Pang, L. Li, “Novel high efficiency polarizing backlighting system with a polarizing beam splitter,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1999), pp. 916–919.
[CrossRef]

Pang, Z.

Z. Pang, L. Li, “Novel high efficiency polarizing backlighting system with a polarizing beam splitter,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1999), pp. 916–919.
[CrossRef]

Pedrotti, F. J.

F. J. Pedrotti, L. S. Pedrotti, Introduction to Optics, 2nd ed. (Prentice Hall, London, 1993), p. 38.

Pedrotti, L. S.

F. J. Pedrotti, L. S. Pedrotti, Introduction to Optics, 2nd ed. (Prentice Hall, London, 1993), p. 38.

Weber, M. F.

M. F. Weber, “Retroreflecting sheet polarizer,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1992), pp. 427–429.

Other (7)

M. F. Weber, “Retroreflecting sheet polarizer,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1992), pp. 427–429.

Z. Pang, L. Li, “Novel high efficiency polarizing backlighting system with a polarizing beam splitter,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 1999), pp. 916–919.
[CrossRef]

H. Jagt, H. Cornelissen, D. Broer, C. Bastiaansen, “Micro-structured polymeric linearly polarized light-emitting lightguide for LCD illumination,” in Society for Information Display International Symposium Digest, J. Morreale, ed. (Society for Information Display, San Jose, Calif., 2002), pp. 1236–1239.
[CrossRef]

E. Hecht, Optics, 2nd ed. (Addison-Wesley, Reading, Mass., 1987), p. 84.

F. J. Pedrotti, L. S. Pedrotti, Introduction to Optics, 2nd ed. (Prentice Hall, London, 1993), p. 38.

H. Jagt, Polymeric Polarisation Optics for Energy Efficient Liquid Crystal Display Illumination (University Press Facilities, Eindhoven, The Netherlands, 2001), p. 114.

G. R. Fowles, Introduction to Modern Optics, 2nd ed. (Holt, Rineheart Winston, New York, 1975), p. 168.

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Figures (7)

Fig. 1
Fig. 1

Schematics of polarized backlight. Birefringent layer with microgrooves filled with index-matching layer was aimed to extract the s-polarized light at the interface. Additionally, p-polarized light was trapped in the polymethyl methacrylate (PMMA) lightguide to be recycled.

Fig. 2
Fig. 2

Illustration of outcoupled s-polarized light due to selective TIR at the interface for different half-top angles relative to the critical angle θ c3,4 of the anisotropic layer with respect to air: (a) ϕ < θ c3,4, (b) φ = θ c3,4, (c) φ > θ c3,4.

Fig. 3
Fig. 3

Illustration of contrast ratio at a different refractive index of index-matching layer. Contrast ratio achieves maximum at perfectly matched refractive index n = 1.53 for PET foil, whereas n = 1.56 for PEN foil.

Fig. 4
Fig. 4

(a) Angular distributions and (b) Inclined angular cross-sections of outcoupled s-polarized light at perfectly matched index for PEN and PET foils, respectively.

Fig. 5
Fig. 5

Measured angular profiles of (a) s-polarized light and (b) p-polarized light and (c) contrast ratio of s-polarized to p-polarized light.

Fig. 6
Fig. 6

For PEN foil adhered on the substrate of PMMA, luminous intensity versus position from light source. Squares, circles, and triangles illustrate luminous intensity of s-polarized light with no reflectors, diffuse end reflector only, and both back and end reflectors, respectively.

Fig. 7
Fig. 7

Measurement set up of flux by (a) clear PMMA and (b) polarized backlight with both back and end reflectors.

Equations (4)

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t=EtE=2 cos θicos θi+n2-sin2 θi1/2,
t=EtE=2n cos θin2 cos θi+n2-sin2 θi1/2,
r=ErE=cos θi-n2-sin2 θi1/2cos θi+n2-sin2 θi1/2,
r=ErE=n2 cos θi-n2-sin2 θi1/2n2 cos θi+n2-sin2 θi1/2,

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