摘要
在顯示器的技術領域中，唯有持續將顯示功能品質的提昇才能因應視覺上永不滿足的追求。薄膜液晶顯示器本身並不會發光，而是利用過濾來自背光源的光線，所以改善背光的效能就成為提昇薄膜液晶顯示器最重要的途徑之一。
在本論文中，提出並驗證了兩項創新的背光系統，其結果顯示能有效改善傳統背光模組的兩項常見課題 - 效率與重量。
本論文的第一部分，在設計並評估一種次波長奈米結構以執行一偏極分光器之功能。此偏極分光器可應用於液晶投影相關顯示器中之平面式偏極轉換系統。在論文中提出並分析一具變化週期結構之二元次波長光學光柵。依據等效介質理論此二元次波長光柵結構之功能等效一具漸變折射率之材料，可使入射光線彎曲而改變其路徑。如果適當選取此次波長光學元件之表面結構與材料，則入射光中平行於與垂直於光柵刻痕結構之二個偏極分量將感受到不同之等效折射率梯度，而此機制則可被使用與將二互相正交之偏極狀態分離之偏極光學元件。因此有效利用經此偏極轉換系統轉換的偏極分光就能達成高效率背光模組目的。

本論文的第二部分，在提出並驗證一種新的反射式導光板(lightguide)結構，為側光型背光模組提出輕量化的解決之道。結合了傳統的光學膜；諸如擴散片(diffuser)、稜鏡膜(prismatic film)及反射式偏光膜(reflective polarizer)將光分散，在製作的原型樣本結果顯示其能有效將光線均勻化，並驗證了其可行性與應用在平面顯示器的背光模組的潛力。因此利用此反射式中空導光板去取代傳統使用的實心固體的偏光板，就能達成輕量化背光模組目的。

Abstract
The display technology is never overemphasized the image performance enhancement for satisfying human’s visual demands. The TFT-LCD panel does not illuminate itself but simply utilize the filtered light from a backlight source, therefore the performance improvement with backlight is one of the major direction to enhance the quality of the TFT-LCD.
In this dissertation, two novel backlight systems were proposed and demonstrated to improve two frequently concerned subjects on conventional backlight system, namely efficiency and weight.
In the first part, a subwavelength nanostructure is designed and evaluated which can perform the function of a polarization beam splitter for the application of planar polarization conversion system in liquid crystal based disply. A binary SOE (Subwavelength Optical Element) grating with varied duty cycle has been proposed and analyzed. According to effective medium theory, such binary SOE grating structure behaves like a gradient-index material which can bend the incoming light beam. If a proper profile and material of the SOE is chosen, the polarization state of the incoming light parallel and perpendicular to the grating groove will experience different gradient of the effective indices, which could be utilized as a mechanism for splitting two orthogonal polarization states. Thus a high efficiency backlight module can be achieved by utilizing the splitted orthogonal polarized light with the polarization conversion system.
In the second part, a novel light guide fully composed of reflective plate has been proposed and demonstrated as a light weight solution for planar illuminator with the light source located at the side edge. Accompanying with the conventional optical films such as diffuser, prismatic film and reflective polarizer to spread light distribution, the uniformity of the prototype has shown the feasibility and potential for applying to backlight module of flat panel displays. Thus a light weight backlight module was achieved by utilizing the reflective hollow lightguide to replace the conventional solid ones.

References

Chapter 1
[1]E. Lueder, Liquid Crystal Displays: Addressing Schemes and Electro-Optical Effects, J. Wiley, pp55-56, 2001
[2]W. C. O'Mara, Liquid crystal flat panel display: manufacturing science & technology, Van Nostrand Reinhold, pp. 1-13, 1993
[3]P. Yeh and C. Gu, Optics of Liquid Crystal Displays, John Wiley & Sons., pp 252-253, 1999
[4]Chunhwa Picture Tube Company, http://www.cptt.com.tw
[5]H. Greiner, “A Novel Concept for Large Area Light Source: Cavity-Lit Lightguides,” Proc. SPIE, vol. 4775, Modeling and Characterization of Light Sources, pp.155-162, 2002
[6]P. L. Yang, “Hollow Backlight Module,” US patent 7,029,158, 2006
[7]Electronics information online, http://www.electronics-manufacturers.com/info/digital-projectors/lcd-projector.html

Chapter 2
[8]D. K. Cheng, Field and Wave Electromagnetics, Addison-Wesley, pp352-354, 1983
[9]S. Sinzinger and J. Jahns, Microoptics, Wiley-VCH, pp166-167, 2003
[10] M. Born and E. Wolf, Principle of Optics, Pergamon Press, Loton, 6th ed,
sec14.4.2, 1980
[11] G. Wyszecki, W. S. Stiles, Color Science, Concept and Methods, Quantitive
Data and Formulae, 2nd ed., John Wiley and Sons, 1982
[12] Charles P. Halsted, “Brightness, Luminance, and Confusion,” Information
Display, March, 1993

Chapter 3
[13] Stanley Electric Company, http://www.stanley-components.com/en/index.cfm
[14] Inverters for LCD Backlight, Displays Division, Hitachi Company,
http://www.hitachi.com.sg/inverters_backlight.shtml

[15] A. Tagaya, M. Nagai, Y. Koike, and K. Yokoyama, “Thin Liquid-Crystal
Display Backlight System with Highly Scattering Optical Transmission Polymers,” Applied Optics, Vol. 40, Issue 34, pp. 6274-6280, 2001
[16] X. P. Yang, Y. B. Yan and G. F. Jin, “Plaorized light-guide plate for
liquid crystal display,” Optics Express, vol.13, No.21, 17 Oct., 2005
[17] J. G. Chang and P. H. Yang, “A gererallized model for luminance
prediction in a bottom-lit backlight with cold cathode fluorescent lamps,”
Pure Appl. Opt, 8, 981-990, 2006
[18]W. Y. Lee, T. K. Lim, Y. W. Lee and I. W. Lee, “Fast ray-tracing methods for LCD backlight simulation using the characteristics of the pattern,” Optical Engineering, vol. 44, issue 1, 014004, 2005
[19] K. Kalantar, “Modified functional light-guide plate for backlighting transmissive
LCDs,” Journal of Society for Information Display, vol.11, issue 4, pp.641-645, 2003
[20] Y. Ye, D. L. Pu, Y. Zhou, and L. S. Chen, “Diffraction characteristics of
a submicrometer grating for a light guide plate,” Applied Optics, Vol. 46, Issue 17, pp. 3396-3399, 2007
[21] R. C. Allen, L. W. Carlson, A. J. Ouderkirk, M. F. Weber, A. L. Kotz, T. J.
Nevitt, C. A. Stover, B. Majumdar, “Brightness enhancement film,” US patent 6111696, 2000
[22] Prismatic film applications guidelines, Brightness Enhancement Film(BEF), 3M
http://products3.3m.com/catalog/us/
[23] M. F. Weber, O. Benson, Jr., S. Cobb, Jr., J. M. Jonza, A. J. Ouderkirk, D. L.
Wortman, C. A. Stover, “Brightness enhancing reflective polarizer,” US patent 7038745, 2006
[24] Reflective polarizer applications guidelines, Dual Brightness Enhancement
Film (DBEF), 3M, http://products3.3m.com/catalog/us/
[25]S. I. Kim, Y. S. Choi, Y. N. Ham, C. Y. Park, and J. M. Kim ,“Holographic Diffuser by use of a Silver Halide Sensitized Gelatin Process,” Applied Optics, Vol. 42, Issue 14, pp. 2482-2491, 2003
[26]M. Parikka, T. Kaikuranta, P. Laakkonen, J. Lautanen, J. Tervo, M. Honkanen, M. Kuittinen, and J. Turunen, “Deterministic Diffractive Diffusers for Displays,” Applied Optics, Vol. 40, Issue 14, pp. 2239-2246, 2001

[27]The optical film “Light-Diffuser Film” of Keiwa company, http://www.keiwa.co.jp
[28] S. Arnold et al, “An improved polarizing beamsplitter LCoS projection display
based on wire-grid polarizers” SID Digest’01, pp1282-1285, ,2001

Chapter 4
[29] P. Yeh, A. Yariv and C. S. Hong, “Electromagnetic propagation in periodic
stratified media I. General theory,” JOSA 67, pp.423-438, , 1977
[30] A. Yariv and P. Yeh, “Electromagnetic propagation in periodic stratified
media II Birefringence, phase matching and X-ray lasers,” JOSA 67, pp.438-448, 1977
[31]C. W. Haggans, L. Li and R. K. Kostuk, “Effective medium theory of zeroth-order lamellar gratings in conical mountings,” JOSA A10 , pp.2217-2225, 1993
[32] M. Born and E. Wolf, Principles of Optics, 6th ed. Pergamon, sec14.4.2, 1980
[33] C. W. Haggans et al, “Lamellar gratings as polarization components for
specularly reflected beams,” J. Mod. Opt. 40, pp675-686
[34] Y. Ono et al., “Antireflection effect in ultra high spatial-frequency holographic
relief gratings,” Appl. Opt. 26, pp. 1142-1146, 1987
[35] D. H. Raguin and G. M. Morris, “Analysis of antireflection-structured surfaces
with one-dimensional surface profile,” Applied Optics, 32, pp2582-2596, 1993
[36] L. Pajewski et al, “Design of a binary grating with subwavelength features that
acts as a polarizing beam splitter,” Applied Optics, 40, pp.5898-5905, 2001
[37] W. Stork et al, “Artifical distributed-index media fabricated by zero-ordewr
gratings,” Optics Letter, 16, pp1981-1923, 1991
[38] A. G. Lopez and H. G. Craighead, “Wave-plate polarizing beam splitter based
on a form birefringent multilayer grating,” Optics Letter, Vol.23 No.20, pp.1627-1629, 1998
[39] K. S. Yee, IEEE, Trans. Antennas Propagat., vol. AP-14, 1966, pp. 302-307
[40] J. P. Berenger, J. Comput. Phys., vol. 114, pp. 185-200, 1994

Chapter 5
[41] K. Hathaway, J. Hawthorne, and A. Fleischer, “Advancements in backlighting
technologies for LCD,” Proc. SPIE 1664, 108-116, 1992
[42] K. Kashima, N. Yoshida, O. Shoji, E. Yanagi, and T. Fukunishi, “Back lighting
device for a panel,” US patent 5,093,765, 1992
[43] H. Greiner, “A Novel Concept for Large Area Light Source: Cavity-Lit
Lightguides,” Proc. SPIE, vol. 4775, Modeling and Characterization of Light Sources, pp.155-162, 2002
[44]T. Ide, H. Mizuta, H. Numata, Y. Taira, M. Suzuki, M. Noguchi and Y. Katsu,” Dot pattern generation technology using molecular dynamics,” J. Opt. Soc. Am. A 20, 2, 248-255, 2003
[45]K, Kalantar, M. Shingo, and O. Tomohisa,“ Functional light-guide plate characterized by optical micro-deflector and micro-reflector for LCD backlight,” IEICE E84-C, 11, 1637-1646, 2001
[46]M. K. Lamvik, S. Grego, R. LaBennett, and D. Temple, “Polymer light guide arrays for tiling large scale displays,” Proc. SPIE 5443, 196-204, 2004
[47]W. H. Steel, “Luminosity, throughput, or Etendue? Further comments,” Appl. Opt. 14, 2, 252, 1975
[48]H. T. Wang, C.F Chen and C. H Chen, “Light Weight Backlight Module with Reflective Light Guide,” SID Digest, 473-475, 2007

[49]K. W. Chien and H. P. D. Shieh, “Design and Fabrication of an Integrated Polarized Light Guide for Liquid-Crystal-Display Illumination,” Applied Optics, Vol. 43, Issue 9, pp. 1830-1834 , 2004
[50]C. F. Chen, H. T. Wang and C. H. Chen, “High Throughput Reflective Light Guide for Planar Illuminator,” Applied Optics, Vol. 47, No. 6, 2008
[51] P. H. Yao, I. K. Pan, and T. H. Lin, “Micro-Structure Optical Film with Hybrid
Functions for LCD Backlight,” SID Symposium Digest of Technical Papers , Vol. 37, Issue 1, pp. 851-853, 2006
[52]A. Nagasawa and K. Fujisawa “An Ultra Slim Backlight System using Optical-Patterned Film,” SID Symposium Digest 36, 70–573, 2005