近年來，政府極力推動「兩兆雙星」計畫，使得光電平面顯示器儼然成為我國重點發展產業科技項目之一；例如，2005年台灣顯示器產業在全球該類產品的市場佔有率已達31%。該項科技產值在台灣光電產業中，佔有63%之比例(約新台幣7,141億)，位居第一名，且預計逐年擴增，其中液晶顯示器佔有絕大多數的比例(約新台幣7,013億)。因此，為了有效提升液晶平面顯示器產量與品質管制之需求，進行液晶顯示單元之光學參數量測系統技術之研究與發展是刻不容緩的。
我們的目標係發展一套多功能且具成本效益之液晶顯示單元光學參數量測系統，來降低該類儀器的成本，以期能減少對國外廠家的依賴，進而提高國內顯示器產業的競爭力。在本論文中，我們首先進行過去作法之系統架構的學理分析與性能評估，然後提出一個簡單的系統結構且相當經濟的方法，來達成多功能的量測系統。此系統是以起偏器-液晶單元-補償器-檢偏器架構為基礎，透過晶體旋轉法量測液晶單元之預傾角(pretilt angle)，再使用極化量測法來量測其間隙(cell gap)與扭動角(twist angle)等，攸關液晶顯示品質的重要光學參數。除此之外，此系統還可測量電壓-穿透率曲線(voltage-transmittance (V-T) curve)等光電特性。針對此系統，我們提出學理、模擬、實驗與系統製作的方法，並且說明整體的可行性分析。實驗的結果顯示此方法所量測的結果是相當令人滿意的(例如，液晶單元間隙的誤差百分比為1.45%)。

For years, the government has promoted the “Two Trillion and Twin Star Industries Development” plan. As a result, the flat panel displays (FPDs) had become one of the most important industrial applications. For example, the FPDs in Taiwan occupied 63% (about $NT 7,141 hundred million dollars) of the optoelectronics industry in Taiwan and 31% in the market of the FPDs in the world in 2005. Therefore, to promote effectively the output and quality of the FPDs, it is very urgent to research and develop the LC cell optical parameter measurement systems.
The objective of this paper is to develop a multiple-function and cost-effective measurement system to lower the dependency of foreign instrument makers and to reduce the manufacturing cost for the industry. In the paper, we first study the past approaches and analyze their measurement performance. Then, a simple and cost-effective method will be proposed to achieve the multiple functions. This system on the basis of the PSCA configuration uses the crystal rotation method to measure the pretilt angle of the sample under test, and the polarimetry to measure the cell gap and twist angle of it. These optical parameters highly influence the display quality. That is, in addition to the measurement of the three important optical parameters, this system can also measure the voltage-transmittance (V-T) curve. For this system, we will do the theoretical study, simulation, experiment, system implementation to show its feasibility. From the experiment results, it is shown that the measured results were quite satisfactory. For example, the error percentage was 1.45 %.

[1] 2006 PIDA成果發表暨記者聯誼會新聞稿，PIDA。(http://www.pida.org.tw/pida/060118.newsrelease.doc)
[2]Melchers網站。
(http://www.autronic.melchers.com/Cell_and_Material_ch.21.0.html)
[3] Shintech型錄。(http://www.photal.co.jp/english/product/lcd.html)
[4] 大塚電子型錄。(http://www.shintech.jp/eng/index_e.html)
[5] K.-Y. Han, T. Miyashita and T. Uchida, “Accurate determination and measurement error of pretilt angle in liquid crystal cell,” Jpn. J. Appl. Phys., vol. 32, pp. L277.L279, Part 2, no. 2B, Feb. 1993.
[6] T. Nishioka and T. Kurata, “Novel pretilt angle measurement method for twisted-nematic liquid-crystal cells by apparent retardation measurement,” Jpn. J. Appl. Phys., vol. 40, pp. 6017-6023, Part 1, no. 10, Oct. 2001.
[7] J. S. Gwag, et al., “Simple method for measuring the high pretilt angle of nematic liquid crystals,” J. Appl. Phys., vol. 93, no. 8, Apr. 2003.
[8] A. Lien and H. Takano, ” Cell gap measurement of filled twisted nematic liquid crystal displays by a phase compensation method,” J. Appl. Phys., 69 (3), Feb. 1991.
[9] S. H. Lee, et al., “Low-cell.gap measurement by rotation of a wave retarder,” Jpn. J. Appl. Phys., vol. 41, pp. 379.383, Part 1, no. 1, Jan. 2002.
[10] J. S. Gwag, et al., ”Simple cell gap measurement method for twisted-nematic liquid crystal cells,” Jpn. J. Appl. Phys., vol. 43, no. 1A/B, pp. L30.L32, 2004.
[11] J. S. Chae and S. G.. Moon, “Cell parameter measurement of a twisted.nematic liquid crystal cell by the spectroscopic method,” J. Appl. Phys., vol. 95, no. 7, Apr. 2004.
[12] S. J. Hwang, “Precise optical retardation measurement of nematic liquid crystal display using the phase-sensitive technique,” IEEE. J. Display Tech., vol. 1, no. 1, Sep. 2005.
[13] Y..P. Lan, et al., “Intracavity measurement of liquid crystal layer thickness by wavelength tuning of an external cavity laser diode,” Opt. Exp., vol. 13, no. 20, Oct. 2005.
[14] T. Akahane, H. Kaneko and M. Kimura, “Novel method of measuring surface torsional anchoring strength of nematic liquid crystals,” Jpn. J. Appl. Phys., vol. 35, pp. 4434. 4437, Part 1, no. 8, Aug. 1996.
[15] Y. Zhou, Z. He and S. Sato, “A novel method for determining the cell thickness and twist angle of a twisted nematic cell by stokes parameter measurement,” Jpn. J. Appl. Phys., vol. 36, pp. 2760-2764, Part 1, no. 5A, May 1997.
[16] C..C. Tsai, et al., “Determination of optical of parameters of a twisted.nematic liquid crystal by phase.sensitive optical heterodyne interferometric ellipsometry,” Appl. Opt., vol. 44, no. 35, Dec. 2005.
[17] Lueder, Liquid crystal displays: addressing schemes & electro.optical effects 2001, 2001.
[18] 液晶顯示器工業中液晶分子取向排列控制技術的研究進展，中華液晶資訊網論壇。(http://172.16.18.35:7751/cn.china.tft.com/forum)
[19] 台灣大學物理系教授趙治宇老師，液晶顯示器上課講義，2005.
[20] Edward Collett, Polarized Light in Fiber Optics, the polawave group, Lincroft, New Jersey, USA, 2003
[21] P. Yeh and C. GU, Optics of Liquid Crystal Displays, wiley, pp. 200, 1999.
[22] Max Born and Emil Wolf, Princiiples of Optics, 7th ed, cambridge university press, pp.823.828, 2002.
[23] Eugene Hecht, Optics, 4th ed., international edition, pp. 328, 2002.
[24] F. L. Pedrotti, Introduction to Optics, 2nd ed, prentice hall, pp. 280.301, 1993.
[25] S. T. Tang and Hoi-Sing Kwok, “Characteristic parameters of liquid crystal cells and their measurements,” IEEE. J. Display Tech., vol. 2, no. 1, 2006.
[26] T. Akahane, “The influence of multiple-beam interference in a liquid crystal cell on the determination of the optical retardation and the twist angle,” Jpn. J. Appl. Phys., vol. 37, Part I, no. 6A, pp. 3428-3435, June 1998.
[27] E. Garcia-Caurel, A. D. Martino, B. Drevillon, “Spectroscopic Mueller polarimeter based on liquid crystal devices,” Thin Solid Films, pp. 120-123, 2004.
[28] A. D. Martino, et al., “Optimized Mueller polarimeter with liquid crystals,” Opt. Let., vol. 28, no. 8, Apr. 2003.
[29] I. Dahl, “How to measure the Mueller matrix of liquid-crystal cells,” Institute of Phys. Publishing, pp. 1938-1948, Oct. 2001.
[30] S. T. Tang, H. S. Kwok, “3X3 matrix for unitary optical systems,” J. Opt. Soc. Am., vol. 18, no. 9, Sep. 2001.
[31] S. T. Tang, H. S. Kwok, “Characteristic parameters of liquid crystal cells and their measurements,” IEEE. J. of Display Tech., vol. 2, no. 1, Mar. 2006.
[32] M. Kawamura, et al., “A two-dimensional pretilt angle distribution measurement of twisted nematic liquid cells using Stokes parameters at plural wavelengths,” Jap. J. of App. Phys., vol. 43, no. 2, pp. 709-714, 2004.
[33] P. Yeh and C. Gu, “Optics of liquid crystal display,” p.120-122, John Wiley & Sons, 1999.