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研究生： 王冠文
Wang, Guan-Wen
論文名稱： 改良式史托克參數法之扭轉向列型液晶盒多參數量測
An Improved Stokes Parameters Method for Measurements of the Cell hickness, Twist Angle, and Azimuth Angle of twisted-Nematic Liqud Crystal Cells
指導教授： 呂宗行
Leu, Tzong-Shyng
羅裕龍
Lo, Yu-Lung
學位類別： 碩士
Master
系所名稱： 工學院 - 微機電系統工程研究所
Institute of Micro-Electro-Mechancial-System Engineering
論文出版年： 2006
畢業學年度： 94
語文別： 英文
論文頁數： 78
中文關鍵詞： 史托克參數 、扭轉向列型液晶 、方位角 、扭轉繳 、厚度
外文關鍵詞： Stokes parameters, azimuthal angle, twisted-nematic liquid crystals, cell thickness, twist angle
相關次數： 點閱：121  下載：4 
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    • 改良式史托克參數法的研究重點是計算液晶分子在扭轉向列型液晶盒內的方位角、厚度和扭轉角。以往有關利用史托克參數計算液晶盒厚度和扭轉角的文獻，皆受限於精確的初始已知條件─方位角。當一道線性偏振光穿透液晶盒之後，由於扭轉向列型液晶具有光學異向性和旋光性，將造成原本的線性偏振態發生改變。透過簡單的光學實驗架構測量線性偏振光經過液晶盒之後的四組穿透光強度(Ix, Iy, I45o, Iq,45o)，將所測量到的光強度配合史托克參數法計算穿透光束的偏振態。最後，利用曲線擬合法計算方位角並調整至最佳化，進而提高計算液晶盒厚度、扭轉角的精確性。
    對扭轉向列型液晶而言，其入射面液晶分子長軸方向與實驗座標軸x所夾的角度，可稱之為方位角。此外，史托克參數(S0, S1, S2, S3)可在邦加球(poincaré sphere)座標系統上描繪出任意偏振光的偏振現象。當線性偏振光偏振方向與液晶分子的夾角改變時，將會影響史托克參數在邦加球上曲線的分布。基於此種因素，我們分析方位角與偏振方向的關係並找出最佳化角度進而降低其他參數的計算誤差。經過多次實驗証實，調整後的方位角的確提高計算厚度與扭轉角的精確度。

    An improved Stokes parameter method for measuring the azimuthal angle, cell thickness, and twist angle of twisted-nematic liquid crystal (TNLC) cells is proposed. After adjusting the azimuthal angle to be around 0° by a cross-polarizer setup and curve fitting method, the optimum cell thickness and twist angle extractions based on an improved Stokes parameters method could be achieved and the azimuth angle could be further modified.
    The preliminary experimental results verify the measurement value is more accurate than that without roughly adjusting the azimuth angle of a TNLC cell to be 0°. The accuracy of the azimuthal angle, cell thickness, and twist angle depends on the measurement error in Stokes parameters. Even if the maximum errors of Stokes parameters by light intensities have △S1=6.220% , △S2=6.677% , △S3=10.966% respectively, the maximum errors of the cell thickness and twist angle approximately have △d=0.082㎛ and △φ=1.909°, respectively.

    中文摘要.................... I Abstract.................... II 誌謝.................... III Table of Contents.................... IV List of Tables.................... VII List of Figures.................... VIII Chapter 1 Introduction.................... 1 1.1 Preface.................... 1 1.2 Review of measurements for Twisted-Nematic Liquid Crystal Cells.................... 1 1.2.1 An extinction measurement method.................... 2 1.2.2 Opto-electrical measurement method.................... 3 1.2.3 Stokes parameters method.................... 4 1.3 Destinations and motivations of the research.................... 5 1.4 Overview of chapters.................... 6 Chapter 2 Introduction of Liquid Crystals.................... 11 2.1 Structure of liquid crystal phases.................... 11 2.2 Alignment techniques of liquid crystal molecules.................... 12 2.3 Light propagation in homogeneous uniaxial LC materials.................... 13 2.4 Visible and infrared absorption.................... 16 2.5 Adiabatic following.................... 16 Chapter 3 Optical Properties of a Twisted-Nematic Liquid Crystal.................... 24 3.1 Operation principle.................... 24 3.2 Twist effect.................... 25 3.3 Jones matrix method.................... 26 3.4 Analyzed the simplified Jones matrix representation for TN cells with an arbitrary twist angle and Pretilt Angle.................... 30 3.5 Surface anchoring energy.................... 33 3.6 Partially polarized and unpolarized light.................... 35 3.7 Poincaré sphere.................... 38 Chapter 4 Measuring System and Methods.................... 46 4.1 Basic Stokes parameters method.................... 46 4.2 Determination of twist angle.................... 49 4.3 Determination of cell thickness.................... 51 4.4 Determination of azimuthal angle.................... 51 4.5 Flow chart in procedure of an improved Stokes parameters method.................... 52 Chapter 5 Experimental Results and Error Analysis.................... 61 5.1 Error analysis.................... 61 5.1.1 Error by azimuthal angle.................... 62 5.1.2 Percentage of error.................... 63 5.2 Saddle point and experimental result.................... 64 Chapter 6 Conclusions and future works.................... 71 6.1 Conclusions.................... 71 6.2 Future works.................... 72 Reference ....................74 Autobiography.................... 78

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