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研究生： 李東諺
Tung-Yen Li
論文名稱： LED模組及光學干涉技術於TFT-LCD系統之應用發展
Development of LED Module and Optical Interference Technology for TFT-LCD Applications
指導教授： 蔡章仁
Jang-Zern Tsai
張榮森
Rong-Seng Chang
口試委員:
學位類別： 博士
Doctor
系所名稱： 資訊電機學院 - 電機工程學系
Department of Electrical Engineering
論文出版年： 2013
畢業學年度： 101
語文別： 英文
論文頁數： 76
中文關鍵詞： 背光模組 、干涉光學 、類神經網路 、液晶面板
外文關鍵詞： backlight module, interference pattern, neural network, LCD panel
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    • TFTLCD顯示器為目前平面顯示器中的主流，TFTLCD顯示器主要是由液晶面板模組，背光模組以及電路驅動模組三個部份所構成。
    本篇論文提供了TFTLCD組件中有關新型背光模組的設計以及液晶面板的檢驗方式。我們使用LED模組為背光光源同時搭配微反射結構和光學擴散元件進行新型直下式背光模組的設計。經過實際測量，我們的設計相對於2003年R.S.West的設計，在均勻度上我們增加了24%（由60%到84%），亮度上我們增加了23.29%(由10000nt到12329nt)。另一方面，本論文提出了應用光學干涉的方法搭配類神經網路及統計分類方式進行TFTLCD面板中有關Gap Mura Defect的檢驗分類。我們目前可以將固定膠過多，面板內有外來物以及固定膠內有纖維聚集這3種造成Gap Mura Defect的原因檢出。搭配使用Neural Network Classification方法，Mean Squared Error (MSE)經過反覆學習後可以降低至0.01以下。由此方式可以將製程中不良的面板提前檢出，減低製作不良品的機率，藉以提高產線的良率。

    Recently, TFT-LCD is the most popular display application in the flat panel display application. The main parts in the TFT-LCD system includes: LCD panel module, backlight module and electronic driver module. This paper provides the novel design of direct-in backlight module of the TFT-LCD system and the inspection method for the gap mura defect of the LCD panel. We applied the LED light source, secondary light-guide component and micro reflector structure to design the novel backlight module. Compared with West’s work in 2003, the uniformity ratio for our new design shows an increase of 24%, from 60% to 84%, and the luminance a 23.29% improvement, from 10 000 nits to 12 329 nits. On the other hand, we combine the optical interference method and neural network classification to detect the gap mura defect of the LCD panel. Three kinds of mura defects including non-uniformity sealant panel; panel with foreign material and fiber-cluster panel are tested. After learning process of Neural Network Classification method, the Mean Squared Error could decrease less than 0.01. By this method, we could sort out the bad panel and increase the yield rate of the production line.

    Table of Contents 中文摘要……………………………………………………………………………..……I 英文摘要……………………………………………………………………………..……II 誌謝………………………………………………………………………………….……III Table of Content………………………………….………………………………….……IV List of figures………………………………….…………………………………………VII List of tables…………………………………………..………………………………….X Explanation of Symbols……………………………….………………………………....XI Chapter 1 Overview of Thin Film Transistor Liquid Crystal Display………………1 1.1 Introduction to TFT-LCD System……………………………………………………1 1.2 Current status of TFT-LCD…………………………………………………………..3 1.2.1 The Status of Back Lighting Module of TFT LCD System…………..………3 1.2.2 The Status of TFT LCD Panel Inspection …………………………..………..5 1.3 Research Motivation and Contributions……………………………………..………6 1.3.1 Research of the LED Backlight Module by a Light Guide Component……6 1.3.2 Research of the Mura Inspection of TFT LCD Panel……………………..…7 1.4 Dissertation Outline……………………………………………………….………...8 Chapter 2 LED Backlight Module by a Lightguide- Component…………………..9 2.1 Abstract……………………………………………………………………………..9 2.2 Introduction…………………………………………………………………………10 2.3 Material and Method…………………………………………………….………….12 2.3.1 Preliminary Design………………………………………………………….12 2.3.1.1 Preliminary Design of the LED Backlight module…………………..12 2.3.1.2 Evaluation of the Simulated Results of the Backlight Module……….14 2.3.1.3 Thermal Design of the LED Backlight module……………….……..15 2.3.1.4 Preliminary Simulation of the Backlight Module……………….…..16 2.3.2 Advanced Design…………………………………………………….……..26 2.3.3 Measurement and Methodlogy……………………………………………..30 2.4 Results……………………………………………………………………………..32 2.5 Summary…………………………………………………………………………..34 Chapter 3 Detection of Gap Mura in TFT LCDs by the Interference Pattern Method…………………………………………………….…….36 3.1 Abstract…………………………………………………………………….……..36 3.2 Introduction………………………………………………………………….……37 3.3 Materials and Methods……………………………………………………………42 3.3.1 Theory-Fringes of equal thickness…………………………………….…..42 3.3.2 Experimental Equipment………………………………………………….46 3.3.3 Image Processing Method…………………………………………..…….47 3.3.4 Experimental Methodology of Panel Inspection…………….…………..48 3.3.4.1 Definition of Cross Points……………………………….………49 3.3.4.2 Definition of Binary Classification Method……………….…….52 3.3.5 Neural Network Classification System ...………………………………54 3.3.5.1 Definition of the parameters……………………………….……54 3.3.5.2 Experimental Procedure of Neural Network Classification….…60 3.4 Results…………………………………………………………………………64 3.5 Summary………………………………………………………………………71 Chapter 4 Conclusion and Future Work………………………………………..73 4.1 Conclusion……………………………………………………………………..73 4.2 Future Work……………………………………………………………………74 Reference………………………………………………………………………….76 List of figures Fig. 1.1. Schematic of a basic element of a LCD system………………………….……….1 Fig. 2.1. Structure of the direct illumination-type LED Backlight module……………...11 Fig. 2.2. Secondary lightguide component model……………………………………….12 Fig. 2.3. Illustration of the backlight module with four secondary Lightguide components………………………………………………………...13 Fig. 2.4. Positions of points P1- P16……………………………………………………..15 Fig. 2.5. Simulation results for the flat reflector…………………………………………16 Fig. 2.6. Illustration of ray tracing with total reflection in the backlight module………..17 Fig. 2.7. Schematic representation of ray tracing with a tilted reflector…………………17 Fig. 2.8. Diagram of the secondary lightguide component…………………………….18 Fig. 2.9. Right-hand spherical coordinates……………………………………………….18 Fig. 2.10. Relation of P0, P1, P2 and P’……………………………………………………19 Fig.2.11. Illustration of ray tracing with total reflecting in the backlight module…………22 Fig.2.12. Schematic representation of the ray tracing with a tilted reflector.……….….….22 Fig. 2.13. Structures and locations of the Triangle Cylinder Structured Array (units: mm)……………………………………………………………………..23 Fig. 2.14. Schematic representation of the six sections (sections N1-N6)…………..…….23 Fig. 2.15. Triangle Cylinder Structured Array simulation results: (a) N (5,10,5,6,6,6); (b) N (5,10,5,6,8,6); (c) N (5,10,5,8,8,8)……………..….25 Fig. 2.16. Triangle Cylinder Structured Array polar candela plot: Blue line-N (5,10,5,6,6,6); Red line-N (5,10,5,6,8,6); Black line-N (5,10,5,8,8,8)....26 Fig. 2.17. Structures and locations of the Tetrahedron Reflector Structured Array (units: mm)………………………………………………………………27 Fig. 2.18. Tetrahedron Reflector Structured Array simulation results: (a) N (5,10,5,6,6,6); (b) N (5,10,5,6,8,6); (c) N (5,10,5,8,8,8)………….………29 Fig. 2.19. Tetrahedron Reflector Structure Array polar candela plot: Blue line-N (5,10,5,6,6,6); Red line-N (5,10,5,6,8,6); Black line-N (5,10,5,8,8,8)…29 Fig.2.20. Test platform for the backlight module………………………………………….30 Fig. 2.21. Simulation results of the uniformity ratio………………………………………33 Fig. 2.22. Simulation results of the angle of the luminous intensity………………………34 Fig. 3.1. Examples of mura in TFT LCDs…………………………………………………38 Fig. 3.2 Interference patterns observed in a 7 inch TFT LCD panel without Liquid Crystal under a sodium lamp……………………………………………………..40 Fig. 3.3. Different sealant problems that can cause mura defects…………………………41 Fig. 3.4. Different sealant problems which can cause mura………………………………41 Fig. 3.5. Normal interference patterns of a TFT LCD under sodium light………………..43 Fig. 3.6. Abnormal interference patterns of a TFT LCD under sodium light……………..44 Fig. 3.7. Light path of point source S through planar parallel plates……………….…….44 Fig. 3.8. Schematic representation of the interference pattern analysis system. An image catcher is used to capture the panel image.…………………………..47 Fig. 3.9. Image processing flow chart…………………………………………………….48 Fig. 3.10. Panel judging flow chart……………………………………………………….49 Fig. 3.11. (a) 5 cross points on the top and 5 cross points on the left side. (b) 7 cross points on the top. (c) 35 cross points in the central area………………..……..52 Fig. 3.12. Neural Network configuration built with one input layer, one hidden layer, and one output layer.............................................................................................56 Fig. 3.13. 16 panels prepared for this experiment, 10 panels prepared for learning and training, and 6 panels are for testing…………………………………………..60 Fig. 3.14. Set of good panels without mura. (a) section No. 34, (b) section No. 180……61 Fig. 3.15. Set of bad panels with mura. (a) section No. 122, dense image (b) section No. 42, star shape image……………………………….…………..62. Fig. 3.16. The judgement results of each sections on the LCD panels…………………..63 Fig. 3.17 Test results based on two different criteria: (a) Criterion 1: threshold = 130 points; (b) Criterion 2: threshold = 120 points………………..68 List of tables Table 2.1 The relation of α,β, l , m , n and θ2……………………………………………21 Table 2.2 Simulated Results of the Triangle Cylinder Structure Array and Tetrahedron Reflector Structure Array………………………….……….…………………29 Table 2.3 Candela Plot Results of The Triangle Cylinder Structure Array and Tetrahedron Reflector Structure Array…………….……….…………………29 Table 2.4 Measurement Result of The R.S.West’s Work and our design (Original design and Advance design with Triangle Cylinder Array)………………...…31 Table 3.1 The features of the interference fringes…………………………….……….. 59 Table 3.2 Definition of output vectors and mura status defects………………..……….60 Table 3.3 Cross Points of 15 Panels………………………………………….…………64 Table 3.4 Compare Results of 15 Panels…………………………………….………….65 Table 3.5 Statistical Results for A Binary Classification Test………………….……….66 Table 3.6 Statistical Results When Acceptability Criterion=130 Points………….…….66 Table 3.7 Statistical Results When Acceptability Criterion=120 Points………….…….67 Table 3.8 Training data for input and output vectors…………………….……………..70 Table 3.9 The result of the test set………………………………………………………70

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