臺灣博碩士論文加值系統

傳統液晶電視的表面發光源是由一固定、均勻且高亮的背光所構成。但是這種結構造成了在低灰階畫面有比較明顯的漏光。因此，傳統液晶電視在連續的影像上無法表現出最好的動態對比畫質，如畫面景深不夠，無立體感。液晶並非是光線發射材料(非發光型式)。因此，它需要有背光模組(BLU)提供一個能維持整個螢幕有均勻亮度的表面亮度光源。當光線到達眼睛，觸擊了視網膜上的視覺感受器，然後經由神經細胞傳送電子訊號到大腦形成影像。此外，人類視覺系統(HVS)有一個重要的特性就是隨著不同的適應性變化的程度做改變稱為差異閾限(Difference Threshold)或恰可察覺差(Just Noticeable Difference (JND))。動態背光調整就是根據此基礎(JND)來做設計的。本方法採取影像處理技術的統計長方圖(Histogram)來操作。然後我們逐幅畫面計算和平均Histogram的輸入影像亮度值，液晶電視的背光亮度會根據每幅畫面的平均影像亮度值的變化動態調整。
根據本研究結果顯示，和傳統背光模式的液晶電視相比，動態背光模式的全螢幕對比的結果增加了7.38倍。因此，本方法「運用影像亮度訊號的變化動態調整背光」在增加LCD TV的動態對比(特殊場景或畫面的最大亮度除以最小亮度的比值)產生實際效益的效果。就製造上而言，本方法可以達到低成本，無需額外支出購買專用面板(低漏光的面板)，且設計容易等需求。符合目前台灣LCD TV OEM/ODM製造廠的生產模式。

A conventional surface light source of LCD TV is composed by a “constant, uniform and high bright backlight”. But this architecture makes light leakage at low grey levels picture more pronounced. For this reason, the conventional LCD TV can’t perform the best picture quality of dynamic contrast ratio in sequence video as like no enough depth of field, no stereognosis in pictures. Liquid crystals are not light-emitting materials (non-luminous type). Thus, it is necessary to have Backlight Unit (BLU) to supply a superficial light source type which can maintain the overall screen in uniform brightness. When light reaches eye, it hits the photoreceptors on the retina, which then send an electrical signal through neurons to the brain where an image is formed. In addition, one of the most important HVS characteristics that changes with different adaptation levels is called Difference Threshold or Just Noticeable Difference (JND) Dynamic Backlight Adjustment was base on this foundation (JND) to be designed. The method was adopted Histogram processing of image process technology. And then we calculated and averaged input video Luma values of histogram frame by frame. Luminance of LCD TV backlight would be adjusting dynamically base on the variance of average video Luma value every frames.
According to results of the research, the full screen contrast ratio of dynamic backlight mode was increased to 7.38 times as compare with conventional backlight mode of LCD TV. Thus, the method “Dynamic backlight Adjustment with video Luma signal variance” had the beneficial effect of increasing the dynamic contrast (the ratio of the maximum luminance to minimum luminance of a particular field or frame) of the LCD TV. For manufacture, the method may achieve requirements, which are low cost, no extra expenditure to purchase special panel (low light leakage panel) and easy design etc. It would satisfy the mode of production of LCD TV OEM/ODM makers presently in Taiwan.

書名頁.......................................i
論文口試委員審定書..........................ii
授權書.....................................iii
摘要........................................iv
ABSTRACT....................................vi
ACKNOWLEDGMENTS...........................viii
TABLE OF CONTENTS............................x
LIST OF FIGURES...........................xiii
LIST OF TABLES.............................xvi
CHAPTER 1 INTRODUCTION.......................1
1.1 Motivation...............................1
1.2 Objective of this study..................2
1.3 Thesis organization......................3
CHAPTER 2 THEORY REVIEW......................4
2.1 Human visual system (HVS)................4
2.1.1 The human eye..........................4
2.1.2 Reflectivity and luminance.............8
2.1.3 Psychophysics..........................9
2.2 TFT-LCD overview........................12
2.2.1 LCD structure.........................12
2.2.2 Backlight unit........................14
CHAPTER 3 METHODS AND EXPERIMENTAL PROCESSES..20
3.1 LCD TV system function block............20
3.2 Video transmission......................22
3.3 Image processing and color space conversion..25
3.3.1 A/D conversion....................... 25
3.3.2 Color space conversion................26
3.4 System software structure...............34
3.4.1 Software algorithm....................35
3.4.2 Operating threshold...................37
3.5 Photometry..............................38
3.6 Methods of measurements.................40
3.6.1 Center of luminance and darkroom contrast ration of full screen measurements....................40
3.6.2 Luminance & contrast of centered box measurements..42
3.7 Material characterization...............44
3.7.1 Display color analyzer CA-210.........44
3.7.2 Video test instrument- Quantum data 881 / 882..46
CHAPTER 4 RESULTS AND DISCUSSION............47
4.1 Procedure of setup before measurement...47
4.1.1 Equipment self calibration............47
4.1.2 Measurement setup.....................47
4.1.3 Darkroom conditions and ambient lighting..49
4.2 Results of full screen measurements.....49
4.2.1 Conventional backlight operation in full white/black pattern.....................................50
4.2.2 Dynamic backlight operation in full white/black pattern.....................................52
4.2.3 Brief discussion......................54
4.3 Results of centered box measurements....55
4.3.1 Conventional backlight operation in centered box pattern.....................................56
4.3.2 Dynamic backlight operation in centered box pattern.....................................60
4.3.3 Brief discussion......................64
4.4 Results of video image..................65
4.4.1 Video image of conventional backlight operation..65
4.4.2 Video image of dynamic backlight operation..66
4.4.3 Brief discussion......................66
4.5 Discussion..............................68
CHAPTER 5 CONCLUSION AND FUTURE DIRECTION...70
5.1 Conclusion..............................70
5.2 Future direction........................71
REFERENCES..................................73
APPENDIX....................................76
A.1 Video format in common use for LCD TV...76
A.2 LCD panel specification.................77
VITA........................................78

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