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標題: 彩色液晶顯示系統之亮度增強、色域擴張與功率改善技術研究
Brightness Enhancement, Wide Color-Gamut Expansion and Power Consumption Reduction for Improving Color LCD Systems
作者: 賴志章
Lai, Chih-Chang
關鍵字: Brightness Enhancement;彩色液晶顯示系統;Wide Color-Gamut Expansion;Power Consumption Reduction;Color LCD Systems;亮度增強;色域擴張;功率改善
出版社: 電機工程學系所
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本論文的目的是針對彩色液晶顯示系統,探討與研究其亮度增強、色域擴張、功率改善以及提昇畫面品質的方法與實作技術。兩種新的紅、綠、藍、白( RGBW) 結構被提出,用以提高亮度;一雙層磷光粉之發光二極體被當作背光源,達到高色域之目的;一新型的適應性背光調變技術被研發,用以降低整體彩色液晶顯示系統之功率消耗。針對以上四種技術,本文提出各別之影像處理引擎,用以改善畫面品質,並對其特性作詳盡之研究。
一種創新的RGBW彩色濾光片結構改善50 % 的顯示器亮度與模糊法則的映射演算法保持畫面品質。根據人類視覺對藍色顏色較低的辨識能力,將藍色的畫素一半的區域設計為白色畫素來增加亮度,且不降低色彩飽和度與解析度。然後配合模糊法則的映射演算法,輸入因子為白色畫素周圍的紅、綠、藍畫素資料,可得到相對應的白色畫素以得到較佳的影像品質。
另一種為調整條紋式RGBW彩色濾光片結構,與傳統的直條紋式RGB彩色濾光片結構比較具有保持解析度與提高50%亮度的效果。此結構中的每一個子畫素大小與傳統的RGB直條紋式一樣,且每一行的子畫素排列只需位移兩個子畫素,所以可以使用RGB直條紋的TFT array基版,達到低成本的目的。搭配此結構,一種影像處理器可使影像更加銳利。此影像處理器包含RGB對應到RGBW與子畫素分享兩種演算法:RGB對應到RGBW演算法可以得到色調與色彩飽和度沒有失真的RGBW影像資料;子畫素分享演算法將RGBW的影像資料轉換到調整條紋式RGBW的彩色濾光片結構且達到影像更加銳利的效果。
雙層磷光粉發光二極體(MPW LED)與一般的白光方光二極體在一樣的消耗功率與亮度底下比較可擴展13% 的顯示器色域,且依照此顯示面板的特性調整一先進的色彩增艷的方法,得到具有色彩飽和度平均45%提昇且一樣色調的影像品質。

This dissertation presents methodologies and techniques for achieving high-quality color LCD systems. The four developed techniques include brightness enhancement using two novel RGBW color filter structures, wide color gamut expansion employing multi-phosphors white (MPW) light-emitting-diodes (LEDs), and power reduction using an adaptive dimming approach. These four techniques are accompanied by their own image processing engines to improve overall image quality.
The first color filter structure, called half-subpixel RGBW (HS-RGBW), is constructed based on the working principle of human vision. On the basis of human vision lower discrimination in blue color, the half sub-pixels of blue color is replaced by white sub-pixels to enhance brightness without loss of their original color saturation and resolution. A fuzzy mapping algorithm using RGB sub-pixel data around white sub-pixels is proposed to obtain better image quality. The HS-RGBW color filter structure together with the fuzzy mapping algorithm is shown to improve 50% brightness of color LCD display systems.
The second RGBW color filter structure is the modified stripe RGBW (MS-RGBW) that keeps the same high resolution and obtains a higher 50% brightness in comparison with conventional RGB color filters. In the MS-RGBW color filter structure, each pixel with three sub-pixels is the same area to that in the conventional RGB stripe color filter and each row shifts two sub-pixels, thereby achieving a low-cost solution with the existing TFT array in any RGB stripe color filter. An image-processing engine is also designed to achieve sharp text image for thin-film-transistor (TFT) LCD with the MS-RGBW color filter. The image-processing engine consists of two new algorithms: RGB-RGBW mapping algorithm and sub-pixel rendering algorithm. The RGB-RGBW mapping algorithm outputs new RGBW image data without distortion in hue and saturation. The sub-pixel rendering algorithm transfers the RGBW data into corresponding ones in a MS-RGBW color filter structure in order to achieve sharp text image.
The proposed MPW LEDs expand 13% of the display color gamut in comparison with conventional white LEDs under the assumption of equal power consumption and brightness. The MPW LEDs can be not only easily applied to any customized LCM without increasing power consumption and reducing brightness, but also effectively used to enlarge the color gamut expansion. In addition, a rich color image processing method obtains a superior image data by showing about 45% saturation enhancement without hue distortion.
The proposed adaptive dimming technique reduces backlight power consumption and enhances image contrast for global backlight applications. This adaptive dimming technique consists of two new algorithms: backlight dimming algorithm and contrast enhancement algorithm. The backlight-dimming algorithm obtains appropriate 0% to 50% backlight power reduction to save 25% backlight power depending on characteristics of the image data. The contrast enhancement algorithm not only reduces the adverse effect of backlight power saving, but also improves 20.75% enhancement of image contrast ratio on the average.
In addition to detailed descriptions of these four techniques, several computer simulations and experimental results are conducted to show the effectiveness and merits of the proposed methods along with their experimental LCD systems. The developed techniques may be of interest to professionals working in the field of color LCD systems and consumer electronics.
其他識別: U0005-2807200821515100
Appears in Collections:電機工程學系所

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