- 學位論文
以CIE日光軌跡為基礎之 估測LCD TV白平衡研究
Estimated White Balance of LCD TV Based on CIE Daylight Locus
摘要
摘要 以往常見的陰極射線管產品，近幾年已被全平面板顯示器取代。在多元化的競爭，當前使用者對性價比接受度最高的產品應是TFT液晶電視。拜各國制定嚴格節能規範之賜，加速了LED背光源液晶電視的市場滲透率。當價格合理時，終將以後起之秀追上CCFL背光源。在此，改善LED面板的弱點應是當務之急。 針對LED型液晶電視與CCFL型比較時會發現三大類色彩變異問題，概述如下 : (1)生產上的色偏導因於傳統白平衡調整(WBA)不精確，目視參考白(色溫)異常偏紅。 (2)應用上的色偏導因於定型化PC模式設定，出現相近色(灰階)漸層表現不良的色斑。 (3)研發上的色偏導因於畫質評比樣機之色域非sRGB標準，其色彩再現性有偏移失真。 本文主要目的是歸納LED面板的色彩變異問題並提出改善方案，概述如下 : (1)以新的白平衡處理方式改善工廠生產液晶電視 (a)制定標準化程序(最佳熱機時間、設備校正對照表)，有效提升量測面板光學的可靠性和重複性。儲存RGBW等顏色的特定灰階亮度、色度量測值，建立必要的面板光學資料庫。並制定參考白新規範兼顧色度座標和相關色溫的允收誤差。 (b)透過使用者介面OSD設定優化與SoC內建對照表預校正，將兩極串聯gamma (CGOG)模式簡化成類似CRT的電光轉換函數，過程中配合迴歸分析擬合出三通道分段簡易式γ(PSG)模式。再透過光學資料庫中的色度座標，提出LCD TV獨自的色彩空間轉換數學模式。最後完成估算式白平衡演算法(EAWB)，進而免除傳統的白平衡調整。 (2)以新的白色發光二極體光條改良高色溫型LED面板的色彩正確性 (a)取得關鍵上游元件的原始光譜分佈曲線資料(例如白光LED、彩色濾光片)，計算出面板顯示最高階紅、綠、藍信號的理想三刺激值和最大色域。 (b)修正光條中的白色LED完成涵蓋sRGB色域的LED面板樣品，使畫質對比機的色彩整體表現超越CCFL面板。 綜觀本研究提出之白平衡估測演算法是基於CIE日光軌跡找出相關色溫間隔500K的多個參考白點，再根據客戶指定的高、中、低色溫規格儲存三組相吻合的參數(WBA_RGB_gain)於機內記憶體中。此做法的好處不僅有效節省液晶電視生產調整時間進而增加液晶電視產出量，亦能使消費性產品在IT的應用(PC模式)下更符合sRGB的標準，期能有助於未來之電子顯示設備在色彩標準化的實際應用。
並列摘要
Abstract Obviously, CRT display had been almost replaced by FPD in these years. During competitions among various FPD, end user has accepted TFT-LCD TV for the higher performance to cost ratio now. Due to saving energy policy of many countries, it is increasing the market share in LED backlight type once the price gap between CCFL type is closing on. So, we must focus on the improvement of LED panel right now. There are three kind major color deviations in LED panel mentioned as follows. (1) After conventional manufacturing process for white balance adjustment (WBA), the CCT of white point seems not same as CCFL panel. (2) At PC mode which is one kind setting of the smart picture quality, color tone performance is not smoothly. (3) The gamut of golden sample for PQ benchmark does not meet sRGB requirement, so that we can not follow it to reproduce correct colors. The aims of this paper can offer solutions to control color deviations of LED panel. (1) Manufacturing improvement for LCD TV by new white balance process. (a) Setup measurement SOP for optimized warm-up time、color analyzer correction of any kind panel. Collect reliable data about basic optical characteristics of panel. (b) Modify cascade GOG (CGOG) model by OSD pre-settings and SoC LUT correction. Use regression to get piecewise simple gamma (PSG) model. Complete the RGB-to-XYZ color space transfer matrix for each LCD TV. According estimated algorithm for white balance (EAWB), replace conventional WBA. (2) Colorimetric improvement for CCT panel by new type LED lightbar. (a) According to the relative SPDs of white LED and LCM color filters, calculate idea tristimulus values and color gammut of panel. (b) Modify W-LED on lightbar, let PQ perfomance of golden sample can meet sRGB, as well as make it better than CCFL panel. Overview the benefit to use EAWB based on CIE daylight locus to find out several desired white points and saving relative parameters into TV memory. First, save much time in order to get more product outputs in factory. Second, let LCD TV meet sRGB standards under PC mode for IT application. Finally, wish that it can help us to study colorimetric applied new field of display devices.