場序全彩液晶顯示器之時空域調變技術設計與評估

Abstract

近年來，為滿足低耗能、高效率之綠色環保訴求，顯示器學界、業界再次興起研發場序全彩液晶顯器的熱潮。然而，受限於當前液晶顯示器系統的信號寫入模式與液晶模態的響應速率，不僅尚未攻克基本的色度難題，諸如色域縮減、接續色場混雜干擾及背光亮度侷限等，更遑論潛在的視覺效應，色分離現象，仍待克服。本研究探討上述色度難題成因，並提出對應之解決方案，同時建置評估色分離現象之指標。 本論文提出一種新穎的雙色場混色驅動法及其搭配之系統架構，以實現無彩色濾光片之場序全彩液晶顯示器。該混色驅動法採用可空間調控之彩色背光模組以提供額外的空間自由度，滿足三原色系統除了兩個時間自由度外所需之維度，得以呈現全彩影像。採用本架構之系統，最大特色在於擁有最長的單色場時間週期，一方面使現有之商業化液晶模態，例如多區域垂直配向液晶模態，可適用於本系統，降低成本，另一方面則可通過充裕的時間調配，無須犧牲前述之色度參數。除此之外，採用本驅動法之單一色場，通常由雙原色混成，故雙色場通常為非高對比之對立色，例如紅－綠、黃－藍;而對比敏感度的降低，有助於抑制色分離條紋的感知。最後，所提出之心理物理指標，相對對比敏感度，已初步驗證其評估色分離現象的適用性，將可作為評量、反饋於系統優化的參考項目。

Field-sequential-color (FSC) liquid-crystal-display (LCD) has been driven by the demand for energy-efficient Green display in recent years. The driving scheme and slow LC response, however, have led to issues such as color gamut shrinkage, color crosstalk between successive fields, and insufficient backlight intensity, etc., not to mention the visual artifact, color break-up (CBU). This research is to study those colorimetric issues and the feasible solution, based on spatial-temporal modulation, and to develop a methodology to evaluate CBU. A novel two-field driving scheme and the associated system have been proposed to facilitate the FSC LCD without color filters. A spatially-modulated color backlight is implemented to provide degrees of freedom in spatial domain in addition to the two temporal ones for conveying full-color information. This configuration of FSC LCD specifically features the feasibility of commercial LC modes, e.g. Multi-domain Vertical Alignment (MVA), without sacrificing the mentioned colorimetric properties. Additionally, the innate nature of reduced contrast sensitivity between two primary-mixed fields suppresses the CBU to be less sensitive than that appears in the fundamental three-field FSC LCD. Finally, the psychophysical index, relative contrast sensitivity (RCS), has demonstrated the applicability to evaluate CBU among various driving schemes, which can be a useful feedback for system optimization.