功率優化及色彩表現提升之分光光柵設計

Abstract

現行的液晶顯示系統中利用彩色濾光片來達到全彩的效果是非常普遍且必要的，然而利用彩色濾光片，會使光使用效率下降至只有33%。為了解決這個問題，我們在現有的液晶顯示系統裡，在背光源和彩色濾光片之間加入分光光柵結構，以達到讓背光源經過此光柵結構後分別分成紅色、綠色及藍色，且分別射入不同次像素。 我們利用Fraunhofer 繞射理論為基礎來模擬分析光柵結構並且分析其繞射效率以及色彩表現。我們利用調整光柵參數(包含光柵階數、光柵高度以及中心波長)，分別對三種不同的光源(CCFL、UHP和LEDs)來做模擬。 從模擬的結果得知，在加入光柵結構後光的使用效率跟傳統CCFL系統比可以增加93.8%，且在色空間方面可以增加20.8%。對於UHP和LEDs 光源而言，光使用效率分別增加91%及107%，並且色空間分別增加10.2%及12.7%。所以我們可以藉由加入分光光柵結構來同時達到提高光的使用效率，並且增加色域空間的結果。

It is fundamental to use the color filter (CF) in LCD system to achieve a full-color display. For this purpose, however, the total power efficiency will plummet to 33% when the light passes through the CF. In order to alleviate this problem, we have developed a novel approach by inserting a diffractive color separation grating between the backlight and the CF to spatially separate the RGB (red, green, and blue) lights and then the three bands can be directed into three different corresponding sub-pixels. We simulated such multiple-level gratings based on Fraunhofer diffraction theory and analyze the diffraction power efficiency and color performance for the new backlight systems. We take three different light sources (CCFL, UHP, and LED) as our simulation examples and design the corresponding grating structure (the period, step and height of the grating) for each light source. The simulation results we derived for CCFL backlight demonstrate that we can get the best power efficiency improvement by 93.8% as compared with the conventional system. The gamut area can be improved by 20.8% as well. For the other two backlight systems (UHP and LED), we can design the gratings and get the best brightness efficiency improvement by 91% and 107% and gamut area improvement by 10.2 % and 12.7%, respectively. In conclusion, by adopting this novel approach we can successfully achieve the goal of improving total power efficiency and enhance the color performance at the same time.