利用分色光柵提高液晶面板的光學效率之分析與探討

Abstract

現行的液晶顯示器架構中，彩色濾光片會降低顯示器的光學效率至33%，為了增加光學效率，我們使用了一種基於Dammann 光柵為基礎的分色光柵。 首先，我們先探討改變光柵的參數對繞射效率的影響，對此種分色光柵來說，適合用純量理論來模擬它的效果，我們利用Fresnel 近似來模擬光穿過分色光柵後的光場分布，但是我們發現，光場出現了重疊而且穿透次畫素的效率不高，然而為了解決這個問題，我們在分色光柵之後再加上微透鏡來聚焦光束，而且適當的焦距之下，Frensel 近似可以在被化簡成Fraunhofer 近似，理論上，當使用三個單一頻率的波長入射時，使用這樣的系統可以比是單純使用彩色濾光片提高二倍到二點五倍的光學效率。 接下來，我們用多波長的光源來入射分色光柵，由結果發現，不同的入射光源會對我們分色光柵有很重大的影響，最後，當我們在液晶顯示器內加入分色光柵時，顯示器的色彩表現，也就是色彩座標上的色域空間並不大，然而，我們可以重新的設計較適合入射光源的分色光柵，或者加上彩色濾光片來解決這個問題，我們模擬了一個加入彩色濾光片與分色光柵的系統，它可以明顯的提高色域的範圍，但是又不會降低光學效率太多。

In LCD (liquid crystal display) system, the color filters decrease the optical efficiency to 33% in LCD. In order to increase the efficiency, the CSG (color separation grating) which is realized by Damman grating is used. First, changing the parameters of the CSG will influence the diffraction efficiency of the CSG. The scalar theory is the suitable theory to simulate the CSG. The Fresnel approximation is used to simulate the light passing through the CSG, but the optical fields of the light have cross-talk and low throughout efficiency. However, to solve the problem, the microlens is used to focus the light to improve the performance. Under some condition, the Frensel approximation will be reduced to the Fraunhofer approximation, and the theoretical optical efficiency for three discrete wavelengths can 2 to 2.5 times of that using color filters. Next, from the simulation of the multi-wavelength, the different incident light source will affect the design of the CSG importantly. Finally, the color gamut is not very large when the CSG is used in the LCD. However, the new design of the CSG or the color filter will solve the problem. The LCD with color filter and CSG will enhance the color gamut obviously, but not decrease the optical efficiency of the LCD.