次波長光柵於背光模組中作為偏光分離用途之分析

Abstract

隨著科技的進步，傳統的CRT已逐漸被TFT-LCD所取代。在LCD發展的過程中，效率一直是急欲解決的問題。造成LCD效率損耗的原因主要是彩色濾光片的損耗及背光模組的損耗。在本文中，主要是探討如何在背光損耗上做補償藉以提升顯示器的效率。根據傳統的做法，3M的DBEF被用來作為偏光回收的解決方法，但是卻有專利的問題。為了規避掉專利，很多欲取代掉DBEF的元件被提出。根據先前被發表過文獻，一種含有次波長光柵結構能達成偏光分離及偏光轉換的元件被提出。在此元件中，為了達到最好的偏光分離效率，次波長光柵的設計便顯得極為重要。 在本論文中所使用的是GSolver這套商用軟體，首要的工作在於設計出能提高偏光分離效率的次波長光柵。在模擬的結果中顯示，對於p-ray的穿透效率在藍光波段有所謂共振的情形發生，這會影響元件在可見光波段的使用效率。我們提供了解決此缺點的方法來試圖提升p-ray在藍光波段的穿透效率，並試著解釋其間的關係。藉由最佳化次波長光柵的幾何結構及材料，我們可以得到能夠應用在可見光波段之光柵。

With the evolution of technology, traditional CRT has been substituted for TFT-LCD gradually. In the development of LCD, problem of efficiency is always important. The main reason of the reduction of efficiency for LCD is the loss of color filter and backlight module, and we focus on the loss caused by the backlight module in this thesis. Conventionally, DBEF of 3M is used to solve the problem but it is patented. To avoid patent violation, many devices are proposed to take replace of DBEF. According to bibliography, a device with sub-wavelength grating was proposed to achieve polarization splitting and polarization conversion. In such device, design of sub-wavelength becomes very important to achieve satisfying efficiency of polarization splitting. A suit of commercial software “GSolverTM” is used to design a sub-wavelength grating with high efficiency of polarization splitting. Just as shown in our simulation, there exists the situation of what we called resonance for transmission efficiency of p-ray in blue-light region and that will affect the performance in visible-light spectrum. We provide several solutions to enhance the transmission efficiency of p-ray in blue-light region and try to explain the reason of these solutions. By optimizing geometrical parameters and material of sub-wavelength, we can obtain the sub-wavelength grating well performed in the visible-light region.