液晶顯示器擁有比傳統顯示器更輕、更薄、更省電的優點，且生產尺寸也由小尺寸的側邊式背光發展為大尺寸的直下式背光。在本文中著重於提升直下式背光模組之光學特性。現今直下式背光模組之設計均須依賴試誤法加以實作並分析，如此一來便曠日費時且無法精確的找出其最佳設計，本論文使用田口方法的設計來同時兼顧效率與性能，達到均勻性與亮度等光學特性之設計需求。由於在直下式背光模組的設計中，其研究結果顯示幾何尺寸的改變對於光學特性有相當的影響，因此使用五種設計參數來提高背光模組的均勻性與亮度，這五個參數分別為燈管至底板的距離、背光模組側邊的角度、燈管至背光模組頂端的距離、燈管的數目與燈管至背光模組側邊的距離。經由設計與分析的驗證，成功的在滿足設計要求之情況下，將奇美公司的背光模組由原本的74%均勻性與6900cd/m2的亮度提升為85%的均勻性與6700cd/m2的亮度。並提供了一個較明確的設計流程來縮短整個背光模組開發所需的時間。

This thesis attempts to improve the optical performance of direct lighting backlight system. Current design practices of try-and-error and relying on expert-only can be significantly improved. Optical performance of backlight system with linear isotropic light source satisfying the uniformity and brightness can be achieved by the Taguchi method. In the development of the direct lighting backlight system, the geometric design and modification dominate the system characteristics. There are five parameters can be adjusted to enhance the optical performance and they are the distance between the lamp and the bottom of the backlight unit, the angle of the side surface, the distance between lamp and the top of the backlight unit, numbers of the lamp and the distance between lamp and the side of the case. Results of this study show that the original model from Chi-Mei company has the optical performance with 74% uniformity and 6900 cd/m2 mean luminance the optimal model provides 85% uniformity with 6700 cd/m2 mean luminance. Compared with the original model, it is improved about 11% uniformity. This thesis improves the previous studies’ findings by providing a much more systematic design process. The designed model can improve the optical performance.

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