反射式顯示器之均勻前光照明系統設計與應用

Abstract

近年來隨著顯示技術的發展，膽固醇反射式液晶顯示器開始應用於大型電子看板。反射式顯示器不需要背光源，而是利用周圍的環境光源作為照明來源以顯示影像，因此反射式顯示器的影像品質與環境照明密切相關，在戶外陽光充足或明亮的環境下能擁有好的影像品質，但當使用於夜晚時或昏暗的室內環境下，由於不足的照明度而需要提供一前光照明給顯示看板。然而，常見的照明燈具例如MR lamp，自斜向的照射角度造成顯示器表面亮度不均勻，影響影像品質。 本論文研究提出一以均勻照明為目標的前光照明設計。此燈具設計使用CCFL 作為光源，利用自由型式的鏡面反射罩來分佈光線，均勻地照射在目標顯示器上。根據燈源與目標平面的距離，照射範圍，及燈源與目標平面之間的相對位置，以數值分析計算出所需的自由型式反射罩的形狀。模擬結果驗證所設計的照明系統明顯地改善照明均勻度，均勻度偏移量在5%內。初步的燈具模型的製作方法與實驗結果，以及實際照射在膽固醇液晶顯示器上的效果，在論文中有詳細的討論與分析。

Recently, Cholesteric reflective LCDs have been applied to electronic billboards. Reflective LCDs, without the back-light source, utilize ambient light as the main source for illumination. The image qualities of electronic billboards are ideal in well-lit locations or under diffuse sunlight. At night or in dim indoor environments, front lighting is necessary due to insufficient surrounding illumination. However, conventionally available Luminaires, such as MR lamps, generally illuminate the display with non-uniform brightness, resulting in poor image quality. A front-lighting design for uniform illumination was proposed. The Luminaire applies a free-form mirror surface reflector to redistribute light from the CCFL source. The shape of the free-form reflector was numerically calculated according to the normal distance between the source and the target plane, the illuminated region, and the positions of the source and the target plane. Simulation results show that the proposed illuminating system improves illumination uniformity where uniformity deviation is within 5%. Fabrication and experimental results for a Luminaire prototype, and demonstration on a Cholesteric LCD, are discussed and analyzed.