脈衝方式驅動LED背光模組降低動態影像陰影

Abstract

隨著液晶顯示器的大型化，人們對顯示器的品質越來越高，如高色彩飽和度、動態影像品質，於是發光二極體逐漸被應用在大型顯示器，而當液晶顯示器被應用在電視多媒體上，人們對動態影像的要求就越高。動態畫質模糊調校是近幾年來相當熱門的話題，而陸續也有部分液晶顯示電視說明書上，開始出現「動態畫面模糊改善」的訴求。 而液晶顯示器目前無法完全取代映像管的地方就在於色彩及動態影像的表現，雖然發光二極體已可大大改善色彩飽和度到達NTSC 105%，但液晶顯示器受限於液晶的反應時間及液晶顯示光源表現為持續方式，使在動態影像表現上因人眼的視覺停留的因素導致影像移動的邊界上產生陰影。本文的研製重點在於製作15吋發光二極體背光模組，並利用脈衝(Impulse)方式驅動發光二極體背光模組，讓人眼避開液晶反應時間，及改變了液晶光源顯示表現方式，從持續方式變成較接近脈衝方式，使人眼的視覺停留畫面均勻化了，因而降低了動態影像陰影，且實際以15吋冷陰極管光源的液晶顯示器做比較，並利用現場可編程閘陣列，經液晶顯示器的掃描訊號來同步產生脈衝訊號驅動發光二極體背光模組，且比較不同的形式的脈衝對動態影像改善的程度。

With the trend for bigger LCD, people are demanding on higher quality of LCD, such as “High Color Saturation” and “Motion Image”. That’s why LED are gradually used in large size LCD. When LCDs are used for TV multi-media, people’s demand on motion image are get higher and higher. Calibration of the fuzzy motion image has become a popular issue in recent years, and some of the instruction manual even begin to show the need for “improvement on fuzzy motion image”.However, the reason that LCD can’t fully take the place of the tube is mainly on the performance of color and motion image. Though LCD can greatly improve the Color Saturation up to NTSC 105%, LCD is limited on reaction time and continue LCD light source, which create image shape shadows while the image moves due to photogene. This paper focuses on producing 15”-LED Back Light Module, and use impulse to driver the LED Back Light Module components in order to let human eyes avoid the LCD reaction time and change the display form of the LCD light source – from continue way to near-impulse, which average the photogene of human eyes to reduce the moving image shadows. Besides, through actual comparison with the 15” cold Cathode Tube light source LCD, and utilities field programmable gate array (FPGA), through LCD’s scan signal to generate the impulse signal simultaneously to drive the LED Back Light Module, and compare the image improve level caused by various form of impulses.