At present, LCD displays occupy a dominant position in the flat panel display market, among which the backlight module is an important component of LCD displays. Since 2008, light-emitting diode (LED) backlighting has rapidly replaced traditional cold cathode tube (CCFL) backlighting as the mainstream technology with advantages such as high light efficiency, long service life, good color rendering performance, compact size, and no mercury content. LED backlight modules can be divided into two categories based on the position of the light source: side down and straight down. Considering the characteristics of two types of backlight modules, this paper applies full array direct down LED backlight to the backlight module of large-sized LCD displays, and conducts research on several key technical issues of large-sized and high-performance full array direct down LED backlight modules. Firstly, based on the previous research on the uniform lighting conditions of the generalized Lambertian LED array lighting system based on the Sparrow criterion, we collaborated with Shenzhen Longxiang Zhuoyue Electronic Technology Co., Ltd. to study the uniform lighting conditions of an array lighting system composed of any type of LED using the Sparrow criterion. For the first time, we found that for certain wide angle LEDs, the lighting uniformity of the array lighting system varies non monotonically with the LED spacing or system thickness. Based on the discovered abnormal uniform lighting conditions, this paper presents a general design method for a uniform lighting LED array lighting system based on the Sparrow criterion. Then, this paper applies the contrast sensitivity function in human vision to study the uniform lighting conditions of LED array lighting systems, and re derives the uniform lighting conditions of generalized Lambertian and wide angle LED array lighting systems. It is found that the obtained structural parameters are more accurate and practical than those obtained based on the Sparrow criterion. Then, based on the contrast sensitivity function, the normal and abnormal uniform lighting conditions are more systematically discussed. This paper also presents a design method for a uniform LED array lighting system based on human visual effects. The use of brightening film for backlighting reduces the viewing angle and increases axial brightness, but it also generates high light loss, which limits the further improvement of backlight module brightness. For this purpose, this paper actually fabricated a 19 inch straight down LED backlight module, and studied the transmittance of light passing through the brightening film in different spatial directions at different angles through simulation and simulation, obtaining the spatial transmittance characteristics of the "petal shaped" brightening film. Then, this paper designs a free form surface lens that matches the angle range of the light source's output with the transmittance characteristics of the brightening film, which can improve the axial brightness of the backlight module without changing the viewing angle.The experimental results show that, in the presence of degraded optical effects caused by diffusion film, the axial brightness increase reaches 22.8%, and the viewing angle only shows a very slight decrease. Localized dimming dynamic backlighting technology is another key technology for high-performance large-sized full array straight down LED backlighting, which can improve the contrast of the output image and reduce power consumption. Using the testing and manufacturing equipment of Shenzhen Longxiang Excellent Electronic Technology Co., Ltd., the effects and corresponding computational complexity of the three main steps of determining backlight source brightness, simulating real backlight, and grayscale compensation in local dimming dynamic backlight processing were studied. The effects of different dimming algorithms and the number of dimming blocks on distortion rate and energy-saving performance were analyzed, It is pointed out that increasing the number of dimming blocks is the only way to fundamentally improve both distortion rate and energy-saving performance. This paper proposes a technical solution using grid reflective panels, which allows the real backlight simulation step to be completely omitted, thereby reducing overall complexity by several times and weakening its correlation with the number of dimming blocks. With the help of grid reflective panels, this paper uses more dimming blocks and a critical overflow dimming algorithm that matches the grid reflective panel technology scheme. The distortion rate and energy-saving performance have been significantly improved.
---Source//Paper "Key Technology Research on Large Size and High Performance LED Backlight Module" | Qinzong Huazhong University of Science and Technology Classification Number: TN873.93 Shenzhen Longxiang Zhuoyue Electronic Technology Co., Ltd