LED背光源缺陷检测方法的研究
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摘要
直下式LED背光源广泛应用于大尺寸液晶显示屏,发光晶片和光学透镜装配于PCB板上形成单个背光源,晶片和透镜间可能存在装配缺陷,即水平、高度、角度偏移,要求偏移量不得超过0.02mm、0.1mm、0.2°,否则会对显示屏显示质量造成不利影响。针对背光源的装配缺陷,提出了基于图像灰度曲线对背光源缺陷进行检测的方法。分析了透镜对晶片光线的作用,在光学软件Tracepro中建立了背光源工作模型并进行了仿真,得到了光线在显示屏上形成光斑的照度分布和照度曲线,获得了偏移类型与照度曲线的关系,设计了相应的图像采集平台,基于VC6.0设计了灰度曲线求取算法,进行了试验。试验结果表明,该检测方法可有效检测LED背光源的水平、高度、角度缺陷,检测精度分别为0.01mm、0.04mm、0.1°。
LED backlight of straight down type is widely used in large size LCD screen. Light emitting chip and optical lens are assembled on PCB board. They form a single backlight. Assembly defects,namely horizontal offset,height offset and angle offset,may exist between emitting chip and optical lens. The respective offset is required to be less than 0.02 mm,0.1 mm,0.2°. Otherwise,the display quality of screen will be adversely affected. In view of the defects,a method of detecting backlight defects based on image gray curve was carried out. The effects of optical lens on the light from emitting chip was analyzed. In the optical software,namely Tracepro,backlight working model was established and simulating was carried out.Illuminance distribution and illumination curve of light spot forming on the display screen was obtained. The relationship between different offset type and illumination curve was acquired. The corresponding platform of collecting images was designed,algorithm for calculating gray curve was designed based on VC 6.0,and the experiment was carried out. The testing results show that the backlight defects detection method can effectively detect LED backlight horizontal,height,and angle offset defects.The detecting precision was 0.01 mm and 0.04 mm,0.1° respectively.
LED backlight of straight down type is widely used in large size LCD screen. Light emitting chip and optical lens are assembled on PCB board. They form a single backlight. Assembly defects,namely horizontal offset,height offset and angle offset,may exist between emitting chip and optical lens. The respective offset is required to be less than 0.02 mm,0.1 mm,0.2°. Otherwise,the display quality of screen will be adversely affected. In view of the defects,a method of detecting backlight defects based on image gray curve was carried out. The effects of optical lens on the light from emitting chip was analyzed. In the optical software,namely Tracepro,backlight working model was established and simulating was carried out.Illuminance distribution and illumination curve of light spot forming on the display screen was obtained. The relationship between different offset type and illumination curve was acquired. The corresponding platform of collecting images was designed,algorithm for calculating gray curve was designed based on VC 6.0,and the experiment was carried out. The testing results show that the backlight defects detection method can effectively detect LED backlight horizontal,height,and angle offset defects.The detecting precision was 0.01 mm and 0.04 mm,0.1° respectively.
引文
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[4]史艳琼,卢荣胜,张腾达.液晶显示屏背光源模组表面缺陷自动光学检测系统设计[J].传感技术学报,2015,28(5):769-770.(Shi Yan-qiong,Lu Rong-sheng,Zhang Teng-da.Defect inspection system design based on the automated optical inspection technique for LCD backlight modules[J].Chinese Journal of Sensors and Actuators,2015,28(5):769-770.)
[5]赵朋,颉俊,傅建中.塑料光学透镜的磁悬浮检测[J].光学精密工程,2016,24(4):757-758.(Zhao Peng,Xie Jun,Fu Jian-zhong.Magnetic levitation detection for plastic optical lenses[J].Optics and Precision Engineering,2016,24(4):757-758.)
[6]王希靖,史吉鹏,柴廷玺.铜始极片表面缺陷检测系统研究与设计[J].机械设计与制造,2013,8(8):252-253.(Wang Xi-jing,Shi Ji-peng,Chai Ting-xi.Research and design on surface defect detection system for copper starting sheet building materials[J].Machinery Design&Manufacture,2013,8(8):252-253.)
[7]钟球盛,胡广华,李静蓉.光学薄膜表面微细缺陷在线检测方法研究[J].机械设计与制造,2011,10(10):102-103.(Zhong Qiu-sheng,Hu Guang-hua,Li Jing-rong.Research on on-line inspecting algorithm for micro-defects of optical films surface[J].Machinery Design&Manufacture,2011,10(10):102-103.)
[8]秦莉,董丽丽,许文海.CCD图像灰度与照度的转换标定方法[J].仪器仪表学报,2015,36(3):640-641.(Qin Li,Dong Li-li,Xu Wen-hai.Method for conversion calibration between CCD image gray value and illumination[J].Chinese Journal of Scientific Instrument,2015,36(3):640-641.)
[9]刘书桂,李蓬,那永林.基于最小二乘原理的平面任意位置椭圆的评价[J].计量学报,2001,23(4):245-249.(Liu Shu-gui,Li Peng,Na Yong-lin.Evaluation of the form error of ellipse based on least square method[J].Acta Metrologica Sinica,2002,23(4):245-247.)
[10]陈维义,罗晓沛.基于Hough变换和变形曲线技术的椭圆提取研究[J].微电子学与计算机,2004,21(9):91-95.(Chen Wei-yi,Luo Xiao-pei.Extracting ellipse based hough transform and active snake technique[J].Microelectronics and Computer,2004,21(9):91-95.)