摘要
针对大尺寸TFT-LCD(第五代到第八代)生产检测过程中要求成像系统成像速度快、精度高的情况,研究快速的显微镜自动对焦方法。提出一种间接清晰度评价函数和一种用于TFT-LCD玻璃板检测的显微镜自动对焦的方法,采用一个激光器和一个黑白CMOS相机作为辅助手段,通过寻找CMOS相机最大的通光率的值确定CCD相机对焦最好的目标点,在此基础上,通过求取CMOS相机获得图片中的激光光斑质心并查表确定镜头调节的方向和距离。实验结果表明,对于放大倍率为5倍至50倍的物镜,当玻璃板在焦平面上下正负50μm范围内进行自动对焦时,对焦时间在0.4 s以内,重复对焦精度可达到景深的0.1~0.5倍以内。
To meet the requirement of high speed and accurate performance test of large TFT-LCD(the fifth to the eighth generation LCD),fast auto-focus method is studied.A clarity evaluation function and an auto-focus method used to inspect the glass by microscope are presented.It used a laser and a black /white CMOS camera as an auxiliary means.The CMOS camera is used for getting image of the laser spot.Evaluation criteria of definition can be acquired by calculating the transparent rate of the CMOS camera.The focus of CCD camera can be obtained by the clarity evaluation function.On this basis,how to adjust the distance between the microscope lens and the glass in order to achieve focus is determined by the position of the spot centroid of the image in the spot centroid table.Experimental results show that when the objective lens with magnification of 5 to 50 times of depth of field are used for test,auto-focus time is 0.4 seconds or less and repetitive focusing accuracy can be less than 0.1 times to 0.5 times when the glass is in the focal plane up and down within ±50 μm.
出处
《激光与红外》
CAS
CSCD
北大核心
2010年第12期1358-1363,共6页
Laser & Infrared
基金
广东省教育部产学研项目(No.2007A090302071)
广东省教育部产学研项目(No.2009B090300242)资助
关键词
成像系统
自动对焦
通光率
光斑质心
对焦时间
imaging systems
auto-focus
rate of pass-ray
spot centroid
focus time