【作者】 肖磊；

【导师】 程良伦；

【作者基本信息】 广东工业大学 ， 控制理论与控制工程， 2011， 硕士

【摘要】 自二十世纪九十年代TFT-LCD开始正式量产以来,其产品被广泛应用于数码相机、车载显示器、笔记本电脑和液晶显示等几乎所有的显示器领域。TFT-LCD自动光学检测设备是一个集成了光、机、电、自动化等技术的精密机器视觉识别系统,在液晶显示屏缺陷检测中,需要一种调焦装置实现高精度非接触的自动对焦来获取清晰玻璃基板图片。本文针对TFT-LCD面板尺寸大、厚度薄、光透过率高的特性,设计了基于激光三角测距法的自动对焦系统。主要包含以下内容：(1)对自动对焦技术、激光测距的发展现状进行了研究,比较了各种对焦方法和激光测距方法的优缺点,提出了基于激光三角测距法的自动对焦系统来实现大尺寸玻璃基板的非接触快速对焦。(2)根据TFT-LCD面板光学检测设计的要求,提出采用三维立体机构的机械平台,压电陶瓷主要驱动6个不同倍数的显微物镜上下移动来实现微小行程调焦,具有调焦负载小,调焦速度快,精度高的特点。(3)分析了激光三角法原理,在其理论基础上提出了自动对焦系统光学回路设计方案,并从原理上进行了论证,根据光斑图像的中心位置和离焦量之间的相关性实现快速对焦,该方法具有调焦方向明确,准确度高的优点。(4)给出了自动对焦系统的控制方案,通过分析TFT-LCD面扳反射的能量对光斑图像的影响,提出在焦平面附近调节相机快门和增益以消除鬼影,比较了几种常用的调焦评价函数,提出了根据光斑中心位置误差允许范围作为调焦评价的依据,具有调焦准确、精度高的优点。(5)软件部分设计,自主研发的显微镜自动对焦系统软件,通过1394图像采集卡实现了激光光斑图像的采集处理,通过动念函数的调用实现了三轴电机的运动控制,压电陶瓷的微调焦控制,通过手柄设计快速实现显微镜不同镜头的控制。(6)实验结果表明：在行程100um的自动对焦范围内,5X物镜下,自动对焦时间为0.237s,重复定位精度为±1.97um。50X物镜下，自动对焦时间为0.29s,重复定位精度为±0.26um。该系统稳定性好,对焦精度高,抗干扰能力强，基本满足大尺寸玻璃基板光学检测的需要。更多还原

【Abstract】 Since the 1990s, People started to mass produce TFT-LCD and the products have been widely used in almost all display areas,such as digital cameras, automotive displays, notebook computers, LCD monitors and so on. The TFT-LCD Automatic Optic Inspection is a precision machinery visual recognition system which integrates the light,electronics, automation and so on. The TFT-LCD defect detection need one kind of focusing mechanism to realize high accuracy non-contact automatic focusing to get the clear glass substrate images. In view of the TFT-LCD panel have the characteristics of large size,thin depth and high light transmittance,people established a autofocus system based on the Laser-triangulation. Primarily contains the following content:Firstly, this article makes research to the current development of auto focus technology and laser range finder, compares the advantages and disadvantages of all kinds of focusing methods and laser range methods, put forth the auto-focus system based on laser triangulation to realize the large size glass substrate non-contact quick focusing.Secondly, According to the requirements of TFT-LCD optical detection, using the three-dimensional organization mechanical platform and the piezoelectric ceramic mainly to driver six different multiples micro objective lens moving up and down to achieve the small stroke focusing, with the characteristics of small focusing load, fast focusing speed and high accuracy.Thirdly, it analyses the principle of laser triangulation method and proposed the auto-focus system optical circuit design program base on the theoretical principle, and has a demonstration in principle, according to the center of focal spot and the correlation of between the defocusing amount to achieve the quick focusing, this method has the advantages of clearly focusing direction and high accuracy.Fourthly, giving the control scheme of auto-focus system, It advances the methods about adjusting the shutter and gain around the focal plane to eliminate the ghost according to analyse the effect of reflection energy of TFT-LCD to the light spot image,compared with several kinds of commonly used focusing evaluation functions, proposing according to the the range of allowable error of light spot center as the basis of the focusing evaluation,it has the merit of accurately focusing and high precision.Fifthly, in the software design part, the independent research microscope autofocus system software adopts the 1394 image acquisition card to achieve the acquisition and processing of the laser spot image, according to call the dynamic function to realize the motion control of three-axis electric motor and the micro focusing control of ceramics piezoelectric, through the handle design quickly realize the different lens control of microscope.Finally, the experimental results indicate that within the 100um distance auto-focus and under the five times objective lens, the autofocus time is 0.237 seconds, the repetitive positioning accuracy is±1.97um.Under the conditions of fifty times objective lens, the autofocus time is 0.29 seconds, the repetitive positioning accuracy is±0.26um. It can satisfy the system requirements of non-contact, online, real time, higher precision and rapid speed, as well as strong anti-jamming and stabilization.更多还原