Research And Development On LCD Defect Inspection And Recovery System Using Laser Based On Machine Vision

With the rapid development of liquid crystal technology,Thin-film transistor liquid crystal display(TFT-LCD)is being widely used,flat panels have completely replaced the CRT displays.However defective products are inevitably produced in the large scale manufacture because of the complex processing technique.Yet the companies specifically inspect the defect and repair the LCD mostly overhaul by artificial way,which efficiency and cost are not satisfactory.Therefore,it is very necessary and urgent to develop an automatic system to defect and repair the LCD screen defect.Through the study and analysis of LCD defect features and laser repair methods,this paper designs and develops a set of LCD defect detection and repair software,based on machine vision technology,which improves the accuracy and real-time performance.AT first the software uses the autofocus algorithm to adjust the motion axis to the right height to capture a clear image,and then uses the defect inspection algorithm to locate the defect,afterwards prompts the workers to repair by laser.A focus windows choice method based on template matching is proposed to highlight the foreground objects in the light of LCD image,and the focusing experience value is utilized to limit the focus range to the near of focal plane to speed up the focusing of the image.The macroscopic detection is used to locate the defect sub-regions and then microscopic examination is performed.To detect the Mura inspection this paper uses DCT background reconstruction method to rebuild the background image,and then the Gaussian filter,morphology processing and connected components analysis to locate the defect.Experiment results show that this method can locate the Mura defect effectively.Finally,the real-time performance of the system is improved in various aspects,including Xenomai real-time patching for Linux system,multi-thread of image acquisition and processing,image pyramids technology.According to the whole process of detection and repair,a fast defect location and repairing process is designed.A set of practical LCD repair software is developed by QT in Linux.The software has a friendly human-machine interface.The key components are optional,a universal interface is designed and developed to satisfy the different market price needs.At present,the software has been applied to the actual commercial system,which has a good competitiveness.