Research On Defect Detection System For Printed Matter Based On Machine Vision Technology

With the continuous progress of the society, much higher quality of printed matter is required. However, some defects often come out in the printing process, which is due to printing technology or mechanical vibration. But with the enhancing of printing speed and more and more strict with request of printing quality, traditional methods which detect the defects of the printed matter with eyes can not work well because of the subjective aspects. With the development of computer software and hardware and image processing technology, machine vision technology is widely used in the on-line inspection system in the industry field. While an automatic detection method for printed matter based on machine vision becomes feasible.In this paper, defect detection system for printed matter based on machine vision technology is researched, in which image processing and machine vision and printing basic principle are combined to be applied in the printing industry. First of all, based on analyzing and studying the common machine-vision-based inspection system, an on-line defect detection experiment system for printed matter based on machine vision is designed and built, which provides a platform for studying on-line printing defect detection. This system is consist of a computer, a line scan CCD camera, a frame grabber, a light source and a device for synchronism, exactly a rotary encoder. Then some typical defect detection algorithm in image processing technology is discussed and analyzed. After this a novel defect detection algorithm based on image differencing is proposed. At the same time, this method can detect the location and the size of the defect. Finally, a software of defect detection system for printed matter is developed with Visual C++6.0 platform, which can detect the hackneyed defects during printing process in real time without eyes. When a defect is detected, the defect image is displayed, and the information such as the location and the area of the defect is offered. This software also can stores the defect images into computer and activates alarm.The defect detection system for printed matter built in this paper meets the real-time requirement. The system function is relatively complete and convenient to be used.The project is funded by the fund of youthful teacher with a master's degree in Xi'an University of Technology.