Optical System Design In PCB Automatic Optical Inspection

With the continuous development of the electronics industry technology, the printed circuit board is tend to be high-density and miniaturized, which makes shortcomings have been rising in production, therefore, PCB production should do inspection of defects.The traditional testing method such as artificial visual inspection and electrical testing, can not meet the efficient accurate and intelligent requirement. This paper puts forward a auto-testing method based on optical imaging. This method captures and identifies the defect of PCB automatically in production procedure and alarm timely. Non-contact measurement will not damage components, so this method has been widely applied in PCB production more and more.In the paper, a zoom imaging system and its supporting lighting system are designed based on automated optical inspection technology. According the theory of conjugation, imaging system can meet the zoom requirement and image different sizes PCB and this system can be lighted by three kinds of light source so that it is able to adapt to different production environment. A method of designing lighting system based on orthogonal testing is put forward. By orthogonal testing of various factors affect the uniformity of illumination, find the optimal values of the various factors, and then combined them. The results of experiment showed that this method greatly improves illumination uniformity and light utilization of lighting system.The problems encountered in the actual design of the system are summarized and some improved methods for optimization design raises are put forward.