Printed circuit board (PCB) is a substrate for electronic parts assembly, manufacturing quality of PCB plate directly affects the reliability of electronic products, so the PCB known as the "mother of the modern electronics industry". Along with the electronic assembly to the PCB hybrid technology with higher density, smaller size of the depth development, checking means only depend on the traditional functional testing and manual visual inspection, has been unable to meet the scale of modern PCB requirements of industrial production. At present, a yield of general PCB is still around 60% to 70%, in order to reduce the number of defects in circuit board into the next process, the key equipment - automatic optical detection in PCB detection (AOI) system, the demand is also growing.