Visual Inspection System Of SMT Based On LabVIEW

Computer vision inspection is an important method of modern industry inspection. The technique has characteristics of high speed, precise, reliable and untouched. Advancement of production technology, computer techniques and image processing technique accelerate the spread and application of computer vision inspection technique.At first the basic theories of the machine vision and the virtual instrument techniques is introduced, and the feasibility and advantage after they were combined is analyzed. Then the virtual instrument developing platform LabVIEW and machine vision software IMAQ Vision are introduced as followed, and a computer vision inspection system used to inspect the printed circuit board subassemblies is developed based on them. The Image processing techniques such as pre-processing, thresholding, morphology and pattern identification are applied in the system.In the fault inspection system of bared PCB, the image is segmented by means of maximum entropy thresholding method. The parameters Euler's number and region area are chosen as characteristic values to built the fault module identification tree for the sake of auto-identification of several ordinary faults. Pattern matching is selected for the inspection of the components on PCB to detect the lost and polarity fault of components. In a case of solder inspection, maximum variance method and morphological operators are used to deal with the images;the solder' s area is selected as characteristic value for the auto-identification of solder fault modules.Several images have been tested using this system. The results show that it can recognize the faults effectively mentioned in the paper, which proved the methods used in the system is succeed and thus have practical value .