High precision 2-D geometrical inspection

Automated visual inspection has become important for modern industry mainly because production rates and the level of automation have continually increased. The paper presents a system for automated visual inspection of large two-dimensional parts. The system is capable of inspecting sheet metal parts using CAD data. The inspection is performed based on a CAD model. There are existing systems that perform this function but they are not particularly well suitable for in-place inspection. In the proposed system, the high precision inspection of individual features is performed by firstly estimating the global position of a part. Next, each local feature is measured using subpixel techniques. Finally, the measurements are compared with a CAD model. Experiments are presented to evaluate the precision of system components. According to the results, the calibration procedure seems to be the factor that has the greatest effect on the final precision. Last, a comparison to similar systems is made and some suggestions are given how the precision could be further improved.