Visual defect inspection of rotating screw heads

We propose a visual defect inspection method for manufactured screws using screw head images. Because screws are rotating while moving on the inspection table, first we estimate the rotating angle in the screw image using the eigen space method. Next, we obtain the pose of the screw head precisely by matching reference images which are edge point images of screw heads moving infinitesimally. And finally, we extract defects using a mask image corresponding to a matched reference image. As a result, proposed method can inspect about 250 screws per a minute, and the effectiveness for the practical use is shown.