A Telecentric vision system for broach verification

A common machine vision task is to verify that a product has been properly fabricated or assembled. In the following paper, a vision system is described for confirming that a type of gear has been processed properly. The main problem in this application is the relatively large depth of the gear which results in a more complex image than the desired silhouette of the part. The resulting image shows a portion of the inner wall due to the varying magnification because some points on this wall are closer to the lens than others. Employing telecentric optics, however, greatly simplifies the problem since only light rays parallel to the optical axis create the image so that a good silhouette of the part is obtained. Gear teeth can then be isolated using mathematical morphology techniques to verify that the part has been properly broached.