A tracking vision sensor system

The initial aim was to develop a nontactile scanner capable of tracking a weld seam during robot welding operations. In addition, it was intended to investigate AGV guidance and surface inspection applications. The scanner is based on the `flying spot´ principle as described by Batchelor et al. (1985), with a low power helium-neon laser scanned across the work-piece by means of a mirror rotated at constant speed using a stepper motor. Clearly the scan rate of the laser across the work-piece is determined by the number of sides on the mirror and the switching rate of the motor, while the scan length is a function of the distance between mirror and work-piece and the number of sides on the mirror. An eight-sided mirror has been selected as this gives the maximum scan rate with the required scan length and stand off height