A Dual-Imager And Its Applications For Active Vision Robot Welding, Surface Inspection And Two Color Pyrometry

Abstract

Vision systems are required for quality control and process monitoring in a wide variety of industrial applications. Increasing demand is developping for noncontact, nondestructive, fast reliable systems even in harsh environmental conditions, particularly in the presence of external noise perturbations or high temperature. A double spectral image sensing device has been developed for industrial tasks. The device comprises a common objective shared by two detectors which see the same field of view by means of a 50-50 beam splitter and a back-reflective mirror. Proper adjustment of the optics and of both detectors, one with respect to the other, yield to almost two identical signals at the output of the detectors. If limited bandwidth interference filters are inserted in front of each detector, many useful applications arise. Lines or bidimen-sional detectors can be incorporated depending on the scene observed: fixed or moving. Both analog and digital processing are deployed for proper signal extraction. Many different uses of this device are presented, including robot welding, pyrometry and metrology. Two-color pyrometry is possible using plain CCD detectors to obtain bidimensional thermal images in the 820°C-1350°C range. Metrological applications in the visible spectrum are also presented, such as contrast enhancement of nonuniformities in surface inspection. Particularly attractive and original for active vision robot welding, is the combination of video analog subtraction with the imager: arclight noise-free images are obtained in real time.