Stereo vision system using semiconductor laser structured illumination to work under severe solar irradiance

The paper presents work by Carlos III University, of Madrid, as part of the ROBTET project, sponsored by IBERDROLA, and ETSI Industrial of the Polytechnic University of Madrid. The objective of the ROBTET project, is the development of a teleoperated system for the inspection and maintenance of live electrical lines. There is an important security problem involved, since any contact between the manipulators and the electric lines may result in a fatal accident. To overcome this problem, a stereo vision system is used to keep track of the position of the electrical lines, so that any movement of the manipulators that will bring them too close to any of the lines is detected and prevented. This vision system employs two CCD cameras in a stereo system, that visualises the scene illuminated by a vertical laser slit, or planar laser beam, which scans the scene horizontally. In this way, the position of each of the electrical lines can be determined by joining the points of incidence of the planar laser beam on the electric wires for different horizontal positions of the beam. The position of these points of incidence can be obtained by triangulation from the position in the CCD cameras of the reflection of the laser beam on the electric lines. The problem arises when one tries to single out the point of incidence of the laser beam on an aluminium wire under intense solar irradiance. The authors describe the development of a semiconductor laser illumination system that scans the scene horizontally in synchronism with the CCD cameras.