Specular objects in range cameras: reducing ambiguities by motion

Abstract

Range cameras using structured light and triangulation are essentially based on the assumption of one diffuse reflection from the measured surfaces, Specular and transparent objects usually give multiple reflections and direct triangulation can give different types of 'ghosts' in the range images. These 'ghosts' are likely to cause serious errors during gripping operations. As the robot moves some of the 'ghosts' move in an inconsistent way. In this paper, the authors study, experimentally and theoretically, how the range measurements can be integrated in a consistent way during the motion of the robot. Emphasis is on parts with 'optical complications' including multiple scattering. For a scene with one planar mirror the 'ghosts' are shown to lie in a plane separated from the laser plane. In this case the orientation and position of the mirror can be estimated.<>