RANGE IMAGE ACQUISITION WITH A SINGLE BINARY-ENCODED LIGHT PATTERN

This paper addresses the problem of strike identification in range image acquisition systems based on triangulation with periodically structured illumination. The existing solutions to strike identification rely on subsequent projection of multiple encoded illumination patterns. These coding techniques are restricted to static scenes. We present a novel coding scheme based on a single fixed binary encoded illumination pattern, which contains all the information required to identify the individual strikes visible in the camera image. Every sample point indicated by the light pattern, is made identifiable by means of a binary signature, which is locally shared among its closest neighbors. The applied code is derived from pseudonoise sequences, and it is optimized as to make the identification fault-tolerant to the largest extent. This instantaneous illumination encoding scheme is suited for moving scenes. We realized a working prototype measurement system based on this coding principle. The measurement setup is very simple, and it involves no moving parts. It consists of a commercial slide projector and a CCD-camera. A minicomputer system is currently used for easy development and evaluation. Experimental results obtained with the measurement system are also presented. The accuracy of the range measurement was found to be excellent. The method is quite insensitive to reflectance variation, geometric distortion due to oblique surface inclination, and blur of the projected pattern. The major limitation of this illumination coding scheme was felt to be its susceptibility to the effects of high contrast textured surfaces. © 1990 IEEE