Grey-scale ranging-a technique for real time range mapping

Three-dimensional information for every point in an image is often essential and several practical range mapping systems have been developed. The paper describes a method developed by the authors that could approach the ideal of real-time operation. Only two images are required and the range map is determined simply by dividing one image by the other. The method is restricted to convex scenes, is inexpensive to implement and leads to real-time applications. The method is called grey-scale ranging referring to the nature of the scene illumination that is used. The principle of triangulation is briefly reviewed and the selection of the projected pattern and the pattern through which the scene is viewed are discussed in some detail. Consideration is given to the assumptions made in the initial description of the method and the consequential errors introduced into the range maps. This leads to a discussion of the need for normalization and for precise registration. Consideration is given to the limitations in the types of scene that can be analyzed