Occlusions as a Guide for Planning the Next View

The task of constructing a volumetric description of a scene from a single image is an underdetermined problem, whether it is a range or an intensity image. To resolve the ambiguities that are caused by occlusions in images, we need to take sensor measurements from several different views. We have limited ourselves to range images obtained by a laser scanning system. It is an active system which can encounter two types of occlusions. An occlusion arises either when the reflected laser light does not reach the camera or when the direct laser light does not reach the scene surface. The task of 3-D data acquisition is divided into two subproblems: to acquire the depth information from one scanning plane and to select the proper scanning planes from which the direct laser light illuminates the entire scene. The first kind of occlusions (range shadows) are easily detected and can be used in designing an efficient algorithm. We develop a strategy to determine the sequence of different views using the information in a narrow zone around the occluded regions. Occluded regions are approximated by polygons. Based on the height information of the border of the occluded regions and geometry of the edges of the polygonal approximation, the next views in the same scanning plane the directions of the next scanning planes for further data acquisition are computed.