Development of measurement system of three-dimensional shape and surface reflectance

Abstract

We describe a three-dimensional measurement system which can acquire not only three-dimensional shapes of target objects but also these surface reflectance parameters. The system is constructed by one or some digital cameras, digital projector, and a computer which controls cameras and projectors. For 3-D geometrical reconstruction, we use well known gray code structured light method. The method projects gray code light patterns from the projector and obtain illuminated scenes by cameras. We add additional light patterns for surface reflectance measurement. These patterns are all white and gray light pattern. To recover complete shape of the target object, the object is measured from various viewpoints repeatedly, or measured repeatedly from fixed viewpoint while be moving by hand or turn table. To end the measurement, relative positions of each obtained range data are calculated by ICP algorithm. For each small region of the target object surface, we calculate reflectance parameters from surface normals, viewpoint (camera viewpoint), and light position (the projector viewpoint). Enough sampling of these three information sources are obtained for each small surface, we estimate reflectance parameters for each surface points. We demonstrate this geometrical and reflectance measurement method by experiments for fewer objects.