3D Modeling Based On Reflectance Polarization Analysis

In the field of computer vision, many methods which measure the surface shape of opaque objects have been proposed; however, a successful method which measures the surface shape of transparent objects such as glasses has never been developed. In this paper, we propose a convenient and beneficial method to measure the surface shape of transparent objects.The light which is reflected from the surface of the object is partially polarized.The degree of polarization depends upon the incident angle which, in turn, depends upon the surface normal of the object. Thus, we can obtain the surface normal of the object by observing the degree of polarization. But unfortunately, the correspondence between the degree of polarization and the surface normal is not one to one. Thus, to obtain the correct surface normal, we had to solve this ambiguity problem. To disambiguate this problem, we use the differential-geometrical characteristics of the object surface.We developed a method for using the differential-geometrical property of the object surface. This method solves the ambiguity by comparing two types of data, one of which is obtained straightforwardly observing the object, while the other is obtained by observing the object while it is inclined at a slight angle. In this method, we have to compare these two data at identical points on the object surface. We find two identical points by considering the invariant value on the object surface, and we compare the data of polarization at these two points. We discuss the relationship between the geometrical property on object surface and the degree of polarization based on the knowledge of differential geometry, and we propose a method for matching two pieces of polarization data at identical points on the object surface.In this paper, we describe how we applied the method using geometrical property to real transparent objects in order to obtain the correct surface normal of transparent objects.