Absolute scale structure from motion using a refractive plate

Three-dimensional (3D) measurement methods are becoming more and more important to obtain information about the surrounding environment in many fields. Structure from Motion is one 3D measurement method using a single camera. This technique calculates the 3D reconstruction of objects from images captured by a single camera with motion. The camera motion can be estimated simultaneously as well as 3D information of objects. However, it is impossible to calculate the absolute scale of objects using Structure from Motion. Only the relative position can be obtained. In this paper, we propose a Structure from Motion method which can calculate the absolute scale of objects using refraction. Refraction occurs when light ray passes through different media. The absolute scale can be calculated using this change in light ray path. In order to generate the refraction, a refractive plate is placed in front of a camera. In a previous study we proposed a Structure from Motion method using refraction. However, the refractive plate was required to be placed perpendicular to the optical axis of the camera. In this new method, the refractive plate can be placed with any orientation in front of camera. In this aspect, the proposed method is more general than the previous one.