A marker calibration method utilizing a priori knowledge on marker arrangement

This paper describes a calibration method of markers which are used for registration in MR applications. There have been many vision-based approaches proposed as registration methods in MR. When multiple markers are utilized in a vision-based method, it is necessary that the geometric information of the marker arrangement such as their positions and orientations be known in advance. In this paper, we propose a hybrid method combining the "bundle adjustment method," which is a photogrammetric technique that calculates the geometric information from a set of images, with some constraints on the marker arrangement which are obtained a priori (e.g. the multiple markers are located on a single plane). After considering marker arrangements seen in many MR systems, we summarize some constraints seen in these arrangements. Then, we explain the basic framework of this method as well as a solution method under some practical constraints. We further describe several experiments and their results in order to show the effectiveness of this method.