Using Lego pieces for camera calibration: a preliminary study

Camera calibration is an important operation for a number of applications in the field of Computer Graphics and Computer Vision. In particular, if the intrinsic parameters of the camera are known in advance, the accuracy of results is extremely improved. For this reason, several easy procedures to calibrate a camera have been proposed. The accuracy and ease-of-use of these procedures is strongly related to the needed calibration target, which is usually a single 2D printed pattern (i.e. a checkerboard). In this paper we propose the use of an alternative: a Lego structure. Lego pieces exhibit several strong-points, like the off-the-shelf availability and the geometric accuracy. Additionally, it's easy to prepare a structure and obtain the corresponding 3D model using freeware tools. Hence, we present the preliminary tests on the use of Lego structures for camera calibration. The tests have been performed on a user-friendly ad-hoc tool, which takes advantage of the peculiar features of Lego to automatically correct the positions of the 2D and 3D correspondences used for calibration. Results show that it's possible to obtain accurate results starting from a few photos, and that the entire procedure can be completed in a very short time.