A Convenient Calibration of a 3D Foot Scanning System using a Solid Paper Object

In this study, a new method is proposed for developing an effective calibration object by using commonly available papers. The proposed method uses a pyramid-shaped solid paper as a calibration object for foot scanners with two sensors. The design of this calibration object allows simultaneous scanning of its inner and outer surfaces. The three-dimensional (3D) shape information collected from the two sensors is used to derive an initial 3D transformation relationship between the two sensors. Next, the intersections between the four facets of the pyramid-shaped object are used in conjunction with a minimization algorithm to improve the precision of the 3D transformation relationship. The proposed method is applied to an actual foot scanning system to calibrate the upper and lower 3D sensors of the foot scanner, and the 3D model is reconstructed. The performance of this method is verified by comparing the reconstructed models with ground truth models. The calibration error between the two sensors was less than 0.6 mm on average when using the proposed calibration method. The proposed method offers the advantage of simple operation as it uses a single sheet of paper, thus avoiding the difficulties encountered in conventional calibration methods.