A Three-Step Calibration Method of Sensors’ Pose for Magnetic Localization System

Calibrating the pose of all magnetic sensors is a necessary prepossessing step in tracking intrabody objects such as wireless capsule endoscopy (WCE) by magnetic fields. The existing calibration methods are optimization-based and need good initial values for the pose of the sensors. Manual measurement of the initial values can be a cumbersome and sometimes challenging process. Therefore, we propose a three-step calibration method to automatically obtain the rough initial value of the sensor pose. First, the initial sensor orientation can be estimated by rotating the system. Next, the initial position is obtained using the orientation estimated earlier and restricting a strong magnet to face two specific orientations. We provide a detailed deduction process for obtaining the analytical solution for the position. Finally, bundle adjustment is used to further optimize the sensor orientation and position. Experimental results have shown that the magnetic localization system achieves higher accuracy after applying the proposed calibration method.