Patent ID: 8032320

Claim:
A position detection system comprising: a device having a magnetic induction coil; a driving coil that generates an alternating magnetic field to be applied to the magnetic induction coil, the alternating magnetic field having a position-calculating frequency in the vicinity of a resonant frequency of the magnetic induction coil; a plurality of magnetic sensors that detects an induced magnetic field generated by the magnetic induction coil when the alternating magnetic field is applied thereto; a measurement-reference-value calculating section that determines a measurement reference value at the position-calculating frequency, based on an output of the magnetic sensors at the position-calculating frequency when only the alternating magnetic field is applied thereto; a position-analyzing section that calculates at least one of the position and orientation of the device, based on a component at the position-calculating frequency of a difference measurement value that is a difference between an output of the magnetic sensors when the alternating magnetic field and the induced magnetic field are applied thereto and the measurement reference value; a frequency-change detecting section that detects a change in frequency characteristics related to the magnetic induction coil from magnetic-field information obtained by the plurality of magnetic sensors; and a redetermining section that redetermines the position-calculating frequency at a predetermined timing based on the change in the frequency characteristics.