Patent ID: 8050738

Claim:
A position detecting apparatus that detects a position of a body-insertable device, the body-insertable device being introduced into a subject to acquire intra-subject information while moving inside the subject, the position detecting apparatus comprising: a linear magnetic-field generator adapted to generate a linear magnetic field in an area inside the subject, the area including the position of the body-insertable device; a diffuse magnetic-field generator adapted to generate a diffuse magnetic field having a magnetic field direction that is position dependent in the area inside the subject; a magnetic-field line orientation database adapted to record a correspondence between a magnetic field direction of the diffuse magnetic field and a position of the diffuse magnetic field in the subject in a reference coordinate axis, the reference coordinate axis being fixed to the subject; an earth magnetism sensor adapted to be arranged on the surface of the subject and adapted to detect strength of magnetic field components of earth magnetism in the reference coordinate axis; an earth magnetism orientation calculator adapted to calculate the magnetic field direction of earth magnetism in the reference coordinate axis based on the strength of the magnetic field components detected by the earth magnetism sensor; an orientation calculator adapted to acquire linear magnetic-field information relating to the magnetic field direction of the linear magnetic field and the magnetic field direction of earth magnetism calculated by the earth magnetism orientation calculator, and calculate correspondence between the reference coordinate axis and a target coordinate axis, which is fixed to the body-insertable device, as orientation information of the body-insertable apparatus based on the acquired linear magnetic-field information and the magnetic field direction of earth magnetism; and a position calculator adapted to acquire information on the strength of the linear magnetic-field, the orientation information, and diffuse magnetic-field information relating to the magnetic field direction of the diffuse magnetic field at the position of the body-insertable device in the target coordinate axis, calculate the magnetic field direction of the diffuse magnetic field at the position of the body-insertable device in the reference coordinate axis based on the information on the strength of the linear magnetic-field, the orientation information, and the diffuse magnetic-field information, and calculate the position of the body-insertable device based on the calculated magnetic field direction and the correspondence recorded in the magnetic-field line orientation database.