A distortion immune tablet (20) for a position and orientation system (22). The tablet includes a plurality of magnetic field generators (40), a layer of magnetic material (60) and a layer of conductive, non-magnetic material (80). The coils (42) of the generators are oriented relative to the magnetic...http://www.google.co.uk/patents/US20010045826?utm_source=gb-gplus-sharePatent US20010045826 - Distortion immune magnetic field generator for magnetic tracking systems and method of generating magnetic fields
