Position and orientation measuring system having anti-distortion source

Abstract

A method and apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame includes providing a source having a plurality of field-generating elements, wherein the field-generating elements generate electromagnetic fields and have spatially independent components defining a source reference coordinate frame. A driver applies signals to the source to generate a plurality of electromagnetic fields which are distinguishable from one another and a remote sensor has a plurality of field-sensing elements which sense each of the generated electromagnetic fields. A processor processes the output of the sensor in a remote object position and orientation relative to the source reference coordinate frame. At least one of the field-generating elements of the source has at least one electrically conductive sheet and a planar coil including a plurality of coplanar concentric rings above the conductive sheet. The planar coil is configured in a manner that a signal applied to that coil will cause a current density at each ring that is inversely proportional to the square of the radius of that ring. The planar coil may be made from a conductor formed as a simple or foliated spiral. The planar coil and the electrically conductive sheet may be formed from printed circuit board stock. A dihedral source may be made from a pair of orthogonal electrically conductive sheets each having a planar coil above the sheet. A trihedral source may be made from three electrically conducting sheets each having a planar coil above the sheet.