Patent ID: 8446147

Claim:
A position detecting device comprising: a first magnetic-field generating unit that includes at least one magnetic-field generating coil and that generates a first magnetic field in a detection space where a detected object provided with a circuit including at least one built-in coil is disposed; a magnetic-field detecting unit that includes a plurality of detecting coils arrayed to detect an induced magnetic field generated from the built-in coil by the first magnetic field generated by the first magnetic-field generating unit; and a second magnetic-field generating unit that includes at least one magnetic-field generating coil and that generates a second magnetic field, which includes a magnetic-field component having a phase substantially opposite to the first magnetic field generated by the first magnetic-field generating unit and entering the detecting coils, wherein the first magnetic-field generating unit and the detecting coils are disposed so that a generating direction, normal to the cross-section of the at least one magnetic-field generating coil of the first magnetic-field generating unit, and a detecting direction, normal to the cross-section of the detecting coils, intersect each other, wherein the second magnetic-field generating unit is disposed at a location where at least one of the plurality of detecting coils disposed adjacent to the first magnetic-field generating unit is disposed; and wherein the second magnetic-field generating unit is not disposed at a location where at least one of the plurality of detecting coils disposed apart from the first magnetic-field generating unit in comparison to the at least one of the plurality of detecting coils disposed adjacent to the first magnetic-field generating unit is disposed.