High precision coordinate input device using sequentially driven

Abstract

A coordinate input apparatus for detecting a coordinate position on the basis of a signal detected by a coordinate designator which can freely point on an input surface in which a plurality of conductors are embedded in parallel to each other, the conductors constituting in combination a main loop to which scaning signals are supplied sequentially. A compensating loop which is composed of a conductor is provided in the vicinity of a common conductor of the main loop separately therefrom such as to surround the main loop. A constant current is delivered to the compensating loop in the reverse direction to that flowing on the main loop to mitigate the magnetic field produced by a common conductor. A compensationg value which corresponds to the approximate position of the coordinate designator is called from a first storing means to calculate the interpolating value thereof. A correction value for correcting the error between the interpolating value and the actual position of the coordinate designator is called from a second storing means in order to specify the position pointed by the coordinate designator on the basis of the interpolating value and the correction value.