Edge linearization device for a contact input system

Abstract

An edge linearization device for linearizing the electric fields in a resistive surface is described. A plurality of electrodes are disposed on the perimeter of an area on a surface having a substantially uniform resistivity. The device utilizes the geometry of the spaces between adjacent conductive elements to provide resistive elements. At least one of the electrodes has an extension. The extension or extensions of the electrodes are progressively inwardly displaced into the area from the perimeter so that there is at least one center-most extension on a first portion of said perimeter and also on a second, opposing portion of said perimeter. In a preferred embodiment, the invention utilizes a surface with a substantially rectangular area having four sides and four corners. Disposed along the sides are a plurality of electrodes and corner electrodes and disposed in the corners of the surface are corner connectors. The use of T-shaped extensions of the electrodes on such a surface is also disclosed. When an electric potential is selectively applied across the surface, a unique electric potential exists which corresponds to the location of a movable object on the surface. A contact input system utilizing such an edge linearization device is disclosed. The contact input system utilizes the surface with the electrodes, corner electrodes, and corner connectors disposed thereon with a movable object for selectively contacting the surface, means responsive to the object for determining the object's location on the surface, and means for selectively applying an electric potential across the surface.