Touch sensitive device with increased linearity

Abstract

An electrographic touch sensor of simplified construction having an increased proportion of area for providing linear output signals. The sensor utilizes a resistive layer of a substantially uniform resistivity throughout. A resistance element of resistance value borders and is in contact with the resistive layer. Positioned along a selected path proximate the resistance element borders are a plurality of insulator regions having a selected effective length along the path to define spaces of a selected effective length therebetween. These spaces, having the resistive layer therein, define resistive electrode elements by which voltages are applied from the resistance element borders into the resistive layer whereby orthogonal electrical fields can be generated in the resistive layer. The effective length of the insulator regions and the spaces are chosen to produce a voltage gradient along the path that substantially compensates for any voltage drop along the resistance element while orthogonal fields are being generated. In this manner, an increased proportion of the resistive layer provides a linear response in the output signals. Provision is made to generate output signals corresponding to the coordinates of a selected point on the resistive layer.