Electrographic touch sensor having reduced bow of equipotential field

Abstract

A resistor electrode type touch sensor having reduced bow of equipotential lines in the sensor and simplified construction. Orthogonal electrical fields are produced on a resistive surface so as to give coordinates of a selected position. Overlying, but spaced from, the resistive surface is an optional flexible conductive pick-off sheet facing the resistive surface which will contact the resistive surface when touched at a selected position. Other elements are described to obtain signals corresponding to the coordinates of a selected point. Electrodes of a selected effective length and spacing to substantially eliminate the bow of equipotential fields produced in the resistive surface are located along selected paths proximate the edges of the resistive surface and attached thereto. Each electrode is connected to a selected connection point along a resistance element along each edge of the resistive to provide selected voltages to the resistive surface. Each resistance element is made up of at least one resistance unit between each electrode connection point, and each unit has a pair of space-apart conductive lines applied to the resistive layer. For a given value of the resistive surface, the value of the resistance unit is determined by the length and width of any gaps between the conductive lines.