Electrographic touch sensor with Z-axis capability

摘要

An electrographic touch sensor having Z-axis capability. In one embodiment, a uniform resistive coating is applied to one surface of a substrate and it is within this coating that orthogonal electrical fields are produced using suitable electrodes and voltage applications to give coordinates of a selected position. Overlying the resistive coating is a flexible pickoff sheet having a conductive layer facing the combination. Interposed between the resistive coating and the conductive layer is an array of a material having a substantially greater resistivity than that of the resistive coating. Signals corresponding to the X- and Y-coordinates of a touched point on the sensor are obtained in a substantially conventional manner using an amplifier and an analog to digital converter. If desired, a Z-axis component signal due to pressure/force can be obtained in a separate part of the measuring cycle. This Z-axis signal is inversely related to a change in the effective contact resistance between the resistive coating and the pick-off sheet caused by the pressure/force. The change in this contact resistance is "enhanced" by the high resistance material such that different values of pressure/force can be determined. Numerous other embodiments are described including two resistive sheet sensors and enhancing materials that are considered to be insulators.