Elographics, Inc.

John E Talmage

William A Gibson

L Dexter Bates

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.

Electrographic touch sensor with Z-axis capability

An electrographic sensor for the generation of coordinate signals corresponding to contacted positions on the sensor is described. This sensor is of particular value for placing in intimate contact with the nonplanar face of a cathode ray tube or the like. The sensor has a rigid, optically transparent substrate with a nonplanar configuration matching the nonplanar face of the CRT to reduce parallax. This normally involves a radius of curvature, in one or more directions, in a range of 15-50 inches (38-127 cm). The surface of the substrate which will not contact the CRT is coated to provide a very uniform, substantially transparent, electrically resistive layer, and electrodes are connected to the resistive layer whereby orthogonal electrical potentials may be applied to the layer. Overlying and spaced from the resistive layer is a semirigid transparent cover sheet, the face toward the resistive layer being appreciably conducting. Dispersed small areas of insulation, of minimum height, prevent contact of the resistive layer and the conducting face unless the cover sheet is depressed by an object such as a finger or stylus.

Nonplanar transparent electrographic sensor

An electrographic sensor for determining planar coordinates is described whereby graphical material to be analyzed may be placed beneath, or projected against, the rear surface of the sensor. This sensor is of particular value for placing on the face of a cathode ray tube. The sensor includes a rigid, optically transparent substrate having an extremely uniform, substantially transparent resistive layer applied to one surface, small electrodes in contact with the resistive layer and individual resistors connected between adjacent electrodes to produce a resistance network around the perimeter of the substrate. Means are provided to produce orthogonal electrical fields in the resistive layer whereby the contacting of the resistive layer with a conductive stylus produces voltage signals at the stylus which are proportional to the coordinates of the point of contact. The second surface of the substrate may be made translucent for projecting optical images thereagainst.

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Oak Ridge, TN, United States of America

John E Talmage