A touch sensors that maintain uniform touch sensitivity on a touch sensor with a non uniform cover

摘要

A two-dimensional capacitive touch sensor (e.g. touch screen or touch pad) has a cover layer (fig 5) of varying thickness arranged on top of its electrode structure. An array of sensing nodes is formed between edge portions of the receiver (802) electrodes and adjacent portions of the transmitter electrodes (803) or the electrode structure. To compensate for the varying thickness of the cover layer, the length of the edge portions per sensing node is varied to equalize node sensitivity across the sensor and thus suppress the systematic variation in node sensitivity which would otherwise arise as a result of the varying thickness of the cover layer. If the electrodes are coplanar then the gap between receiver and transmitter electrodes may be varied. In an alternative embodiment with an alternative electrode structure the surface area of electrodes (fig 12) may be varied to compensate for variation of touch sensitivity.