Touch sensor for non-uniform panels
A two-dimensional capacitive touch sensor having a cover layer of varying thickness arranged on top of its electrode structure. An array of sensing nodes is formed between edge portions of the receiver electrodes and adjacent portions of the transmitter electrodes. 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.
1. A two-dimensional capacitive sensor comprising a cover panel of varying thickness and an electrode panel arranged under the cover panel, the electrode panel comprising a plurality of transmitter electrodes extending in a first direction and a plurality of receiver electrodes extending in a second direction, wherein an array of sensing nodes is formed between edge portions of the receiver electrodes and adjacent portions of the transmitter electrodes, wherein the length of the edge portions per sensing node is varied with the thickness of the cover panel so that the edge portion length per sensing node increases as the thickness increases, so as to provide part or substantially complete compensation for variation in node sensitivity across the sensor which would otherwise exist as a result of the varying thickness of the cover panel,
wherein the transmitter electrodes are arranged in a first plane and the receiver electrodes are arranged in a second plane, the sensing nodes being formed by the receiver electrodes crossing the transmitter electrodes, and
wherein the receiver electrodes are formed with a spine extending in the second direction and cross-bars extending in the first direction, the edge portion length being varied by varying the length of the cross-bars.
2. The sensor of claim 1 , wherein islands of electrode material are arranged adjacent the transmitter electrodes and/or the receiver electrodes to reduce visual impact of the transmitter electrodes and/or the receiver electrodes.
3. The sensor of claim 1 , wherein the length of the edge portions per sensing node is varied only in the first direction or the second direction to compensate for variation in the cover panel thickness in the first direction or the second direction respectively.
4. The sensor of claim 1 , wherein the length of the edge portions per sensing node is varied both in the first direction and the second direction to compensate for variation in the cover panel thickness in the first direction and the second direction.
5. A two dimensional capacitive sensor comprising a cover panel of varying thickness and an electrode panel arranged under the cover panel, the electrode panel comprising a plurality of transmitter electrodes extending in a first direction and a plurality of receiver electrodes extending in a second direction, where an array of sensing nodes is formed between edge portions of the receiver electrodes and adjacent portions of the transmitter electrodes, wherein the length of the edge portions per sensing node is varied with the thickness of the cover panel so that the edge portion length per sensing node increases as the thickness increases, so as to provide part of substantially complete compensation for variation in node sensitivity across the sensor which would otherwise exist as a result of the varying thickness of the cover panel,
wherein the transmitter electrodes are arranged in a first plane and the receiver electrodes are arranged in a second plane, the sensing nodes being formed by the receiver electrodes crossing the transmitter electrodes, and
wherein at each sensing node there is an overlap area between crossing portions of the transmitter and receiver electrodes, and wherein the crossing portions of the receiver electrodes are adapted in shape not only to vary the edge portion length with cover panel thickness but also to reduce or substantially eliminate variations in the overlap area caused by varying the edge portion length.
6. The sensor of claim 5 , wherein the receiver electrodes are formed with a spine extending in the second direction and cross-bars extending in the first direction, the edge portion length being varied by varying the length of the cross-bars, and variations in the overlap area being reduced or eliminated by making the spine thicker when the cross-bars extend less.
7. The sensor of claim 5 , wherein islands of electrode material are arranged adjacent the transmitter electrodes and/or the receiver electrodes to reduce visual impact of the transmitter electrodes and/or the receiver electrodes.
8. The sensor of claim 5 , wherein the length of the edge portions per sensing node is varied only in the first direction or the second direction to compensate for variation in the cover panel thickness in the first direction or the second direction respectively.
9. The sensor of claim 5 , wherein the length of the edge portions per sensing node is varied both in the first direction and the second direction to compensate for variation in the cover panel thickness in the first direction and the second direction.