Proportional area weighted sensor for two-dimensional locations on a touch-screen

1. A touch sensor comprising:

a touch controller;

a touch surface comprising a planar touch sensor layout, the layout having an edge portion and an interior portion;

a connector coupling the touch controller to the layout;

a substrate made of a first material comprising the layout; and

sensing elements made of a second material formed on the substrate and covering the layout without overlapping, wherein:

the sensing elements each have a width that varies non-monotonically from a center of the sensing element along two substantially perpendicular directions on the layout, and a centroid;

at least one pass-through trace to couple the edge portion of the layout to a sensing element in the interior portion of the layout; and

the sensor determines a two-dimensional location for a touch overlapping the sensing elements using a weighting that is proportional to an overlap area of the sensor elements and their centroids.

2. The touch sensor of claim 1 , wherein the touch controller comprises a processor circuit and a memory.

3. The touch sensor of claim 1 wherein the connector comprises a plurality of coupling channels, each of the coupling channels coupling a single sensing element to the touch controller.

4. The touch sensor of claim 1 , wherein the sensing elements are separated from each other by a fixed gap.

5. The touch sensor of claim 1 , wherein the sensing elements completely embedded in the interior portion have a shape that is substantially symmetric upon reflections about two axes in the plane of the layout, excepting the pass through traces.

6. The touch sensor of claim 1 , wherein the sensing elements have a shape interlaced with other sensing elements so that a line joining a point inside one element to its centroid crosses over a neighboring element at least once.

7. The touch sensor of claim 1 , wherein the touch sensor comprises a single layer capacitive sensor.

8. A touch sensor comprising:

a touch controller;

a touch surface comprising a planar touch sensor layout, the layout having

an edge portion and an interior portion;

a connector coupling the touch controller to the layout;

a substrate made of a dielectric material comprising the layout; and

sensing elements made of a conductive material formed on the substrate and covering the layout without overlapping, wherein:

the sensing elements each have a width that varies non-monotonically from a center of the sensing element along two substantially perpendicular directions on the layout, and a centroid;

at least a pass-through trace to couple the edge of the layout to a sensing element in the interior portion of the layout; and

the sensor determines a two-dimensional location for a touch overlapping the sensing elements using a weighting that is proportional to an overlap area of the sensor elements and their centroids.

9. The touch sensor of claim 8 , wherein the touch controller comprises a processor circuit and a memory.

10. The touch sensor of claim 8 , wherein the sensing elements are capacitively coupled by a touch from a capacitive element.

11. The touch sensor of claim 8 , wherein the capacitive element is selected from the group consisting of at least a finger, a stylus and a pointing device made of a dielectric material.

12. The touch sensor of claim 8 , wherein the conductive material comprises Indium Tin Oxide (ITO).

13. A controller circuit comprising a processor and a memory, the memory including instructions that, when executed by the processor, cause the processor to perform a method for determining a two-dimensional location on a touch screen having an interior portion and an edge portion, the method comprising:

obtaining, by the controller, overlap proportions from a plurality of sensing elements in the touch screen, each sensing element of the plurality of sensing elements having a centroid, wherein

the centroid locations are stored in the memory;

determining, by the processor, a first two-dimensional touch location by an average of the centroid locations of the plurality of sensing elements weighted by the overlap proportion;

determining, by the processor, complementary factors using the first two-dimensional touch location; and

determining, by the processor, a second two-dimensional touch location by an average of the locations of each of a plurality of sensing elements weighted by the overlap proportion and the complementary factors.

14. The method of claim 13 , wherein determining complementary factors using the first two-dimensional touch location comprises determining whether or not the first two-dimensional touch location is included in the interior portion or the edge portion of the touch screen.

15. The method of claim 13 , determining complementary factors using the first two-dimensional touch location comprises determining the distance between the first two-dimensional touch location and the centroid of each sensing element.

16. The method of claim 15 , wherein the complementary factor associated to a sensing element for a touch location is inversely proportional to the distance of the first two-dimensional touch location and the centroid of each sensing element.

17. The method of claim 13 , wherein the sensing elements are electronically coupled to the controller circuit, the method further comprising:

adjusting the complementary factor associated to a sensing element for a touch location for aberrations caused by the sensing capability of each sensing element and their electronic coupling to the controller circuit.

18. The method of claim 13 , wherein determining complementary factors using the first two-dimensional touch location comprises obtaining the complementary factors from the memory.

19. The method of claim 13 , wherein determining complementary factors using the first two-dimensional touch location comprises using a function stored in a memory circuit in the controller circuit.

20. The method of claim 13 , wherein determining complementary factors using the first two-dimensional touch location comprises using a lookup table stored in a memory circuit in the controller circuit.