ANISOTROPIC TOUCH SCREEN ELEMENT

• US 20110043482A1
• Filed: 10/29/2010
• Published: 02/24/2011
• Est. Priority Date: 08/21/2003
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Philipp, Harald
• Granted Patent: US 8,049,738 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A touch sensitive position sensor for detecting the position of an object in two dimensions is described. The position sensor has first and second resistive bus-bars spaced apart with an anisotropic conductive area between them. Electric currents induced in the anisotropic conductive area by touch or proximity flow preferentially towards the bus-bars to be sensed by detection circuitry. Because induced currents, for example those induced by drive circuitry, flow preferentially along one direction, pin-cushion distortions in position estimates are largely constrained to this single direction. Such one-dimensional distortions can be corrected for very simply by applying scalar correction factors, thereby avoiding the need for complicated vector correction.

Claims

1. A touch sensitive position sensor comprising:

a substrate defining a touch sensitive platform;

a first resistive bus-bar on the substrate;

a second resistive bus-bar substantially parallel to the first resistive bus-bar on the substrate;

a third resistive bus-bar substantially parallel to the first resistive bus-bar and the second resistive bus-bar on the substrate, the third resistive bus-bar being between the first resistive bus-bar and the second resistive bus-bar; and

an anisotropic conductive area having non-zero resistance arranged between the first, second and third bus-bars such that currents induced in the anisotropic conductive area flow preferentially towards the first, second and third bus-bars.

2. A touch sensitive position sensor according to claim 1, wherein the first resistive bus-bar extends between a first and a second electrode, the second resistive bus-bar extends between a third and a fourth electrode and the third resistive bus bar extends between a fifth and a sixth electrode, the position sensor further comprising first, second, third, fourth, fifth and sixth drive channels associated with respective ones of the first, second, third, fourth, fifth and sixth electrodes, each drive channel being operable to generate an output signal dependent on the resistance between the respective first, second, third, fourth, fifth and sixth electrode and the position of the object.

3. A touch sensitive position sensor according to claim 2 further comprising a processor operable to generate an estimate for the position of the object by comparing the output signals from the fifth and sixth drive channels and the output signals from a selected pair of the output signals from either the first and second drive channels or the third and fourth drive channels.

4. A touch sensitive position sensor according to claim 3, wherein the processor is configured to estimate the position of the object in a first direction running between the bus-bars from a ratiometric analysis of the sum of the signals associated with the fifth and sixth electrodes and the sum of the signals associated with the selected pair of the other output signals.

5. A touch sensitive position sensor according to claim 4, wherein the processor is configured to estimate the position of the object in a second direction running along the bus-bars from a ratiometric analysis of the sum of the signals associated with the fifth and the one of the selected pair of the other output signals associated with the first resistive bus bar, and the sum of the signals associated with the sixth and the one of the selected pair of the other output signals associated with the second resistive bus bar.

6. A touch sensitive position sensor according to claim 1, wherein the anisotropic conducting area includes a plurality of resistive strips such that some of the resistive strips extend between the first resistive bus-bar and the third resistive bus-bar and other of the resistive strips extend between the second resistive bus-bar and the third resistive bus-bar.

7. A touch sensitive position sensor according to claim 6, wherein the resistance of the resistive strips is five to ten times greater than the resistance of the first, second and third resistive bus-bars.

8. A touch sensitive position sensor according to claim 6, wherein the resistive strips are in a zigzag pattern.

9. A touch sensitive position sensor according to claim 1, wherein the anisotropic conducting area includes a plurality of resistive strips that extend between the first resistive bus-bar and the second resistive bus-bar.

10. A touch sensitive position sensor according to claim 9, wherein the resistance of the resistive strips is five to ten times greater than the resistance of the first, second and third resistive bus-bars.

11. A touch sensitive position sensor according to claim 9, wherein the resistive strips are in a zigzag pattern.

12. A touch sensitive position sensor comprising:

a substrate defining a touch sensitive platform;

a first resistive bus-bar on the substrate;

a second resistive bus-bar substantially parallel to the first resistive bus-bar on the substrate;

a third resistive bus-bar substantially parallel to the first resistive bus-bar and the second resistive bus-bar on the substrate, the third resistive bus-bar being between the first resistive bus-bar and the second resistive bus-bar;

a fourth resistive bus-bar substantially parallel to the first resistive bus-bar, the second resistive bus-bar and the third resistive bus bar on the substrate, the fourth resistive bus-bar being between the third resistive bus-bar and the second resistive bus-bar; and

an anisotropic conductive area having non-zero resistance arranged between the first, second, third and fourth bus-bars such that currents induced in the anisotropic conductive area flow preferentially towards the first, second, third and fourth bus-bars.

13. A touch sensitive position sensor according to claim 12, wherein the first resistive bus-bar extends between a first and a second electrode, the second resistive bus-bar extends between a third and a fourth electrode, the third resistive bus bar extends between a fifth and a sixth electrode and the fourth resistive bus bar extends between a seventh and an eighth electrode, the position sensor further comprising first, second, third, fourth, fifth, sixth, seventh and eighth drive channels associated with respective ones of the first, second, third, fourth, fifth, sixth, seventh and eighth electrodes, each drive channel being operable to generate an output signal dependent on the resistance between the respective first, second, third, fourth, fifth, sixth, seventh and eighth electrode and the position of the object.

14. A touch sensitive position sensor according to claim 13 further comprising a processor operable to generate an estimate for the position of the object by comparing the output signals from one pair of drive channels with the output signals from another pair of drive channels.

15. A touch sensitive position sensor comprising:

a substrate defining a touch sensitive platform;

a first resistive bus-bar on the substrate, wherein the first resistive bus bar is configured to have a path length between two locations which is greater than the straight line distance between the two locations;

a second resistive bus-bar substantially parallel to the first resistive bus-bar on the substrate, wherein the second resistive bus bar is configured to have a path length between two locations which is greater than the straight line distance between the two locations;

a third resistive bus-bar substantially parallel to the first resistive bus-bar and the second resistive bus-bar on the substrate, the third resistive bus-bar being between the first resistive bus-bar and the second resistive bus-bar, wherein the third resistive bus bar is configured to have a path length between two locations which is greater than the straight line distance between the two locations; and

an anisotropic conductive area having non-zero resistance arranged between the first, second and third bus-bars such that currents induced in the anisotropic conductive area flow preferentially towards the first, second and third bus-bars.

16. A touch sensitive position sensor according to claim 15, wherein the first resistive bus-bar extends between a first and a second electrode, the second resistive bus-bar extends between a third and a fourth electrode and the third resistive bus bar extends between a fifth and a sixth electrode, the position sensor further comprising first, second, third, fourth, fifth and sixth drive channels associated with respective ones of the first, second, third, fourth, fifth and sixth electrodes, each drive channel being operable to generate an output signal dependent on the resistance between the respective first, second, third, fourth, fifth and sixth electrode and the position of the object.

17. A touch sensitive position sensor according to claim 16, wherein each of the first, second and third resistive bus bars is configured in a zigzag pattern.

18. A touch sensitive position sensor according to claim 17, wherein the anisotropic conducting area includes a plurality of resistive strips such that some of the resistive strips extend between the first resistive bus-bar and the third resistive bus-bar and other of the resistive strips extend between the second resistive bus-bar and the third resistive bus-bar.

19. A touch sensitive position sensor according to claim 18, wherein the resistance of the resistive strips is five to ten times greater than the resistance of the first, second and third resistive bus-bars.

20. A touch sensitive position sensor according to claim 18, wherein each of the resistive strips is configured in a zigzag pattern.