Circular Touch Sensor

• US 20080047765A1
• Filed: 10/30/2007
• Published: 02/28/2008
• Est. Priority Date: 04/07/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Proctor, David
• Granted Patent: US 7,786,981 B2
• Time in Patent Office: Days
• US Class Current: 178/18.06
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers

Abstract

A circular touch sensor has three or more sensors arranged in an iris pattern. Each pad is defined by continuous edges that spiral outward about a center point. The unique geometric shape allows measurement of relative amounts of contact on adjoining sensors. In one implementation, the sensors measure relative capacitance of two or more sensors, thereby enabling high precision identification of the point of contact. With as few as three pads, the circular touch sensor is less expensive than traditional 12-pad to 16-pad circular sensors.

Claims

1. A method for determining a location of a contact to a touch sensor comprising:

detecting the contact to the touch sensor, the touch sensor comprising a plurality of sensor pads arranged about a center point in an iris pattern, each sensor pad having at least one edge that spirals about the center point to an outer boundary;

measuring a capacitance change in one or more of the sensor pads resulting from the contact;

determining a contact ratio for one or more of the sensor pads based on the capacitance change; and

assigning a positional location in accordance with the contact ratio.

2. The method of claim 1, wherein determining a contact ratio comprises comparing the capacitance change for each sensor pad to a capacitance change for all the sensor pads.

3. The method of claim 1, wherein the positional location is assigned by comparing the contact ratio to positional locations residing in a lookup table.

4. The method of claim 3, further comprising interpolating between the positional locations residing in the look-up table.

5. The method of claim 1, further comprising contacting the center point to input a selection.

6. One or more computer readable storage media containing computer-executable instructions that, when executed by a processor, perform the following:

detect a contact to a touch sensor, the touch sensor comprising multiple sensor pads arranged about a center point in an iris pattern, each sensor pad having at least one edge that spirals about the center point to an outer boundary;

generate values indicative of the contact to one or more of the sensor pads; and

determine a contact ratio based on the generated values, the contact ratio being used to determine the positional location of the contact.

7. The computer readable storage media of claim 6, wherein detecting the contact comprises one or more of detecting a pressure change, a capacitance change, or a conductance change.

8. The computer readable storage media of claim 6, wherein the values are generated by subtracting a sensed value from a baseline value, the sensed value resulting from the contact to one or more of the sensor pads.

9. The computer readable storage media of claim 6, wherein the contact ratio is determined by comparing the generated values for each sensor pad to a generated value for all the sensor pads.

10. The computer readable storage media of claim 6, wherein the positional location is determined by comparing the contact ratio to positional locations residing in a lookup table.

11. The computer readable storage media of claim 10, further comprising instructions that when executed by a processor interpolates between the positional locations residing in the look-up table.

12. A device comprising:

a touch sensor for detecting a contact, the touch sensor comprising multiple sensor pads arranged about a center point in an iris pattern, each sensor pad having at least one edge that spirals about the center point to an outer boundary; and

a processor for generating values indicative of the contact to one or more of the sensor pads, and calculating a contact ratio based on the generated values, the contact ratio being used to determine a positional location of the contact.

13. The device of claim 12, wherein detecting a contact comprises one or more of detecting a pressure change, a capacitance change, or a conductance change.

14. The device of claim 12, wherein the values are generated by subtracting a sensed value from a baseline value, the sensed value resulting from the contact to one or more of the sensor pads.

15. The device of claim 12, wherein the ratio is calculated by comparing the generated values for each sensor pad to a generated value for all the sensor pads.

16. The device of claim 12, wherein the processor determines the positional location of the contact by comparing the contact ratio to positional locations residing in a lookup table.

17. The device of claim 16, wherein the processor interpolates between the positional locations residing in the look-up table.

18. The device of claim 12, wherein the sensor pads are arranged such that the outer boundary forms a circle

19. The device of claim 12, wherein the edge originates at a first point on the center point and terminates at a second point on the outer boundary, wherein the first and second points are at least 120 degrees apart.

20. The device of claim 12, wherein the first and second points are approximately 180 degrees apart.