Circular touch sensor

• US 7,786,981 B2
• Filed: 10/30/2007
• Issued: 08/31/2010
• Est. Priority Date: 04/07/2005
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Proctor, David W.
• Primary Examiner(s): Lefkowitz; Sumati
• Assistant Examiner(s): SITTA, GRANT
• Application Number:
  US11/928,524
• Publication Number:
  US 20080047765A1
• Time in Patent Office: 1,036 Days
• Field of Search: 345173-177, 178 1801- 1807
• US Class Current: 345/173
• 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 at least three adjoining sensor pads arranged about a common center point in an iris pattern, each sensor pad having at least one continuous, arcuate edge that spirals about outward from a first point on the common center point to a second point on an outer circular boundary such that the edges comprise the iris pattern and form an overlapping relationship amongst the sensor pads, wherein the first and second points are between approximately 120 and approximately 180 degrees apart and a curve of the continuous, arcuate edge is such that any radius from the common center point to the outer circular boundary crosses over at least two sensor pads;

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

determining a continuously variable contact ratio for the two or more of the iris-shaped arcuate edged sensor pads based on a ratio of the capacitance change;

assigning an angular position in accordance with the contact ratio by comparing the contact ratio to discrete angular positions residing in a lookup table; and

corresponding sensor values in the lookup table to a plurality of discrete angular positions of contact, the touch sensor is correlated with a relative contribution of each of the sensor pads to a total capacitance increase across all of the sensor pads based on the overlapping relationship amongst the sensor pads, wherein the relative contribution of each of the sensor pads is represented as a percentage of the total capacitance increase, the total capacitance increase across all of the sensor pads equaling 100%.

2. The method of claim 1, further comprising interpolating between the discrete angular positions residing in the lookup table.

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

4. A machine for determining a location of a contact to a touch sensor, the machine comprising:

a processor; and

a tangible memory coupled to the processor, containing computer-executable instructions that, when executed by the processor, direct the processor to perform the following acts comprising;

detecting the contact to a touch sensor, the touch sensor comprising at least three adjoining sensor pads arranged about a common center point in an iris pattern, each sensor pad having at least one continuous, arcuate edge that spirals about outward from a first point on the common center point to a second point on an outer circular boundary such that the edges comprise the iris pattern and form an overlapping relationship amongst the sensor pads, wherein the first and second points are between approximately 120 and approximately 180 degrees apart and a curve of the continuous, arcuate edge is such that any radius from the common center point to the outer circular boundary crosses over at least two sensor pads;

generating values indicative of the contact to two or more of the sensor pads;

determining a contact ratio based on a continuously variable ratio of the generated values indicative of the contact to the two or more of the iris-shaped arcuate edged sensor pads;

assigning an angular position in accordance with the contact ratio by comparing the contact ratio to discrete angular positions residing in a lookup table, and

corresponding sensor values in the lookup table to a plurality of discrete angular positions of contact, the touch sensor is correlated with a relative contribution of each of the sensor pads to a total contact increase across all of the sensor pads based on the overlapping relationship amongst the sensor pads, wherein the relative contribution of each of the sensor pads is represented as a percentage of the total contact increase, the total contact increase across all of the sensor pads equaling 100%.

5. The machine of claim 4, wherein detecting the contact comprises one or more of detecting a pressure change, a capacitance change, or a conductance change.

6. The machine of claim 4, 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.

7. The machine of claim 4, wherein the computer-executable instructions further comprise interpolating between the discrete angular positions residing in the lookup table.

8. A device comprising:

a touch sensor for detecting a contact, the touch sensor comprising at least three adjoining sensor pads arranged about a common center point in an iris pattern, each sensor pad having at least one continuous, arcuate edge that spirals about outward from a first point on the common center point to a second point on an outer circular boundary such that the edges comprise the iris pattern and form an overlapping relationship amongst the sensor pads, wherein the first and second points are between approximately 120 and approximately 180 degrees apart and a curve of the continuous, arcuate edge is such that any radius from the common center point to the outer circular boundary crosses over at least two sensor pads;

capacitance detection circuitry configured to generate values indicative of the contact to two or more of the sensor pads; and

a processor configured to;

calculate a continuously variable contact ratio for the two or more of the iris-shaped arcuate edged sensor pads based on a ratio of the generated values;

assign an angular position in accordance with the continuously variable contact ratio by comparing the continuously variable contact ratio to discrete angular positions residing in a lookup table; and

correspond the sensor values in the lookup table to a plurality of discrete angular positions of contact, the touch sensor is correlated with a relative contribution of each of the sensor pads to a total contact increase across all of the sensor pads based on the overlapping relationship amongst the sensor pads, wherein the relative contribution of each of the sensor pads is represented as a percentage of the total contact increase, the total contact increase across all of the sensor pads equaling 100%.

9. The device of claim 8, wherein detecting a contact comprises one or more of detecting a pressure change, a capacitance change, or a conductance change.

10. The device of claim 8, 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.

11. The device of claim 8, wherein the processor interpolates between the discrete angular positions residing in the lookup table.