Multi-touch sensor apparatus and method

• US 8,427,451 B2
• Filed: 12/30/2009
• Issued: 04/23/2013
• Est. Priority Date: 12/30/2009
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Waterbury, Charles A.
• Primary Examiner(s): Dharia, Prabodh M
• Application Number:
  US12/650,400
• Publication Number:
  US 20110157066A1
• Time in Patent Office: 1,210 Days
• Field of Search: 345156-179, 178 1801- 1806, 463/37, 455/566
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

A device and method for detecting actual touch points in a multi-touch input device. Embodiments include a measurement sharing device configured to combine a measurement of an electrical characteristic on a first axis with a measurement of an electrical characteristic on a second axis. The combined measurement is compared with electrical characteristics measured separately on each axis to determine which intersections correspond to actual touch points.

Claims

1. A method executed by a multi-touch input device including multiple conductors on a first axis and multiple conductors on a second axis different from the first axis, for detecting actual touch points that are simultaneously indicated, the method comprising:

determining a first conductor on the first axis at which one of multiple simultaneous touches is indicated;

determining a first conductor and a second conductor on the second axis at which one of the multiple simultaneous touches is indicated;

multiplexing the first conductor on the first axis and the first conductor on the second axis to perform a first combined measurement by coupling both the first conductor on the first axis and the first conductor on the second axis to a signal measuring device at the same time;

multiplexing the first conductor on the first axis and the second conductor on the second axis to perform a second combined measurement by coupling both the first conductor on the first axis and the second conductor on the second axis to the signal measuring device at the same time; and

comparing the first combined measurement and the second combined measurement to determine a first actual touch point and a second actual touch point that are simultaneously indicated as opposed to a ghost point.

2. The method of claim 1, wherein comparing the first combined measurement and the second combined measurement further comprises comparing separate measurements performed on the first conductor on the first axis, on the first conductor on the second axis, and on the second conductor on the second axis to the first combined measurement and the second combined measurement, including adding a measurement performed on the first conductor on the first axis to a measurement performed on the first conductor on the second axis.

3. The method of claim 2, wherein comparing separate measurements further comprises adding a measurement performed on the first conductor on the first axis to a measurement performed on the second conductor on the second axis.

4. The method of claim 3, wherein the first touch point is the intersection of the first conductor on the first axis and the first conductor on the second axis when a sum of the separate measurements performed on the first conductor on the first axis and the first conductor on the second axis minus the first combined measurement is greater than or equal to a sum of the separate measurements performed on the first conductor on the first axis and the second conductor on the second axis minus the second combined measurement.

5. The method of claim 4, wherein the second touch point is determined to be the intersection of the second conductor on the first axis and the second conductor on the second axis by virtue of the determination of the first touch point.

6. The method of claim 1, further comprising:

determining a second conductor on the first axis at which a touch is indicated;

multiplexing the second conductor on the first axis and the second conductor on the second axis to perform a combined measurement that supplements the first combined measurement; and

multiplexing the first conductor on the first axis and the second conductor on the second axis to perform a combined measurement that supplements the second combined measurement.

7. A method in a multi-touch sensor including a plurality of X conductors and a plurality of Y conductors, for detecting actual touch points that are simultaneously indicated as opposed to a ghost point, the method comprising:

determining a first X conductor at a first X location at which one of multiple simultaneous touches is indicated;

determining a first Y conductor at a first Y location and a second Y conductor at a second Y location at which one of the multiple simultaneous touches is indicated;

obtaining a first combined capacitance value by measuring a combined capacitance of the first X conductor and the first Y conductor by energizing both the first X conductor and the first Y conductor simultaneously;

obtaining a second combined capacitance value by measuring a combined capacitance of the first X conductor and the second Y conductor by energizing both the first X conductor and the second Y conductor simultaneously;

comparing the combined capacitance values to a separate capacitance value of the first X conductor, the first Y conductor, and the second Y conductor to determine which intersections of the first X location, a second X location, the first Y location, and the second Y location correspond to actual touch points on the sensor as opposed to a ghost point; and

providing the intersections which are determined to correspond to the actual touch points on the sensor for further processing.

8. The method of claim 7, wherein comparing the combined capacitance values includes:

adding a first X capacitance value of the first X conductor to a first Y capacitance value of the first Y conductor to determine a first XY capacitance value;

adding the first X capacitance value to a second Y capacitance value of the second Y conductor to determine a second XY capacitance value;

subtracting the first combined capacitance value from the first XY capacitance value to determine a first difference value;

subtracting the second combined capacitance value from the second XY capacitance value to determine a second difference value;

identifying the intersection of the first X location and the first Y location, along with the intersection of the second X location and the second Y location, as locations that correspond to objects in contact with the sensor when the first difference value is greater than or equal to the second difference value; and

identifying the intersection of the first X location and the second Y location, along with the intersection of the second X location and the first Y location, as locations that correspond to objects in contact with the sensor when the first difference value is less than the second difference value.

9. The method of claim 7, wherein obtaining the first combined capacitance value by measuring the combined capacitance of the first X conductor and the first Y conductor includes coupling the first X conductor and the first Y conductor to a signal measuring device at the same time.

10. The method of claim 7, wherein obtaining the second combined capacitance value by measuring the combined capacitance of the first X conductor and the second Y conductor includes coupling the first X conductor and the second Y conductor to a signal measuring device at the same time.

11. The method of claim 7, further comprising coupling only the first X conductor to a signal measuring device to obtain a first X capacitance value of the first X conductor.

12. The method of claim 7, further comprising coupling only the first Y conductor to a signal measuring device to obtain a first Y capacitance value of the first Y conductor, and coupling only the second Y conductor to the signal measuring device to obtain a second Y capacitance value of the second Y conductor.

13. The method of claim 7, further comprising measuring a capacitance of each of the plurality of X conductors, and choosing the first X location and the second X location according to the relative capacitance of the plurality of X conductors.

14. The method of claim 7, further comprising measuring a capacitance of each of the plurality of Y conductors, and choosing the first Y location and the second Y location according to the relative capacitance of the plurality of Y conductors.

15. A multi-touch sensor capable of discerning an actual touch from a ghost touch amongst multiple simultaneous touches, comprising:

a first plurality of conductors arranged in a first direction;

a second plurality of conductors arranged in a second direction and intersecting the first plurality of conductors;

a signal measurement device configured to receive measurement signals from the conductors;

a measurement sharing device coupled to the signal measurement device;

a conductor selecting device configured to couple a conductor of the first plurality of conductors to the measurement sharing device, and to separately couple a conductor of the second plurality of conductors to the measurement sharing device; and

a position identification device configured to instruct the measurement sharing device and the conductor selecting device, in case multiple simultaneous touches are detected based on a first conductor and a second conductor arranged in the first direction and based on a first conductor and a second conductor arranged in the second direction;

to couple the first conductor arranged in the first direction and the first conductor arranged in the second direction to the signal measurement device at the same time to perform a first combined measurement; and

to couple the first conductor arranged in the first direction and the second conductor arranged in the second direction to the signal measurement device at the same time to perform a second combined measurement,

and further configured to receive representations of the first and second combined measurements from the signal measurement device and to compare the first and second combined measurements to determine a first actual touch point and a second actual touch point that are simultaneously indicated as opposed to a ghost point.

16. The multi-touch sensor of claim 15, wherein the position identification device is further configured to receive the first and second combined measurements each representing a result of a test of capacitance of coupled two conductors.

17. The multi-touch sensor of claim 15, wherein the position identification device is further configured to compare the first or second combined measurements to a sum of separate measurements of the coupled two conductors to identify an actual touch point.

18. The multi-touch sensor of claim 15, wherein the measurement sharing device is configured to couple the output of the conductor selecting device with respect to the first plurality of conductors with the output of the conductor selecting device with respect to the second plurality of conductors before coupling the output to the signal measurement device.

19. The multi-touch sensor of claim 15, wherein the first plurality of conductors is arranged on a first layer and the second plurality of conductors is arranged on a second layer separated from the first layer by a dielectric layer.

20. The multi-touch sensor of claim 15, wherein the multi-touch sensor is configured to return an indication of an actual touch point corresponding to a location where a sum of measurements of capacitance of two separate conductors minus a combined measurement of capacitance of the two conductors is greater than a similar measurement at a location corresponding to a ghost point.

21. A multi-touch sensor capable of discerning an actual touch from a ghost touch amongst multiple simultaneous touches, comprising:

a first signal measurement device configured to apply a signal to and receive measurement signals from a first plurality of conductors arranged in a first direction;

a second signal measurement device configured to apply a signal to a second plurality of conductors arranged in a second direction crossing the first plurality of conductors;

a conductor selecting device configured to selectively couple a conductor of the first plurality of conductors to the first signal measurement device, and to selectively couple a conductor of the second plurality of conductors to the second signal measurement device; and

a position identification device configured to, in case multiple simultaneous touches are detected based on a first conductor and a second conductor arranged in the first direction and based on a first conductor and a second conductor arranged in the second direction;

instruct the conductor selecting device to couple the first conductor arranged in the first direction to the first signal measurement device;

instruct the conductor selecting device to couple the first conductor arranged in the second direction to the second signal measurement device;

instruct the first signal measurement device and second signal measurement device to each apply a signal to the coupled conductors at the same time to obtain a first combined measurement of the first conductor arranged in the first direction and the first conductor arranged in the second direction;

instruct the conductor selecting device to decouple the first conductor arranged in the second direction and couple the second conductor arranged in the second direction to the second signal measurement device;

instruct the first signal measurement device and second signal measurement device to each apply a signal to the coupled conductors at the same time to obtain a second combined measurement of the first conductor arranged in the first direction and the second conductor arranged in the second direction; and

compare the first combined measurement and the second combined measurement to determine a first actual touch point and a second actual touch point that are simultaneously indicated as opposed to a ghost point.

22. The multi-touch sensor of claim 21, wherein the first signal measurement device and the second signal measurement device are configured to apply a DC signal to associated conductors.