Touch sensor with touch object discrimination
In one embodiment, a method includes conducting a first signal to a first source electrode external to a touch sensor. The first source electrode is capacitively coupled to the touch sensor through a touch object. The method further includes measuring a mutual capacitance between the first source electrode and the first measuring electrode. The method further includes identifying, based at least in part on the measured mutual capacitance and using a controller of the touch sensor, the touch object touching the touch sensor at a detected touch position.
1. A method comprising:
during a position-detecting mode, determining, independent of an electrode external to a touch sensor, a position of a touch object touching the touch sensor; and
during an object-identification mode, in response to determining the position of the touch object:
conducting a first signal to a first source electrode external to the touch sensor, the first source electrode capacitively coupled to a first measuring electrode of a plurality of measuring electrodes of the touch sensor through the touch object;
measuring a mutual capacitance between the first source electrode and the first measuring electrode while conducting the first signal;
conducting a second signal to a second source electrode external to the touch sensor, the second source electrode capacitively coupled to a second measuring electrode of the plurality of measuring electrodes of the touch sensor through a second touch object;
measuring a mutual capacitance between the second source electrode and the second measuring electrode while conducting the second signal; and
determining the touch object touching the touch sensor at the determined position by comparing the measured mutual capacitance between the first source electrode and the first measuring electrode with the measured mutual capacitance between the second source electrode and the second measuring electrode and selecting the touch object based on the relative magnitude of the measured mutual capacitance between the first source electrode and the first measuring electrode and the measured mutual capacitance between the second source electrode and the second measuring electrode.
2. The method of claim 1 , wherein the first measuring electrode is a drive electrode during the position-detection mode and is a sense electrode during the object-identification mode.
3. The method of claim 1 , further comprising tracking, during the position-detection mode, a change in the determined position of the touch object.
4. An apparatus comprising:
a substrate;
a plurality of sense electrodes distributed across an active touch screen area of the substrate; and
a controller configured to:
during a position-detecting mode, determine, independent of an electrode external to a touch sensor, a position of a touch object touching the active touch screen; and
during an object-identification mode, in response to determining the position of the touch object, determine the touch object touching the active touch screen area at the determined position by:
comparing a measured mutual capacitance between a first source electrode and a first measuring electrode, the first source electrode capacitively coupled to the touch screen area through a first touch object, with a measured mutual capacitance between a second source electrode and a second measuring electrode, the second source electrode capacitively coupled to the touch screen area through a second touch object; and
determining the touch object based on the relative magnitude of the measured mutual capacitance between the first source electrode and the first measuring electrode and the measured mutual capacitance between the second source electrode and the second measuring electrode.
5. The apparatus of claim 4 , further comprising a signal generator configured to induce charge through mutual capacitance, at least in part, by providing the signal to the first source electrode.
6. The apparatus of claim 4 , wherein the first source electrode is embedded in a chair.
7. The apparatus of claim 6 , wherein the chair is disposed within a vehicle.
8. The apparatus of claim 6 , wherein the chair is disposed within a room.
9. The apparatus of claim 4 , wherein the first source electrode is embedded in a stylus.
10. A system comprising:
a signal source configured to time-multiplex a signal among each of a plurality of source electrodes, such that only one of the source electrodes is provided the signal at a time;
a plurality of chairs each comprising a respective one of the plurality of source electrodes; and
a touch sensor comprising a plurality of measuring electrodes, the touch sensor configured to:
during a position-detecting mode, determine, independent of an electrode external to a touch sensor, a position of a touch object; and
during an object-identification mode, in response to determining the position of the touch object, determine the touch object touching the touch sensor at the determined position by:
comparing a measured mutual capacitance between a first source electrode of the plurality of source electrodes and a first measuring electrode of the plurality of measuring electrodes, the first source electrode capacitively coupled to the touch sensor through a first touch object, with a measured mutual capacitance between a second source electrode of the plurality of source electrodes and a second measuring electrode of the plurality of measuring electrodes, the second source electrode capacitively coupled to the touch sensor through a second touch object; and
determining the touch object based on the relative magnitude of the measured mutual capacitance between the first source electrode and the first measuring electrode and the measured mutual capacitance between the second source electrode and the second measuring electrode.
11. The system of claim 10 , further comprising a controller configured to synchronize a timing of the respective mutual capacitance measurement with the signal time-multiplex among each of the plurality of source electrodes.
12. The system of claim 10 , wherein the system is disposed within a vehicle.
13. The system of claim 10 , wherein the system is disposed within a room.
14. The system of claim 10 , wherein the touch sensor is further configured to determine the touch object touching the touch sensor based at least in part on a determination that the respective mutual capacitance measurement between at least the measuring electrode and one of the plurality of source electrodes is greater than a predetermined threshold.
15. The system of claim 10 , wherein at least a portion of each source electrode is disposed inside one or more of a back of its respective chair, a base of its respective chair, and a handle of its respective chair.
16. The system of claim 10 , wherein each source electrode comprises non-flexible conductive material at least partially covered in a dielectric material.
17. The system of claim 10 , wherein each source electrode comprises flexible conductive material.