Scanned piezoelectric touch sensor device
Embodiments of the disclosure generally provide an integrated input device that is configured to sense the position and amount of force applied by input objects that are in contact with an input region of an input device. The input device is generally configured to sense the position and amount of force applied by an input object that is in contact with the input region using a piezoelectric material. The input device generally includes a plurality of electrodes that are positioned to measure an electrical characteristic of the piezoelectric layer at different points within the input region to determine the position and/or amount force applied by the input object(s). The input device may also include one or more components that are able to simultaneously or sequentially sense the position of an input object using a touch sensing technique that does not rely on the electrical properties of the piezoelectric material to sense the position of the input object.
1. An input device comprising
a plurality of first electrodes;
a plurality of second electrodes;
a plurality of sensing elements, wherein each sensing element comprises:
a portion of a first electrode;
a portion of a second electrode; and
a piezoelectric material disposed between the portion of the first electrode and the portion of the second electrode,
wherein each first electrode forms part of two or more sensing elements and each second electrode forms part of two or more sensing elements; and
a processing system electrically connected to each of the first electrodes and each of the second electrodes, and configured to detect forces applied to one or more of the sensing elements by applying a time-varying electrical excitation signal to at least one of the plurality of first electrodes and detecting a resulting electrical signal on one or more of the second electrodes, and wherein the processing system is further configured to measure an electrical impedance of the piezoelectric material disposed between the portion of the first electrode and the portion of the second electrode for each sensing element.
2. The input device of claim 1 , wherein
the first electrodes and the second electrodes comprise a non-opaque electrically conductive material, and
the piezoelectric material is non-opaque.
3. The input device of claim 2 , further comprising
a display device having a display region, wherein the first electrodes, the second electrodes, and the piezoelectric material are at least partially disposed over the display region.
4. The input device of claim 1 , wherein
the first electrodes have an elongated shape, wherein an elongated portion of each of the first electrodes is aligned parallel to a first direction that lies within a first plane,
the second electrodes have an elongated shape, wherein an elongated portion of each of the second electrodes is aligned parallel to a second direction that lies within a second plane,
the first plane and the second plane are parallel to one another, and the piezoelectric material is disposed between the first and second planes,
the first direction and the second direction are at an angle to each other, so that the second electrodes cross over the first electrodes, and
each of the sensing elements is formed at a location where a second electrode crosses over a first electrode.
5. The input device of claim 1 , further comprising:
a plurality of groups of sensing elements, wherein each group of sensing elements comprises sensing elements associated with exactly one of the first electrodes, wherein
the processing system is further configured
to simultaneously detect the forces applied to the sensing elements in a first group of sensing elements, and then
to simultaneously detect the forces applied to the sensing elements in a second group of sensing elements.
6. The input device of claim 1 , wherein the processing system is further configured
to drive the time-varying electrical excitation signals onto groups of one or more first electrodes in a coded sequence that comprises a series of steps,
to measure electrical signals on the second electrodes resulting from each step in the coded sequence, and
to detect the force applied to each sensing element by analyzing the measured electrical signals.
7. The input device of claim 6 , wherein analyzing the measured electrical signals comprises applying a matrix computation.
8. The input device of claim 1 , wherein the time-varying electrical excitation signal is a time-varying voltage signal or a time-varying current signal.
9. The input device of claim 1 , wherein the electrical impedances are measured by applying time-varying voltages to the first electrodes and measuring currents induced in the second electrodes.
10. The input device of claim 1 , wherein the electrical impedances are measured by applying time-varying electrical currents to the first electrodes and measuring voltage changes on the second electrodes.
11. The input device of claim 1 , wherein the processing system is further configured to detect the presence of an input object by measuring a capacitance associated with a first electrode or a second electrode.
12. The input device of claim 11 , wherein the measured capacitance is the mutual capacitance between at least one first electrode and at least one second electrode.
13. The input device of claim 11 , wherein the measured capacitance comprises measuring the self-capacitance associated with the first electrode or the second electrode.
14. The input device of claim 11 , wherein
the measured capacitance provides presence and position information regarding the input object touching a surface of the input device, and
at least one of the detected of forces provides information regarding the amount of force applied to the surface of the input device by the input object.
15. The input device of claim 11 , wherein
the processing system is further configured to distinguish between a conductive input object and a non-conductive input object based on at least one of the detected forces and the measured capacitance.
16. The input device of claim 1 , wherein the processing system is further configured to detect the presence of one or more conductive objects by measuring a capacitance associated with each of the plurality of first electrodes.
17. The input device of claim 16 , wherein the processing system is further configured to determine a sequence of positions of one or more input objects proximate to the input device, based on a sequence of capacitance measurements.
18. The input device of claim 1 , further comprising
a plurality of third electrodes, wherein each third electrode is electrically connected to the processing system, wherein
the processing system is further configured to detect the presence of an input object near one or more of the third electrodes by measuring the capacitance associated with each of the third electrodes.
19. The input device of claim 1 , wherein the processing system is further configured
to implement a power conservation mode wherein the processing system is completely powered off so as to consume zero power while the power conservation mode is active, and
to harvest energy from the piezoelectric effect caused by an input object applying a force to one or more of the sensing elements, and
to use the harvested energy to emerge from the power conservation mode and return to its normal operating mode.
20. A method of detecting forces applied to a plurality of sensing elements formed from a plurality of first electrodes and a plurality of second electrodes of an input device,
each sensing element comprising a portion of a first electrode, a portion of a second electrode, and a piezoelectric material disposed between the portion of the first electrode and the portion of the second electrode, wherein each first electrode forms part of two or more sensing elements and each second electrode forms part of two or more sensing elements,
the method comprising:
applying a time-varying electrical excitation signal to at least one of the plurality of first electrodes;
detecting a resulting electrical signal on one or more of the second electrodes; and
measuring, for each sensing element, an electrical impedance of the piezoelectric material disposed between the portion of the first electrode and the portion of the second electrode.
21. The method of claim 20 , wherein:
the first electrodes and the second electrodes comprise a non-opaque electrically conductive material, and
the piezoelectric material is non-opaque.
22. The method of claim 21 , wherein the input device further comprises:
a display device having a display region, wherein the first electrodes, the second electrodes, and the piezoelectric material are at least partially disposed over the display region.
23. The method of claim 20 , wherein:
the first electrodes have an elongated shape, wherein an elongated portion of each of the first electrodes is aligned parallel to a first direction that lies within a first plane,
the second electrodes have an elongated shape, wherein an elongated portion of each of the second electrodes is aligned parallel to a second direction that lies within a second plane,
the first plane and the second plane are parallel to one another, and the piezoelectric material is disposed between the first and second planes,
the first direction and the second direction are at an angle to each other, so that the second electrodes cross over the first electrodes, and
each of the sensing elements is formed at a location where a second electrode crosses over a first electrode.
24. The method of claim 20 , wherein the input device further comprises:
a plurality of groups of sensing elements, wherein each group of sensing elements comprises sensing elements associated with exactly one of the first electrodes,
the method further comprising:
simultaneously detecting forces applied to the sensing elements in a first group of sensing elements, and
simultaneously detecting the forces applied to the sensing elements in a second group of sensing elements.
25. The method of claim 20 , further comprising:
driving time-varying electrical excitation signals onto groups of one or more first electrodes in a coded sequence that comprises a series of steps,
measuring electrical signals on the second electrodes resulting from each step in the coded sequence, and
detecting force applied to each sensing element by analyzing the measured electrical signals.
26. The method of claim 25 , wherein analyzing the measured electrical signals comprises applying a matrix computation.
27. The method of claim 20 , wherein the time-varying electrical excitation signal is a time-varying voltage signal or a time-varying current signal.
28. The method of claim 20 , further comprising:
implementing a power conservation mode wherein an associated processing system is completely powered off so as to consume zero power while the power conservation mode is active, and
harvesting energy from a piezoelectric effect caused by an input object applying a force to one or more of the sensing elements, and
using the harvested energy to emerge from the power conservation mode and return to a normal operating mode of the processing system.