Differential force and touch sensing

• US 10,067,590 B2
• Filed: 04/28/2017
• Issued: 09/04/2018
• Est. Priority Date: 04/29/2016
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Reynolds, Joseph Kurth
• Primary Examiner(s): Abdin, Shaheda
• Application Number:
  US15/582,255
• Publication Number:
  US 20170315650A1
• Time in Patent Office: 494 Days
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

An input device is configured to detect force being applied to an input region of the device by an input object, in addition to the position of the input object using touch sensing methods. Aspects include driving a force sensing electrode of the input device using an anti-guarding voltage alternating with a ground or guard voltage, while driving the touch sensing electrodes with a reference voltage, to obtain touch measurements, force measurements, interference measurements, double the force signal, and/o double the touch signal for differential touch and force detection. Aspects also include driving sensor electrodes using orthogonal signals and performing in-phase and quadrature demodulation of the received signal for simultaneous and independent touch and force measurements.

Claims

1. An input device, comprising:

an input surface;

at least one force electrode;

a plurality of sensor electrodes disposed between the input surface and the at least one force electrode, the plurality of sensor electrodes configured to deflect toward the at least one force electrode in response to a force applied to the input surface; and

a processing system coupled to the plurality of sensor electrodes, the processing system configured to;

drive the plurality of sensor electrodes with a modulated reference voltage;

while driving the plurality of sensor electrodes with the modulated reference voltage, drive the at least one force electrode by alternating between a guarding voltage and an anti-guarding voltage, wherein the guarding voltage is in-phase with respect to the modulated reference voltage, and wherein the anti-guarding voltage is anti-phase with respect to the modulated reference voltage;

receive resulting signals comprising effects of user input upon a coupling of at least one of the modulated reference voltage, the guarding voltage, or the anti-guarding voltage, the effects indicative of changes in capacitance of the plurality of sensor electrodes; and

determine both position information and force information for an input object based on at least two of the resulting signals.

2. The input device of claim 1, wherein:

the position information is determined based on a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the guarding voltage.

3. The input device of claim 1, wherein the force information is determined based on subtracting a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the anti-guarding voltage from a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the guarding voltage.

4. The input device of claim 1, wherein the processing system is further configured to:

drive the plurality of sensor electrodes and the at least one force electrode with a constant voltage signal to acquire first changes of capacitance of the plurality of sensor electrodes and the at least one force electrode; and

determine interference information for the input device based on the first changes in capacitance.

5. The input device of claim 1, wherein the processing system is further configured to update a display, and wherein the alternating comprises alternating between the guarding voltage and the anti-guarding voltage multiple times in a single display update frame.

6. The input device of claim 1, wherein the at least one force electrode comprises an internal chassis of the input device.

7. The input device of claim 1, wherein the at least one force electrode comprises a transmitter electrode and the plurality of sensor electrodes comprises a plurality of receiver electrodes.

8. The input device of claim 1, wherein at least one of the plurality of sensor electrodes is disposed on a color filter glass.

9. The input device of claim 1, wherein the processing system is further configured to update a display, and wherein the plurality of sensor electrodes comprises at least one common electrode configured for display updating and capacitive sensing.

10. A processing system for an input device, comprising:

sensor circuitry configured to;

drive a plurality of sensor electrodes with a modulated reference voltage, the plurality of sensor electrodes disposed between an input surface of the input device and at least one force electrode of the input device, the plurality of sensor electrodes configured to deflect toward the at least one force electrode in response to a force applied to the input surface;

while driving the plurality of sensor electrodes with the modulated reference voltage, drive the at least one force electrode by alternating between a guarding voltage and an anti-guarding voltage, wherein the guarding voltage is in-phase with respect to the modulated reference voltage, and wherein the anti-guarding voltage is anti-phase with respect to the modulated reference voltage; and

receive resulting signals comprising effects of at least one of the modulated reference voltage, the guarding voltage, or the anti-guarding voltage, the effects indicative of changes in capacitance of the plurality of sensor electrodes; and

a determination module coupled to the sensor circuitry and configured to determine both position information and force information for an input object based on at least two of the resulting signals.

11. The processing system of claim 10, wherein the determination module is configured to:

determine the position information based on a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the guarding voltage.

12. The processing system of claim 10, wherein the determination module is configured to:

determine the force information based on subtracting a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the anti-guarding voltage from a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the guarding voltage.

13. The processing system of claim 10, wherein:

the sensor circuitry is further configured to drive the plurality of sensor electrodes and the at least one force electrode with a constant voltage signal to acquire first changes of capacitance of the plurality of sensor electrodes and the at least one force electrode; and

the determination module is further configured to determine interference information for the input device based on the first changes in capacitance.

14. The processing system of claim 10, wherein the processing system is further configured to update a display, and wherein the alternating comprises alternating between the guarding voltage and the anti-guarding voltage multiple times in a single display update frame.

15. The processing system of claim 10, wherein the at least one force electrode comprises an internal chassis of the input device.

16. The processing system of claim 10, wherein the at least one force electrode comprises a transmitter electrode and the plurality of sensor electrodes comprises a plurality of receiver electrodes.

17. The processing system of claim 10, wherein at least one of the plurality of sensor electrodes is disposed on a color filter glass.

18. The processing system of claim 10, wherein the processing system is further configured to update a display, and wherein the plurality of sensor electrodes comprises at least one common electrode configured for display updating and capacitive sensing.

19. A method of operating an input device, the method comprising:

driving a plurality of sensor electrodes with a modulated reference voltage, the plurality of sensor electrodes disposed between an input surface of the input device and at least one force electrode of the input device, the plurality of sensor electrodes configured to deflect toward the at least one force electrode in response to a force applied to the input surface;

while driving the plurality of sensor electrodes with the modulated reference voltage, driving the at least one force electrode by alternating between a guarding voltage and an anti-guarding voltage, wherein the guarding voltage is in-phase with respect to the modulated reference voltage, and wherein the anti-guarding voltage is anti-phase with respect to the modulated reference voltage;

receiving resulting signals comprising effects of at least one of the modulated reference voltage, the guarding voltage, or the anti-guarding voltage, the effects indicative of changes in capacitance of the plurality of sensor electrodes; and

determining both position information and force information for an input object based on at least two of the resulting signals.

20. The method of claim 19, wherein the determination of the position information is based on a resulting signal, of the resulting signals, comprising effects of the user input upon the coupling of the guarding voltage.