Projected capacitive touch detection with touch force detection using self-capacitance and mutual capacitance detection

Patent metadata

Field	Value
Publication number	US-9904417-B2
Application number	US-201414254407-A
Country	US
Kind code	B2
Filing date	Apr 16, 2014
Priority date	Apr 16, 2014
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

A force sensing touch sensor comprises a substrate having a plurality of conductive electrode rows and a plurality of conductive electrode columns substantially perpendicular to and over the plurality of conductive electrode rows on a surface of the substrate, and a force sensor at each corner of the substrate. When a touch is applied to the surface of the touch sensor, the capacitance value will change of a capacitor formed by an intersection of an electrode row and column proximate to the location of the touch to the surface of the touch sensor. These force sensors detect total and proportional force on the touch sensor substrate. This force information is then combined with the touch location(s) previously determined, and the individual touch force(s) can then be interpolated with sufficient resolution for three dimensional (3D) gesturing applications.

First claim

What is claimed is:

1. An apparatus for determining a location of a touch thereto and a force thereof on a touch sensing surface, comprising:
a first plurality of electrodes arranged in a parallel orientation having a first axis, wherein each of the first plurality of electrodes comprises a self capacitance;
a second plurality of electrodes arranged in a parallel orientation having a second axis perpendicular to the first axis, the first plurality of electrodes are located over the second plurality of electrodes and form a plurality of nodes comprising overlapping intersections of the first and second plurality of electrodes, wherein each of the plurality of nodes comprises a mutual capacitance;
a substrate having the first and second plurality of electrodes disposed thereon, wherein the substrate has a plurality of corners;
a plurality of pressure sensors arranged below the substrate and at each corner of the substrate, wherein each pressure sensor receives pressure caused by a touch from a bottom surface of the substrate;
whereby each of the plurality of pressure sensors measures a portion of a force applied to the substrate during a touch thereto, and
a processing system configured to calculate force point (CFP) and a geometric center of mass (CM) from the pressure values measured by the plurality of pressure sensors, wherein the processing device is further configured to determine a vertical movement of the touches when the CFP matches the CM and to determine a rotational movement when the CFP does not match the CM, and to generate gesture commands corresponding to the vertical movement or the rotational movement with regard to a displayed object that corresponds to the touches.

2. The apparatus according to claim 1 , wherein the substrate is light transmissive and the first and second plurality of electrodes comprise Indium Tin Oxide (ITO).

3. The apparatus according to claim 1 , wherein the substrate is light transmissive and the first and second plurality of electrodes comprise Antimony Tin Oxide (ATO).

4. The apparatus according to claim 1 , wherein the substrate comprises four corners.

5. The apparatus according to claim 1 , wherein the processing system comprises a microcontroller comprising a digital processor and memory.

6. The apparatus according to claim 5 , wherein the microcontroller further comprises a capacitive touch analog front end.

7. The apparatus according to claim 6 , wherein the microcontroller further comprises an analog-to-digital converter (ADC) controller.

8. A method for determining a location of a touch thereto and a force thereof on a touch sensing surface, said method comprising the steps of:
providing a first plurality of electrodes arranged in a parallel orientation having a first axis, wherein each of the first plurality of electrodes comprises a self capacitance;
providing a second plurality of electrodes arranged in a parallel orientation having a second axis perpendicular to the first axis, the first plurality of electrodes are located over the second plurality of electrodes and form a plurality of nodes comprising overlapping intersections of the first and second plurality of electrodes, wherein each of the plurality of nodes comprises a mutual capacitance;
providing a substrate having the first and second plurality of electrodes disposed thereon, wherein the substrate has a plurality of corners;
providing a plurality of pressure sensors arranged below the substrate and at each corner of the substrate, wherein each pressure sensor receives pressure caused by a touch from a bottom surface of the substrate;
scanning the first plurality of electrodes for determining values of the self capacitances thereof;
comparing the values of the scanned self capacitances to determine which one of the first plurality of electrodes has the largest value of self capacitance;
scanning the nodes of the one of the first plurality of electrodes having the largest value of self capacitance for determining values of the mutual capacitances of the respective plurality of nodes;
comparing the values of the scanned mutual capacitances of the respective plurality of nodes on the first electrode having the largest value of self capacitance, wherein the node having the largest value of mutual capacitance is a location of a touch on the touch sensing surface; and
determining a force of the touch on the touch sensing surface from pressure values measured by the plurality of pressure sensors by determining a calculated force point (CFP) and a geometric center of mass (CM) from the pressure values, wherein when the CFP matches the CM a vertical movement of the touches is determined and wherein when the CFP does not match the CM a rotational movement of the touches is determined, and wherein gesture commands corresponding to the vertical movement or the rotational movement are performed with regard to a displayed object that corresponds to the touches.

9. The method as recited in claim 8 , wherein the self and mutual capacitance values are measured with an analog front end and an analog-to-digital converter (ADC).

10. The method as recited in claim 9 , wherein the self and mutual capacitance values are stored in a memory of a digital device.

11. The method as recited in claim 10 , wherein a digital processor in the digital device uses the stored self and mutual capacitance values in determining the touch location of the touch and the force applied by the touch to the touch sensing surface at the touch location.

12. The method as recited in claim 8 , wherein the step of determining a force of the touch on the touch sensing surface comprises the step of determining a calculated force point (CFP) by adding together the pressure values measured by the plurality of pressure sensors.

13. A method for determining locations of a plurality of touches thereto and a combined force thereof on a touch sensing surface, said method comprising the steps of:
providing a first plurality of electrodes arranged in a parallel orientation having a first axis, wherein each of the first plurality of electrodes comprises a self capacitance;
providing a second plurality of electrodes arranged in a parallel orientation having a second axis perpendicular to the first axis, the first plurality of electrodes are located over the second plurality of electrodes and form a plurality of nodes comprising overlapping intersections of the first and second plurality of electrodes, wherein each of the plurality of nodes comprises a mutual capacitance;
providing a substrate having the first and second plurality of electrodes disposed thereon, wherein the substrate has a plurality of corners;
providing only four pressure sensors arranged below the first and second plurality of electrodes under the substrate and one of the four pressure sensors at each corner of the substrate, wherein each pressure sensor receives pressure caused by a touch from a bottom surface of the substrate;
scanning the first plurality of electrodes for determining values of the self capacitances thereof;
comparing the values of the scanned self capacitances to determine which ones of the first plurality of electrodes have the largest values of self capacitance;
scanning the nodes of the ones of the first plurality of electrodes having the largest values of self capacitance for determining values of the mutual capacitances of the respective plurality of nodes;
comparing the values of the scanned mutual capacitances of the respective plurality of nodes on the first electrodes having the largest values of self capacitance, wherein the nodes having the largest values of mutual capacitance are locations of tou

Assignees

• Microchip Tech Inc

Inventors

• Hanauer Jerry
• Curtis Keith E

Classifications

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/0414 Primary

  using force sensing means to determine a position · CPC title

• G06F2203/04106

  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 title

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F2203/04111

  Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate · CPC title