Force Sensing X-Y Touch Sensor

• US 20140267152A1
• Filed: 12/05/2013
• Published: 09/18/2014
• Est. Priority Date: 03/12/2013
• Status: Abandoned Application

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Microchip Technology Incorporated
• Inventors: Curtis, Keith E.
• Application Number:
  US14/097,370
• Publication Number:
  US 20140267152A1
• Time in Patent Office: Days
• US Class Current: 345/174
• 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 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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
• 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
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

A force sensing X-Y touch sensor comprising a plurality of conductive electrode rows, a plurality of electrode columns substantially perpendicular to and over the plurality of conductive electrode rows, a flexible electrically conductive cover over the electrode columns and a plurality of deformable spacers between the cover and the electrode columns, wherein the deformable spacers maintains a distance between the cover and the electrode columns. When a touch is applied to the surface of X-Y touch sensor, the flexible cover is biased toward the electrode columns and rows and changes the capacitance value thereof at the location of the touch thereto. This change in capacitance value is proportional to the force of the touch on the surface of the flexible electrically conductive cover. Therefore the location of the touch and the force thereof may be determined by how much the capacitance value changes.

Claims

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 substantially 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 flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface; and

a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes.

2. The apparatus according to claim 1, wherein the flexible electrically conductive cover comprises a flexible metal substrate.

3. The apparatus according to claim 1, wherein the flexible electrically conductive cover comprises a flexible non-metal substrate and an electrically conductive coating on a surface thereof.

4. The apparatus according to claim 1, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Indium Tin Oxide (ITO) on a surface of the flexible substrate.

5. The apparatus according to claim 1, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Antimony Tin Oxide (ATO) on a surface of the flexible substrate.

17. The system as recited in claim 1S2, wherein the digital device comprises a microcontroller.

18. The system as recited in claim 1S2, wherein the digital device is selected from the group consisting of a microprocessor, a digital signal processor, an application specific integrated circuit (ASIC) and a programmable logic array (PLA).

6. 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 substantially 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 flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface;

providing a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes;

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 a change in the values of the mutual capacitance of the node at the touch location during no touch and during the touch.

7. The method as recited in claim 6, wherein the self and mutual capacitance values are measured with an analog front end and an analog-to-digital converter (ADC).

8. The method as recited in claim 7, wherein the self and mutual capacitance values are stored in a memory of a digital device.

9. The method as recited in claim 8, 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.

10. A method for determining locations of a plurality of touches thereto and respective forces 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 substantially 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 flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface;

providing a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes;

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 touches on the touch sensing surface; and

determining a force for each of the respective touches on the touch sensing surface from a change in the values of the mutual capacitances of the nodes at the touch locations during no touch and during respective touches.

11. The method as recited in claim 10, wherein the self and mutual capacitance values are measured with an analog front end and an analog-to-digital converter (ADC).

12. The method as recited in claim 11, wherein the self and mutual capacitance values are stored in a memory of a digital device.

13. The method as recited in claim 12, wherein a digital processor in the digital device uses the stored self and mutual capacitance values in determining the touch locations of the touches and the respective forces applied by the touches to the touch sensing surface at the touch locations.

14. A system for determining locations of touches thereto and respective forces thereof on a touch sensing surface, said system 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 substantially 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 flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface;

a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes;

a digital processor and memory, wherein digital outputs of the digital processor are coupled to the first and second plurality of electrodes;

an analog front end coupled to the first and second plurality of electrodes;

an analog-to-digital converter (ADC) having at least one digital output coupled to the digital processor;

wherein

values of the self capacitances are measured for each of the first plurality of electrodes by the analog front end,

the values of the measured self capacitances are stored in the memory;

values of the mutual capacitances of the nodes of at least one of the first electrodes having at least one of the largest values of self capacitance are measured by the analog front end,

the values of the measured mutual capacitances are stored in the memory; and

the digital processor uses the stored self and mutual capacitance values for determining locations of the touches and the respective forces applied to the touch sensing surface.

15. The system as recited in claim 14, wherein the digital processor, memory, analog front end and ADC are provided by a digital device.

16. The system as recited in claim 14, wherein the digital processor, memory, analog front end and ADC are provided by at least one digital device.

19. The system as recited in claim 14, wherein the flexible electrically conductive cover comprises a flexible metal substrate.

20. The system as recited in claim 14, wherein the flexible electrically conductive cover comprises a flexible non-metal substrate and an electrically conductive coating on a surface thereof.

21. The system as recited in claim 14, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Indium Tin Oxide (ITO) on a surface of the flexible substrate.

22. The system as recited in claim 14, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Antimony Tin Oxide (ATO) on a surface of the flexible substrate.