Force Sensing Based on Capacitance Changes

• US 20150370396A1
• Filed: 03/15/2013
• Published: 12/24/2015
• Est. Priority Date: 12/14/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hotelling, Steven P., Richards, Peter W., Grunthaner, Martin P., Teil, Romain A., Ogata, Charley T., Wittenberg, Michael E.
• Granted Patent: US 10,168,814 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 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 device for electronic device. The force inputs may be detected by measuring changes in capacitance, as measured by surface flex of a device having a flexible touchable surface, causing flex at a compressible gap within the device. A capacitive sensor responsive to changes in distance across the compressible gap. The sensor can be positioned above or below, or within, a display element, and above or below, or within, a backlight unit. The device can respond to bending, twisting, or other deformation, to adjust those zero force measurements. The device can use measure of surface flux that appear at positions on the surface not directly the subject of applied force, such as when the user presses on a part of the frame or a surface without capacitive sensors.

Claims

13. An electronic device, comprising:

a first capacitive sensing element;

a ground layer capacitively coupled to the first capacitive sensing element and separated therefrom by a sensing gap;

a processing unit operatively coupled to the first capacitive sensing element;

wherein

the first capacitive sensing element and the ground layer are disposed to provide a measure of capacitance based on a force applied to a user input surface of the electronic device; and

the processing unit is configured to correlate the measure of capacitance to the force.

1. An electronic device, comprising:

a first capacitive sensing element; and

a second capacitive sensing element capacitively coupled to the first capacitive sensing element;

wherein

a sensing gap is disposed between the first capacitive sensing element and the second capacitive sensing element; and

the first and second capacitive sensing elements are disposed to provide a measure of capacitance based on a force applied to a user input surface of the electronic device.

2. The electronic device as in claim 1, wherein the force sensor is included in a display stack of the electronic device and the user input surface comprises a cover glass of the display stack.

3. The electronic device as in claim 2, wherein the display stack further includes one or more display circuits disposed below the cover glass, and wherein the first and second capacitive sensing elements are disposed below the one or more display circuits.

4. The electronic device as in claim 3, wherein the display stack further includes a back light unit disposed between the first and second capacitive sensing elements.

5. The electronic device as in claim 4, further including a compressible gap disposed between the first and second capacitive sensing elements.

6. The electronic device as in claim 4, further including a compressible gap disposed above the one or more display circuits.

7. The electronic device as in claim 4, further including a compressible gap disposed below at least a portion of the one or more display circuits.

8. The electronic device as in claim 3, further including an adhesive layer disposed between the cover glass and the one or more display circuits.

9. The electronic device as in claim 1, further including a support structure disposed between the first and second capacitive sensing elements.

10. The electronic device as in claim 1, wherein the first or the second capacitive sensing element is included in a flexible substrate.

11. The electronic device as in claim 10, wherein the flexible substrate includes a shield.

12. The electronic device as in claim 1, the force sensor further including a piezoelectric film.

14. The electronic device as in claim 13, wherein the force sensor is included in a display stack of the electronic device and the user input surface comprises a cover glass of the display stack.

15. The electronic device as in claim 14, wherein the display stack further includes one or more display circuits disposed below the cover glass, and wherein the first capacitive sensing element and the ground layer are disposed below the one or more display circuits.

16. The electronic device as in claim 15, wherein the display stack further includes a back light unit disposed between the first capacitive sensing element and the ground layer.

17. The electronic device as in claim 16, further including a compressible gap disposed between the first capacitive sensing element and the ground layer.

18. The electronic device as in claim 16, further including a compressible gap disposed below at least a portion of the one or more display circuits.

19. The electronic device as in claim 15, further including an adhesive layer disposed between the cover glass and the one or more display circuits.

20. The electronic device as in claim 13, further including a support structure disposed between the first capacitive sensing element and the ground layer.

21. The electronic device as in claim 13, wherein the first capacitive sensing element is included in a flexible substrate.

22. The electronic device as in claim 21, wherein the flexible substrate includes a shield.

23. The electronic device as in claim 13, the force sensor further including a piezoelectric film.

17-1. The electronic device as in claim 16, further including a compressible gap disposed above the one or more display circuits.

24. A method for determining an amount of force applied to a user input surface in an electronic device, comprising:

measuring a capacitance between a first capacitive sensing element and a second capacitive sensing element based on the applied force to the user input surface;

correlating the measured capacitance to the amount of force applied to the user input surface.