Detecting applied forces on a display

• US 10,061,428 B2
• Filed: 06/30/2016
• Issued: 08/28/2018
• Est. Priority Date: 06/30/2016
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Shepelev, Petr, Park, Byunghwee
• Primary Examiner(s): Moon, Patrick
• Application Number:
  US15/199,307
• Publication Number:
  US 20180004336A1
• Time in Patent Office: 789 Days
• Field of Search: None
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2201/07 buffer layer
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements
• CPC Class Codes: G06F 2203/04101 2.5D-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 and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 2203/04102 Flexible digitiser, i.e. constructional details for allowing the whole digitising part of a device to be flexed or rolled like a sheet of paper
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• 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 3/0412 Digitisers structurally integrated in a display
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

The input devices described herein include force sensor electrodes that use capacitive sensing to measure the force with which an input object (e.g., a finger or stylus) presses down on the input device. To measure this force, the input device includes a compressible layer disposed between a backlight of a display in the input device and a cover window of the display. In one embodiment, the compressible layer is disposed between the backlight and a transparent thin-film transistor (TFT) layer in the display. In one embodiment, the compressible layer includes an air gap which has a thickness defined by adhesive material disposed on at least two edges of the display.

Claims

1. An input device, comprising:

a transparent thin-film transistor (TFT) layer;

a backlight;

a first compressible layer disposed between the TFT layer and the backlight;

a plurality of force sensor electrodes disposed on a first side of the first compressible layer, wherein the plurality of force sensor electrodes is disposed between the first compressible layer and a cover window;

a device housing, wherein a conductive grounding layer forms at least a portion of the device housing, wherein the conductive grounding layer is disposed on a second side of the first compressible layer opposite the first side; and

a processing system configured to;

perform absolute capacitive sensing by modulating the plurality of force sensor electrodes to acquire a plurality of capacitive measurements using the plurality of force sensor electrodes when the portion of the device housing that includes the conductive grounding layer is electrically grounded, wherein the plurality of capacitive measurements is affected by compression of the first compressible layer by an input object pressing on the cover window; and

determine at least one force measurement of the input object based on the plurality of capacitive measurements.

2. The input device of claim 1, wherein the plurality of force sensor electrodes is disposed on a common layer, wherein the first compressible layer is between the common layer and the backlight.

3. The input device of claim 2, wherein the input device comprises:

a liquid crystal material layer, wherein the common layer is between the liquid crystal material layer and the first compressible layer.

4. The input device of claim 1, wherein the first compressible layer comprises an air gap.

5. The input device of claim 4, wherein a thickness of the air gap is defined by an adhesive material spacing the backlight and the TFT layer.

6. The input device of claim 1 further comprising:

a second compressible layer disposed between the backlight and the device housing, wherein the second compressible layer faces a first side of the backlight that is opposite of a second side of the backlight facing the first compressible layer.

7. The input device of claim 6, wherein the second compressible layer is thicker than the first compressible layer.

8. The input device of claim 6, wherein the second compressible layer comprises a compressible solid material while the first compressible layer comprises an air gap.

9. The input device of claim 1, wherein the plurality of force sensor electrodes comprise:

a plurality of capacitive sensor electrodes, wherein the processing system is configured to;

determine a location of the input object in a sensing region using the capacitive sensor electrodes.

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

performing absolute capacitive sensing by modulating a plurality of force sensor electrodes of the input device to acquire, when grounding a portion of a device housing forming a conductive grounding layer, a plurality of capacitive measurements, wherein the plurality of capacitive measurements is affected by compression of a first compressible layer in the input device when an input object presses on a cover window, wherein the first compressible layer is disposed between a transparent thin-film transistor (TFT) layer and a backlight in the input device, wherein the plurality of force sensor electrodes is disposed between the first compressible layer and the cover window, and wherein the plurality of force sensor electrodes is disposed on a first side of the first compressible layer and the conductive grounding layer is disposed on a second side of the first compressible layer opposite the first side; and

determining force measurements corresponding to the input object based on the plurality of capacitive measurements.

11. The method of claim 10, wherein the plurality of force sensor electrodes is disposed on a common layer, wherein the first compressible layer is between the common layer and the backlight.

12. The method of claim 11, wherein the input device comprises:

a liquid crystal material layer, wherein the common layer is between the liquid crystal material layer and the first compressible layer.

13. The method of claim 10, wherein the first compressible layer comprises an air gap.

14. The method of claim 13, wherein a thickness of the air gap is defined by an adhesive material spacing the backlight and the TFT layer.

15. The method of claim 10, wherein the input device comprises:

a second compressible layer disposed between the backlight and the device housing, and wherein the second compressible layer faces a first side of the backlight that is opposite of a second side of the backlight facing the first compressible layer.

16. A display comprising:

a liquid crystal material layer;

a first layer comprising a plurality of force sensor electrodes; and

a transparent thin-film transistor (TFT) layer, wherein the first layer is disposed between the liquid crystal material layer and the TFT layer;

a backlight;

a compressible layer disposed between the TFT layer and the backlight, wherein the plurality of force sensor electrodes is disposed on a first side of the compressible layer, and wherein the plurality of force sensor electrodes is disposed between the compressible layer and a cover window; and

a device housing, wherein a conductive grounding layer forms at least a portion of the device housing, wherein the conductive grounding layer is disposed on a second side of the compressible layer opposite the first side,

wherein, when performing absolute capacitive sensing by modulating the plurality of force sensor electrodes, the plurality of force sensor electrodes is configured to generate capacitive signals affected by compression of the compressible layer in response to force applied by an input object on the cover window while the portion of the device housing that includes the conductive grounding layer is electrically grounded.

17. The display of claim 16, wherein the compressible layer is between the first layer and the backlight, and wherein the compressible layer is between the liquid crystal material layer and the backlight.

18. The display of claim 16, wherein the compressible layer comprises an air gap.

19. The display of claim 18, wherein a thickness of the air gap is defined by an adhesive material spacing the backlight and the TFT layer.