Piezo Based Force Sensing

• US 20160306481A1
• Filed: 10/28/2014
• Published: 10/20/2016
• Est. Priority Date: 10/28/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Shahpamia, Shahrooz, Filiz, Sinan, Huppi, Brian Q., Butler, Christopher J., Grunthaner, Martin P., Kang, Sunggu, Wang, Kai
• Granted Patent: US 10,120,478 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 1/16 using properties of piezoelectric 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 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 3/04144 using an array of force sensing means position sensing using the local deformation of sensor cells G06F3/0447
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/964 Piezoelectric touch switches
• CPC Class Codes: H03K 17/9643 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2217/96031 Combination of touch switch and LC display
• CPC Class Codes: H03K 2217/960735 characterised by circuit details
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches
• CPC Class Codes: H10N 30/302 Sensors

Abstract

Systems for detecting an amount and/or location of a force applied to a device using a piezoelectric film are provided. One example system can include a transparent piezoelectric film for generating an electric charge in response to a deformation of the film. Electrodes positioned on opposite surfaces of the piezoelectric film can be used to detect the generated electric charge and determine an amount and/or location of force applied to the film based on the generated electric charge. In another embodiment, the system can include a capacitive touch sensor for determining a location of a touch event on the device.

Claims

1. A system comprising:

a cover material;

a piezoelectric film operably coupled to the cover material;

a first set of coplanar electrodes coupled to a first surface of the piezoelectric film;

a second set of coplanar electrodes coupled to a second surface of the piezoelectric film; and

;

a sense circuitry operable to detect an electric charge generated by the piezoelectric film in response to a deformation of the piezoelectric film;

wherein

at least one of the first and second sets of coplanar electrodes is patterned; and

the sense circuitry is further operative to estimate a force exerted on the cover material from the electric charge.

2. The system of claim 1, wherein the piezoelectric film comprises a transparent film.

3. The system of claim 1, further comprising a display coupled to the piezoelectric film.

4. The system of claim 3, wherein the display is coupled to the piezoelectric film by a first layer of optically clear adhesive, and wherein the piezoelectric film is coupled to the cover material by a second layer of optically clear adhesive.

5. The system of claim 1, wherein:

the first set of coplanar electrodes forms a first pattern;

the second set of coplanar electrodes forms a second pattern; and

the first and second patterns are different.

6. The system of claim 1, wherein the first set of electrodes comprises a first sheet of conductive material coupled to ground, and wherein the second set of electrodes comprises a second sheet of conductive material coupled to the sense circuitry.

7. The system of claim 1, wherein:

the sense circuitry comprises a plurality of sense circuits;

the first set of coplanar electrodes comprises a sheet of conductive material coupled to ground; and

the second set of coplanar electrodes comprises a plurality of discrete electrodes, each discrete electrode coupled to a different sense circuit of the plurality of sense circuits.

8. The system of claim 1, wherein:

the sense circuitry comprises a plurality of sense circuits;

the first set of coplanar electrodes comprises a first plurality of discrete electrodes, each discrete electrode of the first plurality of discrete electrodes coupled to ground; and

the second set of coplanar electrodes comprises a second plurality of discrete electrodes, each discrete electrode of the second plurality of discrete electrodes coupled to a different sense circuit of the plurality of sense circuits.

9. The system of claim 1, wherein:

the first set of coplanar electrodes comprises a plurality of rows of conductive material; and

the second set of electrodes comprises a plurality of columns of conductive material.

10. The system of claim 9, wherein the plurality of rows of conductive material is coupled to ground, and wherein the plurality of columns of conductive material is coupled to the sense circuitry.

11. The system of claim 1, wherein:

The piezoelectric film is located on a first side of a display;

a third set of electrodes is located on a second side of a display;

a fourth set of electrodes is separate from the third set of electrodes and positioned further from the display than the third set of electrodes;

wherein

the third and fourth sets of electrodes are operably coupled to the cover material and closer to the cover material than the first and second sets of electrodes.

12. A system comprising:

a first piezoelectric film;

a second piezoelectric film coupled to the first piezoelectric film;

a cover material coupled to the second piezoelectric film by a first layer of adhesive;

a first set of electrodes coupled to the first piezoelectric film;

a second set of electrodes coupled between the first and second piezoelectric films;

a third set of electrodes coupled between the second piezoelectric film and the cover material; and

sense circuitry operable to detect an electric charge generated by the first and second piezoelectric films in response to a deformation of the piezoelectric films and determine an exerted force based on the electric charge.

13. The system of claim 12, further comprising

a display coupled to the first piezoelectric film by a second layer of adhesive.

14. The system of claim 12, wherein:

the first set of electrodes comprises a plurality of columns of conductive material;

the second set of electrodes comprises a sheet of conductive material; and

the third set of electrodes comprises a plurality of rows of conductive material.

15. The system of claim 12, wherein:

the first set of electrodes comprises a plurality of rows of conductive material;

the second set of electrodes comprises a sheet of conductive material; and

the third set of electrodes comprises a plurality of columns of conductive material.

16. A system comprising:

a piezoelectric film;

a touch sensor coupled to the piezoelectric film by a first layer of adhesive;

a cover material coupled to the second piezoelectric film by a second layer of adhesive;

a first set of electrodes coupled to the piezoelectric film;

a second set of electrodes coupled between the piezoelectric film and the touch sensor; and

sense circuitry operable to detect an electric charge generated by the piezoelectric film in response to a deformation of the piezoelectric film and output an estimated force based on the electric charge.

17. The system of claim 16, further comprising a display coupled to the piezoelectric film by a second layer of adhesive.

18. The system of claim 16, wherein the touch sensor comprises a plurality of drive electrodes and a plurality of sense electrodes.

19. The system of claim 16, wherein the first set of electrodes comprises a first sheet of conductive material, and wherein the second set of electrodes comprises a second sheet of conductive material.

20. The system of claim 19, wherein the first sheet of conductive material is coupled to ground, and wherein the second sheet of conductive material is coupled to the sense circuitry.

21. The system of claim 19, wherein the first sheet of conductive material is coupled to the sense circuitry, and wherein the second sheet of conductive material is coupled to ground.

22. The system of claim 16, wherein:

the sense circuitry comprises a plurality of sense circuits;

the first set of electrodes comprises a sheet of conductive material coupled to ground; and

the second set of electrodes comprises a plurality of discrete electrodes, each discrete electrode coupled to a different sense circuit of the plurality of sense circuits.