Temperature Compensating Transparent Force Sensor Having a Flexible Substrate

• US 20160147353A1
• Filed: 06/03/2015
• Published: 05/26/2016
• Est. Priority Date: 01/13/2014
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Filiz, Sinan, Pedder, James E., Ogata, Charley T., Smith, John Stephen, Patel, Dhaval Chandrakant, Choi, Shin John, Huppi, Brian Q., Butler, Christopher J., Grunthaner, Martin P.
• Application Number:
  US14/729,769
• Publication Number:
  US 20160147353A1
• Time in Patent Office: Days
• CPC Class Codes: G01L 1/005 by electrical means and not provided for in G01L1/06 - G01L1/22
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• 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 2203/04111 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 Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An optically transparent force sensor element is compensated for effects of environment by comparing a force reading from a first force-sensitive component with a second force-sensitive components. The first and second force-sensitive components disposed on opposite sides of a flexible substrate within a display stack.

Claims

1. An optically transparent force sensor comprising:

a force-receiving layer;

a substrate disposed below the force-receiving layer and formed from an optically transparent material

a first force-sensitive component disposed on a first side of the substrate and formed from an optically transparent, strain-sensitive material; and

a second force-sensitive component disposed on a second side of the substrate that is opposite to the first side, wherein the second force-sensitive component is formed from the optically transparent, strain-sensitive material.

2. The force sensor of claim 1, further comprising:

sensor circuitry that is operatively coupled to the first force-sensitive component and the second force-sensitive component, wherein

the sensor circuitry is configured to measure a relative difference between an electrical response of the first and second force-sensitive components in response to a force of a touch on the force-receiving layer, and compute a temperature-compensated force estimate using the relative difference.

3. The force sensor of claim 1, wherein the substrate is configured to conduct heat between the first force-sensitive component and the second force-sensitive component to achieve a substantially uniform temperature distribution.

4. The force sensor of claim 1, wherein the substrate is disposed below a display element of an electronic device.

5. The force sensor of claim 1, wherein the substrate is disposed between a cover and a display element of an electronic device.

6. The force sensor of claim 1, wherein the first force-sensitive component is placed in compression in response to a force of a touch on the force-receiving layer, and the second force-sensitive component is placed in tension in response to the force of the touch.

7. The force sensor of claim 1, further comprising:

a first array of rectilinear force-sensitive components including the first force-sensitive component; and

a second array of rectilinear force-sensitive components including the second force-sensitive component.

8. The force sensor of claim 1, wherein the force-receiving layer is a cover of a display of a device and is formed from a glass material.

9. The force sensor of claim 1, wherein the first and second force-sensitive components have substantially identical temperature coefficients of resistance.

10. The force sensor of claim 1, wherein the substrate has a thermal conductivity of greater than 0.5 Watts per square meter per degree Kelvin.

11. The force sensor of claim 1, wherein the first and second force-sensitive components are formed from a piezoresistive material.

12. The force sensor of claim 1, wherein the first and second force-sensitive components are formed from one or more of:

a carbon nanotube material, graphene, a semiconductor material, a metal oxide material.

13. The force sensor of claim 1, wherein the first and second force-sensitive components are formed from a indium oxide material that is doped with Sn.

14. The force sensor of claim 13, wherein the indium oxide material doped with Sn to a proportion of less than 5%.

15. An electronic device having an optically transparent force sensor comprising:

a cover;

a substrate disposed below the cover and formed from an optically transparent material;

a first array of force-sensitive components disposed on a first side of the substrate and formed from an optically transparent, strain-sensitive material; and

a second array of force-sensitive components disposed on a second side of the substrate that is opposite to the first side, wherein the second array of force-sensitive components is formed from the optically transparent, strain-sensitive material

sensor circuitry that is configured to compare a relative electrical response between respective components of the first array of force-sensitive components and the second array of force-sensitive components, and configured to compute a temperature-compensated force estimate.

16. The electronic device of claim 15, further comprising:

a display element disposed above the first array of force-sensitive components.

17. The electronic device of claim 15, further comprising:

a display element disposed below the second array of force-sensitive components.

18. The electronic device of claim 15, wherein the first array of force-sensitive components includes a subset of edge force-sensitive components positioned along an edge of the first array, wherein the edge force-sensitive components are formed from traces that are oriented along a direction that is substantially perpendicular to the edge.

19. The electronic device of claim 15, wherein the first array of force-sensitive components includes a subset of corner force-sensitive components positioned at corners of the first array, wherein the corner force-sensitive components are formed from traces that are oriented along a diagonal direction.

20. The electronic device of claim 15, wherein the first array of force-sensitive components includes component having a first portion that includes traces that are substantially oriented along a first direction and a second portion that includes traces that are substantially oriented along an second direction, wherein the first direction is substantially perpendicular to the second direction.