Pressure compensation for force-sensitive touch screen

• US 10,139,975 B2
• Filed: 12/23/2016
• Issued: 11/27/2018
• Est. Priority Date: 09/23/2016
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Shutzberg, Julian Kevin, Monkowski, Adam, Gowreesunker, Baboo
• Primary Examiner(s): Sherman, Stephen G
• Application Number:
  US15/390,219
• Publication Number:
  US 20180088702A1
• Time in Patent Office: 704 Days
• CPC Class Codes: G06F 1/1656 Details related to functional adaptations of the enclosure, e.g. to provide protection against EMI, shock, water, or to host detachable peripherals like a mouse or removable expansions units like PCMCIA cards, or to provide access to internal components for maintenance or to removable storage supports like CDs or DVDs, or to mechanically mount accessories mounting of accessories to a computer display G06F1/1607; display hoods G06F1/1603; cooling arrangements for portable computers G06F1/203
• 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 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• 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 3/0445 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

Pressure compensation can be used to improve performance of force-sensitive touch screens. Changes in pressure, particularly transient, internal pressure changes in an electronic device due to an object applying force to a touch screen of the electronic device, can degrade force sensing performance of the touch screen. For example, when a finger presses a force-sensitive touch screen of a sealed electronic device, the applied force can increase internal pressure of the sealed electronic device until internal pressure can equalize. The increased internal pressure can cause a normal force to oppose the deflection of the touch screen, resulting in inaccurate force measurements of applied user force. In some examples, an electronic device including a force-sensitive touch screen can include a pressure sensor configured to measure internal pressure of the electronic device. The measured pressure can be used to compensate the amount of force measured by the force sensor.

Claims

1. An electronic device comprising:

a force-sensitive surface comprising;

one or more force sensors configured to measure an amount of force applied to the force-sensitive surface by an object touching the force-sensitive surface; and

a pressure sensor coupled proximate to the one or more force sensors and configured to measure an internal pressure of the electronic device associated with one or more force measurements by the one or more force sensors; and

one or more processors coupled to the one or more force sensors and capable of;

compensating the amount of force measured by the one or more force sensors based on the internal pressure associated with the one or more force measurements by the one or more force sensors.

2. The electronic device of claim 1, wherein the one or more force sensors are capacitive force sensors including one or more first electrodes and one or more second electrodes, wherein a change in a gap between the one or more first electrodes and the one or more second electrodes due to the amount of applied force changes a capacitance formed between the one or more first electrodes and the one or more second electrodes.

3. The electronic device of claim 2, wherein:

the force-sensitive surface further comprises one or more touch sensors configured to detect the object touching the surface; and

the one or more processors are capable of compensating the amount of force in response to detecting the object touching the surface.

4. The electronic device of claim 3, wherein in response to detecting the object touching the surface, an internal pressure baseline is updated.

5. The electronic device of claim 1, wherein compensating the amount of force measured by the one or more force sensors based on the internal pressure associated with the one or more force measurements by the one or more force sensors comprises:

determining a measured gap based on a capacitance formed between one or more first electrodes and one or more second electrodes of the one or more force sensors;

determining an estimated gap associated with a pressure change introduced into the electronic device by the object touching the surface based on the internal pressure associated with the one or more force measurements by the one or more force sensors;

determining a pressure compensated gap by subtracting the estimated gap associated with the pressure change from the measured gap.

6. The electronic device of claim 5, wherein compensating the amount of force measured by the one or more force sensors based on the internal pressure associated with the one or more force measurements by the one or more force sensors comprises:

determining the compensated amount of force based on the pressure compensated gap.

7. The electronic device of claim 5, wherein the one or more processors are further capable of tracking a baseline internal pressure, and wherein determining the estimated gap associated with the pressure change comprises subtracting the baseline internal pressure from the internal pressure measured by the pressure sensor to determine the pressure change.

8. The electronic device of claim 5, further comprising:

a motion sensor configured to measure motion of the electronic device;

wherein the one or more processors are capable of;

determining an estimated gap associated with a motion change introduced into the electronic device by movement of the electronic device based on the measured motion of the electronic device;

determining a pressure and motion compensated gap by subtracting the estimated gap associated with the motion change from the pressure compensated gap; and

determining the compensated amount of force based on the pressure and motion compensated gap.

9. The electronic device of claim 5, wherein the estimated gap associated with the pressure change is determined by applying a pressure compliance parameter to the pressure change.

10. A method for compensating force measurements, the method comprising:

measuring, with a force sensor, an amount of force applied to a force-sensitive surface by an object touching the force-sensitive surface;

measuring an internal pressure of an electronic device associated with one or more force measurements by the force sensor; and

compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor.

11. The method of claim 10, further comprising:

tracking a baseline internal pressure associated with the force sensor; and

determining a change in pressure associated with the one or more force measurements by the force sensor by subtracting the baseline internal pressure from the measured internal pressure;

wherein compensating the amount of force measured by the force sensor is based on the change in pressure associated with the one or more force measurements by the force sensor.

12. The method of claim 10, wherein compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor comprises:

determining a measured gap based on a capacitance formed between one or more first electrodes and one or more second electrodes of the force sensor;

determining an estimated gap associated with a pressure change introduced into the electronic device by the object touching the surface based on the internal pressure associated with the one or more force measurements by the force sensor;

determining a pressure compensated gap by subtracting the estimated gap associated with the pressure change from the measured gap.

13. The method of claim 12, wherein compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor comprises:

determining the compensated amount of force based on the pressure compensated gap.

14. The method of claim 12, further comprising:

determining an estimated gap associated with a motion change associated with the force sensor;

determining a pressure and motion compensated gap by subtracting the estimated gap associated with the motion change from the pressure compensated gap; and

determining the compensated amount of force based on the pressure and motion compensated gap.

15. The method of claim 12, wherein the estimated gap associated with the pressure change is determined by applying a pressure compliance parameter to the pressure change.

16. A non-transitory computer readable storage medium storing instructions, which when executed by an electronic device including one or more processors, cause the one or more processors to perform a method for compensating force measurements, the method comprising:

measuring, with a force sensor, an amount of force applied to a force-sensitive surface by an object touching the force-sensitive surface;

measuring an internal pressure of the electronic device associated with one or more force measurements by the force sensor; and

compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor.

17. The non-transitory computer readable storage medium of claim 16, the method further comprising:

tracking a baseline internal pressure associated with the force sensor; and

determining a change in pressure associated with the one or more force measurements by the force sensor by subtracting the baseline internal pressure from the measured internal pressure;

wherein compensating the amount of force measured by the force sensor is based on the change in pressure associated with the one or more force measurements by the force sensor.

18. The non-transitory computer readable storage medium of claim 16, wherein compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor comprises:

determining a measured gap based on a capacitance formed between one or more first electrodes and one or more second electrodes of the force sensor;

determining an estimated gap associated with a pressure change introduced into the electronic device by the object touching the surface based on the internal pressure associated with the one or more force measurements by the force sensor;

determining a pressure compensated gap by subtracting the estimated gap associated with the pressure change from the measured gap.

19. The non-transitory computer readable storage medium of claim 18, wherein compensating the amount of force measured by the force sensor based on the internal pressure associated with the one or more force measurements by the force sensor comprises:

determining the compensated amount of force based on the pressure compensated gap.

20. The non-transitory computer readable storage medium of claim 18, wherein the estimated gap associated with the pressure change is determined by applying a pressure compliance parameter to the pressure change.