U.S. patent application number 14/972055 was filed with the patent office on 2016-04-14 for force determination employing sheet sensor and capacitive array.
The applicant listed for this patent is Apple Inc.. Invention is credited to Christopher J. Butler, Shin John Choi, Sinan Filiz, Martin P. Grunthaner, Steven J. Martisauskas, Charley T. Ogata, Christian M. Sauer, John Stephen Smith.
Application Number | 20160103544 14/972055 |
Document ID | / |
Family ID | 52595450 |
Filed Date | 2016-04-14 |
United States Patent
Application |
20160103544 |
Kind Code |
A1 |
Filiz; Sinan ; et
al. |
April 14, 2016 |
Force Determination Employing Sheet Sensor and Capacitive Array
Abstract
A device configured to sense a touch on a surface of the device.
The device includes a cover and a force-sensing structure disposed
below the cover. The force-sensing structure may be positioned
below a display and used in combination with other force-sensing
elements to estimate the force of a touch on the cover of a
device.
Inventors: |
Filiz; Sinan; (Cupertino,
CA) ; Grunthaner; Martin P.; (Cupertino, CA) ;
Smith; John Stephen; (Cupertino, CA) ; Ogata; Charley
T.; (Cupertino, CA) ; Sauer; Christian M.;
(Cupertino, CA) ; Choi; Shin John; (Cupertino,
CA) ; Butler; Christopher J.; (Cupertino, CA)
; Martisauskas; Steven J.; (Cupertino, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
52595450 |
Appl. No.: |
14/972055 |
Filed: |
December 16, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14727601 |
Jun 1, 2015 |
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14972055 |
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14619807 |
Feb 11, 2015 |
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14727601 |
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62047645 |
Sep 8, 2014 |
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61941988 |
Feb 19, 2014 |
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61939252 |
Feb 12, 2014 |
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Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 2203/04105
20130101; G06F 3/044 20130101; G06F 3/0416 20130101; G06F 3/0414
20130101; G06F 2203/04106 20130101; G06F 3/0412 20130101 |
International
Class: |
G06F 3/041 20060101
G06F003/041; G06F 3/044 20060101 G06F003/044 |
Claims
1-20. (canceled)
21. An electronic device comprising: a cover; a transparent touch
sensor disposed below the cover and configured to detect a location
of a touch on the cover; a display disposed below the cover; a
force-sensing structure disposed below the cover and around a
perimeter of the display and comprising: an upper capacitive
electrode; a lower capacitive electrode disposed below the upper
capacitive electrode; a compressible element disposed between the
upper and lower capacitive electrodes; wherein the force-sensing
structure is configured to produce an output that corresponds to an
amount of force applied by the touch.
22. The electronic device of claim 21, wherein: the electronic
device further comprises a housing defining an opening in which the
cover is positioned; and the force-sensing structure forms a gasket
between the housing and the cover.
23. The electronic device of claim 22, wherein: the housing defines
a bezel having a shelf surrounding the opening; and the
force-sensing structure is positioned between the shelf and a
perimeter portion of the cover.
24. The electronic device of claim 21, wherein: the force-sensing
structure is a first force-sensing structure; and the electronic
device further comprises: a second force-sensing structure disposed
below the display, wherein the second force-sensing structure
comprises: an upper capacitive layer; a lower capacitive layer
disposed below the upper capacitive layer; and a compressible layer
disposed between the upper and lower capacitive layers; and a plate
affixed to and supporting the second force-sensing structure.
25. The electronic device of claim 24, wherein an air gap is
located below the display and above the second force-sensing
structure.
26. The electronic device of claim 21, wherein the force-sensing
structure comprises: a first force-sensing segment disposed along a
first edge of the periphery of the cover; and a second
force-sensing segment disposed along a second edge of the periphery
of the cover; and the electronic device further comprises
force-sensing circuitry operatively coupled to the first and second
force-sensing segments and is configured to detect changes in
capacitive coupling due to deflection of the first and second
force-sensing segments and to produce a signal that corresponds to
a magnitude the touch force on the cover.
27. The electronic device of claim 21, wherein the force-sensing
structure comprises: a first force-sensing segment disposed along a
first edge of the periphery of the transparent touch sensor, the
electronic device further comprising: a second force-sensing
segment disposed along a second edge of the periphery of the cover;
a third force-sensing segment disposed along a third edge of the
periphery of the cover; and a fourth force-sensing segment disposed
along a fourth edge of the periphery of the cover, wherein the
second, third, and fourth force-sensing segments each comprise an
upper capacitive electrode, a lower capacitive electrode, and a
compressible element disposed between the upper and lower
capacitive electrodes.
28. The electronic device of claim 21, wherein: the electronic
device further comprises: an enclosure having an opening; and a
display element disposed within the opening; and the compressible
element comprises a compliant sheet having a center opening through
which the display is positioned.
29. The electronic device of claim 28, wherein the compliant sheet
includes multiple segmented compressible elements that define the
opening.
30. An electronic device comprising: a cover; a first force-sensing
structure disposed along a first edge of the cover and comprising a
first pair of capacitive elements separated by a compressible
layer; and a second force-sensing structure disposed along a second
edge of the cover and comprising a second pair of capacitive
elements separated by the compressible layer.
31. The electronic device of claim 30, further comprising: a third
force-sensing structure disposed along a third edge of the cover
and comprising a third pair of capacitive elements separated by the
compressible layer; and a fourth force-sensing structure disposed
along a fourth edge of the cover and comprising a fourth pair of
capacitive elements separated by the compressible layer.
32. The electronic device of claim 30, further comprising a housing
defining and opening having a shelf; wherein: the cover is
positioned within the opening; and the first and second
force-sensing structures are positioned along the shelf of the
housing.
33. The electronic device of claim 30, wherein the compressible
layer includes multiple segmented compressible elements.
34. An electronic device comprising: a housing defining an opening;
a cover disposed within the opening; a transparent touch sensor
disposed below the cover and configured to detect a location of a
touch on the cover; a strain-sensitive layer disposed below the
cover and configured to produce an output that corresponds to a
deflection of the cover; and a force-sensing structure disposed
below the strain-sensitive layer, wherein an air gap is located
between the strain-sensitive layer and the sheet sensor.
35. The electronic device of claim 34, further comprising a support
structure fixed relative to the housing and supporting the
force-sensing structure.
36. The electronic device of claim 34, wherein: the
strain-sensitive layer comprises a capacitive electrode; the
force-sensing structure comprises an upper capacitive layer and a
lower capacitive layer separated by a compressible layer; and the
capacitive electrode of the strain-sensitive layer is configured to
capacitively couple to the upper capacitive layer of the
force-sensing structure.
37. The electronic device of claim 36, wherein: the electronic
device further comprises sensing circuitry that is operatively
coupled to the capacitive layer and the force-sensing structure;
and the sensing circuitry is configured to estimate the force of a
touch on the cover based on a change in mutual capacitance between
the capacitive electrode of the strain-sensitive layer and the
upper capacitive layer of the force-sensing structure.
38. The electronic device of claim 37, wherein the sensing
circuitry is configured to: obtain a first capacitance between the
upper capacitive layer and the lower capacitive layer of the
force-sensing structure; obtain a second capacitance between the
capacitive electrode of the strain-sensitive layer and the upper
capacitive layer of the force-sensing structure; and generate an
estimate of a force of a touch on the cover using the first and
second capacitances.
39. The electronic device of claim 34, further comprising: a
display disposed between the cover and the force-sensing structure;
and the air gap is located between the display and the
force-sensing structure.
40. The electronic device of claim 39, wherein: the air gap is
configured to at least partially collapse in response to a force of
a touch that exceeds a first threshold; and the first threshold is
less than a second threshold that corresponds to a maximum force
that can be detected by the strain-sensitive layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/619,807, filed Feb. 11, 2015, and titled
"Force Determination Employing Sheet Sensor and Capacitive Array,"
which claims priority to U.S. Provisional Patent Application No.
62/047,645, filed Sep. 8, 2014, and titled "Force Determination
Employing Sheet Sensors and Capacitive Array," U.S. Provisional
Patent Application No. 61/941,988, filed Feb. 19, 2014, and titled
"Force Determination Employing Sheet Sensors and Capacitive Array,"
and U.S. Provisional Patent Application No. 61/939,252, filed Feb.
12, 2014, and titled "Force Determination Employing Multiple
Force-Sensing Structures," the disclosure of each of which is
incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This application generally relates to systems and methods
sensing the force of a touch, and in particular to a capacitive
force sensor integrated with a device for detecting and measuring
the amount or magnitude of a touch applied to a surface of the
device.
BACKGROUND
[0003] Touch devices can be generally characterized as devices that
are capable of receiving touch input on the surface of the device.
The input may include the location of one or more touches on the
device, which may be interpreted as a command, gesture, or other
type of user input. In one example, touch input on a touch device
may be relayed to an a computing system and used to interpret user
interaction with a graphical user interface (GUI), including, for
example, selecting elements on a display, reorienting or
repositioning elements on a display, entering text, and user input.
In another example, touch input on a touch device may be relayed to
a computer system and used to interpret a user's interaction with
an application program. The user's interaction may include, for
example, the manipulation of audio, video, photographs,
presentations, text, and the like.
[0004] Typically, touch input on a touch device is limited to the
location of a touch on the device. However, in some cases, it may
be advantageous to also detect and measure the force of a touch
that is applied to the device. For example, it might be
advantageous for a user to be able to manipulate a
computer-generated object on a display in a first way using a
relatively light touch and, alternatively, interact with the object
a second way using a relatively heavy or sharper touch. By way of
example, it might be advantageous for a user to move a
computer-generated object on the display using a relatively light
touch and then, alternatively, select or invoke a command with
respect to the same computer using a relatively heavy or sharper
touch. More generally, it might be advantageous for the user to be
able to provide input in multiple ways depending on the force of
the touch. For example, a user may provide input that is
interpreted a first way for a light touch, a second way for a
medium touch, and a third way for a heavy touch, and so on.
Additionally, it might be advantageous for the user to be able to
provide an analog input using a varying amount of force. This type
of input may be useful for controlling, for example, a gas pedal on
a simulated car or a control surface of an airplane in a flight
simulator, or similar applications. It may be further advantageous
for the user to be able to provide input, such as simulated body
movements or otherwise, in a virtual reality (VR) simulation
(possibly with haptic feedback), or in an augmented reality
program. It might be further advantageous to use the force of a
touch to interpret the relative degree (e.g., force) and locations
of multiple touches that are provided to multiple user interface
objects or elements that are in use on a touch device at the same
time. For example, the force of a touch could be used to interpret
multiple touches due to a user pressing more than one element in an
application for playing a musical instrument. In particular, the
force of multiple touches may be used for interpreting multiple
touches by a user on the keys of a piano. Similarly, the force of
multiple touches can be used to interpret a user's multiple touches
in an application for controlling a motor vehicle (having separate
controls for accelerating, braking, signaling, and turning).
SUMMARY
[0005] This application provides techniques, which can be used to
measure or determine the amount or magnitude of force applied, and
changes in the amount or magnitude of force applied, by a user
contacting a touch device (such as a touch-sensitive surface, one
example of which is a touch display), or other pressure-sensitive
input elements (such as a virtual analog control or keyboard), or
other input device. These techniques can be incorporated into
various devices using touch recognition, touch elements of a GUI,
and touch input or manipulation in an application program, such as
touch devices, touch pads, and touch screens. This application also
provides systems and techniques that can be used to measure or
determine the amount or magnitude of force applied, and changes in
the amount or magnitude of force applied, by the user when
contacting a touch device, and in response thereto, provide
additional functions available to a user of a touch device.
[0006] Certain embodiments described herein are directed to a force
sensor, also referred to as a "force-sensing structure" or a "force
sensitive sensor." The force sensor may be integrated with the
housing of an electronic device, one example of which is a touch
sensitive electrical device or simply a touch device. A sample
force sensor may include an upper portion and a lower portion
separated by a compressible element or by an air gap. The upper
portion may include an upper body connected to an upper capacitive
plate and the lower portion may include a lower body connected to a
lower capacitive plate. In some cases, the upper portion and the
lower portion form a capacitor that can be used to measure or
detect an amount or magnitude of applied force. The compressible
element is typically formed form a compliant or springy material.
In some cases, the compressible element is referred to as a
"deformable middle body," an intermediate element, or a
"compressible layer." In some cases, the force sensor includes
other force-sensing elements, such as a resistive strain gauge,
piezoelectric element, and the like.
[0007] Some example embodiments are directed to an electronic
device having a cover, a display positioned below the cover, and a
force-sensing structure disposed below the display. The
force-sensing structure may include an upper capacitive plate, a
compressible element disposed on one side of the upper capacitive
plate, and a lower capacitive plate disposed on a side of the
compressible element that is opposite the upper capacitive plate.
The force-sensing structure may also include a plate affixed to and
supporting the force-sensing structure. In some embodiments, the
electronic device also includes sensing circuitry that is
operatively coupled to the force-sensing structure. The sensing
circuitry may be configured to estimate the force of a touch on the
cover based on a change in capacitance between the upper capacitive
plate and the lower capacitive plate of the force-sensing
structure.
[0008] In some embodiments, the force-sensing structure is
separated from the display by a compliant layer including an air
gap. In some cases, the force-sensing structure is separated from
the display by a compliant layer comprised of compressible foam.
The force-sensing structure may be separated from the display by a
compliant layer comprised of an array of compliant pillars and an
optically transparent fluid.
[0009] In some embodiments, the electronic device also includes a
housing having a bezel surrounding the cover and a gasket disposed
in a gap between the cover and the bezel. The device may also
include an oleophobic coating disposed over at least a portion of
the gap.
[0010] Some example embodiments are directed to an electronic
device including a housing, a cover disposed within an opening of
the housing, and a strain-sensitive gasket disposed between the
cover and the housing along a perimeter of the cover. The device
may also include a force-sensing structure disposed below the
cover. The device may also include a plate fixed relative to the
housing and supporting the force-sensing structure. In some cases,
the strain-sensitive gasket includes a gasket upper capacitive
plate, a gasket lower capacitive plate, and a gasket compressible
element disposed between the gasket upper capacitive plate and the
gasket lower capacitive plate.
[0011] In some embodiments, the electronic device also includes a
display disposed between the cover and the force-sensing structure,
and a compressible layer comprising an air gap between the display
and the force-sensing structure. In some implementations, the air
gap of the compressible layer is configured to at least partially
collapse in response to a force of a touch that exceeds a first
threshold. The first threshold may be less than a second threshold
that corresponds to a maximum force that can be detected by the
strain-sensitive gasket.
[0012] In some embodiments, the electronic device also includes a
display disposed between the cover and the force-sensing structure,
and a compressible layer between the display and the force-sensing
structure. In some cases, the compressible layer may be configured
to at least partially collapse in response to a force of a touch
that exceeds a first threshold. The first threshold may be less
than a second threshold that corresponds to a maximum force that
can be detected by the strain-sensitive gasket.
[0013] In some embodiments, the force-sensing structure includes:
an upper capacitive plate, a lower capacitive plate; and a
compressible element disposed between the upper capacitive plate
and the lower capacitive plate. In some embodiments, the
force-sensing structure includes a strain gauge and/or a
piezoelectric element.
[0014] Some example embodiments are directed to an electronic
device including a cover, a capacitive sense layer positioned below
the cover, and a compressible layer below the capacitive sense
layer. In some embodiments, the compressible layer comprises an air
gap. The electronic device may also include a force-sensing
structure disposed below the compressible layer, which includes an
upper capacitive plate, a compressible element disposed on one side
of the upper capacitive plate, and a lower capacitive plate
disposed on a side of the compressible element that is opposite the
upper capacitive plate. Some embodiments include a plate positioned
below the force-sensing structure and supporting the force-sensing
structure.
[0015] In some embodiments, the electronic device includes a
display positioned below the cover. The device may also include a
backlight positioned below the display. The capacitive sense layer
may be disposed between the display and the backlight.
[0016] In some embodiments, the electronic device includes sensing
circuitry that is operatively coupled to the capacitive sense layer
and the force-sensing structure. The sensing circuitry may be
configured to estimate the force of a touch on the cover based on a
change in mutual capacitance between the capacitive sense layer and
the upper capacitive plate of the force-sensing structure. In some
embodiments, the sensing circuitry may be configured to obtain a
first capacitance between the upper capacitive plate and the lower
capacitive plate of the force sensing structure. The circuitry may
also be configured to obtain a second capacitance between the upper
capacitive plate and the capacitive sense layer. The circuitry may
also be configured to generate an estimate of a force of a touch on
the cover using the first and second capacitances.
[0017] While multiple embodiments are disclosed, including
variations thereof, still other embodiments of the present
disclosure will become apparent to those skilled in the art from
the following detailed description, which shows and describes
illustrative embodiments of the disclosure. As will be realized,
the disclosure is capable of modifications in various obvious
aspects, all without departing from the spirit and scope of the
present disclosure. Accordingly, the drawings and detailed
description are to be regarded as illustrative in nature and not
restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 depicts an example touch device.
[0019] FIG. 2A depicts a cross-sectional view taken along line 1-1
of FIG. 1, of an example touch device having a force-sensing
structure.
[0020] FIG. 2B depicts a cross-sectional view taken along line 1-1
of FIG. 1, of an example touch device having an alternative
force-sensing structure.
[0021] FIG. 3 depicts a cross-sectional view taken along line 2-2
of FIG. 2, of an example touch device having a force-sensing
structure.
[0022] FIG. 4 depicts a cross-sectional view taken along line 2-2
of FIG. 2, of an example touch device having a force-sensing
structure.
[0023] FIG. 5 depicts a cross-sectional view taken along line 2-2
of FIG. 2, of an example touch device having a force-sensing
structure.
[0024] FIG. 6 depicts a cross-sectional view of an embodiment of a
touch device having a capacitive force sensor.
[0025] FIG. 7 depicts another embodiment of a touch device having a
capacitive force sensor.
[0026] FIG. 8 depicts a cross sectional view of another embodiment
of a touch device having a capacitive force sensor.
[0027] FIG. 9 depicts an exemplary communication between a touch
I/O device and a computing system.
[0028] FIG. 10 depicts a schematic of a system including a force
sensitive touch device.
[0029] FIG. 11A depicts an example method of operation.
[0030] FIG. 11B depicts another example method of operation.
[0031] FIG. 12 depicts a force-sensitive structure having an
electrical connector tail.
[0032] FIG. 13 depicts a cross-sectional view of an electrical
connector tail.
[0033] FIG. 14 depicts an example method of manufacturing a
force-sensitive structure having an electrical connector tail.
[0034] FIG. 15A depicts a sample cross-section of another
force-sensitive structure incorporated into an electronic
device.
[0035] FIG. 15B depicts a sample cross-section of still another
force-sensitive structure incorporated into an electronic
device.
[0036] FIG. 15C depicts a sample cross-section of yet another
force-sensitive structure incorporated into an electronic
device.
[0037] FIGS. 15D-E depict a portion of the cross-section of FIG.
15C in greater detail.
[0038] FIG. 16 depicts a sample cross-section of an electronic
device incorporating two force-sensitive structures.
[0039] FIG. 17 depicts a sample cross-section of an electronic
device incorporating a multi-layered sheet force sensor, coupled
with a capacitive sensing array positioned in a display stack.
DETAILED DESCRIPTION
[0040] Generally, embodiments may take the form of an electronic
device capable of sensing force and distinguishing between multiple
different levels of force, beyond simple binary sensing. Some
embodiments may have an enclosure incorporating a force sensor
therein (e.g., a force-sensitive sensor, a force-sensing element,
or force-sensing structure). The force sensor may be incorporated
in, for example in a groove, cutout, or aperture formed in one or
more sidewalls or other surfaces of the device. The force-sensing
element may extend along an entire periphery, sidewall, or set of
sidewalls in certain embodiments. For example, the force sensor may
encircle an interior cavity formed within the device, or may
otherwise extend around an interior of the device. As force is
exerted on an exterior of the device, such as an upper surface, the
force sensor may detect the force and generate a corresponding
input signal to the device.
[0041] Some embodiments may incorporate multiple force sensors
spaced about a perimeter of the electronic device, rather than a
single force-sensing structure or element. Further, the multiple
force sensors need not form a continuous array or structure, but
may be discretely spaced from one another. The number of force
sensors may vary between embodiments, as may the spacing. Each
force sensor may sense a force exerted on an adjacent or nearby
surface within a certain region of the device. Thus, a force
exerted at a point that is between two underlying force sensors may
be sensed by both.
[0042] Generally, the force sensor or device may include one or
more capacitive plates, traces, flex, or the like that are
separated by a compressible element (e.g., a compliant member). As
a force is transmitted through the device enclosure and to the
force sensor, the compressible element may compress, thereby
bringing the capacitive plates closer together. The change in
distance between the capacitive plates may increase a measured
capacitance therebetween. A circuit may measure this change in
capacitance and output a signal that varies with the change in
capacitance. A processor, integrated circuit or other electronic
element may correlate the change in capacitance to a force exerted
on the enclosure, thereby facilitating the detection, measurement,
and use of force as an input to an electronic device. Although the
term "plate" may be used to describe the capacitive elements, it
should be appreciated that the capacitive elements need not be
rigid but may instead be flexible (as in the case of a trace or
flex).
1. TERMINOLOGY
[0043] The following terminology is exemplary, and not intended to
be limiting in any way.
[0044] The text "applied force", and variants thereof, generally
refers to the force of a touch applied to a surface of the device.
Generally, the degree, amount, or magnitude of the applied force
can be detected and measured using the techniques described herein.
The degree, amount, or magnitude of an applied force need not have
any particular scale. For example, the measure of applied force can
be linear, logarithmic, or otherwise nonlinear, and can be adjusted
periodically (or otherwise, such as aperiodically, or otherwise
from time to time) in response to one or more factors, either
relating to applied force, location of touch, time, or
otherwise.
[0045] The text "finger", and variants thereof, generally refers to
a user's finger, or other body part. For example and without
limitation, a "finger" can include any part of the user's finger or
thumb and any part of the user's hand. A "finger" may also include
any covering on the user's finger, thumb, or hand.
[0046] The text "touch," and variants thereof, generally refers to
the act of an object coming into contact with a surface of a
device. The object may include a user's finger, a stylus or other
pointing object. Example objects include, a hard stylus, a soft
stylus, a pen, finger, thumb or other part of the user's hand. A
"touch" typically has an applied force and a location that can
detected and measured using the techniques described herein.
[0047] After reading this document, those skilled in the art would
recognize that these statements of terminology would be applicable
to techniques, methods, physical elements, and systems (whether
currently known or otherwise), including extensions thereof
inferred or inferable by those skilled in the art after reading
this application. Likewise, it should be appreciated that any
dimensions set forth herein are meant to be examples only, and may
change from embodiment to embodiment.
2. FORCE-SENSITIVE DEVICE
[0048] In one embodiment, a force sensitive device and system can
include a cover glass element, such as a relatively transparent (in
most or all locations) substance capable of isolating circuitry or
other internal elements of the touch device from external objects.
The term "glass" refers to the relatively hard sheet-like qualities
of the material and does not limit the material of the cover glass
element to only glass materials. The cover glass element may be
made from a variety of materials including, for example, glass,
treated glass, plastic, treated plastic, and sapphire. In many
cases, the cover glass is transparent, however it is not necessary
that the cover glass be completely or even partially transparent.
The cover glass can be disposed in a substantially rectilinear
shape, such as to cover the circuit for the touch device and to
serve as a touch plate for the user. The cover glass may also be
formed in a variety of other shapes depending on the
application.
[0049] In some embodiments, the cover glass is integrated with or
attached to a transparent or non-transparent touch sensor that is
configured to detect the location of a touch. The transparent touch
sensor may be a capacitive touch sensor formed from one or more
arrays of transparent conductive lines. For example, the
transparent touch sensor may be a mutually capacitive touch sensor
formed from two arrays of transverse transparent conductive lines
operatively coupled to touch sensing circuitry. Such a transparent
touch sensor may be able to detect and track multiple touches on
the surface of the cover glass. The touches may include multiple
finger touches, multiple stylus touches, or a combination of
different types of touches on the cover glass. Other types of
transparent touch sensors may also be used, including, for example,
self-capacitive touch sensors, resistive touch sensors, and the
like.
[0050] In one embodiment, the cover glass element is coupled to a
frame or housing for the touch device, such as a case constructed
of metal, elastomer, plastic, a combination thereof, or some other
substance. In such cases, the frame for the touch device can
include a shelf or ledge on which the cover glass element is
positioned. The cover glass is typically positioned above the
circuitry for the touch device. For example, the frame can include
a shelf on which an edge of the cover glass element is positioned,
with the (or some of the) remainder of the cover glass element
positioned over the circuitry for the touch device.
[0051] In many of the embodiments described herein, a force sensor,
(e.g. a force-sensing structure, force-sensing element, or force
sensitive sensor), is positioned below the cover glass and the
shelf or ledge of the frame or housing. The force sensor typically
includes a compressible element and is configured to detect and
measure a relative displacement between the cover glass and the
frame or housing. As previously mentioned, the amount that the
cover glass is displaced can be used to estimate the applied force.
The following embodiments are directed to different techniques and
methods of detecting and measuring this displacement.
3. EXEMPLARY DEVICES HAVING A FORCE SENSOR
[0052] FIG. 1 depicts an exemplary device 100 that incorporates one
or more force-sensing structures, as described herein. With respect
to FIG. 1, the device 100 is depicted as a tablet computing device,
but it should be appreciated that it may also be any of a number of
other devices, including a mobile phone, portable computer,
wearable device, touch screen, and the like. The device 100 may
have an enclosure 102 including multiple sidewalls and a bezel 106.
In other embodiments, the device 100 may be flush-mounted into a
larger surface or enclosure and so the device may lack an
identifiable bezel or sidewall.
[0053] As shown in FIG. 1, the electronic device 100 includes an
electronic display, located beneath a cover glass 104, for
conveying graphical and/or textual information to the user. The
electronic display may include a liquid crystal display (LCD),
organic light omitting diode (OLED), or other electronic display
component. In some embodiments, the display may be omitted. For
example, the cover glass may be placed over a control button or
track pad that is not configured to convey graphical and/or textual
information to the user. (In such a case, the cover glass may not
be transparent.)
[0054] As shown in FIG. 1, the device includes multiple ports and
mechanisms for electrically and mechanically coupling the device to
external devices or elements. The input mechanisms, ports, and the
like may vary between versions, types and styles of the electronic
device 100. Accordingly, they are shown in FIG. 1 only as examples
of such devices and in sample positions.
[0055] FIG. 2A depicts a cross-sectional view taken along line 1-1,
shown in FIG. 1. The cross-sectional view depicts the interior of a
device 100 having one type of force-sensing structure. A central
portion of the enclosure 102 may enclosure electronic circuitry,
mechanical structures, and other internal elements. As shown in the
figure, a bezel 106 is formed around the perimeter of the device
100.
[0056] A ledge 202 may be formed along the perimeter of the bezel
106. The exact dimensions of the ledge 202 may vary between
embodiments. In this embodiment, the ledge 202 includes a width
configured to support the base of a force-sensing structure 200.
The base of the force-sensing structure 200 may abut and attach to
the top of the ledge 202 in certain embodiments. Likewise, as shown
in FIG. 2A, an inner edge of the force-sensing structure 200 may be
parallel and approximately aligned with an inner surface of the
bezel 106. In other embodiments, the inner edge of the
force-sensing structure 200 may be offset from an inner edge of the
bezel 106.
[0057] As shown in FIG. 2A, a single force-sensing structure 200
may encircle the entirety of the inner cavity of the enclosure 102.
That is, the force-sensing structure 200 may extend along the
entirety of the perimeter of the device and along the ledge 202.
Thus, it may be appreciated that the force-sensing structure 200
may be formed as a single unit or element.
[0058] FIG. 2B depicts an alternate cross-sectional view taken
along line 1-1, shown in FIG. 1. As shown in FIG. 2B, the device
100b includes an alternative force-sensing structure 200b. In the
alternative embodiment of FIG. 2B, multiple force-sensing
structures 200b may be placed at different locations along the
perimeter of the bezel 106. In this example, a force-sensing
structure 200b is placed at or near each edge of the bezel 106 of
the electronic device 100b. Additionally, a force-sensing structure
200c is placed at each of the corners of the bezel. Thus, in the
example device 100b shown in FIG. 2B, there are eight force-sensing
structures (200b, 200c).
[0059] With regard to FIG. 2B, it should be appreciated that more
or fewer force-sensing structures 200b may be used. For example,
three force-sensing structures 200b may be used and a location of a
force may be triangulated by comparing the outputs of each device.
Alternately, an array of more than four force-sensing structures
200b may be used in a device. Additionally, each of the
force-sensing structures shown in FIG. 2B may represent a number of
individual force-sensing structures in a linear or two-dimensional
array, for example. Accordingly, the number and positioning of the
various force-sensing structures 200b depicted in FIG. 2B is merely
exemplary and other variations are possible.
[0060] FIG. 3 depicts a cross-sectional view taken along 2-2 of the
electronic device 100, as shown in FIG. 2A. As shown in FIG. 3, the
physical relationship between the cover glass 104, bezel 106, and
force-sensing structure 300 is shown in more detail, although it
should be appreciated that the exact geometry, sizes, tolerances,
positions and the like may vary. As shown in FIG. 3, the
force-sensing structure 300 may be mounted or otherwise be
positioned beneath a portion of the cover glass 104. A display
element 304 may likewise be positioned beneath the cover glass 104.
In some embodiments, the force-sensing structure 300 may be
concealed from external view by an ink or print layer deposited on
the cover glass between the cover glass 104 and the force-sensing
structure 300. In other embodiments, the ink or print layer may be
omitted.
[0061] In some embodiments, the display element 304 may act as an
shield to electrically isolate the force-sensing structure from
other components within the electronic device. Likewise, a shield
may be formed on the ledge 202 and portion of the housing 102
adjacent the gap 302 in order to electrically isolate the
force-sensing structure 300 from external signals, or at least
reduce the impact of external noise on the force-sensing structure.
The shield layers may be deposited by physical vapor deposition, as
one non-limiting example. Further, any or all of the shield layers
may extend into the interior of the electronic device to connect to
a common or system ground. For example, the shield layer may extend
from the ledge down the interior wall of the enclosure 102 to a
system ground.
[0062] In certain embodiments, the ledge and/or portion of the
housing may themselves act as shielding structures, rather than
having any shield formed thereon. It should be appreciated that one
or more of the various shield layers/structures may be electrically
tied to one another in certain embodiments, although this is not
necessary.
[0063] As shown in FIG. 3, the bezel 106 is adjacent to the ledge
202, which is recessed from the surface of the bezel 106 and is
configured to support the force-sensing structure 300. As shown in
FIG. 3, a gap 302 may exist between the interior edge of the bezel
106 and the outer edge of the cover glass 104. The gap may allow
free movement of the cover glass 104 with respect to the enclosure
102.
[0064] In certain embodiments, a portion or all of the surfaces of
the gap 302 may be coated with an oleophobic material. The
oleophobic material may serve as a barrier against, or repel, oils,
dust, dirt and other similar materials from entering the gap 302
and/or impacting the force-sensing structure 300. In this fashion
the coating may serve to maintain operation of the force-sensing
structure over time. Coatings other than an oleophobic coating may
be used; other dust- and/or oil- and/or dirt-repellent coatings may
be used in different embodiments.
[0065] As shown in FIG. 3, the force-sensing structure 300 includes
multiple layers. In this example, the force-sensing structure
includes an upper portion 310 and a lower portion 320 separated by
a deformable middle body or compressible element 330. The upper
portion 310 includes an upper body 311 which may be formed from a
layer of polyimide flex material. The upper portion 310 also
includes an upper capacitive plate 312 formed from a layer of
copper bonded to or deposited on the upper body 311. Likewise, the
lower portion 320 includes a lower body 321 which may also be
formed from a layer of polyimide flex material. The lower portion
320 also includes a lower capacitive plate 322 formed from a layer
of copper bonded to or deposited on the lower body 321. In this
example, the polyimide flex material is approximately 0.05
millimeters thick. However, other thicknesses and other materials
may be used to form the force-sensing structure 300.
[0066] As shown in FIG. 3, a capacitance (shown by the capacitor
symbol) may be formed between the upper and lower capacitive plates
312, 322, which, in this example, are separated by the compressible
element 330. In this example, the compressible element 300 is
formed from a silicone material approximately 0.2 millimeters thick
with a tolerance of plus or minus 0.09 millimeters. In other
embodiments, the compressible element 300 may be formed from a
different material and have a different thickness.
[0067] The force-sensing structure 300 depicted in FIG. 3 can be
used to detect and measure a user-applied force. For example, a
user may press down on the cover glass 104 (or on an upper surface
of the electronic device 100, in embodiments lacking a display
and/or cover glass) to exert a force on the device 100. The cover
glass 104 may move downward in response to the force, compressing
the compressible element 330 of the force-sensing structure 300. In
some cases, the compressible element 330 becomes flattened by the
compression resulting the in first and second capacitive plates
312, 322 moving closer together. As a result, the capacitance
between the first and second capacitive plates 312, 322 may change.
As previously mentioned, a change in capacitance may produce an
electrical signal or change in an electrical signal, which may be
detected and measured by associated circuitry and may be used to
estimate the force exerted on the cover glass 104 by the user.
[0068] As shown in FIG. 3, the upper and lower capacitive plates
312, 322 may extend outward from the upper and lower bodies 311,
321, respectively. That is, at certain locations along the length
of the force-sensing structure 300, a portion of the capacitive
plates 312, 322 may be bare and exposed. The exposed portion of the
capacitive plates may facilitate connection to a wire, conduit, or
other electrical connection and allow signals to be communicated
between the force-sensing structure 300 and associated electronic
circuitry in order to measure capacitance changes and estimate
force.
[0069] In some embodiments, a second, auxiliary structure may be
formed within the device 100 or within a segment of the
force-sensing structure. The auxiliary structure may also include
an upper capacitive plate and a lower capacitive plate separated by
a compressible element. However, the auxiliary structure may not be
configured to be compressed by the cover glass 104, and instead may
serve as a reference capacitance used to account for changes in
environmental conditions surrounding the device. For example, the
elasticity and/or compressibility of the compressible element
(e.g., a silicone material) may vary due to changes in the amount
of absorbed moisture. In this case, it may be advantageous to use
an auxiliary structure to measure (directly or indirectly) changes
in the physical properties of the compressible element to account
for changes in the moisture content. In one example, the auxiliary
structure may form a capacitor with the upper and lower capacitive
plates separated by a compressible element. The capacitor may be
connected to a second electrical circuit that monitors the
capacitance between the plates of the auxiliary structure
separately from any force-sensitive structure. The auxiliary
structure may be positioned in a part of the device such that it
does not experience any (or very little) compression when a user
presses down on the cover glass but is still exposed to the same or
a similar environment as the force-sensing structure. Thus, any
changes in the capacitance between the plates of the auxiliary
structure may be purely due to absorbed moisture and/or aging of
the compressible element (e.g., a silicone material). The output
signal from the auxiliary structure may be used to adjust readings
from force-sensitive structure to compensate for changes in the
environmental conditions that affect the physical properties of the
compressible element.
[0070] FIGS. 4 and 5 depict alternative embodiments of a
force-sensitive structure. Specifically, FIG. 4 depicts a
force-sensitive structure 400 having an upper portion 410 including
an upper body 411 attached to an upper capacitive plate 412. The
force-sensitive structure 400 also includes a lower portion 420
including a lower body 421 attached to a lower capacitive plate
422. The upper and lower portions 410, 420 are separated by a
compressible element 430 and form a capacitor that can be used to
detect a force applied to the cover glass 104. In the example
depicted in FIG. 4, the upper and lower capacitive plates 412, 422
do not extend beyond the upper and lower bodies 411, 421. In this
case, electrical communication with the force-sensitive structure
400 may be facilitated by an electrical terminal or conduit located
within the profile of the force-sensitive structure 400.
[0071] FIG. 5 depicts another alternative embodiment of an
electronic device 100 incorporating a force-sensitive structure
500. In this embodiment, an environmental seal 550 may be
positioned between the cover glass 104 and the force-sensitive
structure 500 to prevent ingress of moisture, dust, dirt, and other
potential environmental contaminants. The environmental seal 550
may be formed, for example, from an extruded compliant material,
such as Buna rubber, Viton, EPDM, or the like. In some cases, the
environmental seal 550 is formed as a bead of sealant material that
cures after being applied to an element of the device 100.
[0072] Optionally, as shown in FIG. 5, the device may also include
a support 552 positioned between the seal 550 and the cover glass
104 to provide a bonding surface for the environmental seal 550. In
this example, the support 552 is attached to the cover glass 104
and, therefore, is movable with respect to the enclosure 102. Thus,
as a force is applied to the cover glass 104, the cover glass 104,
optional support 552, and seal 550 may all move downward to
compress the force-sensing structure 500. Thus, in the present
embodiment, the seal 550 can be used to isolate the force-sensing
structure 500 from moisture and external debris while still
allowing operation force-sensing structure 500. In addition to or
in place of the seal 550, the device 100 may also include one or
more wiping seals located between an edge of the cover glass 104
and a portion of the enclosure 102. Furthermore, a baffle seal or
membrane may be installed between the cover glass 104 and a portion
of the enclosure 102, the baffle seal configured to prevent
contaminates from entering the internal portion of the device
100.
[0073] In some embodiments, the environmental seal 550 is compliant
and in other embodiments, the environmental seal 550 is not
compliant and may be rigid. A rigid seal may be advantageous by
transmitting force to the force-sensing structure 500 directly,
while a compliant or flexible seal may compress somewhat before
transmitting any force. Either type of seal may be used, although
the output of the force-sensitive structure 500 may be affected by
compression of a flexible seal.
[0074] FIG. 6 depicts another alternative embodiment of a device
having a capacitive force sensor. As shown in FIG. 6, a touch
device case 605 (e.g., housing) can be shaped and positioned to
hold a cover glass element 610. For example, the touch device case
605 can include a rectilinear frame, such as having a shape of a
picture frame, with the cover glass element 610 having the shape of
a picture cover (as would occur if a picture were placed below the
cover glass element 610). The touch device case 605 can include a
backing (not shown) or a midframe element (not shown), which can
stabilize the touch device case 605 against bending, warping, or
other physical distortion. The touch device case 605 can also
define a space in which circuitry for the touch device (as
described herein) can be positioned. This has the effect that the
circuitry for the touch device can be protected against foreign
contaminants or unwanted touching, and against bending or warping,
or other electrical or physical effects that might possibly cause
circuitry errors or other problems for the touch device.
[0075] As shown in FIG. 6, the touch device case 605 can include an
outer edge 615, such as can be defined by an outer lip or a
protrusion upward from a baseline of the touch device case 605, and
which can be positioned to prevent excess slippage or other
movement of the cover glass element 610 in either an X or Y
direction. In this context, a Z direction generally indicates a
direction substantially normal (likely to be at a 90 degree angle,
but this is not required) to a plane of the cover glass element 610
and a top surface of the touch device, while the X and Y directions
generally indicate directions substantially within the same plane
of the cover glass element 610 (likely to be at 90 degree angles
with respect to each other, but this is not required).
[0076] As shown in FIG. 6, the cover glass element 610 and the
outer edge 615 define a cover glass gap 620 between them, with the
effect that the cover glass element 610 does not bump or rub
against the touch device case 605. In one embodiment, the touch
device can include an optional elastomer 625, or other substance,
positioned between the cover glass element 610 and the outer edge
615. This can have the effect of providing shock absorption in the
event of a sudden acceleration of the cover glass element 610 in
the direction of the outer edge 615, such as in the event the touch
device is dropped, hit, kicked, or otherwise catastrophically
moved. For example, the elastomer 625 can be disposed around the
edges of the cover glass element 610, with the effect of forming an
O-ring shape or similar shape. The elastomer 625 can also have the
effect of preventing, or at least militating against, foreign
object damage that might be caused by dust or other objects
slipping between the cover glass element 610 and the outer edge
615.
[0077] As shown in FIG. 6, the touch device case 605 includes a
cover glass shelf 630, such as can be defined by an inner lip or
internal protrusion inward from the outer edge 615 of the touch
device case 605, and which can be positioned to support the cover
glass element 610. For example, the cover glass element 610 can
rest on the cover glass shelf 630, which can prevent the cover
glass element 610 from slipping down into the circuitry for the
touch device. In alternative embodiments, the touch device case 605
can include a midframe (not shown), such as can be defined by an
internal support element positioned to support the cover glass
element 610. For example, the midframe can include a relatively
solid (absent optional holes) element positioned to support at
least some of the circuitry for the touch device.
[0078] As shown in FIG. 6, the device includes a force-sensing
structure 600. In this example, the force-sensing structure 600
includes a first upper portion comprising a first pressure
sensitive adhesive (PSA) layer 635, having a thickness of about 100
microns and a first flex circuit 640. The first flex circuit 640
includes a set of drive/sense lines configured to conduct electric
signals and/or act a capacitive plate. The force-sensing structure
600 also includes a lower portion comprising a second PSA layer
645, such as also having a thickness of about 100 microns, and a
second flex circuit 650 also having conductive drive/sense lines
for conducting signals and acting as a capacitive plate. The first
flex circuit 640 and the second flex circuit 650 are configured to
operate in response to control by the drive/sense lines and can
form a capacitive sensor. As explained above with respect to
previous embodiments, changes in the capacitance between the upper
and lower portions of the force-sensing structure 600 may be
related to an amount of deflection or change in distance between
the first flex circuit 640 and the second flex circuit 650. (In
other embodiments, one or more strain gauges can be used instead of
a capacitive sensor.) In one example, if the cover glass element
610 is tilted (such as by pressure or other applied force), the
first flex circuit 640 and the second flex circuit 650 can become
closer or become farther away, depending on location with respect
to the axis and location of tilt. As further described herein, the
first flex circuit 640 and the second flex circuit 650 can be
replicated in several locations on the touch device case 605.
[0079] The force-sensing structure 600 is typically operatively
connected to a force-sensing circuit configured to detect and
measure changes in capacitance. By measuring changes in
capacitance, the force-sensing circuit can be used to estimate
relative displacement of one or more force-sensing structures
which, in turn can be used to determine an axis and location of
tilt of the cover glass element 610. Furthermore, the changes in
capacitance can be used to estimate a force applied to the cover
glass element 610. In some embodiments, the force-sensing circuit
includes or is coupled to a processor.
[0080] In one embodiment, a region between the first flex circuit
640 and the second flex circuit 650 can define a substantially
empty space (that is, filled with air). In alternative embodiments,
the region between the first flex circuit 640 and the second flex
circuit 650 can include a compressible layer 655. For a first
example, the space between the first and second flex circuits 640,
650 can include a set of spring elements interspersed within the
space. In this case, the first flex circuit 640 and the second flex
circuit 650 are held apart by spring forces and do not generally
touch. For a second example, the compressible layer 655 can include
a microstructure constructed at least in part from silicone, such
as a set of silicone pyramids or a set of silicone springs, also
with the effect that the first flex circuit 640 and the second flex
circuit 650 are held apart by a spring force and do not generally
touch.
[0081] As described generally above, the cover glass element 610
may include a transparent touch sensor that is configured to detect
the location of one or more touches. As mentioned previously, the
transparent touch sensor may be formed from one or more arrays of
transparent conductive lines coupled to touch sensor circuitry.
Types of transparent touch sensors that may be integrated into the
cover glass element 610, include, without limitation, mutual
capacitive sensors, self-capacitive touch sensors, and resistive
touch sensors.
[0082] In one embodiment, an area of the cover glass element 610
above the first flex circuit 640 and the second flex circuit 650
can be covered with an ink mask 660. In one embodiment, the ink
mask 660 is disposed below the cover glass element 610 and above
the first flex circuit 640. This has the effect that a user of the
touch device does not generally see either the first flex circuit
640 or the second flex circuit 650, or any of the elements coupling
them to the touch device case 605, the cover glass element 610, or
any circuits for touch device (not shown). For example, the touch
device can include a surface 665, which can include a surface of
the cover glass element 610 in places where the ink mask 660 is
absent, and can include a surface of the ink mask where the ink
mask 660 is present. As described above, a Z direction 670 can
indicate a direction substantially normal to the surface 665 of the
touch device.
[0083] In one embodiment, the interaction between the cover glass
element 610 and the outer edge 615 may result in a set of forces at
the outer edge of the cover glass element 610. In some embodiments,
a force-sensing structure 600 (or alternatively a strain gauge) is
placed at two or more edges of the cover glass element 610. Each of
the two or more force-sensing structures may be operatively coupled
to force-sensing circuitry in the touch device and can be used to
detect and measure these forces. Additionally, by estimating the
relative displacement in each of the two or more force-sensing
structures, the circuit can be used to determine a normal vector to
the cover glass element 610 that represents a location of applied
force (that is, a location of the normal vector) as well as an
amount applied force (that is, a magnitude of the normal
vector).
[0084] In one embodiment, the normal vector can be determined in
response to an amount of tilt of the cover glass element or an
amount of pressure at a X and the Y location. For example, a set of
displacements can be measured using two or more force-sensing
structures located at one or more edges on the perimeter of the
cover glass element. In one embodiment, the displacements are
proportional or can be correlated to one or more applied forces. A
total force Fz can be determined in response to the individual
forces at the edges of the cover glass element, and a centroid
location (x0, y0) can be determined based on a correlation between
the individual forces. Thus, using two or more force-sensing
structures, a total force Fz and central location (x0, y0) can be
computed that correlates to the actual force exerted on the cover
glass element. Additionally, signals generated by multiple
force-sensing structures can be coupled with the output of a touch
sensor (potentially integrated into the cover glass elements) to
resolve both the location a magnitude (applied force) for multiple
finger touches on a cover glass element.
[0085] FIG. 7 depicts another exemplary embodiment of a device
having a capacitive force sensor. The device may include a
touch-sensitive region 710, which may (or may not) coincide with a
display region such as an LED, LCD or OLED display. In this
example, the touch-sensitive region 710 is formed from a
transparent touch sensor integrated with the cover glass element
610.
[0086] FIG. 7 depicts, the touch device as viewed from above and
includes the touch device case 605, the cover glass element 610,
and the outer edge 615. The touch device also includes a home
button 705, and a touch-sensitive region 710 (in which the touch
device can determine a location of one or more touches using, for
example, a capacitive touch sensor). The home button 705 may be
partially or fully within the touch-sensitive region 710, or may be
located outside the touch-sensitive region 710.
[0087] In one embodiment, the shape of the touch device can be
indicated by a pair of centerlines 715, such as an X direction
centerline 715x and a Y direction centerline 715y. The touch device
can include, along one or more edges, such as bordering the
touch-sensitive region 710, a set of force sensors 700. The force
sensors 700 may be formed from one or more capacitive force sensors
similar to those as described with respect to FIGS. 3-6.
Alternatively, the force sensors 700 may include other devices
capable of sensing applied force, such as a strain gauge.
[0088] As shown in FIG. 7, a device may include a plurality of
force sensors 700 located along one or more edges of the perimeter
of the touch-sensitive region 710. Each force sensor 700 includes
at least two capacitive plates separated by a compressible
intermediate layer. In one embodiment, the set of force sensors 700
can be disposed substantially outside a transparent portion of the
touch-sensitive region 710. For example, the force sensors 700 may
be located under an ink mask 660 (such as similar to or like that
described with reference to the FIG. 6). In such cases, the force
sensors 700 can be positioned with a gauge spacing 725 between
pairs of the force sensors 700, and with an edge spacing 730
between individual ones of the force sensors 700 and an edge the
touch device. In alternative embodiments, the force sensors 700 may
be positioned beneath a display stack or located in another
position with respect to the touch-sensitive region 710. The force
sensors 700 may be evenly spaced from one another, spaced at uneven
intervals, at repeating intervals, or as necessary. Likewise, the
force sensors 700 may be positioned along all sides of the
touch-sensitive region 710, at corners of the device, along less
than all sides of the touch-sensitive region 710, or along a single
edge of the touch-sensitive region 710. Accordingly, the sensor
distribution shown in FIG. 7 is meant to be a sample, partial
distribution and not limiting.
[0089] In one embodiment, each force sensor 700 is coupled to
force-sensing circuitry that is configured to measure an amount of
capacitance between a first flex circuit and a second flex circuit,
which may be correlated to estimate a distance between the first
flex circuit and the second flex circuit. The relative position of
the first and second flex circuits may be similar to the
configuration depicted in FIG. 6, discussed above. Similar to
embodiments described above, an amount of capacitance between the
first sensing element defined on the first flex circuit and the
second sensing element defined on the second flex circuit can be
detected and measured using force detection circuitry, which may
include a processor. In such cases, the amount of applied force can
be correlated to a relative change in distance between the first
flex circuit and the second flex circuit, relative to a rest
position when there is no force applied to the cover glass element
610. It should be appreciated that each force sensor 700 may be
formed from first and second flex circuits, or may be a separate
element.
[0090] In an alternative embodiment, each force sensor 700 is
coupled to force-sensing circuitry that is configured to measure an
amount of resistance between the first flex circuit and the second
flex circuit. For example, the first and second flex circuits may
be coupled by resistive layer. By measuring the resistance or
change in resistance, the force-sensing circuitry can be used to
determine a distance between the first flex circuit and the second
flex circuit. For example, an amount of resistance between the
first flex circuit and the second flex circuit can be correlated to
a distance between the first flex circuit and the second flex
circuit. This may occur when, for example the compressible,
resistive layer is formed from a material that has a variable
resistivity dependent on its thickness or an amount of compression.
In one such case, the compressible, resistive layer includes a
microstructure that has a resistance that increases like a spring
force, similar to a strain gauge. The force-sensing circuitry may
estimate the distance between the flex circuits by measuring the
resistance or changes to the resistance in the compressible,
resistive layer.
[0091] With reference to FIG. 7, the force sensors 700 can be
operatively coupled to force-sensing circuitry (including a
processor) that is configured to determine a set of distances (at
distinct locations along the edge of the cover glass element 110)
corresponding to the set of force sensors 700. That is, the
force-sensing circuitry can estimate the distance between the first
flex circuit and the second flex circuit based on the measured
capacitance at each force sensor. In one embodiment, the
displacements at each sensor 700 correlate to applied forces at the
locations of those force sensors 700. Similar to the technique
described above with respect to FIG. 6, a total force Fz can be
determined based on an estimate of the individual forces, and a
centroid location (x0, y0) can be determined based on a weighting
of the estimate of the individual forces. In one embodiment, the
total force Fz and the centroid location (x0, y0) is calibrated
such that a set of computed forces and moments in response to the
values of the total force Fz and the centroid location (x0, y0)
best matches the observed values for displacements and forces at
each of the set of force sensors 700. Thus, using multiple force
sensors, a total force Fz and central location (x0, y0) can be
computed that correlates to the actual force exerted on the device.
Additionally, signals generated by multiple force sensors can be
coupled with the output of a touch sensor (potentially integrated
into the cover glass elements) to resolve both the locations and
magnitudes (due to applied forces) for multiple finger touches on
the device.
[0092] FIG. 8 depicts another exemplary embodiment of a device
having a capacitive force sensor. In particular, the device
depicted in FIG. 8 includes a cover glass element that is
deformable.
[0093] As shown in FIG. 8, a cover glass element 805 can be coupled
to a frame element 810, which can be coupled to a touch device
frame 815. In one embodiment, there is a spatial separation between
the cover glass element 805 and the frame element 810. For a first
example, the cover glass element 805 can have a thickness of about
0.90 mm, although this particular thickness is merely exemplary and
is not required. For a second example, the frame element 810 can
include an elastomer, a plastic, or include construction from other
substances. The cover glass element 805 can also be positioned
above a display stack 820, such as a display stack from a touch
device and adapted to provide a graphical or text display.
[0094] In one embodiment, the display stack 820 can be positioned
above a reflector sheet 825 including an electrode pattern, such as
can be used for drive and sense lines in a rectilinear capacitive
array or individual sensor structures in an array. The reflector
sheet 825 can be positioned above an air gap 830, such as can be
used for capacitance between the reflector sheet 825 and another
element. For example, the air gap 830 can have a thickness of about
0.10 mm, although this particular thickness is merely exemplary and
is not required.
[0095] In one embodiment, the air gap 830 can be positioned above a
circuit 835 having capacitive traces or elements, which may include
a set of drive and sense traces/elements or be formed from an array
of individual sensing traces/elements. For example, the circuit 835
can have a thickness of about 0.10 mm, although this particular
thickness is merely exemplary and is not required.
[0096] In one embodiment, the circuit 835 can be positioned above a
pressure sensitive adhesive (PSA) element 840. For example, the PSA
element 840 can have a thickness of about 0.03 mm, although this
particular thickness is merely exemplary and is not required.
Further, a primer may be used between PSA and the housing to affix
the structure to the housing. The structure may be optically
aligned with the housing prior to bonding.
[0097] In one embodiment, the PSA element 840 can be positioned
above a midplate element 845. For a first example, the midplate
element 845 can have a thickness of about 0.25 mm, although this
particular thickness is merely exemplary and is not required. For a
second example, the midplate element 845 can be supportive of the
elements coupled thereto and below the air gap 830.
[0098] In one embodiment, the cover glass element 805, the display
stack 820, and related elements can be relatively deformable. This
can have the effect that applied force to the surface of the touch
device can cause a change in distance between elements near the air
gap 830, and a change in measured capacitance by circuits
positioned near the air gap 830. For example, a set of drive and
sense lines, or an array of individual sensing elements, could be
positioned in the reflector sheet 825 or in the circuit 835, can
measure a capacitance across the air gap 830.
[0099] In such cases, the capacitance across the air gap 830 would
be subject to change in response to deformation of the cover glass
element 805, the display stack 820, and related elements. This
would have the effect that elements positioned near the air gap 830
would be able to measure the change in capacitance, and would be
able to determine an amount or magnitude of an applied force in
response thereto.
[0100] In some embodiments, multiple force sensors may be formed
over the area of the cover glass element 805. In one embodiment,
the set of force sensors can be positioned in a rectilinear array,
such as an array in which each one of the force sensors is
positioned at an [X, Y] location over the area of the cover glass
element 805. For example, each one of the force sensors can include
a capacitive force sensor exhibiting mutual capacitance between
drive and sensor elements, or exhibiting self-capacitance. In
another example, each one of the sensors can include a resistive
strain gauge exhibiting a change in resistance in response to
applied force, such as a resistive strain gauge as described with
respect to FIG. 6, above.
[0101] In one embodiment, the applied force can affect each force
sensor that is substantially near the applied force. The applied
force affects each such force sensor differently depending on an
amount of the applied force and a distance between the [X, Y]
location of the applied force and the [X, Y] location of the
affected force sensor. This has the effect that a processor or
other circuit in the touch device can determine a mapping of
applied force, and in response thereto, a set of [X, Y] locations
and a Z displacement of the cover glass element 805. For example,
particular Z displacement of points along the edges of the cover
glass element 805 (or within a touch-sensitive region) can be used
to determine the [X, Y] location of the applied force. In one
embodiment, the cover glass element 805 may be approximately 700
microns thick, although this thickness may vary between
embodiments.
[0102] In one embodiment, the same or similar information can be
used to determine the [X, Y] location and Z displacement of more
than one such applied force. In such cases where multiple forces
are applied, a processor or other circuit in the touch device can
determine a centroid of applied force, from which the touch device
can determine one or more individual forces. For example, from this
information, a processor or other circuit can determine one or more
[X, Y] locations where force is being applied, and an amount or
magnitude of force being applied at each such location.
[0103] In one embodiment, the interaction between the cover glass
element 805 and the air gap 830 defines a set of forces at each
location of applied force. A processor or other circuit in the
touch device can measure these forces, such as using one or more
capacitive sensing elements (as described herein) or using one or
more strain gauges, distributed at locations throughout cover glass
element 805. In response to those forces, the circuit can determine
a set of normal vectors to the cover glass element 805 representing
one or more locations of applied force and one or more amounts or
magnitudes of the applied force.
[0104] In one embodiment, the locations of applied force can be
determined in response to the distribution of sensed applied force
at each location on the cover glass element 805, as described
above, at each of the X and the Y locations, thus assigning each
such location a Z amount of applied force. For a first example, a
total centroid of applied force can be determined in response to
the distribution of sensed applied force. The processor or other
circuit can then locate each individual likely applied force,
identify its amount of force, and subtract out that identified
force from the sensed applied force at each location. This can have
the effect of providing the processor or other circuit with a way
to identify each applied force individually, until all such
individual applied forces have been found.
[0105] In one embodiment, an amount or magnitude of force can be
determined at each of a set of distinct locations at which a
distinct force sensor is disposed below the cover glass element
805. For example, in one embodiment, the force sensors can be
disposed in a grid below the cover glass element 805. Having the
amount of force at each such location, a weighted centroid of that
set of force amounts can be computed using a weighted sum of the
locations at which each applied force is measured. Having
determined such a centroid, the processor can determine a nearest
local maximum force, either in response to the nearest maximum
force sensor, or in response to a touch location sensor, or both.
Having determined a nearest local maximum force, the processor can
subtract that force and its expected effect on each force sensor,
and repeat the process until each individual applied force is
determined. In alternative embodiments, other and further
techniques could be used in addition or instead.
4. FORCE-SENSITIVE DEVICE SYSTEM
[0106] FIG. 9 depicts an exemplary communication between a touch
I/O device and a computing system. In this example, the touch I/O
device 901 includes one or more sensors for detecting a touch by an
operator or user. The touch device 901 transmits electronic signals
from the one or more sensors to a computing system 903 over a
communication channel 902. An example computing system 903 is
described below with respect to FIG. 10 and includes one or more
computer processors and computer-readable memory for storing
computer-executable instructions. The touch I/O device,
communication channel 902 and computing system 903 may all be
integrated together as a part of the same touch device.
[0107] As shown in FIG. 9, embodiments may include touch I/O device
901 that can receive touch input and force input (such as possibly
including touch locations and applied force at those locations) for
interacting with computing system 903 via wired or wireless
communication channel 902. Touch I/O device 901 may be used to
provide user input to computing system 903 in lieu of or in
combination with other input devices such as a keyboard, mouse, or
possibly other devices. In alternative embodiments, touch I/O
device 901 may be used in conjunction with other input devices,
such as in addition to or in lieu of a mouse, trackpad, or possibly
another pointing device. One or more touch I/O devices 901 may be
used for providing user input to computing system 903. Touch I/O
device 901 may be an integral part of computing system 903 (e.g.,
touch screen on a laptop) or may be separate from computing system
903.
[0108] Touch I/O device 901 may include a touch sensitive and/or
force sensitive panel which is wholly or partially transparent,
semitransparent, non-transparent, opaque or any combination
thereof. Touch I/O device 901 may be embodied as a touch screen,
touch pad, a touch screen functioning as a touch pad (e.g., a touch
screen replacing the touchpad of a laptop), a touch screen or
touchpad combined or incorporated with any other input device
(e.g., a touch screen or touchpad disposed on a keyboard, disposed
on a trackpad or other pointing device), any multi-dimensional
object having a touch sensitive surface for receiving touch input,
or another type of input device or input/output device.
[0109] In one example, touch I/O device 901 is a touch screen that
may include a transparent and/or semitransparent touch-sensitive
and force-sensitive panel at least partially or wholly positioned
over at least a portion of a display. (Although, the touch
sensitive and force sensitive panel is described as at least
partially or wholly positioned over at least a portion of a
display, in alternative embodiments, at least a portion of
circuitry or other elements used in embodiments of the touch
sensitive and force sensitive panel may be at least positioned
partially or wholly positioned under at least a portion of a
display, interleaved with circuits used with at least a portion of
a display, or otherwise.) According to this embodiment, touch I/O
device 901 functions to display graphical data transmitted from
computing system 903 (and/or another source) and also functions to
receive user input. In other embodiments, touch I/O device 901 may
be embodied as an integrated touch screen where touch sensitive and
force sensitive components/devices are integral with display
components/devices. In still other embodiments a touch screen may
be used as a supplemental or additional display screen for
displaying supplemental or the same graphical data as a primary
display and to receive touch input, including possibly touch
locations and applied force at those locations.
[0110] Touch I/O device 901 may be configured to detect the
location of one or more touches or near touches on device 901, and
where applicable, force of those touches, based on capacitive,
resistive, optical, acoustic, inductive, mechanical, chemical, or
electromagnetic measurements, in lieu of or in combination or
conjunction with any phenomena that can be measured with respect to
the occurrences of the one or more touches or near touches, and
where applicable, force of those touches, in proximity to the touch
I/O device 901. Software, hardware, firmware or any combination
thereof may be used to process the measurements of the detected
touches, and where applicable, force of those touches, to identify
and track one or more gestures. A gesture may correspond to
stationary or non-stationary, single or multiple, touches or near
touches, and where applicable, force of those touches, on touch I/O
device 901. A gesture may be performed by moving one or more
fingers or other objects in a particular manner on touch I/O device
901 such as tapping, pressing, rocking, scrubbing, twisting,
changing orientation, pressing with varying pressure and the like
at essentially the same time, contiguously, consecutively, or
otherwise. A gesture may be characterized by, but is not limited to
a pinching, sliding, swiping, rotating, flexing, dragging, tapping,
pushing and/or releasing, or other motion between or with any other
finger or fingers, or any other portion of the body or other
object. A single gesture may be performed with one or more hands,
or any other portion of the body or other object by one or more
users, or any combination thereof.
[0111] Computing system 903 may drive a display with graphical data
to display a graphical user interface (GUI). The GUI may be
configured to receive touch input, and where applicable, force of
that touch input, via touch I/O device 901. Embodied as a touch
screen, touch I/O device 901 may display the GUI. Alternatively,
the GUI may be displayed on a display separate from touch I/O
device 901. The GUI may include graphical elements displayed at
particular locations within the interface. Graphical elements may
include but are not limited to a variety of displayed virtual input
devices including virtual scroll wheels, a virtual keyboard,
virtual knobs or dials, virtual buttons, virtual levers, any
virtual UI, and the like. A user may perform gestures at one or
more particular locations on touch I/O device 901 which may be
associated with the graphical elements of the GUI. In other
embodiments, the user may perform gestures at one or more locations
that are independent of the locations of graphical elements of the
GUI. Gestures performed on touch I/O device 901 may directly or
indirectly manipulate, control, modify, move, actuate, initiate, or
generally affect graphical elements such as cursors, icons, media
files, lists, text, all or portions of images, or the like within
the GUI. For instance, in the case of a touch screen, a user may
directly interact with a graphical element by performing a gesture
over the graphical element on the touch screen. Alternatively, a
touch pad generally provides indirect interaction. Gestures may
also affect non-displayed GUI elements (e.g., causing user
interfaces to appear) or may affect other actions within computing
system 903 (e.g., affect a state or mode of a GUI, application, or
operating system). Gestures may or may not be performed on touch
I/O device 901 in conjunction with a displayed cursor. For
instance, in the case in which gestures are performed on a
touchpad, a cursor (or pointer) may be displayed on a display
screen or touch screen and the cursor may be controlled via touch
input, and where applicable, force of that touch input, on the
touchpad to interact with graphical objects on the display screen.
In other embodiments in which gestures are performed directly on a
touch screen, a user may interact directly with objects on the
touch screen, with or without a cursor or pointer being displayed
on the touch screen.
[0112] Feedback may be provided to the user via communication
channel 902 in response to or based on the touch or near touches,
and where applicable, force of those touches, on touch I/O device
901. Feedback may be transmitted optically, mechanically,
electrically, olfactory, acoustically, haptically, or the like or
any combination thereof and in a variable or non-variable
manner.
[0113] As previously mentioned, the touch I/O device, communication
channel 902, and the computing system 903 may all be integrated
into a touch device or other system. The touch device or system may
be a portable or non-portable device, including, but not limited
to, a communication device (e.g., mobile phone, smart phone), a
multi-media device (e.g., MP3 player, TV, radio), a portable or
handheld computer (e.g., tablet, netbook, laptop), a desktop
computer, an all-in-one desktop, a peripheral device, or any other
(portable or non-portable) system or device adaptable to the
inclusion of system architecture depicted in FIG. 10, including
combinations of two or more of these types of devices.
[0114] FIG. 10 depicts a block diagram of one embodiment of system
1000 that generally includes one or more computer-readable mediums
1001, processing system 1004, Input/Output (I/O) subsystem 1006,
electromagnetic frequency circuitry, such as possibly radio
frequency (RF) or other frequency circuitry 1008 and audio
circuitry 1010. These components may be coupled by one or more
communication buses or signal lines 1003. Each such bus or signal
line may be denoted in the form 1003-X, where X can be a unique
number. The bus or signal line may carry data of the appropriate
type between components; each bus or signal line may differ from
other buses/lines, but may perform generally similar
operations.
[0115] It should be apparent that the architecture shown in FIG. 10
is only one example architecture of system 1000, and that system
1000 could have more or fewer components than shown, or a different
configuration of components. The various components shown in FIG.
10 can be implemented in hardware, software, firmware or any
combination thereof, including one or more signal processing and/or
application specific integrated circuits.
[0116] Shown in FIG. 10, RF circuitry 1008 is used to send and
receive information over a wireless link or network to one or more
other devices and includes well-known circuitry for performing this
function. RF circuitry 1008 and audio circuitry 1010 are coupled to
processing system 1004 via peripherals interface 1016. Interface
1016 includes various known components for establishing and
maintaining communication between peripherals and processing system
1004. Audio circuitry 1010 is coupled to audio speaker 1050 and
microphone 1052 and includes known circuitry for processing voice
signals received from interface 1016 to enable a user to
communicate in real-time with other users. In some embodiments,
audio circuitry 1010 includes a headphone jack (not shown).
[0117] Peripherals interface 1016 couples the input and output
peripherals of the system to processor 1018 and computer-readable
medium 1001. One or more processors 1018 communicate with one or
more computer-readable mediums 1001 via controller 1020.
Computer-readable medium 1001 can be any device or medium that can
store code and/or data for use by one or more processors 1018.
Medium 1001 can include a memory hierarchy, including but not
limited to cache, main memory and secondary memory. The memory
hierarchy can be implemented using any combination of RAM (e.g.,
SRAM, DRAM, DDRAM), ROM, FLASH, magnetic and/or optical storage
devices, such as disk drives, magnetic tape, CDs (compact disks)
and DVDs (digital video discs). Medium 1001 may also include a
transmission medium for carrying information-bearing signals
indicative of computer instructions or data (with or without a
carrier wave upon which the signals are modulated). For example,
the transmission medium may include a communications network,
including but not limited to the Internet (also referred to as the
World Wide Web), intranet(s), Local Area Networks (LANs), Wide
Local Area Networks (WLANs), Storage Area Networks (SANs),
Metropolitan Area Networks (MAN) and the like.
[0118] One or more processors 1018 run various software components
stored on medium 1001 to perform various functions for system 1000.
In some embodiments, the software components include operating
system 1022, communication module (or set of instructions) 1024,
touch and applied force processing module (or set of instructions)
1026, graphics module (or set of instructions) 1028, and one or
more applications (or set of instructions) 1030. Each of these
modules and above noted applications correspond to a set of
instructions for performing one or more functions described above
and the methods described in this application (e.g., the
computer-implemented methods and other information processing
methods described herein). These modules (i.e., sets of
instructions) need not be implemented as separate software
programs, procedures or modules, and thus various subsets of these
modules may be combined or otherwise rearranged in various
embodiments. In some embodiments, medium 1001 may store a subset of
the modules and data structures identified above. Furthermore,
medium 1001 may store additional modules and data structures not
described above.
[0119] Operating system 1022 includes various procedures, sets of
instructions, software components and/or drivers for controlling
and managing general system tasks (e.g., memory management, storage
device control, power management, etc.) and facilitates
communication between various hardware and software components.
[0120] Communication module 1024 facilitates communication with
other devices over one or more external ports 1036 or via RF
circuitry 1008 and includes various software components for
handling data received from RF circuitry 1008 and/or external port
1036.
[0121] Graphics module 1028 includes various known software
components for rendering, animating and displaying graphical
objects on a display surface. In embodiments in which touch I/O
device 1012 is a touch sensitive and force sensitive display (e.g.,
touch screen), graphics module 1028 includes components for
rendering, displaying, and animating objects on the touch sensitive
and force sensitive display.
[0122] One or more applications 1030 can include any applications
installed on system 1000, including without limitation, a browser,
address book, contact list, email, instant messaging, word
processing, keyboard emulation, widgets, JAVA-enabled applications,
encryption, digital rights management, voice recognition, voice
replication, location determination capability (such as that
provided by the global positioning system, also sometimes referred
to herein as "GPS"), a music player, and otherwise.
[0123] Touch processing module 1026 includes various software
components for performing various tasks associated with touch I/O
device 1012 including but not limited to receiving and processing
touch input and applied force input received from I/O device 1012
via touch I/O device controller 1032. In some cases, the touch
processing module 1026 includes computer instructions for operating
the force sensor 1060. For example, the touch processing module
1026 may include instructions for performing one or more operations
described below with respect to processes 1100 and 1150 of FIGS.
11A-B. In some cases, the touch processing module 1026 includes
parameters or settings that may be implemented in the operation of
the force sensor 1060.
[0124] I/O subsystem 1006 is coupled to touch I/O device 1012 and
one or more other I/O devices 1014 for controlling or performing
various functions. Touch I/O device 1012 communicates with
processing system 1004 via touch I/O device controller 1032, which
includes various components for processing user touch input and
applied force input (e.g., scanning hardware). One or more other
input controllers 1034 receives/sends electrical signals from/to
other I/O devices 1014. Other I/O devices 1014 may include physical
buttons, dials, slider switches, sticks, keyboards, touch pads,
additional display screens, or any combination thereof.
[0125] If embodied as a touch screen, touch I/O device 1012
displays visual output to the user in a GUI. The visual output may
include text, graphics, video, and any combination thereof. Some or
all of the visual output may correspond to user-interface objects.
Touch I/O device 1012 forms a touch-sensitive and force-sensitive
surface that accepts touch input and applied force input from the
user. Touch I/O device 1012 and touch screen controller 1032 (along
with any associated modules and/or sets of instructions in medium
1001) detects and tracks touches or near touches, and where
applicable, force of those touches (and any movement or release of
the touch, and any change in the force of the touch) on touch I/O
device 1012 and converts the detected touch input and applied force
input into interaction with graphical objects, such as one or more
user-interface objects. In the case in which device 1012 is
embodied as a touch screen, the user can directly interact with
graphical objects that are displayed on the touch screen.
Alternatively, in the case in which device 1012 is embodied as a
touch device other than a touch screen (e.g., a touch pad or
trackpad), the user may indirectly interact with graphical objects
that are displayed on a separate display screen embodied as another
I/O device 1014.
[0126] In embodiments in which touch I/O device 1012 is a touch
screen, the touch screen may use LCD (liquid crystal display)
technology, LPD (light emitting polymer display) technology, OLED
(organic LED), or OEL (organic electro luminescence), although
other display technologies may be used in other embodiments.
[0127] Feedback may be provided by touch I/O device 2012 based on
the user's touch, and applied force, input as well as a state or
states of what is being displayed and/or of the computing system.
Feedback may be transmitted optically (e.g., light signal or
displayed image), mechanically (e.g., haptic feedback, touch
feedback, force feedback, or the like), electrically (e.g.,
electrical stimulation), olfactory, acoustically (e.g., beep or the
like), or the like or any combination thereof and in a variable or
non-variable manner.
[0128] System 1000 also includes power system 1044 for powering the
various hardware components and may include a power management
system, one or more power sources, a recharging system, a power
failure detection circuit, a power converter or inverter, a power
status indicator and any other components typically associated with
the generation, management and distribution of power in portable
devices.
[0129] In some embodiments, peripherals interface 1016, one or more
processors 1018, and memory controller 1020 may be implemented on a
single chip, such as processing system 1004. In some other
embodiments, they may be implemented on separate chips.
[0130] In one embodiment, an example system includes a force sensor
1060 integrated with the touch I/O device 2012. The force sensor
1060 may include one or more of the force-sensitive structures
described above with respect to any one of the example embodiments.
Generally, the force sensor 1060 is configured to generate an
electronic signal or response that can be interpreted or processed
as a magnitude of force of a touch on touch O/I device 1012. In
some cases, the force sensor 1060 transmits electronic signals
directly to the touch I/O device via signal line 1003-10. The
signals may be relayed to the force sensor controller 1061 in the
I/O subsystem 1006. In some cases, the force sensor 1060 transmits
signals directly to the force sensor controller 1061 via signal
line 1003-11 without passing through the touch I/O device 1012.
[0131] The force sensor controller 1061 either alone or in
combination with one or more of the processors (e.g., processor
1018 or secure processor 1040) may serve as the force sensing
circuitry for the force sensor 1060. In particular, the force
sensor controller 1061 can be coupled to a processor or other
computing device, such as the processor 1018 or the secure
processor 1040. In one example, the force sensor controller 1061 is
configured to calculate and estimated force based on electronic
signals generated by the force sensor 1060. Data regarding
estimated force may be transmitted to the processor 1018 or secure
processor 1040 for use with other aspects of the system 1000, such
as the touch processing module 1026. In one example, the force
sensor controller 1061 performs signal processing on the electronic
signal that is produced by the force sensor 1060, including, for
example, analog to digital conversion, filtering, and sampling
operations. In some cases, other processors in the system 1000
(e.g., processor 1018 or secure processor 1040) that calculate an
estimated force based on the processed signal. As a result, the
system 1000 can utilize signals or data produced by the force
sensor controller 1061, which can be measured, calculated,
computed, or otherwise manipulated. In one embodiment, the output
of the force sensor 1060 is used by one or more processors or other
computing devices, coupled to or accessible to the force sense
controller 1061 or the touch I/O device, such as the processor
1018, the secure processor 1040, or otherwise. Additionally, output
from the force sensor 1060 can be used by one or more analog
circuits or other specialized circuits, coupled to or accessible to
the force sensor controller 1061 or the touch I/O device 1012.
[0132] After reading this application, those skilled in the art
would recognize that techniques for obtaining information with
respect to applied force and contact on a touch I/O device, and
using that associated information to determine the magnitude and
locations of applied force and contact on a touch I/O device, is
responsive to, and transformative of, real-world data such as
attenuated reflection and capacitive sensor data received from
applied force or contact by a user's finger, and provides a useful
and tangible result in the service of detecting and using applied
force and contact with a touch I/O device. Moreover, after reading
this application, those skilled in the art would recognize that
processing of applied force and contact sensor information by a
computing device includes substantial computer control and
programming, involves substantial records of applied force and
contact sensor information, and involves interaction with applied
force and contact sensor hardware and optionally a user interface
for use of applied force and contact sensor information.
[0133] Certain aspects of the embodiments described in the present
disclosure may be provided as a computer program product, or
software, that may include, for example, a computer-readable
storage medium or a non-transitory machine-readable medium having
stored thereon instructions, which may be used to program a
computer system (or other electronic devices) to perform a process
according to the present disclosure. A non-transitory
machine-readable medium includes any mechanism for storing
information in a form (e.g., software, processing application)
readable by a machine (e.g., a computer). The non-transitory
machine-readable medium may take the form of, but is not limited
to, a magnetic storage medium (e.g., floppy diskette, video
cassette, and so on); optical storage medium (e.g., CD-ROM);
magneto-optical storage medium; read only memory (ROM); random
access memory (RAM); erasable programmable memory (e.g., EPROM and
EEPROM); flash memory; and so on.
[0134] While the present disclosure has been described with
reference to various embodiments, it will be understood that these
embodiments are illustrative and that the scope of the disclosure
is not limited to them. Many variations, modifications, additions,
and improvements are possible. More generally, embodiments in
accordance with the present disclosure have been described in the
context of particular embodiments. Functionality may be separated
or combined in procedures differently in various embodiments of the
disclosure or described with different terminology. These and other
variations, modifications, additions, and improvements may fall
within the scope of the disclosure as defined in the claims that
follow.
5. METHODS OF OPERATION
[0135] FIG. 11A depicts an exemplary process for operating a device
having a force sensor. The process may be applied using the force
sensors described above with respect to FIGS. 2A, 2B, 3-8,
discussed above.
[0136] FIG. 11A depicts an exemplary flow chart for a process 1100
that includes flow points and operational steps or functions.
Although these flow points and operations are shown in a particular
order, in the context of a more generalized technique, there is no
particular requirement that the order of the operations must be
followed as shown. For example, the flow points and operations
could be performed in a different order, concurrently, in parallel,
or otherwise. Similarly, although these flow points and operations
are shown performed by a general purpose processor in a device, in
the context of a more generalized approach, there is no particular
requirement for any such limitation. For example, one or more such
operations could be performed by a special purpose processor, by
another circuit, or be offloaded to other processors or other
circuits in other devices, such as by offloading those functions to
nearby devices using wireless technology or by offloading those
functions to cloud computing functions. In some cases, prior to
performing the operations of process 1100, the electronic device
has been turned on and the operating system has been loaded and is
running. Also, the relevant hardware including, for example, touch
screen sensors, display devices, and force sensor devices may have
been powered and may have been initialized.
[0137] At operation 1105, a force is applied to a location [X, Y]
on the cover glass of the device. The force may be applied using
either a finger or other pointing devices, such as a stylus or pen.
In some cases, multiple touches may be applied to the cover glass
of the device. For example, a multi-touch gesture or command may be
input on the cover glass resulting in a net applied force.
[0138] At operation 1110, an electrical signal is detected and
measured in response to the applied force. In one example,
force-sensing circuit (which may include a processor) in the device
measures a value from one or more force sensors in response to the
applied force. In one embodiment, as described above with respect
to FIGS. 2A, 2B, and 3-5, a force-sensing circuit detects a change
in the capacitance at one or more force-sensing structures. The
change in capacitance may be correlated or used to estimate a
deflection in the cover glass resulting from the applied force. In
another embodiment, as described with respect to FIG. 6, the
force-sensing circuit estimates an amount of tilt applied to the
cover glass based on a signal or signals received from one or more
force sensors. In yet another embodiment, as described with respect
to FIG. 7, the force-sensing circuit is used to detect a change in
capacitance between capacitive sensors (or with respect to a single
sensor, in a self-capacitance mode) at a set of distinct locations
below the cover glass. The change in capacitance can be used to
estimate the displacement on the cover glass resulting from the
applied force.
[0139] At operation 1115, the location of the one or more touches
is determined. In one example, the force-sensing circuit determines
one or more locations at which the force is being applied to the
cover glass element based on the signal or signals received from
one or more force sensors. The location may be determined by, for
example, comparing the output from multiple force sensors and using
the output to triangulate or estimate a location of the applied
force.
[0140] At operation 1120, the amount or magnitude of the force
being applied at each location is estimated. For example, the
force-sensing circuit may be used to determine an amount or
magnitude of force being applied at each measured location, such as
using the weighted centroid technique described with respect to the
FIG. 8. In some embodiments, the operations of method 1100 are
repeated multiple times. In some embodiments, the operations of
method 1100 are repeated so long as the force sensitive device is
powered on.
[0141] FIG. 11B depicts another process for operating a device
having a force sensor. The process may be applied using the force
sensors described above with respect to FIGS. 2A, 2B, 3-8,
discussed above.
[0142] FIG. 11B depicts another exemplary flow chart for a process
1150 that includes flow points and operational steps or functions.
Although these flow points and operations are shown in a particular
order, in the context of a more generalized technique, there is no
particular requirement that the order of the operations must be
followed as shown. Similarly, although these flow points and
operations are shown performed by a general purpose processor in a
device, in the context of a more generalized approach, there is no
particular requirement for any such limitation. In some cases,
prior to performing the operations of process 1150, the electronic
device has been turned on and the operating system has been loaded
and is running. Also, the relevant hardware including, for example,
touch screen sensors, display devices, and force sensor devices may
have been powered and may have been initialized.
[0143] At operation 1155, a charge signal is transmitted to a
force-sensitive structure. In a typical implementation, the charge
signal includes a series of charge pulses is transmitted to one of
the capacitive plates in a force-sensitive structure. Each charge
pulse comprises a momentary change in the voltage applied to the
capacitive plates of the force-sensitive structure resulting in an
induced current across the plates. In some instances, the charge
signal is an alternating current (AC) that is applied across the
capacitive plates of the force-sensing structure. In many cases, if
the charge signal is a discrete charge pulse, the charge pulse is
transmitted at regular intervals during the operation of the
device. If the charge signal is an alternating current, the charge
signal may be transmitted continuously during operation. In either
case, operation 1155 is typically performed simultaneously with
operations 1160, 1165, and 1170, described below.
[0144] At operation 1160, a first capacitance is measured for the
force-sensitive structure. Typically, the capacitance is measured
while the force-sensitive structure is in an uncompressed or
unactuated state. For example, the measurement of operation 1160
may be taken when the device is stationary and is not being touched
by an operator. In some cases, multiple measurements are taken over
a period of time and a composite or average capacitance value is
determined.
[0145] At operation 1165, a force is applied to the device. In
accordance with the embodiments described above with respect to
FIGS. 2A, 2B, 3-8, a user may touch the cover glass of a device
applying a force at a location on the cover glass. The user may
touch the device with a finger, stylus, pen, or the like. In some
cases, multiple touches are applied to the cover glass at the same
time in accordance with a multi-touch gesture or user input. In
accordance with the embodiments described above with respect to
FIGS. 2A, 2B, 3-8, an applied force typically results in the
compression or deflection of a force-sensitive structure resulting
in a relative change in position of the two capacitive plates.
[0146] At operation 1170, a second capacitance is measured for the
force-sensitive structure. Typically, the capacitance is measured
while the force-sensitive structure is in a compressed or deflected
state due to the force applied in operation 1165, described above.
In some cases, multiple measurements are taken over a period of
time and a composite or representative capacitance value is
determined.
[0147] At operation 1175, a force is estimated using the first and
second capacitance measurements. In accordance with the embodiments
described above with respect to FIGS. 2A, 2B, 3-8, an applied force
results in a change in the position of the two capacitive plates,
thus changing the capacitance of the force-sensitive structure. In
operation 1175, the change in capacitance is correlated with or
used to compute an estimated force. For example, if compressible
element of a force-sensitive structure behaves as a linear force
spring, the change in capacitance (which is proportional to the
change in distance between the capacitive plates) will be
proportional to the change in force. Because the material
properties, such as the spring rate, of the compressible element
are known the amount of force can be estimated as the difference
between the first and second capacitance measurements multiplied by
a constant. In some embodiments, the operations of method 1150 are
repeated multiple times. In some embodiments, the operations of
method 1150 are repeated so long as the force sensitive device is
powered on.
6. ELECTRICAL CONNECTION TO A FORCE SENSOR AND METHOD OF
MANUFACTURING
[0148] In accordance with certain embodiments described above, a
capacitive force sensor typically includes a force-sensitive stack
having two capacitive plates separated by an intermediate,
compressible element. In a typical implementation, a charge signal
is applied to at least one of the capacitive plates and a
capacitive measurement is taken. To deliver both the charge signal
(drive signal) and receive the capacitive measurement (sense
signal) from the capacitive plates, the force-sensitive structure
is typically connected to other elements of the system by an
electrical connection. To facilitate assembly during manufacturing,
it may be advantageous that the electrical connection be a
detachable electrical connection formed from a flexible
conduit.
[0149] FIG. 12 depicts an example touch device 1200 having two
force-sensing structures 1210, 1220 located around the perimeter of
a display element 1202 or a portion thereof. The two force-sensing
structures 1210, 1220 are electrically connected to an electrical
connector tail 1250. In this example, each of the two force-sensing
structures (1210, 1220) is formed from a first and second
capacitive plate separated by an intermediate, compressible
element. Generally, the force-sensing structures 1210 and 1220 can
be used to determine a magnitude of a touch on a surface of the
device. As explained above with respect to FIGS. 3-5, a force
applied to the device compresses or deforms the compressible
element, changing the distance between the first and second
capacitive plates. The change in distance can be measured as a
change in capacitance between the two plates using force-sensing
circuitry. Accordingly, the two structures 1210, 1220 cooperate to
sense a force; in this manner, they may be referred to as either
separately or together as a "force-sensing structure."
[0150] The electrical connector tail 1250 can be used to
electrically couple the two force-sensing structures 1210, 1220
with the force-sensing circuitry, which may be located on a
separate circuit component within the device. In some cases, it may
be advantageous that the electrical connector tail 1250 is formed
from a flexible conduit to facilitate connection with the
force-sensing circuitry. For example, the electrical connector tail
1250 may be formed from a laminate of polyimide materials that have
been printed or formed with electrical conductive traces. In some
cases, it may be further advantageous that the flexible conduit be
configured to bend easily to facilitate routing within the limited
space of the device enclosure. To improve the flexibility or bend
radius of the connector tail 1250, it may be advantageous to
eliminate or remove the intermediate, compressible element in at
least an end portion of the connector tail 1250. Removing the
intermediate, compressible element may also facilitate electrical
connection with one or more internal surfaces of the electrical
connector tail 1250.
[0151] FIG. 13 depicts a cross-sectional view along line 3-3 of the
electrical connector tail 1250. As shown in FIG. 13, the electrical
connector tail 1250 is formed from four circuit layers 1211, 1212,
1221, 1222. In this example, each of the circuit layers includes at
least one flexible dielectric layer and at least one flexible
conductive layer. The flexible dielectric layer may be formed from
a polyimide sheet and the electrical conductive layer may be formed
from a metal film or metallized trace material. Further, in this
example, each of the circuit layers is electrically connected with
a capacitive plate of one of the force-sensitive structures 1210,
1220 (depicted in FIG. 12). For example, the electrical conductive
layer of circuit layer 1211 may be electrically connected to a
first (upper) capacitive plate of the force-sensitive structure
1210. Similarly, the electrical conductive layer of circuit layer
1212 may be electrically connected to a second (lower) capacitive
plate of the force-sensitive structure 1210. Similarly, the circuit
layers 1221 and 1222 are electrically connected to a first (upper)
and a second (lower) capacitive plate, respectively, of the force
sensitive structure 1220. In this example, each of the circuit
layers 1211, 1221, 1222, and 1212 are electrically coupled to a
respective terminal 1213, 1223, 1224, and 1214.
[0152] Alternatively, one or more of the circuit layers 1211, 1221,
1222, and 1212 may serve as a ground layer for the force-sensitive
structure 1250. In one example either of both of the outer circuit
layers 1211 or 1212 are held at a constant voltage during the
operation of the sensor to act as an electromagnetic shield. In
some cases, the outer circuit layers 1211 or 1212 are connected to
ground during the operation of the sensor to facilitate
electromagnetic shielding. One or more of the outer circuit layers
may serve as a ground shield, depending on the location of the
source of the interference. In some cases, one or more additional
ground shield circuit layers are added to the force-sensitive
structure. These additional ground shield layers may be added, for
example, to the outer surfaces of the outer circuit layers 1211 and
1212. In one example, the conductive traces in any ground shield
layer may extent substantially across the entire surface of the
circuit layer to maximize the area that is shielded by the ground
shield layer.
[0153] As shown in FIG. 13, the two circuit layers 1211 and 1221
are separated from the other two circuit layers 1212, and 1222 by
the intermediate compressible layer 1230. In this example, the
compressible layer 1230 serves as the compressible element in the
force sensors 1210, 1220. As also shown in FIG. 13, the
compressible layer 1230 does not extend into an end portion 1255 of
the electrical connector tail 1250. As shown in FIG. 13, a void
region 1350 is formed between the pairs of circuit layers. In some
embodiments, the tail may lack any intermediate compressible
layer.
[0154] As explained above, this configuration may be advantageous
from a few aspects. First, because there is no material connection
between the upper and lower pairs of circuit layers, the
bendability of the electrical connector tail 1250 is improved,
which may facilitate a smaller bending radius. Additionally,
because there is no material between the pairs of circuit layers,
additional internal electrical terminals 1223 and 1224 may be used
for electrical connections. This reduces the need for circuit vias
or additional electrical routing that may otherwise be required to
electrically connect the electrical conductive layers of internal
circuit layers 1221, 1222 to an external terminal.
[0155] The tail 1250 may extend from the force-sensing structures
1210, 1220 and bend one or more times to connect to a flex or other
electrical connection within the device. As one non-limiting
example, the tail 1250 or, more appropriately, the flexible
dielectric and flexible conductive layers may bend in a serpentine
fashion to each an interconnect. Two separate structures may form
the tail; each such structure may be formed from one flexible
dielectric and one flexible conductive layer. Generally, the two
tail structures may follow different paths insofar as one extends
from the upper force-sensing structure 1210 and one from the lower
force-sensing structure 1220. Nonetheless, the constituent
structures of the tail 1250 are typically routed such that they do
not experience any force exerted on a cover glass, housing or other
external force-sensitive surface. Thus, the tail 1250 may not
present a secondary path for an exerted force to bypass the force
sensor which, in turn, may increase the accuracy of the force
sensor. Likewise, other components of the electronic device may be
structured such that they do not absorb or divert force exerted
against a force-sensitive surface of the electronic device.
[0156] While the device 1200 depicted in FIG. 12 includes two
force-sensing structures located around the periphery of a display
element 1202, an alternative embodiment may include only a single
force-sensing structure. In this case, the electrical connector
tail may only include two conductive layers (on two circuit
layers). In other alternative embodiments, a device may include
more than two force-sensing structures and the electrical connector
tail may have multiple conductive layers to facilitate connection
with each of the force-sensing structures.
[0157] FIG. 14 depicts an example process 1400 for manufacturing a
force sensor having an electrical connector tail. The process 1400
can be used to manufacture the force sensors 1210, 1220 having an
electrical connector tail 1250 in accordance with the embodiments
of FIGS. 12 and 13. The process 1400 may also be used to
manufacture force sensors having a variety of configurations,
including configurations having a single pair of conductive
layers.
[0158] In operation 1405, a first circuit layer is obtained. In
this example, the first circuit layer comprises at least a first
flexible conductive layer and a first flexible dielectric layer.
With reference to FIG. 13, the first circuit layer may include one
of either of the circuit layers pairs 1211, 1221 or 1222, 1212. In
some cases, the first circuit layer may be obtained by forming the
first conductive layer on the first dielectric layer. The
conductive layer may be formed by, for example, bonding a metal
foil to a surface of the first dielectric layer. In some cases, the
conductive layer may be formed by a deposition or sputtering
process that deposits a conductive material onto the dielectric
layer. In one example, the conductive layer also forms one or more
of the capacitive plates used for the force sensor. In some cases,
the first circuit layer is pre-manufactured and obtained as a sheet
or die-cut component.
[0159] In operation 1410, a second circuit layer is obtained. In
this example, the second circuit layer also comprises at least a
second flexible conductive layer and a second flexible dielectric
layer. With reference to FIG. 13, the second circuit layer may also
include one of either circuit layer pairs 1211, 1221 or 1222, 1212
(that is also separated from the first circuit layer by the
intermediate compressible layer 1230). As described above, the
first circuit layer may be obtained by forming the first conductive
layer on the first dielectric layer by laminating a metal foil or
depositing a conductive material onto a surface of the dielectric
layer. The second circuit layer may also be pre-manufactured as a
sheet or die-cut component.
[0160] In operation 1415, a laminate structure is formed. In
particular, a laminate structure is formed such that the
compressible layer is disposed between the first and second circuit
layers. With reference to FIG. 13, an exemplary laminate structure
includes the four circuit layers 1211, 1221, 1222, 1212 and the
compressible layer 1230. In many cases, other layers are formed as
part of the laminate structure. For example, additional circuit
layers, adhesive layers, and coatings may be formed as part of the
laminate structure. In particular, an adhesive layer is typically
used to bond the intermediate compressible layer with the other,
adjacent components of the laminate structure. It is not necessary
that either the first or second circuit layers (obtained in
operations 1405 and 1410) be immediately adjacent or bonded
directly to the compressible layer.
[0161] Operation 1415 may be performed by, for example, placing
pressure sensitive adhesive (PSA) layers between the components of
the laminate structure. The laminate may then be subjected to a
pressing operation to bond the layers. In some cases, heat or other
curing techniques may be employed to bond the layers together. In
some embodiments, the PSA may be applied, all layers bonded, and
then the structure die cut to its final form.
[0162] Operation 1415 may also be performed using an injection or
insertion molding process. In this case, the first and second
circuit layers may be laminated or pre-formed with other layers or
components. The layers may then be placed in opposite halves of an
injection mold cavity and the intermediate compressible layer may
be formed between the layers by injecting a molten or liquid
material into the injection mold. In one example, a spacer element
is placed between the first in second circuit layers to hold the
first and second circuit layers against the respective halves of
the injection mold. The spacer element may be approximately the
same thickness as the final dimension of the compressible layer. In
one example, the spacer element is compressible and is slightly
larger than the final dimension of the compressible layer to be
injection molded between the first and second circuit layers. In
this case, the spacer element exerts a force against the first and
second circuit layers, which are pressed against respective cavity
walls of the injection mold. By pressing the circuit layers against
the cavity walls, the injected molded material is more likely to
fill the area between the circuit layers rather than filling an
area between the circuit layers and the cavity walls. In one
example, multiple spacer elements are used, each spacer element
formed from a semi-circular ring. The spacer elements may be placed
near the injection point of the mold, which is typically near the
center of the part. The spacer elements can then be removed by
die-cutting the center portion of the part, which may also
facilitate the creation of a viewing area for the display.
[0163] As part of operation 1415, one or more electrical vias may
be formed between the various layers of the laminate structure. In
some cases, electrical vias are formed through the compressible
layer to connect circuit layers that are disposed on opposite sides
of the compressible layer. The vias may be formed by, for example,
the addition of conductive pillar elements that electrically
connect the conductive layers of different circuit layers.
Additionally or alternatively, conductive regions within the
compressible layer may be formed and then reflowed or otherwise
electrically connected with conductive layers of the laminate
structure.
[0164] In some cases, the laminate structure that is formed in
operation 1415 is cut to form the force sensor having an electrical
connector tail. For example, if the first and second circuit layers
(obtained in operations 1405 and 1410) are formed as a solid sheet
of material, the laminate structure may be die cut to form the
desired geometric profile features of the force sensor.
Specifically, a center portion may be cut out of the middle of the
laminate structure to facilitate installation with a display
element. Thus, the display element will be visible through the hole
created in the middle of the laminate structure. As mentioned
above, if the laminate structure includes spacer elements used for
an injection molding process, they may be removed by this die
cutting operation. Additional cuts may be performed to form the
connector tail portion of the force sensor.
[0165] The cutting operation may be optional if, for example, the
first and second circuit layers (obtained in operations 1405 and
1410) have been pre-cut or have been formed in the desired
geometric profile shape. In this case, operation 1415 may also
include an indexing operation to align the layers of the laminate
structure.
[0166] In operation 1420, a portion of the compressible layer is
removed from the laminate structure. In this example, a portion of
the compressible layer located in an end portion of electrical
connector tail is removed from the laminate structure leaving a
void region between the first and second circuit elements. As
explained above with respect to FIGS. 12 and 13, removal of the
compressible layer may improve the flexibility or bendability of
the laminate structure. It may also provide access to terminals or
electrical connections on circuit layers that are internal to the
laminate structure.
[0167] Removing the compressible layer may be accomplished using
one or more techniques. In a first example, the compressible layer
is perforated or pre-cut near the end portion of the electrical
connector tail. Also, within the end portion of the electrical
connector tail, the pressure sensitive adhesive or other bonding
layer may be omitted between the compressible layer and the
adjacent layers of the laminate structure. In this case, the
pre-cut or perforation and the absence of a bonding layer allows
the portion of the compressible layer in the end portion of the
electrical connector tail to be removed.
[0168] In a second example, one or more layers of the laminate
structure are delaminated or stripped from the compressible layer
exposing the compressible layer. In this case, as secondary cut
operation may be performed to remove the portion of the
compressible layer in the end portion of the electrical connector
tail.
[0169] In a third example, the compressible layer may be cut from
the end portion of the electrical connector tail without first
delaminating or stripping layers of the laminate structure. For
example, the portion of the compressible layer within the end
portion of the connector tail may be removed by passing a knife or
cutting implement between the layers of the laminate structure.
[0170] As an alternative to operation 1420, the laminate structure
may be formed such that the end portion of the electrical connector
tail does not include the compressible layer. For example, if the
laminate structure is formed using an injection or insertion
molding process, an insert mold element may be placed in the end
portion of the electrical connector tail preventing the formation
of a compressible layer in this region. In this case, the laminate
structure is formed with a void region between the first and second
circuit layers.
[0171] As described above, the process 1400 may also be used to
manufacture force sensors having a variety of configurations,
including configurations having a single pair of conductive layers.
For example, a force sensor having only two circuit layers (one on
each side of the intermediate compressible layer) may be formed
using process 1400. Alternatively, a force sensor having multiple
circuit layers formed on either side of the intermediate
compressible layer may also be formed using process 1400.
[0172] The operations of process 1400 are provided as one example.
However, a force sensor may also be formed by omitting one or more
of the operations described above. For example, depending on how
the laminate structure is created, it may not be necessary to
perform operation 1420 to remove a portion of the compressible
layer.
[0173] In certain embodiments, the tail may be connected to a flex,
circuit board or other electronic contact. In some embodiments, the
entire force-sensing structure may be placed into an oven to bond
the tail to the electrical contact through, for example, a
surface-mount technology (SMT) process. In some embodiments, the
SMT process may heat the tail (or portions thereof) and/or the
electrical contact to 200 degrees or more. This elevated
temperature may have deleterious effects on the silicone of the
force-sensing structure, however. Thus, the force-sensing structure
may be placed in a heat-resistant envelope, pouch or other
container with the tail extending outwardly therefrom. Thus, when
the oven is heated for the SMT process, the tail may be heated to
the appropriate temperature while the silicone and other layers of
the force-sensing structure may be maintained at a temperature that
does not cause damage. Further, it should be appreciated that the
force-sensing structure may not be singulated or cut into its final
form prior to heating in the oven.
[0174] FIG. 15A depicts another embodiment 1500 of a force-sensing
electronic device. Similar to other embodiments described herein,
the embodiment 1500 may include and electronic device having a
cover 1505 positioned over a display stack 1515, which may be
configured to detect the touch of a force on the surface of the
cover 1505. The cover 1505 may be formed from a variety of
materials including, for example, glass, polycarbonate or other
plastic, sapphire and the like. The display stack 1515 may include
a liquid crystal display (LCD), organic light omitting diode
(OLED), or other electronic display component.
[0175] In some embodiments, the cover 1505 may move with respect to
the housing 1510. When a force is exerted on the cover 1505, by,
for example, the touch of a user, the cover 1505 may travel
downwardly. It should be appreciated that the entirety of the cover
1505 may travel in such a fashion, rather than only deflecting
locally while edges of the cover 1505 remain substantially
immobile. Whether the cover 1505 deflects locally or not may depend
on the relative stiffness of the cover 1505 and the
components/elements positioned below the cover 1505.
[0176] In some embodiments, the downward travel of the cover 1505
likewise moves the display stack 1515 downward, which in turn may
impact and/or compress a sheet sensor 1520 positioned beneath the
display stack 1515. The sheet sensor 1520 may include a
capacitive-plate type force sensor, strain gauge sensor, or other
force-sensitive sensor, and may generally be referred to as a force
sensing structure, sensor, or sheet sensor. In general, the sheet
sensor 1520 may extend over a substantial portion of the display
stack 1515. In some cases, the sheet sensor 1520 is formed from an
array or series of force-sensing elements that are disposed
throughout the area of the sheet sensor 1520.
[0177] As shown in FIG. 15A, the sheet sensor 1520 may
substantially abut the display stack 1515. In some embodiments, the
sheet sensor 1520 may be separated therefrom by an air gap and/or
other components or layers in certain embodiments. In some
embodiments, the sheet sensor 1520 may be affixed directly to an
element of the display stack 1515.
[0178] The sheet sensor 1520 may be supported by a plate 1525
positioned below the sensor 1520 opposite the side facing the
display stack 1515. In some embodiments the plate 1525 may be rigid
or substantially rigid, while in other embodiments the plate 1525
may be flexible. Typically, although not necessarily, the sheet
sensor 1520 is affixed to the plate 1525. In some embodiments, the
plate 1525 may be fixed relative to the housing 1510 of the device.
In some embodiments, the plate 1525 may be a mid-plate providing
structural support and/or stiffness to the housing 1510 of the
electronic device 1500, while in other embodiments the plate 1525
may be used primarily or solely to support the sheet sensor 1520.
In still other embodiments, other electronic components (not shown)
may share the plate 1525 with the sheet sensor 1520.
[0179] As the cover 1505 and display stack 1515 move downward, the
sheet sensor 1520 may be compressed. This compression may be sensed
by the sheet sensor 1520 and a corresponding output generated. For
example, the sheet sensor 1502 may have first and second capacitive
plates or arrays 1530, 1535 (as used herein, the term "plate" is
intended to cover an array as well) defining an upper surface and a
lower surface of the sheet sensor, or otherwise positioned in an
upper and lower region of the sensor. The first and second
capacitive plates 1530, 1535 may be separated from one another by a
compressible inner layer 1540, such as silicone or a compliant gel
or polymer.
[0180] In some embodiments, the first and second capacitive plates
1530, 1535 are operatively coupled to a sensing circuit that is
configured to estimate the force of a touch on the cover based on a
change in capacitance between the first and second capacitive
plates 1530, 1535. In some implementations, sensing circuit is
configured to generate a drive signal or electrical current that is
used to detect and measure changes in capacitance between the first
and second capacitive plates 1530, 1535. As the first capacitive
plate 1530 moves toward the second capacitive plate 1535, the
reduction in distance may correspond to a change in capacitance
between the plates, which may be correlated to the force exerted on
the cover 1505.
[0181] It should be appreciated that the sheet sensor 1520 may
operate as a self-capacitance or mutual capacitance sensor to
measure force in this fashion. Accordingly, in a mutual capacitance
configuration, one of the first and second capacitive plates may be
a drive plate and the other may be a sense plate. In a
self-capacitance configuration, one of the first and second plates
maybe a ground or shield layer while the other is a sense plate.
Further, one or both plates of the sheet sensor 1520 may be formed
in a pixel pattern (as may the sheet sensor 1520 itself) in order
to locally register the application of a force and provide a
localized region at which a force is applied.
[0182] In an embodiment having a flexible or deflectable plate 1525
supporting the sheet sensor 1520, changes in capacitance may still
be measured so long as the layers of the sensor sheet 1520
compress, even if the plate 1525 itself flexes. Similarly, in
embodiment having an air gap between the sheet sensor 1520 and
display stack 1515, a force of a touch may not be sensed until the
display stack moves far enough to compress or impact the sheet
sensor.
[0183] It should be appreciated that the sheet sensor 1520, as
shown in FIG. 15A, need not be transparent insofar as it is located
beneath the display stack 1515. Further, such a configuration may
be suitable not only for use with a display stack having an LED or
LCD display, but also with a display stack incorporating an OLED
display layer.
[0184] FIG. 15B depicts an alternative embodiment 1500B of the
embodiment shown in FIG. 15A. In this embodiment 1500B, foam 1545
or other compliant material or compliant layer may be placed
between the display stack 1515 and sheet sensor 1520. The foam 1545
may generally stiffen the display stack 1515 and/or cover 1505 and
thus prevent the entire stack/glass from moving downward. Instead,
when a force is exerted on the cover 1505, the foam 1545 may deform
locally and thereby concentrate the deformation and/or force in a
localized region, which may in turn enhance the force-sensing
capabilities of the embodiment 1500B. It should be appreciated that
any suitable material may be placed between the display stack 1515
and the sheet sensor 1520; foam is but one example material.
[0185] In some embodiments, a compliant environmental gasket 1550
or seal may be positioned between the cover 1505 and housing 1510.
The compliant gasket may prevent the ingress of dirt, dust and the
like into the interior of the electronic device 1500B, but may
still permit downward travel of the cover 1505 and display stack
1515. In alternative embodiments, the gasket 1550 may be relatively
rigid and may cooperate with the foam 1545 (or operate in the
absence of the foam 1545) to restrict downward motion of the cover
1505 at one or more edges, with the net result that the cover may
deflect locally instead of traveling as a whole. Force may still be
sensed in such an embodiment through localized compression of the
sheet sensor 1520.
[0186] In some embodiments, a portion or all of the region occupied
by the gasket 1550 may be coated with an oleophobic material. The
oleophobic material may serve as a barrier against, or repel, oils,
dust, dirt and other similar materials from entering the housing
1510 and/or impacting the force-sensing structure 1520. In this
fashion the coating may serve to maintain operation of the
force-sensing structure over time. Coatings other than an
oleophobic coating may be used; other dust- and/or oil- and/or
dirt-repellent coatings may be used in different embodiments.
[0187] FIG. 15C depicts still another embodiment of a
force-sensitive electronic device 1500. This embodiment is
generally similar to that of FIG. 15B, except for the structure of
the sheet sensor 1520C. Here, the sheet sensor 1520C may be
patterned from one or more strain gauges rather than taking the
form of a capacitive sensor. Individual strain gauges may be
arranged in an array, grid, or other pattern to form the sheet
sensor 1520C. The strain gauges may be formed from a material that
changes electrical properties or produces an electrical response
due to a deflection of the sheet sensor 1520C. The strain gauges
may be formed, for example, from a resistive material,
piezoelectric resistive material, piezoelectric material, and the
like. The strain gauges may also be formed as an array of strain
gauge elements, each element comprised of a series of traces or
patterns that may be configured to detect a localized strain or
deflection.
[0188] As force is exerted on the cover 1505, it is transferred
through the display stack 1515, through the foam 1545 (or other
compliant layer), and to the strain gauge(s) of the sheet sensor
1520C. The strain gauges may experience an increase in strain due
to the exerted force; this increase in strain may be correlated to
determine the magnitude of the exerted force as generally described
elsewhere herein. In some embodiments, the sheet sensor 1520C is
operatively coupled to sense circuitry that is configured to
monitor and detect changes in an electrical property or measure and
electrical response of the strain gauges of the sheet sensor 1520C.
For example, the sense circuitry may be configured to detect a
change in resistance and/or charge due to a deflection of the
sensor sheet 1520C.
[0189] In the embodiments shown in FIGS. 15A-15C, the cover and
display stack are generally free to translate with respect to the
housing. In some embodiments, the cover and/or display stack may be
adhered to the housing or otherwise fixed with respect to the
housing, such that force exerted on the cover causes local
deformation of the cover rather than translation. In such
embodiments, force may be relatively localized insofar as the
boundary conditions of the cover prevent motion. Since the cover
may still deflect locally, a force may still be transmitted through
the various layers and sensed by the force sensor (e.g., the sheet
sensor).
[0190] FIG. 15D depicts a close-up of area 15D in FIG. 15C, showing
one embodiment of a compliant layer 1545D positioned between the
sheet sensor 1520 and the base of the display stack 1515. In the
cross-sectional view of the electronic device 1500 shown in FIG. 1,
the compliant layer 1545D is formed from a series or array of
pillar-like structures 1560 sandwiched between an upper compliant
substrate 1555 and a lower rigid substrate 1565 made of glass or
the like. (In some embodiments, the lower substrate may also be
compliant). In certain embodiments, the upper sheet 1555 may be
formed from silicone, as may the pillar structures 1555. A sheet
sensor 1520C is located beneath the lower substrate 1565. In the
present embodiment, the sheet sensor 1520C is formed of one or more
strain gauges, as discussed above with respect to FIG. 15C. The
sheet sensor 1520C may be supported by a sense plate 1525, as
generally discussed above.
[0191] In some implementations, the pillar structures 1555 may
deform under downward pressure exerted on the compliant layer 1545C
by the display stack 1515, or any other element of the electronic
device 1500C that exerts pressure on the compliant layer 1545D. One
or more void spaces 1550 may be defined between and/or around the
pillars 1555. For example, adjacent pillars 1550 may be separated
by a void space 1560 and each void space 1560 may be separate and
distinct. As another option, a single void space 1560 may encompass
all the pillars 1555. Different configurations of void spaces and
pillar structures are thus contemplated.
[0192] As the pillar structures 1555 deform, the top sheet 1555
moves closer to the bottom sheet 1565 and the resistance of the
pillar structure to further collapse increases. Further, the strain
exerted on the sheet sensor 1520C through the compliant layer 1545D
generally increases, causing the strain gauge output to increase.
This increase in output may be correlated to a force exerted on the
exterior of the housing.
[0193] In some embodiments, the void space or spaces 1550 may be
filled with an optically transparent or near-transparent fluid, gel
or the like (collectively, "fluid"). In some embodiments, the fluid
may be optically indexed matched to the optical index of the pillar
structures. That is, in certain embodiments, the index of
refraction of the fluid may match or approximate that of the pillar
structures 1555. In such an embodiment, the combination of fluid in
the void spaces 1550 and pillar structures 1560 may render the
compliant layer 1545D optically transparent and/or near-invisible.
This may be useful when the display is an OLED display, for
example.
[0194] In yet another embodiment and as shown in FIG. 15E, the
compliant layer 1545D may separate a lower capacitive sensing array
1570 from an upper capacitive sensing array 1575. In such an
embodiment 1500E, the capacitive sensing arrays 1570, 1575 may
operate as described elsewhere herein, such that one array is a
drive array (or reference array) and one is a sense array. The
compliant layer 1545D may serve to prevent the two layers from
approaching too close to one another and thus prevent, or at least
reduce the likelihood of, contact between the two layers and/or
excessive capacitive coupling between the two layers, which may
result in inaccurate force measurement.
[0195] FIG. 16 depicts a partial cross-section of another
embodiment of a force-sensing electronic device 1630. This
embodiment may include a force-sensing structure 1600 similar to
that shown in FIGS. 2A and 3, and described elsewhere herein. For
example, the force-sensing structure 1500 may be configured with
multiple capacitive layers separated by a deformable middle body,
as generally discussed with respect to FIG. 3 and/or the variants
shown in FIGS. 4-6. The force-sensing structure 1600 may take the
form of a gasket any may be located between the cover 1505 and a
housing 1510. In one embodiment, the portion of the housing 1510
adjacent the cover 1505 may include a bezel or bezel portion.
[0196] The force-sensing structure 1600 may extend partly or fully
about a perimeter of the electronic device, cover, and/or portion
of either. Alternately, multiple force-sensing structures 1600 may
cooperate to extend partly or fully about a perimeter of the
electronic device 1630, cover, and/or portion of either. In some
embodiments, the force-sensing structure 1600 may be configured to
prevent the ingress of contaminants into the interior of the
housing 1510 and, therefore, may also function as a gasket. In some
cases, the combination gasket and sensor is referred to as a
strain-sensitive gasket or gasket force-sensing structure.
[0197] As with prior embodiments, the force-sensing structure 1600
may capacitively sense a distance between the first and second
plates 1620, 1625 or other sensor structures; the output of the
force-sensing structure 1600 may be correlated to a force by a
sensing circuit, processor, or other electronic component of the
force-sensing electronic device 1630. In some embodiments, the
force-sensing structure 1600 is operatively coupled to sense
circuitry that is configured to detect and measure changes to an
electrical property of the force-sensing structure 1600, which may
be correlated to the force of a touch on the cover 1505.
[0198] In addition to the force-sensing structure 1600 generally
positioned between the cover 1505 and bezel or housing 1510, the
present embodiment may incorporate a force-sensitive sheet sensor
1520. The sheet sensor 1520 is generally similar in configuration
and operation to any of the sheet sensors described above with
respect to FIGS. 15A-15D.
[0199] As shown in FIG. 16, the sheet sensor 1520 may be separated
from the display stack by a small air gap. Additionally or
alternatively, the sheet sensor 1520 may be separated from the
display stack by a compressible layer similar to the compressible
layer described above with respect to FIGS. 15B-E. When the cover
1505 and display stack 1515 deflect in response to a force, the
gasket force-sensing structure 1600 may compress and sense force,
as generally described herein. To prevent bottoming out of the
cover and display stack when a force is applied away from the edges
of the cover, the sheet sensor 1520 may be included. When the
display stack and cover deform sufficiently, they may contact the
sheet sensor 1520 and transmit force thereto. The two force sensors
1600 and 1520 may cooperate to determine a force. For example, the
output of both force sensors may be taken and manipulated to
determine the force exerted on the cover. In this manner, the
dynamic force sensing range of the device 1500 may be extended to
sense and react to forces that would otherwise be sufficiently
large to cause the cover to bottom out and the single gasket sensor
1600 to register a maximum value. In some embodiments, the air gap
is configured to at least partially collapse in response to a force
of a touch that exceeds a first threshold. In some implementations,
the first threshold is less than a second threshold that
corresponds to a maximum force that can be practically or reliably
detected by gasket force-sensing structure 1600.
[0200] FIG. 17 depicts yet another embodiment of an electronic
device 1700 that may employ a sheet or pad sensor 1520 for
capacitively measuring a force exerted on a cover 1505 (or, in
other embodiments, a portion of a housing or a different type of
input surface). Generally, the structure and operation of the sheet
sensor 1520 is similar to that described herein with respect to
prior figures.
[0201] In addition to the upper and lower capacitive arrays of the
sheet sensor 1520, a second capacitive sense layer/array 1705 may
be placed within the display stack 1515. In one embodiment, the
second capacitive sense layer 1705 may be formed from
indium-tin-oxide, silver nanowire, PEDOT, or any other suitable
conductive material. In certain embodiments, it may be desirable
for the second capacitive sense layer 1705 to be transparent.
[0202] In the embodiment 1700 of FIG. 17, the second capacitive
sense layer 1705 may be placed relative to the display stack 1515.
The capacitive sense layer 1705 may, in some instances, function as
a capacitive touch sensor for sensing the location of a touch on
the cover 1505. In some embodiments, the capacitive sense layer
1705 is positioned above a backlight unit 1710. If the second
capacitive sense layer 1705 is transparent or nearly so, it may not
interfere with the operation of the backlight unit 1710 and/or the
remainder of the display stack 1515.
[0203] As shown in FIG. 17, an air gap may be located between the
capacitive sense layer 1705 and the sheet sensor 1520. Additionally
or alternatively, the sheet sensor 1520 may be separated from the
capacitive sense layer 1705 by a compressible layer similar to the
compressible layer described above with respect to FIGS. 15B-E.
[0204] As a force is exerted on the cover 1505 (or housing or input
surface, in some embodiments), the cover and display stack 1515 are
moved closer to the sheet sensor 1520. Thus, the second capacitive
sense layer 1705 is likewise moved closer to the sheet sensor 1520.
Accordingly, a capacitance between at least a portion of the second
capacitive sense layer 1705 and the upper capacitive array 1530 of
the sheet sensor 1520 may increase with such motion. Further,
because the cover 1505, display stack 1515 and second capacitive
sense layer 1705 may deform locally in response to the force, the
capacitance may increase (or increase more) in the general region
corresponding to the exerted force. This change in capacitance may
be used to estimate the applied force, as generally described
elsewhere herein.
[0205] Under sufficient force, the backlight unit 1710 (or other
base of the display stack) will contact the upper surface of the
sheet sensor 1520. Once this occurs, the capacitance between the
second capacitive sense layer 1705 and the upper capacitive array
1530 of the sheet sensor 1520 will generally reach a maximum value.
Additional force may cause the sheet sensor 1520 to compress,
thereby moving at least a portion of the upper capacitive array
1530 closer to the lower capacitive array 1535 and increasing a
capacitance between these two elements, at least within a given
region. Thus, even though the capacitance between the second
capacitive sense layer 1705 and the upper capacitive array 1530 may
be at maximum or near-maximum value, the increase in capacitance
between the arrays 1530, 1535 of the sheet sensor 1520 may be used
to determine estimates of an exerted force.
[0206] In some embodiments, sensing circuitry is operatively
coupled to the capacitive sense layer 1705 and the sheet sensor
1520. The sensing circuitry may be configured to estimate the force
of a touch on the cover based on a change in mutual capacitance
between the capacitive sense layer 1705 and the upper and/or
capacitive plate of the sheet sensor 1520. In some embodiments, the
sensing circuitry may be configured obtain a first capacitance
between the upper capacitive plate and the lower capacitive plate
of the sheet sensor and also obtain a second capacitance between
the upper capacitive plate and the capacitive sense layer. An
estimate of a force of a touch on the cover may be computed or
generated using the first and second capacitances measured using
the sensing circuitry.
[0207] It may be considered, then, that the capacitance between the
second capacitive sense layer 1705 and the upper capacitive array
1530 may be used to determine or estimate an exerted force between
zero and some first threshold value, and the capacitance between
the upper and lower capacitive arrays 1530, 1535 of the sheet
sensor 1520 may be used to determine an exerted force between the
first threshold value and a second threshold value. This
combination of sensing structures may provide force sensing about a
wider range of values than may be achieved by the use of a single
sensor.
[0208] It should be appreciated that embodiments described herein
may measure changes in force, thereby providing a non-binary or
even substantially continuous input to an associated electronic
device, corresponding to changes in distance or less than 2 microns
between two capacitive structures or arrays. Thus, although one or
both of the capacitive structures or arrays may move with respect
to the other, the motion may be imperceptible to a human
interacting with the device. Changes in distance on the measure of
nanometers may correspond to approximately one gram of force being
exerted on a surface, as one non-limiting example.
[0209] While the present disclosure has been described with
reference to various embodiments, it will be understood that these
embodiments are illustrative and that the scope of the disclosure
is not limited to them. Many variations, modifications, additions,
and improvements are possible. More generally, embodiments in
accordance with the present disclosure have been described in the
context of particular embodiments. Functionality may be separated
or combined in procedures differently in various embodiments of the
disclosure or described with different terminology. These and other
variations, modifications, additions, and improvements may fall
within the scope of the disclosure as defined in the claims that
follow.
* * * * *