U.S. patent application number 15/435649 was filed with the patent office on 2017-08-24 for force sensing architectures.
The applicant listed for this patent is Apple Inc.. Invention is credited to Se Hyun Ahn, Wookyung Bae, Christopher L. Boitnott, Po-Jui Chen, Eugene C. Cheung, Yindar Chuo, Rasmi R. Das, Yi Gu, Nathan K. Gupta, Sunggu Kang, Pey-Jiun Ko, Wei Lin, Xiaofan Niu, Dhaval C. Patel, Robert W. Rumford, Steven M. Scardato, Mookyung Son, Steve L. Terry, Chun-Hao Tung, Victor H. Yin, John Z. Zhong, Xiaoqi Zhou.
Application Number | 20170242506 15/435649 |
Document ID | / |
Family ID | 58191689 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170242506 |
Kind Code |
A1 |
Patel; Dhaval C. ; et
al. |
August 24, 2017 |
Force Sensing Architectures
Abstract
An electronic device with a force sensing device is disclosed.
The electronic device comprises a user input surface defining an
exterior surface of the electronic device, a first capacitive
sensing element, and a second capacitive sensing element
capacitively coupled to the first capacitive sensing element. The
electronic device also comprises a first spacing layer between the
first and second capacitive sensing elements, and a second spacing
layer between the first and second capacitive sensing elements. The
first and second spacing layers have different compositions. The
electronic device also comprises sensing circuitry coupled to the
first and second capacitive sensing elements configured to
determine an amount of applied force on the user input surface. The
first spacing layer is configured to collapse if the applied force
is below a force threshold, and the second spacing layer is
configured to collapse if the applied force is above the force
threshold.
Inventors: |
Patel; Dhaval C.; (San Jose,
CA) ; Cheung; Eugene C.; (Redwood City, CA) ;
Ko; Pey-Jiun; (Redwood City, CA) ; Chen; Po-Jui;
(Taipei City, TW) ; Rumford; Robert W.;
(Cupertino, CA) ; Terry; Steve L.; (Cupertino,
CA) ; Lin; Wei; (Santa Clara, CA) ; Niu;
Xiaofan; (Cupertino, CA) ; Zhou; Xiaoqi;
(Cupertino, CA) ; Gu; Yi; (Palo Alto, CA) ;
Chuo; Yindar; (San Jose, CA) ; Das; Rasmi R.;
(Sunnyvale, CA) ; Scardato; Steven M.; (Sunnyvale,
CA) ; Ahn; Se Hyun; (Cupertino, CA) ; Yin;
Victor H.; (Cupertino, CA) ; Bae; Wookyung;
(San Jose, CA) ; Boitnott; Christopher L.;
(Cupertino, CA) ; Tung; Chun-Hao; (San Jose,
CA) ; Son; Mookyung; (Cupertino, CA) ; Kang;
Sunggu; (San Jose, CA) ; Gupta; Nathan K.;
(San Francisco, CA) ; Zhong; John Z.; (Saratoga,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
58191689 |
Appl. No.: |
15/435649 |
Filed: |
February 17, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62297676 |
Feb 19, 2016 |
|
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|
62395888 |
Sep 16, 2016 |
|
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62382140 |
Aug 31, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 3/0443 20190501;
G06F 3/0446 20190501; G06F 3/0447 20190501; G06F 2203/04102
20130101; G06F 3/044 20130101; G06F 2203/04105 20130101; G06F 3/041
20130101 |
International
Class: |
G06F 3/044 20060101
G06F003/044 |
Claims
1. An electronic device, comprising: a user input surface defining
an exterior surface of the electronic device; a first capacitive
sensor comprising a first pair of sensing elements having an air
gap therebetween and configured to determine a first amount of
applied force on the user input surface that results in a collapse
of the air gap; and a second capacitive sensor below the first
capacitive sensor comprising a second pair of sensing elements
having a deformable element therebetween and configured to
determine a second amount of applied force on the user input
surface that results in a deformation of the deformable
element.
2. The electronic device of claim 1, wherein: the first pair of
sensing elements comprises: a shared sense element; and a first
drive element set apart from and capacitively coupled to the shared
sense element; and the second pair of sensing elements comprises:
the shared sense element; and a second drive element set apart from
and capacitively coupled to the shared sense element.
3. The electronic device of claim 2, further comprising: a display
layer comprising: a display element positioned below the user input
surface; and a back polarizer positioned below the display element;
a sheet of conductive material formed over a back surface of the
back polarizer to produce a conducting surface on the back surface
of the back polarizer; and a conductive border formed along at
least one edge of the sheet of conductive material.
4. The electronic device of claim 3, wherein the conductive border
is positioned outside of a user-viewable region of the display
layer.
5. The electronic device of claim 3, wherein the sheet of
conductive material comprises silver nanowire.
6. The electronic device of claim 2, further comprising: a display
element coupled to the first drive element; and a base structure,
wherein: the display element is configured to flex relative to the
base structure; the deformable element is coupled to the base
structure; and the air gap is positioned between the deformable
element and the display element.
7. The electronic device of claim 6, wherein the shared sense
element is coupled to the deformable element.
8. A capacitive force sensor for an electronic device, comprising:
a first drive layer; a second drive layer positioned relative to
the first drive layer; a shared sense layer between the first and
second drive layers; a first spacing layer between the first drive
layer and the shared sense layer; and a second spacing layer
between the shared sense layer and the second drive layer.
9. The capacitive force sensor of claim 8, wherein: the first
spacing layer comprises an air gap; and the capacitive force sensor
further comprises: a pair of opposed surfaces defining the air gap;
and an anti-adhesion layer configured to prevent adhesion between
the opposed surfaces.
10. The capacitive force sensor of claim 9, wherein the second
spacing layer comprises an array of deformable protrusions
extending from a base layer.
11. The capacitive force sensor of claim 8, further comprising
sensing circuitry operatively coupled to the first drive layer, the
second drive layer, and the shared sense layer, and configured to
determine: a first amount of applied force resulting in a change in
thickness of the first spacing layer; and a second amount of
applied force resulting in a change in thickness of the second
spacing layer.
12. The capacitive force sensor of claim 6, wherein the first drive
layer comprises: an insulating substrate; a sheet of conductive
material formed over a back surface of the insulating substrate to
produce a conducting surface on the back surface of the insulating
substrate; and a conductive border formed along at least one edge
of the sheet of conductive material.
13. The capacitive force sensor of claim 12, wherein the conductive
border comprises a continuous conductive border that extends along
the edges of the sheet of conductive material.
14. The capacitive force sensor of claim 12, wherein the conductive
border comprises one or more conductive strips formed along a
respective edge of the sheet of conductive material.
15. An electronic device, comprising: a cover defining a user input
surface of the electronic device; a first sensing element coupled
to the cover within an interior volume of the electronic device; a
frame member coupled to the cover and extending into the interior
volume of the electronic device; a second sensing element coupled
to the frame member; and a third sensing element coupled to a base
structure and set apart from the sense layer.
16. The electronic device of claim 15, wherein: the frame member
defines an opening; and the third sensing element capacitively
couples with the second sensing element through the opening.
17. The electronic device of claim 15, wherein the first sensing
element comprises a continuous layer of transparent conductive
material covering substantially an entire surface of a
substrate.
18. The electronic device of claim 17, wherein: the second sensing
element comprises a plurality of sensing regions; and the
continuous layer of transparent conductive material overlaps
multiple sensing regions of the plurality of sensing regions.
19. The electronic device of claim 18, wherein: the third sensing
element comprises a plurality of drive regions; and each drive
region overlaps multiple sensing regions of the plurality of
sensing regions.
20. The electronic device of claim 17, wherein: the first sensing
element further comprises a connection element electrically coupled
to the continuous layer of transparent conductive material; and the
electronic device further comprises: sensing circuitry configured
to provide an electrical signal to the first sensing element; and a
connector segment electrically coupling the sensing circuitry to
the connection element.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application No. 62/297,676,
filed Feb. 19, 2016, and entitled "Force Sensing Architectures,
U.S. Provisional Patent Application No. 62/395,888, filed Sep. 16,
2016, and entitled "Force-Sensitive Structure in an Electronic
Device," and U.S. Provisional Patent Application No. 62/382,140,
filed Aug. 31, 2016, and entitled "Force Sensing Architectures,"
the contents of all of which are incorporated by reference as if
fully disclosed herein.
FIELD
[0002] The disclosure relates generally to sensing a force exerted
against a surface, and more particularly to sensing a force through
capacitive changes.
BACKGROUND
[0003] Touch devices generally provide for identification of
positions where the user touches the device, including movement,
gestures, and the like. As one example, touch devices can provide
information to a computing system regarding user interaction with a
graphical user interface (GUI), such as pointing to elements,
reorienting or repositioning those elements, editing or typing, and
other GUI features. As another example, touch devices can provide
information to a computing system suitable for a user to interact
with an application program, such as relating to input or
manipulation of animation, photographs, pictures, slide
presentations, sound, text, other audiovisual elements, and
otherwise.
[0004] Generally, however, touch inputs are treated as binary
inputs. A touch is either present and sensed, or it is not. A force
of a touch input may provide another source of input information to
a device. For example, a device may respond differently to a touch
with a low application force than to a touch with a high
application force. Force sensing devices may determine an amount or
value of an applied force based on an amount of deformation of a
component that is subjected to the force.
[0005] In devices where force inputs are applied to a touchscreen,
such as a multi-touch touchscreen that the user touches to select
or interact with an object or application displayed on the display,
the noise produced by the display can interfere with the operation
of the touchscreen. In some situations, the display noise can
electrically couple to the touchscreen and interfere with the
operation of the touchscreen. Such display noise can also
electrically couple to a force sensing device. The magnitude of the
display noise can be much greater than the magnitude of the force
signals, making it difficult to discern the force signals from the
display noise.
SUMMARY
[0006] An electronic device includes a user input surface defining
an exterior surface of the electronic device, a first capacitive
sensor comprising a first pair of sensing elements having an air
gap therebetween and configured to determine a first amount of
applied force on the user input surface that results in a collapse
of the air gap, and a second capacitive sensor below the first
capacitive sensor comprising a second pair of sensing elements
having a deformable element therebetween and configured to
determine a second amount of applied force on the user input
surface that results in a deformation of the deformable
element.
[0007] The first pair of sensing elements comprises a shared sense
element and a first drive element set apart from and capacitively
coupled to the shared sense element. The second pair of sensing
elements comprises the shared sense element and a second drive
element set apart from and capacitively coupled to the shared sense
element. The shared sense element may be disposed between the first
drive element and the second drive element. The shared sense
element may include an array of sensing regions.
[0008] The electronic device may further include a display element
coupled to the first drive element. The electronic device may
further include a base structure, wherein the display element is
configured to flex relative to the base structure, the deformable
element is coupled to the base structure, and the air gap is
positioned between the deformable element and the display element.
The shared sense element may be coupled to the deformable
element.
[0009] The electronic device may further include a display layer
comprising a display element positioned below the user input
surface and a back polarizer positioned below the display element.
The electronic device may also include a sheet of conductive
material formed over a back surface of the back polarizer to
produce a conducting surface on the back surface of the back
polarizer, and a conductive border formed along at least one edge
of the sheet of conductive material. The conductive border may be
positioned outside of a user-viewable region of the display layer.
The sheet of conductive material may comprise silver nanowire.
[0010] A capacitive force sensor for an electronic device includes
a first drive layer, a second drive layer positioned relative to
the first drive layer, a shared sense layer between the first and
second drive layers, a first spacing layer between the first drive
layer and the shared sense layer, and a second spacing layer
between the shared sense layer and the second drive layer.
[0011] The first spacing layer may comprise an air gap. The
capacitive force sensor may further comprise a pair of opposed
surfaces defining the air gap, and an anti-adhesion layer
configured to prevent adhesion between the opposed surfaces. The
air gap may have a thickness of about 1.0 mm or less. The second
spacing layer may comprise a deformable material. The second
spacing layer may comprise an array of deformable protrusions
extending from a base layer.
[0012] The capacitive force sensor may further include sensing
circuitry operatively coupled to the first drive layer, the second
drive layer, and the shared sense layer, and configured to
determine a first amount of applied force resulting in a change in
thickness of the first spacing layer and a second amount of applied
force resulting in a change in thickness of the second spacing
layer.
[0013] The first drive layer may include an insulating substrate, a
sheet of conductive material formed over a back surface of the
insulating substrate to produce a conducting surface on the back
surface of the insulating substrate, and a conductive border formed
along at least one edge of the sheet of conductive material. The
conductive border may include a continuous conductive border that
extends along the edges of the sheet of conductive material. The
conductive border may include one or more conductive strips formed
along a respective edge of the sheet of conductive material
[0014] An electronic device may include a cover defining a user
input surface of the electronic device, a first sensing element
coupled to the cover within an interior volume of the electronic
device, a frame member coupled to the cover and extending into the
interior volume of the electronic device, a second sensing element
coupled to the frame member, and a third sensing element coupled to
a base structure and set apart from the sense layer.
[0015] The frame member may define an opening, and the third
sensing element may capacitively couple with the second sensing
element through the opening.
[0016] The first sensing element may comprise a continuous layer of
transparent conductive material covering substantially an entire
surface of a substrate. The second sensing element may comprise a
plurality of sensing regions, and the continuous layer of
transparent conductive material may overlap multiple sensing
regions of the plurality of sensing regions.
[0017] The third sensing element may comprise a plurality of drive
regions, and each drive region may overlap multiple sensing regions
of the plurality of sensing regions. The first sensing element may
further comprise a connection element electrically coupled to the
continuous layer of transparent conductive material, and the
electronic device may further comprise sensing circuitry configured
to provide an electrical signal to the first sensing element and a
connector segment electrically coupling the sensing circuitry to
the connection element.
[0018] An electronic device may include an insulating substrate
positioned below a cover layer, a sheet of conductive material
formed over a back surface of the insulating substrate to produce a
conducting surface on the back surface of the insulating substrate,
a conductive border formed along at least one edge of the sheet of
conductive material, and an electrode layer positioned below the
insulating substrate, wherein the sheet of conductive material and
the electrode layer together form a force-sensitive structure that
is configured to detect a force input on the cover layer.
[0019] The electronic device may further include drive circuitry
coupled to the sheet of conductive material, and sense circuitry
coupled to the electrode layer. The electrode layer may comprise an
array of electrodes. The conductive border may comprise a
continuous conductive border that extends along the edges of the
sheet of conductive material. The conductive border may comprise
one or more conductive strips formed along a respective edge of the
sheet of conductive material.
[0020] An electronic device includes a display layer, comprising a
display element positioned below a cover layer and a back polarizer
positioned below the display element, a sheet of conductive
material formed over a back surface of the back polarizer to
produce a conducting surface on the back surface of the back
polarizer, a conductive border formed along at least one edge of
the sheet of conductive material, and a first electrode layer
positioned below the display layer. The sheet of conductive
material and the first electrode layer together may form a
force-sensitive structure that is configured to detect a force
input on the cover layer.
[0021] The electronic device may further comprise a touch-sensitive
layer positioned between the cover layer and the front polarizer.
The electronic device may further comprise a conductive layer
positioned between the touch-sensitive layer and the front
polarizer. The conductive border may comprise a continuous
conductive border that extends along the edges of the sheet of
conductive material. The conductive border may comprise one or more
conductive strips formed along a respective edge of the sheet of
conductive material.
[0022] The force-sensitive structure may comprise a first
force-sensitive structure, the force input may comprise a first
amount of force, and the electronic device may further comprise a
second force-sensitive structure comprising a second electrode
layer positioned below and spaced apart from the first electrode
layer. The second force-sensitive structure may be configured to
detect a second amount of force on the cover layer, wherein the
second amount of force is greater than the first amount of force.
The conductive border may be positioned outside of a user-viewable
region of the display layer.
[0023] The electronic device may further comprise drive circuitry
coupled to the sheet of conductive material and sense circuitry
coupled to the first electrode layer. The first electrode layer may
comprise an array of electrodes. The sheet of conductive material
may comprise silver nanowire.
[0024] A method of forming conductive borders on a surface of a
film substrate may include applying a plurality of masks to the
surface of the film substrate, each mask defining an area of the
surface of the film substrate that will be surrounded by a
respective conductive border, forming a conductive material over
the surface of the film substrate and the masks, removing each mask
from the surface of the film substrate to produce the conductive
borders, and singulating the conductive borders to produce
individual sections of the film substrate that each includes a
respective conductive border. The method may further include
forming a protective layer over the surface of the film prior to
singulating the conductive borders.
[0025] Forming the conductive material over the surface of the film
substrate and the masks may comprise blanket depositing the
conductive material over the surface of the film substrate and the
masks. The film substrate may comprise a polarizer film with a
sheet of conductive material formed on the surface of the polarizer
film. The polarizer film may be attached to a display element in an
electronic device.
[0026] An electronic device may comprise a user input surface
defining an exterior surface of the electronic device, a first
capacitive sensing element, a second capacitive sensing element
capacitively coupled to the first capacitive sensing element, a
first spacing layer between the first and second capacitive sensing
elements, a second spacing layer between the first and second
capacitive sensing elements and having a different composition than
the first spacing layer, and sensing circuitry coupled to the first
and second capacitive sensing elements configured to determine an
amount of applied force on the user input surface. The first
spacing layer may be configured to collapse if the applied force is
below a force threshold, and the second spacing layer may be
configured to collapse if the applied force is above the force
threshold.
[0027] The exterior surface may deflect substantially linearly with
respect to force when the applied force is below the force
threshold, and the exterior surface may deflect substantially
non-linearly with respect to force when the applied force is above
the force threshold. The sensing circuitry may determine the amount
of applied force using different force-deflection correlations
based on whether the first spacing layer is fully collapsed.
[0028] The first spacing layer may be an air gap, and the second
spacing layer may comprise a deformable element. The deformable
element may comprise an array of deformable protrusions extending
from a base layer. The electronic device may further include a
sensor configured to detect whether the first spacing layer is
fully collapsed.
[0029] A force sensing device for an electronic device includes a
stack comprising a first capacitive sensing element, a structure
below the stack and comprising a second capacitive sensing element
capacitively coupled to the first capacitive sensing element, an
air gap between the stack and the structure, and a contact sensor.
The stack may be configured to move relative to the structure in
response to a force applied to a user input surface of the
electronic device, thereby causing a change in thickness of the air
gap, the first and second capacitive sensing elements may be
configured to provide a measure of capacitance corresponding to the
change in thickness of the air gap, and the contact sensor may be
configured to detect contact between the stack and the structure
resulting from the air gap being fully collapsed. The force sensing
device may further include a deformable element between the first
and second capacitive sensing elements.
[0030] The contact sensor may comprise sensing regions and
conductive elements configured to contact the sensing regions when
the stack contacts the structure through the air gap. The force
sensing device may further comprise a deformable element on a first
side of the air gap, wherein the conductive elements are disposed
on the deformable element, and the sensing regions are disposed on
a second side of the air gap opposite the first side. The
deformable element may comprise protrusions extending from a base
layer, and the conductive elements may be coupled to the
protrusions.
[0031] The contact sensor may comprise capacitive sensing regions
on a first side of the air gap and dielectric elements on a second
side of the air gap opposite the first side and capacitively
coupled with the capacitive sensing regions. The capacitive sensing
regions may be integrated with the first capacitive sensing
element, and the dielectric elements are coupled to the deformable
element.
[0032] A sensor component for an electronic device may include a
base, a plurality of protrusions comprising deformable material
extending from the base, and a plurality of sense elements disposed
at free ends of the protrusions. The sense elements may be at least
partially embedded in the protrusions. The sense elements may be
coated on the protrusions. The sense elements may comprise a
conductive material. The sense elements may comprise a dielectric
material. The base and the plurality of protrusions may be a
unitary component. The sensor component may further comprise at
least one additional protrusion that does not include any sense
elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The disclosure will be readily understood by the following
detailed description in conjunction with the accompanying drawings,
wherein like reference numerals designate like structural elements,
and in which:
[0034] FIG. 1 shows an example computing device incorporating a
force sensing device.
[0035] FIG. 2 shows another example computing device incorporating
a force sensing device.
[0036] FIGS. 3A-3E show partial cross-sectional views of the device
of FIG. 1 viewed along line A-A in FIG. 1.
[0037] FIG. 4 shows a force versus deflection curve of the device
of FIG. 1.
[0038] FIG. 5 shows a cross-sectional view of an example force
sensing device viewed along line A-A in FIG. 1.
[0039] FIG. 6 shows a force versus deflection curve of the force
sensing device of FIG. 5.
[0040] FIG. 7 shows an exploded view of the sensing elements of the
force sensing device of FIG. 5.
[0041] FIG. 8 shows a partial cross-sectional view of the sensing
elements of FIG. 7 viewed along line C-C in FIG. 7.
[0042] FIG. 9 shows a sensing element of the force sensing device
of FIG. 5.
[0043] FIGS. 10A-10B show embodiments of another sensing element of
the force sensing device of FIG. 5.
[0044] FIG. 11 shows yet another sensing element of the force
sensing device of FIG. 5.
[0045] FIG. 12 shows a cross-sectional view of another example
force sensing device viewed along line A-A in FIG. 1.
[0046] FIG. 13 shows a force versus deflection curve of the force
sensing device of FIG. 12.
[0047] FIG. 14 shows a cross-sectional view of yet another example
force sensing device viewed along line A-A in FIG. 1.
[0048] FIG. 15 shows a force versus deflection curve of the force
sensing device of FIG. 14.
[0049] FIG. 16 shows a cross-sectional view of yet another example
force sensing device viewed along line A-A in FIG. 1.
[0050] FIG. 17 shows a force versus deflection curve of the force
sensing device of FIG. 16.
[0051] FIGS. 18A-18B show expanded cross-sectional views of the
force sensing device of FIG. 17.
[0052] FIG. 19 shows a perspective view of a deformable
element.
[0053] FIG. 20 shows a perspective view of a sensing element.
[0054] FIGS. 21A-21B show cross-sectional views of an example
contact sensor.
[0055] FIGS. 22A-22B show cross-sectional views of another example
contact sensor.
[0056] FIGS. 23A-23B show partial cross-sectional views of the
device of FIG. 1 viewed along line A-A in FIG. 1, showing an
embodiment with a force sensing system integrated therein.
[0057] FIG. 24 shows a force versus deflection curve of the force
sensing system of FIGS. 23A-23B.
[0058] FIG. 25 shows a sensor of the force sensing system of FIGS.
23A-23B.
[0059] FIG. 26 shows a cross-sectional view of an example
embodiment of the electronic device of FIG. 1 viewed along line B-B
in FIG. 1.
[0060] FIG. 27 depicts a first example arrangement of the
conductive border on the polarizer shown in FIG. 26.
[0061] FIG. 28 depicts a second example arrangement of the
conductive border on the polarizer shown in FIG. 26.
[0062] FIG. 29 depicts a third example arrangement of the
conductive border on the polarizer shown in FIG. 26.
[0063] FIG. 30 shows example components of an electronic
device.
[0064] FIG. 31 shows an example process for determining an amount
of force applied to a user input surface.
[0065] FIG. 32 shows an example process for manufacturing the
conductive border on a surface of a polarizer.
[0066] FIGS. 33A-33B depict the application of masks to a surface
of a film.
[0067] FIGS. 34A-34B show the formation of the conductive material
over the film and the masks.
[0068] FIGS. 35A-35B show the removal of the masks from the
film.
[0069] FIGS. 36A-36B show the formation of the protective layer
over the film and the conductive material.
[0070] FIGS. 37A-37B show the production of each individual section
of film that is surrounded by a conductive border.
[0071] FIG. 38 shows a first example technique for determining the
geometry of the conductive border.
[0072] FIG. 39 shows a first example technique for determining the
geometry of the conductive border.
[0073] FIG. 40 shows a first example technique for determining the
geometry of the conductive border.
[0074] The use of cross-hatching or shading in the accompanying
figures is generally provided to clarify the boundaries between
adjacent elements and also to facilitate legibility of the figures.
Accordingly, neither the presence nor the absence of cross-hatching
or shading conveys or indicates any preference or requirement for
particular materials, material properties, element proportions,
element dimensions, commonalties of similarly illustrated elements,
or any other characteristic, attribute, or property for any element
illustrated in the accompanying figures.
DETAILED DESCRIPTION
[0075] Reference will now be made in detail to representative
embodiments illustrated in the accompanying drawings. It should be
understood that the following descriptions are not intended to
limit the embodiments to one preferred embodiment. To the contrary,
it is intended to cover alternatives, modifications, and
equivalents as can be included within the spirit and scope of the
described embodiments as defined by the appended claims.
[0076] The present disclosure is related to force sensing devices
that may be incorporated into a variety of electronic or computing
devices, such as, but not limited to, computers, smart phones,
tablet computers, track pads, wearable devices, small form factor
devices, and so on. The force sensing devices may be used to detect
one or more user force inputs on an input surface, and then a
processor (or processing unit) may correlate the sensed inputs into
a force measurement and provide those inputs to the computing
device. In some embodiments, the force sensing devices may be used
to determine force inputs to a track pad, a touchscreen display, or
another input surface.
[0077] Devices may be configured to respond to or use force inputs
in various ways. For example, a device may be configured to display
affordances with which a user can interact by touching the surface
of a touchscreen. Affordances may include application icons,
virtual buttons, selectable regions, text input regions, virtual
keys, or the like. The touchscreen may be able to detect the
occurrence and the location of a touch event. By incorporating
force sensors such as those disclosed herein, the device may be
able to not only detect the occurrence and location of a touch, but
also an amount of force with which the input is applied. The device
can then take different actions based on the amount of applied
force. For example, if a user touches an application icon with a
force input below a threshold, the device may open the application.
If the user touches the application icon with a force above the
threshold, the device may open a pop-up menu containing additional
affordances related to the application. As another example, force
sensors may be used to determine a weight associated with an
applied force, such that a device can act as a scale. Other
applications for force inputs are also contemplated.
[0078] The force sensing device may include an input surface, one
or more sensing layers (such as capacitive sensing elements, drive
layers, sense layers, and the like), one or more spacing layers
(e.g., air gaps, deformable elements), and a substrate or support
layer. The input surface provides an engagement surface for a user,
such as the external surface of a track pad or the cover glass of a
display. The force sensing device may be incorporated with other
components of an electronic device, such as a touchscreen, a
display, or the like. In such cases, the components of the force
sensing device, such as the one or more sensing layers, may be
interspersed with other layers, such as a cover glass, filters,
touch sensing layers, backlighting components, a display element
(e.g., a liquid crystal display assembly), or the like.
[0079] A user input applied to an input surface of the force
sensing device may cause one or more layers of the force sensing
device to deflect in a direction of the applied force such that a
spacing layer (e.g., an air gap) is collapsed. This deflection
changes the distance between components of the force sensing
device, such as between two complementary sensing layers, which can
be detected by the force sensing device and correlated to a
particular applied force. When the spacing layer has been fully
collapsed (e.g., the components defining opposite sides of the gap
have come into contact with each other), additional force applied
to the input surface will not result in a significant additional
change in distance between the layers of the force sensing device.
That is, the force sensing device has reached the maximum value of
force that it can detect.
[0080] Force sensing devices described herein include a first
spacing layer, such as an air gap, and a second spacing layer, such
as a deformable element, that produce a progressive deformation
response to an applied force. For example, an air gap and a
deformable element may be disposed between the first and second
sensing layers such that an applied force first causes the air gap
to collapse, and, once the air gap has fully collapsed, causes the
deformable element to compress or otherwise deform. As the applied
force increases and the deformable element becomes more compressed,
the deformable element imparts a progressively higher reaction
force against the applied force. Thus, a force sensing device with
a deformable element and an air gap may be able to sense a larger
force for a given deflection than would be possible in a similar
force sensing device without the deformable element.
[0081] Force sensing devices described herein may also include
contact sensors that indicate when adjacent layers defining an air
gap come into contact with each other (e.g., when the air gap has
been fully collapsed). Such contact sensors may be used to indicate
to a processor or sensing circuitry whether the force sensing
device is operating in an air-gap force regime or a
deformable-element force regime, which may improve the quality
and/or accuracy of the force sensing device.
[0082] Air gaps, deformable elements, and contact sensors may be
used in various different force sensing architectures having
various numbers and arrangements of spacing layers, sensing layers,
contact sensors, and the like. Examples of such architectures are
described herein.
[0083] FIGS. 1-2 show example electronic devices that may
incorporate the force sensing devices described herein. For
example, FIG. 1 shows an electronic device 100 (e.g., a mobile
computing device) that may incorporate the force sensing devices
described herein. The electronic device 100 may include a housing
104 and a display 102. The display 102 can provide a visual output
to a user in a user-viewable region 108. The display 102 can be
implemented with any suitable technology, including, but not
limited to, a multi-touch sensing touchscreen that uses a liquid
crystal display (LCD) element, a light emitting diode (LED)
element, an organic light-emitting display (OLED) element, an
organic electroluminescence (OEL) element, and the like. In some
embodiments, the display 102 can function as an input device that
allows the user to interact with the mobile computing device 100.
For example, the display can be a multi-touch touchscreen LED
display.
[0084] The device 100 may also include an I/O device 106. The I/O
device 106 can take the form of a home button, which may be a
mechanical button, a soft button (e.g., a button that does not
physically move but still accepts inputs), an icon or image on a
display, and so on. Further, in some embodiments, the I/O device
106 can be integrated as part of a cover 110 and/or the housing 104
of the electronic device. The device 100 may also include other
types of I/O devices, such as a microphone, a speaker, a camera, a
biometric sensor, and one or more ports, such as a network
communication port and/or a power cord port.
[0085] The cover 110 may be positioned over the front surface (or a
portion of the front surface) of the device 100. At least a portion
of the cover 110 can function as an input surface that receives
touch and/or force inputs. The cover 110 can be formed with any
suitable material, such as glass, plastic, sapphire, or
combinations thereof. In one embodiment, the cover 110 covers the
display 102 and the I/O device 106. Touch and force inputs can be
received by the portion of the cover 110 that covers the display
102 and by the portion of the cover 110 that covers the I/O device
106.
[0086] In another embodiment, the cover 110 covers the display 102
but not the I/O device 106. Touch and force inputs can be received
by the portion of the cover 110 that covers the display 102. In
some embodiments, the I/O device 106 may be disposed in an opening
or aperture formed in the cover 110. The aperture may extend
through the housing 104 one or more components of the I/O device
106 can be positioned in the housing 104.
[0087] A force sensing device may be configured to detect force
inputs on the display 102. A force sensing device may also be
configured to detect force inputs on a portion of the housing 104,
such as a back or side of the housing 104, or a bezel portion
surrounding the display 102. In addition to the force sensing
device, the display 102 may also include one or more touch sensors,
such as a multi-touch capacitive grid, or the like. In these
embodiments, the display 102 may detect both force inputs as well
as position or touch inputs. The device 100 in FIG. 1 is embodied
as a tablet computer (e.g., a mobile computing device), but this is
merely one example device that may include the force sensing
devices described herein. Examples of other devices that may
include the force sensing devices described herein include other
mobile computing devices, wearable electronic devices (e.g.,
watches), mobile phones, laptop or desktop computers, computer
peripherals (e.g., trackpads that provide input to computers), or
the like.
[0088] FIG. 2 shows a laptop computer 200 that includes a trackpad
206 (or other input surface), a display 202, and an enclosure 204.
The enclosure 204 may extend around a portion of the trackpad 206
and/or the display 202. Force sensing devices may be configured to
detect force inputs on the trackpad 206, the display 202, or
both.
[0089] In another example (not shown), a force sensing device may
be incorporated into a trackpad that is connectible to a computer,
but housed in a separate enclosure or housing. For example, a
standalone trackpad that includes a force sensing device may be
configured to be connected to a computer as a peripheral input
device, similar to a mouse or trackball.
[0090] FIG. 3A is a cross-sectional view of the device 100 viewed
along line A-A in FIG. 1, showing an assembly 300 that may provide
display, touch sensing, and force sensing functionality to the
device 100, or may be integrated with other components to provide
such functionality. For example, FIGS. 5, 12, 14, 16, 23A, and 26
illustrate examples of force sensing structures and/or devices that
may be integrated with the assembly 300 or an assembly similar to
the assembly 300.
[0091] The device 100 includes a cover 303 coupled to the housing
104 and defining an external surface of the device 100. The cover
303 may be a single layer or it may include multiple layers, and
may be formed from or include any appropriate material(s), such as
glass, treated glass, plastic, diamond, sapphire, ceramic,
oleophobic coatings, hydrophobic coatings, or the like. The device
100 may also include other internal components, including circuit
boards, cameras, sensors, antennas, processors, haptic elements,
speakers, or the like, which are omitted from FIG. 3A for
clarity.
[0092] The cover 303 may be coupled to the housing 104 via an
interfacing member 305. FIG. 3B is an expanded view of the area 317
shown in FIG. 3A, showing the joint between the cover 303 and the
housing 104 in greater detail.
[0093] The interfacing member 305 may be or may include an adhesive
that fixes the cover 303 to a ledge 307 or other feature of the
housing 104. For example, the interfacing member 305 may be a
pressure sensitive adhesive (PSA), heat sensitive adhesive (HSA),
epoxy, or other bonding agent. The interfacing member 305 may be
compliant or rigid. Where the interfacing member 305 is compliant,
it may help protect the cover 303 (which may include glass or other
breakable materials) from damage due to shocks and impacts.
Moreover, as discussed herein with reference to FIGS. 23A-25, the
interfacing member 305 may include or cooperate with sensing
elements that, along with appropriate processing circuitry, can
detect a degree of deformation of the interfacing member 305. The
detected degree of deformation of the interfacing member 305 can
then be used to determine information such as an amount of force
applied to the cover 303.
[0094] With reference to FIG. 3A, the assembly 300 includes an
upper stack 304, which may include one or more layers or components
of a display, including a liquid crystal matrix, light emitting
diodes (LEDs), light guides, filters (e.g., polarizing filters),
diffusers, electrodes, shielding layers (e.g., layers of indium tin
oxide), or the like. The upper stack 304 may be coupled to the
cover 303, such as with PSA, HSA, or the like. The upper stack 304
may also include sensing elements for detecting the presence and/or
location of a touch input on the cover 303, including, for example,
capacitive sensing elements, resistive sensing elements, and the
like.
[0095] The assembly 300 also includes a lower stack 308, which may
be separated from the upper stack 304 over at least a portion of
the lower stack 308 by an air gap 306. The air gap 306 that
separates the upper and lower stacks 304, 308 may be approximately
25 microns to approximately 100 microns thick, though other
dimensions are also possible. The air gap 306 may help prevent
deformation of components in the lower stack 308 in response to an
applied force on the cover 303 which may cause undesirable optical
artifacts on the display 102. For example, the lower stack 308 may
include light sources, light guides, diffusers, or other optical
components that, if rigidly coupled to the upper stack 304, may
deflect when a force is applied to the cover 303. By separating
these elements from the upper stack 304 by the air gap 306,
undesirable deformations may be reduced.
[0096] The lower stack 308 may include a frame member 309 that
supports other components of the lower stack 308 and couples the
lower stack 308 to the upper stack 304. For example, the frame
member 309 may support components of the lower stack 308 (including
light sources, light guides, diffusers, sensing elements, or the
like) in a spaced apart configuration relative to the upper stack
304 and/or the cover 303.
[0097] The frame member 309 may be coupled to the upper stack 304
and/or the cover 303 and may extend into an interior volume of an
electronic device. The frame member 309 may be coupled to the upper
stack 304 and/or the cover 303 by a joining member 311, which may
be or include an adhesive or other bonding agent. The frame member
309 may be formed from or include any appropriate material, such as
metal, plastic, or the like. As described herein, the assembly 300
may include sensing elements for sensing an applied force on the
cover 303. Such sensing elements may rely on the ability to
electromagnetically interact with other sensing elements in order
to determine the applied force. For example, a capacitive sense
layer may need to capacitively couple to a capacitive drive layer
in order to detect a change in distance between the sense and drive
layers. Accordingly, the frame member 309 may define an opening in
a central portion of the frame member 309. The opening may reduce
or eliminate interference, shielding, or other negative effects of
a solid layer between the sensing elements. As shown, a stiffening
member 312 formed from dielectric material (or any other material
that does not shield or otherwise interfere with the sense and
drive layers) is disposed in the opening. In some embodiments, the
stiffening member 312 may be omitted from the frame member 309, and
the opening may remain unfilled.
[0098] In cases where the frame member 309 defines an opening to
facilitate or improve electrical, capacitive, and/or
electromagnetic interaction between sensing elements, the opening
may be substantially coincident with a display and/or
touch-sensitive region of the display 102. Accordingly, sensing
elements may be able to provide force (or other) sensing
functionality to substantially the entire display and/or
touch-sensitive region of the display 102.
[0099] The lower stack 308 may include one or more layers or
components of a display. For example, the lower stack 308 may
include a light source 313 comprising one or more LEDs, fluorescent
lights, or the like. The light source 313 may emit light into an
optical stack 315 that includes one or more optical components
including but not limited to reflectors, diffusers, polarizers,
light guides (e.g., light guide films), and lenses (e.g., Fresnel
lenses). The lighting configuration shown in FIGS. 3A-3B is merely
exemplary, and the lower stack 308 may include lighting
configurations other than that shown in FIGS. 3A-3B.
[0100] The upper and lower stacks 304, 308 are described above as
including display elements. In applications where the assembly 300
does not provide display functionality, such as where the assembly
300 is part of or coupled to the trackpad 206, the upper and lower
stacks 304, 308 may include different components and/or layers as
those described above, or may be omitted or replaced with other
components.
[0101] Below the lower stack 308 are a first spacing layer, such as
an air gap 310, and a second spacing layer, such as a deformable
element 314. The air gap 310 may be approximately 0.5 to
approximately 1.0 mm thick, though other dimensions are also
possible.
[0102] The first and second spacing layers are configured to change
thickness in response to an applied force. For example, a thickness
of the air gap 310 (e.g., the distance between the opposed surfaces
that define the air gap) may be decreased as a force is applied to
the cover 303. Similarly, a thickness of the deformable element 314
may be decreased as a force is applied to the cover 303.
[0103] The deformable element 314 may include any appropriate
material, such as silicone, polyurethane foam, rubber, gels, or the
like. Moreover, the deformable element 314 may have any appropriate
structure, such as multiple compliant or deformable protrusions (as
shown), which may be formed as columns, beams, pyramids, channels
with sidewalls, cones, wave-shaped protrusions, bumps, or the like.
The deformable element 314 may also or instead comprise open or
closed cells, such as a sponge or a foam. The deformable element
314 may also have a substantially homogenous, nonporous
composition. As yet another example, the deformable element 314 may
include multiple discrete pieces of deformable material, such as
dots, pads, or the like.
[0104] The foregoing materials and configurations for the first and
second spacing layers are merely examples, however, and the first
and second spacing layers may be formed from any appropriate
materials or combinations thereof. For example, the air gap 310 may
be replaced with a first foam material, and the deformable element
314 may include a second foam material having a different density,
thickness, composition, or spring constant, than the first. As
another example, the first and second spacing layers may be
substantially identical, and may include or be formed from the same
materials.
[0105] The deformable element 314 may be coupled to or adjacent a
base structure or layer 316. The base structure 316 may be a
substrate or support layer dedicated to the assembly 300, or it may
be another component of an electronic device, such as a battery, a
portion of a housing or enclosure, a circuit board, or any other
component.
[0106] FIGS. 3C-3E illustrate a progression of the physical
response of the assembly 300 to an input force 302 on the upper
stack 304. As noted above, the input force 302 may correspond to a
user contacting a user input surface of an electronic device, such
as the cover 303, with a finger, stylus, or other object. The input
force 302 may be transferred through the cover 303 to the surface
of the upper stack 304.
[0107] FIG. 3C illustrates the portion of the assembly 300
represented by area 301 in FIG. 3A prior to the input force 302
being applied to the upper stack 304. FIG. 3D illustrates the
assembly 300 after the force input has caused the upper stack 304
to deflect or flex sufficiently to fully collapse the air gap 306.
In particular, the upper stack 304 has been flexed towards the
lower stack 308 such that the upper stack 304 is in contact with
the lower stack 308 in at least one location. The stiffness of the
upper stack 304 and the size of the air gap 306 may determine the
amount of force that causes the upper stack 304 to come into
contact with the lower stack 308. In some cases, even a slight
touch from the user will be sufficient (e.g., a touch that a user
would not consider to be "pressing" on the cover).
[0108] FIG. 3E illustrates the assembly 300 after the force input
has caused the lower stack 308 to deflect sufficiently to fully
collapse the air gap 310, thus bringing the lower stack 308 into
contact with and at least partially deforming the deformable
element 314.
[0109] As used herein, the term "collapse" may refer to a partial
collapse of a layer (e.g., corresponding to any reduction in
thickness of a material or an air gap at any location), or a full
collapse of a layer (e.g., corresponding to opposing surfaces that
define an air gap coming into contact with one another at any
point, or reaching a maximum deformation of a deformable
material).
[0110] FIG. 4 is an example force versus deflection curve
illustrating how a user input surface of the assembly 300 (e.g.,
the cover 303) deflects in response to the force input in FIGS.
3C-3E. In particular, as the force increases from zero to a force
threshold (e.g., corresponding to point 402), the deflection
increases along a first profile 406. In some cases, the first
profile 406 corresponds to the deflection of the assembly 300 until
all of the air gaps in the assembly 300 (e.g., the air gap 306 and
the air gap 310) have been fully collapsed. As the force increases
beyond the force threshold (e.g., point 402) and the deformable
element 314 compresses, the deflection increases along a second
profile 408 extending from point 402 to point 404. Accordingly, the
force threshold corresponds to the amount of force at the
transition from collapse of the air gaps only to deformation of the
deformable element.
[0111] The first profile 406 may be substantially linear, such that
an incremental increase in force produces substantially the same
incremental increase in deformation of the cover 303 at any point
in the first profile 406. In contrast, the second profile 408 may
be non-linear, and may plateau as the force increases. For example,
an incremental increase in force at the beginning of the second
profile 408 may result in a greater amount of deformation of the
cover 303 than the same incremental increase in force at the end of
the second profile 408. However, these profiles are merely
exemplary, and the force sensing devices described herein may
exhibit any other force versus deflection curves or profiles.
[0112] The systems and methods described herein, including the
force sensing devices 500, 700, 900, and 1100 described below,
facilitate the detection of whether a force sensing device is
operating according to the first profile 406, such that only air
gaps are being collapsed, or the second profile 408, such that a
deformable element is being deformed. By detecting the different
profiles, accurate force measurements may be provided.
[0113] While FIGS. 3A-4 relate to the assembly 300 of the device
100, the components, structures, and principles of operation of the
assembly 300 may apply to other devices as well, such as the
display 202 or the trackpad 206 of the device 200 (or any other
appropriate device). In cases where a display is not present, such
as the trackpad 206, some components of the assembly 300 may be
omitted, replaced, or rearranged. For example, the upper and lower
stacks 304, 308 may include components other than display elements,
or they may be omitted or replaced with spacers or other
components.
[0114] FIG. 5 is a partial cross-sectional view of an example force
sensing device 500 that may be incorporated in an electronic device
(e.g., the devices 100, 200), depicting an area similar to the area
301 in FIG. 3A. The cover 303 and the housing 104 are omitted for
clarity.
[0115] The force sensing device 500 includes an upper stack 504,
similar to the upper stack 304, which may include one or more
layers or components of a display, including a liquid crystal
matrix, light emitting diodes (LEDs), light guides, filters (e.g.,
polarizing filters), diffusers, electrodes, or the like. The upper
stack 504 may be configured to flex or be capable of flexing in
response to an applied force on the force sensing device 500.
[0116] A first sensing element 505 is coupled to the upper stack
504 (for example, to a cover 303 or to a component that is coupled
to the cover 303, such as a filter) and is within an interior
volume of an electronic device. The first sensing element 505 may
be a capacitive sensing element that is configured to capacitively
couple with another capacitive sensing element. For example, the
first sensing element 505 may be a drive layer that is capacitively
coupled to a sense layer (e.g., the second sensing element 512,
below) that facilitates detection of a distance between the sense
and drive layers using mutual capacitance. As another example, the
first sensing element 505 may be a sense layer instead of a drive
layer. As yet another example, the first sensing element 505 may be
configured to capacitively couple to a ground layer to facilitate
detection of a distance between itself and the ground layer using
self-capacitance. As yet another example, the first sensing element
505 may be a ground layer that capacitively couples to a separate
sense layer.
[0117] In the presently described examples, the sensing elements
are described as elements for capacitive sensing. However, other
types of sensors (and sensor components) may be used instead of or
in addition to capacitive sensors. Indeed, other types of sensors
or sensing technologies that can detect changes in distance, or
absolute distance, between components or otherwise detect force may
be used. For example, inductive sensors, optical sensors, sonic or
ultrasonic sensors, or magnetic sensors may be used. Moreover, the
components of the sensors may be integrated in the force sensors as
shown herein (e.g., with sensing elements set apart from one
another by one or more layers including air gaps, deformable
layers, other components, or the like), or they may be integrated
in any other manner suitable for that type of sensor (e.g., an
optical sensor may include one or more light emitters in place of a
sensing layer).
[0118] The first sensing element 505 may be coupled to the upper
stack 504 in any appropriate way, such as with a pressure sensitive
adhesive (PSA), heat sensitive adhesive (HSA), or the like. The
first sensing element 505 may also be patterned on the upper stack
504, such as with physical vapor deposition, electron beam
evaporation, sputter deposition, or any other appropriate
technique. The first sensing element 505 may be formed from or
include any appropriate material, such as indium tin oxide (ITO),
disposed on a substrate.
[0119] A lower stack 508 may be disposed below the first sensing
element 505 and separated from the first sensing element 505 by an
air gap 506. Like the air gap 306, the air gap 506 may be any
appropriate thickness, such as from about 25 microns to about 100
microns.
[0120] The lower stack 508 may include any appropriate components
or layers, such as those described above with respect to the lower
stack 308 (e.g., LEDs, an optical stack, backlights, reflectors, or
light guides), and may be coupled to the upper stack 504 and/or the
housing 104 as described with respect to the lower stack 308 of
FIG. 3A (e.g., via the frame member 309). In embodiments where the
force sensing device 500 does not include a display or does not
provide display functionality, lower stack 508 (as well as the
upper stack 504) may include different components or be
omitted.
[0121] The lower stack 508 may be coupled to and/or supported by a
frame member, which may be similar to the frame member 309 in FIG.
3A. The frame member may include a stiffening member 509, similar
to the stiffening member 312 in FIG. 3A. The stiffening member 509
may be formed from or include a dielectric material to facilitate
or improve electrical, capacitive, and/or electromagnetic
interaction between sensing elements (e.g., between the first
sensing element 505 and the second sensing element 512).
[0122] The frame member, and in particular the stiffening member
509, may support the lower stack 508 in a spaced apart
configuration relative to the upper stack, a base structure 516, a
deformable element 514, or other components of the electronic
device. FIG. 5 shows the second sensing element 512 coupled to a
deformable element 514. However, in some cases, the second sensing
element 512 may be coupled to the lower stack 508. In such cases,
the second sensing element 512 may be coupled to the frame member,
such as to the stiffening member 509 or a component of the lower
stack 508.
[0123] An air gap 510 separates the lower stack 508 from a second
sensing element 512. The air gap 510 may be any appropriate
thickness, such as from about 0.5 mm to 1.0 mm.
[0124] The second sensing element 512 may be a sense layer for a
capacitive sensor, and may be capacitively coupled to the first
sensing element 505. The second sensing element 512 may include an
array of discrete capacitive sensing regions that facilitate
detection of a location (and/or a magnitude) of a force input on
the upper stack 504. The second sensing element 512 may be formed
from or include any appropriate material, such as ITO traces
disposed on a substrate. The second sensing element 512 may be
coupled to the deformable element 514, the stiffening member 509
(or other component of the frame member or lower stack 508), or any
other component or structure in the interior volume of the
electronic device such that the second sensing element 512 is
between the first sensing element 505 and a third sensing element
515 (discussed below).
[0125] An optional anti-adhesion layer 511 may be disposed on a
surface defining a side of the air gap 510 in order to prevent the
opposite sides of the air gap from sticking together, either
temporarily or permanently, when they contact each other. Thus,
when an applied force is removed from a user input surface, the
components of the force sensing device 500 can return to or near
their original orientations. The anti-adhesion layer 511 may be
formed from or include any appropriate material, and may have any
appropriate shape or structure. For example, the anti-adhesion
layer 511 may comprise posts, protrusions, channels, or other
structures that permit airflow therethrough to reduce or prevent
the formation of sealed areas between the surfaces of the air gap
510 when the air gap 510 is fully collapsed. Without the
anti-adhesion layer 511, such sealed areas may result in negative
pressure zones that could act similar to "suction cups" that
prevent the separation of the sides of the air gap 510. The
anti-adhesion layer 511 may prevent adhesion caused by other
mechanisms or forces as well, such as van der Waals forces,
electrostatic forces, or the like.
[0126] The force sensing device 500 includes a deformable element
514 between the second sensing element 512 and a third sensing
element 515. Similar to the deformable element 314, the deformable
element 514 may include any appropriate material (such as silicone,
polyurethane foam, rubber, gels, or the like) and may have any
suitable structure, such as multiple compliant columns (as shown),
beams, pyramids, cones, wave-shaped protrusions, open or closed
cells, or the like. The deformable element 514 may deflect
non-linearly with respect to an applied force, as described
above.
[0127] The deformable element 514 is shown in FIG. 5 below the air
gap 510 and between the second sensing element 512 and the third
sensing element 515. However, the relative positions of the air gap
510 and the deformable element 514 may be swapped. For example, the
deformable element 514 may be coupled to the lower stack 508.
[0128] The third sensing element 515, disposed between the
deformable element 514 and a base structure 516, may be a drive
layer for a capacitive sensor, and may be capacitively coupled to
the second sensing element 512. For example, the second sensing
element 512 may be a sense layer, and the third sensing element 515
may be a drive layer, thus forming a capacitive sensor spanning the
deformable element 514.
[0129] The base structure 516 may be a frame, bracket, or support
structure of the force sensing device. In some cases, the base
structure 516 is a component of an electronic device that is
beneath a user input surface, such as a circuit board, a battery,
an interior wall of a housing or enclosure, or the like. The base
structure 516 may be stiffer or otherwise more resistant to
deflection in response to an applied force than the components
above it. Thus, once the air gap 510 has been fully collapsed,
additional force may primarily deform the deformable element 514
rather than deflecting the base structure 516.
[0130] The first, second, and third sensing elements 505, 512, and
515 may form two capacitive sensors. For example, as described
above, the first and third sensing elements 505, 515 may each act
as a distinct drive layer, and the second sensing element 512 may
be a sense layer that capacitively couples to (and senses changes
in distance to) both the first and third sensing elements 505,
515.
[0131] Where the second sensing element 512 is a shared sense
layer, it may include a first set of sensors for detecting the
distance to the first sensing element 505 and a second set of
sensors for detecting the distance to the third sensing element
515. The second sensing element 512 may also or instead use the
same sensors to detect the distance to both the first and third
sensing elements 505, 515. In the latter cases, the first and third
sensing elements 505, 515 may be driven with different electrical
signals, thus allowing the second sensing element 512 (and/or
sensing circuitry coupled to the second sensing element 512) to
differentiate between capacitance changes that are caused by
changes in a size of the air gap 510 and capacitance changes that
are caused by changes in a size of the deformable element 514. In
another embodiment (not shown), the second sensing element 512 may
be replaced with two discrete sensing elements, each acting as a
sense layer for a different one of the first and third sensing
elements 505, 515.
[0132] FIG. 6 is an example force versus deflection curve
illustrating how the force sensing device 500 in FIG. 5 deflects in
response to a force input applied (directly or indirectly) to the
upper stack 504. The force response is similar to that shown in
FIG. 4, with a first profile from point 401 to point 402
(corresponding to collapse of the air gaps 506 and 510) and a
second profile from point 402 to point 404 (corresponding to
deformation of the deformable element 514).
[0133] As noted above, the force sensing device 500 has two
capacitive sensors--a first capacitive sensor 518 formed by the
first and second sensing elements 505, 512, and a second capacitive
sensor 519 formed by the second and third sensing elements 512,
515. The first capacitive sensor 518 spans the air gaps 506 and
510, and the second capacitive sensor 519 spans the deformable
element 514. Thus, the first capacitive sensor 518 is positioned
within the force sensing device 500 to detect deformation of the
upper stack 504 along the line 602 in FIG. 6, and the second
capacitive sensor 519 is positioned within the force sensing device
500 to detect deformation of the upper stack 504 along the line 604
in FIG. 6. By detecting the deformation of the air gaps with one
sensor and the deformation of the deformable element with a
different sensor, sensing circuitry can process the signals
according to different force-deflection correlations. For example,
deflections from the first capacitive sensor 518 may be correlated
to an amount of applied force according to the substantially linear
profile between point 401 and point 402, and the deflections from
the second capacitive sensor 519 may be correlated to an amount of
applied force according to the non-linear profile between point 402
and point 404. Of course, the linear and non-linear profiles shown
in FIG. 6 are merely examples, and the deformation of a force
sensing device may follow or exhibit different profiles.
[0134] Sensing circuitry may apply force-deflection correlations in
any appropriate manner. For example, force-deflection correlations
may be implemented in mathematical functions that output a
particular force value for a particular determined amount of
deflection (which may in turn have been determined based on a
measured or detected capacitance value, or any other electrical
measurement or value). As another example, force-deflection
correlations may be implemented using lookup tables, where
particular deflection values are correlated with particular force
values. Other techniques are also possible, and these examples do
not limit the mathematical or programmatic techniques that may be
used to produce force values from measured or detected electrical
properties (e.g., capacitance, resistance, current, signals,
etc.).
[0135] FIG. 7 is an exploded view of the sensing elements 505, 512,
and 515 of the force sensing device 500 of FIG. 5, illustrating
example configurations of the sensing elements in an implementation
of the force sensing device 500 that uses capacitive sensing to
detect changes in distance between the sensing elements. FIG. 7
omits components of the force sensing device 500 and the electronic
device in which it is configured. For example, FIG. 7 omits the
deformable element 514 that is shown between the second sensing
element 512 and the third sensing element 515. Moreover, FIG. 7
omits some details of the sensing elements 505, 512, 515 for
clarity, such as conductive traces or leads used to couple the
sensing elements (or portions thereof) to other electrical
circuitry.
[0136] As noted above, in the force sensing device 500, the first
and third sensing elements 505, 515 may be drive layers for a
capacitive sensing scheme, and the second sensing element 512 may
be a sense layer. In operation, the first and third sensing
elements 505, 515 (also referred to as drive layers 505, 515) may
be excited with an electrical signal, such as a substantially
sinusoidal signal, a square or edge signal (e.g., a substantially
instantaneous transition from a first voltage to a second voltage),
or any other appropriate signal. Properties of the signal, such as
frequency, voltage, or amplitude, may be selected to avoid or
minimize interference with other electronic circuits of a device,
such as display circuits, processors, antennas, and the like.
Because the second sensing element 512 (also referred to as a sense
layer) is capacitively coupled to a drive layer, a corresponding
electrical signal may be induced in (or otherwise detected by) the
sense layer. For a given electrical signal applied to the drive
layers, the induced electrical signal in the sense layer may be
different depending on the distance between the drive layer and the
sense layer. Thus, the force sensing device 500 (or the associated
sensing circuitry) may determine the distance between the sense
layer and drive layer by analyzing the signal induced in the sense
layer.
[0137] The first drive layer 505 may include a conductive material
coupled or otherwise applied to a substrate. For example, the first
drive layer 505 may include a layer of ITO, nanowire (e.g.,
metallic nanowire, including silver or gold nanowire), or any other
appropriate material. As shown in FIG. 5, the drive layer 505 is
disposed in the light path of the display 102 (e.g., it is above
the lower stack 508, which produces the light used to illuminate
the display 102). Thus, the conductive material may be
substantially transparent. Even when a substantially transparent
material is used, if the material is arranged in a regular pattern,
such as in a grid or columns, it may be visible on the display 102.
Accordingly, the conductive material of the first drive layer 505
may be substantially uniformly distributed (e.g., as a layer,
sheet, coating, or other continuous element) on the first drive
layer 505 instead of being arranged in a regular pattern. In some
cases, the conductive material may be a continuous layer covering
or extending over an entire surface of a substrate of the first
drive layer 505 (or substantially an entire surface, such as about
80% or more of the surface area of the substrate). The layer of
conductive material may be configured so that there are no borders
or edges of the layer positioned within the boundaries of a display
in which the force sensing device 500 is incorporated.
[0138] The first drive layer 505 may also include a connection
element 706 that is electrically coupled to the conductive material
and facilitates the coupling of the electrical material to other
electronic components or circuitry. The connection element 706 may
be formed from or include any material, such as silver, copper,
nickel vanadium, or any other appropriate material. The connection
element 706 may form a continuous frame along an outer portion of
the first drive layer 505 (as shown), or it may be formed from
discontinuous or distinct segments. In some cases, the connection
element 706 does not form a frame, but instead may be a strip along
one side of the first drive layer 505, for example. Other
configurations are also possible. Connection elements 706, such as
conductive strips formed on an edge of a drive layer 505 (or any
other conductive substrate, layer, coating, etc.) are discussed
herein with respect to FIGS. 26-29 and 32-40.
[0139] The sense layer 512 may include sensing regions 702 formed
from (or including) a conductive material and arranged in a
substantially regular pattern, such as a grid. The sensing regions
702 may be formed from or include any appropriate material, such as
ITO, metallic nanowire, or the like.
[0140] Each of the sensing regions 702 may act as a discrete area
or pixel-like region that may be used to determine a distance
between the first drive layer 505 and that particular sensing
region. By analyzing all of the sensing regions 702, the force
sensing device 500 can detect an amount of an applied force on the
cover 303. Moreover, pixelating the sense layer 512 as shown may
allow the force sensing device 500 to detect force with greater
accuracy than if a single, uniform sense layer were used. For
example, if a single sense layer were used, it may be difficult or
impossible to tell the difference between a large force applied
near an edge of the cover 303 and a small force applied near a
center of the cover 303. By using a pixelated sense layer 512, the
force sensing device 500 can account for differences in stiffness
among the different regions of the cover 303. Using a pixelated
sense layer 512 may also allow the force sensing device 500 to
determine the location of an applied force, detect multi-touch
inputs (e.g., corresponding to multiple fingers or styli being
applied to the cover 303), or the like.
[0141] The second drive layer 515 may include a plurality of drive
regions 704. Like the first drive layer 505 and the sensing regions
702 of the sense layer 512, the drive regions 704 may be formed
from or include any appropriate conductive material, such as ITO,
metallic nanowire, or the like.
[0142] The drive regions 704 may be arranged in any appropriate
pattern or orientation, and may have any appropriate size. For
example, the drive regions 704 may be a plurality of substantially
rectangular areas of conductive material, and may be substantially
aligned with a column of sensing regions 702 in the sense layer
512, as shown and described with respect to FIG. 8. Thus, the drive
regions 704 may each overlap multiple ones of the sensing regions
702 of the sense layer 512.
[0143] Like the first drive layer 505, the drive regions 704 may be
excited with an electrical signal (e.g., a substantially sinusoidal
or edge signal) that induces a corresponding signal in the sensing
regions 702 of the sense layer 512 (or that can otherwise be
detected by the sense layer 512). Because a single sense layer 512
is used to detect the distance between it and two different drive
layers 505, 515, the force sensing device 500 needs to
differentiate between signals from the first drive layer 505 and
the second drive layer 515. Accordingly, the signals from the first
and second drive layers 505, 515 may have different frequencies,
amplitudes, phases, or other properties such that the signals they
induce in the sense layer 512 are differentiable from one another.
More particularly, the signal applied to the first drive layer 505
may have a first frequency, and the signal applied to the second
drive layer 515 may have a second frequency different from the
first frequency. Alternatively or additionally, the first and
second drive layers 505, 515 may be excited (e.g., with an edge
signal) at different times, such that the signal induced in the
sense layer 512 can be attributed to one or the other drive layer.
For example, sensing circuitry may alternate between exciting the
first and second drive layers 505, 515. These (or other) techniques
may be used so that the distance between the first drive layer 505
and the sense layer 512 can be detected independently of the
distance between the second drive layer 515 and the sense layer
512.
[0144] The drive regions 704 may be electrically isolated from one
another, or they may be electrically coupled to one another. In
embodiments where the drive regions 704 are electrically coupled to
one another, all of the drive regions 704 may be simultaneously
excited by a single signal.
[0145] Alternatively, where the drive regions 704 are electrically
isolated, they may be driven or excited independently of one
another. This may be useful when not all of the sensing regions 702
are analyzed at a time. More particularly, circuitry associated
with the force sensing device 500 may cyclically poll subsets of
the sensing regions 702. The drive regions 704 may therefore
correspond to the polled groups of sensing regions 702, and a
signal may be provided to drive regions 704 while the corresponding
group of sensing regions 702 is being polled. This may help to
reduce power consumption by the force sensing device 500 when a
cyclic polling technique is used, as not all of the drive regions
704 will be energized when the corresponding sensing regions 702
are not being polled.
[0146] The drive layers 505, 515 and the sense layer 512 may be
distinct layers or components, as shown in FIG. 7, or they may be
incorporated into other layers or components. For example, the
first drive layer 505 may be a conductive material coated on,
applied to, or otherwise incorporated with a polarizing filter that
is part of the upper stack 304 (FIG. 3A). Indeed, the conductive
material of any of the sense and drive layers may be incorporated
on another component or layer of the electronic device in which it
is incorporated. Alternatively, the sense and drive layers may be
formed separately, such as by applying a conductive material on
substrate such as a flexible circuit material (e.g., polyimide,
polyethylene terephthalate, polyether ether ketone, or transparent
conductive polyester), and then incorporating the substrate into
the electronic device.
[0147] FIG. 8 is a partial cross-sectional view of the first and
second drive layers 505, 515 and the sense layer 512, viewed along
line C-C in FIG. 7, illustrating relative sizes and positions of
the sensing and drive regions 702, 704 of the force sensing device
500. The first drive layer 505 includes a substrate 802, a
conductive layer 804, and the connection element 706. The substrate
802 may be any appropriate material or component, such as a
flexible circuit material, a polarizing filter, or any other
material or component of an electronic device or display stack. The
conductive layer 804 may be ITO, a layer of metallic or conductive
nanowire, or any other appropriate material, as described above.
The conductive layer 804 may be a continuous sheet (e.g., having a
single expanse of conductive material, rather than a segmented or
pixelated configuration) that overlaps multiple sense regions 702.
The connection element 706 may be a conductive material such as
copper, silver, nickel vanadium, or the like.
[0148] The sense layer 512 may include a substrate 806, which may
be any appropriate material or component, such as flexible circuit
material, and the sensing regions 702. As described above, the
sensing regions 702 may be formed from or include any appropriate
material, including ITO, conductive nanowire, or the like.
[0149] The second drive layer 515 may include a substrate 808,
which may be any appropriate material or component, such as
flexible circuit material, and the drive regions 704. The drive
regions 704 and the sensing regions 702 of the sense layer 512 may
be sized and positioned relative to one another such that the
sensing regions 702 shield the drive regions 704 from sources of
interference such as the first drive layer 505. For example, the
drive regions 704 may be substantially the same width as, or
narrower than, the sensing regions 702, and may be vertically
aligned with the sensing regions 702 (with the positional terms
being relative to the orientation of the layers in FIG. 8). In this
way, the conductive material of the sensing regions 702 may
substantially shield the drive regions 704 from the first drive
layer 505 or other potential sources of interference above the
sense layer 512. Some portions of the drive regions 704 may not be
directly covered by a sensing region 702. However, the unshielded
area of the substantially rectangular drive regions 704 is
significantly less than would be present if the second drive layer
515 were a single continuous sheet of conductive material, such as
that on the first drive layer 505.
[0150] FIG. 8 shows the sensing regions 702 and the drive regions
704 extending above the surface of their respective substrates.
This is merely one example configuration, however. Indeed, the
sensing and drive regions 702, 704 may be substantially flush with
or recessed in their respective substrates.
[0151] FIG. 9 shows the sense layer 512 with an example
distribution of sensing regions 702. FIG. 9 also shows conductive
paths 902 that may electrically couple the sensing regions 702 to
other electronic components or circuits. The conductive paths 902
may be any appropriate material and may be formed in any
appropriate way. For example, they may be formed from ITO applied
using a photolithography technique. Other materials and techniques
are also contemplated. In embodiments where the sensing regions 702
are independently polled to provide unique force values for a
particular display location (as shown in FIG. 9), each sensing
region 702 may be connected to a unique conductive path 902. In
embodiments where multiple sensing regions 702 are polled or
monitored as a single unit, those sensing regions 702 may share or
be connected to a common conductive path 902 (not shown). The
pattern of sensing regions 702 and conductive paths 902 shown in
FIG. 9 is merely one example of a suitable configuration, and other
configurations, including the number and arrangement of the sensing
regions 702 and conductive paths 902, are also contemplated.
[0152] FIG. 10A shows the first drive layer 505, illustrating an
example configuration of an electrical connection to the conductive
layer 804 of the first drive layer 505 via the connection element
706 (e.g., a conductive strip or border around the first drive
layer 505). In particular, FIG. 10A illustrates a pair of connector
segments 1002 positioned proximate the connection element 706. Each
connector segment 1002 may be formed from or include an electrical
conductor that is electrically connected to a signal generator or
other electronic circuitry. For example, the connector segment 1002
may be formed from a flexible circuit material with a metallic or
conductive material (e.g., copper, gold, ITO) disposed thereon. In
some cases, the connector segment 1002 may be formed substantially
entirely of conductive material, such as when the connector segment
1002 is a strip of copper, silver, or any other metal or conductive
material.
[0153] A conductive joining material 1004 may be deposited over
connector segments 1002 and a portion of the connection element 706
such that an electrical connection is formed between the connector
segments 1002 and the connection element 706. The conductive
material may be any appropriate material, such as silver, gold,
copper, conductive adhesives, or the like.
[0154] As noted above, the connection element 706 is electrically
connected to the conductive layer 804. Accordingly, drive signals
can be applied from the connector segments 1002 to the conductive
layer 804. In some cases, more or fewer connector segments 1002 may
be used to electrically couple circuitry to the conductive layer
804, or the connector segments 1002 may be positioned at different
locations around the drive layer 505, such as along opposite edges
of the drive layer 505.
[0155] FIG. 10B shows the first drive layer 505, illustrating
another example configuration of an electrical connection to the
conductive layer 804 of the first drive layer 505. As shown, the
first drive layer 505 does not include the connection element 706.
In this example, instead of connecting to the conductive layer 804
via the connection element 706 (as shown in FIG. 10A), the
connector segments 1006 connect to the conductive layer 804 via a
conductive adhesive 1008. Like the connector segments 1002 (FIG.
10A), the connector segments 1006 may be formed from or include an
electrical conductor that is electrically connected to a signal
generator or other electronic circuitry. The connector segments
1006 may be electrically and physically coupled to the conductive
layer 804 via the conductive adhesive 1008, which may be disposed
between overlapping portions of the connector segments 1006 and the
conductive layer 804. FIG. 10B illustrates an example embodiment
where two connector segments 1006 couple to opposite sides of the
first drive layer 505. Other configurations, including different
numbers, sizes, shapes, and coupling locations of the connector
segments 1006 are also contemplated. For example, in some cases,
only one connector segment 1006 is used. In other cases, four
connector segments 1006 are arranged around the first drive layer
505 (e.g., with one connector segment 1006 on each side of the
first drive layer 505).
[0156] FIG. 11 shows the second drive layer 515, with an example
distribution of drive regions 704. FIG. 11 also shows conductive
paths 1102 that may electrically couple the drive regions 704 to
other electronic components or circuits. The conductive paths 1102
may be any appropriate material and may be formed in any
appropriate way. For example, they may be formed from ITO applied
using a photolithography technique. Other materials and techniques
are also contemplated. In embodiments where the drive regions 704
are independently driven or excited, as discussed above with
respect to FIG. 8, each drive region 704 may be connected to a
unique conductive path 1102. In embodiments where multiple drive
regions 704 are driven or excited together (e.g., a signal is
applied to multiple drive regions 704 simultaneously), those drive
regions 704 may share or be connected to a common conductive path
(not shown). The pattern of drive regions 704 and conductive paths
1102 shown in FIG. 11 is merely one example of a suitable
configuration, and other configurations, including the number and
arrangement of the drive regions 704 and conductive paths 1102, are
also contemplated.
[0157] FIG. 12 is a partial cross-sectional view of an example
force sensing device 1200 that may be incorporated in an electronic
device (e.g., the devices 100, 200), depicting an area similar to
the area 301 in FIG. 3A. The cover 303 and the housing 104 are
omitted for clarity. While the force sensing device 1200 is similar
to the force sensing device 500, the force sensing device 1200 has
a different number and arrangement of sensing elements within the
electronic device, as described herein.
[0158] The force sensing device 1200 includes an upper stack 1204,
similar to the upper stack 304, which may include one or more
layers or components of a display, including a liquid crystal
matrix, light emitting diodes (LEDs), light guides, filters (e.g.,
polarizing filters), diffusers, electrodes, or the like. The upper
stack 1204 may be configured to flex or be capable of flexing in
response to an applied force on the force sensing device 1200.
[0159] A lower stack 1208 may be disposed below the upper stack
1204 and separated from the upper stack 1204 by an air gap 1206.
The lower stack 1208 may include a frame member 1207 (similar to
the frame member 309), an optical stack 1213 (similar to the
optical stack 315 described above), and any other appropriate
components, such as a light source. As described with respect to
the assembly 300, the air gap 1206 may be any appropriate
thickness, such as 25 to 100 microns. In embodiments where the
force sensing device 1200 does not include a display or does not
provide display functionality, the lower stack 1208 (as well as the
upper stack 1204) may include different components or be
omitted.
[0160] A first sensing element 1209 is coupled to the lower stack
1208. The first sensing element 1209 may be a capacitive sensing
element that is configured to capacitively couple with another
capacitive sensing element. For example, the first sensing element
1209 may be a drive layer that is capacitively coupled to a sense
layer (e.g., the second sensing element 1215, described below) that
facilitates detection of a distance between the sense and drive
layers using mutual capacitance. As another example, the first
sensing element 1209 may be a sense layer instead of a drive layer.
As yet another example, the first sensing element 1209 may be
configured to capacitively couple to a ground layer and facilitate
detection of a distance between itself and the ground layer using
self-capacitance. As yet another example, the first sensing element
1209 may be a ground layer that capacitively couples to a sense
layer.
[0161] The first sensing element 1209 may be formed from or include
any appropriate material, such as ITO traces disposed on a flexible
substrate, and may be coupled to the lower stack 1208 in any
appropriate way, such as with a PSA or HSA, or patterned directly
onto the lower stack 1208. Because the first sensing element 1209
is below the lower stack 1208, the frame member 1207 of the lower
stack 1208 may be formed from a conductive material, such as a
metal. More particularly, because the frame member 1207 is not
between the first sensing element 1209 and a second sensing element
1215 (discussed below), the frame member 1207 may not shield or
otherwise negatively interfere with the capacitive coupling between
the first and second sensing elements 1209, 1215. Accordingly, more
materials may be suitable for use in the frame member 1207, and the
frame member 1207 may define a continuous layer or panel, rather
than having an opening therein to avoid undesirable shielding or
interference.
[0162] An air gap 1210 and a deformable element 1214 may be
disposed between the first sensing element 1209 and a second
sensing element 1215. The air gap 1210 and the deformable element
1214 correspond to the air gap 510 and deformable element 514, and
may have similar compositions, structures, dimensions, and
functions.
[0163] The second sensing element 1215 may be capacitively coupled
to the first sensing element 1209, and together these components
may form a capacitive sensor 1218 that spans the air gap 1210 and
the deformable element 1214 to detect deformation of these layers.
The second sensing element 1215 may be a sense layer, a drive
layer, or a ground layer, depending on the principle of operation
of the capacitive sensor 1218 and/or the configuration of the first
sensing element 1209.
[0164] The second sensing element 1215 may be coupled to a base
structure 1216, which may be a frame, a bracket, a circuit board, a
battery, an interior wall of a housing or enclosure, or the like,
as described above with respect to the base structure 516 of FIG.
5.
[0165] FIG. 13 is an example force versus deflection curve
illustrating how the force sensing device 1200 in FIG. 12 deflects
in response to a force input applied (directly or indirectly) to
the upper stack 1204. The force response is similar to that shown
in FIG. 4, with a first profile extending from point 401 to point
402 (corresponding to collapse of the air gaps 1206 and 1210) and a
second profile extending from point 402 to point 404 (corresponding
to deformation of the deformable element 1214).
[0166] As noted above, the force sensing device 1200 has one
capacitive sensor 1218 formed by the first and second sensing
elements 1209, 1215. The first and second sensing elements 1209,
1215 span the air gap 1210 and the deformable element 1214, but do
not span the air gap 1206. Thus, the capacitive sensor 1218 does
not detect deflection of the upper stack 1204 that causes the air
gap 1206 to collapse (corresponding to line 1302 in FIG. 13), but
does detect deflection that causes the air gap 1210 to collapse and
the deformable element 1214 to be deformed (corresponding to line
1304 in FIG. 13). Accordingly, the collapse of the air gap 1206 is
decoupled from the collapse of the air gap 1210, and a force
detected using the capacitive sensor 1218 of the force sensing
device 1200 corresponds to the force required to collapse the air
gap 1210.
[0167] Because the capacitive sensor 1218 spans both the air gap
1210 and the deformable element 1214, sensing circuitry coupled to
the first and second sensing elements 1209, 1215 may be configured
to algorithmically determine when the air gap 1210 has fully
collapsed. For example, the sensing circuitry may monitor a rate of
change of deformation (e.g., a slope of the force versus deflection
curve) as a force is applied. If the slope satisfies a first
condition (e.g., it is constant or it is below a threshold value),
the sensing circuitry may determine that only the air gap 1210 is
being or has been collapsed, and may apply a first force-deflection
correlation. If the slope satisfies a second condition (e.g., it is
increasing or it is above the threshold value), the sensing
circuitry may determine that the air gap 1210 has been fully
collapsed and the deformable element 1214 is about to be deformed
or has been at least partially deformed. In the latter case, the
sensing circuitry may apply a second force-deflection correlation
to determine a value of the applied force.
[0168] FIG. 14 is a partial cross-sectional view of an example
force sensing device 1400 that may be incorporated in an electronic
device (e.g., the devices 100, 200), depicting an area similar to
the area 301 in FIG. 3A. In this example, the force sensing device
1400 is the same as the force sensing device 1200 except that the
first sensing element 1209 is coupled to the upper stack 1204 such
that the capacitive sensor 1402 formed by the first and second
sensing elements 1209, 1215 spans both the air gap 1206 and the air
gap 1210. Accordingly, as illustrated in the force versus
deflection curve in FIG. 15, the capacitive sensor 1402 detects
deflection of the upper stack 1204 from point 401 to point 404
(corresponding to line 1502). Moreover, as described herein,
sensing circuitry may be configured to algorithmically determine
when the air gap 1210 and optionally the air gap 1206 have fully
collapsed in order to apply an appropriate force-deflection
correlation.
[0169] Whereas in FIG. 12, the frame member 1207 was not between
the first and second sensing elements 1209, 1215, in FIG. 14 the
frame member 1207 is between the first and second sensing elements
1209, 1215. Accordingly, the frame member 1207 may be formed from a
dielectric material or may have an opening in which a dielectric
material is positioned such that the frame member 1207 does not
shield or otherwise interfere with the sensing elements 1209,
1215.
[0170] FIG. 16 is a partial cross-sectional view of an example
force sensing device 1600 that may be incorporated in an electronic
device (e.g., the devices 100, 200), depicting an area similar to
the area 301 in FIG. 3A. In this example, the force sensing device
1600 includes an upper stack 1604 (corresponding to the upper stack
1204), a first sensing element 1605 (corresponding to the first
sensing element 1209), an air gap 1606 (corresponding to the air
gap 1206), a lower stack 1608 (corresponding to the lower stack
1208), a deformable element 1610, an air gap 1615, a second sensing
element 1614, and a base structure 1620 (corresponding to the base
structure 1216). The lower stack 1608 may include an optical stack
1617 and a frame member 1607 supporting the optical stack 1617 and
coupling the lower stack 1608 to the upper stack 1604. Because the
frame member 1607 is between the first and second sensing elements
1605, 1614 (similar to the configuration in the force sensing
device 500, FIG. 5), the frame member 1607 may be formed from or
include a dielectric material, such as a dielectric material
disposed in an opening in the frame member 1607.
[0171] The first and second sensing elements 1605, 1614 form a
capacitive sensor 1619 that spans both the air gap 1606 and the air
gap 1615. Thus, like in the force sensing device 1400, the
capacitive sensor 1619 detects deformation that corresponds to the
collapse of both air gaps 1606, 1615, as well as the deformable
element 1610. Accordingly, as illustrated in the force versus
deflection curve in FIG. 17, the capacitive sensor 1619 detects
deflection of the upper stack 1604 from point 401 to point 404,
corresponding to line 1702.
[0172] The force sensing device 1600 also includes a contact sensor
that is configured to detect contact between the upper and lower
stacks. As shown in FIG. 16, the contact sensor is integrated with
the deformable element 1610 and the second sensing element 1614.
For example, the deformable element 1610 may include protrusions
1611 extending from a base portion of the deformable element 1610.
The protrusions 1611 may include a sense element 1612 that is
configured to be sensed or otherwise detected by a contact sensing
region (e.g., a contact sensing region 1616, discussed herein) when
the air gap 1615 has been fully collapsed and the deformable
element 1610 contacts the second sensing element 1614. As shown in
FIG. 16, the sense elements 1612 are disposed at free ends of the
protrusions 1611.
[0173] The sense elements 1612 may be formed from any appropriate
material and may have any appropriate size and shape. These
properties, as well as any other property of the sense elements
1612, may be selected based on the principle of operation of the
contact sensor. For example, if a contact sensing region 1616 is a
capacitive sensor, the sense elements 1612 may be a conductive
material, and/or a dielectric material. A suitable dielectric
material may have a dielectric constant (or relative permittivity)
greater than about 3.9 (e.g., a high-k dielectric material). Where
the contact sensing region 1616 is a continuity sensor, the sense
elements 1612 may be a conductive material such as carbon, metal,
or the like.
[0174] The sense elements 1612 may be incorporated in the
deformable element 1610 in any appropriate way. For example, the
sense elements 1612 may be co-molded with the deformable element
1610. In another example, the sense elements 1612 may be deposited
on the deformable element 1610. For example, a layer or layers of
metal (or any other appropriate material) may be deposited on free
ends of the protrusions 1611. In yet another example, the
deformable element 1610 may be formed of a material that is itself
configured to be sensed by a corresponding contact sensing region
1616, and thus discrete sense elements 1612 may not be used. For
example, the material may be a silicone or other elastomer with
conductive particles, such as carbon, embedded therein. Other
materials and techniques for integrating the materials with the
deformable element 1610 are also contemplated.
[0175] The contact sensor of the force sensing device 1600 also
includes contact sensing regions 1616 that are configured to detect
the sense elements 1612 to determine when the air gap 1615 has been
fully collapsed and the deformable element 1610 has begun to be
compressed. The contact sensing regions 1616 may be configured to
detect the sense elements 1612 in any appropriate way. For example,
the contact sensing regions 1616 may include capacitive sensing
components that are configured to detect a change in capacitance
caused by the proximity of the sense elements 1612 to the contact
sensing regions 1616. As another example, the contact sensing
regions 1616 may include electrical switches that are configured to
detect a closed circuit when a conductive sense element 1612
contacts the electrical switches.
[0176] The contact sensing regions 1616 may be integrated with the
second sensing element 1614. For example, the contact sensing
regions 1616 for the contact sensor and sensing regions for the
capacitive force sensor 1619 may be patterned on or otherwise
incorporated in the same substrate. As another example, the contact
sensing regions 1616 may be disposed on top of the second sensing
element 1614. For example, contact sensing regions 1616 comprising
electrical contacts, capacitive sensing components, or the like may
be placed on top of and optionally adhered to the second sensing
element 1614.
[0177] Similar to the force sensing device 1400 in FIG. 14, the
force sensing device 1600 forms a capacitive sensor 1619 that spans
both the air gap 1615 and the deformable element 1610, and thus the
capacitive sensor 1619 exhibits a force response curve (shown in
FIG. 17) that extends from point 401 to point 404 (corresponding to
line 1702). However, the capacitive sensor 1619 may not provide a
discrete indication when the force sensing device 1600 is operating
in the first force profile (e.g., from point 401 to point 402) or
the second force profile (e.g., from point 402 to point 404). The
contact sensor of the force sensing device 1600 provides this
indication, allowing sensing circuitry to apply an appropriate
force-deflection correlation. For example, before the air gap 1615
is fully collapsed and before the contact sensor indicates a
contact event (corresponding to point 1704 in FIG. 17), the sensing
circuitry may apply a first force-deflection correlation
corresponding to the collapse of the air gap 1615 (from point 401
to point 402). After the air gap 1615 has fully collapsed, as
detected and indicated by a signal from the contact sensor (at
point 1704), the sensing circuitry may apply a second
force-deflection correlation corresponding to compression of the
deformable element 1610 (e.g., from point 402 to point 404).
[0178] While FIG. 16 illustrates an embodiment where the first
sensing element 1605 is disposed on the upper stack 1604, and thus
includes the air gap 1606 in the space between the first and second
sensing elements 1605, 1614, other configurations are possible. For
example, the first sensing element 1605 may be disposed on the
lower stack 1608 on the opposite side of the air gap 1606, or it
may be disposed between the lower stack 1608 and the deformable
element 1610. Regardless of where the first and second sensing
elements 1605, 1614 are located in the force sensing device 1600,
an air gap, a deformable element, and a contact sensor may be
disposed between them. Moreover, FIG. 16 illustrates the deformable
element 1610 positioned on the lower stack 1608, with the
protrusions 1611 extending towards the base structure 1620, and
illustrates the contact sensing regions 1616 positioned on the base
structure 1620. In other embodiments, the relative positioning of
these components may be exchanged, such that the deformable element
1610 is positioned on the base structure 1620 with the protrusions
1611 extending towards the lower stack 1608, and the sensing
regions 1616 are positioned on the lower stack 1608. It will be
understood that this modification may produce an equivalent result
at least with respect to the operation of the deformable element
1610 and the contact sensing regions 1616.
[0179] FIG. 18A is an expanded view of the area 1800 in FIG. 16,
showing an example configuration of the protrusions 1611, sense
elements 1612, and contact sensing regions 1616 that may form the
contact sensor in FIG. 16. The second sensing element 1614 may
include sensing regions 1810, such as capacitive plates or leads
that capacitively couple to a ground or drive layer, as well as the
contact sensing regions 1616. The contact sensing region 1616 in
FIG. 18A includes leads 1802, 1804, 1806, and 1808. The leads may
be any appropriate material (such as traces of conductive material
(e.g., metal, carbon, ITO), wires, plates, pads, or the like), and
may be coupled to appropriate circuitry for detecting contact with
or proximity to the sense element 1612. For example, the leads may
be capacitive elements that facilitate detection of a change in
capacitance resulting from the sense element 1612 being brought
into contact with or proximity to the leads. As another example,
the leads may be electrical contacts that facilitate detection of a
closed circuit between two or more contacts.
[0180] FIG. 18B illustrates the area 1800 in FIG. 16 when the air
gap 1615 has been fully collapsed and the deformable element 1610
is in contact with the second sensing element 1614. As shown, the
proximity or contact between the sense element 1612 and the leads
1802, 1804, 1806, and 1808 results in detection by corresponding
pairs of the leads 1802, 1804, 1806, and 1808. While FIGS. 18A-18B
illustrate four leads, this is merely an example, and more or fewer
leads may be used. Moreover, the relative sizes of the contact
sensing region 1616, the sense element 1612, and the leads 1802,
1804, 1806, and 1808 are merely exemplary, and may be selected
based on various factors and considerations. For example, the
contact sensing regions 1616 may be large enough to accommodate
misalignments between the deformable elements 1610 and the contact
sensing regions 1616. Thus, even if the centers of the protrusions
1611 and the contact sensing regions 1616 do not line up exactly,
the contact sensor will still effectively detect when the air gap
1615 has fully collapsed.
[0181] FIG. 19 shows an example of the deformable element 1610, or
a portion thereof. The deformable element 1610 comprises an array
of protrusions 1611 extending from a base surface 1900. The
protrusions 1611 may be integrally formed with the base surface
1900. For example, the deformable element 1610 may be molded (e.g.,
injection molded) as a unitary, monolithic component of a
substantially uniform composition. As noted above, the sense
elements 1612 may be co-molded with the deformable element 1610 or
they may be applied (e.g., adhered, coated, or deposited) to or on
the protrusions 1611 after the deformable element 1610 is formed.
In either case, the sense elements 1612 may be at least partially
embedded in the protrusions 1611. Other techniques for securing the
sense elements 1612 to the protrusions 1611 are also contemplated.
It will be understood that the protrusions 1611 are for
illustrative purposes, and are not necessarily to scale relative to
the size of the base surface 1900 or any other components depicted
in the figures.
[0182] FIG. 20 shows an example of the second sensing element 1614,
or a portion thereof, that includes both sensing regions 1810
(indicated by plain squares) and contact sensing regions 1616
(indicated by cross-hatched squares), and which may be used in
conjunction with the deformable element 1610 shown in FIG. 19. Both
the sensing regions 1810 and the contact sensing regions 1616 may
be formed on the same substrate 2000 (e.g., a flexible circuit
material), and may include conductive traces, such as metals,
carbon, ITO, or the like.
[0183] In the examples shown in FIGS. 19 and 20, each protrusion
1611 includes a sense element 1612 and corresponds to a contact
sensing region 1616 on the second sensing element 1614. This need
not be the case, however, as the considerations that determine the
amount, arrangement, and distribution of the protrusions 1611 that
provide a suitable resistance to compression may be different than
the considerations driving the amount, arrangement, and
distribution of contact sensing regions. For example, in some
implementations, some of the protrusions 1611 do not correspond to
contact sensing regions 1616. In such cases, the protrusions 1611
that do not correspond to contact sensing regions 1616 may omit the
sense element 1612, but may be formed or shaped to ensure that all
of the protrusions 1611 have substantially the same height.
Alternatively, all of the protrusions 1611 may include a sense
element 1612 regardless of whether they all correspond to a contact
sensing region 1616. This may ensure that all of the protrusions
have the same height and contact an opposing surface at
substantially the same time.
[0184] FIG. 21A is a cross-sectional view of an example contact
sensor 2100, showing a section similar to those shown in FIGS.
18A-18B. Whereas the contact sensor formed by the protrusions 1611
and the contact sensing regions 1616 shown in FIGS. 18A-18B places
the sensing component and the sensed component on opposite sides of
the air gap 1615, the contact sensor 2100 is configured such that
both the sensed and sensing components can be disposed on one side
of an air gap.
[0185] The contact sensor 2100 includes a deformable protrusion
2102, which may be formed of any appropriate deformable material,
such as silicone, polyurethane foam, rubber, gel, or the like. A
sense element 2104 may be incorporated with the protrusion 2102.
For example, the sense element 2104 may be placed within a cavity
2106 or other internal region of the protrusion 2102. The sense
element 2104 may also be embedded in the material of the protrusion
2102 (e.g., via co-molding or insert molding). Like the sense
element 1612, the sense element 2104 may be formed from or include
any appropriate material, such as a dielectric material and/or a
conductive material.
[0186] The contact sensor 2100 also includes leads 2110 in an
adjacent layer 2108. The adjacent layer 2108 may be a sensing
element, such as the sensing element 1614, in or on which the leads
2110 are incorporated. Alternatively, the adjacent layer 2108 may
be dedicated to containing the leads 2110. Like the leads 1802,
1804, 1806, and 1808 in FIGS. 18A-18B, the leads 2110 may be
configured to act as capacitive elements (e.g., capacitive plates
to capacitively couple to and detect the proximity of the sense
element 2104), contacts for a continuity sensor, or the like.
Moreover, the leads 2110 may be formed from or include any
appropriate material, such as traces of conductive material (e.g.,
metal, carbon, ITO), wires, plates, pads, or the like. The leads
2110 may be coupled to appropriate circuitry for detecting contact
with or proximity to the sense element 2104.
[0187] Where the contact sensor 2100 is a capacitive sensor,
physical contact between the leads 2110 and the sense element 2104
may not be necessary to detect contact between the protrusion 2102
and another component. Rather, when the protrusion 2102 contacts
another component (e.g., because an adjacent air gap has been fully
collapsed), the leads 2110, along with associated circuitry, may
detect the change in distance between the sense element 2104 and
the leads 2110, thereby triggering the contact sensor 2100. In such
cases, the cavity 2106 may be filled with a deformable material,
such as silicone, thereby encapsulating the sense element 2104.
[0188] FIG. 21B illustrates the contact sensor 2100 after the
protrusion 2102 has been deformed by a layer 2112 forming an
opposite side of an air gap in which the protrusion 2102 has been
disposed. As shown, the sense element 2104 has been brought into
contact with the leads 2110, thus triggering the contact sensor
2100. It may not be necessary for the sense element 2104 to
actually contact the leads 2110, however, in order for the contact
sensor 2100 to be triggered. For example, where the leads 2110 are
configured as capacitive sensors (or any other type of sensor
capable of detecting a change in distance between it and another
object), the contact sensor 2100 may be triggered by any detectable
change in distance between the sense element 2104 and the leads
2110 caused by the layer 2112 deforming or otherwise contacting the
protrusion 2102.
[0189] FIG. 22A is a cross-sectional view of an example contact
sensor 2200, showing a section similar to those shown in FIGS.
18A-18B. Whereas the contact sensor formed by the protrusions 1611
and the contact sensing regions 1616 shown in FIGS. 18A-18B places
the sensing component and the sensed component on opposite sides of
the air gap 1615, the contact sensor 2200 is configured such that
both the sensed and sensing components can be disposed on one side
of an air gap.
[0190] The contact sensor 2200 includes a deformable protrusion
2202, which may be formed of any appropriate deformable material,
such as silicone, polyurethane foam, rubber, gel, or the like. A
sense element 2204 may be disposed over the protrusion 2202. For
example, a material may be disposed over at least a portion of the
protrusion 2202, such as by coating, deposition (e.g., physical
vapor deposition or chemical vapor deposition), or any other
appropriate mechanism. The contact sensor 2200 also includes leads
2208 in a layer 2206 that is proximate the protrusion 2202.
[0191] The leads 2208 may be configured to act as capacitive
elements that capacitively couple to the sense element 2204,
thereby sensing changes in distance from the leads 2208 to the
sense element 2204. Accordingly, the sense element 2204 may be
formed from or include a conductive material, a dielectric material
(e.g., a high-k dielectric material), or any other appropriate
material that may be capacitively coupled to and sensed by the
leads 2208.
[0192] FIG. 22B illustrates the contact sensor 2200 after the
protrusion 2202 has been deformed by a layer 2210 forming an
opposite side of an air gap in which the protrusion 2202 is
disposed. As shown, the sense element 2204 has been brought into
closer proximity to the leads 2208, thus triggering the contact
sensor 2200.
[0193] The contact sensors 2100, 2200 may be used instead of or in
conjunction with the contact sensors described with respect to
FIGS. 18A-20. For example, instead of the protrusions 1611 and the
sensing regions 1616, which together form a contact sensor to
detect contact with the deformable element 1610, the deformable
element 1610 may include a plurality of contact sensors 2100 or
2200 that serve the same or a similar function.
[0194] The contact sensing systems described herein may be applied
between any of the layers or components of a force sensing device.
For example, while FIG. 16 depicts a contact sensor to detect when
the air gap 1615 has collapsed, a contact sensor may also or
instead be configured to detect contact when the air gap 1606 has
collapsed. In some cases, multiple air gaps in a stack of a force
sensing device may include a contact sensor. By providing
additional contact sensors in this manner, an electronic device may
determine which layers have been or are being deflected, and may
therefore apply force-deflection correlations that are tailored for
the particular layer or layers that are being deflected. By
providing a distinct force-deflection correlation for each of
multiple layers, an amount of force applied to a surface may be
determined with a high degree of accuracy.
[0195] The deformable elements described in each of the foregoing
examples above may have different thicknesses and/or different
protrusion heights in different areas when the deformable element
is in an undeformed state. For example, the base structures and/or
the upper or lower stacks of the force sensing devices (or any
other layer of a force sensing device) may not have uniformly
planar surfaces. Accordingly, in order to provide a relatively
constant air gap size across the air gap, the deformable elements
may have different thicknesses in different areas. For example,
protrusions may be larger in some areas to account for a greater
distance between a layer or stack (e.g., the lower stack 308) and a
base structure (e.g., the base structure or layer 316).
[0196] In some cases, input surfaces may not deflect uniformly
across the entire input surface area. For example, a force applied
near an edge of the cover 303 (e.g., close to the joint between the
housing 104 and the cover 303) may cause less deflection of the
cover 303 (and hence the upper and lower stacks 304, 308) than a
force of the same magnitude that is applied in the center of the
cover 303. Accordingly, the deformable elements may be thicker in
areas where less deformation is expected (e.g., around the edges or
perimeter of the cover 303) so that the deformable element begins
to be compressed at substantially the same magnitude of force
regardless of where on the input surface the force is applied.
[0197] FIG. 23A is a cross-sectional view of an embodiment of the
device 100, viewed along line A-A in FIG. 1, showing an assembly
2300 that may provide display, touch sensing, and/or force sensing
functionality to the device 100, or may be integrated with other
components to provide such functionality. As shown in FIG. 23A, the
device 100 includes force sensing system in the assembly 2300,
similar to the sensors described above with respect to FIGS. 5-22,
as well as a sensor 2302 (FIG. 23B) positioned between the housing
104 and the cover 303. The sensor 2302 works in conjunction with
the sensing elements in the assembly 2300 to determine an amount of
deflection of, and thus an amount of force applied to, the cover
303.
[0198] The assembly 2300 includes the upper and lower stacks 304,
308, the air gaps 306, 310, and the deformable element 314, all of
which are described above with respect to FIGS. 3A-3E. The assembly
2300 also includes a first sensing element 2304 positioned on a
first side of (e.g., above) the deformable element 314 and a second
sensing element 2306 positioned on a second side of (e.g., below)
the deformable element 314. Together, the first and second sensing
elements 2304, 2306 may be referred to as a force sensor.
[0199] The first and second sensing elements 2304, 2306 may be
similar to any of the sensing elements described herein. For
example, the first sensing element 2304 may be a capacitive drive
layer, and the second sensing element 2306 may be a capacitive
sense layer that is capacitively coupled to the drive layer. The
first and second sensing elements 2304, 2306 and associated
circuitry may detect an amount of deformation or deflection of the
deformable element 314, and thus determine an amount of force
applied to the cover 303. While the assembly 2300 shows the first
and second sensing elements 2304, 2306 positioned on opposite sides
of the deformable element 314, other configurations are also
possible. For example, the first sensing element 2304 may be
disposed on the bottom of the frame member 309, on (or in) the
upper stack, or the like. In some cases, any of the force sensing
devices described herein, such those shown and described with
respect to FIG. 5, 12, 14, or 16, may be used in the assembly
2300.
[0200] In addition to the force sensor in the assembly 2300, the
device 100 may include a sensor 2302 disposed between the housing
104 and the cover 303. The sensor 2302 may include a compliant
material that can deflect or deform in response to an applied force
on the cover 303. The sensor 2302, along with associated sensing
circuitry, may be able to detect an amount of deflection of the
cover 303 in response to an applied force, and, in conjunction with
the sensing elements 2304, 2306 in the assembly 2300, determine an
amount of force applied to the cover 303.
[0201] FIG. 23B shows an exploded view of the area 2308 in FIG.
23A, showing details of the sensor 2302. The sensor 2302 may be
positioned between the ledge 307 of the housing 104 and a portion
of the cover 303 such that when a force is applied to the cover
303, the sensor 2302 is pressed between the ledge 307 and the
portion of the cover 303, thus deforming the sensor 2302. The
geometry of the ledge 307 and the cover 303 in FIG. 23B are merely
exemplary, and different embodiments of the housing 104 and the
cover 303 may have shapes, geometries, and/or features that are
different from those shown in FIG. 23B.
[0202] The sensor 2302 includes a deformable portion 2310. The
deformable portion 2310 may be formed from or include any
appropriate material, such as silicone, polyurethane foam, rubber,
gels, elastomers, or the like. In some cases, the deformable
portion 2310 may have adhesive properties, such that the sensor
2302 retains the cover 303 to the housing 104.
[0203] The sensor 2302 also includes a first sensing element 2312
and a second sensing element 2314. The first and second sensing
elements 2312, 2314 may be positioned on opposite sides of the
deformable portion 2310 (e.g., a top and bottom, as shown in FIG.
23B). The first and second sensing elements 2312, 2314 may form a
capacitive sensor, in which case one of the first or second sensing
element 2312, 2314 may be a capacitive drive layer, and the other
may be a capacitive sense layer. The capacitive sensor may detect
an amount of deformation of the deformable portion 2310, and thus
facilitate detection of an amount of applied force, as discussed
herein. In some cases, the sensor 2302 may be a resistive sensor
(or any other appropriate sensor), in which case the first and
second sensing elements 2312, 2314 may be omitted or substituted
with other components.
[0204] When a force is applied to the cover 303, the deformable
portion 2310 of the sensor 2302 may deflect or deform such that the
first and second sensing elements 2312, 2314 are brought closer
together. The first and second sensing elements 2312, 2314 and
associated circuitry may determine the amount of deformation and
correlate it with an amount of force applied to the cover 303. As a
certain amount of applied force is reached, however, the deformable
portion 2310 may reach a maximum deformation, where greater applied
forces may not result in further deformation of the deformable
portion 2310. In some cases, it may be desirable to detect applied
forces greater than this amount, however. Accordingly, the sensor
2302 and the sensing elements in the assembly 2300 may sense
different ranges of applied forces.
[0205] For example, the sensor 2302 may be configured to determine
forces spanning from no applied force to an amount of force that
results in the collapse of the air gaps 306 and 310 in FIG. 23A. Up
until that point, the sensor in the assembly 2300 (formed by the
first and second sensing elements 2304, 2306) may not detect any
force, as the lower stack 308 had not yet been brought into contact
with the deformable element 314. Once the lower stack 308 contacts
the deformable element 314, increasing amounts of force may be
determined by the sensing elements 2304, 2306 in the assembly
2300.
[0206] The first and second sensing elements 2312, 2314 may be
formed from or include any appropriate material, such as metals,
ITO, or the like. Moreover, the first and second sensing elements
2312, 2314 may be applied to or otherwise incorporated with the
deformable portion 2310 in any appropriate manner. For example, the
first and second sensing elements 2312, 2314 may be or may include
conductive sheets (e.g., copper, silver, or gold) embedded in,
positioned on, or otherwise integrated with the deformable portion
2310. As another example, the first and second sensing elements
2312, 2314 may be ITO that is deposited on the deformable portion
2310.
[0207] In some cases, either or both of the first and second
sensing elements 2312, 2314 may not be integrated with the
deformable material 2310, but rather may be separate components.
For example, the first and/or second sensing elements 2312, 2314
may be layers of material (e.g., flexible circuit material) with
conductive materials disposed thereon. The layers may be positioned
between the deformable portion 2310 and the cover 303, and/or
between the deformable portion 2310 and the housing 104, and may be
bonded or otherwise adhered to those components. As another
example, the first and/or second sensing elements 2312, 2314 may be
patterned directly on the cover 303 and/or the housing 104. For
example, ITO, conductive nanowires, or any other appropriate
material, may be formed directly on the portions of the cover 303
and the housing 104 that are opposite each other when the device
100 is in its assembled configuration. Any combinations of the
foregoing examples may be used to integrate the first and/or second
sensing elements 2312, 2314 with the device 100.
[0208] FIG. 24 is an example force versus deflection curve
illustrating how the cover 303 of the device illustrated in FIG.
23A deflects in response to a force input applied thereto. The
force response is similar to that shown in FIG. 4, with a first
profile from point 401 to point 402 (corresponding to collapse of
the air gaps 306 and 310) and a second profile from point 402 to
point 404 (corresponding to deformation of the deformable element
314). The sensor 2302 may detect deformation of the air gaps 306,
310, as indicated by the line 2402 in FIG. 24, while the force
sensor in the assembly 2300 detects deformation of the deformable
element 314, as indicated by line 2404. While the lines 2402, 2404
are shown as non-overlapping, this may not be the case. For
example, the sensor 2302 may continue to deflect and thus provide
meaningful force information even after the air gaps 306, 310 have
collapsed. In such cases, sensing circuitry associated with the
sensors may process the information from both sensors to determine
an amount of applied force.
[0209] FIG. 25 shows a portion of the sensor 2302 as viewed through
the cover 303 of the device. The illustrated portion of the sensor
2302 corresponds to a corner portion of the sensor 2302. The sensor
2302 includes first drive regions 2502 each electrically coupled
together (e.g., via conductors 2503) and second drive regions 2504
each electrically coupled together (e.g., via conductors 2505). The
first and second drive regions 2502, 2504 may together form the
second sensing element 2314 shown in FIG. 23B, and may be driven or
excited with a signal. As shown, the first and second drive regions
2502, 2504 are shown in an alternating, interdigitated pattern,
though this is merely one example configuration for the first and
second drive regions 2502, 2504.
[0210] The sensor 2302 also includes sensing regions 2506. The
sensing regions 2506 capacitively couple to the drive regions 2502,
2504 and may be connected to circuitry that detects and analyzes
signals induced in the sensing regions 2506 by the drive regions
2502, 2504. Each sensing region 2506 may overlap one first drive
region 2502 and one second drive region 2504. As the drive regions
may be driven at different times and/or with different signals
(e.g., signals having different frequencies), a single sensing
region can provide two distinct capacitive measurements, each
corresponding to a different location along the sensor 2302. In
this way, the sensor 2302 is pixelated, allowing for more precise
force measurements and for detection of a location of an applied
force on the cover 303.
[0211] FIG. 26 is a cross-sectional view of an embodiment of the
device 100, viewed along line A-A in FIG. 1, showing a display
stack 2600 positioned below the cover 110. Force and/or touch
sensing systems, or components thereof, may be incorporated with
the display stack 2600 to facilitate touch and force input
detection on the device 100. As described herein, device 100 may
include conductive sheets (such as the first drive layer 505, FIG.
5) that may facilitate sensing force and/or touch inputs on the
device 100.
[0212] The display stack 2600 may include a touch sensor 2602
positioned between the cover 110 and a display layer 2604. The
touch sensor 2602 can include sensors that are each configured to
detect user inputs (e.g., touch and/or force inputs), and the
locations of the user inputs, on the cover 110. Any suitable touch
sensor 2602 can be used. For example, in one embodiment, the touch
sensor 2602 is formed with a dielectric substrate positioned
between two electrode layers. The electrode layers may be made of
any suitable optically transparent material. For example, in one
embodiment the electrode layers are made of indium tin oxide (ITO).
Other suitable materials include, but are not limited to, nanowires
or nanowire meshes, a transparent conducting film (e.g., a polymer
film), carbon nanotubes, and ultra-thin metal films.
[0213] Each electrode layer in the touch sensor 2602 can include
one or more electrodes. The electrode(s) in one layer are aligned
in at least one direction (e.g., vertically) with respective
electrodes in the other electrode layer to form one or more
capacitive sensors. User inputs, and the locations of the user
inputs, are detected through changes in the capacitance of one or
more capacitive sensors. As will be described in more detail later,
touch and sense circuitry 2632 is coupled to the electrode layers
and configured to receive an output signal from each capacitive
sensor that represents the capacitance of each capacitive
sensor.
[0214] One or both of the electrode layers in the touch sensor 2602
may be patterned. For example, in one embodiment one electrode
layer is patterned into strips positioned along a first axis (e.g.,
rows) and the other electrode layer is patterned into strips
positioned along a second axis that is transverse to the first axis
(e.g., columns). Capacitive sensors are formed at the intersections
of the strips in the two electrode layers. User inputs, and the
locations of the user inputs, can be determined based on the
capacitance (or changes in capacitance) of one or more capacitive
sensors.
[0215] The display layer 2604 can include a front polarizer 2606, a
display element 2608 attached to a back surface of the front
polarizer 2606, and a back polarizer 2610 attached to a back
surface of the display element 2608. Any suitable display element
2608 can be used. Example display elements 2608 include, but are
not limited to, a LCD element, a LED element, an OLED element, or
an OEL element. In the illustrated embodiment, the display element
2608 is a LCD element.
[0216] In some situations, noise signals that are produced by the
display element 2608 can electrically couple with the touch sensor
2602. This coupling can adversely impact the detection of user
inputs by the touch sensor 2602. To reduce or eliminate the display
noise from coupling with the touch sensor 2602, a conductive layer
2612 can be positioned between the touch sensor 2602 and the front
polarizer 2606. The conductive layer 2612 may be made of any
suitable optically transparent material. For example, in one
embodiment the conductive layer 2612 is made of ITO.
[0217] A sheet of conductive material 2614 is formed or coated over
the back surface of the back polarizer 2610. The sheet of
conductive material 2614 can be made of any suitable conductive
material. For example, in one embodiment, the sheet of conductive
material 2614 is made of a silver nanowire film.
[0218] The back polarizer 2610 may be made of an electrically
insulating material. The sheet of conductive material 2614 enables
the back surface of the back polarizer 2610 to function as a
conducting surface. As will be described in more detail below, the
conducting surface of the back polarizer 2610 is used to transmit
drive signals for a force sensor that includes the conducting
surface.
[0219] Attached to the back surface of the back polarizer 2610 is a
conductive border 2616 (which may be the same or similar in
structure, materials, function, etc., to the connection element
706, FIGS. 7, 10A). The conductive border 2616 is positioned along
at least a portion of a perimeter or edge of the back polarizer
2610. As will be described in more detail in conjunction with FIGS.
27-29, the conductive border 2616 can be a continuous border that
extends around the entire perimeter, or the conductive border 2616
can include one or more discrete conductive strips with each
conductive strip positioned along a respective portion of the
perimeter of the back polarizer 2610.
[0220] In the illustrated embodiment, the display stack 2600
extends across the user-viewable region 108 (FIG. 1) of the display
102 and into non-viewable regions 2618 that do not correspond to a
viewable output from the display 102. Alternatively, in some
embodiments, only a subset of the layers in the display stack 2600
extend into the non-viewable regions 2618. For example, portions of
the display layer 2604 can extend into the non-viewable regions
2618 while other layers in the display stack 2600 do not extend
into the non-viewable regions 2618.
[0221] In some embodiments, the conductive border 2616 can be
positioned on the portions of the back polarizer 2610 that reside
in the non-viewable regions 2618, which allows the conductive
border 2616 to be formed with any suitable material or materials
(e.g., opaque or transparent material(s)). For example, the
conductive border 2616 may be formed with a metal or metal alloy,
such as copper, aluminum, molybdenum, and nickel vanadium. Other
embodiments can form at least a portion of the conductive border
2616 within the user-viewable region 108. In such embodiments, at
least the portion of the conductive border 2616 that is in the
user-viewable region 108 may be formed with an optically
transparent material, such as ITO.
[0222] In the illustrated embodiment, a backlight unit 2620 is
positioned below the back polarizer 2610 and the conductive border
2616. The display layer 2604, along with the backlight unit 2620,
is used to output images on the display 102. In some
implementations, the backlight unit 2620 may be omitted.
[0223] A first electrode layer 2622 is positioned below and
attached to the backlight unit 2620. In some implementations, the
first electrode layer 2622 represents an array of electrodes (e.g.,
two or more electrodes). In other implementations, the first
electrode layer 2622 is a single electrode. The first electrode
layer 2622 can be formed with any suitable conductive material
(opaque or transparent), such as a metal or metal alloy. Example
metals and metal alloys include, but are not limited to, copper,
aluminum, titanium, tantalum, nickel, chromium, zirconium,
molybdenum niobium, and nickel vanadium.
[0224] Together, the sheet of conductive material 2614 on the back
surface of the back polarizer 2610 and the first electrode layer
2622 form a force sensor. The force sensor can be used to detect a
magnitude or an amount of force that is applied to the cover 110.
When the first electrode layer 2622 is implemented as an array of
electrodes, the sheet of conductive material 2614 and the first
electrode layer 2622 form an array of capacitive sensors. Each
capacitive sensor includes an electrode formed by the sheet of
conductive material 2614 and a respective electrode in the first
electrode layer 2622. When a user input is applied to the cover
110, the cover 110 deflects and a distance between the electrodes
in at least one capacitive sensor changes, which varies the
capacitance of that capacitive sensor. For example, in the
illustrated embodiment, the gap 2623 varies based on a user input
applied to the cover 110, which in turn varies the capacitance of
at least one capacitive sensor.
[0225] In some embodiments, the first electrode layer 2622 can be
used to detect one or more touches on the cover 110. In such
embodiments, the touch-sensing layer 2602 may be omitted since the
first electrode layer 2622 has a dual function in that it is used
to detect both touch and force inputs.
[0226] The device 100 can also include a support structure 2624
(which may be the same or similar in structure, materials,
function, etc., to the frame members 309, 1207, discussed above).
In the illustrated embodiment, the support structure 2624 is made
from a conductive material (e.g., a metal), although other
embodiments can form the support structure 2624 with a different
material, such as a plastic, ceramic, or a composite. In the
illustrated embodiment, the support structure 2624 extends along a
length and a width of the display stack 2600, although this is not
required. The support structure 2624 can have any shape and/or
dimensions in other embodiments. For example, the support structure
2624 may have an opening in which a stiffening member may be
positioned (as described with respect to the frame member 309 and
the stiffening member 312, FIG. 3A).
[0227] In the illustrated embodiment, the support structure 2624
has a U-shaped cross-section and is attached to the cover 110 such
that the support structure 2624 is suspended from the cover 110. In
other embodiments, the support structure 2624 may be connected to a
component other than the cover 110. For example, the support
structure 2624 can be attached to a housing of the device 100
(e.g., the housing 104 in FIG. 1) or to a frame or other support
component in the housing.
[0228] In some embodiments, the support structure 2624 may be
constructed and attached to the cover 110 to define a gap 2626
between the support structure 2624 and the first electrode layer
2622. The gap 2626 allows the display stack 2600 to flex or move in
response to an applied force on the cover 110. In some embodiments,
the first electrode layer 2622 may be attached to the support
structure 2624 instead of the backlight unit 2620.
[0229] The device 100 may also include a battery 2628. The battery
2628 provides power to the various components of the device 100. As
shown in FIG. 26, a second electrode layer 2630 can be disposed on
a top surface of the battery 2628. In some embodiments, the amount
of force applied to the cover 110 may be sufficient to cause the
display stack 2600 to deflect such that the back polarizer 2610
contacts the first electrode layer 2622. When the display stack
2600 is deflected to a point where the back polarizer 2610 contacts
the backlight unit 2620 (or first electrode layer 2622 if no
backlight unit 2620 is present), the amount of force detected by
the force sensor reaches a maximum level (e.g., a first amount of
force). The force sensor cannot detect force amounts that exceed
the maximum level. The deflection of the display stack 2600 to a
point where the back polarizer 2610 contacts the backlight unit
2620 or the first electrode layer 2622 may correspond with the
first profile 406 of the force versus deflection curve in FIG. 4.
For example, the maximum level of force detected by the force
sensor that includes the first electrode layer 2622 and the
conductive material 2614 may correspond to the point 402 in FIG.
4.
[0230] In such embodiments, the second electrode layer 2630 (in
conjunction with the first electrode layer 2622 or other
components) can form a second force sensor that detects the force
that exceeds the first amount of force by associating an amount of
deflection between the first electrode layer 2622 and the second
electrode layer 2630 (e.g., a second amount of force). For example,
in some embodiments, the second electrode layer 2630 can be used to
measure a change in capacitance between the first and the second
electrode layers 2622, 2630. Alternatively, the second electrode
layer 2630 may be used to detect a change in capacitance between
the back surface 2627 of the support structure 2624 and the second
electrode layer 2630. The deflection between the first electrode
layer 2622 and the second electrode layer 2630 (or between the back
surface 2627 of the support structure and the second electron layer
2630) may correspond to the second profile 408 in FIG. 4.
[0231] As described earlier, drive and sense circuitry 2632 is
coupled to the touch sensor 2602. The drive and sense circuitry
2632 may be positioned at any suitable location in the device 100.
The drive and sense circuitry 2632 is configured to provide drive
signals to the touch sensor 2602 and to receive output signals from
the touch sensor 2602. For example, when the touch sensor 2602
includes an array of capacitive sensors, the drive and sense
circuitry 2632 is coupled to each capacitive sensor and configured
to sense or measure the capacitance of each capacitive sensor. A
processing device may be coupled to the drive and sense circuitry
2632 and configured to receive signals representing the measured
capacitance of each capacitive sensor. The processing device can be
configured to correlate the measured capacitances into an amount of
force.
[0232] Similarly, drive circuitry 2634 is coupled to the sheet of
conductive material 2614 and is configured to provide drive signals
to the back surface of the back polarizer 2610 (e.g., to the sheet
of conductive material 2614). In some embodiments, the drive
circuitry 2634 is coupled to the conductive border 2616.
[0233] Sense circuitry 2636 is coupled to the first electrode layer
2622 and is configured to receive one or more output signals from
the first electrode layer 2622. For example, when the first force
sensor includes an array of capacitive sensors, the drive and sense
circuitry 2634, 2636 are coupled to each capacitive sensor and
configured to sense or measure the capacitance of each capacitive
sensor. A processing device may be coupled to the drive and sense
circuitry 2634, 2636 and configured to receive the output signals
representing the measured capacitance of each capacitive sensor.
The processing device can be configured to correlate the measured
capacitances into an amount of force. Like the drive and sense
circuitry 2632, the drive circuitry 2634 and the sense circuitry
2636 may be situated at any suitable location in the device
100.
[0234] The drive signals transmitted on the back surface of the
back polarizer 2610 (e.g., on the sheet of conductive material
2614) can be decoupled from the noise produced by the display
element 2608 (e.g., a TFT layer) because the insulating back
polarizer 2610 physically separates the sheet of conductive
material 2614 from the display element 2608. Additionally, the
conductive border 2616 may reduce the contact resistance between
the back polarizer 2610 and the sheet of conductive material 2614,
as well as reduce the sheet resistance of the sheet of conductive
material 2614. Reducing the contact resistance and/or the sheet
resistance can increase the suppression of the display noise
produced by the display element 2608.
[0235] With respect to the second electrode layer 2630, drive
circuitry 2638 is coupled to the second electrode layer 2630 and is
configured to provide drive signals to the second electrode layer
2630. The drive circuitry 2638 can be located at any suitable
location in the electronic device 100. In some embodiments, the
sense circuitry 2636 may be configured to receive one or more
output signals from the first electrode layer 2622. A processing
device coupled to the sense circuitry 2636 can be configured to
receive the output signals and correlate the measured capacitances
into an amount of force.
[0236] FIGS. 27-29 depict example arrangements of the conductive
border on the polarizer 2610 shown in FIG. 26. As shown in FIG. 27,
the conductive border can include four discrete conductive strips
2702, 2704, 2706, 2708 that are formed on a sheet of conductive
material 2710 coated over a polarizer 2700. Each conductive strip
2702, 2704, 2706, 2708 is formed along a respective edge of the
polarizer 2700. Although FIG. 27 depicts four conductive strips,
other embodiments are not limited to this arrangement. Other
embodiments can include one or more conductive strips. The
embodiments shown in FIGS. 27-29 may represent embodiments of the
conductive material 2614 and the conductive border 2616 on the
polarizer 2610 in FIG. 26.
[0237] In some embodiments, the sheet of conductive material 2710
may be formed with an anisotropic material that is more conductive
in one direction compared to another direction. In such
embodiments, the discrete conductive strip or strips 2702, 2704,
2706, 2708 can be more effective at reducing the sheet and/or
contact resistance of the sheet of conductive material 2710.
[0238] FIG. 28 depicts a discrete L-shaped conductive strip 2802
that is positioned on a sheet of conductive material 2804 on a
polarizer 2800. In the illustrated embodiment, the conductive strip
2802 is formed along two edges of the polarizer 2800. Other
embodiments can include two "L" shaped conductive strips that are
arranged to position a conductive strip along each edge of the
polarizer 2800.
[0239] FIG. 29 illustrates a continuous conductive border 2902 that
is positioned along the entire edge of the polarizer 2900. In some
situations, the continuous conductive border 2902 may reduce the
sheet conductivity and/or the contact resistivity of the sheet of
conductive material 2904 more effectively than a conductive strip
or strips. The conductive strips 2702, 2704, 2706, 2708 and/or the
conductive borders 2802, 2902 may form the connection element 706
described above with respect to FIGS. 7 and 10A.
[0240] Although the embodiments shown in FIGS. 26-29 are described
in conjunction with a display stack in an electronic device, other
embodiments are not limited to displays. A force sensor can be
formed below any suitable cover, such as the housing of an
electronic device (e.g., the housing 104 in FIG. 1, the trackpad
206 in FIG. 2). An insulating substrate may be positioned below the
cover. A sheet of conductive material is formed over a back surface
of the insulating substrate to produce a conducting surface on the
back surface of the insulating substrate. In other words, the sheet
of conductive material transforms the back surface of the
insulating substrate into a conducting surface. A conductive border
is formed along at least one edge of the sheet of conductive
material and an electrode layer is positioned below the insulating
substrate. The conducting surface of the insulating substrate and
the electrode layer together form a force sensor that is configured
to detect a force input on the cover.
[0241] Throughout the foregoing discussion, force sensing devices
and contact sensors are described with respect to various examples.
However, these examples are not meant to be limiting of the
particular elements, layers, or components described. For example,
components (e.g., layers of the force sensing devices) that are
described herein as being separate and/or distinct may be combined,
and components described herein as being combined or integrated may
be separated. Moreover, some components may be substituted, added,
or removed without departing from the spirit of the disclosure. For
example, as noted above, a display structure may be omitted from a
force sensing device if the force sensing device is not integrated
with or part of a display device. Furthermore, any individual layer
or structure described herein may include one or more sub-layers.
For example, a cover may include multiple sub-layers, including
glasses, coatings, adhesives, filters, and the like. As another
example, any of the layers or components of the force sensing
devices and contact sensors described herein may be secured to
adjacent layers or structures with adhesives, bonding layers, or
the like, though such adhesives and bonding layers are not
necessarily described herein.
[0242] FIG. 30 depicts example components of an electronic device
in accordance with the embodiments described herein. The schematic
representation depicted in FIG. 30 may correspond to components of
the devices depicted in FIGS. 1-2, and indeed any device in which
the force sensing described herein may be incorporated.
[0243] As shown in FIG. 30, a device 3000 includes a processing
unit 3002 operatively connected to computer memory 3004 and/or
computer-readable media 3006. The processing unit 3002 may be
operatively connected to the memory 3004 and computer-readable
media 3006 components via an electronic bus or bridge. The
processing unit 3002 may include one or more computer processors or
microcontrollers that are configured to perform operations in
response to computer-readable instructions. The processing unit
3002 may include the central processing unit (CPU) of the device.
Additionally or alternatively, the processing unit 3002 may include
other processors within the device including application specific
integrated chips (ASIC) and other microcontroller devices.
[0244] The memory 3004 may include a variety of types of
non-transitory computer-readable storage media, including, for
example, read access memory (RAM), read-only memory (ROM), erasable
programmable memory (e.g., EPROM and EEPROM), or flash memory. The
memory 3004 is configured to store computer-readable instructions,
sensor values, and other persistent software elements.
Computer-readable media 3006 also includes a variety of types of
non-transitory computer-readable storage media including, for
example, a hard-drive storage device, a solid state storage device,
a portable magnetic storage device, or other similar device. The
computer-readable media 3006 may also be configured to store
computer-readable instructions, sensor values, force-deflection
correlations, and other persistent software elements.
[0245] In this example, the processing unit 3002 is operable to
read computer-readable instructions stored on the memory 3004
and/or computer-readable media 3006. The computer-readable
instructions may adapt the processing unit 3002 to perform the
operations or functions described above with respect to FIGS. 1-25
or below with respect to the example process FIG. 31. In
particular, the processing unit 3002, the memory 3004, and/or the
computer-readable media 3006 may be configured to cooperate with
the force sensor 3022, described below, to determine an amount of
force applied to a user input surface by applying different
force-deflection correlations based on whether a deflection of the
user input surface is collapsing an air gap in a force sensor or
compressing a deformable element. The computer-readable
instructions may be provided as a computer-program product,
software application, or the like.
[0246] As shown in FIG. 30, the device 3000 also includes a display
3008. The display 3008 may include a liquid-crystal display (LCD),
organic light emitting diode (OLED) display, LED display, or the
like. If the display 3008 is an LCD, the display 3008 may also
include a backlight component that can be controlled to provide
variable levels of display brightness. If the display 3008 is an
OLED or LED type display, the brightness of the display 3008 may be
controlled by modifying the electrical signals that are provided to
display elements. The display 3008 may correspond to the upper
and/or lower stacks described above.
[0247] The device 3000 may also include a battery 3009 that is
configured to provide electrical power to the components of the
device 3000. The battery 3009 may include one or more power storage
cells that are linked together to provide an internal supply of
electrical power. The battery 3009 may be operatively coupled to
power management circuitry that is configured to provide
appropriate voltage and power levels for individual components or
groups of components within the device 3000. The battery 3009, via
power management circuitry, may be configured to receive power from
an external source, such as an AC power outlet. The battery 3009
may store received power so that the device 3000 may operate
without connection to an external power source for an extended
period of time, which may range from several hours to several
days.
[0248] In some embodiments, the device 3000 includes one or more
input devices 3010. The input device 3010 is a device that is
configured to receive user input. The input device 3010 may
include, for example, a push button, a touch-activated button, a
keyboard, a key pad, or the like. In some embodiments, the input
device 3010 may provide a dedicated or primary function, including,
for example, a power button, volume buttons, home buttons, scroll
wheels, and camera buttons. Generally, a touch sensor (e.g., a
touchscreen) or a force sensor may also be classified as an input
device. However, for purposes of this illustrative example, the
touch sensor 3020 and the force sensor 3022 are depicted as
distinct components within the device 3000.
[0249] The device 3000 may also include a touch sensor 3020 (e.g.,
the touch sensor 2602, FIG. 26) that is configured to determine a
location of a touch over a touch-sensitive surface of the device
3000. The touch sensor 3020 may include a capacitive array of
electrodes or nodes that operate in accordance with a
mutual-capacitance or self-capacitance scheme. As described herein,
the touch sensor 3020 may be integrated with one or more layers of
a display stack or a force sensing device to provide the
touch-sensing functionality of a touchscreen. The capacitive arrays
of the touch sensor 3020 may be integrated with the force sensing
devices described above, and may be in addition to the capacitive
sensing elements that provide force sensing functionality.
[0250] The device 3000 may also include a force sensor 3022 that is
configured to receive and/or detect force inputs applied to a user
input surface of the device 3000. The force sensor 3022 may
correspond to any of the force sensing devices or force sensors
described herein, and may include or be coupled to capacitive
sensing elements that facilitate the detection of changes in
relative positions of the components of the force sensor (e.g.,
deflections caused by a force input).
[0251] As described herein, the force sensor 3022 may include
contact sensors that are configured to signal when an air gap has
been fully collapsed by a force input. The force sensor 3022,
including the contact sensors, may be operatively coupled to the
processing unit 3002, which can process signals from the force
sensor 3022 to determine an amount of applied force on the user
input surface, as described above.
[0252] The device 3000 may also include one or more sensors 3024
that may be used to detect an environmental condition, orientation,
position, or some other aspect of the device 3000. Example sensors
3024 that may be included in the device 3000 include, without
limitation, one or more accelerometers, gyrometers, inclinometers,
goniometers, or magnetometers. The sensors 3024 may also include
one or more proximity sensors, such as a magnetic hall-effect
sensor, inductive sensor, capacitive sensor, continuity sensor, and
the like.
[0253] The sensors 3024 may also be broadly defined to include
wireless positioning devices including, without limitation, global
positioning system (GPS) circuitry, Wi-Fi circuitry, cellular
communication circuitry, and the like. The device 3000 may also
include one or more optical sensors including, without limitation,
photodetectors, photosensors, image sensors, infrared sensors, and
the like. While the camera 3026 is depicted as a separate element
in FIG. 30, a broad definition of sensors 3024 may also include the
camera 3026 with or without an accompanying light source or flash.
The sensors 3024 may also include one or more acoustic elements,
such as a microphone used alone or in combination with a speaker
element. The sensors may also include a temperature sensor,
barometer, pressure sensor, altimeter, moisture sensor, or other
similar environmental sensor.
[0254] The device 3000 may also include a camera 3026 that is
configured to capture a digital image or other optical data. The
camera 3026 may include a charge-coupled device, complementary
metal oxide semiconductor (CMOS) device, or other device configured
to convert light into electrical signals. The camera 3026 may also
include one or more light sources, such as a strobe, flash, or
other light-emitting device. As discussed above, the camera 3026
may be generally categorized as a sensor for detecting optical
conditions and/or objects in the proximity of the device 3000.
However, the camera 3026 may also be used to create photorealistic
images that may be stored in an electronic format, such as JPG,
GIF, TIFF, PNG, raw image file, or other similar file types.
[0255] The device 3000 may also include a communication port 3028
that is configured to transmit and/or receive signals or electrical
communication from an external or separate device. The
communication port 3028 may be configured to couple to an external
device via a cable, adaptor, or other type of electrical connector.
In some embodiments, the communication port 3028 may be used to
couple the device 3000 to an accessory, such as a smart case, smart
cover, smart stand, keyboard, or other device configured to send
and/or receive electrical signals.
[0256] The device 3000 may determine an amount of force applied to
a user input surface using any appropriate techniques or
algorithms. For example, the device 3000 may use data, readings, or
other information from force sensing devices, and then apply
mathematical formulas or consult models or lookup tables to
determine an amount of applied force based on the information from
the force sensing devices. More particularly, one example technique
for determining an amount of force applied to a structure that
includes a force sensing device includes consulting a lookup table
or other data structure that correlates a sensor value (e.g., a
detected capacitance value) to a particular known force. The lookup
table may be populated by a calibration process whereby a known
force is applied to various locations on the user input surface.
For each location, the resulting sensor values, which may be
referred to as calibration values, for each pixel or sensing region
of the sensor are stored in the lookup table (or other data
structure). Accordingly, for each user input location there exists
in the lookup table a set of calibration values representing the
sensor values of all pixels or sensing regions of the sensor when
the sensor is subjected to a known force. In some cases, multiple
sets of calibration values exist for each location, such as values
associated with forces of different known magnitudes.
[0257] In order to determine an amount of force applied to the user
input surface during normal operation, a location of a touch event
on the input surface is determined (e.g., with the touch sensor
3020), and calibration values for that location are used in
conjunction with the detected sensor values to determine the actual
applied force. As one example, if the detected sensor values
corresponding to a touch event at a given location are
approximately three times the calibration values associated with a
touch event at that location, the device 3000 may determine that
the applied force is approximately three times larger than the
calibration force.
[0258] Another technique for determining an amount of applied force
includes determining an amount of force applied to each pixel or
sensing region of a sensor, and then adding the force from each
pixel or sensing region to determine the total amount of force
applied to that sensor. Where this technique is used, the change in
distance between two sensing elements may be used in conjunction
with a known stiffness of a material between the two sensing
elements to determine the force applied to that pixel or region. As
one specific example, a deformable element (e.g., the deformable
element 514, FIG. 5) may be positioned between capacitive sensing
elements. The capacitive sensing elements may correspond to the
second and third sensing elements 512, 515 in FIG. 5, which may be
capacitive sense and drive layers, respectively. The capacitive
sensing elements may also correspond to the first electrode layer
2622 and the conductive material 2614 in FIG. 26. By measuring a
capacitance value between the capacitive sensing elements, the
device 3000 can determine a distance (or a change in distance)
between the sensing elements resulting from a force applied to the
deformable element. The change in distance can be multiplied by a
stiffness of the deformable element (e.g., a constant correlating
an expected deflection or deformation of the material to a given
force) to determine the amount of force corresponding to the
detected change in distance. As noted above, the second and third
sensing elements 512, 515 may define a number of different pixels
or sensing regions (e.g., regions 702, FIG. 7). Accordingly, the
foregoing technique can be used to determine the force applied to
each individual pixel or sensing region, and those forces can be
combined (e.g., added) to determine the total amount of force
applied to the user input surface and/or to the sensor.
[0259] In some cases, the stiffness (e.g., a stiffness constant) of
the deformable element may be determined for each sensing region.
Thus, the distance measurement for each region may be multiplied by
a stiffness constant specific to that region, which may improve the
accuracy of the force measurements for each pixel or region, and
thus may improve the overall accuracy of the force sensor. The
stiffness constant for each pixel or sensing region may be
determined manually, for example, by applying a known force to each
area of the deformable element corresponding to a pixel or sensing
region, and measuring the amount or distance that the deformable
element has deflected. In some cases, multiple measurements can be
taken at different forces to determine an average stiffness
constant or a stiffness profile for the deformable material. This
may increase the accuracy of a sensor as compared to using the same
stiffness constant for each sensing region, as the stiffness may
vary from region to region.
[0260] Either of the foregoing techniques (e.g., consulting a
lookup table or calculating the force based on a stiffness
constant) may be used to determine the force applied to a given
sensor or sensing device described herein. In embodiments where a
device includes multiple sensors, a different technique may be used
for each sensor. For example, for the force sensing device 500,
which includes first and second capacitive sensors 518, 519 (FIG.
5), a lookup table may be used to determine the force applied to
the first capacitive sensor 518, and a stiffness-based force
calculation may be used to determine the force applied to the
second capacitive sensor 519. As another example, the device of
FIGS. 23A-23B includes a sensor 2302 positioned between a housing
and a cover, as well as a sensor within the housing (e.g.,
including the first and second sensing elements 2304, 2306 with a
deformable element 314 therebetween). In this case, a lookup table
may be used to determine the force applied to the sensor 2303, and
a stiffness-based calculation may be used to determine the force
applied to the sensor within the housing (e.g., the first and
second sensing elements 2304, 2306). Alternatively, a lookup table
technique may be used for both sensors.
[0261] Where two or more sensors are used, the force values that
are determined for each sensor may be combined to produce a single
value that represents the force applied to the user input surface.
For example, with reference to the force sensing device 500 (FIG.
5), the first and second capacitive sensors 518, 519 may deflect in
response to different applied forces. More particularly, the air
gaps 506 and 510 (between the first and second sensing elements
505, 512) may collapse in response to an applied force having a
particular value. Because the air gaps 506, 510 are between the
first and second sensing elements 505, 512, the first capacitive
sensor 518 defined by these sensing elements can be used to
determine the force up to the particular value. Because the
distance between the first and second sensing elements 505, 512
cannot be further reduced, however, the first capacitive sensor 518
will not detect values of applied forces in excess of the
particular value. The second capacitive sensor 519, however, may
detect force after the collapse of the air gaps 506, 510.
Accordingly, where both the first and second capacitive sensors
518, 519 produce force values, the values may be added together to
determine the overall force applied to the force sensing device
500. The same or a similar process may be used in conjunction with
the force sensors described with respect to FIG. 26, in which the
conductive material 2614 and the first electrode layer 2622 form a
first force sensor, and the first electrode layer 2622 and the
second electrode layer 2630 form a second force sensor.
[0262] FIG. 31 depicts an example process 3100 for determining an
amount of force applied on a user input surface of an electronic
device. The process 3100 may be implemented on any of the example
devices discussed herein. The process 3100 may be used, for
example, to determine what actions (if any) the electronic device
should perform in response to the force input, and may be
implemented using, for example, the processing unit and other
hardware elements described with respect to FIG. 30. The process
3100 may be implemented as processor-executable instructions that
are stored within the memory of the electronic device.
[0263] In operation 3102, it is determined whether a sensor signal
corresponds to a deformation of a first spacing layer (e.g., an air
gap, as described above) or of a second spacing layer (e.g., a
deformable element, as described above), or a combination of both.
For example, the device may monitor a rate of change of a sensor
signal. If the rate of change of the sensor signal satisfies a
first condition (e.g., it is constant over a particular deformation
range or it is below a threshold value), the device may determine
that an air gap is being or has been collapsed. If the rate of
change of the sensor signal satisfies a second condition (e.g., it
is increasing over a particular deformation range or it is above
the threshold value), the device may determine that an air gap has
been fully collapsed and a deformable element has been or is about
to be at least partially compressed. As another example, the device
may determine whether a sensor signal corresponds to a collapse of
a first spacing layer or a second spacing layer based on whether or
not a contact sensor (e.g., the contact sensors described with
respect to FIGS. 16 and 18A-22B) indicates that the first spacing
layer has fully collapsed.
[0264] In operation 3104, a force-deflection correlation is
selected. As described herein, a different force-deflection
correlation may be used to determine an amount of applied force,
depending on whether the deflection of the force sensor corresponds
to a collapse of a first spacing layer (e.g., an air gap) or
deformation of a second spacing layer (e.g., a deformable element).
Thus, if the device determines at operation 3102 that the sensor
signal corresponds to a deformation of the first spacing layer,
such as the collapse of an air gap, the device may at operation
3104 select a first force-deflection correlation. If the device
determines at operation 3102 that the sensor signal corresponds to
a deformation of the second spacing layer, such as compression of a
deformable element, the device may at operation 3104 select a
second force-deflection correlation that is different than the
first.
[0265] In embodiments where the device includes multiple sensors
spanning different spacing layers (such as the first and second
capacitive sensors 518, 519, FIG. 5), the device may select and use
multiple force-deflection correlations. For example, if the device
determines at operation 3102 that the deflection corresponds to an
at least partial collapse of both a first and a second spacing
layer, the device may select an appropriate force-deflection
correlation for each sensor.
[0266] In operation 3106, an amount of applied force is determined
based on the selected force-deflection correlation(s). For example,
the device correlates the amount of deflection indicated by the
sensor signal to a particular applied force by using a lookup
table, a stiffness-based force calculation, or another technique
that implements the selected force-deflection correlation. In
embodiments where the device includes multiple sensors, the device
may correlate the amount of deflection indicated by each sensor
with a force value, and then add the force values from each sensor
to determine the total amount of applied force.
[0267] Based on the determined amount of applied force, the device
may perform (or not perform) certain actions. For example, if the
applied force is lower than a threshold value, the device may
perform one action, and if the applied force is higher than the
threshold value, the device may perform another action. As one
example, if the force is lower than the threshold value, the device
may move a cursor to a position corresponding to the location of
the touch event, whereas if the force is higher than the threshold
value, the device may register a selection (e.g., a mouse click) at
the location of the cursor. This is merely one example, however,
and the range of possible actions that the device can perform based
on the determined amount of applied force are limited only by the
capabilities of the device.
[0268] As noted above, force sensors may use sheets or layers with
conductive borders. For example, as described with respect to FIGS.
7, 10A, and 26-29, conductive sheets may be used as drive layers
for capacitive force sensing systems. Conductive borders may be
applied to or otherwise included in the conductive sheets. FIG. 32
shows a flowchart of a method of manufacturing the conductive
borders on a surface of a sheet, such as a polarizer as described
with respect to FIGS. 26-29 or a force sensing element 505
described with respect to FIGS. 5, 7, and 10A. FIG. 32 will be
described in conjunction with FIGS. 33-37. The method is described
in conjunction with a roll-to-roll production process. Although
described in conjunction with a polarizer, the process can be used
to produce a conductive border on any suitable film or substrate.
Additionally, the method is described in conjunction with forming
continuous conductive borders (e.g., see FIGS. 7, 29), although
embodiments are not limited to this type of conductive border.
[0269] In other embodiments, a conductive border can be fabricated
on a polarizer or substrate using other manufacturing processes.
Example manufacturing processes include, but are not limited to,
physical or chemical vapor deposition, screen printing or inkjet
coating technology using a shadow mask, and film mask and
photolithography.
[0270] Initially, as shown in block 3200, masks are applied to a
surface of a film. In one embodiment, the film is a polarizer film
that includes a sheet of conductive material formed or coated over
a surface of the polarizer film. As describe earlier, the polarizer
film will be attached (e.g., laminated) to the back surface of a
display element and function as a polarizer for the display (e.g.,
display element 2608 and back polarizer 2610 in FIG. 26).
[0271] Each mask defines the area that will be surrounded by, or
inside of, the conductive border. For example, the masks can define
the user-viewable region (e.g., the user-viewable region 108) of a
display. Although depicted as having a rectangular shape, a mask
can have any given shape and/or dimensions.
[0272] In some embodiments, each mask can be one of multiple masks.
For example, when forming multiple conductive strips (e.g., see
FIG. 27) on a film substrate, a mask defines the area that will not
include the conductive strips.
[0273] FIGS. 33A-33B depict the application of masks to a surface
of a film. As shown in FIG. 33A, the application process 3300
includes moving the film 3302 from a first roller 3304 towards a
second roller 3306 in a roll-to-roll production system. This
movement is represented in FIGS. 33A and 33B by arrow 3308. In one
embodiment, the second roller 3306 includes the finished product of
the method shown in FIG. 32 (e.g., a collection of conductive
borders formed on the surface of the polarizer film). In another
embodiment, the second roller 3306 includes a collection of masks
formed on the surface of the film (e.g., the finished product of
block 3200).
[0274] A third roller 3310 is positioned between the first and the
second rollers 3304, 3306. The third roller 3310 includes a
collection of masks 3312 that are applied to the film 3302 as the
film 3302 moves below the third roller 3310. FIG. 33B illustrates a
top view of the film 3302 after the masks 3312 have been applied to
the film 3302 by the third roller 3310.
[0275] Referring now to block 3202 in FIG. 32, a conductive
material is formed over the masks and the surface of the film. The
conductive material is the material used to form the conductive
borders. FIGS. 34A-34B show the formation of the conductive
material over the film and the masks. The formation process 3400
includes moving the film 3302 from a fourth roller 3402 towards a
fifth roller 3404 (movement represented by arrow 3406). In one
embodiment, the fourth roller 3402 corresponds to the first roller
3304 and the fifth roller 3404 corresponds to the second roller
3306. In such embodiments, the fifth roller 3404 includes a
collection of conductive borders formed on the surface of the
polarizer film (e.g., the finished product of the method shown in
FIG. 32). In other embodiments, the fourth roller 3402 includes the
finished product of block 3200.
[0276] In the illustrated embodiment, the film 3302 with the masks
3312 enters a deposition chamber 3408 where a nozzle 3410 deposits
the conductive material 3412 onto the film 3302 and the masks 3312.
The deposition can be a blanket deposition such that the entire
film 3302 and masks 3312 have conductive material deposited
thereon. FIG. 34B illustrates a top view of the film 3302 after the
conductive material 3412 has been deposited onto the film 3302 and
the masks 3312 by the deposition chamber 3408.
[0277] Referring now to block 3204 in FIG. 32, the masks are
removed from the surface of the film after the conductive material
has been formed over the masks and the film. FIGS. 35A-35B show the
removal of the masks 3312 from the film 3302. The removal process
3500 includes moving the film 3302 from a sixth roller 3502 towards
a seventh roller 3504 (movement represented by arrow 3506). In one
embodiment, the sixth roller 3502 corresponds to the first roller
3304 and the seventh roller 3504 corresponds to the second roller
3306. In such embodiments, the seventh roller 3504 includes the
finished product of the method shown in FIG. 32. In other
embodiments, the sixth roller 3502 includes the finished product of
block 3202.
[0278] An eighth roller 3508 is positioned between the sixth and
seventh rollers 3502, 3504. The eighth roller 3508 removes the
masks 3312, which leaves regions 3514 that include only the film
3302. The conductive material is disposed on the areas around the
regions 3514. FIG. 35B illustrates a top view of the film 3302
after the masks 3312 have been removed by the eighth roller
3508.
[0279] Any suitable process can be used to remove the masks 3312.
For example, in one embodiment, the eighth roller 3508 employs an
electrostatic technique to remove the masks 3312.
[0280] In some embodiments, an imaging system (e.g., a camera) can
be positioned over the film 3302 between the eighth roller 3508 and
the seventh roller 3504. The imaging or automated optical
inspection system may be used to inspect the film for defects after
the masks have been removed by the eighth roller 3508.
[0281] Referring now to block 3206 in FIG. 32, a protective layer
is formed over the surface of the film and the conductive material.
FIGS. 36A-36B show the formation of the protective layer over the
film and the conductive material. The formation process 3600
includes moving the film 3302 from a ninth roller 3602 towards a
tenth roller 3604 (movement represented by arrow 3606). In one
embodiment, the ninth roller 3602 corresponds to the first roller
3304 and the tenth roller 3604 corresponds to the second roller
3304. In such embodiments, the tenth roller 3604 includes the
finished product of the method shown in FIG. 32. In other
embodiments, the ninth roller 3602 includes the finished product of
block 3204.
[0282] An eleventh roller 3608 is positioned between the ninth and
tenth rollers 3602, 3604. The eleventh roller 3608 applies the
protective layer 3610 over the film 3302 and the conductive
material 3412. FIG. 36B illustrates a top view of the film 3302
after the protective layer 3610 has been applied by the eleventh
roller 3608.
[0283] Referring now to block 3208 in FIG. 32, the conductive
borders are cut (e.g., singulated) to produce individual sections
of film that are each surrounded by a conductive border. FIGS.
37A-37B show the production of each individual section of film that
is surrounded by a conductive border. The cutting process 3700
includes moving the film 3302 from a twelfth roller 3702 towards a
thirteenth roller 3704 (movement represented by arrow 3706). In one
embodiment, the twelfth roller 3702 corresponds to the first roller
3304 and the thirteenth roller 3704 corresponds to the second
roller 3306. In such embodiments, the thirteenth roller 3704
includes the finished product of the method shown in FIG. 32. In
other embodiments, the twelfth roller 3702 includes the finished
product of block 3206.
[0284] In the illustrated embodiment, a singulation system 3708 is
positioned over the film 3302 between the twelfth roller 3702 and
the thirteenth roller 3704. The singulation system 3708 includes a
precision die cut tool 3710 that is aligned by one or more
alignment cameras 3712.
[0285] In one embodiment, the precision die cut tool 3710 uses one
or more corners of the regions 3514 (FIG. 35) as a cut reference
3714 to position the die cut pattern 3716. FIG. 37B illustrates top
view of the film 3302 with the cut references 3714 and die cut
pattern 3716 before the die cut tool 3710 cuts the individual
sections. Two singulated sections 3718 are also depicted in FIG.
37B. Each singulated section 3718 includes a section of film 3720
surrounded by a conductive border 3722. As described earlier, the
section of film 3720 includes a sheet of conductive material formed
over a polarizer film (e.g., the sheet of conductive material 2614
coated over the back polarizer 2610 in FIG. 26).
[0286] Referring to block 3210 in FIG. 32, each singulated section
may then be attached to a display layer. In particular, each
singulated section can be laminated to a back surface of a back
polarizer in the display layer.
[0287] The geometry of the mask (e.g., mask 3312 in FIG. 33B)
and/or the geometry of the die cut pattern (e.g., die cut pattern
3716 in FIG. 37B) can be varied to adjust the geometry of the
conductive border. FIGS. 38-40 show example techniques for
determining the geometry of the conductive border. In FIG. 38, the
die cut pattern 3800 is a rectangular shape that is situated to
center the mask 3802 in the center of the die cut pattern 3800.
After the singulation process is performed, the film 3806 includes
a continuous rectangular conductive border 3804 that extends along
the edges of the film 3806.
[0288] As shown in FIG. 39, the die cut pattern 3900 is offset from
the mask 3902 such that one edge of the mask 3902 is outside the
die cut pattern 3900. After the singulation process is performed,
the film 3906 includes a U-shaped conductive border 3904. In the
illustrated embodiment, the top edge of the mask 3902 is located
outside the die cut pattern 3900 to produce a U-shaped conductive
border 3904 that extends along the two side edges and the bottom
edge of the film 3906. However, other embodiments are not limited
to this presentation. The shape and orientation of the conductive
border 3804 determines which edge (or edges) of the mask 3902 are
located outside of the die cut pattern 3900.
[0289] FIG. 40 illustrates a die cut pattern 4000 that situates
three of the four edges of the mask 4002 outside of the die cut
pattern 4000. After the singulation process is performed, the film
4006 includes a linear conductive border 4004 that extends along
one edge of the film 4006. In the illustrated embodiment, only a
portion of the bottom edge of the mask 4002 is positioned within
the die cut pattern 4000 to produce a linear conductive border 4004
that extends along the bottom edge of the film 4006. However, other
embodiments are not limited to this configuration. The shape and
orientation of the conductive border determines which edge (or
edges) of the mask 4002 are located outside of the die cut pattern
4000.
[0290] The foregoing description, for purposes of explanation, uses
specific nomenclature to provide a thorough understanding of the
described embodiments. However, it will be apparent to one skilled
in the art that the specific details are not required in order to
practice the described embodiments. Thus, the foregoing
descriptions of the specific embodiments described herein are
presented for purposes of illustration and description. They are
not targeted to be exhaustive or to limit the embodiments to the
precise forms disclosed. It will be apparent to one of ordinary
skill in the art that many modifications and variations are
possible in view of the above teachings. Also, when used herein to
refer to positions of components, the terms above and below, or
their synonyms, do not necessarily refer to an absolute position
relative to an external reference, but instead refer to the
relative position of components with reference to the figures.
* * * * *