U.S. patent application number 16/042872 was filed with the patent office on 2019-01-03 for pseudo driven shield.
The applicant listed for this patent is ATMEL CORPORATION. Invention is credited to Samuel Brunet, Richard Paul Collins, Luben Hristov Hristov, Steinar Myren, Trond Jarle Pedersen, Paul Stavely.
Application Number | 20190004629 16/042872 |
Document ID | / |
Family ID | 52017583 |
Filed Date | 2019-01-03 |
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United States Patent
Application |
20190004629 |
Kind Code |
A1 |
Brunet; Samuel ; et
al. |
January 3, 2019 |
Pseudo Driven Shield
Abstract
In an embodiment, a touch-sensitive device includes a
controller, a shield sensor, a plurality of first electrodes, and a
plurality of second electrodes. The plurality of first electrodes
spans a first direction and the plurality of second electrodes
spans a second direction that is different than the first
direction. The controller electrically couples the plurality of
first electrodes to the shield sensor. The shield sensor charges
the plurality of first electrodes to cause substantially equal
voltages to be present on the plurality of first electrodes and the
plurality of second electrodes.
Inventors: |
Brunet; Samuel; (Cowes,
GB) ; Collins; Richard Paul; (Southampton, GB)
; Hristov; Luben Hristov; (Sofia, BG) ; Myren;
Steinar; (Vikhammer, NO) ; Pedersen; Trond Jarle;
(Trondheim, NO) ; Stavely; Paul; (Southampton,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ATMEL CORPORATION |
Chandler |
AZ |
US |
|
|
Family ID: |
52017583 |
Appl. No.: |
16/042872 |
Filed: |
July 23, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15477866 |
Apr 3, 2017 |
10031632 |
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16042872 |
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13930754 |
Jun 28, 2013 |
9612677 |
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15477866 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 3/0446 20190501;
G06F 3/044 20130101; G06F 2203/04108 20130101; G06F 3/0416
20130101; G06F 3/0418 20130101; G06F 3/0445 20190501; G06F
2203/04104 20130101; G06F 2203/04107 20130101; G06F 3/0443
20190501; G06F 3/04164 20190501 |
International
Class: |
G06F 3/044 20060101
G06F003/044; G06F 3/041 20060101 G06F003/041 |
Claims
1.-20. (canceled)
21. A touch-sensitive device comprising: a controller; a shield
sensor; a plurality of first electrodes spanning a first direction;
and a plurality of second electrodes spanning a second direction
that is different than the first direction; wherein: the controller
is operable to electrically couple the plurality of first
electrodes to the shield sensor; and the shield sensor is operable
to charge the plurality of first electrodes to cause substantially
equal voltages to be present on the plurality of first electrodes
and the plurality of second electrodes.
22. The device of claim 21, wherein each of the plurality of first
electrodes is coupled to a single line that is coupled to the
shield sensor.
23. The device of claim 21, wherein: the plurality of first
electrodes and the plurality of second electrodes form a
symmetrical pattern such that an exposed area of the plurality of
first electrodes and an exposed area of the plurality of second
electrodes are equal; and the exposed area of each of the first and
second electrodes has a diamond pattern.
24. The device of claim 21, the controller further operable to
measure capacitances of the plurality of second electrodes while
substantially equal voltages are present on the plurality of first
electrodes and the plurality of second electrodes.
25. The device of claim 21, the controller further operable to
control a plurality of switches to electrically couple the
plurality of first electrodes or the plurality of second electrodes
to the shield sensor.
26. The device of claim 21, wherein the shield sensor comprises a
sampling capacitor that has a value that produces identical
voltages on the plurality of first electrodes coupled to the shield
sensor as voltages on the plurality of second electrodes not
coupled to the shield sensor.
27. The device of claim 21, wherein the shield sensor comprises a
shield current source sensor, and the plurality of first and second
electrodes are charged with limited currents that are tuned to
produce identical charging.
28. A controller operable to: electrically couple a plurality of
first electrodes to a shield sensor; and charge the plurality of
first electrodes to cause substantially equal voltages to be
present on the plurality of first electrodes and a plurality of
second electrodes; wherein: the plurality of first electrodes span
a first direction; and the plurality of second electrodes span a
second direction that is different than the first direction.
29. The controller of claim 28, wherein each of the plurality of
first electrodes is coupled to a single line that is coupled to the
shield sensor.
30. The controller of claim 28, wherein: the plurality of first
electrodes and the plurality of second electrodes form a
symmetrical pattern such that an exposed area of the plurality of
first electrodes and an exposed area of the plurality of second
electrodes are equal; and the exposed area of each of the first and
second electrodes has a diamond pattern.
31. The controller of claim 28, the controller further operable to
measure capacitances of the plurality of second electrodes while
substantially equal voltages are present on the plurality of first
electrodes and the plurality of second electrodes.
32. The controller of claim 28, the controller further operable to
control a plurality of switches to electrically couple the
plurality of first electrodes or the plurality of second electrodes
to the shield sensor.
33. The controller of claim 28, wherein the shield sensor comprises
a sampling capacitor that has a value that produces identical
voltages on the plurality of first electrodes coupled to the shield
sensor as voltages on the plurality of second electrodes not
coupled to the shield sensor.
34. The controller of claim 28, wherein the shield sensor comprises
a shield current source sensor, and the plurality of first and
second electrodes are charged with limited currents that are tuned
to produce identical charging.
35. A method comprising: electrically coupling a plurality of first
electrodes to a shield sensor; and charging the plurality of first
electrodes to cause substantially equal voltages to be present on
the plurality of first electrodes and a plurality of second
electrodes; wherein: the plurality of first electrodes span a first
direction; and the plurality of second electrodes span a second
direction that is different than the first direction.
36. The method of claim 35, wherein each of the plurality of first
electrodes is coupled to a single line that is coupled to the
shield sensor.
37. The method of claim 35, wherein: the plurality of first
electrodes and the plurality of second electrodes form a
symmetrical pattern such that an exposed area of the plurality of
first electrodes and an exposed area of the plurality of second
electrodes are equal; and the exposed area of each of the first and
second electrodes has a diamond pattern.
38. The method of claim 35, the method further comprising measuring
capacitances of the plurality of second electrodes while
substantially equal voltages are present on the plurality of first
electrodes and the plurality of second electrodes.
39. The method of claim 35, the method further comprising
controlling a plurality of switches to electrically couple the
plurality of first electrodes or the plurality of second electrodes
to the shield sensor.
40. The method of claim 35, wherein the shield sensor comprises a
sampling capacitor that has a value that produces identical
voltages on the plurality of first electrodes coupled to the shield
sensor as voltages on the plurality of second electrodes not
coupled to the shield sensor.
Description
TECHNICAL FIELD
[0001] This disclosure generally relates to touch sensors.
BACKGROUND
[0002] A touch sensor detects the presence and location of a touch
or the proximity of an object (such as a user's finger) within a
touch-sensitive area of the touch sensor overlaid, for example, on
a display screen. In a touch-sensitive-display application, the
touch sensor enables a user to interact directly with what is
displayed on the screen, rather than indirectly with a mouse or
touchpad. A touch sensor may be attached to or provided as part of
a desktop computer, laptop computer, tablet computer, personal
digital assistant (PDA), smartphone, satellite navigation device,
portable media player, portable game console, kiosk computer,
point-of-sale device, or other suitable device. A control panel on
a household or other appliance may include a touch sensor.
[0003] There are different types of touch sensors, such as (for
example) resistive touch screens, surface acoustic wave touch
screens, capacitive touch screens, infrared touch screens, and
optical touch screens. Herein, reference to a touch sensor
encompasses a touch screen, and vice versa, where appropriate. A
capacitive touch screen may include an insulator coated with a
substantially transparent conductor in a particular pattern. When
an object touches or comes within proximity of the surface of the
capacitive touch screen, a change in capacitance occurs within the
touch screen at the location of the touch or proximity. A
controller processes the change in capacitance to determine the
touch position(s) on the touch screen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 illustrates an example touch sensor, according to
certain embodiments;
[0005] FIG. 2 illustrates an example device that utilizes the touch
sensor of FIG. 1, according to certain embodiments;
[0006] FIG. 3 illustrates an example embodiment of the touch sensor
of FIG. 1, according to certain embodiments;
[0007] FIG. 4 illustrates another example embodiment of the touch
sensor of FIG. 1, according to certain embodiments;
[0008] FIGS. 5A-5D illustrate pseudo driven shield switch
architectures of the touch sensor of FIG. 1, according to certain
embodiments;
[0009] FIG. 6 illustrates example voltages present on the
electrodes of FIGS. 5A, 5B, and 5D, according to certain
embodiments;
[0010] FIGS. 7-9 illustrate effects of water or moisture on touch
sensors, according to certain embodiments; and
[0011] FIG. 10 illustrates an example method that is used in
certain embodiments to perform proximity and hovering detection
using the pseudo driven shields of FIGS. 5A-5D, according to
certain embodiments.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0012] Proximity detection for capacitive touch screens involves
the ability to detect the presence of an external object in the
near vicinity to the screen surface without determining the exact
spatial position of the object. For example, the typical detection
range may vary from 40 mm to 200 mm and more. Hovering detection,
however, involves determining the spatial position of the object
relative to the surface before the object touches the surface. A
typical range for hovering detection may be between 10 mm and 30
mm.
[0013] Information from proximity and hovering detection may be
used by a touch-sensitive device such as a smart phone or tablet
computer in many different ways. For example, proximity event
information may be utilized to wake up the device, for changing the
behavior of the system, for illuminating the screen, for showing
alerts, and the like. As another example, hovering event
information may be utilized to determine where a person's finger is
located related to the surface of the screen. Proximity and
hovering detection, however, typically involves separate
measurement processes and/or cycles by a touch sensor.
[0014] The teachings of the disclosure recognize that it would be
desirable to combine proximity and hovering detection by a touch
sensor. Certain embodiments of the disclosure utilize a pseudo
driven shield to cause a substantially equal voltage to be present
on non-measured electrodes of a touch sensor as the voltage that is
present on electrodes of the touch sensor that are being measured.
As a result, the touch sensor is able to simultaneously detect
proximity and hovering of objects relative to the surface of the
screen of the touch sensor. FIGS. 1 through 10 below illustrate a
touch sensor of a touch-sensitive device that utilizes a pseudo
driven shield to simultaneously perform proximity and hovering
detection.
[0015] FIG. 1 illustrates an example touch sensor 10 with an
example controller 12. Herein, reference to a touch sensor may
encompass a touch screen, and vice versa, where appropriate. Touch
sensor 10 and controller 12 detect the presence and location of a
touch or the proximity of an object within a touch-sensitive area
of touch sensor 10. Herein, reference to a touch sensor encompasses
both the touch sensor and its controller, where appropriate.
Similarly, reference to a controller encompasses both the
controller and its touch sensor, where appropriate. Touch sensor 10
includes one or more touch-sensitive areas, where appropriate.
Touch sensor 10 includes an array of touch electrodes (i.e., drive
and/or sense electrodes) disposed on a substrate, which in some
embodiments is a dielectric material.
[0016] In certain embodiments, one or more portions of the
substrate of touch sensor 10 are made of polyethylene terephthalate
(PET) or another suitable material. This disclosure contemplates
any suitable substrate with any suitable portions made of any
suitable material. In particular embodiments, the drive or sense
electrodes in touch sensor 10 are made of indium tin oxide (ITO) in
whole or in part. In particular embodiments, the drive or sense
electrodes in touch sensor 10 are made of fine lines of metal or
other conductive material. As an example and not by way of
limitation, one or more portions of the conductive material are
copper or copper-based and have a thickness of approximately 5
.mu.m or less and a width of approximately 10 .mu.m or less. As
another example, one or more portions of the conductive material
are silver or silver-based and similarly have a thickness of
approximately 5 .mu.m or less and a width of approximately 10 .mu.m
or less. This disclosure contemplates any suitable electrodes made
of any suitable material.
[0017] In certain embodiments, touch sensor 10 implements a
capacitive form of touch sensing. In a mutual-capacitance
implementation, touch sensor 10 includes an array of drive and
sense electrodes forming an array of capacitive nodes. In certain
embodiments, a drive electrode and a sense electrode form a
capacitive node. The drive and sense electrodes forming the
capacitive node come near each other, but do not make electrical
contact with each other. Instead, the drive and sense electrodes
are capacitively coupled to each other across a gap between them. A
pulsed or alternating voltage applied to the drive electrode (i.e.,
by controller 12) induces a charge on the sense electrode, and the
amount of charge induced is susceptible to external influence (such
as a touch or the proximity of an object). When an object touches
or comes within proximity of the capacitive node, a change in
capacitance occurs at the capacitive node and controller 12
measures the change in capacitance. By measuring changes in
capacitance throughout the array, controller 12 determines the
position of the touch or proximity within the touch-sensitive
area(s) of touch sensor 10.
[0018] In particular embodiments, one or more drive electrodes
together form a drive line running horizontally or vertically or in
any suitable orientation. Similarly, one or more sense electrodes
together form a sense line running horizontally or vertically or in
any suitable orientation. In particular embodiments, drive lines
run substantially perpendicular to sense lines. Herein, reference
to a drive line encompasses one or more drive electrodes making up
the drive line, and vice versa, where appropriate. Similarly,
reference to a sense line encompasses one or more sense electrodes
making up the sense line, and vice versa, where appropriate.
[0019] In certain embodiments, touch sensor 10 has a single-layer
mutual capacitance configuration, with drive and sense electrodes
disposed in a pattern on one side ofa substrate. In such a
configuration, a pair of drive and sense electrodes capacitively
coupled to each other across a space between them forms a
capacitive node. In a configuration for a self-capacitance
implementation, as illustrated in FIG. 4, electrodes of only a
single type (e.g. sense) are disposed in a pattern on the
substrate. Although this disclosure describes particular
configurations of particular electrodes forming particular nodes,
this disclosure contemplates any suitable configuration of any
suitable electrodes forming any suitable nodes. Moreover, this
disclosure contemplates any suitable electrodes disposed on any
suitable number of any suitable substrates in any suitable
patterns.
[0020] As described above, a change in capacitance at a capacitive
node of touch sensor 10 may indicate a touch or proximity input at
the position of the capacitive node. Controller 12 is operable to
detect and process the change in capacitance to determine the
presence and location of the touch or proximity input. Certain
embodiments if controller 12 communicate information about the
touch or proximity input to one or more other components (such one
or more central processing units (CPUs) or digital signal
processors (DSPs)) of a device that includes touch sensor 10 and
controller 12, which may respond to the touch or proximity input by
initiating a function of the device (or an application running on
the device) associated with it. Although this disclosure describes
a particular controller having particular functionality with
respect to a particular device and a particular touch sensor, this
disclosure contemplates any suitable controller having any suitable
functionality with respect to any suitable device and any suitable
touch sensor.
[0021] In certain embodiments, controller 12 is one or more
integrated circuits (ICs)--such as for example general-purpose
microprocessors, microcontrollers, programmable logic devices or
arrays, and application-specific ICs (ASICs). In some embodiments,
controller 12 is coupled to a flexible printed circuit (FPC) bonded
to the substrate of touch sensor 10, as described below. In some
mutual capacitance embodiments, controller 12 includes a processor
unit, a drive unit, a sense unit, and a storage unit. The drive
unit supplies drive signals to the drive electrodes of touch sensor
10. The sense unit senses charge at the capacitive nodes of touch
sensor 10 and provides measurement signals to the processor unit
representing capacitances at the capacitive nodes. The processor
unit controls the supply of drive signals to the drive electrodes
by the drive unit and process measurement signals from the sense
unit to detect and process the presence and location of a touch or
proximity input within the touch-sensitive area(s) of touch sensor
10. The processor unit also tracks changes in the position of a
touch or proximity input within the touch-sensitive area(s) of
touch sensor 10. The storage unit, which includes one or more
memory devices, stores programming for execution by the processor
unit, including programming for controlling the drive unit to
supply drive signals to the drive electrodes, programming for
processing measurement signals from the sense unit, and other
suitable programming, where appropriate. In self capacitance
embodiments, controller 12 is operable to both drive and measure
electrodes that are each individually a sense and drive electrode.
Although this disclosure describes a particular controller having a
particular implementation with particular components, this
disclosure contemplates any suitable controller having any suitable
implementation with any suitable components.
[0022] Tracks 14 of conductive material disposed on the substrate
of touch sensor 10 couple the drive or sense electrodes of touch
sensor 10 to connection pads 16, also disposed on the substrate of
touch sensor 10. As described below, connection pads 16 facilitate
coupling of tracks 14 to controller 12. In certain embodiments,
tracks 14 extend into or around (e.g. at the edges of) the
touch-sensitive area(s) of touch sensor 10. Particular tracks 14
provide drive connections for coupling controller 12 to drive
electrodes of touch sensor 10, through which the drive unit of
controller 12 supplies drive signals to the drive electrodes. Other
tracks 14 provide sense connections for coupling controller 12 to
sense electrodes of touch sensor 10, through which the sense unit
of controller 12 senses charge at the capacitive nodes of touch
sensor 10. In certain embodiments, tracks 14 are made of fine lines
of metal or other conductive material. As an example and not by way
of limitation, the conductive material of tracks 14 is copper or
copper-based and have a width of approximately 100 .mu.m or less.
As another example, the conductive material of tracks 14 is silver
or silver-based and have a width of approximately 100 .mu.m or
less. In particular embodiments, tracks 14 are made of ITO in whole
or in part in addition or as an alternative to fine lines of metal
or other conductive material. Although this disclosure describes
particular tracks made of particular materials with particular
widths, this disclosure contemplates any suitable tracks made of
any suitable materials with any suitable widths. In addition to
tracks 14, certain embodiments of touch sensor 10 include one or
more ground lines terminating at a ground connector (similar to a
connection pad 16) at an edge of the substrate of touch sensor 10
(similar to tracks 14).
[0023] In certain embodiments, connection pads 16 are located along
one or more edges of the substrate, outside the touch-sensitive
area(s) of touch sensor 10. As described above, controller 12 is on
an FPC in certain embodiments. In some embodiments, connection pads
16 are made of the same material as tracks 14 and are bonded to the
FPC using an anisotropic conductive film (ACF). In certain
embodiments, connection 18 includes conductive lines on the FPC
coupling controller 12 to connection pads 16, in turn coupling
controller 12 to tracks 14 and to the drive or sense electrodes of
touch sensor 10. In another embodiment, connection pads 160 are
inserted into an electro-mechanical connector (such as a zero
insertion force wire-to-board connector); in this embodiment,
connection 180 does not need to include an FPC. This disclosure
contemplates any suitable connection 18 between controller 12 and
touch sensor 10.
[0024] FIG. 2 illustrates an example device 20 that utilizes touch
sensor 10 of FIG. 1. Device 20 includes any personal digital
assistant, cellular telephone, smartphone, tablet computer, and the
like. For example, a certain embodiment of device 20 is a
smartphone that includes a touchscreen display 22 (e.g., screen)
occupying a significant portion of the largest surface of the
device. In certain embodiments, the large size of touchscreen
display 22 enables the touchscreen display 22 to present a wide
variety of data, including a keyboard, a numeric keypad, program or
application icons, and various other interfaces as desired. In
certain embodiments, a user interacts with device 20 by touching
touchscreen display 22 with a stylus, a finger, or any other
appropriate object in order to interact with device 20 (i.e.,
select a program for execution or to type a letter on a keyboard
displayed on the touchscreen display 22). In certain embodiments, a
user interacts with device 20 using multiple touches to perform
various operations, such as to zoom in or zoom out when viewing a
document or image.
[0025] FIG. 3 illustrates a touch sensor 30 that may be utilized as
touch sensor 10 of FIG. 1. Touch sensor 30 includes x-axis
electrodes 32, y-axis electrodes 34, a substrate 35, and a panel
36. In some embodiments, x-axis electrodes 32 and y-axis electrodes
34 are electrodes in a self capacitance implementation (i.e., each
x-axis electrode 32 and y-axis electrode 34 is capable of being
driven and measured during the acquisition). In some embodiments,
x-axis electrodes 32 are drive electrodes and y-axis electrodes 34
are sense electrodes in a mutual capacitance implementation. In
some embodiments, x-axis electrodes 32 and y-axis electrodes 34
have a diamond pattern as illustrated in FIGURES SA-5D below.
[0026] In some embodiments, panel 36 is a transparent panel. In
other embodiments, panel 36 is not transparent. In some
embodiments, substrate 35 is sandwiched between x-axis electrodes
32 and y-axis electrodes 34, and y-axis electrodes 34 are coupled
to an underside of panel 36 with, for example, an adhesive. In
other embodiments, touch sensor 30 includes any appropriate
configuration and number of layers of electrodes and substrates.
For example, some embodiments of touch sensor 30 include additional
layers of sense electrodes 32 that run perpendicular (or any other
appropriate angle) to y-axis electrodes 34. In some embodiments,
x-axis electrodes 32 and y-axis electrodes 34 are on the same layer
in any appropriate pattern (e.g., a design in which x-axis
electrodes 32 and y-axis electrodes 34 have interdigitated
teeth).
[0027] In certain mutual capacitance embodiments, touch sensor 30
determines the location of touch object 38 at least in part by
using controller 12 to apply a pulsed a or alternating voltage to
x-axis electrodes 32, which induces a charge on y-axis electrodes
34. In certain self capacitance embodiments, touch sensor 30
determines the location of touch object 38 at least in part by
using controller 12 to apply a pulsed or alternating voltage to
x-axis electrodes 32 and y-axis electrodes 34. When touch object 38
touches or comes within proximity of an active area of touch sensor
30, a change in capacitance may occur, as depicted by electric
field lines 39 in FIG. 3. In mutual capacitance embodiments, the
change in capacitance is sensed by the sense (i.e., receiving)
electrodes and measured by controller 12. In self capacitance
embodiments, the change in capacitance is sensed by x-axis
electrodes 32 and y-axis electrodes 34 and measured by controller
12. By measuring changes in capacitance throughout an array of
x-axis electrodes 32 and y-axis electrodes 34, controller 12
determines the position of the touch or proximity within the
touch-sensitive area(s) of touch sensor 30.
[0028] FIG. 4 illustrates a self-capacitance embodiment of touch
sensor 10. In a self-capacitance implementation, touch sensor 10
may include an array of electrodes of a single type that may each
form a capacitive node. When an object touches or comes within
proximity of the capacitive node, a change in self-capacitance may
occur at the capacitive node and controller 12 may measure the
change in capacitance, for example, as a change in the amount of
charge needed to raise the voltage at the capacitive node by a
pre-determined amount. As with a mutual-capacitance implementation,
by measuring changes in capacitance throughout the array,
controller 12 may determine the position of the touch or proximity
within the touch-sensitive area(s) of touch sensor 10. This
disclosure contemplates any suitable form of capacitive touch
sensing, where appropriate.
[0029] FIGS. 5A-5D illustrate pseudo driven shield switch
architectures 50 of touch sensor 10 of FIG. 1 for various self
capacitance measuring techniques. FIGS. 5A and 5D illustrate switch
architectures 50A and 50D that utilize current source sensors. FIG.
5B illustrates a switch architecture 50B that utilize capacitive
sensors. FIG. 5C illustrates a switch architecture 50C that
utilizes QTouch.RTM. sensors. While specific sensors are
illustrated in FIGS. 5A-5D, other embodiments may utilize any
appropriate sensor.
[0030] Switch architectures 50A-50D of FIGS. 5A-5D include
horizontal electrodes 52, vertical electrodes 54, sensors 56 (i.e.,
56A-56D), switches 58 (i.e., 58A-58D), and one or more shield
sensors 59. Switches 58 may be any appropriate switch and operate
to electrically couple horizontal electrodes 52 and vertical
electrodes 54 to sensors 56 and shield sensor 59. For example,
switches 58A are operable to electrically couple some or all of
horizontal electrodes 52 to sensors 56A, switches 58B are operable
to electrically couple some or all of vertical electrodes 54 to
sensors 56B, switches 58C are operable to electrically couple
horizontal electrodes 52 to shield sensor 59, and switches 58D are
operable to electrically couple vertical electrodes 54 to shield
sensor 59.
[0031] Horizontal electrodes 52 and vertical electrodes 54 are any
appropriate electrodes in any appropriate configuration. In some
embodiments, horizontal electrodes 52 and vertical electrodes 54
are the x-axis 32 and y-axis 34 electrodes described above. In
certain embodiments, horizontal electrodes 52 and vertical
electrodes 54 form a symmetrical pattern (i.e., the exposed area of
horizontal electrodes 52 and vertical electrodes 54 are
substantially equal). In some embodiments, the pattern of
horizontal electrodes 52 and vertical electrodes 54 is a diamond
pattern (as illustrated) or any appropriate clone of a diamond
pattern. In certain embodiments, horizontal electrodes 52 may not
be exactly horizontal and vertical electrodes 54 may not be exactly
vertical. Rather, horizontal electrodes 52 may be any appropriate
angle to horizontal and vertical electrodes 54 may be any
appropriate angle to vertical. This disclosure is not limited to
the configuration and pattern of the illustrated horizontal
electrodes 52 and vertical electrodes 54. Instead, this disclosure
anticipates any appropriate pattern, configuration, design, or
arrangement of electrodes.
[0032] Sensors 56 and shield sensor 59 are any appropriate sensors
to sense and/or measure capacitances from horizontal electrodes 52
and vertical electrodes 54. For example, sensors 56 and shield
sensor 59 may be current source sensors in some embodiments, as
illustrated in FIGS. 5A and 5D. In such embodiments, current
sources are used to inject a fixed amount of charge into the
measured capacitance by sourcing or sinking a constant current for
a fixed amount of time (Q=I*t). The change in the capacitance will
result in change in the voltage at the end of the charge injection.
As another example, sensors 56 and shield sensor 59 may be
capacitive sensors in some embodiments, as illustrated in FIG. 5B.
In some embodiments, sensors 56 and shield sensor 59 are
communicatively coupled to or incorporated within controller
12.
[0033] In some embodiments, sensors 56 and shield sensor 59 may be
channels of any appropriate microcontroller such as the QTouch.RTM.
microcontroller, as illustrated in FIG. 5C, and may utilize any
appropriate charge transfer technology. Such embodiments may
include sample capacitors 57, as illustrated in FIG. 5C. For
example, each sensor 56A and 56B may include an associated sample
capacitor 57 (i.e., Cs) as illustrated, and shield sensor 59 may
include an associated shield sample capacitor 57 (i.e., Csh), as
illustrated. In some embodiments, the shield sample capacitor 57 of
shield sensor 59 may be a capacitor in the range of approximately 5
nF to 100 nF. Sample capacitors 57 are adjusted in such a way to
produce identical or nearly identical voltages to horizontal
electrodes 52 and vertical electrodes 54 during charge
transfers.
[0034] Switches 58 may be any appropriate switch that may be
selectively opened or closed in order to connect or disconnect two
electrical nodes. In some embodiments, switches 58 are analog
switches. In other embodiments, switches 58 are any other
appropriate switch. In certain embodiments, switches 58 may be
controlled by controller 12.
[0035] In operation, certain embodiments combine hovering detection
and proximity detection by utilizing switches 58, sensors 56, and
shield sensor 59 to cause substantially equal voltages (e.g.,
voltages as illustrated in FIG. 6) to be present on non-measured
electrodes 52 or 54 while capacitance measurements are performed on
other electrodes 52 or 54. Ideally, hovering and proximity
detection should be done by measuring self capacitance
simultaneously on all rows and columns of a screen. However,
parallel measurements of a whole screen for hovering detection
requires individual capacitive sensing modules on each of the
electrodes or each of the clusters of electrodes (where the
proximity detection requires a single sensing module connected to
all screen electrodes). For large touch screens, the number of the
individual sensing modules required for hovering detection may
become too numerous, so hovering detection is typically done by
sequentially scanning part of screen (e.g., first all rows and then
all columns).
[0036] Partial measurements of a screen, however, may create
problems. For example, partial measurements may create an unwanted
interaction between measured electrodes and non-measured
electrodes. This interaction may affect the distribution of
electrical field lines around the screen surface. One
solution--holding the non-measured electrodes to a fixed voltage
(e.g., GND or Vdd)--has negative effects on the measurements. For
example, holding the non-measured electrodes to a fixed voltage
reduces the hovering range and increase stray capacitance to GND on
the boundary electrodes (i.e., measured electrodes immediately next
to non-measured electrodes). As another example, if some of the
electrodes are connected to a fixed voltage, the dielectric has the
ability to concentrate the field lines. The result is that more of
the field lines are trapped inside the dielectric and few lines can
escape the dielectric in order to interact with the objects in
close vicinity to the surface. In short, the combination of
increased capacitive loading plus the change in the electrical
field lines trajectory causes decreased ability to detect far away
objects.
[0037] To remove the interaction between measured electrodes and
non-measured electrodes, embodiments of the disclosure attempt to
cause identical or substantially identical voltages on both
measured and non-measured electrodes (i.e., make non-measured
electrodes equipotential to measured electrodes) while capacitance
measurements are being performed. In typical solutions, fast, high
current output OpAmps may be used to drive all non-measured
electrodes to the same voltage as the measured electrodes. Such
solutions, however, increase the power consumption of the chip and
require large silicon areas. Instead of using OpAmps for driving
the non-measured electrodes, embodiments of the disclosure
illustrated in FIGS. 5A-5D create a pseudo driven shield by
connecting all non-measured electrodes to one or more shield
sensors 59. In some embodiments, all non-measured electrodes are
connected to a single line that is coupled to a single shield
sensor 59. In other embodiments, all non-measured electrodes are
connected to two or more shield sensor 59 using multiple lines. The
pseudo driven shield architecture allows voltages on all
non-measured electrodes to be equal or substantially equal to
voltages of the measured electrodes.
[0038] In FIGS. 5A and 5D, a current source method is utilized to
cause identical or substantially identical voltages (e.g., as
illustrated in FIG. 6) on both measured and non-measured electrodes
52 and 54 while capacitance measurements are performed. In this
embodiment, shield sensor 59 charges the shield (i.e., the
non-measured electrodes 52 or 54) with current sources that are
tuned to produce an identical charging curve as measured electrodes
52 or 54. In addition, the sensitivity of the pseudo driven shield
is N times higher (when measuring charge) compared to the
sensitivity of a single electrode, where N is the number of the
electrodes connected to the shield (the sensitivity in the current
sources method depends on the integrator gain multiplied by the
ratio Cx/Cint and Cx in N times bigger). As a result, the voltage
on the shield is equal to the voltages of all other measured
electrodes 52 or 54.
[0039] In FIG. 5B, a current mirror method is utilized to cause
identical or substantially identical voltages on both measured and
non-measured electrodes 52 and 54 while capacitance measurements
are performed. In this embodiment, shield sensor 59 charges the
shield and the measured electrodes 52 or 54 with limited currents
that are tuned to produce an identical charging curve as measured
electrodes 52 or 54. For example, current mirrors are used to
charge both a measured capacitor and an internal sampling capacitor
as described in U.S. patent application Ser. No. 13/445,748, which
is incorporated herein by reference. As a result, the voltage on
the shield is equal to the voltages of all other measured
electrodes 52 or 54. Without current limiters, the voltage on the
shield may deviate from the voltages on the measured electrodes and
hence an uncontrolled amount of charge will be transferred between
the shield and the measured electrodes. While FIG. 5B illustrates a
current mirror method being utilized, any other appropriate method
for causing identical or substantially identical voltages on both
measured and non-measured electrodes 52 and 54 while capacitance
measurements are performed may be utilized.
[0040] In FIG. 5C, a QTouch.RTM. method is utilized to cause
identical or substantially identical voltages on both measured and
non-measured electrodes 52 and 54 while capacitance measurements
are performed. In some embodiments, QTouch.RTM. uses bursts to
perform the capacitance measurements. For example, the number of
pulses in the burst before the input flips is the measured signal
itself. As illustrated in the embodiment of FIG. 5C, the shield is
connected to a shield sample capacitor 57 that has a value that
produces identical voltages on non-measured electrodes 52 or 54 and
the measured electrodes 52 or 54 during charge transfers. As a
result, the voltage on the shield is equal to the voltages of all
other measured electrodes 52 or 54.
[0041] While FIGS. 5A-5D illustrate particular measuring
techniques, other embodiments may utilize any other measuring
technique in which shield voltages of the shield are equal or
substantially equal to the voltages on the measured electrodes 52
or 54. This disclosure anticipates using any appropriate measuring
technique with the pseudo driven shield.
[0042] In some embodiments, screen measurements using the pseudo
driven shield as illustrated in FIGS. 5A-5D are done in two passes.
For example, in the first pass, all horizontal electrodes 52 are
connected to the individual sensors 56 and all vertical electrodes
54 are connected to shield sensor 59. The measurements of all
horizontal electrodes 52 and the shield are then performed
simultaneously. In some embodiments, if the silicon is not able to
support measurements on all horizontal electrodes 52, the unused
horizontal electrodes 52 may also be connected to shield sensor 59.
In the second pass, all vertical electrodes 54 are connected to the
individual sensors 56 and all horizontal electrodes 52 are
connected to shield sensor 59. The measurements of all vertical
electrodes 54 and the shield are then performed simultaneously. In
some embodiments, if the silicon is not able to support
measurements on all vertical electrodes 54, the unused vertical
electrodes 54 may also be connected to the shield.
[0043] When measurements using the pseudo driven shield are done in
two passes as described above, the signals measured from the shield
(i.e., from shield sensor 59) have some specific features. First,
it is detecting the object presence evenly across the area covered
by the shield because all horizontal electrodes 52 or vertical
electrodes 54 are connected together. This creates a virtual
electrode with the dimensions of the screen (and half of the screen
area). Second, it can detect the object presence from a long
distance because the parallel measurements of the shield and the
horizontal electrodes 52 or vertical electrodes 54 project the
electrical field lines far away from the screen surface. This
allows the proximity detection signal to be obtained without having
to do an additional measuring cycle. This makes the signal from the
shield ideal for proximity detection.
[0044] In certain embodiments, only a portion of horizontal
electrodes 52 or vertical electrodes 54 may be measured in a
measurement cycle. For example, FIG. 5D illustrates an example
embodiment in which there are not enough sensors 56 to connect to
each of the electrodes. In this case, the measurements may be split
into two or more measurements. For example, the vertical electrodes
54 may first be split into two or more groups: GROUP 1 and GROUP 2.
Similarly, horizontal electrodes 52 may be split into GROUP 3 and
GROUP 4. Next, GROUP 1 measurements are taken by connecting GROUP 1
electrodes to sensors 56 and connecting all other electrodes to the
shield (i.e., to shield sensor 59). Next, GROUP 2 measurements are
taken by connecting GROUP 2 electrodes to sensors 56 and connecting
all other electrodes to the shield. Next, GROUP 3 measurements are
taken by connecting GROUP 3 electrodes to sensors 56 and connecting
all other electrodes to the shield. Finally, GROUP 4 measurements
are taken by connecting GROUP 4 electrodes to sensors 56 and
connecting all other electrodes to the shield.
[0045] FIG. 6 illustrates example voltages that may be present on
the electrodes of FIGS. 5A, 5B, and 5D. In general, embodiments of
the disclosure strive to keep voltages on measured lines (i.e.,
electrodes; top graph) and the voltage on the shield (bottom graph)
identical or substantially identical. In the illustrated
embodiment, the voltages increase linearly, which are specific to
current source methods. In addition, the voltages include bumps
where the voltages go from increasing linearly to
horizontal--another feature specific to current source methods. It
should be noted that FIG. 6 is not directly applicable to
QTouch.RTM. embodiments (e.g., FIG. 5C) in which the voltage rises
on steps during the burst and is not increasing linearly.
[0046] FIGS. 7-9 illustrate effects of water or moisture on touch
sensors and how embodiments of the pseudo driven shield may
mitigate such effects. One benefit of using embodiments of the
pseudo driven shield is an increased immunity of the screen against
moisture and water film. Moisture or water film on the surface of a
touch screen creates a conductive film which works as distributed
RC array as illustrated in FIG. 7. The presence of the conductive
film on the surface can create false touches or false hover
detections if a grounded object is in contact with this film, as
illustrated in FIG. 8. Through the water film the presence of the
object is affecting the measuring electrode via Cx1 and the water
film distributed R and C (capacitive coupling between measuring
electrode and the water film on top of this electrode). As
illustrated in FIG. 8, some current Iwf will flow through Cx1.
[0047] When using a shield electrode as illustrated in FIG. 9, a
large portion of the water film effect is cancelled through the
capacitance Csh (the capacitive coupling between the shield
electrode and the water film). The shield has a shunting effect and
prevents the propagation of the capacitance changes introduced by
the grounded object through the water film. As illustrated in FIG.
9, the same current Iwf from FIG. 8 is flowing but through
capacitance Csh to the shield electrode. Although the currents
continue to flow (Iwf) and may be the same strength, they are
changed from where they flow. Until the active electrode and the
shield are substantially equipotential, substantially no currents
can flow between them. The result is that no currents are flowing
through Cx1 but rather the current Iwf is flowing through Csh.
[0048] FIG. 10 illustrates an example method 1000 that is used in
certain embodiments to perform proximity and hovering detection
using the pseudo driven shields of FIGS. 5A-5). Method 1000 begins
in step 1010 where a first, second, third, and fourth plurality of
switches of a touch sensor are selectively controlled. In some
embodiments, the touch sensor is touch sensor 10 described above.
In some embodiments, the switches of step 1010 are controlled by
controller 12. In some embodiments, the first plurality of switches
may refer to all or a portion of switches 58A, the second plurality
of switches may refer to all or a portion of switches 58B, the
third plurality of switches may refer to all or a portion of
switches 58C, and the fourth plurality of switches may refer to all
or a portion of switches 58D. In other embodiments, the first,
second, third, and fourth plurality of switches may refer to any
other appropriate group of switches. In some embodiments, the
switches of step 1010 may be analog switches.
[0049] In some embodiments, the first plurality of switches of step
1010 are operable to electrically couple a plurality of first
electrodes of the touch sensor to a plurality of sensors, the
second plurality of switches are operable to electrically couple a
plurality of second electrodes of the touch sensor to the plurality
of sensors, the third plurality of switches are operable to
electrically couple the plurality of first electrodes to a shield
sensor, and the fourth plurality of switches are operable to
electrically couple the plurality of second electrodes to the
shield sensor. In some embodiments, the plurality of sensors may
refer to sensors 56 described above (e.g., all or a portion of
sensors 56A or sensors 56B). In some embodiments, the first
electrodes may refer to all or a portion of horizontal electrodes
52 and the second electrodes may refer to all or a portion of
vertical electrodes 54, or vice versa. In some embodiments, the
first electrodes are horizontal (i.e., x-axis) electrodes and the
second electrodes are vertical (i.e., y-axis) electrodes, or vice
versa. In certain embodiments, the first and second electrodes have
exposed areas in a diamond pattern or any clone of a diamond
pattern.
[0050] In some embodiments, the shield sensor of step 1010 may
refer to one or more shield sensors 59 above. In certain
embodiments, the shield sensor is a shield current source sensor,
and electrodes coupled to the shield current source sensor are
charged with current sources that are tuned to produce a similar
charging curve as electrodes of the touch sensor that are not
coupled to the shield current source sensor. In some embodiments,
the shield sensor is a shield current source sensor, and the
plurality of first and second electrodes are charged with limited
currents that are tuned to produce identical charging. In some
embodiments, the shield sensor is QTouch.RTM. channel with a
sampling capacitor that has a value that produces identical
voltages on electrodes coupled to the shield sensor as voltages on
electrodes of the touch sensor not coupled to the shield
sensor.
[0051] In some embodiments, controlling the first, second, third,
and fourth plurality of switches of step 1010 includes closing at
least a portion of the first plurality of switches to couple each
of at least a portion of the plurality of first electrodes to a
particular one of the plurality of sensors, opening the second
plurality of switches to decouple (i.e., disconnect) the plurality
of second electrodes from the plurality of sensors, opening the
third plurality of switches to decouple the plurality of first
electrodes from the shield sensor, and closing the fourth plurality
of switches to couple all electrodes of the plurality of second
electrodes to the shield sensor. In some embodiments, controlling
the first, second, third, and fourth plurality of switches of step
1010 includes opening the first plurality of switches to decoiuple
the plurality of first electrodes from the plurality of sensors,
closing at least a portion of the second plurality of switches to
couple each of at least a portion of the plurality of second
electrodes to a particular one of the plurality of sensors, closing
the third plurality of switches to couple all electrodes of the
plurality of first electrodes to the shield sensor, and opening the
fourth plurality of switches to decouple the second electrodes from
the shield sensor. In general, controlling the first, second,
third, and fourth plurality of switches of step 1010 includes
coupling each of the electrodes that are to be measured to one of
the plurality of sensors and coupling the remaining electrodes
(i.e., the non-measured electrodes) to the shield (e.g., one or
more shield sensors 59).
[0052] In step 1020, substantially equal voltages are caused to be
present on the plurality of first and second electrodes of step
1010. In general, a variable amount of charge is injected into each
electrode in such a way to cause equal or substantially equal
voltages on all electrodes (when there is no touch/hovering object
on the surface). In some embodiments, current sources are used and
the currents are adjusted to produce an identical or substantially
identically charging profile for each electrode. In embodiments
where integration is used, the electrodes are charged to the same
voltage and then the charge is integrated. In some embodiments, an
amount of charge is injected into each of the electrodes which
produces equal or substantially equal voltages on all electrodes.
If current sources are used, the charging currents are adjusted in
such a way to produce equal voltage profiles (but the amount of the
injected charge may be different for each electrode because each
electrode has a different capacitance). In some embodiments, the
charge Q is found by the equation: Q=CU (where C is the
capacitance, U is the voltage). In general, embodiments strive to
keep U constant across all electrodes. In some embodiments, unless
C is different for each electrode, Q is adjusted to keep U constant
across all electrodes.
[0053] In step 1030, capacitances of certain electrodes of step
1010 are measured with the plurality of sensors while the first and
second electrodes are at substantially equal voltages. In certain
embodiments, step 1030 includes performing simultaneous hovering
and proximity detection by causing substantially equal voltages to
be present on the first and second electrodes while measuring
capacitances of non-measured electrodes using the shield sensor and
measuring capacitances of measured electrodes using the plurality
of sensors. In some embodiments, the capacitances of step 1030 are
measured using one or more of sensors 56 and/or one or more shield
sensors 59. In some embodiments, measuring the capacitances of step
1030 includes measuring capacitances of one or more of the first
electrodes using the plurality of sensors, measuring a single
capacitance for all of the second electrodes using the shield
sensor, measuring capacitances of one or more of the second
electrodes using the plurality of sensors, or measuring a single
capacitance for all of the first electrodes using the shield
sensor.
[0054] Accordingly, example embodiments disclosed herein provide a
touch sensor that is capable of simultaneously performing hover and
proximity detection using a pseudo driven shield. As a result,
devices utilizing embodiments of the disclosed touch sensor may
have improved efficiency and power management and therefore may
consume less power. Accordingly, embodiments of the disclosure
provide numerous enhancements over typical touch sensors.
[0055] Although the preceding examples given here generally rely on
self capacitance or mutual capacitance to operate, other
embodiments of the invention will use other technologies, including
other capacitance measures, resistance, or other such sense
technologies.
[0056] Herein, reference to a computer-readable storage medium
encompasses one or more non-transitory, tangible computer-readable
storage media possessing structure. As an example and not by way of
limitation, a computer-readable storage medium may include a
semiconductor-based or other integrated circuit (IC) (such, as for
example, a field-programmable gate array (FPGA) or an
application-specific IC (ASIC)), a hard disk, an HDD, a hybrid hard
drive (HHD), an optical disc, an optical disc drive (ODD), a
magneto-optical disc, a magneto-optical drive, a floppy disk, a
floppy disk drive (FDD), magnetic tape, a holographic storage
medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL
card, a SECURE DIGITAL drive, or another suitable computer-readable
storage medium or a combination of two or more of these, where
appropriate. Herein, reference to a computer-readable storage
medium excludes any medium that is not eligible for patent
protection under 35 U.S.C. .sctn. 101. Herein, reference to a
computer-readable storage medium excludes transitory forms of
signal transmission (such as a propagating electrical or
electromagnetic signal per se) to the extent that they are not
eligible for patent protection under 35 U.S.C. .sctn. 101. A
computer-readable non-transitory storage medium may be volatile,
non-volatile, or a combination of volatile and non-volatile, where
appropriate.
[0057] Herein, "or" is inclusive and not exclusive, unless
expressly indicated otherwise or indicated otherwise by context.
Therefore, herein, "A or B" means "A, B, or both," unless expressly
indicated otherwise or indicated otherwise by context. Moreover,
"and" is both joint and several, unless expressly indicated
otherwise or indicated otherwise by context. Therefore, herein, "A
and B" means "A and B, jointly or severally," unless expressly
indicated otherwise or indicated otherwise by context.
[0058] This disclosure encompasses all changes, substitutions,
variations, alterations, and modifications to the example
embodiments herein that a person having ordinary skill in the art
would comprehend. For example, while the illustrated embodiments of
the pseudo driven shield depict connecting horizontal electrodes 52
and vertical electrodes 54 to a single shield sensor 59 to form the
shield, other embodiments may connect the shield to multiple shield
sensors 59. Moreover, reference in the appended claims to an
apparatus or system or a component of an apparatus or system being
adapted to, arranged to, capable of, configured to, enabled to,
operable to, or operative to perform a particular function
encompasses that apparatus, system, component, whether or not it or
that particular function is activated, turned on, or unlocked, as
long as that apparatus, system, or component is so adapted,
arranged, capable, configured, enabled, operable, or operative.
* * * * *