U.S. patent application number 13/271054 was filed with the patent office on 2012-04-19 for fabrication of touch, handwriting and fingerprint sensor.
This patent application is currently assigned to QUALCOMM MEMS TECHNOLOGIES, INC.. Invention is credited to Nicholas Ian Buchan, Srinivasan Kodaganallur Ganapathi, Kurt Edward Petersen.
Application Number | 20120090757 13/271054 |
Document ID | / |
Family ID | 45933061 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120090757 |
Kind Code |
A1 |
Buchan; Nicholas Ian ; et
al. |
April 19, 2012 |
FABRICATION OF TOUCH, HANDWRITING AND FINGERPRINT SENSOR
Abstract
Fabrication methods for combined sensor devices include
substantially transparent substrates and materials to increase the
optical performance of underlying displays. A substantially
transparent elastomeric material may be disposed between the
substantially transparent substrates. Some fabrication processes
utilize flexible substrates for at least a portion of the sensor
device, and lend themselves to roll-to-roll processing for low
cost.
Inventors: |
Buchan; Nicholas Ian; (San
Jose, CA) ; Ganapathi; Srinivasan Kodaganallur; (Palo
Alto, CA) ; Petersen; Kurt Edward; (Milpitas,
CA) |
Assignee: |
QUALCOMM MEMS TECHNOLOGIES,
INC.
San Diego
CA
|
Family ID: |
45933061 |
Appl. No.: |
13/271054 |
Filed: |
October 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61394054 |
Oct 18, 2010 |
|
|
|
Current U.S.
Class: |
156/60 |
Current CPC
Class: |
G06F 21/83 20130101;
G02B 26/0833 20130101; Y10T 29/49124 20150115; G06F 3/04144
20190501; G06F 3/044 20130101; G06F 3/0446 20190501; G06F
2203/04106 20130101; G06F 3/04146 20190501; G06F 2203/04103
20130101; G06F 3/03547 20130101; Y10T 156/10 20150115; G06F 3/045
20130101; G06K 9/0002 20130101; G06F 21/32 20130101; G06F 3/04166
20190501; G06F 3/0447 20190501 |
Class at
Publication: |
156/60 |
International
Class: |
H05K 3/00 20060101
H05K003/00; B32B 37/12 20060101 B32B037/12; B32B 37/02 20060101
B32B037/02 |
Claims
1. A method, comprising: depositing a first layer of substantially
transparent conductive material on a first substantially
transparent substrate, wherein depositing the first layer involves
forming a first plurality of substantially transparent electrodes
in a first region of the first substrate and forming a second
plurality of substantially transparent electrodes in a second
region of the first substrate; forming a layer of resistive
material on the first layer of substantially transparent conductive
material, wherein the forming includes forming a first plurality of
resistors on some, but not all, of the first plurality of
electrodes and forming a second plurality of resistors on the
second plurality of electrodes; depositing a second layer of
substantially transparent conductive material on a second
substantially transparent and flexible substrate, wherein
depositing the second layer involves forming a third plurality of
substantially transparent electrodes in a first region of the
second substrate and forming a fourth plurality of substantially
transparent electrodes in a second region of the second substrate
with a pitch that is substantially the same as that of the second
plurality of electrodes; forming a substantially transparent
elastomeric material in the first region of the first substrate;
and attaching the second substrate to the elastomeric material.
2. The method of claim 1, further including forming a
force-sensitive resistor material between the second plurality of
electrodes and the fourth plurality of electrodes.
3. The method of claim 1, wherein a first index of refraction of
the first substrate substantially matches a second index of
refraction of the elastomeric material.
4. The method of claim 1, wherein an index of refraction of the
elastomeric material substantially matches an index of refraction
of the second substrate.
5. The method of claim 1, wherein a modulus of elasticity of the
elastomeric material is substantially lower than a modulus of
elasticity of the first substrate.
6. The method of claim 1, further including forming the elastomeric
material on the first electrodes having the first plurality of
resistors deposited thereon.
7. The method of claim 1, further including forming the elastomeric
material on the first electrodes not having the first plurality of
resistors deposited thereon.
8. The method of claim 1, further including forming a
force-sensitive resistor material between the first plurality of
electrodes and the third plurality of electrodes.
9. The method of claim 1, further including attaching the first
substantially transparent substrate to a display device.
10. The method of claim 1, further including configuring a sensor
control system for communication with the first and third
pluralities of substantially transparent electrodes.
11. The method of claim 1, wherein at least the depositing involves
a roll-to-roll manufacturing process.
12. The method of claim 1, further including applying an adhesive
layer to the elastomeric material, but not to the resistive
material, prior to the attaching process.
13. The method of claim 6, wherein forming the elastomeric material
on the first electrodes having the first plurality of resistors
deposited thereon involves forming the elastomeric material on the
first electrodes not having the first plurality of resistors
deposited thereon, further including removing the elastomeric
material from the first electrodes having the first plurality of
resistors deposited thereon.
14. The method of claim 10, further including configuring the
sensor control system for communication with the second and fourth
pluralities of substantially transparent electrodes.
15. The method of claim 10, further including configuring the
sensor control system for communication with a processor of a
display device.
16. The method of claim 10, further including configuring the
sensor control system for processing handwriting and touch sensor
data according to electrical signals received from the first and
third pluralities of substantially transparent electrodes.
17. The method of claim 13, wherein the removing involves removing
the elastomeric material from less than 5% of the first region.
18. The method of claim 14, further including configuring the
sensor control system for processing fingerprint sensor data
according to electrical signals received from the second and fourth
pluralities of substantially transparent electrodes.
19. The method of claim 16, wherein configuring the sensor control
system for processing handwriting and touch sensor data involves
configuring the sensor control system for projected capacitive
touch sensing.
20. The method of claim 16, wherein configuring the sensor control
system for processing handwriting and touch sensor data involves
configuring the sensor control system for resistive handwriting
sensing.
21. The method of claim 16, wherein configuring the sensor control
system for processing handwriting and touch sensor data involves
configuring the sensor control system for capacitive handwriting
sensing.
22. A method, comprising: depositing a first layer of substantially
transparent conductive material on a first substantially
transparent substrate, wherein depositing the first layer involves
forming a first plurality of substantially transparent electrodes
in a first region of the first substrate and forming a second
plurality of substantially transparent electrodes in a second
region of the first substrate, the second plurality of electrodes
being spaced more closely than the first plurality of electrodes;
forming a layer of resistive material on the first layer of
substantially transparent conductive material, wherein the forming
includes forming a first plurality of resistors on some, but not
all, of the first plurality of electrodes and forming a second
plurality of resistors on the second plurality of electrodes;
depositing a second layer of substantially transparent conductive
material on a second substantially transparent and flexible
substrate, wherein depositing the second layer involves forming a
third plurality of substantially transparent electrodes in a first
region of the second substrate and forming a fourth plurality of
substantially transparent electrodes in a second region of the
second substrate with a pitch that is substantially the same as
that of the second plurality of electrodes; forming a substantially
transparent elastomeric material in the first region of the first
substrate; and attaching the second substrate to the elastomeric
material.
23. The method of claim 22, wherein an index of refraction of the
first substrate substantially matches an index of refraction of the
elastomeric material.
24. The method of claim 22, wherein a modulus of elasticity of the
elastomeric material is substantially lower than a modulus of
elasticity of the first substrate.
25. The method of claim 22, wherein forming the substantially
transparent elastomeric material involves substantially filling a
space between only a portion of the first plurality of electrodes
and the third plurality of electrodes with the elastomeric
material.
26. The method of claim 22, wherein forming the substantially
transparent elastomeric material involves substantially filling a
space between substantially all of the first plurality of
electrodes and the third plurality of electrodes with the
elastomeric material.
27. The method of claim 22, further including forming substantially
transparent and force-sensitive resistor material extending from
the second plurality of electrodes to the fourth plurality of
electrodes.
28. The method of claim 23, wherein the index of refraction of the
elastomeric material substantially matches an index of refraction
of the second substrate.
29. The method of claim 24, wherein the modulus of elasticity of
the elastomeric material is between about 0.5 and 50
megapascals.
30. The method of claim 24, wherein the modulus of elasticity of
the first substrate is between about 0.5 and 5.0 gigapascals.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/394,054, entitled "COMBINATION TOUCH,
HANDWRITING AND FINGERPRINT SENSOR" (Attorney Docket No.
QUALP045P/102908P1) and filed on Oct. 18, 2010, which is hereby
incorporated by reference and for all purposes. This application is
related to U.S. patent application Ser. No. ______, entitled
"COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR" (Attorney
Docket No. QUALP045A/102908U1) and filed on Oct. 11, 2011, to U.S.
patent application Ser. No. ______, entitled "TOUCH, HANDWRITING
AND FINGERPRINT SENSOR WITH ELASTOMERIC SPACER LAYER" (Attorney
Docket No. QUALP045C/102908U3) and filed on Oct. 11, 2011, to U.S.
patent application Ser. No. ______, entitled "TOUCH SENSOR WITH
FORCE-ACTUATED SWITCHED CAPACITOR" (Attorney Docket No.
QUALP045D/102908U4) and filed on Oct. 11, 2011, to U.S. patent
application Ser. No. ______, entitled "WRAPAROUND ASSEMBLY FOR
COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR" (Attorney
Docket No. QUALP045E/102908U5) and filed on Oct. 11, 2011, to U.S.
patent application Ser. No. ______, entitled "MULTIFUNCTIONAL INPUT
DEVICE FOR AUTHENTICATION AND SECURITY APPLICATIONS" (Attorney
Docket No. QUALP045F/102908U6) and filed on Oct. 11, 2011, to U.S.
patent application Ser. No. ______, entitled "CONTROLLER
ARCHITECTURE FOR COMBINATION TOUCH, HANDWRITING AND FINGERPRINT
SENSOR" (Attorney Docket No. QUALP045G/102908U7) and filed on Oct.
11, 2011, all of which are hereby incorporated by reference and for
all purposes.
TECHNICAL FIELD
[0002] This disclosure relates to display devices, including but
not limited to display devices that incorporate multifunctional
touch screens.
DESCRIPTION OF THE RELATED TECHNOLOGY
[0003] Electromechanical systems (EMS) include devices having
electrical and mechanical elements, actuators, transducers,
sensors, optical components (including mirrors) and electronics.
Electromechanical systems can be manufactured at a variety of
scales including, but not limited to, microscales and nanoscales.
For example, microelectromechanical systems (MEMS) devices can
include structures having sizes ranging from about a micron to
hundreds of microns or more. Nanoelectromechanical systems (NEMS)
devices can include structures having sizes smaller than a micron
including, for example, sizes smaller than several hundred
nanometers. Electromechanical elements may be created using
deposition, etching, lithography, and/or other micromachining
processes that etch away parts of substrates and/or deposited
material layers, or that add layers to form electrical and
electromechanical devices.
[0004] One type of EMS device is called an interferometric
modulator (IMOD). As used herein, the term interferometric
modulator or interferometric light modulator refers to a device
that selectively absorbs and/or reflects light using the principles
of optical interference. In some implementations, an
interferometric modulator may include a pair of conductive plates,
one or both of which may be transparent and/or reflective, wholly
or in part, and capable of relative motion upon application of an
appropriate electrical signal. In an implementation, one plate may
include a stationary layer deposited on a substrate and the other
plate may include a reflective membrane separated from the
stationary layer by an air gap. The position of one plate in
relation to another can change the optical interference of light
incident on the interferometric modulator. Interferometric
modulator devices have a wide range of applications, and are
anticipated to be used in improving existing products and creating
new products, especially those with display capabilities.
[0005] The increased use of touch screens in handheld devices
causes increased complexity and cost for modules that now include
the display, the touch panel and a cover glass. Each layer in the
device adds thickness and requires costly glass-to-glass bonding
solutions for attachment to the neighboring substrates. These
problems can be further exacerbated for reflective displays when a
frontlight also needs to be integrated, adding to the thickness and
cost of the module.
SUMMARY
[0006] The systems, methods and devices of the disclosure each have
several innovative aspects, no single one of which is solely
responsible for the desirable attributes disclosed herein. Some
implementations described herein provide a combined sensor device
that combines aspects of capacitive and resistive technologies for
touch sensing, handwriting input and fingerprint imaging. Some such
implementations provide a touch sensor that combines capacitive and
resistive technologies to enable a multi-feature user input sensor
overlaid on a display.
[0007] In some such implementations, a cover glass apparatus of a
consumer device such as a cell phone, an e-reader, or a tablet
computer serves additionally as part of a combined sensor device
having a single or multi-touch sensor, a handwriting or stylus
input device, and/or a fingerprint sensor. The cover glass
apparatus may include 2, 3 or more layers. The substrates used to
form a cover glass apparatus may be formed of various suitable
substantially transparent materials, such as actual glass, plastic,
polymer, etc. Such a cover glass apparatus with touch, handwriting
and/or fingerprint detection capability may, for example, be
overlaid on a display.
[0008] One innovative aspect of the subject matter described in
this disclosure can be implemented in a method that may involve
depositing a first layer of substantially transparent conductive
material on a first substantially transparent substrate. The
depositing process may involve forming a first plurality of
substantially transparent electrodes in a first region of the first
substrate and forming a second plurality of substantially
transparent electrodes in a second region of the first substrate.
The method may involve forming a layer of resistive material on the
first layer of substantially transparent conductive material. The
forming process may include forming a first plurality of resistors
on some, but not all, of the first plurality of electrodes and
forming a second plurality of resistors on the second plurality of
electrodes.
[0009] The method may involve depositing a second layer of
substantially transparent conductive material on a second
substantially transparent and flexible substrate. Depositing the
second layer may involve forming a third plurality of substantially
transparent electrodes in a first region of the second substrate
and forming a fourth plurality of substantially transparent
electrodes in a second region of the second substrate with a pitch
that is substantially the same as that of the second plurality of
electrodes. The method may involve forming a substantially
transparent elastomeric material in the first region of the first
substrate and attaching the second substrate to the elastomeric
material.
[0010] The method may involve forming a force-sensitive resistor
material between the second plurality of electrodes and the fourth
plurality of electrodes and/or between the first plurality of
electrodes and the third plurality of electrodes. An index of
refraction of the first substrate may substantially match an index
of refraction of the elastomeric material. An index of refraction
of the elastomeric material may substantially match an index of
refraction of the second substrate. The modulus of elasticity of
the elastomeric material may be substantially lower than a modulus
of elasticity of the second substrate.
[0011] The method may involve forming the elastomeric material on
the first electrodes having the first plurality of resistors
deposited thereon. Forming the elastomeric material on the first
electrodes having the first plurality of resistors deposited
thereon may involve forming the elastomeric material on the first
electrodes not having the first plurality of resistors deposited
thereon and then removing the elastomeric material from the first
electrodes having the first plurality of resistors deposited
thereon. The removing process may involve removing the elastomeric
material from less than 5% of the first region. However, in some
implementations, the method may involve forming the elastomeric
material on the first electrodes not having the first plurality of
resistors deposited thereon and not removing the elastomeric
material from the first electrodes having the first plurality of
resistors deposited thereon.
[0012] The method may involve applying an adhesive layer to the
elastomeric material, but not to the resistive material, prior to
the attaching process. The method may involve attaching the first
substantially transparent substrate to a display device. At least
some aspects of the method (such as the depositing) may involve a
roll-to-roll manufacturing process.
[0013] The method may involve configuring a sensor control system
for communication with the first and third pluralities of
substantially transparent electrodes and/or with the second and
fourth pluralities of substantially transparent electrodes. The
method may involve configuring the sensor control system for
processing fingerprint sensor data according to electrical signals
received from the second and fourth pluralities of substantially
transparent electrodes. The method may involve configuring the
sensor control system for communication with a processor of a
display device.
[0014] The method may involve configuring the sensor control system
for processing handwriting and touch sensor data according to
electrical signals received from the first and third pluralities of
substantially transparent electrodes. Configuring the sensor
control system for processing handwriting and touch sensor data may
involve configuring the sensor control system for projected
capacitive touch sensing. Configuring the sensor control system for
processing handwriting and touch sensor data may involve
configuring the sensor control system for resistive handwriting
sensing. Configuring the sensor control system for processing
handwriting and touch sensor data may involve configuring the
sensor control system for capacitive handwriting sensing.
[0015] Another innovative aspect of the subject matter described in
this disclosure can be implemented in an alternative method that
may involve depositing a first layer of substantially transparent
conductive material on a first substantially transparent substrate.
Depositing the first layer may involve forming a first plurality of
substantially transparent electrodes in a first region of the first
substrate and forming a second plurality of substantially
transparent electrodes in a second region of the first substrate.
In some implementations, the second plurality of electrodes may be
spaced more closely than the first plurality of electrodes.
[0016] The method may involve forming a layer of resistive material
on the first layer of substantially transparent conductive
material. The forming may include forming a first plurality of
resistors on some, but not all, of the first plurality of
electrodes and forming a second plurality of resistors on the
second plurality of electrodes.
[0017] The method may involve depositing a second layer of
substantially transparent conductive material on a second
substantially transparent and flexible substrate. Depositing the
second layer may involve forming a third plurality of substantially
transparent electrodes in a first region of the second substrate
and forming a fourth plurality of substantially transparent
electrodes in a second region of the second substrate with a pitch
that is substantially the same as that of the second plurality of
electrodes.
[0018] The method may involve forming a substantially transparent
elastomeric material in the first region of the first substrate and
attaching the second substrate to the elastomeric material. An
index of refraction of the first substrate and/or the second
substrate may substantially match an index of refraction of the
elastomeric material. The method may involve forming substantially
transparent and force-sensitive resistor material extending from
the second plurality of electrodes to the fourth plurality of
electrodes.
[0019] A modulus of elasticity of the elastomeric material may be
substantially lower than a modulus of elasticity of the second
substrate. For example, the modulus of elasticity of the
elastomeric material may be between about 0.5 and 50 megapascals
and the modulus of elasticity of the second substrate may be
between about 0.5 and 5.0 gigapascals.
[0020] Forming the substantially transparent elastomeric material
may involve substantially filling a space between only a portion of
the first plurality of electrodes and the third plurality of
electrodes with the elastomeric material. Forming the substantially
transparent elastomeric material may involve substantially filling
a space between substantially all of the first plurality of
electrodes and the third plurality of electrodes with the
elastomeric material.
[0021] Details of one or more implementations of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Although the examples provided
in this summary are primarily described in terms of MEMS-based
displays, the concepts provided herein may apply to other types of
displays, such as liquid crystal displays, organic light-emitting
diode ("OLED") displays and field emission displays. Other
features, aspects, and advantages will become apparent from the
description, the drawings, and the claims. Note that the relative
dimensions of the following figures may not be drawn to scale.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows an example of an isometric view depicting two
adjacent pixels in a series of pixels of an interferometric
modulator (IMOD) display device.
[0023] FIG. 2 shows an example of a system block diagram
illustrating an electronic device incorporating a 3.times.3
interferometric modulator display.
[0024] FIG. 3 shows an example of a diagram illustrating movable
reflective layer position versus applied voltage for the
interferometric modulator of FIG. 1.
[0025] FIG. 4 shows an example of a table illustrating various
states of an interferometric modulator when various common and
segment voltages are applied.
[0026] FIG. 5A shows an example of a diagram illustrating a frame
of display data in the 3.times.3 interferometric modulator display
of FIG. 2.
[0027] FIG. 5B shows an example of a timing diagram for common and
segment signals that may be used to write the frame of display data
illustrated in FIG. 5A.
[0028] FIG. 6A shows an example of a partial cross-section of the
interferometric modulator display of FIG. 1.
[0029] FIGS. 6B-6E show examples of cross-sections of varying
implementations of interferometric modulators.
[0030] FIG. 7 shows an example of a flow diagram illustrating a
manufacturing process for an interferometric modulator.
[0031] FIGS. 8A-8E show examples of cross-sectional schematic
illustrations of various stages in a method of making an
interferometric modulator.
[0032] FIG. 9A shows an example of sensor electrodes formed on a
cover glass.
[0033] FIG. 9B shows an alternative example of sensor electrodes
formed on a cover glass.
[0034] FIG. 10A shows an example of a cross-sectional view of a
combined sensor device.
[0035] FIGS. 10B-10D show examples of cross-sectional views of
alternative combined sensor devices.
[0036] FIGS. 11A-11D show examples of cross-sectional views of
combined sensor devices having high-modulus and low-modulus
compressible layers.
[0037] FIG. 12 shows an example of a device that includes a cover
glass with a combination touch, handwriting and fingerprint
sensor.
[0038] FIG. 13 shows an example of a top view of a force-sensitive
switch implementation.
[0039] FIG. 14 shows an example of a cross-section through a row of
the force-sensitive switch implementation shown in FIG. 13.
[0040] FIG. 15A shows an example of a circuit diagram that
represents components of the implementation shown in FIGS. 13 and
14.
[0041] FIG. 15B shows an example of a circuit diagram that
represents components of an alternative implementation related to
FIGS. 13 and 14.
[0042] FIG. 16 shows an example of a flow diagram illustrating a
manufacturing process for a combined sensor device.
[0043] FIGS. 17A-17D show examples of partially formed combined
sensor devices during various stages of the manufacturing process
of FIG. 16.
[0044] FIG. 18A shows an example of a block diagram that
illustrates a high-level architecture of a combined sensor
device.
[0045] FIG. 18B shows an example of a block diagram that
illustrates a control system for a combined sensor device.
[0046] FIG. 18C shows an example representation of physical
components and their electrical equivalents for a sensel in a
combined sensor device.
[0047] FIG. 18D shows an example of an alternative sensel of a
combined sensor device.
[0048] FIG. 18E shows an example of a schematic diagram
representing equivalent circuit components of a sensel in a
combined sensor device.
[0049] FIG. 18F shows an example of an operational amplifier
circuit for a combined sensor device that may be configured for
handwriting or stylus mode sensing.
[0050] FIG. 18G shows an example of the operational amplifier
circuit of FIG. 18F configured for touch mode sensing.
[0051] FIG. 18H shows an example of an operational amplifier
circuit for a combined sensor device that includes a clamp
circuit.
[0052] FIG. 18I shows examples of clamp circuit transfer
functions.
[0053] FIG. 18J shows an example of a circuit diagram for a clamp
circuit.
[0054] FIG. 19 shows an example of a cross-section of a portion of
an alternative combined sensor device.
[0055] FIG. 20 shows an example of a top view of routing for a
combined sensor device.
[0056] FIG. 21A shows an example of a cross-sectional view through
the combined sensor device shown in FIG. 20.
[0057] FIG. 21B shows an example of a cross-sectional view of a
wrap-around implementation.
[0058] FIG. 22 shows an example of a flow diagram illustrating a
fingerprint-based user authentication process.
[0059] FIG. 23A shows an example of a mobile device that may be
configured for making secure commercial transactions.
[0060] FIG. 23B shows an example of using a fingerprint-secured
mobile device for physical access applications.
[0061] FIG. 24A shows an example of a secure tablet device.
[0062] FIG. 24B shows an example of an alternative secure tablet
device.
[0063] FIGS. 25A and 25B show examples of system block diagrams
illustrating a display device that includes a combined sensor
device.
[0064] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0065] The following description is directed to certain
implementations for the purposes of describing the innovative
aspects of this disclosure. However, a person having ordinary skill
in the art will readily recognize that the teachings herein can be
applied in a multitude of different ways. The described
implementations may be implemented in any device or system that can
be configured to display an image, whether in motion (e.g., video)
or stationary (e.g., still image), and whether textual, graphical
or pictorial. More particularly, it is contemplated that the
described implementations may be included in or associated with a
variety of electronic devices such as, but not limited to: mobile
telephones, multimedia Internet enabled cellular telephones, mobile
television receivers, wireless devices, smartphones, Bluetooth.RTM.
devices, personal data assistants (PDAs), wireless electronic mail
receivers, hand-held or portable computers, netbooks, notebooks,
smartbooks, tablets, printers, copiers, scanners, facsimile
devices, GPS receivers/navigators, cameras, MP3 players,
camcorders, game consoles, wrist watches, clocks, calculators,
television monitors, flat panel displays, electronic reading
devices (i.e., e-readers), computer monitors, auto displays
(including odometer and speedometer displays, etc.), cockpit
controls and/or displays, camera view displays (such as the display
of a rear view camera in a vehicle), electronic photographs,
electronic billboards or signs, projectors, architectural
structures, microwaves, refrigerators, stereo systems, cassette
recorders or players, DVD players, CD players, VCRs, radios,
portable memory chips, washers, dryers, washer/dryers, parking
meters, packaging (such as in electromechanical systems,
microelectromechanical systems, and non-MEMS applications),
aesthetic structures (e.g., display of images on a piece of
jewelry) and a variety of EMS devices. The teachings herein also
can be used in non-display applications such as, but not limited
to, electronic switching devices, radio frequency filters, sensors,
accelerometers, gyroscopes, motion-sensing devices, magnetometers,
inertial components for consumer electronics, parts of consumer
electronics products, varactors, liquid crystal devices,
electrophoretic devices, drive schemes, manufacturing processes and
electronic test equipment. Thus, the teachings are not intended to
be limited to the implementations depicted solely in the Figures,
but instead have wide applicability as will be readily apparent to
one having ordinary skill in the art.
[0066] Some implementations described herein combine novel aspects
of capacitive and resistive technologies for touch sensing, stylus
detection for handwriting input, and fingerprint imaging. Some such
implementations provide a combined sensor device, at least part of
which is incorporated in a cover glass apparatus that may be
overlaid on or otherwise combined with a display. The cover glass
apparatus may have 2, 3 or more layers. In some implementations,
the cover glass apparatus includes a substantially transparent and
flexible upper substrate and a substantially transparent and
relatively more rigid lower substrate. In some such
implementations, the lower substrate of the cover glass apparatus
may be overlaid on a display substrate. In alternative
implementations, the lower substrate of the cover glass apparatus
may be a display substrate. For example, the lower substrate of the
cover glass apparatus may be the same transparent substrate on
which IMOD devices are fabricated, as described below.
[0067] Various implementations of such sensor devices are described
herein. In some implementations, the cover glass of a display
device serves as a single or multi-touch sensor, as a handwriting
(or note capture) input device, and as a fingerprint sensor. Sensor
functionality and resolution can be tailored to specific locations
on the cover glass. In some such implementations, the area in which
the fingerprint sensing elements are located may provide not only
fingerprint detection, but also handwriting and touch
functionality. In some other implementations, the fingerprint
sensor may be segregated in a separate, high-resolution zone that
only provides fingerprint functionality. In some implementations,
the sensor device serves as a combination touch and stylus input
device. Various methods of fabrication are described herein, as
well as methods for using a device that includes a combined sensor
device.
[0068] Particular implementations of the subject matter described
in this disclosure can be implemented to realize one or more of the
following potential advantages. Some implementations described
herein combine aspects of capacitive and resistive technologies for
touch sensing, handwriting input and in some cases fingerprint
imaging. Some such implementations provide a touch sensor that
combines capacitive and resistive technologies to enable a
multi-functional user input sensor that can be overlaid on a
display. Some implementations of the combined sensor device
eliminate a middle touch sensor layer that is disposed between the
cover glass and the display glass in some conventional projected
capacitive touch (PCT)-based devices. Accordingly, some such
implementations can mitigate or eliminate at least some drawbacks
of PCT and resistive technologies.
[0069] A hybrid PCT and digital resistive touch (DRT)
implementation allows, for example, detection of a narrow stylus
tip pressing onto the display with the DRT aspect while also
allowing the detection of very light brushing or close hovering
over the display with a finger using the PCT aspect. The sensor
device can accept any form of stylus or pen input, regardless of
whether it is conducting or non-conducting. Transparent or
effectively transparent force-sensitive resistors may be included
within some or all of the sensels to improve optical and electrical
performance.
[0070] According to some implementations, the combination sensor
may include two or more patterned layers, some of which may be on a
different substrate. The upper (or outer) substrate may, for
example, be formed of a plastic such as polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), polyimide, or a similar
material. The upper substrate also may be substantially transparent
and have a substantially transparent conductor such as
indium-tin-oxide (ITO) patterned on its underside. The lower
substrate may be formed of a substantially transparent substrate
material, such as glass, with another suitable material. The top
surface of the substantially transparent substrate can be a
patterned layer of substantially transparent conductor material
such as ITO. In some implementations, the conductors on the
underside of the upper substrate and the upper side of the lower
substrate may be patterned into diamond-shaped electrodes,
connected as rows or columns on each of the two different
layers
[0071] Some such implementations include a wrap-around
configuration wherein a flexible upper substrate of the sensor
device has patterned metallization on an extended portion to allow
routing of signal lines, electrical ground, and power. This
flexible upper substrate may be wrapped around an edge of a
relatively more rigid lower substrate of the cover glass apparatus.
One or more ICs or passive components including connecting sockets
may be mounted onto the flexible layer to reduce cost and
complexity. Signal lines that address sensor electrodes on the
lower substrate may be routed and connected to corresponding
patterns on the underside of the flexible upper substrate. Such
implementations have the potential advantage of eliminating the
need for a flex cable for electrically connecting signal lines of
the upper layer to integrated circuits and/or other devices. The
approach allows a bezel-less configuration for some versions of the
final cover glass apparatus.
[0072] Fabrication methods include predominantly transparent
substrates and materials to increase the optical performance of
underlying displays. The fabrication processes may utilize flexible
substrates for at least a portion of the sensor device, and lend
themselves to roll-to-roll processing for low cost.
[0073] Use of a compliant, elastomeric layer between upper and
lower portions of the combination sensor can increase the
sensitivity to applied pressure or force from a stylus, while
increasing the lateral resolution for a given sensel pitch. The
elastomeric material may include open regions for the inclusion of
force-sensitive resistors. With careful selection of the
elastomeric and FSR materials, the loss of transmissivity that can
accompany air gaps is minimized.
[0074] An array of force-sensitive switches and local capacitors
may be used to connect the local capacitor into associated PCT
detection circuitry, where each capacitor is formed with a thin
dielectric layer to achieve a high capacitance increase when the
force-sensitive switch is closed by the pressing of a stylus or
finger. The same PCT detection circuitry can therefore be used to
detect changes in mutual capacitance when touched with a finger
(touch mode) and changes in sensel capacitance when the
force-sensitive switch is depressed (stylus or fingerprint
mode).
[0075] The combined, multi-functional sensor device enables a
single touchscreen to perform additional functions such as
handwriting input and fingerprint recognition. In some
implementations, these multiple features allow increased security
through user authentication, and allow better capture of
handwriting and a more interactive approach to user interfaces. A
handheld mobile device such as a cell phone with the sensor device
enables an array of applications, including using the mobile device
as a gateway for user authentication to enable transactions and
physical access; using the handwriting input function for signature
recognition and transmittal for transaction applications; and using
the handwriting input feature to automatically capture notes and
other documents of students in an academic setting or employees in
a corporate setting.
[0076] In some such implementations, a separate controller may be
configured for the sensor device, or the controller may be included
as part of an applications processor. Software for handwriting,
touch and fingerprint detection may be included on one or more
controllers or the applications processor. Low, medium and high
resolution can be obtained with a single sensor device by scanning
a subset of the sensels, or by aggregating lines or columns. Power
consumption may be reduced by aggregating sensor pixels (or rows or
columns) electrically using the controller, so that they perform as
a low power small array until higher resolution with a larger array
is needed. Power consumption may be reduced by turning off portions
or all of the sensor device, turning off parts of the controller,
or employing first-level screening at a reduced frame rate. In some
such implementations, a combination PCT sensor and digital
resistive touch (DRT) sensor has a passive array of capacitors
(PCT) and a passive array of resistive switches (DRT). While the
touch sensor and stylus sensor systems generally use different
sensing techniques, a holistic approach with a common structure
saves on PCB part count, reduces area in an ASIC implementation,
reduces power, and eliminates the need for isolation between touch
and stylus subsystems.
[0077] An example of a suitable EMS or MEMS device, to which the
described implementations may apply, is a reflective display
device. Reflective display devices can incorporate interferometric
modulators (IMODs) to selectively absorb and/or reflect light
incident thereon using principles of optical interference. IMODs
can include an absorber, a reflector that is movable with respect
to the absorber, and an optical resonant cavity defined between the
absorber and the reflector. The reflector can be moved to two or
more different positions, which can change the size of the optical
resonant cavity and thereby affect the reflectance of the
interferometric modulator. The reflectance spectrums of IMODs can
create fairly broad spectral bands which can be shifted across the
visible wavelengths to generate different colors. The position of
the spectral band can be adjusted by changing the thickness of the
optical resonant cavity. One way of changing the optical resonant
cavity is by changing the position of the reflector.
[0078] FIG. 1 shows an example of an isometric view depicting two
adjacent pixels in a series of pixels of an interferometric
modulator (IMOD) display device. The IMOD display device includes
one or more interferometric MEMS display elements. In these
devices, the pixels of the MEMS display elements can be in either a
bright or dark state. In the bright ("relaxed," "open" or "on")
state, the display element reflects a large portion of incident
visible light, e.g., to a user. Conversely, in the dark
("actuated," "closed" or "off") state, the display element reflects
little incident visible light. In some implementations, the light
reflectance properties of the on and off states may be reversed.
MEMS pixels can be configured to reflect predominantly at
particular wavelengths allowing for a color display in addition to
black and white.
[0079] The IMOD display device can include a row/column array of
IMODs. Each IMOD can include a pair of reflective layers, i.e., a
movable reflective layer and a fixed partially reflective layer,
positioned at a variable and controllable distance from each other
to form an air gap (also referred to as an optical gap or cavity).
The movable reflective layer may be moved between at least two
positions. In a first position, i.e., a relaxed position, the
movable reflective layer can be positioned at a relatively large
distance from the fixed partially reflective layer. In a second
position, i.e., an actuated position, the movable reflective layer
can be positioned more closely to the partially reflective layer.
Incident light that reflects from the two layers can interfere
constructively or destructively depending on the position of the
movable reflective layer, producing either an overall reflective or
non-reflective state for each pixel. In some implementations, the
IMOD may be in a reflective state when unactuated, reflecting light
within the visible spectrum, and may be in a dark state when
unactuated, absorbing and/or destructively interfering light within
the visible range. In some other implementations, however, an IMOD
may be in a dark state when unactuated, and in a reflective state
when actuated. In some implementations, the introduction of an
applied voltage can drive the pixels to change states. In some
other implementations, an applied charge can drive the pixels to
change states.
[0080] The depicted portion of the pixel array in FIG. 1 includes
two adjacent interferometric modulators 12 (i.e., IMOD pixels). In
the IMOD 12 on the left (as illustrated), a movable reflective
layer 14 is illustrated in a relaxed position at a distance (which
may be predetermined based on design parameters) from an optical
stack 16, which includes a partially reflective layer. The voltage
V.sub.0 applied across the IMOD 12 on the left is insufficient to
cause actuation of the movable reflective layer 14. In the IMOD 12
on the right, the movable reflective layer 14 is illustrated in an
actuated position near, adjacent or touching the optical stack 16.
The voltage V.sub.bias applied across the IMOD 12 on the right is
sufficient to move and can maintain the movable reflective layer 14
in the actuated position.
[0081] In FIG. 1, the reflective properties of pixels 12 are
generally illustrated with arrows 13 indicating light incident upon
the pixels 12, and light 15 reflecting from the pixel 12 on the
left. A person having ordinary skill in the art will readily
recognize that most of the light 13 incident upon the pixels 12 may
be transmitted through the transparent substrate 20, toward the
optical stack 16. A portion of the light incident upon the optical
stack 16 may be transmitted through the partially reflective layer
of the optical stack 16, and a portion will be reflected back
through the transparent substrate 20. The portion of light 13 that
is transmitted through the optical stack 16 may be reflected at the
movable reflective layer 14, back toward (and through) the
transparent substrate 20. Interference (constructive or
destructive) between the light reflected from the partially
reflective layer of the optical stack 16 and the light reflected
from the movable reflective layer 14 will determine the
wavelength(s) of light 15 reflected from the pixel 12.
[0082] The optical stack 16 can include a single layer or several
layers. The layer(s) can include one or more of an electrode layer,
a partially reflective and partially transmissive layer and a
transparent dielectric layer. In some implementations, the optical
stack 16 is electrically conductive, partially transparent and
partially reflective, and may be fabricated, for example, by
depositing one or more of the above layers onto a transparent
substrate 20. The electrode layer can be formed from a variety of
materials, such as various metals, for example indium tin oxide
(ITO). The partially reflective layer can be formed from a variety
of materials that are partially reflective, such as various metals,
such as chromium (Cr), semiconductors, and dielectrics. The
partially reflective layer can be formed of one or more layers of
materials, and each of the layers can be formed of a single
material or a combination of materials. In some implementations,
the optical stack 16 can include a single semi-transparent
thickness of metal or semiconductor which serves as both an optical
absorber and electrical conductor, while different, more
electrically conductive layers or portions (e.g., of the optical
stack 16 or of other structures of the IMOD) can serve to bus
signals between IMOD pixels. The optical stack 16 also can include
one or more insulating or dielectric layers covering one or more
conductive layers or an electrically conductive/optically
absorptive layer.
[0083] In some implementations, the layer(s) of the optical stack
16 can be patterned into parallel strips, and may form row
electrodes in a display device as described further below. As will
be understood by one having ordinary skill in the art, the term
"patterned" is used herein to refer to masking as well as etching
processes. In some implementations, a highly conductive and
reflective material, such as aluminum (Al), may be used for the
movable reflective layer 14, and these strips may form column
electrodes in a display device. The movable reflective layer 14 may
be formed as a series of parallel strips of a deposited metal layer
or layers (orthogonal to the row electrodes of the optical stack
16) to form columns deposited on top of posts 18 and an intervening
sacrificial material deposited between the posts 18. When the
sacrificial material is etched away, a defined gap 19, or optical
cavity, can be formed between the movable reflective layer 14 and
the optical stack 16. In some implementations, the spacing between
posts 18 may be approximately 1-1000 um, while the gap 19 may be
approximately less than 10,000 Angstroms (.ANG.).
[0084] In some implementations, each pixel of the IMOD, whether in
the actuated or relaxed state, is essentially a capacitor formed by
the fixed and moving reflective layers. When no voltage is applied,
the movable reflective layer 14 remains in a mechanically relaxed
state, as illustrated by the pixel 12 on the left in FIG. 1, with
the gap 19 between the movable reflective layer 14 and optical
stack 16. However, when a potential difference, e.g., voltage, is
applied to at least one of a selected row and column, the capacitor
formed at the intersection of the row and column electrodes at the
corresponding pixel becomes charged, and electrostatic forces pull
the electrodes together. If the applied voltage exceeds a
threshold, the movable reflective layer 14 can deform and move near
or against the optical stack 16. A dielectric layer (not shown)
within the optical stack 16 may prevent shorting and control the
separation distance between the layers 14 and 16, as illustrated by
the actuated pixel 12 on the right in FIG. 1. The behavior is the
same regardless of the polarity of the applied potential
difference. Though a series of pixels in an array may be referred
to in some instances as "rows" or "columns," a person having
ordinary skill in the art will readily understand that referring to
one direction as a "row" and another as a "column" is arbitrary.
Restated, in some orientations, the rows can be considered columns,
and the columns considered to be rows. Furthermore, the display
elements may be evenly arranged in orthogonal rows and columns (an
"array"), or arranged in non-linear configurations, for example,
having certain positional offsets with respect to one another (a
"mosaic"). The terms "array" and "mosaic" may refer to either
configuration. Thus, although the display is referred to as
including an "array" or "mosaic," the elements themselves need not
be arranged orthogonally to one another, or disposed in an even
distribution, in any instance, but may include arrangements having
asymmetric shapes and unevenly distributed elements.
[0085] FIG. 2 shows an example of a system block diagram
illustrating an electronic device incorporating a 3.times.3
interferometric modulator display. The electronic device includes a
processor 21 that may be configured to execute one or more software
modules. In addition to executing an operating system, the
processor 21 may be configured to execute one or more software
applications, including a web browser, a telephone application, an
email program, or any other software application.
[0086] The processor 21 can be configured to communicate with an
array driver 22. The array driver 22 can include a row driver
circuit 24 and a column driver circuit 26 that provide signals to,
e.g., a display array or panel 30. The cross section of the IMOD
display device illustrated in FIG. 1 is shown by the lines 1-1 in
FIG. 2. Although FIG. 2 illustrates a 3.times.3 array of IMODs for
the sake of clarity, the display array 30 may contain a very large
number of IMODs, and may have a different number of IMODs in rows
than in columns, and vice versa.
[0087] FIG. 3 shows an example of a diagram illustrating movable
reflective layer position versus applied voltage for the
interferometric modulator of FIG. 1. For MEMS interferometric
modulators, the row/column (i.e., common/segment) write procedure
may take advantage of a hysteresis property of these devices as
illustrated in FIG. 3. An interferometric modulator may require,
for example, about a 10-volt potential difference to cause the
movable reflective layer, or mirror, to change from the relaxed
state to the actuated state. When the voltage is reduced from that
value, the movable reflective layer maintains its state as the
voltage drops back below, e.g., 10-volts, however, the movable
reflective layer does not relax completely until the voltage drops
below 2-volts. Thus, a range of voltage, approximately 3 to
7-volts, as shown in FIG. 3, exists where there is a window of
applied voltage within which the device is stable in either the
relaxed or actuated state. This is referred to herein as the
"hysteresis window" or "stability window." For a display array 30
having the hysteresis characteristics of FIG. 3, the row/column
write procedure can be designed to address one or more rows at a
time, such that during the addressing of a given row, pixels in the
addressed row that are to be actuated are exposed to a voltage
difference of about 10-volts, and pixels that are to be relaxed are
exposed to a voltage difference of near zero volts. After
addressing, the pixels are exposed to a steady state or bias
voltage difference of approximately 5-volts such that they remain
in the previous strobing state. In this example, after being
addressed, each pixel sees a potential difference within the
"stability window" of about 3-7-volts. This hysteresis property
feature enables the pixel design, e.g., illustrated in FIG. 1, to
remain stable in either an actuated or relaxed pre-existing state
under the same applied voltage conditions. Since each IMOD pixel,
whether in the actuated or relaxed state, is essentially a
capacitor formed by the fixed and moving reflective layers, this
stable state can be held at a steady voltage within the hysteresis
window without substantially consuming or losing power. Moreover,
essentially little or no current flows into the IMOD pixel if the
applied voltage potential remains substantially fixed.
[0088] In some implementations, a frame of an image may be created
by applying data signals in the form of "segment" voltages along
the set of column electrodes, in accordance with the desired change
(if any) to the state of the pixels in a given row. Each row of the
array can be addressed in turn, such that the frame is written one
row at a time. To write the desired data to the pixels in a first
row, segment voltages corresponding to the desired state of the
pixels in the first row can be applied on the column electrodes,
and a first row pulse in the form of a specific "common" voltage or
signal can be applied to the first row electrode. The set of
segment voltages can then be changed to correspond to the desired
change (if any) to the state of the pixels in the second row, and a
second common voltage can be applied to the second row electrode.
In some implementations, the pixels in the first row are unaffected
by the change in the segment voltages applied along the column
electrodes, and remain in the state they were set to during the
first common voltage row pulse. This process may be repeated for
the entire series of rows, or alternatively, columns, in a
sequential fashion to produce the image frame. The frames can be
refreshed and/or updated with new image data by continually
repeating this process at some desired number of frames per
second.
[0089] The combination of segment and common signals applied across
each pixel (that is, the potential difference across each pixel)
determines the resulting state of each pixel. FIG. 4 shows an
example of a table illustrating various states of an
interferometric modulator when various common and segment voltages
are applied. As will be readily understood by one having ordinary
skill in the art, the "segment" voltages can be applied to either
the column electrodes or the row electrodes, and the "common"
voltages can be applied to the other of the column electrodes or
the row electrodes.
[0090] As illustrated in FIG. 4 (as well as in the timing diagram
shown in FIG. 5B), when a release voltage VC.sub.REL is applied
along a common line, all interferometric modulator elements along
the common line will be placed in a relaxed state, alternatively
referred to as a released or unactuated state, regardless of the
voltage applied along the segment lines, i.e., high segment voltage
VS.sub.H and low segment voltage VS.sub.L. In particular, when the
release voltage VC.sub.REL is applied along a common line, the
potential voltage across the modulator (alternatively referred to
as a pixel voltage) is within the relaxation window (see FIG. 3,
also referred to as a release window) both when the high segment
voltage VS.sub.H and the low segment voltage VS.sub.L are applied
along the corresponding segment line for that pixel.
[0091] When a hold voltage is applied on a common line, such as a
high hold voltage VC.sub.HOLD.sub.--.sub.H or a low hold voltage
VC.sub.HOLD.sub.--.sub.L, the state of the interferometric
modulator will remain constant. For example, a relaxed IMOD will
remain in a relaxed position, and an actuated IMOD will remain in
an actuated position. The hold voltages can be selected such that
the pixel voltage will remain within a stability window both when
the high segment voltage VS.sub.H and the low segment voltage
VS.sub.L are applied along the corresponding segment line. Thus,
the segment voltage swing, i.e., the difference between the high
VS.sub.H and low segment voltage VS.sub.L, is less than the width
of either the positive or the negative stability window.
[0092] When an addressing, or actuation, voltage is applied on a
common line, such as a high addressing voltage
VC.sub.ADD.sub.--.sub.H or a low addressing voltage
VC.sub.ADD.sub.--.sub.L, data can be selectively written to the
modulators along that line by application of segment voltages along
the respective segment lines. The segment voltages may be selected
such that actuation is dependent upon the segment voltage applied.
When an addressing voltage is applied along a common line,
application of one segment voltage will result in a pixel voltage
within a stability window, causing the pixel to remain unactuated.
In contrast, application of the other segment voltage will result
in a pixel voltage beyond the stability window, resulting in
actuation of the pixel. The particular segment voltage which causes
actuation can vary depending upon which addressing voltage is used.
In some implementations, when the high addressing voltage
VC.sub.ADD.sub.--.sub.H is applied along the common line,
application of the high segment voltage VS.sub.H can cause a
modulator to remain in its current position, while application of
the low segment voltage VS.sub.L can cause actuation of the
modulator. As a corollary, the effect of the segment voltages can
be the opposite when a low addressing voltage VC.sub.ADD L is
applied, with high segment voltage VS.sub.H causing actuation of
the modulator, and low segment voltage VS.sub.L having no effect
(i.e., remaining stable) on the state of the modulator.
[0093] In some implementations, hold voltages, address voltages,
and segment voltages may be used which always produce the same
polarity potential difference across the modulators. In some other
implementations, signals can be used which alternate the polarity
of the potential difference of the modulators. Alternation of the
polarity across the modulators (that is, alternation of the
polarity of write procedures) may reduce or inhibit charge
accumulation which could occur after repeated write operations of a
single polarity.
[0094] FIG. 5A shows an example of a diagram illustrating a frame
of display data in the 3.times.3 interferometric modulator display
of FIG. 2. FIG. 5B shows an example of a timing diagram for common
and segment signals that may be used to write the frame of display
data illustrated in FIG. 5A. The signals can be applied to the,
e.g., 3.times.3 array of FIG. 2, which will ultimately result in
the line time 60e display arrangement illustrated in FIG. 5A. The
actuated modulators in FIG. 5A are in a dark-state, i.e., where a
substantial portion of the reflected light is outside of the
visible spectrum so as to result in a dark appearance to, e.g., a
viewer. Prior to writing the frame illustrated in FIG. 5A, the
pixels can be in any state, but the write procedure illustrated in
the timing diagram of FIG. 5B presumes that each modulator has been
released and resides in an unactuated state before the first line
time 60a.
[0095] During the first line time 60a: a release voltage 70 is
applied on common line 1; the voltage applied on common line 2
begins at a high hold voltage 72 and moves to a release voltage 70;
and a low hold voltage 76 is applied along common line 3. Thus, the
modulators (common 1, segment 1), (1,2) and (1,3) along common line
1 remain in a relaxed, or unactuated, state for the duration of the
first line time 60a, the modulators (2,1), (2,2) and (2,3) along
common line 2 will move to a relaxed state, and the modulators
(3,1), (3,2) and (3,3) along common line 3 will remain in their
previous state. With reference to FIG. 4, the segment voltages
applied along segment lines 1, 2 and 3 will have no effect on the
state of the interferometric modulators, as none of common lines 1,
2 or 3 are being exposed to voltage levels causing actuation during
line time 60a (i.e., VC.sub.REL--relax and
VC.sub.HOLD.sub.--.sub.L--stable).
[0096] During the second line time 60b, the voltage on common line
1 moves to a high hold voltage 72, and all modulators along common
line 1 remain in a relaxed state regardless of the segment voltage
applied because no addressing, or actuation, voltage was applied on
the common line 1. The modulators along common line 2 remain in a
relaxed state due to the application of the release voltage 70, and
the modulators (3,1), (3,2) and (3,3) along common line 3 will
relax when the voltage along common line 3 moves to a release
voltage 70.
[0097] During the third line time 60c, common line 1 is addressed
by applying a high address voltage 74 on common line 1. Because a
low segment voltage 64 is applied along segment lines 1 and 2
during the application of this address voltage, the pixel voltage
across modulators (1,1) and (1,2) is greater than the high end of
the positive stability window (i.e., the voltage differential
exceeded a predefined threshold) of the modulators, and the
modulators (1,1) and (1,2) are actuated. Conversely, because a high
segment voltage 62 is applied along segment line 3, the pixel
voltage across modulator (1,3) is less than that of modulators
(1,1) and (1,2), and remains within the positive stability window
of the modulator; modulator (1,3) thus remains relaxed. Also during
line time 60c, the voltage along common line 2 decreases to a low
hold voltage 76, and the voltage along common line 3 remains at a
release voltage 70, leaving the modulators along common lines 2 and
3 in a relaxed position.
[0098] During the fourth line time 60d, the voltage on common line
1 returns to a high hold voltage 72, leaving the modulators along
common line 1 in their respective addressed states. The voltage on
common line 2 is decreased to a low address voltage 78. Because a
high segment voltage 62 is applied along segment line 2, the pixel
voltage across modulator (2,2) is below the lower end of the
negative stability window of the modulator, causing the modulator
(2,2) to actuate. Conversely, because a low segment voltage 64 is
applied along segment lines 1 and 3, the modulators (2,1) and (2,3)
remain in a relaxed position. The voltage on common line 3
increases to a high hold voltage 72, leaving the modulators along
common line 3 in a relaxed state. Then the voltage on common line 2
transitions back to low hold voltage 76.
[0099] Finally, during the fifth line time 60e, the voltage on
common line 1 remains at high hold voltage 72, and the voltage on
common line 2 remains at low hold voltage 76, leaving the
modulators along common lines 1 and 2 in their respective addressed
states. The voltage on common line 3 increases to a high address
voltage 74 to address the modulators along common line 3. As a low
segment voltage 64 is applied on segment lines 2 and 3, the
modulators (3,2) and (3,3) actuate, while the high segment voltage
62 applied along segment line 1 causes modulator (3,1) to remain in
a relaxed position. Thus, at the end of the fifth line time 60e,
the 3.times.3 pixel array is in the state shown in FIG. 5A, and
will remain in that state as long as the hold voltages are applied
along the common lines, regardless of variations in the segment
voltage which may occur when modulators along other common lines
(not shown) are being addressed.
[0100] In the timing diagram of FIG. 5B, a given write procedure
(i.e., line times 60a-60e) can include the use of either high hold
and address voltages, or low hold and address voltages. Once the
write procedure has been completed for a given common line (and the
common voltage is set to the hold voltage having the same polarity
as the actuation voltage), the pixel voltage remains within a given
stability window, and does not pass through the relaxation window
until a release voltage is applied on that common line.
Furthermore, as each modulator is released as part of the write
procedure prior to addressing the modulator, the actuation time of
a modulator, rather than the release time, may determine the
necessary line time. Specifically, in implementations in which the
release time of a modulator is greater than the actuation time, the
release voltage may be applied for longer than a single line time,
as depicted in FIG. 5B. In some other implementations, voltages
applied along common lines or segment lines may vary to account for
variations in the actuation and release voltages of different
modulators, such as modulators of different colors.
[0101] The details of the structure of interferometric modulators
that operate in accordance with the principles set forth above may
vary widely. For example, FIGS. 6A-6E show examples of
cross-sections of varying implementations of interferometric
modulators, including the movable reflective layer 14 and its
supporting structures. FIG. 6A shows an example of a partial
cross-section of the interferometric modulator display of FIG. 1,
where a strip of metal material, i.e., the movable reflective layer
14 is deposited on supports 18 extending orthogonally from the
substrate 20. In FIG. 6B, the movable reflective layer 14 of each
IMOD is generally square or rectangular in shape and attached to
supports at or near the corners, on tethers 32. In FIG. 6C, the
movable reflective layer 14 is generally square or rectangular in
shape and suspended from a deformable layer 34, which may include a
flexible metal. The deformable layer 34 can connect, directly or
indirectly, to the substrate 20 around the perimeter of the movable
reflective layer 14. These connections are herein referred to as
support posts. The implementation shown in FIG. 6C has additional
benefits deriving from the decoupling of the optical functions of
the movable reflective layer 14 from its mechanical functions,
which are carried out by the deformable layer 34. This decoupling
allows the structural design and materials used for the reflective
layer 14 and those used for the deformable layer 34 to be optimized
independently of one another.
[0102] FIG. 6D shows another example of an IMOD, where the movable
reflective layer 14 includes a reflective sub-layer 14a. The
movable reflective layer 14 rests on a support structure, such as
support posts 18. The support posts 18 provide separation of the
movable reflective layer 14 from the lower stationary electrode
(i.e., part of the optical stack 16 in the illustrated IMOD) so
that a gap 19 is formed between the movable reflective layer 14 and
the optical stack 16, for example when the movable reflective layer
14 is in a relaxed position. The movable reflective layer 14 also
can include a conductive layer 14c, which may be configured to
serve as an electrode, and a support layer 14b. In this example,
the conductive layer 14c is disposed on one side of the support
layer 14b, distal from the substrate 20, and the reflective
sub-layer 14a is disposed on the other side of the support layer
14b, proximal to the substrate 20. In some implementations, the
reflective sub-layer 14a can be conductive and can be disposed
between the support layer 14b and the optical stack 16. The support
layer 14b can include one or more layers of a dielectric material,
for example, silicon oxynitride (SiON) or silicon dioxide
(SiO.sub.2). In some implementations, the support layer 14b can be
a stack of layers, such as, for example, a SiO.sub.2/SiON/SiO.sub.2
tri-layer stack. Either or both of the reflective sub-layer 14a and
the conductive layer 14c can include, e.g., an aluminum (Al) alloy
with about 0.5% copper (Cu), or another reflective metallic
material. Employing conductive layers 14a, 14c above and below the
dielectric support layer 14b can balance stresses and provide
enhanced conduction. In some implementations, the reflective
sub-layer 14a and the conductive layer 14c can be formed of
different materials for a variety of design purposes, such as
achieving specific stress profiles within the movable reflective
layer 14.
[0103] As illustrated in FIG. 6D, some implementations also can
include a black mask structure 23. The black mask structure 23 can
be formed in optically inactive regions (e.g., between pixels or
under posts 18) to absorb ambient or stray light. The black mask
structure 23 also can improve the optical properties of a display
device by inhibiting light from being reflected from or transmitted
through inactive portions of the display, thereby increasing the
contrast ratio. Additionally, the black mask structure 23 can be
conductive and be configured to function as an electrical bussing
layer. In some implementations, the row electrodes can be connected
to the black mask structure 23 to reduce the resistance of the
connected row electrode. The black mask structure 23 can be formed
using a variety of methods, including deposition and patterning
techniques. The black mask structure 23 can include one or more
layers. For example, in some implementations, the black mask
structure 23 includes a molybdenum-chromium (MoCr) layer that
serves as an optical absorber, a SiO.sub.2 layer, and an aluminum
alloy that serves as a reflector and a bussing layer, with a
thickness in the range of about 30-80 .ANG., 500-1000 .ANG., and
500-6000 .ANG., respectively. The one or more layers can be
patterned using a variety of techniques, including photolithography
and dry etching, including, for example, carbon tetrafluoromethane
(CF.sub.4) and/or oxygen (O.sub.2) for the MoCr and SiO.sub.2
layers and chlorine (Cl.sub.2) and/or boron trichloride (BCl.sub.3)
for the aluminum alloy layer. In some implementations, the black
mask 23 can be an etalon or interferometric stack structure. In
such interferometric stack black mask structures 23, the conductive
absorbers can be used to transmit or bus signals between lower,
stationary electrodes in the optical stack 16 of each row or
column. In some implementations, a spacer layer 35 can serve to
generally electrically isolate the absorber layer 16a from the
conductive layers in the black mask 23.
[0104] FIG. 6E shows another example of an IMOD, where the movable
reflective layer 14 is self-supporting. In contrast with FIG. 6D,
the implementation of FIG. 6E does not include support posts 18.
Instead, the movable reflective layer 14 contacts the underlying
optical stack 16 at multiple locations, and the curvature of the
movable reflective layer 14 provides sufficient support that the
movable reflective layer 14 returns to the unactuated position of
FIG. 6E when the voltage across the interferometric modulator is
insufficient to cause actuation. The optical stack 16, which may
contain a plurality of several different layers, is shown here for
clarity including an optical absorber 16a, and a dielectric 16b. In
some implementations, the optical absorber 16a may serve both as a
fixed electrode and as a partially reflective layer.
[0105] In implementations such as those shown in FIGS. 6A-6E, the
IMODs function as direct-view devices, in which images are viewed
from the front side of the transparent substrate 20, i.e., the side
opposite to that upon which the modulator is arranged. In these
implementations, the back portions of the device (that is, any
portion of the display device behind the movable reflective layer
14, including, for example, the deformable layer 34 illustrated in
FIG. 6C) can be configured and operated upon without impacting or
negatively affecting the image quality of the display device,
because the reflective layer 14 optically shields those portions of
the device. For example, in some implementations a bus structure
(not illustrated) can be included behind the movable reflective
layer 14 which provides the ability to separate the optical
properties of the modulator from the electromechanical properties
of the modulator, such as voltage addressing and the movements that
result from such addressing. Additionally, the implementations of
FIGS. 6A-6E can simplify processing, such as patterning.
[0106] FIG. 7 shows an example of a flow diagram illustrating a
manufacturing process 80 for an interferometric modulator, and
FIGS. 8A-8E show examples of cross-sectional schematic
illustrations of corresponding stages of such a manufacturing
process 80. In some implementations, the manufacturing process 80
can be implemented to manufacture, e.g., interferometric modulators
of the general type illustrated in FIGS. 1 and 6, in addition to
other blocks not shown in FIG. 7. With reference to FIGS. 1, 6 and
7, the process 80 begins at block 82 with the formation of the
optical stack 16 over the substrate 20. FIG. 8A illustrates such an
optical stack 16 formed over the substrate 20. The substrate 20 may
be a transparent substrate such as glass or plastic, it may be
flexible or relatively stiff and unbending, and may have been
subjected to prior preparation processes, e.g., cleaning, to
facilitate efficient formation of the optical stack 16. As
discussed above, the optical stack 16 can be electrically
conductive, partially transparent and partially reflective and may
be fabricated, for example, by depositing one or more layers having
the desired properties onto the transparent substrate 20. In FIG.
8A, the optical stack 16 includes a multilayer structure having
sub-layers 16a and 16b, although more or fewer sub-layers may be
included in some other implementations. In some implementations,
one of the sub-layers 16a, 16b can be configured with both
optically absorptive and conductive properties, such as the
combined conductor/absorber sub-layer 16a. Additionally, one or
more of the sub-layers 16a, 16b can be patterned into parallel
strips, and may form row electrodes in a display device. Such
patterning can be performed by a masking and etching process or
another suitable process known in the art. In some implementations,
one of the sub-layers 16a, 16b can be an insulating or dielectric
layer, such as sub-layer 16b that is deposited over one or more
metal layers (e.g., one or more reflective and/or conductive
layers). In addition, the optical stack 16 can be patterned into
individual and parallel strips that form the rows of the
display.
[0107] The process 80 continues at block 84 with the formation of a
sacrificial layer 25 over the optical stack 16. The sacrificial
layer 25 is later removed (e.g., at block 90) to form the cavity 19
and thus the sacrificial layer 25 is not shown in the resulting
interferometric modulators 12 illustrated in FIG. 1. FIG. 8B
illustrates a partially fabricated device including a sacrificial
layer 25 formed over the optical stack 16. The formation of the
sacrificial layer 25 over the optical stack 16 may include
deposition of a xenon difluoride (XeF.sub.2)-etchable material such
as molybdenum (Mo) or amorphous silicon (Si), in a thickness
selected to provide, after subsequent removal, a gap or cavity 19
(see also FIGS. 1 and 8E) having a desired design size. Deposition
of the sacrificial material may be carried out using deposition
techniques such as physical vapor deposition (PVD, e.g.,
sputtering), plasma-enhanced chemical vapor deposition (PECVD),
thermal chemical vapor deposition (thermal CVD), or
spin-coating.
[0108] The process 80 continues at block 86 with the formation of a
support structure e.g., a post 18 as illustrated in FIGS. 1, 6 and
8C. The formation of the post 18 may include patterning the
sacrificial layer 25 to form a support structure aperture, then
depositing a material (e.g., a polymer or an inorganic material,
e.g., silicon oxide) into the aperture to form the post 18, using a
deposition method such as PVD, PECVD, thermal CVD, or spin-coating.
In some implementations, the support structure aperture formed in
the sacrificial layer can extend through both the sacrificial layer
25 and the optical stack 16 to the underlying substrate 20, so that
the lower end of the post 18 contacts the substrate 20 as
illustrated in FIG. 6A. Alternatively, as depicted in FIG. 8C, the
aperture formed in the sacrificial layer 25 can extend through the
sacrificial layer 25, but not through the optical stack 16. For
example, FIG. 8E illustrates the lower ends of the support posts 18
in contact with an upper surface of the optical stack 16. The post
18, or other support structures, may be formed by depositing a
layer of support structure material over the sacrificial layer 25
and patterning portions of the support structure material located
away from apertures in the sacrificial layer 25. The support
structures may be located within the apertures, as illustrated in
FIG. 8C, but also can, at least partially, extend over a portion of
the sacrificial layer 25. As noted above, the patterning of the
sacrificial layer 25 and/or the support posts 18 can be performed
by a patterning and etching process, but also may be performed by
alternative etching methods.
[0109] The process 80 continues at block 88 with the formation of a
movable reflective layer or membrane such as the movable reflective
layer 14 illustrated in FIGS. 1, 6 and 8D. The movable reflective
layer 14 may be formed by employing one or more deposition steps,
e.g., reflective layer (e.g., aluminum, aluminum alloy) deposition,
along with one or more patterning, masking, and/or etching steps.
The movable reflective layer 14 can be electrically conductive, and
referred to as an electrically conductive layer. In some
implementations, the movable reflective layer 14 may include a
plurality of sub-layers 14a, 14b, 14c as shown in FIG. 8D. In some
implementations, one or more of the sub-layers, such as sub-layers
14a, 14c, may include highly reflective sub-layers selected for
their optical properties, and another sub-layer 14b may include a
mechanical sub-layer selected for its mechanical properties. Since
the sacrificial layer 25 is still present in the partially
fabricated interferometric modulator formed at block 88, the
movable reflective layer 14 is typically not movable at this stage.
A partially fabricated IMOD that contains a sacrificial layer 25
also may be referred to herein as an "unreleased" IMOD. As
described above in connection with FIG. 1, the movable reflective
layer 14 can be patterned into individual and parallel strips that
form the columns of the display.
[0110] The process 80 continues at block 90 with the formation of a
cavity, e.g., cavity 19 as illustrated in FIGS. 1, 6 and 8E. The
cavity 19 may be formed by exposing the sacrificial material 25
(deposited at block 84) to an etchant. For example, an etchable
sacrificial material such as Mo or amorphous Si may be removed by
dry chemical etching, e.g., by exposing the sacrificial layer 25 to
a gaseous or vaporous etchant, such as vapors derived from solid
XeF.sub.2 for a period of time that is effective to remove the
desired amount of material, typically selectively removed relative
to the structures surrounding the cavity 19. Other etching methods,
e.g. wet etching and/or plasma etching, also may be used. Since the
sacrificial layer 25 is removed during block 90, the movable
reflective layer 14 is typically movable after this stage. After
removal of the sacrificial material 25, the resulting fully or
partially fabricated IMOD may be referred to herein as a "released"
IMOD.
[0111] In some implementations described herein, at least part of a
combined sensor device may be incorporated in a cover glass
apparatus that can be overlaid on or otherwise combined with a
display. The cover glass apparatus may have 2, 3 or more layers. In
some implementations, the cover glass apparatus may include a
substantially transparent and flexible upper substrate and a
substantially transparent and relatively more rigid lower
substrate. The cover glass may include intermediate layers disposed
on and/or between the substrates, such as electrodes, a
substantially transparent elastomeric layer and/or force-sensitive
resistor material. In some such implementations, the lower
substrate of the cover glass apparatus may be overlaid on a display
substrate.
[0112] FIG. 9A shows an example of sensor electrodes formed on
substrates of a cover glass apparatus. In the example shown in FIG.
9A, three rows 915 of diamond-shaped substantially transparent
electrodes are depicted on the substantially transparent upper
substrate 905 and seven columns 920 of substantially transparent
diamond-shaped electrodes are located on the substantially
transparent lower substrate 910. Relatively few rows and columns
are shown here for illustrative purposes, while in actual sensor
devices the number of rows and columns may extend from tens to
hundreds or even a thousand or more. One may note that the rows and
columns are largely interchangeable, and no limitation is intended
here. In some implementations, the upper substrate 905 of the
combined sensor device 900 may be formed of a relatively flexible
material, such as a flexible polymer. In some such examples, the
upper substrate 905 may be a clear plastic film made of
polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
polyimide, or a similar material. In some implementations, the
upper substrate 905 may have a modulus of elasticity in the range
of 0.5-5 GPa. The lower substrate 910 may be formed of glass,
plastic, a polymer, etc. In some implementations, the lower
substrate 910 may be a display substrate. For example, in some
implementations the lower substrate 910 may be the same substrate
as the transparent substrate 20 described above.
[0113] In this example, every other column electrode 920 includes
diamond electrodes that are located directly under corresponding
diamonds of the row electrodes 915 in overlapping regions 925a.
Some implementations have offsets of the diamonds of the row
electrodes 915 and the column electrodes 920, whereby the diamonds
in the row electrodes 915 and the columns 920 partially overlie
each other.
[0114] In some implementations, the row electrodes 915 and/or the
column electrodes 920 may be formed into other shapes, such as
squares, rectangles, triangles, circles, ovals, etc., and shapes
that include predominantly open regions in the center of the shape
such as a frame, a ring, or a series of connected line segments. A
description of some such shapes is included in various parts of
pending U.S. patent application Ser. No. 12/957,025 filed Dec. 21,
2010 and entitled "Capacitive Touch Sensing Devices and Methods of
Manufacturing Thereof," (see, e.g., FIGS. 11A-11J and the
corresponding description) the contents of which are hereby
incorporated by reference in their entirety. Moreover, in
alternative implementations the row electrodes 915 may be formed on
the lower substrate 910 and the column electrodes 920 may be formed
on the upper substrate 905. In some implementations, such as that
described below with reference to FIGS. 10C and 10D including a
compressible material 1025 positioned between the row electrodes
915 and the column electrodes 920, a light touch may be detected by
measuring the change in mutual capacitance between adjacent
diamonds (also referred to as projective capacitive touch (PCT)).
In such implementations, contact with a stylus may be detected when
the upper substrate 905 is depressed by measuring the change in
capacitance between the row electrodes 915 and the column
electrodes 920.
[0115] In implementations with a patterned dielectric material
between the row electrodes 915 and the column electrodes 920, gaps
may be formed between corresponding row electrodes 915 and column
electrodes 920. In such implementations, light touches can be
detected with PCT measurements between adjacent electrodes, and
stylus depressions can be detected either by a change in the
effective parallel plate capacitance between the row electrodes 915
and the column electrodes 920 (see FIG. 10B) or by measuring
changes in resistance that occur when the row electrodes 915 and
the column electrodes 920 come in direct mechanical and electrical
contact (see FIG. 10A), or by measuring changes in a
force-sensitive resistor positioned between row electrodes 915 and
column electrodes 920 when pressed with a finger, a stylus tip,
ridges of a finger, or the like (see FIG. 10D). The force-sensitive
resistors may be included between row electrodes 915 and column
electrodes 920 in a handwriting and touch sensor zone 1005, in a
fingerprint sensor zone 1010, or both. In some such
implementations, a high resistivity layer may be formed on the row
electrodes 915 or the column electrodes 920 to minimize the effect
of parasitic signals during the sensing of the location of the
stylus.
[0116] FIG. 9B shows an alternative example of sensor electrodes
formed on a cover glass. In the example shown in FIG. 9B, the
column electrodes 920 in which diamonds lay beneath the diamonds of
the row electrodes 915 have been removed from the design. Ohmic
membrane switches, resistive membrane switches, resistive switches
with force-sensitive resistive (FSR) material, FSR switches with a
fixed series resistor, or capacitive membranes of the combined
sensor device 900 may be formed at the intersections between the
row electrodes 915 and the column electrodes 920 (in overlapping
regions 925b) for detecting stylus contact and, in some cases, a
fingertip or ridges of a finger. Such implementations can reduce
the number of column electrodes 920 (note that the number of column
electrodes 920 and associated connection pads in FIG. 9B is fewer
than the column electrodes 920 and connection pads in FIG. 9A) that
need to be connected to the external processing circuitry, because
the same columns can serve the purpose of detecting a light touch
through the PCT method or detecting the stylus contact through
either a capacitance change method or a resistive change
method.
[0117] For example, in the touch mode, only a very light force may
be required to register a touch. However, in the handwriting mode,
the sensor may be configured to accept many forms of stylus, pen,
or other pointer input, regardless of whether or not the pointing
device is conducting or non-conducting. Some implementations
described herein provide sensors capable of distinguishing a large
number of multi-touch events simultaneously, such as may occur when
reading a fingerprint while operating in a fingerprint sensor mode,
or detecting and rejecting an inadvertent palm touch when operating
in a handwriting sensor mode.
[0118] FIG. 10A shows an example of a cross-sectional view of a
combined sensor device. While the sensor array shown in FIG. 10A is
depicted as a combination touch, stylus, and fingerprint sensor, it
should be noted that the configuration of FIG. 10A and other
configurations described below may serve as only a touch sensor, a
stylus sensor, a fingerprint sensor, or a combination thereof. In
the example shown in FIG. 10A, two repeating cells are shown in a
first region referred to as a handwriting and touch sensor zone
1005. Such sensing elements may be referred to herein as "sensels."
An optional second region, referred to as a fingerprint sensor zone
1010, generally has a finer pitch between electrodes to allow for
higher resolution often needed for fingerprint detection. As noted
elsewhere herein, in some implementations the fingerprint sensor
and the handwriting and touch sensor are not in different zones.
FIGS. 10B-10D show examples of cross-sectional views of alternative
combined sensor devices. FIGS. 10A-10D, like many other drawings
provided herein, may not be drawn to scale. Touch, handwriting, and
fingerprint zones are shown in FIGS. 10A-10D, although not all
zones would normally be activated simultaneously. Nor may all zones
and operating modes be available in a sensor device. Single or
multi-touching using one or more fingers is depicted as being
sensed using PCT in handwriting and touch sensor zone 1005, where
particularly light touches as well as moderate and heavy touches
may be detected. In the example shown in FIG. 10A, proximity of a
finger 1047 alters the electric field 1050 between the upper
electrode 1015 and the lower electrode 1030b, producing a change in
mutual capacitance. This effect is schematically depicted by the
variable capacitor of the associated circuit diagram 1055a. In some
implementations, the upper electrode 1015 may be a row electrode
and, as mentioned above, in some other implementations the upper
electrode 1015 may be a column electrode (see FIGS. 9A and 9B).
[0119] High forces or high localized pressure (such as that
incurred when a tip of a stylus such as a pen, pencil, or pointer
is pressed against the surface of the combined sensor device 900)
may be detected with ohmic or resistive membrane switches. One
example is shown in FIG. 10A, in which high localized pressure
produced by a pen or stylus 1042 can be detected by a mechanical
switch that includes the upper electrode 1015 and the lower
electrode 1030a. A resistor 1035, sometimes referred to as a fixed
resistor, may be positioned between upper electrode 1015 and lower
electrode 1030a to prevent direct shorting of the upper electrode
1015 and the lower electrode 1030a. The switch including a vertical
or serpentine fixed resistor is represented schematically in the
circuit diagram 1055a. The resistor 1035 may have an additional
metal layer disposed thereon (not shown) to aid in electrical
contact between it and the upper electrode 1015. While a resistive
membrane switch as defined here includes at least a fixed resistor
in each sensel (the resistive membrane switch also may include a
force-sensitive resistor in series with the fixed resistor or in
lieu of the fixed resistor), an ohmic membrane switch does not
require an additional fixed resistor in series with the upper and
lower electrodes. The fixed resistor may be formed of an ohmic
material in some implementations. In some other implementations,
the fixed resistor may be a non-linear device such as a leaky diode
or other device that provides a relatively high resistance to
current flow. The fixed resistor may include a thin-film conductive
cap that serves as a conductive contact surface. Whereas a
one-to-one correspondence with digital resistive touch (DRT) lower
electrodes 1030a and PCT lower electrodes 1030b is shown in FIG.
10A, in some configurations the PCT lower electrodes 1030b could
span one or more adjacent sensels. In some configurations, the PCT
lower electrode 1030b is wider and longer than the DRT lower
electrode 1030a.
[0120] In some implementations, the upper electrodes 1015 and the
lower electrodes 1030a may be configured to form two plates of a
deformable parallel plate capacitor, instead of the mechanical
switch described above. In some implementations, the electrodes
1015 and 1030a may be separated by an air gap, as shown in areas
1065 of FIG. 10B, and may have a spacing corresponding to a
baseline capacitance in the normal unpressed state. Upon the
application of force or pressure, upper electrode 1015 is displaced
and the electrodes 1015 and 1030a come closer. When the
inter-electrode distance between the electrodes 1015 and 1030a is
reduced, the capacitance changes (e.g., increases), enabling the
sensing of an analog change in the displacement and allowing
inference of the presence of the applied force or pressure.
Accordingly, high localized pressure or force from a pen, a stylus,
etc., may be detected via parallel plate capacitance changes
between upper electrodes 1015 and lower electrodes 1030a. The
capacitance changes caused by such localized changes in pressure
are represented schematically by the variable capacitor 1056 of the
circuit diagram 1055b. In the configuration shown, the fixed
resistor 1035 is in series with the variable capacitor 1056. In
other configurations (not shown), the fixed resistor 1035 may be
omitted.
[0121] In some implementations, an interlayer separation 1032 may
be formed between the upper substrate 905 and the lower substrate
910 by disposing a compressible layer 1025 between the upper and
lower electrodes. In some implementations, the compressible layer
1025 may be a patternable, thin (e.g., 1 to 10 microns) polymer
with a low elastic modulus, such as an elastomer. In some such
implementations, the compressible layer 1025 may allow direct
measurement of capacitance changes when the upper substrate 905 is
depressed by a touch of a pen, a stylus, a finger, etc. and the
distance between an upper electrode 1015 and a lower electrode
1030a changes. The compressible layer 1025 may have a lower modulus
of elasticity than the upper substrate 905. For example, the upper
substrate 905 may be a clear plastic film made of PET, PEN,
polyimide, or a similar material having a modulus of elasticity in
the range of 0.5-5 GPa. The compressible layer 1025 may have a
significantly lower modulus of elasticity, such as in the range of
0.5-50 MPa.
[0122] In some implementations, the compressible layer 1025 may be
patterned to include spaces or voids (which also may be referred to
herein as "air gaps") between the upper substrate 905 and the lower
substrate 910. Some implementations, such as those shown in FIGS.
10A and 10B, include voids in the areas 1065, wherein the
compressible layer 1025 is not formed between the upper electrodes
1015 and the lower electrodes 1030a. However, in these examples the
compressible layer 1025 extends without voids between the upper
substrate 905 and the lower electrodes 1030b in the areas 1070.
According to some such implementations, the compressible layer 1025
may be patterned such that there are air gaps in the areas 1065 and
1080. The indicated thickness and spacing of the compressible layer
1025 regions are merely indicated by way of example. The locations
and lateral dimensions of the air gaps in the areas 1065 and 1080
may be selected according to desired parameters of force
sensitivity, reliability and/or optical performance, as a person
having ordinary skill in the art will readily comprehend. For
example, the interlayer separation 1032 may be a fraction of a
micron to several microns. The thickness of the air gaps in the
areas 1065 and 1080 also may be a fraction of a micron to several
microns thick. The pitch or spacing between adjacent upper
electrodes 1015 (adjacent sensels) may range from a few tenths of a
millimeter to over five millimeters in the handwriting and touch
sensor zone 1005 (with the pitch between lower electrodes 1030a and
1030b approximately half that), while the pitch or spacing between
adjacent electrodes 1040 in the fingerprint sensor zone 1010 may be
as small as 50 microns or so.
[0123] The compressible layer 1025 may aid in enabling measurable
deflections of the upper substrate 905. In some implementations,
the compressible layer 1025 also may be formed in the areas 1065,
as shown in FIG. 10C and described below. In some such
implementations, the compressible layer 1025 may include an
elastomeric material (or a similar material) that allows direct
measurement of capacitance changes when the upper substrate 905 is
depressed by a touch of a pen, a stylus, a finger, etc. and the
distance between an upper electrode 1015 and a lower electrode
1030a changes. Alternatively the mutual capacitance between an
upper electrode 1015 and a laterally displaced lower electrode
1030b also may change to allow the detection of a pen, stylus,
finger, etc.
[0124] The fingerprint sensor zone 1010 may be configured for
fingerprint detection. In the implementation shown in FIG. 10A, the
upper fingerprint electrodes 1020 and the lower fingerprint
electrodes 1040 form an array of resistive membrane switches, one
of which is schematically represented in the circuit diagram 1060a.
In the examples shown in FIGS. 10A-10C, the compressible layer 1025
is not formed between the upper fingerprint electrodes 1020 and the
lower fingerprint electrodes 1040 in the area 1080. However, in the
implementation depicted in FIG. 10D (which will be described in
more detail below), the compressible layer 1025 is formed in the
area 1080 except for regions where FSR material 1085 is
located.
[0125] In the examples shown in FIGS. 10A-10D, the upper
fingerprint electrodes 1020 and the lower fingerprint electrodes
1040 have a smaller pitch than that of the upper electrodes 1015
and the lower electrodes 1030 in the handwriting and touch sensor
zone 1005, in order to provide relatively higher resolution in the
fingerprint sensor zone 1010. However, in some alternative
implementations, the pitch of the upper fingerprint electrodes 1020
and the lower fingerprint electrodes 1040 may be substantially the
same as that of the upper electrodes 1015 and the lower electrodes
1030 in the handwriting and touch sensor zone 1005.
[0126] The compressible layer 1025 may be patterned using
lithography and etch techniques (or other lithography-based
techniques). In some implementations, the compressible layer 1025
can keep the ohmic or resistive switches of areas 1065 and 1080
open until a suitable force is applied to the outer surface of the
sensor (which is the top surface of the upper substrate 905 in this
example). Because the compressible layer 1025 is part of a sensor
that would overlay a display, the compressible layer 1025 can be
substantially transparent.
[0127] In some implementations, the compressible layer 1025 may
have an index of refraction closely matched to that of the lower
substrate 910 and the upper substrate 905. In some implementations,
the compressible layer 1025 may have an index of refraction that
differs from that of the lower substrate 910 and the upper
substrate 905 by less than 5%, by less than 10%, by less than 20%,
etc. For example, a 6% or less difference in the index of
refraction may result in less than 0.2% reduction in transmission
through the material stack. Such implementations can provide good
optical transmission in areas where the compressible layer 1025
extends from the upper substrate 905 to the lower substrate 910.
However, the optical transmission may be reduced in the air gap
regions, caused by reflections at each air-material interface. Such
reflections may be greater than, e.g., 4%, as calculated using the
index of refraction of the upper substrate 905 (which may be
approximately n=.about.1.5) and the index of refraction of air
(n.sub.o=1), in Equation 1:
(n-n.sub.o).sup.2/(n+n.sub.o).sup.2=R, where R is reflectance.
(Equation 1)
[0128] Accordingly, implementations having air gaps with minimal
lateral dimensions can provide better optical performance. However,
some such implementations may result in less deflection for a given
pressure and may therefore be less sensitive to pressure or applied
forces.
[0129] Therefore, some implementations provide an index-matched
compressible layer 1025, which can improve the optical performance.
Even in some implementations having air gaps in the areas 1065, the
optical performance may already be quite good due to an
architecture having the areas 1065 occupy a relatively small
fraction of the handwriting and touch sensor zone 1005. For
example, the areas 1065 with air gaps may occupy less than about
50% of the total area, whereas in other examples the areas 1065 may
occupy less than about 10% of the total area. In such
implementations, the majority of the sensor area will not have an
air gap, and therefore will exhibit much reduced reflection at the
layer 905/layer 1025 and the layer 1025/layer 910 interfaces, i.e.,
such that the total reflection for both interfaces may be
<<1%, as estimated per Equation 1.
[0130] The sensitivity to pressure or force from a pen, stylus, or
finger of the individual sensing elements (regardless of whether
they are used in a resistive switch mode or in a deformable
parallel plate capacitor mode) may be increased by the use of a
low-modulus compressible layer 1025, as shown in FIGS. 11A-11D. The
low-modulus compressible layer 1025 may remove the clamped boundary
condition that can be imposed by a higher-modulus material. Having
a low modulus compressible layer 1025 can effectively increase the
diameter of an area 1110 of the compressible layer 1025 that is
deflected by the stylus tip 1105, thereby increasing the deflection
of the upper substrate 905 in the area 1110.
[0131] FIGS. 11A-11D show examples of cross-sectional views of
combined sensor devices having high-modulus and low-modulus
compressible layers. FIG. 11A shows a stylus tip 1105 in contact
with a flexible upper substrate 905 of a portion of a simplified
combination touch, handwriting, and fingerprint sensor, wherein the
compressible layer 1025a is a patterned high-modulus material that
is sandwiched between the upper substrate 905 and the lower
substrate 910. Air gaps 1115 in the compressible layer 1025a allow
the upper substrate 905 of the combined sensor device 900 to deform
with applied forces, although the deflected area 1110 obtained is
limited in part by the small air gaps 1115 in the relatively stiff
compressible layer 1025a.
[0132] FIG. 11B shows a low-modulus compressible layer 1025b
sandwiched between the relatively more flexible upper substrate 905
and the relatively less flexible lower substrate 910. In this
example, the deflected area 1110 of the upper substrate 905 from
stylus forces is larger due to the ability of the compressible
layer 1025b to compress and deform as the stylus tip 1105 is
pressed against the outer surface of the upper substrate 905. In
the example shown in FIG. 11C, the stylus 1105 has been pressed
hard enough for the flexible upper substrate 905 to make (or nearly
make) physical contact with the lower substrate 910.
[0133] Use of a low-modulus elastomeric compressible layer 1025b
also may effectively increase the lateral resolution from applied
pressure or force without decreasing the pitch of the row or column
electrodes, as illustrated in FIG. 11D. Appreciable deflections of
the upper substrate 905 can occur even when the tip of the stylus
tip 1105 is not directly above an air gap 1115 in the compressible
layer 1025, thus allowing detection of the stylus tip 1105 even if
the combined sensor device 900 has relatively wide spacings between
adjacent sensing elements. For example, handwriting might be
resolved at a resolution of 0.2 mm even if the pitch between
adjacent rows or columns were 0.5 mm by averaging the responses
from adjacent sensels. By allowing a relatively larger pitch
between adjacent rows or columns, such configurations may enable
the reduction of the total number of row electrodes and column
electrodes for a given resolution, thereby reducing the number of
I/Os on the handwriting sensor controller. This reduction can
reduce the number of leadouts and reduce the cost and complexity of
the handwriting controller.
[0134] An alternative implementation of a combination sensor is
shown in FIG. 10C. As compared to the implementations shown in
FIGS. 10A and 10B, the air gaps have been removed from the areas
1065 of the handwriting and touch sensor zone 1005. Thus, the
optical performance of the handwriting and touch sensor zone 1005
may be enhanced with respect to the implementation of the combined
sensor device 900 shown in FIGS. 10A and 10B. The handwriting
sensor in the implementation of the combined sensor device 900
shown in FIG. 10C functions as a variable parallel plate capacitor,
where heavy touches or deflections of the upper layer are detected
from changes in the parallel plate capacitance. This functionality
is represented by the variable capacitor 1056 of the circuit
diagram 1055c.
[0135] FIG. 10D illustrates another example of an alternative
implementation. In the example shown in FIG. 10D, the air gaps have
been removed in the area 1080 of the fingerprint sensor zone 1010
and replaced with a commercially available FSR material 1085. The
FSR material 1085 provides a relatively high value of resistance
when not compressed and a relatively low value of resistance when
compressed, thereby functioning as a switch though without a direct
contact region. This functionality is represented by the variable
resistor 1087 of the circuit diagram 1060b. A fixed resistor 1045
such as a vertical resistor or a serpentine resistor may be
included in series with the FSR material 1085 in each sensel.
Transparent FSR material 1085 that includes either transparent
particles or low fill ratios of particles may be used in some
implementations. Non-transparent FSR material 1085 may be used in
some applications where, for example, the diameter or width of the
resistors is sufficiently small (on the order of a few to tens of
microns) to avoid excessive occlusion of an underlying display.
[0136] FIG. 12 shows an example of a device that includes a cover
glass with a combination touch, handwriting and fingerprint sensor.
In this example, the cover glass includes an implementation of the
combined sensor device 900 and is overlaid on the display of a
display device 40, such as a mobile phone. Some examples of the
display device 40 are described below with reference to FIGS. 25A
and 25B. The combined sensor device 900 can serve as a single or
multi-touch sensor, a handwriting input sensor, and a fingerprint
image sensor. In this example, the fingerprint sensor zone 1010 is
in a dedicated portion above the display. The remaining portion of
the combined sensor device 900 is configured as the handwriting and
touch sensor zone 1005. In some other configurations, fingerprint
sensor zone 1010 may be positioned anywhere throughout the combined
sensor device 900. In yet other configurations, the position of
fingerprint sensor zone 1010 is software programmable and software
selectable.
[0137] An example of touch mode operation will now be described
with reference to FIG. 10A. When a finger is used to touch anywhere
in the handwriting and touch sensor zone 1005, either all or a
selected subset of the upper electrodes 1015 on the upper substrate
905 and the lower electrodes 1030b on the lower substrate 910 may
be addressed during a scanning sequence. In some implementations,
the capacitance between the upper electrodes 1015 and the lower
electrodes 1030b may be measured at each of the intersections
between row and column electrodes (see FIGS. 9A and 9B). The
conducting surface of the finger 1047 interferes with the electric
field lines 1050, as shown in FIGS. 10A-10D, and modifies the
capacitance between the upper electrodes 1015 and the lower
electrodes 1030b. Detecting this change in capacitance allows a
reading of which sensels of the handwriting and touch sensor zone
1005 are in the vicinity of the finger. In this example, the
electrodes on the upper substrate 905 and the lower substrate 910
that are scanned during touch mode are not necessarily disposed
directly above and below each other. In the examples shown in FIGS.
10A-10D, a change in capacitance can be detected between an upper
electrode 1015 on the upper substrate 905 and an adjacent lower
electrode 1030b of the lower substrate 910. Note that for this PCT
measurement, a very light touch or even the proximity of a finger
may be detectable, because the capacitance change does not depend
on the pressure being applied to the upper substrate 905.
[0138] When a pointing device, such as a stylus (either conducting
or non-conducting) is placed on the sensor surface, the resultant
pressure can be significantly higher than that associated with a
finger touch, due to the smaller area of contact between the stylus
and the surface. This pressure can be up to two orders of magnitude
(or more) greater than the pressure exerted by a finger touch. In
some implementations, during the readout process in handwriting
mode, a different set of electrodes from those used for the touch
mode (such as upper electrodes 1015 and lower electrodes 1030a
depicted in FIG. 10A) may be excited and a different circuit may be
deployed for the measurement. The different circuit may sense
either the closure of a switch for an implementation such as that
shown in FIG. 10A, or the change in parallel plate capacitance for
an implementation such as that shown in FIGS. 10B-10D.
[0139] In some implementations, the addressing and/or measurement
circuitry for a touch mode, handwriting mode and/or fingerprint
sensing mode may be contained within one or more controller or
driver Application Specific Integrated Circuit (ASIC) chips. The
ASIC chip or chips may be attached directly to the underside of the
upper substrate 905 or connected electrically to the electrodes on
the upper substrate 905 and the lower substrate 910 by means such
as direct die attach using solder or anisotropic conductive film,
or connection through a cable or traces on a flex tape that are
coupled to ICs on the tape or on an external printed circuit
board.
[0140] In some implementations described above, the electrodes
scanned during the handwriting mode on the upper substrate 905 and
the lower substrate 910 are disposed directly above and below each
other (for example, see FIG. 10A). When the stylus tip 1105 (which
may be a tip of pen 1042 as shown in FIG. 10A or 10B) is applied
with sufficient force, the pressure exerted by the stylus tip 1105
may cause the upper substrate 905 and the compressible layer 1025
to deflect (see FIG. 11C) and may cause the upper electrodes 1015
and the resistor 1035 on the lower electrode 1030a to make physical
contact, resulting in a closure of a membrane switch (see FIG.
10A). A large resistance at each switch may be enabled by the
inclusion of a fixed resistor 1035. This resistance may
substantially lower the current and allow determination of the
sensel locations that are being pressed in the handwriting,
fingerprint or touch mode when one or more membrane switches are
being pressed simultaneously. This may occur, for example, when a
palm is resting on the surface of the combined sensor device 900
and a stylus is also applied to the surface. The resistor 1035 may
be formed from a resistive layer that is fabricated to be in series
with the lower electrodes 1030a. Alternatively, the displacement of
the upper substrate 905 with the force or pressure from a stylus or
finger on the outer surface can be measured from a change in the
parallel plate capacitance between an upper electrode 1015 and a
corresponding lower electrode 1030a.
[0141] Some implementations allow operation of the combined sensor
device 900 in a fingerprint acquisition mode, such as in a specific
region of the combined sensor device 900 that is configured to
enable this mode. Examples of fingerprint sensor zones 1010 are
shown in the far right portion of FIGS. 10A-10D and in the lower
right portion of FIG. 12. In some implementations, the fingerprint
sensor zones 1010 may be fabricated using the same process flow and
materials as those used for fabricating the rest of the combined
sensor device 900. However, in some implementations, the
fingerprint sensor zone 1010, the upper fingerprint electrodes 1020
and the lower fingerprint electrodes 1040, as well as the resistors
1045 of the lower fingerprint electrodes 1040, may be arranged with
a significantly closer pitch or spacing than the upper electrodes
1015 or the lower electrodes 1030 of the handwriting and touch
sensor zone 1005. For example, the pitch or spacing in the
fingerprint sensor zone 1010 may be on the order of about 10
microns to 100 microns. Such configurations can provide a sensor
with sufficiently high resolution to distinguish between the ridges
and valleys of a fingerprint.
[0142] When a finger is pressed down on the surface of the upper
substrate 905 in the fingerprint sensor zone 1010, certain regions
of the upper substrate 905 that are directly below the ridges of
the fingerprint may deflect and cause the upper fingerprint
electrodes 1020 to make contact with the fixed resistors 1045 on
the lower fingerprint electrodes 1040. This switch closure may be
through a resistor, such as a large value resistor, which can
provide for distinguishing which of the many sensor elements are
being pressed and which are not. Scanning rows or columns of such a
fingerprint sensor array can produce digital output that represents
the fingerprint ridges or absence of the same. Such fingerprint
sensor implementations can enable scanning of the fingerprint array
and acquisition of a fingerprint image.
[0143] The use of the digital resistive technique for handwriting
and fingerprint recognition can result in a fast scan rate. This is
due in part to the "digital" nature of the output from each cell
during the scanning process, which can enable high frame rates for
fingerprint capture and handwriting recognition.
[0144] In some implementations, a force-sensitive membrane switch
may be used to locally connect an extra capacitor into a PCT
measurement circuit, thus causing a large change in capacitance
when the switch is closed with applied pressure from, for example,
a finger or a stylus tip. The switches may be formed near the
intersections of sensor rows and columns. The extra capacitor may
be formed in series with the switch using conductive material to
connect with row and column lines. In some implementations, this
capacitor can produce a large change in capacitance relative to the
change in mutual capacitance of a PCT-only configuration.
[0145] One such implementation is depicted in FIGS. 13 and 14. FIG.
13 shows an example of a top view of a force-sensitive switch
implementation. FIG. 13 indicates portions of two columns and two
rows of such a combined sensor device 900, wherein the column
electrodes 1305 have a width 1310 and a spacing or "pitch" 1315.
The widths of the column and row electrodes are generally made
small, on the order of a few microns, to improve overall
transparency of the combined sensor device. The pitch can range
from about 10-50 microns, suitable for fingerprint detection, to
about 5 mm for lower resolution devices. Alternative
implementations may have pitches of less than 50 microns or more
than 5 mm. FIG. 14 shows an example of a cross-section through a
row of the force-sensitive switch implementation shown in FIG.
13.
[0146] In the implementation depicted in FIGS. 13 and 14, a
capacitor 1317 is formed over the rows between the row electrodes
1335 and the capacitor top electrode 1320 in each sensel. A
connection between the column electrodes 1305 and the capacitors
1317 may be made through a contact 1325 at the intersection of the
rows and columns, which may include a fixed resistor in series with
the contact. This contact 1325 may be electrically connected to the
capacitor top electrode 1320, forming an electrode of a switch that
may be open or closed. In some alternative configurations there may
be no separate contact 1325--physical contact may be made directly
between the column electrode 1305 and the capacitor top electrode
1320. The row electrodes 1335 may be disposed on a substantially
transparent lower substrate 910, which may be made of a material
such as glass, plastic, etc. In some implementations, the other
components depicted in FIGS. 13 and 14 also may be substantially
transparent.
[0147] In this example, a compressible layer 1025 is disposed
between the upper substrate 905 and the capacitor top electrode
1320. The compressible layer 1025 may be an insulator that is
formed of a material having a sufficiently low elastic modulus that
may be easily compressed and does not interfere with the switch to
the capacitor. Here, the upper substrate 905 is a flexible membrane
disposed on top of the sensor to protect the surface and yet
deflect locally when touched, in order to actuate the switches.
[0148] FIG. 15A shows an example of a circuit diagram that
represents components of the implementation shown in FIGS. 13 and
14. In the circuit 1500a, a signal may be applied at the input 1505
and sensed by the analog-to-digital converter (ADC) 1540. The
signal may be modulated by a change in mutual capacitance, C.sub.m,
when a finger is on or near the flexible membrane. Such changes in
C.sub.m are represented by a variable capacitor 1525. The
self-capacitances of rows and columns are represented by capacitors
1530 and 1535, respectively. The contacts at the intersection of
the rows and columns (see FIGS. 13 and 14) are represented as a
switch 1510 having a resistance R1 represented by the resistor 1515
and a capacitance C1 represented by the series capacitor 1520. The
resistance R1 also may include the line resistance of the
corresponding row or column electrodes. When force (such as a
touch) on the flexible upper substrate 905 closes the switch 1510,
capacitance C1 is added to the mutual capacitance C.sub.m. In some
implementations, C1 is substantially larger than C.sub.m because a
touch can generally reduce C.sub.m whereas closing the switch 1510
adds capacitance: when the switch is closed, the mutual capacitive
effect of the touch may be masked by the value of C1.
[0149] In one example, a high-resolution sensor may be formed
having row and column widths of 5 um and a pitch of 50 um between
rows and columns (for example, see FIGS. 13 and 14). If, for
example, the capacitor insulator 1330 is 1000 .ANG. thick and
formed of silicon nitride (SiN), and the capacitor top electrodes
1320 cover a 40 um.times.5 um area (see FIG. 14), a modulation of
greater than 60 femtofarads (fF) may be obtained using the
parallel-plate capacitor equation C=e.sub.re.sub.oA/d where e.sub.r
is the relative permittivity of the insulator, e.sub.o is the
permittivity of free space, A is the area of the top electrodes,
and d is the thickness of the dielectric. In some implementations,
this can be considered adequate for determination by PCT controller
circuitry. Decreasing the length or the width of the capacitor
electrodes will decrease the capacitance value, whereas decreasing
the thickness of the dielectric insulator will increase the
capacitance. In some implementations, the capacitance value can be
made appreciably larger by spanning a portion of the sensel area
between the row and column electrodes with the capacitor top
electrode or by increasing the row and column widths. In some
implementations, the value of the capacitance can be reduced by
reducing the electrode width or the pitch of the sensel. By
changing the dimensions of the capacitor electrodes and the
thickness of the insulator, values of capacitance in the range from
less than about 10 fF to more than about 0.1 pF may be
obtained.
[0150] FIG. 15B shows an example of a circuit diagram that
represents components of an alternative implementation related to
FIGS. 13 and 14. The circuit 1500b can be used to consider the
response times for a sensor such as that depicted in FIGS. 13 and
14. Here, a leakage resistor 1545 having a resistance R2 has been
added to the circuit to allow for the discharge of series capacitor
1520 when switch 1510 is open. If, for example, R2 were 100
megaohms and R1 were 10 kilohms, then the frequency response (1/RC)
for the C1 value for a 40 um.times.5 um capacitor as described
above would be a minimum of 150 KHz for a closed-to-open transition
of the switch 1510 and a maximum value of 1.5 GHz to charge the
capacitor though the series resistor 1515 when switch 1510 is
closed. The frequency response may be helpful in determining a
minimum obtainable frame rate for the combination sensor. The
frequency response and frame rate may be increased, if needed, by
decreasing the RC time constant with reductions to the resistor
values R1 or R2 or with reductions in the capacitance.
[0151] In some implementations, the resistor 1515 represents the
contact resistance of contact 1325 (e.g., no fixed resistor and no
FSR). In some other implementations, the resistor 1515 represents
the contact resistance directly between the column electrode 1305
and the capacitor top electrode 1320 as shown in FIG. 14 (e.g., no
fixed resistor, no FSR, and no contact 1325). In some
implementations, the resistor 1515 may include the resistance of an
additional fixed resistor such as a vertical or serpentine fixed
resistor (not shown) positioned between a contact 1325 and the
capacitor top electrode 1320 in FIG. 14. The fixed resistor may
include a thin-film conductive cap disposed thereon serving as the
contact 1325 to aid in electrical contact with a column electrode
1305. The resistor 1515 may include a force-sensitive resistor in
series with a fixed resistor or in lieu of a fixed resistor. The
resistor 1515 may include an ohmic material such as a resistive or
metal thin film. Alternatively, the resistor 1515 may include a
non-linear device such as a leaky diode or other device. According
to some implementations, the resistor 1515 may have a resistance
ranging from less than a few ohms to over 100 megaohms. In some
implementations, the leakage resistor 1545 may have a value on the
order of 100 kilohms or larger.
[0152] The switched capacitor configuration described with respect
to FIGS. 13 through 15B encompass what may be called digital
capacitive touch (DCT), in that a local capacitor near the
intersection of a row and a column of a DCT sensor array can be
digitally switched in or out, depending on whether a force-actuated
switch at the intersection is open or closed. The DCT array, in
some configurations, may serve as a fingerprint sensor, a stylus or
handwriting sensor, a touch sensor, or a combination thereof
without a corresponding PCT array. The DCT array, in some other
configurations, may be combined with a PCT array. In one such
configuration, one or more capacitive electrodes electrically
connected near each intersection between overlapping rows and
columns in an array surround a force-actuated capacitive switch
located at each intersection (for example, see FIG. 9B). The
combined sensor array may use the force-sensitive capacitive switch
for stylus detection and the PCT array for light touch or proximity
sensing. As noted above, the same PCT detection circuitry may be
used for detecting the application of force or pressure from the
pressing of a stylus, pen or finger in the DCT aspect, as well as
the light touch from a finger or stylus in the PCT aspect. As noted
earlier, the designations regarding rows and columns, the manner of
overlapping, the various aspect ratios, and other features are
intended to be illustrative and not limiting. For example, the rows
and columns may be interchanged, the column electrodes may pass
over or under the row electrodes, and the pitch or resolution may
be changed without loss of generality.
[0153] FIG. 16 shows an example of a flow diagram illustrating a
manufacturing process for a combined sensor device. FIGS. 17A-17D
show examples of partially formed combined sensor devices during
various stages of the manufacturing process of FIG. 16. According
to some implementations, block 1605 of the process 1600 involves
depositing a substantially transparent conductor, such as ITO, on
upper and lower substantially transparent substrates. In this
example, the lower substrate 910 is a glass substrate. However, in
alternative implementations, the lower substrate 910 may be formed
of plastic or a similar material. Some such implementations can
lend themselves to a roll-to-roll manufacturing process.
[0154] Block 1605 also may involve patterning the substantially
transparent conductive material into electrodes, using
photolithography and etching processes or other "additive"
processes such as plating, screen printing, etc. In some
implementations, this patterning process results in diamond
electrode shapes (or other shapes as appropriate), connected to one
another within columns or rows patterned on the upper substrate 905
and the lower substrate 910.
[0155] A resistive material may subsequently be deposited (e.g., by
sputter deposition) on at least some electrodes of the lower
substrate 910 and on or connected to the patterned electrodes, as
shown in block 1610. In alternative implementations, resistive
material may be deposited on at least some electrodes of the upper
substrate 905. The resistive material may be patterned to be in
series with all or a subset of the sensing locations on the
electrodes. According to some implementations, the resulting
resistors may have a resistance on the order of 1 megaohm; other
implementations may produce resistors having a smaller or greater
resistance such as between 100 kilohm and 10 megaohm.
[0156] The electrodes and resistors may be patterned in at least
two general ways, as shown in FIGS. 17A and 17B. A first option
(top view illustrated in FIG. 17A) is to form a serpentine resistor
1035 by patterning the lower electrode material or other resistive
material deposited on lower substrate 910 into a thin, narrow
sequence of one or more connected segments that conduct in the
plane of the film to achieve a sufficiently high resistance. A
conductive contact region 1036 formed from the lower electrode
material or other suitable material may be included at the end of
the resistor 1035. A second option (side view illustrated in FIG.
17B) is to pattern a vertical resistor 1035 directly on top of the
lower electrodes 1030, in which case the conduction path is through
the resistor in a direction substantially normal to the plane of
the film. In some implementations, a thin metal contact region 1037
may be included above the vertical resistor 1035.
[0157] Block 1615 of the process 1600 may involve depositing or
otherwise disposing the compressible layer 1025 on the lower
substrate 910. In some implementations, the compressible layer 1025
may be a patternable, thin (e.g., 1 to 10 microns) polymer with a
low elastic modulus, such as an elastomer. In some implementations
that include gaps in the compressible layer 1025 (such as those
discussed above with reference to FIGS. 10A-10C), the compressible
layer 1025 may be patterned such that the regions above the
resistors 1035 are opened up. FIG. 17C provides a cross-sectional
view of a portion of a combined sensor device 900 that has been
partially fabricated according to one such example. In some other
implementations, the regions above resistors 1035 that are opened
up may be filled with a force-sensitive resistor material (not
shown). In some other implementations with or without the FSR
material, an upper surface of vertical or serpentine resistors 1035
may be covered with a thin metal layer.
[0158] At this stage of the process 1600, the compressible layer
1025 has been patterned to expose the lower electrodes 1030 on
which the resistors 1035 have been formed. In some implementations
of the process 1600, FSR material may be formed on fingerprint
sensor electrodes of the lower substrate 910 (see optional block
1620), the handwriting and touch sensor electrodes of the lower
substrate 910, or both. FIG. 10D provides an example of the
force-sensitive resistor material 1085 formed on the lower
fingerprint electrodes 1040. The force-sensitive material may be
formed on the electrodes by methods such as dispensing, screening,
depositing, or patterning. Force-sensitive resistor material also
may be included on the handwriting and touch sensor electrodes of
the lower substrate 910 (not shown).
[0159] Subsequent to the patterning and curing (if needed) of the
compressible layer 1025, an additional thin layer of adhesive 1705
(such as .about.1-5 microns) may be applied on the surface of the
compressible layer 1025 (see optional block 1625) to improve
adhesion, taking care not to apply the adhesive on the top surface
of the resistors 1035. Methods to apply the adhesive include
photolithography, screen printing, squeegeeing, and dispensing. An
example of such an adhesive layer 1705 may be seen in FIG. 17D.
[0160] FIG. 17D depicts the apparatus after the upper substrate 905
has been joined to the compressible layer 1025. The upper substrate
905 may be formed of a substantially transparent material and may
have substantially transparent upper electrodes 1015 patterned on
the underside. The upper substrate 905 may, for example, be formed
of a plastic film such as polyethylene terephthalate (PET),
polyethylene naphthalate (PEN), polyimide, or a similar material.
In this example, the upper electrodes 1015 are made of ITO that has
been formed into rows that are continuous in the plane of FIG. 17D.
In alternative implementations, the upper electrodes 1015 as well
as the lower electrodes 1030 may be patterned into similarly-shaped
pads, connected as rows or columns. In some implementations, the
two substrates may be joined by bringing the upper substrate 905
into alignment with the lower substrate 910 and attaching the
layers via the adhesive 1705 that has been applied over the
compressible layer 1025. Other techniques may be used, such as hot
pressing the two layers together, mechanical clamping the periphery
of the substrates, or an adhesive-free method.
[0161] Implementations such as those depicted in FIGS. 17C and 17D
include air gaps in the compressible layer 1025 around the
electrodes on which resistors have been formed. Such air gaps are
depicted in areas 1065 of FIG. 17D. Air gaps can result in higher
levels of undesirable reflectance from the air-substrate
interfaces. Details are described above with reference to Equation
1. Accordingly, in some implementations, the air gap regions may be
spatially limited, so that the air gaps do not materially impact
the overall optical transmission of the stack. For example, the air
gap regions may be limited to an area in the range of 1-5% of the
total area of the sensor. Alternatively, the air gaps may be
limited to the region of the fingerprint imaging area only, which
may be a limited region of lower optical transmission, and
therefore may be on the cover glass but not directly above the
display area.
[0162] In alternative implementations, such as the examples
described with reference to FIGS. 10C and 10D, the compressible
layer 1025 also may be deposited on at least some of the lower
electrodes 1030 on which the resistors 1035 have been formed. In
some such implementations, there are no air gaps in the handwriting
and touch sensor zone 1005. However, other electrodes on which
resistors have been formed (such as in the fingerprint sensor zone
1010) may or may not have the compressible layer 1025 deposited on
them. In still other implementations, however, the fingerprint
sensor zone 1010 may include no air gaps. As shown in FIG. 10D,
such implementations may include FSR material 1085 in the
fingerprint sensor zone 1010. In some other implementations, the
FSR material 1085 also may be included above lower electrodes 1030
in the handwriting and touch sensor zone 1005, with or without
fixed vertical or serpentine resistors 1035.
[0163] Some implementations of the process 1600 involve a process
flow with relatively few masking steps. Some such implementations
involve two masking steps for depositing material on the lower
substrate 910 and a single masking step for depositing material on
the upper substrate 905. Structures may be formed on at least the
upper substrate 905 using roll-to-roll manufacturing processes. For
implementations wherein the lower substrate 910 is plastic or a
similar material, a roll-to-roll manufacturing process may be used
for depositing material on the lower substrate 910. In such
implementations, the lower substrate 910 may be thicker than the
upper substrate 905. In some examples, the upper substrate 905 may
be laminated onto the lower substrate 910 to form the sensor stacks
described above. The resultant combined sensor device 900 may be
inexpensive, light, thin and highly suitable for mobile and other
handheld electronic devices. In some implementations, this laminate
of an upper plastic layer and a lower plastic layer may be further
laminated onto or otherwise attached to a substantially transparent
and relatively more rigid substrate, such as a glass substrate. In
some implementations, the substantially transparent substrate may
be a display substrate such as the transparent substrate 20
described above.
[0164] In this implementation, block 1635 involves processing and
packaging. Block 1635 may involve the singulation of individual
combined sensor devices 900 from large substrates such as large
plates of glass or long rolls of plastic having multiple combined
sensor devices 900 formed thereon by cutting, cleaving, sawing, or
other suitable methods. Singulation of sensor devices from larger
substrates may be performed prior to block 1635, such as prior to
attaching the upper substrate (see block 1630) or prior to applying
adhesive to the compressible material (see block 1625). Block 1635
may involve configuring combined sensor devices 900 for electrical
communication with one or more sensor controllers, such as the
combined sensor controller 77 described below with reference to
FIG. 25B. Block 1635 may involve attaching combined sensor devices
900 to a display device 40 such as described elsewhere herein.
Block 1635 may involve packaging individual combined sensor devices
900 for shipment or storage.
[0165] FIG. 18A shows an example of a block diagram that
illustrates a high-level architecture of a combined sensor device.
In this example, a multi-touch sensor 1801, a high resolution
handwriting sensor 1803, and a fingerprint sensor 1805 are
integrated into the combined sensor device 900. A cover glass
included with the combined sensor device 900 can be overlaid onto
many displays, including but not limited to LCD, OLED and
reflective displays. Some such displays may be displays suitable
for mobile devices and some may be suitable for other devices, such
as consumer electronic devices, depending on the implementation.
The multi-touch sensor 1801, such as a PCT sensor, and the
high-resolution handwriting sensor 1803, such as a parallel-plate
capacitive displacement sensor or a DRT sensor, may be interleaved
at the intersection of rows and columns of an addressable sensor
device as described above with respect to FIGS. 9A and 9B and FIGS.
10A-10D. The fingerprint sensor 1805 with even higher resolution
may be included in a preselected region over a portion of the
display area, such as in the example shown in FIG. 12.
Alternatively, the multi-touch sensor 1801 and the high-resolution
handwriting sensor 1803 may serve as a fingerprint sensor 1805
anywhere above the display area when the combined sensor device has
sufficient resolution.
[0166] In the example shown in FIG. 18A, the control system 1807
includes at least one microcontroller 1809 and at least one
application processor 1810. In some implementations, hardware,
software and/or firmware for all sensors of the combined sensor
device 900 may be integrated on a single microcontroller 1809,
whereas in other implementations separate microcontrollers 1809 may
be used for touch sensing, handwriting sensing and fingerprint
sensing functionality. Applications for all sensors may be
integrated on a single application processor 1810 or on multiple
application processors 1810. These processors may reside, for
example, within a display device or within a mobile device.
[0167] Here, the sensors in the combined sensor device 900
communicate with the microcontroller 1809, which in turn
communicates with application processor 1810. The communication
between these devices may go in both directions. In some
implementations, the microcontroller 1809 drives the sensors of the
combined sensor device 900 and receives sense data from the
sensors. The application processor 1810 may be configured both to
monitor the output of the microcontroller 1809 and to send commands
to the microcontroller 1809. The microcontroller 1809 may, for
example, be located on the lower substrate 910, on an attached flex
cable, or on an electrically connected printed circuit board. In
some implementations, the microcontroller 1809 also may be
configured to control a display and/or to perform other
functions.
[0168] Some implementations may be provided via application
software stored in one or more tangible, machine-readable media.
Such media may be part of the applications processor 1810 or may be
separate media accessible by the applications processor 1810. The
application software may include instructions for controlling one
or more devices to perform various functions. For example, the
application software may include instructions to activate the
fingerprint sensor zone 1010 for fingerprint sensing only when
fingerprint sensing is needed. Otherwise, the fingerprint sensor
zone 1010 may be de-activated or activated for multi-touch and/or
handwriting functionality, depending on the implementation.
[0169] Alternatively, or additionally, the application software may
include instructions to reduce power consumption by turning off
sensors, turning off parts of the microcontroller 1809 and/or
employing first-level screening at a reduced frame rate on a
low-resolution sensor before activating power-hungry
higher-resolution sensors. For example, the application software
may include instructions for reducing power consumption by
aggregating sensels (or aggregating rows or columns of the combined
sensor device 900) electronically using the microcontroller 1809,
so that the combined sensor device 900 performs at a lower
resolution and may consume less power and provide a higher signal
until higher resolution is needed.
[0170] In some implementations, the combined sensor device 900 can
be configured to function in either a touch mode or a handwriting
mode (which also may be referred to herein as a stylus mode),
instead of being configured to function in both modes
simultaneously. It may be advantageous not to have the combined
sensor device 900 function in both modes simultaneously. For
example, when a user is writing on the combined sensor device 900
with a stylus, it may be preferable to avoid sensing the user's
palm or fingers that also may be resting on the device. Operating
the combined sensor device 900 to function as a handwriting sensor
may influence and/or interfere with the combined sensor device
900's functionality as a touch sensor, and vice versa. Accordingly,
some implementations provide separate drive and/or sense subsystems
for touch and handwriting mode functionality. Some implementations
provide drive and/or sense subsystems that may be switched quickly
between touch mode functionality and handwriting mode
functionality.
[0171] FIG. 18B shows an example of a block diagram that
illustrates a control system for a combined sensor device. In this
example, the control system 1807 includes a stylus drive circuit
1811 and a touch drive circuit 1813. When the combined sensor
device 900 is being operated in a handwriting mode, the stylus
drive circuit 1811 sends one or more drive signals 1814 to the
handwriting and touch sensor zone 1005. When the combined sensor
device 900 is being operated in a touch mode, the touch drive
circuit 1813 sends the drive signals 1814 to the handwriting and
touch sensor zone 1005. However, in some alternative
implementations, the drive signals 1814 are substantially the same
whether the combined sensor device 900 is being operated in a
handwriting mode or in a touch mode.
[0172] In this example, the control system 1807 includes a stylus
sense circuit 1815 and a touch sense circuit 1817. When the
combined sensor device 900 is being operated in a handwriting mode,
the stylus sense circuit 1815 processes one or more sense signals
1818 from the handwriting and touch sensor zone 1005. When the
combined sensor device 900 is being operated in a touch mode, the
touch sense circuit 1817 processes the sense signals 1818 from the
handwriting and touch sensor zone 1005. In some implementations,
the control system 1807 may include a single circuit that can be
switched from a touch configuration to a handwriting configuration.
Some examples are described below.
[0173] FIG. 18B also shows an example of a circuit diagram
representing components of a sensel 1819 in the handwriting and
touch sensor zone 1005. In this enlarged view of the sensel 1819,
the resistance of a switch 1823 is schematically depicted, as well
as the mutual capacitance 1824 between associated electrodes of the
sensel 1819.
[0174] FIG. 18C shows an example representation of physical
components and their electrical equivalents for a sensel in a
combined sensor device. In this example, the sensel 1819 includes a
switch 1823 formed in an overlapping region between a drive
electrode 1820 and a sense electrode 1821. The switch 1823 is
represented by a switch capacitance 1826 and a leakage resistance
1828 positioned between the drive electrode 1820 and the sense
electrode 1821 that accounts for small amounts of leakage current
that can flow through switch 1823 when the switch is open. The
leakage resistor 1828 may have a value on the order of 1 megaohms
or larger. A fixed resistor 1822 may be positioned between the
drive electrode 1820 and the sense electrode 1821, electrically
connected in series with the contacts of the sensel switch 1823.
The fixed resistor 1822 may be a serpentine resistor, a vertical
resistor, a high-resistivity film, a leaky diode, or other linear
or non-linear resistive element. The fixed resistor 1822 may be in
the range of a hundred kilohms to 10 megaohms or larger. In this
example, the switch 1823 includes a serpentine fixed resistor 1822,
which may be similar to the configuration depicted in FIG. 17A.
[0175] When the finger 1047, a stylus, etc., presses on the switch
1823, portions of the drive electrode 1820 are brought closer to
the sense electrode 1821, increasing a parallel capacitance 1832
between the drive electrode 1820 and the sense electrode 1821. A
sufficiently high applied pressure or force will close the switch
1823. The proximity of the finger 1047, a conductive stylus, etc.,
also may result in a change in inter-electrode mutual capacitances
1824 between adjacent drive electrodes 1820 and sense electrodes
1821.
[0176] FIG. 18D shows an example of an alternative sensel of a
combined sensor device. The configuration shown in FIG. 18D is
similar to that of FIG. 9B, which is described above. In this
example, the drive electrodes 1820 and the sense electrodes 1821
include diamond-shaped sections 1825 and narrow portions 1827. In
this example, the switches 1823 are formed in the overlapping
regions 925b (see also FIG. 9B).
[0177] The parallel capacitance 1832 is formed between the drive
electrode 1820 and the sense electrode 1821 in the overlapping
regions 925b. The total mutual capacitance of the sensel 1819 is
equal to the sum of each of the individual inter-electrode mutual
capacitances 1824 between adjacent drive electrodes 1820 and sense
electrodes 1821. In this example, the total mutual capacitance is
about four times the inter-electrode mutual capacitance. Each of
the diamond-shaped sections 1825 of the drive electrodes 1820 has a
sensel drive resistance 1853 and each of the diamond-shaped
sections 1825 of the sense electrodes 1821 has a sensel sense
resistance 1854.
[0178] FIG. 18E shows an example of a schematic diagram
representing equivalent circuit components of a sensel in a
combined sensor device. The axis 1829 represents various levels of
applied drive signals, such as the drive signals 1814 from the
stylus drive circuit 1811 or the touch drive circuit 1813 (for
example, see FIG. 18B). The axis 1831 represents various levels of
responsive sense signals, e.g., the sense signals 1818 to the
stylus sense circuit 1815 or the touch sense circuit 1817 of FIG.
18B.
[0179] Mutual capacitance component 1833 may represent the mutual
capacitance between the drive electrodes 1820 and the sense
electrode 1821 and the changes caused by the proximity of the
finger 1047, as shown in FIG. 18C. Parasitic capacitance component
1835 represents self-capacitance of an electrode, such as sense
electrode 1821 of FIG. 18C, and the changes caused by the proximity
of the finger 1047 or of another conductive body. Parallel
capacitance component 1836 represents the parallel-plate
capacitance, and changes such as that caused by the pressure of
finger 1047, a stylus, etc., causing the drive electrode 1820 to be
moved closer to the sense electrode 1821 of FIG. 18C. The position
of the switch 1823 represents the closure or non-closure of the
switch 1823. In one example, mutual capacitance component 1833 has
a value of about 0.5 pF; parasitic capacitance component 1835 has a
value between about 0.5 pF and 20 pF; parallel capacitance
component 1836 has a value of about 0.5 pF; and switch 1823 has a
value of about 10 gigaohm when open and about 1 kilohm when closed.
A person having ordinary skill in the art will readily understand
that other capacitance and resistance values are also possible
depending on the desired implementation. In some alternative
implementations, the switch 1823 will have a value of less than 100
ohms (such as when the fixed resistor is omitted) when closed. In
some other implementations, the switch 1823 will have a value
effectively equal to the fixed resistor when closed.
[0180] Some implementations described herein provide a single
circuit that can be switched between a touch mode configuration and
a handwriting mode configuration. For example, a single circuit may
be configured to perform the functions of the stylus sense circuit
1815 and the touch sense circuit 1817 of FIG. 18B.
[0181] FIG. 18F shows an example of an operational amplifier
circuit for a combined sensor device that may be configured for
handwriting or stylus mode sensing. When operating in handwriting
mode, the circuit 1837 is configured to function as an integrator
with reset capability. The circuit 1837 may be configured to
generate relatively large output voltages from the relatively small
input currents that result from handwriting sensing of the combined
sensor device 900 when one or more switches 1823 are closed.
[0182] In this example, the circuit 1837 includes an operational
amplifier 1839, a feedback capacitor 1841 and a feedback resistor
1843, as well as switches 1842 and 1844. In one example, the
feedback capacitor 1841 has a value between about 6 pF and 20 pF,
and the feedback resistor 1843 has a value of about 5 megaohm or
higher. However, the circuit 1837 may be implemented with other
capacitance and resistance values and have other configurations
that provide similar functionality. For example, alternative
implementations may include a transistor (such as a metal oxide
semiconductor field effect transistor (MOSFET)) operating in the
off state instead of feedback resistor 1843. Instead of the switch
1842, some implementations may include a lossy device such as a
high-value resistor or an NMOS or PMOS transistor with a known
resistance. Moreover, some implementations may include an
additional resistor in series with the switch 1842.
[0183] When operating in the stylus mode, the switch 1844 can be
left open and the switch 1842 can be opened and closed. The graphs
1845, 1847 and 1849 show examples of steady-state input current
operation. The graph 1845 indicates input current over time. In
this example, the current is held constant at a steady-state value
I.sub.ss. At time t.sub.1, the switch 1842 is opened. Referring to
the graph 1847, it may be seen that to open switch 1842, the
voltage applied to switch 1842 is changed to switch open voltage
1848. The switch open voltage 1848 may vary according to the
particular implementation. In some implementations, the switch open
voltage 1848 may be 1.8V, whereas in other implementations the
switch open voltage 1848 may be 3.3V, 5V, 10V, 20V or some other
voltage.
[0184] The graph 1849 indicates the output voltage that results
from opening the switch 1842. In this example, because the input
current is constant, the output voltage 1850a increases linearly
between time t.sub.1, when the switch 1842 is opened, and time
t.sub.2, when the switch 1842 is closed again. The time interval
(t.sub.2-t.sub.1) during which the switch 1842 is open may be, for
example, on the order of 0.1 to 10 .mu.sec, or even less. In this
example, the output voltage 1850a reaches a maximum output voltage
1851. Here, the maximum output voltage 1851 is opposite in sign
from the switch open voltage 1848 and has a lower absolute value
than the switch open voltage 1848. When the switch 1842 is closed
(at time t.sub.2), the capacitor 1841 may be discharged and the
output voltage 1850a is reset.
[0185] FIG. 18G shows an example of the operational amplifier
circuit of FIG. 18F configured for touch mode sensing. In this
configuration, the switch 1844 is closed, which allows the circuit
1837 to function as a charge amplifier for detecting changes in
mutual capacitance C.sub.m between adjacent drive electrodes 1820
and sense electrodes 1821 (for example, see FIGS. 18C and 18D). In
this example, drive signal 1852 is a square wave having a voltage
V.sub.drv.
[0186] An example of the resulting output voltage 1850b is shown in
FIG. 18G. The output voltage 1850b is not a linear response like
that of the output voltage 1850a, but instead is an inverted and
non-linear response to the leading and trailing edges of the drive
signal 1852. This response follows from the basic relationship
between the current into a capacitor I=C dV/dt, where I is the
current, C is the capacitance of the capacitor and dV/dt is the
derivative of voltage with respect to time.
[0187] A PCT sensor can exhibit shorted sensels when, for example,
a sensel is pressed with a finger or a stylus and the sensel switch
is closed. This condition has the potential to create
larger-than-normal signals that can saturate the operational
amplifier 1839 of the circuit 1837. While a saturated state can be
sensed and identified, saturation recovery time can be problematic
for array sensing systems. Amplifier recovery time is usually not
known with a high degree of confidence, typically being
characterized in a testing facility. If the operational amplifier
1839 remains saturated, subsequent sensel measurements may be
corrupted. Thus, recovery time can have a significant impact on the
achievable scan rate of a sensor array.
[0188] In addition, the circuit 1837 may have feedback components
with large time constants that also can contribute to a long
recovery period. In some implementations, the circuit 1837 may
include a large feedback resistor (such as the resistor 1843) to
provide DC feedback to stabilize the circuit 1837. A large feedback
resistor in parallel with the capacitor 1841 can create a larger
time constant that can inhibit sensor scan rates.
[0189] Accordingly, some implementations of the circuit 1837 are
configured to inhibit or prevent saturation of the operational
amplifier 1839. Some such implementations provide a low-impedance
path to bleed off charge of the capacitor 1841, allowing for fast
re-set of the circuit 1837 and/or fast recovery from a saturated
state of the operational amplifier 1839.
[0190] FIG. 18H shows an example of an operational amplifier
circuit for a combined sensor device that includes a clamp circuit.
The clamp circuit 1855 may be configured to inhibit or prevent
saturation of the operational amplifier 1839 by limiting the output
voltage of the circuit 1837. In this example, the clamp circuit
1855 is disposed in parallel with other components of the circuit
1837.
[0191] FIG. 18I shows examples of clamp circuit transfer functions.
The function 1857 is an ideal clamp circuit transfer function,
whereas the function 1859 is an example of an actual clamp circuit
transfer function. Both of the functions 1857 and 1859 indicate a
very high impedance while the clamp circuit 1855 is operating
within the clamp voltage range (V.sub.c-<V.sub.o<V.sub.+).
The clamp circuit 1855 may be configured with clamp voltages
V.sub.c- and V.sub.c+ with absolute values that are less than those
of the corresponding saturation voltages V.sub.sat- and
V.sub.sat+.
[0192] Within the clamp voltage range, the circuit 1837 can operate
in a touch mode with little or no influence from the clamp circuit
1855. When the operational amplifier is "clamped" (when V.sub.out
reaches or exceeds V.sub.c+ or V.sub.c-), the impedance of the
clamp circuit 1859 is very low, as shown by the significant
increase in the absolute value of I.sub.out. If the impedance of
the clamp circuit 1855 is made very low, this essentially shorts
the feedback components of the circuit 1837, thereby allowing the
feedback capacitor 1841 to discharge (see FIG. 18H).
[0193] FIG. 18J shows an example of a circuit diagram for a clamp
circuit. In the configuration depicted in FIG. 18J, the clamp
circuit 1855 includes n diodes 1861 arranged in series and having a
first forward direction. The diodes 1861 are disposed in parallel
with the diodes 1863. In this example, there are n diodes 1863
arranged in series and having a second forward direction that is
opposite to that of the diodes 1861. In some implementations, the
forward voltage of each of the diodes 1861 and 1863 may be on the
order of 1V or less, e.g., 0.2V, 0.3V or 0.6V. The value of n, as
well as the forward voltage of the diodes 1861 and 1863, may vary
according to the implementation. The clamp circuit transfer
function of a clamp circuit 1855 having a relatively larger number
of diodes, each with a relatively lower forward voltage, will
approximate an ideal clamp circuit transfer function more closely
than a clamp circuit 1855 having a relatively smaller number of
diodes, each with a relatively higher forward voltage.
[0194] However, the clamp circuit 1855 may be configured in various
other ways. In some alternative implementations, at least one of
the diodes 1861 and 1863 may be a Zener diode. In some such
implementations, one of the diodes 1861 is a Zener diode having a
first forward direction and one of the diodes 1863 is a Zener diode
having a second and opposing forward direction. In some such
implementations, each of the Zener diodes may be paired, in series,
with a Schottky diode having an opposing forward direction. In some
implementations, the Schottky diodes may have forward voltage drops
of about 0.2V or 0.3V. The Zener breakdown voltage of the
corresponding Zener diodes may be substantially higher. For
example, in a .+-.5V analog system, the Zener breakdown voltage may
be 4.2V in one implementation.
[0195] In some implementations described herein, the lower
substrate may form at least a portion of the cover glass apparatus
of a display device. In some such implementations, the signal lines
may be formed on the upper surface of the cover glass, rather than
underneath the cover glass. Such a configuration has implications
for the design of the sensing elements in the array, because these
elements may be routed outside the array and attached to integrated
circuits (ICs) that are configured to address and sense the signals
from the various sensing elements in the array.
[0196] Previous approaches (such as covering these routing wires or
attaching ICs on the top side of the cover glass and covering them
with black border epoxy) may not be optimal. One reason is that the
epoxy may result in topography on the touch surface that may be
felt by the user.
[0197] Accordingly, some implementations described herein provide
novel routing configurations. Some implementations involve the use
of a flexible upper substrate 905 of a combined sensor device 900
as a platform for direct attachment of one or more ICs, including
but not limited to ASICs. The flexible upper substrate 905 may be
wrapped around the edge of the lower substrate 910 (the edge of a
glass substrate or another such substantially transparent
substrate). Some such implementations involve wrapping the sensing
wires and routing leads, and attaching ICs to these leads in a
manner that enables the cover glass to extend all the way to the
edge of a mobile display device, such as a smart phone device. The
IC(s) may be directly attached to the wrap-around portion of the
upper substrate 905, thus enabling a minimal edge border on the
device, eliminating or minimizing the need for a bezel, and
reducing cost by integrating the cover layer and flexible printed
circuit. Some such implementations may not result in a topography
that can be felt by a user.
[0198] Some examples will now be described with reference to FIGS.
19 through 21B. FIG. 19 shows an example of a cross-section of a
portion of an alternative combined sensor device. In this
implementation, the lower substrate 910 is formed of glass and the
upper substrate 905 is formed of a flexible and substantially
transparent material, such as a clear polyimide. Here, conductive
material (metallization in this example) has been patterned into
the upper electrodes 1015 on the upper substrate 905. The upper
electrodes 1015 on the underside of the upper substrate 905 may be
used to route the sensor's signal lines. The portion 1910 of the
upper substrate 905 (which is not drawn to scale) may be configured
to wrap around the edge of the lower substrate 910 in some
implementations, such as the implementation shown in FIG. 21B. In
the example shown in FIG. 19, the lower electrodes 1030 on the
lower substrate 910 may be bonded electrically to upper electrodes
1015 or other electrical traces or circuitry on the upper substrate
905 using an anisotropic conductive film (ACF) 1905 or a similar
connection scheme.
[0199] FIG. 20 shows an example of a top view of routing for a
combined sensor device. The combined sensor device 900 illustrated
in FIG. 20 includes both flex-on-glass (FOG) 2005 and chip-on-flex
(COF) 2010a configurations. FIG. 20 also indicates the handwriting
and touch sensor zone 1005 and the fingerprint sensor zone 1010 of
the combined sensor device 900. A ground ring 2015 may be included
around portions of the handwriting, touch and fingerprint sensor
zones 1005 and 1010 to isolate noise coupling from the system and
to minimize false touches. While fingerprint sensor zone 1010 is
shown as physically distinct from handwriting and touch sensor zone
1005, in some implementations with sufficiently high resolution in
the handwriting and touch zone, the two zones merge and are
indistinguishable. Software may be used to allocate a portion of
the combined sensor device 900 for fingerprint detection. When
combined with an underlying display device, the software may be
used to display a box or other suitable designator for prompting a
user where (and when) to place a finger on the sensor device.
[0200] FIG. 21A shows an example of a cross-sectional view of the
device through the combined sensor device shown in FIG. 20. In this
example, the upper substrate 905 is bonded to the lower substrate
910 with the adhesive layer 1705. An additional COF 2010b may be
seen in this view of the combined sensor device 900. Additional
components such as passive devices (not shown) and connective
traces for signals, power, ground, and external connectors may be
included on an extended portion of the upper substrate 905 along
with a controller or other integrated circuits such as COF 2010a
and 2010b. Electrical or connective vias (not shown) may be
included in the flexible upper substrate 905 to aid in connectivity
of any electrical and electronic components. A stiffener 2120 such
as a Kapton.RTM. tape may be attached to an extended portion of
upper substrate 905.
[0201] FIG. 21B shows an example of a cross-sectional view of a
wrap-around implementation. In the combined sensor device 900
illustrated in FIG. 21B, the flexible upper substrate 905 is
wrapped around the edge of the lower substrate 910. FIG. 21B
depicts the connection of IC 2105, which is an ASIC in this
example, to the upper electrodes 1015 on the inside (lower side) of
the upper substrate 905. The IC 2105 may, for example, be
configured for controlling the combined sensor device 900 to
provide touch sensor, handwriting sensor and/or fingerprint sensor
functionality. An electrical connector 2110 is attached to the
upper electrodes 1015 or to other traces on one or both sides of
upper substrate 905 in this example. A bezel 2115 is shown in FIG.
21B. However, other implementations may not include the bezel
2115.
[0202] Here, the signal lines that address the electrodes on the
lower substrate 910 are routed and connected to corresponding upper
electrodes 1015 on the underside of the flexible upper substrate
905. According to some such implementations, both the cost and the
complexity of the combined sensor device 900 may be reduced by
integrating the functionality of the flexible upper substrate 905
with that of a flexible printed circuit.
[0203] Using devices such as those described above, an array of
applications can be enabled. Some such implementations involve
using a mobile handheld device as a user authentication-based
secure gateway to enable transactions and/or physical access. Some
implementations involve using a fingerprint sensor as part of a
user authentication system, such as for commercial or banking
transactions. In some implementations, a handwriting input function
may be used for signature recognition and related applications.
Alternatively, or additionally, some implementations involve using
the handwriting input feature to automatically capture notes and
stylus input from people in an enterprise, such as students an
educational setting, employees in a corporate setting, etc.
[0204] For example, there is a growing trend to enable use of a
mobile device for commercial transactions, in a manner similar to
that in which a credit card is used. In this usage model, a user
may simply input a PIN number into a cellular telephone that is
equipped with a communication interface such as Near Field
Communication (NFC) configured to communicate with payment
terminals.
[0205] One challenge with this model is that of user
authentication. PINS and passwords may be ineffective for
preventing unauthorized access. A stolen mobile device or cellular
telephone could result in improper usage of the device or phone for
credit or debit transactions.
[0206] Some implementations provided herein relate to the use of a
built-in fingerprint sensor, such as the fingerprint sensor of the
combined sensor device 900, to enable local user authentication.
FIG. 22 shows an example of a flow diagram illustrating a
fingerprint-based user authentication process. The process 2200 may
involve using a cellular telephone as a fingerprint-based user
authentication system to enable transactions and/or physical
access.
[0207] According to some such implementations, the user may be
enrolled on a mobile device, such as a cellular telephone, by
providing one or more fingerprints. In some such implementations,
the mobile device includes a combined sensor device 900.
Alternatively, or additionally, the user may provide handwriting
data. The fingerprint and/or handwriting data may be encrypted and
stored securely within the mobile device. However, some alternative
implementations provide for authentication by a remote device, such
as a server. Such implementations may involve storing the
fingerprint and/or handwriting data in a remote device. Moreover,
some implementations involve acquiring fingerprint and/or
handwriting data from more than one person, so that more than one
person may be authenticated using the same mobile device.
[0208] During an authentication process, the user provides
fingerprint and/or handwriting data to the mobile device, such as
through one or more sensors integrated in a cover glass apparatus
of the mobile device (block 2205). The user may do so, for example,
when the user wishes to make a commercial transaction using the
mobile device. The obtained fingerprint and/or handwriting data may
be processed securely, either within the mobile device or via a
remote device such as an authentication server, and compared to the
previously enrolled and stored fingerprint and/or handwriting data
(block 2210). In block 2210, the mobile device or the
authentication server determines whether there is a match between
the obtained fingerprint and/or handwriting data and the stored
fingerprint and/or handwriting data.
[0209] If and only if there is a match will the transaction be
permitted. If no match is found in block 2215, the process 2200 may
allow the user to try again, e.g., for a limited number of times
(block 2220). If the user cannot provide matching fingerprint
and/or handwriting data within this number of times, the process
may end (block 2230). In some implementations, the mobile device or
the authentication server may send a notification to, e.g., a
financial institution and/or to local governmental authorities if
improper data is received. In this example, either the mobile
device or the authentication server is configured to send an
authorization signal to another device if the transaction is
permitted (block 2225). Examples of such devices include the mobile
device 40 and the payment terminal 2310 shown in FIG. 23A.
[0210] FIG. 23A shows an example of a mobile device that may be
configured for making commercial transactions. In this example, the
mobile device is a fingerprint-secured cellular telephone that is
configured for wireless communication with the payment terminal
2310, such as via NFC. The cellular telephone is an instance of the
display device 40, described elsewhere herein, and may include a
combined sensor device 900 such as that described above.
Alternatively, the cellular telephone may include a fingerprint
sensor zone 1010 that is not part of a combined sensor device
900.
[0211] According to some implementations, a user may provide
fingerprint data to the mobile device according to a process such
as that described above with reference to FIG. 22. If there is a
match between the stored and recently-provided fingerprint data,
the transaction can be permitted. For example, the payment terminal
2310 of FIG. 23A may send a signal to a corresponding device of a
financial institution indicating that a payment should be
authorized. The financial institution may or may not approve the
payment, depending on factors such as the availability of funds or
credit. FIG. 23A shows a mobile device used to authorize a payment
at a payment terminal in physical proximity to the phone. In some
other implementations, the mobile device can be used to authorize
payments made remotely, such as an e-commerce transaction made via
a web browser or other application running on the mobile device, or
to authorize a payment made through a separate system, such as an
e-commerce transaction made via a web browser or other application
running on a personal computer under the control of a user.
Referring to FIGS. 22 and 23A, the authorization signal of block
2225 can be used to control the release of data on the mobile
device itself, such as a control bit to authorize transmission of
payment or credit card information to payment terminal 2310. In
another implementation, the authorization signal of block 2225 may
be sent to another device or process server, such as a device or
server of a financial institution indicating that a payment should
be authorized.
[0212] Many physical facilities in corporate and government
locations are secured electronically, and are accessed using
wireless radio frequency identification (RFID) cards, key fobs,
etc., that operate on specific wireless frequencies, such as 128
kHz. These are short-range devices that draw energy by inductively
coupling power from a card reader or a similar device located near
a door. If an RFID card or key fob falls into the wrong hands,
security could be compromised at these access points.
[0213] Instead of using a separate RFID card or key fob, some
implementations involve the use of a fingerprint-secured mobile
device, such as a fingerprint-secured cellular telephone, to gain
access to such physical facilities. FIG. 23B shows an example of
using of a fingerprint-secured mobile device for physical access
applications. The mobile device is an instance of the display
device 40, described elsewhere herein, and may include a combined
sensor device 900.
[0214] In some such implementations, a fingerprint-secured mobile
device may be used for opening an NFC-enabled access point 2320,
such as a door 2315 of a building, an automobile, a locker, a safe,
etc., that may be electronically locked. In some implementations,
the access point may be configured for communication with other
devices, such as an authentication server, via a network. The
fingerprint sensor zone 1010 of the mobile device 40 may be used to
implement (at least in part) an authentication process for the user
before the mobile device 40 initiates its communications with the
access point 2320. The authentication procedure may be similar to
that described above for the secure payment gateway; however, the
application enabled is that of physical access, rather than a
transaction.
[0215] Mobile devices are becoming a ubiquitous means for storage,
transmission, and playback of documents, music, videos, and other
digital assets. In order to preserve digital and other rights, and
to prevent unauthorized access, distribution and copying of such
digital assets, some implementations involve the use of a
fingerprint sensor and/or a handwriting sensor to be "married" to
the asset in question. In this manner, only the person (or persons)
authorized to access the digital asset can access the asset through
the use of the fingerprint sensor and/or the handwriting sensor,
which may be sensors of a combined sensor device 900 described
herein.
[0216] In many enterprises, including corporate, government,
educational and other settings, it may be beneficial to have an
individual write notes on the screen of a mobile device. A device
such as a tablet with a large screen can substitute as a notepad,
allowing meeting notes, interactive discussions between colleagues
and other important discoveries to be automatically captured. One
such device is depicted in FIG. 24A.
[0217] FIG. 24A shows an example of a secure tablet device. The
tablet device 2400a of FIG. 24A may be configured for wireless
communication with a network, such as a network maintained by an
enterprise. The tablet device 2400a may include a combined sensor
device 900 such as described elsewhere herein. Such network
communications can facilitate storage of information captured by
the tablet device 2400a on an enterprise's database of documents.
Due to the often confidential and private nature of the information
contained within these devices, access to such tablets and phones
should be restricted only to the authorized user(s). Otherwise,
loss of such devices can result in unauthorized usage and
compromise of the data contained within.
[0218] Some such implementations provide access control according
to a handwriting recognition process and/or a fingerprint
recognition process. Access to the tablet device 2400a may be
controlled according to an analysis of a user's handwriting on the
tablet device 2400a and/or according to fingerprint data received
from a fingerprint sensor provided on the cover glass apparatus, as
described above. In the example depicted in FIG. 24A, the stylus
tip 1105 can be used to provide the handwriting data 2410 via the
tablet device 2400a. Such data may be used for an authentication
process similar to that described above with reference to FIG.
22.
[0219] FIG. 24B shows an example of an alternative secure tablet
device. The screen of the tablet device 2400b illustrated in FIG.
24B may act as the handwriting input device or notepad. The tablet
device 2400b may include a combined sensor device 900 such as
described elsewhere herein. As shown in FIG. 24B, access to the
tablet device 2400b may be controlled according to a handwriting
authentication procedure: here, the stylus tip 1105 can be used to
provide the handwriting data 2410. Alternatively, or additionally,
access to the tablet device 2400b may be controlled according to a
fingerprint authentication procedure using fingerprint data
acquired via the fingerprint sensor zone 1010. The tablet device
2400b may or may not be configured for finger touch sensing,
depending on the particular implementation. Information may be
automatically captured on the screen and, in some implementations,
may be wirelessly synchronized with an enterprise's database.
Alternatively, or additionally, such data can be stored locally.
Some such data may subsequently be synchronized with the
enterprise's database, such as through a wired or wireless
interface.
[0220] FIGS. 25A and 25B show examples of system block diagrams
illustrating a display device that includes a combined sensor
device. The display device 40 can be, for example, a smart phone, a
cellular phone, or a mobile telephone. However, the same components
of the display device 40 or slight variations thereof are also
illustrative of various types of display devices such as
televisions, tablets, e-readers, hand-held devices and portable
media players.
[0221] The display device 40 includes a housing 41, a display 30, a
combined sensor device 900, an antenna 43, a speaker 45, an input
device 48, and a microphone 46. The housing 41 can be formed from
any of a variety of manufacturing processes, including injection
molding, and vacuum forming. In addition, the housing 41 may be
made from any of a variety of materials, including, but not limited
to: plastic, metal, glass, rubber, and ceramic, or a combination
thereof. The housing 41 can include removable portions (not shown)
that may be interchanged with other removable portions of different
color, or containing different logos, pictures, or symbols.
[0222] The display 30 may be any of a variety of displays,
including a bi-stable or analog display, as described herein. The
display 30 also can be configured to include a flat-panel display,
such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel
display, such as a CRT or other tube device. In addition, the
display 30 can include an interferometric modulator display, as
described herein. The combined sensor device 900 may be a device
substantially as described herein.
[0223] The components of the display device 40 are schematically
illustrated in FIG. 25B. The display device 40 includes a housing
41 and can include additional components at least partially
enclosed therein. For example, the display device 40 includes a
network interface 27 that includes an antenna 43 which is coupled
to a transceiver 47. The network interface 27 may be a source for
image data that could be displayed on the display device 40.
Accordingly, the network interface 27 is one example of an image
source module. The transceiver 47 is connected to a processor 21,
which is connected to conditioning hardware 52. The conditioning
hardware 52 may be configured to condition a signal (e.g., filter a
signal). The conditioning hardware 52 is connected to a speaker 45
and a microphone 46. The processor 21 is also connected to an input
device 48 and a driver controller 29. The driver controller 29 is
coupled to a frame buffer 28, and to an array driver 22, which in
turn is coupled to a display array 30. In some implementations, a
power supply 50 can provide power to substantially all components
in the particular display device 40 design.
[0224] In this example, the display device 40 also includes a
combined sensor controller 77. The combined sensor controller 77
may be configured for communication with the combined sensor device
900 and/or configured for controlling the combined sensor device
900. The combined sensor controller 77 may be configured to
determine a touch location of a finger, a conductive or
non-conductive stylus, etc., proximate the combined sensor device
900. The combined sensor controller 77 may be configured to make
such determinations based, at least in part, on detected changes in
capacitance in the vicinity of the touch location. The combined
sensor controller 77 also may be configured to function as a
handwriting sensor controller and/or as a fingerprint sensor
controller. The combined sensor controller 77 may be configured to
supply touch sensor, handwriting sensor, fingerprint sensor and/or
user input signals to the processor 21.
[0225] Although the combined sensor controller 77 is depicted in
FIG. 25B as being a single device, the combined sensor controller
77 may be implemented in one or more devices. In some
implementations, separate sensor controllers may be configured to
provide touch, handwriting and fingerprint sensing functionality.
Such sensor controllers may, for example, be implemented in
separate integrated circuits. In some such implementations, the
addressing and/or measurement circuitry for touch mode, handwriting
mode and/or fingerprint sensing mode may be contained within one or
more controller or driver ASIC chips. In some alternative
implementations, however, the processor 21 (or another such device)
may be configured to provide some or all such sensor controller
functionality.
[0226] The network interface 27 includes the antenna 43 and the
transceiver 47 so that the display device 40 can communicate with
one or more devices over a network. The network interface 27 also
may have some processing capabilities to relieve, for example, data
processing requirements of the processor 21. The antenna 43 can
transmit and receive signals. In some implementations, the antenna
43 transmits and receives RF signals according to the IEEE 16.11
standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11
standard, including IEEE 802.11a, b, g, n, and further
implementations thereof. In some other implementations, the antenna
43 transmits and receives RF signals according to the BLUETOOTH
standard. In the case of a cellular telephone, the antenna 43 is
designed to receive code division multiple access (CDMA), frequency
division multiple access (FDMA), time division multiple access
(TDMA), Global System for Mobile communications (GSM), GSM/General
Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE),
Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA),
Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev
B, High Speed Packet Access (HSPA), High Speed Downlink Packet
Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved
High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS,
or other known signals that are used to communicate within a
wireless network, such as a system utilizing 3G or 4G technology.
The transceiver 47 can pre-process the signals received from the
antenna 43 so that they may be received by and further manipulated
by the processor 21. The transceiver 47 also can process signals
received from the processor 21 so that they may be transmitted from
the display device 40 via the antenna 43.
[0227] In some implementations, the transceiver 47 can be replaced
by a receiver. In addition, in some implementations, the network
interface 27 can be replaced by an image source, which can store or
generate image data to be sent to the processor 21. The processor
21 can control the overall operation of the display device 40. The
processor 21 receives data, such as compressed image data from the
network interface 27 or an image source, and processes the data
into raw image data or into a format that is readily processed into
raw image data. The processor 21 can send the processed data to the
driver controller 29 or to the frame buffer 28 for storage. Raw
data typically refers to the information that identifies the image
characteristics at each location within an image. For example, such
image characteristics can include color, saturation, and gray-scale
level.
[0228] The processor 21 can include a microcontroller, CPU, or
logic unit to control operation of the display device 40. The
conditioning hardware 52 may include amplifiers and filters for
transmitting signals to the speaker 45, and for receiving signals
from the microphone 46. The conditioning hardware 52 may be
discrete components within the display device 40, or may be
incorporated within the processor 21 or other components.
[0229] The driver controller 29 can take the raw image data
generated by the processor 21 either directly from the processor 21
or from the frame buffer 28 and can re-format the raw image data
appropriately for high speed transmission to the array driver 22.
In some implementations, the driver controller 29 can re-format the
raw image data into a data flow having a raster-like format, such
that it has a time order suitable for scanning across the display
array 30. Then the driver controller 29 sends the formatted
information to the array driver 22. Although a driver controller
29, such as an LCD controller, is often associated with the system
processor 21 as a stand-alone Integrated Circuit (IC), such
controllers may be implemented in many ways. For example,
controllers may be embedded in the processor 21 as hardware,
embedded in the processor 21 as software, or fully integrated in
hardware with the array driver 22.
[0230] The array driver 22 can receive the formatted information
from the driver controller 29 and can re-format the video data into
a parallel set of waveforms that are applied many times per second
to the hundreds, and sometimes thousands (or more), of leads coming
from the display's x-y matrix of pixels.
[0231] In some implementations, the driver controller 29, the array
driver 22, and the display array 30 are appropriate for any of the
types of displays described herein. For example, the driver
controller 29 can be a conventional display controller or a
bi-stable display controller (such as an IMOD controller).
Additionally, the array driver 22 can be a conventional driver or a
bi-stable display driver (such as an IMOD display driver).
Moreover, the display array 30 can be a conventional display array
or a bi-stable display array (such as a display including an array
of IMODs). In some implementations, the driver controller 29 can be
integrated with the array driver 22. Such an implementation can be
useful in highly integrated systems, for example, mobile phones,
portable-electronic devices, watches or other small-area
displays.
[0232] In some implementations, the input device 48 can be
configured to allow, for example, a user to control the operation
of the display device 40. The input device 48 can include a keypad,
such as a QWERTY keyboard or a telephone keypad, a button, a
switch, a rocker, a touch-sensitive screen, a touch-sensitive
screen integrated with the display array 30, or a pressure- or
heat-sensitive membrane. The microphone 46 can be configured as an
input device for the display device 40. In some implementations,
voice commands through the microphone 46 can be used for
controlling operations of the display device 40.
[0233] The power supply 50 can include a variety of energy storage
devices. For example, the power supply 50 may include a
rechargeable battery, such as a nickel-cadmium battery or a
lithium-ion battery. In implementations using a rechargeable
battery, the rechargeable battery may be chargeable using power
coming from, for example, a wall socket of a photovoltaic device or
array. Alternatively, the rechargeable battery can be wirelessly
chargeable. The power supply 50 also can include a renewable energy
source, a capacitor, or a solar cell, including a plastic solar
cell or solar-cell paint. The power supply 50 also can be
configured to receive power from a wall outlet.
[0234] In some implementations, control programmability resides in
the driver controller 29 which can be located in several places in
the electronic display system. In some other implementations,
control programmability resides in the array driver 22. The
above-described optimization may be implemented in any number of
hardware and/or software components and in various configurations.
The various illustrative logics, logical blocks, modules, circuits
and algorithm steps described in connection with the
implementations disclosed herein may be implemented as electronic
hardware, computer software, or combinations of both. The
interchangeability of hardware and software has been described
generally, in terms of functionality, and illustrated in the
various illustrative components, blocks, modules, circuits and
steps described above. Whether such functionality is implemented in
hardware or software depends upon the particular application and
design constraints imposed on the overall system.
[0235] The hardware and data processing apparatus used to implement
the various illustrative logics, logical blocks, modules and
circuits described in connection with the aspects disclosed herein
may be implemented or performed with a general purpose single- or
multi-chip processor, a digital signal processor (DSP), an
application specific integrated circuit (ASIC), a field
programmable gate array (FPGA) or other programmable logic device,
discrete gate or transistor logic, discrete hardware components, or
any combination thereof designed to perform the functions described
herein. A general purpose processor may be a microprocessor, or,
any conventional processor, controller, microcontroller, or state
machine. A processor also may be implemented as a combination of
computing devices, such as a combination of a DSP and a
microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration. In some implementations, particular steps and
methods may be performed by circuitry that is specific to a given
function.
[0236] In one or more aspects, the functions described may be
implemented in hardware, digital electronic circuitry, computer
software, firmware, including the structures disclosed in this
specification and their structural equivalents thereof, or in any
combination thereof. Implementations of the subject matter
described in this specification also can be implemented as one or
more computer programs, i.e., one or more modules of computer
program instructions, encoded on a computer storage media for
execution by, or to control the operation of, data processing
apparatus.
[0237] If implemented in software, the functions may be stored on
or transmitted over as one or more instructions or code on a
computer-readable medium. The steps of a method or algorithm
disclosed herein may be implemented in a processor-executable
software module which may reside on a computer-readable medium.
Computer-readable media includes both computer storage media and
communication media including any medium that can be enabled to
transfer a computer program from one place to another. A storage
media may be any available media that may be accessed by a
computer. By way of example, and not limitation, such
computer-readable media may include RAM, ROM, EEPROM, CD-ROM or
other optical disk storage, magnetic disk storage or other magnetic
storage devices, or any other medium that may be used to store
desired program code in the form of instructions or data structures
and that may be accessed by a computer. Also, any connection can be
properly termed a computer-readable medium. Disk and disc, as used
herein, includes compact disc (CD), laser disc, optical disc,
digital versatile disc (DVD), floppy disk, and blu-ray disc where
disks usually reproduce data magnetically, while discs reproduce
data optically with lasers. Combinations of the above also may be
included within the scope of computer-readable media. Additionally,
the operations of a method or algorithm may reside as one or any
combination or set of codes and instructions on a machine readable
medium and computer-readable medium, which may be incorporated into
a computer program product.
[0238] Various modifications to the implementations described in
this disclosure may be readily apparent to those skilled in the
art, and the generic principles defined herein may be applied to
other implementations without departing from the spirit or scope of
this disclosure. Thus, the claims are not intended to be limited to
the implementations shown herein, but are to be accorded the widest
scope consistent with this disclosure, the principles and the novel
features disclosed herein. The word "exemplary" is used exclusively
herein to mean "serving as an example, instance, or illustration."
Any implementation described herein as "exemplary" is not
necessarily to be construed as preferred or advantageous over other
possibilities or implementations. Additionally, a person having
ordinary skill in the art will readily appreciate, the terms
"upper" and "lower" are sometimes used for ease of describing the
figures, and indicate relative positions corresponding to the
orientation of the figure on a properly oriented page, and may not
reflect the proper orientation of an IMOD as implemented.
[0239] Certain features that are described in this specification in
the context of separate implementations also can be implemented in
combination in a single implementation. Conversely, various
features that are described in the context of a single
implementation also can be implemented in multiple implementations
separately or in any suitable subcombination. Moreover, although
features may be described above as acting in certain combinations
and even initially claimed as such, one or more features from a
claimed combination can in some cases be excised from the
combination, and the claimed combination may be directed to a
subcombination or variation of a subcombination.
[0240] Similarly, while operations are depicted in the drawings in
a particular order, a person having ordinary skill in the art will
readily recognize that such operations need not be performed in the
particular order shown or in sequential order, or that all
illustrated operations be performed, to achieve desirable results.
Further, the drawings may schematically depict one more example
processes in the form of a flow diagram. However, other operations
that are not depicted can be incorporated in the example processes
that are schematically illustrated. For example, one or more
additional operations can be performed before, after,
simultaneously, or between any of the illustrated operations. In
certain circumstances, multitasking and parallel processing may be
advantageous. Moreover, the separation of various system components
in the implementations described above should not be understood as
requiring such separation in all implementations, and it should be
understood that the described program components and systems can
generally be integrated together in a single software product or
packaged into multiple software products. Additionally, other
implementations are within the scope of the following claims. In
some cases, the actions recited in the claims can be performed in a
different order and still achieve desirable results.
* * * * *