U.S. patent application number 16/006640 was filed with the patent office on 2018-12-27 for ultrasonic fingerprint sensor for under-display applications.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Ila Ravindra Badge, Nicholas Ian Buchan, David William Burns, Kostadin Dimitrov Djordjev, Leonard Eugene Fennell, Suryaprakash Ganti, Tsongming Kao, Yipeng Lu, Hrishikesh Vijaykumar Panchawagh, Firas Sammoura, Jessica Liu Strohmann, Chin-Jen Tseng.
Application Number | 20180373913 16/006640 |
Document ID | / |
Family ID | 64693310 |
Filed Date | 2018-12-27 |
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United States Patent
Application |
20180373913 |
Kind Code |
A1 |
Panchawagh; Hrishikesh Vijaykumar ;
et al. |
December 27, 2018 |
ULTRASONIC FINGERPRINT SENSOR FOR UNDER-DISPLAY APPLICATIONS
Abstract
Disclosed are methods, devices, apparatuses, and systems for an
under-display ultrasonic fingerprint sensor. A display device may
include a platen, a display underlying the platen, and an
ultrasonic fingerprint sensor underlying the display, where the
ultrasonic fingerprint sensor is configured to transmit and receive
ultrasonic waves via an acoustic path through the platen and the
display. A light-blocking layer and/or an electrical shielding
layer may be provided between the ultrasonic fingerprint sensor and
the display, where the light-blocking layer and/or the electrical
shielding layer are in the acoustic path. A mechanical stress
isolation layer may be provided between the ultrasonic fingerprint
sensor and the display, where the mechanical stress isolation layer
is in the acoustic path.
Inventors: |
Panchawagh; Hrishikesh
Vijaykumar; (Cupertino, CA) ; Badge; Ila
Ravindra; (San Jose, CA) ; Lu; Yipeng; (Davis,
CA) ; Djordjev; Kostadin Dimitrov; (Los Gatos,
CA) ; Ganti; Suryaprakash; (Los Altos, CA) ;
Tseng; Chin-Jen; (Fremont, CA) ; Buchan; Nicholas
Ian; (San Jose, CA) ; Kao; Tsongming;
(Sunnyvale, CA) ; Fennell; Leonard Eugene; (San
Jose, CA) ; Sammoura; Firas; (Dublin, CA) ;
Strohmann; Jessica Liu; (Cupertino, CA) ; Burns;
David William; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
64693310 |
Appl. No.: |
16/006640 |
Filed: |
June 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62525154 |
Jun 26, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2251/5338 20130101;
G01S 7/52079 20130101; H01L 51/0097 20130101; B06B 1/0677 20130101;
G01S 15/8925 20130101; G01S 15/8913 20130101; H01L 27/3234
20130101; G06K 9/0002 20130101; H01L 27/3225 20130101 |
International
Class: |
G06K 9/00 20060101
G06K009/00; G01S 15/89 20060101 G01S015/89; G01S 7/52 20060101
G01S007/52; H01L 27/32 20060101 H01L027/32; H01L 51/00 20060101
H01L051/00; B06B 1/06 20060101 B06B001/06 |
Claims
1. An apparatus comprising: a display; an ultrasonic sensor system
underlying the display and configured to transmit and receive
ultrasonic waves in an acoustic path through the display; a
light-blocking layer between the ultrasonic sensor system and the
display, the light-blocking layer positioned in the acoustic path;
and an adhesive layer between the display and the ultrasonic sensor
system, the adhesive layer positioned in the acoustic path and
configured to allow the ultrasonic sensor system to be separated
from the display.
2. The apparatus of claim 1, further comprising: an electrical
shielding layer between the ultrasonic sensor system and the
display, the electrical shielding layer being electrically
conductive and grounded, the electrical shielding layer positioned
in the acoustic path.
3. The apparatus of claim 2, wherein each of the electrical
shielding layer and the light-blocking layer is non-porous or
substantially non-porous.
4. The apparatus of claim 2, wherein the light-blocking layer
includes an opaque plastic material and the electrical shielding
layer includes a metal or metalized plastic having a thickness
between about 0.1 .mu.m and about 9 .mu.m.
5. The apparatus of claim 1, wherein the display is an organic
light-emitting diode (OLED) display.
6. The apparatus of claim 5, wherein the display is a flexible OLED
display formed on a plastic substrate.
7. The apparatus of claim 1, wherein the adhesive layer includes a
pressure-sensitive adhesive.
8. The apparatus of claim 1, wherein the adhesive layer includes an
epoxy-based adhesive, the epoxy-based adhesive including a
thermoplastic ink.
9. The apparatus of claim 1, further comprising: a mechanical
stress isolation layer between the adhesive layer and the
ultrasonic sensor system, wherein the mechanical stress isolation
layer includes a plastic material.
10. The apparatus of claim 1, wherein the ultrasonic sensor system
includes: a sensor substrate having a plurality of sensor pixel
circuits disposed thereon; a piezoelectric transceiver layer
coupled to the sensor substrate and including a piezoelectric
material configured to generate the ultrasonic waves; and an
electrode layer coupled to the piezoelectric transceiver layer.
11. The apparatus of claim 10, wherein the piezoelectric
transceiver layer is underlying the sensor substrate and the
electrode layer is underlying the piezoelectric transceiver
layer.
12. The apparatus of claim 10, wherein the piezoelectric
transceiver layer is underlying the electrode layer and the sensor
substrate is underlying the piezoelectric transceiver layer.
13. The apparatus of claim 10, wherein the piezoelectric
transceiver layer includes polyvinylidene fluoride (PVDF),
polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) copolymer,
lead zirconate titanate (PZT), aluminum nitride (A1N), or
composites thereof.
14. The apparatus of claim 10, wherein the sensor substrate
comprises a material selected from the group consisting of: glass,
plastic, silicon, and stainless steel.
15. An apparatus comprising: a display; an ultrasonic sensor system
underlying the display and configured to transmit and receiving
ultrasonic waves in an acoustic path through the display; and an
adhesive layer between the ultrasonic sensor system and the
display, the adhesive layer positioned in the acoustic path.
16. The apparatus of claim 15, further comprising: a mechanical
stress isolation layer between the adhesive layer and the
ultrasonic sensor system, the mechanical stress isolation layer
including a plastic material and positioned in the acoustic
path.
17. The apparatus of claim 15, wherein the ultrasonic sensor system
spans across an entirety or substantial entirety of an active area
of the display.
18. The apparatus of claim 15, wherein the display is an organic
light-emitting diode (OLED) display.
19. The apparatus of claim 15, wherein the adhesive layer is
reworkable and configured to allow the ultrasonic sensor system to
be separated from the display, the adhesive layer including a
pressure-sensitive adhesive or an epoxy-based adhesive.
20. The apparatus of claim 15, further comprising: a light-blocking
layer between the adhesive layer and the display, the
light-blocking layer positioned in the acoustic path; and an
electrical shielding layer between the adhesive layer and the
display, the electrical shielding layer being electrically
conductive and grounded, the electrical shielding layer positioned
in the acoustic path, wherein each of the light-blocking layer and
the electrical shielding layer is non-porous or substantially
non-porous.
21. An apparatus comprising: a display; an ultrasonic sensor system
underlying the display and configured to transmit and receiving
ultrasonic waves in an acoustic path through the display; and a
multi-functional film between the ultrasonic sensor system and the
display, wherein the multi-functional film includes a
light-blocking layer, an electrical shielding layer, an adhesive
layer, a mechanical stress isolation layer, or combinations
thereof, the multi-functional film positioned in the acoustic
path.
22. A method of manufacturing an apparatus, the method comprising:
providing a display device, wherein the display device includes a
platen and a display underlying the platen; bonding a
light-blocking layer, an electrical shielding layer, a mechanical
stress isolation layer, or combinations thereof to the display,
wherein the electrically shielding layer is electrically conductive
and grounded; and bonding an ultrasonic sensor system to the
light-blocking layer, the electrical shielding layer, the
mechanical stress isolation layer, or combinations thereof, wherein
the ultrasonic sensor system is underlying the display and
configured to transmit and receive ultrasonic waves in an acoustic
path through the display and the platen, wherein the light-blocking
layer, the electrical shielding layer, the mechanical stress
isolation layer, or combinations thereof are in the acoustic
path.
23. The method of claim 22, wherein bonding the light-blocking
layer, the electrical shielding layer, the mechanical stress
isolation layer, or combinations thereof include laminating the
light-blocking layer, the electrical shielding layer, the
mechanical stress isolation layer, or combinations thereof to the
display.
24. The method of claim 22, further comprising: bonding an adhesive
layer to the display to allow at least the ultrasonic sensor system
to be separated from the display, wherein the adhesive layer is
positioned in the acoustic path.
25. An apparatus comprising: a display; an ultrasonic sensor system
underlying the display and configured to transmit and receive
ultrasonic waves in an acoustic path through the display, wherein
the ultrasonic sensor system comprises: a flexible substrate
including a plurality of sensor pixel circuits disposed thereon;
and a piezoelectric transceiver layer coupled to the flexible
substrate and including a piezoelectric material configured to
generate the ultrasonic waves; and a first high acoustic impedance
layer between the piezoelectric transceiver layer and the
display.
26. The apparatus of claim 25, wherein the first high acoustic
impedance layer includes a one or both of a light-blocking layer
and an electrical shielding layer.
27. The apparatus of claim 25, wherein the first high acoustic
impedance layer includes an electrode layer adjacent to the
piezoelectric transceiver layer.
28. The apparatus of claim 25, wherein the high acoustic impedance
value layer has an acoustic impedance value greater than about 5.0
MRayls.
29. The apparatus of claim 25, further comprising: an adhesive
layer between the display and the ultrasonic sensor system, the
adhesive layer positioned in the acoustic path and configured to
allow the ultrasonic sensor system to be separated from the
display.
30. The apparatus of claim 25, wherein the flexible substrate
includes polyethylene terephthalate (PET), polyethylene naphthalate
(PEN), a polyimide, stainless steel foil, thin film silicon, or
other flexible material.
31. The apparatus of claim 25, further comprising: a second high
acoustic impedance layer on a back side of the ultrasonic sensor
system.
Description
PRIORITY CLAIM
[0001] This application claims priority to U.S. Provisional Patent
Application No. 62/525,154, filed Jun. 26, 2017, and entitled
"ULTRASONIC FINGERPRINT SENSOR FOR UNDER-OLED DISPLAY
APPLICATIONS," which is hereby incorporated by reference in its
entirety and for all purposes.
TECHNICAL FIELD
[0002] This disclosure relates generally to ultrasonic fingerprint
sensor systems and more particularly to ultrasonic fingerprint
sensor systems incorporated under display applications.
DESCRIPTION OF RELATED TECHNOLOGY
[0003] In an ultrasonic sensor system, an ultrasonic transmitter
may be used to send an ultrasonic wave through an ultrasonically
transmissive medium or media and towards an object to be detected.
The transmitter may be operatively coupled with an ultrasonic
sensor configured to detect portions of the ultrasonic wave that
are reflected from the object. For example, in ultrasonic
fingerprint imagers, an ultrasonic pulse may be produced by
starting and stopping the transmitter during a very short interval
of time. At each material interface encountered by the ultrasonic
pulse, a portion of the ultrasonic pulse is reflected.
[0004] For example, in the context of an ultrasonic fingerprint
imager, the ultrasonic wave may travel through a platen on which a
person's finger may be placed to obtain a fingerprint image. After
passing through the platen, some portions of the ultrasonic wave
encounter skin that is in contact with the platen, e.g.,
fingerprint ridges, while other portions of the ultrasonic wave
encounter air, e.g., valleys between adjacent ridges of a
fingerprint, and may be reflected with different intensities back
towards the ultrasonic sensor. The reflected signals associated
with the finger may be processed and converted to a digital value
representing the signal strength of the reflected signal. When
multiple such reflected signals are collected over a distributed
area, the digital values of such signals may be used to produce a
graphical display of the signal strength over the distributed area,
for example by converting the digital values to an image, thereby
producing an image of the fingerprint. Thus, an ultrasonic sensor
system may be used as a fingerprint imager or other type of
biometric scanner. In some implementations, the detected signal
strength may be mapped into a contour map of the finger that is
representative of the depth of the ridge structure detail.
[0005] Ultrasonic sensor systems can be incorporated in display
devices as fingerprint sensor systems to authenticate a user.
Advances in display devices have resulted in flexible displays,
three-dimensional cover glasses, and bezel-less designs.
Consequently, more and more display devices have limited space to
incorporate a discrete button for a fingerprint sensor system or an
under-glass fingerprint sensor system that is positioned
peripherally to the display of the display device. An under-glass
and under-display fingerprint sensor system may provide additional
functionality and space to the display device and may open up
additional authentication software applications for improved user
interfaces.
SUMMARY
[0006] The devices, systems, and methods of this disclosure each
have several aspects, no single one of which is solely responsible
for the desirable attributes disclosed herein.
[0007] One aspect of the subject matter of this disclosure can be
implemented in an apparatus. The apparatus includes a display, an
ultrasonic sensor system underlying the display and configured to
transmit and receive ultrasonic waves in an acoustic path through
the display, a light-blocking layer between the ultrasonic sensor
system and the display, the light-blocking layer positioned in the
acoustic path, and an adhesive layer between the display and the
ultrasonic sensor system. The adhesive layer is positioned in the
acoustic path and configured to allow the ultrasonic sensor system
to be separated from the display.
[0008] In some implementations, the apparatus further includes an
electrical shielding layer between the ultrasonic sensor system and
the display, the electrical shielding layer being electrically
conductive and grounded, the electrical shielding layer positioned
in the acoustic path. Each of the electrical shielding layer and
the light-blocking layer may be non-porous or substantially
non-porous. In some implementations, the display is an organic
light-emitting diode (OLED) display. In some implementations, the
display is a flexible OLED display formed on a plastic substrate.
In some implementations, the adhesive layer includes an epoxy-based
adhesive, the epoxy-based adhesive including a thermoplastic ink.
In some implementations, the apparatus further includes a
mechanical stress isolation layer between the adhesive layer and
the ultrasonic sensor system, where the mechanical stress isolation
layer includes a plastic material. In some implementations, the
ultrasonic sensor system includes a sensor substrate having a
plurality of sensor pixel circuits disposed thereon, a
piezoelectric transceiver layer coupled to the sensor substrate and
including a piezoelectric material configured to generate the
ultrasonic waves, and an electrode layer coupled to the
piezoelectric transceiver layer. In some implementations, the
piezoelectric transceiver layer includes polyvinylidene fluoride
(PVDF), polyvinylidene fluoride trifluoroethylene (PVDF-TrFE)
copolymer, lead zirconate titanate (PZT), aluminum nitride (AlN),
or composites thereof. In some implementations, the sensor
substrate comprises a material selected from the group consisting
of: glass, plastic, silicon, and stainless steel.
[0009] Another innovative aspect of the subject matter described in
this disclosure can be implemented in an apparatus. The apparatus
includes a display, an ultrasonic sensor system underlying the
display and configured to transmit and receiving ultrasonic waves
in an acoustic path through the display, and an adhesive layer
between the ultrasonic sensor system and the display, the adhesive
layer positioned in the acoustic path.
[0010] In some implementations, the apparatus further includes a
mechanical stress isolation layer between the adhesive layer and
the ultrasonic sensor system, the mechanical stress isolation layer
including a plastic material and positioned in the acoustic path.
In some implementations, the ultrasonic sensor system spans across
an entirety or substantial entirety of an active area of the
display. In some implementations, the display is an organic
light-emitting diode (OLED) display. In some implementations, the
adhesive layer is reworkable and configured to allow the ultrasonic
sensor system to be separated from the display, the adhesive layer
including a pressure-sensitive adhesive or an epoxy-based adhesive.
In some implementations, the apparatus further includes a
light-blocking layer between the adhesive layer and the display,
the light-blocking layer positioned in the acoustic path, and an
electrical shielding layer between the adhesive layer and the
display, the electrical shielding layer being electrically
conductive and grounded, the electrical shielding layer positioned
in the acoustic path, where each of the light-blocking layer and
the electrical shielding layer is non-porous or substantially
non-porous.
[0011] Another innovative aspect of the subject matter described in
this disclosure can be implemented in an apparatus. The apparatus
includes a display, an ultrasonic sensor system underlying the
display and configured to transmit and receiving ultrasonic waves
in an acoustic path through the display, and a multi-functional
film between the ultrasonic sensor system and the display, where
the multi-functional film includes a light-blocking layer, an
electrical shielding layer, an adhesive layer, a mechanical stress
isolation layer, or combinations thereof, the multi-functional film
positioned in the acoustic path.
[0012] Another innovative aspect of the subject matter described in
this disclosure can be implemented in a method of manufacturing an
apparatus. The method includes providing a display device, wherein
the display device includes a platen and a display underlying the
platen, bonding a light-blocking layer, an electrical shielding
layer, a mechanical stress isolation layer, or combinations thereof
to the display, where the electrically shielding layer is
electrically conductive and grounded, and bonding an ultrasonic
sensor system to the light-blocking layer, the electrical shielding
layer, the mechanical stress isolation layer, or combinations
thereof, where the ultrasonic sensor system is underlying the
display and configured to transmit and receive ultrasonic waves in
an acoustic path through the display and the platen, where the
light-blocking layer, the electrical shielding layer, the
mechanical stress isolation layer, or combinations thereof are in
the acoustic path.
[0013] In some implementations, bonding the light-blocking layer,
the electrical shielding layer, the mechanical stress isolation
layer, or combinations thereof include laminating the
light-blocking layer, the electrical shielding layer, the
mechanical stress isolation layer, or combinations thereof to the
display. In some implementations, the method further includes
bonding an adhesive layer to the display to allow at least the
ultrasonic sensor system to be separated from the display, wherein
the adhesive layer is positioned in the acoustic path.
[0014] Another innovative aspect of the subject matter described in
this disclosure can be implemented in an apparatus. The apparatus
includes a display, and an ultrasonic sensor system underlying the
display and configured to transmit and receive ultrasonic waves in
an acoustic path through the display. The ultrasonic sensor system
includes a flexible substrate including a plurality of sensor pixel
circuits disposed thereon, and a piezoelectric transceiver layer
coupled to the flexible substrate and including a piezoelectric
material configured to generate the ultrasonic waves. The apparatus
further includes a first high acoustic impedance layer between the
piezoelectric transceiver layer and the display.
[0015] In some implementations, the first high acoustic impedance
layer includes a one or both of a light-blocking layer and an
electrical shielding layer. In some implementations, the first high
acoustic impedance layer includes an electrode layer adjacent to
the piezoelectric transceiver layer. In some implementations, the
high acoustic impedance value layer has an acoustic impedance value
greater than about 5.0 MRayls. The apparatus further includes an
adhesive layer between the display and the ultrasonic sensor
system, the adhesive layer positioned in the acoustic path and
configured to allow the ultrasonic sensor system to be separated
from the display. In some implementations, the flexible substrate
includes polyethylene terephthalate (PET), polyethylene naphthalate
(PEN), a polyimide, stainless steel foil, thin film silicon, or
other flexible material. In some implementations, the apparatus
further includes a second high acoustic impedance layer on a back
side of the ultrasonic sensor system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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. Other features, aspects, and
advantages will become apparent from the description, drawings and
claims. Note that the relative dimensions of the following figures
may not be drawn to scale.
[0017] Like reference numbers and designations in the various
drawings indicate like elements.
[0018] FIG. 1 shows a front view of a diagrammatic representation
of an example mobile device that includes an ultrasonic sensing
system according to some implementations.
[0019] FIG. 2A shows a block diagram representation of components
of an example ultrasonic sensing system according to some
implementations.
[0020] FIG. 2B shows a block diagram representation of components
of an example mobile device that includes the ultrasonic sensing
system of FIG. 2A.
[0021] FIG. 3A shows a cross-sectional projection view of a
diagrammatic representation of a portion of an example ultrasonic
sensing system according to some implementations.
[0022] FIG. 3B shows a zoomed-in cross-sectional side view of the
example ultrasonic sensing system of FIG. 3A according to some
implementations.
[0023] FIG. 4A shows an exploded projection view of example
components of the example ultrasonic sensing system of FIGS. 3A and
3B according to some implementations.
[0024] FIG. 4B shows an exploded projection view of example
components of an ultrasonic transceiver array in an ultrasonic
sensor system of FIGS. 3A and 3B according to some
implementations.
[0025] FIG. 5 shows an example of using a fingerprint sensor where
the fingerprint sensor is not under display according to some
implementations.
[0026] FIG. 6 shows an example of using a fingerprint sensor where
the fingerprint sensor is under display according to some
implementations.
[0027] FIG. 7 shows a cross-sectional view of an example
under-platen ultrasonic sensor system with a flexible printed
circuit (FPC).
[0028] FIG. 8A shows a cross-sectional schematic view of an example
device including a platen and a display underlying the platen
according to some implementations.
[0029] FIG. 8B shows a cross-sectional schematic view of an example
ultrasonic fingerprint sensor system according to some
implementations.
[0030] FIG. 9A shows a cross-sectional schematic view of an example
device including a platen, a display underlying the platen, and a
light-blocking layer and an electrical shielding layer underlying
the display according to some implementations.
[0031] FIG. 9B shows a cross-sectional schematic view of an example
ultrasonic fingerprint sensor system to be attached or bonded to
the device of FIG. 9A and to be underlying the display according to
some implementations.
[0032] FIG. 10A shows a cross-sectional schematic view of an
example device including an ultrasonic fingerprint sensor system
underlying a display and an acoustic path from the ultrasonic
fingerprint sensor system according to some implementations.
[0033] FIG. 10B shows a cross-sectional schematic view of an
example device including an ultrasonic fingerprint sensor system
underlying a display and an acoustic path from the ultrasonic
fingerprint sensor system according to some other
implementations.
[0034] FIGS. 11A-11F show cross-sectional schematic views of
various example ultrasonic sensor systems in a "receiver down"
orientation according to some implementations.
[0035] FIGS. 12A-12F show cross-sectional schematic views of
various example ultrasonic sensor systems in a "receiver up"
orientation according to some implementations.
[0036] FIGS. 13A-13B show cross-sectional schematic views of
various example ultrasonic sensor systems including a foam backing
layer according to some implementations.
[0037] FIG. 14A shows a cross-sectional schematic view of an
example flexible ultrasonic sensor system in a "receiver up"
orientation according to some implementations.
[0038] FIG. 14B shows a cross-sectional schematic view of an
example flexible ultrasonic sensor system in a "receiver down"
orientation according to some implementations.
[0039] FIG. 15 shows data of reflected acoustic signals in "soft"
and "hard" substrates and with different layers overlying and/or
underlying the "soft" substrates.
[0040] FIGS. 16A-16D show cross-sectional schematic views of
various example devices including a display and incorporating a
light-blocking layer, an electrical shielding layer, and an
ultrasonic sensor system underlying the display.
[0041] FIG. 17 shows an example method of manufacturing an
apparatus including an ultrasonic sensor system underlying a
display.
[0042] FIG. 18 shows an example of using a capacitive sensing mode
and an ultrasonic sensing mode with an ultrasonic fingerprint
sensor positioned behind a display of an electronic device to wake
up the electronic device.
[0043] FIG. 19 shows a cross-sectional side view schematic of a
configuration with an ultrasonic fingerprint sensor positioned
behind a display of a mobile device.
[0044] FIG. 20 shows an example of a flowchart for a method of
guiding a user of an LCD or OLED display device to position a
finger above an under-LCD or under-OLED fingerprint sensor.
DETAILED DESCRIPTION
[0045] 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, apparatus, or
system that includes a biometric system as disclosed herein for
ultrasonic sensing. In addition, 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, smart cards,
wearable devices such as bracelets, armbands, wristbands, rings,
headbands and patches, etc., 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, global positioning
system (GPS) receivers/navigators, cameras, digital media players
(such as MP3 players), camcorders, game consoles, wrist watches,
clocks, calculators, television monitors, flat panel displays,
electronic reading devices (e.g., e-readers), mobile health
devices, 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, automatic teller machines (ATMs), parking meters,
packaging (such as in electromechanical systems (EMS) applications
including microelectromechanical systems (MEMS) applications, as
well as non-EMS applications), aesthetic structures (such as
display of images on a piece of jewelry or clothing) and a variety
of EMS devices. The teachings herein also can be used in
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.
[0046] An under-display fingerprint sensor system may be provided
in a display device or apparatus. Many high-end displays use
organic light-emitting diode (OLED) displays or active matrix
organic light-emitting diode (AMOLED) displays. Some displays of
the present disclosure may be provided in plastic organic
light-emitting diode (pOLED) displays, which may also be referred
to as flexible OLED displays. Capacitive-based fingerprint sensors
may require electromagnetic signals that can interfere with the
electrical functions of the display. Signals generated or
transferred within the display along with associated conductive
traces may reduce capacitive fingerprint-sensing capability.
Optical-based fingerprint systems may be limited or rendered
useless where display devices include a light-blocking layer or a
large number of metal traces. An ultrasonic-based fingerprint
sensor may be incorporated in a display device under a display. The
ultrasonic-based fingerprint sensor may be incorporated under the
display of a display device with a light-blocking layer and without
interfering with the electrical functions of the display
device.
[0047] The configurations and techniques for ultrasonic fingerprint
sensor systems described herein may be suitable for used with
flexible displays, curved displays, curved cover glass, and
emerging 2.5D or three-dimensional displays. The ultrasonic imaging
of fingerprints is largely unaffected by small features in OLED
displays and other display types such as pixels or the touchscreen
electrodes. As the ultrasonic and electrical domains are
intrinsically different, crosstalk between electro-optical and
electro-acoustic domains is reduced. Crosstalk and undesirable
interactions between the ultrasonic fingerprint sensor system and
other portions of the display is further reduced or minimized in
part due to use of the light-blocking, electromagnetic interference
(EMI) reducing, electrical shielding, stress isolating, heat
sinking and heat-spreading layers that are described below.
[0048] The ultrasonic-based fingerprint sensor is configured to
transmit and receive ultrasonic waves in an acoustic path through a
display of a display device. At least one of a light-blocking layer
and an electrical shielding layer may be positioned between the
ultrasonic-based fingerprint sensor and the display, where the
light-blocking layer and the electrical shielding layer can be in
the acoustic path. In some implementations, each of the
light-blocking layer and the electrical shielding layer is
substantially non-porous. In some implementations, a mechanical
stress isolation layer may be positioned between the
ultrasonic-based fingerprint sensor and the display. Specifically,
the mechanical stress isolation layer may include a plastic
material and the mechanical stress isolation layer may be
positioned between an adhesive layer underlying the display and the
ultrasonic-based fingerprint sensor. In some implementations, the
ultrasonic-based fingerprint sensor may include a piezoelectric
layer and an array of pixel circuits disposed on a flexible
substrate, where a high acoustic impedance layer is disposed
between the piezoelectric layer and the display. In some
implementations, an additional high acoustic impedance layer may be
disposed between the piezoelectric layer and a surface opposite the
display, where the additional high acoustic impedance layer is not
in the acoustic path. In some implementations, a low acoustic
impedance layer is disposed between the piezoelectric layer and the
display to create an impedance mismatch. High or low acoustic
impedance layers create acoustic impedance mismatches to reflect
more acoustic energy at interfaces between the high and low
acoustic impedance layers. In some implementations, the
ultrasonic-based fingerprint sensor may include a porous foam
backing layer underlying the piezoelectric layer. In some
implementations related to flexible or bendable displays, the
ultrasonic-based fingerprint sensor may include a piezoelectric
layer and an array of pixel circuits disposed on a flexible plastic
substrate, where the flexible plastic substrate is attached to and
extends edge-to-edge with the flexible display.
[0049] Particular implementations of the subject matter described
in this disclosure may be implemented to realize one or more of the
following potential advantages. An under-display fingerprint sensor
increases the functionality of the active display area of a display
device. Furthermore, an under-display fingerprint sensor may reduce
form factor and may be incorporated in bezel-less display devices.
Under-display configurations allow larger sensor active areas for
improved performance, more flexibility in sensor placement, and a
better user experience. A light-blocking layer may serve a
mechanical function in the display device by providing mechanical
stress isolation and may serve an optical function by providing a
non-reflective absorbing layer so that visible light does not
penetrate through. Ultrasonic fingerprint sensor systems may
transmit and receive ultrasonic waves through light-blocking
layers. An electrical shielding layer may serve an electrical
function by providing an electrical or electromagnetic barrier or
an EMI shield from other electrical components and reduce
electromagnetic interference. The electrical shielding layer may
serve a thermal function by providing heat dissipation and
improving temperature uniformity at the back of the display.
Ultrasonic fingerprint sensor systems may transmit and receive
ultrasonic waves through an electrical shielding layer. The
light-blocking layer and electrical shielding layer may reduce the
amount of "noise" received by the ultrasonic fingerprint sensor
system. Attaching, laminating or otherwise bonding an ultrasonic
fingerprint sensor system to a display may result in mechanical
stresses that can adversely affect display appearance and
performance. However, a mechanical stress isolation layer
positioned between the ultrasonic fingerprint sensor and the
display may eliminate or otherwise reduce such stresses. In
addition, the mechanical stress isolation layer may provide an area
for a housing and/or edge seal to mechanically protect the
ultrasonic fingerprint sensor from physical and/or environmental
influences. A detachable (e.g., peelable) adhesive layer on the
mechanical stress isolation layer and underlying the display may
allow easier separation of the ultrasonic sensor from the display
for ease of replacement and/or refurbishment. The ultrasonic
fingerprint sensor may be implemented as a flexible sensor and
incorporated in flexible electronics, three-dimensional displays,
and curved displays for additional functionality. The ultrasonic
fingerprint sensor system may be implemented globally across a
display area of a display device and not just locally, which allows
for continuous user authentication and for authentication and
verification of a finger anywhere on the display. Moreover, the
ultrasonic fingerprint sensor may include selected low and high
acoustic impedance layers to reduce reflections of ultrasonic waves
along the acoustic path for improved performance. A porous foam
backing layer at the back of the display may provide a mechanical
cushion or support and increase acoustic reflections at the backing
layer interface for improved fingerprint imaging.
[0050] FIG. 1 shows a diagrammatic representation of an example
mobile device 100 that includes an ultrasonic sensing system
according to some implementations. The mobile device 100 may be
representative of, for example, various portable computing devices
such as cellular phones, smartphones, smart watches, multimedia
devices, personal gaming devices, tablet computers and laptop
computers, among other types of portable computing devices.
However, various implementations described herein are not limited
in application to portable computing devices. Indeed, various
techniques and principles disclosed herein may be applied in
traditionally non-portable devices and systems, such as in computer
monitors, television displays, kiosks, vehicle navigation devices
and audio systems, among other applications. Additionally, various
implementations described herein are not limited in application to
devices that include displays.
[0051] The mobile device 100 generally includes an enclosure (also
referred to as a "housing" or a "case") 102 within which various
circuits, sensors and other electrical components reside. In the
illustrated example implementation, the mobile device 100 also
includes a touchscreen display (also referred to herein as a
"touch-sensitive display") 104. The touchscreen display 104
generally includes a display and a touchscreen arranged over or
otherwise incorporated into or integrated with the display. The
display 104 may generally be representative of any of a variety of
suitable display types that employ any of a variety of suitable
display technologies. For example, the display 104 may be a digital
micro-shutter (DMS)-based display, a light-emitting diode (LED)
display, an organic LED (OLED) display, a liquid crystal display
(LCD), an LCD display that uses LEDs as backlights, a plasma
display, an interferometric modulator (IMOD)-based display, or
another type of display suitable for use in conjunction with
touch-sensitive user interface (UI) systems.
[0052] The mobile device 100 may include various other devices or
components for interacting with or otherwise communicating
information to or receiving information from a user. For example,
the mobile device 100 may include one or more microphones 106, one
or more speakers 108, and in some cases one or more at least
partially mechanical buttons 110. The mobile device 100 may include
various other components enabling additional features such as, for
example, one or more video or still-image cameras 112, one or more
wireless network interfaces 114 (for example, Bluetooth, Wi-Fi or
cellular) and one or more non-wireless interfaces 116 (for example,
a universal serial bus (USB) interface or an HDMI interface).
[0053] The mobile device 100 may include an ultrasonic sensing
system 118 capable of scanning and imaging an object signature,
such as a fingerprint, palm print or handprint. In some
implementations, the ultrasonic sensing system 118 may function as
a touch-sensitive control button. In some implementations, a
touch-sensitive control button may be implemented with a mechanical
or electrical pressure-sensitive system that is positioned under or
otherwise integrated with the ultrasonic sensing system 118. In
other words, in some implementations, a region occupied by the
ultrasonic sensing system 118 may function both as a user input
button to control the mobile device 100 as well as a fingerprint
sensor to enable security features such as user authentication
features. In some implementations, the ultrasonic sensing system
118 may be positioned under the cover glass of the display or under
a portion of the display itself as described herein. In some
implementations, the ultrasonic sensing system 118 may be
positioned on a sidewall or on the backside of the mobile device
enclosure 102.
[0054] FIG. 2A shows a block diagram representation of components
of an example ultrasonic sensing system 200 according to some
implementations. As shown, the ultrasonic sensing system 200 may
include a sensor system 202 and a control system 204 electrically
coupled to the sensor system 202. The sensor system 202 may be
capable of scanning an object and providing raw measured image data
usable to obtain an object signature such as, for example, a
fingerprint of a human finger. The control system 204 may be
capable of controlling the sensor system 202 and processing the raw
measured image data received from the sensor system. In some
implementations, the ultrasonic sensing system 200 may include an
interface system 206 capable of transmitting or receiving data,
such as raw or processed measured image data, to or from various
components within or integrated with the ultrasonic sensing system
200 or, in some implementations, to or from various components,
devices or other systems external to the ultrasonic sensing
system.
[0055] FIG. 2B shows a block diagram representation of components
of an example mobile device 210 that includes the ultrasonic
sensing system 200 of FIG. 2A. For example, the mobile device 210
may be a block diagram representation of the mobile device 100
shown in and described with reference to FIG. 1 above. The sensor
system 202 of the ultrasonic sensing system 200 of the mobile
device 210 may be implemented with an ultrasonic sensor array 212.
The control system 204 of the ultrasonic sensing system 200 may be
implemented with a controller 214 that is electrically coupled to
the ultrasonic sensor array 212. While the controller 214 is shown
and described as a single component, in some implementations, the
controller 214 may collectively refer to two or more distinct
control units or processing units in electrical communication with
one another. In some implementations, the controller 214 may
include one or more of a general purpose single- or multi-chip
processor, a central processing unit (CPU), a digital signal
processor (DSP), an applications processor, an application specific
integrated circuit (ASIC), a field programmable gate array (FPGA)
or other programmable logic device (PLD), discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions and operations described
herein.
[0056] The ultrasonic sensing system 200 of FIG. 2B may include an
image processing module 218. In some implementations, raw measured
image data provided by the ultrasonic sensor array 212 may be sent,
transmitted, communicated or otherwise provided to the image
processing module 218. The image processing module 218 may include
any suitable combination of hardware, firmware and software
configured, adapted or otherwise operable to process the image data
provided by the ultrasonic sensor array 212. In some
implementations, the image processing module 218 may include signal
or image processing circuits or circuit components including, for
example, amplifiers (such as instrumentation amplifiers or buffer
amplifiers), analog or digital mixers or multipliers, switches,
analog-to-digital converters (ADCs), passive filters or active
analog filters, among others. In some implementations, one or more
of such circuits or circuit components may be integrated within the
controller 214, for example, where the controller 214 is
implemented as a system-on-chip (SoC) or system-in-package (SIP).
In some implementations, one or more of such circuits or circuit
components may be integrated within a DSP included within or
coupled to the controller 214. In some implementations, the image
processing module 218 may be implemented at least partially via
software. For example, one or more functions of, or operations
performed by, one or more of the circuits or circuit components
just described may instead be performed by one or more software
modules executing, for example, in a processing unit of the
controller 214 (such as in a general-purpose processor or a DSP).
In some implementations, the image processing module 218 or
portions thereof may be implemented in software that may run on an
applications processor such as processor 220 associated with the
mobile device 210. The applications processor may have a dedicated
coprocessor and/or software modules for secure processing of the
biometric image data within the applications processor (sometimes
referred to as the "trust zone").
[0057] In some implementations, in addition to the ultrasonic
sensing system 200, the mobile device 210 may include a separate
processor 220, a memory 222, an interface 216 and a power supply
224. In some implementations, the controller 214 of the ultrasonic
sensing system 200 may control the ultrasonic sensor array 212 and
the image processing module 218, and the processor 220 of the
mobile device 210 may control other components of the mobile device
210. In some implementations, the processor 220 communicates data
to the controller 214 including, for example, instructions or
commands. In some such implementations, the controller 214 may
communicate data to the processor 220 including, for example, raw
or processed image data (also referred to as "image information").
It should also be understood that, in some other implementations,
the functionality of the controller 214 may be implemented
entirely, or at least partially, by the processor 220. In some such
implementations, a separate controller 214 for the ultrasonic
sensing system 200 may not be required because the functions of the
controller 214 may be performed by the processor 220 of the mobile
device 210.
[0058] Depending on the implementation, one or both of controller
214 and processor 220 may store data in the memory 222. For
example, the data stored in the memory 222 may include raw measured
image data, filtered or otherwise processed image data, estimated
image data, or final refined image data. The memory 222 may store
processor-executable code or other executable computer-readable
instructions capable of execution by one or both of controller 214
and the processor 220 to perform various operations (or to cause
other components such as the ultrasonic sensor array 212, the image
processing module 218, or other modules to perform operations),
including any of the calculations, computations, estimations or
other determinations described herein. It should also be understood
that the memory 222 may collectively refer to one or more memory
devices (or "components"). For example, depending on the
implementation, the controller 214 may have access to and store
data in a different memory device than the processor 220. In some
implementations, one or more of the memory components may be
implemented as a NOR- or NAND-based flash memory array. In some
other implementations, one or more of the memory components may be
implemented as a different type of non-volatile memory.
Additionally, in some implementations, one or more of the memory
components may include a volatile memory array such as, for
example, a type of RAM.
[0059] In some implementations, the controller 214 or the processor
220 may communicate data stored in the memory 222 or data received
directly from the image processing module 218 through an interface
216. For example, such communicated data can include image data or
data derived or otherwise determined from image data. The interface
216 may collectively refer to one or more interfaces of one or more
various types. In some implementations, the interface 216 may
include a memory interface for receiving data from or storing data
to an external memory such as a removable memory device.
Additionally or alternatively, the interface 216 may include one or
more wireless network interfaces or one or more wired network
interfaces enabling the transfer of raw or processed data to, as
well as the reception of data from, an external computing device,
system or server.
[0060] A power supply 224 may provide power to some or all of the
components in the mobile device 210. The power supply 224 may
include one or more of a variety of energy storage devices. For
example, the power supply 224 may include a rechargeable battery,
such as a nickel-cadmium battery or a lithium-ion battery.
Additionally or alternatively, the power supply 224 may include one
or more supercapacitors. In some implementations, the power supply
224 may be chargeable (or "rechargeable") using power accessed
from, for example, a wall socket (or "outlet") or a photovoltaic
device (or "solar cell" or "solar cell array") integrated with the
mobile device 210. Additionally or alternatively, the power supply
224 may be wirelessly chargeable. The power supply 224 may include
a power management integrated circuit and a power management
system.
[0061] As used hereinafter, the term "processing unit" refers to
any combination of one or more of a controller of an ultrasonic
system (for example, the controller 214), an image processing
module (for example, the image processing module 218), or a
separate processor of a device that includes the ultrasonic system
(for example, the processor 220). In other words, operations that
are described below as being performed by or using a processing
unit may be performed by one or more of a controller of the
ultrasonic system, an image processing module, or a separate
processor of a device that includes the ultrasonic sensing
system.
[0062] FIG. 3A shows a cross-sectional projection view of a
diagrammatic representation of a portion of an example ultrasonic
sensing system 300 according to some implementations. FIG. 3B shows
a zoomed-in cross-sectional side view of the example ultrasonic
sensing system 300 of FIG. 3A according to some implementations.
For example, the ultrasonic sensing system 300 may implement the
ultrasonic sensing system 118 described with reference to FIG. 1 or
the ultrasonic sensing system 200 shown and described with
reference to FIG. 2A and FIG. 2B. The ultrasonic sensing system 300
may include an ultrasonic transducer 302 that overlies a substrate
304 and that underlies a platen (e.g., a "cover plate" or "cover
glass") 306. The ultrasonic transducer 302 may include both an
ultrasonic transmitter 308 and an ultrasonic receiver 310.
[0063] The ultrasonic transmitter 308 is generally configured to
generate and transmit ultrasonic waves towards the platen 306, and
in the illustrated implementation, towards a human finger 312
positioned on the upper surface of the platen 306. In some
implementations, the ultrasonic transmitter 308 may more
specifically be configured to generate and transmit ultrasonic
plane waves towards the platen 306. For example, the piezoelectric
material of the ultrasonic transmitter 308 may be configured to
convert electrical signals provided by the controller of the
ultrasonic sensing system into a continuous or pulsed sequence of
ultrasonic plane waves at a scanning frequency. In some
implementations, the ultrasonic transmitter 308 includes a layer of
piezoelectric material such as, for example, polyvinylidene
fluoride (PVDF) or a PVDF copolymer such as PVDF-TrFE. In some
implementations, other piezoelectric materials may be used in the
ultrasonic transmitter 308 and/or the ultrasonic receiver 310, such
as aluminum nitride (A1N), lead zirconate titanate (PZT) or bismuth
sodium titanate. In some implementations, the ultrasonic
transmitter 308 and/or ultrasonic receiver 310 may additionally or
alternatively include capacitive ultrasonic devices such as
capacitive micromachined ultrasonic transducers (CMUTs) or
piezoelectric ultrasonic devices such as piezoelectric
micromachined ultrasonic transducers (PMUTs, also referred to as
"piezoelectric micromechanical ultrasonic transducers").
[0064] The ultrasonic receiver 310 is generally configured to
detect ultrasonic reflections 314 resulting from interactions of
the ultrasonic waves transmitted by the ultrasonic transmitter 308
with ridges 316 and valleys 318 defining the fingerprint of the
finger 312 being scanned. In some implementations, the ultrasonic
transmitter 308 overlies the ultrasonic receiver 310 as, for
example, illustrated in FIGS. 3A and 3B. In some implementations,
the ultrasonic receiver 310 may overlie the ultrasonic transmitter
308 (as shown in FIG. 4A described below). The ultrasonic receiver
310 may be configured to generate and output electrical output
signals corresponding to the detected ultrasonic reflections. In
some implementations, the ultrasonic receiver 310 may include a
second piezoelectric layer different from the piezoelectric layer
of the ultrasonic transmitter 308. For example, the piezoelectric
material of the ultrasonic receiver 310 may be any suitable
piezoelectric material such as, for example, a layer of PVDF or a
PVDF-TrFE copolymer. The piezoelectric layer of the ultrasonic
receiver 310 may convert vibrations caused by the ultrasonic
reflections into electrical output signals. In some
implementations, the ultrasonic receiver 310 further includes a
thin-film transistor (TFT) layer. In some such implementations, the
TFT layer may include an array of sensor pixel circuits configured
to amplify or buffer the electrical output signals generated by the
piezoelectric layer of the ultrasonic receiver 310. The electrical
output signals provided by the array of sensor pixel circuits may
then be provided as raw measured image data to the processing unit
for use in processing the image data, identifying a fingerprint
associated with the image data, and in some applications,
authenticating a user associated with the fingerprint. In some
implementations, a single piezoelectric layer may serve as the
ultrasonic transmitter 308 and the ultrasonic receiver 310 (as
shown in FIG. 4B described below). In some implementations, the
substrate 304 may be a glass, plastic or silicon substrate upon
which electronic circuitry may be fabricated. In some
implementations, an array of sensor pixel circuits and associated
interface circuitry of the ultrasonic receiver 310 may be
configured from CMOS circuitry formed in or on the substrate 304.
In some implementations, the substrate 304 may be positioned
between the platen 306 and the ultrasonic transmitter 308 and/or
the ultrasonic receiver 310. In some implementations, the substrate
304 may serve as the platen 306. One or more protective layers,
acoustic matching layers, anti-smudge layers, adhesive layers,
decorative layers, conductive layers or other coating layers (not
shown) may be included on one or more sides of the substrate 304
and the platen 306.
[0065] The platen 306 may be formed of any suitable material that
may be acoustically coupled to the ultrasonic transmitter 308. For
example, the platen 306 may be formed of one or more of glass,
plastic, ceramic, sapphire, metal or metal alloy. In some
implementations, the platen 306 may be a cover plate such as, for
example, a cover glass or a lens glass of an underlying display. In
some implementations, the platen 306 may include one or more
polymers, such as one or more types of parylene, and may be
substantially thinner. In some implementations, the platen 306 may
have a thickness in the range of about 10 microns (.mu.m) to about
1000 .mu.m or more.
[0066] In some implementations, the ultrasonic sensing system 300
may further include a focusing layer (not shown). For example, the
focusing layer may be positioned above the ultrasonic transmitter
308. The focusing layer may generally include one or more acoustic
lenses capable of altering the paths of ultrasonic waves
transmitted by the ultrasonic transmitter 308. In some
implementations, the lenses may be implemented as cylindrical
lenses, spherical lenses or zone lenses. In some implementations,
some or all of the lenses may be concave lenses, whereas in some
other implementations some or all of the lenses may be convex
lenses, or include a combination of concave and convex lenses.
[0067] In some implementations that include such a focusing layer,
the ultrasonic sensing system 300 may additionally include an
acoustic matching layer to ensure proper acoustic coupling between
the focusing lens(es) and an object, such as a finger, positioned
on the platen 306. For example, the acoustic matching layer may
include an epoxy doped with particles that change the density of
the acoustic matching layer. If the density of the acoustic
matching layer is changed, then the acoustic impedance will also
change according to the change in density, if the acoustic velocity
remains constant. In alternative implementations, the acoustic
matching layer may include silicone rubber doped with metal or with
ceramic powder. In some implementations, sampling strategies for
processing output signals may be implemented that take advantage of
ultrasonic reflections being received through a lens of the
focusing layer. For example, an ultrasonic wave coming back from a
lens' focal point will travel into the lens and may propagate
towards multiple receiver elements in a receiver array fulfilling
the acoustic reciprocity principle. Depending on the signal
strength coming back from the scattered field, an adjustment of the
number of active receiver elements is possible. In general, the
more receiver elements that are activated to receive the returned
ultrasonic waves, the higher the signal-to-noise ratio (SNR). In
some implementations, one or more acoustic matching layers may be
positioned on one or both sides of the platen 306, with or without
a focusing layer.
[0068] FIG. 4A shows an exploded projection view of example
components of the example ultrasonic sensing system 300 of FIGS. 3A
and 3B according to some implementations. The ultrasonic
transmitter 308 may include a substantially planar piezoelectric
transmitter layer 422 capable of functioning as a plane wave
generator. Ultrasonic waves may be generated by applying a voltage
across the piezoelectric transmitter layer 422 to expand or
contract the layer, depending upon the voltage signal applied,
thereby generating a plane wave. In this example, the processing
unit (not shown) is capable of causing a transmitter excitation
voltage to be applied across the piezoelectric transmitter layer
422 via a first transmitter electrode 424 and a second transmitter
electrode 426. The first and second transmitter electrodes 424 and
426 may be metallized electrodes, for example, metal layers that
coat opposing sides of the piezoelectric transmitter layer 422. As
a result of the piezoelectric effect, the applied transmitter
excitation voltage causes changes in the thickness of the
piezoelectric transmitter layer 422, and in such a fashion,
generates ultrasonic waves at the frequency of the transmitter
excitation voltage.
[0069] The ultrasonic waves may travel towards a target object such
as a finger, passing through the platen 306. A portion of the
ultrasonic waves not absorbed or transmitted by the target object
may be reflected back through the platen 306 and received by the
ultrasonic receiver 310, which, in the implementation illustrated
in FIG. 4A, overlies the ultrasonic transmitter 308. The ultrasonic
receiver 310 may include an array of sensor pixel circuits 432
disposed on a substrate 434 and a piezoelectric receiver layer 436.
In some implementations, each sensor pixel circuit 432 may include
one or more TFT or silicon-based CMOS transistor elements,
electrical interconnect traces and, in some implementations, one or
more additional circuit elements such as diodes, capacitors and the
like. Each sensor pixel circuit 432 may be configured to convert
surface charge generated in the piezoelectric receiver layer 436
proximate to the pixel circuit into an electrical signal. Each
sensor pixel circuit 432 may include a pixel input electrode 438
that electrically couples the piezoelectric receiver layer 436 to
the sensor pixel circuit 432.
[0070] In the illustrated implementation, a receiver bias electrode
440 is disposed on a side of the piezoelectric receiver layer 436
proximal to the platen 306. The receiver bias electrode 440 may be
a metallized electrode and may be grounded or biased to control
which signals may be passed to the array of sensor pixel circuits
432. Ultrasonic energy that is reflected from the exposed
(upper/top) surface 442 of the platen 306 may be converted into
surface charge by the piezoelectric receiver layer 436. The
generated surface charge may be coupled to the pixel input
electrodes 438 and underlying sensor pixel circuits 432. The charge
signal may be amplified or buffered by the sensor pixel circuits
432 and provided to the processing unit. The processing unit may be
electrically connected (directly or indirectly) with the first
transmitter electrode 424 and the second transmitter electrode 426,
as well as with the receiver bias electrode 440 and the sensor
pixel circuits 432 on the substrate 434. In some implementations,
the processing unit may operate substantially as described above.
For example, the processing unit may be capable of processing the
signals received from the sensor pixel circuits 432.
[0071] Some examples of suitable piezoelectric materials that may
be used to form the piezoelectric transmitter layer 422 or the
piezoelectric receiver layer 436 include piezoelectric polymers
having appropriate acoustic properties, for example, an acoustic
impedance between about 2.5 MRayls and 5 MRayls. Specific examples
of piezoelectric materials that may be employed include
ferroelectric polymers such as polyvinylidene fluoride (PVDF) and
polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymers.
Examples of PVDF copolymers include 60:40 (molar percent)
PVDF-TrFE, 70:30 PVDF-TrFE, 80:20 PVDF-TrFE, and 90:10 PVDR-TrFE.
Other examples of piezoelectric materials that may be utilized
include polyvinylidene chloride (PVDC) homopolymers and copolymers,
polytetrafluoroethylene (PTFE) homopolymers and copolymers, and
diisopropylammonium bromide (DIPAB). In some implementations, other
piezoelectric materials may be used in the piezoelectric
transmitter layer 422 and/or the piezoelectric receiver layer 436,
such as aluminum nitride (A1N), lead zirconate titanate (PZT) or
bismuth sodium titanate.
[0072] The thickness of each of the piezoelectric transmitter layer
422 and the piezoelectric receiver layer 436 is selected so as to
be suitable for generating and receiving ultrasonic waves,
respectively. In one example, a PVDF piezoelectric transmitter
layer 422 is approximately 28 .mu.m thick and a PVDF-TrFE receiver
layer 436 is approximately 12 .mu.m thick. Example frequencies of
the ultrasonic waves may be in the range of about 1 megahertz (MHz)
to about 100 MHz, with wavelengths on the order of a millimeter or
less.
[0073] FIG. 4B shows an exploded projection view of example
components of an ultrasonic transceiver array in an ultrasonic
sensing system 300 of FIGS. 3A and 3B according to some
implementations. In this example, the ultrasonic sensing system 300
includes an ultrasonic transceiver array 450 under a platen 306.
The ultrasonic transceiver array 450 may serve as the ultrasonic
sensor array 212 that is shown in FIG. 2B and described above. The
ultrasonic transceiver array 450 may include a substantially planar
piezoelectric transceiver layer 456 capable of functioning as a
plane wave generator. Ultrasonic waves may be generated by applying
a voltage across the transceiver layer 456. The control system 204
may be capable of generating a transceiver excitation voltage that
may be applied across the piezoelectric transceiver layer 456 via
one or more underlying pixel input electrodes 438 or one or more
overlying transceiver bias electrodes 460. The generated ultrasonic
wave may travel towards a finger or other object to be detected,
passing through the platen 306. A portion of the wave not absorbed
or transmitted by the object may be reflected so as to pass back
through the platen 306 and be received by the ultrasonic
transceiver array 450. The ultrasonic transceiver array 450 may
serve as both an ultrasonic transmitter and an ultrasonic receiver
using a single piezoelectric transceiver layer 456.
[0074] The ultrasonic transceiver array 450 may include an array of
sensor pixel circuits 432 disposed on a sensor substrate 434. In
some implementations, each sensor pixel circuit 432 may include one
or more TFT- or silicon-based elements, electrical interconnect
traces and, in some implementations, one or more additional circuit
elements such as diodes, capacitors and the like. Each sensor pixel
circuit 432 may include a pixel input electrode 438 that
electrically couples the piezoelectric transceiver layer 456 to the
sensor pixel circuit 432.
[0075] In the illustrated implementation, the transceiver bias
electrode 460 is disposed on a side of the piezoelectric
transceiver layer 456 proximal to the platen 306. The transceiver
bias electrode 460 may be a metallized electrode and may be
grounded or biased to control which signals may be generated and
which reflected signals may be passed to the array of sensor pixel
circuits 432. Ultrasonic energy that is reflected from the exposed
(top) surface 442 of the platen 306 may be converted into surface
charge by the piezoelectric transceiver layer 456. The generated
surface charge may be coupled to the pixel input electrodes 438 and
underlying sensor pixel circuits 432. The charge signal may be
amplified or buffered by the sensor pixel circuits 432 and provided
to the control system 204.
[0076] The control system 204 may be electrically connected
(directly or indirectly) to the transceiver bias electrode 460 and
the sensor pixel circuits 432 on the sensor substrate 434. In some
implementations, the control system 204 may operate substantially
as described above. For example, the control system 204 may be
capable of processing the amplified or buffered electrical output
signals received from the sensor pixel circuits 432.
[0077] The control system 204 may be capable of controlling the
ultrasonic transceiver array 450 to obtain ultrasonic image data,
which may include fingerprint image data. According to some
implementations, the control system 204 may be capable of providing
functionality such as that described herein, e.g., such as
described herein with reference to FIGS. 1-3B, 5-14B, and
16A-16D.
[0078] In other examples of an ultrasonic sensor system with an
ultrasonic transceiver array, a backside of the sensor substrate
434 may be attached directly or indirectly to an overlying platen
306. In operation, ultrasonic waves generated by the piezoelectric
transceiver layer 456 may travel through the sensor substrate 434
and the platen 306, reflect off surface 442 of the platen 306, and
travel back through the platen 306 and the sensor substrate 434
before being detected by sensor pixel circuits 432 on or in the
substrate sensor 434.
[0079] Many electronic devices, including mobile devices and smart
phones, use fingerprint authentication as one method of access
control. An ultrasonic fingerprint sensor may authenticate a user's
fingerprint, where ultrasonic waves generated by a piezoelectric
material may travel through a platen on which a person's finger is
placed. Some portions of an ultrasonic wave encounter skin that is
in contact with the platen, e.g., fingerprint ridges, while other
portions of an ultrasonic wave encounter air, e.g., valleys between
two ridges of a fingerprint. The ultrasonic waves are reflected
back with different intensities towards an ultrasonic sensor array.
Reflected signals associated with the finger may be processed and
converted to a digital value representing the signal strength of
the reflected signal, and a fingerprint image may be obtained.
[0080] FIG. 5 shows an example of using a fingerprint sensor where
the fingerprint sensor is not under display according to some
implementations. In FIG. 5, an electronic device 505 (e.g., mobile
device 210) includes controller circuit (e.g., controller 214 in
FIG. 2B) which may operate a sensor 525 (e.g., at least one of the
ultrasonic sensors or ultrasonic sensor array 212 of the ultrasonic
sensor system 202 in FIG. 2B). In some implementations, the
controller circuit may switch sensor 525 to operate between a
capacitive sensing mode and an ultrasonic sensing mode. For
example, the sensor 525 may be configured to be in a capacitive
sensing mode to determine whether an object has touched or is
positioned near the receiver bias electrode of the ultrasonic
sensor, and then subsequently configured to be in an ultrasonic
sensing mode to determine whether that object is a finger 515.
[0081] As shown in FIG. 5, at time 550, a finger 515 is placed
above sensor 525 that is part of an ultrasonic authenticating
button (e.g., "home button") of the electronic device 505. In some
implementations, the sensor 525 may be part of an electromechanical
button that can authenticate a user and is inserted through a
cut-out region in the cover glass of display 510. Accordingly, the
sensor 525 may be positioned separate from where visual image
content is displayed in the display 510. At time 550, the
electronic device 505 may be in a locked state, turned off, or in a
relatively low-power "sleep" mode. An object or finger 515 may be
determined to have been positioned near or on the display 510,
sensor 525, or other sensing electrode. Then at time 555, the
controller circuit may "wake up" an applications processor and
cause the display 510 to be turned on if a fingerprint of the
finger 515 is authenticated. For example, an applications processor
may obtain the fingerprint image data (e.g., by receiving the
corresponding data stored in memory by the controller circuit) and
then determine whether the fingerprint image data represents a
fingerprint of an authorized user of the electronic device 505. The
image data for the authorized fingerprint may have been previously
provided by the user (e.g., the owner), for example, during the
setup of the electronic device 505 or during enrollment and setup
of the security features of the electronic device 505.
[0082] FIG. 6 shows an example of using a fingerprint sensor where
the fingerprint sensor is under display according to some
implementations. In FIG. 6, an electronic device 605 (e.g., mobile
device 210) includes controller circuit (e.g., controller 214 in
FIG. 2B) which may operate a sensor 625 (e.g., at least one of the
ultrasonic sensors or ultrasonic sensor array 212 of the ultrasonic
sensor system 202 in FIG. 2B). In contrast to FIG. 5 where the
sensor 525 is placed in a cut-out region of the cover glass of the
display 510, the sensor 625 in FIG. 6 is placed in a region of a
display 610 through which visual image content can be displayed.
Having the sensor 625 in a display area of the display 610 can
improve the user interface and increase the functionality of the
display 610 of the electronic device 605. The sensor 625 does not
have to be part of an electromechanical button as discussed in FIG.
5. Accordingly, when a finger 615 is positioned near or on the
sensor 625, the sensor 625 may authenticate a user's fingerprint.
The sensor 625 may authenticate the user's fingerprint using an
ultrasonic fingerprint sensor system as described below.
[0083] FIG. 7 shows a cross-sectional view of an example
under-platen ultrasonic sensor system with a flexible printed
circuit (FPC). In FIG. 7, an ultrasonic sensor system 700 is
located underneath or underlying a platen 710. The platen 710 may
be deemed "in front of," "above," or "overlying" the ultrasonic
sensor system 700, and the ultrasonic sensor system 700 may be
deemed "behind," "below," or "underlying" the platen 710. Such
terms as used herein are relative terms depending on the
orientation of the device. In some implementations, the ultrasonic
sensor system 700 is coupled to the platen 710 by a first adhesive
760. A finger 705 may press against the platen 710 to activate the
ultrasonic sensor system 700. In some implementations, the platen
710 may be a cover glass of a display device (e.g., mobile device).
In some implementations, the platen 710 may include a portion of a
display such as an organic light-emitting diode (OLED) or active
matrix organic light-emitting diode (AMOLED) display.
[0084] The ultrasonic sensor system 700 may include a sensor
substrate 740, a plurality of sensor circuits 745 disposed on the
sensor substrate 740, a transceiver layer 720, and an electrode
layer 715. The transceiver layer 720 may be referred to as a
"piezoelectric layer" or as a "piezoelectric transceiver layer."
The electrode layer 715 may be referred to as a "transceiver
electrode layer." In some implementations, the transceiver layer
720 may correspond to the piezoelectric transceiver layer 456 of
FIG. 4B or may correspond to one or both of the piezoelectric
receiver layer 436 and the piezoelectric transmitter layer 422 of
FIG. 4A. The ultrasonic sensor system 700 may further include a
passivation layer (not shown). Different implementations may use
different materials for the sensor substrate 740. For example, the
sensor substrate 740 may include a silicon substrate, a
silicon-on-insulator (SOI) substrate, a thin-film transistor (TFT)
substrate, a glass substrate, a plastic substrate, a ceramic
substrate, and/or a combination thereof.
[0085] The plurality of sensor circuits 745 may be formed over or
on the sensor substrate 740, such as TFT circuits formed on a TFT
substrate or complementary metal-oxide-semiconductor (CMOS)
circuits formed on or in a silicon substrate. In some
implementations, the transceiver layer 720 may be positioned over
the plurality of sensor circuits 745. The transceiver layer 720 may
serve as both a transmitter and a receiver of ultrasonic waves,
where the transceiver layer 720 is configured to transmit at least
one ultrasonic wave/signal and receive or detect at least one
ultrasonic wave/signal. Accordingly, the transceiver layer 720 may
include one or more piezoelectric layers and one or more electrode
layers to enable the transceiver layer to transmit and receive
ultrasonic waves.
[0086] An ultrasonic wave is an acoustic wave that has a frequency
above about 20 kHz. In some implementations, ultrasonic waves have
a frequency between about 1 MHz and about 100 MHz, such as between
about 5 MHz and about 20 MHz. Acoustic waves are longitudinal waves
that have the same direction of vibration as their direction of
travel. Acoustic waves push particles in a medium, whether the
medium is a solid, liquid, or gas. Acoustic waves travel at the
speed of sound, which depends on the medium that they are passing
through. Acoustic impedance in a material measures the opposition
to acoustic flow resulting from an acoustic pressure applied to the
material. Acoustic impedance enables determination of the
reflection and transmission of acoustic energy at boundaries. If
the acoustic impedance of two media is very different, then most
acoustic energy will be reflected, rather than transmitted across
the boundary. Acoustic impedance may be measured in terms of
Pascal-seconds per meter (Pa-s/m or kg/s/m.sup.2) with units of
Rayls or MRayls.
[0087] The plurality of sensor circuits 745 may include an array of
thin-film transistor circuits. For example, the sensor circuits 745
may include an array of pixel circuits, where each pixel circuit
may include one or more TFTs. A pixel circuit may be configured to
convert an electric charge generated by the transceiver layer
proximate to the pixel circuit into an electrical signal in
response to a received ultrasonic wave. Output signals from the
sensor circuits 745 may be sent to a controller or other circuitry
for signal processing.
[0088] In some implementations, the transceiver electrode layer 715
may be disposed, positioned, placed, or formed over the transceiver
layer 720. The transceiver electrode layer 715 may include one or
more electrically conductive layers/traces that are coupled to the
transceiver layer 720. In some implementations, the transceiver
electrode layer 715 may include silver ink. In some
implementations, the transceiver electrode layer 715 may include
copper. Ultrasonic waves may be generated and transmitted by
providing an electrical signal to the transceiver electrode layer
715. In addition, a passivation layer (not shown) may be disposed,
positioned, placed, or formed over at least portions of the
transceiver electrode layer 715. The passivation layer may include
one or more layers of electrically insulating material. The sensor
substrate 740 and sensor circuits 745, the piezoelectric
transceiver layer 720 and the transceiver electrode layer 715 may
be positioned under a platen 710.
[0089] FIG. 7 shows a flexible printed circuit (FPC) 725 coupled to
the sensor substrate 740. However, it will be understood in the
present disclosure that the sensor substrate 740 may be coupled to
a rigid printed circuit board (PCB) or other circuitry. The FPC 725
may be referred to as a flex tape, flex cable, flex circuit, or
simply as "flex." The FPC 725 may include one or more dielectric
layers and one or more interconnects (e.g., traces, vias and pads).
In some implementations, the FPC 725 may be electrically coupled to
a controller or other circuitry for signal processing of signals
to/from the sensor circuits 745. In some implementations, the FPC
725 may wrap around from a front side of the ultrasonic sensor
system 700 to a back side of the ultrasonic sensor system 700.
[0090] In FIG. 7, the ultrasonic sensor system 700 may be attached
to the platen 710 using a first adhesive 760 and an edge sealant
755. The ultrasonic sensor system 700 may further include a sensor
housing or cap 730 for protecting the ultrasonic sensor system 700.
The sensor housing 730 may be coupled to a portion of the platen
710 via a second adhesive 765 and may be coupled to a portion of
the sensor substrate 740 and to a portion of the FPC 725 via a
third adhesive 750. In some implementations, the sensor housing 730
may be largely cantilevered over the active area of the sensor
substrate 740. The sensor housing 730 may be coupled to the sensor
substrate 740 such that a cavity 735 is formed between the back
side of the sensor substrate 740 and the sensor housing 730. In
some implementations, the sensor housing 730 may include one or
more layers of plastic or metal. In some implementations, the
sensor housing 730 and the cavity 735 may allow the interface
between the sensor substrate 740 and the cavity 735 to operate as
an acoustic barrier for the ultrasonic sensor system 700. In some
implementations, the cavity 735 may provide a space for
accommodating an acoustic shielding structure that is configured to
absorb, trap, or otherwise attenuate ultrasonic waves. The FPC 725
may be wrapped around the sensor substrate 740 and the sensor
housing 730, where the FPC 725 is attached to a backside of the
sensor housing 730.
[0091] An under-platen ultrasonic sensor system 700 may be provided
in a display device as shown in FIG. 7, but an under-display
ultrasonic sensor system is not necessarily provided in a display
device as in an under-platen ultrasonic sensor system. Accordingly,
a display device including an under-display ultrasonic sensor
system may be constructed differently than an under-platen
ultrasonic sensor system.
[0092] FIG. 8A shows a cross-sectional schematic view of an example
device including a platen and a display underlying the platen
according to some implementations. A display device may include a
display 865, such as a DMS-based display, an LED display, an OLED
display, an LCD, a plasma display, an IMOD-based display, or
another type of display suitable for use in conjunction with a
touch-sensitive user interface. In some implementations, the
display 865 may be modified to reduce or remove air gaps that can
hinder ultrasonic imaging capability. In FIG. 8A, the display 865
is an OLED display underlying a platen 805, such as a cover glass,
cover lens or outer layer of the OLED stack or any associated
touchscreen.
[0093] The OLED display 865 in FIG. 8A may include a plurality of
thin film layers 810, 815, 820, 825, 830, 835, 845, and 850. At
least some of the thin film layers 810, 815, 820, 825, 830, 835,
845, and 850 include layers of organic or plastic materials. The
organic or plastic materials may provide a range of colors
depending on which materials are employed. The OLED display 865 may
include a plurality of pixels 840 arranged in a matrix. The OLED
display 865 may include rows and columns of pixel circuits driven
by an active matrix for addressing the pixels 840. In some
implementations, the OLED display 865 may further include one or
more layers 810, 815 of touch-sensitive film, including one or more
layers of sensing electrodes. The one or more layers 810, 815
formed upon an organic light-emitting material in the OLED display
865 (e.g., OLED stack) may be substantially transparent to visible
light. Substantial transparency as used herein may be defined as
transmittance of visible light of about 70% or more, such as about
80% or more, or even about 90% or more. Additional layers in the
OLED display 865 may optionally include color filters, polarizers,
anti-reflective film, anti-shatter film, adhesive layers, barrier
layers, optical layers and one or more coatings or cover layers. In
some implementations, the OLED display 865 may be a glass OLED
display with a glass cover layer. Pixel circuits in the glass OLED
display 865 may be disposed between a glass substrate and the glass
cover layer.
[0094] Typically, an OLED display 865 may include one or more
backing layers 855, 860. The one or more backing layers 855, 860
may separate the OLED display 865 from other electronics or
components of the display device, such as a battery, RF components,
printed circuit boards, framing to support the electronic
components, etc. In some implementations, the one or more backing
layers 855, 860 may include a light-blocking layer 855 and an
electrical shielding layer 860. The light-blocking layer 855 may
include one or more materials that are opaque or substantially
opaque to visible light. Being substantially opaque or
substantially non-transparent as used herein may be defined as
absorbance of visible light of about 70% or more, such as about 80%
or more, or even about 90% or more. When an OLED display 865 is
functioning or turned on, the light-blocking layer 855 may prevent
or otherwise limit transmission of visible light to the back of a
display device. Moreover, the light-blocking layer 855 may provide
a mechanical function as a cushion for protecting the OLED display
865 from external forces. In some implementations, the
light-blocking layer 855 in the OLED display 865 may include a
porous black foam.
[0095] In some implementations, the one or more backing layers 855,
860 may include an electrical shielding layer 860. The electrical
shielding layer 860 may include one or more electrically conductive
materials and may be electrically grounded. The electrical
shielding layer 860 may serve to prevent or otherwise limit
electrical interference with the OLED display 865, particularly
when the OLED display 865 is functioning or turned on. For example,
the electrical shielding layer 860 may limit electrical
interference from nearby electronics, such as a battery charger,
digital or analog electronics, RF components, etc. Furthermore, the
electrical shielding layer 860 may provide heat dissipation and
improve temperature uniformity at the back of the display, as high
temperature gradients can occur near the OLED display 865 that may
be caused by electronic circuits and other devices (e.g.,
batteries) near the OLED display 865. In some implementations, the
electrical shielding layer 860 in the OLED display 865 may include
a thick copper tape. For example, the copper tape may have a
thickness that is greater than about 50 .mu.m, greater than about
20 .mu.m, greater than about 10 .mu.m, or greater than about 6
.mu.m.
[0096] However, one or both of the light-blocking layer 855 and the
electrical shielding layer 860 as described above may include
pores, voids, or air gaps that do not allow ultrasonic waves to
effectively pass through. Voids and air gaps may also exist at an
interface with one or both of the light-blocking layer 855 and the
electrical shielding layer 860. Voids and air gaps may also exist
between a glass cover layer and a glass substrate in a glass OLED
display. Additionally, the electrical shielding layer 860 may be
excessively thick and reduce the signal of ultrasonic waves
propagating therethrough.
[0097] A display device as disclosed herein may include an
ultrasonic fingerprint sensor system integrated with a display,
such as an OLED display 865 in FIG. 8A, that retains the
light-blocking and electrical shielding functionality of an OLED
display 865 without degrading the performance of the ultrasonic
fingerprint sensor system. Integration can occur, for example, by
bonding (e.g., laminating) the ultrasonic fingerprint sensor system
to a back side of the display 865. Integration of the ultrasonic
fingerprint sensor system with the display 865 can occur without
degrading the performance of the display device. In some
implementations, integration of the ultrasonic fingerprint sensor
system may provide for ease of replacement and/or refurbishment of
one or both of the ultrasonic fingerprint sensor system and the
display 865 without damaging the display device and its
components.
[0098] FIG. 8B shows a cross-sectional schematic view of an example
ultrasonic fingerprint sensor system according to some
implementations. The ultrasonic fingerprint sensor system 895 in
FIG. 8B may include a sensor substrate 870, a piezoelectric
transceiver layer 880 coupled to the sensor substrate 870, a
transceiver electrode layer 885, a passivation layer 890, and an
FPC 875 coupled to the sensor substrate 870. Aspects of the
ultrasonic fingerprint sensor system 895 in FIG. 8B may be
identical or similar to the ultrasonic fingerprint sensor systems
in FIGS. 1, 2A-2B, 3A-3B, 4A-4B, and 5-7. However, integration of
an ultrasonic fingerprint sensor system 895 with an OLED display
865 in FIG. 8A may limit or degrade the performance of one or both
of the ultrasonic fingerprint sensor system 895 and the display
865. For example, integration of the ultrasonic fingerprint sensor
system 895 may introduce stresses that can distort the appearance
and degrade the performance of the OLED display 865. In addition or
in the alternative, integration of the ultrasonic fingerprint
sensor system 895 with the OLED display 865 of FIG. 8A may reduce
the effectiveness of the ultrasonic fingerprint sensor system 895
by limiting transmission of acoustic signals.
[0099] One or both of the display 865 and the ultrasonic
fingerprint sensor system 895 may be modified to effectively
integrate the ultrasonic fingerprint sensor system 895 with the
display 865 without degrading the performance of either the
ultrasonic fingerprint sensor system 895 or the display 865. FIG.
9A shows a cross-sectional schematic view of an example device 900
including a cover glass 905, a display 965 underlying the cover
glass 905, and a light-blocking layer 955 and an electrical
shielding layer 960 underlying the display 965 according to some
implementations. FIG. 9B shows a cross-sectional schematic view of
an example ultrasonic fingerprint sensor system 995 to be attached
or bonded to the device 900 of FIG. 9A and to be underlying the
display 965 according to some implementations. As described above,
the ultrasonic fingerprint sensor system 995 includes a sensor
substrate 970, a piezoelectric transceiver layer 980 coupled to the
sensor substrate 970, a transceiver electrode layer 985, a
passivation layer 990, and an FPC 975 coupled to the sensor
substrate 970.
[0100] In FIG. 9A, the light-blocking layer 855 of FIG. 8A is
replaced with a non-porous light-blocking layer 955 in FIG. 9A to
permit effective transmission of ultrasonic waves and the
electrical shielding layer 860 of FIG. 8A is replaced with a thin
electrical shielding layer 960 in FIG. 9A to permit effective
transmission of ultrasonic waves. The non-porous light-blocking
layer 955 and/or the electrical shielding layer 960 may be
positioned locally between the active area of the ultrasonic
fingerprint sensor system 995 in some implementations, while in
other implementations the non-porous blocking layer 955 and/or the
electrical shielding layer 960 may extend beyond the active area of
the ultrasonic fingerprint sensor system 995 and may extend to the
edges of the display 965. In some implementations, where the
display 965 of FIG. 9A includes a glass cover layer, voids and/or
air gaps between the glass cover layer and a substrate glass may be
filled with a filling material such as a substantially transparent
oil or polymer, thereby allowing effective transmission of
ultrasonic waves. The non-porous light-blocking layer 955 and the
thin electrical shielding layer 960 may be part of a
multi-functional film positioned between a display 965 and an
ultrasonic fingerprint sensor system, such as an ultrasonic
fingerprint sensor system 995 in FIG. 9B or any of the ultrasonic
fingerprint sensor systems described in FIGS. 11A-11F, 12A-12F, and
13A-13B. In some implementations, the non-porous light-blocking
layer 955 may include a colored plastic material such as black
polyethylene terephthalate (PET) or colored polyethylene
naphthalate, polyimide, polycarbonate or PMMA, etc., one or more
paint layers, one or more colored ink layers, or a coated plastic
layer. In some implementations, the thin electrical shielding layer
960 may include a metalized plastic or a metal such as copper. In
some implementations, a thin metal foil may serve as a
light-blocking layer and as an electrical shielding layer. The thin
metal foil may be positioned on or attached to a layer of plastic
material. In some implementations, the thin electrical shielding
layer 960 may have a thickness between 0.05 .mu.m and about 10
.mu.m, or between about 0.1 .mu.m and about 9 .mu.m. In some
implementations, the thickness of the electrical shielding layer
960 comprising a thin metal layer or a metallized plastic layer may
between about 0.1 .mu.m and about 25 .mu.m or between about 0.1
.mu.m and about 50 .mu.m. Each of the non-porous light-blocking
layer 955 and the thin electrical shielding layer 960 and the
interfaces therebetween are substantially free of voids and
substantially non-porous. While FIG. 9A shows the non-porous
light-blocking layer 955 and the thin electrical shielding layer
960 as at least two discrete layers, it will be understood that the
non-porous light-blocking layer 955 and the thin electrical
shielding layer 960 may be integrated as a single layer or single
material. For example, a paint layer with conductive components
such as metal flakes may serve both as a light-blocking layer and
as an electrical shielding layer on the display 965. In some
implementations, a single adhesive positioned between the
ultrasonic fingerprint sensor system 995 and the display 965 may
serve as an adhesive layer, a light-blocking layer, an
ultrasonically conductive layer, and an electrical shielding
layer.
[0101] The display 965 in FIG. 9A may include an OLED display
stack, where the OLED display stack includes a plurality of thin
film layers 910, 915, 920, 925, 930, 935, 945, and 950. The OLED
display stack may include a plurality of pixels 940 arranged in
matrix. In some implementations, the light-blocking layer 955
disposed between the OLED display stack and the ultrasonic sensing
system 995 may include an index-matching layer that is
index-matched with the lower layers of the OLED display stack. For
example, the optical index of refraction of the light-blocking
layer 955 may be matched or substantially matched to the optical
index of refraction of the lowest layer of the OLED display stack
to minimize optical reflections from the interface between the OLED
display stack and the light-blocking layer 955. The optical index
of the light-blocking layer 955 may be controlled to be within, for
example, 0.05 of the optical index of the lowest layer in the OLED
display stack to avoid unwanted internal reflections. In some
implementations, the light-blocking layer 955 may include an
index-controlled optically clear adhesive or optically clear resin
that has been combined with a suitable light-blocking component
such as a paint, an ink, a pigment, a colorant, colored fibers or
carbon, graphite, graphene or metal particles. The metal particles
or other conductive materials in the light-blocking layer 955 may
also serve as an electrical shield. In some implementations, a
portion of a foam layer in the OLED display stack may be injected
with a light-blocking material to minimize voids and to allow
effective transmission of ultrasonic waves through the OLED display
stack. In some implementations, the foam layer in the OLED display
stack may be electrically conductive and serve as an electrical
isolation layer. In some implementations, the light-blocking layer
955 or the injected foam layer may extend throughout the active
area and in some examples extend to the edges of the display
965.
[0102] In FIG. 9B, a mechanical stress isolation layer 993 and an
adhesive layer 994 may be added to the ultrasonic fingerprint
sensor system 995 to allow for attachment or bonding to the display
965 with minimal transference of stresses to the display 965 and/or
ultrasonic fingerprint sensor system 995. Mechanical stresses
caused by curing of dispensed epoxies, edge sealant or other
adhesive materials may lead to mechanical distortions of the OLED
display stack and generate artefacts that may be visible to a user.
The mechanical stress isolation layer 993 and the adhesive layer
994 may be part of a multi-functional film positioned between the
display 965 and the ultrasonic fingerprint sensor system 995. In
some implementations, the adhesive layer 994 for attaching or
bonding to the display 965 may include a pressure-sensitive
adhesive (PSA) or epoxy. In some implementations, the mechanical
stress isolation layer 993 may include a plastic material, such as
PET, polyethylene naphthalate (PEN), or polyimide. In some
implementations, the materials used in the mechanical stress
isolation layer 993 may be selected to minimize thermal coefficient
of expansion mismatches with materials in the OLED display stack.
In some implementations, an adhesive layer 992 may be provided
underlying the mechanical stress isolation layer 993. For example,
such an adhesive layer 992 may include a structural adhesive, such
as a thermally curable epoxy or a UV-curable epoxy. The mechanical
stress isolation layer 993 may be selected with a material and
thickness to limit the transference of stress between the
ultrasonic fingerprint sensor system 995 and the display 965 upon
attaching or bonding the ultrasonic fingerprint sensor system 995
to the display 965. While FIGS. 9A-9B show the non-porous
light-blocking layer 955, thin electrical shielding layer 960 and
mechanical stress isolation layer 993 as discrete layers, it will
be understood that the mechanical stress isolation layer 993 may be
integrated as a single layer or single material with one or both of
the non-porous light-blocking layer 955 and the thin electrical
shielding layer 960.
[0103] The multi-functional film may include the non-porous
light-blocking layer 955 and the thin electrical shielding layer
960 so that the ultrasonic fingerprint sensor system 995 couples
with a display 965 (e.g., OLED display) ultrasonically, allows
ultrasonic waves to pass from the ultrasonic fingerprint sensor
system 995 through the display 965, eliminates or reduces
transmission of visible light to the ultrasonic fingerprint sensor
system 995, and eliminates or reduces electrical noise to the
ultrasonic fingerprint sensor system 995. In some implementations,
the multi-functional film may include an adhesive layer 994 over a
mechanical stress isolation layer 993 so that the ultrasonic
fingerprint sensor system 995 eliminates or reduces stresses (e.g.,
lamination stresses) that may be introduced from attaching or
bonding the ultrasonic fingerprint sensor system 995 or that may be
introduced from an edge seal application process. For example, the
ultrasonic fingerprint sensor system 995 may be laminated onto the
display 965 while minimizing lamination stresses that can distort
the appearance and performance of the display 965. The adhesive
layer 994 may also allow for ease of reworking, replacement and
refurbishment of the ultrasonic fingerprint sensor system 995 and
the display 965. In some implementations, a tab or extension may be
included on one or more of the adhesive layer 994 or mechanical
stress isolation layer 993 to allow peeling and removal of the
ultrasonic fingerprint sensor system 995 from the display 965
without causing cosmetic or functional damage to the display 965.
The adhesive layer 994 may be reworkable and configured to allow
the ultrasonic fingerprint sensor system 995 to be separated from
the display 965. In some implementations, the adhesive layer 994
may be a pressure sensitive adhesive layer to permit ease of
reworking. In some implementations, the adhesive layer 944 may
include an epoxy-based adhesive such as a thermoplastic ink. The
thermoplastic ink may be configured to dissolve in a suitable
organic solvent, thereby allowing for separation between the
ultrasonic fingerprint sensor system 995 and the display 965 for
ease of reworking. It will be understood that reattachment or
replacement of the ultrasonic fingerprint sensor system 995 onto
the back of the display 965 as part of a reworking process may
impose similar scrutiny to avoid gaps, particulates, voids and
other detrimental features that may impede the conveyance of
ultrasonic image information and reduce signal integrity.
[0104] The mechanical stress isolation layer 993 may be disposed
over or on the ultrasonic fingerprint sensor system 995. In some
implementations, a surface area of the mechanical stress isolation
layer 993 extends beyond a surface of the ultrasonic fingerprint
sensor system 995 to which the mechanical stress isolation layer
993 is attached or bonded to. As shown in FIG. 9B, the mechanical
stress isolation layer 993 may extend beyond a periphery of the
ultrasonic fingerprint sensor system 995. In some implementations,
the mechanical stress isolation layer 993 may span the entire
display region of the display 965 and in some implementations to
the edges of the display 965. The extended area provides a landing
for a housing or cap so that the ultrasonic fingerprint sensor
system 995 can be protected and enclosed. The extended area also
provides an area for an edge seal 991 to be formed around the
sidewalls of a sensor and the sensor substrate 970 to protect and
package the ultrasonic fingerprint sensor system 995 for improved
reliability of the ultrasonic fingerprint sensor system 995 without
causing image artefacts in the OLED stack. In some implementations,
the mechanical stress isolation layer 993 provides a substantially
planar surface for sensor-to-display lamination. In some
implementations, the mechanical stress isolation layer 993 allows
the ultrasonic fingerprint sensor system 995 to be packaged so that
it can be handled with thin layers (e.g., thinned glass and silicon
substrates) and handled for attachment or bonding to glass,
plastic, metal or other materials.
[0105] FIG. 10A shows a cross-sectional schematic view of an
example device 1000 including an ultrasonic fingerprint sensor
system 1095 underlying a display 1065 and an acoustic path 1050
from the ultrasonic fingerprint sensor system 1095 according to
some implementations. As described above, an ultrasonic fingerprint
sensor system 1095 may include a sensor substrate 1070, a
piezoelectric transceiver layer 1080 coupled to the sensor
substrate 1070, a transceiver electrode layer 1085, a passivation
layer 1090, and an FPC 1075 coupled to the sensor substrate 1070.
The ultrasonic fingerprint sensor system 1095 may be configured to
transmit and receive ultrasonic waves in an acoustic path 1050
through a display 1065 of a display device 1000, where the
ultrasonic fingerprint sensor system 1095 is underlying the display
1065 of the display device 1000. At least some of the ultrasonic
waves transmitted from the ultrasonic fingerprint sensor system
1095 may be reflected back by an object 1030 (e.g., a finger)
positioned on an outer surface of the display 1065, touchscreen,
platen, or cover glass 1005. The acoustic path 1050 may be defined
by the propagation of ultrasonic waves to and from the ultrasonic
fingerprint sensor system 1095 that allows an object 1030 such as a
finger placed in contact with the outer surface of the display
1065, touchscreen, platen, or cover glass 1005 to be imaged. To
integrate the display 1065 and the underlying ultrasonic
fingerprint sensor system 1095, a multi-functional film 1055 may be
positioned between the ultrasonic fingerprint sensor system 1095
and the display 1065 so that the multi-functional film 1055 is in
the acoustic path 1050. In some implementations, the
multi-functional film 1055 includes one or more of a light-blocking
layer, an electrical shielding layer, an adhesive layer, and a
mechanical stress isolation layer, one or more of which are in the
acoustic path 1050. In some implementations, each of the
light-blocking layer, the electrical shielding layer, the
mechanical stress isolation layer, and the adhesive layer between
the mechanical stress isolation layer and the display 1065 are
positioned in the acoustic path 1050.
[0106] FIG. 10B shows a cross-sectional schematic view of an
example device 1000 including an ultrasonic fingerprint sensor
system 1095 underlying a display 1065 and an acoustic path 1050
from the ultrasonic fingerprint sensor system 1095 according to
some other implementations. In FIG. 10B, the multi-functional film
1055 may be replaced by an adhesive layer 1060 that connects the
ultrasonic fingerprint sensor system 1095 to the display 1065. In
some implementations, the adhesive layer 1060 includes an epoxy or
a pressure-sensitive adhesive. An epoxy may include an epoxy-based
adhesive, where the epoxy-based adhesive may include a
thermoplastic ink that is configured to dissolve in a suitable
organic solvent. In some implementations, the adhesive layer 1060
may serve functions in addition to adhering the ultrasonic
fingerprint sensor system 1095 to the display 1065, including
mechanical stress isolation and light-blocking functions.
[0107] The mechanical stress isolation layer may be integrated with
the ultrasonic fingerprint sensor system according to various
implementations as shown in FIGS. 11A-11F, 12A-12F, and 13A-13B.
FIGS. 11A-11F show cross-sectional schematic views of various
example ultrasonic fingerprint sensor systems 1100 in a "receiver
down" orientation according to some implementations. FIGS. 12A-12F
show cross-sectional schematic views of various example ultrasonic
fingerprint sensor systems 1200 in a "receiver up" orientation
according to some implementations. The ultrasonic fingerprint
sensor system may be oriented in a "receiver down" orientation or
"receiver up" orientation. In the "receiver down" orientation, a
piezoelectric transceiver layer is underlying a sensor substrate so
that the sensor substrate is in the acoustic path. An FPC may be
coupled to the sensor substrate so that the FPC is underlying the
sensor substrate in the "receiver down" orientation. In the
"receiver up" orientation, a piezoelectric transceiver layer is
overlying a sensor substrate so that the sensor substrate is not in
the acoustic path. Rather, a transceiver electrode layer and a
passivation layer are in the acoustic path. An FPC may be coupled
to the sensor substrate so that the FPC is overlying the sensor
substrate in the "receiver up" orientation.
[0108] In FIGS. 11A-11F, each of the ultrasonic fingerprint sensor
systems 1100 includes a sensor substrate 1130, a piezoelectric
transceiver layer 1140, a transceiver electrode layer 1145, a
passivation layer 1150 (except in FIG. 11F), and an FPC 1120
coupled to the sensor substrate 1130. The piezoelectric transceiver
layer 1140 may include a piezoelectric material configured to
transmit ultrasonic waves upon the application of a voltage.
Examples of a suitable piezoelectric material include PVDF or
PVDF-TrFE copolymers. In some implementations, the piezoelectric
material is configured to receive ultrasonic waves and generate a
surface charge that is provided to sensor pixel circuits disposed
in or on the sensor substrate 1130. The sensor substrate 1130 may
include a plurality of sensor pixel circuits 1135 such as a TFT
array of sensor pixel circuits. The sensor pixel circuits 1135 on
the sensor substrate 1130 may amplify or buffer the generated
surface charge to provide electrical output signals to the FPC 1120
or control system (not shown). The ultrasonic fingerprint sensor
system 1100 in the "receiver down" orientation includes a
transceiver electrode layer 1145 underlying the piezoelectric
transceiver layer 1140 and coupled to the piezoelectric transceiver
layer 1140. In some implementations, the transceiver electrode
layer 1145 may include a metallized electrode that may be grounded
or biased to control which signals may be generated and which
reflected signals may be passed to the plurality of sensor pixel
circuits 1135 disposed on the sensor substrate 1130. The ultrasonic
fingerprint sensor system 1100 in the "receiver down" orientation
may include a passivation layer 1150 underlying the transceiver
electrode layer 1145 or at least portions of the transceiver
electrode layer 1145. The passivation layer 1150 may include one or
more layers of electrically insulating material, such as silicon
nitride, silicon dioxide, benzocyclobutene (BCB), polyimide, a
thermosetting material such as a thermosetting epoxy, a UV-curable
resin, an acrylic, an epoxy, or other suitable material to provide
protection for underlying electrodes, the piezoelectric transceiver
layer 1140, interconnects, electrical traces, electrical and
electronic components, and electronic circuits. The thickness of
the passivation layer 1150 may be selected to maximize the
efficiency of the ultrasonic fingerprint sensor system 1100. In
some implementations, the passivation layer 1150 may be printed,
sprayed or laminated onto an outer portion of the transceiver
electrode layer 1145.
[0109] In each of the ultrasonic fingerprint sensor systems in
FIGS. 11A-11F, a mechanical stress isolation layer 1110 may be
disposed over the sensor substrate 1130 in the "receiver down"
orientation. While the mechanical stress isolation layer 1130 is
shown as a separate and discrete layer in FIGS. 11A-11F, it will be
understood that the non-porous light-blocking layer 955 in FIG. 9A
or the multi-functional film 1055 in FIG. 10 may serve as a
mechanical stress isolation layer in addition or in the alternative
to the mechanical stress isolation layer 1110 shown in FIGS.
11A-11F.
[0110] In each of the ultrasonic fingerprint sensor systems 1100 in
FIGS. 11A-11D, the mechanical stress isolation layer 1110 is
positioned between two adhesive layers 1105, 1125. In some
implementations, a first adhesive layer 1105 positioned between the
mechanical stress isolation layer 1110 and a display (not shown)
may include a pressure-sensitive adhesive. In some implementations,
a second adhesive layer 1125 between the mechanical stress
isolation layer 1110 and the sensor substrate 1130 may include a
structural adhesive, such as a thermally curable epoxy. An edge
seal 1115 may be provided on the mechanical stress isolation layer
1110 and around the sides of the ultrasonic fingerprint sensor
system 1100 and in some implementations on the back side to seal
and protect the ultrasonic fingerprint sensor system 1100 as a
package. The edge seal 1115 may serve to protect the ultrasonic
fingerprint sensor system 1100 against the ambient environment,
moisture ingress and external forces. In some implementations, the
edge seal 1115 may include a thermally curable epoxy. The
mechanical stress isolation layer 1110 enables the edge seal 1115
so that the edge seal 1115 is not directly attached or bonded to
the display, which could otherwise result in stresses and
distortions being imparted to the display.
[0111] FIG. 11A as shown does not include additional backing layers
or structures underlying the passivation layer 1150 of the
ultrasonic fingerprint sensor system 1100. In this configuration,
air serves as an effective backing layer. However, air backing
layers may provide insufficient protection against inadvertent
contact with other components, which may result in interference
with the ultrasonic imaging and potential mechanical damage to the
sensor system 1100. In FIG. 11B, the ultrasonic fingerprint sensor
system further includes a foam backing layer 1155 (also referred to
as a "foam backer" or "foam layer") and a stiffener 1160 underlying
the foam backing layer 1155 relative to the ultrasonic fingerprint
sensor system 1100 of FIG. 11A. In some implementations, the
ultrasonic fingerprint sensor system 1100 includes a stiffener 1160
and an electrical shield underlying the foam backing layer 1155.
The stiffener 1160, which may be a stamped layer of stainless steel
or aluminium in some implementations, may be electrically grounded
to provide an effective electrical shield.
[0112] The foam backing layer 1155 may have an acoustic impedance
very close to air and substantially lower than the piezoelectric
transceiver layer 1140 such that acoustic wave transmission into
the foam backing layer 1155 and subsequent layers is significantly
reduced. The foam backing layer 1155 may have an acoustic impedance
substantially different than the piezoelectric transceiver layer
1140. The acoustic impedance mismatch between the foam backing
layer 1155 and the piezoelectric transceiver layer 1140 are
substantially different. The term "substantially different" with
respect to acoustic impedance throughout this disclosure refers to
an acoustic impedance value that is at least five times, at least
eight times, at least ten times, or at least 100 times greater or
less than an acoustic impedance value being compared to. That way,
the foam backing layer 1155 can provide total or near-total
reflection of propagating ultrasonic waves. In addition, the foam
backing layer 1155 may provide a mechanical support and cushion for
protecting the ultrasonic fingerprint sensor system 1100. When
external forces are applied to the ultrasonic fingerprint sensor
system 1100 from other components or objects touching the back side
of the sensor, acoustic energy may be lost unless a foam backing
layer or other protection (e.g., a sensor housing and an air
cavity) is provided. Details regarding the foam backing layer 1155
are discussed further with respect to FIGS. 13A-13B.
[0113] In FIG. 11B, the stiffener 1160 may serve as a cap and may
be coupled to the back side of the ultrasonic fingerprint sensor
system 1100. In some implementations, the stiffener 1100 may
comprise a wafer, substrate, panel, sub-panel, or one or more
layers of plastic, metal, glass, or silicon. In some
implementations, the stiffener 1160 may have a high flexural
modulus and mechanical strength to structurally and environmentally
protect the ultrasonic fingerprint sensing system 1100. The foam
backing layer 1155 and the stiffener 1160 may combine to provide
the ability to seal the sensor system 1100 from external moisture
and to improve moisture protection for higher reliability. In some
implementations, an air backing layer may be combined with the foam
backing layer 1155 and positioned between the transceiver electrode
layer 1145 and the stiffener 1160 to provide additional acoustic
isolation.
[0114] In FIG. 11C, the ultrasonic fingerprint sensor system 1100
further includes a stiffener 1160 and a cavity 1165 relative to the
ultrasonic fingerprint sensor system 1100 of FIG. 11A. The cavity
1165 may be an air gap defined between the stiffener 1160 and the
passivation layer 1150 of the ultrasonic fingerprint sensor system
1100. One or more spacers may be used to control the gap height or
height of the cavity 1165. The cavity 1165 forms an air backing
layer that may provide a substantial acoustic impedance mismatch
with the piezoelectric transceiver layer 1140, transceiver
electrode layer 1145, and passivation layer 1150 so that the cavity
1165 can provide total or near-total reflection of propagating
ultrasonic waves. An electrical shield may be further provided on
the back side of the ultrasonic fingerprint sensor system 1100
along with the stiffener 1160. In some implementations, the
stiffener 1160 may be electrically grounded and serve as an
electrical shield.
[0115] In FIG. 11D, the ultrasonic fingerprint sensor system 1100
further includes a sensor housing 1170 and a cavity 1165 relative
to the ultrasonic fingerprint sensor system 1100 of FIG. 11A. The
cavity 1165 forms an air gap or air backing layer (also referred to
as an "air backer") between the sensor housing 1170 and at least
the passivation layer 1150 of the ultrasonic fingerprint sensor
system 1100. In some implementations, the sensor housing 1170
includes one or more layers of plastic or metal. The sensor housing
1170 may be disposed on the mechanical stress isolation layer 1110
to provide encapsulation of the ultrasonic fingerprint sensor
system 1100. An electrical shield may be provided on the back side
of the ultrasonic fingerprint sensor system 1100 along with the
sensor housing 1170. As described with respect to FIG. 11C, a
stiffener may be electrically grounded and serve as an electrical
shield. The stiffener may be included as part of the sensor housing
1170 or on the sensor housing 1170.
[0116] In the ultrasonic fingerprint sensor systems 1100 shown in
FIGS. 11E-11F, the mechanical stress isolation layer 1110 may be
formed as a molded structure around the ultrasonic fingerprint
sensor system 1100. Instead of an adhesive layer positioned between
the mechanical stress isolation layer 1110 and the sensor substrate
1130 and instead of an edge seal around the ultrasonic fingerprint
sensor system 1100 in the "receiver down" orientation, the
mechanical stress isolation layer 1110 may be molded to surround
the ultrasonic fingerprint sensor system 1100 as a package. Thus,
the mechanical stress isolation layer 1110 is formed on the front
side, edges, and back side of the ultrasonic fingerprint sensor
system 1100. In some implementations, a cavity may be formed in the
molded mechanical stress isolation layer 1110 behind the sensor
active area to serve as an air backing layer for improved acoustic
isolation.
[0117] In FIG. 11E, the ultrasonic fingerprint sensor system 1100
includes a foam backing layer 1155 underlying the passivation layer
1150. The foam backing layer 1155 may serve one or both of a
mechanical function (e.g., cushion) and acoustic function (e.g.,
reflection of ultrasonic waves). An electrical shield 1175 may be
disposed on the back side of the ultrasonic fingerprint sensor
system 1100, where the mechanical stress isolation layer 1110 on
the back side is positioned between the electrical shield 1175 and
the foam backing layer 1155. In some implementations, an air
backing layer may be combined with the foam backing layer 1155 and
both positioned between the transceiver electrode layer 1145 and
the backside portion of the molded mechanical stress isolation
layer 1110 to provide additional acoustic isolation.
[0118] In FIG. 11F, the ultrasonic fingerprint sensor system 1100
includes an electrical shield 1175 underlying the mechanical stress
isolation layer 1110 on the back side. However, in contrast to FIG.
11E, the ultrasonic fingerprint sensor system 1100 does not include
a foam backing layer or a passivation layer. In some
implementations, an air backing layer may be formed in the molded
mechanical stress isolation layer 1110 behind the sensor active
area.
[0119] In FIGS. 12A-12F, each of the ultrasonic fingerprint sensor
systems 1200 is in a "receiver up" orientation and includes a
sensor substrate 1230, a piezoelectric transceiver layer 1240, a
transceiver electrode layer 1245, a passivation layer 1250, and an
FPC 1220 coupled to the sensor substrate 1230 similar to that shown
in FIGS. 11A-11F. Similar to the configurations shown in FIGS.
11A-11D, a mechanical stress isolation layer 1210 may be positioned
between at least two adhesive layers 1205, 1225 as shown in FIGS.
12A-12D. Similar to the configurations shown in FIGS. 11E-11F, a
mechanical stress isolation layer 1210 may be molded around the
ultrasonic fingerprint sensor system 1200 as shown in FIGS.
12E-12F.
[0120] The ultrasonic fingerprint sensor system 1200 in the
"receiver up" orientation includes the piezoelectric transceiver
layer 1240 coupled to and overlying the sensor substrate 1230 with
a plurality of sensor pixel circuits 1235 disposed thereon. The
transceiver electrode layer 1245 may be coupled to and overlying
the piezoelectric transceiver layer 1240, and the passivation layer
1250 may be overlying the transceiver electrode layer 1245 or at
least portions of the transceiver electrode layer 1245. In FIG.
12B, a foam backing layer 1255 along with one or both of a
stiffener 1260 and an electrical shield underlies the sensor
substrate 1230 at the back side of the ultrasonic fingerprint
sensor system 1200. In FIG. 12C, a cavity 1265 and one or both of a
stiffener 1260 and an electrical shield underlies the sensor
substrate 1230 at the back side of the ultrasonic fingerprint
sensor system 1200. In FIG. 12D, a cavity 1265 and one or both of a
housing 1270 and an electrical shield underlies the sensor
substrate 1230 at the back side of the ultrasonic fingerprint
sensor system 1200. In FIG. 12E, the mechanical stress isolation
layer 1210 may be molded around the ultrasonic fingerprint sensor
system 1200, where a foam backing layer 1255 underlies the sensor
substrate 1230 and an electrical shield 1275 underlies the
mechanical stress isolation layer 1210 at the back side of the
ultrasonic fingerprint sensor system 1200. In FIG. 12F, the
mechanical stress isolation layer 1210 may be molded around the
ultrasonic fingerprint sensor system 1200, where an electrical
shield 1275 underlies the mechanical stress isolation layer 1210 at
the back side of the ultrasonic fingerprint sensor system 1200.
There is no foam backing layer 1255. In some implementations, a
cavity may be formed in the molded stress isolation material behind
the sensor active area to serve as an air backing layer. In the
implementations shown in FIGS. 12B-12D, the stiffener 1260 may be
electrically grounded and serve as an electrical shield. In the
implementations shown in FIGS. 12E-12F, the electrical shield 1275
may be electrically grounded and serve as a mechanical
stiffener.
[0121] FIGS. 13A-13B show cross-sectional schematic views of
various example ultrasonic sensor systems 1300 including a foam
backing layer 1355 according to some implementations. The
ultrasonic sensor systems 1300 in FIGS. 13A-13B are in a "receiver
down" orientation, though it will be understood that the foam
backing layer 1355 may be provided also in a "receiver up"
orientation. The ultrasonic sensor systems 1300 include at least a
sensor substrate 1330, a piezoelectric transceiver layer 1340
coupled to the sensor substrate 1330, a transceiver electrode layer
1345 coupled to the piezoelectric transceiver layer 1340, a
passivation layer 1350, and an FPC 1320 coupled to the sensor
substrate 1330. In FIGS. 13A-13B, a multi-functional film 1310 may
be positioned between the ultrasonic sensor system 1300 and a
display 1301. The multi-functional film 1310 may include one or
more of a mechanical stress isolation layer, a non-porous
light-blocking layer, and a thin electrical shielding layer. In
some implementations, the mechanical stress isolation layer, the
non-porous light-blocking layer, and the thin electrical shielding
layer may be integrated as a single layer or single material. The
multi-functional film 1310 may be positioned between at least two
adhesive layers 1305, 1325 for attaching or bonding to the
ultrasonic sensor system 1300 as well as for attaching or bonding
to the display 1301. An edge seal 1315 may be provided around the
ultrasonic sensor system 1300 and disposed on the multi-functional
film 1310.
[0122] In FIGS. 13A-13B, the foam backing layer 1355 underlies the
ultrasonic sensor system 1300 at the back side. In some
implementations, the foam backing layer 1355 may be attached or
bonded to the passivation layer 1350 via an adhesive layer 1353. In
some implementations, the adhesive layer 1353 may include a
pressure-sensitive adhesive. The foam backing layer 1355 may be
sufficiently porous with air pockets to provide total or near-total
reflection of ultrasonic waves. In some implementations, the foam
backing layer 1355 may have a thickness between about 10 .mu.m and
about 500 .mu.m, or between about 50 .mu.m and about 200 .mu.m. In
some implementations, the foam backing layer 1355 may include a
substantially non-transparent polymer material, such as a
substantially non-transparent polypropylene foam material. For
example, the substantially non-transparent polypropylene foam
material may be one of an SCF-400 series of foam materials
manufactured by the Nitto Denko Corporation in Osaka, Japan. Closed
cell foam or semi-closed cell foam for use in the foam backing
layer 1355 allows improved edge seal and acoustic performance in
that the edge sealant is restrained from entering the foam and
altering the acoustic impedance of the foam backing layer 1355.
[0123] In FIG. 13A, one or both of a stiffener 1360 and an
electrical shield underlies the foam backing layer. One or both of
the stiffener 1360 and the electrical shield may be attached or
bonded to the foam backing layer 1355 via an adhesive layer 1357.
In FIG. 13B, a plastic layer 1365 underlies the foam backing layer
1355, and a metal layer 1370 underlies the plastic layer 1365. The
plastic layer 1365 is attached or bonded to the foam backing layer
1355 via an adhesive layer 1357.
[0124] More and more electronic devices include materials that are
compatible with flexible display devices and flexible electronics.
Incorporation of organic materials in display devices can introduce
mechanical flexibility to the devices. In some implementations, the
ultrasonic sensor systems as described herein may be implemented as
a flexible ultrasonic sensor system. In some implementations, the
flexible ultrasonic sensor system may include a flexible substrate
including a polymer material, such as polyimide, PEN or PET. In
some implementations, the flexible substrate may include a thin
layer of stainless steel, a stainless steel foil, thinned glass,
thinned silicon, thin-film silicon, or other flexible material. The
thickness of the flexible substrates may be below about 250 .mu.m
and in some examples below about 100 .mu.m and in some examples
between about 50 .mu.m and about 100 .mu.m with TFT or CMOS
circuitry formed in or on the flexible substrates. The flexible
substrates may be suitable for use with flexible displays, curved
displays, curved cover glass, and emerging 2.5D and
three-dimensional displays. Flexible substrates may allow the
ultrasonic sensor system to cover an entire active area or
substantially an entire active area of the display.
[0125] FIG. 14A shows a cross-sectional schematic view of an
example flexible ultrasonic sensor system 1495 in a "receiver up"
orientation according to some implementations. The flexible
ultrasonic sensor system 1495 underlies a display 1465 with an
adhesive 1494 positioned between the flexible ultrasonic sensor
system 1495 and the display 1465. In some implementations, the
adhesive 1494 may be a pressure-sensitive adhesive or an
epoxy-based adhesive. The display 1465 may underlie a platen or
cover glass 1405. In some implementations, the display 1465 may
include an OLED display or an AMOLED display or a pOLED (plastic
OLED) also called as a flexible OLED display. In some
implementations, an electrical shielding layer 1460 may be
positioned between the display 1465 and the adhesive 1494. For
example, the electrical shielding layer 1460 may include an
electrically conductive material such as a metal coating. In some
implementations, a light-blocking layer 1455 may be positioned
between the display 1465 and the adhesive 1494.
[0126] The flexible ultrasonic sensor system 1495 in the "receiver
up" orientation may include a flexible substrate 1470 having a
plurality of sensor pixel circuits 1496 disposed thereon. A
piezoelectric transceiver layer 1480 may be coupled to and disposed
on the flexible substrate 1470. An electrode layer 1485 may be
coupled to and disposed on the piezoelectric transceiver layer
1480, and a passivation layer 1490 disposed on at least a portion
of the electrode layer 1485. An FPC 1475 may be electrically and
mechanically coupled to the flexible substrate 1470. The flexible
ultrasonic sensor system 1495 may further include an optional
backing layer 1492 on the back side of the flexible ultrasonic
sensor system 1495. The backing layer 1492 may include one or both
of an optically non-transparent layer and an electrically
conductive blocking layer to serve a light-blocking function and/or
an electrical shielding function.
[0127] Generation of a strong transmission-side pressure wave may
facilitate the flexible ultrasonic sensor system 1495 to be
effective. The strong transmission-side pressure wave may be
generated by designing film stacks with strong acoustic impedance
mismatch interfaces for reflecting ultrasonic waves. The strong
acoustic pressure creates greater reflection of ultrasonic waves
for improving the quality of ultrasonic imaging. A strong acoustic
impedance mismatch between layers of materials can result in total
or near-total reflection of ultrasonic waves. By way of an example,
an interface between air and plastic creates a low acoustic
impedance mismatch whereas an interface between air and metal or
glass creates a high acoustic impedance mismatch.
[0128] Layers or materials with high acoustic impedance values may
be referred to herein as "hard" materials, and layers or materials
with low acoustic impedance values may be referred to herein as
"soft" materials. Acoustic impedance values may be measured in
MRayls. Table 1 below lists a series of materials and their
acoustic impedance values. High acoustic impedance values may be
greater than about 5.0 MRayls, and low acoustic impedance values
may be between about 0.0 MRayls and about 5.0 MRayls. Generally,
metals, ceramics and glasses may be considered to have high
acoustic impedance values; plastics and polymers may be considered
to have low acoustic impedance values; and air may be considered to
have a very low acoustic impedance value.
TABLE-US-00001 TABLE 1 Material Acoustic Impedance (MRayl)
Stainless Steel 45.7 Copper 39.1 Glass 13.1 Silver Ink 8.9
Piezoelectric Polymer 4.0 Epoxy 3.4 PET (polyethylene
terephthalate) 3.3 Passivation Epoly Film 3.1 Pressure-Sensitive
Adhesive 2.0 Air 0.0
[0129] In FIGS. 14A and 14B, an acoustic impedance mismatch between
the flexible substrate 1470 and layers 1410, 1415, 1420, 1425,
1430, 1435, and 1445 may not be sufficient or significant enough to
create a strong transmission-side pressure wave. Whereas
non-flexible ultrasonic sensor systems may include a "hard"
substrate material such as glass adjacent to a piezoelectric
transceiver layer 1480, the flexible ultrasonic sensor system 1495
may compensate by incorporating "hard" materials between the
piezoelectric transceiver layer 1480 and the display 1465 and/or
between the piezoelectric transceiver layer 1480 and a back side of
the flexible ultrasonic sensor system 1495. Incorporation of a
layer with a high acoustic impedance value to create a strong
acoustic impedance mismatch may facilitate generation of the strong
transmission-side pressure wave. In some implementations, the layer
with the high acoustic impedance value may be between the display
1465 and the piezoelectric transceiver layer 1480. In addition or
in the alternative, a layer with a high acoustic impedance value
may be between the piezoelectric layer 1480 and the back side of
the flexible ultrasonic sensor system 1495.
[0130] In FIG. 14A, in some implementations, the light-blocking
layer 1455 may include a material with a high acoustic impedance
value. In some implementations, the electrical shielding layer 1460
may include a material with a high acoustic impedance value. One or
both of the light-blocking layer 1455 and the electrical shielding
layer 1460 may provide a high acoustic impedance mismatch at an
interface with the adhesive 1494 or the piezoelectric transceiver
layer 1480. The adhesive 1494 and/or the piezoelectric transceiver
layer 1480 may include a "soft" material that has a low acoustic
impedance value. In some implementations, the electrode layer 1485
may include a material with a high acoustic impedance value. The
electrode layer 1485 may provide a high acoustic impedance mismatch
at an interface with the piezoelectric transceiver layer 1480.
Examples of materials with high acoustic impedance values are shown
above, which can include but are not limited to copper, plated
electrodes, or filled materials like silver ink. The high acoustic
impedance values may result in an acoustic impedance mismatch that
is substantial enough to result in total or near-total reflection
of ultrasonic waves.
[0131] In some implementations, the backing layer 1492 may have a
high acoustic impedance. Thus, underlying the flexible substrate
1470 is a layer with a high acoustic impedance, which provides a
substantial acoustic impedance mismatch with one or more adjacent
layers or materials (e.g., air). For example, where the backing
layer 1492 forms an interface with air, the acoustic impedance
mismatch can be substantial enough to result in total or near-total
reflection of ultrasonic waves. Generally speaking, air at the
interface provides a readily available boundary condition for
reflection of ultrasonic waves.
[0132] FIG. 14B shows a cross-sectional schematic view of an
example flexible ultrasonic sensor system 1495 in a "receiver down"
orientation according to some implementations. The flexible
ultrasonic sensor system 1495 underlies a display 1465 with an
adhesive 1494 positioned between the flexible ultrasonic sensor
system 1495 and the display 1465. In some implementations, the
adhesive 1494 may be a pressure-sensitive adhesive or an
epoxy-based adhesive. The display 1465 may underlie a platen or
cover glass 1405. In some implementations, the display 1465 may
include an OLED display or an AMOLED display. In some
implementations, an electrical shielding layer 1460 may be
positioned between the display 1465 and the adhesive 1494. For
example, the electrical shielding layer 1460 may include an
electrically conductive material such as a metal coating. In some
implementations, a light-blocking layer 1455 may be positioned
between the display 1465 and the adhesive 1494.
[0133] The flexible ultrasonic sensor system 1495 in the "receiver
down" orientation may include a flexible substrate 1470 having a
plurality of sensor pixel circuits 1496 disposed on a side of the
flexible substrate 1470 facing away from the display 1465. A
piezoelectric transceiver layer 1480 may be coupled to and underlie
the flexible substrate 1470. An electrode layer 1485 may be coupled
to and underlie the piezoelectric transceiver layer 1480, and a
passivation layer 1490 may underlie at least a portion of the
electrode layer 1485. An FPC 1475 may be coupled to and underlie
the flexible substrate 1470. The flexible ultrasonic sensor system
1495 may further include an optional backing layer 1492 on the back
side of the flexible ultrasonic sensor system 1495. The backing
layer 1492 may include one or both of an optically non-transparent
layer and an electrically conductive blocking layer to serve a
light-blocking function and/or an electrical shielding
function.
[0134] In FIG. 14B, in some implementations, the light-blocking
layer 1455 may include a material with a high acoustic impedance
value. In some implementations, the electrical shielding layer 1460
may include a material with a high acoustic impedance value. One or
both of the light-blocking layer 1455 and the electrical shielding
layer 1460 may provide a high acoustic impedance mismatch at an
interface with the adhesive 1494 or the flexible substrate 1470.
The adhesive 1494 and/or the flexible substrate 1470 may include a
"soft" material that has a low acoustic impedance value. In some
implementations, the array of pixel circuits 1496 may be plated or
coated with a metal or "hard" material that has a high acoustic
impedance value to provide a high acoustic impedance mismatch at an
interface with the piezoelectric transceiver layer 1480. In some
implementations, a layer (not shown) between the flexible substrate
1470 and the adhesive 1494 may include a material with a high
acoustic impedance value. Examples of materials with high acoustic
impedance values are shown above, which can include but are not
limited to copper, plated electrodes, or filled materials like
silver ink. The high acoustic impedance values may result in an
acoustic impedance mismatch that is substantial enough to result in
total or near-total reflection of ultrasonic waves.
[0135] Underlying the piezoelectric transceiver layer 1480 may be
one or more layers of "hard" materials. In some implementations,
the electrode layer 1485 may include a material with a high
acoustic impedance value. The electrode layer 1485 may provide a
high acoustic impedance mismatch at an interface with the
piezoelectric transceiver layer 1480. In some implementations, the
backing layer 1492 may have a high acoustic impedance. Thus,
underlying the piezoelectric transceiver layer 1480 is a layer with
a high acoustic impedance, which provides a substantial acoustic
impedance mismatch with one or more adjacent layers or materials
(e.g., air). For example, where the backing layer 1492 forms an
interface with air, the acoustic impedance mismatch can be
substantial enough to result in total or near-total reflection of
ultrasonic waves.
[0136] The flexible ultrasonic sensor system enables the production
of large area sensors. In some implementations, the flexible
substrate spans across an entire active area of the display. In
some implementations, the TFT array of sensor pixel circuits and
the piezoelectric transceiver layer spans across the entire active
area of the display. The piezoelectric transceiver layer and the
plurality of sensor pixel circuits disposed upon the flexible
substrate are not necessarily localized to a particular area of the
display. Rather, the substrate upon which the piezoelectric
transceiver layer and the plurality of sensor pixel circuits
disposed thereon may span across the display. Flexible ultrasonic
sensor systems may cover an entire active area of the display due
at least in part to the ease of laminating a flexible substrate
compared to a rigid substrate. Authentication of a user via
acquiring and authenticating a fingerprint image need not be
performed at a specific region of the display, allowing for
continuous authentication anywhere on the display of the display
device.
[0137] FIG. 15 shows simulated data of reflected acoustic signals
in "soft" and "hard" substrates and with different layers overlying
and/or underlying the "soft" substrates. The data in FIG. 15 shows
a percentage of reflected acoustic signals through a series of
materials as a function of transmitter frequency. Each of the
series of materials includes at least a substrate material, an
electrode material and a passivation material. Each of the series
of materials further includes a piezoelectric material. An
electrode material in FIG. 15 made of copper has a thickness of
either 9 .mu.m or 15 .mu.m. A passivation material in FIG. 15 has a
thickness of either 0.1 .mu.m or 12.5 .mu.m. The "reference" data
in FIG. 15 shows the percentage of reflected acoustic signals in a
glass substrate, a silicon substrate, and a stainless steel
substrate. The percentage of reflected acoustic signals in the
"reference" data is relatively high, particularly for the glass
substrate and the silicon substrate.
[0138] The percentage of reflected acoustic signals for a PET
substrate where the series of materials are arranged in a "receiver
down" orientation is reduced. The addition of a plated metal over
the PET substrate substantially increases the percentage of
reflected acoustic signals in the "receiver down" orientation,
where the plated metal includes either 12.5 .mu.m of copper or 5
.mu.m of copper. Adding a metal film between the display and the
PET substrate, however, did not increase the percentage of
reflected acoustic signals. When the series of materials are
arranged in a "receiver up" orientation, the percentage of
reflected acoustic signals for the PET substrate is relatively
high. Without being limited by any theory, the interface with the
electrode layer and the interface with air in the "receiver up"
orientation provide substantial acoustic impedance mismatches that
provided greater reflection of acoustic signals.
[0139] FIGS. 16A-16D show cross-sectional schematic views of
various example devices 1600 including a display 1610 and
incorporating a light-blocking layer 1615, an electrical shielding
layer 1620, and an ultrasonic sensor system 1630 underlying the
display 1610. Each of the different implementations in FIGS.
16A-16D represent different ways of modifying or manufacturing a
display 1610 to attach or bond an ultrasonic sensor system 1630
underlying the display 1610.
[0140] In FIG. 16A, the display may include a porous black foam as
a second light-blocking layer 1625 and a thick copper tape as a
second electrical shielding layer 1635. At least a portion of the
porous black foam and the thick copper tape may be removed to form
a cut-out region to expose the back side of the display 1610. A
first light-blocking layer 1615, such as a non-porous opaque
plastic material, may be bonded to the back side of the display
1610. A first electrical shielding layer 1620, such as a thin metal
layer or a metalized plastic, may be bonded to the back side of the
first light-blocking layer 1615. An ultrasonic sensor system 1630
as described earlier herein in FIGS. 8B, 9B, 10A-10B, 11A-11F,
12A-12F, 13A-13B, and 14A-14B may be bonded to the back side of the
first electrical shielding layer 1620.
[0141] In FIG. 16B, the porous black foam as the second
light-blocking layer 1625 and the thick copper tape as the second
electrical shielding layer 1635 is entirely removed or never
provided on the back side of the display 1610. In such
implementations, the first light-blocking layer 1615, such as a
non-porous opaque plastic material, may be bonded directly to the
back side of the display 1610. A first electrical shielding layer
1620, such as a thin metal layer or a metalized plastic layer, may
be bonded to the back side of the first light-blocking layer 1615.
The first light-blocking layer 1615 and the first electrical
shielding layer 1620 are not necessarily localized to a region in
the display 1610, but may span across an entire active area of the
display 1610. An ultrasonic sensor system 1630 as described earlier
herein in FIGS. 8B, 9B, 10A-10B, 11A-11F, 12A-12F, 13A-13B, and
14A-14B may be bonded to the back side of the first electrical
shielding layer 1620.
[0142] In FIG. 16C, a porous black foam and a thick copper tape may
be provided with or subsequent to bonding the first light-blocking
layer 1615 and the first electrical shielding layer 1620 to the
back side of the display 1610. The porous black foam as a second
light-blocking layer 1625 and the thick copper tape as a second
electrical shielding layer 1635 may be provided on portions of the
first electrical shielding layer 1620. An ultrasonic sensor system
1630 as described earlier herein in FIGS. 8B, 9B, 10A-10B, 11A-11F,
12A-12F, 13A-13B, and 14A-14B may be bonded to the back side of the
first electrical shielding layer 1620. Such an arrangement in FIG.
16C may offer additional protection against light interference and
electrical interference with the ultrasonic sensor system 1630.
[0143] In FIG. 16D, a porous black foam and a thick copper tape may
be provided with or subsequent to bonding the first light-blocking
layer 1615 and the first electrical shielding layer 1620 to the
back side of the display 1610. The porous black foam as a second
light-blocking layer 1625 and the thick copper tape as a second
electrical shielding layer 1635 may be disposed on the back side of
the first electrical shielding layer 1620. Unlike in FIG. 16C, the
porous black foam and the thick copper tape in FIG. 16D cover an
ultrasonic sensor system 1630 at the back side. An ultrasonic
sensor system 1630 as described earlier herein in FIGS. 8B, 9B,
10A-10B, 11A-11F, 12A-12F, 13A-13B, and 14A-14B may be bonded to
the back side of the first electrical shielding layer 1620. Such an
arrangement in FIG. 16D may offer additional protection against
light interference and electrical interference with the ultrasonic
sensor system 1630. Note that the dimensions of the features in
FIGS. 16A-16D, as elsewhere in this disclosure, may not be drawn to
scale. For example, the thickness of the ultrasonic fingerprint
sensor system 1630 may be appreciably thinner than the porous black
foam and thinner than the layers in the display stack.
[0144] In some implementations, a midframe that supports the
display and other electronic components in a phone assembly may be
modified to serve as a protective cap over the ultrasonic
fingerprint sensor system. The protective cap region may be
supported with a porous black foam layer and an adhesive layer that
has cut-out regions for the ultrasonic fingerprint sensor system
and may surround the ultrasonic fingerprint sensor system on each
of the four sides and the back. A layer of selectively configured
copper tape may be included between the porous black foam layer and
the midframe. The midframe may serve as a sensor housing. The
midframe may allow a cavity or an air backing layer to be formed
between the ultrasonic fingerprint sensor system and an inner
surface of the midframe. The midframe may be contoured, stamped or
otherwise formed to provide a suitable cavity region between the
display and the midframe for the ultrasonic fingerprint sensor to
reside. In some implementations, a foam backing layer may be
included in the cavity region with or without an air backing layer.
In some implementations, an opening may be provided in the phone
midframe to accommodate the ultrasonic fingerprint sensing system
and associated layers. In some implementations, a portion of an FPC
associated with the ultrasonic fingerprint sensing system may be
positioned over the opening in the midframe to provide a cap for
the sensing system.
[0145] One or more of the electrical shielding layer, the
light-blocking layer and the mechanical stress isolation layer may
serve a thermal function by providing for improved heat dissipation
and better temperature uniformity at the back of the display. Heat
may be non-uniformly generated, for example, from portions of the
display or from nearby components such as batteries in a mobile
device. In some implementations, a single layer or a composite
layer of selected materials positioned between the display and the
ultrasonic sensor system may serve the thermal function. For
example, a single layer of copper may provide electrical shielding,
light blocking and stress isolation capability, in addition to
thermal heat spreading and heat dissipation functions for improved
display performance. In another example, a layer of graphene with
or without other electrical shielding layers, light-blocking layers
or mechanical stress isolation layers may serve the thermal
function.
[0146] One or more acoustic matching layers may be included in the
ultrasonic fingerprint sensor system to minimize acoustic
reflections within the sensor stack and between the sensor stack
and the OLED display. For example, one or more acoustic matching
layers may be inserted between any of the passivation layer,
piezoelectric layer, electrode layer, substrate layer,
light-blocking layer, electrical shielding layer, mechanical stress
isolation layer, thermally conductive layer or adhesive layers to
improve the acoustic performance of the sensor stack.
[0147] FIG. 17 shows an example method of manufacturing an
apparatus including an ultrasonic sensor system underlying a
display. The process 1700 may be performed in a different order or
with different, fewer or additional operations.
[0148] At block 1710 of the process 1700, a display device is
provided where the display device includes a platen and a display
underlying the platen. In some implementations, the platen may
include a cover glass, a cover lens, or an outer layer of the
display or any associated touchscreen. In some implementations, the
display may include an OLED display or an AMOLED display. In some
implementations, the display may include a black foam tape layer
and a copper tape layer on a back side of the display.
[0149] At block 1720 of the process 1700, at least a portion of the
black foam tape layer and the copper tape layer is optionally
removed from the display device. This can expose the back side of
the display. In some implementations, the black foam tape layer is
sufficiently porous to prevent effective transmission of ultrasonic
waves and the copper tape layer is sufficiently thick to prevent
effective transmission of ultrasonic waves.
[0150] At block 1730 of the process 1700, a light-blocking layer,
an electrical shielding layer, a mechanical stress isolation layer,
or combinations thereof may be bonded to the display, where the
electrical shielding layer is electrically conductive and grounded.
In some implementations, bonding the light-blocking layer, the
electrical shielding layer, and/or the mechanical stress isolation
layer includes laminating the light-blocking layer, the electrical
shielding layer, and/or the mechanical stress isolation layer to
the display. For example, the light-blocking layer, the electrical
shielding layer, and/or the mechanical stress isolation layer may
be laminated to a back side of the display using roll-to-roll
lamination. In some implementations, the light-blocking layer is
substantially non-transparent and substantially non-porous. In some
implementations, the electrical shielding layer may include a metal
or metalized plastic having a thickness between about 0.05 .mu.m
and about 10 .mu.m, or between about 0.1 .mu.m and about 6 .mu.m.
In some implementations, the mechanical stress isolation layer may
include a plastic material. The mechanical stress isolation layer
may underlie an adhesive to reduce stresses that may be imparted to
one or both of the display and the ultrasonic sensor system.
[0151] At block 1740 of the process 1700, an ultrasonic sensor
system is bonded to the light-blocking layer, the electrical
shielding layer, the mechanical stress isolation layer, or
combinations thereof, where the ultrasonic sensor system is
underlying the display and configured to transmit and receive
ultrasonic waves in an acoustic path through the display and the
platen, and where the light-blocking layer, the electrical
shielding layer, the mechanical stress isolation layer, or
combinations thereof are in the acoustic path. In some
implementations, bonding the ultrasonic sensor system includes
laminating the ultrasonic sensor to the light-blocking layer, the
electrical shielding layer, and/or the mechanical stress isolation
layer. For example, the ultrasonic sensor system may be laminated
using vacuum lamination.
[0152] The ultrasonic sensor system may include a sensor substrate,
a piezoelectric transceiver layer coupled to the sensor substrate,
a transceiver electrode layer, a passivation layer, and an FPC
coupled to the sensor substrate. In some implementations, the
ultrasonic sensor system may further include one or more backing
layers on the back side of the ultrasonic sensor system, where the
one or more backing layers may include an electrically conductive
and/or substantially optically non-transparent material.
[0153] In some implementations, at least one of the light-blocking
layer and the electrical shielding layer may be bonded to the back
side of the display so that the ultrasonic sensor system is
detachable (e.g., peelable) from the display. Detaching may occur
without damaging the ultrasonic sensor system or the display. For
example, at least one of the light-blocking layer and the
electrical shielding layer may be bonded via an adhesive layer to
the back side of the display, where the adhesive layer may include
a pressure-sensitive adhesive or an epoxy-based adhesive. In some
implementations, the ultrasonic sensor system may be bonded to at
least one of the light-blocking layer and the electrical shielding
layer so that the ultrasonic sensor system is detachable from the
display. Detaching may occur without damaging the ultrasonic sensor
system or the display. For example, the ultrasonic sensor system
may be bonded via an adhesive layer to at least one of the
light-blocking layer and the electrical shielding layer, where the
adhesive layer may include a pressure-sensitive adhesive or an
epoxy-based adhesive.
[0154] FIG. 18 shows an example of using a capacitive sensing mode
and an ultrasonic sensing mode with a fingerprint sensor 525
positioned behind a display 510 of an electronic device 505 to wake
up the electronic device 505. Electronic device 505 may include a
controller 214 that may switch sensor 525 to operate between a
capacitive sensing mode and an ultrasonic sensing mode. The
electronic device 505 may initially be in a locked state in which a
display 510 and an applications processor of the electronic device
505 are turned off or in a low-power sleep mode, as illustrated in
FIG. 18 at time 1850. When an object such as a finger 515 is
detected on or near the sensor 525 using the capacitive sensing
mode and/or the ultrasonic sensing mode, a portion of display 510
may turn on to indicate and highlight the position where the
fingerprint sensor is located as illustrated in FIG. 18 at time
1855. As depicted in FIG. 18, text indicating "Place Finger Here to
Unlock" is shown along with a graphically generated circular icon
565, although many other icons and/or text provided as guidance to
a user to indicate the position of the fingerprint sensor have been
contemplated. The capacitive and/or ultrasonic sensing modes may
continue to be used until the finger 515 is imaged, at which time
the image data may be analyzed and the electronic device 505
unlocked if the authentication process is successfully performed.
The sensor 525 may be positioned underneath a portion of the
display 510, which may be an LCD display, an OLED display or other
type of display. In some implementations, one or more electrodes of
a touchscreen of electronic device 505 may serve as a sensing
electrode for the fingerprint sensor 525 when operating in a
capacitive sensing mode, allowing signals from non-active portions
of the display 510 without the fingerprint sensor 525 to be ignored
by the controller circuit 520 while allowing signals due to a
finger touch from active portions of the display 510 with the
fingerprint sensor 525 to be detected, further reducing inadvertent
wakeup of the electronic device 505.
[0155] FIG. 19 shows a side view of a configuration 1900 with a
fingerprint sensor 525 positioned behind a portion of a display
510. The fingerprint sensor 525 is positioned beneath an LCD or
OLED display 510 and a cover glass or touchscreen that serves as a
platen 306 for the sensor 525. The sensor 525 and associated
sensing electrodes may be configured to operate in a capacitive
sensing mode or an ultrasonic sensing mode. In some
implementations, the sensor 525 may be located near the top,
bottom, edge or in somewhere in an interior portion of the display,
which may include a TFT substrate layer 1920 and other layers 1940
of an LCD or OLED display. In other examples, the sensor 525 may be
positioned beneath or behind all of display 510. In other examples,
the sensor 525 may be integrated within the display TFT substrate
layer 1920. The sensor 525 may be integrated with the display TFT
substrate, sharing common TFT substrates with the active area of
the sensor 525 covering some, none or all of the active area of the
display.
[0156] FIG. 20 shows an example of a flowchart for a method 2000 of
guiding a user of an LCD or OLED display device to position a
finger above an under-LCD or under-OLED fingerprint sensor.
Graphical display-based icons may be helpful for under-display
configurations as use of colored inks or other permanent indicia to
mark the position of the fingerprint sensor that may occlude the
view of a user of the display device (e.g., a mobile device or an
electronic device) can be avoided. In some implementations, the
presence of a finger may be detected by capacitive sensing
electrodes of a touchscreen overlying the display while the display
is off. In some implementations, dedicated sensing electrodes as
part of or near the ultrasonic fingerprint sensor may be used to
detect the presence of a finger. In block 2005, a finger of a user
positioned on a surface of the display may be detected using a
capacitive sensing mode with, for example, the touchscreen or a
dedicated sensing electrode. In block 2010, after detecting the
presence of the finger, a fingerprint sensor icon may be
illuminated on the display. In some implementations, the display
may be partially unlocked to display only the fingerprint sensor
icon or other selective information to guide the user. In some
implementations, a portion of the display may be illuminated while
in a low-power mode, and the icon may be enhanced or other
selective information provided to the user when the finger is
detected. In block 2015, a finger may be detected on the display
above the fingerprint sensor using a capacitive sensing mode, an
ultrasonic sensing mode, or both a capacitive and ultrasonic
sensing mode. In block 2020, the user may be authenticated and the
display unlocked. In alternative configurations such as use of an
OLED screen, the display may continuously show the fingerprint
sensor icon or other selective information using a subset of the
display pixels to guide the user while the mobile device remains
locked.
[0157] As used herein, a phrase referring to "at least one of" a
list of items refers to any combination of those items, including
single members. As an example, "at least one of: a, b, or c" is
intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
[0158] The various illustrative logics, logical blocks, modules,
circuits and algorithm processes 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 processes
described above. Whether such functionality is implemented in
hardware or software depends upon the particular application and
design constraints imposed on the overall system.
[0159] 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 may be implemented as a combination of
computing devices, e.g., 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 processes and
methods may be performed by circuitry that is specific to a given
function.
[0160] In one or more aspects, the functions described may be
implemented in hardware, digital electronic circuitry, computer
software, firmware, 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 may 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.
[0161] 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, such as a non-transitory medium. The
processes of a method or algorithm disclosed herein may be
implemented in a processor-executable software module that may
reside on a computer-readable medium. Computer-readable media
include both computer storage media and communication media
including any medium that may be enabled to transfer a computer
program from one place to another. Storage media may be any
available media that may be accessed by a computer. By way of
example and not limitation, non-transitory 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 may 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 should also 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.
[0162] Various modifications to the implementations described in
this disclosure may be readily apparent to those having ordinary
skill 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 disclosure is not intended
to be limited to the implementations shown herein, but is to be
accorded the widest scope consistent with the claims, the
principles and the novel features disclosed herein. The word
"exemplary" is used exclusively herein, if at all, 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 implementations.
[0163] Certain features that are described in this specification in
the context of separate implementations may also be implemented in
combination in a single implementation. Conversely, various
features that are described in the context of a single
implementation may also 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 may in some cases be excised from the
combination, and the claimed combination may be directed to a
subcombination or variation of a subcombination.
[0164] Similarly, while operations are depicted in the drawings in
a particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results. 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 may 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 may be performed in a different order
and still achieve desirable results.
[0165] It will be understood that unless features in any of the
particular described implementations are expressly identified as
incompatible with one another or the surrounding context implies
that they are mutually exclusive and not readily combinable in a
complementary and/or supportive sense, the totality of this
disclosure contemplates and envisions that specific features of
those complementary implementations may be selectively combined to
provide one or more comprehensive, but slightly different,
technical solutions. It will therefore be further appreciated that
the above description has been given by way of example only and
that modifications in detail may be made within the scope of this
disclosure.
* * * * *