U.S. patent application number 15/828209 was filed with the patent office on 2021-05-06 for ambient light determination using physiological metric sensor data.
The applicant listed for this patent is Fitbit, Inc.. Invention is credited to Sebastian Joseph CAPELLA, Heiko Gernot Albert Panther, Felix Antoine TURGEON, Subramaniam Venkatraman, Shelten Gee Jao Yuen.
Application Number | 20210131863 15/828209 |
Document ID | / |
Family ID | 1000005535198 |
Filed Date | 2021-05-06 |
![](/patent/app/20210131863/US20210131863A9-20210506\US20210131863A9-2021050)
United States Patent
Application |
20210131863 |
Kind Code |
A9 |
TURGEON; Felix Antoine ; et
al. |
May 6, 2021 |
AMBIENT LIGHT DETERMINATION USING PHYSIOLOGICAL METRIC SENSOR
DATA
Abstract
A wearable computing device includes an electronic display with
a configurable brightness level setting, a physiological metric
sensor system including a light source configured to direct light
into tissue of a user wearing the wearable computing device and a
light detector configured to detect light from the light source
that reflects back from the user. The device may further include
control circuitry configured to activate the light source during a
first period, generate a first light detector signal indicating a
first amount of light detected by the light detector during the
first period, deactivate the light source during a second period,
generate a second light detector signal indicating a second amount
of light detected by the light detector during the second period,
generate a physiological metric based at least in part on the first
light detector signal and the second light detector signal, and
modify the configurable brightness level setting based on the
second light detector signal.
Inventors: |
TURGEON; Felix Antoine;
(Poway, CA) ; CAPELLA; Sebastian Joseph; (San
Diego, CA) ; Venkatraman; Subramaniam; (Walnut Creek,
CA) ; Yuen; Shelten Gee Jao; (Berkeley, CA) ;
Panther; Heiko Gernot Albert; (Berlin, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fitbit, Inc. |
San Francisco |
CA |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20180156660 A1 |
June 7, 2018 |
|
|
Family ID: |
1000005535198 |
Appl. No.: |
15/828209 |
Filed: |
November 30, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15436440 |
Feb 17, 2017 |
10209365 |
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15828209 |
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13924784 |
Jun 24, 2013 |
8954135 |
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15436440 |
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14940072 |
Nov 12, 2015 |
9572533 |
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15436440 |
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14700069 |
Apr 29, 2015 |
9198604 |
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14940072 |
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14290909 |
May 29, 2014 |
9044171 |
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14700069 |
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13924784 |
Jun 24, 2013 |
8954135 |
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14290909 |
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62428158 |
Nov 30, 2016 |
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61662961 |
Jun 22, 2012 |
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61752826 |
Jan 15, 2013 |
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61752826 |
Jan 15, 2013 |
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61662961 |
Jun 22, 2012 |
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61973614 |
Apr 1, 2014 |
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61955045 |
Mar 18, 2014 |
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61946439 |
Feb 28, 2014 |
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61830600 |
Jun 3, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/1455 20130101;
G01J 1/4204 20130101; G01J 1/32 20130101; G06K 9/2027 20130101;
A61B 5/681 20130101; A61B 5/489 20130101; G09G 5/10 20130101 |
International
Class: |
G01J 1/42 20060101
G01J001/42; A61B 5/1455 20060101 A61B005/1455; G09G 5/10 20060101
G09G005/10; G01J 1/32 20060101 G01J001/32; A61B 5/00 20060101
A61B005/00; G06K 9/20 20060101 G06K009/20 |
Claims
1. A wearable computing device comprising: an electronic display
with a configurable brightness level setting; a physiological
metric sensor system, including a light source configured to direct
light into tissue of a user when the user is wearing the wearable
computing device and a light detector configured to detect light
from the light source that reflects back from the user; and control
circuitry configured to: activate the light source during a first
period; generate a first light detector signal indicating a first
amount of light detected by the light detector during the first
period; deactivate the light source during a second period;
generate a second light detector signal indicating a second amount
of light detected by the light detector during the second period;
generate a physiological metric based at least in part on the first
light detector signal and the second light detector signal; and
modify the configurable brightness level setting based at least in
part on the second light detector signal.
2. The wearable computing device of claim 1, wherein the control
circuitry is further configured to: determine one or more
physiological characteristics of the user; adjust one or more
illumination parameters of the light source based on the determined
one or more physiological characteristics; and adjust one or more
reception parameters of the light detector based on the determined
one or more physiological characteristics.
3. The wearable computing device of claim 1, wherein the control
circuitry is further configured to adjust the one or more reception
parameters of the light detector before generating the second light
detector signal.
4. The wearable computing device of claim 1, wherein the control
circuitry is further configured to adjust the one or more
illumination parameters and to adjust the one or more reception
parameters before activating the light source during the first
period.
5. The wearable computing device of claim 1, wherein the control
circuitry is configured to generate the physiological metric at
least in part by partially cancelling an effect of ambient light on
the first light detector signal.
6. The wearable computing device of claim 5, wherein cancelling the
effect of ambient light on the first light detector signal
comprises subtracting out the second amount of light from the first
amount of light.
7. The wearable computing device of claim 1, wherein the control
circuitry is configured to generate the first light detector signal
and the second light detector signal using a transimpedance
amplifier coupled to sample-and-hold circuitry.
8. The wearable computing device of claim 1, wherein the electronic
display is associated with a first side of the wearable computing
device and the light source and light detector are associated with
a second side of the wearable computing device.
9. The wearable computing device of claim 1, wherein said modifying
the configurable brightness level setting comprises changing the
configurable brightness level setting associated with a first mode
to a second mode.
10. The wearable computing device of claim 9, wherein the first
mode corresponds to an outdoor lighting condition and the second
mode corresponds to an indoor lighting condition.
11. The wearable computing device of claim 9, wherein the first
mode corresponds to an indoor lighting condition and the second
mode corresponds to an outdoor lighting condition.
12. The wearable computing device of claim 9, wherein the second
mode is associated with a relatively higher brightness level
compared to the first mode.
13. The wearable computing device of claim 9, wherein the second
mode is associated with a relatively lower brightness level
compared to the first mode.
14. The wearable computing device of claim 9, wherein the control
circuitry is further configured to lock the configurable brightness
level setting of the electronic display in the second mode until
the electronic display is powered down.
15. The wearable computing device of claim 9, wherein the first
mode and the second mode form a subset of a group of three or more
operational brightness modes for the electronic display.
16. The wearable computing device of claim 1, wherein the light
source comprises a plurality of LED light sources.
17. The wearable computing device of claim 1, wherein the control
circuitry is further configured to: determine whether an amplitude
of the second light detector signal is greater than a threshold
value; and modify the configurable brightness level setting based
at least in part on said determination.
18. A biometric monitoring device comprising: an electronic display
associated with a first side of the biometric monitoring device,
the electronic display having a configurable brightness level
setting; a physiological metric sensor system including a light
source and a light detector associated with a second side of the
biometric monitoring device, the physiological metric sensor system
being configured to generate a physiological metric signal at least
in part by: directing light from the light source into a user
during a first period of time; detecting a first amount of light
detected by the light detector during the first period of time, the
first amount of light including reflected light from the light
source and first ambient light; detecting a second amount of light
detected by the light detector during a second period of time, the
second amount of light including second ambient light; and
cancelling at least a part of the first ambient light in the first
amount of light based on the second amount of light; and control
circuitry configured to adjust the configurable brightness level
setting of the electronic display based at least in part on the
second amount of light.
19. The biometric monitoring device of claim 18, wherein the
physiological metric sensor system is configured to generate the
physiological metric signal substantially continuously.
20. The biometric monitoring device of claim 18, wherein the second
period of time occurs temporally before the first period of
time.
21. The biometric monitoring device of claim 18, wherein the
control circuitry is further configured to: determine one or more
physiological characteristics of the user; adjust one or more
illumination parameters of the light source based on the determined
one or more physiological characteristics; and adjust one or more
reception parameters of the light detector based on the determined
one or more physiological characteristics.
22. A method of managing power in a wearable computing device, the
method comprising: directing light from a light source into tissue
of a user during a first time period; generating a first light
detector signal using a skin-facing light detector, the first light
detector signal indicating a first amount of light detected by the
light detector during the first period; deactivating the light
source during a second period; generating a second light detector
signal using the skin-facing light detector, the second light
detector signal indicating a second amount of light detected by the
light detector during the second period; generating a physiological
metric signal based at least in part on the first light detector
signal and the second light detector signal; and modifying a
brightness level of an electronic display based at least in part on
the second light detector signal.
23. The method of claim 22, wherein said generating the
physiological metric signal comprises generating an ambient light
cancellation signal based on the second light detector signal and
cancelling ambient light in the first light detector signal using
the ambient light cancellation signal.
24. The method of claim 23, wherein said generating the ambient
light cancellation signal further comprises conditioning the second
light detector signal to account for skin tone characteristics of
the user.
25. The method of claim 24, further comprising at least partially
reversing the conditioning of the second light detector signal to
produce a raw ambient light signal, wherein said modifying the
brightness level of the electronic display is based at least in
part on the raw ambient light signal.
26. The method of claim 25, further comprising determining whether
an amplitude of the raw ambient light signal is greater than a
threshold.
27. The method of claim 22, further comprising determining an
amount of sun exposure of the user based at least in part on the
second light detector signal.
28. The method of claim 22, further comprising storing a value
associated with the second light detector signal in a circular
buffer.
29. The method of claim 22, further comprising determining whether
an amplitude of the second light detector signal is greater than a
threshold.
30. The method of claim 22, wherein said modifying the brightness
level of the electronic display comprises adjusting the brightness
level from a first state to a second state.
31. The method of claim 30, wherein the first state corresponds to
a low-light mode and the second state corresponds to a high-light
mode.
32. The method of claim 22, further comprising: determining one or
more physiological characteristics of the user; adjusting one or
more illumination parameters of the light source based on the
determined one or more physiological characteristics; and adjusting
one or more reception parameters of the light detector based on the
determined one or more physiological characteristics.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 62/428,158 filed Nov. 30, 2016, entitled AMBIENT
LIGHT DETERMINATION USING PHYSIOLOGICAL METRIC SENSOR DATA, the
disclosure of which is expressly incorporated by reference herein
in its entirety.
BACKGROUND
Field
[0002] The present disclosure generally relates to the field of
wearable electronic devices.
Description of Related Art
[0003] Wearable electronic devices can generate and/or provide
information related to physiological metrics associated with a
user. Information may be presented to the user through the use of
an electronic display that is illuminated using a display
illumination component.
SUMMARY
[0004] In some implementations, the present disclosure relates to a
wearable computing device comprising an electronic display with a
configurable brightness level setting, a physiological metric
sensor system including a light source configured to direct light
into tissue of a user when the user is wearing the wearable
computing device and a light detector configured to detect light
from the light source that reflects back from the user, and control
circuitry. The control circuitry is configured to activate the
light source during a first period, generate a first light detector
signal indicating a first amount of light detected by the light
detector during the first period, deactivate the light source
during a second period, generate a second light detector signal
indicating a second amount of light detected by the light detector
during the second period, generate a physiological metric based at
least in part on the first light detector signal and the second
light detector signal, and modify the configurable brightness level
setting based at least in part on the second light detector
signal.
[0005] The control circuitry may be further configured to determine
one or more physiological characteristics of the user, adjust one
or more illumination parameters of the light source based on the
determined one or more physiological characteristics and adjust one
or more reception parameters of the light detector based on the
determined one or more physiological characteristics.
[0006] In some embodiments, the control circuitry is further
configured to adjust the one or more reception parameters of the
light detector before generating the second light detector signal.
The control circuitry may be further configured to adjust the one
or more illumination parameters and to adjust the one or more
reception parameters before activating the light source during the
first period.
[0007] The control circuitry may be configured to generate the
physiological metric at least in part by partially cancelling an
effect of ambient light on the first light detector signal. For
example, cancelling the effect of ambient light on the first light
detector signal may involve subtracting out the second amount of
light from the first amount of light. In certain embodiments, the
control circuitry is configured to generate the first light
detector signal and the second light detector signal using a
transimpedance amplifier coupled to sample-and-hold circuitry. The
electronic display may be associated with a first (e.g., front)
side of the wearable computing device and the light source and
light detector may be associated with a second (e.g., back) side of
the wearable computing device.
[0008] Modifying the configurable brightness level setting may
involve changing the configurable brightness level setting from a
first mode to a second mode. In certain embodiments, the first mode
corresponds to an outdoor lighting condition and the second mode
corresponds to an indoor lighting condition. In certain
embodiments, the first mode corresponds to an indoor lighting
condition and the second mode corresponds to an outdoor lighting
condition. The second mode may be associated with a relatively
higher brightness compared to the first mode. Alternatively, the
second mode may be associated with a relatively lower brightness
compared to the first mode. The control circuitry may be further
configured to lock the configurable brightness level setting of the
electronic display in the second mode until the electronic display
is powered down. In certain embodiments, the first mode and the
second mode are a subset of a group of three or more operational
brightness modes for the electronic display.
[0009] In certain embodiments, the light source comprises a
plurality of LED light sources. In certain embodiments, the control
circuitry is further configured to determine whether an amplitude
of the second light detector signal is greater than a threshold
value, wherein said modifying the configurable brightness level
setting is based at least in part on said determination.
[0010] In some implementations, the present disclosure relates to a
biometric monitoring device comprising an electronic display
associated with a first (e.g., front) side of the biometric
monitoring device, the electronic display having a configurable
brightness level setting, and a physiological metric sensor system
including a light source and a light detector associated with a
second (e.g., back) side of the biometric monitoring device. The
physiological metric sensor system is configured to generate a
physiological metric signal at least in part by directing light
from the light source into a user during a first period of time,
detecting a first amount of light during the first period of time,
the first amount of light including reflected light from the light
source and first ambient light, detecting a second amount of light
during a second period of time using the light detector, the second
amount of light including second ambient light, and at least
partially cancelling the first ambient light in the first amount of
light based on the second amount of light. The biometric monitoring
device further comprises control circuitry configured to adjust the
configurable brightness level setting of the electronic display
based at least in part on the second amount of light.
[0011] The physiological metric sensor system may be configured to
generate the physiological metric signal substantially
continuously. In certain embodiments, the second period of time
occurs temporally before the first period of time.
[0012] In some embodiments, the control circuitry of the biometric
monitoring device is further configured to determine one or more
physiological characteristics of the user, adjust one or more
illumination parameters of the light source based on the determined
one or more physiological characteristics and adjust one or more
reception parameters of the light detector based on the determined
one or more physiological characteristics.
[0013] In some implementations, the present disclosure relates to a
method of managing power in a wearable computing device. The method
comprises directing light from a light source into tissue of a user
during a first time period, generating a first light detector
signal using a skin-facing light detector, the first light detector
signal indicating a first amount of light detected by the light
detector during the first period, deactivating the light source
during a second period, generating a second light detector signal
using the skin-facing light detector, the second light detector
signal indicating a second amount of light detected by the light
detector during the second period, generating a physiological
metric signal based at least in part on the first light detector
signal and the second light detector signal, and modifying a
brightness level of an electronic display based at least in part on
the second light detector signal.
[0014] Generating the physiological metric signal may comprise
generating an ambient light cancellation signal based on the second
light detector signal and cancelling ambient light in the first
light detector signal using the ambient light cancellation signal.
In certain embodiments, generating the ambient light cancellation
signal further comprises conditioning the second light detector
signal to account for skin tone characteristics of the user. The
method may further comprise at least partially reversing the
conditioning of the second light detector signal to produce a raw
ambient light signal, wherein said modifying the brightness level
of the electronic display is based at least in part on the raw
ambient light signal. In certain embodiments, the method further
comprises determining whether an amplitude of the raw ambient light
signal is greater than a threshold.
[0015] In certain embodiments, the method further comprises
determining an amount of sun exposure of the user based at least in
part on the second light detector signal. In certain embodiments,
the method may further comprise storing a value associated with the
second light detector signal in a circular buffer. In certain
embodiments, the method further comprises determining whether an
amplitude of the second light detector signal is greater than a
threshold. In certain embodiments, modifying the brightness level
of the electronic display comprises adjusting the brightness level
from a first state to a second state. For example, the first state
may correspond to a low-light mode and the second state may
correspond to a high-light mode.
[0016] The method may further include determining one or more
physiological characteristics of the user, adjusting one or more
illumination parameters of the light source based on the determined
one or more physiological characteristics and adjusting one or more
reception parameters of the light detector based on the determined
one or more physiological characteristics.
[0017] In some implementations, the present disclosure relates to a
biometric monitoring device comprising a physiological metric
monitor module including a light source and a light detector
associated with a back side of the biometric monitoring device, the
physiological metric monitor module being configured to generate a
physiological metric signal when the light source is turned on, and
control circuitry configured to determine an amount of ambient
light present using the light detector associated with the back
side of the biometric monitoring device when the light source is
turned off.
[0018] In certain embodiments, the biometric monitoring device
further comprises an electronic display associated with a front
side of the biometric monitoring device, wherein the control
circuitry is further configured to adjust a brightness level
setting of the electronic display based at least in part on the
determined amount of ambient light. The physiological metric
monitor module may be further configured to generate the
physiological metric signal when the light source is turned
off.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Various embodiments are depicted in the accompanying
drawings for illustrative purposes, and should in no way be
interpreted as limiting the scope of the inventions. In addition,
various features of different disclosed embodiments can be combined
to form additional embodiments, which are part of this disclosure.
Throughout the drawings, reference numbers may be reused to
indicate correspondence between reference elements.
[0020] FIG. 1 is a block diagram illustrating an embodiment of a
biometric monitoring device according to one or more
embodiments.
[0021] FIG. 2 provides a perspective front and side view of a
wearable biometric monitoring device according to one or more
embodiments.
[0022] FIG. 3 provides a perspective back and side view of the
wearable biometric monitoring device of FIG. 2 according to one or
more embodiments.
[0023] FIG. 4 provides a cross-sectional view of the biometric
monitoring device of FIG. 2 according to one or more
embodiments.
[0024] FIG. 5 provides a cross sectional view of a sensor
protrusion of a biometric monitoring device according to one or
more embodiments.
[0025] FIG. 6 provides a cross sectional view of a sensor
protrusion of a biometric monitoring device according to one or
more embodiments.
[0026] FIG. 7A illustrates photoplethysmograph (PPG) sensor module
according to one or more embodiments.
[0027] FIGS. 7B and 7C illustrate examples of a PPG sensor having a
photodetector and two LED light sources according to one or more
embodiments.
[0028] FIG. 8 illustrates an example of an optimized PPG detector
according to one or more embodiments.
[0029] FIG. 9 provides a perspective front and side view of a
wearable biometric monitoring device according to one or more
embodiments.
[0030] FIG. 10 provides a perspective back and side view of a
wearable biometric monitoring device according to one or more
embodiments.
[0031] FIG. 11A illustrates an example block diagram of a PPG
sensor which has a light source, light detector, ADC, processor,
DAC/GPIOs, and light source intensity and on/off control according
to one or more embodiments.
[0032] FIG. 11B illustrates an example block diagram of a PPG
sensor that is similar to that of FIG. 11A which additionally uses
a sample-and-hold circuit as well as analog signal conditioning
according to one or more embodiments.
[0033] FIG. 11C illustrates an example block diagram of a PPG
sensor that is similar to that of FIG. 11A which additionally uses
a sample-and-hold circuit according to one or more embodiments.
[0034] FIG. 11D illustrates an example block diagram of a PPG
sensor having multiple switchable light sources and detectors,
light source intensity/on and off control, and signal conditioning
circuitry according to one or more embodiments.
[0035] FIG. 11E illustrates an example block diagram of a PPG
sensor which uses synchronous detection. To perform this type of
PPG detection, it has a demodulator according to one or more
embodiments.
[0036] FIG. 11F illustrates an example block diagram of a PPG
sensor which, in addition to the features of the sensor illustrated
in FIG. 11A, has a differential amplifier according to one or more
embodiments.
[0037] FIG. 11G illustrates an example block diagram of a PPG
sensor according to one or more embodiments.
[0038] FIG. 12A illustrates an example schematic of a
sample-and-hold circuit and differential/instrumentation amplifier
which may be used in PPG sensing according to one or more
embodiments.
[0039] FIG. 12B illustrates an example schematic of a circuit for a
PPG sensor using a controlled current source to offset "bias"
current prior to a transimpedance amplifier according to one or
more embodiments.
[0040] FIG. 12C illustrates an example schematic of a circuit for a
PPG sensor using a sample-and-hold circuit for current feedback
applied to photodiode according to one or more embodiments.
[0041] FIG. 12D illustrates an example schematic of a circuit for a
PPG sensor using a differential/instrumentation amplifier with
ambient light cancellation functionality according to one or more
embodiments.
[0042] FIG. 12E illustrates an example schematic of a circuit for a
PPG sensor using a photodiode offset current generated dynamically
by a DAC according to one or more embodiments.
[0043] FIG. 12F illustrates an example schematic of a circuit for a
PPG sensor using a photodiode offset current generated dynamically
by a controlled voltage source according to one or more
embodiments.
[0044] FIG. 12G illustrates an example schematic of a circuit for a
PPG sensor including ambient light removal functionality using a
"switched capacitor" method according to one or more
embodiments.
[0045] FIG. 12H illustrates an example schematic of a circuit for a
PPG sensor that uses a photodiode offset current generated by a
constant current source according to one or more embodiments.
[0046] FIG. 12I illustrates an example schematic of a circuit for a
PPG sensor that includes ambient light removal functionality and
differencing between consecutive samples according to one or more
embodiments.
[0047] FIG. 12J illustrates an example schematic of a circuit for
ambient light removal and differencing between consecutive samples
according to one or more embodiments.
[0048] FIG. 13 shows an example light emission driver circuit for
driving a light emitter to emit a light signal onto a region of the
skin of a user according to one or more embodiments.
[0049] FIG. 14 shows a block diagram of an example light detection
circuit for detecting a scattered light signal and for outputting
an output signal based on the scattered light signal according to
one or more embodiments.
[0050] FIG. 15 shows an example circuit for implementing the light
detection circuit of FIG. 14 according to one or more
embodiments.
[0051] FIG. 16 is a flow diagram illustrating a process for
adjusting a backlighting setting of an electronic display according
to one or more embodiments.
[0052] FIG. 17 is a block diagram illustrating an embodiment of a
display control feedback system according to one or more
embodiments.
DETAILED DESCRIPTION
[0053] The headings provided herein are for convenience only and do
not necessarily affect the scope or meaning of the claimed
invention. Like reference numbers and designations in the various
drawings may or may not indicate like elements.
[0054] Although certain preferred embodiments and examples are
disclosed below, inventive subject matter extends beyond the
specifically disclosed embodiments to other alternative embodiments
and/or uses and to modifications and equivalents thereof. Thus, the
scope of the claims that may arise herefrom is not limited by any
of the particular embodiments described below. For example, in any
method or process disclosed herein, the acts or operations of the
method or process may be performed in any suitable sequence and are
not necessarily limited to any particular disclosed sequence.
Various operations may be described as multiple discrete operations
in turn, in a manner that may be helpful in understanding certain
embodiments; however, the order of description should not be
construed to imply that these operations are order dependent.
Additionally, the structures, systems, and/or devices described
herein may be embodied as integrated components or as separate
components. For purposes of comparing various embodiments, certain
aspects and advantages of these embodiments are described. Not
necessarily all such aspects or advantages are achieved by any
particular embodiment. Thus, for example, various embodiments may
be carried out in a manner that achieves or optimizes one advantage
or group of advantages as taught herein without necessarily
achieving other aspects or advantages as may also be taught or
suggested herein.
Overview
[0055] Biometric monitoring devices, including wrist-worn biometric
monitoring devices, can include display screens powered by an
internal power source. Due to power and/or visibility
considerations, it may be desirable for the brightness setting of
the display screen to be adjusted from time to time. For example,
when ambient light levels are high, it may be desirable for the
brightness setting of the display to be at a high level, while when
ambient light levels are low, it may be desirable for the
brightness setting of the display to be at a lower level in order
to save power and/or reduce the visual strain on the user or reduce
other effects associated with over-lighting.
[0056] In order to make backlight setting adjustment based on
ambient lighting, it may be necessary to generate or otherwise
determine information indicating the ambient light level.
Brightness level settings for electronic displays, as described
herein in connection with various embodiments, may be implemented
in any suitable or desirable manner. For example, with respect to
liquid crystal display (LCD) devices, the brightness level of the
display may be controlled using one or more backlighting devices
and/or subsystems. Backlighting devices/subsystems may generally
direct light to the electronic display from behind the display. In
certain devices, display brightness may be achieved at least in
part by reflecting environmental ambient light to light the display
as an alternative to, or in addition to, providing light from a
backlight device/subsystem. For example, certain devices may
include an at least partially transparent light guide structure
configured to reflect light entering the light guide from side or
edge portions thereof towards the display screen. Although certain
embodiments disclosed herein may be described in the context of
backlighting devices and/or subsystems, it should be understood
that display brightness level setting adjustment in accordance with
the present disclosure may implement any suitable or desirable
lighting mechanism, and that description herein of backlighting
brightness level adjustment should be understood to relate to
brightness level setting adjustment for non-backlighting
devices/subsystems as well.
[0057] Ambient light determinations may be made using dedicated
ambient light sensors, such as in the form of an outward-facing
sensor disposed on or below the display screen of a biometric
monitoring device. Dedicated ambient light sensors may provide
relatively high fidelity data indicating ambient lighting
conditions. Biometric monitoring devices that do not include
ambient light sensing functionality may lack the ability to adjust
display brightness settings based on ambient lighting conditions,
and therefore may necessarily maintain the display brightness at a
maximum operational level at all times to account for the brightest
expected ambient light conditions, such as direct outdoor sunlight
conditions. The inability to intelligently modify the brightness
level setting of the display can have an adverse effect on a
biometric monitoring device's battery life, among other things.
Therefore, dedicated ambient light sensors may be used to adjust
the brightness of a display to conserve battery power and/or
provide an improved user experience.
[0058] Certain embodiments disclosed herein provide for display
brightness level setting adjustment, such as backlighting
adjustment, without the aid of an outward-facing dedicated ambient
light sensor. For example, biometric monitoring devices in
accordance with the present disclosure may incorporate one or more
existing functional components or modules designed for determining
one or more physiological metrics associated with a user (e.g.,
wearer) of the device, such as a heart rate sensor or the like.
Such components/modules may be disposed or associated with an
underside/backside of the biometric monitoring device, and may
generally not be in direct exposure to a substantial portion of the
ambient light that is present when the biometric monitoring device
is worn by a user. For example, where the biometric monitoring
device is worn on the user's wrist, the physiological metric
component(s)/module(s) may be associated with an underside/backside
of the device substantially opposite the display and facing the arm
of the user. However, certain underside/backside physiological
metric sensor devices or subsystems, such as heart rate sensors in
accordance with the present disclosure, may nevertheless be
configurable to provide signals indicative of ambient lighting
conditions through indirect, or reflective, light detection.
[0059] Certain embodiments disclosed herein provide for biometric
monitoring devices that utilize ambient light readings derivable
from a physiological metric sensor, such as a hear rate sensor
(e.g., photoplethysmograph sensor) associated with an underside of
a wrist-worn device, for adjusting brightness level settings for
the device's electronic display. For example, ambient light
readings from a backside physiological metric sensor may be
converted to a common reference frame for utilization thereof.
Ambient light determination using a backside physiological metric
sensor may provide relatively more basic ambient light information
than may be achievable using a dedicated outward-facing ambient
light sensor, but may still provide adequate information from which
to make ambient light determinations among a finite set of ambient
light level ranges, such as determining whether ambient lighting
conditions indicate indoor or outdoor lighting. Therefore, certain
embodiments disclosed herein allow for the detection of indoor
versus outdoor lighting conditions without a dedicated
outward-facing ambient light sensor by leveraging an existing
physiological metric sensor, thereby providing savings with respect
to power and extended battery life.
Biometric Monitoring
[0060] In some implementations, the present disclosure is related
to biometric monitoring devices. The term "biometric monitoring
device" is used herein according to its broad and ordinary meaning,
and may be used in various contexts herein to refer to any type of
biometric tracking devices, personal health monitoring devices,
portable monitoring devices, portable biometric monitoring devices,
or the like. In some embodiments, biometric monitoring devices in
accordance with the present disclosure may be wearable devices,
such as may be designed to be worn (e.g., continuously) by a person
(i.e., "user," "wearer," etc.). When worn, such biometric
monitoring devices may be configured to gather data regarding
activities performed by the wearer, or regarding the wearer's
physiological state. Such data may include data representative of
the ambient environment around the wearer or the wearer's
interaction with the environment. For example, the data may
comprise motion data regarding the wearer's movements, ambient
light, ambient noise, air quality, etc., and/or physiological data
obtained by measuring various physiological characteristics of the
wearer, such as heart rate, perspiration levels, and the like.
[0061] In some cases, a biometric monitoring device may leverage
other devices external to the biometric monitoring device, such as
an external heart rate monitor in the form of an EKG sensor for
obtaining heart rate data, or a GPS receiver in a smartphone may be
used to obtain position data, for example. In such cases, the
biometric monitoring device may communicate with these external
devices using wired or wireless communications connections. The
concepts disclosed and discussed herein may be applied to both
stand-alone biometric monitoring devices as well as biometric
monitoring devices that leverage sensors or functionality provided
in external devices, e.g., external sensors, sensors or
functionality provided by smartphones, etc.
Biometric Monitoring Devices
[0062] Systems, devices and/or methods/processes in accordance with
the present disclosure may comprise, or be implemented in
connection with, a biometric monitoring device Embodiments of the
present disclosure may provide biometric monitoring devices
configured to adjust electronic display brightness level settings
using ambient light information derived from one or more
physiological metric sensors associated with an underside/backside
of the biometric monitoring device. It is to be understood that
while the concepts and discussion included herein are presented in
the context of biometric monitoring devices, these concepts may
also be applied in other contexts as well if the appropriate
hardware is available. For example, some or all of the relevant
sensor functionality may be incorporated in one or more external
computing devices (e.g., smartphone) communicatively coupled to the
biometric monitoring device.
[0063] FIG. 1 is a block diagram illustrating an embodiment of a
biometric monitoring device 100 in accordance with one or more
embodiments disclosed herein. The biometric monitoring device 100
may be worn by a user 10. The biometric monitoring device 100 may
include one or more electronic display units or modules 130, such
as a touchscreen display, or the like. In certain embodiments, the
electronic display 130 may be associated with the front side of the
biometric monitoring device 100. For example, in wearable
embodiments of the biometric monitoring device 100, the electronic
display 130 may be configured to be externally presented to a user
viewing the biometric monitoring device 100. In certain
embodiments, the electronic display is illuminated using
backlighting, or other lighting mechanism, according to a
brightness level setting. In certain embodiments, the display 130
is a front-facing organic light emitting diode (OLED) display.
Driving the illumination of the electronic display 130 may
represent one of the largest power consumers of the biometric
monitoring device 100. In certain embodiments, the brightness of
the electronic display is modified according to an ambient light
determination, which may, in some cases, provide a power savings of
approximately 20-30%, or more, with respect to battery life of the
device by reducing the power applied to illuminate the display 130
during certain periods.
[0064] Front-facing ambient light sensors may have additional
hardware/circuitry associated therewith. Furthermore, it may be
desirable to provide display screen treatment to accommodate
front-facing ambient light sensors, such as a window in the display
screen where the display screen is at least partially covered
underneath with a dark paint or the like. While certain
front-facing displays of biometric monitoring devices may have
dedicated ambient light sensors associated therewith, the biometric
monitoring device 100 may be configured to make ambient light
determinations without a dedicated ambient light sensor, and may
instead repurpose ambient-light-related data from a separate
back-facing physiological metric sensor 141 (e.g., optical sensor).
By leveraging ambient light data generated using a back-facing
physiological metric sensor, certain embodiments disclosed here may
advantageously provide cost savings and/or reduced device
complexity
[0065] The biometric monitoring device 100 includes control
circuitry 110. Although certain modules and/or components are
illustrated as part of the control circuitry 110 in the diagram of
FIG. 1, it should be understood that control circuitry associated
with the biometric monitoring device 100 and/or other components or
devices in accordance with the present disclosure may include
additional components and/or circuitry, such as one or more of the
additional illustrated components of FIG. 1. Furthermore, in
certain embodiments, one or more of the illustrated components of
the control circuitry 110 may be omitted and/or different than that
shown in FIG. 1 and described in association therewith. The term
"control circuitry" is used herein according to its broad and
ordinary meaning, and may include any combination of software
and/or hardware elements, devices or features, which may be
implemented in connection with operation of the biometric
monitoring device 100. Furthermore, the term "control circuitry"
may be used substantially interchangeably in certain contexts
herein with one or more of the terms "controller," "integrated
circuit," "IC," "application-specific integrated circuit," "ASIC,"
"controller chip," or the like.
[0066] The control circuitry 110 may comprise one or more
processors, data storage devices, and/or electrical connections.
For example, the control circuitry 110 may comprise one or more
processors configured to execute operational code for the biometric
monitoring device 100, such as firmware or the like, wherein such
code may be stored in one or more data storage devices of the
biometric monitoring device 100. In one embodiment, the control
circuitry 110 is implemented on an SoC (system on a chip), though
those skilled in the art will recognize that other
hardware/firmware implementations are possible.
[0067] The control circuitry 110 may comprise a brightness level
management module 111. The brightness level management module 111
may comprise one or more hardware and/or software components or
features configured to control a brightness level setting for the
electronic display 130. In certain embodiments, the brightness
level management module 111 may comprise ambient light detection
functionality, wherein data associated with, or indicative of,
ambient lighting conditions of an environment in which the
biometric monitoring device 100 is disposed may be used to
determine an appropriate or desirable brightness level setting for
the electronic display 130.
[0068] The control circuitry 110 may further comprise an optical
physiological metric sensor 141 that includes: a physiological
metric calculation module 115, which may be configured to determine
one or more physiological metrics associated with the user 10 of
the biometric monitoring device 100; light source(s) 140 located on
the backside of the device, which may be configured to emit light
in one or more wavelengths; and light detector(s) 145 located on
the backside of the device, which may be configured to detect light
reflected from the tissue of the user 10. As is discussed below,
the optical physiological metric sensor 141 may include circuitry
configured to detect ambient lighting conditions using the light
detector(s) 145 in order to subtract or cancel the unwanted ambient
light from the optical readings of the light detector(s) 145. For
example, ambient light reflected into the light detector(s) 145 may
distort the sensor signal that is designed to generate readings
indicative of light originating from the light sources(s) 140.
[0069] The physiological metric calculation module 115 may be
configured to generate physiological metric data based on readings
from one or more light detectors 145, and/or one or more other
sensor devices 155. The light detectors 145 may be configured to
detect light generated by one or more light sources 140, as well as
ambient light to which the detector 145 is exposed.
[0070] As mentioned above, the light sources 140 and/or light
detector 145 may be associated with the backside of the biometric
monitoring device 100. For example, in a wearable configuration of
the biometric monitoring device 100, whereas the electronic display
may be generally outward-facing, the light sources 140 and/or light
detectors 145 may be physically connected to and/or associated with
an underside (i.e., backside) of the biometric monitoring device
that may be generally skin-facing when worn by the user 10, such as
on a wrist, arm, leg, or other appendage or body part of the user
10.
[0071] In operation, in certain embodiments, the physiological
metric calculation module 115 may be configured to activate the
light source(s) 140 and/or otherwise cause the light source(s) 140
to generate or direct the light in a direction towards the tissue
or body of the user 10, wherein the light detector(s) 145 detects
light reflecting back from the user. Such detected reflected light
from the user may be used to determine one or more physiological
metrics associated with the user 10, such as heart rate, blood
oxygenation, or the like. To the extent that the reflected light
detected by the light detector 145 includes direct or reflected
ambient light in addition to the light generated by the light
source(s) 140, such additional light may undesirably obfuscate the
determination of the relevant physiological metric(s). Therefore,
in certain embodiments, the physiological metric calculation module
115 may be configured to at least partially cancel out the detected
ambient light in order to provide more accurate physiological
metric calculation. In certain embodiments, the physiological
metric calculation module 115 may cancel out the ambient light at
least in part by utilizing a reading from the light detector 145
during a period of time in which the light sources 140 are not
activated in order to obtain a reading indicative of the ambient
light exposed to the light detector 145. In order to promote
correspondence between the ambient light detected during the period
in which the light sources 140 are not active and the period in
which the light sources 140 are active, such periods may
advantageously be temporally close to one another.
[0072] The biometric monitoring device may further comprise one or
more data storage modules 151, which may include any suitable or
desirable type of data storage, such as solid-state memory, which
may be volatile or non-volatile. In some embodiments the memory is
non-transitory. Solid-state memory of the biometric monitoring
device 100 may comprise any of a wide variety of technologies, such
as flash integrated circuits, Phase Change Memory (PC-RAM or PRAM),
Programmable Metallization Cell RAM (PMC-RAM or PMCm), Ovonic
Unified Memory (OUM), Resistance RAM (RRAM), NAND memory, NOR
memory, EEPROM, Ferroelectric Memory (FeRAM), MRAM, or other
discrete NVM (non-volatile solid-state memory) chips. The data
storage 151 may be used to store system data, such as operating
system data and/or system configurations or parameters. The
biometric monitoring device 100 may further comprise data storage
utilized as a buffer and/or cache memory for operational use by the
control circuitry 110.
[0073] The biometric monitoring device 100 further comprises power
storage 153, which may comprise a rechargeable battery, one or more
capacitors, or other charge-holding device(s). The power stored by
the power storage module 153 may be utilized by the control
circuitry 110 for operation of the biometric monitoring device 100,
such as for powering the light sources 140 and/or display 130. The
power storage module 153 may receive power over the host interface
176 or through other means.
[0074] The biometric monitoring device 100 may further comprise one
or more connectivity components 170, which may include, for
example, a wireless transceiver 172. The wireless transceiver 172
may be communicatively coupled to one or more antenna devices 195,
which may be configured to wirelessly transmit/receive data and/or
power signals to/from the biometric monitoring device. For example,
the wireless transceiver 172 may be utilized to communicate data
and/or power between the biometric monitoring device 100 and an
external host system (not shown), which may be configured to
interface with the biometric monitoring device 100. In certain
embodiments, the biometric monitoring device 100 may comprise
additional host interface circuitry and/or components 176, such as
wired interface components for communicatively coupling with a host
device or system to receive data and/or power therefrom and/or
transmit data thereto.
[0075] The connectivity circuitry 170 may further comprise user
interface components 174 for receiving user input. For example, the
user interface 174 may be associated with the electronic display
130, wherein the electronic display is a touchscreen display
configured to receive user input from user contact therewith. The
user interface module 174 may further comprise one or more buttons
or other input components or features.
[0076] The connectivity circuitry 170 may further comprise the host
interface 176, which may be, for example, an interface for
communicating with a host device or system (not shown) over a wired
or wireless connection. The host interface 176 may be associated
with any suitable or desirable communication protocol and/or
physical connector, such as Universal Serial Bus (USB), Micro-USB,
WiFi, Bluetooth, FireWire, PCIe, or the like. For wireless
connections, the host interface 176 may be incorporated with the
wireless transceiver 172.
[0077] The biometric monitoring device 100 may be configured to
implement intelligent brightness level setting adjustment for the
electronic display based on data generated by the physiological
metric sensor 141. Although certain functional modules and
components are illustrated and described herein, it should be
understood that ambient light sensing and/or brightness level
setting adjustment functionality in accordance with the present
disclosure may be implemented using a number of different
approaches. For example, in some implementations the control
circuitry 110 may comprise one or more processors controlled by
computer-executable instructions stored in non-transitory memory
(e.g., a non-transitory storage medium) so as to provide
functionality such as is described herein. In other
implementations, such functionality may be provided in the form of
one or more specially-designed electrical circuits. In some
implementations, such functionality may be provided by one or more
processors controlled by computer-executable instructions stored in
a memory coupled with one or more specially-designed electrical
circuits. Various examples of hardware that may be used to
implement the concepts outlined herein include, but are not limited
to, application specific integrated circuits (ASICs),
field-programmable gate arrays (FPGAs), and general-purpose
microprocessors coupled with memory that stores executable
instructions for controlling the general-purpose
microprocessors.
[0078] Standalone biometric monitoring devices may be implemented
in a number of form factors and may be designed to be worn in a
variety of ways. In some implementations, a biometric monitoring
device may be designed to be insertable into a wearable case or
into one or more of multiple different wearable cases (e.g., a
wristband case, a belt-clip case, a pendant case, a case configured
to be attached to a piece of exercise equipment such as a bicycle,
etc.). Certain such implementations are described in more detail
in, for example, U.S. Pub. No. 2014/0180019, published on Jun. 26,
2014, which is hereby incorporated by reference for such purpose.
In other implementations, a biometric monitoring device may be
designed to be worn in limited manners, such as a biometric
monitoring device that is integrated into a wristband in a
non-removable manner and may be intended to be worn specifically on
a person's wrist (or perhaps ankle).
[0079] Wearable biometric monitoring devices according to
embodiments and implementations described herein may have shapes
and sizes adapted for coupling to (e.g., secured to, worn, borne
by, etc.) the body or clothing of a user. An example of a wearable
biometric monitoring device 201 is shown in FIG. 2. FIG. 2 shows
perspective front and side views of the wearable biometric
monitoring device 201. The wearable biometric monitoring device 201
includes both a biometric monitoring device 200, as well as a band
portion 207. In certain embodiments, the band portion 207 includes
first and second portions that may be connected by a clasp portion
209. The biometric monitoring device portion 200 may be insertable,
and may have any suitable or desirable dimensions. Wearable
biometric monitoring devices may generally be relatively small in
size so as to be unobtrusive for the wearer. The biometric
monitoring device 200 may be designed to be able to be worn without
discomfort for long periods of time and to not interfere with
normal daily activity.
[0080] The electronic display 230 may comprise any type of
electronic display known in the art. For example, the display 230
may be a liquid crystal display (LCD) or organic light emitting
diode (OLED) display, such as a transmissive LCD or OLED display.
The electronic display 230 may be configured to provide brightness,
contrast, and/or color saturation features according to display
settings maintained by control circuitry and/or other internal
components/circuitry of the biometric monitoring device 200. The
brightness of the display 230 may be implemented through the use of
a brightness component. In certain embodiments, the brightness
component can include backlighting mechanisms, which may comprise
one or more internal light sources positioned behind the display
screen to provide illumination thereto. In some embodiments, the
backlighting component comprises one or more light-emitting diodes
(LEDs) (e.g., white LEDs). The terms "backlight," "backlighting,"
"backlighting component," "backlighting mechanism," "backlighting
subsystem," and "backlighting module" are used herein according to
their broad and ordinary meanings, and may be used to refer
generally to one or more lighting devices that may be activated to
illuminate a display or otherwise make a display more visible to a
user, and/or to circuitry (hardware and/or code) for managing or
controlling a brightness setting of an electronic display. In some
contexts, the above-recited terms may be used to refer to an actual
brightness, or quantity of light, produced or generated by an
electronic display. In other contexts, the above-recited terms may
be used to refer to a separate lighting component that produces or
generates ambient light (reflective light or illumination),
transmissive light, or some combination thereof (transflective
light or illumination) with respect to the electronic display. By
adjusting the brightness of the electronic display 130, the
brightness level management module 111 may provide power
savings.
[0081] The power consumption associated with the display
illumination component can be relatively high in some embodiments,
particularly when implementing a maximum brightness level. Although
a maximum brightness level setting may be desirable in outdoor
daylight conditions, certain embodiments of the present disclosure
advantageously provide for intelligent brightness level adjustment,
which may provide power savings when the brightness level is set to
a reduced brightness state, such as when the ambient light levels
are below outdoor daylight levels. In some implementations, such
power savings may be achieved without the use of dedicated ambient
light sensors on, or associated with, the outward-facing surface of
an electronic display
[0082] FIG. 3 is a perspective back and side view of the wearable
biometric monitoring device 201 of FIG. 2. The wearable biometric
monitoring device 201 comprises a band portion 207, which may be
configured to be latched or secured about a user's arm or other
appendage via a securement mechanism of any suitable or desirable
type. For example, the band 207 may be secured using a hook and
loop clasp component 209. In certain embodiments, the band 207 is
designed with shape memory to promote wrapping around the user's
arm.
[0083] The wearable biometric monitoring device 201 includes a
biometric monitoring device component 200, which may be at least
partially secured to the band 207. The view of FIG. 3 shows a
backside 206 (also referred to herein as the "underside") of the
biometric monitoring device 200, which may generally face and/or
contact skin or clothing associated with the user's arm, for
example. The terms "backside" and "underside" are used herein
according to their broad and ordinary meaning, and may be used in
certain contexts to refer to a side, panel, region, component,
portion and/or surface of a biometric monitoring device that is
positioned and/or disposed substantially opposite to a user display
screen, whether exposed externally of the device, or at least
partially internal to an electronics package or housing of the
device.
[0084] The biometric monitoring device 200 may include one or more
buttons 203, which may provide a mechanism for user input. The
biometric monitoring device 200 may further comprise a device
housing, which may comprise one or more of steel, aluminum,
plastic, and/or other rigid structure. The housing 208 may serve to
protect the biometric monitoring device 200 and/or internal
electronics/components associated therewith from physical damage
and/or debris. In certain embodiments, the housing 208 is at least
partially waterproof.
[0085] The backside 206 of the biometric monitoring device 200 may
have an optical physiological metric sensor 243 associated
therewith, which may comprise one or more sensor components, such
as one or more light sources 240 and/or light detectors 245, the
collection of which may represent an example of the optical
physiological metric sensor 141 of FIG. 1. In certain embodiments,
the optical physiological metric sensor 243 comprises a protrusion
form protruding from the back surface of the biometric monitoring
device 200. The sensor components may be used to determine one or
more physiological metrics of a user wearing the wearable biometric
monitoring device 201. For example, the optical physiological
sensor components associated with the sensor 243 may be configured
to provide readings used to determine heart rate (e.g., in
beats-per-minute (BPM)), blood oxygenation (e.g., SpO.sub.2), blood
pressure, or other metric. In certain embodiments, the biometric
monitoring device 200 further includes an electrical charger mating
recess 209.
[0086] As the sensor 243 may be present and configured to detect
ambient light in connection with heart-rate-related optical
measurements, or other type of physiological parameter measurement,
certain embodiments disclosed herein may advantageously leverage or
repurpose the ambient light signal(s) associated with the sensor
243 for the purpose of making a determination relating to ambient
light conditions. For example, ambient light determinations may
advantageously indicate whether the biometric monitoring device 200
is indoors or outdoors.
[0087] Generally, lighting conditions outdoors may be substantially
greater with respect to luminous flux than lighting conditions
indoors. When the sensor 243 is used to take optical readings of
light that is reflected back into the sensor from the user's
tissue/blood, such readings may generally comprise a combination of
ambient light and reflected light from the light sources 240.
Therefore, in order to obtain a reading that is not influenced by
the ambient light, it may be desirable to cancel the ambient light
from the sensor signal(s)/data. In order to achieve such
cancellation, the sensor 243 may implement a phase during which the
light sensor(s) 245 is/are read without the light source(s) being
active, such that detected light is substantially wholly
attributable to ambient light. The light source(s) 140 may then be
activated, wherein the resulting light detection is processed in
such a way as to at least partially subtract the ambient light read
during the off phase, thereby providing a signal/data that is
estimated to be attributable substantially wholly to the light
generated by the device 200. In certain embodiments, the ambient
light readings used to cancel ambient light may be obtained during
a phase in which the light source(s) are actively emitting light.
For example, in one implementation, the sensor 243 may be
configured to detect ambient light in a first phase in which the
light emitter(s) of the sensor 243 are turned off, and again in a
second phase in which the light emitter(s) are turned on. For
example, in the second phase, the light emitter(s) may be driven at
a relatively low level. Additional embodiments and details relating
to ambient light detection are disclosed in U.S. patent application
Ser. No. 15/223,589, entitled "Circuits and Methods for
Photoplethysmographic Sensor," filed on Jul. 29, 2016, the
disclosure of which is hereby explicitly incorporated by reference
in its entirety.
[0088] Because the light detector 245 is disposed on the backside
of the device 200, which is generally at least partially shielded
from direct light when worn by the user, the ambient light reading
from the light detector 245 may not be as precise as certain other
ambient light sensor embodiments. However, when making a simple
binary determination of whether the device is indoors or outdoors,
the relatively crude ambient light information may nevertheless be
sufficient. Therefore, it may not be necessary to implement a
forward-facing ambient light sensor; rather, relatively basic
assessment of ambient light conditions may be adequate, and dynamic
adjustment of display brightness level may be unnecessary. When it
is determined that the biometric monitoring device 200 is outdoors,
the device may implement a full brightness setting or mode, whereas
a less bright setting or mode may be used where indoor lighting is
detected.
[0089] Although the sensor 243 is illustrated as comprising a
protrusion form certain figures herein, it should be understood
that backside sensor modules in accordance with the present
disclosure may or may not be associated with a protrusion form. In
certain embodiments, the protrusion form on the backside of the
device may be designed to engage the skin of the user with more
force than the surrounding device body. In certain embodiments, an
optical window or light-transmissive structure may be incorporated
in a portion of the protrusion 243. The light emitter(s) 240 and/or
detector(s) 245 of the sensor module 243 may be disposed or
arranged in the protrusion 243 near the window or
light-transmissive structure. As such, when attached to the user's
body, the window portion of the protrusion 243 of the biometric
monitoring device 200 may engage the user's skin with more force
than the surrounding device body, thereby providing a more secure
physical coupling between the user's skin and the optical window.
That is, the protrusion 243 may cause sustained contact between the
biometric monitoring device and the user's skin that may reduce the
amount of stray light measured by the photodetector 245, decrease
relative motion between the biometric monitoring device 200 and the
user, and/or provide improved local pressure to the user's skin,
some or all of which may increase the quality of the cardiac signal
of interest generated by the sensor module. Notably, the protrusion
243 may contain other sensors that benefit from close proximity
and/or secure contact to the user's skin. These may be included in
addition to or in lieu of a heart rate sensor and may include
sensors such as a skin temperature sensor (e.g., noncontact
thermopile that utilizes the optical window or thermistor joined
with thermal epoxy to the outer surface of the protrusion), pulse
oximeter, blood pressure sensor, EMG, or galvanic skin response
(GSR) sensor.
[0090] In certain embodiments, a portion of the backside of the
biometric monitoring device 200 may include a friction-enhancing
mechanism or material. For example, the backside of the biometric
monitoring device 200 may include a plurality of raised or
depressed regions or portions (for example, small bumps, ridges,
grooves, and/or divots). Moreover, a friction enhancing material
(for example, a gel-like material such as silicone or other
elastomeric material) may be disposed on the skin-side, while may
further improve user comfort and/or prevent stray light from
entering. The use of a protrusion and/or friction may improve
measurement accuracy of data acquisition corresponding to certain
parameters (e.g., heart rate, heart rate variability, galvanic skin
response, skin temperature, skin coloration, heat flux, blood
pressure, blood glucose, etc.) by reducing motion of the biometric
monitoring device 200 (and thus of the sensor) relative to the
user's skin during operation, particularly while the user is in
motion.
[0091] Some or all of the backside housing 208 of the biometric
monitoring device 200 may comprise a metal material (for example,
steel, stainless steel, aluminum, magnesium, or titanium). Such a
configuration may provide desirable structural rigidity. In certain
embodiments, the housing 208 is at least partially ferrous (for
example, a grade of stainless steel that is ferrous). In such
embodiments, the biometric monitoring device 200 may interconnect
with a charger via a connector that secures itself to the biometric
monitoring device using magnets that couple to the ferrous
material. The biometric monitoring device 200 may also engage a
dock or docking station, using such magnetic properties, to
facilitate data and/or power transfer. Moreover, such a housing may
provide enhanced electromagnetic shielding that may enhance the
integrity and/or reliability of the optical physiological sensor
(e.g., heart rate sensor) and the physiological metric data
acquisition process/operation.
[0092] The biometric monitoring device 200 may be configured to
collect one or more types of physiological and/or environmental
data from embedded sensors and/or external devices and communicate
or relay such information to other devices, including devices
capable of serving as an Internet-accessible data sources, thus
permitting the collected data to be viewed, for example, using a
web browser or network-based application. For example, while the
user is wearing the biometric monitoring device 200, the biometric
monitoring device 200 may calculate and store the user's step count
using one or more biometric sensors. The biometric monitoring
device may then transmit data representative of the user's step
count to an account on a web service, computer, mobile phone, or
health station where the data may be stored, processed, and
visualized by the user. Indeed, the biometric monitoring device 200
may measure or calculate a plurality of other physiological metrics
in addition to, or in place of, the user's step count. These
include, but are not limited to, energy expenditure, e.g., calorie
burn, floors climbed and/or descended, heart rate, heart rate
variability, heart rate recovery, location and/or heading, e.g.,
through GPS or a similar system, elevation, ambulatory speed and/or
distance traveled, swimming lap count, swimming stroke type and
count detected, bicycle distance and/or speed, blood pressure,
blood glucose, skin conduction, skin and/or body temperature,
muscle state measured via electromyography, brain activity as
measured by electroencephalography, weight, body fat, caloric
intake, nutritional intake from food, medication intake, sleep
periods, e.g., clock time, sleep phases, sleep quality and/or
duration, pH levels, hydration levels, respiration rate, and other
physiological metrics.
[0093] The biometric monitoring device 200 may also measure or
calculate metrics related to the environment around the user such
as barometric pressure, weather conditions (e.g., temperature,
humidity, pollen count, air quality, rain/snow conditions, wind
speed), light exposure (e.g., ambient light, UV light exposure,
time and/or duration spent in darkness), noise exposure, radiation
exposure, and magnetic field. Furthermore, the biometric monitoring
device 200 or the system collating the data streams from the
biometric monitoring device may calculate metrics derived from such
data. For example, the device or system may calculate the user's
stress and/or relaxation levels through a combination of heart rate
variability, skin conduction, noise pollution, and sleep quality.
In another example, the biometric monitoring device 200 may
determine the efficacy of a medical intervention, e.g., medication,
through the combination of medication intake, sleep data, and/or
activity data. In yet another example, the biometric monitoring
device or system may determine the efficacy of an allergy
medication through the combination of pollen data, medication
intake, sleep and/or activity data. These examples are provided for
illustration only and are not intended to be limiting or
exhaustive. Further embodiments and implementations of sensor
devices may be found in U.S. Pat. No. 9,167,991, titled "Portable
Biometric Monitoring Devices and Methods of Operating Same" filed
Jun. 8, 2011, which is hereby incorporated herein by reference in
its entirety.
Physiological Metric Sensor Module
[0094] An optical physiological metric sensor such as
photoplethysmography (PPG) sensors may generally utilize light
sensors and/or detectors to obtain a volumetric measurement
relating to pulsatile blood flow in the body. PPG information may
be obtained illuminating the skin of a subject and measuring
changes in light absorption. A PPG sensor can be designed to
monitor the perfusion of blood to the dermis and/or subcutaneous
tissue of the skin. PPG data may be determined using a wrist-worn
biometric monitoring device based on the pumping of blood to the
periphery during each cardiac cycle. While the pressure pulse may
be somewhat damped by the time it reaches the skin, it may
nevertheless be enough to distend the arteries and/or arterioles in
the subcutaneous tissue of the wearer of the biometric monitoring
device. The change in volume caused by the pressure pulse may be
detected by illuminating the skin with the light from one or more
light source (e.g., light-emitting diodes (LEDs)) and then
measuring the amount of light either transmitted or reflected to
one or more light sensors (e.g., photodiode(s)). In certain
embodiments, as blood flow to the skin can be modulated by various
other physiological systems, the PPG sensor may further be used to
monitor breathing, hypovolemia, and/or other circulatory
conditions.
[0095] PPG readings can be used to determine heart rate, SpO2, and
the like. While PPGs can be obtained in certain systems using
transmissive absorption, with respect certain wrist-worn biometric
monitoring devices disclosed herein, PPG information may be
obtained using reflective absorption. For PPG signals, the DC
component of the signal may be attributable to the bulk absorption
of the skin tissue, while the AC component may be attributable to
variation in blood volume in the skin caused by the pressure pulse
of the cardiac cycle. Generally, the height of the AC component of
the PPG signal may be proportional to the pulse pressure, which is
the difference between the systolic and diastolic pressure in the
arteries. Although certain embodiments are presented herein in the
context of PPG sensors, it should be understood that ambient light
data for electronic display brightness level management in
accordance with the present disclosure may incorporate ambient
light signals from any suitable or desirable physiological metric
sensor.
[0096] FIG. 4 shows a cross-sectional view of the biometric
monitoring device 200 of FIGS. 2 and 3 according to one or more
embodiments, which is attached to a band portion 207. The diagram
of FIG. 4 shows a cross-section of the sensor protrusion 243 shown
in FIG. 3, example embodiments of which are illustrated in further
detail in FIGS. 5 and 6 and described below. Certain
electronic/circuitry components of the biometric monitoring device
200 may be mounted to or otherwise associated with a controller
board 219, which may comprise, for example, one or more printed
circuit boards (PCBs). The controller board 219 may comprise
controller circuitry operating the biometric monitoring device 200.
In certain embodiments, the sensor module 243 may be configured to
generate sensor signals and provide such sensor signals to the
controller board circuitry for processing thereof. For example, the
controller circuitry 110 of FIG. 1 and described above may be
implemented at least in part as a controller board like that shown
in FIG. 4.
[0097] The sensor protrusion 243 and/or associated components may
be part of a backside, or underside, 206 of the biometric
monitoring device 200. The backside 206 of the biometric monitoring
device 200 may be positioned substantially opposite a front side
202, which may be associated with an electronic display 230, which
may be illuminated using backlighting or other lighting mechanism
according to a brightness level setting managed at least in part by
the controller board 219 as described herein.
[0098] In some implementations, the sensor protrusion 243 may
comprise an optical sensor, which may be positioned on the backside
206 (e.g., skin-side) of the device and arranged or positioned to
reduce or minimize the distance between the light source(s) and/or
the associated detector(s) and the skin of the user. FIG. 5 shows a
cross-sectional view of a backside sensor module for a biometric
monitoring device according to one or more embodiments. For
example, the sensor module 543 may be part of a sensor protrusion
like that shown in FIG. 4 and described above. In FIG. 5, two light
sources 540 (e.g., LEDs) are placed on either side of a
photodetector 545 to enable photoplethysmograph (PPG) sensing in
accordance with the present disclosure. A light-blocking material
503 may be placed between the light sources 540 and the
photodetector 545 to at least partially prevent light from the
light sources 540 from reaching the photodetector 545 without first
exiting the housing of the biometric monitoring device. In certain
embodiments, a flexible transparent layer 505 may be placed on the
lower surface of the sensor module 543 to form a seal. The
transparent layer 505 may further serve certain other functions,
such as preventing liquid from entering the device where the light
sources 540 or photodetectors 545 are placed. The transparent layer
505 may be formed through in-mold labeling, or other process. In
certain embodiments, the light sources 540 and/or photodetector 545
may be placed on a flexible circuit board 501.
[0099] The configuration of FIG. 5 may improve the efficiency of
light flux coupling between the components of the optical sensor
module 543 and the user's body. For example, in one embodiment, the
light source(s) 540 and/or associated detector(s) 545 may be
disposed on a flexible or pliable substrate. Such flexibility may
allow the backside of the biometric monitoring device, which may be
made from a compliant material, to at least partially conform to
the shape of the body part (for example, the user's wrist, arm,
ankle, and/or leg) to which the biometric monitoring device is
coupled to or attached during normal operation, such that the light
source(s) 540 and/or associated detector(s) 545 are close to the
skin of the user (i.e., with little or no gap between the skin-side
of the device and the adjacent surface of the skin of the user.
[0100] FIG. 6 depicts a cross-sectional view of a sensor protrusion
643 of an example wearable biometric monitoring device. In the
embodiment of FIG. 6, one or more of the light sources 640 and
photo detector(s) 645 may be disposed on a flat and/or rigid
circuit board (PCB).
[0101] FIGS. 7A-7C provide diagrams of physiological metric sensor
components according to certain embodiments. Physiological metric
sensor modules, such as optical sensor modules, in biometric
monitoring devices of the present disclosure may employ light pipes
747 or other light-transmissive structures to facilitate
transmission of light from light sources 740 to a user's body 702
and skin 701. In this regard, in some embodiments, light may be
directed from the light source(s) 740 to the skin 701 of the user
through such light pipes 747 or other light-transmissive
structures. Scattered light from the user's body may be directed
back to optical circuitry in the biometric monitoring device
through the same or similar structures. Indeed, the
light-transmissive structures 747 may employ a material and/or
optical design to facilitate low light loss (for example, the
light-transmissive structures 747 may include a lens to facilitate
light collection, and portions of the light-transmissive structures
may be coated with or adjacent to reflective materials to promote
internal reflection of light within the light-transmissive
structures), thereby improving the signal-to-noise-ratio of the
photo detector(s) 745 and/or facilitating reduced power consumption
of the light source(s) 740 and/or light detector(s) 745. In some
embodiments, the light pipes 747 or other light-transmissive
structures may include a material that selectively transmits light
having one or more specific or predetermined wavelengths with
higher efficiency than others, thereby acting as a bandpass filter.
Such a bandpass filter may be tuned to improve the signal of a
specific physiological data type. For example, in one embodiment,
an In-Mold-Labeling (IML) light-transmissive structure may be
implemented, wherein the light-transmissive structure uses a
material with predetermined or desired optical characteristics to
create a specific bandpass characteristic, for example, so as to
pass infrared light with greater efficiency than light of other
wavelengths (for example, light having a wavelength in human
visible spectrum). In another embodiment, a biometric monitoring
device may employ a light-transmissive structure having an
optically opaque portion (including certain optical properties) and
an optically-transparent portion (including optical properties
different from the optically-opaque portion). Such a
light-transmissive structure may be provided via a double-shot or
two-step molding process wherein optically opaque material and
optically transparent material are separately injected into a mold.
A biometric monitoring device implementing such a
light-transmissive structure may include different light
transmissivity properties for different wavelengths depending on
the direction of light travel through the light-transmissive
structure. For example, in one embodiment, the optically-opaque
material may be reflective to a specific wavelength range so as to
more efficiently transport light from the user's body back to the
light detector (which may be of a different wavelength(s) relative
to the wavelength(s) of the emitted light).
[0102] In certain embodiments, reflective structures may be placed
in the field of view of the light emitter(s) 740 and/or light
detector(s) 745. For example, the sides of the light transmission
channels may be at least partially covered in a reflective material
(e.g., chromed) to facilitate light transmission. The reflective
material may increase the efficiency with which the light is
transported to the skin 701 from the light source(s) 740 and then
from the skin back into the detector(s) 745. The
reflectively-coated channel may be filled in with an optical epoxy
or other transparent material to prevent liquid from entering the
device body while still allowing light to be transmitted with low
transmission loss.
[0103] In certain embodiments, light-transmissive
channels/structures 747 may include a mask consisting of an opaque
material that limits the aperture of one, some, or all of the light
source(s) and/or detector(s). In this way, the light-transmissive
structures 747 may selectively define a preferential volume of the
user's body that light is emitted into and/or detected from.
Notably, other mask configurations may be employed or implemented
in connection with the concepts described and/or illustrated herein
that improve the photoplethysmography signal and which are
implemented in connection with the concepts described and/or
illustrated herein are intended to fall within the scope of the
present disclosure.
[0104] In certain embodiments, the light emitter(s) 740 and/or
detector(s) 745 may be configured to transmit light through a hole
or series of holes in the device exterior. This hole or series of
holes may be filled in with light-transmissive epoxy (e.g. optical
epoxy). The epoxy may form a light pipe that allows light to be
transmitted from the light emitter(s) to the skin and from the skin
back into the light detector(s). Such technique may provide the
advantage that the epoxy may form a watertight seal, preventing
water, sweat or other liquid from entering the device body though
the hole(s) on the device exterior that allow the light emitter(s)
and detector(s) to transmit to, and receive light from, the
biometric monitoring device body exterior. An epoxy with a high
thermal conductivity may be used to help prevent the light
source(s) 745 (e.g., LED's) from overheating.
[0105] FIG. 7A illustrates an example embodiment of a
photoplethysmography (PPG) light source and photodetector geometry.
In the embodiment of FIG. 7A, two light sources 740 are placed on
either side of a photodetector 745. These three devices may be
located in a protrusion form on the backside of a wristband-type
biometric monitoring device (e.g., the side which faces the skin of
the user), as described above.
[0106] FIGS. 7B and 7C illustrate examples of a physiological
metric (e.g., PPG) sensor having a light detector 745 (e.g.,
photodetector) and two light sources 740 (e.g., LED). Such
components may be disposed in a biometric monitoring device that
has a protrusion form on the backside. In certain embodiments,
light pipes 747 optically connect the LEDs 740 and photodetector
745 with the surface of the user's skin 701. Beneath the skin 701,
the light from the light sources 740 may scatter off of blood 703
in the body, some of which may be scattered or reflected back into
the photodetector 745.
[0107] FIG. 8 illustrates an example of a biometric monitoring
device 800 with an optimized PPG detector that has a protrusion
with curved sides so as not to discomfort the user. Additionally,
the surface of light pipes 847 that optically couple the
photodetector 845 and the LEDs 840 to the wearer's skin may be
contoured to improve light flux coupling between the LEDs 840 and
photodetector(s) 845 and the light pipes 847. The ends of the light
pipes that face the user's skin may also be contoured. This contour
may focus or defocus light to optimize the PPG signal. For example,
the contour may focus emitted light to a certain depth and location
that coincides with an area where blood flow is likely to occur.
The vertex of these foci may overlap or be very close together so
that the photodetector receives the maximum possible amount of
scattered light.
[0108] In certain embodiments, the biometric monitoring device may
include a concave or convex shape, e.g., a lens, on the skin-side
of the device, to focus light towards a specific volume at a
specific depth in the skin and increase the efficiency of light
collected from that point into the photodetector. Where such a
biometric monitoring device also employs light pipes to selectively
and controllably route light, it may be advantageous to shape the
end of the light pipe with a degree of cylindricity, e.g., the end
of the light pipe may be a be a cylindrical surface (or portion
thereof) defined by a cylinder axis that is nominally parallel to
the skin-side (for example, rather than use an axially-symmetric
lens). For example, in a wristband-style biometric monitoring
device, such a cylindrical lens may be oriented such that the
cylinder axis is nominally parallel to the wearer's forearm, which
may have the effect of limiting the amount of light that enters
such a lens from directions parallel to the person's forearm and
increasing the amount of light that enters such a lens from
directions perpendicular to the person's forearm--since ambient
light is more likely to reach the sensor detection area from
directions that are not occluded by the straps of the biometric
monitoring device, i.e., along the user's forearm axis, than from
directions that are occluded by the straps, i.e., perpendicular to
the user's forearm. Such a configuration may improve the
signal-to-noise-ratio by increasing the efficiency of light
transferred from the emitter onto or into the skin of the user
while decreasing "stray" light from being detected or collected by
the photodetector. In this way, the signal sampled, measured and/or
detected by the photodetector consists less of stray light and more
of the user's skin/body response to such emitted light (signal or
data that is representative of the response to the emitted
light).
[0109] In one embodiment, the optical sensors (sources and/or
detectors) may be disposed on an interior or skin-side of the
biometric monitoring device (i.e., a side of the biometric
monitoring device that contacts, touches, and/or faces the skin of
the user (hereinafter "skin-side"). (See, for example, FIGS. 2A
through 3C). In another embodiment, the optical sensors may be
disposed on one or more sides of the device, including the
skin-side and one or more sides of the device that face or are
exposed to the ambient environment (environmental side). (See, for
example, FIGS. 6A through 7).
[0110] FIG. 9 illustrates an example of a portable monitoring
device having a band 907 with one or more optical sensors and light
emitters 941 disposed in association with the inside of the band.
For example, there may be a plurality of photodetectors and photo
emitters placed at various sites along the circumference of the
interior of the band 907. A heart rate signal-quality metric
associated with each site may be calculated to determine the best
or set of best sites for estimating the user's heart rate.
Subsequently, some of the sites may be disabled or turned off to,
for example, reduce power consumption. The device may periodically
check the heart rate signal quality at some or all of the sites to
enhance, monitor and/or optimize signal and/or power
efficiency.
[0111] FIG. 10 illustrates an example of a portable biometric
monitoring device 1001 having a display 1030 and wristband 1007.
Additionally, optical PPG (e.g., heart rate) detection sensors
and/or emitters 1041 may be located on the side of the biometric
monitoring device. In one embodiment, these may be located in
side-mounted buttons.
[0112] All of the optical sensors discussed herein may be used in
conjunction with other sensors to improve detection of the data
described above or be used to augment detection of other types of
physiological or environmental data.
[0113] FIG. 11A depicts an example schematic block diagram of an
optical heart rate sensor where light is emitted from a light
source toward the user's skin and the reflection of such light from
the skin/internal body of the user is sensed by a light detector,
the signal from which is subsequently digitized by an analog to
digital converter (ADC). The intensity of the light source may be
modified (e.g., through a light source intensity control module) to
maintain a desirable reflected signal intensity. For example, the
light source intensity may be reduced to avoid saturation of the
output signal from the light detector. As another example, the
light source intensity may be increased to maintain the output
signal from the light detector within a desired range of output
values. Notably, active control of the system may be achieved
through linear or nonlinear control methods such as
proportional-integral-derivative (PID) control, fixed step control,
predictive control, neural networks, hysteresis, and the like, and
may also employ information derived from other sensors in the
device such as motion, galvanic skin response, etc. FIG. 11A is
provided for illustration and does not limit the implementation of
such a system to, for instance, an ADC integrated within a MCU, or
the use of a MCU for that matter. Other possible implementations
include the use of one or more internal or external ADCs, FPGAs,
ASICs, etc.
[0114] In another embodiment, system with an optical heart rate
sensor may incorporate the use of a sample-and-hold circuit (or
equivalent) to maintain the output of the light detector while the
light source is turned off or attenuated to save power. In
embodiments where relative changes in the light detector output are
of primary importance (e.g., heart rate measurement), the
sample-and-hold circuit may not have to maintain an accurate copy
of the output of the light detector. In such cases, the
sample-and-hold may be reduced to, for example, a diode (e.g.,
Schottky diode) and capacitor. The output of the sample-and-hold
circuit may be presented to an analog signal conditioning circuit
(e.g., a Sallen-Key bandpass filter, level shifter, and/or gain
circuit) to condition and amplify the signal within frequency bands
of interest (e.g., 0.1 Hz to 10 Hz for cardiac or respiratory
function), which may then be digitized by the ADC. See, for
example, FIG. 11B.
[0115] In operation, circuit topologies such as those already
described herein (e.g. a sample-and-hold circuit) remove the DC and
low frequency components of the signal and help resolve the AC
component related to heart rate and/or respiration. The embodiment
may also include the analog signal conditioning circuitry for
variable gain settings that can be controlled to provide a suitable
signal (e.g., not saturated). The performance characteristics
(e.g., slew rate and/or gain bandwidth product) and power
consumption of the light source, light detector, and/or
sample-and-hold may be significantly higher than the analog signal
conditioning circuit to enable fast duty cycling of the light
source. In some embodiments, the power provided to the light source
and light detector may be controlled separately from the power
provided to the analog signal conditioning circuit to provide
additional power savings. Alternatively, or additionally, the
circuitry can use functionality such as an enable, disable and/or
shutdown to achieve power savings. In another embodiment, the
output of the light detector and/or sample-and-hold circuit may be
sampled by an ADC in addition to or in lieu of the analog signal
conditioning circuit to control the light intensity of the light
source or to measure the physiologic parameters of interest when,
for example, the analog signal conditioning circuit is not yet
stable after a change to the light intensity setting. Notably,
because the physiologic signal of interest is typically small
relative to the inherent resolution of the ADC, in some
embodiments, the reference voltages and/or gain of the ADC may be
adjusted to enhance signal quality and/or the ADC may be
oversampled. In yet another embodiment, the device may digitize the
output of only the sample-and-hold circuit by, for example,
oversampling, adjusting the reference voltages and/or gain of the
ADC, or using a high resolution ADC. See, for example, FIG.
11C.
[0116] in some embodiments, the color or wavelength of the light
emitted by the light source, e.g., an LED (or set of LEDs), may be
modified, adjusted, and/or controlled in accordance with a
predetermined type of physiological data being acquired or
conditions of operation. Here, the wavelength of the light emitted
by the light source may be adjusted and/or controlled to optimize
and/or enhance the "quality" of the physiological data obtained
and/or sampled by the detector. For example, the color of the light
emitted by the LED may be switched from infrared to green when the
user's skin temperature or the ambient temperature is cool in order
to enhance the signal corresponding to cardiac activity. (See, for
example, FIG. 11D)
Ambient Light Determination
[0117] In another embodiment, the sensor device may incorporate a
differential amplifier to amplify the relative changes in the
output of the light detector. See, for example, FIG. 11F. In some
embodiments, a digital average or digital low-pass filtered signal
may be subtracted from the output of the light detector. This
modified signal may then be amplified before it is digitized by the
ADC. In another embodiment, an analog average or analog low-pass
filtered signal may be subtracted from the output of the light
detector through, for example, the use of a sample-and-hold circuit
and analog signal conditioning circuitry. The power provided to the
light source, light detector, and differential amplifier may be
controlled separately from the power provided to the analog signal
conditioning circuit to improve power savings.
[0118] In another embodiment, a signal (voltage or current,
depending on the specific sensor implementation) may be subtracted
from the raw PPG signal to remove any bias in the raw PPG signal
and therefore increase the gain or amplification of the PPG signal
that contains heart rate (or other circulatory parameters such as
heart rate variability) information. This signal may be set to a
default value in the factory, to a value based on the user's
specific skin reflectivity, absorption, and/or color, and/or may
change depending on feedback from an ambient light sensor, or
depending on analytics of the PPG signal itself. For example, if
the PPG signal is determined to have a large DC offset, a constant
voltage may be subtracted from the PPG signal to remove the DC
offset and enable a larger gain, therefore improving the PPG signal
quality. The DC offset in this example may result from ambient
light (for example from the sun or from indoor lighting) reaching
the photodetector from or reflected light from the PPG light
source.
[0119] In another embodiment, a differential amplifier may be used
to measure the difference between current and previous samples
rather than the magnitude of each signal. Since the magnitude of
each sample is typically much greater than the difference between
each sample, a larger gain can be applied to each measurement,
therefore improving the PPG signal quality. The signal may then be
integrated to obtain the original time domain signal.
[0120] In another embodiment, the light detector module may
incorporate a transimpedance amplifier stage with variable gain.
Such a configuration may avoid or minimize saturation from bright
ambient light and/or bright emitted light from the light source.
For example, the gain of the transimpedance amplifier may be
automatically reduced with a variable resistor and/or multiplexed
set of resistors in the negative feedback path of the
transimpedance amplifier. In some embodiments, the device may
incorporate little to no optical shielding from ambient light by
amplitude-modulating the intensity of the light source and then
demodulating the output of the light detector (e.g., synchronous
detection). See, for instance, FIG. 11E. In other aspects, if the
ambient light is of sufficient brightness to obtain a heart rate
signal, the light source may be reduced in brightness and/or turned
off completely.
[0121] In yet another embodiment, the aforementioned processing
techniques may be used in combination to optically measure
physiological parameters of the user. See, for example, FIG. 11G.
This topology may allow the system to operate in a low power
measurement state and circuit topology when applicable and adapt to
a higher power measurement state and circuit topology as necessary.
For instance, the system may measure the physiologic parameter
(e.g., heart rate) of interest using analog signal-conditioning
circuitry while the user is immobile or sedentary to reduce power
consumption, but switch to oversampled sampling of the light
detector output directly while the user is active.
Circuits for Performing PPG
[0122] PPG circuitry may be optimized to obtain the best quality
signal regardless of a variety of environmental conditions
including, but not limited to, motion, ambient light, and skin
color. The following circuits and techniques may be used to perform
such optimization (see FIGS. 12A through 12J); a sample-and-hold
circuit and differential/instrumentation amplifier which may be
used in PPG sensing. The output signal is an amplified difference
between current and previous sample, referenced to a given voltage.
controlled current source to offset "bias" current prior to
transimpedance amplifier. This allows greater gain to be applied at
transimpedance amplifier stage. a sample-and-hold circuit for
current feedback applied to photodiode (prior to transimpedance
amplifier). This can be used for ambient light removal, or "bias"
current removal, or as a pseudo differential amplifier (may require
dual rails). a differential/instrumentation amplifier with ambient
light cancellation. a photodiode offset current generated
dynamically by a DAC. a photodiode offset current generated
dynamically by controlled voltage source. ambient light removal
using a "switched capacitor" method. photodiode offset current
generated by a constant current source (also can be done with a
constant voltage source and a resistor). ambient light removal and
differencing between consecutive samples. ambient light removal and
differencing between consecutive samples.
[0123] FIG. 12A illustrates an example schematic of a
sample-and-hold circuit and differential/instrumentation amplifier
which may be used in PPG sensing. The output signal in such a
circuit may be an amplified difference between a current sample and
a previous sample, referenced to a given voltage.
[0124] FIG. 12B illustrates an example schematic of a circuit for a
PPG sensor using a controlled current source to offset "bias"
current prior to a transimpedance amplifier. This allows greater
gain to be applied at the transimpedance amplifier stage.
[0125] FIG. 12C illustrates an example schematic of a circuit for a
PPG sensor using a sample-and-hold circuit for current feedback
applied to photodiode (prior to a transimpedance amplifier). This
circuit may be used for ambient light removal, or "bias" current
removal, or as a pseudo-differential amplifier.
[0126] FIG. 12D illustrates an example schematic of a circuit for a
PPG sensor using a differential/instrumentation amplifier with
ambient light cancellation functionality.
[0127] FIG. 12E illustrates an example schematic of a circuit for a
PPG sensor using a photodiode offset current generated dynamically
by a DAC.
[0128] FIG. 12F illustrates an example schematic of a circuit for a
PPG sensor using a photodiode offset current generated dynamically
by a controlled voltage source.
[0129] FIG. 12G illustrates an example schematic of a circuit for a
PPG sensor including ambient light removal functionality using a
"switched capacitor" method.
[0130] FIG. 12H illustrates an example schematic of a circuit for a
PPG sensor that uses a photodiode offset current generated by a
constant current source (this may also be done using a constant
voltage source and a resistor).
[0131] FIG. 12I illustrates an example schematic of a circuit for a
PPG sensor that includes ambient light removal functionality and
differencing between consecutive samples.
[0132] FIG. 12J illustrates an example schematic of a circuit for
ambient light removal and differencing between consecutive
samples.
[0133] Various circuits and concepts related to heart rate
measurement using a PPG sensor are discussed in more detail in U.S.
Provisional Patent Application No. 61/946,439, filed Feb. 28, 2014
which is hereby incorporated by reference with respect to content
directed at heart rate measurements with a PPG sensor and at
circuits, methods, and systems for performing such
measurements.
[0134] FIG. 13 shows an example light emission driver circuit 440
for driving a light emitter to emit an incident light signal
L.sub.E onto a region of the skin of a user according to some
implementations. For example, the light emission driver circuit 440
can be used in conjunction with the any light source of a biometric
monitoring device of the present disclosure. As described above, a
portion of the incident light signal L.sub.E is reflected,
refracted, or otherwise scattered by the skin of the user, and more
particularly, the arteries below the skin of the user. The portion
of the incident light scattered by the skin of the user also is
referred to herein as the "scattered light signal" L.sub.S. FIG. 14
shows a block diagram of an example light detection circuit 560 for
detecting the scattered light signal L.sub.S and for outputting an
output signal OUT based on the scattered light signal L.sub.S
according to some implementations. For example, the light detection
circuit 560 can be used in conjunction with any of the light
detectors of physiological metric sensor modules of the present
disclosure. FIG. 15 shows an example circuit 660 for implementing
the light detection circuit 560 of FIG. 14 according to some
implementations.
[0135] The light emission driver circuit 440 includes, at a high
level, a voltage-controlled current source that drives a light
emitter 442 arranged to emit an incident light signal L.sub.E onto
a region of the skin of a user. For example, the light emitter 442
can be the light emitter 336 described above and, as described
above, can include one or more LEDs, laser, or other light sources.
In the illustrated implementation, the voltage-controlled current
source is implemented by a driver circuit 444 that powers the light
emitter 442 based on one or more control signals Cntrl.sub.D
received from, for example, the processing unit 104. In some
implementations, the driver circuit 44 is configured to drive (or
"power") the light emitter 442 for certain intervals of time based
on the control signals Cntrl.sub.D (for example, when enabled by a
control signal) such that the light emitter 442 emits a light
signal L.sub.E in the form of a series (or "train") of pulses
during the intervals of time. For example, in some cases, the light
emitter 442 may be a relatively costly component of the portable
monitoring device 100 in terms of power consumption. Thus, it may
be desirable to power the light emitter 442 for only a short amount
of time, hence the use of a series of short pulses.
[0136] While other implementations of a driver circuit 444,
including other implementations of a voltage-controlled current
source, are within the scope of this disclosure, in the illustrated
implementation the driver circuit 444 includes an operational
amplifier 446 having a first input terminal, a second input
terminal and an output terminal. The driver circuit also includes a
digital to analog converter (DAC) 448 electrically coupled with the
first input terminal of the operational amplifier 446. The DAC 448
provides an input signal V.sub.IN to the first input terminal of
the operational amplifier 446 based on a reference signal V.sub.REF
and the control signals Cntrl.sub.D. A power supply rail supplies a
power source to a first terminal of the light emitter 442.
[0137] The driver circuit 440 may also include a switch, and more
particularly, a transistor 450. In the illustrated implementation,
the transistor 450 may be a metal-oxide-semiconductor field-effect
transistors (MOSFET), such as an n-channel MOSFET (an "NMOS
transistor"). In some other implementations, the transistor 450 may
be implemented by another type of switch or transistor such as, for
example, a bipolar junction transistor. The transistor 450 includes
a gate terminal, a drain terminal D and a source terminal S. In
certain embodiments, the gate terminal may be electrically coupled
with the output terminal of the operational amplifier 446. The
drain terminal D may be electrically coupled with a second terminal
of the light emitter 442. The source terminal S may be electrically
coupled, via a resistor 452 having a resistance R.sub.S, to a
reference voltage, such as a ground. The source terminal S may be
further electrically coupled with the second input terminal of the
operational amplifier 446 for providing a feedback signal to the
operational amplifier. In the illustrated implementation, the
driver circuit 444 further includes a capacitor 454 having a
capacitance C.sub.P electrically coupled between the output
terminal of the operational amplifier 446 and the second input
terminal of the operational amplifier. The driver circuit 444 also
can include a resistor 456 having a resistance R.sub.P1; between
the output terminal of the operational amplifier 446 and the gate
terminal of the transistor 450. The driver circuit 444 also can
include a resistor 458 having a resistance R.sub.P2; between the
source terminal S of the transistor 450 and the second input
terminal of the operational amplifier 446. The resistances
R.sub.P1; and R.sub.P2; and the capacitance C.sub.P can be
configured to tune the driver circuit 444 to obtain fast settling
times, which can save power because can be operated for less time,
while maintaining stability. During operation, the operational
amplifier 446 may be configured to, based on the feedback signal
received at the second input terminal of the operational amplifier,
maintain a substantially constant voltage across the resistor 452.
In this way, the driver circuit 444 behaves as a constant current
source with a current I.sub.E=V.sub.IN/R.sub.S passing through the
light emitter 442 and resistor 452. This may be desirable because
any change or ripple in the current I.sub.E provided to the light
emitter 452 will result in undesired artifacts in the incident
light signal L.sub.E, which will also show in the scattered light
signal L.sub.S.
[0138] Referring now to FIG. 14, the light detection circuit 560
may be configured to detect a scattered light signal L.sub.S, (for
example, a portion of the incident light signal L.sub.E scattered
by the skin of the user), generate a detected electrical signal
I.sub.D based on the scattered light signal, sample the electrical
signal to generate a sampled signal S.sub.1, and digitize the
sampled signal to generate an output signal OUT that represents,
for example, heart rate data. As described above, ambient light
conditions, skin color (pigmentation) and user motion all can make
it difficult to extract a user's heart rate from data signal. In
some implementations, the light detection circuit 560 may be
configured to correct for a low frequency or "DC" offset resulting
from ambient light. For example, ambient light conditions can
change as a user moves or changes orientation (for example, hand or
body) or as external lighting conditions (for example, sun light or
interior lighting) change over time. In some implementations, the
light detection circuit 560 may be configured to correct for
ambient light conditions by effectively subtracting an ambient
light component of the detected signal I.sub.D obtained when a
light source (for example, the light emitter 334) may be off from
the detected signal when the light source may be on and the signal
may be to be sampled.
[0139] In some implementations, the light detection circuit 560
also may be configured to adjust a gain of the detected signal
I.sub.D to prevent saturation of various electrical components (for
example, operational amplifiers) of the light detection circuit 560
or to bring the values of the sampled signal S.sub.1 into a range
that may be suitable for an ADC that digitizes the sampled signal
to generate the output signal OUT. For example, because the
time-varying "AC" component of the scattered light signal L.sub.S
due to the user's cardiac output can be relatively small in
comparison to the low frequency or "DC" component due to ambient
light, and because it may be desirable to use high frequency short
pulses to reduce the power consumption of the light emitter 442, it
may be desirable to subtract the DC ambient light component prior
to the sampled signal reaching the ADC. More specifically, if the
DC ambient component is not subtracted, the ADC may not be able to
take measurements/receive data at the speed for which it may be
desired to pulse the emitted light because the detected signal may
be so large that the ADC can't resolve the desired AC component at
the desired bit depth in the short time required (for example, high
precision/high bit depth ADCs tend to be slow because of the
processing requirements). Additionally, it can be advantageous to
for the light detection circuit 560 to adjust the gain of the
detected light signal I.sub.D to account for differences in users'
skin tones (pigmentations). For example, different skin tones will
absorb and scatter light differently. For example, because darker
skin tones can absorb more light and scatter less light, it can be
desirable to increase the gain of the detected light signal
I.sub.D.
[0140] The light detection circuit 560 includes a light detector
562 positioned and configured to receive (or "sense" or "detect")
at least a portion of the scattered light signal L.sub.S and to
generate the detected electrical signal I.sub.D based on the
received light. In some implementations, the light detector 562 may
be configured to generate the first electrical signal I.sub.D in
the form of a time-varying current signal. In such implementations,
the magnitude of the current in the first electrical signal I.sub.D
may be proportional to the intensity of the scattered light signal
L.sub.S (and ambient light) currently being received by the light
detector 562 in its detectable range of wavelengths. In some other
implementations, the light detector 562 can be configured to
generate the first electrical signal I.sub.D in the form of a
time-varying voltage signal. In such implementations, the magnitude
of the voltage in the first electrical signal I.sub.D would be
proportional to the intensity of the scattered light signal L.sub.S
(and ambient light) currently being received by the light detector
in its detectable range of wavelengths.
[0141] In accordance with certain embodiments, where the generated
electrical signal I.sub.D, or other signal derived at least in part
therefrom, is representative of detected light while the light
emitter 442 (see FIG. 13) is off, such signal may be analyzed or
otherwise utilized to make an ambient lighting condition
determination upon which display brightness level setting
modification for an associated electronic display is based.
[0142] The light detection circuit 560 may also include a switching
circuit 564. The switching circuit 564 can be implemented using a
variety of suitable switching technologies including one or more
analog or digital switching elements. For example, in some
implementations, the switching circuit 564 includes an analog
integrated circuit. In some implementations, the first switching
circuit 564 may be comprised of one or more transistors, such as,
for example, one or more pairs of MOSFETs (for example, where each
pair includes an NMOS device and a P-channel MOSFET (PMOS) device).
In various implementations, the switching circuit 564 includes at
least a first configuration a and a second configuration b (in some
implementations, the switching circuit 564 also includes a third
configuration c). The switching circuit 564 may be configured to
receive a voltage signal V.sub.S that may be based on the detected
signal I.sub.D, as described in more detail below. The switching
circuit 564 also may be configured to receive one or more first
control signals Cntrl.sub.1 received from, for example, the
processing unit 104. The switching circuit 564 switches among at
least the first configuration a and the second configuration b
based on the one or more first control signals Cntrl.sub.1.
[0143] The light detection circuit 560 also includes a first
sampling circuit 566 configured to sample a value of the voltage
signal V.sub.S when the switching circuit 564 may be in the first
configuration a. The light detection circuit 560 also includes a
second sampling circuit 568 configured to sample a value of the
voltage signal V.sub.S when the first switching circuit 564 may be
in the second configuration b.
[0144] The light detection circuit 560 may also include an
adjustable gain circuit 570 configured to provide (or "output" or
"set") a signal I.sub.1 (for example, a current signal) to adjust a
gain of the voltage signal V.sub.S relative to the detected signal
I.sub.D when the first switching circuit 564 may be in the first
configuration. As described above, it can be desirable to adjust
the gain so that the light detection circuit 560 can accurately and
reliably detect the scattered light signal L.sub.S so that, for
example, an analog-to-digital converter (ADC) 576 can resolve a
digital signal from the sampled signal S.sub.1. In can additionally
be desirable to adjust the gain so that other components of the
light detection circuit 560 (for example, operational amplifiers)
don't saturate or otherwise function improperly or undesirably. The
adjustable gain circuit 570 sets the magnitude and polarity of the
current signal I.sub.1 based on one or more second control signals
Cntrl.sub.2 (received from, for example, the processing unit 104)
and based (directly or indirectly) on the value of the detected
signal I.sub.D as described in more detail below.
[0145] The light detection circuit 560 also includes an ambient
light cancellation circuit 572 configured to provide a countering
current signal I.sub.2 to at least partially counter an undesired
component of the detected signal I.sub.D when the switching circuit
564 may be in the first configuration. The ambient light
cancellation circuit 572 sets the magnitude and polarity of the
current signal I.sub.2 based on one or more third control signals
Cntrl.sub.3 (received from, for example, the processing unit 104)
and based on the value of the signal S.sub.2 (for example, a
voltage signal) sampled by the second sampling circuit 568, as
described in more detail below. For example, as described above,
the component of the detected signal I.sub.D to be canceled can be
the result of ambient light. That may be, the light detector 562
can receive ambient light in addition to the time-varying scattered
light signal L.sub.S, and as a result, the detected signal I.sub.D
can include an ambient component in additional to the time-varying
component resulting from the scattered light signal L.sub.S (It
should be noted that, although the ambient light component can vary
with time as well, such an ambient light time variance may be of a
relatively much lower frequency and effectively "DC" or "static"
when compared with the frequency of the time-varying incident light
signal L.sub.E and the sampling rate of the first and second
sampling circuits 566 and 568, respectively). In some
implementations, the light detection circuit 560 also may be
configured to adjust a gain of the detected signal I.sub.D to
prevent saturation of various electrical components (for example,
operational amplifiers) of the light detection circuit 560 or to
bring the values of the sampled signal S.sub.1 into a range that
may be suitable for the ADC 576.
[0146] As described above, in some implementations, the light
detector 562 may be configured to output the detected signal
I.sub.D as a time-varying current signal. In such implementations,
the light detection circuit 560 can further include an electrical
current-to-voltage converter 574 configured to convert the detected
signal I.sub.D to a voltage signal V.sub.G. In such
implementations, the adjustable gain circuit 570 more specifically
sets the current signal I.sub.1 to adjust a gain of the voltage
signal V.sub.G relative to the first electrical signal I.sub.D when
the first switching circuit 564 may be in the first configuration.
Additionally, in such implementations, the magnitude and polarity
of the current signal I.sub.1 are more specifically based on the
second control signals Cntrl.sub.2 and the voltage signal
V.sub.G.
[0147] In some implementations, the light detection circuit 560
also includes a buffer 578 that buffers the voltage signal V.sub.G
and outputs buffer signal V.sub.S. The light detection circuit 560
also can include a buffer 580 that buffers the sampled signal
S.sub.1 prior to input into the ADC 576. The light detection
circuit 560 also can include a buffer 582 that buffers the sampled
signal S.sub.2 prior to input into the ambient light cancellation
circuit 572.
[0148] In some implementations, the components of the
current-to-voltage converter 574 and the adjustable gain circuit
570 form or function as a transimpedance amplifier 584 with
variable gain. As described above, such a configuration can avoid
or minimize saturation from bright ambient light or bright incident
light from the light emitter. For example, as described in more
detail below, the gain of the transimpedance amplifier 584 may be
automatically increased or decreased with a variable resistors or a
multiplexed set or network of resistors in the negative feedback
path of the transimpedance amplifier. FIG. 15 shows an example
circuit 660 for implementing the light detection circuit 560 of
FIG. 14 according to some implementations. For example, the
current-to-voltage converter 574 can include a first operational
amplifier 674. A first input terminal of the operational amplifier
674 can be electrically coupled with a first terminal of the light
detector 652 (for example, a photodiode) and a first terminal
T.sub.1 of an adjustable impedance stage 670. A second input
terminal of the operational amplifier 674 can be electrically
coupled with a reference voltage, such as a ground. In the circuit
660, the adjustable gain circuit 570 includes an adjustable
impedance stage 670, which may be configured to provide an
adjustable impedance. The output terminal of the operational
amplifier 674 can be electrically coupled with a second terminal
T.sub.2 of the adjustable impedance stage 670. The output terminal
of the operational amplifier 674 also outputs the voltage signal
V.sub.G. As described above, the operational amplifier 674 and the
adjustable impedance stage 670 form or function as a transimpedance
amplifier 684.
[0149] In the example implementation, the adjustable impedance
stage 670 includes an impedance network having a first impedance
path 673a including a resistor having a resistance R.sub.1 and a
capacitor having a capacitance C.sub.1 that provide a first
impedance. The impedance network also includes a second impedance
path 673b including a resistor having a different resistance
R.sub.2 and a capacitor having a capacitance C.sub.2 that provide a
second impedance. The adjustable impedance stage 670 further
includes a second switching circuit 671 configured to transition
between a first configuration d and a second configuration e to
select among the first impedance path 673a and the second impedance
path 673b, respectively, based on the one or more second control
signals Cntrl.sub.2. It should be appreciated that although the
circuit 660 includes only two impedance paths, in some other
implementations three or more impedance paths can be included and
the second switching circuit 671 can select among the three or more
impedance paths. Additionally, in some other implementations,
rather than having an impedance network having multiple paths of
different impedance, the adjustable impedance stage can include a
variable impedance, such as an analog component configured to vary
an impedance to vary the gain.
[0150] In the circuit 660, the ambient light cancellation circuit
572 includes a second adjustable impedance stage 672 between a
first terminal T.sub.3 of the ambient light cancellation circuit
572 and a second terminal T.sub.4 of the ambient light cancellation
circuit 572. The second adjustable impedance stage 672 may be
configured to provide an adjustable impedance to adjust the current
signal I.sub.2. In the example implementation, the adjustable
impedance stage 672 includes an impedance network having a first
impedance path 677a including a resistor having a resistance
R.sub.1. The impedance network also includes a second impedance
path 677b including a resistor having a different resistance
R.sub.2. The adjustable impedance stage 672 further includes a
third switching circuit 675 configured to transition between a
first configuration d and a second configuration e to select among
the first impedance path 677a and the second impedance path 677b
based on the one or more third control signals Cntrl.sub.3.
[0151] Notably, in some implementations, the resistances in the
impedance paths 673a and 677a are the same (R.sub.1) while the
resistances in the impedance paths 673b and 677b are the same
(R.sub.2). That is, in some implementations, for each impedance
path in the adjustable impedance stage 670 of the adjustable gain
circuit 570 there may be a corresponding impedance path in the
adjustable impedance stage 672 of the ambient light cancellation
circuit 572 having the same resistance. Thus, in some
implementations, when the second switching circuit 671 may be in
configuration d, the third switching circuit 675 also may be in
configuration d, and similarly, when the second switching circuit
671 may be in configuration e, the third switching circuit 675 also
may be in configuration e. In some implementations, the second
switching circuit 671 and the third switching circuit 675 can
include the same switching elements or be a part of a single switch
(for example, a single analog switch) that controls both the
impedance stage 670 and the impedance stage 672. In such
implementations, the third control signals Cntrl.sub.3 can be the
second control signals Cntrl.sub.2.
[0152] Additionally, as described above with reference to the
adjustable impedance stage 670 of the adjustable gain circuit 570,
in some other implementations, rather than having an impedance
network having multiple paths of different impedance, the
adjustable impedance stage 672 of the ambient light cancellation
circuit 572 can include a variable impedance, such as an analog
component configured to vary an impedance.
[0153] In the circuit 660, the buffer 578 includes a second
operational amplifier 678. A first input terminal of the second
operational amplifier 678 may be electrically coupled with the
output terminal of the operational amplifier 674. The output
terminal of the second operational amplifier 678 may be
electrically coupled with the second input terminal of the second
operational amplifier. In some implementations, the circuit further
includes an isolation resistor 686, having a resistance R.sub.ISO,
electrically coupled in series between the output terminal of the
second operational amplifier 678 and the switching circuit 564. For
example, the isolation resistor 686 can serve as a dampening
mechanism to minimize ringing.
[0154] The first sampling circuit 566 includes a first
sample-and-hold (S/H) circuit configured to receive the voltage
signal V.sub.S, sample a value of the voltage signal V.sub.S, and
hold (or "maintain," "capture," or "store") the sampled value
S.sub.1 for a time interval in between consecutive samples. In the
circuit 660, the first S/H circuit may be implemented by the
switching circuit 564 and a capacitor 666 having a capacitance
C.sub.S1. For example, a first terminal of the capacitor 666 can be
electrically coupled to the switching circuit 564 to receive the
voltage signal V.sub.S when the switching circuit 564 may be in the
first configuration a. The second terminal of the capacitor 666 can
be electrically coupled with a reference voltage, such as a ground.
When the switching circuit 564 transitions from the first
configuration a to, for example, the second configuration b or a
third configuration c, the capacitor 666 holds the sampled value
S.sub.1. In some implementations, it may be desirable to have a
large capacitance C.sub.S1 so that the capacitor 666 may be able to
store a lot of charge without leaking appreciably.
[0155] In some implementations, because it may be desirable to have
a large capacitance C.sub.S1 (and a large capacitance C.sub.S2 as
described below), it may be desirable to include the first buffer
578, and specifically the operational amplifier 678, to drive the
large capacitance of the capacitor 666 (and the capacitor 668
described below). In this way, the first operational amplifier 574
may not have to drive any capacitors and the performance of the
operational amplifier 678 may be improved, which could otherwise be
destabilized if required to drive a large capacitance.
[0156] The ADC 576 may be configured generate and output a digital
voltage signal OUT based on the sampled signal S.sub.1. As
described above, in some implementations, the light detection
circuit 560 includes a second buffer 580 for buffering the sampled
signal S.sub.1. For example, the second buffer 580 can reduce or
prevent instability or leakage that may be caused by the ADC 576.
In some such implementations, the second buffer 580 includes a
third operational amplifier 680. For example, the first input
terminal of the third operational amplifier 680 can be electrically
coupled to an output of the first sampling circuit 566--the first
terminal of the capacitor 666. The output terminal of the third
operational amplifier 680 can be electrically coupled with the
second input terminal of the third operational amplifier and with
the ADC 576.
[0157] The second sampling circuit 568 may include a second
sample-and-hold (S/H) circuit configured to receive the voltage
signal V.sub.S, sample a value of the voltage signal VS, and hold
the sampled value S.sub.2 for a time interval in between
consecutive samples. In the circuit 660, the second S/H circuit may
be implemented by the switching circuit 564 and a capacitor 668
having a capacitance C.sub.S2. For example, a first terminal of the
capacitor 668 can be electrically coupled to the switching circuit
564 to receive the voltage signal V.sub.S when the switching
circuit 564 may be in the second configuration b. The second
terminal of the capacitor 668 can be electrically coupled with a
reference voltage, such as a ground. When the switching circuit 564
transitions from the second configuration b to, for example, the
first configuration a or a third configuration c, the capacitor 668
holds the sampled value S.sub.2. Similar to the first sampling
circuit 566, in some implementations, it may be desirable to have a
large capacitance C.sub.S2 so that the capacitor 668 may be able to
store a lot of charge without leaking appreciably.
[0158] As described above, in some implementations, the light
detection circuit 560 includes a third buffer 582 for buffering the
sampled signal S.sub.2 before it may be received by the ambient
light cancellation circuit 572, and in the implementation of FIG.
15, by the adjustable impedance stage 672. In some such
implementations, the third buffer 582 includes a fourth operational
amplifier 682. For example, the first input terminal of the fourth
operational amplifier 682 can be electrically coupled to an output
of the second sampling circuit 568--the first terminal of the
capacitor 668. The output terminal of the fourth operational
amplifier 682 can be electrically coupled with the second input
terminal of the fourth operational amplifier. The output terminal
of the fourth operational amplifier 682 also may be electrically
coupled with the ambient light cancellation circuit 572, and more
specifically, the adjustable impedance stage 672. In some
implementations, the third buffer 582, and more specifically the
fourth operational amplifier 682, may be configured to output the
sampled signal S.sub.2, and more particularly the charge stored on
the capacitor 668 associated with the value of the sampled signal
S.sub.2, to the adjustable impedance stage 672 only when an enable
signal EN may be asserted or received. For example, in some
implementations, the enable signal EN may be asserted at least
during the time interval during which the switching circuit 564 may
be in the first configuration a. In this way, while the switching
circuit 564 may be in the first configuration a, the charge stored
on the capacitor 668 may be transferred in the form of electrical
current to the adjustable impedance stage 672 of the ambient light
cancellation circuit 572 where it passes through one of the
impedance paths 677a or 677b selected by the third switching
circuit 675 and results in the current I.sub.2 described above.
[0159] In some implementations, the circuit 660 further includes a
fourth switching circuit 688 coupled with the first terminal of the
light detector 562. The fourth switching circuit 688 can be
configured to electrically couple the first terminal of the light
detector 562 to a voltage reference, such as a ground, based on one
or more fourth control signals Cntrl.sub.4 (received from, for
example, the processing unit 104). In this way, for example, while
the light detection circuit 560/660 may be not sampling the
detected light signal I.sub.D, such as when the switching circuit
564 may be in the second configuration b or the third configuration
c, the charge accumulating on the light detector 562 as a result of
receiving ambient light can be drained off. In some other
implementations, it can be useful for the fourth switching circuit
688 to electrically couple the light detector 562 to a non-ground
reference voltage, such as, for example, in implementations in
which it may be desirable to reverse bias the light detector 562
(for example, to reverse bias a photodiode).
[0160] An example three-stage cycle of operation of the light
emission driver circuit 440 and the light detection circuit 560
(and 660) will now be described. It should be appreciated that the
stages of the example cycle can encompass intervals of time (as
opposed to discreet time points) involving multiple operations or
reconfigurations, and can be overlapping with one another in some
implementations. In a first stage of operation, the one or more
control signals Cntrl.sub.D cause the driver circuit 444 to drive
the light emitter 442 to emit the incident light signal L.sub.E.
Also in the first stage, the one or more first control signals
Cntrl.sub.1 cause the switching circuit 564 to transition to the
first configuration a to enable the first sampling circuit 566 to
sample a detected signal I.sub.D (or more specifically a signal
derived from the detected signal I.sub.D such as the signal V.sub.G
or V.sub.S) and subsequently, to enable the ADC 576 to digitize the
sampled signal S.sub.1 and to output the output signal OUT
(including, for example, heart rate data). Also in the first stage,
the one or more second control signals Cntrl.sub.2 cause the
adjustable gain circuit 670 to adjust or select an impedance and to
generate the signal I.sub.1 to adjust the gain of the voltage
signal V.sub.S relative to the detected signal I.sub.D. Also at
stage 702, the enable signal EN may be asserted causing the charge
stored by the second sampling circuit 582 to be transferred via
electric current to the ambient light cancellation circuit 572. In
response to the one or more third control signals Cntrl.sub.3, the
ambient light cancellation circuit 572 adjusts or selects an
impedance and generates the cancelling signal I.sub.2 based on the
charge received from the second sampling circuit 582 to cancel (or
counter) an ambient component of the detected signal I.sub.D. Also
in the first stage, the one or more fourth control signals
Cntrl.sub.4 cause the fourth switching circuit 688 to decouple the
light detector 562 from the reference voltage such that the light
detector 562 can generate the detected signal I.sub.D.
[0161] In some implementations, in a second stage of operation, the
one or more first control signals Cntrl.sub.1 cause the switching
circuit 564 to transition to the second configuration b to disable
the first sampling circuit 566 and to enable the second sampling
circuit 568 to sample the detected signal I.sub.D while the light
emitter 442 may be off to, for example, store a charge proportional
to an ambient component of the detected signal I.sub.D. Also in the
second stage, the enable signal EN may be de-asserted to enable the
second sampling circuit 582 to store charge (for example, on
capacitor 668) associated with the sampled signal S.sub.2. As
described above, it may be the charge associated with the sampled
signal S.sub.2 that may be later used to provide the signal I.sub.D
to cancel the ambient component of the detected light signal during
the first stage of operation.
[0162] In some implementations, in a third stage of operation, the
one or more fourth control signals Cntrl.sub.4 cause the fourth
switching circuit 688 to couple the light detector 562 to the
reference voltage (for example, a ground) such that the charge that
would otherwise accumulate in the light detector 562 due to ambient
light can be drained away. In some implementations, the light
emission driver circuit 440 and the light detection circuit 560
then repeat the first stage of operation, and so on.
[0163] Additional embodiments and details relating to
photoplethysmography circuits are disclosed in U.S. patent
application Ser. No. 15/223,589, entitled "Circuits and Methods for
Photoplethysmographic Sensor," filed on Jul. 29, 2016, the
disclosure of which was incorporated by reference in its entirety
above.
Display Brightness Level Setting Adjustment
[0164] In certain embodiments, the brightness of an electronic
display of a biological monitoring device can be adjusted using the
ambient light readings from a light detector associated with an
optical physiological metric sensor module, such as a
phytoplethysmograph (PPG) signal on a wrist worn device. For
example, readings from a photodetector that are utilized for PPG
generation may be converted to a common reference frame. Such
leveraging of existing PPG circuitry and/or components may be more
rudimentary than a dedicated front-side ambient light sensor, but
may nevertheless provide adequate measurement of lighting
conditions. In certain embodiments, ambient data from a PPG sensor
may be sufficient for detecting the difference in lighting
conditions between indoor and outdoor environments. Therefore,
biometric monitoring devices in accordance with the present
disclosure can be configured to adjust electronic display
brightness settings between at least indoor and outdoor modes,
thereby resulting in power savings and extending battery life for
the biometric monitoring device.
[0165] Generally, electronic displays may be tuned for external
visibility in certain devices. For example, the display brightness
level may be tuned to have different settings for inside versus
outside lighting conditions. In certain embodiments, biometric
monitoring devices in accordance with the present disclosure are
configured to implement a three-mode brightness level scheme, with
low-, intermediate-, and high-light settings. Wherein a PPG sensor
is designed to modify detected light signals to account for factors
having an effect on PPG calculations/determinations, such
modifications may be substantially undone for the purpose of making
ambient lighting determinations for display brightness level
management. Alternatively, the light detector signal may be
obtained by the display brightness level management circuitry
before it is processed/modified by the PPG circuitry. In certain
embodiments, the display brightness level management circuitry may
utilize the modified/processed PPG signals for the purpose of
obtaining a more complex solution. In certain embodiments, the
display brightness level management and/or PPG circuitry may
utilize hysteresis information in processing light detector signals
to improve the quality of determinations based thereon.
[0166] With further reference back to FIGS. 2 and 3, biometric
monitoring devices in accordance with the present disclosure may
include an electronic display 230 with a configurable brightness
setting. In certain embodiments, the biometric monitoring device
200 is configured to leverage ambient light signals from the
optical physiological metric sensor module 243 associated with a
backside of the biometric monitoring device 200 to detect
indoor/outdoor ambient lighting conditions, thereby allowing for
the brightness of the display 230 to be decreased or increased in
accordance therewith. In certain embodiments, the display 230 is an
organic light-emitting diode (OLED) display. In certain
embodiments, display brightness level adjustment based on backside
ambient light detection may provide reduced power consumption by up
to 50% or more when the display 230 is on and the user is indoors.
Such savings may be achieved without the benefit of a front-side
dedicated ambient light sensor component, which would generally be
associated with increased price, complexity, and battery
consumption. Biometric monitoring devices employing display
brightness level adjustment in accordance with the present
disclosure may further provide an improved user viewing experience
compared to displays that always display at a maximum brightness
setting, even when used indoors.
[0167] The display 230 of FIG. 2 may be representative of an
embodiment of the electronic display 130 of FIG. 1, and the
biometric monitoring device 200 may be an embodiment of the
biometric monitoring device 100. With reference to FIG. 1, the
biometric monitoring device 100 includes a brightness level
management system 113, which may be configured to adjust a
brightness level setting for the electronic display 130. As
described above, it may be desirable for the brightness level
management module 111 of the control circuitry 110 to adjust the
brightness level setting of the electronic display 130 according to
an intensity of the environmental ambient light. In certain
embodiments, when the ambient light is not greater than a first
threshold level, the brightness level management module 111 may
maintain the brightness level setting at a low level. In certain
embodiments, when the ambient light falls between the first
threshold level and a second threshold level, the brightness level
setting may be set to an intermediate level. In certain
embodiments, when the ambient light is greater than the second
threshold, the brightness level setting may be set to a high level.
In certain embodiments, only a single ambient light threshold is
used, wherein setting the brightness level setting involves setting
the brightness level to one of two settings, namely a low mode
setting and a high mode setting.
[0168] In certain embodiments, the optical physiological metric
sensor of the biometric monitoring device runs substantially
continuously. In determining the heart rate parameter(s) and/or
other physiological metric(s), the optical physiological metric
sensor system may make ambient light determinations at any point,
or in connection with any process or functionality. For example, in
certain embodiments, the optical physiological metric sensor
components may be configured to take ambient light readings when
the light sources and/or physiological metric (e.g., heart rate)
determination circuitry are not active. The use of the
physiological metric determination circuitry may be extended to
provide ambient light information for display brightness level
control purposes. Where the optical physiological metric sensor
circuitry is designed to modify the light detector signal(s) to
account for skin color or other factors, the display brightness
level management circuitry may be configured to reconvert the
ambient signal back to the raw ambient signal so as to provide a
baseline signal for ambient light determination. For example, PPG
circuitry may be designed to apply scaling and/or gain biasing to
the light detector signal(s) to account for different lighting
conditions, skin tone, or the like; such processing may effectively
be reversed to get the raw ambient signal.
[0169] In addition to, or as an alternative to, using ambient light
information for display brightness level management, certain
embodiments disclosed herein provide for the use of such
information for determining sun exposure, sleep detection, or the
like. In certain embodiments, the PPG circuitry may be configured
to store ambient light data values during operation; such values
may be used by the display brightness level management subsystem to
determine display brightness level settings. In certain
embodiments, the PPG sensor runs at a 25 Hz sampling rate. The
display brightness level management subsystem may store samples in
a circular buffer.
Display Brightness Level Adjustment Processes
[0170] Certain embodiments disclosed herein provide processes for
adjusting a brightness level setting of an electronic display, such
as a backlighting setting, for a biometric monitoring device
without the use of a dedicated front-side ambient light sensor.
Reducing the intensity of display brightness in certain conditions
may provide power savings and/or reduce strain on the user's eyes
when viewing the display in low-light conditions. FIG. 16 is a flow
diagram illustrating a process 1600 for adjusting a brightness
level setting of an electronic display according to one or more
embodiments. The process 1600 may provide power savings and may be
implemented as part of a power management scheme in a biometric
monitoring device, such as a wrist-wearable biometric monitoring
device.
[0171] At block 1602, the process 1600 involves directing light
from a light source of a wearable biometric monitoring device into
tissue of a user during a first time period. For example, the step
of block 1602 may involve activating one or more light sources
associated with a backside (i.e., skin-facing when the biometric
monitoring device is worn on a user's wrist) of the biometric
monitoring device.
[0172] At block 1604, the process 1600 involves generating a first
light detector signal using a skin-facing light detector, the first
light detector signal indicating a first amount of light detected
by the light detector during the first period. For example, the
first light detector signal may be generated using a photodetector
or other light detector, which may be a component of a
physiological metric sensor module, such as a module configured to
implement optical components for determining heart rate, blood
oxygenation, or other physiological metric of the user.
[0173] At block 1606, the process 1600 involves deactivating the
light source during a second period of time. For example, one or
more light sources may be pulsed or otherwise activated and
deactivated, wherein the first period of time corresponds with a
period during which the light source(s) are active, while the
second period of time corresponds to a period during which the
light source(s) are deactivated, such that the photodetector(s) do
not detect light from the light sources during the second period of
time.
[0174] At block 1608, the process 1600 involves generating a second
light detector signal indicating a second amount of light detected
by the light detector during the second period. For example, the
second light detector signal may be generated using the light
detector utilized in connection with step 1604. Because the light
source(s) are not activated during the second period of time, the
second light detector signal may provide a reading that indicates
ambient light presence, as the light detected during the second
period of time is not generally attributable to the light
source(s).
[0175] At block 1610, the process 1600 involves generating a
physiological metric signal based at least in part on the first
light detector signal and the second light detector signal. The
physiological metric signal may be generated at least in part by
generating an ambient light cancellation signal using the second
light detector signal, which may be indicative of ambient light
because it indicates detected light at a time when the light
sources are not activated. The process 1600 may involve cancelling
ambient light in the first light detector signal by subtracting out
the ambient light indicated by the second light detector signal.
Generating the ambient light cancellation signal can involve
conditioning the second light detector signal to account for skin
tone characteristics of the user, which may be determined in any
suitable or desirable way, such as through a calibration process or
accessing profile data. In certain embodiments, it may be necessary
to at least partially reverse the conditioning of the second light
detector signal to produce a raw ambient light signal, which may be
used in determining whether or how to modify the display brightness
level setting.
[0176] At block 1612, the process 1600 involves modifying a
brightness setting of an electronic display based at least in part
on the second light detector signal. For example, the brightness
level may be modified based on the second light detector signal,
but not the first light detector signal. Because the second light
detector signal may be indicative of ambient light, the utilization
of such signal may be used to modify the brightness of the display
to account for ambient light conditions. For example, the process
1600 may involve determining whether an amplitude of the raw
ambient light signal is greater than a threshold. The ambient light
data from the second light detector signal may further be used to
determine other metrics, such as sun exposure. Ambient light data
determined from the second light detector signal may be stored in a
buffer (e.g., circular buffer) or other storage. When the amplitude
of the second light detector signal is greater than a threshold,
such condition may trigger modifying the brightness of the display
to a higher level. In certain embodiments, when the display
brightness level management system determines that ambient lighting
conditions are high, the high-level brightness level setting may be
locked for a period of time, such as until the display and/or
biometric monitoring device is powered down or placed in a sleep
mode or low-power mode. Locking the brightness level setting may
help reduce or prevent unwanted flickering or dimming of the
display.
[0177] FIG. 17 is a block diagram illustrating an embodiment of a
display control feedback system according to one or more
embodiments. In some embodiments, a display control feedback system
includes one or more hardware components, one or more software
components and a communication bus to interface between said
hardware and software components. In some embodiments, a display
control feedback system includes one or more LEDs 1702 or another
illumination device or light source. An example display control
system may also include an output driver 1708 electrically and/or
communicatively coupled to LEDs 1702 and a timing controller 1710.
In some embodiments, the display control feedback system includes
one or more light sensors 1704 (e.g., light detectors or devices
configured to detect light), electrically and/or communicatively
coupled to a receiver/gain amplifier/filter chain block 1712. In
some embodiments, light sensors 1704 and/or block 1712 include a
transducer or another device to convert sensed readings (e.g.,
illumination) into one or more electrical parameters (e.g., current
or voltage). In some embodiments, the circuitry and/or
functionality of block 1712 is split across more than one hardware
component. For example, block 1712 may represent in FIG. 17 a
distinct hardware component for managing reception of detected
light/illumination at the one or more light sensors 1704, a
distinct hardware component for managing the gain of an amplifier
on the receive path of the light control feedback system, and a
distinct hardware component for filtering a detected
light/illumination value received by the one or more light sensors
1704. The display control feedback system may also include an
analog-to-digital converter (ADC) 1714, and a display 1706.
[0178] The display 1706, may be electrically and/or communicatively
coupled to a display adjust block 1722. A display adjust block 1722
may be electrically and/or communicatively coupled to a data
processing block 1720. Data processing block 1720 may be
electrically and/or communicatively coupled to several software
and/or hardware components, as shown in FIG. 17. For example, data
processing block 1720 may be electrically and/or communicatively
coupled to gain mode control/adjust block 1716, data sampler block
1718, and timing controller 1710.
[0179] In some embodiments, a display control feedback system
begins obtaining feedback for a display system by driving one or
more LEDs 1702 (e.g., using output driver 1708). As described
above, in some embodiments, light from a light source such as LEDs
1702, is transmitted into the skin and/or flesh of a user. In some
embodiments, light is received by one or more light sensors 1704.
The received light from light sensor(s) 1704 is processed by
receiver/gain amplifier/filter chain block 1712. For example, block
1712 may convert a level of determined illumination into an
electrical parameter (e.g., voltage and/or current). In some
embodiments, block 1712 includes one or more transducer blocks.
Processed light/illumination information from the one or more light
sensors 1704 may be communicated to ADC 1714, which converts an
analog representation of the received light/illumination
information into a digital representation passed to data sampler
1718 (e.g., through a communication bus).
[0180] In some embodiments, one or more software components operate
together to assess received light/illumination information
initially received by the one or more light sensors 1704, and
correspondingly make adjustments to one or more illumination
parameters of LEDs 1702 (or of a light source), and/or adjust one
or more reception parameters of the light sensor(s) 1704. The one
or more software components may be software modules or blocks
residing in a non-transitory computer-readable storage medium, or
memory. As an example, the data processing block 1720 may receive
sampled illumination information from data sampler 1718 and use the
sampled illumination information to determine one or more
physiological characteristics of the user. Examples of
physiological characteristics that may be determined include, but
are not limited to a user's skin tone, level of melatonin in the
skin, moisture level of the user's skin and proximity of the skin
to the one or more light sensors 1704. In some embodiments,
determining one or more physiological characteristics of a user
allows for adjustment of light transmission (e.g., illumination
using LEDs 1702) applied to the user's skin and/or flesh, and/or
adjustment of light reception (e.g., illumination detection by
light sensor(s) 1704).
[0181] As shown in FIG. 17, data processing block 1720 may be
communicatively coupled to gain mode control/adjust block 1716.
Data processing block 1720 may transmit sampled, processed
illumination information received from the one or more light
sensors 1704 and processed by block 1712 and ADC 1714 and sampled
by data sampler 1718, to gain mode control/adjust block 1716. The
gain mode control/adjust block 1716 may adjust one or more
illumination parameters through an electrical and/or communicative
coupling to output driver 1708. For example, gain mode
control/adjust block 1716 may instruct output driver 1708 to
increase or decrease an applied voltage corresponding to
illumination intensity of the one or more LEDs 1702. Additionally,
gain mode control/adjust block 1716 may return instructions to data
processing block 1720, which may use the instructions to adjust one
or more illumination and/or reception parameters, using timing
controller 1710. In some embodiments, data processing block 1720
instructs timing controller 1710 to adjust a duration of time for
illumination of the one or more LEDs 1702 (e.g., one or more light
sources), and/or instructs timing controller 1710 to adjust a
duration of time for reception of detected illumination/light at
the one or more light sensors 1704 (e.g., one or more light
detectors). Although not shown in FIG. 17, in some embodiments,
gain mode control/adjust block 1716 is directly coupled
electrically and/or communicatively to the receiver/gain
amplifier/filter chain block 1712 of the receive path. Whether
coupled directly, or indirectly, gain mode control/adjust block
1716 may instruct block 1712 to adjust receiver amplifier gain
settings (e.g., by adjusting one or more corresponding register
values). Alternatively, or additionally, gain mode control/adjust
block 1716 may instruct block 1712 to adjust filtration of the
received illumination from light sensor(s) 1704, in the filter
chain processing portion of block 1712.
[0182] In some embodiments, data processing block 1720 uses the
result of a feedback-driven sampled, processed illumination reading
to determine one or more operational brightness modes of the
display control feedback system. For example, data processing block
1720 may determine that the user is in an environment with an
operational brightness mode of 3 out of 6. That is to say, that
data processing block 1720 may rank an order of operational
brightness modes, based on detected levels of illumination
corresponding to each mode. In another example, data processing
block 1720 may qualitatively determine that the user is in an
indoor lighting setting with dim lights. In some embodiments, the
determined operational brightness mode is transmitted by data
processing block 1720 to display adjustment block 1722. An
operational brightness mode may correspond to a brightness level of
display 1706. In some embodiments, display adjust block 1722 uses
the operational brightness mode determined by data processing unit
1720 to instruct display 1706 to change a brightness level of
display 1706. For example, if the user is in a relatively brightly
lit environment, display adjustment block 1722 may instruct display
1706 to increase brightness of display 1706, so that the
information on display 1706 is easier to read. In some embodiments,
an operational brightness mode corresponds to additional or
alternative parameters of display 1706 other than brightness alone,
such as but not limited to duration of brightness level and a rate
of increase or decrease in illumination.
[0183] As described earlier, data processing block 1720 may
determine an ambient light level or value. In some embodiments,
this determined ambient light level or value corresponds to an
operational brightness mode. For example, a measured or determined
ambient light level may be compared to one or more threshold values
(e.g., level of illumination), to determine a specific operational
brightness mode. The determined operational brightness mode may
then be used to adjust one or more brightness parameters of display
1706 (e.g., brightness level, rate of illumination). In some
embodiments, the determined ambient light level or value is
determined with respect to determining or generating a
physiological metric (e.g., heart rate) of the user. Data
processing block 1720, display adjustment block 1722 and/or an
additional processing block (not shown) between blocks 1720 and
1722, may further process an ambient light level or value
determined for generating the physiological metric, for purposes of
determining display adjustment information. For example, the
feedback loop described with respect to FIG. 17 may result in a
first value for ambient light level, used by the data processing
block 1720 to determine a heart rate for the user. The first
ambient light level may further be processed by the data processing
block 1720 for purposes of assessing an operational brightness
mode, into a second ambient light level (e.g., outdoors and sunny).
The additionally processed ambient light level may be a
quantitative value (e.g., 3/10) and/or a qualitative value (e.g.,
dim, indoors).
[0184] The one or more LEDs 1702, output driver 1708, timing
controller 1710, receiver/gain amplifier/filter chain block 1712,
one or more light sensors 1704, display 1706, ADC 1714, gain mode
control/adjust block 1716, data processing block 1720, data sampler
block 1718 and/or display adjust block 1722 may have one or more
characteristics of corresponding modules, blocks, components or
units described within this disclosure.
Additional Embodiments
[0185] Depending on the embodiment, certain acts, events, or
functions of any of the processes or algorithms described herein
can be performed in a different sequence, may be added, merged, or
left out altogether. Thus, in certain embodiments, not all
described acts or events are necessary for the practice of the
processes. Moreover, in certain embodiments, acts or events may be
performed concurrently, e.g., through multi-threaded processing,
interrupt processing, or via multiple processors or processor
cores, rather than sequentially.
[0186] Certain methods and/or processes described herein may be
embodied in, and partially or fully automated via, software code
modules executed by one or more general and/or special purpose
computers. The word "module" refers to logic embodied in hardware
and/or firmware, or to a collection of software instructions,
possibly having entry and exit points, written in a programming
language, such as, for example, C or C++. A software module may be
compiled and linked into an executable program, installed in a
dynamically linked library, or may be written in an interpreted
programming language such as, for example, BASIC, Perl, or Python.
It will be appreciated that software modules may be callable from
other modules or from themselves, and/or may be invoked in response
to detected events or interrupts. Software instructions may be
embedded in firmware, such as an erasable programmable read-only
memory (EPROM). It will be further appreciated that hardware
modules may be comprised of connected logic units, such as gates
and flip-flops, and/or may be comprised of programmable units, such
as programmable gate arrays, application specific integrated
circuits, and/or processors. The modules described herein are
preferably implemented as software modules, but may be represented
in hardware and/or firmware. Moreover, although in some embodiments
a module may be separately compiled, in other embodiments a module
may represent a subset of instructions of a separately compiled
program, and may not have an interface available to other logical
program units.
[0187] In certain embodiments, code modules may be implemented
and/or stored in any type of computer-readable medium or other
computer storage device. In some systems, data (and/or metadata)
input to the system, data generated by the system, and/or data used
by the system can be stored in any type of computer data
repository, such as a relational database and/or flat file system.
Any of the systems, methods, and processes described herein may
include an interface configured to permit interaction with
patients, health care practitioners, administrators, other systems,
components, programs, and so forth.
[0188] Embodiments of the disclosed systems and methods can be used
and/or implemented with local and/or remote devices, components,
and/or modules. The term "remote" may include devices, components,
and/or modules not stored locally, for example, not accessible via
a local bus. Thus, a remote device may include a device which is
physically located in the same room and connected via a device such
as a switch or a local area network. In other situations, a remote
device may also be located in a separate geographic area, such as,
for example, in a different location, building, city, country, and
so forth.
[0189] Conditional language used herein, such as, among others,
"can," "could," "might," "may," "e.g.," and the like, unless
specifically stated otherwise, or otherwise understood within the
context as used, is intended in its ordinary sense and is generally
intended to convey that certain embodiments include, while other
embodiments do not include, certain features, elements and/or
steps. Thus, such conditional language is not generally intended to
imply that features, elements and/or steps are in any way required
for one or more embodiments or that one or more embodiments
necessarily include logic for deciding, with or without author
input or prompting, whether these features, elements and/or steps
are included or are to be performed in any particular embodiment.
The terms "comprising," "including," "having," and the like are
synonymous, are used in their ordinary sense, and are used
inclusively, in an open-ended fashion, and do not exclude
additional elements, features, acts, operations, and so forth.
Also, the term "or" is used in its inclusive sense (and not in its
exclusive sense) so that when used, for example, to connect a list
of elements, the term "or" means one, some, or all of the elements
in the list. Conjunctive language such as the phrase "at least one
of X, Y and Z," unless specifically stated otherwise, is understood
with the context as used in general to convey that an item, term,
element, etc. may be either X, Y or Z. Thus, such conjunctive
language is not generally intended to imply that certain
embodiments require at least one of X, at least one of Y and at
least one of Z to each be present.
[0190] Reference throughout this specification to "certain
embodiments" or "an embodiment" means that a particular feature,
structure or characteristic described in connection with the
embodiment is included in at least some embodiments. Thus,
appearances of the phrases "in some embodiments" or "in an
embodiment" in various places throughout this specification are not
necessarily all referring to the same embodiment and may refer to
one or more of the same or different embodiments. Furthermore, the
particular features, structures or characteristics can be combined
in any suitable manner, as would be apparent to one of ordinary
skill in the art from this disclosure, in one or more
embodiments.
[0191] It should be appreciated that in the above description of
embodiments, various features are sometimes grouped together in a
single embodiment, figure, or description thereof for the purpose
of streamlining the disclosure and aiding in the understanding of
one or more of the various inventive aspects. This method of
disclosure, however, is not to be interpreted as reflecting an
intention that any claim require more features than are expressly
recited in that claim. Moreover, any components, features, or steps
illustrated and/or described in a particular embodiment herein can
be applied to or used with any other embodiment(s). Further, no
component, feature, step, or group of components, features, or
steps are necessary or indispensable for each embodiment. Thus, it
is intended that the scope of the inventions herein disclosed and
claimed below should not be limited by the particular embodiments
described above, but should be determined only by a fair reading of
the claims that follow.
* * * * *