U.S. patent application number 16/118117 was filed with the patent office on 2020-03-05 for focusing mechanism for biosignals measurement with mobile devices.
The applicant listed for this patent is CMOS Sensor, Inc.. Invention is credited to Sun-Teck See, Weng Lyang Wang, Jason Wu.
Application Number | 20200073055 16/118117 |
Document ID | / |
Family ID | 69410764 |
Filed Date | 2020-03-05 |
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United States Patent
Application |
20200073055 |
Kind Code |
A1 |
Wang; Weng Lyang ; et
al. |
March 5, 2020 |
Focusing mechanism for biosignals measurement with mobile
devices
Abstract
A focusing mechanism or module is designed to reduce the size of
an optical lens-based focusing system that would be otherwise used
in a portable device. According to one aspect of the present
invention, the focusing mechanism includes a light guide with first
and second sides. The light guide includes a plurality of light
passages slanted inwardly formed evenly from the first side towards
a center of the second side, wherein the light guide, disposed on
top of the image sensor, collects a reflected light from a human
body part and focuses the reflected light onto the image sensor,
each of photosensors generates an proportional charge from the
reflected light.
Inventors: |
Wang; Weng Lyang; (Saratoga,
CA) ; Wu; Jason; (Daly City, US) ; See;
Sun-Teck; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CMOS Sensor, Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
69410764 |
Appl. No.: |
16/118117 |
Filed: |
August 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/4259 20130101;
G02B 6/325 20130101; H04M 1/0266 20130101; H04M 2250/12 20130101;
G02B 6/0025 20130101 |
International
Class: |
G02B 6/32 20060101
G02B006/32; F21V 8/00 20060101 F21V008/00; G02B 6/42 20060101
G02B006/42; H04M 1/02 20060101 H04M001/02 |
Claims
1. A focusing module for acquiring sensing signals, the focusing
module comprising: a light guide with first and second sides,
including a plurality of light passages slanted inwardly formed
evenly from the first side towards a center of the second side,
wherein the light guide, disposed on top of an array of
photosensors, collects a reflected light from a human body part and
focuses the reflected light through the light passages onto the
photosensors, each of photosensors generates a charge, wherein the
light guide is made with a plurality of sheets, each of the sheets
includes a transparent patch forming part of one of the light
passages.
2. (canceled)
3. The focusing module as recited in claim 1, wherein transparent
patches on each of the sheets have their own diameters and centers
of the transparent patches.
4. The focusing module as recited in claim 3, wherein all of the
sheets are stacked to form the light passages slanted inwardly
formed evenly from the first side towards the center of the second
side.
5. The focusing module as recited in claim 4, wherein the first
side of the light guide is larger than the array of photosensors in
size, and the centers of the transparent patches on the plurality
of sheets are progressively moving towards the center of the second
side.
6. The focusing module as recited in claim 4, wherein the
transparent patches are round in shape and formed by blackening
each of the sheets except for areas of the transparent patches.
7. The focusing module as recited in claim 4, wherein each of the
sheets is painted to form the transparent patches.
8. The focusing module as recited in claim 1, wherein the light
guide is disposed under a display screen to collect the reflected
light from the human body part via the display screen, and wherein
the human body part is placed against the display screen.
9. The focusing module as recited in claim 8, wherein the display
screen is part of a mobile device.
10. The focusing module as recited in claim 1, wherein the light
guide is disposed next to a display screen to collect the reflected
light from the human body part, and wherein the human body part is
placed upon the second side of display screen.
11. A system for acquiring sensing signals via a focusing module,
the system comprising: an image sensor including an array of
photosensors; a light guide with first and second sides, including
a plurality of light passages slanted inwardly formed evenly from
the first side towards a center of the second side, wherein the
light guide, disposed on top of the image sensor, collects a
reflected light from a human body part and focuses the reflected
light through the light passages onto the image sensor, each of
photosensors generates a charge, and wherein the light guide is
made with a plurality of sheets, each of the sheets includes a
transparent patch forming part of one of the light passages.
12. (canceled)
13. The focusing module as recited in claim 11, wherein transparent
patches on each of the sheets have their own diameters and centers
of the transparent patches.
14. The focusing module as recited in claim 13, wherein all of the
sheets are stacked to form the light passages slanted inwardly
formed evenly from the first side towards the center of the second
side.
15. The focusing module as recited in claim 14, wherein the first
side of the light guide is larger than the image sensor in size,
and the centers of the transparent patches on the plurality of
sheets are progressively moving towards the center of the second
side.
16. The focusing module as recited in claim 14, wherein the
transparent patches are round in shape and formed by blackening
each of the sheets except for areas of the transparent patches.
17. The focusing module as recited in claim 14, wherein each of the
sheets is painted to form the transparent patches.
18. The focusing module as recited in claim 10, wherein the light
guide is disposed under a display screen to collect the reflected
light from the human body part via the display screen, and wherein
the human body part is placed against the display screen.
19. The focusing module as recited in claim 18, wherein the image
sensor is part of a mobile device.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention is related to the area of image
sensors. More particularly, the present invention is related to an
optical sensor, circuitry for such sensors, and a light source for
acquiring biosignals from a human body part (e.g., a finger).
2. Description of Related Art
[0002] Smart phones have become the fastest-selling gadgets in
history, outstripping the growth of the simple mobile phones that
preceded them many years ago. Today about half the adult population
owns a smart phone; by 2020, 80% will. Smart phones have also
penetrated every aspect of daily life. With proper applications, a
smart phone can fulfill the needs for a telephone, digital camera
and video camera, GPS navigation, a media player, clock, news,
calculator, web browser, handheld video game player, flashlight,
compass, an address book, note-taking, digital messaging, an event
calendar, and etc. With the rapid improvement of hardware and
software in smart phones, the need and development of point-of-care
testing (POC Testing) based on the smart phones is rapidly
growing.
[0003] Point-of-care (POC) testing, originally referred to as
bedside testing, is defined as medical diagnostic testing at or
near a point of care, that is, at the time and place of patient
care. The POC testing contrasts with the tradition in which testing
was wholly or mostly confined to a medical laboratory, thus
requiring a patient to travel away from home. Now with a smart
phone equipped with certain sensors and loaded with certain
applications, many simple medical tests could be performed anywhere
close to the patient.
[0004] The driving notion behind the POC testing is to bring some
medical tests conveniently and immediately to a patient, which
increases the likelihood that the patient, his/her physician or
care team receives the results quickly, for possible clinical
management or decisions if needed. Although still limited in the
types of the POC tests that may be conducted by a patient
him/herself, a smart phone is mainly used in biosensing assays,
acting as detectors, data processors, and even signal inducers with
or without an additional custom designed cradle or attachment used
to mount other components.
[0005] Almost all smart phones have an image sensor. One
application of the image sensor in the field of biometrics is to
verify an identity of a user by capturing an image of the user, for
example, a body part (e.g., skin, finger, eye or face) so as to
wake up a device, activate an application and pay bills. Typical
biometric measurement is based on digitized images of fingerprints,
iris patterns in the eye, hand shape, or hand vein patterns as a
basis for identity verification. However, the image sensor used for
the biometric applications is the one primarily designed for photos
or videos, typically in high-resolution and low sensitive to
biological changes (e.g., inferred or heat in a finger), they are
not ideal for some common biological measurements, such as heart
rate and blood pressure. Thus there is a need for sensors that are
low in cost but sensitive to the biological changes on a body
part.
[0006] Given the fact that an image sensor designed for scenic
images/video are not suitable for some biological measurements,
such as, heart rate or blood pressure, many companies have
introduced dedicated sensors specifically used for these
measurements. For example, Samsung Galaxy 5 is equipped with a
standalone detector to detect the heart rate. The location of such
a sensor in a smart phone would require a user to move a body part
(e.g., finger) in contact with or close to the sensor to allow the
sensor to sense certain biological changes (e.g., fingertip pulse
or blood volume changes) to derive a biological measurement.
However, such a measurement can sometimes be misleading, causing
unwanted concern, as the user may not position the sensor right on
a preferable area of the body part. Thus, there is another need for
sensors that are small in sizes but provide certain freedom to
position a sensor onto or near a selected area of a body part.
[0007] More needs for various embodiments of the present invention
can be appreciated in the following description.
SUMMARY OF THE INVENTION
[0008] This section is for the purpose of summarizing some aspects
of the present invention and to briefly introduce some preferred
embodiments. Simplifications or omissions in this section as well
as in the abstract or the title of this description may be made to
avoid obscuring the purpose of this section, the abstract and the
title. Such simplifications or omissions are not intended to limit
the scope of the present invention.
[0009] In general, the present invention pertains to designs of a
sensor module and its placement in a portable device. According to
one aspect of the present invention, a sensor module is designed to
take advantage of the architecture of CMOS sensors to capture
biological changes in multiple areas of a body part to derive a
measurement for blood. To increase the signal sensitivity, sensing
elements or pixels in a sensor module may be dynamically adjusted
or combined to effectively capture the biological changes in these
areas.
[0010] According to another aspect of the present invention,
multiple sensing signals are generated from multiple areas on a
body part. These signals are preprocessed in analog or digital to
increase the reliability and accuracy of the measurement on the
body part.
[0011] According to still another aspect of the present invention,
a software module or application is provided to control how the
sensor module operates. Depending on what measurement is to get
from a body part, a control signal is initiated via the application
to define a number of zones in the sensor and a number of pixels in
each of the zones to produce a sensing signal from such a zone.
[0012] According to still another aspect of the present invention,
a light guide is provided to focal a reflected light onto a sensor.
The light guide is made of a plurality of sheets, each of the
sheets includes an array of holes, where the diameters of the holes
and the distances between the holes may be different or equal from
one sheet to another to form a plurality of inward light passages,
when stacked.
[0013] According to still another aspect of the present invention,
each of the sheets is a film, where the holes are formed by an
opaque substance printed on the film, hence transparent (round)
patches, to enhance the focusing of the light guide.
[0014] According to yet another aspect of the present invention,
the sensing signals are digitized and analyzed in accordance with
the control signal to derive from the multiple sensing areas an
intended biological measurement (e.g., a heart rate or blood
pressure).
[0015] The present invention may be implemented in various ways
including a method, a circuit, an apparatus or a system. According
to one embodiment, the present invention is an integrated circuit
of a sensor apparatus for both imaging device and a biological
measurement, the integrated circuit comprises: an array of pixels,
each of the pixels including one photosensor and generating a
charge, wherein the charge represents a reflected light; a readout
circuit generating sensing signals from charges of the pixels; and
a post processing circuit provided to select N sets of sensing
signals, the sensing signals in each of the N sets being from a
group of pixels focusing on an area of a body part, wherein the N
sets of sensing signals are used for deriving multiple
measurements, and the biological measurement is concluded from the
multiple measurements, and where N is an integer.
[0016] According to another embodiment, the present invention is a
method for acquiring a biological measurement, the method
comprises: generating charges from an array of pixels, each of the
pixels including one photosensor, wherein each of the charges
represents a reflected light from a body part; generating in a
readout circuit sensing signals from the charges; and selecting N
sets of the sensing signals, the sensing signals in each of the N
sets being from a group of pixels focusing on an area of the body
part, wherein the N sets of sensing signals are used for deriving
multiple measurements, and the biological measurement is concluded
from the multiple measurements, and where N is an integer.
[0017] According to still another embodiment, the present invention
is a focusing module for acquiring sensing signals, the focusing
module comprising: a light guide, with first and second sides,
including a plurality of light passages slanted inwardly formed
evenly from the first side towards a center of the second side,
wherein the light guide, disposed on top of an array of
photosensors, collects a reflected light from a human body part and
focuses the reflected light onto the photosensors, each of
photosensors generates a charge. The light guide may be made with a
plurality of sheets, each of the sheets includes a transparent
patch forming part of one of the light passages. The transparent
patches on each of the sheets have their own diameters and centers
of the transparent patches. The diameters of the transparent
patches on the sheets may be identical or different depending on an
implementation.
[0018] According to yet another embodiment, the present invention
is a system for acquiring sensing signals via a focusing module.
The system comprises an image sensor including an array of
photosensors; a light guide, with first and second sides, including
a plurality of light passages slanted inwardly formed evenly from
the first side towards a center of the second side. The light
guide, disposed on top of the image sensor, collects a reflected
light from a human body part and focuses the reflected light onto
the image sensor. Each of photosensors generates a charge from the
reflected light. The light guide is integrated on top of the image
sensor as the focusing module disposed under or next to a display
screen.
[0019] Different objects, features, and advantages of the present
invention will become apparent upon examining the following
detailed description of an embodiment thereof, taken in conjunction
with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0021] FIG. 1A shows a configuration in which an optical sensor is
used to detect biological changes on a body part;
[0022] FIG. 1B shows an example of a partial finger image, where
only a small area is captured or used by a sensor for the
measurement of the biological changes in the finger;
[0023] FIG. 1C shows a PPG signal (e.g., fingertip pulse) generated
from the sensor from the area shown in FIG. 1B;
[0024] FIG. 2A shows a configuration diagram of a sensor including
an array of sensing elements (e.g., photodiodes) and an array of
lights;
[0025] FIG. 2B shows an example of a square array of N.times.N
pixels, only signals from certain areas of the pixels are
effectively used;
[0026] FIG. 2C shows another control of a sensing elements to sense
two elongated but separated areas of a body part, from which two
signals from the areas are generated and may be used to derive a
more reasonable measurement;
[0027] FIG. 3A shows a block diagram of an exemplary system using a
sensor according to one embodiment of the present invention;
[0028] FIG. 3B shows an example of a photoplethysmographic (PPG)
waveform that can be captured by a portion of a sensor;
[0029] FIG. 3C shows an exemplary APS pixel circuit including a
pixel element and an active amplifier followed by a readout
circuit;
[0030] FIG. 3D shows an exemplary integrator to integrate n charges
from n pixels;
[0031] FIG. 3E shows a flowchart or process that may be implemented
in hardware (e.g., integrated circuit) or a combination of hardware
or software;
[0032] FIG. 4A shows an exemplary placement of a sensor in a
portable device, such as a smartphone, a tablet, or a laptop
computer;
[0033] FIG. 4B shows an example of stacking sheets, each printed
with a type of opaque material (e.g., black ink) to form an array
of transparent patches thereon;
[0034] FIG. 4C shows one exemplary perforated sheet, where the
holes are made equal or slightly changed in diameters;
[0035] FIG. 4D shows a light guide with straight passages;
[0036] FIG. 5A shows a simplified cross-section of what is referred
to herein as a placement under display;
[0037] FIG. 5B shows an exemplary smart phone in which a package
including a light guide and a sensor is disposed on the back of the
smart phone;
[0038] FIG. 5C shows other possible locations of the package;
[0039] FIG. 6A shows a functional block diagram of a portable
device equipped with one embodiment of the present invention;
and
[0040] FIG. 6B shows an exemplary display, where an indication of
measurements on multiple areas of a finger is also shown.
DETAILED DESCRIPTION OF THE INVENTION
[0041] The detailed description of the present invention is
presented largely in terms of procedures, steps, logic blocks,
processing, or other symbolic representations that directly or
indirectly resemble the operations of devices or systems
contemplated in the present invention. These descriptions and
representations are typically used by those skilled in the art to
most effectively convey the substance of their work to others
skilled in the art.
[0042] Reference herein to "one embodiment" or "an embodiment"
means that a particular feature, structure, or characteristic
described in connection with the embodiment can be included in at
least one embodiment of the invention. The appearances of the
phrase "in one embodiment" in various places in the specification
are not necessarily all referring to the same embodiment, nor are
separate or alternative embodiments mutually exclusive of other
embodiments.
[0043] Embodiments of the invention are discussed below with
reference to FIGS. 2A-6B. However, those skilled in the art will
readily appreciate that the detailed description given herein with
respect to these figures is for explanatory purposes as the
invention extends beyond these limited embodiments. As used herein,
any pronoun references to gender (e.g., he, him, she, her, etc.)
are meant to be gender-neutral. Unless otherwise explicitly stated,
the use of the pronoun "he", "his" or "him" hereinafter is only for
administrative clarity and convenience. Additionally, any use of
the singular or to the plural shall also be construed to refer to
the plural or to the singular, respectively, as warranted by the
context.
[0044] FIG. 1A shows a configuration 100 in which an optical sensor
102 is used to detect biological changes on a body part 104. In
general, an optical lens 106 is used to focus optical signals
reflected from the body part 104 onto the sensor 102. The optical
lens is a lens reduction type system to focus the large area of
object plane to a small area of the image plane. A transparent
substrate 108 (e.g., a piece of glass) is used to protect the
sensor 102 and the lens 106 while holding the focal distance
between the body part 104 and the lens 106. The total height of the
whole module may be pretty high and would not be suitable for
current smart phone applications.
[0045] FIG. 1B shows an example of a partial finger image 110,
where only a small area 112 is captured or used by the sensor 102
for the measurement of the biological changes in the finger. FIG.
1C shows a signal (e.g., fingertip pulse) generated from the sensor
102 from the area 112. It can be observed that the measurement of
the biological changes in the finger could be changed or subject to
errors as the area 112 changes. In other words, the measurement
could be wrong if a user moves an undesirable part of his finger
onto the focusing area of the sensor 102.
[0046] Referring now to the drawings, in which like numerals refer
to like parts throughout the several views, FIG. 2A shows a
configuration diagram of a sensor 200 including an array of sensing
elements 202 (e.g., photodiodes) and an array of lights 204.
According to one embodiment of the present invention, the sensing
elements 202, or simply a sensor or sensors, are CMOS-based
photodiodes with light guide 203, and the lights 204 are
light-emitting diodes. Depending on an application of the sensor
200, the light-emitting diodes are controlled to generate an
appropriate colored light (e.g., infrared, red) to facilitate the
sensor to capture possible biological changes in a focused area of
a body part.
[0047] In one embodiment, the sensing elements 202 form an array of
predefined shape (e.g., square, rectangular or round). FIG. 2B
shows an example of a square array of N.times.N pixels. Instead of
focusing only one area of a body part, the sensor 200 can be
controlled to focus onto multiple areas of the body part, resulting
in simultaneous signals representing the biological changes in the
areas. As an example, FIG. 2B shows that the five sensing areas 206
are configured or allocated to capture the biological changes in
five independent areas of the body part. Through post-processing,
one or more of these readouts for top to bottom or left to right
may be used to derive a measurement (e.g., blood flow). As a
result, not only is the measurement accuracy increased
considerably, but the requirement of having a user to place the
sensor onto a particular area of the body part or vise versa is
much more relaxed.
[0048] FIG. 2C shows another control of the sensing elements 202 to
sense two elongated but separated areas of a body part, from which
two signals from the areas are generated and may be used to derive
a more reasonable measurement. It should be noted to those skilled
in the art that the number of sensing elements or photodiodes in
each of a predefined area can be adjusted or controlled depending
on a particular application. In some cases, the number of the
sensing elements in a predefined area is enlarged to increase the
sensitivity of the sensing on a particular area while in other
cases the number of the sensing elements in a predefined area is
limited but the number of areas from which sensing signals must be
obtained may be increased. One of the key advantages, benefits or
advantages in one embodiment of the present invention is to provide
multiple readouts or sensing signals from a number of areas in a
body part.
[0049] Referring now to FIG. 3A, it shows a block diagram of an
exemplary multi function readout system 300 using a sensor (e.g.,
the sensor 200 of FIG. 2A) according to one embodiment of the
present invention. The sensor or simply the array 302 is controlled
to have one or more local exposures to certain areas. Given known
dimensions of the array 302, the number of the sensing elements is
defined and controlled to produce a number of readouts. Depending
on operation, the sensing elements in the array 302 may be all or
partially activated with all or only some of the sensing elements
are selectively read out via a readout circuit (not shown) to
measure either finger print pattern or biometrics data.
[0050] According to one embodiment, the readouts from the array 302
are preprocessed in a preprocessing circuit 304 to produce required
sensing signals. For finger print application, all of the M.times.N
sensing element need to readout to form an image pattern. Only a
few frames may be needed for finger print recognition. For
biometrics application, more frames are required to obtain the
necessary PPG waveform. In this case, it is not necessary to read
out all of the sensing elements. For example, there are five areas
(as shown in FIG. 2B), the preprocessing circuit 304 may be
designed to output five or less sensing signals, discarding other
readouts from the array 302 when all are read out from the array
302. In another embodiment, the preprocessing circuit 304 may be
designed to remove the inherent DC component from a sensing element
to facilitate the measurement of biological changes in an area. The
output signals from the preprocessing circuit 304 are selectively
processed depending on what to derive from the sensing signals. As
shown in FIG. 3A, a control signal (labeled as a function
selection) is used to determine how the sensing signals are
processed to derive therefrom a measurement (e.g., a heart
rate).
[0051] An image processing unit 305 is provided to process the
readouts from the preprocessing circuit 304. Depending on an
implementation, some of the functions that are described above for
the preprocessing circuit 304 may be implemented in the image
processing unit 305, such as filtering out those sensing signals
that seem to be too extreme. An extreme signal could happen from
several sensing signals obtained from multiple areas, where one of
the areas happens to be undesirable (e.g., dirt, scare, or
discolored skin). The removal of an extreme signal among several
sensing signals in a group may improve the accuracy of the readings
on a body part.
[0052] A processing unit 306 is provided to perform some additional
signal process and may be referred to as `enhancer" to enhance the
signals per the control signal. In one example, readouts from
several pixels are combined to enhance the sensitivity of the
measurement around an area covered by these pixels. In another
example, readouts from several pixels are accumulated to enhance or
increase the signal-to-noise ratio for an area being sensed.
According to one embodiment, a DC component is removed from the
signals from the preprocessing circuit 304. FIG. 3B shows an
example of a photoplethysmographic (PPG) waveform. A PPG waveform
can be captured by a portion of the sensor 302, hence several PPG
waveforms may be generated from the sensor 302. A PPG waveform
includes both direct current (DC) and alternating current (AC)
components. The DC component of the PPG waveform corresponds to a
detected transmitted or reflected optical signal from a part of
tissue, and depends on the structure of the tissue and the average
blood volume of both arterial and venous blood. The AC component
shows changes in the blood volume that occurs between the systolic
and diastolic phases of the cardiac cycle. In other words, the
fundamental frequency of the AC component depends on the heart rate
and is superimposed onto the DC component. In one embodiment, the
processing unit 306 is designed to remove the DC component from the
PPG waveform, and output only the AC component.
[0053] It should be noted that preprocessing circuit 304, image
processing unit 305 and data processing unit 306 are not
necessarily separate circuits. Depending on an implementation, they
can be implemented in one or more ICs. The processed signals are
then digitized at 307 and the data from the digitizer 307 is then
sent to a different processor 308 or 309 to derive a specific
measurement.
[0054] Not specifically shown in FIG. 3A but indicated in FIG. 2A,
there are LEDs 204 that are designed and controlled to work with
the sensor of FIG. 3A. According to one embodiment, the color of
the LED lights is selectable, for example either blue, green, red
or infrared (IR) or else. In general, body parts do not absorb IR
light well, therefore it can penetrate .about.10.times. deeper than
other colored lights (e.g., blue or green LEDs). Blood absorbs more
light than the surrounding tissue. Therefore, a reduction in the
amount of blood is detected as an increase in the intensity of the
detected light and vice versa. The wavelength and distance between
the light source and photo detector (PD) determine the penetration
depth of the light. In one embodiment, two or more different
colored lights are used. For example, the light source 204 of FIG.
2A is controlled to generate two different colored lights, red and
near inferred red (NIR). Red light source can reflect more
concentration of deoxygenated hemoglobin [C(Hb)] whereas NIR light
source can reflect more concentration of oxygenated hemoglobin
[C(HbO.sub.2)] on the blood. By used two different colors of the
light source, the blood oximeter may be more effectively detected
and measured.
[0055] According to one embodiment, a sensing element is
implemented as an active-pixel sensor (APS). As shown in FIG. 3C,
an APS pixel is an integrated circuit including a pixel element 310
and an active amplifier 312, followed by a readout circuit 314. The
pixel element 310 further includes a photodiode 316 that is
controlled to be turned on or off. The amplifier 312 is an
amplifier provided to amplify the signal produced by the photodiode
316. As an example shown in FIG. 3C, the amplifier 312 is
implemented with what is called unity gain buffer amplifier (UGBA).
As the name suggests, the amplifier is one that provides electrical
impedance transformation from one circuit to another, with the aim
of preventing a signal source from being affected by whatever
currents or voltages that the load may produce. The readout circuit
314 in FIG. 3C uses an exemplary readout circuit provided to read
out the charge accumulated in proportional to the intensity of the
light impinged on the diode 316. As an example, the readout circuit
314 is implemented with correlated double sampling (CDS) circuitry
to read out the sensing signal from the pixel 310. Another
amplifier (not shown) may also be added as a charge integrator to
produce a final sensing signal to be coupled for digitization.
[0056] The correlated double sampling, or CDS, circuitry is a
method employed to improve the signal to noise ratio (S/N) of an
image sensor by reading out the pixel 310 twice. The first readout
happens right after the exposure of the sensor to a scene. The
second readout happens without the sensor is exposed to the scene
but soon after the first readout has successfully occurred.
Accordingly, the first readout is herein referred to as actual
light-induced signal while the second readout is referred to as a
reference signal. The reference signal is largely coming from
internal dark or reference output level in the pixel. By
subtracting the reference output signal from the actual
light-induced signal, static fixed pattern noise (FPN) and several
types of temporal noise are effectively removed from the output of
the sensor. In operation, the first readout of the signal from the
photo detector 316 is stored on a capacitor 318 and the second
readout the signal from the photo detector 316 is stored on a
capacitor 320. The final readout of the signal is the difference
between the signals on the capacitors 318 and 320. Depending on an
implementation, the APS pixel can be selected to capture what is
being focused on (e.g., a point of a finger) or read out the final
charge. When used in a group to capture biological changes in an
area of a body part, final charges from a group of ADS pixels can
be read out and further processed in a pre-processing circuit 304
of FIG. 3A.
[0057] FIG. 3D shows an exemplary integrator to integrate n charges
from n pixels. The n charges are respectively stored in n
capacitors Ch1, Ch2, . . . , Chn of the n pixels. The total charges
Qt can be expressed in the following: in sampling mode:
Qt = Q 1 + Q 2 + + Qn = ( V 1 - Vr ) .times. Ch 1 + ( V 2 - Vr )
.times. Ch 2 + + ( Vn - Vr ) .times. Chn ##EQU00001##
in readout mode: the charges are transferred to Cf, thus
Qf=(Vr-Vo).times.Cf
In one embodiment, Qf=Qt, the output Vo is expressed as
follows:
Vo=-[(V1-Vr).times.Ch1+(V2-Vr).times.Ch2+ . . .
+(Vn-Vr).times.Chn]/Cf+Vr
It is supposed that V1=V2= . . . =Vn=Vi, and Ch1=Ch2= . . .
=Chn=Ch, the output Vo can be rewritten as follows:
Vo=-nCh/Cf.times.(Vi-Vr)+Vr
Thus it can be concluded that the signal of a sensor area with n
pixels is read out with gain of -nCh/Cf, where n is the number of
the inputs to the CDS.
[0058] Referring now to FIG. 3E, it shows a flow chart or process
350 to measure the biometrics data (e.g., heart rate, . . . ) that
may be implemented in hardware or a combination of hardware or
software. FIGS. 2A-3D may be referenced to better understand FIG.
3E according to one embodiment.
[0059] At 352, sensing signals from an array of M.times.N are
collected. As described above, a sensor is used to sense a
plurality of areas of a body part, several sensing elements are
combined to form a large size of a sensing area so as to form a
M'.times.N' of array 354 (less resolution than the array of
M.times.N). This process will reduce the noise and increase the SNR
to biometrics measurement. Accordingly, the received signals are
elected per the predefined areas. It is assumed that a group of 49
(e.g., 7.times.7) pixels is designated to sense an area, sensing
signals from these 49 pixels will be selected and added up, as if
there was one captured signal from the area. The signal was
captured for a period of time, hence a waveform. It is further
assumed that the signal was captured for measuring a heart rate at
356, where the waveform is a PPG. At 358, the DC component is
removed.
[0060] The selected sensing signals are digitized at 360 to
generate a set of or sets of data. The data can now be processed in
digital or by a dedicated module being executed by a processor at
364. The result of the data processing at 364 is shown to a display
screen at 366, were the user sees the result right after the
measurements were took.
[0061] Referring now to FIG. 4A, it shows an exemplary placement of
a sensor (e.g., the sensor 200 of FIG. 2A) in a portable device,
such as a smart phone, a tablet, or a laptop computer. One of the
features in the embodiment of FIG. 4A is the use of an optical
light guide to direct the reflected object image onto the sensing
elements. According to one embodiment, the sensor 402 is placed
under a display screen 404, where the display screen 404 has
considerable transparency, allowing sufficient light to pass
through. Examples of such display screen may include, but not
limited to, an OLED or micro LED display. When a body part 406 is
placed against the screen 404 and illuminated by a light source
(not shown), a light guide 408 is provided to focus the reflected
light from the body part 406 to the sensor 402. The activated
sensing elements in the sensor 402 generate analog signals 410 that
are then digitized to produce digital signals or data 412 for
deriving there from a measurement.
[0062] FIG. 4B shows an enlarged view of the light guide 408 that
includes layers of materials (e.g., sheets or films) providing
slanted inward optical passages. FIG. 4C shows one exemplary
perforated sheet 416, where the holes are made equal or slightly
changed in diameters. According to one embodiment, these holes are
not physically hollow and may be just transparent for easy
alignment or placement among other sheets. In other words, each of
perforated sheets has its own center positions and diameter of the
holes. The centers and diameters of the holes on all the sheets are
so aligned that the resulting passages formed by the holes are
inwardly slanted when these sheets are stacked as shown in FIG. 4B.
According to one embodiment, these sheets are made from films,
where the holes are formed by the opaque (or black) printed on the
films.
[0063] It may be appreciated to those skilled in the art that the
slanted inward passages represent the optical characteristics of a
focal lens or a set of focal lenses. These slanted inward passages
allow reflected lights from an object placed upon the glass 404 to
fall on the sensors 402 mounted under the light guide 408. As a
comparison, FIG. 4D shows a light guide with straight passages. The
lights (reflected) from an object would hit on the walls of the
passages, which can cause a reduction of the incoming light
intensity. With the slanted inward passages, the total internal
reflection may be induced to allow the incoming light to fully pass
through onto the sensors. Total internal reflection is well known
in the art that a phenomenon happens when a propagating wave
strikes a medium boundary at an angle larger than a particular
critical angle with respect to the normal to the surface. The
critical angle is the angle of incidence above which the total
internal reflectance occurs.
[0064] FIG. 5A shows a simplified cross-section 500 of what is
referred to herein as a placement under display. This exemplary
placement works perfect with a display screen 506 that is
substantially transparent at an operation. For example, an OLED
screen, though not completely transparent, allows most of the light
to pass through when it is not driven to display a bright colorful
image. One of the advantages of placing a package including the
light guide 504 and the sensor 502 under the display screen 506 is
that it is operationally feasible for a smart phone manufacturer to
equip their smart phones with the capability of providing the POC
Testing, along with an application preinstalled or downloadable
from a designated server (e.g., Apple Store).
[0065] There are display screens that won't allow lights to pass
through, the package including the light guide 504 has to be placed
or exposed to surface of a portable. FIG. 5B shows an exemplary
smart phone in which the package is disposed on the back of the
smart phone. FIG. 5C shows other possible locations of the
package.
[0066] FIG. 6A shows a functional block diagram of a portable
device equipped with one embodiment of the present invention. The
portable device includes a microprocessor or microcontroller 602, a
memory space 604 (e.g., RAM or flash memory) in which there is a
sensor module 606 for acquiring biological signals, an input
interface 608, an application module 609, a screen driver 610 to
drive a display screen 612 and a network interface 614. The client
module 606 may be implemented as an application implementing one
embodiment of the present invention, and downloadable over a
network from a library (e.g., Apple Store) or a designated
server.
[0067] The input interface 608 includes one or more input
mechanisms. A user may use an input mechanism to interact with the
device 600 by entering a command to the microcontroller 602.
Examples of the input mechanisms include a microphone or mic to
receive an audio command and a keyboard (e.g., a displayed soft
keyboard) to receive a click or texture command. Another example of
an input mechanism is a camera provided to capture a photo or
video, where the data for the photo or video is stored in the
device for immediate or subsequent use with other module(s) or
application(s). The driver 610, coupled to the microcontroller 602,
is provided to take instructions there from to drive the display
screen 612. In one embodiment, the driver 610 is caused to drive
the display screen 612 to display an image or images (e.g., an ad
banner) or play back a video (e.g., an ad video). The network
interface 614 is provided to allow the device 600 to communicate
with other devices via a designated medium (e.g., a data
network).
[0068] According to one implementation, the client module 606 is
loaded in the memory 604 and executed by the controller 602 to
receive. The client module 606 is designed to cause the display
screen 612 to display an interface to receive some input (e.g.,
name, age or gender). The client module 606 is also designed to
acquire other information automatically from the device 600, for
example, the time, location, or temperature. In one embodiment, a
display is shown to allow a user to choose what to measure (a
selection), for example, a heart rate, a blood pressure, a blood
flow, blood oximeter or other biological measurement. When a
selection is made, the display shows an instruction how and where
to have the sensor 609 in close contact with a body part, for
example, a finger. Once all is ready, the client module 606
initiates the measurement via the microcontroller 602.
[0069] As described above, the sensing signals are generated, read
out, preprocessed and digitized in accordance with the selection in
one embodiment. The client module 606 deals now with sensing data
or simply data. Algorithms for deriving corresponding logical
measurements are implemented in the client module 606. Per the
selection, one of the algorithms is activated to receive the data.
The data is further selected from a set of predefined pixels
corresponding to respective areas of a body part. The selected data
is used with the activated algorithm to derive the logical
measurement. In one embodiment, the measurement may be repeated
with different sets of data corresponding to different areas of the
body part, when the measurement derived is way off from a previous
measurement. The final result is shown on the screen 612 and sent
to a designated part with the permission of the user. FIG. 6B shows
an exemplary display, where an indication of measurements on
multiple areas of a finger is also shown.
[0070] The present invention has been described in sufficient
detail with a certain degree of particularity. It is understood to
those skilled in the art that the present disclosure of embodiments
has been made by way of examples only and that numerous changes in
the arrangement and combination of parts may be resorted without
departing from the spirit and scope of the invention as claimed.
While the embodiments discussed herein may appear to include some
limitations as to the presentation of the information units, in
terms of the format and arrangement, the invention has
applicability well beyond such embodiment, which can be appreciated
by those skilled in the art.
[0071] Modifications, additions, or omissions may be made to the
systems, apparatuses, and methods described herein without
departing from the scope of the disclosure. For example, the
components of the systems and apparatuses may be integrated or
separated. Moreover, the operations of the systems and apparatuses
disclosed herein may be performed by more, fewer, or other
components and the methods described may include more, fewer, or
other steps. Additionally, steps may be performed in any suitable
order. As used in this document, "each" refers to each member of a
set or each member of a subset of a set. Accordingly, the scope of
the present invention is defined by the appended claims rather than
the forgoing description of embodiments.
[0072] To aid the Patent Office and any readers of any patent
issued on this application in interpreting the claims appended
hereto, applicants wish to note that they do not intend any of the
appended claims or claim elements to invoke 35 U.S.C. 112(f) unless
the words "means for" or "step for" are explicitly used in the
particular claim.
* * * * *