U.S. patent application number 13/486931 was filed with the patent office on 2012-09-20 for system and method for practicing spectrophotometry using light emitting nanostructure devices.
This patent application is currently assigned to Nellcor Puritan Bennett LLC. Invention is credited to Gilbert Hausmann, Paul Mannheimer, Michael P. O'Neil.
Application Number | 20120238848 13/486931 |
Document ID | / |
Family ID | 38935988 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120238848 |
Kind Code |
A1 |
Hausmann; Gilbert ; et
al. |
September 20, 2012 |
SYSTEM AND METHOD FOR PRACTICING SPECTROPHOTOMETRY USING LIGHT
EMITTING NANOSTRUCTURE DEVICES
Abstract
Embodiments of the present invention relate to a system and
method for practicing spectrophotometry using light emitting
nanostructures. Specifically, embodiments of the present invention
include a physiologic sensor comprising a sensor body configured
for placement adjacent pulsatile tissue of a patient, a first light
emitting nanostructure device configured to emit light at a first
wavelength through the pulsatile tissue, a second light emitting
nanostructure device configured to emit light at a second
wavelength through the pulsatile tissue, and a light detector
configured to detect the light at the first wavelength and the
light at the second wavelength after dispersion through the
pulsatile tissue.
Inventors: |
Hausmann; Gilbert; (Felton,
CA) ; O'Neil; Michael P.; (Pleasanton, CA) ;
Mannheimer; Paul; (Danville, CA) |
Assignee: |
Nellcor Puritan Bennett LLC
Boulder
CO
|
Family ID: |
38935988 |
Appl. No.: |
13/486931 |
Filed: |
June 1, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11524099 |
Sep 20, 2006 |
8219170 |
|
|
13486931 |
|
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Current U.S.
Class: |
600/328 ;
604/323; 977/734; 977/925 |
Current CPC
Class: |
G01J 3/10 20130101; B82Y
20/00 20130101; G01N 2021/3144 20130101; G01N 21/4795 20130101;
A61B 5/14552 20130101; G01N 21/359 20130101; A61B 5/0059
20130101 |
Class at
Publication: |
600/328 ;
604/323; 977/734; 977/925 |
International
Class: |
A61B 5/1455 20060101
A61B005/1455 |
Claims
1. A physiologic sensor, comprising: a sensor body configured for
placement adjacent tissue of a patient; a first light emitting
nanostructure device configured to emit light at a first wavelength
into the tissue; a second light emitting nanostructure device
configured to emit light at a second wavelength into the tissue,
wherein the first and second light emitting nanostructure devices
are arranged to simulate emission of light at the first wavelength
and light at the second wavelength from essentially a single
emission point; and a light detector configured to detect the light
at the first wavelength and the light at the second wavelength from
the tissue.
2. The physiological sensor of claim 1, wherein the first
wavelength is at a point in the electromagnetic spectrum where
absorption by oxyhemoglobin differs from absorption by
deoxyhemoglobin.
3. The physiological sensor of claim 2, wherein the second
wavelength is at a point in the electromagnetic spectrum where
absorption by oxyhemoglobin and the absorption by deoxyhemoglobin
are different than the first wavelength.
4. The physiological sensor of claim 1, comprising a plurality of
light emitting nanotube devices arranged in a matrix, wherein the
plurality of light emitting nanotube devices comprise the first and
second light emitting nanostructure devices.
5. The physiological sensor of claim 4, wherein approximately half
of the plurality of light emitting nanotube devices are configured
to emit light at the first wavelength through the tissue and the
remaining light emitting nanotube devices are configured to emit
light at the second wavelength.
6. The physiological sensor of claim 1, wherein the first light
emitting nanostructure device is configured to emit a red light at
approximately 660 nm.
7. The physiological sensor of claim 1, wherein the first light
emitting nanostructure device is configured to emit an infrared
light at approximately 900 nm.
8. The physiological sensor of claim 1, wherein the first and
second light emitting nanostructure devices comprise nanotubes, and
the first light emitting nanostructure device is arranged within
the sensor body for placement adjacent the tissue and has a
diameter sufficient to accommodate light emitted from the second
light emitting nanostructure device.
9. The physiological sensor of claim 1, comprising a plurality of
light emitting nanostructure devices arranged in a matrix, wherein
a first group of the plurality of light emitting nanostructure
devices is stacked adjacent a second group of the plurality light
emitting nanostructure devices, wherein the first and second group
emit light in the same direction.
10. The physiological sensor of claim 9, wherein an axis of
emission of each of the nanostructure devices in the first group
are aligned with an axis of emission of each of the nanostructure
devices in the second group.
11. The physiological sensor of claim 1, wherein the first
wavelength is different from the second wavelength.
12. A pulse oximeter system, comprising: a pulse oximeter
configured to read signal data and derive patient data from the
signal data; and a sensor configured to detect physiological
characteristics of a patient and to communicate the physiological
characteristics to the pulse oximeter as the signal data,
comprising: a sensor body configured for placement adjacent
pulsatile tissue of the patient; a first light emitting
nanostructure device configured to emit light at a first wavelength
into the pulsatile tissue; a second light emitting nanostructure
device configured to emit light at a second wavelength into the
pulsatile tissue, wherein the first and second light emitting
nanostructure devices are arranged to simulate emission of light at
the first wavelength and light at the second wavelength from
essentially a single emission point; and a light detector
configured to detect the light at the first wavelength and the
light at the second wavelength from the pulsatile tissue.
13. The pulse oximeter system of claim 12, comprising a plurality
of light emitting nanotube devices arranged in a matrix, wherein
the plurality of light emitting nanotube devices comprise the first
and second light emitting nanostructure devices.
14. The pulse oximeter system of claim 13, wherein approximately
half of the plurality of light emitting nanotube devices are
configured to emit light at the first wavelength through the
pulsatile tissue and the remaining light emitting nanotube devices
are configure to emit light at the second wavelength.
15. The pulse oximeter system of 12, wherein the first and second
light emitting nanostructure devices comprise nanotubes.
16. The pulse oximeter system of claim 15, wherein the first light
emitting nanostructure device is arranged within the sensor body
for placement adjacent the pulsatile tissue and has a diameter
sufficient to accommodate light emitted from the second light
emitting nanostructure device.
17. The pulse oximeter system of claim 12, wherein the first
wavelength is different from the second wavelength.
18. A method, comprising: providing a sensor body configured for
placement adjacent tissue of a patient; disposing a first light
emitting nanostructure device in the sensor body, the first light
emitting nanostructure device configured to emit light at a first
wavelength into the tissue; disposing a second light emitting
nanostructure device in the sensor body, the second light emitting
nanostructure device configured to emit light at a second
wavelength into the tissue, wherein the first and second light
emitting nanostructure devices are arranged to simulate emission of
light at the first wavelength and light at the second wavelength
from essentially a single emission point; and providing a light
detector configured to detect the light at the first wavelength and
the light at the second wavelength from the tissue.
19. The method of claim 18, wherein the first and second light
emitting nanostructures are nanotubes.
20. The method of claim 18, wherein the first wavelength is
different from the second wavelength.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/524,099, entitled "System and Method for
Practicing Spectrophotometry Using Light Emitting Nanostructure
Devices", filed Sep. 20, 2006, which is herein incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to
spectrophotometry of physiologic tissue, which may include
quantitative measurement of reflection or transmission properties
of a tissue as a function of wavelength. Specifically, embodiments
of the present invention relate to using light emitting
nanostructures (LEN), such as light emitting nanotubes, in
spectrophotometry.
[0004] 2. Description of the Related Art
[0005] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
present invention, which are described and/or claimed below. This
discussion is believed to be helpful in providing the reader with
background information to facilitate a better understanding of the
various aspects of the present invention. Accordingly, it should be
understood that these statements are to be read in this light, and
not as admissions of prior art.
[0006] Spectrophotometry may include the quantitative measurement
of the reflection or transmission properties of a material as a
function of wavelength. Spectrophotometry of living tissues
includes pulse oximetry, which may include non-invasive techniques
that facilitate monitoring of a patient's physiological
characteristics (e.g., blood flow characteristics). For example,
pulse oximetry may be used to measure blood oxygen saturation of
hemoglobin in a patient's arterial blood and/or the patient's pulse
rate. Specifically, these measurements may be acquired using a
non-invasive sensor that passes light through a portion of a
patient's blood perfused tissue and photo-electrically senses the
absorption and scattering of light through the blood perfused
tissue. A typical signal resulting from the sensed light may be
translated into what is referred to as a plethysmographic waveform.
Once acquired, this measurement of the absorbed and scattered light
may be used with various algorithms to estimate an amount of blood
constituent in the tissue. It should be noted that the amount of
arterial blood in the tissue is time varying during a cardiac
cycle, which is reflected in the plethysmographic waveform.
[0007] The accuracy of blood flow characteristic estimations
obtained via pulse oximetry depends on a number of factors. For
example, variations in light absorption characteristics can affect
accuracy depending on where (e.g., finger, foot, or ear) the sensor
is applied on a patient or depending on the physiology of the
patient. Additionally, various types of noise and interference can
create inaccuracies. For example, electrical noise, physiological
noise, and other artifacts can contribute to inaccurate blood flow
characteristic estimates. One source of inaccuracy in measurements
obtained by traditional pulse oximeter sensors is inequality
between optical pathways from emission to detection points for
lights of different wavelengths. Indeed, light emitted from
different points may not pass through the same portions of tissue.
Such differences in optical pathways make traditional pulse
oximeter sensors sensitive to physiological changes, geometrical
changes and so forth.
[0008] Additionally, traditional pulse oximeter sensors can be
inefficient. For example, traditional pulse oximeter sensors often
use light emitting diodes (LEDs) that consume a significant amount
of power and that produce undesirable heating effects. Indeed, when
deep penetration of light into a patient's tissue is desirable to
detect certain blood flow characteristics, for example, the
increased intensity required of the LEDs may cause discomfort to
the patient due to heating. Further, with respect to coupling a
sensor to fiber optic cables, traditional pulse oximeter sensors
may be inefficient because coupling fiber optics with larger and/or
multiple spaced emitters (e.g., LEDs) results in inappropriate
matching of fiber diameter and numerical aperture.
[0009] Accordingly, it is desirable to provide a system and method
that efficiently and conveniently operates to provide accurate and
consistent spectrophotometric measurements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Advantages of the invention may become apparent upon reading
the following detailed description and upon reference to the
drawings in which:
[0011] FIG. 1 is a block diagram of a pulse oximeter system in
accordance with an exemplary embodiment of the present
invention;
[0012] FIG. 2 is a block diagram of a sensor for use in pulse
oximetry with two light emitting nanostructure devices aligned to
emit light from a single point in accordance with an exemplary
embodiment of the present invention;
[0013] FIG. 3 is a magnified view of the light emitting
nanostructure devices illustrated in FIG. 2 in accordance with an
exemplary embodiment of the present invention;
[0014] FIG. 4 is a block diagram of a sensor for use in pulse
oximetry with light emitting nanostructure devices disposed
horizontally adjacent to one another in accordance with an
exemplary embodiment of the present invention;
[0015] FIG. 5 is a block diagram of a sensor for use in pulse
oximetry with stacked and grouped arrays of light emitting
nanostructure devices in accordance with an exemplary embodiment of
the present invention;
[0016] FIG. 6 is a cross-sectional view of an array formed by the
light emitting nanostructure devices in FIG. 5 taken along line
6-6, in accordance with an exemplary embodiment of the present
invention;
[0017] FIG. 7 is a block diagram of a sensor for use in pulse
oximetry with light emitting nanostructure devices intermingled and
disposed horizontally adjacent to one another in accordance with an
exemplary embodiment of the present invention;
[0018] FIG. 8 is a cross-sectional view of an array formed by the
light emitting nanostructure devices in FIG. 7 taken along line
8-8, in accordance with an exemplary embodiment of the present
invention;
[0019] FIG. 9 is a block diagram of a polychromatic point emitting
light source using light emitting nanostructures in accordance with
an exemplary embodiment of the present invention;
[0020] FIG. 10 is a bock diagram of an emitter coupled with an
optical fiber in accordance with an exemplary embodiment of the
present invention; and
[0021] FIG. 11 is a block diagram of an emitter coupled with an
optical fiber, wherein a lens is incorporated for coupling
efficiency in accordance with an exemplary embodiment of the
present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0022] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, not all features of an actual
implementation are described in the specification. It should be
appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0023] Embodiments of the present invention relate to
spectrophotometry of a physiologic tissue, which may include
quantitative measurement of reflection or transmission properties
of a material as a function of wavelength. Specifically,
embodiments of the present invention may include using light
emitting nanostructure (LEN) devices in spectrophotometry. For
example, some embodiments of the present invention are directed to
using LEN devices as light emitting devices in pulse oximetry
applications, which are included in spectrophotometry. It should be
noted that while embodiments of the present invention are described
herein as including or utilizing light emitting nanotubes, other
embodiments of the present invention may include or utilize other
types of nanostructures such as Bucky balls and other quantum
restricted elements.
[0024] As will be discussed below, certain properties of LEN
devices make them desirable for use in sensors (e.g., pulse
oximeter sensors) for spectroscopic analysis of tissue or blood
constituents. Indeed, LEN-based sensors may improve sensor
functionality by consuming less power than traditional LED-based
sensors and by providing deeper penetration depth without undesired
heating effects. For example, in comparison to the traditionally
utilized light emitting diodes (LEDs), LEN devices provide
significantly improved efficiencies in creating photons. Such
efficiency reduces power requirements and allows for an increase in
light penetration depth without undesirable heating effects, which
typically accompany such penetration when utilizing LEDs.
[0025] In addition to the improvements in efficiency set forth
above, the scale and geometry of LEN devices may allow for improved
sensor operation based on positioning. For example, the small scale
of LEN devices facilitates integration of light emitting devices
for multiple light wavelengths on one substrate of sub-millimeter
size. In other words, the LEN devices can be essentially
co-located. This enables creation of a polychromatic light source
that essentially emanates from a single point and facilitates
passing multiple wavelengths through the same material (e.g.,
tissue). Such a "single point" multi-wavelength light source
facilitates formation of equal or substantially equal optical
pathways from the single emission point to a detection point for
light of different wavelengths. Having equal or substantially equal
optical pathways for the different light wavelengths makes the
sensor less susceptible to measurement discrepancies resulting from
physiological or geometrical changes. In other words, more accurate
measurement may be facilitated by having a sensor with what amounts
to a "single point" multi-wavelength light source.
[0026] FIG. 1 is a block diagram of a pulse oximeter system in
accordance with an exemplary embodiment of the present invention.
The system is generally designated by the reference numeral 10. The
system 10 includes a pulse oximeter or monitor 12 that
communicatively couples to a sensor 14. The pulse oximeter 12 may
be configured to derive patient data (e.g., blood oxygen levels)
from signal data detected from a patient and communicated to the
pulse oximeter 12 by the sensor 14. The sensor 14 includes a sensor
cable 16, a connector plug 18, a body 20 configured to attach to a
patient (e.g., patient's finger, ear, forehead, or toe), a light
emitting device 22, and a light detector 24. Pulse oximetry systems
such as the system 10 may be utilized to observe the oxygenation or
oxygen saturation of a patient's arterial blood to estimate the
state of oxygen exchange in the patient's body by emitting waves
into tissue and detecting the waves after dispersion and/or
reflection by the tissue. For example, the pulse oximeter system 10
may emit light from the light emitting device 22 into pulsatile
tissue and then detect the transmitted light with the light
detector (e.g., a photodiode or photo-detector) 24 after the light
has passed through the pulsatile tissue. The amount of transmitted
light that passes through the tissue varies in accordance with the
changing amount of blood constituent in the tissue and the related
light absorption. It should be noted that, in accordance with
present embodiments, the light emitting device 22 includes one or
more LEN devices configured to emit light of one or more
wavelengths.
[0027] FIG. 2 is a block diagram of a sensor 14 for use in pulse
oximetry in accordance with an exemplary embodiment of the present
invention. It should be noted that while FIG. 2 is directed to
pulse oximetry, the sensor 14, or similar sensors, may be utilized
in different forms of spectrophotometry. Specifically, as
illustrated in FIG. 2, sensor 14 includes two LEN devices 30A and
30B and a photo-detector 32. Device 30A may be referred to as an
inner LEN device and device 30B may be referred to as an outer LEN
device based on their respective relationships to an emission point
33. The illustrated sensor 14 also includes an interface 34 for
communicating with the monitor 12. The LEN devices 30A and 30B
receive drive signals from the monitor 12 via the interface 34, the
drive signals may activate the LEN devices 30A and 30B and cause
them to emit signals alternatively. The sensor 14 is configured
such that light from the activated LEN devices 30A and 30B can pass
into a patient's tissue 36. The light is then dispersed by the
tissue and transmitted from or reflected from the tissue 36. The
photo-detector 32 receives and/or measures the dispersed light from
the tissue 36. Further, in some embodiments, the photo-detector 32
converts the received light into a photocurrent signal, which is
then provided to a signal-processing unit (e.g., monitor 12).
[0028] To measure the oxygen saturation of the patient's arterial
blood, two different wavelengths of light may be emitted from the
respective LEN devices 30A and 30B and used to calculate the ratio
of oxygenated hemoglobin or oxyhemoglobin (O.sub.2Hb) and
deoxygenated hemoglobin or deoxyhemoglobin (HHb), which are
dominant hemoglobin components. The light passed through the tissue
(e.g., tissue 36) may be selected to include two or more
wavelengths that are absorbed by the blood in an amount related to
the amount of blood constituent present in the blood. Specifically,
a first wavelength for one of the LEN devices 30A or 30B may be
selected at a point in the electromagnetic spectrum where the
absorption of O.sub.2Hb differs from the absorption of HHb. A
second wavelength for one of the LEN devices 30A or 30B may be
selected at a different point in the spectrum where the absorption
of Hhb and O.sub.2Hb differs from those at the first wavelength.
For example, wavelength selections for measuring normal blood
oxygenation levels typically include a red light emitted at
approximately 660 nm and an infrared light emitted at approximately
900 nm.
[0029] As set forth above, for pulse oximetry applications, the
oxygen saturation of the patient's arterial blood may be determined
using two or more wavelengths of light, most commonly red and near
infrared wavelengths. Similarly, in other applications a tissue
water fraction (or other body fluid related metric) or a
concentration of one or more biochemical components in an aqueous
environment may be measured using two or more wavelengths of light,
most commonly near infrared wavelengths between about 1,000 nm to
about 2,500 nm. It should be understood that, as used herein, the
term "light" may refer to one or more of infrared, visible,
ultraviolet, or even X-ray electromagnetic radiation, and may also
include any wavelength within the infrared, visible, ultraviolet,
or X-ray spectra. Spectroscopic measurements of other blood or
tissue constituents besides blood oxygen hemoglobin can benefit
from the use of LEN devices. For example, measurements related to
constituents such as carboxyhemoglobin, methemoglobin, total
hemoglobin, bilirubin, glucose, pH, CO.sub.2, and so forth.
[0030] Different wavelengths of light may be emitted by the LEN
devices 30A and 30B based on physical aspects of the
nanostructures. For example, the diameter of an LEN may determine
the wavelength of light the LEN emits. Accordingly, wavelengths of
emitted light can be controlled by growing the nanostructures
(e.g., nanotubes) to have specified diameters. In accordance with
present embodiments, various nanostructures may be grown with
different diameters to facilitate multi-wavelength light emissions
from a single point. For example, as illustrated in FIG. 2, it is
believed that the pair of LEN devices 30A and 30B may be formed
such that they can be aligned to emit two different wavelengths of
light from essentially a single point. In such an embodiment, the
diameters of the corresponding nanostructures should be designed to
allow wavelengths from the outer LEN device 30B to pass through the
inner LEN device 30A. In other words, the diameter of the inner LEN
device 30A should accommodate the wavelength of light emitted from
the outer LEN device 30B. This may be achieved, for example, by
forming the inner LEN device 30A with a larger diameter than the
outer LEN device 30B and aligning the LEN devices 30A and 30B along
their axes, as illustrated in FIG. 3, which is a magnified view of
the LEN devices 30A and 30B in FIG. 2. As set forth above, this may
facilitate establishment of equal or substantially equal optical
pathways for both wavelengths of light produced by the LEN devices
30A and 30B.
[0031] In the embodiment illustrated by FIG. 2, the two LEN devices
30A and 30B are aligned to emit light from essentially a single
point. Use of the term single point indicates that the physical
separation between the multiple wavelength sources is sufficiently
small to have little or no impact on the desired measurement due to
geometrical effects. In other embodiments, the LEN devices 30A and
30B may be disposed horizontally adjacent to one another such that
light emissions are substantially from the same location, as
illustrated in FIG. 4. Further, in some embodiments, a large number
of LEN devices designed to emit one or more wavelengths may be
grouped together. The LEN devices may be grouped together (e.g.,
according to diameter) in arrays and/or stacked atop one another,
as illustrated in FIG. 5, which includes a first group of devices
(e.g., transistors) 42 configured to emit light at a first
wavelength and a second group of devices 44 configured to emit
light at a second wavelength. FIG. 6 is a cross-sectional view of
an array 46 formed by the devices 42 and 44 in FIG. 5. It should be
noted that while the array 46 illustrated in FIG. 6 is generally in
the shape of a parallelogram, in other embodiments the array 46 may
be shaped like an oval, octagon, triangle, and so forth. In some
embodiments, the array 46 may be formed such that it improves
certain functions of the sensor 14. For example, the array 46 may
be shaped to correspond to sensor attachment points (e.g., fingers,
ears, toes) to facilitate transmission of light into the attachment
points.
[0032] In another embodiment, the first and second groups of LEN
devices 42 and 44 may be intermingled and disposed horizontally
adjacent to one another in an array to simulate emission from a
single point, as illustrated in FIG. 7, wherein the LEN devices may
be separated by less than 500 microns or less than 10 microns in
some embodiments. For example, by intermingling a number of LEN
devices that emit a certain wavelength of light with an equal or
approximately equal number of LEN devices that emit a different
wavelength of light, embodiments of the present invention may
create the effect of two different light wavelength emissions from
a single point. FIG. 8 is a cross-sectional view of an array 48
formed by the devices 42 and 44 in FIG. 7. It should be noted that
while the array 48 illustrated in FIG. 8 is generally in the shape
of an oval, in other embodiments the array 48 may be shaped like a
parallelogram, a circle, octagon, triangle, and so forth. In some
embodiments, the array 48 may be formed such that it improves
certain functions of the sensor 14. For example, the array 48 may
be shaped to correspond to sensor attachment points (e.g., fingers,
ears, toes) to facilitate transmission of light into the attachment
points.
[0033] FIG. 9 is a block diagram of a polychromatic point emitting
light source using LEN structures in accordance with an exemplary
embodiment of the present invention. The light source is generally
designated by reference number 100. In the illustrated embodiment,
the light source 100 includes multiple LEN structures 112
(LEN.sub.T through LEN.sub.n) of different wavelengths that are
integrated onto an electrode array 114 with multiple (n) electrodes
116 and a common return 118. An energizing circuit 120 of the light
source 100 is symbolically represented as a common source of
electricity 122 (V) and multiple switches 124 (S.sub.1 through
S.sub.n). The switches 124 may be implemented using solid state
elements such as transistors, which can be integrated onto the same
substrate. The switches 124 may be opened and closed in various
sequences or in unison to provide desired emission characteristics,
e.g., time or frequency multiplexed sequences of two or more
wavelengths.
[0034] Using energizing circuitry or wiring (e.g., energizing
circuit 120) of the light source 100, multiple wavelengths can be
simultaneously emitted, individually emitted, or emitted in varying
combinations from the various LEN structures 112 over time or
frequency as called for by a specific application. For example, the
multiple LEN structures 112 of different wavelengths could be
individually addressed in sequential order to "sweep" the emission
wavelength from one extreme to another (e.g., from 600 nm to 2000
nm). In other words, the switches 124 could be sequentially opened
and closed in order based on the value of the wavelength emitted by
each of the corresponding LEN structures 112. In another example,
the LEN structures 112 may be pseudo-randomly multiplexed by the
energizing circuit according to a sequence to enhance the ratio or
relationship of accurate electrical signals to unwanted signals
(e.g., static disturbances) creating noise. In yet another
embodiment, the light source 100 may be configured to emit groups
of wavelengths to achieve a desired color (as seen by the human
eye) using a one or two-dimensional array of such emitters (e.g.,
the arrays of FIGS. 6 and 8) configured to create a flat-panel type
displayed image, as achieved using liquid crystal displays (LCDs)
or plasma cells.
[0035] In one embodiment, the multiple LEN structures 112 may be
employed as a full spectrum or semi-full spectrum spectrometer. In
other words, the multiple LEN structures 112 may emit a range of
light wavelengths in a full spectrum or semi-full spectrum (e.g.,
600 nm to 700 nm) to facilitate detection of various constituents
in material (e.g., blood, water, cerebral-spinal fluid) being
monitored. For example, emitting a range of light wavelengths in a
full spectrum may facilitate detection of a large number of
different types of constituents, each of which may absorb a
different light wavelength. By emitting light wavelengths over a
range, information may be obtained at and around certain critical
wavelengths that have been found to correspond to particular
constituents of interest (e.g., lipids, sterols, hemoglobin). Thus,
detection of the presence, absence, and/or amount of such
constituents of interest may be facilitated. For example, data
obtained from emitting a range of wavelengths may be utilized to
establish graphical data (e.g., curves), which can be integrated to
determine certain characteristics of the material being monitored.
In a specific example, the area under a curve around a particular
critical wavelength may be correlated to empirical data that
suggests how much of a particular constituent is present in the
monitored material.
[0036] Embodiments of the present invention may facilitate a range
of light emissions in a full spectrum or semi-full spectrum because
the LEN structures 112 are small compared to LEDs, which allows for
emission from what is essentially a single emission point. Further,
the LEN structures 112 may prevent heating effects typically
associated with light emissions over a range of a full or semi-full
spectrum. It should be noted that a semi-full spectrum may be
defined to correspond to a particular material being analyzed. For
example, most constituents of interest in blood may be detected in
a range from 600 nm to 700 nm. Limiting light emissions to a
semi-full spectrum may be beneficial in that it may limit the
number of LEN structures 112.
[0037] FIG. 10 is a block diagram of an emitter 200 coupled with
optical fiber 202 in accordance with an exemplary embodiment of the
present invention. It is often desirable to utilize fiber optics in
spectrophotometry. Fiber optics allow sensor elements (e.g.,
detectors and emitters) to be located remotely from the patient.
For example, fiber optics may be used in pulse oximetry when
measuring blood flow characteristics in a patient during magnetic
resonance imaging (MRI) procedures to avoid the use of certain
materials (e.g., metal) in the MRI machine. Small light emitting
devices, such as the LEN devices described herein, facilitate
efficient transmission of light with multiple wavelengths from the
emitter 200 into optical fiber 202, that is comprised of a cladding
203 and core 204. Because the dimensions of the LEN devices 30A and
30B are small compared to traditional light emitting devices, such
as LEDs, a multi-wavelength source area can be provided that is
smaller than the diameter of the optical fiber core 204. Thus, the
multiple wavelengths of light can be readily lensed to match the
fiber diameter and numerical aperture. In other words, light can be
more efficiently directed into fiber optics utilizing LEN devices
30A and 30B in accordance with present embodiments. As illustrated
in FIG. 11 and as understood by those skilled in the art, the use
of lensing components, such as lens 210, can further improve
coupling efficiency, as enabled by the small size of the
source.
[0038] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and will be described in
detail herein. However, it should be understood that the invention
is not intended to be limited to the particular forms disclosed.
Rather, the invention is to cover all modifications, equivalents
and alternatives falling within the spirit and scope of the
invention as defined by the following appended claims.
* * * * *