U.S. patent application number 15/788909 was filed with the patent office on 2018-03-01 for gas measuring apparatus.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Hiroshi HASEGAWA, Tsutomu KAKUNO, Miyuki KUSABA, Akira MAEKAWA, Yasutomo SHIOMI, Shigeyuki TAKAGI.
Application Number | 20180059012 15/788909 |
Document ID | / |
Family ID | 55580711 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180059012 |
Kind Code |
A1 |
MAEKAWA; Akira ; et
al. |
March 1, 2018 |
GAS MEASURING APPARATUS
Abstract
A gas measuring apparatus includes a cell portion, a light
source portion, a detection portion, and a control portion. The
cell portion includes a space into which a sample gas containing
breath containing a first isotope of carbon dioxide and a second
isotope of carbon dioxide is introduced. The light source portion
changes a wavelength of the light in a band of 4.345 .mu.m or more
and 4.384 .mu.m or less. The detection portion performs an
operation including first detection of an intensity of the light
passing through the space and second detection of an intensity of
the light passing through the space into which the sample gas is
not introduced. The control portion calculates a ratio of an amount
of the second isotope to an amount of the first isotope based on a
result of the first detection and a result of the second
detection.
Inventors: |
MAEKAWA; Akira; (Kamakura,
JP) ; KUSABA; Miyuki; (Meguro, JP) ; TAKAGI;
Shigeyuki; (Fujisawa, JP) ; HASEGAWA; Hiroshi;
(Yokosuka, JP) ; KAKUNO; Tsutomu; (Fujisawa,
JP) ; SHIOMI; Yasutomo; (Koza, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Minato-ku |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Minato-ku
JP
|
Family ID: |
55580711 |
Appl. No.: |
15/788909 |
Filed: |
October 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15260651 |
Sep 9, 2016 |
9829432 |
|
|
15788909 |
|
|
|
|
PCT/JP2015/057700 |
Mar 16, 2015 |
|
|
|
15260651 |
|
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 2021/399 20130101;
A61B 5/00 20130101; H01S 5/343 20130101; G01N 33/004 20130101; G01N
21/3504 20130101; G01N 21/39 20130101; A61B 5/082 20130101; H01S
5/22 20130101; H01S 5/125 20130101; G01N 21/05 20130101; H01S 5/12
20130101; G01N 2201/12 20130101; H01S 5/34346 20130101; A61B 5/0059
20130101; H01S 5/34313 20130101; G01N 33/497 20130101; H01S 5/3401
20130101; H01S 5/3402 20130101 |
International
Class: |
G01N 21/3504 20060101
G01N021/3504; A61B 5/08 20060101 A61B005/08; G01N 21/05 20060101
G01N021/05; A61B 5/00 20060101 A61B005/00; H01S 5/343 20060101
H01S005/343; H01S 5/34 20060101 H01S005/34; G01N 33/497 20060101
G01N033/497; H01S 5/125 20060101 H01S005/125 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2014 |
JP |
2014-192322 |
Claims
1. A method for measuring a sampling gas containing a first isotope
of carbon dioxide and a second isotope of carbon dioxide,
comprising: emitting a light operable to sweep a wavenumber within
a range of 1 cm.sup.-1 toward the sampling gas, the range including
a first wavenumber corresponding to one of absorption peak of the
first isotope, a second wavenumber corresponding to one of
absorption peak of the second isotope and a third wavenumber
corresponding to absorption peak of the first isotope or the second
isotope, absorption of the first isotope at the second wavenumber
not corresponding to absorption peak and being lower than
absorption of the second isotope, the wavenumber being not less
than 2281 cm.sup.-1 and not more than 2301 cm.sup.-1; measuring a
first intensity of the light passing through the sampling gas
within the range; and calculating a ratio of an amount of the
second isotope to an amount of the first isotope based on the first
intensity.
2. The method according to claim 1, wherein a semiconductor
light-emitting element emits the light by energy relaxation of
electrons in subbands in a plurality of quantum wells.
3. The method according to claim 1, wherein the measuring further
includes measuring a second intensity of the light passing through
a reference gas within the range, and the calculating is performed
based on the first intensity and the second intensity.
4. The method according to claim 1, wherein the ratio is calculated
a plurality of times.
5. The method according to claim 3, wherein the ratio is calculated
a plurality of times.
6. The method according to claim 1, wherein the first isotope is
.sup.12CO.sub.2, and the second isotope is .sup.13CO.sub.2.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of and claims the benefit of
priority under 35 U.S.C. .sctn.120 from U.S. application Ser. No.
15/260,651 filed Sep. 9, 2016, which is a continuation of
International Application PCT/JP2015/057700 filed Mar. 16, 2015,
and claims the benefit of priority from Japanese Application No.
2014-192322 filed Sep. 22, 2014, the entire contents of each of
which are incorporated herein by reference.
FIELD
[0002] This invention relates to a gas measuring apparatus.
BACKGROUND
[0003] The gas measuring apparatus includes a breath diagnostic
apparatus and so on. In a breath diagnostic apparatus, a breath gas
is measured. Based on the result of this measurement, prevention
and early detection of diseases are facilitated. In the breath
diagnostic apparatus, it has been desired to obtain high-precision
measurement results.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic view illustrating a breath diagnostic
apparatus according to a first embodiment;
[0005] FIGS. 2A to 2C are schematic views illustrating the breath
diagnostic apparatus according to the first embodiment;
[0006] FIGS. 3A and 3B are graphs illustrating the characteristics
of carbon dioxide;
[0007] FIGS. 4A and 4B are graphs illustrating the characteristics
of carbon dioxide;
[0008] FIGS. 5A and 5B are graphs illustrating the characteristics
of carbon dioxide;
[0009] FIG. 6 is a schematic view illustrating the breath
diagnostic apparatus according to the first embodiment;
[0010] FIG. 7 is a schematic view illustrating the operation of the
breath diagnostic apparatus according to the first embodiment;
[0011] FIG. 8 is a schematic view illustrating an operation of a
breath diagnostic apparatus according to a second embodiment;
and
[0012] FIGS. 9A to 9C are schematic views illustrating a part of
the breath diagnostic apparatus according to the embodiment.
DETAILED DESCRIPTION
[0013] In general, according to one embodiment, a gas measuring
apparatus includes a cell portion, a light source portion, a
detection portion, and a control portion. The cell portion includes
a space into which a sample gas containing a first isotope of
carbon dioxide and a second isotope of carbon dioxide is
introduced. The light source portion allows light to enter the
space and changes a wavelength of the light in a wavelength band of
4.345 .mu.m or more and 4.384 .mu.m or less. The wavelength band
includes at least a first wavelength corresponding to one of
absorption peak of the first isotope and a second wavelength
corresponding to one of absorption peak of the second isotope. The
detection portion performs an operation including first detection
of an intensity of the light passing through the space into which
the sample gas is introduced and second detection of an intensity
of the light passing through the space into which the sample gas is
not introduced. The control portion calculates a ratio of an amount
of the second isotope to an amount of the first isotope in the
sample gas based on a result of the first detection and a result of
the second detection.
[0014] Embodiments of the invention will be described hereinafter
with reference to the accompanying drawings.
[0015] The figures are schematic or conceptual, and a relationship
between the thickness and width in each component, a ratio of size
between components may not necessarily be same as the actual
configuration. Furthermore, even when representing the same
component, the dimension and ratio may be represented differently
in different figures. In the specification and the figures of the
application, the same reference numbers are applied to the same
elements already described in relation to previous figures, and
detailed description will not be repeated as appropriate.
First Embodiment
[0016] FIG. 1 is a schematic view illustrating a breath diagnostic
apparatus according to a first embodiment.
[0017] As shown in FIG. 1, a breath diagnostic apparatus 110
according to the embodiment includes a cell portion 20, a light
source portion 30, a detection portion 40, and a control portion
45.
[0018] Into the cell portion 20, a sample gas 50 is introduced.
That is, into a space 23s provided in the cell portion 20, the
sample gas 50a is introduced. The sample gas 50 contains breath
50a. The breath 50a is, for example, breath of an animal including
a human being. In the breath 50a, first carbon dioxide 51 (first
isotope) containing .sup.12C and second carbon dioxide 52 (second
isotope) containing .sup.13C. The first carbon dioxide 51 is
.sup.12CO.sub.2. The second carbon dioxide 52 is .sup.13CO.sub.2.
In these carbon dioxide species, an isotope of oxygen may be
contained.
[0019] As will be described later, diagnosis can be made by
obtaining a relative ratio of .sup.13CO.sub.2 to .sup.12CO.sub.2
contained in the breath 50a. For example, a person takes a labeled
compound with enriched .sup.13C (.sup.13C-labeled compound). The
breath 50a at this time is evaluated.
[0020] As will be described later, the light absorption of the
first carbon dioxide 51 has a first peak at a first wavelength. The
light absorption of the second carbon dioxide 52 has a second peak
at a second wavelength. By using light with wavelengths
corresponding to the wavelengths of these two peaks, the amounts (a
relative ratio) of the first carbon dioxide 51 and the second
carbon dioxide 52 can be detected.
[0021] The light source portion 30 allows light (measurement light
30L) to enter the space 23s. The light source portion 30 changes
the wavelength of the light (measurement light 30L). The wavelength
is changed in a specific wavelength band. For example, the
wavelength of the light is changed in a wavelength band of 4.34
.mu.m or more and 4.39 .mu.m or less. This wavelength band includes
the first wavelength of the first peak of the light absorption of
the first carbon dioxide 51 and the second wavelength of the second
peak of the light absorption of the second carbon dioxide 52.
[0022] In this example, the light source portion 30 includes a
light-emitting portion 30a and a driving portion 30b. The driving
portion 30b is electrically connected to the light-emitting portion
30a. The driving portion 30b supplies electric power for light
emission to the light-emitting portion 30a. As will be described
later, as the light-emitting portion 30a, for example, a
distributed feedback (DFB) quantum cascade laser is used. As the
light-emitting portion 30a, an interband cascade laser (ICL) may be
used.
[0023] In the light source portion 30, the change in the wavelength
is performed in a short time (for example, about 100 ms or less).
For example, a center value of the wavelength of the measurement
light 30L is 4.34 .mu.m or more and 4.39 .mu.m or less. The
wavenumber is 2278 cm.sup.-1 or more and 2304 cm.sup.-1 or less.
The width of the change in the wavenumber in the wavelength band WL
is, for example, about 1 cm.sup.-1.
[0024] The measurement light 30L passes through the space 23s of
the cell portion 20. A part of the measurement light 30L is
absorbed by substances (the first carbon dioxide 51 and the second
carbon dioxide 52) contained in the sample gas 50. Components with
a wavelength specific to these substances in the measurement light
30L are absorbed. The degree of absorption depends on the
concentration of the substance.
[0025] The detection portion 40 detects the measurement light 30L
passing through the space 23s, for example, in a state where the
sample gas 50 is introduced into the space 23s. The detection
portion 40 detects the intensity of light (measurement light 30L)
passing through the space 23s. As the detection portion 40, an
element having sensitivity to an infrared region is used. As the
detection portion 40, for example, a thermopile or a semiconductor
sensor element (for example, an MCT (HgCdTe)), or the like is used.
In the embodiment, the detection portion 40 is arbitrary.
[0026] The detection portion 40 detects not only the intensity of
light when the sample gas 50 is introduced into the space 23s, but
also the intensity of light when the sample gas 50 is not
introduced into the space 23s. The latter is used as a reference
value in the detection. That is, the detection portion performs
first detection of the intensity of light (measurement light 30L)
passing through the space 23s into which the sample gas 50 is
introduced, and second detection of the intensity of light
(measurement light 30L) passing through the space 23s into which
the sample gas 50 is not introduced.
[0027] The control portion 45 calculates the ratio of the amount of
the second carbon dioxide 52 (second isotope) to the amount of the
first carbon dioxide 51 (first isotope) in the sample gas based on
the result of the first detection and the result of the second
detection.
[0028] In the embodiment, a high-precision breath diagnosis can be
made.
[0029] In the embodiment, the above-mentioned detection may be
performed a plurality of times. That is, the detection portion 40
performs the operation including the first detection of the
intensity of the light (measurement light 30L) passing through the
space 23s into which the sample gas 50 is introduced and the second
detection of the intensity of the light (measurement light 30L)
passing through the space 23s into which the sample gas 50 is not
introduced a plurality of times. At this time, the control portion
45 calculates the ratio of the amount of the second carbon dioxide
52 to the amount of the first carbon dioxide 51 in the sample gas
50 based on the results obtained by the above-mentioned operation
performed a plurality of times. That is, the ratio of the amount of
the second carbon dioxide 52 to the amount of the first carbon
dioxide 51 is calculated based on a plurality of first detection
results obtained by the above-mentioned operation performed a
plurality of times and a plurality of second detection results
obtained by the above-mentioned operation performed a plurality of
times.
[0030] By doing this, a higher-precision breath diagnosis can be
made.
[0031] Further, in carbon dioxide containing isotopes of carbon,
the ratio of .sup.13CO.sub.2 to .sup.12CO.sub.2 is about 1% or so.
Then, it is not easy to measure the relative amount of
.sup.13CO.sub.2 in such a minute amount with high precision. In
view of this, a special configuration capable of measuring the
relative amount of .sup.13CO.sub.2 with high precision has been
desired.
[0032] For example, there is a method in which collected breath is
once stored in a given container or the like, and the breath stored
in the container is analyzed. In this method, breath exhaled by a
person or the like is once stored in a container, and therefore,
the measurement result may sometimes be affected by, for example, a
variation in the container or the like. Due to this, it is
difficult to sufficiently increase the stability of detection.
[0033] On the other hand, in the embodiment, breath exhaled by a
person or the like is introduced into the space 23s of the cell
portion 20 without being stored in a container or the like.
Therefore, it is not affected by a variation in another member such
as a container, and thus, the stability of the detection result is
high.
[0034] Further, the intensity of absorption of .sup.13CO.sub.2 and
the intensity of absorption of .sup.12CO.sub.2 are largely
different. Therefore, there is a reference example in which a cell
for detecting .sup.13CO.sub.2 and a cell for detecting
.sup.12CO.sub.2 are provided separately. However, in this method,
detection is performed using different cells, and therefore,
different samples are evaluated. Due to this, the stability of
detection cannot be sufficiently increased. Further, in the case
where a plurality of cells is provided, a detector is provided for
each cell. In the plurality of detectors, the surrounding
environment (for example, temperature) or temperature drift has a
large effect. For example, the drift of sensitivity (and output)
varies among the plurality of detectors, and the precision of the
measurement results is decreased. In particular, the measurement
light 30L is located in the infrared region, and therefore is
largely affected by a temperature.
[0035] On the other hand, in the embodiment, the absorption
intensities of both .sup.13CO.sub.2 and .sup.12CO.sub.2 are
detected in one space 23s (one cell portion 20). The absorption
intensities of both are detected by one detector (detection portion
40). Then, in the light source portion 30, by changing the
wavelength in a specific wavelength band, the absorption
intensities of both .sup.13CO.sub.2 and .sup.12CO.sub.2 are
detected at substantially the same timing. Therefore, the stability
of the detection results is high. In the embodiment, the effect of
the surrounding environment or temperature drift can be suppressed,
and high precision is obtained.
[0036] Further, in the embodiment, the change in the wavelength can
be performed in a relatively short time. Due to this, detection is
performed a plurality of times for the same sample. By averaging
(integrating) the results of detection performed a plurality of
times, high-precision detection can be performed.
[0037] In the embodiment, by using one cell portion 20, the
absorption intensities of both .sup.13CO.sub.2 and .sup.12CO.sub.2
are detected. Therefore, the apparatus can be miniaturized as
compared with the reference example using a plurality of cells.
[0038] FIGS. 2A to 2C are schematic views illustrating the breath
diagnostic apparatus according to the first embodiment.
[0039] FIG. 2A shows an example of a change in a current Is that
controls the measurement light 30L emitted from the light source
portion 30. The current Is may be a current supplied to the
light-emitting portion 30a. FIG. 2B shows an example of a change in
the wavelength of the measurement light 30L emitted from the light
source portion 30. FIG. 2C shows an example of a change in a signal
detected by the detection portion 40. In these drawings, the
horizontal axis represents a time t. The vertical axis in FIG. 2A
represents a current Is. The vertical axis in FIG. 2B represents a
wavelength .lamda.. The vertical axis in FIG. 2C represents a
signal intensity Sg.
[0040] As shown in these drawings, a reference data measurement
period Pr1 and a sample data measurement period Ps1 are provided.
In the reference data measurement period Pr1, the sample gas 50 is
not introduced into the space 23s. In the sample data measurement
period Ps1, the sample gas 50 is introduced into the space 23s.
[0041] In the reference data measurement period Pr1, the wavelength
of the measurement light 30L emitted from the light source portion
30 is changed. This change is repeatedly performed a plurality of
times. The intensity of this measurement light 30L is detected by
the detection portion 40. In the detection portion 40, the signal
intensity Sg is detected a plurality of times.
[0042] In the sample data measurement period Ps1, the sample gas 50
is introduced into the space 23s, and a part of the measurement
light 30L is absorbed by the first carbon dioxide 51 and the second
carbon dioxide 52. For example, at a first wavelength .lamda.1
corresponding to an absorption peak of the first carbon dioxide 51,
the signal intensity Sg decreases. For example, at a second
wavelength .lamda.2 corresponding to an absorption peak of the
second carbon dioxide 52, the signal intensity Sg decreases.
[0043] By comparing the signal intensity Sg in the reference data
measurement period Pr1 (reference intensity) with the signal
intensity Sg in the sample data measurement period Ps1 (sample
intensity), a value corresponding to the amount of the first carbon
dioxide 51 and a value corresponding to the amount of the second
carbon dioxide 52 are obtained. For example, a ratio of the sample
intensity to the reference intensity is obtained. For example, a
difference between the reference intensity and the sample intensity
is obtained. By doing this, a value corresponding to the amount of
the first carbon dioxide 51 and a value corresponding to the amount
of the second carbon dioxide 52 are obtained. A ratio of the amount
of the second carbon dioxide 52 to the amount of the first carbon
dioxide 51 is obtained.
[0044] In at least one reference data measurement period Pr1 and at
least one sample data measurement period Ps1, one measurement
(calculation of the ratio of the amount of the second carbon
dioxide 52 to the amount of the first carbon dioxide 51) is
performed. That is, one measurement period Pm1 includes at least
one reference data measurement period Pr1 and at least one sample
data measurement period Ps1.
[0045] FIGS. 3A and 3B are graphs illustrating the characteristics
of carbon dioxide.
[0046] FIGS. 4A and 4B are graphs illustrating the characteristics
of carbon dioxide.
[0047] FIG. 3A shows an absorption spectrum of .sup.12CO.sub.2, and
FIG. 3B shows an absorption spectrum of .sup.13CO.sub.2. In these
drawings, the optical path lengths are the same. FIG. 4A shows the
absorption spectra of .sup.12CO.sub.2 and .sup.13CO.sub.2 by
expanding the wavelength. FIG. 4B shows the absorption spectra by
expanding the wavenumber. The horizontal axis of each of FIGS. 3A,
3B, and 4A represents the wavelength .lamda. (.mu.m). The
horizontal axis of FIG. 4B represents the wavenumber .kappa.
(cm.sup.-1). The vertical axis represents the absorption ratio Ab
(%).
[0048] As shown in FIGS. 3A, 3B, 4A, and 4B, each of
.sup.12CO.sub.2 and .sup.13CO.sub.2 has an intrinsic absorption. As
shown in FIG. 4B, for example, the first wavelength .lamda.1
(wavenumber) corresponding to one absorption peak of
.sup.12CO.sub.2 is, for example, 2296.06 cm.sup.-1. For example,
the second wavelength .lamda.2 (wavenumber) corresponding to one
absorption peak of .sup.13CO.sub.2 is, for example, 2295.85
cm.sup.-1. Further, as a third wavelength .lamda.3 (wavenumber)
corresponding to another absorption peak of .sup.12CO.sub.2, a peak
at 2295.50 cm.sup.-1 is present.
[0049] For example, the wavelength of the measurement light 30L
emitted from the light source portion 30 is changed (swept) in a
wavelength band WL. The wavelength band WL includes the first
wavelength .lamda.1 and the second wavelength .lamda.2. The
wavelength band WL preferably further includes at least either of
another absorption peak of .sup.12CO.sub.2 and another absorption
peak of .sup.13CO.sub.2.
[0050] The range of the wavelength band WL (the range of the
wavenumber band) is, for example, about 1 cm.sup.-1.
[0051] The wavelength band WL is determined so as to obtain the
absorption intensity of .sup.13CO.sub.2 relatively close to the
absorption intensity of .sup.12CO.sub.2. According to this, it is
possible to detect the amounts of these carbon dioxide species with
high precision.
[0052] As described above, the width of the change in the
wavelength (wavelength band WL) emitted from the light source
portion 30 is about 1 cm.sup.-1. The number of absorption peaks of
carbon dioxide in the range of the wavelength band WL is more
preferably 3 or more. That is, the wavelength band WL includes the
first wavelength of the first peak of the light absorption of the
first carbon dioxide, the second wavelength of the second peak of
the light absorption of the second carbon dioxide, and the third
wavelength of the third peak of the light absorption of the first
carbon dioxide or the light absorption of the second carbon
dioxide. The third wavelength is, for example, between the first
wavelength and the second wavelength. By performing curve fitting
using the measurement results of three or more absorption peaks, it
becomes possible to perform detection with higher precision.
[0053] In the range of the wavelength band WL, a plurality of
absorption peaks of .sup.13CO.sub.2 may be present. By calculating
the concentration of .sup.13CO.sub.2 based on the change in the
signal (intensity Sg) at the wavelength of a plurality of peaks, it
becomes possible to perform detection with higher precision.
[0054] For example, the wavelength band WL includes 2296.06
cm.sup.-1 corresponding to an absorption peak of .sup.12CO.sub.2
and 2295.85 cm.sup.-1 corresponding to an absorption peak of
.sup.13CO.sub.2. The wavelength band WL further includes 2295.50
cm.sup.-1 corresponding to an absorption peak of
.sup.12CO.sub.2.
[0055] The existing ratio of .sup.12CO.sub.2 is about 98%. On the
other hand, the existing ratio of .sup.13CO.sub.2 is about 1%. In
the embodiment, it is preferred that the absorption ratio of the
absorption peak at the existing ratio of .sup.13CO.sub.2 is
substantially the same as the absorption ratio of the absorption
peak at the existing ratio of .sup.12CO.sub.2. According to this,
it becomes easy to detect the absorption of these isotopes by one
light source portion 30 and one detection portion 40.
[0056] In the embodiment, for example, the absorption of
.sup.12CO.sub.2 at the wavelength of the absorption peak of
.sup.13CO.sub.2 corresponds to a non-peak. At this time, it is
preferred that the absorption ratio of the absorption peak of
.sup.13CO.sub.2 at this wavelength is higher than the absorption
ratio of .sup.12CO.sub.2 (the absorption ratio at a non-peak of
.sup.12CO.sub.2) at this wavelength.
[0057] On the other hand, the range of the wavenumber in the
wavelength band WL swept when using a DFB quantum cascade laser is
about 1 cm.sup.-1. For example, in the range of this wavelength
band WL, an absorption peak of .sup.12CO.sub.2 and an absorption
peak of .sup.13CO.sub.2 are present. The measurement is performed
using light having the wavelength band WL. According to this, it
becomes possible to perform measurement with high speed and high
sensitivity using a DFB quantum cascade laser.
[0058] Further, it is preferred that in the range of the wavenumber
(about 1 cm.sup.-1) in the wavelength band WL, the following three
absorption peaks: one absorption peak of .sup.12CO.sub.2, one
absorption peak of .sup.13CO.sub.2, and one absorption peak of
either of .sup.12CO.sub.2 and .sup.13CO.sub.2 are present.
According to this, it becomes possible to perform high-precision
detection by curve fitting.
[0059] That is, for example, when the isotope ratio is obtained, an
absorption spectrum obtained by measurement and a spectrum (for
example, a theoretical spectrum) to serve as a standard are fitted.
For example, as previously described with respect to FIGS. 2(a) to
2(c), a wavelength (that is, a wavenumber) is determined based on a
time t. For example, first, a time-absorption coefficient
characteristic curve obtained by measurement is converted to a
wavenumber-absorption coefficient characteristic curve. Then, this
characteristic obtained by conversion is fitted to a characteristic
curve of a spectrum (for example, a theoretical spectrum) to serve
as a standard.
[0060] At this time, the time-current characteristic illustrated in
FIG. 2(a) is known (a preset sawtooth wave), however, the
current-wavelength characteristic depends on the quantum cascade
laser characteristic. According to the study made by the inventor,
this current-wavelength characteristic was found to be precise when
it was assumed to be a characteristic of not a linear, but
quadratic function. Therefore, the time-wavenumber characteristic
is a quadratic function.
[0061] For example, three or more absorption peaks are obtained,
and based on the wavenumbers corresponding to the times of the
respective peaks, coefficients (three coefficients) of a
time-wavenumber conversion formula are obtained. By doing this, the
fitting precision can be improved.
[0062] In the embodiment, in the range of the wavenumber (about 1
cm.sup.-1) in the wavelength band WL, three or more absorption
peaks are present. Due to this, it becomes possible to perform
high-precision detection by curve fitting.
[0063] That is, in the embodiment, the wavenumber in the wavelength
band WL is set to 2281 cm.sup.-1 or more and 2301 cm.sup.-1 or
less. That is, the wavelength in the wavelength band WL is set to
4.345 .mu.or more and 4.384 .mu.m or less. According to this, the
above-mentioned conditions can be satisfied. FIGS. 5A and 5B are
graphs illustrating the characteristics of carbon dioxide.
[0064] These graphs show absorption spectra of .sup.2CO.sub.2 and
.sup.13CO.sub.2.
[0065] The wavelength band WL is appropriately determined according
to the absorption spectrum of carbon dioxide. It is preferred that
in the wavelength band WL, the intensity of the absorption peak of
.sup.13CO.sub.2 is higher than the intensity of the non-peak of
.sup.12CO.sub.2.
[0066] FIG. 6 is a schematic view illustrating the breath
diagnostic apparatus according to the first embodiment.
[0067] As shown in FIG. 6, in the breath diagnostic apparatus 110,
a housing 10w is provided. In the housing 10w, the cell portion 20,
the light source portion 30, the detection portion 40, and the
control portion 45 are provided. The control portion 45 may be
provided outside the housing 10w.
[0068] A gas introduction portion 60i is connected to the housing
10w. The gas introduction portion 60i is, for example, a mouth
piece. As the gas introduction portion 60i, a cannula tube or the
like may be used. As the gas introduction portion 60i, a mask may
be used.
[0069] In the housing 10w, a first pipe 61p is provided. One end of
the first pipe 61p is connected to the gas introduction portion
60i. The other end of the first pipe 61p is connected to an
external environment. In this example, on an inlet side of the
first pipe 61p, a flow rate meter 61fm is provided. The flow rate
meter 61fm is connected to the gas introduction portion 60i. On an
outlet side of the first pipe 61p, a one-way valve 61dv is
provided. A part of the sample gas 50 introduced from the gas
introduction portion 60i is released to the external environment
through the one-way valve 61dv.
[0070] To the first pipe 61p, a second pipe 62p is connected. One
end of the second pipe 62p is connected to the first pipe 61p. The
other end of the second pipe 62p is connected to the cell portion
20. In this example, on the route of the second pipe 62p, a
dehumidification portion 62f is provided. As the dehumidification
portion 62f, for example, a filter or the like which adsorbs water
is used. Between the first pipe 61p and the cell portion 20, a
first solenoid valve V1 is provided. In this example, between the
first solenoid valve V1 and the dehumidification portion 62f, a
needle valve 62nv is provided. In this example, between the first
solenoid valve V1 and the cell portion 20, a spiral tube 62s is
provided. The spiral tube 62s may be omitted. The needle valve 62nv
is provided as needed and may be omitted.
[0071] In the cell portion 20, for example, a heater 28 may be
provided. In the cell portion 20, a pressure meter 27 may be
provided.
[0072] To a portion between the first solenoid valve V1 and the
spiral tube 62s, one end of a third pipe 63p is connected. The
other end of the third pipe 63p is connected to a one-way valve
63dv. Through the third pipe 63p, air can be introduced into the
cell portion 20 from the external environment. In the third pipe
63p, a third solenoid valve V3 is provided. Between the third
solenoid valve V3 and the one-way valve 63dv, a CO.sub.2 filter is
provided. A CO.sub.2 filter 63f reduces the amount of carbon
dioxide in the air introduced from the external environment. In
this example, between the third solenoid valve V3 and the CO.sub.2
filter 63f, a needle valve 63nv is provided. The air is introduced
from the external environment through the one-way valve 63dv. By
passing through the CO.sub.2 filter, CO.sub.2 is removed from the
air. The air from which CO.sub.2 is removed can be introduced into
the cell portion 20 by passing through the third solenoid valve V3.
The needle valve 63nv is provided as needed and may be omitted.
[0073] By the operation of the solenoid valve, the sample gas 50 is
introduced into the cell portion 20 through the second pipe 62p.
Alternatively, the air from which CO.sub.2 is removed is introduced
into the cell portion 20 through third pipe 63p.
[0074] On an outlet side of the cell portion 20, one end of a
fourth pipe 64p is connected. The other end of the fourth pipe 64p
is connected to the external environment (outside the housing 10w).
In this example, a second solenoid valve V2 is provided in the
fourth pipe 64p. Between the second solenoid valve V2 and the
external environment, an exhaust portion 65 (a pump, a fan, or the
like) is provided. In this example, between the exhaust portion 65
and the second solenoid valve V2, a needle valve 64nv is provided.
The needle valve 64nv is provided as needed and may be omitted.
[0075] That is, a part of the sample gas 50 introduced from the gas
introduction portion 60i is introduced into the cell portion 20
through the second pipe 62p. The first carbon dioxide 51 and the
second carbon dioxide 52 in this gas (breath 50a) are detected in
the cell portion 20.
[0076] Another part (a large part) of the sample gas 50 introduced
from the gas introduction portion 60i is released to the external
environment through the first pipe 61p. That is, the amount (flow
rate) of the sample gas 50 flowing through the first pipe 61p is
larger than the amount (flow rate) of the sample gas 50 flowing
through the second pipe 62p. According to this, when the sample gas
50 is collected, a test subject (person) is prevented from feeling
suffocated.
[0077] By using the flow rate meter 61fm, a state of introduction
of the sample gas 50 is detected. Based on this detection result, a
detection operation is performed. That is, the start of
introduction of the sample gas 50 becomes clear, and the precision
of detection is improved.
[0078] By using the needle valve 62nv, the flow rate inside the
second pipe 62p is restricted, and thus, it becomes possible to
stably supply the sample gas 50.
[0079] By bringing the first solenoid valve V1 to an open state,
the sample gas 50 is introduced into the cell portion 20. While
detecting the first carbon dioxide 51 and the second carbon dioxide
52 in the sample gas 50 introduced into the cell portion 20 (that
is, during the sample data measurement period Ps1), the first
solenoid valve V1 and the second solenoid valve V2 are brought to a
closed state. By doing this, the state of the gas in the cell
portion 20 is stabilized, and the operation of the detection is
enhanced. In the sample data measurement period Ps1, the third
solenoid valve V3 is in a closed state.
[0080] The temperature of the sample gas 50 to be introduced into
the cell portion 20 is preferably constant. By using the spiral
tube 62s and a heater or the like, the temperature of the sample
gas 50 to be introduced into the cell portion 20 can be controlled
with high precision. The temperature is, for example, about
40.degree. C.
[0081] The third solenoid valve V3 is brought to an open state, and
by the operation of the second solenoid valve V2, the needle valve
64nv, and the exhaust portion 65, the gas in the cell portion 20 is
released to the external environment.
[0082] When the detection operation is performed in a state where
the sample gas 50 is not introduced into the cell portion 20 (that
is, during the reference data measurement period Pr1), the first
solenoid valve V1 is brought to a closed state and the third
solenoid valve V3 is brought to an open state. By doing this, air
from the external environment (air from which CO.sub.2 is removed)
is introduced into the cell portion 20.
[0083] FIG. 7 is a schematic view illustrating the operation of the
breath diagnostic apparatus according to the first embodiment.
[0084] As shown in FIG. 7, the measurement is started.
[0085] First, the solenoid valves are operated (Step S1).
Specifically, the second solenoid valve V2 and the third solenoid
valve V3 are brought to an open state and the first solenoid valve
V1 is brought to a closed state.
[0086] After standing by for a specified time, the solenoid valves
are operated (Step S2). Specifically, the first solenoid valve V1,
the second solenoid valve V2, and the third solenoid valve V3 are
brought to a closed state.
[0087] Reference data are measured (Step S3).
[0088] Thereafter, the solenoid valves are operated (Step S4).
Specifically, the first solenoid valve V1 and the second solenoid
valve V2 are brought to an open state, and the third solenoid valve
V3 is brought to a closed state.
[0089] The flow rate meter data are monitored (Step S5).
[0090] It is determined whether or not the output value of the flow
rate meter exceeds a preset value (for example, a previously set
value) (Step S6). In Step S6, when the output value of the flow
rate meter does not exceed the preset value, the operation returns
to Step 5. In Step S6, when the output value of the flow rate meter
exceeds the preset value, the following Step S7 is performed.
[0091] That is, the solenoid valves are operated (Step S7).
Specifically, the first solenoid valve V1, the second solenoid
valve V2, and the third solenoid valve V3 are brought to a closed
state.
[0092] Thereafter, sample data are measured (Step S8). Then, the
data are analyzed (Step S9).
[0093] It is determined whether or not the measurement time exceeds
a preset time (S10). In Step S10, when the measurement time does
not exceed the preset time, the operation returns to Step S1. In
Step S10, when the measurement time exceeds the preset time, the
measurement is finished. The above-mentioned Steps S1 to S9
correspond to one measurement period Pm1.
Second Embodiment
[0094] FIG. 8 is a schematic view illustrating an operation of a
breath diagnostic apparatus according to a second embodiment.
[0095] As shown in FIG. 8, in the embodiment, the operation in the
measurement period Pm1 is performed a plurality of times
continuously. That is, Steps S1 to S9 described with reference to
FIG. 7 are performed a plurality of times.
[0096] In one measurement period Pm1, a ratio of the amount of the
second carbon dioxide 52 to the amount of the first carbon dioxide
51 is calculated. By continuously providing the measurement period
Pm1 a plurality of times and continuously performing the
measurement, a change over time in the amount of the second carbon
dioxide 52 is known. That is, the control portion 45 performs
calculation of the ratio a plurality of times.
[0097] For example, a change over time in the relative ratio of
.sup.13CO.sub.2 to .sup.12CO.sub.2 contained in the breath 50a can
be measured. For example, the gastric clearance and the relative
amount of .sup.13CO.sub.2 have a relation with each other. Based on
the measurement result of the change over time in the relative
ratio of .sup.13CO.sub.2 to .sup.12CO.sub.2, the diagnosis of
gastric clearance can be made.
[0098] When a person takes a labeled compound with enriched
.sup.13C (.sup.13C-labeled compound), diagnosis of health
conditions of the person can be made. For example, a person takes
.sup.13C-urea as the .sup.13C-labeled compound. At this time, when
Helicobacter pylori is present, the relative amount of
.sup.13CO.sub.2 increases. On the other hand, for example, a person
takes .sup.13C-acetate as the .sup.13C-labeled compound. By
evaluating the breath 50a at this time, diagnosis can be made with
respect to gastric clearance. In the case where .sup.13C-acetate is
taken, the gastric clearance and the relative amount of
.sup.13CO.sub.2 have a relation with each other.
[0099] FIGS. 9A to 9B are schematic views illustrating a part of
the breath diagnostic apparatus according to the embodiment.
[0100] FIG. 9A is a schematic perspective view. FIG. 9B is a
cross-sectional view taken along the line A1-A2 of FIG. 9A. FIG. 9C
is a schematic view illustrating the operation of a light source
portion 30.
[0101] In this example, as the light source portion 30, a
semiconductor light-emitting element 30aL is used. As the
semiconductor light-emitting element 30aL, a laser is used. In this
example, a quantum cascade laser is used.
[0102] As shown in FIG. 9A, the semiconductor light-emitting
element 30aL includes a substrate 35, a stacked body 31, a first
electrode 34a, a second electrode 34b, a dielectric layer 32 (first
dielectric layer), and an insulating layer 33 (second dielectric
layer).
[0103] Between the first electrode 34a and the second electrode
34b, the substrate 35 is provided. The substrate 35 includes a
first portion 35a, a second portion 35b, and a third portion 35c.
These portions are disposed in the same one plane. This plane
crosses (for example, is parallel) in a direction from the first
electrode 34a to the second electrode 34b. Between the first
portion 35a and the second portion 35b, the third portion 35c is
disposed.
[0104] Between the third portion 35c and the first electrode 34a,
the stacked body 31 is provided. Between the first portion 35a and
the first electrode 34a, and between the second portion 35b and the
first electrode 34a, the dielectric layer 32 is provided. Between
the dielectric layer 32 and the first electrode 34a, the insulating
layer 33 is provided.
[0105] The stacked body 31 has a stripe shape. The stacked body 31
functions as a ridge waveguard RG. Two end faces of the ridge
waveguide RG become mirror faces. Light 31L emitted in the stacked
body 31 is emitted from the end face (light emission face). The
light 31L is infrared laser light. An optical axis 31Lx of the
light 31L is along an extending direction of the ridge waveguide
RG.
[0106] As shown in FIG. 9B, the stacked body 31 includes, for
example, a first clad layer 31a, a first guide layer 31b, an active
layer 31c, a second guide layer 31d, and a second clad layer 31e.
These layers are arranged in this order along a direction from the
substrate 35 to the first electrode 34a. Each of the refractive
index of the first clad layer 31a and the refractive index of the
second clad layer 31e is lower than each of the refractive index of
the first guide layer 31b, the refractive index of the active layer
31c, and the refractive index of the second guide layer 31d. The
light 31L generated in the active layer 31c is confined in the
stacked body 31. The first guide layer 31b and the first clad layer
31a are sometimes combined and called "clad layer". The second
guide layer 31d and the second clad layer 31e are sometimes
combined and called "clad layer".
[0107] The stacked body 31 has a first side surface 31sa and a
second side surface 31sb perpendicular to the optical axis 31Lx. A
distance 31w (width) between the first side surface 31sa and the
second side surface 31sb is, for example, 5 .mu.m or more and 20
.mu.m or less. According to this, for example, the control in a
horizontal transverse mode is facilitated, and the improvement of
output is facilitated. When the distance 31w is excessively long, a
higher-order mode is likely to occur in a horizontal transverse
mode, and it is difficult to increase the output.
[0108] The refractive index of the dielectric layer 32 is lower
than the refractive index of the active layer 31c. According to
this, the ridge waveguide RG is formed along the optical axis 31Lx
by the dielectric layer 32.
[0109] As shown in FIG. 9C, the active layer 31c has, for example,
a cascade structure. In the cascade structure, for example, a first
region r1 and a second region r2 are alternately stacked. A unit
structure r3 includes the first region r1 and the second region r2.
A plurality of unit structures r3 is provided.
[0110] For example, in the first region r1, a first barrier layer
BL1 and a first quantum well layer WL1 are provided. In the second
region r2, a second barrier layer BL2 is provided. For example, in
another first region r1a, a third barrier layer BL3 and a second
quantum well layer WL2 are provided. In another second region r2a,
a fourth barrier layer BL4 is provided.
[0111] In the first region r1, intersubband optical transition in
the first quantum well layer WL1 occurs. Due to this, for example,
light 31La having a wavelength of, for example, 3 .mu.m or more and
18 .mu.m or less is emitted.
[0112] In the second region r2, energy of a carrier cl (for
example, an electron) injected from the first region r1 can be
relaxed.
[0113] In the quantum well layer (for example, the first quantum
well layer WL1), a well width WLt is, for example, 5 nm or less.
When the well width WLt is narrow in this manner, an energy level
is discrete, and for example, a first subband WLa (a high level Lu)
and a second subband WLb (a low level Ll), or the like occur. The
carrier cl injected from the first barrier layer BL1 is effectively
confined in the first quantum well layer WL1.
[0114] When the transition of the carrier c1 from a high level Lu
to a low level LI occurs, the light 31La corresponding to the
difference in energy (the difference between the high level Lu and
the low level Ll) is emitted. That is, optical transition
occurs.
[0115] Similarly, in the second quantum well layer WL2 in another
first region r1a, light 31Lb is emitted.
[0116] In the embodiment, the quantum well layer may include a
plurality of wells whose wave functions overlap each other. The
high levels Lu of the respective plurality of quantum well layers
may be the same as each other. The low levels LI of the respective
plurality of quantum well layers may be the same as each other.
[0117] For example, intersubband optical transition occurs in
either of a conduction band and a valence band. For example,
recombination of a hole and an electron by p-n junction is not
needed. For example, optical transition occurs by the carrier c1 of
either of a hole and an electron, and light is emitted.
[0118] In the active layer 31c, for example, by a voltage applied
between the first electrode 34a and the second electrode 34b, the
carrier c1 (for example, an electron) is injected into the quantum
well layer (for example, the first quantum well layer WL1) through
the barrier layer (for example, the first barrier layer BL1).
According to this, intersubband optical transition occurs.
[0119] The second region r2 has, for example, a plurality of
subbands. The subband is, for example, a miniband. The difference
in energy in the subbands is small. It is preferred that the
subbands are close to continuous energy bands. As a result, the
energy of the carrier c1 (electron) is relaxed.
[0120] In the second region r2, for example, light (for example,
infrared light having a wavelength of 3 .mu.m or more and 18 .mu.m
or less) is substantially not emitted. The carrier c1 (electron) at
a low level Ll in the first region r1 passes through the second
barrier layer BL2 and is injected into the second region r2 and
relaxed. The carrier c1 is injected into another first region r1a
connected in cascade. In this first region r1a, optical transition
occurs.
[0121] In the cascade structure, optical transition occurs in each
of the plurality of unit structures r3. According to this, it
becomes easy to obtain a high light output in the entire active
layer 31c.
[0122] In this manner, the light source portion 30 includes the
semiconductor light-emitting element 30aL. The semiconductor
light-emitting element 30aL emits the measurement light 30L by
energy relaxation of electrons in the subbands in the plurality of
quantum wells (for example, the first quantum well layer WL1 and
the second quantum well layer WL2, etc.).
[0123] In the quantum well layers (for example, the first quantum
well layer WL1 and the second quantum well layer WL2, etc.), for
example, InGaAs is used. For example, in the barrier layers (for
example, the first to fourth barrier layers BL1 to BL4, etc.), for
example, InAlAs is used. At this time, for example, when InP is
used as the substrate 35, favorable lattice matching is obtained in
the quantum well layers and the barrier layers.
[0124] The first clad layer 31a and the second clad layer 31e
contain, for example, Si as an n-type impurity. The concentration
of the impurity in these layers is, for example, 1.times.10.sup.18
cm.sup.-3 or more and 1.times.10.sup.20 cm.sup.-3 or less (for
example, about 6.times.10.sup.18 cm.sup.-3). The thickness of each
of these layers is, for example, 0.5 .mu.m or more and 2 .mu.m or
less (for example, about 1 .mu.m).
[0125] The first guide layer 31b and the second guide layer 31d
contain, for example, Si as an n-type impurity. The concentration
of the impurity in these layers is, for example, 1.times.10.sup.16
cm.sup.-3 or more and 1.times.10.sup.17 cm.sup.-3 or less (for
example, about 4.times.10.sup.16 cm.sup.-3). The thickness of each
of these layers is, for example, 2 .mu.m or more and 5 .mu.m or
less (for example, about 3.5 .mu.m).
[0126] The distance 31w (the width of the stacked body 31, that is,
the width of the active layer 31c) is, for example, 5 .mu.m or more
and 20 .mu.m or less (for example, about 14 .mu.m).
[0127] The length of the ridge waveguide RG is, for example, 1 mm
or more and 5 mm or less (for example, about 3 mm). The
semiconductor light-emitting element 30aL operates at an operation
voltage of, for example, 10 V or less. The current consumption is
lower than a carbon dioxide gas laser apparatus or the like.
According to this, an operation with low power consumption can be
achieved.
[0128] According to the embodiment, a high-precision gas measuring
apparatus can be provided. The gas measuring apparatus includes a
breath diagnostic apparatus.
[0129] Hereinabove, exemplary embodiments of the invention are
described with reference to specific examples. However, the
embodiments of the invention are not limited to these specific
examples. For example, one skilled in the art may similarly
practice the invention by appropriately selecting configurations of
components included in the breath diagnostic apparatus such as the
cell portion, the light source portion, the detection portion and
the control portion, etc., from known art. Such practice is
included in the scope of the invention to the extent that similar
effects thereto are obtained.
[0130] Furthermore, any two or more components of the specific
examples may be combined within the extent that the purport of the
invention is included.
[0131] Moreover, all breath diagnostic apparatus practicable by an
appropriate design modification by one skilled in the art based on
the breath diagnostic apparatus described above as embodiments of
the invention also are within the scope of the invention to the
extent that the purport of the invention in included.
[0132] Various other variations and modifications can be conceived
by those skilled in the art within the spirit of the invention, and
it is under stood that such variations and modifications are also
encompassed within the scope of the invention.
[0133] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
invention.
* * * * *