JP3200573B2 - Gas measuring device and isotope concentration ratio measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas measuring apparatus and an isotope concentration ratio measuring apparatus, and more particularly to an apparatus for analyzing a concentration ratio of a plurality of isotopes in a gas to be measured by utilizing absorption of a laser beam.

[0002]

2. Description of the Related Art Analytical methods utilizing isotopes as tracers are known in the fields of chemistry and medicine. Conventionally, radioisotopes are often used as the tracer. This is because the behavior of the tracer can be easily detected by radiation detection. However, non-radioactive isotopes have been used as tracers in recent years because radioisotopes have problems in exposure and management.

[0003] Recently, it has been reported that "Helicobacter pylori", a bacterium that can be present on the stomach wall, is a causative agent that causes gastric ulcer, gastric cancer and the like. Helicobacter pylori decomposes urea to carbon dioxide (C
O ₂ ). Therefore, there has been proposed a method for examining the presence or absence and abundance of Helicobacter pylori by utilizing its properties. Specifically, after a certain period of time after oral administration of the urea-based reagent to the subject, the breath of the subject is collected, and whether the breath contains carbon dioxide generated by Helicobacter pylori or not. , The presence or absence of the presence is determined.

In this case, the above-mentioned urea-based reagent is labeled with ¹³ C, which is a non-radioactive isotope, so that ¹³ CO _{2 in} exhaled air is removed.
¹² CO ₂ ratio and its abundance in nature (1:99)
By measuring the slight deviation between the two, Helicobacter pylori can be quantified.

[0005]

As methods for measuring the concentration ratio of isotopes, various methods such as a method by mass spectrometry and a method by spectral analysis are known. However, it is difficult to analyze the isotope concentration ratio simply and with high sensitivity by any of the conventional methods. In particular, the conventional Helicobacter pylori test method requires a large amount of exhaled air in order to ensure the resolution, and it has been pointed out that the handling is inconvenient and the burden on the subject.

It is to be noted that there is a demand for a device capable of simply and sensitively quantifying a specific substance not only in the above-described analysis of bacteria but also in general gas analysis.

US Pat. No. 4,684,805 describes an apparatus for measuring an isotope ratio by passing a laser beam through a sample gas and detecting light absorption by a photogalvanic effect at that time. However, the absorption of the laser light when the laser light passes through the gas once is very small, and it is difficult to increase the detection sensitivity.

US Pat. No. 5,394,236 (JP-A-7-20054)
JP-A-4-364442 and JP-A-6-18411 disclose an isotope ratio measuring apparatus, which can analyze the isotope ratio with high accuracy while having a simple configuration. A device that can be used has not been realized.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an apparatus capable of analyzing and measuring a gas to be measured at high sensitivity and at low cost by utilizing the absorption of laser light. It is in.

Another object of the present invention is to provide an apparatus which can obtain sufficient sensitivity with a small amount of exhalation when performing exhalation analysis.

[0011]

[Means for Solving the Problems]

(1) In order to achieve the above object, according to the present invention, at least one laser medium cell containing a laser medium is provided in series with the laser medium cell, and different measurement target gases are respectively contained. A plurality of absorption cells, a first mirror provided at one end of a cell row including the laser medium cell and the plurality of absorption cells, and reflecting a laser beam generated by the laser medium cell; and the other of the cell row. A second mirror provided at an end and reflecting the laser light, and an absorption cell selecting means for selectively functioning a desired absorption cell among the plurality of absorption cells,
Light absorption detecting means for detecting absorption of the laser light in the absorption cell, wherein a resonator is constituted by the cell row, the first mirror, and the second mirror.

According to the above configuration, the laser medium cell and the plurality of absorption cells are connected in series, and the first and second mirrors are provided at both ends of the cell row. Between the mirrors, laser light generated by the action of the laser medium cell resonates while being reflected back and forth many times. Also, in this case, the light in the laser resonator becomes much larger than the output light. As a result, a part of the laser light is absorbed by the gas to be measured each time the laser light passes, so that the degree of light absorption can be increased to perform measurement with higher sensitivity than before.
Further, the amount of gas introduced into the cell can be reduced as compared with the related art. As described above, according to the present invention, the analysis of a specific atom or molecule can be realized by disposing an absorption cell inside a laser device or its laser resonator. The optical path length between the mirrors is set so that the resonance condition is satisfied.

In the above configuration, the laser light is absorbed in the absorption cell selected by the absorption cell selection means, while the laser light is not substantially absorbed in the absorption cell not selected but exists as a transparent passage. . Therefore,
There is no need to replace the absorption cell, and it is not necessary to configure a plurality of resonators.

In a preferred aspect of the present invention, the absorption cell selecting means causes a gas discharge to be performed only in the desired absorption cell. That is, the absorption cell to be operated is switched by switching the gas discharge target.
Even if the laser beam passes through a gas that has not been ionized, its absorption does not substantially occur.

In a preferred embodiment of the present invention, a plurality of laser medium cells containing different laser mediums are provided, and a laser medium cell selection function for selectively functioning a desired laser medium cell among the plurality of laser medium cells is provided. Means are provided. Preferably, the laser medium cell selecting means causes the gas discharge to be performed only in the desired laser medium cell. That is, the functioning laser medium cell is switched by switching the gas discharge target similarly to the selection of the absorption cell.

(2) In order to achieve the above object, the present invention provides a first laser medium cell containing a first laser medium and a second laser medium cell containing a second laser medium. A first absorption cell containing a sample gas, a second absorption cell containing a reference gas, and the first and second laser medium cells and the first and second absorption cells are arranged in series. A first laser light generated by the first laser medium cell and a second laser light generated by the second laser medium cell provided at one end of the cell line A mirror, a second mirror provided at the other end of the cell row, for reflecting the first laser light and the second laser light, and a second mirror medium cell for the first laser medium cell and the second laser medium cell. One of Medium selecting means for selectively functioning, an absorbing cell selecting means for selectively operating one of the first absorption cell and the second absorption cell, the sample gas and the reference gas Calculating means for calculating the isotope concentration ratio based on the absorption of the first and second laser beams by the cell array, the first mirror, and the second mirror. It is characterized by having.

According to the above configuration, the first laser medium cell and the first absorption cell, the first laser medium cell and the second absorption cell, the second laser medium cell and the first absorption cell,
In each combination of the second laser medium cell and the second absorption cell, laser light absorption measurement is performed, and the concentration ratio of atoms or molecules is calculated based on the measurement result. In the above configuration, the measurement for each gas is performed in a time sharing manner,
All or some of the measurement results are temporarily stored in the storage means.

If the concentration ratio of the isotope in the reference gas is known, the two laser beams passing through the sample gas are determined based on the light absorption amounts (or light amounts) of the two laser beams passing through the reference gas. The concentration ratio of the isotope in the sample gas can be converted from the light absorption amount (or light amount) of the sample gas.

In a preferred aspect of the present invention, the laser medium selection means and the absorption cell selection / selection means cause only the cell to be operated to perform gas discharge.

[0020] In preferred embodiments of the present invention has the first laser medium ¹³ CO _2, said second laser medium has a ¹² CO _2, the arithmetic means, ¹² CO in the sample gas It is characterized in that the concentration ratio between ₂ and ¹³ CO ₂ is calculated. That is, the first laser light and the second laser light are generated so as to respectively match the resonance absorption lines of the isotope to be measured. In a preferred aspect of the present invention, the sample gas is exhaled air.

(3) In order to achieve the above object, the present invention provides a substrate on which a waveguide is formed, at least one transparent partition for dividing the waveguide into a plurality of cells, The first is provided at both ends of the
And a second mirror partition, wherein the plurality of cells include:
A laser medium cell containing a laser medium and an absorption cell containing a gas to be measured are provided, and the laser light resonates between the first and second mirror partitions.

According to the above waveguide type resonator,
Higher sensitivity measurement can be realized and the apparatus can be downsized. There is also an advantage in temperature control.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an overall configuration of an isotope concentration ratio measuring apparatus which is a gas measuring apparatus according to the present embodiment. This device measures the concentration ratio of isotopes using the absorption of laser light. In particular, for the above-mentioned test of Helicobacter pylori, the isotope in the breath of the subject after administration of the reagent is used. Concentration ratio ( ¹² CO
₂ : A breath analyzer that analyzes ¹³ CO ₂ ).

In FIG. 1, the composite resonator 300 has two functions of a function of generating a laser beam and a function of measuring light absorption by a gas to be measured. In other words, the composite resonator 300 has a structure in which an absorption cell is incorporated in a laser device or a resonator inside the laser device.

More specifically, the composite resonator 30
0 denotes two laser medium cells 31 provided in series
4, 316, and an absorption cell 320 for a sample gas and an absorption cell 322 for a reference gas further provided in series with them.
And a mirror 300a provided at one end of a cell row (cell group) composed of these cells, and a mirror 300b provided at the other end of the cell row.

The laser medium cells 314 and 316 have the same structure and function as the laser medium cell included in a general carbon dioxide laser device, and therefore have the same gas composition (eg, CO ₂₎ as that of a general carbon dioxide laser. ,
N ₂ , He) and the partial pressure ratio. However, the laser medium cell 316, conventional CO ₂ gas as CO ₂ gas (
¹² CO ₂ gas) is used. This is because the isotope abundance ratio is the natural isotope abundance ratio ( ¹² CO ₂ : ¹³ CO ₂ is 99:
1) is a gas. On the other hand, the laser medium cell 314
In, CO ₂ ^{gas 13} CO ₂ becomes mainly ⁽¹³ CO ₂ gas) are used. Therefore, the laser medium cell 31
4 induces a laser beam having a wavelength centered at 11.0 μm, and the laser medium cell 316 induces a laser beam having a wavelength centered at 10.6 μm.

The device according to the present embodiment is capable of measuring ¹² C
Since the concentration ratio between O ₂ and ¹³ CO ₂ is measured, ¹² CO ₂ gas and ¹³ CO ₂ gas are used as the laser medium as described above. Of course, when measuring another isotope concentration ratio, a laser medium that generates laser light having a specific wavelength that causes light absorption is prepared for each isotope to be measured.

The mirror 300a is a mirror that causes complete reflection, while the mirror 300b is a mirror that transmits a part (for example, 1% light amount). That is, the mirror 30
A laser beam is emitted through Ob. Each mirror is formed on a mirror substrate.

These mirrors are arranged perpendicular to the optical axis, and are composed of, for example, a known dielectric multilayer film or a gold vapor deposition film. The surface of each mirror may be flat, but may be curved to enhance the light collecting property. The distance between the mirrors is set so that each laser beam resonates between the two mirrors. Note that a sweep device that periodically vibrates one mirror at a constant amplitude in the optical axis direction may be provided. According to such a means, the optical path length between the mirrors can be repeatedly matched with the resonance condition.

In the apparatus of this embodiment, the absorption cell 32
Reference numerals 0 and 322 denote mechanisms for measuring laser light absorption by the gas. Each absorption cell 320 and 322
For example, it is formed as a columnar or columnar glass bulb,
The internal gas pressure is, for example, several Torr-100 Torr.

The sample gas absorption cell 320 is filled with a sample gas (sample gas) as the breath of the subject.
The exhaled breath was collected from the subject a certain time after orally administering the ^13C- labeled urea-based reagent to the subject. Absorption cell 322 for reference gas
Is filled with CO ₂ gas having a natural isotope abundance ratio or the breath of the subject before administration of the above-mentioned urea-based reagent.

In order to cause laser oscillation in the laser medium cells 314, 316,
A discharge electrode (or discharge coil) or the like is provided in each cell or in the vicinity of the cell in order to cause light absorption at 22, but is not shown. These discharge devices are supplied with electric power from discharge power sources 342 and 344.

That is, in the configuration shown in FIG. 1, a discharge DC or AC power is selectively supplied from the discharge power supply 342 to the laser medium cell 314 and the laser medium cell 316. The selecting device 346 selects a power supply destination according to the first synchronization signal. Similarly, a discharge power source 344 is provided in the absorption cells 320 and 322.
, DC or AC power for discharge is selectively supplied. The selecting device 348 selects a power supply destination according to a second synchronization signal having a higher (or lower) frequency than the first synchronization signal.

That is, in this embodiment, since only CO ₂ molecules excited by the discharge absorb (or emit), the selection of the cell is performed according to the presence or absence of the discharge.
Here, the cells that are discharged function, and the cells that are not discharged are optically transparent.

As can be understood from the above description, there are four selection patterns depending on the combination of cell selections, and the density ratio described later is calculated based on the measurement result of the light absorption in each selection pattern.

According to the composite resonator as described above, a laser beam is generated in one of the laser medium cells, and
The laser light is repeatedly reflected back and forth between the two mirrors.
At that time, laser light is selectively absorbed by gas molecules excited by discharge in one of the absorption cells. Therefore, high sensitivity can be obtained as in the case where a long measurement cell is configured. Further, there is an advantage that the apparatus can be downsized and the amount of gas used can be reduced.

Incidentally, in the composite resonator 300,
Since it is necessary to observe the optical absorption to be observed multiple times, use mirrors with high reflection coefficients for each laser beam to sufficiently reduce other losses in the complex resonator. Is desirable.

The photodetector 330 is an optical sensor that outputs a signal of a level according to the amount of light, and the output signal is input to an amplifier 332 that is a narrow band amplifier. It is desirable that the center frequency of the amplifier be made to coincide with the cell switching frequency (first or second synchronization signal) by the control unit 349. That is, it is possible to extract only a target signal, such as synchronous detection. Note that a lock-in amplifier that operates according to the frequency of the first or second synchronization signal may be provided.

The signal that has passed through the amplifier 332 is converted to a digital signal by an A / D converter 334. Then, the digital signal is temporarily stored in the memory 336. That is, the measurement result is temporarily stored in order to absorb the measurement time difference between the four cell selection patterns as described above. The arithmetic circuit 338 is constituted by a microcomputer or the like, and, based on the two detected light amounts of the sample gas and the two detected light amounts of the reference gas stored in the memory 336, the concentration ratio of the isotope, that is, ^{12 as described later.} CO ₂ and ^{1 3} CO ₂
Is a circuit for calculating the density ratio. The calculated concentration ratio is displayed on the display 340 as a numerical value. Based on the numerical value, the presence or absence of Helicobacter pylori may be determined and quantified, and the result of the determination may be displayed.

The control unit 349 includes two selection devices 346,
348 is controlled so that measurement is performed in a desired cell combination. In addition, the control unit 349 controls the memory 3
The writing and reading at 36 are also controlled.

The arithmetic circuit calculates the density ratio by executing the following calculation, for example.

[0043]

(Equation 1) However,

(Equation 2) Indicates the concentration ratio of ¹³ CO ₂ to ¹² CO ₂ for the sample gas,

(Equation 3) Represents the concentration ratio (known value) of ¹³ CO ₂ to ¹² CO ₂ of the natural or reference gas. I ¹¹ _M indicates the relative value (detected light amount) of the absorption when the first laser beam ( ¹³ CO ₂ laser beam) is absorbed by the sample gas, and I ^10.6 _M indicates the second laser beam. The light ( ¹² CO ₂ laser light) shows the relative value when absorbed by the sample gas, and I ^10.6 _REF shows the relative value when the second laser light is absorbed by the reference gas. ,
I ¹¹ _REF indicates a relative value when the first laser beam is absorbed by the reference gas.

In the above embodiment, the concentration ratio is calculated using the ratio between the light amounts of the first laser light and the second laser light for the sample gas and the reference gas. The density ratio can be calculated using the difference. In this case, for example, the amplification degree is adjusted so that the difference between the amounts of the two laser beams becomes zero using the reference gas, and then the amounts of the two laser beams are detected for the sample gas. Then, the concentration ratio may be converted from the difference. It is desirable to provide a device for cooling the composite resonator 300.

Next, an example of the composite resonator will be described with reference to FIG. FIG. 2 shows the composite resonator 3 shown in FIG.
An example where 00 is configured as a waveguide type is shown.

The flat main body 450 is formed of a ceramic substrate or the like, and a single groove-shaped waveguide 456 is formed on the main body 450 by cutting or the like. Waveguide 45
Mirror partition walls 452 and 454 are arranged at one end and the other end of the reference numeral 6. The surfaces facing the insides of the mirror partition walls 452 and 454 constitute mirrors 452A and 454A.

In the middle of the waveguide 456, three optically transparent intermediate partition walls (partition plates) 45 at a fixed interval from each other.
8, 460 and 462 are arranged. The waveguide 456 is divided into four cells 456A, 456B, 456C, 456D by these intermediate partitions and mirror partitions at both ends. Each cell is airtight, for example, cell 456A is the first laser medium cell and cell 456A
B is a second laser medium cell, cell 456C is a first absorption cell, and cell 456D is a second absorption cell. Cells 456C and 456D have inlet ports 450A and 450C and exhaust ports 450B and 45B, respectively.
OD is connected. Each port is provided with a cock (not shown) or the like. The order of the laser medium cell and the absorption cell can be changed as appropriate.

In FIG. 2, a discharge electrode is provided near each cell in order to cause gas discharge in each cell, but this is not shown. Although it is desirable to provide a cooling device for cooling the composite resonator, it is not shown.

In the composite resonator shown in FIG.
The light generated at 56A or 456B is
Laser light is generated by reciprocating reflection at 2A and 454A,
In the reciprocating path, the laser light is absorbed by the gas in the absorption cell 456C or 456D.
The mirror partition 454 allows a part of each laser beam to pass therethrough, and the laser beam passing through the partition 454 is detected by a photodetector.

FIG. 3 shows another example of the composite resonator.

The plate-shaped main body 470 is formed of a ceramic substrate or the like, and two groove-shaped waveguides 476 and 478 are formed in the main body 470 in parallel with each other by cutting or the like. Mirror partition walls 472 and 474 are arranged at one end and the other end of the two waveguides 476 and 478, respectively. The surface facing the inside of the mirror partitions 472, 474 is the mirror 472.
A and 474A.

In the middle of the waveguides 476 and 478, two optically transparent intermediate partition walls 48 are provided at a fixed interval from each other.
0 and 482 are arranged. Each of the waveguides 476 and 478 is divided into cells 476A, 478A and 476B, and 478B and 476 by these intermediate partitions and mirror partitions at both ends.
C and 478C. Each cell is airtight, for example, cells 456A, 478A are first and second laser medium cells, respectively, and cells 476B,
478B is a first absorption cell, and cells 476C, 47
8C is a second absorption cell. Cells 476B, 478B
Are connected to each other by a connection path at an intermediate portion. Similarly, the cells 476C and 478C are connected to each other by a connection path at an intermediate portion. The introduction port 470A is connected to the cell 476B,
On the other hand, an exhaust port 470B is connected to the cell 478B. Similarly, the introduction port 4 is provided in the cell 476C.
70C, and a port 470D is connected to the cell 478C. Each port is provided with a cock (not shown) or the like.

In FIG. 3, a discharge electrode is provided in the vicinity of each cell in order to cause gas discharge in each cell, but this is not shown. Although it is desirable to provide a cooling device for cooling the composite resonator, it is not shown.

In the composite resonator shown in FIG.
The light generated at 76A and 476B is divided into two mirrors 47.
The first and second laser beams are reciprocally reflected at 2A and 474A to generate first and second laser beams. In the reciprocating path, the first laser beam is absorbed by the gas in the cell 476B or 476C which functions selectively. . Similarly, the second laser light is absorbed by the gas in the selectively functioning cell 478B or A78C.

The mirror partition 474 allows a part of each laser beam to pass therethrough, and each laser beam passing therethrough is detected by a photodetector. Two photodetectors are provided corresponding to the two laser beams.

According to the composite resonator shown in FIG. 3, since the measurement using the first laser beam and the measurement using the second laser beam can be performed in parallel, the composite resonator shown in FIG. The measurement time can be shortened as compared with the above. However, the selection of the absorption cell is made according to the presence or absence of discharge, as in the example of FIG.

The composite resonator shown in FIGS. 2 and 3 is made of a ceramic such as alumina or aluminum nitride, for example.
The waveguide is, for example, a circular or square thin hole having an inner diameter of about 2-3 mm. The small-diameter hole surrounded by the substance having a high refractive index functions as a leakage waveguide for light. In this case, although there is some leakage loss, the leakage loss is extremely small for light such as laser light that can be obtained at a low incident angle, and a low-loss optical waveguide can be formed. Also,
In the present embodiment, since such a waveguide is used as a laser medium cell and an absorption cell, the best discharge condition of the gas filled therein can be set to a relatively high gas pressure. Therefore, according to such a waveguide-type composite resonator, gain or absorption per unit length can be increased, so that higher sensitivity can be obtained as compared with a non-waveguide-type composite resonator. Further, since the size of the composite resonator itself can be reduced, there is an advantage that the amount of required gas can be reduced. In addition, when the composite resonator is made of ceramic as described above, its thermal conductivity is large, so that a better gain and absorption coefficient can be expected, and since it can be cooled well, it is excellent in temperature stability. ing. Moreover, since a plurality of waveguides can be formed closely on the same substrate, there is an advantage that a temperature balance among them can be easily secured. Furthermore, since a large number of waveguides can be formed in parallel and compactly, there is another aspect that parallel processing for simultaneously processing a large number of samples in a short time can be realized.

[0058]

As described above, according to the present invention,
The analysis and measurement of the gas to be measured can be performed at high sensitivity and at low cost by utilizing the absorption of laser light. Also, when performing breath analysis, sufficient sensitivity can be obtained with a small amount of breath.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an isotope concentration ratio measuring device according to the present invention.

FIG. 2 is a diagram illustrating an example of a composite resonator.

FIG. 3 is a diagram showing another example of the composite resonator.

[Explanation of symbols]

300 composite resonator, 300a, 300b mirror, 3
14 first laser medium cell, 316 second laser medium cell, 320 sample gas absorption cell, 322 reference gas absorption cell, 330 photodetector, 336 memory, 338 arithmetic circuit, 342, 344 discharge power supply,
346,348 Selection device.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Junichi Kawanabe 6-22-1, Mure, Mitaka-shi, Tokyo Aloka Co., Ltd. (56) References JP-A-11-94737 (JP, A) JP-A-Hei JP-A-11-94738 (JP, A) JP-A-11-94740 (JP, A) JP-A-8-261922 (JP, A) JP-A-7-270308 (JP, A) JP-A-7-294418 (JP, A) A) JP-A-52-114390 (JP, A) JP-A-52-100276 (JP, A) JP-A-52-98578 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) G01N 21/00-21/61 WPI / L (QUESTEL) WPI (DIALOG)

Claims (9)

(57) [Claims] 1. At least one containing a laser medium
One laser medium cell, a plurality of absorption cells provided in series with the laser medium cell, each containing a different gas to be measured, and one end of a cell row including the laser medium cell and the plurality of absorption cells A first mirror that is provided at the other end of the cell array and reflects the laser light generated by the laser medium cell; a second mirror that is provided at the other end of the cell row and reflects the laser light; And a light absorption detecting means for detecting the absorption of the laser light in the absorption cell, wherein the cell row, the first mirror and the A gas measuring device, wherein a resonator is constituted by a second mirror. 2. The gas measuring apparatus according to claim 1, wherein said absorption cell selection means causes a gas discharge to occur only in said desired absorption cell. 3. The apparatus according to claim 1, further comprising a plurality of laser medium cells each containing a different laser medium, wherein a desired one of the plurality of laser medium cells functions. A gas measuring device provided with a laser medium cell selecting means. 4. The gas measuring apparatus according to claim 3, wherein said laser medium cell selecting means causes a gas discharge only in said desired laser medium cell. 5. A first laser medium cell containing a first laser medium, a second laser medium cell containing a second laser medium, and a first absorption cell containing a sample gas. And a second absorption cell containing a reference gas, provided at one end of a cell row in which the first and second laser medium cells and the first and second absorption cells are arranged in series, A first laser light reflecting the first laser light generated by the first laser medium cell and a second laser light generated by the second laser medium cell;
A mirror provided at the other end of the cell row and reflecting the first laser light and the second laser light; and a first mirror medium cell and the first absorption cell. A laser medium cell selecting unit that selectively functions one of the following: an absorption cell selecting unit that selectively functions one of the second laser medium cell and the second absorption cell; and the sample gas. And calculating means for calculating the isotope concentration ratio based on the absorption of the first and second laser beams by the reference gas, wherein the cell array, the first mirror and the second mirror resonate. An isotope concentration ratio measuring device, comprising a detector. 6. The isotope concentration ratio measuring apparatus according to claim 5, wherein the laser medium cell selecting means and the absorption cell selecting means perform gas discharge only on the cell to be operated. . 7. The apparatus according to claim 5, wherein the first laser medium has ¹³ CO ₂ , the second laser medium has ¹² CO ₂ , and the calculating means includes a control unit for controlling the operation of the sample gas. ¹² CO _{2 at}
An isotope concentration ratio measuring apparatus, which calculates a concentration ratio between 13CO ₂ and ¹³ CO ₂ . 8. The isotope concentration ratio measuring apparatus according to claim 5, wherein the sample gas is exhaled air. 9. A substrate on which a waveguide is formed, and at least one substrate for dividing the waveguide into a plurality of cells.
Two transparent partition walls, and first and second mirror partition walls provided at both ends of the waveguide and reflecting a laser beam, wherein the plurality of cells are covered with a laser medium cell containing a laser medium. A gas measuring device, comprising: an absorption cell containing a measurement gas; wherein a laser beam resonates between the first and second mirror partitions.