JP2844503B2 - Gas measurement 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 for measuring the concentration ratio of two kinds of gases using a semiconductor laser device.

[0002]

2. Description of the Related Art Stress and bacteria are known as the main causes of gastritis. In the case of bacteria, the administration of antibiotics is effective, so it is necessary to confirm whether or not bacteria are present in the patient. Since this kind of bacteria has the property of decomposing certain urea ¹² CO (NH ₂ ) ₂ to emit carbon dioxide ¹² CO ₂ , patients include carbon ¹³ C which is an isotope of carbon ¹² C as a tracer in patients. administered urea ¹³ CO (NH _{2) 2,} may be detected carbon dioxide ¹³ CO ₂ in the breath discharged from the patient.

On the other hand, in the atmosphere, the concentration ratio (carbon dioxide ¹³ C
The concentration of O ₂ in the carbon dioxide ¹³ CO ₂ concentration and carbon dioxide ¹²
The value obtained by dividing the sum of the concentration of CO ₂₎ is contained carbon dioxide ¹³ CO ₂ such that approximately 0.011, if the bacteria are not present in the body of gastritis patients were discharged from the patient During exhalation, this atmospheric carbon dioxide ¹³ C
Since only O ₂ is contained, the concentration ratio is about 0.01. However, when bacteria are present in the patient's body, exhaled air contains carbon dioxide ¹³ C contained in the atmosphere.
In addition to O ₂ bacteria with discharges of carbon dioxide ¹³ CO ₂
Is contained, the concentration ratio is about 0.011 to about 0.015.
Increase to ~ 0.02. Therefore the carbon dioxide ¹³ the concentration of carbon dioxide ¹³ CO ₂ in order to detect the presence or absence of bacteria
It may be obtained by dividing the sum of the concentration and the concentration of carbon dioxide ¹² CO ₂ in the CO _2.

[0004] An infrared spectrometer is known as a device for measuring the concentration ratio of two different types of gases, and FIG. 2 is a schematic configuration diagram of one example thereof.

In the figure, an infrared spectrometer 1
Detecting the ¹² CO ₂ and its carbon dioxide ¹³ CO ₂ ¹³ CO ₂
It comprises an analyzer 2, a data processor 3 for performing data processing, and a two-pen recorder 4 for simultaneously recording a change in the concentration of carbon dioxide ¹² CO _{2 and} a change in the concentration of carbon dioxide ¹³ CO ₂ over time as a graph. .

The ¹³ CO ₂ analyzer 2 includes a light source 5 that emits infrared light, and a reflecting mirror 6 that reflects infrared light from the light source 5.
, A sample cell 7 for taking in the patient's expiration from the intake port A and exhausting it from the exhaust port B, a control cell 8 for filling a gas for comparison and comparison, and a sector for alternately reflecting and passing incident light. Mirror 9, monochromator 10, PbSe
(Lead selenide) detector 11, automatic gain adjusting mechanism 14 including amplifier 12 and sample hold circuit 13,
And a logarithmic converter 15. Monochromator 1
Numeral 0 is composed of a slit 16, a collimator mirror 17, a diffraction grating 18, and a chopper 19, and splits one light beam into two.

The light emitted from the light source 5 is split into two by a reflecting mirror 6, passes through a sample cell 7 and a control cell 8, and alternately enters a monochromator 10 by a sector mirror 9, and outputs ¹² CO ₂ and ¹³ CO _2.
And is incident on the detector 11. The detection signal output from the detector 11 is automatically gain-controlled by an automatic gain adjustment mechanism 12 so that the intensity of light passing through the reference cell 8 becomes constant, and is input to a logarithmic converter 13. The output of the logarithmic converter 15 is corrected by the data processor 3 and printed on the two-pen recorder 4.

[0008]

However, in such an infrared spectrometer, since the sensitivity of the detector 11 is temperature-dependent, a cooling mechanism using dry ice-ethyl alcohol as a cooling medium is used. Since the device must be cooled, the device becomes complicated and the device becomes large. Also,
When the concentrations of the two types of gases are separately recorded on the recording paper of the two-pen recorder 4, and the operator looks at the judgment to make a determination, there is a problem that it takes time because the concentration ratio is difficult to understand.

The present invention has been made in view of the above points, and an object of the present invention is to provide an apparatus for detecting the concentration ratio of two types of gases using a semiconductor laser, which has a simple structure without using a cooling mechanism. Accordingly, an object of the present invention is to provide a measuring device for accurately measuring the concentration ratio of two types of gases in a short time.

[0010]

According to the present invention, there is provided a semiconductor device comprising: two semiconductor lasers having different oscillation wavelengths and modulation frequencies; mixing means for mixing laser light emitted from the semiconductor laser; A measuring cell for temporarily containing a gas containing two types of gases to be measured, a reference cell containing the same type of gas as the two types of gas, and a laser mixed by the mixing means and transmitted through the reference cell First light receiving means for receiving light, wavelength stabilizing means for detecting a frequency component equal to the modulation frequency from the output of the first light receiving means, and stabilizing the wavelength of each semiconductor laser based on the frequency component, A second light receiving unit that receives the laser light that has been mixed by the mixing unit and has passed through the measuring cell, two detection devices that detect the concentrations of the two types of gases from the output of the second light receiving unit, It is achieved by the gas measuring device including a divider for calculating the concentration ratio by dividing the value of one of the output of the detection device by the sum of the values of the outputs of the two detecting devices.

[0011]

According to the present invention, a reference cell in which laser beams emitted from two semiconductor lasers having different oscillation wavelengths and modulation frequencies are mixed and the same type of gas is sealed as two types of gases whose concentration ratios are to be measured. Receiving the laser beam transmitted through the first light receiving means, detecting a frequency component equal to the modulation frequency from the output of the first light receiving means, stabilizing the wavelength of each semiconductor laser based on the modulation frequency component,
A second light receiving means for receiving, by the second light receiving means, a laser beam transmitted through the measuring cell in which the gas containing the two gases whose concentration ratios are to be measured after being mixed by the mixing means is temporarily stored; , The concentrations of the two gases are detected by two detectors, and one of the outputs of the two detectors is
The concentration ratio is calculated by dividing by the sum of the output values of the two detection devices.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a gas measuring apparatus according to the present invention. In this example, carbon dioxide ¹² CO ₂ and its isotope carbon dioxide ¹³ C are obtained from the exhaled gas of a gastritis patient.
An example in which the present invention is applied to an apparatus that measures the concentration ratio of O ₂ to determine the presence or absence of bacteria from the change is illustrated.

[0014] Gas measuring devices illustrated in the drawings, two semiconductor laser elements 20a, and 20b, as well as stabilizing the oscillation wavelength of the semiconductor laser device 20a is modulated at a frequency f ₁ ¹²
CO ₂ wavelength control device 21a and semiconductor laser device 20
¹³ and CO ₂ for the wavelength control unit 21b for modulating at frequency f ₂ as well as stabilizing the oscillation wavelength of b, the carbon dioxide ¹² CO
₂ and the reference cell 22 where a mixed gas of carbon dioxide ¹³ CO ₂ is sealed is this isotope, the semiconductor laser elements 2
A beam splitter 23 that mixes the modulated laser beams emitted from the first and second laser beams 0a and 20b, and a first light receiving unit that receives the laser beam output from the beam splitter 23 and transmitted through the reference cell 22 and converts the laser beam into an electric signal. Photodetector 2
4 and urea ¹³ C containing carbon ¹³ C which is an isotope of carbon ¹² C
The breathing of the patient to whom O (NH ₂ ) ₂ was administered (including unknown concentration of carbon dioxide ¹³ CO ₂ ) is temporarily stored therein, and the measurement cell 25 is output from the beam splitter 23 and passes through the measurement cell 25. A photodetector 26 as a second light receiving means for receiving a laser beam and converting it into an electric signal;
Signal output from 6 and wavelength controller ₂ for ¹² CO 2
A ¹² CO ₂ detecting device 27 a for detecting the concentration of ¹² CO ₂ from the signal of frequency f ₁ output from ₁ a, and a photodetector 2
Signal output from 6 and wavelength controller ₂ for ¹³ CO 2
From the signal of frequency f ₂ output from 1b
¹³ and CO ₂ detector 27b for detecting the ¹³ CO ₂ concentration,
A divider 28 for dividing the sum of the ¹³ outputs of the CO ₂ detector 27b outputs the output (concentration) ¹³ CO ₂ detector 27b (the concentration) ¹² CO ₂ detector 27a (concentration), divider And a recorder 29 for recording 28 values.

The semiconductor laser elements 20a and 20b have such characteristics that the oscillation wavelength becomes longer when the temperature of the element itself becomes higher, and the oscillation wavelength becomes shorter when the temperature becomes lower. The semiconductor laser elements 20a and 20b are not shown. A Peltier element is mounted via a heat conducting plate.

The Peltier element is composed of a P-type semiconductor and an N-type semiconductor connected alternately via a metal plate. The connection portion is heated or cooled depending on the direction of current flow, and is applied to the Peltier element. The oscillation wavelength of the semiconductor laser elements 20a and 20b can be stabilized by controlling the voltage or the current.

The beam splitter 23 is generally constituted by a half mirror, and divides a light beam incident on the half mirror at a predetermined angle into two parts, a reflected light and a transmitted light.
Note that a fiber coupler may be used instead of the beam splitter 23. Laser light passing through the optical path L ₁ emitted from the semiconductor laser device 20a, the then partially transmitted through the beam splitter 23 make incidence to the measurement cell 25, a reference reflecting another part by the beam splitter 23 The light enters the cell 22. Is emitted from the semiconductor laser device 20b laser beam likewise passing through the optical path L _2, a portion thereof is reflected by the beam splitter 23, transmitted along with entering the measurement cell 25, the other part of the beam splitter 23 And enters the reference cell 22.

The semiconductor laser device 20a, and 20b, and the reference cell 22, the measuring cell 25, the optical path L ₃ of the laser beam is emitted from the semiconductor laser element 20a passes through the beam splitter 23, the semiconductor laser device 20b And the laser beam reflected by the beam splitter 23 is arranged so as to coincide with the optical path L3 of the laser beam.
Is emitted from 0b to the optical path L ₄ of the laser beam transmitted through the beam splitter 23, the optical path L ₄ of the laser beam reflected by the outgoing beam splitter 23 is arranged to coincide from the semiconductor laser 20a. Therefore, the optical path L ₃ ,
Since L so that the laser beam emitted from the semiconductor laser device the laser light emitted from 20a and the semiconductor laser device 20b are mixed on ₄ the beam splitter 23 functions as a mixing means.

Each of the photodetectors 24 and 26 is an element for converting incident laser light into an electric signal. For example, a photodiode is used. However, the present invention is not limited to this, and a phototransistor may be used.

The ¹² CO ₂ wavelength control device 21 a monitors the wavelength of the semiconductor laser device 20 a from the output component from the photodetector 24 and controls the Peltier device attached to the semiconductor laser device 20 a to stabilize the oscillation wavelength. the driving current of the semiconductor laser device 21a is modulated at a frequency f ₁ with temperature adjusting a temperature to a predetermined temperature. ¹³
Similarly, the wavelength control device 21b for CO ₂ adjusts the temperature of the semiconductor laser element 20b so that the temperature of the Peltier element attached to the semiconductor laser element 20b becomes a predetermined temperature, and reduces the drive current of the semiconductor laser element 20b. modulated at f _2.

The ¹² CO ₂ detecting device 27 a includes a phase sensitive detector that outputs a fundamental phase sensitive signal (which is proportional to the intensity of the laser beam transmitted through the measuring cell 25), and a second harmonic phase sensitive signal ( Intensity of laser light transmitted through measurement cell 25 and carbon dioxide ¹² CO contained in measurement cell 25
And a divider that outputs a signal that is proportional to the density of ₂ ) and a divider, and divides the value of the second-harmonic phase-sensitive detection signal by the value of the fundamental-wave phase-sensitive detection signal. The concentration of carbon ¹² CO ₂ is output.

As in the case of the ¹² CO ₂ detecting device 27 a, the ¹³ CO ₂ detecting device 27 b includes a phase-sensitive detector that outputs a fundamental-wave phase-sensitive detection signal, and a phase-sensitive detector that outputs a second-harmonic phase-sensitive detecting signal. And a divider, and outputs the concentration of carbon dioxide ¹³ CO ₂ by dividing the value of the second-harmonic phase-sensitive detection signal by the value of the fundamental-wave phase-sensitive detection signal.

The divider 28 has a concentration from the value of the output of the ¹³ CO ₂ detector 27b (the concentration of carbon dioxide ¹³ CO _2), the value of ¹² CO ₂ detector 27a (the concentration of carbon dioxide ¹² CO ₂₎ Ratio (concentration of carbon dioxide ¹³ CO ₂ mentioned above
^The value obtained by dividing the sum of the concentration of ¹³ CO _{2 and} the concentration of carbon dioxide ¹² CO ₂ ) is calculated, and the recorder 29 records the result of the divider 28.

It is known that the larger the least common multiple of the modulation frequencies f ₁ and f ₂ of the semiconductor laser elements 20 a and 20 b is, the higher the measurement accuracy is. Therefore, for example, a semiconductor laser for carbon dioxide ¹² CO ₂ the modulation frequency f ₁ of the element 20a to 51KH _z, chose modulation frequency f ₂ of the semiconductor laser device 20b for carbon dioxide ¹³ CO ₂ to 49KH _z. If the modulation frequencies are not integral multiples of each other, another frequency may be selected.

Next, the operation of the gas measuring apparatus having the above configuration and the determination of the presence or absence of bacteria will be described.

First, the wavelength controller 21a for ¹² CO ₂ and ¹³ C
It drives the O ₂ wavelength controller 21b. The semiconductor laser element 20a is modulated at a frequency 51KH _z with excitation at a wavelength equal to the absorption wavelength of carbon dioxide ¹² CO _2, the semiconductor laser device 20b is frequency 49KH _z with excitation at a wavelength equal to the absorption wavelength of carbon dioxide ¹³ CO ₂ Is modulated by As a result, each of the semiconductor laser elements 20a, 20a
From b, a laser beam modulated at a predetermined frequency around a predetermined bias current is oscillated.

Of the two laser beams thus oscillated, the laser beam emitted from the semiconductor laser device 20a and transmitted through the beam splitter 23 and the semiconductor laser device 20a
The mixed light with the laser light emitted from b and reflected by the beam splitter 23 passes through the reference cell 22 and is converted into an electric signal by the photodetector 24. The output signal each wavelength control device 21a obtained from the light detector 24, but is input to 21b, ¹² CO only modulation wave frequency 51KH _z in ₂ wavelength controller 21a for signal processing is performed by the Peltier element Since the voltage is controlled and the temperature of the semiconductor laser element 20a is controlled, the oscillation wavelength is stabilized at the absorption wavelength of carbon dioxide ¹² CO ₂ . On the other hand, ¹³ CO
For only the modulation wave frequency 49KH _z in ₂ control unit 21b signal processing is the voltage of the Peltier element is controlled conducted, the temperature of the semiconductor laser device 20b is controlled. The wavelength control devices 21a and 21b are composed of a phase sensitive detector, an integrator, a power supply for a Peltier element, and the like.
9KH _z, obtains a phase sensitive detection signal of a fundamental wave for 51KH _z, its value is controlled semiconductor laser device 20a, the temperature of 20b so that zero. As a result, the oscillation wavelengths of the semiconductor laser elements 20a and 20b are simultaneously stabilized at the centers of the absorption lines of carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂ , respectively.

On the other hand, the laser beam emitted from the semiconductor laser element 20a and transmitted through the beam splitter 23 and the laser beam emitted from the semiconductor laser element 20b and
The mixed light with the laser light reflected by 3 passes through the measuring cell 25 and is converted into an electric signal by the photodetector 26, and the ¹² CO ₂
It is input to the detecting device 27a and the detecting device 27b for ¹³ CO ₂ . ^{The 12} CO ₂ detecting device 27a is provided with carbon dioxide ¹² CO ₂
And outputs a signal corresponding to the concentration of ¹³ CO ₂ detector 27
b outputs a signal corresponding to the concentration of carbon dioxide ¹³ CO ₂ , and the divider 28 outputs a signal value corresponding to the concentration of carbon dioxide ¹³ CO ₂ and a signal value corresponding to the concentration of carbon dioxide ¹² CO _2. , And the recorder 29 records this density ratio.

When the bacteria causing gastritis do not exist in the exhaled breath in the measuring cell 25 in the patient's body, the concentration ratio does not change to about 0.011, but the bacteria remain in the measuring cell 25. When present in exhaled breath, the concentration ratio increases to about 0.015 to 0.02, so the presence or absence of bacteria is determined.

As described above, according to the present embodiment, the frequency f ₁
A laser beam modulated semiconductor laser element 20a in the laser beam of the semiconductor laser device 20b which is modulated at a different frequency f ₂ to the frequency f ₁ are mixed by the beam splitter 23, two types should be measured concentration ratio After the gas in the reference cell 22 in which the same type of gas is sealed is permeated, the gas is received by the photodetector 24, and the ¹² CO ₂ wavelength controller 21a
Stabilizes the oscillation wavelength of the laser beam corresponding to the frequency f ₁ , and the ¹³ CO ₂ wavelength controller 21 b stabilizes the oscillation wavelength of the laser beam corresponding to the frequency f ₂ , and the two types of which the concentration ratio should be measured. After allowing the gas in the measuring cell 25 temporarily containing the gas containing the gas to pass therethrough, the light detector 26
In receiving, carbon dioxide ¹² CO ₂ detector 27a ¹² CO
Detecting a _second concentration, and detecting the concentration of carbon dioxide ¹³ CO ₂ in ¹³ CO ₂ detector 27b, the divider 28 ¹³ CO ₂
By dividing the output value of the detection device 27b by the sum of the output value of the ¹³ CO ₂ detection device 27b and the output value of the ¹² CO ₂ detection device 27a to obtain a concentration ratio, two pen values are obtained as in a conventional infrared spectroscope. There is no need to compare the graphs of the recorder 4 to find the concentration ratio, and the concentration ratio of the two gases can be accurately measured with a simple configuration without providing a cooling mechanism.

In this embodiment, carbon dioxide ¹² CO ₂ and carbon isotope ¹³ CO _{2 as} its isotope are exemplified as two kinds of gases for obtaining the concentration ratio. However, the present invention is not limited to this. Similarly, it is of course possible to measure the concentration ratio.

[0032]

As described above, in the present invention,
Laser light emitted from two semiconductor lasers having different oscillation wavelengths and modulation frequencies should be mixed to measure the concentration ratio.
The first light receiving means receives the laser beam transmitted through the reference cell in which the same type of gas is sealed, and
Detecting the frequency component equal to the modulation frequency from the output of the light receiving means, stabilizing the wavelength of each semiconductor laser based on the modulation frequency component, and mixing the two gases by the mixing means to measure the concentration ratio. The second light receiving means receives the laser light transmitted through the measuring cell in which the gas containing the gas is temporarily stored, and detects the concentrations of the two kinds of gases from the output of the second light receiving means by the two detecting devices. Since the density ratio can be calculated by dividing one of the outputs of the two detectors by the sum of the outputs of the two detectors, the two-pen recorder can be used as in a conventional infrared spectrometer. The concentration ratio of the two types of gas can be accurately measured with a simple configuration without using a cooling mechanism without the trouble of finding the concentration ratio by comparing the graphs.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a gas measuring device according to the present invention.

FIG. 2 is a schematic configuration diagram of a conventional infrared spectroscope.

[Explanation of symbols]

20a, 20b semiconductor laser element 21a ¹² CO ₂ wavelength controller 21b ¹³ CO ₂ wavelength control device 22 reference cell 23 beam splitter 24 optical detector 25 measuring cell 27a ¹² CO ₂ detector 27b ¹³ CO ₂ detector Equipment 28 Divider 29 Recorder

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-5702 (JP, A) JP-A-5-10876 (JP, A) JP-A-5-79976 (JP, A) JP-A-4- 326042 (JP, A) JP-A-3-277945 (JP, A) JP-A-63-9843 (JP, A) JP-A-2-198340 (JP, A) JP-A-63-231245 (JP, A) 58-84557 (JP, U) Acta Physica Acad emia Scientiarum Hungaricae, Tomus 48 (1) p93-102 (1980) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 21/00- 21/61

Claims (4)

(57) [Claims] 1. A semiconductor device comprising two semiconductor lasers having different oscillation wavelengths and modulation frequencies, mixing means for mixing laser beams emitted from the semiconductor lasers, and a gas containing two gases whose concentration ratios are to be measured. And a reference cell in which the same type of gas as the two types of gas is sealed, and a first light receiving unit that receives the laser beam mixed by the mixing unit and transmitted through the reference cell. A wavelength stabilizing means for detecting a frequency component equal to the modulation frequency from the output of the first light receiving means and stabilizing the wavelength of each of the semiconductor lasers based on the frequency component; A second light-receiving means for receiving the laser light transmitted through the measuring cell after being subjected to the measurement, two detection devices for detecting the concentrations of the two types of gases from the output of the second light-receiving means, and Inspection A divider for calculating a concentration ratio by dividing one value of the output of the output device by the sum of the output values of the two detection devices. 2. The two gases whose concentration ratio is to be measured are carbon dioxide ¹² CO ₂ and carbon dioxide ¹³ CO ₂ , and the oscillation wavelengths of the two semiconductor lasers are carbon dioxide ¹² CO _2.
Gas measuring apparatus according to claim 1 in which the absorption wavelength of, characterized in that respectively equal to the absorption wavelength of carbon dioxide ¹³ CO ₂ to. 3. The gas measuring device according to claim 1, wherein said mixing means is a beam splitter. 4. The gas measuring device according to claim 1, wherein said mixing means is a fiber coupler.