WO2021085331A1

WO2021085331A1 - Laser gas concentration meter

Info

Publication number: WO2021085331A1
Application number: PCT/JP2020/039933
Authority: WO
Inventors: 雅志大島
Original assignee: ゼネラルパッカー株式会社; 雅志大島
Priority date: 2019-10-28
Filing date: 2020-10-23
Publication date: 2021-05-06
Also published as: JP2021067635A; JP7321453B2

Abstract

[Problem] To provide a laser gas concentration meter that enables measurement of gas concentrations even under atmospheric conditions and that has a simplified configuration to achieve space saving. [Solution] A laser gas concentration meter 10 measures the concentration of residual specific gas by transmitting laser light of a specific wavelength through a gas-substituted and hermetically-sealed packaging material 50 in a measurement unit 13 disposed between a laser generating unit 11 and a laser receiving unit 12. The measurement unit has a total light path 20 of laser light including an incident light path 21, an attenuated light path 22 where the laser light transmitted through the packaging material is attenuated, and a transmitted light path 23. An attenuated absorbance of a specific wavelength on the attenuated light path is determined by eliminating, from a total absorbance with which the laser light has been absorbed by the specific gas on the total light path, an incident absorbance with which the laser light has been absorbed on the incident light path, and a transmitted absorbance with which the laser light has been absorbed on the transmitted light path. The concentration of residual gas in the packaging material is calculated from the attenuated absorbance and the length of the attenuated light path 22.

Description

Laser gas densitometer

In the present invention, a laser beam having a specific wavelength is transmitted through a packaging container or bag sealed by gas substitution or similar packaging, and an absorption spectrum of a specific wavelength that changes before and after transmission of the packaging. The present invention relates to a laser gas densitometer for measuring the gas concentration of a specific gas remaining inside the package based on the above.

Conventionally, in the packaging process, the air in the packaging bag containing a specific oxidation-causing gas that may shorten the storage period or the taste period of the packaged object is removed, and the gas is converted into an inert gas such as nitrogen or carbon dioxide. Gas replacement packaging is performed after replacement and sealing. As a result, the oxidation-causing gas inside the packaging bag is removed, and the packaged object, particularly the food, can secure a long storage period and a shelf life.
Then, in the inspection step after the gas replacement packaging, inspection is performed to see if the concentration of the oxidation-causing gas, particularly oxygen, is equal to or less than the predetermined value.
However, the current mainstream method for measuring oxygen concentration is a sampling test in which an injection needle is inserted into a packaging bag arbitrarily selected as a sample and the composition of a small amount of gas sucked from the packaging bag is inspected. In the sampling inspection, the packaging bag on which the injection mark is formed must be discarded. Further, if the number of samples is increased in order to improve the inspection accuracy, the inspection time becomes long, and there is a disadvantage that the economic and time loss increases due to the increased amount of waste.

On the other hand, the applicant of the present application has developed a gas concentration measuring device capable of measuring the concentration of a specific gas inside without damaging the packaging bag.
As shown in FIG. 7, the packaging bag gas concentration measuring device 1 disclosed in Japanese Patent Application Laid-Open No. 2010-107197 is connected to a laser generating unit 2 having a transmitter and the laser generating unit 2, and a laser beam is emitted. It is composed of a main head 3 to be generated, a laser light receiving unit 4 having a receiver, and a sub head 5 which is connected to the laser light receiving unit 4 and receives laser light. The main head 3 and the sub-head 5 provided so as to be relatively close to each other and separated from each other sandwich the packaging bag B to be inspected held by the pair of

grips

6 and 6, and the sub-head 5 is relative to the main head 3. Are arranged so that they face each other. As a result, the laser beam can pass through the packaging bag from the main head 3 to the sub head 5 at the shortest distance, and when measuring the concentration of a specific gas such as oxygen remaining in the packaging bag, the packaging bag It has become possible to quickly measure all of the packaging bags without damaging the packaging bags.

JP-A-2010-107197

However, in the gas concentration measuring device 1 described above, when the laser beam is transmitted through the packaging bag B, the main head 3 and the sub head 5 are attracted to the packaging bag B, or a laser forming a laser gas concentration meter is generated. When measuring the gas concentration of oxygen gas by purging the inside of the part and the laser receiving part with nitrogen gas to remove oxygen gas, the influence of the atmosphere around the packaging bag B is suppressed as much as possible. .. As described above, when the adsorption step is provided for each packaging bag to be measured, the time for measuring the packaging bag becomes long, so that the productivity of the packaging machine may decrease. Further, if the gas purge mechanism is provided in the laser gas densitometer, the structure of the instrument becomes complicated, so that it may be difficult to install the gas purge mechanism in the limited space on the packaging machine.

Therefore, the problem to be solved by the present invention is to provide a laser gas densitometer capable of measuring the gas concentration even in an atmospheric atmosphere, simplifying the configuration, and saving space. Is.

The laser gas densitometer according to claim 1 transmits laser light of a specific wavelength through a packaging container or bag that is gas-replaced and sealed, or a packaging body similar thereto, and transmits the packaging body. It is a laser type gas densitometer that measures the gas concentration of the specific gas remaining inside the package based on the absorption spectrum of the specific wavelength that changes before and after.
The laser gas densitometer is
The laser generating part that emits the laser light and
A laser receiving unit that receives the laser light and
The laser beam including an incident optical path from the laser generating portion to the packaging, an attenuated optical path through which the laser light is transmitted through the packaging and attenuated, and a transmitted optical path from the packaging to the laser receiving portion. With a measuring unit that has a total optical path of
Based on the incident intensity of the laser beam in the laser generating section and the transmittance of the laser beam transmitted through the package obtained from the transmitted light intensity of the laser beam in the laser receiving section, the said on the attenuated optical path. It has a measuring unit that measures the attenuated absorbance of the specific wavelength absorbed by the specific gas inside the package and calculates the concentration of the specific gas inside the package based on the attenuated absorbance.
From the total absorbance of the specific wavelength in which the laser light is absorbed by the specific gas on the total optical path, the measuring unit determines the incident absorbance of the specific wavelength in which the laser light is absorbed by the specific gas on the incident light path. When,
Excluding the transmitted absorbance of the specific wavelength in which the laser beam is absorbed by the specific gas on the transmitted light path,
The attenuated absorbance of the specific wavelength on the attenuated optical path is measured.
It is characterized in that the concentration of the specific gas inside the package is calculated based on the attenuated absorbance and the optical path length of the attenuated optical path.

The laser gas densitometer according to claim 2 is characterized in that, in the invention according to claim 1, the optical path length of the attenuated optical path is constant at a predetermined length.

The laser gas densitometer according to claim 3 is characterized in that, in the invention according to claim 1, the incident optical path and the transmitted optical path are in an atmospheric atmosphere.

The laser gas densitometer according to claim 4 is characterized in that the optical path length of the attenuated optical path is longer than the optical path length of the incident optical path or the transmitted optical path.

The laser gas densitometer according to claim 5 is the invention according to claim 1, when the incident absorbance and the transmitted absorbance change due to a predetermined disturbance in an atmospheric atmosphere.
The laser beam is emitted to the measuring unit a plurality of times to obtain the total average absorbance of the specific gas on the total optical path.
Based on the total average absorbance, the incident absorbance and the corrected absorbance for correcting the transmitted absorbance are determined.
When measuring the attenuated absorbance of the specific wavelength on the attenuated optical path inside the package,
It is characterized in that the incident absorbance corrected by the corrected absorption and the transmitted absorbance are applied.

The laser gas densitometer according to claim 6 is based on the invention according to claim 5, wherein the disturbance is caused by a change in the air temperature or atmospheric pressure in the atmosphere, or the optical path length of the incident optical path or the transmitted optical path. It is characterized by being.

According to the laser gas densitometer according to the present invention, the incident light intensity of the laser light emitted from the laser generating portion and the transmitted light intensity of the laser light transmitted through the package to be measured and incident on the laser receiving portion can be determined. The measurement was made so that the transmittance of the transmitted light with respect to the incident light was measured. Since the total absorbance of the laser light absorbed between the laser generating part and the laser receiving part can be obtained based on the transmittance, the incident light from the laser generating part to the package is absorbed by the specific gas from the total absorbance. By subtracting the incident absorbance obtained and the transmitted light absorbance of the transmitted light from the package to the laser receiving portion absorbed by the specific gas, the attenuated absorbance absorbed by the specific gas in the package can be obtained. The gas concentration inside the package is measured based on the attenuated absorbance and the optical path length inside the package.
Thereby, the gas concentration can be measured even when the incident light or the transmitted light of the laser light is absorbed by the specific gas other than the inside of the package.
In addition, the total absorbance including the incident absorbance related to the incident light and the transmitted absorbance related to the transmitted light is measured, and the attenuated absorbance related to the inside of the package is obtained from the total absorbance, so that the incident light or the transmitted light can be specified. Even when absorbed by the gas, the gas concentration of the specific gas inside the package can be measured. Therefore, it is not necessary to purge the gas on the optical path of the incident light or the transmitted light to remove the specific gas, so that the configuration of the laser gas densitometer can be simplified. Space can be achieved.
Further, the laser beam was emitted a plurality of times to obtain the total average absorbance on the total light path, and the corrected absorbance was obtained from the total average absorbance. By applying the corrected absorbance to the incident absorbance or the transmitted absorbance, even if the measured value is disturbed by disturbance, it can be kept within a predetermined range, and the gas concentration of a specific gas inside the package is measured. be able to.

It is a block diagram which shows the outline of the structure of the laser type gas densitometer which concerns on 1st Example. It is a graph which shows the result of the 1st experiment about the laser type gas densitometer which concerns on 1st Example. It is a graph which shows the result of the 2nd experiment about the laser type gas densitometer which concerns on 1st Example. It is a graph which shows the result of the 3rd experiment about the laser type gas densitometer which concerns on 1st Example. It is a top view which shows the outline of the structure of the conventional gas concentration measuring apparatus.

The laser gas densitometer according to this embodiment will be described with reference to the attached drawings. FIG. 1 is a block diagram showing an outline of the configuration of a laser gas densitometer according to the present embodiment.
The laser gas densitometer 10 is installed between a laser generating unit 11 that emits laser light, a laser receiving unit 12 that receives laser light, and a laser generating unit 11 and a laser receiving unit 12, and measures a specific gas to be measured. It includes a measuring unit 13 capable of measuring the gas concentration.

As shown in FIG. 1, the laser generation unit 11 includes a laser light source 14 and a control unit 15 that sets the wavelength of the laser light emitted from the light source 14 to a specific wavelength and adjusts the wavelength to a predetermined light intensity. ing.
The laser light source 14 includes a semiconductor laser element made of a diode having a variable wavelength, and is formed so as to be able to output laser light in the near infrared region. The semiconductor laser device according to this embodiment is a high-power semiconductor laser device called a DFB (Distributed Feed Back) laser.
The control unit 15 adjusts the wavelength of the laser light output from the semiconductor laser element to a specific wavelength peculiar to the specific gas to be measured, and controls to amplify the laser light so that it is emitted at a predetermined incident light intensity. It is formed like this. Further, the control unit 15 is formed so as to output an incident light signal related to the emitted incident light intensity to the measuring unit 17.
Here, the specific gas measured by the laser gas densitometer according to this embodiment is oxygen gas (O ₂ ). The absorption wavelength band peculiar to the oxygen gas is the 760 nm band, and among the plurality of absorption lines included in the absorption wavelength band, a specific wavelength related to one absorption line is selected as the output wavelength of the laser beam.

As shown in FIG. 2, the laser light receiving unit 12 measures the gas concentration based on the light receiving sensor 16 that receives the laser light transmitted through the measuring unit 13 and attenuated, and the light receiving signal from the light receiving sensor 16. It has a part 17.
The light receiving sensor 16 is composed of an element that converts the transmitted light intensity of the laser light transmitted through the measuring unit 13 into an electrically transmitted light signal, for example, a photodiode. As a result, the transmitted light intensity of the laser light transmitted through and attenuated by the measuring unit 13 can be electrically processed.
The measuring unit 17 calculates the transmittance based on the transmitted light signal related to the transmitted light intensity and the incident light signal related to the incident light intensity of the laser light output from the control unit 15 of the laser generating unit 11, and the transmittance is calculated. The absorbance of the laser beam from the specific gas is determined based on the above, and the gas concentration of the specific gas in the packaging bag is measured based on the absorbance.

As shown in FIG. 1, the measuring unit 13 is configured to be capable of transmitting laser light to the measurement target.
Here, the measurement target is a packaging bag or a packaging container or a packaging body 50 similar thereto, such as a plastic bag, a packaging bag such as a pouch, or a packaging container such as a bottle or a plastic case. , Used for various packaging. In this embodiment, the transmittance of the laser beam related to these packages 50 is assumed to be 0.00001% or more and less than 100%. That is, the laser gas densitometer according to the present embodiment is effective as long as the laser light is transmitted even when the package 50 is colored.
As shown in FIG. 1, the optical path related to the laser light in the measuring unit 13 is a total optical path 20 from the laser generating unit 11 to the laser receiving unit 12, and the total optical path 20 is from the laser generating unit 11 to the package. It is composed of an incident light path 21 related to incident light up to 50, an attenuated light path 22 in which laser light is absorbed by a specific gas and attenuated inside the package 50, and a transmitted light path 23 related to transmitted light from the package 50 to the laser receiving portion 12. ..

The laser gas densitometer 10 having the above configuration analyzes a specific gas by tunable semiconductor laser absorption spectroscopy.
Variable Diameter Laser Absorption Spectroscopy (TDLAS) is a cell in which a predetermined incident light intensity related to a laser beam output from a semiconductor laser element and a gas containing a specific gas to be measured are sealed. This is a method in which the transmittance is obtained from the transmitted light intensity of the transmitted laser light absorbed by the specific gas, and the gas concentration is measured from the absorbance of the laser light based on the transmittance.
It is known that each gas including a specific gas has a unique absorption wavelength band, and the absorption wavelength band includes a plurality of absorption lines related to wavelengths that absorb light more strongly. TDLAS modulates and amplifies the wavelength of the output laser light in the near-infrared region so as to match the specific wavelength of one absorption line among the plurality of absorption lines of the specific gas to be measured. It is configured as follows. Then, the gas concentration is measured by obtaining the absorbance of the laser beam based on the absorption spectrum of a specific wavelength that changes before and after the transmission of the cell.

Tunable semiconductor laser absorption spectroscopy (TDLAS) measures gas concentration based on Lambert-Beer's law. The Lambert-Beer's law, the incident light intensity I _0, packaging bag B to the transmitted light intensity transmitted through I _t, the transmittance of the transmitted light to incident light as T, and the optical path length L, and gas concentration C Then, Equation 1 is established with the luminous intensity A of the laser light emitted in the absorption spectrum of a specific wavelength. Here, ε is a unique absorption coefficient at which a predetermined gas to be measured absorbs laser light.

Here, with respect to the measuring unit 13 provided between the laser generating unit 11 and the laser receiving unit 12, the total optical path length related to the total optical path 20 is L, and the gas concentration absorbed by the total optical path 20 is defined as shown in FIG. If C, the by equation 1, the incident light intensity I _0, the transmitted light intensity I _t, Sadamari total absorbance a of emitted laser light in the absorption spectrum of a specific wavelength on Sohikariro 20, the total optical path The gas concentration C absorbed in can be determined.

Then, the total optical path length L is incident optical path length L _0, packaging such internal attenuation optical path length L _a, a sum of the transmitted light path length L _t, the total absorbance A is incident absorbance is the absorbance in the incident light path 21 A ₀ _{is the sum of the attenuated absorbance A a} absorbed in the attenuated optical path 22 inside the package and the transmitted absorbance At absorbed in the transmitted optical path 23.
Accordingly, the gas concentration of a specific gas on the incident light path 21 C _0, if the gas concentration of a specific gas on the transmission optical path 23 and C _t, on the attenuation optical path 22, i.e., the gas concentration inside the package such 50 C _a is , Can be obtained by the formula 2.

According to Equation 2 (2), if with respect to the incident optical path length L ₀ and the transmission optical path length L _t, and the package such 50 inside the attenuation optical path length L _a relatively long, incident optical path length L ₀ it is possible to reduce the influence of the gas concentration in the transmission optical path length L _t.
Thus, for example, by a laser generator 11 and a laser light receiving section 12 and separable freely configured, length of the wrapper class 50 to be measured, i.e. transmission optical path as the incident optical path length L ₀ with respect to attenuation optical path length L _a The length L _t may be adjusted so as to be relatively extremely short. Thereby, the measurement accuracy of the gas concentration Ca of the specific gas inside the package 50 can be improved.
Further, in the case of a configuration in which the entire measuring unit 13 is gas _{purged with nitrogen gas (N 2} ) to remove a specific gas, or when the measuring unit 13 is in an atmospheric atmosphere, the gas concentration C ₀ on the incident optical path 21 is set. _{Since the gas concentration C t} on the transmitted light path 23 can be regarded as the same value or a value close to each other, the gas concentration on the transmitted light path 23 _{is set to C 0,} and the gas concentration C on the incident light path 21 is set. It can be summarized by _0.
Thereby, the gas concentration Ca inside the package 50 can be measured not only in the gas-purged environment but also in the atmospheric atmosphere.
Furthermore, a case where the incident optical path length L ₀ and the transmission optical path length L _t is short enough to be relatively negligible with respect to the attenuation path length L _a, the gas concentration C ₀ of the incident light path 21 on transmission optical path 23 of the gas If it is the concentration C _t is the same value as or close to the gas concentration C on Sohikariro 20, gas concentration C _a of the inner package such 50, determining the ratio of the attenuation optical path length L _a to the total optical path length L Can be done.
In this case, a constant attenuation optical path L _a is, i.e., it is preferred size of the package such 50 is constant, a package such 50 inside the attenuation path 22 is constant. This can be obtained stably the gas concentration C _a of the inner wrapper class.

Here, the density per unit of the atmosphere containing a specific gas changes from moment to moment depending on the atmospheric pressure and the air temperature. That is, since the number of atoms or molecules of the specific gas contained in the atmosphere per unit also changes from moment to moment, one of the multiple absorption lines of the specific gas is obtained by TDLAS. When a laser beam that matches a specific wavelength related to the absorption line of is emitted, the number of atoms or molecules that absorb the laser beam per unit changes with atmospheric pressure or temperature, so the gas concentration measured based on that changes is stable. There is a risk that it will not work.
When the packaging body 50 is a predetermined packaging bag, the thickness of the packaging bag, that is, the attenuated optical path length L, depends on the amount of the inert gas sealed in the packaging bag and the internal pressure. _{As a} changes, the incident optical path length L ₀ and the transmitted optical path length L _t with respect to the total optical path length L also change accordingly.

The above-described momentarily with varying air pressure, the change in laser type gas densitometer 10 of the surrounding environment such as temperature, or incident that changes based on the attenuation optical path length L _a that varies with the thickness and the length of the wrapper class 50 The gas concentration Ca inside the package 50 may easily change due to _a disturbance such as an optical path length L ₀ or a transmitted optical path length L _{t length.}
Therefore, the laser gas densitometer 10 according to the present embodiment sets the measurement time to a predetermined length and emits the laser beam onto the total optical path 20 a plurality of times within the measurement time to obtain a plurality of actually measured values. It is configured to get.

Based on a plurality of measured values, the total absorbance A when the laser light emitted from the laser generating unit 11 onto the total optical path 20 passes through the measuring unit 13 including the packaging 50 and is received by the laser receiving unit 12. _{The total average absorbance Av} , which is the average of the above, can be obtained. The total average absorbance A _av a number of measurements, the variation of the measured actual values, can be obtained and the standard deviation, a correction absorbance A _c.
Further, by applying the correction absorbance A _c based on the standard deviation relative to the measured value of the total absorbance A, it is possible to keep the measured value obtained by correcting the measured values within a predetermined range. The correction absorbance A _c, since those affect all absorbance on Sohikariro 20, seeking correction factor of the correction the absorbance A _c to the total absorbance A, incident on the incident light path 21 the correction factor by applying relative absorbance a _0, and transmission absorbance a _t on transmission optical path 23, it is possible to improve the measurement accuracy of the wrapper class 50 inside the gas concentration C _a.

Moreover, by actually measuring a plurality of times within a predetermined measuring time, with obtaining the correction absorbance A _av, the correction factor for correcting the absorbance A _av with respect to the total absorbance A, to feedback to the measured value when the gas concentration measurement As a result, the measured value can be converged to a predetermined value included in the predetermined range, and the measurement accuracy can be further improved.

A plurality of experiments were conducted to verify the effect of the laser gas densitometer 10 having the above configuration. The experimental results of each of the experiments will be described with reference to the attached drawings. FIG. 2 is a graph showing the results of the first experimental example, FIG. 3 is a graph showing the results of the second experimental example, and FIG. 4 is a graph showing the results of the third experimental example.

First, the first experiment will be described with reference to FIG.
The first experiment, the attenuation path length L _a of the attenuation optical path 22 on the measuring unit 13 is obtained by setting the 17 mm. Here, as described above, transmitted light path length L _t and the incident optical path length L ₀ is as relatively sufficiently shorter than the attenuation path length L _a, i.e., the laser generator 11 and the packaging member such 50, Alternatively, the distance between the package 50 and the laser receiving unit 12 is set to be shorter than the length of the package 50. As a result, the incident optical path length L ₀ and the transmitted optical path length L _t are ignored in this first experiment.
Then, the measurement time was set to 300 ms, and the measurement unit 13 was irradiated with the laser beam 1000 times within the measurement time.
FIG. 2 is a graph showing the measurement results when the packages 50 are not installed in the measuring unit 13. That is, the measurement result in the case that can be regarded as total optical path length L and attenuation optical path length L _a match. At this time, the standard deviation of the measured values relating to the gas concentration of oxygen gas was 0.05%.
Further, when a transparent polyethylene packaging bag capable of sufficiently securing the attenuated optical path length La was installed in the measuring unit 13 and the same experiment was performed, the standard deviation of the measured value related to the gas concentration of oxygen gas was 0. It showed 0.08%, and the variation of the measured values became larger than that when the package 50 was not installed. This is because when the laser light is incident on the package 50 and when the laser light is transmitted through the package 50, the laser light is reflected on the interface between the atmosphere of the measuring unit 13 and the package 50. Alternatively, it is considered that scattering has occurred.

Next, the second experiment will be described with reference to FIG.
The second experiment, the length of the attenuation optical path length L _a of the first experiment for it was 17 mm, the point where the attenuation optical path length L _a and 38mm are different. As in the first experiment, as described above, transmitted light path length L _t and the incident optical path length L ₀ is as relatively sufficiently shorter than the attenuation path length L _a, i.e., the laser generating unit 11 And the packaging body 50, or the distance between the packaging body 50 and the laser receiving unit 12 was set to be shorter than the length of the packaging body 50. As a result, the incident optical path length L ₀ and the transmitted optical path length L _t are ignored in this second experiment.
Then, as in the first experiment, the measurement time was set to 300 ms, and the laser beam was irradiated onto the measurement unit 13 1000 times within the measurement time.
FIG. 3 is a graph showing the measurement results when the packages 50 are installed in the measuring unit 13. Here, the packaging body 50 is a packaging bag used in the experiment performed auxiliary in the first experiment, and is _a transparent polyethylene packaging bag capable of sufficiently securing the attenuated optical path length La.
At this time, the standard deviation of the measured values relating to the gas concentration of oxygen gas was 0.031%. Compared with FIG. 3 according to the first experiment, it is clear that the measured value is within a predetermined range.
Further, when the same experiment was conducted without installing the package 50 in the measuring unit 13, the standard deviation of the measured values relating to the gas concentration of oxygen gas was 0.028%.
That is, it is confirmed that the variation in the measured value can be suppressed and the measurement accuracy can be improved by lengthening the total optical path 20 and also lengthening the attenuated optical path 22 inside the package 50. Was done.

Further, the third experiment will be described with reference to FIG.
The third experiment, as in the second experiment, and sets the attenuation optical path length L _a to 38mm. Then, as in the second experiment, transmission optical path length L _t and the incident optical path length L ₀ is as relatively sufficiently shorter than the attenuation path length L _a, i.e., the laser generator 11 and the packaging member such 50 Or, the distance between the package 50 and the laser receiving unit 12 is set to be shorter than the length of the package 50. As a result, the incident optical path length L ₀ and the transmitted optical path length L _t are ignored in this third experiment.
In the third experiment, five packaging bags in which the gas concentration of oxygen gas inside the packaging body 50 was already adjusted to a predetermined low oxygen concentration were prepared. Their gas concentrations are 0.3% for the packaging bag B1, 0.25% for the packaging bag B2, 0.5% for the packaging bag B3, 0.2% for the packaging bag B4, and 0.35% for the packaging bag B5. It is adjusted to be.
Then, the measurement unit 13 was repeatedly measured 20 times by changing the position of each packaging bag 5 times. Therefore, the number of measurements is 100 for each packaging bag. The graph shown in FIG. 4 shows the measurement results for the packaging bags B1 to B5.
The standard deviation of the total number of measurements of 500 was 0.04%, which was measured by changing the packaging bags adjusted to different low oxygen concentrations and changing the position of the packaging bags.
Further, as is clear from the graph of FIG. 4, it was confirmed that the packaging bag B3 in which the gas concentration of oxygen gas was adjusted to 0.5% could be detected in the third experiment.

Here, when the applicant of the present application inspects the gas concentration of the oxygen gas sealed inside the package 50 in the gas concentration measuring device incorporating the laser gas concentration meter 10 according to the present embodiment, the package 50 The normal value is set when the gas concentration of the oxygen gas is 0.2% or less with respect to the gas concentration of the inert gas filled therein. Then, the case where the gas concentration of the oxygen gas is 0.2% to 0.5% is set as the allowable range, and when the gas concentration is 0.5% or more, it is judged as a defective product and 0.5% or more. The packaging 50 in which oxygen gas is sealed is set to be excluded. From the viewpoint of quality assurance, the standard deviation of the measured value of gas concentration is targeted to be within 0.033%.
As is clear from FIG. 4, since the packaging bag B having a gas concentration of 0.5% can be detected, the laser type gas concentration meter 10 according to the present embodiment is in an air atmosphere. Can also measure gas concentration.
However, a sufficient standard deviation cannot be obtained in the third experiment with respect to the desired standard deviation.
Therefore, in order to fit within 0.033 percent standard deviation The target, for example, improves the detection sensitivity by extending the total optical path length L and attenuation optical path length L _a, further incident upon the attenuation path length L _a When a device for holding the packages 50 is provided so that the optical path length L ₀ and the transmitted optical path length L _t are kept relatively short, it is considered that the value related to the standard deviation can be further improved.

According to the laser gas densitometer 10 according to the present embodiment, even if the measuring unit 13 between the laser generating unit 11 and the laser receiving unit 12 is in an atmospheric atmosphere, the inside of the packaging body 50 arranged in the measuring unit 13 The gas concentration of a specific gas can be measured. As a result, the device related to the gas purge can be omitted, so that the configuration of the gas concentration measuring device using the laser type gas concentration meter 10 according to the present embodiment can be simplified, and further, thereby, on the packaging machine. It can be easily installed in a limited space.

10 ... Laser gas densitometer,
11 ... Laser generating unit, 12 ... Laser receiving unit, 13 ... Measuring unit,
14 ... laser light source, 15 ... control unit, 16 ... light receiving sensor, 17 ... measurement unit,
20 ... total optical path, 21 ... incident optical path, 22 ... attenuated optical path, 23 ... transmitted optical path,
50 ... Packaging,
1 ... Conventional gas concentration measuring device, 2 ... Conventional laser generator, 3 ... Main head, 4 ... Conventional laser receiver, 5 ... Sub head, 6 ... Grip,
B ... Packaging bag.

Claims

Laser light of a specific wavelength is transmitted through a packaging container or bag sealed by gas substitution or similar packaging, and the absorption spectrum of the specific wavelength that changes before and after transmission of the packaging is used as the basis for the above. A laser gas densitometer that measures the gas concentration of a specific gas remaining inside the packaging.
The laser gas densitometer is
The laser generating part that emits the laser light and
A laser receiving unit that receives the laser light and
The laser beam including an incident optical path from the laser generating portion to the packaging, an attenuated optical path through which the laser light is transmitted through the packaging and attenuated, and a transmitted optical path from the packaging to the laser receiving portion. With a measuring unit that has a total optical path of
Based on the incident intensity of the laser beam in the laser generating section and the transmittance of the laser beam transmitted through the package obtained from the transmitted light intensity of the laser beam in the laser receiving section, the said on the attenuated optical path. It has a measuring unit that measures the attenuated absorbance of the specific wavelength absorbed by the specific gas inside the package and calculates the concentration of the specific gas inside the package based on the attenuated absorbance.
From the total absorbance of the specific wavelength in which the laser light is absorbed by the specific gas on the total optical path, the measuring unit determines the incident absorbance of the specific wavelength in which the laser light is absorbed by the specific gas on the incident light path. When,
Excluding the transmitted absorbance of the specific wavelength in which the laser beam is absorbed by the specific gas on the transmitted light path,
The attenuated absorbance of the specific wavelength on the attenuated optical path is measured.
A laser gas densitometer characterized in that the concentration of the specific gas inside the package is calculated based on the attenuated absorbance and the optical path length of the attenuated optical path.
The laser gas densitometer according to claim 1, wherein the optical path length of the attenuated optical path is constant at a predetermined length.
The laser gas densitometer according to claim 1, wherein the incident optical path and the transmitted optical path are in an atmospheric atmosphere.
The laser gas densitometer according to claim 1, wherein the optical path length of the attenuated optical path is longer than the optical path length of the incident optical path or the transmitted optical path.
When the incident absorbance and the transmitted absorbance change due to a predetermined disturbance in an atmospheric atmosphere,
The laser beam is emitted to the measuring unit a plurality of times to obtain the total average absorbance of the specific gas on the total optical path.
Based on the total average absorbance, the incident absorbance and the corrected absorbance for correcting the transmitted absorbance are determined.
When measuring the attenuated absorbance of the specific wavelength on the attenuated optical path inside the package,
The laser gas densitometer according to claim 1, wherein the incident absorbance corrected by the corrected absorbance and the transmitted absorbance are applied.
The laser gas densitometer according to claim 5, wherein the disturbance is due to a change in the air temperature or atmospheric pressure in the atmosphere, or the optical path length of the incident optical path or the transmitted optical path.