JP6044760B2 - Laser gas analyzer - Google Patents

Description

  The present invention relates to a laser type gas analyzer that measures various gas concentrations such as gas in a flue with a laser beam.

It is known that each gas molecule / atom has its own light absorption spectrum.
FIG. 19 is an example of a light absorption spectrum of ammonia (NH ₃ ). The horizontal axis of the graph indicates the wavelength, and the vertical axis indicates the light absorption rate.
Laser gas analyzers are known as gas analyzers that detect various gas concentrations using such light absorption spectra. This analyzer irradiates the measurement target gas with light emitted from a laser light source having the same emission wavelength region as the light absorption spectrum of the measurement target gas, and utilizes the absorption of laser light by the molecules and atoms of the measurement target gas. Concentration is measured.

The gas analyzer using laser light measures the gas concentration based on the principle that the absorption amount at a specific wavelength is proportional to the gas concentration. Here, the attenuation at the wavelength fc at the center of the absorption line is proportional to the gas concentration. Therefore, the concentration of the gas can be estimated by irradiating the gas with semiconductor laser light having an oscillation wavelength of fc, measuring the attenuation, and multiplying the gas by an appropriate coefficient.

  As described above, the concentration measurement method based on the gas analysis using the laser beam includes a differential absorption method and a frequency modulation method. Usually, in the differential absorption method, the gas concentration can be measured with a relatively simple configuration. On the other hand, with the frequency modulation method, signal processing is complicated, but highly sensitive gas concentration measurement is possible.

  An apparatus for measuring a gas concentration by a differential absorption method is described in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 7-151681, “Gas Concentration Measuring Device”). As shown in FIG. 8 of Patent Document 1, this gas concentration measuring device is a device including a two-wavelength semiconductor laser, a gas cell, a light receiving lens, a light receiving unit, and a gas concentration measuring device.

Then, as shown in concentration measurement principle of the differential absorption method of FIG. 20, a laser beam for the laser beam to the center wavelength f _c of the absorption line and the oscillation wavelength, the free central wavelength f _r absorption line and the oscillation wavelength, The gas is irradiated with the two types of laser light, and the signal intensity difference obtained by subtracting the intensity of the signal output from each light receiving unit is multiplied by an appropriate proportionality constant to be converted into a concentration.

  An apparatus for measuring a gas concentration by a frequency modulation method is also described in, for example, Patent Document 1 described above. As shown in FIG. 7 of Patent Document 1, this gas concentration measuring device is a device including a frequency modulation type semiconductor laser, a gas cell, a light receiving lens, a light receiving unit, and a gas concentration measuring device.

Then, as shown in concentrations measuring principle according to the frequency modulation scheme of Figure 21, the center wavelength f _c, the output of the semiconductor laser is frequency-modulated at a modulation frequency f _m, is irradiated to the measurement target gas of interest. Since the absorption line of the gas is almost quadratic function with respect to the wavelength, twice the frequency of the signal (second harmonic) is obtained in the modulation frequency f _m in the role played light receiving portion of the absorption lines discriminator It is done. The fundamental wave by amplitude modulation can be estimated by performing envelope detection at the light receiving unit, and the ratio of the amplitude of the fundamental wave to the amplitude of the second harmonic wave is phase-synchronized to be proportional to the gas concentration regardless of the distance. To get a value.

  For example, a laser gas analyzer shown in FIG. 22 is known as a conventional technique of a gas analyzer using laser light. This laser type gas analyzer is described in Patent Document 2 (Japanese Patent Laid-Open No. 2009-47677, title of the invention “laser type gas analyzer”).

  In FIG. 22, reference numerals 101a and 101b denote flue walls through which the measurement target gas flows. On these flue walls 101a and 101b, the light emitting portion flange 201a and the light receiving portion flange 201b are arranged at positions facing each other.

  A light emitting unit housing 203a is attached to the light emitting unit flange 201a via a mounting bracket 202a. The light emitting unit housing 203a incorporates optical components such as a laser light source 204 and a collimating lens 205. A light receiving portion housing 203b is attached to the light receiving portion flange 201b via a mounting bracket 202b. The light receiving unit housing 203b includes a lens 206, a light receiving element 207, and a light receiving unit circuit board 208 that processes output signals of the light receiving element 207.

In the above configuration, the laser light emitted from the laser light source 204 is applied to the inside of the flue, which is the measurement target space, and is received by the light receiving element 207 in the light receiving unit housing 203b disposed to face the laser light source 204. .
When the measurement target gas is present inside the flue due to this light reception, the laser light is absorbed. Therefore, the light absorption circuit board 208 is utilized by utilizing the fact that this light absorption is related to the concentration of the measurement target gas. The above received light signal processing circuit calculates the gas concentration to be measured.

Japanese Patent Laid-Open No. 7-151681 (paragraphs [0004], [0030], FIG. 7, FIG. 8, etc.) Japanese Patent Laying-Open No. 2009-47677 (paragraphs [0029] to [0038], FIGS. 1 to 7 etc.)

  This type of laser gas analyzer is often installed in a flue such as a garbage incinerator. In this flue, dust and water are present in addition to the gas to be measured. The influence of light amount attenuation due to dust can be corrected by the conventional technique described in Patent Document 2, and even if dust exists in the flue, the gas concentration can be accurately measured.

However, in recent years, in the field of refuse incineration and the like, there is an increasing need for finely measuring gas concentrations of SO ₂ , NO, NO _{2 and the} like in the exhaust gas treatment process with the aim of realizing optimal process control.
These gases have a light absorption spectrum in the mid-infrared region. For example, FIG. 23 shows a light absorption spectrum of SO _{2. In} order to detect such a light absorption spectrum, a laser light source that emits laser light having a wavelength in the mid-infrared region such as a quantum cascade laser is used. It is preferable to use it.

However, in this mid-infrared region, there are many light absorption spectra of water in addition to the light absorption spectrum of SO ₂ that is the measurement target gas. FIG. 24 shows the light absorption spectrum of water, and it is very difficult to measure the SO ₂ concentration by removing this light absorption spectrum.
That is, when the moisture concentration in the measurement target space is high, the laser light emitted from the quantum cascade laser as the laser light source is affected by water other than the measurement target gas, and thus is significantly attenuated.

For example, FIG. 25 shows the level of the received light signal (in other words, the received light amount) when the influence of absorption by water is experimentally investigated under the condition for detecting the optical absorption spectrum wavelength (about 7.2 μm) of SO ₂ .
If the attenuation of the amount of received light is only affected by dust, it can be corrected by the method described in Patent Document 2, but according to FIG. 25, the amount of received light attenuates as the water concentration (volume concentration) increases. I understand that. For this reason, the conventional laser gas analyzer has a problem in that if there is moisture in the measurement target space, the measurement value of the measurement target gas is attenuated and the gas concentration cannot be measured accurately.

  Further, as described in Patent Document 1, the gas concentration measurement method is a method of capturing a slight change in the amount of light by scanning the vicinity of the peak of the absorption spectrum with a laser element that emits light near the oscillation wavelength. For example, the HCl gas having a spectrum as shown in FIG. 26 can include light of a wavelength that does not absorb the measurement target gas component in a wavelength range that can be scanned by the near-infrared laser element to be used. Therefore, it is possible to accurately measure the gas concentration using the received light amount correction using light having a wavelength that is not absorbed by the measurement target gas component.

However, the SO ₂ gas having a spectrum as shown in FIG. 27 does not include light of a wavelength that does not receive absorption of the gas component to be measured in the wavelength range in which the mid-infrared laser element used can emit light. Therefore, DC absorption occurs due to the measurement target gas. Light amount decreasing by dust is DC, when measured in the mid-infrared light gases such as SO _2, either the absorption by the gas for measurement, determines whether the amount of light attenuation due to dust, perform light amount correction It is difficult to perform accurate gas concentration measurement.

  Therefore, a problem to be solved by the present invention is to provide a laser type gas analyzer capable of measuring the concentration of a measurement target gas with high accuracy even in a measurement environment where a high concentration of moisture and dust exists.

In order to solve the above problem, the invention according to claim 1
A mid-infrared laser emitting section that emits laser light having a wavelength in the mid-infrared region including the light absorption spectrum of the gas to be measured;
A mid-infrared laser driving section for driving the mid-infrared laser emitting section;
A mid-infrared laser optical unit that collimates the laser light emitted from the mid-infrared laser emission unit and irradiates the measurement target space where the measurement target gas exists; and
A mid-infrared light receiving unit that receives the laser light emitted from the mid-infrared laser optical unit and outputs it as an electrical mid-infrared light reception signal;
A gas concentration calculation unit that extracts a signal component affected by light absorption by the measurement target gas from the mid-infrared light reception signal, and calculates a measurement target gas concentration from a change amount of the signal component;
In a laser gas analyzer having
A near-infrared laser emitting section that emits laser light having a wavelength in the near-infrared region that does not include at least the light absorption spectrum of the gas to be measured;
A near infrared laser driving section for driving the near infrared laser emitting section;
A near-infrared laser optical unit that collimates the laser light emitted from the near-infrared laser light emitting unit and irradiates the space to be measured;
A near-infrared light receiving unit that receives the laser light emitted from the near-infrared laser optical unit and outputs it as an electrical near-infrared light reception signal;
A reduction in the amount of light detection unit that detects a reduction in the amount of light due to the dust of the space from the near-infrared light receiving optical signals,
A gas concentration correction unit that corrects the concentration measurement value of the measurement target gas obtained by the gas concentration calculation unit using the light amount reduction amount obtained by the light amount reduction amount detection unit;
It is characterized by comprising.

The invention according to claim 2
A mid-infrared laser emitting section that emits laser light having a wavelength in the mid-infrared region including the light absorption spectrum of the gas to be measured;
A mid-infrared laser driving section for driving the mid-infrared laser emitting section;
A mid-infrared laser optical unit that collimates the laser light emitted from the mid-infrared laser emission unit and irradiates the measurement target space where the measurement target gas exists; and
A mid-infrared light receiving unit that receives the laser light emitted from the mid-infrared laser optical unit and outputs it as an electrical mid-infrared light reception signal;
A gas concentration calculation unit that extracts a signal component affected by light absorption by the measurement target gas from the mid-infrared light reception signal, and calculates a measurement target gas concentration from a change amount of the signal component;
In a laser gas analyzer having
A near-infrared laser emitting section that emits laser light having a wavelength in the near-infrared region that does not include the light absorption spectrum of the measurement target gas and includes the light absorption spectrum of water present in the measurement target space;
A near infrared laser driving section for driving the near infrared laser emitting section;
A near-infrared laser optical unit that collimates the laser light emitted from the near-infrared laser light emitting unit and irradiates the space to be measured;
A near-infrared light receiving unit that receives the laser light emitted from the near-infrared laser optical unit and outputs it as an electrical near-infrared light reception signal;
A moisture concentration calculation unit that extracts a signal component affected by light absorption by water existing in the measurement target region from the near-infrared light reception signal, and calculates a light amount reduction amount corresponding to the moisture concentration from the change amount of the signal component When,
A gas concentration correction unit that corrects the concentration measurement value of the measurement target gas obtained by the gas concentration calculation unit using a light amount reduction amount corresponding to the water concentration obtained by the moisture concentration calculation unit;
It is characterized by comprising.

The invention according to claim 3
The laser gas analyzer according to claim 2, wherein
Water concentration calculation unit, have rows together reduction in the amount of light detected by the dust, is characterized in that the corrected using the reduction in the amount of light corresponding to the reduction in the amount of light and water content by dust.

The invention according to claim 4
In the laser type gas analyzer according to any one of claims 1 to 3,
The wavelength of the laser beam in the mid-infrared region emitted from the mid-infrared laser emission unit is 3 to 10 μm, and the wavelength of the laser beam in the near-infrared region emitted from the near-infrared laser emission unit is 0. It is 7 to 3 μm.

According to the present invention, even when measuring the gas concentration of SO ₂ or the like using a mid-infrared laser emitting unit in an environment where high concentration of moisture or dust exists, the influence of moisture present in the measurement target space is reduced. The amount of laser light required for the measurement can be secured by removing, and the target gas concentration can be measured with high accuracy.

It is a block diagram of the laser type gas analyzer which concerns on the 1st, 2nd embodiment of this invention. It is a circuit block diagram of the laser type gas analyzer concerning a 1st embodiment of the present invention. It is a circuit block diagram of a laser light emission part and a laser drive part. FIG. 4A is a characteristic diagram showing the relationship between the light emission wavelength of the laser element and the current, and FIG. 4B is a characteristic diagram showing the relationship between the light emission wavelength of the laser element and temperature. is there. It is a figure which shows a wavelength scanning drive signal. It is a figure which shows the drive signal with respect to a laser element. It is a block diagram of a gas concentration calculation part, a light quantity reduction amount detection part, and a water concentration calculation part. It is a characteristic view which shows the relationship between the light-receiving light quantity level and the amplitude level of a gas absorption waveform. It is a light-receiving signal waveform diagram in an environment without dust. It is a light-receiving signal waveform diagram in an environment with dust. It is an output waveform figure of the synchronous detection part in the environment without dust. It is an output waveform figure of the synchronous detection part in the environment with dust. It is an output waveform figure of the filter part in the environment without dust. It is an output waveform figure of the filter part in the environment with dust. It is a characteristic view which shows the relationship between the received light quantity of near-infrared light with respect to dust amount, and the received light quantity of mid-infrared light. It is a characteristic view which shows the relationship between the received light amount reduction amount of near infrared light, and the received light amount reduction amount of middle infrared light. It is a circuit block diagram of the laser type gas analyzer which concerns on the 2nd Embodiment of this invention. Is a diagram illustrating an optical absorption spectrum of water _(H 2 O) in the wavelength region 1.3～1.5Myuemu. It is a diagram illustrating an optical absorption spectrum of ammonia (NH _3). It is a figure which shows the density | concentration measurement principle by a differential absorption system. It is a figure which shows the density | concentration measurement principle by a frequency modulation system. It is a block diagram of the conventional laser type gas analyzer described in patent document 2. FIG. It is a diagram illustrating an optical absorption spectrum of sulfur dioxide (SO _2). Is a diagram illustrating an optical absorption spectrum of water _(H 2 O) in the wavelength region 7.1～7.7Myuemu. It is a figure which shows the light reception signal level in case there exists an influence of absorption by water. It is a figure which shows the spectral characteristic of HCl gas. Is a diagram showing spectral characteristics of SO ₂ gas.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In this embodiment, especially in the environment where dust exists, even when measuring the gas concentration of SO ₂ or the like using the mid-infrared laser light emitting unit, it is necessary for measurement by removing the influence of dust existing in the measurement target space. The laser light quantity can be secured, and the target gas concentration is measured with high accuracy.

  First, FIG. 1 shows an overall configuration of a laser gas analyzer according to this embodiment. In FIG. 1, a light emitting portion flange 201a and a light receiving portion flange 201b are fixed to, for example, a flue wall 101a, 101b such as a flue through which the measurement target gas passes, by welding or the like.

A light emitting unit housing 203a is attached to the light emitting unit flange 201a, and a mid infrared laser light emitting unit 7 that emits mid infrared laser light and a near infrared laser beam are emitted inside the light emitting unit housing 203a. The near-infrared laser light emitting unit 8, the lens 9, and the concave mirror 10 are arranged in an airtight manner. As shown in the block diagram of FIG. 2, by arranging the window 18 that transmits the light having the wavelength to be used, the inside of the light emitting unit housing 203 a is secured.
Returning to FIG. 1, the light emitting unit case 203 is attached to the light emitting unit casing 203 a, and the light emitting unit circuit board 4 inside the light emitting unit casing 203 a has a mid-infrared as shown in detail in the block diagram of FIG. 2. A laser driving unit 20 and a near infrared laser driving unit 21 are mounted. Electrical signals are sent from the mid-infrared laser driving unit 20 and the near-infrared laser driving unit 21 to the mid-infrared laser emitting unit 7 and the near-infrared laser emitting unit 8 so that the mid-infrared laser emitting unit 7 The near-infrared laser light emitting unit 8 is configured to emit outside light and near-infrared light, respectively.

Here, the mid-infrared laser light emitting unit 7 is an element such as a quantum cascade laser that emits mid-infrared laser light having a wavelength of 3 to 10 μm in the mid-infrared region including the light absorption spectrum of the measurement target gas. The outer laser drive unit 20 generates a laser drive signal that sweeps the wavelength in the mid-infrared region and causes the mid-infrared laser emission unit 7 to emit light.
On the other hand, the near-infrared laser light emitting unit 8 does not include the light absorption spectrum of the measurement target gas, and has a wavelength in the near-infrared region for detecting scattering of dust existing in the flue interior 1 (measurement target space). It is an element such as a semiconductor laser that emits a 7 to 3 μm near-infrared laser beam. The near-infrared laser drive unit 21 generates a laser drive signal that sweeps the wavelength in the near-infrared region to generate a near-infrared laser beam. The infrared laser emission unit 8 is caused to emit light.

The emitted light from the mid-infrared laser light emitting unit 7 is collimated by the concave mirror 10 serving as the mid-infrared laser optical unit of the present invention to become parallel light, passes through the center of the light emitting unit flange 201a, and the mid-infrared laser light 2 As shown in FIG. The mid-infrared laser beam 2 is affected by light absorption by the measurement target gas existing in the flue interior 1.
The light emitted from the near-infrared laser light-emitting unit 8 is converted into parallel light by the lens 9 and becomes the near-infrared laser light 17 from the opening 11 formed near the central portion of the concave mirror 10 to the light-emitting unit flange 201a. It irradiates the flue interior 1 through the center. In addition, the lens 9 and the opening part 11 comprise the near-infrared laser optical part of this invention.
As described above, the near-infrared laser beam 17 is emitted coaxially inside the mid-infrared laser beam 2, and this near-infrared laser beam 17 is simultaneously with the measurement target gas inside the flue 1. It is affected by light scattering by existing dust.

On the other hand, the light receiving unit casing 203b is attached to the light receiving unit flange 201b. The mid-infrared laser beam 2 that has passed through the flue interior 1 is collected by the concave mirror 15 that is airtightly arranged inside the light receiving unit housing 203 b and received by the mid-infrared light receiving element 12. As shown in the block diagram of FIG. 2, by arranging the window 19 that transmits light of the wavelength to be used, the inside of the light emitting unit housing 203 a is secured. The concave mirror 15 and the mid-infrared light receiving element 12 constitute a mid-infrared light receiving unit of the present invention.
The mid-infrared light receiving element 12 is an MCT (Mercury Cadmium Tellurium) photoconductive element having sensitivity to wavelengths in the mid-infrared region, and the output signal of the mid-infrared light receiving element 12 is a light-receiving unit circuit in the light-receiving unit case 5 The gas is input to a gas concentration calculation unit 22 (see FIG. 2) such as SO ₂ mounted on the substrate 6. The gas concentration calculation unit 22 performs signal processing on the signal of the mid-infrared light receiving element 13, extracts a signal change component due to light absorption of the measurement target gas and obtains it as a gas concentration signal, and does not correct the light amount attenuation. Measure the SO ₂ concentration.

The near-infrared laser beam 17 is condensed by the lens 14 through the opening 16 formed near the center of the concave mirror 15 and received by the near-infrared light receiving element 13. In addition, the opening part 16, the lens 14, and the near-infrared light receiving element 13 comprise the near-infrared light-receiving part in this invention.
The near-infrared light receiving element 13 is an element such as a photodiode having sensitivity to wavelengths in the near-infrared region, and an output signal from the near-infrared light receiving element 13 is an amount-of-light-reduction detecting unit 23 ( 2). The light amount decrease amount detection unit 23 performs signal processing on the signal of the near-infrared light receiving element 14, thereby extracting a signal change component due to light scattering of dust and measuring the light amount decrease amount.

  The gas concentration calculation unit 22 and the light amount decrease amount detection unit 23 are connected to a gas concentration correction unit 24, and perform correction to calculate an accurate gas concentration in consideration of reduction due to dust.

  Next, the operation of each unit will be described. As shown in detail in FIG. 3, the light emitting unit 10 includes a mid-infrared laser driving unit 20, a wavelength scanning driving signal generating unit 20a, a high frequency modulation signal generating unit 20b, a laser driving signal generating unit 20c, and a temperature control unit 20d. Is provided. Further, the mid-infrared laser light emitting section 7 further includes a mid-infrared laser element 7a, a temperature detection section (thermistor) 7b, and a temperature adjustment section (Peltier element) 7c.

The mid-infrared laser element 7a can emit light at a wavelength where the emission wavelength coincides with the light absorption characteristic of the gas and its peripheral region. Further, as shown in FIG. 4A, the emission wavelength can be varied by the drive current. Further, as shown in FIG. 4B, the emission wavelength can be made variable depending on the temperature. In this embodiment, sulfur dioxide gas (SO ₂ gas) is measured as a specific example of the measurement target gas, and a wavelength that absorbs sulfur dioxide gas (SO ₂ gas) is also adopted as the wavelength.

  In FIG. 3, the temperature of the mid-infrared laser element 7a is detected using a temperature detector 7b such as a thermistor. This temperature detection unit 7 b is connected to the temperature control unit 20 d of the mid-infrared laser driving unit 20. The temperature control unit 20d performs PID control or the like so that the resistance value obtained from the temperature detection unit 7b such as a thermistor becomes constant in order to stabilize the emission wavelength of the mid-infrared laser element 7a and adjust the wavelength. The temperature of the temperature adjusting unit 7c such as a Peltier element is controlled to adjust the temperature of the mid-infrared laser element 7a.

  The output signal of the wavelength scanning drive signal generator 20a that changes the emission wavelength of the laser so as to scan the absorption wavelength of the measurement target gas, and a sine wave of about 10 kHz for detecting the absorption waveform of the measurement target gas, for example. When the output signal of the high frequency modulation signal generator 20b for frequency modulating the emission wavelength is input to the drive signal generator 20c, the drive signal generator 20c combines these output signals to generate a drive signal, and this drive The signal is V-I converted and supplied to the mid-infrared laser element 7a.

Here, the modulation of the laser light will be described. FIG. 5 shows an output signal of the wavelength scanning drive signal generator 20a. Wavelength scanning driving signals S ₁ to scan the absorption characteristics of the measurement target gas is gradually changed the emission wavelength of the mid-infrared laser element 7a linearly changing the drive current value of the mid-infrared laser element 7a, e.g. Scan the light absorption characteristics of about 0.2 nm. On the other hand, the signal S ₂ is the mid-infrared laser element 7a a drive current value is maintained above the threshold current to stabilize, is intended for illuminating at a certain wavelength. Furthermore, keep the signal _{S 3,} the drive current value to 0 mA.

A waveform diagram of a modulation signal output from the high-frequency modulation signal generation unit 20b is illustrated below the high-frequency modulation signal generation unit 20b in FIG. 3. This modulation signal is, for example, a sine wave having a frequency of 10 kHz. The wavelength width is about 0.02 nm.
FIG. 6 is a waveform diagram of a drive signal output from the laser drive signal generation unit 20c of FIG. 3 (a combined signal of the output signal of the wavelength scanning drive signal generation unit 20a and the output signal of the high frequency modulation signal generation unit 20b). . This drive signal has a trapezoidal shape that is repeated at a constant period. When the laser drive signal generator 20c supplies this drive signal to the mid-infrared laser element 7a, the mid-infrared laser element 7a emits a light absorption characteristic of the measurement target gas of about 0.2 nm with a wavelength width of about 0.02 nm. Detectable modulated light is output.

  As a result, a laser beam having a predetermined wavelength that is frequency-modulated for scanning the light absorption characteristics of the measurement target gas is emitted from the mid-infrared laser element 7a. As shown in FIG. 1, the laser light emitted from the mid-infrared laser element 7 a is emitted as parallel mid-infrared laser light 2 by the concave mirror 10. The temperature of the mid-infrared laser element 7a is adjusted in advance so that gas is measured at the central portion of the wavelength scanning drive signal.

  Such mid-infrared laser light 2 propagates through the interior of the flue, which is the inner section of the walls 3a and 3b (the space in which the measurement target gas flows), and receives gas absorption when passing through this space. The operations and functions of the mid-infrared laser driving unit, mid-infrared laser light emitting unit, and mid-infrared laser optical unit of the present invention are as described above.

  As shown in FIG. 3, the near-infrared laser light emitting unit 21 of the present invention includes a wavelength scanning drive signal generation unit 20a, a high frequency modulation signal generation unit 20b, a laser drive signal generation unit 20c, and a temperature control unit 20d. The near-infrared laser emission unit 8 further includes a near-infrared laser element 8a, a temperature detection unit (thermistor) 7b, and a temperature adjustment unit (Peltier element) 7c. The near-infrared laser optical unit includes a lens 9 and an opening 11. Is provided. The operation is the same as that of the above-described mid-infrared laser, and the near-infrared laser element 8a emits laser light having a wavelength in the near-infrared region that does not include the light absorption spectrum of the measurement target gas. The modulated near-infrared laser beam is output, and redundant description is omitted. The near-infrared laser light 17 has a wavelength that does not receive absorption by the measurement target gas, and emits light so as to sweep a wavelength region that does not include the absorption spectrum of the measurement target gas component. If there is no dust inside the flue, the same amount of light can be obtained when receiving light.

Next, the mid-infrared light receiving unit of the present invention will be described.
The detection light that has propagated through the space where the measurement target gas exists and has absorbed the gas is collected by the concave mirror 15 and then received by the mid-infrared light receiving element 12. The mid-infrared light receiving element 12 outputs a detection signal based on an electric signal according to the amount of received light. The mid-infrared light receiving element 12 is, for example, a photodiode, and an element having sensitivity to the emission wavelength of the laser is applied.

  Next, the gas concentration calculation unit 22 will be described. As shown in FIG. 7, the gas concentration calculation unit 22 includes an I / V conversion unit 22a, a synchronous detection unit 22b, an oscillator 22c, a filter 22d, and a calculation unit 22e. The detection signal input from the mid-infrared light receiving element 12 to the gas concentration calculation unit 22 is converted from a current signal to a voltage signal by the I / V conversion unit 22a. This voltage signal has an output waveform as shown in FIG. This voltage signal is input to the synchronous detector 22b. Further, the reference signal generator (oscillator) 22c outputs a signal having a frequency twice that of the high-frequency modulation signal generated by the high-frequency modulation signal generator 20b (see FIG. 3) to the synchronous detector 22b as a reference signal. The synchronous detection unit 22b extracts only the amplitude of the double frequency component of the modulation signal.

This is because the output of the laser emission part 12a is frequency-modulated at the center wavelength f _c and the modulation frequency f _{m as} shown in the concentration measurement principle by the frequency modulation method of FIG. Upon irradiation, since the absorption lines of the gas is almost quadratic function with respect to the wavelength, twice the frequency of the signal of the absorption lines serve discriminator modulation frequency f _m (2 harmonic) is can get. By performing envelope detection, the fundamental wave by amplitude modulation can be estimated, and by synchronizing the phase ratio between the fundamental wave amplitude and the amplitude of the second harmonic wave, a value proportional to the gas concentration is obtained regardless of the distance. This signal is input to the calculation unit 22e after noise is removed by the filter unit 22d, and the concentration of the measurement target gas is calculated in the calculation unit 22e.

Next, the principle of detecting the concentration of the measurement target gas by the frequency modulation method will be described. Here, to detect the sulfur dioxide (SO ₂ gas). When the measurement target gas, that is, sulfur dioxide (SO ₂ gas) has an absorption characteristic, a synchronous detection signal as shown in FIG. 11 is extracted from the synchronous detection unit 22b. The synchronous detection signal is output to the calculation unit 22e. Since this peak value becomes the gas concentration, the calculation unit 22e may measure the peak amplitude or integrate the signal change.

In one example, the computing unit 22e can detect a gas concentration by multiplying the span calibration value G _A and gas temperature correction coefficient alpha _A such relative amplitude W _A of the synchronous detection signal as shown in FIG. 11.

[Equation 1]
Measured gas concentration _{= α A × G A × W} A

The gas temperature correction coefficient α _A may be any coefficient that is uniquely determined with respect to the gas temperature, and the format such as the function format or the table format is not limited.

The calculation unit 22 e sends the measurement target gas concentration to the gas concentration correction unit 24. The processing performed by the gas concentration correction unit 24 will be described later. Gas concentration detection by mid-infrared light is performed in this way.

Next, calculation of the amount of light reduction due to dust using near infrared light will be described.
Near-infrared laser light 17 propagated through the space in which the gas to be measured exists and whose amount of light has decreased due to scattering by dust passes through the opening 16 of the concave mirror 15 and is condensed by the lens 14 before being near-red. Light is received by the external light receiving element 13. The near-infrared light receiving element 13 outputs a detection signal based on an electrical signal according to the amount of received light.

  Next, the light amount decrease amount detection unit 23 will be described. The light quantity reduction amount detection unit 23 has the same configuration as the gas concentration calculation unit 22 inside, and as shown in FIG. 7, an I / V conversion unit 22a, a synchronous detection unit 22b, an oscillator 22c, and a filter 22d. And an arithmetic unit 22e. The detection signal input from the near-infrared light receiving element 13 to the gas concentration calculation unit 22 is converted from a current signal to a voltage signal by the I / V conversion unit 22a. This voltage signal has an output waveform as shown in FIG. This voltage signal is input to the synchronous detector 22b. Further, the reference signal generation unit (oscillator) 22c outputs a signal having a frequency twice the high frequency modulation signal by the high frequency modulation signal generation unit 20b of FIG. 3 to the synchronous detection unit 22b as a reference signal. The synchronous detection unit 22b extracts only the amplitude of the double frequency component of the modulation signal. Then, a value proportional to the amount of dust is obtained by the principle of concentration measurement by the frequency modulation method. This signal is input to the calculation unit 22e after the noise is removed by the filter unit 22d, and the reduction amount is calculated in the calculation unit 22e.

  Next, calculation of the light amount reduction amount by calculation will be described. First, the detection principle will be described. As described above, the laser gas analyzer is installed, for example, in a flue of a garbage incinerator. In the flue, dust is present in addition to the measurement target gas. In this case, the laser light is blocked by the influence of dust, and the amount of received light is reduced. When the amount of received light decreases, the amplitude of the detected gas absorption waveform also decreases, so that the gas concentration cannot be measured accurately.

For example, Figure 9 dust environment with no, if the received signal and the synchronous detection signal as shown in FIG. 11 is obtained, to measure the gas concentration by detecting the amplitude w (= w _a) of this waveform it can. On the other hand, in an environment with dust, the received light signal level decreases as shown in FIGS. 10 and 12, the amplitude w (= w _b ) of the synchronous detection signal decreases, and accurate gas concentration detection cannot be performed.

  Therefore, paying attention to the fact that the received light quantity level and the amplitude level of the gas absorption waveform are substantially proportional as shown in FIG. 8, the received light quantity for calculating the correction coefficient is calculated in the light quantity reduction amount detector 23, and the gas Correcting by the concentration correction unit 24 enables accurate gas concentration detection even in an environment where dust or the like is present.

  Next, details of light amount correction will be described. The change in the amount of received light with respect to the dust amount of near-infrared light and mid-infrared light is as shown in FIG. In particular, in the case of near infrared light, the amount of received light greatly decreases as the amount of dust increases. From this value, the amount of light reduction is calculated by the following equation.

[Equation 2]
Light reduction amount = -log (Received light intensity relative value)

  Then, when the correlation between the near-infrared light quantity reduction amount and the mid-infrared light quantity reduction amount is taken, a graph as shown in FIG. 16 is obtained, and the characteristics of the near-infrared light and mid-infrared light quantity reduction against dust are strong. It can be seen that there is a correlation. Therefore, the amount of received mid-infrared light that is reduced by dust can be estimated based on the amount of received near-infrared light that is reduced by dust.

  When the received light signal shown in FIGS. 9 and 10 is input to the filter 22d of the light amount decrease detection unit 23 to extract the wavelength scanning drive signal component, waveforms as shown in FIGS. 13 and 14 are obtained. FIG. 13 shows a case where there is no dust and the amount of received light is not reduced, and FIG. 14 is a case where there is dust and the amount of received light is reduced. Since this near infrared light is not affected by the measurement target gas, only the decrease due to the influence of dust can be detected.

As shown in FIG. 13, at a certain point of time at the time of factory shipment or calibration, the level P _max of the received light signal when there is no dust and the received light amount is maximum is set in advance in the calculation unit 22e as the received light amount setting value. The computing unit 22e detects the received light signal level Ps when there is dust as shown in FIG. 14, and calculates the ratio between this Ps and P _max at the same time as the received light amount correction coefficient β by Equation 3.

[Equation 3]
β = P _max / P _s

The light amount decrease amount detection unit 23 outputs the received light amount correction coefficient β to the gas concentration correction unit 24. Gas density correction unit 24, the received light quantity correction coefficient beta, by multiplying or dividing the amplitude w of the gas absorption waveform, as in Equation 4, the amplitude w _h corrected for variation in quantity of received light due to dust Can be obtained.

[Equation 4]
Measurement target gas concentration (after correction) = β x Measurement target gas concentration (before correction)
= P _max / P _s × Measurement gas concentration (before correction)

  Then, it is expressed by the following formula by Equation 1.

[Equation 5]
Gas concentration to be measured (after correction) = α _A × G _A × W _A × P _max / P _s

  The gas concentration correction unit 24 sends the measurement target gas concentration to the output unit. The output unit is, for example, a display device or an alarm device, or a transmission device that transmits to another computer. Detection of the concentration of the measurement target gas by the frequency modulation method is performed in this way. By calculating the gas concentration in which the amount of decrease in light amount is corrected in this way, accurate gas concentration measurement is possible even in an environment where the amount of received light varies due to dust.

Although the present invention has been described above, the present invention can be variously modified. For example, according to the laser gas analyzer of the present invention, FIG. 5, focusing on the point that a signal S ₃ signal is output for each cycle as shown in Figure 6, from the detection of the S ₃ signal Since the peak value of the synchronous detector output waveform appears when a predetermined time has elapsed, the concentration should be calculated at this timing.
Although the concentration is measured, the presence or absence of the measurement target gas can be detected by determining that the measurement target gas does not exist when the concentration is almost zero.

Also, SO ₂ in the embodiment described above, with has been described as an exemplary sulfurized oxygen gas (SO _2), but not intended to be limited to this, the light absorption spectrum in the wavelength of the mid-infrared region , NO, NO ₂ , and other gas components may be used. In that case, a laser emission unit having a wavelength capable of detecting other component gases is employed, and the calculation processing content of the calculation unit is changed so as to be detected at this wavelength.

  In this embodiment, the optical paths of the mid-infrared light and the near-infrared light are the same, but a configuration in which the optical paths are separated may be employed. However, since the dust distribution in the flue is not always uniform, it is desirable that the optical path for performing gas analysis and the optical path for measuring the reduction in the amount of light due to dust coincide.

In this embodiment, the near-infrared laser light 17 may be coaxially passed through the inside of the mid-infrared laser light 2. For example, the mid-infrared laser light-emitting unit 7 and the near-infrared laser light-emitting unit 8 are used. May be reversed so that the mid-infrared laser beam 2 passes coaxially through the inside of the near-infrared laser beam 17.
The present invention is not limited to the above-described embodiment other than the arrangement of the laser light emitting units 7 and 8, and includes many changes without departing from the essence thereof.

According to the present invention, the amount of light on the optical path for measuring the gas concentration is reduced by an optical system that emits laser light having a wavelength that is not attenuated by the measurement target gas coaxially with laser light having a wavelength that is absorbed by the measurement target gas. The amount can be measured, and the concentration of a gas having an absorption spectrum over the entire laser light wavelength scanning range such as SO ₂ can be accurately measured.

Next, a second embodiment of the present invention will be described with reference to the drawings. In this embodiment, even when measuring the concentration of gas such as SO ₂ using the mid-infrared laser emission section, especially in an environment where a high concentration of moisture exists, measurement is performed by removing the influence of moisture existing in the measurement target space. Therefore, it is possible to secure a necessary amount of laser light and to measure the target gas concentration with high accuracy.

  First, FIG. 17 shows a circuit block diagram of a laser type gas analyzer according to this embodiment. As shown in the overall configuration diagram of FIG. 1, also in the second embodiment, the light emitting portion flange 201a and the light receiving portion flange 201b are provided on the flue walls 101a and 101b such as the flue through which the measurement target gas passes, for example. It is fixed by welding or the like.

A light emitting unit housing 203a is attached to the light emitting unit flange 201a, and a mid infrared laser light emitting unit 7 that emits mid infrared laser light and a near infrared laser beam are emitted inside the light emitting unit housing 203a. The near-infrared laser element 8, the lens 9, and the concave mirror 10 are arranged in an airtight manner.
A light emitting unit case 3 is attached to the light emitting unit casing 203a, and a light emitting unit circuit board 4 inside the light emitting unit case 203a includes a mid-infrared laser driving unit 20 as shown in detail in the circuit block diagram of FIG. A near infrared laser drive unit 21 is mounted. Electrical signals are sent from the mid-infrared laser driving unit 20 and the near-infrared laser driving unit 21 to the mid-infrared laser light-emitting unit 7 and the near-infrared laser light-emitting unit 8, and the mid-infrared laser light-emitting unit 7 outputs the mid-red light. The outside laser light and the near infrared laser light are emitted from the near infrared laser light emitting unit 8.

Here, the mid-infrared laser element 7 is an element such as a quantum cascade laser that emits mid-infrared laser light having a wavelength of 3 to 10 μm in the mid-infrared region including the light absorption spectrum of the measurement target gas. As described above, the laser drive unit 20 generates a laser drive signal that sweeps the wavelength of the mid-infrared region, and causes the mid-infrared laser emission unit 7 to emit light.
On the other hand, the near-infrared laser light emitting unit 8 does not include the light absorption spectrum of the measurement target gas, but includes a light absorption spectrum of water existing in the flue interior 1 (measurement target space) at a wavelength of 0.7 in the near infrared region. This is an element such as a semiconductor laser that emits a near-infrared laser beam of ˜3 μm, and the near-infrared laser drive unit 21 generates a laser drive signal that sweeps the wavelength in the near-infrared region to generate near-red The outer laser element 8 is caused to emit light.

The emitted light from the mid-infrared laser light emitting unit 7 is collimated by the concave mirror 10 serving as the mid-infrared laser optical unit of the present invention to become parallel light, passes through the center of the light emitting unit flange 201a, and the mid-infrared laser light 2 As shown in FIG. The mid-infrared laser beam 2 is affected by light absorption by the measurement target gas existing in the flue interior 1.
The light emitted from the near-infrared laser light-emitting unit 8 is converted into parallel light by the lens 9 and becomes the near-infrared laser light 17 from the opening 11 formed near the central portion of the concave mirror 10 to the light-emitting unit flange 201a. It irradiates the flue interior 1 through the center. In addition, the lens 9 and the opening part 11 comprise the near-infrared laser optical part of this invention.
As described above, the near-infrared laser beam 17 is emitted coaxially inside the mid-infrared laser beam 2, and this near-infrared laser beam 17 is simultaneously with the measurement target gas inside the flue 1. It is affected by light absorption by existing water.

On the other hand, the light receiving unit casing 203b is attached to the light receiving unit flange 201b. The mid-infrared laser beam 2 that has passed through the flue interior 1 is collected by the concave mirror 15 that is airtightly arranged inside the light receiving unit housing 203 b and received by the mid-infrared light receiving element 12. The concave mirror 15 and the mid-infrared light receiving element 12 constitute a mid-infrared light receiving unit of the present invention.
The mid-infrared light receiving element 12 is an MCT (Mercury Cadmium Tellurium) photoconductive element having sensitivity to wavelengths in the mid-infrared region, and the output signal of the mid-infrared light receiving element 12 is a light-receiving unit circuit in the light-receiving unit case 5 Amplified by a processing circuit in the gas concentration calculation unit mounted on the substrate 6, a signal change component due to light absorption of the measurement target gas is extracted and obtained as a gas concentration signal.

The near-infrared laser beam 17 is condensed by the lens 14 through the opening 16 formed near the center of the concave mirror 15 and received by the near-infrared light receiving element 13. In addition, the opening part 16, the lens 14, and the near-infrared light receiving element 13 comprise the near-infrared light-receiving part of this invention.
The near-infrared light receiving element 13 is an element such as a photodiode having sensitivity to wavelengths in the near-infrared region, and an output signal from the near-infrared light receiving element 13 is output from the moisture concentration correction unit 26 of the light-receiving unit circuit board 6. Amplified by a signal processing circuit, a signal change component due to light absorption of water is extracted and obtained as a moisture concentration signal.

Now, the measurement target gas in the present embodiment is a gas such as SO ₂ , NO, NO ₂ having a light absorption spectrum at a wavelength in the mid-infrared region, and hereinafter, the operation when the measurement target gas is SO _2. Will be explained.
As described above, the light absorption spectrum of SO ₂ is as shown in FIG. 25, and the wavelength of the laser light emitted from the mid-infrared laser element 7 is selected based on this light absorption spectrum. The gas concentration calculation unit 21 in the light-receiving unit circuit board 6 extracts and amplifies the absorption component due to SO ₂ from the output signal (mid-infrared light receiving signal) of the mid-infrared light receiving element 12 by receiving the mid-infrared laser light 2. Then, the SO ₂ concentration is calculated. Since the method for obtaining the gas concentration is the same as the method described in the first embodiment (the method described in Patent Document 2), detailed description thereof is omitted.

The problem here is the presence of the light absorption spectrum of water as described above, and this light absorption spectrum is widely distributed in the mid-infrared region as shown in FIG.
When water is present in the measurement target space, light absorption by SO ₂ interferes with light absorption by water, so that it is difficult to accurately measure the SO ₂ concentration. In order to eliminate the influence of light absorption by water, it is conceivable to compare the light absorption spectrum of water and the light absorption spectrum of SO ₂ and select a wavelength at which the light absorption spectrum of water does not exist as much as possible. According to this countermeasure, it is possible to cope with a certain level of water concentration. For example, in a high concentration environment where the water concentration is 10 vol% (volume concentration) or more, light absorption by water is very strong, and SO ₂ that is a measurement object Since the measured value decreases, the SO ₂ concentration cannot be measured with high accuracy. Therefore, in order to accurately measure the SO ₂ concentration, it is necessary to correct the SO ₂ concentration in response to the moisture concentration.

For this reason, in the present embodiment, the moisture concentration is measured in a wavelength region where the light absorption spectrum due to SO ₂ does not exist, and the measured value of the SO ₂ concentration is corrected using this moisture concentration. This correction process is realized by the gas concentration correction unit 26 mounted on the light receiving unit circuit board 6.
Hereinafter, this correction method will be described in detail.

The light absorption spectrum of water exists in the near infrared region in addition to the mid infrared region. The light absorption spectrum of water in the wavelength region of 1.3 to 1.5 μm is shown in FIG.
On the other hand, the light absorption spectrum of SO ₂ does not exist in the near infrared region of 2 μm or less.
Therefore, for example, a semiconductor laser element that emits laser light having a wavelength of 1.3 μm is selected as the near-infrared laser element 8 for measuring the moisture concentration. The moisture concentration calculation unit 25 in the light receiving unit circuit board 6 extracts and amplifies an absorption component due to water from the output signal (near infrared light reception signal) of the near infrared light receiving element 13 receiving the near infrared laser beam. Calculate moisture concentration. As shown in FIG. 7, the moisture concentration calculation unit 25 has the same configuration as the gas concentration calculation unit 22, and includes an I / V conversion unit 22a, a synchronous detection unit 22b, an oscillator 22c, a filter 22d, A calculation unit 22e is provided. And the density | concentration of a water molecule is calculated by the frequency modulation system similar to the gas light quantity reduction | decrease amount detection part 22. FIG.

Based on the water concentration thus obtained, the previously determined SO ₂ concentration measurement value is corrected.
As this correction method, it is possible to measure in advance how much the gas concentration measurement value decreases according to the moisture concentration in the measurement target space, so the known gas concentration measurement value decrease amount according to the light amount decrease amount due to the moisture concentration Is used to correct the previously obtained gas concentration measurement value. The amount of light reduction due to moisture concentration can be calculated by the same method as the amount of light reduction due to dust.

  Specifically, when the received light signal shown in FIGS. 9 and 10 is input to the filter 22d of the moisture concentration calculator 25 to extract the wavelength scanning drive signal component, waveforms as shown in FIGS. 13 and 14 are obtained. FIG. 13 shows a case where there is no moisture and the amount of received light is not reduced, and FIG. 14 shows a case where there is moisture and the amount of received light is reduced.

As shown in FIG. 13, at a certain point in time, the level P _max of the received light signal when there is no moisture and the received light amount is maximum is preset in the calculation unit 22 e as the received light amount setting value. The computing unit 22e detects the received light signal level Ps when there is moisture as shown in FIG. 14, and calculates the ratio of this Ps to P _max at the same time as the received light amount correction coefficient γ using Equation 6.

[Equation 6]
γ = P _max / P _s

The moisture concentration calculator 25 outputs the received light amount correction coefficient γ to the gas concentration corrector 26. Gas density correction unit 26, the received light quantity correction coefficient gamma, by multiplying or dividing the amplitude w of the gas absorption waveform, as shown in Equation 7, the amplitude w _h corrected for variation in the received light amount due to moisture Can be obtained.

[Equation 7]
Measurement target gas concentration (after correction) = γ x Measurement target gas concentration (before correction)
= P _max / P _s × Measurement gas concentration (before correction)

  Then, it is expressed by the following formula by Equation 1.

[Equation 8]
Gas concentration to be measured (after correction) = α _A × G _A × W _A × P _max / P _s

  As described above, according to this embodiment, even when moisture is present at a high concentration in a measurement target space such as the inside of a flue, the gas concentration measurement value is obtained by measuring the moisture concentration using the near-infrared laser beam 17. Therefore, the concentration of the measurement target gas can be measured with high accuracy.

In this embodiment, the near-infrared laser beam 17 passes coaxially through the inside of the mid-infrared laser beam 2, but the arrangement of the mid-infrared laser device 7 and the near-infrared laser device 8 is reversed. By doing so, the mid-infrared laser beam 2 may pass coaxially through the inside of the near-infrared laser beam 17.
The present invention is not limited to the above-described embodiment other than the arrangement of these laser elements 7 and 8, and includes many more modifications without departing from the essence thereof.

Now, in the first embodiment employs a wavelength other than the absorption line of the gas for measurement corrects dust, also, the wavelength of moisture absorption lines with the second embodiment is a wavelength other than the absorption line of the gas for measurement Was used to compensate for moisture. However, when there are both dust and moisture in the environment, a correction that takes both into account is necessary. Therefore, considering the second embodiment, moisture is taken into consideration, but at this time, detection is also influenced by scattering by dust. That is, the moisture concentration calculation unit 25 also performs the light amount decrease detection.
In such a second embodiment, it is possible to perform accurate detection without the influence of dust and moisture.

Laser Shikiga scan analyzer of the present invention is optimal boiler, as combustion exhaust gas measurement, such as waste incineration. In addition, gas analysis for steel [blast furnace, converter, heat treatment furnace, sintering (pellet equipment), coke oven], fruit and vegetable storage and ripening, biochemistry (microorganism) [fermentation], air pollution [incinerator, flue gas desulfurization / Denitration], automobile exhaust gas (remove tester), disaster prevention [explosive gas detection, toxic gas detection, new building material combustion gas analysis], plant growth, chemical analysis [oil refinery plant, petrochemical plant, gas generation plant], It is also useful as an analyzer for environmental [landing concentration, tunnel concentration, parking lot, building management], and various physics and chemistry experiments.

1: Inside the flue (measurement target space)
2: Mid-infrared laser beam 3: Light-emitting part case 4: Light-emitting part circuit board 5: Light-receiving part case 6: Light-receiving part circuit board 7: Mid-infrared laser light-emitting part 7a: Mid-infrared laser element 7b: Temperature detection part ( Thermistor)
7c: Temperature control unit (Peltier element)
8: Near-infrared laser light emitting part 8a: Near-infrared laser element 9, 14: Lens 10, 15: Concave mirror 11, 16: Aperture 12: Mid-infrared light receiving element 13: Near-infrared light receiving element 17: Near-red light Outside laser light 18, 19: Window 20: Mid-infrared laser drive unit 20a: Wavelength scanning drive signal generation unit 20b: High frequency modulation signal generation unit 20c: Laser drive signal generation unit 20d: Temperature control unit 21: Near infrared laser drive Unit 22: Gas concentration calculation unit 23: Light quantity reduction amount detection unit 24: Gas concentration correction unit 25: Water concentration calculation unit 26: Gas concentration correction unit 101a, 101b: Flue wall 201a: Light emitting unit flange 201b: Light receiving unit flange 203a : Light emitting unit housing 203b: Light receiving unit housing

Claims (4)

A mid-infrared laser emitting section that emits laser light having a wavelength in the mid-infrared region including the light absorption spectrum of the gas to be measured;
A mid-infrared laser driving section for driving the mid-infrared laser emitting section;
A mid-infrared laser optical unit that collimates the laser light emitted from the mid-infrared laser emission unit and irradiates the measurement target space where the measurement target gas exists; and
A mid-infrared light receiving unit that receives the laser light emitted from the mid-infrared laser optical unit and outputs it as an electrical mid-infrared light reception signal;
A gas concentration calculation unit that extracts a signal component affected by light absorption by the measurement target gas from the mid-infrared light reception signal, and calculates a measurement target gas concentration from a change amount of the signal component;
In a laser gas analyzer having
A near-infrared laser emitting section that emits laser light having a wavelength in the near-infrared region that does not include at least the light absorption spectrum of the gas to be measured;
A near infrared laser driving section for driving the near infrared laser emitting section;
A near-infrared laser optical unit that collimates the laser light emitted from the near-infrared laser light emitting unit and irradiates the space to be measured;
A near-infrared light receiving unit that receives the laser light emitted from the near-infrared laser optical unit and outputs it as an electrical near-infrared light reception signal;
A reduction in the amount of light detection unit that detects a reduction in the amount of light due to the dust of the space from the near-infrared light receiving optical signals,
A gas concentration correction unit that corrects the concentration measurement value of the measurement target gas obtained by the gas concentration calculation unit using the light amount reduction amount obtained by the light amount reduction amount detection unit;
A laser gas analyzer characterized by comprising: A mid-infrared laser emitting section that emits laser light having a wavelength in the mid-infrared region including the light absorption spectrum of the gas to be measured;
A mid-infrared laser driving section for driving the mid-infrared laser emitting section;
A mid-infrared laser optical unit that collimates the laser light emitted from the mid-infrared laser emission unit and irradiates the measurement target space where the measurement target gas exists; and
A mid-infrared light receiving unit that receives the laser light emitted from the mid-infrared laser optical unit and outputs it as an electrical mid-infrared light reception signal;
A gas concentration calculation unit that extracts a signal component affected by light absorption by the measurement target gas from the mid-infrared light reception signal, and calculates a measurement target gas concentration from a change amount of the signal component;
In a laser gas analyzer having
A near-infrared laser emitting section that emits laser light having a wavelength in the near-infrared region that does not include the light absorption spectrum of the measurement target gas and includes the light absorption spectrum of water present in the measurement target space;
A near infrared laser driving section for driving the near infrared laser emitting section;
A near-infrared laser optical unit that collimates the laser light emitted from the near-infrared laser light emitting unit and irradiates the space to be measured;
A near-infrared light receiving unit that receives the laser light emitted from the near-infrared laser optical unit and outputs it as an electrical near-infrared light reception signal;
A moisture concentration calculation unit that extracts a signal component affected by light absorption by water existing in the measurement target region from the near-infrared light reception signal, and calculates a light amount reduction amount corresponding to the moisture concentration from the change amount of the signal component When,
A gas concentration correction unit that corrects the concentration measurement value of the measurement target gas obtained by the gas concentration calculation unit using a light amount reduction amount corresponding to the water concentration obtained by the moisture concentration calculation unit;
A laser gas analyzer characterized by comprising: The laser gas analyzer according to claim 2, wherein
Water concentration calculation unit, have rows together reduction in the amount of light detected by the dust, the laser gas analyzer and correcting with reduction in the amount of light corresponding to the reduction in the amount of light and water content by dust. In the laser type gas analyzer according to any one of claims 1 to 3,
The wavelength of the laser beam in the mid-infrared region emitted from the mid-infrared laser emission unit is 3 to 10 μm, and the wavelength of the laser beam in the near-infrared region emitted from the near-infrared laser emission unit is 0. A laser type gas analyzer characterized by being 7 to 3 μm.

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