JP2016085073A - Laser type analysis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser type analysis device with which it is possible to create an appropriate reference line I(t).SOLUTION: Provided is a laser type analysis device 1 including an arithmetic unit 61a for calculating specific component amount information on the basis of the received light intensity value change I (t) of measurement light in a prescribed wavelength range of an n'th cycle and the reference intensity value change I(t) of the measurement light in the prescribed wavelength range of the n'th cycle that is assumed to have passed through a sample S to be measured that does not include a specific component, the analysis device further including a storage unit 62 for storing a reference intensity value creation map [MAP(P',P)=I] indicating relationship between a combination of an emission intensity value P and the first-order differential value P' of the emission intensity value P and a reference intensity value I, the arithmetic unit 61a finding the emission intensity value P and the first-order differential value P' from an emission intensity value change P (t) detected by a detection unit 10b, applying the emission intensity value P and the first-order differential value P' to the reference intensity value creation map [MAP(P',P)=I], and creating a reference intensity value change I(t).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a laser-type analyzer that measures information on specific component amounts using laser absorption spectroscopy, and in particular, in a vacuum region, in a flue, in a combustion process, in a vehicle measurement target gas, or in a fuel cell in a semiconductor manufacturing apparatus. The present invention relates to a laser-type gas analyzer that measures specific gas amount information in a flow path or the like.

  As one of the methods for measuring the amount of water vapor (specific component amount information) in the measurement target gas, absorption spectroscopy using the fact that water molecules absorb only light in a specific wavelength region (for example, 1.3 μm band) is used. Can be mentioned. Since this absorption spectroscopy can be measured without contact with the measurement target gas, the amount of water vapor in the measurement target gas can be measured without disturbing the field of the measurement target gas.

  Among such absorption spectroscopy, in particular, “tunable wavelength semiconductor laser absorption spectroscopy” using a tunable semiconductor laser (laser element) as a light source can be realized with a simple apparatus configuration. For example, in a laser-type gas analyzer using "tunable semiconductor laser absorption spectroscopy", an incident optical window and an emission optical window formed in a pipe with respect to a pipe in which a measurement target gas flows in a predetermined direction It is common to add a wavelength tunable semiconductor laser and a light detection sensor (light receiving part) provided to face each other so that an optical path (optical path length L) is formed across the pipe via ( For example, see Patent Literature 1 and Patent Literature 2).

According to such a laser type gas analyzer, laser light (measurement light) of a predetermined wavelength oscillated from a wavelength tunable semiconductor laser shields water molecules present in the measurement target gas while passing through the pipe. The laser beam is prevented from advancing, and the amount of light (light intensity value) incident on the photodetection sensor decreases corresponding to the concentration of water molecules in the gas to be measured. The concentration of water molecules is calculated by measuring the amount of laser light incident on the light detection sensor with respect to the amount of laser light. FIG. 9 is a graph showing an example of an absorption spectrum obtained by a laser gas analyzer. The vertical axis represents the received light intensity value I, and the horizontal axis represents the frequency ν. Note that I ₀ (ν) is a change in received light intensity value when water molecules are not absorbed at the frequency ν, and an approximate polynomial (reference line) is created based on the change in the received light intensity value of the non-absorption wavelength. It is derived by curve fitting.

  Here, an example of arithmetic processing using the absorption spectrum shown in FIG. 9 will be described. From Lambert-Beer's law, the following formula (1) holds.

Here, I ₀ (ν) is a change in light intensity value when water molecules are not absorbed at the frequency ν, I (ν) is a change in transmitted light intensity value (change in received light intensity value) at the frequency ν, and c (mol / cm ³ ) is the number density of water molecules, L (cm) is the length of the optical path passing through the gas to be measured, and S (T) (cm ⁻¹ / (mol / cm ⁻² )) is a predetermined absorption line intensity. It is a function of the gas temperature T.

Here, FIG. 10 is a graph in which the vertical axis is ln (I ₀ (ν ₀ ) / I (ν ₀ )) and the horizontal axis is the frequency ν. Therefore, the value on the left side of Equation (1) can be obtained by determining the area of the graph shown in FIG. As an example of a method for obtaining the area of the graph of FIG. 10, rectangular approximation is taken as an example, and the left side of Equation (1) can be transformed as shown in Equation (2) below.

Note that ν _max is the upper frequency limit of the absorption band (absorption peak), ν _min is the lower frequency limit of the absorption band, and n is the number of measurement points per waveform.

  On the other hand, the following equation (3) holds for S (T) on the right side of equation (1).

S ₀ is the line intensity in the standard state, Q (T) is a partition function, B (T) is a Boltzmann factor, and SE (T) is a correction formula for stimulated emission.
Furthermore, Q (T), B (T), and SE (T) on the right side of Expression (3) can be expressed as the following Expressions (4), (5), and (6), respectively.

Note that S ₀ , constants a to d, and E ₁ can be obtained from the HITRAN database or the like. Therefore, if the gas temperature value T and the light intensity value changes I (ν), I ₀ (ν) can be obtained, the number density c of water molecules can be calculated.

Here, FIG. 11 is a schematic configuration diagram showing an example of a laser type gas analyzer using wavelength tunable semiconductor laser absorption spectroscopy. One direction horizontal to the ground is defined as an X direction, a direction horizontal to the ground and perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the X direction and the Y direction is defined as a Z direction.
The laser gas analyzer 201 includes a light source unit (semiconductor laser module) 210, a laser light receiving unit 20, a laser control unit 250 that controls the light source unit 210, and a control unit 260 configured by a microcomputer or a PC. .

  Such a laser gas analyzer 201 is used to measure the amount of water vapor in the measurement target gas S flowing in the sample flow path 70 connected to each line of supply and exhaust to the combustion process. The sample flow path 70 extends in the Z direction, and on the side wall of the sample flow path 70, there are an incident optical window 71, and an emission optical window 72 facing the incident optical window 71 with a distance L1 in the X direction. Is formed. The measurement target gas S flows in the Z direction in the sample flow path 70.

The light source unit 210 includes a semiconductor laser (for example, a distributed feedback (DFB) semiconductor laser diode for optical communication) 10a that emits laser light, and a power monitor 10b that detects a light intensity value (power monitor signal). And a beam splitter 10c that splits the laser light in two directions, for example, a butterfly module or a TO-CAN type module.
In such a configuration of the light source unit 210, the laser light oscillated by the semiconductor laser 10a is divided into two directions by the beam splitter 10c. One of the two directions in which the laser beam split by the beam splitter 10c travels enters the sample channel 70 from the incident optical window 71 in the X direction and irradiates the measurement target gas S. It has come to be. On the other hand, the light intensity value (power monitor signal) of the remaining one of the two directions in which the laser beam split by the beam splitter 10c travels is determined by the power monitor 10b at a predetermined sampling interval (for example, 1 MHz, It is detected at intervals of 0.001 milliseconds.

  Further, when such a light source unit 210 is used for continuous monitoring of the amount of water vapor, a drive current value applied to the semiconductor laser 10a is changed at a predetermined period, specifically, a drive current value having a sawtooth shape is applied. As a result, laser light in a predetermined wavelength range is oscillated at a predetermined period. FIG. 12 is a conceptual diagram showing the relationship between the drive current value and the oscillation wavelength of the laser beam, and FIG. 12A is a waveform diagram showing the drive current value applied to the semiconductor laser 10a. b) is a waveform diagram showing the oscillation wavelength of the laser beam oscillated from the semiconductor laser 10a to which the drive current value is applied. The waveform of the drive current value shown in FIG. 12A is input by a measurer or the like at the start of continuous monitoring or stored in advance, and the laser control unit 250 transmits a D / A to the light source unit 210 as a laser control signal. The signal is output via the converter 80.

  The laser light receiving unit 20 may be anything as long as it can convert light intensity into an electric signal. For example, a photodiode is used. The laser light receiving unit 20 is disposed so as to receive the laser light emitted in the X direction from the emission optical window 72 to the outside of the sample flow path 70, and the light reception intensity value of the laser light that has passed through the measurement target gas S. I is received.

Then, the received light intensity value I of the laser beam is converted into a digital value by the A / D converter 81 at a predetermined sampling interval (for example, 1 MHz, 0.001 millisecond interval), and the calculation unit 261 has the center wavelength of the absorption peak in each cycle. A reference intensity value is obtained by obtaining a received light intensity value change I (t) including a received light intensity value change of a portion of the laser light and a received light intensity value change of the laser light of the non-absorption wavelength portion on both sides of the central wavelength portion. A change (reference line) I ₀ (t) is created. Thereafter, the calculation unit 261 applies the generated reference intensity value change I ₀ (t) and the received light intensity value change I (t) detected by the laser light receiving unit 20 to the expressions (1) and (2). The number density c is obtained.

JP 2010-237075 A JP 2012-237636 A

By the way, in the laser type gas analyzer 201 as described above, when the reference line I ₀ (t) is created, an absorption line (absorption peak of water molecule) is generated due to a large change in the state (pressure, temperature, etc.) of the measurement target gas. ) The width increases and the non-absorption wavelength portion decreases, and the accuracy of the polynomial approximation may decrease.
Further, in order to create the reference line I ₀ (t), a method of using the power monitor signal detected by the power monitor 10b in the light source unit (semiconductor laser module) 210 as it is via the A / D converter 82, There is a method of using a light reception signal by providing a reference optical path that passes through the reference gas. However, even if the power monitor 10b and the reference optical path are provided, distortion and signal rounding are caused by many nonlinear elements and the like. It is sometimes difficult to use the generated power monitor signal and the received light signal as a reference signal (reference intensity value I ₀ ). That is, since many of the circuits and photodiodes that receive laser light are composed of non-linear elements, it is impossible to analyze and create the reference line I ₀ (t) from the actually obtained power monitor signal or light reception signal. It was difficult.

In view of the above, the present applicant has studied a method of creating an appropriate reference line I ₀ (t). Further, since a power monitor signal (output intensity value) P and a light reception signal (light reception intensity value) I detected by the laser light receiving unit 20 pass through a non-linear element or circuit, it is difficult to perform a prior analysis. Since there is some relationship, the power monitor signal P and the light reception signal I having various values are obtained in a state where there is no influence of water vapor in the measurement target gas, and the light reception signal I and the power monitor signal P are obtained. It has been found that the above relationship is created in advance as a reference signal creation map [MAP (P ′, P) = I ₀ ].

That is, the laser analyzer of the present invention has a light source unit having a laser element that irradiates measurement light to a measurement target sample, and a drive current value applied to the laser element in a predetermined cycle, thereby changing the wavelength range. A laser control unit that oscillates measurement light from a laser element at a predetermined period, a light reception unit that detects a light reception intensity value I of the measurement light that has passed through the measurement target sample at a predetermined sampling interval, and an emission intensity value P of the measurement light. A detection unit that detects at a predetermined sampling interval, a received light intensity value change I (t) of measurement light in a predetermined wavelength range of the nth cycle, and an nth cycle that is assumed to have passed through a measurement target sample that does not contain a specific component. A laser-type analyzer that includes a calculation unit that calculates specific component amount information based on a reference intensity value change I ₀ (t) of measurement light in a predetermined wavelength range, and includes an emission intensity value P and an emission intensity value P 1 of Differential value P 'and the combination of the reference intensity value creation map showing the relationship between the reference intensity value _{I 0 [MAP (P',} P) = 0] includes a storage unit for storing the arithmetic unit, The emission intensity value P and the first-order differential value P ′ are obtained from the emission intensity value change P (t) detected by the detection unit, and the emission intensity value P and the first-order differential value P ′ are obtained as the reference intensity value creation map. By applying [MAP (P ′, P) = I ₀ ], the reference intensity value change I ₀ (t) is created.

Here, the “predetermined period” is an arbitrary time determined by a measurer or the like. For example, in order to oscillate measurement light in a predetermined wavelength range from the laser element, the frequency becomes, for example, several tens Hz to several tens kHz. Can be mentioned. Further, the “predetermined sampling interval” is an arbitrary time (predetermined data acquisition interval) determined by a measurer or the like, which is shorter than a predetermined cycle and requires several hundred data points in one sweep. It is several MHz, and 1 MHz is exemplified.
Furthermore, the “specific component” is an arbitrary component determined by a measurer, for example, water vapor, carbon dioxide, carbon monoxide, or the like.

As described above, according to the laser analyzer of the present invention, even when the absorption line (absorption peak of a specific component) is widened, the emission intensity value change P (t) is represented by the reference intensity value creation map [MAP (P By fitting to ', P) = I ₀ ], an appropriate reference line I ₀ (t) can be created. Further, an appropriate reference line I ₀ (t) can be created even if the slope or height of the waveform of the drive current value is varied in accordance with the absorption of the specific component during measurement.

(Means and effects for solving other problems)
In the above invention, the light source unit may include a power monitor as the detection unit.

  Further, in the above invention, the measurement unit includes a measurement beam splitting unit that splits the split measurement beam to be irradiated onto the measurement target sample and the reference beam to be irradiated onto the reference sample that does not contain the specific component, and the detection unit has an emission intensity value The intensity value of the reference light that has passed through the reference sample may be detected as P.

In the above invention, the reference intensity value creation map [MAP (P ′, P) = I ₀ ] may be created using a measurement target sample that does not contain the specific component. .

Further, in the above invention, the reference intensity value creation map [MAP (P ′, P) = I ₀ ] is such that the absolute value of the second-order differential value P ″ of the emission intensity value P is equal to or less than a predetermined threshold value. It may be made by using.
According to the laser type analyzer of the present invention, when the change amount of the emission intensity value P is large, nonlinear features such as circuits and elements appear greatly, so the reference line I ₀ (t) is created. Therefore, the reference intensity value creation map [MAP (P ′, P) = I ₀ ] is used for a portion where the absolute value of the second-order differential value P ″ of the emission intensity value P is equal to or greater than a predetermined threshold value. Is not reflected in. Note that a portion where the absolute value of the second-order differential value P ″ of the emission intensity value P is equal to or greater than a predetermined threshold is not used for measurement, and can be ignored.

The schematic block diagram which shows an example of the laser type gas analyzer of 1st embodiment. Reference intensity value creation map [MAP (P ', P) = 0] table showing an example of. The graph which shows an example of output intensity value change P (t), 1st-order differential value change P '(t), and 2nd-order differential value change P' '(t). The elements on larger scale of FIG. The elements on larger scale of FIG. The elements on larger scale of FIG. The schematic block diagram which shows an example of the laser type gas analyzer of 2nd embodiment. The conceptual diagram which shows the relationship between a drive current value and an absorption spectrum. The graph which shows an example of the absorption spectrum obtained with the laser type gas analyzer. A graph in which the vertical axis is ln (I ₀ (ν ₀ ) / I (ν ₀ )) and the horizontal axis is frequency ν. The schematic block diagram which shows an example of the laser type gas analyzer using a wavelength-tunable semiconductor laser absorption spectroscopy. The conceptual diagram which shows the relationship between a drive current value and the oscillation wavelength of a laser beam.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and it goes without saying that various aspects are included without departing from the spirit of the present invention.

<First embodiment>
FIG. 1 is a schematic configuration diagram showing an example of a laser gas analyzer according to the first embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the thing similar to the conventional laser type gas analyzer 201 mentioned above.
The laser gas analyzer 1 includes a light source unit (semiconductor laser module) 10, a laser light receiving unit 20, a laser control unit 50 that controls the light source unit 10, and a control unit 60 that includes a microcomputer or a PC. .

When the “input signal for measuring the amount of water vapor” is input, the laser control unit 50 has a laser control signal having a waveform of a drive current value having a predetermined inclination and height as shown in FIG. Is converted into a digital value by the D / A converter 80 and applied to the semiconductor laser 10 a of the light source unit 10.
Further, when the “input signal for creating the reference intensity value creation map [MAP (P ′, P) = I ₀ ]” is input, the laser control unit 50 has drive currents having various inclinations and heights. A laser control signal having a value waveform is converted into a digital value by the D / A converter 80 and applied to the semiconductor laser 10 a of the light source unit 10. The laser control signal preferably covers a waveform of a drive current value that is considered to be actually output during measurement.

The control unit 60 includes a CPU 61, a memory 62, and an input device (not shown). Further, the function processed by the CPU 61 will be described as a block. The calculation unit 61a for calculating the amount of water vapor in the measurement target gas and the creation for creating the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. Part 61b. Further, the memory 62 includes a reference intensity value creation map storage area 62a for storing a reference intensity value creation map [MAP (P ′, P) = I ₀ ]. FIG. 2 is a table showing an example of the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. The vertical column indicates the emission intensity value P, and the horizontal column indicates the first-order differential value P ′ of the emission intensity value P.

When the “input signal for creating the reference intensity value creation map [MAP (P ′, P) = I ₀ ]” is input, the creation unit 61b receives the received light intensity value I detected by the laser light receiving unit 20. The output intensity value (power monitor signal) P detected by the power monitor (detection unit) 10b is converted into a digital value by the A / D converters 81 and 82 at a predetermined sampling interval (for example, 1 MHz), and a reference intensity value creation map [MAP (P ′, P) = I ₀ ] is created and stored in the reference intensity value creation map storage area 62a of the memory 62.
Here, FIG. 3A is a graph showing an example of the emission intensity value change P (t), and FIG. 3B is a first-order differential value change of the emission intensity value P shown in FIG. 3 is a graph of P ′ (t), and FIG. 3C is a graph of the second-order differential value change P ″ (t) of the emission intensity value P shown in FIG.

For example, a measurer or the like first causes a measurement target gas that does not contain water vapor to flow into the sample flow path 70. Then, the measurer or the like inputs “an input signal for creating a reference intensity value creation map [MAP (P ′, P) = I ₀ ]” using an input device. As a result, the laser control unit 50 applies laser control signals having waveforms of drive current values having various inclinations and heights to the semiconductor laser 10a.
As a result, when the emission intensity value P is detected as “120” and the first-order differential value P ′ is “0.06”, when the received light intensity value I is detected as “139”, the value is changed. Record in the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. Further, when the emission intensity value P is detected as “130” and the first-order differential value P ′ is “0.06”, when the received light intensity value I is detected as “148”, the value is used as a reference. Record in the intensity value creation map [MAP (P ′, P) = I ₀ ]. In this way, the information is sequentially recorded in the reference intensity value creation map [MAP (P ′, P) = I ₀ ].

When recording in the reference intensity value creation map [MAP (P ′, P) = I ₀ ], the second-order differential value P ″ is the absolute value of the threshold (a sufficiently small value, ideally 0). However, in practice, the output intensity value P and the first-order differential value P ′ that are less than or equal to the amount of change in which the non-linear operation by the configured elements or circuits is sufficiently negligible may be used. preferable. 4A to 4C are enlarged views of the numerical range 80 to 120 in FIGS. 3A to 3C, and FIGS. 5A to 5C are FIGS. It is an enlarged view of numerical range 480-520 in (c), and Drawing 6 (a)-(c) is an enlarged view of numerical range 880-920 in Drawing 3 (a)-(c).

When the “input signal for measuring the amount of water vapor” is input, the calculation unit 61a receives the received light intensity value I detected by the laser light receiving unit 20 and the emission intensity value detected by the power monitor 10b (power monitor signal). ) P is converted into a digital value by A / D converters 81 and 82 at a predetermined sampling interval (for example, 1 MHz), and applied to the reference intensity value creation map [MAP (P ′, P) = I ₀ ] in each cycle. Control to create a reference intensity value change (reference line) I ₀ (t) is performed.
For example, when a laser control signal having a waveform of a drive current value having a predetermined inclination and height as shown in FIG. 12A is applied to the semiconductor laser 10a by the laser control unit 50, the first sampling time. If the output intensity value P detected at 1 is “120” and the first-order differential value P ′ is “0.06”, the reference intensity value I _{0 at} the first sampling time is determined as the reference intensity value creation map [ MAP (P ′, P) = I ₀ ] is changed to “139”. Further, if the emission intensity value P detected at the second sampling time is “130” and the first-order differential value P ′ is “0.06”, the reference intensity value I _{0 at} the second sampling time is It becomes “148” from the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. Thus, the reference intensity value change I ₀ (t) is created by obtaining the reference intensity value I ₀ at each sampling time.
Thereafter, the calculation unit 61a applies the created reference intensity value change I ₀ (t) and the received light intensity value change I (t) detected by the laser light receiving unit 20 to the expressions (1) and (2). Control for obtaining the number density c is performed.

As described above, according to the laser gas analyzer 1 of the first embodiment, even when the absorption line (absorption peak of water molecule) width is widened, the emission intensity value change P (t) is used as the reference intensity value creation map. By applying [MAP (P ′, P) = I ₀ ], an appropriate reference line I ₀ (t) can be created.

<Second embodiment>
FIG. 7 is a schematic configuration diagram showing an example of a laser gas analyzer according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the thing similar to the laser type gas analyzer 1 mentioned above.
The laser type gas analyzer 101 includes a light source unit (semiconductor laser module) 110, a measurement beam splitting unit 15 that splits into split measurement beam and reference beam, a laser beam receiver 20, a reference beam receiver 21, and water vapor. Reference gas cell 90 filled with a standard gas (reference gas) not containing a light source, a laser control unit 150 that controls the light source unit 110, and a control unit 160 that includes a microcomputer or a PC.

The measurement light splitting unit 15 is, for example, a beam splitter that splits laser light in two directions, and split measurement light that irradiates the measurement target gas S by transmitting part of the laser light emitted from the semiconductor laser 10a. By reflecting the remainder of the laser light, it is divided into reference light that is not irradiated onto the measurement target gas S. The reference light is applied to the reference gas cell 90.
The reference light receiving unit (detecting unit) 21 may be anything as long as it can convert light intensity into an electrical signal. For example, a photodiode is used. The reference light receiving unit 21 receives the intensity P of the laser light (reference light) reflected in the Z direction by the measurement light dividing unit 15 and passed through the reference gas cell 90.

When the “input signal for measuring the water vapor amount” is input, the laser control unit 150 has a laser control signal that has a waveform of a drive current value having a predetermined inclination and height as shown in FIG. Is converted into a digital value by the D / A converter 80 and applied to the semiconductor laser 10a of the light source unit 110.
In addition, when the “input signal for creating the reference intensity value creation map [MAP (P ′, P) = I ₀ ]” is input, the laser control unit 150 has drive currents having various inclinations and heights. A laser control signal having a value waveform is converted into a digital value by a D / A converter and applied to the semiconductor laser 10 a of the light source unit 110.

The control unit 160 includes a CPU 161, a memory 162, and an input device (not shown). Further, the function processed by the CPU 161 will be described as a block. The calculation unit 161a that calculates the amount of water vapor in the measurement target gas and the creation that creates the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. Part 161b.

When the “input signal for creating the reference intensity value creation map [MAP (P ′, P) = I ₀ ]” is input, the creation unit 161b receives the received light intensity value I detected by the laser light receiving unit 20. The output intensity values (light reception signals) P detected by the reference light receiving unit 21 are converted into digital values by A / D converters 81 and 82 at a predetermined sampling interval (for example, 1 MHz), respectively, and a reference intensity value creation map [MAP ( P ′, P) = I ₀ ] is generated and stored in the memory 162.

For example, a measurer or the like first causes the measurement target gas S not containing water vapor to flow into the sample flow path 70. Then, the measurer or the like inputs “an input signal for creating a reference intensity value creation map [MAP (P ′, P) = I ₀ ]” using an input device. Accordingly, the laser control unit 150 applies a laser control signal having a waveform of drive current values having various inclinations and heights to the semiconductor laser 10a.
As a result, when the emission intensity value P is detected as “120” and the first-order differential value P ′ is “0.06”, when the received light intensity value I is detected as “139”, the value is changed. Record in the reference intensity value creation map [MAP (P ′, P) = I ₀ ]. Further, when the emission intensity value P is detected as “130” and the first-order differential value P ′ is “0.06”, when the received light intensity value I is detected as “148”, the value is used as a reference. Record in the intensity value creation map [MAP (P ′, P) = I ₀ ]. In this way, the information is sequentially recorded in the reference intensity value creation map [MAP (P ′, P) = I ₀ ].

When the “input signal for measuring the amount of water vapor” is input, the calculation unit 161a uses the received light intensity value I detected by the laser light receiving unit 20 and the emission intensity value P detected by the reference light receiving unit 21. The A / D converters 81 and 82 respectively convert the digital values into digital values at a predetermined sampling interval (for example, 1 MHz), and apply the reference intensity values to the reference intensity value creation map [MAP (P ′, P) = I ₀ ] in each cycle. Control to create the change I ₀ (t) is performed.
In the laser gas analyzer 101 of the second embodiment, since a constant driving current value is applied as shown in FIG. 8A at a predetermined time between cycles, it is in the optical path (optical path length L). At the start of measurement when the amount of light (light intensity value I) decreases as a whole as shown in FIG. 8B due to contamination of the lens (incident optical window 71, outgoing optical window 72, etc.), etc. Attenuation rate can be obtained by comparing with the amount of light (light intensity value I) during the period of the reference, and the reference obtained from the reference intensity value creation map [MAP (P ′, P) = I ₀ ] based on the attenuation rate. It corrects the intensity value _{I 0.} For example, if the attenuation rate is calculated as “10%”, the emission intensity value P detected at the first sampling time is “120”, and the first-order differential value P ′ is “0.06”, The reference intensity value I ₀ in one sampling time becomes “139” from the reference intensity value creation map [MAP (P ′, P) = I ₀ ], and further becomes “125 (= 139 × 90%)”. Further, if the emission intensity value P detected at the second sampling time is “130” and the first-order differential value P ′ is “0.06”, the reference intensity value I _{0 at} the second sampling time is From the reference intensity value creation map [MAP (P ′, P) = I ₀ ], “148” is obtained, and “133 (= 148 × 90%)” is obtained. Thus, the reference intensity value change I ₀ (t) is created by obtaining the reference intensity value I ₀ at each sampling time.
Thereafter, the calculation unit 161a applies the created reference intensity value change I ₀ (t) and the received light intensity value change I (t) detected by the laser light receiving unit 20 to the expressions (1) and (2). Control for obtaining the number density c is performed.

As described above, according to the laser gas analyzer 101 of the second embodiment, the emission intensity value change P (t) is used as the reference intensity value creation map even when the absorption line (absorption peak of water molecule) width is widened. By applying [MAP (P ′, P) = I ₀ ], an appropriate reference line I ₀ (t) can be created.

<Other embodiments>
(1) In the laser gas analyzer 1 described above, when an “input signal for measuring the amount of water vapor” is input, a drive current having a predetermined inclination and height as shown in FIG. Although the laser control signal having a waveform of the value is applied to the semiconductor laser 10a, the configuration may be such that the slope and height of the waveform of the drive current value are varied according to the absorbance of water molecules during the measurement. According to such a laser gas analyzer, an appropriate reference line I ₀ (t) can be created even if the slope or height of the waveform of the drive current value is varied depending on the absorbance of water molecules during measurement. Can do.

(2) Creation of the reference line I ₀ (t) by the reference intensity value creation map [MAP (P ′, P) = I ₀ ] and creation of the reference line I ₀ (t) by the conventional technique (polynomial approximation) It is good also as a structure which switches with depending on the case. According to such a laser gas analyzer, particularly when the absorption line (absorption peak of water molecule) is narrow, the reference line I ₀ (t) is created by a method using polynomial approximation, and the absorption line width is In the wide case, the reference line I ₀ (t) can be created by the method of the present invention.

  The present invention can be used in a laser type gas analyzer that measures specific gas amount information in a gas by using laser absorption spectroscopy.

DESCRIPTION OF SYMBOLS 1 Laser type gas analyzer 10 Light source part 10a Semiconductor laser (laser element)
10b Power monitor (detector)
20 laser light receiving unit 50 laser control unit 61a calculation unit 61b creation unit 62 memory (storage unit)

Claims (5)

A light source unit having a laser element that irradiates the measurement target sample with measurement light;
A laser controller that oscillates measurement light in a predetermined wavelength range from the laser element at a predetermined period by changing a drive current value applied to the laser element at a predetermined period;
A light receiving unit that detects a light receiving intensity value I of the measurement light that has passed through the measurement target sample at a predetermined sampling interval;
A detector for detecting the emission intensity value P of the measurement light at a predetermined sampling interval;
Change in received light intensity value I (t) of the measurement light in the predetermined wavelength range of the nth period and the reference intensity value of the measurement light in the predetermined wavelength range of the nth period that is assumed to have passed through the measurement target sample not containing the specific component A laser-type analyzer including a calculation unit that calculates specific component amount information based on the change I ₀ (t),
A reference intensity value creation map [MAP (P ′, P) = I ₀ ] indicating the relationship between the combination of the emission intensity value P and the first-order differential value P ′ of the emission intensity value P and the reference intensity value I ₀ A storage unit for storing,
The calculation unit obtains an emission intensity value P and a first-order differential value P ′ from the emission intensity value change P (t) detected by the detection unit, and calculates the emission intensity value P and the first-order differential value P ′. A laser-type analyzer characterized by creating a reference intensity value change I ₀ (t) by applying it to a reference intensity value creation map [MAP (P ′, P) = I ₀ ].   The laser-type analyzer according to claim 1, wherein the light source unit includes a power monitor as the detection unit. A measurement light dividing unit that divides the divided measurement light to be irradiated onto the measurement target sample and the reference light to be irradiated onto the reference sample that does not contain the specific component;
The laser analysis apparatus according to claim 1, wherein the detection unit detects an intensity value of reference light that has passed through the reference sample as an emission intensity value P. The reference intensity value creation map [MAP (P ′, P) = I ₀ ] is created using a measurement sample that does not contain the specific component. The laser analysis apparatus according to any one of the above. The reference intensity value creation map [MAP (P ′, P) = I ₀ ] is created using the map in which the absolute value of the second-order differential value P ″ of the emission intensity value P is equal to or less than a predetermined threshold value. The laser type analyzer according to claim 4, wherein the laser type analyzer is provided.