JP2009156815A - Gas concentration measurement device and gas concentration measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas concentration measurement device with a simplified device constitution and measuring even dilute gas with excellent sensitivity, and a gas concentration measurement method. <P>SOLUTION: This gas concentration measurement device includes for creating a signal for driving of a preset waveform, a laser diode section for oscillating a laser beam transmitting through a measuring object based on the signal for driving, a photodiode section for receiving the laser beam having transmitted through the measuring object and creating a received signal, a reference signal creating section for creating a reference signal of a waveform corresponding to the waveform of the signal for driving, a differential amplifying section for creating a differential amplifying signal based on the received signal and the reference signal, and a concentration calculation section for calculating the concentration of the object to be measured based on the differential amplifying signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas concentration measuring device and a gas concentration measuring method, and more particularly to a gas concentration measuring device and a gas concentration measuring method for measuring a gas concentration using a laser absorption method.

  It is known to use a laser absorption method to measure the concentration of exhaust gas or the like in a combustion plant or engine. In the laser absorption method, it is used that the gas has a specific absorption wavelength. When a gas is irradiated with laser light, the laser light is absorbed at an absorption wavelength unique to the gas, and the light intensity is reduced. The amount of light absorbed at the gas-specific absorption wavelength depends on the gas concentration. Therefore, the gas concentration can be measured based on the light intensity of the transmitted light at the absorption wavelength unique to the gas.

  In order to perform gas concentration measurement with high sensitivity, a gas measuring device is known that has both an optical path that transmits gas and an optical path that does not transmit gas. FIG. 1 is a schematic configuration diagram showing an example of such a gas measuring device. The gas measuring apparatus includes a waveform generation unit 101, an LD driver 102, a laser diode 103, a duplexer 104, photodiodes 106 and 107, and a detection unit 108. In this gas measurement device, the waveform generator 101 generates a drive signal having a waveform such that the wavelength of the laser light changes within a predetermined range, and supplies the drive signal to the LD driver 102. The LD driver 102 causes the laser diode 103 to emit light based on the driving signal. The laser beam from the laser diode 103 is divided into two by the duplexer 104. One laser beam passes through the measurement gas 105 and is received by the photodiode 106. The other laser beam is directly received by the photodiode 107 without passing through the gas to be measured 105. When the photodiode 106 receives the laser beam, the photodiode 106 generates a measurement signal. When the photodiode 107 receives the laser light, the photodiode 107 generates a reference signal. The detection unit 108 compares the measurement signal with the reference signal to obtain the amount of light absorbed by the gas to be measured, and calculates the concentration of the gas to be measured.

  As described above, examples of the gas concentration measuring device having a configuration in which the laser beam is divided into two include Patent Document 1 (Japanese Patent No. 3784473) and Patent Document 2 (Japanese Patent No. 3108420).

However, as in the example shown in FIG. 1, in order to divide one laser beam into two, it is necessary to prepare a duplexer, an optical path for reference light, a photodiode for reference light, and the like. This complicates the device configuration, increases the number of parts, and increases the device price. Moreover, since one light is divided into two, the light intensity is halved, which is disadvantageous when measuring a dilute gas.
Japanese Patent No. 3784473 Japanese Patent No. 3108420

  SUMMARY OF THE INVENTION An object of the present invention is to provide a gas concentration measuring device and a gas concentration measuring method that can simplify the apparatus configuration and can measure even a dilute gas with high sensitivity.

  In the following, means for solving the problem will be described using reference numerals with parentheses used in [Best Mode for Carrying Out the Invention]. These symbols are added to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention], and [Claims] It should not be used for the interpretation of the technical scope of the invention described in.

The gas concentration measuring apparatus according to the present invention includes a driving signal generation unit (11) that generates a driving signal having a preset waveform, and a laser that oscillates a laser beam that passes through the measurement target based on the driving signal. A diode section (12), a photodiode section (13) that receives a laser beam transmitted through the object to be measured and generates a received light signal, and a reference signal that generates a reference signal having a waveform corresponding to the waveform of the driving signal A generation unit (15), a differential amplification unit (30) for generating a differential amplification signal based on the light reception signal and the reference signal, and a concentration for calculating the concentration of the measurement target based on the differential amplification signal And a calculator (8). The optical path of the laser light from the laser diode section (12) to the photodiode section (13) is one optical path, which is an optical path that passes through the object to be measured.
According to this invention, the reference signal generation unit generates a reference signal having a waveform corresponding to the waveform of the driving signal. In generating the reference signal, it is not necessary to provide an optical path for the reference light separately from the optical path of the measurement light. Since it is not necessary to divide the measurement light into two, the light intensity of the measurement light is not halved.

  The drive signal has a waveform such that the laser beam is scanned in a wavelength region including both the first wavelength band where the absorption by the measurement target exists and the second wavelength band where the absorption by the measurement target does not exist. The reference signal generation unit (15) preferably generates the reference signal by interpolating a portion corresponding to the first wavelength band based on the received light signal corresponding to the second wavelength band.

  The reference signal generation unit (15) includes a received light signal corresponding to a wavelength shorter than the first wavelength band in the second wavelength band, and a wavelength longer than the first wavelength band in the second wavelength band. It is preferable to interpolate a portion corresponding to the first wavelength band based on the received light signal corresponding to.

  When the driving signal is a sawtooth wave, the reference signal generator (15) preferably interpolates a portion corresponding to the first wavelength band by linear interpolation.

  When the driving signal is a sine wave, the reference signal generator (15) preferably interpolates a portion corresponding to the first wavelength band so that the reference signal becomes a sine wave.

  When the correspondence relationship between the drive signal and the reference signal is set in advance in the reference signal generation unit (15), the drive signal generation unit (11) converts the drive signal into the reference signal generation unit (15). To notify. The reference signal generation unit (15) performs processing based on the correspondence relationship set for the notified drive signal, and generates a reference signal.

  A gas concentration measuring method according to the present invention includes a step of generating a driving signal having a preset waveform, a step of oscillating laser light that passes through the measurement target based on the driving signal, and a measurement target. Based on the steps of receiving the transmitted laser light and generating a light reception signal, generating a reference signal having a waveform corresponding to the waveform of the driving signal, and the light reception signal and the reference signal A step of generating an amplified signal; and a step of calculating a concentration of the measurement target based on the differential amplified signal.

  The drive signal is scanned such that the laser beam is scanned in a wavelength region including both a first wavelength band where absorption by the measurement target exists and a second wavelength band where absorption by the measurement target does not exist. And generating the reference signal includes generating the reference signal by interpolating a portion corresponding to the first wavelength band based on the received light signal corresponding to the second wavelength band. Preferably, the method includes the step of:

  The step of generating the reference signal includes a received light signal corresponding to a wavelength shorter than the first wavelength band in the second wavelength band, and longer than the first wavelength band in the second wavelength band. Preferably, the method includes a step of interpolating a portion corresponding to the first wavelength band based on the received light signal corresponding to the wavelength on the wavelength side.

  When the driving signal is a sawtooth wave, the step of generating the reference signal preferably includes a step of interpolating a portion corresponding to the first wavelength band by linear interpolation.

  When the driving signal is a sine wave, the step of generating the reference signal preferably includes a step of interpolating a portion corresponding to the first wavelength band so that the reference signal becomes a sine wave.

  When the method includes the step of setting a correspondence relationship between the driving signal and the reference signal in advance, the step of generating the reference signal processes the driving signal based on the correspondence relationship, Preferably, the method includes the step of generating

  ADVANTAGE OF THE INVENTION According to this invention, the apparatus structure is simplified and the gas concentration measuring device and the gas concentration measuring method which can measure with a sufficient sensitivity also with a rare gas are provided.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram showing a gas concentration measuring system using the gas concentration measuring apparatus 10 according to the present embodiment. This gas concentration measurement system includes a measurement probe portion 20 and a gas concentration measurement device 10. This gas concentration measurement system is configured to measure the concentration of the gas to be measured in the exhaust pipe.

  The measurement probe portion 20 includes a measurement probe 21 in which a collimating lens 22 and a condenser lens 23 are housed, and a mirror 25. The collimating lens 22 and the condenser lens 23 are connected to the gas concentration measuring apparatus 10 via a fiber cable. The collimating lens 22 is disposed so as to emit the laser beam sent from the gas concentration measuring device 10 into the exhaust pipe. The mirror 25 is arranged so as to reflect the laser beam emitted from the collimator lens 22 and passed through the exhaust pipe toward the condenser lens 23. The condensing lens 23 is disposed so as to guide the laser beam reflected by the mirror 25 to the gas concentration measuring device 10 via a fiber cable.

  The laser light from the gas concentration measuring device 10 is guided to the gas concentration measuring device 10 again through one optical path that passes through the gas to be measured in the exhaust pipe.

The gas concentration measuring device 10 is a device that measures the concentration of a specific component of gas in the exhaust pipe. Examples of the gas component to be measured of the gas concentration measuring apparatus 10 include CO, CO ₂ , and NOx. The gas to be measured has a specific absorption wavelength. In the following description, the absorption wavelength band unique to the gas to be measured will be described as the first wavelength band. In addition, a wavelength band that is not absorbed by the gas to be measured is referred to as a second wavelength band.

  Schematically, the gas concentration measurement device 10 oscillates laser light in a wavelength range including the first wavelength band and supplies the laser beam to the measurement probe portion 20. Then, the gas concentration is measured by receiving laser light transmitted through the measurement gas from the measurement probe portion 20 and measuring the amount of absorption in the first wavelength band. A reference signal is used to accurately determine the amount of absorption in the first wavelength band. The reference signal is a signal that simulates the case where the gas to be measured is not transmitted. A signal (light reception signal) by a laser beam that actually passes through the gas to be measured is compared with a reference signal, and an absorption amount in the first wavelength band is obtained.

  Below, the structure of the gas concentration measuring apparatus 10 is demonstrated in detail.

  The gas concentration measuring apparatus 10 includes a signal generation circuit 11 that generates a driving signal, a laser diode unit 12 that oscillates a laser beam that is scanned in a predetermined wavelength range based on the driving signal, and a laser that transmits the gas to be measured. Photodiode unit 13 that receives light and generates a light reception signal, reference signal generation unit 15 that generates a reference signal, and differential amplification that differentially amplifies the light reception signal and the reference signal to generate a differential amplification signal The unit 30 and the concentration calculation unit 8 that calculates the gas concentration based on the differential amplification signal are provided.

  The laser diode unit 12 includes a laser diode 19 and an LD driver 16. The LD driver 16 is a circuit for supplying current to the laser diode 19, and includes a current amplifier 18 and a digital / analog converter 17. The digital / analog converter 17 converts the driving signal generated by the signal generation circuit 11 into an analog signal and supplies the analog signal to the current amplifier 18. The current amplifier 18 converts the supplied analog signal into a current and supplies it to the laser diode 19. The laser diode 19 oscillates laser light when supplied with current. The oscillated laser light is introduced into the collimating lens 22 through a fiber cable.

  The signal generation circuit 11 is a circuit for generating a driving signal. The drive signal is a digital signal and is a signal for scanning the wavelength of the laser beam oscillated in the laser diode unit 12. The wavelength of the oscillated laser beam is determined by the level of this driving signal. The waveform of the driving signal is such that the laser light is scanned in a wavelength range that completely includes the first wavelength band and includes at least a part of the second wavelength band. That is, the laser light oscillated by the laser diode 19 is scanned in a wavelength range that completely includes the first wavelength band and includes at least a part of the second wavelength band. In the present embodiment, it is assumed that a sawtooth wave is generated as such a driving signal.

  The photodiode unit 13 includes a photodiode 1 and a preamplifier 2. Laser light is incident on the photodiode 1 from the condenser lens 23 via a fiber cable. Thereby, an electromotive force is generated in the photodiode 1. The preamplifier 2 amplifies the electromotive force generated in the photodiode 1 and generates a light reception signal. The received light signal is input to one of the input ends of the differential amplifier 30 and also input to the reference signal generator 15.

  The reference signal generation unit 15 is provided for generating a reference signal. The reference signal is a signal that simulates a light reception signal when there is no gas to be measured. The reference signal generation unit 15 includes an analog / digital converter 3, an arithmetic processing unit 4, and a digital / analog converter 5. The analog / digital converter 3 converts the received light signal input from the photodiode unit 13 into a digital signal, and extracts a plurality of data in the second wavelength band. The extracted data (hereinafter, extracted data) is notified to the arithmetic processing unit 4. The arithmetic processing unit 4 performs processing on the extracted data based on the waveform of the driving signal, and interpolates a portion corresponding to the first wavelength band. The interpolated data is input to the digital / analog converter 5 as reference signal data. The digital / analog converter 5 converts the reference signal data into an analog signal, and inputs this to the differential amplifier 30 as a reference signal.

  Note that such a reference signal generation unit 15 may be realized by a combination of a plurality of logic circuits, or may be realized by executing software by a computer having a ROM, a RAM, a CPU, and the like.

  The differential amplifying unit 30 includes an operational amplifier 14 and an analog / digital converter 9. The light reception signal from the photodiode unit 13 is input to the non-inverting input (−) terminal of the operational amplifier. The reference signal from the reference signal generator 15 is input to the inverting input (+) terminal of the operational amplifier. The output signal of the operational amplifier is converted into a digital signal via the analog / digital converter 9 and supplied to the concentration calculation unit 8 as a differential amplification signal.

  The concentration calculation unit 8 includes a pulse extraction circuit 6 and a pulse peak value detection circuit 7. The pulse extraction circuit 6 extracts a pulse portion from the differential amplification signal to generate a pulse signal, and supplies the pulse signal to the pulse peak value detection circuit 7. The pulse peak value detection circuit 7 calculates the peak value of the pulse signal. This peak value is used for calculating the concentration of the gas to be measured. The calculation of the density can be realized by a computer having a ROM, a RAM, a CPU, and the like, for example.

  Next, the operation of the gas concentration measurement system in this embodiment will be described.

  The signal generation circuit 11 generates a sawtooth wave as a driving signal. FIG. 3A shows a waveform pattern of the generated driving signal. In FIG. 3A, the horizontal axis is time and the vertical axis is signal voltage. As shown in FIG. 3A, the voltage of the drive signal rises linearly from V1 to V3 between times t1 and t3, and returns to V1 again at time t3.

  In the laser diode unit 12 that has received the drive signal, the laser diode 19 oscillates the laser beam. FIG. 3B shows the relationship between the wavelength of the oscillated laser beam and the time. The wavelength of the laser light changes in proportion to the current supplied to the laser diode 19. Since the current supplied to the laser diode 19 is obtained by converting the driving signal, the wavelength of the laser light corresponds to the waveform of the driving signal. Accordingly, at time t1, laser light having a wavelength λ1 corresponding to the voltage V1 of the driving signal is generated. At time t3, laser light having a wavelength λ3 corresponding to the voltage V3 of the driving signal is generated. The wavelength of the laser light rises linearly from λ1 to λ3 between time t1 and time t3. Although not shown, the light intensity of the laser light is also proportional to the current supplied to the laser diode 19.

  Here, it is assumed that the absorption wavelength band (first wavelength band) unique to the gas to be measured is a wavelength band from λ2-1 to λ2-2 with λ2 as the center. Further, the wavelength of the laser light is in the first wavelength band (λ2-1 to λ2-2) between time t2-1 and time t2-2 (hereinafter referred to as a first period). The laser light oscillated within the first period is absorbed by the gas to be measured in the exhaust pipe.

  The laser light generated by the laser diode 19 passes through the measurement gas in the measurement probe portion 20, is received by the photodiode 1, and is converted into an electromotive force. The preamplifier 2 amplifies the electromotive force generated in the photodiode 1 and generates a light reception signal.

  FIG. 3C shows the relationship between the voltage of the received light signal and time. The magnitude of the electromotive force in the photodiode 1 is proportional to the light intensity and the wavelength of the laser beam. Therefore, the voltage of the light reception signal rises in proportion to the time in the period in which the gas to be measured is not absorbed (time t1 to t2-1, time t2-2 to t3; hereinafter, second period). However, in the first period in which absorption by the gas to be measured is received, the voltage of the light reception signal decreases due to absorption by the gas to be measured.

  The received light signal is input to the differential amplifier 30 and also input to the reference signal generator 4.

  FIGS. 4A and 4B are explanatory diagrams for explaining processing in the reference signal generation unit 4. In the reference signal generation unit 4, the analog / digital converter 3 converts the received light signal into a digital signal. As shown in FIG. 4A, the analog / digital converter 3 extracts six light reception signals in the second period. Specifically, the points a1, a2, and a3 are extracted from the second period before the first period, and the points b1, b2, and b3 are extracted from the second period after the first period. The analog / digital converter 3 notifies the arithmetic processing unit 4 of the extracted data as extracted data.

  As shown in FIG. 4B, the arithmetic processing unit 4 interpolates the extracted data to generate reference signal data. At this time, the arithmetic processing unit 4 interpolates the extracted signal data by a process corresponding to the waveform of the driving signal generated by the signal generating circuit 11. In the present embodiment, the waveform pattern of the driving signal is a sawtooth wave. For this reason, the light reception signal assuming no absorption by the gas to be measured should also be a sawtooth wave. That is, the voltage of the light reception signal should rise linearly between times t1 and t3. Therefore, the arithmetic processing unit 4 generates reference signal data by linearly interpolating the extracted data. The calculation process 4 interpolates extraction data, for example using the least squares method.

  The reference signal data generated by the arithmetic processing unit 4 is converted to analog by the digital / analog converter 5 and input to the differential amplifier 30 as a reference signal. The reference signal is a signal generated based on a portion of the received signal that is not absorbed by the gas to be measured, and accurately simulates the received signal when there is no absorption by the gas to be measured. The generated reference signal is input in synchronization with a light reception signal directly input from the photodiode unit 13 by a timer circuit (not shown) or the like.

  In the differential amplification unit 30, a differential amplification signal indicating a difference between the reference signal and the light reception signal is generated. FIG. 5 shows the waveform of the differential amplification signal. As shown in FIG. 5, the signal voltage of the differential amplification signal rises by an amount corresponding to the amount of absorption of the laser beam in the first period in which the laser beam in the absorption wavelength band of the gas to be measured is emitted. become. The differential amplification signal is input to the concentration calculation unit 8. In the concentration calculator 8, the pulse extraction circuit 6 extracts the pulse portion of the differential amplification signal. Then, the peak value (peak value) of the extracted pulse portion is detected by the pulse peak value detection circuit 7. This peak value is a value depending on the concentration of the gas to be measured. Therefore, the concentration of the gas to be measured can be calculated based on the detected peak value.

  As described above, according to the present embodiment, the reference signal is generated by performing processing based on the waveform of the drive signal on the light reception signal by the laser light that actually passes through the gas to be measured. The Here, there is no need to provide an optical path for reference light that does not transmit the gas to be measured. Therefore, the device configuration can be simplified and an inexpensive configuration can be achieved. Further, since there is no need to divide the laser beam into two, the laser beam can be incident on the measurement gas while maintaining the light intensity when emitted. Thereby, even a dilute gas can be measured with high sensitivity.

In the present embodiment, since the driving signal is a sawtooth wave, the case where the arithmetic processing unit 4 generates reference signal data by linear interpolation has been described. However, if the waveform of the driving signal is a waveform other than the sawtooth wave, the arithmetic processing unit 4 is not limited to linear interpolation, and generates reference signal data by interpolation corresponding to the waveform of the driving signal.
For example, assume that the driving signal is a sine wave. FIG. 6A is an explanatory diagram illustrating processing of the reference signal generation unit 15 when the driving signal is a sine wave. As shown in FIG. 6A, the voltage of the light reception signal decreases within the first period. This is the same as in the case of a sawtooth wave. The analog / digital converter 3 extracts 6 points (a4, a5, a6, b4, b5, b6) of data from the second period. Next, as shown in FIG. 6B, the arithmetic processing unit 4 interpolates the extracted data to generate reference signal data. Here, since the driving signal is a sine wave, the received light signal when the gas to be measured is not transmitted should also be a sine wave. Therefore, the arithmetic processing unit 4 does not perform linear interpolation but performs interpolation so that the reference signal data becomes a sine wave.

In the present embodiment, the case where the reference signal generation unit 15 extracts 6 points from the second period of the received light signal data has been described. However, the number of extracted points is not limited to six. For example, when linear interpolation is performed, if the inclination of the received light signal corresponding to the waveform of the driving signal is set in advance, even if there is only one extracted point, the extracted point and the preset inclination The reference signal data can be generated based on the above.
However, in order to generate reference signal data with higher accuracy, it is preferable to extract a plurality of points so as to sandwich the first period. That is, it is preferable to extract data at least one point from the second period before and after the first period. The waveform of the light reception signal generated by the photodiode unit 13 may be affected by dirt or the like due to aged use of the collimating lens 22 or the condenser lens 23. For example, when the driving signal is a sawtooth wave, the inclination of the received light signal may change due to the influence of dirt or the like. Therefore, when only one point is extracted, the accuracy of the reference signal may be reduced. In contrast, if a plurality of points are extracted from the second period so as to sandwich the first period, the reference signal can be generated without being affected by dirt or the like.

(Second Embodiment)
Next, the second embodiment will be described. FIG. 7 is a schematic configuration diagram showing the concentration measuring apparatus 10 according to the present embodiment. In addition, illustration regarding the measurement probe part 20 is abbreviate | omitted. Compared with the first embodiment, in this embodiment, the driving signal generated by the signal generation circuit 11 is also input to the reference signal generation unit 15, and the reference signal generation unit 15 is related to the received light signal. The difference is that the reference signal is generated based on the driving signal. Since other points can be the same as those in the first embodiment, a detailed description thereof will be omitted.

  The driving signal generated by the signal generation circuit 11 is supplied to the laser diode unit 12 and also to the reference signal generation unit 15.

  In the reference signal generation unit 15, a correspondence relationship between the driving signal and the reference signal is set in advance. The correspondence is set in, for example, a RAM. The correspondence relationship is a relationship in which the path from the signal generation circuit 11 to the generation of the light reception signal through the laser diode unit 12 and the photodiode unit 13 is taken into account, and can be obtained, for example, by conducting an experiment in advance. it can.

  The arithmetic processing unit 4 processes the driving signal acquired from the signal generation circuit 11 based on a preset correspondence relationship, and generates reference signal data. As a result, the reference signal data generated here corresponds to the waveform of the driving signal. The reference signal data is converted into a reference signal by the digital / analog converter 5 and input to the differential amplifier 30.

  In the present embodiment, the reference signal is generated regardless of the light reception signal based on the laser light that actually passes through the measurement gas. Therefore, the influence due to the contamination of the optical surface as described in the first embodiment is not considered. However, as in the first embodiment, it is not necessary to provide an optical path for reference light that does not transmit the gas to be measured. Therefore, it is possible to achieve an effect that the device configuration can be simplified. Further, it is not necessary to divide the laser beam into two, and from the viewpoint of maintaining the light intensity of the laser beam, it is possible to measure with high sensitivity as in the first embodiment.

It is a schematic block diagram of a gas concentration measuring device. It is a schematic block diagram of the gas concentration measuring device concerning 1st Embodiment. It is a timing chart which shows operation | movement of a gas concentration measuring apparatus. It is a timing chart which shows operation | movement of a reference signal production | generation part. It is explanatory drawing for demonstrating a differential amplification signal. It is a timing chart which shows operation | movement in case a drive signal is a sine wave. It is a schematic block diagram of the gas concentration measuring device concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photodiode 2 Preamplifier 3 Analog / digital converter 4 Arithmetic processing part 5 Digital / analog converter 6 Pulse extraction circuit 7 Pulse peak value detection circuit 8 Concentration calculation part 9 Analog / digital converter 10 Gas concentration measurement apparatus 11 Drive signal generation part 12 Laser diode section 13 Photodiode section 14 Operational amplifier 15 Reference signal generation section 16 LD driver 17 Digital / analog converter 18 Current amplifier 19 Laser diode 20 Measurement probe section 21 Measurement probe 22 Collimating lens 23 Condensing lens 24 Exhaust pipe 25 Mirror 30 Differential Amplifier 101 Waveform generator 102 LD driver 103 Laser diode 104 Divider 105 Gas to be measured 106 Photodiode 107 Photodiode 10 Detection unit

Claims (12)

A drive signal generator for generating a drive signal having a preset waveform;
A laser diode unit that oscillates laser light based on the driving signal;
A photodiode unit that receives the laser beam and generates a light reception signal;
A reference signal generator for generating a reference signal having a waveform corresponding to the waveform of the driving signal;
A differential amplification unit that generates a differential amplification signal based on the light reception signal and the reference signal;
Based on the differential amplification signal, a concentration calculator that calculates the concentration of the measurement target;
Comprising
An optical path of the laser beam from the laser diode section to the photodiode section is a single optical path, and is a gas concentration measuring device that is an optical path that passes through the measurement target. A gas concentration measuring device according to claim 1,
The waveform of the driving signal is scanned with the laser beam in a wavelength region including both a first wavelength band where absorption by the measurement target exists and a second wavelength band where absorption by the measurement target does not exist. Is a waveform like
The gas concentration measuring device that generates the reference signal by interpolating a portion corresponding to the first wavelength band based on the received light signal corresponding to the second wavelength band. A gas concentration measuring device according to claim 2,
The reference signal generation unit includes the received light signal corresponding to a wavelength shorter than the first wavelength band in the second wavelength band, and a wavelength longer than the first wavelength band in the second wavelength band. A gas concentration measuring device that interpolates a portion corresponding to the first wavelength band based on the received light signal corresponding to the wavelength on the side. A gas concentration measuring device according to claim 2 or 3, wherein
The driving signal is a sawtooth wave,
The reference signal generation unit is a gas concentration measurement device that interpolates a portion corresponding to the first wavelength band by linear interpolation. A gas concentration measuring device according to claim 2 or 3, wherein
The driving signal is a sine wave,
The gas concentration measuring device that interpolates a portion corresponding to the first wavelength band so that the reference signal is a sine wave. A gas concentration measuring device according to claim 1,
In the reference signal generation unit, a correspondence relationship between the driving signal and the reference signal is set in advance,
The drive signal generation unit notifies the reference signal generation unit of the drive signal,
The reference signal generation unit is a gas concentration measurement device that performs processing based on the correspondence set for the notified driving signal and generates the reference signal. Generating a driving signal having a preset waveform;
Oscillating laser light based on the driving signal;
Receiving the laser light through one optical path that passes through the object to be measured, and generating a light reception signal;
Generating a reference signal having a waveform corresponding to the waveform of the driving signal;
Generating a differential amplification signal based on the light reception signal and the reference signal;
Calculating the concentration of the object to be measured based on the differential amplification signal;
A gas concentration measuring method comprising: The gas concentration measuring method according to claim 7,
The drive signal is scanned in a wavelength region in which the laser light includes both a first wavelength band where absorption by the measurement target exists and a second wavelength band where absorption by the measurement target does not exist. Have a strong waveform,
The step of generating the reference signal includes a step of generating the reference signal by interpolating a portion corresponding to the first wavelength band based on the received light signal corresponding to the second wavelength band. Measurement method. A gas concentration measurement method according to claim 8, wherein
The step of generating the reference signal includes: the received light signal corresponding to a wavelength shorter than the first wavelength band in the second wavelength band; and the first wavelength band among the second wavelength bands. A gas concentration measurement method including a step of interpolating a portion corresponding to the first wavelength band based on the light reception signal corresponding to a wavelength on a long wavelength side. A gas concentration measurement method according to claim 8 or 9, wherein
The driving signal is a sawtooth wave,
The step of generating the reference signal includes the step of interpolating a portion corresponding to the first wavelength band by linear interpolation. A gas concentration measuring method according to claim 8 or 9, wherein
The driving signal is a sine wave,
The step of generating the reference signal includes a step of interpolating a portion corresponding to the first wavelength band so that the reference signal becomes a sine wave. The gas concentration measuring method according to claim 7,
Furthermore,
Setting a correspondence relationship between the driving signal and the reference signal in advance;
Comprising
The step of generating the reference signal includes a step of processing the driving signal based on the correspondence relationship to generate the reference signal.

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