JP5834765B2 - Multi-component laser gas analyzer - Google Patents

Description

  The present invention relates to a multi-component laser gas analyzer that analyzes the presence and concentration of various measurement target gases in a space.

  As conventional techniques of multi-component laser gas analyzers, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-74830 (Patent No. 4038631)), title of the invention “temperature / concentration / chemistry using semiconductor laser spectroscopy” The invention described in “High-Speed Measurement Method and Measurement System of Species” is known. This measurement system will be described with reference to the drawings.

FIG. 15 is an overall configuration diagram showing an embodiment of a laser gas analyzer using a conventional optical fiber. In FIG. 15, reference numerals 501 and 502 denote semiconductor lasers as light emitting units, which emit laser beams having different wavelengths λ ₁ (for example, 1.996 μm) and λ ₂ (for example, 2.050 μm). DFB) consisting of a semiconductor laser. These semiconductor lasers 501 and 502 are current-controlled by a function generator 503, respectively.

  Reference numerals 504 and 505 denote fiber couplers connected to the semiconductor lasers 501 and 502 via optical fibers 506 and 507, and reference numeral 508 denotes a fiber for sending laser light emitted from the semiconductor lasers 501 and 502 to a cell 513 described later as measurement light. Reference numerals 509 and 510 denote optical fibers. Note that optical fibers 511 and 512 for laser light as reference light are connected to the fiber couplers 504 and 505, respectively.

Reference numeral 513 denotes a cell provided in the subsequent stage of the fiber coupler 508. Both ends of the cell 513 are sealed with cell windows 513a and 513b that transmit laser light in the vicinity of 2 μm, and are provided with a gas inlet 513c and a gas outlet 513d. The gas inlet 513c includes, for example, CO ₂ Gas supply lines 516 and 517 having opening / closing valves 514 and 515 are connected so that air can be supplied at an appropriate ratio, and a gas discharge line 520 having an opening / closing valve 518 and a vacuum pump 519 is connected to the gas outlet 513d. It is connected.

In addition, mirrors 521 and 522 are provided outside the cell windows 513a and 513b, and the laser beam incident on the cell 513 passes through the cell 513 several times and then is emitted.
Reference numerals 523 and 524 denote collimators provided on the front side and the rear side of the cell 513, respectively, and a branching filter 525 is provided on the rear side of the collimator 524 on the rear side. The demultiplexer 525 separates laser light (measurement light) having two wavelengths transmitted through the cell 513 into laser light having wavelengths λ ₁ and λ ₂ .

Reference numerals 526 and 527 are photodiodes for measurement light, and reference numerals 528 and 529 are photodiodes for reference light. These photodiodes 526 and 527 have laser light beams with wavelengths λ ₁ and λ ₂ separated by a demultiplexer 525 ( Measurement light) is incident, and laser light (reference light) having wavelengths λ ₁ and λ ₂ is incident on the photodiodes 528 and 529 through the optical fibers 511 and 512.

  Reference numerals 530 to 533 are preamplifiers provided corresponding to the photodiodes 526 to 529, respectively. These preamplifiers 530 to 533 are input to a signal processing device (for example, a computer) (not shown) via an A / D converter 534. It is comprised so that.

In the laser type gas analyzer configured as described above, a gas in which CO ₂ and air are mixed in an appropriate ratio is supplied to the cell 513 as a gas to be measured. In this state, laser light λ ₁ and λ _{2 of} two wavelengths respectively emitted from the semiconductor lasers 501 and 502 are transmitted as measurement light through a cell 513 filled with a measurement gas in a mixed state. This measurement light is converted into laser light having the original wavelengths λ ₁ and λ _{2 in} the demultiplexer 525 and is incident on the photodiodes 526 and 527. On the other hand, laser beams λ ₁ and λ ₂ having two wavelengths respectively emitted from the semiconductor lasers 501 and 502 are directly incident on the photodiodes 528 and 529 through the optical fibers 511 and 512 as reference lights.

  The photodiodes 526 to 529 output signals corresponding to the incident light. These output signals pass through the preamplifiers 530 to 533 and enter the A / D converter 534, and the converted output is input to the computer. Signal processing. The temperature, concentration, and chemical species of the gas to be measured supplied to the cell 513 are obtained.

In this laser gas analyzer, the laser light used for the measurement, different wavelengths lambda ₁ of 2μm around a longer wavelength than _{conventional,} because of the use of laser beam of lambda _2, measured by absorption of strong absorption lines Thus, the required optical path length can be shortened and the S / N can be improved in the measurement of temperature, concentration and chemical species. The prior art is like this.

JP 2000-74830 A (Patent No. 4038631), title of invention “High-speed measurement method and measurement system for temperature, concentration, and chemical species using semiconductor laser spectroscopy”

  In this prior art, laser beams having different wavelengths are coupled onto one optical fiber by the fiber coupler 508 on the light emitting side, but generally there is an insertion loss in the fiber coupler. For example, in the case of a melt-input fiber coupler with two inputs and one output, there is an insertion loss of 3 dB or more at at least one input port. When only two different wavelengths are combined, it is possible to use a wavelength division multiplexing (WDM) type fiber coupler designed to reduce the insertion loss to 3 dB or less for these two specific wavelengths. The wavelength division multiplexing method cannot be applied to three or more different wavelengths.

  That is, for example, when combining three wavelengths of a wavelength 763 nm laser for oxygen detection, a wavelength 2004 nm laser for carbon dioxide detection, and a wavelength 2330 nm laser for carbon monoxide detection on one optical fiber by a fiber coupler. Even if two wavelengths are coupled to one optical fiber in advance using a wavelength division multiplexing fiber coupler, and each insertion loss is suppressed to 3 dB or less, the remaining one wavelength is already coupled with the two wavelengths. The coupling is performed by a single-stage fiber coupler, and at least one wavelength eventually causes an insertion loss of 3 dB or more.

  As described above, when laser beams having three or more different wavelengths on the light emitting side are coupled onto one optical fiber by the fiber coupler, the power of the light emitted from the laser light source can be efficiently transmitted to the light receiving element. However, there is a problem that the intensity of the absorption signal of the measurement gas is lowered.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to radiate light emitted from laser light sources having a plurality of different wavelengths on a light emitting side into a space without using a fiber coupler. Accordingly, it is an object of the present invention to provide a multi-component laser gas analyzer that increases the intensity of an absorption signal of a measurement gas by eliminating insertion loss on the light emission side and efficiently transmitting light power to the light receiving element.

In order to solve the above-described problem, an invention according to claim 1 includes: a light emitting unit that emits detection light by laser light ; and a light receiving unit that receives detection light propagated through a space in which a plurality of measurement target gases exist. A multi-component laser gas analyzer of frequency modulation type that measures the concentration of a plurality of types of gas to be measured,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses the detection light transmitted through the space while reducing the influence of aberration, a multimode optical fiber that combines the condensed light output from the parabolic mirror, and the multimode light Demultiplexing means for demultiplexing the laser light transmitted through the fiber, a visible light receiving element having sensitivity in the visible wavelength region of the demultiplexed light demultiplexed by the demultiplexing means, and demultiplexing by the demultiplexing means. A near-infrared light receiving element having sensitivity in the near-infrared wavelength region of the demultiplexed light, a visible light processing circuit for performing gas analysis based on a detection signal from the visible light receiving element, A near infrared light processing circuit that performs gas analysis based on a detection signal from the infrared light receiving element,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. It is characterized by comprising detection means and calculation means for calculating the concentration of the gas to be measured based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal.

請 Motomeko 2 according the invention comprises a light emitting unit for emitting detecting light by a laser beam, a light receiving unit that receives the detection light that is propagated through a space in which a plurality of measurement target gas is present, a plurality of types A multi-component laser gas analyzer for frequency modulation that measures the concentration of the gas to be measured,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses detection light transmitted through the space while reducing the influence of aberration, a visible light receiving element having sensitivity in the visible wavelength range, and near infrared light having sensitivity in the near infrared wavelength range The light receiving element for integrating the light receiving element for outputting light from the light receiving side optical unit and gas analysis based on the detection signal from the light receiving element for visible light of the light receiving elements. includes a visible light processing circuit for performing, and a near-infrared light processing circuit for performing gas analysis based on the detection signal from the near-infrared light-receiving element of the light receiving element,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. It is characterized by comprising detection means and calculation means for calculating the concentration of the gas to be measured based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal .

請 Motomeko according to 3 invention includes a light emitting portion for emitting detecting light by a laser beam, a light receiving unit that receives the detection light that is propagated through a space in which a plurality of measurement target gas is present, a plurality of types A multi-component laser gas analyzer for frequency modulation that measures the concentration of the gas to be measured,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses the detection light transmitted through the space while reducing the influence of aberration, and a peak of sensitivity in the near-infrared wavelength region that outputs a detection signal for the light collected from the light receiving side optical unit. A broadband near-infrared light receiving element having sensitivity in the visible wavelength range, and a near-infrared light processing circuit for performing gas analysis based on a detection signal from the broadband near-infrared light receiving element. ,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. It is characterized by comprising detection means and calculation means for calculating the concentration of the gas to be measured based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal .

  According to the present invention, on the light emitting side, light emitted from laser light sources having a plurality of different wavelengths or more is emitted to the space without using a fiber coupler, thereby eliminating insertion loss on the light emitting side and reducing the light power. By efficiently transmitting to the light receiving element, the intensity of the absorption signal of the measurement gas can be increased.

1 is an overall configuration diagram of a multi-component laser gas analyzer according to an embodiment of the present invention. It is an internal block diagram of a pigtail type light emitting element. FIG. 3A is a characteristic diagram showing a change in emission wavelength of a semiconductor laser, FIG. 3A is a drive current-emission wavelength characteristic diagram, and FIG. 3B is a temperature-emission wavelength characteristic diagram. It is a section lineblock diagram of a fiber bundle end part. It is a characteristic view which shows the wavelength-light reception sensitivity characteristic about the light receiving element for visible light. It is a characteristic view which shows the wavelength-light reception sensitivity characteristic about the light receiving element for near-infrared light. FIG. 7A is a partial configuration diagram of an analysis unit, FIG. 7A is a configuration diagram of a visible light receiving element and a visible light processing circuit, and FIG. 7B is a near infrared light receiving element and a near infrared light use. It is a block diagram of a processing circuit. O ₂ gas, HCL gas, CO ₂ gas, is a characteristic diagram showing an absorption spectrum example of CO gas. FIGS. 9A and 9B are explanatory diagrams of waveforms detected at respective portions, FIG. 9A shows an output waveform of a wavelength scanning drive signal generation circuit of a laser element, and FIG. 9B shows an output waveform of a harmonic modulation signal generation circuit. FIG. 9C shows the output waveform of the drive signal generating circuit. It is a wave form diagram which shows a light reception signal, the output signal of a synchronous detection circuit, and a trigger signal. It is a wave form diagram which shows a light reception signal, the output signal of a synchronous detection circuit, and a trigger signal. It is a structural diagram of a light receiving element for visible light and near infrared light. It is a block diagram explaining the detection part of another form. It is a block diagram explaining the detection part of another form. It is explanatory drawing of the laser type gas analyzer for multicomponents of a prior art.

Next, a multi-component laser gas analyzer according to an embodiment for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a multi-component laser gas analyzer according to the present embodiment.
The multi-component laser gas analyzer 1 of this embodiment employs a frequency modulation method. The multi-component laser gas analyzer 1 includes a modulated light generation unit 10, a light emission side optical unit 20, a light reception side optical unit 30, and an analysis unit 40. Among these, as shown in FIG. 1, the modulated light generation unit 10 and the light emission side optical unit 20 constitute the light emission unit 100 of the present invention. In addition, the light receiving side optical unit 30 and the analyzing unit 40 constitute the light receiving unit 200 of the present invention.

The modulated light generation unit 10 further includes pigtail light emitting elements 11a, 11b, 11c, and 11d and single mode fibers (pigtails) 12a, 12b, 12c, and 12d.
The light emitting side optical unit 20 further includes a fiber bundle end portion 21, a collimating parabolic mirror 22, and a window plate 23 with a light emitting side wedge.

The light receiving side optical unit 30 further includes a condensing parabolic mirror 31, a fiber end 32, and a window plate 33 with a light receiving side wedge.
The analysis unit 40 further includes a multimode optical fiber 41, 43a, 43b, a duplexer 42, a visible light receiving element 44a, a near infrared light receiving element 44b, a visible light processing circuit 45a, and a near red light. And an external processing circuit 45b.

  As shown in FIG. 1, the light-emitting side optical unit 20 and the light-receiving side optical unit 30 are flanges 72a and 72b fixed by welding or the like to walls 71a and 71b such as pipes through which a plurality of gases to be measured flow. And optical axis adjusting flanges 73a and 73b. Here, the optical axis adjusting flanges 73a and 73b are for adjusting the optical axis so that the detection light 60 emitted from the light emitting side optical unit 20 is received by the light receiving side optical unit 30 with the maximum light amount. .

  Note that the window plate 23 with the light emitting side wedge and the window plate 33 with the light receiving side wedge are in the optical path, and the gas containing the plurality of measurement target gases is transmitted through the light emitting side optical unit 20 and the light receiving side optical while transmitting the detection light 60. The collimating parabolic mirror 22, the condensing parabolic mirror 31, the fiber bundle end 21, and the fiber end 32 are protected from direct gas contact so that they do not enter the portion 30.

Next, detailed configurations of the light emitting unit 100 and the light receiving unit 200 will be described. First, the light emitting unit 100 will be described in detail with reference to FIGS.
The modulated light generation unit 10 is provided with a plurality of laser light emitting elements corresponding to the light absorption characteristics of the measurement target gas, and irradiates the laser light of the number of measurement target gases. This is a unit that generates a plurality of modulated lights that are modulated and transmits the plurality of modulated lights to the light-emitting side optical unit 20.

  As shown in FIG. 1, the modulated light generation unit 10 further has a number of pigtail light emitting elements 11a, 11b, 11c, and 11d equal to the number of types of measurement target gases (illustrated as four in this embodiment). And the same number of single-mode optical fibers (pigtails) 12a, 12b, 12c, and 12d as the number of pigtail type light emitting elements (explained as four in this embodiment). The pigtail type light emitting elements 11a, 11b, 11c, and 11d and the single mode optical fibers 12a, 12b, 12c, and 12d are commercially available as pigtail type laser elements in an optically connected state in advance. In some cases, no optical adjustment is necessary.

The pigtail-type light emitting elements 11a, 11b, 11c, and 11d are configured as shown in FIG.
The pigtail type light emitting elements 11a, 11b, 11c, and 11d incorporate light emitting element bodies 111a, 111b, 111c, and 111d, respectively. These light emitting element main bodies 111a, 111b, 111c, and 111d are configured to use one light emitting element for each measurement target gas component. These are laser elements called DFB laser (Distributed Feedback Laser) or VCSEL (Vertical Cavity Surface Emitting Laser), for example.

  These laser elements can emit light in the visible region or near-infrared region where the emission wavelength matches the light absorption characteristic of the gas, and the emission wavelength can be varied by current and temperature. In this embodiment, for the sake of concrete explanation, it is assumed that the visible region emits the pigtail light emitting element 11a, and the near infrared region emits the pigtail light emitting elements 11b, 11c, and 11d.

  Such a configuration is determined according to the actual state of the measurement target gas. For example, two pigtail light emitting elements emitting a visible region and four pigtail light emitting elements emitting a near infrared region are referred to as, for example. It can be selected as appropriate. In general, m pigtail light emitting elements emitting a visible region and n pigtail light emitting devices emitting a near infrared region are arranged.

In this embodiment, oxygen gas (O ₂ gas), chlorine gas (HCl gas), carbon dioxide gas (CO ₂ gas), and carbon monoxide gas (CO gas) are measured as measurement target gases.
The visible region is, for example, a pigtail light emitting element 11a that emits a wavelength of 763 nm for detecting oxygen gas (O ₂ gas), and the near infrared region is, for example, a wavelength of 1780 nm for detecting chlorine gas (HCl gas). And a pigtail light emitting element 11c that emits a wavelength of 2004 nm for detecting carbon dioxide gas (CO ₂ gas), and a wavelength of 2330 nm for detecting carbon monoxide gas (CO gas). Is a laser element 11d emitting light.

  These pigtail-type light emitting elements 11a, 11b, 11c, and 11d can emit light at wavelengths in the visible region and near infrared region that match the gas absorption characteristics. Further, as shown in FIG. In addition, the emission wavelength can be made variable by the drive current. Further, as shown in FIG. 3B, the emission wavelength can be made variable depending on the temperature. In this way, the emission wavelength of the laser can be varied by temperature and current. Other than the laser element, other types of light emitting elements may be used as long as the above conditions are satisfied, that is, they can be swept in the absorption wavelength band of the measurement target gas.

Next, control in the pigtail type light emitting elements 11a, 11b, 11c, and 11d will be described.
In FIG. 2, the temperatures of the light emitting element bodies 111a, 111b, 111c, and 111d are detected using temperature detecting elements 112a, 112b, 112c, and 112d such as thermistors. These temperature detection elements 112a, 112b, 112c, and 112d are connected to temperature control circuits 113a, 113b, 113c, and 113d. These temperature control circuits 113a, 113b, 113c, and 113d stabilize the light emission wavelength of the light emitting element bodies 111a, 111b, 111c, and 111d, so that the resistance values of the temperature detection elements 112a, 112b, 112c, and 112d are constant. PID control or the like is performed to control the temperature of the Peltier elements 114a, 114b, 114c, and 114d, and the temperature of the light emitting element bodies 111a, 111b, 111c, and 111d is adjusted.

  Further, output signals from the wavelength scanning drive signal generation circuits 115a, 115b, 115c, and 115d that change the emission wavelength and output signals from the high-frequency modulation signal generation circuits 1116a, 116b, 116c, and 116d for frequency modulation of the emission wavelength are provided. The drive signal generation circuits 117a, 117b, 117c, and 117d combine to generate a drive signal, and the drive signal is subjected to VI conversion and supplied to the light emitting element bodies 111a, 111b, 111c, and 111d. As a result, laser light having a predetermined wavelength, which is frequency-modulated, is emitted from the light emitting element bodies 111a, 111b, 111c, and 111d to scan the light absorption characteristics of different types of measurement target gases. Therefore, laser light having a predetermined wavelength is emitted from the pigtail type light emitting elements 11a, 11b, 11c, and 11d.

  The wavelength scanning drive signal generation circuits 115a, 115b, 115c, and 115d output a trigger signal a, a trigger signal b, a trigger signal c, and a trigger signal d, respectively. The trigger signal a is input to the arithmetic circuit 455a of the visible light processing circuit 45a via the communication line 50 (see FIG. 7A), and the trigger signal b, the trigger signal c, and the trigger signal d are near red. This is input to the arithmetic circuits 455b, 455c, 455d of the external light processing circuit 45b (see FIG. 7B). These trigger signals will be described later.

  Returning to FIG. 1, the laser beams emitted from the pigtail type light emitting elements 11a, 11b, 11c, and 11d are transmitted through the single mode optical fibers 12a, 12b, 12c, and 12d, respectively. These single mode optical fibers 12a, 12b, 12c, and 12d can be selected to have an appropriate core diameter and refractive index according to the emission wavelength of each of the pigtail light emitting elements 11a, 11b, 11c, and 11d.

  As a result, the transmission loss can be reduced compared to the case where a plurality of wavelengths are transmitted together using a multimode optical fiber. Further, since no optical fiber coupler is used in the middle, there is an advantage that no insertion loss occurs and light can be transmitted efficiently. Thus, the laser light emitted from the pigtail type laser elements 11a, 11b, 11c, and 11d is efficiently transmitted to the fiber bundle end portion 21 in the light emitting side optical unit 30.

  Next, details of the fiber bundle end portion 21 will be described. As shown in FIG. 4, the fiber bundle end portion 21 plays a role of bundling the end portions of the single mode type optical fibers 12 a, 12 b, 12 c, and 12 d by the ferrule 211 so that the emission points of the respective laser beams are close to each other. FIG. 4 shows an example of a cross section when four optical fibers are bundled.

  The ferrule 211 has a hollow hole 212 having a square cross section at the center thereof. The size of the hollow hole 212 is set to be inscribed when the single mode optical fibers 12a, 12b, 12c, and 12d are arranged so that the cross sections thereof are in a square lattice shape, and the positional relationship between the optical fibers is Fixed.

  For example, since the diameter of a typical single mode type optical fiber is 125 μm, the length of one side of the square hollow hole 212 is set to 250 μm, and the positional relationship between the optical fibers is fixed. Thus, the light emitting point from a laser element is made to adjoin by making single mode type optical fiber 12a, 12b, 12c, 12d adjoin.

  In the case of FIG. 4, since the single mode type optical fibers 12a, 12b, 12c, and 12d are arranged in a square lattice shape, the interval between the light emitting points is 125 μm at the nearest point. As a result, the laser beams emitted from the plurality of single mode optical fibers 12a, 12b, 12c, and 12d are emitted by being brought close to each other at the fiber bundle end portion 21 to be combined to generate coupled light.

  Further, the tip of the fiber bundle end portion 21 can be subjected to oblique polishing or oblique spherical polishing in order to reduce the influence of return light due to reflection on the cross section. The shape of the hollow hole 212 is not limited to a square, and may be a circle, for example, as long as the positional relationship between optical fibers can be fixed. Even when the number of single-mode optical fibers is 2, 3, 5, or 6, it is possible to form a hollow hole 212 having an appropriate shape and hold it by the fiber bundle end portion 21.

  Returning to FIG. Laser light emitted from the fiber bundle end 21 is converted into parallel light by the collimating parabolic mirror 22. Here, the parabolic mirror will be described. A parabolic mirror is a mirror whose reflecting surface is a part of a rotating paraboloid. The light incident on the reflecting surface parallel to the rotation axis of the parabolic mirror is collected at the focal point of the parabolic mirror. On the other hand, light emitted from the focal point of the parabolic mirror and incident on the reflecting surface is converted into light parallel to the rotation axis of the parabolic mirror. The collimating optical system is configured as follows using the above-described properties.

  That is, by arranging the fiber bundle end 21 at the focal point of the collimating parabolic mirror 22, the combined light 24 emitted from the fiber bundle end 21 is reflected by the collimating parabolic mirror 22, and the detection light 60 is parallel light. It becomes. Actually, even if the optical fiber bundle end portion 21 is arranged at the focal point, all of the light emitting points of the single mode type optical fibers 12a, 12b, 12c, and 12d cannot be completely matched with the focal point. The distance will be about a radius.

  This effect appears because the cross-sectional shape of the plurality of laser beams included in the detection light 60 becomes non-circular or has a slight angle with respect to the optical axis, but the optical path length is about several meters. If so, the impact is small enough. The reason for adopting a parabolic mirror instead of a lens for the collimation of the laser beam will be described. The lens is affected by chromatic aberration because of the use of refraction for the principle of collimation, and a broadband laser beam ranging from 760 nm to 2330 nm. This is because it is difficult to make them equally parallel. Since a parabolic mirror uses reflection for the principle of collimation, chromatic aberration does not occur as in the case of a lens, so that laser light can be collimated equally regardless of wavelength.

The detection light 60 that has become parallel light as described above is transmitted through the window plate 23 with the light emission side wedge, propagates through the inner section of the walls 71a and 71b (a space in which a plurality of measurement target gases circulate), and receives the light reception side wedge. It passes through the attached window plate 33. Here, the reason for adopting the window plate with a wedge instead of the parallel plane window plate will be described.
In general, laser light causes some reflection on the front or back surface of the window plate. For this reason, among the front surface or the back surface of the window plate (in the case of this embodiment, there are a total of four surfaces including the front surface and the back surface of the window plate with light emitting side wedge 23 and the front surface and the back surface of the window plate with light receiving side wedge 33) If the surface is arranged perpendicular to the optical axis, multiple reflections occur and optical interference noise occurs. As a result, the intensity of the received light signal is modulated, and the measurement of the gas concentration becomes inaccurate. In order to avoid this phenomenon, a window plate with a wedge is used instead of a parallel plane window plate. Further, it is desirable to arrange the front and back surfaces of the window plate with wedges so that none of them is perpendicular to the optical axis.

  Next, the light receiving unit 200 will be described. The light receiving unit 200 is a unit that receives the detection light 60 and analyzes the light absorbed by the light absorption characteristics of the measurement target gas. That is, in the light-receiving side optical unit 30, as shown in FIG. 1, the detection light 60 that is parallel light that has passed through the window plate 33 with the light-receiving side wedge is incident on the condensing parabolic mirror 31, reflected, and reflected by the fiber. The condensed light 34 converges to the end 32 and is coupled to the multimode optical fiber 41. By arranging the fiber end 32 at the focal point of the concentrating parabolic mirror 31 and arranging the rotation axis of the concentrating parabolic mirror 31 in parallel to the detecting light 60, the detection light 60 is a multimode type light. Efficiently couples to the fiber 41. Therefore, according to this embodiment, collimation and condensing can be performed without depending on the wavelength of the laser light, so that the detection light 60 can be reliably input to the multimode optical fiber 41.

  Next, the analysis unit 40 will be described. The analysis unit 40 is a unit that receives the detection light 60 through the multimode optical fiber 41 and analyzes the light absorbed by the light absorption characteristics of the measurement target gas.

Here, the reason why the multimode optical fiber 41 is employed (the reason why it is a multimode type instead of a single mode type) will be described. This is because the multimode optical fiber has a larger core diameter and higher laser beam coupling efficiency than the single mode optical fiber. The laser beam condensed by the condensing parabolic mirror 31 is not necessarily condensed at one point but is condensed with a finite spread. The influence of the light-emitting points of the single-mode optical fibers 12a, 12b, 12c, and 12d being shifted from the focus of the collimating parabolic mirror 22 and the reflection of the collimating parabolic mirror 22 and the focusing parabolic mirror 31 Due to the influence of the surface quality, the cross-sectional shape of the focused laser beam has a certain extent.
Furthermore, when the optical axis adjustment gradually shifts due to vibrations or temperature changes around the device, the focused laser beam is detached from the optical fiber end 32, so that the core diameter must be sufficiently large to allow for a margin. Is desirable.

  For this reason, an optical fiber having a core diameter of 50 μm or more, such as a multimode optical fiber, is used instead of an optical fiber having a core diameter of about 10 μm as in a single mode optical fiber. The laser beam is efficiently combined, and a margin for deviation in optical axis adjustment is given. Note that an appropriate value can be selected for the core diameter of the multimode optical fiber 41. However, it should be noted that the transmission loss increases as the core diameter increases.

  In the analyzing unit 40, the demultiplexer 42 demultiplexes the laser light transmitted through the multimode optical fiber 41 with an appropriate branching ratio. The demultiplexer 42 only needs to have a demultiplexing function, and specifically, a multimode type optical fiber coupler or a multimode type optical fiber switch can be employed.

These demultiplexed lights are respectively received by the visible light receiving element 44a and the near infrared light receiving element 44b through the multimode optical fibers 43a and 43b. Oxygen gas (O ₂ gas), chlorine gas (HCl gas), carbon dioxide gas (CO ₂ gas), and carbon monoxide gas (CO gas) are measured as measurement target gases. In order to detect gas (O ₂ gas), an Si photodiode having sensitivity in the visible wavelength region having sensitivity in the range of 400 nm to 1000 nm can be employed as shown in FIG. In addition, the near-infrared light receiving element 44b detects a chlorine gas (HCl gas), a carbon dioxide gas (CO ₂ gas), and a carbon monoxide gas (CO gas) as shown in FIG. An InGaAs photodiode having sensitivity in the near-infrared wavelength region having sensitivity at 2500 nm can be employed.

  The demultiplexed light demultiplexed by the demultiplexer 41 includes laser light of all wavelengths, but the visible light receiving element 44a and the near infrared light receiving element 44b are sensitive to the wavelength. Since each wavelength region having a wavelength is determined, it is possible to receive light in different regions. For example, light having a wavelength of 763 nm is detected only by the visible light receiving element 44a. Of the detected light, light having a wavelength of 1780 nm, 2004 nm, and 2330 nm is detected only by the near-infrared light receiving element 44b.

  The visible light receiving element 44a and the near infrared light receiving element 44b are converted into detection signals by electrical signals according to the amount of received light, and sent to the visible light processing circuit 45a and the near infrared light processing circuit 45b. . The visible light processing circuit 45a and the near-infrared light processing circuit 45b detect the density by, for example, performing amplification or noise filtering on the detection signal.

FIG. 7A is an internal configuration diagram of the visible light processing circuit 45a. The detection signal input from the visible light receiving element 44a to the visible light processing circuit 45a is converted from a current signal to a voltage signal by the IV conversion circuit 451a. The reference signal generation circuit (oscillation circuit) 452a outputs a signal having a frequency twice that of the high frequency modulation signal generated by the high frequency modulation signal generation circuit 116a as a reference signal. The voltage signal converted by the IV conversion circuit 451a and the reference signal are input to the synchronous detection circuit 453a, and a signal having a double frequency component is extracted from the voltage signal. These signals are input to the filter 454a, subjected to processing such as noise removal and amplification, and input to the arithmetic circuit 455a. In the arithmetic circuit 455a, the measurement target gas (specifically, oxygen gas (O ₂ gas)) is input. The density will be calculated.

FIG. 7B is an internal configuration diagram of the near-infrared light processing circuit 45b. The detection signal input from the near-infrared light receiving element 44b to the near-infrared light processing circuit 45b is converted from a current signal to a voltage signal by the IV conversion circuit 451b. Further, the reference signal generation circuits (oscillation circuits) 452b, 452c, and 452d output signals having a frequency twice as high as the high frequency modulation signals generated by the high frequency modulation signal generation circuits 116b, 116c, and 116d as reference signals. The voltage signal converted by the IV conversion circuit 451b and the reference signal are input to the synchronous detection circuits 453b, 453c, and 453d, and a signal having a double frequency component is extracted from the voltage signal. These signals are input to the filters 454b, 454c, and 454d, subjected to processing such as noise removal and amplification, and input to the arithmetic circuits 455b, 455c, and 455d, and the measurement target gas in the arithmetic circuits 455b, 455c, and 455d. Specifically, the concentrations of chlorine gas (HCl gas), carbon dioxide gas (CO ₂ gas), and carbon monoxide gas (CO gas) are calculated.

Next, the principle of detecting the concentration of the measurement target gas in the above configuration will be described. Here, oxygen gas (O ₂ gas) in the visible region and chlorine gas (HCl gas), carbon dioxide gas (CO ₂ gas), and carbon monoxide gas (CO gas) in the near infrared region are detected. As shown in FIG. 8, oxygen has a light absorption characteristic at 760 nm to 768 nm. In order to detect oxygen, a pigtail light emitting element 11a that emits light having a wavelength of 763 nm is used as a visible region. Similarly, as the near-infrared region, for example, a pigtail light emitting element 11b that emits a wavelength of 1780 nm to detect chlorine gas, and a pigtail light emitting element 11c that emits a wavelength of 2004 nm to detect carbon dioxide gas, In order to detect carbon monoxide gas, a pigtail light emitting element 11d that emits light having a wavelength of 2330 nm is used. In the present invention, since light of 500 to 2500 nm is propagated through the optical fiber and the duplexer, detection is possible.

First, it is assumed that the detection light 60 emitted from the modulated light generation unit 10 passes through the spaces in the walls 71a and 71b through which the measurement target gas flows and is absorbed. These detection lights are incident on the analysis unit 40.
The visible light receiving element (Si photodiode) 44a having sensitivity to visible light receives only light from the 763 nm pigtail type light emitting element 11a, and also has a near infrared having sensitivity in the near infrared wavelength region. The light receiving element for light (InGaAs photodiode) 44b receives laser light from the pigtail light emitting element 11b with a wavelength of 1780 nm, laser light from the pigtail light emitting element 11c with 2004 nm, and laser light from the pigtail light emitting element 11d with wavelength of 2330 nm. Receive light.

FIG. 9A shows an example of a drive current waveform of the pigtail type light emitting element 11a, for example.
The wavelength scanning drive signal S ₁ for scanning the light absorption characteristics of the measurement target gas gradually changes the emission current of the pigtail light emitting element 11a by linearly changing the drive current value of the pigtail light emitting element 11a. Scan the light absorption characteristics of about 2 nm. On the other hand, the signal S ₂ is pigtail-type light emitting element 11a of the driving 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.

9 (b) is a waveform diagram of the modulation signal output from the high-frequency modulation signal generation circuit 116a of FIG. 2, the signal S ₄ for detecting the light absorption characteristics of the measurement target gas, for example a frequency of 10kHz sine The wave width is modulated by about 0.02 nm.
FIG. 9C is a waveform diagram of the drive signal (the combined signal of the output signal of the wavelength scanning drive signal generation circuit 115a and the output signal of the high frequency modulation signal generation circuit 116a) output from the drive signal generation circuit 117a of FIG. , and the when supplying the driving signal _{S 5} to the light-emitting element body 111a, a light-emitting element body 111a, detectable modulated light output 0.2nm about light absorption characteristics of the gas to be measured at about wavelength width 0.02nm Is done.

The other light emitting element bodies 111b, 111c, and 111d are also analyzed in accordance with the light absorption characteristics of the measurement target gas in the same manner as described above.
When the modulation wave frequencies of the four light emitting element bodies 111a, 111b, 111c, and 111d are, for example, 10 kHz, 12.5 kHz, 15 kHz, and 17.5 kHz, the double frequency components of the modulation signal are 20 kHz, 25 kHz, 30 kHz, and 35 kHz, respectively. When the reference signal generation circuits 452a, 452b, 452c, and 452d output the reference signals of these frequencies, the synchronous detection circuits 453a, 453b, 453c, and 453d have the measurement target gas having absorption characteristics in the double frequency components. That is, only the absorption characteristics of O ₂ gas, CO ₂ gas, HCl gas, and CO gas can be detected and output, respectively.

When the measurement target gas, that is, O ₂ gas, CO ₂ gas, HCl gas, and CO gas has an absorption characteristic, the absorption characteristics as shown in FIG. 10 are obtained from the synchronous detection circuits 453a, 453b, 453c, and 453d. When there is no measurement target gas on the optical path of the detection light 60, the light absorption characteristics as shown in FIG. 10 do not appear in the outputs of the synchronous detection circuits 453a, 453b, 453c, and 453d, and the output as shown in FIG. It becomes.

Next, a concentration calculation method using an arithmetic circuit will be described. Here, the O ₂ gas will be described as an example.
The trigger signal a is input from the wavelength scanning drive signal generation circuit 115a to the arithmetic circuit 455a.
The trigger signal in FIG. 9A is a signal that is output every one cycle including the above S1, S2, and S3, and is output from the wavelength scanning drive signal generation circuit 116a, and through the communication line 50, the arithmetic circuit 455a. The trigger signal is synchronized with S3 of the wavelength scanning drive signal. As shown in FIG. 10, when a predetermined time tb, tc, td elapses from the trigger signal, a minimum value B at the point B, a maximum value C at the point C, and a minimum value D at the point D appear in the output waveform of the synchronous detection circuit. . These predetermined times tb, tc, and td are preliminarily calculated experimentally before factory shipment or at the time of calibration, and are registered in a memory (not shown). The concentration is calculated using this value.

The arithmetic circuit 455a reads and stores the value of the synchronous detection circuit output waveform when a predetermined time tb, tc, td elapses from the trigger signal, and then performs a process of calculating the concentration. This synchronous detection circuit output waveform outputs the maximum value as the concentration, for example, because the maximum value at the peak of the waveform directly represents the gas concentration. Alternatively, the difference value obtained by subtracting the minimum value from the maximum value is used as the density. The concentration detection operation of other measurement target gases (CO ₂ gas, HCL gas, CO gas) may be performed in the same manner.

  In particular, when the gas concentration is low, the influence of noise caused by interference of laser light from optical window materials and lenses becomes stronger, and these noises are detected as peaks, making it difficult to find peaks. In the present invention, since the portion where gas absorption occurs is set in advance and the peak of gas absorption is detected based on the trigger signal, it is possible to accurately detect the gas concentration without being affected by noise or the like. There is.

  With such an apparatus configuration, the gas concentration can be measured by detecting a double frequency signal, as in the prior art. In the present invention, since a multimode optical fiber is used as an optical fiber in particular, measurement is possible in a wide wavelength range of 500 to 2500 nm. Therefore, not only the pigtail type light emitting elements 11a, 11b, 11c, and 11d exemplified in this embodiment, but also by changing the modulation frequency or emitting laser light in series, the light receiving elements can be separated even in the same wavelength region. And can be measured.

In addition, since the loss is low, the peak can be surely displayed to improve the detection ability of the low concentration gas. In addition, since the peak position can be accurately detected by synchronization, the detection ability of the low concentration gas is also improved.
With such an apparatus configuration, the gas concentration can be measured. In the present invention, measurement is possible in a wide wavelength range of 500 to 2500 nm.

The multicomponent laser gas analyzer of the present invention has been described above. This multi-component laser gas analyzer can be modified in various ways.
Next, another embodiment will be described. In this form, only the analysis part 40 is changed among the previous forms. Specifically, the analysis unit 40 of the previous form has a configuration using the branching filter 41 as shown in FIG. 1, but in this embodiment, the analysis unit 40 side has visible light as shown in FIG. Using a visible light / near infrared light receiving element 46 in which a Si photodiode having sensitivity in a region and an InGaAs photodiode having sensitivity in a near infrared region are integrated, as shown in FIG. The visible light / near-infrared light receiving element 46 receives the laser light directly emitted from the multimode optical fiber 41 without using a device, and outputs it from the Si photodiode to the visible light processing circuit 45a. The InGaAs photodiode may output to the near-infrared light processing circuit 45b, and each of the visible light processing circuit 45 and the near-infrared light processing circuit 45b may perform signal processing. Even if such a configuration is adopted, the present invention can be implemented.

Next, another embodiment will be described. In this embodiment, the light emitting unit 100 has the same configuration as the first embodiment described with reference to FIGS. 1 to 11, but the light receiving unit 200 is changed.
In detail, the light receiving unit 200 according to the first embodiment is configured to use the duplexer 42 in the analysis unit 40 as illustrated in FIG. 1, but in the present embodiment, in the analysis unit 40 of the light reception unit 200, As shown in FIG. 14, a configuration including a broadband near-infrared light receiving element 47 and a near-infrared light processing circuit 45 b without using a duplexer. A broadband near-infrared light receiving element 47 having a sensitivity peak in the near-infrared wavelength region and also in the visible wavelength region is used to focus the light directly irradiated from the multimode optical fiber 41 into the broadband near-infrared region. The detection signal received by the light receiving element 47 and output from the broadband near-infrared light receiving element 47 is received by the near-infrared light processing circuit 45b so that the near-infrared wavelength region signal and the visible wavelength region signal are received. Each signal is processed. Even if such a configuration is adopted, the present invention can be implemented.

  Next, another embodiment will be described. In each of the embodiments described above, it has been described that the detection light is a combination of a plurality of light beams having different frequencies. In this embodiment, each pigtail type optical element is operated in a time division manner. In the detection means, the fundamental wave component and the second harmonic wave component of the high frequency modulation are detected from the signal of the light receiving means in synchronization with the operating pigtail light emitting element. For example, the light emitting element bodies 111a, 111b, 111c, and 111d and the reference signal generation circuits 452a, 452b, 452c, and 452d in FIG. 8 are connected to the arithmetic circuits 455a, 455b, 455c, and 455d, respectively, so that they operate one by one. The modulation frequency component is measured from the signal of the detection means in synchronization with the signal. Thus, it is good also as a multi-component laser type gas analyzer which measures a some gas component by a time division.

  Next, another embodiment will be described. In each embodiment described above, the end face of the fiber end portion 32 is not limited. However, in this embodiment, the fiber bundle end portion 21 and the fiber end portion 32 are both inclined polishing ends. With this configuration, the return light does not return to the optical fiber due to reflection at the oblique polishing end, and the influence of the return light can be removed.

  Next, another embodiment will be described. In each of the embodiments described above, the light receiving side is a multimode optical fiber coupler, but it may be a branch coupler. In this case, the modulation frequencies may not be divided.

Next, another embodiment will be described. In the embodiments described above, the oxygen gas (O ₂ gas), the chlorine gas (HCl gas), the carbon dioxide gas (CO ₂ gas), and the carbon monoxide gas (CO gas) are described as examples. However, it is not limited to these gases, and may contain other component gases. In that case, a pigtail light-emitting element having a wavelength capable of detecting other component gases is added, and the arithmetic processing content of the arithmetic circuit is changed and used so that detection can be performed at this wavelength. For example, in order to detect m gas having a wavelength in the visible region and n gas emitting in the near infrared region, m pigtail light emitting elements emitting in the visible region and n pigtail light emitting in the near infrared region are used. Even when the elements are arranged, m + n single-mode optical fibers are fixed in close proximity at the fiber bundle end 21, and m sets of IV conversion circuits, reference signal generating circuits, and synchronous detection are provided on the light receiving side. A processing circuit for visible light using circuits, filters, and arithmetic circuits, and a processing circuit for near infrared light using n sets of IV conversion circuits, reference signal generating circuits, synchronous detection circuits, filters, and arithmetic circuits. It is. It is changed appropriately according to the actual situation.

  The present invention has been described above. According to the laser gas analyzer of the present invention, it is possible to accurately detect a gas component with respect to a measurement target gas including a plurality of gases that absorb light in the visible light and near infrared light. In particular, light emitted from laser light sources having three or more different wavelengths over a wide wavelength range from 500 nm to 2500 nm is radiated into space without using a fiber coupler, and is combined on a single optical fiber on the light receiving side. Thus, the insertion loss on the light emission side is eliminated, and the intensity of the absorption signal of the measurement gas can be increased by efficiently transmitting the light power to the light receiving element.

  In addition, in a laser gas analyzer based on absorption spectroscopy using a semiconductor laser, the conventional optical fiber gas analyzer performs signal processing to detect the peak of the absorption spectrum waveform of the gas. However, it is difficult to detect the gas concentration at low concentration. However, in the proposal of this application, the loss is low, so that the peak appears reliably and the detection capability of the low concentration gas is improved. I let you. Furthermore, by detecting the gas absorption peak based on the trigger signal of the wavelength scanning signal, the low concentration gas can be detected. In addition, simultaneous measurement of multiple components is possible.

  The multi-component laser gas analyzer of the present invention is optimal for measuring flue gas such as boilers and garbage 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.

100: light emitting unit 10: modulated light generating units 11a, 11b, 11c, 11d: pigtail type light emitting elements 111a, 111b, 111c, 111d: light emitting element bodies 112a, 112b, 112c, 112d: temperature detecting elements 113a, 113b, 113c, 113d: Temperature control circuits 114a, 114b, 114c, 114d: Peltier elements 115a, 115b, 115c, 115d: Wavelength scanning drive signal generation circuits 116a, 116b, 116c, 116d: High frequency modulation signal generation circuits 117a, 117b, 117c, 117d: Drive signal generation circuits 12a, 12b, 12c, 12d: single mode type optical fiber (pigtail)
20: Light emitting side optical unit 21: Fiber bundle end 22: Collimated parabolic mirror 23: Window plate with light emitting side wedge 24: Coupled light 200: Light receiving unit 30: Light receiving side optical unit 31: Condensing parabolic mirror 32 : Fiber end 33: Window plate with light emitting side wedge 34: Condensing 40: Analyzing unit 41: Multimode type optical fiber 42: Demultiplexers 43 a and 43 b: Multimode type optical fiber 44 a: Light receiving element for visible light 44 b: Near-infrared light receiving element 45a: visible light processing circuit 45b: near-infrared light processing circuit 46: visible light / near-infrared light receiving element 47: broadband near-infrared light receiving element 50: communication line 60 : Detection light 71a, 71b: Walls 72a, 72b: Flange 73a, 73b: Optical axis adjustment flange

Claims (3)

A light emitting unit that emits detection light by laser light and a light receiving unit that receives detection light propagated through a space in which a plurality of measurement target gases exist, and measure the concentration of a plurality of types of measurement target gases A frequency modulation type multi-component laser gas analyzer,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses the detection light transmitted through the space while reducing the influence of aberration, a multimode optical fiber that combines the condensed light output from the parabolic mirror, and the multimode light Demultiplexing means for demultiplexing the laser light transmitted through the fiber, a visible light receiving element having sensitivity in the visible wavelength region of the demultiplexed light demultiplexed by the demultiplexing means, and demultiplexing by the demultiplexing means. A near-infrared light receiving element having sensitivity in the near-infrared wavelength region of the demultiplexed light, a visible light processing circuit for performing gas analysis based on a detection signal from the visible light receiving element, A near infrared light processing circuit that performs gas analysis based on a detection signal from the infrared light receiving element,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. A multi-component laser comprising: a detection unit; and a calculation unit that calculates a concentration of a measurement target gas based on a value of an output signal of the synchronous detection unit when a predetermined time has elapsed with reference to a trigger signal. Gas analyzer. A light emitting unit that emits detection light by laser light and a light receiving unit that receives detection light propagated through a space in which a plurality of measurement target gases exist, and measure the concentration of a plurality of types of measurement target gases A frequency modulation type multi-component laser gas analyzer,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses detection light transmitted through the space while reducing the influence of aberration, a visible light receiving element having sensitivity in the visible wavelength range, and near infrared light having sensitivity in the near infrared wavelength range The light receiving element for integrating the light receiving element for outputting light from the light receiving side optical unit and gas analysis based on the detection signal from the light receiving element for visible light of the light receiving elements. includes a visible light processing circuit for performing, and a near-infrared light processing circuit for performing gas analysis based on the detection signal from the near-infrared light-receiving element of the light receiving element,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. A multi-component laser comprising: a detection unit; and a calculation unit that calculates a concentration of a measurement target gas based on a value of an output signal of the synchronous detection unit when a predetermined time has elapsed with reference to a trigger signal. Gas analyzer. A light emitting unit that emits detection light by laser light and a light receiving unit that receives detection light propagated through a space in which a plurality of measurement target gases exist, and measure the concentration of a plurality of types of measurement target gases A frequency modulation type multi-component laser gas analyzer,
The light emitting unit
A plurality of pigtail-type light-emitting elements that are provided for each measurement target gas and emit frequency-modulated laser light, and a plurality of single-mode optical fibers that respectively transmit laser light of these pigtail-type light-emitting elements, , Fiber bundle end for bundling the ends of these single-mode optical fibers and bringing the laser beam exit points close to each other, and reducing the influence of aberration on the combined light emitted from the fiber bundle end And a parabolic mirror that emits as detection light in the space,
The light receiving unit is
A parabolic mirror that condenses the detection light transmitted through the space while reducing the influence of aberration, and a peak of sensitivity in the near-infrared wavelength region that outputs a detection signal for the light collected from the light receiving side optical unit. A broadband near-infrared light receiving element having sensitivity in the visible wavelength range, and a near-infrared light processing circuit for performing gas analysis based on a detection signal from the broadband near-infrared light receiving element. ,
The pigtail type light emitting element is
According to the temperature detected by the temperature detecting means, the temperature detecting means of the light emitting element main body, the heating / cooling means of the light emitting element main body, and the emission wavelength from the light emitting element main body become a predetermined value. Temperature control means for controlling the heating / cooling means, and wavelength scanning drive signal generation for generating a wavelength scanning drive signal and a trigger signal for scanning the light absorption characteristics of the measurement target gas by changing a supply current to the light emitting element body And a drive signal generating means for generating a drive signal for the light emitting element body by modulating the wavelength scanning drive signal with the high frequency modulation signal. ,
The visible light processing circuit comprises:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronous detection means for detecting the double frequency component from the output signal of the visible light receiving element, respectively. And a calculation means for calculating the concentration of the measurement target gas based on the value of the output signal of the synchronous detection means when a predetermined time has elapsed with reference to the trigger signal,
The near infrared light processing circuit is:
Reference signal generating means for generating a reference signal having a double frequency component of the high frequency modulation signal in each pigtail light emitting element, and synchronization for detecting the double frequency component from the output signal of the near-infrared light receiving element. A multi-component laser comprising: a detection unit; and a calculation unit that calculates a concentration of a measurement target gas based on a value of an output signal of the synchronous detection unit when a predetermined time has elapsed with reference to a trigger signal. Gas analyzer.

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