JP2007199076A - Method and system for measuring laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and system for measuring laser which remove a noise component to enable high-precision sensing in laser absorption process-based measuring of temperature/density of combustion gas, etc. <P>SOLUTION: When detecting density of gas on light path, etc. by utilizing the fact that such the gas absorbs measuring laser beam and its absorption is associated with density of the above gas, this system functions as follows. In processing of the measuring laser beam transmitted the gas or others, signal component A being data of specific frequency band unique to the gas to be detected is deleted from data indicating intensity to wavelength of this measuring laser beam. Noise component C is generated by complementing this deleted data with polynomial data so as to be succeeded with other remaining part of the data, while extracting only the data of the signal component A corresponding to molecule or atom detected with noise component C removed by subtracting the noise component C from the above data of measuring laser beam. An S/N ratio is improved thereby. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a laser measurement method and a laser measurement system, and in particular, to contribute to lower pollution (lower NOx, lower dioxin) of a garbage incinerator, boiler, etc. (hereinafter referred to as a combustion furnace), This is useful when monitoring various gas concentrations such as CO, O _{2 and the} like.

In order to reduce the pollution of the combustion furnace (lower NOx, lower dioxin), it is necessary to control the combustion air ratio and the like by monitoring the temperature in the combustion furnace and the concentration of various gases such as CO and O ₂ . A laser absorption method is known as a suitable method for irradiating a laser beam to a combustion atmosphere to detect the temperature in the combustion furnace, various gas concentrations such as CO, O _{2 and the} like. This utilizes the fact that the laser beam is absorbed by molecules / atoms existing in the optical path of the laser beam. As a laser measurement system that realizes such a laser absorption method, a laser light source that irradiates measurement laser light toward the inside of the combustion furnace, a laser light detector that detects the measurement laser light transmitted through the inside of the combustion furnace, A system having an arithmetic processing unit that processes an output signal of the laser light detector has been proposed. In such a system, the laser beam for measurement is irradiated into the combustion furnace while continuously changing the wavelength (modulating), and the output signal of the resulting laser beam detector is analyzed and processed by an arithmetic processing unit. By calculating, the average concentration and average temperature data of the molecules / atoms to be detected are obtained.

  In the above system, two types of methods are mainly used for processing the measurement laser beam. One is to FM-modulate the measurement laser beam at high speed and obtain the amount of absorption of the measurement laser beam 3 in the in-furnace gas from the second derivative value of the output signal. The other is to divide the measurement laser beam 3 into “signal light that receives the absorption of the measurement molecule” and “reference light that does not receive the absorption”, and measure the difference while maintaining the balance of the signal intensities of the two. Thus, the amount of absorption is obtained (hereinafter referred to as auto balance light detection method).

  The laser beam for measurement obtained by this type of laser measurement system is ideally as shown in FIG. In the figure, the horizontal axis represents the wavelength of the measurement laser beam, and the vertical axis represents the intensity of the measurement laser beam, and shows the wavelength dependence of the intensity (absorbance) of the measurement laser beam. The temperature dependence is shown by a) to (f), respectively. Here, for a specific molecule or atom (in this example, a CO molecule), the wavelength of the measurement laser beam to be absorbed is uniquely determined by theoretical calculation, and a drop in the light intensity of the measurement laser beam is detected at the specific wavelength. Is done. This drop is caused by absorption of the laser beam for measurement by molecules or atoms. The depression pattern has a unique shape depending on the temperature on the optical path of the measurement laser beam (for example, the temperature in the combustion furnace). That is, the concentration of molecules or atoms specified by the absorption wavelength of the measurement laser beam can be detected by the amount of fall (absorption amount) of the measurement laser beam, and the temperature can be detected by the pattern. 6A to 6F are characteristic diagrams in the case of 300 ° K, 500 ° K, 700 ° K, 900 ° K, 1100 ° K, and 1300 ° K in this order.

Japanese Patent Laid-Open No. 10-142148

However, in the actual measurement laser light obtained in the laser light detection means of the laser measurement system according to the prior art, absorption of H ₂ O or the like on the optical path causes noise and affects the measurement laser light. give. As a result, the actual measurement characteristics are as shown in FIG. 7, for example. The portion A in the figure is a drop in the measurement laser beam due to the molecule (atom) to be measured, and the drop in the other portion B is due to a noise component. Therefore, when the measurement laser beam including the noise component B is used, a sufficient S / N ratio cannot be obtained, and it is difficult to perform highly accurate detection.

  In recent years, there has been a growing demand to measure the concentration and temperature of gases and the like at many points in the combustor and without increasing the cost of the system as much as possible.

  In view of the above prior art, the present invention enables high-precision detection by removing noise components when measuring the temperature and concentration of combustion gas or the like by the laser absorption method. It is an object of the present invention to provide an inexpensive laser measurement method and laser measurement system capable of measuring a plurality of points with a plurality of laser beams.

  The configuration of the present invention that achieves the above object is characterized by the following points.

1) A laser beam for measurement is emitted from a laser light source toward a target space while continuously changing the wavelength, and the laser beam for measurement that has passed through the target space is detected by a laser light detection unit, and predetermined processing is performed. In a laser measurement method for detecting the concentration of a specific molecule or atom on the optical path by
During processing of the measurement laser beam, data in a predetermined frequency band specific to the molecule or atom to be detected is deleted from the data representing the intensity with respect to the wavelength of the measurement laser beam,
The deleted data is supplemented with polynomial data whose degree is determined according to the molecule or atom so that the deleted data is continuous with the rest of the data, and a baseline including a noise component is obtained.
Corresponding to the molecule or atom to be detected that minimizes the result by applying the least square method to the sum of the data corresponding to the baseline and the molecule or atom to be detected and the data of the measurement laser beam. By obtaining the data of the part to be
Remove the noise component and extract only the data corresponding to the molecule or atom to be detected.

2) In the laser measurement method described in [Claim 1],
The numerator serving as the noise component is H ₂ O, and the order of the polynomial is determined according to the H ₂ O.

3) In the laser measurement method described in [Claim 1] or [Claim 2],
Facing the target space, a plurality of pairs of laser light sources and laser light detection means are arranged to detect the concentration of molecules or atoms on the optical path at a plurality of locations in the target space.

4) In the laser measurement method described in [Claim 1] or [Claim 2],
Each laser is irradiated with a plurality of measurement laser beams divided according to the number of optical paths from one laser light source, and only one specific measurement laser beam is detected at a certain time. Time to receive light is time-divided so that one laser light detection means sequentially captures the light.

5) In the laser measurement method described in [Claim 4],
The measurement laser light emitted from the laser light source is branched into a predetermined number by a branching means using a fiber splitter, and is branched using a single mode optical fiber in which the end faces of the connecting portions facing each other are cut obliquely. Each measurement laser beam is guided to a predetermined position in the target space.

6) A laser light source that irradiates the target laser beam while continuously changing the wavelength toward the target space;
Laser light detection means for detecting the measurement laser light transmitted through the interior of the target space;
In a laser measurement system having arithmetic processing means for detecting the concentration of a specific molecule or atom on the optical path by processing the output signal of this laser light detection means,
The arithmetic processing means deletes the data of a predetermined frequency band specific to the molecule or atom to be detected from the data representing the intensity with respect to the wavelength of the measurement laser light when processing the measurement laser light. The above-mentioned deleted data is complemented with polynomial data whose degree is determined according to the molecule or atom so that the data is continuous with the rest of the data, and a baseline including a noise component is obtained. And applying the least square method to the sum of the data of the part corresponding to the molecule or atom to be detected and the data of the laser beam for measurement, to minimize the result of the part corresponding to the molecule or atom to be detected. By obtaining data, the noise component is removed and only the data corresponding to the molecule or atom to be detected is extracted.

7) In the laser measurement system according to [Claim 6],
The arithmetic processing means determines the order of a polynomial according to H ₂ O, where the numerator that becomes the noise component is H ₂ O.

8) In the laser measurement system according to [Claim 6] or [Claim 7],
A plurality of pairs of the laser light source and the laser light detection means are provided to detect the concentration of molecules or atoms on the optical path at a plurality of locations in the target space.

9) In the laser measurement system according to [Claim 6] or [Claim 7],
The laser light source and the laser light detection means are formed as a single unit, and a plurality of measurement laser lights divided according to the number of optical paths are irradiated from the single laser light source into the target space. In order to detect only one specific measurement laser beam, the time for receiving each laser beam is time-divisionally taken in sequentially.

10) In the laser measurement system according to [Claim 9],
The measurement laser light emitted from the laser light source is branched into a predetermined number by a branching means using a fiber splitter, and each branched measurement laser light is placed at a predetermined position in the target space using a single mode optical fiber. In addition, the end faces of the optical fibers facing each other were cut obliquely at the connection portion of the optical fiber itself.

  According to the invention described in [Claim 1] and [Claim 6], the S / N ratio can be made sufficiently large, and the detection accuracy can be improved accordingly. In addition, noise component data in the measurement laser beam can be reproduced easily and faithfully.

  According to the invention described in [Claim 2] and [Claim 7], the data of the noise component in the laser beam for measurement can be reproduced easily and faithfully.

  According to the invention described in [Claim 3] and [Claim 8], it is possible to detect gas concentrations and the like in a plurality of regions of the target space at a time.

  According to the invention described in [Claim 4] and [Claim 9], the effect of the invention described in [Claim 3] and [Claim 8] is achieved by one laser light source and one laser light detection means. be able to. As a result, the system configuration is simplified and the cost can be reduced as much as possible. Incidentally, the laser light source and the laser beam detection means for irradiating the measurement laser beam are the most expensive components in the system.

  According to the invention described in [Claim 5] and [Claim 10], it is possible to irradiate the measurement laser beam, which is a narrow-band single mode laser beam, into the target space without scattering.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, in each embodiment, the same parts are denoted by the same reference numerals, and redundant description is omitted.

<First Embodiment>
FIG. 1 is an explanatory view conceptually showing the first embodiment of the present invention. As shown in the figure, the combustion furnace 1 has windows 1b and 1c at portions facing each other on both sides (left and right sides in the figure) of the furnace wall 1a. The laser light source 2 irradiates a measurement laser beam 3 (indicated by a thick solid line in the figure, the same applies hereinafter) toward the inside of the combustion furnace 1, and in the case of this embodiment, vertically upward. The laser beam 3 for measurement irradiated in the direction is reflected by the mirror 4 in the horizontal direction, transmitted through the half mirror 5, and irradiated into the furnace through the window portion 1b. Here, the laser light source 2 is integrated with an optical fiber that guides the measurement laser light 3 generated by a remote laser device as well as the laser device itself that generates the measurement laser light 3, and measurement is performed from the end face of the optical fiber. Also included are those that irradiate the laser beam 3 for use. The measurement laser beam 3 at this time is strictly required to have a specific wavelength determined according to the gas to be detected. Therefore, the laser light source 2 that irradiates the laser beam 2 has a narrow-band single mode. A semiconductor laser device capable of generating laser light is optimal. For the same reason, the optical fiber used at this time needs to be of a single mode. Moreover, the wavelength of the measuring laser beam 3 is continuously changed during irradiation. That is, modulation is applied.

  The laser beam detector 6 detects the measurement laser beam 3 that has passed through the gas in the furnace of the combustion furnace 1. More specifically, the measurement laser beam 3 that has passed through the gas in the furnace reaches the outside of the furnace through the window 1 c, is reflected vertically downward by the half mirror 7, and then enters the laser light detector 6.

  The arithmetic processing unit 8 processes the output signal of the laser light detector 6 to detect the gas concentration and temperature in the combustion furnace 1. Such detection is performed using a method known as a laser absorption method. In this embodiment, the measurement laser beam 3 is FM-modulated at a high speed, and the absorption amount of the measurement laser beam 3 in the furnace gas is obtained from the second derivative value of the output signal. Of course, a balanced light detection method may be used.

  Further, when processing the measurement laser beam 3, the arithmetic processing unit 8 processes the output signal of the laser beam detector 6 to remove noise components as follows. That is, first, from data representing the intensity with respect to the wavelength of the measurement laser beam 3 which is an output signal of the laser beam detector 6 (data shown in the characteristic diagram of FIG. 7), a predetermined frequency band specific to the molecule or atom to be detected is obtained. Delete the data. Next, the deleted data is complemented with polynomial data so that the deleted data is continuous with the remaining data of the other part. As a result, data representing the noise component C is obtained as data supplemented with the data deleted as described above, as shown in FIG. Finally, the complemented data is subtracted from the data of the measurement laser beam 3 which is an output signal of the laser beam detector 6. As a result, the noise component C can be removed, and only the data corresponding to the molecule or atom to be detected, that is, the signal component A is extracted.

  Here, the polynomial is given as specific to the molecule or atom to be detected, and the order of the polynomial is determined according to the molecule or atom, thereby complementing the above-described deletion portion by the least square method. In this case, as a complementary expression, a polynomial is generally optimal, but is not limited thereto. Any specific formula corresponding to the molecule or atom to be detected may be used.

  The pulse laser light source 9 irradiates an optical axis locking pulse laser beam 10 (indicated by a thick dotted line in the figure, the same applies hereinafter) that coincides with the optical axis of the measurement laser beam 3. In the case of the embodiment, the pulse laser beam 10 irradiated downward in the vertical direction is reflected in the horizontal direction by the half mirror 5 and irradiated into the furnace through the window portion 1b. Unlike the measurement laser beam 3, the pulse laser beam 10 does not need to be a laser beam having a specific wavelength. However, the light intensity of the pulse laser beam 10 directly affects the measurement accuracy of the optical axis position. Select in consideration of the points. That is, the light intensity is relatively higher than that of the single mode semiconductor laser device that constitutes the laser light source 2, but it can be suitably configured with an inexpensive ordinary semiconductor laser laser device. The position detection sensor 11 receives the pulsed laser light 10 transmitted through the half mirror 7 on the opposite side of the pulsed laser light source 9 with respect to the combustion furnace 1 and detects the position of the optical axis. 1 includes two-dimensionally arranged photoelectric conversion elements that convert voltage signals corresponding to the light intensity of the received pulsed laser beam 10. That is, the two-dimensional position of the optical axis of the pulse laser beam 10 is detected.

  Note that the optical axis of the measurement laser beam 3 and the optical axis of the pulsed laser beam 10 are completely coincident with each other. Therefore, the solid line and the dotted line in the drawing representing these actually overlap, but for convenience of explanation, both are used. They are shown slightly apart (the same applies hereinafter).

  The optical axis adjustment unit 12 is based on the position information of the optical axis of the pulse laser beam 10 that is an output signal of the position detection sensor 11, the optical axis of the measurement laser beam 3 (pulse laser beam 10), the laser beam detector 6, The positional relationship between the two is adjusted so that the relative positional relationship is always constant. In this embodiment, the output signal of the position detection sensor 11 is processed by the arithmetic processing unit 8 to obtain a deviation signal representing the deviation amount with respect to the predetermined position, and the optical axis adjustment unit so that the deviation signal becomes zero. 12 is moved integrally with the mirror 4, the half mirror 5, and the pulsed laser beam 10 to adjust the relative position and posture with respect to the combustion furnace 1. Here, the optical axis adjusting unit 12 is configured to move two-dimensionally in the vertical plane with respect to the combustion furnace 1 and rotate around the horizontal axis. The movement is controlled to the predetermined position as described above by the control.

  In this embodiment, the laser beam 3 for measurement is irradiated from the laser light source 2 toward the inside of the combustion furnace 1, the laser beam for measurement 3 that has passed through the gas inside is detected by the laser light detector 6, The output signal is subjected to predetermined processing by the arithmetic processing unit 8 to detect the concentration and temperature of the gas. On the other hand, a pulse laser beam 10 for locking the optical axis that coincides with the optical axis of the laser beam 3 for measurement is irradiated into the furnace separately from the laser beam 3 for measurement, and the position of the optical axis of the pulse laser beam 10 is positioned. Detection is performed by the detection sensor 11. Thereafter, the positional relationship between the optical axis of the pulsed laser beam 10 (measurement laser beam 3) and the laser beam detector 6 is adjusted so that the relative positional relationship is always constant. Such optical axis adjustment is performed by irradiating the inside of the furnace with the pulsed laser beam 10 while the arithmetic processing unit 8 performs predetermined processing for detecting the gas concentration and temperature. This is to prevent the irradiation with the pulse laser beam 10 from affecting the measurement by the measurement laser beam 3.

  In addition, since the arithmetic processing unit 8 performs the above-described processing for removing the noise component C from the output signal of the laser light detector 6, the measurement laser light 3 based on the detection target obtained as a result of this processing. Can be accurately detected.

<Second Embodiment>
FIG. 3 is an explanatory view conceptually showing the second embodiment of the present invention. As shown in the figure, the laser measurement system according to the present embodiment reciprocates the measurement laser light 3 irradiated in the combustion furnace 1 in the combustion furnace 1, and is on the same side as the laser light source 2 with respect to the combustion furnace 1. The laser beam detector 16 is used for detection. Therefore, in the present embodiment, the optical path length of the measuring laser beam 3 in the combustion furnace 1 is twice that of the first embodiment. As a result, as the optical path length increases, the amount of absorption of the measurement laser beam 3 by the gas also increases, and the measurement of the gas concentration and temperature based on the output signal of the laser detector 16 can be performed easily and with high accuracy. .

  Here, in the measurement laser light 3 emitted from the laser light source 2, the component that has passed through the half mirror 23 is reflected by the mirror 4 and reaches the combustion furnace 1, and is disposed on the opposite side of the combustion furnace 1. After reciprocating in the combustion furnace 1 by being reflected by the half mirror 17, the component reflected by the half mirror 24 enters the laser light detector 16. On the other hand, of the measurement laser light 3 emitted from the laser light source 2, the component reflected by the half mirror 23 is reflected by the mirror 25 and reaches the laser light detector 16. In the laser light detector 16, the measurement laser light 3, which is signal light reciprocating in the combustion furnace 1, and the measurement laser light 3, which is reference light taken directly without reciprocating in the combustion furnace 1, are obtained. In comparison, the amount of absorption of the measuring laser beam 3 is detected. That is, it is a detection unit using the above-described “autobalance light detection method”. However, this configuration is not essential. Of course, the same method as in the first embodiment is also acceptable. The output signal of the laser light detector 16 is processed by the arithmetic processing unit 18 to obtain the gas concentration and temperature in the combustion furnace 1. The processing procedure at this time is exactly the same as in the first embodiment. That is, the same noise removal process is performed.

  Also in this embodiment, the pulse laser light source 9 irradiates the combustion furnace 1 with the pulse laser beam 10 for optical axis locking that coincides with the optical axis of the measurement laser beam 3, but the optical path of the measurement laser beam 3 is Since the inside of the combustion furnace 1 is reciprocated, the pulsed laser beam 10 is also reciprocated within the combustion furnace 1 correspondingly. For this reason, a position detection sensor 26 is also provided along with a position detection sensor 21 that receives the pulse laser light 10 transmitted through the half mirror 17 in the pulse laser light 10 and detects the position of its optical axis. This position detection sensor 26 transmits the component reflected by the half mirror 17 in the pulse laser beam 10 and transmitted through the half mirror 24 on the same side as the pulse laser light source 9 of the combustion furnace 1 (the same side as the laser light source 2). As the light is received. Here, the position detection sensor 21 adjusts the position of the optical axis in the forward path of the measurement laser beam 3, and the position detection sensor 26 adjusts the position of the optical axis in the return path of the measurement laser beam 3. .

  That is, the output signal of the position detection sensor 21 is first processed by the arithmetic processing unit 18 to control the position and posture of the optical axis adjustment unit 12. As a result, the positional relationship between the optical axis of the forward path and the position detection sensor 21 is adjusted to a predetermined value. This is exactly the same processing as in the first embodiment shown in FIG. After the forward optical axis lock is thus completed, this optical axis and the laser are based on the positional information of the optical path of the backward path of the pulsed laser beam 10 reflected by the half mirror 17, which is the output signal of the position detection sensor 26. The angle of the reflection surface of the half mirror 17 is adjusted so that the relative positional relationship with the photodetector 26 is constant. Such adjustment is performed by processing the output signal of the position detection sensor 26 by the control unit of the arithmetic processing unit 18 and controlling the rotation of the half mirror 17 around the horizontal axis by the output signal.

  In this embodiment, the concentration and temperature of the gas in the combustion furnace 1 are detected by the autobalance detection method using the measurement laser beam 3 irradiated into the combustion furnace 1 and reciprocating in the combustion furnace 1.

  On the other hand, the optical axis lock is first performed on the forward optical axis using the output signal of the position detection sensor 21, and after the optical axis lock is completed, the optical axis lock is performed on the return optical axis. The irradiation of the pulse laser beam 10 for locking the optical axis is performed while the arithmetic processing unit 18 performs predetermined processing for detecting the gas concentration and temperature. The reason is exactly the same as in the case of the first embodiment shown in FIG.

<Third Embodiment>
FIG. 4 is an explanatory view conceptually showing the third embodiment of the present invention. As shown in the figure, the present embodiment is provided with a plurality of sets of transmission / reception systems for the measurement laser beam 3 so that the concentration and temperature of the gas on the plurality of optical paths in the combustion furnace 1 can be detected. is there. Basically, the laser measuring system according to the first embodiment has a structure in which a plurality of sets (four sets in the figure) of light transmission / reception systems are distributed around the combustion furnace 1.

  However, the laser measurement system according to the present embodiment branches the measurement laser light 3 generated by one laser light source 2 to four measurement laser lights 3-1, 3-2, 3-3, 3-. 4 and the laser beams for measurement 3-1 to 3-4 transmitted through the combustion furnace 1 are processed by one laser light detector 36. The laser light source 2 must strictly irradiate a single mode laser beam. As a result, the laser light source 2 becomes expensive, and the laser light detector 36 is also expensive, and these are required to reduce the cost of the system. This is because it is most effective to reduce the number of laser light sources 2 and laser light detectors 36 as much as possible. In this way, various measures are taken to detect the gas concentrations and temperatures on the plurality of optical paths in the combustion furnace 1 while keeping the laser light source 2 and the laser light detector 36 as one unit. Specifically, it is as follows.

  The measurement laser light 3 emitted from the laser light source 2 is branched into four at the branching portion 43, guided by the optical fibers 44-1, 44-2, 44-3, 44-4, and sent to the respective light transmission head portions 2. Irradiation is directed toward the inside of the combustion furnace 1 through -1, 2-2, 2-3, 2-4. Here, each light transmission head part 2-1 to 2-4 is arrange | positioned at equal intervals around the furnace wall 1a. Measurement laser beams 3-1, 3-2, 3-3, and 3-4 irradiated into the combustion furnace 1 through the light transmission head units 2-1 to 2-4 sandwich the combustion furnace 1. The optical fibers 45-1, 45-2, 45- are respectively connected to the opposite sides of the light transmission heads 2-1 to 2-4 via the light receiving heads 6-1, 6-2, 6-3, 6-4. 3, 45-4. The measurement laser beams 3-1 to 3-4 guided by the optical fibers 45-1 to 45-4 are selected by the signal switching unit 47 at a predetermined interval in which any one is time-divided, The laser light is sequentially introduced into the laser detector 36. The arithmetic processing unit 38 processes the output signal of the laser beam detector 36 based on the measurement laser beams 3-1 to 3-4 to detect the gas concentration and temperature on each optical path in the combustion furnace 1. Further, the arithmetic processing unit 38 controls the frequency modulator 48 to modulate the wavelength of the measurement laser beam 3 emitted from the laser light source 2. Further, the processing of each measurement laser beam 3-1, 3-2, 3-3, 3-4 is performed in the same manner as in the first embodiment. That is, the same noise removal process is performed.

  The pulse laser light sources 9-1, 9-2, 9-3, and 9-4 for locking the optical axis transmit light along with the movement of the optical axis adjusting units 12-1, 12-2, 12-3, and 12-4. It is configured to move integrally with the head portions 2-1 to 2-4 and to control the position and posture with respect to the combustion furnace 1. The pulsed laser beams 10-1, 10-2, 10-3, and 10-4 irradiated from the pulsed laser light sources 9-1 to 9-4 into the furnace 1 of the combustion furnace 1 have the optical axis of the measuring laser beam 3. -1 to 3-4 respectively coincide with the optical axes (in the figure, they are separated for convenience of explanation), and after passing through the inside of the combustion furnace 1, the same as the embodiment shown in FIG. In this manner, the position detection sensors 11-1, 11-2, 11-3, and 11-4 detect the position. The output signals of the position detection sensors 11-1, 11-2, 11-3, and 11-4 are respectively supplied to the arithmetic processing unit 38, and the optical processing unit 12 is subjected to predetermined processing by the arithmetic processing unit 38. -1,12-2,12-3,12-4 are controlled so that the relative positional relationship between the optical axis and the light receiving head sections 6-1 to 6-4 (laser light detector 36) is as prescribed. Adjust so that Such position adjustment is performed independently for each of the measurement laser beams 3-1 to 3-4, but the mode of control is exactly the same as in the embodiment shown in FIG. 1.

  The branch portion 43 is formed by a fiber splitter, and the end faces of the optical fibers facing each other are cut obliquely at the connection portions of the optical fibers 44-1 to 44-4 and the optical fibers 45-1 to 45-4. is there. As a result, interference due to scattering and reflection of the measurement laser beams 3-1 to 3-4 can be prevented, and gas absorption can be performed satisfactorily, and measurement accuracy can be kept sufficiently high. I am trying to do it. The optical fibers 44-1 to 44-4 and the optical fibers 45-1 to 45-4 are single mode. This is to prevent the modes of the measurement laser beams 3-1 to 3-4 from being distorted.

  FIG. 5 is a timing chart showing a procedure for detecting four laser beams in the third embodiment. As shown in the figure, in Ch1, the measurement laser light 3-1 transmitted through the optical fiber 45-1 is selected by the signal switch 47 and taken into the laser light detector 36, and the same is applied to Ch2 in the same manner. The measurement laser beam 3-2 transmitted through the fiber 45-2, the measurement laser beam 3-3 transmitted through the optical fiber 45-3 in Ch3, and the optical fiber 45-4 transmitted through Ch4. The measured laser light 3-4 is sequentially taken into the laser light detector 36 and subjected to predetermined processing.

  On the other hand, the pulsed laser beams 10-1 to 10-4 have timings other than the capturing timing of the measuring laser beams 3-1 to 3-4 having the same optical axis (each measuring laser beam 3-1 to 3-4). -4), and position adjustment based on this is performed. In the case shown in FIG. 5, the pulse laser beam 10-1 is Ch3, the pulse laser beam 10-2 is Ch4, the pulse laser beam 10-3 is Ch1, and the pulse laser beam 10-4 is Ch2. Lights 10-1 to 10-4 are irradiated. This is because the measurement laser beams 3-1 to 3-4 and the pulse laser beams 10-1 to 10-4 having a common optical axis are separated into any of different channels Ch1 to Ch4 without overlapping. Just do it. This is because the measurement laser beams 3-1 to 3-4 may be taken in with the influence of the pulse laser beams 10-1 to 10-4 removed.

  As described above, in this embodiment, channels Ch1 to Ch4 corresponding to the number of measurement laser beams 3-1 to 3-4 are provided, and one specific measurement is performed in a predetermined period assigned to each channel Ch1 to Ch4. The laser beams 3-1 to 3-4 are selected by the signal switch 47. Thus, the data of the four measurement laser beams 3-1 to 3-4 can be processed by one laser beam detector 36. Further, the adjustment of the optical axis position is performed by using pulse laser beams 10-1 to 10- whose optical axes are common during periods other than the period during which the measurement laser beams 3-1 to 3-4 are taken into the laser light detector 36. 4 is irradiated, the irradiation of the pulsed laser beams 10-1 to 10-4 does not affect the measurement of the gas concentration or the like by the measuring laser beams 3-1 to 3-4. .

  In the present embodiment, the case where the analysis processing of the measurement laser beams 3-1 to 3-4 is performed by the differential method has been described. Similarly, of course, a so-called reciprocating system using the system shown in FIG. Moreover, the number of light transmission / reception systems and the installation position with respect to the combustion furnace 1 can also be suitably selected as needed. Furthermore, if the point of cost is not considered, the laser light source 2 and the laser beam detector 36 can be provided by the number of the measurement laser beams 3-1 to 3-4.

  In the first to third embodiments, in addition to the measurement laser beam 3, a pulse laser beam 10 for optical axis locking is also prepared. As described above, this is because the characteristic required for the measurement laser beam 3 (having a single wavelength) is different from the characteristic required for the pulse laser beam 10 (high light intensity). This is because, in principle, it is not necessary to prepare two types of laser beams in this way. If a single laser beam with sufficient intensity can be obtained at low cost, the optical axis can be locked only with the measurement laser beam 3. That is, while the measurement laser beam 3 is taken in and the gas concentration or the like is being processed, the measurement laser beam 3 is used as the laser beam for locking the optical axis, and the first to the above-described pulse laser beam 10 is used. What is necessary is just to adjust the optical-axis position of the laser beam 3 for a measurement by the aspect similar to 3rd Embodiment.

It is explanatory drawing which shows the 1st Embodiment of this invention notionally. It is a characteristic view which shows the intensity | strength (absorbance) characteristic after processing the measuring laser beam with the arithmetic processing unit which concerns on the said embodiment. It is explanatory drawing which shows the 2nd Embodiment of this invention notionally. It is explanatory drawing which shows the 3rd Embodiment of this invention notionally. It is a timing chart which shows the detection procedure of the four laser beams in the said 3rd Embodiment. It is a characteristic view which shows the ideal intensity | strength characteristic of the laser beam for a measurement absorbed by the molecule | numerator or atom which is a detection object for every temperature of the molecule | numerator etc. which are a detection object. It is a characteristic view which shows the actual intensity | strength characteristic in the prior art of the laser beam for a measurement absorbed by the molecule | numerator or atom which is a detection target.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion furnace 1a Furnace wall 2 Laser light source 3 Laser beam for measurement 6 Laser light detector 8 Arithmetic processor 9 Pulse laser light source 10 Pulse laser light 11 Position detection sensor 12 Optical axis adjustment part 16 Laser light detector 17 Half mirror 18 Operation Processing device 21 Position detection sensor 26 Position detection sensor 3-1, 3-2, 3-3, 3-4 Laser beam for measurement 9-1, 9-2, 9-3, 9-4 Pulse laser light source 10-1 , 10-2, 10-3, 10-4 Pulse laser light sources 11-1, 11-2, 11-3, 11-4 Position detection sensors 12-1, 12-2, 12-3, 12-4 Optical axis Adjustment unit 47 Signal switcher A Signal component C Noise component

Claims (10)

A laser beam for measurement is irradiated from the laser light source toward the target space while continuously changing the wavelength, and the laser beam for measurement that has passed through the target space is detected by the laser light detection means and subjected to predetermined processing. In the laser measurement method for detecting the concentration of a specific molecule or atom on the optical path by
During processing of the measurement laser beam, data in a predetermined frequency band specific to the molecule or atom to be detected is deleted from the data representing the intensity with respect to the wavelength of the measurement laser beam,
The deleted data is supplemented with polynomial data whose degree is determined according to the molecule or atom so that the deleted data is continuous with the rest of the data, and a baseline including a noise component is obtained.
Corresponding to the molecule or atom to be detected that minimizes the result by applying the least square method to the sum of the data corresponding to the baseline and the molecule or atom to be detected and the data of the measurement laser beam. By obtaining the data of the part to be
A laser measurement method characterized by removing noise components and extracting only data of a portion corresponding to a molecule or atom to be detected. In the laser measurement method according to claim 1,
A numerator serving as a noise component is H ₂ O, and a polynomial order is determined according to the H ₂ O. In the laser measurement method according to [Claim 1] or [Claim 2],
A laser measurement method characterized by facing a target space and arranging a plurality of pairs of laser light sources and laser light detection means to detect the concentration of molecules or atoms on the optical path at a plurality of locations in the target space. In the laser measurement method according to [Claim 1] or [Claim 2],
Each laser is irradiated with a plurality of measurement laser beams divided according to the number of optical paths from one laser light source, and only one specific measurement laser beam is detected at a certain time. A laser measurement method, characterized in that the time for receiving light is time-divided and sequentially captured by one laser light detection means. In the laser measurement method according to claim 4,
The measurement laser light emitted from the laser light source is branched into a predetermined number by a branching means using a fiber splitter, and is branched using a single mode optical fiber in which the end faces of the connecting portions facing each other are cut obliquely. A laser measurement method characterized by guiding each measurement laser beam to a predetermined position in a target space. A laser light source that irradiates the target laser beam while continuously changing the wavelength toward the target space;
Laser light detection means for detecting the measurement laser light transmitted through the interior of the target space;
In a laser measurement system having arithmetic processing means for detecting the concentration of a specific molecule or atom on the optical path by processing the output signal of this laser light detection means,
The arithmetic processing means deletes the data of a predetermined frequency band specific to the molecule or atom to be detected from the data representing the intensity with respect to the wavelength of the measurement laser light when processing the measurement laser light. The above-mentioned deleted data is complemented with polynomial data whose degree is determined according to the molecule or atom so that the data is continuous with the rest of the data, and a baseline including a noise component is obtained. And applying the least square method to the sum of the data of the part corresponding to the molecule or atom to be detected and the data of the laser beam for measurement, to minimize the result of the part corresponding to the molecule or atom to be detected. A laser measurement system characterized in that, by obtaining data, a noise component is removed and only data corresponding to a molecule or atom to be detected is extracted. In the laser measurement system according to claim 6,
Said processing means, the molecules of the noise component as H ₂ O, a laser measuring system, characterized in that in response to the H ₂ O, to determine the degree of the polynomial. In the laser measurement system according to [Claim 6] or [Claim 7],
A laser measurement system comprising a plurality of pairs of the laser light source and the laser light detection means to detect the concentration of molecules or atoms on the optical path at a plurality of locations in the target space. In the laser measurement system according to [Claim 6] or [Claim 7],
The laser light source and the laser light detection means are formed as a single unit, and a plurality of measurement laser lights divided according to the number of optical paths are irradiated from the single laser light source into the target space. The laser measurement system is characterized in that the time for receiving each laser beam is sequentially taken in a time-sharing manner so that only one specific measurement laser beam is detected. In the laser measurement system according to claim 9,
The measurement laser light emitted from the laser light source is branched into a predetermined number by a branching means using a fiber splitter, and each branched measurement laser light is placed at a predetermined position in the target space using a single mode optical fiber. Further, the laser measurement system is characterized in that the end faces of the optical fibers facing each other are cut obliquely at the connection portion of the optical fiber itself.

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