JP6425178B2 - Raman scattered light detection device and Raman scattered light detection method - Google Patents

Description

  The present invention relates to a Raman scattered light detection apparatus and a Raman scattered light detection method, and more particularly to a Raman scattered light detection apparatus for detecting Raman scattered light emitted from gas molecules using an optical interference filter.

  When the mixed gas is irradiated with laser light, a considerable amount of Raman scattering phenomenon is generated which is converted to the internal energy of each gas molecule. Table 1 shows the Raman shift of each gas when the wavelength of the laser light is 355 nm, the Raman scattering wavelength, the relative intensity to N2, the difference with the short wavelength adjacent line, and the difference with the long wavelength adjacent line. FIG. 7 shows the relative intensity of Raman scattered light relative to the wavelength of each gas and N 2 when the wavelength of the laser light is 355 nm, and (b) the measured value of Raman scattered light (horizontal axis represents wavelength, vertical The axes show strength), (c) to (f) an enlargement of (b) of each gas.

  The Raman scattered light wavelength is different for each gas type. Also, at the laboratory level, it has been realized that the molecular species identification and concentration measurement can be performed remotely by Raman scattered light of gas molecules. For example, Raman scattered light is separated by transmitting only a specific wavelength using a narrow band interference filter (see Patent Document 1). Also, as shown in FIG. 7, since the individual Raman bandwidths are narrow, the Raman bands of various mixed gas molecules rarely overlap each other. There is a method of separating Raman scattered light of a specific molecular species by transmitting only specific wavelength light by spectroscopy.

Patent No. 5159799

  However, in the background art using the spectroscope of the optical precision instrument, although it could be realized at the laboratory level, there were many problems such as mechanical rigidity and heavy when taking it out outdoors. For example, an optical interference filter is used to reduce the size and weight of the spectroscopic system, but the Raman wavelength range of the target gas is 360 nm to 420 nm, and the wavelength difference between adjacent gases is at least 0.79 nm, and the transmission half width is 2 nm It is narrow as follows (it raises SN ratio with disturbance light noise). Therefore, the incident angle accuracy of the Raman scattered light is important. For example, it is necessary to make parallel light incident at a vertical incident angle of ± 0.3 degrees or less. When the optical axis angle shifts, the transmittance decreases and the measurement becomes impossible. For this reason, advanced and complicated operations such as structural design of the light receiving system, manufacture of the fine movement mechanism and alignment adjustment are required. Depending on the background art, it has been difficult to realize a portable detector aiming to reduce the size and weight by maintaining the reliability of the device.

  Then, this invention aims at proposing the Raman scattered light detection apparatus etc. which are simple in a light reception mechanism and can reduce the precision of optical axis adjustment.

  A first aspect of the present invention is a Raman scattered light detection device for detecting Raman scattered light emitted from gas molecules using an optical interference filter, in which the Raman scattered light is emitted from the gas molecules A transmission wavelength sweeping unit that changes the transmission center wavelength of the light interference filter by rotating the light interference filter, a light receiving unit that receives light transmitted through the light interference filter, and the light receiving unit receives the Raman scattered light Detection unit that detects that the light reception unit is receiving light and detects the rotation angle value of the light interference filter, and the light reception unit using the rotation angle value detected by the detection unit An arithmetic unit is provided to calculate the wavelength of the received Raman scattered light.

  A second aspect of the present invention is the Raman scattered light detection device according to the first aspect, wherein the transmission wavelength sweeping unit rotates the optical interference filter to continuously transmit the transmission center wavelength of the optical interference filter. The sweep direction is changed and swept by increasing and decreasing, and the calculation unit changes the sweep direction and sweeps the wavelength of the Raman scattered light using the rising and falling wavelengths of the Raman scattered light detected by sweeping. Calculate

  A third aspect of the present invention is the Raman scattered light detection device according to the first or second aspect, which stores an irradiation unit that irradiates a gas laser with a pulse laser, and stores a reference wavelength of Raman scattered light of N2. A Raman scattered light reference wavelength storage unit is provided, and the transmission center wavelength at which the optical interference filter rotates and includes the wavelength of the Raman scattered light of N2, and the operation unit detects the Raman scattering of the detected N2 The error is determined by comparing the wavelength of light with the reference wavelength of N 2 stored in the Raman scattered light reference wavelength storage unit, and the Raman scattered light of the other gas molecules obtained by calculation using the error Correct the wavelength.

  A fourth aspect of the present invention is the Raman scattered light detection device according to any one of the first to third aspects, wherein the control unit determines whether light received by the light receiving unit satisfies a reference condition. The transmission wavelength sweep unit rotates the light interference filter in a state where the gas light molecules emit or do not emit the Raman scattered light, and the control unit is configured to receive the light received by the light receiving unit. If the reference condition is satisfied, the wavelength of the Raman scattered light is detected, and if the reference condition is not satisfied, the wavelength of the Raman scattered light is not detected.

  A fifth aspect of the present invention is a Raman scattered light detection method for detecting Raman scattered light emitted from a gas molecule using an optical interference filter, wherein the transmission wavelength sweeping unit detects the Raman scattering from the gas molecule. A rotating step of rotating the light interference filter in a state where light is emitted, a light receiving step of receiving light transmitted through the light interference filter, a light receiving unit, a detection unit, the Raman scattered light of the light receiving unit The light receiving portion is detected to detect the rotation angle value of the light interference filter when the light receiving portion receives light, and the operation portion receives the light reception using the rotation angle value detected by the detection portion. A wavelength calculating step of calculating a wavelength of the Raman scattered light received by the unit.

  In each aspect of the present invention, a Raman scattered light reference wavelength storage unit that stores the reference wavelength of Raman scattered light corresponding to each gas molecule is provided, and the computing unit calculates the wavelength of the Raman scattered light and the Raman scattering. The gas molecule that has emitted the Raman scattered light may be identified by comparing with the reference wavelength stored in the light reference wavelength storage unit.

  Also, the optical interference filter may be a band pass filter, or may be a combination of a high pass filter and a low pass filter. By using a combination of a high pass filter and a low pass filter, it is possible to make a relatively inexpensive and highly accurate band pass filter.

  According to each aspect of the present invention, for example, the pulsed laser irradiation unit irradiates the gas molecules with the pulse laser, and when the gas molecules emit the Raman scattered light, the transmission wavelength sweep unit rotates the light interference filter. By sweeping the transmission center wavelength continuously by continuously changing the angle of the optical interference filter with respect to the incident direction in which the Raman scattered light is incident from the light entrance (for example, see the pinhole 25 in FIG. 1). The detection unit can detect the Raman scattered light, and the operation unit can calculate the wavelength of the Raman scattered light. At this time, the rotation angle of the optical interference filter can be used to specify the wavelength. Thus, significant cost reduction can be realized due to the simple mechanical structure.

  Furthermore, using this continuous sweep, one optical interference filter enables real-time measurement of a mixed gas (for example, seven kinds of Raman measurement gases) in the atmosphere. Here, as "multi-gas measurement", operation becomes easier by classifying and registering measurement target gas in advance according to the measurement target such as atmospheric environment monitoring such as O 2 and CO 2 and flammable gas, toxic gas, etc. . Further, by specifying the target gas as “specific gas measurement”, the wavelength band is limited (for example, the sweep range is ± 5 nm of the central wavelength), and measurement time can be shortened and real time measurement can be performed.

  Furthermore, according to a second aspect of the present invention, Raman scattering light is detected by changing the sweep direction by utilizing the fact that the transmission center wavelength increases and decreases because the transmission wavelength sweeper rotates the optical interference filter. By doing this, it is possible to detect the rise and fall of the Raman scattered light and detect the (center) wavelength of the Raman scattered light using this. For example, as will be described later, while the optical interference filter is rotated by 120 degrees, the transmission center wavelength is reciprocated once, four points of the transmission edge portion are detected and arithmetic processing is performed. A resolution of 4 to 10 nm) can ensure 1 nm order resolution.

  Furthermore, according to the third aspect of the present invention, self-checking of the wavelength axis can be performed using the N2 gas wavelength stably present in the atmosphere. By self-correcting the relative error with the registered N2 value (stage angle and wavelength), the stage angle can be calibrated to realize maintenance free.

  Furthermore, according to the fourth aspect of the present invention, the transmission wavelength sweep unit continuously sweeps the transmission center wavelength of the optical interference filter, thereby making it possible to measure disturbances such as disturbance light noise and scattering noise caused by particles and water vapor. You can improve the reliability by realizing the function of checking automatically.

It is a figure which shows an example of a structure of the Raman scattered light detection apparatus based on embodiment of this invention. It is a figure which shows an example of a structure of the wavelength sweep stage 35 of FIG. It is a flowchart which shows an example of operation | movement of the Raman scattered light detection apparatus 1 of FIG.1 and FIG.2. FIG. 7 is a diagram for explaining an example of the operation of the optical interference filter 51 of FIG. 2; It is a time chart which shows an example of operation | movement of the Raman scattered light detection apparatus 1 of FIG.1 and FIG.2. An example of the detection of the wavelength of a standup of Raman scattering light by the Raman scattering light detection apparatus 1 of FIG.1 and FIG.2 and a wavelength of a fall is shown. It is a figure for demonstrating the Raman scattered light of each gas in case the wavelength of a laser beam is 355 nm.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the examples.

  FIG. 1 is a view showing an example of the configuration of a Raman scattered light detection apparatus according to an embodiment of the present invention. When the target gas 3 is irradiated with the pulse laser, Raman scattered light is emitted from gas molecules contained in the target gas 3. The Raman scattered light detection device 1 detects this Raman scattered light. The display unit 5 displays the detection result of the Raman scattered light detection device 1 or allows the user to input the Raman scattered light detection device 1.

  Referring to FIG. 1A, the Raman scattered light detection device 1 includes a pulse laser irradiation unit 11, a marker laser irradiation unit 13, a half mirror 15, a mirror 17, a first right-angle prism 19, and a second The right-angle prism 21, the condensing lens 23, the pinhole 25, the convex lens 27, the high pass filter 29, the light receiver 31, the power monitor 33, the wavelength sweeping stage 35, and the control unit 37 are provided.

  Referring to FIG. 1B, control unit 37 includes main CPU 41, stage driver 43, multistage parallel high speed AD circuit 45, high speed delay circuit 47, and laser driver 49.

  FIG. 2 is a diagram showing an example of the configuration of the wavelength sweeping stage 35 of FIG. (A) is a side view and (b) is a plan view. The wavelength sweeping stage 35 includes an optical interference filter 51, a fixing unit 53, an axis 55, a pulse motor 57, and an encoder 59. The pulse motor 57 rotates the shaft 55. The shaft 55 and the optical interference filter 51 are fixed by the fixing portion 53. The encoder 59 specifies the rotation angle of the light interference filter 51. The optical interference filter 51 is a band pass filter in which a low pass filter and a high pass filter are combined. By finely adjusting the parallel angle of the low-pass filter and the high-pass filter (parallel angle fine adjustment screws on the left and right of the filter mounting holder of the fixed portion 53), it is possible to obtain a narrow band transmission width in principle. The detailed analysis such as the overlap of the Raman scattered light from the target gas 3 and the S / N ratio are improved with the resolution of (1 to 2 degrees).

  As shown in FIG. 2, the wavelength sweeping stage 35 uses a mechanism for rotating the optical interference filter 51. The optical interference filter 51 is manufactured, for example, with the characteristic that the transmission wavelength shifts to the short wavelength side by a variation of 1 nm per degree when an angle deviation (difference) with the optical axis occurs. With respect to the optical axis, the transmission center wavelength is 360 nm at 60 degrees, and the transmission center wavelength is 420 nm at 0 degrees. Therefore, when the optical interference filter 51 is rotated by 120 degrees, the transmission center wavelength of the filter sweeps (moves) continuously as 360 nm → 420 nm → 360 nm. As a result, by rotating the light interference filter 51, the transmission center wavelength of the filter can be increased or decreased, and the wavelengths of the Raman scattered light of each gas in FIG. 7 can be detected at both increasing time and decreasing time.

  Conventionally, Raman light is separated using a narrow band interference filter. In this case, if a shift between the filter and the optical axis occurs, the transmission center wavelength of the filter is shifted, and the wavelength of the Raman scattered light can not be detected. In particular, when detecting the wavelengths of a plurality of Raman scattered light, narrow band interference filters corresponding to the respective wavelengths need to be prepared and switched. Therefore, many narrow band interference filters were prepared, and it was necessary to adjust the optical axis with high accuracy, and a more expensive filter switching mechanism was also required. On the other hand, according to the present invention, since the sweep (move) is performed continuously, the adjustment accuracy of the optical interference filter 51 can be relaxed. Furthermore, without changing the optical interference filter 51, the wavelengths of Raman scattered light of a plurality of gas molecules can be detected. Therefore, the hardware is relatively simple, there is no need for a filter switching mechanism, the accuracy of adjustment can be relaxed, significant reduction in size and weight can be achieved, and cost reduction and long-term durability accuracy can be realized.

  FIG.3 and FIG.5 is a flowchart and time chart which show an example of operation | movement of the Raman scattered light detection apparatus 1 described in FIG.1 and FIG.2, respectively. FIG. 4 is a diagram for explaining an example of the operation of the optical interference filter 51 of FIG. An example of the operation of the Raman scattered light detection device 1 described in FIGS. 1 and 2 will be described with reference to FIGS. 3 to 5.

  The feature of the present invention is that the disturbance light noise discrimination function is prepared. The Raman light intensity is weak, and it is further scattered and absorbed by the fine particles suspended in the air, and the Raman scattered light is attenuated. The atmosphere has a large amount of light such as natural light (sun), artificial light (illumination), scattered light from suspended matter, and background light such as fluorescence and phosphorescence. On the other hand, since Raman scattered light is weak, optical noise due to scattering and absorption of fine particles suspended in the atmosphere affects the measurement and causes malfunction. Therefore, the present invention separates, removes, recognizes, etc. these disturbance light noises by the disturbance light noise discrimination function which monitors the measurement environment, constantly monitors the situation of the disturbance noises, and measures the reliability of the Raman scattered light detection device 1 Raise.

  Referring to FIG. 3, first, the user operates the display unit 5 to emit marker light, adjusts the direction of the Raman scattered light detection device 1, and aligns the marker light with a point to be measured. Specifically, the marker light emitted from the marker laser irradiation unit 13 is reflected by the mirror 17 and reaches the half mirror 15. The power monitor 33 monitors marker light which has traveled straight by the half mirror 15. The marker light reflected by the half mirror 15 is changed in direction by the first right angle prism 19 and the second right angle prism 21. The second right angle prism 21 is located behind the center of the condenser lens 23. Therefore, the marker light whose direction is changed by the second right-angle prism 21 travels straight even though it passes through the condenser lens 23. The user aims the marker light at the point to be measured.

  Subsequently, the control unit 37 performs initial setting (step ST1). Specifically, the temperature is controlled by turning on the power. Then, as indicated by P1 in FIG. 4, the pulse motor 57 of the wavelength sweeping stage 35 sets the angle difference between the light interference filter 51 and the optical axis to 60 degrees. The (starting) origin of the θ-axis stage in FIG. 5 is in this state. Thus, the transmission center wavelength of the optical interference filter 51 is 360 nm.

  In FIG. 4, light from the outside is incident from the top. A circle indicates the pulse motor 57, and a line segment on the circle indicates the light interference filter 51. When the stage angle (the angle of rotation by the pulse motor 57 where the direction in which the Raman scattered light is incident is 0 °) is 30 °, the Raman scattered light is incident on the F plane and the filter incident angle is + 60 °. The wavelength is 360 nm. When the stage angle is 90 °, the Raman scattered light is incident on the F plane, the filter incident angle is + 0 °, and the central transmission wavelength is 420 nm. When the stage angle is 150 °, the light interference filter 51 is at P2, the Raman scattered light is incident on the F plane, the filter incident angle is −60 °, and the central transmission wavelength is 360 nm. When the stage angle is 210 °, the Raman scattered light is incident on the R surface, the filter incident angle is + 60 °, and the central transmission wavelength is 360 nm. When the stage angle is 270 °, the Raman scattered light is incident on the R surface, the filter incident angle is + 0 °, and the central transmission wavelength is 420 nm. When the stage angle is 330 °, the light interference filter 51 is at P2, the Raman scattered light is incident on the R surface, the filter incident angle is −60 °, and the central transmission wavelength is 360 nm. Data are acquired using the F-plane when the optical interference filter 51 rotates from 30 ° to 150 °, and data transfer processing is performed when the optical interference filter 51 rotates from 150 ° to 210 °. Data are acquired using the R surface when the optical interference filter 51 rotates from 210 ° to 330 °, and data transfer processing is performed when the optical interference filter 51 rotates from 150 ° to 210 °. The Raman scattered light that has passed through the light interference filter 51 passes through the high pass filter 29 and is received by the light receiver 31.

  In the wavelength sweeping stage 35, a step pulse is applied to the pulse motor 57 to rotate the optical interference filter 51 (step ST2). The light transmitted through the optical interference filter 51 passes through the high pass filter 29 and reaches the light receiver 31. The high pass filter 29 is a high pass filter that does not transmit the wavelength of the laser but passes the wavelength of the Raman scattered light of each substance, and eliminates the influence of the laser.

  The control unit 37 analyzes the light received by the light receiver 31 and performs disturbance light check (step ST3). Then, it is judged whether the influence of disturbance light noise is sufficiently small (step ST4). If the influence of disturbance light noise is sufficiently small, the process proceeds to step ST6. If the influence of disturbance light noise is large, after step ST5, the process returns to step ST3 according to an instruction from the user.

  In step ST6, the control unit 37 starts laser irradiation. Specifically, the pulse laser irradiation unit 11 is irradiated with a laser. The laser reaches the half mirror 15. The power monitor 33 monitors the laser reflected by the half mirror 15. The laser traveling straight through the half mirror 15 is changed in direction by the first right angle prism 19 and the second right angle prism 21, and the laser is irradiated. Reflected noise such as Rayleigh scattered light due to floating matter or fine particles in the air or fluorescence generated from the wall is collected by the collecting lens 23 and reaches the wavelength sweeping stage 35 via the pinhole 25 and the convex lens 27.

  The control unit 37 analyzes the light received by the light receiver 31 and performs a scattered light check (step ST7). Then, it is judged whether the influence of the scattered light noise is sufficiently small (step ST8). If the influence of the scattered light noise is sufficiently small, the process proceeds to step ST10. If the influence of the scattered light noise is large, after step ST9, the process returns to step ST7 according to the instruction from the user.

  The disturbance light check (natural light (sun), artificial light (illumination), etc.) (step ST3) will be specifically described. While rotating from the starting origin (stage angle: 30 degrees) by 120 degrees, it is measured by the F surface, and the transmission center wavelength of the optical interference filter 51 moves continuously from 360 nm → 420 nm → 360 nm to receive light. The required time is 1.2 seconds. Further, while rotating by 60 degrees, the disturbance light noise is checked. In FIG. 5, the number of measurement points is four, and the number of averaging times is 64. Since disturbance light illuminates a continuous spectrum of high light intensity from 360 nm to 420 nm, it is possible by photometry at four points.

  When the disturbance light amount is lower than the first reference value, the influence of disturbance light noise is small. Therefore, in step ST4, it is determined whether the general light amount is smaller than the first reference value. If smaller, the process proceeds to the scattered light check in step ST6 and subsequent steps. Here, in accordance with the disturbance light intensity, the output saturation is prevented by the sensitivity control of the photomultiplier tube which is the light receiver. If the disturbance light amount is higher than the first reference value, it is determined that the reference condition is not satisfied, and the main CPU 41 of the control unit 37 uses the spectrum of disturbance light noise such as sunlight, indoor illumination light, or fluorescence registered. The light spectrum distribution and the light quantity value are analyzed, and either natural light or artificial illumination light is displayed on the display unit 5 and a message is output (step ST5). The disturbance light check operation is repeated, and the process returns to step ST3 and is stopped by the user's instruction.

  The scattered light check (due to suspended matters such as dust and exhaust gas and particulates) (step ST7) will be described. The scattered light check is performed continuously from the disturbance light check. After the disturbance light check, while rotating from 210 degrees to 330 degrees, it is measured by the R surface, and the transmission center wavelength of the light interference filter 51 is continuously moved and received from 360 nm → 420 nm → 360 nm. The required time is 1.2 seconds. While rotating further 60 degrees, the scattered light noise is checked. In FIG. 5, the number of measurement points is four, and the number of averaging times is 64. Scattered light has a high light intensity.

  The source of scattered light noise is Rayleigh scattering by a pulse laser, which is difficult to completely remove in data processing averaging processing. Therefore, when the scattered light noise is lower than the second reference value, the influence of the scattered light noise is considered to be small, and the processes after step ST10 are performed. Here, the amount of attenuation due to absorption and scattering of particles is detected. If it is higher than the scattered light second reference value, the scattered light noise is analyzed and a message is output to the display unit 5 (step ST9). The scattered light check operation is repeated, and the process returns to step ST7 and is stopped by an instruction of the user.

  In step ST7, the reflection noise such as fluorescence or phosphorescence generated from the wall surface or the like is determined. The reflected light noise from the observation window glass, obstacle or wall is generated on the optical axis of the laser, but it is difficult to remove by the light interference system light receiver, but the reflected light noise by the background in front of or behind the measurement area is controlled It is possible to take action (removal) in data acquisition by the unit 37. If removal is possible, the criteria are satisfied. If removal is difficult, output analysis results.

  Therefore, in step ST10, the disturbance light noise and the scattered light noise are sufficiently small and it can be judged that there is no influence, and furthermore, the reference condition is satisfied when there is no reflected light noise or if it can be removed. It has been confirmed that the measurement environment is secured, and the process of gas measurement after step ST11 can be performed.

  The emission of Raman scattered light will be described. When the control unit 37 causes the pulse laser irradiation unit 11 to emit a laser, a Raman scattering phenomenon corresponding to the energy occurs in gas molecules contained in the target gas 3 irradiated with the laser. As shown in FIG. 7, the wavelength of the Raman scattered light differs depending on the gas type. The Raman scattered light is condensed by the condensing lens 23 and reaches the wavelength sweeping stage 35 via the pinhole 25 and the convex lens 27.

  An example of detection of the rising wavelength and falling wavelength of the Raman scattered light will be described with reference to FIG. In the present invention, as the light interference filter 51 rotates, the transmission center wavelength repeatedly increases and decreases. The rising and falling wavelengths are detected using this. Here, it is assumed that the half width of the interference filter 51 is λt.

The central wavelength λ ₀ of the Raman scattered light can be calculated by λ ₀ = (λ _1f + λ _2r ) / 2. Here, λ 1 _r is a wavelength value at which detection of a Raman scattered light falling curve value is started with a filter rising curve value at the time of short wavelength → long wavelength sweep. λ 1 _f is a wavelength value at which detection of the Raman scattered light rise curve value is started with the filter falling curve value at the time of short wavelength → long wavelength sweep. λ _{2 r} is a wavelength value at which detection of a Raman scattered light falling curve value is started with a filter rising curve value at the time of long wavelength → short wavelength sweep. λ _{2 f} is a wavelength value at which detection of the Raman scattered light rise curve value is started with the filter falling curve value at the time of long wavelength → short wavelength sweep.

The process in the case of hydrogen gas H2 will be described with reference to FIG. The horizontal axis is wavelength λ (nm), and the vertical axis is the transmittance of the optical interference filter. Raman scattering spectra of H2 is in the center wavelength lambda _0, .DELTA..lambda.1 the short wavelength side, .DELTA..lambda.2 is long wavelength side. It rotates clockwise from the starting origin, first detects the wavelength value λ _1f (light reception value = Hi), and then detects the wavelength value λ _1r (light reception value = Lo). Further, the light passes through a 90 degree angle, and wavelength value λ _2r (light reception value = Hi) is detected, and wavelength value λ _2f (light reception value = Lo) is detected. The central wavelength λ ₀ of Raman light can be calculated from the rising and falling detection wavelength values in the sweep direction (360 → 420/420 → 360 nm). From the calculated central wavelength λo of the Raman light and the Raman registration value, the specification of the measurement gas and the overlap within the filter half width are confirmed.

The process in the case where a plurality of gases (H20) are mixed around the hydrogen gas H2 will be described with reference to FIG. 6 (b). The horizontal axis is wavelength λ (nm), and the vertical axis is the transmitted light amount of the light interference filter. Raman scattering spectra of H2 is in the center wavelength lambda _0, .DELTA..lambda.1 the short wavelength side, .DELTA..lambda.2 is long wavelength side. The Raman scattering spectrum of H20 has a central wavelength λ ₀ '. λ ₀ and λ ₀ 'are close and can simultaneously pass through the optical interference filter. Therefore, the rising curve value of the Raman scattered light is detected by the falling curve value of the optical interference filter. Similarly, the falling curve value of the Raman scattered light is detected by the rising curve value of the optical interference filter. Then, rising / falling can be derived by calculation, accurate measurement of the target gas can be performed, and the central wavelength λ ₀ can be specified.

  In step ST11, the measurement mode is selected (step ST11) The measurement mode includes a multi mode and a specific gas mode. If the multi mode is instructed, measurement at each measurement point is performed (step ST12). Then, the process proceeds to step ST15.

  If the specific gas is to be measured, the process proceeds to step ST13. In step ST13, the control unit 37 rotates the light interference filter 51 to an angle corresponding to the specified specific wavelength. Then, a pulse laser is irradiated to increase the transmission center wavelength, and the falling or rising wavelength of the Raman scattered light is measured. Again, the angle corresponding to the specified specific wavelength is rotated in the opposite direction to decrease the transmission center wavelength, and the rising or falling wavelength of the Raman scattered light is measured. As described above, the increase and decrease of ± 5 nm is repeated around the Raman registration wavelength. Also, check the disturbance (check) around the specific Raman wavelength. It is determined whether this process has been performed for all specific wavelengths (step ST14). If there is something that has not been processed, the process returns to step ST13. If processing has been performed at all specific wavelengths, the process proceeds to step ST15.

  In the control unit 37, the main CPU 41 performs control of pulsed laser irradiation and the like using the laser driver 49. The measuring instrument of the present invention can achieve spatial resolution of, for example, 1 GS / s = 30 cm or 2 GS / s = 15 cm because of the speed of light. When high spatial resolution is required, high speed AD circuits of several GS (giga samples) per second are required, but these circuits are very expensive and technically difficult. Therefore, in the multistage parallel high-speed AD circuit 45 and the high-speed delay circuit 47 shown in FIG. 1B, a plurality of AD circuits of several hundreds MS / s are mounted in parallel, and a time difference is given to each AD circuit to input signals. Show an example of obtaining equivalent performance at low cost. For example, the first stage has no delay, the second stage has Δt1, the third stage has Δt1 + Δt2,..., And the nth stage has a time difference of Δt1 + Δtn. By increasing the number of AD circuits, it is possible to obtain spatial resolution on the order of several centimeters. Further, the Raman scattered light is analyzed using the stage driver 43. For example, in the case of hydrogen gas, it detects Raman scattered light specific to hydrogen molecules emitted by hydrogen gas that has received laser light, and measures concentration and distance from signal intensity and time difference. The gas concentration can be calculated, for example, by Equation 1.

  A qualitative and quantitative value is calculated by comparing and processing the disturbance light noise value and the Raman light value stored separately in the memory. For example, using the wavelength at the center of the rising and falling wavelengths measured using the wavelength sweeping stage 35, while comparing with the wavelength of each substance in FIG. 7, the substance is identified and the concentration and distance are analyzed Do. When an angular shift of the optical interference filter occurs due to temperature change or long-term vibration, etc., if a shift of ± 2 nm or more is detected from the stage origin / correction value and the registered gas wavelength value, the Raman value registered by the main CPU And comparison correction (software correction) is possible, and there is no influence on measurement accuracy.

  In step ST15, data transfer is performed, and the main CPU performs processing, calculation, and determination. First, in step ST16, it is determined whether the same reference conditions as in steps ST4 and ST8 are satisfied. If satisfied, the process proceeds to step ST18. If not satisfied, the process proceeds to step ST17, the same process as step ST5 and step ST9 is performed, and the process returns to step ST7. (Note that when processing similar to step ST5 is performed, the process may return to step ST3, and when processing similar to step ST9 is performed, the process may return to step ST7.)

  In step ST18, it is determined whether a gas is detected using the wavelength of the Raman scattered light. If it is detected, the process proceeds to step ST19, where an alarm is displayed or a signal indicating that is outputted, and the process proceeds to step ST21. If not detected, the process proceeds to step ST20.

  In step ST20, the measurement result is displayed (updated), and it is determined whether the measurement has ended (step ST21). If the measurement has not ended, the process returns to step ST11. When the measurement is completed, the process proceeds to step ST22, the stage angle is set as the starting origin point and stopped, the pulse laser is stopped, the measurement result is stored (step ST23), and the process is ended.

  DESCRIPTION OF SYMBOLS 1 Raman scattering light detection apparatus, 3 object gas, 5 display part, 11 pulse laser irradiation part, 13 marker laser irradiation part, 15 half mirror, 17 mirror, 19 1st right angle prism, 21 2nd right angle prism, 23 condensing lens , 25 pin holes, 27 convex lenses, 29 high pass filters, 31 light receivers, 33 power monitors, 35 wavelength sweep stages, 37 control units, 41 main CPUs, 43 stage drivers, 45 multistage parallel high speed AD circuits, 47 high speed delay circuits, 49 Laser driver, 51 light interference filters, 53 fixed parts, 55 axes, 57 pulse motors, 59 encoders

Claims (5)

A Raman scattered light detection device for detecting Raman scattered light emitted from gas molecules using an optical interference filter, comprising:
A transmission wavelength sweeping unit that rotates the optical interference filter in a state in which the Raman scattered light is emitted from the gas molecules to change the transmission center wavelength of the optical interference filter;
A light receiving unit that receives the Raman scattered light emitted from the gas molecules and transmitted through the light interference filter;
And a calculating unit that calculates a numerical value of the Raman scattered light received by the light receiving unit ,
The number of optical interference filters that are rotated is one,
The transmission wavelength sweep unit rotates the optical interference filter to continuously increase and decrease the transmission center wavelength of the optical interference filter, thereby changing the sweep direction and sweeping.
When the operation unit analyzes the Raman scattered light of a specific target gas, there are cases and cases where there is Raman scattered light of another gas transmitted through the optical interference filter simultaneously with the Raman scattered light of the specific target gas A Raman scattered light detection device that divides cases into cases. The arithmetic unit is
If Raman scattered light of another gas transmitted through the optical interference filter is present simultaneously with Raman scattered light of the specific target gas, Raman scattering of the specific target gas detected by sweeping with the sweep direction changed The short wavelength side and the long wavelength side of the light are analyzed, and not the curve value of the light by the Raman scattered light of the other gas but the curve value of the light by the Raman scattered light of the specific target gas Analyze the Raman scattered light of the target gas
If there is no Raman scattered light of another gas transmitted through the optical interference filter simultaneously with the Raman scattered light of the specific target gas, the curve value of light by the Raman scattered light of the specific target gas is used. The Raman scattered light detection device according to claim 1, wherein the Raman scattered light of a specific target gas is analyzed. The half width of the rotating optical interference filter is 4 nm or more and 10 nm or less,
The transmission center wavelength changed by rotating the optical interference filter includes a range of 360 nm to 420 nm,
The arithmetic unit is
The Raman scattered light of the specific target gas is detected when the Raman scattered light of the specific target gas is detected from the undetected state, which is detected by increasing the transmission center wavelength. When it comes to undetected state from the state, and
The Raman scattered light of the specific target gas is detected when the Raman scattered light of the specific target gas is detected from the undetected state, which is detected by decreasing the transmission center wavelength. When the condition is not detected,
The Raman scattered light detection apparatus according to claim 2, wherein the Raman scattered light of the target gas is analyzed using The Raman scattered light detection apparatus according to any one of claims 1 to 3, further comprising: a control unit that separately determines disturbance light noise and scattered light noise with respect to a continuous spectrum in a measurement range by the optical interference filter. A Raman scattered light detection method for detecting Raman scattered light emitted from gas molecules using an optical interference filter, comprising:
A rotation step of rotating the optical interference filter in a state transparently wavelength sweep unit, said Raman scattered light from the gas molecules are released,
A light receiving step of receiving the Raman scattered light emitted from the gas molecules and transmitted through the light interference filter;
Calculation unit, viewed contains a calculation output step the light receiving portion you analyzing the Raman scattered light received,
The number of optical interference filters that are rotated is one,
In the rotation step, the transmission wavelength sweep unit rotates the optical interference filter to continuously increase and decrease the transmission center wavelength of the optical interference filter, thereby changing the sweep direction and sweeping.
In the calculation step, when the operation unit analyzes Raman scattered light of a specific target gas, Raman scattered light of another gas transmitting through the light interference filter simultaneously with the Raman scattered light of the specific target gas A Raman scattered light detection method that divides cases of presence and absence .