A raman spectrum gas concentration measuring device based on light intensity compensation

Abstract

The utility model discloses a kind of Raman spectrum gas concentration measuring device based on light intensity compensation in the technical field of gas concentration measurement, including laser emission unit, gas cell unit, scattered light collection unit, light intensity monitoring unit and data analysis processing unit;The laser emission unit includes laser controller, laser and raman probe, the raman probe outlet is provided with convex lens, the laser controller drives laser to emit excitation light, and is transmitted to raman probe by optical fiber;Through the unique front-back two-way light collection design, in combination with real-time light intensity monitoring and normalization compensation mechanism, the efficient collection of Raman scattering signal and the real-time correction of laser power fluctuation are realized.

Description

Technical Field

[0001] This utility model relates to the field of gas concentration measurement technology, specifically a Raman spectroscopy gas concentration measurement device based on light intensity compensation. Background Technology

[0002] Gas composition analysis and concentration detection are crucial in many fields. Raman spectroscopy, with its molecular vibrational "fingerprint" characteristics, can achieve qualitative and quantitative analysis of multiple gas components and is widely used in industrial online monitoring.

[0003] However, existing Raman spectroscopy techniques still have certain limitations in long-term operation in actual industrial settings: cavity enhancement techniques require extremely high optical path stability, are complex systems, and have poor environmental adaptability; fiber enhancement methods are limited by fiber type and transmission characteristics, have poor versatility, and are difficult to cover the entire wavelength range; surface enhancement techniques rely on specific enhancement substrates, have stability and repeatability issues, and are not suitable for long-term continuous monitoring. While conventional Raman spectroscopy systems are simple, they generally face signal drift problems caused by fluctuations in laser output power, which seriously affect the accuracy and long-term reliability of quantitative measurements. Therefore, there is currently a lack of a gas Raman spectroscopy measurement method and device that is relatively simple in structure, has high signal collection efficiency, can effectively suppress light source fluctuations, and is suitable for long-term stable operation in industrial settings.

[0004] Based on this, the present invention designs a Raman spectroscopy gas concentration measurement device based on light intensity compensation to solve the above problems. Utility Model Content

[0005] The purpose of this invention is to provide a Raman spectroscopy gas concentration measurement device based on light intensity compensation to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a Raman spectroscopy gas concentration measurement device based on light intensity compensation, comprising a laser emission unit, a gas cell unit, a scattered light collection unit, a light intensity monitoring unit, and a data analysis and processing unit; The laser emitting unit includes a laser controller, a laser, and a Raman probe. The Raman probe has a convex lens at its outlet. The laser controller drives the laser to emit excitation light, which is then transmitted to the Raman probe via an optical fiber. The gas cell unit includes a gas cell and a barometer, and the Raman probe is connected to the gas cell through a sealed structure. The scattered light collection unit includes a collection optical path and a spectrometer located inside the Raman probe, used to collect and analyze gas Raman scattering signals; The light intensity monitoring unit includes a beam-splitting concave mirror, a focusing lens, and a photodetector disposed in the gas cell, used for beam splitting and real-time monitoring of the excitation light intensity; The data analysis and processing unit includes the spectrometer, data acquisition card, and computer, and is used to synchronously acquire spectral signals and light intensity signals, and perform normalization processing.

[0007] As a further embodiment of this invention, the emission wavelength of the laser is 532 nm; the convex lens at the outlet of the Raman probe is used to focus the excitation laser onto the center of the sample cavity of the gas cell.

[0008] As a further embodiment of this invention, the Raman probe integrates a laser transmission optical path and a scattered light collection optical path, which are separated and transmitted independently through built-in optical elements. The laser transmission optical path is connected to a laser, and the scattered light collection optical path is connected to a spectrometer.

[0009] As a further embodiment of this invention, the beam-splitting concave mirror is positioned directly in front of the Raman probe within the gas cell, used to reflect a portion of the forward-scattered light back to the Raman probe, while the other portion of the transmitted light is transmitted to the photodetector via a focusing lens.

[0010] As a further embodiment of this utility model, the output end of the photodetector is connected to a data acquisition card, which is connected to a computer to convert the monitored light intensity signal into an electrical signal and transmit it to the data analysis and processing unit.

[0011] As a further embodiment of this invention, the computer has a built-in signal processing algorithm for normalizing the Raman spectrum signal acquired by the scattered light collection unit based on the real-time light intensity signal acquired by the light intensity monitoring unit, so as to suppress the measurement error introduced by laser power fluctuation.

[0012] As a further embodiment of this utility model, the gas pool adopts an orthogonal layout in which the gas path and the optical path are perpendicular to each other, with the air inlet and the air outlet located on both sides of the gas pool and set separately from the optical window.

[0013] As a further embodiment of this utility model, the gas pool is a pressure-resistant and sealed structure that can withstand an internal pressure of not less than 500 kPa, and is equipped with a barometer interface for enhancing the Raman scattering signal under pressurized conditions and for real-time monitoring of the pressure status inside the pool.

[0014] Compared with the prior art, the beneficial effects of this utility model are: 1. It solves the problem of large measurement error and poor long-term stability caused by laser power fluctuations in conventional Raman spectroscopy in industrial field applications, thereby improving the accuracy and reliability of multi-component concentration and calorific value calculation of industrial gases (such as coke oven gas and converter gas).

[0015] 2. Through a unique forward and backward dual-path light collection design, combined with real-time light intensity monitoring and normalization compensation mechanism, efficient collection of Raman scattering signals and real-time correction of laser power fluctuations are achieved.

[0016] 3. By orthogonally arranging the gas path and optical path, background noise and stray light are effectively suppressed, improving the signal-to-noise ratio. The device of this invention has a compact structure, excellent sealing, corrosion resistance, and supports pressurized measurement. It is suitable for online gas monitoring in various harsh industrial environments and possesses high economic efficiency, stability, and engineering practical value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the Raman spectroscopy gas concentration measurement device with light intensity compensation according to this utility model; Figure 2 This is a three-dimensional schematic diagram of the internal optical path structure of the gas cell of this utility model; Figure 3 This is a top view schematic diagram of the internal optical path structure of the gas cell of this utility model.

[0018] In the attached diagram, the components represented by each number are as follows: 1. Laser controller; 2. Laser; 3. Raman probe; 4. Convex lens; 5. Gas cell; 6. Spectroscopic concave mirror; 7. Focusing lens; 8. Photodetector; 9. Barometer; 10. Spectrometer; 11. Data acquisition card; 12. Computer. Detailed Implementation

[0019] Please see Figures 1-3 This utility model provides a technical solution: such as Figure 1 As shown, the gas Raman spectroscopy analysis device based on light intensity compensation provided in this embodiment mainly includes a laser control unit, an optical detection unit, and a signal processing unit.

[0020] Laser controller 1 drives laser 2 to emit laser light of a specific wavelength. This laser light is transmitted via optical fiber to the laser incident end of Raman probe 3. Raman probe 3 is sealed to gas cell 5 via an O-ring, ensuring the safety and airtightness of the device when measuring flammable, explosive, or toxic gases. At the exit of Raman probe 3, a convex lens 4 with a focal length of 7.5 mm is installed to efficiently focus the incident laser beam onto the center of the sample cavity inside gas cell 5, forming a high-power-density detection spot. This significantly enhances the interaction between the laser beam and gas molecules, exciting a stronger Raman scattering signal.

[0021] After the laser excitation interacts with the gas molecules, Raman scattered light is generated that propagates in all directions. Among them, the backscattered light that propagates in the opposite direction of the laser incident direction is directly received by the convex lens 4 with a focal length of 7.5 mm. The convex lens first collimates the scattered light into parallel light, enabling it to be transmitted efficiently inside the Raman probe 3, and finally coupled into the spectrometer 10 through the scattered light output end of the Raman probe 3 to complete the signal acquisition.

[0022] To comprehensively improve signal collection efficiency and achieve light intensity monitoring, a beam-splitting concave mirror 6 with a semi-transparent and semi-reflective function and a focal length of 5mm is installed inside the gas cell 5 and directly in front of the Raman probe 3. The forward scattered light and residual excitation light generated after the laser interacts with the gas and propagate along the laser's direction are incident on the surface of the beam-splitting concave mirror 6. The beam-splitting concave mirror 6 reflects a portion of the light, mainly the Raman scattered signal, back to the Raman probe 3 at a 180° angle, and then it is transmitted to the spectrometer 10.

[0023] Through this design, the device achieves simultaneous collection of scattered light in both forward and backward directions, significantly improving the overall collection efficiency of Raman scattered light. Simultaneously, another portion of the light transmitted through the beam-splitting concave mirror 6, containing residual excitation light and some scattered light, is focused by a 10mm focal length focusing lens 7 and transmitted to the photosensitive surface of a silicon-based photodetector 8. The photodetector 8 performs photoelectric conversion, converting the received light intensity signal into a corresponding electrical signal and outputting it to the data acquisition card 11 for real-time monitoring of the light intensity state inside the gas cell.

[0024] In this embodiment, the gas flow direction inside the gas cell 5 is orthogonally perpendicular to the laser propagation direction in the optical path. This design ensures, on the one hand, that the flowing gas and the laser beam interact fully and uniformly; on the other hand, it effectively prevents direct reflected light from the cell wall and gas path connectors from entering the signal collection optical path, thereby helping to suppress background noise, eliminate stray light, and ultimately improve the signal-to-noise ratio of the Raman scattering signal. The gas cell 5 housing has a pre-installed air inlet, an air outlet, and an interface for connecting the barometer 9. All interfaces are sealed, allowing the gas cell to perform measurements on static, sealed samples as well as real-time online monitoring of the flowing gas in the pipeline.

[0025] The real-time gas Raman spectrum signal acquired by spectrometer 10, along with the light intensity signal inside gas cell 5 synchronously acquired by photodetector 8 via data acquisition card 11, are transmitted together to computer 12 for processing. The algorithm built into computer 12 uses the measured light intensity signal to normalize the intensity of characteristic peaks in the Raman spectrum. This compensation mechanism effectively suppresses measurement errors introduced by fluctuations in laser output power, significantly improving the accuracy and long-term stability of quantitative gas concentration analysis.

[0026] This device supports simultaneous detection of multiple gas components, and its detectable Raman shift range is determined by the spectral response range of the selected spectrometer 10. The main structure of the gas cell 5 is made of highly corrosion-resistant and high-strength stainless steel, making it suitable for industrial gas environments containing corrosive components, such as coke oven gas and converter gas.

[0027] The gas cell used in this device can withstand high internal pressure. Based on the physical property that Raman scattering intensity is proportional to gas density, under pressurized conditions, the number of gas molecules per unit volume increases, thereby significantly enhancing the Raman scattering signal. In this embodiment, the internal pressure of the gas cell can be controlled above 500 kPa by an external gas source and is read and monitored in real time by a barometer 9.

[0028] The wavelength of the light source used in this invention is not limited to 532nm as described in the embodiments. Depending on the specific characteristics of the gas being measured, other wavelengths (such as 785nm, 1064nm, etc.) of the excitation light source can also be used in this device.

[0029] Compared with conventional Raman spectroscopy measurement methods, this invention achieves extremely high Raman scattering signal collection efficiency through a unique forward and backward dual-path light collection design. Simultaneously, the introduction of real-time light intensity monitoring and normalization compensation mechanisms effectively eliminates the influence of laser power fluctuations on quantitative results. Therefore, the device of this invention exhibits higher accuracy, repeatability, and long-term operational stability in gas concentration analysis. Furthermore, the device is compact, economical, and practical, possessing promising engineering application prospects and wide applicability to gas detection scenarios in various fields such as environmental protection, industrial safety, and energy management.

Claims

1. A Raman spectroscopy gas concentration measurement device based on light intensity compensation, characterized in that: It includes a laser emitting unit, a gas cell unit, a scattered light collection unit, a light intensity monitoring unit, and a data analysis and processing unit; The laser emitting unit includes a laser controller (1), a laser (2) and a Raman probe (3). The Raman probe (3) has a convex lens (4) at its outlet. The laser controller (1) drives the laser (2) to emit excitation light, which is then transmitted to the Raman probe (3) via an optical fiber. The gas cell unit includes a gas cell (5) and a barometer (9), and the Raman probe (3) is connected to the gas cell (5) through a sealing structure; The scattered light collection unit includes a collection optical path and a spectrometer (10) located inside the Raman probe (3) for collecting and analyzing gas Raman scattering signals; The light intensity monitoring unit includes a beam-splitting concave mirror (6), a focusing lens (7), and a photodetector (8) disposed in the gas cell (5), for beam splitting and real-time monitoring of excitation light intensity; The data analysis and processing unit includes the spectrometer (10), the data acquisition card (11), and the computer (12), which are used to synchronously acquire spectral signals and light intensity signals and perform normalization processing.

2. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 1, characterized in that: The laser (2) emits at a wavelength of 532 nm; the convex lens (4) at the outlet of the Raman probe (3) is used to focus the excitation laser onto the center of the sample cavity of the gas cell (5).

3. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 1, characterized in that: The Raman probe (3) integrates a laser transmission optical path and a scattered light collection optical path. The two are separated and transmitted independently through built-in optical elements. The laser transmission optical path is connected to the laser (2), and the scattered light collection optical path is connected to the spectrometer (10).

4. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 1, characterized in that: The beam-splitting concave mirror (6) is located in front of the Raman probe (3) inside the gas cell (5) to reflect a portion of the forward-scattered light back to the Raman probe (3), while the other portion of the transmitted light is transmitted to the photodetector (8) via the focusing lens (7).

5. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 4, characterized in that: The output end of the photodetector (8) is connected to the data acquisition card (11), and the data acquisition card (11) is connected to the computer (12) to convert the monitored light intensity signal into an electrical signal and transmit it to the data analysis and processing unit.

6. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 5, characterized in that: The computer (12) has a built-in signal processing algorithm for normalizing the Raman spectrum signal obtained by the scattered light collection unit based on the real-time light intensity signal obtained by the light intensity monitoring unit, so as to suppress the measurement error introduced by the laser power fluctuation.

7. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 1, characterized in that: The gas pool (5) adopts an orthogonal layout in which the gas path and the optical path are perpendicular to each other. The air inlet and the exhaust outlet are located on both sides of the gas pool (5) and are set separately from the optical window. This can reduce the deposition of dust or pollutants in the gas on the optical window, so as to realize long-term continuous monitoring of the industrial site.

8. The Raman spectroscopy gas concentration measurement device based on light intensity compensation according to claim 1, characterized in that: The gas pool (5) is a pressure-resistant and sealed structure that can withstand an internal pressure of not less than 500 kPa and is equipped with a barometer (9) interface to enhance the Raman scattering signal under pressurized conditions and monitor the pressure status inside the pool in real time.

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