A Raman probe for reducing stray light

Abstract

This utility model discloses a Raman probe for reducing stray light, relating to the field of gas monitoring technology. The Raman probe includes a housing, a gas chamber, and a light-absorbing component. The gas chamber is fixed to the housing, and the housing has a laser inlet and a Raman light receiving outlet. The housing, gas chamber, and laser inlet are configured such that the laser inlet is used for laser beam entry, which enters the gas chamber along a predetermined laser beam path within the housing. The housing, gas chamber, and Raman light receiving outlet are configured such that Raman light is generated in the gas chamber, enters the housing, and travels along a predetermined Raman beam path within the housing to the Raman light receiving outlet. The predetermined Raman beam path does not overlap with the laser beam path at least in the portion away from the gas chamber and is a predetermined single Raman beam path. The light-absorbing component is disposed on the single Raman beam path to absorb a portion of the Raman light containing stray light. By adding a light-absorbing component, this Raman probe can improve the monitoring capability of certain gases.

Description

Technical Field

[0001] This utility model relates to the field of gas monitoring technology, specifically to a Raman probe that reduces stray light. Background Technology

[0002] Laser Raman spectroscopy is a spectroscopic technique that uses a laser as a light source to obtain information about the vibration and rotation of molecules by measuring the frequency difference (i.e., Raman shift) between the scattered and incident light. Its core principle is to analyze the inelastic scattering process of laser light by a substance, obtaining characteristic spectral information related to the internal motion of molecules, thereby enabling qualitative and quantitative analysis of the substance.

[0003] Because the molecular density of gases is much lower than that of solids and liquids, the number of gas molecules involved in scattering is far less than that of solids and liquids for the same volume. The intensity of the Raman scattering signal is closely related to the number of molecules involved in scattering; the fewer the molecules, the weaker the Raman scattering signal. Therefore, to obtain a sufficiently strong Raman signal in gas detection, the parameters of the Raman spectrometer need to be adjusted to enhance signal collection and detection capabilities.

[0004] Currently, Raman spectrometers for gas detection typically employ high laser power and long integration times. However, high laser power also introduces stray light problems. For example, when the laser propagates between optical elements inside the spectrometer, reflection and scattering may occur, generating stray light. Furthermore, the higher the laser power, the higher its energy, and the greater the likelihood of stray light generation through interaction with optical elements. For instance, laser light may scatter on the surfaces of lenses, mirrors, and other components; this scattered light is part of the stray light. Longer integration times also lead to the accumulation of stray light. This stray light is also collected by the detector during the integration time and amplified along with the Raman signal. This means that as the integration time increases, the proportion of stray light relative to the Raman signal may increase, thus having a more severe impact on the Raman spectroscopy measurement results.

[0005] Chinese utility model patent CN222762082U discloses a high-temperature Raman probe. In this patent, although an extinction element is detachably installed at the end of the gas chamber away from the housing to absorb stray light from other substances that do not collide with the target gas, preventing interference with the Raman scattered light and signal drift, some stray laser light may still enter the optical fiber. Furthermore, after the incident laser light passes through a preset laser path, some of it may scatter or reflect directly onto the inner wall of the probe before entering the optical fiber. It should be noted that although a long-pass filter is included in this patent, some stray laser light still cannot be filtered out. This stray laser light, after entering the optical fiber, can cause significant interference in the low wavenumber region, affecting the measurement results of the Raman spectra of some gases. Utility Model Content

[0006] In view of this, the main objective of this invention is to propose a Raman probe that reduces stray light, thereby improving the monitoring capability of certain gas concentrations.

[0007] To achieve the above objectives, this utility model proposes a Raman probe for reducing stray light. The Raman probe includes a housing, a gas chamber, and a light-absorbing component. The gas chamber is fixed to the housing, and the housing has a laser inlet and a Raman light receiving outlet. The housing, the gas chamber, and the laser inlet are configured such that: the laser inlet is used for laser beam entry, which enters the gas chamber along a predetermined laser beam path within the housing; the housing, the gas chamber, and the Raman light receiving outlet are configured such that: Raman light is generated in the gas chamber, enters the housing, and travels along a predetermined Raman beam path within the housing to the Raman light receiving outlet; wherein, at least a portion of the predetermined Raman beam path away from the gas chamber does not overlap with the laser beam path and is a predetermined single Raman beam path; the light-absorbing component is disposed on the single Raman beam path and is used to absorb a portion of the Raman light containing stray light.

[0008] Compared with existing technologies, the technical solution of this utility model has the following beneficial effects: By setting a light-absorbing component on the preset single Raman optical path, the light-absorbing component can absorb stray light on the preset single Raman optical path, and can specifically handle stray light from various sources. This reduces the possibility of it directly entering the signal receiver connected to the Raman probe. For example, for stray light generated by reflections from the front and rear surfaces of the focusing lens, the light-absorbing component can effectively absorb / attenuate the intensity of these stray lights, reducing their interference with the Raman signal. At the same time, for lasers that are consistent with the preset single Raman optical path, the light-absorbing component can also play an absorption role, so that these stray lasers will not cause significant interference to the low wavenumber region during fiber transmission, thus improving the quality and accuracy of the Raman spectral signal. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0010] Figure 1 This is a three-dimensional structural schematic diagram of the Raman probe for reducing stray light in an embodiment of this utility model; Figure 2 This is an exploded structural diagram of the Raman probe for reducing stray light in an embodiment of this utility model; Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure along the AA direction; Figure 4 This is a cross-sectional view of the shell structure and the air chamber in an embodiment of the present invention; Figure 5 This is a cross-sectional view of the shell structure and the signal receiver in an embodiment of the present invention; Figure 6 For Figure 5 This is a schematic diagram of the cross-sectional structure in the ZY-axis plane. Figure 7 This is a schematic diagram of another adjustment structure for the light-absorbing component in an embodiment of this utility model; Figure 8 This is a schematic diagram of the laser, Raman light, and scattered light in a Raman probe; Figure 9 The Raman spectrum of the Raman probe without the light-absorbing component when air is introduced. Figure 10 Raman spectrum of air introduced when an absorber is added to a Raman probe; Figure 11 Raman spectrum of a mixed gas when an absorber is added to a Raman probe.

[0011] Explanation of reference numerals in the attached figures: 1-Shell; 11-Laser inlet; 12-Raman light receiver outlet; 13-Signal transmitter; 14-Signal receiver; 15-Fiber optic collimator; 2-Cavity; 21-Cavity; 22-Air inlet; 23-Air outlet; 24-Air inlet pipe; 25-Air outlet pipe; 3-First focusing lens; 4- Beam splitter; 5-Second focusing lens; 6-Long-pass filter; 7-Light-absorbing component; 71-First elastic element; 72-Second elastic element; 73-First top post; 74-Second top post; 75-Connector; 76-Sleeve; 8-Concave mirror; 9-Light-shielding film layer. Detailed Implementation

[0012] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0013] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0014] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0015] Raman spectroscopy is based on the principle of inelastic light scattering. When a laser irradiates a sample, photons interact with molecules. Most of them undergo elastic scattering (Rayleigh scattering, with no change in frequency), while a few photons lose or gain energy due to molecular vibration, resulting in a frequency shift (Raman scattering). This shift (Raman shift, in cm⁻¹) corresponds to the molecular vibrational / rotational energy levels, reflecting chemical bond and structural information.

[0016] In Raman spectroscopy, the Raman shift is determined by the vibrational energy levels of the molecule itself and is independent of the frequency of the incident laser. This is because the physical essence of Raman scattering is an inelastic collision between a photon and the vibrational / rotational energy levels of a molecule, and the amount of energy transferred depends only on the intrinsic vibrational frequency of the molecule.

[0017] In Raman spectroscopy, molecules contain various vibrational modes (stretching, bending, and deformation vibrations), each corresponding to different energy transitions, which manifest as distinct peaks in the spectrum. When performing Raman spectroscopy on mixed gases, it is crucial to differentiate between the different gaseous substances, such as the CH stretching vibration peak of ethane (approximately 2950-3000 cm⁻¹). -¹ The peak of the CH bond stretching vibration of methane overlaps with that of methane, and its C-C stretching vibration peak (approximately 995 cm⁻¹) can be used as a reference. -¹ ( ) can be used to distinguish them.

[0018] Because gases have a lower molecular density, the number of molecules involved in scattering is much lower than that of solids and liquids for the same volume. Therefore, Raman spectrometers used for gas detection often employ larger laser power and longer integration time. Under these conditions, when stray light is present, its influence becomes more severe as the stray light increases with the laser power and integration time.

[0019] Therefore, regarding the issue of stray light from unremoved laser beams, reflections from the front and back surfaces of the cemented doublet, and laser beams that follow the same path as the main optical path but have a significant offset and cannot be filtered by a long-pass filter, which cause significant interference in the low-wavenumber region after entering the optical fiber and severely affect the accuracy of the test results, this study addresses these problems. Figures 1 to 7 The image shows a Raman probe for reducing stray light according to an embodiment of the present invention. The Raman probe includes a housing 1, a gas chamber 2, and a light-absorbing component 7, wherein: The gas chamber 2 is fixed to the housing 1, and the housing 1 has a laser inlet 11 and a Raman light receiving outlet 12. The housing 1, the gas chamber 2, and the laser inlet 11 are configured such that: the laser inlet 11 is used for laser injection, and the laser light enters the gas chamber 2 along a preset laser light path inside the housing 1; the housing 1, the gas chamber 2, and the Raman light receiving outlet 12 are configured such that: Raman light is generated in the gas chamber 2, and enters the housing 1 and is directed to the Raman light receiving outlet 12 along a preset Raman light path inside the housing 1; wherein, at least a portion of the preset Raman light path away from the gas chamber 2 does not overlap with the preset laser light path and is a preset single Raman light path; a light-absorbing component is disposed on the preset single Raman light path and is used to absorb a portion of the Raman light containing stray light.

[0020] by Figure 8 Taking this example, the preset laser path is represented by a green line, the preset Raman path by a red line, the preset single Raman path by a red line on the right side of the beam splitter, and stray laser by a purple line.

[0021] In this invention, the laser inlet 11 can be connected to a signal transmitter 13, which emits laser light and transmits it along a predetermined optical path. The Raman light receiving outlet 12 can be connected to a signal receiver 14. When the laser light enters the housing 1 from the laser inlet 11 and propagates along the predetermined laser optical path, it ensures that the laser light can effectively enter the gas chamber 2 and interact with the gas molecules therein. When the laser light enters the gas chamber 2 and interacts with the gas molecules, Raman light is generated. The generated Raman light then enters the interior of the housing 1 and propagates along the predetermined Raman light optical path, eventually reaching the Raman light receiving outlet 12. In the predetermined Raman light optical path, the portion of the housing 1 away from the gas chamber 2 is designed as a predetermined single Raman light path that does not overlap with the predetermined laser optical path. A light-absorbing component 7 is provided on this predetermined single Raman light path, the main function of which is to absorb the Raman light containing stray light. In this way, stray light is effectively removed, thereby improving the purity and detection accuracy of the Raman light.

[0022] In this embodiment, the light-absorbing component 7 is mainly used to process the stray laser light that has not been removed in the preset single Raman optical path. This stray light can interfere with the detection in the low wavenumber region. When this stray light propagates to the light-absorbing component 7, the light-absorbing component 7 absorbs or scatters this stray light, reducing its energy and thus reducing interference to the signal receiver 14. That is, a physical isolation method is adopted. By setting the light-absorbing component 7 before the collecting fiber, some Raman scattering signal is sacrificed in exchange for enhanced gas concentration detection accuracy. The Raman scattering signal processed by the light-absorbing component 7 is received by the signal receiver 14. The signal receiver 14 converts the received optical signal into an electrical signal, and then performs subsequent signal processing and analysis to obtain the Raman spectral information of the gas to be detected, which is used to detect parameters such as its composition and concentration.

[0023] By incorporating a light-absorbing component in the preset single Raman optical path, the component can absorb these laser beams, effectively handling stray light from various sources. This reduces the likelihood of stray light directly entering the signal receiver connected to the Raman probe. For example, for stray light reflected from the front and rear surfaces of the focusing lens, the light-absorbing component can effectively absorb / attenuate the intensity of these stray lights, reducing their interference with the Raman signal. Simultaneously, for laser beams aligned with the preset single Raman optical path, the light-absorbing component also suppresses them, preventing these stray laser beams from causing significant interference in the low wavenumber region during fiber transmission, thus improving the quality and accuracy of the Raman spectral signal. For details, see [link to documentation]. Figure 11 With light-absorbing structure 7 installed, when a mixed gas containing hydrocarbons is introduced, light absorption occurs at 400-1300 cm⁻¹. -1 The region contains C2H6 (1000cm). -1 ), n_C4H10 (850cm) -1 Characteristic positions of gases such as ) and ). And in Figure 9 In the middle, due to the lack of a light-absorbing structure, 7,400-1300cm -1 The area is so strong that it cannot be identified even when gases such as C2H6 and n_C4H10 are introduced.

[0024] Furthermore, the signal-to-noise ratio of the Raman scattering signal received by the signal receiver 14 is also improved due to the reduction of stray light interference. In spectral analysis, a higher signal-to-noise ratio means that weak Raman signal characteristic peaks can be distinguished more clearly, thereby more accurately identifying information such as the composition and concentration of the gas to be detected. This improves the detection accuracy and reliability of the Raman probe, making the test results more credible and better meeting the high-precision requirements for gas detection.

[0025] For details, see Figure 9 Without light-absorbing structure 7, when air is introduced, at 2300cm -1 There is a peak value (for nitrogen gas), at which point the signal-to-noise ratio (SNR) is 4.64. The SNR is calculated as: (Peak Value - Average Noise Floor) / (3 * Root Mean Square of Noise Floor). See also... Figure 10 A light-absorbing structure 7 is set up. When air is introduced, the light is absorbed at 2300cm. -1 There is a peak value (for nitrogen gas), at which point the signal-to-noise ratio is 246.95.

[0026] Therefore, by setting the light-absorbing component in the preset single Raman optical path, the Raman light containing stray light can be effectively adsorbed, reducing the influence of stray light on Raman light detection and improving the purity of Raman light. This improves the signal-to-noise ratio of the Raman spectrum, enabling the detection instrument to more clearly distinguish the Raman scattering signal, thereby improving the detection accuracy and sensitivity of gas components and enabling more accurate identification of some gases.

[0027] It is important to clarify that stray light refers to a collective term for various types of light, other than the target signal light, that interfere with measurement results in a specific optical detection system or related application scenario. This mainly includes unfiltered laser light, fluorescence generated by the excitation of non-target gases, and Raman light. In this case, the stray light primarily consists of the unfiltered laser portion, and this stray light increases with increasing laser power and integration time, thus causing a more severe impact on detection accuracy and other aspects.

[0028] It should also be noted that, in one embodiment of this utility model, the signal transmitter 13 is a laser and the signal receiver 14 is an optical fiber.

[0029] It should also be noted that the gas chamber 2 can form a cavity 21 together with the housing 1. The gas chamber 2 has an air inlet 22 and an air outlet 23 that communicate with the cavity 21. An air inlet pipe 24 is inserted into the air inlet 21 to introduce the gas to be tested into the cavity 21, and an air outlet pipe 25 is inserted into the air outlet 23 to discharge the gas to be tested from the cavity 21. Preferably, the air inlet pipe 24 and the air outlet pipe 25 on the gas chamber 2 are arranged opposite to each other.

[0030] Please see Figure 4 As shown, in some other embodiments, the housing 1 may also be formed of multiple structural members, one of which may be integrally formed with the air chamber 2.

[0031] For more details, please refer to Figures 2 to 3 As shown, in one embodiment of this utility model, the housing 1 has a first focusing lens 3, a beam splitter 4, and a second focusing lens 5 arranged sequentially along a preset direction, wherein: The preset laser optical path includes a first laser optical path and a second laser optical path arranged at an angle greater than 0° and less than 180°; the first laser optical path extends from the laser inlet 11 to the beam splitter 4; the second laser optical path extends from the beam splitter 4 through the first focusing lens 3 and exits the housing 1; the preset Raman optical path is arranged along the preset direction.

[0032] In this utility model, the beam splitter 4 is disposed inside the housing 1 and faces the signal transmitter 13 and the gas chamber 2 at 45 degrees respectively, so that the laser can effectively enter the gas chamber 2 and collect the Raman scattering signal; the first focusing lens 3 is disposed on the side of the housing 1 near the gas chamber 2. In the preset laser optical path, the first focusing lens 3 will reflect the laser, and the front and rear surfaces have a certain curvature, so the reflected light has a deflection angle and cannot be filtered by the filter, resulting in a small amount of laser entering the signal receiver 14, causing interference to the low wavenumber region test; the second focusing lens 5 is disposed on the side of the housing 1 near the signal receiver 14. Through the focusing effect of the second focusing lens 5 on the Raman scattering signal, more signal can be focused onto the signal receiver 14, thereby improving the signal strength and sensitivity.

[0033] Specifically, the laser emitted by the signal transmitter 13 first enters the beam splitter 4 through the laser inlet 11. The beam splitter 4 reflects a portion of the laser beam to the first focusing lens 3, which further concentrates the laser beam. After being focused by the first focusing lens 3, the laser beam enters the gas chamber 2. In the gas chamber 2, the laser interacts with gas molecules to generate Raman light, producing Raman scattering signals. These Raman scattering signals contain information about the vibration and rotation of gas molecules and are key signals for Raman spectroscopy detection. After the Raman scattering signals are generated, a portion of the signal returns along the original optical path and passes through the beam splitter 4 again. Due to the transmission characteristics of the beam splitter 4, this portion of the Raman scattering signal will propagate along the preset Raman light path and pass through the second focusing lens 5. The second focusing lens 5 focuses the Raman light, making it more concentrated and improving the intensity and quality of the light signal. Finally, it exits from the Raman light receiving outlet 12 and enters the subsequent detection system.

[0034] Therefore, the first focusing lens 3, the beam splitter 4, and the second focusing lens 5 are arranged sequentially along a preset direction, and a preset laser optical path is designed including a first segment and a second segment of the laser optical path at an angle. This not only improves the flexibility of the optical path, but also realizes the preliminary focusing and beam splitting functions of the laser, providing a good optical path foundation for the subsequent Raman light generation and detection.

[0035] In one embodiment of this utility model, the light-absorbing component 7 is a light-shielding film layer 9 disposed on the side of the beam splitter 4 facing the Raman light receiving outlet 12. After the laser enters the housing 1 from the laser inlet 11, it propagates along the preset optical path and reaches the beam splitter 4. After passing through the beam splitter 4, the laser enters the gas chamber 2 to excite Raman light. The generated Raman light propagates along the preset optical path to the position of the light-shielding film layer 9. At this time, the light-shielding film layer 9 adsorbs the Raman light and the stray light therein, making the remaining Raman light purer, and finally, after being focused by the second focusing lens 5, it is emitted from the Raman light receiving outlet 12.

[0036] In another embodiment of this utility model, the light-absorbing component is a light-shielding film layer 9 disposed on any surface of the second focusing lens 5. In this way, after the Raman light passes through the gas chamber 2, it propagates to the second focusing lens 5 along the preset optical path. The light-shielding film layer 9 on any surface of the second focusing lens 5 can absorb the Raman light and the stray light components therein, reducing the interference of stray light on subsequent detection. After being treated by the light-shielding film layer 9, the Raman light beam is more concentrated under the focusing effect of the second focusing lens 5, improving the intensity and quality of the optical signal, and finally exits from the Raman light receiving outlet 12 and enters the subsequent detection system.

[0037] Stray light often interferes with the detection of Raman signals, reducing detection accuracy. The adsorption effect of the light-shielding film layer 9 reduces stray light in the Raman light, thereby improving the purity of the Raman light. This allows the detection system to more accurately identify and analyze Raman spectra, thus improving detection accuracy.

[0038] It is understandable that by setting a light-shielding film layer 9 on the beam splitter 4 and the second focusing lens 5 to reduce stray light interference, there is no need to add additional complex optical components or significantly change the optical path structure. This design effectively reduces stray light interference while maintaining the simplicity and compactness of the optical path, which is conducive to the miniaturization and portability of the instrument and reduces its size.

[0039] It should be noted that, in Figure 5 In this context, the light-shielding film layer 9 and the light-absorbing component 7 are either or both can be used. The attached diagram is for illustrative purposes only.

[0040] For more details, please refer to Figures 2 to 3 As shown, in one embodiment of this utility model, the housing 1 also includes a long-pass filter 6. The beam splitter 4, the long-pass filter 6, and the second focusing lens 5 are arranged sequentially along the preset direction, making the optical path more compact and reasonable. The main function of the long-pass filter 6 is to filter out low-wavelength stray light, which may come from unremoved laser light, stray light generated by reflection from the front and rear surfaces of the beam splitter 4, etc. The long-pass filter 6 only allows light with wavelengths higher than a specific wavelength (usually the wavelength of a Raman signal) to pass through, thereby effectively eliminating interference from low-wavelength stray light.

[0041] Preferably, in one embodiment of the present invention, the light-absorbing component is a light-shielding film layer 9 disposed on any surface of the long-pass filter 6.

[0042] Thus, when the laser enters the housing 1 through the laser inlet 11, it propagates along the first laser beam path to the beam splitter 4. The beam splitter 4 reflects the laser into the gas chamber 2, where it interacts with gas molecules to generate Raman light. The generated Raman light then passes sequentially through the long-pass filter 6 and the second focusing lens 5 along a preset Raman beam path. The light-shielding film layer 9 on any surface of the long-pass filter 6 can absorb some of the unexpected reflected and scattered light, reducing the amount of these stray lights passing through the long-pass filter 6. After being processed by the light-shielding film layer 9, the Raman light, under the focusing effect of the second focusing lens 5, becomes more concentrated, improving the intensity and quality of the optical signal, and finally exits from the Raman light receiving outlet 12 to enter the subsequent detection system.

[0043] More specifically, in one embodiment of this invention, the light-absorbing component is directly fixed to the inner wall surface of the housing 1. Since the light-absorbing component is directly fixed to the inner wall surface of the housing 1, it can be closer to the propagation path of the Raman light, thereby more effectively absorbing stray light. Compared to other installation methods, this arrangement can reduce multiple reflections and propagation of stray light within the housing 1, improve the stray light absorption efficiency, make the Raman light purer, and improve detection accuracy.

[0044] Specifically, a light-absorbing component is directly fixed at a suitable position on the inner wall of the housing 1 to ensure that the light-absorbing component can effectively absorb stray light in the preset single Raman optical path without affecting the normal operation of other optical components. When the laser enters the housing 1 from the laser inlet 11, it propagates along the preset laser optical path, passes through the beam splitter 4 and the first focusing lens 3, and then enters the gas chamber 2. It interacts with gas molecules to generate Raman light, which propagates along the preset Raman optical path. When it passes through the light-absorbing component, the light-absorbing component absorbs part of the Raman light containing stray light, making the remaining Raman light purer. The purified Raman light continues to propagate along the preset optical path, is focused by the second focusing lens 5 to improve the intensity and quality of the light signal, and finally exits from the Raman light receiving outlet 12 to enter the subsequent detection system.

[0045] Furthermore, directly fixing the light-absorbing component to the inner wall of housing 1 eliminates the need for additional brackets or other fixing devices, simplifying the assembly process and reducing production costs. Simultaneously, it reduces potential light loss and optical path deviation issues caused by multiple connecting components, improving assembly efficiency and lowering costs.

[0046] In a preferred embodiment, the light-absorbing component is located on the side of the second focusing lens 5 away from the beam splitter 4 and is directly fixed to the inner wall of the housing 1. The purpose of this position is that, since the Raman light is already focused, the beam is more concentrated, allowing the light-absorbing component to more accurately absorb stray light components, improving stray light removal efficiency, increasing the purity of the Raman light, and ensuring that the light-absorbing component can completely cover part of the Raman light's propagation path after passing through the second focusing lens 5.

[0047] Furthermore, in one preferred embodiment, the light-absorbing member 7 is configured to be adjustable in position in a first direction and a second direction, both perpendicular to the preset single Raman light path; wherein the first direction is perpendicular to the second direction.

[0048] Please see Figure 1 , Figure 2 , Figure 5 As shown, the light-absorbing component 7 is adapted to operate in a first direction perpendicular to the preset single Raman optical path (i.e., the attached direction). Figure 1 The Z-axis direction and the second direction (i.e., the attached direction) Figure 1 The position of the light-absorbing component in the ZY plane is adjustable (in the Y-axis direction); this allows for precise adjustment of the position of the light-absorbing component within the ZY plane. During adjustment, based on actual testing requirements and optical path conditions, the operator or automatic control system can control the movement of the light-absorbing component in the Z and Y axes to achieve the optimal extinction effect.

[0049] Therefore, by adjusting the position of the light-absorbing components along the Z and Y axes, it is possible to better match the distribution and propagation direction of stray light in the optical path. This helps to process stray light more accurately, reduce its interference with the effective signal, and lower the signal noise level. A higher signal-to-noise ratio means that the signal receiver can more clearly capture weak effective signals, thereby improving the accuracy and reliability of detection and enabling more accurate identification and resolution of the spectral characteristics of the substance to be detected.

[0050] For further details, please refer to Figure 6 As shown, in one embodiment of this utility model, the Raman probe further includes a first elastic element 71, a second elastic element 72, a first top post 73, and a second top post 74, wherein: The first elastic member 71 is connected along the first direction to one side between the sleeve of the light-absorbing member and the inner wall of the housing 1; the second elastic member 72 is connected along the second direction to one side between the sleeve of the light-absorbing member and the inner wall of the housing 1.

[0051] The first top post 73 is connected along the first direction to the other side between the sleeve of the light-absorbing component and the inner wall of the housing 1; the second top post 74 is connected along the second direction to the other side between the sleeve of the light-absorbing component and the inner wall of the housing 1.

[0052] The sleeve position of the light-absorbing component is suitable for fine adjustment under the driving action of the first top post 73 and the second top post 74.

[0053] Therefore, when fine-tuning of the position of the light-absorbing component is required, controlling the pushing force of the first top post 73 and the second top post 74 can cause corresponding small displacements in the Z-axis and Y-axis directions. For example, increasing the pushing force of the first top post 73 will cause the light-absorbing component to move a certain distance in the positive Z-axis direction, while the first elastic element 71 will be compressed, generating an elastic restoring force opposite to the direction of the pushing force; conversely, decreasing the pushing force will cause the restoring force of the elastic element to move the light-absorbing component in the negative Z-axis direction. Similarly, by controlling the pushing force of the second top post 74, fine-tuning of the light-absorbing component in the Y-axis direction can be achieved. During the fine-tuning of the position of the light-absorbing component, the optical signal (including the effective signal and stray light) enters the effective area of ​​the light-absorbing component. As the position of the light-absorbing component changes, its processing effect on stray light in the optical signal will also change accordingly. By continuously adjusting the pushing force of the top posts, the optimal position that minimizes stray light interference and allows the effective signal to pass through can be found, thereby optimizing the quality of the optical signal and providing favorable conditions for subsequent signal reception and detection.

[0054] For details, please refer to Figure 7 As shown, in another embodiment of this utility model, the Raman probe includes a connector 75 and a sleeve 76, wherein the connector 75 is along a first direction (i.e., attached). Figure 1The sleeve 76 (in the Z-axis direction) is inserted into the inner wall of the housing 1 and connected to the connector 75. The diameter of the sleeve 76 is variable, which allows the light-absorbing component to have a certain degree of adjustability in the second direction. This facilitates fine-tuning of the position of the light-absorbing component during installation and use to achieve the best light-absorbing effect.

[0055] Specifically, sleeve 76 along the first direction (i.e., the attached direction) Figure 1 The sleeve 76 (located in the Z-axis direction) is set inside the housing 1, and the diameter of the sleeve 76 is variable. By changing the diameter of the sleeve 76, the size of the space it occupies can be adjusted, thereby affecting the propagation path and mode of the optical signal within it.

[0056] For further details, please refer to Figure 3 , Figure 4 In one embodiment of this utility model, a concave mirror 8 is provided on the side of the air chamber 2 away from the housing 1, and the concave mirror 8 is directed toward the first focusing lens along the second laser optical path.

[0057] For more details, please refer to Figure 2 , Figure 3 As shown, a fiber optic collimator 15 is provided on the side of the signal transmitter 13 near the housing 1. The fiber optic collimator 15 is used to convert the diverging light output from the fiber optic cable into parallel light. The fiber optic collimator 15 typically contains a fiber optic connector and a lens. After the optical signal is output from the end face of the fiber, it is collimated by the lens and becomes a parallel beam. The collimated parallel light signal propagates along the optical path to the beam splitter 4. Because the optical signal has been collimated, its beam quality is higher, and its coordination with the beam splitter 4 is more precise.

[0058] The specific working process of the Raman probe in this embodiment is as follows: The laser beam passes through the signal transmitter 13 and collimator 15 in sequence, becoming parallel light. It then enters the reflective cavity of the housing 1 through the laser inlet 11. Inside the housing 1, it is reflected by the beam splitter 4 and enters the gas chamber 2. The first focusing lens 3 is used to focus the laser beam reflected by the beam splitter 4 onto the gas chamber 2 to facilitate the excitation of the Raman signal. The excited Raman signal is converted into parallel light by the first focusing lens 3 and then passes through the beam splitter 4 and the long-pass filter 6 in sequence. It is then focused by the second focusing lens 5 on the preset single Raman optical path and the light-absorbing component reduces stray light to the fiber end face for collection.

[0059] Compared with the prior art, the technical solution of this utility model has the following beneficial effects: 1. In the technical solution of this utility model, the signal transmitter emits a laser beam, which is transmitted along a set optical path. When the laser beam reaches the gas chamber, it excites the molecules of the gas to be detected to generate a Raman scattering signal. The light-absorbing structure between the signal receiver and the housing is mainly used to process the laser beam that has not been removed, stray light generated by reflections from the front and back surfaces of the doublet mirror, and laser beams that are consistent with the main optical path but have a significant deflection angle. These beams can interfere with the detection in the low wavenumber region. When these stray lights propagate to the extinction structure, the extinction structure absorbs or scatters these stray lights, weakening their energy and thus reducing interference to the signal receiver. That is, a physical isolation method is used. By setting an extinction structure before the optical fiber on the collection side (between the long-pass filter and the optical fiber), a portion of the Raman scattering signal is sacrificed in exchange for an enhanced signal-to-noise ratio and gas concentration detection accuracy. The Raman scattering signal processed by the extinction structure is received by the signal receiver, which converts the received optical signal into an electrical signal for subsequent signal processing and analysis to obtain the Raman spectral information of the gas to be detected, which is used to detect parameters such as its composition and concentration.

[0060] 2. By using a light-absorbing structure, the laser reflected from the front and back surfaces of the doublet mirror is prevented from entering the spectrometer, thus reducing the interference of light on the signal. The extinction column has ample setting points, the light is in a focused state, and the position of the collecting fiber is determined, which is conducive to adjusting the extinction column to the optimal position. It can also determine the optimal placement position of the extinction column to block reflected laser and maximize the transmission ratio of Raman signal.

[0061] 3. The extinction structure is fixed to the inner wall of the receiving lens tube by springs in the Z and Y directions. The position of the extinction structure inside the receiving lens tube is then adjusted by a top post, thereby adjusting the transmission ratio of laser and Raman light and achieving fine-tuning of the extinction structure in the ZY axis directions. During the fine-tuning of the extinction structure's position, the optical signal (including the effective signal and stray light) enters the effective area of ​​the extinction structure. As the position of the extinction structure changes, its processing effect on stray light in the optical signal also changes accordingly. By continuously adjusting the pushing force of the top post, the position that minimizes stray light interference and optimizes the passage of the effective signal is found, thus optimizing the quality of the optical signal and providing favorable conditions for subsequent signal reception and detection.

[0062] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A Raman probe with reduced stray light, characterized in that, The Raman probe includes a housing, a gas chamber, and a light-absorbing component. The gas chamber is fixed to the housing, and the housing has a laser inlet and a Raman light receiving outlet. The housing, the air chamber, and the laser inlet are configured such that the laser inlet is used for laser injection, and the laser beam enters the air chamber along a preset laser path inside the housing; The housing, the gas chamber, and the Raman light receiving outlet are configured such that Raman light is generated in the gas chamber and enters the housing and is directed to the Raman light receiving outlet along a preset Raman light path within the housing. Wherein, the preset Raman optical path does not overlap with the preset laser optical path in at least a portion away from the gas cell and is a preset single Raman optical path; the light-absorbing component is disposed on the preset single Raman optical path and is used to absorb part of the Raman light containing stray light.

2. The reduced stray light Raman probe of claim 1, wherein, The housing contains a first focusing lens, a beam splitter, and a second focusing lens arranged sequentially along a preset direction. The preset laser optical path includes a first laser optical path and a second laser optical path arranged at an angle greater than 0° and less than 180°; the first laser optical path extends from the laser inlet to the beam splitter; the second laser optical path extends from the beam splitter through the first focusing lens and exits the housing. The preset Raman optical path is set along the preset direction.

3. The reduced stray light Raman probe of claim 2, wherein, The light-absorbing component is a light-shielding film layer disposed on the side of the beam splitter facing the Raman light receiving outlet; or, The light-absorbing component is a light-shielding film layer disposed on any surface of the second focusing lens.

4. The reduced stray light Raman probe of claim 2, wherein, The housing also includes a long-pass filter, and the beam splitter, the long-pass filter, and the second focusing lens are arranged sequentially along the preset direction.

5. The reduced stray light Raman probe of claim 4, wherein, The light-absorbing component is a light-shielding film layer disposed on any surface of the long-pass filter.

6. The reduced stray light Raman probe of claim 1, wherein, The light-absorbing component is directly fixed to the inner wall surface of the housing.

7. The Raman probe for reducing stray light according to claim 2, characterized in that, The light-absorbing component is located on the side of the second focusing lens away from the beam splitter and is directly fixed to the inner wall of the housing.

8. The Raman probe with reduced stray light according to claim 6 or 7, characterized in that, The light-absorbing component is configured such that its position is adjustable in a first direction and a second direction, both perpendicular to the preset single Raman optical path. Wherein, the first direction is perpendicular to the second direction.

9. The reduced stray light Raman probe of claim 8, wherein, Also includes: A first elastic element is connected along the first direction to one side between the sleeve of the light-absorbing member and the inner wall of the housing; The second elastic element is connected along the second direction to one side between the sleeve of the light-absorbing member and the inner wall of the housing; The first top post is connected along the first direction to the other side between the sleeve of the light-absorbing member and the inner wall of the housing; The second top post is connected along the second direction to the other side between the sleeve of the light-absorbing member and the inner wall of the housing; The position of the sleeve of the light-absorbing component is adapted to be finely adjusted under the driving action of the first top post and the second top post.

10. The reduced stray light Raman probe of claim 8, wherein, The light-absorbing component includes: A connector is provided on the inner wall of the housing along the first direction or the second direction; And a sleeve, connected to the connector; the diameter of the sleeve is variable.

11. The reduced stray light Raman probe of any of claims 2-5, wherein, A concave mirror is provided on the inner wall surface of the gas chamber on the side away from the housing, and the concave surface of the concave mirror is arranged along the second laser light path toward the first focusing lens.

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