A spectrometer and a spectrometric method for solar blind narrow Raman spectroscopy
Patent Information
- Application Number
- CN202611393345.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-09
- Publication Date
- 2026-11-03
AI Technical Summary
Existing solar-blind ultraviolet narrow Raman spectroscopy spectrometers are difficult to effectively separate and extract extremely narrow Raman signals of water vapor, nitrogen, and oxygen. Furthermore, the devices are complex in structure and suffer from severe light energy attenuation, which affects the signal-to-noise ratio and inversion accuracy.
Employing a single-grating multi-level diffraction structure, multiple diffraction beams are performed using a collimating lens and a planar holographic diffraction grating. Combined with a reflecting mirror and a focusing lens group, high-precision separation of Miralli, oxygen, nitrogen, and water vapor signals is achieved, which are then converted into electrical signals by a photodetector.
It improves stray light suppression, shortens the optomechanical assembly length, reduces light energy attenuation, and achieves high-precision separation and efficient extraction of daytime atmospheric water vapor vibration Raman spectra, meeting the requirements of high-precision inversion detection.
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Figure CN123028698A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of spectroscopic technology, specifically relating to a spectroscopic device and method for solar-blind narrow Raman spectra. Background Technology
[0002] Atmospheric water vapor is a key atmospheric physical parameter. Its spatiotemporal variations constitute complex weather phenomena, playing a decisive stabilizing and amplifying role in Earth's long-term climate. It is one of the most efficient energy carriers in Earth's energy balance system and an indispensable and most active component of Earth's climate system. Since human activities mainly occur during the day, obtaining daytime water vapor vertical profiles is a key research topic in global meteorology and remote sensing. Lidar, with its advantages of high spatiotemporal resolution and real-time detection, provides an effective means for atmospheric water vapor detection. Among them, vibrational Raman lidar in the solar-blind ultraviolet band, due to its emission wavelength being located in the solar-blind zone (266.0 nm), can effectively avoid interference from solar background light, making it an ideal solution for daytime atmospheric water vapor detection. This technology retrieves water vapor distribution profiles by receiving vibrational Raman scattering echo signals of water vapor (294.6 nm), nitrogen (283.6 nm), Miralles, and oxygen.
[0003] Currently, solar-blind ultraviolet narrow Raman spectroscopy spectrometers typically employ filters, Fabry-Perot etalons, atomic filters, prisms, or single-order diffraction gratings as the core components for spectral analysis. These components are distributed sequentially along the optical axis to ultimately obtain Miraley diffraction light and composite diffraction light containing oxygen, nitrogen, and water vapor signals through the prism or single-order diffraction grating structure. However, due to the extremely narrow Raman spectral signals of water vapor and nitrogen in the solar-blind ultraviolet band, and the fact that the intensity of Miraley elastic scattering signals in atmospheric detection is typically several orders of magnitude higher than that of inelastic vibrational Raman scattering signals, the internal stray light suppression ratio can only reach 10. -3 ~10 -4 The magnitude of this means that the relatively weak Raman signal is easily overwhelmed or crosstalked by the strong Mirrell stray light remaining inside the optical path, making it difficult to effectively separate the various optical signals in the beam. The poor extraction effect of the optical signal seriously affects the detection signal-to-noise ratio and inversion accuracy of the Raman spectral signal. Moreover, this device uses a beam splitting structure with multiple filters or etalon stacked, and the components are arranged sequentially along the optical axis. This not only increases the axial length and spatial redundancy of the optomechanical assembly, but also causes severe light energy attenuation due to multi-interface transmission, further degrading the beam splitting accuracy. It is difficult to achieve high-spectral fine beam splitting of the weak vibration Raman echo scattering signal of lidar, and cannot meet the high-precision inversion detection requirements of water vapor profile during the day. Summary of the Invention
[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a spectroscopic device and method for solar-blind narrow Raman spectroscopy, which can achieve high-precision separation and efficient extraction of four extremely narrow spectral signals: Miraleil, oxygen, nitrogen, and water vapor in the solar-blind ultraviolet band. This meets the requirements for accurate separation of atmospheric water vapor vibrational Raman spectral signals and high-precision inversion detection of water vapor profiles under complex daytime backgrounds.
[0005] The technical solution of this invention is: A spectroscopic device for solar-blind narrow Raman spectroscopy, comprising: The first-stage beam splitting component includes a collimating lens, a planar holographic diffraction grating, and a first focusing lens group. The atmospheric echo detection signal received by the lidar is coupled to form a beam and input into the collimating lens. The collimating lens collimates the beam into a parallel beam, which is then incident on the planar holographic diffraction grating. After the planar holographic diffraction grating performs a first diffraction and splitting, a Miraleli signal first-stage diffraction beam and a composite first-stage diffraction beam are generated. The Miraleli signal first-stage diffraction beam is converged by the first focusing lens group. A multi-stage beam splitting assembly, disposed on the optical path of the composite first-order diffracted light, includes a reflector and multiple second-focusing lens groups. The reflector reflects the composite first-order diffracted light back to a planar holographic diffraction grating for secondary diffraction, generating second-order diffracted light for oxygen, nitrogen, and water vapor signals. The second-order diffracted light for water vapor signals is reflected again by the reflector back to the planar holographic diffraction grating for tertiary diffraction, generating third-order diffracted light for water vapor signals. Second-focusing lens groups are respectively disposed on the optical paths of the second-order diffracted light for oxygen, nitrogen, and water vapor signals. Multiple photodetectors are respectively disposed on the outgoing light paths of the first focusing lens group and multiple second focusing lens groups, and are used to convert the corresponding optical signals into electrical signals.
[0006] Preferably, an optical fiber is provided between the collimating lens and the lidar. One end of the optical fiber is connected to the lidar, and the other end is connected to the collimating lens. The end face of the optical fiber facing the collimating lens is located at the focal point of the collimating lens. The center point of the optical fiber and the collimating lens are on the same axis. The optical fiber is used to couple the atmospheric echo detection signal received by the lidar to form a beam and transmit it to the collimating lens. The optical fiber is a multimode ultraviolet quartz double-clad optical fiber with a core diameter range of [980μm, 1020μm] and a numerical aperture range of [0.215μm, 0.225μm].
[0007] Preferably, both the first focusing lens group and the second focusing lens group include one or more focusing lenses, and both the focusing lens and the collimating lens are plano-convex lenses made of ultraviolet fused silica and with a working wavelength of 190nm~2500nm.
[0008] Preferably, the planar holographic diffraction grating is a planar holographic blazed grating with a blazed wavelength range of [228nm, 232nm] and a grating groove density range of [3590 grooves / mm, 3610 grooves / mm].
[0009] Preferably, the angle between the optical axis of the collimating lens and the surface normal of the planar holographic diffraction grating is in the range of 9.5° to 10.5°.
[0010] Preferably, the reflector is a plane reflector coated with an ultraviolet-enhanced aluminum film, and the angle between the reflective surface of the reflector and the horizontal direction ranges from 51.5° to 52.5°.
[0011] Preferably, the plurality of photodetectors include a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector. The first photodetector, the second photodetector, the third photodetector, and the fourth photodetector are all cylindrical photomultiplier tubes. The central axis of the first photodetector coincides with the principal optical axis of the first focusing lens group, and the central axes of the second photodetector, the third photodetector, and the fourth photodetector respectively coincide with the principal optical axis of their corresponding second focusing lens groups.
[0012] A spectroscopic method for solar-blind narrow Raman spectroscopy, implemented using any of the spectroscopic devices for solar-blind narrow Raman spectroscopy described above, includes the following steps: The atmospheric echo detection signal received by the lidar is coupled to form a beam, and then collimated by a collimating lens to form a parallel beam. The parallel beam is incident on a planar holographic diffraction grating at a preset incident angle, and then undergoes one diffraction and beam splitting by the planar holographic diffraction grating to obtain the first-order diffraction beam of the Miraley signal and the composite first-order diffraction beam. The first-order diffracted light of the Miralle signal is focused by the first focusing lens group and then incident on the photodetector located at its focal plane. The photodetector converts the optical signal into an electrical signal. The first-order diffracted light is reflected back to the plane holographic diffraction grating by a mirror, and then subjected to secondary diffraction and spectral dispersion by the plane holographic diffraction grating to obtain the second-order diffracted light of oxygen signal, nitrogen signal, and water vapor signal; the second-order diffracted light of water vapor signal is further incident on the mirror again and reflected back to the plane holographic diffraction grating for a second time, and then subjected to tertiary diffraction and spectral dispersion by the plane holographic diffraction grating to obtain the third-order diffracted light of water vapor signal; The corresponding beams are converged by the second focusing lens groups located on the optical paths of the second-order diffraction beams of the oxygen signal, the second-order diffraction beams of the nitrogen signal, and the third-order diffraction beams of the water vapor signal, respectively. The converged beams are then converted into electrical signals by photodetectors set on the output optical paths of each of the second focusing lens groups. The electrical signals acquired by each of the photodetectors are collected and processed to obtain the spectral signals of each channel corresponding to the Miralles channel, oxygen channel, nitrogen channel and water vapor channel, respectively.
[0013] Compared with the prior art, the spectroscopic device and method for solar-blind narrow Raman spectroscopy of the present invention have the following advantages: This device collimates the atmospheric echo detection signal into a parallel beam using a collimating lens before incident on a planar holographic diffraction grating. Using the same planar holographic diffraction grating, it directly acquires the Miraleli signal, oxygen signal, nitrogen signal, and water vapor signal from the composite first-order diffraction beam through first-order diffraction, second-order diffraction, and third-order diffraction acquisition, respectively. This single-grating multi-order diffraction structure allows the incident beam to travel back and forth multiple times between the grating and the mirror, undergoing multiple diffraction stages. Each diffraction process effectively suppresses stray light from the Miraleli background signal. Thus, through the step-by-step superposition effect of multi-order diffraction, the stray light suppression effect on the Miraleli scattering signal is effectively improved. This invention effectively avoids crosstalk of strong background signals to the Raman channel. Simultaneously, it abandons the traditional beam splitting structure of multiple filters or etalons arranged serially along the optical axis. Instead, it uses a mirror to reflect the beam and performs beam splitting multiple times using the same planar holographic diffraction grating. This significantly shortens the axial length of the optomechanical assembly, reduces spatial redundancy, and avoids light energy attenuation caused by multi-interface transmission and reflection. This enables high-precision separation and efficient extraction of four extremely narrow spectral signals—Mireille, oxygen, nitrogen, and water vapor—in the solar-blind ultraviolet band, meeting the requirements for accurate separation of atmospheric water vapor vibration Raman spectral signals under complex daytime backgrounds and high-precision inversion detection of water vapor profiles. Attached Figure Description
[0014] Figure 1 This is a structural diagram of the overall beam splitting device in an embodiment of the present invention.
[0015] Figure 2 This is a flowchart illustrating the operation of the spectrophotometer in an embodiment of the present invention.
[0016] Explanation of reference numerals in the attached figures: 1. Optical fiber; 2. Collimating lens; 3. Planar holographic diffraction grating; 4. First focusing lens; 5. First photodetector; 6. Mirror; 7. Second focusing lens; 8. Second photodetector; 9. Third focusing lens; 10. Third photodetector; 11. Fourth focusing lens; 12. Fourth photodetector. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0018] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.
[0019] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0020] Example 1 See appendix Figure 1 As shown, in order to achieve high-precision separation and extraction of four extremely narrow spectral signals—Mirrell, oxygen, nitrogen, and water vapor—in the solar-blind ultraviolet band, this embodiment provides a spectroscopic device for solar-blind narrow Raman spectroscopy.
[0021] The spectrometer mainly comprises a beam splitting section for the laser echo beam positioned and mounted on the main support structure, and a spectral acquisition section based on photomultiplier tubes. The beam splitting section includes a first-stage beam splitting assembly and a multi-stage beam splitting assembly. The first-stage beam splitting assembly includes a collimating lens 2, a planar holographic diffraction grating 3, and a first focusing lens group. The first focusing lens group includes one or more focusing lenses; in this embodiment, the first focusing lens group uses one focusing lens, denoted as the first focusing lens 4. The multi-stage beam splitting assembly includes a reflecting mirror 6 and multiple second focusing lens groups. Each second focusing lens also includes one or more focusing lenses; in this embodiment, there are three second focusing lens groups, each using one focusing lens, and they are sequentially denoted as the second focusing lens 7, the third focusing lens 9, and the fourth focusing lens 11. The spectral acquisition section includes multiple photodetectors; in this embodiment, there are four photodetectors: the first photodetector 5, the second photodetector 8, the third photodetector 10, and the fourth photodetector 12.
[0022] The specific positional relationships and optical path structure of the above components are as follows: One side of the collimating lens 2 is used to receive the atmospheric echo detection signal transmitted by the lidar, and to collimate the beam corresponding to the atmospheric echo detection signal into a parallel beam. A planar holographic diffraction grating 3 is disposed on the outgoing optical path of the collimating lens 2. A reflecting mirror 6 is disposed on the optical path of the composite first-order diffracted light generated by the planar holographic diffraction grating 3. The composite first-order diffracted light includes oxygen signal first-order diffracted light, nitrogen signal first-order diffracted light, and water vapor signal first-order diffracted light.
[0023] The first focusing lens 4 is positioned on the optical path of the first-order diffracted light of the Milley signal generated by the planar holographic diffraction grating 3, and the first photodetector 5 is positioned on the outgoing light path of the first focusing lens 4.
[0024] The second focusing lens 7 is positioned on the second-order diffraction path of the oxygen signal generated by the oxygen signal after being reflected by the mirror 6 and then incident on the planar holographic diffraction grating 3. The second photodetector 8 is positioned on the outgoing light path of the second focusing lens 7.
[0025] The third focusing lens 9 is positioned on the second-order diffraction path of the nitrogen signal generated by the nitrogen gas signal after being reflected by the mirror 6 and then incident on the planar holographic diffraction grating 3. The third photodetector 10 is positioned on the outgoing light path of the third focusing lens 9.
[0026] The fourth focusing lens 11 is placed on the third-order diffraction path of the water vapor signal generated by the water vapor signal after being reflected twice by the mirror 6 and incident three times on the planar holographic diffraction grating 3. The fourth photodetector 12 is placed on the outgoing light path of the fourth focusing lens 11.
[0027] In an embodiment of the present invention, one side of the incident light path of the collimating lens 2 is connected to the lidar via an optical fiber 1. Specifically, one end of the optical fiber 1 is connected to the lidar, and the other end is connected to the collimating lens 2, with the end face of the optical fiber 1 facing the collimating lens 2 located at the focal point of the collimating lens 2. The optical fiber 1 is a multimode ultraviolet quartz double-clad fiber. Based on the optical coupling efficiency tolerance range and the beam divergence angle matching criterion, the core diameter of the optical fiber 1 is in the range of [980μm, 1020μm], and the numerical aperture is in the range of [0.215μm, 0.225μm]. The optical fiber 1 is clamped on an optical fiber 1 fixing holder. By adjusting the front-to-back position and height of the holder, the end face of the optical fiber 1 is precisely located on the focal plane of the collimating lens 2. The center points of the optical fiber 1, the collimating lens 2, and the planar holographic diffraction grating 3 are on the same axis.
[0028] In the embodiments of the present invention, the collimating lens 2, the first focusing lens 4, the second focusing lens 7, the third focusing lens 9 and the fourth focusing lens 11 are all plano-convex lenses made of ultraviolet fused silica material, and are all aspherical aberration-correcting lenses, with a working wavelength range of 190nm~2500nm and an optical transmittance of not less than 90% within the working wavelength range.
[0029] Based on the theory of diffraction efficiency plateau and the tolerance theory of grating spectral equations, the grating blaze wavelength is generally set to [228 nm, 232 nm], and the grating groove density is set to [3590 grooves / mm, 3610 grooves / mm]. In the embodiment of this invention, the planar holographic diffraction grating 3 is a planar holographic blaze grating with a blaze wavelength of 230 nm, a peak diffraction efficiency of not less than 75%, a grating groove count of 3600 grooves / mm, and a diffraction order of 1st order blaze. Based on the basic equation of grating diffraction and the principle of interval boundary constraints, the collimated parallel beam is incident on the grating surface of the planar holographic diffraction grating 3 at an incident angle of 9.5° to 10.5° (the angle between the optical axis of the collimating lens and the surface normal of the planar holographic diffraction grating).
[0030] In an embodiment of the present invention, the reflector 6 is a planar reflector 6 coated with an ultraviolet-enhanced aluminum film, with a reflectivity greater than 99% in the 262nm~266nm wavelength range, and the angle between the reflector 6 and the horizontal direction ranges from 51.5° to 52.5°.
[0031] In an embodiment of the present invention, the first photodetector 5 is a photomultiplier tube used in the Miralles acquisition channel, with a detectable spectral range of 185 nm to 900 nm, a quantum efficiency of 30% at a wavelength of 260 nm, and a pulse width of 80 ns. The second photodetector 8 (oxygen channel), the third photodetector 10 (nitrogen channel), and the fourth photodetector 12 (water vapor channel) also use cylindrical photomultiplier tubes, with the same parameters, a detectable spectral range of 185 nm to 320 nm, a quantum efficiency of 30% at a wavelength of 254 nm, and a pulse width of 80 ns.
[0032] In the laser receiving and transmitting section, the center points of optical fiber 1 and collimating lens 2 are on the same axis, and the center points of the focusing lens and photodetector of each channel are also on the same axis. Furthermore, the photosensitive surface of each photodetector is located at the focal plane of its corresponding focusing lens.
[0033] Based on the structure of the single-grating multi-level diffraction spectrometer described above, its spectroscopic working principle and assembly and debugging methods are explained below. The entire spectroscopic structure can be divided into a first-order, second-order, and third-order spectroscopic section according to diffraction order. The first-order spectroscopic section is the first-order spectroscopic assembly, while the second-order and third-order spectroscopic sections together constitute the multi-level spectroscopic assembly. Specifically:
[0034] The first-order diffraction section includes a collimating lens 2, a planar holographic diffraction grating 3, a first focusing lens 4, and a first photodetector 5. The collimating lens 2 is located between the planar holographic diffraction grating 3 and the optical fiber 1, and the first focusing lens 4 is located between the planar holographic diffraction grating 3 and the first photodetector 5. The atmospheric echo detection signal, after being transmitted through the optical fiber 1, exits from the end face and is collimated into a parallel beam by the collimating lens 2, then incident on the planar holographic diffraction grating 3 at an incident angle of 10°. After the incident beam completes first-order diffraction and diffraction by the planar holographic diffraction grating 3, a composite first-order diffracted beam is generated, containing a Miraley signal (266 nm), an oxygen signal (277.5 nm), a nitrogen signal (283.6 nm), and a water vapor signal (294.6 nm). In this process, the first-order diffracted light of the Miralles signal is emitted along its corresponding diffraction angle direction and directly incident on the first focusing lens 4. After being converged by the first focusing lens 4, it is incident on the photosensitive receiving end of the first photodetector 5 located at its focal plane. The first photodetector 5 converts the optical signal into an electrical signal and collects it.
[0035] The second-order diffraction section includes a planar holographic diffraction grating 3, a mirror 6, a second focusing lens 7, a second photodetector 8, a third focusing lens 9, and a third photodetector 10. The second focusing lens 7 and the third focusing lens 9 are both located between the planar holographic diffraction grating 3 and their respective photodetectors. After first-order diffraction, the first-order diffracted light of the oxygen and nitrogen signals is separated from the Mirallelic signal and incident on the mirror 6. The mirror 6 reflects the oxygen and nitrogen signals back to the planar holographic diffraction grating 3, and the two signals are incident on the grating surface again at appropriate incident angles, resulting in secondary diffraction. The second-order diffracted light of the oxygen signal is converged by the second focusing lens 7 and then incident on the second photodetector 8 located at its focal plane. The second-order diffracted light of the nitrogen signal is converged by the third focusing lens 9 and then incident on the third photodetector 10 located at its focal plane.
[0036] The third-order beam splitting section includes a planar holographic diffraction grating 3, a reflecting mirror 6, a fourth focusing lens 11, and a fourth photodetector 12. The fourth focusing lens 11 is located between the planar holographic diffraction grating 3 and the fourth photodetector 12. After first-order diffraction, the first-order diffracted light of the water vapor signal separates from the Miralli signal and is incident on the reflecting mirror 6. After being reflected back to the planar holographic diffraction grating 3 by the reflecting mirror 6 for the first time, it undergoes second diffraction. This second-order diffracted light is then incident on the reflecting mirror 6 again, and after being reflected a second time by the reflecting mirror 6, it is incident on the planar holographic diffraction grating 3 for the third time, resulting in third-order diffraction. The third-order diffracted light of the water vapor signal is converged by the fourth focusing lens 11 and then incident on the fourth photodetector 12, which is located at its focal plane.
[0037] During assembly and debugging, the horizontal placement angles of the planar holographic diffraction grating 3 and the reflector 6 need to be calibrated using a two-dimensional precision optical bench. Based on the diffraction angles of the beams corresponding to the four atmospheric echo signals (Mirrell, oxygen, nitrogen, and water vapor), the lateral arrangement of the four focusing lenses and photodetectors is calibrated. The axial front-back positions of the four photodetectors are adjusted along the four optical paths so that the central through-hole of each photodetector coincides with the center of the focal plane of the focusing lens corresponding to the four atmospheric echo optical paths (Mirrell, oxygen, nitrogen, and water vapor) after beam splitting, thereby ensuring maximum collection of echo signals from each channel.
[0038] Four photoelectric detectors transmit the atmospheric echo signals detected from each channel to a signal processing module (such as a digital oscilloscope or computer data acquisition card), thereby obtaining the spectral signals of each channel after high-precision separation, and completing the fine detection of atmospheric water vapor during the day.
[0039] Example 2 See appendix Figure 2 As shown, based on the aforementioned single-grating multi-level diffraction spectrometer, this embodiment provides a specific working method for solar-blind narrow Raman spectral separation using this spectrometer, which is implemented according to the following steps: Step 1: Adjust the front-to-back position and height of fiber 1 for receiving atmospheric echo signals from the lidar, so that the core end face of fiber 1 is located at the focal point of collimating lens 2. The atmospheric echo detection signal received by the lidar is coupled and transmitted through fiber 1, and then emitted from the end face of fiber 1.
[0040] Step 2: The emitted beam is collimated by the collimating lens 2 and becomes a parallel beam. This parallel beam is incident on the planar holographic diffraction grating 3 at an incident angle of 10°, and first-order diffraction occurs.
[0041] Step 3: After first-order diffraction, the first-order diffracted light of the Miralle signal is emitted along its corresponding diffraction angle direction and directly incident on the first focusing lens 4. After being converged by the first focusing lens 4, it is incident on the photosensitive receiving end of the first photodetector 5 located at its focal plane. The first photodetector 5 converts the optical signal into an electrical signal and collects it.
[0042] Step 4: After first-order diffraction, the first-order diffracted light of the oxygen signal, nitrogen signal and water vapor signal are incident on mirror 6 and efficiently reflected by mirror 6.
[0043] Step 5: The reflector 6 reflects the oxygen and nitrogen signals back to the planar holographic diffraction grating 3. The two signals are then incident on the grating surface again, resulting in secondary diffraction. The second-order diffracted light from the oxygen signal is converged by the second focusing lens 7 and then incident on the second photodetector 8 located at its focal plane. The second-order diffracted light from the nitrogen signal is converged by the third focusing lens 9 and then incident on the third photodetector 10 located at its focal plane.
[0044] Step 6: The first-order diffracted light of the water vapor signal is reflected back to the planar holographic diffraction grating 3 by the mirror 6 and undergoes secondary diffraction. This secondary diffracted light is then incident on the mirror 6 again, and after being reflected a second time, it is incident on the planar holographic diffraction grating 3 for a third time, resulting in tertiary diffraction. The third-order diffracted light of the water vapor signal is converged by the fourth focusing lens 11 and then incident on the fourth photodetector 12 located at its focal plane.
[0045] Step 7: The first photodetector 5, the second photodetector 8, the third photodetector 10, and the fourth photodetector 12 convert the detected echo light signals of the Miralleli channel, oxygen channel, nitrogen channel, and water vapor channel into electrical signals, respectively, and transmit them to the signal processing module. After amplification, analog-to-digital conversion, and cumulative averaging, the spectral signals of each channel corresponding to the Miralleli channel, oxygen channel, nitrogen channel, and water vapor channel are obtained.
[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A spectroscopic device for solar-blind narrow Raman spectroscopy, characterized in that, include: The first-stage beam splitting component includes a collimating lens, a planar holographic diffraction grating, and a first focusing lens group. The atmospheric echo detection signal received by the lidar is coupled to form a beam and input into the collimating lens. The collimating lens collimates the beam into a parallel beam, which is then incident on the planar holographic diffraction grating. After the planar holographic diffraction grating performs a first diffraction and splitting, a Miraleli signal first-stage diffraction beam and a composite first-stage diffraction beam are generated. The Miraleli signal first-stage diffraction beam is converged by the first focusing lens group. A multi-stage beam splitting assembly, disposed on the optical path of the composite first-order diffracted light, includes a reflector and multiple second-focusing lens groups. The reflector reflects the composite first-order diffracted light back to a planar holographic diffraction grating for secondary diffraction, generating second-order diffracted light for oxygen, nitrogen, and water vapor signals. The second-order diffracted light for water vapor signals is reflected again by the reflector back to the planar holographic diffraction grating for tertiary diffraction, generating third-order diffracted light for water vapor signals. Second-focusing lens groups are respectively disposed on the optical paths of the second-order diffracted light for oxygen, nitrogen, and water vapor signals. Multiple photodetectors are respectively disposed on the outgoing light paths of the first focusing lens group and multiple second focusing lens groups, and are used to convert the corresponding optical signals into electrical signals.
2. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 1, characterized in that, An optical fiber is provided between the collimating lens and the lidar. One end of the optical fiber is connected to the lidar, and the other end is connected to the collimating lens. The end face of the optical fiber facing the collimating lens is located at the focal point of the collimating lens. The center point of the optical fiber and the collimating lens are on the same axis. The optical fiber is used to couple the atmospheric echo detection signal received by the lidar to form a beam and transmit it to the collimating lens. The optical fiber is a multimode ultraviolet quartz double-clad optical fiber with a core diameter range of [980μm, 1020μm] and a numerical aperture range of [0.215μm, 0.225μm].
3. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 2, characterized in that, The first focusing lens group and the second focusing lens group each include one or more focusing lenses. The focusing lenses and the collimating lenses are both plano-convex lenses made of ultraviolet fused silica and with a working wavelength range of 190nm to 2500nm.
4. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 1, characterized in that, The planar holographic diffraction grating is a planar holographic blazed grating with a blazed wavelength range of [228nm, 232nm] and a grating groove density range of [3590 grooves / mm, 3610 grooves / mm].
5. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 2, characterized in that, The angle between the optical axis of the collimating lens and the surface normal of the planar holographic diffraction grating ranges from 9.5° to 10.5°.
6. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 1, characterized in that, The reflector is a plane reflector coated with an ultraviolet-enhanced aluminum film, and the angle between the reflective surface of the reflector and the horizontal direction ranges from 51.5° to 52.5°.
7. A spectroscopic device for solar-blind narrow Raman spectroscopy according to claim 2, characterized in that, The plurality of photodetectors include a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector. The first photodetector, the second photodetector, the third photodetector, and the fourth photodetector are all cylindrical photomultiplier tubes. The central axis of the first photodetector coincides with the principal optical axis of the first focusing lens group. The central axes of the second photodetector, the third photodetector, and the fourth photodetector respectively coincide with the principal optical axis of their corresponding second focusing lens groups.
8. A spectroscopic method for solar-blind narrow Raman spectroscopy, implemented using a spectroscopic apparatus for solar-blind narrow Raman spectroscopy as described in any one of claims 1-7, characterized in that, Includes the following steps: The atmospheric echo detection signal received by the lidar is coupled to form a beam, and then collimated by a collimating lens to form a parallel beam. The parallel beam is incident on a planar holographic diffraction grating at a preset incident angle, and then undergoes one diffraction and beam splitting by the planar holographic diffraction grating to obtain the first-order diffraction beam of the Miraley signal and the composite first-order diffraction beam. The first-order diffracted light of the Miralle signal is focused by the first focusing lens group and then incident on the photodetector located at its focal plane. The photodetector converts the optical signal into an electrical signal. The first-order diffracted light is reflected back to the plane holographic diffraction grating by a mirror, and then subjected to secondary diffraction and spectral dispersion by the plane holographic diffraction grating to obtain the second-order diffracted light of oxygen signal, nitrogen signal, and water vapor signal; the second-order diffracted light of water vapor signal is further incident on the mirror again and reflected back to the plane holographic diffraction grating for a second time, and then subjected to tertiary diffraction and spectral dispersion by the plane holographic diffraction grating to obtain the third-order diffracted light of water vapor signal; The corresponding beams are converged by the second focusing lens groups located on the optical paths of the second-order diffraction beams of the oxygen signal, the second-order diffraction beams of the nitrogen signal, and the third-order diffraction beams of the water vapor signal, respectively. The converged beams are then converted into electrical signals by photodetectors set on the output optical paths of each of the second focusing lens groups. The electrical signals acquired by each of the photodetectors are collected and processed to obtain the spectral signals of each channel corresponding to the Miralles channel, oxygen channel, nitrogen channel and water vapor channel, respectively.