An ultra-narrow field-of-view temperature and humidity Raman laser radar and off-axis reflective beam expansion system

Abstract

The present invention relates to an ultra-narrow field-of-view temperature and humidity Raman laser radar and an off-axis reflective beam expansion system, comprising: a laser emitting device, wherein the laser emitting device comprises a polarization isolation spectrometer and an off-axis reflective beam expansion device, wherein the polarization isolation spectrometer and the off-axis reflective beam expansion device are coaxially arranged. The present invention provides an ultra-narrow field-of-view temperature and humidity Raman laser radar and an off-axis reflective beam expansion system, wherein the polarization isolation spectrometer and the off-axis reflective beam expansion device are arranged coaxially, wherein the polarization isolation spectrometer can make the optical receiving and transmitting systems coaxial, and the off-axis reflective beam expansion device can make the receiving field angle ultra-narrow, thereby reducing the interference of background radiation, avoiding the signal loss caused by light blocking, and improving the near-ground signal quality.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to an ultra-narrow field-of-view temperature and humidity Raman laser radar and an off-axis reflective beam expansion system. Background Art

[0002] The laser is emitted by a laser source, and after being expanded and collimated by the transmitting system, it is emitted into the atmosphere. After being attenuated by the atmosphere, it is scattered by particles in the atmosphere. Atmospheric backscattering includes Mie scattering, Rayleigh scattering, Raman scattering, etc., among which Raman scattering includes rotational Raman scattering and vibrational Raman scattering. The backscattered laser is extinguished by the atmosphere again on the return journey, and then received by the receiving optical system, after photoelectric conversion by the photodetector, the echo signal is finally collected, calculated and data processed. The receiving optical system of the laser radar provided by the prior art usually uses a Cassegrain telescope system. This system usually has a large field of view and is more interfered by background radiation. It is also affected by the shielding of the secondary mirror or the shielding of the transmitting component, and some echo signals will be missing. Summary of the invention

[0003] The present invention provides an ultra-narrow field-of-view temperature and humidity Raman laser radar and an off-axis reflective beam expansion system, which are provided with a polarization isolation spectrometer and an off-axis reflective beam expansion device. The polarization isolation spectrometer can make the optical receiving and transmitting systems coaxial and coaxial, and the off-axis reflective beam expansion device can make the receiving field of view ultra-narrow, which not only reduces the interference of background radiation, but also avoids the signal loss caused by light blocking, thereby improving the quality of near-ground signals.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] An ultra-narrow field-of-view temperature and humidity Raman laser radar comprises: a laser emitting device, wherein the laser emitting device comprises a polarization isolation spectrometer and an off-axis reflection beam expander, wherein the polarization isolation spectrometer and the off-axis reflection beam expander are coaxially arranged.

[0006] Preferably, the polarization isolation spectrometer comprises a polarization beam splitter cube 1 and a quarter wave plate 2, and the off-axis reflective beam expander comprises a first curved reflector 3 and a second curved reflector 4;

[0007] The quarter wave plate 2 and the first curved reflector 3 are arranged in sequence on the left or right side of the polarization beam splitter cube 1 from near to far, and the second curved reflector 4 is arranged off-axis from the first curved reflector 3 and the main optical axes of the two are parallel.

[0008] Preferably, the laser emitting device further comprises a laser emitter 5 and a beam expander 6;

[0009] The beam expander 6, the polarization beam splitter cube 1, the quarter wave plate 2 and the first curved reflector 3 are arranged in sequence on the left or right side of the laser emitter 5 from near to far. The second curved reflector 4 is arranged off-axis from the first curved reflector 3 and the main optical axes of the two are parallel.

[0010] Preferably, it also includes a receiving light splitting device, and the receiving light splitting device is arranged on the reflected light path of the light split by the polarization beam splitting cube 1;

[0011] The receiving spectroscopic device comprises a neutral density filter 10 and a first dichroic mirror 71 , and the neutral density filter 10 and the first dichroic mirror 71 are sequentially arranged on the reflection light path of the polarization beam splitter cube 1 .

[0012] Preferably, a second dichroic mirror 72 , a first interference filter 81 , a first focusing lens 91 and a nitrogen vibration Raman channel 11 are sequentially disposed on the left or right side of the first dichroic mirror 71 from near to far.

[0013] Preferably, a second interference filter 82 , a second focusing lens 92 and a water vapor vibration Raman channel 12 are sequentially disposed below the second dichroic mirror 72 .

[0014] Preferably, a third dichroic mirror 73 , a third interference filter 83 , a third focusing lens 93 and a main channel 13 are sequentially disposed below the first dichroic mirror 71 .

[0015] Preferably, a fourth dichroic mirror 74, a fourth interference filter 84, a fourth focusing lens 94 and a first rotational Raman channel 14 are sequentially arranged on the left or right side of the third dichroic mirror 73 from near to far;

[0016] A fifth interference filter 85 , a fifth focusing lens 95 and a second rotational Raman channel 15 are sequentially disposed below the fourth dichroic mirror 74 .

[0017] Preferably, the nitrogen vibration Raman channel 11, the water vapor vibration Raman channel 12, the main channel 13, the first rotational Raman channel 14 and the second rotational Raman channel 15 are respectively provided with a first detector, a second detector, a third detector, a fourth detector and a fifth detector.

[0018] An off-axis reflective beam expansion system comprises a temperature and humidity Raman laser radar for ultra-narrow field of view as described in any of the above technical solutions.

[0019] By implementing the above technical scheme, the following technical effects are achieved: an ultra-narrow field-of-view temperature and humidity Raman lidar and an off-axis reflective beam expansion system provided by the present invention can make the receiving field of view angle ultra-narrow through a polarization isolation spectrometer, thereby avoiding signal loss caused by light blocking; the off-axis reflective beam expansion device can reduce the interference of background radiation and improve the quality of near-ground signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of an ultra-narrow field-of-view temperature and humidity Raman lidar provided by the present invention. DETAILED DESCRIPTION

[0021] In order to better understand the technical solution of the present invention, the embodiments provided by the present invention are described in detail below with reference to the accompanying drawings.

[0022] Embodiment 1

[0023] like Figure 1 As shown, an ultra-narrow field-of-view temperature and humidity Raman lidar provided in this embodiment includes a laser emitting device, and the laser emitting device includes a polarization isolation spectrometer and an off-axis reflection beam expander, and the polarization isolation spectrometer and the off-axis reflection beam expander are coaxially arranged; in this embodiment, the polarization isolation spectrometer and the off-axis reflection beam expander can not only emit laser into the atmosphere, but also receive backscattered laser. When receiving the backscattered laser, the polarization isolation spectrometer and the off-axis reflection beam expander can make the receiving field of view ultra-narrow, which not only reduces the interference of background radiation and blind spots, but also avoids the signal loss caused by light blocking, thereby improving the near-ground signal quality.

[0024] The polarization isolation spectrometer comprises a polarization beam splitter cube 1 and a quarter wave plate 2, and the off-axis reflection beam expansion device comprises a first curved reflector 3 and a second curved reflector 4. The quarter wave plate 2 and the first curved reflector 3 are arranged in sequence on the left or right of the polarization beam splitter cube 1 from near to far, and the second curved reflector 4 is arranged off-axis from the first curved reflector 3 and the main optical axes of the two are parallel. The laser emitting device also comprises a laser emitter 5 and a beam expander 6. The beam expander 6, the polarization beam splitter cube 1, the quarter wave plate 2 and the first curved reflector 3 are arranged on the left or right of the laser emitter 5 from near to far, and the second curved reflector 4 is arranged off-axis from the first curved reflector 3 and the main optical axes of the two are parallel. In this embodiment, the left or right setting depends on the direction of laser emission. The second curved reflector 4 and the first curved reflector 3 are arranged according to the route of laser emission. In this embodiment, the second curved reflector 4 is arranged on the upper left of the first curved reflector 3, and in other embodiments, it can also be arranged at other positions that are convenient for laser passage.

[0025] In this embodiment, the laser emitter 5, the beam expander 6, the polarization beam splitter cube 1, the quarter wave plate 2, the first curved reflector 3 and the second curved reflector 4 together constitute a laser emission device, and together complete the process of emitting laser light into the atmosphere. The laser emitter 5 emits laser light, and the laser light passes through the beam expander 6, and the beam expander 6 converts the laser light into a parallel light beam, and the parallel light beam becomes horizontally polarized light after passing through the polarization beam splitter cube 1, and the horizontally polarized light is converted into circularly polarized light after passing through the quarter wave plate 2, and the circularly polarized light passes through the first curved reflector 3 and the second curved reflector 4 and is emitted into the atmosphere, thereby completing the process of emitting laser light into the atmosphere.

[0026] In this embodiment, the emitted laser is attenuated by the atmosphere and scattered by atmospheric particles. The scattering process includes Mie scattering, Rayleigh scattering, Raman scattering, etc., among which Raman scattering includes rotational Raman scattering and vibrational Raman scattering. These backscattered lasers are returned and received by the off-axis reflection expansion device, namely the first first curved reflector 3 and the second curved reflector 4. At this time, the echo signal is still circularly polarized light, which becomes vertically polarized light after passing through the quarter-wave plate 2, and is perpendicular to the polarization direction of the emitted light. Since the polarization beam splitter cube 1 transmits horizontally polarized light and reflects vertically polarized light, an isolation effect is achieved. In this embodiment, the polarization isolation splitter device and the off-axis reflection expander can make the receiving field of view ultra-narrow, which not only reduces the interference of background radiation and blind spots, but also avoids signal loss caused by light blocking, thereby improving the near-ground signal quality.

[0027] Embodiment 2

[0028] like Figure 1 As shown, an ultra-narrow field-of-view temperature and humidity Raman laser radar provided in this embodiment includes a receiving spectrometer, which is arranged on the reflected light path of the polarization beam splitter cube 1, and the receiving spectrometer includes a neutral density filter 10 and a first dichroic mirror 71, and the neutral density filter 10 and the first dichroic mirror 71 are arranged in sequence on the reflected light path of the polarization beam splitter cube 1; the left or right side of the first dichroic mirror 71 are provided with a second dichroic mirror 72, a first interference filter 81, a first focusing lens 91 and a nitrogen vibration Raman channel 11 in sequence from near to far, and in this embodiment, the left or right setting depends on the direction of laser emission; the second interference filter 82, the second focusing lens 92 and the water vapor vibration Raman channel 12 are arranged in sequence below the second dichroic mirror 72; the nitrogen vibration Raman channel 11 and the water vapor vibration Raman channel 12 are provided with a first detector and a second detector respectively.

[0029] The vertically polarized light of the echo after passing through the polarization beam splitter cube 1 is reflected to the receiving spectrometer. The light entering the receiving spectrometer first passes through the neutral density filter 10, undergoes a certain attenuation, and then is split by the first dichroic mirror 71. The reflected light is split again by the second dichroic mirror 72, and the transmitted part is filtered by the first interference filter 81. The interference filter can efficiently filter out stray signals and efficiently filter the echo signals of specific wavelengths. Finally, it is focused to the first detector by the first focusing lens 91. This channel is the nitrogen vibration Raman channel 11.

[0030] The reflected light from the second dichroic mirror 72 is filtered by the second interference filter 82 and then focused by the second focusing lens 92 to the second detector, which is the water vapor vibration Raman channel 12. By detecting the vibration Raman scattering of water vapor molecules and nitrogen molecules in the atmosphere, the water vapor mixing ratio and the water vapor density at the height can be obtained, and then the height distribution of relative humidity can be obtained.

[0031] Embodiment 3

[0032] like Figure 1 As shown, in the embodiment, a temperature and humidity Raman laser radar with an ultra-narrow field of view is provided. A third dichroic mirror 73, a third interference filter 83, a third focusing lens 93 and a main channel 13 are arranged in sequence below the first dichroic mirror 71; a fourth dichroic mirror 74, a fourth interference filter 84, a fourth focusing lens 94 and a first rotational Raman channel 14 are arranged in sequence to the left or right of the third dichroic mirror 73 from near to far. In the embodiment, the arrangement to the left or right depends on the direction of laser emission. A fifth interference filter 85, a fifth focusing lens 95 and a second rotational Raman channel 15 are arranged in sequence below the fourth dichroic mirror 74; a third detector, a fourth detector and a fifth detector are arranged in the main channel 13, the first rotational Raman channel 14 and the second rotational Raman channel 15 respectively.

[0033] The transmitted light through the first dichroic mirror 71 is split again by the third dichroic mirror 73, wherein the transmitted light is filtered by the third interference filter 83 and then focused to the third detector by the third focusing lens 93. This channel is the main channel 13. The main channel 13 mainly contains Mie scattering echo signals, which are used to invert the optical parameter profile of atmospheric aerosols.

[0034] The reflected light split by the third dichroic mirror 73 is split again by the fourth dichroic mirror 74, wherein the transmitted part is filtered by the fourth interference filter 84 and then focused to the fourth detector by the fourth focusing lens 94, and this channel is the first rotational Raman channel 14, and the reflected part is filtered by the fifth interference filter 85 and then focused to the fifth detector by the fifth focusing lens 95, and this channel is the second rotational Raman channel 15. The intensities of the low quantum number and high quantum number lines of the pure rotational Raman spectrum will decrease and increase respectively with the increase of temperature. The Raman signals of multiple central wavelengths are selected, and the atmospheric temperature is obtained according to the relationship between their signal intensities.

[0035] The first detector and the second detector in the nitrogen vibration Raman channel 11 and the water vapor vibration Raman channel 12 detect the vibration Raman scattering of water vapor molecules and the vibration Raman scattering of nitrogen molecules in the atmosphere to obtain the water vapor mixing ratio and the water vapor density at the height, and then the height distribution of the relative humidity is obtained; the fourth detector and the fifth detector in the first rotational Raman channel 14 and the second rotational Raman channel 15 detect the low quantum number and high quantum number spectrum lines of the pure rotational Raman spectrum, which will decrease and increase respectively with the increase of temperature, and select Raman signals of multiple central wavelengths, and obtain the atmospheric temperature according to the relationship between their signal intensities. The temperature and humidity Raman lidar uses this principle to invert the temperature and humidity profiles of the atmospheric boundary layer.

[0036] Embodiment 4

[0037] like Figure 1 As shown, an off-axis reflective beam expansion system provided in this embodiment includes any of the above-mentioned embodiments for ultra-narrow field of view temperature and humidity Raman laser radars. The laser is emitted by the laser emitter 5, and then emitted to the atmosphere after passing through the laser emitting device. After being attenuated by the atmosphere, it is scattered by particles in the atmosphere. Atmospheric backscattering includes Mie scattering, Rayleigh scattering, Raman scattering, etc., wherein Raman scattering includes rotational Raman scattering and vibrational Raman scattering. The backscattered (scattered back along the original optical path) laser is extinguished by the atmosphere again on the return journey, and then received by the receiving optical system, after photoelectric conversion by the photoelectric detector, the echo signal is finally collected and calculated and data processed. An off-axis reflective beam expansion system provided in this embodiment is provided with a polarization isolation spectrometer system and an off-axis reflective beam expansion system. The polarization isolation spectrometer system can make the backscattered laser coaxial with the transmitting system when receiving, and the off-axis reflective beam expansion system can make the receiving field of view ultra-narrow, which not only reduces the interference of background radiation and blind spots, but also avoids signal loss caused by light blocking, and improves the quality of near-ground signals.

[0038] The above is a detailed introduction to an ultra-narrow field-of-view temperature and humidity Raman laser radar and an off-axis reflective beam expansion system provided in an embodiment of the present invention. For a person skilled in the art, according to the idea of ​​the embodiment of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An ultra-narrow field of view temperature and humidity Raman laser radar, characterized in that: The invention comprises: a laser emitting device, wherein the laser emitting device comprises a polarization isolation beam splitter and an off-axis reflection beam expander, wherein the polarization isolation beam splitter and the off-axis reflection beam expander are coaxially arranged; The polarization isolation beam splitting device comprises a polarization beam splitting cube (1) and a quarter wave plate (2), and the off-axis reflection beam expanding device comprises a first curved reflector (3) and a second curved reflector (4); The quarter wave plate (2) and the first curved reflector (3) are arranged in sequence on the left or right side of the polarization beam splitter cube (1) from near to far, and the second curved reflector (4) is arranged off-axis from the first curved reflector (3) and the main optical axes of the two are parallel; It also includes a receiving light splitting device, which is arranged on the reflected light path of the light split by the polarization beam splitting cube (1); The receiving spectroscopic device comprises a neutral density filter (10) and a first dichroic mirror (71), wherein the neutral density filter (10) and the first dichroic mirror (71) are sequentially arranged on a reflection light path of the polarization beam splitting cube (1); The laser emitting device also includes a laser emitter (5) and a beam expander (6); The beam expander (6), the polarization beam splitter cube (1), the quarter wave plate (2) and the first curved reflector (3) are arranged in sequence on the left or right side of the laser emitter (5) from near to far, and the second curved reflector (4) is arranged off-axis from the first curved reflector (3) and the main optical axes of the two are parallel.

2. The ultra-narrow field-of-view temperature and humidity Raman laser radar according to claim 1, characterized in that: A second dichroic mirror (72), a first interference filter (81), a first focusing lens (91) and a nitrogen vibration Raman channel (11) are arranged in sequence from near to far to the left or right of the first dichroic mirror (71).

3. The ultra-narrow field-of-view temperature and humidity Raman laser radar according to claim 2, characterized in that: A second interference filter (82), a second focusing lens (92) and a water vapor vibration Raman channel (12) are sequentially arranged below the second dichroic mirror (72).

4. The ultra-narrow field-of-view temperature and humidity Raman laser radar according to claim 3, characterized in that: A third dichroic mirror (73), a third interference filter (83), a third focusing lens (93) and a main channel (13) are sequentially arranged below the first dichroic mirror (71).

5. The ultra-narrow field-of-view temperature and humidity Raman laser radar according to claim 4, characterized in that: A fourth dichroic mirror (74), a fourth interference filter (84), a fourth focusing lens (94) and a first rotational Raman channel (14) are arranged in sequence from near to far to the left or right of the third dichroic mirror (73); A fifth interference filter (85), a fifth focusing lens (95) and a second rotational Raman channel (15) are sequentially arranged below the fourth dichroic mirror (74).

6. The ultra-narrow field-of-view temperature and humidity Raman laser radar according to claim 5, characterized in that: A first detector, a second detector, a third detector, a fourth detector and a fifth detector are respectively provided in the nitrogen vibration Raman channel (11), the water vapor vibration Raman channel (12), the main channel (13), the first rotational Raman channel (14) and the second rotational Raman channel (15).

7. An off-axis reflective beam expansion system, comprising the ultra-narrow field-of-view temperature and humidity Raman laser radar according to any one of claims 1 to 6, characterized in that: It includes a polarization isolation splitter system and an off-axis reflection beam expansion system.

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