A coaxial dual-wavelength lidar for simultaneous measurement of wind field and cloud height

Abstract

The invention discloses a coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height. The radar comprises a cloud measuring module, a wind measuring module and a transmitting and receiving telescope. The wind measuring module comprises a first laser, a first optical fiber coupling mirror, a second optical fiber coupling mirror, a wind measuring polarization isolation module, a polarization-maintaining optical fiber coupler and a balanced detector; the cloud measuring module comprises a second laser, a cloud measuring polarization isolation module, a third optical fiber coupling mirror, a fourth optical fiber coupling mirror and a photoelectric detector; wherein the wind measuring detection laser generated by the first laser forms a first optical signal after being emitted, and the cloud measuring detection laser generated by the second laser forms a second optical signal after being emitted, and the first optical signal and the second optical signal are beam-combined by a dichroic mirror and then transmitted to the transmitting and receiving telescope. Through the above arrangement, wind field information and cloud height information in a low-altitude environment are simultaneously obtained, and the emission optical paths of the wind measuring module and the cloud measuring module overlap, so that the volume and weight of the laser radar can be reduced to the maximum extent.

Description

Technical Field

[0001] The present invention relates to a wind detection laser radar in the field of laser radar technology, and in particular to a coaxial dual-wavelength laser radar that simultaneously measures a wind field and a cloud height. Background Art

[0002] Global climate change and the booming low-altitude economy have put forward an urgent need for refined meteorological observation. As key meteorological parameters, wind field and cloud height are crucial to weather forecasting, flight safety and environmental monitoring. Traditional meteorological detection methods have the limitation of insufficient temporal and spatial resolution, while LiDAR has become an important means of wind field and cloud height detection with its advantages of high precision, high resolution and strong real-time performance.

[0003] Wind field information is crucial in the fields of meteorology, aerospace, wind power generation, etc. Wind detection lidar uses the Doppler effect to measure the frequency shift of the backscattered echo to invert the wind speed. Coherent Doppler lidar (such as 1550nm or 2μm) detects aerosols and achieves high-precision wind measurement over long distances; direct detection Doppler lidar (such as ultraviolet or visible light) infers wind speed by measuring the scattered signals of molecules or aerosols.

[0004] Cloud height information is crucial for weather forecasting, climate research and aviation safety. Cloud height lidar uses the time-of-flight principle to measure the round-trip time of laser pulses and determine the distance to the cloud layer.

[0005] At the same time, the current urgent needs under the development of low-altitude economy, such as drone logistics and urban air traffic, put forward higher requirements for low-altitude environmental perception. Accurate low-altitude wind field and cloud height information is crucial to ensure flight safety, optimize flight paths and improve operational efficiency. Drone flight is greatly affected by wind speed and cloud layer, and requires real-time and accurate wind field and cloud height data support. Summary of the invention

[0006] In order to obtain wind field and cloud height data in a low-altitude environment in real time and accurately, the present invention provides a coaxial dual-wavelength laser radar for measuring wind field and cloud height simultaneously.

[0007] The present invention is implemented by the following technical scheme: a coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height, the laser radar comprising a cloud measuring module, a wind measuring module, a transmitting and receiving telescope, a scanning system and a data processing module, the cloud measuring module and the wind measuring module are respectively fixedly connected to the scanning system through optical fibers, and the data processing module is respectively connected to the cloud measuring module and the wind measuring module through optical fibers; the wind measuring module comprises a first laser, a first optical fiber coupling mirror, a second optical fiber coupling mirror, a wind measuring polarization isolation module, a polarization-maintaining optical fiber coupler and a balanced detector; the wind measuring polarization isolation module is respectively connected to the first optical fiber coupling mirror and the second optical fiber coupling mirror through optical fibers, the first optical fiber coupling mirror is connected to the first laser through optical fibers, and the second optical fiber coupling mirror is connected to the polarization-maintaining optical fiber coupler through optical fibers;

[0008] The cloud measuring module includes a second laser, a cloud measuring polarization isolation module, a third fiber coupling mirror, a fourth fiber coupling mirror and a photodetector; the cloud measuring polarization isolation module is connected to the third fiber coupling mirror and the fourth fiber coupling mirror through optical fibers, the second laser is connected to the cloud measuring polarization isolation module through the third fiber coupling mirror, and the fourth fiber coupling mirror is connected to the photodetector through optical fibers;

[0009] Among them, the wind measurement detection laser generated by the first laser forms a first optical signal after being emitted by the wind measurement polarization isolation module, and the cloud measurement detection laser generated by the second laser forms a second optical signal after being emitted by the cloud measurement polarization isolation module. The first optical signal and the second optical signal are combined by a dichroic mirror and then emitted to the transmitting and receiving telescope.

[0010] As a further improvement of the above solution, the wind measurement polarization isolation module includes a first quarter wave plate and a first polarization beam splitter, and the cloud measurement polarization isolation module includes a second quarter wave plate and a second polarization beam splitter.

[0011] As a further improvement of the above solution, a pinhole diaphragm is arranged at the focus of the transmitting and receiving telescope, and an achromatic lens is also arranged on the laser light path between the pinhole diaphragm and the dichroic mirror.

[0012] As a further improvement of the above solution, the transmitting and receiving telescope is a catadioptric off-axis telescope composed of a parabolic mirror and a reflecting mirror.

[0013] As a further improvement of the above solution, the scanning system includes a wedge-shaped mirror and a driving motor, and the driving motor is rotationally connected to the wedge-shaped mirror to drive the wedge-shaped mirror to rotate.

[0014] As a further improvement of the above solution, the laser radar also includes a narrowband filter, the input end of the narrowband filter is connected to the fourth fiber coupling mirror, and the output end of the narrowband filter is connected to the photodetector.

[0015] As a further improvement of the above solution, the data processing module includes a multi-channel acquisition card, a multi-channel gate control card and a digital processor; the digital processor is electrically connected to the multi-channel acquisition card and the multi-channel gate control card respectively.

[0016] The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height of the present invention has the following beneficial effects:

[0017] The laser radar in the present application includes a cloud measurement module, a wind measurement module, a transmitting and receiving telescope, a scanning system and a data processing module. The wind measurement module includes a first laser, a first fiber coupling mirror, a second fiber coupling mirror, a wind measurement polarization isolation module, a polarization-maintaining fiber coupler and a balanced detector; the cloud measurement module includes a second laser, a cloud measurement polarization isolation module, a third fiber coupling mirror, a fourth fiber coupling mirror and a photoelectric detector; wherein, the wind measurement detection laser generated by the first laser forms a first optical signal after being emitted by the wind measurement polarization isolation module, and the cloud measurement detection laser generated by the second laser forms a second optical signal after being emitted by the cloud measurement polarization isolation module. The first optical signal and the second optical signal are combined by a dichroic mirror and then emitted to the transmitting and receiving telescope, and wind field information and cloud height information in a low-altitude environment are simultaneously obtained through the wind measurement module and the cloud measurement module, and the emission optical paths of the wind measurement module and the cloud measurement module overlap, which can minimize the volume and weight of the laser radar and is more suitable for small platform integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural diagram of a coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] See also Figure 1 In the embodiment of the present application, a specific structure of a coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height is proposed. The laser radar includes a cloud measuring module 7, a wind measuring module 6, a transmitting and receiving telescope 1, a scanning system 2 and a data processing module. The cloud measuring module 7 and the wind measuring module 6 are respectively fixedly connected to the scanning system 2 through optical fibers, and the data processing module is respectively connected to the cloud measuring module 7 and the wind measuring module 6 through optical fibers;

[0021] The wind measurement module 6 includes a first laser 65, a first fiber coupling mirror 64, a second fiber coupling mirror 63, a cloud measurement polarization isolation module, a polarization-maintaining fiber coupler 66 and a balanced detector 67; the wind measurement polarization isolation module is connected to the first fiber coupling mirror 64 and the second fiber coupling mirror 63 through optical fibers, the first fiber coupling mirror 64 is connected to the first laser 65 through optical fibers, and the second fiber coupling mirror 63 is connected to the polarization-maintaining fiber coupler 66 through optical fibers; wherein, the wind measurement polarization isolation module includes a first quarter-wave plate 61 and a first polarization beam splitter 62; the wind measurement polarization isolation module combines the transmitting optical path and the receiving optical path of the wind measurement module by polarization isolation.

[0022] It should be noted that the first laser 65 is a 1550nm fiber laser. The first laser 65 is used to emit vertical linear polarized light, which is collimated by the first fiber coupling mirror 64, incident on the first polarization beam splitter 62 and reflected, and converted into circular polarized light through the first quarter wave plate 61. The circular polarized light is emitted into the atmosphere through the transmitting and receiving telescope 1 to obtain the first echo signal; the first echo signal passes through the first quarter wave plate 61 again, and its phase is rotated by π / 2 relative to the vertical linear polarized light at the time of emission, that is, it is converted into horizontal polarized light, so it is transmitted when passing through the first polarization beam splitter 62, and then enters the second fiber coupling mirror 63 to be focused and coupled to the polarization-maintaining single-mode optical fiber 661, thereby realizing the separation of the emission and reception optical paths.

[0023] The cloud measuring module 7 includes a second laser 74, a cloud measuring polarization isolation module, a third fiber coupling mirror 73, a fourth fiber coupling mirror 76 and a photodetector 77; the cloud measuring polarization isolation module is connected to the third fiber coupling mirror 73 and the fourth fiber coupling mirror 76 through optical fibers, the second laser 74 is connected to the cloud measuring polarization isolation module through the third fiber coupling mirror 73, and the fourth fiber coupling mirror 76 is connected to the photodetector 77 through optical fibers; wherein, the cloud measuring polarization isolation module includes a second quarter wave plate 71 and a second polarization beam splitter 72, and the cloud measuring polarization isolation module combines the transmitting optical path and the receiving optical path of the cloud measuring module by polarization isolation; the laser radar also includes a narrowband filter 75, the input end of the narrowband filter 75 is connected to the fourth fiber coupling mirror 76, and the output end of the narrowband filter 75 is connected to the photodetector 77 to filter out background light.

[0024] It should be noted that the second laser 74 is a 1064nm fiber laser, which emits vertical linear polarized light, which is collimated by the third fiber coupling mirror 73, incident on the polarization beam splitter 72 and reflected, and becomes circularly polarized light after passing through the second quarter wave plate 71. The circularly polarized light is emitted into the atmosphere through the transmitting and receiving telescope 1 to obtain the second echo signal; the transmitting and receiving telescope 1 receives the second echo signal, and passes through the second quarter wave plate 71 again. The phase is rotated by π / 2 relative to the vertical linear polarized light emitted by the second laser 74, that is, it becomes horizontally polarized light. Therefore, the horizontally polarized light is transmitted when passing through the polarization beam splitter 72, and then enters the fourth fiber coupling mirror 76 for focusing and coupling to the multimode optical fiber 771. The multimode optical fiber 771 guides the horizontally polarized light to the photodetector 77 and converts it into an electrical signal through photoelectric conversion.

[0025] In particular, the wind detection laser generated by the first laser 65 is emitted by the wind measurement polarization isolation module to form a first optical signal, and the cloud detection laser generated by the second laser 74 is emitted by the cloud measurement polarization isolation module to form a second optical signal. The first optical signal and the second optical signal are combined by the dichroic mirror 5 and then emitted to the transmitting and receiving telescope 1. For the receiving optical path direction, after the received signal light is collimated by the achromatic lens 4, the dichroic mirror 5 separates the signal lights of two different wavelengths into transmitted light entering the wind measurement module 6 and reflected light entering the cloud measurement module 7; for the transmitting optical path direction, the emission lights of different wavelengths of the wind measurement and cloud measurement modules are combined, and then expanded and collimated by the transmitting and receiving telescope 1.

[0026] The data processing module includes a multi-channel acquisition card 8, a multi-channel gating card 9 and a digital processor 10; the digital processor 10 is electrically connected to the multi-channel acquisition card 8 and the multi-channel gating card 9 respectively; wherein, for the synchronization of signals, the multi-channel gating card 9 provides corresponding synchronization signals for the multi-channel acquisition card 8, the first laser 65 and the second laser 74.

[0027] Specifically, in the wind measurement module, the local oscillator light generated by the first laser 65 is input from the first polarization-maintaining single-mode optical fiber 652 to one of the input ends of the polarization-maintaining optical fiber coupler 66, and is coupled to the first echo signal of the second polarization-maintaining single-mode optical fiber 661 and input to the other input end. The two are split into two output ends after coupling, and are respectively input to the two input ends of the balanced detector 67. The intermediate frequency signal obtained through photoelectric conversion is transmitted to one channel of the multi-channel acquisition card 8 for data acquisition, and is analyzed and processed by the digital processor 10 to invert the wind field information; in the cloud measurement module, the multi-mode optical fiber guides the signal light to the photoelectric detector 77, which is converted into an electrical signal through photoelectric conversion and transmitted to one channel of the multi-channel acquisition card 8 for data acquisition. Finally, it is analyzed and processed by the digital processor 10 to invert the cloud height, cloud amount and other information.

[0028] The laser radar in the embodiment of the present application includes a cloud measurement module, a wind measurement module, a transmitting and receiving telescope, a scanning system and a data processing module. The wind measurement module includes a first laser, a first fiber coupling mirror, a second fiber coupling mirror, a wind measurement polarization isolation module, a polarization-maintaining fiber coupler and a balanced detector; the wind measurement module includes a first laser, a first fiber coupling mirror, a second fiber coupling mirror, a wind measurement polarization isolation module, a polarization-maintaining fiber coupler and a balanced detector; the cloud measurement module includes a second laser, a cloud measurement polarization isolation module, a third fiber coupling mirror, a fourth fiber coupling mirror and a photoelectric detector; wherein, the wind measurement detection laser generated by the first laser forms a first optical signal after being emitted by the wind measurement polarization isolation module, and the cloud measurement detection laser generated by the second laser forms a second optical signal after being emitted by the cloud measurement polarization isolation module. The first optical signal and the second optical signal are combined by a dichroic mirror and then emitted to the transmitting and receiving telescope, and wind field information and cloud height information in a low-altitude environment are simultaneously obtained through the wind measurement module and the cloud measurement module, and the emission optical paths of the wind measurement module and the cloud measurement module overlap, which can minimize the volume and weight of the laser radar and is more suitable for small platform integration.

[0029] In an application embodiment, please continue to refer to Figure 1 , a pinhole diaphragm 3 is provided at the focus of the transmitting and receiving telescope 1, and an achromatic lens 4 is also provided on the laser optical path between the pinhole diaphragm 3 and the dichroic mirror 5. In the embodiment of the present application, the pinhole diaphragm is placed at the focus of the transmitting and receiving telescope to limit the size of the field of view, reduce the stray light entering the subsequent optical system, and improve the signal-to-noise ratio; the achromatic lens is used to reduce the chromatic aberration between the two wavelengths, and is used to collimate the telescope to collect the received signal light after focusing and passing through the diaphragm, or to focus the emitted light of the wind measurement module and the cloud measurement module on the central hole of the pinhole diaphragm, and then the divergent light beam is collimated by the transmitting and receiving telescope 1, and emitted into the atmosphere at an angle through the scanning system.

[0030] In an application embodiment, please continue to refer to Figure 1 The scanning system includes a wedge mirror 21 and a driving motor 22. The driving motor 22 is rotatably connected to the wedge mirror 21 to drive the wedge mirror 21 to rotate. The wedge mirror 21 can refract the original light path according to the designed angle, and then the rotation of the wedge mirror is controlled by the driving motor to realize scanning at different azimuth angles. In this way, not only the wind field information of the scanning area can be obtained, but also the cloud height and cloud amount information in all directions can be obtained after angle conversion.

[0031] In an application embodiment, please continue to refer to Figure 1The transmitting and receiving telescope 1 is a folding and reflecting off-axis telescope composed of a parabolic mirror 12 and a reflecting mirror 11; in the embodiment of the present application, the transmitting and receiving telescope 1 has both the functions of transmitting and receiving, and has the advantages of a large receiving aperture, wide wavelength compatibility, no chromatic aberration, and small spherical aberration; and the folding and reflecting structure compresses the space length and saves volume.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height, characterized in that: The laser radar comprises a cloud measurement module, a wind measurement module, a transmitting and receiving telescope, a scanning system and a data processing module. The cloud measurement module and the wind measurement module are respectively fixedly connected to the scanning system through optical fibers, and the data processing module is respectively connected to the cloud measurement module and the wind measurement module through optical fibers; The wind measurement module comprises a first laser, a first fiber coupling mirror, a second fiber coupling mirror, a wind measurement polarization isolation module, a polarization-maintaining fiber coupler and a balanced detector; the wind measurement polarization isolation module is respectively connected to the first fiber coupling mirror and the second fiber coupling mirror through optical fibers, the first fiber coupling mirror is connected to the first laser through optical fibers, and the second fiber coupling mirror is connected to the polarization-maintaining fiber coupler through optical fibers; The cloud measuring module includes a second laser, a cloud measuring polarization isolation module, a third fiber coupling mirror, a fourth fiber coupling mirror and a photodetector; the cloud measuring polarization isolation module is connected to the third fiber coupling mirror and the fourth fiber coupling mirror through optical fibers, the second laser is connected to the cloud measuring polarization isolation module through the third fiber coupling mirror, and the fourth fiber coupling mirror is connected to the photodetector through optical fibers; The wind measurement polarization isolation module includes a first quarter wave plate and a first polarization beam splitter, and the cloud measurement polarization isolation module includes a second quarter wave plate and a second polarization beam splitter; Among them, the wind measurement detection laser generated by the first laser forms a first optical signal after being emitted by the wind measurement polarization isolation module, and the cloud measurement detection laser generated by the second laser forms a second optical signal after being emitted by the cloud measurement polarization isolation module. The first optical signal and the second optical signal are combined by a dichroic mirror and then emitted to the transmitting and receiving telescope.

2. The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height according to claim 1, characterized in that: A pinhole diaphragm is arranged at the focal point of the transmitting and receiving telescope, and an achromatic lens is also arranged on the laser light path between the pinhole diaphragm and the dichroic mirror.

3. The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height according to claim 1, characterized in that: The transmitting and receiving telescope is a catadioptric off-axis telescope composed of a parabolic mirror and a reflecting mirror.

4. The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height according to claim 1, characterized in that: The scanning system includes a wedge-shaped mirror and a driving motor, wherein the driving motor is rotationally connected to the wedge-shaped mirror to drive the wedge-shaped mirror to rotate.

5. The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height according to claim 1, characterized in that: The laser radar also includes a narrowband filter, an input end of the narrowband filter is connected to the fourth fiber coupling mirror, and an output end of the narrowband filter is connected to the photodetector.

6. The coaxial dual-wavelength laser radar for simultaneously measuring wind field and cloud height according to claim 1, characterized in that: The data processing module includes a multi-channel acquisition card, a multi-channel gate control card and a digital processor; the digital processor is electrically connected to the multi-channel acquisition card and the multi-channel gate control card respectively.

Images