CN113176582B - Flow velocity detection laser radar and flow velocity detection method based on double-frequency pumping - Google Patents
Flow velocity detection laser radar and flow velocity detection method based on double-frequency pumping Download PDFInfo
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- CN113176582B CN113176582B CN202110460135.6A CN202110460135A CN113176582B CN 113176582 B CN113176582 B CN 113176582B CN 202110460135 A CN202110460135 A CN 202110460135A CN 113176582 B CN113176582 B CN 113176582B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/26—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention discloses a flow velocity detection laser radar and a flow velocity detection method based on double-frequency pumping, which divide a detection period into two stages, each stage adopts pulse laser to detect fluid and receives echo signals, echo signals of different stages are mixed with pumping lasers of different frequencies, frequency conversion is carried out, then meter scattering signals in the echo signals are extracted, and a frequency discriminator outputs transmitted light to a detector to detect light intensity and carries out data processing to obtain fluid flow velocity; wherein the two stages of the rice scattering signals should be located at the rising edge and the falling edge of the discriminator respectively. The technical scheme utilizes a direct detection technology to detect the flow velocity, and has the effects of small data processing capacity, simple signal extraction and high detection distance resolution; the visible light with good transmittance can be adopted to detect the water body by utilizing the frequency conversion technology, so that the flow velocity of each vertical section of the water body can be obtained; by using the double-edge technology, only one detector is needed to detect the light intensity of the transmission signal of the frequency discriminator, thereby reducing the cost.
Description
Technical Field
The invention relates to the technical field of laser radar detection, in particular to a flow velocity detection laser radar based on double-frequency pumping and a flow velocity detection method.
Background
Ocean currents are sea water flows caused by density gradients created by earth gravitational fields or by sea water temperature and salinity maldistributions. It is an important component of marine hydrodynamic action, affecting various aspects of biological, physical and chemical processes in the ocean.
Conventional ocean current measurement tools include buoys, field measurements, acoustic doppler flowmeters (Acoustic Doppler Current Profiler, ADCP), radar detection. The buoy flow measurement has low spatial resolution and is only suitable for measuring the surface flow. The site measurement can only obtain fixed-point data, and can not completely detect sea currents in the sea. ADCP can navigate and detect and can measure the three-dimensional velocity of flow of each layer of water in succession, but because of the sound wave characteristic, ADCP current measurement has the blind area. The method can overcome the defects of the method by using the microwave radar to detect the ocean, but the microwave signal is difficult to penetrate through the sea-air interface, and can not provide the ocean current information below the surface flow.
The blue-green band laser is a window of the water body, which can penetrate the sea-air interface, thereby providing possibility for flow velocity profile detection. Laser flow rate detection based on doppler shift includes coherent detection and direct detection. Chinese application CN111257852a discloses a coherent lidar and a method for detecting water flow velocity, but the coherent detection technology provided by the method has the problems of large data processing capacity, difficult extraction of wide spectrum signals, and difficult improvement of detection distance resolution.
Disclosure of Invention
The invention aims to overcome the defects or problems in the background art and provides a flow velocity detection laser radar and a flow velocity detection method based on double-frequency pumping, which have the advantages of small data processing amount, simple signal extraction and high detection distance resolution compared with a coherent detection technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a dual-frequency pump-based flow rate detection lidar, comprising: a pulse laser module for generating pulse laser, wherein the laser frequency of the pulse laser is suitable for detecting fluid to be detected; a transmitting-receiving module which transmits the pulse laser to the fluid to be measured and receives a echo signal; a pump laser generating pump laser light; a frequency shifter which introduces the pump laser and outputs a first pump signal or a second pump signal having a frequency difference; a controller controlling the frequency shifter to selectively output the first pump signal or the second pump signal; a wavelength division multiplexer coupling the echo signal and the first pump signal to output a first mixing signal or coupling the echo signal and the second pump signal to output a second mixing signal; a nonlinear waveguide frequency-converting the first or second mixing signal to output a first or second converted signal, respectively; a filtering module that extracts the rice scattering signal in the first or second converted signal to output a first or second rice scattering signal, respectively; a frequency discriminator for discriminating the first or second meter scattered signal to output a first or second transmission signal in a transmission manner, respectively; the frequency discriminator is configured such that the first meter scattered signal and the second meter scattered signal are located at a rising edge and a falling edge of a transmittance curve thereof, respectively; a detector for detecting the light intensity of the first transmission signal or the light intensity of the second transmission signal and converting into a first electrical signal or a second electrical signal, respectively; an analog-to-digital conversion module that performs analog-to-digital conversion on the first electrical signal or the second electrical signal to output first data or second data, respectively; and a data processing module that obtains a flow rate of the fluid under test based on the first data and the second data.
Preferably, the frequency discriminator is configured such that the first reference frequency and the second reference frequency are both located at a semi-transmission position of the transmittance curve thereof; the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the first pumping signal when the nonlinear waveguide performs frequency up-conversion, and is the difference between the laser frequency of the pulse laser and the frequency of the first pumping signal when the nonlinear waveguide performs frequency down-conversion; the second reference frequency is a sum of a laser frequency of the pulse laser and a frequency of the second pump signal when the nonlinear waveguide performs frequency up-conversion, and is a difference between the laser frequency of the pulse laser and the frequency of the second pump signal when the nonlinear waveguide performs frequency down-conversion.
Preferably, the filtering module comprises a filter and a first fabry-perot interferometer; the filter is connected with the first conversion signal or the second conversion signal, performs filtering processing and outputs the first conversion signal or the second conversion signal to the first Fabry-Perot interferometer; the first fabry-perot interferometer extracts the rice scattering signals therein and outputs first or second rice scattering signals, respectively.
Further, the device also comprises a first circulator and an isolator; the frequency discriminator is a second Fabry-Perot interferometer; one end of the isolator is connected with the first Fabry-Perot interferometer, and the other end of the isolator is connected with the first circulator; the first channel of the first circulator is used for receiving a first meter scattering signal or a second meter scattering signal output by the isolator and sending the first meter scattering signal or the second meter scattering signal to the second Fabry-Perot interferometer; the second channel of the first circulator is for passing a reflected signal of the second fabry-perot interferometer.
Preferably, the transmitting and receiving module adopts a transmitting and receiving separation structure or a transmitting and receiving coaxial structure; the transmitting and receiving module comprises a transmitting telescope and a receiving telescope when adopting a receiving and transmitting separation structure; the transmitting telescope is used for receiving the pulse laser and transmitting the pulse laser to the fluid to be measured; the receiving telescope is used for receiving echo signals and transmitting the echo signals to the wavelength division multiplexer; the transmitting and receiving module comprises a second circulator and a transmitting and receiving telescope when adopting a transmitting and receiving coaxial structure; the receiving and transmitting telescope is used for receiving the pulse laser and transmitting the pulse laser to the fluid to be tested, and is also used for receiving echo signals; the first channel of the second circulator is used for receiving the pulse laser and sending the pulse laser to the receiving and sending telescope, and the second channel of the second circulator is used for receiving the echo signal and sending the echo signal to the wavelength division multiplexer.
Preferably, the nonlinear waveguide is a periodically poled lithium niobate waveguide.
Preferably, the fluid is a body of water; the pulse laser is positioned in a visible light wave band; the frequency conversion is frequency down-conversion; the first meter scattered signal and the second meter scattered signal are located in a near infrared band or an infrared band.
The flow velocity detection method based on the double-frequency pumping is used for detecting the flow velocity of the fluid to be detected in a detection period, wherein the detection period comprises two stages, and each stage adopts pulse laser to detect the fluid and receives a echo signal; mixing echo signals at different stages with pumping signals at different frequencies, performing frequency conversion, and extracting rice scattering signals; the frequency discriminator is used for discriminating the frequency of the rice scattering signals in different stages and outputting corresponding transmission signals, and is configured to be respectively positioned at the rising edge and the falling edge of the transmittance curve of the rice scattering signals in different stages; detecting the light intensity of the transmission signals at different stages and converting the light intensity into corresponding data; and processing the data of the two stages to obtain the flow rate of the fluid to be measured.
Preferably, the frequency discriminator is configured such that the first reference frequency and the second reference frequency are both located at a semi-transmission position of the transmittance curve thereof; the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the pump signal in the first stage when the frequency conversion is frequency up-conversion and is the difference of the laser frequency of the pulse laser and the frequency of the pump signal in the first stage when the frequency conversion is frequency down-conversion; the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the pump signal in the second stage when the frequency conversion is frequency up-conversion and is the difference of the laser frequency of the pulse laser and the frequency of the pump signal in the second stage when the frequency conversion is frequency down-conversion.
Preferably, the fluid is a body of water; the pulse laser is positioned in a visible light wave band; the frequency conversion is frequency down-conversion; the first meter scattered signal and the second meter scattered signal are located in a near infrared band or an infrared band.
As can be seen from the above description of the present invention, the present invention has the following advantages over the prior art:
the invention adopts a direct detection mode to detect the flow velocity of the fluid to be detected, converts the laser Doppler frequency shift into the transmittance change of the echo signal on the frequency discriminator, thereby extracting the flow velocity information of the fluid.
The invention adopts the frequency conversion technology, which is favorable for adopting the pulse laser with the wave band suitable for detecting the fluid on one hand and converting the frequency of the echo signal to the wave band suitable for transmission, frequency discrimination and detection on the other hand, and is favorable for the optical fiber connection between instruments and the adaptation with a detector. For ocean current detection, as the blue-green wave band has good transmittance to the water body, the pulse laser of the visible light wave band, especially the pulse laser of the blue-green wave band, is utilized to detect ocean current, and the pulse laser can effectively penetrate through the ocean gas interface to obtain ocean current flowing conditions on each vertical section.
The most important technical contribution of the invention is that the double-frequency pump laser is creatively introduced to modulate the frequency of the echo signal. The method is characterized in that the direct detection technology in the prior art utilizes the frequency discriminator to process the echo signals, obtains the transmissivity of the echo signals after passing through the frequency discriminator, and compares the transmissivity curve of the frequency discriminator with the transmissivity curve of the frequency discriminator, so as to obtain the frequencies of the echo signals, further determine the frequency difference between the echo signals and the detection signals, and then determine the fluid flow rate by utilizing the Doppler frequency shift principle. The transmittance of the echo signal after passing through the frequency discriminator needs to detect the transmission signal intensity and the reflection signal intensity of the frequency discriminator at the same time, so that two groups of detectors are required to be respectively arranged in the equipment corresponding to the transmission signal and the reflection signal of the frequency discriminator, which results in complex equipment structure and high use cost. In a detection period, the method is divided into two stages, wherein the first pumping signal and the second pumping signal are respectively coupled with the echo signal, frequency converted and filtered, the rice scattering signal is extracted and transmitted through the frequency discriminator to output corresponding first transmission signal and second transmission signal, and the positive and negative values and the magnitude of Doppler frequency shift of the echo signal can be directly obtained through detection, so that the flow velocity condition of each vertical section of the fluid to be detected is obtained correspondingly. Therefore, only one detector for detecting the transmission signal intensity of the frequency discriminator is needed, the integral structure is simplified, and the use cost is reduced.
The invention further sets the two semi-transmission positions of the frequency discriminator at the first reference frequency and the second reference frequency, which is beneficial to eliminating the influence of the power jitter of the pulse laser and is also beneficial to the processing of data.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments below are briefly introduced, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a flow rate detection laser radar based on dual frequency pumping in an embodiment;
FIG. 2 is a signal diagram at point a in FIG. 1;
FIG. 3 is a graphical representation of the signal at point b in FIG. 1;
FIG. 4 is a graph of the transmittance of the first Fabry-Perot interferometer of FIG. 1;
FIG. 5 is a graph showing the transmittance of the second Fabry-Perot interferometer of FIG. 1.
The main reference numerals illustrate:
1. a pulse laser module; 2. a transmitting and receiving module; 21. a transmitting telescope; 22. receiving a telescope; 31. a pump laser; 32. a frequency shifter; 33. a controller; 4. a wavelength division multiplexer; 5. a nonlinear waveguide; 6. a filtering module; 61. a filter; 62. a first fabry-perot interferometer; 7. an isolator; 8. a first circulator; 9. a frequency discriminator; 10. a detector; 11. an analog-to-digital conversion module; 12. and a data processing module.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are preferred embodiments of the invention and should not be taken as excluding other embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without creative efforts, are within the protection scope of the present invention.
In the claims, specification and drawings hereof, unless explicitly defined otherwise, the terms "first," "second," or "third," etc. are used for distinguishing between different objects and not for describing a particular sequential order.
In the claims, specification and drawings of the present invention, the terms "comprising," having, "and variations thereof as used herein, are intended to be" including but not limited to.
Referring to fig. 1, fig. 1 shows a structure of an embodiment of a flow rate detection laser radar based on dual-frequency pumping according to the present invention.
As shown in fig. 1, the laser radar in this embodiment includes a pulse laser module 1, a transmitting and receiving module 2, a pump laser 31, a frequency shifter 32, a controller 33, a wavelength division multiplexer 4, a nonlinear waveguide 5, a filtering module 6, an isolator 7, a first circulator 8, a frequency discriminator 9, a detector 10, an analog-to-digital conversion module 11, and a data processing module 12.
The pulse laser module 1 is used for pulse laser, the laser frequency of the pulse laser is suitable for detecting fluid to be detected, and for the application of detecting ocean currents, the visible light wave band can be preferred, and the blue-green wave band can be further preferred. The pulse laser module may preferably include a pulse laser and an amplifier that amplifies the pulse laser light generated by the pulse laser to obtain a pulse laser light capable of achieving the emission requirement.
The transmitting and receiving module 2 is used for transmitting pulse laser as a detection signal to the water body and receiving echo signals. The transmitting and receiving module 2 in this embodiment is a transceiver separation structure, which includes a transmitting telescope 21 and a receiving telescope 22. The transmitting telescope 21 is juxtaposed with the receiving telescope 22 with the axes parallel.
The input end of the transmitting telescope 21 is connected with the output end of the pulse laser module 1, and is used for receiving the pulse laser generated by the pulse laser module 1 and transmitting the pulse laser to the water surface as a detection signal. When measuring ocean current flow velocity in the vertical direction, the angle of incidence with respect to the sea surface may be selected to be zero or near zero; when measuring the radial flow rates of different water layers, the angle of incidence to the sea surface may be selected in the range of greater than zero degrees and less than ninety degrees.
The output end of the receiving telescope 22 is connected to the wavelength division multiplexer 4, and is used for receiving the echo signal of the water body and sending the echo signal to the wavelength division multiplexer 4.
In other embodiments, the transceiver module 2 may also adopt a transceiver coaxial structure. When the receiving-transmitting coaxial structure is adopted, the transmitting-receiving module 2 comprises a second circulator and a receiving-transmitting telescope; the receiving and transmitting telescope is used for receiving the pulse laser and transmitting the pulse laser to the fluid to be tested, and is also used for receiving echo signals; the first channel of the second circulator is used for receiving the pulsed laser and sending to the transceiver telescope, and the second channel is used for receiving the echo signal and sending to the wavelength division multiplexer 4.
The pump laser 31 is used to generate pump laser light, which is preferably laser light of a narrow linewidth.
The frequency shifter 32 in this embodiment adopts an acousto-optic frequency shifter, the input end of which is connected with the output end of the pump laser 31 to access the pump laser generated by the pump laser 31, and the output end of which is connected with the wavelength division multiplexer 4. The frequency shifter 32 in this embodiment can selectively output the first pump signal or the second pump signal. The frequency of the first pump signal or the second pump signal may be identical to or different from the frequency of the pump laser. But the frequency of the second pump signal is different from the frequency of the first pump laser.
The controller 33 is for controlling the frequency shifter 32 to selectively output the first pump signal and the second pump signal.
The wavelength division multiplexer 4 has two inputs and one output, a first input of which is connected to the output of the frequency shifter 32 and a second input of which is connected to the output of the receiving telescope 22 and an output of which is connected to the nonlinear waveguide 5. When the frequency shifter 32 generates the first pump signal, the wavelength division multiplexer 4 couples the first pump signal and the echo signal into a beam to form a first mixing signal and transmit the first mixing signal to the nonlinear waveguide 5; when the frequency shifter 32 generates the second pump signal, the wavelength division multiplexer 4 couples the second pump signal with the echo signal in a beam to form a second mixed signal, which is fed to the nonlinear waveguide 5.
The nonlinear waveguide 5 has an input terminal connected to the output terminal of the wavelength division multiplexer 4 for receiving the first mixing signal or the second mixing signal, and an output terminal connected to the filtering module 6 for outputting the first conversion signal or the second conversion signal, respectively. The frequency conversion of the nonlinear waveguide 5 may be either frequency down conversion or frequency down conversion. In this embodiment, the nonlinear waveguide 5 performs frequency down-conversion, which may specifically be a periodically polarized lithium niobate waveguide, and in this embodiment, the first mixing signal and the second mixing signal output by the nonlinear waveguide 5 are both located in a near infrared band or an infrared band suitable for transmission, frequency discrimination and detection.
The filtering module 6 comprises a filter 61 and a first fabry-perot interferometer 62. Wherein the input end of the filter 61 is connected to the output end of the nonlinear waveguide 5, and the output end thereof is connected to the input end of the first Fabry-Perot interferometer 62 for filtering clutter in the first or second converted signals, and the signal output by the filter 61 mainly comprises the brillouin scattering signal A in the echo signal at the point a in FIG. 1 as shown in FIG. 2 1 Brillouin scattering signal a 2 And meter scattered signal B.
The input end of the first fabry-perot interferometer 62 is connected to the output end of the filter 61, and the output end thereof is connected to the input end of the isolator 7, which is used to filter out the brillouin scattering signal in the signal output by the filter 61, and extract the rice scattering signal therein. Referring to fig. 3 and 4, fig. 4 is a transmittance curve of the first fabry-perot interferometer 62, fig. 3 is a schematic diagram of a signal at a b point in fig. 1, and when the signal output from the filter 61 passes through the first fabry-perot interferometer 62, the brillouin signal in the signal is filtered, and only the rice scattering signal required for measuring the frequency shift remains. In general, the first fabry-perot interferometer 62 should be configured to have a relatively wide bandwidth and to have the frequencies of the rice scattering signals in the first and second converted signals both near the location of the highest transmittance of the first fabry-perot interferometer 62 so that the transmittance of the rice scattering signals in the first and second converted signals is as uniform as possible or with only negligible error across the first fabry-perot interferometer 62.
The first meter scattered signal or the second meter scattered signal is output to the first circulator 8 after passing through the isolator 7, the first circulator 8 is provided with a first channel and a second channel, the input end of the first channel is connected with the output end of the isolator 7 and used for receiving the first meter scattered signal or the second meter scattered signal, the output end of the first channel is connected with the input end of the frequency discriminator 9, and the input end of the second channel is connected with the reflected signal output end of the frequency discriminator 9 and used for allowing the reflected signal of the frequency discriminator 9 to pass through.
In this embodiment, the frequency discriminator 9 is a second fabry-perot interferometer, and the frequency discriminator 9 is connected to the first meter scattering signal or the second meter scattering signal output by the first circulator 8, and transmits and outputs the first transmission signal or the second transmission signal to the detector 10. The discriminator 9 should be configured such that the first and second meter scattered signals lie on the rising and falling edges of its transmittance curve, respectively, to implement a double-edge technique. Referring to fig. 5, in the present embodiment, it is configured as a first reference frequency h 1 And a second reference frequency h 2 All are positioned at the semi-transmission position of the transmittance curve; wherein the first reference frequency h 1 A difference between the laser frequency of the pulse laser and the frequency of the first pump signal when the nonlinear waveguide is frequency down-converted, and a first reference frequency h when the nonlinear waveguide is frequency up-converted 1 The sum of the laser frequency of the pulse laser and the frequency of the first pumping signal; second reference frequency h 2 A difference between the laser frequency of the pulse laser and the frequency of the second pump signal when the nonlinear waveguide performs frequency down-conversion, and a second reference frequency h when the nonlinear waveguide performs frequency up-conversion 2 The sum of the laser frequency of the pulsed laser and the frequency of the second pump signal. Since the amount of frequency shift of the echo signal with respect to the laser frequency of the pulse laser is small in magnitude compared with the frequency range occupied by the rising edge or the falling edge of the transmittance curve of the discriminator 9, the above configuration of this example can ensure that the positions of the first meter scattered signal and the second meter scattered signal are at the rising edge and the falling edge of the transmittance curve of the discriminator 9. The arrangement is beneficial to eliminating the influence of the power jitter of the pulse laser and is also beneficial to the processing of data.
The isolator 7 may here act to isolate the first fabry-perot interferometer 62 from the frequency discriminator 9, preventing the two fabry-perot interferometers from being connected in series to form a resonant cavity.
The detector 10 is configured to detect light intensity of the first transmission signal or the second transmission signal output by the frequency discriminator 9, and may specifically be a single photon detector, and after detecting light intensity of the first transmission signal or the second transmission signal, may output a first electrical signal or a second electrical signal, respectively.
The analog-to-digital conversion module 11 is configured to output the first data or the second data after analog-to-digital conversion of the first electrical signal or the second electrical signal.
The data processing module 12 combines the known frequency parameters of the pulse laser, the first pump signal and the second pump signal according to the first data and the second data to obtain the Doppler frequency shift of the echo signal of each vertical section relative to the pulse laser, and obtains the flow velocity information of each vertical section according to the Doppler frequency shift.
The flow velocity detection laser radar based on the double-frequency pumping only needs to be provided with one detector 10 for detecting the transmission signal intensity of the frequency discriminator 9, and then the flow velocity information of each vertical section of the water flow can be obtained through data processing, so that the flow velocity detection laser radar based on the double-frequency pumping has the advantages of being simple in structure and low in use cost.
The method for detecting the flow rate by adopting the flow rate detection laser radar in the embodiment comprises the following steps:
dividing a detection period into a first stage and a second stage, wherein each stage adopts pulse laser to detect fluid and receives a echo signal; mixing echo signals at different stages with pumping signals at different frequencies, performing frequency conversion, and extracting rice scattering signals; the frequency discriminator 9 discriminates the frequency of the meter scattering signals in different stages and outputs corresponding transmission signals; detecting the light intensity of the transmission signals at different stages and converting the light intensity into corresponding data; and processing the data of the two stages to obtain the flow rate of the fluid to be measured.
Specifically, the procedure in the first stage is as follows:
the pulse laser module 1 generates pulse laser, and transmits the pulse laser to a water body as a detection signal through the transmitting and receiving module 2 and receives a corresponding echo signal;
the pump laser 31 generates pump laser light;
controlling the acousto-optic frequency shifter 33 to generate a first pumping signal by the controller 32;
the first pumping signal and the echo signal are connected into a wavelength division multiplexer 4 and coupled into a first mixing signal;
outputting the first pump signal to the nonlinear waveguide 5 and generating a first converted signal;
extracting the rice scattering signal in the first conversion signal through a filtering module 6 and outputting a first rice scattering signal;
enabling the first meter scattering signal to sequentially pass through the isolator 7 and the first circulator 8 to reach the input end of the frequency discriminator 9, and enabling the frequency discriminator 9 to transmit and output a first transmission signal;
the detector 10 detects the light intensity of the first transmission signal and forms a first electrical signal;
the analog-to-digital conversion module 11 converts the first electric signal into first data;
the data processing module 12 stores the first data;
the second stage is as follows:
the pulse laser module 1 generates pulse laser, and transmits the pulse laser to a water body as a detection signal through the transmitting and receiving module 2 and receives a corresponding echo signal;
the pump laser 31 generates pump laser light;
controlling the acousto-optic frequency shifter 33 to generate a second pumping signal by the controller 32;
the second pumping signal and the echo signal are connected into a wavelength division multiplexer 4 and coupled into a second mixing signal;
outputting the second pump signal to the nonlinear waveguide 5 and generating a second converted signal;
extracting the rice scattering signal in the second conversion signal through a filtering module 6 and outputting a second rice scattering signal;
enabling the second meter scattered signal to sequentially pass through the isolator 7 and the first circulator 8 to reach the input end of the frequency discriminator 9, and enabling the frequency discriminator 9 to transmit and output a second transmission signal;
the detector 10 detects the light intensity of the second transmission signal and forms a second electrical signal;
the analog-to-digital conversion module 11 converts the second electric signal into second data;
according to the first data and the second data to be stored, the data processing module 12 is configured to obtain the frequency shift of the m-scattering signal of each vertical section according to the first data and the second data, because the first m-scattering signal and the second m-scattering signal are both located at the rising edge and the falling edge of the transmittance curve of the frequency discriminator 9, the doppler shift in the m-scattering signal causes the transmittance change, and the frequency shift directions and the amounts of the two stages are equal, so that the frequency shift of the m-scattering signal of each vertical section can be obtained by combining the transmittance curve of the frequency discriminator according to the first data and the second data, and the frequency of the m-scattering signal is the frequency shift of the echo signal because the m-scattering is elastic scattering. The flow velocity information of each vertical section in the pulse laser emission direction can be obtained from the frequency shift of the echo signal of each vertical section.
The foregoing description of the embodiments and description is presented to illustrate the scope of the invention, but is not to be construed as limiting the scope of the invention. Modifications, equivalents, and other improvements to the embodiments of the invention or portions of the features disclosed herein, as may occur to persons skilled in the art upon use of the invention or the teachings of the embodiments, are intended to be included within the scope of the invention, as may be desired by persons skilled in the art from a logical analysis, reasoning, or limited testing, in combination with the common general knowledge and/or knowledge of the prior art.
Claims (10)
1. The utility model provides a velocity of flow detection laser radar based on dual-frenquency pumping which characterized in that includes:
a pulse laser module (1) which generates a pulse laser, the laser frequency of the pulse laser being adapted to detect a fluid to be measured;
a transmitting-receiving module (2) which transmits the pulse laser light to the fluid to be measured and receives a return wave signal;
a pump laser (31) that generates pump laser light;
a frequency shifter (32) that introduces the pump laser light and outputs a first pump signal or a second pump signal having a frequency difference;
a controller (33) that controls the frequency shifter (32) to selectively output the first pump signal or the second pump signal;
a wavelength division multiplexer (4) that couples the echo signal and the first pump signal to output a first mixed signal or couples the echo signal and the second pump signal to output a second mixed signal;
a nonlinear waveguide (5) that frequency-converts the first or second mixed signal to output a first or second converted signal, respectively;
a filtering module (6) that extracts the rice-scatter signal in the first or second converted signal to output a first or second rice-scatter signal, respectively;
a frequency discriminator (9) for discriminating the first or second meter scattered signal to output a first or second transmission signal in transmission, respectively; the frequency discriminator (9) is configured such that the first meter scattered signal and the second meter scattered signal are located at a rising edge and a falling edge of the transmittance curve thereof, respectively;
a detector (10) for detecting the light intensity of the first transmission signal or the light intensity of the second transmission signal and converting into a first electrical signal or a second electrical signal, respectively;
an analog-to-digital conversion module (11) that performs analog-to-digital conversion on the first electrical signal or the second electrical signal to output first data or second data, respectively; and
a data processing module (12) that obtains a flow rate of the fluid under test based on the first data and the second data.
2. A dual frequency pump based flow rate detection lidar as claimed in claim 1, wherein the discriminator (9) is arranged such that both the first reference frequency and the second reference frequency are located in a semi-transmission position of its transmittance curve;
the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the first pumping signal when the nonlinear waveguide (5) performs frequency up-conversion and is the difference of the laser frequency of the pulse laser and the frequency of the first pumping signal when the nonlinear waveguide (5) performs frequency down-conversion;
the second reference frequency is a sum of a laser frequency of the pulse laser and a frequency of the second pump signal when the nonlinear waveguide (5) performs frequency up-conversion, and is a difference between the laser frequency of the pulse laser and the frequency of the second pump signal when the nonlinear waveguide (5) performs frequency down-conversion.
3. A dual frequency pump based flow rate detection lidar as claimed in claim 1, characterized in that the filtering module (6) comprises a filter (61) and a first fabry-perot interferometer (62); the filter (61) is connected with the first conversion signal or the second conversion signal, performs filtering processing and outputs the first conversion signal or the second conversion signal to the first Fabry-Perot interferometer (62); the first fabry-perot interferometer (62) extracts the rice scattering signals therefrom and outputs first or second rice scattering signals, respectively.
4. A dual frequency pump based flow rate detection lidar as claimed in claim 3, further comprising a first circulator (8) and an isolator (7); the frequency discriminator (9) is a second Fabry-Perot interferometer; one end of the isolator (7) is connected with the first Fabry-Perot interferometer (62), and the other end is connected with the first circulator (8); the first channel of the first circulator (8) is used for receiving a first meter scattering signal or a second meter scattering signal output by the isolator (7) and sending the first meter scattering signal or the second meter scattering signal to the second Fabry-Perot interferometer; the second channel of the first circulator (8) is for passing a reflected signal of the second fabry-perot interferometer.
5. The dual-frequency pump based flow rate detection lidar of claim 1, wherein: the transmitting and receiving module (2) adopts a receiving and transmitting separation structure or a receiving and transmitting coaxial structure;
the transmitting and receiving module (2) comprises a transmitting telescope (21) and a receiving telescope (22) when adopting a receiving and transmitting separation structure; the transmitting telescope (21) is used for receiving the pulse laser and transmitting the pulse laser to the fluid to be measured; the receiving telescope (22) is used for receiving echo signals and transmitting the echo signals to the wavelength division multiplexer (4);
the transmitting and receiving module (2) comprises a second circulator and a transmitting and receiving telescope when adopting a transmitting and receiving coaxial structure; the receiving and transmitting telescope is used for receiving the pulse laser and transmitting the pulse laser to the fluid to be tested, and is also used for receiving echo signals; the first channel of the second circulator is used for receiving the pulse laser and sending the pulse laser to the receiving and sending telescope, and the second channel of the second circulator is used for receiving the echo signal and sending the echo signal to the wavelength division multiplexer (4).
6. A dual frequency pump based flow rate detection lidar according to claim 1, characterized in that the nonlinear waveguide (5) is a periodically poled lithium niobate waveguide.
7. The dual-frequency pump based flow rate detection lidar of claim 1, wherein the fluid is a body of water; the pulse laser is positioned in a visible light wave band; the frequency conversion is frequency down-conversion; the first meter scattered signal and the second meter scattered signal are located in a near infrared band or an infrared band.
8. The flow velocity detection method based on the double-frequency pumping is used for detecting the flow velocity of fluid to be detected in a detection period and is characterized in that:
the detection period comprises two stages, wherein each stage adopts pulse laser to detect fluid and receives an echo signal;
mixing echo signals at different stages with pumping signals at different frequencies, performing frequency conversion, and extracting rice scattering signals;
the frequency discriminator (9) is used for discriminating the frequency of the rice scattering signals in different stages and outputting corresponding transmission signals, and the frequency discriminator (9) is configured to enable the rice scattering signals in different stages to be respectively located at the rising edge and the falling edge of the transmittance curve;
detecting the light intensity of the transmission signals at different stages and converting the light intensity into corresponding data;
and processing the data of the two stages to obtain the flow rate of the fluid to be measured.
9. The flow rate detection method based on dual frequency pumping as claimed in claim 8, wherein:
the frequency discriminator (9) is configured such that the first reference frequency and the second reference frequency are both located at a semi-transmission position of the transmittance curve thereof;
the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the pump signal in the first stage when the frequency conversion is frequency up-conversion and is the difference of the laser frequency of the pulse laser and the frequency of the pump signal in the first stage when the frequency conversion is frequency down-conversion;
the first reference frequency is the sum of the laser frequency of the pulse laser and the frequency of the pump signal in the second stage when the frequency conversion is frequency up-conversion and is the difference of the laser frequency of the pulse laser and the frequency of the pump signal in the second stage when the frequency conversion is frequency down-conversion.
10. The dual frequency pump based flow rate detection method of claim 8, wherein the fluid is a body of water; the pulse laser is positioned in a visible light wave band; the frequency conversion is frequency down-conversion; the meter scattered signal is in the near infrared band or the infrared band.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3045876A1 (en) * | 2013-09-09 | 2016-07-20 | Pioneer Corporation | Flow rate detection apparatus and flow rate detection method |
| CN110187362A (en) * | 2019-05-24 | 2019-08-30 | 中国科学技术大学 | A kind of double frequency anemometry laser radar of ultraviolet infrared synchronous work |
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| WO1999035519A2 (en) * | 1998-01-12 | 1999-07-15 | The Board Of Regents, The University Of Texas System | Modulated filtered rayleigh scattering |
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