An Atmospheric Optical Effect Simulation Device and Method for Laser Velocimetry Radar

Abstract

This invention belongs to the field of atmospheric detection and relates to an atmospheric optical effect simulation device and method for laser velocity radar. The device includes: an optical coupling system (1), a control system (3), a modulation system (2), and a detection system (4). The optical coupling system (1) is aligned with the transceiver lens of the laser velocity radar (5), and the optical coupling system (1) couples the laser emitted by the radar into the subsequent optical path. The optical coupling system (1) is optically connected to the modulation system (2), and the laser passes through the modulation system (2) to simulate the changes of the laser during atmospheric transmission. The control system (3) is connected to the modulation system (2) via an RS232 bus to set and modify the modulation parameters of the modulation system (2). The detection system (4) is optically connected to the modulation system (2), and the control system (3) communicates with the laser velocity radar (5) via RS232.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric detection and relates to an atmospheric optical effect simulation device and method for laser velocimetry radar. Background Technology

[0002] Doppler laser speed measuring radar primarily retrieves wind speed by identifying the Doppler frequency shift of the echo signal. It can be used in various fields such as atmospheric meteorological observation, wind speed measurement at drop zones, wind speed monitoring of wind power generation devices, and wind speed measurement at airports or decks. The testing methods for laser speed measuring radar typically include: wind tunnel testing, runway testing, airborne flight testing, and natural wind testing. A brief introduction to these four testing methods follows.

[0003] Wind tunnel testing requires high-quality airflow within the wind tunnel and is only suitable for testing continuous-mode, short-focal-length laser velocimeters. The high cost of building and maintaining wind tunnel laboratories hinders widespread adoption. Vehicle testing typically involves synchronous detection with laser velocimeters and other speed measuring devices, verifying the accuracy of the laser velocimeter by comparing the results from different devices. However, this method lacks standardized testing procedures and is complex and inconvenient. Airborne flight testing is primarily for aviation-grade laser velocimeters and can effectively test their performance in real-world environments. However, it is costly, and most laser velocimeters lack the capability for airborne flight testing. Natural wind testing is the primary testing method for most ground-based laser velocimeters, relying entirely on natural wind and its flow field environment. Similar to vehicle testing, it also lacks standardized testing procedures.

[0004] In summary, the four existing testing methods have the following drawbacks:

[0005] 1. It has a single applicable target and cannot be compatible with both continuous and pulsed lidar at the same time;

[0006] 2. The equipment setup and maintenance costs are high, making it difficult to promote and test it on a large scale;

[0007] 3. The test environment has high requirements and the test process is complex.

[0008] To address the above shortcomings, researchers in the field have proposed new testing methods: one is the hard target test method, which uses certain optomechanical devices in the laboratory to measure the rotational speed of the laser velocimeter radar at a certain speed, reducing costs. However, the accuracy of the rotational speed of the laser velocimeter radar is not very high, making it impossible to perform precise testing. The test system has a simple structure, but the simulation of the atmospheric flow field is not comprehensive enough. Another method is to fill the hollow optical fiber with gas to simulate the atmospheric environment. The disadvantage of this method is that it has low controllability.

[0009] As can be seen from the above analysis, the existing testing methods for laser velocity radar all have limitations, and there is a need to design a testing device that is compatible with both continuous and pulse types, has a simple structure, and is easy to operate. Summary of the Invention

[0010] Purpose of the invention: To provide an atmospheric optical effect simulation device and method for laser velocity measurement radar, solving the problems of difficulty in testing continuous and pulsed laser velocity measurement radar and the lack of standard testing equipment, and conveniently applicable to the testing of various laser velocity measurement radars.

[0011] Technical solution:

[0012] An atmospheric optical effect simulation device for laser velocity measuring radar includes: an optical coupling system 1, a control system 3, a modulation system 2, and a detection system 4. The optical coupling system 1 is aligned with the transceiver lens of the laser velocity measuring radar 5, and couples the laser emitted by the radar into the subsequent optical path. The optical coupling system 1 is optically connected to the modulation system 2, and the laser passes through the modulation system 2 to simulate the changes in the laser during atmospheric transmission. The control system 3 is connected to the modulation system 2 via an RS232 bus to set and modify the modulation parameters of the modulation system 2. The detection system 4 is optically connected to the modulation system 2 to detect the actual changes in various parameters after the laser is modulated. The control system 3 communicates with the laser velocity measuring radar 5 via RS232, simulating the information of the mounting platform and sending this information to the radar.

[0013] Furthermore, the optical coupling system 1 includes: an optical wedge 11, a matching lens 12, a mode field adapter 13, and an optical fiber circulator 14. The optical wedge 11 is aligned with the transceiver lens of the laser velocity measuring radar 5, the optical wedge 11 is aligned with the matching lens 12, the matching lens 12 is aligned with the mode field adapter 13, and the mode field adapter 13 is connected to the 2-port optical fiber of the optical fiber circulator 14. The optical wedge 11 collimates the laser, and the collimated laser is received by the matching lens 12. The mode field adapter 13 adapts optical fibers of different core diameters to the matching lens 12, and focuses the laser into the 2-port of the optical fiber circulator 14, which then enters the subsequent optical path.

[0014] Further, the modulation system 2 includes: an adjustable attenuation module 21, an adjustable delay module 22, an adjustable frequency shift module 23, and a polarization modulation module 24. The second port of the fiber optic circulator 14 is connected to the optical input interface of the adjustable attenuation module 21 via optical fiber; the first optical output interface of the adjustable attenuation module 21 is connected to the first optical input interface of the detection system 4 via optical fiber; the second optical output interface of the adjustable attenuation module 21 is connected to the optical input interface of the adjustable delay module 22; the first optical output interface of the adjustable delay module 22 is connected to the second optical input interface of the detection system 4 via an RF line; the second optical output interface of the adjustable delay module 22 is connected to the optical input interface of the adjustable frequency shift module 23; and the first optical output interface of the adjustable frequency shift module 23 is connected to the third optical input interface of the detection system 4 via optical fiber. The second optical output interface of the frequency shift module 23 is connected to the optical input interface of the polarization modulation module 24; the first optical output interface of the polarization modulation module 24 is optically connected to the fourth optical input interface of the detection system 4; the second optical output interface of the polarization modulation module 24 is optically connected to the 3-port optical fiber of the fiber optic circulator 14; the communication ports of the adjustable attenuation module 21, the adjustable delay module 22, and the polarization modulation module 24 are respectively connected to the control system 3 via an RS232 bus. The adjustable attenuation module 21 is used to simulate the energy attenuation of laser during atmospheric transmission; the adjustable delay module 22 is used to simulate the change of optical path length of laser during atmospheric transmission; the adjustable frequency shift module 23 is used to simulate the change of Doppler frequency shift of laser during atmospheric transmission; and the polarization modulation module 24 is used to simulate the change of polarization state of laser during atmospheric transmission.

[0015] Furthermore, the optical wedge 11 includes optical wedges with angles of 5°, 10°, 20° and 30°.

[0016] Furthermore, the detection system 4 includes an optical power meter 31, an oscilloscope 32, a spectrum analyzer 33, and a polarization measuring instrument 34. The first optical output interface of the adjustable attenuation module 21 is connected to the optical power meter 31 via an optical fiber; the first optical output interface of the adjustable delay module 22 is connected to the oscilloscope 32 via an RF cable; the first optical output interface of the adjustable frequency shift module 23 is connected to the spectrum analyzer 33 via an optical fiber; and the first optical output interface of the polarization modulation module 24 is connected to the polarization measuring instrument 34 via an optical fiber.

[0017] Furthermore, the adjustable attenuation module 21 includes an adjustable attenuator 211 and a first beam splitter 212; the adjustable delay module 22 includes an adjustable delay fiber 221 and a second beam splitter 222; the adjustable frequency shift module 23 includes a frequency shifter 231 and a third beam splitter 232; and the polarization modulation module 24 includes a three-paddle polarization modulator 241 and a fourth beam splitter 242.

[0018] Furthermore, the first beam splitter 212, the second beam splitter 222, the third beam splitter 232 and the fourth beam splitter 242 are all 95:5 beam splitters. The high-power 95% output end of the beam splitter is connected to the subsequent optical path, and the low-power 5% output end is connected to the detection system 4.

[0019] A method for simulating atmospheric optical effects for laser velocity measurement radar, the method being executed using the aforementioned atmospheric optical effects simulation device for laser velocity measurement radar, the method comprising:

[0020] Set a preset wind speed value;

[0021] After the device is powered on, the parameters of modulation system 2 are set;

[0022] Modulation system 2 will modulate the laser according to the set values. Modulation system 2 communicates with the control system via RS232.

[0023] The modulated laser returns to the optical coupling system 1 and is received by the optical lens of the laser speed radar 5 as a simulated atmospheric echo signal. The laser wind radar 5 then retrieves the wind speed. The retrieved wind speed is compared with the preset wind speed to complete the test of the laser speed radar.

[0024] Beneficial effects:

[0025] The atmospheric optical effect simulation device and method for laser velocity radar of the present invention fills the gap in laser velocity radar testing equipment. A single device can be used to test both continuous and pulsed laser velocity radars. The testing process is simple and easy to operate. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an atmospheric optical effect simulation device for a laser velocity measuring radar, where 1-optical coupling system, 2-modulation system, 3-control system, 4-detection system, 5-laser velocity measuring radar, 11-optical wedge, 12-matching lens, 13-mode field adapter, 14-fiber circulator, 21-adjustable attenuation module, 22-adjustable delay module, 23-adjustable frequency shift module, 24-polarization modulation module, 31-optical power meter, 32-oscilloscope, 33-spectrum analyzer, and 34-polarization measuring instrument.

[0027] Figure 2 Matching lens structure diagram, where 121-beam expander and 122-collimator;

[0028] Figure 3Modulation system structure diagram, wherein 211-adjustable attenuator, 212-95:5 beam splitter, 221-adjustable delay fiber, 222-95:5 beam splitter, 231-frequency shifter, 232-95:5 beam splitter, 241-three-paddle polarization modulator, 242-95:5 beam splitter;

[0029] Figure 4 The control system interconnection diagram shows that 3 is the control system, 5 is the laser velocimetry radar, 211 is the adjustable attenuator, 221 is the adjustable delay fiber, and 241 is the three-propeller polarization modulator. Detailed Implementation

[0030] This invention provides an atmospheric optical effect simulation device for laser velocimetry radar, which simulates the changes in parameters such as energy, polarization state, and frequency of laser during atmospheric transmission, and is used for testing Doppler laser velocimetry radar.

[0031] like Figure 1-4 The atmospheric optical effects simulation device consists of four parts: an optical coupling system 1, a control system 3, a modulation system 2, and a detection system 4. The atmospheric optical effects simulation device connects to a laser velocimetry radar 5 via the optical coupling system 1, coupling the laser emitted by the radar into the device's subsequent optical path. The laser undergoes modulation through the modulation system 2, simulating its changes during atmospheric transmission. The control system 3 sets and modulates the modulation parameters, and the detection system 4 detects the actual changes in various parameters after modulation.

[0032] Optical coupling system 1 is connected to laser velocity radar. The laser emitted by the radar enters the subsequent optical path through optical coupling system 1. Control system 3 sets the parameters of modulation system 2. After the laser passes through modulation system 2, the corresponding parameters change. The modulated laser, as an atmospheric echo signal, is input to laser velocity radar 5 again through optical coupling system 1. Detection system 4 is used to detect the modulated laser signal.

[0033] The optical coupling system 1 consists of four parts: optical wedge 11, matching lens 12, mode field adapter 13, and fiber optic circulator 14. It is equipped with optical wedges 11 at angles of 5°, 10°, 20°, and 30°. The appropriate angle of the optical wedge 11 is selected based on the deflection angle of the laser emitted from the laser velocity measuring radar 5. The optical wedge 11 collimates the laser, and the collimated laser is received by the matching lens 12. The mode field adapter 13 allows optical fibers of different core diameters to be matched with the matching lens 12, focusing the laser into port 2 of the fiber optic circulator 14, where it enters the subsequent optical path.

[0034] Figure 2 To match the lens structure block diagram, the laser beam is collimated by the optical wedge 11 and then incident on the beam expander telescope. The expanded laser beam is then focused onto the mode field adapter 13 by the collimator.

[0035] The control system 3 consists of two parts: an industrial computer and a display. The control system 3 enables human-computer interaction through host computer software, communicates with the modulation system 2 via RS232, and can set and modify the parameters of the modulation system 2; at the same time, it can simulate the pitch, roll, heading, position, speed, time and other information of the radar platform, and communicate with the laser velocity radar 5 via RS232 to send the information of the platform to the radar.

[0036] The modulation system 2 is divided into four parts: an adjustable attenuation module 21, an adjustable delay module 22, an adjustable frequency shift module 23, and a polarization modulation module 24. The adjustable attenuation module 21 can achieve arbitrary power attenuation from 0 to 27 dBm; the adjustable delay module 22 can achieve arbitrary time delay within 33 μs; the adjustable frequency shift module 23 uses frequency shifters of -40 MHz, 40 MHz, 80 MHz, 100 MHz, and 200 MHz. Each frequency shifter can be used independently in the optical path or in combination with other frequency shifters to achieve a minimum frequency shift of -40 MHz and a maximum of 420 MHz; the polarization modulation module 24 uses a three-propeller electrically controlled polarization modulator, which can realize the transition from input light of arbitrary polarization state to output light of arbitrary polarization state.

[0037] Figure 3 This is a structural diagram of modulation system 2. The laser enters modulation system 2 through optical coupling system 1. Modulation modules are selected and connected to the optical path according to actual needs. Each module is connected to a beam splitter. The high-power (95%) output of the beam splitter is connected to the subsequent optical path, and the low-power (5%) output is connected to the detection equipment.

[0038] Figure 4 The control system 3 communicates with the modulation system 2 via RS232 to control the parameters of each modulation module; at the same time, the control system 3 simulates the information of the laser velocity measuring radar 5 platform and sends the relevant simulation information to the radar.

[0039] Based on the potential changes that may occur during laser transmission in the real atmosphere, the simulation functions of the four modules of modulation system 2 are as follows:

[0040] 1. Adjustable attenuation module 21: Simulates the energy attenuation of laser light during atmospheric transmission;

[0041] 2. Adjustable delay module 22: Simulates the change in optical path length of laser light during atmospheric transmission;

[0042] 3. Adjustable frequency shift module 23: Simulates the Doppler frequency shift of laser during atmospheric transmission;

[0043] 4. Polarization Modulation Module 24: Simulates the change of polarization state of laser during atmospheric transmission.

[0044] Some or all of the four modules can be selected according to actual needs. There is no specific order among the modules; the order can be adjusted as needed for testing. Each modulation module's output is connected to a 95:5 beam splitter. 95% of the beam splitter's output is connected to the subsequent optical path, and 5% of the output is connected to the corresponding detection device in detection system 4. The input of the first selected modulation module is connected to port 3 of the fiber optic circulator 14. The last selected modulation module has 95% of its beam splitter output connected to port 1 of the fiber optic circulator 14. The modulated analog echo signal is returned to the laser velocimetry radar 5 through port 1, allowing the radial velocity to be calculated.

[0045] The detection system 4 is divided into four parts: optical power meter 31, energy meter, oscilloscope 32, spectrum analyzer 33, and polarization meter 34.

[0046] The optical path of this invention adopts an all-fiber structure, and the device can be adapted to both continuous and pulsed laser velocity measuring radars 5. The optical coupling system 1 uses an optical wedge 11 to collimate the incident laser. A mode field adapter 13 is used to ensure that the optical coupling system 1 can adapt to optical fibers with different core diameters. The control system 3 can communicate not only with the modulation system 2 to set its parameters, but also with the laser velocity measuring radar 5 to simulate the radar platform's pitch, roll, heading, position, speed, and time information, and transmit this information to the radar. The adjustable frequency shift module 23, by selecting five different frequency shifters, can be combined to achieve multiple frequency shift amounts ranging from a minimum of -40MHz to a maximum of 420MHz.

[0047] Working principle:

[0048] When a laser beam travels through the atmosphere, it interacts with atmospheric substances, primarily causing laser energy attenuation, laser frequency shift, and changes in laser polarization state. Additionally, it takes a certain amount of time for a lidar to receive the echo signal, which is known as laser delay transmission.

[0049] The device simulates four atmospheric phenomena through a modulation system. The laser emitted by the laser wind radar passes through an optical coupling system and is then transmitted to the modulation system via an optical fiber circulator. The four modulation modules of the modulation system transmit the laser through optical fibers.

[0050] First, a preset wind speed value is established. An acousto-optic frequency shifter (AOM) corresponding to that wind speed is connected to the optical path (one wind speed corresponds to one frequency shift). The laser beam is modulated sequentially through an adjustable attenuator 211, an optical fiber delay 221, an AOM 231, and a polarization modulator 241 (the order of the four modulation modules can be arbitrarily changed). After the device is powered on, the host computer program controls the parameter settings of the adjustable energy attenuator, adjustable optical fiber delay, and polarization modulator. The modulation devices modulate the laser beam according to the set values. The three modulation devices communicate with the control system via RS232. The modulated laser beam returns to the optical coupling system through an optical fiber circulator, serving as a simulated atmospheric echo signal received by the optical lens of the laser wind radar. The laser wind radar then retrieves the wind speed. By comparing the retrieved wind speed with the preset wind speed, the laser wind radar can be tested.

[0051] In summary, the present invention has the following advantages:

[0052] 1. Continuous-wave lidar emits continuous laser light, which is focused at a single point by a transmitting lens; pulsed lidar emits pulsed laser light, which exits as approximately parallel light through a transmitting lens. The optical coupling system, through a combination of optical wedges and matching lenses, collimates and focuses the incident light, converging it. The incident laser light is then transmitted to the subsequent modulation system via a mode field adapter and fiber optic circulator, thus enabling compatibility with both continuous-wave and pulsed lidar.

[0053] 2. The equipment is mostly composed of mature optoelectronic devices, and the construction cost is much lower than that of wind tunnel and other testing methods; the vulnerable parts of the equipment, such as optical fibers, are easy to repair and replace, and the maintenance cost is also relatively low.

[0054] 3. The device is used in a ground-based laboratory and has no special environmental adaptability requirements. The testing process is simple and easy to learn.

[0055] 4. AOM is a mature device that is widely used in the optical path of laser wind measurement radar systems. It has high precision and can be used in the testing system of laser wind measurement radar.

[0056] 5. The modulation module can be configured with parameters via host computer software, and the modulation process is fully controllable.

Claims

1. An atmospheric optical effect simulation device for laser velocimetry radar, characterized in that, include: The optical coupling system includes: an optical wedge, a matching lens, a mode field adapter, and a fiber optic circulator. The optical wedge is aligned with the transceiver lens and the matching lens of the laser velocity radar. The matching lens is aligned with the mode field adapter. The mode field adapter is connected to the fiber optic cable at port 2 of the fiber optic circulator. The optical wedge collimates the laser, and the collimated laser is received by the matching lens. The mode field adapter adapts fibers of different core diameters to the matching lens, focusing the laser into port 2 of the fiber optic circulator. The modulation system includes: an adjustable attenuation module, an adjustable delay module, an adjustable frequency shifting module, and a polarization modulation module. Port 2 of the fiber optic circulator is optically connected to the optical input interface of the adjustable attenuation module; the first optical output interface of the adjustable attenuation module is optically connected to the first optical input interface of the detection system; the second optical output interface of the adjustable attenuation module is connected to the optical input interface of the adjustable delay module; the first optical output interface of the adjustable delay module is connected to the second optical input interface of the detection system via an RF line; the second optical output interface of the adjustable delay module is connected to the optical input interface of the adjustable frequency shifting module; and the first optical output interface of the adjustable frequency shifting module is optically connected to the third optical input interface of the detection system. The adjustable frequency shifting module... The second optical output interface of the module is connected to the optical input interface of the polarization modulation module; the first optical output interface of the polarization modulation module is optically connected to the fourth optical input interface of the detection system; the second optical output interface of the polarization modulation module is optically connected to the 3-port fiber of the fiber optic circulator; the communication ports of the adjustable attenuation module, the adjustable delay module, and the polarization modulation module are respectively connected to the control system via an RS232 bus. The adjustable attenuation module simulates the energy attenuation of laser light during atmospheric transmission; the adjustable delay module simulates the change in optical path length of laser light during atmospheric transmission; the adjustable frequency shift module simulates the change in Doppler frequency shift of laser light during atmospheric transmission; and the polarization modulation module simulates the change in polarization state of laser light during atmospheric transmission. The control system is connected to the modulation system and laser velocity radar via an RS232 bus. It is used to set and modify the modulation parameters of the modulation system, simulate the information of the mounting platform, and send the information of the mounting platform to the radar. The detection system includes an optical power meter, an oscilloscope, a spectrum analyzer, and a polarization meter. The first optical output interface of the adjustable attenuation module is connected to the optical power meter via an optical fiber; the first optical output interface of the adjustable delay module is connected to the oscilloscope via an RF cable; the first optical output interface of the adjustable frequency shift module is connected to the spectrum analyzer via an optical fiber; and the first optical output interface of the polarization modulation module is connected to the polarization meter via an optical fiber.

2. The atmospheric optical effect simulation device for laser velocimetry radar according to claim 1, characterized in that, Optical wedges include those with angles of 5°, 10°, 20°, and 30°.

3. The atmospheric optical effect simulation device for laser velocimetry radar according to claim 1, characterized in that, The adjustable attenuation module includes an adjustable attenuator and a first beam splitter; the adjustable delay module includes an adjustable delay fiber and a second beam splitter; the adjustable frequency shift module includes a frequency shifter and a third beam splitter; and the polarization modulation module includes a three-paddle polarization modulator and a fourth beam splitter.

4. The atmospheric optical effect simulation device for laser velocimetry radar according to claim 1, characterized in that, The first, second, third, and fourth beam splitters are all 95:5 beam splitters. The high-power (95%) output of the beam splitter is connected to the subsequent optical path, and the low-power (5%) output is connected to the detection system.

5. A method for simulating atmospheric optical effects for laser velocimetry radar, characterized in that, The method is performed using the atmospheric optical effects simulation device for laser velocimetry radar as described in any one of claims 1-4, and the method includes: Set a preset wind speed value; After the device is powered on, the parameters of the modulation system are set; The modulation system will modulate the laser according to the set values, and the modulation system communicates with the control system via RS232. The modulated laser returns to the optical coupling system and is received by the optical lens of the laser speed radar as a simulated atmospheric echo signal. The laser wind radar then retrieves the wind speed. The retrieved wind speed is compared with the preset wind speed to complete the test of the laser speed radar.

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