Scanning system based on laser Doppler velocity measurement

Abstract

The invention discloses a scanning system based on laser Doppler velocity measurement. The scanning system comprises a laser and a data analysis module. A laser beam emitted by the laser can be split into a first sub-beam advancing along a reference light path and a second sub-beam advancing along an experimental light path; the second sub-light beam can be coupled with the first sub-light beam after being folded back by a moving object along an experimental light path, and the first sub-light beam and the second sub-light beam can be mixed after being coupled so as to obtain Doppler frequency shift data; and the data analysis module can receive the Doppler frequency shift data and analyze and process the Doppler frequency shift data to obtain point cloud distribution in the target scanning space. The scanning system based on laser Doppler velocity measurement can effectively solve the problem that a receiving system is affected by ground clutter and multipath effect due to complex environment, can effectively detect low, small and slow targets in low-altitude areas around a city, and accurately and reliably provides early warning information in real time.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radar, and in particular relates to a scanning system based on laser Doppler velocity measurement. Background Art

[0002] At present, the rapid development and widespread popularity of drone technology has brought great challenges to public safety. The miniaturization and portability of drones make them easily available to more ordinary consumers. They are characterized by low altitude (mostly below 500 meters in altitude), slow speed (generally below 50 meters per second), small target size (usually around 1 square meter), and limited flight distance (mostly 5 kilometers in distance). They are collectively referred to as "low, small, and slow" targets, which increase the threat to sensitive areas and departments. In response to the dangers brought about by the large-scale popularization of drones, many institutions have developed systems to detect drones, including radar detection, acoustic detection, visual detection, radio signal detection, etc.

[0003] Among them, radar detection technology has difficulty detecting low-altitude, slow-moving or hovering drones, has a high false alarm rate, is easily interfered by ground clutter, has poor effects on drones with plastic shells, and relies on manual operation, which is costly. Visual detection technology has a short detection distance and a small range, and is easily affected by complex backgrounds and weather conditions. Acoustic detection technology has a limited detection distance and is sensitive to environmental noise, so it can only be used in low-noise environments. Radio signal detection technology can only detect passively, cannot identify encrypted signals, and relies on a continuously updated spectrum database, so it cannot detect autonomously flying drones.

[0004] For low, small and slow targets, they have the following characteristics: low altitude, slow speed and small target size. The small geometric size and weak infrared characteristics of "low, small and slow" targets, coupled with the complex background of the urban low-altitude environment, make early warning and tracking difficult. Even if the current short-range microwave radar is used for detection, it is not suitable for use in urban environments and major events due to the close distance of the target and the complex background waves.

[0005] Therefore, in view of the above technical problems, it is necessary to provide a scanning system based on laser Doppler velocimetry. Summary of the invention

[0006] The object of the present invention is to provide a scanning system based on laser Doppler velocity measurement, which can solve the problem that the velocity measurement of low, small and slow targets using the common method mentioned above is easily disturbed, resulting in low detection accuracy.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A scanning system based on laser Doppler velocimetry comprises a laser and a data analysis module; the laser beam emitted by the laser can be split into a first sub-beam travelling along a reference optical path and a second sub-beam travelling along an experimental optical path; the second sub-beam can be coupled with the first sub-beam after returning along the experimental optical path via a moving object, and the first sub-beam and the second sub-beam can be mixed after coupling to obtain Doppler frequency shift data; the data analysis module can receive the Doppler frequency shift data and perform analysis and processing to obtain point cloud distribution in a target scanning space.

[0009] In one or more embodiments of the present invention, the scanning imaging system also includes a circulator, a collimator and a galvanometer. The second sub-beam travels along the experimental optical path through the circulator, the collimator and the galvanometer in sequence and is emitted to the moving object. After returning from the moving object, it travels along the experimental optical path until it couples with the first sub-beam.

[0010] In one or more embodiments of the present invention, the scanning imaging system further includes a grating driving module, which can output sine wave and triangle wave data signals to control the movement of the galvanometer so that the galvanometer performs grating scanning.

[0011] In one or more embodiments of the present invention, the grating driving module includes a first signal driver and a first signal converter, and the first signal driver can drive the first signal converter to output the sine wave and triangle wave signals.

[0012] In one or more embodiments of the present invention, the scanning imaging system further comprises a first beam splitter, and the laser beam emitted by the laser can be split by the first beam splitter, and the light intensity of the first sub-beam is smaller than the light intensity of the second sub-beam.

[0013] In one or more embodiments of the present invention, the scanning imaging system also includes a second beam splitter and a balanced detector. After the first sub-beam and the second sub-beam are coupled, they pass through the second beam splitter and the balanced detector. The balanced detector can perform mixing processing on the coupled first sub-beam and the second sub-beam.

[0014] In one or more embodiments of the present invention, the first sub-beam may enter the second beam splitter via a time-delay optical fiber.

[0015] In one or more embodiments of the present invention, the data analysis module includes a second signal driver, a second signal converter, and an FFT accelerator;

[0016] The second signal driver can drive the second signal converter to operate, and the second signal converter can collect the mixed signal of the balanced detector and output it to the FFT accelerator. The FFT accelerator can perform Fourier transform on the data corresponding to each scanning point to obtain the maximum spectrum value of each point.

[0017] In one or more embodiments of the present invention, the data analysis module further includes a memory, the memory being used to store the data received by the second signal converter; and / or,

[0018] The data analysis module also includes a computer, and the FFT accelerator can transmit the analysis and processing results to the computer to obtain the point cloud distribution in the target scanning space.

[0019] In one or more embodiments of the present invention, the laser beam emitted by the laser is a continuous wave, a frequency modulated continuous wave, or a pulse wave; and / or,

[0020] The galvanometer mirror is a MEMS galvanometer mirror, a mechanical galvanometer mirror, or a galvanometer mirror.

[0021] Compared with the prior art, in the scanning system based on laser Doppler velocity measurement of the present invention, the laser beam emitted by the laser is first divided into a first sub-beam and a second sub-beam. When the second sub-beam irradiates a moving object, its frequency will change. Subsequently, the data analysis module can obtain the point cloud distribution in the target scanning space by analyzing the Doppler frequency shift data of the first sub-beam and the second sub-beam. The system can effectively overcome the problem that the receiving system is affected by ground clutter and multipath effects caused by complex environments, and can effectively detect "low, small and slow" targets in low-altitude areas around cities, and provide early warning intelligence information in real time, accurately and reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 Schematic diagram of the structure of a scanning system based on laser Doppler velocimetry in one embodiment of the present invention.

[0024] Description of main reference numerals:

[0025] 1. Laser; 2. First beam splitter; 3. Circulator; 4. Collimator; 5. Galvanometer; 6. Second beam splitter; 7. Balanced detector; 8. First signal driver; 9. First signal converter; 10. Second signal driver; 11. Second signal converter; 12. FFT accelerator; 13. Memory. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] Reference Figure 1 The scanning system based on laser Doppler velocimetry in one embodiment of the present invention includes a laser 1, a first beam splitter 2, a circulator 3, a collimator 4, a galvanometer 5, a second beam splitter 6, a balanced detector 7 and a data analysis module.

[0028] The laser beam emitted by the laser 1 can be split into a first sub-beam traveling along a reference optical path and a second sub-beam traveling along an experimental optical path; the second sub-beam can be coupled with the first sub-beam after returning along the experimental optical path through a moving object, and the first sub-beam and the second sub-beam can be mixed after coupling to obtain Doppler frequency shift data. The data analysis module can receive the Doppler frequency shift data and perform analysis and processing to obtain the point cloud distribution in the target scanning space.

[0029] The laser Doppler effect refers to the fact that when a moving object is irradiated by a laser, the laser frequency received by the moving object will also change. Therefore, after the second sub-beam reaches the moving object, the Doppler frequency shift data of the first sub-beam and the second sub-beam can be obtained, and then the data analysis module can be used to analyze and process to describe the moving speed of the moving object. The above point cloud distribution can also be understood as the speed distribution in the target scanning space.

[0030] Based on the above characteristics, the scanning system based on laser Doppler velocity measurement in this embodiment can effectively overcome the problem that the receiving system is affected by ground clutter and multipath effects caused by complex environments. At the same time, it can effectively detect "low, small and slow" targets (such as small drones) in low-altitude areas around cities, and provide early warning intelligence information in real time, accurately and reliably.

[0031] Reference Figure 1In this embodiment, the laser beam emitted by the laser 1 can be split by the first beam splitter 2, and the light intensity of the first sub-beam is less than the light intensity of the second sub-beam. Among them, the first sub-beam is configured as a reference beam, and the second sub-beam is configured as an experimental beam and is used to pass through the moving object. Therefore, compared with the first sub-beam, the loss generated by the second sub-beam during the travel process is greater than that of the first sub-beam, so the first beam splitter 2 can make the light intensity of the first sub-beam less than the light intensity of the second sub-beam. In this embodiment, the light intensity ratio of the first sub-beam to the second sub-beam is 2:98 as an example for illustrative explanation, which is not a limitation on the ratio of the first sub-beam to the second sub-beam in this embodiment. It can be understood that the specific ratio setting can be specifically adjusted according to actual conditions.

[0032] Reference Figure 1 , the second sub-beam passes through the circulator 3, the collimator 4 and the galvanometer 5 in sequence along the experimental optical path and is emitted to the moving object. After being turned back by the moving object, it travels along the experimental optical path to couple with the first sub-beam. After the first sub-beam and the second sub-beam are coupled, they pass through the second beam splitter 6 and the balanced detector 7. The balanced detector 7 can perform frequency mixing processing on the coupled first sub-beam and the second sub-beam. After the processing is completed, the received Doppler data can be analyzed and processed by the data analysis and processing module to obtain the point cloud distribution in the target scanning space.

[0033] Among them, the reference optical path and experimental optical path involved between the laser 1, the first beam splitter 2, the circulator 3, the collimator 4, the second beam splitter 6 and the balanced detector 7 in this embodiment are optical fiber optical paths, and the optical path between the galvanometer 5 and the moving object is a spatial optical path.

[0034] Reference Figure 1 , further, the first sub-beam can enter the second beam splitter 6 through the time-delay optical fiber, so that the first sub-beam can be delayed to enter the second beam splitter 6. Among them, the laser beam emitted by the laser 1 is a continuous wave, or a frequency-modulated continuous wave, or a pulse wave. In this embodiment, the laser beam is preferably a continuous wave. The system structure corresponding to the continuous wave is simple and has excellent speed resolution, that is, it can effectively detect slow objects and has good anti-interference performance.

[0035] Reference Figure 1 The scanning system based on laser Doppler velocimetry in one embodiment of the present invention further includes a grating driving module, which can output sine wave and triangle wave data signals to control the movement of the galvanometer 5 so that the galvanometer 5 performs grating scanning. By inputting sine wave and triangle wave signals of corresponding frequencies, the galvanometer 5 can be driven to move, so that the laser emitted by the laser 1 performs grating scanning.

[0036] By making the galvanometer 5 perform raster scanning, the velocity distribution of multiple points in the target scanning space can be obtained simultaneously, thereby improving the detection efficiency of the target scanning space. In this embodiment, the output sine wave frequency of 715 Hz and the triangular wave frequency of 55 Hz are used as an example for illustrative explanation, which is not a limitation on the sine wave and triangular wave frequencies in this implementation.

[0037] Reference Figure 1 Specifically, the grating driving module includes a first signal driver 8 and a first signal converter 9. The first signal driver 8 can drive the first signal converter 9 to output sine wave and triangle wave signals. Specifically, the first signal driver 8 can be driven by DAC, and the first signal converter 9 can be matched with DAC. DAC (Digital--to-Analog Converter), that is, a digital-to-analog converter, is a circuit that converts digital signals into analog signals. Its input is a digital signal and its output is an analog signal. Specifically, the galvanometer 5 is a MEMS galvanometer, or a mechanical galvanometer, or a galvanometer. The first signal driver 8, the first signal converter 9 and the galvanometer 5 are connected by a circuit.

[0038] In this embodiment, the galvanometer 5 is preferably a MEMS galvanometer. The MEMS galvanometer is a tiny drivable reflector manufactured based on the micro-electromechanical system (MEMS) technology, usually composed of a movable structure (such as a mirror, a torsion beam, and a movable comb tooth) and a fixed structure (such as a static comb tooth), and has the advantages of fast scanning speed, fast response, high precision, etc. Exemplarily, the MEMS galvanometer can adopt multiple driving modes such as electrostatic drive, electromagnetic drive, and piezoelectric drive, and provide motion modes such as translation or torsion according to the needs of the application scenario, which is not limited in this application.

[0039] Reference Figure 1 , the data analysis module includes a second signal driver 10, a second signal converter 11, and an FFT accelerator 12. The second signal driver 10 can drive the second signal converter 11 to operate, and the second signal converter 11 can collect the mixed signal of the balanced detector 7 and output it to the FFT accelerator 12. The FFT accelerator 12 can perform Fourier transform on the data corresponding to each scanning point to obtain the maximum spectrum value of each point. Specifically, the second signal driver 10 can be driven by ADC, and the second signal converter 11 can be driven by ADC. ADC (Analog-to-Digital Converter), that is, an analog-to-digital converter, is a circuit that converts a continuous analog signal into a digital signal, and its input is an analog signal and its output is a digital signal. Among them, the FFT accelerator 12 can also communicate data with the computer through a USB driver and USB. The second signal driver 10 and the second signal converter 11 are connected by a circuit.

[0040] Reference Figure 1 In an optional embodiment, the data analysis module further includes a memory 13, and the memory 13 is used to store the data received by the second signal converter 11. The memory 13 of this embodiment can be a FIFO memory 13.

[0041] Reference Figure 1 In an optional embodiment, the data analysis module further includes a computer, and the FFT accelerator 12 can transmit the analysis and processing results to the computer to obtain the point cloud distribution in the target scanning space. The above-mentioned computer can be a personal computer, a server computer, a workstation, a desktop computer, a laptop computer, a notebook computer, a mobile electronic device, a smart phone, a tablet computer, a cellular phone, a personal digital assistant (PDA), a handheld device, a messaging device, a wearable electronic device, a consumer electronic device, etc.

[0042] The scanning system based on laser Doppler velocimetry of the present invention can effectively detect "low, small and slow" targets in low-altitude areas around cities. The grating drive module can perform grating scanning on multiple points in the target scanning space, and the data analysis module can process the data corresponding to each scanning point to obtain the point cloud distribution in the target scanning space, thereby providing early warning intelligence information in real time, accurately and reliably.

[0043] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0044] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A scanning system based on laser Doppler velocimetry, characterized in that: It comprises a laser (1) and a data analysis module; The laser beam emitted by the laser (1) can be split into a first sub-beam traveling along a reference light path and a second sub-beam traveling along an experimental light path; the second sub-beam can be coupled with the first sub-beam after returning along the experimental light path through a moving object, and the first sub-beam and the second sub-beam can be mixed after being coupled to obtain Doppler frequency shift data; The data analysis module can receive the Doppler frequency shift data and perform analysis and processing to obtain the point cloud distribution in the target scanning space.

2. The scanning system based on laser Doppler velocimetry according to claim 1, characterized in that: The scanning imaging system further comprises a circulator (3), a collimator (4) and a galvanometer (5); the second sub-beam travels along an experimental optical path through the circulator (3), the collimator (4) and the galvanometer (5) in sequence and is emitted to a moving object; after being reflected by the moving object, the second sub-beam travels along the experimental optical path until it couples with the first sub-beam.

3. The scanning system based on laser Doppler velocimetry according to claim 2, characterized in that: The scanning imaging system further comprises a grating driving module, which can output sine wave and triangle wave data signals to control the movement of the galvanometer (5) so that the galvanometer (5) performs grating scanning.

4. The scanning system based on laser Doppler velocimetry according to claim 3, characterized in that: The grating driving module comprises a first signal driver (8) and a first signal converter (9), and the first signal driver (8) can drive the first signal converter (9) to output the sine wave and triangle wave signals.

5. The scanning system based on laser Doppler velocimetry according to claim 1, characterized in that: The scanning imaging system further comprises a first beam splitter (2), and the laser beam emitted by the laser (1) can be split by the first beam splitter (2), and the light intensity of the first sub-beam is smaller than the light intensity of the second sub-beam.

6. The scanning system based on laser Doppler velocimetry according to claim 1, characterized in that: The scanning imaging system further comprises a second beam splitter (6) and a balanced detector (7); the first sub-beam and the second sub-beam are coupled and then pass through the second beam splitter (6) and the balanced detector (7); the balanced detector (7) can perform frequency mixing processing on the coupled first sub-beam and the second sub-beam.

7. The scanning system based on laser Doppler velocimetry according to claim 6, characterized in that: The first sub-beam can enter the second beam splitter (6) via the time-delay optical fiber.

8. The scanning system based on laser Doppler velocimetry according to claim 6, characterized in that: The data analysis module comprises a second signal driver (10), a second signal converter (11), and an FFT accelerator (12); The second signal driver (10) can drive the second signal converter (11) to operate, and the second signal converter (11) can collect the mixed signal of the balanced detector (7) and output it to the FFT accelerator (12). The FFT accelerator (12) can perform Fourier transform on the data corresponding to each scanning point to obtain the maximum spectrum value of each point.

9. The scanning system based on laser Doppler velocimetry according to claim 8, characterized in that: The data analysis module further comprises a memory (13), wherein the memory (13) is used to store data received by the second signal converter (11); and / or, The data analysis module also includes a computer, and the FFT accelerator (12) can transmit the analysis and processing results to the computer to obtain the point cloud distribution in the target scanning space.

10. The scanning system based on laser Doppler velocimetry according to claim 2, characterized in that: The laser beam emitted by the laser (1) is a continuous wave, a frequency modulated continuous wave, or a pulse wave; and / or, The oscillating mirror (5) is a MEMS oscillating mirror, or a mechanical oscillating mirror, or a galvanometer oscillating mirror.

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