Fiber-optic coaxial laser radar, noise reduction device and aerosol detection method thereof

Abstract

The present invention belongs to the field of radar technology, and specifically relates to a fiber-optic coaxial laser radar, a method for eliminating crosstalk noise in the fiber-optic coaxial laser radar and a noise reduction device, and an atmospheric aerosol detection method based on the fiber-optic coaxial laser radar. The fiber-optic coaxial laser radar includes a coaxial transceiver system composed of a laser, a circulator, a scanning system and a detector, as well as a spatial optical chopper and a signal noise reduction module. The spatial optical chopper is installed at the output end of the telescope in the coaxial transceiver system; the spatial optical chopper is used to adjust the continuity of the external signal entering the telescope, and the signal noise reduction module is used to use a differential algorithm to process the original echo signal into an echo signal with the crosstalk noise filtered out. When the developed new coaxial laser radar is used to complete the atmospheric aerosol concentration analysis or other meteorological detection tasks, the installation cost, use difficulty and maintenance cost of the equipment can be effectively reduced while ensuring the detection accuracy of the relevant data.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and specifically relates to a fiber-optic coaxial laser radar, a method for eliminating crosstalk noise in the fiber-optic coaxial radar and a noise reduction device, and an atmospheric aerosol detection method based on the fiber-optic coaxial laser radar. Background Art

[0002] Lidar is an active optical remote sensing technology with the advantages of high precision, high temporal and spatial resolution, and long-distance detection. It is widely used in meteorological parameter detection, environmental perception, special military, etc. After the laser beam emitted by the lidar interacts with the target, some spatial physical characteristics of the target can be obtained through direct detection or coherent detection.

[0003] According to the signal transmission method, laser radar can be divided into two categories: space light and fiber laser radar. According to whether the optical axes of the transceiver in the radar coincide, laser radar can be divided into two categories: coaxial system and off-axis system. Among them, the transmitter and receiver of the off-axis system are composed of two different telescopes, which collimate, expand and couple the laser respectively. When in use, the optical axes of the two telescopes need to be adjusted to be completely parallel. At the same time, the focal length and spacing of the telescopes need to be adjusted according to the geometric overlap factor of the field of view of the two telescopes. The early optical system design of the laser laser radar using the off-axis system is relatively complex and the debugging process is cumbersome. The separation of the receiving optical path and the transmitting optical path also brings about the problems of large volume and high cost. In addition, the system also requires frequent maintenance during application to compensate for mechanical displacement caused by vibration, temperature changes, etc.

[0004] A single telescope is used for transmitting and receiving in the coaxial system's lidar. Compared with the off-axis system, the coaxial system can effectively reduce the cost and volume, and optimize the system complexity and robustness. The coaxial system has obvious advantages over the off-axis system, but the coaxial system also has an inherent defect, that is, the coaxial lidar usually has a high system crosstalk noise. When the coaxial lidar is used for direct detection tasks such as atmospheric aerosol concentration, this crosstalk noise will have a great impact on the detection accuracy, causing the detection results to deviate seriously from the true value.

[0005] Therefore, considering that when using a coaxial laser radar system for direct detection, there is crosstalk between the outgoing light path and the receiving light path, which leads to a sharp decrease in the signal-to-noise ratio, there will be defects such as reduced detection distance and poor data accuracy, which cannot meet the use requirements. Existing fiber-optic coaxial laser radars are usually only suitable for coherent detection tasks such as wind speed measurement, and cannot be used in direct detection tasks such as aerosol distribution. Aerosol distribution detection usually still requires the use of a more complex off-axis system laser radar. Summary of the invention

[0006] In order to solve the problem that the existing fiber-optic coaxial laser radar cannot be applied to intensity detection tasks such as atmospheric aerosols, the present invention provides a fiber-optic coaxial laser radar, a method for eliminating crosstalk noise in the fiber-optic coaxial radar and a noise reduction device, and an atmospheric aerosol detection method based on the fiber-optic coaxial laser radar.

[0007] The present invention is implemented by the following technical solutions:

[0008] A fiber-optic coaxial laser radar comprises a coaxial transceiver system consisting of a laser, a circulator, a scanning system and a detector. In particular, the fiber-optic laser radar also comprises a spatial light chopper and a signal noise reduction module.

[0009] The spatial optical chopper is installed at the output end of the telescope in the coaxial transceiver system. The spatial optical chopper is used to adjust the continuity of the external signal entering the telescope, so that the detector receives the original echo signal containing two signal components at different time periods within a complete signal cycle T. One of the signal components a contains the external signal, and the other signal component b does not contain the external signal.

[0010] The function of the signal noise reduction module is to use the two signal components contained in the original echo signal to perform noise reduction on the crosstalk noise contained in the original echo signal. The signal noise reduction module receives the original echo signal and first separates the original echo signal into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b. Then, by resampling, the first discrete signal and the second discrete signal in each cycle are expanded from a short cycle to a complete cycle, thereby obtaining the first extended signal and the second extended signal. Then, the first extended signal and the second extended signal are aligned on the time axis according to the timestamps of each signal component. After alignment, the first extended signal and the second extended signal are differentially processed to obtain an echo signal with the crosstalk noise filtered out.

[0011] In the fiber-optic coaxial laser radar provided by the present invention and equipped with a spatial optical chopper, the crosstalk noise in the collected signal is related to the hardware structure of the system. The present invention uses the data without external signals measured by the detector when the spatial optical chopper is turned off as the calibration of the internal crosstalk noise of the system. The data with external signals obtained by the detector when the spatial optical chopper is turned on is considered to be the superposition of crosstalk noise and external signals. Therefore, when two signal components are included in one cycle at the same time, the signal noise reduction module provided by the present invention can be used to convert the original echo signal into an echo signal that eliminates the crosstalk noise by differential processing.

[0012] As a further improvement of the present invention, when some periods in the original echo signal acquired by the signal noise reduction module are filtered out during sampling because they contain interference that cannot be processed, after obtaining the first extended signal and the second extended signal, the signal noise reduction module first uses an interpolation algorithm to fill in the data of the missing partial periods in the filtered signal, and then performs time axis alignment and differential processing on the first extended signal and the second extended signal; the order of the signals after alignment, differentiation and interpolation completion is not fixed.

[0013] In the technical solution of the present invention, the circulator includes port 1, port 2 and port 3. Port 1 and port 2 of the circulator are respectively connected to the laser and the telescope, forming the signal transmitting part of the coaxial transceiver system. Port 2 and port 3 of the circulator are respectively connected to the telescope and the detector, forming the signal receiving part of the coaxial transceiver system.

[0014] In the technical solution of the present invention, the circulator transmits optical signals through optical fibers; the signal between port 1 and port 2 of the circulator is unidirectionally transmitted from 1 to 2; the signal between port 2 and port 3 is unidirectionally transmitted from 2 to 3.

[0015] In the technical solution of the present invention, the telescope is used to collimate and expand the laser emitted by the laser, and at the same time receive the echo signal of the detection target; the scanning system is used to adjust the emission direction of the collimated laser beam emitted by the telescope, and then align it with the target area to be detected.

[0016] As a further improvement of the present invention, an optical switch and a filter are also provided between the port 3 of the circulator and the detector. The optical switch is used to modulate the optical signal transmitted to the detector to filter out the optical pulse crosstalk; the filter is used to filter the optical signal input to the detector.

[0017] The invention also includes a method for eliminating crosstalk noise of a fiber-optic coaxial laser radar, and the method for eliminating crosstalk noise comprises the following steps:

[0018] S1: A spatial optical chopper is installed at the telescope output end of the fiber-optic coaxial laser radar.

[0019] S2: The chopping frequency of the spatial light chopper is preset according to the integral frequency of the original echo signal of the fiber-optic coaxial laser radar, so that each signal period T of the original echo signal is divided into at least two sub-periods, and the spatial light chopper switches between the on mode and the off mode in any two adjacent sub-periods.

[0020] S3: Obtain the original echo signal received by the detector of the fiber-optic coaxial laser radar, and define that in each cycle of the original echo signal, the signal component a contains the external signal, and the signal component b does not contain the external signal. Then perform the following noise reduction processing:

[0021] S31: Separate the original echo signal into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b.

[0022] S32: Extending the parts of the first discrete signal and the second discrete signal in each period from a short period to a complete period by resampling, thereby obtaining a first extended signal and a second extended signal.

[0023] S33: Time-axis aligning the first extended signal and the second extended signal according to the timestamps of the signal components.

[0024] S34: performing differential processing on the first extended signal and the second extended signal to obtain an echo signal with crosstalk noise filtered out.

[0025] As a further improvement of the present invention, when the original echo signal loses information in part of the period after filtering, the data in the missing part of the period in the first extended signal and the second extended signal are supplemented according to the information in the adjacent period by an interpolation algorithm before step S33, and then the time axis alignment of step S33 and the differential processing step of step S34 are executed.

[0026] The present invention also includes a noise reduction device for a fiber-optic coaxial laser radar, which is used to eliminate the crosstalk noise contained in the original echo signal received by the coaxial transceiver system of the fiber-optic coaxial laser radar. The noise reduction device includes a spatial optical chopper and a signal noise reduction module, and the spatial optical chopper and the signal noise reduction module are respectively used as products in the aforementioned fiber-optic coaxial laser radar.

[0027] The present invention also includes an atmospheric aerosol detection method based on a fiber-optic coaxial laser radar, which detects and analyzes aerosol distribution information in the atmosphere through a fiber-optic coaxial laser radar. The detection method includes the following steps:

[0028] S01: Build the required aerosol detection system according to the hardware solution of the fiber-optic coaxial lidar as mentioned above.

[0029] S02: Preset the system parameters of the aerosol detection system and then perform preliminary detection.

[0030] S03: Debug the module parameters of the signal noise reduction module in the aerosol detection system according to the difference between the pre-detection result and the reference signal.

[0031] S04: Use the aerosol detection system debugged in the previous step to perform real-time detection of atmospheric aerosols, and obtain real-time echo signals with crosstalk noise filtered out.

[0032] S05: Based on the real-time echo signal obtained in the previous step, the target characteristics of the aerosol in the atmosphere are obtained by inverting the preset aerosol distribution state physical model.

[0033] The technical solution provided by the present invention has the following beneficial effects:

[0034] The present invention installs a spatial optical chopper at the telescope output end of the existing fiber-optic coaxial laser radar, and uses the spatial optical chopper's ability to mask external light to adjust the components in the echo signal received by the detector in each cycle. This allows the detector to collect data in two working modes with / without external signals in the same sampling cycle, and then use the corresponding noise reduction algorithm designed by the present invention to eliminate information such as crosstalk noise contained in the echo signal through methods such as difference and background removal. This significantly improves the signal-to-noise ratio of the echo signal received by the fiber-optic coaxial laser radar.

[0035] The technical solution provided by the present invention can effectively solve the problem that the coaxial laser radar system is limited by crosstalk noise and cannot perform long-distance high-precision direct intensity detection at a very low cost. This greatly increases the application scenarios of the coaxial laser radar system and overcomes the technical difficulty that in traditional solutions, the long-distance intensity detection task at the single-photon level can only be done using an off-axis system. The laser radar for atmospheric aerosol detection can also be used in airborne, vehicle-mounted, and other ways. It reduces the equipment installation cost, comprehensive application cost, and maintenance difficulty of meteorological observation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a system architecture diagram of the existing fiber-optic coaxial lidar.

[0037] Figure 2 This is a system architecture diagram of the improved fiber-optic coaxial laser radar in Example 1 of the present invention (the signal noise reduction module belongs to the data processing part and is not shown in the figure).

[0038] Figure 3 This is a flowchart of the signal noise reduction module in Example 1 of the present invention performing noise reduction processing on the original echo signal.

[0039] Figure 4 The figure is a flowchart of the noise reduction process of the signal module for the echo signal containing periodic missing in the embodiment of the present invention.

[0040] Figure 5 A flowchart of the steps of a method for eliminating crosstalk noise of a fiber-optic coaxial laser radar provided in Example 2 of the present invention.

[0041] Figure 6 This is a schematic diagram of the connection between a noise reduction device of a fiber-optic coaxial laser radar provided in Example 3 of the present invention and an existing laser radar.

[0042] Figure 7This is a flowchart of the steps of an atmospheric aerosol detection method based on fiber-optic coaxial laser radar provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Example 1

[0045] The fiber-optic coaxial laser radar provided in this embodiment is a fiber-optic coaxial laser radar with the performance of automatically suppressing system crosstalk noise; the fiber-optic coaxial laser radar is improved on the basis of existing products. Among them, the system architecture of the existing fiber-optic coaxial laser radar adopted in this embodiment is as follows Figure 1 As shown, the coaxial transceiver system includes a laser, a circulator, a scanning system and a detector. The laser generates a laser beam for detection that meets the preset repetition frequency, pulse width and pulse energy. The telescope is used to collimate and expand the laser emitted by the laser, and at the same time receive the echo signal of the detection target; the scanning system is used to adjust the emission direction of the collimated laser beam emitted by the telescope, and then align it with the target area to be detected.

[0046] The circulator in this embodiment includes port 1, port 2 and port 3. Port 1 and port 2 of the circulator are respectively connected to the laser and the telescope, forming the signal transmission part of the coaxial transceiver system. Port 2 and port 3 of the circulator are respectively connected to the telescope and the detector, forming the signal receiving part of the coaxial transceiver system. Among them, the circulator transmits optical signals through optical fibers; the signal between port 1 and port 2 of the circulator is unidirectionally transmitted from 1 to 2; the signal between port 2 and port 3 is unidirectionally transmitted from 2 to 3.

[0047] In the coaxial laser radar used in this embodiment, an optical switch and a filter are also provided between port 3 of the circulator and the detector. The optical switch is used to modulate the optical signal transmitted to the detector; the filter is used to filter the optical signal input to the detector. Specifically, due to factors such as external environmental background noise and laser spontaneous radiation, the signal input end contains noise light different from the light source band. The filter plays a bandpass role, which can filter out the light in the non-light source band in the signal and allow the light in the light source band to pass, thereby reducing noise and improving the signal-to-noise ratio.

[0048] like Figure 2 As shown, the present embodiment improves the existing fiber-optic coaxial laser radar in two main aspects: 1. adding a spatial light chopper to the hardware part of the existing product; 2. adding a signal noise reduction module to the software part of the existing product.

[0049] The spatial optical chopper is installed at the output end of the telescope in the coaxial transceiver system. The spatial optical chopper is used to adjust the continuity of the external signal entering the telescope, so that the detector receives the original echo signal containing two signal components at different time periods within a complete signal cycle T. One of the signal components a contains the external signal, and the other signal component b does not contain the external signal.

[0050] The function of the signal noise reduction module is to use the two signal components contained in the original echo signal to reduce the crosstalk noise contained in the original echo signal. Figure 3 As shown, the signal noise reduction module works as follows: first, the original echo signal is separated into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b. Then, the first discrete signal and the second discrete signal are extended from a short period to a complete period in each cycle by resampling, thereby obtaining a first extended signal and a second extended signal. Then, the first extended signal and the second extended signal are aligned on the time axis according to the timestamps of each signal component. After alignment, the first extended signal and the second extended signal are differentially processed to obtain an echo signal with crosstalk noise filtered out.

[0051] In the fiber-optic coaxial laser radar provided in the present embodiment and equipped with a spatial optical chopper, the crosstalk noise inside the system is relatively stable and is related to the hardware structure of the system. In fact, the crosstalk noise in the present embodiment is due to the fact that ports 1 to 3 of the circulator itself cannot be completely isolated, so the light from the transmitting end will directly reach the receiving end from the inside of the system, which is the so-called crosstalk noise. The present invention uses the data without external signals measured by the detector when the spatial optical chopper is turned off as the calibration of the crosstalk noise inside the system. The data with external signals obtained by the detector when the spatial optical chopper is turned on is considered to be the superposition of crosstalk noise and external signals. Therefore, when two signal components are included in one cycle at the same time, the signal noise reduction module provided by the present invention can convert the original echo signal into an echo signal that eliminates the crosstalk noise by differential processing.

[0052] The fiber-optic coaxial laser radar in this embodiment usually performs the task of long-distance target detection. Therefore, during the long-term operation of the fiber-optic coaxial laser radar, when some obstacles that affect normal detection appear between the radar and the target area, such as being blocked by some moving objects, some obvious abnormal waveforms will appear in the echo signal. At this time, the data processing part of the radar will automatically remove the abnormal signal, which will cause information loss in some cycles of the original echo signal received by the system.

[0053] In view of this feature, the present embodiment also optimizes and adjusts the working mode of the signal noise reduction module. When some periods in the original echo signal acquired by the signal noise reduction module are filtered out due to interference during sampling, after obtaining the first extended signal and the second extended signal, the signal noise reduction module first uses an interpolation algorithm to complete the data in the missing partial periods in the filtered signal, and then performs time axis alignment and differential processing on the first extended signal and the second extended signal; align the sequence of the signals after differential and interpolation completion. Specifically, in this case, the workflow of the signal noise reduction module is as follows: Figure 4 shown.

[0054] Combined with the above description, it can be seen that the fiber-optic coaxial laser radar with added crosstalk noise reduction function provided by this embodiment not only has similar portability and ease of operation as the traditional coaxial laser radar. It also solves the problem that the crosstalk noise of the traditional fiber-optic coaxial laser radar affects the detection accuracy of the intensity detection task, so that the fiber-optic coaxial laser radar can also be used in detection tasks such as aerosol detection. It solves the problems of large equipment, difficult debugging, high equipment cost and maintenance difficulty in the traditional off-axis system.

[0055] It should be noted that the spatial light chopper used in this embodiment is an existing product. The spatial light chopper is usually used as a pulse frequency modulation tool to modulate continuous light into pulse light. In this embodiment, the spatial light chopper is installed at the front end of the telescope as a gating device to control the external space light entering the telescope. This is a new application of the spatial light chopper. This special application method can construct a signal containing two different signal sources in each cycle of the echo signal received by the detector. The commonality of the two signal components is the crosstalk noise of the system. In this case, the special noise reduction algorithm designed based on this case can generate a new echo signal with crosstalk noise removed through a differential algorithm based on the original echo signal containing different signal components.

[0056] Example 2

[0057] Based on Example 1, this embodiment further provides a method for eliminating crosstalk noise of a fiber-optic coaxial laser radar, such as Figure 5 As shown, the crosstalk noise elimination method includes the following steps:

[0058] S1: A spatial optical chopper is installed at the telescope output end of the fiber-optic coaxial laser radar.

[0059] S2: The chopping frequency of the spatial light chopper is preset according to the frequency of the original echo signal of the fiber-optic coaxial laser radar, so that each signal period T of the original echo signal is divided into at least two sub-periods, and the spatial light chopper switches between the on mode and the off mode in any two adjacent sub-periods.

[0060] S3: Obtain the original echo signal received by the detector of the fiber-optic coaxial laser radar, and define that in each cycle of the original echo signal, the signal component a contains the external signal, and the signal component b does not contain the external signal. Then perform the following noise reduction processing:

[0061] S31: Separate the original echo signal into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b.

[0062] S32: Extending the parts of the first discrete signal and the second discrete signal in each period from a short period to a complete period by resampling, thereby obtaining a first extended signal and a second extended signal.

[0063] S33: Time-axis aligning the first extended signal and the second extended signal according to the timestamps of the signal components.

[0064] S34: performing differential processing on the first extended signal and the second extended signal to obtain an echo signal with crosstalk noise filtered out.

[0065] In particular, when the original echo signal loses information within a partial period after filtering, the data within the missing partial periods in the first extended signal and the second extended signal are supplemented according to the information in adjacent periods by an interpolation algorithm before step S33, and then the time axis alignment of the original step S33 and the differential processing step of the original step S34 are performed.

[0066] The fiber-optic coaxial laser radar provided in Example 1 is a new product with a crosstalk noise reduction function. These new products usually come with a crosstalk noise reduction function when they leave the factory. During the production process of new products, the spatial light chopper is directly installed at the telescope output end of the original solution, and then the product is tested. According to the relevant test results, the corresponding noise reduction program is written into a general chip or a dedicated data processing chip, that is, as the signal noise reduction module required in the fiber-optic coaxial laser radar.

[0067] The crosstalk noise elimination method provided in this embodiment can be used as a solution to improve the performance of a large number of existing old-style fiber-optic coaxial laser radars. In this case, it is only necessary to add a specific type of spatial light chopper to the old equipment, and then set the operating parameters of the spatial light chopper. Then, the original echo signal received by the detector is obtained, and a related computer program is run in a general device, and the signal noise reduction process is implemented as step S3, so that the original echo signal containing the crosstalk noise can be converted into a new echo signal with the crosstalk noise removed, thereby overcoming the performance defects of the existing fiber-optic coaxial laser radar.

[0068] In the scheme of Example 1 and this embodiment, the time proportion of different component signals in each cycle is regulated by the spatial optical chopper. When the spatial optical chopper is blocked, the echo signal received by the detector only contains crosstalk noise. When the spatial optical chopper is turned on, the echo signal received by the detector contains both crosstalk noise and external signals. Considering that the crosstalk noise of the system is usually constant, a premise for the expected noise reduction effect to be obtained in the principle of the above two embodiments is that in different time periods of a single cycle, the difference in the actual external signal when the two types of signals are sampled is small, and the signal difference can be ignored relative to the detection accuracy. In this embodiment, since the target detected by the fiber-optic coaxial laser radar is usually data with extremely small fluctuations in a short period of time such as meteorological data, and the signal sampling period of the radar is usually short, then in a short time (i.e., within the signal sampling period), the external signal generated by the target will basically not change significantly, that is, the approximate processing used for the echo signal in the noise reduction process of this embodiment is appropriate. Therefore, the noise reduction algorithm used in the signal noise reduction model of this embodiment is feasible and the error is controllable.

[0069] In the practical application of the present scheme, the proportion of different signal components in each sampling period can be manually set as needed. Generally speaking, when the signal component containing external signals is too high, the accuracy of internal noise measurement will be reduced, and when the signal component containing external signals is too low, the accuracy of external signal measurement will be reduced and the final result will not be smooth enough. Therefore, technicians can adjust the time proportion of the two in a single signal period according to the performance requirements of the detection results. In the scheme of each embodiment of the present invention, the time proportion of the data of the external signal and the data with the external signal is usually set to 1:3, that is: when the signal sampling period is set to 1min, it contains 15s of data without external signals and 45s of data with external signals.

[0070] Example 3

[0071] On the basis of the above-mentioned embodiments, this embodiment further provides a noise reduction device for a fiber-optic coaxial laser radar, which is used to eliminate the crosstalk noise contained in the original echo signal received by the coaxial transceiver system of the fiber-optic coaxial laser radar. Figure 6 As shown, the noise reduction device includes a spatial light chopper and a signal noise reduction module, and the spatial light chopper and the signal noise reduction module respectively adopt products such as those in the aforementioned fiber-optic coaxial laser radar. This embodiment provides a product solution corresponding to the solution of embodiment 2. The signal noise reduction module in this product solution is a dedicated data processing module. Therefore, the corresponding spatial light chopper and signal noise reduction module can be directly installed in the traditional fiber-optic coaxial laser radar to improve the performance of the traditional laser radar.

[0072] Example 4

[0073] The detection of atmospheric aerosol distribution is an important task of meteorological data detection, which can be detected by LiDAR. The basic principle of aerosol LiDAR is to emit a collimated laser beam into the atmosphere, and the telescope collects the backscattered signal of atmospheric molecules or aerosols. The signal is input into the reflection algorithm to obtain meteorological information such as aerosol extinction coefficient, backscattering coefficient, aerosol content, distance, polarization state, atmospheric temperature, etc.

[0074] In existing solutions, atmospheric aerosol detection is usually measured using an off-axis system. When using a coaxial lidar system for direct detection, crosstalk between the outgoing light path and the receiving light path causes a sharp decrease in the signal-to-noise ratio, resulting in defects such as reduced detection distance and poor data accuracy.

[0075] This embodiment provides an atmospheric aerosol detection method based on a fiber-optic coaxial laser radar. The method detects and analyzes the aerosol distribution information in the atmosphere through a fiber-optic coaxial laser radar. Figure 7 As shown, the detection method includes the following steps:

[0076] S01: Build the required aerosol detection system according to the hardware solution of the fiber-optic coaxial laser radar in Example 1.

[0077] S02: Preset the system parameters of the aerosol detection system and then perform preliminary detection.

[0078] S03: Debug the module parameters of the signal noise reduction module in the aerosol detection system according to the difference between the pre-detection result and the reference signal.

[0079] S04: Use the aerosol detection system debugged in the previous step to perform real-time detection of atmospheric aerosols, and obtain real-time echo signals with crosstalk noise filtered out.

[0080] S05: Based on the real-time echo signal obtained in the previous step, the target characteristics of the aerosol in the atmosphere are obtained by inverting the preset aerosol distribution state physical model.

[0081] The atmospheric aerosol detection method provided in this embodiment is a new application made by utilizing the new features of the product in Example 1. This detection method has the advantages of the coaxial system such as miniaturization and simplified operation, and can also achieve high-precision detection like the off-axis system, so it has very outstanding practical value.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fiber-optic coaxial laser radar, comprising a coaxial transceiver system consisting of a laser, a circulator, a scanning system and a detector, characterized in that; The fiber-optic laser radar also includes a spatial light chopper and a signal noise reduction module; The spatial optical chopper is installed at the output end of the telescope in the coaxial transceiver system; the spatial optical chopper is used to adjust the continuity of the external signal entering the telescope, so that the detector receives the original echo signal containing two signal components at different time periods within a complete signal cycle T; one signal component a contains the external signal, and the other signal component b does not contain the external signal; The signal noise reduction module is used to first separate the original echo signal into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b; then, by resampling, the first discrete signal and the second discrete signal are extended from a short period to a complete period, thereby obtaining a first extended signal and a second extended signal; and then, the first extended signal and the second extended signal are time-axis aligned according to the timestamps of the signal components; After alignment, the first extended signal and the second extended signal are differentially processed to obtain an echo signal with crosstalk noise filtered out.

2. The optical fiber coaxial laser radar according to claim 1, characterized in that: When part of the period of the original echo signal is filtered out due to interference during sampling, the signal noise reduction module first uses an interpolation algorithm to fill in the missing data in the part of the period of the filtered signal after obtaining the first extended signal and the second extended signal, and then performs time axis alignment and difference processing on the first extended signal and the second extended signal; The order of the signals after alignment difference and interpolation completion is not fixed.

3. The optical fiber coaxial laser radar according to claim 2, characterized in that: The circulator includes port 1, port 2 and port 3; port 1 and port 2 of the circulator are respectively connected to the laser and the telescope, forming the signal transmitting part of the coaxial transceiver system; port 2 and port 3 of the circulator are respectively connected to the telescope and the detector, forming the signal receiving part of the coaxial transceiver system.

4. The optical fiber coaxial laser radar according to claim 1, characterized in that: The circulator transmits optical signals through optical fibers; the signal between port 1 and port 2 of the circulator is transmitted unidirectionally from 1 to 2; the signal between port 2 and port 3 is transmitted unidirectionally from 2 to 3.

5. The optical fiber coaxial laser radar according to claim 1, characterized in that: The telescope is used to collimate and expand the laser beam emitted by the laser device, and at the same time receive the echo signal of the detection target; the scanning system is used to adjust the emission direction of the collimated laser beam emitted by the telescope, and then align it with the target area to be detected.

6. The optical fiber coaxial laser radar according to claim 1, characterized in that: An optical switch and a filter are also provided between the port 3 of the circulator and the detector; the optical switch is used to modulate the optical signal transmitted to the detector; and the filter is used to filter the optical signal input to the detector.

7. A method for eliminating crosstalk noise of a fiber-optic coaxial laser radar, characterized in that: The steps include: S1: Install a spatial optical chopper at the telescope output end of the fiber-optic coaxial laser radar; S2: Presetting the chopping frequency of the spatial optical chopper according to the frequency of the original echo signal of the optical fiber coaxial laser radar, so that each signal period T of the original echo signal is divided into at least two sub-periods, and the spatial optical chopper switches between the on mode and the off mode in two adjacent sub-periods respectively; S3: Obtain the original echo signal received by the detector of the optical fiber coaxial laser radar, define that in each cycle of the original echo signal, the signal component a contains the external signal, and the signal component b does not contain the external signal; then perform the following noise reduction processing: S31: separating the original echo signal into a first discrete signal containing only signal component a and a second discrete signal containing only signal component b; S32: Extending the parts of the first discrete signal and the second discrete signal in each period from a short period to a complete period by resampling, thereby obtaining a first extended signal and a second extended signal; S33: aligning the time axis of the first extended signal and the second extended signal according to the timestamps of the signal components; S34: performing differential processing on the first extended signal and the second extended signal to obtain an echo signal with crosstalk noise filtered out.

8. The method for eliminating crosstalk noise of a fiber-optic coaxial laser radar as claimed in claim 7, characterized in that: When the original echo signal loses information within some periods after filtering, an interpolation algorithm is used before step S33 to supplement the missing data within some periods in the first extended signal and the second extended signal using information in adjacent periods, and then the time axis alignment of step S33 and the differential processing steps of step S34 are performed.

9. A noise reduction device for a fiber-optic coaxial laser radar, which is used to eliminate the crosstalk noise contained in the original echo signal received by the coaxial transceiver system of the fiber-optic coaxial laser radar; characterized in that: The noise reduction device includes a spatial light chopper and a signal noise reduction module, and the spatial light chopper and the signal noise reduction module are products corresponding to the fiber-optic coaxial laser radar as described in any one of claims 1-6.

10. A method for detecting atmospheric aerosols based on fiber-optic coaxial laser radar, characterized in that: The aerosol detection method detects and analyzes the distribution information of aerosols in the atmosphere by using a fiber-optic coaxial laser radar. The aerosol detection method includes the following steps: S01: Building the required aerosol detection system according to the hardware solution of the fiber-optic coaxial laser radar as described in any one of claims 1 to 6; S02: presetting system parameters of the aerosol detection system, and then performing preliminary detection; S03: Debugging the module parameters of the signal noise reduction module in the aerosol detection system according to the difference between the pre-detection result and the reference signal; S04: using the aerosol detection system debugged in the above step to perform real-time detection of atmospheric aerosols, and obtain a real-time echo signal with crosstalk noise filtered out; S05: Based on the real-time echo signal obtained in the previous step, the target characteristics of the aerosol in the atmosphere are obtained by inverting the preset aerosol distribution state physical model.

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