A method for self-calibration of focal length of coherent wind lidar telescope

Abstract

The present invention discloses a method for self-calibrating the focal length of a coherent wind laser radar telescope, comprising the following steps: (1) rapidly and continuously zooming the laser radar to collect echoes; (2) normalizing the echo signal curve; (3) determining the distance corresponding to the maximum value of the normalized signal; (4) determining the real telescope focal length according to the position of the signal maximum value; and (5) fitting to obtain a telescope zoom calibration curve. The present invention can quickly calibrate the relationship curve between the focal length of the laser radar telescope and the displacement of a focusing mechanism, thereby ensuring the rapid setting and effective recording of the real focal length and improving the measurement accuracy and stability of the laser radar system.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a zoom self-calibration method for a coherent wind-measuring laser radar telescope focal length. Background Art

[0002] In recent years, with the continuous development of lidar technology, some wind lidar systems have introduced automatic focal length adjustment functions, which adjust the focal length position through motor displacement, piezoelectric ceramic displacement, etc. These systems usually achieve automatic focal length adjustment by optimizing the signal strength at the target distance. However, this adjustment strategy based on the optimization method has the following shortcomings: 1. The focal length position cannot be recorded: The current automatic adjustment strategy only focuses on the optimization of the signal strength at the target, and cannot record the specific position of the focal length in real time. This brings inconvenience to subsequent data processing and system maintenance. 2. Lack of calibration of the relationship between focusing displacement and focal length: During the adjustment of the telescope focal length, the relationship curve between the focusing mechanism (such as motor displacement, piezoelectric ceramic displacement, etc.) and the actual focal length has not been clearly calibrated. This relationship curve is crucial for calibrating the lidar echo signal and accurately inverting the aerosol backscattering coefficient. In addition, changes in environmental factors inside and outside the telescope (such as temperature, humidity, and mechanical vibration) often cause the relationship curve between the focusing mechanism and the actual focal length to shift. This shift will significantly affect the true focal length position and measurement accuracy of the lidar. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a zoom self-calibration method for the focal length of a coherent wind measurement lidar telescope, which is used to quickly calibrate the relationship curve between the telescope focusing displacement and the actual focal length, ensure the measurement accuracy and stability of the lidar system, and solve the problems existing in the background technology.

[0004] Technical solution: The zoom self-calibration method of a coherent wind laser radar telescope focal length described in the present invention comprises the following steps:

[0005] (1) Rapidly and continuously zoom in on the laser radar to collect echoes;

[0006] (2) Normalizing the echo signal curve;

[0007] (3) Determine the distance corresponding to the maximum value of the normalized signal;

[0008] (4) Determine the actual telescope focal length based on the position of the signal maximum value;

[0009] (5) The telescope zoom calibration curve is obtained by fitting.

[0010] Furthermore, step (1) is specifically as follows: Specifically as follows: the telescope system of the laser radar is set to a fast zoom mode, within a set displacement range Internal traversal focusing mechanism displacement; at each displacement position At the point, record the corresponding echo signal strength curve , where R represents the radial distance between the target echo and the laser radar, and i represents the serial number of the data recording time; the focusing mechanism includes a motor or piezoelectric ceramic device that can adjust the telescope's output laser wavefront; the signal acquisition accumulation time at each position is set according to the signal-to-noise ratio of the actual echo.

[0011] Further, step (2) is as follows: The curve at the moment is the reference curve, and the signal curves at all moments are normalized to the reference curve to calculate the relative signal strength. The formula is as follows:

[0012] ;

[0013] The reference curve is selected in the following way: Determine the maximum effective detection distance of the echo signal ; at a distance Search The maximum value of and determine the corresponding time is ; Traverse all echo signal curves, when there is a curve Satisfied in Within the distance range, When Heng is established, Determine it as the reference curve; otherwise, you need to set a larger zoom range and re-calibrate the zoom.

[0014] Furthermore, step (3) is as follows: for each normalized signal curve at time i , find the distance corresponding to its maximum value, and record it as ,Right now:

[0015] .

[0016] Furthermore, step (4) is as follows: First, according to the laser radar echo signal formula, the normalized signal maximum position is calculated Focal length of a real telescope The theoretical relationship curve between Invert the real telescope focal length ; Among them, the laser radar echo signal formula is expressed as:

[0017] ;

[0018] in , They are the constant parameters related to the lidar configuration; , represent the aerosol backscattering coefficient and atmospheric transmittance, respectively.

[0019] Furthermore, step (5) is as follows: normalize the signal curve The data that are all less than 1 are considered invalid focus displacement data. After removing all invalid data, the remaining valid data points are used. Polynomial fitting is performed to obtain the zoom calibration curve of the real focal length of the telescope.

[0020] The present invention provides a coherent wind laser radar telescope focal length zoom self-calibration system, comprising:

[0021] Acquisition module: used to collect echoes of laser radar with fast and continuous zoom;

[0022] Normalization module: used to normalize the echo signal curve;

[0023] Distance module: used to determine the distance corresponding to the maximum value of the normalized signal;

[0024] Focal length module: used to determine the real telescope focal length according to the signal maximum position;

[0025] Fitting module: used to fit the telescope zoom calibration curve.

[0026] An electronic device described in the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, any one of the methods for self-calibrating the focal length of a coherent wind laser radar telescope described in the present invention is implemented.

[0027] A storage medium described in the present invention stores a computer program, and when the computer program is executed by a processor, it implements any one of the methods for self-calibrating the focal length of a coherent wind laser radar telescope.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention calibrates the relationship curve between the coherent laser radar zoom displacement and the real telescope focal length, and records the real focal length position while achieving the optimal detection distance through real-time focusing. It is helpful to accurately calibrate the echo signal intensity and accurately invert parameters such as the aerosol backscattering coefficient. Self-calibration is achieved by utilizing the characteristic that the laser radar echo signal changes with distance, which is independent of external reference equipment and has the advantages of fast speed, high flexibility and high precision. The present invention is not affected by the aerosol concentration distribution, can adapt to changes in internal and external environments, can quickly and accurately calibrate the focal length relationship curve, and significantly improves the measurement accuracy and stability of the laser radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of the present invention;

[0030] Figure 2 is an example diagram of a laser radar echo signal curve of the present invention;

[0031] Figure 3 is an example diagram of a normalized echo signal curve of the present invention;

[0032] Figure 4 is an example diagram of the relationship between the focus displacement and the maximum position of the normalized signal curve of the present invention;

[0033] Figure 5 is an example diagram of a theoretical relationship curve between the signal peak position and the focal length of the telescope of the present invention;

[0034] Figure 6 It is an example diagram of the zoom calibration curve of the real focal length of the telescope of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a method for self-calibration of the focal length of a coherent wind laser radar telescope, comprising the following steps:

[0037] Step S1: The laser radar rapidly and continuously zooms to collect echoes. Specifically, point the laser radar telescope toward the clear sky without any building obstruction and keep the detection direction unchanged. Set the system to the fast zoom mode and set the displacement range of the zoom mechanism. , gradually adjust the displacement of the focusing mechanism within this range and make it traverse. The focusing mechanism includes but is not limited to devices such as motors or piezoelectric ceramics that can adjust the laser wavefront emitted by the telescope. At each displacement position At the point where the acquired echo signal strength curve is recorded , where R represents the radial distance between the target echo and the laser radar, and i represents the serial number of the data recording time. The signal acquisition accumulation time at each position is set according to the actual echo signal-to-noise ratio, and can be set to 0.1~10 seconds without loss of generality. Figure 2 The 1-second accumulated atmospheric echo signal intensity curve collected when the zoom range is between 0 and 60 a.u. is given. It can be seen that the shape of the curve changes due to the change in focal length.

[0038] Step S2, normalize the echo signal curve. The curve at the moment is the reference curve, and the signal curves at all moments are normalized to the reference curve to calculate the relative signal strength. The formula is as follows:

[0039] ;

[0040] The reference curve is selected in the following way: Determine the maximum effective detection distance of the echo signal ,like Figure 2 As shown, it is 4km; at a distance Search The maximum value of and determine the corresponding time is ; Traverse all echo signal curves, when there is a curve Satisfied in Within the distance range, When Heng is established, Otherwise, a larger zoom range needs to be set and zoom calibration needs to be performed again. Figure 3 As shown in the figure, an example of a normalized echo signal curve is shown. After normalization, the echo changes caused by environmental factors such as aerosol distribution will be eliminated.

[0041] in, Figure 2 The curve in the figure represents the echo signal intensity curve of the laser radar detecting atmospheric aerosols. The curves of different colors represent the corresponding different focal length displacements, that is, the echo signal curves collected by the laser radar when the telescope focusing mechanism is at different focusing displacements. The specific focusing displacement value is represented by the color bar.

[0042] Figure 3 The curve in represents the relative intensity curve of the atmospheric echo signal after normalization of the reference curve. The curves of different colors represent the corresponding different focal length displacements, that is, the echo signal curves collected by the lidar when the telescope focusing mechanism is at different focusing displacements. The specific focusing displacement value is represented by the color bar.

[0043] Step S3, determine the distance corresponding to the maximum value of the normalized signal. For each normalized signal curve at time i , find the distance corresponding to its maximum value, and record it as ,Right now:

[0044] ;

[0045] like Figure 4 As shown, an example diagram of the relationship between the maximum position of the normalized echo signal curve and the displacement of the focusing system is given.

[0046] Step S4, determine the actual telescope focal length according to the signal maximum position. First, calculate the normalized signal maximum position according to the laser radar echo signal formula Focal length of a real telescope The theoretical relationship curve between Figure 5Then, the theoretical relationship curve is used to calculate the Invert the real telescope focal length Among them, the laser radar echo signal formula can be expressed as:

[0047] ;

[0048] in , They are the constant parameters related to the lidar configuration; , represent the aerosol backscattering coefficient and atmospheric transmittance, respectively.

[0049] Step S5, fitting to obtain the telescope zoom calibration curve. Data that are all less than 1 are considered invalid focus displacement data, such as Figure 4 The data points marked with × in the middle correspond to the cases of focal length divergence. After removing all invalid data, the remaining valid data points are used Polynomial fitting is performed to obtain the zoom calibration curve of the real focal length of the telescope. Figure 6 The zoom calibration curve fitted by a second-order polynomial is given in .

[0050] The present invention achieves real-time focusing and focal length recording by calibrating the relationship curve between the laser radar zoom displacement and the real focal length, thereby improving the accuracy of echo signal calibration and aerosol parameter inversion. This method does not require external reference equipment and uses the characteristics of the echo signal to complete self-calibration. It has the advantages of fast speed, strong flexibility and high precision. It can also adapt to different environmental changes and effectively improve the measurement accuracy and stability of the laser radar system.

[0051] The embodiment of the present invention further provides a focal length self-calibration system for a coherent wind laser radar telescope, comprising:

[0052] Acquisition module: used to collect echoes of laser radar with fast and continuous zoom;

[0053] Normalization module: used to normalize the echo signal curve;

[0054] Distance module: used to determine the distance corresponding to the maximum value of the normalized signal;

[0055] Focal length module: used to determine the real telescope focal length according to the signal maximum position;

[0056] Fitting module: used to fit the telescope zoom calibration curve.

[0057] An embodiment of the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, the method for self-calibration of the focal length of a coherent wind laser radar telescope as described in any one of the items is implemented.

[0058] An embodiment of the present invention further provides a storage medium storing a computer program. When the computer program is executed by a processor, the method for self-calibration of the focal length of a coherent wind laser radar telescope described in any one of the above is implemented.

Claims

1. A method for self-calibration of focal length of a coherent wind laser radar telescope, characterized in that: The following steps are involved: (1) Continuously zoom the laser radar to collect echoes; (2) Normalizing the echo signal curve; (3) Determine the distance corresponding to the maximum value of the normalized signal; (4) Determine the actual telescope focal length based on the signal maximum position; specifically: First, calculate the normalized signal maximum position based on the lidar echo signal formula: Focal length of a real telescope The theoretical relationship curve between Invert the real telescope focal length ; Among them, the laser radar echo signal formula is expressed as: ； in , They are the constant parameters related to the lidar configuration; , represent the aerosol backscattering coefficient and atmospheric transmittance, respectively; (5) The telescope zoom calibration curve is obtained by fitting. The details are as follows: the normalized signal curve The data that are all less than 1 are considered invalid focus displacement data. After removing all invalid data, the remaining valid data points are used. Polynomial fitting is performed to obtain the zoom calibration curve of the real focal length of the telescope.

2. The method for self-calibration of the focal length of a coherent wind laser radar telescope according to claim 1, characterized in that: Step (1) is as follows: Set the telescope system of the laser radar to zoom mode within the set displacement range. Internal traversal focusing mechanism displacement; at each displacement position At the point, record the corresponding echo signal strength curve , where R represents the radial distance between the target echo and the laser radar, and i represents the serial number of the data recording time; the focusing mechanism includes a motor or piezoelectric ceramic device that can adjust the telescope's output laser wavefront; the signal acquisition accumulation time at each position is set according to the signal-to-noise ratio of the actual echo.

3. The method for self-calibration of focal length of a coherent wind laser radar telescope according to claim 2, characterized in that: Step (2) is as follows: Select The curve at the moment is the reference curve, and the signal curves at all moments are normalized to the reference curve to calculate the relative signal strength. The formula is as follows: ； The reference curve is selected by: Determine the maximum effective detection distance of the echo signal ; at a distance Search The maximum value of and determine the corresponding time is ; Traverse all echo signal curves, when there is a curve Satisfied in Within the distance range, When Heng is established, Confirm as the reference curve; otherwise set the zoom range and re-calibrate the zoom.

4. The method for self-calibration of focal length of a coherent wind laser radar telescope according to claim 3, characterized in that: Step (3) is as follows: For each normalized signal curve at time i , find the distance corresponding to its maximum value, and record it as ,Right now: 。 5. A zoom self-calibration system for a coherent wind laser radar telescope focal length, characterized in that: include: Acquisition module: used to collect echoes of laser radar with continuous zoom; Normalization module: used to normalize the echo signal curve; Distance module: used to determine the distance corresponding to the maximum value of the normalized signal; Focal length module: used to determine the real telescope focal length according to the maximum signal position; the details are as follows: First, according to the lidar echo signal formula, calculate the maximum position of the normalized signal Focal length of a real telescope The theoretical relationship curve between Invert the real telescope focal length ; Among them, the laser radar echo signal formula is expressed as: ； in , They are the constant parameters related to the lidar configuration; , represent the aerosol backscattering coefficient and atmospheric transmittance, respectively; Fitting module: used to fit the telescope zoom calibration curve; the details are as follows: normalize the signal curve The data that are all less than 1 are considered invalid focus displacement data. After removing all invalid data, the remaining valid data points are used. Polynomial fitting is performed to obtain the zoom calibration curve of the real focal length of the telescope.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, the method for self-calibration of the focal length of a coherent wind laser radar telescope according to any one of claims 1 to 4 is implemented.

7. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a method for self-calibration of the focal length of a coherent wind laser radar telescope according to any one of claims 1 to 4 is implemented.

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