CN118501848A - Laser reflection point distance and azimuth calculating device and method for inner wall of wading space - Google Patents

Abstract

The present invention discloses a device and method for calculating the distance and azimuth of laser reflection points on the inner wall of a water-wading space. The device includes a vortex laser transceiver module for generating, transmitting and receiving vortex lasers, a control and information processing unit for performing echo data analysis and calculating the distance and azimuth of laser reflection points, a 360° rotating component for driving other components such as the vortex laser transceiver module to rotate, scan and collect information during the detection process, and an external watertight structure for waterproofing other internal components. The present invention utilizes a front-end optical structure to suppress the scattering noise caused by the propagation of laser beams through water, and divides the three-dimensional detection conditions inside the water-wading space into three conditions: three-dimensional detection of waterless sections, three-dimensional detection of full water sections and three-dimensional detection of local water accumulation sections, and respectively proposes methods for calculating the distance and azimuth of reflection points in full air links, full water links, and air-water-air links. The present invention has a wider scope of application and higher measurement accuracy.

Description

Device and method for calculating distance and orientation of laser reflection points on inner wall of wading space

Technical Field

The invention relates to a device and method for calculating the distance and orientation of laser reflection points on the inner wall of a wading space, belonging to the technical field of three-dimensional information perception.

Background Art

LiDAR scanning 3D detection technology can quickly obtain a 3D laser point cloud containing the surrounding scene by comparing the laser signal actively emitted to the outside with the received echo signal and calculating the distance and direction of the laser reflection point. It has the advantages of non-contact and fast scanning speed, and has been widely used in the acquisition of 3D point cloud data in various scenarios.

However, underground pipelines, tunnels, caves and other scenes may have different degrees of local water accumulation. In this scene, three-dimensional detection may pass through waterless sections, local water accumulation sections and full water sections. Especially in the local water accumulation section, the laser beam emitted by the lidar and its reflected beam will pass through two different media, air and water, and will be affected by reflection and refraction at the air-water interface and scattering interference of suspended particles in the water, resulting in changes in the optical path and propagation speed and the introduction of a large amount of backward noise in the echo signal, causing deviations in the calculation results of the distance and azimuth of the laser reflection point under the water, which will greatly reduce the accuracy of the three-dimensional point cloud coordinate solution. Therefore, it is of great significance to propose a lidar three-dimensional detection technology with a wider range of applications and higher measurement accuracy for accurate three-dimensional perception and safety status diagnosis of water-related spaces.

Summary of the invention

Purpose of the invention: The technical problem to be solved by the present invention is: to propose a device and method for calculating the distance and azimuth of laser reflection points on the inner wall of a water-wading space, to overcome the influence of signal attenuation, optical path and propagation speed change on laser ranging caused by air-water cross-medium transmission in the laser transmission and receiving optical path link, and to realize accurate calculation of laser point cloud coordinates inside a water-filled space with uncertainty.

The above purpose is achieved through the following technical solutions:

The present invention first provides a device for calculating the distance and azimuth of a laser reflection point on the inner wall of a wading space, the device comprising: a vortex laser transceiver module for generating, transmitting and receiving vortex lasers, a control and information processing unit for performing echo data analysis and calculating the distance and azimuth of laser reflection points, a 360° rotating component for driving other components such as the vortex laser transceiver module to rotate, scan and collect information during detection, and an external watertight structure for waterproofing other internal components; the vortex laser transceiver module comprises a vortex laser transmitting module and a vortex laser receiving module, the vortex laser transmitting module comprises a laser transmitting light source, a shaping system and a spiral phase plate 1 are sequentially arranged at the front end of the laser transmitting light source; the vortex laser receiving module comprises a receiving mirror, a filter, a spiral phase plate 2 and a shading plate, and is finally received by a photoelectric detector, the spiral phase plate 1 and the spiral phase plate 2 having the same structure; the shading plate is located on the central axis of the spiral phase plate 2.

Furthermore, the laser emission light source adopts a 905nm pulse laser; the filter adopts a 905nm filter.

Furthermore, in the vortex laser receiving module, the receiving mirror is composed of a receiving optical lens and an APD avalanche photodiode, the shading plate is placed in the central area of the photodetector receiving port, and the diameter of the shading plate is half the diameter of the vortex light beam, that is, L _la /2, where L _la represents the diameter of the vortex laser beam, and the data is obtained by multiple measurements and taking the average value.

The present invention also provides a method for calculating the distance and azimuth of the laser reflection point on the inner wall of the wading space by using the above-mentioned device for calculating the distance and azimuth of the laser reflection point on the inner wall of the wading space. The method is as follows: in the vortex laser emission module, the laser emitted by a 905nm pulse laser as the laser emission light source is shaped by the beam shaping system, and then the Gaussian laser is modulated into a vortex laser as a distance measurement emission light source through a spiral phase plate, and emitted to the periphery. The emitted laser enters the inner wall point of the wading space and the reflected echo signal is reflected to the vortex laser receiving module. After the receiving mirror in the vortex laser receiving module receives the reflected echo signal, it is filtered by a 905nm filter and then filtered by the spiral phase plate. The spiral phase plate 2 is of the same specification as the plate 1, and the returned noisy vortex laser is obtained. The central part of the vortex laser is blocked by a black shading sheet. The transmission characteristics of the vortex laser in the scattering medium are used to realize the spatial filtering of the backscattered echo of the water body, and then the filtered echo signal with a high signal-to-noise ratio is transmitted to the photoelectric detection system and is recognized and detected by the system. According to the intensity of the received echo signal, the type of optical path link composition of the current laser detection is judged; the echo signal is analyzed according to the type of optical path link composition to realize the distance and azimuth calculation of the laser reflection point; the three-dimensional reflection point coordinates around the echo signal reflected from the inner wall of the water bottom are calculated according to the time difference between the transmitted and received signals and the angle information of the rotating components to obtain a three-dimensional laser point cloud.

Furthermore, the method of judging the type of the optical path link composition of the current laser detection according to the received echo signal strength includes the following steps:

Assume that the echo signal strength is R, the two thresholds of the echo signal strength are {T _l , _Th } and T _l <_Th;

When R＞ _Th , the laser echo signal is strong, indicating that the current laser light path does not pass through the water body, and there is no water in the laser scanning area. Then the reflection point distance and azimuth solution method in the full air link is adopted;

When R＜T _l , it means that the laser is severely attenuated, indicating that the current laser optical path is all within the water body range, and the scanning area is full of water. The reflection point distance and azimuth solution method in the full water body link is adopted;

When T _l ＜R＜ _Th , it means that there is local water accumulation in the current scanning area. The laser passes through two media, air and water, during the propagation process, which causes partial attenuation of the laser signal. The distance and azimuth solution method of the reflection point in the air-water-air link is adopted.

Furthermore, the method for calculating the distance and azimuth of the reflection point in the all-air link is specifically calculated as follows: Assuming that the time of the laser beam emission is The receiving time of the echo signal is Calculate the time difference between laser emission and received signal The distance Dis ₁ = Td ₁ · _va between the reflection point and the vortex laser transceiver module is calculated using the propagation time v _a of the laser in the air medium. The direction of the reflection point is the rotation angle of the laser radar device. You can get the coordinates of the current reflection point

Furthermore, the method for calculating the distance and azimuth of the reflection point in the full water link is specifically calculated as follows: Assuming that the time of the laser beam emission is The receiving time of the echo signal is Calculate the time difference between laser emission and received signal The distance Dis ₂ = Td ₂ · v _b between the reflection point and the vortex laser transceiver module is calculated using the propagation time v _b of the laser in the water medium. The direction of the reflection point is the rotation angle of the laser radar device. You can get the coordinates of the current reflection point

Furthermore, the method for calculating the distance and azimuth of the reflection point in the air-water-air link adopts an echo signal decomposition method based on Gaussian fitting, which is as follows:

Two Gaussian functions are used to fit the water surface echo and the bottom echo respectively:

Wherein, N=2 is used to fit the surface signal and the underwater signal respectively, t is the time corresponding to the laser receiving module receiving the echo signal, α _i , μ _i , δ _i represent the intensity, position and pulse half-height width of the i-th Gaussian waveform classification respectively;

An objective function f _C is constructed and minimized to find the parameter values in the Gaussian function.

Among them, Y(t) is the original waveform of the echo signal obtained by the laser receiving module. The initial value of the Gaussian component is estimated according to the peak detection method, and then the Levenberg-Marquardt nonlinear recursive least squares method is used to solve the optimal solution of the parameters, and the Gaussian function fitting waveform function of the water surface echo signal is obtained respectively. And the Gaussian function fitting waveform function of the bottom echo signal And the time corresponding to the two echo peaks Assume that the laser beam is emitted at a time of The distance between the vortex laser three-dimensional detection device and the incident point on the water surface can be calculated based on the propagation speed of the laser in the air medium v _a and the water body v _b. Distance between the incident point and the reflection point on the inner wall below the water body

In addition, affected by the change of transmission medium, the refraction effect of laser at the air-water interface causes its transmission direction to be deflected. Given the incident angle of laser on the water surface _θa , the underwater refraction angle _θw , and the refraction factors of air and water _na and _nw , according to the Snell method, _sinθa n _a = _sinθw n _w , the angle between the current vortex laser transceiver module and the initial direction, that is, the vertical direction of the ground, is The laser emission angle is and but Directly calculate the distance value of the reflection point on the inner wall below the water body in the coordinate system of the laser transceiver as Dis ₃ = _Da + D _w and the azimuth angle as

Furthermore, under the refraction effect of air-water cross-medium propagation, according to The coordinates of the three-dimensional point P′ obtained by reverse positioning from the coordinate system of the laser transceiver cannot coincide with P, indicating that cross-medium refraction causes the positioning of the reflection point P on the inner wall of the bottom of the water body to shift in the coordinate system of the laser transceiver, affecting the accuracy of the three-dimensional coordinate solution of the reflection point. It is necessary to correct the distance measurement result and the current reflection point orientation according to the change of the refracted light path. The corrected distance of the reflection point on the inner wall below the water body can be derived according to the light propagation geometric model. With the corrected azimuth angle

You can get the coordinates of the current reflection point

Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention establishes three-dimensional coordinate measurement schemes for three different optical path link conditions: single air medium propagation, single water medium propagation, and air-water cross-medium propagation. The scheme is independently selected by judging the laser transmission optical path link condition according to the echo signal intensity. An interference elimination and error correction mechanism combining front-end optical control technology and back-end information processing technology is established to obtain high-precision laser three-dimensional point cloud of water-related space, which has high engineering application value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for calculating the distance and orientation of laser reflection points on the inner wall of a wading space;

FIG2 is a schematic diagram of the optical structure design of vortex laser three-dimensional detection inside a water-wading space;

FIG3 is a schematic diagram of the structure of a vortex laser transceiver module;

FIG4 is a schematic diagram of three types of laser three-dimensional detection optical path links in water-wading space;

FIG5 is a schematic diagram of a method for calculating the distance and azimuth of a reflection point in an air-water-air link.

DETAILED DESCRIPTION

The method for calculating the distance and orientation of the laser reflection point on the inner wall of a water-enclosed space of the present invention is as shown in FIG1 .

(1) First, a laser reflection point distance and orientation calculation device for the inner wall of a water-wading space of the present invention is constructed as shown in FIG2 . The device comprises:

The vortex laser transceiver module is used for generating, transmitting and receiving vortex lasers. As shown in FIG3 , the vortex laser transceiver module is further divided into a vortex laser transmitting module and a vortex laser receiving module. In the laser transmitting module, a 905nm pulse laser is used as the laser transmitting light source. After the transmitting laser is shaped by the shaping system, the Gaussian laser is modulated into a vortex laser as a ranging transmitting light source through the vortex phase plate and emitted to the periphery. The echo signal is reflected to the vortex laser receiving module, received by the receiving mirror, filtered by a 905nm filter, and then passed through a spiral phase plate of the same specification to obtain the returned noisy vortex laser. The center part of the vortex laser is blocked by a black shading sheet, and the transmission characteristics of the vortex laser in the scattering medium are used to realize the spatial filtering of the backscattered echo of the water body, and then the filtered echo signal with a high signal-to-noise ratio is transmitted to the photoelectric detection system and recognized and detected by the system, and the time difference between the echo signal and the transmitting signal is analyzed to calculate the distance and direction between the current transmitting laser device and the reflection point on the inner wall of the pipeline. The receiving mirror is composed of a receiving optical lens and an APD avalanche photodiode. The shading plate is placed in the central area of the photodetector receiving port, and the diameter of the shading plate is half of the diameter of the vortex light beam, that is, L _la /2, where L _la represents the diameter of the vortex laser beam. The data is obtained by multiple measurements and taking the average value.

Control and information processing unit, used to analyze echo data and calculate the distance and direction of the laser reflection point;

The 360° rotating component is used to drive the vortex laser transceiver module and other components to rotate and scan and collect information during the detection process:

The external watertight structure is a watertight shell made of highly light-transmitting material, which is used to provide waterproof protection for other internal components.

The operation process of the vortex laser three-dimensional detection optical structure inside the wading space is as follows: the 360° rotating component drives the vortex laser transceiver module, the vortex laser transmitting module sends the vortex laser and receives the echo signal, and calculates the coordinates of the surrounding three-dimensional reflection points according to the time difference between the transmitting and receiving signals, the angle of the rotating component and other information to obtain the three-dimensional laser point cloud.

(2) When using laser three-dimensional detection technology in water-related spaces, the optical path link may include the three situations shown in Figure 4.

Case 1: In the waterless section of space, the entire link of laser propagation and reflection reception is within the air range. The laser propagation speed in the full air link is consistent and there is almost no energy loss, with a strong echo signal.

Case 2: In the water-filled section of the space, the entire link of laser wave generation and reflection reception is within the water body, and the laser propagation speed is consistent. However, during the laser propagation process, it will be absorbed by the water body, causing energy attenuation, and the echo signal will be submerged by noise due to scattering interference from suspended particles in the water body.

Case 3: In the local wading section of space, the laser first propagates in the air, then irradiates the surface of the water body. When passing through the air-water interface, part of the laser is scattered and reflected, and is received by the receiving device to form a water surface echo; the remaining laser enters the water body and reaches the inner wall surface of the underground space below the water body; after diffuse reflection on the inner wall surface, the laser echo signal penetrates the water body again, passes through the water-air interface, and is received by the receiving device to form an underwater echo. Because the local silted water in the underground space usually has a certain turbidity and contains a large number of suspended particles. In the air-water-air link, the laser beam signal penetrates the water body twice. During the transmission process, it will be affected by energy attenuation caused by water absorption, confusion of water surface reflection signals, changes in light trajectory and propagation speed caused by cross-medium refraction between air and water, and noise caused by scattering of suspended particles in the water body. Therefore, the echo waveform of laser detection will include three parts: water surface echo, water backscattered echo, and bottom echo.

Since water will absorb and attenuate lasers to varying degrees, the laser reflection echo signal in the all-air link is the strongest, the laser reflection echo signal in the all-water link is the weakest, and the laser reflection echo signal intensity in the air-water-air link under water permeability is between the first two. The composition of the optical path link can be determined by detecting the intensity of the echo signal, providing a basis for autonomously selecting different reflection point azimuth and angle calculation methods.

After the laser is emitted, the laser echo signal is received by the receiving module. The echo signal strength is set to R, and two thresholds of the echo signal strength are set to {T _l , _Th }, and T _l < _Th .

(21) When R> _Th , the laser echo signal is strong, indicating that the current laser light path does not pass through the water body, and there is no water in the laser scanning area, then the reflection point azimuth and angle solution method of step 31) is adopted;

(22) When R < T _l , it means that the laser is severely attenuated, indicating that the current laser optical path is all within the water body range and the scanning area is full of water. The distance and azimuth solution method of the reflection point in the full water body link in step 32) is adopted;

(23) When T _l ＜R＜ _Th , it means that the laser passes through two media, air and water, during the propagation process, and there is partial attenuation. There is local water accumulation in the current scanning area. The distance and azimuth solution method of the reflection point in the air-water-air link in step 33) is adopted.

(3) According to the current scanning laser propagation link situation, the distance and azimuth of the reflection point are calculated respectively.

(31) Method for calculating the distance and azimuth of the reflection point in the all-air link. Assume that the time of the laser beam emission is The receiving time of the echo signal is Calculate the time difference between laser emission and received signal The distance between the reflection point and the laser transceiver is calculated using the propagation time v _a of the laser in the air medium: Dis ₁ = Td ₁ · v _a . The direction of the reflection point is the rotation angle of the laser radar device. You can get the coordinates of the current reflection point

(32) Method for calculating the distance and azimuth of the reflection point in the full water link. Assume that the time of the laser beam emission is The receiving time of the echo signal is Calculate the time difference between laser emission and received signal The distance Dis ₂ between the reflection point and the laser transceiver is calculated using the propagation time v _b of the laser in the water medium _. The direction of the reflection point is the rotation angle of the laser radar device _. You can get the coordinates of the current reflection point

(33) Method for calculating the distance and azimuth of reflection points in air-water-air links. In the case of water-penetrating three-dimensional detection, it is necessary to consider the different echo signals in the echo waveform caused by cross-medium transmission and the azimuth deviation caused by refraction when the laser penetrates the air-water interface. See Figure 5.

The distance between the laser transceiver in the water area and the reflection point on the inner wall of the space needs to be divided into two parts: the distance between the laser transceiver and the water surface incident point, and the distance between the incident point and the reflection point on the inner wall below the water body. It is necessary to further distinguish and extract the water surface echo signal and the bottom echo signal from the echo waveform.

The present invention adopts an echo signal decomposition method based on Gaussian fitting, and adopts two Gaussian functions to fit the water surface echo and the water bottom echo respectively.

Wherein, N=2 is used to fit the water surface signal and the underwater signal respectively, t is the time corresponding to the laser receiving module receiving the echo signal, and α _i , μ _i , δ _i represent the intensity, position and pulse half-width of the i-th Gaussian waveform classification respectively.

An objective function f _C is constructed and minimized to find the parameter values in the Gaussian function.

Among them, Y(t) is the original waveform of the echo signal obtained by the laser receiving module. The initial value of the Gaussian component is estimated according to the peak detection method, and then the Levenberg-Marquardt nonlinear recursive least squares method is used to solve the optimal solution of the parameters, and the Gaussian function fitting waveform function of the water surface echo signal is obtained respectively. And the Gaussian function fitting waveform function of the bottom echo signal And the time corresponding to the two echo peaks Assume that the laser beam is emitted at a time of The distance between the vortex laser three-dimensional detection device and the incident point on the water surface can be calculated based on the propagation speed of the laser in the air medium v _a and the water body v _b. Distance from incident point to reflection point on the inner wall below the water body

In addition, affected by the change of transmission medium, the refraction effect of laser at the air-water interface causes its transmission direction to be deflected. It is known that the incident angle of laser on the water surface is _θa , the underwater refraction angle is _θw , and the refraction factors of air and water are _na and _nw . According to the Snell method, it can be known that _sinθa n _a = _{sinθw nw} . The angle between the current vortex laser 3D detection device and the initial direction (vertical direction of the ground) is The laser emission angle is and but Directly calculate the distance value of the reflection point P on the inner wall below the water body in the coordinate system of the laser transceiver as Dis ₃ = _Da + D _w and the azimuth angle as However, under the refraction effect of air-water cross-medium propagation, according to The coordinates of the three-dimensional point P′ obtained by reverse positioning from the laser transceiver coordinate system cannot coincide with P, indicating that cross-medium refraction causes the positioning of the reflection point P on the inner wall of the bottom of the water body to shift in the laser transceiver coordinate system, affecting the accuracy of the three-dimensional coordinate solution of the reflection point. It is necessary to correct the distance measurement result and the current reflection point orientation according to the change in the refracted light path. The corrected distance of the inner wall reflection point under the water body can be derived based on the light propagation geometric model. With the corrected azimuth angle

You can get the coordinates of the current reflection point

Claims (8)

1. The utility model provides a wading space inner wall's laser reflection point distance and position solution device which characterized in that, this device includes: the device comprises a vortex laser receiving and transmitting module for generating, transmitting and receiving vortex laser, a control and information processing unit for analyzing echo data and resolving the distance and the direction of a laser reflection point, a 360-degree rotating component for driving other components such as the vortex laser receiving and transmitting module to rotationally scan and collect information in the detection process, and an external watertight structure for performing waterproof protection on the other components inside; the vortex laser receiving and transmitting module comprises a vortex laser transmitting module and a vortex laser receiving module, the vortex laser transmitting module comprises a laser transmitting light source, and a shaping system and a first spiral phase plate are sequentially arranged at the front end of the laser transmitting light source; the vortex laser receiving module comprises a receiving mirror, an optical filter, a spiral phase plate II and a shading sheet, and is finally received by the photoelectric detector, wherein the spiral phase plate I and the spiral phase plate II have the same structure; the shading sheet is positioned on the central shaft of the second spiral phase plate.

2. The laser reflection point distance and azimuth solving device for the inner wall of the wading space according to claim 1, wherein the laser emission light source adopts a 905nm pulse laser; the filter adopts a 905nm filter.

3. The device for resolving the distance and the azimuth of the laser reflection point on the inner wall of the wading space according to claim 1, wherein in the vortex laser receiving module, the receiving mirror is composed of a receiving optical lens and an APD avalanche photodiode, the light shielding sheet is arranged in the central area of the receiving opening of the photoelectric detector, the diameter of the light shielding sheet is half of the diameter of the vortex light beam, namely L _la/2, wherein L _la represents the diameter of the vortex laser beam, and the data are obtained through multiple measurement and averaging.

4. A method for calculating the distance and the azimuth of the laser reflection point of the inner wall of the wading space by using the device for calculating the distance and the azimuth of the laser reflection point of the inner wall of the wading space according to any one of claims 1 to 3, which is characterized in that the method comprises the following steps: in the vortex laser emission module, after laser emitted by using a 905nm pulse laser as a laser emission light source is shaped by a shaping system, gaussian laser is modulated into vortex laser serving as a ranging emission light source through a first spiral phase plate and emitted to the periphery, reflected echo signals of the inner wall points of a wading space are reflected to the vortex laser receiving module, a receiving mirror in the vortex laser receiving module receives the reflected echo signals and then filters the reflected echo signals through a 905nm optical filter, the reflected echo signals are filtered through a second spiral phase plate with the same specification as the first spiral phase plate, returned noise-containing vortex laser is obtained, the center part of the vortex laser is blocked by a black shielding sheet, the space filtering of backward scattered echoes of a water body is realized by using the transmission characteristic of the vortex laser in a scattering medium, the filtered echo signals with high signal to noise ratio are transmitted to a photoelectric detection system and are recognized and detected by the system, and the type of the current laser detected optical path condition of a link is judged according to the intensity of the received echo signals; echo signal analysis is carried out according to the optical path link composition condition type, so that the distance and azimuth calculation of the laser reflection point is realized; and calculating coordinates of three-dimensional reflection points around the echo signal reflected by the inner wall of the water bottom according to the time difference between the transmitted signal and the received signal and the angle information of the rotating part, so as to obtain the three-dimensional laser point cloud.

5. The method for calculating the distance and the azimuth of the laser reflection point on the inner wall of the wading space according to claim 4, wherein the method for determining the type of the current optical path link composition condition of the laser detection according to the intensity of the received echo signal comprises the following steps:

setting the intensity of the echo signal as R, two thresholds { T _l,T_h } of the intensity of the echo signal and T _l＜T_h;

When R is more than T _h, the laser echo signal is strong, which indicates that the current laser optical path does not pass through the water body, and no ponding exists in the laser scanning area, a method for resolving the distance and the azimuth of the reflection point in the all-air link is adopted;

When R is less than T _l, the laser is severely attenuated, the current laser optical path is completely in the water body range, the scanning area is full of the water body, and a method for resolving the distance and the azimuth of the reflection point in the full water body link is adopted;

when T _l＜R＜T_h shows that local ponding exists in the current scanning area, laser passes through two media of air-water body in the propagation process, partial attenuation is generated on the laser signal, and a method for resolving the distance and the azimuth of a reflection point in an air-water body-air link is adopted.

6. The method for calculating the distance and the azimuth of the reflecting point of the laser beam on the inner wall of the wading space according to claim 5, wherein the method for calculating the distance and the azimuth of the reflecting point in the all-air link is characterized in that the specific calculation process is as follows: assuming that the beam is emitted for a time ofThe echo signal receiving time isCalculating the time difference between laser emission and reception signalsCalculating the distance Dis ₁＝Td₁·v_a between the reflecting point and the vortex laser transceiver module by using the propagation time v _a of laser in the air medium, wherein the azimuth of the reflecting point is the rotation angle of the laser radar deviceThe coordinates of the current reflection point can be obtained

7. The method for calculating the distance and the azimuth of the reflecting point of the laser on the inner wall of the wading space according to claim 5, wherein the method for calculating the distance and the azimuth of the reflecting point in the all-water link is characterized by comprising the following specific calculation process: assuming that the beam is emitted for a time ofThe echo signal receiving time isCalculating the time difference between laser emission and reception signalsCalculating the distance Dis ₂＝Td₂·v_b between the reflecting point and the vortex laser transceiver module by using the propagation time v _b of laser in the water medium, wherein the azimuth of the reflecting point is the rotation angle of the laser radar deviceThe coordinates of the current reflection point can be obtained

8. The method for calculating the distance and the azimuth of the laser reflection point on the inner wall of the wading space according to claim 5, wherein the method for calculating the distance and the azimuth of the reflection point in the air-water-air link is characterized in that an echo signal decomposition method based on Gaussian fitting is adopted in the specific calculation process, and specifically comprises the following steps:

Fitting the water surface echo and the water bottom echo respectively by adopting 2 Gaussian functions:

Wherein n=2 to fit the water surface signal and the underwater signal respectively, t is the time corresponding to the echo signal received by the laser receiving module, and α _i、μ_i、δ_i represents the intensity, position and pulse half-width of the ith gaussian waveform classification respectively;

An objective function f _C is constructed and minimized to solve for the parameter values in the gaussian.

Wherein Y (t) is an original waveform of the echo signal obtained by the laser receiving module, initial value estimation of a Gaussian component is set according to a peak detection method, and an optimal solution of parameters is solved by using a Levenberg-Marquardt nonlinear recursion least square method to respectively obtain a Gaussian function fitting waveform function of the echo signal of the water surfaceGaussian function fitting waveform function of underwater echo signalTime corresponding to two echo wave peaksAssuming that the beam is emitted for a time ofThe distance between the vortex laser three-dimensional detection device and the water surface incidence point can be obtained according to the propagation speed v _b of the laser in the air medium v _a and the water bodyIncident point-inner wall reflection point distance below water body

In addition, under the influence of the change of a transmission medium, the transmission direction of the laser is deflected by the refraction effect of the laser at an air-water body interface, the angle of incidence theta _a of the laser on the water surface, the underwater refraction angle theta _w and the refraction factor n _a、n_w of the air and the water body are known, sin theta _an_a＝sinθ_wn_w is known according to the Snell method, and the angle between the current vortex laser receiving and transmitting module and the initial direction, namely the ground vertical direction isThe laser emission angle is alsoAnd is also provided withThenDirectly calculating the distance value Dis ₃＝D_a+D_w and azimuth angle of the inner wall reflection point below the water body in the coordinate system of the laser transceiver

Further, under the refraction of air-water propagating across the medium, according toThe point coordinates of the three-dimensional point P' obtained by reverse positioning in the coordinate system of the laser receiving and transmitting device cannot coincide with the point coordinates P, which shows that the positioning of the reflecting point P of the inner wall at the bottom of the water body in the coordinate system of the laser receiving and transmitting device is offset due to cross-medium refraction, the three-dimensional coordinate resolving precision of the reflecting point is affected, the ranging result and the current reflecting point azimuth are required to be corrected according to the refraction ray path change, and the correction distance of the reflecting point of the inner wall below the water body can be deduced according to the ray propagation geometric modelAnd correcting azimuth angle

The coordinates of the current reflection point can be obtained