CN118501848A - Laser reflection point distance and azimuth calculating device and method for inner wall of wading space - Google Patents
Laser reflection point distance and azimuth calculating device and method for inner wall of wading space Download PDFInfo
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Abstract
The invention discloses a laser reflection point distance and azimuth solving device and method for the inner wall of a wading space. 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 rotate and scan and collect information in the detection process, and an external watertight structure for carrying out waterproof protection on other components in the device. The invention utilizes a front-end optical structure to inhibit scattered noise caused by the water-permeable propagation of laser beams, and divides the three-dimensional detection condition in the wading space into three conditions of anhydrous section three-dimensional detection, full water section three-dimensional detection and local water section three-dimensional detection, and respectively provides reflection point distance and azimuth resolving methods in all-air links, all-water links and air-water-air links. The invention has wider application range and higher measurement precision.
Description
Technical Field
The invention relates to a laser reflection point distance and azimuth calculating device and method for the inner wall of a wading space, and belongs to the technical field of three-dimensional information perception.
Background
The laser radar scanning three-dimensional detection technology can rapidly obtain the three-dimensional laser point cloud containing peripheral scenes by comparing the externally actively emitted laser signals with the received echo signals and resolving the distance and the azimuth of the laser reflection points, has the advantages of non-contact, high scanning speed and the like, and has been widely applied to three-dimensional point cloud data acquisition of various scenes.
However, local ponding conditions of varying degrees may occur in scenes such as underground pipes, tunnels, caverns, etc. In the scene, three-dimensional detection is performed, and laser beams emitted by the laser radar and reflected beams thereof possibly pass through two different media of air and water through a water-free section, a local water-accumulating section and a water-full section, and are influenced by reflection and refraction at an air-water interface and scattering interference of suspended particles in water, so that an optical path and a propagation speed are changed, a large amount of backward noise in an echo signal is introduced, deviation occurs between a distance of a laser reflection point below the water body and an azimuth calculation result, and the three-dimensional point cloud coordinate calculation precision is greatly reduced. Therefore, the laser radar three-dimensional detection technology with wider application range and higher measurement precision is provided, and has important significance for accurate three-dimensional perception and safety state diagnosis of wading space.
Disclosure of Invention
The invention aims to: the technical problems to be solved by the invention are as follows: the device and the method for resolving the distance and the azimuth of the laser reflection point on the inner wall of the wading space overcome the influence of signal attenuation, optical path and propagation speed change on laser ranging caused by air-water cross-medium transmission in a laser transmission and reception optical path link, and realize the accurate resolving of the laser point cloud coordinates in the uncertainty ponding space.
The above purpose is achieved by the following technical scheme:
The invention provides a laser reflection point distance and azimuth calculating device for the inner wall of wading space, which comprises: 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.
Further, the laser emission light source adopts a 905nm pulse laser; the filter adopts a 905nm filter.
Further, 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 port of the photoelectric detector, the diameter of the light shielding sheet is half of the diameter of the vortex laser 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 average.
The invention also provides a method for solving the distance and the azimuth of the laser reflection point of the inner wall of the wading space by the device, which 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.
Further, the method for judging the type of the current optical path link composition condition of the laser detection according to the received echo signal intensity comprises the following steps:
setting the intensity of the echo signal as R, two thresholds { T l,Th } of the intensity of the echo signal and T l＜Th;
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＜Th 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.
Further, the method for resolving the distance and the azimuth of the reflecting point in the all-air link comprises the following specific resolving 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 1＝Td1·va 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
Further, the method for calculating the distance and the azimuth of the reflecting point in the all-water link comprises the following specific calculation processes: 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·vb 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
Further, the method for resolving the distance and the azimuth of the reflecting point in the air-water-air link adopts an echo signal resolving method based on Gaussian fitting in the concrete resolving process, and the method 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、μi、δi 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、nw of the air and the water body are known, sin theta ana＝sinθwnw 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＝Da+Dw 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
Compared with the prior art, the invention has the beneficial effects that: according to the method, a three-dimensional coordinate measuring and calculating scheme of three different optical path link conditions including single air medium transmission, single water medium transmission and air-water cross-medium transmission is established, the optical path link condition of laser transmission is judged according to the intensity of echo signals, the scheme is selected autonomously, an interference elimination and error correction mechanism combining a front-end optical regulation technology and a rear-end information processing technology is established, a high-precision laser three-dimensional point cloud of a wading space is obtained, and the method has high engineering application value.
Drawings
FIG. 1 is a flow chart of a method for resolving the distance and direction of a laser reflection point on the inner wall of a wading space;
FIG. 2 is a schematic diagram of a three-dimensional detection optical structure of vortex laser inside a wading space;
FIG. 3 is a schematic diagram of a vortex laser transceiver module;
FIG. 4 is a schematic diagram of three types of laser three-dimensional detection optical path links in wading space;
fig. 5 is a schematic diagram of a method for resolving distances and directions of reflection points in an air-water-air link.
Detailed Description
The method for resolving the distance and the azimuth of the laser reflection point on the inner wall of the wading closed space is shown in figure 1.
(1) First, the laser reflection point distance and azimuth calculating device for the inner wall of the wading space of the present invention is constructed as shown in fig. 2, and comprises:
And the vortex laser receiving and transmitting module is used for generating, transmitting and receiving vortex laser. As shown in fig. 3, the vortex laser transceiver module is further divided into a vortex laser transmitting module and a vortex laser receiving module. In the laser emission module, a 905nm pulse laser is used as a laser emission light source, after the emitted laser is shaped to a beam by a shaping system, gaussian laser is modulated into vortex laser which is used as a ranging emission light source through a vortex phase plate, and the vortex laser is emitted to the periphery. The method comprises the steps of reflecting echo signals to a vortex laser receiving module, filtering the echo signals through a 905nm optical filter after the echo signals are received by a receiving mirror, enabling the echo signals to pass through a spiral phase plate with the same specification, obtaining returned vortex laser containing noise, blocking the center of the vortex laser by using a black shading sheet, realizing space filtering of backward scattered echoes of a water body by using the transmission characteristic of the vortex laser in a scattering medium, transmitting the filtered echo signals with high signal-to-noise ratio to a photoelectric detection system, identifying and detecting the echo signals by the system, analyzing the time difference between the echo signals and the transmitted signals, and calculating the distance and the azimuth between a current transmitted laser device and a reflection point on the inner wall of a pipeline. 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 port of the photoelectric detector, the diameter of the light shielding sheet is half of the diameter of the vortex laser 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 average value.
The control and information processing unit is used for analyzing echo data and resolving the distance and the azimuth of the laser reflection point;
360 rotating component for driving other components such as vortex laser transceiver module and rotatory scanning acquisition information in the detection process:
The outside watertight structure is the watertight shell of high printing opacity material preparation for carry out waterproof protection to other subassemblies in the inside.
The operation process of the vortex laser three-dimensional detection optical structure in the wading space is as follows: the 360-degree rotating component drives the vortex laser receiving and transmitting module, the vortex laser transmitting module transmits vortex laser and receives a wave-back signal, and the coordinates of the peripheral three-dimensional reflection points are calculated according to the time difference between the transmitted and received signals, the angle of the rotating component and other information, so that the three-dimensional laser point cloud is obtained.
(2) The laser three-dimensional detection technology is adopted in the wading space, and the optical path link of the laser three-dimensional detection technology can comprise three conditions as shown in fig. 4.
Case 1: in the space anhydrous section, the laser propagation and reflection receiving all links are in the air range, the laser propagation speed in the all-air link is consistent, the energy is almost free from loss, and the laser has a stronger echo signal.
Case 2: in the full water section of the space, the laser wave generation and reflection receiving full links are in the water body range, the laser propagation speed is consistent, but the laser propagation process is subjected to energy attenuation caused by water body absorption and echo signals are submerged by noise caused by scattering interference of suspended particles in the water body.
Case 3: in the space local wading section, laser firstly propagates in air and irradiates on the surface of a water body, and when the laser passes through an air-water body interface, part of the laser is scattered and reflected and is received by a receiving device to form a water surface echo; the residual laser enters the water body and reaches the inner wall surface of the underground space below the water body; after diffuse reflection occurs on the surface of the inner wall, the laser echo signal penetrates through the water body again, and is received by the receiving device through the water body-air interface to form an underwater echo. Because of the turbidity typically present in locally stagnant water in subterranean spaces, it contains a large number of suspended particles. In an air-water-air link, laser beam signals penetrate through water twice, and the problems of energy attenuation caused by water absorption, confusion of water surface reflection signals, light ray track and propagation speed change caused by air-water cross-medium refraction, noise caused by water suspended particles and the like are caused in the transmission process. Thus, the echo waveform of the laser detection will contain three parts, a water surface echo, a water body back-scatter echo and a water bottom echo.
Because the water body absorbs and attenuates the laser to different degrees, the laser reflection echo signal in the all-air link is strongest, the laser reflection echo signal in the all-water link is weakest, and the laser reflection echo signal intensity in the air-water-air link under the water permeability condition is between the two. The composition condition of the optical path link can be judged by detecting the intensity of the echo signals, and a basis is provided for autonomously selecting different reflection point azimuth and angle resolving methods.
After laser emission, the laser echo signals are received through the receiving module, and the echo signal intensity is set to be R, two thresholds { T l,Th } of the echo signal intensity and T l＜Th.
(21) 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, no ponding exists in the laser scanning area, and a reflection point azimuth and angle resolving method of 31) is adopted;
(22) 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 filled with the water body, and the method for resolving the distance and the azimuth of the reflection point in the all-water-body link in the step 32) is adopted;
(23) When T l＜R＜Th, the laser passes through two media of air-water body in the propagation process, partial attenuation exists, partial water accumulation exists in the current scanning area, and the method for resolving the distance and the azimuth of the reflection point in the air-water body-air link in the step 33) is adopted.
(3) And respectively calculating the distance and the azimuth of the reflection point according to the current scanning laser propagation link condition.
(31) A method for calculating the distance and azimuth of reflecting point in all-air link. 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·va between the reflecting point and the laser transceiver by using the propagation time v a of the 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
(32) A method for calculating the distance and azimuth of a reflecting point in an all-water link. 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·vb between the reflection point and the laser transceiver by using the propagation time v b of the laser in the water medium, wherein the azimuth of the reflection point is the rotation angle of the laser radar deviceThe coordinates of the current reflection point can be obtained
(33) A method for calculating the distance and direction of reflecting point in air-water-air link. Under the condition of water-permeable three-dimensional detection, the situation of azimuth deviation caused by refraction when different echo signals exist in echo waveforms caused by cross-medium transmission and laser penetrates through an air-water body interface needs to be considered. As shown in fig. 5.
The distance between the laser transceiver and the reflecting point of the inner wall of the space in the water body area is divided into two parts, namely the distance between the laser transceiver and the incident point of the water surface and the distance between the incident point and the reflecting point of the inner wall below the water body, and the echo signals of the water surface and the echo signals of the water bottom are required to be further distinguished and extracted from echo waveforms.
The invention adopts an echo signal decomposition method based on Gaussian fitting. The water surface echo and the water bottom echo were fitted separately using 2 gaussian functions.
Wherein n=2 is used 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、μi、δi represents the intensity, the position and the 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 the original waveform of the echo signal obtained by the laser receiving module. Setting initial value estimation of Gaussian components according to a peak detection method, and then utilizing an optimal solution of a Levenberg-Marquardt nonlinear recursion least square method solving parameter to respectively obtain a water surface echo signal Gaussian function fitting waveform functionGaussian 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, the refraction effect of the laser at the air-water interface deflects the transmission direction under the influence of the change of the transmission medium. The incidence angle θ a of the laser on the water surface, the underwater refraction angle θ w, and the refractive index n a、nw of air and water are known, and sin θ ana＝sinθwnw is known from the Snell method. The angle between the current vortex laser three-dimensional detection device and the initial direction (the vertical direction of the ground) isThe laser emission angle is alsoAnd is also provided withThenDirectly calculating the distance value Dis 3＝Da+Dw and azimuth angle of the inner wall reflection point P below the water body in the coordinate system of the laser transceiverHowever, under the refraction of air-water propagating across the medium, according toThe coordinate 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 P, which shows that the positioning of the reflecting point P on the inner wall of the water body bottom 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, and the ranging result and the current reflecting point azimuth are required to be corrected according to the refractive ray path change. The correction distance of the reflection point of the inner wall below the water body can be deduced according to the light propagation geometric modelAnd correcting azimuth angle
The coordinates of the current reflection point can be obtained
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,Th } of the intensity of the echo signal and T l＜Th;
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＜Th 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·va 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·vb 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、μi、δi 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、nw of the air and the water body are known, sin theta ana＝sinθwnw 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＝Da+Dw 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
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