An underwater elastic scattering laser radar system

Abstract

The present invention relates to the field of underwater laser detection, and in particular to an underwater elastic scattering laser radar system, comprising: a hoisting component, which is arranged on a water carrier; an elastic scattering laser radar component, which comprises a sealed cabin, a laser fixed in the sealed cabin, and a signal receiving component; the hoisting component is connected to the elastic scattering laser radar component through a cable, and is used to adjust the underwater depth of the elastic scattering laser radar component, and the central axis of the laser optical axis of the laser is arranged at an angle to the central axis of the receiving field of view of the signal receiving component; without changing the field of view angle of the receiving lens, the profile test of underwater elastic backscattering signals in the upper layer of the ocean or even deeper waters is met, and at the same time, the blind area is greatly reduced, meeting the needs of underwater detection.

Description

Technical Field

[0001] The invention relates to the field of underwater laser detection, and in particular to an underwater elastic scattering laser radar system. Background Art

[0002] Elastic scattering lidar has been widely used in the study of meteorology, environmental pollution and atmospheric dynamics. Based on this, researchers considered using elastic scattering lidar for ocean research and achieved success. Ocean elastic scattering lidar can detect pelagic fish and zooplankton. Thanks to the development of inversion algorithms, it is also used to invert the inherent optical properties of seawater and study the scattering layer of marine phytoplankton and its generation mechanism. With the deepening of research, the application potential of ocean elastic scattering lidar has gradually been tapped.

[0003] At present, ocean elastic scattering lidar can be carried on satellites, aircraft and ships. For example, the CALIPSO satellite equipped with the satellite-borne lidar CALIOP was launched in 2006 by the National Aeronautics and Space Administration (NASA) of the United States and the French National Space Center. It has obtained ten years of vertical distribution data of global cloud and aerosol types. Its data has also been used in the testing of marine life and ocean optical parameters, providing important information for the study of global climate and environmental changes. In 2006, the Ocean University of China successfully developed my country's first airborne ocean lidar system for remote sensing measurement of chlorophyll a concentration in the ocean surface. In 2017, Zhejiang University developed a ship-borne ocean lidar for detecting the vertical profile of seawater optical parameters, and conducted experimental measurements in the Yellow Sea. "Ocean lidar inversion of water optical parameters"; In 2018, the Shanghai Institute of Optics and Fine Mechanics and the Second Institute of Oceanography of the Ministry of Natural Resources used the Mapper5000 airborne lidar to conduct three flight tests in Sanya Bay, South China Sea, successfully detecting the plankton layer within a water depth of 50m, and obtaining the spatial distribution and seasonal changes of the sub-surface plankton layer in Sanya Bay.

[0004] "Subsurface plankton layers observed from airborne lidar in SanyaBay".

[0005] In order to meet the needs of longer distance and deeper water depth testing, the existing elastic scattering laser radar technology uses high-power lasers and large-aperture receiving lenses, resulting in large system size and weight. In addition, in order to achieve long-distance measurement, satellite-borne, airborne and ship-borne elastic scattering laser radars generally use the method of parallel detection of the laser emission optical axis and the receiving lens optical axis. The detection blind area is relatively large, with a minimum of about ten meters and a maximum of several kilometers. However, since the blind area is located in the water area, it has no effect on the underwater detection results. Therefore, the existing elastic scattering laser radar does not need to consider the impact of the blind area.

[0006] Due to the strong absorption and scattering of lasers by seawater, lasers decay exponentially rapidly in water. In order to increase the measurement depth, a high-power laser with a large-aperture receiving lens is required. Despite this, it is still difficult for ocean elastic scattering lidars to measure depths greater than 100m underwater. The maximum measurement depth of most ocean elastic scattering lidars is between 70m and 80m, which is far from meeting the testing and research needs of the upper ocean (200m). In addition, in the process of building the inversion model, there are many interference factors such as complex sea surface waves, foam, and sea surface reflections. For the detection of the upper 200m of the ocean, the method of fixed-point measurement using a water body inherent optical property measuring instrument is generally used. The measurement process is complicated, and the measurement data is very limited and not continuous.

[0007] In order to meet the testing and research needs of the upper ocean (200m), an underwater elastic scattering laser radar system is developed to achieve testing from the water surface to 200m underwater or even deeper. However, based on the existing technology, the sealed cabin is directly sealed. On the one hand, the underwater elastic scattering laser radar system will be huge in size and weight. On the other hand, since the test blind areas of the underwater elastic scattering laser radar are all located underwater, they occupy a large part of the laser radar measurement distance, which will result in very limited effective test distance and effective data, which cannot meet the needs of actual testing and research.

[0008] Therefore, it is an urgent problem to develop a miniaturized underwater elastic scattering lidar system that can significantly reduce the test blind area without affecting the detection distance of the lidar. Summary of the invention

[0009] In view of the deficiencies existing in the above-mentioned prior art, the present invention provides a miniaturized underwater elastic scattering laser radar system which meets the requirements of underwater work and greatly reduces the test blind area.

[0010] The present invention provides an underwater elastic scattering laser radar system, comprising:

[0011] A hoisting assembly is installed on a water transport device;

[0012] An elastic scattering laser radar component comprises a sealed cabin, a laser fixed in the sealed cabin, and a signal receiving component, wherein the signal receiving component is used to receive a back elastic scattering signal of a laser beam of the laser within its receiving field of view and complete data acquisition;

[0013] The signal receiving component includes a receiving lens, a photoelectric detection module, and a data acquisition module;

[0014] The hoisting assembly is connected to the elastic scattering laser radar assembly through a cable, and is used to adjust the underwater depth of the elastic scattering laser radar assembly.

[0015] Among them, the central axis of the laser optical axis of the laser is set at an angle with the central axis of the receiving field of view of the receiving lens, and the blind area formed at this time is smaller than the blind area formed when the laser optical axis of the elastic scattering laser is parallel to the central axis of the receiver.

[0016] The underwater elastic scattering laser radar system of this technical solution is miniaturized and sealed by a sealed cabin. The laser optical axis is designed to be at an angle to the receiving lens of the receiving lens. Without changing the field of view of the receiving lens, it can meet the profile test of underwater elastic backscattering signals in the upper ocean and even deeper waters, while greatly reducing blind spots and meeting the needs of underwater detection.

[0017] In some embodiments of the present application, in the elastic scattering laser radar component, the signal receiving component is vertically arranged underwater, the laser is tilted toward the central axis of the receiving lens, and the tilt angle of the laser is determined according to the detection depth.

[0018] In some embodiments of the present application, the receiving lens is parallel to the laser and both are vertically arranged underwater. The laser and / or the receiving lens are provided with a reflector. After the laser optical axis of the laser is reflected by the reflector at least once, it is arranged at an angle with the central axis of the receiving lens.

[0019] In some embodiments of the present application, a transition zone is formed between the laser optical axis and the field of view of the receiving lens. The transition zone is smaller than the transition zone formed when the laser optical axis of the elastic scattering laser is parallel to the central axis of the receiver, and the signal in the transition zone needs to be corrected for the overlap factor.

[0020] In some embodiments of the present application, the underwater elastic scattering laser radar system also includes a control terminal, which is arranged on the water and connected to the elastic scattering laser radar component through a watertight cable. The control terminal is used to control the laser and receive and process in real time the test data received and collected by the signal receiving component.

[0021] In some embodiments of the present application, a measurement method of the above-mentioned underwater elastic scattering laser radar system is also provided, comprising the following steps:

[0022] S1. Determine the tilt angle of the laser:

[0023] According to the preset detection depth, the inclination angle between the laser optical axis of the laser and the central axis of the receiving lens is calculated, and the laser and the receiving lens are fixedly arranged in the sealed cabin according to the calculated inclination angle;

[0024] S2. Lower the elastic scattering laser radar assembly to the preset depth:

[0025] The hoisting assembly lowers the elastic scattering laser radar assembly to a preset depth by lowering the cable and the watertight cable;

[0026] S3, elastic scattering laser radar component for detection:

[0027] The control terminal controls the laser and the signal receiving component to start, and at the same time, the control terminal receives the data received and collected by the signal receiving component, and saves and processes the data;

[0028] S4. End of test:

[0029] After the test is completed, the control terminal controls the laser and the signal receiving component to turn off, and the hoisting component recovers the cable and the watertight cable, and recovers the elastic scattering laser radar component to the water transport equipment.

[0030] In some embodiments of the present application, in step S1, the relationship between the tilt angle of the laser and the measured depth is:

[0031] R×θ1+D+K=R×(θ+θ2) (1)

[0032] Where R is the measurement depth,

[0033] θ is the angle between the laser optical axis of the laser and the central axis of the receiving lens, that is, the tilt angle of the laser;

[0034] D is the lens aperture of the receiving lens;

[0035] K is the shortest distance between the edge of the lens aperture of the receiving lens and the edge of the laser outlet of the laser;

[0036] θ1 is the half field of view angle of the receiving lens in water;

[0037] θ2 is the half divergence angle of the laser in water;

[0038] When the specifications of the receiving lens and the laser are determined, D, K, θ1, and θ2 are all fixed values.

[0039] Based on the above technical scheme, the underwater elastic scattering laser radar system of the present invention can effectively make up for the shortcomings of insufficient test depth of satellite-borne, airborne and ship-borne laser radars. The elastic scattering laser radar components are lifted and placed deep underwater. The test depth is controllable and can fully cover the test and research needs of the upper ocean (200m), and can even reach a test depth of several hundred meters to thousands of meters.

[0040] Design a certain angle between the laser optical axis of the laser and the central axis of the receiving lens field of view, which greatly reduces the blind area and significantly increases the effective data of the laser radar test while ensuring the detection distance of the laser radar.

[0041] Compared with realizing low blind spot testing by increasing the field of view of the receiving lens, the stray light noise of the present application is small and the signal-to-noise ratio is large; at the same time, multiple scattering is avoided, so that the calculation model is simple and the error of the solution result is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0043] Figure 1 It is a schematic diagram of the positional relationship between the laser and the receiver of the water elastic scattering laser radar in the prior art;

[0044] Figure 2 A schematic diagram of the structure of an underwater elastic scattering laser radar system according to an embodiment of the present invention;

[0045] Figure 3 A schematic diagram of the positional relationship between a laser and a signal receiving component of an elastic scattering laser radar component according to an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of the angle relationship between a laser and a signal receiving component of an elastic scattering laser radar component according to an embodiment of the present invention;

[0047] Figure 5 A schematic structural diagram of the positional relationship between a laser, a signal receiving component and a reflector of an elastic scattering laser radar component according to another embodiment of the present invention;

[0048] Figure 6 Schematic diagram of the relationship between the geometric overlap factors of the blind area, transition area, and test area.

[0049] In the figure,

[0050] 10. Water transport equipment; 20. Hoisting assembly; 21. Cable; 22. Watertight cable; 30. Elastic scattering laser radar assembly; 31. Sealed cabin; 32. Laser; 321. Laser optical axis; 3211. Test area; 3212. Blind area; 3213. Transition area; 33. Signal receiving assembly; 331. Receiving field of view. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0053] The terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features.

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] Figure 1 This is a schematic diagram of the laser emission axis used by the water elastic scattering laser radar in the prior art when it is parallel to the central axis of the receiving lens field of view, where l is the depth of the blind area tested, and its signal cannot be received by the receiver; L is the depth of the transition area tested, and the signal in this area needs to be corrected for the overlap factor before use, and errors are inevitable in the correction process. Figure 6 As shown, when the model specifications of the laser 32 and the receiving lens are determined, the geometric overlap factor η can be calculated. The calculation of the geometric overlap factor η is a relatively conventional technical solution in the prior art and will not be repeated here. Since the blind area of ​​the water elastic scattering laser radar is located in the water area, the water elastic scattering laser radar does not consider the blind area effect.

[0056] But when Figure 1When the laser radar shown is used underwater, due to the strong absorption and scattering of light by seawater, the underwater laser radar is characterized by a small test distance and its blind spot occupies most of the detection distance.

[0057] Therefore, this embodiment provides an underwater elastic scattering laser radar system, which is applied underwater, such as Figure 2-Figure 4 As shown, including:

[0058] The hoisting assembly 20 is arranged on the water transport equipment 10; in this embodiment, the water transport equipment 10 is a ship, and the hoisting assembly 20 is fixed on the deck of the ship;

[0059] The elastic scattering laser radar assembly 30 includes a sealed cabin 31, a laser 32 and a receiver 33 fixed in the sealed cabin 31, and the signal receiving assembly 33 is used to receive the back elastic scattering signal of the laser beam of the laser 33 within its receiving field of view and complete data acquisition;

[0060] The hoisting assembly 20 is connected to the elastic scattering laser radar assembly 30 through a cable 21. The hoisting assembly 20 adjusts the underwater depth of the elastic scattering laser radar assembly 30 by adjusting the length of the cable 21 to meet the measurement requirements of different water depths;

[0061] Among them, Figure 4 As shown, the central axis of the laser optical axis 321 of the laser 32 is set at an angle with the central axis of the receiving field of view 331 of the signal receiving component 33, and the angle is θ. The laser optical axis of the laser 32 includes a test area 3211, a transition area 3213 and a blind area 3212. Figure 3 As shown; in this embodiment, the blind area 3212, transition area 3213 and test area 3211 are also determined based on the "geometric overlap factor" η. In this embodiment, the blind area 3212, transition area 3213 and test area 3211 are all distance quantities. The area where η=0 is the blind area, the area where 0<η<1 is the transition area, and the area where η=1 is the normal test area. The backscattered signal of the blind area 3212 cannot be acquired by the receiver 33 at all, and the backscattered signal of the transition area 3213 is partially acquired by the receiver 33. In this embodiment, the depth of the blind area 3212 is less than Figure 1 The depth of the blind zone formed when the central axis of the laser optical axis of the laser 32 is parallel to the central axis of the receiver 33.

[0062] The underwater elastic scattering laser radar system of the present technical solution is miniaturized and sealed by a sealed cabin 31. The laser optical axis 321 is designed to be at an angle to the receiving field of view of the signal receiving component 33. Without changing the field of view of the receiving lens, it can meet the profile test of underwater elastic backscattering signals in the upper layer of the ocean, i.e., 200 or even deeper waters underwater, while greatly reducing blind spots and meeting the needs of underwater detection.

[0063] like Figure 3 As shown, in the elastic scattering laser radar component 30, the signal receiving component 33 is vertically arranged underwater, and the laser 32 is inclined toward the central axis of the signal receiving component 33. In this embodiment, underwater, the central axis of the signal receiving component 33 is vertically downward, and the laser 32 is inclined so that the central axis of the laser optical axis 321 of the laser 32 is inclined at a certain angle toward the central axis of the signal receiving component 33. The inclination angle of the laser 32 is determined according to the detection depth.

[0064] like Figure 3 As shown, the laser optical axis 321 region outside the field of view of the receiver 33 also includes a transition region 3213, and the signal in the transition region 3213 needs to be corrected for the overlap factor. Figure 1 In comparison, after the laser 32 is tilted, the length L of the transition zone 3213 is greatly reduced, thereby reducing the generation of errors; performing overlapping factor correction on the signal in the transition zone 3213 is a conventional technical means in the prior art and will not be described in detail here.

[0065] In order to facilitate the control of the elastic scattering laser radar, the underwater elastic scattering laser radar system of this embodiment also includes a control terminal 40, which is arranged on the water. In this embodiment, the control terminal 40 is a computer, and the computer is connected to the elastic scattering laser radar component 30 through a watertight cable 22. The control terminal 40 is used to control the laser 32 and receive and process the test data received and collected by the signal receiving component 33 in real time.

[0066] In another embodiment, if Figure 5 As shown, the signal receiving component 33 is parallel to the laser 32, and both are vertically arranged underwater. A reflector 34 is arranged in front of the laser 32 and the signal receiving component 33. The laser optical axis 321 of the laser 32 enters the receiving field of view 331 of the signal receiving component 33 after being reflected twice. At this time, the central axis of the laser optical axis 321 of the laser 32 is designed to be at an angle to the central axis of the receiving field of view of the signal receiving component 33; in another embodiment, only one or more reflectors 34 are arranged at the front end of the laser 32, and no reflector is arranged at the front end of the signal receiving component 33. After the laser optical axis 321 is reflected once or multiple times, its central axis is arranged to be at an angle to the central axis of the signal receiving component 33; both can achieve the inclination of the laser optical axis.

[0067] The measurement method of the underwater elastic scattering laser radar system includes the following steps:

[0068] S1. Determine the tilt angle of the laser:

[0069] like Figure 4As shown, according to the preset detection depth R, the inclination angle between the laser optical axis 321 of the laser 32 and the central axis of the receiving field of view 331 of the signal receiving component 33 is calculated, and the laser 32 and the signal receiving component 33 are fixedly arranged in the sealed cabin 31 according to the calculated inclination angle;

[0070] S2. Lower the elastic scattering laser radar assembly to the preset depth:

[0071] The hoisting assembly 20 lowers the elastic scattering laser radar assembly 30 to a preset depth by lowering the cable and the watertight cable 21;

[0072] S3, elastic scattering laser radar component for detection:

[0073] The control terminal 40 controls the laser 32 and the signal receiving component 33 to start. At the same time, the control terminal 40 receives the data received and collected by the signal receiving component 33, and saves and processes the data;

[0074] S4. End of test:

[0075] After the test is completed, the control terminal 40 controls the laser 32 signal receiving component 33 to be turned off, and the hoisting component 20 recovers the cable 21 and the watertight cable 22, and recovers the elastic scattering laser radar component 30 to the water transport equipment.

[0076] like Figure 4 As shown, in step S1, the relationship between the tilt angle of the laser and the measured depth is:

[0077] R×θ1+D+K=R×(θ+θ2) (1)

[0078] Where R is the measurement depth, which is the distance from the entrance of the receiving lens to the point where the laser optical axis just begins to leave the lens field of view;

[0079] θ is the angle between the laser optical axis of the laser and the central axis of the receiver, that is, the tilt angle of the laser;

[0080] D is the lens aperture of the receiving lens;

[0081] K is the shortest distance between the edge of the lens aperture of the receiving lens and the edge of the laser outlet of the laser;

[0082] θ1 is the half field of view of the receiving lens in water; 2θ1 is the field of view of the receiving lens of the receiver;

[0083] θ2 is the half divergence angle of the laser in water; 2θ2 is the divergence angle of the laser;

[0084] When the specifications of the signal receiving component 33 and the laser 32 are determined, D, K, θ1, and θ2 are all fixed values, and the tilt angle θ can be obtained by substituting them into formula (1).

[0085] Due to the size limitation of the sealed cabin 31, the detection distance of the underwater elastic scattering laser radar is generally less than 50m. This application takes the detection depth R of 50m as an example to calculate the blind area, transition area, and tilt angle θ. It is assumed that the shortest distance K between the edge of the lens aperture of the receiver and the edge of the laser exit port of the laser is 30mm, the lens aperture of the receiving lens is D=100mm, the exit spot size of the laser 32 is d=10mm, θ1=5mrad, θ2=0.5mrad;

[0086] Substituting into formula (1), the inclination angle θ=7.1 mrad is calculated.

[0087] like Figure 3 As shown, the depth l of the blind area 3212 is:

[0088]

[0089] Calculate l = 2.38m;

[0090] The depth L of the transition zone 3213 is

[0091]

[0092] The calculation shows that L = 1.07m;

[0093] As a comparison, the existing technology is calculated respectively. Figure 1 As shown, when the laser is parallel to the receiving lens, the depth of the transition zone 3212 and the blind zone 3213, at this time, θ = 0mrad, and the above formula is substituted to obtain:

[0094] l=5.45m; L=3.44m.

[0095] It can be seen that by tilting the laser 32, the depth of the blind zone and the transition zone can be greatly reduced.

[0096] For example, when the above-mentioned underwater elastic scattering laser radar is used to measure the optical characteristic parameters within the range of 100m underwater, it is assumed that the maximum measurement depth of the laser radar is 30m. First, the laser radar receiving window is placed under the water surface to measure the backscattering data from 2.38m to 30m, then the laser radar is lowered to 27.62m to measure the backscattering data from 30m to 57.62m, then the laser radar is lowered to 27.62m to measure the backscattering data from 57.62m to 85.24m, and then the laser radar is lowered to 27.62m to measure the backscattering data from 85.24m to 112.86m, and finally the optical parameter measurement within the range of 100m underwater is completed.

[0097] If the method of greatly increasing the receiving field of view of the receiving lens is used to reduce the blind area and transition area, it will also cause a significant increase in the noise of stray light. In addition, the multiple scattering effect will be greatly enhanced due to the increase in the field of view, making the inversion model and solution process complicated and the error greatly increased.

[0098] The underwater elastic scattering laser radar system of this embodiment controls the underwater depth of the elastic scattering laser radar assembly 30 through a ship-borne hoisting device, and can achieve a test depth from the water surface to 200m underwater, or even up to several hundred meters to thousands of meters. The complex influences of water surface roughness, water surface foam, water surface reflection, etc. are avoided in the process of constructing the inversion model, which can effectively simplify the inversion model;

[0099] The laser optical axis of the laser 32 and the receiving field of view of the receiving lens are designed to have a certain angle, which greatly reduces the blind area and greatly increases the effective data of the laser radar test while ensuring the detection distance of the laser radar. The elastic scattering laser radar is miniaturized and sealed with a sealed cabin. The control terminal controls the working status of the laser radar and observes, saves and processes the test data in real time.

[0100] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0101] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for testing an underwater elastic scattering laser radar system, characterized in that: The steps include: S1. Determine the tilt angle of the laser: According to the preset detection depth, the inclination angle between the laser optical axis of the laser and the central axis of the receiving lens is calculated, and the laser and the receiving lens are fixedly arranged in the sealed cabin according to the calculated inclination angle; S2. Lower the elastic scattering laser radar assembly to the preset depth: The hoisting assembly lowers the elastic scattering laser radar assembly to a preset depth by lowering the cable and the watertight cable; S3, elastic scattering laser radar component for detection: The control terminal controls the laser and the signal receiving component to start, and at the same time, the control terminal receives the data received and collected by the signal receiving component, and saves and processes the data; S4. End of test: After the test is finished, the control terminal controls the laser and the signal receiving component to be turned off, and the hoisting component recovers the cable and the watertight cable, and recovers the elastic scattering laser radar component to the water transport equipment; In step S1, the relationship between the tilt angle of the laser and the measured depth is: （1） Where R is the measurement depth, θ is the angle between the laser optical axis of the laser and the central axis of the receiving lens, that is, the tilt angle of the laser; D is the lens aperture of the receiver; K is the shortest distance between the edge of the receiver's lens aperture and the edge of the laser's laser outlet; θ1 is the half field of view angle of the receiving lens in water; θ2 is the half divergence angle of the laser in water; When the specifications of the receiver and the laser are determined, D, K, θ1, and θ2 are all fixed values.

2. The radar system of the underwater elastic scattering laser radar system testing method according to claim 1 is characterized in that: include: Lifting assembly, installed on water transport equipment: An elastic scattering laser radar component comprises a sealed cabin, a laser fixed in the sealed cabin, and a signal receiving component, wherein the signal receiving component is used to receive a back elastic scattering signal of a laser beam of the laser within its receiving field of view and complete data acquisition; The signal receiving component includes a receiving lens, a photoelectric detection module, and a data acquisition module; The hoisting assembly is connected to the elastic scattering laser radar assembly through a cable, and is used to adjust the underwater depth of the elastic scattering laser radar assembly. Among them, the central axis of the laser optical axis of the laser is set at an angle with the central axis of the receiving field of view of the receiving lens, and the blind area formed at this time is smaller than the blind area formed when the laser optical axis of the elastic scattering laser is parallel to the central axis of the receiver.

3. The radar system according to claim 2, characterized in that In the elastic scattering laser radar component, the signal receiving component is vertically arranged underwater, the laser is tilted toward the central axis of the receiving lens, and the tilt angle of the laser is determined according to the detection depth.

4. The radar system according to claim 2, characterized in that The receiving lens is parallel to the laser and both are arranged vertically underwater. The laser and / or the receiving lens are provided with a reflector. The laser optical axis of the laser is arranged at an angle with the central axis of the receiving lens after being reflected by the reflector at least once.

5. The radar system according to claim 3 or 4, characterized in that: A transition zone is also formed between the laser optical axis and the field of view of the receiving lens. The transition zone is smaller than the transition zone formed when the laser optical axis of the elastic scattering laser is parallel to the central axis of the receiver. The signal in the transition zone needs to be corrected for the overlap factor.

6. The radar system according to claim 5, characterized in that The underwater elastic scattering laser radar system also includes a control terminal, which is arranged on the water and connected to the elastic scattering laser radar component through a watertight cable. The control terminal is used to control the laser and receive and process the test data received and collected by the signal receiving component in real time.

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