A method for detecting intrinsic optical parameters of water bodies based on multiple scattering profiles of off-axis lidar

Abstract

The present invention discloses a method for detecting intrinsic optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar. The method is characterized by comprising the following steps: obtaining a multiple scattering profile of a target water body by an off-axis laser radar; taking the logarithm of the obtained multiple scattering profile of the target water body and fitting it with a linear function; determining the scattering coefficient of the target water body based on the intercept in the fitting function and a preset first relationship; determining the beam attenuation coefficient of the target water body based on the slope in the fitting function and a preset second relationship; and determining the absorption coefficient of the target water body based on the scattering coefficient, the beam attenuation coefficient, and a preset third relationship; the fitting parameters are determined by the following steps: obtaining a multiple scattering profile of a sampled water body by an off-axis laser radar and measuring the scattering coefficient and beam attenuation coefficient of the sampled water body; taking the logarithm of the obtained multiple scattering profile of the sampled water body and fitting it with a linear function; and determining the fitting parameters in the first and second relationship based on the intercept and slope in the fitting function and the obtained scattering coefficient and beam attenuation coefficient of the sampled water body. The detection method can simply and conveniently obtain intrinsic optical parameters of water bodies using detection results of the off-axis laser radar.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a method for detecting inherent optical parameters of water bodies based on off-axis laser radar multiple scattering profiles. Background Art

[0002] The intrinsic optical parameters of water bodies include the absorption coefficient a, the scattering coefficient b, and the beam attenuation coefficient c. Accurately measuring these parameters is crucial for assessing primary productivity, particulate organic carbon content, chlorophyll concentration, and underwater imaging quality. Currently, methods for obtaining intrinsic optical parameters of water bodies can be categorized as direct measurement or indirect estimation. Direct measurement involves sampling water bodies on-site using specific instruments and then analyzing the sampled material in the laboratory. For example, a spectrophotometer can be used to measure the absorbance of the water and subsequently calculate the absorption coefficient. Alternatively, in-situ measurement instruments can be used to directly measure the intrinsic optical parameters of water bodies. Indirect estimation involves remotely acquiring relevant optical data from water bodies using detectors carried by satellites, aircraft, or ships. These data are then combined with relevant models and algorithms to estimate the intrinsic optical parameters of water bodies.

[0003] Among indirect estimation methods, lidar (lidar) is an important detection tool, widely used in fields such as measuring intrinsic optical parameters of water bodies, underwater bubble detection, shallow water mapping, fish monitoring, and ocean internal wave detection. However, when using lidar to measure intrinsic optical parameters of water bodies, the multiple scattering process of water bodies significantly affects the accurate inversion of intrinsic optical parameters of water bodies, resulting in significant difficulties in inverting intrinsic optical parameters of water bodies using lidar. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and provide a method for detecting the inherent optical parameters of water bodies based on the multiple scattering profile of off-axis laser radar, which can simply and conveniently obtain the inherent optical parameters of water bodies using the detection results of off-axis laser radar.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] Technical Solution 1: A method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar, characterized by comprising the following steps: obtaining multiple scattering profiles of target water bodies by off-axis laser radar; taking the logarithm of the obtained multiple scattering profiles of target water bodies and using the linear function log m (P(r))=K·r+B fitting; based on the intercept in the fitting function and the preset first relationship b=p1·n p2·B, determine the scattering coefficient of the target water body, and determine the beam attenuation coefficient of the target water body based on the slope of the fitting function and the preset second relationship c=p3·K+p4, and determine the absorption coefficient of the target water body based on the scattering coefficient and the beam attenuation coefficient and the preset third relationship a=cb; wherein P(r) is the multiple scattering profile signal at a distance r, K is the slope, and B is the intercept; p1, p2, p3 and p4 are fitting parameters; a is the absorption coefficient, b is the scattering coefficient, and c is the beam attenuation coefficient; the fitting parameters are determined by the following steps: obtaining the multiple scattering profile of the sampled water body by an off-axis laser radar, and measuring the scattering coefficient and the beam attenuation coefficient of the sampled water body; taking the logarithm of the obtained multiple scattering profile of the sampled water body and using the linear function log m (P(r)) = K·r + B fitting; Based on the intercept and slope in the fitting function, as well as the scattering coefficient and beam attenuation coefficient of the sampled water body, the first relationship b = p1·n is determined p2·B , the fitting parameters in the second relationship c=p3·K+p4.

[0007] Technical solution 2 based on technical solution 1: In the step of determining the fitting parameters, the sampled water bodies include multiple ones, and the fitting parameters in the first relationship are obtained by fitting according to the exponential relationship between the scattering coefficient of all sampled water bodies and the intercept in the fitted linear function, and the fitting parameters in the second relationship are obtained according to the linear relationship between the beam attenuation coefficient of all sampled water bodies and the slope in the fitted linear function.

[0008] Technical solution three based on technical solution one: in the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the multiple scattering profile is the part of the off-axis lidar where the geometric overlap factor is 0, which only contains multiple scattering signals.

[0009] Technical solution 4 based on technical solution 1: In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, an off-axis laser radar with the same structure is used.

[0010] Technical solution five based on technical solution one: in the linear function, m is the base, which is any positive real number that is not 1, and in the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the value of m selected is the same.

[0011] Technical solution six based on technical solution one: In the first relationship formula, n is the base, which is any positive real number that is not 1, and in the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the value of n selected is the same.

[0012] Technical Solution 7 based on Technical Solution 1: In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the laser emitter of the off-axis lidar and the central axis of the receiving telescope are parallel or intersecting, and the wavelength range of the emitted laser is 350nm to 700nm.

[0013] From the above description of the present invention, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention provides a method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radars. The method is based on the multiple scattering profiles of the target water body obtained by the off-axis laser radar, takes the logarithm of the multiple scattering profiles and fits them using a pre-designed linear function. The intercept and slope in the fitted function are directly linked to the scattering coefficient and beam attenuation coefficient of the target water body through preset first and second relationship equations, and the absorption coefficient of the target water body is determined based on the calculated scattering coefficient and beam attenuation coefficient of the target water body, thereby directly obtaining the scattering coefficient, beam attenuation coefficient and absorption coefficient inherent optical parameters of the target water body through a single measurement. In addition, during the detection process, there is no need to make assumptions about other characteristics of the target water body, nor is there any need to solve the laser radar attenuation coefficient and establish the relationship between correlation coefficients such as the laser radar attenuation coefficient and the 180° volume scattering coefficient and the inherent optical parameters. Instead, the inherent optical parameters of the target water body are simply and conveniently obtained by directly using the influence of the multiple scattering process on the inherent optical parameters of the target water body and solving the relevant first, second and third relationship equations.

[0015] Among them, the inventor creatively established the relationship between the multiple scattering profile of the target water body and the scattering coefficient and beam attenuation coefficient of the target water body. By pre-sampling the multiple scattering profile, scattering coefficient and beam attenuation coefficient of the sampled water body, the values ​​of the fitting parameters in the first and second relationship equations were determined on this basis. During the detection process, the first and second relationship equations can be directly used to solve the inherent optical parameters of the target water body, such as the scattering coefficient, beam attenuation coefficient and absorption coefficient, and ultimately achieve the goal of directly obtaining the inherent optical parameters of the target water body through a single measurement.

[0016] In addition, in the step of determining the fitting parameters, multiple different sampling water bodies can be sampled to obtain the relationship between multiple sets of scattering coefficients, beam attenuation coefficients and multiple scattering profiles of the water body, and then by fitting the exponential relationship and the linear relationship, the corresponding fitting parameters are obtained and used as the fitting parameters in the first and second relationship equations during the detection process.

[0017] At the same time, in the step of determining the intrinsic optical parameters of the water body, the multiple scattering profile is the part where the geometric overlap factor is 0 in the off-axis lidar, so that the multiple scattering profile only includes the multiple scattering signals of the target water body, reducing the interference of other signals.

[0018] In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, an off-axis lidar with the same structure is used to ensure that the fitting parameters obtained by detecting the sampled water body can be applied to the actual detection of the target water body, avoiding the situation where the predetermined fitting parameters cannot be applied due to the different structures of the off-axis lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of the steps for determining the intrinsic optical parameters of a water body in a method for detecting the intrinsic optical parameters of a water body based on off-axis lidar multiple scattering profiles provided in an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of the steps for determining fitting parameters in a method for detecting intrinsic optical parameters of a water body based on off-axis lidar multiple scattering profiles provided in an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of multiple scattering profiles obtained by an off-axis lidar in different sampled water bodies when determining fitting parameters in a method for detecting intrinsic optical parameters of a water body based on multiple scattering profiles of an off-axis lidar provided in an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the relationship between the scattering coefficient and the intercept of a linear function in a method for detecting intrinsic optical parameters of a water body based on multiple scattering profiles of an off-axis lidar provided in an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of the relationship between the beam attenuation coefficient and the slope of a linear function in a method for detecting intrinsic optical parameters of a water body based on off-axis lidar multiple scattering profiles provided by an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of experimental results of the method for detecting inherent optical parameters of water bodies based on off-axis lidar multiple scattering profiles provided by the embodiment of the present invention Figure 1 ;

[0026] Figure 7 Schematic diagram of experimental results of the method for detecting inherent optical parameters of water bodies based on off-axis lidar multiple scattering profiles provided by the embodiment of the present invention Figure 2 . DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0029] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0030] As used in the claims, specification, and accompanying drawings of this invention, off-axis lidar is a type of lidar technology characterized by an angular offset between the optical axes of the laser transmitter and receiver, rather than their exact alignment. This design reduces interference from direct light and better captures multiple scattered signals. It is commonly used to measure the optical properties of the atmosphere and water, particularly in applications requiring the distinction between single and multiple scattered signals.

[0031] In the claims, description, and accompanying figures of the present invention, the multiple scattering profile refers to the light intensity distribution curve resulting from multiple scattering of laser light by particles (such as suspended matter and phytoplankton) and molecules in water when the laser propagates through the water. The multiple scattering profile contains optical information about the water, and by analyzing this information, the optical properties of the water can be inferred.

[0032] In the claims, description and drawings of the present invention, intrinsic optical parameters are parameters that describe the optical properties of water, including absorption coefficient, scattering coefficient and beam attenuation coefficient. The scattering coefficient is used to describe the degree to which photons deviate from their original path due to scattering within a unit length, and the unit is usually m -1 The scattering coefficient is one of the inherent optical parameters of water, which reflects the scattering ability of suspended particles and molecules in water to light.

[0033] In the claims, description and drawings of the present invention, the beam attenuation coefficient is used to describe the ratio of photon loss due to absorption and scattering per unit length, and the unit is usually m -1The beam attenuation coefficient is one of the inherent optical parameters of water, which comprehensively reflects the absorption and scattering effects of water on light.

[0034] In the claims, description and drawings of the present invention, the absorption coefficient is used to describe the degree of photon loss due to absorption per unit length, and the unit is usually m -1 The absorption coefficient is one of the inherent optical parameters of water, which reflects the light absorption capacity of dissolved substances and suspended particles in water.

[0035] In the claims, specification, and accompanying figures of the present invention, the geometric overlap factor (GFA) is a parameter describing the degree of overlap between the optical paths of the laser transmitter and receiver in a lidar system. When the GFA is 0, there is no interference from direct light, only multiple scattered signals. In the analysis of multiple scattering profiles, the portion with a GFA of 0 provides a purer multiple scattered signal, reducing interference from other signals.

[0036] In the claims, specification, and accompanying drawings of the present invention, a laser transmitter is a device in a lidar system that emits laser light. It generates a high-energy, highly directional laser beam for illuminating a target body of water. A receiving telescope is a device in a lidar system that receives laser signals reflected from the target body of water. It collects scattered light signals and converts them into electrical signals for subsequent processing.

[0037] In the claims, specification and the above drawings of the present invention, the central axis is the optical axis of the laser transmitter and the receiving telescope, and the relative position of the central axis of the laser transmitter and the receiving telescope will affect the geometric overlap factor of the system.

[0038] Example

[0039] An embodiment of the present invention provides a method for detecting the intrinsic optical parameters of a water body based on the multiple scattering profile of an off-axis lidar, which is used to detect the intrinsic optical parameters of a target water body, wherein the intrinsic optical parameters of the water body include a scattering coefficient, a beam attenuation coefficient, and an absorption coefficient.

[0040] The detection method provided in this embodiment mainly includes the step of determining the inherent optical parameters of the water body. On this basis, the fitting parameters in the first and second relationship equations used in the step of determining the inherent optical parameters of the water body are obtained by the step of determining the fitting parameters performed in advance.

[0041] Reference Figure 1 , which shows the relevant process of determining the intrinsic optical parameters of water, specifically:

[0042] S101, obtaining a multiple scattering profile of a target water body by using an off-axis laser radar;

[0043] S102, take the logarithm of the multiple scattering profile of the target water body and use the linear function log m (P(r)) = K·r + B fit;

[0044] S103, based on the intercept in the fitting function and the preset first relationship b=p1·n p2·B , determine the scattering coefficient of the target water body, and determine the beam attenuation coefficient of the target water body based on the slope of the fitting function and the preset second relationship c=p3·K+p4;

[0045] S104 : Determine the absorption coefficient of the target water body based on the scattering coefficient, the beam attenuation coefficient, and a preset third relationship a=cb.

[0046] Where P(r) is the multiple scattering profile signal at distance r, K is the slope, B is the intercept; p1, p2, p3, and p4 are fitting parameters; a is the absorption coefficient, b is the scattering coefficient, and c is the beam attenuation coefficient.

[0047] Reference Figure 2 , which shows the relevant process of determining the fitting parameters, specifically:

[0048] S201, obtaining a multiple scattering profile of a sampled water body by an off-axis laser radar, and measuring a scattering coefficient and a beam attenuation coefficient of the sampled water body;

[0049] S202, take the logarithm of the multiple scattering profile of the sampled water body and use the linear function log m (P(r)) = K·r + B fit;

[0050] S203, based on the intercept and slope of the fitting function, and the obtained scattering coefficient and beam attenuation coefficient of the sampled water body, determine the first relationship b=p1·n p2·B , the fitting parameters in the second relationship c=p3·K+p4.

[0051] Specifically, before conducting the detection of the inherent optical parameters of the target water body in this embodiment, it is necessary to first calculate and fix the fitting parameters in the first and second relationship equations in order to solve them when the scattering coefficient and beam attenuation coefficient of the target water body are unknown.

[0052] In the step of determining the fitting parameters, the sampled water body is first measured by an off-axis lidar to obtain the multiple scattering profile of the sampled water body. At the same time, the scattering coefficient and beam attenuation coefficient of the sampled water body are measured by a measuring instrument. At this time, the multiple scattering profile, scattering coefficient and beam attenuation coefficient of the sampled water body are obtained. Then the logarithm of the multiple scattering profile of the sampled water body is taken, that is, log m(P(r)), where m is the base, which can be any positive real number other than 1. In this embodiment, m is selected as the natural constant e. Then, the multiple scattering profile after taking the logarithm is fitted with a linear function, and the slope K and intercept B of the linear function are determined based on the fitting results. Finally, the intercept and slope of the fitting function, as well as the scattering coefficient and beam attenuation coefficient of the sampled water body, are substituted into the first relationship b = p1·n p2·B , the second relational expression c=p3·K+p4, and the fitting parameters p1, p2, p3 and p4 are calculated. Where n is the base of the exponential, which can be any positive real number not equal to 1. In this embodiment, n is selected as the natural constant e.

[0053] In the step of determining the fitting parameters, the sampled water bodies include multiple ones, the fitting parameters in the first relationship are obtained by fitting the exponential relationship between the scattering coefficients of all sampled water bodies and the intercepts in the fitted linear function, and the fitting parameters in the second relationship are obtained by fitting the linear relationship between the beam attenuation coefficients of all sampled water bodies and the slopes in the fitted linear function.

[0054] Specifically, refer to Figure 3 , which shows the multiple scattering profiles obtained by detection in multiple different sampled water bodies. In the step of determining the fitting parameters, the laser transmitter of the off-axis lidar is parallel to or intersecting with the central axis of the receiving telescope, the wavelength range of the laser emitted is 350nm to 700nm, the center wavelength of the filter is located at the laser wavelength, and the bandwidth of the filter is less than 50nm. In this embodiment, the laser transmitter and the central axis of the receiving telescope are parallel and spaced 15.5mm apart; the laser wavelength is 532nm, and the filter bandwidth is 10nm. At the same time, the multiple scattering profile is located in the portion of the off-axis lidar where the geometric overlap factor is 0, which only contains multiple scattering signals. Figure 3 The multiple scattering profile in is the signal in the range of 0-3m.

[0055] Figure 3 After taking the logarithm of the multiple scattering profile of each sampled water body, a linear function with a certain slope and intercept can be fitted. Figure 4 , the intercept of each sampled water body and the scattering coefficient of the sampled water body obtained by measurement are plotted and recorded in the rectangular coordinate system. It can be seen that there is an exponential relationship between the two. Therefore, the relationship between the intercept and scattering coefficient of the sampled water body is fitted in the form of an exponential function, and the fitting parameters p1 and p2 in the first relationship are obtained accordingly. Similarly, refer to Figure 5The slope of each sampled water body and the measured beam attenuation coefficient of the sampled water body are plotted and recorded in a rectangular coordinate system. It can be seen that there is a linear relationship between the two. Therefore, the relationship between the slope of the sampled water body and the beam attenuation coefficient is fitted in the form of a linear function, and the fitting parameters p3 and p4 in the second relationship are obtained accordingly.

[0056] For example, in this embodiment, when both m and n are taken as the natural constant e, the values ​​of the fitting parameters are as follows: the value of p1 is 0.003, the value of p2 is 0.592, the value of p3 is -0.574, and the value of p4 is 0.126.

[0057] After determining the fitting parameters in the first and second relationship expressions, the target water body with unknown inherent optical parameters can be detected according to the obtained first and second relationship expressions, and the inherent optical parameters of the target water body can be obtained.

[0058] Specifically, during detection, the multiple scattering profile of the target water body is first obtained by using an off-axis laser radar. The off-axis laser radar used here has the same structure as the off-axis laser radar used in the step of determining the fitting parameters to ensure that the preset first and second relationships are still applicable. Then, the logarithm of the multiple scattering profile of the target water body is taken and the linear function log is used. m (P(r)) = K·r+B fitting, where the slope and intercept of the fitting function can be obtained. Then based on the intercept of the fitting function and the preset first relationship b = p1·n p2·B , determine the scattering coefficient of the target water body, determine the beam attenuation coefficient of the target water body based on the slope of the fitting function and the preset second relationship c=p3·K+p4, and then determine the absorption coefficient of the target water body according to the calculated scattering coefficient and beam attenuation coefficient of the target water body and the preset third relationship a=cb, thereby completing the detection of the inherent optical parameters of the target water body.

[0059] In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the values ​​of m and n are both the same, which are the natural constant e.

[0060] To further verify the effectiveness of the aforementioned method for detecting inherent water optical parameters, a field experiment was conducted using the method provided in this embodiment. In-situ measurement instruments were used to obtain measurements of the inherent water optical parameters. The measurements began at 7:00 AM on May 16, 2024, at 12 locations in the northern South China Sea, and ended at 2:00 PM on May 24, 2024.

[0061] Detection results reference Figure 6, where the red dashed line represents the absorption coefficient of the target water body obtained by the method for detecting the inherent optical parameters of water bodies provided by this embodiment, the black dashed line represents the scattering coefficient of the target water body obtained by the method for detecting the inherent optical parameters of water bodies provided by this embodiment, and the blue dashed line represents the beam attenuation coefficient of the target water body obtained by the method for detecting the inherent optical parameters of water bodies provided by this embodiment. A red five-pointed star represents the absorption coefficient of the target water body measured by an in-situ measurement instrument, a black five-pointed star represents the scattering coefficient of the target water body measured by an in-situ measurement instrument, and a blue five-pointed star represents the beam attenuation coefficient of the target water body measured by an in-situ measurement instrument.

[0062] The inherent optical parameters of the target water body obtained by the method for detecting inherent optical parameters of water body provided in this embodiment are compared with the results measured by the in-situ measuring instrument. The results are as follows: Figure 7 As shown. It can be seen that the variation trends of the intrinsic optical parameter measurements of the off-axis lidar and the in-situ measurement instrument at each site are basically consistent (refer to Figure 7 (a) Figure 7 (c) Figure 7 (e)). For b, c, and a, the root mean square error of the measurements of the off-axis lidar and the in-situ measurement instrument is 0.007m, respectively. -1 ( Figure 7 (b)), 0.012m -1 ( Figure 7 (d)) and 0.014m -1 ( Figure 7 (f)), verifying the feasibility of the detection method.

[0063] The present invention provides a method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radars. The method is based on the multiple scattering profiles of the target water body obtained by the off-axis laser radar, takes the logarithm of the multiple scattering profiles and fits them using a pre-designed linear function. The intercept and slope in the fitted function are directly linked to the scattering coefficient and beam attenuation coefficient of the target water body through preset first and second relationship equations, and the absorption coefficient of the target water body is determined based on the calculated scattering coefficient and beam attenuation coefficient of the target water body, thereby directly obtaining the inherent optical parameters of the target water body, such as the scattering coefficient, beam attenuation coefficient and absorption coefficient, through a single measurement. In addition, during the detection process, there is no need to make assumptions about other characteristics of the target water body, nor is there any need to solve the laser radar attenuation coefficient and establish the relationship between the correlation coefficients such as the laser radar attenuation coefficient and the 180° volume scattering coefficient and the inherent optical parameters. Instead, the inherent optical parameters of the target water body are simply and conveniently obtained by directly using the influence of the multiple scattering process on the inherent optical parameters and solving the relevant first, second and third relationship equations. Among them, the inventors creatively established the relationship between the multiple scattering profile of the target water body and the scattering coefficient, beam attenuation coefficient and absorption coefficient of the target water body. By pre-sampling the multiple scattering profile, scattering coefficient and beam attenuation coefficient of the sampled water body, the values ​​of the fitting parameters in the first and second relationship equations were determined on this basis. During the detection process, the first and second relationship equations can be directly used to solve the inherent optical parameters of the target water body, such as the scattering coefficient, beam attenuation coefficient and absorption coefficient, and ultimately achieve the goal of directly obtaining the inherent optical parameters of the target water body through a single measurement.

[0064] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis lidar, characterized by: The following steps are involved: The multiple scattering profile of the target water body is obtained by off-axis lidar; Take the logarithm of the multiple scattering profile of the target water body and use the linear function log m (P(r)) = K·r + B fit; Based on the intercept in the fitting function and the preset first relationship b=p1·n p2·B , determining a scattering coefficient of the target water body, and determining a beam attenuation coefficient of the target water body based on a slope in the fitting function and a preset second relationship c=p3·K+p4, and determining an absorption coefficient of the target water body based on the scattering coefficient and the beam attenuation coefficient and a preset third relationship a=cb; in, P(r) is the multiple scattering profile signal at distance r, K is the slope, B is the intercept; p1, p2, p3, and p4 are fitting parameters; a is the absorption coefficient, b is the scattering coefficient, and c is the beam attenuation coefficient; The fitting parameters are determined by the following steps: The multiple scattering profile of the sampled water body is obtained by off-axis lidar, and the scattering coefficient and beam attenuation coefficient of the sampled water body are measured; The multiple scattering profile of the sampled water body is obtained by taking the logarithm and using the linear function log m (P(r)) = K·r + B fit; Based on the intercept and slope of the fitting function, as well as the scattering coefficient and beam attenuation coefficient of the sampled water body, the first relationship b = p1·n is determined p2·B , the fitting parameters in the second relationship c=p3·K+p4.

2. The method for detecting inherent optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, characterized in that: In the step of determining the fitting parameters, the sampled water bodies include multiple water bodies, the fitting parameters in the first relationship are obtained by fitting the exponential relationship between the scattering coefficients of all sampled water bodies and the intercepts in the fitted linear function, and the fitting parameters in the second relationship are obtained by fitting the linear relationship between the beam attenuation coefficients of all sampled water bodies and the slopes in the fitted linear function.

3. The method for detecting inherent optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, wherein In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the multiple scattering profile is a part of the off-axis laser radar where the geometric overlap factor is 0, and it only contains multiple scattering signals.

4. The method for detecting intrinsic optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, wherein: In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, an off-axis laser radar with the same structure is used.

5. The method for detecting intrinsic optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, wherein: In the linear function, m is a base, which is any positive real number that is not 1, and in the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the value of m selected is the same.

6. The method for detecting intrinsic optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, wherein: In the first relational expression, n is a base number, which is any positive real number not equal to 1, and in the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the value of n selected is the same.

7. The method for detecting intrinsic optical parameters of water bodies based on off-axis laser radar multiple scattering profiles according to claim 1, wherein: In the step of determining the inherent optical parameters of the water body and the step of determining the fitting parameters, the laser transmitter of the off-axis lidar is parallel to or intersects with the central axis of the receiving telescope, and the wavelength range of the laser emitted is 350nm to 700nm.

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