Method for detecting inherent optical parameters of water body based on multiple scattering profiles of off-axis laser radar

Abstract

The invention discloses a water body inherent optical parameter detection method based on an off-axis laser radar multiple scattering profile, and the method is characterized in that the method comprises the following steps: obtaining the multiple scattering profile of a target water body through an off-axis laser radar; the logarithm of the obtained multiple scattering profiles of the target water body is obtained, and a linear function is used for fitting; determining a scattering coefficient of the target water body based on an intercept in the fitting function and a preset first relational expression, determining a light beam attenuation coefficient of the target water body based on a slope in the fitting function and a preset second relational expression, and determining an absorption coefficient of the target water body based on the scattering coefficient, the light beam attenuation coefficient and a preset third relational expression; the fitting parameters are determined by the following steps: acquiring multiple scattering profiles of a sampled water body through an off-axis laser radar, and measuring and acquiring a scattering coefficient and a light beam attenuation coefficient of the sampled water body; the logarithm of the obtained multiple scattering profiles of the sampling water body is obtained, and a linear function is used for fitting; and determining fitting parameters in the first relational expression and the second relational expression based on the intercept and the slope in the fitting function and the acquired scattering coefficient and the light beam attenuation coefficient of the sampling water body. The detection method can simply and conveniently use the detection result of the off-axis laser radar to obtain the inherent optical parameters of the water body.

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 absorption coefficient a, scattering coefficient b, beam attenuation coefficient c, etc. Accurate determination of these parameters is of great significance for the evaluation of primary productivity, particulate organic carbon content, chlorophyll concentration, and underwater imaging quality of water bodies. At present, the methods for obtaining the intrinsic optical parameters of water bodies can be divided into direct measurement methods and indirect estimation methods. The direct measurement method is to sample the water body on site through a specific instrument, and then analyze the sampled materials in the laboratory. For example, a spectrophotometer can be used to measure the absorbance of the water body, and then the absorption coefficient can be calculated; or the intrinsic optical parameters of the water body can be directly measured using an in-situ measurement instrument. The indirect estimation method is to remotely obtain the relevant optical data of the water body through detectors carried by satellites, aircraft or ships, and then combine relevant models and algorithms to estimate the intrinsic optical parameters of the water body.

[0003] Among the indirect estimation methods, LiDAR is an important detection method, which is widely used in the fields of water body intrinsic optical parameter measurement, underwater bubble detection, shallow sea mapping, fish monitoring and ocean internal wave detection. However, in the process of using LiDAR to measure the intrinsic optical parameters of water bodies, the multiple scattering process of water bodies has a great influence on the accurate inversion of the intrinsic optical parameters of water bodies, resulting in great difficulties in using LiDAR to invert the intrinsic optical parameters of water bodies. 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 to provide a method for detecting the inherent optical parameters of water bodies based on the multiple scattering profiles 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 in that it includes the following steps: obtaining multiple scattering profiles of target water bodies through off-axis laser radar; taking the logarithm of the multiple scattering profiles of the acquired 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 = p 1 ·n p2·B , determine the scattering coefficient of the target water body, and based on the slope of the fitting function and the preset second relationship c=p 3·K+p 4 , determine the beam attenuation coefficient of the target water body, and 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; wherein P(r) is the multiple scattering profile signal at a distance r, K is the slope, and B is the intercept; p 1 、p 2 、p 3 and p 4 is the fitting parameter; 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 off-axis laser radar, and measuring the scattering coefficient and beam attenuation coefficient of the sampled water body; taking the logarithm of the 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 = p is determined 1 ·n p2·B , the second relation c = p 3 ·K+p 4 The fitting parameters in .

[0007] Technical solution 2 based on technical solution 1: In the step of determining the fitting parameters, the sampled water bodies include multiple water bodies, 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 laser radar where the geometric overlap factor is 0, and it 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 seven 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 laser transmitter of the off-axis lidar is parallel or intersecting with the central axis of the receiving telescope, and the wavelength range of the emitted laser is 350nm to 700nm.

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

[0014] The method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar provided by the present invention 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, and the intercept and slope in the fitted function are directly related to the scattering coefficient and beam attenuation coefficient of the target water body through a preset first relationship and a second relationship, 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 one measurement, and in the detection process, there is no need to make assumptions about other characteristics of the target water body, nor to solve the laser radar attenuation coefficient and establish the relationship between the laser radar attenuation coefficient, 180° body scattering coefficient and other related coefficients and the inherent optical parameters, but directly through the influence of the multiple scattering process on the inherent optical parameters of the target water body, by solving the related first relationship, second relationship and third relationship, the inherent optical parameters of the target water body are simply and conveniently obtained.

[0015] Among them, the inventor creatively established the relationship between the multiple scattering profiles of the target water body and the scattering coefficient and beam attenuation coefficient of the target water body, and sampled the multiple scattering profiles, scattering coefficients and beam attenuation coefficients of the sampled water body in advance, and determined the values ​​of the fitting parameters in the first and second relationship equations on this basis, so that 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 bodies, and then the corresponding fitting parameters are obtained by fitting the exponential relationship and the linear relationship, and used as the fitting parameters in the first relationship and the second relationship in the detection process.

[0017] Meanwhile, 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, thereby 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 creative work.

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

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

[0022] Figure 3 A schematic diagram of multiple scattering profiles obtained by an off-axis laser radar measured 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 laser radar provided in an embodiment of the present invention;

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

[0024] Figure 5A 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 multiple scattering profiles of an off-axis laser radar provided in an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of experimental results of a method for detecting intrinsic optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar provided in an embodiment of the present invention Figure 1 ;

[0026] Figure 7 Schematic diagram of experimental results of a method for detecting intrinsic optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar provided in an embodiment of the present invention Figure 2 . DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0028] In the claims, description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" etc. are for 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] In the claims, specification and the above drawings of the present invention, off-axis laser radar is a laser radar technology characterized in that the optical axes of the laser transmitter and the receiver are not completely coincident, but have a certain angle offset. This design can reduce the interference of direct light and better capture multiple scattered signals. It is often used in the measurement of optical properties of the atmosphere and water bodies, especially in applications where single scattered and multiple scattered signals need to be distinguished.

[0031] In the claims, specification and the above drawings of the present invention, the multiple scattering profile refers to the light intensity distribution curve formed by the multiple scattering phenomenon caused by particles (such as suspended matter, phytoplankton, etc.) and molecules in the water body when the laser propagates in the water body. The multiple scattering profile contains the optical information inside the water body, and the optical properties of the water body can be inferred by analyzing this information.

[0032] In the claims, description and the above drawings of the present invention, intrinsic optical parameters are parameters that describe the optical properties of water itself, including absorption coefficient, scattering coefficient and beam attenuation coefficient. The scattering coefficient is used to describe the degree to which photons deviate from the 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, specification and the above 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. -1 The 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, specification and the above 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 absorption capacity of dissolved substances and suspended particles in water to light.

[0035] In the claims, specification and the above drawings of the present invention, the geometric overlap factor is a parameter used to describe the degree of overlap of the optical paths of the laser transmitter and the receiver in the laser radar system. When the geometric overlap factor is 0, it means that there is no interference from direct light, only multiple scattered signals. In the analysis of multiple scattering profiles, the part with a geometric overlap factor of 0 can provide a purer multiple scattered signal and reduce interference from other signals.

[0036] In the claims, specification and the above drawings of the present invention, the laser transmitter is a device for emitting laser in the laser radar system, which can generate a high-energy, highly directional laser beam for irradiating the target water body. The receiving telescope is a device for receiving the laser signal reflected from the target water body in the laser radar system, which can collect the scattered light signal and convert it into an electrical signal 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 intrinsic optical parameters of a water body based on multiple scattering profiles of an off-axis laser radar, 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 relationship and the second relationship 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 an off-axis laser radar;

[0043] S102, taking the logarithm of the multiple scattering profile of the target water body and using 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=p 1 ·n p2·B , determine the scattering coefficient of the target water body, and based on the slope of the fitting function and the preset second relationship c=p 3 ·K+p 4 , determine the beam attenuation coefficient of the target water body;

[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, and B is the intercept; 1 、p 2 、p 3 and p 4 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, taking the logarithm of the multiple scattering profile of the sampled water body and using the linear function log m (P(r)) = K·r + B fit;

[0050] S203, based on the intercept and slope in the fitting function, and the scattering coefficient and beam attenuation coefficient of the sampled water body obtained, determine the first relationship b=p 1 ·np2·B , the second relation c = p 3 ·K+p 4 The fitting parameters in .

[0051] Specifically, before detecting 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 laser radar to obtain the multiple scattering profile of the sampled water body, and 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 obtained 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 not equal to 1. In this embodiment, m is selected as the natural constant e. Then, the multiple scattering profile after taking the logarithm is fitted using a linear function, and the slope K and intercept B in the linear function are determined according to the fitting result. Finally, according to the intercept and slope in the fitting function, as well as the scattering coefficient and beam attenuation coefficient of the sampled water body obtained, they are substituted into the first relational equation b=p 1 ·n p2·B , the second relation c = p 3 ·K+p 4 And calculate the fitting parameter p 1 、p 2 、p 3 and p 4 Where n is the base of the exponent, which can be any positive real number not equal to 1. In this embodiment, n is selected as the natural constant e.

[0053] Wherein, 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 according to the exponential relationship between the scattering coefficients of all the sampled water bodies and the intercepts in the fitted linear function, and the fitting parameters in the second relationship are obtained according to the linear relationship between the beam attenuation coefficients of all the 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. Wherein, in the step of determining the fitting parameters, the laser transmitter of the off-axis laser radar used 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 central 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 the spacing is 15.5mm; the laser wavelength is 532nm and the filter bandwidth is 10nm. At the same time, the multiple scattering profile is the part of the off-axis laser radar where the geometric overlap factor is 0, which only contains multiple scattering signals. Figure 3 The multiple scattering profiles in are signals 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 parameter p in the first relationship is obtained accordingly. 1 、p 2 . Similarly, refer to Figure 5 , the 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 parameter p in the second relationship is obtained accordingly. 3 and p 4 .

[0056] For example, in this embodiment, when both m and n are natural constants e, the values ​​of the fitting parameters are as follows: 1 The value of is 0.003, p 2 The value of is 0.592, p 3 The value of is -0.574, p 4 The value of is 0.126.

[0057] After the fitting parameters in the first relational expression and the second relational expression are determined, the target water body with unknown inherent optical parameters can be detected according to the obtained first relational expression and the second relational expression, 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 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 relationship equations are still applicable. Then, the multiple scattering profile of the target water body is logarithmically calculated 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 in the fitting function and the preset first relationship b = p 1 ·n p2·B , determine the scattering coefficient of the target water body, based on the slope of the fitting function and the preset second relationship c = p 3 ·K+p 4 , determine the beam attenuation coefficient of the target water body, 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 selected values ​​of m and n are the same, both of which are the natural constant e.

[0060] In order to further verify the effectiveness of the above-mentioned water body inherent optical parameter detection method, an outdoor experiment was conducted using the water body inherent optical parameter detection method provided in this embodiment, and the measurement results of the water body inherent optical parameters were obtained simultaneously using an in-situ measurement instrument. The measurement time was from 7:00 on May 16, 2024, at 12 sites located in the northern part of the South China Sea, and the measurement ended at 14:00 on May 24, 2024.

[0061] Detection results reference Figure 6 , wherein the red dotted line represents the absorption coefficient of the target water body obtained by the water body inherent optical parameter detection method provided by this embodiment, the black dotted line represents the scattering coefficient of the target water body obtained by the water body inherent optical parameter detection method provided by this embodiment, and the blue dotted line represents the beam attenuation coefficient of the target water body obtained by the water body inherent optical parameter detection method provided by this embodiment. The red five-pointed star represents the absorption coefficient of the target water body measured by the in-situ measuring instrument, the black five-pointed star represents the scattering coefficient of the target water body measured by the in-situ measuring instrument, and the blue five-pointed star represents the beam attenuation coefficient of the target water body measured by the in-situ measuring instrument.

[0062] The intrinsic optical parameters of the target water body obtained by the method for detecting intrinsic 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 7As shown in Figure 2, 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 measuring 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 method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar provided by the present invention 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, and the intercept and slope in the fitted function are directly related to the scattering coefficient and beam attenuation coefficient of the target water body through a preset first relationship and a second relationship, 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 one measurement, and in the detection process, there is no need to make assumptions about other characteristics of the target water body, nor to solve the laser radar attenuation coefficient and establish the relationship between the laser radar attenuation coefficient, 180° body scattering coefficient and other correlation coefficients and the inherent optical parameters, but directly through the influence of the multiple scattering process on the inherent optical parameters of the target water body, by solving the related first relationship, second relationship and third relationship, the inherent optical parameters of the target water body are simply and conveniently obtained. Among them, the inventor creatively established the relationship between the multiple scattering profiles of the target water body and the scattering coefficient, beam attenuation coefficient and absorption coefficient of the target water body, and sampled the multiple scattering profiles, scattering coefficients and beam attenuation coefficients of the sampled water body in advance, and determined the values ​​of the fitting parameters in the first and second relationship equations on this basis, so that in 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 finally achieve the goal of directly obtaining the inherent optical parameters of the target water body through a single measurement.

[0064] The description of the above specification and embodiments is used to explain the protection scope of the present invention, but does not constitute a limitation on the protection scope of the present invention. Through the enlightenment of the present invention or the above embodiments, ordinary technicians in this field can obtain modifications, equivalent substitutions or other improvements to the embodiments of the present invention or part of the technical features thereof through logical analysis, reasoning or limited experiments, which should be included in the protection scope of the present invention.

Claims

1. A method for detecting inherent optical parameters of water bodies based on multiple scattering profiles of off-axis laser radar, characterized in that: 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 relational expression 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 in the fitting function and a 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 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 laser radar, 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 taken logarithmically and the linear function log is used 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 according to 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 according to 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 intrinsic 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 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 inherent optical parameters of water bodies based on off-axis laser radar multiple scattering profiles as claimed in claim 1, characterized in that: In the step of determining the intrinsic 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 inherent optical parameters of water bodies based on off-axis laser radar multiple scattering profiles as claimed in claim 1, characterized in that: 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 as claimed in claim 1, characterized in that: In the first relational expression, n is a base, 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 as claimed in claim 1, characterized in that: 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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