A polarization 3D reconstruction method for marine oil spills under ambiguity and its application

Abstract

The present invention discloses a polarization three-dimensional reconstruction method of marine oil spill under ambiguity, through the three-dimensional relationship formed by incident light, medium, and reflected light, the incident light is polarized light, the oil film corresponds to the refractive index, and the zenith angle and azimuth angle correspond to the geometric relationship, and the normal of the sea surface oil film is obtained and integrated by relying on the three elements, so as to obtain the three-dimensional shape of the ocean surface. The present invention introduces in detail the sun-sea surface-a certain point in the sky, a certain point in the sky-sea surface-detector, the zenith angle and azimuth angle formed, the cause of ambiguity and the reconstruction and pseudo-reconstruction methods. The polarization degree and polarization angle obtained by the detector, as well as the polarization reconstruction method are digitally simulated; the fence oil film and marine oil spill are reconstructed in three dimensions under ambiguity. The results show that the refractive index of the oil spill has an influence of about 7.28% on the fluctuation degree of the three-dimensional reconstruction.

Description

Technical Field

[0001] The invention relates to a three-dimensional reconstruction method and application thereof, and in particular to a polarization three-dimensional reconstruction method of marine oil spill under ambiguity and application thereof. Background Art

[0002] In the remote sensing detection of marine oil spills, the use of intensity, spectrum, and laser is currently a widely used technology. Polarization has unique advantages in identifying authenticity, avoiding flares, and penetrating smoke and fog. Therefore, polarization can have certain characteristics in detecting marine oil spills, identifying oil types, and measuring oil thickness. At the same time, polarization is one of the characteristics that can be used to obtain the normal of a smooth surface. The polarization three-dimensional modeling technology formed by integrating the normal has been widely studied in the field of computer vision. However, in the field of ocean research, due to the ambiguity of zenith and azimuth, it is difficult to obtain correct stereo images in the field and in a very short time.

[0003] Three-dimensional imaging technology can be divided into two categories: active and passive. Active technology uses active illumination for three-dimensional reconstruction, such as time of flight (TOF), lidar, and structured light three-dimensional imaging; passive technology mainly includes stereo vision and light field cameras. Since the 1970s, researchers at home and abroad have studied the use of polarization information to recover the three-dimensional shape of the target surface and developed a series of polarization three-dimensional imaging methods. The core of these methods is to use the Fresnel law to establish a functional relationship between the polarization characteristics of the reflected light and the three-dimensional profile, with the representative SfP (Shape from Polarization) technology.

[0004] Early studies reconstructed specular surfaces by assuming a separate diffuse reflection polarization model or by using the polarization characteristics of specular reflection. In fact, light reflected from the surface of a material is a mixture of diffuse reflection and specular reflection, so the method of using a mixed diffuse and specular model can generate more realistic objects, which is the first improvement. The second improvement is that the reconstruction was previously performed under a lighting environment where the incident irradiance was controlled, but now it is a reconstruction under unpolarized input irradiance in outdoor clear weather, which can be extended to biased irradiance incident under clear skies, and in the future it can be applied to the reconstruction of biased irradiance in outdoor fields in general weather. The third improvement is that it was previously targeted at solids, but is currently targeted at the three-dimensional reconstruction of dynamic sea surfaces. Summary of the invention

[0005] In order to solve the defects in the prior art, the present invention discloses a polarization three-dimensional reconstruction method of marine oil spill under ambiguity, and its technical solution is as follows:

[0006] A polarization three-dimensional reconstruction method for marine oil spill under ambiguity, characterized by comprising the following steps:

[0007] Step 1: Acquisition of raw data: When the weather is close to ideal, use an ocean polarization camera to take pictures of the polarization degree and polarization angle of the sea surface; when the weather is not ideal, in addition to using an ocean polarization camera to take pictures of the polarization degree and polarization angle of the sea surface, a sky polarization camera is also needed to take pictures of the polarization degree and polarization angle of the sky;

[0008] Step 2: Calculation of zenith angle: Select the specular reflection used by the oil film on the sea surface; set the range of the zenith angle to a monotonic interval and less than the Brewster angle, and calculate the zenith angle using the polarization degree of the sea surface and the refractive index of the oil film or seawater;

[0009] Step 3: Calculation of azimuth angle: The polarization angle is obtained by rotation or directly. At this time, the polarization angle is ambiguous. On the incident and exit planes, any elevation angle is taken as the azimuth angle, which is called pseudo-azimuth angle. Or in the case of ambiguity, the azimuth angle only takes positive and monotonic values.

[0010] Step 4: Polarization 3D reconstruction: Use the Frankot-Chellapp global integration method to convert the mirror normal into the gradient of the surface;

[0011] In digital 3D reconstruction, the ambiguity of polarization 3D reconstruction is known; p and q represent the gradient on the 2D plane; where, when the azimuth angle is less than or equal to 0 and the pitch angle is less than or equal to 0, the azimuth angle of the sine in the p value is taken , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is less than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is less than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; The three-dimensional graph of the ocean oil film is obtained through Frankot-Chellapp integration;

[0012] When there is ambiguity in the true 3D reconstruction, the x and y directions of the ocean oil film increase monotonically; if random positive and negative values ​​are added artificially, a pseudo reconstruction can be obtained, reflecting the value of the polarization degree.

[0013] Beneficial Effects

[0014] Through the polarization 3D reconstruction of the ocean oil film under ambiguity, the height difference of the ocean oil film can be used to reflect the type of oil, and the pseudo reconstruction can be used to reflect the size of the waves, which can lay the foundation for the unambiguous 3D reconstruction of the oil film. Among them, the acquisition of the zenith angle based on mirror reflection adopts the form of a table, and at the same time combines the artificial selection of angles to avoid the ambiguity of the zenith angle; the azimuth angle of digital reconstruction uses four segments to construct the input and output parameters to avoid the ambiguity of the azimuth angle; finally, the Frankot-Chellapp integral is used to obtain the reconstruction effect, and the introduction of random amplitude can achieve the pseudo reconstruction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of target surface normal measurement in the present invention;

[0016] Figure 2 Schematic diagram of polarization azimuth in Rayleigh scattering of the present invention;

[0017] Figure 3 Schematic diagram of four reflection conditions of light waves on the surface of an object of the present invention;

[0018] Figure 4 Schematic diagram of specular reflection and diffuse reflection of the present invention, wherein (a) is specular reflection polarization; (b) is diffuse reflection polarization;

[0019] Figure 5 It is a schematic diagram of the relationship between phase and azimuth;

[0020] Figure 6 Schematic diagram of the azimuth and pitch angle of the sea surface / scattering angle and azimuth angle of the sun and sky / scattering angle and azimuth angle of the sky and detector of the present invention; upper left - the azimuth angle of the sea surface, upper middle - the scattering angle of the sun and sky, upper right - the scattering angle of the sky and detector; lower left - the pitch angle of the sea surface, lower middle - the phase angle of the sun and sky, lower right - the phase angle of the sky and detector;

[0021] Figure 7 Schematic diagram of sky light input, specular reflection output and diffuse reflection output of the present invention; wherein, Figure 7 The top 4 images are S0, S1, S2, S3 of the sky, the middle 4 images are S0, S1, S2, S3 of reflection, and the bottom 4 images are S0, S1, S2, S3 of transmission.

[0022] Figure 8 Schematic diagram of the degree of polarization and polarization angle of specular reflection and diffuse reflection of the present invention; wherein, the upper left is the degree of polarization of specular reflection, the upper right is the degree of polarization of diffuse reflection, the lower left is the polarization angle of specular reflection, and the lower right is the polarization angle of diffuse reflection;

[0023] Fig. 9Schematic diagram of digital simulation of three-dimensional reconstruction of the sea surface according to the present invention; (a) indicates that the angle between the propagation direction of the sea wave and the reference direction is 45°, and the wind direction is consistent with the reference direction (i.e., the wind direction is along the reference direction); (b) indicates that the angle between the propagation direction of the sea wave and the reference direction is 0°, and the wind direction is consistent with the reference direction (i.e., the wind direction is along the reference direction);

[0024] Fig.10 Schematic diagram of data collection of the sea surface test flight platform of the present invention; wherein, the upper 4 figures are S0, S1, S2, S3 of the oil film, and the lower 4 figures are I, Q, U, V of the oil film, respectively;

[0025] Fig.11 Schematic diagram of the zenith angle, azimuth angle, reconstruction and pseudo-reconstruction of the oil film and the sea surface of the present invention; wherein the upper four figures are the zenith angle, azimuth angle, reconstruction and pseudo-reconstruction of the oil film, and the lower four figures are the zenith angle, azimuth angle, reconstruction and pseudo-reconstruction of the sea water, respectively;

[0026] Fig.12 Schematic diagram of the sky and oil film polarization data collected by the platform of the present invention; wherein the upper 4 images are S0, S1, S2, and S3 of the sky, and the lower 4 images are I, Q, U, and V of the oil film, respectively;

[0027] Fig.13 Schematic diagram of the zenith angle, azimuth angle, reconstruction and pseudo-reconstruction of the oil film of the present invention. DETAILED DESCRIPTION

[0028] A polarization three-dimensional reconstruction method for marine oil spill under ambiguity includes the following steps:

[0029] Step 1: Acquisition of raw data: Under ideal weather conditions, use an ocean polarization camera to take pictures of the polarization degree and polarization angle of the sea surface, such as Figure 1 ; When the weather is not ideal, the sky polarization camera captures the polarization degree and polarization angle of the sky;

[0030] When the weather is ideal, the polarization degree of the sky is calculated by the angle between the incident and outgoing light and the maximum polarization degree. The polarization angle is calculated by the azimuth and elevation angles of the light source and the azimuth and elevation angles of the ocean camera. The azimuth and elevation angles of the light source depend on the position of the sky reflected by the oil spill on the sea surface. The brightness of the sky is calculated by the Perez model.

[0031] In order to briefly explain the polarization effect of sky light, Rayleigh particle scattering is used for demonstration. First, the mechanism and distribution pattern of sky polarized light are studied. During the atmospheric transmission process, sunlight is absorbed and scattered by atmospheric molecules and aerosol particles. The sunlight incident on the atmosphere consists of two orthogonal linearly polarized waves, but there is no coherence relationship. The oscillating electric field excites individual molecules, causing them to produce sinusoidal vibrations, that is, polarized light is generated. The electric field vectors of the polarized components are arranged in concentric circles along the original propagation direction, and the polarized electric field components are tangent to the surface of the sphere.

[0032] The normalized Stokes parameters of linearly polarized light are expressed as:

[0033] (1)

[0034] Where P represents the degree of polarization, Ψ represents the azimuth angle, Χ represents the ellipticity angle, and Χ=0°.

[0035] Rayleigh theory has:

[0036] (2)

[0037] Assuming that incident unpolarized light is scattered by small isotropic particles (air molecules much smaller than the wavelength of light), the scattering angles are given in spherical coordinates:

[0038] (3)

[0039] Figure 2 shows the geometry for deriving the polarization azimuth. The derivation starts with a unit vector pointing toward the sun, given , where , , The observer's unit vector is , where , , .

[0040] Tangent Perpendicular to R and Q, we have T=Q×R, and vector N is perpendicular to the plane containing the z-axis and Q, N=Q×k. If t is a vector parallel to T, and n is a vector parallel to N, then we have , is the angle between n and t, i.e. the azimuth of polarization The formula is as follows;

[0041] (4)

[0042] Rayleigh does not take into account the interaction between incident solar radiation and large atmospheric particles (cloud droplets, ice crystals, aerosols, etc.), as well as the effects of multiple scattering and particle anisotropy.

[0043] Referring to the Perez model, the brightness of the sky light can be expressed as follows:

[0044] (5)

[0045] (6)

[0046]

[0047] In the formula, is the angle between the observation point in the sky and the zenith axis Z, is the angle between the observation point in the sky and the sun. is the angle between the sun and the zenith axis Z, is the brightness of the zenith, and is a constant.

[0048] Step 2: Calculation of zenith angle: Select the specular reflection used by the oil film on the sea surface; set the range of the zenith angle to a monotonic interval, using a value less than the Brewster angle; calculate the zenith angle using the refractive index and polarization degree;

[0049] Generally speaking, the reflection of marine oil spills is mainly specular reflection. Usually, the degree of polarization can be obtained from the refractive index and the angle between the incident and reflected light (zenith angle). In fact, the zenith angle obtained from the degree of polarization and the refractive index is nonlinear, with the Brewster angle as the turning point. A table can be made according to the magnitude of the degree of polarization and the zenith angle. The nearest value of the actual degree of polarization can be obtained by looking up the table to get the corresponding zenith angle. When it is less than or greater than the Brewster angle, it is linear; when it is on both sides of the Brewster angle, it is nonlinear and ambiguous.

[0050] When the seawater is turbid, the reflection of ocean oil spills is mainly diffuse reflection. The zenith angle is a function of the refractive index and polarization degree, so it is linear and there is no ambiguity.

[0051] According to the analytical model of reflected light from the surface of an object proposed by Wolff, four types of light will be generated after passing through the surface and / or the interior, such as Figure 3 As shown in the figure. Represents the light reflected once from the surface of an object, also known as specular polarized reflected light; It refers to light that has been reflected multiple times by the surface of an object. Generally, it is very weak and unbiased. It means that the light that enters the object and then appears on the surface of the object after multiple scattering by particles inside the object is mostly diffusely reflected, resulting in polarization; The light diffracted on the surface of an object is called diffracted light, which is also weak and unbiased. Below we only consider the polarized light of reflection and diffuse reflection.

[0052] The zenith angle of specular reflected light is the angle between the incident light and the normal, or between the normal and the outgoing light. Specular reflected light refers to the reflected light formed by one reflection when the light wave is incident on a plane much larger than the wavelength. According to the Fresnel formula, the polarization degree of specular reflected light is:

[0053] (7)

[0054] In the formula, is the refractive index, is the zenith angle.

[0055] like Figure 4 As shown in the middle left figure, when the polarization degree is 0.7, as indicated by the horizontal line in the figure, there are two zenith angles of about 40° and 70° for water, gasoline, and crude oil, which can achieve the same polarization degree. It can be seen that ambiguity occurs in specular reflection.

[0056] When the object is diffuse, according to the Fresnel formula:

[0057] (8)

[0058] The zenith angle of diffuse reflection refers to the angle between the normal and the outgoing light. Compared with the specular reflection light, Figure 4 As shown in the figure on the right, the polarization degree of 0.5 is represented by a horizontal line, and the polarization degree of diffuse reflection increases monotonically and is maximum when approaching the zenith angle of 90°. There is no ambiguity in diffuse reflection.

[0059] When calculating the zenith angle, the mirror reflection cannot be matched one to one due to the existence of ambiguity, and the relationship between the zenith angle and the degree of polarization is determined by the table lookup method. Since there is no ambiguity in diffuse reflection, cosθ can be approximately written in the form of refractive index and degree of polarization:

[0060] (9)

[0061] Step 3: Calculation of azimuth angle: The polarization angle is obtained by rotation or directly. At this time, the polarization angle is ambiguous. On the incident and exit planes, any angle is taken as the azimuth angle, which is called the pseudo-azimuth angle. Or in the case of ambiguity, the azimuth angle only takes positive and monotonic values.

[0062] As the polarizer angle changes, the light intensity will change. It is the value of maximum light intensity, minimum light intensity, phase angle and polarizer angle. When diffuse reflection is dominant, the phase angle can be or ; When specular reflection is dominant, the phase angle can be or .

[0063] Assuming that a rotatable linear polarizer is placed before the polarization imaging device, the reflected light intensity obtained by the polarization acquisition device will change with the rotation angle of the linear polarizer. The maximum light intensity observed when the polarizer is rotated is I max , the minimum light intensity is I min . Observed I max The angle of the polarizer is called the phase angle Ψ, such as Figure 4 The surface normal vector is expressed in polar coordinates, where the azimuth angle is denoted by ϕ and the zenith angle is denoted by θ. The azimuth angle ϕ is the same as the angle φ of the reflection plane (ϕ = φ).

[0064] like Figure 5 As shown, for point P on the surface of the object, the normal on the surface is N. φ represents the azimuth of P, that is, the angle between the x-axis and the plane where the incident light and the reflected light are located; is the direction of the polarizer, that is, the angle between the x-axis and the polarization direction of the polarizer (red dotted line); θ represents the angle between the vertical plane of the incident plane and the polarization direction of the linear polarizer (red dotted line), so:

[0065] (10)

[0066] When specular reflection and diffuse reflection occur, the Stokes vector is:

[0067] (11)

[0068] (12)

[0069] In the formula, , are the vectors for specular and diffuse reflection, is the Meuller matrix of the polarizer, , is the Meuller matrix for reflection and transmission, is the incident light, whether it is specular reflection or diffuse reflection, assuming it is unpolarized, it is the [1,0,0,0] vector.

[0070] The law of light intensity changing with linear polarization is:

[0071] (13)

[0072] in, , Refers to the maximum and minimum values ​​of the received light intensity. is the angle of the linear polarizer, Refers to the phase angle, which is related to the azimuth The relationship is as follows:

[0073] (14)

[0074] In fact, sky light is biased.

[0075] Step 4: Polarization 3D reconstruction:

[0076] The Frankot-Chellapp global integration method is used to transform the mirror normal into the gradient of the surface.

[0077] The surface function can be expressed as a linear combination of a series of orthogonal basis functions to solve the problem of integral reconstruction of surface discontinuities, so:

[0078] (15)

[0079] (16)

[0080] In the formula, and For function The expansion coefficients of . We can take the Fourier coefficients with a complete orthogonal basis for expansion, so:

[0081] (17)

[0082] In the formula, are the dimensions of the two-dimensional image respectively. At this time, the gradient field of the surface function is obtained by Fourier transform and combining (9) and (10). , is the coordinate system after Fourier transformation.

[0083] (18)

[0084] From this, we can get the expression of the gradient field of the object surface with respect to the microfacet point cloud:

[0085] (19)

[0086] The model establishes a connection between the discrete gradient field information in the spatial domain and the surface field information in the Fourier domain through the decomposition of the Fourier orthogonal basis to reconstruct the surface function.

[0087] When there is ambiguity in the true 3D reconstruction, the x and y directions of the ocean oil film increase monotonically; if random positive and negative values ​​are added artificially, a pseudo reconstruction can be obtained, reflecting the value of the polarization degree.

[0088] Example 1 (Digital)

[0089] Set 128×128 pixels, the refractive index of seawater is 1.339, and the refractive index of crude oil is 1.526. The time is set to 11:00 am on October 16, 2022, 120°58.5′ east longitude, 35°43.8′ north latitude, the azimuth of the sun is -0.568 (south is 0, west is positive), the pitch angle is 0.673, and the vector of the sun is [0.660, -0.421, 0.623]. The azimuth of the detector is 160°, the pitch angle is 10°, and the vector is [-0.937, 0.304, 0.1736]. The normal of the sea surface wave element (abbreviated as surface element) is random, which is and The cross product of the inclination angles in two directions is denoted by the vector , so the pitch angle of the sea surface is The azimuth is The value of the azimuth angle is determined by the sign of the vector element. When the first and second vector elements are -+ and ++ respectively, the value of the azimuth angle is determined by the sign of the vector element. When the first and second vector elements are - and + respectively, take the second vector element The sky light source's vector is determined by the probe and the sea surface normal vector.

[0090] The dot product of the sun and the sea surface normal vector is normalized and the cosine is taken to obtain the scattering angle from the sun to the sky, and half of it is taken as the zenith angle; when the cross product of the sun and the sea surface normal vector is normalized, the unit T tangent is obtained; when the cross product of the sun and the z-axis vector is normalized, the unit N tangent is obtained; the dot product of T and N tangents obtains the azimuth angle from the sun to the sky. Similarly, the dot product of the sea surface normal and the detector vector is normalized and the cosine is taken to obtain the scattering angle from the sky to the detector, and half of it is taken as the zenith angle; when the cross product of the sea surface normal and the detector pointing vector is normalized, the unit T tangent is obtained; when the cross product of the sea surface normal and the z-axis vector is normalized, the unit N tangent is obtained; the dot product of T and N tangents obtains the azimuth angle from the sky to the detector.

[0091] like Figure 6 As shown in the figure on the left, the elevation angle and azimuth of the ocean are shown in the figure on the right. The value fluctuates slightly around, while the azimuth value is It can be seen from the figure that the waves are mostly chaotic. In the lower right (the sea surface with 110-130 pixels on the x-axis and 10-30 pixels on the y-axis), the basic direction is consistent, indicating that the waves are heading in one direction, with large crests or troughs. The middle figure shows the scattering angle and phase angle of the sun and the sky, which shows the fluctuations caused by the waves on the sea surface. When the pitch angle is low, the azimuth angle does not change much; when the pitch angle is high, the change in azimuth angle is similar to that of the sea surface. The right figure shows the scattering angle and phase angle of the sky and the detector. Its fluctuations are similar to those of the sun and the sky, except that there will be changes between the two values.

[0092] Skylight is the incident light. Let the unpolarized light be 0.2. For polarized light, the polarization degree is obtained from equation (13). If the azimuth angle is known, the Stokes vector of the incident light can be obtained. For the sea surface, its reflected light is divided into specular reflection light and diffuse reflection light. Regardless of specular reflection light or diffuse reflection light, half of the scattering angle is the incident angle. Combined with the refractive index of seawater or oil film, the reflectance ratio of s and p waves can be calculated, and thus the matrix of specular and diffuse reflection can be calculated, as shown in Fig. 9 shown.

[0093] Figure 7 The top 4 figures show the Stokes vector of the input skylight, S0 is 1; S1 and S2 are complementary, and they jitter in a small range due to the tilt of the sea surface; S3 is assumed to be 0. The middle 4 figures show the Stokes vector of specular reflection, S1 and S2 of specular reflection are the same as those of incident light, and S1 and S2 are complementary. The bottom 4 figures show the Stokes vector of diffuse reflection, S0 does not have an obvious peak of specular reflection, and is basically consistent with the skylight in terms of S1 and S2, and S1 and S2 are complementary.

[0094] When the Stokes vectors of specular reflection and diffuse reflection are known, the polarization degree and polarization angle of specular reflection and diffuse reflection can be known, such as Figure 8 As shown. Upper left - the polarization degree of specular reflection, upper right - the polarization degree of diffuse reflection, lower left - the polarization angle of specular reflection, lower right - the polarization angle of diffuse reflection. When the positions of the sky (light source), sea surface and detector are known, the polarization degree of specular reflection is stronger than that of diffuse reflection, reaching about 0.5 for specular reflection and 0.2 for diffuse reflection. The peak and valley values ​​of specular reflection are stronger than those of diffuse reflection. The polarization angles of specular reflection and diffuse reflection are different, and the difference between the two is , which is where the ambiguity arises.

[0095] In digital simulations, the ambiguity of polarization 3D reconstruction is known. When the azimuth angle is less than or equal to 0 and the elevation angle is less than or equal to 0, the azimuth angle of the sine in the p value is taken as , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is less than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is less than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is Then, using the Depth from Gradient simulation program, we can get the polarization 3D reconstruction result of the ocean surface, such as Fig. 9 shown. Fig. 9 In a), the surge height is 0.5m, the wind and wave are 5m / s; the surge angle is 45°, and the wind and wave are 0°. The original image of the wave is shown on the left, and the reconstructed image is shown on the right. The dark lines on the left represent depressions, and the bright lines represent convexities; in the right, when viewed along the 45° direction, blue represents troughs and yellow represents crests. It can be clearly seen from the figure that surges dominate the waves, and the waves propagate in the 45° direction. In b), the surge angle is 0°, the wind and wave are 0°, and the waves have no obvious directionality.

[0096] Example 2 (real object)

[0097] Sea flight experiment

[0098] A total of two physical experiments were conducted, the first was sea flight and the second was enclosure. The sea test flight platform was a DJI M300 drone with dimensions of 810×670×430mm. 3 . The experimental device is a Sony XCG-CP510 monochrome linear polarization camera with an intensity resolution of 2056×2464 pixels and a field of view of 30° (23.0°×19.2°). The location is a sea area in Qingdao, 120°58′.5 east longitude and 35°43′.8 north latitude. The time is May 1, 2021, and the northwest wind force is level 3. The azimuth of observation is 180° and the pitch angle is 80°. The acquired images are divided into three bands: red, green and blue, with intensity, degree of polarization, polarization angle, Stokes vector diagram, and 0° / 45° / 90° / 135° polarization diagram. The image at 12:53 noon is as follows Fig.12 As shown, the sun is located at an azimuth of -0.12° and an elevation of 65.94°.

[0099] Fig.10In the figure, S0, S1, S2, and S3 represent the combined effect of the mixture of red, green, and blue light. From the data, the polarized light of the three colors is the same. In order to make the polarization measurement more rigorous, the Stokes vector of the red light is taken, which are called I, Q, U, and V. The refractive index of crude oil is 1.526 and the Brewster angle is 44.03°. The refractive index of seawater is 1.339 and the Brewster angle is 53.07. According to the azimuth and pitch angles of the sun and the platform, the maximum zenith angles are 56.81° and 53.16°. The morphology of seawater and crude oil is consistent. From the maximum zenith angle of seawater, it can be seen that By looking up the table on one side, the true zenith angle θ can be obtained. The azimuth angle is generally only , but not .

[0100] use Fig.11 , through reconstruction, we can get the three-dimensional image of oil film and seawater. Due to the ambiguity between zenith and azimuth, the growth direction of both oil film and sea surface is monotonically increasing. If the height of oil film and seawater is 117.70m and 109.71m at [1,1] and [320,320] pixels, the difference between the two is 7.28% based on seawater. If the ambiguity of azimuth has been resolved, it can be found from the figure that the sea surface is convex at about [300,300] pixels, and it is not obvious in other places.

[0101] Enclosure test

[0102] The second test is an enclosure test. The test equipment is the same as above. The location is a certain urban area in Qingdao, 120°6′20″E, 35°55′37″N. The time is July 16, 2023, and the northwest wind force is level 2. The azimuth angle of observation is 0° and the pitch angle is 45°. At 10:35 am, the sun is at an azimuth of -13.16° and a pitch of 54.34°.

[0103] Fig.12 In the figure, S0, S1, S2, and S3 represent the Stokes vectors of the sky. From the vectors, we can see that the weather is cloudy, which has a certain impact on the three-dimensional reconstruction of the oil film. I, Q, U, and V represent the Stokes vectors of crude oil, among which three elliptical shapes appear saturated. The refractive index of crude oil is 1.526 and the Brewster angle is 44.03°. From the azimuth and pitch angles of the sun and the platform, we can see that the tentative azimuth is in the latter section [44.03°, 90°]. In fact, it exists in [0°, 90°], but the unsaturated or azimuth in the latter section is still valid.

[0104] use Fig.13, through reconstruction, a three-dimensional image of the oil film can be obtained. At [1,1] and [320,320] pixels, the oil film height is 764.40m, and the seawater is 565.77m. Taking the seawater as the reference, the difference between the two is 35.11%. If the azimuth ambiguity has been resolved, it can be found from the figure that the enclosure is concave in the middle and convex around.

[0105] The present invention mainly demonstrates the process and results of three-dimensional reconstruction from two aspects: digital three-dimensional reconstruction of oil film polarization and physical three-dimensional reconstruction of marine oil spills and external enclosures. Because the azimuth angle of digital three-dimensional reconstruction can be allocated in four quadrants, while the physical object can only be allocated in two quadrants, the ambiguous three-dimensional reconstruction of the physical object can only increase monotonically. The ambiguity of the zenith angle can be set artificially in the physical object. Taking the Brewster angle as the breakpoint, the front half and the back half are separated, which can avoid the ambiguity of the zenith angle to a certain extent. If the waves want to generate a real three-dimensional image, there are at least three methods, multi-wavelength, multi-axis, and multi-depth. Multi-wavelength refers to using the difference in polarization degree of different wavelengths to determine which area the azimuth falls in; multi-axis uses different axes to determine the direction of the normal; multi-depth refers to using millimeter waves to determine the depth of the object, and then combining it with the polarization image. In addition, using the prior knowledge of the object, such as a few points or faces are known, the three-dimensional image is restored by Monte Carlo calculation. Compared with the previous three polarization reconstructions, the new polarization reconstruction does not require additional equipment, but it brings new challenges to the selection of prior knowledge.

[0106] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A polarization 3D reconstruction method for marine oil spills under ambiguity, characterized by: The steps include: Step 1: Acquisition of raw data: When the weather is close to ideal, use an ocean polarization camera to take pictures of the polarization degree and polarization angle of the sea surface; when the weather is not ideal, in addition to using an ocean polarization camera to take pictures of the polarization degree and polarization angle of the sea surface, a sky polarization camera is also needed to take pictures of the polarization degree and polarization angle of the sky; Step 2: Calculation of zenith angle: Select the specular reflection used by the oil film on the sea surface; set the range of the zenith angle to a monotonic interval and less than the Brewster angle, and calculate the zenith angle using the polarization degree of the sea surface and the refractive index of the oil film or seawater; Step 3: Calculation of azimuth angle: The polarization angle is obtained by rotation or directly. At this time, the polarization angle is ambiguous. On the incident and exit planes, any elevation angle is taken as the azimuth angle, which is called pseudo-azimuth angle. Or in the case of ambiguity, the azimuth angle only takes positive and monotonic values. Step 4: Polarization 3D reconstruction: Use the Frankot-Chellapp global integration method to convert the mirror normal into the gradient of the surface; In digital 3D reconstruction, the ambiguity of polarization 3D reconstruction is known; p and q represent the gradient on the 2D plane; where, when the azimuth angle is less than or equal to 0 and the pitch angle is less than or equal to 0, the azimuth angle of the sine in the p value is taken , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is less than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is less than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; When the azimuth angle is greater than 0 and the elevation angle is greater than 0, the azimuth angle of the sine in the p value is , the cotangent of the pitch angle is , the azimuth of the cosine of the q value is ; The three-dimensional graph of the ocean oil film is obtained through Frankot-Chellapp integration; When there is ambiguity in the true 3D reconstruction, the x and y directions of the ocean oil film increase monotonically; if random positive and negative values ​​are added artificially, a pseudo reconstruction can be obtained, reflecting the value of the polarization degree.

2. The polarization 3D reconstruction method of marine oil spill under ambiguity according to claim 1, characterized in that the step 1 further comprises the following contents: When the weather is close to ideal, the degree of polarization is calculated by the angle between the incident and outgoing light and the maximum degree of polarization. The polarization angle is calculated by the azimuth and elevation of the light source and the azimuth and elevation of the ocean camera. The azimuth and elevation of the light source depend on the position of the sky reflected by the oil spill on the sea surface. The brightness of the sky is calculated by the Perez model.

3. A non-volatile storage medium, characterized in that: The non-volatile storage medium includes a stored program, wherein when the program is executed, the device where the non-volatile storage medium is located is controlled to execute the method according to any one of claims 1 to 2.

4. An electronic device, characterized in that: It comprises a processor and a memory; the memory stores computer-readable instructions, and the processor is used to execute the computer-readable instructions, wherein the computer-readable instructions execute the method described in any one of claims 1 to 2 when executed.

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