Polarization scattering model parameter measurement method and device based on Monte Carlo method

Abstract

The present invention provides a method and device for measuring polarization scattering model parameters based on the Monte Carlo method. The method includes: simulating the multiple scattering process of polarized light during diffuse reflection based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient of polarized light and the scattering distance of polarized light scattered within the material; establishing a functional curve between the depolarization coefficient and the scattering coefficient based on the second functional relationship and the first functional relationship between the scattering coefficient and scattering distance of different materials; fitting the functional curve with a pre-constructed initial model to generate a polarization scattering model; and optimizing the polarization parameters and intensity parameters in the polarization scattering model to obtain an optimized polarization scattering model. The polarization scattering model of the embodiment of the present invention can more accurately restore the polarization information of an object and can handle non-traditional high-scattering objects.

Description

Technical Field

[0001] The present invention relates to the field of polarized light technology, and in particular to a method and device for measuring polarization scattering model parameters based on a Monte Carlo method. Background Art

[0002] The polarization reflection model, a fundamental model that describes the changes in intensity and polarization state of polarized light after reflection, combines the two dimensions of light to model light interactions while respecting physics. The concepts of specular and diffuse reflection are equally applicable. However, the existing polarization reflection model, which assumes complete depolarization when dealing with polarized diffuse reflection, is inappropriate for non-traditional, highly scattering objects and cannot accurately restore the object's polarization information. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and device for measuring polarization scattering model parameters based on the Monte Carlo method, which is used to solve the problem that the polarization reflection model in the prior art follows the complete depolarization assumption when processing polarized diffuse reflection, is not applicable when processing non-traditional high-scattering objects, and cannot accurately restore the polarization information of the object.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides a method for measuring polarization scattering model parameters based on the Monte Carlo method, comprising:

[0005] Simulating the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered inside the material;

[0006] establishing a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficients of different materials and the scattering distance and the first functional relationship;

[0007] Fitting the function curve with a pre-built initial model to generate a polarization scattering model;

[0008] The polarization parameters and intensity parameters in the polarization scattering model are optimized respectively to obtain the optimized polarization scattering model.

[0009] Optionally, simulating the multiple scattering process of the polarized light in the diffuse reflection process based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material includes:

[0010] Tracking the polarized light during the diffuse reflection process based on the meridian plane method in the Monte Carlo method to obtain a multiple scattering matrix corresponding to the polarized light during the multiple scattering process;

[0011] The multiple scattering matrix is ​​decomposed according to a polar decomposition method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material.

[0012] Optionally, optimizing the polarization parameter and the intensity parameter in the polarization scattering model respectively to obtain the optimized polarization scattering model includes:

[0013] Optimizing the polarization parameters in the polarization scattering model at a pixel level to obtain first optimized parameters;

[0014] Optimizing the intensity parameter in the polarization scattering model according to the first optimization parameter to obtain a second optimization parameter;

[0015] Error correction is performed on the Stokes vectors in the first optimization parameter and the second optimization parameter to obtain the optimized polarization scattering model.

[0016] Optionally, after performing pixel-level optimization on the polarization parameters in the polarization scattering model to obtain first optimized parameters, the method further includes:

[0017] In a case where the first optimization parameters include non-pixel level parameters, the non-pixel level parameters are converted into material level parameters, and the first optimization parameters are updated.

[0018] Optionally, the method further includes:

[0019] The initial model is constructed according to the first polarization and the first intensity corresponding to the polarized light during diffuse reflection and the second polarization and the second intensity corresponding to the polarized light during specular reflection.

[0020] Optionally, the method further includes:

[0021] generating the first intensity according to the normalized diffusion principle and albedo;

[0022] The first polarization is generated according to the depolarization coefficient, the Fresnel reflection principle, and the rotation angle of the polarized light.

[0023] Optionally, the first functional relationship includes:

[0024] formula Where λ is the depolarization coefficient, l d is the average distance, and r is the actual scattering distance of polarized light scattered inside the material;

[0025] The second functional relationship includes:

[0026] formula in, σ′s is the scattering coefficient, σ a is the absorption coefficient.

[0027] An embodiment of the present invention further provides a device for measuring polarization scattering model parameters based on the Monte Carlo method, comprising:

[0028] A first simulation module is configured to simulate a multiple scattering process of polarized light in a diffuse reflection process based on a Monte Carlo method, and obtain a first functional relationship between a depolarization coefficient of the polarized light and a scattering distance of the polarized light scattered inside a material;

[0029] A first establishing module is configured to establish a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficient of different materials and the scattering distance and the first functional relationship;

[0030] A first fitting module is used to fit the function curve with a pre-built initial model to generate a polarization scattering model;

[0031] The first optimization module is used to optimize the polarization parameters and intensity parameters in the polarization scattering model respectively to obtain the optimized polarization scattering model.

[0032] An embodiment of the present invention also provides a network device, comprising: a processor, a memory, and a program stored in the memory and runnable on the processor, wherein when the program is executed by the processor, the polarization scattering model parameter measurement method based on the Monte Carlo method as described in any one of the above items is implemented.

[0033] An embodiment of the present invention further provides a readable storage medium, comprising: a program stored on the readable storage medium, wherein when the program is executed by a processor, the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method as described above are implemented.

[0034] An embodiment of the present invention further provides a computer program product, comprising computer instructions, which, when executed by a processor, implement the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method as described above.

[0035] At least one of the above technical solutions of the present invention has the following beneficial effects:

[0036] In the above scheme, the polarized light is set to have a depolarization coefficient. During the diffuse reflection process, the polarized light gradually reduces its polarization degree based on the depolarization coefficient during the scattering process inside the material. First, the Monte Carlo method is used to simulate the multiple scattering process of polarized light during the diffuse reflection process to obtain a first functional relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered inside the material. Then, based on the second functional relationship between the scattering coefficient of different materials and the scattering distance, a functional curve between the depolarization coefficient and the scattering coefficient is established; secondly, the functional curve is fitted with a pre-constructed initial model to generate a polarization scattering model; finally, the polarization parameters and intensity parameters in the polarization scattering model are optimized respectively to obtain an optimized polarization scattering model. The optimized polarization scattering model takes into account the depolarization coefficient, can more accurately restore the polarization information of the object, and can handle non-traditional high-scattering objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of a process for measuring polarization scattering model parameters based on the Monte Carlo method according to an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the meridian plane of light when describing the mixed scattering phenomenon of polarized light based on the Monte Carlo method in an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of a multiple scattering matrix in an embodiment of the present invention;

[0040] Figure 4 is a schematic diagram of a two-dimensional attenuation matrix after decomposing the multiple scattering matrix in an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of a phase delay matrix after decomposing a multiple scattering matrix in an embodiment of the present invention;

[0042] Figure 6 Schematic diagram of a generalized depolarization matrix after decomposing a multiple scattering matrix in an embodiment of the present invention;

[0043] Figure 7 Schematic diagram of the relationship between the depolarization coefficient and the scattering distance in an embodiment of the present invention;

[0044] Figure 8 Schematic diagram of the relationship between the depolarization coefficient and the scattering coefficient in an embodiment of the present invention;

[0045] Figure 9 A schematic diagram of a process for optimizing parameters in a polarization scattering model according to an embodiment of the present invention;

[0046] Figure 10This is a scatter plot of the relationship between the polarization degree and the incident angle of the strong specular reflective material obtained by direct observation;

[0047] Figure 11 In order to utilize the polarization scattering model provided by the present invention in the rendering system Figure 10 Scatter plot of the relationship between polarization degree and incident angle after simulation of medium-strong specular reflective material;

[0048] Figure 12 This is a scatter plot of the relationship between the polarization degree and the incident angle of the diffuse reflective material obtained by direct observation;

[0049] Figure 13 In order to utilize the polarization scattering model provided by the present invention in the rendering system Figure 12 Scatter plot of the relationship between polarization degree and incident angle after simulation of diffuse reflective materials;

[0050] Figure 14 Schematic diagram of the results of fitting various materials using the polarization scattering model provided in an embodiment of the present invention;

[0051] Figure 15 Schematic diagram of the structure of a polarization scattering model parameter measurement device based on the Monte Carlo method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] 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 only part of the embodiments of the present invention and not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] The polarized bidirectional reflectance distribution function (pBRDF) model in the prior art focuses on the expression of specular reflection components and diffuse reflection components. Some models expand the field of view to the scattering field and extend the model to single scattering, but are limited to the same exit point. Admittedly, the scattering phenomenon is generally approximated by the diffuse reflection component, but when the scattering distance of the scattering phenomenon generated by our illuminated object is greater than the observation distance, the scattering cannot be ignored. This is also subsurface scattering. The prior art believes that polarized light that penetrates the surface of an object and emerges is completely depolarized, but when the scattering phenomenon cannot be ignored, the model established based on this assumption obviously has errors.

[0054] Therefore, the present invention believes that such reflected light after scattering has a certain polarization-maintaining property, that is, the polarized light has a depolarization coefficient, and during the diffuse reflection process, the polarized light gradually reduces its polarization degree during scattering inside the material based on the depolarization coefficient.

[0055] like Figure 1 As shown, an embodiment of the present invention provides a method for measuring polarization scattering model parameters based on the Monte Carlo method, comprising:

[0056] Step S101, simulating the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method, and obtaining a first functional relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered inside the material;

[0057] Step S102, establishing a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficient of different materials and the scattering distance and the first functional relationship;

[0058] Step S103, fitting the function curve with a pre-built initial model to generate a polarization scattering model;

[0059] In step S103, the initial model is constructed based on the traditional pBRDF model. According to the components of the reflected light, it is classified into two parts: intensity and polarization. The specific form is as follows:

[0060]

[0061] Among them, k s is the intensity parameter corresponding to the mirror reflection, k d is the intensity parameter corresponding to diffuse reflection, which is used to reflect the intensity change of light after reflection; is the polarization parameter corresponding to the mirror reflection, It is the polarization parameter corresponding to diffuse reflection. The polarization parameter is the normalized Mueller matrix, which reflects the change of polarization state of light after reflection.

[0062] Different from the existing technology, The multiple scattering matrix M multiple , M multiple The depolarization coefficient λ is included.

[0063] Step S104 : optimizing the polarization parameters and the intensity parameters in the polarization scattering model respectively to obtain the optimized polarization scattering model.

[0064] In an embodiment of the present invention, polarized light is set to have a depolarization coefficient. During the diffuse reflection process, the polarized light gradually reduces its polarization degree based on the depolarization coefficient during the scattering process inside the material. First, the multiple scattering process of polarized light during the diffuse reflection process is simulated based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered inside the material. Then, based on the second functional relationship between the scattering coefficient of different materials and the scattering distance, a functional curve between the depolarization coefficient and the scattering coefficient is established; secondly, the functional curve is fitted with a pre-constructed initial model to generate a polarization scattering model; finally, the polarization parameters and intensity parameters in the polarization scattering model are optimized respectively to obtain an optimized polarization scattering model. The optimized polarization scattering model takes into account the depolarization coefficient, can more accurately restore the polarization information of the object, and can handle non-traditional high-scattering objects.

[0065] Optionally, simulating the multiple scattering process of the polarized light in the diffuse reflection process based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material includes:

[0066] Tracking the polarized light during the diffuse reflection process based on the meridian plane method in the Monte Carlo method to obtain a multiple scattering matrix corresponding to the polarized light during the multiple scattering process;

[0067] The multiple scattering matrix is ​​decomposed according to a polar decomposition method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material.

[0068] In the embodiment of the present invention, in terms of polarization, the scattering of polarized light inside the material will cause a change in the polarization state and a rotation of the coordinate system. Therefore, the embodiment of the present invention uses the Monte Carlo method to describe the mixed scattering phenomenon of polarized light, and simulates the scattering process of light inside the object as a collision and reflection process between photons and particles in the material. For each collision and reflection, it is regarded as a mirror-like reflection process, such as Figure 2 As shown, s i is the incident light, s o is the outgoing light, the Z axis is the reference axis and will not change during the entire simulation process, AOB is the scattering plane, AOC and BOC are the incident and exit meridian planes, which will change with each scattering. According to the meridian plane method in the Monte Carlo method, the incident and reflected light of the polarized light in the diffuse reflection process are tracked to simulate the transmission of polarized light in the scattering medium, and the reference plane corresponding to the polarization state of the photon before and after each scattering is updated in time.

[0069] Referring to the specular reflection process, single scattering can be expressed as:

[0070] M single=R(-γ)M(θ)R(β).

[0071] Among them, R(-γ) and R(β) are rotation matrices, which can be expressed as:

[0072]

[0073] When δ is -γ, M R (δ) is the matrix expression of R(-γ). When δ is β, M R (δ) is the matrix expression of R(β).

[0074] Where M(θ) is the single scattering matrix, which can be expressed as follows for an isotropic uniform spherical particle medium:

[0075]

[0076] Among them, α is the scattering angle AOB, and the matrix contains s 11 ,s 12 ,s 33 ,s 34 It can be obtained by solving the scattering amplitude of Mie scattering. It should be noted that s here 11 ,s 12 ,s 33 ,s 34 This is not the focus of the present invention and can be simplified in subsequent parts, so it will not be described here in detail.

[0077] Based on this, the multiple scattering matrix for the multiple scattering process can be expressed as:

[0078]

[0079] Specifically, in the simulation, the light beam can be viewed as composed of a large number of photons. By simulating the multiple scattering process of a large number of photons, the simulation results are determined based on the distribution of photons received by the detector. In theory, when the coherence condition is not met between the light beams, the Stokes vectors corresponding to each photon are additive. If enough data is collected, the average polarization degree of the polarized light can be very close to the actual scattering and detection process. The outgoing light and the incident light can be expressed as:

[0080]

[0081] Furthermore, in the process of describing the mixed scattering phenomenon of polarized light based on the Monte Carlo method, in order to eliminate interference factors such as particle scattering properties, particle size and density, it is stipulated that the light is incident vertically, the scattering object is a plane with a curvature of 0 and the internal medium parameters are uniform, and the polarized light backscattered on the specified scattering plane is detected. Then, the polarization state of the incident light is changed, such as Figure 3As shown, the multiple scattering matrix M is obtained by solving the overdetermined equations multiple .

[0082] In order to obtain the multiple scattering matrix M multiple Then, the M multiple Decomposed into product form, assuming that the order of occurrence of each polarization effect is bidirectional attenuation M △ , phase delay M R and generalized depolarization M D Three polarization effects:

[0083] M multiple =M △ M R M D

[0084] The decomposition results are as follows Figure 4-6 As shown, the two-way attenuation matrix M △ ( Figure 4 ) can be basically regarded as a unit matrix, and the two-way attenuation scalar is almost 0, indicating that the multiple scattering process will hardly produce a two-way attenuation effect; for the phase delay effect M R ( Figure 5 ), the phase delay is taken into account when calculating the Fresnel refraction term; for the depolarization matrix M D ( Figure 6 ), further observations are made to generate a depolarization coefficient map on the scattering plane, such as Figure 7 As shown, the depolarization coefficient also presents a diffuse distribution on the scattering plane, and the depolarization of the outgoing polarized light is highly correlated with the outgoing distance. This is because each scattering event of polarized light inside the object will reduce its polarization. When a certain number is reached, that is, a certain scattering distance, the depolarization of the light reaches its strongest point, and the outgoing light is closer to unpolarized light. However, the light scattered before this still has a certain polarization due to the small number of scattering events. Therefore, the embodiment of the present invention believes that the depolarization property of the outgoing light should be related to the sampling distance. Based on this, the first two matrices after the multiple scattering matrix decomposition can be ignored, and only the third depolarization matrix is ​​retained, and then the multiple scattering matrix M multiple It is approximately in the following form:

[0085]

[0086] Where λ is the depolarization coefficient.

[0087] Introducing the average scattering distance l d As a reference scale for distance sampling, according to the average scattering distance l d exist Figure 8 Specifically, Gaussian distribution is used as the sampling strategy, l dBy controlling the sampling range, the first functional relationship between the depolarization coefficient and the scattering distance of polarized light scattered inside the material can be obtained:

[0088]

[0089] Where λ is the depolarization coefficient, l d is the average distance, and r is the actual scattering distance of polarized light scattered inside the material.

[0090] Furthermore, in step S102, the second functional relationship between the scattering coefficient and the average scattering distance of different materials is:

[0091]

[0092] in, σ′ t =σ′ s +σ a ,σ′ s is the scattering coefficient, σ a is the absorption coefficient.

[0093] According to the first functional relationship and the second functional relationship, the function curves between the scattering coefficient and the depolarization coefficient of different materials can be obtained, such as Figure 8 As shown, the expression is:

[0094]

[0095] It should be noted that the error between the function curve obtained in the embodiment of the present invention and the actual sampling result is about 0.71%, and the root mean square error (RMSE) is 0.011, which is relatively small and has high accuracy.

[0096] Optionally, optimizing the polarization parameter and the intensity parameter in the polarization scattering model respectively to obtain the optimized polarization scattering model includes:

[0097] Optimizing the polarization parameters in the polarization scattering model at a pixel level to obtain first optimized parameters;

[0098] Optimizing the intensity parameter in the polarization scattering model according to the first optimization parameter to obtain a second optimization parameter;

[0099] Error correction is performed on the Stokes vectors in the first optimization parameter and the second optimization parameter to obtain the optimized polarization scattering model.

[0100] In the embodiment of the present invention, polarization parameters include but are not limited to a p ,σ′ s and η, where a pis the unitized polarization coefficient, which is an optimized intermediate parameter defined in the embodiment of the present invention, indicating the ratio of the mirror reflection amount to the total reflection amount obtained by optimizing the polarized reflection model; σ′ s is the material scattering coefficient, which is the material level; η is the material refractive index, which is the material level. Intensity parameters include but are not limited to k s , σ, and k d , where k s is the specular albedo, which can be optimized to obtain the pixel level; σ is the material roughness; k d is the diffuse albedo, which is optimized at the pixel level. It should be noted that during the optimization process, the initial value of each parameter needs to be input into the model first and then optimized.

[0101] like Figure 9 As shown, the process of optimizing the parameters of the polarization scattering model provided by the embodiment of the present invention is as follows:

[0102] Step S901: polarization parameter a p ,σ′ s and η are optimized at the pixel level to obtain the first optimization parameter, i.e., the optimized a p ,σ′ s and η:

[0103]

[0104] in, represents the Mueller matrix of the observed object, represents the mirror reflection Mueller matrix fitted by the model, represents the diffuse reflectance Mueller matrix fitted by the model, b p =1-a p , so It can be expressed as the Mueller matrix of the object obtained by model fitting, ρ obv It is expressed as the magnitude of the linear polarization of the observed object, ρ is expressed as the magnitude of the linear polarization of the model fitted, and λ m and λ ρ are the objective function coefficient weights, which are set to 1 and 10 according to the fitting function results.

[0105] Step S902: According to the first optimization parameter, especially a in the first optimization parameter p (a p As the normalized polarization coefficient determines the reflected light during the reflection process), the intensity parameter k s , σ and k d Optimize and obtain the second optimization parameter, namely the optimized k s , σ and k d :

[0106]

[0107] Where K is the number of effective pixels after the mask, s0 is the first dimension of the outgoing Stokes vector, that is, the light intensity. is the first element of the Mueller matrix of the specular reflection in the model before normalization, is the first element of the Mueller matrix for the diffuse reflectance in the model before normalization.

[0108] Step S903: σ′ in the first optimization parameter and the second optimization parameter s ,η,k s , σ and k d The Stokes vector is corrected for errors to obtain the optimized polarization scattering model.

[0109] Optionally, after performing pixel-level optimization on the polarization parameters in the polarization scattering model to obtain first optimized parameters, the method further includes:

[0110] In a case where the first optimization parameters include non-pixel level parameters, the non-pixel level parameters are converted into material level parameters, and the first optimization parameters are updated.

[0111] In the embodiment of the present invention, the polarization parameter a p ,σ′ s After performing pixel-level optimization with η and obtaining the first optimization parameter, due to σ′ s and η are not pixel-level. After the first step, the following optimization is performed to s and η converted to material level:

[0112]

[0113] Where K is the number of effective pixels after the mask, from which the material level result can be obtained.

[0114] Optionally, the method further includes:

[0115] The initial model is constructed according to the first polarization and the first intensity corresponding to the polarized light during diffuse reflection and the second polarization and the second intensity corresponding to the polarized light during specular reflection.

[0116] In the embodiment of the present invention, the initial model is constructed based on the traditional pBRDF model, which is classified into two parts: intensity and polarization according to the components of the reflected light. The specific form is as follows:

[0117]

[0118] Among them, k s is the intensity parameter corresponding to the mirror reflection (i.e. the second intensity), k d is the intensity parameter corresponding to diffuse reflection (i.e., the first intensity), which is used to reflect the intensity change of light after reflection; is the polarization parameter corresponding to the mirror reflection (i.e. the second polarization), is the polarization parameter corresponding to diffuse reflection (i.e., the first polarization). The polarization parameter is a normalized Mueller matrix, which reflects the change in the polarization state of light after reflection.

[0119] Different from the existing technology, The multiple scattering matrix M multiple , M multiple The depolarization coefficient λ is included.

[0120] Specifically, the k corresponding to the specular reflection is s and The expression is the same as that in the prior art:

[0121]

[0122] Among them, k s is the specular albedo, D(θ h ; σ s ) is the normal distribution function, which describes the normal distribution of the tiny mirror at a microscopic angle, G(θ i ,θ o ; σ s ) is a geometric function that describes the self-occlusion properties of the microsurface.

[0123]

[0124] in, To rotate along the incident light axis from the initial incident plane The rotation Mueller matrix F R (θ h ; η) is the Fresnel reflection matrix of the pure linear bidirectional attenuation effect of polarized light; The plane rotation occurs along the outgoing light axis due to mirror reflection The rotation Mueller matrix of .

[0125] Optionally, the method further includes:

[0126] generating the first intensity according to the normalized diffusion principle and albedo;

[0127] The first polarization is generated according to the depolarization coefficient, the Fresnel reflection principle, and the rotation angle of the polarized light.

[0128] In the embodiment of the present invention, the k corresponding to the diffuse reflection isd and The expression of is different from the existing technology. From the aspect of intensity, the normalized diffusion principle is introduced:

[0129]

[0130] Among them, k d is the albedo of diffuse reflection, r is the sampling value for the scattering distance, and d is a parameter that affects the shape of the curve.

[0131] From the perspective of polarization, the introduction of M multiple Matrix, the traditional diffuse reflection polarization part in the prior art is expressed as:

[0132] M d =R(φ o )F T (θ o ;η)M0F T (θ i ;η)R(φ i ).

[0133] Where R(φ o ), R(φ i ) is the rotation Mueller matrix, F T (θ o ; η), F T (θ i η) is the transmission Fresnel matrix, which describes the Fresnel transmission effect produced by light penetrating the surface of an object. Its specific form is:

[0134]

[0135] Where F represents the Fresnel transmission coefficient, The complete depolarization assumption is followed.

[0136] The embodiment of the present invention uses M multiple The matrix replaces M0, where M multiple for:

[0137]

[0138] Where λ is the depolarization coefficient of polarized light.

[0139] The specific embodiments of the present invention are further described in detail below in conjunction with Example 1 and Example 2. It should be noted that the following examples are only used to illustrate the present invention and are not intended to limit the present invention.

[0140] In Example 1, a virtual simulation experiment is performed using the polarization scattering model parameter measurement method based on the Monte Carlo method provided by the present invention:

[0141] The rendering system (Mitsuba) was selected as the rendering tool for the simulation experiments. Mitsuba supports the use of measured polarized materials as object materials. Measured polarized materials are derived from real-world data and possess high accuracy and reliability. It should be noted that rendering systems generally do not include rendering datasets for non-traditional translucent media. Therefore, in this example, traditional materials were selected for simulation.

[0142] A variety of traditional materials including strong specular reflection and diffuse reflection were selected to conduct fitting experiments on polarization degree and intensity, such as Figures 10 to 13 As shown, Figure 10 This is a scatter plot of the relationship between the polarization degree and the incident angle of the strong specular reflective material obtained by direct observation. Figure 11 In order to utilize the polarization scattering model provided by the present invention in the rendering system Figure 10 Scatter plot of the relationship between polarization degree and incident angle after simulation of medium-strong specular reflective materials. Figure 12 This is a scatter plot of the relationship between the polarization degree and the incident angle of the diffuse reflection material obtained by direct observation. Figure 13 In order to utilize the polarization scattering model provided by the present invention in the rendering system Figure 12 A scatter plot of the polarization degree and incident angle after simulation of diffuse reflection material. In this embodiment, a scatter plot of the polarization degree and incident angle is used to visually display the distribution of the object's polarization state. This demonstrates that the polarization scattering model provided by this embodiment of the present invention accurately fits the polarization degree for objects made of traditional materials, regardless of whether the object's surface is dominated by specular or diffuse reflection.

[0143] In Example 2, a physical experiment was conducted using the polarization scattering model parameter measurement method based on the Monte Carlo method provided by the present invention:

[0144] High scattering materials, especially highly scattering translucent materials, were selected as experimental objects. The experimental results are as follows: Figure 14 As shown, the polarization scattering model provided by the embodiment of the present invention is used to fit the three materials A, B, and C respectively, and the fitting results are compared with the observation results to obtain error values. Among them, the transparency relationship of the three materials is C>B>A. The final experiment obtains that the error value corresponding to material A is 0.0153, the error value corresponding to material B is 0.0185, and the error value corresponding to material C is 0.0081.

[0145] Specifically, in the physical experiment, A and B are the same material, namely, cured liquid silicone rubber, and C is made of translucent resin. According to the method proposed in the present invention, the scattering coefficient of the test material can be measured, and the scattering coefficient of the cured liquid silicone rubber σ can be obtained. s ' is 1.395mm-1 , the scattering coefficient of translucent resin is 0.723mm -1 It can be concluded that the latter is more likely to have a scattered optical effect than the former. At the same time, based on simulation experiments, the scattering coefficient of the first type (specular reflection) material, namely synthetic plastic, is 15.413 mm -1 The second type (diffuse reflection) material, Teflon synthetic resin, has a scattering coefficient of 14.449 mm -1 , it is obvious that the scattering coefficient of opaque materials is much higher than that of translucent materials.

[0146] From this, it can be concluded that for highly scattering objects, their overall linear polarization degree is higher than that of traditional non-transparent objects, and the depolarization coefficient of translucent objects is lower than that of traditional non-translucent objects. In addition, the polarization scattering model provided by the embodiment of the present invention has a high fitting accuracy for the intensity and polarization degree of the object.

[0147] like Figure 15 As shown, an embodiment of the present invention further provides a polarization scattering model parameter measurement device based on the Monte Carlo method, comprising:

[0148] A first simulation module 1501 is configured to simulate the multiple scattering process of polarized light in a diffuse reflection process based on a Monte Carlo method, and obtain a first functional relationship between a depolarization coefficient of the polarized light and a scattering distance of the polarized light scattered within a material;

[0149] A first establishing module 1502 is configured to establish a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficient of different materials and the scattering distance and the first functional relationship;

[0150] A first fitting module 1503 is configured to fit the function curve with a pre-built initial model to generate a polarization scattering model;

[0151] The first optimization module 1504 is configured to optimize the polarization parameters and the intensity parameters in the polarization scattering model respectively to obtain the optimized polarization scattering model.

[0152] Optionally, the first simulation module 1501 includes:

[0153] A first tracking unit is configured to track the polarized light in the diffuse reflection process based on a meridian plane method in a Monte Carlo method, and obtain a multiple scattering matrix corresponding to the polarized light in the multiple scattering process;

[0154] The first decomposition unit is configured to decompose the multiple scattering matrix according to a polar decomposition method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material.

[0155] Optionally, the first optimization module 1504 includes:

[0156] A first optimization unit is configured to perform pixel-level optimization on polarization parameters in the polarization scattering model to obtain first optimized parameters;

[0157] A second optimization unit is configured to optimize the intensity parameter in the polarization scattering model according to the first optimization parameter to obtain a second optimization parameter;

[0158] The third optimization unit is configured to perform error correction on the Stokes vectors in the first optimization parameters and the second optimization parameters to obtain the optimized polarization scattering model.

[0159] Optionally, the first optimization module 1504 further includes:

[0160] The fourth optimization unit is configured to, when the first optimization parameters include non-pixel level parameters, convert the non-pixel level parameters into material level parameters and update the first optimization parameters.

[0161] Optionally, the device further comprises:

[0162] The first construction unit is configured to construct the initial model according to a first polarization and a first intensity corresponding to the polarized light during diffuse reflection and a second polarization and a second intensity corresponding to the polarized light during specular reflection.

[0163] Optionally, the first building block includes:

[0164] a first generating unit, configured to generate the first intensity according to a normalized diffusion principle and albedo;

[0165] The second generating unit is configured to generate the first polarization according to the depolarization coefficient, the Fresnel reflection principle, and the rotation angle of the polarized light.

[0166] Optionally, the first functional relationship generated by the first simulation module 1501 includes:

[0167] formula Where λ is the depolarization coefficient, l d is the average distance, and r is the actual scattering distance of polarized light scattered inside the material;

[0168] The second functional relationship in the first establishing module 1502 includes:

[0169] formula in, σ′ t =σ′ s +σ a ,σ′s is the scattering coefficient, σ a is the absorption coefficient.

[0170] It should be noted that the embodiment of the device is a device corresponding to the embodiment of the above method, and all implementation methods in the embodiment of the above method are applicable to the embodiment of the device and can achieve the same technical effect.

[0171] An embodiment of the present invention also provides a network device, comprising: a processor, a memory, and a program stored on the memory and runnable on the processor. When the program is executed by the processor, the polarization scattering model parameter measurement method based on the Monte Carlo method as described in any of the above items is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0172] An embodiment of the present invention further provides a computer-readable storage medium, comprising: a program stored on the computer-readable storage medium, wherein when the program is executed by a processor, the program implements the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method as described in any of the above items, and can achieve the same technical effect. To avoid repetition, the steps are not described here. The computer-readable storage medium is, for example, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0173] An embodiment of the present invention also provides a computer program product, including computer instructions. When the computer instructions are executed by a processor, the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method as described in any of the above items are implemented, and the same technical effects can be achieved. To avoid repetition, they are not described here.

[0174] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0175] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for measuring polarization scattering model parameters based on the Monte Carlo method, characterized in that: include: Simulating the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered inside the material; establishing a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficients of different materials and the scattering distance and the first functional relationship; Fitting the function curve with a pre-built initial model to generate a polarization scattering model; The polarization parameters and intensity parameters in the polarization scattering model are optimized respectively to obtain the optimized polarization scattering model.

2. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 1, characterized in that: The method of simulating the multiple scattering process of the polarized light in the diffuse reflection process based on the Monte Carlo method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material includes: Tracking the polarized light during the diffuse reflection process based on the meridian plane method in the Monte Carlo method to obtain a multiple scattering matrix corresponding to the polarized light during the multiple scattering process; The multiple scattering matrix is ​​decomposed according to a polar decomposition method to obtain a first functional relationship between the depolarization coefficient and the scattering distance of the polarized light scattered inside the material.

3. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 1, wherein: Optimizing the polarization parameter and the intensity parameter in the polarization scattering model respectively to obtain the optimized polarization scattering model includes: Optimizing the polarization parameters in the polarization scattering model at a pixel level to obtain first optimized parameters; Optimizing the intensity parameter in the polarization scattering model according to the first optimization parameter to obtain a second optimization parameter; Error correction is performed on the Stokes vectors in the first optimization parameter and the second optimization parameter to obtain the optimized polarization scattering model.

4. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 3, characterized in that: After performing pixel-level optimization on the polarization parameters in the polarization scattering model to obtain first optimized parameters, the method further includes: In a case where the first optimization parameters include non-pixel level parameters, the non-pixel level parameters are converted into material level parameters, and the first optimization parameters are updated.

5. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 1, wherein: The method further comprises: The initial model is constructed according to the first polarization and the first intensity corresponding to the polarized light during diffuse reflection and the second polarization and the second intensity corresponding to the polarized light during specular reflection.

6. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 5, characterized in that: The method further comprises: generating the first intensity according to the normalized diffusion principle and albedo; The first polarization is generated according to the depolarization coefficient, the Fresnel reflection principle, and the rotation angle of the polarized light.

7. The method for measuring polarization scattering model parameters based on the Monte Carlo method according to claim 1, wherein: The first functional relationship includes: formula Where λ is the depolarization coefficient, l d is the average distance, and r is the actual scattering distance of polarized light scattered inside the material; The second functional relationship includes: formula in, σ′ t =σ′ s +σ a ,σ′ s is the scattering coefficient, σ a is the absorption coefficient.

8. A polarization scattering model parameter measurement device based on the Monte Carlo method, characterized in that: include: A first simulation module is configured to simulate a multiple scattering process of polarized light in a diffuse reflection process based on a Monte Carlo method, and obtain a first functional relationship between a depolarization coefficient of the polarized light and a scattering distance of the polarized light scattered inside a material; A first establishing module is configured to establish a function curve between the depolarization coefficient and the scattering coefficient according to a second functional relationship between the scattering coefficient of different materials and the scattering distance and the first functional relationship; A first fitting module is used to fit the function curve with a pre-built initial model to generate a polarization scattering model; The first optimization module is used to optimize the polarization parameters and intensity parameters in the polarization scattering model respectively to obtain the optimized polarization scattering model.

9. A network device, characterized in that: include: A processor, a memory, and a program stored in the memory and executable on the processor, wherein when the program is executed by the processor, the method for measuring polarization scattering model parameters based on the Monte Carlo method according to any one of claims 1 to 7 is implemented.

10. A readable storage medium, characterized in that: include: The readable storage medium stores a program, and when the program is executed by a processor, the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method according to any one of claims 1 to 7 are implemented.

11. A computer program product, characterized in that The method comprises computer instructions, which, when executed by a processor, implement the steps of the polarization scattering model parameter measurement method based on the Monte Carlo method as claimed in any one of claims 1 to 7.

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