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

Abstract

The invention provides a polarization scattering model parameter measurement method and device based on a Monte Carlo method, and the method comprises the steps: simulating the multiple scattering processes of polarized light in a diffuse reflection process based on the Monte Carlo method, obtaining a first function relationship between the depolarization coefficient of the polarized light and the scattering distance of the polarized light scattered in the material; establishing a function curve between the depolarization coefficient and the scattering coefficient according to the second function relationship and the first function relationship between the scattering coefficients and the scattering distances of different materials; fitting the function curve with a pre-constructed initial model to generate a polarization scattering model; and respectively optimizing a polarization parameter and an intensity parameter in the polarization scattering model to obtain an optimized polarization scattering model. According to the polarization scattering model provided by the embodiment of the invention, the polarization information of the object can be more accurately restored, and a non-traditional high-scattering object can be processed.

Description

Technical Field

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

[0002] As a basic model that describes the changes in intensity and polarization state of polarized light after reflection, the polarized reflection model combines the two dimensions of light and constructs the interaction of light under the premise of following physics. The concepts of specular reflection and diffuse reflection are equally applicable, but the polarized reflection model in the prior art follows the complete depolarization assumption when dealing with polarized diffuse reflection, which is not applicable when dealing with non-traditional high-scattering objects and cannot accurately restore the polarization information of the object. 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 a 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 coefficient 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 the 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 in 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 in 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, respectively optimizing the polarization parameter and the intensity parameter in the polarization scattering model 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] According to the first optimization parameter, optimizing the intensity parameter in the polarization scattering model 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 the first optimized parameters, the method further includes:

[0017] In the case that 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 comprises:

[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 comprises:

[0021] generating the first intensity according to the normalized diffusion principle and the 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, 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] The embodiment of the present invention further provides a polarization scattering model parameter measurement device based on the Monte Carlo method, comprising:

[0028] A first simulation module is used to simulate the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method, and 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;

[0029] A first establishing module, used for 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;

[0030] A first fitting module, used for fitting 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 parameter and the intensity parameter 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 executable 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 is stored on the readable storage medium, 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 as described in any one of the above items 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 method for measuring polarization scattering model parameters based on the Monte Carlo method as described in any one of the above items.

[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 the degree of polarization 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 the 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 function curve between the depolarization coefficient and the scattering coefficient is established; secondly, the function curve is fitted with the 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 the optimized polarization scattering model. The optimized polarization scattering model takes into account the depolarization coefficient, can restore the polarization information of the object more accurately, and can handle non-traditional high-scattering objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the flow of a method 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 a 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-way attenuation matrix after decomposing a multiple scattering matrix in an embodiment of the present invention;

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

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

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

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

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

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

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

[0048] Fig.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] Fig.13 In order to use the polarization scattering model provided by the present invention in the rendering system Fig.12 Scatter plot of the relationship between polarization degree and incident angle after simulation of diffuse reflection materials;

[0050] Fig.14 It is a schematic diagram of the results of fitting various materials respectively using the polarization scattering model provided by the embodiment of the present invention;

[0051] Fig.15 It is a schematic structural diagram 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 only limited to the same exit point. It is true that the scattering phenomenon is generally approximated by the diffuse reflection component, but when the scattering distance of the scattering phenomenon generated by our irradiated object is greater than the observation distance, the scattering cannot be ignored. This is also subsurface scattering. The prior art believes that the polarized light that is transmitted into the surface of the object and emitted is completely depolarized, but when the scattering phenomenon cannot be ignored, it is obvious that the model established based on this assumption 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 the scattering process 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 a 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, which is classified into two parts, intensity and polarization, according to the components of the reflected light. The specific form is as follows:

[0060]

[0061] Among them, k s is the intensity parameter corresponding to the specular reflection, k d It is the intensity parameter corresponding to diffuse reflection. The intensity parameter is used to reflect the intensity change of light after reflection. is the polarization parameter corresponding to the specular reflection, It is the polarization parameter corresponding to diffuse reflection. The polarization parameter is the unitized 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, the polarized light is set to have a depolarization coefficient. During the diffuse reflection process, the polarized light gradually reduces the degree of polarization 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 function curve between the depolarization coefficient and the scattering coefficient is established; secondly, the function 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 restore the polarization information of the object more accurately, 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 in 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 in 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:

[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 It is not the focus of the present invention and can be simplified in the 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 regarded 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 according to the distribution of photons received by the detector. In theory, when the coherence conditions are 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, and 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 interfering 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 backscattered polarized light 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 the 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 observation generates a depolarization coefficient map on the scattering plane, such as Figure 7 As shown in FIG. 1 , the depolarization coefficient also presents a diffuse distribution on the scattering plane, and the depolarization of the outgoing polarized light is strongly correlated with the outgoing distance. This is because each scattering event of the 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 the strongest, 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 Approximately 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 of different materials and the average scattering distance 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, respectively optimizing the polarization parameter and the intensity parameter in the polarization scattering model 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] According to the first optimization parameter, optimizing the intensity parameter in the polarization scattering model 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, the 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 proportion of the mirror reflection amount obtained by optimizing the polarized reflection model to the total reflection amount; σ′ s is the material scattering coefficient, is the material level; η is the material refractive index, 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 entered in the model first and the initial value needs to be optimized.

[0101] like Fig. 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 specular 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 represented by the magnitude of the linear polarization of the observed object, ρ is represented by the magnitude of the linear polarization of the model fitting, 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, that is, the optimized k s , σ and k d :

[0106]

[0107] Where K is the number of valid pixels after masking, s 0 is the first dimension of the outgoing Stokes vector, i.e. the magnitude of the light intensity, is the first element of the Mueller matrix for the specular reflection in the normalized model, is the first element of the Mueller matrix for 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 the first optimized parameters, the method further includes:

[0110] In the case that 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 the first optimization parameter is obtained, due to σ′ s and η are not pixel-level. After the first step, the following optimization is performed to convert σ′ s and η converted to material level:

[0112]

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

[0114] Optionally, the method further comprises:

[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 specular 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 (ie, the first polarization). The polarization parameter is a unitized Mueller matrix, which reflects the change in the polarization state of the 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 of 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 tiny mirror surfaces at a microscopic angle. 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 the mirror reflection The rotation Mueller matrix of .

[0125] Optionally, the method further comprises:

[0126] generating the first intensity according to the normalized diffusion principle and the 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, k corresponding to diffuse reflection is d 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)M 0 F 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 Matrix instead of M 0 , where M multiple for:

[0137]

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

[0139] The specific implementation of the present invention is 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] Embodiment 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] A rendering system (Mitsuba) is selected as a rendering tool for simulation experiments. In Mitsuba, measured polarized materials can be used as object materials. The measured polarized materials are measured by real data and have high accuracy and credibility. In addition, it should be noted that, in general, the rendering system does not include rendering data sets of non-traditional translucent media. Therefore, traditional materials are selected for simulation in this embodiment.

[0142] A variety of traditional materials including strong specular reflection and diffuse reflection were selected to carry out fitting experiments on polarization degree and intensity, such as Figures 10 to 13 As shown, Fig.10 This is a scatter plot of the relationship between the polarization degree and the incident angle of the strong specular reflection material obtained by direct observation. Fig.11 In order to use the polarization scattering model provided by the present invention in the rendering system Fig.10 Scatter plot of the relationship between polarization degree and incident angle after simulation of medium-strong specular reflective materials. Fig.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. Fig.13 In order to use the polarization scattering model provided by the present invention in the rendering system Fig.12 The relationship between the polarization degree and the incident angle after the simulation of the diffuse reflection material is shown in the scatter plot. In this embodiment, the relationship between the polarization degree and the exit angle is used as a scatter plot to intuitively display the distribution of the polarization state of the object. It can be concluded that the polarization scattering model provided by the embodiment of the present invention has extremely high accuracy in fitting the polarization degree on objects made of traditional materials, and the accuracy is equally high regardless of whether the object has a higher proportion of specular reflection or diffuse reflection.

[0143] Example 2: A physical experiment is 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: Fig.14 As shown, the polarization scattering model provided in 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, wherein the transparency relationship of the three materials is C>B>A, and 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 prone to scattering optical effects 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 Obviously, the scattering coefficient of opaque materials is much higher than that of translucent materials.

[0146] It can be concluded that for highly scattering objects, their overall linear polarization degree is higher than that of traditional non-transparent objects, the depolarization coefficient of translucent objects is lower than that of traditional non-translucent objects, and 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 Fig.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 used to simulate the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method, and 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;

[0149] A first establishing module 1502, 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 used to fit the function curve with a pre-built initial model to generate a polarization scattering model;

[0151] The first optimization module 1504 is used to optimize the polarization parameter and the intensity parameter 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 used to track the polarized light in 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 in the multiple scattering process;

[0154] The first decomposition unit is used 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, configured to optimize the polarization parameters in the polarization scattering model at a pixel level to obtain first optimization parameters;

[0157] A second optimization unit, 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 used to perform error correction on the Stokes vector in the first optimization parameter and the second optimization parameter to obtain the optimized polarization scattering model.

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

[0160] The fourth optimization unit is used 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 used to construct the initial model 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.

[0163] Optionally, the first building unit 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 used 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, 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 in the memory and executable 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 can be implemented, and the same technical effect can be achieved. To avoid repetition, it will not be described here.

[0172] The embodiment of the present invention further provides a readable storage medium, including: a program is stored on the readable storage medium, and when the program is executed by the 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 effect can be achieved. To avoid repetition, it is not repeated here. Among them, the computer-readable storage medium is such as a read-only memory (Read-Only Memory, referred to as ROM), a random access memory (RandomAccess Memory, referred to as RAM), a disk or an optical disk, etc.

[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 effect can be achieved. To avoid repetition, they are not repeated here.

[0174] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including 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, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

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

Claims

1. A method for measuring polarization scattering model parameters based on 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 coefficient 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 the 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 in 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 in 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 Monte Carlo method according to claim 1, characterized in that: 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; According to the first optimization parameter, optimizing the intensity parameter in the polarization scattering model 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 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 the first optimization parameters, the method further includes: In the case that 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 Monte Carlo method according to claim 1, characterized in that: 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 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 the 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 Monte Carlo method according to claim 1, characterized in that: The first functional relationship includes: formula Where λ is the depolarization coefficient, l d is the average distance, 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 used to simulate the multiple scattering process of polarized light in the diffuse reflection process based on the Monte Carlo method, and 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; A first establishing module, used for 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; A first fitting module, used for fitting 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 parameter and the intensity parameter 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 as claimed in 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 method for measuring polarization scattering model parameters based on the Monte Carlo method as claimed in 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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