阅读说明：本技术 一种透过窗玻璃与偏振贴膜成像的透窗观察方法 (Transparent window observation method for imaging of transparent window glass and polarization film ) 是由 吴国通 蒋涛 张贺 于 2020-12-01 设计创作，主要内容包括：一种透过窗玻璃与偏振贴膜成像的透窗观察方法,包括以下步骤：步骤1,获取不同偏振角度下的偏振图像I(x,y)；步骤2,估计正交偏振分量I-⊥(x,y)和I-(||)(x,y)；步骤3,估计环境光A(x,y),对获得的图像进行偏振滤波处理；步骤4,估计薄膜系统pMTF(x,y)；步骤5,重构目标信息。本发明利用车内目标光和环境光偏振信息的差异,分离出车内目标光和环境光,进而提取出目标的真实信息,实现玻璃和薄膜遮掩下目标的信息重构；克服了现有技术下无法对车内信息进行重构或重构效果不佳的技术难题。(A method of through-window viewing through a glazing and a polarizing film imaging, comprising the steps of: step 1, obtaining polarization images I (x, y) under different polarization angles; step 2, estimating orthogonal polarization component I ⊥ (x, y) and I || (x, y); step 3, estimating ambient light A (x, y), and carrying out polarization filtering processing on the obtained image; step 4, estimating a membrane system pMTF (x, y); and 5, reconstructing target information. According to the method, the difference of polarization information of the target light and the ambient light in the vehicle is utilized to separate the target light and the ambient light in the vehicle, so that the real information of the target is extracted, and the information reconstruction of the target under the shielding of glass and a film is realized; the technical problem that the interior information cannot be reconstructed or the reconstruction effect is poor in the prior art is solved.)

1. A method of viewing through a window by imaging through the window glass with a polarizing film, comprising the steps of:

step 1, obtaining polarization images I (x, y) under different polarization angles, collecting images by using a three-channel polarization image imaging system, and obtaining polarization images I under three polarization angles of 0 degree, 60 degrees and 120 degrees through one-time shooting₀(x，y)、I₆₀(x，y)、I₁₂₀(x，y))；

Step 2, estimating orthogonal polarization component I_⊥(x, y) and I_||(x, y) by comparing the three sets of different polarization angle images (I) obtained in step 1₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) fitting the intensity of the emergent light I according to Malus' law_θCalculating the maximum value I in the angle period along with the sine variation curve of the polarization angle theta_max(x, y) and a minimum value I_min(x, y) as an orthogonally polarized image I_⊥(x, y) and I_||(x, y) and saving the corresponding two angles theta_maxAnd theta_min；

And 3, estimating ambient light A (x, y), carrying out polarization filtering processing on the three obtained polarization images, and estimating the ambient light A (x, y) under corresponding three angles according to the edge contour information of the target in the smoothed image₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)), fitting the ambient light intensity A_θAccording to the sine variation curve of the polarization angle theta, the polarization angle theta is obtained in the step 2_maxAnd theta_minCalculate the orthogonal ambient light intensity A at this angle_⊥(x, y) and A_||(x，y)；

Step 4, estimating the film system pMTF (x, y), and utilizing the obtained orthogonal polarization component I_⊥(x, y) and I_||(x, y) obtaining a target light D_⊥(x, y) and then with the polarization image D of the object light_⊥(x, y) estimating pixel-by-pixel pMTF (x, y) of the thin film system as an input image;

step 5, reconstructing target information according to the obtained orthogonal polarization image I_⊥(x，y)、I_||(x, y) and orthogonal ambient light intensity A_⊥(x, y) and A_||(x, y), and the pMTF (x, y) of the thin film system reconstruct an in-vehicle target image J (x, y) in the following formula:

2. a method of viewing through a window by imaging a transparent glazing with a polarizing film according to claim 1, wherein: the total light intensity I (x, y) reaching the imaging system includes two parts: target light J (x, y) containing effective information of the target in the vehicle passes through the film system to reach target light D (x, y) of the imaging system, and ambient reflected light A of sunlight A (x, y) reflected by the film system_ref(x, y), namely: i (x, y) ═ D (x, y) + a_ref(x，y)。

3. A method of viewing through a window by imaging a transparent glazing with a polarizing film according to claim 2, wherein: the target light D (x, y) reaching the imaging system and the reflected light A reaching the imaging system after being reflected by the thin film system_ref(x, y), the light intensity transmittance t (x, y) and reflectance r (x, y) using the thin film system are expressed as:

D(x，y)＝J(x，y)·t(x，y)，

A_ref(x，y)＝A(x，y)·r(x，y)，

and t (x, y) + r (x, y) ═ 1,

wherein r (x, y) represents the intensity of the environment containing sunlight, t (x, y) represents the ratio of the emergent intensity to the incident intensity of the light after the light passes through the film system and is subjected to the projection action of medium particles in the film system;

further, the transmission glass window and the film imaging can be expressed as:

I(x，y)＝J(x，y)·t(x，y)+A(x，y)·(1-t(x，y))。

4. a method of viewing through a window by imaging a transparent glazing with a polarizing film according to any one of claims 1 to 3, wherein: in the step 2, after the polarized light passes through the polarizing plate of the imaging system, the emergent light intensity value and the polarization angle approximate to a sine function relationship, and Stokes vectors (I, Q, U, V) are adopted^TIntensity of light I emitted through the polarizing device describing the polarization state of the light_θThe functional relationship with the polarization angle θ is:

wherein Q represents the difference value of linearly polarized light components of 0-90 degrees, U represents the difference value of linearly polarized light components of +/-45 degrees, and V represents the difference value of left circularly polarized light and right circularly polarized light components;

when obtaining the polarization images under the three polarization angles of 0 degrees, 60 degrees and 120 degrees, solving out Stokes vectors I, Q and U, and then solving out the polarization image under any polarization angle in an angle period by fitting out a relation function curve of light intensity I (theta) and the polarization angle theta;

the polarized light intensity value I (theta) has a maximum value and a minimum value in a period of a polarization angle theta, and polarization images (I) at three angles are obtained₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) by curve fitting, θ can be obtained_maxAnd theta_minCorresponding under angle I_max(x, y) and a minimum value I_min(x, y) as I for two orthogonally polarized images in the reconstruction algorithm, respectively_⊥(x, y) and I_||(x，y)。

5. A method of viewing through a window by imaging a transparent glazing with a polarizing film according to any one of claims 1 to 3, wherein: in the step 3, the reflected light of the ambient light is far greater than the transmitted light of the target in the process of transmitting the glass and the film, the film system in the image mainly takes the ambient information as the main part, and the edge contour of the target is smoothed by adopting a polarization filtering mode to estimate the ambient light A (x, y);

for three polarized images (I)₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) is filtered to obtain an estimated image (A) of the ambient light A (x, y)₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)), fitting a relation function curve of the ambient light A (theta) and the polarization angle theta, and obtaining theta according to the step 2_maxAnd theta_minEstimating an orthogonal image A of the atmospheric environment_⊥(x, y) and A_||(x，y)。

6. A method of viewing through a window by imaging a transparent glazing with a polarizing film according to claim 5, wherein: the filtering algorithm is as follows:

A(x，y)＝max(min(αI″(x，y)，I′(x，y)，0)，

in the formula I_vIs the domain size of the median filtering, alpha is the proportional parameter, and the empirical value is taken to be 0.9;

using filtered images (A)₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)) calculating to obtain Stokes vector of the ambient light A (x, y)

S_A＝(I_A，Q_A，U_A)^T；

Wherein, Q is_ARepresenting the difference between linearly polarized light of ambient light in the 0 and 90 directions, U_ARepresenting the difference of linearly polarized light of ambient light in the + 45-degree and-45-degree directions;

fitting a relation function curve of A (theta) and the polarization angle theta, and estimating the orthogonal component by using the theta obtained in the previous middle pair I (x, y) image_maxAnd theta_minCalculating the ambient light orthogonal image A under the response angle_⊥(x, y) and A_||(x，y)：

7. A method of viewing through a window by imaging a transparent glazing with a polarizing film according to any one of claims 1 to 3, wherein: in said step 4, to obtain pixel-by-pixel pMTF (x, y), the target light D is used_⊥(x, y) is used as algorithm input, a frequency iteration busy deconvolution algorithm is adopted to estimate a point spread function of the thin film system, and then Fourier transform is carried out to obtain an optical modulation function; and taking the average value of the calculated values of the optical modulation transfer functions as the average modulation capability of the film system on the input light, namely pixel-by-pixel pMTF (x, y) of the film system.

8. A method of viewing through a window by imaging a transparent glazing with a polarizing film according to claim 7, wherein: the frequency domain convolution algorithm is characterized in that a frequency domain iteration is repeated in a frequency domain by applying space domain constraint including non-negative constraint and energy constraint conditions to an objective function, and finally an estimated point spread function h (x, y) is obtained, wherein a frequency domain iteration formula is as follows:

after the above formula is iterated repeatedly, the solution is converged to a unique solution,

will be composed of a polarized image A_⊥(x, y) and I_⊥Target light D obtained by (x, y)_⊥(x, y) asAnd the blurred image modulated by the thin film optical system is brought into a frequency iteration busy deconvolution algorithm, a point spread function h (x, y) is alternately solved through frequency domain iteration, the obtained point spread function h (x, y) obtains a normalized modulus value through Fourier transform to obtain an optical modulation transfer function, and the average value is taken as pMTF (x, y).

Technical Field

The invention relates to the field of polarization imaging, in particular to a transparent window observation method for imaging of transparent window glass and a polarization film.

Background

Nowadays, with the improvement of living standard of people, people are used to driving automobiles as a tool for riding instead of walk, and in order to achieve attractive appearance of the automobiles, reduce damage of ultraviolet rays to people or objects in the automobiles and improve the temperature in the automobiles, owners can stick a layer of heat-insulating explosion-proof film on the inner surface of the window glass of the automobiles.

In order to protect the privacy of people in the vehicle, the owner of the vehicle is biased to select the vehicle film with the darker color when selecting the heat-insulating explosion-proof film, and the visible light transmittance of the vehicle film with the darker color is generally low, so that the intensity of light in the vehicle after penetrating through the vehicle film is weaker, and the privacy can be protected by the condition that the interior of the vehicle cannot be clearly seen due to the weaker light in the vehicle when the vehicle is observed from the outside of the vehicle to the inside of the vehicle. Meanwhile, after the car film is adhered to the car window glass, when external environment light irradiates the surface of the car window glass, mirror reflection occurs and the external environment light returns to human eyes or video equipment, so that the human eyes or the video equipment receive a large amount of environment reflected light, at the moment, the proportion of transmitted light in the car is further inhibited due to the fact that the intensity of the reflected light is strong, and as a result, the external people or the video monitoring equipment cannot observe or monitor people or objects in the car through the film-adhered car window.

The polarization imaging method not only utilizes light intensity information, but also expands the dimension of information acquisition, can detect richer target information, and can effectively identify and detect the target by utilizing the difference of the polarization state of light, so that the polarization imaging method can be adopted to realize the imaging of the transparent glass transparent film.

Disclosure of Invention

In light of the problems raised by the background art, the present invention provides a method of through-window viewing through a window pane and imaging with a polarizing film, as further described below.

A method of viewing through a window by imaging through the window glass with a polarizing film, comprising the steps of:

step 1, obtaining polarization images I (x, y) under different polarization angles, collecting images by using a three-channel polarization image imaging system, and obtaining polarization images I under three polarization angles of 0 degree, 60 degrees and 120 degrees through one-time shooting₀(x,y)、I₆₀(x,y)、I₁₂₀(x,y))；

Step 2, estimating orthogonal polarization component I_⊥(x, y) and I_||(x, y) by comparing the three sets of different polarization angle images (I) obtained in step 1₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) according to MalusidineLaw fitting emergent light intensity I_θCalculating the maximum value I in the angle period along with the sine variation curve of the polarization angle theta_max(x, y) and a minimum value I_min(x, y) as an orthogonally polarized image I_⊥(x, y) and I_||(x, y) and saving the corresponding two angles theta_maxAnd theta_min；

And 3, estimating ambient light A (x, y), carrying out polarization filtering processing on the three obtained polarization images, and estimating the ambient light A (x, y) under corresponding three angles according to the edge contour information of the target in the smoothed image₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)), fitting the ambient light intensity A_θAccording to the sine variation curve of the polarization angle theta, the polarization angle theta is obtained in the step 2_maxAnd theta_minCalculate the orthogonal ambient light intensity A at this angle_⊥(x, y) and A_||(x，y)；

Step 4, estimating the film system pMTF (x, y), and utilizing the obtained orthogonal polarization component I_⊥(x, y) and I_||(x, y) obtaining a target light D_⊥(x, y) and then with the polarization image D of the object light_⊥(x, y) estimating pixel-by-pixel pMTF (x, y) of the thin film system as an input image;

step 5, reconstructing target information according to the obtained orthogonal polarization image I_⊥(x，y)、I_||(x, y) and orthogonal ambient light intensity A_⊥(x, y) and A_||(x, y), and the pMTF (x, y) of the thin film system reconstruct an in-vehicle target image J (x, y) in the following formula:

has the advantages that: according to the method, the difference of polarization information of the target light and the ambient light in the vehicle is utilized to separate the target light and the ambient light in the vehicle, so that the real information of the target is extracted, and the information reconstruction of the target under the shielding of glass and a film is realized; the technical problem that the interior information cannot be reconstructed or the reconstruction effect is poor in the prior art is solved.

Drawings

FIG. 1: schematic illustration of the present invention;

FIG. 2: the invention reconstructs a schematic diagram;

Detailed Description

A specific embodiment of the present invention will be described in detail with reference to fig. 1-2.

According to the background technology, the invention provides a transparent window observation method for imaging through window glass and a polarization film, the polarization imaging method not only utilizes light intensity information, but also expands the dimension of information acquisition, richer target information can be detected, and the target can be effectively identified and detected by utilizing the difference of light polarization states, so that transparent glass film-penetrating imaging is realized.

The embodiment firstly explains the polarization to a certain extent, the polarization not only contains light intensity information, but also contains characteristic information capable of reflecting the surface of the target in the polarization state, such as texture information, roughness, shape and the like, the polarization of the light provides physical characteristics representing different material objects, and provides useful information for the detection, tracking and identification of the target, and the method has great benefits for improving the signal-to-noise ratio, the speed and the precision of edge detection and the accuracy and the reliability of the target identification in the target detection process. In the earth surface and the atmosphere, electromagnetic waves with certain wave bands are always reflected and radiated by the surfaces of natural objects and artificial targets, and light rays can generate polarization characteristics in the process of reflection and radiation on the surfaces of the objects; since the roughness of the surface of a natural object tends to be high, the degree of linear polarization of the natural object is almost zero, and the polarization component of an artificial object is larger than the natural background, as compared with an artificial object. In the images with the polarization degree and the polarization direction, the artificial target is generally brighter than the natural target, and a good clue is provided for target detection, so that the polarization imaging can utilize the polarization difference between the artificial object and the natural object to improve the contrast of the target and the background.

In the application, for reasons such as beauty, heat insulation and privacy protection, a car film is generally pasted on a car window, and after the car film is pasted, when an ordinary camera is used for collecting images, the collected images comprise two conditions: one is that the window area in the image has strong reflected light or has obvious reflection of external scenery on the window, and the other is that although there is not strong reflected light or obvious reflection of the window in the image, the contrast of the window area in the image is still very low, and both of them are difficult to realize perspective monitoring.

The reason for these two conditions in the window area is: on one hand, because the glass and the film have strong reflection effect on light, when the ambient light irradiates the surfaces of the glass and the film, most of the ambient light is reflected, so that the imaging system obtains stronger ambient light; on the other hand, because the glass and the film have a strong blocking and attenuation effect on the target light in the vehicle, the light intensity penetrating through the glass and the film is weak, so that the image brightness of an effective target area is reduced, the image contrast is reduced, and the perspective effect cannot be realized.

Based on the above analysis, in order to achieve the effect of the see-through filmed glass, it is necessary to reduce or suppress the influence of ambient light on the one hand, and to increase the proportion of the target light in the vehicle interior in the image on the other hand. In practice, however, the transmission characteristics of the car film to light rays are not expressed clearly because the car film is complex and diversified in types and structural compositions; in addition, the target light in the vehicle and the ambient light are mutually interfered and superposed in the transmission process, so that part of the target light in the vehicle can be lost while the reflected light on the surface of the vehicle window is separated, and the specific gravity of the target light in the vehicle cannot be directly improved.

The invention provides a transparent window observation method for imaging a transparent window glass and a polarization adhesive film by utilizing the characteristics of orthogonal polarization information of ambient light and a target. Although the in-vehicle target light of the ambient light intensity in the image acquired by the common imaging system is weak and the in-vehicle target light cannot be directly improved by mutual interference and superposition, the in-vehicle target light and the ambient light have different propagation processes and different polarization state representation information from media with reflection, scattering and other effects. Therefore, the invention separates the target light and the environment light in the vehicle by utilizing the difference of the polarization information of the target light from the vehicle and the polarization information of the environment light, further extracts the real information of the target and realizes the information reconstruction of the target under the shielding of glass and film.

The total light intensity I (x, y) reaching the imaging system is mainly composed of two parts: part of the target light J (x, y) in the vehicle passes through the thin film system to reach the target light D (x, y) of the imaging system, and contains effective information of the target in the vehicle; another part is ambient reflected light A, in which sunlight A (x, y) is reflected by the thin-film system_ref(x, y), namely:

I(x，y)＝D(x，y)+A_ref(x，y)，(1)

the optical properties of the thin film system are reflectivity, transmissivity and absorptivity. In the embodiment, the reflection coefficient r (x, y) is adopted to represent the reflection characteristic of the film system at each pixel point to light; the transmittance t (x, y) is used for representing the transmission characteristic of the film system at each pixel point to light, namely the ratio of the emergent light intensity to the incident light intensity of the light after the light passes through the film system and is subjected to the projection action of medium particles in the film system.

The incident light intensity of the thin film system is the target light J (x, y) in the vehicle, the emergent light intensity of the thin film system is D (x, y), and the transmittance t (x, y) is expressed as:

the target light D (x, y) reaching the imaging system and the reflected light A reaching the imaging system after being reflected by the thin film system_ref(x, y), the light intensity transmittance t (x, y) and reflectance r (x, y) of the thin film system can be expressed as:

D(x，y)＝J(x，y)·t(x，y)，(3)

A_ref(x，y)＝A(x，y)·r(x，y)，(4)

wherein r (x, y) represents the intensity of the ambient light including sunlight; it is noted that the sum of the reflectivity and the transmission of the medium, i.e. the thin-film system, is 1, i.e.:

t(x，y)+r(x，y)＝1，(5)

further, the transparent glass window and the film imaging model can be expressed as:

I(x，y)＝J(x，y)·t(x，y)+A(x，y)·(1-t(x，y))，(6)

the polarization properties of light change when the light is refracted at the interface of the medium or scattered by particles in the transmission medium. In this embodiment, the plane of incidence is defined as the plane formed by the light source, the scattering particles and the observer, and the light intensity I (x, y) can be divided into two parts, namely a vertical plane of incidence and a plane parallel to the plane of incidence: i is_⊥(x, y) and I_||(x, y), then the total light intensity can be expressed as:

I(x，y)＝I_⊥(x，y)+I_||(x，y)，(7)

the system transmittance expression obtained by combining the formulas (2) and (7) is as follows:

for light with total light intensity I (x, y), when a polarization image is obtained by using an analyzer in a certain polarization direction, the polarization image in the direction is equal to the sum of the polarization components, and then when the detection system obtains polarization images in two polarization directions, the model expressions in the vertical and parallel directions can be expressed as follows:

I_⊥(x，y)＝D_⊥(x，y)+A_ref，⊥(x，y)＝J_⊥(x，y)·t(x，y)+A_⊥(x，y)·(1-t(x，y))，(9)

I_||(x，y)＝D_||(x，y)+A_ref，||(x，y)＝J_||(x，y)·t(x，y)+A_||(x，y)·(1-t(x，y))，(9)

the transmittance t (x, y) of each point of the thin film system represents the transmission capacity of the thin film system to light, and in the optical imaging system, the modulation capacity of the optical system to input light is usually expressed by a Modulation Transfer Function (MTF) at each point of the system, and a pixel-by-pixel point pMTF (x, y) capable of reflecting the projection rate t (x, y) of each point is obtained by adopting a calculation method of the Modulation Transfer Function (MTF):

wherein, D is as described in the formula_max(x，y)、D_min(x, y) represents the maximum and minimum values of the intensity of the target light D (x, y) at each pixel point, J_max(x，y)、J_min(x, y) represents the maximum value and the minimum value of the intensity of the target light D (x, y) at each pixel point.

After linearly polarized light transmits through the analyzer, the transmitted light intensity has a maximum value and a minimum value along with the change of the analyzing angle, and the corresponding analyzing angles at the maximum value and the minimum value are relatively orthogonal, so that a polarization component I which is relatively orthogonal is adopted_⊥(x, y) and I_||(x, y) represents the maximum value of the intensity of the projected light I_max(x, y) and a minimum value I_min(x, y); a polarization component I perpendicular to the direction of the incident linearly polarized light_⊥(x, y) represents the maximum value component I_max(x, y), a polarization component I parallel to the direction of the incident linearly polarized light_||(x, y) represents the maximum value component I_min(x, y), the optical transfer function expression expressed by orthogonal components can be obtained:

the transmittance of the film system is obtained by combining the formulas (8) and (12):

then, combining the formulas (9), (10) can obtain:

combining the formulas (7), (9) and (10) to obtain the formula of polarization imaging of the transmitted glass and the film as follows:

in practice, although the intensity of the ambient light is reduced after reflection, the intensity of the ambient reflected light entering the imaging system is close to the intensity of the ambient light due to the high reflectivity of the glass. In addition, there is still ambient light entering the system that is not reflected, and this portion of ambient light has an effect on the image formation through the glass and film and needs to be compensated for.

In this embodiment, the target light D (x, y) is approximated as the difference between the total light intensity I (x, y) received by the imaging system and the ambient light a (x, y), that is:

D(x，y)＝D(x，y)-A(x，y)，(16)

combining the equations (14), (15) and (16) to obtain the formula of the polarization image transmitted through the glass and the film:

each parameter in the formula (17) is a value of each pixel point, and J (x, y) is reconstructed in-vehicle target information.

As can be seen from equation (17), in this embodiment, the polarization information of the target light and the ambient light and the transmission characteristics of the thin film system to the light are utilized, and the reconstruction of the in-vehicle target information requires knowing the polarization components of the light I (x, y) and the ambient light a (x, y) received by the imaging system and the pixel-by-pixel pMTF (x, y) of the thin film system.

From the above analysis, it can be seen from the obtained polarization imaging formula of the transparent glass and the thin film that in order to reconstruct the light information of the transparent glass and the thin film, the vertical polarization component I (x, y) of the light intensity I (x, y) received by the imaging system needs to be calculated_⊥(x, y) and a parallel polarization component I_||(x, y), the vertically polarized component A of the ambient light A (x, y)_⊥(x, y) and a parallel polarization component A_||(x, y), and pixel-by-pixel pMTF (x, y) of the thin film system, for a total of three sets of positional parameters.

In order to obtain the three sets of parameters, the present embodiment implements estimation of the above parameters by using fitting estimation, polarization filtering, and frequency iterative algorithm, and a flowchart of the specific algorithm is shown in fig. 1, and includes the following steps:

acquiring polarization images under different polarization angles, acquiring images by using a three-channel polarization image system, and acquiring polarization images under three polarization angles through one-time shooting, wherein the three polarization angles are respectively 0 degree, 60 degrees and 120 degrees;

estimating orthogonal polarization component I_⊥(x, y) and I_||(x, y) by imaging the three sets of different polarization angles obtained above₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) fitting the emergent light intensity I according to Malus law_θCalculating the maximum value I in the angle period along with the sine variation curve of the polarization angle theta_max(x, y) and a minimum value I_min(x, y) as an orthogonally polarized image I_⊥(x, y) and I_||(x, y) and saving the corresponding two angles theta_maxAnd theta_min；

Estimating ambient light A (x, y), carrying out polarization filtering processing on the three obtained images, and estimating the ambient light (A) under corresponding three angles by smoothing edge contour information of the target in the images₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)), fitting the ambient light intensity A according to the three polarized images of the ambient light_θAccording to the sine variation curve of the polarization angle theta, the polarization angle theta is obtained by calculation in the last step_maxAnd theta_minCalculate the orthogonal ambient light intensity A at this angle_⊥(x, y) and A_||(x，y)；

Estimation of the thin film System pMTF (x, y) Using the orthogonal polarization component I obtained above_⊥(x, y) and I_||(x, y) calculating the target light D according to the formula (9)_⊥(x, y) and then with the polarization image D of the object light_⊥(x, y) estimating pixel-by-pixel pMTF (x, y) of the thin film system as an input image;

reconstructing target information using the orthogonal polarization image I obtained by the above equation (17)_⊥(x，y)、I_||(x, y) and orthogonal ambient light intensity A_⊥(x, y) and A_||(x, y), and pMTF (x, y) for Membrane systems reconstitution of in-vehicleTarget image J (x, y).

Through the steps, the target light and the ambient light in the vehicle are separated by utilizing the difference of the polarization information of the target light from the vehicle and the polarization information of the ambient light from the vehicle, so that the real information of the target is extracted, and the information reconstruction of the target under the shielding of glass and films is realized.

For estimating orthogonal polarization component I_⊥(x, y) and I_||(x, y) after the polarized light passes through a polarizing plate of the imaging system, the emergent light intensity value and the polarization angle approximate to a sine function relationship, and the Stokes vector (I, Q, U, V) is adopted in the embodiment^TIntensity of light I emitted through the polarizing device describing the polarization state of the light_θThe functional relationship with the polarization angle θ can be expressed as:

when the polarization images under the three polarization angles of 0 degrees, 60 degrees and 120 degrees are obtained, Stokes vectors I, Q and U can be solved, and then a relation function curve of the light intensity I (theta) and the polarization angle theta is fitted through a formula (18), so that the polarization image under any polarization angle in an angle period can be solved.

According to the polarization image, a maximum value and a minimum value of a polarization intensity value I (theta) can appear in a period of a polarization angle theta, the difference between the two angles with the maximum value is 90 degrees, the two maximum values have a relative orthogonal position relation, and the polarization image (I) under three angles is obtained₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) by curve fitting, θ can be obtained_maxAnd theta_minCorresponding under angle I_max(x, y) and a minimum value I_min(x, y) as I for two orthogonally polarized images in the reconstruction algorithm, respectively_⊥(x, y) and I_||(x，y)。

In the step of estimating the ambient light a (x, y), the film system in the image is mainly based on the environmental information, considering that the reflected light of the ambient light is much larger than the target transmitted light in the process of transmitting the glass and the film. In order to obtain the polarization information of the environmental information, the present embodiment employs a polarization filtering method in the model to smooth the edge contour of the target to estimate the environmental light a (x, y), which is as follows:

for three polarized images (I)₀(x，y)、I₆₀(x，y)、I₁₂₀(x, y)) is filtered to obtain an estimated image (A) of the ambient light A (x, y)₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)), fitting a relation function curve of the ambient light A (theta) and the polarization angle theta, and finally estimating an orthogonal image A of the atmospheric environment_⊥(x, y) and A_||(x，y)。

The adopted filtering algorithm is as follows:

A(x，y)＝max(min(αI″(x，y)，I′(x，y)，0)，(21)

wherein I (x, y) is a received light intensity map, I_vIs the median filtered domain size, alpha is the scale parameter, and the empirical value is taken to be 0.9.

Using filtered images (A)₀(x，y)、A₆₀(x，y)、A₁₂₀(x, y)) calculating to obtain Stokes vector of the ambient light A (x, y)

S_A＝(I_A，Q_A，U_A)^T；

Wherein the content of the first and second substances,

similarly, a function curve of A (theta) with respect to the polarization angle theta is fitted according to equation (18), and theta, which was previously obtained when orthogonal components were estimated for the I (x, y) image, is used_maxAnd theta_minCalculating ambient light orthogonality at response angleImage A_⊥(x, y) and A_||(x, y), namely:

in the pMTF (x, y) step of estimating the thin film system, the optical function of the thin film system directly reflects the transmission characteristic of the system, and the transmittance of the thin film system is determined by the ratio of the intensity of the emergent light after the incident target light J (x, y) passes through the thin film system, to the intensity of the incident light, so that the optical transfer function of the thin film system reflects the capability of the emergent target light D (x, y) to reproduce the incident light J (x, y). Therefore, when estimating the modulation transfer function of the thin film system, the target light D (x, y) should be approximated by equation (16), and thus the polarization component A_⊥(x, y) and I_⊥(x, y) calculating to obtain the vertical polarization component D of the target light D (x, y)_⊥(x, y) as input image for the estimation algorithm.

According to the Fourier optical theory, the imaging process of the optical system is a linear superposition process, the gray values of object images at all positions in the field of view of the optical system are modulated by the point spread function PSF of the field of view and then superposed on the imaging surface of the optical system, and the noise at the image surface is the gray value of the final image of the optical image IT.

The Point Spread Function (PSF) is a unit pulse (delta function) generated at a point element on an object plane in an optical system, an impulse response obtained after the system is processed is the point spread function of the system, and a normalized module value of the point spread function after fourier transform is an optical Modulation Transfer Function (MTF).

In order to obtain the pixel-by-pixel pMTF (x, y), only the Point Spread Function (PSF) needs to be obtained, and since the transmission characteristic of the film is unknown, the Point Spread Function (PSF) cannot be measured and has no prior knowledge, the frequency iteration busy deconvolution algorithm (IBD algorithm) is adopted, and the target light D is utilized_⊥And (x, y) is used as algorithm input, the point spread function of the thin film system is estimated, and then Fourier transform is carried out to obtain an optical modulation function. The value of each point in the modulation transfer function represents the optical systemThe modulation capability of the system to incident light with a certain wavelength is unified, and the modulation transfer function obtained by utilizing image calculation is reflected by the modulation capability of all wave bands in a response wave band, so that the average value of the numerical values of the modulation transfer function obtained by calculation is taken as the average modulation capability of the thin film system to the input light, namely the pixel-by-pixel point pMTF (x, y) of the thin film system.

In the frequency domain convolution algorithm described in this embodiment, by applying space domain constraints including non-negative constraints and energy constraint conditions to the target function, iterative iteration is performed in the frequency domain to finally obtain an estimated point spread function h (x, y), and according to the polarization imaging formula of the transparent glass and the thin film, the frequency domain iterative formula can be obtained as follows:

due to the constraint condition of the limited support domain, the blind deconvolution has a unique solution, so that the blind deconvolution converges to the unique solution after repeated iteration of the formula.

Therefore, the polarization image A_⊥(x, y) and I_⊥Target light D obtained by (x, y)_⊥(x, y) is taken as a blurred image after being modulated by the thin film optical system, the blurred image is taken into an IBD algorithm, a point spread function h (x, y) is obtained through iterative alternation of a frequency domain, the obtained point spread function h (x, y) obtains a normalized modulus value through Fourier transform to obtain an optical modulation transfer function, and an average value is taken as pMTF (x, y)

In summary, the estimated orthogonal polarization image I_⊥(x, y) and I_||(x, y), orthogonal ambient light component A_⊥(x, y) and A_||(x, y), and pMTF (x, y) of the thin film system are applied to equation (17) to obtain a reconstructed image J (x, y) of the transmission glass and the thin film, and to reconstruct polarization imaging information of the transmission glass and the thin film.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.