CN111929203A - Aspheric dust-haze particle distinguishing method based on solar blind ultraviolet light polarization degree - Google Patents
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Abstract
The invention discloses a method for distinguishing aspheric haze particles based on solar blind ultraviolet light polarization degree, which comprises the following steps of 1, modeling the aspheric haze particles; step 2, establishing an ultraviolet light scattering polarization model of the dust-haze particles; step 3, calculating matrix elements of an ultraviolet light scattering amplitude matrix of the non-spherical haze particles by using a T matrix method; step 4, simulating the change of ultraviolet light scattering linear polarization degrees of the non-spherical haze particles in different forms by using the ultraviolet light scattering polarization model in the step 2 and the T matrix method in the step 3; and 5, comparing and analyzing the difference rule of the ultraviolet light scattering linear polarization degrees of the spherical and non-spherical haze particles in different forms, thereby distinguishing the spherical and non-spherical haze particles with different deformations. The method can analyze the influence of specific deformation parameters on the ultraviolet light scattering linear polarization degree of the non-spherical haze particles, can make up the defect that a visible light measuring method is easily interfered by background light, and achieves the purpose of improving the detection accuracy.
Description
Technical Field
The invention belongs to the field of ultraviolet light detection technology and atmospheric environment science, and particularly relates to a method for distinguishing aspheric dust-haze particles based on solar blind ultraviolet light polarization degree.
Background
Dust haze, also known as atmospheric brown cloud, is defined as follows in the ground meteorological observation standard of the chinese meteorological office: a large amount of extremely fine dry dust particles and the like uniformly float in the air, so that the air with horizontal visibility of less than 10 kilometers generally has a turbid phenomenon, bright objects at a distance are slightly yellow and red, and dark objects are slightly blue. The dust haze is complex in composition and mainly consists of particles such as dust, sulfuric acid, nitric acid and organic hydrocarbon in air, wherein PM2.5 (Particulate Matter 2.5) is generally considered as a 'representative' of the dust haze. At present, atmospheric haze is considered to be a part of the urban disastrous weather for the following reasons: firstly, the dust haze influences the sight of drivers and pedestrians, and traffic accidents are easily caused; secondly, toxic and harmful substances are easily attached to the dust haze, so that diseases are easily caused; third, the dust haze can cause the change of atmospheric optical characteristic, produces not negligible influence to the wireless optical communication in area. According to statistics, the number of people who died in China in 2017 due to dust-haze weather diseases is up to 32 thousands, 14877551 people are sick due to dust-haze pollution, and the health economic loss is 12625 million yuan. Therefore, it is necessary to effectively and accurately monitor the dust haze, and the monitoring result can provide a reference for treating dust haze pollution and improving the quality of atmospheric wireless optical communication.
Because the atmospheric ozone has strong absorption effect on ultraviolet light with the wave band of 200nm-280nm, the wave band ultraviolet light is also called solar blind ultraviolet light, and the ultraviolet light has the characteristics of strong anti-interference capability and high secrecy. Therefore, the solar blind ultraviolet light is used in the field of dust haze detection, and the defect that a visible light measuring method is easily interfered by background light can be overcome. Polarization is one of the basic attributes of light, and when day blind ultraviolet light scatters with the dust haze particle, the ultraviolet light after the scattering can have corresponding polarization characteristic, and this polarization characteristic also can be used for distinguishing different physical characteristics's non-spherical dust haze particle.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for distinguishing aspheric dust-haze particles based on solar blind ultraviolet light polarization degree, aiming at analyzing the ultraviolet light scattering polarization characteristics of dust-haze particles with different physical characteristics by utilizing an ultraviolet light polarization model of the dust-haze particles so as to distinguish the aspheric dust-haze particles with different forms; another objective is to analyze the influence of different physical properties on the degree of polarization of ultraviolet light scattering linear rays of non-spherical haze particles by using the method of the present invention.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for distinguishing aspheric dust-haze particles based on solar blind ultraviolet ray polarization degree specifically comprises the following steps:
and 5, comparing and analyzing the difference rule of the ultraviolet light scattering linear polarization degrees of the spherical and non-spherical haze particles in different forms, thereby distinguishing the spherical and non-spherical haze particles with different deformations.
Further, the step 1 is to make the non-spherical haze particles equivalent to three common particles, namely an ellipsoid, a cylinder and a chebyshev, and establish a non-spherical haze particle model, and specifically comprises the following steps:
step 1.1: an ellipsoidal dust-haze particle model is established, the formula (1) is an expression of the ellipsoidal dust-haze particle model,
the semi-axis ratio of the ellipsoidal dust-haze particles is a/b, b and a are respectively a vertical semi-axis and a horizontal semi-axis, the ellipsoidal dust-haze particles have rotational symmetry, the shape of the ellipsoidal dust-haze particles is generally determined by the size of a/b by taking the vertical semi-axis as a rotating axis, the ellipsoidal dust-haze particles are flat ellipsoidal dust-haze particles when a/b is larger than 1, and the oblong ellipsoidal dust-haze particles when a/b is smaller than 1;
step 1.2: establishing a cylindrical dust-haze particle model, wherein the shape of the cylindrical dust-haze particles is determined by the D/L ratio of the diameter of the bottom circle to the length, the cylindrical dust-haze particles are long cylindrical when the D/L is less than 1, the compact cylindrical dust-haze particles are when the D/L is equal to 1, and the flat cylindrical dust-haze particles are when the D/L is greater than 1;
step 1.3: establishing a Chebyshev-shaped dust-haze particle model, wherein the Chebyshev-shaped dust-haze particles are non-spherical dust-haze particles with the diameters following an n-order Chebyshev polynomial, and the shapes can be described by an expression (2):
wherein the content of the first and second substances,
is a spherical quantization radius of the image,
is a parameter of the deformation of the material,
is an n-order Chebyshev polynomial, and when n is more than 2, the Chebyshev-shaped dust-haze particles can be sunken; as n increases, a rippled rough surface is created around the Chebyshev-shaped dust-haze particles, and therefore n is also referred to as a ripple parameter.
Further, the ultraviolet light scattering polarization model of the dust-haze particles in the step 2 comprises that ultraviolet light is irradiated in parallel along the positive direction of the Z axis and is scattered once with the dust-haze particles, the direction of incident light and the direction of scattered light determine a scattering plane, a plane XOZ is taken as a reference plane,
is the angle of the scattering of the light,
is the rotation angle between the plane XOZ and the scattering plane, the Stokes vector of the ultraviolet light before and after scattering through the dust-haze particles
、
The expression is shown in (3):
wherein the content of the first and second substances,
is a Mueller matrix of the dust-haze particles,
is a rotation matrix, and the specific expression is as follows (4):
further, the step 3 specifically includes the following steps:
step 3.1: under the irradiation of incident field, scattered field is formed around the surface of non-spherical particles
And a scattered field
Are expressed as (5) and (6):
wherein the content of the first and second substances,
is the number of light waves,
in order to be an equivalent radius,
is the minimum circumscribed spherical radius of the non-spherical particle,
and
is a regular vector spherical wave function of the wave,
is a vector wave function; expansion coefficient of incident field
Is represented by the formula (7):
similarly, the scattering field expansion coefficient
Is (8):
the expansion coefficients of the incident field and the scattered field satisfy a linear relationship and are expressed by T matrixes as (9) and (10):
according to the solved T matrix, the expressions of each matrix element of the scattering amplitude matrix are (11) to (14):
step 3.2: in studying the ultraviolet light scattering polarization characteristics of haze particles, a Stokes vector of incident light and a Stokes vector of scattered light are combined into formula (15) using a Mueller matrix, wherein,
for the matrix elements in the Mueller matrix,
the relationship between each matrix element in the Mueller matrix and the scattering amplitude matrix is as follows:
further, the step 5 uses the difference D between the linear polarization degrees to represent the difference of the scattering linear polarization degrees of the spherical and non-spherical haze particles, and the difference D is expressed by formula (16):
wherein the content of the first and second substances,
which represents the linear polarization degree of the spherical haze particles,
indicating the degree of linear polarization of the non-spherical haze particles.
Compared with the prior art, the invention has the beneficial effects that:
1. the method specifically models the non-spherical haze particles, three non-spherical particles such as an ellipsoid shape, a cylindrical shape and a Chebyshev shape are used for simulating the non-spherical haze particles, and the influence of specific deformation parameters on the ultraviolet light scattering linear polarization degree of the non-spherical haze particles can be analyzed;
2. an ultraviolet light scattering polarization model of the dust-haze particles is constructed by using the 266nm solar blind ultraviolet light, and the scattering linear polarization degree of the dust-haze particles is analyzed by using the 266nm solar blind ultraviolet light, so that the defect that a visible light measuring method is easily interfered by background light can be overcome, and the purpose of improving the detection accuracy is achieved;
3. the method is also an improvement and innovation of the method for measuring the particles by light scattering.
Drawings
FIG. 1 is a schematic illustration of three non-spherical haze particles;
FIG. 2 is a schematic diagram of an ultraviolet light scattering polarization model of haze particles;
FIG. 3 is a simulation graph of the degree of polarization of ultraviolet light scattering linear rays of three non-spherical haze particles;
FIG. 4 is a graph showing the difference in the degree of polarization of scattered linear haze particles between spherical and non-spherical haze particles.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
A method for distinguishing aspheric dust-haze particles based on solar blind ultraviolet ray polarization degree specifically comprises the following steps:
step 1: when the light scattering properties of haze particles are studied, they are generally regarded as equivalent spherical particles, but aerosol particles such as haze in the actual atmosphere are different in form and are not spherical in a strict sense. In order to better analyze the influence of different deformation parameters on the ultraviolet light scattering polarization characteristics of the non-spherical dust-haze particles, the non-spherical dust-haze particles are equivalent to three common particles, namely an ellipsoid, a cylinder and a Chebyshev, and a non-spherical dust-haze particle model is established, as shown in FIG. 1:
step 1.1: establishing an ellipsoidal dust-haze particle model, wherein half-axis ratios a/b of ellipsoidal dust-haze particles are 1/2, 1/3, 2/1, 2/3, 3/1 and 3/2 respectively; formula (1) is an ellipsoidal haze particle model expression.
The vertical half shaft and the horizontal half shaft are respectively arranged on the b and the a, the ellipsoidal dust-haze particles have rotational symmetry, the vertical half shaft is generally used as a rotating shaft, the size of the a/b determines the shape of the ellipsoidal dust-haze particles, the flat ellipsoidal dust-haze particles are arranged when the a/b is larger than 1, and the long ellipsoidal dust-haze particles are arranged when the a/b is smaller than 1.
Step 1.2: the method comprises the steps of establishing a cylindrical dust-haze particle model, determining the shape of cylindrical dust-haze particles by the D/L (D/L) ratio of the diameter of a bottom circle to the length, enabling the cylindrical dust-haze particles to be long cylindrical when the D/L is smaller than 1, enabling the cylindrical dust-haze particles to be compact when the D/L is equal to 1, and enabling the cylindrical dust-haze particles to be flat cylindrical when the D/L is larger than 1. The diameter-to-length ratios D/L of the cylindrical dust-haze particles are 1/2, 1/3, 2/1, 2/3, 3/1 and 3/2 respectively;
step 1.3: establishing a Chebyshev-shaped dust-haze particle model, wherein the Chebyshev-shaped dust-haze particles are non-spherical dust-haze particles with the diameters following an n-order Chebyshev polynomial, and the shapes can be described by an expression (2):
wherein the content of the first and second substances,
is a spherical quantization radius of the image,
is a parameter of the deformation of the material,
is an n-order chebyshev polynomial. When n is greater than 2, the Chebyshev-shaped haze particles may appear as depressed portions. As n increases, a rippled rough surface is created around the Chebyshev-shaped dust-haze particles, and therefore n is also referred to as a ripple parameter. Deformation parameter of Chebyshev-shaped dust-haze particles
Respectively taking 0.1, 0.05 and 0.02; the ripple parameter n takes 2, 4 and 6 respectively.
Step 2: the ultraviolet light scattering polarization model of the dust-haze particles is established by using the 266nm solar blind ultraviolet light, and as shown in fig. 2, the ultraviolet light is irradiated in parallel along the positive direction of the Z axis and is scattered once with the dust-haze particles. The direction of the incident light and the direction of the scattered light determine a scattering plane, and the plane XOZ is taken as a reference plane,
is the angle of the scattering of the light,
is the angle of rotation of the plane XOZ with respect to the scattering plane. Then the ultraviolet light is the Stokes vector before and after the scattering of the haze particles
、
The expression formula is shown as (3):
wherein the content of the first and second substances,
is a Mueller matrix of the dust-haze particles,
is a rotation matrix, and the specific expression is as follows (4):
and step 3: and calculating matrix elements of an ultraviolet light scattering amplitude matrix of the non-spherical haze particles by using a T matrix method.
Step 3.1: under the irradiation of incident field, scattered field is formed around the surface of non-spherical particles
And a scattered field
Are expressed as (5) and (6):
wherein the content of the first and second substances,
is the number of light waves,
in order to be an equivalent radius,
is the minimum circumscribed spherical radius of the non-spherical particle,
and
is a regular vector spherical wave function of the wave,
is a vector wave function. Expansion coefficient of incident field
Is represented by the formula (7):
similarly, the scattering field expansion coefficient
Is (8):
the expansion coefficients of the incident field and the scattered field satisfy a linear relationship and are expressed by T matrixes as (9) and (10):
according to the solved T matrix, the expressions of each matrix element of the scattering amplitude matrix are (11) to (14):
step 3.2: in studying the ultraviolet light scattering polarization characteristics of haze particles, a Stokes vector of incident light and a Stokes vector of scattered light are combined into formula (15) using a Mueller matrix, wherein,
are the matrix elements in the Mueller matrix.
The relationship between each matrix element in the Mueller matrix and the scattering amplitude matrix is as follows:
and 4, step 4: and (3) simulating the change of the ultraviolet light scattering linear polarization degree of the dust-haze particles with different forms by using the ultraviolet light scattering polarization model in the step (2) and the T matrix method in the step (3), as shown in fig. 3.
The equivalent radius of the ellipsoidal haze particles is 0.2 μm, and as can be seen from fig. 3 (a), when the scattering angle is smaller than 40 °, the change range of the linear polarization degree of the ellipsoidal haze particles with different semiaxial ratios is not large, and when the scattering angle is larger than 40 °, the change range of the linear polarization degree gradually increases with the increase of the scattering angle, and the ellipsoidal haze particles are in an oscillation trend. The linear polarization degree variation amplitude is the largest in the backscattering angle range of 140 ° to 180 °. The maximum values of the linear polarization degrees of the ellipsoidal haze particles with the semi-axial ratios of 1/2, 1/3, 2/1 and 3/1 are all at backscatter angles around 160 °, while the maximum values of the linear polarization degrees of the ellipsoidal haze particles with the semi-axial ratios of 2/3 and 3/2 are all at backscatter angles around 150 °. For the ellipsoidal haze particles with half axis ratios reciprocal to each other, the maximum values of the linear polarization degrees of the ellipsoidal haze particles are very close to each other, and for the ellipsoidal haze particles with different half axis ratios, when the phase difference between the vertical half axis and the horizontal half axis is smaller, namely the particles are closer to a sphere, the maximum value of the linear polarization degree is larger, and the change amplitude of the linear polarization degree on the backscattering angle is larger. Therefore, the ellipsoidal haze particles with different semiaxial ratios can be distinguished by analyzing the maximum value of the linear polarization degree on the backscattering angle, and the maximum value of the linear polarization degree of the ellipsoidal haze particles is larger as the deformation quantity of the ellipsoidal haze particles is smaller.
The equivalent radius of the cylindrical haze particles is 0.2 μm, and as can be seen from fig. 3(b), the change amplitude of the linear polarization degree of the cylindrical haze particles is gradually increased along with the increase of the scattering angle. The amplitude of the change in the degree of linear polarization is relatively large in the backscattering angle range of 130 ° to 180 °. For the cylindrical haze particles, when the difference between the diameter and the length of the bottom surface circle is smaller, the maximum value of the linear polarization degree is larger, and the change amplitude of the linear polarization degree is larger. Under the condition that D/L are reciprocal to each other, the maximum values of the linear polarization degrees of the cylindrical haze particles with different deformations are very close. For the cylindrical haze particles having D/L of 2/3 and 3/2, the maximum values of the linear polarization degrees thereof are both at a backscattering angle of about 160 °, when the D/L is 1/2 and 2/1, the maximum values of the linear polarization degrees thereof are both at a backscattering angle of about 150 °, and when the D/L ratio is 1/3 and 3/1, the maximum values of the linear polarization degrees thereof are both at a backscattering angle of about 140 °, and thus it can be seen that the maximum values of the linear polarization degrees of the cylindrical haze particles are gradually shifted toward the backscattering angle as the difference between the diameter and the length of the base circle is reduced. In the backscattering angle range of 160-180 degrees, the smaller the difference between the diameter and the length of the bottom circle is, the larger the linear polarization degree of the cylindrical haze particles is. Therefore, the cylindrical haze particles with different D/L can be distinguished by analyzing the difference of the linear polarization degree on the backscattering angle according to the rule.
The equivalent radius of the Chebyshev-shaped particles is 0.2 μm, and as can be seen from FIGS. 3 (c) and 3 (d), the linear polarization degree of the Chebyshev-shaped haze particles with different deformations is in oscillation change over the whole scattering angle, and the change amplitude of the linear polarization degree is relatively large at the backscattering angle of 150-180 degrees. When deformation parameter
And the smaller the ripple parameter n, the larger the maximum value of the linear polarization degree is, and the larger the variation width of the linear polarization degree is. For Chebyshev-shaped dust-haze particles with different deformations, the maximum value of the linear polarization degree is positioned at the backward scattering angle of about 160 degrees. Therefore, the degree of deformation of the chebyshev-shaped haze particles can be judged by analyzing the change of the degree of linear polarization at the backscatter angle.
And 5: the difference law of the ultraviolet ray scattering linear polarization degree of the spherical and different forms of non-spherical dust-haze particle of contrastive analysis to distinguish spherical and different deformation non-spherical dust-haze particles, the ultraviolet ray scattering polarization characteristic of the dust-haze particle of different shapes also is different. The difference D between the linear polarization degrees is used to represent the scattering linear polarization degree difference between spherical and non-spherical haze particles, and the linear polarization degree difference D is defined as (16):
wherein the content of the first and second substances,
which represents the linear polarization degree of the spherical haze particles,
indicating the degree of linear polarization of the non-spherical haze particles. Particle equivalent radius of 0.2
Complex refractive index of 1.53+0.005i, incident light of 266nm solar blind ultraviolet light, and Stokes vector thereof
。
As shown in fig. 4, the ultraviolet light scattering linear polarization degree difference of the spherical dust-haze particles and the ellipsoidal dust-haze particles different from a/b changes along with the scattering angle change rule, and as can be seen from fig. 4(a), the spherical dust-haze particles are larger than the ellipsoidal dust-haze particles in the linear polarization degree at most of the scattering angles, and the spherical dust-haze particles and the ellipsoidal dust-haze particles are not large in the linear polarization degree difference and are not obvious in distinction within the forward scattering range with the scattering angle smaller than 60 degrees. The difference of the linear polarization degrees tends to increase and decrease as the scattering angle increases, and the difference of the linear polarization degrees is relatively large at the backward scattering angle, and reaches a maximum value when the scattering angle is about 140 °. The difference in the degree of linear polarization is also relatively large at backscattering angles of around 170 deg., the greater the difference in the degree of linear polarization when the vertical and horizontal half axes of the ellipsoidal haze particles differ. Therefore, spherical and ellipsoidal dust-haze particles can be distinguished according to the difference of the linear polarization degree of the backscattering angle, and the difference can also provide reference for distinguishing ellipsoidal dust-haze particles with different semi-axis ratios.
The ultraviolet light scattering linear polarization degree difference of spherical dust haze particles and the different cylindrical dust haze particles of D/L changes along with the scattering angle law, and can be seen from fig. 4(b), and on the backward scattering angle, the linear polarization degree difference of spherical dust haze particles and cylindrical dust haze particles is also relatively great. The difference in linear polarization is positive for most backscatter angles, i.e., spherical haze particles are more linearly polarized than cylindrical haze particles. The difference in the degree of linear polarization reaches a maximum when the scattering angle is around 130 °. The linear polarization degree of the cylindrical haze particles with D/L of 3/2 and 2/3 is significantly greater than the linear polarization degree of the spherical haze particles at backscattering angles around 160 deg.. On the scattering angle after 170 degrees, the difference of the linear polarization degrees of the spherical dust-haze particles and the cylindrical dust-haze particles with different D/L is obvious, and the larger the difference of the diameter and the length of the bottom surface circle of the cylindrical dust-haze particles is, the larger the difference of the linear polarization degrees is. Therefore, the difference in linear polarization degree at the backscattering angle can also provide a reference for distinguishing spherical and cylindrical haze particles.
The ultraviolet light scattering linear polarization degree difference of spherical dust-haze particle and the Chebyshev-shaped dust-haze particle of different deformations changes the rule along with the scattering angle, can be seen from figure 4(c) and figure 4 (d), and on the backward scattering angle, the difference of linear polarization degree is great relatively, and mostly is positive value. The difference in the degree of linear polarization reaches a maximum when the scattering angle is around 140 °. At backscattering angles around 160 deg., n =4,
=0.02 and n =2,
the linear polarization degree of the chebyshev-shaped haze particles of =0.1 is significantly greater than that of the spherical haze particles. At a scattering angle after 170 degrees, the linear polarization degree of the spherical dust-haze particles is larger than that of the Chebyshev-shaped dust-haze particles with different deformations, and under the condition that the ripple parameter n is the same, when the deformation parameter n is the same
The larger the difference in the degree of linear polarization; in the parameter of deformation
Under the same condition, the difference of the linear polarization degree is larger when the ripple parameter n is smaller. Therefore, the spherical Chebyshev-shaped dust-haze particles with different parameters can be distinguished according to the difference of the linear polarization degree on the backscattering angle.
Simulation results show that: the change of the ultraviolet light scattering linear polarization degree of the dust-haze particles is mainly concentrated on a backscattering angle, and for the non-spherical dust-haze particles, when the deformation amount of the particles is larger, the maximum value of the linear polarization degree is smaller. The linear polarization degree of the spherical haze particles is greater than the linear polarization degree of the non-spherical haze particles at most backscatter angles. Therefore, the change rule of the ultraviolet ray polarization degree in the backscattering angle can be combined to distinguish spherical and non-spherical haze particles with different deformations.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (5)
1. A method for distinguishing aspheric dust-haze particles based on solar blind ultraviolet ray polarization degree is characterized by comprising the following steps:
step 1, modeling non-spherical dust-haze particles;
step 2, establishing an ultraviolet light scattering polarization model of the dust-haze particles;
step 3, calculating matrix elements of an ultraviolet light scattering amplitude matrix of the non-spherical haze particles by using a T matrix method;
step 4, simulating the change of ultraviolet light scattering linear polarization degrees of the non-spherical haze particles in different forms by using the ultraviolet light scattering polarization model in the step 2 and the T matrix method in the step 3;
and 5, comparing and analyzing the difference rule of the ultraviolet light scattering linear polarization degrees of the spherical and non-spherical haze particles in different forms, thereby distinguishing the spherical and non-spherical haze particles with different deformations.
2. The method for distinguishing aspheric haze particles based on solar-blind ultraviolet ray polarization degree according to claim 1, wherein the step 1 is to equivalently form the aspheric haze particles into three common particles, namely an ellipsoid, a cylinder and a chebyshev, and establish an aspheric haze particle model, and specifically comprises the following steps:
step 1.1: an ellipsoidal dust-haze particle model is established, the formula (1) is an expression of the ellipsoidal dust-haze particle model,
the semi-axis ratio of the ellipsoidal dust-haze particles is a/b, b and a are respectively a vertical semi-axis and a horizontal semi-axis, the ellipsoidal dust-haze particles have rotational symmetry, the shape of the ellipsoidal dust-haze particles is generally determined by the size of a/b by taking the vertical semi-axis as a rotating axis, the ellipsoidal dust-haze particles are flat ellipsoidal dust-haze particles when a/b is larger than 1, and the oblong ellipsoidal dust-haze particles when a/b is smaller than 1;
step 1.2: establishing a cylindrical dust-haze particle model, wherein the shape of the cylindrical dust-haze particles is determined by the D/L ratio of the diameter of the bottom circle to the length, the cylindrical dust-haze particles are long cylindrical when the D/L is less than 1, the compact cylindrical dust-haze particles are when the D/L is equal to 1, and the flat cylindrical dust-haze particles are when the D/L is greater than 1;
step 1.3: establishing a Chebyshev-shaped dust-haze particle model, wherein the Chebyshev-shaped dust-haze particles are non-spherical dust-haze particles with the diameters following an n-order Chebyshev polynomial, and the shapes can be described by an expression (2):
wherein the content of the first and second substances,
is a spherical quantization radius of the image,
is a parameter of the deformation of the material,
is an n-order Chebyshev polynomial, and when n is more than 2, the Chebyshev-shaped dust-haze particles can be sunken; as n increases, a rippled rough surface is created around the Chebyshev-shaped dust-haze particles, and therefore n is also referred to as a ripple parameter.
3. The method for distinguishing aspheric dust-haze particles based on the degree of polarization of ultraviolet rays for solar blindness as claimed in claim 1, wherein the ultraviolet light scattering polarization model of dust-haze particles in step 2 comprises that ultraviolet light is irradiated in parallel along the positive direction of Z axis and is scattered once with dust-haze particles, the direction of incident light and the direction of scattered light determine a scattering plane, and the XOZ plane is taken as a reference plane,
is the angle of the scattering of the light,
is the rotation angle between the plane XOZ and the scattering plane, the Stokes vector of the ultraviolet light before and after scattering through the dust-haze particles
、
The expression is shown in (3):
wherein the content of the first and second substances,
is a Mueller matrix of the dust-haze particles,
is a rotation matrix, and the specific expression is as follows (4):
4. the method for distinguishing aspheric haze particles based on degree of polarization of solar-blind ultraviolet light as claimed in claim 1, wherein the step 3 specifically comprises the following steps:
step 3.1: under the irradiation of incident field, scattered field is formed around the surface of non-spherical particles
And a scattered field
Are expressed as (5) and (6):
wherein the content of the first and second substances,
is the number of light waves,
in order to be an equivalent radius,
is the minimum circumscribed spherical radius of the non-spherical particle,
and
is a regular vector spherical wave function of the wave,
is a vector wave function; expansion coefficient of incident field
Is represented by the formula (7):
similarly, the scattering field expansion coefficient
Is (8):
the expansion coefficients of the incident field and the scattered field satisfy a linear relationship and are expressed by T matrixes as (9) and (10):
according to the solved T matrix, the expressions of each matrix element of the scattering amplitude matrix are (11) to (14):
step 3.2: in studying the ultraviolet light scattering polarization characteristics of haze particles, a Stokes vector of incident light and a Stokes vector of scattered light are combined into formula (15) using a Mueller matrix, wherein,
for the matrix elements in the Mueller matrix,
the relationship between each matrix element in the Mueller matrix and the scattering amplitude matrix is as follows:
5. the method for distinguishing aspheric haze particles based on degree of polarization of solar-blind ultraviolet rays as claimed in claim 1, wherein the step 5 uses difference D of linear polarization degree to represent scattering linear polarization degree difference of spherical haze particles and aspheric haze particles, and the linear polarization degree difference D is expressed by formula (16):
wherein the content of the first and second substances,
which represents the linear polarization degree of the spherical haze particles,
indicating the degree of linear polarization of the non-spherical haze particles.
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