CN113324879B - Method for measuring anisotropic rotational movement particles - Google Patents
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Abstract
The invention discloses a method for measuring anisotropic rotational movement particles. The method uses a cylindrical vector polarized light field as a probe light to irradiate anisotropic rotating particles with spin and revolution, reflects a vector Doppler polarized signal, detects the vector Doppler polarized signal by adopting a Stokes parameter method or a dual-polarization detection method, and aims at the Stokes parameter S of the vector Doppler polarized signal 1 And S 2 Or the projection components in the two polarization directions are respectively subjected to Fourier analysis, a plurality of peak frequency values and peak relative amplitude ratios are extracted from a Fourier amplitude spectrum, relative phase difference values corresponding to the peak frequency values are extracted from a Fourier relative phase spectrum, and the size and the direction of the spin and the revolution speed of the anisotropic rotating particles and the simultaneous measurement of the anisotropic parameters are realized through calculation. The invention breaks through the limitation of the traditional scheme on the measurement of the anisotropic particles, has wide application prospect in the aspects of optical measurement, sensing and the like, and fills the blank of the related technical field.
Description
Technical Field
The invention belongs to the field of optical measurement, and particularly relates to a method for measuring anisotropic rotary motion particles.
Background
It is well known that the doppler effect is caused by the relative motion between the source and the observer, which has a wide role in the field of optical and acoustic measurements. The doppler velocity measurement technology developed based on the doppler effect generally has the advantages of high spatial resolution, wide measurement range, non-contact and the like. In the diffuse history of doppler effect development, researchers often focus on the frequency change of a scalar field during interaction with an object. Recently, as researchers have explored the dimensions of optical fields, a novel vector doppler effect was disclosed and demonstrated based on a vector polarized optical field with polarization varying spatially. The vector Doppler effect is used as a brand-new expansion of the traditional Doppler effect, a new way is provided for obtaining the magnitude and direction of the rotational movement speed at the same time, and the limitation of judging and missing the movement direction in the traditional Doppler speed measurement research is broken through. In general, an isotropic medium has no influence on the polarization state of light, and thus an isotropic object exhibits a uniform and regularly simple vector doppler polarization signal in the vector doppler effect. For anisotropic particles, the polarization state of the optical field is changed, and the change is related to the fast and slow axes of anisotropy. It can be seen that the vector doppler polarization signal generated by the anisotropic rotating motion particle in the vector doppler effect will exhibit extremely complex variation characteristics. When the anisotropic particles simultaneously have two basic rotary motion forms of spin and revolution, an effective measurement scheme for acquiring information of the anisotropic particles is lacked at present. Considering the motion measurement method based on the vector Doppler effect, the complex vector Doppler polarization signals generated by anisotropic particles are difficult to directly detect by adopting the conventional means. Therefore, it is necessary to find a detection means for complex vector doppler polarization signals, and then to implement a method for measuring anisotropic rotational motion particles.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for measuring anisotropic rotary motion particles, aiming at breaking through the limitation of the traditional scheme on the measurement of the anisotropic particles, realizing the simultaneous measurement of the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotary motion particles, acquiring the anisotropic parameters of the anisotropic rotary motion particles and filling the blank of the related technology.
The Stokes parametric method is an effective means for describing and measuring the polarization state of the light field, and provides a good solution for detecting the Doppler polarization signal of the complex vector. In addition, dual polarization detection methods are generally used as a simplified form of the stokes parameter method, and may also be used for detection of polarized signals. A vector Doppler polarization signal detection means is invented based on a Stokes parametric method and a dual-polarization detection method so as to realize the measurement of anisotropic particles.
The anisotropic rotating particle can have the movement form of spin and revolution, and under the condition that the anisotropic parameters of the anisotropic rotating particle are known, the magnitude and the direction of the spin and revolution angular speed of the anisotropic rotating particle are only required to be measured. In case the anisotropic parameters of the anisotropic rotational motion particles are unknown, the measurement parameters further comprise the anisotropic parameters.
To achieve the above object, according to an aspect of the present invention, there is provided a method for measuring an anisotropic rotating particle, in which, under the condition that an anisotropic parameter of the anisotropic rotating particle is known, the method includes irradiating the anisotropic rotating particle with a cylindrical vector polarized light field, the anisotropic rotating particle may have a motion form of spin and revolution, an optical axis of the cylindrical vector polarized light field coincides with a revolution axis of the anisotropic rotating particle, the anisotropic rotating particle reflects a vector doppler polarization signal, detecting the vector doppler polarization signal by using a stokes parameter method, and detecting a stokes parameter S of the vector doppler polarization signal 1 And S 2 Respectively carrying out Fourier analysis, extracting a plurality of Doppler frequency shift peaks in a Fourier magnitude spectrum, wherein the peak frequencies are respectively | delta f 1 |＝lΩ/π、|Δf 2 |＝Θ/π、|Δf 3 (2 Θ + σ l Ω)/π (where Ω is the revolution angular velocity, Θ is the spin angular velocity, l is the mode order of the cylindrical vector polarized light field, σ takes +1 to represent the cylindrical vector polarized light field as HE formula, and σ takes-1 to represent the cylindrical vector polarized light field as EH formula), and the Stokes parameter S for the vector Doppler polarized signal 1 And S 2 Subtracting the Fourier phase spectrum to obtain a Fourier relative phase spectrum, extracting a relative phase difference value corresponding to a peak frequency in the Fourier relative phase spectrum, judging a sign corresponding to the peak frequency through the relative phase difference value, calculating the magnitude and direction information of the spin and revolution angular velocity of the anisotropic rotary motion particles by using the peak frequency and the relative phase difference value, and calculating a Stokes parameter S of a vector Doppler polarization signal 1 And S 2 The amplitude ratio of each Doppler frequency shift peak in the Fourier amplitude spectrum is analyzed and calculated to obtain the anisotropic parameter information of the anisotropic rotational motion particles, so that the measurement of the anisotropic rotational motion particles based on the vector Doppler effect is realized.
Preferably, the doppler frequency peak shifts are a first doppler frequency peak shift, a second doppler frequency peak shift, and a third doppler frequency peak shift in sequence from small to large peak frequency, and the relative amplitudes are:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Where τ and δ are known anisotropy parameters of the anisotropic rotating motion particle: τ is the ratio of the reflection coefficients of the anisotropically rotationally moving particle along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropically rotationally moving particle.
Preferably, the stokes parameter S of the vector doppler polarization signal is known for the case of anisotropic parameters of the anisotropically rotationally moving particles during measurement 1 And S 2 The relative amplitude difference of each peak frequency in the anisotropic rotating particle is known, and the peak frequencies are directly in one-to-one correspondence with formulas by utilizing the difference, so that the magnitude and the direction of the spin and the revolution angular velocity of the anisotropic rotating particle are calculated.
According to a second aspect of the present invention, there is provided a method for measuring an anisotropic rotational motion particle, wherein, in a case where an anisotropic parameter of the anisotropic rotational motion particle is unknown during measurement, a step-by-step measurement manner of adjusting the order (l → 2l) of a cylindrical vector polarized light field during measurement is adopted, and the corresponding relationship between the step-by-step measurement manner and a formula is distinguished and identified according to the variation law difference of each peak frequency during the step-by-step measurement, wherein only a peak frequency component related to a spin angular velocity remains unchanged (| Δ f) 2 |＝Θ/π→|Δf′ 2 Θ/pi), only the degree of change of the peak frequency component relating to the revolution angular velocity and the peak frequency component relating to both the spin and revolution angular velocities is different (| Δ f) 1 |＝lΩ/π→|Δf′ 1 |＝2lΩ/π、|Δf 3 |＝(2Θ+σlΩ)/π→|Δf′ 3 I | ═ 2 Θ +2 σ l Ω)/pi), i.e., the second doppler shift peak is only related to the spin angular velocity, its peak frequency remains unchanged; the first Doppler frequency peak shift is only related to the revolution angleThe speed is related, the third Doppler frequency shift peak is related to both the spin angular speed and the revolution angular speed, the peak frequencies of the two are changed, and the change degrees are different. Corresponding the obtained peak frequencies to formulas one by one, namely calculating the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotating particles, and finally passing the Stokes parameter S of the vector Doppler polarization signal 1 And S 2 Measuring the anisotropic parameter by using the relative amplitude ratio of each peak frequency, wherein the relative amplitude corresponding to each peak frequency is as follows: a. the 1 ＝1+τ 2 +2τcosδ、A 2 ＝2(τ 2 -1)、A 3 ＝1+τ 2 2 τ cos δ, the ratio of the reflectance τ of the anisotropically rotationally moving particle along the fast and slow axes, and the phase delay δ caused by the anisotropically rotationally moving particle can be calculated.
Preferably, when the anisotropic parameter of the anisotropic rotating particle is τ 1, δ is (2n +1) pi (n is 0,1, 2.) the amplitudes of only the peak frequency component related to the revolution angular velocity and the peak frequency component related to the spin angular velocity are zero, and if the anisotropic parameter of the anisotropic rotating particle is related to the wavelength, the phase delay of the anisotropic rotating particle is adjusted by changing the optical wavelength of the cylindrical vector polarized optical field in the measurement, so as to avoid the occurrence of the zero amplitude, thereby completing the measurement; if the anisotropic parameters of the anisotropic rotating particles are not related to the wavelength, two measurement values (| delta f) of the peak frequency component related to both the spin and the revolution angular velocity are obtained by adopting a step-by-step measurement mode of adjusting the order (l → 2l) of the cylindrical vector polarized light field in the measurement 3 L ═ 2 Θ + σ l Ω)/π and | Δ f' 3 And (2 Θ +2 σ l Ω)/pi), solving and calculating a simultaneous equation, and further realizing measurement.
Preferably, for the stokes parameter method, the equation S is used 1 ＝I x -I y 、S 2 ＝I 45° -I -45° To obtain the Stokes parameters S of the vector Doppler polarization signal 1 And S 2 Wherein, the vector Doppler polarization signal is split into two paths, the first path of signal light is split again and then is deflected along x and yVibration direction detection intensity signal I x And I y The second path of signal light is split again to detect the intensity signal I along the polarization directions of 45 degrees and-45 degrees 45° And I -45° From which the parameters S for Stokes are constructed 1 And S 2 The detection device of (1).
According to the third aspect of the present invention, in the case that the anisotropic parameters of the anisotropic rotationally moving particles are known, a dual polarization detection method may be adopted instead of the stokes parameter method to detect the vector doppler polarization signal, wherein the fourier analysis is performed on the projection components of the vector doppler polarization signal in two polarization directions, respectively, a plurality of doppler frequency shift peaks are extracted from the fourier magnitude spectrum, and the peak frequencies are the peak frequencies respectively
|Δf 2 |＝Θ/π、|Δf 3 |＝(2σΘ+lΩ)/π、|Δf 4 The relative amplitudes are respectively A, and are respectively represented by | - ([ sigma ] theta + l Ω)/π (Ω is revolution angular velocity, Θ is spin angular velocity, l is mode order of cylindrical vector polarized light field, σ takes +1 to represent cylindrical vector polarized light field as HE formula, σ takes-1 to represent cylindrical vector polarized light field as EH formula), and corresponding relative amplitudes are respectively represented by A 1 ＝1+τ 2 +2τcosδ、A 2 ＝2(1-τ 2 )、A 3 ＝1+τ 2 -2τcosδ、A 4 ＝2(1-τ 2 ) (τ and δ are known anisotropy parameters for anisotropic rotational motion particles: tau is the reflection coefficient ratio of the anisotropic rotating particles along the fast axis and the slow axis, delta is the phase delay caused by the anisotropic rotating particles), Fourier phase spectrums of projection components of the vector Doppler polarization signals in two polarization directions are subtracted to obtain Fourier relative phase spectrums, relative phase difference values corresponding to peak frequencies are extracted from the Fourier relative phase spectrums, and the peak frequency delta f can be judged according to the relative phase difference values 1 、Δf 2 、Δf 3 Finally, according to the peak frequency and the corresponding relative amplitude and relative phase difference value, the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotating particle and the anisotropic parameter information can be calculated.
According to the fourth aspect of the present invention, in the case that the anisotropic parameters of the anisotropic rotational motion particles are unknown, a step-by-step measurement mode is also adopted, in which the order (l → 2l) of the cylindrical vector polarized light field is adjusted during measurement, the correspondence between the peak frequencies and the formula is distinguished and identified according to the variation rule difference of the peak frequencies during step-by-step measurement, the obtained peak frequencies are in one-to-one correspondence with the formula, that is, the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotational motion particles are calculated, and the reflection coefficient ratio τ of the anisotropic rotational motion particles along the fast axis and the slow axis and the phase delay δ caused by the anisotropic rotational motion particles are calculated.
Preferably, for the dual polarization detection method, the vector doppler polarization signal is split into two paths, and the first path of signal light is along θ 1 Polarization direction detection intensity signal I 1 The second path of signal light is along theta 2 Polarization direction detection intensity signal I 2 And theta 1 And theta 2 The angle Δ θ between the two polarization directions may take any value other than 0 and ± 90 °, thereby constructing a dual polarization detection device.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
1. the invention is based on the vector Doppler effect in principle, has innovativeness compared with a common rotary Doppler velocity measurement method, provides two general detection means for complex vector Doppler polarization signals, and has guiding significance for more general velocity measurement research.
2. The invention can realize one-time simultaneous measurement of the complex rotational motion state of the anisotropic particles, not only can obtain the revolution angular velocity and the direction of the anisotropic particles, but also can obtain the spin angular velocity and the direction of the anisotropic particles, and ensures the integrity of motion information acquisition.
3. The invention can realize the measurement of the unknown anisotropic parameters of the anisotropic rotating particles, thereby greatly widening the application range of the object to be measured.
4. The invention takes the cylindrical vector polarized light field as the detection light, and does not need to adopt additional reference light in the measurement, so the measurement device is simple and more compact, the integration level is easy to improve, the cost is reduced, and the measurement result is less interfered by the environment.
Drawings
FIG. 1 is a schematic structural diagram of a method for measuring anisotropic rotational motion particles according to the present invention;
FIG. 2 is a schematic diagram of an apparatus for generating a cylindrical vector polarized light field according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the interaction of an anisotropically rotationally moving particle with a cylindrical vector polarized light field provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a Stokes parameter detection apparatus for vector Doppler polarization signals according to an embodiment of the present invention;
FIG. 5 shows Stokes' parameters S for detecting particles having anisotropic rotary motion and revolving clockwise and spinning clockwise in an embodiment of the present invention 1 And S 2 Is the Stokes' parameter S 1 And S 2 The time domain signal of (a); (b) is the Stokes parameter S 1 A Fourier magnitude spectrum of (1); (c) is the Stokes parameter S 2 A Fourier magnitude spectrum of (1); (d) is the Stokes parameter S 1 And S 2 Fourier relative phase spectrum therebetween;
FIG. 6 shows Stokes parameters S for detecting particles having anisotropic rotary motion and revolving counterclockwise and spinning counterclockwise in an embodiment of the present invention 1 And S 2 Is the Stokes' parameter S 1 And S 2 The time domain signal of (a); (b) is the Stokes parameter S 1 A Fourier magnitude spectrum of (1); (c) is the Stokes parameter S 2 A Fourier magnitude spectrum of (1); (d) is the Stokes parameter S 1 And S 2 Fourier relative phase spectrum in between.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a method for measuring anisotropic rotational movement particles, which comprises the following steps of: irradiating anisotropic rotation motion particles by a cylindrical vector polarization light field, wherein the anisotropic rotation motion particles can have a rotation and revolution motion mode, the optical axis of the cylindrical vector polarization light field is superposed with the revolution rotating shaft of the anisotropic rotation motion particles, the anisotropic rotation motion particles reflect vector Doppler polarization signals, the vector Doppler polarization signals are detected by adopting a Stokes parameter method, and the Stokes parameter S of the vector Doppler polarization signals is detected 1 And S 2 Respectively carrying out Fourier analysis, extracting a plurality of Doppler frequency shift peaks in a Fourier magnitude spectrum, wherein the peak frequencies are respectively | delta f 1 |＝lΩ/π、|Δf 2 |＝Θ/π、|Δf 3 (2 Θ + σ l Ω)/π (where Ω is the revolution angular velocity, Θ is the spin angular velocity, l is the mode order of the cylindrical vector polarized light field, σ takes +1 to represent the cylindrical vector polarized light field as HE formula, and σ takes-1 to represent the cylindrical vector polarized light field as EH formula), and the Stokes parameter S for the vector Doppler polarized signal 1 And S 2 The relative phase difference value is extracted corresponding to the peak frequency in the Fourier relative phase spectrum, the sign corresponding to the peak frequency is judged through the relative phase difference value, the magnitude and the direction information of the spin and revolution angular velocity of the anisotropic rotary motion particles are calculated by utilizing the peak frequency and the relative phase difference value, and in addition, the Stokes parameter S of the vector Doppler polarization signal 1 And S 2 The amplitude ratio of each Doppler frequency shift peak in the Fourier amplitude spectrum is analyzed and calculated to obtain the anisotropic parameter information of the anisotropic rotary motion particles, so that the measurement of the anisotropic rotary motion particles based on the vector Doppler effect is realized.
Specifically, the doppler frequency peak shifts are a first doppler frequency peak shift, a second doppler frequency peak shift, and a third doppler frequency peak shift in sequence from small to large peak frequency, and the relative amplitudes are:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Where τ and δ are known anisotropy parameters of the anisotropic rotating motion particle: τ is the ratio of the reflection coefficients of the anisotropically rotationally moving particle along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropically rotationally moving particle.
Under the condition that the anisotropic parameters of the anisotropic rotating particles are unknown during measurement, a step measurement mode of adjusting the order (l → 2l) of a cylindrical vector polarized light field during measurement is adopted, and the corresponding relation between the step measurement mode and a formula is distinguished and identified according to the variation rule difference of each peak frequency in the step measurement, wherein only the peak frequency component related to the spin angular velocity is kept unchanged (| delta f) 2 |＝Θ/π→|Δf′ 2 Θ/pi), only the degree of change of the peak frequency component relating to the revolution angular velocity and the peak frequency component relating to both the spin and revolution angular velocities is different (| Δ f) 1 |＝lΩ/π→|Δf′ 1 |＝2lΩ/π、|Δf 3 |＝(2Θ+σlΩ)/π→|Δf′ 3 Corresponding the obtained peak frequency to a formula one by one, namely calculating the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotary motion particles, and finally passing the stokes parameter S of the vector Doppler polarization signal 1 And S 2 Measuring the anisotropic parameter by using the relative amplitude ratio of each peak frequency, wherein the relative amplitude corresponding to each peak frequency is as follows: a. the 1 ＝1+τ 2 +2τcosδ、A 2 ＝2(τ 2 -1)、A 3 ＝1+τ 2 2 τ cos δ, the ratio of the reflectance τ of the anisotropically rotationally moving particle along the fast and slow axes, and the phase delay δ caused by the anisotropically rotationally moving particle can be calculated.
Specifically, when the anisotropy parameter of the anisotropic rotating particle is τ 1, δ is (2n +1) pi (n is 0,1, 2.) the amplitudes of only the peak frequency component related to the revolution angular velocity and the peak frequency component related to the spin angular velocity are zero, and when the anisotropy parameter of the anisotropic rotating particle is related to the wavelength, the phase delay of the anisotropic rotating particle is adjusted by changing the optical wavelength of the cylindrical vector polarized optical field in the measurement, thereby avoiding the occurrence of the zero amplitude, and further completing the measurement; if the anisotropic parameters of the anisotropic rotating particles are not related to the wavelength, two measurement values (| delta f) of the peak frequency component related to both the spin and the revolution angular velocity are obtained by adopting a step-by-step measurement mode of adjusting the order (l → 2l) of the cylindrical vector polarized light field in the measurement 3 L ═ 2 Θ + σ l Ω)/π and | Δ f' 3 (2 Θ +2 σ l Ω)/pi), simultaneous equations are solved and calculated, and then measurement is achieved.
In particular, for the stokes parametric method, the equation S is used 1 ＝I x -I y 、S 2 ＝I 45° -I -45° To obtain the Stokes parameters S of the vector Doppler polarization signal 1 And S 2 Wherein, the vector Doppler polarization signal is split into two paths, the first path of signal light is split again to detect the intensity signal I along the x and y polarization directions x And I y The second path of signal light is split again to detect the intensity signal I along the polarization directions of 45 degrees and-45 degrees 45° And I -45° From which the parameters S for Stokes are constructed 1 And S 2 The detection device of (1).
Under the condition that the anisotropic parameters of the anisotropic rotational motion particles are known, a dual-polarization detection method can be adopted to replace a stokes parameter method to detect the vector Doppler polarization signals, wherein the Fourier analysis is respectively carried out on the projection components of the vector Doppler polarization signals in two polarization directions, a plurality of Doppler frequency shift peaks are extracted from a Fourier magnitude spectrum, and the peak frequencies are respectively | delta f 1 |＝lΩ/π、|Δf 2 |＝Θ/π、|Δf 3 |＝(2σΘ+lΩ)/π、|Δf 4 I | (σ Θ + l Ω)/π, the corresponding relative amplitudes are A, respectively 1 ＝1+τ 2 +2τcosδ、A 2 ＝2(1-τ 2 )、A 3 ＝1+τ 2 -2τcosδ、A 4 ＝2(1-τ 2 ) The Fourier phase spectrums of the projection components of the vector Doppler polarization signal in the two polarization directions are subtracted to obtain a Fourier relative phase spectrum, and relative phase difference values corresponding to each peak frequency are extracted from the Fourier relative phase spectrum, so that the peak frequency delta f can be judged 1 、Δf 2 、Δf 3 Finally, according to the peak frequency and the corresponding relative amplitude and relative phase difference value, the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotating particle and the anisotropic parameter information can be calculated.
Under the condition that the anisotropic parameters of the anisotropic rotational motion particles are unknown, a step-by-step measurement mode of adjusting the order (l → 2l) of the cylindrical vector polarization light field in the measurement can be adopted, the corresponding relation between the peak frequency and the formula is distinguished and identified according to the variation rule difference of each peak frequency in the step-by-step measurement, the obtained peak frequencies are in one-to-one correspondence with the formula, namely the magnitude and the direction of the spin and revolution angular speed of the anisotropic rotational motion particles are calculated, and the reflection coefficient ratio tau of the anisotropic rotational motion particles along the fast axis and the slow axis and the phase delay delta caused by the anisotropic rotational motion particles are calculated.
Specifically, for the dual-polarization detection method, the vector Doppler polarization signal is split into two paths, and the first path of signal light is along theta 1 Polarization direction detection intensity signal I 1 The second path of signal light is along theta 2 Polarization direction detection intensity signal I 2 And theta 1 And theta 2 The angle Δ θ between the two polarization directions may take any value other than 0 and ± 90 °, thereby constructing a dual polarization detection device.
The following description is made with reference to the embodiments and the accompanying drawings.
As shown in fig. 1, the structural schematic diagram of the method for measuring anisotropic rotational motion particles provided by the present invention includes: cylindrical vector polarized light source 1, cylindrical vector polarizationThe device comprises an optical field 2, anisotropic rotary motion particles 3, a vector Doppler polarization signal 4 and a Stokes parameter detection device 5. The cylindrical vector polarized light source 1 generates and outputs a cylindrical vector polarized light field 2 as probe light, the cylindrical vector polarized light field 2 perpendicularly irradiates anisotropic rotating motion particles 3, the anisotropic rotating motion particles 3 reflect vector Doppler polarization signals 4, and the vector Doppler polarization signals 4 are collected and information extracted through a Stokes parameter detection device 5, so that the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotating motion particles 3 and the one-time simultaneous measurement of the anisotropic parameters of the anisotropic rotating motion particles are realized. Wherein, the optical axis of the cylindrical vector polarized light field 2 is aligned with the revolution rotating shaft of the anisotropic rotating particle 3; the anisotropic rotary motion particles 3 can perform spin and revolution, the revolution track of the particles is positioned in the cylindrical vector polarized light field 2, and the particles can reflect light fields at different spatial positions; stokes parameter S of vector Doppler polarized signal 4 by Stokes parameter detection device 5 1 And S 2 The magnitude and direction information of the spin and revolution angular velocities of the anisotropic rotating particles 3 is calculated by extracting a plurality of doppler frequency shift peaks in the fourier amplitude spectrum and corresponding relative phase difference values in the fourier relative phase spectrum, respectively, and the anisotropic parameter information of the anisotropic rotating particles 3 is calculated by using the amplitude ratios of the plurality of doppler frequency shift peaks in the fourier amplitude spectrum.
As shown in fig. 2, a schematic diagram of a device for generating a cylindrical vector polarized light field according to an embodiment of the present invention includes: the device comprises a laser 11, a half-wave plate 12, a polarization beam splitter 13, a first reflector 14, a spiral phase plate 15, a second reflector 16, a third reflector 17, a quarter-wave plate 18 and a cylindrical vector polarized light field 2. The laser 11 outputs a linearly polarized Gaussian beam, the polarization direction of the Gaussian beam is adjusted to be 45-degree linear polarization by the half-wave plate 12, the 45-degree linearly polarized Gaussian beam is divided into an x-polarization direction straight-through path and a y-polarization direction reflected two paths by the polarization beam splitter 13, the x-polarization direction Gaussian beam is reflected by the first reflector 14 and then converted into a phase vortex beam by the spiral phase plate 15, then the phase vortex beam is reflected by the second reflector 16 and the third reflector 17 and then is straight-through to the quarter-wave plate 18 along the polarization beam splitter 13, the y-polarization direction Gaussian beam is reflected by the third reflector 17 and the second reflector 16 and then converted into a phase vortex beam by the spiral phase plate 15, then the phase vortex beam is reflected by the first reflector 14 and then is reflected to the quarter-wave plate 18 along the polarization beam splitter 13, and the quarter-wave plate 18 respectively adjusts the phase vortex beams in the x-polarization direction and the y-polarization direction into circularly polarized phase vortex beams in opposite directions, finally, the two light beams are superposed to synthesize a cylindrical vector polarized light field 2. The spiral phase plate 15 works independently of polarization, the Gaussian beam enters the spiral phase plate 15 from the positive direction and the negative direction and is modulated into the phase vortex beam with opposite helicity, the two phase vortex beams are reflected by the reflector for the same number of times in the process from generation to beam combination, and circular polarization and phase helicity of two superposed beams in the beam combination are opposite.
As shown in fig. 3, a schematic diagram of interaction between an anisotropic rotational particle and a cylindrical vector polarized light field provided in an embodiment of the present invention is that the anisotropic rotational particle performs a spinning motion and a revolving motion simultaneously (the spinning angular velocity is Θ, and the revolving angular velocity is Ω), under irradiation of the cylindrical vector polarized light field, a revolving center of the anisotropic rotational particle coincides with an optical axis of the cylindrical vector polarized light field, a revolving track of the anisotropic rotational particle is located in a region where the energy density of the cylindrical vector polarized light field is high, a size of the anisotropic rotational particle is smaller than a light spot size of the cylindrical vector polarized light field, and a part of the light field is locally reflected during the interaction process, so as to generate a signal whose polarization changes with time, that is, a vector doppler polarization signal.
As shown in fig. 4, a schematic diagram of a stokes parameter detection apparatus for a vector doppler polarization signal according to an embodiment of the present invention includes: the device comprises a vector Doppler polarization signal 4 to be detected, a first beam splitter 51, a second beam splitter 52, a first polarizing plate 53, a first lens 54, a first photoelectric detector 55, a second polarizing plate 56, a second lens 57, a second photoelectric detector 58, a third beam splitter 59, a third polarizing plate 510, a third lens 511, a third photoelectric detector 512, a fourth polarizing plate 513, a fourth lens 514, a fourth photoelectric detector 515, a radio frequency line 516 and a signal processing module 517. The vector Doppler polarization signal 4 to be detected is equally divided into two parts by a beam splitter 51, the first part is equally divided into two paths by a second beam splitter 52, the first path sequentially passes through a first polarizing film 53 to extract an x polarization direction signal component, is focused by a first lens 54 and is received by a first photoelectric detector 55 and is subjected to photoelectric conversion, the second path sequentially passes through a second polarizing film 56 to extract a y polarization direction signal component, is focused by a second lens 57 and is received by a second photoelectric detector 58 and is subjected to photoelectric conversion, the second part is equally divided into two paths by a third beam splitter 59, the first path sequentially passes through a third polarizing film 510 to extract a 45-degree polarization direction signal component, is focused by a third lens 511 and is received by a third photoelectric detector 512 and is subjected to photoelectric conversion, the second path sequentially passes through a fourth polarizing film 513 to extract a-45-degree polarization direction signal component, is focused by a fourth lens 514 and is received by a fourth photoelectric detector 515 and is subjected to photoelectric conversion, the electrical signals converted by the first photodetector 55, the second photodetector 58, the third photodetector 512, and the fourth photodetector 515 are transmitted to the signal processing module 517 by the radio frequency line 516 for fourier analysis.
As shown in fig. 5, a diagram of the detection result of the anisotropic rotational motion particles revolving clockwise and spinning clockwise according to the embodiment of the present invention is provided. (a) For the detected Stokes parameter S 1 And S 2 The time domain signal of (a); (b) for the detected Stokes' parameters S 1 A fourier magnitude spectrum of (a); (c) for the detected Stokes' parameters S 2 A Fourier magnitude spectrum of (1); (d) for the detected Stokes' parameters S 1 And S 2 Fourier relative phase spectrum therebetween, wherein the probe light adopted for this result is HE 41 In the cylindrical vector polarized light field of the formula, the spin angular velocity of the anisotropic rotating particle is theta-160 pi rad/s, and the revolution angular velocity is omega-40 pi rad/s. As shown in fig. 6, a diagram of the detection result of the anisotropic rotating particle revolving counterclockwise and spinning counterclockwise according to the embodiment of the present invention is provided. (a) For the detected Stokes' parameters S 1 And S 2 The time domain signal of (a); (b) for the detected Stokes' parameters S 1 A Fourier magnitude spectrum of (1); (c) for the detected Stokes' parameters S 2 A Fourier magnitude spectrum of (1); (d) for the detected Stokes' parameters S 1 And S 2 Cross reference to related applicationsInner leaf relative phase spectrum, wherein the detection light adopted by the result is HE 41 In the cylindrical vector polarized light field of the formula, the spin angular velocity of the anisotropic rotating particle is theta-160 pi rad/s, and the revolution angular velocity is omega-40 pi rad/s. It can be seen from the results that the Stokes parameter S is detected at a fixed particle rotation speed 1 And S 2 All have three peak frequency components in common, of which | Δ f 1 | and | Δ f 2 | is the peak frequency component relating to revolution only and spin only, | Δ f 3 L is a peak frequency component related to both revolution and spin; as can be seen from the difference in the fourier relative phase spectra in the two rotation directions in fig. 5 (d) and fig. 6 (d), the signs of the relative phase difference values corresponding to the three peak frequency components are inverted in both the revolution and spin reversal directions of the anisotropic rotationally moving particles, and thus the signs of the three peak frequencies can be determined. By using the relational expression between each peak frequency and the revolution and spin angular velocity, the magnitude and direction of the revolution and spin angular velocity of the anisotropic rotating particle can be calculated. In addition, as can be seen from (b) and (c) in fig. 5 and (b) and (c) in fig. 6, there is a difference in the relative amplitude of each frequency peak, and thus it is possible to distinguish the correspondence of each frequency peak to the expression for the fine particles whose anisotropy is unknown, and to estimate the anisotropy parameter for the fine particles whose anisotropy is unknown.
The present invention is not limited to the above embodiments, and those skilled in the art can implement the present invention in other various embodiments according to the disclosure of the present invention, so that all designs and concepts of the present invention can be changed or modified without departing from the scope of the present invention.
Claims (10)
1. A method for measuring an anisotropic rotating particle, wherein the anisotropic rotating particle has a motion form of spin and revolution under the condition that an anisotropy parameter of the anisotropic rotating particle is known, the method comprising the steps of:
irradiating the anisotropic rotary motion particles by a cylindrical vector polarized light field with the optical axis coinciding with the revolution rotating shaft of the anisotropic rotary motion particles, and detecting a vector Doppler polarized signal reflected by the anisotropic rotary motion particles by adopting a Stokes parameter method;
a first Stokes parameter S to said vector Doppler polarized signal 1 And a second Stokes parameter S 2 Respectively carrying out Fourier analysis to respectively obtain a first Fourier phase spectrum, a first Fourier amplitude spectrum, a second Fourier phase spectrum and a second Fourier amplitude spectrum, extracting relative amplitudes of a plurality of Doppler frequency shift peaks from the first Fourier amplitude spectrum and the second Fourier amplitude spectrum, comparing the relative amplitudes with known relative amplitudes corresponding to peak frequency, and determining the ordering of the Doppler frequency shift peaks; subtracting the first Fourier phase spectrum and the second Fourier phase spectrum to obtain a Fourier relative phase spectrum, and extracting a relative phase difference value in the Fourier relative phase spectrum according to the ordering of Doppler frequency shift peaks; and judging the sign of each peak frequency according to the relative phase difference value, and calculating the magnitude and the direction of the spin and revolution angular velocity of the anisotropic rotary motion particles by using the peak frequency and the relative phase difference value.
2. The measurement method according to claim 1, wherein the doppler frequency shift peaks are a first doppler frequency shift peak, a second doppler frequency shift peak, and a third doppler frequency shift peak in order from small to large peak frequency, and the peak frequencies are:
first doppler frequency peak shift: | Δ f 1 |＝lΩ/π
Second doppler frequency peak shift: | Δ f 2 |＝Θ/π
Third doppler frequency peak shift: | Δ f 3 |＝(2Θ+σlΩ)/π
Wherein Ω is a revolution angular velocity, Θ is a spin angular velocity, l is a mode order of the cylindrical vector polarized light field, σ takes +1 to represent that the cylindrical vector polarized light field is an HE formula, and σ takes-1 to represent that the cylindrical vector polarized light field is an EH formula.
3. The measurement method according to claim 1, wherein the doppler frequency shift peaks are a first doppler frequency shift peak, a second doppler frequency shift peak, and a third doppler frequency shift peak in order from small to large peak frequency, and the relative amplitudes are:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Where τ and δ are known anisotropy parameters of the anisotropic rotating motion particle: τ is the ratio of the reflection coefficients of the anisotropically rotationally moving particle along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropically rotationally moving particle.
4. A method for measuring an anisotropic rotationally moving particle, wherein, in a case where an anisotropic parameter of the anisotropic rotationally moving particle is unknown, the anisotropic rotationally moving particle has a motion form of spin and revolution, and the measurement comprises the steps of:
irradiating the anisotropic rotary motion particles by using a first cylindrical vector polarized light field, and detecting a first vector Doppler polarized signal reflected by the anisotropic rotary motion particles by using a Stokes parameter method; a first Stokes parameter S to said first vector Doppler polarized signal 1 And a second Stokes parameter S 2 Respectively carrying out Fourier analysis to respectively obtain a first Fourier phase spectrum, a first Fourier amplitude spectrum, a second Fourier phase spectrum and a second Fourier amplitude spectrum, and respectively extracting a plurality of Doppler frequency shift peaks from the first Fourier amplitude spectrum and the second Fourier amplitude spectrum;
changing the order of a cylindrical vector polarized light field, irradiating the anisotropic rotary motion particles by using a second cylindrical vector polarized light field, and detecting a second vector Doppler polarization signal reflected by the anisotropic rotary motion particles by adopting a Stokes parameter method; for the second vector DopplerFirst Stokes parameter S of the polarized signal 1 And a second Stokes parameter S 2 Respectively carrying out Fourier analysis to respectively obtain a third Fourier phase spectrum, a third Fourier amplitude spectrum, a fourth Fourier phase spectrum and a fourth Fourier amplitude spectrum, and respectively extracting a plurality of Doppler frequency shift peaks from the third Fourier amplitude spectrum and the fourth Fourier amplitude spectrum;
comparing the variation difference of the peak frequency of each Doppler frequency peak shift obtained by two times of measurement, determining the sequence of each Doppler frequency peak shift, and sequentially arranging a first Doppler frequency peak shift, a second Doppler frequency peak shift and a third Doppler frequency peak shift according to the sequence of the peak frequency from small to large;
extracting a first measurement peak frequency of a third Doppler frequency peak shift from the first Fourier magnitude spectrum and the second Fourier magnitude spectrum, and extracting a second measurement peak frequency of the third Doppler frequency peak shift from the third Fourier magnitude spectrum and the fourth Fourier magnitude spectrum; subtracting the first Fourier phase spectrum from the second Fourier phase spectrum to obtain a first Fourier relative phase spectrum, and extracting a first relative phase difference value from the first measured peak frequency corresponding to the third Doppler frequency shift peak in the first Fourier relative phase spectrum; subtracting the third Fourier phase spectrum from the fourth Fourier phase spectrum to obtain a second Fourier relative phase spectrum, and extracting a second relative phase difference value from a second measured peak frequency corresponding to the third Doppler frequency shift peak in the second Fourier relative phase spectrum; the signs of the peak frequencies of the third Doppler frequency shift peak in the two measurements are respectively judged through the first relative phase difference value and the second relative phase difference value, and the magnitude and the direction of the spin and revolution angular velocity of the anisotropic rotary motion particles are calculated by utilizing the signs of the peak frequencies of the third Doppler frequency shift peak in the two measurements and the peak frequencies in the two measurements;
and extracting relative amplitudes of a plurality of Doppler frequency shift peaks from the first Fourier amplitude spectrum and the second Fourier amplitude spectrum, and calculating relative amplitude ratios to obtain anisotropic parameter information of the anisotropic rotary motion particles.
5. The measurement method according to claim 4, wherein in two measurements, after the order of the cylindrical vector polarized light field is changed from l → 2l, the peak frequency of each Doppler frequency shift peak is changed as follows:
first doppler frequency peak shift: | Δ f 1 |＝lΩ/π→|Δf 1 ′|＝2lΩ/π
Second doppler frequency peak shift: | Δ f 2 |＝Θ/π→|Δf 2 ′|＝Θ/π
Third doppler frequency peak shift: | Δ f 3 |＝(2Θ+σlΩ)/π→|Δf 3 ′|＝(2Θ+2σlΩ)/π
Wherein Ω is a revolution angular velocity, Θ is a spin angular velocity, l is a mode order of the cylindrical vector polarized light field, σ takes +1 to represent that the cylindrical vector polarized light field is an HE formula, and σ takes-1 to represent that the cylindrical vector polarized light field is an EH formula.
6. The method of claim 4, wherein the relative amplitudes of the Doppler frequency shifts are:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Wherein τ and δ are unknown anisotropy parameters of the anisotropically rotationally moving particle: τ is the ratio of the reflection coefficients of the anisotropically rotationally moving particle along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropically rotationally moving particle.
7. The measurement method according to claim 1 or 4, wherein the detection manner of the vector Doppler polarization signal by the Stokes parametric method is as follows:
first Stokes parameter S 1 ＝I x -I y
Second Stokes parameter S 2 ＝I 45° -I -45°
Wherein, I x Intensity signal projected in horizontal direction for said vector Doppler polarized signal, I y Intensity signal projected in the vertical direction for said vector Doppler polarization signal, I 45° Intensity signal projected along a 45 ° polarization direction for said vector doppler polarization signal, I -45° Intensity signal projected along-45 ° polarization direction for the vector doppler polarization signal.
8. A method for measuring an anisotropic rotating particle, wherein the anisotropic rotating particle has a motion form of spin and revolution under the condition that an anisotropic parameter of the anisotropic rotating particle is known, and the measurement comprises the following steps:
irradiating the anisotropic rotation movement particles by using a cylindrical vector polarization light field, and detecting a vector Doppler polarization signal reflected by the anisotropic rotation movement particles by using a dual-polarization detection method;
respectively carrying out Fourier analysis on the first polarization direction projection component and the second polarization direction projection component of the vector Doppler polarization signal to respectively obtain a first Fourier magnitude spectrum, a first Fourier phase spectrum, a second Fourier magnitude spectrum and a second Fourier phase spectrum, and subtracting the first Fourier phase spectrum and the second Fourier phase spectrum to obtain a Fourier relative phase spectrum;
respectively extracting peak frequencies and relative amplitudes of a plurality of Doppler frequency shift peaks from the first Fourier magnitude spectrum and the second Fourier magnitude spectrum, wherein the peak frequencies are respectively as follows:
first doppler frequency peak shift: | Δ f 1 |＝lΩπ
Second doppler frequency peak shift: | Δ f 2 |＝Θ/π
Third doppler frequency peak shift: | Δ f 3 |＝(2σΘ+lΩ)/π
Fourth doppler frequency peak shift: | Δ f 4 |＝(σΘ+lΩ)/π
Wherein Ω is a revolution angular velocity, Θ is a spin angular velocity, l is a mode order of the cylindrical vector polarized light field, σ takes +1 to represent that the cylindrical vector polarized light field is an HE formula, and σ takes-1 to represent that the cylindrical vector polarized light field is an EH formula;
the relative amplitudes are respectively:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Fourth doppler frequency peak shift: a. the 4 ＝2(1-τ 2 )
Where τ and δ are known anisotropy parameters of the anisotropic rotating motion particle: τ is the reflection coefficient ratio of the anisotropic rotationally moving particles along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropic rotationally moving particles;
extracting relative phase difference values corresponding to the peak frequencies in the Fourier relative phase spectrum, distinguishing a fourth Doppler frequency shift peak through the relative phase difference values and judging signs of the peak frequencies, wherein the relative phase difference value corresponding to the fourth Doppler frequency shift peak is 0, and the signs of the relative phase difference values of the other Doppler frequency shift peaks correspond to the signs of the peak frequencies; and calculating the magnitude and direction of the spin and revolution angular velocity of the anisotropic rotating particle by using the difference of the relative amplitudes of the first, second and third Doppler frequency shift peaks.
9. A method for measuring an anisotropic rotationally moving particle, wherein, in a case where an anisotropic parameter of the anisotropic rotationally moving particle is unknown, the anisotropic rotationally moving particle has a motion form of spin and revolution, the method comprising the steps of:
irradiating the anisotropic rotation movement particles by using a first cylindrical vector polarization light field, and detecting a first vector Doppler polarization signal reflected by the anisotropic rotation movement particles by using a dual-polarization detection method; respectively carrying out Fourier analysis on the first polarization direction projection component and the second polarization direction projection component of the first vector Doppler polarization signal to respectively obtain a first Fourier magnitude spectrum, a first Fourier phase spectrum, a second Fourier magnitude spectrum and a second Fourier phase spectrum, and subtracting the first Fourier phase spectrum and the second Fourier phase spectrum to obtain a first Fourier relative phase spectrum;
changing the order of a cylindrical vector polarized light field, irradiating the anisotropic rotation motion particles by using a second cylindrical vector polarized light field, and detecting a second vector Doppler polarization signal reflected by the anisotropic rotation motion particles by adopting a dual-polarization detection method; respectively carrying out Fourier analysis on the first polarization direction projection component and the second polarization direction projection component of the second vector Doppler polarization signal to respectively obtain a third Fourier phase spectrum, a third Fourier magnitude spectrum, a fourth Fourier phase spectrum and a fourth Fourier magnitude spectrum, and subtracting the third Fourier phase spectrum and the fourth Fourier phase spectrum to obtain a second Fourier relative phase spectrum;
for two measurements, after the order of the cylindrical vector polarized light field is changed from l → 2l, the peak frequency formula is changed as follows:
first doppler frequency peak shift: | Δ f 1 |＝lΩ/π→|Δf 1 ′|＝2lΩ/π
Second doppler frequency peak shift: | Δ f 2 |＝Θ/π→|Δf′ 2 |＝Θ/π
Third doppler frequency peak shift: | Δ f 3 |＝(2σΘ+lΩ)/π→|Δf 3 ′|＝(2σΘ+2lΩ)/π
Fourth doppler frequency peak shift: | Δ f 4 |＝(σΘ+lΩ)/π→|Δf 4 ′|＝(σΘ+2lΩ)/π
Wherein, omega is revolution angular velocity, theta is spin angular velocity, sigma takes +1 to represent that the cylindrical vector polarized light field is HE formula, and sigma takes-1 to represent that the cylindrical vector polarized light field is EH formula;
extracting first measurement peak frequency of a plurality of Doppler frequency shift peaks respectively in a first Fourier magnitude spectrum and a second Fourier magnitude spectrum, extracting second measurement peak frequency of a plurality of Doppler frequency shift peaks respectively in a third Fourier magnitude spectrum and a fourth Fourier magnitude spectrum, extracting relative phase difference values corresponding to the first measurement peak frequency respectively in the first Fourier relative phase spectrum, extracting relative phase difference values corresponding to the second measurement peak frequency respectively in the second Fourier relative phase spectrum, distinguishing fourth Doppler frequency shift peaks through the relative phase difference values and judging signs of the peak frequency respectively, wherein the relative phase difference value corresponding to the fourth Doppler frequency shift peak is 0, and the signs of the relative phase difference values of the other Doppler frequency shift peaks correspond to the signs of the peak frequency;
after the fourth Doppler frequency peak shift is screened out, comparing the variation difference of the peak value frequency of other Doppler frequency peak shifts obtained by two times of measurement, and determining the sequence of the Doppler frequency peak shifts; the peak frequency of the second Doppler frequency peak shift is kept unchanged, the peak frequencies of the first Doppler frequency peak shift and the third Doppler frequency peak shift are changed, and the change degrees are different;
solving simultaneous equations of the two-time measurement peak frequency and the peak frequency formula of the first Doppler frequency shift peak, the second Doppler frequency shift peak and the third Doppler frequency shift peak, and calculating the magnitude and the direction of the spin and revolution angular velocity of the anisotropic rotary motion particles;
for the two measurements, the relative amplitude of the doppler shift peak remains unchanged, which is:
first doppler frequency peak shift: a. the 1 ＝1+τ 2 +2τcosδ
Second doppler frequency peak shift: a. the 2 ＝2(τ 2 -1)
Third doppler frequency peak shift: a. the 3 ＝1+τ 2 -2τcosδ
Fourth doppler frequency peak shift: a. the 4 ＝2(1-τ 2 )
Wherein τ and δ are unknown anisotropy parameters of the anisotropically rotationally moving particle: τ is the reflection coefficient ratio of the anisotropic rotationally moving particles along the fast axis and the slow axis, and δ is the phase delay caused by the anisotropic rotationally moving particles;
and extracting the relative amplitudes of the first Doppler frequency shift peak, the second Doppler frequency shift peak and the third Doppler frequency shift peak from the first Fourier amplitude spectrum and the second Fourier amplitude spectrum, calculating the relative amplitude ratio, and obtaining the anisotropic parameter information of the anisotropic rotary motion particles by utilizing the sequencing of the Doppler frequency shift peaks.
10. A method of measurement according to claim 8 or 9, characterized in that for the dual polarization detection method, the first polarization direction projection component I 1 For the vector Doppler polarization signal along theta 1 Intensity signal projected in polarization direction, second polarization direction projection component I 2 For the vector Doppler polarization signal along theta 2 Intensity signal projected in polarization direction, and θ 1 And theta 2 The angle Δ θ between the two polarization directions is arbitrarily set to values other than 0 and ± 90 °.
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