Method and device for measuring polarization of suspended particles and method for synchronously calibrating all polarizations thereof

Abstract

The application discloses a kind of full polarization synchronous calibration methods of suspended particle measuring device, comprising the following steps: S1, with a variety of different polarization state incident polarized light is sequentially irradiated standard sample particle after scattering occurs, and the stokes vector of corresponding multiple actual exit polarized light is measured;S2, the stokes vector of the multiple actual exit polarized light is spliced into first matrix, the theoretical value of the stokes vector of multiple exit polarized light that step S1 can obtain under ideal condition is spliced into second matrix, and calibration matrix is obtained according to the first matrix and the second matrix;S3, when measuring suspended particle, the calibration matrix is used to calibrate measurement result. Thus, the calibration of multiple incident polarized light of the same particle is realized, the instrument calibration of multiple incident state is realized, and the steps and time of calibration can be greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of system parameter calibration technology, and in particular to a method and apparatus for measuring the polarization of suspended particles and a method for synchronous calibration of full polarization. Background Technology

[0002] Atmospheric aerosols are particles with diameters ranging from a few nanometers to tens of micrometers. They are emitted directly in particle form or formed in the atmosphere through gas-particle conversion processes. Studies have shown that exposure to high concentrations of aerosol particles can damage the human respiratory and cardiovascular systems, posing a significant threat to human health. Therefore, measuring aerosol particles is essential. Most aerosol particle detection methods measure aerosol swarms, but measurements of high-concentration aerosols are susceptible to multiple scattering effects, leading to experimental errors. Angular scattering of single particles avoids the adverse effects of multiple scattering and is a practical method for resolving multiple scattering and achieving accurate aerosol measurements.

[0003] The single-particle multi-angle suspended particle polarization vector measurement device is used for precise measurement of single-particle aerosols. It can perform real-time, continuous, dynamic, and non-destructive measurements of aerosol particles in the environment, providing a very large range of information. These characteristics make it a highly effective suspended particle measurement device. However, in actual measurement processes, it is sometimes necessary to use multiple incident polarized lights to scatter the same particle, thereby observing the differences in the emitted polarized light after the same particle is irradiated by different incident polarized lights. Under different incident polarized lights, the systematic error of the single-particle multi-angle suspended particle measurement device will fluctuate. Therefore, calibration for only one incident polarization light is not applicable to measurements when the incident polarization state is changed. Summary of the Invention

[0004] To address the problem that calibration of the same particle under one type of incident polarized light cannot be applied to measurements under other incident polarized light, this invention proposes a method and apparatus for measuring the polarization of suspended particles, as well as a method for synchronous calibration of all polarizations.

[0005] The technical problem of this invention is solved by the following technical solution:

[0006] A method for full polarization synchronous calibration of a suspended particle measurement device includes the following steps:

[0007] S1. After irradiating standard sample particles with incident polarized light of various different polarization states in sequence, scattering occurs, and the Stokes vectors of the corresponding actual outgoing polarized light are measured.

[0008] S2. Combine the Stokes vectors of the various actual emitted polarized light into a first matrix, and combine the theoretical values ​​of the Stokes vectors of the various emitted polarized light that can be obtained in step S1 under ideal conditions into a second matrix. Obtain the calibration matrix based on the first matrix and the second matrix.

[0009] S3. Use the calibration matrix to calibrate the measurement results when measuring suspended particles.

[0010] In some embodiments, measuring the Stokes vectors of the corresponding multiple actual emitted polarized lights includes: measuring the Stokes vector of each emitted polarized light over a period of time and taking its average value.

[0011] In some embodiments, the incident polarized light with different polarization states includes incident polarized light with horizontal linear polarization state H, 45° linear polarization state P, and right-hand circular polarization state R.

[0012] In some embodiments, for each polarization state of incident polarized light, the outgoing polarized light passes through a four-quadrant polarization analyzer to obtain the horizontal linear polarization component I of the outgoing polarized light. H 45° linear polarization component I P Right-hand circular polarization component I R and left-hand circular polarization component I L .

[0013] In some embodiments, the theoretical values ​​of the Stokes vectors of the various emitted polarized lights are:

[0014] S oiH =M×S iH ;

[0015] S oiP =M×S iP ;

[0016] S oiR =M×S iR ;

[0017] Among them, S iH S iP S iR These are the Stokes vectors of the incident polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively; S oiH S oiP S oiR These are the theoretical values ​​of the Stokes vectors of the outgoing polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively, and M is the Müller matrix of the standard sample.

[0018] The second matrix is:

[0019] S oi =[SoiH S oiP S oiR ];

[0020] The first matrix is:

[0021] S oa =[S oaH S oaP S oaR ];

[0022] Among them, S oaH S oaP S oaR These are the measured values ​​of the Stokes vectors of the outgoing polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively.

[0023] The calibration matrix is ​​calculated as follows:

[0024] T = S oi ×pinv(S oa );

[0025] Where pinv represents the pseudo-inverse of the matrix.

[0026] In some embodiments, the standard sample particles are polystyrene microspheres.

[0027] The present invention also proposes a method for measuring the polarization of suspended particles, comprising: calibrating the measurement results using the calibration matrix obtained by the above-described full polarization synchronous calibration method.

[0028] The present invention also proposes a suspended particle polarization measurement device, including a processor, which is configured to calibrate the measurement results using the calibration matrix obtained by the above-described full polarization synchronous calibration method.

[0029] The present invention also proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, uses the calibration matrix obtained by the above-described full polarization synchronous calibration method to calibrate the polarization measurement results of suspended particles.

[0030] The beneficial effects of this invention compared to the prior art include:

[0031] This invention involves sequentially irradiating a standard sample particle with incident polarized light of various different polarization states, causing scattering, and measuring the corresponding Stokes vectors of the actual emitted polarized light. These vectors are then combined into a first matrix, and their theoretical values ​​under ideal conditions are combined into a second matrix. A calibration matrix is ​​obtained based on the first and second matrices. This calibration matrix is ​​used to calibrate the measurement results when measuring suspended particles, thus achieving calibration for multiple incident polarized lights of the same particle and instrument calibration for multiple incident states. Unlike previous methods that calibrated data under a single incident state individually, this invention considers all errors under all incident states as a unified systematic error. Therefore, it integrates multiple systematic errors under different incident states into a single error, significantly reducing calibration steps and time, and improving calibration accuracy. This invention is particularly suitable for measurements where the incident polarization state is changed.

[0032] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0033] Figure 1 This is a flowchart of the full polarization synchronization calibration method in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the suspended particle measuring device in an embodiment of the present invention;

[0035] Figure 3 This is a flowchart illustrating the full polarization synchronization calibration method in this embodiment of the invention.

[0036] Figure 4 This is a comparison chart of error data before and after calibration using the full polarization synchronous calibration method in this embodiment of the invention; Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0038] It should be noted that the directional terms such as left, right, up, down, top, and bottom used in this embodiment are only relative concepts or are based on the normal use of the product, and should not be considered as restrictive.

[0039] The suspended particle measuring device used in the embodiments of the present invention is as follows: Figure 2As shown, the suspended particle measurement device consists of a laser, a linear polarizer, a quarter-wave plate, a polarization measuring instrument translation stage, a polarization analyzer channel, a photoelectric converter, and a computer. The laser 1 is used to emit laser light; the linear polarizer 2 and the quarter-wave plate 3 form a polarizer to generate the desired polarization state; the polarization measuring instrument translation stage 4 is used to measure the generated polarization state; the polarization analyzer channel 5 includes a four-quadrant polarizer 5-1, used to decompose the emitted polarized light into four-quadrant components; the photoelectric converter 6 is used to convert the optical signal at the polarization analyzer into an electrical signal; and the computer 7 is used to process the electrical signal.

[0040] It should be understood that the suspended particle measuring device that can be used with the method of the present invention is not limited thereto.

[0041] To address the problem that calibration using only one incident polarization for the same particle cannot be applied to measurements with different incident polarizations, this invention proposes a synchronous calibration method for a suspended particle measurement device with full polarization. This method treats the systematic errors under different incident states as a single error source and assumes a calibration matrix T to synchronously calibrate the errors for three incident polarization states (horizontal H, 45° P, and right-handed R). By performing three measurements on a sample particle and then comparing the experimental measurements with simulations using a standard sample, the calibration matrix can be obtained, thus achieving instrument calibration for multiple incident states.

[0042] like Figure 1 and Figure 3 As shown, the specific operation is as follows:

[0043] First, a suspended particle measurement device is set up and standard sample particles are configured. In this embodiment, the standard sample particles used are polystyrene microspheres.

[0044] S1. After irradiating standard sample particles with incident polarized light of various different polarization states in sequence, scattering occurs, and the Stokes vectors of the corresponding actual outgoing polarized light are measured.

[0045] The following describes incident polarized light with various polarization states:

[0046] The first incident state is set as horizontal linear polarization incident H. When the sample particles are irradiated, they are scattered, and the outgoing polarized light is obtained.

[0047] A fully polarized four-quadrant polarization analyzer consisting of a horizontal line analyzer H, a 45° line analyzer P, a right-hand circular analyzer R, and a left-hand circular analyzer L is placed at the end of the scattering channel.

[0048] After the emitted polarized light passes through a four-quadrant polarizer, the horizontal linear polarization component I of the emitted polarized light is obtained. H 45° linear polarization component I P Right-hand circular polarization component I Rand left-hand circular polarization component I L ;

[0049] The four-quadrant polarization components of the emitted polarized light are transmitted to the computer via subsequent optical fiber and photoelectric converter to obtain their respective values. The Stokes vector of the emitted polarized light is obtained according to the following formula.

[0050] S = [S0 S1 S2 S3] T =[S0 I H -I V I P -I Q I R -I L ] T ;

[0051] In the formula, S is the Stokes vector of the emitted polarized light, which is a 4×1 column vector; the first element S0 is the total light intensity; and the second element S1 represents the horizontal linear polarization component I. H and vertical linear polarization component I V The intensity difference; the third element S2 represents the 45° linear polarization component I. P and 135° linear polarization component I Q The intensity difference; the fourth element S3 represents the right-hand circular polarization component I. R and left-hand circular polarization component I L Difference in light intensity.

[0052] The formula for the total light intensity S0 is as follows:

[0053] S0 = I H +I V =I P +I Q =I R +I L ;

[0054] Therefore, we can substitute the Stokes vector formula for the emitted polarized light and simplify it to obtain the following formula:

[0055] S = [S0 S1 S2 S3] T

[0056] =[I R +I L 2*I H -I R -I L 2*I P -I R -I L I R -I L ] T ;

[0057] Then, by changing the second incident state to a 45° linearly polarized state and repeating the above steps, the corresponding measured outgoing polarized light can be obtained.

[0058] By changing the third incident state to a right-handed circularly polarized state and repeating the above steps, the corresponding measured outgoing polarized light can be obtained.

[0059] S2. Combine the Stokes vectors of various actual outgoing polarized light into a first matrix, and combine the theoretical values ​​of the Stokes vectors of various outgoing polarized light that can be obtained in step S1 under ideal conditions into a second matrix. Obtain the calibration matrix based on the first matrix and the second matrix.

[0060] The specific steps are as follows:

[0061] By performing Mie scattering simulations using polystyrene microspheres as standard sample particles, we can obtain the scattering data of polystyrene microspheres under theoretical conditions.

[0062] By substituting theoretical and actual scattering data into the derived mathematical equations, we can obtain a first matrix composed of the Stokes vectors of various actual emitted polarized light sources, and a second matrix composed of the theoretical values ​​of the Stokes vectors of various emitted polarized light sources under ideal conditions. The calibration matrix is ​​then obtained based on the first and second matrices.

[0063] S3. When measuring suspended particles, this calibration matrix can be used to perform full polarization synchronous calibration of the actual measurement results.

[0064] In some embodiments, the standard sample particles are polystyrene microspheres.

[0065] This invention also proposes a method for measuring the polarization of suspended particles, comprising: calibrating the measurement results using a calibration matrix obtained by the above-described full polarization synchronous calibration method.

[0066] This invention also proposes a suspended particle polarization measurement device, including a processor, which is configured to calibrate the measurement results using a calibration matrix obtained by the above-described full polarization synchronous calibration method.

[0067] This invention also proposes a computer-readable storage medium storing a computer program that, when executed by a processor, uses a calibration matrix obtained by the aforementioned full polarization synchronous calibration method to calibrate the polarization measurement results of suspended particles.

[0068] In one embodiment, incident polarized light with three polarization states—H, P, and R—is provided, and the Stokes vectors of these three incident polarized lights are as follows:

[0069]

[0070] Ideally, after the incident polarized light is scattered by the sample, the theoretical formula for the Stokes vector of the outgoing polarized light is:

[0071] S oiH =M×S iH ;

[0072] S oiP =M×S iP ;

[0073] S oiR =M×S iR ;

[0074] Where S iH S iP S iR These are the Stokes vectors of the incident polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively; S oiH S oiP S oiR These are the theoretical values ​​of the Stokes vectors of the outgoing polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively, and M is the Müller matrix of the standard sample.

[0075] However, in reality, due to differences in the error caused by different incident states, the Stokes vector S of the actual emitted light will vary. oaH ≠S oiH S oaP ≠S oiP S oaR ≠S oiR To achieve synchronous calibration for different incident states, this experimental example combines the outgoing Stokes vectors obtained from the three incident states into a 4x3 matrix, as shown in the following formula:

[0076] The second matrix, composed of the theoretical values ​​of the Stokes vectors of the three types of outgoing polarized light, is as follows:

[0077] S oi =[S oiH S oiP S oiR ];

[0078] The first matrix formed by concatenating the Stokes vectors of the three actual emitted polarized beams is:

[0079] S oa =[S oaH S oaP S oaR ];

[0080] Among them, S oaH S oaP SoaR These are the measured values ​​of the Stokes vectors of the outgoing polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively.

[0081] The calibration matrix is ​​calculated as follows:

[0082] T = S oi ×pinv(S oa );

[0083] Where pinv represents the pseudo-inverse of the matrix.

[0084] Therefore, only one calibration matrix is ​​needed to achieve synchronous calibration of three incident states.

[0085] To further verify the effectiveness of the full polarization synchronous correction method proposed in this embodiment of the invention, a set of specific experimental data is given here. Using 0.7 μm polystyrene microspheres as experimental samples, the calibration matrix T is obtained under three incident states (H / P / R) to calibrate 2.5 μm polystyrene microspheres.

[0086] Data before and after calibration using the full polarization synchronous calibration method, and simulated data, are as follows: Figure 4 As shown in the figure, after calibration using the full polarization synchronous calibration method proposed in this experimental example, the maximum error decreased from 1.01 to 0.14, and the root mean square error decreased from 0.35 to 0.06. The calibrated data shows better agreement with the theoretical results, which verifies the effectiveness of the full polarization synchronous calibration method.

[0087] Table 1 shows the comparison of results before and after calibration after changing different experimental samples.

[0088] Table 1

[0089]

[0090]

[0091] Through multiple experiments, it was found that the maximum error after calibration is approximately 0.2, and the root mean square error is below 0.1. Furthermore, by reducing the number of calibration steps, the full polarization synchronous calibration method used in this experimental example can save two-thirds of the calibration time.

[0092] The embodiments of the present invention have the following beneficial effects:

[0093] This invention relates to a single-particle multi-angle suspended particle polarization vector measurement system, which enables real-time, dynamic, continuous, and non-destructive measurement of individual particles. It considers errors such as dynamic beam drift, gas path instability, and circuit noise as a single systematic error, and obtains the average value of the entire error based on measurements over a period of time. Calibration is then performed based on this average value. Since changing different polarization states requires a considerable amount of time for measurement, a more stable systematic error can be obtained. Therefore, it integrates multiple systematic errors under different incident states into a single error, significantly reducing calibration steps and time. Calibration performed on this basis effectively improves calibration accuracy.

[0094] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A method for full polarization synchronous calibration of a suspended particle measuring device, characterized in that, Includes the following steps: S1. After irradiating standard sample particles with incident polarized light of various different polarization states in sequence, scattering occurs, and the Stokes vectors of the corresponding actual outgoing polarized light are measured. S2. Combine the Stokes vectors of the various actual emitted polarized light into a first matrix, and combine the theoretical values ​​of the Stokes vectors of the various emitted polarized light that can be obtained in step S1 under ideal conditions into a second matrix. Obtain a calibration matrix based on the first matrix and the second matrix, thereby taking the dispersed systematic error generated by the incident light of different polarization states during measurement as an error source. S3. Use the calibration matrix to calibrate the measurement results when measuring suspended particles; The incident polarized light with various polarization states includes incident polarized light with horizontal linear polarization state H, 45° linear polarization state P, and right-hand circular polarization state R; For each polarization state of the incident polarized light, the emitted polarized light passes through a four-quadrant polarization analyzer to obtain the horizontal linear polarization component of the emitted polarized light. 45° linear polarization component Right-hand circular polarization component and left-handed circular polarization component ; Substituting and simplifying the Stokes vector formula for the emitted polarized light, we obtain the following formula: ； The theoretical values ​​of the Stokes vectors for the various emitted polarized beams are: in, These are the Stokes vectors of the incident polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively. Incident polarized light was set with three polarization states: H, P, and R. The Stokes vectors of these three incident polarized lights are as follows: ； These are the theoretical values ​​of the Stokes vectors of the emitted polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively. The Müller matrix for the standard sample; The second matrix is: ； The first matrix is: ； in, These are the measured values ​​of the Stokes vectors of the outgoing polarized light in the horizontal linear polarization state H, the 45° linear polarization state P, and the right-hand circular polarization state R, respectively. To achieve synchronous calibration for different incident states, the outgoing Stokes vectors obtained from the three incident states are assembled into a 4x3 matrix. The calibration matrix is ​​calculated as follows: ； in This represents the pseudo-inverse of a matrix.

2. The full polarization synchronous calibration method as described in claim 1, characterized in that, The measurement of the Stokes vectors of various actual emitted polarized light includes: measuring the Stokes vector of each emitted polarized light over a period of time and taking its average value.

3. The full polarization synchronous calibration method according to any one of claims 1 to 2, characterized in that, The standard sample particles are polystyrene microspheres.

4. A method for measuring the polarization of suspended particles, characterized in that, include: The measurement results are calibrated using the calibration matrix obtained by the full polarization synchronous calibration method as described in any one of claims 1 to 3.

5. A suspended particle polarization measurement device, comprising a processor, characterized in that, The processor is configured to calibrate the measurement results using the calibration matrix obtained by the full polarization synchronous calibration method as described in any one of claims 1 to 3.

6. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it uses the calibration matrix obtained by the full polarization synchronous calibration method as described in any one of claims 1 to 3 to calibrate the polarization measurement results of suspended particles.

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