Method and device for multi-angle mueller matrix measurement of suspended particles in water body

Abstract

The application discloses a device and method for multi-angle Mueller matrix measurement of suspended particles in water body, which comprises an illumination light path, a receiving light path, a sample cell and a processing module; the illumination light path comprises a light source, a polarization modulation module and a first lens, and the receiving light path comprises a receiving light path optical module and a one-dimensional polarization analysis module; the light beam emitted by the light source generates polarized light with time-sequential change of polarization state after the polarization modulation module, and the polarization state of the incident light is monitored in the polarization modulation module; the polarized light is irradiated on the suspended particles in the sample cell after the first lens; the scattered light of the particles after scattering is received and shaped by the receiving light path module, and the multi-angle Stokes vector of the scattered light of the particles is calculated by the one-dimensional polarization analysis module; and the multi-angle Mueller matrix of the particles is calculated by the processing module according to the Stokes vector of the incident light and the Stokes vectors of the multiple scattering angles of the scattered light. The application can quickly measure the multi-angle Mueller matrix of the particles.

Description

Technical Field

[0001] This invention relates to the detection of suspended particulate matter in water, and in particular to a method and apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water. Background Technology

[0002] The detection of particulate matter in water bodies is of great significance for aquatic ecology research and environmental safety monitoring. Suspended particulate matter in water includes microalgae, microplastics, and sediment. Marine microalgae are major contributors to primary productivity, an important source of oxygen for the Earth, and a pillar of marine ecosystems; the detection of marine microalgae is a necessary link in marine ecology and environmental fields. Microplastics, as a new type of pollutant, have become an important target for marine environmental safety monitoring in recent years. The transport and deposition of suspended sediment shape the landforms of estuaries and nearshore areas; the identification and concentration detection of suspended sediment are important indicators for water remote sensing and pollution monitoring. Therefore, the detection of suspended particulate matter in water bodies is essential.

[0003] Optical methods have garnered significant attention in particulate matter detection due to their advantages such as high resolution, ease of in-situ measurement, and non-contact operation. Various methods have been developed for detecting suspended particulate matter, including optical imaging, fluorescence, excitation-emission spectroscopy, light scattering, and flow cytometry. However, optical imaging is hampered by the trade-off between depth of field, resolution, and field of view, limiting its technological advantages. Fluorescence and the more comprehensive excitation-emission spectroscopy utilize the specificity of pigments within particles to detect them; however, they are limited by relatively weak signals, require overall measurement, and have limited ability to classify particles in detail. Light scattering measures the intensity and angular distribution of particles to infer their size, morphology, and structure, but its resolution is slightly lower. Flow cytometry uses hydrodynamic focusing to separate particles into individual units, measuring their scattering, fluorescence, or images to obtain information on size, structure, and pigments; however, its sample preparation is cumbersome, and its results are not always satisfactory for samples with large particle size distributions. Therefore, the development of new detection methods for suspended particulate matter remains crucial.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method and apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water.

[0006] The present invention adopts the following technical solution: In a first aspect, an apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water is provided, comprising an illumination optical path, a receiving optical path, a sample cell, and a processing module; the illumination optical path includes a light source, a polarization modulation module, and a first lens; the receiving optical path includes a receiving optical path optical module and a one-dimensional polarization analysis module; the light beam emitted by the light source, after passing through the polarization modulation module, generates polarized light with a polarization state changing sequentially, and the polarization state of the incident light is monitored in the polarization modulation module; after being focused by the first lens, the incident light illuminates the suspended particulate matter in the sample cell, and the suspended particulate matter scatters and emits scattered light; the scattered light is received and shaped by the receiving optical path optical module, and then the one-dimensional polarization analysis module calculates the Stokes vectors of multiple scattering angles of the scattered light from the suspended particulate matter; the processing module is connected to the polarization modulation module and the receiving optical path respectively, and is used to receive the Stokes vectors of the incident light and the Stokes vectors of multiple scattering angles of the scattered light, and calculate the multi-angle Müller matrix of the suspended particulate matter.

[0007] Preferably, the receiving optical path is positioned at a scattering angle of 90° where the suspended particulate matter is scattered.

[0008] Preferably, the device further includes a light trap for absorbing excess transmitted light and reducing ambient light interference.

[0009] Preferably, the polarization modulation module includes a first electro-optic modulator, a second electro-optic modulator, and a beam splitter; the light beam emitted by the light source passes sequentially through the first electro-optic modulator, the second electro-optic modulator, the beam splitter, and the first lens before irradiating the suspended particles in the sample cell; the processing module is connected to the beam splitter and is used to acquire and subsequently process the Stokes vector of the incident light.

[0010] Preferably, the fast axis angle of the first electro-optic modulator is 45 degrees and the fast axis angle of the second electro-optic modulator is 90 degrees, so that the light beam emitted by the light source can generate periodically rapidly changing polarized light after passing through the first electro-optic modulator and the second electro-optic modulator.

[0011] Preferably, the beam splitter includes a first 30:70 unequal beam splitter prism, a second 30:70 beam splitter prism, a 50:50 beam splitter prism, a horizontal polarizer, a vertical polarizer, a 45-degree polarizer, a left-handed polarizer, a first photomultiplier tube, a second photomultiplier tube, a third photomultiplier tube, and a fourth photomultiplier tube; wherein, the light emitted from the second electro-optic modulator is split into two beams by the first 30:70 beam splitter prism, one beam passes sequentially through the horizontal polarizer and the first photomultiplier tube, and the other beam is incident on the second 30:70 beam splitter prism. A 70:70 beam splitter splits the light into two beams. One beam passes sequentially through the vertical polarizer and the second photomultiplier tube. The other beam is incident on the 50:50 beam splitter and split into two beams. One beam passes sequentially through the 45-degree polarizer and the third photomultiplier tube. The other beam passes sequentially through the left-handed polarizer and the fourth photomultiplier tube. The processing module is connected to the first, second, third, and fourth photomultiplier tubes, respectively.

[0012] Preferably, the processing module includes a first acquisition card, a second acquisition card, and a processing unit. The first acquisition card collects Stokes vectors of multiple scattering angles of the scattered light received by the receiving optical path and sends them to the processing unit. The second acquisition card collects the Stokes vectors of the incident light received by the polarization modulation module and sends them to the processing unit. The processing unit calculates the multi-angle Müller matrix of the suspended particulate matter.

[0013] Preferably, the first acquisition card is connected to the second acquisition card, and the first acquisition card is configured to generate a trigger voltage to the second acquisition card when it is triggered to start acquiring Stokes vectors of multiple scattering angles of the scattered light, so that the second acquisition card starts acquiring the Stokes vectors of the incident light.

[0014] Preferably, the receiving optical path optical module includes a second lens, a third lens, a pinhole, a fourth lens, a 10:90 beam splitter, a fifth lens, a fifth photomultiplier tube, and a sixth lens. The one-dimensional polarization analysis module is a polarization line scanning camera. The pinhole is placed at the image point position after the light passes through the third lens. The scattered light emitted by the suspended particulate matter passes sequentially through the second lens, the third lens, the pinhole, and the fourth lens, and is converted into parallel light. The 10:90 beam splitter splits the light into two beams. One beam is focused by the fifth lens onto the fifth photomultiplier tube, which then triggers the first acquisition card for acquisition. The other beam is focused by the sixth lens and received by the polarization line scanning camera, obtaining the multi-angle Stokes vector of the scattered light. The polarization line scanning camera is connected to the first acquisition card.

[0015] Preferably, the light source is a 532nm high-power laser with an optical power ≥0.5W, providing continuous illumination.

[0016] Preferably, the size of the detection area is adjusted by adjusting the size of the aperture, the relative positions of the second lens, the third lens, and the aperture, so that the scattering volume is small enough that there is only a single particle within the scattering volume; the second lens and the third lens are used to expand the angular range of the received scattered light to be in the range of 60-120°.

[0017] Secondly, the present invention also provides a method for measuring the multi-angle Müller matrix of suspended particulate matter in water, using the apparatus described in the first aspect to detect the multi-angle Müller matrix.

[0018] Preferably, the method further includes the following steps: inputting the detected multi-angle Müller matrix into a pre-trained prediction model to predict the refractive index, particle size, and particle type of the tested particles.

[0019] The present invention has the following beneficial effects: This invention proposes a method and apparatus for rapid measurement of the multi-angle Müller matrix of suspended particulate matter. By using a polarization modulation module to rapidly change the incident polarization light, multiple incident lights with different Stokes vectors are irradiated onto the same suspended particulate matter in a short period of time. Simultaneously, the Stokes vectors of the scattered light at multiple scattering angles are measured, and the multi-angle Müller matrix of the suspended particulate matter can be derived and calculated, thereby achieving the purpose of rapid in-situ identification of suspended particulate matter. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a device for measuring the multi-angle Müller matrix of suspended particulate matter in water, according to a preferred embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of a device for measuring the multi-angle Müller matrix of suspended particulate matter in water, according to a preferred embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the spectrometer cage in the apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water according to a preferred embodiment of the present invention.

[0023] Figure 4 This is a schematic flowchart of a preferred embodiment of the present invention for measuring the multi-angle Müller matrix of suspended particulate matter in water. Detailed Implementation

[0024] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0025] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for fixing, coupling, or communication.

[0026] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] Polarization is a fundamental property of light. The polarization state of light is generally described using Stokes vectors, while the Müller matrix of a particle describes its ability to alter the polarization state of light, representing the particle's polarization characteristics. Therefore, this invention proposes a method and apparatus for measuring the multi-angle Müller matrix of suspended particles in water. This aims to simultaneously measure the multi-angle Müller matrix of a single suspended particle, thereby obtaining physical characteristic information such as refractive index and relative diameter, which is beneficial for particle classification, identification, and attribute detection. This invention increases the information dimension, enriches the particle's characteristic data, and utilizes polarization characteristics to understand the particle's structure, enabling further interpretation of the particles.

[0029] See Figure 1An embodiment of the present invention provides a device for measuring the multi-angle Müller matrix of suspended particulate matter in water, comprising an illumination optical path, a receiving optical path, a sample cell 7, and a processing module 4; the illumination optical path includes a light source 1, a polarization modulation module 2, and a first lens 3; the receiving optical path includes a receiving optical path optical module 5 and a one-dimensional polarization analysis module 6; the light beam emitted by the light source 1, after passing through the polarization modulation module 2, generates polarized light whose polarization state changes sequentially; simultaneously, the polarization state of the incident light (i.e., the Stokes vector of the incident light) is monitored in the polarization modulation module 2; after being focused by the first lens 3, the light illuminates the sample cell. The suspended particulate matter 8 in the sample cell 7 emits scattered light after scattering. The scattered light is received and shaped by the optical module 5 of the receiving optical path, and then the Stokes vectors of multiple scattering angles of the scattered light of the suspended particulate matter are calculated by the one-dimensional polarization analysis module 6. The processing module 4 is connected to the polarization modulation module 2 and the receiving optical path respectively, and is used to receive the Stokes vector of the incident light and the Stokes vectors of multiple scattering angles of the scattered light (also written as the multi-angle Stokes vectors of the scattered light in this article), and calculate the multi-angle Müller matrix of the suspended particulate matter.

[0030] like Figure 1 and 2 As shown, in a preferred embodiment, the receiving optical path is positioned at a scattering angle of 90° where the suspended particulate matter scatters. Preferably, the device further includes an optical trap 9 for absorbing excess transmitted light and reducing ambient light interference.

[0031] like Figure 1 and 2 As shown, in a preferred embodiment, the polarization modulation module 2 includes a first electro-optic modulator 21, a second electro-optic modulator 22, and a beam splitter 23; the light beam emitted by the light source 1 passes sequentially through the first electro-optic modulator 21, the second electro-optic modulator 22, the beam splitter 23, and the first lens 3 before irradiating the suspended particulate matter 8 in the sample cell 7; the processing module 4 is connected to the beam splitter 23 and is used to acquire and subsequently process the Stokes vector of the incident light. Preferably, the fast axis angle of the first electro-optic modulator 21 is 45 degrees, and the fast axis angle of the second electro-optic modulator 22 is 90 degrees, so that the light beam emitted by the light source 1 can generate periodically rapidly changing polarized light after passing through the first electro-optic modulator 21 and the second electro-optic modulator 22.

[0032] like Figure 1 , 2As shown in Figure 3, the beam splitter uses an amplitude splitting method, that is, the light incident on the beam splitter is divided into four parts, and a horizontal polarizer P1, a vertical polarizer P2, a 45-degree polarizer P3, and a left-handed polarizer P4 are respectively added to the four channels (in this example, the left-handed polarizer is a 90-degree polarizer + a 1 / 4 wave plate). Then, the light is amplified by a photomultiplier tube and transmitted to the second acquisition card 42. Specifically, the beam splitter 23 includes a first 30:70 unequal beam splitter 231, a second 30:70 beam splitter 232, a 50:50 beam splitter 233, a horizontal polarizer P1, a vertical polarizer P2, a 45-degree polarizer P3, a left-handed polarizer P4, a first photomultiplier tube PD1, a second photomultiplier tube PD2, a third photomultiplier tube PD3, and a fourth photomultiplier tube PD4; wherein, the light emitted from the second electro-optic modulator 22 is split into two beams by the first 30:70 beam splitter 231, one beam passes sequentially through the horizontal polarizer P1 and the first photomultiplier tube PD1, and the other beam is incident on the second 30:70 beam splitter 233. A 70:70 beam splitter 232 splits the light into two beams. One beam passes sequentially through the vertical polarizer P2 and the second photomultiplier tube PD2. The other beam is incident on a 50:50 beam splitter 233, where it splits into two beams. One beam passes sequentially through the 45-degree polarizer P3 and the third photomultiplier tube PD3, while the other beam passes sequentially through the left-handed polarizer P4 and the fourth photomultiplier tube PD4. The processing module 4 is connected to the first photomultiplier tube PD1, the second photomultiplier tube PD2, the third photomultiplier tube PD3, and the fourth photomultiplier tube PD4. By using a combination of two unequal 30:70 beam splitters and one equal 50:50 beam splitter in the beam splitter cage, the light intensity of the four channels can be kept as similar as possible.

[0033] like Figure 1 and 2As shown, in a preferred embodiment, the processing module 4 includes a first acquisition card 41, a second acquisition card 42, and a processing unit 43. The two acquisition cards respectively acquire the Stokes vectors of the incident light and the scattered light. The first acquisition card 41 collects the Stokes vectors of multiple scattering angles of the scattered light received by the polarization scanning camera. Due to the large amount of information in the polarization scanning camera, the first acquisition card 41 must have a high transmission speed. The second acquisition card 42 collects the Stokes vectors of the incident light received by the beam splitter. Since four channels of data are received separately, the second acquisition card 42 needs to meet the requirements of multi-channel parallel acquisition. Specifically, the first acquisition card 41 collects Stokes vectors of multiple scattering angles of the scattered light received by the receiving optical path and sends them to the processing unit 43. The second acquisition card 42 collects the Stokes vector of the incident light received by the polarization modulation module 2 and sends it to the processing unit 43. The processing unit 43 calculates the multi-angle Müller matrix of the suspended particulate matter. Preferably, the first acquisition card 41 is connected to the second acquisition card 42. The first acquisition card 41 is configured to generate a trigger voltage to the second acquisition card 42 when it is triggered to start collecting Stokes vectors of multiple scattering angles of the scattered light, causing the second acquisition card 42 to start collecting the Stokes vector of the incident light. More specifically, when the suspended particulate matter passes through the scattering volume, its scattered light is collected by the receiving optical path. A portion of the light is split by the 10:90 beam splitter 55 and illuminates the fifth photomultiplier tube 57 after passing through the fifth lens 56. The fifth photomultiplier tube 57 provides a voltage, triggering the first acquisition card 41 to start collecting the Stokes vector of the scattered light. When the first acquisition card 41 starts acquiring data, a trigger voltage is generated for the second acquisition card 42, causing it to start acquiring the Stokes vector of the incident light. The delay of this type of hard triggering method is on the order of microseconds, which meets the requirements of synchronous acquisition.

[0034] like Figure 1 and 2As shown, in a preferred embodiment, the receiving optical path optical module 5 includes a second lens 51, a third lens 52, a pinhole 53, a fourth lens 54, a 10:90 beam splitter 55, a fifth lens 56, a fifth photomultiplier tube 57, and a sixth lens 58. The one-dimensional polarization analysis module 6 is a polarization line scanning camera. The pinhole 53 is placed at the image point position after the light passes through the third lens 52. The scattered light emitted by the suspended particles passes sequentially through the second lens 51, the third lens 52, the pinhole 53, and the fourth lens 54, and is converted into parallel light. The 10:90 beam splitter 55 splits the light into two beams. One beam passes through the fifth lens 56 and is focused onto the fifth photomultiplier tube 57, which triggers the first acquisition card 41 for acquisition. The other beam passes through the sixth lens 58 and is received by the polarization line scanning camera 6, obtaining the multi-angle Stokes vector of the scattered light. The polarization line scanning camera 6 is connected to the first acquisition card 41. The second lens 51 and the third lens 53 are used to expand the angular range of the received scattered light, realizing the measurement of the Stokes vector of the scattered light within a large scattering angle range. The sixth lens 58 (which is a cylindrical lens) is used to shape the beam and focus the collected scattered light into a linear spot. On the one hand, the scattering angle is converted into a spatial position on the linear spot, realizing the measurement of a large angular range. On the other hand, the spot size is compressed in the direction perpendicular to the linear spot, which increases the intensity of the scattered light and improves the signal-to-noise ratio. A polarization line scanning camera with low sensitivity can be used as a sensor to measure the Stokes vector. Finally, the multi-angle Müller matrix of a single suspended particulate matter can be calculated by using multiple illumination light polarization states (with the Stokes vector being monitored) and simultaneously measuring the corresponding multi-angle Stokes vector of the scattered light.

[0035] In a preferred embodiment, the scattering volume can be limited, i.e., the size of the intersection volume between the incident light and the detection area can be limited, to achieve the measurement of individual suspended particles. For example... Figure 1 and 2As shown, in a preferred embodiment, the first lens 3 focuses the incident light at a focal point. The size of the focal point is changed by selecting the focal length, beam width, etc. of the first lens 3 (in this example, the focal diameter is preferably less than 100 micrometers). Simultaneously, since the aperture 53 in the receiving optical path and the detection area are in an object-image relationship with respect to the lens system in the receiving optical path (composed of the second lens 51 and the third lens 52), the size of the detection area is adjusted by changing the size of the aperture 53 and the relative positions of the second lens 51, the third lens 52, and the aperture 53. This makes the scattering volume V sufficiently small so that only a single particle exists within the scattering volume V, enabling the measurement of a single suspended particle. The second lens 51 and the third lens 53 are used to expand the angular range of the received scattered light to within the range of 60-120°, enabling the measurement of the Stokes vector of the scattered light within this scattering angle range.

[0036] To ensure the signal-to-noise ratio of the polarization signal, the selection of the light source's optical power, wavelength, and whether it provides pulsed or continuous illumination can be designed as needed. In a preferred embodiment, the light source 1 uses a 532nm high-power laser with an optical power ≥0.5W for continuous illumination. In this example, the signal-to-noise ratio is 5:1, the laser power is 500mW, and the wavelength is 532nm. After the laser beam passes through two electro-optic modulators with a certain fixed angle (the fast axis angle of the first electro-optic modulator is 45 degrees, and the fast axis angle of the second electro-optic modulator is 90 degrees), it can generate periodically rapidly changing polarized light. After passing through the beam splitter and the first lens 3, it illuminates the suspended particulate matter, illuminating the same suspended particulate matter with multiple incident lights of different polarization states in a short period of time.

[0037] This invention also provides a method for measuring the multi-angle Müller matrix of suspended particulate matter in water. and the Stokes vector of the incident light and the multi-angle Stokes vector of scattered light Satisfy the following formula:

[0038] From the above formula, we can obtain the multi-angle Müller matrix of particulate matter. Required incident light Stokes vector and the multi-angle Stokes vector of scattered light Therefore, use Figure 1 The device shown performs multi-angle Müller matrix detection. The illumination optical path rapidly changes the incident light Stokes vector, which describes the polarization state of the incident light, using a polarization modulation module. The receiving optical path obtains the multi-angle Stokes vector of the scattered light. When multiple incident lights with different Stokes vectors are irradiated onto the same suspended particulate matter within a short period of time, and the one-dimensional polarization analysis module 6 uses the measured data to calculate the multi-angle Stokes vectors of the scattered light, the multi-angle Müller matrix of the suspended particulate matter can be derived and calculated. Specifically, as shown in... Figure 1-3 As shown, the light beam emitted by the light source 1, after passing through the polarization modulation module 2, generates polarized light with a polarization state that changes sequentially over time. Simultaneously, the polarization state of the incident light is monitored in the polarization modulation module 2. After being focused by the first lens 3, the incident light illuminates the suspended particles 8 in the sample cell 7. The suspended particles scatter the light, emitting scattered light. This scattered light is received and shaped by the receiving optical path optical module 5, and then the one-dimensional polarization analysis module 6 calculates the Stokes vectors of multiple scattering angles of the scattered light from the suspended particles. The processing module 4 is connected to both the polarization modulation module 2 and the receiving optical path, and is used to receive the Stokes vectors of the incident light. and the multi-angle Stokes vector of scattered light The multi-angle Müller matrix of suspended particulate matter was calculated.

[0039] More specifically, in a preferred embodiment, after the beam modulated by the polarization modulation module 2 irradiates the suspended particles and is scattered, the scattered light signal from the suspended particles is received by a receiving optical path located at a scattering angle of 90° and collected by a lens system composed of a second lens 51 and a third lens 52. Due to the lens system, the pinhole 53 and the detection area in the sample form an object-image relationship; that is, a pinhole is placed at the image point position behind the third lens 52 in the detection area of ​​the sample to perform spatial filtering and remove stray light not in the detection area. After passing through the pinhole 53, the beam passes through the fourth lens 54 and is converted into parallel light. It is then split into two beams by a 10:90 beam splitter prism 55. One beam is focused onto the fifth photomultiplier tube 57 after passing through the fifth lens 56. The fifth photomultiplier tube 57 provides a trigger voltage to the first acquisition card 41 for acquisition, thus forming a trigger mechanism and improving acquisition efficiency. The other beam is focused by the sixth lens 58, and its signal is received by the polarization line scanning camera 6 to obtain the multi-angle Stokes vector of the scattered light. .

[0040] As can be derived from the above formula,

[0041] As can be seen from the above formula, the incident light Stokes vector measured synchronously can be used. and the multi-angle Stokes vector of scattered light The multi-angle Müller matrix of particulate matter was calculated.

[0042] In a preferred embodiment, the method further includes the following step: inputting the detected multi-angle Müller matrix into a pre-trained prediction model to predict the refractive index, particle size, and particle type of the tested particles. Specifically, as follows... Figure 4 As shown, feature extraction is performed on the multi-angle Müller matrix of known standard spherical particles, extracting waveform features such as peak-to-peak value, waveform factor, and margin factor. These waveform feature datasets [peak-to-peak value, waveform factor, ..., margin factor] are labeled with [refractive index, particle size, type], and then mathematically modeled and trained to obtain a prediction model. By inputting the measured waveform features of the multi-angle Müller matrix into the prediction model, the refractive index, particle size, and particle type of the measured standard spherical particles can be predicted.

[0043] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A device for measuring suspended particulate matter in water from multiple angles using the Müller matrix, characterized in that, It includes an illumination optical path, a receiving optical path, a sample cell, and a processing module; the illumination optical path includes a light source, a polarization modulation module, and a first lens; the receiving optical path includes a receiving optical path optical module and a one-dimensional polarization analysis module, wherein the one-dimensional polarization analysis module is a polarization line scanning camera. The light beam emitted by the light source, after passing through the polarization modulation module, generates polarized light with a polarization state that changes sequentially over time. Simultaneously, the polarization state of the incident light is monitored within the polarization modulation module. After being focused by the first lens, the incident light with multiple different Stokes vectors illuminates a single suspended particle in the sample cell. The suspended particle scatters the light, emitting scattered light. This scattered light is received and shaped by the receiving optical path module, which includes a cylindrical lens. The cylindrical lens shapes the beam, focusing the collected scattered light into a linear spot. This converts the scattering angle into a spatial position on the linear spot, enabling measurement over a large angle range. Furthermore, it compresses the spot size in the direction perpendicular to the linear spot, increasing the intensity of the scattered light and improving the signal-to-noise ratio. Then, the one-dimensional polarization analysis module receives the linear spot and calculates the Stokes vectors of multiple scattering angles of the scattered light from the suspended particle. The processing module is connected to the polarization modulation module and the receiving optical path respectively, and is used to receive multiple different Stokes vectors of the incident light and multiple Stokes vectors of the scattered light at multiple scattering angles, and calculate the multi-angle Müller matrix of the suspended particulate matter.

2. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 1, characterized in that: The receiving optical path is positioned at a scattering angle of 90° where the suspended particulate matter is scattered.

3. The device for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 1, characterized in that: The device also includes an optical trap for absorbing excess transmitted light and reducing ambient light interference.

4. The apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water as described in claim 1, characterized in that: The polarization modulation module includes a first electro-optic modulator, a second electro-optic modulator, and a beam splitter; the light beam emitted by the light source passes sequentially through the first electro-optic modulator, the second electro-optic modulator, the beam splitter, and the first lens before irradiating the suspended particulate matter in the sample cell; the processing module is connected to the beam splitter and is used to acquire and subsequently process the Stokes vector of the incident light.

5. The apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water as described in claim 4, characterized in that: The fast axis angle of the first electro-optic modulator is 45 degrees, and the fast axis angle of the second electro-optic modulator is 90 degrees, so that the light beam emitted by the light source can generate periodically rapidly changing polarized light after passing through the first electro-optic modulator and the second electro-optic modulator.

6. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 4, characterized in that: The beam splitter includes a first 30:70 unequal beam splitter prism, a second 30:70 beam splitter prism, a 50:50 beam splitter prism, a horizontal polarizer, a vertical polarizer, a 45-degree polarizer, a left-handed polarizer, a first photomultiplier tube, a second photomultiplier tube, a third photomultiplier tube, and a fourth photomultiplier tube. Light emitted from the second electro-optic modulator is split into two beams by the first 30:70 beam splitter prism. One beam passes sequentially through the horizontal polarizer and the first photomultiplier tube, while the other beam is incident on the second 30:70 beam splitter prism. The beam splitter splits the beam into two beams by the first 30:70 beam splitter. One beam passes sequentially through the vertical polarizer and the second photomultiplier tube. The other beam is incident on the 50:50 beam splitter and split into two beams by the 50:50 beam splitter. One beam passes sequentially through the 45-degree polarizer and the third photomultiplier tube. The other beam passes sequentially through the left-handed polarizer and the fourth photomultiplier tube. The processing module is connected to the first photomultiplier tube, the second photomultiplier tube, the third photomultiplier tube, and the fourth photomultiplier tube, respectively.

7. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 1, characterized in that: The processing module includes a first acquisition card, a second acquisition card, and a processing unit. The first acquisition card collects Stokes vectors of multiple scattering angles of the scattered light received by the receiving optical path and sends them to the processing unit. The second acquisition card collects the Stokes vectors of the incident light received by the polarization modulation module and sends them to the processing unit. The processing unit calculates the multi-angle Müller matrix of the suspended particulate matter.

8. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 7, characterized in that: The first acquisition card is connected to the second acquisition card. The first acquisition card is configured to generate a trigger voltage to the second acquisition card when it is triggered to start acquiring Stokes vectors of multiple scattering angles of the scattered light, so that the second acquisition card starts acquiring the Stokes vectors of the incident light.

9. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 7, characterized in that: The receiving optical path optical module includes a second lens, a third lens, a pinhole, a fourth lens, a 10:90 beam splitter, a fifth lens, a fifth photomultiplier tube, and a sixth lens, wherein the sixth lens is a cylindrical lens. The pinhole is positioned at the image point after the light passes through the third lens. The scattered light emitted by the suspended particles passes sequentially through the second lens, the third lens, the pinhole, and the fourth lens, and is converted into parallel light. The 10:90 beam splitter then splits the light into two beams. One beam is focused by the fifth lens onto the fifth photomultiplier tube, which triggers the first acquisition card for acquisition. The other beam is focused by the sixth lens and received by the polarization line scanning camera, resulting in a multi-angle Stokes vector of the scattered light. The polarization line scanning camera is connected to the first acquisition card.

10. The apparatus for measuring the multi-angle Müller matrix of suspended particulate matter in water as described in claim 1, characterized in that: The light source uses a 532nm high-power laser with an optical power of ≥0.5W for continuous illumination.

11. The apparatus for measuring multi-angle Müller matrix of suspended particulate matter in water as described in claim 9, characterized in that: The size of the detection area is adjusted by adjusting the size of the aperture, the relative positions of the second lens, the third lens, and the aperture, so that the scattering volume is small enough that there is only a single particle within the scattering volume; the second lens and the third lens are used to expand the angular range of the received scattered light to be in the range of 60-120°.

12. A method for measuring the multi-angle Müller matrix of suspended particulate matter in water, characterized in that, Detection of the multi-angle Müller matrix is ​​performed using the apparatus as described in any one of claims 1 to 11.

13. The method for measuring the multi-angle Müller matrix of suspended particulate matter in water as described in claim 12, characterized in that, It also includes the following steps: inputting the detected multi-angle Müller matrix into a pre-trained prediction model to predict the refractive index, particle size, and particle type of the tested particles.

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