Probe type multi-wavelength measuring device and measuring method for measuring particle size distribution in water

Abstract

According to the probe-type multi-wavelength measuring device and method for measuring particle size distribution in water, light beams with different wavelengths are emitted in sequence and irradiate particles in a sample, the scattered light intensities of the particles in the sample at at least two angles are measured at the same time under different wavelengths, and the particle size distribution in the sample is measured. The particle size distribution of the particulate matter in the sample is obtained according to the scattered light intensity of the light beam measured at different wavelengths and different angles at the same time, according to the measuring device and method, the technical scheme of greatly changing the wavelength of the irradiation light is used for replacing the technical scheme of measuring the scattered light intensity at all angles to calculate the inversion particle size distribution, and the measurement accuracy is improved. The particle distribution can be measured only by measuring the intensity of scattered light at two or more fixed angles, the use of an optical filter is avoided, a grating is not needed for light splitting, the power consumption of a power supply is greatly reduced while the size of the device is reduced, and the device can be used for marine scientific investigation, deep sea resource development and marine environment investigation.

Description

Technical Field

[0001] The present application relates to the technical field of particle size distribution measurement in small analytical instruments, and particularly relates to a probe-type multi-wavelength measurement device and method for measuring the particle size distribution in water. Background Art

[0002] Measuring the distribution of particulate matter in water bodies, especially the particle size distribution of particulate matter in the deep sea, is necessary for evaluating the deep-sea ecosystem and biological habitat environment, tracking environmental pollution and microplastic distribution, resource exploration, submarine engineering construction assessment, and searching for hydrothermal vents on the seabed. The particle size distribution of particulate matter spans from the nanometer scale to the millimeter scale, and the particulate matter with a particle size of 0.1 micrometer to 100 micrometers is the measurement range of this technology and also the most in demand in seawater measurement.

[0003] Existing commercial particle size analyzers for measuring the particle size range of 0.1 micrometer to 100 micrometers are all laboratory devices. A single-wavelength laser light source is used to irradiate the sample in the sample cell, and the diffracted light intensity is measured at an angle of 5° to 175°, and even in the range of 185° to 355° with respect to the incident light within a certain distance range. Then, the particle size distribution range and intensity of the particulate matter are calculated by the Fraunhofer diffraction formula or the Mie diffraction formula and mathematical inversion.

[0004] However, the volume, power consumption, and weight of this kind of instrument are relatively large. If it is used for in-situ measurement in the deep sea, a very thick pressure-resistant shell is required, resulting in a weight of up to hundreds of kilograms. The power supply for deep-sea applications is battery-powered, and it is difficult to supply power to this kind of high-power-consumption device for a long time. Summary of the Invention

[0005] In view of this, it is necessary to provide a probe-type multi-wavelength measurement device and method for measuring the particle size distribution in water that can achieve in-situ measurement, has a small volume, and low power consumption, aiming at the defects of the existing measurement instruments with relatively large volume, power consumption, and weight.

[0006] To solve the above problems, the present application adopts the following technical solutions:

[0007] One of the purposes of the present application is to provide a probe-type multi-wavelength measurement device for measuring the particle size distribution in water, including:

[0008] A light source unit, which is used to sequentially emit light beams of different wavelengths;

[0009] A light guiding unit, which is coupled with the light source unit and is used to receive the light beam and irradiate the light beam onto the particulate matter in the sample;

[0010] A photodetector unit, the photodetector unit including at least two photodetectors for simultaneously measuring the scattered light intensities of particulate matters in a sample at at least two angles at different wavelengths;

[0011] A measurement module for obtaining the particle size distribution of particulate matters in a sample according to the corrected scattered light intensities measured simultaneously by the light beam at different wavelengths and different angles.

[0012] In some embodiments, the light source unit includes an LED array, the LED array including N LED light sources with different wavelengths, N≥6, and the LED array is lit in a time-division sequential manner such that only one wavelength of LED light source emits light at each moment.

[0013] In some embodiments, the timing and pulse width of the light emission of the LED array are such that each LED light source is extinguished after the end of the lighting time ΔT and then delayed by Δt, and then the next LED light source is lit, and so on, and the entire measurement period H≥N×(ΔT + Δt).

[0014] In some embodiments, the two photodetectors are used to simultaneously measure the scattered light intensities of particulate matters in a sample at at least two different angles at different wavelengths, and the axes of the two photodetectors are respectively set at an angle X and 90° with the axis of the outgoing light of the light guiding unit, and X≤80°.

[0015] In some embodiments, the light output window of the light guiding unit and the detection window of the photodetector are on the same plane and are in direct contact with the sample to be measured; or the light output window of the light guiding unit and the detection window of the photodetector are on different planes and are in direct contact with the sample to be measured.

[0016] In some embodiments, the photodetector unit further includes a third photodetector, and the third photodetector is arranged on the side surface of the light output end of the light guiding unit, and the third photodetector is used to measure the change in the light output intensity of each wavelength in real time.

[0017] In some embodiments, a first temperature probe and a second temperature probe are further included, and the first temperature probe and the second temperature probe are respectively used to measure the temperature value T W and the temperature value Tc inside the measuring device.

[0018] In some embodiments, the calculation unit is used to inversely obtain the particle size distribution of particulate matters in a sample according to the Fraunhofer equation and the Mie equation based on the scattered light intensities measured simultaneously by the light beam at different wavelengths and different angles.

[0019] In some embodiments, the measurement module includes:

[0020] A conditioning circuit, the photodetector and the third photodetector are connected to the conditioning circuit, and the conditioning circuit is used to amplify the optical intensity electrical signal output by the photodetector;

[0021] An analog-to-digital conversion circuit, the analog-to-digital conversion circuit is electrically connected to the conditioning circuit, and the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the optical intensity electrical signal output by the conditioning circuit;

[0022] A sampling and filtering circuit, the sampling and filtering circuit is electrically connected to the analog-to-digital conversion circuit, and the sampling and filtering circuit is used to perform sampling and filtering processing on the optical intensity value obtained by the analog-to-digital conversion of the analog-to-digital conversion circuit;

[0023] A background subtraction circuit, the background subtraction circuit is electrically connected to the sampling and filtering circuit, and the background subtraction circuit is used to subtract the interference of the sample background light on the measurement data from the optical intensity data after sampling and filtering processing;

[0024] A temperature measurement circuit, the temperature measurement circuit is used to obtain the temperature value T of the measured sample W and the temperature value Tc inside the measuring device;

[0025] A response value data correction circuit, the response value data correction circuit is electrically connected to the background subtraction circuit and the temperature measurement circuit, and the response value data correction circuit is used to correct the influence of the sample background light, the change of the output light intensity of each wavelength, the temperature of the sample and the change of the temperature inside the measuring device on the particulate matter scattering signal in the sample and the influence on the response value of the photodetector;

[0026] A calculation unit, which stores the numerical calculation formulas of the Fraunhofer equation and the Mie equation, as well as the calculation parameters corresponding to this measuring device, and reads the data output by the response value data correction circuit to perform numerical calculation inversion to obtain particle size distribution data;

[0027] An LED logic driving circuit, the LED logic driving circuit is used to control the light source unit to emit light beams of different wavelengths in sequence;

[0028] A timing control circuit, the LED logic driving circuit, the background subtraction circuit, the response value data correction circuit and the interface circuit are all controlled by the timing control circuit for timing, so that the wavelength of the emitted light, the wavelength and response value of the detected scattered light signal, the response value after subtracting the background light and the temperature correction relationship corresponding to each moment, and the correction values of the scattered light intensity signals at different angles can be obtained according to the timing.

[0029] In some embodiments, the photodetector obtains uncorrected scattered light intensity signals I1, I2...I Nand the background light signal I b1 、I b2 …I bN The background subtraction circuit performs a subtraction operation to obtain the scattered light intensity I that subtracts the background light of the sample i ’ =I i -I bi , where i = 1, 2, … N. The sample background light is expressed as setting a 0-level interval time Δt between each pulse of the light beams of different wavelengths emitted in sequence. At this time, there is no emitted light, and the light measured by the photodetector is the background light of the sample to be measured, that is, it is expressed as the sample background light.

[0030] In some embodiments, the algorithm used by the calculation unit is based on the Fraunhofer equation and the Mie equation. According to the corrected intensity of the scattered light measured by the light beam at different wavelengths and different angles, the particle size distribution in the sample is inversely obtained.

[0031] The second object of this application also provides a measurement method for measuring the particle size distribution in water with a probe-type multi-wavelength, including the following steps:

[0032] Emit light beams of different wavelengths in sequence and irradiate the particles in the sample;

[0033] Measure the scattered light intensity of the particles in the sample at at least 2 angles at different wavelengths;

[0034] Obtain the particle size distribution of the particles in the sample according to the scattered light intensity measured by the light beam at different wavelengths and different angles simultaneously.

[0035] This application adopts the above technical solutions, and the beneficial effects are as follows:

[0036] The measurement device and measurement method for measuring the particle size distribution in water with a probe-type multi-wavelength provided by this application emit light beams of different wavelengths in sequence and irradiate the particles in the sample. At different wavelengths, measure the scattered light intensity of the particles in the sample at at least 2 angles. According to the scattered light intensity measured by the light beam at different wavelengths and different angles simultaneously, obtain the particle size distribution of the particles in the sample. The measurement device and method provided by this application use the technical solution of greatly changing the wavelength of the irradiation light to replace the technical solution of measuring the scattered light intensity at all angles to calculate and invert the particle distribution. Only by measuring the scattered light intensity at at least 2 fixed angles can the measurement of the particle distribution be realized. Avoid using filter plates and do not require the use of grating spectroscopy. While reducing the volume of the device, the power consumption is greatly reduced, and it can be used for ocean scientific research, deep-sea resource development and ocean environmental investigation. Description of the Drawings

[0037] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments of the present application or the prior art. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 It is a schematic structural diagram of a measuring device for measuring the particle size distribution in water with a probe-type multi-wavelength provided in Embodiment 1 of the present application.

[0039] Figure 2 It is a schematic structural diagram of a light source unit provided in Embodiment 1 of the present application.

[0040] Figure 3 It is a schematic diagram of the positions of the light output window of the light guiding unit and the detection window of the light detector of the measuring device provided in Embodiment 1 of the present application.

[0041] Figure 4 It is another schematic diagram of the positions of the light output window of the light guiding unit and the detection window of the light detector 31 of the measuring device provided in Embodiment 1 of the present application.

[0042] Figure 5 It is a schematic structural diagram of a measuring module provided in Embodiment 1 of the present application.

[0043] Figure 6 It is a step flowchart of a measuring method for measuring the particle size distribution in water with a probe-type multi-wavelength provided in Embodiment 2 of the present application. Detailed Embodiments

[0044] The following will describe in detail the embodiments of the present application. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and should not be construed as a limitation to the present application.

[0045] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0046] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0047] In order to make the objectives, technical solutions and advantages of this application more clear and understandable, the following further details this application in conjunction with the accompanying drawings and embodiments.

[0048] Embodiment 1

[0049] Please refer to Figures 1 to 4 , which is a schematic structural diagram of a probe-type multi-wavelength device for measuring particle size distribution in water provided for Embodiment 1 of this application, including a light source unit 10, a light guiding unit 20, a light detector unit, and a calculation unit 40. The following details the specific implementation manners of each unit.

[0050] The light source unit 10 is used to sequentially emit light beams of different wavelengths.

[0051] Please refer to Figure 2 , the light source unit 10 includes an LED array 11. The LED array 11 includes 10 LED light sources 111 of different wavelengths. The wavelengths of the 10 LEDs are 330 nm, 365 nm, 420 nm, 470 nm, 520 nm, 590 nm, 630 nm, 700 nm, 820 nm, and 980 nm respectively. The LED array 11 is lit in a time-sharing sequence, so that only 1 kind of wavelength LED light source emits light at each moment.

[0052] Furthermore, by controlling the timing and pulse width of the LED array 11 to emit light, each LED is extinguished after the lighting time ΔT = 50 ms and then delayed by Δt = 2 ms, and then the next LED is lit, and so on. The entire measurement period H ≥ 10×(50 ms + 2 ms) = 520 ms.

[0053] It can be understood that since only 1 LED is lit and emits light at each light-emitting moment, there is no need to select the wavelength at the detection end, avoiding the use of a filter and also not requiring grating spectroscopy, reducing the volume of the entire device, and the power consumption of the light source is only 1 / 10 of that when all 10 LEDs are fully lit, greatly reducing the power consumption of the device.

[0054] The light guiding unit 20 is coupled to the light source unit 10. The light guiding unit 20 is used to receive the light beam and irradiate the light beam onto the particulate matter in the sample.

[0055] In this embodiment, the light guide unit 20 is a light guide rod. The light guide rod is coupled to the light source unit 10. The light guide rod receives the light beam and irradiates the light beam onto the particulate matter 100 in the sample. A reflector 22 is further provided on the opposite side of the light guide rod with respect to the light beam emission direction.

[0056] The light detector unit includes at least two light detectors 31. The light detectors 31 are used to simultaneously measure the scattered light intensities of the particulate matter in the sample at at least two angles at different wavelengths.

[0057] In this embodiment, the light detector unit includes at least two light detectors. The two light detectors are used to simultaneously measure the scattered light intensities of the particulate matter in the sample at at least two different angles at different wavelengths. The axes of the two light detectors are respectively set at an angle of 45° and 90° with the axis of the outgoing light of the light guide unit.

[0058] Please refer to Figure 3 , the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 are located on the same plane and are in direct contact with the sample to be measured.

[0059] It can be understood that the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 are located on the same plane, which can greatly reduce the volume and weight of the measuring device, and the device shape is similar to an optical sensor, such as a chlorophyll a fluorescence sensor, greatly reducing the volume of the device.

[0060] Please refer to Figure 4 , the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 can also be located on different planes and are in direct contact with the sample to be measured.

[0061] It should be noted that the above-mentioned measuring device of the present application further includes a housing 200. The housing 200 provides mechanical support and overall protection for the above-mentioned devices and circuits.

[0062] In this embodiment, the light detector unit further includes a third light detector 33. The third light detector 33 is disposed on the side surface of the light output end of the light guide unit 20. The third light detector 33 is used to measure the change in the light output intensity of each wavelength in real time.

[0063] It can be understood that the third light detector 33 is disposed on the side surface near the light output end face of the light guide rod to detect the leakage light, and can measure the change in the light output intensity of each LED, and is used for feedback control of the output light intensity.

[0064] It can be understood that the light detector 31 obtains the uncorrected scattered light intensity signals I1, I2...I 10 and the background light signal I b1 , Ib2 …I b10 The background light of the sample is represented by setting a zero-level interval time Δt between each pulse of the light beams emitted in sequence with different wavelengths. At this time, there is no emitted light, and the light measured by the photodetector is the background light of the sample to be measured, which is represented as the background light of the sample.

[0065] In this embodiment, it further includes a first temperature probe 41 and a second temperature probe 42, and the first temperature probe 41 and the second temperature probe 42 are respectively used to measure the temperature value T of the sample W and the temperature value Tc inside the measuring device.

[0066] The measuring module 40 is used to obtain the particle size distribution in the sample according to the scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam.

[0067] In this embodiment, the measuring module 40 is used to invert the particle size distribution in the sample according to the Fraunhofer equation and the Mie equation, based on the scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam. The range of the measured particle size is 0.05 μm to 30 μm.

[0068] It should be noted that when the particle diameter D is much larger than the incident light wavelength λ, diffraction occurs, and the scattering at this time is called diffraction scattering. The light wave deviates from the straight propagation direction and bends into the geometric shadow area of the obstacle, and a phenomenon of uneven light intensity appears on the light screen behind the obstacle. The diffraction scattering intensity can be obtained according to the Fraunhofer principle, as follows:

[0069]

[0070] In the formula: I0 is the incident light intensity, α is the particle size parameter (α = πD / λ), J1 is the first-order Bessel function, and θ is the diffraction angle. In diffraction scattering, since the distance between the detection point and the sample particles is relatively far, the incident light is approximately considered to be parallel light, and the particle scattering is not affected by the absorption and refraction of the material.

[0071] When the particle diameter is approximately equal to the incident light wavelength, the scattering is between Rayleigh scattering and diffraction scattering, and the scattering at this time is called Mie scattering. The Mie scattering light intensity can be calculated as:

[0072]

[0073] In the formula, θ, λ, and α are the scattering angle, the incident light wavelength, and the particle size parameter respectively, m is the refractive index of the particle relative to the surrounding medium, r is the distance from the particle to the observation plane, Φ is the incident light electric vector relative to the scattering angle, s1 and s2 are the amplitude function components perpendicular and parallel to the scattering plane respectively, and they are infinite series composed of Bessel functions and Legendre functions.

[0074] It can be understood that the calculation unit provided in this embodiment can measure the particle size distribution by measuring the scattered light intensity at a fixed angle by greatly changing the incident light wavelength according to the Fraunhofer equation and the Mie equation.

[0075] Please refer to Figure 5 , which is a schematic structural diagram of the measurement module 40, and it includes:

[0076] A conditioning circuit 41, the photodetector 31 and the third photodetector 33 are connected to the conditioning circuit 41, and the conditioning circuit 41 is used to amplify the optical intensity electrical signal output by the photodetector.

[0077] An analog-to-digital conversion circuit 42, the analog-to-digital conversion circuit 42 is electrically connected to the conditioning circuit 41, and the analog-to-digital conversion circuit 42 is used to perform analog-to-digital conversion on the optical intensity electrical signal output by the conditioning circuit 41.

[0078] A sampling and filtering circuit 43, the sampling and filtering circuit 43 is electrically connected to the analog-to-digital conversion circuit 42, and the sampling and filtering circuit 43 is used to perform sampling and filtering processing on the optical intensity value obtained by the analog-to-digital conversion of the analog-to-digital conversion circuit 42.

[0079] A background subtraction circuit 44, the background subtraction circuit 44 is electrically connected to the sampling and filtering circuit 43, and the background subtraction circuit 44 is used to subtract the interference of the sample background light on the measurement data from the optical intensity value after sampling and filtering processing.

[0080] A temperature measurement circuit 45, the temperature measurement circuit 45 is used to obtain the temperature value T of the measurement sample W and the temperature value Tc inside the measurement device.

[0081] A response value data correction circuit 46, the response value data correction circuit 46 is electrically connected to the background subtraction circuit 44 and the temperature measurement circuit 45, and the response value data correction circuit 46 is used to correct the influences of the sample background light, the change of the output light intensity of each wavelength, the temperature of the sample, and the temperature change inside the measurement device on the scattering signal of the particulate matter in the sample and on the response value of the photodetector.

[0082] It can be understood that the response value data correction circuit stores the following correction data: 1) data on the relationship between the scattered light intensity and temperature of given-sized particulate matter under excitation light of different wavelengths measured in the laboratory at a given scattering angle; 2) the temperature coefficient of the photodetector.

[0083] Specifically, the photodetector obtains uncorrected scattered light intensity signals I1, I2…I 10 and background light signals I b1 、I b2 …I b10 , and the background subtraction circuit performs a subtraction operation to obtain the scattered light intensity I i ’ =I i -I bi , where i = 1, 2, … 10. The sample background light is expressed as setting a 0-level interval time Δt between each pulse of the sequentially emitted light beams of different wavelengths. At this time, there is no emitted light, and the light measured by the photodetector is the background light of the sample to be measured, which is expressed as the sample background light.

[0084] It can be understood that a 0-level interval time Δt is set between each pulse (width ΔT) of the sequential light emission. At this time, there is no emitted light, and the light measured by the detector is the background light of the water body to be measured. Therefore, the background light before and after each lighting (LEDi lit by the previous pulse) can be subtracted in real time by subtraction, eliminating the influence of the background light on the measurement.

[0085] The calculation unit 49 stores the numerical calculation formulas of the Fraunhofer equation and the Mie equation, as well as the calculation parameters corresponding to this measurement device, reads the data output by the response value data correction circuit, and performs numerical calculation inversion to obtain the particle size distribution data.

[0086] In this embodiment, the algorithm used by the calculation unit is based on the Fraunhofer equation and the Mie equation, and the corrected intensity of the scattered light measured simultaneously at different wavelengths and different angles of the light beam is used to inversely obtain the particle size distribution of the particulate matter in the sample.

[0087] The LED logic drive circuit 47 is used to control the light source unit 10 to sequentially emit light beams of different wavelengths.

[0088] The timing control circuit 48 controls the timing of the LED logic drive circuit 47, the background subtraction circuit 44, the response value data correction circuit 46, and the interface circuit 50, so that the wavelength of the emitted light, the wavelength of the detected scattered light signal, the response value of the photodetector and the corresponding wavelength and temperature correction relationship, and the corrected values of the scattered light intensity signals at different wavelengths and different angles can be obtained according to the timing. Then it is input to the calculation unit 49 for mathematical inversion using the diffraction formula to calculate the particle size distribution data.

[0089] For the probe-type multi-wavelength measuring device for measuring the particle size distribution in water provided in Embodiment 1 of the present application, the technical solution of greatly changing the wavelength of the irradiation light is used to replace the technical solution of measuring the scattered light intensity at all angles to calculate and invert the particle distribution. Only by measuring the scattered light intensity at two fixed angles can the particle distribution be measured, avoiding the use of a filter and not requiring the use of a grating spectrometer, while reducing the volume of the device and significantly reducing the power consumption.

[0090] The probe-type multi-wavelength measuring device for measuring the particle size distribution in water provided in Embodiment 1 of the present application is applicable to measuring the particle size distribution of particles with a size of 0.05 microns to 30 microns in water, and has the characteristics of in-situ measurement, small volume, and low power consumption. It can be used for ocean scientific research, deep-sea resource development, and ocean environmental investigation.

[0091] Embodiment 2

[0092] Please refer to Figure 6 , Embodiment 2 of the present application also provides a method for measuring the particle size distribution in water with a probe-type multi-wavelength, which is applied to the measuring device provided in Embodiment 1 and includes the following steps:

[0093] Step S110: Emit light beams of different wavelengths in sequence.

[0094] Please refer to Figure 2 again, in this embodiment, a light source is provided, and the light source unit 10 is used to emit light beams of different wavelengths in sequence.

[0095] Please refer to Figure 2 again, the light source unit 10 includes an LED array 11. The LED array 11 includes 12 different-wavelength LED light sources 111. The first to tenth LEDs are the same as those in Embodiment 1, and the eleventh and twelfth LEDs are infrared LEDs with emission wavelengths of 1.55 μm and 3.3 μm respectively. The LED array 11 is lit in a time-sharing sequence, so that only one wavelength of LED light source emits light at each moment.

[0096] Further, by controlling the timing and pulse width of the light emission of the LED array 11, each LED is extinguished after the lighting time ΔT ends and then delayed by Δt, and then the next LED is lit, and so on. The entire measurement period H≥12×(ΔT + Δt).

[0097] It can be understood that since only 1 LED emits light at each light-emitting moment, there is no need to select the wavelength at the detection end, avoiding the use of a filter, and there is no need to use a grating for spectroscopy, reducing the volume of the entire device, and the power consumption of the light source is only 1 / 12 of that when 12 LEDs are fully lit, greatly reducing the power consumption of the device.

[0098] Step S120: Receive the light beam and irradiate the light beam onto the particulate matter in the sample.

[0099] In this embodiment, a light guide unit is provided. The light guide unit 20 is coupled to the light source unit 10, and the light guide unit 20 is configured to receive the light beam and irradiate the light beam onto the particulate matter in the sample.

[0100] In this embodiment, the light guide unit 20 is a light guide rod. The light guide rod is coupled to the light source unit 10, and the light guide rod receives the light beam and irradiates the light beam onto the particulate matter in the sample.

[0101] Step S130: Measure the scattered light intensities of the particulate matter in the sample at 2 angles at different wavelengths.

[0102] In this embodiment, a light detector unit is provided. The light detector unit includes 3 light detectors 31. The light detectors 31 are configured to simultaneously measure the scattered light intensities of the particulate matter in the sample at 2 angles and the light intensity on the side surface of the light output end of the light guide rod at different wavelengths.

[0103] Please refer to Figure 3 , the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 are located on the same plane and are in direct contact with the sample to be measured.

[0104] It can be understood that the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 are located on the same plane, which can greatly reduce the volume and weight of the measurement device, and the shape of the device is similar to an optical sensor, such as a chlorophyll a fluorescence sensor, greatly reducing the volume of the device.

[0105] Please refer to Figure 4 , the light output window 21 of the light guide unit 20 and the detection window 32 of the light detector 31 can also be located on different planes and are in direct contact with the sample to be measured.

[0106] In this embodiment, the photodetector unit further includes a third photodetector 33, which is disposed on the side surface of the light-emitting end of the light guide unit 20. The third photodetector 33 is used to measure the change in the light-emitting intensity of each wavelength in real time.

[0107] It can be understood that the third photodetector 33 is disposed on the side detection side close to the light-emitting end surface of the light guide rod to detect the side leakage light, and can measure the change in the light-emitting intensity of each LED, and is used for feedback control of the output light intensity.

[0108] Step S140: Obtain the particle size distribution of the particles in the sample according to the scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam.

[0109] The measurement module 40 is used to obtain the particle size distribution of the particles in the sample according to the scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam.

[0110] In this embodiment, a measurement module 40 is provided. The measurement module 40 numerically calculates and inversely obtains the particle size distribution of the particles in the sample according to the Fraunhofer equation and the Mie equation, based on the scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam.

[0111] It should be noted that when the particle diameter D is much larger than the incident light wavelength λ, diffraction occurs, and the scattering at this time is called diffraction scattering. The light wave deviates from the straight propagation direction and bends into the geometric shadow area of the obstacle, and a phenomenon of uneven light intensity appears on the light screen behind the obstacle. The diffraction scattering intensity can be obtained according to the Fraunhofer principle, as follows:

[0112]

[0113] In the formula: I0 is the incident light intensity, α is the particle size parameter (α = πD / λ), J1 is the first-order Bessel function, and θ is the diffraction angle. In diffraction scattering, since the distance between the detection point and the sample particle is relatively far, the incident light is approximately considered to be parallel light, and the particle scattering is not affected by the absorption and refraction of the material. Therefore, its application range is wider.

[0114] When the particle diameter is approximately equal to the incident light wavelength, the scattering is between Rayleigh scattering and diffraction scattering, and the scattering at this time is called Mie scattering. The Mie scattering light intensity can be calculated as:

[0115]

[0116] In the formula, θ, λ, and α are the scattering angle, the wavelength of the incident light, and the particle size parameter, respectively; m is the refractive index of the particle relative to the surrounding medium; r is the distance from the particle to the observation plane; Φ is the electric vector of the incident light relative to the scattering angle; s1 and s2 are the amplitude function components perpendicular and parallel to the scattering plane, respectively, which are infinite series composed of Bessel functions and Legendre functions.

[0117] It can be understood that the calculation unit provided in this embodiment can also measure the particle size distribution by significantly changing the wavelength of the incident light and measuring the scattered light intensity at a fixed angle according to the Fraunhofer equation and the Mie equation.

[0118] Please refer to Figure 5 , which is a schematic structural diagram of the measurement module 40, and includes:

[0119] A conditioning circuit 41, the photodetector 31 and the third photodetector 33 are connected to the conditioning circuit 41, and the conditioning circuit 41 is used to amplify the optical intensity electrical signal output by the detector.

[0120] An analog-to-digital conversion circuit 42, the analog-to-digital conversion circuit 42 is electrically connected to the conditioning circuit 41, and the analog-to-digital conversion circuit 42 is used to perform analog-to-digital conversion on the optical intensity electrical signal output by the conditioning circuit 41.

[0121] A sampling and filtering circuit 43, the sampling and filtering circuit 43 is electrically connected to the analog-to-digital conversion circuit 42, and the sampling and filtering circuit 43 is used to perform sampling and filtering processing on the optical intensity value obtained by the analog-to-digital conversion of the analog-to-digital conversion circuit 42.

[0122] A background subtraction circuit 44, the background subtraction circuit 44 is electrically connected to the sampling and filtering circuit 43, and the background subtraction circuit 44 is used to subtract the interference of the sample background light on the measurement data from the optical intensity value after sampling and filtering processing.

[0123] A temperature measurement circuit 45, the temperature measurement circuit 45 is used to obtain the temperature value T of the measured sample W and the temperature value Tc inside the measurement device.

[0124] A response value data correction circuit 46, the response value data correction circuit 46 is electrically connected to the background subtraction circuit 44 and the temperature measurement circuit 45, and the response value data correction circuit 46 is used to correct the influences of the sample background light, the change in the output optical intensity of each wavelength, the temperature of the sample, and the change in the temperature inside the measurement device on the scattering signal of the particulate matter in the sample and on the response value of the photodetector.

[0125] It can be understood that the response value data correction circuit stores the following correction data: 1) Relationship data of the scattered light intensity and temperature of given-sized particulate matter under excitation light of different wavelengths measured in the laboratory at a given scattering angle; 2) Temperature coefficient of the photodetector.

[0126] Specifically, the photodetector obtains uncorrected scattered light intensity signals I1, I2…I 12 and background light signals I b1 、I b2 …I b12 , and the background subtraction circuit performs a subtraction operation to obtain the scattered light intensity I i ’ =I i -I bi , where i = 1, 2, … 12. The sample background light is represented as setting a 0-level interval time Δt between each pulse of the sequentially emitted light beams of different wavelengths. At this time, there is no emitted light, and the light measured by the photodetector is the background light of the measured sample, which is represented as the sample background light.

[0127] It can be understood that a 0-level interval time Δt is set between each pulse (width ΔT) of the sequential light emission. At this time, there is no emitted light, and the light measured by the detector is the background light of the measured water body. Therefore, the background light before and after each lighting (LEDi lit by the previous pulse) can be subtracted in real time by subtraction, eliminating the influence of the background light on the measurement.

[0128] The calculation unit 49 stores the numerical calculation formulas of the Fraunhofer equation and the Mie equation, as well as the calculation parameters corresponding to this measurement device, reads the data output by the response value data correction circuit, and performs numerical calculation inversion to obtain the particle size distribution data.

[0129] In this embodiment, the algorithm used by the calculation unit is based on the Fraunhofer equation and the Mie equation, and the corrected intensity of the scattered light measured simultaneously at different wavelengths and different angles of the light beam is used to inversely obtain the particle size distribution of the particulate matter in the sample.

[0130] The LED logic drive circuit 47 is used to control the light source unit 10 to sequentially emit light beams of different wavelengths.

[0131] The timing control circuit 48, the LED logic drive circuit 47, the background subtraction circuit 44, the response value data correction circuit 46, the calculation unit 49 and the interface circuit 50 all control the timing through the timing control circuit 48, so that the wavelength of the emitted light at each moment, the wavelength of the detected scattered light signal, the relationship between the light detector response value and the corresponding wavelength and temperature correction, and the scattered light intensity signal correction value at different wavelengths and different angles can be obtained according to the timing, and then input into the calculation unit 49 for mathematical inversion to calculate the particle size distribution data.

[0132] The probe-type multi-wavelength measurement method for particle size distribution in water provided in the above-mentioned embodiment 2 of the present application uses a technical solution of significantly changing the wavelength of the irradiated light to replace the technical solution of measuring the scattered light intensity at all angles to calculate and invert the particle distribution. The particle distribution can be measured by measuring the scattered light intensity at only two fixed angles, avoiding the use of filters and grating splitting, thereby reducing the size of the device and significantly reducing power consumption.

[0133] The probe-type multi-wavelength measurement method for measuring the particle size distribution in water provided in the above-mentioned embodiment 2 of the present application is suitable for measuring the distribution of particles with a particle size of 0.1 microns to 100 microns in water bodies. It has the characteristics of in-situ measurement, small size, and low power consumption. It can be used for marine scientific research, deep-sea resource development, and marine environmental investigations.

[0134] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A probe-type multi-wavelength measuring device for measuring the particle size distribution in water, characterized in that, Comprising: A light source unit for sequentially emitting light beams of different wavelengths; A light guiding unit coupled to the light source unit, for receiving the light beam and irradiating the light beam onto the particulate matter in the sample; A light detector unit including at least two light detectors for measuring the scattered light intensities of the particulate matter in the sample at at least two angles at different wavelengths; A measurement module for inversely obtaining the particle size distribution of the particulate matter in the sample based on the corrected scattered light intensities measured simultaneously at different wavelengths and different angles of the light beam.

2. The measuring device for measuring the particle size distribution in water by a probe-type multi-wavelength as described in claim 1, characterized in that, The light source unit includes an LED array, the LED array includes N LED light sources of different wavelengths, N≥6, and the LED array is lit in a time-sharing sequence such that only one wavelength of LED light source emits light at each moment.

3. The measuring device for measuring the particle size distribution in water by means of a probe-type multi-wavelength as described in claim 2, characterized in that, The timing and pulse width of the light emission of the LED array are such that each LED light source is extinguished after the end of the lighting time ΔT and then delayed by Δt, and then the next LED light source is lit, and so on, and the entire measurement period H≥N×(ΔT + Δt).

4. The measuring device for measuring the particle size distribution in water by a probe-type multi-wavelength as claimed in claim 1, characterized in that, The two light detectors are used to simultaneously measure the scattered light intensities of the particulate matter in the sample at at least two different angles at different wavelengths. The axes of the two light detectors are respectively set at an angle X and 90° with the axis of the light emitted by the light guiding unit, and X≤80°.

5. The measuring device for measuring the particle size distribution in water by a probe type multi-wavelength as claimed in claim 4, wherein, The light output window of the light guiding unit and the detection window of the light detector are on the same plane and are in direct contact with the sample to be measured; or the light output window of the light guiding unit and the detection window of the light detector are on different planes and are in direct contact with the sample to be measured.

6. The measuring device for measuring the particle size distribution in water with a probe-type multi-wavelength as claimed in claim 4, wherein, The light detector unit further includes a third light detector disposed on the side of the light output end of the light guiding unit for real-time measuring the change in the light intensity output at each wavelength.

7. The measuring device for measuring the particle size distribution in water with a probe-type multi-wavelength according to claim 6, characterized in that, It further includes a first temperature probe and a second temperature probe, and the first temperature probe and the second temperature probe are respectively used for measuring the temperature value T of the sample W and the temperature value Tc inside the measuring device.

8. The measuring device for measuring the particle size distribution in water by a probe-type multi-wavelength as claimed in claim 7, characterized in that, The measurement module includes: A conditioning circuit, the light detectors and the third light detector are connected to the conditioning circuit, and the conditioning circuit is used to amplify the light intensity electrical signal intensity output by each light detector; An analog-to-digital conversion circuit electrically connected to the conditioning circuit, and the analog-to-digital conversion circuit is used to perform analog-to-digital conversion on the light intensity electrical signal output by the conditioning circuit; A sampling and filtering circuit electrically connected to the analog-to-digital conversion circuit, and the sampling and filtering circuit is used to perform sampling and filtering processing on the light intensity data obtained by the analog-to-digital conversion of the analog-to-digital conversion circuit; A background subtraction circuit electrically connected to the sampling and filtering circuit, and the background subtraction circuit is used to subtract the interference of the sample background light on the measurement data from the light intensity data after sampling and filtering processing; Temperature measurement circuit, which is used to obtain the temperature value T of the measured sample W and the temperature value Tc inside the measuring device; A response value data correction circuit electrically connected to the background subtraction circuit and the temperature measurement circuit, and the response value data correction circuit is used to correct the influences of the sample background light, the change in the light intensity output at each wavelength, the temperature of the sample, and the change in the temperature inside the measurement device on the scattered signal of the particulate matter in the sample and on the response value of the light detector. A calculation unit, which stores the numerical calculation formulas of the Fraunhofer equation and the Mie equation, as well as the calculation parameters corresponding to this measurement device, reads the data output by the response value data correction circuit, and performs numerical calculation inversion to obtain particle size distribution data; An LED logic drive circuit, which is used to control the light source unit to emit light beams of different wavelengths in sequence; A timing control circuit, the LED logic drive circuit, the background subtraction circuit, the response value data correction circuit, and the interface circuit are all controlled by the timing control circuit for timing, so that the wavelength of the emitted light, the wavelength and response value of the detected scattered light signal, the response value of the corresponding background light subtraction, the temperature correction relationship, and the correction values of the scattered light intensity signals at different wavelengths and different angles can be obtained according to the timing.

9. The measuring device for measuring the particle size distribution in water by means of a probe-type multi-wavelength as claimed in claim 8, wherein, The photodetector obtains uncorrected scattered light intensity signals I1, I2… I N and background light signals I b1 , I b2 … I bN . The background subtraction circuit performs a subtraction operation to obtain the scattered light intensity I i ’ = I i - I bi , where i = 1, 2, … N. The sample background light is represented by setting a 0-level interval time Δt between each pulse of the sequentially emitted light beams of different wavelengths. At this time, there is no emitted light, and the light measured by the photodetector is the background light of the sample to be measured, which is represented as the sample background light.

10. The measuring device for measuring the particle size distribution in water with a probe-type multi-wavelength as described in claim 9, characterized in that, The algorithm used by the calculation unit is based on the Fraunhofer equation and the Mie equation. According to the corrected intensity of the scattered light measured by the light beam at different wavelengths and different angles, the particle size distribution of the particulate matter in the sample is inversely obtained.

11. A measurement method for measuring the particle size distribution in water by a probe-type multi-wavelength, characterized in that, It includes the following steps: Emit light beams of different wavelengths in sequence and irradiate the particulate matter in the sample; Measure the scattered light intensity of the particulate matter in the sample at at least 2 angles at different wavelengths; Obtain the particle size distribution of the particulate matter in the sample according to the scattered light intensity measured by the light beam at different wavelengths and different angles simultaneously.

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