Coaxial multi-beam multi-wavelength positive and negative Fourier laser particle analyzer and measuring method thereof

Abstract

The invention discloses a coaxial multi-beam multi-wavelength forward and reverse Fourier laser particle analyzer which comprises a beam combiner, a coupler, a first Fourier lens, a dichroscope, a second laser, a second Fourier lens, a sample window, a forward detector, a lateral detector, a backward detector and a plurality of first lasers. The light propagation direction of the second laser is perpendicular to the light propagation direction of each first laser. The invention further discloses a measuring method of the coaxial multi-beam multi-wavelength forward and reverse Fourier laser particle analyzer. The measuring method comprises the following steps: step 1, collecting system background light intensity; 2, collecting the light intensity of the system after sample adding; 3, respectively calculating the scattering light intensity of each wavelength; and 4, calculating the particle size distribution of the particles. The measurement lower limit and the measurement upper limit of the laser particle analyzer are effectively expanded, the lower limit and the upper limit of the particle size detection range are smaller, and particle detection within the range of the upper limit and the lower limit of the measuring range is prevented from being missed.

Description

Technical Field

[0001] The present invention relates to the technical field of particle measurement, and particularly to a coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer and a measurement method thereof. Background Art

[0002] A laser particle size analyzer is an instrument based on the principle of laser diffraction or scattering to measure the particle size and its distribution, and is widely used in fields such as pharmaceuticals, chemicals, materials science, food, and environmental monitoring. By analyzing the scattering pattern of laser light by suspended or dry particles, the particle size distribution is calculated. Its basic principle is to infer the particle size by analyzing the scattered light generated by the interaction between the laser and the particles. The selection of the laser wavelength directly affects its particle detection range. Short-wavelength lasers are usually 400nm - 480nm, suitable for detecting fine particles, capable of providing higher resolution, especially suitable for detecting sub-micron or even nano-scale particles, and can more sensitively capture the scattered signals of fine particles, reducing the omission of particle detection. Long-wavelength lasers are usually 630nm - 1100nm, suitable for detecting coarse particles, and can better analyze large particles in the micron or even millimeter scale. At the same time, it is not easily absorbed or scattered in many materials, especially in water or organic substances. The long-wavelength laser has better penetration ability, which can reduce the measurement error.

[0003] Most traditional laser particle size analyzers use single-wavelength light sources, usually red light or near-infrared light sources. Although they perform well in detecting larger particles, their limitations are also very obvious. When facing a complex particle system, single-wavelength lasers cannot simultaneously meet the detection requirements of small particles and large particles. Due to its relatively low resolution, especially in the detection of nano-scale or sub-micron scale particles, the sensitivity is insufficient, and small particles are easily missed. In addition, single-wavelength lasers are not sensitive to the light absorption and scattering of certain materials, which may lead to inaccurate measurements. Especially in the case where multiple particle size ranges need to be detected simultaneously, a particle size analyzer with a single-wavelength light source is difficult to provide comprehensive particle size distribution information. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer and a measurement method thereof.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer includes a beam combiner, a coupler, a first Fourier lens, a dichroic mirror, a second laser, a second Fourier lens, a sample window, a forward detector, a lateral detector, a backward detector, and a plurality of first lasers; The light propagation direction of the second laser is perpendicular to the light propagation direction of each first laser; The dichroic mirror can simultaneously satisfy the passing of each first laser and the second laser according to requirements. The first Fourier lens and the second Fourier lens can both perform Fourier transform on the laser beam and obtain the converging beam required by the particle size analyzer. The sample window is perpendicular to the laser beam passing through the dichroic mirror.

[0006] Preferably, the first laser can be a fiber laser with a wavelength of 400 - 1100 nm, and its laser wavelengths are short, medium, and long respectively, and the maximum number can reach 10.

[0007] Preferably, the forward detector, the side detector, and the backward detector are respectively placed on the front side, the side, and the rear side of the sample window, and the forward detector, the side detector, and the backward detector are all photodetectors.

[0008] Preferably, the beam combiner couples each first laser into a single optical fiber through a coupler.

[0009] The measurement method of the above coaxial multi-beam multi-wavelength forward and reverse Fourier laser particle size analyzer includes the following steps: Step 1: Collect the background light intensity of the system: Number each first laser 1 from top to bottom as a, b... i, j; (1) Turn on laser a, and collect the background light intensity and incident light intensity on the forward detector, the side detector, and the backward detector; (2) Turn off laser a, turn on laser b, and collect the background light intensity and incident light intensity on the forward detector, the side detector, and the backward detector; (3) Turn off laser b, turn on laser c, and collect the background light intensity and incident light intensity on the forward detector, the side detector, and the backward detector; ... (12) Turn off laser j, turn on the second laser, and collect the background light intensity and incident light intensity on the forward detector, the side detector, and the backward detector; Step 2: Collect the light intensity after adding the sample to the system: (1) Turn on laser a, and collect the scattered light intensity and transmitted light intensity on the forward detector, the side detector, and the backward detector after adding the sample; (2) Turn off laser a, turn on laser b, and collect the scattered light intensity and transmitted light intensity on the forward detector, the side detector, and the backward detector; (3) Turn off laser b, turn on laser c, and collect the scattered light intensity and transmitted light intensity on the forward detector, the side detector, and the backward detector; ... (12) Turn off laser j, turn on the second laser, and collect the scattered light intensity and transmitted light intensity on the forward detector, the side detector, and the backward detector; Step 3: Calculate the scattered light intensity at each wavelength respectively: Calculate the scattered light intensity at the wavelengths of the first laser and the second laser in sequence according to the formula that the scattered light intensity at a wavelength = the light intensity after sample addition - the background light intensity * the transmitted light intensity / the incident light intensity; Step 4: Calculate the particle size distribution; First, calculate the particle size distribution at each wavelength through an inversion algorithm, and then fuse these 11 groups of particle size distributions together to obtain a group of particle size distributions.

[0010] The present invention has the following beneficial effects: 1. The coaxial multi-wavelength laser particle size analyzer of the present invention can collect the scattered light signals of coaxial lasers with 3 - 11 different wavelengths passing through the sample window. By selecting laser beams with different wavelengths, the detection requirements for both small particles and large particles can be taken into account simultaneously. The short-wavelength laser can detect fine particles, and the long-wavelength laser can detect coarse particles, effectively expanding the measurement lower limit and upper limit of the laser particle size analyzer, making the lower limit of the particle size detection range smaller and the upper limit larger, and avoiding missing the detection of particles within the range of the upper and lower limits of the measurement range; 2. Different samples have different light absorption and scattering characteristics. The present invention can select a laser beam with a suitable wavelength for detection according to the light absorption characteristics of the sample. This avoids measurement errors caused by the mismatch between the laser wavelength and the sample characteristics, and effectively improves the detection accuracy of the laser particle size analyzer. For example, when detecting a sample with strong absorption of light at a specific wavelength, selecting a laser with a suitable wavelength can more accurately measure its particle size distribution; 3. The particle size analyzer and its measurement method of the present invention can meet the detection requirements of various samples for particle size distribution. Whether it is a simple sample with a single particle size range or a complex sample containing multiple particle size ranges, accurate and comprehensive particle size distribution information can be provided, providing a reliable basis for production process control, product quality detection, etc. Description of the Drawings

[0011] Figure 1 It is a top view schematic diagram of a coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer proposed by the present invention.

[0012] In the figure: 1 First laser, 2 Beam combiner, 3 First Fourier lens, 4 Sample window, 5 Backward detector, 6 Dichroic mirror, 7 Second Fourier lens, 8 Second laser, 9 Lateral detector, 10 Forward detector. Detailed Embodiments

[0013] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Embodiment 1:

[0014] A coaxial multi-beam multi-wavelength forward and reverse Fourier laser particle size analyzer, comprising a beam combiner 2, a coupler, a first Fourier lens 3, a dichroic mirror 6, a second laser 8, a second Fourier lens 7, a sample window 4, a forward detector 10, a lateral detector 9, a backward detector 5, and a plurality of first lasers 1; The light propagation direction of the second laser 8 is perpendicular to the light propagation directions of the first lasers 1. The dichroic mirror 6 can simultaneously satisfy the passage of the first lasers 1 and the second laser 8 according to requirements. Both the first Fourier lens 3 and the second Fourier lens 7 can perform Fourier transform on the laser beam and obtain the converging beam required by the particle size analyzer. The sample window 4 is perpendicular to the laser beam passing through the dichroic mirror 6. The beam combiner 2 couples the first lasers 1 into a single optical fiber through the coupler. The present invention can select a laser beam with a suitable wavelength for detection according to the light absorption characteristics of the sample. This avoids measurement errors caused by the mismatch between the laser wavelength and the sample characteristics, and effectively improves the detection accuracy of the laser particle size analyzer. For example, when detecting a sample with strong absorption of a specific wavelength of light, selecting a laser with a suitable wavelength can more accurately measure its particle size distribution. Embodiment 2:

[0015] Compared with Embodiment 1, the first lasers 1 can be selected as fiber lasers with wavelengths in the range of 400 - 1100 nm, with short, medium, and long laser wavelengths, and the maximum number can reach 10. The forward detector 10, the lateral detector 9, and the backward detector 5 are respectively placed on the front side, the lateral side, and the rear side of the sample window 4, and the forward detector 10, the lateral detector 9, and the backward detector 5 are all photodetectors.

[0016] By selecting laser beams with different wavelengths, the detection requirements for both small particles and large particles can be taken into account simultaneously. Short-wavelength lasers can detect fine particles, and long-wavelength lasers can detect coarse particles, effectively expanding the lower and upper limits of the measurement range of the laser particle size analyzer, making the lower limit of the particle size detection range smaller and the upper limit larger, and avoiding missing the detection of particles within the upper and lower limits of the measurement range. The coaxial multi-beam multi-wavelength forward and reverse Fourier laser particle size analyzer as described above performs measurements using the following steps: Step 1: Collect the background light intensity of the acquisition system: Number the first lasers 1 from top to bottom as a, b... i, j; (1) Turn on laser a, and collect the background light intensity and incident light intensity on the forward detector 10, the lateral detector 9, and the backward detector 5; (2) Turn off laser a, turn on laser b, and collect the background light intensity and incident light intensity on the forward detector 10, the lateral detector 9, and the backward detector 5; (3) Turn off laser b and turn on laser c, and collect the background light intensity and incident light intensity on the forward detector 10, lateral detector 9, and backward detector 5. …… (12) Turn off laser j and turn on the second laser 8, and collect the background light intensity and incident light intensity on the forward detector 10, lateral detector 9, and backward detector 5. Step 2: Collect the light intensity after adding samples to the acquisition system: (1) Turn on laser a and collect the scattered light intensity and transmitted light intensity on the forward detector 10, lateral detector 9, and backward detector 5 after adding samples. (2) Turn off laser a and turn on laser b, and collect the scattered light intensity and transmitted light intensity on the forward detector 10, lateral detector 9, and backward detector 5. (3) Turn off laser b and turn on laser c, and collect the scattered light intensity and transmitted light intensity on the forward detector 10, lateral detector 9, and backward detector 5. …… (12) Turn off laser j and turn on the second laser 8, and collect the scattered light intensity and transmitted light intensity on the forward detector 10, lateral detector 9, and backward detector 5. Step 3: Calculate the scattered light intensity of each wavelength respectively: Calculate the scattered light intensity of each wavelength of the first laser 1 and the second laser 8 in turn according to the formula that the scattered light intensity by wavelength = the light intensity after adding samples - the background light intensity * the transmitted light intensity / the incident light intensity. Step 4: Calculate the particle size distribution; First, calculate the particle size distribution of each wavelength through the inversion algorithm, and then fuse these 11 groups of particle size distributions together to obtain a group of particle size distributions.

[0017] The particle size analyzer and its measurement method of the present invention can meet the detection requirements of various samples for particle size distribution. Whether it is a simple sample with a single particle size range or a complex sample containing multiple particle size ranges, it can provide accurate and comprehensive particle size distribution information, providing a reliable basis for production process control, product quality inspection, etc.

Claims

1. A coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer, characterized in that It includes a beam combiner (2), a first Fourier lens (3), a dichroic mirror (6), a second laser (8), a second Fourier lens (7), a sample window (4), a forward detector (10), a lateral detector (9), a backward detector (5), and multiple first lasers (1); The light propagation direction of the second laser (8) is perpendicular to the light propagation directions of the first lasers (1); The dichroic mirror (6) can simultaneously allow the first lasers (1) and the second laser (8) to pass through according to requirements. The first Fourier lens (3) and the second Fourier lens (7) can both perform Fourier transform on the laser beam and obtain a converging beam required by the particle size analyzer. The sample window (4) is perpendicular to the laser beam passing through the dichroic mirror (6).

2. The coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer according to claim 1, characterized in that The first laser (1) can be a fiber laser with a wavelength of 400 - 1100 nm, and its laser wavelengths are short, medium, and long, and the maximum number can reach 10.

3. A coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer according to claim 1, characterized in that, The forward detector (10), the lateral detector (9), and the backward detector (5) are respectively placed on the front side, the lateral side, and the rear side of the sample window (4), and the forward detector (10), the lateral detector (9), and the backward detector (5) are all photodetectors.

4. A coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer according to claim 1, characterized in that The beam combiner (2) couples the first lasers (1) into a single optical fiber through a coupler.

5. The measuring method of a coaxial multi-beam multi-wavelength forward and inverse Fourier laser particle size analyzer according to any one of claims 1-4, characterized in that It includes the following steps: Step 1: Collect the background light intensity of the system: The first lasers 1 are sequentially numbered a, b... i, j from top to bottom; (1) Turn on laser a, and collect the background light intensity and incident light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); (2) Turn off laser a, turn on laser b, and collect the background light intensity and incident light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); (3) Turn off laser b, turn on laser c, and collect the background light intensity and incident light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); …… (12) Turn off laser j, turn on the second laser (8), and collect the background light intensity and incident light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); Step 2: Collect the light intensity after adding the sample to the system: (1) Turn on laser a, and collect the scattered light intensity and transmitted light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5) after adding the sample; (2) Turn off laser a, turn on laser b, and collect the scattered light intensity and transmitted light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); (3) Turn off laser b, turn on laser c, and collect the scattered light intensity and transmitted light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); …… (12) Turn off laser j, turn on the second laser (8), and collect the scattered light intensity and transmitted light intensity on the forward detector (10), the lateral detector (9), and the backward detector (5); Step 3: Calculate the scattered light intensity of each wavelength respectively: Calculate the scattered light intensity at the wavelengths of each first laser (1) and second laser (8) in sequence according to the formula: scattered light intensity according to wavelength = light intensity after sample addition - background light intensity * transmitted light intensity / incident light intensity; Step 4: Calculate the particle size distribution; First, calculate the particle size distribution at each wavelength through the inversion algorithm, and then fuse these 11 groups of particle size distributions together to obtain a group of particle size distributions.

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