Method and device for measuring particulate matters

Abstract

The invention provides a particulate matter measuring method. Acquiring a plurality of section frame images of the particulate matters in the particulate matter container along a preset direction to form an image sequence; and processing and analyzing the image sequence, and extracting to obtain the particle number, concentration, color, morphology and / or particle size distribution of the particulate matters. The step of processing and analyzing the images comprises: identifying particles in each image of the image sequence through threshold segmentation or a neural network target identification model; the particles of the (n-1) th frame and the nth frame are matched in a cross-frame mode according to the particle recognition result, the same particle of different frames is numbered uniquely, the number of the particles in the container is obtained, and n is the sequence number of the image sequence; intercepting images of the same particle in different frames to perform image focusing evaluation to obtain a clearest image; and carrying out contour extraction and color extraction operation on the clearest image of each particle to obtain the shape, particle size and color features of the particle.

Description

Technical Field

[0001] This invention belongs to the field of measurement technology, and specifically relates to a method and apparatus for measuring particulate matter. Background Technology

[0002] Liquid particle counters are precision instruments used to detect the number and size distribution of suspended particles in liquids (such as water, oil, pharmaceutical solutions, and chemicals). They are crucial for controlling liquid cleanliness in fields such as pharmaceuticals, semiconductors, power, and aerospace. Common liquid particle counters come in various types, and can be classified as follows:

[0003] (1) According to the testing principle, it includes: optical obscuration method, light scattering method, and resistance method (also known as the Coulter method), among which,

[0004] (a) Optical obstruction method - When liquid flows through a transparent channel, the particles contained therein block the laser light path, causing the detector to receive a light intensity attenuation signal. The particle projection area can be determined based on the attenuation amplitude, and then converted into the equivalent particle size.

[0005] (b) Light scattering method - similar to the light obstruction method, when the liquid flows through the transparent channel, the particles contained therein block the laser light path. The particles will scatter light in all directions of space and be captured by the detector (generally, they can be arranged in the forward, side, backward or multi-angle arrangement). Then, according to the Mie scattering theory, the equivalent particle size is calculated using the intensity of the scattered light.

[0006] (c) Resistance method - When particles pass through micropores in the electrolyte, a resistance pulse is generated. The particle volume and equivalent particle size can be calculated based on the pulse amplitude.

[0007] All three methods described above belong to the category of flow cytometry particle counters and employ flow cytometry technology. This involves focusing fluid to allow particles to pass through the detection zone in a single line, followed by individual signal analysis. To ensure no particles are missed during counting, a special sample cell design is used, allowing a minute amount of liquid to flow through the measurement zone. This measurement zone is very small, ensuring that particles can only pass through sequentially, thus enabling particle counting. Simultaneously, changes in signals (photoresistance, light scattering, electrical resistance) as particles pass through are used to determine particle size. Figure 4 As shown. In recent years, the optical obscuration method and the light scattering method have also been combined and collectively referred to as laser particle counters or optical particle counters. Due to their advantages such as fast testing speed, wide dynamic range, and immunity to human influence, they have become the mainstream products in many industries in recent years.

[0008] It should be noted that particle counting methods differ from particle size measurement methods. The former emphasizes measuring each individual particle and outputting statistical results, while the latter directly measures the particle group. Common measurement techniques for the latter include optical obscuration, light scattering (laser diffractometer / laser particle size analyzer), gravimetric analysis, inertial analysis, diffusion analysis, and condensation nucleation (CNC) analysis. Due to inherent limitations in these measurement methods, existing liquid flow particle counters suffer from the following problems:

[0009] (a) The upper limit of particle size measurement by flow cytometry particle counter is affected by the size of the measurement area. For particle systems with a wide particle size distribution, problems such as missed detection of small particles and false increase of large particles may occur.

[0010] (b) The flow focusing technology has high requirements, as particles must pass through the measurement zone sequentially. Therefore, to improve measurement accuracy, the flow rate needs to be reduced, resulting in a long measurement time. Moreover, for viscous fluids, ensuring good flow focusing and particle flow control is even more difficult.

[0011] (c) Unable to provide information such as shape and color. Summary of the Invention

[0012] One aspect of this disclosure is a rapid, non-destructive method for full-field scanning imaging to count all particles, comprising the following steps;

[0013] Multiple cross-sectional frame images of the particles located in the container holding the particles along a preset direction are acquired to form an image sequence;

[0014] By processing and analyzing the image sequence, the particle number, concentration, color, morphology, and / or particle size distribution of the particulate matter can be extracted.

[0015] The particulate matter is a discrete particulate matter in a solid, liquid, or gaseous state dispersed in a liquid.

[0016] Another aspect of this disclosure is a particulate matter measuring device, which includes an image acquisition device for capturing particulate matter, a container for holding particulate matter, and a light source for illuminating the container. The device measures particulate matter using the aforementioned total particulate matter counting method.

[0017] The detection device and method proposed in this disclosure utilize imaging technology to directly count particle groups within large-volume samples, achieving high speed and accuracy. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0019] Figure 1 A schematic diagram of a particulate matter measuring device according to one embodiment of the present invention.

[0020] Figure 2 A schematic diagram of a particulate matter measuring device according to one embodiment of the present invention.

[0021] Figure 3 A schematic diagram of a particulate matter measuring device according to one embodiment of the present invention.

[0022] Figure 4 A schematic diagram of an existing particulate matter measuring device.

[0023] in,

[0024] 1—The first light source;

[0025] 2—Sampling bottle;

[0026] 3—Second light source;

[0027] 4—Sampling bottle fixing device;

[0028] 5 — Lens;

[0029] 6—Camera;

[0030] 7 - Stepper motor. Detailed Implementation

[0031] According to one or more embodiments, this disclosure proposes a particulate matter measuring device to solve the detection of sampled particulate pollutants, including particle size, concentration, color, and morphology detection. The particulate matter to be detected is loaded into a container. An embodiment of this disclosure provides a container-based particulate matter measuring device, with a sampling bottle (a type of container), a camera, a lens, dual light sources, and a stepper motor as its core components. The first light source is parallel light, coaxial with the imaging optical path, illuminating from the top of the sampling bottle; the second light source is a ring light, illuminating from the bottom of the sampling bottle upwards; the imaging system acquires images from the bottom of the container, and then moves the camera and lens via the stepper motor to focus and image at each height position of the sampling bottle, obtaining images of each height section of the container, forming a multi-focus image sequence. By analyzing these image sequences, particulate matter characteristics such as number concentration and particle size distribution are extracted. Here, the image processing steps mainly include the following four steps:

[0032] (1) Particle recognition: Particles in each image of a multi-focus sequence image are identified by threshold segmentation or neural network target recognition model. In this case, the image processing algorithm includes threshold segmentation, boundary recognition segmentation, and / or region growing segmentation.

[0033] (2) Cross-frame matching: Based on the particle identification results, match the particles in frame t-1 and frame t, assign a unique number to the same particle in different frames, and obtain the number of particles in the container; here t is both a time series and a position series.

[0034] (3) Focus evaluation: The same particle in step (2) has different focus in different frames. The image of each frame of the same particle is extracted for focus evaluation to obtain the image at the clear moment;

[0035] (4) Feature extraction: Perform contour extraction, color extraction and other operations on the image of each particle at the clearest moment obtained in step (3) to obtain the features such as particle shape, particle size and color.

[0036] In the container particulate matter measurement system of this disclosure, a motor moves a camera lens to acquire cross-sectional images of the container at each height. The particle concentration is obtained from the cross-sectional images at each height of the container by identifying the particles in each frame and then performing cross-frame matching.

[0037] According to one or more embodiments, this disclosure provides a particulate matter measuring device, such as... Figure 1 As shown, after the sampling bottle for holding particulate matter is fixed, a first light source illuminates the particulate matter inside the container from above, while a second light source surrounds the outside of the container. A reflector is placed at the bottom of the container to change the angle of the light path for the particulate matter image, so that a camera with a lens (which can be a zoom lens) faces the reflector and captures an image of a cross-section of the particulate matter. The camera is mounted on a slide rail or lead screw and driven by a stepper motor, allowing the camera to move on the slide rail or lead screw to change the focal length. Here, the camera can use a fixed focal length lens, a zoom lens, or a liquid lens. Therefore, in this embodiment, a zoom lens can be used alone to capture particulate matter images, or a fixed focal length lens can be used alone in combination with a stepper motor to capture particulate matter images, or both can be combined for more flexible and precise adjustment of the focal length for capturing particulate matter. Figure 1 A central reflector is not necessary; the lens and camera can be positioned directly on the vertical line of the cross-sectional frame image, facing the bottom. The reflector is primarily for ease of system setup, preventing the equipment from being designed too high.

[0038] According to one or more embodiments, this disclosure provides a particulate matter measuring device, such as... Figure 2As shown, a first light source illuminates the particles inside the container from below, while a second light source surrounds the outside of the container. A camera lens captures images of the particles from above, and the camera itself is driven by a stepper motor to move on a lead screw, changing the focal length. By changing the focal length, a sequence of frame images of different cross-sections of the particles is obtained. Here, the first light source can be a parallel light source or a diffused light source. The second light source can be set as a 0° ring light, positioned to move with the camera's focal plane. A 0° ring light refers to a ring light source with an angle of 0° between the light ray and the horizontal plane. Alternatively, the second light source can also be set as a ring light source with an angle of 0-90°. However, the purpose of setting up the second light source is to ensure that the particles at the focal plane can be clearly imaged without producing reflective points that affect the acquisition of information such as particle size and color. Therefore, the form of the second light source is not limited to a ring light source; various forms of light sources can be used as long as they can ensure clear particle imaging.

[0039] According to one or more embodiments, this disclosure provides a particulate matter measuring device, such as... Figure 3 As shown, the first light source illuminates the particulate matter inside the container from below, while the second light source surrounds the outside of the container. A camera is positioned below the container, with its lens facing the bottom. The camera is also driven by a stepper motor to move along a lead screw, thus changing the focal length. Alternatively, a fixed camera focal length can be used, with the sampling bottle positioned on a movable rail, and the camera's focal length changed by altering the bottle's position; the effect is the same.

[0040] In the particulate matter measuring device disclosed herein, the inner diameter and height of the sampling bottle are determined based on the particle size range of the particulate matter and the volume of the sample liquid to be measured. The bottom imaging of the sampling bottle should be flat and distortion-free. Alternatively, the magnification of the imaging system can be determined based on the outer diameter of the sampling bottle; the stepper motor stroke and camera working distance can be determined based on the height of the sampling bottle; and the camera type can be determined based on the measurement parameter requirements. The camera and lens are moved by the stepper motor to scan and acquire images from the bottom to the top of the sampling bottle, obtaining multi-sequence focused images. The image processing procedure for the obtained particulate matter image sequence includes:

[0041] Identify particles in each frame of a multi-focus sequence image (using threshold segmentation or deep learning).

[0042] Match the same particles in different frames, assign a unique number to the same particle, and obtain the particle concentration in the sampling bottle;

[0043] Obtain particle location information and capture images of individual particles to obtain the position and image of each particle in different frames;

[0044] The image captured for each particle goes through a process of defocusing-focusing-defocusing. The image is evaluated to obtain the image of each particle at the clearest moment, and the particle shape, size and color information are obtained.

[0045] This disclosure proposes a particulate matter measuring device and method, which has a wide range of applications, including at least the following measurement needs:

[0046] Application 1: Detection of contaminants in fuel oil (especially aviation fuel and other oils with high requirements for impurities), generally 10-50μm;

[0047] Application 2: Detection of liquid pharmaceuticals, such as injections and ophthalmic preparations, generally 10-50 μm / 1-5 μm.

[0048] Application 3: Food and beverage testing, such as bottled water, typically 10-50μm.

[0049] Application 4: Detection of electronic chemicals, such as battery electrolytes, typically 1-5μm.

[0050] Application 5: Detection of biological agents, such as cell culture media, typically 1-5 μm.

[0051] These tests share the common characteristics of requiring transparent or semi-transparent liquids; opaque liquids are not applicable. The detection limit for particulate matter size is generally 5-1000 micrometers, with a maximum limit down to 1 μm; detection of nanoscale particles is not applicable.

[0052] In summary, the beneficial effects achieved by this disclosure include:

[0053] 1. It avoids sample transfer and flow interference, allowing for non-destructive, high-resolution characterization of particles within the sealed container of the finished product. It belongs to a non-flow cytometry particle counting method, which is significantly different from common flow cytometry particle counters.

[0054] 2. It is a non-contact measurement method with a simple structure, which can meet the needs of real-time monitoring.

[0055] 3. The measuring device and method proposed in this disclosure can not only count particles, but also measure particle size, color and morphology, thereby achieving the goal of tracing the source of particulate pollutants.

[0056] It should be understood that in the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, the character " / " in this document generally indicates that the preceding and following associated objects have an "or" relationship.

[0057] It is worth noting that although the spirit and principles of this invention have been described with reference to several specific embodiments, it should be understood that this invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that the features in these aspects cannot be combined; such division is merely for the convenience of description. This invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for measuring particulate matter, characterized in that, Includes the following steps; Multiple cross-sectional frame images of the particles located in the container holding the particles along a preset direction are acquired to form an image sequence; The image sequence is processed and analyzed to extract the number, concentration, color, morphology, and / or particle size distribution of the particulate matter.

2. The method according to claim 1, characterized in that, The steps for processing and analyzing the image include, A1, using threshold segmentation or a neural network target recognition model to identify particles in each image of the image sequence; A2, based on the particle recognition results, match the particles in the (n-1)th frame and the nth frame across frames, assign a unique number to the same particle in different frames, and obtain the number of particles in the container. Here, n is the sequential number of the image sequence. A3: Extract images of the same particle from different frames and evaluate image focus to obtain the clearest image; A4 performs contour extraction and color extraction on the clearest image of each particle to obtain the shape, particle size, and color features of the particle.

3. The method according to claim 1, characterized in that, The particulate matter is discrete particulate matter in a solid, liquid, or gaseous state dispersed in a liquid.

4. The method according to claim 1, characterized in that, The preset direction includes the container's top view or bottom view.

5. A particulate matter measuring device, characterized in that, The device includes an image acquisition device for capturing particulate matter, a container for holding the particulate matter, and a light source for illuminating the container. The particulate matter is measured using the method described in claim 1.

6. The apparatus according to claim 5, characterized in that, The light source includes a first light source and / or a second light source.

7. The apparatus according to claim 6, characterized in that, The first light source is fixed to irradiate the particulate container. Preferably, the second light source moves synchronously with the image acquisition device as it captures the cross-sectional frame image to illuminate the cross-sectional position of the particulate container.

8. The apparatus according to claim 5, characterized in that, The image acquisition device has a fixed-focus or zoom lens.

9. The apparatus according to claim 5, characterized in that, The image acquisition device is mounted on a linear motion device for fixed-focus or zoom shooting.

10. The apparatus according to claim 5, characterized in that, The image acquisition device has a reflector on the optical path of the particle, which is used to change the angle of the optical path.

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