Definition
Image particle size meter is a particle characterization instrument based on static image analysis technology. It collects projected images of particles and uses digital image processing algorithms to quantitatively measure the size, shape and distribution of particles. The instrument is suitable for the analysis of a wide range of solid particle samples and provides richer morphological information than traditional screening or laser diffraction methods.
Principle
The core principle of image particle size meter is optical imaging and image analysis. The sample particles are dispersed in a stage or flow cell and illuminated by a light source (usually an LED or halogen lamp) to capture a projected image of the particles through an optical lens. Image sensors, such as CMOS or CCDs, convert light signals into digital images. The dedicated software then identifies the individual particle profiles in the image and calculates the geometric parameters of each particle based on the correspondence between the pixel size and the calibration scale. For non-spherical particles, instruments usually describe their dimensions with parameters such as equivalent circle diameter, long diameter, short diameter, etc., and can calculate shape factors such as roundness and aspect ratio.
Measurement method
Common measurement methods include static image analysis and dynamic image analysis. In the static method, the sample particles are dispersed in a flat slide or sample cell, and the instrument photographs and analyzes the stationary field of view, which is suitable for dry or wet preparation of fixed samples. The dynamic method allows the particles to pass through the measurement area in the fluid, and the instrument continuously shoots the particles in motion, with a larger number of statistics and stronger representativeness, especially suitable for the rapid analysis of a large number of particles. Both methods require good sample dispersion and avoid overlapping or agglomeration of particles to ensure measurement accuracy. The measurement process usually includes sample preparation, image acquisition, threshold segmentation, contour extraction, parameter calculation, and statistical report generation.
Influencing factors
The reliability of the measurement results is affected by several factors. Sample preparation is a key link, and the particle dispersion directly affects the image quality. Excessive agglomeration can lead to large measurements, and improper dispersant selection can alter the surface state of the particles. Optical system parameters, such as lens resolution, depth of field, and illumination uniformity, determine the ability to capture image details. The accuracy of image processing algorithms, especially threshold setting and edge detection methods, has a significant impact on particle recognition and segmentation. In addition, the sampling statistics need to be large enough to represent the overall particle size distribution. For widely distributed samples, multiple samples may need to be sampled or the measurement field of view may be adjusted.
Application:
Image particle size meters are widely used in fields where both particle size and shape information need to be obtained. In the building materials industry, it is used to analyze the particle size and sphericity of cement and sand particles to evaluate their fluidity and strength effects. In metal powder metallurgy, the size distribution and morphology of powder particles are characterized, and the pressing and sintering properties are correlated. In the chemical field, the morphology of particles such as catalysts, pigments, and fillers is detected to optimize product performance. In the food industry, the particle uniformity of sugars, salts, powder additives is analyzed. In environmental monitoring, sediments and suspended particles can be morphologically classified. The shape parameters provided by the instrument help to understand the processing behavior and application characteristics of the particles.
Selection
When selecting a model, it is necessary to comprehensively consider the measurement requirements and technical parameters. First, the characteristics of the sample to be tested are determined, such as particle size range, concentration, and whether wet or dry measurement is required. The optical magnification and resolution should match the particle size to ensure that the smallest detectable particles are clearly imaged. Software features should support the necessary shape parameter analysis and provide a report format that complies with relevant standards such as ISO 13322-2. For dynamic measurement, it is necessary to pay attention to whether the flow system design is easy to clean and prevent blockage. Instrument calibration methods, repeatability metrics, and data export flexibility are also important considerations. In addition, the user-friendly design, maintenance complexity and technical support capabilities of the operation interface are of practical significance for long-term stable use.