Dynamic Image Analysis (DIA)

Dynamic Image Analysis (DIA) is a modern high-performance method for the characterization of particle size and particle shape of powders, granules and suspensions.

Retsch Technology’s optical analyzers CAMSIZER P4 and CAMSIZER X2 are based on this technology, covering a measuring range from 0.8 µm to 30 mm.

Dynamic Image Analysis is used in many industries for quality control as well as in research & development. It increasingly replaces more established methods such as laser diffraction or sieve analysis.

  • CAMSIZER® P4

    CAMSIZER<sup>®</sup> P4
    • Measuring principle: Dynamic Image Analysis (ISO 13322-2)
    • Measuring range: 20 µm to 30 mm
    • Type of analysis: dry analysis of powders, granulates and bulk materials
  • CAMSIZER® X2

    CAMSIZER<sup>®</sup> X2
    • Measuring principle: Dynamic Image Analysis (ISO 13322-2)
    • Measuring range: Standard
      0.8 µm to 8 mm
      10 µm to 8 mm (gravity dispersion)
      0.8 µm to 5 mm (air pressure dispersion)
      0.8 µm to 1 mm (wet dispersion)
      extended measuring ranges
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    • Type of analysis: dry and wet analysis

Dynamic Image Analysis: Technological Basics

Dynamic Image Analysis analyzes the shadow projections of particles. Both the CAMSIZER P4 and CAMSIZER X2 transform grayscale images through a multistep algorithm into binary images to determine the exact outlines.

All particle size and particle shape parameters are measured on this basis. The values of the single measurements are assigned to 10,000 size classes during the measurement, providing an extremely high resolution.

Size and Shape Parameters of Dynamic Image Analysis (DIA)

Imaging methods offer the crucial advantage of using various size definitions, allowing for direct length and shape measurement.

Depending on the application, a variety of size parameters may be of interest:

  1. If, for example, elongated particles such as cellulose fibers, catalyst rods, plastic extrudates or rice grains are analyzed, the length of the particles is the relevant parameter.
  2. If, however, the sample needs to be compared to a sieve analysis, the focus is on particle width as the particles’ orientation allows them to pass the sieve apertures with their smallest projection area.
In Dynamic Image Analysis particle size distributions are based on different size definitions. The parameter xc min defines the particle width, xFe max describes the length. Consequently, the xFe max result is bigger than xc min. The size definition xarea is based on the calculation of a circle with equivalent surface from each particle.

Measuring Range of Dynamic Image Analysis (DIA)

The lower and upper limits of the measurement range of image analysis systems are determined by various factors (see ISO 13322-1 and -2). The lower limit is defined by the resolution of the camera. The decisive criterion is the smallest particle size which the optics can still reproduce on a single pixel (= picture element) on the camera chip.

The reproduction scale is ascertained with the help of calibration objects with exactly defined dimensions. The smallest measurable particle shadows at least half a pixel on the camera chip and this size is usually defined as the detection limit or lower limit of the measuring range.

The upper limit of the measuring range of DIA analyzers is determined by the field of view of the cameras.

Particle projections on the edge of the field of view have to be rejected because the correct particle size cannot be determined. This results in larger particles being underrepresented as they are more likely to be located near the edge. The software of the CAMSIZER systems features an algorithm in accordance with ISO 13322-1 which compensates for this effect, which ensures that the percentage of large particles is correctly represented.