Digital Image Processing

In many applications particle size and shape information provides an important process and quality indicator. Based on digital image processing the CAMSIZER is immediately able to analyze the particle shape of the sample material in a detailed and representative manner. The advantages of the full-frame cameras used in the CAMSIZER for the distortion-free recording of all the particle projections is particularly obvious when measuring the particle shape and size.

The patented measuring setup – two digital cameras as an adaptive measuring unit – improves and optimizes particle analysis by digital image processing. Thus, it is possible to measure a wide range of particles from 30 µm to 30 mm extremely accurately, without having to switch measuring ranges or make adjustments.

The sample is fed in from the feed channel so that all particles fall through the measurement field. During the measurement procedure the two digital cameras (CCD) perform different tasks. The basic camera (CAM-B) records large particles, the zoom camera (CAM-Z) records the small ones. The contact-free optical measurement is carried out in real time and simultaneously obtains all the required information about particle size and particle shape.

Particle shape analysis and its applications

As a result of the high information content obtained from the digital images made during the measurement procedure, the particle projections can be evaluated in many different ways. Depending on the application, the CAMSIZER measures the particle projections according to various areas, circumferences and lengths by making a high-resolution scan of each individual particle in 64 directions. The results obtained can be, for example:

• chord length
• width/length aspect ratio
• Martin diameter
• roundness
• Feret diameter
• symmetry
• straight length
• convexity

Examples of particle shape analysis applications are:

• determination of fractions of mixture components (see graph)
  e.g. of ion exchangers and active charcoal for water filters as well as glass beads and corundum in colors used for road markings
• determination of edge-holding property (angularity)
  e.g. quality assessment of abrasives as a preliminary to further processing
• analysis of the broken fraction of granules
  e.g. as a replacement for time-consuming breakage studies on the rolling properties of granules
• determination of width/length distribution of extrudates (“rods”)
  e.g. determining the volumetric density of catalysts in reactor containers
• prediction of flow and compacting behavior
  e.g. press-molding powders and granules to form tablets