TECHNIQUES

Interferometric Mie Imaging (IMI)

The Interferometric Mie Imaging (IMI) method is a sizing technique for the evaluation of the diameter of spherical particles, droplets and bubbles similar to PDI. The working principle is based on the out-of-focus imaging of particles illuminated by a laser light sheet. The optical setup of a standard IMI system consists of a laser-light sheet and a digital camera with a high quality lens. Moving the CCD chip of the camera to an out-of-focus position an interference fringe pattern becomes visible in the overlapping region. The visible fringe pattern corresponds exactly to the far field scattering which can be calculated by the Mie theory.

The number of fringes within the aperture image depends on the diameter of the droplet and the aperture angle. With an increasing size of particles, the number of fringes increases when the aperture angle is fixed by the experimental setup. The size of the aperture image is a measure for the z-position of the particles and depends on the corresponding z-displacement. Increasing the latter leads to an increasing size of the aperture image. Using the planar coordinates of the aperture images the corresponding x- and y-positions of the particles in the object plane can be calculated. The size of the particles is determined by analysis of the fringe patterns.

Information
- Particle size (d)
- Particle position (x, y, z)
- Statistics, histograms (D10, SMD, Dv10, Dv50, Dv90,
  v-d correlation)
- Velocity (u, v, w)
- Number density
- Mass flux

Applications
-liquid sprays (fuels, water, paint, pharmaceutical, crop)
-droplet atomization
-bubbles (heat exchangers, industrial processes)