2. Diffraction techniques

Diffraction techniques analyze scattering patterns at infinity, in angular regions dominated by an optical singularity. They use the same coherent, collimated illumination system and the same signal recording and analysis methods. They differ in terms of the angular positioning of the detection optics and the relative refractive index of the particles they can characterize: towards the front and whatever the index for conventional diffractometry, near the rainbow angle and for indices m > 1 for rainbow angle diffractometry, near the critical angle and for indices m < 1 for critical angle diffractometry.

The switch between characterizing individual particles, or clouds of particles, is made by widening/focusing the illumination beam and adjusting the spatial filtering rate of the detection. Thus, from a direct, punctual technique,...