Laser diffraction analysis

Commercial laser diffraction analyzers leave to the user the choice of using either Fraunhofer or Mie theory for data analysis, hence the importance of understanding the strengths and limitations of both models.

Its main advantage is that it does not require any knowledge of the optical properties (complex refractive index) of the particle’s material.

The model’s main limitation is that it requires precise knowledge of the complex refractive index (including the absorption coefficient) of the particle’s material.

The lower theoretical detection limit of laser diffraction, using the Mie theory, is generally thought to lie around 10 nm.

A lens is placed between the object being analyzed and the detector's focal point, causing only the surrounding laser diffraction to appear.

[9] Because the light energy recorded by the detector array is proportional to the volume of the particles, laser diffraction results are intrinsically volume-weighted.

This is in contrast to counting-based optical methods such as microscopy or dynamic image analysis, which report the number of particles in the different size classes.