A method for measuring properties of particels by means of interference fringe analysis and corresponding apparatus

A method of measuring properties of particles comprises the steps of: generating a beam of radiation (IB) which is propagated along a principal axis (z), illuminating with the beam (IB) an observation region (MR) with particles (B), a portion of the beam (IB) giving rise to radiation (SW) which is scattered by interaction of the portion of the beam (IB) with the particles (B) and another portion (TB) being transmitted substantially undisturbed through the observation region (MR), and detecting, in a plane (M) disposed on the propagation axis (z), radiation intensity values which are determined by the interference between the scattered radiation (SW) and the transmitted radiation (TB). The method further comprises the steps of: identifying systems of interference fringes associated with the particles (B) in which the interference pattern is affected by a phase delay of the scattered radiation (SW) relative to the transmitted radiation (TB), the delay being determined by the interaction of the radiation beam (IB) with the particles (B), and determining the properties of the particles (B) on the basis of the lower-order interference fringes.