Method of measuring properties of particles and corresponding apparatus

Abstract

A method of measuring properties of particles includes generating a beam of radiation (IW); illuminating with the beam (IW) an observation region (MR) which is transited by a particle (B). A portion of the beam (IW) gives rise to radiation (SW) which is scattered by scattering interaction with the particle (B), and another portion (TW) is transmitted substantially undisturbed through the observation region (MR). In a detection plane (M), a plurality of radiation intensity values are detected which are determined by the interference between the scattered radiation (SW) and the transmitted radiation (TW). The detection of the radiation intensity values in the detection plane (M) is carried out according to a time sequence of acquisitions corresponding to successive transit positions of the particle through the observation region (MR). On the basis of the time sequence of acquisitions, the trend of a parameter of asymmetry of the distribution of the plurality of radiation intensity values with respect to the optical axis (z), due to the successive transit positions of the particle (B), is determined as a function of time. Depending on the trend of the parameter of asymmetry determined as a function of time, the trends of phase delay and amplitude of the scattered radiation (SW) with respect to the transmitted radiation (TW) are determined as a function of time, and the properties of the particle (B) are determined on the basis of the trends of the phase delay and amplitude of the scattered radiation (SW) as a function of time.