Apparatus for the characterization of particle objects by means of a radiation beam, which propagates along an optical axis (z), comprising one or more observation regions suitable to be illuminated by the radiation beam and suitable to be transited by at least one particle object, said observation region being arranged near or at a focus (F1;F1') of the radiation beam, wherein a fraction of the radiation beam - hereinafter, scattered fraction - is scattered following interaction with the particle object transiting in the observation region, and another fraction of the radiation beam - hereinafter, transmitted fraction - is transmitted through the respective observation region, without interacting with the particle object transiting in the observation region, at least one sensor suitable for detecting an interference image determined by the interference between the transmitted fraction and at least a part of the scattered fraction that propagates around the direction of the optical axis (z) of the radiation beam; and at least one processing unit configured to determine a characteristic of said particle object from said interference image; said apparatus being characterized in that it comprises optical means (31, 32; 33, 34; 41, 42) acting on at least one of said radiation beam, scattered fraction and transmitted fraction such that the transmitted fraction and the scattered fraction of the radiation beam are distributed in a spatially differentiated manner in a space interposed between the observation region and the sensor, wherein an attenuator (10;10') is provided arranged in a region (F2;PF2') of said space occupied mainly by the transmitted fraction of the radiation beam, the attenuator (10;10') being configured to attenuate the transmitted fraction of the radiation beam without substantially altering the scattered fraction of the radiation beam. one or more observation regions suitable to be illuminated by the radiation beam and suitable to be transited by at least one particle object, said observation region being arranged near or at a focus (F1;F1') of the radiation beam, wherein a fraction of the radiation beam - hereinafter, scattered fraction - is scattered following interaction with the particle object transiting in the observation region, and another fraction of the radiation beam - hereinafter, transmitted fraction - is transmitted through the respective observation region, without interacting with the particle object transiting in the observation region, at least one sensor suitable for detecting an interference image determined by the interference between the transmitted fraction and at least a part of the scattered fraction that propagates around the direction of the optical axis (z) of the radiation beam; and at least one processing unit configured to determine a characteristic of said particle object from said interference image; said apparatus being characterized in that it comprises optical means (31, 32; 33, 34; 41, 42) acting on at least one of said radiation beam, scattered fraction and transmitted fraction such that the transmitted fraction and the scattered fraction of the radiation beam are distributed in a spatially differentiated manner in a space interposed between the observation region and the sensor, wherein an attenuator (10;10') is provided arranged in a region (F2;PF2') of said space occupied mainly by the transmitted fraction of the radiation beam, the attenuator (10;10') being configured to attenuate the transmitted fraction of the radiation beam without substantially altering the scattered fraction of the radiation beam.