Method for characterising a particle on the basis of a hologram

A method for characterizing a particle within a sample, the sample lying between an image sensor and a light source, the image sensor lying in a detection plane, the method comprising:

• a) illuminating the sample with the light source, the light source emitting an incident light wave that propagates along a propagation axis;
• b) acquiring an image of the sample with the image sensor, the image comprising a plurality of elementary diffraction patterns, each elementary diffraction pattern corresponding to one particle;
• c) on the basis of the acquired image, reconstructing a complex image representative of a complex amplitude of the exposure light wave on at least one reconstruction surface passing through the sample, the reconstruction being achieved by implementing an iterative reconstruction algorithm, the algorithm comprising, in each iteration, updating a phase of the exposure light wave in the detection plane or on the reconstruction surface;
• d) selecting a region of interest of the complex image, the selected region of interest corresponding to a selected particle of interest;
• e) forming an extracted complex image, the extracted complex image being extracted from the region of interest of the complex image selected in d);
• f) applying a propagation operator to the extracted complex image formed in e), so as to obtain, in at least one propagation plane, an elementary diffraction pattern of the particle of interest selected in d), such that the elementary diffraction pattern obtained is isolated from elementary diffraction patterns of other particles present in the sample;
• and
• g) characterizing the particle of interest depending on the elementary diffraction pattern resulting from f).