Holographic method for characterising a particle in a sample

16:

• A method for characterizing a particle combined in a sample, the method comprising:
• a) illuminating the sample using a light source, the light source emitting an incident light wave propagating towards the sample along a propagation axis;
• b) acquiring, using an image sensor, an image of the sample, formed in a detection plane, the sample being positioned between the light source and the image sensor, the image being representative of a light wave, transmitted by the sample under effect of the illumination;
• c) applying a propagation operator to the image acquired in b), to calculate a reference complex image, which is a complex image representative of the sample in a reconstruction plane:
• d) selecting a radial position of the particle in a plane parallel to the detection plane;
• e) from the reference complex image calculated in c), determining at least one characteristic quantity of the light wave transmitted by the sample, at a plurality of distances from the detection plane or from the reconstruction plane, wherein e) further includes:
• ei) applying a propagation operator to the reference complex image, to calculate secondary complex images for a plurality of distances from the reconstruction plane or from the detection plane;
• eii) determining a characteristic quantity of the light wave transmitted by the sample at each of the plurality of distances, from the secondary complex images;
• f) forming a profile representing a variation of the characteristic quantity determined in e) along an axis parallel to the propagation axis, the axis passing through the radial position selected in d);
• g) characterizing the particle using the profile formed in f).

22:

• The method of claim 16, wherein, in c), the calculation of the reference complex image comprises:
• ci) defining an initial image of the sample in the detection plane, from the image acquired by the image sensor:
• cii) determining a complex image of the sample in a reconstruction plane by applying a propagation operator to the initial image of the sample defined in ci) or to the image of the sample in the detection plane resulting from the preceding iteration;
• ciii) calculating a noise indicator from the complex image determined in cii), the noise indicator depending on a reconstruction noise affecting the complex image;
• civ) updating the image of the sample in the detection plane by adjusting phase values of the pixels of the image, the adjustment being carried out according to a variation of the indicator calculated in ciii) with the phase values;
• cv) reiterating cii) to civ) until a convergence criterion is reached, so as to obtain a complex reference image of the sample in the detection plane, or in the reconstruction plane.

29:

• The method of claim 16, wherein the characterization is:
• a classification of the particle according to a plurality of predetermined particle classes;
• or a determination of a state of the particle, according to a plurality of predetermined states;
• or an estimation of a geometric parameter of the particle;
• or an estimation of an optical parameter of the particle.

30:

• A device for characterizing a particle contained in a sample, the device including:
• a light source configured to emit an incident light wave propagating towards the sample;
• an image sensor;
• a holder, configured to hold the sample between the light source and the image sensor;
• a processor, configured to receive an image of the sample acquired by the image sensor and to implement c) to f) of the method of claim 16.