Method for observing a sample, the sample lying in a plane ( P 10) of the sample defining radial coordinates (r), each radial coordinate corresponding to a pair of two coordinates ( x, y) on two orthogonal axes (X, Y) of the plane of the sample, the method comprising the following steps: a) illuminating the sample using a light source, configured to emit an incident light wave that propagates toward the sample along a propagation axis; b) acquiring, using an image sensor, an image I 0 λ of the sample, said image being formed in a detection plane ( P 0), said image of the sample forming a hologram of the sample, the sample being placed between the light source and the image sensor, such that the incident light wave experiences an optical path difference, parallel to the propagation axis, on passing through the sample; c) processing the image acquired by the image sensor; the method being such that the processing of the acquired image comprises the following iterative steps: i) initializing a set () of vectors ( F n ( r)) of parameters, modelling the sample, the vectors of parameters being respectively defined at a plurality of radial coordinates ( r), in the plane of the sample, each vector of parameters being associated with one radial coordinate ( r), and comprising at least one component F w n r representative of an optical parameter of the sample at said radial coordinate, at least one optical parameter being an optical path difference induced by the sample at said radial coordinate; ii) on the basis of the vectors ( F n ( r)) of parameters, forming a complex image A 10 λ, n of the modelled sample in the plane ( P 10) of the sample; iii) applying a holographic propagation operator to the complex image of the modelled sample formed in the plane of the sample, in order to compute an image Î 0 λ, n of the modelled sample in the detection plane; iv) comparing the image I 0 λ acquired in step b) and the image Î 0 λ, n computed in step iii), in order to compute a validity indicator ε | F n; v) updating all of the vectors of parameters, so as to make the validity indicator ε | F n tend toward a preset value; vi) reiterating steps ii) to v) taking into account the vectors ( F n +1 ( r)) of parameters updated in step v); the method being characterized in that: step v) comprises computing a morphological criterion ε 10 | F n from the vectors ( F n ( r)) of parameters, the morphological criterion quantifying a deviation of the vectors of parameters, describing the sample, with respect to a morphological constraint of the sample, such that the validity indicator ε | F n is obtained from a combination: - of an error criterion ε 0 | F n, determined from a comparison between the image acquired in step b) and the image obtained in step iii); - and of the morphological criterion ε 10 | F n. a) illuminating the sample using a light source, configured to emit an incident light wave that propagates toward the sample along a propagation axis; b) acquiring, using an image sensor, an image I 0 λ of the sample, said image being formed in a detection plane ( P 0), said image of the sample forming a hologram of the sample, the sample being placed between the light source and the image sensor, such that the incident light wave experiences an optical path difference, parallel to the propagation axis, on passing through the sample; c) processing the image acquired by the image sensor; i) initializing a set () of vectors ( F n ( r)) of parameters, modelling the sample, the vectors of parameters being respectively defined at a plurality of radial coordinates ( r), in the plane of the sample, each vector of parameters being associated with one radial coordinate ( r), and comprising at least one component F w n r representative of an optical parameter of the sample at said radial coordinate, at least one optical parameter being an optical path difference induced by the sample at said radial coordinate; ii) on the basis of the vectors ( F n ( r)) of parameters, forming a complex image A 10 λ, n of the modelled sample in the plane ( P 10) of the sample; iii) applying a holographic propagation operator to the complex image of the modelled sample formed in the plane of the sample, in order to compute an image Î 0 λ, n of the modelled sample in the detection plane; iv) comparing the image I 0 λ acquired in step b) and the image Î 0 λ, n computed in step iii), in order to compute a validity indicator ε | F n; v) updating all of the vectors of parameters, so as to make the validity indicator ε | F n tend toward a preset value; vi) reiterating steps ii) to v) taking into account the vectors ( F n +1 ( r)) of parameters updated in step v); - of an error criterion ε 0 | F n, determined from a comparison between the image acquired in step b) and the image obtained in step iii); - and of the morphological criterion ε 10 | F n.