1. A method for estimating at least one sought deformation of the wave front of an observation system or of an object observed by said observation system, comprising: acquiring, in the vicinity of the focal plane of the observation system, at least one diversity image in at least one diversity plane, the diversity image comprising a known diversity deformation; and in each diversity plane: determining an image model according to at least the following steps: decomposition of a physical pupil of the observation system into a plurality of sub-pupils; decomposition on each sub-pupil of the sought deformation in the form of linear combination polynomials of at least one known deformation weighted by sought deformation coefficients; determination of a transfer function of the observation system by autocorrelation of its pupil; linearization of each of the terms of the autocorrelation depending on the sought deformation coefficients, the linearization being carried out relative to a vector based on the sought deformation; determination of a criterion of distance between the image model and data obtained in each diversity plane, the criterion of distance being quadratic in the image model, the image model being linear in the sought deformation; and analytical minimization of the criterion of distance for estimating at least one of the sought deformation and the object as close as possible to the data obtained in each diversity plane, a difference between the data obtained and the image model being noise, said analytical minimization comprising: obtaining from the criterion of distance for a known deformation, an analytical solution of the object; injecting the obtained object into the criterion of distance to obtain a new criterion which only depends on the sought deformation; and minimizing the new criterion to obtain the sought deformation.