The invention provides a method for obtaining the object-plane field without a pure theoretical estimation or a direct experimental measurement of a point spread function (PSF) of an imaging system. Instead, at least two image-plane fields have to be recorded. It is essential that the resolutions of the system producing the images have to be quite different from each other. Although both PSFs of the system are unknown, the recording conditions have to be chosen so that the second PSF could be expressed via the first PSF. Two integral equations—(1) a convolution of the object-plane field with the first PSF and (2) a convolution of the object-plane field with the second PSF (expressed via the first PSF)—can be reduced to one functional equation in the Fourier space. The reverse Fourier transform of the solution of this equation is the object-plane field.