1. Convergent beam diffraction

1.1 Information in both areas

A priori, there should be as much information in direct space (image mode) as in reciprocal space (diffraction mode), since we know how to switch from one to the other by Fourier transformation. This information can only be obtained by measurement, and in both cases, image or diffraction, the distribution of intensities must be collected. In diffraction mode, the phase associated with each of the beams is therefore lost, and this is the basic problem of all diffraction techniques, which led to the development of direct methods. This correspondence of information between the two spaces has already been examined in the determination, using a Fourier transform code, of the power spectra of various objects