Patent ID: 9243957
Filing Date: 2016-01-26
CPC Classification: G01J

Claim Text:
1. A method for characterizing a light beam comprising the steps: a) arranging the entry ends of N≧3 optical fibers on the route of said light beam, in such a way that a respective portion of said beam is coupled and propagates in each optical fiber and is emitted from its exit end so as to form a respective secondary beam, each of said portions corresponding to a different point of the cross section of said light beam; b) introducing an angular spectral dispersion on said secondary beams by at least one dispersive element; c) propagating the spectrally dispersed secondary beams in such a way that they overlap to form an interferogram; d) acquiring an image of said interferogram; and e) extracting from said image of said interferogram an item of information relating to the spatial variation of the phase of said light beam at a plurality of wavelengths in which the optical path lengths of said portions of said light beam are adjusted in such a way that they are not all equal to one another; and in which said step e) comprises: e1) the calculation of a two-dimensional Fourier transform of said image of said interferogram; e2) the identification of at least N−1 peaks of said two-dimensional Fourier transform, each of which is representative of the interference between two, and only of two, spectrally dispersed secondary beams; and e3) for each of said peaks, and for a plurality of wavelengths, the determination of the phase difference between the two corresponding secondary beams, each said phase difference being corrected of said differences between the optical path lengths.