
{"publication_number": "US-9652865-B2", "abstract": "an optical method for characterizing a diffractive surface having a crystal grain structure , including the steps of : a ) successively illuminating said surface with a plurality of light beams having propagation directions inclined by a same angle \u03b8 ; relative to the normal to the surface and of which the projections on the surface form azimuth angle \u03c6 