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 (Fi) having propagation directions inclined by a same angle Θ; relative to the normal to the surface and of which the projections on the surface form azimuth angle φ{umlaut over (ι)} that are different relative to a reference direction; b) acquiring an image of the surface corresponding to each of the light beams; and c) digitally processing images to obtain at least one item of information on at least one property of the surface chosen from: the grain structure, texture and level of ordering thereof. An optical head (TO) and apparatus for implementing such a method.