Abstract
A generalization of the method of J. Chandezon et al. (1982) is presented for conical diffraction mounting. The applicability of the invariance theorem for real metal and dielectric gratings is discussed and the existence of some polarization effects is demonstrated. A formulation of the reciprocity theorem in conical diffraction mounting is proposed, valid not only for the efficiencies of the diffracted orders but for the amplitudes, too.