The name "FRINGE-CONTRAST DITERFEROMETRY" /FCl/ is proposed for such measuring techniques and interpretation methods which are based on information contained in the fringe-visibility distribution in interference images. In general, the fringe-visibility distribution depends on kind and direction of object illumination, shape and microstructure of object surface, such parameters of imaging system as focusing distance, aperture size, as well as shape and orientation of diaphragm, and - on differences between two states of object surface being compared using an interferometry technique. The early papers on this subject have concerned the case of imaging system focused exactly on the object surface, with circularly [1,2,3] and arbitrarily Du shaped diaphragm. In this case, the fringe visibility depends on the differences described only by the displacement components perpendicular to viewing and/or illumination directions. The recent works [5,6,7, and unpublished yet] have been based on the general equations describing the fringe visibility formed by imaging system focused on the object plane which is arbitrarily situated with respect to the object surface. These equations allow to apply FCI to arbitrarily-shaped object surfaces for automated determination of the shape of object surface, the fringe-order distribution, 3-D dis-placement field, as well as the surface-strain and rotation tensor fields - directly from fringe-contrast measurement, without differentiating the displacement field.