Large deformation analysis by holographic interferometry

The method presented permits one to study large deformation quantitatively by a simple compensation technique: in real-time, the modification of the reference beam direction delivers the three components of the displacement, and the modification of the object beam direction provides the strain and rotation components of the surface element. For an object which may show large deflections under normal load conditions, only a small portion of the illuminated surface will be covered with visible fringes. Thus, the compensation has to be repeated from one object point to another in order to get a full field deformation analysis. Since the method is based on the fringe vector and on the visibility vector, which are obtained from the derivation of the fringe order function, it is better adapted to the determination of the strain and rotation components. However, the procedure provides automatically the displacement components in an intermediate step