Evaluation of phase changes of interferograms during continuous deformations

A method for measurement of continuous displacements and deformations is presented. The method may be used in e.g. speckle interferometry, moire, structured light and other optical measurement methods based on evaluation of phase changes. The initial random phase of the interference pattern is either known or evaluated before displacement take place using e.g. phase shifting. The changing phase thereafter is achieved only from one image at a time by a least square algorithm. The technique can be used for measuring shape deformations such as transients and other dynamic events, heat expansion as well as other phenomena where it is difficult to accomplish phase shifting during deformation.