Electronic speckle pattern shearing interferometry for displacement and vibration measurement

In this technique the speckle shear interferometer is combined with the electronic speckle pattern interferometry technique. Two pinholes of the same diameter 'a', separated by a distance 'd' is used to image through object through an imaging lens. The formed speckle pattern which is the resultant of mutual interference between the two speckle patterns formed by each pinhole, is modulated by a grid structure inside it. This pattern is imaged by a CCD camera combined with a reference beam through a beam splitter. The object under investigation is now photographed in its first state, without any deformation, and this signal is allowed to be stored in the computer as a data file. During the object vibration or deformation, a second signal is to be sorted on the same data filet. A fast Fourier transform has been used to add such tow signals and after processing the two overlapped signals data one can obtain the deformation suffered by the object in the form of interference fringes displaying such deformation.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.