In-plane displacement measurement using electronic-speckle-pattern-interferometry-based on spatial fringe analysis method

Speckle interferometry is used to measure the deformation of an object with a rough surface. In particular, the precise measurement can be easily performed with electronic-speckle-pattern interferometry (ESPI) using fringe scanning technology. Then, the measurement accuracy is influenced by the ratio between the speckle size and the pixel size of a CCD. Sometimes, this causes a problem concerning optical dislocations. An in-plane displacement is measured by the optical measurement arrangement using the two collimated beams. The measurement is performed by ESPI technology with the spatial fringe analysis method under an optimal measurement condition. Then, the optimum condition is discussed as the measurement parameters concerning the speckle's size and the passband of the bandpass filter. In the experimental measurement of in-plane displacement, it is shown that the optimal measurement condition can evade the problem of optical dislocations. At the same time, it is confirmed that a precise measurement can be performed.