Control of phase of fringes in speckle interferometry for application of fringe scanning methods

The speckle interferometry is an effective technique in the displacement measurement of a structure with a rough surface. However, when the fringe scanning technology is introduced to speckle interferometry for improving the measurement resolution, two speckle patterns before and after the deformation of the measurement object and another speckle pattern under different situation from two speckle patterns shown before generally are required. In this paper, the methods for introducing the fringe scanning method are proposed by controlling the phase of specklegram as a fringe image using filtering technologies. Then, the spatial and the temporal fringe analysis methods that use only two speckle patterns are proposed for speckle interferometry. As results, the high precise fringe analysis can be realized by the fringe scanning methods using only two speckle patterns in the displacement measurement with a large deformation. The results show that the possibility of the method based on spatial fringe analysis methods in practical uses would be higher than that of temporal methods.