Displacement measurements in micro-region with generalized digital speckle correlation method

High magnifying optics is now widely used in micro-region imaging, which leads to the special image structures on the recording plane, such as continue-gray distributions, large granules and spread structures. As a result, the deformation analyses are unreliable and divergent by using the conventional speckle correlation methods and these generalized speckle patterns. A new correlation algorithm, high-order gradient digital correlation method, has been proposed in this paper to measure the displacements in a micro-region. The performance of the proposed algorithm is illustrated using the generalized speckle patterns captured from the micro-regions.