Island analysis of low-activity dynamic speckles

In this work we present a method to evaluate activity in low dynamic speckle patterns. It consists of binarizing the speckle image and analyzing the displacements and deformations of the resulting speckle grain regions, here called islands. Numerical simulations and controlled experiments were used to study the variations of the island features with the aim of finding a correlation with the activity of the speckle pattern. From the obtained results it was possible to conclude that the developed method can be useful for the analysis of low activity speckle patterns with the advantage of requiring only pairs of frames, thus permitting the assessment of nonstationary processes. In the case of stationary phenomena, so that stacks of frames registers are representative of them, dilute activity images can also be constructed.