Gradient-based Estimators for One and Two-dimensional Speckle Motion

摘要

Demonstrated herein is the performance of gradient-based estimators for assessing small motions in specklepatterns. Such estimators are important in a variety of speckle techniques used in non-destructive evaluation. Thesespeckle patterns can be two-dimensional (one spatial dimension and one temporal dimension) as obtained in objectivespeckle techniques or three-dimensional (two spatial dimensions and one temporal dimension) as typically seen insubjective (imaged) speckle methods. Both theoretical and experimental performance estimates are presented. Through aseries of numerical simulations, performance (velocity bias and RMS variation) is characterized in terms of the signal-tonoiseratio. This SNR parameter is a convenient surrogate for the decorrelation of sequential speckle patterns such asthose observed in biological tissues. Experimental evaluations are performed on an optically rough metal coupon. Wedemonstrate that under easily met experimental conditions, estimates of speckle motions on the order of one tenth of apixel can be obtained reliably.