Speckle Pattern Correlation with Lateral Aperture Translation: Experimental Results and Implications for Spatial Compounding

Abstract

In order to design improved spatial compounding ultra- sound scanning systems it is necessary to determine the correlation of speckle patterns as a function of aperture translation. We have con- ducted experiments measuring the speckle correlation with lateral ap- erture translation for linear phased array pulse-echo ultrasonic im- aging systems. Results are presented for variable frequency, range, transducer length, focus error, and reflecting material. Tests were con- ducted on two commercially availahle and one research imaging sys- tem. The measured rates of correlation coefficient decrease are inde- pendent of frequency, reflecting material, and target range when the target is in the focal zone. The experimentally determined correlations are used to derive the optimal spatial separation of images for speckle reduction.