Small element array algorithm for correcting phase aberrations using near-field signal redundancy. Part II: Experimental results

For part I see ibid., vol.47, p.29 (2000). A small element array algorithm for phase-aberration correction using near-field signal redundancy was proposed in part I. Using this algorithm, subarrays are formed to narrow the transmitted and received beams when collecting common midpoint signals, so that angle-dependent aberration profiles across the array can be measured. In this paper, this algorithm is tested on data collected from a phantom with a non-isoplanatic aberrator attached to the front surface of a phased array. The aberrator is made from cast room temperature vulcanizing (RTV) silicone rubber, which has a sound velocity of about 1.02 mm/spl middot//spl mu/s/sup -1/. Results show that the subarray technique can be used to measure and correct angle-dependent, phase-aberration profiles. The theoretical results regarding the performance of several implementation methods for dynamic near-field delay correction on subarrays are also experimentally tested using data from a phantom.