A novel, rapid method to measure the effective aperture of array elements

Abstract

Effective aperture is a commonly used measure of the amount of acoustic or electrical crosstalk between elements in ultrasonic arrays. It is also important to assess element-to-element uniformity and quality of the separation between the elements. This parameter is obtained from the beam profile obtained by pulsing each individual element with a known excitation function. The traditional method, using hydrophones, presents many challenges that are overcome by the proposed method. Using a quantitative schlieren system, we imaged the acoustic burst from an array element. Automated processing allows determination of the average intensity over the burst at all angles (angular beam profile) and its width is used to determine the effective aperture for that element. Examples are presented for floating and purposefully coupled neighboring elements, and the results are in good agreement with those obtained with a hydrophone. The algorithm used for image analysis is also described.