Choosing Phased Array Pitch in Ultrasonic Tomography of Materials with Inhomogeneous Structure

Abstract

The influence of phased array (PA) pitch on signal/pattern-noise ratio when probing objects with inhomogeneous structure by low-aperture transducers of transverse acoustic waves is considered. A saturation phenomenon has been discovered for small PA pitches. The phenomenon is due to the influence of positive cross correlation between pattern-noise instances at neighboring receiving transducers. The optimum PA pitch has been determined to be approximately 0.5 of the wavelength when probing the object area across the PA and 0.4 of the wavelength when probing areas at the side of the PA. Experimental research has been carried out and proved the validity of the theoretical results.