A Polyvinylidene Fluoride Bow-Tie Imaging Element

Polyvinylidene fluoride is a piezoelectric polymer film useful for imaging elements. It has many ultrasonic applications and is well suited to array technology as a replacement to ceramic piezoelectric materials. In a bow-tie configuration, this film effectively couples ultrasonic energy to and from air, producing a radiation pattern matched to the imaging requirements of array systems. We have designed and built a bow-tie array useful at frequencies up to 100 kHz. This frequency limit is imposed by element dimensions as well as ultrasonic attenuation in air. Experimental measurements confirm our model predictions. Typical applications of this device are intrusion detectors, tactile imagers, phased array sector scanners, and any other requirement where efficient coupling to air is a major objective.