Ultrasonic imaging using air-coupled P(VDF/TrFE) transducers with through-transmission method at 2 MHz

Abstract

Concave-type twin transducers with a center frequency of 1.93 MHz have been fabricated using polyvinylidene fluoride trifluoroethylene (P(VDF/TrFE)) resonators that have a transducer insertion loss of 100 dB (although this figure does not include the air absorption loss). A through-transmission acoustic imaging system was constructed using these twin (transmitting/receiving) P(VDF/TrFE) transducers. Burst waves composed of 50 cycles of sine-waves from a radio-frequency (RF) source were excited to approximately 600 V_pp by using a high-voltage power amplifier, and these high voltage burst waves were then input into the transmitting P(VDF/TrFE) transducer. Acquisition of the resulting small signal after it had passed through a sample object (a Rockwell 11229-12 logic integrated circuit) allowed the through-transmission image to be displayed on a personal computer monitor. The transverse resolution of this imaging system is approximately 0.5 mm. The results of this study demonstrate that these P(VDF/TrFE) piezoelectric films with their low acoustic impedances are applicable to through-transmission imaging in air in the MHz range.