Analyse av en Ultralyd Transduser med et Laser Doppler Vibrometer

Abstract

Ultrasonic transducers are an integral part of underwater imaging, with a wide range of applications. In this thesis, analysis of a underwater echo sounder transducer operating at 200kHz is done underwater with a Laser Doppler Vibrometer(LDV). Measurements and analysis where done at Kongsberg Maritimes ultrasonic lab and at the USN ultrasonic lab. The LDV measures the velocity of the transducer surface as the transducer is exited. This data is compared to simulation models and hydrophone measurements of the pressure field created by the transducer. It was shown that the LDV is capable of reproducing the directivity of the ultrasonic beam for angles up to 15◦−20◦ and that power and efficiency can be investigated, but there are challenges involving a phenomena called the acousto optic effect that complicates the measurements. Power estimations for angles higher than 15◦−20◦ proved to be highly unreliable.