Photoacoustic inspection of matching layers of ultrasonic air-coupled transducers

The quality of matching layers suitable for air-coupled transducers was studied with an air-coupled photoacoustic microscope. The matching layers studied were silica aerogel and balsa wood. Ultrasonic pulses were used to determine the ultrasound absorption profiles of aerogel-glass and balsa-wood-glass interfaces. The results show a need for developing bonding techniques. The main advantages of the method considered are its noncontacting character and the good control of the bandwidth, the power, and the geometry of the sound beam. The drawback of the method is a fairly long measurement time, because of which the main use of the measurement method would be the development of transducer-manufacturing techniques.<>