Spherically focused capacitive-film, air-coupled ultrasonic transducer
A spherically focused no mirrors capacitive-film, air-coupled ultrasonic transducer, constructed using a spherically deformed backplate and metalized polymer film, has been designed, fabricated, and its performance characterized. A 1 cm diameter device has a center frequency of 805 kHz and a 6 dB bandwidth of 760 kHz. Comparisons of field strength in the focal zone with theoretical calculations for a spherically focused piston show that the device achieves diffraction-limited focusing. The nominal focal point of 25 mm lies within 0.01 mm of the calculated value for this device.
This article was originally published in Journal of the Acoustical Society of America 119, no. 2 (2006): EL1–EL6, doi:10.1121/1.2152293.