Non-Contact Ultrasonic Imaging
Abstract
Ultrasound provides an excellent method of imaging objects embedded within a medium having high water content. For example, at a frequency of 2 MHz, the imaging resolution is on the order of a millimeter. The dramatic mismatch of acoustic impedance between air and water, however, typically necessitates good acoustic contact between the transducer and the medium to be studied. This mismatch causes the transmitted intensity to drop by a factor of one thousand from that incident on the boundary. This difficulty in directly coupling acoustic energy into the medium via an air gap is the fundamental reason why non-contact ultrasound imaging remains infeasible. We propose to overcome this long standing problem by developing new methods of coupling into the medium at standoff. In particular, we believe that the acoustic nonlinearity of both the air and the medium may yield a range of effects in the vicinity of the surface permitting an efficient transmission of ultrasound from the air into the medium. Experimentally, we have conducted this study by directing commercially available sources of 45 and 96 kHz ultrasound beams at the air-water free surface and measuring acoustic transmission and surface deformation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 30, 2017
- Source ID
- W911NF1510634
Entities
People
- Seth Putterman
Organizations
- Army Contracting Command
- United States Army
- University of California, Los Angeles