Ultrasound scans IN THIN AIR

Better transducers and inexpensive, high-accuracy gantries expand the scope of noncontact ultrasound imaging. The marriage of Airtech 4000 ultrasonic imagers and Techno-Isel gantries lets users generate ultrasound-image scans without having the probe touch the sample. The gantry accurately moves the transducer above a test specimen while recording transducer position. Gantry cost was a major factor because the manufacturing market is highly price-sensitive, says Neeraj Bhardwaj, a spokesperson for Second Wave. Ultrasound imaging is widely used in laboratories for nondestructive materials testing and in health care as a noninvasive diagnostic tool. But for it to work, transducers and an acoustic-coupling liquid must touch the specimen. This rules out testing of such materials as uncured plastics, green ceramics and powered metals, materials that are continuously rolled on a production line, or those with a large surface area to be scanned. But the advent of highly sensitive piezoelectric transducers and an inexpensive precision positioning system help overcome these limitations. Boals-burg, Pa., measure a sample's thickness, density, mechanical properties, and defects, as a transducer moves above its surface. This task is challenging because an extremely large acoustic impedance mismatch between air and sample can attenuate ultra-sound waves by seven orders of magnitude compared with water as the transmission media. This is where the better transducers come in. The updated transducers operate in air. They lose just 12 to 40 dB of sensitivity over a frequency range of 50 kHz to 5 MHz. In one configuration, a CNC gantry from New Hyde Park, N.Y., accurately positions the transducer over a test article. This makes possible the ultrasound imaging of large surface areas in the familiar C-Scan mode. C-Scan mode or pulse-echo gives planar images of samples at a specific depth. Airtech 4000 imagers use the two-axis linear motion control platforms to scan a 50 54-cm area.