Micromachined capacitive transducer array for imaging in air

Micromachined transducer arrays for use in air have been fabricated using a low temperature process to give 1 mm square transducer elements. Cross-coupling between elements has been measured, and is due to a wave which travels at a velocity close to that in air. Individual elements have been used to image reflecting objects in air, and to locate simple point and line reflectors. In addition, it is shown that an image of a coin can be produced, without the need for focussing in air. The resolution of such images has been estimated by scanning a single device over a step feature on a surface. A rectangular array has also. been used a passive receiver to image the beam emitted by a focussed air-coupled device.