Air coupled ultrasonic transducer

摘要

An acoustic transducer which is operable in air up to at least 2MHz is described. A conducting substrate, usually a silicon wafer is etched to provide a selected pattern of micro pits up to about 30 (my)m or more deep. A dielectric film, such as a polyimide film is placed over the etched surface so as to trap air in each individual pit. A conducting upper layer is then superimposed over the dielectric film. When a potential is applied between the substrate and the upper layer the upper layer is driven into motion and enhanced by the vibrations of the air pockets. Alternatively a smooth substrate may be employed in conjunction with an etched dielectric film to achieve the same result. These transducers are useful for non-destructive testing of large structures or for medical diagnostic and therapeutic purposes, without the need for a liquid or gel coupling agent.