ONE CHANNEL ACOUSTIC 3D IMAGING DEVICE OF LARGE APERTURE WORKING IN ECHOGRAPHIC MODE

摘要

Imaging devices generally use a 1D or 2D array of transducers to focus anywhere acoustic waves in space. The resolution of such systems depends on the aperture of the array. However, these systems require a large number of transducers to get optimal aperture and then complex multichannel electronics to control the focalization. In this work, an alternative one channel imaging device is proposed. It uses only one piezoelectric transducer glued to an aluminium plate of non-regular geometry. The plate is used as an acoustic cavity which mixes the flexural waves emitted by the transducer. Part of waves radiates into the air and the plate is then comparable to an acoustic aperture of large dimension. In emission mode, the focusing process is realized over a large frequency bandwidth from 5 kHz to 100 kHz. To focus acoustic waves anywhere in front of the plate, the electric impulse responses used to drive the piezoelectric transducer are computed from the knowledge of the vibration patterns of the plate. For a given focusing position a corresponding impulse response is computed. Finally beam steering is achieved and the acoustic waves should be focused anywhere in front of the plate. This result is comparable to a 2D transducer array. Finally, using a single microphone receiver working in echographic mode our imaging device is able to locate any object placed in front of it.