Fresnel focusing with short ultrasonic pulses

This paper describes an investigation of different Fresnel focusing techniques in the case of short excitation signals, for circular and for rectangular arrays. A study of the impulse response is performed and a typical impulse echographic process, which appears only in transmit-receive mode, is emphasized. Comparison between 2-state amplitude modulated Fresnel array and more sophisticated array combining delay correction and a 2-state amplitude modulation is recorded. And it shows that great improvements in the focusing process is obtained with this last technique.