Experimental investigation on improvement of range resolution in B-mode images by inverse filtering technique

For B-mode ultrasonic tomography, an active control radiation method was developed for a ringing-less pulse by a pseudo-inverse filtering technique. A low center frequency pulse has a high range resolution if it does not have ringing. The pseudo-inverse filtering technique in the discrete-Fourier-transform (DFT) domain compensates well for the frequency characteristic of an ultrasonic system. Using this active waveform control technique, one can radiate ringing-less short pulses in any medium. The active method is much better than the usual passive signal processing methods such as deconvolutions in the human body. Despite a low center frequency pulse, one can get a high range resolution image by the method. Experiments were carried out mainly in degassed water and also in castor oil, which has a high attenuation coefficient. The improvement of the range resolution in the B-mode ultrasonic images was studied