February 29, 1996
A real-time high speed pulse-echo imaging system capable of parallel processing multiple image lines is presented. The system uses transmitter arrays with coded-excitation. Mathematically, it can be formulated into a discretized linear image equation via a newly introduced discrete spatio-temporal model of the received sampled echo data. The implementation of the system is realized by a transversal filter bank with each filter designed for processing echoes from a specific direction in the region of interest. The filter coefficients are derived from a pseudo-inverse image operator obtained from the image equation. Preliminary results show that, in addition to being well-suited for real-time parallel processing implementation, the transversal filters are capable of decoupling echoes from different directions before performing matched filtering. Thus, the proposed approach eliminates a major drawback of conventional coded-excitation systems designed based only on matched filtering. Without complicating the transducer array, our results also show that the new system offers high spatial resolution which may exceed the conventional diffraction limit. Since the system complexity is primarily in the filter bank which can be implemented by using VLSI technology, the proposed approach allow us for implementing very high speed pulse-echo imaging systems with much lower hardware costs. This leads to a possible solution to the currently unsolved real-time 3D imaging problem. The method may also find many applications in SONAR, NDE, and biomedical imaging areas.