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Time reversal imaging of 3-D objects based on time focusing conception

A new time-reversal imaging method for 3-D objects based on time focusing (TRITF) conception is presented in this work. Compared with the traditional time-reversal imaging method based on the field values at a given instant in the imaging domain, TRITF give the imaging results based on the maximum focusing values at the optimal focusing instants of the retransmitted time-reversal back-propagating waves. Especially, for imaging of multi-targets whose scattering signals may overlap in the time axis at the receivers, a grouping technique is devised, which divides the receiving array, namely the time reversal mirror (TRM), into a group of sub-arrays or macro-elements that would separate out the corresponding target signal from the mixing signal at the target places. Local normalization schemes are employed to favor farer or weaker targets that may be swamped by nearer or stronger targets, and to permit all targets displayed at the same brightness. Simulation results show that the proposed method is promising for real applications.