Fast 3-D Qualitative Method for Through-Wall Imaging and Structural Health Monitoring

A fast non-iterative 3-D imaging method is developed which incorporates several critical approximations to overcome computational burden and data collection constraints associated with imaging layered media. The method first invokes dyadic Green's function to relate the object reflectivity function (or image) to the collected data. Then, calculating the reflectivity function requires solving a computationally-intensive and ill-posed inverse problem. The data collection constraints and layered media modeling uncertainties also add to the complexity associated with this inverse problem. To address these challenges, a set of approximations are considered which simplify the imaging problem and cast it into a de-convolution problem with much less computational burden which is implemented using fast Fourier transform. The performance of the method is verified for through-wall imaging and structural health monitoring, indicating that it is reasonably tolerant to constraint associated with data collection limitations and modeling inaccuracies.