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.