Real-Time Quantitative Reconstruction Methods in Microwave Imaging

Direct inversion methods, also known as linear inversion methods, such as holography and diffraction tomography are the working horses of microwave imaging. They provide fast qualitative estimates of an object’s shape and electrical contrast. However, these traditional methods cannot be used as linearized solvers at the core of nonlinear iterative reconstruction schemes because of their inability to provide a quantitative estimate of the electromagnetic constitutive parameters. In the past decade, advances have led to two powerful approaches to linear quantitative inversion, specifically developed for microwave imaging based on scattering-parameter data. These two approaches, quantitative microwave holography (QMH) and scattered-power mapping (SPM), provide quantitative images in real time. Thus they add new capability to real-time microwave imaging and offer new linearized core solvers for nonlinear reconstruction schemes. The performance of QMH and SPM is compared utilizing three different strategies of acquiring the resolvent kernel in the forward model: analytical, simulated, and measured. The results ascertain that the quantitative reconstruction is attainable only with experimentally acquired resolvent kernel.