Subsurface Near-Field Scanning Tomography

Abstract

The scanning tomography method is developed for electromagnetic sounding of a 3D structure of an inhomogeneous dielectric half-space. It is shown that known methods of physical diagnostics are suitable for this tomography with the depth of analysis from nanometers at optical frequencies up to several kilometers at ultralow frequencies. The areas of application include nanophysics, biological and medical diagnostics, subsurface remote sensing in geophysics and geology, etc. This approach is realized in the microwave scanning tomography of living tissues where a subwavelength resolution is achieved.

Inverse scattering problems in subsurface diagnostics of inhomogeneous media

“…In some methods of subsurface tomography (radiometry, impedance, low-frequency sounding of earth crust [2], total-internal-reflection tomography [3]) such problems have been reduced one-dimensional integral equations by 2D Fourier transform over transversal co-ordinates. This approach has been developed in [4] for the scheme of measurements with the fixed source-receiver vector δr , when the structure of the probing field is invariable relative to the receiver position, and it appeared possible to express the k-space spectrum (2D inverse Fourier transform over x and y) of the scattered field in k th layer in frameworks of the Born approximation:…”

“…Among them, inverse scattering problems can be also applied in various methods of electromagnetic tomography 3D distributions of media parameters [2][3][4][5] and in profile retrieval of one-dimensional inhomogeneities [6][7][8][9][10]. In frameworks of electromagnetic perturbation theory, inverse scattering problems in has been reduced to the non-linear integral equation that can be solved iteratively at each step as linear Fredholm integral equations of the 1 st kind, beginning with the Born approximation using, for example, Tikhonov's method of generalized discrepancy.…”

Perfect lens tomography

“…This representation makes it possible to reduce the 3D integral equation to 1D integral equation relative to the depth profile of the lateral spectrum of 1 ε [3]: (3), the mathematically consistent algorithm based on the Tikhonov's method of generalized discrepancy has been developed in [2]. The regularization parameter is determined by the integral error of measured lateral spectrum of the scattered field.…”

“…The general scheme of the scanning tomography [2] based on the lateral decomposition of 3D integral equations that has been developed for the near-field inverse problem of scattering in [3], can also be applied in the proposed method of perfect lens tomography. The method of data acquisition at the condition of the fixed emitter-receiver distance, invented in [3], reduces the 3D integral equation for the scattered field to a convolution equation over lateral co-ordinates for an arbitrary probes' position (including the near-field zone) relative to the studied inhomogeneous region in multilayered media.…”

Performance Enhancement of Microwave Sub-Wavelength Imaging and Lens-Type Doa Estimation Systems by Using Signal Processing Techniques (Invited Paper)

“…Microwave imaging with a resolution at the sub-wavelength level is attractive in many applications, which include: high-directivity arrays used in modern self-tracking wireless communication systems [5]; electromagnetic sounding of 3D structures of an inhomogeneous dielectric half-space for nanophysics, biological and medical diagnostics [6]; and short-range Ultra-wide Band (UWB) radar imaging [7], to name a few. Many approaches have been proposed for microwave sub-wavelength imaging, including nonlinear metamaterial elements [8], periodic layered metal-dielectric structures [9], metallic screens comprised of closely spaced and unequal slits [10], Fresnel zone-plates [11], etc.…”