Hard-field THz tomography in amplitude contrast

We have performed THz tomography imaging in amplitude contrast of shaped Styrofoam phantoms, using a time-domain spectroscopy system. Object cross-sections were reconstructed at certain THz frequencies by separating the Fourier transformed frequency components and using standard filtered backprojection. The resulting images show strong edge attenuation. We introduce a modified Rayleigh roughness factor and present evidence that edge attenuation is produced by Fresnel refraction at high incidence angles and surface scattering. The image quality is best in the range 0.8-2.0THz and depends on the porosity of the Styrofoam, confirming that volume scattering is the main loss mechanism in that range.