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An active frequency-modulated continuous wave (FMCW) terahertz (THz) system has been developed to image objects in millimeter-scale resolution in three dimensions. The two-dimensional (2-D) aperture synthesis enables the improvement of cross range resolution, and its high range resolution is achieved through the use of the broadband sweep signal, whose frequency ranges from 514 to 565 GHz. The 3-D data are sufficiently focused by the wavenumber domain approach derived for the dechirped data. We present the THz 3-D imaging strategy using synthetic aperture radar (SAR) techniques, the related theoretical background and the experimental results in this paper.

We present a simulation and data-processing framework that incorporates full 3-D configuration, simulation, and reconstruction functionalities for hybrid synthetic aperture THz systems, which combine mechanically scanned real imaging projection (1-D) and synthetic imaging reconstruction (2-D). The simulation is based on a ray-casting approach including models for reflections at rough surfaces and angular antenna sensitivity. A near real-time GPU reconstruction is introduced to process large amounts of data in parallel. Techniques for fast fusion of reconstructed data from several acquisition directions are presented. They serve as basis to visualize a fully consistent 3-D object. The modular framework allows a fast, easy, and efficient evaluation and prediction of system properties including scattering behavior for these types of scanner setups.