Three-dimensional terahertz imaging with sparse multistatic line arrays

Many established terahertz imaging modalities are on one side restricted by the tradeoff between resolution and field of view such as in the case of focal plane arrays and on the other side suffer from a limited depth of field such as in the case of quasi-optical terahertz imaging configurations. Furthermore, typical scanning solutions require time-consuming measurement procedures and restrict significant potential industrial deployments of terahertz imaging technology. Imaging with sparse multistatic line arrays in combination with digital beam forming (DBF) techniques enables us to overcome these limitations and offer three-dimensional (3D) terahertz image reconstructions of the object. This contribution addresses the design of such terahertz imaging systems from a general point of view with the focus on the design of sparse line arrays, while considering objects scattering properties. Based on this design concept, the realization of a novel highly sparse 3D terahertz imaging system is discussed. The sparse line array of the system is operating within a frequency range from 75 to 110 GHz and is used in combination with a conveyor in order to generate a synthetic sampling aperture. The system is capable to generate 3D terahertz images with tens of megavoxels at feed motions of up to a few 10 cm/s. Also, a sparse array design in regard to an imaging system operating at 240 GHz with integrated SiGe sensor elements is discussed. In addition, three different DBF algorithms are compared in regard to their computational efficiency.