3D Printed Quasi-Fresnel Lens with Oblique Incidence for Sub-Terahertz Near-Field Imaging

In this paper, a 3D printed quasi-Fresnel lens with oblique incidence is proposed for sub-Terahertz (THz) near-field imaging. The proposed lens can focus the spherical wave to a focal point on the other side with an incident angle of 30°. The design process is based on the discrete dielectric lens using a uniform dielectric post as a unit cell (UC), and its period is minimised to generate a nearly continuous surface. Phase distribution is calculated using Fermat's principle. The printed prototype is measured by a THz camera, and a focal spot is generated.