Millimeter-Wave and Submillimeter-Wave Imaging for Security and Surveillance

TLDR

Passive millimeter‑wave and submillimeter‑wave imaging systems (30 GHz–3 THz) offer penetration of obscurants and material identification via spectral information, enabling surveillance and contraband detection under clothing. The study develops a passive millimeter‑wave imaging system using a folded Schmidt camera for navigation and security in poor weather. The system employs a rotating mirror and polarization folding to realize the Schmidt camera optics. The resulting imager is well corrected over a wide field of view, compact, and requires few receivers, making it suitable for surveillance and security.

Abstract

Passive equipments operating in the 30-300 GHz (millimeter wave) band are compared to those in the 300 GHz-3 THz (submillimeter band). Equipments operating in the submillimeter band can measure distance and also spectral information and have been used to address new opportunities in security. Solid state spectral information is available in the submillimeter region making it possible to identify materials, whereas in millimeter region bulk optical properties determine the image contrast. The optical properties in the region from 30 GHz to 3 THz are discussed for some typical inorganic and organic solids. In the millimeter-wave region of the spectrum, obscurants such as poor weather, dust, and smoke can be penetrated and useful imagery generated for surveillance. In the 30 GHz-3 THz region dielectrics such as plastic and cloth are also transparent and the detection of contraband hidden under clothing is possible. A passive millimeter-wave imaging concept based on a folded Schmidt camera has been developed and applied to poor weather navigation and security. The optical design uses a rotating mirror and is folded using polarization techniques. The design is very well corrected over a wide field of view making it ideal for surveillance and security. This produces a relatively compact imager which minimizes the receiver count.