Bifocal dual reflector system for active terahertz imaging

Abstract

This paper introduces a method for optimizing the terahertz (THz) imaging resolution in a specified field of view (FoV) for a scanning dual reflector system (Gregory or Cassegrain system) based on the theory of field curvature. The authors built a Gregory scanning system to verify the ability of this method. The operating frequency of the verification system is 220 GHz, the FoV at a specified distance of 8 m is approximately 50 cm * 100 cm, and the imaging resolution throughout the entire FoV is better than 3 cm. Experimental results show that the imaging resolution of the classical dual reflector system can be optimized, and the proposed verification system can realize active THz imaging of the human body.

Simulation for embedded-defects foam terahertz images of active bifocal terahertz imaging system at 0.22 THz based on geometric optics

“…Figure 1(a) shows a photograph of the quasi-optical system, which includes the main mirror (MR), submirror (SR), tertiary feed reflector mirror (TFR), rotating mirror (RM), source (S), detector (D), and beam splitter (BS). The building process and principle of the system that only changes the imaging distance to achieve bifocal imaging are given in the previous work [20] . Figure 1(b) shows the parameters that describe the system.…”

“…In this paper, the THz images of foams with embedded stripe defects measured by an active bifocal THz imaging system [20] are rapidly simulated based on geometric optics (GO) and compared with the measurements. Due to the electrically large reflectors and imaging at long standoff distances, angular spectrum theory and ray tracing are used to obtain the incident field of the foam surface and the electric field distribution at the detector.…”

Broadband terahertz reflector through electric and magnetic resonances by all dielectric cylinder microstructure

“…Therefore, at this stage, there is an urgent need for efficient and miniaturized terahertz control devices to achieve modulation of terahertz pulses in terahertz systems . Among them, broadband high‐efficiency terahertz reflector is a key component of terahertz source and detector, so designing a broadband‐efficient terahertz perfect reflector has important application value …”