Bifocal Gregorian reflector antenna designed for terahertz imaging

Due to the size of the mirror and scanning region, the beam quality and imaging speed of the active scanning terahertz imaging system based on the mirror are limited. Based on the theory of astigmatism and field curvature of physical optics, by simple calculation and adjustment of the mirror type parameters, we can keep the system and the measured position and realize the dual focus at the measured position to improve the quality of imaging system. The simulation results show that the proposed method can realize dual focus scanning imaging and optimize the imaging quality.