Novel operating band design schemes for high-contrast passive terahertz security screening systems

Abstract

A passive terahertz security screening system utilizes the contrast of imaged targets in the terahertz band to identify concealed contraband. The variety of covered clothing textures presents a wide distribution of transmission characteristics, resulting in the diversity of high-contrast detection frequencies within the terahertz band. Thus the commonly used single operating band system modelled under one clothing texture is inadequate in multi-type clothing scenarios in practical applications. In this study, the concept of relative contrast is proposed for the detection of concealed metal contraband, and the relationship between the operating band and relative contrast is revealed. Two novel operating band design schemes, a reconfigurable multi-band single-system design and a fixed multi-band dual-system design, are presented. Computer simulation results show that these two design schemes can effectively improve the imaging contrast and enhance the detection effect of passive terahertz security screening systems.