Advanced active imaging system for fires based on terahertz electromagnetic waves: Experimental study of effectiveness in smoky and high-temperature environments

Abstract

An active imaging system for fires is proposed, based on terahertz (THz) electromagnetic waves. The purpose of this study is to assess the effectiveness of the proposed imaging system compared with an existing system based on near-infrared (NIR) radiation. An experimental study was conducted in several fire environments using both a developed THz array illuminator and an NIR system. As a result, the target object was clearly visible with THz active imaging regardless of the presence or absence of smoke, whereas the image contrast of the target deteriorated with increasing smoke density when using NIR active imaging. There were no appreciable image changes due to temperature differences. Therefore, THz active imaging using an incoherent array illuminator seems to be an effective method to ensure visibility in a fire environment such as a room filling with smoke in the early stages of a fire.