Passive Terahertz Wave Imaging of Concealed Threats with a Single Semiconductor Bolometer and an Array of Superconducting Bolometers

Abstract

Detection of concealed threats is of prime importance for public security. In short range applications, passive imagers operating at millimeter wavelengths have been demonstrated to fulfill this task. However, for larger distances, they will suffer from limited spatial resolution and sensitivity. In this paper we demonstrate passive indoor imaging at a distance up to 7 meters using radiation in the teraherz range and a commercial Silicon bolometer. Images with a resolution of about 2 cm were taken using a mechanical scanner, which moved the field of view of the detector across the object under investigation. Although it was possible to detect a metal weapon hidden under clothing, the frame time was restricted by the sensitivity of the bolometer. To increase the imaging speed, we implemented a focal-plane array of millimeter-wave superconducting transition-edge sensors red out via superconducting quantum interference device current sensors. Implementation of the array drastically reduced the acquisition time.