Illumination Aspects in Active Terahertz Imaging

Our paper focuses on illumination aspects in active terahertz imaging. First, we introduce our fast 620-GHz camera and discuss imaging with focused illumination. After that, we switch to global illumination and discuss its benefits and drawbacks. The loss in intensity-compared to focused illumination-does not fully come to bear on the dynamic range because losses at the beam-splitter and back-reflection by the optics into the detection path can be avoided. The adaptation to the angular range accepted by the detector optics is more difficult, but flexibility is gained with separated illumination and detection paths. An outlook is given on a 812-GHz camera currently being developed and exhibiting global illumination and a 32-pixel detector for improved frame rates. Furthermore, a concept for high-accuracy topography reconstruction from multiple terahertz images taken with several angles of illumination is discussed.