Video-rate terahertz spectral imaging of spherical surfaces

Curved surfaces present a specific challenge for reflection-mode imaging due to the difficulty in collecting the returning light. In the case of imaging using terahertz time-domain spectroscopy (THz-TDS), this is compounded by the lack of large-scale array detectors, limiting imaging to slow, point-by-point scanning. For approximately spherical targets, THz imaging systems have been developed to reduce the complicated task of steering the beam normal to the surface to simple translation or gimbal control. Meanwhile, single pixel compressed sensing techniques have been demonstrated in the THz regime to form images with a reduced number of total acquisitions. Here, we present a system which combines spherical scanning geometry with a compressed-sensing design and fast ECOPS acquisition to perform video-rate THz-TDS imaging on curved surfaces.