Powder retection with T-ray imaging

Pulsed THz imaging systems have a number of potential advantages in inspection applications. They provide amplitude and phase information across a broad spectral range in the far-infrared, and many common packaging materials are relatively transparent in this frequency range. We use T-ray imaging to allow the identification of different powdered materials concealed inside envelopes. Using the terahertz spectral information we show that different powders may be uniquely identified. Different thicknesses of the powders are imaged to investigate the influence of scattering on the measured THz pulses and the classification model is extended to allow it to identify different materials independent of the material thickness.