Terahertz time-gated spectral imaging for content extraction through layered structures.
Spatial resolution, spectral contrast and occlusion are three major bottlenecks for non-invasive inspection of complex samples with current imaging technologies. We exploit the sub-picosecond time resolution along with spectral resolution provided by terahertz time-domain spectroscopy to computationally extract occluding content from layers whose thicknesses are wavelength comparable. The method uses the statistics of the reflected terahertz electric field at subwavelength gaps to lock into each layer position and then uses a time-gated spectral kurtosis to tune to highest spectral contrast of the content on that specific layer. To demonstrate, occluding textual content was successfully extracted from a packed stack of paper pages down to nine pages without human supervision. The method provides over an order of magnitude enhancement in the signal contrast and can impact inspection of structural defects in wooden objects, plastic components, composites, drugs and especially cultural artefacts with subwavelength or wavelength comparable layers.
Department of Media arts and Sciences, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Albert
A
Redo-Sanchez
Department of Media arts and Sciences, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Barmak
B
Heshmat
Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Alireza
A
Aghasi
Department of Media arts and Sciences, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Salman
S
Naqvi
Department of Media arts and Sciences, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Automation, Tsinghua University, Beijing 100084, China.
Mingjie
M
Zhang
Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Justin
J
Romberg
Department of Media arts and Sciences, MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Ramesh
R
Raskar