Reading through closed books

Spatial resolution, spectral contrast, and occlusion are three major bottlenecks in current imaging technologies for non-invasive inspection of complex samples such as closed books. We empower the time-of-flight capabilities of conventional THz time domain spectroscopy and combine it with its spectral capabilities to computationally overcome these bottlenecks. Our study reports successful unsupervised content extraction through a densely layered structure similar to that of a closed book.