Terahertz imaging super-resolution for documental heritage diagnostics

Terahertz (THz) imaging is a non-invasive tool for cultural heritage diagnostics, but its spatial resolution is limited by diffraction. This study presents a super-resolution technique using structured illumination with a knife-edge (KE) in a reflective THz time-domain spectroscopy (THz-TDS) setup. By modulating the THz beam with a KE placed 150μm from the sample, spatial resolution is enhanced beyond the Rayleigh limit. Experiments on cinnabar (HgS) and carbon black mock-ups validate the method across 0.3 to 0.9THz frequencies, showing sharper images at higher frequencies due to smaller beam waists. KE-based super-resolution reduces blurring and noise while preserving THz imaging’s non-destructive nature. This advancement offers sub-diffraction insights for analyzing historical documents, artworks, and multilayered artifacts.