High-speed non-spatial scanning terahertz three-dimensional imaging

Terahertz (THz) imaging offers unique advantages for nondestructive evaluation, security screening, and biomedical diagnostics due to its spectral fingerprinting of low-energy excitations, high penetration. However, THz focal plane arrays are expensive and lack spectral and volumetric resolution, while scanning-based THz-time-domain spectroscopy (TDS) systems remain bulky and slow. Here, we present a compact, high-speed single-pixel THz 3D imager (THZ-TOFSPI), which integrates a DMD-based optically controlled THz spatial encoder with a reflective fiber-coupled layout. To overcome mechanical delay limitations, we introduce an ultra-stable voice-coil-motor-driven oscillating delay line (VCM-ODL), enabling THz-TDS sampling at up to 120 Hz with excellent amplitude and phase stability (0.39% and 0.0013 ps). Leveraging compressed sensing, the system achieves 3D imaging of a 16 × 16-pixel target in 5.3 s-over 1000× faster than traditional point-scanning THz-TDS. The lightweight and scalable THz-TOFSPI system offers the possibility of large-area, high-resolution 3D imaging in industrial inspection, security, and biomedical applications, with potential pathways toward integration into robotic, handheld, and wearable platforms.