Terahertz real-time imaging for non-destructive detection of concealed small insects

Rapid non-destructive detection of concealed small insects is essential for biosecurity and customs inspection, but remains challenging for conventional imaging techniques. Terahertz (THz) radiation, with its low photon energy, high penetration through many packaging materials, and strong sensitivity to water, offers an attractive solution. Here we investigated two THz real-time imaging systems with focal plane array for insect detection: a lens-free system A at 0.1 THz and a lens array system B at 0.34 THz. The operating frequencies of both systems fell within the 0.1–0.5 THz biological low-water absorption window, ensuring signal quality and enabling scan-free, high-rate imaging under free-space and occluded conditions. Quantitative resolution tests show that the system B at 0.34 THz achieves a spatial resolution of 0.25 lp/mm, significantly surpassing the diffraction-limited performance of the 0.1 THz system. Imaging experiments on live insects, replicas, and resin-embedded specimens demonstrate that system A features a simple structure, excellent contrast, and strong robustness, though limited by diffraction effects in resolving detailed structures. System B, optimized with lens array and adapted to high-frame-rate cameras, enables characterization of insect anatomy and features. Specifically, a physics-guided image algorithm incorporating absorption correction, total-variation regularization, and iterative deconvolution further improves contrast and edge sharpness. This research achieves real-time high-resolution imaging of live insects for the first time, capable of penetrating occlusions while distinguishing insects from interference objects. These results provide novel solutions for logistics quarantine and biological monitoring, filling a gap in rapid, non-destructive imaging of shielded living organisms.