High-angular-resolution adaptive terahertz scanning imaging via dynamic zoom optics and beam steering metasurfaces

Limited by the output power of available terahertz (THz) sources, detector sensitivity, and the resolution of focal-plane arrays (FPA), THz imaging systems face a critical challenge in simultaneously achieving a wide field-of-view (FOV) for multi-target detection and high angular resolution for single-target discrimination. In this work, we present an adaptive THz scanning imaging system that integrates a dual-lens zoom objective (numerical aperture, NA = 0.66-0.65), a 64 × 64 FPA with a pixel size of 0.4 mm × 0.4 mm, and a frequency-dispersive metasurface for beam steering. The zoom lens provides continuous FOV adjustment from ±8.1° to ±4.1°, while the metasurface enables two-dimensional scanning via frequency tuning (<i>θ</i>-direction) and mechanical rotation (<i>φ</i>-direction), producing a collimated beam with a divergence of 2.5°. Operating in the 0.332-0.358 THz band, the system achieves an angular resolution of 0.2°. By combining the zoom optics, the THz FPA, and the metasurface, the system delivers high-quality imaging through obscurants such as smoke and camouflage, supporting both wide-area multi-target detection and high-resolution single-target discrimination.