Scalable Multi-Target Illusion via a Segmented Spatiotemporal Metasurface.

A kaleidoscope converts a few physical fragments into numerous images through repeated mirror reflections, yielding visual scene richer than the objects themselves. This optical phenomenon shows that a perceived scene can be reconstructed by beam redirection and spatial reorganization. Inspired by this principle, we propose a scalable multi-target illusion based on a segmented spatiotemporal metasurface. It acts as an electromagnetic kaleidoscope and operates through the proposed parallel-sequence spectral translation mechanism (PSTM): one physical aperture is partitioned into independently driven segments, each loaded with a distinct time-varying bias sequence. Under linear frequency-modulated signal illumination, PSTM translates the echo spectrum into multiple independently coded frequency-shifted components. After signal processing by the detector, these sequence-translated spectral components are reconstructed as scalable false targets in the range-velocity plane. Moreover, the reflection amplitudes of individual targets can be further tuned by aperture allocation. A programmable metasurface is designed and fabricated to validate the concept. Experiments demonstrate the generation of two, three, four, and five false targets, with the measured range-velocity features closely matching theoretical predictions. This work extends metasurface-based illusion from single-response modulation to scalable multi-target scene reconstruction with controllable multidimensional features, providing a flexible framework for electromagnetic illusion generation from a single physical aperture.