  Structured light (SL) systems acquire high-fidelity 3D geometry with active
illumination projection. Conventional systems exhibit challenges when working
in environments with strong ambient illumination, global illumination and
cross-device interference. This paper proposes a general-purposed technique to
improve the robustness of SL by projecting redundant optical signals in
addition to the native SL patterns. In this way, projected signals become more
distinguishable from errors. Thus the geometry information can be more easily
recovered using simple signal processing and the ``coding gain" in performance
is obtained. We propose three applications using our redundancy codes: (1) Self
error-correction for SL imaging under strong ambient light, (2) Error detection
for adaptive reconstruction under global illumination, and (3) Interference
filtering with device-specific projection sequence encoding, especially for
event camera-based SL and light curtain devices. We systematically analyze the
design rules and signal processing algorithms in these applications.
Corresponding hardware prototypes are built for evaluations on real-world
complex scenes. Experimental results on the synthetic and real data demonstrate
the significant performance improvements in SL systems with our redundancy
codes.
