Quantitative methane leak imaging via wavelength spatial-encoding single-pixel imaging

Quantitative methane leak imaging based on line-of-sight path-integrated concentration is constrained by the difficulty of combining spectroscopic selectivity with low-cost spatial detection. Here, we present a WMS-assisted spatially encoded single-pixel imaging method that converts two-dimensional methane distributions into a sequence of spatially encoded measurements acquired by a single WMS detector. A continuously rotating transmissive mask provides high-throughput and high-speed spatial encoding, while second-harmonic demodulation extracts methane-selective absorption signals. During imaging, the laser is operated at the calibrated absorption peak near 1653.7 nm, eliminating repeated wavelength scans for individual mask patterns and reducing pixel-wise WMS imaging to single-channel detection. The system reconstructs 64 × 64 line-of-sight path-integrated concentration maps at 12 Hz. A linear response with R 2 = 0.998 is obtained over the range of 500–7000 ppm ⋅ m, and static measurements show good quantitative consistency. Dynamic experiments further resolve plume evolution under different methane concentrations, release rates, and airflow disturbances. The proposed architecture provides a compact and low-cost solution for real-time quantitative methane leak imaging.