Fig. 1. Methane gas imaging system based on a shortwave infrared camera

Fig. 2. Incident angle on galvanometric scanning mirror

Fig. 3. Flowchart of dual-band gas detection method

Fig. 4. Comparison of dual-band image differential data processing results. (a) Differential image and intensity distribution obtained by subtracting the 1653.72 nm band image from the 1653.62 nm band image; (b) differential image and intensity distribution obtained by subtracting the 1653.62 nm band image from the 1653.72 nm band image; (c) differential image and intensity distribution obtained by subtracting the 1653.82 nm band image from the 1653.72 nm band image

Fig. 5. Comparison of ratio and logarithmic processing results of dual-band images. (a) Ratio image and intensity distribution obtained by dividing the 1653.62 nm band image by the 1653.72 nm band image; (b) logarithmic image and intensity distribution obtained by dividing the 1653.62 nm band image by the 1653.72 nm band image

Fig. 6. Methane multi-gas cloud scanning experimental scenario

Fig. 7. Imaging intensity distribution of methane multi-gas clouds at different volume fractions under different laser wavelengths. (a) 1653.62 nm wavelength; (b) 1653.72 nm wavelength

Fig. 8. Imaging comparison test results of methane gas with different volume fractions. (a) Ratio image and intensity distribution obtained by dividing the 1653.72 nm band image by the 1653.62 nm band image; (b) logarithmic ratio image and intensity distribution obtained by dividing the 1653.72 nm band image by the 1653.62 nm band image

Fig. 9. Fitting results between dual-band image processing results and gas volume fraction. (a) Fitting result between differential value and gas volume fraction; (b) fitting result between ratio and gas volume fraction; (c) fitting result between logarithmic value and gas volume fraction