Fig. 1. Effect of scattering coefficient term on harmonic signal. (a) First harmonic signal; (b) second harmonic signal

Fig. 2. Simulated signal and gas concentration. (a) Normalized second harmonic signal; (b) relationship between measured gas concentration and real concentration

Fig. 3. Simulated signal and particle concentration after eliminating gas absorption effect. (a) First harmonic amplitude; (b) relationship between the mean of amplitudes and the mass concentration of particulate matter

Fig. 4. Schematic of experimental verification system based on light intensity modulation

Fig. 5. Measured original signal

Fig. 6. Spectrum measured by LIM

Fig. 7. Experimental measurement results. (a) First harmonic signal measured by LIM; (b) comparison of eigenvalue and value measured by dust meter

Fig. 8. Schematic of experimental system for synchronous measurement of gas and particle concentrations

Fig. 9. Experimental and verification results of WMS-LS method. (a) Normalized second harmonic amplitude; (b) comparison of water vapor volume fraction measured by WMS-LS with that by temperature-humidity sensor

Fig. 10. Amplitudes of first harmonic R1f of scattered light signals

Fig. 11. Experimental and verification results of WMS-LS method after eliminating gas absorption effect. (a) Amplitude of first harmonic; (b) comparison of mass concentration of particulate matter measured by WMS-LS with that by dust meter