Fast wavelength modulated TDLAS imaging system for flame monitoring

In this paper, a fast wavelength modulated tunable diode laser absorption spectroscopy (TDLAS) imaging system was proposed and implemented on the hardware. Two different harmonics of the modulation frequency were utilized to improve the signal-to-noise ratio. Five fan beams of tunable laser passed through the region of interest and projected on the photodiode arrays. Only 60 photodiodes were available on the five arrays, however, 120 measurements of the modulated signals can be achieved through the cascade laser scanning. Three different distributions of temperature and water vapor's molar concentration were fabricated and reconstructed in the numerical simulations. In experiments, the positions of the flame generated by an alcohol lamp were imaged by the proposed system at a framerate of 1k frames per second and the dynamic ignition process can be captured.