The spectra correction is essential for the quantification of laser induced breakdown spectroscopy in combustion environments, due to the uncertainties in plasma morphology. In this work, we determined the plasma morphology using a CCD camera and introduced the spectral correction method based on plasma images in a combustion environment. Plasma length, width, volume, and location were extracted from the plasma images. Using a back-scattering setup, the contribution of plasma location fluctuation to the total spectral fluctuation was mitigated. The integral intensity of plasma image was used as a proxy of total number density to correct the spectra. Linear relationships were established between the integral intensities of plasma images and the spectral intensities, under different laser energy levels and gas temperatures. The image-based correction method can significantly reduce the fluctuation of raw spectral intensities when the laser energy was below 240mJ. Compared with the correction method based on total spectral areas, the proposed method offered significant improvements in the low energy region, which held the promise to reduce the signal fluctuation in combustion environment while preserving the spatial resolution and mitigating the flow disturbance.

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The monitoring of energy deposition behavior during the plasma formation process is the basis of recently developed laser-induced breakdown thermometry techniques. Utilizing the acoustic waveforms from laser-induced plasmas, a method to monitor the deposited energy was proposed. The linear relationships between the acoustic energy and the deposited energy were established under four different focal lengths. After the distortions in the sound propagation were corrected, the applicable range of this method was extended to a deposited energy from 10 to 240 mJ. The further spectra analysis in the deposited energy space suggested that the total number density of excited species increased with the deposition energy, without significant fluctuations in plasma temperature in the high-energy region.