Automatic estimation of varying continuum background emission in laser-induced breakdown spectroscopy

In laser-induced breakdown spectroscopy (LIBS), plasma emission is extremely unstable because of many factors, such as the fluctuation of laser energy, inhomogeneity of sample surfaces, and variable distance between lens and samples. Therefore, the detection and correction of varying continuum background emission are not easily accomplished. The aim of this work is to present a method that can automatically estimate and correct varying continuum background emission, which is representative in laser-induced plasma. In this method, we first find all minima on a spectrum, and then deduct the unreasonable minima by a proper threshold. Finally, we use one or multiple polynomial functions through the minima left to approximate the continuum backgrounds. The validity of this method was evaluated by using several spectra with different complexities and wavelength ranges. We also applied this method to optimize the measurement time delays of detectors. In addition, for five aluminum alloy samples, we compared their elemental calibration cures between original spectra and background-corrected spectra. Experimental results proved that the method proposed in this paper can well estimate varying continuum backgrounds over a wide range of wavelengths.