Research on improving the accuracy of laser-induced breakdown spectroscopy analysis by considering plasma attenuation rate characteristics.

BACKGROUND: Laser-induced breakdown spectroscopy (LIBS) is widely applied in various fields, but accuracy issues limit its further development. Signal uncertainty is the main reason that affects the accuracy of LIBS measurements, but the signal uncertainty caused by different plasmas exhibiting different radiation attenuation rates during the integration time is often neglected. There is a need for a method to correct LIBS signals by quantifying the radiation attenuation rate. RESULTS: In order to reduce the uncertainty due to different plasma attenuation rates, the attenuation rates of the energy level radiation emitted by plasma are described as attenuation coefficients, which are obtained by linearly fitting the logarithm of the time series of line intensities. The calibration curve was corrected by attenuation coefficients for 4 major elements in 7 standard samples. The results showed that the line intensities corrected by attenuation coefficients showed better linearity with elemental concentrations. SIGNIFICANCE: This study is important for improving the accuracy of LIBS measurements, and is also significant for modeling the plasma radiative attenuation of laser-induced plasma, and is expected to be applied to spectrometers that can obtain time series spectra of the same plasma to improve the accuracy of in-situ fast LIBS analysis.

Absolute phase retrieval for colored objects based on three phase-shifting amount codes.

We propose an absolute phase retrieval method based on three phase-shifting amount codes (3-PSA-codes) to measure the colored object with one additional pattern. 3-PSA-codes adopt the coding concept of 3-digit-codes, in which the code elements of three consecutive periods are treated as a unique code word for one period. However, to measure the colored object more effectively in the proposed method, each code element is embedded into the PSA domain and retrieved from the phase difference. Fringe patterns for the wrapped phase are artfully employed in the code element retrieval. Hence, for the first time, to the best of our knowledge, the code element related to the phase can be determined by one additional pattern. It breaks the constraint that temporal methods require multiple additional patterns to overcome the adverse effect of the surface color of objects on absolute phase retrieval. Experimental results demonstrate that the proposed 3-PSA-codes have strong robustness in the measurement of the colored object.