In-situ and fast classification of origins of Baishao (Radix Paeoniae Alba) slices based on auto-focus laser-induced breakdown spectroscopy

In this Letter, a rapid origin classification device and method for Baishao (Radix Paeoniae Alba) slices based on auto-focus laser-induced breakdown spectroscopy (LIBS) is proposed. The enhancement of spectral signal intensity and stability through auto-focus was investigated, as were different preprocessing methods, with area normalization (AN) achieving the best results-increasing by 7.74%-but unable to replace the improved spectral signal quality pro-vided by auto-focus. A residual neural network (ResNet) was used as both a classifier and feature extractor, achiev-ing higher classification accuracy than traditional machine learning methods. The effectiveness of auto-focus was eluci-dated by extracting LIBS features from the last pooling layer output using uniform manifold approximation and projec-tion (UMAP). Our approach demonstrated that auto-focus could efficiently optimize the LIBS signal, providing broad prospects for rapid origin classification of traditional Chi-nese medicines. & COPY; 2023 Optica Publishing Group