This paper studied the classification method of tea using portable Laser Induced Breakdown Spectroscopy (LIBS) system to distinguish different kinds of tea with similar appearances from each other. The basic classification algorithm was Random Forests, and an improved data processing method of spectroscopies was presented to increase the classification accuracy. The provenance of tea was set as the classification label because that tea produced in some specific areas may have higher economic value. Fifteen kinds of green tea were collected from the market, of which nine were produced in Guizhou Province and the other six were produced in six other provinces. The spectral integral normalization method, and element window filtering method were proposed to process spectral normalization and screening. The parameters of Random Forests algorithm were optimized to achieve both high accuracy and low time cost. Finally, the classification accuracy of green tea from Guizhou Province was 97.75%, and green tea from different provinces was 100%. The research results of this paper made it a bright future of LIBS in application of tea quality appraisal and other food industry.
This paper studied the data process methods of Laser-Induced Breakdown Spectroscopy (LIBS) and proposed a spectral intensity correction method utilizing laser energy monitoring and plasma morphology imaging, combined with neural network algorithm to improve the spectral stability. We set up a LIBS system, which had a laser beam sampling module to monitor laser output energy and a CMOS camera imaging module to capture plasma flame outlines. A back propagation neural network (BPNN) model was designed for standardizing the spectrum to a lower relative standard deviation (RSD) of emission line intensities, in which training spectrum, sample energy and image parameters were inputs, and the average of all the training spectrums were outputs. This method was applied in both aluminum and soil LIBS tests, and got effective results in reducing spectral intensity fluctuations. This data processing method not only provided a practical access to acquire stable spectrum information for both qualitative and quantitative LIBS analysis but also showed a bright future of combining LIBS data processing with machine learning methods.
The identification of tea varieties and producing areas has an increasingly important market value as the continuous development of the tea industry. A method combining laser induced breakdown spectroscopy (LIBS) and neural network algorithm is proposed in order to identify tea varieties and producing areas rapidly and accurately. In this paper, LIBS spectra of six major tea varieties and eight green tea samples from different producing areas in the range of 200-430 nm are collected, elemental analysis and spectra pre-processing are performed, principal component analysis (PCA) method is applied to select the features, and error back propagation (BP) neural network is used to model the tea classification problem. Key issues such as feature dimensions, network parameters, network structure, and the size of dataset are discussed. The result shows that the best model accuracy reaches 100%, indicating that this method can be used to establish a practicable tea classification model as long as sufficient data are obtained, which is feasible for solving the problems of the identification of tea varieties and producing areas.
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