A Novel Hyperspectral Feature-Extraction Algorithm Based on Waveform Resolution for Raisin Classification.

Near-infrared hyperspectral imaging technology was adopted in this study to discriminate among varieties of raisins produced in Xinjiang Uygur Autonomous Region, China. Eight varieties of raisins were used in the research, and the wavelengths of the hyperspectral images were from 900 to 1700 nm. A novel waveform resolution method is proposed to reduce the hyperspectral data and extract the features. The waveform-resolution method compresses the original hyperspectral data for one pixel into five amplitudes, five frequencies, and five phases for 15 feature values in all. A neural network was established with three layers-eight neurons for the first layer, three neurons for the hidden layer, and one neuron for the output layer-based on the 15 features used to determine the varieties of raisins. The accuracies of the model, which are presented as sensitivity, precision, and specificity, for the testing data set, are 93.38, 81.92, and 99.06%. This is higher than the accuracies of the model using a conventional principal component analysis feature-extracting method combined with a neural network, which has a sensitivity of 82.13%, precision of 82.22%, and specificity of 97.45%. The results indicate that the proposed waveform-resolution feature-extracting method combined with hyperspectral imaging technology is an efficient method for determining varieties of raisins.