[Study on Nondestructive Detecting Gannan Navel Pesticide Residue with Hyperspectral Imaging Technology]

Hyperspectral imaging technology is a rapid, non-destructive, and non-contact technique which integrates spectroscopy and digital imaging to simultaneously obtain spectral and spatial information. Hyperspectral images are made up of hundreds of contiguous wavebands for each spatial position of a sample studied and each pixel in an image contains the spectrum for that specific position. With hyperspectral imaging, a spectrum for each pixel can be obtained and a gray scale image for each narrow band can be acquired, enabling this system to reflect componential and constructional characteristics of an object and their spatial distributions. In this study, hyperspectral image technology is used to discuss the application of hyperspectral imaging detection technology of Jiangxi navel orange surface of different concentrations of pesticide residue changes with time relationship. The pesticide was diluted to 1 : 20, 1 : 100 and 1 : 1 000 solution with distilled water. A 1×2 matrix of dilutions was applied to each of 30 cleaned samples with different density pesticide residue. After 0, 4 and 20 d respectively, hyperspectral images in the wavelength range from 900 to 1 700 nm are taken. The characteristic wavelengths are achieved by using principal component analysis (PCA) and the PC-2 image based on PCA using characteristic wavelengths (930, 980, 1 100, 1 210, 1 300, 1 400, 1 620 and 1 680 nm) as the classification and recognition of image. Based on these 8 characteristic wavelengths for a second principal component analysis, the application of PC-2 image and appropriate image processing methods for different concentrations and different days of placing pesticide residues in non-destructive testing were applied. Using hyperspectral imaging technology to detect three periods a higher dilution of the fruit surface pesticide residues are more obvious. This research shows that the technology of hyperspectral imaging can be used to effectively detect pesticide residue on Gannan navel surface.