The hyperspectral image system mainly includes a hyperspectral camera (SWIR-CL-400-N25E, SPECIM, Finland), two 150-Watt halogen lamps, two focusing lenses, and a mobile sorting platform setup, as show in Figure 2 . Before collecting hyperspectral images, the lamp was turned on for about 15 min, and the white and black calibration images of the hyperspectral camera were captured. The white calibration image was acquired from a 99.9% reflectance white board (Spectralon SRT-99-100, Labsphere Inc., North Sutton, NH, USA) 30 cm below the camera. The black calibration image was acquired when the lens was completely shielded.
The hyperspectral images of samples were corrected using Equation (1):
Here, Idata represents the acquired hyperspectral image, Iblack represents the black calibration image, Iwhite represents the white calibration image, and I represents the corrected image. The exposure time and the frame rate of the hyperspectral camera were 1.8 ms and 120 f/s, respectively.
The hyperspectral images of samples were corrected using Equation (1):
Here, Idata represents the acquired hyperspectral image, Iblack represents the black calibration image, Iwhite represents the white calibration image, and I represents the corrected image. The exposure time and the frame rate of the hyperspectral camera were 1.8 ms and 120 f/s, respectively.