Experimental study on the influence of illuminance and spectral wavelength on image and spectral parameters of coal and gangue

Abstract

ABSTRACT To reveal the effects of illuminance and spectral band changes on coal and gangue image and spectral parameters, and to provide fundamental data for using multispectral images in coal and gangue recognition research, this paper analyzes image parameters (standard deviation, skewness, entropy, and contrast) and the spectral parameter using experimental methods, and compares the differences between coal and gangue parameter values. First, we analyze the variations of parameters, and find that as illuminance increases, the image parameters fluctuate in shorter spectral bands but change slightly in longer ones, while the spectral parameter increases across all bands; as wavelength increases, the image parameters rise or fluctuate within 546–622 nm, while the spectral parameter increases; in other bands, all parameters initially decrease before stabilizing. Second, we compare parameter deviation by normalizing coal and gangue values, and find that coal and gangue have the largest deviation in the spectral parameter, and the smallest in skewness; they have the largest fluctuation range in entropy, and the smallest in skewness; image parameters are more sensitive to changes in illuminance and spectral bands than the spectral parameter; and the deviations in both image and spectral parameters are larger at 7000lux and 585 nm than at other settings.