Cotton lint trash is a serious problem in the textile industry. The principle upon which this research is based is that different materials have different spectral absorption, excitation, and emission characteristics. Although white-light imaging is widely used to detect colored foreign-matter contaminants, or "trash", it is almost useless for detecting white trash. The objective of the research described in this paper was to achieve the best trash detection result possible in the spectral range from 250 to 850 nm. Diffuse reflection spectroscopy indicated that the differences in gray value between lint and white trash become significant in the ultraviolet (UV) range, especially from 250 to 350 nm. Fluorescence spectroscopy gave reliable evidence that the UV-induced fluorescence intensity of white trash is much stronger than that of lint. To detect several types of trash simultaneously, the interaction of white-light imaging and UV-induced fluorescence imaging was studied. To avoid the spectral interference caused by white light in fluorescence imaging, a novel method—an alternating imaging detection method—is proposed. Experiments indicated that the advantages of both white-light imaging and UV-induced fluorescence imaging were preserved in the method. The novel method could effectively detect both colored and white trash in real time. This method can also be applied to trash detection in seed cotton, wool, tea leaf, and tobacco leaf.
Fei Zhou and Tianhuai Ding, "Detection of Cotton Lint Trash Within the Ultraviolet–Visible Spectral Range," Appl. Spectrosc. 64, 936-941 (2010)