イメージング分光法による材色分布の特徴抽出

概要

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Warm color distributed on lumber surface is one of the most important visual characteristics of wood, and would affect aesthetics of various wood products. The objective of this study is to characterize the wooden colors quantitatively by imaging spectroscopy. Twelve different specimens of coated and uncoated fancy veneer overlaid plywood of six species were prepared. These surfaces were scanned by the imaging spectroscope system, and color values of metric lightness (L*), chroma (C*) and hue (H°) were measured in every pixel. Resolution of the image was approximately 0.20mm /pixel. Results were summarized as follows. (1) In comparison with the same species, the coated specimen became darker than the uncoated specimen, because spectral reflectance in the visible light of the coated was lower than the uncoated. And by the coating, decrement of the reflectance of dark spots in the surface, for example latewood, tended to be greater than light spots such as earlywood. (2) Histograms of L*, C* and H° were constructed by counting every pixel. By the coating, peak positions of L* and C* histograms shifted to lower (darker) and upper (more saturated) sides, respectively. (3) Multi-resolution contrast analysis (MRCA) was applied to images with the three color attributes, and revealed that the color difference, especially contrast of the lightness and the chroma, were enlarged by the coating.