Spectral Reflectance and Polarization Characteristics of Leaves
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概要
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The spectral reflectance and degree of polarization of plant leaves of different species (conifer, broad leaf tree and different surface roughness, etc.) are measured in a laboratory. It was found that reflectance characteristics of each plant leaf are influenced by the pigments contained in leaves, especially by chlorophyll in visible spectrum with the minimum values at blue and red bands (approximately 4 %) and the maximum value of 18% at green band. It was found that the degree of polarization depends on the surface condition of a leaf.<BR>In case of smooth surface leaves, a general trend of the degree of polarization increases between 0.56, um and 0.68 km with a little variation. The numerical values of the degree of polarization are 0. 13 at 0.56 pm and 0.40 at 0.68 um for the smooth surface leaves (Pasania edulis Makino.). While in case of rough surface leaves the degree of polarization increases monotonously with the numerical values of 0.22 at 0.56 pm and 0.35 at 0.68, um respectively.<BR>Both the reflectance and degree of polarization of leaves are influenced by leaf moisture content of leaves in the near IR spectrum due to the fact that water absorption band exsists in this spectrum and that its influence on the reflectance is larger than that on the degree of polarization. The reflectance of leaves in the near IR spectrum increases in proportion to decrease of moisture content of leaves. For a leaf dried to 50% of moisture content of a fresh leaf the increase reaches as large as 26% of the reflectance of fresh leaves, while in case of the degree of polarization it decreases by 1.7% of that of fresh leaves. The effect of superposition of leaves on both reflectance and polarization was also measured up to a stack of five leaves. In case of a stack of two leaves the reflectance decreases by approximately 1% throughout the spectrum ranging from 0.46 um to 0.68 pm however it increases as much as approximately 10% in near IR spectrum. For a stack of more than three leaves no further significant decreases is observed in visible spectrum while in near IR spectrum the further increases of reflectance is observed reaching by 14%, 15% and of 16% of that of the case of one leaf respectively. As to the relation between reflectance and degree of polarization, a negative correlation was observed.
- 社団法人 日本リモートセンシング学会の論文