Dombrovsky Leonid, Henry Jean-François, Lorreyte Clarisse, Pron Hervé, Randrianalisoa Jaona
Appl Opt. 2018 Aug 10;57(23):6657-6663. doi: 10.1364/AO.57.006657.
The spectral absorption and scattering properties of oakwood are retrieved from the measurements of both the normal-hemispherical reflectance and transmittance in the visible and near-infrared ranges of semi-transparency. We employ two alternative methods for the radiative transfer in wood samples: the modified two-flux approximation and the high-order discrete ordinate method. The modifications of both methods take into account the effect of total internal reflection at both surfaces of the wood samples. The analytical approximate solution of the first method gives very accurate results for the absorption coefficient, but the transport scattering coefficient of wood appeared to be systematically underestimated. Fortunately, this error is between 7% and 12%, and that is acceptable for the estimates. The oakwood samples of four different thicknesses were used in the experiments. The effect of the wood cell orientation appears to be insignificant and can be observed in the reflectance from optically thin samples only. There is a considerable decrease in the transport scattering coefficient of oakwood with the wavelength. This effect is explained by a predominant contribution of micron-sized longitudinal pores in oakwood. The latter is used to develop an approximate theoretical model of scattering based on the rigorous solution for arbitrary-oriented cylindrical pores. The model suggested is in good agreement with the experimental data.
通过对半透明橡木在可见光和近红外波段的法向半球反射率和透射率的测量，获取了橡木的光谱吸收和散射特性。我们采用两种替代方法来研究木材样品中的辐射传输：改进的二流近似法和高阶离散坐标法。这两种方法的改进都考虑了木材样品两个表面的全内反射效应。第一种方法的解析近似解给出了非常准确的吸收系数结果，但木材的输运散射系数似乎被系统地低估了。幸运的是，这个误差在7%到12%之间，对于估计来说是可以接受的。实验中使用了四种不同厚度的橡木样品。木材细胞取向的影响似乎不显著，并且只有在光学薄样品的反射率中才能观察到。橡木的输运散射系数随波长有相当大的降低。这种效应可以用橡木中微米级纵向孔隙的主要贡献来解释。后者被用于基于任意取向圆柱孔的严格解来建立一个近似的散射理论模型。所提出的模型与实验数据吻合良好。
