Construction of novel measurement method of wood property by TOF-NIR densitometory

为了从飞行时间近红外（TOF-NIR）光谱的角度研究木材的光学特性，介绍了一种以条纹相机和半导体激光器为主要组成部分的新型光学测量系统。另一个系统，这是由LED近红外激光器（CW型）和光电探测器组成。透光强度在早材和晚材中存在差异，这是由于密度的差异造成的。密度和细胞结构直接影响透射时间分辨轮廓。基于光传输方程的前向和后向模型，从时间分辨轮廓的变化计算木材的吸收和散射系数。结果表明，木材的吸收和散射系数随木材次表层和样品内部的水分状况而变化。与传统的近红外光谱相比，多元统计量作为时间分辨轮廓的解释变量，显示了木材含水率的高精度估计。基于辐射传递方程的扩散近似的光学模型被证明是有用的厚样品，它可以被视为一个理想的扩散光学，虽然木材是一种结构材料与非均匀的cellularstructure。

A new optical measurement system, the main components of which are a streak camera and semiconductor laser , was introduced to clarify the optical characteristics of wood from the viewpoint of time-of-flight near infrared (TOF-NIR) spectroscopy. Another system, which is composed of LED NIR laser (CW type) and photodetector, was also constructed. Intensity of transmitted light varied with early wood and late wood, which was due to the difference of density. The density and cellular structure directly affected the transmitted time-resolved profile. Absorption and scattering coefficient of wood were calculated from the variation of time-resolved profile based on the forward and backward model of light transportation equations. It was known thatabsorption and scattering coefficient of wood were varied with the moisture condition of subsurface layer and inside of the sample. Multivariate statistics as the explanatory variables of time-resolved profile showed high accurate estimation of moisture content of wood compared to that of traditional NIR spectroscopy. The optical model based on the diffusion approximation to the radiative transfer equation proved to be useful for thick samples, which can be optically regarded as an ideal diffuser, although wood is a structural material with non-homogeneous cellularstructure.