In-process measurement of the orientations of fibers and the moisture contents of wood by using near infrared spectroscopy

木材被广泛应用于不仅保留细胞结构而且保留其粗大形状的状态。近红外光谱（NIRS）是一种很有前途的分析材料物理状态和化学成分的技术。本文研究了木材数控加工系统中不可缺少的水分含量和纤维取向的过程测量。利用带探测器的近红外激光光源，进行了以下实验。(1)测定了不同含水率试样的透射光功率。透射光随含水率的增加而增加。(2)测定了不同纤维取向试样的透射光功率。透射光的功率随光纤的方向和激光束的入射角而有明显的变化。(3)考察了不同含水率和纤维取向试样的最大可测深度极限。现在，设计具有足够输出的仪器的数据已经有了。讨论了最佳波长的选择标准。利用谱的二阶导数可以得到较好的结果。

Wood is widely used in a state where not only cellular structure but also its bulky shape is retained. Near infrared spectroscopy (NIRS) may be called for as a promising technique to analyze the physical state of such materials as well as the chemical composition. This study deals with the inprocess measurement of the moisture content and the orientation of fibers, which are the indispensable information in the nemerically controlled machining system for wood.1. By the use of a near infrared laser light source with a detector, the following experiments were carried out.(1) The power of the transmitted light from the specimens with various moisture contents was examined. It was revealed that transmitted light increased with increasing moisture content.(2) The power of the transmitted light from the specimens with various orientations of fibers was examined. The power of the transmitted light varies characteristically with the orientation of fibers and the angle of incidence of laser beam.(3) Maximum limit of measurable depth of the specimens with various moisture content and orientations of fibers was examined. Now, the data to design the instrument with enough output is available.2. The criteria for the selection of the optimum wavelength were discussed. The better result is obtained when the second derivatives of a spectrum are used.