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

木材在不仅保持蜂窝结构而且保持其庞大形状的状态下被广泛使用。近红外光谱（NIRS）可以被称为是一种有前途的技术来分析这些材料的物理状态以及化学组成。本研究针对木材数控加工系统中不可或缺的含水率与纤维取向的在线测量进行了研究。通过使用带有检测器的近红外激光光源，进行以下实验。(1)研究了不同含水量试样的透射光功率。结果表明，透射光随含水量的增加而增加。(2)测试了不同取向纤维的透射光功率。透射光的功率随光纤的取向和激光束的入射角而变化。(3)考察了不同含水率和纤维取向试样的最大可测深度。目前，已有了设计具有足够输出的仪器的数据.讨论了选择最佳波长的准则。当使用光谱的二阶导数时，得到更好的结果。

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.