Optical measurement of wood grain direction

锯木厂的成功运营关键取决于其从高度可变的原材料中实现尽可能高的价值回收的能力。准确的材料评估是实现这一目标的关键，否则优质木材最终将得不到充分利用，劣质木材将达不到规格。木材纹理方向是木材的主要质量控制特征。它对木材强度影响很大，最常见的是节子周围扭曲的纹理和螺旋纹理。仅仅15度的纹理偏差就会使木材强度减半。 该项目使用光学方法来测量木材纹理方向。木纹的蜂窝状结构导致木材表面的光在垂直于木纹的方向上进行定向反射。正是这种行为赋予了抛光木材独特的光泽。这种光的定向反射响应可以用来确定颗粒在三维方向上的方向，包括表面颗粒角度和俯冲颗粒角度。以前，一些颗粒角度探测器被开发出来，在沿环线的离散点上进行光学测量。这些只能提供表面反射的有限视图。本文提出的方法是利用现代CCD摄像技术的能力、速度和低成本来制作木材表面光反射的全图，并开发一种适用于工业用途的实用木材纹理角度传感器。

The successful running of a sawmill depends critically on its ability to achieve the highest possible value recovery from the highly variable raw material. Accurate material evaluation is essential to make this happen, else good wood will end up underutilized and inferior wood will fail to meet specifications. Wood grain direction is a primary quality-controlling feature of wood. It strongly affects wood strength, most commonly in the distorted grain around knots and in spiral grain. A grain deviation of just 15 degrees can halve wood strength. This project uses an optical approach to measure wood grain direction. The cellular structure of the wood grain causes directional reflection of light from the wood surface in the direction perpendicular to the grain. It is this behaviour that gives polished wood its characteristic sheen. This directional reflection response of light can be exploited to determine grain direction in three dimensions, both the surface and diving grain angles. Previously, some grain angle detectors were developed that made optical measurements at discrete points along a circular line. These could give only a limited view of the surface reflection. The approach proposed here is to exploit the capability, speed and low cost of modern CCD camera technology to make full maps of the light reflection from a wood surface and to develop a practical wood grain angle sensor suitable for industrial use.