The Development of CAD for the Sawing of Timber : 1st Report, The Method of Recognizing Knots Using the Image Processing Technique

Abstract

In the process of sawing a timber into a square bar, knots directly influence the quality of the square bar. The recognition of knots depends on the operator and he determines the cutting position based on many years of experience. As skilled workers become few and old, and the cost of imported square bars decreases, it is necessary to develop a computer aided design (CAD) for the sawing of timber. In this paper, we propose a method for recognizing knots on the surface of timber (Japanese cypress) using the image processing technique. The wave lengths 625 to 770nm (red) or 900 to 1 000 nm (an infrared) are useful for distinguishing clearly between knots and other parts on the timber surface. The knot can be recognized in the process of thresholding the input image, calculating the marginal distribution, approximating an ellipse, and judging the knot.