Laser transillumination imaging for determining wood defects and grain angle

Abstract

Wood defects and grain angle correlate strongly with timber strength and grading. In this study a laser transillumination imaging method was developed to determine wood defects and grain angle. The method uses a near infrared laser light source which illuminates a wood sample with a round beam and the image generated by the light transmitted through the sample is captured for further analysis. In basic and flawless wood, the transmitted light pattern is an ellipse and wood defects and grain angle deviation will change the shape, size and location of the ellipse. The method could be used for determining the strength of wood, grading sawn timber, studying finger and glue joints, estimating moisture and differentiating between heartwood and sapwood.

Contactless moisture content measurement on green veneer based on laser light scattering patterns

“…This diffusion varies according to the species, and its physical explanation is not yet fully understood (Nyström 2003;Zhou and Shen 2003;Simonaho et al 2004). The tracheid effect has for many years been used in commercial timber scanners as a mean to detect wood defects such as knots (Nieminen et al 2013;Briggert et al 2018). It has recently been used for machine grading purposes by measuring the fiber direction (Olsson et al 2013;Viguier et al 2015Viguier et al , 2018Ehrhart et al 2018).…”