# A Comparative Analysis of Oak Wood Defect Detection Using Two Deep Learning (DL)-Based Software
## 2 Materials and Methods  
### Material and Observed Defects  
Lamellae manufactured from oak wood were prepared for the study, with dimensions of 700 \(\times\) 100 \(\times\) 2 mm (length \(\times\) width \(\times\) thickness). The study was conducted on a total of forty lamellae, all of which exhibited at least one of the six defects that were previously identified. The overall database has around 800 pictures, and it is wholly partitioned into clusters of defects intended for analysis and for the comparison of the performance of the two defect detection software. Thirty specimens were purposefully chosen to facilitate a comparative analysis of the software's performance and its ability to produce accurate outcomes. This approach created a realistic manufacturing scenario, acknowledging that not all defects are uniformly prevalent throughout all saws or lamellae. The number of specimens on which a specific defect was found is presented in Table 1 (data in the table are based on visual assessment).  
Wood rays refer to the part of the rays in the inner side of the cambium, the secondary xylem part (they appear on the elements of the radial texture, i.e., radially sawn timber). The mentioned elements are easily recognized as places of greater brightness or mirroring of the surface of the strips. On oak, the defect in the wood rays manifests itself as a wide and bright line, which is much brighter than the rest of the longitudinal tissue. It is important to note that wood rays are a stunning aesthetic feature of oak, but the problem arises when they appear on the veneer when glue penetration occurs during the veneering process. Ambrosia wood has a variety of tiny larval pathways, varying in color from gray to black, which can be found in the wood's bark, core, sapwood, and heartwood. Occasionally, these hidden pathways stand out by their visual qualities, while they provide significant technological difficulties at other times. The dark color observed in the larval pathways can be attributed to the presence of mycelium from symbiotic fungi. Under favorable conditions, the mycelia of these fungi can extend into the surrounding wood,  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Wood Defects** & **Testing Specimens** \\ \hline Wood ray & 11 \\ Ambrosia wood & 5 \\ Sapwood & 5 \\ Ingrown bark & 7 \\ Knots & 27 \\ Crack & 20 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Six different wood defects and their occurrence on specimens.  
Figure 2: A simple CNN architecture [33].  
significantly altering its color to a bright blue. Sapwood is mainly the part of wood that consists of the outer layers closer to the bark. In most cases, it is lighter than the pith, and in a living tree, it contains living cells, reserves substances, and conducts water. In contrast to sapwood, heartwood, consisting of extractives, exhibits greater dryness, weight, and hardness, along with a reduced fiber saturation point and lower hygroscopicity [34]. Moreover, the differentiation between sapwood and heartwood can be entirely attributed to differences in their chemical composition [35]. In addition to what has been previously stated, sapwood was eliminated as a defect since it is less resistant to biological decay. Ingrown bark is a defect that occurs when the wood wholly or partially covers the bark and can be superficial if it only appears on one side of the sawn wood or penetrating if it occurs on both sides. A knot marks a part of a branch that has grown into the trunk and represents a defect that inevitably appears divided according to origin, fusion, growth, size, shape, degree of health, and consistency. A crack is a line of separation of consistent material in the longitudinal direction, and it may appear on the saw's face, surface, or internals. Their presence significantly decreases the material utilization rate. Figure 3 provides pictures of each of the mentioned defects.