JPH0330814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knot detection device for wood veneers.

In general, among the knots that exist in wood veneers, the diameter of the knots called fresh knots or leaf knots is 1 to 2 mm.
Small knots cannot be detected using changes in shading. In other words, in large knots called dead knots, the tissue in the center is literally dead and appears black. Therefore, as shown in FIG. 1, a light beam 3 is projected perpendicularly to the center of a dead joint 2 on the surface of a wood veneer 1, and an eye is placed at a position to receive the scattered light of the projected light 3. If a light receiving means such as 4 is set, node 2 can be easily detected based on the difference in shading. However, live nodes (leaf nodes) do not have black parts like dead nodes, so they cannot be detected using the above method. Therefore, a method was devised to detect live nodes by utilizing the phenomenon that reflection characteristics differ between nodes and other parts based on the difference in the direction of the conduit (tissue direction). That is, as shown in FIG. 2, light 7 is projected obliquely onto the raw knots 6 on the surface of the wood veneer 5, and a light receiving means such as an eye 4 is set at a position where the light 7 is specularly reflected. A method for detecting changes in gloss was devised. However, according to this method, as shown in FIG. 3, when the conduits 9 are concentrated on the surface of the wood veneer 8, the projected light 10 is scattered due to the influence of the concave portions, resulting in a change in gloss. Therefore, there was a drawback that the conduit 9 was erroneously determined to be a node.

This invention was made in view of the above circumstances, and includes a light projecting device that shines light in a strip on the surface of a wood veneer, and a waist portion of the strip-shaped transmitted light pattern that passes through the wood veneer and appears on the back surface. The gist of the present invention is to provide a knot detection device for a wood veneer, which is equipped with a sensor that detects the presence or absence of a waist portion, and a signal output section that outputs a knot detection signal in response to a signal indicating the presence of a waist portion from the sensor.

In other words, this device detects knots by utilizing the phenomenon that when a band of light projected onto the surface of a wood veneer passes through the veneer and appears on the back side, if a knot exists, the area constricts. This makes it possible to accurately detect live knots without being confused by conduits or the like.

Next, this invention will be explained in detail.

A wood veneer is usually 1 to 2 mm thick and transmits light to a certain extent, so it is a semi-transparent object. This invention detects live knots by shining light onto the surface of such a wood veneer and detecting differences in the transmitted light pattern appearing on the back surface of the veneer. For example, as shown in FIG. 4, a He-Ne laser beam (circular cross section) 1 mm in diameter (other laser or white light may be used) is applied to a semi-transparent acrylic plate 11.
2, the transmitted light pattern 13 that passes through the acrylic plate 11 and appears enlarged on the back side is photographed with the TV camera 14 and binarized at a certain slice level. The valued image 16 appears in an enlarged, circular shape without distortion. This is because the acrylic plate 12 is homogeneous as a whole and has no anisotropy (directivity) in its structure, so that light entering the acrylic plate 12 is uniformly diffused. Next, if a knotless wood veneer 17 as shown in FIG. 5 is used instead of the acrylic board 12, an elliptical transmitted light will be formed on the back side of the wood veneer 17 as shown in FIG. Pattern 18 appears. Therefore, a similar binarized image appears on the monitor 15 as well. The reason why an elliptical transmitted light pattern 18 appears on the back side of the wood veneer 17 even when a beam with a circular cross section is emitted is because the fibers of the veneer 17 exhibit a glass fiber-like effect. This is because the light diffused within the veneer 17 is stretched in the fiber direction shown by the arrow in FIG. However, as shown in FIG. 7, in the wood veneer 21 with knots 19 and 20, the fibers are swirled at the knot 19, and the fibers are perpendicular to the surface of the veneer at the knot 20. (in the thickness direction), the transmitted light patterns of those parts are as shown in Figure 8 (corresponding to node 19) and Figure 9 (corresponding to node 20).
As shown in , the shape is distorted compared to the transmitted light pattern of the parts other than the nodes. Therefore, knots can be detected by detecting differences in the transmitted light patterns.

Next, examples will be described.

FIG. 10 is a block diagram of an embodiment of the present invention. In the figure, 24 is a light source made of white light, a laser, etc., 25 is a cylindrical lens that converges the light from the light source 24 into a band shape, and 26 is a wood veneer, which is moved in the direction of the arrow. Here, the light source 24 and the cylindrical lens 25 constitute a light projecting means that emits a band-shaped light onto the wood veneer 26 in a direction intersecting the fiber direction thereof. 27 is wood veneer 2
6, 28 is a transmitted light pattern appearing on the back surface of the wood veneer 26, 29 is an imaging lens, and 30 and 31 are one-dimensional first and second nodes arranged on the imaging surface of the imaging lens 29. line sensor. Analog signals from the line sensors 30 and 31 are binarized by binarization blocks 32 and 33, respectively, and input to an OR gate 34, from which a node detection signal is output.

In this configuration, the light from the light source 24 is converged by the cylindrical lens 25 into a band shape and is irradiated onto the surface of the wood veneer 26 as shown in FIG. In FIG. 11, 35 is a band-shaped irradiation light, and 27 is a node. On the back surface of the veneer 26, this band-shaped irradiation light 35 is stretched in the fiber direction and becomes wider, as shown in FIG. However, since the light is not stretched at the node 27, that portion becomes constricted. Therefore, on the surface of the veneer, there is a transmitted light pattern 28 in which the knots 27 are constricted.
appears. In FIG. 12, dotted lines indicate band-shaped irradiation light. This transmitted light pattern 28 is transmitted to the first and second line sensors 3 by an imaging lens 29.
It is imaged on 0,31. In this case, the first and second line sensors 30 and 31 are positioned so as to capture the stretched upper and lower edges of the transmitted light pattern 28, as shown in FIG. If there is, the constriction part 2
8a is immediately detected. This line sensor 3
The analog outputs (signals) from 0 and 31 are binarized by binarization blocks 32 and 33, and then passed through the OR gate 3.
4 is input. Then, the OR gate 34 determines whether or not there is a constriction in the transmitted light pattern 28 by taking the OR of both, and outputs a knot detection signal when there is a constriction. In this way, the binarization block 3
2, 33 and the OR gate 34 constitute a signal processing output section.

In this manner, by moving the wood veneer 26 in the direction of the arrow as shown in FIG. 10, it is possible to easily inspect the entire veneer for the presence or absence of live knots.

FIG. 14 is a block diagram of the main parts of another embodiment of the present invention. That is, this device not only provides first and second line sensors 40 and 41 to capture the upper and lower edges of the transmitted light pattern 38, but also a third line sensor that captures the central part.
The signals from the first and second line sensors 40 and 41 are divided by the signal from the line sensor 42. The other parts are the same as those of the previous embodiment.

By doing this, it becomes possible to correct the increase or decrease in the amount of transmitted light due to the moisture content of the veneer, and knot detection becomes stable. In other words, since the amount of transmitted light is affected by the water content, the output of the third line sensor 42, which always provides an appropriate amount of transmitted light regardless of the joint portion or other portions, is used as a reference. By dividing the outputs of the first and second line sensors, the influence of the water content can be reduced. Therefore, even if the moisture content of the core material and sapwood differs greatly, it becomes possible to stably test the material without being affected by the moisture content.

As described above, the wood veneer knot detection device of the present invention includes a light projecting means that emits band-shaped light in a direction crossing the fiber direction on the surface of the wood veneer, and a light projecting means that projects light in a band shape in a direction that intersects with the fiber direction on the surface of the wood veneer. A first and second line sensor detects both edges along the length of the band-shaped transmitted light pattern appearing on the back surface, and a waist portion of the band-shaped transmitted light pattern is detected based on output signals from these two line sensors. Since it is equipped with a signal processing output section that determines the presence or absence of a constricted part and outputs a knot detection signal when a constricted part is present, it is possible to detect raw knots without being confused by conduits or the like. When detecting knots, there is a method of scanning a laser beam in a direction that crosses the fiber direction of the wood veneer, but with this method, it is necessary to slow down the movement speed of the wood veneer by the time required for scanning. However, since the node detection device according to the present invention applies band-shaped light, the detection time is short. It is also possible to use only one line sensor to detect distortion of transmitted light, but since distortion does not necessarily occur only on the side where the line sensor is installed, only one line sensor is used. This may cause an oversight, but the knot detection device according to the present invention uses two line sensors to capture both edges of the transmitted light pattern, so the above-mentioned oversight can be prevented.

[Brief explanation of the drawing]

Figures 1 to 3 are explanatory diagrams of the conventional example, Figures 4 to 9 are illustrations of the principle of the present invention, Figure 10 is a configuration diagram of an embodiment of the present invention, and Figures 11 to 13. 14 is a diagram illustrating its operation, and FIG. 14 is a configuration diagram of a main part of another embodiment. 24... Light source, 25... Cylindrical lens, 26... Wood veneer, 27... Knot, 28... Transmitted light pattern, 28a... Narrow portion, 29...
Imaging lens, 30, 31... Line sensor, 3
2, 33... Binarization block, 34... OR gate, 35... Belt-shaped irradiation light.

Claims (1)

[Claims] 1. A light projection means that emits a strip of light in a direction crossing the fiber direction on the surface of the wood veneer, and both ends along the length of the strip-shaped transmitted light pattern that passes through the wood veneer and appears on the back surface. A first and second line sensor detects the edge, and based on the output signals from these two line sensors, it is determined whether or not there is a constriction in the band-shaped transmitted light pattern, and if a constriction is present, a knot detection signal is output. This is a wood veneer knot detection device equipped with a signal processing output section.