Single plate defect determination device, defect determination method, and defect determination program

Abstract

Holes H1, H2, and H3 are detected for a continuous single plate 101B, the length of the single plate cut by one rotation for each round of the raw wood is calculated as circumferential contact plate lengths L1, L2, and L3. The shape of the detected specific round hole is aligned to a position after one rotation corresponding to the upstream side in the conveyance direction by the circumferential contact plate length. In a region defined by the shape of the aligned specific round hole, it is estimated that there is a possibility that plate thickness deficiency sites T2, T3, and T4 formed by cutting a recessed part having an inclination in the raw wood surface layer portion may be included, thereby, it is possible to estimate a region in which there is possibility that plate thickness deficiency sites T2, T3, and T4, which are difficult to determine by a method for viewing the color difference between the reflected light and the captured image, are included.

Description

Veneer defect determination device, defect determination method, and defect determination program

[0001] The present invention relates to a veneer defect determination device, a defect determination method, and a defect determination program, and is particularly suitable for use in a system for estimating defects such as insufficient board thickness present in veneers cut from logs.

[0002] Generally, veneer panels (hereinafter simply referred to as "veneer panels") for manufacturing plywood or laminated veneer lumber are produced by cutting natural logs with a veneer lathe. When veneer panels are cut from logs using a veneer lathe, as shown in Figure 8, discontinuous veneer panels 101A are cut from the irregular periphery of the logs, either containing only the unused portion y that cannot be used for board production or containing the unused portion y and the useful portion f that can be used for board production, and continuous veneer panels 101B are cut, each containing both the unused portion y and the useful portion f. After the logs are cut into a roughly cylindrical shape, continuous veneer panels 101C are cut, containing only the useful portion f but not the unused portion y. The useful portion f refers to a portion that can secure a rectangular area having the required width w required for the board.

[0003] When each of the veneers 101A-101C is used to manufacture plywood, laminated veneer lumber, etc., it is necessary to perform a suitable shaping process. For example, it is necessary to remove the unnecessary portions y from the veneers 101A and 101B. More preferably, in addition to removing the unnecessary portions y, it is more appropriate to connect the useful portions f together and form them into a veneer of the required size. On the other hand, the veneer 101C consisting only of the useful portions f can be simply cut into predetermined lengths h one by one to successively form veneers of the required size (hereinafter referred to as fixed-length veneers).

[0004] There is also known a technique for predicting the total length of the strip-shaped veneer that will be produced when a log is cut to a specified core-stripping diameter, and for calculating a specific point where the distance calculated backward from the boundary between the veneer with the above-mentioned unused portion and the veneer without the unused portion to the core-stripping of the log is within the range of the predicted total length and is an integer multiple of the fixed length of the fixed-length veneer, and for starting the fixed-length cutting process from this specific point (see, for example, Patent Document 1).

[0005] In conventional techniques including the invention described in Patent Document 1, the detection of unnecessary portions of the veneer shaved by the veneer lace is performed by veneer detection mechanisms installed at multiple locations in the direction perpendicular to the veneer conveyance direction. Here, recesses present on the outer periphery of the log appear as holes in the shaved veneer, so portions where no veneer exists are detected as holes, and portions of the veneer included in a rectangular region of the required veneer width that is set so as to inscribe the detected holes are detected as unnecessary portions.

[0006] However, logs, being natural objects, do not always have vertical depressions in the direction normal to the log, i.e., in the thickness direction of the veneer, but rather have inclined depressions. Because the veneer lace knife cuts the veneer along a trajectory that peels off the outer periphery at a constant thickness, the veneer shaved from the surface layer of the log gradually loses thickness, resulting in an inclined portion leading to the hole. In other words, in most cases, there is an insufficient thickness around the hole. It would be desirable to detect these insufficient thickness areas as waste, but Patent Document 1 makes no mention of this.

[0007] Here, when a photoelectric sensor or the like that detects the presence or absence of an object by the reflected light from the target is used as a veneer detection mechanism, it is possible to detect the presence or absence of a veneer (presence or absence of a hole), but with regard to the area around the hole, it can only determine that the veneer exists as a plate, and it is not possible to detect that the plate is insufficiently thick.

[0008] Also known is a defect inspection device that photographs the veneer with an imaging means while irradiating the veneer with visible light, and detects defective portions due to discoloration of the veneer by utilizing the color distribution of the photographed image (see, for example, Patent Document 2). However, it has been difficult to determine portions of the veneer that are insufficient in thickness, which are unlikely to have a different hue from normal portions, simply by looking at the color difference (color difference) of the image photographed with visible light irradiation.

[0009] JP 2009-160834 A JP 2007-147442 A

[0010] The present invention has been made to solve such problems, and aims to make it possible to estimate areas that may contain areas with insufficient plate thickness, which are difficult to determine using methods such as using a photoelectric sensor to determine the presence or absence of an object based on reflected light, or methods that look at the color difference in a captured image.

[0011] To solve the above-mentioned problems, the present invention detects holes in a continuous strip of veneer that is shaved by a veneer lathe from a log rotating around its axis and transported on a transport path, and calculates the length of the veneer that is shaved per rotation of the log as the board length per circumference.Then, the detected shape of the hole in a specific circumference is aligned with a position one rotation later that is the board length per circumference, which is upstream in the transport direction, and it is estimated that there is a possibility that a portion of the board that is insufficient in thickness is included within the area defined by the aligned shape of the hole in the specific circumference.

[0012] According to the present invention configured as described above, it is possible to estimate that an area in which the shape of the hole detected for each rotation of the log is aligned based on the board length per rotation of each rotation may contain an insufficient board thickness portion formed when a sloped recess in the surface layer of the log is cut with a veneer lace knife. In other words, according to the present invention, it is possible to estimate an area that may contain an insufficient board thickness portion in the surface layer of the log, which is difficult to determine using a method of determining the presence or absence of an object based on reflected light using a photoelectric sensor or the like, or a method of looking at color differences in a photographed image.

[0013] FIG. 1 is a diagram showing an example of a schematic configuration of a log processing line to which a veneer defect determination device according to the present embodiment is applied. FIG. 2 is a block diagram showing an example of a functional configuration of a defect determination device according to the present embodiment. FIG. 3 is a diagram showing an example of a hole detected by a hole detection unit according to the present embodiment. FIG. 4 is a schematic diagram for explaining the processing content of a board thickness insufficiency estimation unit according to the present embodiment. FIG. 5 is a flowchart showing an example of operation of a defect determination device according to the present embodiment. FIG. 6 is a diagram showing an example of a case where recesses exist in multiple places in the surface layer of a log. FIG. 7 is a block diagram showing another example of a functional configuration of a defect determination device according to the present embodiment. FIG. 8 is a diagram showing an example of a veneer cut from a log by a veneer lace.

[0014] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a diagram showing a schematic configuration example of a log processing line to which a veneer defect determination device according to this embodiment (hereinafter simply referred to as a defect determination device) is applied. As shown in Fig. 1, the processing line to which the defect determination device of this embodiment is applied is configured to include a veneer lace 10, veneer transport conveyors 21 and 22, a defect inspection system 30, and a veneer cutting device 40.

[0015] In the processing line shown in Figure 1, a log 100 rotating around an axis 11 is cut by knives 12 of a veneer lace 10 to produce veneers 101, which are then transported by veneer transport conveyors 21 and 22 and cut to a predetermined length by a veneer cutting device 40. While the veneer 101 is being transported from the veneer lace 10 to the veneer cutting device 40, a defect inspection system 30 detects defects, and the cutting position of the veneer 101 by the veneer cutting device 40 is controlled based on the detection results.

[0016] The knives 12 of the veneer lace 10 gradually move parallel to the axis 11 while the log 100 is rotating, and cut the surface of the log 100 in a manner similar to "peeling," thereby shaving off the veneer 101. That is, in the veneer lace 10, both ends of the log 100 are supported by spindles with claws (chucks) at the ends, and while the log 100 is rotated at a constant speed, the knives 12 are moved at a predetermined speed toward the axis 11, which is the center of rotation of the log 100, to shave off the veneer 101 to a constant thickness d.

[0017] The horizontal movement distance of the knife 12 per one rotation of the log 100 is equal to the thickness d of the veneer 101 to be shaved, and this value is set in advance. The veneer lace 10 is provided with a knife movement distance sensor 13 that detects the horizontal movement distance of the knife 12. The horizontal movement distance of the knife 12 detected by the knife movement distance sensor 13 is notified to the defect inspection system 30.

[0018] The defect inspection system 30 includes a defect determination device 31, an illumination device 32, and a line sensor camera 33, and detects or estimates defects present in the veneer 101 conveyed by the veneer conveyor 21. In this embodiment, the defects detected by the defect inspection system 30 are holes (holes that penetrate from the front side to the back side of the veneer 101). The holes referred to here include holes formed by the knife 12 cutting a sloped depression in the veneer lace 10, i.e., holes that exist at the end of a gradual decrease in thickness. The defects estimated by the defect inspection system 30 are areas that may contain insufficient thickness (hereinafter referred to as "possible insufficient thickness areas"). The defect inspection system 30 can also detect other defects, but these are not the subject of the present invention and will not be described further.

[0019] As shown in Figure 8, when veneer 101 is cut from a log 100 using a veneer lathe 10, discontinuous veneer 101A and continuous veneer 101B including a useful portion f and an unused portion y are cut from the irregular outer periphery of the log 100. After the log 100 is cut into a substantially cylindrical shape, continuous veneer 101C including only the useful portion f is cut. The estimation of the possible thickness insufficiency area is performed on the continuous veneer 101B.

[0020] In the conventional example of Figure 8, the portion of the veneer included in the rectangular region of the required veneer width w that is set so that the detected hole is inscribed is detected as the unused portion y. In contrast, in this embodiment, when a possible region of insufficient thickness is estimated, the unused portion is detected including the possible region of insufficient thickness. For example, the portion of the veneer included in the rectangular region of the required veneer width w that is set so that the possible region of insufficient thickness is inscribed is detected as the unused portion. The detection of the unused portion may be performed by the defect determination device 31 or by the cutting control device 41 of the veneer cutting device 40.

[0021] The lighting device 32 irradiates visible light onto the surface of the veneer 101 being transported by the veneer transport conveyor 21. A white light source such as an LED is used as the light source of the visible light. The lighting device 32 extends in a line in a direction perpendicular to the transport direction of the veneer 101 (the width direction of the veneer 101), and irradiates the veneer 101 with white visible light in a strip shape. Note that although an example using white visible light has been described here, this is not limiting. For example, blue visible light or green visible light may also be used.

[0022] The line sensor camera 33 takes color images of the surface of the veneer 101 that is shaved by the veneer lace 10 from the log 100 that rotates around the axis 11 and is transported by the veneer transport conveyor 21. The line sensor camera 33 extends linearly in a direction (width direction of the veneer 101) perpendicular to the transport direction of the veneer 101, and takes linear images of the veneer 101. While the veneer 101 is transported on the veneer transport conveyor 21, the line sensor camera 33 repeatedly generates one line's worth of images at predetermined sampling times and outputs them sequentially to the defect determination device 31.

[0023] The line sensor camera 33 is equipped with a light receiving element that is sensitive to the white visible light irradiated by the illumination device 32. The line sensor camera 33 receives the white visible light irradiated by the illumination device 32 and reflected by the single panel 101, and generates a photographed image of one line of the single panel 101 by photoelectrically converting the received light.

[0024] The defect determination device 31 detects or estimates defects present in the veneer 101 by analyzing the captured images output from the line sensor camera 33 (in the following description, "detection or estimation" may be collectively referred to as "determination" unless otherwise specified). As described above, the defects determined in this embodiment are holes and areas where there is a possibility of insufficient thickness. The areas where there is a possibility of insufficient thickness are estimated using the captured images acquired from the line sensor camera 33 and the horizontal movement distance of the knife 12 acquired from the knife movement distance sensor 13. The defect determination device 31 notifies the veneer cutting device 40 of information related to the defect determination results. Details of the processing by the defect determination device 31 will be described later.

[0025] The veneer cutting device 40 is equipped with a cutting control device 41, a cutting blade 42, and a blade holder 43. The cutting control device 41 controls the operation of the cutting blade 42 based on the defect determination results from the defect determination device 31, and cuts the continuous veneer 101. For example, for discontinuous veneer 101A and continuous veneer 101B including unused portions (including areas where thickness may be insufficient), the veneer cutting device 40 cuts the veneer 101 at a position that removes the unused portions and leaves a rectangular useful portion. On the other hand, for continuous veneer 101C that does not include unused portions, standard-length veneer is sequentially formed by cutting it at predetermined length h intervals.

[0026] Fig. 2 is a block diagram showing an example of the functional configuration of a defect determination device 31 according to this embodiment. As shown in Fig. 2, the defect determination device 31 of this embodiment includes, as functional components, an image acquisition unit 1, a knife travel distance acquisition unit 2, a hole detection unit 3, a plate length per circumference calculation unit 4, and a plate thickness insufficiency estimation unit 5. The plate length per circumference calculation unit 4 includes, as more specific functional components, a knife position detection unit 4A, a conveyance distance calculation unit 4B, a log diameter acquisition unit 4C, and a plate length calculation unit 4D.

[0027] These functional blocks 1 to 5 can be configured using any of hardware, a DSP (Digital Signal Processor), and software. For example, the functional blocks 1 to 5 are realized by the operation of a defect determination program stored in a storage medium such as RAM, ROM, a hard disk, or a semiconductor memory under the control of a microcomputer configured with a CPU, RAM, ROM, etc.

[0028] The image acquisition unit 1 sequentially acquires one line of photographed images generated by the line sensor camera 33 at predetermined sampling times. Then, an image of the veneer 101 is generated by synthesizing (combining) the photographed images of each acquired line. The generated image of the veneer 101 includes images of the discontinuous veneer 101A, the continuous veneer 101B including the unused portion, and the continuous veneer 101C not including the unused portion. Note that, depending on the shape of the log 100, there may be no discontinuous veneer 101A.

[0029] The knife travel distance acquisition unit 2 sequentially acquires information about the horizontal travel distance of the knife 12 detected by the knife travel distance sensor 13. Note that the knife travel distance acquisition unit 2 may transmit an information acquisition request to the knife travel distance sensor 13 when the hole detection unit 3 detects a hole in the veneer 101 for the first time, and acquire the horizontal travel distance information of the knife 12 in response.

[0030] The hole detection unit 3 detects holes present in the veneer 101 by analyzing the photographed image of the veneer 101 acquired by the image acquisition unit 1. As described above, the holes detected by the hole detection unit 3 are holes that penetrate vertically (in the thickness direction) from the front side to the back side of the veneer 101 (including holes that exist at the end of a gradual decrease in thickness). The hole detection unit 3 stores the shapes of the detected holes. The stored hole shapes are used to estimate possible areas of insufficient thickness, as will be described later.

[0031] 3A and 3B are diagrams showing examples of holes detected by the hole detection unit 3. FIG. 3A shows a cross section of a log 100 being cut. A recess 111 with an inclined surface exists in the surface layer of the log 100. When the log 100 is cut to a constant thickness d while being rotated, the area around the recess 111 is cut as shown in FIG. 3B. Then, as shown in FIGS. 3B and 3C, holes H1, H2, and H3 are sequentially detected by the hole detection unit 3 with each revolution. In FIG. 3C, the right side is the downstream side in the conveying direction, and the left side is the upstream side in the conveying direction.

[0032] The first round of cutting creates a large outermost hole H1, which is detected by the hole detection unit 3. The hole H1 detected here is an area where there is no log 100 on the path of the knife 12, shown by the two-dot chain line in Figure 3(b), i.e., an area where the space of the recess 111 exists. As shown by the hatched area in Figure 3(b), around the hole H1 there is an area that corresponds to the slope of the recess 111 and does not meet the plate thickness d, i.e., an insufficient plate thickness area T1. This insufficient plate thickness area T1 is difficult to detect by analyzing the hole shape in the photographed image.

[0033] Furthermore, the second cutting round forms a hole H2 more inward than the first cutting round (toward the bottom of the recess 111), and this hole is detected by the hole detection unit 3. The hole H2 detected here is also in an area where no log 100 is present on the path of the knife 12, as indicated by the two-dot chain line. Because the hole H2 is formed deeper than in the first cutting round, the hole H2 formed in the second cutting round is smaller than the hole H1 formed in the first cutting round. An area of ​​insufficient board thickness T2 also exists around this hole H2.

[0034] Similarly, a hole H3 is formed inward (toward the bottom of the recess 111) from the second round by cutting in the third round, and this hole is detected by the hole detection unit 3. The hole H3 formed in the third round is even smaller than the hole H2 formed in the second round. A thickness-insufficient portion T3 also exists around this hole H3.

[0035] During the fourth cutting round, there is no area where the log 100 is not present on the path of the knife 12, as indicated by the two-dot chain line, and therefore no holes are detected by the hole detection unit 3. However, there is an area T4 where the plate thickness is insufficient in the area corresponding to the bottom of the recess 111. Although not shown, from the fifth cutting round onwards, the hole detection unit 3 does not detect any holes, and there are no more areas where the plate thickness is insufficient.

[0036] Returning to Figure 2, the length-per-circumference calculation unit 4 calculates the length of the veneer shaved off per rotation of the log 100 as the length of the veneer shaved off per rotation. When the surface of the log 100 is cut with the knife 12 in a stripping manner while the log 100 is rotating, the radius of the log 100 decreases by the thickness d with each rotation, and the length of the veneer 101 shaved off per rotation of the log 100 decreases with each rotation. This decreasing length of the veneer 101 per rotation, i.e., the lengths of the veneer 101 per rotation L1, L2, and L3, is shown in Figure 4 (described in detail below). After the hole detection unit 3 detects a starting hole (hereinafter referred to as the starting hole), the length-per-circumference calculation unit 4 sequentially calculates the lengths of the veneer 101 per rotation L1, L2, and L3 each time a hole is detected by the hole detection unit 3 for each rotation.

[0037] Here, the starting hole is the hole that is first detected in the continuous veneer 101B including the unused portion. When discontinuous veneer 101A is cut as shown in FIG. 8 immediately after starting cutting the log 100, holes that traverse the width direction (hereinafter referred to as width-direction transverse holes) are detected by the hole detection unit 3 while the discontinuous veneer 101A is being cut. While width-direction transverse holes are continuously detected, they are not considered to be starting holes. When a hole that does not traverse the width direction is detected after a width-direction transverse hole has been detected, the last detected width-direction transverse hole is considered to be the starting hole. Note that if discontinuous veneer 101A is not cut immediately after starting cutting the log 100 and no width-direction transverse hole is detected, the hole that is actually first detected by the hole detection unit 3 is considered to be the starting hole.

[0038] First, when the hole detection unit 3 detects a starting hole, the length-per-circumference calculation unit 4 calculates the length L1 of the veneer 101 per rotation from a reference position set at or near the hole. The reference position is a position used as a reference when calculating the lengths L1, L2, and L3 per circumference, and can be set arbitrarily. In the example of Figure 4, the center position of the starting hole H1 in the conveying direction is set as the reference position (indicated by a two-dot chain line extending vertically), and the length L1 per circumference is calculated from there. The center position in the conveying direction can be, for example, the center position between the upstream end of the hole in the conveying direction and the downstream end of the hole in the conveying direction at the center position in the width direction of the veneer 101.

[0039] 4, when a hole H2 is detected by the hole detection unit 3 after one rotation, the plate length per circumference calculation unit 4 calculates the next plate length per circumference L2 from the center position of the hole H2 in the conveying direction as a reference position. Furthermore, when a hole H3 is detected by the hole detection unit 3 after one rotation, the plate length per circumference calculation unit 4 calculates the next plate length per circumference L3 from the center position of the hole H3 in the conveying direction as a reference position. Since no hole is detected by the hole detection unit 3 after another rotation, the plate length per circumference calculation unit 4 does not calculate the next plate length per circumference.

[0040] The reference positions for the plate lengths per circumference L1, L2, and L3 may be the end portions of the holes H1, H2, and H3 on the downstream side of the conveying direction or a position a predetermined distance downstream from that end in the conveying direction, or the end portions of the holes H1, H2, and H3 on the upstream side of the conveying direction or a position a predetermined distance upstream from that end in the conveying direction.

[0041] The following describes the specific processing performed by the circumference length calculation unit 4. The knife position detection unit 4A detects the position of the knife 12 as it moves toward the axis 11 as the veneer lace 10 cuts the log 100, based on the horizontal movement distance information of the knife 12 acquired by the knife movement distance acquisition unit 2. The position of the knife 12 refers to the position (hereinafter referred to as the knife position) reached by horizontal movement in the direction of the axis 11 from the initial position at the start of cutting the log 100.

[0042] For example, the knife position detection unit 4A sequentially detects the knife position based on horizontal movement distance information sequentially acquired by the knife movement distance acquisition unit 2 from the knife movement distance sensor 13. Then, in response to a request from the conveying distance calculation unit 4B, the knife position detected at the time of request acquisition is sent to the conveying distance calculation unit 4B. Alternatively, when a starting hole is detected in the continuous veneer 101B by the hole detection unit 3, the knife position detection unit 4A may send an information acquisition request to the knife movement distance sensor 13 in response to the request from the conveying distance calculation unit 4B, and detect the knife position based on the horizontal movement distance information of the knife 12 acquired in response to the request, and send the information to the conveying distance calculation unit 4B.

[0043] The conveying distance calculation unit 4B calculates the veneer conveying distance from the knife position detected by the knife position detection unit 4A to the position of the line sensor camera 33 (which corresponds to an imaging device for acquiring information used for hole detection by the hole detection unit 3). The position of the line sensor camera 33 is the position obtained by vertically projecting the position of the line sensor camera 33 onto the veneer conveyor 21 (hereinafter referred to as the sensor position), and this information is known. The knife position used in the calculation by the conveying distance calculation unit 4B is the position of the knife 12 when the start hole is detected by the hole detection unit 3. Therefore, the veneer conveying distance means the distance on the veneer conveyor 21 from the start hole to the knife 12 at the time the start hole is detected by the hole detection unit 3.

[0044] If the initial position of the knife 12 at the start of cutting the log 100 is predetermined (for example, the home position of the knife 12), the veneer conveying distance can be calculated by adding the horizontal movement distance of the knife 12 acquired by the knife movement distance acquisition unit 2 to the known distance from the home position of the knife 12 to the line sensor camera 33. In this case, the knife position detection unit 4A only needs to have the function of detecting the horizontal movement distance information acquired from the knife movement distance acquisition unit 2 as the knife position.

[0045] The log diameter acquisition unit 4C back-calculates the knife position when the starting hole detected by the hole detection unit 3 is formed by cutting with the knife 12, based on the veneer conveying distance calculated by the conveying distance calculation unit 4B when the starting hole is detected by the hole detection unit 3, and acquires the distance between the back-calculated knife position and the shaft center 11 as log diameter information during cutting.

[0046] For example, the log diameter acquisition unit 4C calculates the transport time required to transport the veneer 101 the veneer transport distance calculated by the transport distance calculation unit 4B based on the transport distance per unit time of the veneer 101 transported by the veneer transport conveyor 21. Next, based on that transport time and the movement distance per unit time of the knife 12, it calculates the distance traveled by the knife 12 during the transport time and back-calculates the knife position after moving it horizontally to the opposite side from the shaft center 11 by that movement distance. The distance between the back-calculated knife position and the shaft center 11 is then acquired as log diameter information during cutting (the radius of the log 100 when the starting hole detected by the hole detection unit 3 at the position of the line sensor camera 33 was located at the position of the knife 12).

[0047] The board length calculation unit 4D sequentially calculates the board lengths L1, L2, ... per rotation of the log 100 each time a hole is detected by the hole detection unit 3, based on the log diameter information during cutting acquired by the log diameter acquisition unit 4C and known information on the thickness of the veneer 101. The board thickness information is information that is set in advance depending on the veneer 101 to be cut, and in this embodiment is information indicated by the board thickness d.

[0048] Here, if the log radius during cutting acquired by the log diameter acquisition unit 4C is r1, the board length per circumference L1 for the first round can be calculated based on this log radius during cutting r1. If the radius of the log 100 when the log 100 has made exactly one rotation is r2 (= r1 - d), the board length per circumference L2 for the second round can be calculated based on this log radius r2. Similarly, the board length per circumference L3 for the third round can be calculated based on the log radius r3 (= r2 - d). Note that each time holes H1, H2, and H3 are detected by the hole detection unit 3, the knife position detection unit 4A, the transport distance calculation unit 4B, and the log diameter acquisition unit 4C may be executed to calculate the log radius during cutting r1, r2, and r3 for each round.

[0049] The thickness insufficiency estimation unit 5 aligns the shape of the hole in the specific rotation detected by the hole detection unit 3 with a position one rotation later, which corresponds to the plate length per rotation calculated by the plate length per rotation calculation unit 4, upstream in the conveying direction, and estimates the area defined by the aligned hole shape in the specific rotation as a possible thickness insufficiency area. In other words, it estimates that a thickness insufficiency portion is included within the area defined by the aligned hole shape in the specific rotation. Here, the specific rotation refers to each rotation during the period in which holes are detected in the continuous veneer 101B, such as the first rotation, second rotation, third rotation, etc. In contrast, the possible thickness insufficiency area is estimated one rotation later from the specific rotation, i.e., the second rotation, third rotation, fourth rotation, etc.

[0050] 4A and 4B are schematic diagrams for explaining the processing performed by the thickness deficiency estimation unit 5. The topmost diagram, Fig. 4A, shows the veneer 101 (discontinuous veneer 101A, continuous veneer 101B including unused portions, and continuous veneer 101C not including unused portions) being shaved using the veneer lace 10. The right side of the diagram is downstream in the conveying direction, and the left side is upstream in the conveying direction. In Fig. 4A, the central positions in the conveying direction of holes H1, H2, and H3 sequentially detected in the continuous veneer 101B by the hole detection unit 3 are set as reference positions, and the plate lengths L1, L2, and L3 per circumference of the log 100 are shown downstream from those reference positions.

[0051] 4(b) shows the shapes of holes H1, H2, and H3 (hereinafter referred to as hole shapes H1', ​​H2', and H3') detected in the veneer 101B by the hole detection unit 3. FIG. 4(c) in the bottom row shows the hole shapes H1', ​​H2', and H3' detected by the hole detection unit 3 aligned to their positions after one rotation in the same veneer 101 as in FIG. 4(a). That is, the hole shape H1' detected in the first rotation is aligned to the position of the second rotation, which is upstream by the plate length per rotation L1; the hole shape H2' detected in the second rotation is aligned to the position of the third rotation, which is upstream by the plate length per rotation L2; and the hole shape H3' detected in the third rotation is aligned to the position of the fourth rotation, which is upstream by the plate length per rotation L3.

[0052] The thickness insufficiency estimation unit 5 estimates the area defined by the hole shapes H1', ​​H2', and H3' shown in Figure 4(c) (the area indicated by diagonal lines) as a possible thickness insufficiency area. That is, the thickness insufficiency estimation unit 5 estimates the area defined by the hole shape H1' detected in the first round as a possible thickness insufficiency area in the second round at the position of the second round where the hole shape H1' detected in the first round is aligned based on the plate length L1 per round.

[0053] Similarly, the thickness deficiency estimation unit 5 estimates the area defined by the hole shape H2' detected in the second lap as the possible area of ​​thickness deficiency in the third lap at the position of the third lap where the hole shape H2' detected in the second lap is aligned based on the plate length per lap L2.

[0054] Similarly, the thickness deficiency estimation unit 5 estimates the area defined by the hole shape H3' detected in the third lap as the possible area of ​​thickness deficiency in the fourth lap at the position of the fourth lap where the hole shape H3' detected in the third lap is aligned based on the plate length per lap L3.

[0055] 4(c) shows a state in which the hole shapes H1', ​​H2', and H3' detected by the hole detection unit 3 are aligned on the veneer 101, but this is for the sake of convenience of explanation and does not necessarily mean that they are aligned on the veneer 101. In other words, it is sufficient if the hole shapes {H1', H2', and H3'} of a specific rotation are aligned with the hole shapes {H2', H3', no hole} after one rotation, respectively.

[0056] 5 is a flowchart showing an example of the operation of the defect determination device 31 configured as described above. The processing of the defect determination device 31 shown in the flowchart of FIG. 5 starts, for example, at the same time as the operation of the processing line for the logs 100 starts.

[0057] First, the image acquisition unit 1 sequentially acquires one line of photographed images generated by the line sensor camera 33 at predetermined sampling intervals, and sequentially combines the acquired photographed images of each line (step S1). The hole detection unit 3 analyzes the photographed images of the veneer 101 acquired by the image acquisition unit 1 to determine whether a starting hole (the first hole H1 shown in FIG. 4) has been detected in the continuous veneer 101B (step S2). If it is determined that the first hole H1 in the continuous veneer 101B has not been detected, the process returns to step S1, and acquisition of photographed images of the veneer 101 continues.

[0058] On the other hand, when the hole detection unit 3 determines that the first hole H1 in the continuous veneer 101B has been detected, the length-per-circumference calculation unit 4 calculates the length per circumference L1 of the first round using the center position of the hole H1 in the conveying direction as the reference position through the processing of steps S3 and S4. That is, the length-per-circumference calculation unit 4 issues an information acquisition request to the knife travel distance acquisition unit 2. In response, the knife travel distance acquisition unit 2 acquires horizontal movement distance information of the knife 12 detected by the knife travel distance sensor 13 and responds to the length-per-circumference calculation unit 4 (step S3). The length-per-circumference calculation unit 4 calculates the veneer conveyance distance based on the horizontal movement distance information of the knife 12, calculates the radius r1 of the log being cut by back-calculating the knife position based on the veneer conveyance distance, and calculates the length per circumference L1 of the veneer 101 for the first round from the radius r1 of the log being cut and the thickness d of the veneer 101 (step S4).

[0059] Next, the thickness deficiency estimation unit 5 aligns the shape of the first hole H1 detected by the hole detection unit 3 in step S2 to a position one rotation later, which is upstream in the conveying direction by the plate length L1 per rotation of the first rotation, and estimates the area defined by the shape of the aligned hole H1 as a possible thickness deficiency area (step S5).

[0060] Thereafter, the image acquisition unit 1 sequentially acquires one line of photographed images generated by the line sensor camera 33 at predetermined sampling intervals, and sequentially combines the acquired photographed images of each line (step S6). The hole detection unit 3 analyzes the photographed images of the veneer 101 acquired by the image acquisition unit 1 to determine whether the next hole has been detected (step S7).

[0061] If the hole detection unit 3 determines in step S7 that the next hole has not been detected, the thickness deficiency determination unit 5 determines (step S8) whether the conveyance distance of the veneer 101 from the time when the previous hole was detected by the hole detection unit 3 exceeds the peripheral plate length calculated by the peripheral plate length calculation unit 4. If the conveyance distance of the veneer 101 does not exceed the peripheral plate length, the process returns to step S6, and acquisition of photographed images of the veneer 101 continues.

[0062] On the other hand, if the hole detection unit 3 detects a hole H2 next to hole H1 in step S7, this means that the continuous veneer 101B is still continuing, and the process returns to step S4. In step S4, the length-per-circumference calculation unit 4 calculates the length-per-circumference L2 of the second round using the center position of hole H2 in the conveying direction as a reference position. Then, in step S5, the thickness insufficiency estimation unit 5 aligns the shape of hole H2 to a position that is the length-per-circumference L2 of the second round upstream in the conveying direction, and estimates the area defined by the aligned shape of hole H2 as a possible thickness insufficiency area.

[0063] Similarly, when hole H3 is detected in step S7, the process returns to step S4, the plate length per circumference L3 for the third round is calculated, and the area where the plate thickness may be insufficient is estimated based on the shape of hole H3 aligned to the position of plate length per circumference L3 (step S5).

[0064] In the loop process of steps S4 to S8 described above, if it is determined that the conveying distance of the veneer 101 exceeds the sheet length per revolution L3 for the third revolution (step S8: Yes) while the hole next to hole H3 remains undetected (step S7: No), this means that the section of continuous veneer 101B including unused portion y and useful portion f has ended and the section of continuous veneer 101C including only useful portion f has begun, and the process of the flowchart shown in Figure 5 ends. In reality, however, continuous veneer 101C will be conveyed after this, so the image acquisition unit 1 and hole detection unit 3 continue to execute their processes.

[0065] As described above in detail, in this embodiment, holes H1, H2, and H3 are detected in the continuous veneer boards 101B that are shaved by the veneer lace 10 from the log 100 rotating around the axis 11 and transported on the veneer transport conveyor 21, and the lengths of the veneer boards 101B shaved in each rotation of the log 100 are calculated as per-circumference lengths L1, L2, and L3. The shapes of the detected holes H1, H2, and H3 in a specific rotation are then aligned with positions one rotation later that are upstream in the transport direction by the per-circumference lengths L1, L2, and L3, and the area defined by the aligned shapes of the holes H1, H2, and H3 in the specific rotation is estimated to be a possible thickness insufficiency area (an area that may include the thickness insufficiency portions T2, T3, and T4).

[0066] With this embodiment configured as described above, it is possible to estimate that the areas obtained by aligning the shapes of holes H1, H2, H3 detected for each rotation of the log 100 based on the lengths L1, L2, L3 per rotation of each rotation may contain thickness-insufficient areas T2, T3, T4 formed when the inclined recesses 111 in the surface layer of the log are cut by the knives 12 of the veneer lace 10. In other words, this embodiment makes it possible to estimate areas that may contain thickness-insufficient areas T2, T3, T4 in the surface layer of the log, which are difficult to determine using methods such as photoelectric sensors to determine the presence or absence of an object based on reflected light, or methods that look at color differences in photographed images.

[0067] In the above embodiment, an example was described in which there is only one recess 111 in the surface layer of the log 100 as shown in Figure 3(a), and only one hole is detected during one rotation of the log 100. In contrast, as shown in Figure 6, there are recesses 111 in multiple places in the surface layer of the log 100. -1 , 111 -2 In this case, the number of holes H1 detected in the continuous veneer 101B during the first rotation may be 1 / 2. -1 , H1 -2 Each of these is used as a starting hole, and the plate length per circumference {L1 -1 , L2 -1 , ...}, {L1 -2 , L2 -2 , ...} may be calculated to estimate the area where the thickness may be insufficient.

[0068] In this case, the plate length calculation unit 4 calculates the plate length per circumference by detecting the hole H1 in the continuous veneer 101B by the hole detection unit 3. -1 is detected first, the hole H1 -1 is the starting hole, and hole H1 -1 The plate length L1 per revolution of the first revolution is measured upstream in the conveying direction from the reference position of -1 Also, the plate length per circumference L1 -1 Before the veneer 101B is conveyed, another hole H1 -2 is detected by the hole detection unit 3, the other hole H1 -2 Also, hole H1 is used as the starting hole. -2 The plate length L1 per revolution of the first revolution is measured upstream in the conveying direction from the reference position of -2 Then, the two starting holes H1 -1 , H1 -2 For each rotation, the plate length per rotation {L1 -1 , L2 -1 , ...}, {L1 -2 , L2 -2 , ...} are calculated in sequence.

[0069] In the above embodiment, the position of the hole to be aligned may be corrected using a captured image acquired by the line sensor camera 33 (an imaging device for acquiring information used for hole detection by the hole detection unit 3). For example, as shown in Fig. 7, the defect determination device 31 may further include a position correction unit 6, and may include a plate thickness insufficiency determination unit 5' instead of the plate thickness insufficiency determination unit 5.

[0070] The veneer 101 cut into the plywood lace 10 has flexibility due to the cracks (lace checks) that occur during cutting. However, because the veneer 101 is a natural material, there are some areas where deformation is unlikely due to variations in density or knots. Therefore, irregular deformation may occur in the veneer 101 during transport at the rear of the veneer lace 10. As a result, even if the position for aligning the hole shape is determined by the plate lengths L1, L2, and L3 per perimeter, accurate alignment may be difficult due to dimensional errors in the deformed veneer 101.

[0071] In response to this, the position correction unit 6 performs image matching by comparing an image captured by the line sensor camera 33 during a specific rotation of the log 100 (hereinafter referred to as a specific rotation image) with an image captured by the line sensor camera 33 during the rotation following the specific rotation (hereinafter referred to as a next rotation image), and corrects the position of the hole to be aligned based on the positional deviation between the specific rotation image and the next rotation image. The board thickness insufficiency determination unit 5' aligns the shape of the hole in the specific rotation detected by the hole detection unit 3 to the position corrected by the position correction unit 6.

[0072] Any method of image matching can be used. For example, image feature information can be obtained from a specific rotation image of a predetermined range around a hole acquired by the image acquisition unit 1 during a specific rotation, and a next rotation image of a predetermined range acquired by the image acquisition unit 1 one rotation after the specific rotation (a captured image of a predetermined range including a position upstream in the conveying direction by the plate length per rotation calculated by the plate length per rotation calculation unit 4), and image patterns can be matched by comparing the image feature information. As an example of image feature information, it is possible to use a feature amount obtained by Fourier transforming the captured image. Here, since the holes in the specific rotation image and the holes in the next rotation image are different sizes, it is preferable to match images of areas other than the holes.

[0073] When a positional misalignment between the specific orbital photographed image and the next orbital photographed image is detected by image matching, the position correction unit 6 corrects the position of the hole shape detected from the specific orbital photographed image based on the amount and direction of the misalignment. In this embodiment, image matching is performed using the plate length per circumference calculated by the plate length per circumference calculation unit 4. Therefore, even if a hole of a similar shape is detected in a position different from the position specified by the plate length per circumference, accurate image matching can be performed without being affected by the hole, making it possible to estimate the possible plate thickness insufficiency area with high accuracy.

[0074] In the above embodiment, an example has been described in which the line sensor camera 33 (an imaging device capable of capturing color images) is used as a sensor for acquiring information used for hole detection by the hole detection unit 3, but this is not limiting. For example, multiple photoelectric sensors arranged in a line in the width direction of the veneer 101 may be used. In this case, the hole detection unit 3 can detect holes by analyzing the information acquired by the multiple photoelectric sensors using a simple method that does not involve image processing.

[0075] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereby. In other words, the present invention can be carried out in various forms without departing from the gist or main characteristics thereof.

[0076] REFERENCE SIGNS LIST 1 Image acquisition unit 2 Knife movement distance acquisition unit 3 Hole detection unit 4 Perimeter board length calculation unit 4A Knife position detection unit 4B Conveying distance calculation unit 4C Log diameter acquisition unit 4D Board length calculation unit 5, 5' Board thickness deficiency estimation unit 6 Position correction unit 10 Veneer lace 11 Axis (log rotation center) 12 Knife 13 Knife movement distance sensor 21, 22 Veneer transport conveyor 30 Defect inspection system 31 Defect determination device 32 Lighting device 33 Line sensor camera (imaging device) 40 Veneer cutting device 41 Cutting control device

Claims

1. A veneer defect determination device comprising: a hole detection unit which detects holes in veneer which is shaved by a plywood lath from a log which rotates around its axis and is transported on a transport path; a length-per-circumference calculation unit which calculates the length of the veneer which is shaved in one rotation of the log for each rotation as the length per circumference; and a thickness deficiency estimation unit which aligns the shape of the hole in a specific rotation detected by the hole detection unit to a position one rotation later which is upstream in the transport direction by the length per circumference calculated by the length-per-circumference calculation unit, and estimates that a portion of the veneer which is insufficient in thickness is included within an area defined by the shape of the hole in the aligned specific rotation.

2. The veneer defect determination device according to claim 1, characterized in that the circumference length calculation unit calculates the circumference length for each revolution of the log based on log diameter information during cutting, which represents the radius of the log when the starting hole detected by the hole detection unit was formed by cutting with the veneer lace, and thickness information of the veneer to be cut.

3. The veneer defect determination device according to claim 2, characterized in that the board length per circumference calculation unit comprises: a knife position detection unit which detects the position of a knife which moves in the direction of the axis as cutting of the log by the veneer lace progresses; a conveying distance calculation unit which calculates a veneer conveying distance from the knife position detected by the knife position detection unit to a sensor position for acquiring information used for hole detection by the hole detection unit; a log diameter acquisition unit which, based on the veneer conveying distance calculated by the conveying distance calculation unit when the starting hole is detected by the hole detection unit, reverse-calculates the knife position when the starting hole was formed by cutting with the knife, and acquires the distance between the reverse-calculated knife position and the axis as the log diameter information during cutting; and a board length calculation unit which calculates the board length per circumference for each revolution of the log based on the log diameter information during cutting acquired by the log diameter acquisition unit and board thickness information of the veneer.

4. The veneer defect determination device according to claim 2, characterized in that when the hole detection unit detects another hole within the section of the board length per circumference of the first round calculated upstream in the conveying direction from the position of the hole first detected by the hole detection unit, the board length per circumference calculation unit calculates the board length per circumference for each round of the log, assuming that a plurality of holes including the first detected hole and the another hole are each the starting hole.

5. A veneer defect judgment device as described in any one of claims 1 to 4, characterized in that the sensor for acquiring information used for hole detection by the hole detection unit is an imaging device that photographs the veneer, and the hole detection unit detects the holes by analyzing the photographed image acquired by the imaging device.

6. The veneer defect determination device described in claim 5, further comprising a position correction unit that performs image matching by comparing a specific rotation image acquired by the imaging device during the specific rotation with a next rotation image acquired by the imaging device during the rotation next to the specific rotation, and corrects the position of a hole to be aligned based on the positional deviation between the specific rotation image and the next rotation image.

7. A veneer defect judgment device as described in any one of claims 1 to 4, characterized in that the sensors for acquiring information used for hole detection by the hole detection unit are a plurality of photoelectric sensors arranged in a line in the width direction of the veneer, and the hole detection unit detects the holes by analyzing the information acquired by the plurality of photoelectric sensors.

8. A method for determining defects in veneer, comprising the steps of: a hole detection unit of a defect determination device detecting holes in veneer that is shaved by a veneer lath from a log rotating about its axis and transported on a transport path; a board length per circumference calculation unit of said defect determination device calculating the length of veneer that is shaved in one rotation of the log for each revolution as board length per circumference; and a board thickness deficiency estimation unit of said defect determination device aligning the shape of the hole in a specific revolution detected by the hole detection unit to a position one revolution later that is upstream in the transport direction by the board length per circumference calculated by the board length per circumference calculation unit, and estimating that a part of the board thickness deficiency is included within an area defined by the shape of the hole in the aligned specific revolution.

9. A veneer defect determination program which causes a computer to function as: hole detection means for detecting holes in veneer which is shaved by a plywood lath from a log rotating about its axis and transported on a transport path; length per circumference calculation means for calculating the length of veneer which is shaved in each revolution of the log as the length per circumference; and thickness deficiency estimation means for aligning the shape of a hole in a specific revolution detected by the hole detection means to a position one revolution later which is upstream in the transport direction by the length per circumference calculated by the length per circumference calculation means, and estimating that a portion of the veneer which is insufficient in thickness is included within an area defined by the shape of the hole in the aligned specific revolution.

Images