Identification of defect in wood panel

Abstract

A computer-implemented method for identifying at least one defect in a wood panel (110) is provided, the method comprises: receiving (310) X-ray image data; receiving (330) ultrasound image data; the method further comprises: analyzing (320) the X-ray image data; analyzing (340) the ultrasound image data; and generating (350) a detection result to express at least one of: i) the defect originating from the error in glueing is present in the wood panel (110), ii) the defect originating from a missing portion of a layer is present in the wood panel (110) Also a computing system (120), a computer program and a detection system are provided to.

Description

[0001] IDENTIFICATION OF DEFECT IN WOOD PANEL

[0002] TECHNICAL FIELD

[0003] The invention concerns in general the technical field of wood processing. More particularly, the invention concerns an identification of defects in wood panels.

[0004] BACKGROUND

[0005] Manufacturing of wood panels is a sophisticated process comprising a plurality of manufacturing phases. In spite of sophisticated processing techniques there occurs various kinds of events that may generate a defect to the wood panel during the manufacturing. The defects may be present in an edge of the wood panel, on a surface of the wood panel or even inside the wood panel. The detection of the defects is traditionally made by an operator of the system during the manufacturing process. However, the approach is problematic due to a fact that the operator may only review the outer surfaces of the wood panels and, thus, at least some of the defects cannot be detected by the operator. Moreover, the visual detection is difficult due to the fact that the manufacturing process is fast and the panels travel fast in the manufacturing process.

[0006] To overcome the challenges in the visual inspection there are introduced solutions for automatically detecting specific defects in the wood panels. The following prior art solutions are available:

[0007] • Laser based detection: o Laser profiling technique works only for analysing the surface(s) of the wood panels. In other words, it does not enable an analysis inside the panel.

[0008] • Ultrasound based detection: o Ultrasound based approach enables an analysis of an inner part of the wood panel together with a surface layers. It may be used to detect a failed glue bond e.g. in a layered wood panels, but it does not enable differentiating the failed glue bond from another type of defects in a reliable manner, such as if material is missing and / or if extra material exists in the structure e.g. due to overlaying.

[0009] The prior art solutions are operative as such in their specific fields and with respect to specific defects. However, there is room for introducing novel approaches to improve defect analysis of the wood panels.

[0010] SUMMARY

[0011] The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

[0012] An object of the invention is to present a method, a computing system, a computer program and a detection system for identifying a defect in a wood panel.

[0013] The objects of the invention are reached by a method, a computing system, a computer program and a detection system for identifying a defect in a wood panel as defined by the respective independent claims.

[0014] According to a first aspect, a method for identifying at least one defect in a wood panel comprising a plurality of layers is provided, the method, performed by a computing system, comprises: receiving X-ray image data representing a first portion of the wood panel, receiving an ultrasound image data representing a second portion of the wood panel, wherein at least part of the X-ray image data and at least part of the ultrasound image data are representing a common portion of the wood panel, the method further comprises: analyzing the X-ray image data, analyzing the ultrasound image data, generating a detection result, based on an analysis of the X-ray image data and an analysis of the ultrasound image data, to express at least one of: i) the defect originating from a missing portion of a layer is present in the wood panel in response to that the analysis of the ultrasound image data generates a detection of the defect in a position and the analysis of the X-ray image data generates a detection of the defect in the position, ii) the defect originating from the error in glueing is present in the wood panel in response to that the analysis of the ultrasound image data generates a detection of the defect in a position and the analysis of the X-ray image data does not generate a detection of the defect in the position.

[0015] A capture of an X-ray image may be triggered on a basis of a result of analysis of the ultrasound image data. For example, the triggering may be performed in response to a detection of the detection based on a detection of a deviation in the ultrasound image data in the position. Still further, the triggering of the capture of the X-ray image may be performed by generating a control signal to an X-ray imaging unit. The control signal may be arranged to carry data defining a portion of the wood panel from which the X-ray image is to be captured, the portion at least comprising the position of the defect detected from the ultrasound image data.

[0016] The method may further comprise: determining data indicative of a size of the defect from at least one of the following: the X-ray image data; the ultrasound image data in response to that, associating the data indicative of the size of the defect to the detection result.

[0017] Further, the position of the defect detected from the ultrasound image data and the position of the defect detected from the X-ray image data may be compared by defining the positions in a same coordinate system.

[0018] Still further, a detection result expressing that the defect originating from a missing portion of a layer is present in the wood panel and the defect originating from the error in glueing is present in the wood panel at least in part in a corresponding position may be generated in response to a detection that a size of the defect detected from the X-ray image data is smaller than a size of the defect detected from the ultrasound image data.

[0019] According to a second aspect, a computing system of a detection system for identifying a defect in a wood panel comprising a plurality of layers is provided, the computing system is configured to carry out the method according to the first aspect as defined above.

[0020] According to a third aspect, a computer program is provided, the computer program comprising instructions, when the program is executed by a computing system according to the second aspect as defined above, cause the computing system to carry out the method according to the first aspect as defined above.

[0021] According to a fourth aspect, a detection system is provided, the detection system comprising: an ultrasound imaging unit, an X-ray imaging unit, and the computing system according to the second aspect as defined above.

[0022] The expression "a number of” refers herein to any positive integer starting from one, e.g. to one, two, or three.

[0023] The expression "a plurality of” refers herein to any positive integer starting from two, e.g. to two, three, or four.

[0024] Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

[0025] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

[0026] BRIEF DESCRIPTION OF FIGURES

[0027] The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0028] Figure 1 illustrates schematically a detection system according to an example from a first viewing angle.

[0029] Figure 2 illustrates schematically a detection system according to an example from a second viewing angle.

[0030] Figure 3 illustrates schematically a method according to an example.

[0031] Figure 4 illustrates schematically a computing system according to an example.

[0032] DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS The specific examples provided in the description given below should not be construed as limiting the scope and / or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

[0033] Figure 1 illustrates schematically an example of a detection system 100 configured to implement the present invention to identifying a defect in a wood panel 110 comprising a plurality of layers as a side-view. The detection system 100 comprises a computing system 120, an X-ray imaging unit 130 and an ultrasound imaging unit 140. The computing system 120 is communicatively connected to the X-ray imaging unit 130 and the ultrasound imaging unit 140 at least to receive image data from the respective units. In some embodiments the computing system 120 may also perform control operations with respect to the imaging units 130, 140. The X-ray imaging unit at least comprises an X- ray source and an X-ray detector (cf. sensor) wherein the X-rays generated by the X-ray source (cf. tube) at least in part penetrate an object (cf. the wood panel 110) and end up to the detector to form an image of at least part of the object. The detector is preferably such that it generates the X-ray image as digital data directly transmittable to the computing system 120. Correspondingly, the ultrasound imaging unit 140 comprises an ultrasound source and a detector for receiving ultrasound from various vertical levels of the wood panel 110. The implementation of the ultrasound imaging unit 140 may be such that the ultrasound source and the detector are at different sides of the wood panel 110 under measurement (i.e. the ultrasound travels through the panel from the source to the detector) or such that the ultrasound source and the detector are on the same side. As such the imaging units 130, 140 comply with commonly known techniques. Naturally, the intensities and wavelengths of the applied X-ray radiation and ultrasound waves are selected for the application area so as to generate respective image data to the computing system 120 as is described in the forthcoming description.

[0034] The implementation of the imaging may correspond to the embodiment of

[0035] Figure 1 wherein wood panels are transported with a number of conveyors 150 over the imaging units 130, 140 that are arranged statically on the travel path of the wood panel 110 in a manner that the images may be captured. Advantageously, each imaging unit 130, 140 is arranged to capture respective image over a full width of the wood panel 110 thus making the imaging to occur over the whole wood panel 110 as shown in Figure 2 as a top-view of the detection system 100. This may require at least a selection of the imaging unit 130, 140 in a necessary way and adjustment its operation accordingly with respect to the travel path of the wood panel 110. However, it is also possible that only a portion of the wood panel 110 is imagined but both the X-ray image data and the ultrasound image data comprise at least one common portion imagined, i.e. both image data comprise a portion that represents the image captured with the different imaging techniques on the same portion of the wood panel 110. This means that the first portion and the second portion imaged with the respective imaging techniques are overlapping at least in part.

[0036] The implementation according to Figure 1 is based on that the source of X-ray radiation and the ultrasound unit 140 are above the travel path of the wood panel 110. Naturally, the detector of the X-ray unit 130 is then below the travel path of the wood panel 100. However, the implementation of the imaging units 130, 140 may be arranged so that the source or X-ray radiation and the ultrasound unit 140 are below the travel path of the wood panel 110 and the detector of the X-ray unit 130 is above the travel path. Naturally, it is also possible that the ultrasound unit 140 is arranged on the same side as the X- ray detector. Any of the implementations shall be implemented so that the number of conveyors 150 does not block the imaging of the wood panel 110 with any of the imaging techniques. For example, the X-ray imaging unit 130 may be arranged between the conveyors 150 so that the wood panel travels between the X-ray source and the X-ray detector when the panel 150 travels from one conveyor 150 to another as shown in Figures 1 and 2. It may also be arranged that the conveyor 150 applied in the context of the present invention is such that it is arranged to grip the panel 110 with specific gripping devices, such as suction units, and the wood panel 110 may then be imaged without any blocking elements of the conveyor(s) 150. For avoidance of doubt, it is worthwhile to mention that in accordance with at least some embodiments of the invention the capturing of images with the mentioned imaging techniques is performed from a direction facing a surface layer of the wood panel 110 as e.g. derivable from Figure 1.

[0037] In accordance with another embodiment the imaging units 130, 140, or at least one of them, may be configured to be movable so that it may be arranged to perform the imaging by moving with respect to the wood panel 110 at a different speed than the wood panel 110 is moving. For example, the wood panel 110 may be stopped at a predefined position wherein a scanning of the wood panel 1 10 with at least one of the imaging techniques is performed with a movable imaging unit 130, 140. The movable imaging unit 130, 140 may refer to that it is arranged to move above or below the stopped wood panel 110 e.g. over a predefined area of the wood panel 110, such as over the whole area of the wood panel 110. Alternatively or in addition, the at least one imaging unit 130, 140 may be arranged to be movable at a predefined position over at least one axis, i.e. the imaging unit 130, 140 performs the movement over at least one axis so that it may direct the beam over the wood panel 110 from the position the imaging unit 130, 140 resides. Naturally, the respective detector unit(s) is / are arranged to follow the source of the X-ray radiation and / or the source of the ultrasound so that the measurement data may be captured. The movement of the mentioned entities may be arranged with movable arms and / or by arranging the movable entities to guide rails along which the entities may be moved with a help of actuators / motors providing the force for movement.

[0038] For avoidance of doubt it is worthwhile to mention that the imaging units 130, 140 may be controlled in a desired manner, such as the wood panel 110 is automatically imaged with both imaging techniques. Alternatively, the operations of the imaging units 130, 140 may be made dependent on each other. For example, in a preferred approach each wood panel 110 may be imaged with the ultrasound imaging unit 130 and the ultrasound image data is analyzed. If the analysis generates one or more predefined detections, the imaging with the X-ray imaging unit 130 is triggered. This kind of approach may require that the imaging units 130, 140 are positioned with respect to each other so that the analysis and the control of them may be optimally performed. Alternatively or in addition, it may be arranged that the movement of the wood panel 110 in the travel path is arranged so that the wood panel 110 may be brought to the X-ray imaging unit 130 if it is triggered by the analysis of ultrasound image data, i.e. due to one or more predefined detections therein. When one of the imaging methods is made dependent on the other the order of the imaging units 130, 150 in the detection system 100 shall be arranged accordingly. For example, if the analysis of the ultrasound image data may trigger the capture of the imaging with the X-ray imaging unit 130, the ultrasound imaging unit 140 is advantageously arranged prior to the X-ray imaging unit 130 in the travel direction of the wood panel 110.

[0039] Next at least some aspects of the invention are described by referring to Figure 3 schematically illustrating a method according to an example. The computer- implemented method is for identifying a defect, or defects, in a wood panel 110 comprising a plurality of layers. The invention is especially advantageous with wood panels 110 comprising more than three layers because the invention also enables an identification of defects locating inside the wood panel 110, i.e. not visible on the surface portions of the wood panel 110. The computer- implemented method may be performed by a computing system 120 as mentioned.

[0040] In accordance with the method X-ray image data representing a first portion of the wood panel 110 is received 310. This refers to an approach wherein at least a portion of the wood panel 110 is imaged with the X-ray imaging unit 130. The computing system 120 is configured to analyse 320 the X-ray image data to detect if there is possible defects, i.e. candidate defects, in the wood panel 110 on the basis of the analysis 320 of the X-ray image data. The analysis 320 of the X-ray image data may be based on a detection of defects based on density analysis, i.e. since the X-rays attenuate in a different manner in accordance with the density in the imaged object and the differences in the density of the object, i.e. the wood panel 110, may be identified on the basis of variations in contrast in various regions in the X-ray image. In other words, if a portion of a layer being part of the wood panel 110 is missing, the deviation in a density of the wood panel 110 in the area the layer is missing may be detected as a deviating portion, such as a darker or lighter portion in the image data depending on the applied visualization, because there occurs less attenuation of the X-rays than in other portions of the wood panel 110. Hence, the analysis 320 of the X-ray image data may generate detections of defects in one or more positions, or sub-areas, in the wood panel 110. Thus, the analysis 320 may generate a detection of the defect in a position, called as a first position, of the wood panel 110. The data indicative of the detection may comprise a definition of the position of the defect as coordinates in a coordinate system into which the wood panel 110 is computationally positioned to. Additionally, it may comprise a definition with respect to the defect(s), such as a value of a contrast within the position of the defect. In the positioning of the wood panel 110 computationally in the coordinate system predefined markers of the wood panel 110 may be applied to in a known manner (cf. corners / edges of the wood panel 110 / specific markings implemented on the wood panel 110 I etc.). For avoidance of doubt it is worthwhile to mention that in case the analysis 320 of the X-ray image data does not generate the detection of the defect(s), a predefined operation may be performed. The predefined operation may e.g. refer to that an execution of the method according to the present invention is discontinued with respect to the wood panel 110 in question. Alternatively or in addition, a notification indicative of that no defects are detected from the X-ray image data may be generated, for example.

[0041] Correspondingly, in accordance with the present invention an ultrasound image data representing a second portion of the wood panel 110 is received 330. The pieces of image data with the X-ray imaging technique and the ultrasound imaging technique may be captured simultaneously to each other at least in part or consecutively to each other. For example, the capturing of the X-ray image may be triggered by a predefined condition with respect to the ultrasound image data as already mentioned in the foregoing description. In accordance with the invention the images with the different imaging techniques are captured so that the X-ray image and the ultrasound image represent at least in part a common portion of the wood panel 110, i.e. the same area / volume of the wood panel 110 is at least in part imaged with both imaging techniques. In accordance with at least some embodiments the first portion and the second portion correspond exactly to each other. For example, the first portion and the second portion may cover the whole wood panel 110 in question, i.e. the images with both imaging techniques are captured over the whole wood panel 110. In accordance with an embodiment of the invention the detection system 100 may be configured so that the imaging units 130, 140 are configured to capture the images so that there always exists the common portion.

[0042] In response to the receipt 330 of the ultrasound image data the computing system 120 is configured to analyse 340 the ultrasound image data and to detect 340 whether there exists defects in the wood panel 110 based on the analysis of the ultrasound image data. Hence, the analysis 340 of the ultrasound image data may generate detections in one or more positions, or sub-areas, in the wood panel 110. Thus, the analysis 340 may generate a detection of the defect in a position, called as a second position, of the wood panel 110. The data indicative of the detection may comprise a definition of the position of the defect as coordinates in a coordinate system into which the wood panel 110 is computationally positioned to. For avoidance of doubt, the positions of the defects from the X-ray image data analysis 320 and the ultrasound image data analysis 340 are defined in the same coordinate system so as to make them comparable in position with respect to each other. The coordinate system is at least two-dimensional, but also a three-dimensional coordinate system may be applied to. The three-dimensional coordinate system especially allows a positioning of the defects detected from the ultrasound image data more accurately in the thickness direction of the panel (y direction in the coordinate system shown in Figure 1 ) whereas the defects on the basis of the X-ray image data cannot be positioned in the thickness direction, but only in a xz domain as shown as coordinate system in Figure 2. For example, the same kind of computational positioning of the defect(s) to the coordinate system found through the ultrasound image analysis may be applied to as already described in the context of the X-ray image processing in the foregoing description (cf. markers). For avoidance of doubt it is worthwhile to mention that in case the analysis 340 of the ultrasound image data does not generate the detection of the defect(s), a predefined operation may be performed. The predefined operation may e.g. refer to that an execution of the method according to the present invention is discontinued with respect to the wood panel 110 in question. Alternatively or in addition, a notification indicative of that no defects are detected from the ultrasound image data may be generated, for example.

[0043] For avoidance of doubt it is worthwhile to mention that in order to compare the positions of the defects found from at least one of the image data as described there may be preliminary step in which the pieces of image data are made corresponding to each other in resolution. This may mean that at least one of the images, e.g. the X-ray image, is computationally manipulated, e.g. by stretching, so that the resolution of it corresponds to the resolution of the ultrasound image to make the details of the images be comparable to each other. Alternatively or in addition, other aspects e.g. in terms of applied signal processing may be taken into account in the manipulation. The adjustment of the images in the described manner make them, and the data derivable therefrom, compatible to be positioned in the common coordinate system. As such, the techniques of adjusting resolutions of two different pieces of image data to correspond to each other are known as such and they are not necessary to discuss in more detail herein.

[0044] The analysis 340 of the ultrasound image data is based on that different structures, e.g. surfaces of sublayers of the panel etc., in the wood panel 110 generate specific kinds of changes in the intensity or time of flight of transmitted and reflected ultrasound which may identified from the ultrasound image data and, thus, a type of the defect may be determined with a certain probability as is described in the forthcoming description. For example, the measurement data received by the ultrasound detector may be compared to a reference value to decide if a detection is present or not.

[0045] It is also worth mentioning that the steps of analyzing 320, 340 of the respective image data may generate detections of a plurality of defects and these may be processed individually in the corresponding manner as described herein.

[0046] As a result of the method as described above the computing system 120 is aware of the result of the X-ray image data analysis 320 and the result of the ultrasound image data analysis 340 and is configured to generate 350 a detection result based on these. The generation 350 of the detection result may refer to an operation in which the computing system 120 is configured to generate 350 the detection result by evaluating data representing the defect(s) identified with the X-ray image analysis 320 and the defect(s) identified with the ultrasound image analysis 340 with respect to each other. The evaluation at least comprises that the positions of the defects identified based on different types of image data are compared to each other in order to confirm that they represent the same position in the wood panel 110, i.e. if the first position representing the position of the defect and the second position representing the position of the defect match with a predefined accuracy. Thus, in case at least one of the analyses 320, 340 generates a plurality of detections all these are compared to each other in terms of the position in order to find if any of the defects from the various analyses 320, 340 represent the same position. As already mentioned, this is possible since at least part of the X-ray image data and at least part of the ultrasound image data represent the same portion, aka. the common portion, of the wood panel 110. To describe the present invention further it is hereby assumed that the evaluation of the defects generates a detection that they reside in the same position wherein the term ‘position’ refer to a definition of the position in a predefined manner, cf. e.g. as a sub-area of the wood panel 110 defined computationally in the coordinate system. Thus, in response to the detection that both analysis paths have generated at least one identification of defects residing in the same position of the wood panel 110 the evaluation may be continued to generate 350 a detection result expressing a type of the defect more accurately.

[0047] Hence, the generation 350 of the detection result comprises a determination of the type of the defect on the basis of the analysis of the X-ray image data and the analysis of the ultrasound image data. Thus, the combination of the X- ray imaging and the ultrasound imaging according to the present invention is harnessed to identify if the defect originates from an error in in glueing the layers of the wood panel 110 together or if the defect originates from a missing portion of a layer in the analyzed position of the wood panel 110 (e.g. due to a knothole etc.). A detection result to express one of the mentioned outcome may thus be generated 350 based on the following criteria:

[0048] A) The defect originating from a missing portion of layer is present in the wood panel 110 if: i) X-ray image data indicates a detection in a form of a lower density (deviating density) compared to surrounding area in the X-ray image in the position where a defect is also detected in the ultrasound image data, AND ii) ultrasound image data indicates a detection e.g. in a form of one or more deviating intensities in the ultrasound image data (e.g. due to surface(s) of the hole formed due to the missing portion of the layer in the wood panel). The detection of the deviation occurs in the position where a defect is also detected in the X-ray image data.

[0049] B) The defect originating from an error in glueing of layers is present in the wood panel 110 if: i) X-ray image data does not generate a detection in a form of a lower density (deviating density) compared to surrounding area in the X-ray image in the position where a defect is detected in the ultrasound image data, AND ii) ultrasound image data indicates a detection e.g. in a form of one or more deviating intensities in the ultrasound image data. For avoidance of doubt the difference between the situations A), i) and B), i) as defined above is that in the former situation (A), i)) the panel does not comprise all layers in the position which is the case in the latter situation (B), i)).

[0050] Hence, in the step denoted with 350 the computing system 120 is configured to generate, or set, a detection result, based on the outcomes of the analysis steps 320, 340, to express one of: i) the defect origins from the error in glueing, ii) the defect origins from a missing portion of a layer in the position. The detection result expressing that the defect originates from the error in glueing is set, or generated, in response to that the analysis 340 of the ultrasound image data generates a detection (cf. a first detection) of the defect in a position and the analysis 320 of the X-ray image data does not generate a detection (cf. a second detection) of the defect in the position, i.e. in the same position as the analysis of the ultrasound image data. Correspondingly, the detection result expressing that the defect originating from a missing portion of a layer is present in the wood panel 110 is set, or generated, in response to that the analysis 340 of the ultrasound image data generates a detection (cf. a first detection) of the defect in a position and the analysis 320 of the X-ray image data generates a detection (cf. a second detection) of the defect in the position, i.e. in the same position as the analysis of the ultrasound image data. In other words, the detection result combines both the result of the X-ray image analysis 320 and the result of the ultrasound image analysis so as to generate a combined result as the detection result. The generation 350 of the detection result may also comprise a sub-step in which data indicative of the size of the defect may be determined. The determination of the size of the defect identified both from the ultrasound image data and from the X-ray image data may comprise a generation of information as an area, a volume and / or dimensions in one or more directions, such as in xyz directions in the coordinate system shown in Figures 1 and 2. For example, the area may be determined specifically from the X-ray image data whereas a height of the defect in the y direction may be determined from the ultrasound image data. The determination of the size of the defect may be based on that the computing system 120 is provided with a scale of the respective image and the computing system 120 is configured to perform measurements with respect to the defect in the various directions. In response to the determination of the size of the defect, it may be associated to the detection result expressing the type of the defect which may correspond to that a data record is generated wherein the detection result expressing the identified defect is included together with the estimation of the size of the defect as determined.

[0051] In relation to the identification of a defect in the described manner it may also occur that the wood panel 110 comprises a plurality of defects substantially at the same position in different layers of the wood panel 110, i.e. at different heights in y direction as shown in the enclosed figures. A typical example is that there is knothole in a layer belonging to the wood panel 110 but additionally there is a defect in glueing of layers together e.g. in position, i.e. at a different height. The present invention is also applicable to perform a detection of both defects on the basis of the X-ray image data and the ultrasound image data obtained in a manner as described in the foregoing description. In accordance with an embodiment, a defect originating from the missing portion of a layer corresponding e.g. to the knothole may be detected from the X-ray image data in the position as described. Correspondingly, a defect originating from the error in glueing may be detected from the ultrasound image data substantially in the same position, i.e. that the positions overlap at least in part in the y direction. In some cases, such as when the knothole is large in size, it may also be detected from the ultrasound data, i.e. both pieces of image data carries information indicative of the missing portion of the layer, but the error in glueing may only be detected from the ultrasound image data. In some embodiments it may be arranged that a part of the image data is filtered out from the image data based on detection(s) from the other image data. This refers to an approach wherein a number of defects are detected e.g. from the X-ray image data wherein the detection(s) may e.g. represent one or more knotholes. Such defects may be clearly detected from the X-ray image data due to that the deviation in the contrast in the X-ray image is clear and as a result the area defining the defect may be defined in a pixel level (i.e. by determining pixels defining the defect area). In response to this data representing the corresponding area may be filtered out from the ultrasound image data e.g. at least to an extent that they are not taken into account in the analysis of the ultrasound image data. In order to perform the above describe operation and the evaluation if a plurality of defects are present in the same area (cf. xz domain even if in different layers in y direction) there is a need to adjust at least one of the image data, such as the X-ray image data, so that the resolutions of each imaging data are comparable to each other as already discussed in the foregoing description. In response to the filtering out the area(s) of defects from the ultrasound image data on the basis of detections of the defect(s) from the X-ray image data it may be analyzed if the ultrasound image data still comprises data that is indicative of further defects around the position of the defect(s) identified from the X-ray image data. In other words, the analysis of the remaining ultrasound image data may generate information that indicates a further defect around the position of the defect detected from the X-ray image data. Since a part of the area is filtered out as described and the analysis still generates a detection around the position of the defect whose pixels are filtered out, it means that the area of the further defect is larger in size than the defect whose pixels are filtered out since the further defect is found. In accordance with an embodiment of the invention the computing system may generate an indication that there is a further defect in the same position and since it is only detected from the ultrasound image data, it may be concluded, and thus indicated, that the further defect in the position is a glueing error. In order to make the detection of the further defect more accurate the computing system 120 may be arranged to apply one or more margins e.g. defining a size of area that the further defect shall fulfill e.g. compared to the filtered area in order to conclude that there is a further defect in the position as described. As may be concluded from the description above by evaluating an areas of defects from the different pieces of image data in the described manner the present invention also enables a detection of a plurality of overlaying defects in a position, or substantially in the same position (cf. the images representing the imaged portion of the wood panel in xz domain). The method as described to detect the overlaying defects is thus a derivative of the situation A as described above wherein the situation A is concluded when the sizes of the defects detected from the different pieces of image data in the same position corresponds to each other within predefined margin if applied and if the sizes of the defects differ from each other over the predefined margin, a conclusion of the overlaying defects may be made. For avoidance of doubt it is worthwhile to mention that in order to implement the detection of the overlaying defects in the above-described manner the result of analysis 320 of the X-ray image data may be brought into the analysis 340 of the ultrasound image data with necessary information, such as at least a position of the defect(s) identified in the step 320 as well as definition of the defect(s) (e.g. size, shape, etc. expressed in an agreed manner, such as a definition of area by pixels or coordinates etc.). This is shown as an arrow with a dashed line from the step 320 to the step 340 in Figure 3. As a result, the analysis 340 of the ultrasound image data applies the operations as described to decide if there is only one defect or a plurality of overlaying defects.

[0052] Moreover, the detection result generated 350 by the computing system 120 and related information may be used in various methods to handle the wood panel 110 further. Such methods may e.g. relate to sorting of the wood panels 110, to classifying them as well as to selecting how they are processed. For example, the sorting of the wood panels 110 to various categories may be performed on a basis of positions of defects in a direction of thickness of the wood panel (i.e. in y direction in the coordinate system shown in Figure 1 ). The categories may e.g. be defined in an order of preference as follows:

[0053] • Category 1 : No defects identified from the wood panel 110

[0054] • Category 2: The detection result expresses that the defect(s) originates from the error in glueing and the defect(s) reside inside the structure of the wood panel 110 at a predefined distance from the surface layers of the wood panel 110,

[0055] • Category 3: The detection result expresses that the defect(s) originates from the error in glueing or the defect originates from a missing portion of a layer and the defect(s) reside inside the structure of the wood panel 110 at a predefined distance from the surface layers of the wood panel 110,

[0056] • Category 4: The detection result expresses that the defect(s) originates from the error in glueing and the defect(s) reside close to the top surface or the bottom surface of the wood panel 110 at a predefined distance from the respective surface layer of the wood panel 110,

[0057] • Category 5: The detection result expresses that the defect(s) a missing portion of a layer and the defect(s) reside close to the top surface or the bottom surface of the wood panel 110 at a predefined distance from the respective surface layer of the wood panel 1 10.

[0058] The Category 5 as defined above may e.g. cause a refusal of the respective wood panel 110 due to its low quality.

[0059] Another approach in sorting of the wood panels may be based positions of defects in a direction of thickness of the wood panel together with their size and a number of them. The categories available for sorting as an order of preference may then e.g. be defined as follows:

[0060] • Category 1 : No defects identified from the wood panel 110 or at maximum a predefined number N of defects being at maximum a predefined size S (e.g. < 50 mm) are identified and they originate from the error in glueing and the defect(s) reside inside the structure of the wood panel 110 at a predefined distance from the surface layers of the wood panel 110,

[0061] • Category 2: At maximum a predefined number N of defects in a unit area having a size S in a predefined range R (e.g. 50 mm < S < 100 mm) are identified and they originate from a missing portion of a layer and they reside at a predefined distance from the surface layers of the wood panel 110,

[0062] • Category 3: The detection result expresses that the defect(s) are close to surface layers and they either originate from the error in glueing and having at maximum a size S (e.g. < 50 mm) or they originate from a missing portion of a layer and the size of the defect is max 5 mm in any direction and the other criteria of the Category 2 are fulfilled.

[0063] • Category 4: Defects are present but the panel cannot be categorized in any of the preceding categories.

[0064] Again, the wood panels defined to belong to the Category 4 may be refused.

[0065] The classification of the wood panels may e.g. be based on a utilization of the positions of the defects and a size information of an object to be cut, or saw, from the wood panel 110. The classes may e.g. be defined as an order of preference as follows:

[0066] • Class I: The object to be cut from the wood panel 110 comprises defects originating from a missing portion of a layer and having a maximum size of S (e.g. < 10 mm) in any direction.

[0067] • Class II: The object to be cut from the wood panel 110 comprises defects originating from a missing portion of a layer, having a maximum size S in a range R1 (e.g. 0 < S < 40 mm) in any direction and residing in edge areas of the cut piece (e.g. defined as a distance from the edge) or the size S of the defects are in a range R2 (e.g. 10 mm < S < 70 mm) in other parts of the cut piece.

[0068] • Class III: If the cut piece comprises defects originating from the error in glueing or the size of the defects are bigger than defined in the Class I or the Class II.

[0069] The wood panels 110 classified to the Class III may be refused.

[0070] The selection of further processing of the wood panel 110 on the basis of the detection result and the additional information (cf. e.g. positions of defects, sizes of defects and so on) may relate to an approach wherein an aim is to cut a plurality of pieces having different shapes from the wood panel. In such a situation the processing may be defined by matching the plurality of pieces to be cut from the wood panel 110 in various manner to the wood panel 110 by taking into account required characteristics (e.g. in terms of allowable defects) of each piece. Additionally, the waste from the cutting may be used as one parameter in the matching. By making this computationally the optimal processing method, such as a scheme for cutting, may be determined.

[0071] In the foregoing description of at least some aspects of the present invention it is assumed that the X-ray imaging and the ultrasound imaging are performed and processed independently from each other until the final detection result is generated 350. However, the invention may be implemented so that a first image is captured with one of imaging techniques among the X-ray imaging and the ultrasound imaging and the captured image data is processed until it may be used to control an imaging of the wood panel 110 with the other imaging technique among the X-ray imaging and the ultrasound imaging. For example, the imaging may be performed first so that the computing system 120 receives 310 the ultrasound image data. The analysis 340 and the detection of the one or more defects may be performed as described in the foregoing description. As a result, the computing system is 120 aware of the at least one defect in the wood panel 110 and its position. In accordance with an embodiment of the invention the computing system 120 may be configured to control the X-ray imaging unit 140 on the basis of the information generated in the analysis 340 of the ultrasound image data. For example, the control of the X-ray imaging unit 140 may be performed so that it is instructed with a control signal, by the computing system 120, to capture the X-ray image from a portion of the wood panel 110 wherein the portion comprises at least the position in which the defect is detected to reside in the analysis 340 of the ultrasound image data. In response to capturing of the X-ray image from the position and receiving 310 the data the computing system 120 may perform the analysis 320 and the detection of a defect as already described in the foregoing description. The advantage of this kind of approach is that an efficiency of the detection system 100 may be improved since the X-ray imaging is not performed over the whole wood panel 110 and the data needed to be analyzed 320 is optimized. Naturally the order of the imaging may be vice versa, i.e. the X-ray imaging is performed first and the data derived therefrom is used in controlling the ultrasound imaging. Hence, the described approaches make the imagings with the different techniques dependent on each other.

[0072] An example of a computing apparatus suitable to implement a functionality of the computing system 120 is schematically illustrated in Figure 4. The computing apparatus implanting the functionality of the computing system 120 may be a computer device, for example. For sake of clarity, it is worthwhile to mention that the block diagram of Figure 4 depicts some components of an entity that may be employed to implement a functionality of the apparatus.

[0073] The apparatus of Figure 4 comprises a processing unit 410 consisting of a number of processors and a memory 420. The memory 420 may store data, but also computer program code 425, causing an operation in a manner as is described in the foregoing description. The apparatus may further comprise a communication interface 430, such as a wireless communication interface or a communication interface for wired communication, or both to communicate with other entities at least belonging to the charging system as described. The communication interface 430 may thus comprise one or more modems, antennas, and any other hardware and software for enabling an execution of the communication e.g. under control of the processing unit 410. Furthermore, I / O (input / output) components may be arranged, together with the processing unit 410 and a portion of the computer program code 425, to provide a user interface for receiving input from an operator and / or providing output to the operator of the apparatus when necessary. In particular, the I / O components may include user input means, such as one or more keys or buttons, a keyboard, a touchscreen, or a touchpad, etc. The I / O components may also include output means, such as a loudspeaker, a display, or a touchscreen. The components of the apparatus may be communicatively connected to each other via data bus that enables transfer of data and control information between the components.

[0074] The memory 420 and at least a portion of the computer program code 425 stored therein may further be arranged, with the processing unit 410, to cause the apparatus to perform at least a portion of a method as is described in the forthcoming description. The processor 410 may be configured to read from and write to the memory 420. Although the processing unit 410 is depicted as a respective single component, it may be implemented as respective one or more separate processing components. Similarly, although the memory 420 is depicted as a respective single component, it may be implemented as respective one or more separate components, some, or all of which may be integrated I removable and I or may provide permanent I semi-permanent I dynamic / cached storage.

[0075] The computer program code 425 may comprise computer-executable instructions that implement functions that correspond to steps implemented in the method when loaded into the processing unit 410 of the respective computing system 120. As an example, the computer program code 425 may include a computer program consisting of one or more sequences of one or more instructions which may relate to an execution of the guidance data generation but also other operations, such as to control the charging itself. The processing unit 410 is able to load and execute the computer program by reading the one or more sequences of one or more instructions included therein from the memory 420. The one or more sequences of one or more instructions may be configured to, when executed by the processing unit 410, cause the apparatus to perform a method as described. Hence, the apparatus may comprise at least one processing unit 410 and at least one memory 420 including the computer program code 425 for one or more programs, the at least one memory 420 and the computer program code 425 configured to, with the at least one processor 410, cause the apparatus implementing the computing system 120 to perform at least the method as described.

[0076] The computer program code 425 may be provided e.g. a computer program product comprising at least one computer-readable non-transitory medium having the computer program code 425 stored thereon, which computer program code 425, when executed by the at least one processor of the processing unit 410, causes the apparatus to perform the method. The computer-readable non-transitory medium may comprise a memory device or a record medium, such as a CD-ROM, a DVD, a Blu-ray disc, or another article of manufacture that tangibly embodies the computer program. As another example, the computer program may be provided as a signal configured to reliably transfer the computer program.

[0077] Still further, the computer program code 425 may comprise a proprietary application, such as computer program code for causing an execution of the method in the manner as described in the description herein.

[0078] Any of the programmed functions mentioned may also be performed in firmware or hardware adapted to or programmed to perform the necessary tasks.

[0079] The operation of the apparatus implementing the computing system 120 may be implemented with a plurality of apparatuses, such as with the one schematically illustrated in Figure 4, as a distributed computing environment. The distributed computing environment may be implemented as a cloud computing system wherein a number of apparatuses are harnessed to execute operations to generate an implementation of a method as is described herein. In the distributed computing environment the plurality of apparatuses are each configured to perform a dedicated task or dedicated tasks and the cooperation of the apparatuses cause the operation of the controller to occur in the manner as is described herein.

[0080] Hence, the invention is based on utilization various imaging techniques to generate image data based on which conclusions on a wood panel may be made. In other words, the pieces of image data from the different imaging techniques are evaluated and combined in the described manner so that improved conclusions on the wood panel, and specifically defect(s) therein, may be made.

[0081] The specific examples provided in the description given above should not be construed as limiting the applicability and / or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

WHAT IS CLAIMED IS:

1. A method for identifying at least one defect in a wood panel (110) comprising a plurality of layers, the method, performed by a computing system, comprises: receiving (310) X-ray image data representing a first portion of the wood panel (110), receiving (330) an ultrasound image data representing a second portion of the wood panel (110), wherein at least part of the X-ray image data and at least part of the ultrasound image data are representing a common portion of the wood panel (110), the method further comprises: analyzing (320) the X-ray image data, analyzing (340) the ultrasound image data, generating (350) a detection result, based on an analysis (320) of the X-ray image data and an analysis (340) of the ultrasound image data, to express at least one of: i) the defect originating from a missing portion of a layer is present in the wood panel (110) in response to that the analysis (340) of the ultrasound image data generates a detection of the defect in a position and the analysis (320) of the X-ray image data generates a detection of the defect in the position, ii) the defect originating from the error in glueing is present in the wood panel (110) in response to that the analysis (340) of the ultrasound image data generates a detection of the defect in a position and the analysis (320) of the X-ray image data does not generate a detection of the defect in the position.

2. The method according to claim 1 , wherein a capture of an X-ray image is triggered on a basis of a result of analysis (340) of the ultrasound image data.

3. The method according to claim 2, wherein the triggering is performed in response to a detection of the detection based on a detection of a deviation in the ultrasound image data in the position.

4. The method according to any of the preceding claim 2 or 3, wherein the triggering of the capture of the X-ray image is performed by generating a control signal to an X-ray imaging unit (130).

5. The method according to claim 4, wherein the control signal is arranged to carry data defining a portion of the wood panel (110) from which the X-ray image is to be captured, the portion at least comprising the position of the defect detected from the ultrasound image data.

6. The method according to any of the preceding claims, the method further comprises: determining data indicative of a size of the defect from at least one of the following: the X-ray image data; the ultrasound image data in response to that, associating the data indicative of the size of the defect to the detection result.

7. The method according to any of the preceding claims, wherein the position of the defect detected from the ultrasound image data and the position of the defect detected from the X-ray image data are compared by defining the positions in a same coordinate system.

8. The method according to any of the preceding claims, wherein a detection result expressing that the defect originating from a missing portion of a layer is present in the wood panel (110) and the defect originating from the error in glueing is present in the wood panel (110) at least in part in a corresponding position is generated (350) in response to a detection that a size of the defect detected from the X-ray image data is smaller than a size of the defect detected from the ultrasound image data.

9. A computing system (120) of a detection system (100) for identifying a defect in a wood panel (110) comprising a plurality of layers, the computingsystem (120) is configured to carry out the method according to any of the claims 1 to 8.

10. A computer program comprising instructions, when the program is executed by a computing system (120) of claim 9, cause the computing system (120) to carry out the method according to claim 1 .

11. A detection system (120) comprising: an ultrasound imaging unit (140), an X-ray imaging unit (130), and the computing system (120) according to claim 9.

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