Panels made of solid wood or with a natural wood surface are used in very large amounts in the flooring industry, in the furniture industry, and in architecture. Due to the high price of natural wood, these panels very often consist of a composite of fiberboards or of moderately priced woods and a relatively thin, visible layer of natural wood veneer or natural solid wood, which determines the aesthetic impression. Since the natural material wood always has numerous flaws, such as loose or rotten knotholes, medullary tubes that have been cut into, cracks, etc., these flaws must be locally repaired to guarantee good physical quality of the surface (evenness, impermeability, etc.).
This process is still carried out manually in most wood panel production facilities. A large number of workers make a purely visual inspection of the surface of a panel, rout out the flaws, such as knotholes, medullary tubes, etc., with a manual tool, and repair these routed places by introducing a wood putty or by driving in a prefabricated wooden dowel. Sometimes these repair personnel have several wood putty colors available, so that they can select the color that comes closest to the basic color of the wood. Nevertheless, the aesthetic quality of the repaired place is very low compared to an area without flaws. As the image in
Automatic repair systems have recently become commercially available, which consist of a combination of an image-processing system for detecting flaws on the wood panel and a subsequent robot-equipped installation for local routing and the introduction of wood putty or dowels.
The Norwegian company Argus Control SA (http://www.argoscontrol.no) offers an “Argos Panel Repair System”, which consists of an optical black-and-white scanner for the detection and localization of the flaws to be repaired and a numerically controlled xyz-axis system for routing and filling the flaws.
The company Baumer Inspection GmbH, Konstanz (http://www.baumerinspection.com) also offers automatic repair systems under the name ColourBrain®-Putty, which consist of a special multisensory scanner and an automatic routing and puttying system and dowel placement system.
Both of these systems are capable of lowering the costs and the amount of time consumed for the physical repair of panels with a wood surface compared to a purely manual approach. Yet in previously known systems, the repair sites remain visible due to the interruption of the surface texture.
Therefore, there is an economic and technical interest in an automatic wood panel repair system which is capable not only of repairing the physical quality of the wood panels by a repair procedure but also of producing an aesthetic quality of the repaired panels that comes as close as possible to that of a flawless panel.
This objective is achieved by the objects of the independent claims. Advantageous embodiments and refinements of the invention are specified in the respective dependent claims. In accordance with the invention, the objective is achieved by inspecting the panels that are to be automatically repaired by the following process steps:
1. With at least one image-generating scanner necessary for detecting the physical flaws, hereinafter referred to as a “flaw scanner”, the physical flaws in the panel are determined
2. With at least one additional, preferably color-capable, image-generating scanner, hereinafter referred to as an “aesthetic scanner” or “texture scanner”, methods of automatic image analysis use the total image of the panel to compute descriptive features for the overall aesthetic impression, especially for the color impression and the visual impression of the patterning or texture.
3. With the use of the position and shape information of the flaws that were acquired with the flaw scanner, image segments of the given flaws are obtained from the image of the aesthetic scanner, where these image segments comprise the flaws themselves and their immediate surroundings, and methods of automatic image analysis use these image segments to compute descriptive features for the local aesthetic impression.
4. After the repair of the physical flaws by automatic routing, introduction of wood putty or dowels, or other physical repair technologies, a decorating device that can be positioned numerically or under computer control and that can be electronically controlled image point by image point is used to individually decorate the region of each repaired flaw with the use of the features responsible for the overall aesthetic visual impression of the panel as well as the features responsible for the local aesthetic impression of the flaws in question in such a way that the panel gives a visual impression at the site of the repaired flaw that comes as near as possible to a flawless panel and/or that the total repaired panel gives a desired overall aesthetic impression produced by the choice of the local decorative patterns.
The invention thus makes available a method for the automatic repair of flaws, especially in naturally patterned surfaces, in which the local repair otherwise leaves behind a visually disturbing impression compared to the flawless surface, where here the flaw is repaired as inconspicuously as possible by reconstruction or imitation of the texture at the flaw.
In the process steps specified above, two image-generating scanners are provided. However, they can also be combined in a single scanner.
Described in a different way, in general, to carry out the method for the automatic repair of a textured surface of a flat object
A corresponding automatic repair unit for repairing flaws in textured surfaces of flat objects comprises the following devices for accomplishing this:
The removal of surface material from the flaw can be accomplished, for example, by boring or routing. If the flaw is a purely color-related disturbance of the texture, it may be possible to cover the flaw without removing material in order merely to hide the flaw.
In a simple embodiment of the invention, for the computing unit to determine an image of the coloring to be applied to the flaw, a suitable region can be cloned from the image data of the texture.
Dot-matrix printers are especially suitable as part of the decorating unit for producing individual texturing. They produce a printed image by computer-controlled placement of individual image points. In this connection, drop-on-demand printers, such as inkjet printers, are especially well suited. A printer of this type can easily produce almost any desired texturing with individual computer control.
In an advantageous refinement of the invention, to achieve a repair that is as inconspicuous as possible or to achieve an imitation of the texture that is as realistic as possible, the computing unit is set up, in the determination of the textured coloration that imitates the texture of the surface, to continue texture elements into the repaired flaw. Thus, the pattern of the structural elements of adjacent intact surface regions is determined, and the coloration to be applied is computed in such a way, for example, in the form of image data, that this coloration contains texture elements that fit the texture elements that are present. In other words, incorporating the texture of the surface areas bordering on the flaw, the computing unit computes a texture within the flaw that extrapolates the neighboring texture.
There are various possibilities for accomplishing this. One simple possibility consists in cloning a reference image segment of the surface, preferably in the neighborhood of the flaw, and then matching it. To cause the structures of the texture and of the image segment to coincide as much as possible, the image segment can then be deformed in a suitable way. One-sided or two-sided stretching and compression, rotation, scaling and cropping are suitable for this purpose.
In another embodiment of the invention, a reference segment of the texture, i.e., for example, an image of part of the texture in an intact place on the surface is used to produce an imitation of the texture. Naturally, the reference segment can also be obtained on another surface with the proper texture and it can even be obtained synthetically. For a good imitation of the texture, it is advantageous only that the reference segment have a structuring that is typical for the texturing of the surface. An image of the texture is generated recursively in the following way: for a picture element that is to be redetermined, for example, in the form of an individual pixel or several pixels, a surrounding area of previously determined pixels is selected.
Then a picture element in the form of this surrounding area is sought in the reference segment, which corresponds in its color values as much as possible to the color values of the surrounding area of the picture element that is to be redetermined. For example, sums, preferably weighted sums of the color values of corresponding pixels can be compared with one another. If the deviation of the sums is less than a preset limit, the picture element in the reference segment is taken as valid. More generally, the picture element in the reference segment is found if its color values correspond to the color values of the surrounding area of the picture element that is to be redetermined to the extent that the deviation of the color values of corresponding pixels is less than a predetermined limit.
The picture element which in its local relation to the picture element to be redetermined corresponds to its associated surrounding area is now sought in the reference segment. The color values of this picture element are then entered in the texture image that is to be determined at the corresponding place relative to the surrounding area. The process is then repeated with a picture element that is preferably adjacent to the previously determined picture element. By repetition of these process steps, the picture is thus successively filled with color values.
This algorithm can also be used to extrapolate existing textures from the neighborhood of the flaw into the areas of the flaw. To this end, we start from image data that contain, besides the area of the flaw, neighboring areas with the still existing texture. In the determination of the color values of the area surrounding an image region to be redetermined, these texture regions are then integrated in the surrounding area, so that picture elements that match this texture still present beside the flaw are sought from the reference segment and entered in the image of the coloring to be applied.
The idea of the invention will now be explained on the basis of a typical flaw in a wood surface, namely, a knothole. This is merely an example and in no way limits the invention. This explanation will be given with reference to the accompanying drawings.
In accordance with the prior art, as illustrated in
After the routing, the panel is moved into a second unit, in which a putty application head is numerically moved to the position of the routed flaw, which is then filled and smoothed.
The panels, which have an area of up to 8 m2, generally contain numerous flaws. It is also possible to use swing arm robots instead of Cartesian positioning.
After the filling and smoothing operation, the entire surface of the panel is usually smoothed over and provided with a coat of transparent varnish.
As is illustrated in
Therefore, in accordance with the invention, as shown by way of example in
To this end, as is shown in
Naturally, the printing operation is preferably carried out on the panel after it has been smoothed over following the filling of the flaws in order to obtain sharp and precise decorative patterns.
The determination of the decorative patterns follows two guidelines:
The overall aesthetic features, such as dominant color, color statistics, and the corresponding features of the wood grain, are determined from the total picture of the color-capable scanner. Experts in the inspection of natural wood are familiar with these types of methods. These features control the general color of the inkjet printer for the wood background and for the wood grain.
The local aesthetic features of the wood grain are determined from the segment image around each flaw, for example, local background color, colors of the grain in this place, the density, direction and curvature of the grain, etc.
It is possible to use a computer simulation to control these features by means of parameters, so that both a desired local impression and a desired overall impression of the wood panel are obtained.
If, for example, it is desired that the panel should give a rustic impression after the repair, then one might wish to decorate flaws in such a way that they imitate knotholes, resin galls or similar elements. If a fine-textured, high-quality panel is desired, then repaired knotholes would be decorated primarily in such a way that the natural grain is continued over the filled and smoothed flaw.
The method of the invention thus is not limited merely to the repair of panels in such a way that visually disturbing repaired flaws are no longer visible. The electronic monitoring of the decoration process makes it possible to control the overall appearance of the panel by suitable local decoration of the repaired flaws and thus to produce panels of high aesthetic quality from panels of low natural aesthetic quality. This is both an important economic advantage and an ecological advantage that allows better utilization of low-quality wood grades.
The recovery and production of these kinds of features are well known to experts in computer simulation. 3D simulation programs, such as 3D Studio Max or Alias Wavefront, now have available all texture generators, with which colored textures of natural materials, such as wood, can be simulated or extracted from existing images. They can be controlled in a variety of ways by means of parameters.
The numerically controllable decoration process of the invention is not limited to the use of inkjet printing technology. The idea of the invention also includes heat transfer printers and simple manipulators with a high temperature peak for local singeing of the wood surface. should appear here.
Therefore, the idea of the invention comprises the totality of all methods suitable for decorative alteration of a repaired flaw of a wood panel. It is obvious that this idea of the invention can be similarly applied to other natural products, such as natural stone, marble, etc.
The idea of the invention is not limited to repair by filling and smoothing or doweling. It includes all technologies for repairing local physical flaws in aesthetic surfaces, such as foaming, local removal, covering with a covering layer, etc.
The idea of the invention includes all image-generating scanners, such as matrix cameras and line cameras, spectrally selective cameras, flying-spot scanners, 3D scanners, and multisensory scanners, which supply an electronic image of the surface to be repaired.
The idea of the invention also includes scanners that are simultaneously capable of detecting flaws and obtaining the aesthetic features of the surface. Accordingly, the division of the scanner into two separate scanners, as shown in
The idea of the invention also includes the additional local decoration of unflawed places with suitable patterns to furnish the panel with a desired appearance. For example, a less textured panel can be furnished with a rustic appearance by additional decoration with a knothole pattern or a resin gall design in less textured places, so that a new product can be produced.
Another possibility for imitating the grain in the repaired area is to supplement the texture by several smaller picture elements.
First, a reference segment of the texture is again selected. Serving as an example here is a stone plate 52, for example, a granite plate.
First, a reference segment 56 of the texture is determined from the image data of the image-generating scanner.
A textured coloration that comes as close as possible to the texture of the reference segment 56 is then to be determined for the area 54 of the surface. For the sake of simplicity, the image of the color values to be determined, which are then transmitted to the decorating device, corresponds in size and shape to the region of the flaw 54 that has been smoothed with filler.
In addition, it would be desirable if the texture is not interrupted at the edge of the smoothed region. Therefore, the coloration should be such that the shape elements of the texture of the areas surrounding the filler extend continuously into the flaw.
The computing unit then determines the position of a picture element 57 to be redetermined and a surrounding area 58 that borders on the picture element 57. The picture element 57 is arranged at the edge of the flaw, so that parts of the intact texture are present in the surrounding area 58.
A picture element 59 in the form of this surrounding area 58 is then sought in the reference segment 56. This picture element 59 corresponds in its color values as closely as possible to the color values of the surrounding area 58 of the picture element 57 that is to be redetermined. With the picture element 59 found in this way, the position of a picture element 60 can now be determined. This picture element 60 has the same relative position to the picture element 59 as the picture element 57 that is to be redetermined has in relation to the surrounding area 58. In other words, the picture element 60 that corresponds in local relation to the picture element 57 to be redetermined relative to its associated surrounding area 58 is sought in the reference segment 56.
The color values of this picture element 60 are then entered in the texture image to be determined in the corresponding place with respect to the surrounding area, i.e., in picture element 57. This state is shown in
Number | Date | Country | Kind |
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10 2008 048 383.4 | Sep 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP09/06390 | 9/3/2009 | WO | 00 | 4/28/2011 |