Methods, systems, and computer programs for detecting the position of a printed circuit board

Abstract

This document describes a printed circuit board (10) having at least one optical mark (12, 14) for detecting the position of the printed circuit board (10). The optical mark (12, 14) includes an optically detectable structure (18) located within a periphery (20) of the mark (12, 14). Furthermore, a method for detecting the position of the printed circuit board (10) is presented. Additionally, a control unit (38) for a system (36) for detecting the position of the printed circuit board (10) is described, and a system (36) for detecting the position of the printed circuit board (10) is described. Furthermore, a computer program including computer-readable program code is defined for forming the steps of the method.

Description

Technical Field

[0001] The present invention relates to a printing plate having at least one optical mark for detecting the position of the printing plate.

[0002] The present invention also relates to a method for detecting the position of a printed circuit board.

[0003] The present invention also relates to a control unit for a system for detecting the position of a printed circuit board, wherein the control unit is configured to form the steps of the above-described method.

[0004] Furthermore, the present invention relates to a system for detecting the position of a printed circuit board, including the control unit described above.

[0005] Furthermore, the present invention relates to a computer program comprising computer-readable program code methods for forming and / or executing the steps of the above-described methods. Background Technology

[0006] Printing plates typically need to be precisely positioned within the printing press to achieve high-quality print results. This is especially true for multicolor printing. In this case, the image to be printed is broken down into multiple monochrome images, which are then printed sequentially onto the substrate. All the monochrome images together form the multicolor image. Typically, each monochrome image is printed onto the substrate using a specific printing plate. Obviously, these printing plates need to be positioned within the printing press with the highest precision. Otherwise, the areas of different colors will be offset or tilted relative to each other.

[0007] It is known in the art to equip printing plates with optical marks. These marks are used to precisely position the printing plate within the printing press. Such marks can be arranged on the printing plate such that they create a portion of the image to be printed, for example, the marks produce a portion of the printed image on the substrate. Alternatively, the marks can be arranged in the boundary areas of the printing plate. Thus, the marks still produce printing on the substrate, but the marks do not form a portion of the desired image and can therefore be cut off. Especially in the first case, the marks need to be relatively small, i.e., so-called micro-markers, so as not to interfere with the printing result. In the second case, larger marks can be used. In both cases, the printing position created by the marks is analyzed. Based on this, the position of the corresponding printing plate within the printing press is corrected until a satisfactory calibration is achieved.

[0008] Another method is to use a marker to detect the position of the printing plate when it is mounted on the corresponding printing cylinder. In this case, the marker itself needs to be detected, rather than the printing being generated by the marker. Typically, the printing plate needs to be mounted on the corresponding printing cylinder automatically. In known methods, the marker on the printing plate is observed via a camera system. The captured image is then processed to derive the current position of the printing plate and compare it with the desired position. If necessary, the position of the printing plate can be adjusted by manipulators that interact with it.

[0009] However, the quality of sign detection has proven unsatisfactory, especially for relatively small signs. Furthermore, it has been found that the quality of sign detection is highly dependent on environmental conditions, as well as the type and material of the printing plate. Summary of the Invention

[0010] Therefore, the problem this invention aims to solve is to improve the markings on printed circuit boards, thereby enabling high-precision and reliable detection of these markings. The influence of environmental conditions, the type of printed circuit board, and the materials used in its manufacture should be avoided.

[0011] This problem is solved by a printed plate having at least one optical mark for detecting the position of the printed plate, wherein the optical mark includes an optically detectable structure located within the periphery of the mark. The periphery of the mark is understood as a closed line defining the outer boundary of the mark. The optically detectable structure is provided with a certain regularity and purpose, i.e., optical noise is not considered as an optically detectable structure. Since the optically detectable structure is arranged within the periphery, it is also referred to as the internal structure below. In particular, when comparing the mark according to the invention with known marks that rely solely on their periphery for detection, the result is that the mark according to the invention provides more optical edges (i.e., boundary lines between areas with different optical properties) and higher contrast (i.e., differences in optical properties along the edges). This can be summarized as the mark according to the invention including more optical information than known marks. Due to this information, the reliability and accuracy of detection are enhanced. Furthermore, the influence of environmental conditions and the properties of the printed plate are reduced. This is especially true for relatively small marks. And, by providing an internal structure, the rationality of recognition is enhanced, which is due to the reduced probability of a printed plate structure that is not a mark being mistakenly identified as a mark (false positive detection).

[0012] Therefore, the basic idea of ​​this invention is to create a mark with an optically detectable internal structure and, for detection purposes, to utilize the internal structure in addition to the periphery of the mark.

[0013] According to the present invention, the length and / or width of the mark can be from 0.2 mm to 5 mm, preferably from 0.5 mm to 3 mm. It must be remembered that in the printed result, larger marks may be easier to detect, while smaller marks may cause less interference.

[0014] The element of the optically detectable structure is preferably 10 micrometers to 300 micrometers wide, more preferably 20 micrometers to 250 micrometers wide.

[0015] In a preferred embodiment, the printing plate is a flexible letterpress printing plate, such as a letterpress with raised elements receiving ink for printing.

[0016] Optically detectable structures can comprise at least two regions with different brightness and / or spatial frequencies, particularly where the regions differ in their respective grayscale values. In this case, the term "grayscale" is understood to include both black and white. Spatial frequency characterizes a spatial periodic pattern. More precisely, spatial frequency is a measure of the repetition frequency of structural elements per unit distance. All these optical properties are readily detectable. Furthermore, they can be detected with high reliability and accuracy. Moreover, optical signs incorporating structures with these properties can be produced at low cost.

[0017] Preferably, the cumulative length of all boundary lines between at least two regions exceeds the length of the perimeter of the marker. Particularly preferred is that the cumulative length of all boundary lines exceeds the perimeter by at least 50%. The cumulative length of all boundary lines can also be 100%, 150%, 200%, or 300% of the perimeter length. The boundary lines between at least two regions can also be designated as edges. This term is more common in the field of automated image processing. The boundary lines between at least two regions constitute a form of optical information. Detecting a large number of such boundary lines with relatively long cumulative lengths enhances the reliability and accuracy of the detection. Detecting only a portion of the boundary lines is also sufficient.

[0018] At least one of the regions can be in the form of a ring-shaped segment or a polygonal segment, especially where the region is ring-shaped or polygonal. In this case, the polygonal shape points to the polygonal chain, rather than the surface it encloses. In other words, the region has the form of a strip-shaped ring-shaped segment or a polygonal segment. In other words, the region corresponds to a portion of the thick line. The region is preferably circular, elliptical, or rectangular. The geometric elements may also differ in their respective spatial frequencies. Such regions can be used to form internal structures with a high content of optical information, thereby leading to reliable mark detection.

[0019] In the embodiments, at least two of the regions are annular or polygonal, wherein the regions are concentrically arranged. Such annular or polygonal regions may have continuously closed perimeters. Alternatively, the perimeters may be discontinuous, i.e., the perimeters may include gaps. In both cases, the concentrically arranged structure leads to improved accuracy in sign detection.

[0020] In this variant, the optical sign and the printing plate are integrally formed. This means the sign is not formed as a separate component, but rather bonded to the printing plate like a sticker. Therefore, the sign is inseparably attached to the printing plate, eliminating the possibility of sign loss and misalignment relative to the printing plate. Furthermore, integrally forming the sign and printing plate results in relatively lower manufacturing costs, especially compared to producing the sign and printing plate separately and the corresponding bonding operations. If the printing plate comprises multiple layers, integrally forming the sign with one of the layers is understood as integrally forming it with the printing plate.

[0021] In a preferred example, the mark is integrated into a layer of a printing plate made of a UV-curable polymer. This layer can be the top layer of the printing plate. During the production of this type of printing plate, the uncured UV-curable polymer layer is covered by a capping layer. Certain areas of the capping layer are removed by laser processing. These areas may correspond to areas used for printing the image. The capping layer with these areas removed may also be designated as a mask. Subsequently, UV light is applied to the printing plate, where the UV-curable polymer cures or polymerizes in the areas not covered by the capping layer but remains uncured in the areas covered by the capping layer. The uncured portions of the polymer layer can then be removed, for example, by washing. The result of this process is the creation of a letterpress printing plate, where the raised elements of the letterpress are configured to receive ink for printing. Clearly, optical marks can be formed in the UV-curable polymer layer using the same process, simultaneously producing a letterpress. Therefore, the integration of the mark requires only a negligible amount of additional work. Furthermore, very small structures, such as those forming the internal structure of the mark, can be integrated into the printing plate using this process.

[0022] The UV-cured polymer layer of the printed board produced by the above process can be transparent or translucent, thus acting as a light guide. This property may interfere with the recognition of the sign, as areas within it may appear brighter than the sign itself. However, this effect diminishes as the size of the structure decreases. Therefore, when using small-sized signs, the effect of light guidance is negligible. This applies to both glossy and matte printed boards.

[0023] More than one optical mark can be provided on the printed plate, especially when the optical marks are arranged in a straight line. This allows for the positioning of the printed plate with improved accuracy. This is particularly helpful for large printed plates. Furthermore, by using more than one mark, a certain degree of redundancy is created, which further improves the reliability of the inspection.

[0024] This problem is also solved by a method for detecting the position of the printed circuit board, including the following steps:

[0025] a) Provide a printing plate according to the invention.

[0026] b) Capture an image of the printed plate, including the logo, or at least a portion thereof, using a camera unit.

[0027] c) Determine the location of the sign in the captured image by identifying structures located within the periphery of the sign, and

[0028] d) Derive the location of the printing plate from the location of the markers in the captured image.

[0029] Because the internal structure of the sign is identified, the sign can be detected with high reliability. Furthermore, due to the identification of the internal structure, the position of the printing plate can be derived with high accuracy. As mentioned earlier, environmental conditions and the specific properties of the printing plate have only a minor impact on the detection of the sign. Therefore, this method is very robust.

[0030] In the above method, the positions of the mark and the printed plate can be represented as relative or absolute positions. Furthermore, the position can be defined as a one-dimensional or two-dimensional location.

[0031] In particular, step b) of the method can illuminate at least a portion of the printed plate including the logo to improve the quality of the captured image.

[0032] This method can be used to precisely position the printing plate on the corresponding printing cylinder. This means that the derived printing plate position can either be used to determine the correction value to which the printing plate needs to be moved to the desired position, or the derived position can be used as a parameter for the printing press using the printing plate.

[0033] If one or more steps of the method according to the invention are formed or executed by a computer, these steps can be cumulatively specified as a computer-implemented method.

[0034] The above method can be performed by a person, preferably using optical devices such as a magnifying glass and / or measuring devices. Alternatively, the method can be operated at least partially automatically, as will be explained later.

[0035] According to one embodiment, structures are identified by evaluating the grayscale distribution and / or spatial frequency distribution of a captured image. These evaluations can be performed with high speed and high reliability. Furthermore, the evaluation of grayscale distribution and spatial frequency is a known and effective technique in image processing. Therefore, such a method can be implemented in a simple and robust manner.

[0036] Structures can also be identified by applying pattern recognition, object recognition, and / or digital image correlation techniques to captured images. These techniques are effective in image processing and are therefore well-suited for reliably identifying structures in a short time. The reliability and accuracy of the method can also be improved by applying more than one pattern recognition technique or more than one object recognition technique.

[0037] In this variant, edge detection technology is applied to a portion of the captured image, including the sign. Edge detection technology is well-known in image processing and delivers high-quality results quickly. It is important to note that edge detection is only applied to those portions of the image displaying the sign. Otherwise, the edges of printed areas would also be detected.

[0038] In this context, the cumulative length of the detected edges of the structure can be calculated, particularly as an indicator of detection quality. The cumulative length of all detectable edges can be easily calculated by summing the lengths of each detected edge. The actual cumulative length of all edges of the sign is known from the sign's design. It constitutes the theoretical maximum value of the cumulative length of detected edges, since not all edges are detectable or can be detected along their entire length. Since edges are more or less distributed within the perimeter of the sign, the quotient of the cumulative length of detected edges to the theoretical maximum value can be considered an indicator of the percentage of the sign that has been detected. Alternatively, other cumulative lengths of detected edges can be considered as a baseline rather than the theoretical maximum value. In all variations, sign detection is enhanced by quality indicators that further improve the reliability of the method.

[0039] The effects and advantages mentioned in the method according to the invention also apply to the printed circuit board according to the invention, and vice versa.

[0040] This problem is also addressed by a control unit for a system used to detect the position of the printed circuit board, wherein the control unit is configured to form steps b) to d). Preferably, the printed circuit board is a printed circuit board according to the invention. Having such a control unit can support the above method, especially steps b) to d). The effects and advantages mentioned in the method also apply to the control unit, and vice versa. The control unit is preferably a computer.

[0041] The control unit can be configured to cause the camera unit to capture an image of a printed plate including a sign or at least a portion thereof. For this purpose, the control unit may include a camera control module implemented in software and / or hardware, configured to cause the camera unit to capture the aforementioned image.

[0042] Furthermore, the control unit can be configured to determine the position of the sign in the captured image by recognizing structures located within the periphery of the sign in the captured image. For this purpose, the control unit may include an image processing module that receives the image captured by the camera unit as input. The image processing module may include a grayscale evaluation module configured to evaluate the grayscale distribution in the image, a specific frequency evaluation module configured to evaluate the spatial frequency distribution of the image, a pattern recognition module configured to run pattern recognition techniques on the image, an object recognition module configured to run object recognition techniques on the image, a digital image correlation module configured to run digital image correlation techniques on the image, and / or an edge detection module configured to run edge detection techniques on the image. All of the above modules can be implemented as software modules, hardware modules, or combinations thereof. It should be noted that, for example, pattern recognition, object recognition, and edge detection can also be performed by a human.

[0043] In addition, the control unit is configured to derive the position of the printing plate from the position of the marker in the captured image.

[0044] The control unit may also include a calculation module configured to calculate the cumulative length of the detected edges. Preferably, the calculation module is connected to the edge detection module such that data describing the number of detected edges (e.g., coordinates) can be transmitted from the edge detection module to the calculation module. The calculation module is configured to calculate the length of each edge and sum all the lengths to obtain the cumulative length of all detected edges. Furthermore, the calculation module can be implemented as a software module, a hardware module, or a combination thereof.

[0045] All of the above modules contribute to the fact that the control unit allows for reliable and accurate detection of the printed circuit board's position. Furthermore, the influence of environmental conditions and / or the nature of the printed circuit board is significantly reduced.

[0046] Furthermore, this problem is solved by a system for detecting the position of a printed circuit board, particularly a system for detecting the position of a printed circuit board according to the invention. This system includes a control unit and a camera unit according to the invention, wherein the camera unit is coupled to the control unit such that an image captured by the camera unit can be provided to the control unit. Once the printed circuit board with markings is provided, the system can be used to run the remaining steps of the method according to the invention. Therefore, the same effects and advantages of the method already mentioned in relation to the method and / or control unit also apply to the system, and vice versa.

[0047] Furthermore, this problem is solved by a computer program comprising computer-readable program code means, such that the computer program is executed on a computer, particularly on a control unit according to the invention, and that the computer program is used to form step b) of the method according to the invention and to run steps c) and d) of the method according to the invention. In this context, the program code method is an instruction having the form of program code and / or program code modules. The program code or program code modules may be compiled or uncompiled and may be represented in any programming language or machine language.

[0048] The computer program may include program code modules that substantially correspond to the modules of the control unit according to the invention as described above. The features, effects, and advantages described in relation to the modules of the control unit also apply to the program code modules.

[0049] The computer program described above can be stored on any computer-readable data medium. In other words, a computer-readable data medium or data medium signal can be provided on which the computer program according to the present invention is stored. Attached Figure Description

[0050] The invention will now be described with reference to the accompanying drawings. In the drawings,

[0051] Figure 1 A system according to the invention is shown for detecting the position of a printing plate. The system includes a control unit according to the invention, a computer program according to the invention stored and executed on the control unit, and a printing plate according to the invention mounted on a corresponding printing roller.

[0052] Figure 2 It shows Figure 1 The printing plate is not mounted on the corresponding printing roller.

[0053] Figure 3 It shows Figure 1 and Figure 2 A portion of the printed plate, which includes a mark according to the first variant,

[0054] Figure 4 It shows in Figure 3 The distribution of gray values ​​in partition IV,

[0055] Figure 5 A portion of an alternative printed circuit board is shown, where this view corresponds to Figure 3 The view, and the provision of a view on the printed board with Figure 3 The same symbol in

[0056] Figure 6 It shows in Figure 5 The gray value distribution in partition VI,

[0057] Figure 7 It shows Figure 1 and Figure 2 A portion of the printed plate, which includes a mark according to the second variant,

[0058] Figure 8 It shows in Figure 7 The gray value distribution in partition VIII,

[0059] Figure 9 It shows Figure 5 A portion of the printing plate, wherein a mark according to the second variant is provided on the printing plate.

[0060] Figure 10 It shows in Figure 9 The distribution of gray values ​​in partition X,

[0061] Figure 11 A portion of a printed plate equipped with a logo according to the third variant is shown, and

[0062] Figure 12 A portion of a printed plate equipped with a logo according to the fourth variant is shown. Detailed Implementation

[0063] Figure 1 and 2 The printed plate 10 is shown, which includes two optical signs 12 and 14.

[0064] If the printed plate 10 is in a flat position, the optical marks 12 and 14 are arranged along the straight line 16.

[0065] (see Figure 2 ).

[0066] The printing plate 10 is a flexible letterpress printing plate in which a letterpress is formed in a UV-curable polymer layer.

[0067] Optical marks 12 and 14 are integrally formed in the UV-curable polymer layer.

[0068] Optical markings 12 and 14 will be described in detail below. However, for ease of explanation, marking 12 will be used as a reference only. The following description is applied to optical marking 14 with necessary modifications based on the actual situation.

[0069] Figure 3 An optical mark 12 according to a first variant is shown, which is formed on a smooth surface of a printed plate 10.

[0070] The optical mark 12 is substantially square, and the optical mark 12 includes an optically detectable structure 18 within the perimeter 20 of the optical mark 12.

[0071] The structure consists of six regions 22a, 22b, 22c, 22d, 22e, and 22f. Regions 22a, 22b, 22c, 22d, and 22e are basically formed as closed polygonal bands with thick square lines, while region 22f is formed as a square.

[0072] All regions 22a, 22b, 22c, 22d, 22e, and 22f are arranged concentrically.

[0073] from Figure 3 You can see it directly in Figure 4 In more detail, we can see that regions 22a, 22b, 22c, 22d, 22e, and 22f have different gray levels, with high-gray-level regions and low-gray-level regions arranged alternately along the direction extending from the periphery 20 of the sign toward the center of the sign.

[0074] In order to Figure 3 The flag is mapped to Figure 4 In the charts, both graphs show two auxiliary lines, 24 and 26. Additionally, the corresponding area is labeled next to the peak in the grayscale distribution.

[0075] exist Figure 4 In this context, grayscale values ​​are expressed as a relative range from 0% to 100%. The terms grayscale and grayscale value are synonyms.

[0076] The boundary line between two regions with different gray values ​​is defined as the edge, and from Figure 3 It can be clearly concluded that the cumulative length of all edges is a multiple of the length of the perimeter 20 of mark 12.

[0077] Figure 5 An optical mark 12 according to the first variant is also shown, so that mark 12 is essentially the same as... Figure 3 The same as symbol 12 in the text. In the following text, only the similarity to... Figure 3 The difference between the printed plate 10 and the printed plate 10.

[0078] Mark 12 is now formed on the rough surface of the printing plate 10, which is in contact with... Figure 3 The printed circuit board 10 disclosed in the paper provides a lower contrast.

[0079] from Figure 5 It can be seen in and in Figure 6 This can be seen in more detail, which leads to different grayscale distributions.

[0080] Figure 7 A printed plate 10 with an optical mark 12 according to a second variant is shown, the optical mark 12 being applied to a substantially smooth surface of the printed plate 10. Again, only those with... Figure 3 Differences in the implementation examples.

[0081] The optical mark 12 is basically circular, that is, the perimeter 20 of the optical mark 12 is basically a circular line.

[0082] The optically detectable structure 18 within the perimeter 20 consists of eight regions 22a, 22b, 22c, 22d, 22e, 22f, 22g, and 22h. Regions 22a, 22b, 22c, 22d, 22e, 22f, and 22g are basically formed as circular bands, while region 22h is formed as a circle.

[0083] All regions 22a-22h are arranged concentrically.

[0084] from Figure 7 You can see it directly in Figure 8 In more detail, we can see that regions 22a, 22b, 22c, 22d, 22e, 22f, 22g, and 22h differ in their gray levels. When considering the direction extending from the perimeter 20 of the sign to its center, the high-gray-level regions and the low-gray-level regions are arranged in an alternating manner.

[0085] In order to Figure 7 The flag is mapped to Figure 8 In the charts, both graphs show two auxiliary lines, 24 and 26. Additionally, corresponding area labels are marked next to the peaks in the grayscale distribution.

[0086] If the boundary line between two regions with different gray values ​​is redefined as an edge, then from Figure 7 It can be clearly concluded that the cumulative length of all edges is a multiple of the length of the perimeter 20 of mark 12.

[0087] Figure 9 An optical mark 12 according to a second variant is also shown, thus the mark 12 is essentially the same as... Figure 7 The same as symbol 12 in the text. In the following text, only the explanation of the same... Figure 7 The difference compared to the printed circuit board.

[0088] Mark 12 is now formed on the rough surface of the printing plate 10, which is relatively... Figure 7 The printed circuit board 10 shown has a low contrast.

[0089] from Figure 9 It can be seen in and in Figure 10 This can be seen in more detail, which leads to different grayscale distributions.

[0090] Figure 11A portion of a printed plate 10 with an optical mark 12 according to a third variant is shown. The mark 12 according to the third variant differs from the mark according to the second variant in that it provides only four regions 22a, 22b, 22c, and 22d instead of eight regions with different gray values.

[0091] Regions 22a, 22b, and 22c form a continuous circular band, and region 22d forms a circle.

[0092] If we analyze along a line extending from perimeter 20 to the center of marker 12, regions 22a, 22b, and 22c differ in width. In the example shown, regions 22a and 22c are wider than regions 22b and 22d. In other words, regions 22a, 22b, 22c, and 22d differ in spatial frequency.

[0093] In addition, the interpretation of sign 12 according to the second variant also applies to sign 12 according to the third variant.

[0094] Figure 12 A printed plate 10 with an optical mark 12 according to a fourth variant is shown.

[0095] The optical mark 12 is basically square.

[0096] The internal structure 18 consists of five regions 22a, 22b, 22c, 22d, and 22e. Regions 22a, 22b, 22c, and 22d are basically shaped into polygonal bands with thick square lines, while region 22e is shaped into a square.

[0097] However, areas with low gray values ​​provide an interruption of 28.

[0098] In detail, regions 22b and 22d are not formed by closed polygonal bands, but rather by polygonal bands that are interrupted once on each side. The portion of the polygonal band extending between the two interruptions 28 can also be designated as a polygonal segment.

[0099] In addition, see the description regarding the first variant of the symbol 12.

[0100] The position of the printed plate 10, including the mark 12, can be detected by running the following method.

[0101] First, a printing plate 10 including the mark 12 needs to be provided. In this case, the printing plate 10 can be provided in such a way as... Figure 1 The corresponding printing roller 30 is shown.

[0102] Then, the camera unit 32 captures an image of the printed plate 10, including the mark 12, or at least a portion thereof.

[0103] Subsequently, the position of the sign 12 in the captured image is determined by identifying the structure 18 located within the periphery 20 of the sign 12 in the captured image.

[0104] In this embodiment, this is achieved by evaluating, such as Figure 4 , 6 This is achieved using the grayscale distributions shown in 8 and 10.

[0105] From these grayscale distributions and respectively in Figure 3 , 5 As can be seen from the comparison of the corresponding printed plates 10 shown in 7 and 9, the internal structure 18 has the following effect: when the periphery 20 of the mark 12 cannot be clearly detected (see example...). Figure 5 and Figure 6 or Figure 9 and Figure 10 The internal structure 18 is still detectable.

[0106] Therefore, in Figures 3 to 10 In all the cases shown, the position of marker 12 in the image can be determined with high reliability.

[0107] In addition to evaluating the grayscale distribution, edge detection techniques are applied to the image. Therefore, the edges of the boundary lines between regions 22a–22h of different grayscale values ​​are determined, and the corresponding lengths of these edges are calculated.

[0108] The cumulative length of all edges is considered an indicator of detection quality. This means that a large cumulative length indicates high detection quality, and a short cumulative length indicates low detection quality.

[0109] Considering Figures 3 to 6 ,For example Figure 5 The edge between regions 22a and 22b to the right is undetectable. Therefore, Figure 5 In the example, the cumulative length of the detected edges is less than Figure 3 The cumulative length of the detected edges in the example.

[0110] Based on the determination of the position of the marker 12 in the captured image, the position of the printed circuit board 10 is derived.

[0111] There are basically two options.

[0112] The position of the printing plate 10 can be derived relative to an additional mark 34, for example, on the printing cylinder 30, which is not placed on the printing plate 10. This mark 34 needs to be represented in the captured image.

[0113] Alternatively, the position of the printed circuit board 10 can be derived by using the corrected camera unit 32 located at a known position. Therefore, the positions of at least some portions of the captured image (e.g., a single pixel or a group of pixels) are known, and the position of the printed circuit board 10 can be derived based on this.

[0114] It is worth noting that the position of the printing plate can be represented using a coordinate system belonging to a room, printing press, or printing cylinder.

[0115] Figure 1 A system 36 for detecting the position of the printed circuit board 10 is also shown.

[0116] In addition to the camera unit 32 already mentioned, this system 36 includes a control unit 38, which in the illustrated example is a computer.

[0117] The control unit 38 and the camera unit 32 are coupled via a data line 40, so that the image captured by the camera unit 32 can be provided to the control unit 38.

[0118] The control unit 38 also includes a data storage unit 42 and a data processing unit 44.

[0119] A computer program, including computer-readable program code methods, is stored on data storage unit 42 and can be executed by data processing unit 44.

[0120] The control unit 38 and the computer program executable thereon are configured to form method steps for capturing an image of at least a portion of the printed plate 10 including the logo 12 by the camera unit 32.

[0121] Therefore, a signal is sent from the processing unit 44 to the camera unit 32 via the data line 40, triggering the camera unit to capture an image and send the captured image to the control unit 38 via the data line 40.

[0122] The captured image is then stored in data storage unit 42.

[0123] The control unit 38 and the computer program executable thereon are also configured to perform the step of determining the position of the sign 12 in the captured image by identifying the structure 18 located within the periphery 20 of the sign 12 in the captured image.

[0124] Therefore, the data processing unit 44 is used to analyze the grayscale distribution in the captured image.

[0125] The location of the obtained flag 12 is stored in the data storage unit 42.

[0126] Furthermore, the control unit 38 and the computer program executable thereon are configured to derive the position of the printed circuit board 10 from the position of the mark 12 in the captured image.

[0127] The control unit 38 and the computer program executable thereon are configured according to one of the above-mentioned alternatives in this regard.

[0128] The location of the additional marker 34 has also been determined in the captured image and stored in the data storage unit 42.

[0129] Then, the position of the printed circuit board 10 is derived by comparing the position of the mark 34 with the position of the mark 12.

[0130] Alternatively, the camera unit 32 can be corrected such that the corresponding position for at least a portion of the captured image is known.

[0131] In this case, the position of the printing plate 10 is derived by comparing the position of the marker 12 with the known position of the captured image portion.

[0132] The position derived from the printed circuit board 10 can be used to determine the amount and / or orientation of the position of the printed circuit board 10 that should be corrected.

[0133] The detection and corresponding correction of the position of the printed circuit board 10 can be performed in a closed-loop control system.

Claims

1. A method for detecting the position of a printed circuit board, the method comprising: A printing plate is provided, comprising at least one optical mark for detecting the position of the printing plate. The at least one optical mark includes an optically detectable structure located around the periphery of the at least one optical mark, and the optically detectable structure comprises at least two annular or at least two polygonal regions (22a-22h), wherein the regions (22a-22h) are concentrically arranged. The camera unit captures an image of the printed plate, including at least one of the optical marks, or at least a portion thereof. The position of the at least one optical sign in the captured image is determined by identifying structures located within the periphery of the at least one optical sign in the captured image, and The position of the printing plate is derived from the determined position of the at least one optical mark in the captured image.

2. The method according to claim 1, characterized in that, The structure is identified by evaluating the grayscale distribution and / or spatial frequency distribution of the captured image.

3. The method according to claim 1, characterized in that, The structure is identified by applying one or more of pattern recognition, object recognition, or digital image correlation techniques to the captured image.

4. The method according to claim 1, characterized in that, Edge detection technology is applied to a portion of the captured image, including the at least one optical sign.

5. The method according to claim 4, characterized in that, Calculate the cumulative length of the detected edges of the structure.

6. The method according to claim 5, characterized in that, The accumulated length is considered an indicator of detection quality.

7. A system for detecting the position of a printed circuit board, the system comprising: A control unit for detecting the position of a printed circuit board, the printed circuit board including at least one optical marker for detecting the position of the printed circuit board, wherein the at least one optical marker includes an optically detectable structure located within the periphery of the at least one optical marker, and wherein the optically detectable structure includes at least two annular or at least two polygonal regions (22a-22h), wherein the regions (22a-22h) are concentrically arranged. The control unit is configured to perform a method comprising: The camera unit captures an image of the printed plate, including at least one of the optical marks, or at least a portion thereof. The position of the at least one optical sign in the captured image is determined by identifying structures located within the periphery of the at least one optical sign in the captured image, and The position of the printing plate is derived from the determined position of the at least one optical mark in the captured image.

8. The system according to claim 7, further comprising: The camera unit, wherein the camera unit is coupled to the control unit such that the image captured by the camera unit is provided to the control unit.

9. A non-transitory computer-readable medium storing instructions that, when executed by a processor, perform operations including: An image of a printed plate or at least a portion thereof, comprising at least one optical mark, is captured by a camera unit. The printed plate includes at least one optical mark for detecting the position of the printed plate. The at least one optical mark includes an optically detectable structure located around its periphery. The optically detectable structure comprises at least two annular or at least two polygonal regions (22a-22h), wherein the regions (22a-22h) are concentrically arranged. The position of the at least one optical sign in the captured image is determined by identifying structures located within the periphery of the at least one optical sign in the captured image, and The position of the printing plate is derived from the determined position of the at least one optical mark in the captured image.

10. The non-transient computer-readable medium of claim 9, wherein the operation further comprises: Determine the total length of the edges of the first region and the second region; and The quality of the image is determined based on the total length of the determined edges. The determined quality increases as the total length of the determined edge increases.

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