A paper printing defect real-time detection device

Abstract

The application discloses a kind of paper printing defect real-time detection device, it is related to image processing and flaw detection technical field;Including the following steps: using conveying part to convey printed matter, when conveying to the bottom of image acquisition part, image acquisition part carries out image acquisition;Image information collected by image acquisition part is transmitted to data processing center, and the image feature of printed matter is obtained after image pre-processing is carried out to image by data processing center;Image feature is compared with the standard qualified product image pre-recorded, when the comparison result of similarity of two pictures by data processing center is less than threshold value, then it is judged as qualified product, otherwise it is defective product.The flaw is judged by the image acquisition based on image acquisition part, so as to solve the problems of subjectivity, low efficiency, high cost and lack of quantitative data in the prior art manual inspection, and combined with the conveying function of conveying part, the process can be achieved. Full detection effect, increase detection efficiency and detection quality.

Description

Technical Field

[0001] This invention relates to the field of image processing and defect detection technology, and in particular to a real-time detection device for paper printing defects. Background Technology

[0002] During the printing process, various appearance defects are inevitable due to factors such as raw materials, equipment precision, ink performance, environmental fluctuations, and operational factors. These defects (such as scratches, dirt, misregistration, color difference, ink splatter, and missing prints) directly affect the product's pass rate and commercial value. Therefore, defect detection is a crucial aspect of printing quality control.

[0003] Traditionally, this step mainly relies on manual visual inspection, with quality inspectors making judgments based on experience while on-site or at the terminal. This method has obvious drawbacks: 1) It is highly subjective and influenced by the experience, energy, and emotions of the personnel, making it difficult to standardize the criteria; 2) Inefficient and difficult to match the production cycle of high-speed printing presses; 3) It is costly, requires a large investment of manpower, and is difficult to operate continuously 24 / 7; 4) Lack of quantitative data hinders defect tracing and process improvement.

[0004] Therefore, this invention proposes a real-time detection device for paper printing defects. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a real-time detection device for paper printing defects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A real-time detection device for paper printing defects includes a conveying unit, an image acquisition unit, and a data processing center. The image acquisition unit consists of a first image acquisition camera and a second image acquisition camera. The first image acquisition camera is located upstream of the second image acquisition camera in the conveying unit, and the second image acquisition camera can be adjusted laterally by a linear driver. Both the first image acquisition camera and the second image acquisition camera are connected to the data processing center for data communication. in: The image-capturing camera is used to capture images of printed materials and determine physical defects, while simultaneously locating the position of the printed materials relative to the conveyor section. The second imaging camera can combine the position information of the printed matter relative to the conveying unit, and then adjust it to be directly above the printed matter through the adjustment action of the linear driver. At the same time, the second imaging camera is used to acquire images of the printed matter and determine printing defects of the printed matter.

[0007] Preferably, the lateral imaging range of the first imaging camera is not less than the width of the conveying section, and the imaging range of the second imaging camera is not less than the area of ​​the printed matter, along the conveying direction of the conveying section.

[0008] Furthermore, the detection method of the real-time paper printing defect detection device includes the following steps: S1: The printed matter is transported by the conveyor unit. First, it passes the bottom position of the image camera one, and the image camera one takes pictures of the printed matter. S2: The image captured by the first imaging camera is sent to the data processing center. The data processing center uses an edge detection algorithm to extract the contour of the image. The extracted contour is compared with the standard image to determine whether there are physical defects. At the same time, the required position of the second imaging camera is determined based on the extracted contour. S3: Then the linear driver adjusts the image camera 2 to the required position, and then the printed material is transported to the position of the image camera 2. The image camera 2 takes another picture and then transports it to the data processing center. The data processing center extracts features from the image and then compares the printing features with the pre-recorded standard qualified product image. Then, it combines the threshold to determine whether it is qualified or unqualified. In step S2, the physical defect determination specifically includes: comparing with a standard image to determine the similarity of the contour, and using a threshold control method to determine whether there are dimensional defects such as missing corners, folds, or mismatched paper sizes. If any exist, the product is directly determined to be defective, and the second imaging camera will not take images for analysis in the future. In step S3, the printing features include: printing texture features, printing color features, and printing position features.

[0009] Based on the aforementioned scheme: the conveying unit is supported on the ground by a frame, the image acquisition unit and the data processing center are both fixedly installed on the top of the conveying unit, and the first and second image cameras are respectively installed on the top of the conveying unit by a set of light-shielding frames.

[0010] A better embodiment of the aforementioned scheme is: the image capturing camera is rotatably connected to the light-shielding frame, and a rotary driver is fixed to one side of the outer wall of the light-shielding frame by bolts. The output shaft of the rotary driver is fixed to the side wall at the rotation center of the image capturing camera.

[0011] As a further aspect of the present invention: connecting sleeve one and connecting sleeve two are fixed on both sides of the imaging camera two, and linear driver and rotary driver one are fixed on the outer walls of both sides of the light-shielding frame, respectively. The telescopic end of the linear driver is rotatably connected to the inner wall of the connecting sleeve one, and the output shaft of the rotary driver one is movably connected to the inner wall of the connecting sleeve two through the gap fit between the key-shaped groove and the key-shaped protrusion.

[0012] Meanwhile, the light-shielding frame includes a light-shielding cover fixed to the top outer wall of the conveying section and upright plates fixed to both sides of the light-shielding cover. The opposing upright plates are connected by a crossbeam, and a flexible light-shielding pad for light-shielding is provided between the crossbeam and the shooting heads of the first and second imaging cameras.

[0013] As a preferred embodiment of the present invention: a plurality of uniformly arranged supplementary lights are fixed on the inner wall of the light shield, and a light intensity sensor is fixed on the inner wall of the light shield. Both the light shield and the light intensity sensor are electrically connected to the data processing center.

[0014] Meanwhile, a paging section is also provided at the upstream position of the conveying section. The paging section includes a crossbar and rollers. The crossbar is fixed to the top outer wall of the conveying section by a mounting seat. An adjustment seat is provided on the outer wall of the crossbar. An elastic frame is provided on one side of the adjustment seat. The rollers are rotatably connected to the inner side of the end of the elastic frame by a bolt group. There is rotational damping between the rollers and the elastic frame. The rotational damping is less than the friction force of the conveying section on the printed matter and greater than the friction force between the stacked printed matter.

[0015] As a preferred embodiment of the present invention: the adjusting seat is movably installed on the outer wall of the crossbar, and an adjusting bolt is threadedly connected to one side of the outer wall of the adjusting seat, with the end of the adjusting bolt abutting against the outer wall of the crossbar. The other end of the elastic frame is fixed to the side wall of the adjusting seat, and the outer wall of the adjusting seat is connected to the adjusting bolt two by thread. The end of the adjusting bolt two abuts against the top outer wall of the elastic frame.

[0016] The beneficial effects of this invention are as follows: 1. This invention achieves defect judgment by image acquisition based on the image acquisition unit, thereby solving the problems of subjectivity, low efficiency, high cost and lack of quantitative data in the existing manual quality inspection. At the same time, combined with the conveying function of the conveying unit, it can achieve a streamlined full inspection effect, increasing inspection efficiency and inspection quality.

[0017] 2. In this invention, by setting the image acquisition unit as a combination of image acquisition camera one and image acquisition camera two, image acquisition camera one can serve as a "preprocessing" tool for determining the physical size of the printed matter, and can also locate the printed matter based on its outline. Thus, after the position of image acquisition camera two is adjusted, its image acquisition only needs to include the area where the printed matter is located. This realizes the division of labor and cooperation function under mutual coordination, increases the efficiency of image processing, and improves the timeliness of handling defective products after the result determination.

[0018] 3. This invention, by setting up a flexible light-shielding pad, a crossbeam, a light-shielding cover, and a vertical plate, forms an open closed inner cavity, and then uses supplementary lights for supplementary lighting, thereby ensuring the controllability of light during shooting. At the same time, the light intensity sensor can sense the light, and together with the data processing center to control the brightness and color temperature of each supplementary light, a closed-loop control of the supplementary light intensity is realized, ensuring the image acquisition accuracy of image acquisition camera one and image acquisition camera two, thereby increasing the accuracy of final defect detection.

[0019] 4. In this invention, by setting rollers, a certain conveying resistance can be applied to the printed matter using rotational damping. However, the damping is less than the friction force of the conveying part on the printed matter and greater than the friction force between stacked printed matter, thereby achieving the function of separating stacked printed matter and preventing missed detection and incorrect detection.

[0020] 5. The present invention, by setting up bolt groups, adjusting bolt one, adjusting bolt two and other components, can specifically adjust the rotational resistance of the rollers and the elastic contact force between the rollers and the conveying part according to the actual friction properties of the printed materials, so as to ensure the reliability of the separation of stacked printed materials. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of a real-time paper printing defect detection device proposed in this invention. Figure 2 This is a schematic diagram of the image acquisition unit structure of a real-time paper printing defect detection device proposed in this invention; Figure 3 This is a cross-sectional view of the image acquisition unit of a real-time paper printing defect detection device proposed in this invention. Figure 4 This is a schematic diagram of the connection structure between the imaging camera 2 and the linear driver and the rotary driver 1 of the real-time detection device for paper printing defects proposed in this invention. Figure 5 This is a cross-sectional view of the connection between the rotary driver and the connecting sleeve 2 of the real-time detection device for paper printing defects proposed in this invention. Figure 6 This is a schematic diagram of the installation position of the supplementary light and light intensity sensor in a real-time detection device for paper printing defects proposed in this invention. Figure 7 This is a schematic diagram of the pagination section structure of a real-time paper printing defect detection device proposed in this invention.

[0022] In the diagram: 1. Frame; 2. Conveying section; 3. Pager section; 4. Image acquisition section; 5. Data processing center; 6. Imaging camera one; 7. Imaging camera two; 8. Linear driver; 9. Rotary driver one; 10. Rotary driver two; 11. Light-shielding frame; 12. Light-shielding cover; 13. Flexible frame; 14. Vertical plate; 15. Crossbeam; 16. Flexible light-shielding pad; 17. Supplemental light; 18. Light intensity sensor; 19. Connecting sleeve one; 20. Connecting sleeve two; 21. Keyway; 22. Key-shaped protrusion; 23. Bolt group; 24. Mounting base; 25. Crossbar; 26. Adjusting seat; 27. Adjusting bolt one; 28. Adjusting bolt two; 29. ​​Roller. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0024] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0025] Example 1: A real-time detection device for paper printing defects, such as Figure 1 As shown, the detection method includes the following steps: S1: The printed matter is transported by the conveying unit 2. When it is transported to the bottom of the image acquisition unit 4, the image acquisition unit 4 acquires an image. S2: The image information acquired by the image acquisition unit 4 is transmitted to the data processing center 5. The data processing center 5 performs image preprocessing on the image and extracts features to obtain the image features of the printed matter. S3: Compare the image features with the pre-entered standard qualified product images and set a deviation threshold. If the similarity comparison result between the two images by the data processing center is less than the threshold, it is judged as a qualified product; otherwise, it is a defective product.

[0026] This device achieves defect judgment through image acquisition based on the image acquisition unit 4, thereby solving the problems of subjectivity, low efficiency, high cost and lack of quantitative data in the existing technology of manual quality inspection. At the same time, combined with the conveying function of the conveying unit 2, it can achieve a streamlined full inspection effect, increasing inspection efficiency and inspection quality.

[0027] Example 2: A real-time detection device for paper printing defects, such as Figure 1 and 2As shown, this embodiment makes the following improvements based on embodiment 1: The image acquisition unit 4 is composed of a first image acquisition camera 6 and a second image acquisition camera 7. The lateral range of the first image acquisition camera 6 is not less than the width of the conveying unit 2, and the lateral range of the second image acquisition camera 7 is not less than the area of ​​the printed matter. Along the conveying direction of the conveying unit 2, the first image acquisition camera 6 is located upstream of the second image acquisition camera 7, and the lateral position of the second image acquisition camera 7 can be adjusted by the linear driver 8.

[0028] The detection method of the real-time paper printing defect detection device includes the following steps: A1: The printed matter is transported through the conveyor 2. First, it passes the bottom position of the imaging camera 6, and the imaging camera 6 takes an image of the printed matter. A2: The image captured by the imaging camera 6 is sent to the data processing center 5, where the data processing center 5 uses an edge detection algorithm to extract the contour of the image; A21: After extraction, the image is compared with the standard image to determine the similarity of the contour. Threshold control is used to determine whether there are dimensional defects such as missing corners, folds, or mismatched paper sizes. If any are found, the image is directly identified as a defective product and the subsequent image capture camera 27 will not capture or analyze the image. A22: After extraction, the spatial position of the printed matter relative to the conveying unit 2 is determined by combining the installation position of the imaging camera 1 6, and the position of the imaging camera 2 7 is controlled by the linear driver 8 according to the spatial position, so that the imaging center of the imaging camera 2 7 coincides with the physical center of the printed matter in the longitudinal space. A3: The printed material is then transported to the position of the image acquisition camera 2 7, where it takes another image and is then transported to the data processing center 5. The data processing center 5 extracts features from the image, compares the printing features with the pre-recorded standard qualified product image, and then uses the threshold to determine whether the product is qualified or unqualified.

[0029] If a single image acquisition unit 4 is used for image analysis, in order to cover the entire conveying space of the conveying unit 2, the image acquisition range is relatively large, resulting in a large image size. On the other hand, based on the large image size, it also needs to perform operations such as printing pattern feature extraction, contour extraction, and feature comparison. The data processing center 5 performs many processes, resulting in a large delay in the final output result, which leads to untimely processing of defective products.

[0030] In this embodiment, by setting the image acquisition unit 4 as a combination of image acquisition camera 6 and image acquisition camera 7, image acquisition camera 6 can serve as a "preprocessing" tool for determining the physical size of the printed matter, and it can also locate the printed matter based on the outline. Thus, after the position of image acquisition camera 7 is adjusted, its image acquisition only needs to include the area where the printed matter is located, realizing the division of labor and cooperation function under mutual collaboration, increasing the efficiency of image processing and the timeliness of defective product processing after the result determination.

[0031] Example 3: A real-time detection device for paper printing defects, such as... Figures 1-7 As shown, this embodiment makes the following improvements based on embodiments 1 and 2: The conveying unit 2 is supported on the ground by the frame 1. The image acquisition unit 4 and the data processing center 5 are both fixedly installed on the top of the conveying unit 2. The first image acquisition camera 6 and the second image acquisition camera 7 are respectively installed on the top of the conveying unit 2 by a set of light-shielding frames 11.

[0032] The imaging camera 6 is rotatably connected to the light-shielding frame 11. A rotary driver 10 is fixed to one side of the outer wall of the light-shielding frame 11 by bolts. The output shaft of the rotary driver 10 is fixed to the side wall at the rotation center of the imaging camera 6.

[0033] The two sides of the imaging camera 7 are respectively fixed with connecting sleeve 19 and connecting sleeve 20. The two outer walls of the light-shielding frame 11 are respectively fixed with linear driver 8 and rotary driver 9. The telescopic end of the linear driver 8 is rotatably connected to the inner wall of connecting sleeve 19. The output shaft of the rotary driver 9 is movably connected to the inner wall of connecting sleeve 20 through the gap fit between the key groove 21 and the key protrusion 22.

[0034] By rotatably connecting both the first camera 6 and the second camera 7 to the inside of the light-shielding frame 11, the imaging angles of the first camera 6 and the second camera 7 can be changed, ensuring the image clarity under different conditions.

[0035] The simultaneous connection of sleeve 19 and sleeve 20 ensures that the imaging camera 27 can rotate and its position can be adjusted laterally.

[0036] The light-shielding frame 11 includes a light-shielding cover 12 fixed to the top outer wall of the conveying part 2 and upright plates 14 fixed to both sides of the light-shielding cover 12. The opposing upright plates 14 are connected by a crossbeam 15, and a flexible light-shielding pad 16 for light-shielding is provided between the crossbeam 15 and the shooting heads of the first and second cameras 6 and 7.

[0037] Meanwhile, a plurality of uniformly arranged supplementary lights 17 are fixed on the inner wall of the light shield 12, and a light intensity sensor 18 is fixed on the inner wall of the light shield 12. Both the light shield 12 and the light intensity sensor 18 are electrically connected to the data processing center 5.

[0038] In this embodiment, by rotatably connecting both the first camera 6 and the second camera 7 to the inside of the light-shielding frame 11, the imaging angles of the first camera 6 and the second camera 7 can be changed, ensuring the image clarity under different conditions. At the same time, the setting of the first connecting sleeve 19 and the second connecting sleeve 20 ensures that the second camera 7 can be rotated and its position can be adjusted laterally. In addition, the flexible light-shielding pad 16, the crossbeam 15, the light-shielding cover 12 and the upright plate 14 form an open closed inner cavity, which can block external light. At the same time, when the first camera 6 and the second camera 7 are taking pictures, the supplementary light 17 can provide supplementary light, and the light intensity sensor 18 senses the supplementary light intensity to realize closed-loop control.

[0039] This device, by setting up a flexible light-shielding pad 16, a crossbeam 15, a light-shielding cover 12, and a vertical plate 14, forms an open closed inner cavity, and then uses supplementary lights 17 for supplementary lighting, thereby ensuring the controllability of light during shooting. At the same time, the light intensity sensor 18 can sense the light, and together with the data processing center 5 to control the brightness and color temperature of each supplementary light 17, a closed-loop control of the supplementary light intensity is realized, ensuring the image acquisition accuracy of the first image acquisition camera 6 and the second image acquisition camera 7, thereby increasing the accuracy of the final defect detection.

[0040] Example 4: A real-time detection device for paper printing defects. This example is based on the above examples and makes the following improvements: A paging section 3 is also provided upstream of the conveying section 2. The paging section 3 includes a crossbar 25 and a roller 29. The crossbar 25 is fixed to the top outer wall of the conveying section 2 by a mounting base 24. An adjusting seat 26 is provided on the outer wall of the crossbar 25. An elastic frame 13 is provided on one side of the adjusting seat 26. The roller 29 is rotatably connected to the inner side of the end of the elastic frame 13 by a bolt group 23. There is rotational damping between the roller 29 and the elastic frame 13. The rotational damping is less than the friction force of the conveying section 2 on the printed matter and greater than the friction force between stacked printed matter.

[0041] The adjusting seat 26 is movably installed on the outer wall of the crossbar 25. One side of the outer wall of the adjusting seat 26 is connected to an adjusting bolt 27 by a thread, and the end of the adjusting bolt 27 abuts against the outer wall of the crossbar 25.

[0042] The other end of the elastic frame 13 is fixed to the side wall of the adjusting seat 26, and the outer wall of the adjusting seat 26 is connected to the adjusting bolt 28 by thread. The end of the adjusting bolt 28 abuts against the top outer wall of the elastic frame 13.

[0043] In this embodiment, the paging section 3 can be configured with one or more sets. First, loosen the adjusting bolt 27, allowing the roller 29 to naturally contact the conveying surface of the conveying section 2 under gravity. Then, tighten the adjusting bolt 27 for positioning. Next, rotate the adjusting bolt 28, which applies downward pressure to the elastic frame 13, causing the elastic frame 13 to undergo elastic deformation. This results in a certain contact pressure between the roller 29 and the conveying surface of the conveying section 2. Then, adjust the tightness of the bolt group 23 to change the tension of the opening of the elastic frame 13. The friction between the inner side of the opening of the variable elastic frame 13 and the side wall of the roller 29 achieves the purpose of adjusting the rotational damping of the roller 29 relative to the elastic frame 13. Subsequently, when the printed matter moves to the roller 29 with the conveyor 2, if there is a stacking situation, since the top printed matter is in contact with the roller 29 and the bottom one is in contact with the conveyor 2, and the roller 29 has rotational damping, the stacked printed matter will stop being conveyed due to the resistance of the roller 29. The top printed matter will stop being conveyed until the bottom printed matter is completely offset, and then the printed matter in contact with the roller 29 will continue to be conveyed.

[0044] This device, by setting rollers 29, can apply a certain conveying resistance to the printed matter using rotational damping. However, its damping is less than the friction force of the conveying part 2 on the printed matter and greater than the friction force between stacked printed matter, thereby achieving the function of separating stacked printed matter and preventing missed detection and incorrect detection.

[0045] In addition, by setting up components such as bolt group 23, adjusting bolt one 27, and adjusting bolt two 28, this device can specifically adjust the rotational resistance of roller 29 and the elastic contact force between roller 29 and conveying part 2 according to the actual friction performance of the printed matter, so as to ensure the reliability of separation of stacked printed matter.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A real-time detection device for paper printing defects, comprising a conveying unit (2), an image acquisition unit (4), and a data processing center (5), characterized in that, The image acquisition unit (4) includes a first image camera (6) located upstream of the conveyor and a second image camera (7) located downstream of the conveyor. Both the first image camera (6) and the second image camera (7) are connected to the data processing center (5) via data communication. The image capture camera (6) is used to capture the overall image of the printed matter and determine physical defects, while locating the position of the printed matter relative to the conveying unit (2); The second imaging camera (7) can be adjusted laterally in the vertical direction of the conveying direction, and the second imaging camera (7) is used to accurately align and capture images by combining the position information of the printed matter relative to the conveying unit (2), and to detect printing defects in the printed matter.

2. The real-time detection device for paper printing defects according to claim 1, characterized in that, The data processing center (5) automatically adjusts the lateral position of the second camera (7) through the linear driver (8) based on the printed matter position information obtained by the first camera (6) so that the second camera (7) is aligned with the printed matter area.

3. The real-time detection device for paper printing defects according to claim 1, characterized in that, Both the first (6) and the second (7) of the image capture camera are equipped with a light shield (14), and a supplementary light (17) and a light intensity sensor (18) are installed inside the light shield (14). The light intensity sensor (18) feeds back the light intensity signal to the data processing center (5), and the data processing center (5) adjusts the brightness of the fill light (17) in a closed loop according to the intensity signal to keep the ambient light stable.

4. The real-time detection device for paper printing defects according to claim 1, characterized in that, The upstream position of the conveying section (2) is also provided with a paging section (3), which includes a roller (29) with rotational damping. The rotational damping of the roller (29) is less than the conveying friction of the conveying section on the printed matter and greater than the stacking friction between the printed matter, so as to realize single-sheet paging and prevent paper overlap.

5. The real-time detection device for paper printing defects according to claim 1, characterized in that, The first imaging camera (6) is used to detect physical defects such as missing corners, folds, and incorrect dimensions. Once a defect is found, it is directly judged as a defective product, and the second imaging camera (7) is not activated for further analysis. The second imaging camera (7) is used to make precise defect judgments on printing patterns, printing colors, and printing positions.

6. A detection method for a real-time paper printing defect detection device according to any one of claims 1-5, characterized in that, Includes the following steps: S1: The printed matter is transported through the conveyor (2), and first passes the bottom position of the image camera (6), where the image camera (6) takes a picture of the printed matter. S2: The image captured by the first imaging camera (6) is sent to the data processing center (5). The data processing center (5) uses an edge detection algorithm to extract the contour of the image. The extracted contour is compared with the standard image to determine whether there is a physical defect. At the same time, the required position of the second imaging camera (7) is determined based on the extracted contour. S3: Then the linear driver (8) adjusts the image camera 2 (7) to the required position, and then the printed matter is transported to the position of the image camera 2 (7). The image camera 2 (7) takes another image and then transports it to the data processing center (5). The data processing center (5) extracts features from the image and then compares the printing features with the pre-recorded standard qualified product image. Then, it combines the threshold to judge whether it is qualified or unqualified. In step S2, the physical defect determination specifically includes: comparing with the standard image to determine the similarity of the contour, and using threshold control to determine whether there are dimensional defects such as missing corners, folds, and inconsistent paper sizes. If there are, they are directly determined to be defective products, and the subsequent image capture camera two (7) will no longer capture images for analysis. In step S3, the printing features include: printing texture features, printing color features, and printing position features.

Images