A method for detecting appearance defects in laminated products
By forming laser markings on the surface of the film and combining machine vision and AI technology, the problem of distinguishing defects on the film bottom in existing technologies has been solved, achieving efficient and accurate defect detection and improving product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANTOU GOWORLD DISPLAY TECH CO LTD
- Filing Date
- 2025-09-05
- Publication Date
- 2026-07-17
AI Technical Summary
Existing technologies struggle to accurately and efficiently detect defects on the film bottom of protective films used in flat panel products such as touchscreens or displays. This is because the protective film is a transparent plastic film, and defects on the film bottom and surface are mixed together in the images captured by the electronic lens, making it difficult for machine vision to distinguish them.
Laser marking technology is used to create laser marks on the surface of the film. Combined with machine vision and AI technology, the surface defects and bottom defects of the film are identified and distinguished by comparing the first and second images.
It enables accurate and efficient detection of surface defects on laminated products, effectively distinguishing between surface defects and bottom defects, thus ensuring product quality.
Smart Images
Figure CN120971457B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of testing technology, and more specifically to a method for detecting appearance defects in laminated products. Background Technology
[0002] In the manufacturing process of flat products such as touch screens and monitors, a protective film is usually attached to the surface of the product to protect it from scratches, contamination or mechanical damage. The protective film is usually made of transparent plastic film of PE, PP, PVC or PET. Flat products with protective films are generally called film products.
[0003] For screen protectors, both the surface of the tablet itself and the surface of the protective film may have appearance defects (such as damage or dirt), which can be referred to as bottom film defects and surface film defects, respectively. Surface film defects are damage, dirt, or scratches located on the surface of the protective film, usually caused by external factors during transportation or processing. These surface defects have a high probability of occurrence, but since they do not affect the functionality of the product itself, they generally do not require treatment. Bottom film defects are foreign objects, scratches, or damage located on the surface of the tablet itself (i.e., below the film layer). These bottom film defects have a lower probability of occurrence, but they directly affect product quality and require timely treatment. To ensure product quality, bottom film defects in screen protectors need to be detected and addressed during the manufacturing process of tablet products such as touch screens and displays.
[0004] Modern manufacturing widely employs industrial robots and machine vision technology to detect surface defects in laminated products. Currently, many manufacturers of flat panel products such as touchscreens or displays also hope to use electron lenses to image the surface of their products and combine this with machine vision methods to detect defects on the underside of the laminated film. However, since protective films are generally transparent plastic films, defects on the underside and surface of the film are often mixed together in the images acquired by electron lenses, making it difficult for conventional machine vision to distinguish them. Therefore, it is difficult to accurately and efficiently detect defects on the underside of laminated products using machine vision methods. Summary of the Invention
[0005] The technical problem to be solved by this invention is to provide a method for detecting appearance defects in laminated products. This method can detect appearance defects on the surface of laminated products and accurately and efficiently identify defects in the film substrate, thus helping to ensure the quality of laminated products. The technical solution adopted is as follows:
[0006] A method for detecting appearance defects in laminated products includes the following steps:
[0007] S1. Provide the film to be tested, the film including a substrate and a transparent plastic film adhered to the surface of the substrate;
[0008] Its features also include:
[0009] S2. Take a first photograph of the surface of the film-coated product to obtain a first image;
[0010] S3. By distinguishing the first image, all appearance defects on the surface of the film are identified and the location of each appearance defect is marked. Then, according to the location of each appearance defect, a laser is used to mark the surface of the film to form laser marks at the location of each appearance defect.
[0011] S4. Take a second photograph of the surface of the film-coated product to obtain a second image;
[0012] S5. By comparing a certain appearance defect in the second image with its corresponding laser marking, it is determined that the appearance defect is a film surface defect or a film bottom defect.
[0013] In the above-mentioned method for detecting appearance defects, in step S1, the substrate can be a flat structure or device with a film-adhesive surface, such as a glass substrate, glass lens, plastic lens, display screen, touch screen, or display module; the transparent plastic film serves as a protective film for the substrate and can be made of materials such as PE, PP, PVC, or PET; in steps S2-S3, the surface of the film-adhesive product (i.e., the surface of the transparent plastic film) is first photographed to obtain a first image, and then the first image is analyzed to identify all appearance defects on the surface of the film-adhesive product and mark the location of each appearance defect; then, based on the marked locations of each appearance defect, a laser is used to mark the surface of the film-adhesive product, utilizing the interaction between the laser and the surface of the transparent plastic film to make it... The laser marks are applied to the surface defects of the transparent plastic film without penetrating into the film, creating laser markings at the locations of each defect. This facilitates subsequent observation of the laser's influence on the defects, effectively distinguishing between surface and bottom defects. In steps S4-S5, after forming the laser marks on the transparent plastic film, a second image is taken of the film's surface. In steps S3 and S5, machine vision and AI technologies can be combined to differentiate the first and second images, efficiently and accurately identifying the locations of each defect and its corresponding laser marks. By comparing a defect in the second image with its corresponding laser mark, it can be accurately determined whether the defect is a surface or bottom defect.
[0014] As a preferred embodiment of the present invention, in steps S2 and S4, the surface of the film is photographed using a dark field method. This reduces the interference of ambient light on imaging and improves image contrast.
[0015] As a preferred embodiment of the present invention, the laser in step S3 is an ultraviolet laser. Because the transparent plastic film has a high absorption rate for ultraviolet lasers, it is easy to create clear scratches on the surface of the transparent plastic film without penetrating into its interior. Furthermore, its thermal effect is relatively small, thus avoiding any impact on the interior of the transparent plastic film due to high temperatures. Therefore, it is very easy to form scratches on the shallow surface of the transparent plastic film without damaging its interior.
[0016] As a preferred embodiment of the present invention, the laser marking in step S3 is a directional line segment passing through the corresponding appearance defect. The laser marking formed in this way is more easily identified in step S5.
[0017] As a further preferred embodiment of the present invention, in step S5, if a change in the thickness of the laser-etched image is observed, the appearance defect is determined to be a film surface defect.
[0018] As a further preferred embodiment of the present invention, in step S4, the surface of the film is photographed a second time under the scenario of side lighting. Specifically, the axis of the scratch line segment is defined as the first axis, and the side lighting direction of the film is the side of the first axis. Therefore, the laser scratches in the second image obtained in step S4 can be displayed as bright lines, making them easier to identify and analyze.
[0019] As a further preferred embodiment of the present invention, in step S3, for a certain appearance defect, a laser is used to mark the surface of the film to form multiple laser marks arranged side by side, such that one of the laser marks passes through the appearance defect.
[0020] In a preferred embodiment of the present invention, in step S5, the appearance defect is determined to be a film surface defect or a film bottom defect by observing whether the laser marking corresponding to a certain appearance defect in the second image is complete: if the image of the laser marking is complete, the appearance defect is determined to be a film bottom defect; if the laser marking is incomplete, the appearance defect is determined to be a film surface defect.
[0021] As another preferred embodiment of the present invention, in step S5, the appearance defect is determined to be a film surface defect or a film bottom defect by the relative relationship between a certain appearance defect in the second image and its corresponding laser marking: if the appearance defect and its laser marking are just image superposition, then the appearance defect is determined to be a film bottom defect; if the relationship between the appearance defect and its laser marking changes (for example, it may cause the laser marking to be interrupted, or it may cause image fusion), then the appearance defect is determined to be a film surface defect.
[0022] As a preferred embodiment of the present invention, in step S5, for a certain appearance defect, by comparing its first image and second image, and by identifying whether the laser marking changes relative to the appearance defect, it is determined that the appearance defect is a film surface defect or a film bottom defect; if it is found that the laser marking changes relative to the appearance defect, the appearance defect is determined to be a film surface defect.
[0023] In a preferred embodiment of the present invention, in steps S2-S4, an appearance defect detection device is used to complete the first photograph, laser marking, and second photograph of the surface of the laminated product. The appearance defect detection device includes a frame, a laminated product conveying mechanism, a camera, and a laser marking machine. The laminated product conveying mechanism, camera, and laser marking machine are all mounted on the frame. The laminated product conveying mechanism has a conveying section that moves back and forth. The camera and laser marking machine are positioned one in front of the other directly above the conveying section of the laminated product conveying mechanism, with the camera lens facing the conveying section. In use, the laminated product can be placed flat on the conveying section of the laminated product conveying mechanism. First, the laminated product conveying mechanism conveys the laminated product to the area below the camera lens to complete the first photograph. Then, the laminated product conveying mechanism conveys the laminated product to the area directly below the laser marking machine to complete the laser marking process. Finally, the laminated product conveying mechanism conveys the laminated product back to the area below the camera lens to complete the second photograph. This allows the same camera to be used for steps S2 and S4, reducing costs.
[0024] As a further preferred embodiment of the present invention, the film-coated product conveying mechanism includes multiple conveying rollers arranged from front to back and rotating in the same direction. Specifically, the multiple conveying rollers can rotate synchronously in the forward or reverse direction under the drive of a driving mechanism (the driving mechanism may be composed of a driving motor and multiple transmission belt mechanisms), driving the film-coated products on them to move between the camera and the laser marking machine.
[0025] To accommodate the movement of the applied film, as a further preferred embodiment of the present invention, the camera is a line scan camera.
[0026] Compared with the prior art, the present invention has the following advantages:
[0027] This method of detecting surface defects can detect defects on the surface of laminated products and can accurately and efficiently identify defects in the film substrate, which helps to ensure the quality of laminated products. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the appearance defect detection device provided in the preferred embodiment of the present invention, Example 1.
[0029] Figure 2 This is a cross-sectional schematic diagram of the film product and its surface defects affected by laser marking, provided in the preferred embodiment of the present invention, Example 1.
[0030] Figure 3 This is a cross-sectional schematic diagram of the film product and its film bottom defects affected by laser marking, provided in the preferred embodiment of the present invention, Example 1.
[0031] Figure 4 yes Figure 2 A schematic diagram of the first and second images obtained when the film and its surface defects are photographed.
[0032] Figure 5 yes Figure 3 A schematic diagram of the first and second images obtained when the film-coated product and its film-bottom defects are photographed.
[0033] Figure 6 This is a schematic diagram of the appearance defect detection device provided in the preferred embodiment of the present invention, Example 2. Detailed Implementation
[0034] Example 1: As Figures 1-5 As shown, this method for detecting appearance defects in laminated products includes the following steps:
[0035] S1. Provide a film product 10 to be tested, the film product 10 includes a substrate 11 and a transparent plastic film 12 adhered to the surface of the substrate 11.
[0036] S2. Take a first photograph of the surface of the film-coated product 10 to obtain the first image 20;
[0037] S3. By distinguishing the first image 20, all appearance defects on the surface of the film product 10 are identified and the location of each appearance defect is marked. Then, according to the location of each appearance defect, a laser is used to mark the surface of the film product 10 to form laser marks 110 at the location of each appearance defect.
[0038] S4. Take a second photograph of the surface of the film 10 to obtain a second image 30;
[0039] S5. By comparing a certain appearance defect in the second image 30 with its corresponding laser scratch 110, it is determined that the appearance defect is a film surface defect 120 or a film bottom defect 130.
[0040] In this embodiment, in step S1, the transparent plastic film 12 of the film-applied product 10 is adhered to the surface of the substrate 11 by the adhesive layer 13; the substrate 11 can be a flat structure or device with a surface that can be film-applied, such as a glass substrate, glass lens, plastic lens, display screen, touch screen or display module; the transparent plastic film 12 can be made of materials such as PE, PP, PVC or PET.
[0041] In this embodiment, in steps S3 and S5, machine vision and AI technology are combined to distinguish the first image 20 and the second image 30, so as to efficiently and accurately identify the location of each appearance defect and its corresponding laser scratch 110. By comparing a certain appearance defect in the second image 30 with its corresponding laser scratch 110, it can be accurately determined that the appearance defect is a film surface defect 120 or a film bottom defect 130.
[0042] In this embodiment, in steps S2 and S4, the surface of the film-coated product 10 is photographed using a dark field method. This reduces the interference of ambient light on imaging and improves image contrast.
[0043] In this embodiment, the laser in step S3 is an ultraviolet laser; the laser marking 110 is a directional line segment passing through the corresponding appearance defect. Because the transparent plastic film 12 has a high absorption rate for ultraviolet laser, it is easy to create clear markings on the surface of the transparent plastic film 12 without penetrating into its interior. Furthermore, its thermal effect is relatively small, so it will not affect the interior of the transparent plastic film 12 due to high temperatures. Therefore, it is very easy to form laser markings 110 on the shallow surface of the transparent plastic film 12 without damaging its interior. The laser marking 110, being a directional line segment passing through the corresponding appearance defect, is more easily identified in step S5.
[0044] In this embodiment, in step S5, by observing whether the laser scratch 110 corresponding to a certain appearance defect in the second image 30 is complete, it is determined whether the appearance defect is a film surface defect 120 or a film bottom defect 130: if the image of the laser scratch 110 is complete, the appearance defect is determined to be a film bottom defect 130; if the laser scratch 110 is incomplete, the appearance defect is determined to be a film surface defect 120.
[0045] In this embodiment, in step S5, by analyzing the relative relationship between a certain appearance defect in the second image 30 and its corresponding laser marking 110, it is determined whether the appearance defect is a film surface defect 120 or a film bottom defect 130: if the appearance defect and its laser marking 110 are merely image superimposed, then the appearance defect is determined to be a film bottom defect 130; if the relationship between the appearance defect and its laser marking 110 changes (for example, it may cause the laser marking 110 to be interrupted, or it may cause image fusion), then the appearance defect is determined to be a film surface defect 120.
[0046] In this embodiment, in step S5, for a certain appearance defect, by comparing its first image 20 and second image 30, it is determined whether the appearance defect is a film surface defect 120 or a film bottom defect 130 by identifying whether the laser scratch 110 changes relative to the appearance defect; if it is found that the laser scratch 110 changes relative to the appearance defect, the appearance defect is determined to be a film surface defect 120.
[0047] The appearance defect detection device 50 provided in this embodiment can complete the first image, laser marking and second image of the surface of the film-coated product 10 in steps S2-S4. The appearance defect detection device 50 includes a frame (not shown in the figure), a film-coated product conveying mechanism 51, a line scan camera 52 and a laser marking machine 53. The film-coated product conveying mechanism 51, the line scan camera 52 and the laser marking machine 53 are all mounted on the frame. The film-coated product conveying mechanism 51 includes a plurality of conveying rollers 510 arranged from front to back and rotating in the same direction. The line scan camera 52 and the laser marking machine 53 are arranged one in front of the other directly above the film-coated product conveying mechanism 51. The camera of the line scan camera 52 faces the film-coated product conveying mechanism 51. During operation, the film-coated product 10 can be placed flat on the film-coated product conveying mechanism 51. Multiple conveying rollers 510 rotate synchronously in the forward or reverse direction under the drive of a driving mechanism (which may consist of a drive motor and multiple transmission belt mechanisms), causing the film-coated product 10 to move between the area below the line scan camera 52 and the laser marking machine 53. First, the film-coated product conveying mechanism 51 conveys the film-coated product 10 to the area below the camera of the line scan camera 52 to complete the first shot. Then, the film-coated product conveying mechanism 51 conveys the film-coated product 10 directly below the laser marking machine 53 to complete the laser marking process. Finally, the film-coated product conveying mechanism 51 conveys the film-coated product 10 back to the area below the camera of the line scan camera 52 to complete the second shot. This allows steps S2 and S4 to be taken using the same line scan camera 52, which can reduce costs.
[0048] refer to Figure 6 Example 2: In the case that all other parts are the same as in Example 1, the difference is that the appearance defect detection device 50 provided in this example also includes a side lamp 54. The side lamp 54 is set above the conveying section of the film-coated product conveying mechanism 51 and between the line scan camera 52 and the laser marking machine 53. The side lamp 54 shines light obliquely towards the direct underside of the line scan camera 52.
[0049] In this embodiment, in step S4, a second photograph is taken of the surface of the film 10 under side lighting conditions. Specifically, the axis of the scratch line segment is defined as the first axis, and the side lighting direction of the film 10 is the side of the first axis. Therefore, the laser scratch 110 in the second image 30 obtained in step S4 can be displayed as a bright line, making it easier to identify and analyze.
[0050] Furthermore, it should be noted that the names of the various parts of the specific embodiments described in this specification may differ. All equivalent or simple variations made to the structure, features, and principles of this invention are included within the scope of protection of this invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of this invention or exceed the scope defined by the claims, all of which should fall within the scope of protection of this invention.
Claims
1. A method for detecting appearance defects in laminated products, comprising the following steps: S1. Provide the film to be tested, the film including a substrate and a transparent plastic film adhered to the surface of the substrate; Its features Also includes: S2. Take a first photograph of the surface of the film-coated product to obtain a first image; S3. By distinguishing the first image, all appearance defects on the surface of the film are identified and the location of each appearance defect is marked. Then, according to the location of each appearance defect, an ultraviolet laser is used to mark the surface of the film to form laser marks at the location of each appearance defect. The laser marks are directional line segments that pass through the corresponding appearance defects. S4. Take a second photograph of the surface of the film-coated product to obtain a second image; S5. By comparing a certain appearance defect in the second image with its corresponding laser marking, it is determined that the appearance defect is a film surface defect or a film bottom defect.
2. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In steps S2 and S4, the surface of the film is photographed using a dark field method.
3. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In step S5, if a change in the thickness of the laser-etched image is observed, the appearance defect is determined to be a film surface defect.
4. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In step S4, the surface of the film is photographed a second time under side lighting conditions.
5. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In step S3, for a certain appearance defect, a laser is used to mark the surface of the film to form multiple laser marks arranged side by side, such that one of the laser marks passes through the appearance defect.
6. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In step S5, by observing whether the laser markings corresponding to a certain appearance defect in the second image are complete, it is determined whether the appearance defect is a film surface defect or a film bottom defect: if the image of the laser markings is complete, the appearance defect is determined to be a film bottom defect; if the laser markings are incomplete, the appearance defect is determined to be a film surface defect.
7. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In step S5, by analyzing the relative relationship between a certain appearance defect in the second image and its corresponding laser marking, it is determined whether the appearance defect is a film surface defect or a film bottom defect: if the appearance defect and its laser marking are merely image superimposed, then the appearance defect is determined to be a film bottom defect; if the relationship between the appearance defect and its laser marking changes, then the appearance defect is determined to be a film surface defect.
8. The method for detecting appearance defects in laminated products according to claim 1, characterized in that: In steps S2-S4, an appearance defect detection device is used to complete the first photograph, laser marking, and second photograph of the surface of the film-coated product. The appearance defect detection device includes a frame, a film-coated product conveying mechanism, a camera, and a laser marking machine. The film-coated product conveying mechanism, the camera, and the laser marking machine are all mounted on the frame. The film-coated product conveying mechanism has a conveying section that moves back and forth. The camera and the laser marking machine are positioned one in front of the other directly above the conveying section of the film-coated product conveying mechanism, with the camera lens facing the conveying section of the film-coated product conveying mechanism.
9. The method for detecting appearance defects in laminated products according to claim 8, characterized in that: The film-coated product conveying mechanism includes multiple conveying rollers arranged from front to back and rotating in the same direction; the camera is a line scan camera.