A stress mark detection method and a stress mark detection device

Abstract

The present application relates to the field of machine vision detection, and discloses a stress mark detection method and a stress mark detection device, which comprises: forming a detection light spot on a detected surface, wherein the detection light spot is formed by oblique illumination of illumination light on the detected surface; collecting reflected light from the detected surface to form a 2D detection image, and the angle between the reflected light and the detected surface is not greater than 10 degrees; processing the 2D detection image to obtain a gray scale image, and judging whether the illuminated area has a stress mark based on the gray scale image. The stress mark detection method and the stress mark detection device can effectively detect smaller stress marks and improve detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of machine vision inspection, and more particularly to a stress mark detection method and a stress mark detection device. Background Technology

[0002] During material processing and use, stress marks may appear when an object is subjected to external forces such as stretching or squeezing. Therefore, it is necessary to detect stress marks on the surface of the workpiece to determine whether the workpiece is qualified.

[0003] Traditional stress mark detection methods are mostly contact-based measurements and visual inspections. These methods suffer from drawbacks such as slow speed, poor accuracy, and susceptibility to environmental influences. In particular, existing methods struggle to detect fine stress marks on workpiece surfaces.

[0004] Therefore, it is necessary to design a stress trace detection method and device that can effectively detect finer stress traces and improve detection accuracy.

[0005] The above information is provided as background information only to aid in understanding this disclosure and does not constitute an assertion or admission that any of the above content can be used as prior art relative to this disclosure. Summary of the Invention

[0006] This invention provides a stress mark detection method and a stress mark detection device, which can effectively detect finer stress marks and improve detection accuracy.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for detecting stress marks, comprising:

[0009] S01. A detection spot is formed on the surface to be detected, wherein the detection spot is formed by an illumination light beam obliquely shining on the surface to be detected;

[0010] S02. Collect reflected light from the surface being inspected to form a 2D inspection image, and the angle between the reflected light and the surface being inspected is no greater than 10°.

[0011] S03. Process the 2D detection image to obtain a grayscale image, and determine whether there are stress marks in the illuminated area based on the grayscale image.

[0012] Optionally, the detection spot is formed by the illumination light emitted from a strip light source obliquely illuminating the surface being detected;

[0013] The illumination area of ​​the strip light source includes a direct illumination area and a side area surrounding the direct illumination area. The light intensity in the side area is less than the light intensity in the direct illumination area, and the surface to be detected is located in the side area for detection.

[0014] The angle between the illumination light and the surface being inspected is no greater than 30°.

[0015] Optionally, the surface being tested is parallel to the horizontal plane;

[0016] The strip light source is higher than the surface being tested, and the strip light source is parallel to the horizontal plane, with the light outlet of the strip light source set horizontally.

[0017] Optionally, the angle between the reflected light and the surface being tested is in the range of 8±2°.

[0018] Optionally, the angle between the illumination light and the surface being tested is in the range of 5±2°.

[0019] Optionally, acquiring the reflected light from the surface being detected to form a 2D detection image specifically involves:

[0020] S021. Tilt the visual inspection device to the set angle;

[0021] S022. The visual inspection device takes a picture of the surface to be inspected to obtain a 2D inspection image.

[0022] Optionally, the workpiece is cylindrical, and the surface to be detected is the surface of the top region of the outer periphery of the workpiece.

[0023] A stress mark detection device, comprising:

[0024] A strip light source forms a detection spot on the surface of the workpiece to be inspected, and the detection spot is formed by the illumination light obliquely shining on the surface to be inspected;

[0025] A visual inspection device acquires reflected light from the surface being inspected to form a 2D inspection image, wherein the angle between the reflected light and the surface being inspected is no greater than 10°.

[0026] The data processing module processes the 2D detection image to obtain a grayscale image, and determines whether stress marks exist in the illuminated area based on the grayscale image.

[0027] Optionally, the visual inspection device includes a telecentric lens and a camera; the camera is fixedly connected to the telecentric lens, and the camera faces the telecentric lens.

[0028] The angle between the centerline of the telecentric lens and the workpiece is no greater than 10°.

[0029] Optionally, the strip light source and the vision inspection device are spaced apart, and the strip light source and the vision inspection device form a gap for the workpiece to flow through;

[0030] The illumination area of ​​the strip light source includes a direct illumination area and a side area surrounding the direct illumination area. The light intensity in the side area is less than the light intensity in the direct illumination area, and the surface to be detected is located in the side area for detection.

[0031] The angle between the illumination light and the surface being inspected is no greater than 30°.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The stress trace detection method and device provided by the present invention illuminate the surface to be tested with an inclined illumination light, and then collect the reflected light angle of the surface to be tested which is less than 10°, so that the stress trace can be better displayed in the grayscale image (the grayscale of the stress trace is significantly darker), which can help detect finer stress traces and improve detection accuracy.

[0034] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart of the stress mark detection method provided in the embodiments of the present invention;

[0037] Figure 2 This is a schematic diagram of the stress mark detection device provided in an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the light emission from the strip light source provided in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of the visual inspection device provided in an embodiment of the present invention;

[0040] Figure 5This is a three-dimensional structural schematic diagram of the telecentric lens provided in an embodiment of the present invention;

[0041] Figure 6 This is a grayscale image provided in an embodiment of the present invention.

[0042] Reference numerals: 100, surface to be inspected; 1, strip light source; 101, direct illumination area; 102, side area; 2, visual inspection device; 21, telecentric lens; 22, camera. Detailed Implementation

[0043] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0044] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0045] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0046] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0047] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0048] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0049] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0050] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0051] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0052] Example 1

[0053] In view of the shortcomings of existing stress mark detection methods, the applicant, based on years of practical experience and professional knowledge in the design and manufacture of such products, and in conjunction with theoretical application, actively researched and innovated to create a technology that could overcome the shortcomings of existing technologies, making stress mark detection methods more practical. After continuous research, design, and repeated prototype production and improvement, this invention with real practical value was finally created.

[0054] Please refer to Figure 1 and Figure 6 This invention provides a method for detecting stress marks, comprising:

[0055] S01. A detection spot is formed on the surface 100 to be detected. The detection spot is formed by the illumination light being obliquely irradiated onto the surface 100 to be detected.

[0056] S02. Collect reflected light from the surface 100 to form a 2D detection image, and the angle between the reflected light and the surface 100 is no greater than 10°.

[0057] S03. Process the 2D detection image to obtain a grayscale image, and determine whether there are stress marks in the illuminated area based on the grayscale image.

[0058] In this embodiment, the surface 100 to be inspected is illuminated by an inclined illumination light, and the angle of the reflected light is less than 10° when imaging is performed. This allows the stress marks to be better displayed in the grayscale image, meaning the grayscale of the stress marks is significantly darker. This facilitates the detection of finer stress marks and improves detection accuracy. Generally, a black mark will appear on the grayscale image, which is the surface stress mark defect.

[0059] When the illumination light is shone at an angle, and the angle between the reflected light and the surface 100 being tested is no greater than 10°, the following effect can be achieved:

[0060] ① Highlighting the depth information of the tiny protrusions on the surface 100 being inspected: Under the illumination of the tilted light, the shadow on the other side of the tiny protrusions on the surface 100 being inspected can be captured to form a 2D inspection image. The inspection imaging with a tilt angle of less than 10° can make the shadow of the tiny protrusions more obvious, thus facilitating the detection of stress marks. In subsequent processing, the grayscale image can more easily show the stress marks.

[0061] ② The continuity effect of stress marks is more obvious: When imaging along an inclination angle of less than 10°, the continuity effect between stress marks is clearer. That is, small-angle tilt detection makes the shadow stacking effect at the stress mark more obvious, which can better reflect the morphology of the surface being inspected.

[0062] The stress mark detection method in this embodiment has a fast detection speed, high accuracy and precision, and the non-contact detection will not cause damage to the workpiece surface.

[0063] Figure 6 This is a grayscale image obtained by processing the 2D detection image. The red rectangles were added later, simply to outline the location of stress marks for easier understanding. From Figure 6 It can be seen that the stress marks extend in a linear pattern.

[0064] Optionally, the detection spot is formed by the illumination light emitted from the strip light source 1 obliquely illuminating the surface 100 to be detected; the illumination area of ​​the strip light source 1 includes a direct illumination area 101 and a side area 102 surrounding the direct illumination area 101, the illumination intensity in the side area 102 is less than the illumination intensity in the direct illumination area 101, and the surface 100 to be detected is located in the side area 102 for detection; the angle between the illumination light and the surface 100 to be detected is no greater than 30°.

[0065] It should be further noted that in the side region 102, the illuminance gradually decreases along the direction away from the strip light source 1, thus making the shadows of the tiny protrusions on the detection surface 100 more prominent. This makes it easier for the grayscale image after 2D detection image processing to show the tiny stress marks, thereby improving detection accuracy. In particular, the shadow effect of the stress marks in the 2D detection image is more obvious when the stress marks extend away from the strip light source 1.

[0066] In one specific embodiment, the surface to be tested 100 is parallel to the horizontal plane; the strip light source 1 is higher than the surface to be tested 100, and the strip light source 1 is parallel to the horizontal plane, and the light outlet of the strip light source 1 is set horizontally.

[0067] Optionally, the angle between the reflected light and the surface 100 being tested ranges from 8 ± 2°. Preferably, the angle between the reflected light and the surface 100 being tested ranges from 8°.

[0068] Optionally, the angle between the illumination light and the surface 100 being tested ranges from 5 ± 2°. Preferably, the angle between the illumination light and the surface 100 being tested ranges from 5°.

[0069] Optionally, the reflected light from the surface 100 being inspected is acquired to form a 2D inspection image, specifically:

[0070] S021. Tilt the visual inspection device 2 to the set angle;

[0071] S022, the visual inspection device 2 takes pictures of the surface to be inspected 100 to obtain a 2D inspection image.

[0072] Specifically, the strip light source 1 and the visual inspection device 2 are respectively located at both ends of the surface to be inspected 100, so as to better detect the shadow differences of tiny protrusions on the surface to be inspected 100.

[0073] Optionally, the workpiece is cylindrical, and the surface to be detected 100 is the surface of the top region of the outer periphery of the workpiece.

[0074] Example 2

[0075] This embodiment discloses a stress mark detection device, such as Figures 2 to 5 As shown, the stress mark detection device includes: a strip light source 1, which forms a detection spot on the surface 100 of the workpiece to be inspected, the detection spot being formed by the illumination light obliquely illuminating the surface 100 to be inspected; a vision inspection device 2, which acquires the reflected light from the surface 100 to form a 2D inspection image, and the angle between the reflected light and the surface 100 to be inspected is no greater than 10°; and a data processing module, which processes the 2D inspection image to obtain a grayscale image, and determines whether stress marks exist in the illuminated area based on the grayscale image.

[0076] A bar light source 1 illuminates the surface 100 to be inspected at an angle. A visual inspection device 2 acquires the reflected light at an angle and forms a 2D inspection image. The data processing module processes the 2D inspection image to obtain a grayscale image and determines whether stress marks exist. In this embodiment, through a clever structural design, the projection of tiny protrusions on the surface 100 to be inspected can be magnified on the grayscale image, enabling rapid and accurate determination of whether stress marks exist on the surface to be inspected based on the grayscale image.

[0077] Optionally, the visual inspection device 2 includes a telecentric lens 21 and a camera 22; the camera 22 is fixedly connected to the telecentric lens 21, and the camera 22 faces the telecentric lens 21 directly; the angle between the centerline of the telecentric lens 21 and the workpiece is no greater than 10°. The telecentric lens 21 allows for more accurate acquisition of the required 2D inspection image, improving inspection accuracy. In this embodiment, the camera 22 has a resolution of 5MP.

[0078] Optionally, the strip light source 1 and the vision inspection device 2 are spaced apart, forming a gap for the workpiece to pass through. The illumination area of ​​the strip light source 1 includes a direct illumination area 101 and a side area 102 surrounding the direct illumination area 101. The light intensity in the side area 102 is less than the light intensity in the direct illumination area 101, and the surface to be inspected 100 is located in the side area 102 for inspection. The angle between the illumination light and the surface to be inspected 100 is no greater than 30°. The direct illumination area 101 is a strong illumination area, while the side area 102 is a weak illumination area. The weak illumination area can better reflect the shadows of the tiny protrusions on the surface to be inspected 100. Strong light directly hitting the tiny protrusions will reduce the shadow effect of the tiny protrusions due to reflection and scattering, which is not conducive to improving the inspection accuracy.

[0079] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for detecting stress marks, characterized in that, include: A detection spot is formed on the surface to be tested (100), the detection spot being formed by an illumination light obliquely shining on the surface to be tested (100); Reflected light rays collected from the surface being tested (100) are used to form a 2D detection image, and the angle between the reflected light rays and the surface being tested (100) is no greater than 10°; The 2D detection image is processed to obtain a grayscale image, and the presence of stress marks in the illuminated area is determined based on the grayscale image. The detection spot is formed by the illumination light emitted from the strip light source (1) obliquely illuminating the surface (100) to be detected; The illumination area of ​​the strip light source (1) includes a direct illumination area (101) and a side area (102) surrounding the direct illumination area (101). The light intensity in the side area (102) is less than the light intensity in the direct illumination area (101), and the surface to be detected (100) is located in the side area (102) for detection. The angle between the illumination light and the surface (100) being tested is no greater than 30°.

2. The stress mark detection method according to claim 1, characterized in that, The surface being tested (100) is parallel to the horizontal plane; The strip light source (1) is higher than the surface being tested (100), and the strip light source (1) is parallel to the horizontal plane, and the light outlet of the strip light source (1) is set horizontally.

3. The stress mark detection method according to claim 1, characterized in that, The angle between the reflected light and the surface being tested (100) is in the range of 8±2°.

4. The stress mark detection method according to claim 1, characterized in that, The angle between the illumination light and the surface being tested (100) is within the range of 5±2°.

5. The stress mark detection method according to claim 1, characterized in that, The workpiece is cylindrical, and the surface to be tested (100) is the surface of the top region of the outer periphery of the workpiece.

6. A stress mark detection device, characterized in that, include: A strip light source (1) forms a detection spot on the surface (100) of the workpiece to be inspected, the detection spot being formed by the illumination light obliquely shining on the surface (100) to be inspected; The visual inspection device (2) acquires the reflected light from the surface to be inspected (100) to form a 2D inspection image, and the angle between the reflected light and the surface to be inspected (100) is not greater than 10°. The data processing module processes the 2D detection image to obtain a grayscale image, and determines whether there are stress marks in the illuminated area based on the grayscale image. The strip light source (1) and the visual inspection device (2) are arranged at intervals, and the strip light source (1) and the visual inspection device (2) form a gap for the workpiece to flow through; The illumination area of ​​the strip light source (1) includes a direct illumination area (101) and a side area (102) surrounding the direct illumination area (101). The light intensity in the side area (102) is less than the light intensity in the direct illumination area (101), and the surface to be detected (100) is located in the side area (102) for detection. The angle between the illumination light and the surface (100) being tested is no greater than 30°.

7. The stress mark detection device according to claim 6, characterized in that, The visual inspection device (2) includes a telecentric lens (21) and a camera (22); the camera (22) is fixedly connected to the telecentric lens (21), and the camera (22) faces the telecentric lens (21). The angle between the centerline of the telecentric lens (21) and the workpiece is no greater than 10°.

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