Stress mark detection method and stress mark detection device

Abstract

The invention relates to the field of machine vision detection, and discloses a stress mark detection method and a stress mark detection device.The stress mark detection method comprises the steps that a detection light spot is formed on a detected surface, and the detection light spot is formed by obliquely irradiating illumination light on the detected surface; reflected light rays from the detected surface are collected to form a 2D detection image, and the included angle between the reflected light rays and the detected surface is not larger than 10 degrees; and processing the 2D detection image to obtain a gray scale image, and judging whether a stress mark exists in the illuminated area or not based on the gray scale image. According to the stress mark detection method and the stress mark detection device, finer stress marks can be effectively detected, and the detection precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of machine vision detection, and in particular to a stress mark detection method and a stress mark detection device. Background Art

[0002] During the material processing and use process, stress marks will appear when the object is subjected to external force such as stretching, extrusion, etc. Therefore, it is necessary to perform stress mark detection on the surface of the workpiece to determine whether the workpiece is qualified.

[0003] Traditional stress mark detection methods are mostly contact measurement and visual inspection. The existing detection methods have the disadvantages of slow detection speed, poor detection accuracy, and detection results are easily affected by the environment. In particular, the existing detection methods are difficult to detect relatively small stress marks on the surface of the workpiece.

[0004] In view of this, it is necessary to design a stress mark detection method and a stress mark detection device that can effectively detect smaller stress marks and improve detection accuracy.

[0005] The above information is presented as background information only to assist with understanding the present disclosure and no determination or admission is made as to whether any of the above may be used as prior art with respect to the present disclosure. Summary of the invention

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

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A stress mark detection method, comprising:

[0009] S01, forming a detection light spot on the surface to be detected, wherein the detection light spot is formed by obliquely irradiating the illumination light on the surface to be detected;

[0010] S02, 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°;

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

[0012] Optionally, the detection light spot is formed by obliquely irradiating the detection surface with illumination light emitted by a strip light source;

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

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

[0015] Optionally, the detected surface is parallel to a horizontal plane;

[0016] The strip-shaped light source is higher than the detected surface, and the strip-shaped light source is parallel to a horizontal plane, and a light outlet of the strip-shaped light source is arranged horizontally.

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

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

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

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

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

[0022] Optionally, the workpiece is columnar, and the detected surface is the surface of the top area of ​​the periphery of the workpiece.

[0023] A stress mark detection device, comprising:

[0024] A strip light source forms a detection light spot on the detected surface of the workpiece, wherein the detection light spot is formed by oblique illumination of the illumination light on the detected surface;

[0025] A visual inspection device, which obtains reflected light from the inspected surface to form a 2D inspection image, and the angle between the reflected light and the inspected surface is not greater than 10°;

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

[0027] Optionally, the visual inspection device comprises 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 center line of the telecentric lens and the workpiece is no greater than 10°.

[0029] Optionally, the bar-shaped light source and the visual inspection device are arranged at intervals, and the bar-shaped light source and the visual 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 illumination intensity in the side area is less than the illumination intensity in the direct illumination area, and the detected surface is located in the side area for detection;

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

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

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

[0034] The present invention has other features and advantages, which will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain the specific principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 is a flow chart of a stress mark detection method provided by an embodiment of the present invention;

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

[0038] Figure 3 is a light emission schematic diagram of a bar light source provided by an embodiment of the present invention;

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

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

[0041] Figure 6 It is a grayscale image provided by 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 DESCRIPTION

[0043] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0044] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0045] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0046] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0047] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0048] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0049] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0050] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0051] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0052] Embodiment 1

[0053] In view of the defects of the above-mentioned existing stress mark detection methods, the applicant, based on many years of rich practical experience and professional knowledge in the design and manufacture of such products, and in conjunction with the application of theory, actively conducts research and innovation in the hope of creating a technology that can solve the defects in the existing technology and make the stress mark detection method more practical. After continuous research and design, and after repeated trial production and improvement, the present invention with real practical value was finally created.

[0054] Please refer to Figure 1 and Figure 6 , an embodiment of the present invention provides a stress mark detection method, comprising:

[0055] S01, forming a detection light spot on the surface 100 to be detected, where the detection light spot is formed by obliquely irradiating the illumination light on the surface 100 to be detected;

[0056] S02, collecting reflected light from the detected surface 100 to form a 2D detection image, and the angle between the reflected light and the detected surface 100 is not greater than 10°;

[0057] S03. Process the 2D detection image to obtain a grayscale image, and determine whether there is a stress mark 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 then the angle of the reflected light is less than 10°, so that the stress mark can be better displayed in the grayscale image, that is, the grayscale of the stress mark is obviously darker, which is conducive to detecting smaller stress marks and improving the detection accuracy. Generally, a black mark will appear on the grayscale image, which is the surface stress mark defect.

[0059] The following effects can be obtained when the illumination light is irradiated at an angle and the angle between the reflected light and the surface to be inspected 100 is not greater than 10°:

[0060] ① Highlight the depth information of the tiny protrusions on the detected surface 100: Under the irradiation of inclined illumination light, the shadow on the other side of the tiny protrusion on the detected surface 100 can be collected to form a 2D detection image. The detection imaging with an inclination angle of less than 10° can make the shadow of the tiny protrusion more obvious, thereby facilitating the detection of stress marks; in subsequent processing, the grayscale image can more easily reflect the stress marks.

[0061] ② The continuity effect of stress marks is more obvious: when detecting imaging along an inclination angle less than 10°, the continuity effect between stress marks is clearer, that is, small-angle inclination detection makes the shadow stacking effect at the stress marks more obvious, which can better reflect the morphology of the detected surface 100.

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

[0063] Figure 6 The grayscale image is obtained by processing the 2D detection image. The red rectangle is added later just to circle the location of the stress mark for easy understanding. Figure 6 It can be seen that the stress marks extend in a linear shape.

[0064] Optionally, the detection light spot is formed by the illumination light emitted by the strip light source 1 being obliquely irradiated on the detected surface 100; the illumination area of ​​the strip light source 1 includes a direct area 101 and a side area 102 surrounding the direct area 101, the light intensity in the side area 102 is less than the light intensity in the direct area 101, and the detected surface 100 is located in the side area 102 for detection; the angle between the illumination light and the detected surface 100 is not greater than 30°.

[0065] It should be noted that the illumination in the side area 102 gradually decreases in the direction away from the bar light source 1, so that the shadow of the tiny protrusion on the detection surface 100 is more prominent, so that the grayscale image after 2D detection image processing is easier to reflect the tiny stress marks, thereby improving the detection accuracy. In particular, when the stress marks extend in the direction away from the bar light source 1, the shadow effect of the stress marks in the 2D detection image is more obvious.

[0066] In a specific embodiment, the detected surface 100 is parallel to the horizontal plane; the strip light source 1 is higher than the detected surface 100 , and the strip light source 1 is parallel to the horizontal plane, and the light outlet of the strip light source 1 is horizontally arranged.

[0067] Optionally, the angle between the reflected light and the detected surface 100 is in the range of 8±2°. Preferably, the angle between the reflected light and the detected surface 100 is in the range of 8°.

[0068] Optionally, the angle between the illumination light and the inspected surface 100 is in the range of 5±2°. Preferably, the angle between the illumination light and the inspected surface 100 is in the range of 5°.

[0069] Optionally, the reflected light of the detected surface 100 is obtained to form a 2D detection image, specifically:

[0070] S021, tilting the visual inspection device 2 to a set angle;

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

[0072] Specifically, the strip light source 1 and the visual detection device 2 are disposed at two ends of the detected surface 100 , so that the shadow differences of tiny protrusions on the detected surface 100 can be better detected.

[0073] Optionally, the workpiece is columnar, and the detected surface 100 is the surface of the top area of ​​the outer periphery of the workpiece.

[0074] Embodiment 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 detected surface 100 of the workpiece, and the detection spot is formed by the illumination light irradiating the detected surface 100 obliquely; a visual detection device 2, which obtains the reflected light from the detected surface 100 to form a 2D detection image, and the angle between the reflected light and the detected surface 100 is not greater than 10°; a data processing module, which processes the 2D detection image to obtain a grayscale image, and determines whether there is a stress mark in the illuminated area based on the grayscale image.

[0076] The bar light source 1 is tilted to illuminate the surface 100 to be inspected, the visual inspection device 2 is tilted to obtain the reflected light and form a 2D inspection image, and the data processing module processes the 2D inspection image to obtain a grayscale image to determine whether there are stress marks. 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, and the presence of stress marks on the surface to be inspected can be quickly and accurately determined 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 is directly opposite the telecentric lens 21; the angle between the center line of the telecentric lens 21 and the workpiece is not greater than 10°. The setting of the telecentric lens 21 can more accurately obtain the required 2D inspection image and improve the inspection accuracy. In this embodiment, the pixel of the camera 22 is 5MP.

[0078] Optionally, 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 irradiation area of ​​the strip light source 1 includes a direct area 101 and a side area 102 surrounding the direct area 101, the light intensity in the side area 102 is less than the light intensity in the direct 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 not greater than 30°. The direct area 101 is a strong irradiation area, and the side area 102 is a weak irradiation area, which can better reflect the shadow of the tiny protrusions on the surface to be inspected 100. When strong light is directly irradiated on the tiny protrusions, the reflection and scattering on the tiny protrusions will reduce the shadow effect of the tiny protrusions, which is not conducive to improving the detection accuracy.

[0079] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A stress mark detection method, characterized in that: include: Forming a detection light spot on the detected surface (100), wherein the detection light spot is formed by oblique illumination of the illumination light on the detected surface (100); collecting reflected light from the detected surface (100) to form a 2D detection image, wherein the angle between the reflected light and the detected surface (100) is no greater than 10°; The 2D detection image is processed to obtain a grayscale image, and whether stress marks exist in the illuminated area is determined based on the grayscale image.

2. The stress mark detection method according to claim 1, characterized in that: The detection light spot is formed by the illumination light emitted by the strip-shaped light source (1) irradiating the detected surface (100) obliquely; The illumination area of ​​the strip-shaped light source (1) comprises 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 detected surface (100) is located in the side area (102) for detection; The angle between the illumination light and the detected surface (100) is no greater than 30°.

3. The stress mark detection method according to claim 2, characterized in that: The detected surface (100) is parallel to a horizontal plane; The strip-shaped light source (1) is higher than the detected surface (100), the strip-shaped light source (1) is parallel to a horizontal plane, and a light outlet of the strip-shaped light source (1) is arranged horizontally.

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

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

6. The stress mark detection method according to claim 1, characterized in that: The step of acquiring the reflected light of the detected surface (100) to form a 2D detection image is specifically: Tilt the visual inspection device (2) to a set angle; The visual inspection device (2) takes a photograph of the inspected surface (100) to obtain a 2D inspection image.

7. The stress mark detection method according to claim 1, characterized in that: The workpiece is columnar, and the detected surface (100) is the surface of the top area of ​​the outer periphery of the workpiece.

8. A stress mark detection device, characterized in that: include: A strip light source (1) forms a detection light spot on a detected surface (100) of a workpiece, wherein the detection light spot is formed by oblique illumination of illumination light on the detected surface (100); A visual inspection device (2) for obtaining reflected light from the inspected surface (100) to form a 2D inspection image, wherein the angle between the reflected light and the inspected surface (100) is not greater than 10°; The data processing module processes the 2D detection image to obtain a grayscale image, and determines whether there is a stress mark in the illuminated area based on the grayscale image.

9. The stress mark detection device according to claim 8, characterized in that: The visual detection device (2) comprises 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 center line of the telecentric lens (21) and the workpiece is no greater than 10°.

10. The stress mark detection device according to claim 8, characterized in that: The strip-shaped light source (1) and the visual detection device (2) are arranged at intervals, and the strip-shaped light source (1) and the visual detection device (2) form a gap for the workpiece to flow through; The illumination area of ​​the strip-shaped light source (1) comprises 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 detected surface (100) is located in the side area (102) for detection; The angle between the illumination light and the detected surface (100) is no greater than 30°.

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