Surface texture inspection apparatus and surface texture inspection method

Abstract

To provide a surface quality inspection device capable of detecting pattern scars.SOLUTION: A surface quality inspection device has: a housing which faces an inspection region extending in a tube axis direction on an inner surface of an electric resistance welded tube and is movable along the tube axis direction; a lighting part which is held at a position in a normal direction of an object region extracted by the housing from the inspection region and lights an object region from all around; an imaging part which images a region including the object region lighted by the lighting part and generates a captured image; and an inspection part which inspects surface quality of an inner surface of the electric resistance welded tube. The inspection region is a region which faces a welding part where welding is performed when a steel plate is processed into an electric resistance welded tube and is in contact with a roller holding a cutting tool when cutting a weld bead occurring at the welding part, and is a region where there is a possibility that a pattern scar where there is no difference in height from the inner surface of the electric resistance welded tube and reflection light can be observed only from a specific direction. The inspection part determines, on the basis of the captured image, whether or not there is a pattern scar in the object region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface property inspection apparatus and a surface property inspection method, and more particularly to a surface property inspection apparatus and a surface property inspection method for inspecting the surface property of the inner surface of a cathode ray tube based on a captured image.

Background Art

[0002] For example, in the inspection of the inner surface of a steel pipe, a visual inspection in which the inside of the steel pipe is peered into from the end of the steel pipe and the inside of the steel pipe is directly visually inspected, or a visual inspection using a camera inserted from the end of the steel pipe is carried out. In such an inspection of the inner surface of a steel pipe, the portion depending on the skill of the inspector is large, and there are individual differences in the ability to detect defects. In particular, individual differences are likely to occur in the deep part in the axial direction of the steel pipe. However, if the steel pipe flows out with the defect on the inner surface of the steel pipe being overlooked, there is a risk of a serious claim. In addition, ultrasonic flaw detection inspection or eddy current flaw detection inspection may be applied to the inspection of the inner surface of a steel pipe. However, there may be cases where defects that are difficult to detect by ultrasonic flaw detection inspection or eddy current flaw detection inspection occur on the inner surface of the steel pipe.

[0003] Therefore, inspection methods using optical means have been proposed. For example, in the inspection method described in Patent Document 1, light is alternately irradiated from two different predetermined directions at different timings to the same part, and two captured images are obtained by imaging from two different predetermined directions. By taking the difference between the two captured images, unevenness-free harmless pattern defects are eliminated, and unevenness defects in which the received light intensity changes are extracted.

[0004] In addition, in the inspection method described in Patent Document 2, an annular laser beam and a conical illumination beam are irradiated from a position facing the imaging device, and a defect is detected based on a specular reflection image obtained by imaging the specular reflection light of the laser beam and a direct reflection image obtained by imaging the direct reflection light of the illumination beam.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-224069 [Patent Document 2] Japanese Patent Publication No. 2017-053790 [Overview of the project] [Problems that the invention aims to solve]

[0006] Flaws that occur on the surface of an object can be classified into two types: those with depth (a large difference in height from the surface of the object), such as uneven scratches, which can be observed as reflected light regardless of the direction of incidence of light, when viewed from the normal direction of the object's surface; and conversely, those without depth (flat with no difference in height from the surface of the object), such as patterned scratches, which can be observed as reflected light or not depending on the direction of incidence of light (they cannot be observed in most directions of incidence, but can be observed only in a specific direction of incidence).

[0007] However, in a technique where light is alternately irradiated from two predetermined directions, such as the inspection method described in Patent Document 1, if the type of defect has depth (relatively deep relative to its width) (a large difference in height from the surface of the object), irradiation from one direction will create a shadow on the front side of the defect's indentation when viewed from the direction of light irradiation from that direction, and irradiation from the other direction will also create a shadow on the front side of the defect's indentation when viewed from the direction of light irradiation from that direction. By imaging these and taking the difference, the defect will appear relatively dark against the always bright surface, making it possible to make the defect visible. On the other hand, if the type of defect is shallow (flat with no difference in height from the surface of the object), such as a patterned defect, the defect will be brightly illuminated regardless of which of the two directions of light irradiation is used, just like the rest of the object's surface. Therefore, even if the defect is imaged and the difference is taken, it will not be made visible and cannot be detected.

[0008] Furthermore, even when an annular laser beam and a conical illumination beam are irradiated from a position opposite the imaging device, as in the inspection method described in Patent Document 2, it may not be possible to detect pattern defects that can only be observed from a specific direction.

[0009] Therefore, the present invention aims to provide a surface texture inspection device and a surface texture inspection method that can detect pattern defects. [Means for solving the problem]

[0010] A first aspect of the present invention is a surface texture inspection device for inspecting the surface texture of the inner surface of an electric resistance welded pipe, comprising: a housing that faces an inspection area extending in the direction of the pipe axis of the electric resistance welded pipe on the inner surface of the electric resistance welded pipe at a certain distance and is relatively movable along the direction of the pipe axis of the electric resistance welded pipe while maintaining the certain distance; an illumination unit that is held in a position normal to a target area extracted from the inspection area by the housing and illuminates the target area from a direction covering the entire circumference; an imaging unit that is held in a position normal to the target area by the housing and images an area including at least the target area illuminated by the illumination unit to generate an image; and a device that inspects the surface texture of the inner surface of the electric resistance welded pipe based on the image. The surface texture inspection device comprises an inspection unit for inspecting surface texture, wherein the inspection area is on the inner surface of the electric resistance welded pipe, facing the welded area where welding was performed when processing the steel plate into the electric resistance welded pipe, and is in contact with the roller that holds the cutting tool used to cut the weld bead formed in the welded area, and is an area where there is no difference in height between it and the surface of the electric resistance welded pipe and where a pattern defect may occur that can only be observed from a specific direction, and the target area is an area that is set in the inspection area to a position facing the housing each time the housing moves relative to it, and the inspection unit determines whether or not the pattern defect is present in the target area based on the captured image.

[0011] A second aspect of the present invention is a surface property inspection device according to the first aspect, wherein the illumination unit comprises a light diffusing member positioned opposite the target area and a plurality of light sources arranged in the circumferential direction of the light diffusing member and irradiating light toward the light diffusing member.

[0012] A third aspect of the present invention is a surface texture inspection apparatus according to the first aspect, wherein the illumination unit is arranged in a dome shape covering the target area and has a plurality of light sources that irradiate light toward the target area.

[0013] A fourth aspect of the present invention is a surface property inspection device according to the first aspect, wherein the illumination unit comprises a reflective member formed in a dome shape that covers the target area, the surface facing the target area being a reflective surface, and a plurality of light sources arranged in the circumferential direction of the reflective member and irradiating light toward the reflective surface.

[0014] A fifth aspect of the present invention is a surface properties inspection method for inspecting the surface properties of the inner surface of an electric resistance welded pipe, comprising: a housing movement step in which a housing is used that is positioned at a certain distance from the inspection area on the inner surface of the electric resistance welded pipe extending in the direction of the pipe axis of the electric resistance welded pipe, and the housing is moved relative to the inspection area along the direction of the pipe axis of the electric resistance welded pipe while maintaining the certain distance; an illumination step in which an illumination unit is held at a position normal to the target area extracted from the inspection area by the housing, and the target area is illuminated from a direction covering the entire circumference; an imaging step in which an imaging unit is held at a position normal to the target area by the housing, and an imaging unit is used to image an area including at least the target area illuminated by the illumination unit, thereby generating an image; and the image The method comprises an inspection step for inspecting the surface properties of the inner surface of the electric resistance welded pipe, wherein the inspection area is an area on the inner surface of the electric resistance welded pipe that faces the welded portion where welding was performed when processing the steel plate into the electric resistance welded pipe, and is in contact with a roller that holds a cutting tool for cutting the weld bead that occurs in the welded portion, and is an area where there is no difference in height between it and the surface of the electric resistance welded pipe and a pattern defect that can only be observed from a specific direction, and the target area is an area that is set at a position in the inspection area that faces the housing each time the housing moves relative to it, and the inspection step determines whether or not the pattern defect is present in the target area based on the captured image.

[0015] A sixth aspect of the present invention is a surface property inspection method using an illumination unit having a light diffusing member disposed at a position facing the target region and a plurality of light sources arranged in a circumferential direction of the light diffusing member and irradiating light toward the light diffusing member in the illumination step of the inspection method according to the fifth aspect.

[0016] A seventh aspect of the present invention is a surface property inspection method using an illumination unit having a plurality of light sources arranged in a dome shape covering the target region and irradiating light toward the target region in the illumination step of the inspection method according to the fifth aspect.

[0017] An eighth aspect of the present invention is a surface property inspection method using an illumination unit having a reflecting member formed in a dome shape covering the target region and having a reflecting surface on the surface facing the target region, and a plurality of light sources arranged in a circumferential direction of the reflecting member and irradiating the light toward the reflecting surface in the illumination step of the inspection method according to the fifth aspect.

Advantages of the Invention

[0018] According to the present invention, there are provided a surface property inspection apparatus and a surface property inspection method capable of detecting pattern defects.

Brief Description of the Drawings

[0019] [Figure 1] It is a side view showing an example of an inspection apparatus and a steel pipe according to an embodiment. [Figure 2] It is a two-sided view showing an example of an illumination apparatus and an imaging apparatus according to an embodiment. [Figure 3] It is a cross-sectional view showing an example of a steel pipe according to an embodiment. [Figure 4] It is an explanatory view showing an example of a state in which a pattern defect is generated in an inspection region according to an embodiment. <​​​​​It is a flowchart showing an example of the flow of inspection processing according to an embodiment. [Figure 8] It is a cross-sectional view showing an example of a steel pipe according to the first modification. [Figure 9] It is a cross-sectional view showing an example of a steel pipe according to the second modification. [Figure 10] It is a side view showing an example of an inspection device according to the third modification. [Figure 11] It is a side view showing an example of a steel pipe according to the fourth modification. [Figure 12] It is a two-sided view showing an example of a lighting device and an imaging device according to the fifth modification. [Figure 13] It is a two-sided view showing an example of a lighting device and an imaging device according to the sixth modification. [Figure 14] It is a side view showing an example of an inspection device and a steel pipe according to the seventh modification. <B [Figure 15] It is a plan view showing a target area according to the eighth modification. [Figure 16] It is a diagram showing a first captured image and a second captured image according to the eighth modification. [Figure 17] It is a diagram showing a first inspection image and a second inspection image according to the eighth modification. [Figure 18] It is a side view showing an example of an inspection device according to the ninth modification. [Figure 19] It is a diagram showing an example of a pattern defect and a captured image according to the first reference example. [Figure 20] It is a diagram showing an example of a pattern defect and a captured image according to the second reference example. [Figure 21] It is a diagram showing an example of a pattern defect and a captured image according to the third reference example. [Figure 22] It is a diagram showing an example of a concavo-convex defect, a normal undulation part, and a captured image according to the fourth reference example.

Mode for Carrying Out the Invention

[0020] (Explanation of Concavo-Convex Defects and Pattern Defects) First, we will explain uneven scratches and patterned scratches. Scratches that occur on the surface of an object can be broadly categorized into two types: uneven scratches, for example, which have depth (relatively deep relative to their width) (a large difference in height from the surface of the object), allowing their presence to be observed as reflected light regardless of the direction of light incidence; and patterned scratches, for example, which have no depth (no difference in height from the surface of the object and are flat), and their presence may or may not be observable as reflected light depending on the direction of light incidence (they are not observable in most incident directions, but can be observed only in certain incident directions). These will be explained in detail below.

[0021] Figure 19 shows an example of a pattern defect 72 and captured images 106A and 106B related to the first reference example. In the example shown in Figure 19, the target area 104 is alternately illuminated from two predetermined different directions by the first light source 102A and the second light source 102B. The imaging device 100 is positioned opposite the target area 104 in the direction normal to the target area 104.

[0022] The pattern defect 72 shown in Figure 19(A) has a reflective characteristic such that when light is shone in the direction of arrow A, reflected light enters the imaging device 100, and when light is shone in the opposite direction to arrow A, reflected light does not enter the imaging device 100. Therefore, when light is shone in the direction of arrow A by the first light source 102A, the imaging device 100 obtains an image 106A that includes the pattern defect 72 as an image, and when light is shone in the opposite direction to arrow A by the second light source 102B, the imaging device 100 obtains an image 106B that does not include the pattern defect 72 as an image.

[0023] The pattern defect 72 shown in Figure 19(B) has a reflective characteristic such that when light is shone in the direction of arrow B, reflected light enters the imaging device 100, and when light is shone in the opposite direction to arrow B, reflected light does not enter the imaging device 100. Therefore, when light is shone in the direction of arrow B by the second light source 102B, the imaging device 100 obtains an image 106B that includes the pattern defect 72 as an image, and when light is shone in the opposite direction to arrow B by the first light source 102A, the imaging device 100 obtains an image 106A that does not include the pattern defect 72 as an image.

[0024] Thus, for pattern defects 72, which can only be observed with reflected light from a specific direction, detection may not be possible depending on the direction of the incident light.

[0025] Figure 20 shows an example of a pattern defect 72 and captured images 106A and 106B related to the second reference example. In the example shown in Figure 20, the target area 104 is alternately illuminated by the first light source 102A and the second light source 102B from two predetermined different directions.

[0026] The pattern defect 72 shown in Figure 20(A) has a reflective characteristic in which reflected light is incident on the imaging device 100 only when light is irradiated in the direction of arrow A, which is perpendicular to the optical axes of the first light source 102A and the second light source 102B. Therefore, even when the target area 104 is alternately irradiated with light from two predetermined different directions by the first light source 102A and the second light source 102B, the imaging device 100 can obtain captured images 106A and 106B that do not include the pattern defect 72 as an image.

[0027] The pattern defect 72 shown in Figure 20(B) has a reflective characteristic in which reflected light is incident on the imaging device 100 only when light is irradiated in the direction of arrow B, which is perpendicular to the optical axes of the first light source 102A and the second light source 102B. Therefore, even when the target area 104 is alternately irradiated with light from two predetermined different directions by the first light source 102A and the second light source 102B, the imaging device 100 can obtain captured images 106A and 106B that do not include the pattern defect 72 as an image.

[0028] Thus, for pattern defects 72, which can only be observed with reflected light from a specific direction, detection may not be possible depending on the direction of the incident light.

[0029] Figure 21 shows an example of a pattern defect 72 and captured images 106A and 106B related to the third reference example. In the example shown in Figure 21, the reflection characteristics of the pattern defect 72 are the same as in the example shown in Figure 20, but the arrangement of the first light source 102A and the second light source 102B is different from the example shown in Figure 20.

[0030] In other words, in the example shown in Figure 21, the first light source 102A and the second light source 102B are arranged such that the optical axes of the first light source 102A and the second light source 102B are parallel to the directions of arrows A and B. Therefore, in the example shown in Figure 21(A), when light is irradiated in the direction of arrow A by the first light source 102A, the imaging device 100 obtains an image 106A that includes the pattern defect 72 as an image. Similarly, in the example shown in Figure 21(B), when light is irradiated in the direction of arrow B by the second light source 102B, the imaging device 100 obtains an image 106B that includes the pattern defect 72 as an image. However, in the example shown in Figure 21(A), when light is irradiated from the opposite direction to arrow A by the second light source 102B, an image 106B is obtained that does not include the pattern defect 72 as part of the image. Also, in the example shown in Figure 21(B), when light is irradiated from the opposite direction to arrow B by the first light source 102A, an image 106A is obtained that does not include the pattern defect 72 as part of the image.

[0031] Thus, pattern defects 72, which can only be observed from a specific direction, may not be detectable depending on the direction of the incident light.

[0032] Figure 22 shows an example of an uneven surface 70 and a normal surface area 73, and an image 106, according to the fourth reference example. The uneven surface 70 referred to here is a scratch (relatively deep relative to its width) such as a dent or crack that occurs on the surface of an object due to contact between the object and another object. The normal surface area 73 is a region on the surface of the object that is slightly recessed (relatively shallow relative to its width), and is a part that will no longer be a defect of the object by being treated by polishing the surface of the object, and is distinguished from the pattern scratches 72 and uneven surface scratches 70, which are defects. In the example shown in Figure 22, multiple light sources 102 (e.g., eight light sources 102) are arranged around the target area 104, and light is irradiated from all directions around the periphery of the uneven defect 70 and the normal relief area 73. When light is irradiated onto the uneven defect 70 by each light source 102, because the uneven defect 70 has a relatively deep surface relative to its width, the light does not penetrate to the depth of the uneven defect 70, and a shadow is created regardless of the direction of light irradiation. As a result, the uneven defect 70 appears dark on the imaging device 100 (the area surrounding the uneven defect 70 appears bright). In other words, reflected light from the uneven defect 70 can be observed regardless of the direction of light irradiation. On the other hand, when the normal relief portion 73 is illuminated by light from each light source 102, the normal relief portion 73 has almost no depth (it has a relatively shallow depth relative to its width). As a result, the shadow that would normally be created by light irradiated from one direction is canceled out by light irradiated from the opposite direction, and therefore the normal relief portion 73 is not captured by the imaging device 100 (the brightness of the normal relief portion 73 and the brightness of the area surrounding the normal relief portion 73 become the same). Therefore, when light is sequentially irradiated by each light source 102, the uneven defects 70 are included as images in each of the captured images 106 corresponding to each light source 102, while the normal relief areas 73 are not included as images. Thus, in the example shown in Figure 22, by irradiating with light simultaneously by multiple light sources 102, it is possible to detect only the defective uneven defects 70 as images while eliminating the influence of the normal relief areas 73 that do not cause defects.

[0033] (A brief description of the inspection apparatus and inspection method according to the embodiment) The inspection apparatus and inspection method according to the embodiments described below are based on the above findings. In other words, the inspection apparatus and inspection method according to the embodiments can detect pattern defects that can only be observed from a specific direction. A detailed explanation follows below.

[0034] (Description of the configuration of the inspection device 10) Figure 1 shows a side view illustrating an example of the inspection device 10 and steel pipe 60 according to this practical embodiment. Figure 2 shows a two-view drawing illustrating an example of the lighting device 12 and imaging device 14 according to this embodiment. The inspection device 10, an example of a surface property inspection device in this embodiment, is a device for inspecting the inner surface properties of an electric resistance welded pipe (electric resistance welded steel pipe; hereinafter also simply referred to as steel pipe 60) as an example of the surface properties of an object, and comprises an illumination device 12, an imaging device 14, a housing 16, and a processing device 18. The illumination device 12 is an example of the illumination unit of the present invention, and the imaging device 14 is an example of the imaging unit of the present invention. The steel pipe 60 is an example of an object.

[0035] The lighting device 12, the imaging device 14, and the housing 16 are arranged inside the steel pipe 60. The lighting device 12 and the imaging device 14 are housed in the housing 16 and are held in place by the housing 16.

[0036] The housing 16 is a structure that faces the inspection area extending in the axial direction of the steel pipe 60 on the inner surface of the steel pipe 60 at a certain distance, and is relatively movable along the axial direction of the steel pipe 60 while maintaining that constant distance. That is, the housing 16 has a hollow structure and is held by a holding part (not shown) that holds the housing 16 (for example, it may be held from the outside of the steel pipe 60 by an arm, or the housing may be provided with wheels, etc.) so that the distance between the housing 16 and the inner surface of the steel pipe 60 is constant, and the illumination device 12 and the imaging device 14 are fixedly held at specific positions inside the housing 16 so that the distance between the illumination device 12 and the imaging device 14 and the inner surface of the steel pipe 60 (in particular the target area 62 described later) is constant. Furthermore, the housing 16 is configured to be movable in the axial direction of the steel pipe 60 while maintaining a fixed distance from the inner surface of the steel pipe 60 (it may be moved using the holding part described above), and the imaging device 14 held inside the housing 16 is configured to sequentially image the target area on the inner surface of the steel pipe 60, as described later, over the entire length of the inspection area. Note that, as it is referred to as relative movement, the housing 16 may move relative to a stationary steel pipe 60, or the steel pipe 60 may move relative to a stationary housing 16. The housing 16 has a drive unit (for example, a motor actuator) for moving in the axial direction of the steel pipe 60.

[0037] The inspection area referred to here is the area on the inner surface of the steel pipe 60 that is opposite the welded joint where welding was performed when processing the steel plate into the steel pipe 60 (electric resistance welded pipe), and that is in contact with the roller that holds the cutting tool used to cut the weld bead that forms in the welded joint, and is an area where there is no difference in height between the surface of the steel pipe 60 and the area where a pattern defect 72 may have occurred, and where reflected light can only be observed from a specific direction. More specifically, since the inner surface of the steel pipe 60 faces inward, it is unlikely to come into unexpected contact with other objects and become scratched, and the types and causes of scratches are somewhat limited. An example of a scratch that occurs in this context is a pattern scratch 72. When steel plates are welded together to form electric resistance welded pipes by rolling them from a flat shape to a U-shape and then to an O-shape, a weld bead is formed at the weld where the ends of the steel plates abut. Since the weld bead is unnecessary for the finished electric resistance welded pipe, it is removed by cutting. However, the cutting tool used in the cutting process involves lowering a roller, which acts as a wheel, to a position near the bottom of the inside of the steel pipe 60 with the steel pipe 60 positioned so that the weld bead is on the upper side, and then rolling it to cut while changing its position relative to the weld bead. As a result, the roller comes into contact with a predetermined area on the inner surface of the steel pipe 60 that is opposite to the weld bead, which can cause defects. An example of such a defect is the pattern defect 72 referred to in this invention, and the location where the pattern defect 72 occurs is limited to the area where the roller makes contact. This area where the roller makes contact and where the pattern defect 72 may occur is referred to as the inspection area. Since the inspection area is the area in which the roller makes contact and rolls, it extends in a long, narrow shape in the axial direction of the steel pipe 60 on the inner surface of the steel pipe 60 at a position opposite to the position of the weld bead (i.e., if there is one roller, it will be approximately the exact opposite position of the weld bead on the inner surface of the steel pipe 60; if there are multiple rollers, it will be multiple areas on the opposite side of the weld bead, etc., depending on the configuration of the roller).

[0038] The lighting device 12 is held by the housing 16 at a position normal to the target area 62 extracted from the inspection area, and is a light that illuminates the target area 62 from all directions. The target area 62 referred to here is the area set at a position opposite the housing 16 in the inspection area each time the housing 16 moves relative to it. That is, in order to inspect the pattern defects 72, the inspection area will be imaged by the imaging device 14, which will be described later. However, since the inspection area may be wide (long), a range of the inspection area opposite the imaging device 14 (i.e., the housing 16) is distinguished and called the target area 62 so that it fits within the imaging field of the imaging device 14. Each time the housing 16 moves relative to the steel pipe 60, the target position is changed and the inspection is performed in units of the target area 62.

[0039] Figure 3 shows a cross-sectional view of an example of a steel pipe 60 according to this embodiment. On the inner surface of the steel pipe 60, a target area 62 is set within the inspection area where pattern defects 72 may occur. The steel pipe 60, which is an electric resistance welded pipe, has a welded joint 64. The welded joint 64 corresponds to the joint between the end faces of a steel plate, which is created by welding a steel plate while rolling it from a flat plate shape to a U-shape and then to an O-shape. As a result of the butt joint between the end faces of the steel plate during welding, a weld bead is formed in the welded joint 64. The target area 62 is part of the inspection area, which is the area that comes into contact with the roller that holds the cutting tool when cutting the weld bead that occurs in the welded joint 64 on the inner surface of the steel pipe 60, and occurs in the area of ​​the inner surface of the steel pipe 60 that faces the welded joint 64. In the example shown in Figure 3(A), the target area 62 is set in one area facing the welded joint 64, and in the example shown in Figure 3(B), the target area 62 is set in two areas facing the welded joint 64.

[0040] The lighting device 12 can be configured to irradiate the target area 62 with light from all directions, for example, by having a light diffusing member 20 and a plurality of light sources 22. The light diffusing member 20 is positioned opposite the target area 62 in the direction normal to the target area 62. The light diffusing member 20 has a plurality of diffusion prisms 24 that diffuse the irradiated light. The diffusion prisms 24 are formed in a two-dimensional arrangement on a surface facing the target area 62. The light diffusing member 20 has light transmittance, allowing reflected light reflected from the target area 62 to pass through. In the examples shown in Figures 1 and 2, the light diffusing member 20 is formed in a rectangular shape, but it may be formed in a shape other than a rectangular shape (for example, a circular or elliptical shape). Multiple light sources 22 are provided on the outer periphery of the light diffusion member 20 and are arranged in the circumferential direction of the light diffusion member 20. The multiple light sources 22 irradiate the light diffusion member 20 with light. When light is irradiated from the multiple light sources 22, the light is diffused by the light diffusion member 20, generating illumination light L1 that includes light irradiated from all directions around the target area 62. The lighting device 12 illuminates the target area 62 from all directions around its circumference. Here, the light illuminating the target area 62 from all directions around its circumference refers to the light illuminating the target area 62 from all directions around its circumference, viewed from the normal direction of the target area 62, from the outer edge of the target area 62 toward the center of the target area 62. In the example shown in Figure 2, the target area 62 is illuminated from all directions around its circumference. However, even if the target area 62 is illuminated from multiple directions around its circumference (for example, eight or more directions), so that it is effectively illuminated from all directions around its circumference, this is equivalent to illuminating the target area 62 from all directions around its circumference.

[0041] The imaging device 14 is held by the housing 16 in a position normal to the target area 62 and is a camera that captures an area including at least the target area 62 illuminated by the illumination device 12 to generate an image. That is, the imaging device 14 is positioned opposite the target area 62 on the inner surface of the steel pipe 60 that is to be inspected. The target area 62 is, as described above, an area within the inspection area that is opposite the optical axis (visual axis) of the imaging device 14 and falls within the imaging range of the imaging device 14. The imaging device 14 is positioned so that the visual axis of the imaging device 14 coincides with the normal to the target area 62. The illumination device 12 is positioned between the imaging device 14 and the target area 62 on the visual axis of the imaging device 14. The imaging device 14 is positioned behind the illumination device 12 and facing the target area 62. Specifically, the imaging device 14 is positioned on the opposite side of the target area 62 from the illumination device 12, and is positioned to coincide with the center of the illumination device 12 when viewed from the direction normal to the target area 62. If the target area 62 has a pattern defect 72, and reflected light (i.e., diffusely reflected light) is obtained by the pattern defect 72 reflected in the direction normal to the target area 62, the reflected light passes through the light diffusion member 20 and enters the imaging device 14. In other words, the imaging device 14 is positioned to receive reflected light reflected in the direction normal to the target area 62. Note that the reflected light reflected in the direction normal to the target area 62 is an example of reflected light reflected in a specific direction according to the present invention. The imaging device 14 is a camera capable of capturing images of a target area 62 through a light-diffusing member 20 and generating monochrome or color images. The imaging device 14 may be a two-dimensional camera in which image sensors such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) are arranged in two dimensions.

[0042] The processing unit 18 is connected to the imaging device 14 via wired or wireless communication, and determines whether or not there are pattern defects in the target area 62 based on the captured image generated by the imaging device 14.

[0043] Figure 4 shows an example of how pattern defects 72 are generated in the inspection area according to this embodiment. The manufacturing process of electric resistance welded pipes includes a cutting process for cutting the weld bead. In the cutting process, a roller 66 provided on a bar that holds the tool for cutting the weld bead rolls over a target area 62 on the inner surface of the steel pipe 60 that is opposite to the welded portion 64. Here, the cutting process is performed after the welding process, in which the welded portion 64 is formed by the weld bead. In the cutting process, metal particles 68 scattered during the welding process may adhere to the target area 62. When the roller 66 passes over the metal particles 68 while they are adhering to the target area 62, the metal particles 68 are pushed into the base material of the steel pipe 60, and defects in the surface properties are created by the metal particles 68 pushed into the base material, and these defects are referred to as pattern defects 72. The surface of the pattern defect 72 contains minute irregularities due to transfer by the roller 66, but it is formed by a nearly smooth surface, similar to the surrounding surface of the pattern defect 72. Therefore, the patterned defect 72 has the characteristic of having no depth (it is flat with no difference in height from the surface of the object), and depending on the direction of incidence of light on the defect, the presence of the defect may or may not be observable as reflected light (it is not observable in most incident directions, but can be observed only in a specific incident direction).

[0044] Figure 5 shows a block diagram illustrating an example of the functional configuration of the processing unit 18 according to this embodiment. The processing unit 18 is a device that performs various controls related to the inspection device 10 and various calculations related to the inspection of the steel pipe 60, and is composed of a computer with a hardware configuration described later. Functionally, the processing unit 18 includes a control unit 30 and an inspection unit 32.

[0045] The control unit 30 controls the illumination device 12, the imaging device 14, and the housing 16 (the drive unit of the housing 16). Specifically, at the start of the inspection, the control unit 30 moves the housing 16 to a position facing a specific target area 62 within the inspection area, turns on the illumination device 12, and starts illuminating the target area 62 with light. As a result, the illumination device 12 illuminates the target area 62, which may have pattern defects 72, from all directions. The illumination device 12 remains on until the inspection is completed.

[0046] Furthermore, the control unit 30 generates an image by causing the imaging device 14 to image the target area 62 at predetermined timings while the target area 62 is illuminated with light from all directions. The control unit 30 then acquires the image generated by the imaging device 14. The control unit 30 can synchronize the timing of various controls based on the timing signals output from the timing signal generator.

[0047] The inspection unit 32 performs an inspection of the target area 62 based on the captured image acquired by the control unit 30. The inspection unit 32 has an image processing unit 34 and a determination unit 36 ​​as functional units for performing the inspection. In the inspection by the inspection unit 32, each functional unit of the inspection unit 32 performs data processing on the captured image acquired by the control unit 30 to obtain a determination result of whether or not there is a pattern defect 72 in the target area 62.

[0048] The image processing unit 34 performs predetermined image processing on the captured image. Specifically, the image processing unit 34 performs predetermined preprocessing such as shading and smoothing on the captured image. The image processing unit 34 also binarizes the preprocessed captured image based on a predetermined threshold. The threshold may be determined experimentally in advance based on the type of steel pipe 60, etc. Then, the image processing unit 34 removes noise components from the binarized captured image by predetermined processing. As a result, if there is a pattern defect 72 in the target area 62, the portion with the pattern defect 72 is extracted from the captured image.

[0049] The determination unit 36 ​​determines whether or not there is a pattern defect 72 in the target area 62 based on the image captured after image processing. Specifically, if the determination unit 36 ​​detects an image area corresponding to the pattern defect 72 in the binarized image captured, it determines that there is a pattern defect 72 in the target area 62. The determination result by the determination unit 36 ​​is output externally, for example.

[0050] Furthermore, each time an inspection of a target area 62 is completed, the illumination device 12 and the imaging device 14 move in the axial direction of the steel pipe 60, so that the inspection of each target area 62 is performed sequentially in the axial direction of the steel pipe 60. The determination unit 36 ​​may determine whether or not there is a pattern defect 72 in each target area 62 each time an image is obtained for that target area 62, or it may determine whether or not there is a pattern defect 72 in each target area 62 after an image has been obtained for all target areas 62 set on the inspection area.

[0051] Furthermore, since the inner surface of the steel pipe 60 faces inward, it is unlikely to come into unexpected contact with other objects and become scratched. Therefore, the types and causes of scratches are somewhat limited, and it is relatively rare for scratches other than pattern scratches 72 to occur in the target area 62. However, even if the target area 62 has uneven scratches 70 instead of pattern scratches 72, reflected light from the uneven scratches 70 may enter the imaging device 14. In this case as well, the determination unit 36 ​​will determine that there are pattern scratches 72 in the target area 62 based on the captured image. However, since it is more important to be able to detect pattern scratches 72 when the target area 62 has pattern scratches 72 than to distinguish between uneven scratches 70 and pattern scratches 72, it is not particularly problematic for the determination unit 36 ​​to determine that there are pattern scratches 72 when the target area 62 has uneven scratches 70.

[0052] Figure 6 shows an example of the hardware configuration of the processing unit 18. The processing unit 18 is composed of a computer. The processing unit 18 has a CPU (Central Processing Unit) 40, memory 42, storage device 44, input device 46, output device 48, storage medium reader 50, and communication I / F (Interface) 52. Each component is connected to the others so as to be able to communicate with each other via a bus 54.

[0053] The storage device 44 stores a program for executing the inspection process. The CPU 40 is a central processing unit that executes various programs and controls each component. Specifically, the CPU 40 reads a program from the storage device 44 and executes the program using memory 42 as a workspace. The CPU 40 controls each component and performs various calculations according to the program stored in the storage device 44.

[0054] Memory 42 is composed of RAM (Random Access Memory) and temporarily stores programs and data as a working area. Storage device 44 is composed of ROM (Read Only Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive), etc., and stores various programs and data, including the operating system.

[0055] The input device 46 is a device for performing various types of input, such as a keyboard or mouse. The output device 48 is a device for outputting various types of information, such as a display or printer. The output device 48 may also function as the input device 46 by using a touch panel display.

[0056] The storage medium reader 50 reads data stored on various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray disc, or USB (Universal Serial Bus) memory, and writes data to the storage media. The communication I / F 52 is an interface for communicating with other devices. For example, the communication I / F 52 uses an interface that conforms to standards such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark).

[0057] (Explanation of the testing method) Figure 7 shows an example of the flow of the inspection process executed by the CPU 40 of the processing unit 18. The CPU 40 reads a program for executing the inspection process from the storage device 44, loads it into memory 42, and executes it, thereby allowing the CPU 40 to function as each functional unit of the processing unit 18, and the inspection process to be executed. This executes the inspection method in the inspection device 10. In the inspection method, first, in step S10, the control unit 30 controls the housing 16 and moves the housing 16 relative to the steel pipe 60, thereby positioning the illumination device 12 and the imaging device 14 opposite the target area 62. The housing 16 may also be moved manually. Step S10 corresponds to the housing movement step.

[0058] Next, in step S12, the control unit 30 turns on the lighting device 12 by controlling it. This causes the lighting device 12 to perform a lighting step in which it illuminates the target area 62 from all directions.

[0059] Next, in step S14, the control unit 30 controls the imaging device 14 to image the target area 62. As a result, with light illuminating the target area 62 from all directions, the imaging device 14 performs an imaging step to image the target area 62 and generate an image.

[0060] Next, in step S16, the image processing unit 34 performs an image processing step in which it performs predetermined image processing (for example, predetermined preprocessing, binarization, and noise removal) on the captured image. As a result, if there is a pattern defect 72 in the target area 62, the portion of the pattern defect 72 is extracted from the captured image.

[0061] Next, in step S18, the determination unit 36 ​​performs a determination step to determine whether or not there is a pattern defect 72 in the target area 62 based on the image captured after image processing. This provides a determination result of whether or not there is a pattern defect 72 in the target area 62. The inspection process then ends.

[0062] (Effects of the inspection device 10 and inspection method) As described above, in this embodiment, the target area 62 facing the housing 16 (i.e., the imaging device 14), which is one of the inspection areas that may have pattern defects 72 that can only be observed reflected from a specific direction on the imaging device 14, is illuminated by the illumination device 12 from all directions. Furthermore, while the target area 62 is illuminated by light from all directions, the imaging device 14 captures the target area 62 and generates an image. Based on the image, it is determined whether or not there are pattern defects 72 in the target area 62. If there are pattern defects 72 in the target area 62, an image area corresponding to the pattern defects 72 is detected in the image processed image, and in this case, it is determined that there are pattern defects 72 in the target area 62. Thus, according to this embodiment, if there are pattern defects 72 in the target area 62, the pattern defects 72 can be detected. As illustrated in Figure 22, when there is a mixture of defects such as dents and cracks (with a relatively deep depth relative to its width) and normal undulations 73 (with a relatively shallow depth relative to its width) on the surface of an object that does not have defects, irradiating the area where defects may occur with light from all directions around the circumference will cause the normal undulations 73 to disappear and generate an image in which the defects 70 become apparent, thus effectively detecting defects. On the other hand, since pattern defects 72 have no height, the above method should not be applied (it is thought that pattern defects 72, which have no height, will disappear from the image). However, since pattern defects 72 are a special type of defect in which reflected light can only be observed from a specific direction, it has been found that in order to detect pattern defects 72, it is necessary to irradiate the area with light from all directions around the circumference (contrary to the above method), and only by doing so can pattern defects 72 be detected (despite having no height). Therefore, by using this embodiment, it becomes possible to reliably detect pattern defects 72.

[0063] Furthermore, the target area 62 is the area on the inner surface of the electric resistance welded pipe that faces the welded portion 64. Therefore, by inspecting the target area, pattern defects 72 formed by metal particles 68 scattered during the welding process of the electric resistance welded pipe can be efficiently detected.

[0064] Furthermore, the lighting device 12 includes a light-diffusing member 20 positioned opposite the target area 62, and a plurality of light sources 22 arranged circumferentially around the light-diffusing member 20, which irradiate the light-diffusing member 20. As a result, the light irradiated from the plurality of light sources 22 is diffused by the light-diffusing member 20, thereby generating illumination light L1 that includes light irradiated onto the target area 62 from all directions.

[0065] (modified version) Figure 8 shows an example of a steel pipe 60 according to the first modified example. In the above embodiment, the steel pipe 60 is an electric resistance welded pipe, but as shown in Figure 8, the steel pipe 60 may be a steel pipe other than an electric resistance welded pipe. Also, in the above embodiment, the target region 62 is the region facing the welded portion 64, but it may be a region different from the region facing the welded portion 64. Furthermore, when the steel pipe 60 is arranged horizontally, the target region 62 may be the lower vertical region of the inner surface of the steel pipe 60, as shown in Figure 8(A), or the upper vertical region of the inner surface of the steel pipe 60, as shown in Figure 8(B).

[0066] Furthermore, the target area 62 may be the entire circumference of the inner surface of the steel pipe 60. Also, if the target area 62 is changed, the distance between the imaging device 14 and the target area 62 may be kept constant in order to maintain a constant imaging resolution. Additionally, a moving device may be used to maintain a constant distance between the imaging device 14 and the target area 62 when the target area 62 is changed.

[0067] Furthermore, the target region 62 is, for example, the region on the inner surface of an electric resistance welded pipe having a welded portion 64 that faces the welded portion 64, but it may also be the inner surface of a steel pipe 60 other than an electric resistance welded pipe, or the surface of a member other than a steel pipe 60.

[0068] Figure 9 shows an example of a steel pipe 60 according to the second modified example. In the above embodiment, the steel pipe 60 has a configuration with a constant inner diameter, but as shown in Figures 9(A) to 9(B), it may also have a configuration in which the inner diameter changes. Furthermore, if the inner diameter of the steel pipe 60 changes due to a change in the target area 62, the distance between the imaging device 14 and the target area 62 may be kept constant in order to maintain a constant imaging resolution. In addition, a moving device may be used to keep the distance between the imaging device 14 and the target area 62 constant when the inner diameter of the steel pipe 60 changes.

[0069] Figure 10 shows an example of the inspection device 10 according to the third modified example. As shown in Figure 10, the imaging device 14 is positioned so that its viewing axis is parallel to the axial direction of the steel pipe 60, and a mirror 80 may be placed between the imaging device 14 and the illumination device 12 to bend the field of view of the imaging device 14 by 90 degrees toward the target area 62. Even with this configuration, if the target area 62 has a pattern defect 72 and reflected light is obtained that is reflected in the direction normal to the target area 62 by the pattern defect 72, the reflected light can be incident on the imaging device 14 via the mirror 80.

[0070] Figure 11 shows a steel pipe 60 according to the fourth modified example. The inspection device 10 shown in Figure 11 has the same configuration as the inspection device 10 shown in Figure 10. The inspection device 10 having a mirror 80 may be applied to a steel pipe 60 whose inner diameter changes, as shown in Figures 11(A) to 11(B).

[0071] Figure 12 shows a lighting device 12 according to the fifth modified example. In the example shown in Figure 12, the lighting device 12 has a plurality of light sources 22. The plurality of light sources 22 are arranged in a dome shape (for example, a hemispherical shape) that covers the target area 62 and irradiate the target area 62 with light. The plurality of light sources 22 may be in close proximity to each other, or there may be gaps between them. Even with this configuration, it is possible to generate illumination light L1 that includes light irradiated onto the target area 62 from all directions around its circumference.

[0072] Figure 13 shows an illumination device 12 according to the sixth modified example. In the example shown in Figure 13, the illumination device 12 has a reflective member 82 and a plurality of light sources 22. The reflective member 82 is formed in a dome shape (for example, hemispherical) that covers the target area 62. The surface of the reflective member 82 facing the target area 62 is a reflective surface. The plurality of light sources 22 are arranged in a ring in the circumferential direction of the reflective member 82 and irradiate light toward the reflective surface. Even with this configuration, illumination light L1 including light irradiated onto the target area 62 from all directions around the periphery can be generated.

[0073] Figure 14 shows an inspection apparatus 10 according to the seventh modified example. In the example shown in Figure 14, the inspection apparatus 10 has a laser light source 84. The laser light source 84 irradiates the target area 62 with laser light L2 having a different wavelength than the illumination light L1. The imaging device 14 images the target area 62 while it is irradiated with illumination light L1 and laser light L2. The processing device 18 determines the presence or absence of pattern defects 72 and calculates the depth of uneven defects 70 based on the image captured by the imaging device 14. The depth of uneven defects 70 is calculated, for example, by the light section method based on the reflected light of the laser light L2.

[0074] Figure 15 shows the target region 62 according to the eighth modified example. The target region 62 shown in Figure 15 is the target region when the inspection device 10 shown in Figure 14 is used. As shown in Figure 15, the target region 62 may be divided into a first region 62A to which laser light L2 is irradiated and a second region 62B to which illumination light L1 is irradiated. In this case, the process of calculating the depth of unevenness defects 70 for the first region 62A and the process of detecting pattern defects 72 for the second region 62B can be performed separately, so the load on the CPU 40 can be reduced compared to, for example, when the process of calculating the depth of unevenness defects 70 and the process of detecting pattern defects 72 are performed for a common region.

[0075] Figure 16 shows the first image 86A and the second image 86B according to the eighth modified example. The first image 86A shown in Figure 16(A) is an image obtained by imaging the first region 62A shown in Figure 15, and the second image 86B shown in Figure 16(B) is an image obtained by imaging the second region 62B shown in Figure 15. By sequentially imaging each target region 62, multiple first image 86A and multiple second image 86B are obtained.

[0076] Figure 17 shows the first inspection image 88A and the second inspection image 88B related to the eighth modified example. The first inspection image 88A shown in Figure 17(A) is an image generated by concatenating multiple first imaging images 86A, and the second inspection image 88B shown in Figure 17(B) is an image generated by concatenating multiple second imaging images 86B. As an example, the first inspection image 88A includes multiple dents 70 as images, and the second inspection image 88B includes multiple patterned defects 72 as images. In the first inspection image 88A, the color of the images showing the dents 70 differs depending on the depth of the dents 70. By generating the first inspection image 88A and the second inspection image 88B, the position of each dent 70 can be identified based on the coordinates of the first inspection image 88A, and the position of each patterned defect 72 can be identified based on the coordinates of the second inspection image 88B.

[0077] Figure 18 shows an inspection apparatus 10 according to the eighth modified example. As shown in Figure 18, the inspection apparatus 10 having the mirror 80 shown in Figure 10 may be fitted with the laser light source 84 shown in Figure 14.

[0078] Although an example of the present invention has been described above, the present invention is not limited to the above, and it is of course possible to implement it in various ways without departing from its spirit. [Explanation of Symbols]

[0079] 10 Inspection equipment 12 Lighting devices 14 Imaging device 16 cabinets 18 Processing Unit 20 Light Diffusing Member 22 Light source 24 Diffusion prism 30 Control Unit 32 Inspection Department 34 Image Processing Unit 36 Judgment section 40 CPU 42 memory 44 Storage device 46 Input devices 48 Output device 50 Storage medium reader 52 Communication I / F 54 bus 60 Steel pipe 62 Target Area 62A 1st area 62B 2nd area 64 Welded section 66 Laura 68 Metal particles 70. Uneven scratches 72 Pattern scratches 80 Mirror 82 Reflective material 84 Laser light sources 86A First image 86B Second image 88A First examination image 88B Second examination image 100 Imaging device 102 Light source 102A 1st light source 102B 2nd light source 104 Target Area 106 Acquired Images 106A Acquired image 106B Acquired image L1 illumination light L2 laser light

Claims

1. A surface texture inspection device for inspecting the surface texture of the inner surface of an electric resistance welded pipe, A housing is positioned at a certain distance from an inspection area extending in the axial direction of the electric resistance welded pipe on the inner surface of the electric resistance welded pipe, and is relatively movable along the axial direction of the electric resistance welded pipe while maintaining that certain distance. The housing holds the target area extracted from the inspection area in a position normal to that area, and illuminates the target area from all directions around its circumference; An imaging unit that is held in a position normal to the target area by the housing and captures an image of the area including the target area which is at least illuminated by the illumination unit, and generates an image; An inspection unit that inspects the surface properties of the inner surface of the electric resistance welded pipe based on the captured image, It has, The inspection area is on the inner surface of the electric resistance welded pipe, facing the welded portion where welding was performed when the steel plate was processed into the electric resistance welded pipe, and is in contact with the roller that holds the cutting tool used to cut the weld bead formed in the welded portion. It is an area where there is no difference in height between it and the surface of the electric resistance welded pipe, and where a pattern defect may have occurred that can only be observed from a specific direction. The aforementioned target area is an area set at a position in the inspection area opposite to the housing each time the housing moves relative to it. The inspection unit is a surface texture inspection device that determines whether or not the pattern defects are present in the target area based on the captured image.

2. The illumination unit includes a light-diffusing member positioned opposite the target area, The surface property inspection apparatus according to claim 1, further comprising: a plurality of light sources arranged in the circumferential direction of the light diffusing member and irradiating light toward the light diffusing member.

3. The surface texture inspection apparatus according to claim 1, wherein the illumination unit is arranged in a dome shape to cover the target area and has a plurality of light sources that irradiate light toward the target area.

4. The illumination unit is formed in a dome shape that covers the target area, and includes a reflective member whose surface facing the target area is a reflective surface, The surface property inspection apparatus according to claim 1, further comprising: a plurality of light sources arranged in the circumferential direction of the reflective member and irradiating light toward the reflective surface.

5. A surface texture inspection method for inspecting the surface texture of the inner surface of an electric resistance welded pipe, A housing movement step involves using a housing that is positioned opposite the inspection area extending in the axial direction of the electric resistance welded pipe on the inner surface of the electric resistance welded pipe at a certain distance, and moving the housing relative to the inspection area along the axial direction of the electric resistance welded pipe while maintaining the certain distance. A lighting step in which the target area is illuminated from all directions around the entire circumference using a lighting unit held in a position normal to the target area extracted from the inspection area by the housing, An imaging step to generate an image by using an imaging unit held by the housing at a position normal to the target area, to image an area including at least the target area illuminated by the illumination unit, An inspection step to inspect the surface properties of the inner surface of the electric resistance welded pipe based on the captured image, It has, The inspection area is on the inner surface of the electric resistance welded pipe, facing the welded portion where welding was performed when the steel plate was processed into the electric resistance welded pipe, and is in contact with the roller that holds the cutting tool used to cut the weld bead formed in the welded portion. It is an area where there is no difference in height between it and the surface of the electric resistance welded pipe, and where a pattern defect may have occurred that can only be observed from a specific direction. The aforementioned target area is an area set at a position in the inspection area opposite to the housing each time the housing moves relative to it. The inspection step is a surface texture inspection method that determines whether or not the pattern defects are present in the target area based on the captured image.

6. The surface texture inspection method according to claim 5, wherein in the illumination step, an illumination unit is used that has a light diffusing member positioned opposite the target area and a plurality of light sources arranged in the circumferential direction of the light diffusing member and irradiating light toward the light diffusing member.

7. The surface texture inspection method according to claim 5, wherein the illumination step uses an illumination unit having a plurality of light sources arranged in a dome shape to cover the target area and irradiating light toward the target area.

8. The surface properties inspection method according to claim 5, wherein the illumination step uses an illumination unit having a reflective member formed in a dome shape that covers the target area and whose surface facing the target area is a reflective surface, and a plurality of light sources arranged in the circumferential direction of the reflective member and irradiating light toward the reflective surface.

Images