Surface inspection device and surface inspection method

Abstract

To secure inspection precision in inspecting properties of a surface of an object to be inspected which is formed in a columnar or cylindrical shape, based upon an image.SOLUTION: When a line image for generating an inspection image is extracted from a captured image, a line image extraction region setting part sets, as a line image extraction region, a region which includes a center part of a region increasing in luminance value along a direction of a second axis as the center and extends linearly in a direction of a first axis, in the captured image generated by imaging an object to be inspected in a non-rotation state. Then, an inspection image generation part extracts images corresponding to the line image extraction region as line images from a plurality of captured images, respectively, and connects the plurality of extracted line images to generate an inspection image.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface inspection apparatus and a surface inspection method, and more particularly to a surface inspection apparatus and a surface inspection method for inspecting the surface properties of an object to be inspected formed in a columnar or cylindrical shape based on an image.

Background Art

[0002] For example, as a surface inspection apparatus and a surface inspection method for inspecting the surface properties of an object to be inspected formed in a columnar or cylindrical shape based on an image, a technique has been proposed in which light is irradiated onto a rotating object to be inspected, and an image of the entire circumference and entire length of the object to be inspected is acquired while the object to be inspected is rotating.

[0003] For example, in the technique described in Patent Document 1, a camera and illumination are arranged outside a cylindrical body, the inner surface of the cylindrical body is supported by a pair of rollers, and the outer peripheral surface of the cylindrical body is imaged for the entire circumference while the cylindrical body is rotating. Further, in the technique described in Patent Document 2, diffused light is irradiated onto the effective inspection area of a steel pipe by a diffused illumination unit, and while the steel pipe is rotated around its pipe axis by a metal material rotating unit, the effective inspection area is imaged from the normal direction at the top of the effective inspection area of the steel pipe by an imaging unit which is an area camera.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique described in Patent Document 1, by supporting the inner surface of the inspection object with a pair of rollers, the distance between the camera and the cylindrical body becomes constant. Therefore, the resolution of the camera can be made constant regardless of the outer diameter of the cylindrical body. However, in addition to the need for rollers to support the inner surface of the cylindrical body and the reduction in inspection efficiency due to the need for the roller attachment / detachment process, the inspection target is limited to cylindrical bodies such as steel pipes.

[0006] Also, in the technique described in Patent Document 2, although the configuration of the metal material rotating part for rotating the steel pipe around its pipe axis is not clear, it is not a roller for supporting the inner surface of the cylindrical body as described in Patent Document 1. For example, it is conceivable to use a roller that supports the steel pipe from below and rotate the steel pipe by the rotation of the roller. In this case, even if the top of the steel pipe facing the imaging unit is set on the optical axis of the imaging unit (i.e., the center of the field of view) in terms of design, due to the shape defect of the steel pipe (referring to a state that is not a perfect circle), the deviation of the rotation axis of the steel pipe, or the aging deterioration of the roller, etc., in reality, it is assumed that the top of the steel pipe facing the imaging unit deviates from the optical axis of the imaging unit.

[0007] Here, in a state where the top of the steel pipe facing the imaging unit is located on the optical axis of the imaging unit as designed, in the central part of the image acquired by the imaging unit which is an area camera (i.e., the central part in the direction corresponding to the direction orthogonal to the axial direction which is the direction perpendicular to the cylindrical cross-section of the steel pipe), a region with high luminance corresponding to the top of the steel pipe appears. On the other hand, in a state where the top of the steel pipe facing the imaging unit deviates from the optical axis of the imaging unit, in the central part of the image acquired by the imaging unit which is an area camera, a region with low luminance corresponding to the region deviated from the top of the steel pipe appears.

[0008] Therefore, in a method of uniformly extracting the central part of the image acquired by the imaging unit regardless of the luminance, connecting the extracted central part images to generate an inspection image corresponding to the entire circumference of the steel pipe, and inspecting the surface properties of the steel pipe based on the inspection image, when the top of the steel pipe facing the imaging unit deviates from the optical axis of the imaging unit, there is a risk that the luminance of the inspection image is insufficient and the inspection accuracy decreases.

[0009] Therefore, an object of the present invention is to provide a surface inspection apparatus and a surface inspection method capable of ensuring inspection accuracy when inspecting the surface properties of a cylindrical or tubular inspection object based on an image.

Means for Solving the Problems

[0010] A first aspect of the present invention is a surface inspection apparatus for inspecting the surface properties of an inspection object formed in a columnar or cylindrical shape, comprising: a rotation support unit that supports the inspection object from vertically below and rotates the inspection object about an axial direction that is perpendicular to the cylindrical cross-section of the inspection object and serves as a rotation axis; an illumination unit provided substantially vertically above the rotation axis and irradiating light toward the inspection object; an imaging unit provided substantially vertically above the rotation axis and generating an area image having a first axis corresponding to the axial direction of the inspection object and a second axis corresponding to a direction perpendicular to the axial direction of the inspection object by imaging the inspection object irradiated with light by the illumination unit; a line image extraction region setting unit that sets a line image extraction region which is a region for extracting from the area image a line image that is an image forming a part of the direction of the second axis and extending linearly in the direction of the first axis; a inspection image generation unit that generates an inspection image by connecting a plurality of the line images extracted for each area image in the direction of the second axis; and a inspection processing unit that inspects the surface properties of the inspection object based on the inspection image. By using the illumination unit to irradiate light toward the inspection object and using the imaging unit to image the inspection object irradiated with light by the illumination unit, the area image is generated. By using the line image extraction region setting unit, a change in luminance value in the direction of the second axis in the area image is obtained across the direction of the first axis in the area image, and a region determined as a range that is a part of the area image centered on the central portion of a region where the luminance value increases along the direction of the second axis is set as the line image extraction region. By using the rotation support unit, the inspection object is rotated, and by using the inspection image generation unit, a plurality of positions in the circumferential direction on the surface of the inspection object irradiated with light by the illumination unit and rotated by the rotation support unit are imaged by the imaging unit, so that an image corresponding to the line image extraction region is extracted as the line image from each of the generated plurality of area images, and the extracted line images are connected in the direction of the second axis to generate the inspection image. This is the surface inspection apparatus.

[0011] A second aspect of the present invention is a surface inspection method for inspecting the surface properties of an inspection object formed in a columnar or cylindrical shape. The method includes a rotation support unit that supports the inspection object from vertically below and rotates the inspection object with an axial direction, which is a direction perpendicular to the columnar / cylindrical cross-section of the inspection object, as a rotation axis; an illumination unit provided substantially vertically above the rotation axis and irradiating light toward the inspection object; an imaging unit provided substantially vertically above the rotation axis and generating an area image having a first axis corresponding to the axial direction of the inspection object and a second axis corresponding to a direction perpendicular to the axial direction of the inspection object by imaging the inspection object irradiated with light by the illumination unit; a line image extraction region setting unit that sets a line image extraction region, which is a region for extracting, from the area image, a line image that is an image forming a part of the direction of the second axis and extending linearly in the direction of the first axis; a inspection image generation unit that generates an inspection image by connecting a plurality of the line images extracted for each area image in the direction of the second axis; and an inspection processing unit that inspects the surface properties of the inspection object based on the inspection image. Using the surface inspection apparatus having the above components, an irradiation step of irradiating light toward the inspection object using the illumination unit; an imaging step of generating the area image by imaging the inspection object irradiated with light by the illumination unit using the imaging unit; a line image extraction region setting step of using the line image extraction region setting unit to obtain a change in luminance value in the direction of the second axis in the area image across the direction of the first axis in the area image, and setting, as the line image extraction region, a region determined as a range that is a part of the area image centered on the central portion of a region where the luminance value increases along the direction of the second axis; a rotation step of rotating the inspection object using the rotation support unit; a inspection image generation step of using the inspection image generation unit to extract, as the line image, an image corresponding to the line image extraction region from each of the plurality of generated area images by imaging a plurality of circumferential positions on the surface of the inspection object irradiated with light by the illumination unit and rotated by the rotation support unit, and connecting the extracted line images in the direction of the second axis to generate the inspection image; and a step of using the inspection processing unit to based on the inspection image,An inspection processing step for inspecting the surface properties of the object to be inspected, and a surface inspection method having the same.

Advantages of the Invention

[0012] According to the present invention, there are provided a surface inspection apparatus and a surface inspection method capable of ensuring inspection accuracy when inspecting the surface properties of an object to be inspected formed in a columnar or cylindrical shape based on an image.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows an example of the overall configuration of a surface inspection device 10 according to an embodiment of the present invention and a schematic configuration of an object to be inspected 12 that is the object of inspection of the surface properties. In the example shown in FIG. 1, the object to be inspected 12 is formed in a cylindrical shape. The object to be inspected 12 is, as an example, a billet that is the base material of seamless steel pipe. Note that the object to be inspected 12 may be any object other than a billet as long as it is formed in a cylindrical or cylindrical shape. Also, the object to be inspected 12 may be made of metal or may be made of non - metal.

[0016] The surface inspection device 10 is a device for inspecting the properties of the surface (for example, the outer peripheral surface) of the object to be inspected 12. The surface inspection device 10 includes a rotation support device 14, an illumination imaging device 16, a marking device 18, and a processing device 20. Also, the illumination imaging device 16 includes an illumination device 22 and a plurality of imaging devices 24. Hereinafter, in order to explain each direction of the surface inspection device 10, the X - axis direction, the Y - axis direction, and the Z - axis direction are defined. The X - axis direction is a direction perpendicular to the cylindrical cross - section of the object to be inspected 12, the Z - axis direction is the vertical direction, and the Y - axis direction is a direction orthogonal to both the X - axis direction and the Z - axis direction.

[0017] Figures 2 and 3 show an example of the rotation support device 14, the illumination imaging device 16, and the subject 12. FIG. 2 is a side view seen from the X-axis direction, and FIG. 3 is a front view seen from the Y-axis direction. The rotation support device 14 is a mechanism that rotates the subject 12 about the rotation axis 12A of the subject 12. Specifically, the rotation support device 14 rotates the subject 12 about the rotation axis 12A parallel to the direction orthogonal to the optical axis 24A so that the surface of the subject 12 to be inspected faces the optical axis 24A of each imaging device 24 described later.

[0018] The rotation support device 14 includes a drive unit 26 and a pair of roller units 28. The drive unit 26 is a drive source having a speed reducer, a motor, and the like. The pair of roller units 28 are arranged side by side in the Y-axis direction. The pair of roller units 28 are symmetrically configured in the Y-axis direction. Each roller unit 28 includes a plurality of rollers 30 and a shaft member 32. The shaft member 32 is formed in a rod shape and extends in the X-axis direction. The plurality of rollers 30 are coaxially arranged in the X-axis direction and are fixed to the shaft member 32. The output shaft of the drive unit 26 is connected to the shaft member 32 provided on one of the pair of roller units 28.

[0019] The subject 12 is rotatably placed on the pair of roller units 28. The subject 12 is arranged on the pair of roller units 28 so that the rotation axis 12A is parallel to the X-axis direction. In the present embodiment, since the rotation support device 14 supports the subject 12 from below in the vertical direction by the pair of roller units 28, the outer diameter of the subject 12 can be arbitrarily changed within the range where the surface of the subject 12 is within the depth of field of the imaging device 24 described later. As an example, FIGS. 2 and 3 show a state in which a subject 12 with a small outer diameter and a subject 12 with a large outer diameter are placed on the pair of roller units 28. The subject 12 with a small outer diameter is shown by a solid line, and the subject 12 with a large outer diameter is shown by a two-dot chain line.

[0020] In a state where the inspection object 12 is rotatably placed on a pair of roller parts 28, when the drive part 26 operates, the rotational force of the drive part 26 is transmitted to one of the pair of roller parts 28, and one of the roller parts 28 rotates while supporting the inspection object 12 from vertically below. When one of the roller parts 28 rotates, the inspection object 12 rotates about the rotation axis 12A due to the frictional force generated between one of the roller parts 28 and the inspection object 12. The other roller part of the pair of roller parts 28 rotates as a driven roller due to the frictional force generated between it and the inspection object 12, and supports the inspection object 12 from vertically below. The rotational speed of the drive part 26 is adjustable, and by adjusting the rotational speed of the drive part 26, the inspection object 12 can be rotated at a desired speed. The rotation support device 14 is an example of the rotation support part of the present invention.

[0021] The illumination imaging device 16 is provided substantially above the inspection object 12 in the vertical direction. In the description of this specification, "substantially above the vertical direction" means, in addition to the completely vertical upward direction, an error generally acceptable in the technical field to which the technology of the present disclosure belongs and that does not go against the gist of the technology of the present disclosure, including the upward direction in the vertical direction. Among the illumination imaging device 16, the illumination device 22 irradiates light from substantially above the vertical direction toward the inspection object 12 that is rotated by the rotation support device 14. The illumination device 22 is an example of the illumination part of the present invention. Each imaging device 24 among the illumination imaging device 16 images a plurality of circumferential positions on the surface of the inspection object 12 that is irradiated with light from the illumination device 22 and rotated by the rotation support device 14. Each imaging device 24 is an example of the imaging part of the present invention.

[0022] The plurality of imaging devices 24 have the same configuration as an example. The plurality of imaging devices 24 are arranged side by side in the X-axis direction. Also, the plurality of imaging devices 24 are arranged at the same position in the Z-axis direction (i.e., the same height). The fields of view (i.e., imaging ranges) of the plurality of imaging devices 24 are fixed in advance so that the entire length of the surface of the object to be inspected 12 is included without a gap between the fields of view of adjacent imaging devices 24 even when the outer diameter of the object to be inspected 12 changes. The focal length of each imaging device 24 is set so that the surface of the object to be inspected 12 is within the depth of field even when the outer diameter of the object to be inspected 12 changes. Also, the field of view of each imaging device 24 is set so that the value of the pixel resolution [mm / pixel] when the outer diameter of the assumed object to be inspected 12 is the smallest within the assumed range of the outer diameter is equal to or less than a predetermined allowable upper limit value. Thereby, as will be described later, when specifying the dimensions of the defect 72 (see FIG. 11) present on the surface of the object to be inspected 12 in the surface inspection process, the dimensions of the defect 72 can be specified with high resolution as the outer diameter of the object to be inspected 12 increases.

[0023] The illumination imaging device 16 is provided substantially vertically above the rotation axis 12A of the object to be inspected 12. Although the specific configuration of the illumination imaging device 16 will be described later, among the illumination imaging device 16, the illumination device 22 is arranged such that the optical axis 22A of the illumination device 22 intersects the rotation axis 12A of the object to be inspected 12 and the optical axis 22A is parallel to the Z-axis direction. Similarly, among the illumination imaging device 16, each imaging device 24 is arranged such that the optical axis 24A of each imaging device 24 intersects the rotation axis 12A of the object to be inspected 12 and the optical axis 24A is parallel to the Z-axis direction. Each imaging device 24 is arranged to image the surface of the object to be inspected 12 along the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. As an example, each imaging device 24 is arranged such that the optical axis 24A of the imaging device 24 coincides with the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. In other words, the illumination device 22 is arranged to irradiate light coaxially with the optical axis 24A of each imaging device 24 as viewed from the X-axis direction.

[0024] In the design, the rotation axis 12A of the object to be inspected 12 is set on the optical axis 24A of the imaging device 24 (i.e., at the center of the field of view). When the rotation axis 12A of the object to be inspected 12 is located on the optical axis 24A of the imaging device 24 as designed, since the top of the object to be inspected 12 facing each imaging device 24 and the optical axis 24A of each imaging device 24 coincide, the specularly reflected light irradiated from the lighting device 22 and specularly reflected on the surface of the top of the object to be inspected 12 enters each imaging device 24. Here, the top of the object to be inspected 12 facing each imaging device 24 refers to the location of the object to be inspected 12 that is closest to each imaging device 24 in the Z-axis direction. In other words, it refers to the highest point on the surface of the object to be inspected in the Z-axis direction.

[0025] However, due to a shape defect of the object to be inspected 12 (referring to a state that is not a perfect circle), a deviation of the rotation axis 12A of the object to be inspected 12, or aging deterioration of the roller 30, etc., in reality, the top of the object to be inspected 12 facing each imaging device 24 may deviate in the Y-axis direction from the optical axis 24A of the imaging device 24. The process for dealing with the case where the top of the object to be inspected 12 facing each imaging device 24 deviates in the Y-axis direction from the optical axis 24A of the imaging device 24 is executed in the processing device 20 described later.

[0026] FIG. 4 shows an example of the illumination imaging device 16. The lighting device 22 is, as an example, a line-shaped illumination, and is arranged such that its longitudinal direction is parallel to the X-axis direction and its short-side direction is parallel to the Y-axis direction. The lighting device 22 may be, for example, LED illumination, incandescent lamp illumination, or fluorescent lamp illumination, etc. The lighting device 22 is configured to irradiate light uniformly with a diffusion film. The irradiation range of the lighting device 22 is set to be wider than the field of view of each imaging device 24 in order to suppress uneven illumination. The light irradiated from the lighting device 22 may be white light or light of any color. The lighting device 22 is a perforated illumination having a plurality of through holes 34. The plurality of through holes 34 are arranged in the X-axis direction, and each through hole 34 penetrates in the Z-axis direction. Inside each through hole 34, the imaging device 24 is arranged.

[0027] The plurality of imaging devices 24 are arranged side by side in the X-axis direction by being disposed inside each through hole 34. Each imaging device 24 is a camera capable of imaging the surface of the subject 12 as a monochrome or color image. The imaging device 24 is, for example, a two-dimensional camera (i.e., an area camera) in which imaging elements such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) are two-dimensionally arranged. The horizontal axis of the field of view of each imaging device 24 is set parallel to the X-axis direction, and the vertical axis of the field of view of each imaging device 24 is set parallel to the Y-axis direction. In the present embodiment, the number of imaging devices 24 is three, but any number may be used.

[0028] The marking device 18 shown in FIG. 1 is a device for marking the surface of the subject 12. The marking device 18 may be, for example, a robot arm having a drawing tool at its tip. The marking device 18 is configured to draw a specified symbol, character, or mark on a specified position on the surface of the subject 12. FIG. 1 shows an example of a mark 36 marked on the surface of the subject 12 by the marking device 18. The mark 36 is circular as an example, but may have a shape other than circular. The mark 36 is used to identify an image of one circumference of the surface of the subject 12 in an inspection image 66 (see FIG. 11) generated by the processing device 20 described later. The marking device 18 attaches the mark 36 to the position on the surface of the subject 12 where imaging by the imaging device 24 starts. In the example shown in FIG. 1, the mark 36 is attached to the end in the X-axis direction at the top of the subject 12 facing the plurality of imaging devices 24. The marking device 18 is an example of the marking unit of the present invention.

[0029] The processing device 20 is a device that performs various controls related to the surface inspection device 10 and various calculations related to the inspection of the subject 12, and is configured by a computer having a hardware configuration described later. FIG. 5 shows an example of the functional configuration of the processing device 20. The processing device 20 has, as a functional configuration, a control unit 40 and an inspection unit 42.

[0030] The control unit 40 is a functional unit that controls various devices included in the surface inspection apparatus 10 to cause them to exhibit their functions. Specifically, the control unit 40 controls each of the rotation support device 14, the illumination device 22, the imaging device 24, and the marking device 18. The surface inspection process by the surface inspection apparatus 10 starts from a state where the inspection object 12 is rotatably placed on a pair of roller units 28.

[0031] At the start of the surface inspection process, the control unit 40 controls the marking device 18 so that a mark 36 is applied to the position on the surface of the inspection object 12 where imaging by the imaging device 24 starts. Also, at the start of the surface inspection process, the control unit 40 turns on the illumination device 22 to start light irradiation. Further, at the start of the surface inspection process, the control unit 40 operates the rotation support device 14 to rotate the inspection object 12. The control unit 40 synchronizes various control timings by acquiring the rotation angle or the rotation period of the inspection object 12 from a rotary encoder or the like provided in the rotation support device 14.

[0032] FIG. 6 shows an example in which a plurality of imaging images 60 are generated by a plurality of imaging devices 24. The control unit 40 causes each imaging device 24 to image a plurality of positions in the circumferential direction on the surface of the inspection object 12 in accordance with a predetermined period of rotation of the inspection object 12. At this time, specifically, the control unit 40 causes each imaging device 24 to image a range having a length exceeding one circumference of the surface of the inspection object 12 in a plurality of times so that after the position with the mark 36 is imaged on the rotating inspection object 12, the position with the mark 36 is imaged again. As a result, a plurality of imaging images 60 including a range having a length exceeding one circumference of the surface of the inspection object 12 in the circumferential direction of the inspection object 12 and including the entire length of the surface of the inspection object 12 in the axial direction of the inspection object 12 are generated by the plurality of imaging devices 24. Then, the control unit 40 acquires the plurality of imaging images 60 generated by the plurality of imaging devices 24 from each imaging device 24.

[0033] Each captured image 60 is an area image having an x-axis corresponding to the axial direction of the subject 12 and a y-axis corresponding to a direction perpendicular to the axial direction of the subject 12. The captured image 60 is an example of the area image of the present invention, the x-axis is an example of the first axis of the present invention, and the y-axis is an example of the second axis of the present invention. When a plurality of captured images 60 are generated, the control unit 40 controls the rotation support device 14 (see FIG. 1) to stop the rotation of the subject 12.

[0034] The inspection unit 42 shown in FIG. 5 inspects the surface properties of the subject 12 based on a plurality of captured images 60 acquired by the control unit 40. The inspection unit 42 includes a line image extraction area setting unit 43, an inspection image generation unit 44, an inspection processing unit 46, a determination processing unit 48, and an output processing unit 50 as functional units for performing the inspection. In the inspection by the inspection unit 42, using the line image extraction area setting unit 43, on the captured image generated by imaging the subject 12 in a stopped state of rotation, a line image that is an image forming a part in the y-axis direction and extending linearly in the x-axis direction is extracted from the captured image. A line image extraction area, which is an area for extracting the line image, is set. Thereafter, the inspection image generation unit 44, the inspection processing unit 46, the determination processing unit 48, and the output processing unit 50 perform data processing on the plurality of captured images 60 acquired by the control unit 40 to inspect the surface properties of the subject 12.

[0035] FIG. 7 shows an example in which an inspection image 66 is generated from a plurality of captured images 60. The inspection image generation unit 44 extracts a line image 62, which is an image that is a part in the y-axis direction and extends linearly in the x-axis direction, from each of the captured images 60. The extraction process of extracting the line image 62 is performed by the line image extraction area setting unit 43. Then, the inspection image generation unit 44 concatenates the extracted plurality of line images 62 in the y-axis direction for each captured image 60 generated by each imaging device 24 (that is, for each image group A to C corresponding to each imaging device 24) to generate a concatenated image 64, and further concatenates the generated plurality of concatenated images 64 in the x-axis direction to generate an inspection image 66.

[0036] Incidentally, as described above, even though the rotation axis 12A of the inspection object 12 is set on the optical axis 24A of the imaging device 24 in terms of design, due to shape defects of the inspection object 12, misalignment of the rotation axis 12A of the inspection object 12, or aging deterioration of the rollers 30, etc., actually, the top of the inspection object 12 facing each imaging device 24 may be displaced in the Y-axis direction from the optical axis 24A of the imaging device 24 (i.e., the center of the field of view).

[0037] Here, FIG. 8 shows an example of the captured image 60 when the top of the inspection object 12 facing each imaging device 24 is located on the optical axis 24A of the imaging device 24, and an example of the captured image 60 when the top of the inspection object 12 facing each imaging device 24 is displaced from the optical axis 24A of the imaging device 24. In a state where the top of the inspection object 12 facing each imaging device 24 is located on the optical axis 24A of the imaging device 24, as shown in FIG. 8(A), a region with high luminance corresponding to the top of the inspection object 12 appears in the central part of the captured image 60 (i.e., the central part in the y-axis direction). On the other hand, in a state where the top of the inspection object 12 facing each imaging device 24 is displaced from the optical axis 24A of the imaging device 24, as shown in FIG. 8(B), a region with low luminance corresponding to a region deviated from the top of the inspection object 12 appears in the central part of the captured image 60.

[0038] Therefore, if the central part of the captured image 60 acquired by the imaging device 24 is uniformly extracted regardless of luminance, and the extracted central part images are concatenated to generate an inspection image 66 corresponding to the entire circumference of the surface of the inspection object 12, and the surface properties of the inspection object 12 are inspected based on the inspection image 66, when the top of the inspection object 12 facing each imaging device 24 is displaced from the optical axis 24A of the imaging device 24, the luminance of the inspection image 66 may be insufficient, and the inspection accuracy may decrease.

[0039] Therefore, the line image extraction area setting unit 43 extracts the line image 62 from the captured image 60 by executing the extraction process described below. FIG. 9 shows an example in which the line image 62 is extracted when the top of the inspection object 12 facing each imaging device 24 is located on the optical axis 24A of the imaging device 24, and FIG. 10 shows an example in which the line image 62 is extracted when the top of the inspection object 12 facing each imaging device 24 is displaced from the optical axis 24A of the imaging device 24.

[0040] The line image extraction area setting unit 43 uses the captured image 60 generated by imaging the inspection object 12 in a non-rotated state. Subsequently, the line image extraction area setting unit 43 obtains the change in the luminance value in the y-axis direction of the captured image 60 across the x-axis direction in the captured image 60. For example, the line image extraction area setting unit 43 obtains the change in the luminance value in the y-axis direction by executing a luminance addition process of adding the luminance values at each position in the y-axis direction in the x-axis direction. In FIGS. 9 and 10, graphs representing the change in the luminance value in the y-axis direction are shown.

[0041] Subsequently, the line image extraction area setting unit 43 compares a predetermined threshold value with the luminance value in the y-axis direction, and extracts a high-luminance area 68, which is an area where the luminance value is higher than the threshold value along the y-axis direction, from the captured image 60. Subsequently, the line image extraction area setting unit 43 identifies the central part of the extracted high-luminance area 68 based on the coordinates in the y-axis direction of the extracted high-luminance area 68, and sets, as the line image extraction area 70, an area determined as a part of the captured image 60 in the y-axis direction centered on the central part of the identified high-luminance area 68. The line image extraction area 70 may be set to, for example, a pixel area for one row or a pixel area for two rows, or may be set to a pixel area for any number of rows. Then, the inspection image generation unit 44 extracts, as the line image 62, an image corresponding to the line image extraction area 70 from each of the plurality of captured images 60.

[0042] In the above extraction process, as shown in FIG. 9, when the top of the inspection object 12 facing each imaging device 24 is located on the optical axis 24A of the imaging device 24, a line image 62 centered on the central portion of the captured image 60 is extracted. On the other hand, as shown in FIG. 10, when the top of the inspection object 12 facing each imaging device 24 is displaced from the optical axis 24A of the imaging device 24, a line image 62 centered on a position displaced from the central portion of the captured image 60 corresponding to the displacement is extracted. As shown in FIGS. 9 and 10, in any case, a region with high luminance corresponding to the top of the inspection object 12 is extracted as the line image 62. Then, by connecting the plurality of line images 62 obtained in this way to generate an inspection image 66, an inspection image 66 having high luminance over the entire circumference and entire length of the surface of the inspection object 12 is obtained.

[0043] FIG. 11 shows an example of the inspection image 66. As described above, the imaging device 24 images the position where the mark 36 is attached to the rotating inspection object 12, and then images the position where the mark 36 is attached again, imaging a range with a length exceeding one circumference of the surface of the inspection object 12 in a plurality of divided times. Therefore, the mark 36 appears at two locations in the inspection image 66 generated based on the plurality of captured images 60 obtained in this way.

[0044] The inspection processing unit 46 inspects the surface properties of the inspection object 12 based on the inspection image 66. Specifically, the inspection processing unit 46 detects the position of the mark 36 in the inspection image 66, and specifies the image region between the marks 36 appearing at two locations in the inspection image 66 as an image of one circumference of the surface of the inspection object 12. Then, the inspection processing unit 46 detects defects on the surface of the inspection object 12 based on the specified image of one circumference.

[0045] For example, the inspection processing unit 46 identifies the defect 72 shown in the inspection image 66. Specifically, the inspection processing unit 46 executes predetermined image processing on the inspection image 66. For example, the inspection processing unit 46 executes predetermined preprocessing such as shading and smoothing on the inspection image 66. Subsequently, the inspection processing unit 46 binarizes the preprocessed inspection image 66 based on a predetermined threshold value. The threshold value can be determined experimentally in advance based on the type of the inspection object 12 and the like. Subsequently, the inspection processing unit 46 excludes noise components from the binarized inspection image 66 by a predetermined process. As a result, when the defect 72 is included as an image in the inspection image 66, the portion of the defect 72 is extracted from the inspection image 66.

[0046] In addition, when the defect 72 is included as an image in the inspection image 66, the inspection processing unit 46 derives the position, shape, and dimensions of the defect 72. For example, the inspection processing unit 46 derives the position and shape of the defect 72 based on information such as the luminance value on the inspection image 66 of the defect 72 included as an image in the inspection image 66, the coordinates, the pitch obtained from the rotary encoder of the rotary support device 14, and the size of the inspection object 12. Further, the inspection processing unit 46 derives the dimensions of the defect 72 based on the pixel resolution corresponding to the outer diameter of the inspection object 12. The inspection processing unit 46 generates defect map image information including information representing the derived position, shape, and dimensions of the defect 72 and the image obtained by executing the above image processing on the inspection image 66, and stores the generated defect map image information in the processing device 20.

[0047] The determination processing unit 48 determines whether or not there is a defect on the surface of the inspection object 12. For example, when the defect map image information is generated by the inspection processing unit 46, the determination processing unit 48 determines that there is a defect on the surface of the inspection object 12. When it is determined by the determination processing unit 48 that there is a defect on the surface of the inspection object 12, the output processing unit 50 causes the defect map image information generated by the inspection processing unit 46 to be displayed on the display of the processing device 20. Then, the operator identifies the position, shape, and dimensions of the defect 72 based on the defect map image information displayed on the display, and performs a predetermined repair operation on the portion of the defect 72.

[0048] Figure 12 shows an example of the hardware configuration of the processing device 20. The processing device 20 is configured by a computer. The processing device 20 includes a CPU (Central Processing Unit) 90, a memory 92, a storage device 94, an input device 96, an output device 98, a storage medium reader 100, and a communication I / F (Interface) 102. Each component is communicably connected to each other via a bus 104.

[0049] A program for executing surface inspection processing is stored in the storage device 94. The CPU 90 is a central processing unit that executes various programs and controls each component. That is, the CPU 90 reads a program from the storage device 94 and executes the program using the memory 92 as a work area. The CPU 90 performs control of each of the above components and various arithmetic processes according to the program stored in the storage device 94.

[0050] The memory 92 is composed of a RAM (Random Access Memory) and temporarily stores programs and data as a work area. The storage device 94 is composed of a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like, and stores various programs including an operating system and various data.

[0051] The input device 96 is a device for performing various inputs, such as a keyboard and a mouse. The output device 98 is a device for outputting various information, such as a display and a printer. By adopting a touch panel display as the output device 98, it may also function as the input device 96.

[0052] The memory medium reading device 100 reads data stored in various memory 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 memory medium. The communication I / F 102 is an interface for communicating with other devices. For the communication I / F 102, interfaces of standards such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark) are used, for example.

[0053] FIG. 13 shows an example of the flow of the surface inspection process executed by the CPU 90 of the processing device 20. The CPU 90 reads a program for executing the surface inspection process from the storage device 94, expands it in the memory 92, and executes it, whereby the CPU 90 functions as each functional unit of the processing device 20, and the surface inspection process is executed. Thereby, the surface inspection method by the surface inspection device 10 is executed. The surface inspection process is executed for each inspection object 12 carried into the surface inspection device 10.

[0054] First, in step S10, the control unit 40 controls the marking device 18 so that a mark 36 is attached to the position on the surface of the inspection object 12 where imaging by the imaging device 24 starts. Thereby, the marking device 18 operates to attach the mark 36 to the surface of the inspection object 12.

[0055] Next, in step S12, the control unit 40 turns on the illumination device 22 by controlling it. Thereby, the illumination device 22 irradiates the inspection object 12 with light. Step S12 is an example of the illumination step of the present invention.

[0056] Next, in step S13, the line image extraction area setting unit 43 extracts a line image 62 from the captured image 60 using the captured image 60 of the test object 12 in a non-rotated state. Specifically, the line image extraction area setting unit 43 extracts a high-brightness area 68 based on the change in the luminance value in the y-axis direction, and sets, as a line image extraction area 70, an area determined as a part of the captured image 60 in the y-axis direction centered on the central part of the extracted high-brightness area 68. Step S13 is an example of the line image extraction area setting step of the present invention.

[0057] Next, in step S14, the control unit 40 operates by controlling the rotation support device 14. Thereby, the rotation support device 14 rotates the test object 12 about the rotation axis 12A of the test object 12 while supporting the test object 12 from below in the vertical direction. Step S14 is an example of the rotation step of the present invention.

[0058] Next, in step S16, the control unit 40 controls each imaging device 24 to image the surface of the test object 12 in accordance with a predetermined cycle of rotation of the test object 12. Thereby, each imaging device 24 images a plurality of positions in the circumferential direction on the surface of the test object 12. Step S16 is an example of the imaging step of the present invention.

[0059] Next, in step S18, the inspection image generation unit 44 extracts, as a line image 62, an image corresponding to the line image extraction area 70 from each of the plurality of captured images 60.

[0060] Next, in step S20, the inspection image generation unit 44 generates a concatenated image 64 by concatenating the extracted plurality of line images 62 in the Y-axis direction for each captured image 60 generated by each imaging device 24 (that is, for each image group A to C corresponding to each imaging device 24), and further generates an inspection image 66 by concatenating the generated plurality of concatenated images 64 in the X-axis direction. Steps S18 and S20 are examples of the inspection image generation step of the present invention.

[0061] Next, in step S22, the inspection processing unit 46 inspects the surface properties of the inspection object 12 based on the inspection image 66. When the defect 72 is included as an image in the inspection image 66, the inspection processing unit 46 generates defect map image information and causes the processing device 20 to store the generated defect map image information. Step S22 is an example of the inspection processing step of the present invention.

[0062] Next, in step S24, the determination processing unit 48 determines whether or not there is a defect on the surface of the inspection object 12. Here, when it is determined by the determination processing unit 48 that there is no defect on the surface of the inspection object 12, the surface inspection processing ends. On the other hand, when it is determined by the determination processing unit 48 that there is a defect on the surface of the inspection object 12, the surface inspection processing proceeds to step S26.

[0063] Next, in step S26, the output processing unit 50 causes the defect map image information to be displayed on the display of the processing device 20. Thereby, the operator can identify the position, shape, and dimensions of the defect 72 based on the defect map image information displayed on the display, and perform a predetermined maintenance operation on the portion of the defect 72. After the operator performs a predetermined maintenance operation on the portion of the defect 72, the inspection object 12 is conveyed to the next process, and the surface inspection processing ends.

[0064] As described above, in the present embodiment, when extracting the line image 62 for generating the inspection image 66 from the captured image 60, the line image extraction area setting unit 43 acquires the change in the luminance value in the y-axis direction of the captured image 60 across the x-axis direction in the captured image 60 of the inspection object 12 in a non-rotated state, and sets, as the line image extraction area 70, an area determined as a range that is a part of the captured image 60 centered on the central portion of the area where the luminance value increases along the y-axis direction. Then, the inspection image generation unit 44 extracts, as the line image 62, an image corresponding to the line image extraction area 70 from each of the plurality of captured images 60.

[0065] Therefore, whether the top of the test object 12 facing each imaging device 24 is located on the optical axis 24A of the imaging device 24 or is offset from the top of the test object 12 facing each imaging device 24 from the optical axis 24A of the imaging device 24, a region with high luminance corresponding to the top of the test object 12 can be extracted as the line image 62. Then, by connecting a plurality of line images 62 to generate the inspection image 66, an inspection image 66 having high luminance over the entire circumference and full length of the surface of the test object 12 can be obtained. Thereby, the inspection accuracy when inspecting the properties of the surface of the test object 12 based on the inspection image 66 can be ensured.

[0066] Also, at the start of the inspection, a mark 36 is attached by the marking device 18 at the position on the surface of the test object 12 where imaging by the plurality of imaging devices 24 starts. In addition, each imaging device 24 images a range with a length exceeding one circumference of the surface of the test object 12. For this reason, two marks 36 appear in the inspection image 66 generated from the plurality of captured images 60. Then, the inspection processing unit 46 detects the positions of the marks 36 in the inspection image 66, specifies the image region between the two marks 36 appearing in the inspection image 66 as an image of one circumference of the surface of the test object 12, and detects defects on the surface of the test object 12 based on this image of one circumference. Therefore, based on the two marks 36, the surface of the test object 12 can be inspected without excess or deficiency for one circumference.

[0067] Further, the inspection processing unit 46 generates defect map image information including information representing the position, shape, and dimensions of the defect 72 and an image obtained by performing image processing for extracting the portion of the defect 72 with respect to the inspection image 66, and the output processing unit 50 causes the defect map image information to be displayed on the display of the processing device 20. At this time, since the two marks 36 described above are included as images in the image included in the defect map image information, the operator can perform visual reinspection and maintenance work on the test object 12 based on the two marks 36.

[0068] In addition, the field of view of each imaging device 24 is set such that the value of the pixel resolution [mm / pixel] in the case where the outer diameter is the smallest within the range of the assumed outer diameter of the subject 12 is equal to or less than a predetermined upper limit value. As a result, even if the position of the imaging device 24 is not moved along the optical axis 24A for each outer diameter of the subject 12, when specifying the size of the flaw 72 present on the surface of the subject 12 in the surface inspection process, the size of the flaw 72 can be specified with high resolution as the outer diameter of the subject 12 increases.

[0069] In addition, since it is not necessary to use a movable mechanism for moving the position of the imaging device 24 along the optical axis 24A, the configuration of the surface inspection device 10 can be simplified.

[0070] In addition, each imaging device 24 is arranged to image the surface of the subject 12 along the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. Here, as the arrangement of the illumination device 22 and the imaging device 24, an arrangement in which the optical axis 22A of the illumination device 22 and the optical axis 24A of the imaging device 24 form a V shape as viewed from the X-axis direction can be considered. In this arrangement, even if the rotation axis 12A of the subject 12 is located on the optical axis 24A of the imaging device 24, the position on the optical axis 22A on the surface of the subject 12 changes in the Y-axis direction for each outer diameter of the subject 12. As a result, the amount of reflected light incident on the imaging device 24 changes, or the brightest position on the surface of the subject 12 moves within the field of view of the imaging device 24.

[0071] In this regard, in the present embodiment, as described above, each imaging device 24 is arranged to image the surface of the subject 12 along the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. Therefore, it is possible to suppress the position on the optical axis 22A on the surface of the subject 12 from changing in the Y-axis direction for each outer diameter of the subject 12. As a result, it is possible to suppress the amount of reflected light incident on the imaging device 24 from changing, or the brightest position on the surface of the subject 12 from moving within the field of view of the imaging device 24.

[0072] Note that in the above embodiment, the illumination imaging device 16 may be configured as follows. FIG. 14 shows a first modification of the illumination imaging device 16. In the first modification, the illumination imaging device 16 has a plurality of illumination devices 22. The plurality of illumination devices 22 are arranged side by side in the X-axis direction. An imaging device 24 is arranged between adjacent illumination devices 22. Also in the first modification, similar to the above embodiment (see FIG. 2), each imaging device 24 is arranged to image the surface of the inspection object 12 along the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. As an example, each imaging device 24 is arranged such that the optical axis 24A of the imaging device 24 coincides with the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. Even in such a configuration, the same effects as those of the above embodiment can be obtained.

[0073] FIG. 15 shows a second modification of the illumination imaging device 16. In the second modification, the illumination imaging device 16 has a pair of illumination devices 22. Each illumination device 22 is a bar illumination extending in the X-axis direction. The pair of illumination devices 22 are arranged side by side in the Y-axis direction. A plurality of imaging devices 24 are arranged between the pair of illumination devices 22. Also in the second modification, similar to the above embodiment (see FIG. 2), each imaging device 24 is arranged to image the surface of the inspection object 12 along the optical axis 22A of the illumination device 22 as viewed from the X-axis direction. Even in such a configuration, the same effects as those of the above embodiment can be obtained.

[0074] Also, the illumination device 22 may be in a form other than those shown in FIGS. 4, 14, and 15. For example, the illumination device 22 may be a ring illumination arranged coaxially with the imaging device 24, a line illumination in which the optical axis 24A of the imaging device 24 and the optical axis 22A of the illumination device 22 are parallel as viewed from the X-axis direction, or a coaxial epi-illumination that irradiates epi-illumination light coaxially with the imaging device 24.

[0075] Also, in the above embodiment, the surface inspection device 10 inspects the properties of the outer peripheral surface of the inspection object 12 as the surface of the inspection object 12. However, in addition to the properties of the outer peripheral surface of the inspection object 12, the properties of the end face (i.e., the end face in the X-axis direction) of the inspection object 12 may be inspected. FIG. 16 shows a modified example of inspecting the properties of the end face of the inspection object 12 by the surface inspection device 10. In the modified example shown in FIG. 16, the illumination imaging device 16 is arranged to face the end face of the inspection object 12.

[0076] The processing device 20 obtains the change in the luminance value in the y-axis direction in the captured image over the z-axis direction in the captured image generated by capturing the inspection object 12 in a non-rotating state by the imaging device 24, and sets, as a line image extraction region, a region determined as a range that is part of the captured image and centered on the central portion of the region where the luminance value increases along the y-axis direction. An image corresponding to the line image extraction region is extracted as a line image from each of the plurality of captured images. In this case, for example, a line image corresponding to the region 25 at the central portion in the Y-axis direction in the field of view of the imaging device 24 is obtained. Then, the processing device 20 generates an inspection image by connecting the plurality of extracted line images.

[0077] In this way, an inspection image having high luminance can be obtained over the entire end face of the inspection object 12. Thereby, the inspection accuracy when inspecting the properties of the end face of the inspection object 12 based on the inspection image can be ensured.

[0078] Also, in the above embodiment, the rotation support device 14 has a pair of roller portions 28. However, instead of the pair of roller portions 28, or in addition to the pair of roller portions 28, a configuration having other roller portions may be used.

[0079] Also, in the above embodiment, the mark 36 is attached by the marking device 18, but it may be attached by an operator.

[0080] Although one embodiment of the present invention has been described above, the present invention is not limited to the above, and it goes without saying that various modifications can be made without departing from the gist of the invention.

Explanation of Reference Numerals

[0081] 10 Surface inspection device 12 Object to be inspected 12A Rotation axis of the object to be inspected 14 Rotation support device 16 Illumination imaging device 18 Marking device 20 Processing device 22 Illumination device 22A Optical axis of the illumination device 24 Imaging device 24A Optical axis of the imaging device 26 Driving unit 28 Roller unit 30 Roller 32 Shaft member 34 Through hole 36 Mark 40 Control unit 42 Inspection unit 43 Line image extraction area setting unit 44 Inspection image generation unit 46 Inspection processing unit 48 Judgment processing unit 50 Output processing unit 60 Captured image 62 Line image 64 Composite image 66 Inspection image 68 High-brightness area 70 Line image extraction area 72 Defect 90 CPU 92 Memory 94 Storage device 96 Input device 98 Output device 100 Storage medium reading device 102 Communication I / F 104 Bus

Claims

1. A surface inspection apparatus for inspecting the surface properties of a test object formed in a columnar or cylindrical shape, comprising: a rotary support unit that supports the test object from vertically below and rotates the test object with an axial direction, which is a direction perpendicular to the cylindrical cross-section of the test object, as a rotation axis; an illumination unit provided substantially vertically above the rotation axis and irradiating light toward the test object; an imaging unit provided substantially vertically above the rotation axis, which generates an area image having a first axis corresponding to the axial direction of the test object and a second axis corresponding to a direction perpendicular to the axial direction of the test object by imaging the test object irradiated with light by the illumination unit; a line image extraction region setting unit that sets a line image extraction region, which is a region for extracting, from the area image, a line image that is an image forming a part of the direction of the second axis and extending linearly in the direction of the first axis; a test image generation unit that generates a test image by connecting a plurality of the line images extracted for each area image in the direction of the second axis; a test processing unit that inspects the surface properties of the test object based on the test image; and comprising: irradiating light toward the test object using the illumination unit; generating the area image by imaging the test object irradiated with light by the illumination unit using the imaging unit; using the line image extraction region setting unit to obtain a change in luminance value in the direction of the second axis in the area image across the direction of the first axis in the area image, and setting, as the line image extraction region, a region determined as a range that is a part of the area image centered on the central portion of a region where the luminance value increases along the direction of the second axis; rotating the test object using the rotary support unit; A surface inspection apparatus that uses the inspection image generation unit to image a plurality of circumferential positions on the surface of the inspection object that is irradiated with light by the illumination unit and rotated by the rotation support unit by the imaging unit, and extracts, from each of the plurality of generated area images, an image corresponding to the line image extraction area as the line image, and connects the extracted line images in the direction of the second axis to generate the inspection image.

2. A mark is attached to the position on the surface of the inspection object where imaging by the imaging unit starts. The inspection processing unit detects the position of the mark in the inspection image, specifies, as an image for one circumference of the surface of the inspection object, an image area between the marks that appear at two locations in the inspection image, and detects a defect on the surface of the inspection object based on the image for one circumference. The surface inspection apparatus according to claim 1.

3. A surface inspection method for inspecting the surface properties of an inspection object formed in a cylindrical or cylindrical shape, A rotation support unit that supports the inspection object from vertically below and rotates the inspection object with an axial direction, which is a direction perpendicular to the cylindrical cross-section of the inspection object, as a rotation axis, An illumination unit provided substantially vertically above the rotation axis and irradiating light toward the inspection object, An imaging unit provided substantially vertically above the rotation axis and generating an area image having a first axis corresponding to the axial direction of the inspection object and a second axis corresponding to a direction perpendicular to the axial direction of the inspection object by imaging the inspection object irradiated with light by the illumination unit, A line image extraction area setting unit that sets a line image extraction area, which is an area for extracting, from the area image, a line image that is an image forming a part in the direction of the second axis and extending linearly in the direction of the first axis, An inspection image generation unit that connects a plurality of the line images extracted for each area image in the direction of the second axis to generate an inspection image, An inspection processing unit that inspects the surface properties of the inspection object based on the inspection image, Using a surface inspection apparatus having an irradiation step of irradiating light toward the object to be inspected using the illumination unit; an imaging step of generating the area image by imaging the object to be inspected irradiated with light by the illumination unit using the imaging unit; a line image extraction area setting step of obtaining a change in luminance value in the direction of the second axis in the area image across the direction of the first axis in the area image using the line image extraction area setting unit, and setting, as the line image extraction area, an area determined as a range that is part of the area image centered on the central portion of the area where the luminance value increases along the direction of the second axis; a rotation step of rotating the object to be inspected using the rotation support unit; an inspection image generation step of generating an inspection image by extracting, as the line image, an image corresponding to the line image extraction area from each of the plurality of generated area images by imaging, by the imaging unit, a plurality of circumferential positions on the surface of the object to be inspected irradiated with light by the illumination unit and rotated by the rotation support unit, and connecting the extracted line images in the direction of the second axis; an inspection processing step of inspecting the surface properties of the object to be inspected based on the inspection image using the inspection processing unit; A surface inspection method having

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