Surface roughness evaluation method and surface roughness evaluation apparatus

Abstract

To make it possible to more reliably evaluate whether or not the surface roughness of a metal to be evaluated is within the target surface roughness.SOLUTION: The surface roughness evaluation method is for evaluating whether the surface roughness of a metal to be evaluated is the target surface roughness. When the surface of the metal to be evaluated is illuminated with illumination light from an illumination device 10, an area including the intersection point with the irradiation axis of the illumination device is defined as a bright area ARA-1 and an area adjacent to the bright area ARA-1 and relatively lower in brightness than the bright area ARA-1 as a dark area ARA-2. In the bright area ARA-1, the luminance ratio, which is the ratio of areas with a brightness level equal to or higher than a preset brightness level, is calculated, and the average luminance of the dark area ARA-2 is calculated as the luminance of the dark area. When the luminance ratio is less than a first preset threshold and the dark luminance is greater than a second threshold value, the surface roughness of the metal to be evaluated is evaluated as the target surface roughness.SELECTED DRAWING: Figure 13

Description

Technical Field

[0004]

[0001] The present invention relates to a surface roughness evaluation technique for evaluating whether a metal surface to be evaluated has a target surface roughness. The present invention is a technique suitable for, for example, evaluating the surface roughness of a metal surface whose surface has been roughened by surface treatment, that is, evaluating the applied surface treatment. Note that the present invention is a technique applicable to a metal surface without surface treatment.

Background Art

[0002] When a predetermined surface roughness is imparted to a metal surface as the final product shape, the metal surface may be subjected to shot blasting or other surface treatment. For example, the pipe end thread portion formed at the pipe end of an oil well pipe is formed by cutting with an NC threading machine. As shown in FIG. 1, this pipe end thread portion 1 is composed of a thread portion (hereinafter also referred to as a thread portion main body 1A), a seal portion 1B, a shoulder portion 1C, and an inner surface portion 1D. Generally, the thread portion main body 1A and the seal portion 1B together are referred to as an outer surface portion 1E. In addition, as the thread shape of the pipe end thread portion 1 of the pipe, for example, there are a round crest thread, a trapezoidal thread, and a buttress thread.

[0003] The pipe end thread portion manufactured as described above usually has its thread surface roughened by subjecting its metal surface to blasting treatment (surface treatment). Here, the connection between oil well pipes is performed, for example, by applying a compound to the above-described pipe end thread portion and tightening the joint. At this time, if the thread portion is in an unblasted state, seizure may occur during tightening. For the purpose of preventing this, blasting media is sprayed onto the entire pipe end thread portion at a certain pressure to roughen the thread surface.

[0004] The blasting process is carried out by spraying blast media 4, such as SUS beads or alumina, onto the pipe end thread portion 1 using a device like the one shown in Figure 2. For example, as shown in Figure 2, the blast media 4 is sprayed from two nozzles 5A and 5B that are tilted toward the axial side of the oil well pipe 2, in opposite directions from the direction H perpendicular to the axis of the oil well pipe 2. Then, by moving the oil well pipe 2 in the axial direction (longitudinal direction) while rotating it along its axis, the entire metal surface of the pipe end thread portion 1 is blasted. Traditionally, the roughened surface was visually inspected to determine the quality of the surface treatment. However, this method of visually inspecting each individual pipe hindered the productivity of oil well tubular construction.

[0005] Here, although the subject is not an oil well pipe, as a method for evaluating surface-treated metal surfaces that do not require visual inspection, there is, for example, the method described in Patent Document 1. Patent Document 1 describes a surface defect inspection method for detecting surface defects (appearance abnormalities) in a metal plate. The method involves irradiating a target area on the surface of the metal plate with illumination light and capturing the reflected light from the target area. The method then binarizes the captured image and detects surface defects in the metal plate to be evaluated based on predetermined judgment rules in the bright areas of the binarized image. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-184559 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 describes that by illuminating the surface of a metal plate and taking an image, it is possible to determine the condition of defects present on the surface of a metal plate using only the bright areas obtained. However, the inventors confirmed that when a surface treatment is applied to a metal surface with irregularities such as the threaded shape of the pipe end of an oil well pipe, the image judgment described in Patent Document 1 is inaccurate. In other words, on a metal surface with a surface shape like a threaded section, the brightness of the bright areas varies due to the effects of shadows and reflections caused by the irregularities of the metal surface. Therefore, in the method described in Patent Document 1, when a metal surface such as a pipe end thread, where the influence of surface irregularities is unavoidable, was used as the subject, it was not possible to clearly evaluate whether the overall state was unblasted or blasted.

[0008] This invention was made in view of the points mentioned above, and aims to enable more reliable evaluation of whether the surface roughness of the metal surface being evaluated is the target surface roughness. [Means for solving the problem]

[0009] Herein, one aspect of the present invention is not primarily intended to partially (pinpoint) detect surface defects in a region of a surface-treated metal surface. The first objective of one aspect of the present invention is to evaluate whether the metal surface to be evaluated as a whole has a predetermined target surface roughness.

[0010] To address the problem, one aspect of the present invention provides a surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, comprising: irradiating the metal surface to be evaluated with illumination light using an illumination device; imaging the metal surface to be evaluated that is illuminated by the illumination light; defining a bright area in the captured image, which is a region with high brightness, and a dark area, which has lower brightness than the bright area; and evaluating the surface roughness of the metal surface to be evaluated based on the brightness of the bright area and the brightness of the dark area.

[0011] Another aspect of the present invention is a surface roughness evaluation method for evaluating a metal surface having a region whose surface shape is a predetermined uneven shape, and for evaluating whether the surface roughness of the metal surface is a target surface roughness, wherein illumination light is shone on the metal surface of the region having the uneven shape using an illumination device, the metal surface to be evaluated that is illuminated by the illumination light is imaged, a bright region is determined in the imaged image, a bright region is determined which is the bright region of the uneven shape that has a high brightness, a brightness ratio is determined which is the ratio of the bright region to a predetermined brightness or higher, and the surface roughness of the metal surface to be evaluated is evaluated based on the brightness ratio. [Effects of the Invention]

[0012] According to an aspect of the present invention, it is possible to evaluate whether or not the metal surface to be evaluated has the target surface roughness. Furthermore, according to an aspect of the present invention, it is possible to more reliably evaluate surface roughness even when targeting a metal surface that has a predetermined uneven shape (such as a screw shape) formed on it. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view illustrating the structure of the pipe end thread. [Figure 2] This is a schematic diagram showing an example of a device for performing blast treatment on threaded ends of pipes. [Figure 3] This is a schematic diagram showing the relationship between the pipe and nozzle when blasting is performed correctly. [Figure 4] This diagram illustrates an example of blast treatment on a screw when nozzle 5A is clogged. [Figure 5] This diagram illustrates an example of blast treatment on a screw when nozzle 5B becomes clogged. [Figure 6] This is a schematic diagram showing the relationship between the pipe and the nozzle when nozzle 5B becomes clogged during blasting. [Figure 7] This figure shows an example of the configuration of a surface roughness evaluation apparatus according to an embodiment of the present invention. [Figure 8]It is a diagram showing the arrangement relationship between the camera 11A and the lighting device 10A. [Figure 9] It is a diagram for explaining the configuration of the arithmetic processing unit. [Figure 10] It is a diagram showing an image of the threaded portion before blasting. [Figure 11] It is a diagram showing an image of the outer surface portion (threaded portion main body and seal portion) after the blasting process. [Figure 12] It is a diagram showing an image of the outer surface portion (threaded portion main body and seal portion) when the blasting is thin. [Figure 13] It is an example of an image of the outer surface portion (threaded portion main body and seal portion) to be evaluated, and is a diagram exemplifying the bright region and the dark region. [Figure 14] It is a diagram for explaining the configuration of the evaluation arithmetic unit. [Figure 15] It is a diagram showing an example of the processing flow of the first evaluation unit. [Figure 16] It is a diagram showing an example of the processing flow of the second evaluation unit. [Figure 17] It is a diagram for explaining the difference in reflected light due to surface roughness. (a) shows the case where the surface roughness is small and specular reflection is large, and (b) shows the case where the surface roughness is large and diffuse reflected light is large. [Figure 18] It is a diagram showing an example of setting conditions for devices and the like. [Figure 19] It is a diagram of an image showing the occurrence of halation on the inner surface due to non - blasting. [Figure 20] It is a diagram for explaining the method of position correction in the horizontal direction (lateral direction). [Figure 21] It is a diagram for explaining the method of position correction in the vertical direction (up - and - down direction). [Figure 22] It is a diagram showing an example of blasting defect and evaluation method at the pipe - end threaded portion. [Figure 23] It is a diagram showing the evaluation test results in the embodiment.

Mode for Carrying Out the Invention

[0014] Next, embodiments based on the present invention will be described with reference to the drawings. In this embodiment, a metal surface that has been surface-treated and has become rough will be used as an example of the metal surface to be evaluated. That is, the evaluation of surface roughness as an evaluation of surface treatment will be used as an example. However, this disclosure is also applicable to metal surfaces that have not been surface-treated.

[0015] (Regarding surface treatment) In this embodiment, blasting is given as an example of a surface treatment method to increase (roughen) the surface roughness of a metal surface. However, the surface treatment method to which this disclosure can be applied to roughen a surface is not limited to blasting, and other methods such as chemical treatment may also be used. Furthermore, the following explanation will use the example of the case where the metal surface to be evaluated is the surface of the threaded end portion 1 of the oil well pipe.

[0016] (Regarding pipe end thread 1) As described above, the pipe end thread portion 1 formed at the end of the oil well pipe is formed by cutting with an NC threading machine. In this state, the metal surface of the pipe end thread portion 1 has a surface roughness of, for example, Ra: 1.7 μm or less. The surface of the pipe end threaded portion 1 to be evaluated consists of the threaded portion body 1A, the seal portion 1B, the shoulder portion 1C, and the inner surface portion 1D (the inner diameter surface near the pipe end face), as shown in Figure 1. Generally, the threaded portion body 1A and the seal portion 1B together are referred to as the outer surface portion 1E. The threaded portion body 1A is a region with an uneven surface, where a threaded shape (thread peaks and valleys) is formed as a pre-defined uneven shape. This disclosure applies if the uneven surface shape of the metal surface to be evaluated is known in advance. This disclosure is particularly effective for complex surface shapes that produce shadows. This disclosure is applicable when the uneven surface shape of the metal surface to be evaluated is formed in a pre-defined pattern, but it is also applicable when the uneven surface shape is formed in an irregular shape. However, it is more versatile when applied to metal surfaces where the uneven surface shape is formed in a pre-defined pattern.

[0017] (Blast treatment) In this embodiment, the metal surface of the pipe end thread portion 1 formed as described above is subjected to blast treatment (surface treatment). Figure 2 shows the configuration around the blast injection unit of the blasting apparatus 3 used for blasting. This blasting apparatus 3 is configured to perform blasting by injecting blast media 4, such as SUS beads and alumina, onto the pipe end threads 1 in a closed space (box). There are two types of nozzles, nozzle 5A and nozzle 5B, for injecting the blast media 4. As shown in Figure 2, the injection axes of nozzles 5A and 5B are tilted in opposite directions from the direction perpendicular to the axis H (normal direction) of the oil well pipe. This configuration ensures that blasting can be reliably performed on the bottom surface of the threads. In Figure 2, reference numeral 6 denotes an internal plug that prevents the blast media 4 from entering the inside of the oil well pipe 2. Furthermore, the blasting device 3 includes a rotational drive unit (not shown) that rotates the oil well pipe 2 on its axis, and a reciprocating mechanism (not shown) that moves the oil well pipe 2 forward and backward in the axial direction (longitudinal direction).

[0018] Then, while rotating the oil well pipe 2 on its axis, as shown in Figure 3, the blast media 4 is sprayed onto the pipe end threaded portion 1 from two nozzles 5A and 5B while moving in the pipe axis direction (longitudinal direction). This blasts the threaded portion body 1A, seal portion 1B, shoulder portion 1C, and inner surface portion 1D (inner diameter surface of the pipe end) that make up the pipe end threaded portion 1. In other words, the surface roughness of the entire metal surface of the pipe end threaded portion 1, excluding the inner surface of the steel pipe, is increased. Note that the inner surface 1D does not need to be roughened, but when the shoulder portion 1C is roughened, the inner diameter surface near the end of the pipe will also be roughened in the same way.

[0019] Here, if the nozzle 5A becomes clogged and the blast media 4 cannot be sprayed, depending on the thread shape of the threaded body 1A, the threaded bottom corner B may not be blasted, as shown in Figure 4. However, in this case, the seal portion 1B and shoulder portion 1C, which are flat portions 1F, will be blasted by the spray from the nozzle 5B (see Figure 3). Therefore, if the flat portion 1F is blasted, it can be determined that the part indicated by symbol A in Figure 4 has been blasted.

[0020] In blasting, when there are parts of the workpiece surface with different orientations, as shown in Figures 4A and 4B, it can be difficult to blast the entire workpiece surface using nozzles facing the same direction. With such complex metal surface shapes, the following risks exist: the nozzle may become clogged, preventing sufficient media contact, or the impact pressure of the media may decrease due to collisions between media from two directions, resulting in a failure to achieve the desired roughness. This is a problem that can occur not only in the threaded end sections of oil well pipes but also in inspections of objects with significantly different surface orientations, and the effectiveness of this embodiment is significant in such cases.

[0021] On the other hand, if the nozzle 5B becomes clogged and the blast media 4 cannot be sprayed, depending on the screw shape, the bottom corner A of the screw may not be blasted, as shown in Figure 5. In this case, as can be seen from Figure 5, the shoulder portion 1C remains unblasted, and the pipe becomes a defective product.

[0022] (Surface roughness evaluation device) The surface roughness evaluation device of this embodiment is a device for evaluating the surface roughness of a metal surface. The surface roughness evaluation device of this embodiment also targets areas with surface shapes in which multiple irregularities are formed, such as the pipe end thread portion 1. This disclosure is particularly effective when evaluating the effectiveness of a process that increases the surface roughness of a surface in an area where multiple shadows are formed by multiple irregularities. Specifically, the surface roughness evaluation device of this embodiment is a device for evaluating whether a metal surface has achieved a target surface roughness, such as through blasting. In other words, the surface roughness evaluation device of this embodiment is a device for evaluating the surface roughness of a metal surface in order to evaluate whether blasting has been performed correctly.

[0023] <Metal surface (area) to be evaluated> In this embodiment, the metal surface to be evaluated is divided into two regions: a first metal surface region MT1 and a second metal surface region MT2 (see Figure 1). The surface roughness (simply referred to as roughness) of each surface is then evaluated individually for each region MT1 and MT2.

[0024] The first metal surface region MT1 is the region of the metal surface formed by the outer surface portion 1E, which consists of the threaded portion body 1A and the seal portion 1B, and which constitutes the outer diameter surface of the pipe end threaded portion 1. The threaded portion body 1A and the seal portion 1B may be treated as separate regions and evaluated individually. This first metal surface region MT1 is primarily for evaluating the metal surface of the threaded portion body 1A. The threaded portion body 1A constitutes a metal surface on which a predetermined uneven shape is formed.

[0025] The second metal surface region MT2 is a metal surface region composed of a flat portion 1F consisting of a shoulder portion 1C and an inner surface portion 1D (the inner diameter surface near the pipe end face). In this embodiment, evaluation is performed on the inner surface portion 1D, taking into consideration interference with the blasting device 3. This is because if the inner surface portion 1D is blasted, the shoulder portion 1C can be considered to have been blasted. Note that the shoulder portion 1C can be directly evaluated by acquiring an image from an axially outward position of the oil well pipe 2. The inner surface portion 1D consists of a flat metal surface. Note that this embodiment is an example in which a surface roughness evaluation device is provided as part of the equipment of the blasting device 3.

[0026] <Device configuration> As shown in Figures 7 and 9, the surface roughness evaluation apparatus of this embodiment comprises a lighting device 10, an imaging device (camera 11), a setting unit 22, a calculation processing unit 12 consisting of a computer capable of image processing, and a position correction unit.

[0027] <Lighting device 10> As shown in Figure 4, the lighting device 10 includes a lighting device 10A for the first metal surface area MT1 and a lighting device 10B for the second metal surface area MT2. The lighting device 10A is configured to illuminate the pipe end threaded portion 1 from above (for example, perpendicular to the axis) using, for example, the threaded portion body 1A and the seal portion 1B. For example, the lighting device 10A is exemplified by an LED as the light source, and is composed of multiple LEDs arranged in the direction of the pipe axis. That is, the lighting device 10A is configured to illuminate the outer surface of the pipe end threaded portion 1 evenly. In this case, multiple illumination axes 10P of the lighting device 10A are set to be aligned in a straight line along the direction of the pipe axis. The lighting device 10B is configured to illuminate the lower circumferential portion of the inner diameter surface near the end of the pipe with illumination light. There are no particular restrictions on the individual light sources of the lighting device 10.

[0028] <Imaging device> The imaging device consists of a camera 11. The camera 11 includes a camera 11A for a first metal surface region MT1 and a camera 11B for a second metal surface region MT2. The camera 11A is positioned such that its imaging axis 11P is directed towards an illumination axis 10P located near the center of a row of illumination axes 10P arranged in the axial direction (see Figure 8), enabling it to image the illuminated area irradiated by the illumination device 10A. Furthermore, the camera 11A is positioned in the direction of the tube axis so that it can also image the area illuminated by the laser light described later. Camera 11B captures an image of the area including the inner diameter surface portion of the pipe end that is illuminated by the illumination device 10B. The images to be acquired can be either monochrome or color images. Furthermore, illumination and imaging shall be performed in a darkened environment. In other words, the image acquisition process shall be carried out in a darkroom (with a blackout curtain) that constitutes a closed space.

[0029] <Position correction section> The position correction unit comprises a laser beam irradiation device 13 and a correction processing unit 21. As shown in Figure 9, the correction processing unit 21 comprises a horizontal direction correction processing unit 21A and a vertical direction position correction unit 21B. The laser beam irradiation device 13 irradiates the outer diameter surface of the pipe near the threaded portion body 1A at the pipe end with laser light radiating from a direction estimated to be perpendicular to the pipe axis along the circumferential direction. The irradiation position is within the imaging range of the camera 11A.

[0030] The horizontal correction processing unit 21A performs image processing, such as binarization, on the image of the pipe end thread portion 1 to detect the position of the pipe end face within the image. Then, based on the detected pipe end face position (the lateral center position), it corrects the horizontal position of the pipe end thread portion 1 within the image. For example, it corrects the frame position of the image itself, or each region such as a bright area, so that the reference pipe axis position and the actual central axis of the pipe end thread portion 1 within the image coincide. The vertical position correction unit 21B detects the upper and lower end positions of the pipe in the image based on the changes in the intensity of the laser light captured by the camera 11A, and performs vertical position correction.

[0031] Here, as shown in Figure 8, camera 11A is capturing images from diagonally above the pipe. Therefore, if the pipe end thread portion 1 is displaced horizontally or vertically, the actual pipe end thread portion 1 will be captured in the image at a position displaced from the virtual pipe axis (reference axis). The correction processing unit 21 detects this displacement and corrects the image so that the axis of the actual pipe end thread portion 1 coincides with the reference axis. Alternatively, it corrects the position of the reference axis to the axis of the actual pipe end thread portion 1. When camera 11A images from directly above, the effect of vertical displacement is small. However, since camera 11B images the lower circumferential position near the end face of the pipe from an oblique angle above, vertical displacement may prevent the target imaging area from being captured. For this reason, horizontal and vertical correction is necessary. Here, the positions of areas such as the bright region ARA-1 and the dark region ARA-2 are defined based on the position of the reference axis.

[0032] <Settings section 22> The setting unit 22 obtains default values ​​for setting the bright area ARA-1 and the dark area ARA-2 for the image. "Regarding the setting of light and dark areas" Generally, surface roughness and brightness (the brightness of the captured image) are related: lower roughness results in a brighter image, while higher roughness results in a darker image. Furthermore, when the light source is close and the light is shone on the object being inspected at an angle nearly perpendicular to the illumination axis, the image becomes brighter and prone to halation. Conversely, when the point is farther from the light source and the illumination angle is shallower than perpendicular, the image becomes darker. In surface treatment processes, polishing processes such as buffing result in lower roughness, while roughening processes such as shot blasting result in increased roughness after processing.

[0033] In this embodiment, if it is possible to measure the surface roughness at each part and use a test specimen that has been pre-processed to an appropriate surface roughness, and if the range of image information such as the desired brightness of the bright and dark areas can be determined, then it is possible to determine that the product has the predetermined surface roughness based solely on the image information during production. In cases such as threaded components of oil well pipes, where the surface shape changes in a complex manner, using multiple lights and cameras is highly effective because it allows for obtaining a predetermined surface roughness on each of the surfaces.

[0034] Here, the area illuminated by the illumination light from the lighting device 10 is defined as the illumination area. For example, since the lighting device 10A illuminates the outer surface 1E of the pipe end thread portion 1 from above, the illumination area is, for example, the upper half of the circumference of the pipe (see Figure 8).

[0035] The bright area ARA-1 is a region selected from within the illuminated area that is relatively bright. In this embodiment, the bright area ARA-1 was selected from a region that includes a position intersecting the irradiation axis of the illumination device. In this embodiment, the bright area ARA-1 is defined as a region that includes all areas on the surface before surface treatment where halation occurs due to illumination light.

[0036] Here, when illumination light is shone on the metal surface of the outer surface 1E of the pipe end thread portion 1 before surface treatment, as shown in Figure 10, halation HA occurs at the position where it intersects with the irradiation axis and in its vicinity, i.e., at the position where the illumination light hits strongly. The maximum width HH (circumferential width of the pipe) of the area where halation HA occurs is then determined and stored in advance. This maximum width HH can be the same if the diameter of the oil well pipe 2 is approximately the same. Instead of the maximum width HH, the width of the average value detected along the axial direction of the halation HA location may also be used. However, it should be set so that the area where halation occurs is included as little as possible in the dark area described later.

[0037] Then, as shown in Figure 13, the setting unit 22 defines the width position in the circumferential direction of the tube with the maximum width HH stored above, centered on the position where it intersects with the irradiation axis of the lighting device, and defines the illuminated area ARA-1 as a rectangular area along the longitudinal direction that includes the entire seal portion 1B and the threaded body 1A. Note that the threaded body occupies most of the illuminated area ARA-1. Here, in Figure 13, there are positions along the widthwise center of the illuminated area ARA-1 where it intersects with multiple illumination axes 10P. In this embodiment, the bright area ARA-1A is defined as the bright area body region ARA-1A, which is a region within the bright area region ARA-1 that is centered on the position where it intersects the irradiation axis, but with a slightly narrower width in the circumferential direction.

[0038] Furthermore, the setting unit 22 sets a dark area ARA-2 as a region adjacent to the bright area ARA-1 in the circumferential direction of the tube and having a relatively lower luminance than the bright area ARA-1 (see Figure 13). The dark area ARA-2 is also set as a rectangular region having the same length in the longitudinal direction of the tube as the bright area ARA-1. Their lengths may differ. In this embodiment, it is a region that is narrower in width than the bright area ARA-1. The size and shape of the bright area ARA-1 and the dark area ARA-2 do not need to be the same. This is because the information such as luminance, used as an index of brightness to evaluate roughness, is converted into the ratio of the area of ​​a region with a specific luminance or higher to the entire evaluation range, or it is calculated using the average value of the luminance of a specific region.

[0039] Here, instead of determining the maximum width HH beforehand, for example, one-third of the tube diameter may be set as the width of the bright area ARA-1. It can be estimated that a width of approximately one-third of the diameter will include the area where the above-mentioned halation occurs. Also, the dark area ARA-2 may be set as having a width of, for example, one-quarter of the tube diameter.

[0040] Furthermore, the setting unit 22 stores, for example, the brightness of the area where the halation occurs, or a brightness that is reduced by a safety margin from the brightness of the halation, as the halation brightness. Here, the above explanation describes the settings for the outer surface 1E (first metal surface region MT1). The settings for the flat portion 1F (second metal surface region MT2) can be set using the same approach as described above.

[0041] The light area ARA-1 and dark area ARA-2 that form a pair used in each evaluation are selected and set from areas with similar metal surface shapes. When evaluating the surface roughness of a flat area, the light area ARA-1 and dark area ARA-2 that form a pair are selected and set from the flat area that has undergone surface treatment. In the case of the screw body, the light area ARA-1 and dark area ARA-2 that form a pair are selected and set from the area where the screw shape (concave and convex shape) is formed. It is preferable to select and set the light area ARA-1 and dark area ARA-2 that form a pair from areas where the surface shape conditions (concave and convex conditions, etc.) of the metal surface before surface treatment are the same or similar.

[0042] <Evaluation calculation unit 20> As shown in Figure 14, the evaluation calculation unit 20 includes an image area confirmation unit 20A, a brightness ratio calculation unit 20B, a dark area brightness calculation unit 20C, a bright area brightness calculation unit 20D, a comparison brightness calculation unit 20E, an image brightness confirmation unit 20F, and an evaluation unit 20G.

[0043] [Image area confirmation unit 20A] The image area confirmation unit 20A constitutes part of the processing of the setting unit. The image area confirmation unit 20A detects and sets the frames for the bright area ARA-1, the bright main area ARA-1A, and the dark area ARA-2 in the image captured by the camera 11A, based on the position where it intersects with the illumination axis 10P of the illumination device 10A and the respective specified values ​​that define the bright area ARA-1, the bright main area ARA-1A, and the dark area ARA-2 set in the setting unit 22 (see Figure 13). The image area confirmation unit 20A performs the same processing for the second metal surface area MT2. That is, the position where it intersects with the illumination axis 10P of the illumination device 10B and its vicinity is set as the bright area area ARA-1, and the area selected from its outer periphery is set as the dark area area ARA-2. Since the second metal surface area MT2 is not a metal surface with a pre-defined uneven shape, it is not necessary to separately set the bright area main region ARA-1A. The following explanation will use the first metal surface area MT1 as an example.

[0044] The image area confirmation unit 20A detects the bright area ARA-1 and the bright area main area ARA-1A based on the maximum width HH, for example, by taking the position where it intersects with the illumination axis 10P as the widthwise center position. It also sets the frame of the dark area ARA-2 at a position adjacent to the bright area ARA-1 in the circumferential direction of the tube. Here, the captured image is corrected by the correction processing unit 21 so that the position of the pipe end thread in the image coincides with the axis of the reference pipe (reference axis).

[0045] [Brightness ratio calculation unit 20B] The luminance ratio calculation unit 20B determines the luminance ratio, which is the proportion of the area within the bright area ARA-1 that is equal to or greater than a preset luminance (halation luminance). Here, as mentioned above, the halation brightness is the brightness at the location of the halation on an unblasted metal surface. For safety reasons, it is acceptable to set the halation brightness to be slightly lower than the actual halation brightness. Furthermore, if the illumination intensity is constant, the halation brightness measured on a metal surface of the same material with a low surface roughness may be used as the halation brightness. The luminance ratio is determined, for example, by the ratio of the number of pixels with a halation luminance or higher to the total number of pixels in the bright area ARA-1 of an image.

[0046] [Dark area brightness calculation unit 20C] The dark area luminance calculation unit 20C determines the average luminance of the dark area ARA-2 as the dark area luminance. [Brightness calculation unit 20D] The bright area luminance calculation unit 20D determines the bright area luminance as the average luminance of the main bright area region ARA-1A. The bright area luminance calculation unit 20D may determine the bright area luminance as the average luminance of the bright area region ARA-1. In this embodiment, in order to make the luminance of the bright area clearer, the average luminance of the main bright area region ARA-1A is determined. In the second metal surface region MT2, the average luminance of the bright area region ARA-1 is determined as the bright area luminance. [Comparison Brightness Calculation Unit 20E] The comparative luminance calculation unit 20E determines the difference in luminance between the bright area luminance and the dark area luminance obtained above as the luminance difference.

[0047] [Image brightness confirmation unit 20F] The image brightness confirmation unit 20F evaluates whether the brightness of the bright areas is below a preset lower threshold. The image brightness verification unit 20F evaluates that the brightness of the bright areas is below the lower limit threshold C, and if it does, it evaluates this to be a malfunction of the device and interrupts the process. The above-mentioned device malfunction is a detection of a device defect, such as a decrease in the light output of the lighting device 10 or a decrease in brightness due to dirt on the lens of the camera 11. The lower threshold C mentioned above can be determined through experimentation or other means. [Evaluation Unit 20G] The evaluation unit 20G performs an evaluation process to determine whether the metal surface to be evaluated has the target surface roughness. The evaluation unit 20G comprises a first evaluation unit 20G1 for the first metal surface region MT1 and a second evaluation unit 20G2 for the second metal surface region MT2.

[0048] [First evaluation unit 20G1] The processing of the first evaluation unit 20G1 will be explained according to the flow chart in Figure 15. In the first evaluation unit 20G1, in step S10, it is evaluated whether the luminance ratio is less than the first threshold (upper threshold). If the luminance ratio is less than the first threshold (upper threshold), the process proceeds to step S20. On the other hand, if the luminance ratio is above the first threshold (upper threshold), it is evaluated as a blasting abnormality (defect) because the luminance ratio is too high. For example, this abnormality occurs when blasting is not performed. It also occurs when the blasting is too thin and the surface roughness is less than the target surface roughness. In step S20, it is evaluated whether the dark area brightness is greater than a preset second threshold (lower brightness limit). If the dark area brightness is greater than the preset second threshold (lower brightness limit), the process proceeds to step S30.

[0049] On the other hand, if the brightness of the dark area is below a preset second threshold (lower brightness B), it is evaluated as a blasting abnormality. This abnormality occurs, for example, when the pipe end threaded section 1 to be evaluated is not installed. Here, even with just the evaluation in step S10, the metal surface being evaluated can be assessed as having the target surface roughness mentioned above, but in order to further improve the evaluation accuracy, the evaluation in step S20 is performed.

[0050] Figure 10 shows an example of an unblasted state, and Figure 11 shows an example of a blasted state. Figure 12 shows an example of a lightly blasted state. As can be seen in Figures 10 to 12, the dark area brightness is higher in the blasted state than in the unblasted state. Therefore, the second threshold should be set to a value higher than the dark area brightness of the unblasted state. More preferably, the second threshold should be set to a brightness that is, for example, smaller than the dark area brightness measured in the blasted state by a safety margin. Alternatively, the second threshold may be set to, for example, an intermediate value between the brightness in the unblasted state and the brightness in the blasted state. In other words, the second threshold can be determined by experimentation or other means.

[0051] Then, when proceeding to step S30, the metal surface to be evaluated can be evaluated to have the above-mentioned target surface roughness. In step S30, it is evaluated whether the difference in brightness between the bright and dark areas exceeds a preset third threshold. If the difference in brightness between the bright and dark areas exceeds the preset third threshold, the evaluation is changed to indicate that the surface roughness of the metal surface being evaluated is smaller than the target surface roughness, and it is evaluated as a blasting abnormality.

[0052] If the difference in brightness between the bright and dark areas is below a predetermined third threshold, the surface roughness is evaluated as meeting the target, and the blast treatment is deemed successful. In Figure 10, which shows the unblasted surface, the brightness difference was 162. In Figure 11, which shows the blasted surface, the brightness difference was 76. In Figure 12, which shows a lighter blasted surface, the brightness difference was 141. In this case, the third threshold is set to 90, which is greater than 76, taking into account the variability (safety margin).

[0053] In the above example, we introduced an example in which, from the perspective shown in Figure 22, the first camera evaluates all items except (2), and the second camera evaluates part (2), and three threshold conditions are used for the judgment. Based on the above, the number of threshold conditions and their values ​​can be predetermined through experiments or other means, depending on the surface shape of the target metal surface.

[0054] [Second evaluation unit 20G2] The processing of the second evaluation unit 20G2 will be explained according to the flow chart in Figure 16. In the second evaluation unit 20G2, in step S100, it is evaluated whether the luminance ratio is less than the first threshold (upper threshold) and whether the dark area luminance is greater than a preset second threshold (lower luminance). If the conditions are met, proceed to step S110. On the other hand, if the conditions are not met, it will be evaluated as a blast treatment abnormality. For example, abnormalities such as the absence of the pipe end threaded portion 1 to be treated, or insufficient blast treatment.

[0055] In step S110, it is evaluated whether the difference in brightness between the bright and dark areas exceeds a preset third threshold. If the difference in brightness between the bright and dark areas exceeds the preset third threshold, the evaluation is changed to indicate that the surface roughness of the metal surface being evaluated is smaller than the target surface roughness, and it is evaluated as a blasting abnormality. This means that if the difference in brightness between the bright and dark areas is below a predetermined third threshold, the surface roughness of the metal surface being evaluated can be assessed as the target surface roughness. The surface roughness of the metal surface being evaluated can be assessed using only this method.

[0056] If the difference in brightness between the bright and dark areas is below a predetermined third threshold, the surface roughness is evaluated as meeting the target, and the blast treatment is deemed successful. Here, each of the above thresholds can be determined by experimentation or other means. Alternatively, the first evaluation unit 20G1 and the second evaluation unit 20G2 may set similar evaluation threshold values ​​to different values, that is, to be set individually for each. Then, if the first evaluation unit 20G1 gives a passing grade, and the second evaluation unit 20G2 also gives a passing grade, the blast treatment of the entire pipe end threaded portion 1 is evaluated as passing.

[0057] (Operation and other functions) After various studies, the inventors found that, regarding the evaluation of the blast condition of the screw part body 1A, it is impossible to clearly evaluate the quality of the blast treatment by using only the average brightness of the bright areas (bright area brightness) or the average brightness of the area away from the illumination axis (dark area brightness) through image processing. Furthermore, if the sum of the bright area brightness and the dark area brightness, i.e., the average brightness of the entire illuminated area, is calculated, both unblasted and blasted parts will have similar values, making clear evaluation impossible. In this embodiment, the reason for using the luminance ratio in the bright area ARA-1 is as follows:

[0058] Note that the luminance ratio differs from the evaluation using the average luminance in the bright area ARA-1, which was set as the area including the halation occurrence location before blasting. The luminance ratio evaluates how much the luminance above a certain level (luminance that appears bright) has decreased in the bright area ARA-1. The luminance ratio evaluates, for example, how much halation has decreased. In particular, on metal surfaces with uneven shapes, there are clear differences in brightness even within the bright area ARA-1, and the area where halation occurs can be clearly evaluated from the ratio of these differences. Since the above ratio of light and dark is influenced by the pre-set uneven surface shape, for example, the halation brightness can be set based on the brightness ratio of a metal surface that has been properly blasted.

[0059] Now, consider the case where one of the two blast nozzles 5A and 5B becomes clogged during the blasting process. In this case, there is a risk that a small corner of the screw root may remain unblasted (see Figures 4 and 5). In this case, the brightness of the bright areas, the brightness of the dark areas, and the difference between the brightness of the bright and dark areas will each change slightly, but the changes are so small that it is difficult to evaluate them clearly. In contrast, the brightness ratio changes relatively more significantly in the case of such defects. Therefore, it is possible to evaluate whether there is a partially unblasted state by checking whether the brightness ratio is below the first threshold.

[0060] However, in flat surfaces without irregular shapes such as screw-like shapes, such as the second metal surface region MT2, it is estimated that the accuracy will decrease if only the brightness ratio is less than or equal to the first threshold is considered. Therefore, in this embodiment, the evaluation accuracy is improved by evaluating whether the dark area brightness is equal to or greater than the second threshold.

[0061] Next, I will explain the reason for evaluating whether the brightness in dark areas is above a second threshold. First, let's describe metal surfaces that have not undergone blasting. Such metal surfaces have low surface roughness, and when illuminated, halation occurs and the surface is bright at the point where it intersects with the illumination axis 10P and in its vicinity (the bright area equivalent to the bright area ARA-1). However, even in the area illuminated by the illumination light, the area away from the point where it intersects with the illumination axis 10P (the dark area ARA-2) is significantly darker and has low brightness. In other words, as shown in Figure 17(a), when illumination is applied to a surface with little surface roughness, only specularly reflected light is captured by the camera 11. As a result, only the area illuminated by specularly reflected light (the bright area) is halated, and the surrounding areas outside the halated area are imaged as very dark.

[0062] On the other hand, after surface treatment, the metal surface has a high degree of surface roughness. Therefore, when illumination is shone on such a surface, because the surface is rough, a small amount of diffusely reflected light is captured by the camera 11 from multiple directions, as shown in Figure 17(b). As a result, the brightness of the area directly illuminated decreases, and the peripheral area (dark region ARA-2) away from the point where the illumination axes 10P intersect appears relatively brighter in the image. Thus, it can be determined that blast processing is being performed when the brightness of the dark areas exceeds the second threshold.

[0063] This tendency is particularly pronounced on curved surfaces, such as the threaded ends of pipes. In other words, as can be seen from Figure 10, which shows the unblasted state, the surface roughness of the threaded portion is low in the unblasted state, so the illumination light from the lighting device is strongly reflected only near the illumination axis 10P. On the other hand, the surface of the blasted threaded portion is rougher, so as shown in Figure 11, the light from the lighting device is diffusely reflected, allowing the entire end of the tube to be brightly imaged. Note that in Figure 12, where the blasting is light, the average brightness of the dark area ARA-2 is lower compared to Figure 11. Thus, it is possible to evaluate the surface roughness by whether or not the brightness of the dark area is above a second threshold.

[0064] Furthermore, because the oil well pipe 2 is long, the pipe end thread portion 1 may be displaced laterally (horizontally) or vertically (vertically) relative to the pipe axis due to the bending of the oil well pipe 2. If this displacement occurs, it will negatively affect the above evaluation using images, so in this embodiment, the position of the pipe end thread portion 1 in the image is corrected. The correction in this embodiment is, for example, performed on the image itself so that the axis of the actual pipe end thread portion 1 coincides with the axis of the oil well pipe (reference axis).

[0065] For the reasons described above, this embodiment can be applied even to metal surfaces with predetermined irregularities, such as threaded ends 1 of oil well pipes 2. Furthermore, in evaluating the quality of surface treatments such as blasting, automatic evaluation by the device becomes possible instead of visual inspection. As a result, productivity is improved in this embodiment, and it becomes possible to prevent a large number of defective pipes due to blasting defects.

[0066] In this embodiment, the outer surface portion 1E located on the upper side of the entire circumference of the pipe end thread portion 1 (the upper part of the thread portion body 1A and the upper part of the seal portion 1B) is partially sampled and evaluated. In other words, the blast treatment of the entire pipe end thread portion 1 is evaluated by this partial evaluation. Furthermore, the primary objective of this embodiment is not to detect surface treatment defects on the metal surface being evaluated, but rather to evaluate whether the entire metal surface being evaluated has achieved the target surface roughness.

[0067] "Regarding the application to threaded ends of oil well pipes" Below, we will further describe examples of setting conditions and other factors when the apparatus and method of this embodiment are applied to the pipe end thread portion 1. (Example of device configuration and processing) The following provides supplementary information regarding the device configuration and an example of processing in this embodiment. Here, Figure 18 shows an example of the conditions for camera 11A, camera 11B, and laser light irradiation device 13 used in this embodiment. (a) shows an example of the conditions for camera 11A, (b) shows an example of the conditions for camera 11B, and (c) shows an example of the conditions for each of the laser light irradiation devices 13.

[0068] <Regarding optimal imaging conditions> • For the pipe end threaded portion 1, the width (length in the x-axis direction) is preferably, for example, 30 mm to 300 mm. Lighting devices 10A and 10B emit white light with a power consumption of, for example, 16 to 46 watts. The correlated color temperature is, for example, 5600 K. An example of camera 11 specifications is shown below (Figure 18(a)). Type: 2M Gray Image sensor: Interline type, 1 / 1.8-inch fixed CCD image sensor Pixel count: 1600 horizontal pixels × 1200 vertical pixels Pixel size: 4.4μm × 4.4μm Frame rate: Maximum 30 frames / second

[0069] Here, the acquisition of each image, i.e., image capture, is performed as follows, for example. 0.5 msec after imaging begins with camera 11A, illumination light is emitted from illumination device 10A for 1 msec. The exposure time (shutter speed) of camera 11A is, for example, 20 msec. After that, a buffer time of, for example, 80 msec is provided. The reason for providing this buffer time is to prevent the light emitted by illumination device 10A from being captured by the next imaging camera 11B. After allowing sufficient buffer time, imaging is performed using camera 11B. 0.5 msec after imaging by camera 11B begins, light is shone from illumination device 10B for 1 msec. The exposure time (shutter speed) of camera 11B is, for example, 10 msec.

[0070] The reason why the exposure time (shutter speed) of camera 11A is 20 msec is longer than the exposure time (shutter speed) of camera 11B, which is 10 msec, is as follows: In other words, it is to clearly capture the irradiation position RR of the laser beam emitted from the laser beam irradiation device 13 for correcting the vertical position of the pipe end bend of the oil well pipe 2 on the image. The laser light emitted from the laser beam irradiation device 13 for correcting the vertical position of the pipe end bend may be kept lit at all times, or it may be lit only when imaging is being performed.

[0071] <An example of a method for determining the threshold for "bright area brightness"> The brightness threshold for bright areas is set to detect a decrease in the light output of the lighting device 10A. When comparing the "lower limit of brightness in the bright area before blasting" with the "lower limit of brightness in the bright area after blasting," the brightness in the bright area after blasting will always be lower due to diffuse reflection of light. From this, the threshold value of the bright part luminance is, for example, a value obtained by multiplying the lower limit value of the bright part luminance after blasting, which has been determined in advance, by a coefficient T (0.5 ≤ T ≤ 0.9). The coefficient T is a safety factor for adding a safety margin. By this, it becomes possible to evaluate normally. The coefficient T is preferably 0.7 ≤ T ≤ 0.8. When 0.9 < T, there are many false detections. When T < 0.5, there is a possibility that the discovery of the light quantity decrease of the lighting device 10A may be delayed.

[0072] <An example of a method for determining the threshold value (the second threshold value) of the "dark part luminance"> The threshold value of the dark part luminance is mainly for detecting a case where the blasting treatment is thin or a state where the pipe end screw part 1 is not installed. Obtain the "dark part luminance at the time of blasting with the air pressure at which it passes when blasting" and the "dark part luminance at the time of blasting with the air pressure deliberately lowered to a non - passing air pressure when blasting". Then, as the threshold value of the dark part luminance, for example, set the intermediate value of the two dark part luminances.

[0073] Actually, when blasting was performed at an air pressure of 0.24 Mpa, it passed, and when blasting was performed at an air pressure of 0.23 Mpa, it did not pass. The dark part luminance of the qualified product blasted at an air pressure of 0.24 Mpa was 25, and the dark part luminance of the non - qualified product blasted at an air pressure of 0.23 Mpa was 11. Then, for example, set 18, which is the intermediate value between 25 and 11, as the threshold value of the dark part luminance. When an upper limit threshold value is required, for example, by setting 255 as the upper limit threshold value, it becomes possible to evaluate the pass or fail normally.

[0074] <An example of a method for determining the threshold value (the third threshold value) of the "bright part luminance - dark part luminance"> The threshold value of the "bright part luminance - dark part luminance" is mainly for the purpose of detecting a case where the blasting treatment is thin. Obtain the "bright part luminance - dark part luminance at the time of blasting with the passing air pressure" and the "bright part luminance - dark part luminance at the time of blasting with the air pressure deliberately lowered to a non - passing air pressure when blasting". Then, set the intermediate value of the two as, for example, the threshold value (the third threshold value) of the "bright part luminance - dark part luminance".

[0075] In actual testing, an air pressure of 0.24 MPa resulted in a successful blast treatment, while an air pressure of 0.23 MPa resulted in a failed blast treatment. The "bright area brightness - dark area brightness" of the successful product blasted at 0.24 MPa was 52, while the "bright area brightness - dark area brightness" of the failed product blasted at 0.23 MPa was 82. For example, 67, which is the midpoint between 52 and 82, can be set as a third threshold. If a lower threshold for the "bright area brightness - dark area brightness" threshold is needed, setting it to 0, for example, allows for accurate quality evaluation. Furthermore, if there is a discrepancy between the evaluation using the threshold set as described above and the operator's judgment for each threshold, the evaluation accuracy can be improved by fine-tuning the set threshold each time.

[0076] <Camera 11A: Evaluation of blast quality based on brightness ratio on the outer surface 1E> In the unblasted state, the surface roughness of the screw threads is low, and the areas directly hit by light emitted from the illumination device 10A experience halation. If the number of pixels captured by this halation exceeds a set threshold, it can be detected as a high number of halated pixels. In this case, the operator will determine that "the blasting process is unsuccessful because halation has occurred."

[0077] Conversely, if the number of pixels in which halation is captured is below a set threshold, it can be detected as a large number of pixels that are not affected by halation. In this case, the operator will determine that "no halation occurred, therefore the blasting process is acceptable." Furthermore, if the percentage of pixels judged to be "unsuitable for blasting due to halation" is smaller than the brightness percentage of the unblasted pixels, then the pixels can be evaluated as having been blasted. In other words, whether a pixel has been blasted or not can be evaluated based on its brightness percentage.

[0078] Here, when the outer surface 1E of the pipe end thread portion 1 of the oil well pipe 2 is illuminated using the illumination device 10A, the parts of the thread crest, thread base, thread side, the mill scale on the outer surface of the pipe, and the seal portion 1B are not individually evaluated. However, such evaluation is not necessary.

[0079] One method for evaluating the surface roughness (quality of blast treatment) of the thread crest and thread base of a screw is to measure (evaluate) the surface roughness of the seal portion 1B and evaluate the quality of the blast treatment. This evaluation assumes that the surface roughness of the seal portion 1B is equivalent to the surface roughness of the thread crest and thread base of the screw. In other words, as shown in Figure 2, the blast treatment is performed on the entire surface of the oil well pipe 2 with a constant pressure while the oil well pipe 2 is rotated. Therefore, in a single blast treatment, the surface roughness of areas other than the seal portion 1B can be considered equivalent to the surface roughness of the seal portion 1B.

[0080] <An example of a method for determining the threshold for the luminance ratio on the outer surface 1E> "The threshold for the brightness ratio on the outer surface 1E can mainly be used to detect cases where the bottom corner of the hook screw is unblasted, where the screw part including the black scale is unblasted, or where no blasting treatment was performed."

[0081] [When the bottom corner B of the hook screw is not blasted (Figure 4)] When nozzle 5A is clogged, the screw bottom corner B may not be blasted, as shown in Figure 4. Therefore, halation is detected and expressed as the percentage of the halation area (the percentage of pixels where halation occurs). Based on this, for example, the midpoint between the halation area percentage and the halation area percentage of a blasted, approved product is set as the threshold for the brightness percentage.

[0082] In actual testing, when nozzle 5A was clogged, in the case of Figure 4, the screw bottom corner B remained unblasted, and the detected halation area was 82. The unit of the area value is the number of pixels (the same applies below). The threshold value is set to 41, which is the midpoint between this halation area value of 82 and the halation area of ​​0 for a blasted, acceptable product. If a lower limit for the threshold is required, setting it to 0 will allow for proper quality evaluation.

[0083] [When the bottom corner A of the non-hooked screw is not blasted (Figure 5)] When nozzle 5B is clogged, as shown in Figure 5, the screw bottom corner A will not be blasted. As a result, halation is detected and measured as a percentage of the halation area (percentage of pixels). For this reason, for example, an intermediate value between the percentage of the halation area and the percentage of the halation area of ​​a blasted, approved product is set as a threshold (upper threshold).

[0084] In actual testing, when nozzle 5B was clogged, in the case of Figure 7, the screw bottom corner A remained unblasted, and a halation area of ​​94 was detected. For example, the intermediate value of 47 between this halation area value of 94 and the halation area of ​​0 for a blasted, acceptable product should be used as the threshold (upper threshold). If a lower threshold is needed, setting it to 0 will allow for proper quality evaluation. Furthermore, if there is a discrepancy between the evaluation using the thresholds set as described above and the operator's judgment, the evaluation accuracy can be improved by fine-tuning the set thresholds each time.

[0085] <Example of blast quality evaluation based on brightness ratio in the inner surface 1D> As can be seen from Figure 6(b), if the nozzle 5B becomes clogged in the same way as described above, the shoulder portion 1C and the inner surface portion 1D will inevitably remain unblasted. In this case, the surface roughness of the inner surface portion 1D becomes low, causing halation when the light emitted from the lighting device 10B hits the inner surface portion 1D (see Figure 19). Note that the symbol HA in Figure 19 indicates the location where halation occurs.

[0086] If the number of pixels in an image that are affected by the halation exceeds a set threshold, it is detected as a high number of halated pixels. In this case, the operator will determine that "the blasting process is unsuccessful because halation has occurred." Conversely, if the number of pixels in which halation is captured is below a set threshold, it is detected as a large number of pixels without halation. In this case, the operator will determine that "no halation occurred, therefore the blasting process is successful."

[0087] Then, by setting a brightness percentage lower than the brightness percentage (the percentage of pixels judged to be "unsuccessful in blasting due to halation") as a threshold, it is possible to evaluate whether the surface has been blasted or not. This evaluation can be used as a substitute for detecting unblasted areas on the screw root corner A and shoulder 1C (see Figures 4 and 5). In this embodiment, with illumination from diagonally above, the shoulder portion 1C is the end face of the tube, so reflected light cannot be detected. Therefore, the surface roughness of the inner surface portion 1D is used for evaluation.

[0088] <Example of a method for determining the threshold for the luminance ratio of the inner surface 1D> The threshold for the brightness ratio in the inner surface 1D can primarily detect cases where the non-hook screw bottom corners are not blasted. When nozzle 5B is clogged, the shoulder portion 1C and inner surface portion 1D will always remain unblasted, as shown in Figure 6. Therefore, halation is detected in the inner surface portion 1D, and the condition can be detected by the brightness ratio, which is the ratio of the halation area. Then, for example, the midpoint between the ratio of the halation area and the ratio of the halation area of ​​a blasted, acceptable product is set as a threshold.

[0089] In actual testing, when nozzle 5B is clogged, as shown in Figure 6, the shoulder portion 1C and inner surface portion 1D will always remain unblasted. In this case, the halation area on the inner surface portion 1D was detected to be 52. For example, a threshold value of 26 is set as the midpoint between this halation area value of 52 and the halation area of ​​0 for a blasted, acceptable product. If a lower limit for the threshold is required, setting it to 0 allows for accurate quality evaluation. Furthermore, if there is a discrepancy between the evaluation using the threshold set as described above and the operator's judgment, the evaluation accuracy can be improved by fine-tuning the set threshold each time.

[0090] <An example of position correction (horizontal and vertical) for the pipe end thread 1> Because long-axis pipes are transported and processed, slight misalignments occur in the horizontal position of the pipe ends relative to the pipe's axis. Therefore, horizontal (lateral) position correction is required for each pipe. Furthermore, due to the different curvatures of each pipe, the position of the vertical pipe end thread 1 deviates from the reference position for each pipe. Therefore, it is necessary to perform horizontal and vertical position corrections for each pipe.

[0091] [Horizontal direction] Horizontal position correction is performed by image processing. The method for correcting minute deviations in the horizontal position of the pipe end is as follows: Within the evaluation frame shown in Figure 20, detection is performed from right to left, that is, from the side furthest from the pipe end towards the pipe end, and the point where the intensity changes from black to white is detected by image processing to recognize the pipe end. Then, based on the recognized pipe end position (the center position in the width direction), the horizontal (lateral) position of the pipe end thread portion 1 is corrected.

[0092] [Vertical direction] Vertical position correction is performed by using laser light from the laser light irradiation device 13 and performing image processing. Due to the bending of the pipe, the vertical position of the pipe end thread section 1 changes. For example, in small-diameter oil well pipes with an outer diameter of less than 73.1 mm, the bending of the pipe end of the oil well pipe 2 is large, resulting in a change of up to 4 mm / 300 mm. Therefore, laser irradiation is being used as a measure to correct the vertical position.

[0093] As shown in Figure 21, a laser beam is shone from diagonally above, slightly away from the pipe end thread 1 of the oil well pipe 2, towards the pipe axis. The laser beam is shone as light directed vertically to the side of the pipe. Then, in image processing of the image including the laser beam irradiation position RR, the boundary between the black and white areas where the laser beam is interrupted within the evaluation frame is recognized as the upper and lower edges Eg1 and Eg2 of the pipe end thread 1. By recognizing the upper and lower edges Eg1 and Eg2 of the pipe end thread in this way, even if there is a bend in the pipe end thread 1 in the vertical direction, it is possible to accurately recognize the actual axis of the pipe end thread 1 by following the bend. Then, vertical position correction is performed based on the recognized upper and lower edges Eg1 and Eg2. Furthermore, for oil well pipes exceeding the small diameter size 2 (73.1 mm or larger), the rigidity of the pipe increases, and positional displacement tends to decrease. However, minute displacements still occur, so it is preferable to perform correction using laser irradiation for vertical position correction.

[0094] <An example of a blasting failure pattern and evaluation method> Figure 22 shows an example of a defect pattern that occurs at the threaded end portion 1 of the oil well pipe 2. This section provides a summary of possible blast defects that may occur in the pipe end thread section 1, their causes, locations, and examples of evaluation methods.

[0095] (1) When the "blast is thin" The cause of the defect is "a decrease in air pressure during blasting (e.g., holes in hose fittings, wear on nozzle spray holes)." The areas where blasting defects occurred are "the outer surface 1E (threaded section, seal section 1B), and the shoulder section 1C." The evaluation method involves, for example, imaging the outer surface 1E with the camera 11A and then evaluating whether the brightness of the dark areas falls outside a set threshold range. Alternatively, after imaging the outer surface 1E with the camera 11A, the evaluation can be performed by determining whether the difference between the brightness of the bright areas and the brightness of the dark areas falls outside a set threshold range.

[0096] (2) In the case where the bottom corner of the screw on the non-hook part is not blasted. The cause of the defect is "nozzle 5B clogging". The locations where the blasting defect occurred are "outer surface 1E (screw bottom corner of the non-hook part) and shoulder part 1C". The evaluation method involves, for example, imaging the inner surface 1D with the camera 11B, binarizing the halation areas, and evaluating whether the total value of the halation (percentage of halation area: brightness percentage) falls outside the range of a set threshold.

[0097] (3) If the bottom corner of the hook screw is not blasted However, the cause of the malfunction was "nozzle 5A clogging". The location where the blasting malfunction occurred was "external surface 1E (screw bottom corner of the hook)". The evaluation method involves, for example, imaging the outer surface 1E with the camera 11A, binarizing the halation areas, and evaluating whether the total value of the halation (percentage of halation area: brightness percentage) falls outside the range of a set threshold.

[0098] (4) If the threaded portion including the black scale is not blasted The cause of the defect is that "the nozzle fixing jig shifts, causing a significant change in the nozzle angle (this only occurs when changing sizes)." The evaluation method involves, for example, imaging the outer surface 1E with the camera 11A, binarizing the halation areas, and then evaluating whether the total value of the halation (percentage of halation area: brightness percentage) falls outside the range of a set threshold.

[0099] (5) In the case of "no blast" The cause of the malfunction is "a significant drop in air pressure (due to a hole in the hose fitting, wear on the nozzle spray hole, etc.)." The evaluation method involves, for example, imaging the outer surface 1E with camera 11A and then evaluating whether the brightness of the dark areas falls outside the set threshold range. Alternatively, after imaging the outer surface 1E with camera 11A, the evaluation can be performed by checking whether the difference between the brightness of the bright areas and the brightness of the dark areas falls outside the set threshold range. Furthermore, after imaging the outer surface 1E with camera 11A, the halation areas are binarized, and the evaluation can be performed by checking whether the total value of the halation (halation area ratio: brightness ratio) falls outside the set threshold range.

[0100] (6) In the case of "No material to be imaged" The cause of the malfunction is that "the tube is pushed out of the field of view (for example, due to incorrect installation of the inner stopper when changing sizes)." The evaluation method involves, for example, imaging the outer surface 1E with camera 11A and then evaluating whether the brightness of the dark areas falls outside the set threshold range. Alternatively, after imaging the outer surface 1E with camera 11A, the evaluation can be performed by checking whether the difference between the brightness of the bright areas and the brightness of the dark areas falls outside the set threshold range. Furthermore, the decrease in light intensity of the lighting device 10 can be evaluated by imaging the outer surface 1E with the camera 11A and checking whether the brightness of the bright areas falls outside the set threshold range.

[0101] By performing the evaluation process as described above, the apparatus of this embodiment can detect all blast defects based on surface roughness for the pipe end thread portion 1 of the oil well pipe 2. This makes it possible, for example, to automatically evaluate the blast quality of the threaded end portion 1 of the oil well pipe 2.

[0102] (modified version) The above explanation used the evaluation of the surface roughness of a metal surface after processing as an example, where the roughness after processing is higher than before processing due to surface treatment such as blasting on the metal surface. This disclosure is also applicable to evaluating the surface roughness of a metal surface after processing, in cases where the roughness after processing is lower than before processing due to surface treatment such as buffing. In this case, based on the concept described above, for example, if the difference in brightness between the brightness of the bright areas and the brightness of the dark areas exceeds a predetermined third threshold, the metal surface to be evaluated is evaluated as having the target surface roughness. The third threshold can be determined by conducting experiments corresponding to the target surface roughness or by measuring the metal surface after the surface treatment has been properly performed.

[0103] (others) This disclosure may also take the following form: (1) A surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, The illumination device irradiates the metal surface to be evaluated with illumination light. The above-mentioned metal surface to be evaluated, illuminated by the above-mentioned light, is imaged. In the captured image, we define the bright areas, which are regions with high brightness, and the dark areas, which have lower brightness than the bright areas. Based on the brightness of the bright areas and the brightness of the dark areas, the surface roughness of the metal surface to be evaluated is evaluated. A method for evaluating surface roughness characterized by the following features.

[0104] (2) The average brightness of the above bright area is determined as the brightness of the bright area, The average brightness of the dark area described above is calculated as the dark area brightness. If the difference in brightness between the bright area brightness and the dark area brightness is less than or equal to a predetermined third threshold, the metal surface being evaluated is evaluated as having the target surface roughness. (3) Determine the luminance ratio, which is the proportion of the area in the bright area above a predetermined luminance level. Based on the above brightness ratio, the surface roughness of the metal surface to be evaluated is assessed.

[0105] (4) When the above luminance ratio is less than the first threshold set in advance, the metal surface to be evaluated is evaluated as having the target surface roughness. (5) The predetermined brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or the brightness obtained by reducing that brightness by a safety margin. (6) Define the dark area in the captured image that has a lower brightness than the bright area, The average brightness of the dark area described above is calculated as the dark area brightness. Based on the above brightness ratio and dark area brightness, the surface roughness of the metal surface to be evaluated is assessed.

[0106] (7) When the luminance ratio is less than a preset first threshold and the dark area luminance is greater than a preset second threshold, the metal surface to be evaluated is evaluated as having the target surface roughness. (8) The second threshold is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. (9) The average brightness of the above bright area is determined as the brightness of the bright area, If the difference in brightness between the above-mentioned bright area brightness and the above-mentioned dark area brightness exceeds a preset third threshold, the evaluation of the metal surface being evaluated is changed from "as the target surface roughness" to "as having a surface roughness less than the target surface roughness."

[0107] (10) A surface roughness evaluation method that evaluates whether the surface roughness of a metal surface is a target surface roughness, wherein the metal surface has a region whose surface shape is a predetermined uneven shape, The lighting device illuminates the metal surface of the area with the above-mentioned uneven shape with illumination light. The above-mentioned metal surface to be evaluated, illuminated by the above-mentioned light, is imaged. In the captured image, we define the bright areas, which are the brighter regions among the areas with the above-mentioned uneven shape. The luminance ratio, which is the proportion of the area in the above bright region that has a luminance equal to or greater than a predetermined value, is determined. Based on the above brightness ratio, the surface roughness of the metal surface to be evaluated is evaluated. A method for evaluating surface roughness characterized by the following features.

[0108] (11) If the above luminance ratio is less than a first threshold set in advance, the metal surface to be evaluated is evaluated as having the target surface roughness. (12) The predetermined brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or the brightness obtained by reducing that brightness by a safety margin. (13) In the image captured above, define the dark area in the region with the uneven shape above, which has a lower brightness than the bright area above, The average brightness of the dark area described above is calculated as the dark area brightness. The metal surface being evaluated is evaluated as having the target surface roughness when the above-mentioned brightness ratio is less than the first threshold and the above-mentioned dark area brightness is greater than the preset second threshold.

[0109] (14) The second threshold is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. (15) The average brightness of the above bright area is determined as the brightness of the bright area, The metal surface being evaluated is evaluated as having the target surface roughness if the above-mentioned luminance ratio is less than the first threshold, the above-mentioned dark area luminance is greater than the preset second threshold, and furthermore, the difference in luminance between the above-mentioned bright area luminance and the above-mentioned dark area luminance is less than or equal to the preset third threshold. (16) The pre-set groove shape is a screw shape. (17) The metal surface to be evaluated above is a metal surface whose surface has been roughened by surface treatment. (18) The bright area is the area that includes the portion where halation occurs when the illumination light is shone on the metal surface before the surface treatment is applied. (19) The predetermined brightness mentioned above is the brightness at the location of the halation that occurs when the illumination light is shone on the metal surface before the surface treatment is applied, or the brightness reduced by a safety margin from that brightness.

[0110] (20) The metal surface to be evaluated is the threaded end of the oil well pipe, The position of the pipe end is detected by image processing of the image taken of the pipe end. The horizontal position of the pipe end in the image is corrected based on the detected pipe end position. (21) A laser beam is shone on the tube in the circumferential direction, and an image is taken of the tube that has been shone with the laser beam. The vertical position of the tube is detected by the position of the laser beam in the captured image. The vertical position of the pipe end in the image is corrected based on the detected vertical position of the pipe.

[0111] (22) A surface roughness evaluation device for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, A lighting device that illuminates the metal surface to be evaluated with illumination light, An imaging device that images the illuminated area, which is the area illuminated by the above-mentioned illumination light, A setting unit that selects a region within the illuminated area of ​​the captured image and sets a bright area, which is a region with high brightness, and a dark area, which has lower brightness than the bright area. An evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the brightness of the bright area and the brightness of the dark area, A surface roughness evaluation apparatus characterized by comprising the following features.

[0112] (23) A bright area brightness calculation unit that determines the average brightness of the bright area as the bright area brightness, The system includes a dark area brightness calculation unit that determines the average brightness of the dark area as the dark area brightness, The evaluation unit determines that the metal surface being evaluated has the target surface roughness if the difference in brightness between the bright area brightness and the dark area brightness is less than or equal to a preset third threshold. (24) The bright area is provided with a brightness ratio calculation unit that calculates the brightness ratio, which is the proportion of the area with a brightness equal to or greater than a preset brightness, The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio. (25) The evaluation unit evaluates the metal surface to be evaluated as having the target surface roughness when the brightness ratio is less than a preset first threshold.

[0113] (26) The predetermined brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or the brightness obtained by reducing that brightness by a safety margin. (27) The setting unit sets the dark area in the captured image to have a lower brightness than the bright area, Furthermore, it has a dark area brightness calculation unit that determines the average brightness of the dark area as the dark area brightness, The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio and the brightness of the dark areas.

[0114] (28) The evaluation unit evaluates the metal surface to be evaluated as having the target surface roughness when the luminance ratio is less than a preset first threshold and the dark area luminance is greater than a preset second threshold. (29) The second threshold is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. (30) A bright area luminance calculation unit that determines the average luminance of the bright area as the bright area luminance, If the difference in brightness between the brightness of the bright area and the brightness of the dark area exceeds a preset third threshold, the evaluation unit changes the evaluation of the metal surface being evaluated from "with target surface roughness" to "with surface roughness less than the target surface roughness."

[0115] (31) A surface roughness evaluation device that evaluates whether the surface roughness of a metal surface is a target surface roughness, which is a metal surface having a region whose surface shape is a predetermined uneven shape, A lighting device that irradiates illumination light onto the metal surface of the region having the above-mentioned uneven shape, An imaging device that images the illuminated area, which is the area illuminated by the above-mentioned illumination light, A setting unit for setting a bright area, which is a bright area among the areas with the above-mentioned uneven shape, selected from the above-mentioned illumination area within the captured image, A luminance ratio calculation unit that determines the luminance ratio, which is the proportion of the area in the bright area above a predetermined luminance level, An evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the above brightness ratio, A surface roughness evaluation apparatus characterized by comprising the following features.

[0116] (32) The evaluation unit evaluates the metal surface to be evaluated to have the target surface roughness if the brightness ratio is less than a preset first threshold. (33) The predetermined brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or the brightness obtained by reducing that brightness by a safety margin. (34) The setting unit determines the dark area in the captured image where the brightness is lower than the bright area among the areas with the uneven shape, Furthermore, it has a dark area brightness calculation unit that determines the average brightness of the dark area as the dark area brightness, The evaluation unit determines that the metal surface to be evaluated has the target surface roughness when the brightness ratio is less than a preset first threshold and the dark area brightness is greater than a preset second threshold.

[0117] (35) The second threshold is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. (36) The unit comprises a bright area luminance calculation unit that determines the average luminance of the bright area as the bright area luminance, The evaluation unit determines that the metal surface to be evaluated has the target surface roughness if the luminance ratio is less than the first threshold, the dark area luminance is greater than a preset second threshold, and the difference in luminance between the bright area luminance and the dark area luminance is less than or equal to a preset third threshold. (37) The pre-set uneven shape is a screw shape. (38) The metal surface to be evaluated above is a metal surface whose surface has been roughened by surface treatment. (39) The bright area is the area that includes the portion where halation occurs when the illumination light is shone on the metal surface before the surface treatment is applied. (40) The preset luminance is the luminance at the position of the halation generated when the illumination light is applied to the metal surface before the surface treatment, or the luminance reduced by a safety margin from that luminance.

Example

[0118] An automatic evaluation was performed on whether the pipe end thread portion 1 of the oil well pipe 2 was unblasted or blasted by image processing. As the devices, an image processing device PV200 manufactured by Panasonic and a laser light irradiation device LDU20515LZ3 - A manufactured by Takekuma Optonics were used. Here, regarding the surface state, surface roughness (hereinafter referred to as Ra), and quality evaluation, it is as shown in Fig. 23. Note that when it is unblasted, Ra is 1.7μm or less. Also, the target surface roughness was set to be 2.1μm or more and 3.8μm or less.

[0119] First, assuming the possible patterns shown in Fig. 22, an evaluation test using only the camera 11A was carried out. The normal injection pressure P in the blasting process was 0.24 Mpa ≤ P ≤ 0.44 Mpa, preferably 0.29 Mpa ≤ P ≤ 0.39 Mpa.

[0120] When P < 0.24 Mpa, it is equivalent to the unblasted state. If it is unblasted, seizure occurs between the thread portion and the joint when the joint is tightened, resulting in a defective product due to blasting failure. Also, when 0.44 Mpa < P, the surface of the pipe end thread portion 1 will be overly roughened, and the friction coefficient will increase. As a result, seizure occurs between the thread portion and the joint when the joint is tightened, resulting in a non - conforming product. This can be detected by setting a range for the target surface roughness.

[0121] The results of the above evaluation test are shown in Fig. 23. Initially, at level D, it was thought that the outer surface 1E could be imaged from the front using only camera 11A, and that halation of the seal portion 1B and the threaded portion body 1A could be obtained for all screw types. However, it was found that the blasted state of the threaded bottom corner A could be either unblasted or blasted depending on the angle θ1 value shown in Figures 4 and 5.

[0122] <Prerequisites> The prerequisites for the thread shape of the pipe end threads are described (see Figures 4 and 5). θ3 = 40° (Nozzle angles are typically fixed at 40°) θ4 = 40° (40° is the common value) θ5=θ4÷2 →θ5=40°÷2=20° θ6=θ3-θ5 →θ6=40°-20°=20° Due to alternate interior angles, θ1 = θ6 When θ1 > 20°, preferably θ1 > 22°, blasting occurs and diffuse reflected light is imaged. When θ1 ≤ 20°, the screw root corner A is not blasted and remains in an unblasted state.

[0123] <Examples> If the X-thread angle θ1 = 15°, the bottom corner A of the thread will not be blasted and will remain in an unblasted state. Y-thread θ1 = 25° → The bottom corner A of the thread is blasted, resulting in a blasted state. Furthermore, at level D, if nozzle 5B is clogged, the shoulder portion 1C and inner surface portion 1D will inevitably remain unblasted (Figure 6(b)), resulting in a blasted defective product. If this case coincides with the case where the screw bottom corner portion A has been blasted, then evaluating the quality using only camera 11A and lighting device 10A would result in sending a defective product to the next process. In other words, it was found that the quality of the blasting of the shoulder section 1C and the inner surface section 1D could not be determined using only the camera 11A and the lighting device 10A.

[0124] Next, a camera 11B capable of imaging the inner surface 1D and an illumination device 10B were added. Then, an evaluation test was attempted using camera 11A, illumination device 10A, camera 11B, and illumination device 10B. In this case, when the shoulder portion 1C and inner surface 1D of level D were not blasted, halation of the inner surface 1D could be confirmed. In other words, at level D, considering the effect of the clogged nozzle 5B, we consider the following: the case where the shoulder portion 1C and inner surface portion 1D are not blasted and the case in Figure 6 where the screw bottom corner portion A is blasted overlap. Even in this case, the camera 11B could confirm the halation of the inner surface portion 1D, and the tube could be evaluated as a blasted defective product.

[0125] Furthermore, in the case of small-diameter oil well pipes (outer diameter less than 73.1 mm), the bend at the end of oil well pipe 2 is significant, and in such cases, the vertical position changes by a maximum of 4.0 mm / 300 mm. Therefore, a laser beam irradiation device 13 was introduced for vertical position correction. The laser beam is irradiated onto the side surface of the pipe near the pipe end thread portion 1, and the principle is used to recognize the upper and lower edges of the pipe by evaluating the areas where the laser beam is interrupted using image processing evaluation based on differences in density.

[0126] Furthermore, for oil well pipes 2 with diameters exceeding the small size (73.1 mm or larger), positional misalignment tends to decrease, but minute misalignments still occur, so a laser beam irradiation device 13 for vertical position correction is necessary. Based on the above, by combining camera 11A, lighting device 10A, camera 11B, lighting device 10B, and laser light irradiation device 13, it became possible to automatically evaluate the blast quality of the pipe end thread section 1 of the oil well pipe 2. [Explanation of symbols]

[0127] 1. Threaded end of pipe 1A Threaded part body 1B Seal part 1C Shoulder section 1D inner part 1E External part 1F flat area 2 Oil country tubing 5A, 5B Blast nozzle 10,10A10B Lighting device 10P Lighting axis 11, 11A, 11B Camera (imaging device) 11P imaging axis 12. Arithmetic Processing Unit 13. Laser light irradiation device 20 Evaluation Calculation Unit 20A Image area confirmation unit 20B Brightness ratio calculation unit 20C Dark Area Brightness Calculation Unit 20D Bright Area Brightness Calculation Unit 20E Comparative Brightness Calculation Unit 20F Image Brightness Confirmation Section 20G Evaluation Department 20G1 First Evaluation Unit 20G2 Second Evaluation Department 21 Correction Processing Unit 21A Horizontal position correction section 21B Vertical position correction section 22 Setting section ARA-1 Light area ARA-1A light area main body area (light area) ARA-2 Dark region HA (Halation) HH maximum width MT1 First metal surface region MT2 Second metal surface region

Claims

1. A surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, The illumination device irradiates the metal surface to be evaluated with illumination light. The above-mentioned metal surface to be evaluated, illuminated by the above-mentioned light, is imaged. In the captured image, a bright region, which is an area with high brightness, and a dark region, which is adjacent to the bright region and has lower brightness than the bright region, are defined. Based on the brightness of the bright areas and the brightness of the dark areas, the surface roughness of the metal surface to be evaluated is evaluated. The average brightness of the above bright area is calculated as the bright area brightness. The average brightness of the dark area described above is calculated as the dark area brightness. If the difference in brightness between the bright area brightness and the dark area brightness is less than or equal to a predetermined third threshold, the metal surface being evaluated is evaluated as having the target surface roughness. A method for evaluating surface roughness characterized by the following features.

2. A surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, The illumination device irradiates the metal surface to be evaluated with illumination light. The above-mentioned metal surface to be evaluated, illuminated by the above-mentioned light, is imaged. In the captured image, a bright region, which is an area with high brightness, and a dark region, which is adjacent to the bright region and has lower brightness than the bright region, are defined. Based on the brightness of the bright areas and the brightness of the dark areas, the surface roughness of the metal surface to be evaluated is evaluated. The luminance ratio, which is the proportion of the area in the above bright region that has a luminance equal to or greater than a predetermined value, is determined. Based on the above brightness ratio, the surface roughness of the metal surface to be evaluated is evaluated. A method for evaluating surface roughness characterized by the following features.

3. If the above luminance ratio is less than a predetermined first threshold, the metal surface being evaluated is evaluated as having the target surface roughness. The surface roughness evaluation method described in feature 2.

4. The pre-set brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or a brightness reduced by a safety margin from that brightness. The surface roughness evaluation method described in feature 3.

5. In the image captured above, define the dark areas where the brightness is lower than the bright areas. The average brightness of the dark area described above is calculated as the dark area brightness. Based on the above brightness ratio and dark area brightness, the surface roughness of the metal surface to be evaluated is evaluated. The surface roughness evaluation method described in feature 2.

6. When the above luminance ratio is less than a preset first threshold, and the above dark area luminance is greater than a preset second threshold, the metal surface being evaluated is evaluated as having the target surface roughness. The surface roughness evaluation method described in feature 5.

7. The second threshold described above is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. The surface roughness evaluation method described in feature 6.

8. The average brightness of the above bright area is calculated as the bright area brightness. If the difference in brightness between the above-mentioned bright area brightness and the above-mentioned dark area brightness exceeds a predetermined third threshold, the evaluation of the metal surface being evaluated is changed from "as to the target surface roughness" to "as having a surface roughness less than the target surface roughness." The surface roughness evaluation method described in feature 6.

9. The metal surface being evaluated above is a metal surface whose surface has been roughened by surface treatment. A method for evaluating surface roughness according to any one of claims 1 to 8.

10. The above-mentioned brightened area is defined as the region that includes the area where halation occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied. The surface roughness evaluation method described in claim 9.

11. The metal surface being evaluated above is a metal surface whose surface has been roughened by surface treatment. The above-mentioned bright area is defined as the area that includes the portion where halation occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied. The above-mentioned pre-set brightness is the brightness at the location of the halation that occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied, or the brightness reduced by a safety margin from that brightness. A surface roughness evaluation method according to any one of claims 2 to 3 or 5 to 8, characterized by the above.

12. A surface roughness evaluation device that evaluates whether the surface roughness of a metal surface to be evaluated is a target surface roughness, A lighting device that illuminates the metal surface to be evaluated with illumination light, An imaging device for imaging the illuminated area, which is the area illuminated by the above-mentioned illumination light, A setting unit that sets a bright area, which is a bright area, and a dark area, which is adjacent to the bright area and has a lower brightness, within the illuminated area of ​​the captured image. An evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the brightness of the bright area and the brightness of the dark area, A bright area luminance calculation unit that determines the average luminance of the above bright area as the bright area luminance, The system includes a dark area brightness calculation unit that determines the average brightness of the dark area as the dark area brightness, The evaluation unit determines that the metal surface being evaluated has the target surface roughness if the difference in brightness between the bright area brightness and the dark area brightness is less than or equal to a preset third threshold. A surface roughness evaluation apparatus characterized by the following features.

13. A surface roughness evaluation device that evaluates whether the surface roughness of a metal surface to be evaluated is a target surface roughness, A lighting device that illuminates the metal surface to be evaluated with illumination light, An imaging device for imaging the illuminated area, which is the area illuminated by the above-mentioned illumination light, A setting unit that sets a bright area, which is a bright area, and a dark area, which is adjacent to the bright area and has a lower brightness, within the illuminated area of ​​the captured image. An evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the brightness of the bright area and the brightness of the dark area, The system includes a luminance ratio calculation unit that determines the luminance ratio, which is the proportion of the area in the bright area above a predetermined luminance level. The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio. A surface roughness evaluation apparatus characterized by comprising the following features.

14. The evaluation unit determines that the metal surface being evaluated has the target surface roughness when the brightness ratio is less than a preset first threshold. The surface roughness evaluation apparatus according to feature 13.

15. The pre-set brightness mentioned above is the brightness of the portion where halation occurs on the metal surface being evaluated, or a brightness reduced by a safety margin from that brightness. A surface roughness evaluation apparatus as described in feature 14.

16. The above setting unit sets the dark area in the captured image to have a lower brightness than the bright area, Furthermore, it has a dark area brightness calculation unit that determines the average brightness of the dark area as the dark area brightness, The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio and the brightness of the dark area. The surface roughness evaluation apparatus according to feature 13.

17. The evaluation unit determines that the metal surface being evaluated has the target surface roughness when the luminance ratio is less than a preset first threshold and the dark area luminance is greater than a preset second threshold. A surface roughness evaluation apparatus as described in 16, characterized by its features.

18. The second threshold described above is a luminance greater than the average luminance of the dark area when halation occurs throughout the entire bright area. A surface roughness evaluation apparatus as described in 17, characterized by its features.

19. The system includes a bright area luminance calculation unit that determines the average luminance of the bright area as the bright area luminance, The evaluation unit, when the difference in brightness between the brightness of the bright area and the brightness of the dark area exceeds a preset third threshold, changes the evaluation of the metal surface being evaluated from having a target surface roughness to having a surface roughness smaller than the target surface roughness. A surface roughness evaluation apparatus as described in 16, characterized by its features.

20. The metal surface being evaluated above is a metal surface whose surface has been roughened by surface treatment. A surface roughness evaluation apparatus according to any one of claims 12 to 19, characterized by the features described above.

21. The above-mentioned brightened area is defined as the region that includes the area where halation occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied. A surface roughness evaluation apparatus as described in 20, characterized by the features described above.

22. The metal surface being evaluated above is a metal surface whose surface has been roughened by surface treatment. The above-mentioned brightened area is defined as the region that includes the area where halation occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied. The above-mentioned pre-set brightness is the brightness at the location of the halation that occurs when the above-mentioned illumination light is shone on the metal surface before the above-mentioned surface treatment is applied, or the brightness reduced by a safety margin from that brightness. A surface roughness evaluation apparatus as described in any one of claims 13 to 14 or 16 to 19.

Images