JP5954284B2 - Surface defect inspection apparatus and surface defect inspection method - Google Patents

Description

  The present invention provides a surface defect inspection apparatus capable of performing surface defect inspection with a simple configuration and high accuracy while suppressing a decrease in conveyance efficiency of the inspection object when inspecting a surface defect of an inspection object of a cylindrical body or a cylindrical body, and The present invention relates to a surface defect inspection method.

  In the manufacturing process of a steel pipe, defects such as oysters, cracks, foreign matter adhesion, and dirt may occur on the surface of the steel pipe. It is extremely important for quality assurance or quality control to automatically inspect these surface defects over the entire circumference. For example, if the steel pipe that is plated on the surface has poor plating adhesion, the exposed portion may rust and pitting, causing troubles such as leakage of the transport fluid.

  For this reason, the inspection of the surface of a steel pipe has conventionally been conducted by visual inspection, optical inspection using a camera, etc., in addition to inspection by various non-destructive inspection (NDI) methods. In this optical inspection, a surface defect is detected by imaging the surface of a steel pipe with a camera and extracting a brightness change portion in the obtained image as a defect portion.

  For example, Patent Document 1 includes a bright field illumination that illuminates the front surface of a steel pipe, and a pair of dark field illuminations that illuminate both sides of the steel pipe from a lateral direction perpendicular to the bright field illumination, and a camera from the same direction as the bright field illumination. 1 describes that the surface of the steel pipe is imaged and the luminance change portion of the captured image is extracted as a defect. In particular, in Patent Document 1, in the case of a steel pipe or steel bar having a diameter of 300 mm or less, a bright area on the surface of the steel pipe is narrowed only by bright-field illumination. Therefore, a bright area is obtained by using dark-field illumination from both sides. It is possible to illuminate almost the entire upper half of the steel pipe surface.

  Moreover, in patent document 2, the upper part and side edge part of a steel pipe surface are irradiated to a steel pipe side edge part from a diagonally upper side of a steel pipe from a pair of long condensing illuminations extended long along the axial center direction of a steel pipe. Is obtained by photographing the surface of a steel pipe with a television camera from the center position of both illuminations, and extracting a luminance change portion of the photographed image as a defect. In Patent Document 2, surface defects such as surface scars, dirt, and shape defects are detected while rotating a steel pipe around its axis.

  Furthermore, in Patent Document 3, a two-dimensional camera, a one-dimensional camera, and a plurality of halogen lamps are arranged along the axial direction on the upper part of the conveyance path of the steel pipe conveyed in the axial direction. It describes what is inspected using steel pipe surface inspection data by a one-dimensional camera in which luminance correction is performed based on the measured amount of reflected light from the steel pipe surface. In Patent Document 3, it is possible to inspect the entire length of the steel pipe by conveying the steel pipe while rotating it.

JP 2006-292580 A Japanese Patent No. 2962125 Japanese Patent No. 4023295

  By the way, what is described in Patent Documents 1 and 2 is designed to rotate the steel pipe in the circumferential direction without moving the steel pipe in the axial direction in order to inspect the entire surface of the steel pipe. In addition, there is no steel pipe rotating mechanism dedicated to inspection that rotates the steel pipe in the circumferential direction. For this reason, providing a steel pipe rotation mechanism dedicated to inspection increases the cost of steel pipe production, and the addition of an inspection process using this steel pipe rotation mechanism reduces the steel pipe transport efficiency, resulting in production line productivity. In addition, in the inspection using this steel pipe rotation mechanism, there is a possibility that disturbances such as the distance between the imaging unit and the steel pipe surface fluctuate due to bending or flattening of the steel pipe and hinder accurate surface inspection. There was a problem of being big.

  Moreover, in what was described in patent document 3, it inspects while conveying a steel pipe spirally, and since it is widely used by ultrasonic inspection etc., since it is the measurement of only one place of the peripheral direction, If adjustments such as inspection field of view, rotation speed, and conveyance speed are not controlled with high accuracy, an inspection defect may occur. In addition, in the inspection performed while transporting in a spiral shape, as in the case of providing a steel tube rotation mechanism, the deflection or flatness of the steel tube affects the accuracy of the spiral transport, and a highly accurate surface inspection cannot be performed. There is a case.

  The present invention has been made in view of the above, and when inspecting a surface defect of an inspection object of a cylindrical body or a cylindrical body, the surface defect is highly accurate with a simple configuration while suppressing a decrease in the conveyance efficiency of the inspection object. An object of the present invention is to provide a surface defect inspection apparatus and a surface defect inspection method capable of performing inspection.

  In order to solve the above-mentioned problems and achieve the object, a surface defect inspection apparatus according to the present invention is a surface defect inspection apparatus for inspecting a surface defect of a cylindrical body or a cylindrical body, and the inspection object An inclined path formed with a slope that conveys the inspection object while rolling in a direction perpendicular to the axis, a rolling direction length of the inspection object having at least a circumference of the inspection object, and an axial length of the inspection object An imaging unit that images the imaging area on the oblique road, a linear light source that irradiates light to the inspection object that rolls in the imaging area, and whether or not the inspection object has entered the imaging area. When the inspection target enters the imaging region, the approach detection unit to detect and the entrance detection unit capture the image of the imaging region by the imaging unit from the entrance to the exit of the imaging region of the inspection target. Continuous imaging control unit Characterized in that and an image processing unit for detecting a surface defect of the inspection object on the basis of the continuous image captured under the control of the imaging control unit.

  In the surface defect inspection apparatus according to the present invention as set forth in the invention described above, after the inspection object enters the imaging area, the reflected light intensity of the inspection object by the linear light source is maximum. It is characterized in that imaging is continuously performed for each rolling of a predetermined width less than the imaging width in the rolling direction from the value to a predetermined reflected light intensity value.

  Further, the surface defect inspection apparatus according to the present invention includes a movement speed detection unit that detects a movement speed of the inspection object in the rolling direction when the inspection object enters the imaging region in the above invention. The imaging control unit adjusts imaging timing of the inspection object based on the moving speed and the diameter of the inspection object.

  In the surface defect inspection apparatus according to the present invention as set forth in the invention described above, the entry detection unit is a proximity sensor.

  In the surface defect inspection apparatus according to the present invention as set forth in the invention described above, the imaging region has an upstream region widened on the rolling upstream side of the inspection object with respect to the imaging region, and the entry detection unit is The entry of the inspection object is detected by detecting the image of the inspection object in the upstream region.

  Moreover, in the surface defect inspection apparatus according to the present invention, in the above invention, the moving speed detection unit moves the inspection object using two or more proximity sensors arranged along the rolling direction of the inspection object. It is characterized by detecting speed.

  In the surface defect inspection apparatus according to the present invention as set forth in the invention described above, the imaging region has an upstream region widened to the rolling upstream side of the inspection object relative to the imaging region, and the moving speed detection unit Is characterized in that the moving speed of the inspection object is detected by image-detecting the inspection object at two or more points along the rolling direction of the inspection object in the upstream region.

  Further, the surface defect inspection apparatus according to the present invention, in the above invention, has a field of view along the transport direction of the imaging region, and acquires a line image along the transport direction of the imaging region, A line image processing unit that calculates a transport direction movement position of a rolling direction imaging width until the reflected light intensity of the line image captured by the line image capturing unit reaches a predetermined reflected light intensity value from a maximum value; The imaging control unit sequentially captures adjacent captured images at a timing shifted by the imaging width in the rolling direction on the downstream side of conveyance in the imaging region as the inspection object rolls.

  The surface defect inspection method according to the present invention is a surface defect inspection method for inspecting a surface defect of a cylindrical body or a cylindrical body, and at least the rolling direction of the inspection object having a circumference of the inspection object A transporting step of transporting the inspection object while rolling in a direction perpendicular to the axis of the inspection object on a slope provided with an imaging region having a length and an axial length of the inspection object; An entry detecting step for detecting whether or not the imaging object has entered the imaging area; and when the inspection object enters the imaging area, the imaging unit performs the inspection from the entry to the exit of the imaging area. An imaging step of continuously imaging the imaging region and a surface defect detection step of detecting a surface defect of the inspection object based on the captured continuous images are included.

  In the surface defect inspection method according to the present invention as set forth in the invention described above, after the imaging step enters the imaging area, the reflected light intensity of the inspection target is a predetermined reflected light from a maximum value. Imaging is performed continuously for each rolling with a predetermined width less than the imaging width in the rolling direction until the intensity value is reached.

  Further, the surface defect inspection method according to the present invention includes a movement speed detection step of detecting a movement speed of the inspection object in the rolling direction when the inspection object enters the imaging region in the above invention, In the imaging step, the imaging timing of the inspection object is adjusted based on the moving speed and the diameter of the inspection object.

  Further, in the surface defect inspection method according to the present invention, in the above invention, a line image imaging step having a field of view along the transport direction of the imaging region and acquiring a line image along the transport direction of the imaging region; A line image processing step of calculating a moving direction moving position of a rolling direction imaging width until a reflected light intensity of the line image captured in the line image capturing step reaches a predetermined reflected light intensity value from a maximum value. In the imaging step, adjacent captured images are sequentially captured at a timing shifted by the imaging width in the rolling direction on the conveyance downstream side in the imaging region as the inspection object rolls.

  According to the present invention, on an inclined surface provided with an imaging region having at least the rolling direction length of the inspection object having the circumference of the inspection object and the axial length of the inspection object, the axis of the inspection object When the inspection object is transported while rolling in a vertical direction and the inspection object enters the imaging area, imaging of the imaging area is continuously performed from the entry to the exit of the imaging area of the inspection object. Since the surface defect of the inspection object is detected based on the continuous image, the surface defect inspection can be performed with high accuracy with a simple configuration while suppressing a decrease in the conveyance efficiency of the inspection object. .

FIG. 1 is a schematic diagram showing a configuration of a surface defect inspection apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the surface defect inspection apparatus according to the embodiment of the present invention. FIG. 3 is an explanatory diagram for explaining a uniform irradiation region. FIG. 4 is a diagram illustrating an example of a captured image captured by the imaging unit under the control of the imaging control unit. FIG. 5 is a flowchart showing a surface defect inspection processing procedure by the surface defect inspection apparatus according to the embodiment of the present invention. FIG. 6 is a schematic diagram showing a configuration of a surface defect inspection apparatus according to Modification 1 of the embodiment of the present invention. FIG. 7 is a flowchart showing a surface defect inspection processing procedure by the surface defect inspection apparatus according to the first modification of the embodiment of the present invention. FIG. 8 is a schematic diagram showing an imaging region and an extended region of the surface defect inspection apparatus according to Modification 2 of the embodiment of the present invention. FIG. 9 is a schematic diagram showing a configuration of a surface defect inspection apparatus according to Modification 3 of the embodiment of the present invention. FIG. 10 is an explanatory diagram for explaining the concept of detecting the moving position of the steel pipe in the conveyance direction by the line image processing unit. FIG. 11 is a flowchart showing a captured image acquisition processing procedure in the third modification of the embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a configuration of a surface defect inspection apparatus according to an embodiment of the present invention. As shown in FIG. 1, the surface defect inspection apparatus 1 uses a cylindrical steel pipe 2 as an inspection object as an example of a cylindrical body or a cylindrical body. The surface defect inspection apparatus 1 transmits light to the inclined pipe 10 formed with the inclined surface that conveys the steel pipe 2 while rolling without slipping in a direction perpendicular to the axis of the steel pipe 2, and the steel pipe 2 on the imaging area E of the inclined path 10. The linear light sources 11 and 12 to be irradiated, the imaging unit 13 that continuously images the steel pipe 2 on the imaging region E, and the proximity sensor S1 as an entry detection unit that detects whether the steel pipe 2 has entered the imaging region E; After the steel pipe 2 enters the imaging region E, the imaging control unit 14 that controls continuous imaging of the steel pipe 2 by the imaging unit 13 between the entry and exit of the steel pipe 2, and the continuous image captured by the imaging control unit 14 The image processing unit 15 that performs image processing for detecting a surface defect of the steel pipe 2 originally and the display unit 16 that displays and outputs the inspection result by the image processing unit 15 are provided.

  The surface of the ramp 10 is preferably made of a material that has a color tone different from that of the surface of the steel pipe 2 and suppresses reflection in order to easily identify the steel pipe 2 on the captured image. For example, it is preferable to paint matte white or black, or cover with a black rubber plate.

  FIG. 2 is a plan view of the surface defect inspection apparatus. As shown in FIGS. 1 and 2, the pair of linear light sources 11 and 12 are provided above the ramp 10 and irradiate the steel pipe 2 rolling on the ramp 10 with light. In particular, the linear light sources 11 and 12 irradiate the imaging region E on the ramp 10 with uniform light. The linear light sources 11 and 12 are realized by a fluorescent lamp, a light guide, or an array of LED elements.

  Further, the imaging unit 13 is provided between the linear light sources 11 and 12 above the ramp 10 and displays an image of the surface of the steel pipe 2 that rolls in the imaging region E irradiated by the pair of linear light sources 11 and 12. Continuous imaging. The imaging unit 13 is realized by, for example, a CCD or CMOS area sensor camera, and four imaging units 13-1 to 13-4 are arranged along the axial direction of the steel pipe 2.

  Here, it is necessary to determine the number of pixels and the angle of view of the imaging unit 13 according to the size of the defective part to be detected and the inspection visual field (imaging region E). In general, the imaging unit 13 such as a camera is provided with an aspect ratio, and the number of pixels of the imaging unit 13 is such that the number of pixels in the horizontal direction (Nx) is larger than the number of pixels in the vertical direction (Ny), and Nx; = 4: 3 is set. Since the steel pipe 2 is long in the axial direction, it is preferable to cover the length of the steel pipe 2 in the axial direction by aligning the horizontal direction of the imaging field of view with a large number of pixels of the imaging unit 13 with the axial direction of the steel pipe 2. On the other hand, the vertical direction of the imaging field of the imaging unit 13 needs to cover a distance slightly longer than the circumferential length of the steel pipe 2. That is, as shown in FIG. 2, the imaging field of the imaging unit 13 covers the imaging area E determined by the length in the axial direction of the steel pipe 2 and the circumferential length LC in the transport direction that is slightly longer than the circumferential length of the steel pipe 2. There is a need to.

  On the other hand, it is preferable in view of defect inspection that the visual field per pixel is set to be about 1/2 to 1/5 of the size of the defect portion to be detected. For example, when the outer diameter of the steel pipe 2 is 100 mm and a defective part with a diameter of 2 mm is detected, the circumferential length LC in the transport direction LC = π × 100 mm = 314 mm, and the resolution per pixel = 2 mm × (1/5) = 0.4 mm. Therefore, the imaging field of view of the imaging unit 13 in the vertical direction may be 320 mm, and the number of pixels in the vertical direction may be 320 mm / 0.4 mm = 800 pixels.

  In this case, the horizontal imaging field of view of each of the imaging units 13-1 to 13-4 is about 320 mm / 3 × 4 = 430 mm from the aspect ratio, and when the steel pipe 2 is a long body extending several meters, the resolution is Since it is necessary to maintain, a plurality of steel pipes 2 are arranged in the axial direction as shown in FIG. For example, when the length of the steel pipe 2 in the axial direction is 5 m and inspection is performed with the four imaging units 13-1 to 13-4, the horizontal imaging field of view of each imaging unit 13-1 to 13-4 = 5 m / 4 = 1250 mm. Further, assuming that the resolution per pixel is 0.4 mm, the number of pixels in the horizontal direction of the imaging units 13-1 to 13-4 is Nx = 1250 mm / 0.4 mm = 3125 pixels, which is a commercially available imaging unit 13-1 close to this. The resolution of ˜13-4 is 3200 pixels. In this case, the number of pixels in the vertical direction of the imaging units 13-1 to 13-4 is Ny = Nx × (3/4) = 2400 pixels, and the number of pixels in the vertical direction when the outer diameter of the steel pipe 2 is 100 mm = Satisfy 800 pixels.

  Therefore, when the outer diameter of the steel pipe 2 is 100 mm and the axial length is 5 m, four imaging units 13-1 to 13-4 realized by a commercially available area sensor of 3200 × 2400 pixels are shown in FIG. 2. By arranging along the axial direction of the steel pipe 2, the entire imaging region E can be imaged at once. That is, the imaging fields of view of the four imaging units 13-1 to 13-4 cover the imaging areas E1 to E4 that form the imaging area E, respectively.

  By the way, when the steel pipe 2 that rolls in the imaging region E is imaged by the imaging unit 13, as shown in FIG. 3, the site where the linear light sources 11 and 12 can uniformly irradiate the steel pipe 2 (uniform irradiation site 2 a) It is narrower than the entire plan view of the steel pipe 2 and has a belt-like shape at the central portion in the axial direction of the steel pipe 2 on the imaging screen. The imaging width in the rolling direction of the strip-shaped uniform irradiation portion 2a is the uniform irradiation width W. The uniform irradiation width W is a known value obtained in advance based on the curvature of the steel pipe 2 and the arrangement interval of the linear light sources 11 and 12. For example, as shown in FIG. 3, the uniform irradiation width W is a width until the reflected light intensity L reaches a predetermined threshold value Lth from a maximum value Lmax.

  When the proximity sensor S1 detects that the steel pipe 2 has entered the imaging area E, the imaging control unit 14 starts imaging of the imaging area E by the imaging unit 13, and the steel pipe 2 has the uniform irradiation width. Continuous imaging is performed every time a predetermined width W ′ less than W and smaller than the uniform irradiation width W by a predetermined width W ′. For example, when the predetermined width W ′ of the steel pipe 2 having an outer diameter of 100 mm is 15 mm, the imaging control unit 14 performs continuous imaging every time the steel pipe 2 moves within the imaging area E by the predetermined width W ′ = 15 mm. In this case, since the circumferential distance LC in the conveyance direction of the imaging region E is 314 mm (320 pixels), the number of continuous imaging is 320/15 = 21.3 → 22.

  FIG. 4 is a diagram illustrating an example of a captured image captured by the imaging unit 13 under the control of the imaging control unit 14. As shown in FIG. 4, the imaging unit 13 captures an image every time the steel pipe 2 moves by a predetermined width W ′ within the imaging region E, and acquires n (for example, 22) captured images I1 to In. . Since the conveyance direction circumferential long distance LC of the imaging region E corresponds to the circumferential length, the defective portion 21 of the steel pipe 2 is imaged only at the uniform irradiation site 2a on the captured image I3 and is not overlapped. In addition, since the image of the defective portion 21 is not an image inclined with respect to the imaging unit 13, the size of the defective portion 21 is not underestimated. The imaging control unit 14 outputs the acquired captured images I1 to In to the image processing unit 15. In addition, it is preferable that the conveyance direction position where proximity sensor S1 detects the steel pipe 2 is a position of the steel pipe 2 detected by the captured image I1. In this case, the detection of the steel pipe 2 by the proximity sensor S1 serves as a trigger for the imaging start timing by the imaging unit 13. In addition, although proximity sensor S1 detects that the steel pipe 2 approached non-contactingly, proximity sensor S1 in this Embodiment is a metal detector of a LED permeation | transmission light system.

  The image processing unit 15 performs known defect extraction processing such as shading correction and binarization processing on each of the captured images I <b> 1 to In, and extracts a luminance change portion in the image as the defect portion 21. Further, the image processing unit 15 calculates the type and occurrence position of the extracted defect portion 21. The type of the defect portion 21 can be determined based on, for example, a defect feature amount obtained in advance. Further, the axial position of the defective portion 21 can be obtained from the horizontal position of the defective portion 21 in the captured image. In addition, the circumferential position of the defective portion 21 is an order position in the transport direction indicating which captured image is detected from among the n captured images continuously captured, and a vertical position in the captured image in which the defective portion 21 is detected. It can be obtained based on the direction position. Note that the circumferential position of the defective portion 21 can be obtained as a relative circumferential position from the seam position when the seam position or the like can be detected from the captured image.

  The display unit 16 displays and outputs the type and position of the defect portion 21 detected by the image processing unit 15 as a numerical value or a chart.

  Here, the surface defect inspection processing procedure by the surface defect inspection apparatus 1 will be described with reference to the flowchart shown in FIG. As shown in FIG. 5, first, the imaging control unit 14 determines whether or not the proximity sensor S1 detects the steel pipe 2 (step S101). When the proximity sensor S1 detects the steel pipe 2 (step S101, Yes), continuous imaging is performed n times until the circumference is reached at a time interval corresponding to the predetermined width W ′ (step S102). Thereafter, the image processing unit 15 performs a detection process of the defective portion 21 based on the n captured images I1 to In (step S103). After that, the display unit 16 displays and outputs information on the type and position of the defective portion 21 detected by the image processing unit 15 (step S104), and proceeds to step S101.

  In this embodiment, since the surface defect inspection apparatus 1 described above is provided on the production line of the steel pipe 2 and the steel pipe 2 is conveyed while performing the surface defect inspection of the steel pipe 2 described above, the conveyance of the steel pipe 2 is performed. A decrease in efficiency can be suppressed. As a result, it is possible to prevent a decrease in productivity of the production line for the steel pipe 2.

  In this embodiment, it is only necessary to roll the steel pipe 2 on the ramp 10 as a conveying line, and it is not necessary to provide a steel pipe rotating mechanism for surface defect inspection. Defect inspection can be performed. In addition, since the steel pipe 2 rolls on the ramp 10, the imaging accuracy is not deteriorated due to a change in the distance between the surface of the steel pipe and the imaging unit due to bending or flattening of the steel pipe 2, so that a highly accurate surface defect inspection is performed. be able to.

  In the above-described embodiment, assuming that the slope 10 is gentle and the conveyance speed of the steel pipe 2 is constant, the steel pipe 2 is moved to the imaging region E by the detection of the steel pipe 2 by the proximity sensor S1 described above. Detecting the entry, the imaging control unit 14 uses this detection as a trigger to continuously acquire n captured images at a time interval corresponding to the movement of the steel pipe 2 by a predetermined width W ′ within the imaging region E. Like to do.

(Modification 1)
Next, Modification 1 of the surface defect inspection apparatus will be described. As shown in FIG. 6, in the first modification, a proximity sensor S2 is further provided on the upstream side of the conveyance of the proximity sensor S1. In the first modification, the imaging control unit 14 obtains the moving speed of the steel pipe 2 based on the distance between the proximity sensor S2 and the proximity sensor S1 and the detection time difference of the steel pipe 2, and based on this moving speed. The continuous imaging timing of the steel pipe 2 in the imaging area E is adjusted.

  Furthermore, in this modified example 1, when the outer diameter of the steel pipe 2 changes, the imaging control unit 14 in the imaging area E based on the pipe diameter information D1 of the steel pipe 2 being conveyed and the moving speed described above. The continuous imaging timing of the steel pipe 2 is adjusted. The pipe diameter information D1 is used because the predetermined width W ′ changes when the pipe diameter of the steel pipe 2 changes.

  Here, with reference to the flowchart shown in FIG. 7, a surface defect inspection processing procedure according to the first modification will be described. As shown in FIG. 7, first, the imaging control unit 14 determines whether or not the proximity sensor S2 has detected the steel pipe 2 (step S201). When the proximity sensor S2 detects the steel pipe 2 (step S201, Yes), it is further determined whether or not the proximity sensor S1 has detected the steel pipe 2 (step S202). When the proximity sensor S1 detects the steel pipe 2 (step S202, Yes), the moving speed of the steel pipe 2 is calculated based on the known distance between the proximity sensors S1 and S2 and the detection time difference between the proximity sensors S1 and S2. (Step S203).

  Thereafter, the imaging control unit 14 determines the predetermined width W ′ based on the moving speed calculated in step S203 and the predetermined width W ′ obtained in advance corresponding to the acquired pipe diameter information D1 of the steel pipe 2. Are continuously imaged until the circumference is reached at a time interval corresponding to (step S204). Thereafter, the image processing unit 15 performs a detection process of the defective portion 21 based on the acquired plurality of captured images (step S205). Thereafter, the display unit 16 displays and outputs the information on the type and position of the defective portion 21 detected by the image processing unit 15 (step S206), and proceeds to step S201.

  As described above, when the outer diameter of the steel pipe 2 does not change, the predetermined width W ′ does not change, and the continuous imaging is performed so that only the moving speed is obtained and the time interval corresponding to the movement for the predetermined width W ′ is obtained. Adjust timing. This example of obtaining only the moving speed is useful because, even if the outer diameter of the steel pipe 2 does not change, the moving speed changes when the weight varies depending on the material, thickness, etc. of the steel pipe 2.

  Further, in the above-described modified example 1, it is assumed that the moving speed of the steel pipe 2 does not change in the imaging region E regardless of whether the outer diameter of the steel pipe 2 changes or does not change.

  However, the moving speed of the steel pipe 2 may be measured in the imaging area E, and the continuous imaging timing may be adjusted in real time in the imaging area E. The movement speed of the steel pipe 2 in the imaging region E may be detected by, for example, obtaining the movement speed of the steel pipe 2 directly from the conveying direction of the steel pipe 2 using a laser distance meter.

  When the tube diameter of the steel pipe 2 is different, the conveyance direction circumferential distance LC of the imaging region E also changes. Therefore, the imaging field of view and the linear light source of the imaging unit 13 cover the maximum conveyance direction circumferential distance LC. 11 and 12 irradiation areas need to be set.

(Modification 2)
Next, modification 2 of the surface defect inspection apparatus will be described. In the first modification described above, the moving speed of the steel pipe 2 is obtained using the proximity sensors S1 and S2 or the laser distance meter. However, in the second modification, based on the captured image captured by the imaging unit 13. The moving speed of the steel pipe 2 is obtained. Other configurations are the same as those of the first modification.

  That is, as shown in FIG. 8, the moving speed detection of the steel pipe 2 based on the captured image is performed by setting the widened area EA in advance on the upstream side of conveyance of the imaging area E, and two points of the steel pipe 2 imaged in the widened area EA. It is calculated based on the distance between them and the detection time difference. The position detection of the steel pipe 2 in the captured image can be realized, for example, by calculating the center of gravity of a portion where the luminance of a certain horizontal line is bright in the captured image.

  As in Modification 1, the continuous imaging timing is obtained by detecting the position of the steel pipe 2 in real time based on the captured image of the steel pipe 2 imaged in the imaging area E and detecting the movement of the predetermined width W ′. May be adjusted.

(Modification 3)
Next, Modification 3 of the surface defect inspection apparatus will be described. FIG. 9 is a schematic diagram showing a configuration of a surface defect inspection apparatus according to Modification 3 of the embodiment of the present invention. As shown in FIG. 9, in the third modification, a line image imaging unit as a line sensor camera having a field of view in the conveyance direction of the imaging range of the imaging unit 13 as an area sensor camera without using a proximity sensor or a laser distance meter. 23 is provided. The line image processing unit 25 calculates an imaging waveform in the transport direction of the steel pipe 2 based on the line image captured by the line image capturing unit 23 and calculates the transport direction movement position of the steel pipe 2. The imaging control unit 24 determines when the steel pipe 2 enters the imaging area E, which is an inspection area, based on the transport direction movement position of the steel pipe 2 calculated by the line image processing unit 25, or when the steel pipe 2 has a predetermined width W ′. The timing of movement by the amount is determined, and an imaging command is output to the imaging unit 13. In this modified example 3, it is unnecessary to assume that the conveyance speed of the steel pipe 2 is constant, and it is possible to cope with a case where the predetermined width W ′ changes according to the conveyance speed of the steel pipe 2 in the imaging region E. Other configurations are the same as those of the first modification.

  As shown in FIG. 10, the moving position of the steel pipe 2 in the transport direction by the line image processing unit 25 includes the distribution of reflected light intensity (luminance) L of the line image captured by the line image capturing unit 23 and the transport direction of the image capturing unit 13. It can be obtained from the visual field center position C and the conveyance direction position X in the imaging region E. For example, in the luminance distribution of the line image, suppose that the movement direction movement position where the luminance L exceeds a predetermined threshold Lth is xl, xm (xl <xm), and the conveyance direction position X of the imaging region E is X0 <X <X1. When the conveyance direction movement position x1 exceeds the conveyance direction position X0, the imaging unit 13 starts imaging, and the conveyance direction movement position x1 last time exceeds the conveyance direction movement position xm when the imaging unit 13 images. Then, the imaging process of performing imaging by the next imaging unit 13 is repeated, and when the transport direction movement position xm exceeds the transport direction position X1, the imaging of the steel pipe 2 is ended. Thereby, even if the conveyance speed of the steel pipe 2 changes, captured images as shown in FIG. 4 can be obtained sequentially.

  FIG. 11 is a flowchart showing a captured image acquisition processing procedure in the third modification of the embodiment of the present invention. As shown in FIG. 11, the transfer positions xl and xm of the line image are reset to xl and xm = 0, respectively (step S301). Thereafter, one line image is acquired by the line image capturing unit 23 (step S302). Further, it is determined whether or not the maximum value Lmax of the reflected light intensity (luminance) L of the line image exceeds a predetermined value (step S303). This determination is made because it can be determined that the steel pipe 2 has approached the imaging region E if the reflected light intensity of the steel pipe 2 is increased by the irradiation of the linear light sources 11 and 12.

  When the maximum value Lmax of the reflected light intensity (luminance) L of the line image exceeds a predetermined value (step S303, Yes), the conveying direction of the line image based on the reflected light intensity (luminance) L of the line image. The movement positions xl and xm are calculated (step S304). Thereafter, it is determined whether or not the transport direction movement position xl exceeds the transport direction position X0 (step S305). That is, it is determined whether or not the steel pipe 2 has reached the imaging region E. If the transport direction movement position xl exceeds the transport direction position X0 (step S305, Yes), it is further determined whether or not the transport direction movement position xm exceeds the transport direction position X1 (step S306). That is, it is determined whether or not the steel pipe 2 has passed the imaging region E.

  If the transport direction movement position xm does not exceed the transport direction position X1 (No in step S306), it is further determined whether or not the transport direction movement position xl has exceeded the transport direction position xm0 at the time of previous imaging by the imaging unit 13. Is determined (step S307). When the transport direction movement position xl exceeds the transport direction position xm0 at the time of the previous imaging by the imaging unit 13 (step S307, Yes), the imaging unit 13 performs imaging at that timing (step S308). Thereby, the steel pipe 2 can obtain images for the predetermined width W ′ continuously. Thereafter, the conveyance direction movement positions xl and xm of the line image calculated in step S304 are stored as the conveyance direction movement positions xl0 and xm0 (step S309), and at least the conveyance direction position at the time of the previous imaging in the next step S307. Used as xm0. Thereafter, the process proceeds to step S302, the next line image is acquired, and the above-described processing is repeated.

  When the maximum value Lmax of the reflected light intensity (luminance) L of the line image does not exceed the predetermined value (No at Step S303), the transport direction movement position xl does not exceed the transport direction position X0 (Step S305, No). If the transport direction movement position xl does not exceed the transport direction position xm0 at the time of previous imaging by the imaging unit 13 (step S307, No), the process proceeds to step S302 to acquire the next line image. The above process is repeated.

  On the other hand, when the transport direction movement position xm exceeds the transport direction position X1 (Yes in Step S306), the image processing unit 15 acquires a plurality of acquired images as in Steps S103 and S104 or Steps S205 and S206. Based on the image, the defect portion 21 is detected (step S310), and then the display unit 16 displays and outputs information on the type and position of the defect portion 21 detected by the image processing unit 15 (step S311). The process proceeds to step S301.

  In addition, as shown in the modification 3, the ramp 10 may not be planar, and the steel pipe 2 should just roll on the ramp 10.

  In the embodiment and the modification described above, the plurality of imaging units 13-1 to 13-4 are provided. However, the axial length of the steel pipe 2 is short, and imaging is performed only with the imaging field of view of the single imaging unit 13-1. When the area E can be covered, it is only necessary to provide one imaging unit 13-1. In this case, the axial lengths of the linear light sources 11 and 12 can also be shortened.

DESCRIPTION OF SYMBOLS 1 Surface defect inspection apparatus 2 Steel pipe 2a Uniform irradiation part 10 Ramp 11,12 Linear light source 13 Imaging part 14,24 Imaging control part 15 Image processing part 16 Display part 21 Defect part 23 Line image imaging part 25 Line image processing part E Imaging Area EA Widened area D1 Tube diameter information I1 to In Captured image LC Transport direction circumferential distance S1, S2 Proximity sensor W Uniform irradiation width W 'Predetermined width

Claims (2)

A surface defect inspection apparatus for inspecting a surface defect of a cylindrical body or a cylindrical body,
A ramp formed with a slope that conveys the inspection object while rolling in a direction perpendicular to the axis of the inspection object;
An imaging unit for imaging an imaging area on the ramp having at least a rolling direction length of the inspection object having a circumference of the inspection object and an axial length of the inspection object;
A linear light source that emits light to the inspection object that rolls in the imaging region;
An entry detection unit for detecting whether or not the inspection object has entered the imaging region;
When the inspection object enters the imaging area, the entry detection unit continuously captures the imaging area by the imaging unit from the entry to the exit of the imaging area of the inspection object. When,
An image processing unit for detecting a surface defect of the inspection object based on a continuous image captured under the control of the imaging control unit;
A line image imaging unit having a field of view along the conveyance direction of the imaging region and acquiring a line image along the conveyance direction of the imaging region;
A line image processing unit that calculates a transport direction movement position of a rolling direction imaging width until a reflected light intensity of a line image captured by the line image capturing unit reaches a predetermined reflected light intensity value from a maximum value;
With
The imaging controller sequentially captures adjacent captured images at a timing shifted by the imaging width in the rolling direction on the downstream side in the imaging region in accordance with the rolling of the inspection target. Inspection device. A surface defect inspection method for inspecting a surface defect of a cylindrical body or a cylindrical body,
At least on an inclined surface provided with an imaging region having a length in the rolling direction of the inspection object having a circumference of the inspection object and an axial direction length of the inspection object in a direction perpendicular to the axis of the inspection object. A transport step for transporting the inspection object while moving;
An entry detecting step for detecting whether or not the inspection object has entered the imaging region;
When the inspection object enters the imaging area, an imaging step of continuously imaging the imaging area by the imaging unit from the entry to the exit of the imaging area of the inspection object;
A surface defect detection step for detecting a surface defect of the inspection object based on the captured continuous image;
A line image imaging step having a field of view along the transport direction of the imaging region and acquiring a line image along the transport direction of the imaging region;
A line image processing step of calculating a moving direction moving position of the rolling direction imaging width until the reflected light intensity of the line image captured in the line image capturing step reaches a predetermined reflected light intensity value from a maximum value;
Including
The imaging step sequentially inspects adjacent captured images at a timing shifted by the imaging width in the rolling direction on the conveyance downstream side in the imaging region in accordance with the rolling of the inspection target. Method.

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