JP2004144595A - Apparatus for inspecting appearance of long-length member with smooth irregularity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for inspecting the appearance of a long-length member with smooth irregularity, which can stably detect a defective appearance of the long-length member such as defective coating or the like of a stranded wire being coated. <P>SOLUTION: The apparatus is provided with a plurality of lighting devices 10 being arranged in the circumferential direction around a coated PC (prestressed concrete wire) strand (long-length member) (A) in order to light the stranded wire (A), and a plurality of cameras C1, C3, C5 and C7 being arranged in directions in which light beams from the lighting devices 10 are reflected regularly in effect by surfaces of the stranded wire (A). When the surface of the stranded wire (A) is photographed by using the cameras, a photograph timing and a light on/off timing are controlled by a synchronizing means so that the lighting device 10, which is actually positioned opposite to the camera in such a state that the stranded wire is sandwiched between them on the optical axis of the camera, is lit off, and other lighting devices are lit on. Then, image processing is carried out based on images being photographed with the cameras, and thereby detecting the defective coating. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an appearance inspection apparatus and an appearance inspection method for a long body having smooth irregularities. In particular, the present invention relates to a visual inspection apparatus and a visual inspection method capable of stably inspecting resin coating defects on a resin-coated PC steel strand by image processing.
[0002]
[Prior art]
As a technique for inspecting a pinhole or the like in a resin coating of a corrugated pipe, a visual appearance inspection and a technique described in Patent Document 1 are known. In the technique described in Patent Document 1, a camera is arranged in a direction orthogonal to the axial direction of a test material (resin-coated corrugated pipe), and a half mirror is disposed between the camera and the corrugated pipe. Further, lighting for illuminating the test material is provided. The surface of the test material is uniformly illuminated by the balance between the direct light of the illumination and the light reflected by the half mirror, and an image of the test material surface is obtained by a camera. Then, the obtained image is differentiated to detect a resin coating defect on the test material.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-253402
On the other hand, there is also a PC steel stranded wire used as a building material for bridges, etc., on which a coating such as epoxy resin is formed, and air bubbles (micropores), paint undersized portions (cracks), blisters (bulges) on the coating surface. Must be inspected as defective. If there are minute holes or cracks, rust will be generated due to the intrusion of water, and blisters on the surface will be inconvenient during construction. For this reason, it is necessary to inspect these defects over the entire length and circumference of a manufacturing unit of, for example, 3300 m or more, and to assure quality.
[0005]
[Problems to be solved by the invention]
However, when the above-mentioned conventional technology is used for the appearance inspection of a resin-coated PC steel strand, there are the following problems.
[0006]
(1) In a visual inspection, it is difficult to inspect with stable accuracy for a long time.
Since the resin-coated PC steel stranded wire has a resin coating on the surface of the stranded wire, a groove appears on the surface of the stranded wire to have irregularities, and it is difficult to accurately find a defect. In particular, the above-mentioned defect has a similar color to that of the good portion, and it is very difficult to reliably visually detect the defect of a product moving at a high speed of 160 mm / sec on a production line.
[0007]
(2) The technique described in Patent Document 1 has another problem that stable failure detection is difficult due to the following circumstances, and the structure is complicated.
{Circle around (1)} A half mirror storage box or the like is reflected on the surface of the resin-coated PC steel stranded wire, and this is erroneously detected as defective.
{Circle around (2)} The structure is complicated and the assembly workability, detection reproducibility, and maintainability are poor.
(3) It is difficult to optimally combine the sensitivity of the camera, the transmittance of the half mirror, and the amount of illumination light.
[0008]
Accordingly, a main object of the present invention is to provide an appearance inspection apparatus and an appearance inspection method for a long body having smooth irregularities capable of stably detecting a poor appearance of a long body such as a poor covering of a stranded wire. is there.
[0009]
[Means for Solving the Problems]
The present invention achieves the above object by appropriately synchronizing the timing of photographing with a camera and the timing of turning on and off lights.
[0010]
That is, the visual inspection device of the present invention is provided with a plurality of illuminations arranged in the circumferential direction of a long body having smooth irregularities and illuminating the long body, and light from the illumination is substantially regularly reflected on the surface of the long body. A plurality of cameras arranged in the direction of the camera, when shooting the surface of the elongate body with the camera, the illumination substantially positioned on the optical axis of the camera on the opposite side of the camera with the elongate body therebetween is turned off. A synchronizing means for controlling the timing of shooting and the timing of turning on / off the lights so that other lights are turned on, and an image processing means for detecting a poor appearance of a long body based on an image taken by a camera. It is characterized by comprising.
[0011]
Further, the appearance inspection method of the present invention illuminates the elongated body with illumination arranged in the circumferential direction of the elongated body having smooth irregularities, and the direction in which light from the illumination is substantially regularly reflected on the surface of the elongated body. Arrange a plurality of cameras, when shooting the surface of the elongated body with the camera, substantially turn off the illumination located on the optical axis of the camera on the opposite side of the camera with the elongated body sandwiched, It is characterized in that the timing of shooting and the timing of turning on / off the lights are synchronized so that the other lights are turned on, and the image taken by the camera is subjected to image processing to detect the appearance defect of the elongated body. .
[0012]
When shooting with a camera, the lighting on the shooting side of the long body is turned on, and the lighting on the background side is turned off, so that halation can be prevented and a clear image of the long body can be obtained. Defective appearance of the measuring body can be detected.
[0013]
Hereinafter, the present invention will be described in more detail.
The inspection object of the present invention is a long body having smooth irregularities. “Smooth” means a state in which the surface roughness of a long body is small. In particular, when the image is taken with a camera, the surface of the long body has a small surface roughness such that illumination is reflected on the surface of the long body, and the surface is substantially mirror-like. Further, “having irregularities” means that there are irregularities such that shadows are generated by photographing, for example. More specifically, a wire material in which more grooves appear on the surface, such as a stranded wire, may be used. A specific example of the elongated body is a stranded wire. A more typical example is a resin-coated PC steel strand. Furthermore, the inspection object of the present invention may be one having a coating or one having no coating.
[0014]
The illumination is composed of a plurality of elongated bodies having smooth irregularities arranged in a circumferential direction. More specifically, there is a ring-shaped illumination in which a plurality of illumination units are arranged in a circumferential direction so that a part in the circumferential direction can be turned off and the rest can be turned on. The number of illuminations is preferably a number that can divide the circumferential illumination area in accordance with the number of cameras described below. By using such a ring-shaped illumination, it is possible to illuminate a long body having smooth irregularities almost uniformly. A light bulb, a light emitting diode (LED), or the like can be used for the lighting unit.
[0015]
The camera is not particularly limited as long as it can capture an image of a long body. For example, a CCD camera or a C-MOS camera can be used. It is preferable to use at least about four cameras so that images can be taken over the entire circumference of the long body. In particular, it is preferable to use eight long bodies so that they can be photographed from eight directions.
[0016]
The cameras may be arranged such that all cameras are arranged on the same circumference, or cameras whose circumferential arrangement is shifted may be arranged shifted in the longitudinal direction. In particular, by using a single ring-shaped illumination for a plurality of cameras, it is not necessary to use one ring-shaped illumination for one camera, and the number of ring-shaped illuminations can be reduced. it can.
[0017]
Further, the camera is arranged in a direction in which the illumination light is substantially regularly reflected by the elongated body. That is, the photographing point is illuminated from an oblique direction, and the camera is installed in a symmetrical direction about a line orthogonal to the elongated body at the photographing point. With this camera arrangement, the illumination itself can capture an image reflected on a long body, and defect detection can be performed accurately.
[0018]
The synchronizing means controls the photographing timing of the camera and the timing of turning on / off the illumination. In other words, control is performed so that the illumination located substantially on the optical axis of the camera on the opposite side of the long body from the camera is turned off, and the other illuminations are turned on. Thus, by turning on the illumination on the photographing side of the long body and turning off the illumination on the background side, halation can be prevented and a clear image of the long body can be obtained. For example, when ring-shaped illumination is used, control is performed so that the light-off region rotates in the circumferential direction.
[0019]
The image processing means performs various processes based on the obtained image of the surface of the elongated body, and detects whether or not there is a defect. For example, a differentiating means for differentiating the obtained image in the longitudinal direction of the elongated body, and a threshold value for setting a portion capable of complementing a portion where the rate of change in brightness is large, and binarizing the differentiated image data It is preferable to provide a means for converting the value. By such an image processing means, a defect in the appearance of the long body, for example, a defect in the coating, is recognized as black with small holes and cracks and black around the blister, and can be accurately detected.
[0020]
This image processing means preferably has a bright image shrinking means in order to remove foreign matter adhering to the surface of the elongated body in an image taken by the camera. On the surface of the elongate body, there are many places to which foreign substances floating in the production line adhere, despite the good surface properties of the elongate body. As described above, for example, in the case of poor coating, the micropores and cracks are black, and the bulge is recognized as a dark part because its periphery is black. On the other hand, the foreign matter is recognized as a whitish bright part. Therefore, by applying the bright part contraction processing (dark part expansion processing) to the obtained image, foreign matter can be removed from the image, and only the defective part on the surface of the long body can be truly detected.
[0021]
Further, it is preferable that the apparatus of the present invention has a marking mechanism for marking a detected defective portion. If a defective portion on the surface of the long body is found, the surrounding area is cut and discarded, so that marking is performed so that the defective portion can be easily identified later. Various means such as imprinting and labeling can be used for marking.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[Example 1]
<Inspection target>
First, prior to describing the apparatus of the present invention, the configuration of a coated PC stranded wire to be inspected will be described with reference to FIG. FIG. 1A is a sectional view of a resin-coated PC steel strand, and FIG. 1B is a side view. As shown in the figure, a plurality of PC steel wires B are joined to the resin-coated PC steel strand A, and a resin coating C such as an epoxy resin is formed on the outer periphery of the strand. The coating C is formed such that a groove appears on the surface. In this example, a case where a product in which an epoxy coating is formed on a PC steel stranded wire having an outer diameter of 15.2 mm is inspected will be described as an example.
[0023]
<Manufacturing / inspection line>
Such a coating inspection of the coated PC stranded wire is performed in a manufacturing / inspection line shown in FIG. That is, a PC steel strand is supplied from the supply 100 and introduced into the epoxy resin coating machine 110 to form a resin coating. This resin coating is performed by, for example, powder coating. The coated PC steel strand is introduced into a water cooling bath 120 to cool the coating. Thereafter, the coated PC steel stranded wire is introduced into the inspection apparatus 1 of the present invention, and a coating defect is inspected. As a result of the inspection, a label is affixed by the marking means 50 to a portion where a defect is detected, and the coated PC stranded wire is wound around the winding drum 130. The traveling speed of the coated PC strand at the time of the inspection is about 10 m / min at the maximum.
[0024]
<Inspection device>
The configuration of the device of the present invention will be described with reference to FIG. FIG. 3A is a front view showing the arrangement of a camera and lighting in the apparatus of the present invention, and FIG. 3B is an end view thereof.
[0025]
(illumination)
As shown in FIG. 3, the apparatus of the present invention is provided with a ring-shaped lighting 10 through which a coated PC strand A runs. The lighting unit 10 is configured by combining a plurality of lighting units in the circumferential direction of the coated APC strand strand A, so that each unit can be turned on and off independently. In this example, the ring-shaped illumination 10 is equally divided into four regions A1, A3, A5, and A7 in the circumferential direction, and lighting and extinguishing are performed for each region. In FIG. 3B, in a circle shown inside the cameras C1, C3, C5, and C7, a hatched portion indicates a light-off region, and a white portion indicates a light-on region. LED was used for each lighting unit.
[0026]
(camera)
CCD cameras were used as the cameras C1, C3, C5, and C7 (20). The cameras C1, C3, C5, and C7 are combined with one another by arranging four cameras C1, C3, C5, and C7 on the same circumference of the coated PC strand A and combining them with one ring-shaped illumination 10. Is composed. Two of these combined bodies were prepared and staggered in the longitudinal direction of the strand, and a total of eight cameras and two ring-shaped illuminations were used. Each camera C1, C3, C5, C7 in one combination is displaced from the circumferential direction of each camera in the other combination. By using both combinations, the coated PC steel strand A can be drawn from all directions. It was configured to be able to shoot. Although only one combination is shown in FIG. 3 (A), the other combination has cameras C2, C4, C6, and C8 arranged at 45 degrees from cameras C1, C3, C5, and C7. Is provided.
[0027]
As shown in FIG. 3A, the ring-shaped illumination 10 and the cameras C1, C3, C5, and C7 are connected to the respective cameras C1, C3, C5, and C7 in a direction in which the light of each illumination unit is substantially regularly reflected. Are arranged to be located. Further, an illumination unit is also arranged on the optical axis of the cameras C1, C3, C5, C7 on the opposite side to the cameras C1, C3, C5, C7 with the stranded line A interposed therebetween. These cameras C1, C3, C5 and C7 are actually supported by an annular disk (not shown) penetrating through the stranded wire A.
[0028]
(Synchronization means)
Then, by synchronizing the photographing timing of the cameras 20 (C1 to C8) with the turning on / off timing of the lighting 10 by the synchronizing means 30 (FIG. 6 described later), the surface of the coated PC steel strand is photographed.
[0029]
The synchronization means 30 controls the shooting timing and the lighting on / off timing so that the lighting on the camera side to be photographed is turned on for the coated PC strand and the lighting on the background side of the camera is turned off. I do.
[0030]
For example, in FIG. 3B, when shooting with the camera C1, the illumination of the area A5 on the background side of the camera is turned off, and control is performed so that other illuminations are turned on. Next, when taking a picture with the camera C3, control is performed so that the illumination of the area A7 on the background side of the camera is turned off and the other illuminations are turned on. Then, as shown in the timing chart of FIG. 4, not only the cameras C5 and C7, but also the cameras C2, C4, C6 and C8 synchronize the shooting and the partial extinguishing similarly. In this timing chart, a hatched portion is a light-off time. In this way, as the camera captures images in the order of C1, C3, C5, and C7, the area to be turned off moves from A5 to A7 to A1 to A3. By this synchronization, as shown in FIG. 5, only the background of the camera 20 to be photographed is turned off, and the illumination in all other areas is turned on, and the uneven stranded wire surface is uniformly illuminated, and A clear image with less halation can be obtained. In this example, control is performed so that each area is sequentially turned off at a cycle of 57 msec, and this processing is performed in parallel in both combinations, so that a total of eight cameras are used for shooting.
[0031]
(Image processing means)
The obtained image is processed by the image processing means 40. The image processing procedure will be described with reference to FIG. FIG. 6 is a functional block diagram of the device of the present invention.
[0032]
First, a photographed image is converted into digital data and stored in the image memory 41. The image data stored in the memory 41 is read out and the bright part contraction processing 42 is performed. Normally, a normal coating portion is recognized as a bright dark portion, and a coating defect is recognized as a dark dark portion, whereas a foreign matter attached to a normal coating surface is recognized as a bright portion. The bright portion shrinking process 42 is a process for removing foreign matter and the like attached to the coating surface in the production line from the image.
[0033]
The outline will be described with reference to FIG. Each of the squares in FIG. 7 indicates a single pixel in the image, the shaded portion indicates a bright dark portion with normal covering, and the white portion indicates a bright portion with foreign matter attached. In such an image, the brightness of a pixel entering the scanning frame 400 surrounded by a thick line is detected. Here, a 3 × 3 area for a total of 9 pixels is set as the scanning frame 400. When the scanning frame 400 is located at the position shown in FIG. 7, the brightness of the center pixel of the scanning frame 400 is replaced with the brightness of the pixel with the lowest brightness in this frame. In this case, since the central pixel of the scanning frame 400 is a bright part, it is replaced with a dark part. This scanning is performed over the entire screen to reduce the bright portion. In this example, scanning of the entire screen is repeated four times, and almost all bright parts are replaced with dark parts.
[0034]
After performing the bright part contraction processing, the binarization processing 43 is performed, and further, the crack is detected by performing the dark pixel area measurement 44 on the binarized image.
[0035]
On the other hand, for the minute holes and blisters, the differential processing 45 is performed on the bright part contraction processing image. FIG. 8 shows the brightness distribution in the longitudinal direction of the coated PC stranded wire in the bright part shrinkage-processed image. The solid line in the drawing is the lightness distribution of the normal covering portion, and the broken line is the lightness distribution of the portion having the minute holes. As described above, it is difficult to distinguish between a case where the distribution of brightness is uneven due to the presence of the micropores and a case where the distribution of brightness is uneven due to the presence of the grooves due to the presence of the grooves.
[0036]
Therefore, the binarization process 46 is performed after differentiating the bright portion contraction processed image in the horizontal direction (more linear axis direction). FIG. 9 shows the brightness distribution after differentiation. Also in this case, the solid line is the brightness distribution of the normal covering portion, and the broken line is the brightness distribution of the portion having the minute holes. Since this differential value indicates an absolute value, a portion where the brightness is greatly reduced due to the presence of the micropores is shown as a large peak in both the decreasing portion and the increasing portion of the brightness. Therefore, if the binarization processing 46 is performed on the differentiated image with a threshold value that can recognize the presence of the peak portion, and the dark pixel area measurement 47 in the binarized image is further performed, the minute holes and blisters can be reliably detected. can do.
[0037]
In the case of a crack, a defect signal 48 is output to the marking means 50 described below when a defect is found, whether it is a microhole or a blister.
[0038]
(Marking means)
When a defect of the coating is detected by the image processing unit 40, marking is performed at the defective position by the marking unit 50. As shown in FIG. 6, the marking means 50 includes a label attaching section 51 for attaching a label to the coated PC stranded wire, and pressing the attached label so that the label is not easily peeled off the uneven stranded wire. And pressure rollers 55 to 58 to be adhered. The label sticking unit 51 includes a calculating unit 52 that calculates a defect position, and a sticking roller 53 that sticks a label to a coated PC stranded wire in accordance with the calculation result of the calculating unit 52.
[0039]
First, the arithmetic unit 52 calculates the time t at which the defect position is located below the application roller 53 based on the distance from the camera shooting point (defect position) to the application roller 53 and the traveling speed of the stranded line A (see FIG. 10). Ask for. Next, the sticking roller 53 is driven so that the label L (see FIG. 10) can be stuck to the surface of the line just after the time t has elapsed from the photographing time of the camera when the defect signal 48 was output. The sticking roller 53 sequentially feeds out the label L adhered to the release paper, and descends to the surface of the stranded wire A to stick the fed out label L to the stranded wire surface. Then, it rises and prepares for the case where label L is pasted next.
[0040]
When the label L is stuck on the surface of the stranded line A by the sticking roller 53, the label L is not stuck along the surface of the stranded line A having irregularities. That is, when the stranded wire A is viewed from the axial direction, only the middle portion of the label L is in contact with the stranded wire A, and both ends of the label L are raised from the stranded wire A. Therefore, the label L partially lifted by the pressing rollers 55 to 58 is pressed downstream of the sticking roller 53, and is brought into close contact with the strand A. In this example, as shown in FIGS. 10 and 11, a total of four pressing rollers 55 to 58 sandwiching the stranded line A from up and down, diagonally upper right, and diagonally upper left were used. First, the coated PC steel wire A is sent downstream by being sandwiched between upper and lower pressing rollers 55 and 56 located on the upstream side. At this time, the center of the label L is pressed against the stranded wire A by the pressing roller 55. Subsequently, the line A is also sandwiched between the pressing rollers 57 and 58 located diagonally upper right and diagonally upper left, and both ends of the raised label L are pressed against the line A. By attaching such a label L, the label L does not easily come off, and the defect position can be easily determined later.
[0041]
[Example 2]
In the first embodiment, one ring-shaped illumination is combined with four cameras, and two sets of the combined bodies are displaced in the axial direction of the twisted line. However, as shown in FIG. 12, the eight cameras C1 to C8 are combined. May be arranged in substantially the same circumferential direction of the stranded line A, and a single ring-shaped illumination 10 may be combined.
[0042]
In this case, the number of ring-shaped lights 10 can be reduced, which is more preferable. In the case of the second embodiment, the ring-shaped illumination 10 may be configured to be divided into eight regions, and to be turned on and off for each region.
[0043]
【The invention's effect】
As described above, according to the inspection device and the inspection method of the present invention, at the time of shooting with a camera, the illumination on the imaging side of the long body is turned on, and the illumination on the background side is turned off, thereby preventing halation. A clear image of a long body can be obtained. Therefore, it is possible to detect appearance defects such as coating defects with high accuracy.
[Brief description of the drawings]
FIG. 1A is a sectional view of a resin-coated PC steel strand, and FIG. 1B is a side view of the same.
FIG. 2 is an explanatory diagram of a production / inspection line of a resin-coated PC steel strand.
FIG. 3A is a front view showing an arrangement of a camera and lighting in the device of the present invention, and FIG. 3B is an end view thereof.
FIG. 4 is a timing chart showing the timing of turning on and off the illumination in the device of the present invention.
FIG. 5 is an explanatory diagram of an illumination state in the device of the present invention.
FIG. 6 is a functional block diagram of the device of the present invention.
FIG. 7 is an explanatory diagram of a bright part contraction process.
FIG. 8 is a graph showing a lightness distribution in the longitudinal direction of a coated PC stranded wire in a bright part contraction processed image.
FIG. 9 is a graph showing a brightness distribution after differentiation.
FIG. 10 is a side view of the marking means.
FIG. 11 is a layout diagram of a pressing roller.
12A and 12B show a configuration of a second embodiment, in which FIG. 12A is a front view showing an arrangement of a camera and illumination in the device of the present invention, and FIG. 12B is an end view thereof.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inspection apparatus 10 of this invention 10 Ring-shaped illumination 20 (C1-C8) Camera 30 Synchronization means 40 Image processing means 41 Image memory 42 Bright part contraction processing 43 Binarization processing 44 Dark pixel area measurement 45 Differentiation processing 46 Binarization processing 47 Dark pixel area measurement 48 Defect signal 50 Marking means 51 Label sticking unit 52 Calculation unit 53 Sticking roller 55-58 Pressing roller 100 Supply 110 Epoxy resin coating machine 120 Water cooling tank 130 Winding drum 400 Scanning frame A1, A3, A5, A7 Area A Resin-coated PC steel strand B PC steel wire C Resin-coated L Label

Claims (5)

A plurality of illuminations arranged in the circumferential direction of the elongated body having smooth irregularities to illuminate the elongated body,
A plurality of cameras arranged in a direction in which light from the illumination is substantially specularly reflected on the surface of the elongated body,
When taking an image of the surface of the elongate body with the camera, light is turned off substantially on the optical axis of the camera on the opposite side to the camera with the elongate body therebetween, and the other lights are turned on. Synchronization means for controlling the timing of lighting and the timing of turning on and off the lighting,
An image processing means for detecting a defect on the surface of the elongate body based on an image taken by the camera, and a visual inspection apparatus for the elongate body having smooth irregularities. 2. The smooth unevenness according to claim 1, wherein the illumination is a ring shape through which a long body passes, and a single ring illumination is arranged to correspond to a plurality of cameras. 3. Long-body appearance inspection device. 2. The image processing unit according to claim 1, wherein the image processing unit includes a bright image contracting unit for removing a foreign substance attached to the surface of the elongated body recognized as a bright part in an image captured by a camera. 3. Long body appearance inspection device with smooth unevenness. The apparatus for visually inspecting a long body having smooth irregularities according to claim 1, further comprising a marking mechanism for marking a detected defective portion. Illuminate the long body with lighting arranged in the circumferential direction of the long body with smooth irregularities,
Arrange multiple cameras in the direction where the light from the illumination is substantially specularly reflected on the surface of the elongated body,
When taking an image of the surface of the elongate body with the camera, light is turned off substantially on the optical axis of the camera on the opposite side to the camera with the elongate body therebetween, and the other lights are turned on. And the timing of turning on and off the lights,
A method for inspecting the appearance of a long body having smooth irregularities, wherein image processing is performed on an image taken by the camera to detect a poor appearance of the long body.

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