JPH11337502A - Method and apparatus for detecting defect on surface of rolled material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect defects on the surface of a rolled material in a relatively short time and with high accuracy. SOLUTION: An annular light source 2 irradiates a rolled material 1 with light from its ambient. When the light scattered through the rolled material 1 is received above the rolled material 1, the light emitted from the annular light source 2 is made incident in directions expect the direction θ of a predetermined angle range having the direction orthogonal to the rolled direction of the rolled material 1 as the center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a surface defect of a rolled material for detecting a defect such as unevenness or discoloration existing on the surface of a rolled material.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. Hei 7-128253 discloses that a laser is irradiated to a local area, a reflected light thereof is received by a photodetector to detect a glide flaw on an aluminum disk, and a laser section or the aluminum disk is two-dimensionally scanned. A method for detecting a flaw on the entire surface of an aluminum disk by moving the aluminum disk to a position is disclosed. This method has an advantage that defects such as minute scratches can be detected. As a kind of a general dark-field type material surface defect detection method, as shown in FIGS. A method of irradiating light from above is known. In this method, FIG.
As shown in FIG. 2B, the reflected light from the sound part of the test object 102 does not enter the light receiving sensor 103 such as a CCD camera arranged above the center of the test object 102.
When the scattered light at the defective portion 02 enters the light receiving sensor 103, it is possible to observe a large area on the inspection target material 102 at a time.

[0003]

However, the above-described method has the following problems. First, according to the method disclosed in Japanese Patent Application Laid-Open No. 7-128253, a laser is locally irradiated, so that a measuring system (laser device) or a test object (aluminum disk) is relatively moved in order to observe a large area. Therefore, it takes a relatively long time to observe the entire surface of the material to be inspected, and a desired processing speed may not be obtained. Also, according to any of the above-described methods, when the material to be inspected is a rolled material, light is scattered even in a healthy part (normal part), and it becomes difficult to identify a fine defect. This is because, in the rolled material, fine irregularities transferred from the rolling rolls are also formed in the healthy part, and the irregularities and defects that cause problems on the product (generally, the depth is larger than the irregularities caused by the rolling rolls) ) Is difficult to identify. If they are to be identified, it is necessary to extract a lot of information and perform image processing, so that the processing time becomes extremely long.

Further, when the material to be inspected is a rolled material, for example, when the angle range of the incident direction of the irradiated light is limited to a narrow range as in the method of Japanese Patent Application Laid-Open No. 7-128253, a defect However, the light may not be sufficiently scattered, so that the defect may not be detected. This is because the scattering intensity of light at the defect is determined by characteristics such as the shape of the defect, and depends on the angle of incidence of light with respect to the rolling direction as shown in FIG. 17. This is because there is no correlation, that is, the incident angle of the light at which the scattering intensity of the light becomes strong differs depending on each defect.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for detecting a surface defect of a rolled material that can reliably detect a defect in the rolled material in a relatively short time and with high accuracy.

[0006]

In order to achieve the above object, a method for detecting a surface defect of a rolled material according to claim 1 of the present application irradiates the rolled material with light from the periphery of the rolled material. In the method for detecting a surface defect of a rolled material that receives light scattered by the rolled material, the irradiation light is irradiated from a direction excluding a predetermined angle range direction centered on a direction orthogonal to a rolling direction of the rolled material. did.

[0007] In the sound portion of the rolled material 3 shown in FIG.
As shown in FIG. 2B, which is a cross-sectional view taken along line bb of FIG.
Although hardly appearing in the cross section in the rolling direction, as shown in FIG. 2C, which is a cross-sectional view taken along the line cc in FIG. 2A, the cross section in the direction orthogonal to the rolling direction is prominent. Therefore, in a healthy part of a rolled material, scattering is hardly generated when light is irradiated from the rolling direction, but when light is irradiated from a direction perpendicular to the rolling direction, unevenness as shown in FIG. Light is scattered. On the other hand, since the occurrence of scattering at the defective portion of the rolled material is uncorrelated with the rolling direction, in order to accurately detect the defective portion, if the rolling direction dependence in the sound portion of the scattering characteristic is not considered, It is desired to irradiate the rolled material with light from as many directions as possible.

In a dark-field optical system that irradiates light from the periphery of a material to be inspected and observes the side (for example, above) of the material to be inspected, scattering at a defective portion corresponds to signal intensity and scattering at a healthy portion. Corresponds to the noise, it is necessary to increase the relative magnitude of the scattering intensity at the defective portion with respect to the scattering intensity at the healthy portion. However, when light is irradiated from a direction perpendicular to the rolling direction and a direction in the vicinity thereof, the scattering intensity in the healthy portion increases as described above, and thus the scattering intensity in the defect portion with respect to the scattering intensity in the healthy portion. Relative size (SN
Ratio) becomes small, and it becomes difficult to detect a defective portion. Therefore, in the present invention, by irradiating light from a direction excluding a predetermined angle range direction centered on a direction orthogonal to the rolling direction of the rolled material to reduce the proportion of light scattered in the healthy part, accuracy of accuracy is reduced. High defect detection. Further, since light is irradiated from around the rolled material, defect detection can be performed in a relatively short time.

FIGS. 1A and 1B are conceptual diagrams for explaining the principle of the first aspect of the present invention. FIG. 1 (a),
FIG. 1B is a diagram showing an example of a positional relationship between a rolled material and a light source according to the present invention, wherein FIG. 1A is a plan view and FIG.
Is a side view. 1 (a) and 1 (b), a rolled material 1 is irradiated with light by a circular light source 2 from a diagonally upper part around the material. In FIG. 1A, assuming that the upper side of the drawing is the rolling direction, in the method of the present invention, the rolled material 1 is removed from the direction excluding a predetermined angle range θ direction centered on a direction orthogonal to the rolling direction of the rolled material 1. Is irradiated with light. In order to irradiate light in this manner, the corresponding portion of the annular light source 2 may be shielded by a shielding member, or the annular light source 2 may be controlled so that only the corresponding portion of the annular light source 2 does not emit light. . By controlling the light irradiation direction in this way, the ratio of scattering in a healthy portion of the rolled material 1 can be reduced, and thus a defective portion can be detected with high accuracy.

According to a second aspect of the present invention, there is provided a method for detecting a surface defect of a rolled material, wherein light is applied to the rolled material from the periphery of the rolled material except for a predetermined angle range around a direction orthogonal to the rolling direction of the rolled material. Irradiating, receiving a scattered light of the irradiated light by the rolled material, a dark field type surface defect detecting step, irradiating the rolled material with parallel light, and receiving regular reflection light of the irradiated light by the rolled material. A bright-field type surface defect detection step.

According to the surface defect detecting method of the first aspect, it is possible to detect fine and steep unevenness defects in which light is scattered in all directions because the surface is irregularly roughened with high sensitivity. is there. However, according to the above-mentioned method, for example, it is not possible to detect a smooth unevenness defect or a discoloration defect whose surface is not roughened. This is because light is scattered in all directions with steep irregularities, but light is scattered only in a certain direction with gentle irregularities, and light is not scattered with discoloration defects, so in such cases, it is scattered This is because light cannot be received by the light receiving sensor. Therefore, in the invention of claim 2, in addition to the dark field type surface defect detection step according to claim 1, a bright field type surface defect detection step capable of detecting a gentle unevenness defect or a discoloration defect with high accuracy is performed. I have to.

In the bright field type surface defect detection step, the rolled material is irradiated with parallel light, and the reflected light of the irradiated light by the rolled material is received, so that the reflection direction and the reflection direction between the healthy part and the defective part are reflected. Since the difference in the intensity is easy to identify, a gentle unevenness defect or a discoloration defect can be detected with high accuracy. According to the bright-field type surface defect detection step, as shown in FIG. 3A, the parallel light applied to the healthy part 4a is specularly reflected and mostly received by the light receiving means. As shown in ()), the healthy part 4a is recognized as a bright part having a relatively high light receiving intensity. On the other hand, as shown in FIG. 3B, the proportion of the parallel light irradiated on the defective portion 4b is regularly reflected and received by the light receiving means, and as shown in FIG. Is recognized as a dark part having a relatively small light receiving intensity. This bright field type surface defect detection step is performed by the CC
Since the detection sensitivity of fine and steep irregularities is poor due to the limitation of the resolution of the light receiving sensor such as D camera, etc., the combination of the dark field type surface defect detection step and the bright field type surface defect detection step This makes it possible to detect any defect such as a steep irregularity defect, a gentle irregularity defect, and a discoloration defect.

The method for detecting a surface defect of a rolled material according to claim 3 further includes a step of detecting a rolling direction of the rolled material. Thus, regardless of the orientation of the rolled material, the direction of light irradiation in the dark field type surface defect detection step can be determined according to the orientation.

Further, according to the method for detecting a surface defect of a rolled material according to the fourth aspect, the predetermined angle range is such that the light scattering intensity at the defective portion is at least twice as large as the light scattering intensity at the sound portion. This is the determined angle range. Thereby, the relative magnitude of the scattering intensity at the defect portion with respect to the scattering intensity at the sound portion becomes large enough to detect the defect, and the defect detection accuracy can be further improved.

According to the method for detecting a surface defect of a rolled material according to the present invention, the light scattering intensity of the sound portion is 2 to the light scattering intensity of the sound portion when the light is irradiated from the rolling direction. The irradiation light is emitted from a direction excluding an angle range direction that is twice or more. Thereby, the relative magnitude of the scattering intensity at the defect portion with respect to the scattering intensity at the sound portion becomes large enough to detect the defect, and the defect detection accuracy can be further improved.

Further, according to the method for detecting a surface defect of a rolled material according to claim 6, the divergence angle of the light irradiated on the rolled material from the periphery of the rolled material in the inspection surface of the rolled material is equal to or less than a predetermined value. Is restricted to

In general, the cause of scattering in a healthy part is the unevenness caused by the above-mentioned rolling and the spread of irradiated light (direction dependence of light). Depends on the regularity of irregularities caused by rolling and the spread angle (divergence angle) of irradiated light. Among them, the regularity of the irregularities is difficult to deal with by the surface defect detection method, and therefore, in the present invention, the divergence angle of the irradiated light in the inspection surface of the rolled material is limited to a small value, so The predetermined angle referred to in the items 1 and 2 can be reduced.

That is, conventionally, as shown in FIGS. 18A and 18B, in the dark field type defect detection method, the light source 11 is used.
The light from 0 and 112 was given to the rolled material 114 without adjusting the divergence angle. Therefore, it is necessary to set the predetermined angle in claims 1 and 2 to be relatively large. Therefore, in the present invention, as shown in FIGS. 5A and 5B, in dark field type defect detection, divergence angle limiting means 8 and 9 are disposed in front of the light sources 6 and 7, respectively, to irradiate the irradiation light The divergence angle of the rolled material 5 in the inspection surface is limited to a predetermined value or less. The divergence angle limiting means 8 and 9 may be of any type, such as a slit or a cylindrical lens, as long as they can limit the divergence angle of light. As a result, the total irradiation angle of the light on the rolled material can be increased, and the ratio of detectable defects increases, thereby improving the detection accuracy.

Further, the apparatus for detecting a surface defect of a rolled material according to the present invention is characterized in that light is applied to the rolled material from the periphery of the rolled material except for a predetermined angle range centered on a direction orthogonal to the rolling direction of the rolled material. A light irradiating means for irradiating; and a light receiving means for receiving light scattered by the rolled material of the irradiation light from the light irradiating means. ADVANTAGE OF THE INVENTION According to this invention, since the ratio of the scattering in the healthy part of a rolling material can be reduced, it becomes possible to detect a defective part with high precision.

According to a still further aspect of the present invention, there is provided the apparatus for detecting a surface defect of a rolled material, wherein the light irradiating means corresponds to a light source disposed so as to surround the rolled material within a predetermined angle range of the rolled material. And a shielding means for preventing light from being irradiated to the portion to be illuminated. According to the present invention, it is possible to irradiate the rolled material with light except for the direction of the predetermined angle range by simple means. It is to be noted that such a shielding means is not always necessary, and it is possible to irradiate the rolled material with light except for a predetermined angle range direction even if a part of the light source does not irradiate light.

Further, the apparatus for detecting a surface defect of a rolled material according to a ninth aspect of the present invention provides a device for detecting light from the periphery of the rolled material to the rolled material except for a predetermined angle range centered on a direction orthogonal to the rolling direction of the rolled material. A first light irradiating means for irradiating, and a dark field type surface defect detecting means having a first light receiving means for receiving scattered light of the irradiation light from the first light irradiating means by the rolled material; Second light irradiating means for irradiating the rolled material with parallel light, second light receiving means for receiving regular reflection light of the irradiation light from the second light irradiating means on the rolled material, and A bright-field type surface defect detecting means having an image forming means for forming an image on the light receiving surface of the second light receiving means. According to the present invention, by combining a dark-field type surface defect detection unit and a bright-field type surface defect detection unit, it is possible to detect any defect such as a gradual irregularity defect or a discoloration defect other than a fine and steep irregularity defect. Becomes possible.

According to a tenth aspect of the present invention, in the apparatus for detecting a surface defect of a rolled material, the first light irradiating means may include a light source arranged to surround the rolled material, and the predetermined angle range of the rolled material. And shielding means for preventing light from irradiating the corresponding portion inside.

According to another aspect of the present invention, there is provided an apparatus for detecting a surface defect of a rolled material for limiting a divergence angle of light radiated from the periphery of the rolled material within a surface to be inspected of the rolled material to a predetermined value or less. Angle limiting means is further provided. According to the present invention, the predetermined angle described in claims 7 and 9 can be reduced, the total irradiation angle of light on the rolled material can be increased, the ratio of detectable defects increases, and the detection accuracy increases. Is improved.

Further, the apparatus for detecting a surface defect of a rolled material according to claim 12 further comprises means for detecting a rolling direction of the rolled material. Thus, regardless of the orientation of the rolled material, the direction of light irradiation by the dark-field type surface defect detection means can be determined according to the orientation.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 6 (a) and 6 (b) are views showing a state of detecting a surface defect of a rolled material for describing a first embodiment of a method and apparatus for detecting a surface defect of a rolled material according to the present invention. 6A is a plan view, and FIG. 6B is an end view taken along the line VIB-VIB in FIG. 6A. In the present embodiment, a surface defect of a blank material of an aluminum disk (a material having a rolled surface remaining and before being polished for use as a hard disk) mainly used as a hard disk of a computer is detected. .

6 (a) and 6 (b), the aluminum disk 14, which is a rolled material having a substantially circular cross section, is arranged so that the rolling direction is rightward on the paper. Around the aluminum disk 14, a total of 16 linear light sources 16a, 16b, 17a, 17b, 18a, 18b, 1
9a, 19b, 20a, 20b, 21a, 21b, 22
a, 22b, 23a and 23b are arranged so as to form a ring. A CCD camera 25 is disposed above the center of the aluminum disk 14 so as to receive scattered light from the aluminum disk 14 side. The linear light sources 16a, 16b to 23a, 23b are uniformly arranged at an angle of 22.5 degrees with each other on the surface to be inspected, and the CCD camera 25 on a surface perpendicular to the surface to be inspected.
The straight line passing through the central portion of the aluminum disk 14 and the straight lines passing through the linear light sources 16a, 16b to 23a, 23b and the central portion of the aluminum disk 14 are arranged at 70 degrees. In addition, each of the light sources 16a, 16b
Each of the light sources 23a and 23b is provided with a shutter (not shown) so that any one of the 16 light sources can be freely opened and closed. Instead of using a plurality of split linear light sources, an integrated light source such as a ring light may be used. At this time, a shutter may be used to block the irradiation light.

Each of the linear light sources 16a, 16b-2
In front of 3a, 23b, slit members 26a, 26b
33a and 33b are provided respectively. A schematic side view of one linear light source 16a is shown on the left side of FIG.
A schematic front view is shown on the right side. Light is emitted from the opening 24 shown in the schematic front view on the right side of FIG. Further, a schematic side view of the linear light source 16a to which the slit member 26a is attached is shown on the left side of FIG. 7B, and a schematic front view is shown on the right side.

In this embodiment, the CCD camera 25
The reason why the straight line passing through the central portion of the aluminum disk 14 and the straight lines passing through the linear light sources 16a, 16b to 23a, 23b and the central portion of the aluminum disk 14 are formed at 70 degrees is as follows. Light is diffusely reflected on a rough surface such as a rolled material having a slightly uneven surface.
However, when the incident angle approaches 90 degrees, the rough surface where diffuse reflection has occurred up to now has a property close to a mirror surface, and the specular reflection component sharply increases (scene phenomenon). Therefore, it is preferable that the incident angle be as large as possible. However, on the other hand, if the incident angle is too large, the scattering intensity at the small projections due to the fine dust will be too large. Therefore, it is necessary to select an optimum incident angle for the purpose of detection in consideration of these two restrictions. In the present embodiment, when the incident angle is 60 degrees or less, the diffuse reflection component becomes too large, and when the incident angle is 85 degrees or more, fine dust is generated. Since the scattering at the small convex portion due to the above becomes remarkable and causes over-detection, 75 ° was selected as the optimum incident angle.

When detecting defects in the aluminum disk 14 using the apparatus shown in FIGS. 6A and 6B, for example, the light source 16
a, 16b are respectively shielded by shutters attached to the aluminum disk, and the aluminum disk 14 is irradiated with light from the other 14 light sources 17a, 17b to 23a, 23b. Thus, the aluminum disk 14 is irradiated with light from a direction excluding the direction of the angle range of 22.5 degrees centered on a direction perpendicular to the rolling direction of the aluminum disk 14. In this way, by preventing light from being irradiated to the aluminum disk 14 from a direction of an angle range of 22.5 degrees centered on a direction orthogonal to the rolling direction of the aluminum disk 14, the above-described sound portion can be used. Light scattering can be reduced. Accordingly, light scattering occurs substantially only at the defective portion, and the scattered light is received by the CCD camera 25 so that highly accurate defect detection can be performed.

Next, the S / N ratios of the two methods having a defect in the method of shielding only the light sources 16a and 16b as described above and the method of not shielding any of the 16 light sources (irradiation around the entire circumference) are described. (Scattering intensity of light at a defective portion with respect to scattering intensity of light at a healthy portion) was measured. FIG. 8 is a graph showing the results. The horizontal axis indicates the sample name, and the vertical axis indicates the SN ratio. In the graph of FIG. 8, a circle represents data obtained by a method of blocking only the light sources 16a and 16b, and a triangle represents data obtained by a method of blocking none of the 16 light sources. . The data as shown in FIG. 8 is obtained for a rolled material in which sound portions and defective portions are known in advance.

As can be seen from FIG. 8, the light sources 16a, 16a
According to the method of shielding only b, two samples A and B
In each case, an S / N ratio of 2.0 or more, which is an S / N ratio that enables generally stable defect detection, was obtained. On the other hand, according to the method in which none of the 16 light sources is shielded, the SN ratio of each of the two samples A and B is about 1.2 to 1.3, and stable detection of defects cannot be performed. found.

In addition to the example shown in the graph of FIG.
The rolled material is irradiated with light from a direction excluding an angle range direction in which the light scattering intensity at the sound part becomes twice or more the light scattering intensity at the sound part when light is irradiated from the rolling direction. Even so, good results with an SN ratio of 2.0 or more were obtained.

Next, in the apparatus of FIG. 6, each light source 16a,
The slit members 26a, 26b to 33a, 33b attached to the front of 16b to 23a, 23b will be described in more detail. These slit members 26a, 26b to 33
As described above, a and 33b are provided so that the divergence angle of the light emitted from the light source in the inspection surface is equal to or smaller than a predetermined value. In these slit members, assuming that the slit interval is t and the slit length is L, the divergence angle (maximum diffusion angle) x is expressed as x = tan-1 (t / L). For example, the relationship between the slit length L and the divergence angle x when the slit interval t is fixed at 2 mm is represented by a graph as shown in FIG. The divergence angle is preferably smaller as described above. However, if the slit is made longer, there is a problem that the spectrum is blocked and the intensity of light becomes weaker. Therefore, in the present embodiment, the slit interval t is set to 2 mm, the slit length L is set to 6 mm, and the divergence angle is limited to 20 degrees.

Such slit members 26a, 26b-
The following experiment was conducted in order to investigate the effect of performing surface defect detection using the devices 33a and 33b. FIG.
(A) and (b) are diagrams showing a schematic device configuration of this experiment, in which FIG. 10 (a) is a plan view and FIG. 10 (b) is FIG.
It is an end elevation in the XB-XB line of (a). FIG.
In (a) and (b), a rolled material 41 having a substantially circular cross section is used.
Are arranged such that the rolling direction is on the right side of the paper. As the rolled material 41, a material having substantially no defective portion and having only a healthy portion is used. Rolled material 4
A pair of linear light sources 43
a and 43b are arranged. These linear light sources 4
3a and 43b are rotatable on the circumference around the center of the rolled material 41. In addition, a CCD camera 45 is arranged above the center of the rolled material 41 so as to receive scattered light from the rolled material 41 side. In a plane perpendicular to the surface to be inspected, the CCD camera 45 and the rolled material 41
The straight line passing through the central portion and each of the linear light sources 43a and 43b and the straight line passing through the central portion of the rolled material 41 are arranged so as to form 70 degrees. In addition, each light source 43a, 43b
May be provided with a shutter (not shown) similar to that described above.

First, slit members 46a and 46b similar to those described above are provided in front of the linear light sources 43a and 43b, respectively, and the scattering intensity when the linear light sources 43a and 43b are rotated counterclockwise is measured by a CCD. Observed with camera 45. FIG. 11A shows the results in a graph in which the horizontal axis represents the angle of incidence of light with respect to the rolling direction and the vertical axis represents the light scattering intensity in the healthy part. Next, the same measurement was performed without providing a slit member in front of each of the linear light sources 43a and 43b. The result is shown in FIG.

In general, when the scattering intensity at a sound portion when light is incident from a certain direction is twice or more the scattering intensity when light is incident from a rolling direction, an adverse effect is exerted on defect detection and accurate detection is caused. It is considered that the defect cannot be detected. In the example of FIG. 11A provided with the slit members 46a and 46b, the incident angle range in which such accurate defect detection cannot be performed is 30 degrees (± 15 degrees) from 75 degrees to 105 degrees. On the other hand, FIG.
In the example of (b), the incident angle range in which such accurate defect detection cannot be performed is from 55 degrees to 125 degrees and 70 degrees (± 3 degrees).
5 degrees).

That is, when the slit member is provided, light from an angle range of ± 15 degrees around a direction perpendicular to the rolling direction of the rolled material is shielded, and when the slit member is not provided, the rolled material is shielded. ± centered on the direction perpendicular to the rolling direction
Unless light from an angle range of 35 degrees is shielded, accurate defect detection cannot be performed. For example, in the above-described example of the present embodiment, if a slit member is provided, only one set of light sources (for example, the light sources 16a and 16b) needs to be shielded.
If no slit member is provided, two sets of light sources (for example, the light sources 16a and 16b and the light sources 17a and 17b) must be shielded from light. However, when the number of light sources to be shielded increases, the irradiation angle of the light on the rolled material is limited accordingly, so that a defective portion may not be detected.
Therefore, by providing a slit member so that the divergence angle of the rolled material in the surface to be inspected is equal to or less than a predetermined value (20 degrees in this example), it is possible to improve the detection accuracy of the defective portion.

Next, a second embodiment of the present invention will be described. The method and apparatus for detecting a surface defect of a rolled material according to the present embodiment is realized by, for example, an apparatus illustrated in FIG. The apparatus shown in FIG.
And a dark-field type surface defect detection unit 54 and a bright-field type surface defect detection unit 56. Then, the rolled material 58 as the material to be inspected passes through the vicinity of the rolling direction detecting means 52, the dark-field type surface defect detecting means 54, and the bright-field type surface defect detecting means 56 by transporting means such as a belt conveyor 59, respectively. It can be moved rightward on the paper.

The rolling direction detecting means 52 is provided with a CC (not shown).
The image processing apparatus includes a D camera. As shown in FIG. 13, when the rolling material 58 reaches a predetermined position, the rolling direction detecting means 52 captures an image of the rolling material 58 with a CCD camera, processes the captured image, and processes the rolling image on the rolling material surface. (Undulations that look like streaks along the rolling direction)
, The rolling direction of the rolled material 58 is detected. CCD of rolling direction detecting means 52
The camera may be either an area type or a line type as long as it moves the belt conveyor 59 at a constant speed.

The dark-field type surface defect detecting means 54 is the same as that shown in FIG. 6 described in the first embodiment, and a detailed description of its structure is omitted here. In the present embodiment, the dark-field type surface defect detecting means 54 controls according to the rolling direction detected by the rolling direction detecting means 52 so that light is not irradiated from a predetermined angle range centered on a direction orthogonal to the rolling direction. Is done. Therefore, similarly to the above-described first embodiment, it is possible to detect a steep unevenness defect with high sensitivity. The rolling direction detecting means 5
The provision of 2 enables the dark-field type surface defect detection means 54 to detect defects with high accuracy even for a rolled material whose rolling direction is not known in advance.

Incidentally, without providing the rolling direction detecting means 52,
It is also possible to detect the rolling direction of the rolled material using the dark-field type surface defect detecting means 54. For example, in the apparatus shown in FIG.
The scattered light is received by the D camera 25, and the scattered light is received for all sets of light sources. Then, the direction of the light source irradiated with the light when the scattering intensity is maximized is regarded as the direction orthogonal to the rolling direction. Further, a dark-field type surface defect detecting means as shown in FIG. 6 may be provided separately from the dark-field type surface defect detecting means 54 to detect the rolling direction. Therefore, it is preferable to replace the CCD camera with an inexpensive light receiving element.

FIG. 14 shows the detailed structure of the bright field type surface defect detecting means 56. The bright field type surface defect detection means 56
A point light source 61 composed of an LED or the like, a collimating lens (convex lens) 62 for converting light from the point light source 61 into parallel light,
Half mirror 63 that reflects parallel light in the direction of rolled material 58 so as to be perpendicularly incident on rolled material 58 and transmits reflected light from rolled material 58 in the direction of the CCD camera.
And a lens (convex lens) 64 for converging the light from the half mirror 63 and a CCD camera 68. In the CCD camera 65, light incident from a pinhole 66 is focused on a light receiving surface 68 of the CCD by a lens 67. That is, the bright field type surface defect detecting means 56 irradiates the rolled material with parallel light,
An image of the regular reflection light from the rolled material of the irradiation light is formed into an image by CCD.
The camera 65 receives light. The CCD camera of the bright-field type surface defect detecting means 56 may be either an area type or a line type as long as the belt conveyor 59 is moved at a constant speed.

According to the defect detection using the bright-field type surface defect detecting means 56, the rolled material 58 is irradiated with parallel light, and the reflected light of the irradiated light from the rolled material 58 is received, whereby a sound portion and a defect are detected. Since it is easy to identify the difference in the reflection direction and the reflection intensity from the part, it is possible to detect a smooth unevenness defect or a discoloration defect which has been difficult to be detected by the dark-field type surface defect detection means 54 with high accuracy.

As described above, in the present embodiment, the apparatus includes the dark-field type surface defect detecting means 54 and the bright-field type surface defect detecting means 56. Since the process is performed in combination with the surface defect detection step of the mold, the steep unevenness defect can be detected with high accuracy by the dark field type surface defect detection means 54 and the smooth unevenness can be detected by the bright field type surface defect detection means 56. Defects and discoloration defects can be detected with high accuracy. Therefore, according to the present embodiment, any defect can be detected with high accuracy.

In this embodiment, the belt conveyor 59 is used as a transport means for the rolled material 58, but the rolled material 58 may be appropriately moved without using the belt conveyor 59, for example, using a handling robot. Further, in the present embodiment, the rolling direction of the rolled material 58 is automatically detected using the rolling direction detecting means 52. However, such rolling direction detecting means 52 is not necessarily required, and may be performed by another method (for example, visually). The rolled material 58 whose rolling direction has been detected may be arranged on the belt conveyor 59 such that the rolling direction is directed to a predetermined direction. In this case, the dark field type surface defect detecting means 54
Then, light is applied to the rolled material 58 from a predetermined light source.

[0047]

As described above, the method for detecting a surface defect of a rolled material according to claim 1 of the present application irradiates the rolled material with light from the periphery of the rolled material, and scatters the irradiation light of the rolled material. In the method for detecting a surface defect of a rolled material to be received, the irradiation light is irradiated from a direction excluding a predetermined angle range direction centered on a direction orthogonal to the rolling direction of the rolled material. As a result, it is possible to reduce the ratio of the emitted light, and it is possible to detect a defective portion with high accuracy. Further, since light is irradiated from around the rolled material, defect detection can be performed in a relatively short time.

Further, in the method for detecting a surface defect of a rolled material according to the present invention, light is applied to the rolled material from the periphery of the rolled material except for a predetermined angle range centered on a direction orthogonal to the rolling direction of the rolled material. Irradiating, receiving a scattered light of the irradiated light by the rolled material, a dark field type surface defect detecting step, irradiating the rolled material with parallel light, and receiving regular reflection light of the irradiated light by the rolled material. Since it has a bright-field type surface defect detection step, it is possible to detect any defect such as a fine and steep irregularity defect, a gentle irregularity defect, and a discoloration defect.

Further, the method for detecting a surface defect of a rolled material according to claim 3 further includes a step of detecting a rolling direction of the rolled material. Thus, regardless of the orientation of the rolled material, the direction of light irradiation in the dark field type surface defect detection step can be determined according to the orientation.

In the method for detecting a surface defect of a rolled material according to a fourth aspect of the present invention, the predetermined angle range is such that the light scattering intensity at the defective portion is at least twice as large as the light scattering intensity at the sound portion. This is the determined angle range. Thereby, the relative magnitude of the scattering intensity at the defect portion with respect to the scattering intensity at the sound portion becomes large enough to detect the defect, and the defect detection accuracy can be further improved.

In the method for detecting a surface defect of a rolled material according to claim 5, the light scattering intensity at the sound part is twice as high as the light scattering intensity at the sound part when light is irradiated from the rolling direction. The irradiation light is emitted from directions other than the above angle range directions. Thereby, the relative magnitude of the scattering intensity at the defect portion with respect to the scattering intensity at the sound portion becomes large enough to detect the defect, and the defect detection accuracy can be further improved.

Further, in the method for detecting a surface defect of a rolled material according to claim 6, the divergence angle of the light irradiated on the rolled material from the periphery of the rolled material within the inspection surface of the rolled material is set to a predetermined value or less. Is restricted to Therefore, the predetermined angle described in claims 1 and 2 can be reduced, so that the ratio of detectable defects increases, and the detection accuracy improves.

Further, in the apparatus for detecting a surface defect of a rolled material according to claim 7, light is applied to the rolled material from the periphery of the rolled material except for a predetermined angle range centered on a direction orthogonal to the rolling direction of the rolled material. Since the light irradiating means for irradiating and the light receiving means for receiving the scattered light of the irradiating light from the light irradiating means by the rolled material are provided, it is possible to reduce the ratio of scattering in the healthy part of the rolled material. Defective parts can be detected with high accuracy.

In the apparatus for detecting a surface defect of a rolled material according to claim 8, the light irradiating means corresponds to a light source disposed so as to surround the rolled material within a predetermined angle range of the rolled material. Since there is provided a shielding means for preventing light from being irradiated to a portion to be rolled, it is possible to irradiate the rolled material with light except for a predetermined angle range direction by simple means.

In addition, the apparatus for detecting a surface defect of a rolled material according to the ninth aspect of the present invention emits light from the periphery of the rolled material to the rolled material except for a predetermined angle range centered on a direction orthogonal to the rolling direction of the rolled material. A first light irradiating means for irradiating, and a dark field type surface defect detecting means having a first light receiving means for receiving scattered light of the irradiation light from the first light irradiating means by the rolled material; Second light irradiating means for irradiating the rolled material with parallel light, second light receiving means for receiving regular reflection light of the irradiation light from the second light irradiating means on the rolled material, and A bright-field type surface defect detecting means having an image forming means for forming an image on the light receiving surface of the second light receiving means; Any defect such as a defect can be detected.

According to a tenth aspect of the present invention, in the apparatus for detecting a surface defect of a rolled material, the first light irradiating means may include a light source arranged to surround the rolled material, and a light source arranged to surround the rolled material. Since there is provided a shielding means for preventing light from irradiating the corresponding portion inside, it is possible to irradiate the rolled material with light except for a predetermined angle range direction by simple means.

According to a still further aspect of the present invention, there is provided an apparatus for detecting a surface defect of a rolled material for limiting a divergence angle of light irradiated from the periphery of the rolled material within a surface to be inspected of the rolled material to a predetermined value or less. Since the angle limiting means is further provided, the predetermined angle described in claims 7 and 9 can be reduced, and the total irradiation angle of light on the rolled material can be increased, and the ratio of detectable defects can be reduced. And the detection accuracy is improved.

The apparatus for detecting a surface defect of a rolled material according to the twelfth aspect further comprises means for detecting a rolling direction of the rolled material. The direction of light irradiation by the dark field type surface defect detecting means can be determined according to the direction.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a positional relationship between a rolled material and a light source according to the present invention, wherein FIG. 1 (a) is a plan view and FIG. 1 (b).
Is a side view.

2A and 2B are diagrams for explaining the dependence of unevenness due to a rolling roll on a rolling direction in a healthy part of a rolled material, where FIG. 2A is a plan view and FIG. (A) b
FIG. 2C is a cross-sectional view taken along line cc of FIG. 2A.

3A and 3B are diagrams showing how parallel light is reflected on the surface of a rolled material in bright-field type surface defect detection, and FIG. 3A is a schematic diagram showing reflection at a sound part, and FIG. (b) is a schematic diagram showing reflection at a defective portion.

FIG. 4 is a graph showing the relationship between the light receiving position and the light receiving intensity of the irradiation parallel light in the bright field type surface defect detection,
FIGS. 4A and 4B are graphs corresponding to FIGS. 3A and 3B, respectively.

5A and 5B are diagrams showing a state in which a divergence angle limiting unit is arranged in front of a light source in the dark field type defect detection according to the present invention. FIG. 5A is a plan view, and FIG. 5B is a side view. It is.

FIG. 6 is a diagram illustrating a state of detecting a surface defect of a rolled material for explaining the first embodiment of the present invention, and FIG.
FIG. 6B is a plan view, and FIG. 6B is an end view taken along the line VIB-VIB in FIG.

FIG. 7 shows a first embodiment of the present invention;
FIG. 7A is a diagram showing the outer shape of a linear light source, and FIG.
(B) is a figure which shows the positional relationship of a linear light source and a slit member.

FIG. 8 shows two samples A and B in the first embodiment of the present invention in which only light from a pair of opposing light sources is blocked, and in which no light from any light source is blocked. 5 is a graph showing the measurement results of the SN ratio of FIG.

FIG. 9 is a graph showing the relationship between the slit length L and the divergence angle x when the slit interval t is fixed at 2 mm.

10A and 10B are diagrams showing a schematic configuration of an apparatus for examining an effect obtained by performing surface defect detection using a slit member. FIG. 10A is a plan view, and FIG.
It is an end elevation in the XB-XB line of (a).

FIG. 11 is a graph showing the relationship between the incident angle of light with respect to the rolling direction and the scattering intensity of light in a healthy part.
10A is a graph when a slit member is provided in the apparatus of FIG. 10, and FIG. 11B is a graph when no slit member is provided.

FIG. 12 is a diagram showing a device for detecting a surface defect of a rolled material for carrying out a second embodiment of the present invention.

FIG. 13 is a schematic diagram for explaining a procedure of image processing in the rolling direction detecting means of FIG.

FIG. 14 is a diagram showing a detailed structure of a bright-field type surface defect detecting means of FIG. 12;

15A and 15B are views for explaining a general dark-field type material surface defect detection method, wherein FIG. 15A is a plan view and FIG. 15B is a side view.

16A and 16B are diagrams for explaining how light is reflected or scattered by a general dark-field-type material surface defect detection method, and FIG. 16A is a schematic diagram showing a sound part, and FIG.
(B) is a schematic diagram showing a defective portion.

FIG. 17 is a graph showing the relationship between the incident angle of light with respect to the rolling direction and the scattering intensity.

18A and 18B are diagrams illustrating an example of a conventional dark-field defect detection method, in which FIG. 18A is a plan view and FIG.
Is a side view.

[Explanation of symbols]

 1, 3, 5, 14 Rolled material 2 Annular light source 6, 7 Light source 8, 9 Divergence angle limiting means 16a, 16b to 23a, 23b Linear light source 25 CCD camera 26a, 26b to 33a, 33b Slit member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sadaharu Baba 15 Kinuigaoka, Moka City, Tochigi Prefecture Inside Kobe Steel Moka Works Co., Ltd. (72) Keiji Okada 15 Kinuigaoka, Moka City Tochigi Prefecture Kobe Steel Moka Works (72) Inventor Katsuaki Masuda 15 Kinugaoka, Moka City, Tochigi Prefecture Kobe Steel Works Moka Works

Claims (12)

[Claims] 1. A method for detecting a surface defect of a rolled material, which comprises irradiating the rolled material with light from the periphery of the rolled material and receiving scattered light of the irradiation light by the rolled material. A method for detecting a surface defect of a rolled material, wherein the irradiation is performed from a direction excluding a predetermined angle range direction centered on a direction orthogonal to the rolling direction. 2. A method of irradiating the rolled material with light from the periphery of the rolled material except for a predetermined angle range around a direction orthogonal to the rolling direction of the rolled material, and scattered light of the irradiation light by the rolled material. And a bright-field type surface defect detection step of irradiating the rolled material with parallel light and receiving regular reflection light of the irradiation light by the rolled material. A method for detecting a surface defect of a rolled material. 3. The method according to claim 1, further comprising a step of detecting a rolling direction of the rolled material. 4. The predetermined angle range is an angle range determined so that the scattering intensity of light at a defective portion is at least twice the scattering intensity of light at a healthy portion. The method for detecting a surface defect of a rolled material according to any one of claims 1 to 3. 5. The irradiation from a direction excluding an angle range direction in which the light scattering intensity at the sound portion becomes twice or more the light scattering intensity at the sound portion when light is irradiated from the rolling direction. 4. Light is irradiated.
The method for detecting surface defects of a rolled material according to any one of the above items. 6. The method according to claim 1, wherein a divergence angle of light applied to the rolled material from the periphery of the rolled material in a surface to be inspected of the rolled material is limited to a predetermined value or less. The method for detecting a surface defect of a rolled material according to any one of claims 1 to 5. 7. A light irradiating means for irradiating the rolled material with light from around the rolled material except for a predetermined angle range direction centered on a direction orthogonal to the rolling direction of the rolled material; A light receiving means for receiving the scattered light of the irradiation light due to the rolled material. 8. A light source arranged so as to surround the rolled material and a light shielding means for preventing light from being irradiated on a portion of the rolled material corresponding to the predetermined angle range. The surface defect detecting device for a rolled material according to claim 7, further comprising means. 9. A first light irradiating means for irradiating the rolled material with light from around the rolled material except for a direction in a predetermined angle range centered on a direction orthogonal to a rolling direction of the rolled material; Dark field type surface defect detection means having first light receiving means for receiving scattered light of the irradiation light from the light irradiating means by the rolled material, and second light irradiation for irradiating the rolled material with parallel light Means, second light receiving means for receiving the regular reflection light of the irradiation light from the second light irradiation means by the rolled material, and forming an image of the regular reflection light on the light receiving surface of the second light receiving means And a bright-field type surface defect detecting means having an image forming means for causing the surface defect to be detected. 10. A light source arranged to surround a periphery of the rolled material, wherein the first light irradiating means prevents light from being irradiated to a portion corresponding to the predetermined angle range of the rolled material. 10. The apparatus for detecting a surface defect of a rolled material according to claim 9, further comprising: a shielding unit for detecting a surface defect of the rolled material. 11. A divergence angle restricting means for restricting a divergence angle of light irradiated from the periphery of the rolled material in a surface to be inspected of the rolled material to a predetermined value or less. An apparatus for detecting a surface defect of a rolled material according to any one of claims 7 to 10. 12. The apparatus for detecting a surface defect of a rolled material according to claim 7, further comprising means for detecting a rolling direction of the rolled material.