JPH11223610A - Surface defect inspection device and fluorescent magnetic particle flaw inspecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate between a surface defect and the nonsurface defect part of a magnetic particle banks, and to accurately detect a flaw of the surface defect with simple constitution by processing an image of the article surface with a rectangular picture element long in prescribed direction as a unit by an inspection means. SOLUTION: A steel material 2 carried in the DD direction by a carrying device 1 is magnetized by an exciting magnet 3, but when a surface defect SD exists in the steel material 2, there is a magnetic field stronger than the part having no defect SD due to the partial leakage flux. Then, fluorescent magnetic particles FM are sprayed on the surface of the steel material 2 by a magnetic particle sprayer 4 by using water as a medium. The magnetic particles FM are less easily peeled off the defectless part by sticking to the vicinity of the strong magnetic field-generating defect SD in high density. Next, the magnetic particles except those in the defective part SD are washed away, but there still remain magnetic particle FM (a magnetic particle bank). Next, an image of the surface of the steel material 2 is picked up by a line sensor 7 still in the fluorescent magnetic particle FM by irradiating ultraviolet rays in a linear shape by an ultraviolet ray irradiator 6. The defect and the nonsurface detect of a magnetic particle bank can be easily discriminated by using a rectangular picture element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus and a fluorescent magnetic particle inspection method, for example, based on a picked-up image obtained by imaging the surface of a magnetized steel material with the magnetic magnetic powder attached thereto. The present invention relates to a surface defect inspection device and a fluorescent magnetic particle inspection method for inspecting the presence or absence of a surface defect formed on a steel material surface.

[0002]

2. Description of the Related Art For example, a typical technique for detecting a surface defect of a steel material is a technique called a fluorescent magnetic particle flaw detection method. In this fluorescent magnetic particle flaw detection method, fluorescent magnetic powder is attached to a magnetized steel material, and flaw detection is performed based on a difference between the fluorescent luminance of the fluorescent magnetic powder attached to a portion where a defect exists and the fluorescent luminance of the fluorescent magnetic powder attached to a non-existent portion. Things. FIG. 8 is a diagram showing a schematic configuration of an automatic flaw detector for performing the fluorescent magnetic particle flaw detection method. As shown in FIG. 8A, the automatic flaw detector detects an image of a steel material 100, for example, an imaging unit 101 such as a CCD camera, a magnetized steel material 102 for magnetizing the steel material, and scatters fluorescent magnetic powder on the surface of the steel material 100. Magnetic powder scattering section 103 for irradiating, and ultraviolet irradiation section 1 for causing fluorescent magnetic powder to fluoresce
04, a defect determination unit 105 that performs image processing of the captured image and determines the presence or absence of a surface defect. First, the steel material 100 is magnetized in a predetermined direction by the steel material magnetized part. Fluorescent magnetic powder is sprayed on the surface of the magnetized steel material by the fluorescent magnetic powder spraying unit 103 using water or the like as a medium. Steel material 1
Since the leakage magnetic flux as shown in FIG. 8B exists in the portion where the defect is present on the surface of the surface 00, a stronger magnetic field is generated than in the portion where there is no defect. With high density. Next, the fluorescent magnetic powder attached to the surface of the steel material is caused to fluoresce by the ultraviolet irradiation unit 104, and the imaging unit 1
01 is imaged. The captured image output from the imaging unit 101 is input to the defect determination unit 105. Defect determination unit 10
In 5, for example, a predetermined threshold value is compared with the luminance value of the captured image, and an area having a luminance value larger than the predetermined threshold value is determined to be a surface defect. FIG. 9 shows the result of flaw detection of a surface defect of the steel material 100 by the automatic flaw detector. In FIG. 9, black squares indicate surface defects, and white circles indicate magnetic powder pools. Here, the magnetic powder pool means, for example, a substance in which fluorescent magnetic powder solidifies and adheres around oil droplets or the like remaining on the steel material 100, and shows a high luminance value in a captured image as in the case of a surface defect, but a portion which is not a defect. It is.
While this magnetic powder pool is often formed in a point shape, surface defects tend to be formed in a linear shape. As shown by the solid line in FIG. 9, when the luminance threshold value is set to, for example, 80, four of the eight detection results determined by the determination means to be a surface defect are from magnetic powder accumulation. , Erroneous detection (overdetection). Also, surface defects below the threshold value are naturally not detected and four undetected ones occur. As described above, even if the surface defect is determined based only on the magnitude of the luminance value, accurate determination cannot be performed. Therefore, for example, in the technique described in Japanese Patent Application Laid-Open No. Sho 59-225338 (hereinafter referred to as Document 1), it is utilized that the surface defects on the steel material are linear and the magnetic powder pool is often point-like. If the change in the luminance value near the highest luminance value on a certain scanning line is steep, it is a surface defect because the fluorescent magnetic powder is attached in a linear manner. The determination accuracy was improved by determining that the fluorescent magnetic powder was agglomerated, that is, a magnetic powder pool. In the technique described in Japanese Patent Application Laid-Open No. 62-52454 (hereinafter referred to as Document 2), a surface value is determined based on a luminance value obtained from a captured image and shape data of a previously registered surface defect and a magnetic powder pool. By determining whether or not there is a defect, the determination accuracy has been improved. In addition, in the technique described in Japanese Patent Application Laid-Open No. Hei 7-333197 (hereinafter referred to as Document 3), for those which can be clearly identified as surface defects based on the luminance value, judgment using the luminance threshold is made. For the unclear ones, the presence / absence of a surface defect was determined by a neural network model based on the statistical features of the surface defects taught in advance to improve the determination accuracy.

[0003]

However, according to the technique described in the above-mentioned reference 1, when there is a non-defective portion such as a magnetic powder pool in which the change in the luminance value is similar to the surface defect, it is discriminated from the surface defect. And the reliability of surface defect inspection is reduced. In addition, the above document 2
Alternatively, in the technique described in Reference 3, in order to detect a surface defect, it is necessary to teach a feature amount such as a shape of the surface defect to the apparatus in advance, and there is a problem that a burden on an operator is increased. In order to solve such problems in the prior art, the present invention has improved a surface flaw detection apparatus, and is arranged in a row in a direction intersecting with a predetermined direction in which articles are conveyed. By processing a captured image in units of shape pixels, it is possible to distinguish between surface defects and non-surface defect parts such as magnetic powder pools, and to quickly detect surface defects with high accuracy using a simple configuration. A first object is to provide a defect inspection apparatus. In addition, the second
The object of the present invention is to process a captured image by using a plurality of rectangular pixels which are arranged in a row in a direction intersecting a predetermined direction in which articles are conveyed and which are long in the predetermined direction.
By discriminating between surface defects and non-surface defects such as magnetic powder pools,
An object of the present invention is to provide a fluorescent magnetic particle flaw detection method capable of quickly performing high-precision magnetic particle flaw detection with a simple configuration.

[0004]

In order to achieve the first object, the invention according to claim 1 comprises a conveying means for conveying an article in a predetermined direction and a plurality of conveying means arranged in a direction intersecting the predetermined direction. Imaging means for imaging the surface of the article conveyed by the conveyance means, and processing the image of the article surface imaged by the imaging means, and forming a line in the predetermined direction on the surface of the article. A surface defect inspection apparatus comprising inspection means for inspecting the presence or absence of a formed surface defect, wherein the inspection means processes an image of the article surface in units of rectangular pixels long in the predetermined direction. Wherein the length of the short side of the rectangular pixel is set based on the length of a portion having the minimum surface defect to be inspected in a direction intersecting the predetermined direction. Surface flaw detector It is configured as. According to a second aspect of the present invention, in the surface defect inspection apparatus according to the first aspect, the length of the short side of the rectangular pixel is set to be shorter.
The gist is that the length of the portion having the surface defect is set to be equal to or less than half the length in a direction intersecting the predetermined direction. Further, the invention according to claim 3 is based on claim 1 or 2 described above.
Wherein the length of the long side of the rectangular pixel is a point-like non-surface defect portion formed on the surface of the article and a portion having the surface defect in the predetermined direction. The gist is that it is set based on the length. According to a fourth aspect of the present invention, in the surface defect inspection apparatus according to the third aspect, the length of the longer side of the rectangular pixel is equal to the length of the non-surface defect portion in the predetermined direction. The gist of the present invention is that the length is set to be not less than twice and not more than the length of the surface defect portion in the predetermined direction.

According to a fifth aspect of the present invention, in the surface defect inspection apparatus according to any one of the first to fourth aspects, the imaging means periodically exposes all pixels for a predetermined time. The length of the long side of the rectangular pixel is converted into a value obtained by adding the length of the rectangular pixel in the predetermined direction and the movement amount of the article within the predetermined time. Is the gist. According to a sixth aspect of the present invention, in the surface defect inspection apparatus according to any one of the first to fifth aspects, the rectangular pixels are spatially separated from a signal train input from the light receiving element. The gist is that it is created by performing filtering.
According to a seventh aspect of the present invention, in the surface defect inspection apparatus according to any one of the first to sixth aspects, an imaging optical system for imaging the image of the surface of the article on the imaging means is further provided. In addition, the gist of the invention is that the size of the pixel is set based on the size of the portion having the surface defect on the image forming surface in the imaging means. According to an eighth aspect of the present invention, in the surface defect inspection apparatus according to any one of the first to seventh aspects, the inspection means determines whether a luminance value of the pixel is larger or smaller than a predetermined judgment value. The gist of the present invention is to inspect for the presence or absence of surface defects. According to a ninth aspect of the present invention, in the surface defect inspection device according to any one of the first to eighth aspects, the article is a steel material, and the imaging means is provided on the magnetized steel material surface. The gist is to image fluorescence of the attached fluorescent magnetic powder. According to the surface defect inspection apparatus according to any one of claims 1 to 9, by processing a captured image in units of rectangular pixels long in a predetermined direction in which an article such as a steel material is conveyed, A surface defect linearly formed in the predetermined direction and a non-surface defect such as a magnetic powder pool can be easily and accurately discriminated, and the processing speed can be increased and the configuration can be simplified. . In particular, it is effective when detecting a surface defect of a steel material using a fluorescent magnetic particle flaw detection method. Further, by changing the exposure time of the rectangular pixel, by changing the length of the rectangular pixel in the predetermined direction substantially without changing the actual size of the pixel, Adjustment according to the size of the surface defect can be easily performed. Further, the adjustment of the size of the rectangular pixel can be performed by performing spatial filtering on the captured image, which allows more flexible adjustment.

According to a tenth aspect of the present invention, there is provided a magnetizing step of magnetizing a steel material conveyed in a predetermined direction, and a step of magnetizing the steel material in the predetermined direction on the surface of the magnetized steel material. A fluorescent magnetic powder adhering step of adhering the fluorescent magnetic powder to the surface defects, and an imaging step of imaging the fluorescence of the fluorescent magnetic powder adhering to the surface of the steel material by using a plurality of pixels arranged in a direction intersecting the predetermined direction. Processing a captured image of the surface of the steel material and inspecting the surface of the steel material for surface defects linearly formed in the predetermined direction on the surface of the steel material. In the inspection step, the image of the steel material surface is processed in units of rectangular pixels that are long in the predetermined direction, and the length of the long side of the rectangular pixels is determined by a dot-like fluorescence on the steel material surface. Formed by the adhesion of magnetic powder Is set based on the length in the predetermined direction of the non-surface defect portion and the surface defect portion where the fluorescent magnetic powder adheres to the surface defect, and the length of the short side of the rectangular pixel is to be inspected. It is configured as a fluorescent magnetic particle flaw detection method, which is set based on the length of the minimum surface defect portion in a direction intersecting the predetermined direction. Further, the invention according to claim 11 is the invention according to claim 1.
0, the length of the long side of the rectangular pixel is at least twice as long as the length of the non-surface defect portion in the predetermined direction, and the predetermined length of the surface defect portion is The length of the short side of the rectangular pixel is set to be equal to or less than half the length of the surface defect portion in the direction intersecting the predetermined direction. And According to the fluorescent magnetic particle flaw detection method according to claim 10 or 11, a process is performed on a captured image in units of rectangular pixels that are long in a predetermined direction in which a steel material is conveyed, thereby forming a linear shape in the predetermined direction. The determined surface defects and non-surface defects such as the accumulation of magnetic particles can be easily and accurately distinguished, and the processing speed can be increased and the configuration can be simplified.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiment is a specific example of the present invention and does not limit the technical scope of the present invention. As shown in FIG. 1, a fluorescent particle inspection apparatus 0 according to one embodiment of the present invention is an example in which the surface defect inspection apparatus according to the present invention is applied to a fluorescent particle inspection method, For example, an excitation magnet 3 for magnetizing the steel material 2 conveyed to the DD, a magnetic powder spraying device 4 for spraying a fluorescent magnetic powder solution on the steel material 2, and the steel material 2 by the magnetic powder spraying device 4.
A magnetic powder cleaning device 5 for cleaning a part of the fluorescent magnetic powder sprayed on the surface, and an ultraviolet light irradiating device 6 for irradiating the steel material 2 cleaned by the magnetic powder cleaning device 5 with ultraviolet light to make the fluorescent magnetic powder fluorescent. A rectangular pixel 9 which is long in the predetermined direction DD.
Are arranged in a line in a direction orthogonal to the predetermined direction, and are based on a line sensor 7 for imaging the surface of the steel material 2 to which the fluorescent magnetic powder adheres, and an image captured by the line sensor 7. And an inspection unit 8 for inspecting the presence or absence of a surface defect. The fluorescent magnetic particle flaw detector 0 is a device for inspecting the presence or absence of a surface defect SD linearly formed on the surface of the steel material 2 in the predetermined direction DD. This surface defect SD is formed in a linear manner by the minute surface defect SD formed in the shape of a dot on the surface of the steel material 2 being extended in the above-mentioned predetermined direction DD by a rolling process or the like, or being rubbed against a projection during the transportation. Often formed. FIG. 2A shows an example of the shape of a surface defect SD portion to be inspected. In FIG. 2A, the y axis is the predetermined direction DD, and the x axis is the predetermined direction DD.
The length of the surface defect SD portion in the y-axis direction is represented by M, and the length of the surface defect S in the x-axis direction is M.
The length of the D portion is represented by L. When such a surface defect SD is detected, for example, the surface defect S is detected.
The surface of the steel material 2 is repaired by shaving or burying the D portion.

The details of the above-described fluorescent magnetic particle flaw detection apparatus will be described together with the fluorescent magnetic particle flaw detection method according to the present invention.
In order to detect the surface defect SD, in the fluorescent magnetic particle inspection apparatus 0, as a first step, the steel material 2 transported in the predetermined direction DD by the transport device 1 is uniformly magnetized by the excitation magnet 3. (Magnetization step). However,
When the surface defect SD exists in the steel material 2, since a leakage magnetic flux exists in that portion, a stronger magnetic field is generated than in the portion having no surface defect SD. Then, next, the magnetic powder FM is sprayed on the surface of the magnetized steel material 2 by the magnetic powder spraying device 4 using water or the like as a medium (fluorescent magnetic powder attaching step). At this time, the fluorescent magnetic powder FM adheres at a high density in the vicinity of the surface defect SD where a strong magnetic field is generated, and is less likely to be peeled off as compared with other defect-free portions. Next, unnecessary fluorescent magnetic powder attached to portions other than the surface defect SD portion is washed away from the steel material surface by the cleaning device 5. However, the surface defect S
Even in portions other than D, the fluorescent magnetic powder FM solidifies and adheres around oil droplets and the like on the surface of the steel material 2, so that there is also a fluorescent magnetic powder FM that is not washed away and remains on the surface of the steel material 2 as it is. This is a so-called magnetic powder pool. This magnetic powder pool (non-surface defect part)
The MS is usually formed in a point shape. FIG. 2B shows an example of the shape of the non-surface defect portion MS. In FIG. 2B,
The diameter of the non-surface defect portion MS is represented by N. Next, the surface of the steel material 2 is imaged by the line sensor 7 in a state in which the fluorescent magnetic particles FM are fluoresced by irradiating ultraviolet rays linearly with the ultraviolet irradiating device 6 (imaging step).

The line sensor 7 has a plurality of pixels 9 arranged in a line in a direction perpendicular to the direction in which the steel material 2 is conveyed. As shown in FIG. 3, the fluorescence of the fluorescent magnetic powder FS attached to the surface of the steel material 2 is reflected on the pixels 9 of the line sensor 7 by an imaging optical system 10 having an optical axis in a direction perpendicular to or near the surface of the steel material 2. Is imaged. Also,
In the line sensor 7, for example, when light strikes the pixel 9 such as a photodiode, the charge is accumulated by that amount. The charge amount accumulated in each pixel 9 during a predetermined exposure time is read out collectively according to a transfer pulse periodically supplied from the outside. Since the steel material 2 is sequentially conveyed in the predetermined direction DD by the conveyance device 1, a captured image of the surface of the steel material 2 can be obtained by integrating the video output output from the line sensor 7.
Further, a rectangular pixel long in the predetermined direction DD in which the steel material 2 is transported is used as the pixel 9. The length of the short side of the rectangular pixel 9 is set based on the length L of the minimum surface defect SD to be inspected in a direction orthogonal to the predetermined direction DD. Or less than half of the The length of the long side of the rectangular pixel 9 is based on the length M of the surface defect SD in the predetermined direction DD and the length N of the non-surface defect MS in the predetermined direction DD. Is set, for example, the length N
The length is not less than twice and not more than the length M. Further, if the exposure time per pixel or the scanning speed of one line is not sufficiently shorter than the moving speed of the steel material 2 conveyed by the conveyance device 1, the steel material 2 during the exposure time is not used. It is necessary to consider the movement amount based on the length of the long side of the pixel 9. In this case, the light amount of the moved portion during the exposure time is also added to the pixel 9, so that the length of the long side of the rectangular pixel 9 is determined by the predetermined direction of the rectangular pixel 9. It is necessary to convert to the sum of the length of the DD and the amount of movement of the steel material 2 during the above exposure time.

Here, an example of a specific size of the pixel 9 will be determined with reference to FIG. The optical magnification of the imaging optical system 10 is 1/8, and the length of the surface defect SD portion in the y direction is 5
mm, the length in the x direction is 0.5 mm, the diameter of the non-surface defect portion MS is 1 mm, and the moving speed of the steel material 2 is 1000 mm.
/ Sec, and the scanning speed of one line is 1/1000 second. In this case, the surface defect SD on the surface of the steel material 2
The size of the portion on the image plane 11 on the line sensor 7 is 5/8 mm in the y direction and 0. 0 in the x direction.
5/8 mm, and the diameter of the non-surface defect portion MS is 1
/ 8 mm. In addition, each pixel 9 of the line sensor 7
During one scan, the steel material 2 moves in the predetermined direction D
1 mm in the direction D (y direction), and 1 mm on the image plane 10.
/ 8 mm. Therefore, the length (length in the y direction) of the longer side of the rectangular pixel 9 is 2 × １ ／ mm ≦ １ ／ mm + (length in the y direction) ≦ 5 /
8mm, that is, a value between 0.125 mm and 0.500 mm, for example, set to 0.200 mm. On the other hand, the length (length in the x direction) of the short side of the rectangular pixel 9 satisfies (length in the x direction) ≦ 0.5 / 8 mm / 2, that is, a value of 0.03125 mm or less. , For example, set to 0.020 mm. FIG. 4 shows the relationship between the size of the pixel 9, the surface defect SD portion, and the non-defect portion MS obtained as described above. When the scanning speed of one line is sufficiently shorter than the moving speed of the steel material 2 conveyed by the conveying device 1, the moving amount of the steel material 2 during the exposure time may be ignored. Further, the fact that the scanning speed is related to the length of the rectangular pixel 9 in the y direction as described above is based on the fact that the exposure time is changed so that the y of the rectangular pixel 9 can be changed without changing the hardware.
This means that the length in the direction can be substantially changed.
This enables adjustment according to the size of the surface defect SD. However, since the sensitivity changes as the exposure time changes, it is necessary to use pixels with a large dynamic range.

The video signal output from the line sensor 7 is input to the inspection unit 8 and stored. The inspection unit 8 processes the video signal in units of the rectangular pixels 9 and inspects the steel material 2 for the presence or absence of the surface defect SD (inspection step). Here, FIG.
FIG. 4 is a diagram showing a state in which a certain pixel includes the above-mentioned surface defect portion or the above-mentioned non-surface defect portion. In FIG. 5, a case where the surface defect SD portion is included in a certain pixel 9 (see FIG. 5A) and a case where the non-surface defect portion MS is included (see FIG. 5B) are shown. In comparison, since the pixel 9 is rectangular, the area occupied in the pixel 9 when the surface defect SD portion is included is larger than when the non-surface defect portion MS is included. That is, the amount of received light in a certain pixel 9 is larger when the surface defect SD portion is included than when the non-surface defect portion MS is included. For this reason, even when a predetermined threshold value is set for a certain pixel 9 and the presence / absence of a surface defect SD is inspected, a part which is originally a surface defect is not detected as a part which is not a defect, or a part which is not originally a surface defect It is difficult to perform over-detection for determining that is a defect. Further, since the surface defect SD portion is emphasized by a photodiode or the like as hardware, complicated processing is not required, the processing speed is high, and the configuration is simple. Also, the size of the pixel 9 is
As long as it is about half of the above surface defects,
There is no need to increase the pixel density. The threshold value for determining the presence or absence of the surface defect SD in the inspection unit 8 is preferably determined based on a state in which light is applied to almost the entire area of the pixel 9. For example, if the light amount when light hits almost the entire area of the pixel 9 is 10 and the minimum value is 0, the threshold value is set to about 9. With this setting, the surface defect SD portion and the non-surface defect portion MS are separated by the size of the pixel 9 as shown in FIG. In this case, for example, it is determined that the surface defect SD portion exists in the pixels 9a, 9b, and 9c. The inspection unit 8 performs the above-described surface defect S for the adjacent pixels 9.
If it is determined that there is a D portion, the existence range of the surface defect SD is easily specified without performing a process such as shape recognition by performing a process such as treating them as one surface defect SD. can do.

By the way, the size of each pixel is set as described above such that the length of the short side of the rectangular pixel 9 is set to, for example, half or less of the length L. The length of the long side is set to be, for example, not less than twice the length N and not more than the length M, because the light amount from the surface defect SD portion and the light amount of the non-surface defect portion MS are determined. Ratio, ie S
This is for ensuring the / N ratio. As shown in FIG. 5A, when the length of the short side of the rectangular pixel 9 is substantially the same as the length of the surface defect SD portion in the x direction, the surface defect SD in the x direction is substantially the same. The center is the pixel 9 as shown in FIG.
, The amount of light from the surface defect SD becomes almost half. If the surface defect SD portion slightly deviates in the x direction from the state of FIG. 6A, the light amount of either the adjacent pixel 9a or the pixel 9b increases, so that the state shown in FIG. In this state, the S / N ratio is the lowest for a certain surface defect SD. In other words, as shown in FIG. 6B, the length of the short side of the rectangular pixel 9 is determined by the length L in the x direction of the surface defect SD portion.
If the surface defect SD is set to be less than half, it is possible to make a state in which the surface defect SD exists in almost all the pixels 9 in any of the pixels 9 adjacent to a certain surface defect SD. When the S / N ratio is about 2 in order to sufficiently separate the surface defect SD portion and the non-surface defect portion MS, the S / N ratio between the surface defect SD portion and the non-surface defect portion MS is reduced. Assuming that the luminance per unit area is equal,
The length of the long side of the pixel 9 is determined by the non-surface defect portion MS.
Is set to about twice the diameter N of Since the luminance of the non-surface defect portion MS may be higher than the luminance of the surface defect SD portion, it is desirable that the luminance be higher than that. On the other hand, if the length of the long side of the pixel 9 is made longer than the length of the surface defect SD portion in the y direction, the ratio of the surface defect SD portion occupying the inside of the pixel 9 decreases accordingly. 9 is preferably set to be equal to or less than the length of the surface defect SD portion in the y direction.
As described above, the fluorescent magnetic particle flaw detector according to the present embodiment makes it possible to easily discriminate between a surface defect and a non-surface defect such as a magnetic particle pool by using a rectangular pixel that is long in the transport direction of the steel material. As a result, the processing speed can be increased and the configuration can be simplified.

[0013]

EXAMPLE In the above embodiment, the steel material 2 was inspected for the presence or absence of a surface defect SD by applying the fluorescent magnetic particle flaw detection method. However, a linear surface defect SD and a point-like non-surface defect MS are present. The present invention can be applied to surface defect inspection for such other members. Such a surface defect inspection apparatus is also an example of the surface defect inspection apparatus according to the present invention.
In the above-described embodiment, the inspection unit 8 performs the inspection for the presence or absence of the surface defect SD using the video signal from the pixel 9 of the line sensor 7 as it is. Create a two-dimensional image I as shown in
By applying spatial filtering to this, a new pixel 9s composed of, for example, pixel 9a and pixel 9d is created,
The presence or absence of the surface defect SD may be inspected in units of the pixel 9s. Thereby, an effective inspection can be performed for the surface defect SD having an arbitrary shape. In addition, by performing different spatial filtering on a certain image a plurality of times, it is possible to further improve the inspection accuracy. Such a surface defect inspection apparatus and a fluorescent magnetic particle inspection method are also examples of the surface defect inspection apparatus and the fluorescent magnetic particle inspection method in the present invention.

[0014]

As described above, according to the surface defect inspection apparatus according to any one of the first to ninth aspects, a rectangular pixel long in a predetermined direction in which an article such as a steel material is conveyed is used as a unit. By performing processing on the captured image, surface defects linearly formed in the above-mentioned predetermined direction and non-surface defects such as magnetic powder accumulation can be easily and accurately distinguished. Simplification can be achieved. In particular, it is effective when detecting a surface defect of a steel material using a fluorescent magnetic particle flaw detection method. Further, by changing the exposure time of the rectangular pixel, by changing the length of the rectangular pixel in the predetermined direction substantially without changing the actual size of the pixel, Adjustment according to the size of the surface defect can be easily performed. further,
The adjustment of the size of the rectangular pixel can also be performed by performing spatial filtering on the captured image, and more flexible adjustment is possible. Further, the above-mentioned claim 10 or 11
According to the fluorescent magnetic particle flaw detection method described in (1), by processing the captured image in units of rectangular pixels that are long in the predetermined direction in which the steel material is conveyed, the surface defects linearly formed in the predetermined direction and the magnetic powder are processed. Non-surface defects such as pools can be easily and accurately discriminated, and the processing speed can be increased and the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a fluorescent magnetic particle flaw detector according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of the shape of a surface defect portion and a non-surface defect portion.

FIG. 3 is a diagram illustrating an imaging optical system.

FIG. 4 is a diagram showing a specific example of the relationship between the sizes of pixels, surface defect portions, and non-surface defect portions.

FIG. 5 is a diagram for explaining the determination of a surface defect portion and a non-surface defect portion.

FIG. 6 is a view for explaining an S / N ratio of a surface defect portion.

FIG. 7 is a diagram illustrating pixel formation by spatial filtering.

FIG. 8 is a diagram showing a schematic configuration of an automatic flaw detection apparatus capable of performing the fluorescent magnetic particle flaw detection method.

FIG. 9 is a view showing a detection result of a surface defect by the automatic flaw detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conveying apparatus 2 ... Steel material (article) 7 ... Line sensor (imaging means) 8 ... Inspection part (inspection means) 9 ... Pixel FM ... Fluorescent magnetic powder SD ... Surface defect MS ... Non-surface defect part

Continuation of the front page (72) Inventor Hideo Katsumi 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Co., Ltd. No. 1 Inside Kobe Steel, Ltd.Takasago Works (72) Inventor Hironobu Tanaka 1st Kanazawa-cho, Kakogawa-shi, Hyogo Prefecture Inside Kobe Steel, Ltd.Kakogawa Works (72) Inventor Noriyoshi Nanaseya Kanazawa-cho, Kakogawa-shi, Hyogo 1 Kobe Steel Works Kakogawa Works (72) Inventor Hiroaki Kaita 2 Nadahama-Higashi-cho, Nada-ku, Kobe City, Hyogo Prefecture Kobe Steel Works Kobe Steel Works, Ltd. (72) Inventor Katsutoshi Kumagai Natsu-ku, Kobe City, Hyogo Prefecture Nadahama Higashicho 2 Kobe Steel Works Kobe Works

Claims (11)

[Claims] 1. A conveying means for conveying an article in a predetermined direction,
An imager having a plurality of pixels arranged in a direction intersecting with the predetermined direction and imaging the surface of the article conveyed by the conveyor; processing an image of the article surface imaged by the imager; An inspection means for inspecting the presence or absence of a surface defect linearly formed in the predetermined direction on the surface of the article, wherein the inspection means detects a rectangular pixel long in the predetermined direction. The image of the surface of the article is processed as a unit, and the length of the short side of the rectangular pixel is the length of the portion having the smallest surface defect to be inspected in the direction intersecting the predetermined direction. A surface defect flaw detection device characterized by being set based on the surface defect. 2. The device according to claim 1, wherein the length of the short side of the rectangular pixel is set to be less than half the length of the portion having the surface defect in the direction intersecting the predetermined direction. Surface flaw detection equipment. 3. The method according to claim 1, wherein the length of the long side of the rectangular pixel is based on the length of the point-like non-surface defect portion formed on the surface of the article and the portion having the surface defect in the predetermined direction. The surface defect flaw detection device according to claim 1, wherein the surface flaw detection device is set by setting. 4. The length of the long side of the rectangular pixel is at least twice the length of the non-surface defect portion in the predetermined direction and not more than the length of the surface defect portion in the predetermined direction. The surface defect flaw detection apparatus according to claim 3, wherein the flaw detection apparatus is set to: 5. The apparatus according to claim 1, wherein the imaging means periodically performs exposure for all pixels for a predetermined time, and a length of a long side of the rectangular pixel is equal to the predetermined length of the rectangular pixel. The surface defect inspection apparatus according to any one of claims 1 to 4, wherein the apparatus is converted into a value obtained by adding a length in a direction and a movement amount of the article within the predetermined time. 6. The surface defect inspection according to claim 1, wherein the rectangular pixels are created by performing spatial filtering on a signal sequence input from the light receiving element. apparatus. 7. An image forming optical system for forming an image of the surface of the article on the image pickup means, and a portion of the image pickup means having the surface defect on the image forming surface of the image pickup means. Claim 1 which is set based on the size of
7. The surface defect flaw detector according to any one of 6. 8. The surface defect according to claim 1, wherein said inspection means inspects the presence or absence of a surface defect based on whether the luminance value of said pixel is larger or smaller than a predetermined judgment value. Flaw detector. 9. The article according to claim 1, wherein the article is a steel material, and wherein the imaging means images fluorescence of the fluorescent magnetic powder attached to the surface of the magnetized steel material. Surface flaw detection equipment. 10. A magnetizing step of magnetizing a steel material conveyed in a predetermined direction, a fluorescent magnetic powder attaching step of attaching fluorescent magnetic powder to a surface defect formed in the predetermined direction on the surface of the magnetized steel material, and An imaging step of imaging the fluorescence of the fluorescent magnetic powder attached to the surface of the steel material by using a plurality of pixels arranged in a direction intersecting with the direction, and processing the captured image of the surface of the steel material to obtain an image of the surface of the steel material. An inspection step of inspecting the presence or absence of a surface defect linearly formed in the predetermined direction, wherein the inspection step is performed by using the steel material in units of rectangular pixels long in the predetermined direction. The image of the surface is processed. The length of the long side of the rectangular pixel is determined by the non-surface defect portion formed by the point-like fluorescent magnetic powder attached to the steel material surface and the surface defect. Fluorescent magnetic powder attached The length of the short side of the rectangular pixel is set based on the length of the surface defect portion in the predetermined direction. The length of the short side of the rectangular pixel in the direction intersecting the predetermined direction of the minimum surface defect portion to be inspected is set. A fluorescent magnetic particle flaw detection method, wherein the method is set based on the following. 11. The length of the long side of the rectangular pixel is:
The length of the non-surface defect portion is set to be at least twice the length in the predetermined direction and the length of the surface defect portion to be equal to or less than the length in the predetermined direction. The fluorescent magnetic particle flaw detection method according to claim 10, wherein the length of the surface defect portion is set to be equal to or less than half the length in a direction intersecting the predetermined direction.