JP2000111527A - Magnetic particle inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic particle inspection apparatus by which a transverse flaw and a longitudinal flaw are detected with good sensitivity and in which a pretreatment such as a shading correction or the like is not required by a method wherein each differential processing operation is performed in the transverse direction and the longitudinal direction, and a differential filter which performs an integral processing operation in a direction at right angles to the respective directions is used. SOLUTION: In an image processor 8, a transverse-flaw detecting device 10 performs a differential operation in the longitudinal direction along the longitudinal direction of a steel piece, it performs a differential processing operation regarding an imaged image by using a rectangular differential filter which performs an integral operation in the transverse direction along the width direction of the steel piece, it generates a differential image in the longitudinal direction, and it detects a transverse flaw along the transverse direction on the basis of the differential image in the longitudinal direction. A longitudinal-flaw detecting device 11 performs a differential operation in the transverse direction, it performs a differential processing operation regarding the imaged image by using a rectangular differential filter which performs an integral operation in the longitudinal direction, and it detects a longitudinal flaw along the longitudinal direction. In a flaw-judged-result integration device 12, a flaw which is smaller than a prescribed threshold value is integrated on the basis of the distance between respective flaws out of the transverse flaw and the longitudinal flaw which are detected by the transverse and longitudinal-flaw detecting devices 10, 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic particle flaw detector, and more particularly, to a method for attaching fluorescent magnetic powder to the surface of a magnetized steel slab and imaging fluorescence generated by the fluorescent magnetic powder attached to the steel slab. The present invention relates to a magnetic particle flaw detection device for flaw detection of the steel slab based on a captured image obtained.

[0002]

2. Description of the Related Art One of the typical techniques for detecting flaws formed on the surface of a steel slab is a method called a fluorescent magnetic particle flaw detection method. This fluorescent magnetic particle flaw detection method involves applying fluorescent magnetic powder to a magnetized steel slab and detecting the difference between the fluorescent luminance of the fluorescent magnetic powder adhered to the part where the flaw is present and the fluorescent luminance of the fluorescent magnetic powder adhered to the non-existent part. Is what you do. Here, FIG. 5 shows a schematic configuration of a magnetic particle flaw detector for performing the fluorescent magnetic particle flaw detection method. As shown in FIG. 5, the magnetic particle flaw detector comprises a steel slab 2 transported in a predetermined direction DD by a transport device 1.
Magnet 3 for magnetizing the magnet 3, a magnetic powder dispersing device 4 for spraying a fluorescent magnetic powder solution to the steel slab 2 magnetized by the excitation magnet 3, and a fluorescent magnetic powder attached to the surface of the steel slab 2 by irradiating the steel slab 2 with ultraviolet rays. UV irradiation device for fluorescing
An imaging unit 7 for imaging the fluorescence emitted from the fluorescent magnetic powder by the irradiation of the ultraviolet light from the ultraviolet irradiation device 6, an image processing device 8 for flaw detection of the steel slab 2 based on the image captured by the imaging unit 7, and the like. It comprises. In the magnetic particle flaw detector, first, the steel piece 2 is magnetized by the excitation magnet 3. Next, fluorescent magnetic powder is sprayed on the surface of the magnetized steel slab 2 by a magnetic powder spraying device 4 using water or the like as a medium. For example, since a magnetic flux leakage as shown in FIG. 6 is present in a portion where a flaw exists on the surface of the steel slab 2, a stronger magnetic field is generated than in a portion having no flaw. Adheres at high density near the flaws. Next, the surface of the steel slab 2 is irradiated with ultraviolet light from the ultraviolet light irradiating unit 6, and the fluorescence emitted from the fluorescent magnetic powder by the irradiation of the ultraviolet light is emitted to the CCD.
The image is captured by the image capturing unit 7 including the above. The image picked up by the image pickup unit 7 is supplied to an image processing device 8, where predetermined image processing is performed, and flaws on the billet 2 are detected. Incidentally, the flaws formed on the surface of the billet 2 are largely classified into vertical flaws generated along the longitudinal direction of the billet 2 and lateral flaws generated along the width direction of the billet 2, as shown in FIG. However, since the characteristics such as length and shape are different depending on the type of flaw, for example, in the technique described in JP-A-8-82616, a plurality of binary A coded image is generated, and the flaw of the steel slab is discriminated from the feature amount such as the area and length of the flaw appearing in each binarized image.

[0003]

However, when the flaws are detected by binarizing the captured image as it is, as in the technique disclosed in the above-mentioned publication, the surface of the steel slab remains on the slab surface due to the surface properties of the slab. If the fluorescence intensity from the fluorescent magnetic powder is large and the S / N ratio of the captured image is small, the depth becomes shallow,
Due to its small size, flaws with weak fluorescence intensity may not be detected, or noise other than flaws may be detected as flaws. If the intensity of the ultraviolet light emitted from the ultraviolet irradiation device 6 is uneven, or if the fluorescent magnetic powder adhering to the steel slab 2 is uneven, as shown in FIG. When the flaw is detected by binarizing the captured image as it is, it becomes difficult to set a threshold value. For this reason, there have been problems such as the need for a light source having no luminance unevenness, and the necessity of performing pre-processing such as shading correction to make the luminance of the background constant in image processing. In order to solve the problems in the prior art, the present invention has improved a magnetic particle flaw detector, and performs a differential process in each of a horizontal direction and a vertical direction, and performs an integration process in a direction perpendicular to each direction. It is an object of the present invention to provide a magnetic particle flaw detection apparatus which detects horizontal flaws and vertical flaws with high sensitivity and does not require preprocessing such as shading correction. Further, when the difference processing is performed in the horizontal direction and the vertical direction to detect the horizontal flaw and the vertical flaw, the flaw which is originally one may be detected as both the horizontal flaw and the vertical flaw. In this case, the load on the automatic flaw removing device in the post-process increases. Therefore, another object of the present invention is to reduce the load on an automatic flaw removal device in a subsequent process by performing a process of integrating flaws based on horizontal flaws and vertical flaws.

[0004]

In order to achieve the above object, according to the first aspect of the present invention, a fluorescent magnetic powder is attached to a surface of a magnetized steel slab, and the fluorescent magnetic powder attached to the steel slab emits a fluorescent magnetic powder. In a magnetic particle flaw detection device for imaging flaws of the steel slab based on the obtained captured image, a differential operation is performed in a first direction and an integration operation is performed in a direction perpendicular to the first direction. A first differential image is generated by performing a differentiation process on the captured image using a differential filter of the first type, and a flaw in a direction perpendicular to the first direction is detected based on the first differential image. Using the flaw detection means of the above and a rectangular differential filter that performs a differentiation operation in a second direction different from the first direction and performs an integration operation in a direction perpendicular to the second direction. Processing to generate a second differential image, Based on the partial image is configured as a magnetic particle flaw detection apparatus characterized by comprising comprises a second defect detecting means for detecting a flaw in the second direction perpendicular to the direction. According to a second aspect of the present invention, in the magnetic particle flaw detector according to the first aspect, the first flaw detecting means and the second flaw detecting means are arranged so that the first differential image or the second Binarization processing means for generating a binarized image obtained by binarizing the differential image, labeling processing means for performing labeling processing on the binarized image and grouping connected pixels into a group, and collecting by the labeling processing means The gist of the present invention is to provide an evaluation means for evaluating each group obtained and a flaw determination means for determining the presence or absence of a flaw based on the evaluation result of each group by the evaluation means. According to a third aspect of the present invention, in the magnetic particle flaw detection apparatus according to the first or second aspect, the evaluation means includes an area of each of the groups and a first area included in each of the groups.
Alternatively, the gist is that each group is evaluated using the product of the maximum luminance value of the second differential image and the value obtained by subtracting the binarization threshold value. According to a fourth aspect of the present invention, in the magnetic particle flaw detector according to any one of the first to third aspects, each flaw detected by the first flaw detection means and the second flaw detection means is provided. The gist of the invention is to provide a flaw integrating means for integrating flaws satisfying a predetermined standard. Further, according to a fifth aspect of the present invention, in the magnetic particle flaw detector according to the fourth aspect, the predetermined criterion is set between each of the flaws detected by the first flaw detection means and the second flaw detection means. Is smaller than a predetermined threshold value. Claims 1 to 5 above
According to the magnetic particle flaw detection apparatus described in any one of the above, the captured image is obtained by using a rectangular differential filter that performs a differentiation operation in a first direction and performs an integration operation in a direction perpendicular to the first direction. , A first differential image is generated, a flaw in a direction perpendicular to the first direction is detected based on the first differential image, and a second flaw different from the first direction is detected.
A differential operation is performed on the captured image using a rectangular differential filter that performs a differential operation in the direction of and performs an integration operation in a direction perpendicular to the second direction to generate a second differential image. Since flaws in a direction perpendicular to the second direction are detected based on the differential image of No. 2, it is not necessary to perform preprocessing such as shading correction, and horizontal flaws and vertical flaws can be detected with high sensitivity. In particular, in the magnetic particle flaw detector according to the fourth or fifth aspect, among the detected horizontal flaws and vertical flaws, for example, when the distance between the flaws is smaller than a predetermined threshold value, the flaw integration processing is performed. The load on the automatic flaw removing device in the post-process can be reduced.

[0005]

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. Here, FIG. 1 is a functional block diagram for explaining a main part of the magnetic particle flaw detector according to one embodiment of the present invention. A magnetic particle flaw detector according to one embodiment of the present invention attaches a fluorescent magnetic powder to a surface of a magnetized steel slab, captures an image of fluorescence emitted by the fluorescent magnetic powder attached to the steel slab, and, based on the obtained captured image. 5 to detect flaws on the steel slab.
Has the same configuration as the conventional magnetic particle flaw detection apparatus already shown in FIG. That is, the magnetic particle flaw detection apparatus according to the present embodiment includes an excitation magnet 3 for magnetizing a steel slab 2 conveyed in a predetermined direction DD by a conveyance device 1, and a fluorescent magnetic powder solution applied to the steel slab 2 magnetized by the excitation magnet 3. A magnetic powder dispersing device 4 for spraying, an ultraviolet irradiator 6 for irradiating ultraviolet rays to the steel slab 2 to fluoresce the fluorescent magnetic powder attached to the surface of the steel slab 2, This is almost the same as the conventional one in that an imaging unit 7 that captures the fluorescence emitted from the camera and an image processing device 8 that detects flaws on the steel slab 2 based on the image captured by the imaging unit 7 are provided. . On the other hand, the magnetic particle flaw detector according to the present embodiment is particularly different from the conventional one, as shown in FIG. 1 in that the image processing device 8 performs a differential operation in the longitudinal direction along the longitudinal direction of the billet 2. Using a rectangular difference filter that performs a multiplication operation in the horizontal direction along the width direction of the billet 2, the captured image is subjected to difference processing to generate a vertical difference image, and the vertical difference image is generated. A side flaw detection device 10 (an example of a side flaw detection unit) that detects a side flaw along the horizontal direction based on the above, and a rectangular difference filter that performs the horizontal difference operation and performs the vertical integration operation A vertical flaw detection device 11 (vertical flaw detection means) that performs a difference process on the captured image to generate a horizontal difference image, and detects a vertical flaw along the vertical direction based on the horizontal difference image. And an example of the lateral flaws detected by the lateral flaw detection device 10. And the vertical flaw detection apparatus 11
And a flaw determination result integration device 12 (an example of flaw integration means) that integrates flaws in which the distance between the flaws is smaller than a predetermined threshold value among the vertical flaws detected by the method. .

The details of the magnetic particle flaw detector will be described below. However, since the configuration common to the conventional one is as described above, the description will be omitted unless necessary. In the above-described magnetic particle flaw detector, a captured image obtained by capturing the fluorescence emitted from the fluorescent magnetic particles attached to the vicinity of the flaw SD on the surface of the steel piece 2 is supplied from the imaging unit 7 to the image processing device 8. In the image processing device 8, the captured image is input to the lateral flaw detection device 10 and the vertical flaw detection device 11, respectively. The side flaw detection device 10 is, for example, as shown in FIG.
As shown in (a), a vertical difference image is generated by performing a difference process on the captured image using a rectangular difference filter 101a that performs the above-described vertical difference operation and performs the above-described horizontal integration operation. Side flaw difference filter processing means 101
And a horizontal flaw binarization processing means 102 (a binarization processing means) for performing a binarization process on the vertical difference image generated by the horizontal flaw difference filter processing means 101 to generate a horizontal flaw binary image. And the above-mentioned side flaw binarization processing means 102
Flaw labeling processing means 103 (an example of labeling processing means) for performing labeling processing on the horizontal flaw binarized image generated by the above and grouping the connected pixels in the horizontal flaw binarized image into groups, and the above-mentioned horizontal flaw labeling Processing means 10
3. A lateral flaw evaluation value calculation means 104 (an example of an evaluation means) for calculating an evaluation value for each group compiled by 3;
A lateral flaw determining means 105 (an example of a flaw determining means) for determining the presence or absence of a lateral flaw along the lateral direction based on the evaluation value calculated by the lateral flaw evaluation value calculating means 104; The captured image input to the side flaw detection device 10 is subjected to difference processing by the side flaw difference filter processing means 101 using the difference filter 101a. By this difference processing, a vertical difference image is generated from which the steep vertical luminance change is extracted. This makes it possible to detect the lateral flaws effectively even when the lateral flaws are shallow or the size of the lateral flaws is small, so that the lateral flaws can be imaged only with a weak fluorescent luminance. . In addition, due to the integration process in the horizontal direction performed by the difference filter 101a, the intensity of the ultraviolet light emitted from the ultraviolet irradiation device 6 becomes uneven, and the fluorescent magnetic powder adhered in the shape of the billet 2 becomes uneven. Even if there is a change in brightness as shown in (1), the effect of the change in brightness is averaged and suppressed, so there is no need to use a light source without irradiation unevenness or perform shading correction as preprocessing. , Device configuration and image processing can be simplified. further,
Elimination of noise components and the like due to oil contamination is also facilitated. Then, the difference image in the vertical direction generated by the horizontal flaw difference filter processing means 101 is combined with the horizontal flaw binarization processing means 10.
In step 2, a binarization process is performed using a predetermined threshold value to generate a side flaw binarized image. By this binarization processing, the flaw and the other background portion are separated. The binarized image of side flaws is used as the side flaw labeling processing means 103.
Is subjected to labeling processing. That is, among the pixels corresponding to the flaws, the connected pixels are grouped into one group, and a different number is assigned to each group. The information of each group compiled by the lateral flaw labeling processing means 103 is supplied to the lateral flaw evaluation value calculating means 104, and an evaluation value is calculated for each group. Here, the evaluation value is calculated, for example, in accordance with the formula of the area of the region to which the same number is assigned × (the maximum value of the difference image of the region—the threshold for binarization). That is, even when the area of the region assigned the same number is small, the evaluation value is set to be large when the difference luminance is bright. The evaluation value calculated in this way is supplied to the lateral flaw determining means 105. Then, the side flaw determining means 105 determines whether the side flaw is a side flaw based on whether or not the evaluation value is larger than a predetermined threshold value.
The region determined to be a lateral flaw by the lateral flaw determining means 105 is output to the flaw determination result integrating device 12 together with information on its position, size, direction, and the like. on the other hand,
The vertical flaw detection device 11 performs a difference process on the captured image using a rectangular difference filter 111b that performs the horizontal difference operation and performs the vertical integration operation as shown in FIG. 2B, for example. And a vertical flaw difference filter processing means 111 for generating a horizontal difference image, and performing a binarization process on the horizontal difference image generated by the vertical flaw difference filter processing means 111 to binarize the vertical flaw. Vertical flaw binarization processing means 112 (an example of a binarization processing means) for generating an image, and pixels connected by performing a labeling process on the vertical flaw binary image generated by the vertical flaw binarization processing means 112 and connected Flaw labeling processing means 1 for grouping
13 (an example of labeling processing means), a vertical flaw evaluation value calculating means 114 (an example of evaluation means) for calculating an evaluation value for each group compiled by the vertical flaw labeling processing means 113, and a vertical flaw evaluation value calculation A vertical flaw determining means 115 (an example of a flaw determining means) for determining the presence or absence of a vertical flaw along the vertical direction based on the evaluation value calculated by the means 114; In
Vertical flaws are detected and output to the flaw determination result integrating device 12 together with the information. The vertical flaw binarization processing means 11
It is not necessary to set the threshold value used in the binarization process of 2 to be the same as the threshold value used in the binarization process of the side flaw binarization processing means 102. Pre-selected. Then, the flaw integration means 121 of the flaw determination result integration device 12 uses the lateral flaw detection device 10.
Of the horizontal flaws detected by the above and the vertical flaws detected by the vertical flaw detection device 11 are integrated. As shown in FIG. 3, for example, as shown in FIG. 3, in the flaw integration processing, the intervals dx and dy of the circumscribed rectangles of the flaws detected by the horizontal flaw detection device 10 and the vertical flaw detection device 11 are set to predetermined threshold values thx and thy. It is done when smaller. At this time, the horizontal flaw and the vertical flaw may be integrated into one flaw. In this case, for example, the flaw of the flaw in which the number or area of the included horizontal flaw and vertical flaw is larger is integrated. Seeds. This flaw integration processing prevents one flaw from being divided into a plurality of parts due to the above-described vertical and horizontal difference processing, and can reduce the load on an automatic flaw removing device that is a post-process. . The information of the flaw integrated by the flaw integration means 121 is output to a process computer or the like by the transmission means 122 provided in the flaw determination result integration device 12. As described above, according to the magnetic particle flaw detector according to the present embodiment, since the difference is made in the vertical direction and the horizontal direction, even when the fluorescent luminance is small due to a shallow depth or the like, both flaws are removed. Detection can be performed with high sensitivity. In addition, by performing the integration process in the same direction as the flaw, it is possible to eliminate the effects of luminance unevenness and fluorescent magnetic powder adhesion unevenness. Further, since the vertical flaws and the horizontal flaws are detected in parallel, the processing speed can be improved as compared with the case where the processing is performed in a permuted manner. Moreover, since the vertical flaws and the horizontal flaws are integrated by the flaw integrating means and then supplied to an automatic flaw removing device in a subsequent process, the load on the automatic flaw removing device can be reduced, and the flaw removing time can be further reduced. Can be.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the above-described embodiment, a rectangular differential filter for performing a differential process in a predetermined direction and performing an integrating process in a direction perpendicular to the predetermined direction has a 5 × 3 mask and a 3 × 3 mask.
Although 11 masks are used, the present invention is not limited to this, and other rectangular difference filters having different mask sizes and different weighting coefficients may be used. Further, in the above embodiment, the difference processing is performed in the vertical direction and the horizontal direction, but the present invention is not limited to this. Such a magnetic particle flaw detector is also an example of the magnetic particle flaw detector according to the present invention. In the above-described embodiment, the evaluation value is calculated using the evaluation formula of “area of region to which the same number is assigned by the labeling process × (maximum value of difference image of this region−threshold for binarization)”. However, the present invention is not limited to this. For example, only the luminance or the area may be used as the evaluation value, or the evaluation value may be calculated using an evaluation expression of luminance × area. Such a magnetic particle flaw detector is also an example of the magnetic particle flaw detector according to the present invention. Further, in the above-described embodiment, an image is captured only on one surface of the billet 2 and flaw detection formed on the surface of the billet 2 is performed. However, the present invention is not limited to this. For example, FIG. As shown in the figure, for example, eight imaging units 6 may be provided around the steel slab 2 so as to inspect four surfaces and four corners of the steel slab 2 at the same time. In this case, the corresponding number of the image processing devices 6 may be provided, or one image processing device 6 including the corresponding number of the horizontal flaw detection devices 10 and the vertical flaw detection devices 11 may be provided. Good. Further, it is not always necessary to use the eight imaging units 6 at the same time. For example, flaw detection may be performed in two stages of five and three units. Such a magnetic particle flaw detector is also an example of the magnetic particle flaw detector according to the present invention.

[0008]

As described above, according to the magnetic particle flaw detector according to any one of the first to fifth aspects, the differential operation is performed in the first direction, and the differential operation is performed in the direction perpendicular to the first direction. A first differential image is generated by performing a differential process on the captured image using a rectangular differential filter that performs an integrating operation,
A flaw in a direction perpendicular to the first direction is detected based on the first differential image, and a differential operation is performed in a second direction different from the first direction to perform a differential operation in a direction perpendicular to the second direction. A second differential image is generated by performing a differential process on the captured image using a rectangular differential filter that performs an integrating operation,
Since flaws in a direction perpendicular to the second direction are detected based on the second differential image, preprocessing such as shading correction is not required, and horizontal flaws and vertical flaws can be detected with high sensitivity. . In particular, in the magnetic particle flaw detector according to the fourth or fifth aspect, among the detected horizontal flaws and vertical flaws, for example, when the distance between the flaws is smaller than a predetermined threshold value, the flaw integration processing is performed. The load on the automatic flaw removing device in the post-process can be reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram for explaining a main part of a magnetic particle flaw detector according to an embodiment of the present invention.

FIG. 2 is a view for explaining an example of a differential filter used in the magnetic particle inspection apparatus.

FIG. 3 is a diagram for explaining a flaw integration process in the magnetic particle flaw detection apparatus.

FIG. 4 is a diagram showing a schematic configuration of a magnetic particle flaw detector according to one embodiment of the present invention.

FIG. 5 is a view showing an example of a conventional magnetic particle flaw detector.

FIG. 6 is a view for explaining a fluorescent magnetic particle flaw detection method.

FIG. 7 is a view for explaining types of flaws.

FIG. 8 is a diagram illustrating a shading correction process and the like.

[Explanation of symbols]

 Reference Signs List 2 steel billet 8 image processing device 10 lateral flaw detection device 11 vertical flaw detection device 12 flaw determination result integration device 101 horizontal flaw difference filter processing means 102 horizontal flaw binarization processing means 103 horizontal flaw labeling Processing means 104 ... Horizontal flaw evaluation value calculation means 105 ... Horizontal flaw determination means 111 ... Vertical flaw difference filter processing means 112 ... Vertical flaw binarization processing means 113 ... Vertical flaw labeling processing means 114 ... Vertical flaw evaluation value calculation means 115 ... Vertical flaw determination means 121 ... flaw integration means

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yo Okamoto 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel, Ltd. (72) Inventor Masaru Akamatsu Takatsuka, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Institute of Technology, Kobe Steel Ltd. (72) Inventor Takeo Ogawa 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Research Institute F-term ( Reference) 2G051 AA37 AB02 EA08 EA11 EB01 GD02 GD03 2G053 AA11 AB22 CB24 CB27 DC17 DC20

Claims (5)

[Claims] 1. A fluorescent magnetic powder is attached to the surface of a magnetized steel slab, the fluorescence emitted by the fluorescent magnetic powder attached to the steel slab is imaged, and flaws on the steel slab are detected based on the obtained captured image. In the magnetic particle flaw detection apparatus, a differentiation process is performed on the captured image using a rectangular differential filter that performs a differentiation operation in a first direction and performs an integration operation in a direction perpendicular to the first direction to perform a first differentiation. First flaw detecting means for generating an image and detecting a flaw in a direction perpendicular to the first direction based on the first differential image; and performing a differential operation in a second direction different from the first direction. And performing a differentiation process on the captured image using a rectangular differential filter that performs an integration operation in a direction perpendicular to the second direction to generate a second differential image. Detecting a flaw in a direction perpendicular to the second direction based on the second direction A magnetic particle flaw detector comprising a flaw detecting means. 2. A binary system wherein said first flaw detection means and said second flaw detection means generate a binarized image obtained by binarizing the first differential image or the second differential image. Labeling processing means for performing labeling processing on the binarized image to group connected pixels into groups;
2. The apparatus according to claim 1, further comprising: evaluation means for evaluating each group compiled by said labeling processing means; and flaw determination means for determining the presence or absence of a flaw based on the evaluation result of each group by said evaluation means. Magnetic particle flaw detector. 3. The evaluation means uses a product of an area of each group and a value obtained by subtracting a binarization threshold from a maximum luminance value of the first or second differential image included in each group. And the evaluation of each group.
Or the magnetic particle flaw detector according to 2. 4. A flaw integrating means for integrating flaws satisfying a predetermined standard among the flaws detected by the first flaw detection means and the second flaw detection means.
4. The magnetic particle flaw detector according to any one of the items 3 to 5. 5. The method according to claim 4, wherein the predetermined criterion is that a distance between the flaws detected by the first flaw detection means and the second flaw detection means is smaller than a predetermined threshold value. The magnetic particle flaw detector according to the above.