JP3490809B2 - Metal strip surface flaw inspection method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface flaw of a metal strip which automatically inspects the surface flaw of a metal strip such as a stainless steel strip which is passed through a continuous treatment line for bright annealing and determines a grade rating. An inspection method and an apparatus.

[0002]

2. Description of the Related Art For example, in a production line for a metal strip containing stainless steel or the like, a metal steel strip is manufactured through steps such as rolling, annealing, and pickling. After rolling, the deformed crystal grains of the metal strip are recrystallized and heated in an annealing furnace to soften them, and descaling is performed in the pickling step to remove scales and the like attached by the annealing, further washed with water and dried. , Winding up as a coil, and obtaining the final product through many more steps. At each stage of these steps, the state of the front and back surfaces of the metal strip is visually inspected and Grades are assigned to each unit length of the final product depending on the degree of defects (heavy, medium, and light) such as flaws and scales.

As described above, conventionally, the inspection of defects on the front and back surfaces of the metal strip is performed by human visual inspection, so that human cost is required and the inspection result is affected by the physical condition of the inspector. I can't avoid it. In addition, this inspection place is not necessarily a good working environment, and it is required to avoid human placement as much as possible.

Another prior art has a structure in which a laser beam is irradiated in the width direction of a metal strip, and only the specularly reflected light is received and detected, and a grade is given by a flaw in the metal strip. In this prior art, there is a problem that the rating of the surface flaws of the metal strip is low in coincidence with the operator's evaluation.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to make it possible to automatically perform an inspection as much as visual inspection by an operator, and to automatically perform grading of metal bands in real time. It is an object of the present invention to provide a method and an apparatus for inspecting a surface flaw of a metal band.

[0006]

According to the present invention, a laser beam is scanned in the width direction of a metal strip running in the longitudinal direction, the reflected light is received and detected, and a plurality of grade evaluation unit sections Q are detected. Each defect judgment unit section q is configured to include each defect judgment unit section q.
Is composed of a plurality of pixels q1 and the reflected light intensity V and the area S of the defect determination unit section q are determined by the received light detection signal.
The weighted addition value F, which is the product of and, is obtained, and the binary data of each pixel q1 is obtained from the received light detection signal, and the average length of the flaw along the traveling direction of each flaw determination unit section q is obtained from this binary data. A plurality of feature amounts including AH (= HA / NA) are calculated and obtained, and the feature amount is used to determine the defect type for each defect determination unit section q and the defect form for each defect type, and each defect determination unit The judgment grade weight value φ corresponding to the defect type and defect form of the section q and the weight addition value F of the defect determination unit section q is determined,
Different defect types and different defect forms can be graded in common, and the judgment grade weight value φ is added to each defect type of all the defect judgment unit sections q included in the grade evaluation unit section Q to obtain each defect type. The defect type for which the maximum value of the sum of the above is obtained is determined to be the defect type of the grade evaluation unit section Q, and the determination grade weight value φ of all the defect determination unit sections q included in the grade evaluation unit section Q is determined. And a grade weight value Φ that is the sum of the grade evaluation unit section Q is obtained, and the grade of the grade evaluation unit section Q is graded based on the determined flaw type of the grade evaluation unit section Q and the obtained grade weight value Φ. This is a method for inspecting the surface of a metal strip for damage. Further, the present invention is characterized in that the defect types determined for each defect determination unit section q are linear, dot-like, and planar. Further, in the present invention, the reflected light includes specularly reflected light and irregularly reflected light, and the reflected light intensity V of the specularly reflected light of the pixel q1 is the light from the noise average peak value for each pixel included in the pixel q1. The absolute value of the fluctuation of the absorbed component, the reflected light intensity V of the irregularly reflected light of the pixel q1 is the absolute value of the fluctuation of the irregularly reflected component from the noise average peak value, and the absolute value of these fluctuations. Depending on the value, the weight addition values F (P), F (B), F of the defect determination unit section q are determined for each of specular reflection light and irregular reflection light.
(S1), F (S2) are obtained, and the weight addition values F (P), F of the defect determination unit section for each of the specular reflection light and the diffuse reflection light
(B), F (S1) and F (S2) are added to obtain the weight addition value F of the defect determination unit section q. Further, the present invention is characterized in that the degree of the flaw form L1 of the defect determination unit section q is determined by comparing the weight addition value F of the defect determination unit section q. Further, according to the present invention, the weight addition values F (P), F of the defect determination unit section q for each of the regular reflection light and the irregular reflection light are provided.
It is characterized in that (B), F (S1), and F (S2) are compared to determine the defect type and the defect form. The present invention also includes 2
Based on the value data, the number of flaws of each pixel q1 in the width direction in the traveling direction within the flaw determination unit section q is counted to create a histogram, and the number N of flaws within the flaw determination unit section q is N.
A is calculated, and based on this histogram, when the longest value HL in the traveling direction is within the predetermined first range,
It is characterized in that the defect type of the defect determination unit section q is determined to be a dot defect, and the defect form of the dot defect corresponding to the number NA of defects is determined. The present invention also uses binary data to
A histogram is created by counting the number of defects of each pixel q1 in the width direction in the traveling direction within the defect determination unit section q,
Based on this histogram, the longest value H in the running direction
The first area SHL of the flaw having L is obtained, the second area SWW of the flaw having the widest value WW in the width direction is obtained, the total area SA of the flaw in the flaw determination unit section q, and the total length HA in the traveling direction,
The number NA of flaws is obtained, and the ratio AH (= HA / NA) of the total length HA of flaws to the number NA of flaws is calculated as the average length, and the longest value HL in the traveling direction is the first value. Within the second range exceeding the range, and the ratio RA (= SLW / SA) of the larger area SLW of the first and second areas SHL and SWW to the total area SA is less than a predetermined value. When the average length HA / NA is less than a predetermined value, the flaw determination unit section q is characterized by determining that it has a dot-like flaw. Further, the present invention is
The longest count value HL in the traveling direction is within the third range that exceeds the second range, and the ratio RA (= SLW / S
When A) is less than the predetermined value, the defect determination unit section q is determined to have a dot defect. Further, the present invention counts the number of flaws of each pixel q1 in the width direction in the running direction in the flaw determination unit section q based on the binary data to create a histogram, and based on this histogram, creates the histogram in the running direction most. The first area SHL of the flaw having the long value HL is obtained, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaw in the flaw determination unit section q and the total length HA in the traveling direction are obtained. And the number of defects NA
And the ratio of the total length HA of the flaw to the number NA of flaws AH
(= HA / NA) is calculated as the average length, and when the longest value HL in the traveling direction is in the second range that exceeds the first range, the first and second areas S
The total area S of the larger area SLW of HL and SWW
When the ratio RA (= SLW / SA) to A is equal to or greater than a predetermined value, or the first and second areas SHL
And SWW, the ratio RA (= SLW / SA) of the larger area SLW to the total area SA is less than a predetermined value, and the average length AH (= HA / NA) is more than a predetermined value. At this time, it is determined that the flaw evaluation unit section q has a linear flaw. Further, the present invention obtains, based on the histogram, the first weight addition value FHL of the flaw having the longest value HL in the traveling direction and the second weight addition value FHW of the flaw having the widest value WW in the width direction, Of the first weight addition value FHL and the second weight addition value FWW, the larger weight addition value FHLW is set to the larger weight addition value FH.
Divide by the first or second area SLW corresponding to LW,
The feature is that the average intensity AF (= FHW / SLW) is obtained and the flaw form of the linear flaw corresponding to the average intensity AF is determined. Further, the present invention is based on the histogram,
The count value h in the traveling direction is level-discriminated by one or more predetermined discrimination levels h2, h3, and the discrimination level h
The feature of the present invention is that the flaw form of the linear flaw is determined according to the calculation result of calculating the numbers N2 and N3 of the count values h of 2 and h3 or more. Further, in the present invention, the longest value HL in the traveling direction is within the third range exceeding the second range, and the ratio R is
When A (= SLW / SA) is equal to or more than the predetermined value, it is determined that the flaw determination unit section q has a linear flaw, and the count value h in the traveling direction is determined based on the histogram.
Is discriminated by one or a plurality of discrimination levels h2, h3 which are set in advance and the number N2, N3 of the count values h equal to or greater than the discrimination levels h2, h3 is calculated, and in accordance with the calculation result, the linear flaw defect form Is determined. Further, according to the present invention, scanning means for scanning the laser beam in the width direction on the surface of the metal strip traveling in the longitudinal direction, and the regular reflection light P and the irregular reflection lights BS1 and BS2 of the laser light from the surface of the metal strip are received. Light receiving means, a first memory FRM1 for storing multivalued data of a light reception detection signal of the light receiving means for each pixel, and a plurality of pixels q
A grade evaluation unit section Q is composed of a plurality of defect judgment unit sections q each consisting of 1, and the stored contents of the first memory FRM1 are read out to obtain the product of the reflected light intensity V and the area S of the defect judgment unit section q. Certain weighted addition values F (P), F (B), F (S
1), F (S2); first calculating means for obtaining FHL, FHW, binarizing means for converting the light reception detection signal of the light receiving means into binary data, reflected light P from the binarizing means and irregular reflection light B , S
An OR operation means for ORing binary data of 1 and S2 for each pixel, a second memory M2 for storing the output of the OR operation means, and a plurality of feature amounts of each defect determination unit section q are obtained by operation. Responsive to the second computing means and the output of the second computing means,
Responsive to the outputs of the first judging means for judging the flaw type and the flaw form for each flaw judging unit section q, and the outputs of the first computing means and the first judging means, different flaw types and flaw forms can be commonly graded. All the defect judgment units included in the grade evaluation unit section Q in response to the output of the judgment grade weight value determining means for determining the judgment grade weight value φ of each defect evaluation unit section q and the judgment grade weight value determining means. The judgment grade weight value φ is added for each defect type of the section q, and the defect type for which the maximum sum of the defect types is obtained is determined to be the defect type of the grade evaluation unit section Q. In response to the outputs of the judgment means and the judgment grade weight value determining means, the judgment grade weight values φ of all the defect judgment unit sections q included in the grade evaluation unit section Q are added, and the sum of the grade weight values Φ. Of the third computing means for computing In response to the force, it is a surface flaw inspection device of a metal strip, characterized in that it comprises a third judging means for performing a grading grade evaluation unit blocks Q. Further, according to the present invention, in response to the output of the light receiving means, the noise level calculating means for calculating the noise level N, and the outputs of the light receiving means and the noise level calculating means, the light receiving detection signal is divided by the noise level N. In addition, the first memory FRM1 and the normalizing means provided to the binarizing means are included. Further, according to the present invention, the light receiving means includes a first light receiving detection means for the first reflected light P that is specularly reflected in a virtual light receiving plane that includes the irradiation direction of the laser light and that is orthogonal to the virtual scanning plane, and more than the regular reflected light. A second received light detecting means for the second reflected light B reflected toward the irradiation direction and a third reflected light S1 laterally displaced from the virtual light receiving plane.
Of the third reflected light S2 and the fourth reflected light S2 which is laterally displaced from the virtual light receiving plane more than the third reflected light S1.
And a light reception detecting unit. Further, the present invention is a noise level calculation means for calculating the noise level N in response to the output of the light reception means, and a normalization means, and outputs of the first to fourth light reception detection means and the noise level calculation means. In response to the output of the first light-reception detecting means, the variation due to light absorption by the surface and the variation due to light reflection by the surface corresponding to the outputs of the second to fourth light-reception detecting means are detected. It is characterized by including a normalizing means which is used as a signal, is divided by the noise level N, and is given to the first memory FRM1 and the binarizing means. The present invention also includes 2
The quantizing means is characterized in that the output of the normalizing means is level-discriminated. Further, according to the present invention, the reflected light intensity V of the specularly reflected light of the pixel q1 in the first calculation means is, for each pixel included in the pixel q1, the absolute value of the fluctuation of the light absorbed component from the noise average peak value. The reflected light intensity V of the irregularly reflected light of the pixel q1 is the absolute value of the variation of the irregularly reflected component from the noise average peak value, and the specularly reflected light and the irregularly reflected light are determined by the absolute values of these variations. For each time, the weight addition values F (P), F (B), F (S1), F of the defect determination unit section q
(S2) is obtained, and the weight addition values F (P), F (B), F (S
1) and F (S2) are added to obtain the weight addition value F of the defect determination unit section q. The present invention also provides the first
The determination means determines the extent of the defect form L1 of the defect determination unit section q,
It is characterized in that the weight addition value F of the defect determination unit section q is compared to be performed. Further, according to the present invention, the first determination means compares the weight addition values F (P), F (B), F (S1), F (S2) of the defect determination unit section q for each of the regular reflection light and the irregular reflection light. It is characterized in that the flaw type and the flaw form are determined. Further, according to the present invention, the second calculation means uses the binary data to determine each pixel q1 in the width direction in the traveling direction within the defect determination unit section q.
The number of defects representing the number of defects is counted to create a histogram, the number of defects NA in the defect determination unit section q is determined, the longest value HL in the traveling direction is determined based on this histogram, and the first determination means When the longest value HL in the traveling direction is within a predetermined first range, it is determined that the defect type of the defect determination unit section q is a dot defect and a point corresponding to the number NA of defects. It is characterized by determining the flaw form of the flaw. Further, according to the present invention, the second calculation means uses the binary data to determine each pixel q in the width direction in the traveling direction within the defect determination unit section q.
A histogram is created by counting the number of defects of 1 and the longest value HL in the traveling direction is based on this histogram.
Then, the first area SHL of the flaw having the following is obtained, the second area SWW of the flaw having the widest value WW in the width direction is obtained, the total area SA of the flaw in the flaw determination unit section q, the total length HA in the traveling direction, and the flaw. The first determination means determines that the longest value HL in the traveling direction is within the second range that exceeds the first range, and among the first and second areas SHL and SWW. Ratio RA (= larger area SLW to total area SA)
SLW / SA) is less than a predetermined value, and when this average length AH (= HA / NA) is less than a predetermined value, the defect determination unit section q is to determine that it has a dot defect. Is characterized by. Further, in the present invention, the first determination means is such that the longest count value HL in the traveling direction is within a third range exceeding the second range, and the ratio SLW / SA.
However, when it is less than the predetermined value, the defect determination unit section q is determined to have a dot defect. Further, according to the present invention, the second calculation means counts the number of defects of each pixel q1 in the width direction in the traveling direction in the defect determination unit section q based on the binary data to create a histogram, and based on this histogram Then, the first area SHL of the flaw having the longest value HL in the traveling direction is obtained, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaws in the flaw determination unit section q is obtained. And HA in the running direction
And the number NA of defects, and the ratio AH (= HA / NA) of the total length HA of the defects to the number NA of defects is calculated as the average length, and the first determination means is the longest in the traveling direction. Value H
When L is in a second range that exceeds the first range, of the first and second areas SHL and SWW,
Ratio RA of the larger area SLW to the total area SA
When (= SLW / SA) is greater than or equal to a predetermined value,
Alternatively, the ratio RA (= the larger area SLW to the total area SA of the first and second areas SHL and SWW)
When SLW / SA) is less than a predetermined value and when this average length AH (= HA / NA) is more than a predetermined value, it is determined that the flaw evaluation unit section q has a linear flaw. Is characterized by. Further, according to the present invention, the second calculating means is based on the histogram and has the longest value H in the traveling direction.
The first weight addition value FHL of the flaw having L and the second weight addition value FHW of the flaw having the widest value WW in the width direction are obtained, and the first weight addition value FHL and the second weight addition value FWW are obtained. , The larger weight addition value FHLW is divided by the first or second area SLW corresponding to the larger weight addition value FHLW to obtain the average intensity AF (= FHW / SLW).
The first determining means is characterized by determining the flaw form of the linear flaw corresponding to the average intensity AF. In the present invention, the first determination means is based on the histogram,
The count value h in the traveling direction is level-discriminated by one or more predetermined discrimination levels h2, h3, and the discrimination level h
The feature of the present invention is that the flaw form of the linear flaw is determined according to the calculation result of calculating the numbers N2 and N3 of the count values h of 2 and h3 or more. Further, according to the present invention, the first determination means is such that the longest value HL in the traveling direction is within a third range exceeding the second range, and the ratio RA (= SLW / SA) is equal to or more than the predetermined value. When it is, the defect determination unit section q is determined to have a linear defect, based on the histogram,
The count value h in the traveling direction is level-discriminated by one or more predetermined discrimination levels h2, h3, and the discrimination level h
The feature of the present invention is that the flaw form of the linear flaw is determined according to the calculation result of calculating the numbers N2 and N3 of the count values h of 2 and h3 or more.

According to the present invention, laser light is emitted in the width direction of the metal strip and the reflected light is received, whereby the weight addition value F of the defect determination unit section q is obtained, and the binary value is obtained by the light reception detection signal. Obtaining data and calculating a plurality of feature amounts, one of the feature amounts includes the average length AH (= HA / NA) of flaws along the traveling direction, and these feature amounts are used. , The defect type in each defect determination unit section q (that is, the linear defect, the dot defect, and the planar defect) is determined, and the defect type, that is, the defect forms L1 to L9 in the linear defect, the defect in the dot defect, The defects P1 to P6 and the defect form A1 in the planar defect are determined. Based on the defect type, the defect form, and the weight addition value F in the defect evaluation unit section q thus obtained, a determination grade weight value φ is determined, whereby different defect types and different defect forms can be commonly graded, and, for example, Defects with different defect types and defect forms can be regarded as defects of the same degree. According to the present invention, further, the judgment grade weight value φ is added to each defect type of all the defect judgment unit blocks q included in the grade evaluation unit block Q, that is, for each linear defect, dot defect and planar defect. The defect type for which the maximum sum of the defect types is obtained is determined to be the defect type of the grade evaluation determination section Q. The grade weighting value Φ, which is the sum of the judgment grade weighting values φ of all the flaw determination unit divisions q included in this grade evaluation unit division Q, is obtained, and the grade evaluation unit division Q is obtained using the grade weighting value Φ thus obtained. The grade of the grade evaluation unit section Q is classified according to the defect type. In this way, by using the characteristic amount including the average length AH (= HA / NA) of the flaws, the grade rating of the grade evaluation unit section Q having the surface flaw of the metal strip is inspected in the same degree as the visual inspection of the worker. Will be possible for the first time. Further, according to the present invention, not only specular reflected light but also diffuse reflected light is used as the reflected light, and the reflected light intensity V of the specular reflected light necessary for obtaining the weight addition value F is determined by the flaw on the surface of the metal band. The applied laser light is absorbed by light, and the absolute value of the fluctuation of the light-absorbed component obtained by this is used. On the other hand, the reflected light intensity V of diffusely reflected light is diffusely reflected by flaws on the surface of the metal band. The absolute value of the fluctuation of the specular reflected light is increased, and the absolute value of the fluctuation of the diffused reflected light is also increased when the flaw is large. . This makes it possible to more accurately detect flaws. According to the present invention, the weight addition value F is set for each of the specular reflection light and the irregular reflection light, for example, for each of the four channels P, B, S1, S2 in the embodiment described later.
(P), F (B), F (S1), F (S2) are obtained, and these addition values are added to obtain the weight addition value F of the defect determination unit section q. The flaw form L1 of the flaw determination unit section q is performed by comparing the weight addition value F of the flaw determination unit section q, and the weight addition value F of the predetermined channel (S1 in the embodiment described later).
Is larger than the respective weighted addition values F of the other channels P, B, S, it is determined that the linear flaw defect form L1. In addition, the weight addition values F (P), F of the specular reflection light and the diffuse reflection light
(B), F (S1), and F (S2) are compared, and, for example, the weight addition value F (B) of the channel P of specular reflection light is the weight addition value F (of the channels B, S1, S2 of other diffuse reflection light. B), F
When it is larger than (S1) and F (S2), it is determined that the flaw type is a surface flaw and the flaw form is A1 described later. According to the present invention, in determining the flaw form of the dot-like flaw, the binary data is used, the number of pixels representing the flaws in the width direction of the metal band is counted to create a histogram, and the flaw determination unit section q When the longest value HA in the traveling direction within the range is small within the first range determined in advance, it is determined that the defect type of the defect determination unit section q is a dot defect and corresponds to the number NA of defects. Then, the defect forms P1 to P6 are determined. In determining the flaw forms L2 to L7 of linear flaws, it is important to find the average length AH (= HA / NA) of the flaws, and this average length is a predetermined value (for example, 3 as described later). )
If it is less than the above, it is determined to be a dot defect. If the average length AH is equal to or greater than the predetermined value (for example, 3), the longest value HL and the widest value WW in the histogram
Ratio RA (= SLW) of the larger area SLW of the first and second areas SHL and SWW to the total area SA
/ SA) is calculated, and the larger weight addition value FHW of the first and second weight addition values FHL and FWW is
The average intensity AF (= FHW / SL) divided by the first or second area SLW having the larger weight addition value FHW.
W) is obtained, and thereby the flaw forms L2 to L5 of the linear flaws are obtained. Further, in determining the linear flaws L6 to L9. Based on the histogram, the count value h in the scanning direction is level discriminated by one or a plurality of discrimination levels h2, h3, and the flaw forms L6 to L9 of linear flaws are determined by the count values N2, N3 thus obtained. According to the present invention, the diffused reflected light B, S1, S2 that is the second to fourth reflected light is used together with the first reflected light P that is the specularly reflected light, and the feature amount is obtained by this, so that the defect Type and form of flaw,
It is possible to make a determination with higher accuracy.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a simplified side view showing a part of an embodiment of the present invention. The metal strip 1 such as stainless steel, which is a long material, is manufactured through several steps, and in this embodiment, it is bright annealed and traveled in the direction of arrow 2. In the configuration shown in FIG. 1, an electric signal having a level corresponding to the flaws on the front and back surfaces of the metal strip 1 is obtained, and then the electric signal is arithmetically processed as will be described later, and the type of flaw, that is, a line or a dot. Shape and surface state are determined, and further the flaw morphology, that is, each shape of L1 to L9 as described below when it is a linear flaw, each shape of P1 to P6 as described below when it is a dot flaw, and the surface When it is in a defect, the form of A1 described later is determined, and a weight addition value described later is obtained, and based on this, the unit length of the metal strip 1, for example, 1 m.
Determine the grade rating for each.

The traveling metal strip 1 is first of all the hole detecting means 3
Then, it is inspected whether or not there is a hole in the metal strip 1 and then wound around the next guide rolls 4 and 5 to inspect for flaws on both front and back surfaces.

One of the guide rolls 5 is provided with a surface inspection means 6 for inspecting the surface of the metal strip 1 for flaws, and the other guide roll 4 is provided with a back surface of the metal strip 1. The back surface inspection means 7 is arranged to inspect the defects.

The axes 8 and 9 of the guide rolls 4 and 5 lie in a virtual plane 91 perpendicular to the plane of FIG.
Within 1, these axes 8, 9 are parallel to each other. The metal strip 1 has the following directions 10 and 10a of rotation of the guide rolls 4 and 5,
The guide rolls 4 and 5 are wound around the guide rolls 4 and 5 so that the directions are opposite to each other when viewed from one side in the axial direction of the guide rolls 4 and 5. In FIG. 1, the guide roll 4 is rotated clockwise and the guide roll 5 is rotated counterclockwise 11.
The guide rolls 4 and 5 may be configured to be rotationally driven, but may be configured to be driven as the metal strip 1 travels. The outer peripheral surfaces of the guide rolls 4 and 5 and the metal strip 1 do not slip, which prevents the surface of the metal strip 1 from being flawed.

FIG. 2 is a simplified side view of a part near the guide roll 5. In order to inspect the surface of the metal strip 1 for flaws, the surface of the metal strip 1 is scanned and irradiated in the width direction 27 (see FIG. 3), and reflected light 12 reflected by the flaw is obtained. . The laser light 11 includes the axis 9 of the guide roll 5 within a circumferential range in which the metal strip 1 is wound around the guide roll 5, for example, within a range of about 180 degrees in the circumferential direction around the axis 9. Plane 13 and guide roll 5,
Therefore, the scanning means 15 scans in a direction perpendicular to the paper surface of FIGS. 1 and 2 so as to scan the intersection line 14 with the outer peripheral surface of the metal strip 1. This laser beam 11 is applied to the metal strip 1
The spot light has a length of 2 mm in the traveling direction 2 and a width of 0.9 mm in the scanning direction in the width direction of the metal strip 1. The laser beam 11 is irradiated from the one side, which is the left side of FIG. 2, with respect to the plane 13 to the metal strip 1 by scanning the laser beam 11 within a virtual scanning plane 16 parallel to the axis 9 of the guide roll 5. .

The reflected light 12 is shown in FIG.
On the other side, which is to the right of, it is guided from line of intersection 14. The reflected light 12 is received by the light receiving means 18 and converted into an electric signal having a level such as voltage or current corresponding to the light intensity. The other back surface detection means 6 has the same configuration as the above-mentioned front surface detection means 7.

The guide rolls 4 and 5 are in the shape of a right cylinder or a right cylinder, and their outer peripheral surfaces are true circles that are uniform in the axial direction.

The outer diameter of the guide roll 5 is preferably about 500 mmφ or more, whereby the laser beam 11 shown in FIG. 2 is referred to by the reference numeral 11a in FIG. 2 due to the vibration of the polygonal reflecting mirror 22 or the like. Even if the position is undesirably changed, the reflected diffracted light can be received by the light receiving means 18 as indicated by reference numeral 11b.
On the other hand, when the outer diameter of the guide roll 5 is less than about 500 mmφ, when the laser light 11 changes to the reference numeral 11a, the reflected diffracted light 11c is largely deviated and detected by the light receiving means 18. Becomes impossible.

The guide roll 5 is preferably as large as possible, for example values above about 1300 mmφ, but in the present invention a guide roll 5 of less than about 1300 mmφ is chosen to facilitate handling of the guide roll 5.

FIG. 3 is a perspective view showing the entire structure of the surface detecting means 7, FIG. 4 is a perspective view showing a simplified structure of a part of the scanning means 15 and the light receiving means 18, and FIG. FIG. 7 is a simplified front sectional view of an optical system including a scanning unit 15, and FIG. 6 is a simplified sectional view of the optical system shown in FIG. Referring to these drawings,
The laser light from the laser light source 20 is collimated through a collimator 21 that makes it parallel light, and the polygonal reflecting mirror 22 is rotationally driven by a motor 23 to obtain a fan-shaped beam 24. The fan-shaped beam 24 is reflected by the plane reflecting mirror 25 and further reflected by the paraboloidal reflecting mirror 26, so that the laser beam 11 in the virtual scanning plane 16 is indicated by the arrow 27 in the width direction of the metal strip 1. To be scanned.

A semi-transmissive reflecting mirror 28 is arranged at one end of the metal strip 1 in the width direction, and the light receiving element 29 detects the start of the scanned laser beam. In this way, the position of the laser light as the spot light in the width direction of the metal strip 1 can be detected. Although the optical path of the laser light from the collimator 21 is simplified in FIGS. 3 and 4,
5 and 6, reflecting mirrors 31 to 33 are further provided for the laser light. The polygonal reflecting mirror 22 that is driven to rotate is, for example, a 10-sided polygon, and has a length of 20,000 rp.
It is driven to rotate at high speed by m. These components 20 to 3
3 are combined and fixed to the housing 34 to form a unit.

Laser light 1 for scanning in the virtual scanning plane 16
When 1 traverses a flaw existing in the metal strip 1 wound around the guide roll 5, the laser light is momentarily diffracted and reflected, and irregularly reflected light advances in a direction different from the specularly reflected light due to a flawless background. The phenomenon occurs. Therefore, if only the diffusely reflected light of a specific angle is continuously viewed, the diffusely reflected light is generated due to a flaw.
By irradiating the surface of the metal strip 1 to be inspected with coherent laser light in this way, diffraction occurs in accordance with a flaw that is a fine structure of the surface, and the reflected light is received by the light receiving means 18 and the flaw is detected. You can get a unique light and dark pattern. This bright and dark pattern can be called a diffraction pattern, and different diffraction patterns appear on a surface without a flaw and a surface including a flaw.

FIG. 7 is a sectional view showing a simplified structure of the light receiving means 18. The laser light 11 scanned in the virtual scanning plane 16 is specularly reflected by the surface of the metal strip 1, and the first reflected light 36, which is the specularly reflected light, is received by the first light reception detecting means 37. Irradiation direction (Fig. 7)
The second reflected light 38 diffused and reflected to the left of the plane 13 is detected by the second received light detecting means 39.
The first reflected light 36 is in the virtual light receiving plane 40. The third reflected light 41, which is laterally displaced from the virtual light receiving plane 40 in the vicinity of the virtual light receiving plane 40, is detected by the third light receiving detection means 42. Further, the fourth reflected light 43, which is further displaced laterally from the virtual light receiving plane 40 than the third reflected light 41, is provided.
Is detected by the fourth received light detecting means 44. Each of the first to fourth light reception detecting means 37, 39, 42, 4
4 are unitized and fixed to the housing 45.

First to fourth reflected lights 36, 38, 41, 43
May be indicated for each channel by reference signs P, B, S1, S2. Reference numerals P, B, S1 and S2 are also used to indicate the configurations related to the first to fourth reflected lights.

In this way, the light receiving means 18 irradiates the surface of the metal strip 1 to be inspected with the laser beam 11 in order to maximize the optical characteristics of the surface of the metal strip 1 to be inspected, and the reflected light corresponding to the flaw. The diffracted light component is separated into four channels in total and detected. An image of the metal strip 1 to be inspected, which is obtained by the first to fourth received light detecting means 37, 39, 42, 44, is processed online in real time,
It becomes possible to accurately extract the features of surface defects. This makes it possible to deal with the strictness of the surface quality required by the sophistication, diversification of the surface treatment technology for metal strips and the advent of new materials. It becomes possible to detect surface flaws, determine flaw types and flaw forms, and determine the extent of the flaws. This is especially essential in steel processes that produce products such as high value-added stainless steel strips such as bright annealing.

The principle of the embodiment of the present invention shown in FIGS. 1 to 7 will be briefly described with reference to FIG. By irradiating the surface of the metal strip 1 to be inspected with the laser light 11 and receiving the reflected light by the screen 46 that is sufficiently distant, a characteristic diffraction pattern corresponding to the surface flaw of the metal strip 1 can be obtained.

FIG. 9 is an enlarged cross-sectional view of the surface of metal strip 1 shown in FIG. Laser light that is a parallel light beam 11
However, when the surface to be inspected is irradiated, not only the specularly reflected light 36 but also the irregularly reflected light 48 are faithfully obtained according to the inclination of the fine surface of each uneven portion 47 of the surface. Point 49 in FIG.
Can be considered to be equivalent to a micro plane mirror, and reflects the irradiated laser beam 11 depending on the inclination of the micro plane mirror. That is, the diffraction pattern can be said to be a faithful projection of the unevenness information of the unevenness portion 47 on the surface portion irradiated with the laser beam 11 onto the screen 46 (see FIG. 8).

FIG. 10 is a perspective view showing the basic structure of the light receiving means 18. The metal strip 1 to be inspected is XY
In the Z orthogonal coordinate system, the traveling direction 2 coincides with the Y axis direction, and the width direction thereof is the X axis. The screen 46 is
It is a cylindrical surface centered on the X axis. The reflection diffraction pattern by the laser light 11 is generated by converting the undulations in the X-axis and Y-axis directions into the fx-axis and the fy-axis. Metal strip 1
Change in the X-axis direction of the surface to be inspected, which is the surface of the Y-axis (for example, diffraction due to rolling scratches has the origin 51 as the apex and Y
It occurs in the direction of the generatrix of the conical surface with the axis as the central axis. The line of intersection between the screen 46 and this conical surface is the fx axis. Diffraction due to surface undulation changes in the Y-axis direction occurs from the origin 51 in the YZ plane. Let f be the line of intersection between the YZ plane and the plane of the screen 46.
Let y-axis. The intersection point P of the fx axis and the fy axis is the arrival point of the specular reflection light that is the 0th order diffracted light, and the light amount at this point P greatly changes due to the flaw that absorbs light such as dirt and holes.

On the fx axis, the point S1 and the point S2 are displaced from the point P in this order without being separated from each other, and diffraction occurs from a surface having a sharp surface undulation in the X axis direction. For example, a scratch-like flaw is strongly diffracted in this direction. The same applies to the fy axis, and diffraction occurs at a position away from the point P depending on the intensity of the undulations in the Y axis direction. For some types of scratches, strong diffracted light in this direction is obtained. From this, the diffraction pattern contains a wealth of information on surface defects, and a total of 4
For the channels P, B, S1, S2, the type and shape of the surface flaw and its degree are determined.

In the embodiment of the present invention, the light receiving area for each point P, B, S1, S2 in FIG.
(1), FIG. 11 (2), FIG. 11 (3) and FIG.
They are individually shown in (4). The specular reflection light and the diffuse reflection light are detected by the first to fourth light reception detecting means 37, 39, 42, 44, respectively, corresponding to the points P, B, S1, S2. In the above description, the reference symbols P, B, S1 and S2 represent the light receiving area together with the light.

FIG. 12 shows the first and third light reception detecting means 3.
It is sectional drawing which simplifies and shows 7,42. The first reflected light 36, which is specularly reflected light, is guided through the condenser lens 53, the semi-transmissive reflecting mirror 54 (see FIG. 7 described above), and the elongated light guide member 55 corresponding to the screen 46 described above. Further, the third reflected light 41 is transmitted from the condenser lens 53 to the semi-transmissive reflection mirror 54.
And is guided to the light guide member 56. The laser light applied to the surface of the metal strip 1 moves in the width direction thereof, and therefore the position of the diffraction pattern of the reflected light obtained moves in accordance with the scanning of the laser light. Therefore, in order to receive only the reflected light of a specific angle, if the light receiving detection means is moved, the scanning cycle of the laser light is 3300 times / second, and the moving speed of the laser light is 10 k.
Since the speed is m / sec and the speed is extremely high, it is almost impossible to mechanically move the light receiving and detecting means and to synchronize the scanning with the laser light. Therefore, in the present invention, the diffraction pattern is kept stationary and the first to fourth light receiving detection means 37, 3
Allow light to be received at 9, 42 and 44.

A condenser lens 53 is provided in association with the first and third received light detecting means 37, 42. The condenser lens 53 is a convex lens, and the parallel light incident on the condenser lens 53 converges on the position of the focal length f. The condenser lens 53 is composed of a plurality of spherical lenses or aspherical lenses, cuts both ends of the laser beam in the scanning direction at predetermined positions, and uses the cut surfaces as joint surfaces to join adjacent members together. It has a configuration. As a result, all the reflected and diffracted light in the entire scanning range in the width direction of the metal strip 1 which is the surface to be inspected is condensed and guided to the light guide members 55 and 56. A transmission path of light from the surface of the metal strip 1 to the light guide members 55 and 56 is shown in FIG. The regular reflection light 36 from the condenser lens 53 is guided to the light guide member 55, and the second reflected light 41 laterally displaced is largely bent by the action of the condenser lens 53 and guided to the light guide member 56.

The light guide members 55 and 56 have their longitudinal directions parallel to the scanning direction of the laser light 11 and have a cross section perpendicular to the axis of a rectangular parallelepiped or a circle. Acts to guide. Light guide members 55, 56
Is made of, for example, a translucent synthetic resin material such as polycarbonate. These light guide members 55, 5
Reflecting mirrors 58 and 59 are provided at the ends of 6 in the longitudinal axis direction, and the bent reflected light is received by light receiving elements 60 and 61 such as a photomultiplier, and an electric signal having a voltage corresponding to the light intensity is received. Is converted to. Such a light receiving element 6
0 and 61 may be arranged on both sides of the light guide members 55 and 56. The distance between the position 14 where the laser beam of the metal band 1 is irradiated and the condenser lens 53, and the distance between the condenser lens 53 and each of the light guide members 55 and 56 are determined by the condenser lens 53.
Is set to a value equal to the focal length f. Therefore, the reflected diffracted light generated by the surface of the metal strip 1 is guided by the light guide member 5
The light is imaged and incident on 5, 56 as a static diffraction pattern.

As described above, the condenser lens 53 has a structure in which the end portions are cut and the cut surfaces are joined together.
Therefore, each condensing lens 53 individually acts as an independent lens having a focus, and as a single lens having a condensing action at any position in the direction of the scanning range of the laser light. To work. Therefore, the diffracted light reflected in the laser scanning range should be focused by the condenser lens 53 and focused on the light guide members 55 and 56 regardless of the position reflected in the scanning range. become.

When the laser beam is scanned over the entire width of the metal strip 1 in this manner, the diffracted light reflected in the entire laser scanning range is not leaked and the condenser lens 5 is not leaked.
The light is focused by 3 and is focused on the light guide members 55 and 56, which makes it possible to inspect the entire range of the metal strip 1 by providing only one device, and the configuration is simple. You will be able to perform high-performance inspections.

Since the plurality of condenser lenses 53 are joined and integrated with each other, the alignment with respect to the metal strip 1 can be easily performed, and each of the plurality of condenser lenses 53 can be adjusted against variations. There is no positional deviation from each other, the reliability is high, and the mounting structure is simple. A light-shielding partition plate may be interposed between the condenser lenses.

In another embodiment of the present invention, the condenser lenses 53 may not be cemented to each other, but may be arranged to be in contact with each other.

FIG. 14 is a simplified plan view of the second received light detecting means 39. In the second received light detecting means 39, a cylindrical Fresnel lens 63 is used in place of the combination of the plurality of condenser lenses 53 described above. With such a configuration as well, the second reflected light 38 causes the metal band 1 to be reflected. The light guide member 6 through the cylindrical Fresnel lens 63 from the surface of the
And a reflecting mirror 6 which is incident on the optical axis 4 and is arranged at the end in the axial direction thereof.
5 is detected by the light receiving element 66. These and other configurations are similar to the configurations described in connection with FIGS. 12 and 13 above.

The fourth received light detecting means 44 is also the first to the third.
It has a configuration similar to the received light detecting means 37, 39, 42. That is, the reflected diffracted light is incident on the elongated light guide member 68 via the condenser lens 53 (see FIG. 7) such as the condenser lens 53 or the cylindrical Fresnel lens 63, and the end portion of the light guide member 68 in the axial direction. The light is guided to the light receiving element 69 through the reflecting mirror disposed in the position and is received.

FIG. 15 is a partial front view of another embodiment of the present invention. The screen 46 of FIG. 15 is arranged at the focal position of the condensing lens 53 for each of the plurality of condensing lenses 53 arranged adjacent to each other. First to fourth reflected light 3
6, 38, 41 and 43 are imaged at the light receiving positions 71 to 74 of the screen 46. Therefore, each position 71
The light receiving elements are arranged at ~ 74, and each reflected light 36, 38, 4
The light intensity of 1,43 can be detected.

As still another embodiment of the present invention, one end of each optical fiber is arranged at each of the positions 71 to 74, and a light receiving element is provided at each other end of the optical fiber. Good. Such a screen 46
And the respective configurations corresponding thereto, the plurality of condenser lenses 53
It is realized every time.

FIG. 16 is a light guide member 55 which is the screen 46 formed by the condenser lens 53 in each of the embodiments described above.
It is a figure which shows the image formation state above. The reflected and diffracted light of the laser light 11 which is irradiated and scanned on the surface of the metal band 1 is indicated by reference numeral 75 by each of the plurality of condenser lenses 53 regardless of the position of the laser light 11 reflected at any position in the scanning range. Is imaged as. For example, any point 76 on the surface of the metal strip 1
The reflected diffracted light 77 reflected at
Even if the image is formed on 79 and the point 76 is displaced, it is received by the light guide members 55 and 56 or the screen 46 indicated by reference numerals 80 and 81. Therefore, the reflected diffracted light due to the flaws on the surface of the metal strip 1 can be received and detected without leakage.

This will be further described with reference to FIG. Angle θ from the point A1 on the surface of the metal strip 1 to be inspected
The reflected diffracted light rays a1 and a2 diffracted in the 1 and θ2 directions are refracted by the condenser lens 53, which is a convex lens, and are guided to the light guide member 55.
The scanning position of the laser beam 11 at the positions Q1 and Q2 of
The reflected diffracted lights b2 and b2 having the angles θ1 and θ2 are moved to the positions Q1 and Q on the light guide member 55 even when they are moved to.
Reach 2. Therefore, it is understood that the position of the light guide member 55 that receives only a specific angle can be fixed and the reflected light 36 can be detected by scanning the laser light 11 in the width direction of the metal strip 1.

Although the above explanations have been made mainly in relation to the first received light detecting means 37, the same applies to the second to fourth received light detecting means 39, 42, 44, which is further illustrated in the drawings. The same applies to the other embodiment of the present invention shown in FIG. Thus, according to the present invention, the first to fourth light reception detecting means 37, 39, 42, 44
4 channels of reflected diffracted light 36, 38, 41,
As described above, 43 is detected by the so-called multi-sensing method as indicated by the reference signs P, B, S1, and S2, whereby the flaw type and flaw form are accurately determined, and the flaws are detected. The degree, and hence the grade of the metal strip 1, can be easily evaluated.

FIG. 18 is a perspective view showing a simplified structure of the hole detecting means 3. Width 0.3m from laser light source 83
Laser light, which is a spot light of m × 1.7 mm in the flow direction, is generated, collimated by a collimator 84, and guided to a polygonal mirror 85. The polygonal reflecting mirror 85 is, for example, an octahedron and is 12000 rpm by a motor.
The arrow 8 is scanned in the width direction of the metal strip 1 to be inspected.
It is moved at high speed as indicated by 6. Hole 8 in metal strip 1
When 7 is present, the laser light passing through the hole is condensed by the condenser lens 88 and received and detected by the pin photodiode 89. By discriminating the level of the output from the pin photodiode 89, the presence of the hole 87 can be detected.

When a hole 87 is present in the metal strip 1 as described above, a grade evaluation unit section Q which is a predetermined range in the longitudinal direction of the metal strip 1 including the hole 87, for example, a region of 1 m in the longitudinal direction. Is a part that does not become a product,
The worst grade K is determined.

Such a running position of the metal strip 1 in the longitudinal direction can be detected by counting the output of the running position detecting means 90 which generates the number of pulses corresponding to the running distance of the metal strip 1 with a counter. .. This makes it possible to detect the position of the hole 87 in the traveling direction on the metal strip 1.

FIG. 19 shows the first to fourth light reception detecting means 37,
Light receiving elements 60, 6 provided at 39, 42, 44
It is a block diagram which shows the electric circuit following 6,61,69. The received light detection signal for each channel is composed of a regular reflection detection signal of the P channel and an irregular reflection detection signal of each of the B, S1, and S2 channels.
r) are given to FEP1 to FEP4 respectively.

FIG. 20 is a block diagram showing a specific electrical configuration of the P channel subsequent to the light receiving element 60 for specularly reflected light. The output of the preprocessing circuit FEP1 is given to the DC amplification circuit 96. The gain of the DC amplification circuit 96 is set by the gain adjustment circuit 97.

FIG. 21 shows the first to fourth preprocessing circuits FEP1 to FEP1.
The output waveform in FEP4 is shown. First preprocessing circuit FE
In P1, the first gain of the specular reflection detection signal is as shown in FIG.
As shown in, the first average peak value VP of noise is 1.0
It is set by the gain adjusting means 97 so that it becomes V. Similarly, the second to fourth preprocessing circuits FEP2 to FEP
The average peak values VB, VS1, VS2 of 4 are set as shown in Table 1.

[0048]

[Table 1]

Thus, the first average peak value VP of the regular reflection detection signal is set to be equal to or higher than the second average peak value VB, VS1, VS2 of the noise of the second to fourth reflection detection signals. This generally gives a low level reflection detection signal,
It is possible to prevent amplification with an unreasonably high gain to deteriorate the S / N ratio. Therefore, even if there is a slight flaw, not only from the specular reflection light but also from each diffuse reflection light B, S1, S2,
It becomes possible to detect the fluctuation of the level of the reflection detection signal corresponding to the flaw on the surface of the metal band 1.

Each of these reflection detection signals is normalized as described later. Then, for the binarization shown in Table 1, level discrimination is performed at each discrimination level above (that is, positive) and below (that is, negative) the average peak values VP, VB, VS1, VS2, and then binarized. The data are stored in the geometric feature extraction memories GFE1 and GFE2, respectively. On the other hand, the geometric feature extraction memory GFE1 is used for detecting so-called general flaws, and is a memory M that represents a variation of the specular reflection detection signal due to light absorption by the surface of the metal band 1.
Pn (subscript n indicates negative) and memories MBp, MS1p, which represent fluctuations due to light reflection of the residual irregular reflection detection signal.
MS2p (subscript p indicates positive). Further, the geometric feature extraction memory GFE2 for the special flaw is a memory MB for storing the variation due to the optical absorption of the irregular reflection detection signal.
n, MS1n, MS2n are included. The memory provided in each of the geometric feature extraction memories GFE1 and GFE2 is shown in Table 1 with a circle, and also shown in FIG.

Table 2 shows concrete types such as linear flaws, dot flaws, surface flaws, and shape flaws. The general flaws checked by the output of the geometric feature extraction memory GFE1 are the linear flaws and the dot flaws in Table 2. The other special flaws detected by the geometric feature extraction memory GFE2 are the surface flaws and the shape flaws in Table 2. As will be described later, the surface defect can be inspected by using the output of the geometric feature extraction memory GFE1 for general defect.

[0052]

[Table 2]

Referring again to FIG. 19, the timing control circuit TMC generates signals common to the image bus, such as a basic clock of 48 MHz, a second synchronizing pulse, a scan start pulse, a mirror rotation pulse and an effective scan pulse. In addition to being applied to the multi-bus 99, it is applied to the bus 100 for multi-valued data for transmitting grayscale data. The processing circuit MPU realized by a microcomputer or the like is the pin photodiode 8 of the hole detecting means 3.
9 and the output from the traveling position detecting means 90 in the traveling direction of the metal strip 1 is received. The interface 101 enables connection with an external storage device, such as a magnetic hard disk and a magneto-optical disk, and enables the output of the present device to be transferred to and stored in these external magnetic storage devices.

First to fourth light receiving detecting means 60, 66, 6
Analog-to-digital conversion means ABC1 to ABC4 for a total of four channels P, B, S1, and S2 for each 1 and 69 are provided.

Referring to FIG. 20, first light reception detecting means 60
The specific circuit configuration of the analog-to-digital conversion means ADC1 corresponding to will be described. The output from the DC amplification circuit 96 of the preprocessing circuit FEP1 is the analog-digital conversion circuit A
8 is given to the analog-digital converter 102 of DC1,
It is converted into a digital value of bits and given to the next mirror reflectance correction circuit 103. Mirror reflectance correction circuit 103
23 to be corrected from the correction value memory 104.
A signal having the waveform shown in FIG. 2 is given for each scanning in the width direction of the metal strip 1. Analog-digital converter 10
The output waveform of No. 2 is as shown in FIG. The output of the preprocessing circuit FEP1 is also given to the mirror reflectance sampling circuit 105, which sets the output level of the correction value memory 104. In this way, the mirror reflectance correction circuit corrects the unevenness of the reflectance of each output surface of the analog-digital converter 102 for each of the reflecting surfaces of the polygon mirror that is rotationally driven according to the output of the correction value memory 104, and the line 106 is displayed. Derives a signal whose average peak value is constant as shown in FIG.

The signal on the line 106 is applied to the shaving correction circuit 107 and also applied to the shaving sampling circuit 108 to be sampled.
As a result, the average peak value for one scan is calculated as the correction value memory 10
FIG. 25 shows changes in the average peak value of the laser beam stored in memory 9 and stored in the memory 109 for one scan. Thus, the shaving correction circuit 107
Is corrected by correcting the waveform in which the average peak value VP of line 106 shown in FIG. 26A changes in the scanning direction.
The average peak value VP is set to 0 as shown in FIG.
Derives a signal where is constant.

The received light detection signal from the line 110 is given to the positive peak detection circuit 112, the negative peak detection circuit 113, and the envelope detection circuit 114, respectively. The positive peak detection circuit 112 responds to the reflection detection signal on the line 110, samples the peak value thereof, and
The pulse indicated by the reference numeral 115 in (1) is changed to the line 116.
To the subtraction circuit 117. Further, the negative peak detection circuit 113 samples and detects the negative peak of the light reception detection signal of the line 110, and the line 118 is shown in FIG.
The signal 119 representing the negative peak shown in (2) is derived and given to the subtraction circuit 120. These subtraction circuits 11
A signal representing the average peak value indicated by the reference numeral 121 in FIG. 27 (3) is derived from the envelope detection circuit 114 at 7, 120. 27 (1) to 27 (3), the light reception detection signal of the line 110 is also shown.

The subtraction circuit 117 is a positive peak detection circuit 11
2 output Sp to envelope detection circuit 114 output E
Is subtracted, and the subtraction value (= Sp−E) is derived on the line 122. The waveform of the line 122 is as shown in FIG. 28 (1), and the positive peak value having a level equal to or higher than the average peak value is derived. Another subtraction circuit 1
20 is a subtraction value (= E) obtained by subtracting the output Sn of the negative peak detection circuit 113 from the output E of the envelope detection circuit 114.
-Sn) is derived and given to line 123. The output waveform of the line 123 is as shown in FIG. 28 (2), and represents the negative peak value having a level equal to or lower than the average peak value.

The absolute value comparison circuit 124 includes lines 122,
The output of 123 is received, and the signal with the greater absolute value is derived on line 125. The output waveform of the line 125 is as shown in FIG. 29 (1), and whether the absolute value thus obtained is positive or negative is shown in FIG.
As shown in (2), the signal waveform shown in FIG. 29 (2) may be used for determining the defect type and the defect form.

The noise sampling circuit 126 obtains the average peak value VP of the noise contained in the line 110. The average peak value VP is similar to the envelope E obtained by the envelope detection circuit 114 described above, and in this embodiment, the noise level N thereof is obtained with higher accuracy.

The noise sampling circuit 126 shown in FIG.
As shown in, a measurement target range 127 having a length of about 130 mm and a width of about 180 mm is set along the traveling direction 2 of the metal strip 1. Next, as shown in FIG. 31, the measurement target range 1
From the light reception detection signal of the line 110 obtained by a large number of scans including 27, the minimum unit 128 within the measurement target range 127 (running direction length 0.2 mm, width direction 15 mm)
To get The minimum unit 128 includes 16 pixels, and obtains the maximum value VNmax and the minimum value VNmix of the noise level of the reflection detection signal. In this way, a value (= VNmax-VNmin) that is a peak-to-peak value of noise in the minimum unit 128 is obtained, and then an average value of the measurement target range 127 is obtained. In this way, the peak-to-peak value of noise in the measurement target range 127 is obtained,
The half is set as the noise level N. The value of the noise level corresponds to the amplitude of noise from the background level of the metal strip 1 and corresponds to the envelope level E obtained by the envelope detection circuit 114 described above.

The normalization circuit 130 divides the received light detection signal of FIG. 29 (1) obtained on the line 125 by the noise level N obtained by the noise sampling circuit 126, that is, the noise obtained by the noise sampling circuit 126. When the level is N1 and the level of the reflection detection signal obtained on the line 125 is S1, S1 / N1 is divided and the normalized light reception detection signal shown in FIG. Derive. The positive and negative polarities of the signal of FIG. 32 (1) obtained on the line 131 are shown in FIG.
2 (2) represented by the signal shown in FIG.
The positive / negative display signal of (2) is the same as the signal of FIG. 29 (2) described above.

Thus, the analog-digital conversion circuit ADC
From 1, a signal is derived via line 131 for density feature extraction, which represents the density of the flaw consisting of normalized multi-valued bits. The analog-digital conversion circuits ADC2 to ADC4 corresponding to the remaining second to third reflection detection signals also have a configuration similar to that of the analog-digital conversion circuit ADC1 described above. These normalized received light detection signals are
It is led to the multi-value bus 100 including the line 131, stored in the frame memory FRM1 and stored as a multi-value gradation image, and for example, color monitor display becomes possible.
The received light detection signal from the normalized line 31 of the channel P is stored in the memory DFE1 (De
nsty Feature Extraction) and similar memories DFE2 to DF for other channels B, S1 and S2.
E4 is provided.

Further, the analog-digital conversion circuit ADC1
Then, the normalized multilevel reflection detection signal obtained on the line 131 is converted into binary data by the binarization circuit 132. In the binarization circuit 132, the line 131 shown in FIG.
The normalized received light detection signal of 2 (1) is shown in FIG.
This received light detection signal is level discriminated by the binarized discrimination level shown in Table 1 above. Specular reflection signal 36
Is binarized only in the negative polarity, and its discrimination level is set to the line 134 of S2 / N2 = 2.5 dB. Thus, the binarized data is derived from the binarization circuit 132 to the line 135 as shown in FIG. The signal representing the positive polarity or the negative polarity with respect to the average peak value of the binary data obtained by the discrimination level at the binarization discrimination level 134 is as shown in FIG. 32 (4). The binary data obtained from the line 135 is the geometric feature extraction memory GFE1 (Geometrial Feature Extrac).
stored in the memory MPn. Similar binary operation is performed on the remaining analog-digital conversion circuits ADC2 to ADC4, and the binary data is stored in the memories MBp, MBn; MS1p, M as described above.
S1n; Stored in MS2p and MS2n respectively,
It is used to obtain geometric features. The binary data thus obtained is led to the binary bus 136.

The received light detection signal derived on the line 110 in FIG. 20 has 256 gradations, for example, and is obtained as shown in FIG. The binary data obtained on the line 135 is obtained as shown in FIG. The base level shown in a grid pattern in FIG. 34 indicates the average peak value VP, VB, VS1 or VS2 of noise, and corresponds to the background level of the surface of the metal strip 1 to be inspected.

The received light detection signals for four channels in total are shown in FIG.
As shown in FIG. 1, only the positive and negative fluctuations above and below the average peak value of the noise are adopted as described above and stored in the geometric feature extraction memory GFE1, and the density characteristic is also stored. Extraction memories DFE1 to DFE4 and F
Store in RM1 and FRM2. In determining the flaw type and flaw form as described below, by selecting the polarity of the received light detection signal, that the detection of general flaws and special flaws is well achieved, by the experiments of the present inventors, It was confirmed as shown in Table 3.

[0067]

[Table 3]

FIG. 35 is a diagram showing the structure of another embodiment of the present invention. Regarding the discrimination levels VP, VB, VS1, VS2 for binarization shown in FIG. 21, in the present embodiment, the discrimination levels VP, VB, VS1, VS2.
When the value is changed according to the noise level N and is set, a limit value is set. These discrimination levels VP, VB, VS
1 and VS2 are typically designated as VC1 and VC2. The comparison is performed with the upper and lower limit values set in advance, and if it is within the limit value, the binarization discrimination level is used as it is. As the upper and lower limit values, VC2H and VC2L are used for the positive flaw discrimination level. As a result, if the signal VC1 output from the discrimination level calculation circuit 7 is VC1L <VC1 <VC1H, the signal VC1 is output as it is. If VC1 ≦ VC1L or VC1N ≦ VC1, VC1L or VC1H is output instead of the signal VC1. To do. The same applies to the signal VC2 on the negative polarity side. Therefore, the discrimination level set by the binarization circuit 132 is set within the shaded area in FIG.

The measurement target range 127 for obtaining the noise level N in the noise sampling circuit 126 is calculated in response to the output of the traveling position detecting means 90 in the traveling direction 2 of the metal strip 1 every 10 m, and once obtained. The obtained noise level N is commonly used as it is in the traveling direction 10 m of the metal strip 1.

FIG. 36 is a plan view of the metal strip 1. According to the present invention, a grade evaluation unit section for rating by inspection of the metal strip 1 is a section Q having a width W and a length H, as shown in FIG. For example, as an example, W = 1 m, H =
1m. The grade evaluation unit section Q is divided into 16 equal parts, and a section having a width W / 4 and a length H / 4 is defined as a defect type determination unit section (hereinafter, abbreviated as a unit section) q. Quantization, profile creation, feature extraction, and defect type flaw form determination are performed to determine the grade rating of one evaluation unit section Q out of a total of 16 determination unit sections q.

FIG. 37 is a flow chart for explaining the general operation of the processing circuit 140 realized by the microcomputer (see FIG. 19 described above). The processing circuit 140 includes geometric feature extraction memories GFE1 and GFE.
The FE2 is connected to the frame memory FRM1 in which multi-valued data is stored, and each bus 99, 100, 13 is connected.
6 is connected and the arithmetic processing operation is performed.

In order to classify the grade evaluation unit section Q, first in step a1, the frame memory FRM is selected.
Store contents of 1 are used, and aside from this, step a
In 3, memory GFE in which binary data is stored
The stored contents of 1 and GFE2 are read and used. A total of 16 flaw determination unit sections q included in the grade evaluation unit section Q are linear flaws as shown in FIG. 38 (1), and dot-like as shown in FIG. 38 (2). It is a flaw and, as shown in FIG. 38 (3), is a planar flaw. The flaw type for each flaw type and the degree of each flaw type are also evaluated and determined based on such multivalued data and binary data.

Based on the multivalued data, in step a2,
The weight addition value F is obtained. Steps a1 and a in FIG.
A more specific operation of No. 2 is shown in FIG. In calculating the weighted addition value F, the process moves from step b1 to step b2, and the multi-valued data shows the specular reflection light P and the irregular reflection light B, S.
Frame memory FRM1 stored for each of S1 and S2
21 is read out, and the absolute value of the variation of the light-absorbed component from the noise average peak value is calculated for each of a number of pixels q1 included in each defect determination unit section q, that is, FIG.
The absolute value of the signal of the average peak value VP of (1) is read out, and the absolute value of the variation of the irregularly reflected component from the noise average peak value of the irregular reflection lights B, S1, and S2, that is, FIG.
(2) -The absolute value of the variation of the component above the average peak value in FIG. 21 (4) is read. Each channel P, B, S1, S
As an example, the variation for each 2 has a three-dimensional integral shape in the defect determination unit section q as shown in FIG.

F = ∫Vds (1) The density at each defect, that is, the area for each reflected light intensity V is
As shown in FIG. 41. The density in the defect determination unit section q shown in FIG. 41 (1), that is, the exposed area having the reflected light intensities V1 to V5 is shown in FIG. 41 (2).
As shown in.

Based on the data shown in FIGS. 40 and 41, the area S of the flaw can be obtained in step b3.

S = ∫ds (2) Further, the weighted addition value F (P) for each channel is obtained from the equation 2 based on the light reception detection signal of the regular reflection light 36 of the P channel. This is also obtained for the weighted addition values F (B), F (S1) and F (S2) of the other channels B, S1 and S2 in exactly the same manner based on the received light detection signals of the respective channels B, S1 and S2. You can These weight addition values represent, as it were, the volume of each defect in FIG.

At step b5, the weight addition value F of the total sum of all channels P, B, S1, S2 in each defect judgment unit section q is obtained.

F = F (P) + F (B) + F (S1) + F (S2) (3) The binary data in step a3 in FIG. 37 is stored in the geometric feature extraction memory GFE1. The binary data stored is read out, and a plurality of characteristic quantities are obtained in the next step a4. Thus, in step a5, the defect type and the defect form in the defect determination unit section q are determined. The operation for obtaining the feature amount in step a4 described above will be described in more detail with reference to FIG.

In FIG. 43, the process moves from step c1 to step c2, and the memories MPn, MBp, MS1p, MS2 provided in the geometrical feature extracting memory GFE1.
The binary data read from p is added for each pixel q1, and the logical operation of the logical value of each pixel for each channel P, B, S1, S2 is performed in this way. The binary data for each defect cost unit section q obtained by the OR operation in this way is stored in the memory M2 of binary pixels shown in FIG.

At the next step c3, for example, a histogram for each flaw evaluation unit section q shown in FIG. 44 is created.

FIG. 45 shows a large number of pixels q1 included in the defect evaluation unit section q in an enlarged manner. In FIG. 45, the black-painted portion indicates the location of the flaw, that is, the logic "1". In step c3, the length direction (the traveling direction of the metal strip 1 in FIG.
5 (up and down direction) in the width direction (left and right direction in FIG. 45)
46, the frequency of how many flaws have occurred per unit square, that is, per pixel q1 is counted, and the frequency is calculated as shown in FIG.
Create a histogram profile as shown in.

In step c4, based on this histogram, the first area SHL of the flaw 143 on the histogram having the longest value HL and the longest value HL in the traveling direction.
Ask for. Further, based on this histogram, the second area SWW of the flaw 144 having the largest value WW in the width direction on the histogram is obtained. These defects 143, 144 are
On the histogram shown in FIG. 46, the histograms are separated, and the longest value HL and the widest value WW for each of these separated flaws.
Is detected as described above.

At the next step c5, the weighted addition value FHL of the flaw 143 having the longest value HL is obtained by reading the data of the frame memory FRM1 in which the above-mentioned multi-valued data is stored and in the same manner as the equation 2. This weight addition value FH
L is calculated by the product of the area and the value obtained by adding the reflected light intensities of the respective pixels of the respective channels P, B, S1, S2.
Similarly, the weighted addition value FHW of the flaw 144 having the widest value WW is calculated and calculated in the same manner as the above-described Expression 2 over each pixel in all channels.

At step c6, the larger one of the weighted addition values FHL and FHW obtained at step c5 is set to
It is adopted as the weight addition value FHLW.

At step c7, the weight addition value FHLW thus adopted (that is, the weight addition value FHL or FHL
Area S of flaw 143 or 144 of either HW)
Calculate LW. This area SLW is SHL or SWW
Either one of them. Therefore, in step c8, the density AF is obtained from the equation 4.

AF = FHLW / SLW (4) In step c9, the number N of defects in the defect determination unit section q
A is counted and calculated.

In the defect judgment unit section q shown in FIG. 47,
The number of defects NA = 3. If the flaw shown in FIG. 48 is present, the number of flaws NA = 2. That is, in FIG. 48, when the right side 144 of the flaw is continuous from top to bottom, it is counted as one flaw, and when the separated side 145 is present, it is counted as another flaw.

At step c10, FIG. 47 and FIG.
The surface area SA and the total length HA of the flaw in the flaw determination unit section q shown in are calculated and obtained.

SA = S1 + S2 + S3 (5) HA = H1 + H2 + H3 (6) In step c11, the area SHL of the flaw 143 having the longest value HL obtained based on the above-mentioned histogram and the flaw 144 having the widest value WW are obtained. The larger value SHL or SWW of the products SWW is adopted as the value SLW. Next, in step c12, the ratio RA of the adopted area SLW to the total area SA is calculated and obtained. In step c13, the average length AH of the flaw is calculated by the equation 7.

AH = HA / NA (7) In step c14, in the length direction of the flaw determination unit section q shown in FIG. 49 (1), how many flaws are generated per pixel in the unit cell in the width direction. A histogram is created by obtaining the frequency of whether or not the pixel is counted, and thus the pixel count, and such a histogram is obtained by the same method as in FIG.
The histogram of the defect determination unit section q shown in FIG. 49 (1) is as shown in FIG. 49 (2). Defects 145, 1 on the histogram in step c15
46 and 147 are higher than a predetermined high discrimination level h3 and the number N3 = 3. In addition, the number N2 of defects other than that, the number of the defects 148 having the height discrimination level H3 or less and the discrimination level h2 or more, is N2 = 1. Further, the number N1 of defects 149 having the minimum height discrimination level h1 or more is N1 = 1. In the embodiment of the present invention, such number N2
N3 is obtained and used in step c15.

In addition to this, based on the histogram, Table 4 is prepared based on the longest value HL in the running direction and the widest value WW in the width direction for each defect determination unit section q shown in Table 4.

[0092]

[Table 4]

The contents of the table shown in Table 4 will be referred to as a shape defect box. According to the contents of the shape flaw box, the flaw type and flaw form for each flaw judgment unit section q in step a5 of FIG. 37 are determined by the following flowcharts of FIGS. Step d of FIG.
1, in the shape defect box of Table 4, if the maximum value of the weight addition value F for each channel P, B, S1, S2 is the channel of the diffused reflection light S1, the process moves from step d2 to step d3, and the defect type Is a linear flaw, and the flaw form is determined to be L1. When the weight addition value F for each channel P, B, S1, S2 is the maximum weight addition value F (P) for the P channel in step d4, step d5
Then, the defect type is determined to be a surface defect, and the defect form is determined to be A1. The weight addition value F of the other channels D and S2 is equal to the weight addition value F (S of the other channels S1 and P).
1) and F (P) are larger than those shown in FIGS.
Each operation of is started from step d6.

In FIG. 51, when the minimum value HL is 2> HL ≧ 0 (8), steps e2, e4, e6, e8, e10
As shown in, the defect type is determined to be a dot defect and the defect forms are P1 to P6 according to the number Ma of defects.

52, when 5> HL ≧ 2 (9)
, RA ≧ 0.75 (10), and if the expression 10 is not satisfied, the next step f3
And the value AH obtained in step c3 of FIG. 43 described above.
However, it is determined whether AH ≧ 3 (11) holds. If the expression 11 is not established, the process moves to the above-mentioned FIG. 51 and the flaw form of the dot-like flaw is determined.

When the expression 10 or the expression 11 is satisfied, in the next step f4, if the values AF obtained in step c8 of FIG. 43, AF ≧ 75 ... It is determined that the form is L3, and if the expression 12 is not established, the defect form L2 of the linear defect is determined in step f6.

In FIG. 53, when 15> HL ≧ 5 (13), the process moves to step g1, and in the next step g2, RA ≧ 0.75 (14) holds, or in step g3, AH When ≧ 3 (15) is satisfied, the process proceeds to the next step g4, and the flaw forms L5 and L4 of the linear defects are determined in steps g5 and g6 depending on whether AF ≧ 70 (16) is satisfied.

In FIG. 54, when 50> HL ≧ 15 (17) holds, the process moves from step j1 to step j2, and RA ≧ 0.75 (18) holds, or in step j3, AH ≧ 3. When (19) is satisfied, at the next step j4, the values N2 and N3 obtained at step c15 in FIG.
By using N2 + 3 · N3 ≧ 3 (20), the linear flaws L7, L
Judge 6

In FIG. 55, when HL ≧ 50 (21) is satisfied, the process moves from step k1 to step k2, and when RA ≧ 0.75 (22) is satisfied, the process moves to next step k3 and the above-mentioned process is performed. Formula 20
Depending on whether or not is satisfied, the linear flaws L9, L
8 is judged. When the expression 22 is not satisfied in the above-mentioned step k2, it is determined that the dot-like flaw is present, and the operation shown in FIG. 51 is performed.

After the defect type and the defect form in each defect determination unit section q are thus determined in step a5 of FIG. 37, the determination grade weight value φ of the defect determination unit section q is determined in step a6. Obtained from Table 5. This judgment grade weight value φ is set as a range in which an operator can visually recognize that the flaws are of the same degree when the flaws having different flaw types and different flaw forms are prototyped. As a result, if the judgment grade weight value φ is the same, even if the flaw type and the flaw form are different, the grade is graded as being the same degree of flaw visually by the operator.

Defect type, defect form L1 to L9, P1
In P6 and A1, the value shown in parentheses in Table 5 is obtained as the judgment grade weight value φ based on the weight addition value F obtained in step a2 of FIG.

[0102]

[Table 5]

Therefore, in step a7, the judgment grade weight value φ is added for each defect type in the defect judgment unit section q. For example, in FIG. 56, the flaw forms L2 and L that are linear flaws.
The addition value of the judgment grade weight value φ of 2, L5, L6 is 90 (=
20 + 40 + 10 + 20), which is the maximum, the judgment grade weight value φ of the dot-like flaw P3 is 10, and the judgment grade weight value φ of the surface flaw A1 is 20. Therefore, in step a8, the linear flaw, which is the flaw type for which the maximum judgment grade weight value φ is obtained, is determined to be the flaw type of the grade evaluation unit section Q. Further, in step a9, Φ is obtained for the layer of the judgment grade weight value φ of each defect judgment unit section q in the grade evaluation unit section Q. In FIG. 56, for example, 120
(= 20 + 40 + 10 + 20 + 10 + 20). Thus, in step a10, the grade can be obtained from Table 6 by the flaw type obtained in step a of the flaw evaluation unit section Q and the grade weight value Φ obtained in step a9.

[0104]

[Table 6]

Thus, the grade A of the grade evaluation unit section Q
~ D, K, J can be automatically obtained in real time automatically in the same degree as the operator's eyes.

The arithmetic output of the processing circuit 140 is visually displayed on a visual display means 151 such as a cathode ray tube or liquid crystal, and is printed on a recording paper 153 by the printer 152.

FIG. 57 is an electric circuit diagram showing a specific structure of an embodiment of the present invention. The configuration shown in FIG. 57 is achieved by the processing circuit 140 shown in FIG. 19 described above, and is shown in a block diagram to specifically show the configuration. The feature amount calculation means 152 is the same as that shown in FIG.
Each feature amount obtained in 9 is derived and given to the similarity calculation means 153. The similarity calculation unit 153 calculates the similarity between the defect reference pattern sequentially read from the reference pattern memory 154 and the feature amount that is the defect feature data. The calculation of the degree of similarity is achieved by performing a product-sum operation based on the length, width, and area between the flaw reference pattern and the flaw feature amount data. As an example of the calculation of the reference pattern and the feature amount data, a linear discriminant function is used.

When the output of the characteristic amount calculating means 152 is Y, the content of the reference pattern memory 154 is W (i), and the output of the similarity calculating means 153 is Fi, Fi is an inner product of Y and W (i) Given in.

Fi = W (i) .Y (i = 1, 2, 3, ..., D) (23) [D is the number of defect types] Here, the determination unit 155 determines i ₀ that maximizes Fi. Then, the defect type at the address i ₀ is output as an identification result. However, Y = (x1, x2, x3, ..., xd, 1) ^t ... (24) W (i) = {w1 (i), w2 (i), ..., wd (i), wd + 1 (i)} ^t (25) Note that x1, x2, ..., Xd are extracted feature quantities such as length, width, and area. W (1), W (2), ..., W
(D) is a reference pattern to be obtained. That is, the determination unit 155 determines which defect type is the defect type based on the defect reference pattern having the highest similarity output from the similarity calculation unit 153. Has a function to output.

The output control means 156 drives the display means 151 which is a display monitor to display the character corresponding to the defect type information (defect name, grade) from the judging means 155 and the surface from the characteristic amount calculating means 152. A surface image corresponding to the image data is displayed, and the printer 15
2 is driven to record the defect type information and the display image data.

The keyboard 157 allows an operator to manually input data corresponding to defect type information such as a defect name and a grade. A key signal from the keyboard 157 is converted into predetermined defect type information and displayed on the display unit 151.
It has a function of outputting to and displayed on the display unit and outputting to the comparison calculation unit 158. The comparison calculation means 158 is the determination means 1
The defect type information determined in 55 and the defect type information output from the keyboard 157 are compared to determine whether or not they match. If they match, it is determined that the defect reference pattern is correct and correction processing is performed. If there is no match, the defect reference pattern in the reference pattern memory 154 is corrected according to a certain algorithm to obtain a new defect reference pattern.

During operation, the feature quantity computing means 152
At least one feature amount of the length, width, and area of the flaw is obtained, and this feature amount is sent to the similarity calculating means 153 as data of the flaw feature amount, and the reference pattern memory 154.
The degree of similarity is calculated based on a large number of defect reference patterns sequentially read from. Then, the similarity calculation means 15
The defect reference pattern having the highest degree of similarity is output from No. 3, and the determination unit 155 determines which defect type (name) and defect form (grade) the reference pattern is.
As a result, on the display monitor 151, as shown in FIG. 58, the name "hege" 161 and the grade "3" of the flaw image 160 automatically determined together with the still image 159 of the surface image.
“Grade” 162 is displayed for a certain period of time.

In this state, in order to improve the accuracy of the flaw determination, when the work of learning the flaw reference pattern is performed, the operator visually checks the surface image 160 on the display monitor 151 for the flaw image 160. Defect name "Sliver" and grade "4" are judged, and keyboard 157
Operate the corresponding key above. Then, the defect type form (name and grade) corresponding to the key input data is obtained by the keyboard, and these names and grades are stored in the data 151.
Are displayed at the predetermined positions 164 and 165 of the above, and are sent to the comparison calculation means 158. The comparison calculation means 158 compares the automatically determined flaw type (health: grade 3) with the key-input flaw type (sliver: grade 4). In this case, the defect types do not match, and the defect type of the metal strip 1 and the determination unit 1
This means that the defect type and the defect form determined in 55 are incorrect, and thus the defect reference pattern stored in the reference pattern memory 154 is incorrect for a certain defect type on the actual line. , The defect reference pattern in the reference pattern memory 154 is gradually corrected according to a certain algorithm.

When the defect reference patterns are corrected one after another by repeating such a learning operation for the image 160 of the defects which are sequentially input, finally, the judgment defect type based on the defect reference pattern and the keyboard 157 are used. The visual defect types of No. 1 and No. 3 become almost coincident with each other, and the determination algorithm that matches the actual type of defects on the actual line is completed. Therefore, if the flaw reference pattern of the reference pattern memory 154 is corrected using the visual judgment of the operator as described above,
As far as the same type of inspected object or the same line is concerned, it is possible to judge the type of the flaw generated on the surface of the metal strip 1 by the unmanned operation without intervention of the operator, and
An accurate judgment result can be obtained.

As described above, according to the present embodiment, the flaw image 160 in the metal strip 1 on the actual line and the flaw image 160 is automatically detected based on each flaw reference pattern in the reference pattern memory 154. The determined defect type is displayed on the display monitor 151, and the defect reference pattern at this time can be corrected so as to automatically determine the defect type input by visual determination from the keyboard 157. It is possible to create a flaw reference pattern that is closer to the state of the actual line while demonstrating learning ability online without using a sample board. Therefore, it is possible to save labor such as collecting various sample plates and learning work off-line, and to shorten learning time and labor. Further, since the learning work is performed online, it is possible to easily deal with the change of the inspection object 1 and the like, and the effect of correcting the flaw reference pattern by the learning work is promptly reflected in the flaw determination of the actual line. Thus, the surface inspection of the inspection object 1 can be performed with high accuracy and very efficiently.

The criteria for determining the surface quality are not always clear, and the sensory elements are quite strong. In many cases, the inspector who is the worker cannot express the judgment rule clearly. Therefore, as a knowledge information AI method to be introduced into the surface inspection apparatus, a learning machine method for acquiring a parameter for determination by training by a teacher is used, rather than a method like an expert system that takes in know-how of an expert as a rule. Considered to be suitable.

FIG. 59 models the learning function in the human brain in accordance with the present invention and has the ability to learn the classification of patterns. The learning function will be described for this unit. Large circles represent cells (neurons), x1 to xn represent inputs to cells, and small circles represent synapses (functions that control stimulation given to cells).

The operation of this cell is

[0119]

[Equation 1]

It is represented by αi is a real number and is called synaptic weight, and it is a coefficient that expresses the ease with which a stimulus is transmitted, θ is a threshold value for whether cells are excited, and Φ (μ) is 1, μ if μ> 0.
If <0, the quantization function is 0.

Therefore, the output OUT of this cell is

[0122]

[Equation 2]

When exceeds θ, it excites and outputs 1. In addition, the teacher signal is a signal that tells whether or not the cell reaction is correct with respect to the entry, and α = (α1, α2, ..., αn), x = (x1, x2, ..., xn) (28) ), If the reaction is correct, α ← α + cx (c is a positive constant), and if incorrect, α ← α-cx.

If these cells are cells corresponding to a certain specific pattern, even if there are many false reactions at first, the teacher signals sent from humans will gradually make correct reactions.

FIG. 60 shows an embodiment of the present invention in which this principle is applied to the determination of flaw type, flaw type and grade. This is the simplest configuration example. Light receiving detection means 60, 66,
From the video signals sent from 61 and 69, various feature quantities of surface defects x = (x
1, x2, ..., Xn) are extracted. The circuit 168 performs an appropriate conversion y = f (x) on these feature quantities,
This is input to the cells for determining the defect type and grade.

This conversion is performed in order to improve the linear separability of the pattern input given to the cell, and is based on real-time arithmetic operations, logarithmic operations, and the like. For example, if the length of the defect is xi and the width is xj, the ratio between the length and the width is calculated by yk ← xi / xj and is set as a new feature amount.

Training for actually learning by this system is performed by the system as shown in FIG. The images captured by the photodetection means 60, 66, 61, 69 are taken into the frame memory and displayed on the color cathode ray tube CRT. Since the judgment result of the device is displayed at the same time, the inspector (teacher) collates the actual flaw appearing on the downstream side of the line with this CRT screen, and inputs the correctness of the judgment result or the correct result at hand. Input from the device. The contents input by the inspector are sent to the processing circuit MPU, and the predetermined coefficient of the learning unit is corrected so that the correct judgment can be made. By repeating such work, the judgment ability of this device is gradually improved, and after sufficient training, it becomes in good agreement with the judgment of the inspector.

In another embodiment of the present invention, since the surface flaws are formed by fine undulations, unevenness on the surface is reduced to 3
Techniques for dimensional and quantitative measurement have been devised. As an example, FIG. 6 illustrates the sensing principle by light spot scanning velocity modulation.
Shown in 1. A metal beam 1 to be inspected is scanned with a laser beam at a constant speed, and its locus is imaged on a screen 170 by a lens 169. At this time, if the surface of the metal strip 1 to be inspected has irregularities, the screen 170
The moving speed of the upper light spot changes. In FIG. 61, since the inspection target surface is concave when scanning from the point B2 to the point C2, the moving speed on the screen becomes faster. Therefore, it is possible to quantitatively measure the unevenness by drawing the grid pattern 171 having a constant pitch shown in FIG. You can If this principle is applied, a measurement speed equivalent to that of the current laser beam reflection method can be realized.

The present invention is further applicable to the following embodiments.

According to the present invention, the long material is wound around the guide roll to continuously run, and within a circumferential range in which the long material is wound around the guide roll, a plane including the axis of the guide roll is provided. On the line of intersection with the outer peripheral surface of the long material, so that the laser beam is scanned, from one side with respect to the plane, the laser beam is irradiated and scanned in a virtual scanning plane parallel to the axis of the guide roll, and the plane. With respect to, on the other side, the reflected light from the intersection line is received, and the surface of the long material is inspected based on the received reflected light. Further, according to the present invention, the outer peripheral surface is uniform in the axial direction, and a guide roll around which a long material is wound and continuously travels, and a scanning unit, in which a laser beam from a laser light source is elongated. Within a circumferential range in which the material is wound around the guide roll, on a line of intersection between the plane including the axis of the guide roll and the outer peripheral surface of the long material, the guide is provided from one side with respect to the plane so as to scan. A scanning unit that irradiates and scans with a laser beam in a virtual scanning plane parallel to the axis of the roll, and has a light receiving surface that is disposed on the other side with respect to the plane and extends in the axial direction of the guide roll. A light receiving means for receiving the reflected light and generating a level of an electric signal corresponding to the light intensity, and an inspection means for responding to the output of the light receiving means and calculating the output of the light receiving means to inspect the surface of the long material. A surface inspection apparatus for a long material characterized by including According to the present invention, the guide rolls are provided in pairs having parallel axes in one imaginary plane, and the elongate member is provided with the guide rolls such that the rotation directions of the guide rolls are opposite to each other. The laser light source, the scanning unit, and the light receiving unit are provided in combination with each of the guide rolls. According to the present invention, the long material is wound around the guide roll and continuously run, and the surface of the long material is within the circumferential range of the long material wound around the guide roll. , A plane including the axis of the guide roll, so that the laser light scans the intersection of the guide roll, and therefore the outer peripheral surface of the long material, from one side with respect to the plane including the axis of the guide roll, Scanning by irradiating laser light in a virtual scanning plane parallel to the axis, receives reflected light from the intersecting line on the other side with respect to the plane, and based on the reflected light thus obtained, a long material Inspect the surface of the. Therefore, the long material is irradiated with the laser light within the range in which the long material is wound around the guide roll, and the reflected light is received, whereby the long material does not vibrate, and the vibration causes the light receiving means to vibrate. Therefore, the received light level of the reflected light due to does not change due to vibration. This stabilizes the inspection ability of the surface of the long material. Further, since the long material is wound around the guide roll, the vibration is eliminated as described above, and within the circumferential range wound around the guide roll, the long material exists in the natural state. Eliminates wrinkles and bends that may occur. This also makes it possible to accurately inspect the surface of the long material for flaws. In a metal strip as a long material, for example, it is important to eliminate the edge wave, that is, the edge wave, at the edge portion at the time of inspection. Generally speaking, the ear wave has a shorter wavelength of the wave and a higher wave height than those of other shape defects such as medium elongation and C-warp.
This is a strong tendency for thin plates of mm or less. In general, the range of the ear wave is almost 30 to 50 mm from the edge of the metal band, and the steepness of that portion reaches 0.03 to 0.05. In the present invention, as described above, the surface light is inspected by receiving the reflected light of the laser light. Therefore, if the steepness is large, the surface inspection becomes impossible. Therefore, in order to achieve the purpose of the inspection, the long material is wound around the guide roll as described above in order to create a state in which the shape of the ear wave or the like is erased only at the time of the inspection. This makes the ear waves seem to disappear. If the radius of the guide roll is chosen to be large, the selvages escape outward in the width direction without being constrained.In particular, by increasing the outer diameter of the guide roll, the difference in the selvage wavelength is absorbed and stabilized, making it apparent. , The ear wave has disappeared.

In the present invention, the outer diameter of the guide roll is about 5
It is characterized in that it is at least 00 mmφ. Furthermore, the invention is characterized in that the outer diameter of the guide roll is less than about 1300 mmφ. According to the present invention, the outer diameter of the guide roll is selected to be about 500 mmφ or more, for example, about 130 mm.
It may exceed 0mmφ, but in practice it is about 1300
By selecting less than mmφ, the guide roll can be easily handled. When the long material is wound around such a guide roll in the circumferential direction by, for example, about 180 degrees, the ear waves on the surface of the metal strip, which is the long material, disappears, and the inspection can be performed with high accuracy. Like In this way, it becomes possible to automatically inspect the surface online while the long material is running.

Further, the present invention is characterized in that the scanning means includes a polygonal reflecting mirror for reflecting the laser light from the laser light source, and a rotation driving means for rotatably driving the reflecting mirror. According to the invention, a pair of guide rolls are provided with parallel axes in one virtual plane, and are arranged, for example, like a bridle roll, and the rotation direction of each pair of guide rolls The long material is wound around each of the guide rolls so that they are opposite to each other when viewed from one axial side of the roll. Therefore, by scanning the surface of the long material wound around each guide roll with laser light and detecting the reflected light, the front and back surfaces of the long material are inspected at the same time as the long material is running. It becomes possible. The scanning of the laser light is performed by causing the laser light from the laser light source to be reflected by a polygonal reflecting mirror called a trigon mirror, which is rotationally driven at a high speed by a rotational driving means, and scanning the laser light in the width direction of the long material. The scanning can be easily achieved by.

Further, according to the present invention, the light receiving means comprises a plurality of condenser lenses arranged with their ends adjacent to each other in the scanning direction of the laser light, and elongated along the condenser lenses, and the condenser lenses It is characterized by including a light guide member for guiding light in its longitudinal direction, and a light reception detecting unit arranged at an end portion of the light guide member for deriving an electric signal having an electric signal level corresponding to light intensity. Further, the present invention is characterized in that the condensing lens is integrated by cutting the ends of the spot-shaped laser light in the scanning direction at predetermined positions and joining the cut surfaces as joint surfaces. . According to the present invention, in the light receiving means for receiving the reflected light from the surface of the long material, the light receiving means has a plurality of condenser lenses arranged in a state in which the ends are in line contact with each other in the scanning direction of the laser light, The longitudinal light guide member is arranged along the condenser lens, and therefore, the reflected diffracted light by the entire scanning range of the surface to be inspected of the long material is condensed without leakage and guided in the longitudinal direction of the light guide member. be able to. By setting the outside diameter of the guide roll to be large as described above, even if the scanning position accuracy of the polygonal mirror driven to rotate is low, for example, the polygonal mirror driven to rotate is easily affected by vibrations and the like. However, the reflected light can be reliably received by the light guide member via the condenser lens. The light guided by the light guide member is detected by the light receiving detection means arranged at the end of the light guide member,
It is converted into an electric signal having a voltage or current level corresponding to the light intensity. INDUSTRIAL APPLICABILITY The present invention can be widely applied not only to metal strips but also to films such as synthetic resin and other long strips which are long strips.

Further, according to the present invention, the surface of the object to be inspected is irradiated with light, the reflected light thereof is received and detected, the noise level N included in the light reception detection signal is detected, and the light reception detection signal is detected. The surface inspection method is characterized in that the surface is inspected by a normalized signal by dividing by the noise level N obtained. According to the present invention, the surface of the object to be inspected, for example, a metal band such as a brightly annealed stainless steel band, is irradiated with light such as laser light, the reflected light is received, and a light reception detection signal is obtained, and the received light is received. By detecting the noise level N included in the detection signal, dividing the received light detection signal having a level corresponding to the flaw existing on the surface of the inspection object by the detected noise level N, and normalizing It is possible to obtain a flaw detection light reception signal for the background level corresponding to the flaw regardless of the degree of gloss of the surface of the inspection object. Therefore, even a slight flaw on the surface of bright annealed stainless steel or the like having a large surface gloss can be reliably detected.

Further, according to the present invention, the reflected light detected is regular reflection light and irregular reflection light, and the first gain of the regular reflection detection signal and
A second gain larger than the first gain of the irregular reflection detection signal is set so that the first average peak value of noise of the regular reflection detection signal becomes larger than the second average peak value of noise of the irregular reflection detection signal. It is characterized in that the regular reflection detection signal and the irregular reflection detection signal are DC-amplified respectively, and the noise level N of the regular reflection detection signal and the irregular reflection detection signal thus amplified is detected and normalized. According to the invention, the specular reflection light and the diffuse reflection light on the surface of the object to be inspected such as a metal band are detected, and the received light detection signal is amplified by direct current, and the level of the specular reflection detection signal is the level of the scatter reflection detection signal. The first gain that amplifies the specular reflection detection signal is generally higher than the level and thus the second gain that amplifies the diffuse reflection detection signal.
Select a value smaller than the gain and select the first noise of the specular reflection detection signal.
The average crest value, that is, the background level, is set to be larger than the second average crest value of the noise of the diffuse reflection detection signal, and the diffuse reflection detection signal having a generally low level is amplified with an unreasonably high gain. Do not worsen the S / N.

Further, in the present invention, the inspection is the sum of a variation of a normalized specular reflection detection signal due to light absorption by the surface and a variation of a normalized irregular reflection detection signal due to light reflection by the surface. It is characterized by performing based on. According to the present invention, the specular reflection detection signal absorbs light due to the presence of flaws on the surface of the object to be inspected such as a metal band, and therefore the specular reflection detection signal is a signal on the side that is reduced by light absorption. The fluctuation amount is obtained, whereas the irregular reflection detection signal increases the light intensity of the reflected light due to the presence of a flaw, and the fluctuation amount due to the light reflection is obtained. In this way, by determining the sum of the variation due to the light absorption of the regular reflection detection signal and the variation due to the light reflection of the irregular reflection detection signal, the type of flaw, that is, linear, dot-like, and surface-like is determined. Further, the flaw type for each type of flaws, for example, L1 to L9 described later for linear flaws, P1 to P6 for dot flaws, and A1 for surface flaws are determined, and based on this, the inspected object is determined. It is possible to give a rating to a certain metal strip or the like. The variation is binarized by discriminating a predetermined discriminating level, and the grade of the inspected object can also be graded based on such binarized data.

Further, the present invention is characterized in that the variation is level discriminated by a discriminative level determined in advance and binarized, and the inspection is performed by the binarized data. The present invention also provides a scanning means for scanning a laser beam on the surface of the metal strip running in the longitudinal direction and a width direction of the metal strip, and a light receiving means for receiving and detecting the reflected light from the surface of the metal strip. A noise level calculating means for calculating the noise level N in response to the output of the light receiving means, and a normalizing means for responding to the outputs of the light receiving means and the noise level calculating means for dividing the received light detection signal by the noise level N And a processing means for inspecting the surface in response to the output of the normalizing means. Further, according to the present invention, the light receiving means is the specularly reflected light in the virtual light receiving plane which is reflected by the surface of the object to be inspected of the laser light to be scanned.
A first received light detecting means for the reflected light, and a second received light detecting means for the second reflected light B diffusedly reflected closer to the irradiation direction than the regular reflected light,
Third light reception detecting means for the third reflected light S1 laterally displaced from the virtual light receiving plane, and fourth light reception of the fourth reflected light S2 further laterally displaced from the virtual light receiving plane than the third reflected light S1. And a detection means. According to the invention,
The irregular reflection light is irregular reflection light B closer to the irradiation direction than the regular reflection light.
And the irregularly reflected light S1 laterally displaced from the virtual light receiving plane 40.
Then, the fourth reflected light S2, which is further deviated from the third reflected light S1 to the side from the virtual light receiving plane, is detected and used for the defect type and the defect determination.

Further, according to the present invention, each of the first to fourth light receiving and detecting means is adjacent to the laser beam scanning direction, has a plurality of condenser lenses for condensing, and extends along the laser beam scanning direction. And a light receiving element for receiving light passing through the light guiding member and deriving a light reception detection signal having a level corresponding to the light intensity. Further, in the present invention, the processing means is responsive to the output of the normalizing means and corresponds to the output of the first light receiving and detecting means, and the variation due to the light absorption by the surface, and the second to fourth light receiving and detecting means. The surface is inspected based on the variation due to the light reflection by the surface. Further, according to the present invention, the processing means discriminates the level of the fluctuations by 2
Value data is obtained, and this binary data is used for inspection of the surface. According to the present invention, the laser light is scanned by the scanning means in the width direction of the surface of the metal band, and the detection of the entire width direction of the metal band can be inspected in real time while the metal band is running. According to the invention, the light receiving means has a plurality of condenser lenses adjacent to each other in the scanning direction of the laser light, and gives light of specular reflection light and irregular reflection light obtained from the condenser lenses to the light guide member, An electric signal having a level such as voltage or current corresponding to the light intensity of specular reflection light and irregular reflection light is obtained by detection with a light receiving element such as a photomultiplier arranged at the end of the light guide member in the longitudinal direction. be able to.

Further, the present invention is a hole detecting means, which comprises a light source means for irradiating light in the width direction on one surface side of the metal strip and a light source means for the other surface side of the metal strip. And a traveling position detecting means for detecting the traveling position of the metal strip in the longitudinal direction, and the processing means comprises a hole detecting light receiving means and a traveling position detecting means. In response to the output, the position of the hole in the metal strip is calculated, and the grade of the metal strip is prioritized over the determination of the surface inspection. According to the invention, the light source means for irradiating the light in the width direction is arranged on one surface side, for example, the lower side of the metal strip, and the light source means has a configuration for scanning the laser light in the width direction of the metal strip, for example. Alternatively, an elongated fluorescent lamp may be arranged so as to extend in the width direction of the metal strip, and the light from such a light source means is provided with a hole on the other surface side of the metal strip, for example, above. The traveling position in the longitudinal direction of the metal strip is detected by the light receiving means for detection, and the traveling position detecting means detects the traveling position. The traveling position detecting means generates a pulse for each predetermined distance in the traveling direction of the metal strip. If a hole in the metal band is detected by this, the position where the hole in the metal band exists is calculated by calculating the output of the traveling position detecting means, and the hole exists in such a metal band. When performing the The grade is given priority over the determination of the flaw form, and when, for example, a hole exists in such a metal strip, the portion including the hole in a predetermined unit length in the traveling direction, for example, a portion over a range of 1 m is commercialized. Judge and evaluate as having no value.

According to the present invention, the light source means of the hole detecting means is
A laser light source, a polygonal reflecting mirror that reflects the laser light from the laser light source and scans the one surface of the metal strip in the width direction, and a rotation driving unit that rotationally drives the polygonal reflecting mirror. The light receiving means is characterized by including a condensing lens elongated in the width direction of the metal band and a light receiving element for receiving light from the condensing lens. According to the invention, the light source means of the hole detecting means scans the laser light in the width direction of the metal band by rotating the light from the laser light source with the rotation driving means such as a motor of a polygonal reflecting mirror called a polygon mirror. To do. The light receiving means for hole detection collects light by a condenser lens arranged in a slender shape in the width direction of the metal strip.
For example, a large number of condenser lenses may have a configuration in which they are arranged adjacent to each other in the width direction of the metal band, or may be realized by a cylindrical Fresnel lens or the like,
The light from the condensing lens thus obtained is received by a light receiving element such as a pin photodiode, or is also received by a light guide member extending in the scanning direction of the laser light, and the light in the longitudinal direction of the light guide member is detected. For example, the light receiving element arranged at the end receives light. The present invention can be implemented for surface flaw inspection of an inspected object other than a metal strip, such as a synthetic resin.

Further, according to the present invention, the scanning means for scanning the laser beam on the surface of the metal strip running in the longitudinal direction and the width direction of the metal strip, and the reflected light from the surface of the metal strip are received and detected. In response to the output of the light receiving means and the output of the light receiving means, the noise level calculating means for calculating the noise level N, and the output of the light receiving means and the noise level calculating means, the light receiving detection signal is divided by the noise level N. A normalization means, a feature quantity calculation means for calculating a feature quantity of a flaw in a constant section q on the surface of the metal band in response to the output of the normalization section, and a surface image of the constant section q calculated by the feature quantity calculation means. Compute the degree of similarity between the feature amount of flaws and multiple feature order patterns,
Similarity calculation means for outputting a defect reference pattern closest to the defect feature amount, defect type determination means for determining the type of defect based on the operation result obtained by this similarity operation means, and determination by the defect type determination means Display means for displaying the selected defect type together with the surface image of the fixed section q, an input device for inputting the defect type, the defect type input by this input device, and the defect type determined by the defect type determining means. And a pattern correcting means for making a new reference order pattern by correcting the defect reference pattern when there is a mismatch, and a surface defect inspection device for a metal strip. Further, the present invention is characterized in that the display means has a configuration in which the flaw type judged by the flaw type judging means and the flaw type inputted by the input device are compared and displayed together with the surface image. Further, according to the present invention, the light receiving means includes a first reflection light, which is the specular reflection light in the virtual light reception plane reflected by the surface of the inspected object of the laser light to be scanned.
Receiving light detecting means, second receiving light detecting means for the second reflected light B diffusedly reflected closer to the irradiation direction than the regular reflected light, and third receiving light detecting means for the third reflected light S1 laterally displaced from the virtual light receiving plane. And a fourth received-light detecting means for the fourth reflected light S2 that is laterally displaced from the virtual light-receiving plane further than the third reflected light S1, and the feature quantity computing means is responsive to the output of the normalizing means,
The surface is inspected on the basis of the variation due to the light absorption by the surface corresponding to the output of the first light receiving and detecting means and the variation due to the light reflection by the surface corresponding to the second to fourth light receiving and detecting means. A surface flaw inspection device for a metal strip, which is characterized in that Further, the present invention is characterized in that the flaw feature amount computing means obtains binarized data by discriminating the level of the variation and using the binarized data for inspection of the surface.

According to the present invention, the surface of the object to be inspected, for example, the metal band such as the brightly annealed stainless steel band is irradiated with light such as laser light and the reflected light is received to obtain a light reception detection signal. , The noise level N included in the received light detection signal
Is detected, and the received light detection signal having a level corresponding to a flaw existing on the surface of the inspection object is divided by the detected noise level N and normalized to thereby detect the surface of the inspection object. Regardless of the degree of gloss, it is possible to obtain a flaw detection light reception signal for the background level corresponding to the flaw. Therefore, even a slight flaw on the surface of bright annealed stainless steel or the like having a large surface gloss can be reliably detected. By the output of the normalizing means thus obtained, the flaw feature data in the fixed section q is obtained, and the similarity between the flaw feature data and the plurality of flaw reference data is calculated, and the flaw feature data is the closest flaw reference. A pattern is output, the type of flaw is determined based on this output, and it is displayed together with the surface image of a certain area. Here, when the type of flaw is input by the input device, it is determined as the input flaw type. The defect type is compared, and if they do not match, the defect reference pattern is modified to set a new defect reference pattern. Further, according to the invention, the first reflected light that is specularly reflected light, the second reflected light B that is irregularly reflected light closer to the irradiation direction than the specularly reflected light, and the irradiation direction of the laser light, and include a virtual scanning plane. Virtual light receiving plane 40 orthogonal to
And the third reflected light S1 that is laterally displaced from the third reflected light S1.
By using the fourth reflected light S2 further deviated from 1 and using the reflected light of a total of four channels, it becomes possible to reliably perform the flaw inspection of the surface of the metal band. According to the invention,
The specular reflection detection signal absorbs light due to the presence of flaws on the surface of the object to be inspected such as a metal band. , By contrast, the diffuse reflection detection signal is
The presence of the flaw increases the light intensity of the reflected light, and the variation due to the light reflection is obtained. In this way, by obtaining the variation due to the light absorption of the regular reflection detection signal and the variation due to the light reflection of the irregular reflection detection signal, for example, the type of flaw, that is, the line, the point and the surface are distinguished, Further, the flaw type for each type of flaws, for example, L1 to L9 described later for linear flaws, P1 to P6 for dot flaws, and A1 for planar flaws are determined, and based on this, it is an inspection object. It can be used to classify metal bands. The variation is binarized by discriminating a predetermined discriminating level, and the grade of the inspected object can also be graded based on such binarized data.

[0143]

According to the present invention, it is possible to automatically detect and determine the surface flaws of the metal strip to be passed, and also to automatically determine the grade thereof, thereby saving labor. Can be planned.

Further, according to the present invention, each flaw is the same for each flaw type and flaw form occurring in the plurality of flaw judgment unit divisions q constituting the evaluation unit division, as in the case where the operator visually checks each flaw. It is confirmed by the experimental results of the inventor of the present invention that the evaluation can be made with the matching rate of, and by setting the grade weight value Φ with which the degree of the flaw can be evaluated at the same level as the visual inspection, Regardless of the type and form of the flaw, all the flaws that occur in the above can be evaluated collectively by simply adding the grade weight value Φ, and it is equivalent to the visual grade rating. It will be possible to automatically perform grading online in real time.

Further, according to the present invention, the average length AH (= HA / NA) of the flaws along the traveling direction is obtained as one of the plurality of feature quantities in performing the grade classification, and the linear shape is obtained by this. It becomes possible to reliably determine the types of defects, that is, defects and dot-like defects.

Furthermore, according to the present invention, not only specularly reflected light but also diffusely reflected light is used as the reflected light, and the reflected light intensity V of the specularly reflected light is the variation amount of the optically absorbed component from the noise average peak value. On the other hand, the reflected light intensity V of the irregularly reflected light is the absolute value of the variation of the irregularly reflected component from the noise average peak value, and as a result, a slight flaw existing on the surface of the metal band. However, accurate detection is possible, which results in a weighted sum F and thus an average intensity A
By using F, it becomes possible to accurately perform the flaw morphology of the linear flaw.

Further, according to the present invention, the longest value HL in the traveling direction and the widest value WW in the traveling direction are obtained based on the histogram, and the first and second values are obtained.
Of the areas SHL and SWW, the ratio RA (= SLW / SA) of the larger area SLW to the total area SA is used,
The defect type and the defect form are determined, which also makes it possible to make the evaluation evaluation as close to the visual inspection of the operator.

Further, according to the present invention, the count value h in the traveling direction is level-discriminated by one or a plurality of discrimination levels h2, h3 on the basis of the histogram to obtain the numbers N2, N3 thereof. The morphology is judged, and this also makes it possible to perform judgment evaluation with high accuracy.
It can approach the visual grade rating.

Furthermore, according to the present invention, in addition to the regular reflected first reflected light P, the irregularly reflected second to fourth reflected lights B, S1,
Using S2, this makes it possible to more closely match grade ratings that are equivalent to visual grade ratings.

[Brief description of drawings]

FIG. 1 is a simplified side view showing a part of an embodiment of the present invention.

FIG. 2 is a simplified side view of a part near a guide roll 5.

FIG. 3 is a perspective view showing an overall configuration of a surface detection means 7.

FIG. 4 is a perspective view showing a simplified configuration of a part of a scanning unit 15 and a light receiving unit 18.

5 is a simplified front sectional view of an optical system including a scanning unit 15. FIG.

6 is a simplified cross-sectional view of the optical system shown in FIG. 5 viewed from the side.

FIG. 7 is a sectional view showing a simplified structure of a light receiving means 18.

FIG. 8 is a simplified perspective view showing the principle of the embodiment of the present invention.

9 is an enlarged cross-sectional view of the surface of the metal strip 1 shown in FIG.

FIG. 10 is a perspective view showing a basic configuration of light receiving means 18.

11 is a simplified perspective view individually showing a light receiving region for each point P, B, S1, S2 in FIG. 10, and these points P, B, S1, S2 are shaded. Show.

FIG. 12 is a simplified cross-sectional view showing first and third light reception detecting means 37, 42.

13 is a diagram showing optical paths of first and third light reception detecting means 37, 42 shown in FIG.

FIG. 14 is a simplified plan view of a second received light detecting means 39.

FIG. 15 is a front view showing part of the screen 46 according to another embodiment of the present invention.

FIG. 16 is a condenser lens 5 according to each embodiment of the present invention.
6 is a diagram showing an image formation state on the light guide member 55 which is the screen 46 according to FIG.

17 is a diagram showing a state in which an image of the surface of the metal strip 1 shown in FIG. 16 is formed on the light guide member 55.

FIG. 18 is a perspective view showing a simplified configuration of the hole detecting means 3.

FIG. 19 shows first to fourth light reception detecting means 37, 39, 42,
Light receiving elements 60, 66, 61, 69 provided at 44
3 is a block diagram showing an electric circuit subsequent to FIG.

FIG. 20 is a block diagram showing a specific electrical configuration of a P channel following the light receiving element 60 for specularly reflected light.

FIG. 21 is a diagram showing output waveforms in first to fourth preprocessing circuits FEP1 to FEP4.

FIG. 22: Geometric feature extraction memories GFE1 and GFE
It is a figure for demonstrating the store content of No. 2.

FIG. 23 is a waveform diagram showing a waveform of a signal having a waveform to be corrected from the correction value memory 104.

FIG. 24 is a waveform diagram showing an output waveform of the analog-digital converter 102 and a waveform of a signal having a constant average peak value, which is derived on a line 106.

FIG. 25 is a waveform diagram showing changes in the average peak value of one scan of laser light stored in the memory 109.

FIG. 26 is a waveform diagram for explaining the function of the shaving correction circuit 107.

FIG. 27 is a waveform diagram for explaining the functions of the positive peak detection circuit 112, the negative peak detection circuit 113, and the envelope detection circuit 114.

FIG. 28 is a waveform diagram for explaining the operation of the subtraction circuit 117.

FIG. 29 is a waveform diagram for explaining the operation of the absolute value comparison circuit 124.

FIG. 30 is a perspective view for explaining a measurement target range 127 for calculating and obtaining a noise level N.

FIG. 31 is a perspective view for explaining an operation for calculating and obtaining a noise level N from the measurement target range 127.

FIG. 32 is a waveform diagram for explaining a normalized light reception detection signal.

FIG. 33 is a perspective view for explaining data of the multi-value bus 100.

34 is a perspective view for explaining data on the binary bus 136. FIG.

FIG. 35 is a diagram for explaining a state when setting a limit value to each of the discrimination levels VP, VB, VS1, VS2 for binarization according to another embodiment of the present invention.

FIG. 36 is a plan view of the metal strip 1.

FIG. 37 is a flowchart for explaining a schematic operation of a processing circuit 140 realized by a microcomputer.

[Fig. 38] Fig. 38 is a diagram for describing defect types in the defect determination unit section q.

39 is a flowchart for explaining more specific operation of steps a1 and a2 shown in FIG. 38. FIG.

FIG. 40 is a perspective view for explaining an operation for calculating a weight addition value F based on multivalued data.

FIG. 41 is a diagram for explaining the density in the defect determination unit section q.

FIG. 42 is a perspective view for explaining an area S in the defect determination unit section q.

FIG. 43 is a flowchart for explaining the operation for obtaining the characteristic amount in step a4 in FIG.

FIG. 44 is a plan view for obtaining the histogram of the defect determination unit section q.

[Fig. 45] Fig. 45 is a diagram illustrating binary image data for each pixel q1 of the defect determination unit section q.

46 is a diagram showing a histogram in the defect determination unit section q shown in FIG. 45.

FIG. 47 is a diagram showing a state in which there are a total of three defects in the defect determination unit section q.

[Fig. 48] Fig. 48 is a diagram showing a state in which a defect exists in the defect determination unit section q.

[Fig. 49] Fig. 49 is a diagram for explaining the operation of level discrimination of the defect histogram in the defect determination unit section q by heights h1, h2, and h3.

FIG. 50 is a flowchart for explaining an operation of determining a flaw type and a flaw form according to the contents of a shape flaw box.

FIG. 51 is a flowchart for explaining the operation for determining the flaw forms P1 to P6 of the dot flaw according to the contents of the shape flaw box.

FIG. 52 shows the linear flaw L2 according to the contents of the shape flaw box.
8 is a flowchart for explaining an operation of determining A3.

FIG. 53 shows the flaw form L4 according to the contents of the shape flaw box.
It is a flow chart for explaining the operation for determining L5.

FIG. 54 is a flowchart for explaining the operation for determining the flaw forms L6 and L7 of linear flaws according to the contents of the shape flaw box.

FIG. 55 is a flowchart for explaining an operation for determining the flaw forms L8 and L9 of the linear flaw according to the contents of the shape flaw box.

FIG. 56 is a diagram for explaining a defect type and a grade weight value Φ in the grade evaluation unit section Q.

FIG. 57 is an electric circuit diagram showing a specific configuration of the embodiment of the present invention and showing the operation of the processing circuit 140 in a block diagram.

58 is a front view showing a display state of the display means 151. FIG.

FIG. 59 is a diagram for explaining determination of a flaw type, a flaw form, and a grade of the metal strip 1 by a learning method according to another embodiment of the present invention.

FIG. 60 is a block diagram showing a configuration in the exemplary embodiment of the present invention shown in FIG. 59.

FIG. 61 is a block diagram showing a specific configuration for detecting a surface flaw in the metal strip 1 according to still another embodiment of the present invention.

62 is a front view for explaining a lattice 171 for phase detection used in connection with the screen 170 shown in FIG. 61. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 metal band 3 hole detection means 4, 5 guide roll 6 front surface inspection means 7 back surface inspection means 8, 9 axis line 10, 10a rotation direction 11 laser light 12 reflected light 13 plane 14 intersection line 16 virtual scanning plane 18 light receiving means 20,83 Laser light source 22, 85 Polygonal mirror 23 Motor 29, 60, 61, 66, 69 Light receiving element 36 First reflected light 37 First received light detecting means 38 Second reflected light 39 Second received light detecting means 40 Virtual light receiving plane 41 3 reflected light 42 3rd received light detecting means 43 4th reflected light 44 4th received light detecting means 45 housing 46 screen 53, 88 condensing lens 54 semi-transmissive reflecting mirrors 55, 56, 64, 68 light guide member 63 cylindrical Fresnel lens 87 Hole 89 Pin Photodiode 90 Travel Position Detection Means 91 Virtual Plane 96 DC Amplification Circuit 97 Gain Adjustment Circuit 100 Multilevel Bus 102 Analogue digital converter 103 Mirror reflectance correction circuit 104 Correction value memory 105 Mirror reflectance sampling circuit 107 Shaving correction circuit 109 Correction value memory 112 Positive peak detection circuit 113 Negative peak detection circuit 114 Envelope detection circuits 117, 120 Subtraction circuit 124 Absolute value Comparison circuit 126 Noise sampling circuit 130 Normalization circuit 132 Binarization circuit 140 Processing circuit 151 Visual display means 152 Special amount calculation means 153 Similarity degree calculation means 154 Reference pattern memory 155 Determination means 156 Output control means 180 Printer 181 Recording paper ADC1 to ADC4 analog-digital conversion circuits FEP1 to FEP4 first to fourth preprocessing circuits FRM1 frame memories GFE1 and GFE2 geometric feature extraction memory MPn; MBp, MBn; MS1p, M 1n; MS2
p, MS2n Memory P, B, S1, S2 Channel q Defect type judgment unit section Q Evaluation unit section VP, VB, VS1, VS2 Average crest value

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Yamamoto 4976 Nomura-Minami-cho, Shinnanyo-shi, Yamaguchi Nisshin Steel Co., Ltd. Shunan Steel Works (56) Reference JP-A-61-245045 (JP, A) JP-A 4-238207 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 21/84-21/958

Claims (27)

(57) [Claims] 1. A grade evaluation unit section Q is constituted by a plurality of defect judgment unit sections q by scanning a laser beam in the width direction of a metal strip running in the longitudinal direction and receiving and detecting the reflected light. Then, each defect judgment unit section q is composed of a plurality of pixels q1, and the weight addition value F which is the product of the reflected light intensity V of the defect judgment unit section q and the area S is obtained from the received light detection signal, Binary data of each pixel q1 is obtained from the received light detection signal, and a plurality of features including the average length AH (= HA / NA) of flaws along the traveling direction of each flaw determination unit section q are obtained from the binary data. The defect type for each defect determination unit section q and the defect form for each defect type are determined based on this feature amount, and the defect type and the defect form of each defect determination unit section q, and the defect thereof are determined. Judgment grade weight value φ corresponding to the weight addition value F of the judgment unit section q
To determine a common flaw rating for different flaw types and different flaw forms, and all flaw judgment unit sections q included in the grade evaluation unit section Q.
The judgment grade weight value φ is added for each defect type, and the defect type for which the maximum sum of the defect types is obtained is determined to be the defect type of the grade evaluation unit section Q, and the grade evaluation All defect determination unit sections q included in the unit section Q
The grade weight value Φ which is the sum of the judgment grade weight value φ of the grade evaluation unit division Q is obtained, and the grade evaluation unit division Q is determined by the determined flaw type of the grade evaluation unit division Q and the obtained grade weight value Φ.
A method for inspecting a surface of a metal band for flaws, which is characterized by grading. 2. The surface flaw inspection method for a metal strip according to claim 1, wherein the flaw types determined for each flaw determination unit section q are linear, dot-shaped, and planar. 3. The reflected light includes specularly reflected light and irregularly reflected light, and the reflected light intensity V of the specularly reflected light of the pixel q1 is the light from the noise average peak value for each pixel included in the pixel q1. It is the absolute value of the variation of the absorbed component, and the reflected light intensity V of the irregularly reflected light of the pixel q1 is the absolute value of the variation of the irregularly reflected component from the noise average peak value. Depending on the value, the weight addition values F (P), F of the defect determination unit section q are calculated for each of the specular reflection light and the irregular reflection light.
(B), F (S1), F (S2) are obtained, and the weight addition values F (P), F (B), F (S1), F (of the defect determination unit section for each of the specular reflection light and the diffuse reflection light are obtained. The surface flaw inspection method for a metal strip according to claim 1, wherein S2) is added to obtain a weight addition value F of the flaw determination unit section q. 4. The surface flaw inspection of the metal strip according to claim 3, wherein the degree of the flaw form L1 of the flaw determination unit section q is determined by comparing the weight addition value F of the flaw determination unit section q. Method. 5. The weight addition values F (P), F (B), F (S1) of the defect determination unit section q for each of regular reflection light and irregular reflection light,
The surface flaw inspection method for a metal strip according to claim 3, wherein the type of flaw and the flaw form are discriminated by comparing F (S2). 6. A histogram is created by counting the number of flaws of each pixel q1 in the width direction in the traveling direction in the flaw determination unit section q using binary data,
Moreover, the number NA of flaws in the flaw determination unit section q is obtained, and the longest value H in the traveling direction is obtained based on this histogram.
When L is within a predetermined first range, it is determined that the defect type of the defect determination unit section q is a dot defect, and the defect form of dot defect corresponding to the number NA of defects is determined. The surface flaw inspection method for a metal strip according to any one of claims 1 to 5. 7. A histogram is created by counting the number of flaws of each pixel q1 in the width direction in the traveling direction within the flaw determination unit section q based on the binary data, and a histogram is created. First area SHL of a defect having a long value HL
Then, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaw in the flaw determination unit section q, the total length HA in the traveling direction, and the number NA of the flaws are obtained. Ratio of full length HA to number of flaws NA AH (= HA /
NA) is calculated as the average length, and the longest value HL in the traveling direction is within the second range that exceeds the first range, and among the first and second areas SHL and SWW, When the ratio RA (= SLW / SA) of the larger area SLW to the total area SA is less than a predetermined value and this average length HA / NA is less than a predetermined value, the defect determination unit section q is The method for inspecting surface flaws of a metal strip according to claim 1, wherein the method has a point defect. 8. The longest count value HL in the traveling direction is the second count value.
Within the third range exceeding the range of, and the ratio RA
The surface flaw of the metal strip according to claim 6 or 7, wherein when (= SLW / SA) is less than the predetermined value, the flaw determination unit section q is determined to have a dot flaw. Inspection method. 9. The binary data is used to count the number of flaws of each pixel q1 in the width direction in the running direction within the flaw determination unit section q to create a histogram, and based on this histogram, the histogram in the running direction is most determined. First area SHL of a defect having a long value HL
Then, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaw in the flaw determination unit section q, the total length HA in the traveling direction, and the number NA of the flaws are obtained. Ratio of full length HA to number of flaws NA AH (= HA /
NA) is calculated as the average length, and when the longest value HL in the traveling direction is within the second range that exceeds the first range, among the first and second areas SHL and SWW , Ratio RA of the larger area SLW to the total area SA (= SLW /
SA) is equal to or greater than a predetermined value, or a ratio RA (= SLW / SLW / of the larger area SLW of the first and second areas SHL and SWW to the total area SA).
SA) is less than a predetermined value and this average length A
When H (= HA / NA) is a predetermined value or more, it is judged that the flaw evaluation unit section q has a linear flaw. 10. A first weighted addition value FHL of defects having the longest value HL in the traveling direction and a second weighted addition value F of defects having the widest value WW in the width direction based on the histogram.
HW is calculated, and the larger weight addition value FHLW of the first weight addition value FHL and the second weight addition value FWW is set to the first or second area S corresponding to the larger weight addition value FHLW.
The surface flaw inspection of the metal strip according to claim 9, wherein the flaw strength of the linear flaw corresponding to the average strength AF (= FHW / SLW) is determined by dividing by LW. Method. 11. Based on the histogram, the count value h in the traveling direction is level discriminated by one or more predetermined discrimination levels h2, h3, and the discrimination levels h2, h3.
10. The surface flaw inspection method for a metal strip according to claim 9, wherein the flaw morphology of the linear flaw is determined in accordance with the calculation result obtained by calculating the numbers N2 and N3 of the count values h. 12. The longest value HL in the traveling direction is within a third range exceeding the second range, and the ratio RA (=
SLW / SA) is greater than or equal to the predetermined value,
The defect determination unit section q is determined to have a linear defect, and the count value h in the traveling direction is calculated based on the histogram,
Level discrimination is performed using one or more discrimination levels h2 and h3 set in advance, and the flaw form of the linear flaw is determined according to the calculation result obtained by calculating the numbers N2 and N3 of the count values h of the discrimination levels h2 and h3 or more. The surface flaw inspection method for a metal strip according to claim 9, wherein 13. A surface of a metal strip running in the longitudinal direction,
Scanning means for scanning the laser beam in the width direction, specular reflection light P and irregular reflection light B from the surface of the metal band of the laser light
A light receiving unit for receiving S1 and BS2, a first memory FRM1 for storing multi-valued data of a light receiving detection signal of the light receiving unit for each pixel, and a plurality of defect determination unit sections q including a plurality of pixels q1 The evaluation unit section Q is formed, the stored contents of the first memory FRM1 are read, and the weighted addition values F (P), F which are the product of the reflected light intensity V and the area S of the defect determination unit section q are read.
(B), F (S1), F (S2); first calculation means for obtaining FHL, FHW, binarization means for converting the light reception detection signal of the light reception means into binary data, and reflection from the binarization means An OR operation means for ORing binary data of the light P and the irregular reflection lights B, S1, S2 for each pixel, a second memory M2 for storing the output of the OR operation means, and a plurality of defect judgment unit sections q. Second calculating means for calculating and calculating the characteristic amount; first determining means for responding to an output of the second calculating means for determining a defect type and a defect form for each defect determination unit section q; 1. Judgment grade weight value deciding means for deciding the judgment grade weight value φ of each flaw evaluation unit section q, which makes it possible to classify different flaw types and flaw forms into common grades in response to the output from the judgment means, It is included in the grade evaluation unit section Q in response to the output of the weight value determining means. The defect classification weight value φ is added for each defect classification of all the defect evaluation unit sections q, and the defect classification for which the maximum sum of the defect classifications is obtained is the defect classification of the grade evaluation unit section Q. In response to the output of the second judging means for judging, and the judging grade weight value deciding means, the judgment grade weight values φ of all the defect judgment unit sections q included in the grade evaluation unit section Q are added, and the sum thereof is obtained. A third calculating means for calculating a certain grade weight value Φ; and a third judging means for grading the grade of the grade evaluation unit section Q in response to the outputs of the second judging means and the third calculating means. Characteristic metal band surface flaw inspection device. 14. A noise level calculating means for calculating a noise level N in response to the output of the light receiving means, and a light receiving detection signal divided by the noise level N in response to the outputs of the light receiving means and the noise level calculating means. Then, the first memory F
14. The surface flaw inspection apparatus for a metal strip according to claim 13, further comprising a normalizing means provided to the RM1 and the binarizing means. 15. The light receiving means includes a first light receiving detection means of the first reflected light P that is specularly reflected in a virtual light receiving plane that includes the irradiation direction of the laser light and is orthogonal to the virtual scanning plane, and more than the specular reflected light. Second light reception detecting means of the second reflected light B reflected toward the irradiation direction, third light receiving detection means of the third reflected light S1 laterally displaced from the virtual light receiving plane, and laterally from the virtual light receiving plane. The surface flaw inspection apparatus for a metal strip according to claim 14, further comprising a fourth received light detecting means for the fourth reflected light S2 which is further displaced than the third reflected light S1. 16. A noise level calculating means for calculating a noise level N in response to an output of the light receiving means, and a normalizing means, the outputs of the first to fourth light receiving detecting means and the noise level calculating means. In response to the output of the first light-reception detecting means, the variation due to the light absorption by the surface and the variation due to the light reflection by the surface corresponding to the outputs of the second to fourth light-reception detecting means are detected. 16. The surface flaw inspection apparatus for a metal strip according to claim 15, further comprising: a normalizing means which is used as a signal, is divided by a noise level N, and is applied to the first memory FRM1 and the binarizing means. 17. The surface flaw inspection apparatus for a metal strip according to claim 14, wherein the binarizing means discriminates the level of the output of the normalizing means. 18. The reflected light intensity V of the specularly reflected light of the pixel q1 in the first computing means is the absolute value of the fluctuation of the light absorbed component from the noise average peak value for each pixel included in the pixel q1. The reflected light intensity V of the irregularly reflected light of the pixel q1 is the absolute value of the variation of the irregularly reflected component from the noise average peak value, and the specular reflection light and the irregular reflection light are determined by the absolute values of these variations. For each time, the weight addition values F (P), F of the defect determination unit section q
(B), F (S1), F (S2) are obtained, and the weight addition values F (P), F (B), F (S1), F (of the defect determination unit section for each of the specular reflection light and the diffuse reflection light are obtained. 14. The surface flaw inspection apparatus for a metal strip according to claim 13, wherein S2) is added to obtain the weight addition value F of the flaw determination unit section q. 19. The method according to claim 13, wherein the first determining unit compares the degree of the defect form L1 of the defect determination unit section q with the weight addition value F of the defect determination unit section q. Surface flaw inspection device for metal strips. 20. The first determination means is a weight addition value F (P), F of the defect determination unit section q for each of specular reflection light and irregular reflection light.
14. The surface flaw inspection apparatus for a metal strip according to claim 13, wherein (B), F (S1), and F (S2) are compared to determine the flaw type and flaw morphology. 21. The second computing means counts the number of flaws of each pixel q1 in the width direction in the traveling direction in the flaw determination unit section q based on the binary data to create a histogram.
Moreover, the number NA of flaws in the flaw determination unit section q is obtained, and the longest value H in the traveling direction is obtained based on this histogram.
When the value HL that is the longest in the traveling direction is within the predetermined first range, the first determination means determines that the defect type of the defect determination unit section q is a dot defect, 14. The surface flaw inspection apparatus for a metal band according to claim 13, further comprising determining a flaw form of a dot flaw corresponding to the number NA of flaws. 22. The second calculation means counts the number of defects of each pixel q1 in the width direction in the traveling direction within the defect determination unit section q based on the binary data to create a histogram, and based on this histogram The first area SHL of the flaw having the longest value HL in the running direction.
Then, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaw in the flaw determination unit section q, the total length HA in the traveling direction, and the number NA of flaws are calculated. 1 determination means has the longest value HL in the traveling direction within the second range exceeding the first range, and the larger area SLW of the first and second areas SHL and SWW.
The ratio RA (= SLW / SA) to the total area SA of
It is less than a predetermined value, and this average length AH (= H
14. The surface flaw inspection apparatus for a metal strip according to claim 13, wherein when A / NA) is less than a predetermined value, it is determined that the flaw determination unit section q has a dot flaw. 23. The first determination means has a longest count value HL in the traveling direction within a third range exceeding the second range, and the ratio SLW / SA is less than the predetermined value. The surface flaw inspection apparatus for a metal strip according to claim 13, wherein the flaw determination unit section q is determined to have a dot flaw. 24. The second calculation means counts the number of defects of each pixel q1 in the width direction in the traveling direction within the defect determination unit section q based on the binary data to create a histogram, and based on this histogram The first area SHL of the flaw having the longest value HL in the running direction.
Then, the second area SWW of the flaw having the widest value WW in the width direction is obtained, and the total area SA of the flaw in the flaw determination unit section q, the total length HA in the traveling direction, and the number NA of the flaws are obtained. Ratio of full length HA to number of flaws NA AH (= HA /
NA) is calculated as the average length, and the first determining means determines the first and second values when the longest value HL in the traveling direction is within the second range that exceeds the first range. Of the areas SHL and SWW, the ratio RA (= SLW / of the larger area SLW to the total area SA)
SA) is equal to or greater than a predetermined value, or a ratio RA (= SLW / SLW / of the larger area SLW of the first and second areas SHL and SWW to the total area SA).
SA) is less than a predetermined value and this average length A
The surface flaw inspection apparatus for a metal strip according to claim 13, wherein, when H (= HA / NA) is a predetermined value or more, the flaw evaluation unit section q is determined to have a linear flaw. 25. The second calculation means, based on the histogram, the first weight addition value FHL of the flaw having the longest value HL in the traveling direction, and the second weight addition of the flaw having the widest value WW in the width direction. Value F
HW is calculated, and the larger weight addition value FHLW of the first weight addition value FHL and the second weight addition value FWW is set to the first or second area S corresponding to the larger weight addition value FHLW.
25. The average intensity AF (= FHW / SLW) is obtained by division by LW, and the first determining means determines the flaw form of the linear flaw corresponding to this average intensity AF. Surface flaw inspection device for metal strips. 26. The first judging means discriminates the count value h in the traveling direction on the basis of the histogram by one or a plurality of discrimination levels h2, h3 which are set in advance, and a total of the discrimination levels h2, h3 or more. 25. The surface flaw inspection apparatus for a metal strip according to claim 24, wherein the flaw shape of the linear flaw is determined in accordance with a calculation result obtained by calculating the numbers N2 and N3 of the numerical value h. 27. The first determination means is such that the longest value HL in the traveling direction is within a third range exceeding the second range, and the ratio RA (= SLW / SA) is greater than or equal to the predetermined value. When it is, the defect determination unit section q determines that it has a linear defect, and based on the histogram, the count value h in the traveling direction is set to one or more predetermined discrimination levels h.
2. The defect form of the linear defect is determined in accordance with the result of calculating the number N2, N3 of the count values h equal to or higher than the discrimination level h2, h3. 24. The surface flaw inspection apparatus for a metal strip as described in 24.