JP3340879B2 - Surface defect detection 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 method and an apparatus for detecting a surface defect which optically detects a defect occurring on the surface of a running belt-like inspection object such as paper, steel plate, aluminum plate or the like.

[0002]

2. Description of the Related Art There are various types of defects generated on the surface of an object to be inspected, such as paper, steel plate, aluminum plate, etc., and these defects are detected. By judging this, it is useful for managing the surface quality and preventing the occurrence of defects. Conventionally, as a surface defect detection method, there is known a method of irradiating the surface of a running inspection object with light, capturing reflected light from the inspection object with a one-dimensional imager, and detecting a surface defect from a change in the light amount. Have been. There is also known a method in which reflected light from an inspection object is imaged by a plurality of imagers at different light receiving angles, and the image data is processed to determine a defect.

FIG. 3 is a schematic diagram showing a schematic configuration of a surface defect inspection apparatus. The surface defect inspection apparatus includes an illuminating means 2 for irradiating a surface of a running inspection object 1 with light, and a surface of the inspection object surface. One-dimensional imaging device 3 for imaging the object from the regular reflection direction
And a second one-dimensional imaging device 4 for imaging the surface of the inspection object from the irregular reflection direction, and signal processing means 5 for processing imaging signals from the two one-dimensional imaging devices 3 and 4.

Using this surface defect inspection apparatus, for example, an image pickup signal from the first one-dimensional image pickup device 3 is processed to detect a pattern-like surface defect that causes a change in the amount of received light in the regular reflection direction. An image signal from the second one-dimensional image pickup device 4 is processed to detect an irregular surface defect that causes a change in the amount of received light in the irregular reflection direction, thereby simultaneously detecting and discriminating two different types of surface defects. can do. Here, a one-dimensional imaging device is a device in which photoelectric elements are arranged in a line to capture reflected light in a linear region, and a one-dimensional CCD camera is preferably used.

[0005]

When a plurality of one-dimensional imagers are used for surface defect inspection as shown in FIG. 3, all the one-dimensional imagers are located at the same position on the surface of the inspection object. It is important to test for The reason will be described later. Incidentally, the thickness of the object to be inspected is not always constant, and the object to be inspected may fluctuate during traveling and move up and down in a direction perpendicular to the traveling direction. Due to the thickness change or fluttering (height fluctuation) of this inspection object,
It is assumed that the distance between the surface of the inspection object and the optical system of the surface defect inspection apparatus changes as shown in FIG. This distance change amount is referred to as a height change amount Δd of the surface of the inspection object.

When the height of the surface of the inspection object fluctuates, as shown in FIG. 4, the visual field (inspection position) on the surface of the inspection object by a plurality of one-dimensional imaging devices is determined by the traveling direction of the inspection object. Is shifted by the distance δ. As described below, there is a problem that erroneous detection of a defect or erroneous determination of a type of a defect may be caused if the displacement of the visual field on the surface of the object to be inspected among a plurality of one-dimensional imagers in this manner. .

FIG. 5 is a view showing each image showing a defect detected based on image data obtained by each one-dimensional image pickup device in the conventional surface defect inspection apparatus using two one-dimensional image pickup devices shown in FIG. FIG. 4 is a diagram schematically showing outputs of a surface defect detection device obtained by combining these images. FIG. 5A shows the case where there is no inspection position deviation amount δ (see FIG. 4) (δ = 0).
(B) and (c) show the case where there is an inspection position deviation amount δ (δ ≠ 0).

FIG. 5B shows the case where the inspection position deviation amount δ is relatively small. Even in this case, the output of the surface defect inspection apparatus indicates that the detection position of each defect is in the traveling direction (X direction). Due to the shift and overlap, the length of the defect is evaluated to be larger than the actual length. The erroneous evaluation of the defect length may cause an erroneous determination of the defect type. FIG. 5C shows a case where δ is relatively large. In this example, there is a possibility that one defect on the inspection object is erroneously detected as if it were two defects.

The present invention solves the above problems,
An object of the present invention is to provide a surface defect detection method capable of accurately detecting a surface defect and accurately determining the type of the surface defect even when the height of the inspection object varies, and an apparatus for implementing the method. And

[0010]

A first surface defect detection method of the surface defect detection method of the present invention for achieving the above object.
May give the one-dimensional image in the width direction intersecting the traveling direction of the object to be inspected traveling, a plurality of one-dimensional imaging device, and imaging repeated a plurality of light-receiving angles imaging data of the light receiving angle each,
Based on the imaging data, the surface defect detection method for detecting a defect of the inspection object surface, the double with respect to the inspection object
By based rather calculated and height variation of the geometrical arrangement position and obtaining step piece surface one-dimensional image pickup device having, for each receiving angle
Relative displacement of the surface of the inspection object in the imaging data
δ was determined, and the imaging data for each light receiving angle was determined.
It should be relatively delayed by an amount corresponding to the displacement amount δ.
And allows to obtain a position correction imaging data for each receiving angle, the
Received light amount at each light receiving angle based on position corrected imaging data
By detecting the change, a defect on the surface of the inspection object is detected.

Further , in the surface defect detection method of the present invention,
The second surface defect detection method is based on a method of traveling of a traveling inspection object.
One-dimensional images in the width direction intersecting
By repeatedly capturing images from multiple light receiving angles,
Obtain imaging data for each degree, and based on the imaging data,
In a surface defect detection method for detecting defects on the surface of an inspection object,
The geometrical shape of the plurality of one-dimensional imagers with respect to the object to be inspected.
By calculation based on the arrangement position and the height variation of the inspection object
Of the surface of the inspection object of the imaging data for each light receiving angle.
The relative displacement δ is determined, and the relative displacement δ and the
It is a time delay δ / V minutes obtained from the running speed V of the inspected object.
The timing of starting the imaging by the plurality of one-dimensional imaging devices
The relative position of each light receiving angle
Obtain the normal imaging data, and based on the position corrected imaging data,
By detecting the change in the amount of received light at each receiving angle,
It is characterized by detecting defects on the surface of the inspection object .

The method for detecting a surface defect according to the present invention is not limited to a method for obtaining the amount of height variation. For example, the amount of height variation is known as data based on the thickness of the inspection object. If so, it may simply receive the data. However, it is preferable to measure the amount of height variation of the inspection object on the upstream side in the traveling direction, and to determine the positional deviation amount δ based on the measured amount of height variation.

Further, a first one of the surface defect detecting devices of the present invention used for carrying out the surface defect detecting method of the present invention .
The surface defect detection device includes a plurality of one-dimensional imagers that repeatedly image a one-dimensional image in a width direction intersecting a traveling direction of a traveling inspection object from a plurality of light receiving angles, and a height variation amount of a surface of the inspection object. the height variation input means for inputting, to the object to be inspected
Geometric arrangement positions of the plurality of one-dimensional imagers with respect to
Each light receiving angle is calculated by the calculation based on the height variation of the inspection object.
The relative position of the surface of the inspection object in the imaging data for each degree
The shift amount δ is obtained, and the imaging data for each light receiving angle is obtained.
Is relatively delayed by an amount corresponding to the displacement amount δ.
The position-corrected imaging data for each light-receiving angle.
Means for obtaining position-corrected image data, and said position-corrected imaging
Captures the change in received light amount at each light receiving angle based on data
Surface defects to detect defects on the surface of the inspection object
And a detecting means. In addition, the present invention
The second surface defect detection device among the surface defect detection devices includes:
One-dimensional image in the width direction intersecting the traveling direction of the moving inspection object
Multiple primary images that repeatedly capture images from multiple light receiving angles
The original imager and the height to input the height variation of the surface of the inspection object
A variation input means; and the plurality of one-dimensional objects with respect to the inspection object.
The geometric arrangement of the imager and the height variation of the inspection object
By the calculation based on, the imaging data of each light receiving angle,
The relative displacement δ of the surface of the inspection object is determined,
When calculated from the deviation amount δ and the traveling speed V of the inspection object
Shooting by the plurality of one-dimensional imaging devices by the delay δ / V
By relatively shifting the image start timing,
Position corrected imaging data to obtain position corrected imaging data for each light angle
Data acquisition means, and each reception based on the position-corrected imaging data.
By detecting the change in the amount of light received at each light angle,
Surface defect detecting means for detecting defects on the surface of the object.
And features.

Here, the height variation input means does not limit the destination of the input, that is, the output destination of the height variation. For example, the height variation may be input from a host computer, or the height variation may be input. May be provided, and the output of the measuring device may be input.

[0015]

According to the present invention, position-corrected imaging data for each light-receiving angle in which relative displacement in the traveling direction has been corrected based on the height variation of the inspection object is obtained, and based on the position-corrected imaging data. Therefore, the defect on the surface of the inspection object can be detected with high accuracy without erroneous determination or erroneous detection of the size and number of the defects.

Here, in obtaining the position-corrected image data, the position image data is obtained by relatively shifting the timing of starting the image pickup by a plurality of one-dimensional image pickup devices based on the height variation of the inspection object. Then, the position is corrected at the same time as the imaging, and high-speed image processing can be performed.
However, it becomes necessary to add a control circuit for variously changing the timing of starting the imaging in accordance with the height fluctuation amount.

On the other hand, when obtaining position-corrected image data, position-corrected image data is obtained by correcting image data obtained by imaging with a plurality of one-dimensional imagers on the basis of the height fluctuation amount of the inspection object. In this case, since it is necessary to perform the position correction operation after the image pickup, it takes some time for the image processing, but no special hardware for the correction is required, which is advantageous in cost.

As described above, the present invention does not ask a specific method for obtaining position-corrected imaging data, but may employ an arbitrary method in consideration of the advantages and disadvantages of each method. Further, as described above, the present invention is not limited to a method of obtaining the height variation, but measures the height variation of the inspection object on the upstream side in the traveling direction, and determines the measured height. By obtaining position correction data based on the amount of height variation, if there is no height variation data in advance,
Alternatively, even in the case of inaccuracy or fluttering of the test object, it is possible to obtain position-corrected imaging data in which the position in the traveling direction is accurately corrected.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram of a surface defect detection device showing one embodiment of the present invention. The two illuminating units 2 irradiate light in the width direction (direction perpendicular to the running direction) of the running inspection object 1 and reflect light reflected from the surface of the inspection object 1 at different light receiving angle positions. Are imaged by the one-dimensional imaging devices 3 and 4.
On the other hand, a change in the height of the surface of the inspection object 1 due to a change in thickness or fluttering of the inspection object 1 (the inspection object 1 in FIG. 1).
Of the upper surface in the vertical direction) is detected by the height fluctuation detector 6. As the height fluctuation detector 6, an eddy current type, ultrasonic type, or laser type displacement meter is suitable.

The image data obtained by the two one-dimensional imaging devices 3 and 4 and the measurement result of the height fluctuation detector 6 are sent to the signal processing means 5. The signal processing means 5 obtains two-dimensional imaging data of the surface of the inspection object by connecting the one-dimensional imaging data obtained sequentially in time series, and determines a change in the amount of received light in this image by a predetermined threshold processing. Extract and detect surface defects. If the traveling speed of the inspection object 1 is not constant, a means for detecting the traveling speed of the inspection object is separately provided, and the one-dimensional imaging data is connected in synchronization with the change in the traveling speed. After performing such surface defect detection processing independently on the two one-dimensional image pickup devices 3 and 4, the signal processing means 5 combines the two surface defect data to form the defect shape and the amount of received light. The type of the surface defect is determined by the one-dimensional imaging devices 3 and 4 that have contributed to the detection. In this process, when the height variation of the inspection object is detected by the height variation detector 6, the displacement in the traveling direction (see FIG. 4) is corrected based on the height variation Δd.

The displacement δ of the visual field of the two one-dimensional imaging devices 3 and 4 in the running direction is determined by the first and second one-dimensional imaging devices 3 and 4.
If the light receiving angles are θ and φ, respectively, and the height variation of the object to be inspected is Δd, δ = Δd × (tan φ−tan θ) (1) is obtained by a geometric calculation from FIG. This calculation is performed by the signal processing means 5.

Specifically, the scanning speed of the one-dimensional imaging device in the longitudinal direction of the inspection object is f [line / sec], and the inspection object 1
Is the traveling speed of V [m / sec], the image data obtained by the second imager is converted to f · (δ / V) [lin] in the traveling direction.
e] (the unit of δ is [m]). As a method of correcting the positional deviation, the timing of starting the imaging by the two one-dimensional imaging devices may be shifted instead of shifting the imaging data obtained by the imaging by the two one-dimensional imaging devices.

That is, as can be seen from FIG. 4, when the amount of height change Δd of the inspection object 1 is positive (changes upward), the second one-dimensional imaging device 4 performs the first one-dimensional imaging. Since the imaging is performed on the downstream side of the inspection object in the traveling direction of the inspection device 3, the timing of starting the imaging by the second one-dimensional imaging device 4 is determined by the timing of starting the imaging by the first one-dimensional imaging device 3. Is also delayed by the time δ / V during which the inspection object 1 travels the distance δ. By doing so, two one-dimensional imaging devices 3, 4
Can image the same region on the surface of the inspection object.

FIG. 2 is a schematic diagram showing a more specific embodiment of the surface defect detecting device of the present invention. In the present embodiment, linear white light is emitted from the white light source 12 in the width direction of the running steel plate 11 at an incident angle of 10 °, and the reflected light is reflected on two primary light beams having a light receiving angle of 10 ° and a light receiving angle of 45 °. Images are taken by the original CCD cameras 13 and 14, respectively. In addition, a laser displacement gauge 16 is installed at the center of the plate width direction on the upstream side of the light source 12 to detect a change in height of the surface of the steel plate 11 in a non-contact manner. Further, a traveling speed detector 18 is provided on a support roll 17 which rotates as the steel sheet 1 travels. Two CCD cameras 13,
All the outputs of 14, the output of the laser displacement meter 16, and the output of the traveling speed detector 18 are sent to a computer 15, which performs high-speed signal processing. In this processing, C is synchronized with the detected traveling speed V.
Each output of the CD cameras 13 and 14 is taken in, the above equation (1) is calculated using the laser displacement meter output Δd, and the outputs of the two CCD cameras 13 and 14 are divided by the distance δ, that is, the time (δ / V) By combining by shifting by minutes,
It corrects the visual field shift between the CCD cameras.

In this embodiment, the height variation of the steel plate 11 is about ± 5.
In this example, the light receiving angles of the CCD cameras 13 and 14 are 5 mm when the light receiving angles of the CCD cameras 13 and 14 are the angles shown in FIG.
Of the field of view between the cameras δ is 4.12
mm. The scanning frequency of the CCD cameras 13 and 14 in the traveling direction is 10 KHz, and the traveling speed of the steel plate 11 is 300 m / mi.
n, width of steel plate 1 1350 mm, length of steel plate 11 about 50
As a result of detecting and judging the surface defect using this embodiment under the condition of 0 m, the correct answer rate is 92%. On the other hand, in the case of the conventional method in which no camera displacement is corrected without using the output of the laser displacement meter. Under the same conditions as above, the correct answer rate was 75%. As described above, according to the present invention, the performance was significantly improved.

In the above embodiment, the height variation of the steel plate is measured by the non-contact laser displacement meter 16. In the case where the fluttering of the inspection object is small and the thickness of the inspection object is known by another means. However, such a displacement meter may not be provided, and the thickness information may be taken into a computer to correct the field of view deviation. In the above embodiment, 2
Although one one-dimensional imager was used, three or more one-dimensional imagers may be used. In this case, it is necessary to correct the visual field shift amount obtained by Expression (1) for each one-dimensional image pickup device.

[0027]

As described above, according to the present invention,
Even when the thickness of the inspection object and the height change in the direction approaching / separating from the one-dimensional image pickup device occur, the surface defect can be accurately detected, and the type of the defect can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a surface defect detection device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a more specific embodiment of the surface defect detection device of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a conventional surface defect detection device.

FIG. 4 is an explanatory diagram of a visual field shift due to a height change.

FIG. 5 is an explanatory diagram of a problem in a conventional surface defect detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 2 Illumination means 3, 4 One-dimensional imaging device 5 Signal processing means 6 Height fluctuation detector 11 Steel plate 12 White light source 13, 14 CCD camera 15 Computer 16 Laser displacement meter 17 Support roll 18 Traveling speed detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-267745 (JP, A) JP-A-55-87907 (JP, A) JP-A-4-320908 (JP, A) JP-A-58-58 77642 (JP, A) JP-A-6-138055 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/88-21/892

Claims (5)

(57) [Claims] 1. A one-dimensional image in a width direction intersecting a traveling direction of a traveling inspection object is repeatedly imaged from a plurality of light receiving angles by a plurality of one-dimensional imagers to obtain image data for each light receiving angle. In the surface defect detection method for detecting a defect on the surface of the inspection object based on the imaging data, a geometrical detection of the plurality of one-dimensional imaging devices with respect to the inspection object is performed.
Position and based rather calculated and height variation of the object to be inspected surface
The inspection object table of the imaging data for each light receiving angle
The relative displacement δ of the surface is determined, and the
The image data is an amount corresponding to the obtained positional deviation amount δ.
By only relatively delayed to obtain a position correction imaging data for each receiving angle, receiving for each receiving angle based on the position correction captured data
A surface defect detection method characterized by detecting a defect on the surface of an inspection object by detecting a change in the amount . 2. The width of the traveling inspection object crossing the traveling direction.
One-dimensional images in multiple directions can be
The image is repeatedly taken from the light receiving angle of
Data on the surface of the inspection object based on the imaging data.
In the surface defect detection method for detecting a defect , a geometrical detection of the plurality of one-dimensional imagers with respect to an inspection object is performed.
In based rather calculated and height variation of positions and the object to be inspected
Of the surface of the inspection object of the imaging data for each light receiving angle.
The relative displacement δ is determined, and the relative displacement δ and the
It is a time delay δ / V minutes obtained from the running speed V of the inspected object.
Only, by shifting relatively to the timing of the start imaging by the plurality of one-dimensional imaging unit, to obtain a position correction imaging data for each receiving angle, receiving for each receiving angle based on the position correction captured data
By detecting changes in volume, defects on the surface of the inspection object can be detected.
Front surface defect detecting how to characterized by the output. 3. An amount of height variation of an inspection object on an upstream side in a traveling direction.
Is measured and calculated by using the measured height fluctuation.
2. The method according to claim 1, wherein the position shift amount is obtained.
Or the surface defect detection method according to 2. 4. The width of the traveling inspection object crossing the traveling direction.
One-dimensional images in various directions from multiple light receiving angles
And a height change amount input means for inputting a height change amount of the surface of the inspection object.
A step and a geometrical configuration of the plurality of one-dimensional imagers with respect to the object to be inspected.
By calculation based on the arrangement position and the height variation of the inspection object
Of the surface of the inspection object of the imaging data for each light receiving angle.
The relative displacement δ is determined, and the imaging data for each light receiving angle is calculated.
Data by an amount corresponding to the obtained positional deviation amount δ.
Position correction for each light receiving angle
A position correction image data obtaining means for obtaining imaging data; and a receiving unit for each light receiving angle based on the position correction imaging data.
By detecting changes in light intensity, defects on the surface of the inspection object can be detected.
Surface defect detecting means for detecting
Surface defect detection device. 5. A plurality of one-dimensional imagers for repeatedly capturing a one-dimensional image in a width direction intersecting a traveling direction of a traveling inspection object from a plurality of light receiving angles, and inputting a height variation amount of a surface of the inspection object. Height variation input means, and a geometrical configuration of the plurality of one-dimensional imaging devices with respect to the inspection object.
By calculation based on the arrangement position and the height variation of the inspection object
The relative displacement δ of the imaging data at each light receiving angle on the surface of the inspection object is determined, and the displacement δ and the
It is a time delay δ / V minutes obtained from the running speed V of the inspected object.
The timing of starting the imaging by the plurality of one-dimensional imaging devices
A position-corrected image data obtaining means for obtaining position-corrected image data for each light-receiving angle,
A surface defect detection device comprising: a surface defect detection unit configured to detect a defect on a surface of an inspection object by capturing a change in light amount .