JP3510468B2 - Surface defect inspection equipment - 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 defect inspection apparatus used for inspecting surface defects such as irregularities on the surface of a press-formed product such as a vehicle body panel.

[0002]

2. Description of the Related Art As an inspection device for this type of surface defect,
For example, there is one described in JP-A-8-5573. The apparatus described in the publication irradiates light on one side of the surface to be inspected at a shallow irradiation angle of 10 degrees or less from obliquely above, and also on the other side of the surface to be inspected, Image processing is performed by imaging a surface to be inspected obliquely from above at a shallow imaging angle of 10 degrees or less with respect to the inspection surface, and imaging a surface defect such as foreign matter or unevenness on the surface to be inspected as a shadow (dark). In, the surface defect is extracted by binarizing the captured original image with the same threshold value over the entire range.

Further, there is also an inspection apparatus in which the surface to be inspected is imaged at an imaging angle larger than the irradiation angle and the surface defects on the surface to be inspected are imaged as bright.

[0004]

However, in the inspection apparatus which picks up surface defects as bright as described above, when the original image has a brightness gradient, the original image is imaged with the same threshold value over the entire range by image processing. When the binarization process is performed, a portion having a brightness higher than the brightness of the surface defect in the brightness gradient is extracted as noise, so there is a problem that it is difficult to detect only the surface defect. The solution was a challenge.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is suitable for inspecting surface defects in a press-molded product such as a vehicle body panel and the like, and the surface is taken at an imaging angle larger than the illumination angle. Provided is a surface defect inspection device capable of automatically detecting a surface defect such as minute unevenness on a surface to be inspected at a high detection rate when an original image has a brightness gradient in an inspection device which images a defect as bright. The purpose is to do.

[0006]

According to a first aspect of the present invention, there is provided an apparatus for inspecting a surface defect, which comprises illuminating means for irradiating light at an irradiation angle inclined with respect to a surface to be inspected having a curved surface.
An image pickup unit which is arranged so as to face the illumination unit and which picks up an image of the surface to be inspected at an image pickup angle larger than the irradiation angle of the illumination unit;
The image processing unit includes an image processing unit that detects a surface defect from the original image captured by the image capturing unit, and the image processing unit differentially processes the original image having a brightness gradient in the light irradiation direction from the illumination unit in one direction that is the brightness gradient direction. And a unidirectional differential filter that creates a unidirectional differential image, a smoothing filter that smoothes the unidirectional differential image to create a smoothed image, and a differential operation of the smoothed image from the unidirectional differential image The smoothing filter according to claim 2, further comprising: a difference calculation filter that creates an image, and a binarization filter that creates a binarized image by binarizing the difference image with a constant threshold value. Is a cross-reference multiple-time smoothing filter that creates a cross-reference multiple times smoothed image by smoothing the one-way differential image with cross-reference multiple times. Cross reference The smoothing image is configured to be a filter that performs a difference operation on the smoothed image a plurality of times to create a difference image. An all-around reference multiple-time smoothing filter that creates a reference multiple-time smoothed image, and a difference calculation filter creates a difference image by performing a difference operation on the all-around reference multiple-time smoothed image from a one-way differential image. A unidirectional differential filter according to claim 4, wherein the one-way differential filter has a size that matches the size of the surface defect in the original image determined in one direction and in the imaging field of view of the imaging device. Is a one-way optimal size differential filter that performs differential processing to create a one-way differential image, and the smoothing filter is a size that matches the one-way differential image in one direction and the size of surface defects in the one-way differential image. Is a one-way optimal size smoothing filter that creates a one-way smoothed image by performing a smoothing process with a differential calculation filter, and a difference calculation filter creates a difference image by performing a difference operation on the one-way smoothed image from the one-way differential image. The transport means for moving the surface to be inspected in one direction, the type information inputting means for inputting type information of the surface to be inspected, and the object to be inspected corresponding to the type input information of the surface to be inspected. Curved surface angle information selecting means for selecting curved surface angle information, position detecting means for detecting the position of the surface to be inspected being conveyed by the conveying means, and curved surface angle information from the curved surface angle information selecting means The configuration is provided with position control means for controlling the angle and height of the illumination means and the imaging means based on the position detection information from the position detection means, and the above configuration is used as means for solving the problems. There is.

In the above arrangement, the irradiation angle of the illumination means with respect to the surface to be inspected is a low angle of, for example, 10 degrees or less, and the imaging angle of the imaging means with respect to the surface to be inspected is, for example, an intermediate angle of 15 to 40 degrees. Is desirable.

[0008]

In the surface defect inspection apparatus according to the first aspect of the present invention, the illuminating means irradiates light at an irradiation angle inclined with respect to the surface to be inspected, and more preferably, it is directly adjacent to the surface to be inspected. While irradiating light with a small irradiation angle close to
The imaging means images the surface to be inspected at an intermediate imaging angle larger than the irradiation angle on the side opposite to the light irradiation. At this time, if the original image has surface defects such as irregularities on the surface to be inspected,
Since the irradiation light is diffusely reflected at the surface defect portion, the surface defect is imaged as diffuse reflection light, and the field of view has a brightness gradient in the light irradiation direction from the illumination means.

In view of this, in the surface defect inspection apparatus, the image processing means differentiates the original image from the image pickup means in one direction, which is the luminance inclination direction, in order to extract the edge of the surface defect, and the one-way differential image. To create. At this time, since the original image has a brightness gradient and the surface defect changes abruptly with respect to the brightness gradient, the surface defect has a sharper peak-valley shape than the other part in the one-way differential image. Appears. Next, the image processing means smoothes the one-way differential image to create a smoothed image. When this smoothing process is performed, the surface defect, which has a steep ridge-valley shape in the differential image, is compared with the surrounding low-luminance portion, and the top portion thereof is crushed.

Next, the image processing means calculates the difference of the smoothed image from the one-way differential image to create a difference image. Here, only the steep top portion of the surface defect remains due to the difference between the surface defect having a steep peak and valley shape in the one-way differential image and the surface defect having a shape in which the top portion is collapsed in the smoothed image. At this time, the smoothed image corresponding to the degree of tilt also acts as a pseudo threshold value for the tilt component having a tilt in luminance, and is thereby removed. In other words, the creation of this difference image removes the slanted luminance gradient component (absolute value component), and makes the smoothing-processed luminance larger than the absolute value component (pseudo-threshold), that is, a surface defect or the like. Only the protruding part remains. Then, the image processing means can detect only the surface defect in the binarized image by binarizing the difference image from which the luminance gradient component is removed with a constant value.

[0011]

[0012]

In the surface defect inspection apparatus according to the second aspect of the present invention, the one-way differential filter, the cross-reference type multiple smoothing filter, the difference calculation filter and the binarization filter which constitute the image processing means are used to make one direction. Create differential images, cross-referenced multiple smoothed images, difference images, and binarized images.Especially, cross-referenced multiple smoothing filters are used to cross-reference smooth one-way differential images multiple times. By using the difference calculation filter, the cross-reference type smoothed image is subjected to difference calculation from the one-way differential image, and finally the luminance gradient component in the original image can be removed to detect only the surface defect.

In the surface defect inspection apparatus according to the third aspect of the present invention, the unidirectional differential filter, the omnidirectional reference type multiple smoothing filter, the difference calculation filter and the binarization filter which constitute the image processing means, Creates a directional differential image, an omnidirectional multiple-time smoothed image, a difference image, and a binarized image, and in particular, uses a omnidirectional reference-type multiple smoothing filter to smooth a unidirectional differential image multiple times with the omnidirectional reference type. Processing, and the difference calculation filter performs the difference calculation of the omnidirectional multiple times smoothed image from the one-way differential image, and finally the luminance gradient component in the original image can be removed to detect only the surface defect.

In the surface defect inspection apparatus according to the fourth aspect of the present invention, the one-way optimum size differential filter, the one-way optimum size smoothing filter, the difference calculation filter and the binarization filter which constitute the image processing means A directional differential image, a unidirectional smoothed image, a differential image and a binarized image are created, and in particular, the original image from the image pickup means is determined in one direction and in the image pickup field of the image pickup means by the unidirectional optimum size differential filter. Differentiate the size of the surface defects in the original image according to the size, and use the one-way optimal size smoothing filter to match the size of the surface defects in the one-way differential image to the one-way differential image. Only the surface defect can be detected by performing the smoothing processing on the size and finally removing the luminance gradient component in the original image.

[0016]

[0017]

[0018]

[0019]

In the surface defect inspecting apparatus according to the fifth aspect of the present invention, the surface of the surface to be inspected is detected by the position detecting means while the surface of the surface to be inspected is moved by the conveying means in one direction, and the curved surface angle is measured. The information selection means selects curved surface angle information of the surface to be inspected corresponding to the type input information of the surface to be inspected from the type information input means, and the position control means
The angle and height of the illumination means and the image pickup means are controlled based on the curved surface angle information from the curved surface angle information selection means and the position detection information from the position detection means. That is, when a part of a curved surface to be inspected that moves in one direction is irradiated with light to capture an image, the irradiation angle and the imaging angle with respect to the surface to be inspected change as the surface to be inspected moves. Change.
Therefore, in the surface defect inspection apparatus, the irradiation angle and the imaging angle with respect to the surface to be inspected can be made constant by controlling the angle and the height of the illumination unit and the imaging unit by the position control unit.

[0021]

With the surface defect inspection apparatus according to the first aspect of the present invention, even if the original image picked up by the image pickup means has a luminance tilt, the luminance tilt component in the original image is removed. Only surface defects can be reliably detected,
For example, it is suitable for inspecting surface defects in a curved press-formed product such as a vehicle body panel, and can automatically detect surface defects such as minute irregularities on a surface to be inspected at a high detection rate.

[0022]

According to the surface defect inspection apparatus of the second aspect of the present invention, the image processing means including the one-way differential filter, the cross reference type multiple smoothing filter, the difference calculation filter and the binarization filter is adopted. As a result, like the first aspect, it is possible to remove the luminance gradient component in the original image and detect only the surface defect. In particular, the one-way differential filter and the cross-reference type multiple smoothing filter enable detection accuracy. Can contribute to the further improvement of.

According to the surface defect inspection apparatus of the third aspect of the present invention, the image processing means including the one-way differential filter, the omnidirectional reference type multiple smoothing filter, the difference calculation filter and the binarization filter is provided. By adopting, as in claim 1, it is possible to remove the luminance gradient component in the original image and detect only the surface defect, and in particular, by the one-way differential filter and the omnidirectional reference type multiple smoothing filter, This can contribute to further improvement in detection accuracy.

According to the surface defect inspection apparatus of the fourth aspect of the present invention, the image processing means including the one-way optimum size differential filter, the one-way optimum size smoothing filter, the difference calculation filter and the binarizing filter is provided. By adopting the same method as in claim 1, it is possible to remove the luminance gradient component in the original image and detect only the surface defect.
The one-way optimum size differential filter and the one-way optimum size smoothing filter can contribute to further improvement in detection accuracy.

[0026]

[0027]

[0028]

[0029]

According to the surface defect inspection apparatus of the fifth aspect of the present invention, the same effects as those of the first to fourth aspects can be obtained, and in addition, the conveying means, the type information inputting means, and the curved surface angle information selection. Since the means, the position detection means, and the position control means are adopted, even if the surface to be inspected is a curved surface, the irradiation angle and the imaging angle with respect to the surface to be inspected can be made constant at all times. The inspection accuracy for surface defects can be kept constant and good can be maintained.

[0031]

1 to 3 are views for explaining a first embodiment of a surface defect inspection apparatus according to the present invention. In this example, the case of inspecting the surface defects of the press-formed automobile body panel is shown.

The apparatus for inspecting surface defects shown in FIG. 1 illuminates means 1 for irradiating light at an irradiation angle θs inclined with respect to a surface F to be inspected, which is an outer surface of a vehicle body panel P, and faces the illuminating means 1. Image pickup means 2 for picking up the surface F to be inspected at an image pickup angle θc larger than the irradiation angle θs of the illumination means 1.
And an image processing means 3 for detecting a surface defect from an image picked up by the image pickup means 2.

The vehicle body panel P is, for example, a door panel, and therefore the outer surface serving as the surface F to be inspected has a curved surface. The vehicle body panel P is transported in one direction (leftward in FIG. 1) by the transporting unit 4 at a constant speed with the surface F to be inspected facing upward. As the carrying means 4, a conveyor for carrying a vehicle body panel in a press line can be used.

The illuminating means 1 is provided with a light irradiation section L1, a controller 5A including a light source, and an optical fiber 6A for sending light from the controller 5A to the light irradiation section L1. The light irradiation unit L1 includes an optical system that collects light linearly and irradiates the light linearly, and a drive mechanism 7 that uses a motor as a drive source.
It is held so that the irradiation angle θs and height with respect to the surface F to be inspected can be adjusted by A. The light source, for example,
Uses a halogen lamp, metal halide or xenon metal halide. The illuminating means 1 is a conveying means
The light irradiation part L1 is arranged on the upstream side in the conveyance direction of the
On the other hand, light is emitted at a small irradiation angle θs of, for example, 10 degrees or less.

The image pickup means 2 comprises a camera C1. As the camera C1, for example, a CCD camera can be used,
It is held so that the imaging angle θc and height with respect to the surface F to be inspected can be adjusted by a drive mechanism 8A using a motor as a drive source. The image pickup means 2 is located on the downstream side of the conveying means 4 in the conveying direction and faces the illuminating means 1 in the camera C1.
And the irradiation angle θ of the illumination means 1 with respect to the surface F to be inspected
Imaging is performed at an angle larger than s, for example, an intermediate imaging angle θc of 15 to 40 degrees.

In this embodiment, the illuminating means 1 is arranged on the downstream side of the conveying means 4 in the conveying direction, and another set of light irradiating section L is provided.
2, the controller 5B, the optical fiber 6B, and the drive mechanism 7B, and the image pickup means 2 includes the conveying means 4
On the upstream side in the transport direction of the above, another set of the camera C2 and the drive mechanism 8B is provided, and the light irradiation direction and the input image to the image processing means 3 are switched by the switching means described later.

Further, in this embodiment, since the image pickup means 2 is provided with the two cameras C1 and C2, the image pickup means 2 is provided.
An image input switching means 9 for switching an input image to the image processing means 3 is provided between the image processing means 3 and the image processing means 3. Further, the surface defect detection image output from the image processing means 3 is displayed on the display means 10.

The image processing means 3 performs a difference operation on the smoothed image obtained by smoothing the differential image from the differential image obtained by differentiating the original image from the image pickup means 2, and makes the difference image constant. 3, which is a means for obtaining a binarized image by performing binarization processing with a threshold value of 1. As shown in FIG. 3, the original image from the image pickup means 2 is differentiated in one direction, which is a luminance inclination direction described later. A one-way differential filter 21 for creating a one-way differential image, a one-way smoothing filter 22 for smoothing a one-way differential image in one direction to create a one-way smoothed image, and a one-way differential image A difference calculation filter 13 that performs a difference calculation on the direction-smoothed image to create a difference image, and a binarization filter 14 that performs a binarization process on the difference image with a certain threshold value to create a binarized image are provided. There is.

Further, the surface defect inspection apparatus includes, in addition to the above-described transporting means 4, type information input means 15 for inputting type information of the surface F to be inspected, and a type of object corresponding to type input information of the surface F to be inspected. Curved surface angle information selection means 16 for selecting curved surface angle information of the inspection surface F, and position detection means 17 for detecting the position of the surface F to be inspected being conveyed by the conveying means 4.
Position control means 18 for controlling the angle and height of the illumination means 1 and the image pickup means 2 based on the curved surface angle information from the curved surface angle information selecting means 16 and the position detection information from the position detecting means 17, and light irradiation. A switching control unit 19 for switching the direction and the input image to the image processing unit 3 is provided.

The position detecting means 17 is a switch or a sensor, is provided at a fixed portion with respect to the conveying means 4, and detects the surface to be inspected (vehicle body panel P) F that has moved to the inspection area. Based on the detection signal of the position detecting means 17 and the conveying speed of the conveying means 4, the moving position of the surface F to be inspected and the image pickup positions of the cameras C1 and C2 of the image pickup means 2 can be known.

The curved surface angle information selection means 16, the position control means 18 and the switching control means 19 are configured in the host computer 20 in this embodiment. Information from the type information input means 15 outside the host computer 20 is input to the curved surface angle information selection means 16. The type information input means 15 is provided with information (CAD information) such as various dimensions of the vehicle body panel P which varies depending on the type of vehicle. Further, the curved surface angle information selection means 16 inputs the CAD information of the body panel P to be inspected from the type information input means 15 to calculate the degree of curvature of the surface F to be inspected. Therefore, the signal from the previous position detecting means 17 and the curved surface angle information selecting means 1
Based on the signal from 6, it is possible to know the shape of the surface to be inspected at the imaging position that sequentially changes as the surface F to be inspected moves.

The position control means 18 is based on the signals from the position detection means 17 and the curved surface angle information selection means 16, and the drive mechanisms 7A and 7B of the light irradiation sections L1 and L2 in the illumination means 1 and the image pickup means 2 are included. Each camera C1,
A drive command signal is sent to the drive mechanisms 8A and 8B of C2, whereby the irradiation angles θs and the imaging angles θc with respect to the moving inspection surface F are always constant.
1, L2 and the angles and heights of the cameras C1 and C2 are changed.

The switching control means 19 is the position detecting means 1
Based on the signal from 7, the switching command signal is sent to each of the controllers 5A and 5B of the illuminating means 1 and the image input switching means 9 to switch the light irradiation direction and the input image to the image processing means 3. Thus, in the surface defect inspection apparatus, the upstream light irradiation unit L1 and the downstream camera C are used to inspect the front half of the surface F to be inspected in the transport direction.
1 is used, and the light irradiation unit L2 on the downstream side and the camera C2 on the upstream side are used to inspect the second half of the surface F to be inspected in the transport direction.

Next, the operation of the surface defect inspection apparatus having the above structure will be described.

The surface defect inspection apparatus uses the light irradiating section L1 of the illuminating means 1 to move the surface F to be inspected in one direction at a constant speed by means of the transport means 4, while making a small irradiation angle to the surface F to be inspected. While irradiating light at θs, the camera C1 of the image pickup means 2 causes the irradiation angle θ on the opposite side of light irradiation.
The surface F to be inspected is imaged at an intermediate imaging angle θc larger than s. At this time, if the surface F to be inspected has an uneven surface defect, the irradiation light is diffusely reflected at the surface defect portion, so that the surface defect is imaged as diffusely reflected light.

As shown in FIG. 2 (a), the original image includes the optical tongue A due to the low-angle linear light irradiation, and the surface defect E
Is emphasized, and as shown in FIG. 2B, the field of view has a brightness gradient in the light irradiation direction.
It has the characteristic that the brightness in only the brightness tilt direction changes rapidly up and down by the light irradiation from a low angle, so that it becomes a steep ridge-valley shape in the brightness tilt direction, and the brightness changes gently in the direction orthogonal to this. . For this original image, the image processing means 3 first performs the edge extraction of the surface defect E by the one-way differential filter 21 so that the original image is subjected to the luminance inclination so that the sensitivity is increased only in the luminance inclination direction. Differentiation is performed in the direction (y direction) to create the one-way differential image shown in FIG. In this one-way differential image, since the surface defect E has a sharp change in brightness with respect to the brightness gradient,
The surface defect E appears as a steep ridge-valley shape protruding from other portions. Next, the image processing means 3 performs a smoothing process on the unidirectional differential image by the unidirectional smoothing filter 22 by referring only to the luminance inclination direction in which the luminance change is large, and FIG.
The one-way smoothed image shown in (d) is created. In this one-way smoothed image, the peaks of the surface defect E having a steep peak and valley shape are compared with the surrounding low-luminance portions, and the peaks are crushed by averaging.

After that, the image processing means 3 calculates the difference of the unidirectional smoothed image (d) from the unidirectional differential image (c) by the difference calculation filter 13 to create the difference image shown in FIG. 2 (e). To do. In this difference image, the surface defect E having a steep peak-and-valley shape in the one-way differential image is left only in the top portion due to the difference from the surface defect E in which the top portion is collapsed in the one-way smoothed image. . At this time, the one-way smoothed image also acts as a pseudo threshold depending on the degree of inclination, and the inclination component having the inclination in luminance is also removed. In other words, the above-described difference calculation process removes the inclined luminance gradient component (absolute value component), and the surface defect E, which is a portion larger than the smoothed luminance absolute value component (pseudo threshold). Only the protruding part of will remain.
Then, finally, the image processing means 3 binarizes the entire difference image with a constant threshold value by the binarization processing filter 14 to create the binarized image shown in FIG. , Only the surface defect E is detected.

As described above, the surface defect inspection apparatus is
When the surface defect E is imaged with the imaging angle θc larger than the illumination angle θs as bright and the original image has a brightness gradient, the one-way differential filter 21, the one-way smoothing filter 22, the difference calculation filter 13, and the binarization. The image processing means 3 provided with the filter 14 can automatically detect only the surface defect E by removing the luminance gradient component in the original image.

[0049]

[0050]

[0051]

[0052]

FIG. 4 is a view for explaining the second embodiment of the surface defect inspection apparatus according to the present invention, and shows the structure and processing flow of the image processing means.

The image processing means of this embodiment is the image pickup means 2.
Unidirectional differential filter 21 that creates a unidirectional differential image by differentiating the original image from unidirectional differential image, and unidirectional differential image is smoothed multiple times by cross reference type and cross referenced multiple times smoothed image Cross reference multiple smoothing filter 3
2 and a difference calculation filter 1 for generating a difference image by performing a difference calculation on a cross-referenced plural times smoothed image from a one-way differential image
3 and a binarizing filter 14 for binarizing the difference image with a constant threshold value to create a binarized image.

The above-mentioned image processing means has the same basic processing steps as those of the previous embodiment, but in the smoothing processing, for example, by the cross reference type multiple smoothing filter 32 shown in FIG. Smoothing is performed multiple times in a cross shape. As a result, the tilt luminance component is more surely removed, and finally only the surface defect is surely detected.

FIG. 5 is a diagram for explaining the third embodiment of the surface defect inspection apparatus according to the present invention, and shows the configuration and processing flow of the image processing means.

The image processing means of this embodiment is the image pickup means 2.
Unidirectional differential filter 21 that creates a unidirectional differential image by differentiating the original image from unidirectional differential image, and unidirectional differential image is smoothed multiple times by omnidirectional reference type and omnidirectional reference type is smoothed multiple times. An all-surrounding reference type multiple smoothing filter 42 that creates a normalized image; a difference calculation filter 13 that performs a difference calculation on the all-surrounding reference type multiple times smoothing image from a one-way differential image to create a difference image; A binarization filter 14 for binarizing the image with a constant threshold value to create a binarized image is provided.

The above-mentioned image processing means has the same basic processing steps as those of the previous embodiment, but in the smoothing processing, for example, by the all-around reference type multiple smoothing filter 32 shown in FIG. , Perform smoothing processing multiple times over the entire circumference. As a result, the tilt luminance component is more surely removed, and finally only the surface defect is surely detected.

FIG. 6 is a view for explaining the fourth embodiment of the surface defect inspection apparatus according to the present invention, and shows the structure and processing flow of the image processing means.

The image processing means of this embodiment is the image pickup means 2.
One-way optimal size differential filter for differentiating the original image from the image in one direction with a size that matches the size of the surface defect in the original image determined by the image pickup field of the image pickup means 2 to create a one-way differential image. 31 and a unidirectional optimum size smoothing filter 52 that creates a unidirectional smoothed image by smoothing the unidirectional differential image in one direction and with a size that matches the size of the surface defects in the unidirectional differential image. , A difference calculation filter 13 for calculating a difference image by performing a difference calculation on a one-way smoothed image from a one-way differential image, and a binarized image by binarizing the difference image with a certain threshold value. The digitizing filter 14 is provided.

In the above image processing means, the one-way optimum size differential filter 31 as shown in FIG.
Differentiation is performed only in one direction of the brightness gradient and with a size according to the number of dots occupied by surface defects. In other words, the surface defect has the characteristic that the brightness in the brightness inclination direction changes rapidly up and down by light irradiation from a low angle, so in the original image, it becomes a steep ridge-valley shape in the brightness inclination direction, and its top and skirt. In the range of, the number of dots is determined by the imaging field of view.

Therefore, the one-way optimum size differential filter 3
1 shows the size of the surface defect E in the original image shown in FIG.
In accordance with the size of the surface defect E, differentiation can be performed in the range of abrupt luminance change from the top to the foot of the surface defect E, and the most effective differentiation processing suitable for the size of the surface defect E can be obtained. That is, since the resolution (the number of dots) of the original image is individually determined, the size of the resolution (the size occupied by one dot) is determined by the imaging visual field. Therefore, since the size (the number of dots) occupied by the surface defect to be extracted is determined for each imaging field of view, the differential processing is performed with the size of the differential filter having substantially the same size according to the size occupied by the surface defect. As a result, the size (the number of dots) for confirming the degree of inclination of the brightness for extracting the edge of the surface defect is in the range from the top to the skirt of the surface defect, so that the sensitivity to the brightness inclination of the surface defect is high. It becomes the highest and the surface defects appear in the steepest peak-valley shape in the differential image.

Further, the image processing means flattens the steep peaks and valleys of the surface defects in the differential image.
The one-direction optimum size smoothing filter 52 shown in (a) performs the smoothing process with reference to only the brightness inclination direction having a size corresponding to the number of dots occupied by surface defects and having a large brightness change. As a result, the steep peaks and valleys are compared with the low-brightness portion up to the number of dots corresponding to the skirt of the surface defect, and the peak portions are averaged so that the peak portions are crushed. The size of the one-direction optimum size smoothing filter 52 can be smoothed in a range of abrupt luminance change from the top to the skirt of the surface defect by adjusting the size of the surface defect in the differential image. It is the most effective smoothing treatment suitable for the size of surface defects.

FIG. 7 is a view for explaining a reference example of the surface defect inspection apparatus according to the present invention, and shows the structure and processing flow of the image processing means.

The image processing means of this reference example is the image pickup means 2.
A differential filter 11 that differentially processes the original image to create a differential image, a smoothing filter 12 that smoothes the differential image to create a smoothed image, and a smoothed image with a constant value (+ β) A constant value addition calculation filter 30 that performs a calculation process to create a constant value addition image, a difference calculation filter 13 that calculates a difference image of a constant value addition image from a differential image to create a difference image, and a difference image with a constant threshold value. A binarizing filter 14 for binarizing the image to create a binarized image is provided.

In the above image processing means, the constant value addition arithmetic filter 30 adds a constant value (+ β) to the smoothed image smoothed by the smoothing filter 12 to raise the entire image. As a result, when a small noise is generated due to dust or other foreign matter on the surface to be inspected or an electrical factor at the image processing stage, the smoothed image has a constant value (+ β that is smaller than the peak of the surface defect). ) Is added, these noises can be removed at the stage of the difference calculation. Then, if the difference image is binarized using the above-mentioned constant value (+ β) as a threshold value, only surface defects are detected.
Further, it is possible to determine the size of the surface defect by using the size of the constant value to be added.

FIG. 8 is a diagram for explaining another reference example of the surface defect inspection apparatus according to the present invention, showing the configuration and processing flow of the image processing means.

The image processing means of this reference example is the image pickup means 2.
Differentiating filter 41 for differentiating the original image from the above multiple times to create multiple differentiating images, and smoothing filter 22 for smoothing the multiple differentiating images to create smoothed images
And a difference calculation filter 13 that creates a difference image by performing a difference operation on a smoothed image from a plurality of differential images, and a binary value that creates a binarized image by binarizing the difference image with a certain threshold value. The digital filter 14 is provided.

In the image processing means, the original image is differentiated multiple times by the multiple differentiation filter 41. Then, finally, as in the previous embodiment, the luminance gradient component is removed and only the surface defect is detected.

FIG. 9 is a view for explaining still another reference example of the surface defect inspection apparatus according to the present invention, showing the configuration and processing flow of the image processing means.

The image processing means of this reference example is the image pickup means 2.
A differential filter 11 that performs a differential process on the original image to create a differential image, a smoothing filter 62 that performs a smoothing process on the differential image a plurality of times to create a smoothed image a plurality of times, and a plurality of times from the differential image a plurality of times. A difference calculation filter 13 that performs a difference calculation on a smoothed image to create a difference image, and a binarization filter 14 that performs a binarization process on the difference image with a certain threshold value to create a binarized image are provided. .

In the above image processing means, the differential image is smoothed a plurality of times by the smoothing filter 62 a plurality of times.
That is, since the sizes of surface defects are various, the size and number of surface defects that can be obtained by one smoothing process are limited. In order to prevent this, the differential image is smoothed a plurality of times by the smoothing filter 62, so that it is possible to sufficiently crush the steep peaks and valleys of surface defects that do not match the size of the filter.

FIG. 10 is a view for explaining still another reference example of the apparatus for inspecting surface defects according to the present invention, showing the configuration and processing flow of the image processing means.

The image processing means of this reference example is the image pickup means 2.
Differential filter 41 that creates a plurality of differential images by differentiating the original image from the above, and a multiple smoothing filter that creates a plurality of smoothed images by performing a multiple smoothing process on the multiple differential images 62, a difference calculation filter 13 that creates a difference image by performing a difference operation on a smoothed image a plurality of times from a plurality of differential images, and a binarized image by binarizing the difference image with a certain threshold value. The binarizing filter 14 is provided.

In the above-mentioned image processing means, the plural-differential filter 41 and the plural-times smoothing filter 62 make it possible to obtain the working effects of the above-mentioned reference examples.

In each of the above embodiments, the threshold value set to a constant value may be a value smaller than the magnitude of the luminance of the portion extracted by the difference calculation, and can be determined by, for example, an empirical value.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of a surface defect inspection apparatus according to the present invention.

FIG. 2 is an image processing step (a) by image processing means.
It is explanatory drawing which shows (f).

3 is a block diagram showing a configuration and a processing flow of an image processing unit in the surface defect inspection apparatus shown in FIG.

FIG. 4 is a block diagram showing a configuration and a processing flow of image processing means in a second embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 5 is a block diagram showing a configuration and a processing flow of image processing means in a third embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 6 is a block diagram showing a configuration and a processing flow of image processing means in a fourth embodiment of the surface defect inspection apparatus according to the present invention.

FIG. 7 is a block diagram showing a configuration and a processing flow of image processing means in a reference example of a surface defect inspection apparatus according to the present invention.

FIG. 8 is a block diagram showing a configuration and a processing flow of image processing means in another reference example of the surface defect inspection apparatus according to the present invention.

FIG. 9 is a block diagram showing a configuration and a processing flow of an image processing means in still another reference example of the surface defect inspection apparatus according to the present invention.

FIG. 10 is a block diagram showing a configuration and a processing flow of image processing means in still another reference example of the surface defect inspection apparatus according to the present invention.

FIG. 11 is explanatory diagrams (a) and (b) showing an original image and a differential filter.

12A and 12B are explanatory views showing a unidirectional smoothing filter, a cross-reference smoothing filter, and an omnidirectional reference smoothing filter, respectively, and FIGS. 12A and 12B show differential luminance gradients including surface defects. It is explanatory drawing (d) shown.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masafumi Tsuji 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) Reference JP-A-2-108167 (JP, A) JP-A-2 -93313 (JP, A) JP 5-223548 (JP, A) JP 4-148814 (JP, A) JP 8-128965 (JP, A) JP 7-306017 (JP, A) ) JP-A-8-86634 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/30 G01N 21/892

Claims (5)

(57) [Claims] 1. An illuminating means for irradiating light at an irradiation angle inclined to a surface to be inspected having a curved surface, and an inspected object at an imaging angle which is arranged so as to face the illuminating means and is larger than the irradiation angle of the illuminating means. And an image processing unit for detecting a surface defect from an original image captured by the image capturing unit.
A one-way differential filter for creating a one-way differential image by differentiating an original image having a brightness gradient in a light irradiation direction from the illuminating means in one direction which is the brightness gradient direction, and a one-way differential image. Smoothing process to create a smoothed image, a difference calculation filter that calculates the difference of the smoothed image from the one-way differential image to create a difference image, and a difference image with a certain threshold. An apparatus for inspecting a surface defect, comprising a binarizing filter that performs binarization processing to create a binarized image. 2. A smoothing filter is a cross-reference multiple-time smoothing filter that creates a cross-reference multiple-times smoothed image by smoothing a one-way differential image by cross-reference multiple times, and performs a difference calculation. 2. The surface defect inspection apparatus according to claim 1, wherein the filter is a filter that performs a difference operation on a cross-referenced multiple times smoothed image from a one-way differential image to create a difference image. 3. A smoothing filter is a omnidirectional reference type multiple smoothing filter that creates a omnidirectional reference type multiple times smoothed image by performing smoothing processing on a unidirectional differential image multiple times using the omnidirectional reference type. 2. The apparatus for inspecting surface defects according to claim 1, wherein the difference calculation filter is a filter that performs a difference calculation on the omnidirectional reference type plural times smoothed image from the one-way differential image to create a difference image. 4. A one-way differential filter differentially processes the original image from the image pickup means in one direction and with a size corresponding to the size of a surface defect in the original image determined by the image pickup field of view of the image pickup means. It is a one-way optimal size differential filter that creates a directional differential image, and the smoothing filter smoothes the unidirectional differential image in one direction and with a size that matches the size of the surface defects in the unidirectional differential image. It is a one-way optimal size smoothing filter that creates a one-way smoothed image, and the difference calculation filter is a filter that creates a difference image by performing a difference operation on the one-way smoothed image from the one-way differential image. The surface defect inspection apparatus according to claim 1. 5. A conveyance means for moving the surface to be inspected in one direction, a type information input means for inputting type information of the surface to be inspected, and a curved angle of the surface to be inspected corresponding to the input information of type of the surface to be inspected. Curved angle information selecting means for selecting information, position detecting means for detecting the position of the surface to be inspected being conveyed by the conveying means, curved angle information from the curved angle information selecting means and position detecting means 5. The surface defect inspection apparatus according to claim 1, further comprising position control means for controlling an angle and a height of the illumination means and the image pickup means based on the position detection information.