JP2005148047A - Method and device for inspecting surface to be inspected - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an inspection method capable of detecting a defect even if the defect has a complicated shape and is relatively small in the inspection method for obtaining the captured image of a surface to be inspected by irradiating the surface to be inspected with prescribed pattern light to find out the defect existing on the surface to be inspected. <P>SOLUTION: Light beams are used as inspection light. In the light beams, distribution is made in a mesh shape so that a shape in each mesh becomes the same, and an irradiated area on a plane vertical to an optical axis is smaller than a non-irradiated region. The surface to be inspected is inspected, based on the light and shade information of an image area corresponding to the non-irradiated region on the surface to be inspected in the captured image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inspection method for irradiating a surface to be inspected with inspection light having a predetermined pattern shape, and inspecting the surface to be inspected based on a captured image of the surface to be inspected, and an apparatus employing the method. .

  A typical example of this type of inspection method is a technique used for inspecting the painted surface of an automobile body. In the inspection of the painted surface, unevenness / scratches existing on the painted surface, periodic unevenness of the surface called “Yuzu skin”, and the like become inspection targets.

  As an inspection technique that uses pattern-shaped inspection light, a so-called striped pattern, that is, inspection light that forms a light and dark vertical stripe pattern is irradiated onto the painted surface, and the painted surface in the irradiated state is imaged by an imaging device. There is a technique for inspecting a captured image (a technique disclosed in Patent Document 1 and Patent Document 2).

In the technique disclosed in Patent Document 1, when the painted surface is moved in a predetermined direction (for example, the X direction), a defective image portion such as an uneven surface on the painted surface is orthogonal to the moving direction. Defects are detected by utilizing the fact that images are captured while changing the direction coordinate (X coordinate) without changing the coordinate of the direction (for example, the Y direction). In this technique, a defect image is darkened at a bright stripe portion and brightly picked up at a dark stripe portion, so that a defect can be identified. Here, the defect is captured as an intermediate gradation image of a bright part and a dark part of the stripe (see FIGS. 5, 9, 15 and the like).
In this inspection method, an independent defect at a specific position on the painted surface can be the inspection object.

The technique disclosed in Patent Document 2 is intended to detect the above-mentioned defect called “Yuzu skin”, and the coating thickness group is detected by the fluctuation on the captured image of the boundary line of the light and dark stripes as inspection light. It is something to be found. That is, as shown in FIG. 13 of the same document, it is possible to know the state of the painted surface from the fluctuation of the boundary line.
In this inspection method, it is not necessary to move the surface to be inspected, but in general, the coating surface is disturbed so that the boundary image of the stripe is displaced over a relatively wide area of the coating surface. The situation that is being detected becomes the detection target.

In these techniques, the inspection light is so-called indirect light, and the light from the light source is transmitted between the dark stripes, and the pattern light having the stripe distribution is applied to the painted surface as the inspection surface. To reach.
In general, the imaging apparatus has its imaging optical system focused on the painted surface.

JP-A-8-145906 (FIGS. 5, 9, and 15) JP-A-9-126744 (FIG. 13)

When this type of stripe light is used, for example, as shown in FIG. 5, when there is a dark portion of the stripe immediately above the defect, this dark light as shown by the alternate long and short dash line in FIG. A phenomenon may occur in which a bright part on both sides of a part is imaged at a predetermined position on the imaging side, and a defect may be imaged as a local bright part formed in a striped dark part. FIG. 5 shows the light-dark pattern on the irradiation side on the upper side, the defect shape convex on the upper side in the middle, and the position of each pixel on the imaging side on the lower side.
This model shows the state when the light and dark pattern is viewed from the pixel side as a mirror image, and the alternate long and short dash line drawn above the defect is reflected in each pixel with respect to the normal of the defect surface portion indicated by n. It is clarified from which part of the light and dark pattern the light to enter starts under the condition that satisfies the reflection condition at the defect surface part.

  However, there are few actual defects that are left and right objects as shown in the figure, and the reflection direction is not uniform. As a result, for example, in the case of a defect that does not cause reflection to the bright portion of the stripe in the direction crossing the stripe, it cannot be detected using the stripe.

  On the other hand, if there is a relatively wide range such as planar fluctuations in the coating thickness and this occurs in a two-dimensional direction, it may be difficult to capture as simple stripe boundary fluctuations. is there.

  Further, in the generation of inspection light, if this is indirect light, there is a limit to the amount of light due to the relationship with luminance. From this point, there may be a problem that it is difficult to detect relatively small defects.

Therefore, an object of the present invention is to detect a defect existing on the surface by irradiating a surface to be inspected with a predetermined pattern light to find a defect existing on the surface, regardless of the surface shape of the defect. However, it is to obtain an inspection method and apparatus capable of detecting this.
Another object of the present invention is to obtain an inspection method and apparatus capable of detecting a defect with no directionality even if it is a periodic defect over a relatively high range.

The characteristic configuration of the inspection method according to the present application, in which the inspection surface is irradiated with inspection light having a predetermined pattern shape, and the inspection surface is inspected by a captured image of the inspection surface in an irradiation state,
The inspection light is distributed in a mesh shape so that the shape in each mesh is the same, and an irradiation area in a plane perpendicular to the optical axis is irradiated from the irradiation surface with a light beam smaller than the non-irradiation area,
Inspecting the surface to be inspected based on brightness information of an image region corresponding to a non-irradiation region of the surface to be inspected in the captured image.

In this method, the light part is distributed in a mesh shape, and a light beam having a dark part serving as a closed region in the light part is irradiated from the irradiation surface.
When the surface to be inspected irradiated with the inspection light is imaged by an imaging device such as a CCD camera, if the surface to be inspected is flat and there are no defects on the surface, the light-dark pattern on the irradiation side is reflected almost as it is. On the other hand, when there is a defect, for example, as shown in FIG. 5, when the defect is directly under the dark part, the light irradiated from the bright part on the irradiation side is bent in the optical path by the defect. It is possible to form a situation that is reflected in an area that should originally be a dark part.

As a result, an independent bright point can be formed at the approximate center in the mesh that is the dark portion. In the present application, this phenomenon can be used to detect a defect. And since the shape in a mesh is made the same, it becomes possible to detect the defect which may be located in arbitrary meshes on substantially the same conditions.
Furthermore, this configuration has a high probability of detecting a defect as a bright part appearing in a dark part because the mesh corresponds to the irradiation part and the inside of the mesh corresponds to the non-irradiation part, and the non-irradiation area is selected to be large. it can.

Further, in the present application, since the bright portion is formed in a mesh shape, this kind of reflected light is applied to a predetermined position pixel of the imaging device having a two-dimensional spread from the entire circumference surrounding the dark portion. It has become possible to enter light, and it has become possible to detect defects of shape, size and depth, which have been difficult in the past.
In the inventors' study, when the size of the mesh is about 25 mm, the plan view is generally round,
A defect having a radius of about 0.3 mm and a depth of about 0.03 mm could be identified with a common CCD camera.
Also, during inspection, the object to be inspected is normally inspected sequentially with relative movement with respect to the inspection apparatus. It can be detected as a defect image and reliably detected.

  Furthermore, since the boundary line between the bright part and the dark part is knitted, it is possible to solve the problem that the detection of the conventional stripe has a specific direction when detecting defects such as “none skin”.

Use such an inspection method,
Obtained by an irradiating means for irradiating a surface to be inspected with inspection light having a predetermined pattern shape, an imaging means for capturing an image of the surface to be inspected in an irradiated state irradiated with the inspection light, and the imaging means As an inspection apparatus provided with an image processing means for processing a captured image,
The irradiating means distributes a light beam from the irradiation surface as the inspection light so that the shape in each mesh is the same, and the irradiation area in a plane perpendicular to the optical axis is smaller than the non-irradiation area. Irradiated,
An apparatus can be configured by configuring the image processing means to be able to process light / dark information of an image area corresponding to a non-irradiated area of the surface to be inspected in the image processing.

In the above method, the captured image in a state in which the inspection light is irradiated onto a normal inspection surface is a normal captured image, the luminance of the irradiated region in the normal captured image is high, and the luminance of the non-irradiated region is low. In case of brightness
It is preferable that the inspection is performed with an intermediate luminance region that is an intermediate luminance region between the high luminance and the low luminance existing in the captured image as a region of interest.

As described above, in the present application, it is possible to detect a defect by using light reflection from a bright part of a light / dark pattern mainly due to the presence of a defect. The intermediate luminance between the high luminance that is the luminance of the irradiated portion and the low luminance that is the luminance of the non-irradiated portion.
Therefore, by excluding the high-intensity part and the low-intensity part, it is possible to easily extract the area where the probability of existence of the defect is high, and quickly extract the image area considered to be due to the target defect with simple image processing. it can.

An inspection apparatus that performs such processing uses a captured image in a state in which the inspection light is irradiated on a normal inspection surface as a normal captured image, the luminance of the irradiation region in the normal captured image is high, and the non-irradiation When the luminance of the area is set to low luminance, the image processing means
This can be achieved by a configuration including intermediate luminance region extraction means for extracting an intermediate luminance region that is present in the captured image and is an intermediate luminance region between the high luminance and the low luminance.

  Now, the inspection light used in the inspection method of the present application is such that, on the irradiated surface, the bright part on the light emission side has a mesh shape and the inside of the mesh is a dark part. When the image is flat and does not cause distortion in the imaging of the mesh, and when the surface to be inspected is a curved surface and distortion occurs in the imaging of the mesh, both are also followed in the captured image. Therefore, the normal part of the mesh that is substantially unrelated to the defect can be excluded from the attention area as a continuous bright part in the image processing.

  That is, by extracting an image area corresponding to the irradiation area of the surface to be inspected as a continuous bright area and excluding the continuous bright area from the attention area, an area that seems to be an image corresponding to a defect easily. Can be extracted.

In order to execute such an inspection method, the image processing means
Continuous bright area extracting means for extracting a continuous bright area, which is an image area corresponding to the irradiation area of the surface to be inspected;
What is necessary is just to provide the exclusion means which excludes the extracted said continuous bright area | region from an attention area | region.

  Further, in the inspection method, when an image region corresponding to a non-irradiation region of the surface to be inspected is extracted for each closed dark region, and an independent bright region exists in the closed dark region, It is preferable to set an independent bright region as a region of interest.

In this method, paying attention to the fact that the inspection light has a mesh shape, the area in this mesh is recognized as a dark area that is basically closed, and an independent bright area exists in this dark area. In this case, the region of interest is assumed to be an abnormality (defect) on the non-inspected surface.
In this case, for example, even when the surface to be inspected is a curved surface and a relatively large deformation occurs in the basic mesh shape, the shape characteristics of the inspection light are effective. Defect detection can be performed.

When configuring an inspection device that uses this inspection method,
The image processing means described above is
A closed dark area extracting means for individually extracting a closed dark area which is an image area corresponding to a non-irradiated area of the surface to be inspected;
The above-described inspection method can be executed by including an independent bright area extracting unit that extracts an independent bright area existing in the extracted closed dark area.

Furthermore, it is preferable that the light beam is formed by a plurality of light emitting elements distributed in a mesh pattern in the irradiation unit.
In this case, by using a light emitting element, when taking an indirect irradiation structure, etc., it is possible to reduce the possibility of overlooking of micro defects due to insufficient luminance, etc., ensuring sufficient luminance on the irradiation side, A reliable and reliable inspection can be performed. For example, a light beam having an arbitrary mesh distribution can be obtained by changing the distribution of the light emitting elements on the blackboard.
Furthermore, as will be shown later, in the present application, the captured image is obtained by adjusting the focus of the imaging device to the irradiation surface on the irradiation side. In this case, the luminance difference between the light emitting portion of the light emitting element and the background is calculated. Since a large image can be taken, the image on the imaging side can be made sharper, and in general, an image portion caused by a defect that tends to be a blurred and small image can be easily raised.

  On the other hand, it is also preferable that the light beam is formed through the narrow slits distributed in a mesh pattern in the irradiation means. In this case, as has been conventionally done, the diffuser is disposed in front of the light source, and the shield for forming a dark portion in accordance with the shape in the mesh is further distributed and used in this application. Inspection light that matches the purpose can be easily obtained. Furthermore, the boundary line can be made clear.

  Furthermore, in the technology described so far, it is preferable that the size of the mesh is adjustable.

When using reflected light due to a defect as in the present application, it is necessary for the optical path of the light beam reflected through the defect to reach the bright part of the mesh when viewed from the imaging side. Whether or not the reflection occurs is greatly related to the size (including the opening area and depth) and the size of the mesh. Therefore, by making the mesh size adjustable, it is possible to select a mesh having a size that can be satisfactorily detected for a predetermined defect, and to perform good detection.

  Furthermore, it is preferable that the brightness difference between the irradiated area and the non-irradiated area of the surface to be inspected can be adjusted.

For example, when the object to be inspected is a painted surface of an automobile body, there may be a portion that can be regarded as a substantially flat surface, or a curved surface portion. Therefore, there are variations in the optical path distances in the irradiation system and the imaging system, and the amount of light necessary for detecting a defect cannot always be ensured in a good state.
However, if the brightness difference is adjustable, it is easy to select the amount of light necessary for the reflection according to the state of the detection target, and highly reliable detection can be performed.

  In the description so far, the configuration of the inspection method and the inspection apparatus was not asked for the case where the surface to be inspected is a flat surface or the case of a curved surface. When the inspection surface is a curved surface, a phenomenon such as distortion of the mesh in a specific direction occurs. FIG. 7 (b) shows that when a ring-shaped inspection light is irradiated and an inspection surface has a central axis in the horizontal direction of the paper surface, an elliptical eyeglass-shaped ring clogged in the vertical direction of the image is formed. Is shown.

The occurrence of this kind of distortion is an obstacle to the present technique in that an independent bright area is formed in a ring-shaped bright area and is extracted to obtain a defect image.
Therefore, when the surface to be inspected is a curved surface, the inspection light on the irradiation surface corresponding to the curved surface shape of the surface to be inspected is changed to a mesh shape in which the shape of the mesh in the captured image is a circle or a regular polygon. It is preferable to set a mesh distribution.
For example, as shown in FIG. 7C, when a curved surface in which contraction in the vertical direction of the image occurs is targeted, the mesh distribution is assumed to be vertically long in consideration of the contraction.
In this way, in the captured image, the area of the dark part corresponding to the inside of the mesh in the part recognized as a continuous bright part can be secured more than a predetermined area, Even when the luminance region is formed in the mesh, the formation can be made an independent region, and detection can be performed satisfactorily by applying the method of the present application.

Furthermore, the inspection apparatus of this configuration is the irradiation unit,
Corresponding to the curved surface shape of the surface to be inspected, by setting the mesh distribution of the inspection light on the irradiation surface to a mesh shape in which the shape of the mesh in the captured image is a circle or a regular polygon shape, Can be obtained.

[Inspection equipment]
FIG. 1 shows a state in which a painted surface of an automobile body 1 is being inspected using an inspection apparatus 100 according to the present application, and the body 1 that has been painted is conveyed to the left of the paper surface by a conveyor 2.
The inspection apparatus 100 is obtained while controlling the operation of the irradiation apparatus 3 that irradiates inspection light having a pattern peculiar to the present application, the imaging apparatus 4 that images the irradiation surface of the irradiation apparatus 3 through the paint surface, and these apparatuses. An inspection apparatus main body 7 that processes captured images is provided.

  In the inspection, the irradiation device 3 is arranged on the conveyance upper side (the right side in FIG. 1) with respect to the conveyor 2, and the imaging device 4 (for example, a CCD camera) on the conveyance lower side (the left side in FIG. 1) with respect to the conveyor 2. Is placed and used. However, the irradiation surface 3a of the irradiation device 3 and the imaging surface 4a of the imaging device 4 are arranged side by side so as to be substantially orthogonal to the direction A0 orthogonal to the conveying direction of the conveyor 2. In FIG. 1, the illustration is shifted to facilitate understanding.

[Irradiation device]
As shown in FIG. 2, the irradiation device 3 is configured by disposing a plurality of light emitting diodes 6 in the outer frame portion 5 so as to form a predetermined pattern, and the inner wall surface 5 a of the outer frame portion 5. And the part other than the site | part by which the light emitting diode 6 is arrange | positioned in an outer frame part is comprised as the blackboard 5b.
The light emitting diode 6 employed in the present application is a normal light emitting diode, and the irradiation surface 3a of the irradiation device 3 described above is arranged on the blackboard 5b so that the circular tip of the light emitting diode 6 draws a predetermined pattern. It is said that

The present application is characterized by this distributed arrangement, and the plurality of light emitting diodes 6 are arranged so as to constitute a predetermined mesh as a whole. As shown in FIG. 2, the shape in the mesh is the same for each mesh, specifically, it is roughly a circle.
Accordingly, when the irradiation device 3 is viewed from the front side of the irradiation side, it looks as if a plurality of black circles are arranged uniformly, and when imaging, the focus is adjusted to the irradiation surface 3a, thereby imaging the blackboard 5b. In addition, the light / dark pattern composed of the light-emitting diodes 6 is captured as an image in which black circles that are dark portions are dispersedly arranged in a mesh that is a bright portion as shown in FIG.

[Inspection device body]
The inspection apparatus body 7 includes an operation control unit 7a and an image processing unit 7b. The operation control unit 7a controls the operation of the entire inspection apparatus, and the image processing unit 7b is obtained by the imaging device 4. The captured image is processed and output to the monitor 8 side and the computer 9 side.

  The operation control unit 7a controls the operations of the irradiation device 3 and the imaging device 4, and further the operation of the image processing unit 7b. The operation control unit 7a takes a correspondence between the imaging timing and the position information of the automobile 1 input separately. It is configured to be able to.

  In the inspection apparatus 100 configured as described above, as the automobile body 1 is conveyed to the left side of the paper surface by the conveyor 2 as shown in FIG. 1, the imaging apparatus 4 passes through the painted surface of the body 1 at every predetermined timing. The irradiation surface 3a of the imaging device 3 is imaged.

  When there is no defect, the captured image is an image of an irradiation surface that is reflected by a normal paint surface and enters the imaging apparatus. When there is a defect, each pixel provided in the imaging apparatus due to this defect. The light path of the light beam reflected on the light beam is affected as described above with reference to FIG. 5, and the light from the irradiated surface portion irradiated with the light beam affected by this light is reflected.

The image processing unit 7b is a ternary processing unit (intermediate luminance region extracting unit referred to in the present application) that executes ternary processing for removing a high-luminance portion and a low-luminance portion of a captured image when processing a captured image. 70, after the ternarization processing, an exclusion means 71 for removing the normal part is provided. Specifically, this exclusion means is means for executing expansion / contraction processing. However, instead of executing these processes, it is also possible to store a captured image of a painted surface having no defect corresponding to the position of the body 1 and exclude this normal captured image component.
With these ternarization processing and exclusion processing, it is possible to identify a region of interest that should be noted in the inspection. At this time, an area determination unit 72 that determines the likelihood of a defect in the region based on the area of the region of interest is also provided.
Further, a post-processing unit 73 is provided that performs labeling of each region of interest and obtains the area and the center of gravity of these regions.

Information on each region of interest obtained in this way is sent to the computer 9 side together with the vehicle position information at the time of imaging, and is used for judgment of suitability as a defect for inspection purposes and for subsequent reprocessing of the painted surface. Etc. Further, the original image and the image obtained with the image processing are sequentially stored and can be displayed on the monitor 8 as necessary.

[Captured image]
The configuration of the inspection apparatus 100 has been mainly described above. Hereinafter, the forms of the captured image and the image processed image will be described according to cases based on the presence or absence of defects. Here, for ease of explanation, the case where the painted surface is a plane will be described in principle.

FIG. 3 shows an original image (A), an image after ternarization processing (B), and an image after elimination processing (C). FIG. 4 shows a three-dimensional luminance distribution in the original image. It is shown in.
In these images, a white portion indicates a portion having luminance, and a shaded portion indicates a dark image portion.
These images show a case where there is a defect below the mesh that forms the dark image portion in the second row and second column from the upper left end. Other sites indicate normal conditions.

1 Captured image when the painted surface is normal On a painted surface with a flat background, the image is composed of a bright portion (mesh portion on which the light-emitting diode 6 is disposed) C1 corresponding to a bright portion (C1) and a dark portion (blackboard portion 5b). A portion C2 having a low luminance K2 corresponding to the inside of the mesh is obtained, and a portion having a high luminance K1 corresponding to a bright portion in a normal portion of the coating (specifically, there is no defect and no coating thickness section). C1 is imaged in a mesh pattern with the pattern on the irradiation side.
Even in a normal case, when the body surface itself is a curved surface, the captured image of the mesh that appears as continuous bright spots is distorted according to the curved surface shape. However, since the positional relationship between the car, the irradiation system, and the imaging system is known, the normal image can be specified for the captured image of the painted surface having no defect, for example, even if the body surface itself is a curved surface. It is possible to extract a target defect area and an obscure part by excluding a normal image portion from the image.

2. When there is a defect on the painted surface There is a partial defect on the painted surface, and due to the convexity / concaveness of the defect, the luminance is slightly low in the low-luminance K2 portion C2 corresponding to the dark portion (inside the mesh composed of the blackboard 5b) A portion C3 having a high intermediate luminance can be formed.
This captured image is considered to be generated by the reflection of light rays from the bright part on the imaging side described above. Specifically, as shown in FIG. It will be ring-shaped. If the defect is an ideal circular depression in plan view, reflection of light from the entire circumference occurs.

[Extraction of attention area]
Therefore, in the apparatus of the present application, a ternarization process and an expansion / contraction process are performed when extracting a region of interest that is likely to be a defect.

(A) Ternization processing As described above, the captured image is composed of the high-luminance K1 portion C1 corresponding to the bright portion and the low-luminance K2 portion C2 corresponding to the dark portion, and the boundary portion is intermediate. A luminance portion C4 is interposed.
Further, when the defect exists in the mesh referred to in the present application, a bright portion (intermediate luminance portion) C3 appears in the dark portion. According to the inventors' experience, the shape of the portion C3 varies depending on the position of the defect in the mesh, the size of the defect, the imaging distance, etc. Can be identified.
Therefore, when the ternarization process is executed, only the intermediate luminance part C3 and the part C4 remain.

B) Exclusion processing of normal part Further, since the boundary portion C4 described above is minute compared to the intermediate luminance portion C3, when the expansion and contraction processing is performed several times, the boundary portion C4 disappears, and the intermediate luminance formed by the defect. The part C3 of remains.
As a result, as shown in FIG. 3C, only the intermediate luminance portion C3 can be extracted as a region of interest. This area is an area determination target. If the area is larger than a predetermined area that may cause a problem, labeling processing, area and centroid calculation processing are performed, and predetermined data is sent to the computer 9 side.

  In the above-described embodiment, the extraction of the image area due to the defect is performed by applying the ternary processing and the expansion / contraction processing to the extraction of the region of interest, but the binarization processing, An area corresponding to a normal irradiation area of the surface to be inspected may be deleted from the binarized image.

FIG. 6 shows the configuration of such an inspection apparatus corresponding to FIG.
This inspection apparatus includes a binarization processing unit instead of the binarization processing unit.
The processing threshold value in the binarization processing unit is set to a threshold value for identifying, for example, an intermediate luminance area formed by a defect as a bright area.
By setting in this way, as shown in FIG. 7 (a), when the surface to be inspected is a flat surface and the distribution of light emitting diodes on the irradiation surface in the irradiation apparatus is two continuous rings, As shown, a defect image can be obtained as a continuous ring and a bright independent region therein.

In the exclusion means, in the method of the present application, since the bright area on the irradiation side is reflected in the captured image as a continuous bright area having a mesh shape, the continuous area is excluded from the attention area. In this way, the defect can be extracted as a bright independent region.
In order to execute such an inspection method, the image processing means includes continuous bright area extracting means for extracting continuous bright areas that are image areas corresponding to the irradiation area of the surface to be inspected, and the extracted continuous bright areas. Exclusion means for excluding the area from the attention area is provided.

As described above, when the binarization process is performed, it is preferable that the defect image is formed as an independent region. Further, when the ternary processing is executed, it is preferable that the connection between the defect image and the normal bright image does not occur as much as possible.
In order to achieve this object, it is necessary to select a mesh pattern in consideration of the shape of the surface to be inspected.
Accordingly, when the painted surface is a curved surface, the shape distribution in which the mesh is reflected in the captured image is set so that the area of the image dark portion corresponding to the inside of the mesh is as wide as possible. That is, in the captured image, a shape that is a circle or a regular polygon (regular triangle, square, etc.) is selected.
Such an example will be described with reference to FIG. In the same figure, (B) shows the case where the surface to be inspected is a flat surface, and (B) shows the case where it is a curved surface. As shown in the figure, when the surface to be inspected has a cylindrical shape having a rotation axis in the left-right direction of the paper surface, a vertical reduction in the paper surface occurs on the imaging side. The distribution is elongated in the vertical direction. The degree of expansion is considered based on the mesh shape in the image.
By setting the mesh shape on the irradiation surface in this way, an accurate inspection can be performed in the present application and the inspection method.

In the above embodiment, a ternarization process is performed on a captured image, and a region of interest is extracted by deleting a normal region as an intermediate luminance region, or binarization Although the region of interest is extracted by performing processing and deleting a normal region, the following image processing method may be employed.
That is, as a shape characteristic of the inspection light on the irradiation surface in the present application, a dark portion is formed as a closed region, and a bright portion formed by the light-emitting diode 6 exists around this region. The image area corresponding to the non-irradiated area can be extracted as a closed dark area, and if there is an independent bright area in the closed dark area, this independent bright area can be used as the attention area It is.

  As shown in FIG. 8, this type of image processing configuration includes a closed dark region extracting unit 76 that individually extracts closed dark regions that appear in a captured image, and the closed dark region extracted by the unit 76. And an independent bright area extracting unit 77 for extracting an independent bright area existing therein, and performing the extraction process using the independent bright area as a target area.

[Another Embodiment of the Invention]
(1) In the above embodiment, in order to obtain the inspection light, a plurality of light emitting diodes as light emitting elements arranged in a predetermined part of the blackboard is used, but as shown in FIG. An irradiation device provided with a diffusion plate 22 in front of the light source 21 and a light transmission portion 23 that forms a mesh in front of the light source 21 may be used as seen in the prior art described above. In this case, since the boundary line between the bright part and the dark part can be formed relatively clearly, so-called “nothing” can be detected in the inclination direction drawn by the boundary line as the fluctuation of the boundary line.

  In addition, from the intention of making the boundary line between the bright part and the dark part stand out linearly, when the irradiation device is configured by arranging a plurality of light emitting elements as described above, the light emitting elements are arranged as densely as possible in the bright part. It is preferable to install it. It is also a preferable aspect that a diffusion plate is provided only at the front part of the mesh (excluding the inside of the mesh) to make the brightness of the mesh as uniform as possible.

(2) In the above embodiment, the mesh is formed so that the shape in the mesh is a substantially circular shape. For example, according to the shape of the surface to be inspected, the long axis is set in a predetermined direction. And it is good also as an ellipse which has a short axis. In the case of an ellipse, the surface to be inspected is a curved surface as described above, and it is easy to apply when the surface to be inspected has a substantially circular shape on the imaging side. Further, in the case where it is sufficient to examine the direction of defect occurrence in two orthogonal directions, it is preferable to use a square or a square having each side in that direction.

FIG. 10A shows the former example, and FIG. 10B shows the latter example.
Furthermore, as shown in FIG. 10C, it is preferable that square patterns are arranged in a zigzag pattern because the possibility of catching defects increases in any mesh belonging to different columns.
Furthermore, as shown in FIG. 10B, if the shape in the mesh is a triangle, it is possible to execute image processing quickly in three predetermined directions.

  In forming the above-described mesh, there may be a portion where the discriminability of the reflected image due to the defect is lowered due to the relationship between the pattern shape and the repeating direction of the mesh and the moving direction of the surface to be inspected. This kind of decrease in discriminability is due to the fact that the reflected image caused by the defect overlaps with the original imaging position of the light emitting diode 6 and the reflected image caused by the defect does not appear as a bright spot.

  This state will be described with reference to FIG. In this figure, when a reflected image due to a defect moves along a path A in which the light emitting diodes 6 are distributed in a line and the bright image appears, the reflected image (denoted as a defect in the drawing) is partially identified. With difficulty at the site. On the other hand, if the path | route B which is a site | part with comparatively few light emitting diodes 6 moves, high discriminability can be maintained. In this figure, the distribution direction s of the light-emitting diodes 6 and the movement direction S of the surface to be inspected in a specific part of the mesh coincide with each other and are both in the paper width direction.

  An example in which the light emitting diodes 6 are appropriately distributed in consideration of this type of problem is an example shown in FIG. In this example, the distribution directions s1 and s2 of the issuing diode 6 are set to two linear directions that intersect the moving direction S of the surface to be inspected. Therefore, the unit of the mesh is a rhombus. In FIG. 12, even when the defect moves on either the route C or the route D, the discrimination is maintained high. The rhombus is an example, but if the mesh is configured with sides distributed only in the direction S that does not overlap in the direction S (crossing this direction S) with respect to the moving direction S of the surface to be inspected. The above problems can be solved. As a result, inspection with higher reliability can be performed.

(3) In the above embodiment, when the irradiation surface is a blackboard in which light emitting diodes are dispersedly arranged, and the mesh shape is fixed, detection is performed by focusing the imaging device on the irradiation surface. In the present application, since the size of the mesh and the defect are relatively close to each other, an optical system capable of enlarging and reducing the mesh is arranged in front of the irradiation apparatus described so far. Then, while adjusting the size of the mesh and performing imaging while focusing on the light beam exit of the optical system, the inspection can be performed using the mesh of different sizes. In this case, it is possible to cope with defects of various sizes.

(4) Furthermore, by making it possible to adjust the irradiation amount in the irradiation apparatus, for example, when a region of interest that seems to be a defect is found, the irradiation amount is increased, and the brightness difference between the bright and dark portions is obtained. An accurate inspection can also be performed.

  For example, the inspection of the painted surface of an automobile body can be performed with high reliability.

The top view which shows the outline | summary of the inspection apparatus which concerns on this application Irradiation device perspective view The figure which shows the progress and result of the state of a captured image, image processing Schematic explanatory diagram showing the luminance distribution of the captured image Explanatory drawing showing the mechanism of reflection caused by defects The figure which shows another embodiment of this application which performs a binarization process The figure which shows another embodiment of this application which considered the process with respect to a curved surface The figure which shows another embodiment of this application which extracts a defect as an independent bright area | region The figure which shows another embodiment of this application The figure which shows another embodiment of this application Explanatory diagram showing the problem of discrimination The figure which shows the structure of the irradiation apparatus which has arrange | positioned the light emitting diode so that a rhombus pattern may be comprised.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Irradiation device 4 Imaging device 6 Light emitting diode K1 High brightness corresponding to a bright part K2 Low brightness corresponding to a dark part C1 High brightness part corresponding to a bright part C2 Low brightness part corresponding to a dark part C3 Intermediate brightness due to a defect Part C4 The part that is imaged at intermediate luminance due to the luminance distribution on the irradiated surface

Claims (12)

An inspection method for irradiating a surface to be inspected with inspection light having a predetermined pattern shape and inspecting the surface to be inspected with a captured image of the surface to be inspected in an irradiated state,
The inspection light is distributed in a mesh shape so that the shape in each mesh is the same, and an irradiation area in a plane perpendicular to the optical axis is irradiated from the irradiation surface with a light beam smaller than the non-irradiation area,
An inspection method for inspecting the surface to be inspected based on brightness information of an image region corresponding to a non-irradiation region of the surface to be inspected in the captured image. In a case where a captured image in a state in which the inspection light is irradiated on a normal inspection surface is a normal captured image, the luminance of the irradiation region in the normal captured image is high luminance, and the luminance of the non-irradiation region is low luminance,
The inspection method according to claim 1, wherein an intermediate luminance region that is present in a captured image and is an intermediate luminance region between the high luminance and the low luminance is set as a region of interest.   The inspection method according to claim 1, wherein an image area corresponding to an irradiation area of the surface to be inspected is extracted as a continuous bright area, and the continuous bright area is excluded from the attention area.   An image area corresponding to a non-irradiated area of the surface to be inspected is extracted as a closed dark area, and when an independent bright area exists in the closed dark area, the independent bright area is defined as a target area. The inspection method according to claim 1.   When the surface to be inspected is a curved surface, the mesh shape of the inspection light on the irradiation surface corresponding to the curved surface shape of the surface to be inspected is a mesh shape in which the shape of the mesh in the captured image is a circle or a regular polygon shape The inspection method according to claim 1, wherein the distribution is set. Obtained by an irradiating means for irradiating a surface to be inspected with inspection light having a predetermined pattern shape, an imaging means for capturing an image of the surface to be inspected in an irradiated state irradiated with the inspection light, and the imaging means An inspection apparatus comprising image processing means for image processing of a captured image,
The irradiating means distributes, as the inspection light, a light beam that is distributed in a mesh shape so that the shape in each mesh is the same, and the irradiation area in a plane perpendicular to the optical axis is smaller than the non-irradiation area from the irradiation surface. Irradiated,
The image processing means is an inspection apparatus configured to be capable of processing light / dark information of an image area corresponding to a non-irradiated area of the inspection surface in the image processing. The image processing means
In a case where the captured image in a state in which the inspection light is irradiated on a normal inspection surface is a normal captured image, the luminance of the irradiation region in the normal captured image is high luminance, and the luminance of the non-irradiation region is low luminance,
The inspection apparatus according to claim 6, further comprising an intermediate luminance area extracting unit that extracts an intermediate luminance area that is an intermediate luminance area between the high luminance and the low luminance in the captured image.   The inspection apparatus according to claim 6 or 7, wherein the light beam is formed by a plurality of light emitting elements distributed in a mesh pattern in the irradiation unit.   8. The inspection apparatus according to claim 6, wherein the light beam is transmitted through the narrow slits distributed in a mesh pattern in the irradiation unit.   The inspection apparatus according to claim 6, wherein the size of the mesh is adjustable.   The inspection apparatus according to any one of claims 6 to 10, wherein a luminance difference between an irradiation area and a non-irradiation area of the surface to be inspected is adjustable. In the irradiation means,
The mesh distribution of inspection light on the irradiation surface is set to a mesh shape in which the mesh shape in the captured image is a circle or a regular polygon shape corresponding to the curved surface shape of the surface to be inspected. The inspection apparatus of any one of -11.

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