JP2004037248A - Inspection device and inspection method for through hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a through-hole clogging inspection device for a honeycomb-shaped object by means of comparison with a previously photographed reference image, suffering no deterioration in accuracy, and dispensing with an expensive large-diameter telecentric lens. <P>SOLUTION: This inspection device has a main part comprising a diffused illumination lamp for transmitted light, a diffusion plate, a camera, and at least two illumination lamps for reflected light. The diffusion plate is provided parallel to a diffused illumination plane for transmitted light and capable of being put into or out of an optical path at a distance allowing the honeycomb-shaped object to be provided between the diffusion plate and the illumination lamp for transmitted light so as to cause the through hole center line of the honeycomb-shaped object to be vertical to the illumination plane for transmitted light. The camera is provided so that the center line of a lens of the camera is vertical to the illumination plane for transmitted light, and at least two illumination lamps for reflected light are provided centering around the camera at equal intervals so as to illuminate the honeycomb- shaped object. <P>COPYRIGHT: (C)2004,JPO

Description

表１に示すように、本発明の方法は従来の方法に比べて、検査結果の目詰まり穴の個数が少ない。これは、従来の方法では、透過光である平行光束と穴の中心線が平行になるように非常に正確な位置合わせが必要であり、この位置合わせが正確でないと目詰まりしていない穴も暗くなってしまい、目詰まりしていると判断されたものと思われる。
【００２４】
【発明の効果】
本発明は、拡散板と透過光用拡散照明と反射光用照明とを用いてハニカム形状物とカメラとの位置関係を一定に保ちつつハニカム形状物の反射映像と、透過映像とを求め、画像処理によりハニカム形状物の貫通孔の目詰まりを検査する。従って、ハニカム形状物等とカメラとの位置関係は反射映像を得るときと透過映像を得る時とで不変であるため、照明強度や撮影位置等がわずかに異なることによる良否判定の判断ミスはない。また、拡散板を用いるためにハニカム形状物等が大型になっても高価な大口径テレセントリックレンズを必要としない。
【図面の簡単な説明】
【図１】本発明の検査装置の概要図である。
【図２】本発明の画像解析例を示した図である。
【図３】従来の検査装置の概要図である。
【図４】テレセントリックレンズを用いる従来の検査装置の概要図である。
【図５】従来の画像解析例を示した図である。
【符号の説明】
１――――光源
２――――レンズ
３――――平行光線
４――――ハニカム形状物
５――――スクリーン
６――――レンズ
７――――カメラ
８――――テレセントリックレンズ
１１―――透過光用拡散照明
１２―――拡散板
１３―――カメラ
１４―――反射光用照明
１５―――ハニカム形状物
１６―――透過光用拡散照明面
１７―――レンズの中心線[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image inspection apparatus for inspecting an object having a large number of through holes aligned in one direction to determine whether or not the through holes are clogged.
[0002]
[Prior art]
A well-known object having a large number of through holes aligned in one direction is a honeycomb used as a deodorizing filter. Further, as a structure having a similar structure to this, there is an assembly of a large number of pipes or a structure in which a corrugated plate is wound.
[0003]
The above-mentioned honeycomb shape has an important meaning in the through hole, and cannot be used when the through hole is closed. Therefore, it is necessary to inspect whether the through hole is closed.
[0004]
As shown in FIG. 3, for example, a conventional image inspection apparatus that achieves this object converts a light from a light source 1 such as a halogen lamp into a parallel light beam by a lens 2 and converts the honeycomb-shaped object 4 to be inspected into the honeycomb. The center line of the through hole of the shaped object is parallel to the parallel light beam, and the parallel light passes through the through hole. Then, the transmission image of the honeycomb-shaped object is projected on the screen 5 and photographed by the camera 7 equipped with the lens 6. Alternatively, for example, as shown in FIG. 4, the transmitted light of the honeycomb-shaped object is directly photographed by a camera 7 equipped with a telecentric lens 8. The images thus obtained were analyzed to check whether the through-holes were blocked.
[0005]
As shown in FIG. 5, the image analysis method at this time stores an inspection object without clogging in advance as a reference image A, compares this image with an inspection image B obtained by the above method, and When the number of pixels that are darker than the set density (e.g., 128 image density of 256 gradations is 128) exceeds the set number of pixels (e.g., 100 pixels), it is determined that there is a blockage in the through hole of the inspection object It is.
[0006]
By the way, in such a conventional image analysis method, the actual image is compared with a reference image that has been photographed in advance. there is a possibility. Further, in the method of FIG. 4, when the inspection object becomes large, a very expensive large-diameter telecentric lens is required.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide an inspection apparatus and an inspection method for a through-hole of a honeycomb-shaped object that do not have the above-described disadvantage.
[0008]
[Means for Solving the Problems]
The first invention for solving the above-mentioned problems is an apparatus for inspecting whether or not a through-hole of a honeycomb-shaped object is blocked, the main part of which is at least two parts: a diffused illumination for transmitted light, a diffuser, a camera and a camera. A diffused plate, a diffuser plate, a honeycomb-shaped object between the diffuser plate and the transmitted-light diffused illumination, a through-hole center line of the honeycomb-shaped object, and a transmitted-light diffused illumination surface. Are provided at intervals that can be provided so as to be perpendicular, parallel to the diffused illumination surface for transmitted light, and removably into and out of the optical path, and the camera has a camera whose center line is perpendicular to the diffused illumination surface for transmitted light. And at least two reflected light illuminations are provided at regular intervals around the camera so as to illuminate the honeycomb-shaped object.
[0009]
The second invention is a method for inspecting a through-hole of a honeycomb-shaped article, and is a method for inspecting a through-hole mainly including the following steps.
1) A step of capturing a reflection image of the opening of the honeycomb-shaped object into a camera to obtain the reflection image.
2) A step of performing image processing on the reflection image to determine an inspection target range.
3) projecting a transmitted image of the honeycomb-shaped object by the transmitted light emitted from the transmitted light diffused illumination plate on the diffuser plate, and capturing the transmitted image projected on the diffuser plate into the camera;
4) A step of performing image processing on the transmission image to determine whether or not there is an obstruction in the inspection target range.
[0010]
The third invention is a method for inspecting a through-hole of a honeycomb-shaped object using the first measuring device, and mainly includes the following steps.
1) A step of projecting the diffused plate out of the optical path of the transmitted light and projecting it on the honeycomb-shaped object by reflected light illumination, taking in the reflected light of the honeycomb-shaped object into a camera, and obtaining a reflected image.
2) A step of performing image processing on the reflection image to determine an inspection target range.
3) A step of inserting the diffusion plate into the optical path of the transmitted light, projecting the image of the transmitted light emitted from the diffused illumination plate for the transmitted light on the diffusion plate, and capturing the projected transmitted image into the camera.
4) A step of performing image processing on the transmission image to determine whether or not there is an obstruction in the inspection target range.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the first invention, for example, as shown in FIG. 1, the main part is composed of a diffused light 11 for transmitted light, a diffuser 12, a camera 13, and at least two reflected light lights 14; 12 is such that the honeycomb-shaped object 15 is located between the diffuser plate 12 and the transmitted-light diffused illumination 11 so that the center line of the through-hole of the honeycomb-shaped object 15 is perpendicular to the transmitted-light diffused illumination surface 16. At an interval that can be provided, the camera 13 is provided so as to be parallel to the diffused illumination surface 16 for transmitted light and removably into and out of the optical path. This is an inspection apparatus in which two reflected light illuminations 14 and 15 are provided so as to illuminate the honeycomb-shaped object 15 at equal intervals around the camera 13.
[0012]
According to the principle of the present invention, as can be understood from the first invention, a reflection image of an opening of a honeycomb-shaped object is taken into a camera, the reflection image is obtained, and the obtained reflection image is subjected to image processing to determine an inspection target range. Then, without changing the positional relationship between the honeycomb-shaped object and the camera, the transmission image of the honeycomb-shaped object is projected on the diffusion plate, the transmission image projected on the diffusion plate is taken into the camera, and the transmission image is image-processed and inspected. The main element is to determine whether or not there is a closed portion in the range, and the invention is described in claim 2.
[0013]
The third invention described in claim 3 is an inspection method performed using the inspection device of the first invention. In the third aspect of the present invention, when photographing the surface of the honeycomb-shaped object while irradiating the surface of the honeycomb-shaped object with reflection illumination, the diffusion plate is removed outside the system, and the diffused illumination for transmitted light is turned off to remove the honeycomb-shaped object. Take a reflection image of the surface. Here, the reason why the diffuser is removed from the system is that, when photographing using reflected illumination, the illumination irradiation (going) and the reflected light (return) from the contour of the opening are diffused by the diffuser, and the aperture is removed. This is because it is not possible to capture a clear image of the outline of the part.
[0014]
Then, the contour (portion other than the hole) of the surface of the opening of the reflected image captured by the camera while irradiating the reflected illumination is extracted by image processing to set an inspection exclusion range. Next, a through-hole image of the honeycomb-shaped object is obtained by inserting a diffusion plate into the system, turning on diffused light for transmitted light, and photographing an image projected on the diffusion plate with a camera. Then, image processing is performed on this video to determine whether or not there is a closed portion in the through-hole portion. In the method of the present invention, the order of obtaining the reflection image and the transmission image is arbitrary, and it does not matter which one is first.
[0015]
FIG. 2 shows a specific image analysis example. The inspection object has six holes. An inspection exclusion range threshold value (for example, 180 when the image density is 256 gradations) is set for the reflection image (A), and an image density portion that is equal to or greater than the inspection exclusion range threshold value is set as the inspection outside range. Further, a clogging determination threshold value (for example, 170 when the image density is 256 gradations) is set for the transmission image (B), and pixels which are outside the inspection exclusion range and are equal to or less than the clogging determination threshold value are set. It is determined that the hole including is clogged.
[0016]
In the present invention, since diffused light is used to obtain a transmission image, even if a foreign substance adheres to a part of one hole, the foreign substance is not directly photographed, but the hole is determined according to the size of the foreign substance. Average transmittance decreases, resulting in a dark image.
[0017]
【Example】
Next, the present invention will be further described using examples.
(Example 1)
A honeycomb having a diameter of 75 mm, a length of 150 mm, and about 4500 vacant 0.8 mm square through holes in parallel at 1 mm intervals was used as an inspection object. A 1024 × 1024 pixel CCD camera was used, and a lens was used so that the pixel resolution was 0.1 mm / pixel. Therefore, approximately 8 × 8 = 64 pixels correspond to the area of one through hole.
[0018]
In this example, the clogging inspection device of the present invention having the configuration shown in FIG. 1 was used. First, the diffusion plate is removed from the system, the diffused illumination plate for transmitted light is extinguished, and the surface of the opening of the honeycomb (the surface where the through holes are visible) is illuminated by reflected light illumination by reflected illumination. Was taken. In the obtained image, the outline of the honeycomb was bright and the holes were dark as in the case of FIG.
[0019]
This image was recorded as data of 256 gradations, the threshold value of the inspection removal range was set to 180, and the portion above this threshold value (that is, other than holes) was excluded from the inspection range.
[0020]
Next, the diffuser was returned to a predetermined position, the reflected light illumination was turned off, the diffused illumination plate for transmitted light was turned on, the transmitted light image was projected on the diffuser, and a transmitted image was photographed. At this time, the distance between the diffused illumination plate for transmitted light and the honeycomb and the distance between the diffusion plate and the honeycomb were all 2 mm.
[0021]
Next, the obtained video was subjected to image processing. The clogging determination threshold value is set to 170, and it is assumed that the through-holes including pixels below the clogging determination threshold value in the inspection range are clogged. After subjecting the detected pixels to one-pixel expansion / contraction processing, labeling processing was performed to determine the number of clogged through holes.
[0022]
For comparison, clogging inspection was performed by the conventional method using the same honeycomb as described above. Holes including pixels below the clogging determination threshold in the inspection image other than the dark portion (the portion other than the holes) of the reference image were determined to be clogged. Similarly, after the detected pixels are subjected to one-pixel expansion / contraction processing, labeling processing is performed to determine the number of clogged holes.
[0023]
Table 1 shows the results of three clogging inspections performed by the apparatus of the present invention and the conventional apparatus.

As shown in Table 1, the method of the present invention has a smaller number of clogged holes as a result of inspection than the conventional method. This is because, in the conventional method, it is necessary to perform very accurate alignment so that the parallel light flux, which is the transmitted light, and the center line of the hole are parallel. It seems to have been dark and clogged.
[0024]
【The invention's effect】
The present invention obtains a reflection image of a honeycomb-shaped object and a transmission image while maintaining a constant positional relationship between the honeycomb-shaped object and a camera using a diffusion plate, diffused illumination for transmitted light, and illumination for reflected light, and obtains an image. The clogging of the through-hole of the honeycomb-shaped object is inspected by the processing. Therefore, since the positional relationship between the honeycomb-shaped object or the like and the camera is invariable between when a reflected image is obtained and when a transmitted image is obtained, there is no erroneous judgment of quality judgment due to slight differences in illumination intensity, shooting position, and the like. . Further, even if the honeycomb-shaped object becomes large due to the use of the diffusion plate, an expensive large-diameter telecentric lens is not required.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an inspection device of the present invention.
FIG. 2 is a diagram showing an image analysis example of the present invention.
FIG. 3 is a schematic diagram of a conventional inspection device.
FIG. 4 is a schematic diagram of a conventional inspection device using a telecentric lens.
FIG. 5 is a diagram showing a conventional image analysis example.
[Explanation of symbols]
1 --- Light source 2 --- Lens 3 --- Parallel ray 4 --- Honeycomb shaped object 5 --- Screen 6 --- Lens 7 --- Camera 8 --- Telecentric lens 11 --- Diffusion illumination for transmitted light 12 --- Diffusion plate 13 --- Lighting for reflected light 15 --- Honeycomb shaped object 16 --- Diffusion illumination surface 17 for transmitted light ―Center line of lens

Claims (3)

A device for inspecting whether or not a through hole of a honeycomb-shaped object is closed, the main part of which is composed of diffused light for transmitted light, a diffuser, a camera and at least two reflected light illuminations, and a diffuser However, the honeycomb-shaped object between the diffuser plate and the transmitted light diffused illumination, at intervals that can be provided so that the center line of the through-hole of the honeycomb-shaped object and the transmitted light diffused illumination surface are perpendicular, The camera is provided so as to be parallel to the diffused illumination surface for transmitted light and removably into and out of the optical path, and a camera is provided so that the center line of the lens of the camera is perpendicular to the diffused illumination surface for transmitted light. An inspection apparatus, wherein at least two reflected light illuminations are provided at intervals so as to illuminate a honeycomb-shaped object. A method for inspecting a through-hole of a honeycomb-shaped article, which mainly includes the following steps.
1) A step of capturing a reflection image of the opening of the honeycomb-shaped object into a camera to obtain the reflection image.
2) A step of performing image processing on the reflection image to determine an inspection target range.
3) projecting a transmitted image of the honeycomb-shaped object by the transmitted light emitted from the transmitted light diffused illumination plate on the diffuser plate, and capturing the transmitted image projected on the diffuser plate into the camera;
4) A step of performing image processing on the transmission image to determine whether or not there is an obstruction in the inspection target range. A method for inspecting a through-hole of a honeycomb-shaped object using the inspection apparatus according to claim 1, wherein the method mainly includes the following steps.
1) A step of projecting the diffused plate out of the optical path of the transmitted light and projecting it on the honeycomb-shaped object by reflected light illumination, taking in the reflected light of the honeycomb-shaped object into a camera, and obtaining a reflected image.
2) A step of performing image processing on the reflection image to determine an inspection target range.
3) A step of inserting the diffusion plate into the optical path of the transmitted light, projecting the image of the transmitted light emitted from the diffused illumination plate for transmitted light on the diffusion plate, and capturing the projected transmitted image into the camera.
4) A step of performing image processing on the transmission image to determine whether or not there is an obstruction in the inspection target range.

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