JP6425972B2 - Inner surface inspection apparatus for pipe material and inspection method using the same - Google Patents

Description

  The present invention relates to an inspection apparatus and an inspection method used for the inner surface inspection of a pipe material.

For high purity gas piping used in large quantities in semiconductor and liquid crystal manufacturing, high quality clean steel pipes are often used, in which the inner surface of the steel pipe is mirror-finished because internal flaws in the steel pipe greatly affect the manufacturing yield.
This high quality clean steel pipe is as long as 4 m, and the small diameter is as thin as 4.35 mm.
Therefore, in addition to the fact that the shape of the steel pipe is elongated and difficult to handle, and the inner surface flaw is as fine as several tens of microns, the inspection of internal surface flaws etc. can not but rely on visual inspection by a skilled worker.
However, visual inspection relies on human sensory inspection in addition to low inspection efficiency, so its judgment criteria are vague and data accumulation is impossible.
Therefore, the improvement of inspection process is the biggest problem to cope with the cost reduction and the increase of production.

Eddy current inspection and ultrasonic flaw inspection are well known as nondestructive automatic inspection of steel pipes.
However, neither the eddy current inspection method nor the ultrasonic inspection method directly inspects the inner surface flaws of the steel pipe, so the detection sensitivity is extremely low at about 0.5 mm level and is unsuitable for the inspection of the clean steel pipe inner surface flaws. .
Moreover, the method of inserting an inspection apparatus in a pipe material inner surface as an inner surface inspection automatic method of a pipe material is known.
For example, a method using a drive vehicle traveling on the inner surface of "Japanese Patent Application Laid-Open No. 6-130001" and "Japanese Patent Application Laid-Open No. 6-50719", a method of inserting a capsule into a steel pipe of "Japanese Patent Application Laid-open No. And the like.
However, these methods can not be applied to small diameter and long pipes such as clean steel pipes.
That is, in the method using the drive car or the capsule, the inspection object is too thin and the drive car or the capsule can not be inserted, and the method using the fiber cable takes a long time for insertion and the cost of the inspection time increases.
Moreover, when inserting an inspection apparatus, it also leads to the cause which damages the pipe inner surface and reduces quality.

As an invention which solved the above-mentioned subject, JP, 2011-69616, was applied previously.
The technology disclosed in the same publication is an apparatus in which a camera and a movable focus zoom lens are attached to one side of a pipe so as to intersect the pipe at a very small angle, and a diffused light source is installed on the other side. The inner surface is zoomed to capture an image while changing focus, and an integrated image A is created by integrating the images, and the tube is slightly rotated to capture an image, and an integrated image B is created in the same manner. Image analysis and inspection.
The present invention is an improvement to an inspection apparatus in which it is not necessary to cross-cut and photograph a pipe at a minute angle or to make a slight rotation of the pipe.

Unexamined-Japanese-Patent No. 5-332995 JP-A-6-50719 Japanese Patent Application Laid-Open No. 6-66729 Japanese Patent Application Laid-Open No. 6-130001 Unexamined-Japanese-Patent No. 2011-69616 gazette

  An object of the present invention is to provide a low cost inner surface inspection apparatus of a pipe material which can perform high-accuracy image processing with a simple structure and an inspection method using the same.

The inner surface inspection apparatus for a pipe according to the present invention includes a diffused light source disposed on one open end side of the pipe and a camera disposed on the other open end side of the pipe via a movable focus zoom lens. The optical axis adjustment means for aligning the optical axis of the camera with the central axis of the tube material, and the light blocking means for inputting information only to the inner surface of the tube material to the camera It is characterized by comprising a light shielding material which can sandwich and shield the outer peripheral portions on the side, and a light shielding case which shields the periphery between the light shielding material and the movable focus zoom lens .
Here, it is preferable to dispose a close-up ring between the camera and the movable focus zoom lens.
The inspection method according to the present invention uses a tube inner surface inspection apparatus according to claim 1 or 2 to capture a plurality of images obtained by imaging the inner surface of the tube while changing the focus of the movable focus zoom lens. After integrating the image into the omnifocal image, the inner surface of the tube can be inspected by image processing.

In the present invention, imaging is performed from the front of the tube, and a diffused light source is disposed on the opposite side to illuminate the inner surface of the tube.
Further, the inspection table on which the pipe is mounted and the camera table for fixing the camera have a function capable of finely adjusting the optical axis and the central axis of the pipe in order to make the camera optical axis coincide with the central axis of the pipe.
By attaching the light shielding means, it is possible to reliably capture the central axis of the inner surface of the tube and to produce a correct in-focus image.
For example, the tube material is sandwiched by at least one place near the end of the tube and a material such as sponge having high light shielding property having both elasticity and light shielding property that does not apply load to the pipe material, and the entire tube material is covered with a high light shielding property. It is a light shielding mechanism that shields the diffused light source and the outside light, and allows only information on the inner surface of the tube to enter the camera.
At this time, a plurality of places may be interposed by the light shielding sponge. As a light shielding material sandwiching the pipe material, in addition to the light shielding property, select a material that gives load to the pipe material and does not bend the pipe material.
By attaching a close-up ring between the camera and the zoom lens, it is possible to make close-up photography possible, to increase the ratio of the inner surface of the tube to the entire image, and to increase the resolution of the inner surface of the tube.

Here, a close-up ring is a cylindrical imaging device mounted between a camera and a lens, does not have an optical system such as a lens, and is close-up photography simply by expanding the distance between the imaging element and the lens principal point. Make it possible.
When the close-up ring is used, the focus is closer to the front than usual, so close-up shooting can be performed and a large object can be shot.
For example, as shown in FIG. 3, if you try to shoot point B in front of you while focusing on point A, the focus will be blurred, but the position of the pixel element so that the focusing position of point B will be met by the close-up ring You can focus on the B point by shifting the back. In this way, focusing is achieved in front of the original position, close-up photography can be performed, and resolution can be increased.
In addition to close-up rings, equipment and cameras that enable close-up photography include macro-only lenses, close-up lenses attached to existing lenses, and zoom lenses with macro functions, but are limited to close-up only or close-up There is a problem that it is impossible to shoot between the lens and the telephoto, and it is very difficult to focus continuously from one lens to another from close to telephoto as in the present invention.

The camera in the apparatus of the present invention may be anything as long as it can be transferred to a personal computer, such as a CCD camera or a CMOS camera.
In the zoom lens, it is not necessary to focus on the entire length of the tube with the close-up ring, but in this case, it is preferable to inspect from the tube end to the center of the tube twice.
Therefore, it is preferable to use a zoom lens capable of focusing at least to the center of the tube.
In addition, a plurality of cameras may be used for capturing an image of the entire area without using a zoom lens, and an integrated image may be captured later.
In addition, LED, such as white LED and blue LED, a white fluorescent lamp, etc. can be used for a diffused light source.

According to the present invention, it is possible to do the following, and for the first time, it is possible to automate the visual inspection of thin and long steel pipes, and to perform low-cost and objective automatic inspection.
(1) By aligning the camera optical axis and the tube center, the information is not biased at the time of imaging, and information can be acquired uniformly at each angle.
(2) The removal of the conventional rotation mechanism enables simplification and speeding up of the image acquisition mechanism.
(3) By attaching a close-up ring to the zoom lens, close-up photography can be performed, the inner surface of the tube material can be photographed widely, resolution can be greatly increased, high resolution up to at least 5000 mm on the near side 0 mm and telephoto side. It is possible to continuously focus a wide range with one lens while maintaining it.
(4) By providing the light shielding means, image information of only the inner surface of the tube can be stably acquired without being influenced by the external light (environment).

An example of composition of an inspection device concerning the present invention is shown. The schematic diagram of optical axis adjustment is shown. Shows the characteristics of the close-up ring. The structural example of a light-shielding means is shown, (a) shows the top view of the state which removed the cover member 17b, (b) shows a side view. (A) is a perspective view, (b) is an exploded view of a light shielding part, (c) is a cross-sectional view taken along the line A-A, (d) shows an example of a lower light shielding material, and (e) shows an upper light shielding member. An example of an inspection system is shown.

As shown in FIG. 1 as a whole view of the inner surface inspection apparatus according to the present invention, the inner surface inspection apparatus mounts the tube W, the camera 13 and the zoom lens 11 for photographing the tube with high accuracy. A close-up ring 12, a diffused light source 14 for irradiating the inner surface of the pipe, a light shielding means 17 for copying only the inner surface of the pipe to the camera, a computer (image processing means) 15 for controlling them and a monitor 16 for displaying the result. .
In particular, the positions of the tube and the camera are important, and it is necessary to arrange the tube, the camera and the diffused light source in parallel to make the center of the tube coincide with the optical axis of the camera as shown in FIG.
Although not shown, an optical axis adjustment means is provided.
The optical axis adjustment means can be provided on one or both of the camera side and the inspection table side.
Further, the close-up ring 12 is attached between the camera and the lens so that the inner surface of the tube material can be clearly photographed by close-up photography.
A plurality of the light shielding means may be provided.
In order to copy only the inner surface of the tube to the camera, the means for providing a light blocking mechanism is preferably to surround the tube and the camera or the diffused light source with a light blocking material rich in both light blocking property and stretchability.
The tube end on the lens side is formed in the recess of the inverted U-shaped light shielding guide so that outside light does not enter the image, the tube is inserted into this part, and the opening of this recess is closed by another light shielding member There is an example in which the pipe material is clamped.
Further, as shown in FIG. 4B, the light shielding member 17 to the diffused light source 14 may be covered with a cover member 17b.

In the example shown in FIG. 6 as the inspection method, first, the tube W is placed on the first inspection table so that the A end side of the tube W is positioned on the zoom lens side, and the inner surface of the tube is irradiated with the diffusion light source 14.
Next, a plurality of images are taken while changing the zoom value of the zoom lens and the intensity of the diffused light source, and zooming is performed to the center of the tube.
Next, an omnifocal image is generated by image processing. Out-of-focus portions are taken out of the photographed image group, and an omnifocal image in which all the portions from the tube end to the tube half are in focus is generated.
Defect judgment is performed on the omnifocal image.
If there is a flaw etc. in the omnifocal image, it is extracted and it is judged whether it is defective or not.
If the tube W is transferred to the second inspection table and the same is performed from the opposite side (B end), the inspection can be performed on the entire area.

An embodiment of the clean steel pipe inner surface flaw automatic inspection will be specifically described with reference to FIG.
The pipe material W is a clean steel pipe having a length of 4.0 to 4.1 m, an outer diameter of 6.35 to 12.7 mm, and a thickness of 1.00 mm to 1.24 mm. The material is stainless steel, and the special processing of the inner surface is electrolysis. A mirror finish (EP grade) by polishing or a surface finish (BA grade) by bright annealing is performed.
As for the outer diameter, thickness and length, if an optical system (diffuse light source, camera, lens, etc.) and transport device are prepared according to the tube to be inspected, the outer diameter is 5.00 to 450.0 mm, A thickness of 1.00 to 12.7 mm and a length of 3.5 to 4.5 m can be accommodated.
In this embodiment, as stockers for holding steel pipes, a supply stocker S for untested steel pipes, a non-defective stocker S ₁ for non-defective steel pipes, a defective stocker for defective steel pipes S ₂ , a non-defective stocker and a defective stocker are installed. The heights are different.
The equipment used for the automatic inspection apparatus of this embodiment is as follows.
The zoom lens has a focal length of 8-136 mm, a maximum aperture ratio of 1: 1.6, a zoom ratio of 17 times, an inclusive angle of 43.6 ° × 33.4 ° to 2.7 ° × 2.2 °, and an aperture F1.6 The ~ Close one was used.
For the close-up ring, a 1.5 mm thick camera with a CMOS camera with a maximum resolution of 648 × 488 to 2592 × 1944 and a pixel size of 2.2 μm × 2.2 μm to 7.4 μm × 7.4 μm was used. .
In addition, a white LED surface light source was used as a diffused light source, and a black sponge was used as a light shielding material sandwiching a steel pipe as a light shielding means.
In the light shielding material, as shown in FIG. 5, an upper light shielding material 117 having an outer diameter of 6.35 mm and a notch 117a is provided, and a lower light shielding material 217 is disposed so as to close the notch from the lower side.
The tubular material W is wrapped by the light shielding members 117 and 217, and the surrounding between the light shielding member and the zoom lens is shielded from external light by the light shielding case 17a.
The pipe material to be inspected may be anything other than stainless steel pipe, and any pipe such as steel pipe, polyvinyl chloride, plastic, resin and rubber may be used.
The inspection table includes a first inspection table to be inspected from one pipe end (A end) and a second inspection table to inspect from the other pipe end (B end).
The first inspection table is provided with a camera lens unit on the A end side, a white LED on the B end side, and a light shielding mechanism between them, and the steel pipe, the camera and the white LED are installed in parallel.
The 2nd inspection stand is arranged in the reverse of the 1st inspection stand.
The transfer device performs control operation by pneumatic pressure in cooperation with a computer. In conjunction with this, the camera, the zoom lens, and the diffused light source are simultaneously controlled from the computer.
When the start button of the transfer device is pressed, the steel pipe is transferred from the supply stocker to the first inspection table so as to be horizontal to the camera.
After the transfer is completed, the transfer device transmits an A-end inspection start command to the computer.
When the computer receives an A-end inspection start command, it inspects the A-end side.
When the inspection on the A end side is finished, the command is transmitted to the transport device.
Next, the transfer device transfers the steel pipe of the first inspection table to the second inspection table and simultaneously transfers the steel pipe of the supply stocker S to the first inspection table.
When the transport is completed, the transport apparatus sends the A-end inspection start and B-end inspection start commands to the computer, and the computer receives this and starts the both-end inspection.
When both ends of the inspection are completed, the computer sends an instruction to finish the inspection to the transfer device, and the transfer device transfers the steel pipe of the supply stocker to the first inspection table, the steel pipe of the first inspection table to the second inspection device, and the second testing station of each conveyed concurrently otherwise to good stocker S ₁ if good across both the defect stocker S _2.
The inspection of the inner surface of the steel pipe is performed by photographing the inner surface of a plurality of sheets while matching the zoom value of the zoom lens and the intensity of the white LED to the optimum state that can obtain clear images Generate an omnifocal image. Image processing such as a background subtraction method is performed on the omnifocal image to determine whether the image is good or bad.
These series of operations are performed until the supply stocker's steel pipe disappears, and the automatic inspection of the steel pipe is completed.

11 Zoom lens 12 Close-up ring 13 Camera 14 Diffuse light source 15 Image processing means 17 Light shielding means 18 Inspection table W Tube material

Claims (3)

A diffused light source disposed on one open end side of the tube;
A camera is disposed on the other open end side of the tube via a movable focus zoom lens,
The optical axis adjustment means for aligning the optical axis of the camera with the central axis of the tube, and the light shielding means for causing the camera to input information on only the inner surface of the tube .
The light shielding means comprises a light shielding material capable of sandwiching and shielding an outer peripheral portion on the focus movable zoom lens side of the pipe member with each other, and a light shielding case shielding the periphery between the light shielding material and the focus movable zoom lens. The inner surface inspection device of the pipe material to be characterized.   2. The inner surface inspection apparatus of a pipe material according to claim 1, wherein a close-up ring is disposed between the camera and the movable focus zoom lens. The inner surface inspection apparatus for a pipe material according to claim 1 or 2
A plurality of photographed images obtained by photographing the inner surface of the tube while changing the focus of the movable focal zoom lens are integrated into the omnifocal image, and then the inner surface of the tube is inspected by image processing. Internal inspection method.

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