JP2005249495A - Surface inspection method and device for flat plate body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect whether an abnormal point in an image taken by a camera when inspecting a surface of a flat plate body is abnormal on the surface of the flat plate body or not with high speed and high accuracy. <P>SOLUTION: The present invention is a surface inspection method for flat plate body 1 to inspect abnormality on a surface of the flat plate body 1, wherein 2 cameras 10 and 11 are provided at a certain distance from the flat plate body 1 to take images of the surface of the flat plane body. Coordinate data of an abnormal point taken by the camera A10 and that of the abnormal point taken by he camera B11 are obtained. In addition to calculating difference between the coordinate data, difference between the coordinate data of a sample point taken by the both cameras on the surface of the flat plate body is calculated in advance. If the differences of the abnormal point and the sample point agree each other, the abnormal point taken by the camera is detected as abnormality on the surface of the flat plate body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface inspection method and apparatus for a flat body, and more particularly to a technique for determining whether or not an image is abnormal on the surface when an abnormal image is obtained by surface imaging.

  When manufacturing flat plate industrial products such as concrete panels and gypsum boards, it is necessary to inspect the surface of the flat plate for abnormalities such as scratches, faults, and color spots before shipment. Conventionally, when the surface of a product is confirmed visually or when an abnormal image is detected by a known image processing technique after being photographed by a camera, an alarm is given as a product abnormality.

  In particular, in a flat plate production line, the flat plate is often transported horizontally by rollers, etc. When there is a front and back of the product, the front surface is subjected to a strict inspection visually from above. Yes. On the other hand, the back side may not require a very strict inspection, so a mirror is installed on the back side (bottom side), and the back side reflected in the mirror is confirmed at the same time as the front side is viewed, or image processing by the camera An abnormality was detected.

  The method of detecting an abnormality with a camera is preferable because it reduces the burden on the operator and enables high-speed and continuous inspection. However, when there is an abnormal point in the captured image, it detects the surface of the flat plate. In many cases, it is impossible to distinguish whether it is a power abnormality, dust existing between the flat plate and the camera, or dust attached to the camera itself, and it is erroneously detected as an abnormality. For this reason, when an abnormality is detected, it is necessary for the operator to check again, which may lead to a reduction in production efficiency.

Especially when inspecting in an environment with a lot of dust, or when materials with brittle surfaces such as concrete board or gypsum board are transported with rollers, etc., and dust tends to fall off from the surface, take a picture of the back side from the bottom as described above. Then, there is a problem that the influence of dust is large and efficient detection cannot be performed.
Conventionally, as a technique for inspecting a flat surface, a technique for measuring by an optical reflection characteristic as disclosed in Patent Document 1 is known.
Japanese Patent Application Laid-Open No. 11-108636

  The present invention was created in view of the above-described problems of the prior art, and its purpose is to detect whether an abnormal point in a photographed image by a camera is abnormal on the surface of a flat plate with high speed and high accuracy. Is to provide technology to do.

In order to achieve the above object, the surface inspection method for a flat plate according to the present invention has the following features.
That is, the invention described in claim 1 is a method for inspecting a surface of a flat plate for inspecting an abnormality on the surface of the flat plate, and is located at a predetermined distance from the flat plate in parallel with the first camera and the first camera. Two cameras are provided, and the surface of the flat plate is photographed by both cameras.
At that time, the respective coordinate values of the abnormal point photographed by the first camera and the abnormal point photographed by the second camera are obtained, and the difference between the coordinate values is calculated. The difference between the coordinate values of the sample points in both cameras when the image was taken is obtained, and if the difference between the abnormal point coordinate values and the difference between the sample point coordinate values match, It is detected as an abnormality on the surface.

  The invention according to claim 2 is to photograph the lower surface of the flat plate with the first camera and the second camera fixed upward from the lower surface side of the flat plate while moving the flat plate substantially horizontally in a predetermined direction. is there.

  Furthermore, the present invention can provide a flat surface inspection apparatus. That is, the invention described in claim 3 is a flat plate surface inspection apparatus for inspecting abnormalities on the surface of the flat plate, and is located at a predetermined distance from the flat plate and in parallel with the flat plate. In the configuration including the second camera and photographing the surface of the flat body with both cameras, the image input means for inputting the images taken by both cameras, the abnormal points photographed by the first camera from the input images, and the second camera Image processing means for obtaining each coordinate value of the photographed abnormal point, calculation means for calculating the difference between the coordinate values, and the coordinate value of the sample point in both cameras when the sample point on the surface of the flat plate is photographed in advance The storage means for determining and storing the difference, the difference between the abnormal point coordinate values and the difference between the sample point coordinate values match, and if they match, the photographed abnormal points on the surface of the plate body To; and an abnormality judging means for detecting a normal.

  According to a fourth aspect of the present invention, the flat plate surface inspection device is attached to a lower portion of a transfer device that transfers the flat plate substantially horizontally in a predetermined direction, and is fixed upward from the lower surface side of the flat plate. The structure which image | photographs the flat plate lower surface with the said 1st camera and a 2nd camera is disclosed.

  The following effects are produced by the above means. That is, according to the present invention, an abnormal point is photographed from two directions with two cameras, and the abnormal point is detected three-dimensionally to calculate the difference between the coordinate values of the image. Since it can be determined whether it is an abnormal point, it contributes to the improvement of production efficiency. In particular, according to the present invention, high-speed processing is possible, and the configuration of the inspection apparatus is extremely simple, so that costs can be reduced.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best mode for carrying out the invention will be described based on examples shown in the drawings. The embodiment is not limited to the following.
FIG. 1 is a perspective view of a camera portion of a flat surface inspection apparatus according to the present invention. As shown in the drawing, the flat plate body (1) to be inspected is horizontally transferred by the drive rollers (2) and (3) with the front surface of the product being the upper surface and the rear surface being the lower surface side.

The surface of the product is visually inspected by an operator, and not only scratches and cracks but also abnormalities such as color change and color spots are checked in detail. Since it is only necessary to detect serious defects such as scratches and cracks on the back surface, visual inspection is not necessary, and high-speed and efficient inspection is desired.
In the present invention, in order to inspect this, an inspection apparatus (4) for photographing the back surface of the product with the two CCD cameras (10) and (11) facing upward has been created.

  The product is transferred in the direction of the arrow in FIG. 1, and the two cameras A (10) and B (11) are installed parallel to the flat plate along the transfer direction. As shown in FIG. 2, images captured by the camera A (10) and the camera B (11) are subjected to image processing in an image input unit or CPU constituted by a known computer.

The images of the two cameras (10) and (11) are taken into the CPU (21) by the image input unit (20) via a known interface. The image input unit (20) can be composed of a video card or the like.
Then, in the image processing unit (22) which is a processing unit of the CPU (21), the abnormal point is detected from the two input images, and the coordinate value of the abnormal point is acquired. As an abnormal point detection method, a known image processing technique can be used. For example, there is a method of generating a histogram and detecting a point exceeding a certain threshold as an abnormal point.

As shown in FIG. 3, when the camera A (10) is photographed from the back surface of the flat plate, the tomography (40) existing on the flat plate surface is from the left end of the photographing region (41) of the camera A (10). A coordinate value is detected at a distance of L1 (50).
On the other hand, when photographing is performed with the camera B (11) simultaneously with the camera A (10), the coordinate value is detected as L2 (51) from the left end of the photographing region (42). The space where the imaging areas (41) and (42) intersect in the two cameras is the inspection area (43).
Both coordinate values are acquired in the image processing unit (22) and temporarily stored in a memory or the like.

  Further, the calculation unit (23) calculates the difference between the acquired coordinate values. The value obtained by this is L (52) in FIG. In the present invention, the abnormal point on the surface is used as a sample in advance as described above, and the coordinate value difference L (52) when the abnormal point is on the surface is stored as sample point data in the storage means (26) such as a hard disk. deep.

After that, the in-line image is taken as needed while transferring the flat plate (1), and the abnormal point is processed by the image processing unit (22) and the calculation unit (23).
FIG. 4 is a diagram showing coordinate values for the detection object (60) existing on the surface of the flat body, the foreign object a (61) in the inspection region (43), and the foreign object b (62).
First, when the detection object (60) is photographed by both cameras (10) and (11), the coordinate value L1 ′ (70) and the coordinate value L2 are the same as the processing in the sample point data (26). '(71) is acquired, and the calculation unit (23) calculates the difference L' (72).

Then, the abnormality determination unit (24) compares the difference L ′ (72) with the difference L (52) stored as the sample point data (26). Here, when it is on the surface of the flat plate (1), L = L ′ always holds, so that they coincide, and in this case, it is determined as abnormal.
When a product abnormality is detected, a warning is displayed on the monitor (27), for example, by the output unit (25), or a sound is emitted from a speaker (not shown).

On the other hand, in the case of the foreign object a (61), the coordinate value by the camera A (10) is L1a (73), and the coordinate value by the camera B (11) is L2a (74).
L1a (73) is geometrically equal to the value obtained by adding the distance x (75) and the distance w (76) to the above L1 ′ (70) (Equation 1), and L2a (74) is equal to the above L2 ′ (71). This is equal to the sum of the distances w (76) (Equation 2).

[Equation 1] L1a = L1 ′ + x + w
[Expression 2] L2a = L2 ′ + w

Therefore, the difference between the coordinate values of the two cameras at this time is L1a−L2a, and L1′−L2 ′ = L ′ = L, and thus is calculated as L + x.
As a result, the abnormality determination unit (24) does not match the difference and does not determine an abnormal point.

Similarly, in the case of the foreign object b (62), the coordinate value by the camera A (10) is L1b (77), and the coordinate value by the camera B (11) is L2b (78).
Then, geometrically, the number 3 is between L1b (77), L1 ′ (70) and the distance y (79) in the figure, and between L2b (78), L2 ′ (71) and the distance z (80). Equation 4 holds.

[Equation 3] L1b = L1 ′ + y
[Expression 4] L2b = L2′−z

Accordingly, the difference between the coordinate values of the two cameras at this time is L1b−L2b, which is calculated as L + y + z, and does not match L (52).
In the conventional technique, since any foreign matter (61) (62) is included in the inspection region and cannot be determined whether or not it is on the surface, it is a case where it is detected as an abnormality of the flat plate (1). According to the present invention, it is possible to accurately detect whether there is an abnormality.

It is a perspective view explaining the camera part of the surface inspection apparatus by this invention. It is a block diagram of the surface inspection apparatus by this invention. It is explanatory drawing for demonstrating the principle of this invention. It is explanatory drawing for demonstrating the principle of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flat plate 2 Drive roller 3 Drive roller 4 Surface inspection apparatus 10 Camera A
11 Camera B

Claims (4)

A method for inspecting a surface of a flat plate to inspect abnormalities on the surface of the flat plate,
When a first camera and a second camera are provided in parallel to the flat plate at a predetermined distance from the flat plate, and the flat plate surface is photographed by both cameras,
While obtaining the respective coordinate values of the abnormal point imaged by the first camera and the abnormal point imaged by the second camera, calculating the difference between the coordinate values,
Obtain the difference between the coordinate values of the sample points in both cameras when the sample points on the surface of the flat plate are photographed in advance.
A method for inspecting a surface of a flat plate, comprising: detecting a photographed abnormal point as an abnormality on the surface of the flat plate when the difference between the abnormal point coordinate and the difference between the sample point coordinate values match. The surface inspection method of the flat plate is
The surface inspection of the flat plate according to claim 1, wherein the flat plate is photographed by the first camera and the second camera fixed upward from the lower surface side of the flat plate, while the flat plate is transported substantially horizontally in a predetermined direction. Method. A flat surface inspection apparatus for inspecting abnormalities on the surface of a flat body,
In a configuration in which a first camera and a second camera are provided in parallel to the flat plate at a predetermined distance from the flat plate and the surface of the flat plate is photographed by both cameras.
Image input means for inputting captured images of both cameras;
Image processing means for obtaining, from the input image, respective coordinate values of the abnormal point imaged by the first camera and the abnormal point imaged by the second camera;
A computing means for calculating a difference between the coordinate values;
Storage means for obtaining and storing a difference between the coordinate values of the sample points in both cameras when the sample points on the surface of the flat plate are photographed in advance;
Comparing whether or not the difference between the abnormal point coordinate values and the difference between the sample point coordinate values match, and when there is a match, an abnormality determining means for detecting the photographed abnormal point as an abnormality on the surface of the flat body A flat surface inspection apparatus characterized by the above. A surface inspection apparatus for the flat plate,
Attached to the lower part of the transfer device for transferring the flat plate substantially horizontally in a predetermined direction,
The flat plate surface inspection apparatus according to claim 3, wherein the flat plate lower surface is photographed by the first camera and the second camera fixed upward from the lower surface side of the flat plate.

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