JP3332208B2 - Defect detection method and apparatus for netted glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a defect in a glass having a net or a line, and detects a defect by removing a net portion from an image signal irrespective of the shape of a net or a line by an image processing technique.

[0002]

2. Description of the Related Art Many methods and apparatuses for detecting defects in screened glass have been known. For example, JP-A-6-347
No. 410 discloses a step of capturing an image of a screened glass sheet to be inspected, a step of moving the captured image by a predetermined amount corresponding to a mesh shape, and a step of superimposing an image before movement and an image after movement. There is disclosed a method of detecting a defect in a glass-screened glass, comprising: a step of removing an overlapped portion from an overlapped image; and a step of determining a defective portion from the image from which the overlapped portion has been removed.

Japanese Patent Application Laid-Open No. Hei 8-304295 discloses a method for detecting a defect present on the surface of a plate-shaped transparent object that is transported in one direction and includes an object having a high reflectance inside or on the surface. On one side of the plate-shaped transparent object, the length direction has an angle θ with respect to a direction orthogonal to the one direction.
The one surface is illuminated by an illuminating device provided so as to form a line, and the line sensor provided on the one surface side scans a direction making the angle θ with respect to a direction orthogonal to the one direction. As a direction, a surface defect detection method and an apparatus for imaging one surface of the plate-shaped transparent object are disclosed.

Further, Japanese Patent Laid-Open No. 6-148 filed by the present applicant has been disclosed.
In Japanese Patent No. 100, light from a light source is projected onto a ribbon-shaped netted glass that is continuously conveyed, and the two-dimensional cameras provided on the opposite side of the netted glass image the netted glass. Then, in the method of inspecting the netted glass based on the obtained density signal, when there is a density signal that is continuous in a vertical, horizontal or diagonal direction in a predetermined range, the density signal is equally spaced from the center in the width direction. Discloses a method for inspecting a screened glass in which the dark signal is removed to a width larger than the screen, and the defect is inspected by determining the magnitude of the remaining signal.

[0005]

The above-mentioned Japanese Patent Application Laid-Open No. Hei 6-34 is disclosed.
The glass described in Japanese Patent No. 7410 is slightly deformed due to elongation of the net when forming the netted glass, so the pattern in the width direction of the glass ribbon is slightly different and not the same shape, so that the captured image is moved by a predetermined amount. Then, in the process of superimposing the image before the movement and the image after the movement and removing the overlapping portion of the superimposed images, a case where the images do not overlap occurs. Further, when a defect exists on the net, there is a concern that the defect is divided and detected after erasing the net, and the defect size cannot be measured correctly.

The method disclosed in Japanese Patent Application Laid-Open No. Hei 8-304295 is a method for inspecting defects by utilizing reflection, so that it can detect only surface defects of screened glass. Is related to surface defect inspection of objects with high reflectivity.If the surface of the meshed glass before or during polishing is not smooth and there are fine irregularities on the surface, etc. There is a problem that the defect cannot be detected due to scattering.

Further, the method described in Japanese Patent Application Laid-Open No. 6-148100 is a method in which a dark signal is regarded as a net when it is continuous. It is necessary to reduce the width of one pixel so that it is continuous, and in order to remove the net without fail, the masking width must be set to be large, so that the camera's field of view may be large. However, there is a problem that the number of cameras can be increased and the cost is increased. There is also a problem that the detection algorithm differs depending on the type of the mesh, such as a parallel metal wire, a rhombus (rhombus), a square (square mesh), and the like, which is complicated.

[0008]

SUMMARY OF THE INVENTION The present invention provides the above-mentioned problems,
In other words, the purpose of the present invention is to reliably delete only the image of the net portion by the same algorithm regardless of the type of net of the netted glass, discriminate the defective portion from the net portion, and detect the defect.
It is. That is, the present invention projects light from a light source onto a ribbon-shaped net or a lined glass that is continuously conveyed,
In a method of inspecting the net or the lined glass by a signal of the obtained density, the net or the lined glass is imaged by a plurality of area cameras provided on the opposite side to the light source with the net or the lined glass interposed therebetween, After the binarization processing of the captured image data, by performing a predetermined number of times of contraction processing for erasing one pixel around the entire dark signal portion, only the dark signal corresponding to the mesh or line is deleted, and the remaining dark signal is defective. And determining the size, position, etc., based on the image data.
This is a method for detecting defects in a screened glass. Alternatively, according to the present invention , instead of the area camera, a plurality of line cameras that scan in the width direction of the net or lined glass to be conveyed are arranged, and the line camera synchronizes with the conveying speed of the net or lined glass. The captured signal is stored and retained to form two-dimensional image data, and a predetermined number of times of contraction processing for erasing the entire periphery of the dark signal portion by one pixel eliminates only the dark signal corresponding to a net or a line, thereby removing the remaining signal. Defect detection using a dark signal as a defect and determining its size, position, etc. based on image data
Is the way. Alternatively, the present invention collects the light signal portion.
When using an image processing device for shrinking,
After binarizing the image signal of the Las defect detection method,
A method of shrinking a line part and a defect part as a dark signal
Instead of the negative / positive reversal before shrinking,
Minute and defective parts are light signals, and normal parts of glass are thick signals
After the shrinkage process, shrinkage processing is performed to
The light signal portion of the minute
This is a method for detecting defects in screened glass. Alternatively,
The present invention provides a light source that projects light on a ribbon-shaped net or lined glass that is continuously conveyed, and is provided on the opposite side of the light source with the net or lined glass interposed, and images the net or lined glass. A plurality of area cameras, image processing means for processing image data obtained by the area camera, and a net or lined glass defect detection device comprising detection control means for determining a defective portion based on the image data, The detection control means performs a predetermined number of times of contraction processing for erasing the entire periphery of the dark signal portion by one pixel after binarizing the image data, thereby erasing only the dark signal corresponding to a net or a line. Characterized in that it has a function of determining the size, position, etc. of the dark signal as a defect based on the image data.
It is a place . Alternatively, according to the present invention , instead of the area camera, a plurality of line cameras that scan in the width direction of the net or lined glass to be conveyed are arranged, and the line camera synchronizes with the conveyance speed of the net or lined glass. The above-described defect detection apparatus for a glass-screened glass, comprising: a storage device that stores and holds a signal fetched and makes two-dimensional image data.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for manufacturing a glass sheet having a ribbon-like mesh, which is continuously conveyed, and which contains defects such as bubbles, devitrification, sagging, etc. ,
This is to detect defects due to undissolved material such as gravel.

The structure is as described above, but a planar light source is provided below the netted glass to be conveyed, and a plurality of light sources are provided above the light source on the opposite side of the light source with the netted glass therebetween. Area cameras (two-dimensional cameras) are arranged in a line, light is emitted from the light source to the netted glass, the netted glass is imaged by the plurality of area cameras, and light such as mesh lines and defects are not transmitted. Black part, white part that transmits light,
A part that transmits light only partially is a gray part, for example, 25.
An image signal of six gradation levels is obtained and taken into the image processing device.

The image processing apparatus sets captured image data at a predetermined luminance level (slice level) as a boundary, sets a pixel portion darker than the slice level to a dark level (1), and a pixel portion brighter than the slice level to a light level (1). 0) is performed.

After the binarization processing, a predetermined number of times of contraction processing for erasing the entire periphery of the dark signal portion by one pixel is performed, and only the dark signal corresponding to the halftone is erased. Since the defective portion consisting of the number of pixels remains for some pixels without being erased, the remaining dark signal is regarded as a defect, the size of the defect is estimated backward from the number of contractions, and the defect position and size are output and stored in a personal computer etc. Then, in a later step, the glass at the portion including the defective portion may be cut and removed.

The shrinking process is a well-known technique in an image processing apparatus, and is to erase the entire periphery of a dark signal portion or a light signal portion by one pixel. The size of the defect that can be detected is larger than the wire diameter of the mesh line, and depends on the size of the pixel in the field of view of the camera and the number of times of the shrinking process. Is determined by the wire diameter or the like.

As in the present invention, if a halftone line is removed by the contraction process of the image processing apparatus, complicated processing such as storing and processing a halftone pattern becomes unnecessary, and the halftone line is independent of the type of halftone line. Can be removed and the same logic can be used, so that the arithmetic processing speed can be increased.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for detecting a defect of netted glass according to the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a light source 4 such as a high-frequency fluorescent lamp housed in a box for detecting a defect 3 is disposed below a netted glass 1 continuously conveyed in a ribbon shape in the direction of an arrow. The inspection width is set slightly larger than the entire width of the netted glass in order to image the entire width of the netted glass 1 above the netted glass 1, and the inspection width is divided to divide the area of a plurality of CCD cameras and the like. The cameras 5, 5, ... are arranged in a line.

An image signal output from each of the area cameras 5, 5,... Is input to an image processing device 6, and the image processing device 6 removes the image signal representing the reticulated line 2, and outputs Only the image signal representing the defect 3 is output, and signals such as the defect position and size are output to the personal computer 7 or the like.

The procedure for removing the portion of the reticulated line 2 and detecting the defect 3 by the image processing apparatus 6 will be described in further detail. A plurality of area cameras 5, 5,... Capture images of the screened glass 1 illuminated by the light source 4 provided below the screened glass 1, and output image signals to the image processing device 6. The grayscale signal of 256 gradations input to the image processing device 6 is binarized by the image processing device 6 to be either a dark signal (1) or a light signal (0). In the binarization process, it is compared whether the signal level of the luminance is greater than a predetermined value (slice level) for each pixel, and when it is larger, it is displayed as a light signal, and when it is smaller, it is displayed as a dark signal, as shown in FIG. As described above, the net and the defective portion are displayed as dark signals filled in black.

Although there is a difference depending on the resolution of the camera 5, if the size of one pixel is 0.5 mm and the wire diameter of the mesh inserted into the glass is 0.42 to 0.64 mmφ, the mesh 2 Is 1-2 pixels, the intersection of the mesh lines 2 is about 4 pixels, and the detectable defect is about 5 pixels or more in both the vertical and horizontal directions.

As for the contraction processing by the image processing device 6, as shown in FIG. 5, once the contraction processing is performed on the pixel of the dark signal which is the defect 3 which represents the shaded portion and the black portion, The dark signal pixels at the boundary between the dark signal pixels and the light signal pixels, that is, the pixels at the lower left diagonal lines around the entire area are converted to light signals and disappear, and only the pixel portions painted black and the lower right diagonal lines are removed. Remains.

Now, when the image processing apparatus 6 performs the contraction processing once on the image data as shown in FIG. 2, the result becomes as shown in FIG. Each becomes thinner or smaller. In one contraction process, a dark signal may remain at the intersection of the halftone line 2, so it is necessary to perform the contraction process twice to reliably remove the halftone portion.

FIG. 4 is a view in which the second shrinking process has been performed, and shows a state in which the portion of the mesh line 2 has been removed and only the portion of the defect 3 remains. The reason why the number of times of the contraction processing is set to two in this embodiment is that there is a case where a dark signal pixel remains in the cross portion of the mesh line 2. As a result, the dark signal portion of the portion of the mesh line 2 becomes thin, and the portion of the mesh line 2 is removed even by one contraction process. Therefore, the number of times of contraction processing may be appropriately selected depending on the size of the pixel, the diameter of the line, the size of the defect 3 to be detected, the aperture of the camera, and the like.

As described above, the netted glass 1 and the portion of the netted wire 2 of the lined glass are removed to detect defects in the glass, but the present invention is not limited to this. An area camera (two-dimensional camera) 5 was used as the camera, but a line camera was used to scan in the width direction of the netted glass 1 and a signal taken in accordance with the conveyance of the netted glass 1 was stored and stored in a memory. If the image data is two-dimensional, the area camera 5
Can be performed in the same manner as the above processing.

When a line camera is used, the scanning width can be widened with the same resolution, so that the number of cameras can be reduced. Also, the light source 4 can be moved in the scanning direction of the line camera in the width direction of the netted glass 1. Since it may be provided on a straight line, it can be simplified.

After binarizing the image signals picked up by the area cameras 5, 5,..., The portion of the reticulated line 2 and the portion of the defect 3 are contracted as dark signals. A method of shrinking the light signal portions of the portion of the mesh line 2 and the defect 3 by performing shrinkage processing after making the portion of the mesh line 2 and the portion of the defect 3 a light signal and making the normal portion of the glass a dark signal. But it is good. Depending on the type of the image processing device 6, the contraction processing command may cause the light signal portion to contract, and may be appropriately performed as needed.

In the above description, the contraction process of the dark signal portion or the light signal portion has been described. However, the dark signal portion and the light signal portion may be reversed and expressed as expansion processing. The defect 3 detected as described above is further subjected to a calculation process usually called labeling, and information such as the position of the defect 3 and the number of detected pixels is output and stored in the personal computer 7 or the like. Estimating the size of the actual defect from the size, and cutting and removing the glass including the portion determined as the defect 3 based on the instruction control of the personal computer 7 or the like in a later process, or processing the glass into various management information. Can also.

[0027]

According to the present invention, the reticulated portion is removed by the same algorithm by shrinking the image of the reticulated glass or the lined glass regardless of the pattern type of the reticulated glass or the lined glass. It is possible to reliably detect defects in the glass.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of an inspection apparatus according to the present invention.

FIG. 2 is a diagram showing a binarized image signal obtained by imaging a part of netted glass;

FIG. 3 is a diagram showing a state in which a contraction process has been performed on the image signal of FIG. 2;

FIG. 4 is a diagram showing a state in which a contraction process is further performed on the image signal of FIG. 3;

FIG. 5 is a diagram illustrating a contraction process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Netted glass 2 Netting 3 Defect 4 Light source 5 Area camera 6 Image processing device 7 Personal computer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-114432 (JP, A) JP-A-6-347410 (JP, A) JP-A-6-148100 (JP, A) JP-A-6-148100 18432 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/958 C03B 13/12

Claims (5)

(57) [Claims] 1. A plurality of area cameras provided by projecting light from a light source onto a ribbon-shaped net or lined glass which is continuously conveyed, and provided on the opposite side of the light source with the net or lined glass interposed therebetween. In the method of imaging the net or the lined glass by using the obtained grayscale signal and inspecting the net or the lined glass, after binarizing the captured image data, the entire periphery of the dark signal portion is equivalent to one pixel. By performing a predetermined number of contraction processes for erasing, only the dark signal corresponding to the screen or line is erased, and the remaining dark signal is regarded as a defect, and based on the image data,
A method for detecting a defect in a netted glass, comprising determining its size, position, and the like. 2. In place of the area camera, a plurality of line cameras for scanning in the width direction of the net or lined glass to be conveyed are arranged, and the line cameras are synchronized with the conveying speed of the net or lined glass. The captured signal is stored and retained to form two-dimensional image data, and a predetermined number of times of contraction processing for erasing the entire periphery of the dark signal portion by one pixel eliminates only the dark signal corresponding to a mesh or a line, and the remaining signal remains. A method for detecting a defect in a screened glass, wherein a size, a position, and the like of the dark signal are determined based on image data. 3. An image processing apparatus for contracting a light signal portion is used.
If there is, the lack of the netted glass according to claim 1 or 2
After binarizing the image signal of the defect detection method,
Instead of shrinking the defective part as a dark signal
Before shrinking, reverse the negative / positive
The light spot signal is used for the inflected part and the dark signal is used for the normal part of the glass.
After the shrinkage process, the shaded area
Shrink the signal part
Defect detection method. 4. A light source for projecting light onto a ribbon-shaped net or lined glass that is continuously conveyed, and a light source that is provided on the opposite side of the light source with the net or lined glass interposed therebetween. A plurality of area cameras for imaging, and image processing means for processing image data obtained by the area camera,
In a net or line defect detecting apparatus for detecting a defect in a net or a lined glass, the detecting control means erases the entire periphery of the dark signal portion by one pixel after binarizing the image data. A function of deleting only a dark signal corresponding to a screen or a line by performing a predetermined number of times of contraction processing, and a function of determining a size, a position, and the like of the remaining dark signal based on image data as a defect. A defect detection apparatus for a glass-screened glass, comprising: 5. In place of the area camera, a plurality of line cameras for scanning in the width direction of the net or lined glass to be conveyed are arranged, and the line cameras are synchronized with the conveying speed of the net or lined glass. 5. The apparatus according to claim 4, further comprising a storage device that stores and retains the captured signal to generate two-dimensional image data.