JP2001141662A - Method and apparatus for detecting flaw of transparent plate-shaped object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that it is difficult to detect a very fine flaw called a hairline as an image, because the intensity of the light scattered from a flaw depends on the size and shape of the flaw and the intensity of light scattered from the vary fine flaw is weak. SOLUTION: In a method for detecting the flaw of a transparent plate-shaped object by irradiating the transparent plate-shaped object with light to use transmitted light, scattered light is allowed to be incident on the transparent plate- shaped object to photograph the transparent plate-shaped object by a CCD camera, and the shading plate movable on the straight line connecting a light source and the CCD camera is provided between the CCD camera and the transparent plate-shaped object to prevent the direct incidence of the light from the light source on the CCD camera.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a transparent plate such as a glass plate or a transparent plastic plate and the inspection of defects in secondary processing.

[0002]

2. Description of the Related Art A method of inspecting a sheet glass for defects by irradiating the sheet glass with light and transmitting light through the sheet glass or light reflected on the surface of the sheet glass utilizes the fact that light is scattered by the defects. . Since the light is scattered at the defect, the part becomes a secondary light source of light, and it is possible to capture the part as an image with a camera, and where there is no defect, the light is not scattered, so that no image is formed. Only defects are formed in the image as images.

[0003]

The intensity of light scattered by a defect depends on the size and shape of the defect. In a very minute flaw such as a hairline, the scattered light is weak, and Was difficult to detect.

In order to detect such minute defects,
Using a high-intensity lamp and a cylindrical lens, the transparent plate is illuminated in a strip shape, and the difference between scattered light and stray light due to the defect is increased to detect the defect. In order to increase the brightness, the brightness of the light source must be increased, and the light source section becomes high in heat. Therefore, there is a disadvantage that the apparatus becomes large-scale in consideration of the heat resistance of the lens.

[0005]

The inspection method according to the present invention is directed to a method for detecting a defect in a transparent plate using light transmitted through the transparent plate, wherein scattered light is incident on the transparent plate. ,
The transparent plate is photographed with a CCD camera, and a light-shielding plate is provided between the CCD camera and the transparent plate that is movable on a straight line connecting the light source and the CCD camera, so that light from the light source is directly incident on the camera. This is a defect detection method characterized in that it is not performed.

Further, the above-mentioned defect detecting method is characterized in that an illuminance distribution correction process, a binarization process, and a shape process are performed on an image photographed by a CCD camera to detect a defect of a transparent plate-like body. .

Further, an illuminator for illuminating the transparent plate in a strip shape and a CC disposed on a perpendicular line connecting the illuminator and the transparent plate.
A detection device for use in the above-described defect detection method, comprising: a D camera; and a light shielding plate disposed on a line connecting the CCD camera and the illuminator between the CCD camera and the transparent plate. .

[0008]

In the method of detecting a defect by the scattered light of the defect, the defect is illuminated from all directions by using the scattered light in order to detect all fine linear defects. Among the defects illuminated by the scattered light, the scattered light due to the defect has a strong light traveling in almost the same direction as the direction of the illumination light. Therefore, C
If the optical system is configured to directly view the light source with a CD camera, a large amount of scattered light from a defect can be detected. However, in this optical system, since the light from the light source also directly enters the CCD camera, the background of the image photographed by the CCD camera is too bright and the detection of a defect is hardly possible.

To prevent the light from the light source from being directly incident on the CCD camera, there is a method in which a part of the light from the light source is incident on the plate-like body by using a slit. However, it is close to a line connecting the opening of the slit and the light source. However, it is very difficult to image scattered light from minute defects such as scratches, so the position of the light source and the position of the CCD camera must be adjusted by trial and error, and the scattering from the defects is also difficult. Light tends to propagate through the defect like a light guide, and illuminating only a part of the defect reduces the aforementioned effects, reduces the amount of scattered light of the defect and has some disadvantages that do not affect detection .

The method of the present invention in which a light-shielding plate is provided between a transparent plate and a CCD camera eliminates the above-mentioned problems, can detect a large amount of scattered light from the defects, and can block light from a light source. This is an effective method that can detect fine defects without fail.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A transparent plate-like body is illuminated from below or above a transparent plate-like body using an illuminator.

Light sources such as a halogen lamp, a xenon lamp, a high-pressure mercury lamp, and a sodium lamp are used for the illuminator.
The light from the light source is shielded, or the plate-shaped or rod-shaped light guide is used to illuminate the transparent plate-like body in a band-like manner. The light incident on the transparent plate is made to be a scattered light by using a diffuser such as frosted glass or by subjecting the exit side of the light guide to an uneven treatment. Further, a rod-shaped fluorescent lamp may be used as the light source.

The illuminated portion of the transparent plate is photographed by a CCD camera installed on the side opposite to the illuminator of the transparent plate. The CCD camera, the transparent plate and the light source are arranged on a straight line. A light-shielding plate is provided between the transparent plate and the CCD camera, and the light-shielding plate moves on a straight line connecting the light source and the CCD camera so that light from the light source does not directly enter the CCD camera. Adjust the amount of light incident on. In order to increase the luminance of the defect, it is desirable that the light-shielding plate is located at a position close to the transparent plate-like body, and in order to easily adjust the position of the light-shielding plate, the light source and the CCD camera connect the light source and the CCD camera. It is desirable that the lines are arranged at right angles to the transparent plate. Place the transparent plate horizontally, and arrange the CCD camera, light shield plate and illuminator vertically, or stand the transparent plate vertically, CCD camera,
The light shield and the illuminator are arranged horizontally.

In order to inspect the entire transparent plate, the transparent plate is fixed and the light source, the light shielding plate and the CCD camera are moved, or the light source, the light shielding plate and the CCD camera are fixed and the transparent plate is fixed. Move the plate.

The light shielding plate is preferably black in order to increase the difference in brightness from the defect image. Further, it is desirable that the end of the light-shielding plate has a knife-edge shape so that light is not scattered at the end of the light-shielding plate.

The CCD camera may be an ordinary camera,
In an image only in the vicinity of the light-shielding plate, the scattered light of the defect is strong. Therefore, it is preferable to perform data processing on the image only in the vicinity of the light-shielding plate, and use a line camera that captures only one scanning line. desirable.

It is desirable that a non-reflective black paint or the like be applied to a portion of the camera field of view other than the light source light emitting portion so that extra reflected light does not enter the camera.

When a line camera is used, the positional relationship between the light source, the optical axis of the camera, and the field of view is adjusted so as to observe the periphery or slightly away from the edge of the planar or rod-shaped light emitting portion. At this time, the direct light from the light source should hardly enter the camera light receiving unit, but a small amount of light actually enters.

In order to reduce this light, a method of further shifting the optical axis from the light emitting portion of the light source is conceivable. However, this is not desirable because the scattered light of the defect itself is reduced. Insert between the cameras to cut off extra light from the light source.

The image of the transparent plate-like object photographed by the CCD camera is subjected to illuminance adjustment processing, and then subjected to binarization processing of light and dark in accordance with the brightness of the image according to the resolution of the CCD camera. Further, the bright portion of the binarized data is shaped into a width and a length, and a defect recognition process is performed.

An image captured by a CCD camera is a CCD camera.
The data from the camera can be directly taken as image data into a computer such as a small personal computer or a medium-sized workstation, and image processing can be performed using a program pre-installed in the computer, or image processing can be performed between the CCD camera and the computer. An image processor may be used to perform illumination adjustment to binarization, and recognition processing as a defect due to shape may be performed by a procedure incorporated in a computer.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

First Embodiment FIGS. 1 and 2 are a schematic side view and a schematic plan view of an optical system according to a first embodiment.

The transparent plate 3 made of float glass having a thickness of 5 mm was illuminated from below by an illuminator 6, and the transparent plate 3 was photographed by the line camera 1. As the illuminator 6, an illuminator that spreads the light of a halogen lamp with a rod-shaped light guide and illuminates the transparent plate 3 in a band shape was used. With respect to the illumination range 5, the light-shielding plate 4 was arranged such that the edge of the light-shielding plate 4 became the center of the image captured by the line camera 1. Further, the position of the illuminator 6 was shifted from immediately below the line camera 1 so that the light from the illuminator 6 did not directly enter the line camera.

The illumination range 5 of the transparent plate 3 of the illuminator 6 is
The illuminator 6 was installed 300 mm below the transparent plate 3 so that the scattered light from the defect did not decrease, and the transparent plate 3 was illuminated in a band shape with a width of 200 mm.

The photographing by the line camera 1 is performed by the transparent plate 3
Was performed while moving, and the transparent plate-like body 3 seen near the edge of the light-shielding plate 4 was photographed in a line shape.

The linear image taken by the line camera 1 was subjected to illuminance adjustment processing and binarization processing by the image processor 10. The linear image processed by the image processor 10 was taken into a personal computer 11 and connected to the entire transparent plate to form a composite image 12 of the entire transparent plate as shown in FIG. In the composite image 12, the flaw 7 appears as a bright image in the image 9 of the transparent plate. Further, using the personal computer 11, shape analysis was performed on the width and length of the flaw 7 in the bright part, and the defect was recognized as a flaw.

In this embodiment, the composite image 1 shown in FIG.
The scratch defect 7 of No. 2 was detectable up to a width of about 50 μm.

Second Embodiment FIGS. 5 and 6 are a schematic side view and a schematic plan view of an optical system according to a second embodiment. An area camera 1 ′ is used as the CCD camera, and the center of the CCD camera 1 ′, the center of the light shielding plate 4, and the center of the illuminator 6 are arranged on a substantially straight line perpendicular to the transparent plate 3. This is similar to the first embodiment.

The area camera 1 'captures an image 12' as shown in FIG.
Appears. Since the defect is detected around the edge of the light-shielding plate 4, in this case, the transparent plate 3 is moved to photograph the required number of sheets capable of inspecting the entire transparent plate 3, and each photographed image 12 For ', the image processing apparatus 10 performed illuminance correction and binarization, and the personal computer 11 performed shape processing of the width and length of the flaw defect 7 to recognize the defect.

Also in this embodiment, the flaw 7 shown in FIG. 7 can be detected up to a width of about 50 μm.

[0032]

The method and apparatus for detecting a defect according to the present invention make it possible to detect a minute defect such as a hairline of a transparent plate which has been conventionally difficult.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an optical system according to a first embodiment.

FIG. 2 is a schematic plan view of the optical system according to the first embodiment.

FIG. 3 is a configuration diagram of an apparatus that analyzes an image captured by a CCD camera.

FIG. 4 is a diagram conceptually showing a defect of a flaw photographed in the first embodiment.

FIG. 5 is a schematic side view of an optical system according to a second embodiment.

FIG. 6 is a schematic plan view of an optical system according to a second embodiment.

FIG. 7 is a diagram conceptually showing a flaw of a flaw photographed in the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 CCD camera 1 ′ CCD line camera 2, 2 ′ shooting range 3 transparent plate 4 light shielding plate 5 illumination range 6 illuminator 7 scratch defect 8 shadow of light shielding plate 9 image of transparent plate 10 image processing device 11 personal computer 12 Composite image 12 'Image taken with area camera

Claims (3)

[Claims] In a method for detecting a defect of a transparent plate using light transmitted through the transparent plate, a scattered light having a plurality of points as a light source is incident on the transparent plate, and the light is transmitted to the transparent plate. CCD body
Take a picture with a camera, between the CCD camera and the transparent plate
A defect detection method, comprising: providing a light-shielding plate movable on a straight line connecting a light source and a CCD camera so that light from the light source does not directly enter the camera. 2. The defect according to claim 1, wherein an illuminance distribution correction process, a binarization process, and a shape process are performed on the image photographed by the CCD camera to detect a defect of the transparent plate. Detection method. 3. An illuminator for illuminating the transparent plate in a strip shape, a CCD camera arranged on a perpendicular line connecting the illuminator and the transparent plate, and a light source between the CCD camera and the transparent plate. The C
3. The detecting apparatus according to claim 1, comprising a CD camera and a light shielding plate arranged on a line connecting the illuminator.