JP2001208702A - Method and apparatus for inspecting defects - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for inspecting defects, capable of detecting the defects with good sensitivity by preventing halation. SOLUTION: A predetermined region of plate glass 11 is irradiated with inspection light from a light source and the diffused and reflected light from the predetermined region is received by a line CCD camera 13 arranged at a position shifted from the optical axis Lr of the regularly reflected light from the predetermined region. The light applied to the line CCD camera 13 from the light source 12 to cause halation is cut off by the shading plate 14 arranged on the segment X connecting the virtual image 12' of the light source 12 and the line CCD camera 13 between the plate glass 11 and the line CCD camera 13. The angle formed by the sight axis 13c of the line CCD camera 13 and the optical axis Lr of the regularly reflected light is 3-20 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method and a defect inspection apparatus for inspecting an object to be inspected such as a sheet glass for defects such as scratches and bubbles.

[0002]

2. Description of the Related Art Conventional defect inspection methods of this kind include:
The following are known. A predetermined area of the inspection object is irradiated with the inspection light, and the diffuse reflection light (or diffuse transmission light) from the predetermined area is reflected from the optical axis of the regular reflection light (or regular transmission light) from the predetermined area. The light is received by the light receiving means disposed at the deviated position. Here, the diffusely reflected light (or diffusely transmitted light) is generated by the inspection light being scattered, diffracted, or refracted due to a defect existing in the predetermined region. Therefore, it is possible to determine whether or not there is a defect in the predetermined area based on the diffuse reflection light (or diffuse transmission light) received by the light receiving unit.

[0003]

However, in the above-described conventional defect inspection method, there is a case where light applied from the light source to the light receiving means is incident on the light receiving means to cause halation. When halation occurs, it becomes difficult to detect diffused reflected light (or diffuse transmitted light) with a small amount of light due to a minute defect separately from halation, so that the defect can be detected with high sensitivity. There was a problem that you can not.

[0004] The present invention has been made by focusing on the problems existing in the prior art as described above. An object of the present invention is to provide a defect inspection method and a defect inspection apparatus which can detect a defect with high sensitivity while preventing halation.

[0005]

According to a first aspect of the present invention, there is provided a defect inspection method for irradiating a predetermined area of an inspection object with a test light from a light source. In the defect inspection method, the diffuse reflection light from the area is received by the light receiving means disposed at a position off the optical axis of the regular reflection light from the predetermined area. The gist of the invention is that the light that causes the above is blocked by a light shielding unit disposed on a line connecting the virtual image of the light source and the light receiving unit and disposed between the inspection object and the light receiving unit.

According to a second aspect of the present invention, there is provided a defect inspection method comprising:
Irradiate inspection light from a light source to a predetermined area of the inspection object,
In a defect inspection method in which diffused transmitted light from the predetermined area is received by light receiving means disposed at a position off the optical axis of regular transmitted light from the predetermined area, the light receiving means irradiates the light receiving means from the light source. In this case, light that causes halation is blocked by a light-blocking means provided on a line connecting the light source and the light-receiving means.

[0007] The defect inspection method according to the third aspect of the present invention comprises:
In the invention described in claim 1 or 2, the gist is that the angle between the light receiving axis of the light receiving means and the optical axis of the regular reflected light or the optical axis of the regularly transmitted light is 3 to 20 °.

According to a fourth aspect of the present invention, there is provided a defect inspection apparatus comprising:
A light source for irradiating inspection light on a predetermined area of the inspection object, and a light receiving element disposed at a position off the optical axis of the regular reflection light from the predetermined area and receiving diffuse reflection light from the predetermined area Means for blocking light that is emitted from the light source to the light receiving means and causes halation, on a line connecting the virtual image of the light source and the light receiving means, and receiving light from the inspection object. The gist is that it is provided at a position between the means.

According to a fifth aspect of the present invention, there is provided a defect inspection apparatus comprising:
A light source for irradiating a predetermined area of the inspection object with the inspection light, and a light receiver disposed at a position off the optical axis of the regular transmission light from the predetermined area and receiving diffuse transmission light from the predetermined area And light blocking means for blocking light which is emitted from the light source to the light receiving means and causes halation is provided on a line connecting the light source and the light receiving means.

[0010] The defect inspection apparatus of the invention according to claim 6 is
In the invention according to claim 4 or 5, the gist is that an angle between the light receiving axis of the light receiving means and the optical axis of the regular reflected light or the optical axis of the regular transmitted light is 3 to 20 °.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a defect inspection apparatus according to the first embodiment. This defect inspection apparatus is an apparatus for inspecting whether or not there is a defect such as a scratch on the surface 11a of the plate glass 11 as an inspection object.

The glass sheet 11 is set on a defect inspection device with its front surface 11a facing upward, and is conveyed leftward or rightward in FIG. 1 by a conveyance device (not shown).

A light source 12 is provided above the glass plate 11. The light source 12 is constituted by a plurality of fiber illuminations linearly arranged in a direction perpendicular to the plane of FIG. Then, inspection light is applied to a predetermined region of the surface 11a of the sheet glass 11 at a predetermined incident angle (acute angle) θ1. The predetermined area has a linear shape extending in a direction perpendicular to the paper surface of FIG. 1 and has a length corresponding to the width of the sheet glass 11 (dimensions in a direction perpendicular to the paper surface of FIG. 1).

Above the plate glass 11, a line CCD camera 13 (hereinafter abbreviated as camera 13) as a light receiving means is also provided. The camera 13 includes a light source 12
Is arranged at a position deviated from the optical axis Lr of the light (specular reflection light) specularly reflected in the predetermined area, so as to image the predetermined area. For this reason, the specularly reflected light does not enter the camera 13, and only the light (diffuse reflected light) which is diffusely reflected by the inspection light scattered or diffracted due to the defect in the predetermined area is incident. .

A light-shielding plate 14 as light-shielding means is disposed on a line X connecting the virtual image 12 ′ of the light source 12 and the camera 13 and between the sheet glass 11 and the camera 13. Has been established. Furthermore, this light shielding plate 14
It is arranged near the predetermined area. The light shielding plate 1
Numeral 4 is for blocking light that is emitted from the light source 12 to the camera 13 and causes halation, and is characterized in that it has a property of blocking light and has a low surface reflectance. And In the present embodiment, an iron plate covered with a black matte coating film is used as the light shielding plate 14,
It is not limited to that. The edge of the shading plate 14,
In particular, when the light shielding plate 14 is installed at the above position, a portion which is close to the optical axis Lr of the regular reflection light is formed smoothly so as not to irregularly reflect the light.

The magnitude of the incident angle θ1 is determined by
1, the light source 12, the camera 13, the light-shielding plate 14 and the like may be set within a range where they can be installed so as not to interfere with each other, and is preferably set to 5 to 85 °, more preferably 55 to 75 °, and further preferably about 68 °. You. This incident angle θ1 is 5
When the angle is less than °, the light source 12 and the plate glass 11 may interfere with each other, which is not preferable. Conversely, if the angle exceeds 85 °, light source 1
2 and the camera 13 may interfere with each other, which is not preferable. In particular, when the incident angle θ1 is extremely large when the inspection object has light transmittance like the sheet glass 11, most of the inspection light is transmitted through the inspection object, and the reflected light is correspondingly increased. Inspection performance may be reduced due to the decrease. Conversely, when the incident angle θ1 is extremely small, one defect on the front surface 11a may be counted as two when reflected on the rear surface 11b.

The diffuse reflection light is emitted from the predetermined region as a light beam having a predetermined solid angle around the optical axis Lr of the regular reflection light. Looking at the light amount distribution, the light amount increases as the light axis approaches the optical axis Lr of the specularly reflected light, and the optical axis Lr
The shape is such that the light amount decreases as the distance from the camera increases. For this reason, it is preferable that the camera 13 is disposed at a position as close as possible to the optical axis Lr of the specularly reflected light. Specifically, the angle (acute angle) θ2 between the visual axis 13a as the light receiving axis of the camera 13 and the optical axis Lr of the specularly reflected light is 3 to 20
°, preferably about 7 °. If the angle θ2 is less than 3 °, it is not preferable because the installation of the light shielding plate 14 becomes difficult. Conversely, if the angle exceeds 20 °, the amount of diffuse reflected light incident on the camera 13 becomes small, so that the defect detection sensitivity may be reduced.

When performing a defect inspection using this defect inspection apparatus, first, the sheet glass 11 is set in the defect inspection apparatus with the surface (surface 11a) desired to be inspected facing upward. Then, while the plate glass 11 is conveyed to the left or right in FIG. 1 by the conveyance device, the plate glass 11 is irradiated with inspection light from the light source 12, and an area irradiated with the inspection light is imaged by the camera 13.

Normally, the inspection light is applied to the surface 11a of the plate glass 11.
When the surface 11a has a defect, the inspection light is scattered or diffracted by the defect and enters the camera 13. For this reason, the camera 13 detects the defect as a bright portion having a luminance corresponding to the light amount. Further, light that is emitted from the light source 12 to the camera 13 and causes halation is blocked by the light shielding plate 14 and does not enter the camera 13. Therefore, the light is not detected by the camera 13 and halation is prevented.

As described above, according to the first embodiment, the following effects are exhibited. Since the light that is emitted from the light source 12 to the camera 13 and causes halation is blocked by the light-shielding plate 14, the occurrence of halation can be prevented. For this reason, the diffuse reflection light with a small amount of light originating from a minute defect can also be captured by the camera 13.
Thus, even a minute defect can be detected with high sensitivity.

By setting the angle θ2 between the visual axis 13a of the camera 13 and the optical axis Lr of the specularly reflected light to 3 to 20 °, the installation of the light-shielding plate 14 is facilitated, and the camera is caused by defects. The amount of the diffuse reflection light incident on the light source 13 can be increased. For this reason, the detection sensitivity can be further improved.

When the light shielding plate 14 is installed, the light shielding plate 1
Care must be taken so that the light 4 does not block the inspection light from the light source 12 and does not block the diffuse reflection light entering the camera 13 from the predetermined area. That is, it is essential that the light shielding plate 14 does not overlap the optical axis Li of the inspection light or the visual axis 13a of the camera 13. Since the distance between the visual axis 13a and the line segment X is maximum near the predetermined area,
By providing a light-shielding plate at that position, the possibility that the light-shielding plate 14 overlaps the visual axis 13a can be reduced. In addition, the light-shielding plate 14 is disposed so that the angle formed between the optical axis Li and the visual axis 13a is almost equally divided into two.
4 can be less likely to overlap the optical axis Li and the visual axis 13a.

Since the defect inspection is performed using the reflected light on the surface 11a of the sheet glass 11, the defect existing on the surface 11a can be selectively detected. (Second Embodiment) The second embodiment of the present invention
The description will focus on the differences from the embodiment.

FIG. 2 is a conceptual diagram showing a defect inspection apparatus according to the second embodiment. This defect inspection device determines whether the front surface 11a and the rear surface 11b of the sheet glass 11 have defects such as scratches,
This is a device for simultaneously inspecting the inside of a sheet glass for defects such as bubbles.

In the defect inspection apparatus according to the second embodiment, the light source 12 is disposed below the plate glass 11. Then, inspection light is emitted from the rear surface 11b side to a predetermined region of the plate glass 11 at a predetermined incident angle (acute angle) θ3.

The camera 13 is located above the glass sheet,
In addition, the inspection light from the light source 12 is disposed at a position deviated from the optical axis Lt of the light (specularly transmitted light) that has transmitted through the predetermined area. For this reason, the specularly transmitted light does not enter the camera 13, and the inspection light is scattered due to a defect in the predetermined area.
Only light that is diffracted or refracted and diffusely transmitted (diffuse transmitted light) is incident.

Further, a light-shielding plate 14 for blocking light which is emitted from the light source 12 to the camera 13 and causes halation.
Are arranged on a line segment Y connecting the light source 12 and the camera 13.

The size of the incident angle θ3 is determined by the plate glass 1
1, the light source 12, the camera 13, the light shielding plate 14 and the like may be set within a range where they can be installed so as not to interfere with each other, and are preferably set to 10 to 90 °, more preferably to 70 to 90 °, and further preferably to about 83 °. You. If the incident angle θ3 is less than 10 °, the light source 12 and the plate glass 11 may interfere with each other, which is not preferable. In particular, when the incident angle θ3 is extremely small when the inspection target has light reflectivity like the glass sheet 11, most of the inspection light is reflected on the surface of the inspection target, and the transmitted light is reduced. Inspection performance may be reduced due to the decrease.

The diffuse transmitted light is emitted from the predetermined region as a light beam having a predetermined solid angle centered on the optical axis Lt of the regular transmission light. Looking at the light amount distribution, the closer to the optical axis Lt of the specularly transmitted light, the larger the light amount becomes.
The shape is such that the light amount decreases as the distance from the camera increases. For this reason, the camera 13 is preferably disposed at a position as close as possible to the optical axis Lt of the specularly transmitted light. Specifically, the visual axis 13a of the camera 13 and the optical axis Lt of the specularly transmitted light
(Acute angle) θ4 is preferably 3 to 20 °, more preferably about 7 °. If the angle θ4 is less than 3 °, it is difficult to install the light shielding plate 14, which is not preferable. Conversely, if it exceeds 20 °, camera 1
Since the amount of diffuse transmitted light incident on 3 becomes smaller,
There is a possibility that the detection sensitivity of the defect is reduced.

When a defect inspection is performed using this defect inspection apparatus, the sheet glass 11 is conveyed by the conveyance device as in the first embodiment, and the light source 1 is applied to the sheet glass 11.
The inspection light is irradiated from step 2, and the area irradiated with the inspection light is imaged by the camera 13.

Normally, the inspection light is transmitted through the plate glass 11 normally. If there is a defect on the front surface 11a, the back surface 11b or inside thereof, the inspection light is scattered, diffracted or refracted by the defect and enters the camera 13. . For this reason, the camera 13 detects the defect as a bright portion having a luminance corresponding to the light amount. Further, light that is emitted from the light source 12 to the camera 13 and causes halation is blocked by the light shielding plate 14 and does not enter the camera 13. Therefore, the light is not detected by the camera 13 and halation is prevented.

As described above, according to the second embodiment, the following effects are exhibited. Since the light that is emitted from the light source 12 to the camera 13 and causes halation is blocked by the light-shielding plate 14, the occurrence of halation can be prevented. For this reason, the diffused transmitted light having a small light amount due to a minute defect is also transmitted to the camera 13.
Thus, even a minute defect can be detected with high sensitivity.

By setting the angle θ4 between the visual axis 13a of the camera 13 and the optical axis Lt of the specularly transmitted light to 3 to 20 °, the installation of the light-shielding plate 14 is facilitated, and the camera is caused by defects. The amount of the diffuse transmission light incident on the light source 13 can be increased. For this reason, the detection sensitivity can be further improved.

When the light shielding plate 14 is installed, the light shielding plate 1
Care must be taken so that the inspection light 4 does not block the inspection light from the light source 12 and does not block the diffuse transmission light entering the camera 13 from the predetermined area. That is, it is essential that the light shielding plate 14 does not overlap the optical axis Li of the inspection light or the visual axis 13a of the camera 13. Since the distance between the optical axis Li of the inspection light and the line segment Y and the distance between the visual axis 13a and the line segment Y are both maximum in the vicinity of the predetermined area, a light-shielding plate is installed at that position. By doing so, the possibility that the light-shielding plate 14 overlaps the optical axis Li or the visual axis 13a can be reduced. Further, by arranging the light-shielding plate 14 so as to divide the angle between the optical axis Li and the visual axis 13a into approximately two equal parts, the possibility that the light-shielding plate 14 overlaps the optical axis Li and the visual axis 13a is further reduced. Can be.

Since defect inspection is performed using transmitted light transmitted through the glass sheet 11, the surface 1 of the glass sheet 11
1a, the back surface 11b and the defect existing inside can be detected simultaneously.

The above embodiments can be modified as follows. In the above embodiments, the plate glass 11 is used as the inspection object.
However, in the case of the first embodiment, there is no particular limitation as long as the surface has a flat or substantially flat shape and can reflect the inspection light emitted from the light source 12. In the case of the second embodiment, there is no particular limitation as long as it has a plate-like or sheet-like form and can transmit the inspection light emitted from the light source 12. Specifically, a plate or sheet made of metal or synthetic resin, a silicon wafer, or the like may be used, and if any of them can reflect inspection light, the method and apparatus of the first embodiment may be applied. The method and the apparatus according to the second embodiment can be applied as long as the inspection light can be transmitted.

A halogen lamp may be used as the light source 12, or a laser light source for irradiating spot-shaped laser light may be used. A two-dimensional CCD camera, image pickup tube, photomultiplier tube, photodiode, or the like may be used as the light receiving means.

Next, the technical ideas that can be grasped from the above embodiment will be described below. (A) The defect inspection method according to any one of claims 1 to 3, wherein the light shielding means is a light shielding plate. With such a configuration, light that causes halation can be blocked with a simple configuration.

(A) The light shielding means is arranged near the predetermined area.
And the defect inspection method according to any one of the above (A). With this configuration, it is possible to reduce the possibility that the light shielding unit overlaps the light receiving axis of the light receiving unit, and it is possible to easily install the light shielding unit.

(C) The light-shielding means is a light-shielding plate, and the light-shielding plate is disposed at a position at which an angle between the optical axis of the inspection light and the light-receiving axis of the light-receiving means is substantially bisected. The defect inspection method according to any one of claims 1 to 3, and (a) and (c). With this configuration, it is possible to reduce the possibility that the light shielding plate overlaps the optical axis of the inspection light and the light receiving axis of the light receiving means, and it is possible to easily install the light shielding means.

[0042]

The present invention is configured as described above, and has the following effects. According to the defect inspection method according to the first and second aspects of the present invention, a defect can be detected with high sensitivity while preventing halation.

According to the defect inspection method of the third aspect of the present invention, the detection sensitivity can be further improved in addition to the effects of the first or second aspect of the present invention. According to the defect inspection apparatus of the invention described in claims 4 and 5,
Defects can be detected with high sensitivity by preventing halation.

According to the defect inspection apparatus of the invention described in claim 6, in addition to the effects of the invention described in claim 4 or 5, the detection sensitivity can be further improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a defect inspection apparatus according to a first embodiment.

FIG. 2 is a conceptual diagram illustrating a defect inspection apparatus according to a second embodiment.

[Explanation of symbols]

11: plate glass as inspection object, 12: light source, 1
2 ': virtual image of light source, 13: line CC as light receiving means
D camera, 13a: visual axis as light receiving axis, 14: light shielding material as light shielding means, Lr: optical axis of regular reflection light, Lt: optical axis of regular transmission light, X: linking virtual image of light source and light receiving means line segment,
Y: line segment connecting the light source and the light receiving means, θ2: angle formed between the light receiving axis of the light receiving means and the optical axis of the specularly reflected light, θ4: angle formed between the light receiving axis of the light receiving means and the optical axis of the specularly transmitted light.

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Claims (6)

[Claims] An inspection light is emitted from a light source to a predetermined area of an inspection object, and diffused reflected light from the predetermined area is shifted from an optical axis of regular reflection light from the predetermined area. In the defect inspection method of receiving light with the light receiving means provided, light irradiating the light receiving means from the light source and causing halation is disposed on a line connecting the virtual image of the light source and the light receiving means, and the inspection is performed. A defect inspection method characterized in that the light is shielded by a light shielding means provided between the object and the light receiving means. 2. A method according to claim 1, further comprising: irradiating inspection light from a light source onto a predetermined region of the inspection object, and diffusing and transmitting light from the predetermined region to a position deviated from an optical axis of regular transmission light from the predetermined region. In the defect inspection method in which light is received by a light receiving unit provided, light that is emitted from the light source to the light receiving unit and causes halation is blocked by a light blocking unit provided on a line connecting the light source and the light receiving unit. A defect inspection method characterized in that: 3. An angle between a light receiving axis of the light receiving means and an optical axis of specularly reflected light or an optical axis of specularly transmitted light is set to 3 to 20 °. Defect inspection method. 4. A light source for irradiating a predetermined region of an inspection object with inspection light, and a diffuse reflection from the predetermined region which is disposed at a position off the optical axis of regular reflection light from the predetermined region. Light-receiving means for receiving light, a light-shielding means for blocking light that is emitted from the light source to the light-receiving means and causes halation, on a line connecting the virtual image of the light source and the light-receiving means, and A defect inspection apparatus provided at a position between an inspection object and light receiving means. 5. A light source for irradiating a predetermined area of an inspection object with inspection light, and a light source disposed at a position off the optical axis of regular transmission light from the predetermined area and diffusing and transmitting from the predetermined area. Light receiving means for receiving light, and light shielding means for blocking light which is emitted from the light source to the light receiving means and causes halation is provided on a line connecting the light source and the light receiving means. Defect inspection equipment. 6. An angle between a light receiving axis of the light receiving means and an optical axis of specularly reflected light or an optical axis of specularly transmitted light is set to 3 to 20 °. Defect inspection equipment.