JP2004309287A - Defect detection device and defect detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide s defect detection device and its method capable of detecting a defect without being influenced dependent on the angle of scattered light from the defect, when a line sensor is used as a light receiving means of the scattered light from the defect and an inspection object is a plate body conveyed in one direction. <P>SOLUTION: In this dark field type defect detection device equipped with a conveyance mechanism for conveying the plate inspection body in one direction, a linear illuminator and the line sensor, light irradiated from the linear illuminator is scattered by a defect existing on the plate body, and the scattered light is detected by the line sensor, to thereby detect the defect. The device is characterized by being equipped with at least two pairs of detection units arranged so that scanning directions of the linear illuminator and the line sensor are mutually parallel, and by arranging the detection units at different angles respectively with respect to the conveyance direction of the plate body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for detecting a defect such as a linear scratch present on a plate-like body conveyed in a certain direction, such as glass, metal, and film. In particular, the present invention relates to a defect detection device and a detection method for performing an appearance inspection in a glass plate manufacturing process.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, in a manufacturing process of a glass plate, the following technology has been applied to detect a defect existing in a plate-like body conveyed in a certain direction. First, light is irradiated on a glass plate to be inspected. Then, this is a technique for detecting scattered light generated from a defective portion. In the defect detection technique by detecting the scattered light, the scattered light is weak in a minute defect. Therefore, it is difficult to reliably detect a minute defect.
[0003]
As a countermeasure, for example, JP-A-2002-148206 discloses the following inspection apparatus. That is, in this apparatus, the transparent plate is irradiated with scattered light, and the transparent plate is photographed by a CCD camera. A slit-shaped light-shielding plate is provided between the CCD camera and the transparent plate, and the transparent plate is illuminated from multiple directions so that the light of the light source does not directly enter the CCD camera through the slit. The light source is located at
[0004]
Further, JP-A-7-234187 and JP-A-8-193555 disclose the following detection devices. That is, in the former device, the linear band-shaped illumination light is irradiated so as to overlap each other from at least three directions, and at least one of them is guided by an optical fiber array arranged in a band shape, and Scattered light from surface defects is detected by a one-dimensional camera. The latter device irradiates the surface of the glass sheet with a laser light source having an optical axis in a plane, and detects scattered light due to a defect of the glass sheet with a photoelectric detector for the laser light source.
[0005]
Further, Japanese Patent Application Laid-Open No. 1-169343 discloses a technique for detecting a cut defect of a glass plate. In this technique, a one-dimensional CCD camera and a line-shaped light source are provided, and the camera and the light source are inclined at 45 ° with respect to the transport direction of the glass plate, and images are taken in a transmitted bright field in order to inspect four sides of the glass plate.
[0006]
Also, Japanese Patent Application Laid-Open No. 8-304295 discloses a technique for detecting a surface defect of a lined or meshed glass. In this technology, a line sensor and a lighting device are provided on one surface side of a plate-shaped transparent object so as to form an angle θ with respect to a direction orthogonal to a transport direction of the plate-shaped transparent object, and the plate-shaped transparent object is provided by the lighting device. One surface of the transparent object is illuminated, and an image is taken in a reflected bright field by a line sensor. In addition, this publication describes verification of the appearance state of the luminance level based on the angle formed between the line-shaped scratch and the line sensor and the lighting device, and suggests that the scratch has an angle dependency.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-148206 [Patent Document 2]
JP-A-7-234187 [Patent Document 3]
Japanese Patent Application Laid-Open No. 8-193955 [Patent Document 4]
JP-A-1-169343 [Patent Document 5]
JP-A-8-304295
[Problems to be solved by the invention]
In other words, when a line sensor is used, a technique for detecting scattered light from a defect (such as a linear scratch or bubble) existing in a plate-like body conveyed in a certain direction is particularly useful for detecting scattered light from a linear defect. Is dependent not only on its size and shape but also on the scanning direction of the illuminating linear illuminator and line sensor and the angle formed by the defect.
[0008]
For this reason, the scattered light of the defect obtained by the line sensor is weak, and it may be difficult to detect the defect. In particular, since the scattered light of the linear defect is affected by the angle dependence, it is difficult to detect the defect without fail.
[0009]
Further, when the object to be inspected is a continuous ribbon-shaped glass plate or the like, it is difficult to rotate the object to be inspected, and the object to be inspected is easily affected by the angle dependence. Therefore, it is very difficult to detect a fine linear defect.
[0010]
Note that the method of irradiating light from multiple directions in the above-described Japanese Patent Application Laid-Open No. 2002-148206 increases light components scattered by defects as compared with the case of irradiating light from one direction. Can be detected.
[0011]
In addition, the method of using high-intensity illumination for line illumination in JP-A-7-234187 and JP-A-8-193555 can sufficiently detect scattered light from a defect. However, even when irradiating light from multiple directions or irradiating high-intensity light, the scattered light of the linear defect incident on the light-receiving portion of the line sensor depends on the illuminating light and the angle formed by the linear sensor and the linear defect. Will be affected.
[0012]
Here, the angle dependence of the scattered light of the linear defect will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes a linear illuminator, 3 denotes a plate, 4 denotes a scanning area of a line sensor, 5 denotes a linear defect, and the arrows in the figure indicate the transport direction of the plate. As shown in FIG. 1A, when the scanning direction of the line sensor and the direction of the linear defect are parallel, the scattered light from the linear defect can be detected most strongly. On the other hand, as shown in FIG. 1B, when the scanning direction of the line sensor is orthogonal to the direction of the linear defect, the scattered light from the linear defect is weak.
[0013]
Further, in this case, in order to detect scattered light of a linear defect orthogonal to the scanning direction of the line sensor, even if the angle between the detection unit including the linear illuminator and the line sensor and the linear defect is various. In addition, it is necessary to irradiate high-brightness light so that sufficient scattered light can be obtained. However, such illumination requires a large-scale device.
[0014]
As shown in FIG. 1C, when light is emitted from a direction perpendicular to the scanning direction of the line sensor, the light source is within the scanning range of the line sensor, and the line sensor receives the direct light from the light source. Would. For this reason, scattered light from a linear defect cannot be detected in a portion where the scanning range of the line sensor and the light source intersect.
[0015]
Therefore, in the present invention, a line sensor is used as a means for receiving scattered light from a defect, and when an object to be inspected is a plate-like body conveyed in one direction, the influence of the angle dependence of the scattered light of the defect is reduced. Provided are a defect detection device and a method thereof that can detect a defect without receiving the defect. Furthermore, a detection device capable of detecting a linear defect even with general illumination such as a fluorescent lamp, and a method therefor are provided.
[0016]
In addition, the inspection method in the case where the inspection object can be rotated will be exemplified below. For example, in the field of small electronic technology, there is a method of rotating a test object such as a silicon wafer and performing a test a plurality of times (for example, JP-A-2002-257745).
[0017]
[Means for Solving the Problems]
In order to solve the above-described problem, as a first embodiment of the present invention, a defect detection device according to claim 1 is provided.
A transport mechanism for transporting the plate-like inspection object in a certain direction, a linear illuminator, and a line sensor, wherein light radiated by the linear illuminator is present in the plate-like body. A dark-field type defect detection device that detects the defect by being scattered by detecting the scattered light with the line sensor,
The scanning direction of the line illuminator and the line sensor is provided with at least two sets of detection units arranged so as to be parallel to each other, and each of the detection units has a different angle with respect to the transport direction of the plate-like body. Characterized by being arranged in
[0018]
The defect detection device according to claim 2,
The detection unit is characterized in that two sets of units are arranged so that angles formed by the plate-like body with the transport direction are 30 ° to 60 ° and 120 ° to 150 °, respectively.
[0019]
The defect detection device according to claim 3 is
It is characterized in that two sets of the detecting units are provided, and the two sets of units are arranged so that the angles formed by the plate-like body and the conveying direction are 45 ° and 135 °, respectively.
[0020]
The defect detection device according to claim 4 is
The linear illuminator includes at least two linear illumination light sources.
[0021]
The defect detection device according to claim 5,
The linear illuminator is disposed at a position where direct light from the illuminator does not enter the line sensor, or a light-shielding plate is disposed between the linear illumination and the line sensor. It is characterized by having.
[0022]
The defect detection device according to claim 6,
A light-receiving amount correcting unit that corrects a light-receiving amount of the line sensor in accordance with an angle formed between the linear defect on the plate-like body and the detection unit.
[0023]
Further, as a second aspect of the present invention, a defect detection method according to claim 7 is provided.
The plate-shaped body, which is the object to be inspected, is transported in one direction by the transport mechanism,
The plate-like body is irradiated with light from a line-shaped illuminator, the illumination light is scattered by a defect present in the plate-like body, and the scattered light is detected by the line sensor to detect the defect. A dark field type defect detection method,
The scanning direction of the line illuminator and the line sensor is provided with at least two sets of detection units arranged so as to be parallel to each other, and the detection units are respectively arranged at different angles with respect to the transport direction of the plate-like body. It is characterized by being arranged.
[0024]
The defect detection method according to claim 8,
The detection unit is characterized in that two sets of units are arranged so that angles formed by the plate-like body with the transport direction are 30 ° to 60 ° and 120 ° to 150 °, respectively.
[0025]
The defect detection method according to claim 9 is:
Two sets of the detection units are provided, and the two sets of units are arranged so that the angles formed by the plate-like body and the transport direction are 45 ° and 135 °, respectively.
[0026]
The defect detection method according to claim 10,
The linear illuminator includes at least two linear illumination light sources.
[0027]
The defect detection method according to claim 11 is
The linear illuminator is disposed at a position where direct light from the illuminator does not enter the line sensor, or a light-shielding plate is disposed between the linear illuminator and the line sensor. .
[0028]
The defect detection method according to claim 12 is
The amount of light received by the line sensor is corrected according to an angle between a linear defect on the plate and the detection unit.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a defect detection device of the present invention will be described in detail with reference to the drawings.
[0030]
(Preliminary study)
First, when the angle between the object to be inspected having a linear defect (glass substrate 3) and the detection unit including the linear illuminator and the line sensor is changed using the defect detection apparatus shown in FIG. The effect on the scattered light intensity was investigated. 8, reference numeral 1 denotes a linear illuminator, 4 denotes a scanning area of a line sensor, and 5 denotes a linear defect. Specifically, the angle θ formed by the linear illuminator 1 and the scanning area 4 of the line sensor and the linear defect 5 is changed every 10 ° from 0 ° to 90 ° to measure the scattered light intensity. did. As the linear defects 5, glass substrates having five types of linear defects having different lengths were prepared. The width of the line defect, respectively _{W A,} W _B, when formed into a _{W C, W D, W E} , was their magnitude relation as follows.
_{W A <W B <W C} <W D <W E
[0031]
The result is shown in FIG. In FIG. 9, the scattered light intensity from the five types of defects is represented by 256 gradations. The vertical axis is an arbitrary unit, and each plot represents the following linear defect.
_{◇: W A, □: W} B, △: W C, ×: W D, ○: W E
[0032]
From the results shown in FIG. 9, it was found that even for the same linear defect, the scattered light intensity changed depending on the difference in the angle θ. From this, it was confirmed that the angle θ between the direction of the linear defect and the scanning direction of the line sensor affects the intensity of the scattered light.
[0033]
In addition, looking at the intensity of the scattered light at each changed angle, the width of the linear defects W _A , W _B , and W _C is about half when compared to 0 ° around 60 °. ing. Further, as the angle becomes 60 ° to 90 °, the intensity of the scattered light tends to further decrease. Therefore, a range where the angle θ between the scanning direction of the line sensor and the linear defect is about 0 ° to 60 ° is an angle range where the scattered light intensity is strong.
[0034]
Here, in FIG. 10, an angle between the scanning direction 41 of the detection unit including the linear illuminator 1 and the line sensor and the transport direction of the plate 3 is defined as θ. The inspection width at that time is W. Then, a change in the inspection width W when θ was changed was confirmed. The inspection width W can be obtained by W = COSθ, where the length of the illuminator is 1. FIG. 11 is a graph showing a change in the inspection width W when θ is changed.
[0035]
According to the graph shown in FIG. 11, it is desirable to set the angle θ in the range of 45 ° to 135 ° so that the inspection width W is at least half the length of the illumination.
[0036]
(Example 1)
FIG. 2 is a schematic plan view of a detection device according to one embodiment of the present invention. This detection device has two detection units each including a line-shaped illuminator 1 and a line sensor, and θ1 is set with respect to the transport direction of the glass plate 3 so that they can complement each other. They are arranged so that 45 ° and θ2 become 135 °. FIG. 3 is a schematic cross-sectional view of the portion AB in FIG. 2 as viewed from the side. This defect detection apparatus performs dark field type defect detection.
[0037]
In such a defect detection apparatus, for example, a float glass plate 3 having a thickness of 5 mm is irradiated with light from the linear illuminators 1 and 1 above the float glass plate 3 as an object to be inspected. Taken. In the linear illuminator, two straight tube fluorescent lamps, which are linear light sources, are provided with a gap of 10 mm, and the distance from the surface of the glass plate 3 is set to 10 mm, so that reflection illumination is performed. Further, light shielding plates 6 and 6 are arranged above the linear illuminator 1 so that the interval between them is 5 mm so that direct light from the illuminator does not enter the line sensor 2.
[0038]
The aperture of the line sensor 2 is preferably close to open so as to receive scattered light from the defect as much as possible. In this case, scattered light from the minute defect can be received.
[0039]
The image captured by the line sensor 2 was subjected to image processing by the image processing device 7 shown in FIG. The linear image processed by the image processing device 7 was taken into the personal computer 8 and connected as a whole glass plate to form a composite image of the entire glass plate as shown in FIG.
[0040]
Since this detection is of the dark field type, the linear defect 5 appears as a bright line that shines brightly in the entire image of the glass plate in the composite image. Therefore, the bright line may be recognized as a defect.
[0041]
In Example 1, the linear defect 5 in the composite image shown in FIG. 5 was detectable up to a width of about 30 μm.
[0042]
(Example 2)
The conditions of Example 1 were set such that the distance between two straight tube fluorescent lamps in the linear illuminator was 80 mm, and the distance from the surface of the glass plate 3 was 15 mm. Was done.
[0043]
In Example 2, the linear defect in the composite image was detectable up to a width of about 60 μm.
[0044]
In the above-described first and second embodiments, the description has been given by taking as an example a glass plate which is a transparent body as the plate-like body. However, in the reflective illumination, the object to be inspected is not limited to a transparent body, and a metal plate or the like can be inspected.
[0045]
In each of the first and second embodiments, the light-shielding plate is provided. However, the present invention is not limited to this, and as shown in FIG. 6, if the arrangement is such that direct light from the illuminators 1 and 1 does not directly enter the line sensor 2, it is not particularly necessary to provide a light shielding plate. .
[0046]
(Example 3)
FIG. 7 is a schematic cross-sectional view of a detection apparatus according to another embodiment of the present invention. In this alternative embodiment, light is irradiated from below the transparent glass plate 3. FIG. 7 is a schematic cross-sectional view of the portion AB in FIG. 2 as viewed from the side.
[0047]
Further, a light-shielding plate 6 is disposed above the line-shaped illuminator 1 so that the light from the illuminator does not enter the line sensor 2 so that the interval between the slits is about 5 mm, thereby providing transmissive illumination. . As described above, if the inspection object is a transparent body and the defect reflects the illumination light, the defect can be detected even in the case of the transmissive illumination.
[0048]
In Example 3, the linear defect 5 was detectable up to a width of about 40 μm.
[0049]
(Correction of received light amount)
Depending on the angle between the linear defect and the detection unit, the amount of light from the detected linear defect varies. Therefore, it is preferable to previously obtain a light amount correction value for each angle between the linear defect and the detection unit, and correct the light amount based on the correction value.
[0050]
For example, in Examples 1 to 3 described above, the angle formed between the linear defect 5 captured by the line sensor 2 and the detection unit was first determined by the image processing device 7. Then, a correction value corresponding to this angle may be added to the light amount from the linear defect 5. With this correction, the change in the amount of light received by the line sensor 2 due to the angle between the linear defect 5 and the detection unit can be minimized, and the linear defect 5 can be detected with high sensitivity.
[0051]
As described above, the correction unit first provides the image processing apparatus 7 with a correction table corresponding to the above-described angle. Next, when a linear defect is detected, the above-described angle is obtained by the image processing device 7, and a correction value is called from a previously obtained table to correct the amount of received light.
[0052]
【The invention's effect】
As described above, in the present invention, at least two sets of the detection unit including the line illuminator and the line sensor are arranged at different angles with respect to the transport direction of the plate.
[0053]
With such an arrangement, even if the angle between the linear defect and the detection unit is various, scattered light generated by a defect such as a linear scratch, a bubble, or a foreign substance present on the plate-like body is detected by the detection unit. Can complement each other. As a result, linear defects existing at various angles with respect to the transport direction of the plate-like body can be completely detected.
[0054]
Also, by correcting the amount of light received by the line sensor for the angle between the linear defect existing on the plate-shaped body and the detection unit, the change in the brightness of the scattered light caused by the size and depth of the defect is detected. can do. Therefore, by changing the threshold of the scattered light intensity, the size and depth of the defect to be detected can be limited.
[0055]
Note that the defect detection technique of the present invention is not limited to, for example, a glass plate that is not only a linear defect existing in a plate-like body but also a defect that emits scattered light. Is also effective.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a linear defect and angles formed by a linear illuminator and a line sensor.
FIG. 2 is a schematic plan view of the defect detection apparatus according to the first embodiment of the present invention.
FIG. 3 is a schematic sectional view of a defect detection apparatus according to the first embodiment of the present invention.
FIG. 4 is a configuration diagram of an apparatus that performs image processing on an image captured by a line sensor.
FIG. 5 is a diagram conceptually showing a composite image of a linear defect after image processing in the first embodiment.
FIG. 6 is a schematic cross-sectional view of a defect detection device without a light shielding plate.
FIG. 7 is a schematic sectional view of a defect detection apparatus according to a third embodiment of the present invention.
FIG. 8 is a schematic plan view of a defect detection device showing a preliminary study.
FIG. 9 is a graph showing the angle dependence of a linear defect performed in a preliminary study.
FIG. 10 is a view for explaining an angle between a transport direction of a plate-like body and a scanning direction of a line sensor.
FIG. 11 is a graph showing a change in an inspection width depending on an angle between a transport direction of a plate-like body and a scanning direction of a line sensor.
[Explanation of symbols]
1: line illuminator 2: line sensor 3: plate (glass plate)
4: Scanning area 41 of the line sensor 41: Scanning direction of the line sensor 5: Linear defect 6: Light shielding plate 7: Image processing device 8: Personal computer

Claims (12)

A transport mechanism for transporting the plate-like inspection object in a certain direction, a linear illuminator, and a line sensor, wherein light radiated by the linear illuminator is present in the plate-like body. A dark-field type defect detection device that detects the defect by being scattered by detecting the scattered light with the line sensor,
The scanning direction of the line illuminator and the line sensor is provided with at least two sets of detection units arranged so as to be parallel to each other, and each of the detection units has a different angle with respect to the transport direction of the plate-like body. A defect detection device, wherein The detection unit is characterized in that two sets of units are arranged so that angles formed with the conveyance direction of the plate-like body are 30 ° to 60 ° and 120 ° to 150 °, respectively. Item 2. The defect detection device according to Item 1. The apparatus according to claim 2, wherein two sets of the detection units are provided, and the two sets of units are arranged so that angles formed by the plate-shaped body and a conveyance direction thereof are 45 ° and 135 °, respectively. The defect detection device according to the above. The said linear illuminator contains at least 2 linear illumination light sources, The defect detection apparatus of any one of Claims 1-3 characterized by the above-mentioned. The linear illuminator is disposed at a position where direct light from the illuminator does not enter the line sensor, or a light-shielding plate is disposed between the linear illumination and the line sensor. The defect detection device according to any one of claims 1 to 4, wherein: 6. A light receiving amount correcting means for correcting a light receiving amount of the line sensor in accordance with an angle formed by a linear defect on the plate and the detection unit. Item 13. The defect detection device according to Item 1. The plate-shaped body, which is the object to be inspected, is transported in one direction by the transport mechanism,
The plate-like body is irradiated with light from a line-shaped illuminator, the illumination light is scattered by a defect present in the plate-like body, and the scattered light is detected by the line sensor to detect the defect. A dark field type defect detection method,
The scanning direction of the line illuminator and the line sensor is provided with at least two sets of detection units arranged so as to be parallel to each other, and the detection units are respectively arranged at different angles with respect to the transport direction of the plate-like body. A defect detection method characterized by being arranged. 8. The detection unit according to claim 7, wherein two of the detection units are arranged so that angles formed by the plate-shaped body with respect to the conveyance direction are 30 ° to 60 ° and 120 ° to 150 °, respectively. 3. The defect detection method according to 1. 9. The apparatus according to claim 8, wherein two sets of the detection units are provided, and an angle between the two sets of units and a transport direction of the plate-like body is set to 45 ° and 135 °, respectively. 10. Defect detection method. The defect detection method according to any one of claims 7 to 9, wherein the linear illuminator includes at least two linear illumination light sources. The linear illuminator is disposed at a position where direct light from the illuminator does not enter the line sensor, or a light-shielding plate is disposed between the linear illuminator and the line sensor. The defect detection method according to claim 7. The defect detection method according to claim 7, wherein an amount of light received by the line sensor is corrected according to an angle between a linear defect on the plate and the detection unit. .

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