KR20210106776A - Device and method for inspecting defect - Google Patents

Abstract

A defect inspection apparatus according to exemplary embodiments comprises: a transparent support plate for sandwiching an object to be examined in the direction of the upper and lower surfaces of the object; a light source for irradiating light obliquely to the object to be examined fixed by the transparent support plate; and an imaging unit that acquires an image from light that has passed through the object to be examined. Defect detection power can be improved.

Description

DEVICE AND METHOD FOR INSPECTING DEFECT

The present invention relates to a defect inspection method. More particularly, it relates to a defect inspection method of the light transmission method.

Conventional visual inspection methods are automatically performed by a mechanical device through an automated facility. As an automated inspection device, the transmission optical system inspection device is used for detecting surface defects of a material having a flat surface.

For example, glass and various optical films included as parts of an image display device are required to have smooth and flat surfaces in order to improve the image output quality of the image display device.

In particular, in the case of optical films used in an image display device as a retarder, a polarizer, a retardation film, etc., the surface thereof needs to be extremely flat.

However, defects such as scratches, foreign substances, bubbles, irregularities, tears, warping or folding may occur on the surface of glass and optical films during manufacturing or handling.

In order to improve the image quality of an image display device, it is necessary to detect such defects with high sensitivity. For example, Korean Patent Application Laid-Open No. 10-2017-0010675 discloses an optical film inspection apparatus, but has a limit in detecting even finer defects.

Korean Patent Publication No. 10-2017-0010675

One object of the present invention is to provide a defect inspection apparatus having an excellent detection power.

One object of the present invention is to provide a defect inspection method having excellent detection power.

1. A transparent support plate for sandwiching the object to be examined in the direction of the upper and lower surfaces of the object; a light source that obliquely irradiates light to the object to be inspected fixed by the transparent support plate; and an imaging unit configured to acquire an image from the light that has passed through the inspection object.

2. The apparatus of 1 above, wherein the transparent support plate includes a first plate disposed on the upper surface of the inspection object and a second plate disposed on the bottom surface of the inspection object.

3. The defect inspection apparatus according to the above 2, wherein the refractive index of each of the first plate and the second plate is greater than the refractive index of the inspection object.

4. The defect inspection apparatus according to the above 3, wherein the refractive index of the first plate and the refractive index of the second plate are different from each other.

5. The defect inspection apparatus according to the above 3, wherein the refractive index of the first plate and the refractive index of the second plate are the same.

6. The defect inspection apparatus according to the above 1, wherein the light source is disposed such that an inclination angle between a direction of incident light to the inspection object and a vertical direction from the upper surface or the bottom surface of the inspection object is 10 to 80 ^o.

7. The defect inspection apparatus according to the above 6, wherein the imaging unit is disposed along the direction of the incident light.

8. fixing the upper and lower surfaces of the test object between the transparent support plates; irradiating light so as to be inclined with respect to the plane of the object to be inspected fixed by the transparent support plates; and acquiring a defect image of the inspection object from the light transmitted through the inspection object.

9. The defect inspection method according to the above 8, wherein light is scattered or refracted in a region adjacent to the interface between the defect included in the inspection object and the transparent support plate.

10. The method of 9 above, wherein the fixing of the object between the transparent support plates comprises pressing the object between the transparent support plates so that the surface of the object and the defect are not deformed. , how to check for defects.

A defect inspection apparatus according to exemplary embodiments of the present invention inspects a defect by sandwiching an inspection object with a transparent support plate. The object to be inspected may be planarized, and the ability to detect defects may be improved due to a difference in optical characteristics with the transparent support plate.

In addition, by forming a difference in refractive index at the interface between the inspection object and the transparent support plate, the detection intensity of defects formed on the surface of the inspection object may be improved.

1 is a schematic side view showing a defect inspection apparatus according to exemplary embodiments of the present invention.
FIG. 2 is a schematic enlarged view of area A of FIG. 1 .
3 is a schematic side view showing a defect inspection apparatus of a comparative example.

Exemplary embodiments of the present invention provide a defect inspection apparatus and a defect inspection method for acquiring an image by obliquely irradiating light to an inspection object sandwiched by a transparent support plate. Defect detection power can be improved.

Hereinafter, embodiments of the present invention will be described in detail. However, this is merely exemplary and the present invention is not limited to the specific embodiments described by way of example.

1 is a schematic side view showing a defect inspection apparatus according to exemplary embodiments of the present invention.

Referring to FIG. 1 , the defect inspection apparatus may include a transparent support plate 110 , a light source 120 , and an imaging unit 130 .

The transparent support plate 110 may be disposed above and below the test object 100 . The transparent support plate 110 may sandwich the test object 100 in the direction of the upper surface and the lower surface of the test object 100 .

For example, the test object 100 may include wrinkles. The transparent support plate 110 may at least partially planarize the wrinkles of the object 100 . The transparent support plate 110 may fix the object 100 to be examined.

In example embodiments, the transparent support plate 110 includes a first plate 112 disposed on an upper surface of the test object 100 and a second plate 114 disposed on a lower surface of the test object 100 . may include. For example, the first plate 112 and the second plate 114 may be in close contact with or compressed with the test object 100 .

FIG. 2 is a schematic enlarged view of area A of FIG. 1 .

In example embodiments, the inspection object 100 may include uneven defects (eg, dents, scratches, etc.) on the surfaces (top and bottom surfaces).

In exemplary embodiments, when the transparent support plate 110 is pressed against the inspection object 100 , the transparent plate 110 may be compressed with an appropriate strength so that the uneven defect on the surface of the inspection object 100 is not deformed. can

The transparent support plate 110 may include a material having predetermined mechanical strength and hardness. The transparent support plate 110 may include glass or a polymer resin. Preferably, when the transparent support plate 110 includes glass, a difference in refractive index with the object 100 may increase.

In example embodiments, the refractive index of the transparent support plate 110 may be greater than the refractive index of the object 100 . For example, each of the refractive index of the first plate 112 and the refractive index of the second plate 114 may be greater than the refractive index of the object 100 .

In this case, light emitted from the light source 120 may sequentially pass through the high refractive index layer, the low refractive index layer, and the high refractive index layer. Accordingly, the visibility of the defect in the image captured by the imaging unit 130 may increase.

Referring to FIG. 2 , when the transparent support plate 110 is in close contact with the object 100 to be inspected, an empty space ( 102) can be formed. The empty space 102 may be filled with air, for example.

For example, since the empty space 102 filled with air has a low refractive index, the light emitted from the light source 120 has a high refractive index region (second plate 114) and a medium refractive index region (inspection object 100). , a low refractive index region (empty space 102 ) and a high refractive index region (first plate 112 ) may pass sequentially. In this case, the visibility of the empty space 102 on the examination image may be increased due to a difference in refractive index between the examination object 100 and the first plate 112 based on the empty space 102 .

According to exemplary embodiments, the defect site of the inspection object 100 is located at the interface between the inspection object 100 and the transparent support plate 110 by using the difference in refractive index between the inspection object 100 and the transparent support plate 110 . It is possible to effectively change the path of light in the corresponding area (defect area). For example, the defect region (defect image) may appear relatively bright or dark on the inspection image because the path of light in the defect region is changed by scattering, refraction, reflection, or the like.

In example embodiments, the refractive indices of the first plate 112 and the second plate 114 may be the same. In this case, a certain defect detection result can be derived.

In example embodiments, the refractive index of the first plate 112 may be different from the refractive index of the second plate 114 . In this case, the detection result may change depending on the shape of the defect (such as the uneven direction). Preferably, when the refractive index of the second plate 114 is greater than that of the first plate 112 , the defect detection performance may be improved.

The light source 120 may irradiate light in a direction inclined with respect to the vertical (normal) direction of the object 100 to be inspected. In this case, the detection power for small defects (scratches, scratches, etc.) may be improved.

In example embodiments, the light source 120 may irradiate light to form an angle of ^{10 to 80°} with respect to a direction perpendicular to the upper surface or the lower surface of the test object 100 . For example, the incident angle of the light incident on the object 100 may be ^{10 to 80 o.} In the above angle range, the detection power of micro-defects may be significantly improved. More preferably, the incident angle of the incident light may be ^{30 to 70 o.}

As the light source 120, a conventional light emitting means such as a metal halide lamp, an LED lamp, etc. may be used without limitation.

The imaging unit 130 may obtain an inspection image by obtaining light emitted from the light source 100 and passing through the transparent support plate 110 and the inspection object 100 . When a defect is formed in the inspection object 100 , a region corresponding to the defect in the inspection image may be emphasized. For example, a difference between the brightness of the defect image and the brightness of a peripheral area may increase.

The imaging unit 120 may include a line scan camera or an area scan camera.

In example embodiments, the imaging unit 120 may be disposed on an extension line in the light irradiation direction of the light source 120 .

Hereinafter, preferred embodiments are presented to help the understanding of the present invention, but these examples are merely illustrative of the present invention and do not limit the appended claims, and are within the scope and spirit of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible, and it is natural that such variations and modifications fall within the scope of the appended claims.

Example

As shown in FIG. 1, a glass plate (refractive index of about 1.6) is adhered and fixed to both sides of the transparent film on which the engraving defects of defect numbers #1 to #5 are formed, and at an angle of ^{about 45 o with respect to the normal direction of the transparent film.} Light was irradiated. Inspection images were acquired through a camera disposed on an extension line of the incident light.

The size and defect intensity of the defect image were derived from the obtained inspection image and are shown in Table 1 below.

The defect intensity was calculated as the difference between the maximum brightness (grayscale) of the defect image and the average brightness of an adjacent area surrounding the defect image.

division #One #2 #3 #4 #5 inspection image

Measured defect size (μm) 73 102 109 183 142 Fault intensity (peak) 53 98 77 129 135

comparative example

As shown in FIG. 3 , the light source 220 and the camera 230 are arranged in an inclined direction with respect to the plane of the inspection object 200 without disposing transparent support plates on both sides of the inspection object 200 for inspection. Images were acquired.

The analysis of the defect image on the inspection image was performed in the same manner as in the Example, and is shown in Table 2 below.

division #One #2 #3 #4 #5 inspection image

Measured defect size (μm) 66 96 96 120 64 Fault intensity (peak) 26 44 38 90 115

Referring to Tables 1 and 2, in the case of the example in which the object to be inspected was sandwiched with the transparent support plate, the size and strength of the defect were larger than those of the comparative example in which the transparent support plate was not used, and thus the defect inspection sensitivity was increased. Accordingly, the detection power of the micro-defect formed on the object to be inspected is improved.

100: test object 110: transparent support plate
120: light source 130: imaging unit

Claims (10)

a transparent support plate for sandwiching the object to be examined in the direction of the upper surface and the lower surface of the object;
a light source that obliquely irradiates light to the object to be inspected fixed by the transparent support plate; and
and an imaging unit configured to acquire an image from the light that has passed through the inspection object.
The defect inspection apparatus of claim 1 , wherein the transparent support plate includes a first plate disposed on the upper surface of the inspection object and a second plate disposed on the bottom surface of the inspection object.
The defect inspection apparatus according to claim 2, wherein each of the first plate and the second plate has a refractive index greater than a refractive index of the inspection object.
The defect inspection apparatus according to claim 3, wherein the refractive index of the first plate and the refractive index of the second plate are different from each other.
The defect inspection apparatus according to claim 3, wherein the refractive index of the first plate and the refractive index of the second plate are equal to each other.
The defect inspection apparatus according to claim 1, wherein the light source is disposed such that an inclination angle between a direction of incident light to the inspection object and a vertical direction from the upper surface or the bottom surface of the inspection object is 10 to 80 ^o.
The defect inspection apparatus according to claim 6, wherein the imaging unit is disposed along the direction of the incident light.
fixing the upper and lower surfaces of the test object between transparent support plates;
irradiating light so as to be inclined with respect to the plane of the object to be inspected fixed by the transparent support plates; and
Comprising the step of acquiring a defect image of the inspection object from the light transmitted through the inspection object, the defect inspection method.
The method of claim 8 , wherein light is scattered or refracted in a region adjacent to an interface between the defect included in the inspection object and the transparent support plate.
The defect of claim 9 , wherein the fixing of the inspection object between the transparent support plates comprises pressing the inspection object between the transparent support plates so that the surface of the inspection object and the defect are not deformed. method of inspection.

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