KR20210123047A - Device for detecing defect and method for insepction of defect - Google Patents

Abstract

A defect inspection apparatus of exemplary embodiments of the present invention comprises: a light source irradiating light to a predetermined area of an object to be inspected in a plurality of directions inclined with respect to the object to be inspected; and an imaging unit disposed in a vertical direction from a predetermined area of the object to be inspected to collect scattered or refracted light from the object to be inspected. Defects located inside the object to be inspected can be effectively and accurately detected.

Description

DEVICE FOR DETECING DEFECT AND METHOD FOR INSEPCTION OF DEFECT

The present invention relates to a defect inspection apparatus and a defect inspection method. More specifically, it relates to a defect inspection apparatus and a defect inspection method using a difference in brightness of a defect site on a captured image.

Various optical films, such as a polarizing film and retardation film, are used for an image display apparatus. When a defect exists in an optical film, the image quality of an image display apparatus may deteriorate.

Defect inspection of the optical film is performed by a reflectometer inspection apparatus for arranging a light source and a camera on the same side of an inspection object, and a transmission system inspection apparatus for arranging a light source and a camera with the inspection object in the middle.

A reflectometer inspection apparatus has an advantage in detecting surface layer defects, and a transmission system inspection apparatus has an advantage in detecting deep defects.

However, an image display device including a light-opaque member such as an LED display device cannot be inspected by the transmission-based inspection device. When the image display device including the light-opaque member is inspected with a conventional reflectometer inspection device, the defect in the deep part may not be detected, or the defect may be detected as being distorted.

Therefore, there is a need for research and development on a method and apparatus capable of accurately detecting a deep defect even when a transmission-based inspection device cannot be used.

An object of the present invention is to provide a defect inspection apparatus having excellent detection power and reliability.

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

1. A light source irradiating light to a predetermined area of the object to be examined in a plurality of directions inclined with respect to the object; and an imaging unit disposed in a vertical direction from the predetermined region of the inspection object and configured to collect scattered or refracted light from the inspection object.

2. The defect inspection apparatus according to the above 1, wherein the plurality of directions are symmetrical with respect to the predetermined region of the inspection object.

3. The defect inspection apparatus according to 1 above, wherein the light source and the imaging unit are disposed on a dome-shaped orbit.

4. The apparatus of 1 above, wherein the inspection object includes a polarizing plate.

5. The apparatus of 4 above, wherein the polarizing plate includes a polarizer, and the inspection object includes a defect inside the polarizer with respect to the polarizer.

6. The defect inspection apparatus according to the above 1, wherein the inspection object includes a light reflective layer on a bottom surface.

7. The defect inspection apparatus according to the above 1, wherein the inspection object includes a polarizing plate to which an LED display panel is attached on a bottom surface.

8. The defect inspection apparatus according to the above 1, which inspects at least one of a scratch defect, a foreign material defect, and a dent defect.

9. irradiating light to a predetermined area of the object to be examined in a plurality of directions inclined with respect to the object; acquiring a captured image in a vertical direction of the predetermined area; and detecting a defect from the captured image.

10. The defect inspection method according to 9 above, wherein the irradiating the light includes irradiating the light in a symmetrical direction with respect to the predetermined area of the inspection object.

According to example embodiments, light may be irradiated to the inspection object in a plurality of inclined directions, and a captured image may be obtained in a normal direction of the inspection object. In this case, the number, shape, area, etc. of the inner layer defects can be detected substantially accurately through the scattered light.

For example, with respect to a polarizing plate to which an LED display panel is attached, defects present inside the polarizer can be effectively detected.

1 is a schematic cross-sectional view showing a defect inspection apparatus according to exemplary embodiments.
2 and 3 are schematic views for explaining a reflectometer inspection apparatus of a comparative example.
4 is a schematic cross-sectional view of an object to be examined according to example embodiments.
5 is an image obtained by photographing an object to be inspected in which a light reflective layer is formed on the bottom surface through the inspection apparatus of the comparative example.
6 is an image obtained by photographing an object to be inspected in which a light reflective layer is formed on a bottom surface according to an embodiment.
7 and 8 are tables showing defect inspection results according to Examples and Comparative Examples.

Exemplary embodiments of the present invention are a defect inspection apparatus including a light source for irradiating light to a predetermined area in a plurality of directions inclined with respect to an object to be inspected, and an imaging unit disposed in a vertical direction from the predetermined area and collecting scattered or refracted light. and a defect inspection method. Defects located inside the inspection object can be effectively and accurately detected.

The configuration shown in the embodiments and drawings described in this specification is only a preferred example of the disclosed invention, and there may be various modifications that can replace the embodiments and drawings of the present specification at the time of filing of the present application.

In addition, the same reference numbers or reference numerals in each drawing in the present specification indicate parts or components that perform substantially the same functions.

In addition, the terms used herein are used to describe the embodiments, and are not intended to limit and/or limit the disclosed invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It does not preclude the possibility of the presence or addition of figures, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic cross-sectional view showing a defect inspection apparatus according to exemplary embodiments.

Referring to FIG. 1 , the defect inspection apparatus 10 may include a light source 200 and an imaging unit 300 . The defect inspection apparatus 10 may inspect the inspection object 100 . The inspection object 100 may include an inner layer defect 104 .

The light source 200 may irradiate light in a direction inclined with respect to the object 100 to be inspected. An angle between the light irradiation direction of the light source 200 and the plane of the object 100 may be defined as a light irradiation angle θ.

For example, the light irradiation angle may be 10 to 80 ^o . Preferably, the light irradiation angle may be 30 to 60 ^o , and in this case, the detection power for the inner layer defect 104 may be improved.

The light source 200 may irradiate light to a predetermined area of the object 100 to be inspected from a plurality of different directions. For example, the light source 200 may include a first light source 210 and a second light source 220 . The first light source 210 and the second light source 220 may irradiate light to the predetermined area.

In example embodiments, the first light source 210 and the second light source 220 may be symmetrically disposed with respect to the predetermined area. In this case, the light irradiation angle of the first light source 210 and the light irradiation angle of the second light source 220 may be the same.

In example embodiments, the first light source 210 and the second light source 220 may have a bar shape. In this case, light may be linearly irradiated to the predetermined area, and, for example, when a line camera is used as the imaging unit 300 , inspection efficiency may be improved.

In some embodiments, three or more light sources may be used, and the light sources may be symmetrically disposed with respect to the predetermined area. For example, when three light sources are used, the three light sources may be arranged ^{to surround the predetermined area and form an angle of 120°.}

In some embodiments, the light source 200 may include an annular light source. The predetermined region of the test object 100 may be disposed within the ring of the annular light source. In this case, even one light source can irradiate light from a plurality of directions.

In example embodiments, the light source 200 may be disposed on the imaging unit 300 and a dome-shaped orbit. In this case, the ability to detect inner layer defects may be improved.

For example, the light source 200 may include a light emitting diode (LED) lamp, a halogen lamp such as a metal halide lamp, a fluorescent lamp, an incandescent light bulb, and the like.

The imaging unit 300 may be disposed on the same side as the light source 200 with respect to the object 100 to be inspected. The imaging unit 300 may acquire a captured image in a vertical direction of the predetermined area of the object 100 . For example, the imaging unit 300 may be disposed on a normal line with respect to the plane of the predetermined area of the object 100 .

As used herein, the term 'vertical direction' is an angle that collects scattered or refracted light without collecting directly reflected light as well as a direction that ^{mathematically forms a 90 o} angle, a direction having a predetermined error from ^{90 o} can mean For example, the error may be ^{about 10 o.}

In this case, the imaging unit 300 may be disposed at a position deviated from the normal incidence-reflection path of the light emitted from the light source 200 . Accordingly, the captured image obtained by the image capturing unit 300 may be basically displayed as a dark image. When a defect exists in the path of light emitted from the light source 200, reflection, refraction, scattering, etc. of light may occur in the defect.

In exemplary embodiments, the image pickup unit 300 may obtain light that is scattered or refracted from the defect, and deviated from a normal incident-reflection path. In this case, the captured image may include a bright image portion due to scattered or refracted light in the dark image background.

2 and 3 are schematic views for explaining a reflectometer inspection apparatus of a comparative example.

Referring to FIG. 2 , the light emitted from the light source 230 is reflected from the defect 102 located in the surface layer portion and reaches the camera 310 . Accordingly, the surface layer defect 102 can be accurately detected even by the reflectometer inspection method according to the comparative example.

However, referring to FIG. 3 , when the light emitted from the light source 230 reaches the deep defect 104 , the scattered light is reflected by the light reflection layer attached to the bottom of the polarizing plate 110 and is obtained by the camera 310 . can be In this case, the specularly reflected light and the reflected light after scattering are separated, and distortion occurs in the size, number, shape, etc. of the deep part defect 104 .

In the case of the reflectometer inspection apparatus according to the comparative example, a camera is disposed on a general incident-reflection path, and in this case, the light normally reflected from the defect and the light whose path is changed by being re-reflected or refracted after being scattered from the defect can be obtained together with the camera. Accordingly, the number, shape, area, etc. of defects may be inspected excessively compared to actual defects, and a normal product may be determined as defective.

On the other hand, the defect inspection apparatus according to the exemplary embodiments may improve the defect detection accuracy by arranging the imaging unit 300 in the vertical direction of the predetermined area.

The imaging unit 300 may acquire a color or black-and-white image, and a line CCD camera or a two-dimensional area camera may be used, but is not limited thereto.

In example embodiments, the test object 100 may include a polarizing plate 110 and an LED display panel 140 . For example, the LED display panel 140 may be attached to one surface of the polarizing plate 110 . The LED display panel 140 may include an OLED display panel or an inorganic LED display panel.

The polarizing plate 110 may include an outer layer portion 120 and an inner layer portion 130 . The outer layer part 120 may be positioned on the exposed surface side, and the inner layer part 130 may be positioned on the side close to the LED display panel 140 . The inner layer 130 may not be exposed to the outside.

4 is a schematic cross-sectional view of an object to be examined according to example embodiments.

Referring to FIG. 4 , the polarizing plate 110 may include an outer functional layer 122 , an outer polarizer protective film 124 , a polarizer 132 , an inner polarizer protective film 134 , and an inner functional layer 136 . .

The outer functional layer 122 and the outer polarizer protective film 124 positioned outside (the surface side) with respect to the polarizer 132 may define the outer layer part 120 .

The polarizer 132 and the inner polarizer protective film 134 and the inner functional layer 136 positioned inside the polarizer 132 may define the inner layer part 130 .

A defect located in the outer layer part 120 may be defined as an outer layer defect, and a defect located in the inner layer part 130 may be defined as an inner layer defect 104 .

The outer functional layer 122 and the inner functional layer 136 may include a hard coating layer, an antifouling layer, a charging layer, a retardation layer, and the like. Preferably, when the inner functional layer 136 is a retardation layer, it may be suitable as a polarizing plate for an LED display device.

The outer polarizer protective film 124 and the inner polarizer protective film 134 may include, but are not limited to, triacetyl cellulose (TAC).

The polarizer 132 may include a polyvinyl alcohol (PVA) film dyed with iodine or a dichroic dye.

The detection difficulty and method may vary depending on the location of the defect based on the polarizer 132, which has a substantially polarizing function. Defects located in the outer layer 120 may be easily detected by a general reflectometer inspection method, but in the case of defects located in the outer layer 120, it may be difficult to detect due to a decrease in the amount of light and a change in the light path.

According to exemplary embodiments, a defect located in the outer layer part 120 may be easily inspected using the defect inspection apparatus 10 .

In example embodiments, the defect may include at least one of a scratch defect, a foreign material defect, and a dent defect. The scratch defect may be formed on the surface (eg, the outer layer part 120 ) of the polarizing plate 110 . The foreign material defect may include impurities such as dust and air bubbles inserted into the outer layer part 120 or the inner layer part 130 during the manufacturing process of the polarizing plate 110 or formed by itself. The dent defects may include deformations (concavities and convexities) formed up to the inner layer portion 130 of the polarizing plate 110 by external pressure.

According to exemplary embodiments, the detection power for the foreign material defect and the engraving defect located in the inner layer part 130 may be further improved.

In example embodiments, the inspection object 100 may include a light reflective layer on a bottom surface thereof. For example, the LED display panel 140 may include a light reflective layer on a bottom surface thereof.

The light reflective layer may reflect 20% or more of the incident light. Preferably, the light reflective layer may reflect 50% or more of the incident light, more preferably 70% or more of the light.

In example embodiments, the light reflection layer may include at least one of a metal and a conductive metal oxide. The light reflection layer may be formed in a multilayer structure of a metal layer and a conductive metal oxide layer.

The metal may be, for example, silver, gold, copper, aluminum, platinum, palladium, chromium, titanium, tungsten, niobium, tantalum, vanadium, calcium, iron, manganese, cobalt, nickel, zinc and alloys of two or more thereof. The conductive metal oxide may include at least one selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), and indium tin zinc oxide (ITZO). ), zinc tin oxide (ZTO), indium gallium oxide (IGO), tin oxide (SnO2), and may include at least one selected from the group consisting of zinc oxide (ZnO).

5 is an image obtained by photographing an object to be inspected in which a light reflective layer is formed on the bottom surface through the inspection apparatus of the comparative example.

Referring to FIG. 5 , when the reflectometer inspection apparatus of the comparative example is used, the light scattered or refracted in the inner layer defect 104 is reflected by the light reflection layer and obtained by the camera 310, so that one defect is actually separated into two. and can be detected.

6 is an image obtained by photographing an object to be inspected in which a light reflective layer is formed on a bottom surface according to an embodiment.

Referring to FIG. 6 , the defect can be accurately detected by collecting only the light scattered or refracted in the inner layer defect 104 without collecting the light traveling along the general incident-reflection path.

Accordingly, the position and shape of the defect can be accurately detected, and the defect can be prevented from being excessively detected.

According to exemplary embodiments, a defect may be inspected while the inspection object 100 or the imaging unit 300 moves in a predetermined direction.

The defect inspection apparatus 10 may include a defect detection unit (not shown). The defect detector may detect a defect from the captured image.

In example embodiments, a portion having a change in brightness on the captured image may be defined as an abnormal region. When a difference in brightness between the abnormal region and a peripheral region surrounding the abnormal region is greater than or equal to a predetermined value, the abnormal region may be determined as a defect.

In example embodiments, both the outer layer defect 102 and the inner layer defect 104 may be effectively detected by using the defect inspection apparatus 10 and a general reflectometer inspection apparatus together.

In this case, in the light source and the image pickup unit arranged along the general light incidence-reflection path of the general reflectometer inspection apparatus, one of the light source and the image pickup unit can be moved by a predetermined amount in the horizontal direction. In this case, the amount of light and the incident angle of light incident on the defect from the light source may change, and the difference in brightness may increase at the boundary between the abnormal region and the peripheral region. Accordingly, it is possible to secure excellent detection power even with respect to a scratch defect of a fine line width.

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

An object to be inspected was prepared by attaching a polarizing plate on the upper surface of the OLED display panel including the metal electrode layer on the lower surface.

As a polarizing plate, a polarizing film for OLED in which a TAC protective film was attached to both sides of an iodine-dyed PVA film and a quarter wave retardation film was attached to the bottom of the lower TAC protective film was used. The quarter wavelength retardation film side was attached to the upper surface of the OLED display panel.

Two bar-shaped LED lamps with a length of 1,200 mm were respectively placed in symmetrical positions to illuminate ^{one area of the test object at 45°.}

A line scan camera (Dalsa Linea 16k, Lens: VS-L8528/M72) was placed at the midpoint of the two LED lamps so that the imaging line was parallel to the LED lamp.

A captured image was acquired while the object was moved in a direction perpendicular to the LED lamp. The scan rate of the camera was set to 48 kHz, and the resolution was set to 30 μm X 30 μm.

The detection data by detecting various types of foreign substances or engraving defects (#1 to #7) in the test object are shown in the table of FIG. 7 . Defects #1 to #7 were formed in the polarizer, the lower TAC protective film, or the quarter wave retardation film.

In FIG. 7 , Size means an average value of the length of the long side and the length of the short side of the defect. Area means the number of pixels occupied by the defect.

Peak is defined as the grayscale (0~255) difference between the defect area and the surrounding area.

comparative example

Placing a bar-type light source of the one region of the test object to illuminate a 45 ^o angle, followed by placing the line scan camera in an extension forming an angle of 45 ^o from the work area.

Defects #1 to #7 were re-inspected for the test objects tested in the example, and the test results are shown in the table of FIG. 8 .

Referring to FIGS. 7 and 8 , it was confirmed that, when inspected by the defect inspection method of the example, the detection power for defects formed in the inner layer was significantly improved compared to the reflective optical system inspection method of the comparative example.

100: test object 110: polarizing plate
120: outer layer 130: inner layer
140: LED panel 210, 220: light source
300: imaging unit

Claims (10)

a light source irradiating light to a predetermined area of the object to be examined in a plurality of directions inclined with respect to the object; and
and an imaging unit disposed in a vertical direction from the predetermined region of the inspection object and configured to collect scattered or refracted light from the inspection object.
The defect inspection apparatus according to claim 1, wherein the plurality of directions are symmetrical with respect to the predetermined region of the inspection object.
The defect inspection apparatus according to claim 1, wherein the light source and the imaging unit are disposed on a dome-shaped orbit.
The defect inspection apparatus according to claim 1, wherein the inspection object includes a polarizing plate.
The defect inspection apparatus according to claim 4, wherein the polarizing plate includes a polarizer, and the inspection object includes a defect inside the polarizer with respect to the polarizer.
The defect inspection apparatus according to claim 1, wherein the inspection object includes a light reflective layer on a bottom surface thereof.
The defect inspection apparatus according to claim 1, wherein the inspection object includes a polarizing plate to which an LED display panel is attached on a bottom surface.
The defect inspection apparatus according to claim 1, wherein at least one of a scratch defect, a foreign material defect, and a dent defect is inspected.
irradiating light to a predetermined area of the object to be examined in a plurality of directions inclined with respect to the object;
acquiring a captured image in a vertical direction of the predetermined area; and
and detecting a defect from the captured image.
The defect inspection method of claim 9 , wherein the irradiating light comprises irradiating light in a symmetrical direction with respect to the predetermined region of the inspection object.

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