KR20220112599A - An automatic inspection apparatus for stain and method for inspecting stain using thereof - Google Patents

Abstract

The present invention relates to a stain automatic inspection apparatus and a stain inspection method using the same, which may comprise: a light source unit which is arranged at one side of an object to be inspected, and projects light upon the object to be inspected; a filter unit which is arranged at the other side of the object to be inspected and includes a reference polarizing plate which polarizes light passing through the object to be inspected; a filming unit which accommodates light which has passed through the object to be inspected and the filter unit to acquire the image; and an image processing unit which detects the stain by using the image acquired in the filming unit. Here, the image processing unit comprises: a data extracting unit which extracts an orthogonal penetration ratio at a plurality of random points in the acquired image, and the light data including the orthogonal color a* value and the orthogonal color b* value; and an analysis unit which analyzes whether the extracted light data is within a predetermined reference range. Therefore, excellent inspection performance may be provided.

Description

Automated stain inspection apparatus and stain inspection method using the same

The present invention relates to an automatic spot inspection apparatus and a spot inspection method using the same.

LCD (Liquid Crystal Display) is a display device to replace the cathode ray tube (CRT) used in monitors such as TVs and computers. A polarizing film is used to control the vibration direction of light incident on liquid crystal molecules. It is widely used in industry because it is easy to design light and thin, and has advantages such as high quality and low power consumption. The polarizing film used in the LCD is used as a part of the LCD panel by adhering to one or both sides of the liquid crystal cell. Here, the polarizing film refers to an optical device used to transmit light of a specific wavelength to the liquid crystal display device.

In general, a polarizing plate is manufactured by dyeing, crosslinking, and stretching a PVA (polyvinyl alcohol) film. The conventional general polarizing plate manufacturing process consists of dyeing a PVA film with iodine or dye, adding boric acid to crosslink iodine or dye to the PVA film, and stretching the PVA film, in which case the dyeing and crosslinking , the stretching steps may be performed individually or simultaneously, and the order of each of these steps is also not fixed. After the dyeing, crosslinking, and stretching steps of the PVA film are completed, the PVA device having a polarization function is made by drying the PVA film. A polarizing plate is completed by adhering a protective film, such as a TAC (triacetyl cellulose) film, to one or both surfaces of the PVA device manufactured in this way using a PVA adhesive or the like.

When the transmission axes of the two different polarizing plates manufactured in this way are orthogonal to each other and observed on a backlight, in theory, there should be no light passing through, so it should be in a completely dark state. However, in reality, 100% of the light is not blocked due to factors such as uneven dyeing or poor adhesion of the dye, and a difference in transmittance of the polarizing plate appears depending on the position, so that streaks occur in the stretching direction.

When such unevenness appears excessively, it is difficult to implement an image of uniform luminance as a whole, resulting in defects in the final product. Therefore, there is a need for a method capable of accurately selecting the stain intensity of a polarizing plate.

The conventional polarizing plate stain inspection method was performed by the inspector's visual observation, but this inspection method has a problem in that it is difficult to produce a product of uniform quality because the degree of product defect is discriminated according to the subjectivity of the inspector. In addition, if the skill of the inspector was low, the inspection efficiency could be reduced and the false inspection rate could be increased, and there was also a problem in that the production efficiency was lowered because people had to inspect them one by one.

In order to solve this problem, Korean Patent Registration No. 10-1057626 discloses a method and an inspection system for automatically inspecting stains on a polarizing plate by analyzing an image obtained through a triple cross optical system configuration. are doing However, the technology disclosed in the above patent document has a problem in that defective products that do not meet standard specifications may be leaked. Accordingly, there is a need for an automatic spot inspection apparatus with improved accuracy and precision.

Republic of Korea Patent No. 10-1057626

An object of the present invention is to provide an automatic spot inspection apparatus having excellent inspection performance and a spot inspection method using the same.

The present invention is disposed on one side of the object to be examined, the light source for irradiating light to the object; a filter unit disposed on the other side of the object to be examined and including a reference polarizing plate for polarizing light passing through the object; a photographing unit receiving the light passing through the inspection object and the filter unit to obtain an image; and an image processing unit that detects a stain using the image obtained by the photographing unit,

The image processing unit may include: a data extraction unit configured to extract brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of an orthogonal color b* at a plurality of arbitrary points in the acquired image; and an analyzer configured to analyze whether the extracted brightness data is within a preset reference range.

In the present invention, the preset reference range may be set using brightness data of a sample measured with a spectrophotometer.

Also, the preset reference range is adjusted or changed according to the type of the object to be inspected.

In the present invention, the light source unit may irradiate light having the same wavelength as that of the light source used for measuring the brightness data of the sample for setting the reference range.

In the present invention, the size of the acquired image may be 100 mm in width and length.

In the present invention, 10 to 20 points may be selected as arbitrary points for extracting brightness data from the obtained image.

Also, a distance between one point and another point at an arbitrary point from which brightness data is extracted from the acquired image may be 5 to 10 mm.

In the present invention, the light irradiated from the light source unit may be irradiated perpendicular to the object to be inspected and the reference polarizing plate.

In the present invention, the test object may include a polarizing film.

The automatic spot inspection apparatus according to the present invention may further include a display unit displaying the presence or absence of a spot defect derived by the image processing unit.

In addition, the present invention, a light irradiation step (S10) of irradiating light to the object to be inspected; a photographing step (S20) of obtaining an image obtained by photographing the light-irradiated object; extracting brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of orthogonal color b* at a plurality of arbitrary points in an image obtained from the object (S30); and analyzing whether the brightness data extracted in the step S30 is within a preset reference range (S40); Including, it is possible to provide a stain automatic inspection method.

According to the automatic spot inspection apparatus and the spot inspection method using the same according to the present invention, by determining the presence and strength of a spot defect of an object to be inspected by comparing it with the product standard specifications, more accurate inspection performance can be exhibited. The quality can be further improved.

In addition, according to the automatic spot inspection apparatus and the spot inspection method using the same according to the present invention, it is possible to significantly reduce the occurrence of inspection errors such as over-testing that recognizes a normal product as defective, thereby improving the precision of detecting a spot defect in an object to be inspected. It can not only prevent the leakage of defective products that do not meet the product standard specifications, but also prevent leakage of defective products.

In addition, according to the automatic stain inspection apparatus and the stain inspection method using the same according to the present invention, it is possible to synchronize the inspection results through the inspection apparatus with the visual inspection results, so that a person can directly inspect all objects to be inspected in real time on the production line. Since it is possible to check and track whether the inspection object is defective, the quality control capability is improved, the production time is shortened, and the production efficiency is improved compared to the conventional inspection apparatus.

In addition, according to the automatic stain inspection apparatus and the stain inspection method using the same according to the present invention, the quality uniformity of the product is further improved compared to the conventional inspection apparatus by determining whether the object to be inspected is defective or not through an objective criterion based on improved inspection performance. it could be

1 is a schematic side view illustrating an automatic spot inspection apparatus according to an embodiment of the present invention.
2 is a diagram illustrating images obtained by an automatic spot inspection apparatus according to an embodiment of the present invention.
FIG. 3 is a view showing a plurality of arbitrary points for extracting brightness data from the image of FIG. 2 .
4 is a schematic flowchart illustrating an automatic spot inspection method according to an embodiment of the present invention.

The present invention relates to an automatic spot inspection apparatus and a spot inspection method using the same. By comparing and inspecting brightness information of an object to be inspected and brightness information of a product standard specification, more accurate inspection performance can be exhibited, and thus the product compared to a conventional inspection apparatus The quality can be further improved.

In particular, it is possible to significantly reduce the occurrence of inspection errors such as over-testing that recognizes normal products as defective, thereby improving the precision of detecting stain defects in the inspection object, and preventing the leakage of defective products that do not meet the product standard specifications. can be prevented, so that the quality uniformity of the produced product can be further improved.

"Stain" in the present invention includes any defects that occur during the manufacturing process or pre-manufacturing, post-processing and/or distribution process of the inspection object to be inspected. Accordingly, when observing the object to be inspected, it may include an atypical defect in which a color such as brightness is observed non-uniformly, for example, a region including a stain may have a higher or lower brightness than a peripheral portion. In an embodiment of the present invention, when the object to be inspected is a polarizing film, non-uniformity applied in a manufacturing process such as stretching and dyeing may cause the stain defect.

In addition, the stain may extend in a machine direction (MD) of the object to be examined. The machine direction MD may be a direction parallel to the transmission axis of the object to be inspected. The machine direction (MD), that is, a direction perpendicular to the transmission axis of the object to be inspected may be defined as a transverse direction (TD). In an embodiment, the stain may be formed repeatedly in the transverse direction (TD) of the test object.

In the "orthogonal transmittance" and "orthogonal color" of the present invention, "orthogonal" means a state in which the object 10 and the reference polarizing plate 210 are orthogonal to each other, specifically, the absorption axis of the object 10 and the It means that the absorption axes of the reference polarizing plate 210 are disposed in a state that is orthogonal to each other.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. However, the following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the above-described content of the present invention, so the present invention is described in such drawings It should not be construed as being limited only to the matters.

The terminology used herein is for the purpose of describing the embodiments, and is not intended to limit the present invention. In the present specification, the singular also includes the plural unless otherwise specified in the phrase.

As used herein, includes and/or comprising refers to the presence or addition of one or more other components, steps, operations and/or elements other than the recited elements, steps, operations and/or elements. It is used in the sense of not being excluded. The same reference numerals refer to the same components throughout the specification, and components shown in the drawings may be exaggerated, reduced, or omitted for a smooth description.

Spatially relative terms "beneath", "lower", "above", "upper", etc., as shown in the drawings, refer to one element or component and another. It can be used to easily describe a correlation with an element or components. The spatially relative terms should be understood as terms including different orientations of the device during use or operation in addition to the orientation shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above. The device may also be oriented in other orientations, and thus spatially relative terms may be interpreted according to orientation.

<Stain Automatic Inspection Device>

1 is a schematic side view illustrating an automatic spot inspection apparatus according to an embodiment of the present invention. 2 is a diagram illustrating images obtained by an automatic spot inspection apparatus according to an embodiment of the present invention. FIG. 3 is a view showing a plurality of arbitrary points for extracting brightness data from the image of FIG. 2 .

First, referring to FIG. 1 , the automatic spot inspection apparatus of the present invention may include a light source unit 100 , a filter unit 200 , a photographing unit 300 , and an image processing unit 400 , and, if necessary, a display unit (500) may be further included.

Hereinafter, each component of the automatic spot inspection apparatus of the present invention will be described.

light source

The light source unit 100 is configured to irradiate light to the object 10 to visualize defects present in the object 10 . The light source unit 100 may be provided on one side of the filter unit 200 , for example, may be provided under the filter unit 200 .

The light source of the light source unit 100 is not particularly limited as long as it serves to visualize the stain. For example, a backlight unit (BLU), an LED light source, or a metal halide (Metal) commonly used in an image display device. Halide Lamp) may be used. Preferably, in terms of irradiating by adjusting the wavelength of light, it is good to use an LED light source.

In one embodiment, the light source unit 100 may have a bar shape to inspect the entire width of the object 10 to be inspected. The bar shape may have a length greater than or equal to the width of the test object 10 .

In the present invention, the light source unit 100 irradiates light toward the inspection object 10 positioned so that the polarization direction of the filter unit 200 and the reference polarizing plate 210 is orthogonal to the reference polarizing plate 210 may be arranged so that the defect can be recognized. .

For example, the light irradiated from the light source unit 100 is preferably irradiated perpendicularly to the reference polarizing plate 210 of the inspection object 10 and the filter unit 200 in terms of improving spot visibility. At this time, since the transmission axis of the reference polarizing plate 210 and the transmission axis of the inspection object 10 are perpendicular to each other, when there is no defect in the inspection object 10, there is no transmitted light, and the orthogonal transmittance is substantially 0% and a dark image may be obtained. In addition, when there is a stain defect due to non-uniform dyeing, poor adhesion, etc., light leakage occurs and orthogonal transmittance is significantly generated. In particular, stains including light and dark stripes may be observed in the stretching direction of the polarizing plate.

filter unit

The filter unit 200 may serve to polarize an object to be inspected when inspecting a polarizing film.

The filter unit 200 may include a reference polarizing plate 210 positioned adjacent to the examination object 10 on one side and/or the other side of the examination object 10 .

The reference polarizing plate 210 is not particularly limited as long as it can absorb light vibrating in a certain direction among the light irradiated from the light source unit 100, and a polarizing plate or polarizing plate semi-finished product or polarizing element generally used in the art is not particularly limited. can be used In an embodiment, a semi-finished polarizing plate having a single transmittance of 41.0 to 42.5% using Clear TAC (eg, UZ TAC of Fuji Film) that is not surface coated may be used.

The size of the reference polarizing plate 210 is not particularly limited as long as it can obtain a sufficient size of an image photographed by the photographing unit 300 to be described later, but is preferably 8000 mm x 10 mm.

As shown in FIG. 1 , the filter unit 200 may include one reference polarizing plate 210 positioned above the test object 10 . In addition, since the polarization may be changed by various factors, the filter unit 200 may further include at least one reference polarizing plate under the test object 10 as necessary.

When the reference polarizing plate 210 is configured to be respectively disposed on the upper and lower portions of the test object 10 , absorption of a polarization component parallel to the absorption axis of the reference polarizing plate 210 is maximized, and the transmission axis of the test object 10 is maximized. The absorption axes of the plurality of reference polarizing plates 210 are preferably parallel to each other in order to improve the visibility of the spot by minimizing components other than the polarization component parallel to the polarization component.

The inspection object 10 may be a film that transmits a predetermined amount of light, and in an embodiment, the inspection object 10 may be a polarizing film.

The inspection object 10 may be provided parallel to the reference polarizing plate 210 , and in order to improve the visibility of the stain by minimizing components other than the polarization component parallel to the transmission axis of the inspection object 10 , the reference polarizing plate It is preferable that the transmission axis of 210 and the transmission axis of the object 10 be orthogonal to each other.

The distance between the inspection object 10 and the reference polarizing plate 210 is not particularly limited as long as the stain can be visually recognized by the light irradiated from the light source unit 100, but is preferably 30 mm to 60 mm.

cinematographer

The photographing unit 300 is to photograph the examination object 10 in which the stain is visualized by the light irradiated from the light source 200 , and transmit the image to the image processing unit 400 .

The automatic spot inspection apparatus according to the present invention may acquire the images illustrated in FIG. 2 by photographing the inspection object 10 using the photographing unit 300 .

The photographing unit 300 may be provided on one surface of the filter unit 200 , and preferably may be provided opposite the light source unit 100 , for example, on the upper portion of the filter unit 200 . may be provided.

The photographing unit 300 is not particularly limited as long as it can obtain an image of the object 10 in which the stain is visualized. For example, there may be a color line-scan camera, a digital camera, and the like, and a color line-scan camera is preferable in order to emphasize the contrast between the background area and the speckle area.

The photographed image of the object 10 is transmitted to the image processing unit 400, and in general, the image includes data such as brightness, transmittance, color, or position information of each pixel of the light transmitted through the filter unit 200. Included.

image processing unit

The image processing unit 400 may be for determining the presence or absence of a speckle defect of the examination object 10 through a series of calculation processes for each examination area on the image of the examination object 10 photographed by the photographing unit 300 .

In one embodiment of the present invention, the image processing unit 400 may include a data extraction unit and an analysis unit.

The data extraction unit may be configured to extract brightness data from an image of the examination object 10 obtained by the photographing unit 300 to set an examination area according to a location.

The brightness data may include an orthogonal transmittance, a value of an orthogonal color a*, and a value of an orthogonal color b*.

The orthogonal transmittance refers to the intensity (%) of the light transmitted through the two polarizing plates when the two polarizing plates (or polarizing films) are arranged in a state in which the absorption axis is perpendicular to the intensity of light irradiated from the light source. do.

The orthogonal color refers to a color obtained by irradiating light to the two polarizing plates when the two polarizing plates (or polarizing films) are disposed in a state in which absorption axes are perpendicular.

At this time, the value of the orthogonal color a* means a value representing a color in the CIE coordinate system to the extent that it is biased toward either Red or Green in the CIE color space in orthogonal transmission, and a positive (+) value is in Red. close, and a negative (-) value means close to Green. In addition, the value of the orthogonal color b* indicates the degree to which yellow and blue in the CIE color space are biased in the orthogonal transmission, and means a value expressing the color in the CIE coordinate system. A positive (+) value is close to yellow, A negative (-) value means close to Blue.

In the present invention, the orthogonal transmittance, the value of the orthogonal color a*, and the value of the orthogonal color b* are determined when the object 10 and the reference polarizing plate 210 are disposed in a state in which absorption axes are orthogonal to each other. and a value obtained by irradiating light to the reference polarizing plate 210 .

According to an embodiment of the present invention, the data extractor selects a plurality of arbitrary points from the obtained image, and the orthogonal transmittance, the value of the orthogonal color a*, and the value of the orthogonal color b* at the selected plurality of arbitrary points. It is possible to extract brightness data including

Referring to Figure 3, the plurality of arbitrary points, the number is not particularly limited to select, the stain is approximately 5 to 10mm thick in the machine direction (MD; Machine Direction) of the object 10 to be long generated points can be selected.

Specifically, the orthogonal transmittance, the value of the orthogonal color a*, and the value of the orthogonal color b* at a plurality of arbitrary points in a 100 mm X 100 mm region of the acquired image may be measured and extracted.

For example, when the image size is based on an image having a vertical length and a vertical length of 100 mm, it is preferable to select 10 to 20 points for the plurality of arbitrary points. When an arbitrary point from which the brightness data is extracted is selected to be less than the above range, an error in determining a spot defect may occur. It is preferable to use the extraction point by appropriately selecting the number within the above range.

In addition, when the size of the image is 100 mm in width and length, the distance between each point at the plurality of arbitrary points is the distance from one point to another in consideration of the size (thickness) of the stain defect. may be selected as 5 to 10 mm.

According to one embodiment of the present invention, the analysis unit is for determining the presence or absence of a speckle defect present in the object to be inspected, and may be to compare and analyze the brightness data extracted from the data extraction unit and brightness data in a preset reference range. .

The preset reference range may be set in consideration of brightness data of a sample measured using a measuring instrument such as a spectrophotometer. In this case, a sample measured with a spectrophotometer in order to set a reference range may be a normal product without stain defects and a product having standard specifications.

For example, when the object to be inspected is a Slim STP polarizing film, brightness data is obtained by measuring the Slim STP polarizing film with a spectrophotometer, and the reference range is orthogonal transmittance (%) 0% to 2.0% or more, orthogonal color a* It can be set to a value of -4.2 or more and 2.2 or less, and a value of the orthogonal color b* of -16.0 or more to -4.0 or less.

In addition, when the object to be inspected is an IPS NT polarizing film, the reference range is the orthogonal transmittance (%) of 0% to 0.01% or more, the value of orthogonal color a* -1.0 or more to 1.0 or less, and the value of orthogonal color b* -1.8 It can be set to more than or equal to -1.8 or less. In addition, when the object to be inspected is a NUV polarizing film, the reference range is the orthogonal transmittance (%) of 0% to 2.0% or more, the value of orthogonal color a* -6.2 or more to 0.2 or less, and the value of orthogonal color b* -16 It can be set to more than or equal to -4 or less.

The reference ranges are not limited thereto, which correspond to one example for explaining the present invention, and may be changed or adjusted to various numerical ranges according to standard specifications changes according to conditions required for products or changes in technology.

In one embodiment of the present invention, the analysis unit compares the brightness data extracted from the data extraction unit with the brightness data in a preset reference range to obtain orthogonal transmittance, orthogonal color a* values and orthogonal values for the object 10 to be inspected. If all of the brightness data including the value of color b* falls within the reference range, it can be determined as a normal product. Also, when the brightness data of at least one of the orthogonal transmittance, the value of the orthogonal color a*, and the value of the orthogonal color b* for the object 10 is out of the reference range, it may be determined as a defective product.

If necessary, the intensity of the speckle defect present in the object may be determined by using the brightness data for the orthogonal transmittance, the orthogonal color a* value, and the orthogonal color b* value extracted from the data extractor.

For example, the intensity of the speckle defect of the test object increases as the orthogonal transmittance, orthogonal a*, and orthogonal b* values of the test object differ from standard specifications, that is, preset standard orthogonal transmittance, standard orthogonal a*, and standard orthogonal b*. It is judged as strong strength, and the smaller the difference, the weaker strength can be judged.

According to the present invention, as described above, by comparing and inspecting the brightness information of the object to be inspected and the brightness information of the product standard specification, the occurrence of over-examination and under-examination can be reduced and inspection performance can be improved.

display unit

The automatic spot inspection apparatus of the present invention may further include a display unit 500 that displays the inspection result of the image processing unit 400 .

Specifically, when the determination of whether the test object 10 is defective by the image processing unit 400 is completed, the display unit 500 displays whether the test object 10 is defective, so that the operator can check this. can

<Automatic stain inspection method>

The present invention includes an automatic spot inspection method using the above-described automatic spot inspection apparatus.

4 is a schematic flowchart illustrating an automatic spot inspection method according to an embodiment of the present invention.

Referring to FIG. 4 , the automatic spot inspection method of the present invention includes a light irradiation step (S10) of irradiating light to an object to be inspected; a photographing step (S20) of obtaining an image obtained by photographing the light-irradiated object; extracting brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of orthogonal color b* at a plurality of arbitrary points in an image obtained from the object (S30); and analyzing whether the brightness data extracted in the step S30 is within a preset reference range (S40); may include.

Hereinafter, an automatic stain inspection method according to an embodiment of the present invention will be described, but the present invention is not limited thereto.

First, the object to be inspected is provided so that the transmission axis is perpendicular to the reference polarizing plate. Thereafter, by irradiating light from a light source such as a backlight unit (BLU), an LED light source, or a metal halide lamp positioned below the test object and the reference polarizing plate, the stain on the test object is visualized. Preferably, in order to irradiate by controlling the wavelength of light, an LED light source may be used.

The inspection object whose stain is visualized by the irradiated light is photographed using a color line-scan camera, a digital camera, or the like.

Thereafter, brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of orthogonal color b* are extracted at a plurality of arbitrary points in the image of the photographed object.

Then, the gray data converted by summing the RGB data located in the same pixel is converted into a continuous graph such as a graph based on the pixel position value in the lateral direction (TD). In another embodiment, the method of converting the gray data into gray data may include a method of multiplying and summing a correction coefficient.

Thereafter, it is analyzed whether the extracted brightness data is within a preset reference range. At this time, if the orthogonal transmittance, the value of the orthogonal color a*, and the value of the orthogonal color b* in the extracted brightness data are all within the reference range, it is determined as a normal product, and the orthogonal transmittance and the orthogonal color a* in the extracted brightness data If any one or more of the value of and the orthogonal color b* is out of the reference range, it is determined as defective, and the presence or absence of a spot defect is derived.

In addition, according to an embodiment of the present invention, the orthogonal transmittance of the sample, the value of the orthogonal color a*, and the brightness data of the value of the orthogonal color b* are measured using a spectrophotometer before or after performing step S10. The step of setting the range may be further performed.

On the other hand, although it has been described that each step and sub-step are sequentially performed in the above method, each step and sub-step may be individually and simultaneously performed.

The components disclosed in the automatic spot inspection method may exhibit all the characteristics described in the item <automatic spot inspection apparatus> .

In addition, each step of the automatic spot inspection method may be implemented by the components described in the item <Automatic spot inspection apparatus> .

10: test object
100: light source unit
200: filter unit
210: reference polarizing plate
300: shooting department
400: image processing unit

Claims (11)

a light source unit disposed on one side of the examination object and irradiating light to the examination object;
a filter unit disposed on the other side of the object to be examined and including a reference polarizing plate for polarizing light passing through the object;
a photographing unit which receives the light passing through the inspection object and the filter unit to obtain an image; and
It includes an image processing unit that detects a stain using the image obtained by the photographing unit,
The image processing unit,
a data extractor configured to extract brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of orthogonal color b* from a plurality of arbitrary points in the acquired image; and
and an analyzer configured to analyze whether the extracted brightness data is within a preset reference range. The apparatus of claim 1, wherein the preset reference range is set using brightness data of a sample measured with a spectrophotometer. The apparatus of claim 1 , wherein the preset reference range is adjusted or changed according to a type of an object to be inspected. The automatic spot inspection apparatus of claim 1 , wherein the light source unit irradiates light having the same wavelength as that of a light source used when measuring brightness data of a sample for setting a reference range. The apparatus according to claim 1, wherein the size of the acquired image is 100 mm in width and length. 6. The method of claim 5,
10 to 20 points are selected as arbitrary points from which brightness data is extracted from the acquired image. The apparatus of claim 5 , wherein a distance between one point and another point at an arbitrary point from which brightness data is extracted from the acquired image is 5 to 10 mm. The automatic spot inspection apparatus according to claim 1, wherein the light irradiated from the light source unit is irradiated perpendicularly to the object to be inspected and the reference polarizing plate. The automatic spot inspection apparatus according to claim 1, wherein the inspection object includes a polarizing film. The automatic spot inspection apparatus of claim 1, further comprising a display unit displaying the presence or absence of a spot defect derived by the image processing unit. A light irradiation step (S10) of irradiating light to the test object;
a photographing step (S20) of obtaining an image obtained by photographing the light-irradiated object;
extracting brightness data including orthogonal transmittance, a value of an orthogonal color a*, and a value of orthogonal color b* at a plurality of arbitrary points in an image obtained from the object (S30); and
analyzing whether the brightness data extracted in the step S30 is within a preset reference range (S40); Including, automatic stain inspection method.

Images