TWI629665B - Defect inspection method and defect inspection system - Google Patents

Abstract

Defect inspection method and defect detection system. The defect inspection method includes an image acquisition step and a conversion step. The image capturing step includes shooting a surface of an optical film to generate a two-dimensional image. The conversion step includes converting a two-dimensional image into a grayscale value curve. The grayscale value curve includes a defect grayscale value curve corresponding to a concave-convex defect portion of the optical film.

Description

Defect inspection method and defect detection system

The present invention relates to a defect inspection method and a defect inspection system, and more particularly, to a concave-convex defect inspection method for an optical film.

With the advancement of technology, the requirements for various optical components used in liquid crystal display devices are also high. However, in the production process of optical components, defects are easily caused by various factors, thereby reducing the display quality. Therefore, a defect detection system is configured in the production system of the optical component, and the defective optical component is eliminated early.

The invention relates to a defect inspection method and a defect detection system.

According to an aspect of the present invention, a defect inspection method is provided, which includes an image capturing step and a converting step. The image capturing step includes shooting a surface of an optical film to generate a two-dimensional image. The conversion step includes converting a two-dimensional image into a grayscale value curve. The grayscale value curve includes a defect grayscale value curve corresponding to a concave-convex defect portion of the optical film.

According to another aspect of the present invention, a defect inspection method is provided, which includes an image capturing step and a converting step. The image capturing step includes shooting a surface of an optical film to generate a two-dimensional image. The converting step includes converting the data based on the two-dimensional image into a three-dimensional data. The three-dimensional data includes a height difference between an uneven defect portion and a flat portion of the optical film.

According to yet another aspect of the present invention, a defect detection system is proposed. The defect inspection system is used to inspect an optical film. The defect detection system includes a light source, an image capturing device, and a slit plate. The light source is disposed on one side of the optical film. The image capturing device is disposed on the other side of the optical film. The slit plate has a slit. The slit plate is disposed between the light source and the optical film, so that an incident light passes through the slit. The image capture device is offset from the extended connection of the light source and the slit. When the image sensor of the image capture device is aligned with the extended connection between the light source and the slit, the brightness of the image is I ₀ . When the image capturing device is shifted from the extension line of the light source and the slit in the moving direction of the parallel optical film, the brightness of the image sensed is I ₁ . I ₁ / I ₀ is a defect location point of 0.5 ~ 0.9 observable optical film.

In order to have a better understanding of the above and other aspects of the present invention, the following specific examples are described in detail below in conjunction with the accompanying drawings:

10‧‧‧ Optical Film

11‧‧‧ roller

12‧‧‧Image Processing Unit

13‧‧‧Control unit

14‧‧‧ period signal generation unit

17‧‧‧display unit

100‧‧‧ Defect detection system

110‧‧‧light source

110a‧‧‧ light emitting surface

120‧‧‧Image capture device

130‧‧‧Slit Plate

130s‧‧‧Slit

250‧‧‧ 2D image

252‧‧‧Defective image

254‧‧‧plane image

256‧‧‧ the first pixel part

258‧‧‧Second Pixel Section

350‧‧‧ Enhance 2D image

471, 473‧‧‧ images

D1‧‧‧ direction of movement

LA‧‧‧ Optical axis

Li‧‧‧ incident light

Ls‧‧‧ scattered light

P‧‧‧Area

S901‧‧‧Image capture steps

S902‧‧‧ Conversion steps

S903‧‧‧Display steps

S904‧‧‧Judging steps

S9021‧‧‧Signal Steps

S9022‧‧‧First conversion step

S9023‧‧‧Second conversion step

FIG. 1 illustrates a defect inspection method according to an embodiment of the present invention.

FIG. 2 illustrates a defect detection system according to an embodiment of the present invention.

FIG. 3 is a second image obtained by performing an image capturing step on an optical film in an embodiment. Dimensional image.

FIG. 4 is a two-dimensional image obtained after the conversion step in an embodiment.

FIG. 5 is a grayscale value relationship curve of a defect image along a section line of a two-dimensional image obtained through a conversion step in an embodiment.

FIG. 6 shows the relationship between the grayscale value integral and the substantial height value of the concave-convex defect part in an embodiment.

FIG. 7 is an image of a concave-convex defect portion in an embodiment.

Fig. 8 is a graph showing the height value of the cross-sectional position of the concave-convex defect portion in an embodiment.

Please refer to FIG. 1, which illustrates a defect inspection method of an optical film according to an embodiment of the present invention. The method may include an image capture step S901, a conversion step S902, a display step S903, and a determination step S904.

In one embodiment, the defect inspection method can be executed by using the defect detection system 100 shown in FIG. 2. Please refer to FIG. 2. The defect detection system 100 can be used to detect the optical film 10 being transferred. The optical film 10 is transported along the moving direction D1 via the roller 11 on the production line. The defect detection system 100 can instantly identify the defect. , Early exclusion of defective parts. In one embodiment, the present invention can be used to detect optical film rolls or sheet-like optical films.

The defect detection system 100 is applicable to various optical films 10. For example, the optical film 10 may be a single-layer or multi-layer film, such as a polarizer, Retardation film, brightness enhancement film or other films that are helpful for optical gain, alignment, compensation, steering, orthogonal, diffusion, protection, anti-stick, scratch resistance, anti-glare, reflection suppression, high refractive index, etc .; A polarizing plate, a retardation film, and the like with a protective film attached to at least one side of the aforementioned polarizer; the protective film can be selected from, for example, cellulose resin, acrylic resin, amorphous polyolefin resin, and polyester resin. , Polycarbonate resins, and combinations thereof, but this disclosure is not limited to these films.

The defect detection system 100 includes a light source 110 and an image capturing device 120. It can be, for example, a fluorescent lamp, a metal halide lamp or an LED lamp, and the light source 110 has a light emitting surface 110a. In a preferred embodiment, the light source 110 is an LED lamp. The image capture device 120 may be a line scan camera, which has an image sensor. The image sensor is, for example, a Charge Coupled Device (CCD) or any element having a photoelectric conversion capability.

As shown in FIG. 2, the light source 110 and the image capturing device 120 are disposed on two opposite sides of the optical film 10 being transferred. Specifically, the light source 110 irradiates light from one side of the optical film 10, and the image capturing device 120 receives a transmitted light image of light passing through the optical film 10 on the other side of the optical film 10. In this disclosure, the irradiation angle of light is not particularly limited. In one embodiment, the light source 110 irradiates light vertically on one side of the optical film 10, that is, the incident light Li along the optical axis LA of the light emitting surface 110 a of the light source 110 is irradiated perpendicularly to the surface of the optical film 10. Here, the optical axis LA is an imaginary line, which is a normal line of the light emitting surface 110a. In one embodiment, the image capturing device 120 captures an image facing the surface of the optical film 10, that is, the image capturing device 120 faces the light source 110 parallel to the light source 110. The optical film 10 is photographed in the direction of the optical axis LA of the light emitting surface 110a, that is, the image capturing device 120 does not photograph the optical film 10 at an inclined angle.

In one embodiment, the defect detection system 100 further includes a slit plate 130. The slit plate 130 may be made of metal, ceramic, or polymer material. The slit plate 130 is disposed between the light source 110 and the optical film 10 to limit an angle of travel of the light. In an embodiment, the extended connecting line between the optical axis LA of the light emitting surface 110a of the light source 110 and the central axis (not labeled) of the slit 130s is perpendicular to the surface of the optical film 10 to limit incident light passing through the slit 130s Li is irradiated perpendicular to the surface of the optical film 10.

The image capturing device 120 can be moved in a movement direction D1 parallel to the optical film 10. For example, a moving unit can control the movement of the image capturing device 120 so that the image capturing device 120 is offset from the light source 110 and the slit 130s. Extension wiring configuration. In another embodiment, the image capturing device 120 can also be fixed, and the light source 110 and the slit plate 130 can be moved simultaneously (or in the opposite direction) in the moving direction D1 of the parallel optical film 10 at the same time to enable image capturing. The device 120 is offset from the extension line of the light source 110 and the slit 130s.

Because the incident light Li passes through the slit 130s, a diffraction effect is generated, so light and dark interlaced interference fringes are generated on the optical film 10, so that it is easier to detect the brightness change caused by the concave-convex defects on the optical film 10. In addition, when the incident light Li passing through the slit 130s passes through the area P where the thickness is locally changed on the optical film 10, that is, the concave-convex defect, the light is scattered. Since the image capturing device 120 is offset from the extended connection of the light source 110 and the slit 130s, the image capturing device 120 can receive a part of the scattered light Ls, which affects the image receiving device 120 receiving. The amount of light. On the other hand, when there is no concave-convex defect, since scattered light is not generated, the amount of light received by the image capturing device 120 does not change. As a result, as long as the incident light Li passes through the concave-convex defect on the optical film 10, the light will be scattered and affect the amount of light received by the image capturing device 120. Compared with the area without the concave-convex defect, the image capturing device The brightness of the received image 120 will change, so the contrast of the concave and convex defect area can be improved, and it can be more easily detected whether there is a defect.

Wherein, when the image sensor of the image capturing device 120 is aligned with the extended connection between the light source 110 and the slit 130s, the brightness of the image is I ₀ . Then, if the image capturing device 120 moves in the moving direction D1 of the parallel optical film 10 and deviates from the extended connection line between the light source 110 and the slit 130s, the brightness of the sensed image decreases to I ₁ . In the present disclosure, the offset of the image capturing device 120 or the optical film 10 can be adjusted according to the ratio range of I ₁ / I ₀ . When the range of I ₁ / I ₀ falls between 0.5 and 0.9, and the preferred range of I ₁ / I _{0 is} between 0.8 and 0.85, it is sufficient to observe the brightness change caused by the concave-convex defects of the optical film 10, and Locate the defect location. In one embodiment, the position of the concave-convex defect can be marked on the optical film 10 at the same time in this process.

In addition, the defect detection system 100 further includes an image processing unit 12, a periodic signal generating unit 14, a control unit 13 and a display unit 17. The image processing unit 12 may receive and process the image signal sent by the image capturing device 120 to perform image processing on the signal. The image processing unit 12 may be, for example, an image capturing card. The periodic signal generating unit 14 can send one cycle according to the transfer speed of the optical film 10 The signal may be, for example, an encoder. The control unit 13 may be coupled to the image processing unit 12 and the display unit 17, and receives a periodic signal from the periodic signal generating unit 14, and transmits a camera signal to the image capture device 120. The control unit 13 may be a computer, for example. Thereby, the operator can obtain the transmitted light image (information) captured by the image capturing device 120 from the control unit 13 and the display unit 17 to detect whether there is a defect in the image. The display unit 17 may include any display device capable of displaying an image to a user, such as a liquid crystal display, an LED display, or the like, and may also have a touch function for the user to operate the interface in a touch manner.

As shown in FIG. 3, in an embodiment, the two-dimensional image 250 obtained by performing the image capturing step S901 on the optical film 10 is the image signal sent by the image capturing device 120. The two-dimensional image 250 includes regions corresponding to local changes in the thickness of the optical film 10, namely, a defect image 252 of a concave and convex defect portion and a flat portion, ie, a planar image 254 of a non-defective portion with a flat surface. In one embodiment, in the two-dimensional image 250 obtained in the image capturing step S901, the pixel gray level of the defect image 252 is different from the pixel gray level of the planar image 254. As shown in FIG. 3, the defective image 252 includes a first pixel portion 256 and a second pixel portion 258, wherein the first pixel portion 256 is a bright pixel portion and the second pixel portion 258 is a dark pixel portion. The pixel gray level of the bright pixel portion may be higher than the pixel gray level of the planar image 254. The pixel gray level of the dark pixel portion may be lower than the pixel gray level of the planar image 254.

The two-dimensional image 250 obtained by the image capturing step S901 can only display the two-dimensional deformation amount of the bump defect portion, that is, the length, width, diameter, radius, Area, etc. Deformation. However, in some cases, for the quality evaluation of the optical film 10, the third-dimensional variable of the bump defect portion, that is, the height deformation data has more important reference value than the two-dimensional plane deformation data.

Therefore, according to the embodiment concept of the present disclosure, it is possible to know the degree of depression and protrusion of the concave-convex defect portion relative to the flat portion through the conversion step S902 and the display step S903, such as the height value of the concave and convex areas, and greatly Increase the accuracy of detecting the quality of the optical film 10.

In an embodiment, according to the embodiment concept of the present disclosure, it is possible to know the degree of depression and protrusion of the concave-convex defect portion relative to the flat portion through the conversion step S902 and the display step S903, such as the maximum height of the concave and convex areas. value.

In one embodiment, the conversion unit S902 and the determination step S904 are executed by the control unit 13, and the display step S903 is executed by the display unit 17.

In the embodiment, a signal enhancement step S9021 may be selectively performed first to convert the two-dimensional image 250 into an enhanced two-dimensional image 350.

In an embodiment, the signal enhancement step S9021 may include converting the two-dimensional image 250 shown in FIG. 3 according to the pixel gray level into an enhanced two-dimensional image 350 of the gray-scale display pixels shown in FIG. 4.

In an embodiment, the signal enhancement step S9021 sets the planar image 254 as a reference grayscale value, and uses the reference grayscale value to correspond to the grayscale value of the defective image 252. As shown in Figure 4, the planar image 254 can be converted from the original reference grayscale value pixels to a darker background image with a lower grayscale value to enhance the grayscale difference between the planar image 254 and the defect image 252, further Highlights the extent of the defect image 252, In this way, the defective image 252 can be captured more accurately to generate an enhanced two-dimensional image 350.

Next, a conversion step S902 is performed. The conversion step S902 includes a first conversion step S9022. The first conversion step S9022 includes converting the enhanced two-dimensional image 350 into a grayscale value curve, as shown in FIG. 5. For example, conversion can be performed through image processing methods. For example, the planar image 254 can be set as a reference grayscale value, and the grayscale value of the defective image 252 can be adjusted correspondingly with the reference grayscale value to enhance the grayscale value of each position of the defective image 252 of the two-dimensional image 350. The section line AB forms a corresponding grayscale value curve.

In an embodiment, as shown in FIG. 5, the display step S903 may display the grayscale value curve corresponding to the generated defect image 252 of the enhanced two-dimensional image 350 along the section line AB on the display unit 17.

For example, in the grayscale value curve, the grayscale value of the first pixel portion 256 of the defective image 252 is larger than the reference grayscale value 128, and the grayscale value of the second pixel portion 258 is smaller than the reference grayscale value 128. The reference grayscale value is not limited to the value 128 shown in FIG. 5, and is also defined as other values in other embodiments.

In one embodiment, the aforementioned signal strengthening step S9021 may be omitted, and the first conversion step S9022 may be directly executed to generate a grayscale value curve corresponding to the defect image 252 converted to the two-dimensional image 250 along the section line AB. The first conversion step is as described in the previous embodiment, and details are not described herein again.

However, the gray-scale value curve in FIG. 5 can indicate the degree of depression and convexity of the defect, and still cannot directly correspond to the actual height value of the concave-convex defect portion.

Therefore, in an embodiment, the conversion step S902 may further include a first step. The second conversion step S9023 is to convert the grayscale value curve shown in FIG. 5 into a three-dimensional data, where the three-dimensional data includes an actual height difference value of the uneven defect portion of the optical film 10 with respect to the flat portion.

In one embodiment, the second conversion step S9023 includes: an operation step and a comparison step. For example, an operation step is performed on the grayscale value curve in FIG. 5, and then a comparison step is performed to generate a three-dimensional data.

In one embodiment, the calculation step includes performing calculations based on the grayscale value difference of the grayscale value curve, the grayscale value ratio, the grayscale value differentiation, the grayscale value integration, or a combination of the above, but is not limited thereto, and other Statistical analysis of operations. The second conversion step in the following embodiments is described by using the gray-scale value integration as an operation method, but the present invention is not limited thereto.

The comparison step includes: integrating the result of the operation step, such as the integration of the gray scale curve with the actual defect sample data, to obtain a three-dimensional data of the actual defect height.

In an embodiment, for the collection method of actual defect sample data, please refer to FIG. 7 and FIG. 8 at the same time. Figures 7 and 8 show the actual three-dimensional data of the defect sample by using a surface profile measuring instrument in advance to obtain the three-dimensional data of the defect sample.

Referring to FIG. 7, in an embodiment, the three-dimensional data includes an image 471 displaying a height in color, and an image 473 displaying a height value corresponding to the color. In an embodiment, the image 471 can represent the distribution contours of the concave-convex defect portions and the nearby flat portions of the optical film 10, where the portion with a height of 0 is the flat portion, and the height The part greater than, less than 0 is the unevenness part, and the difference value with respect to the flat part, that is, the value 0 is the height value of the actual concave or convex part of the unevenness part. The user can directly understand the actual height value of the concave and convex defect portion of the optical film 10 with respect to the concave or convex portion of the flat portion through this data.

In one embodiment, the maximum height shown in FIG. 7 is used as the corresponding height in the relationship between the gray scale curve integral and the actual height value shown in FIG. 6.

Referring to FIG. 8, in another embodiment, the three-dimensional data includes a relationship curve between a cross-sectional position of a concave and convex defect portion and a corresponding height difference. The user can directly understand the actual height value of the concave and convex defect portion of the optical film 10 with respect to the concave or convex portion of the flat portion through this data.

In an embodiment, the maximum height value shown in FIG. 8 can be used as the corresponding height in the relationship between the gray scale curve integral and the actual height value shown in FIG. 6.

As mentioned above, after the second conversion step S9023, the relationship between the grayscale curve integral and the actual height value shown in FIG. 6 can be obtained.

Next, in an embodiment, the determination step S904 may determine the deformation degree of the optical film 10 according to the substantial height value of the concave-convex defect portion and set the product shipping specification level. In an embodiment, as shown in FIG. 6, for example, a setting specification of a substantial height value may be used as an evaluation basis. For example, the unevenness portion having a substantial height value greater than a set specification can be used as a basis for evaluating whether the optical film 10 can be used as a basis for product shipment, and the unevenness portion that is smaller than the set specification can be ignored.

In one embodiment, the setting specification may set only a single value, or use different values according to different evaluation standards. In one embodiment, the setting specification is 5 μm. If the optical film 10 finds more than 6 concave-convex defect portions with a substantial height value greater than the setting specification in an area of 1 cm ² , which indicates that the cluster density of the defects is too high, the quality of the optical film 10 is judged to be poor. , Cannot be shipped as a product. In another embodiment, the set specification is 7 μm. If the optical film 10 finds concave and convex defect portions with a substantial height value greater than the set specification, regardless of the number of defects, the optical film 10 is judged to be of poor quality and cannot be shipped as a product. The determination step S904 is not limited to the automatic determination by the control unit 13. In other embodiments, in some cases, an operator may also make an artificial judgment by using the information displayed by the display unit 17. This disclosure is not limited to this, and other evaluation methods can be used according to actual needs.

According to the above, in the embodiment of the present invention, the defect image that can only provide two-dimensional plane size information obtained in the image capturing step is converted into three-dimensional information including the actual height value of the defect through the conversion step, and the defect height information can be passed through Determining the degree of deformation of the concave and convex defect portion of the optical film in height, so that the quality of the optical film can be more accurately evaluated.

In summary, although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims (10)

A defect inspection method includes: an image capturing step including photographing a surface of an optical film to generate a two-dimensional image; a conversion step including converting the two-dimensional image into a grayscale value curve, the grayscale The step value curve includes a grayscale value curve of a defect corresponding to a concave and convex defect portion of the optical film; and a determining step includes determining a deformation condition of the concave and convex defect portion of the optical film according to the grayscale value curve of the defect. The defect inspection method according to item 1 of the scope of the patent application, wherein the conversion step includes converting the two-dimensional image obtained by the image capturing step into the grayscale value curve according to the pixel grayscale. The defect inspection method according to item 1 of the scope of patent application, wherein the two-dimensional image includes a defect image and a planar image corresponding to the uneven defect portion and a flat portion of the optical film, respectively, and the grayscale of the defect image is different. The gray level of pixels in the plane image. The defect inspection method according to item 1 of the scope of patent application, further comprising a data display step, including displaying the grayscale value curve in a display unit, wherein the displayed data includes a cross-sectional position of the defect image of the two-dimensional image. Relationship with the corresponding grayscale value. A defect inspection method includes: an image capturing step including performing a photographing action on a surface of an optical film to generate a two-dimensional image; a conversion step including converting data based on the two-dimensional image into a three-dimensional data, The three-dimensional data includes a height difference between an uneven defect portion of the optical film and a flat portion. The defect inspection method described in item 5 of the scope of patent application, further includes performing a signal enhancement step before the conversion step, wherein the signal enhancement step is to adjust the two-dimensional image correspondingly with a reference gray level value to form a gray Image of the display pixel. The defect inspection method according to item 5 of the scope of patent application, wherein the conversion step includes: converting the two-dimensional image into a grayscale value curve; and converting the grayscale value curve into the three-dimensional data. The defect inspection method according to item 7 of the scope of patent application, wherein converting the grayscale value curve into the three-dimensional data includes based on grayscale value difference, grayscale value ratio, grayscale value differentiation, grayscale value integration, or the above Combination to do the operation. The defect inspection method described in item 5 of the scope of patent application, further includes a determining step, including determining a degree of deformation of the optical film according to the height difference. A defect detection system for detecting an optical film and includes: a light source disposed on one side of the optical film; an image capturing device disposed on the other side of the optical film; and a slit plate having A slit, the slit plate is disposed between the light source and the optical film, so that an incident light passes through the slit; wherein the image capturing device is offset from the extension of the light source and the slit; Line, wherein when the image sensor of the image capture device is aligned with the extended connection of the light source and the slit, the brightness of the image sensed is I ₀ ; when the image capture device is parallel to the optical film When the moving direction is shifted from the extended line connecting the light source and the slit, the brightness of the image sensed is I ₁ ; and I ₁ / I ₀ is 0.5 to 0.9, and a defect of the optical film can be observed. Location point.