TWI493177B - Method of detecting defect on optical film with periodic structure and device thereof - Google Patents

Description

Method for detecting flaw detection of optical film with periodic structure and detection device thereof

The present invention relates to an automated optical inspection (AOI) method and a detection apparatus, particularly for detecting an optical film having a periodic structure, such as a phase retardation film for guiding a stereoscopic image, and a guide. Light board, etc.

Generally, the optical film on the optical film is detected by an automatic optical detection method. First, an image having defects is taken from the optical film, and then the threshold value of the bright state and the dark state is used to determine whether the optical film has germanium. However, the above detection method cannot be used to detect an optical film having a periodic texture structure, such as a phase retardation film or a light guide plate or the like.

Referring to Figure 1A, there is shown a gray scale distribution map corresponding to different positions on a flawless phase retardation film. The phase retardation film is composed of a plurality of parallel phase-arranged first phase regions 11 and second phase regions 22. So when When the gray scale values at different positions on the film are calculated, a gray scale distribution map with a periodic grid as shown in FIG. 1A appears, and the gray scale values corresponding to different positions on the phase retardation film structure have different heights. . It can be seen from FIG. 1A that the gray scale value of the flawless phase retardation film falls between the range of the bright state threshold and the threshold of the dark state threshold, wherein the threshold value of the bright state is 200; The dark threshold is 140.

Next, referring to Fig. 1B, there is shown a 相位 phase retardation film whose phase retardation corresponds to a gray scale distribution map at different positions on the film. As shown in FIG. 1B, an abnormal phenomenon (abnormal waveform D) indicating a gray scale distribution value of about 200 on the horizontal axis indicates that the phase retardation film is defective. However, if the above-mentioned bright threshold value and dark state threshold value are used, the defect cannot be detected.

Furthermore, the threshold value is usually set by capturing an image from a standard, calculating the image grayscale value as a threshold value, and inputting the threshold value to the detecting device. Whenever the optical film is detected, it is compared with the previously set threshold value. However, the intensity of the light source that captures the image of the standard is not exactly the same as the intensity of the light source that captures the image of the sample to be tested each time. Therefore, using the standard comparison method, there is still an error caused by the ambient light source. produce.

Therefore, the present invention proposes a flaw detection method for detecting an optical film having a periodic structure, in addition to effectively detecting defects on an optical film having a periodic structure, and avoiding the influence of an ambient light source.

In view of the above, an object of the present invention is to provide a flaw detection method for detecting an optical film having a periodic structure, the method comprising the steps of: (A) drawing on an optical film to be inspected having a periodic structure; An original image having a periodic structure of m periods, wherein m is a positive number; (B) extracting a sub-image from the original image, the first sub-image comprising a periodic structure of n periods, wherein n is a positive number , n<m; (C) extracting a pair of images from the original image, the comparison image contains a periodic structure of n periods, where n is a positive number, n < m, the position and sub-image of the comparison image Different, but the area of the comparison image is the same as the sub-image; (D) image processing the sub-image and the comparison image to obtain a processed image; (E) calculating the average grayscale value of the processed image; and (F) analyzing the average The gray scale value is used to determine whether the optical film corresponding to the sub image has flaws.

Another object of the present invention is to provide a flaw detection apparatus for detecting an optical film having a periodic structure, comprising: an optical image pickup unit; an image processing unit; a gray scale value calculation unit; and an analysis unit. The optical imaging unit is configured to capture an original image on the optical film to be detected, and capture a sub-image and a comparison image from the original image. The image processing unit is coupled to the optical imaging unit for performing image processing on the sub-image and the comparison image to obtain a processed image. The grayscale value calculation unit is coupled to the image processing unit for calculating an average grayscale value of the processed image. Analysis unit is coupled The gray scale value calculation unit is configured to analyze whether the optical film corresponding to the sub image has flaws from the average gray scale value of the processed image.

The above optical film having a periodic structure has at least two texture structures, and the two texture structures are parallel and repeatedly arranged to each other, and may be, for example, a phase retardation film or a light guide plate.

200‧‧‧Detection device

210‧‧‧ Optical camera unit

220‧‧‧Image Processing Unit

230‧‧‧ Gray scale value calculation unit

240‧‧‧Analysis unit

400, 500‧‧‧ original images

401, 402, 501, 502‧‧‧ texture structure

11‧‧‧First phase zone

22‧‧‧Second phase zone

41, 51‧ ‧ sub-image

42, 52‧‧‧ alignment images

D‧‧‧isolated waveform

D1, D2‧‧‧ Defects

S31, S32, S33, S34, S35, S36‧‧ steps

1A is a gray scale distribution diagram of a flawless phase retardation film; 1B is a gray scale distribution diagram of a phase retardation film having a 瑕疵; and FIG. 2 is a periodic structure optical of the detection of the present invention. An embodiment of a film detecting device for a film; FIG. 3 is a flow chart for detecting an optical film having a periodic structure; and FIG. 4 is an original image taken from an optical film of a periodic structure; and The figure is another preferred embodiment of the phase retardation film of the present invention for detecting a periodic structure.

The above and other technical contents, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Please refer to FIG. 2, which is a periodic structure of the detection tool of the present invention. An embodiment of the optical film detection device 200. The periodic structured optical film is a phase retardation film having two texture structures and the two texture structures are arranged parallel to each other and repeatedly.

The flaw detection device 200 of the present invention includes an optical imaging unit 210, an image processing unit 220, a grayscale value calculation unit 230, and an analysis unit 240.

The optical imaging unit 210 is configured to capture an original image on the optical film to be detected, and capture a sub-image and a comparison image from the original image. The image processing unit 220 is coupled to the optical imaging unit 210 for performing image processing on the sub-image and the comparison image to obtain a processed image. The grayscale value calculation unit 230 is coupled to the image processing unit 220 for calculating an average grayscale value of the processed image. The analysis unit 240 is coupled to the grayscale value calculation unit 230 for analyzing the average grayscale value to determine whether the region of the optical film corresponding to the subimage has flaws.

Referring to FIG. 2, FIG. 3 and FIG. 4, and in conjunction with a preferred embodiment of the method for detecting a periodic structured optical film of the present invention, each detecting step performed by the detecting device cooperative detecting method is further described.

Please refer to FIG. 3, which is a flow chart for detecting an optical film having a periodic structure. Figure 4 is an image of one of the original images taken from the optical film of the present invention having a periodic structure.

In step S31, an original image is captured on an optical film to be detected having a periodic structure, and the original image has a periodic structure of m periods, where m is a positive number. The periodic structure referred to in the present invention means that an optical film has at least two texture structures, and the two texture structures are parallel to each other and Repeat the arrangement.

As shown in FIG. 4, the original image 400 is an image captured by the optical imaging unit 210 of FIG. 2 on a phase retardation film having a periodic structure. The original image 400 is composed of a plurality of texture structures 401 and 402, and the texture structures 401 and 402 are parallel and repeatedly arranged. This original image 400 has eight periodic structures (m=8), which is consistent with m being a positive number.

In step S32, a sub-image is captured from the original image, and the sub-image includes a periodic structure of n periods, where n is a positive number and n<m.

As shown in FIG. 4, the sub-image captured by the optical imaging unit 210 of FIG. 2 is 41. The sub-image 41 is composed of a plurality of parallel and repeatedly arranged texture structures 401 and 402. This sub-image 410 has a periodic structure of three cycles (n=3), and n is a positive number and n<m.

Next, in step S33, a comparison image is captured from the original image, and the comparison image includes a periodic structure of n periods, where n is a positive number and n<m. The capture position of the comparison image is different from the sub-image, but the area of the comparison image is the same as the sub-image.

As shown in FIG. 4, the comparison image captured by the optical imaging unit 210 of FIG. 2 is 42. The comparison image 42 includes a periodic structure of three cycles (n=3), and the alignment positions of the comparison image 420 and the sub-image 410 are different, but the image areas of the two are the same.

The difference between the above-mentioned comparison image and the sub-image capture position means that the positions of the two images can still partially overlap, but do not include complete overlap.

In step S34, image processing is performed on the sub-image and the comparison image by image processing to determine whether the optical film corresponding to the sub-image has defect.

The image processing system described above may include image subtraction and/or image filtering. The image processing unit 220 subtracts the sub-image 41 from the comparison image 42 to obtain a first processed image. Image filtering is then performed to confirm whether or not there is a flaw in the first processed image. If the first processed image does not have the 瑕疵 of the matching image 42, the step S35 can be continued. If the first processed image has a contrast to the image 42 , the 瑕疵 is filtered first to avoid the determination of the final flaw.

In step S35, the grayscale value calculation unit 230 of Fig. 2 calculates the average grayscale value of the processed image.

In step S36, the analyzing unit 240 of FIG. 2 determines whether the optical film corresponding to the sub-image has flaws by analyzing the average grayscale value of the processed image. When the average grayscale value of the first processed image is 0, it means that the optical film corresponding to the subimage has no defects. On the contrary, when the average grayscale value is greater than 0, it means that the optical film corresponding to the sub-image is defective. In this embodiment, the average grayscale value of the first processed image is greater than 0, that is, the phase retardation film corresponding to the subimage 410 has a defect D1.

However, in the above step S32, the method of extracting a sub-image from the original image is not limited to the embodiment shown in FIG. Fig. 5 is another embodiment of the phase retardation film of the present invention for detecting a periodic structure.

The original image 500 is an image taken from a phase retardation film of a periodic structure. The original image 500 has a plurality of parallel and repeatedly arranged textures 501 and 502. This original image 500 has eight periodic structures (m=8), which is consistent with m being a positive number.

First, a sub-image 51 is captured from the original image 500, and the sub-image 51 is composed of a plurality of parallel and repeatedly arranged texture structures 501 and 502. This sub-image 51 has a periodic structure of four cycles (n=4), and n is a positive number and n<m.

Next, the comparison image 52 is captured from the original image 500. The alignment image 52 also has four sets of repeating structures (n=4).

Compared with the sub-image and the comparison image of FIG. 4, the sub-image and the comparison image shown in FIG. 5 partially overlap, but still meet the same extraction position and the same area. The subsequent image processing steps, calculation steps and analysis steps are the same as those in the embodiment shown in FIG.

The method for extracting sub-images and comparing images from the original image is not limited to any one of the methods, and can be appropriately adjusted according to the detection requirements and the detection efficiency.

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

S31~S36‧‧‧Steps

Claims (6)

A method for detecting flaws in an optical film having a periodic structure, comprising the steps of: (A) drawing an original image on an optical film to be inspected having a periodic structure, the original image having m cycles a periodic structure, wherein m is a positive number; (B) extracting a sub-image from the original image, the sub-image comprising a periodic structure of n cycles, wherein n is a positive number, and n < m; Obtaining a comparison image in the original image, the comparison image comprises n sets of repeated arrangement structures, wherein n is a positive number, n<m, the position of the comparison image is different from the sub-image, but the comparison image The area is the same as the sub-image; (D) performing an image processing on the sub-image and the comparison image to obtain a processed image; (E) calculating an average grayscale value of the processed image; and (F) analyzing the image The average grayscale value is used to determine whether the optical film corresponding to the sub-image has flaws. The method for detecting flaws as described in claim 1, wherein the image processing comprises an image subtraction and/or an image filtering. The method for detecting flaws as described in claim 1, wherein when the average grayscale value of the processed image is not 0, it indicates that the optical film corresponding to the sub-image has 瑕疵. The method of detecting a flaw according to the first aspect of the invention, wherein the optical film having a periodic structure may be a phase retardation film or a light guide plate. A cymbal detecting device for detecting an optical film having a periodic structure, comprising: an optical imaging unit for capturing an original image on an optical film to be detected, and extracting a sub-image from the original image and An image processing unit coupled to the optical camera unit for performing an image processing on the sub image and the comparison image to obtain a processed image; a gray scale value calculating unit coupled to the image An image processing unit is configured to calculate an average grayscale value of the processed image; and an analyzing unit coupled to the grayscale value calculating unit to analyze the average grayscale value to determine whether the optical film corresponding to the subimage corresponds to the optical film Have a flaw. The detection device of claim 5, wherein the image processing unit further comprises an image subtraction unit and/or an image filtering unit.