KR20060034949A - Plasma display panel inspection device and inspection method using color camera - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pixel defect primary inspection apparatus and an inspection method of a plasma display panel. In particular, the pixel defect inspection apparatus and method of the plasma display panel according to the present invention output a pattern generated by a pattern generator to a plasma display panel. Shooting with a color camera and processing and inspecting the captured images with a computer to identify the type and location of defects such as bright spots, bright spots, dark spots, and dark spots. The LOG mask can be used to detect accurate and various defects without moiré pattern filtering, thereby improving productivity and increasing inspection reliability.

Plasma Display Panel, PDP Panel, Color Camera, Cell Defect, Inspection

Description

Plasma display panel inspection device and inspection method using color camera {Plasma Display Panel Examination Apparatus and Examining Method for the same}             

1 is a view showing an apparatus for inspecting a plasma display panel using a color camera according to the present invention;

2 is a flowchart illustrating a plasma display panel inspection method using a color camera according to the present invention;

3 is a view comparing the moiré pattern according to the camera setting state,

4 is a three-dimensional graph of the LOG mask used in the present invention,

5 is a diagram illustrating an image processing process according to the present invention;

6 is a view showing a bright spot detection process using a color camera according to the present invention;

7 is a view showing a bright spot detection process using a black and white camera according to the prior art.

<Explanation of symbols on main parts of the drawings>                 

10: plasma display panel

20: pattern generator

30: color camera

40: video input board

50: computer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting pixel defects in a plasma display panel and an inspection method using the apparatus. In particular, a plasma display panel inspection apparatus and inspection method for automatically detecting defective pixels and types of defects using a color camera are provided. It is about.

In general, in a plasma display primary inspection, cell defects are made by human visual inspection. In this case, the cell defect refers to a pixel-level defect that occurs when the plasma display upper panel and the lower panel are joined together and then turned on by supplying power to the plasma display. Such cell defects are brighter than the surroundings or may be caused by interference from other cells. The bright spot is a cell that emits a color other than the original color, the dark spot is a cell that is always off regardless of the input, and the bright spot is a cell that is always on, and the flicker is a blinking cell. There is a mixture of phosphors, foreign matters, and electrical factors due to the collapse.

The conventional human visual inspection for detecting such cell defects may be judged differently according to the skill level of the operator and subjective judgment.If the operator observes the plasma display for a long time, the fatigue increases and the concentration decreases. This can overlook defects or cause errors in defect inspections, which will also lengthen your work time. In particular, as the plasma display increases in size, the problem of visual inspection becomes more prominent.

Among the prior arts, there is an apparatus for automatically detecting cell defects of a plasma display panel (published number: 10-2004-0021401). This technique detects defects such as dark spots, bright spots, and dark spots. The algorithm that detects defects by comparing panels with defective panels is adopted, which is vulnerable to moiré patterns, and has a problem of filtering moiré patterns by a separate software method.

The present invention has been made to solve the above problems of the prior art, the object of which is to display a pattern on the plasma display panel in the detection of cell defects in the plasma display panel, and automatically detects defects on a pixel-by-pixel basis in each pattern. It is an object of the present invention to provide a plasma display panel inspection apparatus and an inspection method using the same, which detects accurate cell defects without using software filtering of moiré patterns by using a color camera for detection and proper image conversion.

According to a plasma display panel inspection apparatus using a color camera according to the present invention for solving the above problems, a pattern generator for generating a pattern to output a predetermined pattern to the plasma display panel; A color camera for capturing an image of the plasma display panel on which the pattern generated by the pattern generator is output; An image input board configured to store the image photographed by the color camera as a digital image signal; And a computer for inspecting an image defect by receiving the digital image signal stored in the image input board.

In addition, according to the plasma display panel inspection method using a color camera according to the present invention, generating a pattern in the pattern generator and outputting a predetermined pattern to the plasma display panel; Photographing a pattern output on the plasma display panel with a color camera; And detecting a defect for each channel of the color image signal photographed by the color camera and integrating defect information to determine the type of the defect.

The pattern generator may change the pattern to repeat the first to third steps.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the plasma display inspection apparatus according to the present invention, as shown in FIG. 1, a pattern is generated such that a predetermined pattern is output to the plasma display panel 10 and the plasma display panel 10 to be detected as cell function. A digital image signal is generated by the color camera 30 and the image captured by the color camera 30 to capture an image of the plasma display panel 10 on which the generator 20 and the pattern generated by the pattern generator 20 are output. And an image input board 40 for storing the data, and a computer 50 for receiving the digital image signal stored in the image input board 40 and inspecting an image defect.

 First, the pattern generator 20 is a device for generating and outputting various patterns on the plasma display panel 10 to be inspected. In particular, five patterns using red, green, blue patterns and white and black patterns corresponding to R, G, and B channels for efficient inspection of various defects such as bright spots, bright spots, dark spots, and dark spots as described below. It is based on generating.

The color camera 30 photographs the pattern generated by the pattern generator 20 and output to the plasma display panel 10. In general, color cameras have a mosaic method using one CCD (Charge Coupled Device) and three CCD methods. In the mosaic method, color aliasing occurs at the interface between an object and a background, and the resolution is low. There are disadvantages. Compared to this, a color camera using 3-CCD has three CCDs, and the light passing through the lens is separated by R, G, and B wavelength bands by a prism, which is different in each CCD. You get a color image. By using a 3-CCD color camera, a high resolution image can be obtained and a step phenomenon, which is a disadvantage of the 1-CCD color camera described above, can be eliminated. In particular, in the case of separating the image of the color camera for each of the R, G, B channels, the 3-CCD color camera has an advantage of obtaining an image having a higher resolution and color classification. The color camera used in the present invention comprises a 3-CCD camera.

The image input board 40 stores the image signal received from the color camera 40 and transmits the image signal to the computer 50 to be described later.

The computer 50 processes the image signal received from the image input board 40. In particular, the computer 50 may directly inspect the defects by analyzing the image signal of the color camera, but in order to detect defects such as bright spots, bright spots, etc. more efficiently, the color camera 30 may use the R, G, B channels. It functions to determine the type of image defect by separating the captured video signal. In order to further emphasize image defects, convolution is applied with a LOG mask, and then thresholds are applied and binarized to detect and integrate defects for each channel to detect defects of bright spots, dark spots, bright spots, and dark spots. do.

The plasma display panel inspection method of the present invention configured as described above will be described with reference to FIG. 2.

First, in the first step, a color camera is set using a moiré pattern to photograph a plasma display panel to be inspected. (S1)

The moiré pattern is a low frequency pattern in which similar lattice patterns overlap each other. The moiré pattern is typical when the mosquito nets overlap. When the image of the plasma display panel is measured by a CCD camera, the screen of the camera is also a lattice structure, and since the plasma display panel is also a lattice structure, a moiré pattern is inevitably generated, and the moiré pattern may adversely affect cell defect detection. In order to reduce the effects of moiré patterns and improve cell defect detection, proper magnification and precise camera settings are required.

Although the moiré pattern may cause an error when detecting a cell defect, the moiré pattern may be useful for camera setting by using the point where the moiré pattern is most distinct in the just-focus state.

To this end, the test image is first output to the plasma display panel. In this case, the test image is reduced to 1/4 or 1/8 of the original pattern image so that the moiré pattern can be easily identified, that is, the moiré pattern appears much larger. use.

In order of setting, first adjust the focal length of the lens to adjust the focus so that the moiré pattern appears clearly and clearly, and adjust the position and posture of the camera so that the moiré pattern shown on the plasma display panel through the camera is symmetrical. do. 3 is a result of asymmetric (b) by adjusting the camera posture of the asymmetric moire pattern (a) shown in the plasma display panel.

After setting the camera as described above, the pattern generator generates a pattern of white, red, green, blue, and black to effectively detect various defects such as bright spots, bright spots, dark spots, and dark spots. In the second embodiment, the white pattern is first generated and output to the plasma display panel. (S2)

In the third step after the pattern output, the output pattern is photographed through a color camera. (S3)

 Thereafter, in the fourth step, the defect of the image signal photographed by the color camera is detected and the defect information is integrated to determine the type of the defect. (S4)

In the fourth step S4, the color image signal is separated into R, G, and B channels and converted into three gray image signals, and the converted image is defective in the gray image for each of the R, G, and B channels. The method further includes applying convolution with a Laplacian of Gaussian (LOG) mask to emphasize defects, and highlighting defects and applying a threshold thereto.

When the convolutional conversion using the LOG mask is performed, the defective part is further emphasized. In this case, the moiré pattern itself is highlighted as well as the cell defect because of the moiré pattern mentioned above. In this case, the moiré pattern can be filtered and processed. However, since the moiré pattern appears in a larger period than the cell pattern, the LOG mask with an appropriate window size and sigma value can be used to remove pixel defects without filtering and removing the moiré pattern. Can be detected. The window size and sigma values of the LOG mask are applied by determining the appropriate values that do not affect the moiré pattern. 4 is a three-dimensional graph of the LOG mask used in the present invention.

In addition, the plasma display inspection method using the color camera of the present invention changes the pattern in the pattern generator and repeats the fourth step (S4) in the second step (S2) (S5). The second step S1 to the fourth step S4 may be repeated while sequentially changing to white, red, green, blue, and black, but the pattern order may be changed or the number of patterns may be decreased or increased as necessary. .

FIG. 5 is a diagram illustrating an image appearing in an image processing process when dark spots are detected. First, a plasma display panel displaying a white pattern as an original image (a) is photographed with a 3-CCD color camera. After that, the image taken with the color camera is separated into gray images for each of R, G, and B channels, and convolution is applied to the image to show defects. Next, when binarizing to the specified threshold, the channel-specific defects are clearly shown as dark spots (c). This defect is a G dark spot because a defect was detected in the G channel as a result of the processing.

6 is a diagram illustrating a process of detecting bright spots using a color camera, and (a) shows an image of a blue pattern displayed on a plasma display panel and photographed using a color camera. If you separate the three gray images for each of the R, G, and B channels, and apply convolution with a LOG mask on each image, you can obtain the processing result as shown in (b). As a result of the processing, a defect was detected in the R channel, indicating that the defect is an R bright point.

FIG. 7A illustrates an image captured by using a black and white camera while displaying a blue pattern on the same plasma display panel in the same manner. The image taken with a black and white camera is a gray image. Bright spots are defects that appear in other colors rather than the original ones, and cannot be detected by monochrome cameras if they have the same brightness. Looking at (b), it can be seen that a bright spot defect is not detected when photographing with a black and white camera. Therefore, a color camera must be used to detect the bright spot.

Table 1 below is a table comparing pattern defect types and image processing times.

pattern channel Fault type Total recovery Number of times except duplicate test White R R dark spot One One G G dark spot 2 2 B B dark spot 3 3 Red R R dark spot 4 - G G bright spot 5 4 B B point 6 green G G dark spot 7 - B B point 8 5 R R bright point 9 blue B B dark spot 10 - R R bright point 11 6 G G bright spot 12 Black color R R name 13 7 G G name 14 B B brand 15

As shown in Table 1, it is possible to distinguish the types of defects using color cameras, and the spot detection is much more advantageous than black and white cameras, but the R, G and B channels are divided and inspected using color cameras. This method takes about three times as long as each channel compared to using a black and white camera. White, red, green, blue, and black-5 basic patterns are required to check 5 basic patterns, 5 image processing and 5 image processing when using a color camera. need. Therefore, the use of a color camera requires a computer with a high-performance central processing unit and is also disadvantageous in terms of inspection time.

However, if the same defects are duplicated by analyzing the defect types inspected for each pattern, the number of image processing can be greatly reduced by omitting them. For example, in the case of the R dark spot, the red pattern R channel image processing may be omitted since the white pattern R channel may be inspected and the red pattern R channel may be inspected. The G and B dark spots are also examined in each channel of the white pattern in the same way, so the green and blue patterns can be omitted.

In the red, green, and blue patterns, the image processing is performed once by combining two channels except for the channel of the same color, and in the black pattern, the image processing is performed once by combining three channels. For example, if a defect is detected in the green pattern (R + B) channel and at the same time a defect is detected in the blue pattern (R + G) channel, the defect is an R point, and if a defect is also detected in the black pattern, The final defect is the R bright spot. That is, as shown in Table 1, the number of image processing can be reduced from 15 to 7 times, and the number of image processing can be increased only two times even when compared to a monochrome camera, which can greatly increase the processing speed.

According to the plasma display panel inspection apparatus and the inspection method according to the present invention configured as described above, it is possible to detect bright spots as well as bright spots, dark spots, and dark spots using a color camera, and to detect defects without going through a separate moire pattern filtering step. As it can be detected, the inspection speed can be improved, and accurate cell defects can be detected, thereby providing high reliability in detecting cell defects in the plasma display panel.

Claims (16)

A pattern generator for generating a pattern to output a predetermined pattern to the plasma display panel; A color camera for capturing an image of the plasma display panel on which the pattern generated by the pattern generator is output; An image input board configured to store the image photographed by the color camera as a digital image signal; And a computer for inspecting an image defect by receiving the digital image signal stored in the image input board. The method of claim 1, And the computer is configured to determine the type of image defect by separating the digital image signal transmitted from the image input board for each of R, G, and B channels. The method of claim 2, The computer converts the image separated by the R, G, and B channels into a gray image, applies convolution with a LOG mask, and binarizes by applying a threshold to detect and integrate defects for each channel to detect defects. Plasma display panel inspection device, characterized in that the. The method of claim 1, The pattern generator generates a pattern of white, red, green, blue, and black, respectively. The method of claim 1, And said color camera is a color camera having 3-CCD. Generating a pattern in the pattern generator and outputting a predetermined pattern to the plasma display panel; Photographing a pattern output on the plasma display panel with a color camera; And detecting a defect for each of R, G, and B channels of the color image signal captured by the color camera, and integrating the defect information to determine the type of the defect. And changing the pattern in the pattern generator to repeat the first to third steps. The method of claim 6, The third step may further include converting a color image signal photographed by the color camera into R, G, and B channels and converting the color image signal into a gray image. The method of claim 7, wherein The third step of the plasma display panel inspection method further comprises the step of applying a convolution with a LOG mask on the gray image for each R, G, B channel to emphasize the defect. The method of claim 8, And the third step is further configured to binarize by applying a threshold set to the convolution result image. The method of claim 7, wherein The plasma display inspection method is to determine and apply the window size and sigma value of the LOG mask to prevent the moiré pattern is detected as a defect. The method of claim 6, The plasma display panel inspecting method includes repeating the first to third steps by changing the pattern of the first step into a pattern of white, red, green, blue, and black. The method of claim 6, The method for inspecting the plasma display panel may include reducing or reducing the number of image conversion processes by omitting or combining the channels inspected in the third step when defects overlap with each other. The method of claim 6, And the third step detects the types of image defects of bright spots, dark spots, bright spots, and dark spots. The method of claim 6, The plasma display panel inspection method may further include setting a color camera using a test image to capture an image of the plasma display panel before the first step. The method of claim 14, The color camera setting step may include adjusting the focus of the color camera so that the moiré pattern of the test image is clearly displayed, and adjusting the position of the color camera so that the moiré pattern displayed on the plasma display panel is symmetrical. Plasma display panel inspection method characterized in that the setting. The method according to claim 14 or 15, And the test image used for the setting is an image which is reduced to 1/4 or 1/8 of a pattern generated by the pattern generator.

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