JPH0979946A - Inspection device for display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect a display device to be inspected for defect with high accuracy by storing the picture elements of an image pickup device on an index table by correlating the picture elements to the picture element positions of the display device and converting the picture of the display device into a picture of the resolution corresponding to the number of picture elements of the display device based on the table and inspecting the display device based on the picture. SOLUTION: A CCD camera 4 takes the picture of an LCD panel to be inspected and a picture input board 11 displays the CCD picture of the panel on a monitor 6 by sending the picture signal of the panel and sends the signal to a picture element converting board 12 after A/D conversion for storing the signal in a CCD picture memory 21. The board 12 converts the CCD picture into an LCD picture from an index table storing the correlation between the picture elements of the LCD panel and camera 4 by performing shading correction on the sensitivity variation, etc., of each picture element of the camera 4 and sends the LCD picture to a picture processing board 13 for storing the picture in an LCD picture memory 22. The board 13 extracts the positions, number, sizes, etc., of defects by binarizing and labeling the LCD picture and a CPU board 14 examines the extracted positions, number, sizes, etc., in detail.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device inspection device for inspecting a defect of a display device to be inspected by imaging a display screen of the display device to be inspected such as an LCD panel with an image pickup device such as a CCD camera. .

[0002]

2. Description of the Related Art The inspection of display devices to be inspected, such as LCD (liquid crystal display) panels, is mainly conducted by human eyes. However, in recent years, automatic inspection has been attempted in order to quantify inspection standards and improve productivity.

In the automatic inspection of the LCD panel, the CCD (cha
rge coupled device) The LCD panel is imaged by an imaging device such as a camera, and the defective portion of the LCD panel is extracted based on the captured image. In such an automatic inspection, the processing method and performance differ depending on the resolution of the CCD camera which is the image pickup device.

When a low-resolution CCD camera is used, the processing time is short because the number of pixels is small, but there are problems that moire occurs and fine defects cannot be detected. On the other hand, when using a high resolution CCD camera,
Although moire can be generated and fine defects can be detected, there is a problem that the processing time is long. Therefore, it can be said that the processing speed and the inspection accuracy (reliability) have a trade-off relationship.

From the above, it can be said that the problem of the automatic inspection device of the LCD panel is to maintain high inspection accuracy by using a high resolution CCD camera and to improve the processing speed.

An inspection device using a high resolution CCD camera is disclosed in Japanese Patent Laid-Open No. 27704/1993. In the inspection device described in this publication, the LC of interest
An index table corresponding to the number of pixels of the CCD camera is provided in order to associate the D pixel with the corresponding CCD pixel. Therefore, there is a problem that the capacity of the index table is large. Also CCD
LC based on a high resolution image according to the number of pixels of the camera
Since the D panel is inspected for defects, there is a problem that the processing time is long.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inspection device for a display device which can maintain high inspection accuracy and improve processing speed, and which requires a small index table capacity. To do.

[0008]

An inspection device for a display device according to the present invention is a device for inspecting a display device, in which an image of the display device to be inspected is picked up by an image pickup device and defects of the display device to be inspected are inspected based on the picked-up image. In an index table in which one pixel of the image pickup device is stored in association with each pixel position of the display device under test, an image of the display device under test taken by the image pickup device and Based on the first image having a resolution corresponding to the number of pixels and the index table, a conversion unit for converting the first image into a second image having a resolution corresponding to the number of pixels of the display device under inspection, and based on the second image In addition, an inspection means for inspecting a defect of the display device to be inspected is provided.

Since an index table is used in which one pixel of the image pickup device is stored in association with each pixel position of the display device to be inspected, a high resolution image pickup device is used. Also, the amount of information in the index table depends on the number of images on the display device under inspection. Therefore, the capacity of the index table can be reduced.

Further, since the defect is detected on the basis of the second image having the resolution corresponding to the number of pixels of the display device to be inspected, the processing time is shortened even when the high resolution image pickup device is used.

In the case of using the high resolution image pickup device, after detecting the defect based on the second image of the low resolution,
By performing a detailed defect inspection on only the defective portion based on the high-resolution first image, it becomes possible to perform a highly accurate inspection in a short time.

As the index table, for example, one in which one pixel of the image pickup device corresponding to the central position of each pixel of the inspected display device is stored in association with each pixel of the inspected display device is used. .

The converting means converts the luminance value of the pixel of interest of the display device under inspection into the following (1) (2) (3) (4), for example.
The first image is converted into the second image by determining the value of (5) or (6).

(1) The brightness value of one pixel of the image pickup device corresponding to the target pixel of the display device under inspection.

(2) The highest luminance value among the luminance values of each pixel in a predetermined area centered on one pixel of the image pickup device corresponding to the target pixel of the display device to be inspected.

(3) An added value or an average value of luminance values in a predetermined area centered on one pixel of the image pickup device corresponding to the pixel of interest of the display device to be inspected.

(4) The brightness value of each pixel in a predetermined area centered on one pixel of the image pickup device corresponding to the pixel of interest of the display device to be inspected is added with a value obtained by weighting it according to the position or its value. Average value.

(5) A first predetermined area centered on one pixel of the image pickup device corresponding to the pixel of interest is set, and the luminance value is added for each second predetermined area centered on each pixel in the first predetermined area. The largest added value among the values.

(6) A first predetermined area centered on one pixel of the image pickup device corresponding to the pixel of interest is set, and an average of brightness values for each second predetermined area centered on each pixel in the first predetermined area. The largest average value.

Based on the first image, a deviation amount calculating means for calculating a deviation amount of the display device to be inspected with respect to a reference position to which the index table conforms, and an index based on the deviation amount calculated by the deviation amount calculating means. It is preferable to provide means for correcting the contents of the table so as to match the position of the display device to be inspected, and convert the first image into the second image based on the first image and the corrected index table. .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The LCD panel, which is the display device to be inspected, is
An embodiment in which the present invention is applied to an LCD panel inspection device for inspecting a defect of an LCD panel by capturing an image with a CD camera will be described.

FIG. 1 shows the configuration of an LCD panel inspection device.

The LCD panel inspection device comprises an LCD panel 1
Back light 2, LCD panel 1
An LCD drive unit 3 for driving the LCD panel, a high-resolution CCD camera 4 for capturing an image of the LCD panel 1, an image processing device 5 for performing image processing on the image captured by the camera 4, and an image captured by the camera 4. A monitor 6 for displaying, etc., and a personal computer 7 for controlling the image processing device 5 and the LCD drive unit 3 are provided.

The personal computer 7 sets various conditions and generates an inspection pattern for the LCD panel 1. The inspection pattern of the LCD panel 1 is the LCD drive unit 3
Sent to

FIG. 2 shows the detailed structure of the image processing apparatus 5.

In the following description, an image having a resolution corresponding to the number of pixels of the CCD camera 4 is called a CCD image, which is called LCD.
An image having a resolution corresponding to the number of pixels of the panel 1 will be referred to as an LCD image.

The image processing device 5 includes an image input board 11,
Pixel conversion board 12, image processing board 13 and CPU
A board 14 is provided. The video signal input to the image input board 11 is sent to the monitor 6, and the monitor 6 receives the CCD signal.
The image is displayed. The image input board 11 converts the video signal from the CCD camera 4 into a digital signal and sends it to the pixel conversion board 12.

The digital signal input to the pixel conversion board 12 is stored in the CCD image memory 21. The pixel conversion board 12 is a C stored in the CCD image memory 21.
After performing shading correction on the CD image in order to correct variations in the sensitivity of each pixel of the CCD camera 4 and positional variations in the light amount of the backlight 2,
CC based on the index table that stores the correspondence between the pixels of the CCD camera 4 and the pixels of the LCD panel 1.
Convert D image to LCD image.

The generated LCD image is sent to the image processing board 13 and stored in the LCD image memory 22. The image processing board 13 performs binarization processing, labeling processing, feature amount extraction processing, and the like based on the LCD image stored in the LCD image memory 22. In the feature quantity extraction process,
Defect position, number of defects, defect area, defect continuous length,
The defect brightness and the like are extracted.

The CPU board 14 controls the image processing apparatus 5 as a whole, and the CCD image memory 21 for the defective portion detected by the image processing board 13.
Further detailed inspection is performed on the basis of the CCD image stored in, and final defect determination and defect classification are performed.

The pixel conversion board 12 also generates an index table and shading correction data, which are performed in a pre-process (see FIG. 3) described later. Further, the pixel conversion board 12 also performs a shift amount calculation process (step 12 in FIG. 6) and an index table correction process (step 13 in FIG. 6) which are executed in a defect inspection of the LCD panel described later.

FIG. 3 shows a procedure of preprocessing performed using a reference LCD panel.

In this preprocessing, the reference LCD
The panel is imaged and captured by the CCD camera 4 (step 1). Then, C on the pixel conversion board 12
It is stored in the CD image memory 21. CCD image memory 2
An index table is created based on the image stored in 1 and stored in the memory on the pixel conversion board 12 (step 2). Further, shading correction data is created based on the image stored in the CCD image memory 21 and stored in the memory on the pixel conversion board 12 (step 3).

A method of creating the index table will be described. Here, a case will be described as an example where an LCD panel in which the pixel array of the LCD panel 1 is shifted between an odd-numbered column and an even-numbered column as shown in FIG. 4 is inspected.

First, based on the image picked up by the CCD camera 4, 4 of the even-numbered pixel groups of the reference LCD panel are displayed.
The coordinates of the pixel positions P1, Q1, R1, S1 at the corners and the pixel positions P2, Q2, R2, S2 at the four corners of the odd-numbered pixel group are obtained.

Next, the pixel positions P at the four corners of the pixel group of even-numbered columns
1, Q1, R1, S1 and pixel positions P1, Q1, R1,
The position of each pixel of the even-numbered pixel group is calculated based on the pitch XPITCH in the X-direction and the pitch YPITCH in the Y-direction obtained from S1 and the number of pixels in the even-numbered pixel group.
Similarly, the position of each pixel of the odd-numbered column pixel group is obtained by calculation. Each pixel position of the reference LCD panel thus obtained will be referred to as a temporary pixel position.

Next, based on the peak search method, the LCD
The provisional pixel position of each pixel on the panel is corrected. That is, the provisional pixel position of each pixel of the LCD panel is corrected in the direction of higher brightness. At this time, if the distortion of the captured image due to the lens of the CCD camera 4 is relatively large and cannot be ignored, it is preferable to change the peak search range and direction according to the distortion. Specifically, the amount and direction of the distortion of the image captured by the lens for each location is made into a table in advance,
The peak search method is applied by referring to the table.

Each pixel position of the thus obtained reference LCD panel and the CCD corresponding to the center of each pixel position
By forming a table of the pixel positions of the camera 4, an index table as shown in FIG. 5 is created. Each cell in FIG. 5 shows a pixel of the reference LCD panel, and the coordinates in each cell show the pixel position of the CCD camera 4 corresponding to the center of the reference LCD panel pixel.
Therefore, this index table is
The number of pieces of information corresponds to the number of pixels of the panel.

FIG. 6 shows a processing procedure when the LCD panel is inspected for defects based on the data obtained by the preprocessing.

First, the LCD panel 1 to be inspected is C
An image is taken by the CD camera 4 (step 11). C
The video signal of the CD camera 4 is converted into a digital signal and then stored in the CCD image memory 21.

CCD stored in CCD image memory 21
The amount of deviation of the LCD panel 1 from the reference position is calculated based on the image (step 12). A method of calculating this shift amount will be described.

As shown in FIG. 7, the reference LCD panel P1
The positions of the two corners of A1 (a1, b1), B1 (c1,
d1). Inspection LCD panel P corresponding to these two points
The positions A2 (a2, b2) and B2 (c2, d2) of 2 are obtained.

Then, the reference LC of the inspection LCD panel P2
The rotation angle θ and the movement amounts Δx and Δy with respect to the D panel P1 are obtained as follows.

First, based on the following equations 1 and 2, cos
θ and sin θ can be obtained.

[0046]

[Equation 1]

[0047]

[Equation 2]

Further, Δx and Δy are obtained based on either of the following formulas 3 and 4.

[0049]

(Equation 3)

[0050]

(Equation 4)

Next, the index table is corrected based on the calculated Δx, Δy and θ (step 13). The index table before correction is called the reference table, and the index table after correction is called the inspection table.
Each element (coordinate value) on the inspection table is calculated based on x, Δy, and θ. That is, Δx and Δ in Equation 3
Let the values of y and θ be the obtained Δx, Δy, and θ, and by sequentially substituting each element of the reference table into a1 and b1 of Expression 3, each element of the inspection table is converted to a2 of Expression 3. , B2. The inspection table thus obtained is stored in the memory of the pixel conversion board 12.

On the other hand, after the shading correction is performed on the CCD image stored in the CCD image memory 21 using the shading correction data (step 1).
4) The CCD image is converted into an LCD image using the corrected index table (inspection table) (step 15).

There are the following methods for converting a CCD image into an LCD image.

(1) A pixel of the CCD camera corresponding to the center of the pixel of interest of the LCD panel (a pixel stored as a pixel of the CCD camera corresponding to the pixel of interest in the corrected index table. The brightness value of the CCD pixel (corresponding to the CCD pixel) is set as the brightness value of the pixel of interest. Figure 8 shows a CCD image and this CC
The LCD image obtained by such a method from the D image is shown.

(2) The highest brightness value among the brightness values of each pixel in a predetermined area centered on the CCD pixel corresponding to the pixel of interest (for example, 3 × 3 9 pixels centered on the CCD pixel) Is the luminance value of the pixel of interest.

(3) The addition value or the average value of the brightness values of the respective pixels in a predetermined area centered on the CCD pixel corresponding to the target pixel (for example, 3 × 3 9 pixels centered on the CCD pixel) is calculated. , And the luminance value of the pixel of interest.

(4) The brightness value of each pixel in a predetermined area centered on the CCD pixel corresponding to the target pixel (for example, 9 pixels of 3 × 3 centered on the CCD pixel) is weighted according to the position. The added value or the average value after adding is taken as the brightness value of the pixel of interest.

(5) A first predetermined area centered on the CCD pixel corresponding to the pixel of interest (for example, 3 × 3 9 pixels centered on the CCD pixel) is set, and within the set first predetermined area. A second predetermined region centered on each pixel (for example,
The added value of the brightness values within 3 × 3 (9 pixels centering on each pixel) is calculated. The largest addition value among the calculated addition values of the brightness values is set as the brightness value of the pixel of interest.

(6) A first predetermined area centered on the CCD pixel corresponding to the pixel of interest (for example, 3 × 3 9 pixels centered on the CCD pixel) is set, and within the set first predetermined area. A second predetermined region centered on each pixel (for example,
The average value of the brightness values within 3 × 3 (9 pixels centering on each pixel) is calculated. The largest average value among the calculated average values of the brightness values is set as the brightness value of the pixel of interest.

In this way, the brightness value of each pixel of the LCD panel 1 is determined based on the corrected index table and the CCD image, whereby the CCD image is converted into the LCD image. The obtained LCD image is LC
It is stored in the D image memory 22.

Thereafter, binarization processing and labeling processing are performed on the LCD image (step 16). Then, the feature amount is extracted based on the LCD image and the binarized image of the LCD image (step 17). That is,
Defect position, number of defects, defect area, defect continuous length,
The defect brightness and the like are extracted.

Next, the defective portion detected in step 17 is subjected to a more detailed inspection based on the CCD image stored in the CCD image memory 21, and final defect determination and defect classification are performed. (Step 1
8).

In the above embodiment, the index table stores one pixel of the CCD camera 4 in correspondence with each pixel position of the LCD panel. Therefore, the information amount of the index table is the image of the LCD panel. Since it depends on the number, the capacity of the index table can be small.

Further, first, a defect is detected based on a low-resolution LCD image corresponding to the number of pixels of the LCD panel, and only the detected defective portion is subjected to a detailed defect inspection based on a high-resolution CCD image. Therefore, highly accurate inspection can be performed in a short time.

[0065]

According to the present invention, it is possible to realize an inspection device for a display device, which can maintain high inspection accuracy and improve processing speed, and which requires a small index table capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an LCD inspection device.

FIG. 2 is a block diagram showing a configuration of an image processing apparatus.

FIG. 3 is a flowchart showing a procedure of preprocessing using a reference LCD panel.

FIG. 4 is a schematic diagram for explaining a method of creating an index table.

FIG. 5 is a schematic diagram showing an example of an index table.

FIG. 6 is a flowchart showing a processing procedure when a defect inspection of an LCD panel is performed.

FIG. 7 is a schematic diagram for explaining a method of calculating a deviation amount of an inspection LCD panel with respect to a reference LCD panel.

FIG. 8 is a schematic diagram for explaining a method of converting a CCD image into an LCD image.

[Explanation of symbols]

 1 LCD Panel 2 Backlight 3 LCD Drive Unit 4 CCD Camera 5 Image Processing Device 6 Monitor 7 Personal Computer

Claims (4)

[Claims] 1. An inspection device of a display device for inspecting a defect of the inspected display device based on the picked-up image of the inspected display device by an image pickup device, wherein, for each pixel position of the inspected display device, An index table in which one pixel of the image pickup device is stored correspondingly, a first image which is an image of the display device under inspection picked up by the image pickup device and has a resolution corresponding to the number of pixels of the image pickup device, and an index table A conversion means for converting the first image into a second image having a resolution corresponding to the number of pixels of the inspected display device, and an inspection means for inspecting a defect of the inspected display device based on the second image, An inspection device for a display device, comprising: 2. The index table stores one pixel of the image pickup device corresponding to the center position of each pixel of the display device under test in association with each pixel of the display device under test. Inspection device for the display device described. 3. The conversion means converts (1) the brightness value of one pixel of the image pickup device corresponding to the target pixel of the display device under test, and (2) the one pixel of the image pickup device corresponding to the target pixel of the display device under test. The highest brightness value among the brightness values of the respective pixels in the center predetermined area, (3) addition of the brightness value in the predetermined area centered on one pixel of the image pickup device corresponding to the target pixel of the display device to be inspected Value or average value, (4) added value after weighting according to position to the luminance value of each pixel in a predetermined area centered on one pixel of the image pickup device corresponding to the pixel of interest of the display device under test Or the average value, (5) 1 of the image pickup device corresponding to the pixel of interest
A first predetermined area centered on a pixel is set, and the largest added value among the added values of the brightness values for each second predetermined area centered on each pixel in the first predetermined area, or (6) the target pixel The first predetermined area centered on one pixel of the image pickup device corresponding to the above is set, and the largest average value among the average values of the brightness values for each second predetermined area centered on each pixel in the first predetermined area. 3. The inspection device for a display device according to claim 1, wherein the first image is converted into the second image by determining, as the luminance value of the pixel of interest. 4. A displacement amount calculating means for calculating a displacement amount of the display device to be inspected with respect to a reference position to which the index table conforms based on the first image, and a displacement amount calculated by the displacement amount calculating means. , A means for correcting the contents of the index table so as to match the position of the display device to be inspected, and the converting means includes a first image based on the corrected index table and the first image.
The inspection device for a display device according to claim 1, wherein the image is converted into a second image.