JPH08327497A - Method for inspecting color liquid crystal display panel - Google Patents

Abstract

PURPOSE: To quickly and accurately inspect a color liquid crystal display, panel in a short time by successively displaying color rasters on the panel in advance and, while the rasters are displayed, recording variable leakage density values detected from other kinds of colors at every picture element. CONSTITUTION: A color liquid crystal display panel 1 is put on a light source 4 and a color CCD camera 3 is set in front of the panel 1. When color rasters are successively displayed on the panel 1, variable leakage density values detected by means of the sensor element 5 of the camera 3 from other kinds of colors are recorded at every picture element. Then a white raster is displayed on the panel 1 and the apparent density values received by the sensor element 5 of the camera 3 are measured at every picture element. Then correction is performed for removing the leakage density value of the element 5 recorded at every picture element from the measured apparent density values received by the element 5 at every picture taken when the picture of the white raster is taken. Therefore, the panel 1 is inspected by finding a corrected density value at every picture element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for highly accurately inspecting the luminance of pixels when inspecting a color liquid crystal display panel.

[0002]

2. Description of the Related Art In a manufactured color liquid crystal display panel, it is checked whether all pixels are excited to a predetermined brightness,
When pixels with abnormal brightness are included, the quality of the color liquid crystal panel is evaluated according to the degree of abnormal brightness and the number of abnormal pixels.

Conventionally, a color liquid crystal panel (1) is placed on a light source (4) as shown in FIG.
Place (3). Japanese Patent Laid-Open No. 5-219535 discloses that when all the pixels which display the three primary colors of red, green and blue constituting a liquid crystal panel are excited, that is, when a white raster is formed,
When the brightness of the pixel image projected on the sensor surface (5) of the color CCD camera is measured and similarly only the red pixels of the liquid crystal display panel (1) are excited to form a red raster on the liquid crystal display panel, It discloses a method of measuring the luminance of a pixel image on the sensor element surface (5) with respect to red of a color CCD camera and detecting pixels with abnormal luminance.

[0004]

In this method, theoretically, when a red raster is formed on the liquid crystal panel (1), a pixel image is projected only on the red sensor element surface on the color CCD camera (3), and other There should be no output from the sensor element surface for green and blue, but in reality the color filter (6) used in the liquid crystal display panel and the filter (7) provided on the sensor element surface of the CCD camera Due to the mismatch of characteristics, even when a red raster is formed on the liquid crystal display surface (1),
Although slight, light is incident on the green sensor element surface and the blue sensor element surface of the color CCD camera at positions corresponding to the pixels forming the red raster, and an output is generated. This leakage gray value is output as the gray value of the pixel together with the original gray value of the red sensor element surface, so that the inspection result has a large error.

When the liquid crystal display panel is projected on the sensor element surface, the image of one pixel is projected on several tens of elements on the sensor element surface. Japanese Patent Laid-Open No. 4-
In Japanese Patent No. 244932, as one method for determining the brightness of a pixel captured by a color CCD camera, among a plurality of sensor elements on which a pixel image is projected, a sensor element close to the center of the pixel is used to output a pixel. It is regarded as the gray value of. In this method, since the output level of one CCD sensor element is not high, when the sensor element output is divided into 6 levels, the inspection result of the liquid crystal display panel can be determined only by the evaluation of 6 levels. .

[0006]

An object of the present invention is to correct the apparent measured brightness of a pixel image of a liquid crystal display panel projected on the sensor surface of a color CCD camera, obtain the true brightness, and inspect the liquid crystal display panel correctly. To aim. Further, the present invention clarifies a method capable of performing a detailed inspection of a liquid crystal display panel by obtaining a large gray value output from a pixel image projected on a sensor element surface of a color CCD camera.

[0007]

[Structure] When color rasters are successively displayed on the color liquid crystal display panel (1) in advance, CC of other types of colors are displayed.
The leakage gray level detected by the sensor element of the D camera is recorded for each pixel, and a white raster is displayed on the color liquid crystal display surface. The color CCD camera has an apparent gray level Rw, Gw, which the sensor element receives for each pixel. Bw is measured, and a correction process is performed to remove the leakage gray level value of the sensor element recorded for each pixel from the apparent measured gray level value that the sensor element receives for each image when the white raster is photographed, and then, for each pixel. This is a method of inspecting the color liquid crystal display panel by obtaining the correction grayscale values R ₀ , G ₀ , B ₀ to be inspected by the sensor element.

Further, for each pixel image when the color liquid crystal display surface (1) is projected on the sensor surface (5) of the CCD camera, the corresponding sensor element area on the sensor surface (5) is stored in advance, and the color liquid crystal is stored. When white raster is displayed on the display surface (1),
In the sensor surface (7) of the color CCD camera, the correction gray value of the sensor element included in the element region corresponding to each pixel image is added, and the color liquid crystal panel is inspected using this as the measured gray value for each pixel.

[0009]

[Operation and effect] A white raster is formed on the color liquid crystal display panel to be inspected, and the color CCD camera color-separates the projected white raster, irradiates the three CCD sensor element surfaces for red, green, and blue, and photoelectrically converts them. It is outputting. The relationship between the standard grayscale value and the leakage grayscale value of each pixel recorded in advance is adapted to the apparent measured grayscale value measured by the color CCD camera, and for each sensor element that outputs the grayscale value of the pixel image. By performing the correction process for removing the leakage gray value, the corrected gray value of the pixel can be obtained.

Further, the value of the image output can be greatly increased by adding the outputs of all the sensor elements which are covered with the pixel image and are output. Therefore, the inspection result of the liquid crystal display panel can be displayed in detail.

[0011]

EXAMPLE FIG. 2 shows a color liquid crystal display panel (1) in which pixels RGB of three primary colors provided with a color filter (6) are arranged. The pixels (2) are densely arranged at a pitch of Δx in the horizontal direction and Δy in the vertical direction, and x pixels are arranged in the horizontal direction and y pixels are arranged in the vertical direction. The center coordinates of the p-th pixel 2 in the horizontal direction and the q-th pixel in the vertical direction are

[0012]

[Equation 1]

Can be expressed as When the liquid crystal display panel (1) placed on the light source (4) is photographed by the CCD camera (3), the incident light is decomposed into red, green and blue and projected on the three sensor element surfaces (5) of red, green and blue, respectively. It

FIG. 3 shows one sensor element surface (5) in which the liquid crystal display surface (8) is projected from the edge of the sensor element surface at a distance of X _{0 in} the horizontal direction and Y _{0 in} the vertical direction, and is projected in the horizontal direction. An image is incident across X and Y sensor elements in the vertical direction. The coordinate point (Xa, Ya) in the image (8) of the entire liquid crystal display surface is the coordinate point (Xa + X ₀ , Ya + Y ₀ ) on the sensor element surface (5).
Can be shown as Arbitrary p-th pixel in the horizontal direction and q-th pixel in the vertical direction on the liquid crystal display panel (1) (2)
Are displayed at the above-mentioned coordinate points (Xa, Ya) on the image plane (8) of the sensor element plane (5) of the CCD camera, and the respective coordinates are related as follows.

[0015]

[Equation 2]

Therefore,

[0017]

(Equation 3)

It is Similarly,

[0019]

[Equation 4]

[0020]

An outline of the steps for carrying out the present invention is shown in FIG. Each step will be described with reference to FIG. Prior to the inspection, the following initial setting (step 1) is performed using a standard liquid crystal display surface that is correctly made in advance or a liquid crystal display surface to be inspected. The initial setting is the one in which steps 2 to 6 are performed and stored in FIG. Only the red pixels are excited to form a red raster (step 2). When this is photographed by a color CCD camera, an image (10) of red pixels is projected on the red sensor element surface (5) as shown in FIG. At the same time, as described above, there is incident light at the image position of the red pixel on the green and blue sensor element surfaces of the CCD camera due to the deviation of the characteristics of the filters (6) and (7), and ΔGr and ΔBr are output. Similarly, when a green raster and a blue raster are formed on the liquid crystal display surface (1), the raster image is formed on the other sensor element surfaces at the same time as the pixel image outputs G and B on the sensor element surface of the CCD camera. A leakage gray value appears at the pixel position. After all, the output of the standard liquid crystal display surface raster and the sensor element surface of the CCD camera has the following relationship.

(Pixel of Liquid Crystal Display Panel) (Sensor Element Surface of CCD Camera) Standard Liquid Crystal Display Surface Raster Red R + ΔGr + ΔBr Green ΔRg + G + ΔBg Blue ΔRb + ΔGb + B This leakage gray value is stored in a memory (not shown) built in the CCD camera. (Step 3).

Next, a white raster is formed on the liquid crystal display surface to be inspected (step 7). At this time, the sensor element surface of the CCD camera outputs Rw for the red sensor surface, Gw for the green sensor surface, and Bw for the blue sensor element surface (step 8). This output value is an apparent measured gray value including the above-mentioned leaked gray value, and appears higher than the corrected gray value by the leaked gray value. Therefore, the leakage gray value for each color that is output in advance using the standard liquid crystal display surface must be removed for each pixel. Through this correction process, the corrected grayscale values R ₀ , G ₀ , B ₀ for each pixel can be obtained as follows. In addition,
Output R on the CCD camera sensor surface during standard inspection,
G and B output R of each sensor surface during white raster photography
It is set equal to w, Gw, and Bw.

Inspection liquid crystal display surface Raster CCD camera sensor element surface Rw + Gw + Bw Correction processing R ₀ = Rw-ΔRg-ΔRb G ₀ = Gw-ΔGr-ΔGb B ₀ = Bw-ΔBr-ΔBg

R ₀ , G ₀ , and B ₀ obtained by correcting the output of the CCD camera are the true grayscale values for each liquid crystal pixel (step 9). When evaluating the liquid crystal display panel, R ₀ ,
Correct inspection is performed by setting the values of G ₀ and B ₀ as evaluation targets.

One pixel of the liquid crystal display panel is projected on the sensor element surface of the CCD camera over m sensor elements in the horizontal direction and n sensor elements in the vertical direction. The center positions of all the pixels (2) on the liquid crystal display surface (1) have a predetermined pixel pitch Δx, Δy and the number x × y, and each pixel image projected on the sensor element surface of the CCD camera Center position Xa of
Number of sensor elements that output the gray value of Ya and the pixel image m ×
Since n is predetermined, it is initialized (steps 4 to 6). In the present invention, when inspecting a liquid crystal display panel, all the sensor elements covered by the image (10) for each pixel
The gray value of the pixel is obtained by adding the outputs of (9).

Actually, an image of one pixel may correspond to several tens of sensor elements on the sensor element surface of the CCD camera, but for convenience of explanation, 3 × 2 sensor elements correspond. It shall be. In FIG. 4, for example, for one of the red pixels, a pixel image (10) on the CCD sensor surface
, And the center coordinates are (3.1, 1.8). The area for 3 × 2 sensor elements centered on this coordinate is 3.4-1.
5 = 1.9, 3.4 + 1.5 = 4.9, that is, in the X coordinate, the coordinates range from 1.9 to 4.9. Similarly, the Y coordinate is 1.8-1 = 0.8,1.8
+ 1 = 2.8, that is, the Y coordinate spans the region from 0.8 to 2.8. FIG. 5 is an enlarged view of the pixel image (10) and the sensor element region, and the pixel image (10) spans 12 sensor elements A to L. Pixel image (10) covering each sensor element
The outputs of the respective elements are added in accordance with the area of the following.

[0028]

(Equation 5)

The added value of the sensor element covered by the pixel image (10) is the apparent gray value of one pixel (2) on the liquid crystal display surface.

For each of the sensor elements A to L, a correction process is applied to the apparent measured luminances Rw, Gw, and Bw output by the sensor elements A to L, and true gray values R ₀ , G ₀ , and B ₀ are applied. Therefore, it is possible to obtain the corrected gray value for each pixel on the liquid crystal display surface (step 10).

Since the gray value of the pixel image in the above embodiment of the present invention is the sum of the outputs of 12 sensor elements, the pixel value obtained from the gray value of one sensor element as in the prior art. The output is sufficiently larger than the gray value, and the evaluation stage of the liquid crystal display panel can be divided into multiple stages according to the large output.

When the corrected grayscale value is obtained for each liquid crystal pixel, the image on the liquid crystal panel is reconstructed based on the center coordinates of each pixel and the respective brightnesses (step 11). The luminance of the pixel image stored in the reconstructed liquid crystal display panel image is divided by the threshold value that determines the grade level and binarized (step 12) to detect defective pixels of the liquid crystal display panel and the respective pixels. The brightness can be obtained and the liquid crystal display panel can be inspected (step 13).

According to the present invention, the grayscale value of the liquid crystal display panel photographed by the CCD camera is corrected as described above, and the inspection is performed on the basis of the corrected grayscale value which is not affected by the leakage grayscale value. An inspection can be performed. Furthermore, since the true brightness of each pixel image can be divided into multiple levels,
It is possible to perform highly accurate inspection according to the application of the liquid crystal display panel. Furthermore, a white raster is formed on the liquid crystal display panel, and the CCD camera can inspect all pixels at the same time by the sensor surfaces for red, green, and blue, and the inspection can be processed quickly and in a short time.

Since the drawings and the above description are for the purpose of facilitating the understanding of the invention, they should not be understood to reduce the invention described in the claims. Those skilled in the art can easily make many modifications based on the drawings and the above description.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an implementation status of a method of the present invention.

FIG. 2 is an enlarged view of a liquid crystal display surface.

FIG. 3 is an explanatory diagram showing a situation in which a liquid crystal display panel is projected on one sensor element surface of a CCD camera.

FIG. 4 is an enlarged view of one sensor element surface of a CCD camera.

5 is an enlarged view of one pixel image in FIG.

FIG. 6 is a flowchart of an implementation process of the present invention.

[Explanation of symbols] (1) Color liquid crystal display panel (2) Pixel (3) Color CCD camera (5) Sensor element surface of color CCD camera (8) Liquid crystal display image (9) Sensor element (10) Sensor element surface Upper pixel image

Claims (2)

[Claims] 1. A color raster by exciting three types of pixels (2) such as red, green and blue arranged on a color liquid crystal display panel (1) simultaneously to display a white raster, or by exciting only one type of pixel. Is displayed, and the raster of the color liquid crystal display surface is photographed by a color CCD camera, and pixels with abnormal brightness (2)
In the method for inspecting the presence or absence of color, when color rasters are successively displayed on the color liquid crystal display panel (1) in advance, color CCDs for other types of colors are displayed.
The leak density value detected by the camera sensor element is recorded for each pixel, white raster is displayed on the color liquid crystal display surface, and the color CCD
The camera measures the apparent grayscale values Rw, Gw, and Bw received by the sensor element for each pixel, and for each pixel from the apparent measured grayscale value that the sensor element receives for each image when the white raster is captured. A correction process is performed to remove the recorded leakage gray level value of the sensor element, and the corrected gray level value R ₀ , G ₀ , which the sensor element inspects for each pixel,
A method of inspecting a color liquid crystal display panel for obtaining B ₀ . 2. A color liquid crystal display device in which a corresponding sensor element region on the sensor surface (5) is stored in advance for each pixel image when the color liquid crystal display surface (1) is projected on the sensor surface (5) of a CCD camera. When white raster is displayed on the display surface (1),
The color liquid crystal panel is inspected by adding the correction grayscale values of the sensor elements included in the element area corresponding to each pixel image on the sensor surface (7) of the color CCD camera, and using this as the measured grayscale value for each pixel. Inspection method of color liquid crystal panel.