JPH1031730A - Calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration method capable of obtaining accurate correspondence between a display picture on a LCD(liquid crystal display) panel and a CCD pickup image. SOLUTION: In the method, calibration is carried out an LCD panel testing system for picking up an image displayed on the LCD panel 1 by a CCD camera and carrying out a display test of the CCD panel 1, based on the picked-up image. In this case, a calibration pattern arranging twenty-five display patterns 10 comprising a plurality of luminescent points continued like crosses so as to divide the panel 1 into sixteen parts is displayed on the panel 1, the display is picked up by the CCD camera and the center addresses of respective display patterns 10 of the picked-up image are found out. Then addresses on the picture take by the camera correspondingly to respective pixels of the panel 1 are found out, based on these center addresses and correspondence between the picture taken by the camera and the display picture on the LCD panel 1 is found out, based on the addresses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a CCD camera to capture a test image displayed on an LCD (liquid crystal display) panel, and based on the captured image, performs a display test on the LCD panel (such as a display pixel defect or display pixel defect). The present invention relates to a calibration method performed in an LCD panel test system for performing detection of display unevenness or the like.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a general configuration of an LCD panel test system. In the figure, 1
Is an LCD panel to be tested, and displays an image based on a drive signal from the drive unit 2. The drive unit 2 is configured to output a drive signal based on a signal from the control unit 8, and can display a desired pattern on the LCD panel 1. A CCD camera 3 is arranged on the LCD panel 1, and an image displayed on the LCD panel 1 is captured by the CCD camera 3.

[0005] The image capturing section 4 is provided with the CCD camera 3.
The image data captured by the controller 1 is temporarily captured, and the captured image data is transferred to the data processing unit 5 under the control of the control unit 8.

The data processing section 5 comprises a pre-sampling processing section 6 and a loss detecting section 7. The pre-sampling processing section 6 converts image data from the image capturing section 4 (image data picked up by the CCD camera 3). The image is converted into an image corresponding to the display pixel of the LCD panel 1 and is sampled,
LC based on the sampling processing result in the loss detection unit 7
Detection of display pixel loss or display unevenness of the D panel 1 is performed.

In order to convert the image data captured by the CCD camera 3 into an image corresponding to the display pixels of the LCD panel 1, a calibration is performed for associating the LCD panel display image with the CCD captured image. There is a need. Hereinafter, a conventional calibration method performed in the LCD panel test system will be described.

In the calibration, the LCD panel 1
The position (address) of each pixel of the image captured by the CCD camera 3 is determined. Specifically, as a calibration pattern for associating the LCD panel display image with the CCD image, the LCD panel 1 shown in FIG.
A calibration pattern including 25 divided bright spots is displayed, and the pattern is imaged by the CCD camera 3. The captured images of these bright spots are captured as images shown in FIG. The sampling address on the image relating to each of the luminescent spots thus captured is obtained as follows.

The maximum value is searched for from the vicinity of the bright point of the captured image, and the pixel (CCD pixel) is set as a pixel (Xn) which is the center of the bright point (see FIG. 8). Then, this pixel (X
Focusing on n) and its left and right pixels (Xn-1) and (Xn + 1), the area in the X direction where the area of the hatched portion is equally divided as shown in FIG. 9 is defined as the address in the X direction. The same processing is performed for the pixel (Xn) and the pixels above and below the pixel (Xn), and the address of the center of the luminescent spot in the Y direction is obtained. Such an operation is performed for all the bright points, and the center address (X, Y) of each bright point is obtained.

[0008] The image in which the calibration pattern has been captured is divided into 16 regions having four corners as bright points.
Each region is included in the region based on the relative positional relationship between the center address (X, Y) of the four corners of the bright point on the captured image and the address of the bright point on the LCD panel. An address (sampling address) corresponding to a pixel on the LCD panel is obtained by a real number.

Conventionally, a test image picked up by the CCD camera and a display pixel of an LCD panel are associated with each other based on the sampling address obtained as described above.

In the LCD panel test system shown in FIG. 5, a desired pattern (test image) is
When a display test is performed by displaying the test image on the LCD panel, the test image captured by the CCD camera 3 is converted into an image corresponding to the display pixel of the LCD panel based on the sampling address obtained as described above. Then, sampling of the converted image is performed. Specifically, for each sampling address, the sampling process is performed by performing linear interpolation of four pixels (CCD pixels) near the sampling address or linear interpolation of nine pixels near the sampling address.

In the linear interpolation of four neighboring pixels, FIG.
First, consider a 1 × 1 square centered on the sampling address. This square has 4 pixels (CCD
Pixel), these pixels Da to D
The data values of d (see FIG. 10 (b)) correspond to the ratios Sa to Sd of the overlapping area of each pixel with the square (FIG. 10 (c)).
(= Da · Sa + Db · Sb + Dc ·)
Sc + Dd · Sd) is obtained as a sampling result.

In linear interpolation of nine neighboring pixels, a 2 × 2 square is considered as a sampling address. In this case, since the square covers the captured image of 9 pixels, the sum of the data of each pixel multiplied by the ratio of the overlapping area of each pixel to the square divided by 4 is obtained as the sampling result. Can be

[0013] The sampling result obtained in this way is passed to a loss detecting section, and detection of loss of display pixels, display unevenness, and the like is performed.

[0014]

SUMMARY OF THE INVENTION LCD with higher accuracy
To perform the panel test, the LCD panel display image and C
Correspondence (calibration) with a CD captured image is required to be performed accurately.

In the above-described conventional calibration method, an image of a bright point displayed on an LCD panel is taken, and a CCD is used.
The sampling address (the address corresponding to the LCD panel display image and the CCD captured image) is obtained by obtaining the position of the center of the captured bright spot on the captured image. As described above, in the method of obtaining the sampling address from one bright spot, the method is weak against external noise and cannot accurately correspond to the LCD panel display image and the CCD captured image. Therefore, the results of the LCD panel test were low in reproducibility and low in accuracy.

An object of the present invention is to solve the above-mentioned problems and to provide a calibration method capable of accurately associating an LCD panel display image with a CCD image and performing a highly accurate LCD panel test. Is to do.

[0017]

In order to achieve the above object, a calibration method of the present invention captures an image displayed on an LCD panel using a CCD camera, and based on the captured image, the image of the LCD panel is captured. LCD for display test
A calibration method performed in a panel test system, wherein a plurality of display patterns including a plurality of bright spots are displayed on the LCD panel, and the display is performed by the CCD.
An image is taken by a camera, the center address of each display pattern in the taken image is obtained, and the L
An address on the captured image corresponding to each pixel of the CD panel is obtained, and based on the address, an image captured by the CCD camera and a display pixel of the LCD panel are corresponded.

In the above case, the display pattern may be a display pattern composed of a plurality of bright spots connected in a cross shape.

Further, the X coordinate of the center address of the display pattern on the image picked up by the CCD camera is obtained from the apex of the mountain-shaped data obtained by adding the output value of each pixel in each line in the X direction in the vertical direction. The Y coordinate of the address is
The output value of each pixel may be obtained from the peak of the mountain-shaped data obtained by adding the output value of each pixel in the Y direction in the horizontal direction.

According to the invention as described above, a plurality of display patterns, such as a cross-shaped pattern, composed of a plurality of bright spots are displayed in an arrangement in which the panel is divided into a plurality of regions, and each display mark is displayed on the CCD image. By obtaining the center address, an address on the CCD captured image corresponding to each pixel of the LCD panel is obtained. In such a method in which a display pattern including a plurality of bright spots is used, 1
Compared to the conventional method of displaying multiple bright spots in a layout where the panel is divided into multiple areas, it is more resistant to noise,
The test image captured by the CCD camera can be accurately correlated with the display pixel of the LCD panel, and a more accurate LCD panel test can be performed. As a result, a test result with high reproducibility can be obtained.

[0021]

Next, an embodiment of the present invention will be described with reference to the drawings.

According to the calibration method of the present invention, a system as shown in FIG. 5 described above, that is, an image displayed on an LCD panel is captured by using a CCD camera, and a display on the LCD panel is displayed based on the captured image. Applied to LCD panel test system for testing. Here, it is assumed that the processing is performed in the system shown in FIG. 5, and the description of the system configuration is omitted in the following description.

FIG. 1 shows an example of a calibration pattern used in the calibration method of the present invention. The calibration pattern is a display pattern 10 consisting of a plurality of bright spots connected in a cross shape.
The pattern is such that 25 pieces are arranged so that the panel 1 is divided into 16 parts. In the present embodiment, the correspondence (calibration) between the LCD panel display image and the CCD image is taken using this calibration pattern.

A captured image of each display pattern 10 is captured as an image as shown in FIG. 2, for example. The center address of each display pattern 10 captured in this way is obtained as follows.

First, the center address (X coordinate) of the captured image of the display pattern 10 shown in FIG. 2 in the X direction is obtained. In this embodiment, the output value of each pixel (output value of each CCD pixel) is added in the vertical direction for each line in the X direction. FIG. 3 shows each CCD pixel in the X direction in the image shown in FIG. 2 with respect to Xn-3, Xn-2, Xn-1, Xn, Xn.
FIG. 11 is a diagram showing mountain-shaped data in which Xn + 1, Xn + 2, and Xn + 3 are set, and CCD pixel output values are added in the vertical direction for each line in the X direction. By this addition, mountain-shaped data having a high portion at the center as shown in FIG. 3 is obtained. Here, a vertex of the mountain-shaped data is obtained by focusing on a high portion at the center of the mountain-shaped data, and this is set as a center address in the X direction. Specifically, similarly to the case shown in FIG. 9 described above with respect to the center high portion of the mountain-shaped data, a portion where the areas of the hatched portions on both sides are equally divided is set as an address in the X direction (FIG. 3). Dot-dash line).

Next, the center address (Y coordinate) of the captured image of the display pattern 10 in the Y direction is obtained. In the case of calculating the Y coordinate of the center address, similarly to the calculation of the X coordinate of the center address, the output value (CCD output value) of each pixel is added in the vertical direction for each line in the Y direction to form a mountain shape. Data is obtained, its vertex is obtained, and this is set as the center address in the Y direction.

The above-described calculation of the X and Y coordinates of the center address is performed for each display pattern 10. The center address of each display pattern 10 obtained in this way is stored in the LCD panel 1
It shows which pixel of the CCD camera 2 the upper pixel corresponds to.

The addresses of the LCD pixels in the area divided by the display pattern 10 are obtained as described above.
LCD panel display image and C in each display pattern 10
It can be relatively obtained from the correspondence with the CD picked-up image. For example, as shown in FIG. 4, on a 3 × 3 pixel LCD panel, the addresses (real addresses obtained by address calibration) on the CCD captured images of a, b, c, and d are (Xa, Ya), (Xb, Yb), (X
c, Yc), (Xd, Yd), p,
The estimated address of the q on the captured image is (X
Xp = Xa + (Xb−Xa) ÷ 2 Yp = Ya + (Yb−Ya) ÷ 2 Xq = Xa + (Xc−Xa) ÷ 2 Yq = Ya + (Yc−Ya) ÷ 2. Based on the sampling address obtained in this way, it is possible to make correspondence between each pixel on the LCD panel and the address on the image captured by the CCD.

When the display pattern 10 is displayed on the edge of the LCD panel, since the brightness inside and outside the LCD panel (display area) is not constant, a brightness step appears on the edge. In this embodiment, as shown in FIG. 1, the display pattern of the display pattern 10 is changed to the LCD panel 1 because the difference in height has an effect on the test result.
Is displayed slightly inside the edge of. Since a sampling address is relatively obtained around the edge, the influence of noise appearing around the edge can be prevented.

In the above description, the display pattern 10
Is a cross shape, but the present invention is not limited to this, and any shape may be used as long as it is a shape composed of a plurality of bright spots from which the center of the display pattern can be obtained. Is also good. If the size of the display pattern is too large, the display pattern may be displayed on defective pixels of the LCD panel.

In this embodiment, the display pattern 10
Are arranged so that the LCD panel 1 is divided into 16 parts to reduce the influence of lens distortion in the imaging optical system, but the number of divisions is not limited to this.

[0032]

Since the present invention is configured as described above, it is possible to perform calibration with high resistance to noise and high reproducibility, and to realize an unprecedented high-precision LCD panel test. .

Also, using a cross-shaped display display pattern,
The X coordinate of the center address of the display pattern on the image captured by the CCD camera is obtained from the vertex of the chevron-shaped data obtained by adding the output value of each pixel in the vertical direction for each line in the X direction. Since the coordinates are obtained from the vertices of the chevron data obtained by adding the output value of each pixel in the horizontal direction for each line in the Y direction, the coordinates are more resistant to noise.
Calibration with higher reproducibility can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a calibration pattern used in a calibration method of the present invention.

FIG. 2 is a diagram showing a captured image of a display pattern shown in FIG. 1;

FIG. 3 is a diagram showing mountain-shaped data when CCD pixel output values are added in the vertical direction for each line in the X direction.

FIG. 4 is a diagram showing a correspondence between an LCD panel display image and a CCD captured image in each display pattern.

FIG. 5 is a block diagram showing a general configuration of an LCD panel test system.

FIG. 6 is a diagram showing a calibration pattern used in a conventional calibration method.

FIG. 7 is a view showing an image of capturing bright spots shown in FIG. 6;

8 is a diagram showing a CCD output of each pixel of the bright spot shown in FIG. 7;

FIG. 9 is a diagram for explaining a center address of the luminescent spot shown in FIG. 7;

10A and 10B are diagrams for explaining linear interpolation of four neighboring pixels, in which FIG. 10A shows a sampling address, FIG. 10B shows a CCD pixel output, and FIG. 10C shows an area ratio. .

[Description of Signs] 1 LCD panel 2 Drive unit 3 CCD camera 4 Image capture unit 5 Data processing unit 6 Presampling processing unit 7 Loss detection unit 8 Control unit 10 Display pattern

Claims (3)

[Claims] An image displayed on an LCD panel is converted to a CCD image.
A calibration method performed in an LCD panel test system that performs imaging using a camera and performs a display test on the LCD panel based on the captured image, wherein a plurality of display patterns each including a plurality of bright spots are formed on the LCD panel. Display, image the display with the CCD camera,
A central address of each display pattern in the captured image is obtained, an address on the captured image corresponding to each pixel of the LCD panel is obtained based on the central address, and an image is captured by the CCD camera based on the address. A calibration method, wherein correspondence between an image and a display pixel of the LCD panel is obtained. 2. The calibration method according to claim 1, wherein the display pattern is a display pattern composed of a plurality of cross-shaped bright spots. 3. The calibration method according to claim 1, wherein the X coordinate of the center address of the display pattern on the image picked up by the CCD camera is set to the output value of each pixel in the vertical direction for each line in the X direction. The Y-coordinate of the center address is obtained from the vertex of the added mountain-shaped data, and the output value of each pixel is Y
A calibration method characterized in that it is obtained from vertices of mountain-shaped data added in the horizontal direction for each line in the direction.