JPH1062305A - Sensitivity correcting method of ccd camera, and lcd panel display test system with ccd camera sensitivity correcting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a fixed pattern noise to perform a highly precise image inspection by correcting the dispersion in output of a CCD camera according to the sensitivity characteristic of each CCD element. SOLUTION: This sensitivity correcting method of CCD camera is performed in a LCD panel test system for taking an image displayed on a LCD panel by use of a CCD camera 1 and performing the display test of the LCD panel on the basis of the taken image. The CCD camera 1 is shielded from light to determine the offset value of each CCD element, and a light of the degree to which the output is not saturated is inputted to the CCD camera 1 to determine the bright value of each CCD element, and the sensitivity characteristic of each CCD element is determined from the resulting off set value and bright value. The image taken by the CCD camera 1 is corrected on the basis of this in the display test.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (LCD).
(Crystal display) A test image of a desired pattern is displayed on a panel, an image of the test image is taken using a CCD camera, and a CCD camera correction performed in an LCD panel test system for performing a display test of the LCD panel based on the taken image. About the method. Furthermore, L with CCD camera sensitivity correction function
It relates to a CD panel test system.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a schematic configuration of an LCD panel test system. In FIG.
A backlight 102 is provided on the back side of the LCD. Light from the backlight 102 displays an image on an LCD panel.

The LCD panel test system includes a CCD camera 103, an image conversion means 104, a frame memory 105,
And the image processing test unit 106,
Defective display pixels and display unevenness of the D panel are detected.

[0004] LCD panel 1 by CCD camera 103
01 is displayed. The image conversion means 104 is C
It converts the output video signal of the CD camera 103 into a digital signal and outputs the digital signal as image data corresponding to each pixel of the LCD panel 101, and includes, for example, an A / D converter and a buffer memory. The data of the image conversion means 104 is subjected to well-known sampling compression, and is taken into the frame memory 105. Based on the taken sampling data, the LC
Detection of display pixel defects and display unevenness of the D panel 101 is performed.

As described above, using a CCD camera to perform LC
In a test system for inspecting image quality of D display panel, CC
The sensitivity of each element of the D camera varies, and a captured image includes fixed pattern noise corresponding to the variation in sensitivity. Conventionally, in order to suppress this fixed pattern noise, variations in the output of each element of the CCD camera at the time of incidence of a predetermined amount of light have been obtained and set as fixed values. Correction was performed such as subtracting from In particular,
The variation in the output of each element of the CCD camera in the light-shielded state was determined and set as a fixed value.

[0006]

SUMMARY OF THE INVENTION As described above, the CCD
The output of each element of the camera varies, and the amount of variation varies depending on the amount of incident light. As described above, since the elements constituting each pixel of the CCD camera vary depending on the sensitivity characteristics, the above-described correction method has the following problems.

The conventional method of correcting the output of a CCD camera based on a fixed value is effective for image data captured under the same condition (light quantity) as the condition for calculating the fixed value. However, image data captured under conditions other than those conditions cannot be completely corrected, and fixed pattern noise is included in the image data. For example, when the light amount of the backlight is different from the light amount for which the fixed value is calculated, effective data correction is not performed, and fixed pattern noise is included in the image data, so that the image quality test cannot be performed with high accuracy. Was.

[0008] An object of the present invention is to solve the above-mentioned problems and to provide a CC
Depending on the sensitivity characteristics of the elements constituting each pixel of the D camera, C
Provided is a CCD camera sensitivity correction method and a LCD panel display test system with a CCD camera sensitivity correction function that suppresses fixed pattern noise by correcting variations in the output of a CD camera and enables high-precision image quality inspection. It is in.

[0009]

In order to achieve the above object, a sensitivity correction method for a CCD camera according to the present invention is provided in which an image displayed on an LCD panel is picked up using a CCD camera.
L for performing a display test of the LCD panel based on the captured image
A sensitivity correction method for a CCD camera performed in a CD panel test system, wherein the CCD camera is shielded from light, an offset value of each CCD element is obtained, and
Input light to the camera so that its output does not saturate, and
The brightness value of the CD device is obtained, the sensitivity characteristic of each CCD device is obtained from the offset value and the brightness value, and the captured image taken by the CCD camera at the time of the display test is corrected based on the brightness value. .

In the above case, the result of subtracting the offset value from the bright value for each CCD element is divided by the average value of the subtraction results, and the result of division for each CCD element is used as a correction coefficient for each CCD element. A captured image captured by a CCD camera during the display test may be corrected based on the correction coefficient.

Further, the result obtained by subtracting the offset value from the bright value for each CCD element is divided by an upper limit value that defines the upper limit level of the output of the CCD camera, and the result of the division for each CCD element is calculated for each CCD element. The correction coefficient is used for the display test based on the correction coefficient.
The captured image captured by the camera may be corrected.

An LC with CCD camera sensitivity correction function of the present invention
The D panel test system includes a CCD camera that captures an image displayed on the LCD panel, and an original image memory that stores an image captured by the CCD camera,
In an LCD panel test system in which a display test of the LCD panel is performed based on a captured image stored in the original image memory, an output of each CCD element in a state where the CCD camera is shielded from light is set as an offset value,
The output of each CCD element in a state where the light whose output does not saturate is input to the CCD camera as a bright value, and the sensitivity characteristic of each CCD element is obtained from the offset value and the bright value of each CCD element. CCD
The image processing apparatus further includes a correction processing unit that corrects a captured image stored in the original image memory based on a sensitivity characteristic of the element.

[0013] In the above case, the correction processing means may include the C
An offset image memory for storing an offset image captured in a state where a CD camera is shielded from light, and a bright image memory for storing a bright image captured in a state where light whose output does not saturate the CCD camera is input to the CCD camera. A brightness value read out for each CCD pixel from the bright image memory as one input, an offset value read out for each CCD pixel from the offset image memory as the other input, and subtracting the offset value from the brightness value. 1 subtractor, average value calculating means for obtaining an average value of the subtraction result for each CCD pixel subtracted by the first subtractor, and the first value obtained by the average value obtained by the average value calculating means. A divider for respectively dividing the subtraction result for each CCD pixel, which has been subtracted by the subtractor, and for each CCD pixel from the original image memory. A second subtractor that takes the read original image data as one input, the offset value read for each CCD pixel from the offset image memory as the other input, and subtracts the offset value from the original image data; The output of the subtractor may be one input, the output of the divider may be the other input, and a multiplier that multiplies these inputs for each CCD pixel.

The correction processing means may include an offset image memory for storing an offset image captured in a state where the CCD camera is shielded from light, and an offset image memory in which light whose output does not saturate is input to the CCD camera. A bright image memory in which a captured bright image is stored, a bright value read out for each CCD pixel from the bright image memory, and an offset value read out for each CCD pixel from the offset image memory are used for the other. A first subtractor for subtracting an offset value from a bright value as an input; an average value calculating means for obtaining an average value of subtraction results for each CCD pixel subtracted by the first subtractor; The subtraction result for each CCD pixel, which has been subtracted by the first subtractor at the upper limit value that has determined the upper limit level of the output of Is a divider for dividing said of one original image data read out for each CCD pixel from the original image memory input, the CCD from the offset image memory
The offset value read for each pixel is used as the other input,
A second subtractor for subtracting the offset value from the original image data, an output of the second subtractor as one input, and an output of the divider as the other input, and these inputs are multiplied for each CCD pixel And a multiplier.

According to the present invention as described above, an image captured by a CCD camera for a display test is stored in each CC.
Since the correction is made in accordance with the sensitivity characteristics of the D element, the captured image does not include the fixed pattern noise corresponding to the variation in the sensitivity of the CCD element unlike the related art.

Further, since the variation in the sensitivity of each CCD element is corrected under the same conditions as when the test image is captured in the actual test system, it is possible to effectively correct the image data.

[0017]

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

<First Embodiment> FIG. 1 is a block diagram showing the configuration of an LCD panel test system having a CCD camera sensitivity correction function according to a first embodiment of the present invention.

The LCD panel test system of this embodiment is
It comprises a CCD camera 1, an image conversion means 2, an original image memory 3, a correction processing section 4, a corrected image memory 5, and an image processing test section 6.

The CCD camera 1 has a test object L
It captures an image displayed on a CD panel, and is configured so that gain and sensitivity can be set according to test conditions. The image conversion means 2 converts an output video signal of the CCD camera 1 into a digital signal and outputs one frame of image data, and includes, for example, an A / D converter and a buffer memory.

The original image memory 3 stores an image to be corrected output from the image conversion means 2, that is, an image obtained by capturing a test image of a desired pattern displayed on the LCD panel. In the original image memory 3, the stored correction target image data is read out and output for each CCD pixel.

The correction processing section 4 corrects the variation of the output of each CCD element of the CCD camera 1 according to the sensitivity characteristic of each CCD pixel element, and a correction coefficient for correcting the variation of the sensitivity characteristic of each CCD element. And corrects the correction target image data stored in the original image memory 3 based on the correction coefficient. In a normal use range, the gamma characteristic of the CCD element is almost linear, and the output value (offset image data) of the CCD element in a light-shielded state and the output of the CCD element when a light amount that does not saturate the CCD element are input. The gamma coefficient can be calculated from the value (bright image data). In the present embodiment, a correction coefficient for correcting the variation in the sensitivity characteristic of each CCD element is obtained by utilizing this fact.

The corrected image memory 5 stores the corrected image corrected by the correction processing section 4. Image processing test section 6
Then, after the corrected image stored in the corrected image memory 5 is correlated with each pixel of the LCD panel, well-known sampling compression is performed, and detection of loss of display pixels and display unevenness of the LCD panel is performed. Done.

Hereinafter, a specific configuration of the correction processing section 4 will be described.

The correction processing unit 4 includes an offset image memory 4
1, a bright image memory 42, subtractors 43 and 44, a buffer memory 45, an average value calculating means 46, a divider 47, a correction coefficient memory 48, and a multiplier 49.

The offset image memory 41 stores an offset image of one frame obtained by converting the output data of the CCD camera 1 in the light-shielded state by the image conversion means 2. The bright image memory 42 stores one frame of a bright image obtained by converting the output data of the CCD camera 1 when the light is input to such an extent that the CCD element is not saturated by the image converting means 2. In these memories 41 and 42, the stored image data is read out and output for each CCD pixel.

The subtractor 43 outputs each CC from the original image memory 3.
The correction target image data output for each D pixel is set as one input (input A), and the offset image data output for each CCD pixel from the offset image memory 41 is set as the other input (input B). (A-B).

The subtractor 44 is provided with an offset image memory 41
The offset image data output from each of the CCD pixels is input to one input (input A), and the bright image output from the bright image memory 42 for each CCD pixel is input to the other input (input B). Is subjected to the subtraction process of (BA).

The buffer memory 45 sequentially stores the subtraction result of the subtractor 44 for each CCD pixel. The average value calculating means 46 calculates an average value of the subtraction results for each CCD pixel stored in the buffer memory 45 and outputs the average value. The divider 47 outputs the output of the average value calculating means 46 to one input (input A) and each CC output from the buffer memory 45.
The subtraction result for each D pixel is used as the other input (input B), and
A division process (A ÷ B) is performed for each CD pixel.

The correction coefficient memory 48 stores the result of division for each CCD pixel in the divider 47 as a correction coefficient. The correction coefficient stored in the correction coefficient memory 48 is read out for each CCD pixel.

The multiplier 49 inputs the correction target image for each CCD pixel output from the subtracter 43 to one input (input A), and outputs the correction coefficient for each CCD pixel output from the correction coefficient memory 48 to the other input. As an input (input B), a multiplication process of (A × B) is performed for each CCD pixel. An image obtained from the multiplication result for each CCD pixel output from the multiplier 49 is a corrected image, and is stored in the corrected image memory 5.

Next, a procedure of a display test in the LCD panel test system will be described.

First, a process for obtaining a correction coefficient is performed before the test.

The CCD camera 1 is set in a light-shielded state, and offset image data for one frame is stored in the offset image memory 41. Next, an amount of light that does not saturate the CCD is input to the CCD camera 1, and one frame of bright image data is stored in the bright image memory.

When the offset image data and the bright image data are stored, the subtractor 44 subtracts (bright value)-(offset value) for each CCD pixel based on the image data. The result is stored in the buffer memory 45. Then, the (bright value)-(offset value) stored by the average value calculating means 46.
The average value of the subtraction results is calculated from the value of (bright value)-(offset value) read for each CCD pixel by the divider 47 and the average value calculated by the average value calculating means 46. The correction coefficient of each CCD element is obtained and stored in the correction coefficient memory 48.

When the correction coefficient of each CCD element is obtained as described above, the following correction processing is performed in the display test of the LCD panel.

A desired test pattern is displayed on an LCD display panel (see FIG. 3), which is imaged by the CCD camera 1 and test image data is stored in the original image memory 3. When the test image data (correction target image data) is stored, the stored test image data is stored in the original image memory 3 by each CCD.
It is read for each pixel.

The test image data read from the original image memory 3 is subjected to a subtraction process of the offset value stored in the offset image memory 41 by the multiplier 43 for each CCD pixel, and thereafter, is performed by the multiplier 49. The correction coefficient is multiplied for each CCD pixel. Thus, the original image memory 3
After the sensitivity correction for each CCD element is performed on the test image data stored in the LCD device, the image processing test unit 6 detects the loss of the display pixels of the LCD panel and the display unevenness based on the corrected image data. .

The correction coefficients for each CCD element need only be fetched into the correction coefficient memory 48 once, and the correction is performed based on the correction coefficients from the second and subsequent measurements.

In the above description, the image conversion means 2 uses the CC
The description has been made assuming that the output of the D camera 1 is converted into a digital signal to output one frame of image data.
One frame of image data corresponding to each pixel of the D panel may be output. In this case, the offset image and the bright image are also image data for one frame corresponding to the pixels of the LCD panel, and the correction is performed for each data corresponding to each pixel of the LCD panel.

<Embodiment 2> FIG. 2 is a block diagram showing a main configuration of an LCD panel test system having a CCD camera sensitivity correction function according to a second embodiment of the present invention. The LCD panel test system according to the present embodiment includes an average value calculating unit 4.
The configuration is the same as that of the LCD panel test system of the first embodiment except that a constant section 46 'is used instead of 6. In the drawings, the same components are denoted by the same reference numerals.

The constant section 46 'outputs a constant, for example, outputs an upper limit value defining an upper limit level of the output of the CCD camera. In the divider 47, the subtraction result of (bright value)-(offset value) for each CCD element stored in the buffer memory 45 is normalized, and the result is stored in the correction coefficient memory 48 as a correction coefficient.

In the sensitivity correction of the CCD camera in the system of this embodiment, the data is read from the original image memory 3 on the basis of the normalized subtraction result of (bright value)-(offset value) for each CCD element. The test image data is corrected, and the image processing test unit 6 detects a defect of a display pixel of the LCD panel or a display unevenness.

[0044]

According to the present invention constructed as described above, a display test is performed with high accuracy because the correction is made according to the sensitivity characteristics of each CCD element and fixed pattern noise is not included. be able to. For example, a display defect at a minute level can be detected, and the detection accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an LCD panel test system having a CCD camera sensitivity correction function according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an LCD panel test system having a CCD camera sensitivity correction function according to a second embodiment of the present invention.

FIG. 3 is a block diagram illustrating an example of an LCD panel test system.

[Explanation of symbols]

 Reference Signs List 1 CCD camera 2 Image conversion means 3 Original image memory 4 Correction processing unit 5 Corrected image memory 6 Image processing test unit 41 Offset image memory 42 Bright image memory 43, 44 Subtractor 45 Buffer memory 46 Average value calculation means 46 'Constant part 47 Divider 48 Correction coefficient memory 49 Multiplier

Claims (6)

[Claims] An image displayed on an LCD panel is converted to a CCD image.
A sensitivity correction method for a CCD camera, which is performed in an LCD panel test system that performs imaging test using a camera and performs a display test on the LCD panel based on the captured image, comprising: The brightness of each CCD element is obtained by inputting light to the CCD camera to such an extent that its output does not saturate, and the sensitivity characteristic of each CCD element is obtained from the offset value and the brightness value. In the above display test, C
A sensitivity correction method for a CCD camera, wherein a captured image captured by a CD camera is corrected. 2. The method according to claim 1, wherein the result of subtracting the offset value from the bright value for each CCD element is divided by the average of the subtraction results.
The result of the division for each CCD element is used as a correction coefficient for each CCD element.
A sensitivity correction method for a CCD camera, wherein a captured image captured by a D camera is corrected. 3. The CCD camera sensitivity correction method according to claim 1, wherein a result obtained by subtracting an offset value from a bright value for each CCD element is divided by an upper limit value defining an upper limit level of the output of the CCD camera. The division result for each CCD element is used as a correction coefficient for each CCD element, and a captured image captured by the CCD camera at the time of the display test is corrected based on the correction coefficient. Correction method. 4. A CCD camera for picking up an image displayed on an LCD panel, and an original image memory for storing an image picked up by the CCD camera. An LCD panel test system in which a display test of the LCD panel is performed based on the output of each CCD element in a state where the CCD camera is shielded from light is set as an offset value, and light is input to the CCD camera to such an extent that its output is not saturated. The output of each CCD element in the state of the above is defined as a bright value, and each CC value is obtained from the offset value and the bright value of each CCD element.
An LCD panel test with a CCD camera sensitivity correction function, comprising: correction processing means for determining the sensitivity characteristics of the D elements and correcting the captured image stored in the original image memory based on the sensitivity characteristics of each CCD element. system. 5. The LCD panel test system with a CCD camera sensitivity correction function according to claim 4, wherein the correction processing means comprises: an offset image memory for storing an offset image captured in a state where the CCD camera is shielded from light; A bright image memory for storing a bright image captured in a state in which light whose output does not saturate is input to the CCD camera; and a bright value read for each CCD pixel from the bright image memory. An offset value read for each CCD pixel from the offset image memory as the other input, and a first subtractor for subtracting the offset value from the bright value; and a CCD pixel subtracted by the first subtractor. Average value calculating means for obtaining an average value of the subtraction results for each, and the average value obtained by the average value calculating means A divider for respectively dividing the subtraction result for each CCD pixel subtracted by the first subtractor; one input of the original image data read from the original image memory for each CCD pixel, the offset image An offset value read from the memory for each CCD pixel as the other input, a second subtractor for subtracting the offset value from the original image data, and an output of the second subtractor as one input, A multiplier for taking an output as the other input and multiplying the input for each CCD pixel by a CCD camera sensitivity correction function. 6. The LCD panel test system with a CCD camera sensitivity correction function according to claim 4, wherein the correction processing means includes: an offset image memory for storing an offset image captured in a state where the CCD camera is shielded from light; A bright image memory for storing a bright image captured in a state in which light whose output does not saturate is input to the CCD camera; and a bright value read for each CCD pixel from the bright image memory. An offset value read for each CCD pixel from the offset image memory as the other input, and a first subtractor for subtracting the offset value from the bright value; and a CCD pixel subtracted by the first subtractor. Average value calculating means for obtaining an average value of the subtraction results for each, and an upper limit level of the output of the CCD camera. A divider for dividing the subtraction result of each CCD pixel subtracted by the first subtractor by a predetermined upper limit value, and one input of original image data read for each CCD pixel from the original image memory; An offset value read for each CCD pixel from the offset image memory as the other input, a second subtractor for subtracting the offset value from the original image data, and an output of the second subtractor as one input; A CCD camera sensitivity correction function-equipped LCD panel test system, comprising: a multiplier that takes the output of the divider as the other input and multiplies the input for each CCD pixel.