KR100517324B1 - Method for inspecting dot badness in a flat panel display module - Google Patents

Abstract

The present invention is a method for inspecting the image quality of the LCD panel, the inspection position in consideration of the position and the lens distortion of the LCD panel placed on the stage to accurately inspect the position corresponding to the center of the dot in the LCD module image captured by the camera. Correct it.

According to the present invention, it is possible to automatically check whether light emission is normally performed in each dot of the LCD panel, and the inspection time can be shortened as compared with visual inspection.

Description

How to check the quality of a flat panel display panel {METHOD FOR INSPECTING DOT BADNESS IN A FLAT PANEL DISPLAY MODULE}

The present invention relates to an image quality inspection method, and more particularly, to a method that can automatically inspect the image quality of the LCD panel.

Cathode ray tube (CRT) is conventionally used as a display means of most audio / video systems or data communication devices. However, CRTs require not only high voltages for electron emission and angle adjustment of electron beams, but also reduce size and weight. Had a very difficult issue. Therefore, in recent years, flat panel display technology for light weight, low voltage, and low power consumption has been developed.

These flat panel devices control light through a pixel composed of a plurality of dots. The light control method includes a method of generating light in each pixel and reflecting or transmitting light without generating itself. There is a way to control the amount of light. The former is called an active display, and the LED (Light Emitting Diode) belongs to this, and the latter is a passive display, and an LCD (Liquid Crystal Display) belongs to this.

The inspection items of the flat panel elements vary widely, but inspection of whether or not light emission is normally performed from each of these dots is performed by the human eye. Therefore, not only it takes a lot of time to inspect a single flat plate but also the test result is inaccurate.

An object of the present invention is to provide an image quality inspection method that can accurately and automatically inspect the image quality of a flat panel device such as an LCD.

In order to achieve the above object, the present invention provides a method for inspecting image quality of a flat panel by measuring lens distortion of a camera, placing an object on a stage, and checking an inspection position of an object image so as to correspond to the position of the object placed on the stage. Setting an image, photographing the object on which certain dots are emitted by the camera, transmitting an image of the photographed object to an inspection unit, and a portion of the image corresponding to an inspection position input to the inspection unit. Checking brightness and foreign objects.

The measuring of the lens distortion may include: placing a calibrator having a plurality of detection marks on the stage, imaging the calibrator, and detecting positions of the detection marks in the captured calibrator image to determine the degree of distortion. Measuring.

Preferably, the calibrator has the same size as the object, and the detection mark is formed at a position corresponding to the center of dots of the object.

The setting of the inspection position of the object image may include: imaging the object placed on the stage while the white pattern is turned on; extracting a plurality of points on an outline of the photographed object image; Restoring the plurality of points to a position before distortion in consideration of the measured degree of distortion, obtaining an outline of the linearized object by using the restored points, and forming an outline of the object adjacent to each other. Dividing at equal intervals so as to correspond to the number of dots, forming a plurality of dots by connecting the dividing points corresponding to each other with each other in a straight line, obtaining a center position of each of the dots, and measuring Correct the center position of the dots according to the corrected lens distortion value, It sets to the inspection position.

The setting of the inspection position of the object image may include photographing the object placed on the stage in a state in which dots located at the outermost of the same colors are emitted, the photographed object image. Obtaining the center positions of the dots emitted by the light source, restoring the center positions of the dots to a position before distortion in consideration of the measured degree of distortion, obtaining linearized straight lines using the restored center positions, and performing the linearization. Dividing the straight lines at equal intervals so as to correspond to the number of dots of the object in adjacent portions, connecting the splitting points corresponding to each other of the linearized straight lines with straight lines, the intersections of the straight lines, and these Dots arranged at a distance from the center of the dots of the photographed object image Designating value, and a step of, depending on the measured value, and lens distortion correction to the center positions of dots of the image pickup object images, setting a corrected position to the test position.

Hereinafter, an embodiment of the present invention will be described in more detail with reference to FIGS. 1 and 11.

The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. This embodiment is provided to more completely explain the present invention to those skilled in the art. Therefore, the shape of the elements in the drawings are exaggerated to emphasize a clearer description.

In general, the LCD panel 10 includes a plurality of pixels including a red dot emitting a red dot, a green dot emitting a green light, and a blue dot emitting a blue light. In this embodiment, the LCD panel 10 may have approximately 170 pixels in one row and approximately 117 pixels in one column, but in the figure, a very small number of pixels may be used for simplicity. However, the number of pixels is not limited thereto, and R dots, G dots, and B dots are each arranged in a row in one pixel.

1 is a view schematically illustrating an image quality inspection system of an LCD panel for measuring whether each dot is normally emitted. Referring to FIG. 1, the image quality inspection system includes a stage 100, a camera 140, a calibrator 300, an operator 120, and an inspection part 200. It includes.

The stage 100 is a portion where the LCD panel 10 for inspection is placed, and the camera 140 for capturing the LCD panel 10 or the calibrator 300 placed on the stage 100 is disposed on the stage 100. Is installed. The operation unit 120 is a part that operates the system as a whole, such as positioning of the camera 140 or the stage 100. The inspection unit 200 has an image unit 220 that receives images captured by the camera 140 and a data unit 240 that stores inspection positions of the LCD panel image. In addition, the inspection unit 200 is a comparison unit 260 for checking the brightness of the portion corresponding to the inspection position in the LCD panel image transmitted to the image unit 220 and the upper and lower limits of the brightness to determine whether each dot is defective. It further has an input determination unit 280. The determination unit 280 may also detect whether foreign materials exist in the dots.

It is important that the inspection position input to the data unit 240 exactly matches the center of each dot shown in the captured LCD panel image. 2A shows each dot of the LCD panel. In FIG. 2A, the portion indicated by '·' indicates the center positions of the dots, and the center positions are equally spaced in the vertical direction and the left and right directions.

FIG. 2B is a view showing the center positions of dots of the captured LCD panel image. Referring to FIG. 2B, the boundary lines of the dots in the LCD panel image captured by the camera 140 are curved due to lens distortion, and the center is shown. The spacing between positions is also different. Therefore, if the center position of each dot of the LCD panel displayed at equal intervals is set as the inspection position, the inspection position and the center of the dots of the image do not correspond exactly, and the inspection result is inaccurate. This problem is aggravated towards the edges.

In the present invention, the inspection position is corrected in consideration of lens distortion, and FIG. 3 is a plan view of the calibrator 300 used therein. The calibrator 300 has the same size as the LCD panel 10, and the detection marks 302 are formed at portions corresponding to the center positions of the dots of the LCD panel 10. The position and spacing of these detection marks are formed very precisely. Alternatively, however, various types of marks may be used to indicate the center positions of the dots, and the detection marks may be formed at different positions. The calibrator 300 is placed on the stage 100 before the LCD panel 10 is captured, and the camera 140 captures the calibrator image 300 'after the calibrator 300 is captured by the image unit of the inspection unit 200. 220). 4 shows the calibrator image 300 ′ transmitted to the image unit 220. The data unit 240 measures the distortion degree of the lens from the positions of the detection marks 302 shown in the calibrator image, and stores the measurement data.

Even if the inspection position of the dots is corrected according to the lens distortion, if the LCD panel 10 is placed in an inverted state without being accurately placed on the stage 10, the inspection position and the dot center positions of the captured LCD panel images are correctly Does not match. In addition, even if the size of the LCD panel 10 is not precisely processed, the above-described problem occurs.

FIG. 5 is a view comparing the inspection position corrected in consideration of the lens distortion input to the data unit 240 and the LCD panel image 10 ′ photographed while not accurately placed on the stage. In the drawing, the dotted line is the LCD panel image (10 ″) captured when the LCD panel is normally placed on the stage 100, and the solid line is the LCD panel image captured when the LCD panel is placed on the stage (100) in a distorted state. (10 '),' + 'is the center of dots indicated by solid lines and' · 'is the center of dots indicated by dotted lines. That is, when setting the inspection positions in consideration of only lens distortion, the inspection results are inaccurate because the centers of the dots in the inspection position and the actual captured LCD panel image are inconsistent.

6A to 6G illustrate a method of setting an inspection position in consideration of the position of the LCD panel placed on the stage according to the first embodiment. Initially, the LCD panel 10 is placed on the stage 100. The camera 140 photographs the LCD panel 10 in a white pattern state (all dots of the LCD emit light), and the captured image is transmitted to the image unit 220. The inspection unit 200 finds some points forming the outline of the captured LCD panel image 10 '(FIG. 6A). This includes the corner points of the LCD panel image 10 '. Thereafter, the positions of the corner points are restored from the measured values of the lens distortion (FIG. 6B), and the outline of the LCD module is obtained by linearizing from these points (FIG. 6C). Next, each outline is divided at equal intervals to correspond to the number of dots adjacent to the outline (FIG. 6D), and the corresponding dividing points 13 of the outline 12 facing each other are connected (FIG. 6E). When dots are formed by these connected lines, the center 15 of the dots is obtained (Fig. 6F). Thereafter, the center positions of the dots are corrected to correspond to the shape of the LCD image picked up from the measured values of lens distortion, and the corrected center positions are set as the inspection positions (Fig. 6G).

When the inspection position is finally set, the LCD panel is photographed in the state where dots of the same kind are emitted, and the captured image is transmitted to the image unit 220. The comparison unit 200 examines the brightness of the portion corresponding to the inspection position stored in the data unit. The determination unit 280 recognizes that the dot is a good dot when the brightness is within the allowable range, and recognizes a bad dot when it is out of the allowable range.

7A to 7G illustrate a method of setting an inspection position in consideration of the position of the LCD panel placed on the stage according to the second embodiment.

Initially, the LCD panel 10 is placed on the stage 100. The LCD panel 10 is imaged in a state where the G dots are emitted by the camera 140, and the captured image is transmitted to the image unit 220 (FIG. 7A). The inspection unit 200 obtains the center position 22 of each dot in the captured LCD panel image 10 '(FIG. 7B). Then, the center position 22 'is restored from the measured values of the lens distortion (Fig. 7C), and linearized straight lines 23 are obtained from these points (Fig. 7D). Next, each linearized straight line is divided at equal intervals to correspond to the number of dots adjacent to the linearized straight lines 23, and the corresponding splitting points 24 of the linearized straight lines facing each other are connected (FIG. 7E). ). The intersections 25 of these straight lines and the points 26 (center positions of R dots and B dots located at both outermost sides) disposed at a predetermined distance from them are designated as the center positions of the dots of the image of the captured object image ( 7f). Thereafter, the center positions of the dots are corrected to correspond to the shape of the LCD image picked up from the measured values of lens distortion, and the corrected center positions are set as the inspection positions (Fig. 7G). According to the second embodiment, since the reference points are the central positions of the dots of a certain color rather than the outline of the LCD module, the inspection position is closer to the central positions of the dots than the first embodiment.

Although in the second embodiment, in order to minimize the occurrence of the deflection in the image photographed by the camera, the LCD module is imaged with the G dots emitted. Alternatively, imaging of the LCD module may be performed while the R dots or the B dots are emitted.

FIG. 8 is a flowchart sequentially showing a method for checking an image quality according to an exemplary embodiment of the present invention, FIG. 9 is a flowchart sequentially showing a method of measuring a distortion degree of a lens, and FIGS. 10 and 11 are placed on a stage, respectively. This is a flowchart that shows how to set the inspection position according to the position of the LCD panel. First, the calibrator 300 is placed on the stage 100, and the calibrator 300 is imaged. The captured calibrator image 300 ′ is transmitted to the image unit 220, and the degree of distortion of the lens is measured from the detection mark 302 shown in the calibrator image 300 ′, and the value is transmitted to the data unit 240. Stored.

The calibrator 300 is unloaded from the stage 100, and the LCD panel 10 to be inspected is loaded into the stage 100. Then, the inspection position of the captured LCD panel image is set in consideration of the position of the LCD panel 10 placed on the stage 100. When the inspection position is set, the LCD panel 10 is captured while all the R dots are emitted, and the captured LCD panel image 10 'is transmitted to the image unit 220. The comparator 260 inspects the brightness of the LCD panel image 10 'at a portion corresponding to the inspection position stored in the data unit 240 and determines whether the brightness is within an allowable range. Thereafter, the brightness is also checked for the G dots and the B dots. After the image quality inspection for one LCD panel 10 is finished, the LCD panel is unloaded, and the next LCD panel is loaded onto the stage. The inspection position is corrected again in consideration of the position of the LCD panel, and the above-described process is repeated. That is, the lens distortion of the camera is measured once, and the inspection position correction considering the position of the LCD panel 10 placed on the stage is repeatedly performed for each LCD panel.

According to the present invention, it is possible to automatically check whether light emission is normally performed at each dot of the LCD panel. Therefore, the time required for the inspection can be shortened compared to the visual inspection, and accurate inspection results can be obtained.

1 schematically shows a system for checking the image quality of an LCD panel;

2A is a diagram showing a center position of each dot of the LCD panel;

2B is a diagram showing the center positions of dots of the captured LCD panel image;

3 is a top view of the calibrator;

4 shows a calibrator image picked up by a camera;

5 is a view comparing an inspection position input to a data unit in consideration of lens distortion and an LCD panel image photographed while not correctly placed on a stage;

6A to 6G are views showing a process in which correction is made in consideration of the position of the LCD panel placed on the stage according to the first embodiment;

7A to 7G are views showing a process in which correction is made in consideration of the position of the LCD panel placed on the stage according to the second embodiment;

8 is a flowchart sequentially showing a method for checking an image quality according to an exemplary embodiment of the present invention;

9 is a flowchart sequentially showing a method of measuring a degree of distortion of a lens;

10 is a flowchart showing a step of setting an inspection position in consideration of the position of the LCD panel placed on the stage according to the first embodiment; and

11 is a flowchart showing a step of setting an inspection position in consideration of the position of the LCD panel placed on the stage according to the first embodiment.

Explanation of symbols on the main parts of the drawings

100: stage 120: operation unit

140: camera 200: inspection unit

300: Calibrator

Claims (8)

In the method of inspecting the image quality of the flat panel display panel, Measuring lens distortion of the camera; Placing the object on the stage; Setting an inspection position of an object image to correspond to a position of the object placed on the stage; Photographing the object with certain dots emitted by the camera; Transmitting an image of the photographed object to an inspection unit; And Inspecting the brightness of the portion of the image corresponding to the inspection position input to the inspection unit in consideration of the lens distortion of the camera, And setting the inspection position of the object image to correspond to the position of the object placed on the stage, for each of the object placed on the stage. The method of claim 1, Measuring the lens distortion, Placing a calibrator having a plurality of detection marks formed on the stage; Imaging the calibrator; And And detecting the positions of the detection marks on the calibrated image to measure the degree of distortion. The method of claim 2, The calibrator has the same size as the object, And the detection mark is formed at a position corresponding to the center of dots of the object. The method according to any one of claims 1 to 3, Setting the inspection position of the object image, Imaging the object placed on the stage with the white pattern turned on; Extracting a plurality of points on an outline of the captured object image; Restoring the plurality of points to a position before distortion in consideration of the measured degree of distortion; Obtaining an outline of the linearized object using the restored points; Dividing the outline of the object at equal intervals so as to correspond to the number of dots of the object in adjacent portions, respectively; Forming a plurality of dots by connecting division points corresponding to each other of the outlines facing each other in a straight line; Obtaining a center position of each of the dots; And And correcting a center position of the dots according to the measured lens distortion value, and setting the corrected position as an inspection position. The method according to any one of claims 1 to 3, Setting the inspection position of the object image, Imaging the object placed on the stage while the dots located at the outermost of the same colors are emitted; Obtaining a center position of dots emitted from the picked-up object image; Restoring a center position of the dots to a position before distortion in consideration of the measured degree of distortion; Obtaining linearized straight lines using the reconstructed center positions; Dividing the linearized straight lines at equal intervals so as to correspond to the number of dots of the object in adjacent portions, respectively; Connecting the split points corresponding to each other of the linearized straight lines facing each other in a straight line; Designating the intersections of the straight lines and the points arranged at a certain distance therefrom as the center positions of the dots of the photographed object image; And And correcting a center position of dots of the photographed object image according to the measured lens distortion value, and setting the corrected position as an inspection position. The method of claim 5, Imaging the object placed on the stage while the dots located at the outermost of the same colors are emitted; And the color of the dots to be emitted is green. In the method of inspecting the image quality of the flat panel display panel, Placing the object on the stage; Setting an inspection position of an object image to correspond to a position of the object placed on the stage; Imaging the object with the camera; Transmitting an image of the photographed object to an inspection unit; And Including the step of checking the brightness of the portion of the image corresponding to the inspection position input to the inspection unit, And an inspection position of the object is set for each of the objects to be inspected. The method according to claim 1 or 7, And said object is a liquid crystal display panel.