JPH05223749A - Inspecting method for liquid crystal display board - Google Patents

Abstract

PURPOSE:To detect even one dot failure easily by performing a processing for detecting a dot omission after eliminating a mesh. CONSTITUTION:A peak position which corresponds to a mesh is detected according to a brightness projection distribution by utilizing its up/down or setting a threshold. A position which was detected is shown downward with a black arrow. Then, several picture elements in a region 6 of a detected mesh are erased from an original image. The picture element region to be erased is determined according to magnification of a TV camera. Since the width of most meshes is 0.3mm, one mesh can be eliminated when a line of + or -2 picture elements for 0.06mm/picture element (512X512) is erased if the visual field of a camera is, for example, 30mm. All meshes can be eliminated by performing it for all the mesh positions which have been detected and performing a same treatment in horizontal direction as in vertical direction. A dot position can be detected easily since there are no meshes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting a liquid crystal display panel suitable for inspecting a display defect of a dot display type output device such as a liquid crystal display panel, particularly, dot omission, line omission, brightness and dust. It is about.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display panel has replaced a cathode ray tube and a particularly small OA such as a personal computer or a word processor.
It has been widely used in equipment. Moreover, not only for small-sized liquid crystal display panels, these liquid crystal display panels are in the trend of large screen and high definition. On the other hand, there are items such as dot omissions, line omissions, brightness, dust, etc. in display defects of the current liquid crystal display panel, and most of the display inspections rely on visual inspection. As the liquid crystal display board becomes finer, visual inspection has reached its limit, and in addition to affecting the reliability of the product such as oversight of defects, it is physiologically difficult for the visual inspector. From such a background, there are some proposals for automating the display inspection. Regarding the automatic evaluation device and method for the liquid crystal display panel, for example, JP-A-1-2191048, JP-A-1-270099, and JP-A-2-193271.
Etc. have been applied. Among them, Japanese Patent Laid-Open No. 191048 is an apparatus for inspecting for defects (unevenness, blank, etc.) by forming a reference pattern and comparing it with an input image. There are many methods of comparing with such a reference pattern, but this has a problem in versatility that the reference pattern must be prepared for each lot having a different dot pitch or shape. In particular, in the case of multi-model parts such as liquid crystal display boards, it is a major obstacle to automation.

[0003]

An obstacle to the display inspection of the liquid crystal display panel by image processing other than the comparison with the reference pattern is that there is a wiring line between the dots of the liquid crystal display panel. Is observed as a horizontal and vertical mesh. A dot defect occurs at a black dot when missing or missing dots between the meshes, and at a white dot when a bright spot. When a dot defect is hidden between meshes, such as when one dot is missing, the mesh makes it difficult to separate dot defects such as missing dots. The present invention is to provide a detection method that can easily detect even one dot defect by first performing the mesh removal processing and then the dot dropout detection processing.

[0004]

To solve this problem, the position of a mesh is obtained by image processing, the pixels corresponding to the mesh are deleted from the original image, and the image is reconstructed. Next, the brightness projection distribution of this image is obtained, and dot defect points are extracted by setting a threshold value or the like.

[0005]

By removing the mesh before the display inspection, it is possible to detect a missing dot or small dust. In addition, even if lots with different dot pitches and display sizes are used, the inspection device will not be changed, and the inspection can be performed in the same way.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of the liquid crystal display panel inspection apparatus of the present invention. A liquid crystal display panel 1 with a dot missing defect mounted on a personal computer is used to image the display condition with a TV camera 2.
The image processing device 3 performs various processes such as mesh removal to inspect for defects. Also, the processing result is displayed on the monitor TV.
4 Display on top. The following describes the processing method in the image processing device 3.

FIG. 2 shows a liquid crystal display panel in which defective dots are missing. When no characters are displayed, the backlight is displayed in white, and the missing dots are like black dots 5 in the figure. The wiring pattern between dots is brighter or darker than the backlight and is a vertical and horizontal mesh.

FIG. 3 shows the processing situation when the dot missing image is considered by an image processing method other than the method by comparison with the reference pattern. The brightness projection distribution in the vertical direction of the input image is obtained. As a result, as shown in FIG. 3, the projection distribution had a peak of a mesh in a sawtooth shape, and a dot missing portion was hidden in it, and it was difficult to extract the dot missing portion. This is a problem of dot defect inspection.

Therefore, in the present invention, the process shown in FIG. 4 is performed to remove this mesh. FIG. 4 is an enlarged view of FIG. 3. First, the peak position corresponding to the mesh is detected from the brightness projection distribution previously obtained in FIG. 3 by using its up / down or by setting a threshold value. The detected position is indicated by a downward black arrow in FIG. Next, the pixels in the range 6 of several pixels before and after the detected mesh are deleted from the original image.
The pixel range to be erased is determined by the magnification of the TV camera. Most mesh widths are currently 0.3 mm, so if the camera's field of view is 30 mm, 0.06 m
Since it is m / pixel (512 x 512), one mesh can be removed by deleting the line of ± 2 pixels. This is processed for all the detected mesh positions, and also for the horizontal direction, the same process as for the vertical direction is performed to erase all the meshes from the original image. The image after the processing is as shown in FIG. The wavy line is the size of the original image before mesh removal, and the image was reduced because only pixels proportional to the number of detected meshes were deleted. This reduction also reduces the processing range and shortens the time for subsequent image processing. The flow chart of FIG. 6 summarizes the above mesh removal processing.

Next, the missing dot detection process is performed from FIG. 5 after the mesh removal. An example of the processing is shown in FIG. This is a calculation of the brightness projection distribution in the vertical and horizontal directions in FIG. 5, and since there is no mesh, missing dots are clearly present, and the dot position can be easily detected. Figure 7
It is also possible to make a size evaluation by setting a threshold value in the brightness projection distribution and detecting more points, or by obtaining the position and area of each dot dropout in the labeling process.

FIG. 8 shows an example of the configuration of a general image processing apparatus for performing the above image processing.

[0013]

By carrying out the above-mentioned processing, there is no influence of the mesh between the dots of the liquid crystal display plate which is an obstacle in image processing, or regardless of the dot size, missing dots, missing lines, bright spots, dust, etc. It is possible to easily detect and evaluate the presence or absence of display defective dots and their sizes.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a liquid crystal display panel inspection device.

FIG. 2 is a diagram showing an example of missing dots on a liquid crystal display panel.

FIG. 3 is a diagram showing an example of image processing for detecting missing dots on a liquid crystal display plate.

FIG. 4 is a diagram showing a mesh removal process.

FIG. 5 is a diagram showing an entire image of a liquid crystal display panel after mesh processing.

FIG. 6 is a diagram showing a mesh removal processing flowchart.

FIG. 7 is a diagram showing a process of detecting a dot missing position.

FIG. 8 is a configuration diagram of an image processing apparatus.

[Explanation of symbols]

1 ... Liquid crystal display board, 2 ... TV camera, 3 ... Image processing device,
4 ... Monitor TV, 5 ... Missing dots on liquid crystal display plate, 6 ... Mesh to be removed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G09G 3/36 7319-5G

Claims (1)

[Claims] 1. A liquid crystal display characterized by detecting a defective display such as missing dots, missing lines, bright spots, dust, etc. by removing a mesh between dots in a display inspection of an output device such as a liquid crystal display board. Board inspection method.