JP2000162089A - Method and apparatus for inspection of screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which various defects existing on a display screen can be inspected at high speed and with high accuracy without constituting a complicated system by detecting a defect on the basis of the shade of a single composed shade image in which a plurality of shade signals in different exposure times are composed. SOLUTION: A light source 2 shines light at an object 1 to be inspected. The shade signal in every pixel of the object 1 to be inspected is obtained through a camera 3, and it is sent to a computer 4. The computer 4 controls the light source 2, and it controls the exposure time in the imaging operation of the camera 3. In the computer 4, an image memory 5 stores shade data in a form which corresponds to the row and the column of every pixel. In addition, in the computer 4, a program which executes a processing operation is set in a program memory 6. In Step 1, an image from the object to be inspected is fetched. In Step 2, shade images which are fetched in Step 1 are composed. In Step 3, a part which is changed from the neighborhood is detected with reference to the shade images obtained in Step 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to inspecting, on a manufacturing line, defects appearing in display elements in which display pixels are regularly arranged, such as liquid crystal panels, CRT panels, and PDP panels used in the field of electronic equipment. In addition, the present invention can be applied to a defect inspection apparatus that captures an object to be inspected as an image, evaluates a defective portion, and detects a defect. Hereinafter, this is collectively referred to as screen inspection.

[0002]

2. Description of the Related Art Conventionally, screen inspection has been carried out either by manual inspection or by image processing by an automatic machine.

[0003] In the case of manual operation, even if the model is converted, it can be easily dealt with, and the rise is quick, but it takes time to specify the detailed position of the defect, and there is a drawback that the throughput is poor. There is also a problem in maintaining and unifying inspection sensitivity.

On the other hand, in the case of an automatic machine, a long time is required for adjustment after the model is converted, but there is an advantage that the specific information of the defect position can be quickly recognized. In addition, the inspection sensitivity was maintained and unified.

However, with the recent trend toward higher definition and higher performance of components, the visual inspection has become more and more remarkably low in throughput. One of the difficult inspections for an automatic machine to inspect in a screen inspection is to correctly image and detect defects ranging from a defect having a low contrast to a defect having a high contrast as compared with the surroundings.

In recent years, there has been an increasing demand for automation in response to a demand for quality, but there is no processing method capable of accurately detecting defects in the above-described situation. When detecting a display defect of a liquid crystal panel, which is one of the screen inspections, a problem to be solved is a lack of a dynamic range of an image obtained by imaging.

[0007] Normally, a grayscale image has 256 gradations (8 bits).
Appear in. However, it is not enough to detect a display defect of a liquid crystal panel widely from a low contrast to a high contrast defect. Although it is conceivable to increase the gradation, it is rarely easily performed due to the limitation of the memory area.

[0008] Further, a light receiving element CC which is usually used is used.
Considering noise components in the D sensor, there are few D sensors that have a dynamic range of exactly 8 bits or more in terms of performance. The case of an inspection system that can control the exposure time will be described.

The target liquid crystal panel is shown in FIG.
(A) As shown in FIG.
First, it is assumed that there are two adjacent defects 100 and 101 having high luminance and a defect 102 having low luminance.

FIG. 4 shows a density profile 91 of a line 90 of a grayscale image obtained by imaging at an exposure time of 300 ms.
FIG. 4C shows a density profile 92 of a line 90 of a grayscale image picked up at an exposure time of 100 ms.
Shown in

At an exposure time of 300 ms, a portion 104 corresponding to the defect 102 is observed, but the defect 100, 1
The light-receiving density of the portion 103 corresponding to 01 becomes saturated and becomes one.

On the other hand, when the exposure time is 100 ms,
3 is separated into portions 105 and 106, but the defect 10
The portion 107 corresponding to 2 has an extremely low light receiving density.

[0013]

As described above, the conventional screen inspection method cannot accurately inspect various luminance defects appearing on a display element such as a liquid crystal panel.

Therefore, it is conceivable to change the exposure time, extract defects based on the grayscale images obtained respectively, and combine the results. However, there remains a problem in view of the complexity of synthesizing the result including the detection position and an increase in processing time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a screen inspection method capable of detecting various luminance defects existing on a display screen at high speed and high accuracy without configuring a complicated system.

[0016]

A screen inspection method according to the present invention comprises combining a plurality of grayscale images having different exposure times to obtain a single composite grayscale image, and detecting a defect from the grayscale of the composite grayscale image. It is characterized by.

According to the present invention, it is possible to provide a processing method that accurately detects defects having low contrast to defects having high contrast without configuring a complicated system and has a high correlation with visual sensitivity.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A screen inspection method according to claim 1 is
In the process of manufacturing the display element, when detecting a luminance defect based on display pixel density data of a grayscale image obtained by imaging the screen of the inspection object, the exposure time is changed and the inspection object is imaged. A plurality of grayscale images having different exposure times are synthesized to obtain a single composite grayscale image, and a defect is detected from the grayscale of the composite grayscale image.

According to a second aspect of the present invention, there is provided a screen inspection method.
In producing a composite grayscale image, the grayscale of a plurality of raw data obtained by imaging the object to be inspected is reduced and then combined, and after synthesis, the grayscale approximates the grayscale at the time of imaging. It is characterized in that a tone restoration process is executed, and a defect is detected from the shade of the composite shade image subjected to the tone restoration process.

According to a third aspect of the present invention, there is provided a screen inspection method.
In the case of producing a composite grayscale image, the grayscale of a plurality of raw data obtained by imaging the object to be inspected is increased and then combined, and after the combination, the grayscale is brought close to the grayscale at the time of imaging. Restoration processing is executed, and a defect is detected from the shade of the composite shade image subjected to the tone restoration processing.

According to a fourth aspect of the present invention, there is provided a screen inspection apparatus, comprising: a camera for imaging a screen of a display element of an object to be inspected; an exposure time control means capable of changing an exposure time at the time of the imaging; And a plurality of grayscale images different from each other to obtain a single composite grayscale image, and an image processing means for detecting a defect from the grayscale of the composite grayscale image is provided.

Hereinafter, an image inspection method according to the present invention will be described based on specific embodiments. FIG. 1 shows a screen inspection apparatus used for carrying out the screen inspection method of the present invention. The screen inspection device includes a light source 2, a camera 3, a computer 4, and the like.

The computer 4 instructs the light source 2 to irradiate the test object 1 with light.
Is obtained for each pixel, and this is sent to the computer 4 in a digitized form.

In this embodiment, the computer 4 controls the light source 2 to control the exposure time when the camera 3 captures an image. An image memory 5 exists in the computer 4 and stores, for example, 8-bit density data of 256 gradations (0 to 255) in a form corresponding to the rows and columns of pixels.

In the computer 4, a program for executing the following processing is set in the program memory 6. FIG. 2 shows a processing procedure of the computer 4.

In step # 1, an image from the subject 1 is captured. At this time, it is assumed that the exposure time is changed, for example, twice. Here, the exposure time 30 shown in the conventional example is used.
Assuming that the data is captured at 0 ms and 100 ms, FIG.
(B) It is assumed that the density profiles 91 and 92 of (c) are obtained.

In step # 2, the grayscale image captured in step # 1 is synthesized. Here, in order to simplify the description, the description will be made in one dimension. Each concentration profile 9
1,92 are shown in 256 gradations,
Conversion to 28 gradations. The obtained concentration profile 10,
11 is shown in FIGS. 3 (a) and 3 (b). Before converting the broken lines 7 and 8,
The solid lines 10, 11, and 12 are assumed to be after conversion.

By adding the density profiles 10 and 11, a density profile 12 of 256 gradations is obtained again as shown in FIG. Unlike the conventional example, the obtained density profile 12 shows the separation of the defects 100 and 101 and the defect 102 in one grayscale image.

In step # 3, a portion having a change from the vicinity is detected for the grayscale image selected in step # 2. For example, there is a method in which a density peak point having a specific threshold value of 20 or more is determined as a defect. Thus, the computer 4 can regard the portions 21, 22, and 23 as defective.

As described above, a plurality of grayscale images having different exposure times are combined into a single grayscale image in step # 2, and then the defect detection is performed in step # 3. Of the detection, and combining the results to obtain a defect result, the complexity of synthesizing the result including the detection position, which was a problem that was left, without increasing the processing time, Without configuring the system,
Various brightness defects existing on the display screen can be performed at high speed and with high accuracy.

In the above embodiment, the grayscale image has 256 gradations, but there is no particular limitation. In addition, although the grayscale image is captured twice, there is no particular limitation. For example, in the case of four times, it is conceivable to once convert from 256 gradations to 64 gradations and to combine the four grayscale images again to return to 256 gradations.

In each of the above embodiments, when synthesizing an image, 256 tones are converted into 128 tones once, and an addition process is performed to obtain 256 tones again. However, the method is limited. do not do. For example, add processing first,
A method of changing from 512 gradations to 256 gradations is also conceivable.

In the defect detection method of step # 3, the density profile 12 is processed using a specific threshold value to detect a defect. However, the density profile 12 is processed by another method to detect a defect. Can be detected.

For example, a case where the density difference between the neighboring pixels exceeds a specific threshold value can be detected as a defect.
In addition, as described in the liquid crystal panel, the CRT panel,
The present invention can be similarly applied to other display elements such as a PDP panel.

In each of the above embodiments, the computer 4 controls the lighting time of the lamp 2 to regulate the exposure time, but the light incident on the camera 3 is controlled by a mechanical shutter system.
The exposure time can be defined by controlling with an electronic shutter system or the like.

[0036]

As described above, according to the screen inspection method of the present invention, when detecting a luminance defect based on display pixel density data of a grayscale image obtained by imaging a screen of an object to be inspected, the exposure time is reduced. Since a plurality of grayscale images are obtained by changing the image of the object to be inspected, a plurality of grayscale images having different light times are combined to obtain a single composite grayscale image, and a defect is detected from the grayscale of the composite grayscale image. In addition, various brightness defects existing on the display screen can be performed at high speed and with high accuracy without configuring a complicated system, thereby contributing to an improvement in productivity of a liquid crystal panel or the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a screen inspection apparatus used for implementing a screen inspection method of the present invention.

FIG. 2 is a flowchart of a main part of the computer according to the embodiment;

FIG. 3 is an explanatory diagram of a grayscale image of each unit according to the embodiment;

FIG. 4 is a diagram showing a defect portion and a concentration profile;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 2 Lamp 3 Camera 4 Computer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G051 AA90 AB02 CA04 CB07 CC20 EA11 EA12 EA14 2G086 EE03 EE10 5B057 AA01 CE11 DA03 DB09 DC22

Claims (4)

[Claims] In a manufacturing process of a display element, when detecting a luminance defect based on display pixel density data of a grayscale image obtained by imaging a screen of an object to be inspected, the exposure time is changed to change the exposure time. A screen inspection method for obtaining a plurality of grayscale images by capturing images, combining a plurality of grayscale images having different exposure times to obtain a single composite grayscale image, and detecting a defect from the grayscale of the composite grayscale image. 2. A method of producing a composite gray-scale image, comprising: lowering the gray-scale level of a plurality of raw data obtained by imaging an object to be inspected; 2. The screen inspection method according to claim 1, wherein a tone restoration process is performed to approximate the defect, and a defect is detected from the shade of the composite shade image subjected to the tone restoration process. 3. A method for producing a composite grayscale image, comprising: increasing the grayscale of a plurality of raw data obtained by imaging an object to be inspected and then synthesizing the data; The screen inspection method according to claim 1, wherein a gradation restoration process for approaching the image is performed, and a defect is detected from the gradation of the composite gradation image subjected to the gradation restoration process. 4. A camera for imaging a screen of a display element of an object to be inspected, an exposure time control means capable of changing an exposure time at the time of the imaging, and synthesizing a plurality of gray images having different exposure times taken by the camera. An image processing means for obtaining a single combined grayscale image and detecting a defect from the grayscale of the combined grayscale image.