JPH05240802A - Display element inspection method - Google Patents

Abstract

PURPOSE:To obtain a read method of a static display for inspection capable of reducing the number of sensor pixels corresponding to the pixels for a display. CONSTITUTION:In an inspection method for judging the quality of the display of a display element as a display for inspection, positions of the display element 1 and a sensor camera 2 are set in a reference positional relation. The light intensity information of the display pixel is formed by multiplying the light intensity information sensed by the sensor image element by the correction factor of a corresponding position extracted in the reference position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device such as a liquid crystal display and a plasma display. More specifically, it relates to a method of reading a screen displayed by a display element and inspecting its quality.

[0002]

2. Description of the Related Art As a method for reading a screen displayed on a display element, a method using a line sensor (hereinafter referred to as a first conventional example) is well known. For example, a line sensor with 16 pixels per millimeter is used to input a display screen of a display element with about 3 pixels per millimeter. In addition, a method using a two-dimensional sensor such as a CCD (hereinafter referred to as the second
A known example) is well known. In the method of the second conventional example, pixels arranged in rows and columns of a two-dimensional sensor and pixels arranged in rows and columns of display elements (hereinafter, the pixels of the display elements are referred to as display pixels, unless otherwise specified, The pixel of the sensor is referred to as a sensor pixel), and a plurality of sensor pixels are generally arranged corresponding to one display pixel. The basic idea is to make a display pixel at any position of the display element have a sensor pixel that corresponds to the display pixel in question. Here, the correct correspondence means that the image of the display pixel formed on the light receiving surface of the two-dimensional sensor (hereinafter, the image of the display pixel formed on the light receiving surface of the two-dimensional sensor is simply referred to as a pixel image) and the sensor corresponding to this pixel image. The correspondence is such that the positional relationship of pixels is practically the same for all pixel images. For example, to detect the peak value of the luminous intensity distribution that expresses the intensity of the light emitted by the display pixel (the display pixel itself does not emit light, and is expressed as the light emitted by the display pixel including the transmitted light) The sensor pixel needs to be present at the peak position of the luminous intensity distribution of the display pixel. In order to realize such a correspondence relationship, one display pixel must correspond to many sensor pixels,
The number of sensor pixels must be sufficiently larger than the number of display pixels. Therefore, it is possible to use a two-dimensional sensor in a static reading method to inspect a relatively low-quality display element having a sufficiently small number of display pixels with respect to the number of sensor pixels. On the other hand, in order to apply to the inspection of the display element having the same or more display pixels, the screen of the display element is divided into several areas, and a two-dimensional sensor is arranged in each area, A method of equivalently limiting the number of display pixels shared by the dimension sensor is adopted. One of the methods for realizing this is a static method in which a plurality of two-dimensional sensors are arranged and different areas are shared and read. The other one is a moving type method of reading a limited area while moving the relative position of the two-dimensional sensor and the display element to be inspected, and in the point of movement, it is similar to the case of the line sensor. ..

[0003]

In the method using the line sensor of the first conventional example, it is necessary to move the relative position between the sensor and the display element every time the display pixel in one row of the display element is read, and the mechanical movement is required. Not only is the mechanism necessary and complicated, but it also has the drawback of requiring a great deal of time to read.
Further, the moving type method of moving the two-dimensional sensor of the second conventional example requires a moving mechanism similar to the method using the line sensor, which is complicated and takes a lot of time to read. is there. In the static method in which a plurality of two-dimensional sensors are arranged, the number of two-dimensional sensor cameras to be installed becomes enormous, and the applicability to the inspection of a high-quality display element with a large number of pixels becomes poor. For example, when a CCD sensor camera having the same number of pixels is used for a display element of 640 × 400 pixels, one display pixel corresponds to at least about 5 sensor pixels in each of the vertical direction and the horizontal direction. If so, 25 cameras are required. Since the scale of the image processing circuit increases according to the number of cameras and it is difficult to arrange the cameras facing the display screen, the feasibility becomes poor. The present invention solves the above-mentioned drawbacks, provides a static type inspection screen reading method capable of reducing the number of sensor pixels arranged corresponding to display pixels, and provides a more economical and efficient display element inspection method. is there.

[0004]

When the number of sensor pixels corresponding to display pixels is small, the position of the sensor pixel cannot be fixed to a specific position such as a peak position on the luminous intensity distribution of the display pixel. In order to solve the problem that different luminosity information is detected even though the luminosity is the same, the correction coefficient is extracted in advance by fixing the positional relationship between the display pixel and the sensor pixel corresponding to this display pixel. ,
By multiplying this correction coefficient by the detected light intensity information which is the output of the sensor pixel, it is equivalently converted into the light intensity information when the sensor pixel is arranged at a specific position of the light intensity distribution for all display pixels. , As follows. That is, in the inspection method for determining the quality of the display screen of the display element as the inspection screen, (1) the positional relationship between the display element and the sensor camera is set to the reference position,
The invention of claim 1 and (2) extraction of the corresponding position correction coefficient, wherein the luminous intensity information sensed by the sensor pixel is multiplied by the corresponding position correction coefficient extracted at the reference position to generate the luminous intensity information of the display pixel. In the above, the invention according to claim 2 is constituted, which comprises a display element that has been inspected.

[0005]

Since the present invention is configured as described above, the positional relationship between the display element and the sensor camera can always be kept at a constant reference position even if the display element which is the sample is changed. The positional relationship of sensor pixels can be fixed,
Further, since the relationship between the luminous intensity of the corresponding sensor pixel sensed at this reference position and the luminous intensity of the display pixel corresponding to this corresponding sensor pixel is extracted and stored as the corresponding position correction coefficient, the relative between the display pixel and the corresponding sensor pixel is stored. Even if the positional relationship changes greatly depending on the position of the display pixel, by multiplying the corresponding position correction coefficient by the luminous intensity sensed by the corresponding sensor pixel,
It is possible to extract the luminosity of the display pixel on the same basis not only inside the sample but also between the samples. Therefore, by reducing the number of sensor cameras installed, the number of sensor pixels to be arranged corresponding to the display pixels is reduced, and the relative positional relationship between the display pixels and the corresponding sensor pixels changes greatly depending on the position of the display pixels. Even in a situation, the luminous intensity of each display pixel can be correctly inspected.

[0006]

[Example] A liquid crystal display (LCD) as a display element,
The present invention will be described in detail below with reference to the drawings by taking the case of using a CCD two-dimensional sensor as an example. The display pixel, the pixel image, and the sensor pixel have a two-dimensional spread in both x and y directions which are orthogonal to each other. However, if the explanation is made in a two-dimensional spread, it becomes unnecessarily complicated and hinders understanding. Furthermore, in the case of a two-dimensional spread, it will be easy to explain in the explanation focusing only on one direction of both x and y. Since it can be expanded and understood, in the present specification, description will be given with a one-dimensional spread. Note that in this specification, the intensity of light emitted from a display pixel is expressed by a term called luminous intensity. Luminous intensity is an arbitrary unit, the intensity of light emitted from the display pixel per unit area,
The intensity of light integrated over the entire area of the display pixel, the intensity of light per unit area of the pixel image formed on the light receiving surface of the sensor, and the intensity of light integrated over a certain area of the pixel image are also All of these are expressed in luminosity.

FIG. 1 is an explanatory view of the basic principle of the present invention.
In the figure, the luminous intensity distribution 20 of the pixel image is shown in a positional relationship with the pixel image region 10. Further, the sensor pixel region 11 is shown by the positional relationship with these. In this example, a case where approximately two sensor pixels are correspondingly arranged in one pixel image area is shown. (A) shows the case where the center of the sensor pixel region is at the peak position of the luminous intensity distribution. (B) shows a case where the center of the effective area L of the sensor pixel is at a position at a distance x _A (hereinafter referred to as a peak position distance x _A ) from the peak position of the luminous intensity distribution. The luminous intensity detected by the sensor pixel is the luminous intensity integrated over the effective area L of the sensor pixel, and is the amount shown by the shaded area in the drawing. The luminous intensity distribution of the display pixel generally has a peak value at the central portion of the display pixel and has a characteristic that it gradually decreases as it approaches the end portion. Therefore, the pixel image also has a characteristic having a similar tendency as shown in this example, and the detected light intensity of the sensor pixel becomes lower as the peak position distance x _A has a larger positional relationship.

Since the photolithography technique with high dimensional accuracy is used in the manufacturing process of the liquid crystal display, even if the display element to be inspected, that is, the specimen is changed, the positional relationship between the sensor camera and the specimen is always kept constant. Focusing on a specific display pixel at an arbitrary address n of the display element, there can be a sensor pixel whose peak position distance x _An can always be regarded as practically constant. This holds for all display pixels of the sample, but the peak position distance x _An differs depending on each display pixel. That is, it depends on the address position of the display pixel. Based on this, if the detected light intensity B _An and the peak position distance x _An at position state in advance all the display pixels that display pixel specific peak positions for the distance x _An 0, that is, the center of the effective region L of the sensor pixel Is detected at the peak position of the luminous intensity distribution, the detected luminous intensity B _On (hereinafter referred to as peak position detected luminous intensity B _On ) is calculated, and the ratio B _An / B
_On is obtained as the corresponding position correction coefficient K _n . As a matter of course, the corresponding position correction coefficient K _n has a different value for each display pixel.

The origin of the name of the corresponding position correction coefficient is to correct the difference in detected light intensity due to the difference in corresponding position between the pixel image and the sensor pixel, and the center of the effective area L of the sensor pixel is the peak position of the light intensity distribution as the light intensity evaluation reference. It is based on the fact that it is a correction coefficient for determining the position and converting it into the luminous intensity at this luminous intensity evaluation reference position and evaluating with the same criterion. In the above description, the peak position detection luminous intensity B _On is used as the reference luminous intensity that is a reference for correction, but generally it is not necessary to limit to the detected luminous intensity at the peak position, and an arbitrary peak position distance x can be set for all display pixels. _An
The luminous intensity in the case of being fixed equally to is sufficient as long as it is luminous intensity B _Sn (hereinafter referred to as reference luminous intensity B _Sn ) which can be detected by all display pixels under the same condition and serve as a reference. In extreme cases,
Local distortion and blurring due to the optical system of the sensor camera,
If the difference between the detected light intensity due to the difference in location due like to the difference in viewing angle as negligible, any display pixel reference intensity also equally suitable reference intensity B _Sn of the display pixels from the considered equal to You can even apply a constant. Further, in order to evaluate the luminous intensity of the display pixels, it is not necessary to evaluate the physical absolute value, but the relative luminous intensity between the display pixels may be evaluated. Thus the corresponding location correction factor K _n of the display pixel at the address n may multiplying an arbitrary constant k, as represented by the formula. K _n = k · B _An / B _Sn ───────

Based on the principle of the present invention described above, the inspection operation is executed as follows. First, a reference display element (hereinafter referred to as a reference display element) is used, the positional relationship between the reference display element and the sensor pixel is fixed as a reference position, and the sensor pixel (the sensor pixel for directly reading the luminous intensity of each display pixel ( Hereinafter referred to as corresponding sensor pixel). For this purpose, the sensor pixel located in the pixel image area and having the highest detected light intensity is assigned to the corresponding sensor pixel to specify the sensor pixel. next,
The corresponding position correction coefficient K _n is calculated and stored in the correction coefficient storage memory. The above is the initial setting stage. In the inspection operation stage, the sample is aligned with the reference position, the luminous intensity is detected by the corresponding sensor pixel, and the detected luminous intensity is multiplied by the corresponding position correction coefficient K _n of the display pixel to be converted into the luminous intensity at the luminous intensity evaluation reference position. The quality of the converted light will be judged.

The present invention will be described in detail below with reference to examples. FIG. 2 is a basic configuration block diagram according to the present invention.
A display device 1 is placed on a moving stage 3, and a sensor camera 2 for sensing a display screen is arranged at a certain distance from the display device 1. An output signal of the sensor camera 2 is guided to a processing circuit unit 4 and processed. To be done. Further, the display element 1 has a mark for alignment, and a position control camera (not shown in the figure) for reading the mark and performing alignment control is arranged. Here, one sensor camera 2 is taken as an example, but the same applies when a plurality of sensor cameras 2 are installed. In the case of installing a plurality of units, the display screen of the display element is divided, and one sensor camera is assigned to each divided area for inspection. Under the above-mentioned configuration, first, an inspected display element is placed on the moving stage 3 as a reference display element so that a predetermined display screen area effectively forms an image in the effective light receiving area of the CCD sensor of the sensor camera. With the movement of the sensor camera 2 and the sensor camera 2 (in the z-axis direction), the moving stage is moved in the x-direction and the y-direction orthogonal to the z-axis, and further in the rotation direction with the z-axis as the rotation axis. In this state, the alignment mark of the display element is read and stored by the position control camera as the reference position, and the reference position for aligning the sample at the inspection stage is determined.

FIG. 3 shows an embodiment of the processing circuit unit 4 shown in FIG. 2. The processing circuit unit 4 receives an analog signal from the sensor camera 2 as an input, converts it into a digital signal, and then performs an initial operation such as setting operation of a corresponding position correction coefficient. Starting with the setting operation, the inspection operation is processed in the inspection stage. In the figure, 100 is a memory bus, A
D conversion circuit 101, CCD image memory 102, correspondence relationship information storage memory 103, correction coefficient storage memory 10
4, LCD image memory 105, processing memory 10
6. The processing circuit 107 is connected. The operation of extracting the corresponding position correction coefficient will be described with reference to FIG. For this operation, it is necessary that the correspondence information indicating the correspondence between the display pixel and the sensor pixel is stored in advance in the correspondence information storage memory 103. As a method of detecting the luminous intensity information of each display pixel of the display element based on the information on the correspondence between the display pixel and the sensor pixel, the invention of the patent application relating to the applicant's application dated February 4, 1991 (display There is a screen reading method) (hereinafter referred to as the inventor's invention), and exactly using this method according to the inventor's invention, correspondence information is extracted and display pixels corresponding to sensor pixels are determined based on the correspondence information. Therefore, the details of these operations are described in detail in the specification of the present invention, and therefore, only the outline thereof will be described here. Correspondence information is also extracted by using a display element that has been inspected in advance as a reference display element, a display pixel is turned on in a state of being set at the reference position, and is read by the sensor camera 2, and CC
The image is stored in the D image memory 102. After that, the corresponding relationship information is extracted by detecting the peak of the detected light intensity based on the contents of the CCD image memory 102 to identify the corresponding sensor pixel corresponding to each display pixel, and stored in the corresponding relationship information storage memory. It should be noted here that the specified sensor pixel detects the peak value in the sense that the luminous intensity of the corresponding display pixel is detected most strongly as compared with the neighboring sensor pixels. This means that the peak of is not detected. In this operation of extracting the correspondence information, all the display pixels of the reference display element may be collectively turned on as long as there is resolution. Alternatively, the correspondence information may be extracted while lighting the display pixels one by one. Correspondence information may be extracted by repeating a display pattern of lighting every few pixels in one or both of the row and column directions. Generally speaking, the correspondence information obtained by these operations is the correspondence of the address m of the sensor pixel corresponding to the address n of the display pixel.
In this embodiment, the address n of the display pixel is made to correspond one-to-one to the address n of the correspondence information storage memory, and the address information m of the sensor pixel corresponding to the address n of the display pixel at the address n of this memory. Take the method of storing. In this method, the fact that the address n of the display pixel and the address m of the sensor pixel correspond via the address n of the memory, that is, the correspondence information is stored. The setting operation of the correspondence relationship information in the correspondence relationship information storage memory 103 does not need to execute the correspondence relationship information extraction operation described here each time, and the once extracted information is saved in a file storage or the like. It may be loaded in the correspondence information storage memory in accordance with the above. Transfer of information in the operation of extracting the correspondence information,
Processing such as peak detection is performed by the processing circuit 107. The processing circuit 107 may be configured by a general-purpose processor or dedicated hardware. The processing memory 106 is a memory for storing a program to be executed by the processing circuit 107 and for use as a work.

After the correspondence relation information extracted by the above correspondence relation information extraction operation is set in the correspondence relation information storage memory 103, the display pixel of the reference display element set at the reference position is turned on, and the sensor camera 2 operates. Read and store in CCD image memory 102. Note that the address of the CCD image memory 102 is configured to correspond to the address of the sensor pixel of the sensor camera 1 in a one-to-one manner, and the light intensity information sensed by all the sensor pixels is stored in the CCD image memory 1.
It has been transferred to 02. Next, the address information m of the corresponding sensor pixel corresponding to the display pixel of the address n is retrieved from the address n of the correspondence relationship information storage memory 103, and the address m of the CCD image memory 102 is accessed based on this address information m, The light intensity B _An detected by the sensor pixel at the address m is read out and stored in the address n of the correction coefficient storage memory 104. This operation is executed for all the addresses of the correspondence information storage memory corresponding to all the display pixels. The addresses of the correction coefficient storage memory 104 and the LCD image memory 105 are configured to correspond one-to-one with the addresses of display pixels. Next, a method of _obtaining the reference luminous intensity B _Sn will be described by taking as an example the case where the state in which the center of the sensor pixel is at the peak position of the luminous intensity distribution is used as a reference common to each display pixel. The display screen is read while moving the moving stage in the x and y directions at a pitch that is practically sufficiently small with respect to the luminous intensity distribution area of the display pixel, that is, while shifting the relative position between the display element and the sensor camera.
The maximum value of the luminous intensity of the display pixel at the address n detected by the sensor pixel is obtained. The maximum value is obtained as follows. First, the detected light intensity of the sensor pixel at the address m corresponding to the display pixel at the address n detected at the reference position is displayed on the LCD image memory
Each time the moving stage is moved, the detected luminosity of the sensor pixel of the address m corresponding to the display pixel of the address n is compared with the contents of the address n of the LCD image memory 105, and is newly stored. When the detected sensor pixel has a high light intensity, the new light intensity is used as the LCD image memory 105.
However, if it is small, the peak value of the luminous intensity distribution is obtained by the method of retaining the previous information. As a result of this operation, the reference luminous intensity B _Sn is stored in the address n of the LCD image memory 105. Next, the light intensity B _An and the LCD stored in the address n of the correction coefficient storage memory 104
Reference luminous intensity B stored in address n of the image memory 105
_A corresponding position correction coefficient is obtained by performing a read-type operation on _Sn, and is stored in the address n of the correction coefficient storage memory 104. As a matter of course, the above operation is executed for all the display pixels. Further, also in the operation of extracting the corresponding position correction coefficient, the memory operation, information processing, etc. are carried out by the processing circuit 107. In the above embodiments, the method of finding the reference luminous intensity B _Sn by moving the moving stage by a small amount to find the peak value has been described. However, other methods, for example, by shifting the focus of the sensor camera and blurring the pixel image are applicable. The luminous intensity sensed by the sensor pixel may be used as the reference luminous intensity B _Sn . In this blurred state of the pixel image, the light intensity distribution characteristic is flattened, and the positions of any corresponding sensor pixels can be regarded practically as equal positions on the light intensity distribution.

In the above, the extraction of the inspection parameter such as the determination of the reference position, the extraction of the correspondence information, the extraction of the corresponding position correction coefficient, etc., which is the initial setting operation before the inspection of the display element has been described. Next, the inspection operation using these parameters will be described. Also in the case of the inspection operation, the display element as the sample is first adjusted to the reference position. In that state, the inspection pattern is displayed on the display device, the display screen is read by the sensor camera 2, converted into a digital signal by the AD conversion circuit 101, and then stored in the CCD image memory 102. Next, the correspondence information from the correspondence information storage memory 103,
That is, the address information m of the sensor pixel corresponding to the address n of the display pixel is taken out, and the luminous intensity information B _An corresponding to the display pixels from the address m to the address n of the CCD image memory 102 based on this correspondence information, that is, the address information m. And the correction coefficient K _n relating to the display pixel at the address n from the address n of the correction relation storage memory 104, and these luminous intensities B _An and K are read.
The product of _n is calculated and stored in the address n of the LCD image memory 105. As a matter of course, the above operation is executed for all the display pixels, and as a result, the LCD image memory 1
This means that the luminous intensity information of all the display pixels is stored in 05. Based on this luminous intensity information, the quality of each display pixel is judged,
The quality of the display element is determined by analyzing the defect mode such as an isolated defect or a line defect and the number of defects. In the above inspection operation as well, memory processing, information processing, etc. are carried out by the processing circuit 107. As is clear from the above description, the reference display element in the extraction operation of the correspondence information and the extraction operation of the corresponding position correction coefficient and the display element serving as the sample in the inspection operation are set to the standard position equally. Of course, setting to the standard position in each operation does not mean setting to the reference position in a strict sense, but is related to the inspection accuracy of the luminous intensity of the display pixel to be finally evaluated, and is within an allowable range. It is the setting to the standard position including the error in.

Although the present invention has been described by taking the case where the display element is a liquid crystal display as an example, it can be widely applied to a display manufactured by using a manufacturing technique with high dimensional accuracy, for example, a display element such as a plasma display. Further, although the sensor has been described as an example using a two-dimensional CCD sensor, it can be widely applied even when a general two-dimensional sensor is widely used. Further, even when using a one-dimensional sensor camera and inspecting one line at a time while shifting the positions of the sample and the camera, the same configuration can be obtained by setting the reference position in the inspection of each line, and the same effect can be obtained. Be done.

[0016]

According to the present invention, the positional relationship between the display element and the sensor camera is set to the reference position, and the corresponding position correction coefficient extracted at the reference position is added to the light intensity information sensed by the sensor pixel. The display element inspection method that generates the luminous intensity information of the display pixel by multiplying it can reduce the number of sensor pixels arranged corresponding to the display element, can be inspected with a smaller number of sensor cameras, and the conventional arrangement of sensor cameras It was impossible to realize it because it required a large number of cameras before
There is an effect that a static type inspection for a high-quality display element having a high pixel density can be realized with a practical number of sensor cameras. The present invention according to claim 2 is configured as in claim 2 and configured to use an inspected display element in extracting the corresponding position correction coefficient. The invention according to claim 2 is the same type as the display element to be inspected. Since the element is used, the corresponding position correction coefficient can be extracted in accordance with the actual condition of the inspection, and there is no need for a special reference display element, so that there is an effect of being excellent in economical efficiency.

[Brief description of drawings]

FIG. 1a is an explanatory diagram of the basic principle of the present invention, and is an explanatory diagram in the case where the center of the sensor pixel region is at the peak position of the luminous intensity distribution.

FIG. 1b is an explanatory diagram of the basic principle of the present invention, and is an explanatory diagram when the center of the effective area L of the sensor pixel is at the position of the peak position distance x _A ;

FIG. 2 is a basic configuration block diagram according to the present invention.

3 is a configuration diagram of an embodiment of a processing circuit unit 4 shown in FIG.

[Explanation of symbols]

 1 display element 2 sensor camera 3 moving stage 4 processing circuit section 10 pixel image area 11 sensor pixel area 20 luminous intensity distribution of pixel image 100 memory bus 101 AD conversion circuit 102 CCD image memory 103 correspondence information storage memory 104 correction coefficient storage memory 105 LCD image memory 106 processing memory 107 processing circuit

Claims (2)

[Claims] 1. An inspection method for determining the quality of a display screen of a display device as an inspection screen, wherein the positional relationship between the display device and the sensor camera is set to a reference position, and the reference is set to the light intensity information sensed by the sensor pixel. Display element inspection method characterized by generating luminosity information of display pixels by multiplying corresponding position correction coefficients extracted at positions 2. The display element inspection method according to claim 1, wherein an inspected display element is used in the extraction of the corresponding position correction coefficient.