JPH04133088A - Display element inspection system - Google Patents

Abstract

PURPOSE:To evaluate the influence of background picture elements more accurately by fixing the state setting conditions of the background picture elements in the ON state and OFF state of an object picture element and inspecting the display element according to the difference between brightness information on the screen when the object picture element illuminates and that when the element goes out. CONSTITUTION:Solid-line rectangles show LCD picture element images which are correctly formed on a photodetection surface through the lens of a CCD camera. Enlarged images corresponding to images A and B which are enlarged and correctly formed are conceptionally, for example, 1 and 2. At this time, when the object picture element A to be tested is inspected while the adjacent picture element B turns on, the state setting conditions of background picture elements in the ON and OFF states of the picture element A are fixed and the difference in brightness information between CCD picture elements read out of the enlarged picture elements images in the respective cases is calculated to cancel light from the background picture elements. Consequently, the influence of the background picture elements can correctly be evaluated and the influence of a defective picture element is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inspection method for display elements such as liquid crystal displays and plasma displays. More specifically, it relates to a method of reading a screen displayed by a display element and inspecting its quality.

[Conventional technology]

The method for reading the screen displayed on the display element is C.
A method using a two-dimensional sensor such as a CD is well known. In this method, sensor pixels arranged in rows and columns of a two-dimensional sensor are read in correspondence with display pixels (hereinafter simply referred to as pixels) arranged in rows and columns of a display element. For example, C.C.
In an example using a D camera, an image of a display element is focused on the light-receiving surface of a CCD element, and this correspondence is attached. The basic idea of reading with this two-dimensional sensor is that for any pixel located at any position on the display element, there is at least one sensor pixel of the two-dimensional sensor that correctly corresponds to that pixel. Correct response here means that there are two
This refers to a correspondence in which the sensor pixels of the dimensional sensor overlap so that there is no problem in practical use.

In order to apply a two-dimensional sensor that does not have a sufficient number of pixels to correctly correspond to the pixels of the display element to inspect the display element, the screen of the display element is divided into several areas, and two-dimensional sensors are used for each area. Generally, reading is achieved by arranging a dimensional sensor, limiting the number of display element pixels relative to the number of sensor pixels, and equivalently enlarging the display element pixel image. . One method for realizing this is to arrange a plurality of two-dimensional sensors, and another method is to sequentially read a restricted area while moving the two-dimensional sensors. All of these have the disadvantage of being complicated and expensive. As a method to solve these drawbacks, Japanese Patent Application No. 118782 filed by the present applicant places the light receiving surface of the sensor at a position where the display screen to be inspected is correctly imaged, that is, at a position away from the image forming surface. A method has been proposed in which the image is equivalently enlarged by defocusing the displayed pixel image on the light receiving surface of the sensor. In this method, the image area of the pixel to be inspected is expanded until it overlaps the pixel image area of adjacent pixels, and even neighboring pixels, and the neighboring pixels influence each other, so the pixels to be inspected at the same time are At the same time, pixels other than the selected pixels to be inspected (hereinafter referred to as background pixels) are inspected in a dark state.

[Problem to be solved by the invention]

Equivalently placing the background pixels in a dark state imposes restrictions on the lighting conditions for the background pixels.

This has the disadvantage that the inspection conditions are restricted, such as the inability to evaluate the influence of the lighting state of background pixels, especially neighboring pixels near the pixel to be inspected. Also,
If there is a defective pixel that is always on, pixels in the vicinity of this defective pixel cannot be evaluated correctly.

The present invention solves the above drawbacks and provides a method for alleviating the dark state conditions of all pixel groups other than the pixel to be inspected (hereinafter, this pixel group is referred to as background pixels), thereby further reducing the influence of background pixels. It is an object of the present invention to provide a display element inspection method that allows accurate evaluation and eliminates the influence of defective pixels that are always in a lit state.

[Means to solve the problem]

In order to solve the problem of the influence of light from background pixels, which is a problem with conventional methods, we calculate the influence of light from background pixels by calculating the difference between the luminance information when the pixel to be inspected is turned on and the luminance information when it is turned off. It is designed to exclude. In other words, in a display element inspection method in which the pixel image of the display element is enlarged and inspected to such an extent that the pixel image area of the display element overlaps the pixel image area of a neighboring pixel on the sensor light-receiving surface, the background is The present invention constitutes an invention of a display element inspection method in which the pixel state setting conditions are fixed and the display element inspection method is inspected using the difference between the luminance information of the display screen with the pixel to be inspected in the lit state and the luminance information of the display screen with the pixel to be inspected in the unlit state. It is something.

[For production]

Since the present invention is configured as described above, the influence of light from background pixels can be eliminated. Therefore, the background pixel can be turned on or off as desired, and the lighting state and the off state of the background pixel can be set arbitrarily, so that an inspection can be performed that takes into account the influence of the state of the background pixel. Furthermore, the influence of defective background pixels that are always lit can be eliminated, and pixels in the vicinity of this defective background pixel can also be correctly inspected.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

In this example, the display element is a liquid crystal display (LCD).
As an example, a CCD camera using a CCD two-dimensional sensor is applied to the sensor system. FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, FIG. 2a is a conceptual diagram of a pixel image of a display element formed on the light-receiving surface of a CCD two-dimensional sensor, and FIG. FIG. 3 is a conceptual diagram of illuminance distribution on the -j line.

In Figure 2 and 3, the rectangle indicated by the solid line is the L when the image is correctly formed on the CCD light receiving surface through the lens of the CCD camera.
A CD pixel image is shown. Since the brightness of the LCD pixel cannot be detected correctly in this LCD pixel image due to the relationship with the dimensions of the COD pixel, the LCD pixel image is enlarged. This enlarging method is disclosed in the above-mentioned Japanese Patent Application No. 118782/1999, and although detailed explanation will be omitted here, the CCD is placed at the out-of-focus position.
1.2 conceptually shows the enlarged images corresponding to images A and B when the images are correctly formed.

Hereinafter, A and B will be referred to as LCD pixel names, and 1 and 2 will be referred to as enlarged images of pixel A and pixel B, respectively. FIG. 2 conceptually represents the illuminance distribution on the l-j line in FIG. 2a. 10 is when only the LCD pixel is lit, 20 is L
The brightness distribution when only CD pixel B is turned on is shown. 30
shows the luminance distribution when both pixels A and B are turned on. Of course, 30 is the sum of 10 and 20. 3 is CCD
It shows the positional relationship of the pixel array, and when compared with the correctly formed LCD pixel image shown in FIG. 2a, it shows that the brightness of the LCD pixel cannot be correctly inspected.

Now, when the LCD pixel to be inspected is A, if a pixel in the vicinity of this pixel is turned on, it will affect the enlarged image of the pixel, making it impossible to perform the inspection correctly.

For example, if pixel B adjacent to pixel A lights up at the same time, CC
The illuminance on the D light-receiving surface is 30, where the light from pixels A and B overlaps, making it impossible to test the correct value. In this example, where only B among the adjacent pixels is lit, the flat area is relatively wide as seen at 30, so there is also an evaluation method that detects the peak value of 30 and takes 1/2 of it as the brightness value of pixel A. . However, this evaluation method cannot be applied when efficiency is sought by increasing the number of pixels to be simultaneously inspected by limiting the degree of expansion as much as possible;
Even if only one light is on, inspection will not be possible. Furthermore, if nearby pixels including adjacent pixels turn on at the same time, inspection cannot be performed.

Therefore, in the present invention, the state setting conditions of the background pixel are fixed depending on whether the LCD pixel to be inspected is turned on or off.
CCD read based on the enlarged pixel image in each case
The normality of LCD pixels is tested by taking the difference in luminance information of the pixels. In other words, by taking the difference, the light from the background pixel whose pixel state setting conditions are fixed is canceled, and only the luminance change between the lit state and the unlit state of the pixel to be inspected can be extracted, and the light from the background pixel is It is possible to inspect the LCD by eliminating the influence of The above will be explained in more detail using FIG. If it is desired to check the normality of the pixel to be tested while the adjacent pixel B is in the lit state, first the adjacent pixel B is displayed in the lit state, the pixel to be tested A is in the unlit state, and the other background pixels are displayed in the unlit state. In this case, only pixel B is lit, and the illuminance on the CCD light receiving surface exhibits a distribution of 20. This illuminance distribution value, ie, the output value of the CCD sensor, is stored in a storage device. Next, the test target pixel A is changed to a lit state and displayed while keeping the state of the background pixel unchanged. In this case, the adjacent pixel B remains lit, and the other background pixels remain unlit. Therefore, the illuminance on the CCD light receiving surface exhibits a distribution of 30. These illuminance information is C
By subtracting the stored information when the test target pixel A tested earlier is turned off from this read information read by the CD pixel, information when only the 10 test target pixels are turned on is generated. An example of a circuit configuration for realizing the above operation will be described in detail with reference to FIG.

100 is a two-dimensional CCD sensor of a CCD camera. The analog output signal of the CCD, which is output according to the illuminance of the light receiving surface, is input to the analog-digital conversion circuit 101.
The digitized output signal is sent to the select gate circuit 10.
2. is input in 102□. Select gate circuit 10
The signal that selects 21 and 102□ and outputs a small signal is the output signal of the flip-flop circuit 105, and when reading the illuminance in the first display state in which the pixel under test is displayed in the off state, this flip-flop circuit is 1'' state, and the select gate circuit 102. is selected and the digitized read signal is guided to the storage device 103, written in different word positions corresponding to CCD pixel information, and the information is held. On the other hand, when reading the illuminance in the second display state in which the pixel under test is displayed in a lit state, this flip-flop circuit is set to the "0" state, the select gate circuit 102□ is set to the selected state, and the digitized read signal is output. is led to the subtraction circuit 104. At the same time, the storage device 10
The CCD pixel information when the pixel to be tested that was previously written and held from No. 3 is turned off is read from the storage device 103 and guided to the subtraction circuit 104 . The result of subtracting the illuminance information when the pixel under test is turned off from the illuminance information when the pixel under test is turned on is the output terminal T of the subtraction circuit 104.
is output to. This output signal is information when only the pixel to be inspected is turned on, and based on this signal, the illuminance of the inspection pixel image on the light receiving surface of the CCD sensor can be detected by processing such as peak detection, and it is proportional to this illuminance. The brightness of related test pixels can be evaluated correctly.

The above explanation uses an example in which a specific background pixel is turned on, but the setting conditions may be such that any background pixel or multiple pixels are turned on (or all background pixels are turned off). Further, although an example has been described in which the pixel to be inspected is turned off in the first display state and the pixel to be inspected is turned on in the second display state, the reverse case may be used.

As is clear from the above description, it is necessary to keep the state setting conditions of the background pixel the same when the pixel to be inspected is turned on and when it is turned off.

However, even if the setting conditions are made the same, the brightness conditions of the background pixels are not necessarily the same, and may change to the extent that they affect the value of the test result. This is due to the effect on the background pixels caused by the pixel being inspected changing from a lit state to an off state, or from an off state to a lit state, and should originally be detected as an abnormality, so check the value of the test result. This allows us to detect this abnormality. Furthermore, even if there is an abnormal background pixel that is always on regardless of the state setting conditions, the difference in luminance between when the pixel to be inspected is on and when it is off can be correctly evaluated. In short, it is important to keep the state setting conditions of the background pixels the same, and the actual brightness states of the background pixels do not necessarily have to be the same.

The present invention has been explained above using an example in which a CCD two-dimensional sensor is used to read an inspection screen.
Even when using a dimensional CCD sensor, it can be widely applied regardless of whether it is a one-dimensional or two-dimensional sensor as long as it has linearity with respect to illuminance.

As described above, as a method of enlarging a pixel image, C
Although the present invention has been described using as an example a method of placing a CD sensor light-receiving surface and blurring the image, it is also widely applicable to other inspection methods in which a pixel image is generally enlarged to the image area of other neighboring pixels. .

Furthermore, even if the image is not enlarged again, it can be similarly applied in cases where the image becomes blurred and enlarged due to aberrations of the lens or the like.

〔Effect of the invention〕

The present invention is configured as claimed in claim 1, and the state setting conditions of the background pixel are fixed in the lighting state and the unlit state of the pixel to be inspected, and the brightness information of the display screen with the pixel to be inspected in the lit state and the unlit state of the pixel to be inspected are set. The display element inspection method, which inspects based on the difference in brightness information of the display screen, can eliminate the influence of light from background pixels, regardless of whether the background pixels are lit or turned off, and can eliminate the influence of light from background pixels near the pixels to be inspected. Since a pixel can be arbitrarily set to a lit state or a non-lit state, it is possible to carry out an inspection that takes into consideration the states of neighboring pixels.

Furthermore, there is an effect that the pixel to be inspected can be correctly inspected while avoiding the influence of abnormal background pixels that are always on.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of an embodiment of the present invention, Fig. 2a is a CC
FIG. 2 is a conceptual diagram of a pixel image of a display element formed on a light-receiving surface of a two-dimensional sensor, and a conceptual diagram of an illuminance distribution on the ij line shown in FIG. 2a. 1... Enlarged image of LCD pixel image A, 2... Enlarged image of LCD pixel image B, 3... COD pixel for indicating position,
10... Illuminance distribution when only the LCD pixel is lit, 20... Illuminance distribution when only the LCD pixel is lit, 30... Illuminance distribution when both the LCD pixel and pixel B are lit, 100 ... Two-dimensional CCD sensor of CCD camera, 101 ... Analog-digital conversion circuit, 1
021...Select gate circuit, 102□...Select gate circuit, 103...Storage device, 104...
Subtraction circuit, 105... Frisopflovb circuit, A, B
...LCD pixel image when correctly formed.

Claims (1)

[Claims] (1) In a display element inspection method in which the pixel image of the display element is enlarged to the extent that it overlaps the pixel image area of a neighboring pixel on the sensor light-receiving surface, the pixel image is enlarged to the extent that the pixel image area of the display element overlaps the pixel image area of a neighboring pixel. A display element test characterized by fixing the state setting conditions of a background pixel and performing an inspection based on the difference between the luminance information of the display screen with the pixel to be inspected in a lit state and the luminance information of the display screen with the pixel to be inspected in an unlit state. method