JPH0798574A - Liquid crystal inspection instrument - Google Patents

Abstract

PURPOSE:To save the manpower of the inspecting process of a liquid crystal display device by preventing the variance of adjustment and the unevenness of measurement by a woker from occurring. CONSTITUTION:By giving a pattern generated from a display pattern generation part 6 to a liquid crystal driving part 12 and giving a driving voltage to the driving part 12 by a voltage adjustment device 5, the pattern is displayed on a liquid crystal display panel 11. Besides, the pattern is read by a CCD camera 30 through an optical system 31 and the luminance of the panel 11 and the existence of flicker and a defective picture element are measured by an image processor 4. By a computer 7, the pattern generated from the generation part 6 is instructed according to a detection and adjustment item and the adjustment device 5 is instructed to fluctuate the voltage at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal inspection device,
In particular, the present invention relates to a liquid crystal inspection device for measuring a liquid crystal drive voltage for normally displaying a liquid crystal display panel and measuring a display abnormality of the liquid crystal display panel.

[0002]

2. Description of the Related Art Liquid crystal display devices are also called industrial paper,
It is used in portable TVs and portable computers, and the demand for it continues to grow year by year, but on the other hand, it suffers from low productivity and slow price reduction. One of the causes is that a large number of personnel are required for the inspection process which currently has to rely on visual inspection. A liquid crystal display device is composed of two parts, a liquid crystal display panel and a liquid crystal drive unit. Adjustment of the drive voltage of the liquid crystal drive unit is one of the liquid crystal inspection steps necessary for the liquid crystal display panel to display normally. Is one. In addition, liquid crystal display devices that have an abnormal display that transmits light when it should not be transmitted or does not transmit when it must be transmitted must be removed as a defect, and measurement of the abnormal display is also important. This is one of the major liquid crystal inspection processes.

First, two examples in which the liquid crystal display panel has different display characteristics from the basic structure of the liquid crystal display panel will be described below, and the reason why the liquid crystal drive section needs to be adjusted will be described.

FIG. 5 is a diagram showing an electrical configuration of one pixel in the TFT type liquid crystal display panel 20. Each pixel of the TFT type liquid crystal display panel includes a liquid crystal 21 that contributes to actual display, a liquid crystal electrode 22 that sandwiches the liquid crystal 21, and a TFT 23.
It is composed of a switching element called. TFT2
In 3, the resistance between the source electrode and the drain electrode becomes small while the switching signal is applied to the gate electrode,
It becomes substantially conductive. As a result, the display signal applied to the source electrode is applied to the liquid crystal electrode joined to the drain electrode. When the switching voltage is no longer applied to the gate electrode, the resistance between the source electrode and the drain electrode increases, and the gate electrode becomes substantially insulative. As a result, the display signal applied to the liquid crystal electrode joined to the drain electrode is held until the next switching signal is applied. The TFT 23 has a characteristic that when the voltage of the switching signal applied to the gate electrode is low, it does not normally change to the conductive state, and when it is high, it does not normally change to the insulating state. Since there are variations in this characteristic among the respective elements of the TFT 23, it is necessary to measure and set the voltage of the switching signal applied to the normally operating gate electrode for each liquid crystal display panel.

FIG. 6 is a diagram showing a general relationship between the display signal voltage applied between the liquid crystal electrodes and the resulting change in light transmittance characteristics. In the state of 0 V in which no voltage is applied between the liquid crystal electrodes, light is almost completely transmitted, and the transmittance decreases every time a voltage is applied, and the transmittance does not decrease above a certain value. A liquid crystal display device uses this characteristic to perform display, but in order to prevent deterioration of the liquid crystal material, a method called inversion drive is used in which the voltage polarity of the display signal applied to the liquid crystal is inverted in each field. To be

When performing inversion driving, the state of change in transmittance is symmetrical not about 0 V but about an offset voltage. Therefore, the applied voltage is accurately determined with this offset voltage as the center. Otherwise, flickering called flicker will appear every abnormal display screen or inversion. Unfortunately, since the light transmission characteristics of the liquid crystal display panel are slightly different in each liquid crystal display device, the offset voltage that normally operates must be measured and adjusted for each liquid crystal display device.

The cause of the abnormal display has various causes. For example, in the abnormal display on a pixel-by-pixel basis, it is conceivable that the TFT 23 malfunctions or foreign matter is mixed between liquid crystal electrodes. In the case of malfunction of the TFT 23, no voltage is applied between the liquid crystal electrodes because voltage is not applied, and light is transmitted though it should not be transmitted, or conversely, charge is accumulated and light is not transmitted. An abnormal display is displayed in which it is not transparent but it is not transparent. A liquid crystal display device having an anomaly display is sent to a repair process because it can be repaired into a product when the anomalous part can be repaired.

[0008]

Conventionally, in order to measure a switching voltage or an offset voltage of a normally operating liquid crystal display device, an operator visually adjusts a display state while manually adjusting a volume or the like. Further, in the same manner, the measurement of the abnormality display must be done by visual inspection by the operator. These inspection steps are one of the most labor-intensive steps in the production process of liquid crystal display devices, and reduce the productivity of liquid crystal display devices.

Therefore, a main object of the present invention is to provide a liquid crystal inspecting apparatus capable of preventing the variation of adjustments by the operator and the unevenness of measurement and simplifying the inspection process.

[0010]

The invention according to claim 1 is
A liquid crystal inspection device that displays a pattern on a liquid crystal display panel, images the pattern, processes the imaged output, and inspects the liquid crystal display panel for abnormalities. The liquid crystal drive voltage supplied to the liquid crystal display panel is changed. Meanwhile, it is configured to include a measuring unit that measures the presence or absence of an abnormal display and the abnormal position of the liquid crystal display panel by image processing.

In the invention according to claim 2, the measuring means according to claim 1 measures changes in the brightness and flicker of the liquid crystal display panel while changing the liquid crystal drive voltage.

According to a third aspect of the invention, the measuring means of the first aspect measures the liquid crystal drive voltage for normal display on the liquid crystal display panel based on the measurement result of the first or second aspect.

In the invention according to claim 4, the liquid crystal display panel is a TFT type liquid crystal display panel, and the measuring means is a TFT.
The liquid crystal display panel determines a gate voltage and an offset voltage for normal display.

[0014]

The liquid crystal inspecting apparatus according to the present invention picks up the pattern to be displayed when the liquid crystal driving voltage supplied to the liquid crystal display panel is changed, and processes the picked-up output to perform the image processing. Measure the presence or absence of abnormal display and abnormal position.

[0015]

1 is a diagram showing the configuration of an embodiment of the present invention. In FIG. 1, the liquid crystal display device to be measured is
The liquid crystal display panel 11 and the liquid crystal drive unit 12 are provided. The liquid crystal display panel 11 is irradiated with light from a light source (backlight) 2 from below, and an image of the liquid crystal display panel 11 is formed by an optical system 31.
The image is picked up by the CCD camera 30 via. The image pickup output of the CCD camera 30 is given to the image processing device 4. The image processing device 4 measures the display state based on the image pickup signal and outputs the result to the computer 7. On the other hand, the computer 7 outputs a command signal of a pattern to be displayed on the display pattern generator 6 in order to change the display pattern according to the measurement item. The computer 7 outputs the data to the voltage adjusting device 5 based on the data received from the image processing device 4 to change the voltage applied from the voltage adjusting device 5 to the liquid crystal drive unit 12 to show the change of brightness and flicker. The image processing device 4 is caused to measure again. This process is repeated to measure the voltage for normal operation.

Next, the detailed operation of each unit will be described. The image processing device 4 converts one frame of the image from the CCD camera 30 into a frame memory of 512 pixels × 512 pixels after converting it into 256 gradations of luminance. Although not shown, the frame memory is built in the image processing apparatus 4. Since one frame of image is captured, images in two fields are captured alternately for each scanning line. At this time, the optical system 31 is adjusted so that the number of scanning lines of the liquid crystal display panel 11 itself and the number of scanning lines of the image formed on the CCD camera 30 match. Next, the image processing device 4 determines in which part of the frame memory the image of the liquid crystal display panel 11 is captured, and determines the measurement range.

For example, in the case of measuring the luminance, if the luminance of the entire image is measured, the luminances of all measurement ranges are summed to obtain the measurement result, and if the luminance of a part (for example, the central portion) of the image is measured, It is also possible to specify the range of that portion and sum the luminances of only that portion to obtain the measurement result.

Further, in the case of measuring flicker, for example, when the liquid crystal display panel is reversely driven for each field, two field screens are alternately taken in for each number of scanning lines. Then, the difference is added as the measurement result. When the brightness of the two fields match, there is no flicker. Further, the abnormal display can also be measured by processing the data on the frame memory.

The voltage regulator 5 D / A-converts the command signal given from the computer 7 to reduce the switching voltage to 0.
Change the offset voltage to 1V by changing the range from V to 20V.
To 8V. In addition to this, the voltage may be changed by rotating a volume, a trimmer, or the like by the rotation driving force of a stepping motor or the like.

Similar to the image processing device 4, the display pattern generator 6 has a 512 × 512-bit frame memory built therein, and converts the contents of the frame memory into a video signal to generate a pattern. By rewriting the contents stored in the frame memory, it becomes possible to generate different patterns.

FIG. 2 is a flow chart for explaining the operation of one embodiment of the present invention. An actual measuring method by the computer 7 will be described with reference to FIG. The measurement is an offset voltage measurement as shown in FIG.
Switching voltage measurement and abnormal lighting are performed in this order. In preparation for measuring the offset voltage, the computer 7 sends a command signal to the voltage regulator 5 so as to set the switching voltage to an approximately known value as shown in FIG. 2 (b). The display pattern generation unit 6 is instructed by the computer 7 to generate a pattern for applying a voltage between the liquid crystal electrodes for every two scanning lines that are most prone to flicker. When the computer 7 gives a command to the voltage adjusting device 5 to set the offset voltage to the measurement start voltage, the computer 7 gives the image processing device 4 a command signal to measure the luminance difference between the fields. Every time a command is given to slightly change the offset voltage, the operation of receiving the measurement result of the brightness difference between fields is repeated until the measurement end voltage is reached, and the change in the brightness difference between fields when the offset voltage is changed is changed. The situation is measured by the computer 7.

FIG. 3 is a graph showing the relationship between the offset voltage and the inter-field luminance difference measured according to an embodiment of the present invention. In FIG. 3, when the offset voltage at the time when the inter-field luminance difference changes from positive to negative is 0 is determined as a normal value, the computer 7 sets the offset voltage to a normal value. Command signal to. This completes the measurement of the offset voltage.

Next, the switching voltage is measured. The display pattern generator 6 generates a pattern in which a voltage is applied to all display pixels. In the same manner as when measuring the offset voltage, the computer 7 causes the image processing device 4 to measure the screen brightness while changing the switching voltage by the voltage adjusting device 5.

FIG. 4 is a graph showing the relationship between the switching voltage and the luminance. In FIG. 4, the brightness is constant within a certain range, and the computer 7 determines this switching voltage range as a normal range. In this example, only the brightness of a part of the image is measured, but by measuring the brightness change of the entire image, it is possible to measure the variation in the characteristics of the TFTs in the liquid crystal display panel 11. The computer 7 gives a command signal to the voltage adjusting device 5 so as to set the switching voltage to a normal value, and ends the measurement of the switching voltage.

When the voltage adjusting device 5 is set again so that the voltage for normal display is obtained by using the above measurement results, the computer 7 is set in the display pattern generator 6 in order to measure the presence / absence of abnormal display. The command is given to generate a pattern in which the pixel of becomes transparent to light.
The image processing device 4 measures the presence / absence of a pixel having a low light transmittance, and if there is a pixel having a low light transmittance, the display panel 11 thereof is detected.
The position within is sent to the computer 7 as a result. In response, the CPU 7 outputs a command signal to the display pattern generation unit 6 so as to generate a pattern in which all pixels do not transmit light. The image processing device 4 determines the presence / absence of a pixel having a high light transmittance, and similarly, the result is determined by the computer 7
Send to. Based on these measurement results, the computer 7 determines whether or not the liquid crystal display panel 11 is abnormally lit. Finally,
These results are output on the screen of the computer 7 or an external storage device and the inspection is completed.

[0026]

As described above, according to the present invention, the presence or absence of abnormal display and the abnormal position of the display panel are measured by image processing while changing the liquid crystal drive voltage supplied to the liquid crystal display panel. Therefore, labor saving can be expected in the inspection process of the liquid crystal display panel, work unevenness caused by the physical condition and mood of the worker is eliminated, and stable quality products can be expected. Further, by using the image pickup means, the range of the inspection target of the liquid crystal display panel can be freely changed and the measurement can be performed in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of the embodiment of the present invention.

FIG. 3 is a graph showing a relationship between an offset voltage and an inter-field luminance difference according to an embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a switching voltage and brightness according to an embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional TFT type liquid crystal display unit.

FIG. 6 is a diagram showing a voltage between liquid crystal electrodes and a light transmission characteristic.

[Explanation of symbols]

 2 light source 3 TFT 4 image processing device 5 voltage adjustment device 6 display pattern generation unit 7 computer 11 liquid crystal display panel 12 liquid crystal drive unit 13 liquid crystal 14 liquid crystal electrode 30 CCD camera 31 optical system

Claims (4)

[Claims] 1. A liquid crystal inspecting apparatus for displaying a pattern on a liquid crystal display panel, imaging the pattern, and image-processing the imaged output to inspect the liquid crystal display panel for abnormality, which is supplied to the liquid crystal display panel. A liquid crystal drive voltage is changed, and image processing is performed to measure whether or not there is an abnormal display of the liquid crystal display panel and an abnormal position.
LCD inspection device. 2. The liquid crystal inspecting apparatus according to claim 1, wherein the measuring unit measures changes in the brightness and flicker of the liquid crystal display panel while changing the liquid crystal driving voltage. 3. The liquid crystal inspection device according to claim 1, wherein the measuring means measures a liquid crystal drive voltage for normal display on the liquid crystal display panel based on the measurement result. 4. The liquid crystal display panel is a TFT type liquid crystal display panel, and the measuring means determines a gate voltage and an offset voltage at which the TFT type liquid crystal display panel provides a normal display. The liquid crystal inspection device according to claim 3.