CN107966840B - Method for detecting defective pixel points of liquid crystal panel - Google Patents
Method for detecting defective pixel points of liquid crystal panel Download PDFInfo
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- CN107966840B CN107966840B CN201711386956.XA CN201711386956A CN107966840B CN 107966840 B CN107966840 B CN 107966840B CN 201711386956 A CN201711386956 A CN 201711386956A CN 107966840 B CN107966840 B CN 107966840B
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/1306—Details
- G02F1/1309—Repairing; Testing
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Abstract
The invention discloses a method for detecting defective pixel points of a liquid crystal panel, which comprises the following steps: s101: setting test line scanning time according to the actual line scanning time of the liquid crystal panel; s103: performing line scanning on the liquid crystal panel by using the test line scanning time, and applying a bias voltage to a common electrode of the liquid crystal panel; s105: taking a line scanning starting signal of the liquid crystal panel as a detection starting point, and circularly inputting test voltage signals of first to fifth stages on a data line of the liquid crystal panel in sequence within preset time; s107: and presenting the bad pixel points to an observer in a flashing mode. The invention can simultaneously detect various types of bad pixel points in the liquid crystal panel under one frame of picture, and simultaneously reduce the number of pictures and improve the detection efficiency.
Description
Technical Field
The invention relates to the technical field of display, in particular to a method for detecting defective pixel points of a liquid crystal panel.
Background
With the development of technology and the requirement of narrow frame, more and more liquid crystal panels adopt the goa (gate array) or gip (gate in panel) technology to realize the row driving function, and no additional row driving chip is needed.
For such a liquid crystal panel, the conventional driving method (timing sequence, frame frequency, etc.) is adopted in the current detection method, each line of the liquid crystal panel is scanned, a plurality of pictures such as black, white, gray, etc. are displayed on the liquid crystal panel, and whether various bad pixels such as dots, lines, unevenness, etc. exist is determined. As shown in fig. 1, if a short circuit occurs between the pixel electrode 2 of the tft liquid crystal cell and the pixel electrode 1, the pixel electrode 3, and the pixel electrode 1, the tft cell is abnormal in operation, and will appear as a bright spot on the screen.
However, a defective pixel is found in field detection, a small leakage current exists on a pixel electrode of a liquid crystal due to a process and the like, and at the moment, a thin film transistor normally operates, and no bright point is observed when a black picture or a half-screen black and half-screen white picture is used for testing, so that the missing detection of the defective pixel is caused.
Disclosure of Invention
In order to solve at least one of the above problems, the present invention provides a method for detecting a defective pixel of a liquid crystal panel, including:
s101: setting test line scanning time according to the actual line scanning time of the liquid crystal panel;
s103: performing line scanning on the liquid crystal panel by using the test line scanning time, and applying a bias voltage to a common electrode of the liquid crystal panel;
s105: taking a line scanning starting signal of the liquid crystal panel as a detection starting point, and circularly inputting test voltage signals of first to fifth stages on a data line of the liquid crystal panel in sequence within preset time;
s107: and presenting the bad pixel points to an observer in a flashing mode.
Further, in S101, the test line scanning time is [2.5, 6] times the actual line scanning time of the liquid crystal panel.
Further, in S103, the bias range of the bias voltage is plus or minus [0.5, 2.5] V.
Further, in S105, the preset time range is greater than or equal to 1 second.
Further, in S105, the durations of the first, second, and fifth phases are the same as the test line scan time.
Further, in the S105, the duration of the third phase is the same as the actual line scanning time.
Further, in S105, the duration of the fourth stage is a time difference between the test line scanning time and the actual line scanning time.
Further, in S105, the input voltages of the first and second stages and the third and fifth stages are voltages having opposite phases with respect to the common electrode.
Further, in S105, the input voltage range of the fourth stage is 0 to plus-minus 40% of the input voltage of the third stage.
Further, the input voltages of the first and third stages have the lowest gray scale of positive polarity with respect to the common electrode, and the input voltages of the second and fifth stages have the lowest gray scale of negative polarity with respect to the common electrode.
The invention has the following beneficial effects:
the method for detecting the defective pixel points of the liquid crystal panel can simultaneously detect the defective pixel points existing in the background technology under one frame of picture, solves the problem that the defects can not be detected by using the conventional black picture and half-screen white and half-screen black picture, reduces the number of pictures and improves the detection efficiency.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 shows a schematic diagram of a liquid crystal pixel cell in one embodiment of the invention;
FIG. 2 is a flow chart illustrating a method for detecting defective pixels according to an embodiment of the present invention;
FIG. 3 is a timing diagram illustrating the timing of detecting defective pixels according to an embodiment of the present invention.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
As shown in fig. 2, an embodiment of the present invention provides a method for detecting a defective pixel of an lcd panel, including:
s101: setting test line scanning time according to the actual line scanning time of the liquid crystal panel;
s103: performing line scanning on the liquid crystal panel by using the test line scanning time, and applying a bias voltage to a common electrode of the liquid crystal panel;
s105: taking a line scanning starting signal of the liquid crystal panel as a detection starting point, and circularly inputting test voltage signals of first to fifth stages on a data line of the liquid crystal panel in sequence within preset time;
s107: and presenting the bad pixel points to an observer in a flashing mode.
In this embodiment, in order to clearly detect a defective pixel, a test is performed by driving the liquid crystal panel for a time much longer than the actual line scanning time, for example, 2.5, 6 times the actual line scanning time, and applying a bias voltage to the common electrode of the liquid crystal panel, and simultaneously sequentially applying the detection voltages of the first to fifth stages to the data lines of the liquid crystal panel for screening the liquid crystal panel having the defective pixel.
In a specific example, a full high-definition liquid crystal panel with 1920 × 1080 resolution is taken as an example, the line resolution of the liquid crystal panel is 1920, the power-on time of each liquid crystal pixel is kept unchanged, and the line resolution of the liquid crystal panel is assumed to be 1920 × 3, that is, the example is tested with 3 times of the actual scanning time.
And changing the voltage of the common electrode of the liquid crystal panel, and applying a bias voltage to the common electrode. If the common electrode COM takes a normal voltage (for example, 0v), since the currently displayed image is a black picture (gray scale 0), although the gray scale of the corresponding pixel point is improved in the leakage current, in the actual product, the resistance between the pixel electrodes is small due to the fact that impurities are mixed in the pixels of some liquid crystal panels, the leakage current is large, the voltage change of the pixel electrode 2 is large, and the gray scale change is obvious; however, the leakage current of some liquid crystal panels is very small, the gray scale change caused by the defective pixel point is small (for example, from gray scale 0 to gray scale 10), and the human eye can hardly recognize the difference in the background of the whole black frame.
For the situation, the common electrode COM voltage is deviated from the original normal voltage, so that the contrast display of the weak bright spots can be enhanced, and the missing detection is reduced. Assuming that the pixel electrode 2 is charged to a positive voltage, the voltage of the common electrode COM is shifted from the normal 0V to a positive or negative voltage, specifically ranging from 0.5V to 2.5V, and the voltage difference between the pixel electrode 2 and the common electrode COM is reduced, which corresponds to a slightly bright gray-scale image (e.g. L50) instead of gray-scale 0. If the defective pixel point also leads to 10 gray scales higher than the gray scale of the surrounding normal pixel point, the brightness difference can be obviously distinguished by visual inspection of a detector under a bright background, so that the defective pixel point is identified.
As shown in fig. 3, the timing diagram of the test voltages in the first to fifth stages is a timing diagram, in which the row scanning start signal STV is used as a timing signal, one of the row scanning signals is used as a detection start point, the durations of the first stage T1, the second stage T2 and the fifth stage T5 are the same as the test scanning time, and the duration of the third stage T3 is the same as the actual scanning time, so the duration of the fourth stage T4 is the time difference between the test scanning time and the actual scanning time.
The stage T1 may be specifically divided into an actual scanning stage and an observation stage, where the 1920 rows are scanned in the actual scanning stage of T1, as shown in fig. 1, from the starting time to the completion of the 1920 rows, all the Gate lines Gate of the liquid crystal panel are alternately gated, that is, the thin film transistors are turned on, the pixel electrode 1 and the pixel electrode 2 of each pixel in each row are turned on, the voltage of the pixel electrode 2 is the input voltage V1 of the data line, and at this time, the positive polarity minimum gray scale is obtained with respect to the common voltage COM, and the screen displays a full black picture. After the actual line scanning is finished, the virtual line 1920 × 2 is scanned until the first stage T1, that is, the observation stage, where the Gate line Gate is at a negative voltage and the pixel electrodes 1 and 2 hold the V1. The present embodiment applies a bias voltage of 1V to the common electrode COM of the liquid crystal panel to enhance the contrast of the display.
If a defective pixel exists on the liquid crystal panel, leakage currents exist between the pixel electrode 2 and the pixel electrodes 1 and 3 of the pixel, and between the pixel electrode 2 and the common electrode, and the specific analysis is as follows:
the voltage of the pixel electrode 1 is V1, the voltage of the pixel electrode 2 is V1, the voltage of the pixel electrode 3 is negative, and the common electrode COM is a bias voltage 1V.
● when there is a small amount of leakage current between the pixel electrode 2 and the pixel electrode 3, the voltage of the pixel electrode 2 decreases with time, the gray scale of the corresponding pixel increases, and a weak bright spot appears on the screen.
● if a weak leakage current exists between the pixel electrode 2 and the common electrode COM due to a process or a foreign substance, the charge on the pixel electrode 2 is reduced and the voltage is lowered, the gray scale of the pixel is increased, and a weak bright spot is displayed on the screen.
● the pixel electrode 1 is the voltage on the data line, the voltage V1 is kept, the voltage of the pixel electrode 2 is less than or equal to the voltage of the pixel electrode 1, and the leakage current from the pixel electrode 2 to the pixel electrode 1 will not be generated.
The stage T2 can be divided into an actual scanning stage and an observation stage, in the actual scanning stage, the voltage of the pixel electrode 2 is V3, and is in opposite phase with respect to the common electrode COM and the voltage V1, and at this time, the screen is completely black corresponding to the lowest gray scale of the negative polarity of the pixel liquid crystal. In the observation period, the Gate line Gate is at a negative voltage, the pixel electrode 1 and the pixel electrode 2 are held at V3, and the common electrode COM is at a bias voltage of 1V.
● if the leakage current between the pixel electrode 2 and the common electrode COM is weak, the charge on the pixel electrode 2 will decrease, the voltage will decrease, the gray level of the pixel will increase, and the pixel will appear as a weak bright spot on the screen.
In the period T3, during the line scanning, the voltage of the pixel electrode 2 is V1, and the screen displays full black.
In stage T4, when the other signals are unchanged, the voltage of the pixel electrode 2 is V1, the voltage of the pixel electrode 3 is negative, the voltage of the pixel electrode 1 is V2, the voltage range of V2 is 0 to plus-minus 40% of V1, and the common electrode COM is bias voltage 1V.
● if a small amount of leakage current exists between the pixel electrode 2 and the pixel electrode 3, the voltage of the pixel electrode 2 will be reduced, and the corresponding gray scale of the pixel will be increased, and will appear as a weak bright spot on the screen.
● if there is a weak leakage current between the pixel electrode 2 and the common electrode COM, the charge on the pixel electrode 2 will be reduced, the voltage will be reduced, the gray level of the pixel will be increased, and a weak bright point will appear on the screen.
● if there is a weak leakage current between the pixel electrode 2 and the pixel electrode 1, the charge on the pixel electrode 2 will decrease, the voltage will decrease, the gray scale of the pixel will increase, and a weak bright spot will appear on the screen.
The stage T5 can be divided into an actual scan stage and an observation stage, and the data line is loaded with a voltage V3. The detailed analysis is the same as stage T2.
It should be noted that, if there is a defective pixel with leakage current in the 1600 th row on the liquid crystal panel, after the T3 stage and the T4 stage, the voltage of the normal pixel still maintains V1 (black frame), and the voltage of the pixel electrode 2 of the defective pixel is reduced to a value between V1 and V2 (displayed as a dim bright point). At the beginning stage of T5, when the row of the defective pixel is not scanned yet (i.e. during the period from row 1 to row 1599), the voltage of the Data line Data is negative voltage V3, and the voltage of the pixel electrode 2 of the defective pixel is higher than the voltage of the Data line Data, so that leakage current is generated again between the pixel electrode 2 of the defective pixel and the Data line Data, the positive charge of the pixel electrode 2 is reduced again, and the brightness of the pixel is increased again, i.e. the "secondary enhancement" of the defective pixel is generated.
Therefore, the test voltages of the first stage to the fifth stage are circularly input to the liquid crystal panel within a preset time (for example, more than or equal to 1 second), the steps are repeated on the liquid crystal panel, if a defective pixel point exists on the liquid crystal panel, the defective pixel point is presented to a detector in a flashing mode, the detector can conveniently select the liquid crystal panel with the defective pixel point, and therefore the detection efficiency is improved.
In this embodiment, the voltages V1 and V3 are the lowest gray scale of positive polarity and the lowest gray scale of negative polarity with respect to the common electrode, so that a defective pixel appears as a weak bright point. It should be understood by those skilled in the art that V1 and V3 may also be set to medium-high gray scale voltages, and the bad pixels are represented as weak dark dots, and the detailed analysis process is not repeated.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (8)
1. A method for detecting a defective pixel of a liquid crystal panel is characterized by comprising the following steps:
s101: setting test line scanning time according to the actual line scanning time of the liquid crystal panel;
s103: performing line scanning on the liquid crystal panel by using the test line scanning time, and applying a bias voltage to a common electrode of the liquid crystal panel;
s105: taking a line scanning starting signal of the liquid crystal panel as a detection starting point, and circularly inputting test voltage signals of first to fifth stages on a data line of the liquid crystal panel in sequence within a preset time, wherein input voltages of the first stage and the second stage and input voltages of the third stage and the fifth stage are opposite in phase relative to the common electrode, and the input voltage range of the fourth stage is 0-plus-minus 40% of the input voltage of the third stage;
s107: and presenting the bad pixel points to an observer in a flashing mode.
2. The detecting method according to claim 1, wherein in the S101, the test line scanning time is [2.5, 6] times the actual line scanning time of the liquid crystal panel.
3. The detection method according to claim 1, wherein in S103, the bias range of the bias voltage is plus or minus [0.5, 2.5] V.
4. The detecting method according to claim 1, wherein in the S105, the preset time range is 1 second or more.
5. The detection method according to claim 1, wherein in the S105, the durations of the first, second, and fifth stages are the same as the test line scan time.
6. The detection method according to claim 1, wherein in the S105, a duration of the third stage is the same as the actual line scan time.
7. The detecting method according to claim 1, wherein in the S105, the duration of the fourth stage is a time difference between the test line scanning time and the actual line scanning time.
8. The method as claimed in claim 1, wherein the input voltages of the first and third stages have a negative polarity minimum gray scale with respect to the common electrode, and the input voltages of the second and fifth stages have a positive polarity minimum gray scale with respect to the common electrode.
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| US5608558A (en) * | 1994-04-26 | 1997-03-04 | Sharp Kabushiki Kaisha | Defect detection method and apparatus for active matrix substrate or active matrix liquid crystal panel and defect repairing method thereof |
| CN1794338A (en) * | 2005-12-27 | 2006-06-28 | 友达光电股份有限公司 | Regulation method of panel flash |
| CN101819337A (en) * | 2009-02-27 | 2010-09-01 | 北京京东方光电科技有限公司 | Detection circuit and detection method of liquid crystal display device |
| CN103454792A (en) * | 2013-08-27 | 2013-12-18 | 北京京东方光电科技有限公司 | Method for detecting bright spot of liquid crystal display panel |
| CN103513477A (en) * | 2012-06-26 | 2014-01-15 | 富泰华工业（深圳）有限公司 | Liquid crystal display and detection method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5608558A (en) * | 1994-04-26 | 1997-03-04 | Sharp Kabushiki Kaisha | Defect detection method and apparatus for active matrix substrate or active matrix liquid crystal panel and defect repairing method thereof |
| CN1794338A (en) * | 2005-12-27 | 2006-06-28 | 友达光电股份有限公司 | Regulation method of panel flash |
| CN101819337A (en) * | 2009-02-27 | 2010-09-01 | 北京京东方光电科技有限公司 | Detection circuit and detection method of liquid crystal display device |
| CN103513477A (en) * | 2012-06-26 | 2014-01-15 | 富泰华工业（深圳）有限公司 | Liquid crystal display and detection method thereof |
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