CN100401042C - Detection method and system for liquid crystal display panel - Google Patents

Abstract

The present invention discloses a liquid crystal display panel detection method and system, which uses optical imaging to capture the grayscale change curves of a plurality of image frames of the liquid crystal display panel, and the flicker of the image frame can be determined by the amplitude and center value of the grayscale change curve. The present invention can adjust the potential of the driving circuit of the liquid crystal display panel according to the obtained flicker value to eliminate the flicker phenomenon that can be perceived by the human eye.

Description

Method and system for detecting liquid crystal display panel

technical field

The invention relates to a detection method and system of a liquid crystal display panel, in particular to a detection method and a system thereof for detecting the flicker degree of a liquid crystal display panel by applying machine vision.

Background technique

Flicker phenomenon is an important factor affecting display quality in liquid crystal displays, and it is directly related to the sensitivity of human eyes. Thin-film transistor (TFT) and super-twist (STN) liquid crystal displays are currently the most widely used displays, but both have flickering phenomenon. Generally speaking, the display driving signal needs to apply an AC electric field within a certain period of time to drive it to perform polarity inversion. However, in a general twisted liquid crystal cell, flickering is more likely to occur due to ion charge effects, so although increasing the frequency of the applied electric field can reduce the degree of flickering, the higher the frequency of the applied electric field, the greater the power consumption. However, due to the parasitic capacitance of the thin film transistor, the degree displacement of the signal voltage is caused, so the magnitude of the signal in the positive and negative half cycles is different, so the flicker phenomenon is more serious.

Currently, LCD panel suppliers propose four polarity inversion driving methods, but flickering still occurs when certain test patterns are presented. For example, the dot inversion driving method displays sub-pixels ( The test pattern designed by sub-pixel1) will have flickering points, and the driving method of line inversion (line inversion) is prone to flickering defects when presenting the test pattern of horizontal lines. Certain types of test patterns expose the problem of flickering, and of course visually sensitive users can easily detect the same problem when watching.

Before the liquid crystal display panel is shipped, it is necessary for the quality control personnel to check the display quality of each panel, and try to adjust the display effect of each panel to be consistent. Among them, the degree of flicker is an important defect inspection. However, due to differences in vision, each person has a different ability to detect flickering phenomena, which will cause serious deviations in the implementation of quality inspections. It often happens that LCD panels are shipped to customers after passing quality inspections, but they are detected by visually sensitive people. The customer checks out the defective product and is returned, thus causing the loss of the company's reputation and money.

To sum up, a standardized and automated method is urgently needed in the market to solve the above problems.

Contents of the invention

The main purpose of the present invention is to provide a liquid crystal display panel detection method and its system, which can provide the best detection method to detect the flickering degree of the liquid crystal display panel screen, and can completely replace the manual detection operation method based on the naked eye.

The second object of the present invention is to provide a method for adjusting the driving circuit of the liquid crystal display panel, which can correctly adjust the flickering degree of each panel picture to the minimum, and has good consistency.

In order to achieve the above object, the present invention provides a detection method of a liquid crystal display panel and a system thereof, which is to capture the gray-scale change curves of several image frames of the liquid crystal display panel through optical imaging, and the gray-scale change The amplitude and central value of the curve can determine the flicker of the image frame. The user or an automatic adjustment device can adjust the driving voltage of the liquid crystal display panel according to the obtained scintillation value, so as to reduce the amplitude of the gray scale change curve and increase the scintillation value at the same time. Such repeated detection and feedback adjustment minimizes the degree of flicker, that is, makes the value of the flicker degree the maximum value, and finally eliminates the flicker phenomenon that can be detected by human eyes.

According to one aspect of the present invention, a detection method of a liquid crystal display panel is provided, comprising the following steps: providing a liquid crystal display panel; driving the liquid crystal display panel to display a test pattern picture; setting the way of sampling and measuring the picture; Recording the picture of the liquid crystal display panel by means of optical imaging; analyzing the grayscale change of the sampled picture; and judging whether the flicker of the sampled pixel exceeds a predetermined value by the ratio of the amplitude of the grayscale change to the central value threshold value.

According to another aspect of the present invention, a detection system for a liquid crystal display panel is provided, comprising: a liquid crystal display panel for displaying a test pattern picture, and the liquid crystal display panel also has a knob for adjusting the driving voltage; an optical An imaging device, used to capture the picture of the test pattern; and a controller, used to calculate the grayscale change of the picture captured by the optical imaging device to generate a degree of flicker, and determine whether the degree of flicker is exceeds a predetermined threshold.

Description of drawings

The invention will be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a detection system for a liquid crystal display panel of the present invention.

Fig. 2 is a curve diagram of gray scale changes of pixels measured by the detection device of the present invention;

FIG. 3 is a flow chart of the detection method of the liquid crystal display panel of the present invention.

Fig. 4 is the picture sampling method of measuring the grayscale degree of the liquid crystal display panel of the present invention, and

5( a ) to ( d ) are schematic diagrams of preferred embodiments of the detection and fixing device of the liquid crystal display panel of the present invention.

Explanation of symbols in the figure:

10 Detection system of liquid crystal display panel

11, 11a, 11b, 11' optical imaging device

12 controllers

14 test pattern generator

51, 51' fixed frame

52, 52'panel workbench

53 rotary mechanism

57 hand tools

60, 60' liquid crystal display panel

64, 64' knob

70 operators

80 automatic rotation mechanism

Detailed ways

Fig. 1 is the schematic diagram of liquid crystal display panel detection system of the present invention, and it is to arrange an optical imaging device 11 on the top of liquid crystal display panel 60, generally use CCD or CMOS camera more, and this kind of camera specification can be divided into matrix type or Single line type, can also be divided into two signal output modes of analog or digital. Utilize the test pattern generator 14 to produce specific test patterns, so that the liquid crystal display panel 60 displays the test pattern picture (frame), this test pattern generator 14 can be connected with the controller 12 or not online, and the optical image pickup on the top is fixed simultaneously. The device 11 will continuously capture the images of the liquid crystal display panel 60 over time, and send them to the controller 12 (such as a combination of a general computer and an image capture card) to calculate the changes in the gray scale and record them in the form of curves. .

The detection system 10 described above measures the sampled images, and draws the observed changes in the gray scale as a graph, as shown in FIG. 2 . The abscissa in the figure is the time axis, and the ordinate is the brightness gray scale of the digitized image obtained by the optical imaging device 11 . Apparently, the gray scale of the sampled picture is not a constant value, and the gray scale changes up and down on a curve that approximates a sinusoidal function or a triangular waveform. Each point on the curve represents the gray scale of one of the sampling pictures, where La and Lb can be regarded as the generalized average amplitude and the average upper and lower amplitude values of the curve, respectively, and Lc generally has two definitions, one is the average gray scale Value, at this time unless it is completely the same waveform up and down, otherwise La≠Lb/2; another kind of Lc is the average value of the peak a' and valley b' values, at this time La=Lb/2. The formula (1), formula (2), formula (3), formula (4), formula (5) or formula (6) of the similar flicker degree can be obtained from the brightness change curve> as follows:

FL＝K/Lb+M ... Formula (1)

FL＝K/La+M ... Formula (2)

FL＝KlogLc/La+M ... Formula (3)

FL＝KlogLc/Lb+M ... Formula (4)

FL＝KlogLc/(Lb/2)+M...Formula (5)

FL＝KlogLc/(Lb-La)+M ... Formula (5)

Among them, K and M are coefficients, and the default values are 20 and 0 respectively. These K and M values are used as simulation compensation after correction. The larger the amplitude La or Lb, the more severe the flickering condition, and therefore the smaller the FL value. Conversely, when the amplitude La or Lb is smaller, it means that the flickering condition is better, and the FL value will be larger. Of course, apart from these six formulas, any relational expression that can express the scintillation as the ratio of Lc to La or Lb is the spirit of the present invention, and is not limited to the relational expression expressed by logarithm or natural logarithm.

The present invention can use the scintillation value as a basis for adjusting the driving circuit of the liquid crystal display panel 60 , instead of observing and completing the adjustment with the human eyes with large main differences.

FIG. 3 is a flow chart of the detection method of the liquid crystal display panel of the present invention. According to step 30, a test pattern is set by the test pattern generator. Step 31 , the test pattern is displayed by the liquid crystal display panel. Generally, the test pattern is designed according to the driving mode of the liquid crystal display panel, and its purpose is to present the picture that most easily exposes its detection defects. In step 32, when the liquid crystal display panel presents the test pattern, the imaging device will perform optical imaging of the display image over time, and usually continuously sample the number of samples exceeding a complete cycle of the curve when the liquid crystal display panel follows the test pattern command Each pixel displays a color scale, and the imaging device will perform optical imaging of the display surface over time. In step 33, the grayscale variation of the sampled image in the image is measured from the image data captured in step 32. In step 34, three values such as Lc, La, and Lb can be obtained from the grayscale change curve of the sampled pixel, and these two values are substituted into formula (1), formula (2), formula (3), formula (4) , formula (5) or formula (6), just can determine the numerical value of its scintillation degree, the selection of above-mentioned formula can be decided by the user, has finished the measurement of the scintillation phenomenon of liquid crystal display panel so far, next is the action of adjusting.

According to the numerical value of the scintillation degree and judge whether it is the maximum value, as shown in step 35, if it is not the maximum value, it means that the best state of the liquid crystal display panel has not been reached, so it is necessary to adjust the relevant driving circuit, as shown in step 36. Generally, liquid crystal display panels provide a knob for adjusting the common voltage. When the common voltage is adjusted to the most appropriate value, the angle change of the liquid crystal rotation will be minimized when the polarity of the pixel is switched, so the change range of the gray scale will also be reduced. up to a minimum. After adjustment, return to step 32 in a cyclic manner to perform optical imaging. On the contrary, if the determination in step 35 is yes, the process will proceed to step 37 to determine whether the degree of flicker reaches the preset threshold value. If the threshold value is met, it means that the liquid crystal display panel has been adjusted to be a qualified product, otherwise, it means that the liquid crystal display panel is still a defective product even after being adjusted.

FIG. 4 is a picture sampling method for measuring the gray scale of the liquid crystal display panel of the present invention. The entire screen 61 of the liquid crystal display panel can be divided into several regions vertically or horizontally, and the minimum number of regions is 1, which is used as different ranges for measuring flicker. Taking FIG. 4 as an example, the screen 61 is divided into four vertical measurement areas 611 - 614 , and then the image is captured by the optical imaging device 11 and sent to the controller 12 . According to the set measurement area, there are two ways to complete the curve: the first is to measure the gray scale of all pixels in the area and calculate the average value to make a gray scale change curve. The second is to extract pixels on several or one scanning line 62 as measurement targets. The values of La, Lb and Lc can be obtained in different measurement areas 611-614 respectively, and the scintillation value of each measurement area can be determined by formulas (1)-6. Due to the circuit arrangement of the liquid crystal display panel, the flickering degrees of the measurement areas 611 - 614 on the screen 61 are not consistent. To determine the quality and level of flickering of the panel 60, a threshold value of flickering degree is generally set, which determines the tolerance of flickering of the panel, of course, several flickering degrees can be set to determine the quality of the level. When the number of regions is greater than 1, there will be individual flicker values for each region. At this time, the average scintillation value of each region, the lowest regional scintillation value or other methods can be used for judgment.

Because the position of the knob 64 for adjusting the common voltage of the liquid crystal display panel 60 of each manufacturer is different, some are on the same side as the panel picture as shown in Figure 5(a); and some are on different sides from the panel picture, as shown in Figure 5(b) Liquid crystal display panel 60'. In order to make the detection system of the liquid crystal display panel applicable to the two types of liquid crystal display panels 60 and 60', it is necessary to adopt two sets of optical imaging devices 11a and 11b, which are erected on the fixed frame 51 in a manner of one up and one down, And be respectively positioned at the both sides of panel workbench 52. There is an opening in the central part of the panel workbench 52, which can be placed with the display surface of the liquid crystal display panel 60' facing downwards, and the image can be captured by the optical imaging device 11b below. Of course, the operator 70 can still hold the manual tool 57 and turn the knob 64' from above to adjust the flickering phenomenon of the screen to the slightest. Considering the ergonomic detection and fixing device in this way will improve the work efficiency of the operator 70.

Another detection and fixing device only uses a group of optical imaging devices 11', supplemented by a fixed frame 51' that can rotate 180°, as shown in Figure 5(c) and 5(d). The fixing frame 51' is used to fix the optical imaging device 11', and is combined with the panel workbench 52' clamping the liquid crystal display panel 60 or 60'. Another rotary mechanism 53 controls the fixed frame 51 ' to perform 180 ° of rotation, and this rotary mechanism 53 can use a general rotary cylinder, or an assembly of an actuator and a shaft transmission element.

When the knob 64 for adjusting the common voltage is on the same side as the display surface, the display surface of the liquid crystal display panel 60 can be placed on the drawing board workbench 52' upward, as shown in Figure 5(c). At this time, the operator 70 can hold the manual tool 57 and rotate the knob 64 from above, or use an automatic rotation mechanism 80 to perform adjustments to minimize the flickering phenomenon of the screen. That is, when the numerical value of the flicker reaches the maximum value, the action of turning the knob 64 is stopped. However, as shown in FIG. '' display and place it downward on the panel workbench 52', at this time, the fixed frame 51' can be rotated 180° by the rotary mechanism 53, so the optical imaging device 11' will turn to the bottom of the liquid crystal display panel 60', and The operator 70 or the automatic rotation mechanism 80 can then turn the knob 64' in the same position. Of course, the automatic rotation mechanism 80 can be commanded by the system feedback signal to turn the knob 64' to an optimal position.

The technical content and technical features of the present invention have been disclosed above, but those skilled in the art may still make various substitutions and modifications based on the teaching and disclosure of the present invention without departing from the spirit of the present invention. therefore. The protection scope of the present invention should not be limited to what is disclosed in the embodiments, but should include various replacements and modifications that do not depart from the present invention, and are covered by the claims of the present application.

Claims (26)

1. A detection method for a liquid crystal display panel, comprising the following steps: providing a liquid crystal display panel; driving the liquid crystal display panel to display a test pattern image; Set the sampling and measurement method of this screen; Recording the picture of the liquid crystal display panel by means of optical imaging; Analyzing the gray scale change of the sampled picture; and Whether the flicker of the sampled pixel exceeds a predetermined threshold is judged by the ratio of the amplitude of the gray scale change to the central value. 2 . The inspection method of a liquid crystal display panel according to claim 1 , wherein the optical imaging method is to use a CCD camera, a CMOS camera, a single line camera or a matrix camera. 3. The detection method of a liquid crystal display panel according to claim 1, wherein the test pattern is generated by a test pattern generator, and then drives the liquid crystal display panel to present the test pattern through a display driver interface picture. 4. The detection method of a liquid crystal display panel according to claim 1, wherein the flicker degree FL is determined by the formula FL=K/Lb+M, and Lb represents the upper and lower average amplitudes of the gray scale change, K and M are coefficients. 5. The detection method of liquid crystal display panel according to claim 1, it is characterized in that said scintillation FL is determined by formula FL=K/La+M, La represents the average amplitude of described gray scale change, K with M as the coefficient. 6. The detection method of a liquid crystal display panel according to claim 1, wherein the flicker degree FL is determined by the formula FL=KlogLc/La+M, and Lc represents the central value or peak of the gray scale change and the average value of the trough, La represents the average amplitude of the gray scale change, and K and M are coefficients. 7. The detection method of a liquid crystal display panel according to claim 1, wherein the flicker degree FL is determined by the formula FL=KlogLc/Lb+M, and Lc represents the central value or peak of the gray scale change and the average value of the trough, Lb represents the upper and lower average amplitude of the gray scale change, and K and M are coefficients. 8. The detection method of a liquid crystal display panel according to claim 1, wherein the flicker degree FL is determined by the formula FL=KlogLc/(Lb/2)+M, and Lc represents the change of the gray scale. The central value or the average value of peaks and valleys, Lb represents the upper and lower average amplitudes of the gray scale change, and K and M are coefficients. 9. The detection method of a liquid crystal display panel according to claim 1, wherein the flicker degree FL is determined by the formula FL=KlogLc/(Lb-La)+M, and Lc represents the change of the gray scale. The central value or the average value of peaks and troughs, La represents the average amplitude of the gray scale change, Lb represents the upper and lower average amplitude of the gray scale change, and K and M are coefficients. 10 . The detection method of a liquid crystal display panel according to claim 1 , further comprising a step of adjusting a driving voltage of the liquid crystal display panel so that the flickering degree is higher than the threshold value. 11 . 11. The detection method of liquid crystal display panel according to claim 1, is characterized in that it further comprises the following steps: judging whether the degree of flicker reaches a maximum value; and If the maximum value is not reached, the driving voltage of the liquid crystal display panel is adjusted. 12 . The detection method of a liquid crystal display panel according to claim 1 , further comprising a step of judging whether the maximum value of the scintillation degree exceeds the threshold value. 13 . 13. The inspection method of a liquid crystal display panel according to claim 1, characterized in that the method of sampling and measuring the test pattern screen is to divide the screen into several measurement areas. 14 . The inspection method of a liquid crystal display panel according to claim 1 , wherein the method of sampling and measuring the test pattern is to select at least one scanning line. 15. A detection system for a liquid crystal display panel, comprising: A liquid crystal display panel, which is used to display a test pattern picture, and the liquid crystal display panel also has a knob for adjusting the driving voltage; An optical imaging device, used to capture the test pattern picture; and A controller, used to calculate the grayscale change of the image captured by the optical imaging device to generate a flicker level FL, and determine whether the flicker level FL exceeds a predetermined threshold value, wherein the flicker level FL is the relationship expression of the amplitude itself of the gray scale change or the ratio of the amplitude to the central value. 16. The liquid crystal display panel inspection system according to claim 15, wherein the optical imaging device is a CCD camera, a CMOS camera, a single line camera or a matrix camera. 17. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=K/Lb+M, and Lb represents the upper and lower average amplitudes of the grayscale change, K and M are coefficients. 18. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=K/La+M, La represents the average amplitude of the gray scale change, and K and M is the coefficient. 19. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=KlogLc/La+M, and Lc represents the central value of the gray scale change, or The average value of peaks and troughs, La represents the average amplitude of the gray scale change, and K and M are coefficients. 20. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=KlogLc/Lb+M, and Lc represents the central value or peak of the gray scale change and the average value of the trough, Lb represents the upper and lower average amplitude of the gray scale change, and K and M are coefficients. 21. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=KlogLc/(Lb/2)+M, and Lc represents the change of the gray scale The central value or the average value of peaks and valleys, Lb represents the upper and lower average amplitudes of the gray scale change, and K and M are coefficients. 22. The detection system of a liquid crystal display panel according to claim 15, wherein the flicker degree FL is determined by the formula FL=KlogLc/(Lb-La)+M, and Lc represents the change of the gray scale The central value or the average value of peaks and troughs, La represents the average amplitude of the gray scale change, Lb represents the upper and lower average amplitude of the gray scale change, and K and M are coefficients. 23. The inspection system of a liquid crystal display panel according to claim 15, further comprising a test pattern generator for generating the test pattern. 24. The liquid crystal display panel inspection system according to claim 15, further comprising a fixed frame capable of rotating 180 degrees for adjusting the position of the optical imaging device. 25. The liquid crystal display panel detection system according to claim 15, characterized in that it further comprises an optical imaging device, and the two optical imaging devices are arranged on both sides of the detection position of the liquid crystal display panel . 26. The liquid crystal display panel inspection system according to claim 15, further comprising an automatic rotation mechanism for adjusting the knob.

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