Display panel optical compensation method

Abstract

The invention discloses an optical compensation method for a display panel, which comprises the following steps of: shooting a gray scale test chart of the display panel at different exposure time, acquiring corresponding gray scale data, and establishing a quadratic polynomial fitting model of the exposure time and a gray scale value; and then, in combination with a Gamma correction principle, the Gamma value of the display panel is reversely deduced based on the fitting model, so that accurate mapping between the gray scale and the actual brightness is realized, the nonlinear influence of the display system is eliminated, the accuracy and reliability of a compensation algorithm are ensured, and the overall brightness reduction effect is further improved. And finally, combining the correction result, dividing the display panel into a plurality of grid areas, counting an average gray value of each grid, calculating a local compensation amount, generating a compensation lookup table (LUT), and applying the compensation lookup table to a real-time display compensation process. The display uniformity, the brightness consistency and the terminal visual effect of the panel can be improved, and good adaptability and practicability are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a display panel optical compensation method. BACKGROUND

[0002] With the wide application of display technologies such as liquid crystal display (LCD) and organic light emitting diode (OLED), panels are increasingly common in terminals such as televisions, mobile phones, vehicles and tablets. However, due to process differences, material unevenness or driving control defects, display panels often have optical defects such as uneven brightness, dark corners, color deviation and Mura, which seriously affect the display effect and user experience.

[0003] In the process of optical compensation of display panels, industrial cameras are usually used to collect panel light emission images to obtain the brightness and grayscale information of each region as the basis data for subsequent compensation. However, the existing compensation technology has the following problems: due to the influence of the camera's own response characteristics and exposure conditions, there is a systematic deviation between the collected data and the actual panel light emission brightness, and the non-linear error is obvious, which limits the compensation accuracy; at the same time, for local Mura defects of the panel, traditional compensation methods mostly use simple grayscale mapping or empirical adjustment, which is difficult to achieve effective and accurate correction; in addition, the problem of overall uneven brightness is also difficult to completely solve, which affects the final display effect and panel yield. Therefore, based on the above scheme, the actual accuracy of eliminating the optical defects of the display panel still needs to be improved, and the accuracy and linear restoration ability of the camera grayscale data need to be improved. SUMMARY

[0004] The present application aims to provide a display panel optical compensation method, which has good adaptability and expandability, and can flexibly adjust the grid size and compensation strategy according to different panel resolutions and application scenarios to meet various compensation needs.

[0005] The present application achieves the above-mentioned purposes through the following technical solutions:

[0006] The present application provides a display panel optical compensation method, comprising the following steps:

[0007] Step 1: display a grayscale test pattern on the display panel, and shoot different grayscale value images under different exposure times (T1, T2...T n ) by a high-precision camera, and extract the average grayscale value of the center region of each image to construct a complete exposure time-grayscale data set {(T 1， G1), (T 2， G2)...(T n , G n )};

[0008] Step 2: Collecting the gray scale value as the dependent variable and the exposure time as the independent variable, a quadratic polynomial function is fitted by using the least square method, the fitting coefficients are calculated, and a brightness modeling is established;

[0009] Step 3: Based on the fitting model, the Gamma value of the display panel is calculated by combining the Gamma correction principle, so as to realize the accurate mapping of the gray scale and the actual brightness;

[0010] Step 4: According to the compensation points required by the display panel, the gray scale test image corresponding to the compensation points is shot, the camera is used to shoot under the optimal exposure time, the image is ensured to be clear and not overexposed or underexposed, and the actual gray scale value of each compensation point is extracted;

[0011] Step 5: According to the gray scale value, the standard brightness and the Gamma value of the multiple compensation points, a polynomial function of the gray scale, the brightness and the Gamma value is fitted.

[0012] Step 6: The display panel is divided into multiple grid areas, the average gray scale value of each grid is counted, the local compensation amount of each grid is calculated, a compensation lookup table (LUT) is generated, and is applied to real-time display compensation, so as to realize the compensation of the overall and local brightness unevenness and Mura defects.

[0013] As a preferred embodiment of the present application, the fitting of the exposure time-gray scale value relationship in step 2, the calculation of the fitting coefficients and the establishment of the brightness modeling specifically include the following steps:

[0014] Step 21: The exposure time is taken as the independent variable, the collected gray scale value is taken as the dependent variable, a quadratic polynomial is fitted by using the least square method, and the relationship between the gray scale and the exposure time is obtained: G(t)=a2t 2 +a1t+a0,

[0015] Step 22: Since the display panel is not prone to Mura phenomenon when displaying high-brightness pictures, the average gray scale value of the central area of the maximum gray scale image is the maximum gray scale G max , and the calibration brightness value of the central area of the maximum gray scale image is defined as L max , a brightness model is established: L / t=L max / t n ,

[0016] As a preferred embodiment of the present application, the calculation of the Gamma value of the display panel by combining the Gamma correction principle based on the fitting model in step 3 specifically includes the following steps:

[0017] Step 31: The calibrated maximum brightness L max and the maximum gray scale G max in step 2 are brought into the Gamma correction formula; ,

[0018] Step 32: take natural logarithm of the formula, and solve the value of γ: .

[0019] As a preferred embodiment of the present application, in step 4, according to the compensation point requirements of different models of display panels (such as 100, 240, 512), the gray test chart corresponding to the compensation point (such as 25, 60, 128) is photographed, and the camera is used to take the photograph under the optimal exposure time, so as to ensure that the image is clear and has no overexposure or underexposure, and the actual gray value of each compensation point is extracted;

[0020] As a preferred embodiment of the present application, in step 5, the polynomial function of the gray, brightness and Gamma value of the compensation point is fitted, which specifically includes the following steps:

[0021] Step 51: the center gray value G of the compensation point gray test chart is brought into the Gamma value calculated in step 3, the calibration brightness of the corresponding compensation point is set as L, and the gray-Gamma value-brightness data set {(G i , γ i , L i )} of the compensation point is constructed,

[0022] Step 52: the least square method is used to fit the polynomial: L=(a+bG+cG 2 +dG 3 +eG 4 ) γ .

[0023] As a preferred embodiment of the present application, the real brightness value under the calibration gray is calculated according to L=(a+bG+cG 2 +dG 3 +eG 4 ) γ , and the difference compensation is made based on the real brightness.

[0024] As a preferred embodiment of the present application, in step 6, the display panel is divided into a plurality of grid regions, the average gray value of each grid is counted, and the local compensation amount of each grid is calculated, which specifically includes the following steps:

[0025] Step 61: in order to improve the efficiency of the compensation of the display panel, the panel is divided into 8X8 pixel grids;

[0026] Step 62: first, the average gray value G x，y of each grid is calculated, then the Gamma value of each grid is calculated by bringing it into step 3 and step 4, and then the real brightness L x，y of each grid is calculated by bringing it into step 5;

[0027] Step 63: according to the compensation formula ΔL x，y =L target -L(G x，y) Calculate the compensation value ΔL of each grid x，y :

[0028] Step 64: Generate a compensation lookup table (LUT) according to the compensation, and realize compensation for overall and local brightness unevenness and Mura defects.

[0029] The present application has the beneficial effects that: the present application establishes a response model between camera exposure time, gray scale and brightness by multi-exposure gray scale test data, combines panel Gamma value reverse correction, accurately compensates systematic brightness error caused by camera nonlinear response and structural difference. Further, by dividing the display panel into multiple grid areas, based on the local Demura compensation algorithm, dynamically correcting overall and local brightness unevenness and Mura defects, improving panel display uniformity, brightness consistency and terminal visual effect, having good adaptability and practicality. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The present application is a method flowchart.

[0031] Figure 2 The present application is a schematic diagram of using a camera for display panel optical compensation. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application clearer, the following will combine the drawings and examples to explain the implementation method of the present application in detail, so that the realization process of how to apply technical means to solve technical problems and achieve technical effects can be fully understood and implemented.

[0033] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific examples disclosed below.

[0034] The present application takes a liquid crystal display panel as an example to explain the specific operation steps of the display panel optical compensation method of the present application as shown in Figures 1-2 .

[0035] Step 1: Display a typical gray scale test image on the display panel to be compensated in sequence, and recommend gray scale values including 0, 32, 64, 128, 192, 255, covering the brightness response range of the panel. As shown in Figure 2 , use a high-precision camera to set multiple different exposure times (T1, T2…T n ), and take each gray scale image one by one. During the shooting process, ensure that the camera is fixed and the angle is perpendicular to avoid distortion interference. After each image is taken, extract the average gray scale value (G1, G2…G n), and form a dataset with corresponding exposure time, and build a complete exposure time-gray dataset {(T 1， G1),(T 2， G2)...(T n , G n )} as the basis for subsequent modeling.

[0036] Step 2: Based on the acquired data, the exposure time T and the central region gray value G corresponding relationship is sorted out, and a least square method is used to fit a quadratic polynomial to establish a camera gray response model G(t) = a2t 2 +a1t+a0. Then, the maximum gray scale image (such as 255 gray) is selected, the average gray value G max of the central region is extracted, and the actual brightness L max， of the region is measured by using a standard device such as a luminance meter or an integrating sphere. max / t n .

[0037] Step 3: Based on the fitted model, G max and L max are substituted into the Gamma correction formula to inversely calculate the Gamma value of the display panel, which is used to accurately describe the mapping relationship between the display panel gray and the actual brightness. The maximum brightness L max and the maximum gray G max calibrated in step 2 are brought into the Gamma correction formula based on; , and the Gamma value is solved: .

[0038] Step 4: According to the panel compensation requirements, set several key gray compensation points, and preferably select typical gray values such as 25, 60, 128, etc. Under the condition of the optimal exposure time, display and shoot the test image of each compensation point, and extract the actual gray value G of the central region.

[0039] Step 5: Combine the known Gamma value and the maximum brightness L max to inversely calculate the actual brightness corresponding to each compensation point, form multiple groups of gray, brightness, and Gamma data, use polynomial fitting to build a complete compensation model L=(a+bG+cG 2 +dG 3 +eG 4 ) γ , which reflects the brightness change trend at different gray levels.

[0040] Step 6: Divide the display panel into multiple fixed-size grid areas, preferably 8x8 pixel cells, the specific size can be flexibly adjusted according to the panel resolution. Calculate the average gray value in each grid area, combine the compensation model, Gamma value and maximum brightness L max , calculate the actual brightness L(G x，y ) of each grid, accurately evaluate the local brightness deviation ΔL x，y =L target -L(G x，y ). According to the calculation results, generate a complete compensation lookup table (LUT) for real-time display control of the panel, dynamically adjust the brightness output of each area, eliminate the overall and local brightness unevenness and Mura defects, and improve the display uniformity and visual effect of the panel.

[0041] Although the present application has been described with reference to the explanatory embodiments thereof, the above-described embodiments are merely preferred embodiments of the present application, and the embodiments of the present application are not limited to the above-described embodiments, and it should be understood by those skilled in the art that many other modifications and embodiments can be designed, which will fall within the scope and spirit of the principles disclosed in the present application.

Claims

1. A method for optical compensation of a display panel, characterized in that, Includes the following steps: Step 1: Construct an exposure time-grayscale dataset; Step 2: Fit the exposure time-grayscale value relationship, calculate the fitting coefficient, and establish a brightness model; Step 3: Based on the fitting model and combined with the Gamma correction principle, the Gamma value of the display panel is calculated in reverse to realize the mapping between grayscale and actual brightness; Step 4: Based on the points to be compensated required by the display panel, take a grayscale test image corresponding to the compensation point. Use a camera to take the image at the optimal exposure time to ensure that the image is clear and without overexposure or underexposure, and extract the actual grayscale value of each compensation point. Step 5: Fit a polynomial function of the grayscale, brightness, and Gamma values ​​of the compensation points; Step 6: Divide the display panel into multiple grid areas, calculate the average gray value of each grid, calculate the local compensation amount for each grid, generate a compensation lookup table, and apply it to real-time display compensation to compensate for overall and local brightness unevenness and Mura defects.

2. The optical compensation method for a display panel according to claim 1, characterized in that, Step 1 specifically includes the following steps: Displaying a grayscale test image on the display panel, and using a high-precision camera at different exposure times (T1, T2…T…). n Images were captured, resulting in images with different grayscale values. The average grayscale value of the central region of each image was extracted to construct a complete exposure time-grayscale dataset {(T 1， G1), (T 2， G2)...(T n G n )}.

3. A display panel optical compensation method according to claim 1 or 2, characterized in that, Step 2 specifically includes the following steps: Step 21: Using exposure time as the independent variable and the collected grayscale value as the dependent variable, fit a quadratic polynomial using the least squares method to obtain the relationship between grayscale and exposure time: G(t) = a²t 2 +a1t+a0; Step 22: Select the average gray level value of the central region of the image with the highest gray level as the maximum gray level G. max And define the calibrated brightness value of the central region of the maximum grayscale image as L. max Establish a brightness model: L / t = L max / t n .

4. The optical compensation method for a display panel according to claim 3, characterized in that, Step 3 specifically includes the following steps: Step 31: Set the maximum brightness L as specified in Step 2. max and maximum gray level G max Substitute this into the formula based on Gamma correction; , Step 32: Take the natural logarithm of the formula to solve for the Gamma value: .

5. The optical compensation method for a display panel according to claim 4, characterized in that, Step 5 specifically includes the following steps: Step 51: Substitute the center grayscale value G of the grayscale test image of the compensation point into the calculation of the Gamma value in Step 3, set the calibration brightness of the corresponding compensation point as L, and construct the grayscale-Gamma value-brightness dataset of the compensation point {(G i γ i L i )}, Step 52: Use the least squares method to fit the polynomial: L=(a+bG+cG) 2 +dG 3 +eG 4 ) γ .

6. The optical compensation method for a display panel according to claim 5, characterized in that, According to L=(a+bG+cG) 2 +dG 3 +eG 4 ) γ Calculate the true brightness value under the calibrated grayscale, and perform difference compensation based on the true brightness.

7. The optical compensation method for a display panel according to claim 6, characterized in that, Step 6 specifically includes the following steps: Step 61: Divide the panel into grid areas of a set size; Step 62: First, calculate the average gray value G for each grid cell. x，y Then, substituting the values ​​from steps 3 and 4, we obtain the Gamma value for each grid cell. Finally, substituting these values ​​into step 5, we calculate the true brightness L for each grid cell. x，y ; Step 63: According to the compensation formula ΔL x，y =L target -L(G x，y The compensation value ΔL for each grid is calculated. x，y A compensation lookup table is generated based on the compensation results; Step 64: Based on the compensation lookup table, compensate for overall and local brightness unevenness and Mura defects.

8. A display panel optical compensation method according to claim 7, characterized in that, The grid area is an 8x8 pixel grid.

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