A method for improving color accuracy of a liquid crystal display

Abstract

The application discloses a method for improving color accuracy of a liquid crystal display, which is characterized in that a backlight device of the display is matched, a body color temperature and a luminance characteristic value are designed, a preheating time of the display is set, after the display is started and waits for the preheating time, maximum luminance cycle detection of the whole machine, body color coordinate cycle detection of the whole machine, automatic algorithm debugging of a Gamma multi-stage wide coefficient range, accurate color temperature debugging, sRGB and DCI-P3 color space matrix conversion are carried out in a darkroom environment, then a plurality of color pictures are outputted for color accuracy test, an average color accuracy value is calculated, parameters corresponding to color accuracy values meeting preset requirements are written into the display, and the parameters are called by different color space image modes. The application quantitatively designs liquid crystal backlight luminance, color temperature and other characteristics, then accurately calculates and debugs the display online, corrects color temperature, color gamut overlap, white balance, Gamma and other parameters affecting the color accuracy value, carries out real-time color space conversion according to the measured characteristics of the display screen, adjusts color data and luminance data of each display in real time, so that the color restoration of the liquid crystal display is improved, the color accuracy value of each display is reduced, and the color accuracy is improved.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal display color display technology, specifically, to a method for improving the color accuracy of liquid crystal displays. Background Technology

[0002] Currently, there are many types of LCD monitors. Based on frame rate, they can be divided into high frame rate and standard frame rate monitors; based on color gamut coverage, they can be divided into standard color gamut and high color gamut monitors; based on usage, they can be divided into gaming series and office series; and based on the physical resolution of the screen, they can be divided into FHD, QHD, and 4K monitors. Each type has its own focus, concentrating on aspects such as color accuracy, frame rate, brightness, and resolution. However, regardless of the type of monitor, color accuracy is the most important factor for all monitors. High requirements are placed on color performance and reproduction for web page display, video playback, and gaming. Color accuracy is a characteristic indicator that measures the color accuracy within a specific color gamut range. Currently, many monitors have color accuracy values ​​greater than 2, even between 3 and 8, indicating significant color shift. The lower the color accuracy value, the better the color reproduction; the higher the color accuracy value, the worse the color reproduction. Currently, the main methods to improve the color accuracy of monitors are mainly focused on color temperature adjustment and color matrix algorithm conversion presets, which are close to the standard color gamut. However, this method has certain limitations when there are large differences in the aging and decay characteristics of backlight, panel and other components and the differences between components in the same batch. Therefore, when there are large changes in the characteristics of components and batch differences, there will be a large deviation in color accuracy. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the color accuracy of a liquid crystal display, which solves the problem that existing methods for improving color accuracy suffer from large color accuracy deviations when there are significant variations in device characteristics and batch differences.

[0004] The present invention solves the above problems through the following technical solution:

[0005] A method for improving the color accuracy of a liquid crystal display includes:

[0006] Step S1: Match the backlight device of the display and design the body color temperature and brightness characteristic values;

[0007] Step S2: Set the monitor's warm-up time. The monitor will automatically enter warm-up mode after being powered on. Once the warm-up time meets the preset duration, proceed with the following steps in a dark room environment:

[0008] A. Perform a loop detection of the maximum brightness of the whole machine. When the brightness reaches the preset target brightness value, proceed to the next step; otherwise, return to step S1.

[0009] B. Perform a loop detection of the body color coordinates of the whole machine. When the body color coordinates meet the preset target requirements, proceed to the next step; otherwise, return to step S1.

[0010] C. Execute the automatic algorithm for adjusting the wide range of Gamma coefficients, detect the highest brightness of the screen, automatically calculate and complete the Gamma curve according to different Gamma coefficients. Depending on the different module models, the adjustment steps can be 8-256, and the coefficients can be 1.8-2.6. After completion, proceed to the next step.

[0011] D. Perform precise color temperature adjustment; once the target color temperature requirement is met, proceed to the next step.

[0012] E. Perform sRGB and DCI-P3 color space matrix conversion. Once completed, proceed to the next step.

[0013] F. Output multiple built-in color maps and multi-level grayscale maps for color accuracy testing, automatically calculate the average color accuracy value. When the average color accuracy value meets the preset target requirement (the requirement is less than 1.2 or 1.6, which can be preset according to the requirements, but the maximum preset value is less than 2), store the average color accuracy value test value and test value locally, and simultaneously upload the record to the server. At the same time, write the corresponding debugged data to the display storage for corresponding access when the image mode and color space change. If the preset color accuracy value requirement is not met, return to step C.

[0014] Furthermore, the color map consists of 32 images with different gray levels and different hues.

[0015] Furthermore, the preheating time is set according to the backlight strip of the display and the OC attenuation law.

[0016] Furthermore, the preset target brightness value can be selected and set according to the different brightness requirements of the display.

[0017] For example, the preset target brightness value is 300 nits (adjusted according to the product). For HDR400 certification, it is set to 400 nits.

[0018] Furthermore, the preset target requirement for the body color coordinates is a target value of ±0.015.

[0019] Furthermore, the target color temperature requirement for the precise color temperature adjustment is the target color temperature coordinate value ±0.003.

[0020] Furthermore, the preheating time can be preset to a target value based on the different module models and production line characteristics of the display, ranging from 10 minutes to 1000 hours, to suit different scenario requirements.

[0021] Furthermore, in the preheating time detection method, if the preheating time does not meet the mandatory requirements, the system exits the debugging mode and automatically enters the aging preheating phase.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) This invention, through the design parameters of the backlight system front end, preset parameter cyclic detection and control, combined with environmental control, and precise multi-layer cyclic debugging by software, greatly improves the color display accuracy and color reproduction of the display within the sRGB and DCI-P3 color gamuts, and reduces color deviation ΔE. It achieves a low color accuracy value of <1.2 for sRGB and <1.6 for DCI-P3, thus improving the color display effect of the LCD and solving the problem of large color accuracy deviation in existing methods for improving color accuracy when there are large variations in device characteristics and batch differences.

[0024] (2) This invention quantifies the characteristics of LCD backlight brightness and color temperature, and then uses software to precisely control the parameters of each display that affect color accuracy, such as color temperature, color gamut, white balance, and color space matrix. Based on the measured characteristics of each display, it performs real-time color space conversion and adjusts the color data and brightness data of each display in real time to achieve high color accuracy with low color accuracy.

[0025] (3) This invention calculates the color shift of each of 32 images with different gray levels and hues, including white point, gray point, red point, green point, blue point, etc., and then automatically performs an average calculation to measure the average color accuracy value, which is used as the color accuracy value of the display. At the same time, this value is detected and controlled, and if it exceeds the preset value, it is readjusted to ensure that the color accuracy value of each display meets the preset requirements. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention;

[0027] Figure 2 A chart showing the monitor's warm-up time control. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0029] Example:

[0030] One method to improve the color accuracy of a liquid crystal display (LCD) first analyzes the factors that affect color accuracy, i.e., color precision value:

[0031] (1) Effect of color temperature

[0032] The standard color temperature for LCD monitors is D65, or 6500K, with color coordinates Wx = 0.3127 and Wy = 0.3290. All color accuracy tests are conducted based on this D65 color temperature. Inaccurate color temperature will affect the accuracy of the white point at different gray levels, and also affect the color accuracy values ​​for other color scenes. The closer the color temperature and color coordinates are to the standard color temperature and color coordinates, the lower the color accuracy value and the smaller the color shift value ΔE.

[0033] The device parameters of different monitors have absolute errors, so it is necessary to perform precise and low-error color temperature calibration for each monitor on the production line.

[0034] (2) Color Gamut Influence

[0035] Color gamut refers to the set of all colors a monitor can display. The larger the color gamut value, the more colors the monitor can display, and the closer the colors are to the original colors. A monitor's color gamut is determined by its backlight and LCD panel. The light source generated by the backlight strip passes through the LCD OC (Optical Center) and is then used to display the corresponding image. The parameter design of the backlight strip and the parameter control of the LCD panel are key factors in determining the color gamut.

[0036] Color accuracy is tested based on the standard color gamut range. Within the sRGB color gamut, testing a monitor's ability to reproduce colors requires that the monitor's own color gamut covers or closely approximates the standard sRGB color gamut range. For the DCI-P3 color gamut, it's generally used in high color gamut monitors. Within the DCI-P3 color gamut display range, the monitor needs to achieve 93% or more of the standard DCI-P3 color gamut display range to improve color accuracy within the DCI-P3 color gamut, displaying richer colors and reducing color display deviation ΔE, based on the monitor's hardware support.

[0037] (3) Influence of brightness and brightness curve

[0038] Brightness is a key indicator for evaluating a monitor. Low brightness means that bright areas of an image cannot be displayed, and details in dark areas are too dark to be distinguished; it also affects the brightness and vividness of colors. The higher the brightness, the brighter and more vivid the corresponding colors, and the smaller the color shift.

[0039] The brightness curve is also known as the gamma curve. The gamma curve enables the display to have better gray levels. The gamma coefficient of the display can be set to multiple options from 1.8 to 2.6 (e.g., 1.8, 2.0, 2.2, 2.4, 2.6). The gamma coefficient of each display is different due to the difference in the liquid crystal backlight module. In order to improve color accuracy and display effect, each display must be corrected for at least 16 or 32 levels of gamma with a coefficient of 1.8-2.6.

[0040] (4) Influence of device attenuation characteristics

[0041] Brightness and color temperature characteristics will decline as the monitor ages and continues to operate, before stabilizing. The rate and magnitude of brightness decrease during the transition from cold to warm-up are different; the initial 20 minutes see a rapid and significant drop, up to 20 nits, after which the rate and magnitude of the decrease gradually slow down. Simultaneously, the color coordinates also decrease, leading to changes in color temperature. Experiments show that the monitor reaches a relatively stable state in brightness and color coordinates after 30 minutes.

[0042] Based on the characteristics of the components, it is necessary to understand the attenuation patterns of the backlight system and the LCD screen, and to conduct relevant debugging and testing of the display after the aging process has stabilized.

[0043] (5) Test Environment

[0044] The testing environment mainly includes ambient brightness and test location. Excessive ambient brightness can affect the accuracy of the data collected by the color analyzer. To reduce interference from ambient light on the display and improve the accuracy of the color analyzer's data collection, operation needs to be conducted in a darkroom environment.

[0045] (6) Calculation and conversion of color space

[0046] The display color gamut of the monitor itself differs from the standard sRGB and DCI-P3 color gamuts. Color accuracy testing involves conversion within each of these different color gamuts. Within the sRGB color gamut, conversion according to the sRGB color space is required, while within the DCI-P3 color gamut, conversion according to standard DCI-P3 is necessary. This conversion must be based on the monitor's inherent color gamut. Since monitor data varies from unit to unit, improving the color accuracy of each monitor requires real-time acquisition of its RGBW data. This ensures precise conversion and reduces color deviation.

[0047] Taking the above factors into consideration, the present invention provides a method for improving the color accuracy of a liquid crystal display, such as... Figure 1 As shown, it includes:

[0048] (I) Design the colorimetric parameters of the monitor backlight

[0049] This invention, by modifying the color blocks of the LED strips and combining them with the characteristics of the LCD panel, enables the entire display to achieve a standard color temperature of 6500K in the direct-pass state, with an allowable error of +1000K, color coordinates Wx = 0.3127, Wy = 0.3290, and an allowable error of 0.010. The purpose of this is to bring the body coordinates and color temperature as close to the standard state as possible, reduce the excessive reduction of RGB gain during white balance adjustment, and reduce the attenuation of signal brightness and color due to deviations in body coordinates and color temperature.

[0050] (ii) Calculate the device settling time and set a reasonable preheating and aging time for the whole machine.

[0051] Based on the degradation characteristics of backlight strips and LCD panels, different warm-up times are set for different display device characteristics to ensure the display fully warms up and reaches a stable state. Different warm-up times are set for 30 minutes, 35 minutes, and 40 minutes, depending on the characteristics of different backlights and LCD panels. This time can be expanded in the future based on the addition of new backlight and LCD panel resources, with a designed expansion range of up to 1000 hours. Figure 2 As shown.

[0052] (III) Multi-level grayscale individual Gamma adjustment

[0053] This invention employs 16-level or 32-level grayscale for individual Gamma calibration on each monitor. During Gamma calibration, from full black to full white, 16-level or 32-level Gamma correction is performed online on each monitor (adjusted according to the module model). The monitor has 16 or 32 built-in white field images of different grayscale levels, which are output sequentially from brightest to darkest. Adjustments are made individually on each of the built-in output grayscale images according to a correction coefficient (error ±0.1). The average Gamma coefficient of the 16 or 32 points is calculated and controlled within the corresponding coefficient range of ±0.1.

[0054] In addition to the 2.2 calibration factor, monitors also offer various Gamma modes with different coefficients such as 1.8, 2.0, 2.2, 2.4, and 2.6, which need to be adjusted. Different Gamma coefficients can match application scenarios with different brightness and darkness requirements. The main difference between the 1.8, 2.0, 2.4, and 2.6 Gamma coefficients lies in the dark field; the larger the Gamma coefficient, the darker the dark field, and the smaller the Gamma coefficient, the brighter the dark field. The corresponding colors also exhibit corresponding changes in color brightness to match the appropriate color scene.

[0055] (iv) Precise color temperature adjustment and calculation

[0056] First, input a full white field signal to test the screen brightness. When the screen brightness is lower than the preset brightness, execute the failure process. When the brightness reaches our preset target value, enter the debugging process.

[0057] Second, enter the color coordinate test. When the color coordinate exceeds the target value by 0.015, execute the failure command.

[0058] Third, set the target coordinates Wx = 0.3127, Wy = 0.3290, and set the error range to ±0.003;

[0059] Fourth, set the target brightness value LV, which is 65% of the monitor's maximum brightness value, and set the LV error range to +-80 nits. Cyclicly adjust the RGB gain, slowly lowering it from the optimal RGB value of 128 until we reach our target color coordinates of 0.3127±0.003 and 0.3290±0.003 and the target brightness value.

[0060] Fifth, if the brightness drops to the "LV-error value" during the debugging process, the loop will be exited and a fail command will be executed. The purpose is to prevent the brightness from dropping too much, with the RGB gain of the maximum brightness as the basic principle.

[0061] Sixth, adjust the monitor to the target coordinates and target brightness, write the RGB gain value to the monitor and save it as the final color temperature adjustment value.

[0062] (V) Color Space Conversion

[0063] Different application and content scenarios use different color spaces. For example, most web pages use the sRGB color space, while movies use the DCI-P3 color space. By setting sRGB and DCI-P3 modes on the monitor, and using online testing of each screen's inherent color gamut data (RGB three-color chromaticity data), the parameters for the sRGB and DCI-P3 color conversion matrices are set, and the color gamut conversion parameters are stored for different color spaces. For the sRGB color gamut, the converted color gamut is made close to the standard sRGB color gamut range. For the DCI-P3 color gamut, it is converted in DCI-P3 mode to a color gamut range close to the standard DCI-P3 range.

[0064] Seven base colors—red, green, blue, cyan, purple, yellow, and white—were tested. Each base color was further divided into four different brightness and hue levels. White was represented by eight different grayscale images, while the other colors were represented by four images. The color coordinates of each image were measured and compared with the color points in the standard sRGB and DCI-P3 color spaces, and then adjusted accordingly.

[0065] (vi) Color accuracy value step-by-step testing and debugging value storage

[0066] Test the color difference value of each color, then automatically calculate the average color accuracy of 32 images for judgment and detection. If the preset requirements are met, write all debugging data to the main device storage; if the requirements are not met, repeat the debugging test.

[0067] This invention, through front-end design parameters of the backlight system, preset parameter cyclic detection and control, combined with environmental control, and precise multi-layer cyclic debugging via software, significantly improves the color display accuracy and color reproduction of the display within the sRGB and DCI-P3 color gamuts, while reducing color deviation ΔE. It achieves a low color accuracy value of <1.2 for sRGB and <1.6 for DCI-P3, thus improving the color display effect of the LCD monitor.

[0068] Although the present invention has been described herein with reference to illustrative embodiments, the above embodiments are merely preferred embodiments of the present invention, and the implementation of the present invention is not limited to the above embodiments. It should be understood that those skilled in the art can devise many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A method of improving color accuracy of a liquid crystal display, comprising: The application relates to a display preheating time setting method and device. S1, the display backlight device is matched, the body color temperature and the luminance characteristic value are designed; S2, the preheating time of the display is set, the display is automatically preheated after being started, and the following steps are performed in a darkroom environment after the preheating time meets the preset time length: A, the maximum luminance of the whole machine is detected, the next step is entered when the luminance reaches the preset target luminance value, otherwise, the step S1 is returned; B, the body color coordinate of the whole machine is cyclically detected, the next step is entered when the body color coordinate meets the preset target requirement, otherwise, the step S1 is returned; C, the Gamma multi-stage wide coefficient range automatic debugging is performed, and the next step is entered after the debugging is completed; D, the precise color temperature debugging is performed, and the next step is entered after the target color temperature requirement is met; E, the sRGB and DCI-P3 color space matrix conversion is performed, and the next step is entered after the conversion is completed; F, a plurality of color pictures and graded gray scale pictures are outputted to perform colorimetric test, the average colorimetric value is calculated, the average colorimetric value test value and the test value are stored in the local when the average colorimetric value reaches the preset target requirement, the server record is uploaded at the same time, and the corresponding data after debugging is written into the display, so that the corresponding calling is realized when the image mode changes and the color space changes, otherwise, the step C is returned.

2. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The color pictures are 32 pictures built in the display and including different gray scales and different color tones.

3. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The preheating time is set according to the backlight strip and the OC attenuation law of the display.

4. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The preset target luminance value is selected and set according to the display with different luminance requirements.

5. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The preset target requirement of the body color coordinate is the target value+ / -0.

015.

6. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The target color temperature requirement of the precise color temperature debugging is the target color temperature coordinate value+ / -0.

003.

7. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The preheating time setting method is that the preset target is set according to different module models and different production line characteristics of the display, and the preheating time range is 10 minutes to 1000 hours.

8. The method for improving color accuracy of a liquid crystal display according to claim 1, wherein, The preheating time detection method is that the debugging mode is forced to be exited and the aging preheating is automatically entered if the preheating time does not meet the requirement.

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